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Nov 2001

Volume 19, Issue 6, pp. 2007-2934

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Investigation of molecular beam epitaxial NdF3/Si(111) heterostructures by atomic force microscopy and x-ray diffractometry

J. M. Ko, S. D. Durbin, T. Fukuda, and K. Inaba

J. Vac. Sci. Technol. B 19, 2007 (2001); http://dx.doi.org/10.1116/1.1409388 (6 pages)

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NdF3 layers were grown on Si(111) substrates at 400, 550, and 700 °C by molecular beam epitaxy. The surface morphology observations by atomic force microscopy indicated that the NdF3 layers on Si(111) substrates grew as islands associated with screw dislocations, which coalesced less densely at higher growth temperatures. The layers grown at higher temperatures were more susceptible to formation of microcracks due to larger mismatch of the thermal expansion coefficient. The orientational relationship between NdF3 layers and Si(111) substrates was confirmed to be NdF3(0002)〈11−20〉‖Si(111)〈1−10〉 by x-ray diffraction measurement. As a function of growth temperature and layer thickness, the crystallinity of resulting layers in terms of full width at half maximum values was investigated. In particular, for NdF3 layers grown at a high temperature of 700 °C, lattice relaxation and crystallinity degradation with layer thickening were found. © 2001 American Vacuum Society.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Ct Interface structure and roughness

Polymer pattern formation on SiO2 surfaces using surface monolayer initiated polymerization

Xiaohua Chen, Laren M. Tolbert, Clifford L. Henderson, Dennis W. Hess, and Jurgen Ruhe

J. Vac. Sci. Technol. B 19, 2013 (2001); http://dx.doi.org/10.1116/1.1409391 (7 pages) | Cited 4 times

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The use of surface monolayer initiated polymerization, in which initiators are chemically bound to a surface, can generate robust barrier polymers for pattern formation in silicon by reactive ion etching. The combination of poly(vinylarenes) and a new surface initiator based upon a phenylazo initiator provides excellent etch resistance and superior performance. © 2001 American Vacuum Society.
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82.35.Gh Polymers on surfaces; adhesion
81.65.Cf Surface cleaning, etching, patterning
85.40.Hp Lithography, masks and pattern transfer

Deep plasma etching of piezoelectric PZT with SF6

M. Bale and R. E. Palmer

J. Vac. Sci. Technol. B 19, 2020 (2001); http://dx.doi.org/10.1116/1.1409392 (6 pages) | Cited 5 times

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Reactive ion etching with sulfur hexafluoride (SF6) gas has been employed to create deep structures in bulk samples of the piezoelectric material lead zirconate titanate, Pb(Zr,Ti)O3 (PZT). SF6 is chosen for compatibility with dry etching of silicon with a possibility for production of hybrid silicon-piezoelectric devices. Thick photoresist layers have been used to pattern PZT to a depth of 2 μm at a rate of 120 nm min−1. The use of more durable nickel masks, formed by electroplating through the thick resist, leads to structures greater than 100 μm in height, with an average sidewall angle of ∼72°. The profile of the deep PZT structures is seen to depend on etch duration and the spacing of structures, attributed to the redeposition of mask and etch products, respectively. The addition of nitrogen and argon to the SF6 plasma is shown to produce small improvements in the profiles. By combining gas addition with heating of the substrate PZT etch rates up to 200 nm min−1 have been obtained. © 2001 American Vacuum Society.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Materials aspects, electrical performance, and scalability of Ni silicide towards sub-0.13 μm technologies

Anne Lauwers, An Steegen, Muriel de Potter, Richard Lindsay, Alessandra Satta, Hugo Bender, and K. Maex

J. Vac. Sci. Technol. B 19, 2026 (2001); http://dx.doi.org/10.1116/1.1409389 (12 pages) | Cited 53 times

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Ni-silicide phase formation with and without a Ti capping layer was studied by sheet resistance, x-ray diffraction and transmission electron microscopy. Ni monosilicide is found to be the stable phase in a temperature range from 400 to 600 °C. At lower temperatures the Ni2Si phase is found to be present. For temperatures higher than 700 °C NiSi is converted into NiSi2. Pyramidal NiSi2 precipitates were found to grow epitaxially along the Si〈111〉 planes for annealing temperatures as low as 310 °C. The epitaxial NiSi2 grains were found to disappear when the annealing temperature is increased. Stress buildup during Ni silicidation was measured in situ and could be correlated to the formation of the different Ni-silicide phases. The stress induced by Ni-monosilicide formation compares favorably to the stress induced by Co disilicide and Ti disilicide. The average silicon consumption required to obtain a certain sheet resistance was found to be 35% lower for Ni monosilicide compared for Co disilicide. It was found that a two-step process is needed to obtain complete conversion to the preferred Ni-monosilicide phase without lateral silicide growth. The sheet resistance of Ni-silicided narrow poly-Si and active area lines was found to be low, even when Ni silicide was formed without a Ti cap. No degradation of the Ni silicide on the narrow poly-Si lines was observed when the silicidation temperature was increased to 600 °C. The reverse bias leakage of shallow Ni-silicided and Co-silicided square diodes was compared for varying junction depths and varying silicide thicknesses. For similar junction depth and similar sheet resistance, a lower reverse bias leakage current was obtained for a Ni-silicided junction compared to its Co-silicided counterpart. This may be attributed to the reduced Si consumption of Ni monosilicide compared to Co disilicide. © 2001 American Vacuum Society.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.72.Cc Kinetics of defect formation and annealing
68.60.Bs Mechanical and acoustical properties
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Reduced brightness of the ZrO/W Schottky electron emitter

A. H. V. van Veen, C. W. Hagen, J. E. Barth, and P. Kruit

J. Vac. Sci. Technol. B 19, 2038 (2001); http://dx.doi.org/10.1116/1.1409390 (7 pages) | Cited 18 times

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The reduced brightness for a 〈100〉 ZrO/W Schottky electron emitter with a tip radius of 0.8 μm has been measured. The maximum reduced brightness measured was 2×108 A/(m2 sr V). The measurements of the reduced brightness are compared with the extended Schottky theory and the theory on stochastic Coulomb interactions. At high angular current densities the reduced brightness is limited by statistical Coulomb interactions in the gun lens region. The limits to the maximum reduced brightness in an ideal configuration are explored and found to be 2×109 A/(m2 sr V) for a 0.2 μm tip and a current limiting aperture in the extractor electrode. © 2001 American Vacuum Society.
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79.40.+z Thermionic emission
73.30.+y Surface double layers, Schottky barriers, and work functions

Experimental conditions for a highly ordered monolayer of gold nanoparticles fabricated by the Langmuir–Blodgett method

Shujuan Huang, Gen Tsutsui, Hiroyuki Sakaue, Shoso Shingubara, and Takayuki Takahagi

J. Vac. Sci. Technol. B 19, 2045 (2001); http://dx.doi.org/10.1116/1.1410943 (5 pages) | Cited 20 times

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A highly ordered monolayer film of alkanethiol-encapsulated gold nanoparticles was fabricated on a silicon substrate by using the Langmuir–Blodgett (LB) method. The effects on the particle order, of the particle concentration and the type of solvent of the LB spreading suspension of encapsulated gold particles, were studied. We found that a low particle concentration of 0.06–0.3 mg/mL in chloroform is optimal for the fabrication of high quality gold particle monolayers. Since the proposed method is not restricted to gold particles, it is believed to be a practical process for fabricating quantum dot structures of various particle sizes and compositions. © 2001 American Vacuum Society.
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81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
82.70.Kj Emulsions and suspensions
68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots

Modification of polycarbonate and polypropylene surfaces by argon ion cluster beams

H. Biederman, D. Slavinska, H. Boldyreva, H. Lehmberg, G. Takaoka, J. Matsuo, H. Kinpara, and J. Zemek

J. Vac. Sci. Technol. B 19, 2050 (2001); http://dx.doi.org/10.1116/1.1410944 (7 pages) | Cited 7 times

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Impacts of energetic argon ion clusters on surfaces of inorganic solids have shown modification of the respective surface properties. Polymeric samples such as (PC) polycarbonate and (PP) polypropylene were irradiated by argon ion clusters (average size of 3000 atoms) accelerated to 10 and 20 keV at doses ranging from 109 to 1014 cluster/cm2. The irradiated surfaces were investigated by surfometer (profilometer), atomic force microscope, contact angle measurements and x-photoelectron spectroscopy. Measurements using these techniques show that the smoothing effect and the postirradiation oxidation of the surface take place. The direct evidence was obtained in case of PP that the irradiation dose 1011 cluster/cm2 produces the smoothest surface as measured by surfometer. In the case of PC the same conclusion is suggested indirectly. © 2001 American Vacuum Society.
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81.65.Ps Polishing, grinding, surface finishing
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
61.80.Jh Ion radiation effects
61.82.Pv Polymers, organic compounds
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ps Atomic force microscopy (AFM)
68.03.Cd Surface tension and related phenomena
79.60.Fr Polymers; organic compounds
68.37.Xy Scanning Auger microscopy, photoelectron microscopy

Valence band alignment and work function of heteroepitaxial nanocrystals on GaAs(001)

S. Heun, Y. Watanabe, B. Ressel, Th. Schmidt, and K. C. Prince

J. Vac. Sci. Technol. B 19, 2057 (2001); http://dx.doi.org/10.1116/1.1410942 (6 pages) | Cited 2 times

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The differences in valence band structure and work function between heteroepitaxial nanocrystals and the surrounding substrate were measured with a spectroscopic photoemission and low energy electron microscope which allows laterally resolved photoemission spectroscopy. The nanocrystals were obtained by depositing nominally 2 and 4 monolayers (ML) of InAs on a Se-terminated GaAs(001) surface. The samples showed differences in the valence band edge energy and work function both between nanocrystals and substrate as well as between 2 and 4 ML. We suggest that Se termination of the nanocrystals is the reason for these differences. © 2001 American Vacuum Society.
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73.22.Dj Single particle states
79.60.Jv Interfaces; heterostructures; nanostructures
73.30.+y Surface double layers, Schottky barriers, and work functions

Chemical composition, morphology, and deep level electronic states of GaN (0001) (1×1) surfaces prepared by indium decapping

A. P. Young, L. J. Brillson, Y. Naoi, and C. W. Tu

J. Vac. Sci. Technol. B 19, 2063 (2001); http://dx.doi.org/10.1116/1.1412656 (4 pages)

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Ordered GaN (0001) (1×1) surfaces are prepared after removal from the growth chamber via thermal desorption of a thin In cap layer at 650 °C in combination with one thermal flash of Ga metal to reduce residual O and C contamination. Auger electron spectroscopy (AES) and low energy electron-excited nanoscale luminescence (LEEN) spectroscopy results show that In can prevent contamination during atmospheric exposure if it can cover the surface uniformly. LEEN spectra of the ordered surface show that the In capping layer is desorbed from the GaN without reacting to produce InxGa1−xN or diffusing into the GaN to produce new localized states. Subsequent atomic force microscopy (AFM) measurements reveal an atomically smooth film plus Ga droplets residual to the flash annealing. These results suggest that In decapping may be useful in obtaining clean, LEED-ordered GaN surfaces after transport in air with a minimum of UHV treatment. © 2001 American Vacuum Society.
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68.35.Dv Composition, segregation; defects and impurities
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.20.Hb Impurity and defect levels; energy states of adsorbed species
68.43.Vx Thermal desorption
81.65.Cf Surface cleaning, etching, patterning
61.72.Cc Kinetics of defect formation and annealing
78.60.Hk Cathodoluminescence, ionoluminescence
79.20.Fv Electron impact: Auger emission

Improvement of the SiO2/Si interface characteristics by two-step deposition with intermediate plasma treatment using O2/He gas

Chung Yi, Hyo Uk Kim, Shi Woo Rhee, Sang Ho Oh, and Chan-Gyung Park

J. Vac. Sci. Technol. B 19, 2067 (2001); http://dx.doi.org/10.1116/1.1412657 (6 pages) | Cited 1 time

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We studied two-step deposition with an O2/He intermediate plasma treatment to improve the SiO2/Si interface characteristics. Using this method, we can minimize the plasma damage on the Si surface and improve the interface characteristics such as intermediate oxidation states, interface trap density Dit, and Vfb shift. The interface characteristics were improved with the intermediate plasma treatment after a 6 nm first oxide deposition. The number of Si atoms (NSiOx) in the suboxide region, compared with the sample without plasma treatment, was decreased 14.7% and a sixfold ring structure became dominant. Interface trap density was decreased from 1.65×1011/eV cm2 to 6.87×1010/eV cm2 by the oxygen incorporation in the transition region. The moderate oxygen incorporation near the SiO2/Si interface reduced the Vfb shift due to the decrease of the fixed oxide charge. © 2001 American Vacuum Society.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.35.Ct Interface structure and roughness
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
73.20.Hb Impurity and defect levels; energy states of adsorbed species
79.60.Jv Interfaces; heterostructures; nanostructures
68.37.Lp Transmission electron microscopy (TEM)

In situ submicron patterning with silicon nitride evaporation masks

U. Purbach and A. de Lozanne

J. Vac. Sci. Technol. B 19, 2073 (2001); http://dx.doi.org/10.1116/1.1412658 (4 pages) | Cited 1 time

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We describe a technique for ultra-high-vacuum compatible deposition of structures on flat substrates. This technique allows one to form micrometer and even submicron-sized structures on a flat surface with minimal contamination. It also has the advantage of producing a smooth edge profile similar to those achieved using a two-layered resist.© 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
85.40.Sz Deposition technology
68.55.A- Nucleation and growth
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Dv Composition, segregation; defects and impurities

Parameter extraction for 193 nm chemically amplified resist from refractive index change

Young-Soo Sohn, Hye-Keun Oh, and Ilsin An

J. Vac. Sci. Technol. B 19, 2077 (2001); http://dx.doi.org/10.1116/1.1414016 (5 pages) | Cited 2 times

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Some of the important areas to be improved for lithography simulation are: obtaining correct exposure parameters and determining the change of refractive index. It is known that the real and imaginary refractive indices are changed during exposure. We obtained these refractive index changes during exposure for 193 nm chemically amplified resists. The variations of the transmittance as well as the resist thickness were measured during ArF excimer laser exposure. We found that the refractive index change is directly related to the concentration of the photo acid generator and deprotected resin. It is important to know the exact values of acid concentration from the exposure parameters since a small difference in acid concentration magnifies the variation in the amplified deprotection during postexposure bake. We developed and used a method to extract Dill ABC exposure parameters for 193 nm chemically amplified resist from the refractive index change upon exposure. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Characterization of reactive ion etch lag scaling

D. Keil and E. Anderson

J. Vac. Sci. Technol. B 19, 2082 (2001); http://dx.doi.org/10.1116/1.1414116 (7 pages) | Cited 15 times

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Recent advances in ultralarge-scale integration have typically depended on reductions in etched feature size. This has motivated efforts to find etch processes that will precisely etch increasingly smaller features while retaining the ability to etch larger features. As feature sizes push below 0.25 μm, reactive ion etch (RIE) lag control becomes increasingly important. Knowing how RIE lag scales with feature size for a given process aids in determining if that process must be discarded and a new one developed. In those situations where a process cannot be discarded, an understanding of RIE lag scaling aids in predicting fabrication difficulties for a given device design. Using a minimal set of initial assumptions, it is shown that a relationship can be derived which relates etch rate to the time development of the feature aspect ratio. It is then shown that this relationship can be used to derive an expression for the etch depth as a function of time and feature size. The assumptions made are justified by phenomenological observation rather than by an assumed mechanism. This approach enhances the generality of the results obtained, thus making them useful for a variety of practical etch engineering applications. © 2001 American Vacuum Society.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
68.35.B- Structure of clean surfaces (and surface reconstruction)

Initial surface reactions between Cl2 molecules and the GaAs (001) 2×4 surface

Yu Tanaka and Masashi Ozeki

J. Vac. Sci. Technol. B 19, 2089 (2001); http://dx.doi.org/10.1116/1.1414118 (6 pages) | Cited 2 times

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Initial reactions for Cl2 molecules at the GaAs(001)-(2×4) surface have been investigated by using a supersonic molecular-beam scattering technique. Results with a high corrugation GaAs(001)-(2×4) surface indicate a complex, dynamical behavior of Cl2 molecules interacting with the surface. A fine chemisorption probability measurement at an incident translational energy of 0.12 eV suggests an extremely fast dissociative chemisorption process with an initial probability of ∼93%. Angular distributions measured for scattered Cl2 molecules at 0.06, 0.12, and 1.45 eV strongly indicate three channels of behavior: inelastic direct scattering, trapping/desorption, and multiple scattering. In particular, the multiple scattering channel arises from the corrugation of the surface. © 2001 American Vacuum Society.
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68.43.Mn Adsorption kinetics
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.05.Ea III-V semiconductors
68.49.Df Molecule scattering from surfaces (energy transfer, resonances, trapping)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.20.Pm Rate constants, reaction cross sections, and activation energies
68.35.B- Structure of clean surfaces (and surface reconstruction)

Study of the surface reactivity of optical fibers under aging conditions by flexural resonance

Johann Mertens, Eric Finot, Eric Bourillot, Arnaud Fabre, and Jean Pierre Goudonnet

J. Vac. Sci. Technol. B 19, 2095 (2001); http://dx.doi.org/10.1116/1.1414113 (9 pages) | Cited 1 time

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This article reports an original technique for measuring the flexural resonance response of optical fibers of around 1 mm in length considered as atomic force microscope cantilevers. This technique was found particularly suitable for precisely investigating the effect of aging of optical fibers due to external factors such as temperature, action of hydrogen, or ionic aggressive solutions. Compared to the corresponding atomic force microscopy images, the measurement of the resonance frequency shift leads to the determination of two factors characteristic of the surface reactivity of the fiber: first, the decrease in frequency that can be considered in terms of mass loading, and second both the frequency increase and the loss in Q factor resulting from the variation of the Young modulus and the internal friction of the fiber. © 2001 American Vacuum Society.
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42.81.Cn Fiber testing and measurement of fiber parameters
46.80.+j Measurement methods and techniques in continuum mechanics of solids
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.35.Gy Mechanical properties; surface strains
62.20.D- Elasticity
07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)

Global pattern density effects on aluminum alloy etching for sub-0.25 μm technology logic devices

Kye Hyun Baek, Kil Ho Kim, Chung Ho Hwang, and Dae Hoon Lee

J. Vac. Sci. Technol. B 19, 2104 (2001); http://dx.doi.org/10.1116/1.1414114 (4 pages)

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Global pattern density effects on aluminum alloy etching were quantitatively analyzed for sub-0.25 μm technology logic devices. We found that etching the metal layer with one pattern density while applying the plasma activation parameters optimized for the other pattern density often results in inferior performance, even if the minimum design rules of both layers are the same. Additional studies show that the aluminum etch rate has an almost linear relationship to the pattern density of the etched metal layer when all the activation parameters are fixed. This evokes the necessity that the plasma activation parameters be optimized properly with the pattern density of each metal layer as well as with the minimum design rule. We speculate that these pattern density effects are caused by the variation of etching environment that is solely determined by effective etchants density and their effective residence time. Thus it may be possible to alleviate the global pattern density effects by controlling the plasma activation parameters in such a way that these two effective values are independent of the pattern density. Based on the aforementioned speculation we controlled total pressure and feed gas flow rate and were able to achieve stable etching performance independent of the global pattern density. © 2001 American Vacuum Society.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
82.20.Pm Rate constants, reaction cross sections, and activation energies
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
84.30.Sk Pulse and digital circuits
82.40.Np Temporal and spatial patterns in surface reactions

Investigation of fluorine in dry ultrathin silicon oxides

G. Vereecke, E. Röhr, R. J. Carter, T. Conard, H. De Witte, and M. M. Heyns

J. Vac. Sci. Technol. B 19, 2108 (2001); http://dx.doi.org/10.1116/1.1414050 (6 pages)

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The origins of fluorine in dry ultrathin silicon oxides (<1 nm) were investigated as the incorporation of fluorine in these layers may improve their reliability and interface quality. Oxides were grown at room temperature (RT) by UV/O2 in an integrated tool combining vapor HF surface preparation and oxide growth in a single chamber. The chemical composition and thickness of the layers were characterized by x-ray photoelectron spectroscopy. It is shown that incorporation of fluorine in these oxides originated mainly from the contamination of the tool (dead spaces and surface adsorption) and from the fluorine left at the wafer surface by the in situ HF process. The levels of these sources of fluorine were about two orders of magnitude higher than from a wet HF dip. No evidence was found for the existence of subsurface fluorine [Kasi et al., Appl. Phys. Lett. 58, 2975 (1991)] as oxides grown in a separate noncontaminated cell (UV/O2, 1 atm O2, RT to 200 °C) did not show any significant increase in fluorine content as a function of oxide thickness. Hence the amount of fluorine incorporated into oxides grown in cluster tools under similar conditions will depend not only on the method selected for surface preparation but also on whether surface preparation and oxidation are performed in the same chamber or not. The possible benefits of determined fluorine levels are discussed. © 2001 American Vacuum Society.
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81.65.Mq Oxidation
68.55.Nq Composition and phase identification
68.35.Dv Composition, segregation; defects and impurities
79.60.Dp Adsorbed layers and thin films

Investigation of the bonding strength and interface current of p-Si/n-GaAs wafers bonded by surface activated bonding at room temperature

M. M. R. Howlader, T. Watanabe, and T. Suga

J. Vac. Sci. Technol. B 19, 2114 (2001); http://dx.doi.org/10.1116/1.1414115 (5 pages) | Cited 8 times

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Equivalent bulk strength of the interface between p-Si/n-GaAs bonded through the surface activated bonding (SAB) method is found. The interface current was extensively investigated. Nonideal behavior of the pn junction current is found to be due to the tunneling current between the conduction band and valence band across the transition region associated with band gap states. Interface current decreases with increasing sputtering time and energy and vice versa. Irradiation time and energy dependent behavior indicates that the accumulation of radiation induced defects associated with the doping controls the interface current of p-Si/n-GaAs. Moreover, strong impact of the exposure to an ultrahigh vacuum atmosphere of the activated surfaces on the interface current of p-Si/p-Si is found. Finally it can be suggested that a laser diode can be fabricated by the bonding between p-Si and n-GaAs through the SAB method, because of the achievement of equivalent bulk strength of the interface. © 2001 American Vacuum Society.
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68.35.Np Adhesion
81.05.Cy Elemental semiconductors
81.05.Ea III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Gk Tunneling
73.20.At Surface states, band structure, electron density of states
73.20.Hb Impurity and defect levels; energy states of adsorbed species
42.55.Px Semiconductor lasers; laser diodes

Metamorphic In0.52Al0.48As/In0.53Ga0.47As high electron mobility transistors on GaAs with InxGa1−xP graded buffer

K. Yuan, K. Radhakrishnan, H. Q. Zheng, and G. I. Ng

J. Vac. Sci. Technol. B 19, 2119 (2001); http://dx.doi.org/10.1116/1.1415516 (4 pages) | Cited 1 time

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A new metamorphic In0.52Al0.48As/In0.53Ga0.47As high electron mobility transistor (HEMT) structure was grown on a GaAs substrate with a InxGa1−xP graded buffer layer by solid-source molecular beam epitaxy. The In0.53Ga0.47As channel layer was grown on the InGaP buffer layer directly without an InAlAs buffer as in the conventional design. High-resolution x-ray diffraction reveals that the whole layer structure is nearly fully relaxed. Hall measurement showed that this new layer design exhibits higher electron mobility and carrier concentration as well as lower light sensitivity compared to the reference sample with the conventional design. The promising device performance demonstrates the potential of using this metamorphic HEMT device in high speed and high frequency applications. © 2001 American Vacuum Society.
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85.30.Tv Field effect devices
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

In situ measurement of aspect ratio dependent etch rates of polysilicon in an inductively coupled fluorine plasma

Th. Lill, M. Grimbergen, and D. Mui

J. Vac. Sci. Technol. B 19, 2123 (2001); http://dx.doi.org/10.1116/1.1415514 (6 pages) | Cited 10 times

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The etch rate of polysilicon in high aspect ratio structures has been studied in an inductively coupled fluorine based plasma (pure SF6). The change of the silicon etch rate with increasing aspect ratio [aspect ratio dependent etch rate or reactive ion etching (RIE) lag] has been measured in situ by interferometry. The experimental structures as well as the process conditions were chosen such that (i) the interaction of neutral fluorine atoms with the silicon surface determines the etch rate, (ii) the ion energy is minimized, (iii) the mass transport of neutrals is in a molecular flow (Knudsen) regime, and (iv) the interaction of the etch species with the sidewalls can be neglected. Under these conditions, the experimental findings indicate that the RIE lag effect is reduced for higher pressures and lower cathode temperatures, i.e., for higher fluorine atom coverages of the silicon surface. This is in agreement with the Knudsen transport model by Coburn and Winters [W. Coburn and H. F. Winters, Appl. Phys. Lett. 55, 2730 (1989)]. Probabilities for the reaction of fluorine atoms with the silicon surface between 0.03 and 0.11 can be derived when fitting the experimental data with this model. The findings reported in this work are of relevance for the formation of deep trench storage capacitors and polysilicon plugs. In particular, we show that we can control RIE lag and etch rate independently for the given process conditions. © 2001 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
81.05.Cy Elemental semiconductors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
07.60.Ly Interferometers

Ion-assisted etching of W film by an Ar+ beam in XeF2 with the addition of H2, N2, or O2

Hideo Ichinose

J. Vac. Sci. Technol. B 19, 2129 (2001); http://dx.doi.org/10.1116/1.1415518 (4 pages) | Cited 1 time

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W etching is carried out by an Ar+ beam in XeF2 with the addition of H2, N2 or O2. The energy of the beam is 400 eV and the current is 0.2 μA. The spontaneous etching rate in XeF2 with the addition of N2 or O2 decreases by about 0.6 times compared with that in XeF2 (2×10−6 Torr), for which the total pressure of the mixed gas is 2×10−5 Torr. The nitrogen or oxygen atoms attached on the W surface disturb the attachment between W and fluoride atoms. The ion-assisted etching rate increases by about 1.5 times in XeF2 by adding N2 or O2 compared with that in XeF2 (2×10−6 Torr), for which the total pressure of the mixed gas is 2×10−5 Torr. It is speculated that the addition of N2 or O2 gas to fluorinated gas acts upon the surface reaction to suppress the sidewall etching rate when the mask patterned W gate line is plasma etched by the same kind of gas mixture. The mixing layer is thought to be formed by W and nitrogen or by an oxygen atom by ion-assisted etching. The W–W bond in the mixing layer is thought to be weaker than that in W film both physically and chemically, which makes the etching increase. The thickness of the mixing layer is estimated to be about 10 Å. But the spontaneous ion-assisted etching rate did not change in the case of H2 addition. © 2001 American Vacuum Society.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.20.Pm Rate constants, reaction cross sections, and activation energies
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
61.82.Bg Metals and alloys
85.40.Hp Lithography, masks and pattern transfer

Etching technique for ruthenium with a high etch rate and high selectivity using ozone gas

