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Nov 1996

Volume 14, Issue 6, pp. 3413-4370


Fabrication of gold nanostructures on a vicinal Si(111) 7×7 surface using ultrahigh vacuum scanning tunneling microscope and a gold‐coated tungsten tip

Daisuke Fujita, Qidu Jiang, and Hitoshi Nejoh

J. Vac. Sci. Technol. B 14, 3413 (1996); http://dx.doi.org/10.1116/1.588772 (7 pages) | Cited 20 times

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We have demonstrated that nanometer‐scale gold dots can be deposited on a vicinal Si(111) 7×7 surface using the field‐assisted atom transfer from the gold‐coated tungsten tip of a scanning tunneling microscope operating in ultrahigh vacuum. With the application of negative voltage pulses to the tip, gold nano‐mounds with the size ranging from ∼3 to ∼20 nm across at the base and 0.6–1 nm high can be created on the surface. The deposition is found to be more favored on the step edges than the (111) terraces. Since atomically resolved images of the Si(111) 7×7 structure can be observed even after many cycles of atom transfer using the gold‐coated tip, the shape of the tip apex has been kept very stable. The overall findings clearly suggest that the atom‐transfer technique proposed here is proven to be a good candidate for fabricating nanometer‐scale devices. © 1996 American Vacuum Society
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Characterization of large‐area arrays of nanoscale Si tips fabricated using thermal oxidation and wet etching of Si pillars

C. C. Umbach, B. W. Weselak, J. M. Blakely, and Q. Shen

J. Vac. Sci. Technol. B 14, 3420 (1996); http://dx.doi.org/10.1116/1.588773 (5 pages) | Cited 3 times

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Two‐dimensional periodic arrays containing 108 Si pillars with heights of 600–700 nm, widths of 100 nm, and repeat spacings of 300 nm have been fabricated using electron beam lithography on Si(001) substrates. These pillars have subsequently undergone wet oxidation at 800 °C and etching in hydrofluoric acid to produce an array of sharp tips with a height of ∼4000 Å. The x‐ray diffraction from this array appears to be dominated by scattering from the bases of the tips. Correlated variations in tip shape, observed with scanning electron microscopy, produce a modulated diffuse background in the diffracted x‐ray intensity. These observations demonstrate the feasibility of using high‐resolution x‐ray diffraction for studying defects in large‐area arrays of periodic structures. © 1996 American Vacuum Society
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61.05.cp X-ray diffraction
81.65.Cf Surface cleaning, etching, patterning

Silicon structures for in situ characterization of atomic force microscope probe geometry

K. F. Jarausch, T. J. Stark, and and P. E. Russell

J. Vac. Sci. Technol. B 14, 3425 (1996); http://dx.doi.org/10.1116/1.588774 (6 pages) | Cited 3 times

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Atomic force microscopy (AFM) is increasingly relied on to image and measure micron and submicron scale surface features. Consistent interpretation of AFM information is, however, difficult if the geometry of the probe is not known. In this work, the fabrication of funnel‐like structures and their use in probe characterization were developed from a proof of concept to readiness for field testing. The specifications that determine the structure’s sensitivity to probe shape were identified. The fabrication was tailored to yield large reproducible arrays (>100×100 structure). The geometry of the structures was characterized using low voltage scanning electron microscopy (SEM) techniques. Testing in intermittent contact mode has shown that the structures are stable even at high forces for multiple scans under various conditions. An algorithm was developed that calculates the probe geometry from an image of the structure. The sensitivity of the structures to probe shape was tested by comparing SEM images of probe shape to the probe geometry calculated from the AFM images of the structures. From this analysis it was determined that the structures are sensitive to the cone angle of the probe to within 5° and to the probe radius to within 50 nm. © 1996 American Vacuum Society
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07.79.Lh Atomic force microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
42.30.Va Image forming and processing

Correlation of Raman and optical studies with atomic force microscopy in porous silicon