M. Nakahara, S. Tsunekawa, K. Watanabe, T. Arai, T. Yunogami, and K. Kuroki

J. Vac. Sci. Technol. B 19, 2133 (2001); http://dx.doi.org/10.1116/1.1415517 (4 pages) | Cited 8 times

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We have studied the characteristics of ruthenium etching reactions and the etch selectivity of Ru to photoresist in ozone gas. The Ru was etched at a maximum etch rate of 950 nm/min at between 100 and 150  °C by the formation of a volatile product, RuO4. However, the etch rate decreased at temperatures above 150 °C, since the formation of RuO2 on the Ru surface hindered the etching reaction. A comparison between the etching reaction of Ru and that of photoresist revealed that Ru was etched predominantly by ozone, whereas the photoresist was etched predominantly by atomic oxygen. This difference in etching behavior enables us to control the etch selectivity between Ru and photoresist. Below 150 °C, the Ru/photoresist selectivity was higher than 40 due to a small amount of atomic oxygen. Conversely, above 300 °C, the selectivity of photoresist/Ru was higher than 40 due to RuO2 formation. Therefore, a high degree of selectivity was achieved by manipulating the temperature. © 2001 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Bx Metals, semimetals, and alloys
79.60.Dp Adsorbed layers and thin films
68.43.Vx Thermal desorption

Ultrathin zirconium oxide films as alternative gate dielectrics

J. P. Chang, Y-S. Lin, S. Berger, A. Kepten, R. Bloom, and S. Levy

J. Vac. Sci. Technol. B 19, 2137 (2001); http://dx.doi.org/10.1116/1.1415513 (7 pages) | Cited 35 times

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ZrO2 films were deposited on Si(100) wafers by the rapid thermal chemical vapor deposition process using a zirconium (IV) t-butoxide Zr(OC4H9)4 precursor and oxygen. Interfacial zirconium silicate formation was observed by high resolution transmission electron microscopy and medium energy ion scattering. The intermixing of the interface can be suppressed by forming a thin silicon nitride layer on the silicon substrate prior to ZrO2 deposition. The dielectric constant of ZrO2 achieved in this work is 15–18 with very small capacitance–voltage hysteresis, ideal for metal–oxide–semiconductor field effect transistor (MOSFET) application. The NMOSFET device has good turn-on characteristics, however, the transconductance is lower than expected due to the incomplete removal of zirconium silicate at the source and drain contacts and poses integration challenges to use ZrO2 as the gate dielectric material. © 2001 American Vacuum Society.
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85.30.Tv Field effect devices
77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Ion-implanted photoresist removal using water/carbon dioxide mixtures at elevated temperature and pressure

K. L. Chavez, G. L. Bakker, and D. W. Hess

J. Vac. Sci. Technol. B 19, 2144 (2001); http://dx.doi.org/10.1116/1.1415519 (5 pages) | Cited 3 times

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The ability of water and water/1% carbon dioxide mixtures to remove ion-implanted photoresist from silicon substrates was investigated. Photoresist with implant levels up to 2×1015/cm2 of boron and phosphorus were stripped effectively at a temperature of 165 °C and a pressure of 58.6 bar (850 psi) by both water and water/carbon dioxide. Removal of photoresist at low implant levels (2×1012/cm2) proceeded rapidly, while samples at higher dose levels (>2×1015/cm2) had a thin carbonized layer at the photoresist surface that inhibited the removal rate. Removal of this carbonized layer required approximately 2 min for water/carbon dioxide and approximately 8 min for water, while complete removal of the remaining photoresist film took less than 30 min for both fluids. Patterned, arsenic-implanted (1×1016/cm2) photoresist layers were removed by water/carbon dioxide at 200 °C, 850 psi, 3 ml/min flow rate, and 30 min exposure. Under all conditions investigated, water/carbon dioxide proved more effective than pure water at removing ion-implanted photoresist. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
85.40.Ry Impurity doping, diffusion and ion implantation technology

Interplay of current crowding and current self-quenching effects in planar cold cathodes

Y. Modukuru and M. Cahay

J. Vac. Sci. Technol. B 19, 2149 (2001); http://dx.doi.org/10.1116/1.1415515 (6 pages) | Cited 2 times

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In planar cold cathodes making use of semimetallic thin films to achieve low or negative electron affinity, the effects of dc current crowding can be affected by the trapping of electrons being reflected towards the cathode as a result of space-charge effects in the vacuum gap between cathode and anode. A self-consistent solution of the interplay between current crowding and space-charge effects can lead to a nonmonotonic lateral distribution of the anode current density depending on the width of the emission window. This behavior is in sharp contrast with the monotonic decrease of the anode current density from the edges towards the center of the emission window when space-charge effects in the vacuum region are neglected. © 2001 American Vacuum Society.
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85.45.Bz Vacuum microelectronic device characterization, design, and modeling
77.22.Jp Dielectric breakdown and space-charge effects
79.70.+q Field emission, ionization, evaporation, and desorption
85.45.Db Field emitters and arrays, cold electron emitters

Processing and characterization of ultralow-dielectric constant organosilicate

Shu Yang, Janice C.-H. Pai, Chien-Shing Pai, Gary Dabbagh, Omkaram Nalamasu, Elsa Reichmanis, Joko Seputro, and Yaw S. Obeng

J. Vac. Sci. Technol. B 19, 2155 (2001); http://dx.doi.org/10.1116/1.1417542 (7 pages) | Cited 9 times

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A class of nanoporous organosilicate has been developed that can reach an ultralow-dielectric constant (k⩽2). In this approach a series of triblock polymers, poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-b-PPO-b-PEO), are used as sacrificial materials in silicon based spin-on matrices, poly(methylsilsesquioxane) (MSQ) to generate pores when heated above 400 °C. To improve the electrical and mechanical properties, different parameters, such as temperatures, heating rates, polymer molecular weights, copolymer compositions, and the molecular weight of MSQ prepolymers, were studied. Heating temperatures and ramping rates have no large effect on dielectric constants and dielectric breakdown strength. However, at a higher temperature, 500 °C, the mechanical properties are found stronger than those from 400 °C. A higher molecular weight of MSQ prepolymer will also lead to higher mechanical properties of the final porous MSQ, while no temperature effect is observed. Block copolymers with different molecular weights and compositions give similar dielectric constants depending on the polymer loading in MSQ and no substantial change in the dielectric strength of the films with different compositions. © 2001 American Vacuum Society.
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81.05.Rm Porous materials; granular materials
77.84.Jd Polymers; organic compounds
77.22.Ch Permittivity (dielectric function)
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
77.55.-g Dielectric thin films
77.22.Jp Dielectric breakdown and space-charge effects

Patterning nonflat substrates with a low pressure, room temperature, imprint lithography process

Matthew Colburn, Annette Grot, Byung Jin Choi, Marie Amistoso, Todd Bailey, S. V. Sreenivasan, John G. Ekerdt, and C. Grant Willson

J. Vac. Sci. Technol. B 19, 2162 (2001); http://dx.doi.org/10.1116/1.1417543 (11 pages) | Cited 23 times

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Step and flash imprint lithography (SFIL) is a technique that has the potential to replace photolithography for patterning resist with sub-100 nm features. SFIL is a low cost, high throughput alternative to conventional photolithography for high-resolution patterning. It is a molding process in which the topography of a template defines the patterns created on a substrate. The ultimate resolution of replication by imprint lithography is unknown but, to date, it has only been limited by the size of the structures that can be created on the template. It is entirely possible to faithfully replicate structures with minimum features of a few hundred angströms. SFIL utilizes a low-viscosity, photosensitive silylated solution that exhibits high etch contrast with respect to organic films in O2 reactive ion etching. In this article we describe the SFIL process, the development of a multilayer etch scheme that produces 6:1 aspect ratio features with 60 nm linewidths, a method for patterning high-aspect-ratio features over topography, and a metal lift-off process. A micropolarizer array consisting of orthogonal 100 nm titanium lines and spaces fabricated using this metal lift-off technique is reported. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
81.10.Fq Growth from melts; zone melting and refining
81.65.Cf Surface cleaning, etching, patterning

Deep reactive ion etching of silicon carbide

S. Tanaka, K. Rajanna, T. Abe, and M. Esashi

J. Vac. Sci. Technol. B 19, 2173 (2001); http://dx.doi.org/10.1116/1.1418401 (4 pages) | Cited 14 times

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In this article, we describe more than 100-μm-deep reactive ion etching (RIE) of silicon carbide (SiC) in oxygen-added sulfur hexafluoride (SF6) plasma. We used a homemade magnetically enhanced, inductively coupled plasma reactive ion etcher (ME-ICP-RIE) and electroplated nickel masks. First, 5 h etching experiments using etching gases with 0%, 5%, 10% and 20% oxygen were performed by supplying rf power of 150 and 130 W to an ICP antenna and a sample stage, respectively. They demonstrated a maximum etch rate of 0.45 μm/min and residue-free etching in the case of 5% oxygen addition. Observation of the cross sections of etched samples using a scanning electron microscope confirmed a microloading effect, which is reduction of the etched depth with a decrease in the mask opening width. Next, a 7 h etching experiment using an etching gas with 5% oxygen was performed by increasing the rf power to the sample stage to 150 W. This yielded an etched depth of 216 μm. © 2001 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
81.05.Hd Other semiconductors

Optical and structural studies in InGaN quantum well structure laser diodes

Shigefusa F. Chichibu, Takashi Azuhata, Mutsumi Sugiyama, Toshio Kitamura, Yuuki Ishida, Hajime Okumura, Hisayuki Nakanishi, Takayuki Sota, and Takashi Mukai

J. Vac. Sci. Technol. B 19, 2177 (2001); http://dx.doi.org/10.1116/1.1418404 (7 pages) | Cited 23 times

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An InGaN multiple-quantum-well laser diode wafer that lased at around 400 nm was shown to have the InN mole fraction, x, of only 6% in the wells. Nanometer-probe compositional analysis showed that the fluctuation of x was as small as 1% or less, which is the resolution limit. However, the wells exhibited a Stokes-like shift (SS) of 49 meV at 300 K, which was approximately 65% of the luminescence linewidth, and effective localization depth, E0, was estimated to be 35 meV at 300 K. Since the effective electric field due to polarization in the wells was estimated to be as small as 300 kV/cm, SS was considered to originate from effective band-gap inhomogeneity. Because the well thickness fluctuation was insufficient to reproduce SS or E0 and bulk cubic In0.02Ga0.98N that does not suffer any polarization field or thickness fluctuation effect exhibited a SS of 140 meV at 77 K, the exciton localization is considered to be an intrinsic phenomenon in InGaN, which is due to the large band-gap bowing and In clustering in InGaN material. The spontaneous emission from the InGaN wells was thus assigned as being due to the recombination of excitons localized at the exponential tail-type potential minima in the density of states. The upper bound of the lateral localization size has been estimated to be 50 nm. Such shallow and low density localized states are leveled by injecting high density carriers under the lasing conditions. © 2001 American Vacuum Society.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Organic polymeric coatings deposited by plasma enhanced chemical vapor deposition

Ram W. Sabnis, Mario Cazeca, William L. DiMenna, Mary J. Spencer, Douglas J. Guerrero, and Min-Shyan Sheu

J. Vac. Sci. Technol. B 19, 2184 (2001); http://dx.doi.org/10.1116/1.1418402 (6 pages) | Cited 3 times

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A process of depositing thin organic polymeric coatings on electronic substrates by plasma enhanced chemical vapor deposition (PECVD) has been developed. We have designed halogenated compounds with PECVD reactive functionality attached to optically active moieties. Compounds have been screened selectively to lower the dielectric constant and enhance plasma polymerization efficiency. The chemical, optical, and mechanical properties of the deposited films such as film uniformity, film defectivity, film solubility, resist compatibility, conformality, adhesion to semiconductor substrates, refractive index, optical density, and photolithographic behavior have been studied. Plasma polymerized materials exhibit high sensitivity, excellent resolution, and good process latitude. PECVD provides a completely dry deposition process for wafer coating. The coatings possess high optical density at 193 nm. © 2001 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
82.35.Gh Polymers on surfaces; adhesion

Electromigration performance of AlCu/Ti and AlCu/Ti/TiN/Ti metallization

Kazuyoshi Kamoshida

J. Vac. Sci. Technol. B 19, 2190 (2001); http://dx.doi.org/10.1116/1.1418400 (5 pages)

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The electromigration (EM) lifetimes of top-TiN/Ti/Al-0.5%Cu/Ti-bottom and top-TiN/Ti/Al-0.5%Cu/Ti/TiN/Ti-bottom stacked structures were investigated using five-level Al-alloy interconnections with tungsten-filled vias. TiN/Ti/AlCu /Ti stacked structures had an EM lifetime ten times longer than TiN/Ti/AlCu/Ti/TiN/Ti ones. This longer EM lifetime is probably due to the small grain-boundary diffusivities for the bamboo microstructure. In the TiN/Ti/AlCu/Ti structure, a localized Al3Ti intermetallic compound layer was formed by the reaction between Al and Ti at the AlCu/Ti interface. On the other hand, in the TiN/Ti/AlCu/Ti/TiN/Ti structures, an almost uniform Al3Ti intermetallic compound layer was formed at the AlCu/Ti interface. In the initial nucleation process in Al, the Al grain growth increased on Ti/SiO2 compared with Ti/TiN/Ti/SiO2 according to atomic force microscopy observation. Using the optimum Ti thickness (10 nm) made it possible to form long-EM-lifetime multilevel interconnections without using many metal stacked structures. © 2001 American Vacuum Society.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation

Focus latitude enhancement of symmetrical phase mask design for deep submicron contact hole patterning

Shuo-Yen Chou, Jen-Chung Lou, Li-Jui Chen, Lin-Hung Shiu, Ru-Gun Liu, Chien-Ming Wang, and Tsai-Sheng Gau

J. Vac. Sci. Technol. B 19, 2195 (2001); http://dx.doi.org/10.1116/1.1418398 (11 pages) | Cited 2 times

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The mechanism of focus latitude enhancement for contact/via hole printing is explained by approximating the axis intensity distribution of an image as a series of cosine functions to characterize the interference between each pair of diffraction beams. It is found that a phase-shifting mask (PSM) with symmetrical assist features improves the depth of focus (DOF) by introducing destructive interference to counterbalance the intensity fluctuation from constructive interference as defocus. A simple formula was derived to represent the capability of focus latitude enlargement. It shows that the extent of enhancement depends on the exposure wavelength and numerical aperture of a projection lens only. Increasing the degree of partial coherence degrades the focal range enlargement because a larger illumination angle elongates the destructive interference pattern in the optical-axis direction to weaken its ability for intensity compensation. On the other hand, the lack of constructive interference in dense hole imaging fails the mask pattern transfer, which limits the application of the phase-shifting method to pattern pitch greater than mathλ/NA. A tiny amount of spherical aberration results in prominent asymmetrical defocus behavior because the wave deformation in the projection lens shifts the distribution of constructive and destructive interference patterns to opposite defocus directions. The printing characteristics of 0.17 μm contact using an 18% transmission, rim-type attenuated phase-shifting mask are investigated to corroborate our analysis of defocus behavior. The dependence of depth of focus on pattern duty is stressed to elucidate the difference in mechanisms of focus latitude improvements for a sparse hole and periodic dense hole. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
42.25.Hz Interference
42.79.Bh Lenses, prisms and mirrors
42.15.Eq Optical system design
42.15.Fr Aberrations

Optical, electrical, and structural characteristics of yttrium oxide films deposited on plasma etched silicon substrates

J. J. Araiza, M. A. Aguilar-Frutis, and C. Falcony

J. Vac. Sci. Technol. B 19, 2206 (2001); http://dx.doi.org/10.1116/1.1418399 (6 pages) | Cited 6 times

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Yttrium oxide thin films were deposited on Si(100) substrates using the rf-sputtering technique at low power density and low temperatures (up to 300 °C). Previous to deposition, the substrates were plasma etched during different lengths of time. The characteristics of these films and the effect of surface etching on the substrate were studied by ellipsometry, x-ray diffraction at grazing angle, atomic force microscopy, and x-ray energy dispersive spectroscopy (EDS). The deposited films were polycrystalline, presenting cubic and/or monoclinic phases. The deposition rate, refractive index, surface roughness, and degree of crystallinity were strongly dependent on etching time of the substrate, especially for low deposition temperatures. The electrical characterization of the films incorporated in a metal–oxide–semiconductor structure showed a good dielectric constant value (up to 11), surface states densities as low as 6.7×1011 cm−2 eV−1 at midgap and breakdown strength in the range of 1.16–4.84 MV/cm. EDS measurements on these films showed a higher oxygen content than expected for Y2O3 stoichiometry. © 2001 American Vacuum Society.
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81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
77.55.-g Dielectric thin films
78.66.Nk Insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.22.Ch Permittivity (dielectric function)
73.20.At Surface states, band structure, electron density of states
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
77.22.Jp Dielectric breakdown and space-charge effects

Photoemission study of energy-band alignments and gap-state density distributions for high-k gate dielectrics

Seiichi Miyazaki

J. Vac. Sci. Technol. B 19, 2212 (2001); http://dx.doi.org/10.1116/1.1418405 (5 pages) | Cited 101 times

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The determination of the energy band gaps of thin-gate insulators has been demonstrated from the onsets of the energy-loss spectra of O 1s (or N 1s) photoelectrons. The valence-band lineups of thin high-dielectric-constant (high-k) dielectrics such as Ta2O5, Al2O3, and ZrO2 formed on metals and Si(100) have also been determined by measuring the energy difference between the valence-band density-of-states curves. The energy band diagrams for metal/high-k dielectrics/Si(100) systems have been derived explicitly from considering the measured band gaps, valence-band lineups, electron affinities, and metal work functions in the systems. It is also demonstrated that total photoelectron yield spectroscopy can be used to quantify the energy distributions of both the defect states in high-k gate dielectrics and at the dielectric/Si(100) interfaces over the entire Si band gap without gate formation. © 2001 American Vacuum Society.
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79.60.Jv Interfaces; heterostructures; nanostructures
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
71.20.Ps Other inorganic compounds
73.20.Hb Impurity and defect levels; energy states of adsorbed species
79.60.Dp Adsorbed layers and thin films
73.20.At Surface states, band structure, electron density of states
77.55.-g Dielectric thin films
73.30.+y Surface double layers, Schottky barriers, and work functions

Photoluminescence characterization of Si-based nanostructured films produced by pulsed laser ablation

A. V. Kabashin, M. Meunier, and R. Leonelli

J. Vac. Sci. Technol. B 19, 2217 (2001); http://dx.doi.org/10.1116/1.1420494 (6 pages) | Cited 13 times

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Photoluminescence (PL) properties of nanostructured Si-based films produced by pulsed laser ablation in a residual gas are studied. Two types of PL signals have been identified. Signals of the first type are sensitive to the ablation conditions with the PL peak position depending on the gas pressure during the deposition. Signals of the second type with PL peaks around 1.6–1.7 and 2.2– 2.3 eV are almost independent of the ablation conditions and are mainly determined by the presence of oxygen-related complexes in the film composition. These complexes can be formed through a prolonged natural oxidation or thermal annealing of the films, or through the direct laser ablation in the presence of oxygen. Possible mechanisms of PL signals are discussed. © 2001 American Vacuum Society.
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78.66.Db Elemental semiconductors and insulators
78.55.Ap Elemental semiconductors
81.15.Fg Pulsed laser ablation deposition
81.07.Bc Nanocrystalline materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Etch mechanisms of low dielectric constant polymers in high density plasmas: Impact of charging effects on profile distortion during the etching process

D. Fuard, O. Joubert, L. Vallier, M. Assous, P. Berruyer, and R. Blanc

J. Vac. Sci. Technol. B 19, 2223 (2001); http://dx.doi.org/10.1116/1.1420492 (8 pages) | Cited 13 times

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We have studied the etching of very high aspect ratio contact holes in hydrocarbon materials SiLK™, potential dielectric candidates for the next generation of interconnections. During the etch process, slight deformation of the etch profiles such as bowing are observed. Experiments described in this article suggest that bowing originates from the deflection of ions on the sidewalls of the polymer, generating some etching. The mechanisms leading to the ion deflection on the sidewalls are presented and discussed. This study also shows how the process can be tuned to minimize the bow formation. © 2001 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
85.40.Ls Metallization, contacts, interconnects; device isolation
77.84.Jd Polymers; organic compounds
52.77.Bn Etching and cleaning
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

Etching characteristics and plasma-induced damage of high-k Ba0.5Sr0.5TiO3 thin-film capacitors

D. S. Wuu, C. C. Lin, R. H. Horng, F. C. Liao, and Y. H. Liu

J. Vac. Sci. Technol. B 19, 2231 (2001); http://dx.doi.org/10.1116/1.1420205 (6 pages) | Cited 7 times

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The inductively coupled plasma (ICP) etching behavior of Ba0.5Sr0.5TiO3 (BST) thin films has been characterized with Cl2/Ar gas mixtures by varying the process parameters such as chamber pressure, ICP power, and substrate bias rf power. The etching characteristics of BST were investigated in terms of etch rate, etch profile, surface residue, and electrical properties. The results obtained can be further interpreted by the plasma properties (ion flux and dc bias) in situ measured by a Langmuir probe. Quantitative analysis of the plasma-induced damage in the Pt/BST/Pt capacitor was attempted to discuss the mechanism of leakage current density and dielectric constant with various substrate bias rf power and ICP power levels. Finally, optimization of the etch parameters for fabricating BST capacitors was performed to minimize the plasma-induced damage. The optimum condition appears to be under a 30% Cl2/(Cl2+Ar) gas mixture, ICP power of 800 W, substrate bias rf power of 100 W, and chamber pressure of 0.67 Pa. Furthermore, it is found that the damage samples can be effectively recovered after annealing at 600 °C in oxygen ambient. The result can be confirmed by the x-ray diffraction data, which indicates that an improvement of BST crystalline quality after annealing occurs. This makes the leakage current density of the Pt/BST/Pt capacitor decrease to 3×10−7 A/cm2 under an applied voltage of 1.5 V, while its dielectric constant can recover from 150 to 180. © 2001 American Vacuum Society.
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84.32.Tt Capacitors
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning

Structural and optical properties of ternary Cs–Pb–Cl nanoaggregates in thin films

F. Somma, P. Aloe, S. Lo Mastro, S. Santucci, C. Giampaolo, M. Nikl, K. Nitsch, P. Fabeni, and G. P. Pazzi

J. Vac. Sci. Technol. B 19, 2237 (2001); http://dx.doi.org/10.1116/1.1421542 (3 pages) | Cited 4 times

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Ternary nanophases of CsPbCl3 and Cs4PbCl6 were evidenced in co-evaporated CsCl–PbCl2 thin films using x-ray diffraction spectroscopy. A morphological study by atomic force microscopy revealed the granular nature of the films consisting of the grains of about 150 nm size. The optical properties of CsPbCl3 and Cs4PbCl6 nanostructures were determined. CsPbCl3 is a wide gap semiconductor with direct band transitions and a pronounced Wannier free exciton emission round 418 nm at 5 K with a very small Stokes shift. Cs4PbCl6 is characterized by the auto-localized exciton emission around 365 nm. In both cases, the optical features are closely similar to the bulk ternary crystals which were reported earlier. © 2001 American Vacuum Society.
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61.46.-w Structure of nanoscale materials
68.55.-a Thin film structure and morphology
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.07.Bc Nanocrystalline materials
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.37.Ps Atomic force microscopy (AFM)
78.40.Fy Semiconductors
78.55.Hx Other solid inorganic materials
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Scaling considerations for high performance 25 nm metal–oxide–semiconductor field effect transistors

Samar Saha

J. Vac. Sci. Technol. B 19, 2240 (2001); http://dx.doi.org/10.1116/1.1420207 (7 pages) | Cited 4 times

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This article presents a systematic simulation-based study on scaling gate oxide thickness and the source–drain extension junction depth to achieve high performance 25 nm metal–oxide–semiconductor field effect transistor devices for low power operation. In order to obtain the target 25 nm devices, complementary metal–oxide–semiconductor (CMOS) technologies were designed by scaling source–drain extension junction depths to 14, 20, and 26 nm and the corresponding gate lengths to 40, 50, and 60 nm, respectively. Each technology was separately optimized for each value of the equivalent gate oxide thickness 1, 1.5, and 2 nm to achieve the target value of off-state leakage current of about 10 nA/μm for 25 nm devices. The simulation results show that for a low voltage operation of 25 nm devices with a fixed off-state leakage current, the magnitude of threshold voltage, subthreshold slope, and the drain-induced barrier lowering is too high while the magnitude of drive current is too low for gate oxide thickness ⩾1.5 nm. However, the variation in the magnitude of threshold voltage, subthreshold slope, drain-induced barrier lowering, and the drive current for the similar devices is insignificant within the range of source–drain extension junction depth between 14 and 26 nm. It is also found that the increase in the gate delay is ⩾12% for 25 nm devices with the source–drain extension junction depth ⩾20 nm compared to the similar devices with a source–drain extension junction depth of about 14 nm. This article demonstrates that the continuous scaling of gate oxide thickness below 1.5 nm and the source–drain extension junction depth below 20 nm is essential for achieving high performance CMOS technologies with 25 nm nominal devices for low power application. © 2001 American Vacuum Society.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
81.16.-c Methods of micro- and nanofabrication and processing

Characteristic features of new electron-multiplying channels in a field emission display

Whikun Yi, Taewon Jeong, Sunghwan Jin, SeGi Yu, Jeonghee Lee, Jungna Heo, Jibeom Yoo, and J. M. Kim

J. Vac. Sci. Technol. B 19, 2247 (2001); http://dx.doi.org/10.1116/1.1420206 (5 pages)

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We have developed a microchannel plate (MCP) to increase the efficiency of a field emission display (FED) by introducing new materials and process technologies. A substrate was constructed with alumina, and channel walls of pore arrays of the MCP were deposited with thin films using electroless plating and sol-gel process. The resulting MCP has been evaluated with a high input current source from a continuous electron beam and from Spindt-type field emitters. Some features of the MCP were also characterized in terms of brightness, anode current, input and output pulse, and focused luminescent spot, in a FED. With the MCP between the cathode and the anode of a FED, the brightness and anode current increased four- to fivefold due to electron multiplication through an array of pores in the device. In addition, the fabricated microchannel plate was found to prevent spreading of electrons emitted from the cathode tips, thus improving both display resolution and picture quality. © 2001 American Vacuum Society.
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85.45.Fd Field emission displays (FEDs)
79.70.+q Field emission, ionization, evaporation, and desorption
41.85.Ew Particle beam profile, beam intensity

X-ray photoemission spectroscopy study of silicidation of Ti on BF2+-implanted polysilicon

H. N. Chua, K. L. Pey, W. H. Lai, J. W. Chai, J. S. Pan, D. H. C. Chua, and S. Y. Siah

J. Vac. Sci. Technol. B 19, 2252 (2001); http://dx.doi.org/10.1116/1.1421565 (6 pages) | Cited 1 time

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Evaluation of fluorine-related species during Ti silicidation on BF2+-implanted polycrystalline silicon (polySi) under different temperatures has been studied using x-ray photoemission spectroscopy (XPS). The silicidation was carried out under sequential anneals from 500 to 700 °C with an interval of 50 °C in an ultrahigh vacuum (UHV) within the XPS chamber. The binding energy and peak intensity for Si 2p, Ti 2p, F 1s, O 1s, B 1s, and C 1s XPS peaks have been measured in the same XPS chamber immediately after the silicidation anneal without breaking the vacuum. The results show that fluorine from the BF2+ implantation is dissociated to form a mixture of SiFx (1⩽x⩽4) and TiFx (x=3,4) -like gaseous species at/near the TiSi2/polySi interface upon silicidation anneal. This can be characterized by the approximately 1.2 eV per Si–F bond chemical shift of the Si 2p core level, and the peak position for Ti 2p core levels with the resolved peaks at 465.1 eV corresponding to the Ti–F bond. The F 1s peaks further confirm the presence of SiFx and TiFx species. As the silicidation proceeds to higher temperatures, the intensity of these reaction species decreases due to their out-diffusion from the thin TiSi2 layer. These findings correlate well with the previously reported results on the void formation in sub-quarter-micron BF2+-implanted Ti-salicided polySi lines [H. N. Chua et al., J. Appl. Phys. 87, 8401 (2000)]. © 2001 American Vacuum Society.
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61.72.uf Ge and Si
79.60.Jv Interfaces; heterostructures; nanostructures
61.72.Cc Kinetics of defect formation and annealing
68.35.Fx Diffusion; interface formation
85.40.Ry Impurity doping, diffusion and ion implantation technology
85.40.Ls Metallization, contacts, interconnects; device isolation
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Scanning probe microscopy of domains and domain walls in sol–gel PbTiO3 thin films

Xiaofeng Chen, Weiguang Zhu, Weiguo Liu, and Zhihong Wang

J. Vac. Sci. Technol. B 19, 2258 (2001); http://dx.doi.org/10.1116/1.1421569 (4 pages) | Cited 4 times

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We report results on ferroelectric domain and domain-wall observation in sol–gel PbTiO3 thin films using scanning probe microscopy. By taking the phase and amplitude image of the local domain piezovibration separately, more information is given to interpret the domain contrast owing to the a domain and different crystallographic orientations. Particularly, the a–c and c–c domain walls appear as a transition region and a dark region in the amplitude image, respectively, and the corresponding thickness is estimated to be 70 and 8 nm. A torsion vibration model is proposed to describe the tip vibration at the c–c domain wall, which results in the dark contrast correspondingly. © 2001 American Vacuum Society.
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77.80.Dj Domain structure; hysteresis
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.37.-d Microscopy of surfaces, interfaces, and thin films

Automated Xe adsorption technique to measure small Brunauer–Emmett–Teller surface area of several square centimeters

Hiroshi Yanazawa, Ryoichi Furukawa, Satoshi Yamamoto, Isao Suzuki, and Kazuhisa Miura

J. Vac. Sci. Technol. B 19, 2262 (2001); http://dx.doi.org/10.1116/1.1421564 (6 pages) | Cited 1 time

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An automated Xe adsorption apparatus has been developed that enables the measurement of a Brunauer–Emmett–Teller (BET) surface area of several cm2 with a repeatability of 4% (standard deviation). The apparatus is equipped with a differential type capacitance manometer, each hand of which is connected to a sample and reference adsorption cell having a symmetrical design, that is the temperature-compensated volumetric system which was reported by one of the authors [I. Suzuki, Rev. Sci. Instrum. 53, 1061 (1982); ibid., 66, 5070 (1995); ibid., 68, 4531 (1998)]. All procedures for measuring gas adsorption are computer controlled, and the coolant meniscus height is also computer controlled to keep the adsorption cell volume constant. A specially polished Si crystal rod was adopted as the standard sample. The BET surface area of the standard sample was measured by both the original temperature-compensated system and the newly developed automated system. Obtained results are fully consistent. We propose the adsorption cross section of Xe to be 0.25 nm2 based on our measurements. In addition, we demonstrate a series of experimental results which show a quantitative correlation between the capacitance and surface microroughness of a capacitor with rugged surface electrode. © 2001 American Vacuum Society.
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82.80.-d Chemical analysis and related physical methods of analysis
68.43.Mn Adsorption kinetics
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.07.Mp Transducers
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities

Carrier mobilities and process stability of strained Si n- and p-MOSFETs on SiGe virtual substrates

M. T. Currie, C. W. Leitz, T. A. Langdo, G. Taraschi, E. A. Fitzgerald, and D. A. Antoniadis

J. Vac. Sci. Technol. B 19, 2268 (2001); http://dx.doi.org/10.1116/1.1421554 (12 pages) | Cited 105 times

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Surface channel strained Si metal–oxide–semiconductor field-effect transistors (MOSFETs) are a leading contender for future high performance complementary metal–oxide–semiconductor (CMOS) applications. The carrier mobility enhancement of these devices is studied as a function of channel strain, and the saturation behavior for n- and p-channel devices is compared. Carrier mobility enhancements of up to 1.8 and 1.6 are achieved for n- and p-channel devices, respectively. The process stability of strained Si MOSFETs is also studied, and carrier mobility enhancement is shown to be robust after well implantation and virtual substrate planarization steps. The effects of high-temperature implant activation anneals are also studied. While no misfit dislocation introduction or strain relaxation is observed in these devices, increased interface state densities or alloy scattering due to Ge interdiffusion are shown to decrease mobility enhancements. Channel thickness effects are also examined for strained Si n-MOSFETs. Loss of carrier confinement severely limits the mobility of devices with the thinnest channels. Overall, surface channel strained Si MOSFETs are found to exhibit large carrier mobility enhancements over coprocessed bulk Si devices. This, combined with the high process stability exhibited by these devices, makes them superb candidates for future CMOS applications. © 2001 American Vacuum Society.
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85.30.Tv Field effect devices
85.40.Ry Impurity doping, diffusion and ion implantation technology
81.65.Ps Polishing, grinding, surface finishing
73.50.Dn Low-field transport and mobility; piezoresistance
61.72.Cc Kinetics of defect formation and annealing
68.60.Bs Mechanical and acoustical properties

Growth and characterization of Fe(100)/InAs(100) hybrid structures

Hiroshi Ohno, Kanji Yoh, Toshihiro Doi, Agus Subagyo, Kazuhisa Sueoka, and Koichi Mukasa

J. Vac. Sci. Technol. B 19, 2280 (2001); http://dx.doi.org/10.1116/1.1421563 (4 pages) | Cited 6 times

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We report on the growth of planar/patterned Fe thin films on InAs(100) substrates and their subsequent characterization using reflection high-energy electron diffraction, low-energy electron diffraction, superconducting quantum interference device, and four-terminal contact resistance measurements. Epitaxial growth of body-centered-cubic Fe crystal on InAs(100) was verified for growth temperatures of 23 °C and 175 °C. A patterned Fe wire array showed clear uniaxial shape anisotropy with the easy axis along the wire direction. Its coercive force was found to depend on the growth temperature and the width of the Fe wires. Four-terminal contact resistance measurement of Fe/n-InAs revealed that Fe forms decent ohmic contact to the InAs substrate with a resistivity of the order of 10−6 Ω cm2. Samples grown at room temperature showed equally decent or even better magnetic and electrical characteristics than those obtained by higher temperature growth. These results indicate that the Fe/InAs hybrid structures have definite potential for spin-related semiconductor devices with practical process sequences. © 2001 American Vacuum Society.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
73.40.Ns Metal-nonmetal contacts
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
73.40.Cg Contact resistance, contact potential
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy

Structure analysis of Ba2In2O5 and related compounds by electron microscopy

M. Mitome, M. Okamoto, Y. Bando, and H. Yamamura

J. Vac. Sci. Technol. B 19, 2284 (2001); http://dx.doi.org/10.1116/1.1421566 (5 pages) | Cited 5 times

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Crystal structures of Ba2In2O5: (Ba1−xLax)2In2O5+x (x=0.1, 0.2, 0.3, and 0.5), and Ba2(In1−xGax)2O5 (x=0.1, 0.2 and 0.5) are analyzed by transmission electron microscopy and electron diffraction. Ba2In2O5 has an orthorhombic brownmillerite structure and belongs to space group Ibm2. (Ba1−xLax)2In2O5+x has a tetragonal brownmillerite structure while Ba2(In1−xGax)2O5 has an orthorhombic brownmillerite structure. These compounds consist of small domains that are at 90° orientation to each other. The domain size gets small with increasing La or Ga content. The oxygen vacancies are distributed randomly in the compounds with high La or Ga content, and consequently, the structure approximates as a cubic perovskite structure.© 2001 American Vacuum Society.
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61.66.Fn Inorganic compounds
61.72.J- Point defects and defect clusters

Characteristics of sputtered Ti1−xAlxN films for storage node electrode barriers

Dae-Gyu Park, Tae-Ho Cha, Sang-Hyeob Lee, In-Seok Yeo, Jin Won Park, and Sam-Dong Kim

J. Vac. Sci. Technol. B 19, 2289 (2001); http://dx.doi.org/10.1116/1.1421567 (6 pages) | Cited 8 times

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We report on the characteristics of sputter-deposited Ti1−xAlxN (TiAlN) thin films for storage node electrode barriers of Pt/(BaSr)TiO3(BST)/Pt metal–insulator–metal (MIM) capacitors with a comparative study of TiN films. The substrate temperature (Ts) was found to be one of the key factors affecting the properties of TiAlN thin films, i.e., the resistivity of TiAlN is ∼350 μΩ cm for high Ts deposition (∼450 °C) and ∼1100 μΩ cm for low Ts (∼100 °C). The lower resistivity of TiAlN films deposited at high Ts (450 °C) is attributed to the (200) texture with larger grain size and smaller oxygen concentration compared to those prepared at low Ts. The electrical characteristics of Pt/BST/Pt MIM capacitors on TiAlN were superior to those on the TiN barrier in terms of smaller equivalent oxide thickness (tox), lower tangent δ, and lower leakage current. Better oxidation resistance of TiAlN over TiN appears to be responsible for the better electrical results, especially with the (111) or (200) texture. We also discuss a BST bulge and local thinning due to the Pt deformation on TiAlN over an anneal of 600 °C in O2, resulting in leakage current degradation of the BST MIM capacitor. © 2001 American Vacuum Society.
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84.32.Tt Capacitors
66.30.Ny Chemical interdiffusion; diffusion barriers
81.15.Cd Deposition by sputtering
85.30.Tv Field effect devices

Three-dimensional carrier concentration profiles and ionization energy plots for low-temperature GaAs

N. C. Halder, V. Krishnan, and Bradley Baker

J. Vac. Sci. Technol. B 19, 2295 (2001); http://dx.doi.org/10.1116/1.1421568 (4 pages) | Cited 1 time

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We have investigated the carrier concentration profiles in molecular-beam epitaxy-grown, Si-implanted, low-temperature (LT) GaAs. The samples were grown at 300 °C and the Schottky diodes were fabricated using Au contacts. The capacitance voltage measurements were made in the temperature range 100–350 K at an interval of 2 K. From the field-effect transient spectroscopy experiments, data were collected for the peak positions and peak energy of the trap levels. The effective carrier concentration increased with temperature showing a saturation around 350 °C. The ionization energy of the carriers indicated a linear relationship. The overall results indicate that the carrier concentration in three-dimensional mapping is a reliable indicator of the sample quality and of the Schottky diode characteristics. Additionally, one should be specific about the temperature and the reverse bias voltage before selecting the value of the carrier concentration when determining the deep trap concentration in semiconductors, specifically, in LT GaAs. © 2001 American Vacuum Society.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.55.Eq III-V semiconductors
72.80.Ey III-V and II-VI semiconductors
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Nanostructure patterns written in polycarbonate by a bent optical fiber probe

Sy-Hann Chen and Yung-Fu Chen

J. Vac. Sci. Technol. B 19, 2299 (2001); http://dx.doi.org/10.1116/1.1421555 (2 pages) | Cited 1 time

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An atomic force microscope operated in tapping mode using a homemade bent optical fiber probe was used to pattern nanometer-scale features. Trenches of different dimensions were written on polycarbonate that was pre-exposed to an excimer laser. Lines with widths varying from 260 to 600 nm and depths ranging from 30 to 120 nm have been made. The present technique as a complementary tool to other lithographic processes has been demonstrated to be potentially suitable for low-cost and high-precision applications. © 2001 American Vacuum Society.
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81.16.Rf Micro- and nanoscale pattern formation
81.16.Nd Micro- and nanolithography
07.79.Lh Atomic force microscopes
42.81.Wg Other fiber-optical devices
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Electron-beam CARL resist development for 70 nm direct write

O. Kirch, K. Elian, and G. Falk

J. Vac. Sci. Technol. B 19, 2301 (2001); http://dx.doi.org/10.1116/1.1418403 (3 pages)

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Because of the need of 70 nm structures in the near future, electron-beam (e-beam) lithography as a means for high resolution lithography is discussed mostly for mask or ASIC fabrication but also for the application in standard lithography. Besides the improvement of new e-beam writing concepts including software and hardware enhancement, the development of new resists and processes is a main objective for a high throughput production. To understand the principal reactions that occur during the patterning process we decided to carry out basic examinations based on chemical amplification of resist lines (CARL) [W.-D. Domke et al., Microlithogr. World 42, 2 (1999)] resist materials. The first step was to look at the interaction between the polymer and e-beam. Polymers consisting of chemically identical monomers were synthesized in different molecular ratios and processed as resists without other additives. Detailed investigations of the resists included e-beam patterning with a JEOL JSM-840A/nanobeam pattern generator. The next step was to examine the CAR reaction, i.e., the interaction of the polymer/photoacid generator matrix with the e-beam electrons. Perfluorinated alkysulfonates as PAGs were focused. These compounds generate very strong acids through irradiation. They can be compared, e.g., by their different acid strength, different vapor pressure of the resulting acid, and by their different molecular size. These parameters strongly affect the acid diffusion and consequently the resist resolution as far as the line edge roughness. Within this current article the first complete resist mixtures have been evaluated under process conditions. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Reduction in surface roughness during secondary ion mass spectrometry depth profiling with an ion-milling method

Z. X. Jiang, S. Backer, S. Chen, J. Lerma, T. Guenther, J. J. Lee, and D. Sieloff

J. Vac. Sci. Technol. B 19, 2304 (2001); http://dx.doi.org/10.1116/1.1421553 (3 pages) | Cited 3 times

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Depth resolution for secondary ion mass spectrometry (SIMS) profiling of poly Si/SiO2/Si gate stacks is often hindered by roughness of poly Si surfaces. In order to maintain the high depth resolving power of low-energy SIMS for the gate stacks, an ion-milling method was developed to smoothen and thin poly Si films by O2+ beam bombardment at normal incidence. The ion milling has led to a remarkable smoothening in the sputtered area: the rms roughness in poly Si was reduced from 4.5 to 0.6 nm, after removal of 120 nm poly Si by 5 keV O2+ bombardment at normal incidence. SIMS profile analyses with the ion milling provided detailed in-depth distributions of As and Si in a gate stack, showing vividly the pile up of As at the poly Si/SiO2 interface and the difference in the beam-induced diffusion of As in Si and SiO2. © 2001 American Vacuum Society.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.Cy Elemental semiconductors
61.72.uf Ge and Si
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
68.35.Dv Composition, segregation; defects and impurities
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back to top PLENARY SESSION

From nanometers to gigaparsecs: The role of nanostructures in unraveling the mysteries of the cosmos

Mark L. Schattenburg

J. Vac. Sci. Technol. B 19, 2319 (2001); http://dx.doi.org/10.1116/1.1418410 (10 pages) | Cited 4 times

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High launch costs and the extreme distance to astrophysical objects place a premium on astrophysical instrumentation with the highest attainable sensitivity and resolution at the lowest possible weight and cost. Many interesting and useful optical phenomena occur when the size and placement accuracy of features are comparable to, or smaller than, the wavelength of light. These considerations have compelled us to develop a variety of nanotechnoligies that have now been utilized in space physics instrumentation on nine missions. These include 200- and 400-nm-period membrane-supported transmission gratings for high-resolution spectroscopy of astrophysical x-ray sources, mesh-supported transmission gratings for solar extreme ultraviolet (EUV) monitoring, and UV nanofilters with 45 nm slots that are key components of atom cameras observing Earth’s magnetosphere. This article will describe instruments on space missions where we have applied nanotechnology. One application is the NASA Chandra Observatory x-ray telescope, for which we manufactured a large quantity of transmission gratings for high-resolution spectroscopy. Chandra is now returning a torrent of high-quality x-ray images and spectra from such interesting objects as supernova remnants, the accretion disks around black holes and neutron stars, stellar coronae, galaxy cluster cooling flows, and other x-ray-emitting objects up to gigaparsecs distant. [A short astronomy lesson: As Earth orbits Sol, nearby stars in the sky appear to wobble due to parallax. At a distance of one parsec (a “parallax-second”), the diameter of Earth’s orbit (∼1.5×1011 m) subtends one arcsecond, so a parsec is around 3.3 light years, or 3.1×1016 m. For reference, the nearest star is around a parsec away, our Milky Way galaxy is a few kiloparsecs across, nearby galaxies are megaparsecs away, and the known universe is measured in gigaparsecs (1025 m).] Another application is the atom “camera” on the NASA Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft that studies Earth’s magnetosphere, the belt of plasma around the Earth formed by swept-up ions from the Solar wind trapped in the bottle of Earth’s magnetic field. The camera images the magnetosphere in the “light” of neutral atoms, rather than photons, emitted from the plasma due to charge exchange processes. We developed nanofilters, consisting of 500-nm-thick gold foils with 45-nm-wide slots, that are designed to block unwanted deep-UV and EUV photons which would otherwise overwhelm the detector with a million-to-one noise-to-signal ratio, thus allowing the camera to detect the weak atom fluxes. IMAGE is now sending back spectacular atom movies of the magnetosphere revealing a wealth of new information about this complex and dynamic environment. Finally, I describe work in our laboratory aimed at developing microtechnology for the shaping and assembly of glass microsheet optics to few-nanometer accuracy. We believe these new x-ray optics will spawn a new generation of diffraction-limited x-ray telescopes with massive collecting areas and resolution approaching 0.1 microarcsecond (∼1 picoradian). These new telescopes may enable the direct imaging of the massive black holes believed to lurk at the center of most galaxies. © 2001 American Vacuum Society.
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95.55.Ka X- and γ-ray telescopes and instrumentation
94.80.+g Instrumentation for space plasma physics, ionosphere, and magnetosphere
95.55.Ev Solar instruments
81.07.-b Nanoscale materials and structures: fabrication and characterization
07.85.Nc X-ray and γ-ray spectrometers
41.50.+h X-ray beams and x-ray optics
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Low-k1 optical lithography for 100 nm logic technology and beyond

Anthony Yen, Shinn-Sheng Yu, Jeng-Horng Chen, Chun-Kuang Chen, Tsai-Sheng Gau, and Burn Jeng Lin

J. Vac. Sci. Technol. B 19, 2329 (2001); http://dx.doi.org/10.1116/1.1412894 (6 pages) | Cited 4 times

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In this article, we present 193 nm lithography at a k1 factor of 0.37–0.40 and discuss several topics important to 100 nm logic such as optical proximity correction (OPC), control of critical dimension (CD) variation, and lowering of the mask error factor (MEF). In OPC, the best correction results can be achieved by developing accurate models and using reasonable segmentation rules. The technique of variable-dose exposures is demonstrated as a means to reduce interfield CD variation once the cause is known and can be characterized. A more than 30% reduction in CD variation is realized for variation caused by temperature nonuniformity in hot plates. The concept of two dimensional (2D) MEF is introduced to describe situations at feature ends. Higher numerical aperture or more effectively, quadrupole illumination, can be used to lower 1D and 2D MEFs. We also explore the technique of dipole illumination, which may be a candidate for taking optical lithography to k1<0.35. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
84.30.Sk Pulse and digital circuits

Image metrology and system controls for scanning beam interference lithography

Carl G. Chen, Paul T. Konkola, Ralf K. Heilmann, G. S. Pati, and Mark L. Schattenburg

J. Vac. Sci. Technol. B 19, 2335 (2001); http://dx.doi.org/10.1116/1.1409379 (7 pages) | Cited 12 times

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We are developing scanning beam interference lithography (SBIL) for writing and reading large gratings with nanometer level distortion. Our distortion goals require fringe locking to a moving substrate with subnanometer spatial phase error while measuring and controlling the fringe period to approximately one part per million. In this article, we describe the SBIL optical system design along with some major subsystems. The design incorporates measurements and controls of the parameters that limit the accuracy of our system. We describe in detail a novel image metrology scheme, which uses interferometry to measure in situ both the period and the phase of the grating image formed by the interference of two laser beams. For a grating period of approximately 2 μm, experiments demonstrate a period measurement repeatability of three parts per ten thousand, one sigma. Phase measurement indicates a slow fringe drift at 0.25 mrad/s. Both the repeatability error and the phase drift are expected to improve by about three orders of magnitude after several improvements including the installation of an environmental enclosure and thermally stable metrology frames. © 2001 American Vacuum Society.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
07.60.Ly Interferometers
42.79.Dj Gratings

Digital heterodyne interference fringe control system

Ralf K. Heilmann, Paul T. Konkola, Carl G. Chen, G. S. Pati, and Mark L. Schattenburg

J. Vac. Sci. Technol. B 19, 2342 (2001); http://dx.doi.org/10.1116/1.1410096 (5 pages) | Cited 12 times

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In traditional interference lithography, interference fringes are typically phase locked to a stationary substrate using analog homodyne photodiode signals that are fed back to control a phase-shifting device such as an electro-optic modulator or a piezoelectrically transduced mirror. Commercially available fringe-locking systems based on this approach often achieve stability of the interference fringes to within a small fraction of the fringe period p (typically ±p/20 peak-to-peak). We describe the performance of a heterodyne fringe control system utilizing acousto-optic phase shifters and digital controls that is designed to satisfy the much more stringent fringe control requirements for scanning beam interference lithography. We demonstrate locking to ±p/100, and expect further significant improvements. This versatile system can also be used to lock the phase of moving fringes in almost arbitrary fashion at fringe velocities up to 2.5×107 periods/s and to measure the phase of gratings. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.60.Ly Interferometers
42.79.Jq Acousto-optical devices
07.05.Dz Control systems

Method for reducing hyperbolic phase in interference lithography

Michael E. Walsh and Henry I. Smith

J. Vac. Sci. Technol. B 19, 2347 (2001); http://dx.doi.org/10.1116/1.1421558 (6 pages) | Cited 7 times

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A new method is proposed for correcting nonlinear spatial phase in gratings produced with spherical beam interference lithography. We suggest that a concave exposure surface can be used to compensate for the variations in interference angle and fringe inclination which lead to hyperbolic phase progression on a flat exposure plane. Experiments are shown using a spherical concave exposure surface that demonstrate the validity of the method. © 2001 American Vacuum Society.
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42.79.Dj Gratings
42.25.Hz Interference
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Hp Lithography, masks and pattern transfer
42.30.Ms Speckle and moiré patterns

Immersion lithography at 157 nm

M. Switkes and M. Rothschild

J. Vac. Sci. Technol. B 19, 2353 (2001); http://dx.doi.org/10.1116/1.1412895 (4 pages) | Cited 41 times

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We present a preliminary study on the feasibility of immersion lithography at 157 nm for patterning below 70 nm. This technology can enable an enhancement in resolution of ∼40% without radical changes in lasers, optics, or resist technology. We have identified a class of commercially available liquids, perfluoropolyethers, which are good candidates for use as immersion liquids. They are transparent (α≈10−3 μm−1 base 10), optically clean, chemically inert, and compatible with at least some current resist materials and with the semiconductor manufacturing environment. We have also constructed a high-resolution lensless interference immersion lithography system, preserving much of the design of a previous nonimmersion interference system. With this immersion interference tool, we have patterned resist with 30 nm dense features. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Feasibility of utilizing hexamethyldisiloxane film as a bottom antireflective coating for 157 nm lithography

C. H. Lin and L. A. Wang

J. Vac. Sci. Technol. B 19, 2357 (2001); http://dx.doi.org/10.1116/1.1417549 (5 pages) | Cited 1 time

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The feasibility of utilizing a bottom antireflective coating (BARC) layer composed of hexamethyldisiloxane (HMDSO) film for 157 nm lithography is studied. The vaporized liquid HMDSO is used as a coating material in a conventional electron cyclotron resonance-plasma enhanced chemical vapor deposition process. The required optical constants of suitable HMDSO films can easily be tuned by adjusting the gas flow rate ratio of O2 to HMDSO. The swing effect is experimentally shown to be reduced significantly on Si substrates by applying either a single layer BARC or a bilayer BARC. Additionally, the bilayer BARC is shown by simulation to be capable of providing larger thickness-controlled tolerances than a single layer BARC. © 2001 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Hp Lithography, masks and pattern transfer
42.79.Wc Optical coatings
78.66.Qn Polymers; organic compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Demonstration of two-photon lithography

Ch. J. Schwarz, A. V. V. Nampoothiri, J. C. Jasapara, W. Rudolph, and S. R. J. Brueck

J. Vac. Sci. Technol. B 19, 2362 (2001); http://dx.doi.org/10.1116/1.1418409 (4 pages) | Cited 2 times

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Two-photon exposure is demonstrated using ∼12 fs duration pulses at a center wavelength of 800 nm and a standard I-line photoresist. Using direct-writing with a focused Gaussian beam, developed resist features as small as 300 nm, compared with the ∼1 μm focal spot diameter, have been achieved. The experiments reveal substantial differences (∼104) in the two-photon absorption coefficient for multiple pulse trains (100 MHz) and for single pulses. A simple model involving photoexcitation of an intermediate conformation of the photoactive compound and relaxation back to the ground state can explain this observation. The resolution enhancement of √ resulting from the two-photon absorption is demonstrated by writing two lines as close as possible to each other with both one- and two-photon absorption mechanisms. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Gratings of regular arrays and trim exposures for ultralarge scale integrated circuit phase-shift lithography

M. Fritze, B. Tyrrell, D. Astolfi, D. Yost, P. Davis, B. Wheeler, R. Mallen, J. Jarmolowicz, S. Cann, D. Chan, P. Rhyins, C. Carney, J. Ferri, and B. A. Blachowicz

J. Vac. Sci. Technol. B 19, 2366 (2001); http://dx.doi.org/10.1116/1.1408950 (5 pages) | Cited 5 times

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Current semiconductor technology requires optical lithography to image feature sizes smaller than the exposure tool wavelength. In order to achieve this subwavelength imaging, some form of optical resolution-enhancement technology is required, with phase-shift methods offering the greatest potential enhancement. Major impediments to the wide-scale adoption of this technology have included mask cost, inspectability/repair, and turnaround time. The correction of optical proximity effects, which are typically large in phase-shift techniques, have also been an important issue. In this work, we propose a new type of phase-shift approach utilizing gratings of regular arrays and trim exposures. This method makes use of multiple-exposure phase-shift imaging of dense-only features. Proximity effects can be nearly eliminated along with the complex optical proximity corrections typically required on the mask. The simple phase-shift masters can also be reused for multiple designs, thereby addressing cost and turnaround time issues. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Optimization method of the double exposure technique with alt-PSMs for below a 0.13 μm node

Koji Kikuchi, Hidetoshi Ohnuma, and Hiroichi Kawahira

J. Vac. Sci. Technol. B 19, 2371 (2001); http://dx.doi.org/10.1116/1.1421547 (10 pages)

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A new method to optimize the structure of alternative phase shifting masks (alt-PSMs) with dual trench type and optical proximity effect correction (OPC) has been developed from the viewpoint of pattern placement error and gate width fluctuation. The pattern placement error and gate width fluctuation have been reduced significantly to meet the requirements of overlay margin and critical dimension (CD) accuracy for the 0.13 μm node devices by this method. The optimum mask structure for reducing a pattern placement error was determined by the simulation that takes account of the mask topography effect. The alt-PSM with a deep trench depth of 570 nm and a phase difference of about 170° between the phase shifted and nonshifted area was optimum to reduce pattern placement error. At the optimum condition, a high contrast was also obtained. For the experiment, we used a set of masks to study dependence of mask cross sectional structure. While the dependence of pattern placement error on focus shift is much larger for the nonoptimized mask, it is small with the mask having the optimized value of our study. With respect to the gate width fluctuation, it can be categorized into three folds. We have developed optimization methods for them, respectively. First one is associated with pattern pitches and shifter lengths. It could be reduced by mask bias OPC of a binary mask. Second one is gate width fluctuation at the end of shifter. Third one is what we call necking shape, which is pattern shrinkage near the end of shifter. For the latter two cases, we have applied OPC of extended shifters with additional patterns. Linewidth fluctuation was reduced by applying these OPC to the pattern. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Low-dielectric constant bisbenzo(cyclobutene) and fluorinated poly(arylene)ether films as bottom anti-reflective coating layers for ArF lithography

H. L. Chen, T. C. Chu, M. Y. Li, F. H. Ko, H. C. Cheng, and T. Y. Huang

J. Vac. Sci. Technol. B 19, 2381 (2001); http://dx.doi.org/10.1116/1.1421552 (4 pages) | Cited 1 time

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In this article, we demonstrate a bottom anti-reflective coating (BARC) layer for ArF lithography. The anti-reflective layers are composed of a commercial low-dielectric constant bisbenzo(cyclobutene) (BCB)- and fluorinated poly(arylene)ether (FLARE)-based films. By adding an optimized etching hard-mask layer, reflectance of less than 1% at the resist/silicon substrate interface can be achieved. BCB and FLARE also have great potential to be used as BARC layers on highly reflective substrates for metal interconnect applications. It is easy to reduce reflectance without adding an extra BARC layer for patterning low-dielectric materials. It is convenient to use this BARC structure in ArF lithography. In this article, suitable etching characteristics and thermal stability of BCB- and FLARE-based BARC layers are also described. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
42.79.Wc Optical coatings
77.84.Jd Polymers; organic compounds
78.66.Qn Polymers; organic compounds
85.40.Ls Metallization, contacts, interconnects; device isolation
81.65.Cf Surface cleaning, etching, patterning
68.60.Dv Thermal stability; thermal effects

Spun-on carbon antireflective layer with etch resistance for deep and vacuum ultraviolet lithography processes

Yasuhiko Sato, Yasunobu Onishi, Yoshihiko Nakano, and Shuzi Hayase

J. Vac. Sci. Technol. B 19, 2385 (2001); http://dx.doi.org/10.1116/1.1412900 (4 pages) | Cited 1 time

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Dry etch resistance and antireflective performance were studied for a film containing a high amount of carbon (83.4 wt %), which was named the spun-on carbon film. The film was formed by using a carbon cluster precursor synthesized by reductive coupling of a mixture of carbon tetrabromide and phenylbromide. The refractive indices of the spun-on carbon film at the exposure wavelengths of excimer lasers are n=1.72, k=0.35 (KrF), n=1.46, k=0.67 (ArF), and n=1.37, k=0.14 (F2). A bilayer bottom antireflective coating system composed of upper spun-on glass (SOG) and lower spun-on carbon was evaluated. By optimizing the SOG thickness, the reflectivity is reduced to 0.2% (KrF), 3.3% (ArF), and 0.5% (F2). Remarkable improvement is observed at the KrF and F2 wavelengths. Resist profiles are obtained without any footing, residue, or standing wave using the KrF and ArF scanning steppers. The etch resistance of the spun-on carbon film is 1.34 times greater than that of the thermally oxidized novolak film (i.e., a conventional underlayer for a trilevel resist process). © 2001 American Vacuum Society.
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81.05.U- Carbon/carbon-based materials
85.40.Hp Lithography, masks and pattern transfer
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
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First lithographic results from the extreme ultraviolet Engineering Test Stand

H. N. Chapman, A. K. Ray-Chaudhuri, D. A. Tichenor, W. C. Replogle, R. H. Stulen, G. D. Kubiak, P. D. Rockett, L. E. Klebanoff, D. O’Connell, A. H. Leung, K. L. Jefferson, J. B. Wronosky, J. S. Taylor, L. C. Hale, K. Blaedel, et al.

J. Vac. Sci. Technol. B 19, 2389 (2001); http://dx.doi.org/10.1116/1.1414017 (7 pages) | Cited 13 times

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The extreme ultraviolet (EUV) Engineering Test Stand (ETS) is a step-and-scan lithography tool that operates at a wavelength of 13.4 nm. It has been developed to demonstrate full-field EUV imaging and acquire system learning for equipment manufacturers to develop commercial tools. The initial integration of the tool is being carried out using a developmental set of projection optics, while a second, higher-quality, projection optics is being assembled and characterized in a parallel effort. We present here the first lithographic results from the ETS, which include both static and scanned resist images of 100 nm dense and isolated features throughout the ring field of the projection optics. Accurate lithographic models have been developed and compared with the experimental results. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

At-wavelength characterization of the extreme ultraviolet Engineering Test Stand Set-2 optic

Patrick Naulleau, Kenneth A. Goldberg, Erik H. Anderson, Phillip Batson, Paul E. Denham, Keith H. Jackson, Eric M. Gullikson, Senajith Rekawa, and Jeffrey Bokor

J. Vac. Sci. Technol. B 19, 2396 (2001); http://dx.doi.org/10.1116/1.1421545 (5 pages) | Cited 6 times

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At-wavelength interferometric characterization of a new 4×-reduction lithographic-quality extreme ultraviolet (EUV) optical system is described. This state-of-the-art projection optic was fabricated for installation in the EUV lithography Engineering Test Stand (ETS) and is referred to as the ETS Set-2 optic. EUV characterization of the Set-2 optic is performed using the EUV phase-shifting point diffraction interferometer (PS/PDI) installed on an undulator beamline at Lawrence Berkeley National Laboratory’s Advanced Light Source. This is the same interferometer previously used for the at-wavelength characterization and alignment of the ETS Set-1 optic. In addition to the PS/PDI-based full-field wave front characterization, we also present wave front measurements performed with lateral shearing interferometry, the chromatic dependence of the wave front error, and the system-level pupil-dependent spectral-bandpass characteristics of the optic; the latter two properties are only measurable using at-wavelength interferometry. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
42.87.Bg Phase shifting interferometry
07.60.Ly Interferometers

High sensitivity actinic detection of native defects on extreme ultraviolet lithography mask blanks

Moonsuk Yi, Tsuneyuki Haga, Chris Walton, and Jeffrey Bokor

J. Vac. Sci. Technol. B 19, 2401 (2001); http://dx.doi.org/10.1116/1.1410088 (5 pages) | Cited 6 times

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We present recent experimental results of actinic extreme ultraviolet lithography mask blank defect inspection. The detection sensitivity of the current actinic inspection system is predicted to be able to reach approximately 30 nm in cross correlation experiments done with commercial visible-light, scanning electron microscopy (SEM), and atomic force microscopy (AFM) inspection tools. Random, native defects identified using the visible-light tool were scanned by the actinic tool and the scattering characteristics were compared. SEM and AFM characterization of selected defects were also performed for physical measurement. We found a defect whose size was as small as 60 nm and AFM analysis showed that this defect was a 3 nm high substrate defect that was smoothed-out by the multilayer coating. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.60.Pb Conventional optical microscopes

Observation of speckle patterns in extreme ultraviolet imaging

H. H. Solak, Y. Yang, and F. Cerrina

J. Vac. Sci. Technol. B 19, 2406 (2001); http://dx.doi.org/10.1116/1.1421550 (6 pages) | Cited 3 times

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Light scattered by multilayer coated extreme ultraviolet (EUV) optics is a cause of concern in EUV lithography due to its contribution to flare. Because of the extremely small wavelength of light, even subnanometer roughness on mirror surfaces can cause significant scattering. Flare is usually assumed to be an incoherent additive background, which reduces intensity modulation in the image. However, this is not universally true since flare can add coherently under certain conditions depending on the illumination coherence and mirror roughness properties. Coherent addition of flare can lead to speckle-like fluctuations in the image causing undesirable artifacts in a lithography system such as linewidth variation and line edge roughness. We experimentally observed this phenomenon in the recorded images of a pinhole using a Schwarzchild objective based EUV microscope. These images reveal a high contrast speckle pattern in the scattered halo around the specularly reflected beam. The overall distribution of scattered light is directly related to the power spectral density of roughness on the mirror surfaces. In order to better understand the potential influence of this in a lithography system, we simulated imaging of various object patterns by “rough optics.” Simulation results indicate that the speckle effect is not likely to cause appreciable image degradation if current design goals for EUV lithography systems which call for sub-0.5 nm roughness on mirror surfaces are met. © 2001 American Vacuum Society.
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42.30.Ms Speckle and moiré patterns
85.40.Hp Lithography, masks and pattern transfer
42.30.Lr Modulation and optical transfer functions
07.60.Pb Conventional optical microscopes

Fabrication of parallel-plate nanomirror arrays for extreme ultraviolet maskless lithography

Yashesh Shroff, Yijian Chen, and William Oldham

J. Vac. Sci. Technol. B 19, 2412 (2001); http://dx.doi.org/10.1116/1.1417544 (4 pages) | Cited 3 times

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A micromirror array for extreme ultraviolet (EUV) maskless lithography was designed and fabricated. The arrays are composed of devices with less than a 350 nm actuation gap and a surface area ranging from 1 μm2 to 20 μm2. The mirror layer is composed of silicon in lieu of the Mo/Si stack used for EUV mirrors in order to debug the process and to simplify the initial fabrication. Germanium was used as a sacrificial material while α-Si acts as a hinge for this parallel-plate design. Silicon migration into germanium was observed, so the thermal budget was restrained to 450 °C for the entire process. Scanning electron microscope images of working devices are provided. © 2001 American Vacuum Society.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
42.79.Bh Lenses, prisms and mirrors
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
42.15.Eq Optical system design
81.05.Cy Elemental semiconductors
66.30.Ny Chemical interdiffusion; diffusion barriers
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Recent progress in 1×x-ray mask technology: Feasibility study using ASET-NIST format TaXN x-ray masks with 100 nm rule 4 Gbit dynamic random access memory test patterns

Shinji Tsuboi, Yuusuke Tanaka, Toshiyuki Iwamoto, Hiroaki Sumitani, and Yoshinori Nakayama

J. Vac. Sci. Technol. B 19, 2416 (2001); http://dx.doi.org/10.1116/1.1408952 (7 pages) | Cited 4 times

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This article discusses recent progress in 1×x-ray mask technology in Japan. Proximity x-ray lithography (PXL) using synchrotron radiation light with a wavelength of 0.7–1.0 nm can in principle provide as high a throughput as optical lithography, because PXL and optical lithography both employ photon beams and masks. A high-performance electron-beam mask writer called the EB-X3, suitable for PXL, has been developed by NTT under the Association of Super-Advanced Electronics Technologies (ASET) program. It has a reproducible image placement (IP) accuracy of less than 15 nm. We used the shaped-beam EB-X3 to fabricate 100 nm rule x-ray masks for the gate and contact/hole (C/H) layers of 4 Gbit dynamic random access memory (DRAM) test patterns. The ASET-NIST (National Institute of Standards and Technology) type masks consist of a 350-nm-thick TaBN absorber, a 3-μm-thick SiC membrane (27-mm square membrane area), a 1-mm-thick Si substrate, and a 6.63-mm-thick Pyrex glass frame. We have achieved an IP accuracy for 1×x-ray masks of less than 15 nm at both the gate and C/H levels. The mask-to-mask overlay accuracy between the gate and C/H masks is less than 20 nm; and after magnification correction, it is less than 10 nm. The critical dimension (CD) variations for 100 nm features measured in a 24-mm-square area are less than 100±6.0 nm at both levels. An overlay accuracy for PXL of better than 30 nm (∣mean∣+3σ) was obtained by the double-exposure method using the XRA volume-production x-ray stepper (Canon, Inc.) and 18 nm overlay ASET-NIST type x-ray masks (gate to contact). An IP reproducibility of less than 7 nm has been achieved for the EB-X3 itself (best data). The resist CD accuracy on the membrane for 4 Gbit DRAM patterns is better than 7 nm (Δ∣mean∣+3σ=6.6 nm). These data indicate that PXL has the potential for patterning 50 nm node devices with current tools. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
84.30.Sk Pulse and digital circuits

Can proximity x-ray lithography print 35 nm features? Yes

Mumit Khan, Geng Han, Gene Tsvid, Toyoki Kitayama, Juan Maldonado, and Franco Cerrina

J. Vac. Sci. Technol. B 19, 2423 (2001); http://dx.doi.org/10.1116/1.1418407 (5 pages) | Cited 11 times

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We report on the results of our effort to extend proximity x-ray lithography (PXL) to 35 nm using a harder energy spectrum, and choosing the appropriate materials for the mask and the resist to match the transmission and absorption at higher energies. Previous studies [M. Kahn et al., J. Vac. Sci. Technol. B 17, 3426 (1999); T. Kitayama, J. Vac. Sci. Technol. B 18, 2950 (2000)] have shown that PXL is capable of printing 50 nm features, and in this study, we extend that work to show that PXL can indeed be used for 35 nm generation. We investigate the use of higher energy radiation, in conjunction with novel resist materials, to deliver the 35 nm node and provide a set of requirements to achieve that goal. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Technique for 25 nm x-ray nanolithography

Eijiro Toyota, Toshitada Hori, Mumit Khan, and Franco Cerrina

J. Vac. Sci. Technol. B 19, 2428 (2001); http://dx.doi.org/10.1116/1.1415503 (6 pages) | Cited 3 times

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The image-forming limit of x-ray lithography is said to be ∼70 nm using existing devices and technologies. This article presents methods to extend the limit to 25 nm or even below. Preparatory to the study, a light source was designed to improve x-ray beam toward shorter wavelength. In addition, a simulation code has been developed to evaluate the methods. The first method is to use a mask with a larger period and pattern than deigned images. The mask forms the designed images with an enlarged period. Two-dimensional, 25 nm width images can be formed using a 100 nm period pattern mask at 8 μm gap. The second method is to use a mask with interference slits. Since the image pattern is sharply focused, ⩽25 nm images can be formed at 8–12 μm gaps. Multiple exposures are applied to both methods in order to fill in the clearances of the images. Simulation results are shown in both methods for typical patterns. © 2001 American Vacuum Society.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
41.50.+h X-ray beams and x-ray optics

Focusing x-ray masks for printing very narrow features

M. Feldman, M. Khan, and F. Cerrina

J. Vac. Sci. Technol. B 19, 2434 (2001); http://dx.doi.org/10.1116/1.1410093 (5 pages)

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X-ray masks may be fabricated with features that have parabolic rather than the usual rectangular or trapezoidal cross sections. Phase shift effects in such features cause them to act as tiny lenses that focus the x rays on to the wafer. The lenses may either be cylindrical, to form line images on the wafer, or spherical, to form points. Wider images, with very sharp outlines, may also be formed on the wafer by using wider mask features, which have parabolic cross sections only near their edges. Features down to at least 50 nm may be imaged, with wide latitudes in mask parameters, gap, and resist processing. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.85.-m X- and γ-ray instruments
41.50.+h X-ray beams and x-ray optics
41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles

Effect of secondary electron from the substrate in x-ray lithography using harder radiation spectra

K. Itoga, K. Marumoto, T. Kitayama, H. Sumitani, M. Amemiya, and Y. Watanabe

J. Vac. Sci. Technol. B 19, 2439 (2001); http://dx.doi.org/10.1116/1.1420534 (5 pages) | Cited 3 times

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Proximity x-ray lithography using harder spectra has been proposed as a next generation lithography technology. The secondary electron from the substrate is one of the issues that should be solved to realize this technology. We investigated the effect of the electron from the silicon substrate on the pattern quality when using the shorter wavelength exposure. As a figure of merit for the effect of the electron from the substrate, we proposed a function R which is defined as the ratio of the energy absorption in the substrate to that in the resist. We confirmed the validity of R by comparing it with a Monte Carlo simulation (SPEED). Several exposure experiments, which corresponded to various R values, were carried out by changing mirror, filter, and mask membrane. We found an adequate range of R where the secondary effect can be ignored from these experiments. Furthermore, we showed that R could effectively be reduced by using an absorption edge of the resist material. Bromine is the best material to suppress the value of R in every wavelength region. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.50.+h X-ray beams and x-ray optics

Compact synchrotron radiation lithography system for 70 nm device manufacturing

Tsutomu Miyatake, Xuan Li, Sayumi Hirose, Toshio Monzen, Kiyoshi Fujii, and Katsumi Suzuki

J. Vac. Sci. Technol. B 19, 2444 (2001); http://dx.doi.org/10.1116/1.1409382 (4 pages)

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We report on the performance and reliability of our synchrotron radiation (SR) based x-ray lithography (XRL) system installed in Tanashi Works of Sumitomo Heavy Industries, Ltd. Our XRL facilities include a compact racetrack-type SR light source “AURORA-2S” (A2S), the injector microtron, a 3-m-long beamline, and the second version x-ray aligner. In 2000, A2S proved the beam lifetime of 16 h in regular operation at the designed beam current 500 mA. The XRL beamline offers a high-dose exposure rate of over 43 mW/cm2 on a wafer at beam current 500 mA. The x-ray aligner achieved an overlay accuracy better than 16 nm (3σ) using a video-based scattered-light alignment (SLA) system. In the SLA, edge scattering on matrix array patterns provides multispot video images for mask to wafer alignment. A 70 nm line and space (L/S) pattern was replicated with a gap of 15 μm. In resolution enhancement exposure, we replicated a 100 nm L/S and 1 100 nm hole pattern using a 200 nm L/S and a 200 nm hole pattern of x-ray mask, respectively. © 2001 American Vacuum Society.
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81.16.Nd Micro- and nanolithography

Evaluation of new x-ray stepper, the XRA

Hiroaki Sumitani, Muneyoshi Suita, Soichiro Mitsui, Hajime Aoyama, Kiyoshi Fujii, Hiroshi Watanabe, Takao Taguchi, and Yasuji Matsui

J. Vac. Sci. Technol. B 19, 2448 (2001); http://dx.doi.org/10.1116/1.1410091 (7 pages) | Cited 6 times

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The exposure performance has been evaluated for the new x-ray stepper, the XRA, which is equipped with global alignment and magnification correction systems. Dose uniformity in the exposure field of 3.9%, stage accuracy of less than 20 nm, and good linearity and stability between the magnification change and applied force were obtained. For the 100 nm node, both critical dimension (CD) control of 10 nm and overlay accuracy of less than 30 nm were obtained using two 4 Gbit masks of the gate and contact hole by the double exposure method. Possible improvements of the dose uniformity and mask pattern CD will result in more accurate CD control. By compensating for the alignment offset, overlay accuracy of 23 nm for the 70 nm node is also expected. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.85.-m X- and γ-ray instruments
41.50.+h X-ray beams and x-ray optics
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High-throughput electron-beam lithography with a raster-scanned, variably shaped beam

L. H. Veneklasen, H. M. Kao, S. A. Rishton, S. Winter, V. Boegli, T. Newman, G. Bertuccelli, G. Howard, P. Le, Z. Tan, and R. Lozes

J. Vac. Sci. Technol. B 19, 2455 (2001); http://dx.doi.org/10.1116/1.1414117 (4 pages) | Cited 1 time

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A raster-shaped beam writing strategy has been tested on a prototype 50 keV electron-beam lithography workstation. The test stand was constructed to prove the raster-shaped beam concept by exposing patterns at full throughput over small areas. Patterns are composed in a raster-scanned array of variably shaped flashes at 100 MHz flash rate, with 0.9 μA full beam current, and 2200 A/cm2 current density using a thermal field emission source. Writing speed is independent of resist sensitivity and pattern complexity. By comparison, a typical variably shaped beam system with a LaB6 source would have a current density of 10–30 A/cm2 and a flash rate of 2–10 MHz, depending on resist sensitivity and deflection settling time. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.75.Fr Electron and positron beams

PREVAIL-EPL alpha tool: Early results

S. D. Golladay, H. C. Pfeiffer, C. A. Bohnenkamp, R. S. Dhaliwal, W. A. Enichen, M. S. Gordon, R. A. Kendall, J. E. Lieberman, W. Stickel, J. D. Rockrohr, E. V. Tressler, A. Tanimoto, T. Yamaguchi, K. Okamoto, K. Suzuki, et al.

J. Vac. Sci. Technol. B 19, 2459 (2001); http://dx.doi.org/10.1116/1.1415501 (9 pages) | Cited 3 times

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The IBM/Nikon alliance is developing an EPL stepper alpha tool based on the PREVAIL technology. This article provides a status report on the alliance activity with particular focus on the electron optical subsystem developed at IBM. We have previously described design features of the PREVAIL Alpha system. The state-of-the-art e-beam lithography concepts have since been reduced to practice and turned into functional building blocks of a production level lithography tool. The electron optical subsystem has been designed, built, assembled, and tested at IBM’s Semiconductor Research and Development Center (SRDC) in East Fishkill, NY. After demonstrating subsystem functionality, the column, an interim mechanical system and all associated control electronics hardware and software have been shipped during January 2001 to Nikon’s facility in Kumagaya, Japan, for integration into the Nikon commercial e-beam stepper Alpha tool. Postshipment activity has been directed primarily toward demonstrating subfield stitching, a task which exercises system architecture, calibration, stability, and noise performance. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.-p Beam optics

Direct measurement of Coulomb effects in electron beam projection lithography

Takehisa Yahiro, Shohei Suzuki, Takeshi Irita, Noriyuki Hirayanagi, Hiroyasu Shimizu, Shinichi Kojima, Kenji Morita, Shintaro Kawata, Teruaki Okino, and Kazuaki Suzuki

J. Vac. Sci. Technol. B 19, 2468 (2001); http://dx.doi.org/10.1116/1.1410089 (6 pages) | Cited 5 times

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We describe a direct measurement of the image blur and defocus induced by Coulomb effects (stochastic and global space charge) in electron beam projection lithography. The Nikon 100 kV electron beam projection experimental column was used for the experiments. This column has similar values of electron optical parameters to those of electron beam projection lithography (EPL) systems. The Coulomb effect image blur and defocus were directly measured by a knife-edge method. The experimental data of Coulomb effect image blur and defocus as functions of beam current are shown. The experimental results show excellent agreement with our Monte Carlo simulation results. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Gy Chromatic and geometrical aberrations

Experimental study of electron beam projection lithography mask defect printability

Yoshinori Kojima, Norihiro Katakura, Yoichi Tomo, Hiroshi Takenaka, Akira Yoshida, Isao Shimizu, and Masaki Yamabe

J. Vac. Sci. Technol. B 19, 2474 (2001); http://dx.doi.org/10.1116/1.1412896 (4 pages)

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Mask defect printability of electron beam projection lithography (EPL) was investigated. We fabricated EPL chip reticles including programmed defects. The design of these programmed defects was based on semiconductor equipment and materials international (SEMI) standards, but we modified it from the original to a new design for the 100–70 nm node. In our defect printability experiment, Nikon’s electron beam (EB) projection experimental column was used as an exposure tool with those chip reticles. The acceleration voltage of the electron beam was 100 kV. In the case of the “size shift” defects, the correlation between the defect size on the reticle (×1/4) and the critical dimension (CD) change on the wafer is linear and the defect down to 40 nm was printed. Furthermore mask error enhancement factor is nearly equal to 1. This is the advantage of the EPL over the optical lithography. On the other hand, in the case of “dot” defects, defects smaller than 100 nm on the reticle has a small impact on the CD change. The allowable defect size with a criterion of a given ΔCD became larger at the defocus condition. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Mask split algorithm for stencil mask in electron projection lithography

Hiroshi Yamashita, Kunio Takeuchi, and Hideki Masaoka

J. Vac. Sci. Technol. B 19, 2478 (2001); http://dx.doi.org/10.1116/1.1412897 (5 pages) | Cited 10 times

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We developed a mask split algorithm, “M-Split,” using some theories of computational geometry. First, we determined which patterns to split based on actual stencil mask fabrication and defined singular patterns. These singular patterns consisted of nonconvex polygons and could be identified by computational geometry. The contoured singular patterns were then split into two complementary masks, balancing the pattern area density. The split resulted in an 80 nm design-rule logic device, showing that the original patterns could be completely split into polygons that could safely fabricate a stencil mask with a pattern area balance of 50.00% between two complementary masks. The ratio of increase of polygons caused by splitting was 4.84. The computational time without contouring and data output for one 1-mm-square sub field on a 4× mask was 14.2 s for the logic device. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Proximity effect correction using pattern shape modification and area density map for electron-beam projection lithography

Morimi Osawa, Kimitoshi Takahashi, Masami Sato, Hiroshi Arimoto, Kozo Ogino, Hiromi Hoshino, and Yasuhide Machida

J. Vac. Sci. Technol. B 19, 2483 (2001); http://dx.doi.org/10.1116/1.1410090 (5 pages) | Cited 11 times

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A novel proximity effect correction algorithm using pattern shape modification and the area density map method for electron-beam projection lithography is proposed. This algorithm enables fast, accurate and self-consistent calculation of modified pattern sizes. The correctable minimum feature sizes for shape modification were investigated from two viewpoints, mask fabrication restriction and dose margin. The correctable minimum sizes are mostly determined by the dose margin requirement in the case of isolated and dense repeated patterns, implying that the tool resolution determines correctable minimum sizes. A special technique is required for isolated space patterns where the backscattering energy cannot be reduced by simple sizing. We have implemented an algorithm in which pattern densities at middle parts of large patterns are reduced by using a lines and spaces (L/S) pattern or mesh patterns for that case. Successful correction results down to 60 nm from the simulation and 100 nm from the experiment have been obtained. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Comparative study of resolution limiting factors in electron beam lithography using the edge roughness evaluation method

Masaki Yoshizawa and Shigeru Moriya

J. Vac. Sci. Technol. B 19, 2488 (2001); http://dx.doi.org/10.1116/1.1410087 (6 pages) | Cited 3 times

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Resolution capabilities of a Nikon 100 kV experimental column of electron beam (EB) projection lithography, a proof of concept column of low energy electron beam proximity projection lithography (LEEPL), and a variable-shaped EB direct writer were compared using a negative-type chemically amplified resist. Line edge roughness and resolution limit of an isolated line were 2.8 and 40 nm for the Nikon experimental column, and were 4.9 and 52 nm for the EB direct writer at the resist thickness of 250 nm, while they were 10.7 and 61 nm for LEEPL, and were 9.6 and 57 nm for the EB direct writer at the resist thickness of 70 nm. Quantitative influences of resolution limiting factors such as electron-optical beam blur and resist performance were analyzed using the edge roughness evaluation method. The analysis shows that the Nikon experimental column has an ability to resolve 35 nm patterns if resolution performance of the resist is 10% improved. In the high-throughput EB stepper system with a large beam current, it is necessary for resolving 50 nm patterns to keep the electron-optical beam blur under 36 nm. It is known about LEEPL that a necessary and sufficient condition for realizing 50 nm patterns is to develop a 50 nm thick resist having the same resolution performance as the conventional resist dedicated for the use with thicker film thickness, and to obtain a 50 nm pattern mask having the same aperture roughness as the conventional mask with 70 nm patterns. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
68.35.B- Structure of clean surfaces (and surface reconstruction)
41.85.Gy Chromatic and geometrical aberrations
41.75.Fr Electron and positron beams

Effect of resist sensitivity ratio on T-gate fabrication

Y. Chen, D. S. Macintyre, and S. Thoms

J. Vac. Sci. Technol. B 19, 2494 (2001); http://dx.doi.org/10.1116/1.1420577 (5 pages) | Cited 2 times

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The need for short length T gates with good process control is demanding because pattern resolution is required in the lower level of resist. This article considers different resist systems and uses the resist sensitivity ratio between the head and foot defining layers to build two models. These are useful for determining the optimum parameters for T-gate fabrication and associated gate feeds. We show that the optimum resist sensitivity ratio is about 6 at 50 kV where bloating is negligible and good footwidth control is obtained. We also show that further improvements can be obtained by moving to 100 kV where a sensitivity ratio of 14 can be used. Sensitivity ratios between 6 and 14 can be achieved using either the poly(methylmethacrylate)/UVIII or ZEP520/UVIII bilayers since in both cases the sensitivity ratio can be varied by changing the development times and the bake temperatures. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Performance of the Raith 150 electron-beam lithography system

James G. Goodberlet, J. Todd Hastings, and Henry I. Smith

J. Vac. Sci. Technol. B 19, 2499 (2001); http://dx.doi.org/10.1116/1.1414018 (5 pages) | Cited 17 times

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The performance of a Raith 150 electron-beam lithography system is reported. The system’s resolution, stability, intrafield distortion, stitching, and overlay performance are evaluated. Patterning at low- and high-acceleration voltages is compared. The system was used to pattern sub-20 nm features, and the largest intrafield distortion for a 100 μm field was measured to be 15 nm. Pattern-placement accuracy below 35 nm, mean plus twice the standard deviation, was demonstrated. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.-p Beam optics

Influence of sub-100 nm scattering on high-energy electron beam lithography

Erik H. Anderson, Deirdre L. Olynick, Weilun Chao, Bruce Harteneck, and Eugene Veklerov

J. Vac. Sci. Technol. B 19, 2504 (2001); http://dx.doi.org/10.1116/1.1415506 (4 pages) | Cited 8 times

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Electron beam lithography tools have evolved in the direction of higher beam energy in order to achieve high-resolution, fine feature definition. As the beam energy is increased, the “forward” scattering is reduced and the “backscatter” range is increased. Over the years, tools became available data 20 then 50 kV, and now 100 kV operation is common. Operation at higher voltages has several advantages, such as better resolution and process latitude due to reduced forward scattering, and a few disadvantages such as higher dose requirements, substrate heating, and lower contrast for backscatter electron alignment and calibration signals (due to reduced primary electron backscattering generation in thin film). The backscatter range for 100 kV on silicon is about 27 μm compared to 8 μm at 50 kV resulting in different strategies for efficient proximity correction. However, even at 100 kV, scattering in an intermediate range is observed and must be taken into account in order to achieve good linewidth control at the highest resolution. Measurements of the scattering range for both 50 and 100 kV have been made using the point exposure distribution measurement technique [S. A. Rishton and D. P. Kern, J. Vac. Sci. Technol. B 5, 135 (1987)]. For comparison, measurements taken on the same wafer at different voltages show that 50 and 100 kV scattering range functions overlap, after normalizing for the different resist sensitivity, at length scales below 0.5 μm, suggesting a common mechanism, which is independent of the initial electron energy. For thin resists, this suggests that the significant resolution difference between 50 and 100 kV lithography is limited to the “forward” scattering effect as the incident electrons traverse the resist. Extrapolating the scattering function to the approximate beam diameter of 10 nm allows an impulse response function to be numerically determined. The convolution of this function gives reasonably good agreement with dose versus linewidth measurements. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Energy deposition and transfer in electron-beam lithography

Bo Wu and Andrew R. Neureuther

J. Vac. Sci. Technol. B 19, 2508 (2001); http://dx.doi.org/10.1116/1.1421548 (4 pages) | Cited 7 times

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An analytical electron-resist interaction (ERI) model is developed based on detailed investigation of secondary electron production and binding energy related exposure events. Analysis shows that 80% of the exposure events are directly caused by secondary electrons for 100 keV primary electron energy. The number of secondary electrons and further cascade electrons is 1/20 and 1/300, respectively, of the incoming electrons. An algebraic expression is derived to describe the spatial distribution of the exposure events. The ERI model can be extended to chemically amplified resists. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
79.20.Hx Electron impact: secondary emission
61.80.Fe Electron and positron radiation effects

Mark detection in low-energy electron-beam lithography

G. S. Fritz and D. P. Kern

J. Vac. Sci. Technol. B 19, 2512 (2001); http://dx.doi.org/10.1116/1.1421546 (4 pages)

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An implementation of the Rau-detector has been investigated with respect to its use for mark detection in low-energy electron-beam lithography. The generation of signals from marks commonly used in electron-beam lithography is discussed. With this detector, images of trenches etched into silicon were obtained with electron energies as low as 1 keV. Signal-to-noise ratio and bandwidth were determined from line scans across sequences of etched trenches. The trench depth has been varied from 40 to 500 nm. The measurements have also been performed with resist coated trenches. It is demonstrated that the Rau-detector is well suited for mark detection in low-energy electron- beam lithography systems. Due to its small size, it leads itself to microcolumn application. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.75.Fr Electron and positron beams

Simulation of time-dependent charging of resist on Si under electron-beam irradiation

Masatoshi Kotera

J. Vac. Sci. Technol. B 19, 2516 (2001); http://dx.doi.org/10.1116/1.1421570 (4 pages) | Cited 8 times

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The time-dependent charging mechanism of an electrically insulating resist film on a Si substrate under electron-beam irradiation is proposed based on results obtained by a numerical simulation. The primary electron trajectory and the secondary electron cascade multiplication in the resist are calculated by Monte Carlo simulation, and spatial distributions of the electron deposition and the energy deposition in the resist are obtained. The potential distribution in and above the resist is obtained by solving the Poisson equation. The electron trajectory bending due to the electric field is calculated. The electron-beam-induced conduction is calculated based on the energy deposited. The potential distributions obtained in the resist show quite good agreement with the experimental results. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
61.80.Fe Electron and positron radiation effects
61.82.Ms Insulators
02.70.Uu Applications of Monte Carlo methods
73.61.Ng Insulators
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Characterization of a process development tool for ion projection lithography

Hans Loeschner, Gerhard Stengl, Rainer Kaesmaier, and Andreas Wolter

J. Vac. Sci. Technol. B 19, 2520 (2001); http://dx.doi.org/10.1116/1.1421562 (5 pages) | Cited 5 times

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This article describes the performance of a process development tool for ion projection lithography (IPL), realized as part of the MEDEA program of the European Union. This system was designed for a 12.5×12.5 mm2 exposure field and 4:1 reduction ratio between the mask and the wafer. The design incorporates several novel concepts, including a negative electrostatic lens at the mask to reduce distortion and field-composable lenses to provide electronic fine alignment of the system. Continuous control of magnification, position offset, distortion, and telecentricity is provided by a real-time feedback system (pattern lock) that monitors the position of reference beamlets traveling in parallel with the integrated circuit image through the ion-optical system. After mechanically aligning the center and tilt of the lenses relative to the optical axis to within 10 μm and 50 μrad, respectively, we achieved 100 nm resolution over the full design field, with 75 nm resolution in local areas within the field. The reduction ratio was within 0.01% of design predictions. We also discuss the experimental plan for further demonstrating the efficacy of IPL for integrated circuit manufacturing far below 100 nm design rules. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
41.85.Gy Chromatic and geometrical aberrations
41.85.Ne Electrostatic lenses, septa

Direct patterning of nanometer-scale silicide structures by focused ion-beam implantation through a thin barrier layer

M. M. Mitan, D. P. Pivin, T. L. Alford, and J. W. Mayer

J. Vac. Sci. Technol. B 19, 2525 (2001); http://dx.doi.org/10.1116/1.1408953 (4 pages) | Cited 2 times

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Recently several new approaches have been proposed to manufacture silicide structures using mask-less techniques. We have developed a new technique for direct patterning and formation of cobalt silicide structures using focused ion-beam (FIB) implantation. Utilizing the effects of ion-beam mixing and properties of thin barrier oxides, silicide lines with dimensions down to 170 nm were produced on (100) silicon substrates using the FIB. The process involves the ion implantation of 200 keV As++ through a cobalt thin film. A thin (∼2 nm) oxide (SiOx) at the Si/Co interface acts as a selective reaction barrier. Ion-beam mixing was instrumental in fracturing of the oxide layer, thereby allowing the silicidation reaction to proceed across the boundary during subsequent rapid thermal anneal treatments. Diffusion controlled reactions advanced rapidly in the implanted areas, while it is inhibited elsewhere. A threshold dose of 3×1015 cm−2 was required for process initiation. Four-terminal resistance test structures were formed for electrical measurements. Reported resistivity was in the range of 12 to 23±1 μΩ cm. © 2001 American Vacuum Society.
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85.40.Ls Metallization, contacts, interconnects; device isolation
85.40.Ry Impurity doping, diffusion and ion implantation technology
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation

Ion beam aperture-array lithography

Paul Ruchhoeft, J. C. Wolfe, and Robert Bass

J. Vac. Sci. Technol. B 19, 2529 (2001); http://dx.doi.org/10.1116/1.1420578 (4 pages) | Cited 14 times

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We explore a new technique, ion beam aperture-array lithography (AAL), for fabricating low cost, large area nanostructure arrays. In this approach, a broad beam of light ions illuminates a stencil mask containing a periodic array of circular apertures. The array of transmitted beamlets is moved over the substrate, thereby printing an array with the same period but arbitrary unit cell. AAL has several advantages over ion beam proximity lithography: (1) the mask pattern density is lower, (2) the unit cell patterns are defined by software, and (3) dose and shape correction can be applied to compensate for system blur. Dose optimization methods are discussed and experimental results with 150 nm apertures presented. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Limitations of focused ion beam nanomachining

C. Lehrer, L. Frey, S. Petersen, and H. Ryssel

J. Vac. Sci. Technol. B 19, 2533 (2001); http://dx.doi.org/10.1116/1.1417553 (6 pages) | Cited 27 times

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In this article, some limitations of the processing of structures with dimensions in the nanometer range by focused ion beams will be discussed. In order to enable exact depth control of nanometer structures, the effective sputter yield of silicon was determined as function of the ion dose. At ion doses below 1016 cm−2, the effective sputter yield is not constant and the volume of the area processed increases due to the implantation of ions. Material removal can be measured for doses above 2×1016 cm−2 and it reaches equilibrium for doses of about 3×1017 cm−2. This dose dependence of the effective sputter yield becomes especially effective in beam tail regions with low ion intensity. The shape of nanostructures is further determined by combining the beam shape and the angle dependence of the sputter yield which was experimentally determined. Using this approach with a Gaussian beam shape, a comparison of simulated and measured sidewall angles has shown good agreement for trench structures. Only sidewall regions close to the surface and to the bottom of deep structures show slight deviations. At the surface, non-Gaussian beam tails lead to unintentional sputtering at the corners of the processed area. At the bottom, forward scattered ions lead to higher sputter erosion. © 2001 American Vacuum Society.
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81.16.-c Methods of micro- and nanofabrication and processing
81.07.-b Nanoscale materials and structures: fabrication and characterization
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.20.Wk Machining, milling
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning

Chemically enhanced focused ion beam micromachining of copper

J. C. Gonzalez, D. P. Griffis, T. T. Miau, and P. E. Russell

J. Vac. Sci. Technol. B 19, 2539 (2001); http://dx.doi.org/10.1116/1.1418406 (4 pages) | Cited 5 times

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Chemically enhanced focused ion beam micromachining of thin film Cu on Si substrates has been investigated. Barrier layers and dielectric layers were considered as well. The gases investigated include the Cl containing examples of C2Cl4, C2H4Cl2, and CHCl2CCl3 as well as the oxygen containing gases ethanol, and methanol and water vapor. Crystallographic channeling effect results in nonuniform Cu milling, insufficient selectivity and poor end-point detection. However, the gases investigated were shown to enhance the milling homogeneity, improve the end-point detection, and provide higher selectivity. A Cu/SiO2 selectivity of greater than 4 was obtained when using ethanol as the etching gas. © 2001 American Vacuum Society.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.20.Wk Machining, milling
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning

Contact resistance of focused ion beam deposited platinum and tungsten films to silicon

Anthony J. DeMarco and John Melngailis

J. Vac. Sci. Technol. B 19, 2543 (2001); http://dx.doi.org/10.1116/1.1410094 (4 pages) | Cited 19 times

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Focused ion beam (FIB) techniques are currently being used in industry for circuit repair and rewiring in the prototyping stage. The ability to deposit a conductor directly onto silicon with a good electrical contact using the FIB methods would increase the utility of this technique in repair and circuit function diagnosis. In addition, FIB made contacts may be encountered in microelectromechanical devices (MEMS), and, when combined with FIB direct implantation, may permit local fabrication of transistors [e.g., bipolars and junction field-effect transistors (JFETs)] without conventional, planar techniques. The contact resistance of FIB-deposited platinum and tungsten onto variously doped silicon was investigated. FIB-metal contact to n+ and p+ Si was found to be ohmic after a sintering at 400 °C for 20 min in H2N2 forming gas. Individual contacts were found to vary widely in contact resistance, likely due to nonuniformity in the deposition process. Contacts to lightly doped Si were nonohmic. The contact resistance for Pt contacts to heavily doped Si was found to be on the order of 10−2 Ω cm2, and the contact resistance for W contacts on the order of 10−3 Ω cm2. It is believed that the sintering leads to formation of Pt2Si and PtSi silicides, which may interfere with the metal/semiconductor tunneling contact. Platinum silicides form around 300 °C, at the metal to silicon interface for the platinum contacts. Tungsten silicide, WSi2, forms at 650 °C and is not believed to play a part in the tungsten contact dynamics. © 2001 American Vacuum Society.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
81.15.Jj Ion and electron beam-assisted deposition; ion plating
85.40.Ls Metallization, contacts, interconnects; device isolation

GaN focused ion beam micromachining with gas-assisted etching

I. Chyr and A. J. Steckl

J. Vac. Sci. Technol. B 19, 2547 (2001); http://dx.doi.org/10.1116/1.1417550 (4 pages) | Cited 7 times

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Halide gases, such as Cl2, IBr, or ICl, are common etchant species for the etching of III nitrides and other compound semiconductor materials in plasma etching processes. We have investigated the Ga+ focused ion beam milling of GaN in conjunction with gas-assisted etching (GAE) by halide gases I2 and XeF2. We have observed that I2 and XeF2 GAE with a 30 keV Ga+ ion beam leads to significantly enhanced GaN etch rates. When these gases are utilized with appropriate ion beam scan strategies (such as ion beam current, beam dwell time, and beam overlap), we have measured GaN etch rate enhancements of 6× to 9× and 2× to 3× faster for I2 and XeF2, respectively. © 2001 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors
81.20.Wk Machining, milling
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.35.B- Structure of clean surfaces (and surface reconstruction)

Mg–Ga liquid metal ion source for implantation doping of GaN

J. Cheng and A. J. Steckl

J. Vac. Sci. Technol. B 19, 2551 (2001); http://dx.doi.org/10.1116/1.1410095 (4 pages)

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A magnesium liquid metal ion source was investigated for p-type doping of GaN. The metal is an alloy composed of 33.3% Mg and 66.7% Ga. The source type is a direct heating needle source with a spring-type reservoir, which is constructed using tungsten wire and a ceramic tube. The source has been tested and characterized in a NanoFab 150 focused ion beam (FIB) system. A typical source lifetime was 250 μA h. Mg+ ion implantation of GaN thin films has been performed at different energies between 30 and 100 keV for doses ranging from 5×1013 to 1×1015 cm−2. After Mg+ FIB implantation, samples were annealed at 1100 °C in N2 ambient. Low temperature photoluminescence with a He–Cd laser of 325 nm exhibited the donor—acceptor recombination peak, which was enhanced by the activated magnesium ions. © 2001 American Vacuum Society.
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61.72.uj III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
07.77.Ka Charged-particle beam sources and detectors
78.55.Cr III-V semiconductors
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Outline of a variable-axis lens with arbitrary shift of the axis in one direction

Peter Schmid and Harald Rose

J. Vac. Sci. Technol. B 19, 2555 (2001); http://dx.doi.org/10.1116/1.1418408 (11 pages)

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A sophisticated electrostatic “variable-axis lens” is proposed which allows an arbitrary shift of the axis in one direction. For this purpose we employ a periodic arrangement of the electrodes in a direction perpendicular to the initial axis. The excitations of the electrodes are chosen in such a way that stigmatic imaging is conserved when the axis is shifted. The purely electric field components guarantee a fast dynamic shift of both the axis and the focusing field. Owing to the translational symmetry of the arrangement, the system enables much larger displacements of the axis than the conventional “variable-axis lens.” Moreover, this concept allows the simultaneous shift of many spatially separated lenses. Since the multiple beam system avoids a common crossover of the individual beams, large total currents can be employed. © 2001 American Vacuum Society.
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41.85.Ne Electrostatic lenses, septa

Electron–electron interactions in multibeam lithography columns

M. Mankos, A. Sagle, S. T. Coyle, and A. Fernandez

J. Vac. Sci. Technol. B 19, 2566 (2001); http://dx.doi.org/10.1116/1.1420200 (6 pages) | Cited 5 times

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We have used Monte Carlo simulations to evaluate electron–electron (e–e) interactions in multibeam lithography columns. For a linear array of 32 beams with variable length from 40 to 400 μm at the photocathode, the spot size and placement were calculated for total beam currents of up to 800 nA at the substrate. In general, the e–e interactions are reduced when the linear array size is increased, therefore reducing the total beam blur. However, this is not true for placement errors induced by e–e interactions, specifically when the absolute magnitude of the error at the edge of the array is considered. We have used a multibeam test bed, equipped with a magnification stack for high spatial resolution imaging of the photoemission, to evaluate experimentally the effect of e–e interactions. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
02.70.Uu Applications of Monte Carlo methods

Stochastic Coulomb interaction effect in ion-neutralized electron-beam projection optics

Kimitoshi Takahashi, Liqun Han, R. Fabian Pease, and W. Dan Meisburger

J. Vac. Sci. Technol. B 19, 2572 (2001); http://dx.doi.org/10.1116/1.1410092 (9 pages) | Cited 2 times

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The stochastic Coulomb interaction effect in positive ion-neutralized electron-beam (e-beam) projection optics was investigated using Monte Carlo simulations. Stationary ions in the projection optics neutralize e-beam space charge without causing an unwanted increase in stochastic blur. The Coulomb interaction due to the stationary positive ions only has an effect as that of a continuum space charge. We also found that asymmetric point spreads at the field corners are due to the stochastic Coulomb interaction effect and are not a result of residual space charge effect. Methods of ion cloud generation were preliminary discussed. The ion neutralization potentially increases the throughput of an exemplary electron projection tool for 30 nm devices by a factor of 2. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Gy Chromatic and geometrical aberrations
02.70.Uu Applications of Monte Carlo methods

Progress toward a high-brightness photoemission source for multiple-electron beam lithography

S. T. Coyle, A. Fernandez, G. Janaway, A. Sagle, and M. Mankos

J. Vac. Sci. Technol. B 19, 2581 (2001); http://dx.doi.org/10.1116/1.1420202 (4 pages) | Cited 4 times

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A high-brightness photoemission source is being developed for use in a multiple-electron beam lithography system suitable for mask patterning. Cesium telluride (Cs2Te) photocathodes have achieved stable brightness of 2–3×106 A/cm2 Sr and current densities of 30–60 A/cm2. Magnesium photocathodes have achieved stable brightness of 1–3×106 A/cm2 Sr and current density of 40 A/cm2. Long term current stability of better than the required specification of 17%/5 min has been obtained at photoyields of ∼30 nA/mW. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
85.60.Ha Photomultipliers; phototubes and photocathodes
07.77.Ka Charged-particle beam sources and detectors

Recent tests of negative electron affinity photocathodes as source for electron lithography and microscopy

P. Arcuni, S. Presley, V. Aebi, and W. E. Spicer

J. Vac. Sci. Technol. B 19, 2585 (2001); http://dx.doi.org/10.1116/1.1418416 (6 pages) | Cited 2 times

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We report recent results from tests of laser driven and modulated negative electron affinity photocathodes as high-brightness electron sources. Preliminary tests used an electron column that could image the cathode surface with a resolution of less than 100 nm. We measured a current density of 2.4(±0.2) A/cm2 from an emission area with a diameter [full width at half maximum (FWHM)] of 3.5 μm. However, unwanted field emission in the gun (aided by the presence of Cs) limited the extraction field to about 1 kV/mm and negatively affected quantum efficiency and emission stability. A curve fit of the source angle with accelerating voltage gave a typical transverse energy spread of 44(±2) meV, for an extrapolated brightness at 50 kV of 1.7×106 (±0.2) A/cm2 sr. Indications that space charge above the flat cathode limited the current density are presented; a possible model is discussed. The electron gun has been redesigned for electric fields up to 7 kV/mm (where space-charge effects are unlikely) with no field emission. Lack of access to an imaging column has prevented subsequent measurements of current density and brightness. In a nonimaging column an emission current of 200(±0.4) nA, from a single emission area, has been maintained for more than a week, with no reapplication of cesium. As with other photocathodes, variations of quantum efficiency after sudden changes in illumination intensity are usually present. We suggest that competing effects of Cs mobility and electron trapping explain this behavior. Transverse energy spreads (FWHM) have been studied as a function of extracted current; 20(±5) meV at small currents (<10 nA) and 70 meV at large currents (700 nA), both from an illumination area of less than 2 μm diameter, are typical. © 2001 American Vacuum Society.
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85.60.Ha Photomultipliers; phototubes and photocathodes
85.40.Hp Lithography, masks and pattern transfer
07.77.Ka Charged-particle beam sources and detectors
29.25.Bx Electron sources
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Stability improvement at high emission densities for gold thin film photocathodes used in advanced electron beam lithography

Suresh Gosavi, J. M. McCarthy, J. L. House, Bart G. Scholte van Mast, G. Janaway, and C. N. Berglund

J. Vac. Sci. Technol. B 19, 2591 (2001); http://dx.doi.org/10.1116/1.1418414 (7 pages) | Cited 2 times

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Multi-electron beam lithography has been proposed as a promising approach to achieve high throughput for mask writing and direct wafer writing. Laser driven photocathodes represent an attractive candidate for multiple beam, high brightness sources. Thin film gold photocathodes that can be handled in air are of particular interest because of their potential for practical sources. In this article we present a study of the degradation mechanisms that change photocurrent yield for thin film gold photocathodes. Two general degradation mechanisms were studied: microstructural changes of the gold thin film and surface reactions. Observed microstructural changes included loss of gold coverage of the sapphire substrate, gold grain growth and an increase in surface roughness. A titanium adhesion layer was shown to stabilize coverage and proved stable to 700 °C by in situ transmission electron microscopy (TEM) experiments on planar sections of the Au/Ti/sapphire thin film stack photocathode. Reactions at the surface included physisorption and chemisorption of species and the subsequent reactions that occur when they diffuse to the laser illumination/electron emission site. X-ray photoelectron spectroscopy detected multiple monolayers of hydrocarbons on the surface of the Au following deposition and exposure to air. A product layer at the illumination sites as thick as 28 nm was detected using scanning electron macroscopy, atomic force microscopy and TEM following long term (1000–1200 min.) photoyield stability tests. Photoyield versus time plots for all the Au/Ti/sapphire cathodes were similar with an initial high photoyield, a drop to a minimum, then a rise to a second maximum followed by a slow 2%/h decay. Desorption of weakly bound physisorbed and chemisorbed species and growth of a reaction product layer within the electron emission zone are proposed as mechanisms to explain the photoyield behavior. Similar photoyield stability behavior was observed when Pt/Ti/sapphire photocathodes were tested. The photoyield degradation mechanisms observed in these tests are likely to be active on all thin film transmissive photocathodes subjected to high intensity illumination and will add to changes which occur when more reactive thin film photocathodes are used such as cesium telluride. Stability was improved to less than 1%/h for 16 h within the region of slow decay following the initial transient by illuminating the emission site on the cathode with high intensity UV light with a high O2 partial pressure. Emission current densities in excess of 6.0 A/cm2 were measured with a Faraday cup. Given these results, this work suggests that higher current densities and stability can be achieved. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
85.60.Ha Photomultipliers; phototubes and photocathodes

Microfabricated field emission devices using carbon nanofibers as cathode elements

M. A. Guillorn, A. V. Melechko, V. I. Merkulov, E. D. Ellis, M. L. Simpson, D. H. Lowndes, L. R. Baylor, and G. J. Bordonaro

J. Vac. Sci. Technol. B 19, 2598 (2001); http://dx.doi.org/10.1116/1.1420201 (4 pages) | Cited 21 times

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The digital electrostatic electron beam array lithography concept under development at the Oak Ridge National Laboratory proposes performing direct write electron beam lithography with a massively parallel array of electron emitters operating simultaneously within a digitally programmable microfabricated field emitter array (FEA). Recently we have concentrated our research efforts on the field emission (FE) properties of deterministically grown vertically aligned carbon nanofibers (VACNFs). We have measured the FE properties of isolated VACNFs using a moveable current probe and found that they have low FE turn-on fields and can achieve stable emission for extended periods of time in moderate vacuum. In order to use the VACNF in microfabricated FEA devices we have subjected them to a variety of processing phenomenon including reactive ion etching and plasma enhanced chemical vapor deposition, and found them to be quite robust. Using these processes we have fabricated operational gated cathode structures with single VACNFs cathodes. The issues involved in this fabrication process and the performance of these devices are discussed. © 2001 American Vacuum Society.
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85.45.Db Field emitters and arrays, cold electron emitters
81.05.U- Carbon/carbon-based materials
81.16.Nd Micro- and nanolithography
79.70.+q Field emission, ionization, evaporation, and desorption
81.07.Bc Nanocrystalline materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning

Characterization of multicusp-plasma ion source brightness using micron-scale apertures

K. L. Scott, T.-J. King, K.-N. Leung, and R. F. Pease

J. Vac. Sci. Technol. B 19, 2602 (2001); http://dx.doi.org/10.1116/1.1414019 (5 pages) | Cited 7 times

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The brightness of a multicusp-plasma ion source was characterized to determine its suitability for a proposed maskless ion-beam lithography system. In order to be competitive with similar systems utilizing electron sources, the brightness requirement must be met to satisfy throughput demands. For this requirement, 1 nA into each beam diameter of 50 nm is needed at the target plane; this implies a brightness of about 1000 A/cm2/sr at the entrance to the objective lens. The brightness of the source has been characterized using 5-μm-diam extraction apertures under two different extraction configurations: (1) with the apertures directly illuminated by the source and (2) with the apertures flooded using an extraction system. The maximum brightness achieved for either configuration was 15 A/cm2/sr at 3 keV beam energy, He+ ions, and continuous wave operation. Although this configuration falls short of the requirement for high-throughput exposures, it is also possible to operate the multicusp-plasma ion source in pulsed mode. This would give higher current densities, which may also give adequate brightness as well. © 2001 American Vacuum Society.
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29.25.Ni Ion sources: positive and negative
07.77.Ka Charged-particle beam sources and detectors
52.75.-d Plasma devices
41.75.Ak Positive-ion beams
85.40.Hp Lithography, masks and pattern transfer
41.85.Ar Particle beam extraction, beam injection

Wave optical calculations of electron probes

B. Rafferty and T. R. Groves

J. Vac. Sci. Technol. B 19, 2607 (2001); http://dx.doi.org/10.1116/1.1418412 (5 pages)

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Electron probes used in electron-beam lithography systems are pushing towards the 1 nm scale. This exceeds the limit of accuracy of conventional knife-edge measuring techniques and conventional modeling methods. The only true way to accurately model such probes as their dimensions approach the 1 nm level is to use a wave optical method. Probe sizes are commonly estimated using the root-sum-of-squares method; i.e., by summing in quadrature the individual effects of the geometrical aberrations and diffraction. This method is relatively accurate when the probe size is greater than ∼10–15 nm, but fails with probes of smaller dimensions due to the inherent erroneous assumption that the effect of individual aberrations on the probe size can be treated independently. In this article we present a method for modeling an electron probe both on and off axis using a wave optical method. This method is commonly used to calculated probe sizes in the electron microscopy community but has not been applied to e-beam lithography systems until now. The wave optical method combines the effects of all geometrical aberrations, diffraction, electron source size, and defocus while fully adhering to the physics of the probe formation process. The challenge with applying this method to an e-beam lithography system is the relatively large field size (0.1–10 mm); in electron microscopy 50 nm is considered a large field size for high-resolution work! © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.Gy Chromatic and geometrical aberrations
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Review of progress in extreme ultraviolet lithography masks

Scott Hector and Pawitter Mangat

J. Vac. Sci. Technol. B 19, 2612 (2001); http://dx.doi.org/10.1116/1.1408957 (5 pages) | Cited 21 times

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Extreme ultraviolet lithography (EUVL) is a leading next generation lithography technology. Significant progress has been made in developing mask fabrication processes for EUVL. The mask blank for EUVL consists of a low thermal expansion material substrate having a square photomask form factor that is coated with Mo/Si multilayers. SEMI standards are being developed for mask substrates and mounting. Several commercial suppliers are developing polishing processes for LTEM substrates, and they are progressing toward meeting the requirements for flatness, surface roughness, and defects defined in the a draft SEMI standard. One of the challenges in implementing EUVL is to economically fabricate multilayer-coated mask blanks with no printable defects. Significant progress has been made in developing mask blank multilayer coating processes with low added defect density. Besides lowering the added defect density, methods to reduce defect printability, such as defect compensation and buffer layer smoothing, are being developed. Experiments indicate that Mo/Si multilayers that are deposited with ion beam deposition tend to smooth substrate defects, and buffer layer films are being designed to enhance this effect. Targets for buffer layer smoothing are being defined using defect printability simulations. A method for using an electron beam to repair substrate defects after multilayer coating is also being investigated. The mask patterning process for EUVL is nearly the same as that for conventional binary optical lithography masks. EUVL mask patterning efforts are focused on developing the EUV-specific aspects of the patterning process. Eight absorbers have been evaluated against the requirements for EUVL masks, and two absorbers appear most promising. Conventional membrane pellicles are not practical for EUVL, so thermophoretic protection is being developed. Experiments have indicated that thermophoretic protection is effective for >125 nm particles down to at least 50 mTorr pressure. A removable pellicle will be used to protect the mask from defects at all times except during wafer exposure. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Optical-constant tunable (ZrO2)x/(Cr2O3)y/(Al2O3)1−x−y optical superlattices for attenuated phase shift mask in ArF lithography

F. D. Lai and L. A. Wang

J. Vac. Sci. Technol. B 19, 2617 (2001); http://dx.doi.org/10.1116/1.1408951 (4 pages)

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(ZrO2)x/(Cr2O3)y/(Al2O3)1−x−y optical superlattices composed of ten film stacks with ∼9 nm thickness in each stack, which includes the stoichiometric ZrO2, Cr2O3, and Al2O3 layers, are obtained by using rf unbalanced magnetron sputtering in an atmosphere of argon and oxygen. Binding energies of Cr 2p3/2, Al 2p3/2, and Zr 3d5/2 identified by x-ray photoelectron spectroscopy (XPS) are consistent with those of the theoretical Al2O3, Cr2O3, and ZrO2 XPS spectrum, respectively. The dielectric constants of (ZrO2)0.4/(Cr2O3)y/(Al2O3)0.6−y and (ZrO2)x/(Cr2O3)0.6/(Al2O3)0.4−x optical superlattices are illustrated to satisfy the effective medium approximation. By controlling the thickness percentage of ZrO2, Cr2O3, and Al2O3, the optical constant tunable (ZrO2)x/(Cr2O3)y/(Al2O3)1−x−y optical superlattices can meet the optical requirements of a material blank for an attenuated phase shift mask (APSM). A quadrangular area of thickness percentage of (ZrO2, Cr2O3) that meets the requirement of optical constants for an APSM blank is found to be bounded by (0, 0.25), (0, 0.45), (0.35, 0.65), and (0.45, 0.40). © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.15.Cd Deposition by sputtering
42.79.Wc Optical coatings

Prediction of placement error of extreme ultraviolet lithography mask by simulation model with equivalent layout pattern

Akira Chiba, Eiichi Hoshino, Masashi Takahashi, Hiromasa Yamanashi, Hiromasa Hoko, Byoung Taek Lee, Takashi Yoneda, Masaaki Ito, Taro Ogawa, and Shinji Okazaki

J. Vac. Sci. Technol. B 19, 2621 (2001); http://dx.doi.org/10.1116/1.1414020 (5 pages)

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An equivalent modeling technique for estimating the deformation of extreme ultraviolet lithography (EUVL) masks caused by a complex pattern layout has been developed. An equivalent layout pattern (ELP) model provides a means of investigating ways of improving pattern placement accuracy. The simulation model is based on the finite difference method. In order to investigate the possibility of making EUVL masks with a high pattern placement accuracy, the ELP model was used to simulate how pattern density and substrate thickness affect placement error. The results obtained agree well with those for an exact model, with the relative error being at most 4%. They suggest that, when the stresses of the multilayer and absorber films cannot be reduced, it may be useful to increase the substrate thickness to improve the pattern placement accuracy. In addition, when the exposure field covers two chips, the placement error should be reduced through proper control of the stress of the absorber film rather than by changing the absorber coverage. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
85.30.De Semiconductor-device characterization, design, and modeling
02.70.Bf Finite-difference methods

Predicting pattern-specific distortions induced during optical mask patterning

J. Sohn, R. L. Engelstad, and E. G. Lovell

J. Vac. Sci. Technol. B 19, 2626 (2001); http://dx.doi.org/10.1116/1.1408956 (5 pages) | Cited 1 time

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All mask-related distortions must be minimized in order to meet the stringent error budgets for sub-100 nm lithography. Thermomechanical distortions during mask patterning are one source of image placement errors and may potentially consume a relatively large portion of the overlay error budget. This article investigates the thermomechanical distortions of an optical mask during electron-beam patterning. Pattern-specific distortions have been predicted for actual static random access memory layouts using numerical simulations. Finite element simulation results are presented illustrating the temperature rise and final in-plane distortion vector fields for those layouts. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
84.30.Sk Pulse and digital circuits
02.70.Dh Finite-element and Galerkin methods

Distortion correction in adaptive membrane masks

X. Zhuang and M. Feldman

J. Vac. Sci. Technol. B 19, 2631 (2001); http://dx.doi.org/10.1116/1.1408955 (4 pages) | Cited 2 times

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Image placement accuracy is a limiting factor for all of the next generation lithographies (NGLs). Previous work has shown that thermally induced displacements can improve image placement in membrane masks, compensating errors on the mask as well as errors already printed on the wafer. Consequently, such “adaptive” masks may find applications even in NGLs that do not presently use membrane masks. We have modeled the thermal distributions needed to compensate arbitrary mask distortions both for full-field and scanned exposures. For full field, the membrane is divided into an array of individual heating zones. We find that a 6×6 array is adequate to minimize many slowly varying distortions, and that even better results are obtained with a 12×12 array. The computation for the 6×6 array takes a few seconds on a personal computer. For a scanned exposure, e.g., an x-ray beam on a storage ring, only the line being exposed must be corrected at any given time. This minimizes the heat load on the mask, as well as permitting a simple Fourier analysis. Detailed procedures for both methods of correction are presented. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
02.30.Nw Fourier analysis

Writing, repairing, and inspecting of extreme ultraviolet lithography reticles considering the impact of the materials

J. R. Wasson, B. Lu, P. J. S. Mangat, K. Nordquist, and D. J. Resnick

J. Vac. Sci. Technol. B 19, 2635 (2001); http://dx.doi.org/10.1116/1.1408958 (6 pages) | Cited 2 times

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Extreme ultraviolet lithography (EUVL) is the leading candidate for next generation lithography with the potential for extendibility beyond the 50 nm node. Selecting the proper materials for the absorber stack directly impacts one’s ability to conduct effective electron beam patterning, focused ion beam repair, and inspection of an EUVL reticle. An attempt to define the optimal absorber stack based on the interaction of electrons, ions, and photons with the absorber stack is studied from the perspective of patterning, repair, and inspection of EUVL reticles, respectively. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Thermomechanical distortions of the PREVAIL mask system during exposure

P.-T. Lee, C. Martin, R. Engelstad, E. G. Lovell, C. Robinson, and A. Flamholz

J. Vac. Sci. Technol. B 19, 2641 (2001); http://dx.doi.org/10.1116/1.1409385 (5 pages) | Cited 2 times

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All next-generation lithography (NGL) technologies will be faced with meeting the stringent error budgets for the sub-100 nm regime. One of the major contributors to overlay error in NGL masks is the thermomechanical distortions induced during exposure. The focus of this research is to identify the thermal and structural response of the PREVAIL mask system under typical exposure conditions. Three-dimensional finite element (FE) models were used to simulate the thermomechanical response of the 100 mm PREVAIL prototype mask. Due to the relative size of the pattern features, equivalent modeling techniques were employed for computational expedience. Equivalent thermal properties such as thermal conductivity and thermal emissivity were calculated for the perforated membrane as functions of the void fraction. The resulting mask temperature distributions were used as input into the FE structural model, where equivalent stiffness properties were employed to determine the corresponding thermal displacements. The stitching errors between adjacent subfields were also investigated in this article. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
02.70.Dh Finite-element and Galerkin methods
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Simulating the response of electron-beam projection lithography masks under standardized mounting techniques

C.-f. Chen, R. L. Engelstad, E. G. Lovell, and A. E. Novembre

J. Vac. Sci. Technol. B 19, 2646 (2001); http://dx.doi.org/10.1116/1.1409386 (6 pages) | Cited 5 times

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The mounting standard based upon a proposed four-pad electrostatic chuck for the 200 mm PREVAIL and SCALPEL® masks was assessed to support the electron-beam projection lithography (EPL) mask standardization process. Using numerical simulations, comparative studies were performed to investigate the mask response during fabrication, pattern transfer, and mounting, employing the IBM Falcon/Nighteagle layout as a pattern-specific design for both EPL masks. The results indicated that consistent mounting schemes in the e-beam writer and exposure tool minimized the in-plane distortion (IPD). The proposed chucking configuration appeared to be robust for both EPL technologies for controlling IPD. With additional support enhancement beneath the major strut across the center of the grillage area of the mask, the IPD can be reduced to negligible values. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Simulating the effects of pattern density gradients on electron-beam projection lithography pattern transfer distortions

P. L. Reu, R. L. Engelstad, E. G. Lovell, C. K. Magg, M. J. Lercel, and R. S. Mackay

J. Vac. Sci. Technol. B 19, 2652 (2001); http://dx.doi.org/10.1116/1.1409387 (7 pages) | Cited 4 times

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The development of a low-distortion mask is critical to the success of the sub-0.1 μm lithography technologies. Electron-beam projection lithography (EPL) is one of the potential candidates for next-generation lithography. In order to minimize mask image placement (IP) errors, it is important to understand the factors that induce pattern distortions during mask fabrication and pattern transfer. The fabrication process flows for two EPL mask formats were numerically simulated and experimentally assessed for IP. This study included continuous membranes and stencil membranes for 1 mm ×1 mm and 1 mm ×12 mm window sizes on a 4 in. wafer. Both intramembrane (i.e., within a single window) and intermembrane (i.e., cross-mask) results are reported with excellent correlation between the finite element (FE) data and the experimental measurements. In this article details of the FE simulations are presented; an article by (M. Lercel et al., J. Vac. Sci. Technol. B, these proceedings) describes the corresponding experimental work. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
02.70.Dh Finite-element and Galerkin methods

Pattern placement correction methodology for 200 mm SCALPEL masks

L. E. Ocola, R. C. Farrow, R. J. Kasica, C. G. Caminos, L. Rutberg, R. F. Fullowan, K. Teffeau, M. I. Blakey, M. L. Peabody, C. S. Knurek, G. R. Bogart, A. E. Novembre, J. A. Liddle, M. Lercel, C. Magg, et al.

J. Vac. Sci. Technol. B 19, 2659 (2001); http://dx.doi.org/10.1116/1.1412891 (6 pages)

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Methods for correcting pattern placement errors found on SCALPEL™ masks are addressed. The methodology and implementation of individual membrane image placement correction is presented, showing its advantages over the global image placement correction method. Local image placement corrections are possible by the unique capability of electron projection lithography (EPL) tools to correct placement errors with electron optical components during exposure while addressing each individual mask membrane. Data of pattern placement on a series of 200 mm SCALPEL masks from different sources was collected. Within the mask set and patterning tools used, the placement errors are similar for all masks regardless of source. Local image placement corrections can reduce placement errors to less than 14 nm, which is less than the 20 nm budget allocated for 100 nm node lithography. Implementation of local image placement correction will permit EPL lithography to be ready for sub-100 nm node lithography without the need to burden existing mask writers on severely stringent pattern placement tolerances or chucking procedures. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
41.85.-p Beam optics

Mechanical, geometrical, and electrical characterization of silicon membranes for open stencil masks

E. Sossna, A. Degen, I. W. Rangelow, M. Drzik, P. Hudek, T. E. Tiwald, and J. A. Woollam

J. Vac. Sci. Technol. B 19, 2665 (2001); http://dx.doi.org/10.1116/1.1417548 (6 pages) | Cited 1 time

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Silicon membranes are used for stencil masks which are key to charged particle projection lithography, particularly for ion projection lithography, electron beam projection. Quantitative and qualitative determination of the mechanical properties of the true thickness, thickness variations (morphology), electrical conductivity and stress is critical to the development of next generation lithography. The metrology setup includes high accuracy thickness, refractive index and electrical conductivity measurement based on infrared variable angle spectroscopic ellipsometry, thickness variation characterization based on the Fizeau interferometric scheme and mechanical stress evaluation based on a novel double bulging technique. © 2001 American Vacuum Society.
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68.60.Bs Mechanical and acoustical properties
81.05.Cy Elemental semiconductors
85.40.Hp Lithography, masks and pattern transfer
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
78.66.Db Elemental semiconductors and insulators
68.55.-a Thin film structure and morphology
72.80.Cw Elemental semiconductors
73.61.Cw Elemental semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance

Patterning-induced image placement distortions on electron beam projection lithography membrane masks

Michael Lercel, Christopher Magg, Mark Lawliss, Carey Williams, Neal Caldwell, Robin Ackel, Louis Kindt, Kenneth Racette, Phillip Reu, Roxann Engelstad, and R. Scott Mackay

J. Vac. Sci. Technol. B 19, 2671 (2001); http://dx.doi.org/10.1116/1.1409381 (7 pages) | Cited 3 times

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Membrane masks are needed for charged particle lithography and can include both stencil masks and masks with thin continuous membranes. Producing accurate image placement on membrane masks requires careful control of mask shape, pattern writing, and stress control of the mask materials. Pattern density and pattern density gradients also affect image placement (IP) control. This article discusses IP distortions on electron projection lithography masks caused by patterning the imaging layers with low and high density patterns and patterns with large gradients in the density. The process-induced distortion has been found to be largest with the largest vector distortion at the boundary when high pattern density gradients are present. The anisotropic stiffness of the unit cell also affects the process-induced distortion. Qualitatively, the results between continuous membrane and stencil masks show similar characters. The results provide distortion information that could be used to determine the maximum allowable membrane stress (for stencil masks) and scatterer layer stress (for continuous membrane masks) to meet necessary mask production targets. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
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Development of 157 nm positive resists

H. Ito, G. M. Wallraff, N. Fender, P. J. Brock, W. D. Hinsberg, A. Mahorowala, C. E. Larson, H. D. Truong, G. Breyta, and R. D. Allen

J. Vac. Sci. Technol. B 19, 2678 (2001); http://dx.doi.org/10.1116/1.1415512 (7 pages) | Cited 14 times

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For adequate transparency we have selected hexafluoroisopropanol as an acid group and an α-trifluoromethylacrylic moiety as a repeat unit of our 157 nm resist polymers. The hexafluoroalcohol group is bound to norbornene or styrene. Four platforms are currently available to us: (1) all-acrylic, (2) all-alicyclic, (3) acrylic-alicyclic, and (4) acrylic-aromatic systems. While the all-alicyclic (all-norbornene) polymers are synthesized by transition-metal-initiated addition polymerization, all other polymers involving α-trifluoromethylacrylic monomers are prepared by conventional radical copolymerization. Characterization of the polymers and preliminary lithographic evaluation are reported. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
82.35.-x Polymers: properties; reactions; polymerization

Characterization and modeling of volumetric and mechanical properties for step and flash imprint lithography photopolymers

Matthew Colburn, Itai Suez, Byung Jin Choi, Mario Meissl, Todd Bailey, S. V. Sreenivasan, John G. Ekerdt, and C. Grant Willson

J. Vac. Sci. Technol. B 19, 2685 (2001); http://dx.doi.org/10.1116/1.1420199 (5 pages) | Cited 24 times

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Step and flash imprint lithography (SFIL) is an alternative approach to high-resolution patterning based on a bilayer imprint scheme. SFIL utilizes the in situ photopolymerization of an oxygen etch resistant monomer solution in the topography of a template to replicate the template pattern on a substrate. The SFIL replication process can be affected significantly by the densification associated with polymerization and by the mechanical properties of the cured film. The densities of cured photopolymers were determined as a function of pendant group volume. The elastic moduli of several photopolymer samples were calculated based on a Hertzian fit to force–distance data generated by atomic force microscopy. The current SFIL photopolymer formulation undergoes a 9.3% (v/v) densification. The elastic modulus of the SFIL photopolymer is 4 MPa. The densification and the elastic modulus of the photopolymer layer can be tailored from 4% to 16%, and from 2 to 30 MPa, respectively, by changing the structure of the photopolymer precursors and their formulation. The complex interaction among densification, mechanical properties (elastic modulus and Poisson’s ratio) and aspect ratio (height:width) was studied by finite element modeling. The effect of these parameters on linewidth, sidewall angle, and image placement was modeled. The results indicate that the majority of densification occurs by shrinkage in the direction normal to the substrate surface and that Poisson’s ratio plays a critical role in defining the shape of the replicated features. Over the range of material properties that were determined experimentally, volumetric contraction of the photopolymer is not predicted to adversely affect either pattern placement or sidewall angle. © 2001 American Vacuum Society.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
82.50.-m Photochemistry
82.35.-x Polymers: properties; reactions; polymerization
85.40.Hp Lithography, masks and pattern transfer
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Thin film confinement effects on the thermal properties of model photoresist polymers

Christopher L. Soles, Eric K. Lin, Joseph L. Lenhart, Ronald L. Jones, Wen-li Wu, Darío L. Goldfarb, and Marie Angelopoulos

J. Vac. Sci. Technol. B 19, 2690 (2001); http://dx.doi.org/10.1116/1.1415502 (4 pages) | Cited 12 times

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The demand to print increasingly smaller microelectronic device features means that the thickness of the polymer films used in the lithographic processes must decrease. The thickness of these films is rapidly approaching the unperturbed dimensions of the polymer, length scales at which confinement deviations and dewetting are a significant concern. We combine specular x-ray reflectivity (SXR) and incoherent neutron scattering (INS) to probe the thermal stability and dynamical effects of thin film confinement in poly(hydroxy styrene) (PHS), a polymer used in a majority of the 248 nm deep UV photoresists. PHS forms stable thin films (down to 5 nm) that do not dewet over a wide temperature range on Si surfaces ranging from hydrophilic to hydrophobic. The surface energy has a profound influence on the magnitude of the thin film expansion coefficient, especially above the glass transition, in films as thick as 100 nm. Confinement also appears to suppress the mean-square atomic displacements and the level of anharmonicity in the dynamics, primarily above the bulk glass transition. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
68.60.Dv Thermal stability; thermal effects
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
63.50.-x Vibrational states in disordered systems

Characterization and simulation of surface and line-edge roughness in photoresists

V. Constantoudis, E. Gogolides, G. P. Patsis, A. Tserepi, and E. S. Valamontes

J. Vac. Sci. Technol. B 19, 2694 (2001); http://dx.doi.org/10.1116/1.1420582 (5 pages) | Cited 6 times

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The problem of surface and line-edge roughness characterization and prediction is discussed. Different roughness parameters, such as the root mean square deviation (rms or σ), the fractal dimension, and the Fourier spectrum, are presented and compared. These roughness parameters for three negative tone resists (wet and plasma developed) are analyzed versus exposure dose, photoacid generator concentration, and plasma development conditions. Finally, a molecular type simulator is used to predict the experimental roughness behavior. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Confinement effects on the spatial extent of the reaction front in ultrathin chemically amplified photoresists

Darío L. Goldfarb, Marie Angelopoulos, Eric K. Lin, Ronald L. Jones, Christopher L. Soles, Joseph L. Lenhart, and Wen-li Wu

J. Vac. Sci. Technol. B 19, 2699 (2001); http://dx.doi.org/10.1116/1.1421559 (6 pages) | Cited 6 times

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Sub-100 nm lithography poses strict requirements on photoresist material properties and processing conditions to achieve necessary critical dimension control of patterned structures. As resist thickness and feature linewidth decrease, fundamental materials properties of the confined resist polymer can deviate from bulk values and impact important processing parameters such as the postexposure bake (PEB) temperature. The effects of these confinement-induced deviations on image or linewidth spread have not been explored. In this work, we characterize the resist thickness dependence of the spatial extent of the reaction-diffusion process in a chemically amplified photoresist system under varying processing conditions. Bilayer samples are prepared with a lower layer of a protected polymer (p-tert-butoxycarboxystyrene) and a top layer of a de-protected polymer [poly(4-hydroxystyrene)] loaded with a photoacid generator. After flood exposure, PEB, and development, changes in the thickness of the protected polymer provide a measure of the spatial extent of the reaction front between the polymer layers. The velocity of the reaction front is significantly reduced with decreasing thickness of the protected polymer layer under identical processing conditions. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
82.35.Gh Polymers on surfaces; adhesion
82.40.Ck Pattern formation in reactions with diffusion, flow and heat transfer
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.50.Nd Control of photochemical reactions

Characterization of fluoropolymers for 157 nm chemically amplified resist

Toshiro Itani, Minoru Toriumi, Takuya Naito, Seiichi Ishikawa, Seiro Miyoshi, Tamio Yamazaki, and Manabu Watanabe

J. Vac. Sci. Technol. B 19, 2705 (2001); http://dx.doi.org/10.1116/1.1412889 (4 pages) | Cited 4 times

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Fluoropolymers were characterized for 157 nm lithography resist. We obtained superior optical transparencies, with absorption coefficient of 0.01–2 μm−1 at 157 nm wavelength. The resists based on the fluoropolymers characterized exhibited suitable dissolution behavior into alkaline developer of 0.26 N tetramethylammonium hydroxide solution. Dry-etching resistance of the resist film showed the almost equivalent to conventional ArF resist based on an acrylic polymer. The lithographic evaluation showed that high sensitivities of 1.0–10.0 mJ/cm2 for 157 nm exposure, and high dissolution contrast. Furthermore, the resolution capability of 95 nm lines and spaces was obtained with proper pattern profiles. These results indicate that 157 nm resist based on fluoropolymers we characterized have enough potential for practical use of 157 nm lithography. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Supercritical resist drying for isolated nanoline formation

Hideo Namatsu

J. Vac. Sci. Technol. B 19, 2709 (2001); http://dx.doi.org/10.1116/1.1418411 (4 pages) | Cited 19 times

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Supercritical resist drying enables the formation of fine resist patterns with a nanometer-scale resolution. Fine isolated and dense lines of resist collapse when dried by conventional methods after development, thereby lowering the useful resolution of resist patterns. For nanolines, the collapse is due to the swelling of the resist that results from development and rinsing. To prevent collapse, the cause of the swelling must be removed from the resist before drying. The use of supercritical fluid is the most suitable way to do that because such fluid has a diffusion coefficient as large as that of a gas. Supercritical resist drying with carbon dioxide prevents the collapse of isolated lines and enables the formation of nanolines with a width of about 7 nm and a high aspect ratio of over 10 in the case of the negative tone resist of hydrogen silsesquioxane and 100 kV electron beams. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Linewidth reduction using liquid ashing for sub-100 nm critical dimensions with 248 nm lithography

A. G. Timko, J. Frackoviak, L. C. Hopkins, F. P. Klemens, L. E. Trimble, O. Nalamasu, G. P. Watson, W. M. Mansfield, D. Barr, and J. Li

J. Vac. Sci. Technol. B 19, 2713 (2001); http://dx.doi.org/10.1116/1.1412892 (4 pages) | Cited 1 time

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The need for sub-100 nm semiconductor devices has driven our industry to develop new resists, exposure tools (248 nm, 193 nm, extreme ultraviolet, SCALPEL, etc.), mask technologies, and processing procedures. An enormous amount of research has gone into every aspect of the semiconductor device fabrication process and new techniques to further reduce the critical dimensions need to be investigated. The work that is reported on in this article identifies a process that is referred to as liquid ashing. Liquid ashing is a novel approach to linewidth reduction of resist features patterned with positive 248 nm deep-ultraviolet (DUV) resists. The lashing process reduces linewidth through the use of a second wet development step. This process is isotropic and can be continued once started. A bake prior to the second development improves process control. Various types of phase-shifted patterns have been measured and evaluated to determine the effectiveness of this process. This process has been exercised using different resists, different developers, and several different integrated circuit (IC) test patterns. Linewidth reduction using liquid ashing is controllable, does not increase linewidth variations, and can be accomplished using existing equipment. The process was evaluated with IC test patterns that were printed using attenuated phase shifted mask technology generated photo masks and conventional DUV processes. Scanning electron microscopy was used to obtain critical dimension data and cross-sectional information. Features, ranging from 120 to 280 nm in size were reduced by 60 nm at a controllable rate of approximately 1.25 nm/s. Transistor gates as small as 60 nm have been formed in 248 nm DUV resist and successfully transferred while maintaining >85° wall profile. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
85.30.Tv Field effect devices
81.65.Cf Surface cleaning, etching, patterning
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Hands-on tools for nanotechnology

A. Seeger, S. Paulson, M. Falvo, A. Helser, R. M. Taylor, R. Superfine, and S. Washburn

J. Vac. Sci. Technol. B 19, 2717 (2001); http://dx.doi.org/10.1116/1.1412890 (6 pages) | Cited 1 time

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We describe some mechanical and electrical measurements on carbon nanotubes. We discuss electron beam lithography techniques to form metal wire contacts to the as-found nanometer structures. Starting from a unique collaborative perspective, we suggest some improved design and alignment methods. © 2001 American Vacuum Society.
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85.35.Kt Nanotube devices
81.07.De Nanotubes
81.16.Nd Micro- and nanolithography
81.16.Ta Atom manipulation

“NANOJET”: Tool for the nanofabrication

I. W. Rangelow, J. Voigt, and K. Edinger

J. Vac. Sci. Technol. B 19, 2723 (2001); http://dx.doi.org/10.1116/1.1415504 (4 pages) | Cited 4 times

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A tool for pattern generation and microfabrication based on scanning micro/nanonozzle is presented. Electrically neutral radicals created in a plasma discharge are pumped through a small tube tapered to a nozzle. A small distance between the nozzle and the surface of the substrate allows a localized interaction. A description of the tool and principles of this technology, such as transport of free radicals through a high aspect ratio hollow tip, localized etching and high etching rates without ion bombardment are demonstrated in this work. This article presents the fundamental aspects and the experimental proofs of the outlined nanofabrication technique. © 2001 American Vacuum Society.
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07.79.Lh Atomic force microscopes
81.16.Rf Micro- and nanoscale pattern formation
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning

Investigation of radical–surface reactions

J. Voigt and I. W. Rangelow

J. Vac. Sci. Technol. B 19, 2727 (2001); http://dx.doi.org/10.1116/1.1414014 (5 pages)

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Investigations on some aspects of thermal etching of silicon and polymer substrates are presented. Microscopic mechanisms of thermal degradation of substrate materials commonly applied in microelectronics and microsystem technology by means of radical containing downstream plasma are examined. The role of molecular constituents of the downstream gas flow for the etching process is considered in detail. Transport of free radicals through very high aspect ratio structures is demonstrated experimentally and interpreted in theory. Investigations presented here were performed by means of the Nanojet setup (reported in this volume). © 2001 American Vacuum Society.
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82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Electron induced chemical nanolithography with self-assembled monolayers

W. Geyer, V. Stadler, W. Eck, A. Gölzhäuser, M. Grunze, M. Sauer, T. Weimann, and P. Hinze

J. Vac. Sci. Technol. B 19, 2732 (2001); http://dx.doi.org/10.1116/1.1421560 (4 pages) | Cited 29 times

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We demonstrate a simple scheme to generate chemical surface nanostructures. Electron-beam writing is used to locally modify the terminal nitro functionality in self-assembled monolayers of 4′-nitro-1,1′-biphenyl-4-thiol to amino groups, while the underlying aromatic layer is dehydrogenated and cross linked. Using low energy electron proximity printing and conventional electron-beam lithography with a beam energy of 2.5 keV and doses from 2500 to 50 000 μC/cm2, templates of reactive amino sites with lateral dimensions down to ∼20 nm could be fabricated. The templates were used for the surface immobilization of fluorinated carboxylic acid anhydrides and rhodamine dyes. The molecular structures were then imaged and analyzed by atomic force and scanning confocal fluorescence microscopy. © 2001 American Vacuum Society.
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81.16.Dn Self-assembly
81.16.Nd Micro- and nanolithography
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
81.07.-b Nanoscale materials and structures: fabrication and characterization
85.40.Hp Lithography, masks and pattern transfer
82.40.Np Temporal and spatial patterns in surface reactions

Electrostatic self assembly of nanocomposite polymers in grating structures

Xing Cheng and L. Jay Guo

J. Vac. Sci. Technol. B 19, 2736 (2001); http://dx.doi.org/10.1116/1.1420530 (5 pages) | Cited 2 times

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Electrostatic self-assembly (ESA) is a layer-by-layer approach to synthesize nanocomposite materials with desired functionalities. Thin films with nonlinear optical properties can be deposited by ESA. Although ESA is a versatile technique, it involves laborious and time-consuming deposition steps for practical device applications. We explored the ESA of nanocomposite polymers with nonlinear optical properties in grating structures to create thick films suitable for photonic device applications. We have achieved uniform growth of ESA on the sidewalls of the oxide grating. We proposed an electro-optic modulator configuration based on the Mach–Zehnder interferometer that can make use of the developed method. For nanofabrication, the lateral growth of ESA film on the pattern sidewalls is also potentially useful for creating nanoscale feature sizes with molecular level control. © 2001 American Vacuum Society.
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81.16.Dn Self-assembly
81.07.Bc Nanocrystalline materials
42.70.Jk Polymers and organics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.79.Hp Optical processors, correlators, and modulators
42.79.Dj Gratings
81.16.Rf Micro- and nanoscale pattern formation
82.35.Ej Nonlinear optics with polymers

Lithographically induced self-assembly of microstructures with a liquid-filled gap between the mask and polymer surface

Paru Deshpande and Stephen Y. Chou

J. Vac. Sci. Technol. B 19, 2741 (2001); http://dx.doi.org/10.1116/1.1414015 (4 pages) | Cited 9 times

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We have observed that a featureless polymer thin film on a flat plate that is separated from another flat plate by a liquid filled gap can self-assemble into a periodic micropillar array. Moreover, we have observed that if there is a pattern on one of the plates, the boundary of the pillar array will align with the boundary of the pattern resulting in single domain arrays. The phenomenon is believed to be due to the unstable growth of surface waves in the polymer system caused by an attractive Coulombic interaction between the top plate and polymer. A transition temperature has been found below which ordered patterns are not observed in the bilayer system. This self-assembled phenomenon suggests a novel way of controlling flow in microfluidic devices. © 2001 American Vacuum Society.
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07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
61.41.+e Polymers, elastomers, and plastics
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.20.Wk Machining, milling
81.65.Ps Polishing, grinding, surface finishing
47.85.Np Fluidics

Nanoscale modification of electronic states of graphite by highly charged Ar-ion irradiation

T. Meguro, A. Hida, M. Suzuki, Y. Koguchi, H. Takai, Y. Yamamoto, K. Maeda, and Y. Aoyagi

J. Vac. Sci. Technol. B 19, 2745 (2001); http://dx.doi.org/10.1116/1.1421549 (4 pages) | Cited 4 times

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This article describes a new nanomodification technique of electronic states. This technique involves highly charged ion (HCI) irradiation on the solid surface. The high potential energy of slow HCI, which induces multiple emission of electrons from the surface, provides a strong modification of the electronic states of the local area of surfaces. This unique process, induced by approaching slow HCI, converts metallic highly oriented pyrolytic graphite to a nonconductive structure, indicating the transformation of sp2 graphite to an sp3 nanoscale diamond-like structure. © 2001 American Vacuum Society.
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73.20.At Surface states, band structure, electron density of states
81.05.U- Carbon/carbon-based materials
68.35.Rh Phase transitions and critical phenomena
81.16.Rf Micro- and nanoscale pattern formation
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
72.60.+g Mixed conductivity and conductivity transitions

High-Q photonic crystal microcavities fabricated in a thin GaAs membrane

C. Reese, B. Gayral, B. D. Gerardot, A. Imamoǧlu, P. M. Petroff, and E. Hu

J. Vac. Sci. Technol. B 19, 2749 (2001); http://dx.doi.org/10.1116/1.1412893 (4 pages) | Cited 16 times

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We report on the fabrication of photonic crystal microcavities in GaAs having H1 and H2 defects for lattice constants as small as 255 nm. In H2 microcavities, we observed resonances with Q factors as high as 4000. The degeneracy of these high-Q modes is lifted by the imperfect nature of the fabrication process. © 2001 American Vacuum Society.
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42.70.Qs Photonic bandgap materials
42.82.Cr Fabrication techniques; lithography, pattern transfer
78.55.Cr III-V semiconductors
78.67.Hc Quantum dots
81.65.Cf Surface cleaning, etching, patterning
81.07.Ta Quantum dots
42.50.-p Quantum optics

Patterning processes for fabricating sub-100 nm pseudo-spin valve structures

Bernhard Vögeli, Henry I. Smith, Fernando J. Castaño, Susumu Haratani, Yaowu Hao, and C. A. Ross

J. Vac. Sci. Technol. B 19, 2753 (2001); http://dx.doi.org/10.1116/1.1415507 (4 pages) | Cited 11 times

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Interference lithography (IL) was used to pattern sputtered Co/Cu/NiFe layers into large-area arrays of pseudo-spin valve (PSV) elements. In order to precisely control size, aspect ratio, and shape uniformity of the elements, three methods of increasing complexity were developed. Pattern transfer was achieved by reactive-ion etching and ion milling, and was found to maintain the multilayered structure of the PSV film. The switching field of the PSV elements, and the remanent state, varied with the aspect ratio as expected. Furthermore, IL was employed to fabricate magnetic random access memory-type structures. Both sense and word lines were conductive, and the buried PSV elements had similar magnetic properties to PSV elements patterned in large-area arrays. © 2001 American Vacuum Society.
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85.75.Bb Magnetic memory using giant magnetoresistance
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.47.De Giant magnetoresistance
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Infrared frequency selective surfaces fabricated using optical lithography and phase-shift masks

S. J. Spector, D. K. Astolfi, S. P. Doran, T. M. Lyszczarz, and J. E. Raynolds

J. Vac. Sci. Technol. B 19, 2757 (2001); http://dx.doi.org/10.1116/1.1420198 (4 pages) | Cited 14 times

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A frequency selective surface (FSS) structure has been fabricated for use in a thermophotovoltaic system. The FSS provides a means for reflecting the unusable light below the band gap of the thermophotovoltaic cell while transmitting the usable light above the band gap. This behavior is relatively independent of the light’s incident angle. The fabrication of the FSS was done using optical lithography and a phase-shift mask. The FSS cell consisted of circular slits spaced by 1100 nm. The diameter and width of the circular slits were 870 and 120 nm, respectively. The FSS was predicted to pass wavelengths near 7 μm and reflect wavelengths outside of this pass band. The FSSs fabricated performed as expected with a pass band centered near 5 μm. © 2001 American Vacuum Society.
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84.60.Jt Photoelectric conversion
85.40.Hp Lithography, masks and pattern transfer

Focused ion beam patterned Hall bars and Ohmic columns embedded in molecular-beam-epitaxial-grown GaAs/AlGaAs

S. Vijendran, P. See, A. Ahmed, H. E. Beere, G. A. C. Jones, and C. E. Norman

J. Vac. Sci. Technol. B 19, 2761 (2001); http://dx.doi.org/10.1116/1.1421556 (5 pages) | Cited 1 time

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Focused ion beam lithography combined with molecular-beam-epitaxial growth can be a useful tool for the formation of real-time patterned, embedded structures. For this purpose, sub-50 eV ion beams are essential to minimize ion induced damage and to ensure vertical localization of the deposited ions. The simultaneous patterning of a beam of dopant ions during wafer growth allows the realization of three-dimensional structures with doping profiles otherwise unattainable through conventional methods. This article reports on the successful fabrication of focused ion beam patterned Hall bars in epitaxially grown bulk GaAs and GaAs/AlGaAs heterostructures. The bulk Si2+ doped sample achieved a 77 K mobility of 4000 cm2 V−1 s−1 for a carrier concentration of 3.4×1017 cm−3 while the heterostructure showed a 1.5 K mobility of 1.8×105 cm2 V−1 s−1 at a carrier density of 5.5×1011 cm−2. It is also demonstrated that in situ device patterning reduces the number of required ex situ processing steps while maintaining the high quality of molecular-beam epitaxially grown material. Furthermore, the development of in-grown ohmic contact columns to buried structures is presented. A proposed three dimensionally integrated circuit and future applications of this new technology are also discussed. © 2001 American Vacuum Society.
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72.20.My Galvanomagnetic and other magnetotransport effects
73.40.Ns Metal-nonmetal contacts
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
85.40.Hp Lithography, masks and pattern transfer
81.05.Ea III-V semiconductors
61.72.S- Impurities in crystals

New photon detector for device analysis: Superconducting single-photon detector based on a hot electron effect

Seema Somani, Steven Kasapi, Kenneth Wilsher, William Lo, Roman Sobolewski, and Gregory Gol’tsman

J. Vac. Sci. Technol. B 19, 2766 (2001); http://dx.doi.org/10.1116/1.1412899 (4 pages) | Cited 22 times

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A novel superconducting single-photon detector (SSPD), intrinsically capable of high quantum efficiency (up to 20%) over a wide spectral range (ultraviolet to infrared), with low dark counts (<1 cps), and fast (<40 ps) timing resolution, is described. This SSPD has been used to perform timing measurements on complementary metal–oxide–semiconductor integrated circuits (ICs) by detecting the infrared light emission from switching transistors. Measurements performed from the backside of a 0.13 μm geometry flip–chip IC are presented. Other potential applications for this detector are in telecommunications, quantum cryptography, biofluorescence, and chemical kinetics. © 2001 American Vacuum Society.
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85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
85.30.Tv Field effect devices
85.25.Oj Superconducting optical, X-ray, and γ-ray detectors (SIS, NIS, transition edge)
85.40.Qx Microcircuit quality, noise, performance, and failure analysis

Fabrication of single and coupled quantum dots in single-wall carbon nanotubes

Masaki Suzuki, Koji Ishibashi, Tetsuya Ida, Daiju Tsuya, Kenichirou Toratani, and Yoshinobu Aoyagi

J. Vac. Sci. Technol. B 19, 2770 (2001); http://dx.doi.org/10.1116/1.1415505 (5 pages) | Cited 16 times

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We describe our recent experimental results on the fabrication of single and coupled quantum dots in single-wall carbon nanotubes (SWNTs). As well as our standard method to fabricate electrical contacts on individual SWNTs, an attempt to position them at a desired place is described. For the coupled quantum dot formation a SiO2 layer has been deposited on top of SWNTs, and the transport result which suggests their formation is shown. © 2001 American Vacuum Society.
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73.63.Kv Quantum dots
81.07.De Nanotubes
73.63.Fg Nanotubes
81.07.Ta Quantum dots
81.16.Nd Micro- and nanolithography
85.35.Kt Nanotube devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Nanofabrication of two-dimensional photonic crystal mirrors for 1.5 μm short cavity lasers

T. D. Happ, A. Markard, M. Kamp, A. Forchel, S. Anand, J.-L. Gentner, and N. Bouadma

J. Vac. Sci. Technol. B 19, 2775 (2001); http://dx.doi.org/10.1116/1.1412898 (4 pages) | Cited 17 times

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We have developed a fabrication scheme for two-dimensional (2D) triangular photonic crystals (PCs) on InP-based material systems involving high resolution electron beam lithography, pattern transfer to a SiO2 etch mask, and a Cl2/Ar electron cyclotron resonance reactive ion etch step yielding PCs with periods of a=300–450 nm and air fill factors of f=18%–63%. These PCs are employed as high reflectivity mirrors for 1.5 μm short cavity lasers, which are key components in future highly integrated PC based photonic circuits. We have fabricated lasers with 2 PC mirrors and cavity lengths down to 100 μm. Threshold currents as low as 7.6 mA were achieved for the shortest lasers with 2 PC mirrors. The short laser cavity results in a large Fabry–Pérot mode spacing and mode competition leads to single mode lasing over a reasonably large current range up to 4.5× threshold. Lasers with one PC back mirror and a cleaved output facet show a higher threshold current of 13 mA and a maximum output power of more than 4 mW. The variation of laser performance with different cavity lengths is presented and discussed. © 2001 American Vacuum Society.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.70.Qs Photonic bandgap materials
42.79.Bh Lenses, prisms and mirrors
42.82.Cr Fabrication techniques; lithography, pattern transfer

Nanoimprint lithography of high-density cobalt dot patterns for fine tuning of dipole interactions

M. Natali, A. Lebib, E. Cambril, Y. Chen, I. L. Prejbeanu, and K. Ounadjela

J. Vac. Sci. Technol. B 19, 2779 (2001); http://dx.doi.org/10.1116/1.1421573 (5 pages) | Cited 5 times

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A trilayer nanoimprint process was used to fabricate high-density Co dot arrays. It is shown that choosing hybrane as the top layer resist gives better dimensional control of the replicated patterns compared to PMMA. By adjusting the etching time in the transfer process the dot sizes could be tailored in a wide range. The fabricated dot arrays with different sizes and period have then been studied by magneto-optic and magnetic-force microscopy measurements. The magnetization reversal was found to occur through vortex nucleation/annihilation. Dipolar interactions were clearly identified both in arrays with constant dot diameter and variable period and in arrays with fixed period and variable dot diameters. In the case of closely packed dots vortex chain structures along the field direction can be formed as a consequence of a nucleation cascade process. © 2001 American Vacuum Society.
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81.16.Nd Micro- and nanolithography
78.20.Ls Magneto-optical effects
75.60.Jk Magnetization reversal mechanisms
75.50.Tt Fine-particle systems; nanocrystalline materials
68.37.Rt Magnetic force microscopy (MFM)

Nanoscale patterning using self-assembled polymers for semiconductor applications

K. W. Guarini, C. T. Black, K. R. Milkove, and R. L. Sandstrom

J. Vac. Sci. Technol. B 19, 2784 (2001); http://dx.doi.org/10.1116/1.1421551 (5 pages) | Cited 61 times

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Thin films of self-organizing diblock copolymers may be suitable for semiconductor applications since they enable patterning of ordered domains with dimensions below photolithographic resolution over wafer-scale areas. We investigate the process window for forming ordered arrays of nanoscale polymer domains in thin films across 8-in.-diam silicon wafers, including the effect of substrate material and surface treatment, annealing conditions, copolymer molecular weight, and film thickness. We also demonstrate pattern transfer of the nanoporous polymer template using both reactive ion etching and metal lift off. © 2001 American Vacuum Society.
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81.16.Rf Micro- and nanoscale pattern formation
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
85.40.Hp Lithography, masks and pattern transfer
82.35.Jk Copolymers, phase transitions, structure
61.41.+e Polymers, elastomers, and plastics
81.65.Cf Surface cleaning, etching, patterning
81.16.Nd Micro- and nanolithography
84.32.Tt Capacitors

Field emission emitter array with a self-aligned volcano-type gate: Fabrication and characterization

Tz. Ivanov, I. W. Rangelow, St. Biehl, and I. R. Chakarov

J. Vac. Sci. Technol. B 19, 2789 (2001); http://dx.doi.org/10.1116/1.1417551 (4 pages) | Cited 1 time

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Field electron emitters with self-aligned volcano-type gate arrays were fabricated in order to generate an electron beam and their characteristics were measured. These devices were fabricated by reactive ion etching followed by successive forming of an insulating layer and deposition of a gate electrode. The self-aligned gate is achieved by reactive ion etching a planarizing resist film in 1:2 O2/Ar plasma and high dc bias (200 V). The device presented here has a 0.4 μm gate opening. The fabrication technology and structural and electrical characteristics of a self-aligned volcano-type gate field emission triode emitter array are reported. © 2001 American Vacuum Society.
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85.45.Db Field emitters and arrays, cold electron emitters

Induced crystallization as a nonlithographic pattern transfer technique for nanofabrication

M. J. Cabral, W. K. Lye, J. C. Bean, M. L. Reed, T. Chraska, S. Dj. Mesarovic, R. Hull, and A. B. Phillips

J. Vac. Sci. Technol. B 19, 2793 (2001); http://dx.doi.org/10.1116/1.1420532 (4 pages) | Cited 1 time

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Controlled crystallization of amorphous films through “nanoprinting” is a novel pattern transfer technique that has been demonstrated for submicron features. Amorphous Ge and indium tin oxide (ITO) films are investigated for their suitability as a pattern transfer layer by direct contact with a patterned printhead. The printhead is heated and brought into contact with the amorphous film, transforming the contacted areas from amorphous to crystalline material. After crystallization, the amorphous regions are selectively etched away, leaving the desired pattern in crystalline material. Theoretical modeling suggests that this technique can be used for pattern transfer of features less than 50 nm. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
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Fabrication of T gate structures by nanoimprint lithography

D. S. Macintyre, Y. Chen, D. Lim, and S. Thoms

J. Vac. Sci. Technol. B 19, 2797 (2001); http://dx.doi.org/10.1116/1.1417552 (4 pages) | Cited 12 times

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Nanoimprint lithography is capable of patterning substrates with high definition patterns at relatively high patterning speeds. In this article we describe the fabrication of high resolution “T” gate resist profiles by imprint lithography. The fabrication of high resolution stamping tools and the imprinting process itself are critical to the success or failure of this technique and they are described in the article. Two different techniques were used to fabricate stamping tools. The first involved pattern definition by high resolution electron beam lithography followed by electroforming. The second involved pattern definition by electron beam lithography followed by a two stage silicon etching process. Imprinted T gate resist profiles with footwidths less than 100 nm in length were obtained on gallium arsenide substrates for the purpose of producing metallized gates for a self-aligned gate process. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
85.40.Ls Metallization, contacts, interconnects; device isolation

Room temperature replication in spin on glass by nanoimprint technology

S. Matsui, Y. Igaku, H. Ishigaki, J. Fujita, M. Ishida, Y. Ochiai, M. Komuro, and H. Hiroshima

J. Vac. Sci. Technol. B 19, 2801 (2001); http://dx.doi.org/10.1116/1.1417547 (5 pages) | Cited 22 times

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A compact nanoimprint lithography (NIL) system using the driving power of a stepping motor has been developed. Compared to a conventional NIL system with a hydraulic press, there are some additional features of the NIL system such as compactness and low cost. We propose the use of spin on glass (SOG) instead of PMMA to avoid thermal expansion and demonstrate SOG patterns with 200 nm linewidths at room temperature replications using the NIL system. The SOG patterns were transferred to gold metal using liftoff and to a silicon substrate by reactive ion etching. © 2001 American Vacuum Society.
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81.16.Nd Micro- and nanolithography

Step and flash imprint lithography: Defect analysis

T. Bailey, B. Smith, B. J. Choi, M. Colburn, M. Meissl, S. V. Sreenivasan, J. G. Ekerdt, and C. G. Willson

J. Vac. Sci. Technol. B 19, 2806 (2001); http://dx.doi.org/10.1116/1.1420203 (5 pages) | Cited 22 times

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Step and flash imprint lithography (SFIL) is a promising, low cost alternative to projection printing. This technique has demonstrated very high resolution and overlay alignment capabilities, but it is a contact printing technique so there is concern about defect generation and propagation. A series of experiments has been carried out with the goal of quantifying the effect of defect propagation. To that end, each unit process in SFIL was studied independently. The number of particles added during handling and transportation and due to SFIL machinery was deemed acceptable, and the added particles should not complicate the inspection of process defects. The concept of a “self-cleaning” process in which the imprint template becomes cleaner by imprinting was revisited. Inspection of an imprint template before and after imprinting revealed that the template actually becomes cleaner with imprinting. Visual inspection of multiple imprints did not reveal any systematic generation or propagation of defects. The inspection area used in this study was limited, however, since the inspection was both manual and visual. Imprinting for this defect study was performed at the University of Texas in a Class 10 cleanroom, and inspection was performed at International SEMATECH. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning

Study of the resist deformation in nanoimprint lithography

Yoshihiko Hirai, Masaki Fujiwara, Takahiro Okuno, Yoshio Tanaka, Masataka Endo, Sigeo Irie, Kazuo Nakagawa, and Masaru Sasago

J. Vac. Sci. Technol. B 19, 2811 (2001); http://dx.doi.org/10.1116/1.1415510 (5 pages) | Cited 40 times

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Numerical simulations and experimental studies are carried out to understand the deformation process of thin polymer film in nanoimprint lithography. Deformation of a thin polymer above its glass transition temperature is studied for various imprinting conditions such as the aspect ratios of a mold pattern, initial thickness of the polymer, and imprinting pressure. Cross-sectional profiles of the deformed polymers are simulated by the finite element method based on a rubber elastic model. The results are compared with experimental data. The areal penetration ratio of the polymer into the recessed groove of the mold and residual thickness underneath the mold are quantitatively evaluated. The simulations and the experimental results agree well with each other. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
81.40.Jj Elasticity and anelasticity, stress-strain relations
02.70.Dh Finite-element and Galerkin methods

Fabrication of large area 100 nm pitch grating by spatial frequency doubling and nanoimprint lithography for subwavelength optical applications

Zhaoning Yu, Wei Wu, Lei Chen, and Stephen Y. Chou

J. Vac. Sci. Technol. B 19, 2816 (2001); http://dx.doi.org/10.1116/1.1409384 (4 pages) | Cited 19 times

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In this article we report on the fabrication of 100 nm pitch gratings over a large area (∼10 cm2) using a simple, low-cost, fast process. This method includes (1) generation of the grating pattern using interferometric lithography and spatial frequency doubling and (2) pattern replication using nanoimprint lithography. The form birefringence of a 100 nm pitch Si grating was studied using ellipsometry. Measurements show an index difference of Δn>0.9 at a wavelength of 632.8 nm. The experimental data are in good agreement with effective medium theory. This indicates the possibility of using these structures for wave plates and other subwavelength optical devices operating in the visible. © 2001 American Vacuum Society.
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42.79.Dj Gratings
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography
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Photolithographic patterning of proteins with photoresists processable under biocompatible conditions

Antonios Douvas, Panagiotis Argitis, Constantinos D. Diakoumakos, Konstantinos Misiakos, Dimitra Dimotikali, and Sotirios E. Kakabakos

J. Vac. Sci. Technol. B 19, 2820 (2001); http://dx.doi.org/10.1116/1.1408954 (5 pages) | Cited 7 times

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The microlithographic patterning of proteins on solid substrates using photoresists, which can be processed in the presence of biomolecules without affecting their bioactivity, is reported. Chemically amplified resist materials based on poly(t-butyl acrylate) and a newly synthesized copolymer of t-butyl methacrylate, 2-hydroxyethyl methacrylate, isobornyl methacrylate, and acrylic acid designed for this application, are evaluated regarding capabilities for processing under biocompatible conditions (processing temperatures at about 50 °C or lower and development with dilute aqueous base developers). The photoresist formulations based on the newly synthesized (meth)acrylate copolymer had higher sensitivity and contrast allowing lithographic processing even without postexposure bake. Patterns down to 3.75 μm lines/spaces of two different protein molecules, rabbit Immunoglobulin G and bovine serum albumin, on aminosilane-treated silicon surfaces, were obtained with a photoresist formulation based on the new copolymer and an onium salt photoacid generator under biocompatible processing conditions. © 2001 American Vacuum Society.
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87.14.E- Proteins
85.40.Hp Lithography, masks and pattern transfer

Single cell detection with micromechanical oscillators

B. Ilic, D. Czaplewski, M. Zalalutdinov, H. G. Craighead, P. Neuzil, C. Campagnolo, and C. Batt

J. Vac. Sci. Technol. B 19, 2825 (2001); http://dx.doi.org/10.1116/1.1421572 (4 pages) | Cited 123 times

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The ability to detect small amounts of materials, especially pathogenic bacteria, is important for medical diagnostics and for monitoring the food supply. Engineered micro- and nanomechanical systems can serve as multifunctional, highly sensitive, immunospecific biological detectors. We present a resonant frequency-based mass sensor, comprised of low-stress silicon nitride cantilever beams for the detection of Escherichia coli (E. coli)-cell-antibody binding events with detection sensitivity down to a single cell. The binding events involved the interaction between anti-E. coli O157:H7 antibodies immobilized on a cantilever beam and the O157 antigen present on the surface of pathogenic E. coli O157:H7. Additional mass loading from the specific binding of the E. coli cells was detected by measuring a resonant frequency shift of the micromechanical oscillator. In air, where considerable damping occurs, our device mass sensitivities for a 15 μm and 25 μm long beam were 1.1 Hz/fg and 7.1 Hz/fg, respectively. In both cases, utilizing thermal and ambient noise as a driving mechanism, the sensor was highly effective in detecting immobilized anti-E. coli antibody monolayer assemblies, as well as single E. coli cells. Our results suggest that tailoring of oscillator dimensions is a feasible approach for sensitivity enhancement of resonant mass sensors. © 2001 American Vacuum Society.
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87.85.Lf Tissue engineering
07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Dual exposure glass layer suspended structures: A simplified fabrication process for suspended nanostructures on planar substrates

D. M. Tanenbaum, A. Olkhovets, and L. Sekaric

J. Vac. Sci. Technol. B 19, 2829 (2001); http://dx.doi.org/10.1116/1.1417546 (5 pages) | Cited 5 times

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We have developed and demonstrated here a simplified flexible fabrication process for glass nanomechanical systems. This process uses a single layer of spin on glass (SOG) material with two negative tone electron beam exposures at two different exposure energies to define the suspended and support structures, respectively. After development the SOG can be converted into glass. The process is additive and can be applied to any flat substrate. We have fabricated a variety of glass nanomechanical oscillators and measured their mechanical resonances using a mechanical piezoelectric driving force and optical interferometric detection. Suspended structures were fabricated with thickness of less than 50 nm and lateral dimensions of less than 100 nm supported anywhere from 150 to 800 nm above the substrate. Resonance frequencies for glass wires with both ends fixed (cross section 110 nm×180 nm) and lengths of 4–9 μm range from 7 to 30 MHz, with quality (Q) factors of over 1000. Annealing the structures in an oxygen ambient roughly doubles both the frequencies and the Q factors. © 2001 American Vacuum Society.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.16.Nd Micro- and nanolithography
81.05.Kf Glasses (including metallic glasses)

Observation and characteristics of mechanical vibration in three-dimensional nanostructures and pillars grown by focused ion beam chemical vapor deposition

J. Fujita, M. Ishida, T. Sakamoto, Y. Ochiai, T. Kaito, and S. Matsui

J. Vac. Sci. Technol. B 19, 2834 (2001); http://dx.doi.org/10.1116/1.1417545 (4 pages) | Cited 48 times

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The Young’s modulus of diamond-like carbon (DLC) pillars was measured by means of mechanical vibration using scanning electron microscopy. The DLC pillars were grown using Ga+ focused ion beam-induced chemical vapor deposition with a precursor of phenanthrene vapor. The Young’s modulus of the DLC pillars was around 100 GPa at vapor pressure of 5×10−5 Pa and it had a quality (Q) value of resonance exceeding 1200. There seemed to be a balance between the DLC growth rate and surface bombardment by the ions, and this played an important role in the stiffness of the pillars. Some of the DLC pillars showed a very large Young’s modulus over 600 GPa at low gas pressure conditions. © 2001 American Vacuum Society.
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81.05.U- Carbon/carbon-based materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.Be Chemical synthesis methods
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity

Photoelectrochemical undercut etching for fabrication of GaN microelectromechanical systems

A. R. Stonas, N. C. MacDonald, K. L. Turner, S. P. DenBaars, and E. L. Hu

J. Vac. Sci. Technol. B 19, 2838 (2001); http://dx.doi.org/10.1116/1.1415508 (4 pages) | Cited 16 times

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The authors have developed a wet, band-gap-selective, photoelectrochemical etching process capable of producing cantilever microelectromechanical systems from InGaN/GaN heterostructures. Fabricated cantilevers were successfully actuated, and resonance spectra were measured. The as-grown strain gradient in the GaN film was found to relax upon removal, resulting in upward curvature of the cantilevers. This curvature was shown to be reversible with the integration of strained InGaN layers on the top surface of the cantilever. All photoelectrochemical wet etching was conducted using a benchtop lamp-and-filter arrangement, employing GaN and InGaN films as filters. © 2001 American Vacuum Society.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors
07.10.Cm Micromechanical devices and systems
82.45.-h Electrochemistry and electrophoresis
82.50.-m Photochemistry

Heat-depolymerizable polycarbonates as electron beam patternable sacrificial layers for nanofluidics

C. K. Harnett, G. W. Coates, and H. G. Craighead

J. Vac. Sci. Technol. B 19, 2842 (2001); http://dx.doi.org/10.1116/1.1409383 (4 pages) | Cited 36 times

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This research investigates a heat-depolymerizable polycarbonate (HDP) for use as a sacrificial layer in fabricating nanofluidic devices by electron beam lithography. When solid HDP films are heated to 300 °C, the monomer units separate into a nontoxic vapor. This property suggests that a patterned HDP film may be used as a temporary support for another film which is stable at the depolymerization temperature. Heating the structure removes the HDP, leaving a network of nanofluidic tubes without the use of solvents or other chemicals as required in most other sacrificial layer processes. We found that HDP films may be patterned directly by electron beam lithography, followed by immersion in isopropanol to remove HDP from the exposed areas. The patterns are then sputter coated with silicon dioxide at low temperature, provided with access holes for venting, heated to clear out HDP remaining inside the tubes, and injected with fluorescent dye for observation. Tube dimensions of 140 nm height, 1 μm width, and 1 mm length are reported, and fabrication of other structures is discussed. © 2001 American Vacuum Society.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.16.Nd Micro- and nanolithography

Fabrication of microfluidic devices in silicon and plastic using plasma etching

D. F. Weston, T. Smekal, D. B. Rhine, and J. Blackwell

J. Vac. Sci. Technol. B 19, 2846 (2001); http://dx.doi.org/10.1116/1.1421571 (6 pages) | Cited 8 times

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The move to miniaturization of biomedical systems offers tremendous potential for the improvement of health care, both in terms of reduced analysis time, and in significantly lowering the volume requirements of patient blood, or other bodily fluid. In order to fabricate microchannels for microfluidics, we have investigated two approaches using high-density plasma etching to achieve channel depths of 20–50 microns. The first was plasma etching of tapered silicon masters for hot embossing of plastics to form a capillary electrophoresis device. The second approach was the direct plasma etching of plastic to form a microfluidics device for DNA analysis. In both cases, we report the development of optimized etch conditions using SAS Institute, Inc. design of experiment software. © 2001 American Vacuum Society.
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87.85.Va Micromachining
47.85.Np Fluidics
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
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Electron beam inspection system based on the projection imaging electron microscope

Motosuke Miyoshi, Yuichiro Yamazaki, Ichirota Nagahama, Atsushi Onishi, and Katsuya Okumura

J. Vac. Sci. Technol. B 19, 2852 (2001); http://dx.doi.org/10.1116/1.1421561 (4 pages)

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An electron beam inspection system based on the projection imaging electron microscope was developed and the proof-of-concept system has been constructed and evaluated. The secondary electrons are projected through the projection imaging optics and imaged onto the image detection system. The projected secondary electron image is amplified by the microchannel plate and converted to an optical image by the fluorescent screen and detected by the 2048 element, eight-tap time delay and integration (TDI) image sensor. The stage is linearly moved in synchronism with the TDI signal output data rate, and then, the secondary electron image is continuously captured. The spatial resolution of around 0.1 μm has been obtained in this experiment. Several images obtained by the TDI imaging mode are also demonstrated. © 2001 American Vacuum Society.
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85.40.Qx Microcircuit quality, noise, performance, and failure analysis
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
06.60.Mr Testing and inspecting procedures
79.20.Hx Electron impact: secondary emission
42.79.Ls Scanners, image intensifiers, and image converters
42.79.Pw Imaging detectors and sensors

Novel high resolution scanning thermal probe

K. Edinger, T. Gotszalk, and I. W. Rangelow

J. Vac. Sci. Technol. B 19, 2856 (2001); http://dx.doi.org/10.1116/1.1420580 (5 pages) | Cited 24 times

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Scanning thermal microscopy is a scanning proximal probe technique, which can be used for mapping spatial variation of thermal properties of a surface such as temperature, thermal conductivity, and thermal diffusivity. The sensor presented here is a resistance based probe consisting of a nanometer-sized filament formed at the end of a piezoresistive atomic force microscope type cantilever. The freestanding filament is deposited by focused electron beam deposition using methylcyclopentadienyl trimethyl platinum as a precursor gas. The filament height is in the range of 2–5 μm, with typical “wire” diameters between 30 and 100 nm. Typical deposition times are between 2 and 5 min, and might be further shortened by optimizing the precursor gas flux. Because of its small size, the new probe has a high spatial resolution (<20 nm tip end radius) and, due to the low thermal mass, a high thermal sensitivity and fast response time. In this article, experiments designed to characterize the mechanical stability and electrical and thermal properties of the nanometer-sized probe are presented. © 2001 American Vacuum Society.
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07.79.-v Scanning probe microscopes and components
07.20.-n Thermal instruments and apparatus
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Optical mask metrology for next generation lithography

Wolfgang Vollrath, Gerhard Schlüter, and Gerd Scheuring

J. Vac. Sci. Technol. B 19, 2861 (2001); http://dx.doi.org/10.1116/1.1420204 (3 pages) | Cited 1 time

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This article addresses the state-of-the-art in optical mask CD metrology based on the most recent deep ultraviolet (DUV) microscope optics operating at 248 nm. It further points out the future potential and limitations of optical CD metrology in general and shows that DUV mask metrology has all of the capabilities to meet the ITRS needs, while avoiding the difficulties associated with scanning electron microscopy based metrology tools, including substrate charging and contamination. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.60.Pb Conventional optical microscopes

Contactless testing of wiring networks by an electron beam system utilizing induced current detection

S. D. Golladay

J. Vac. Sci. Technol. B 19, 2864 (2001); http://dx.doi.org/10.1116/1.1415509 (5 pages)

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Flying-probe mechanical test systems which detect opens and shorts in electrical networks within a multichip module substrate by measuring the capacitance of network elements have found application within the manufacturing industry. The feasibility of a contactless capacitance measurement method using an electron beam is reported here. Compared to mechanical probers, an electron beam capacitance tester could have higher throughput, test smaller features, and eliminate the possibility of probe damage to substrates. The test method is easily implemented as it employs a low voltage probe beam with a small deflection range, electron flood guns, a grid or electrode above the substrate, and an induced current detector. The capacitance between the node under test and the conductive plane is measured (indirectly) as the node is charged by the probe beam. Capacitance measurement to the accuracy required to detect opens and shorts has been demonstrated. © 2001 American Vacuum Society.
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84.32.Hh Inductors and coils; wiring
06.60.Mr Testing and inspecting procedures
85.40.Qx Microcircuit quality, noise, performance, and failure analysis

Alignment system using voltage contrast images for low-energy electron-beam lithography

Tetsuro Nakasugi, Atsushi Ando, Kazuyoshi Sugihara, Yuichiro Yamazaki, Motosuke Miyoshi, and Katsuya Okumura

J. Vac. Sci. Technol. B 19, 2869 (2001); http://dx.doi.org/10.1116/1.1421544 (5 pages) | Cited 5 times

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We have proposed an alignment system for low-energy electron-beam lithography. The proposed alignment system is based on the following unique concepts: (1) an alignment mark is detected using voltage contrast images caused by charging, and (2) to improve the alignment accuracy of global alignment, the alignment accuracy can be inspected before the pattern exposure without any loss of time. In order to verify these concepts, we performed a series of experiments. Using an electron beam of a few keV, we detected a mark buried by thick insulator films; even if direct access to the marks by the primary beam is prevented, the mark detection is possible. Also, we confirmed that the simultaneous observation of exposure patterns and alignment mark is possible using the voltage contrast images caused by charging: the inspection is possible for the exposure status without resist development. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer

Thermal conductivity measurements of thin-film resist

Dachen Chu, Maxat Touzelbaev, Kenneth E. Goodson, Sergey Babin, and R. Fabian Pease

J. Vac. Sci. Technol. B 19, 2874 (2001); http://dx.doi.org/10.1116/1.1421557 (4 pages) | Cited 21 times

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In electron-beam and photolithography, local heating can change the resist sensitivity and lead to variations in significant critical dimension. Existing models suffer from the lack of experimental data for the thermal properties of the polymer resist films. We present the measurements of both out-of-plane and in-plane thermal conductivity of thin resist films following different exposure conditions. An optical thermoreflectance technique was used to characterize out-of-plane thermal conductivity; the out-of-plane thermal conductivity of exposed SPR™-700 resist increases as a function of exposure dose. We also designed and fabricated a free-standing micro-electrode structure for measuring the in-plane thermal conductivity and results for poly(methylmethacrylate) films were obtained, indicating that, unlike polyimide films, there is no appreciable anisotropic behavior. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
07.20.-n Thermal instruments and apparatus
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

Subresolution placement using infrared image alignment to the computer-aided design database for backside probing and editing

M. Sengupta, M. Sinha, G. Dajee, and C. C. Tsao

J. Vac. Sci. Technol. B 19, 2878 (2001); http://dx.doi.org/10.1116/1.1421574 (6 pages) | Cited 1 time

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As more integrated circuits are packaged in controlled collapse chip connection format, internal debug tools need to image devices through their silicon packaging. Infrared (IR) optical systems make through-silicon imaging possible, but navigation becomes challenging because IR resolution is often lower than positioning accuracy required for design debug. We perform subresolution image alignment between computer-aided design (CAD) and IR images to obtain the required placement accuracy. Our goal is to automate and improve CAD-based IR navigation for silicon-side probing and editing. Using our alignment algorithm, which combines equalization, oversampling, and cross correlation, we demonstrate the ability to achieve 0.1 μm placement accuracy with a 1 μm resolution optical system. © 2001 American Vacuum Society.
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85.40.Bh Computer-aided design of microcircuits; layout and modeling

Critical dimension error analysis for 0.13 μm photolithography and beyond

Tsai-Sheng Gau, Anthony Yen, Jeng-Horng Chen, Shinn-Sheng Yu, Chun-Kuang Chen, Chih-Ming Ke, Burn J. Lin, and Ping-Ting C. Wang

J. Vac. Sci. Technol. B 19, 2884 (2001); http://dx.doi.org/10.1116/1.1409380 (6 pages) | Cited 2 times

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This article reports on a comprehensive study of critical dimension (CD) error analysis for the 0.13 μm generation and beyond. Systematic CD distribution is extracted by averaging nine wafers. The remaining noise signals are treated as random CD errors. Systematic CD error is further broken down into intra- and interfield CD errors by Fourier analysis. Interfield CD error is brought in comparison with the temperature distribution of postexposure bake hot plate, and they are found in good match. A polynomial expansion method further decomposes the interfield distribution into tilt and spiral parts, which are supposedly contributed by hot-plate and spin modules. The random CD error is also analyzed in this article. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
02.30.Nw Fourier analysis
02.60.Ed Interpolation; curve fitting

Resist line edge roughness and aerial image contrast

J. Shin, G. Han, Y. Ma, K. Moloni, and Franco Cerrina

J. Vac. Sci. Technol. B 19, 2890 (2001); http://dx.doi.org/10.1116/1.1418413 (6 pages) | Cited 48 times

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We report the results of an experimental study of the correlations between line edge roughness (LER) and aerial image contrast for different lithographies in identical processing conditions. The characterization has been performed using atomic force microscopy carbon nanotube tips to image the top and bottom of trenches with very high resolution. Experimental results generally support that higher aerial image contrast leads to lower line edge roughness, but differences exist among the lithographies and resists. Top surface roughness results show similar trends with LER. Higher aerial image modulation also yields higher resist sidewall angle. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
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Substrate cooling efficiency during cryogenic inductively coupled plasma polymer etching for diffractive optics on membranes

Deirdre L. Olynick, Erik H. Anderson, Bruce Harteneck, and Eugene Veklerov

J. Vac. Sci. Technol. B 19, 2896 (2001); http://dx.doi.org/10.1116/1.1414021 (5 pages) | Cited 10 times

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We fabricate high-resolution diffractive optics on membranes using a bilayer resist system consisting of hydrogensilsesquioxane as a negative electron-beam imaging layer and hardbaked AZPN114 as the underlay. To minimize sidewall etching of the polymer, the AZPN114 layer was etched at −100 °C in a cryogenically cooled inductively coupled plasma etcher. Features fabricated on Si supported membrane wafers, where the areas of interest are separated from the platen by the wafer thickness, provide an additional challenge to the low-temperature dry etch process due to low cooling efficiency (and thus membrane heating). Using cooling theory and experimental verification we look at membrane cooling efficiency for different hardware and membrane size combinations. Diffusive cooling in membranes less than 140 μm wide dominates membrane cooling during the etch process. With these small membranes we have fabricated high efficiency x-ray zone plates with linewidths as small as 30 nm and 6:1 aspect ratios. © 2001 American Vacuum Society.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
42.79.Ci Filters, zone plates, and polarizers

High speed, dry etching of Fe for integration of magnetic devices in microelectronics

M. S. P. Andriesse, E. van der Drift, and W. G. Sloof

J. Vac. Sci. Technol. B 19, 2901 (2001); http://dx.doi.org/10.1116/1.1408949 (5 pages)

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Dry etch behavior of Fe in inductively coupled chlorine-based plasma at elevated temperatures has been investigated. Etch rates up to 300 nm/min at 190 °C were achieved, with good selectivity towards SiO2 and Al2O3 masks. Etching did not take place in pure Cl2 plasma or Ar/Cl2 plasma, but required the addition of a few percent BCl3 or SiCl4. The process was found to be a combination of spontaneous and ion enhanced chemical etching. Simultaneous exposure to ultraviolet light from an external source did not enhance the etch rate, but did shorten the inhibition time of the etching. © 2001 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
85.70.Ay Magnetic device characterization, design, and modeling

Cr absorber etch process for extreme ultraviolet lithography mask fabrication

K. H. Smith, J. R. Wasson, P. J. S. Mangat, W. J. Dauksher, and D. J. Resnick

J. Vac. Sci. Technol. B 19, 2906 (2001); http://dx.doi.org/10.1116/1.1414013 (5 pages) | Cited 13 times

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Reactive ion etching (RIE) and inductively coupled plasma (ICP) Cr etch processes have been evaluated for fabrication of extreme ultraviolet lithography masks on 200 mm substrates. Experiments were completed to optimize the Cr etch rate, etch rate uniformity, and Cr to resist selectivity for both etch processes. The best ICP process was found to have superior etch rate, etch rate uniformity, and comparable Cr to resist selectivity to the RIE process. The effect of exposed Cr area on the Cr to resist selectivity, critical dimension (CD) bias, and CD bias 3σ was also investigated. A decrease in exposed Cr area from 95% to 7% was found to dramatically increase the Cr etch rate, leading to an increase in the Cr to resist selectivity. Lower Cr loading was also found to decrease the CD bias and CD bias 3σ. The average CD bias was very high for both processes, with the ICP etch process having a higher CD bias (143 nm) than the RIE process (89 nm). The CD bias uniformity was significantly lower for the ICP process (32 nm, 3σ) when compared to the RIE process (71 nm, 3σ). © 2001 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
85.40.Hp Lithography, masks and pattern transfer

High-resolution nitride etching using hydrogen implantation effect

Mizunori Ezaki, Yoshihide Kato, and Tooru Tojo

J. Vac. Sci. Technol. B 19, 2911 (2001); http://dx.doi.org/10.1116/1.1420581 (6 pages)

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A nitride etching method by oxygen plasma using hydrogen implantation effect is reported. High-resolution patterning of nitride film with sub 50 nm width is demonstrated using this etching method. The mechanism of the nitride etching process has been investigated with various measurements in this study. The measurement results show that the binding of nitrogen and hydrogen in the nitride films is caused by the irradiation of hydrogen-containing gas plasma and the hydrogen implantation into the nitride film plays an important role in the nitride etching by oxygen plasma. No plasma-induced damage in nitride film, such as formation of defects and dislocations, is observed in the case that this etching method is used. This etching method with low damage is applicable to the fabrication of various nitride-based devices. © 2001 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Dq Plasma-based ion implantation and deposition
85.40.Ry Impurity doping, diffusion and ion implantation technology
52.77.Bn Etching and cleaning

Inductively coupled plasma etching of GaN and its effect on electrical characteristics

B. Rong, E. van der Drift, R. J. Reeves, W. G. Sloof, and R. Cheung

J. Vac. Sci. Technol. B 19, 2917 (2001); http://dx.doi.org/10.1116/1.1421543 (4 pages) | Cited 5 times

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Dry etch behavior in the inductively coupled plasma processing of GaN using SF6/N2 plasma has been found to be highly ion induced with an ion energy threshold of about 100 eV. Temperature dependence of the etch rate indicates a small kinetic component. Maximum etch rate of 67 nm/min and good anisotropy have been demonstrated. The most efficient etch regime is observed for an ICP source power between 500–1000 W where the etch mechanism is ion limited. In contrast to reactive ion etching induced damage behavior, almost ideal diodes are obtained at the higher dc bias condition (300 V). X-ray photoelectron spectroscopy and atomic force microscopy studies indicate that smooth surface with minimal surface contamination, coupled with the incorporation of N on the substrate surface help to produce ideal diodes on surfaces etched at 300 V. Sidewall depletion is found to be in the range of 65 nm at the given SF6/N2 plasma process conditions. © 2001 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
73.30.+y Surface double layers, Schottky barriers, and work functions
85.30.Kk Junction diodes
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.60.Dp Adsorbed layers and thin films
68.37.Ps Atomic force microscopy (AFM)

Modeling and development of a deep silicon etch process for 200 mm election projection lithography mask fabrication

W. J. Dauksher, S. B. Clemens, D. J. Resnick, K. H. Smith, P. J. S. Mangat, S. Rauf, P. L. G. Ventzek, H. Ashraf, L. Lea, S. Hall, I. R. Johnston, J. Hopkins, A. Chambers, and J. K. Bhardwaj

J. Vac. Sci. Technol. B 19, 2921 (2001); http://dx.doi.org/10.1116/1.1420574 (5 pages) | Cited 4 times

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Gravitation toward a dry silicon etch process for electron projection lithography (EPL) mask fabrication is beneficial because of the concomitant increase in the available membrane area. In order to help understand the complex Bosch etch process and its dependence upon hardware design and process parameters for scattering with angular limitation in projection election beam lithography (SCALPEL) mask fabrication, a combined equipment and feature scale model has been employed. For case studies such as varying the deposition cycle time or ramping the bias power, computed sidewall profiles from the model deviate from experimental data by only about 5.5%. Given the extreme complexity of the Bosch process, this correlation is considered excellent. The best experimental Bosch etch conditions produce SCALPEL substrates with an effective silicon etch rate of 2.7 μm/min, 6.1% etch uniformity, selectivity to tetraethyl orthosilicate >240:1, and average strut sidewall angles of 87.4°. Introduction of hardware into the chamber results in partially blocking the transport of important etch and polymer deposition species to the wafer, thereby altering the etch and passivation rates. The provided learning is applicable to projection reduction exposure with variable axis immersion lenses format EPL masks as well. © 2001 American Vacuum Society.
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85.40.Hp Lithography, masks and pattern transfer
85.40.Bh Computer-aided design of microcircuits; layout and modeling
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning

Plasma-induced damage study for n-GaN using inductively coupled plasma reactive ion etching

F. A. Khan, L. Zhou, V. Kumar, and I. Adesida

J. Vac. Sci. Technol. B 19, 2926 (2001); http://dx.doi.org/10.1116/1.1418415 (4 pages) | Cited 8 times

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In this article, we report a comprehensive study on plasma-induced damage for n-GaN using inductively coupled plasma (ICP) reactive ion etching. Effect of ICP coil power, etch duration and bias voltage on the electrical characteristics of n-GaN was investigated. It was observed that variation in ICP coil power and etch duration had minimal effect on varying the plasma-induced surface damage. Bias voltage was found to be the most significant cause of variation in plasma-induced damage to the surface of n-GaN. Therefore, low surface damage can be achieved by optimizing the bias voltage at which the sample is being etched. Auger electron spectroscopy analysis showed that the stoichiometry of the etched GaN surfaces was identical, independent of the etching conditions. © 2001 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors
52.77.Bn Etching and cleaning

Balancing the etching and passivation in time-multiplexed deep dry etching of silicon

M. A. Blauw, T. Zijlstra, and E. van der Drift

J. Vac. Sci. Technol. B 19, 2930 (2001); http://dx.doi.org/10.1116/1.1415511 (5 pages) | Cited 37 times

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For the Bosch deep silicon dry etch process with SF6–C4F8 a quantitative approach is developed. Essential plasma surface interactions and the transport properties of ions and radicals in high aspect ratio structures are unravelled. Balancing the interactions during etching and passivation pulses is essential for maximal profile control. In the anisotropic regime the etch rate is aspect ratio dependent largely due to depletion of fluorine radicals and with some involvement of passivation polymer redeposition. The anisotropic process tends to stop at a limiting aspect ratio because of improper removal of polymer passivation at the trench bottom. Both higher ion flux and ion energy are found to be crucial to push the Bosch process to higher achievable aspect ratios. Practical process implications are discussed. In situ ellipsometry shows that the polymer passivation step is a complex process with an ion induced component. More efficient removal of the passivation layer at the trench bottom by adjusting the plasma chemistry could further improve the Bosch plasma etch process. © 2001 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
81.65.Rv Passivation
52.77.Bn Etching and cleaning
81.05.Cy Elemental semiconductors
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