Adam A. Filios, Susan S. Hefner, and Raphael Tsu

J. Vac. Sci. Technol. B 14, 3431 (1996); http://dx.doi.org/10.1116/1.588775 (5 pages) | Cited 5 times

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Atomic force microscopy images of porous silicon samples prepared with different conditions have been correlated with photoluminescence (PL) and Raman spectra, allowing a clear classification of two types of samples, ‘‘gently’’ etched versus ‘‘heavily’’ etched. The gently etched samples show a significantly improved morphology and uniformity, as well as consistent correlation in PL and Raman results with the quantum confinement model for the light emission. © 1996 American Vacuum Society  
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78.30.Am Elemental semiconductors and insulators
78.55.Mb Porous materials
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Use of multiple analytical techniques to confirm improved optical modeling of SnO2:F films by atomic force microscopy and spectroscopic ellipsometry

P. Ruzakowski Athey, F. K. Urban, and P. H. Holloway

J. Vac. Sci. Technol. B 14, 3436 (1996); http://dx.doi.org/10.1116/1.588776 (9 pages) | Cited 4 times

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Variable angle of incidence spectroscopic ellipsometry, reflectance, and transmittance techniques were used to determine the optical constants of a fluorine doped tin oxide film deposited by chemical vapor deposition onto a hot soda‐lime‐silica glass ribbon. To improve the optical characterization, an additional analytical technique, atomic force microscopy (AFM), was used to incorporate information about surface roughness into the optical model. Our earlier work demonstrated the necessity of including a surface roughness layer as six sublayers in the optical model. The present work further confirms the method and demonstrates its accuracy with additional analytical techniques. These include: (1) cross sectional in‐lens field emission scanning electron microscopy to measure total film thickness, determine presence of interface roughness and extent of surface roughness; (2) secondary ion mass spectrometry to give a first approximation of the film layer structure for optical modeling by depth profiling the film composition; (3) Hall measurements to identify the semiconductor carrier density and mobility; (4) x‐ray diffraction to identify the crystalline phase and preferential growth orientation. The use of AFM surface images and surface roughness plus the other compositional and structural information to improve ellipsometric modeling of thin films has been confirmed. © 1996 American Vacuum Society
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78.66.Li Other semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
73.61.Le Other inorganic semiconductors

Optimal filtering of scanning probe microscope images for wear analysis of smooth surfaces

K. Schouterden, B. M. Lairson, and M. H. Azarian

J. Vac. Sci. Technol. B 14, 3445 (1996); http://dx.doi.org/10.1116/1.588777 (7 pages) | Cited 1 time

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A procedure for removing cumulative drift and white noise from scanning probe microscope images has been constructed. Smooth amorphous carbon overcoats on superpolished hard disk media in particular were examined using a scanning probe microscope. The surfaces typically had a ∼1 nm rms roughness over a scan length of 10 μm. The low roughness yielded a relatively low signal to noise ratio in the unfiltered image. While a conventional filter removes a great deal of noise, an optimal Fourier (Wiener) filter that more selectively removes noise from the image is discussed. White noise and drift were modeled and their contributions to the power spectrum are estimated, resulting in an open clamshell‐shaped two‐dimensional filter. The effect of the filter was demonstrated by subjecting filtered images of unworn and worn areas to a smooth surface to second derivative calculations in different directions. Anisotropy in the wear process associated with the wear direction is apparent in the optimally filtered images. © 1996 American Vacuum Society
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07.79.-v Scanning probe microscopes and components
42.30.Va Image forming and processing
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
85.70.Ay Magnetic device characterization, design, and modeling

Atomic structures of Ag2Te studied by scanning tunneling microscopy

M. Ohto and K. Tanaka

J. Vac. Sci. Technol. B 14, 3452 (1996); http://dx.doi.org/10.1116/1.588778 (3 pages) | Cited 2 times

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Atomic structures of Ag2Te in the low‐ and high‐temperature phases have been studied using a scanning tunneling microscope in air and an x‐ray diffraction system. In the low‐temperature phase having a monoclinic lattice, (001) and (01̄0) atomic images are obtained. In the superionic high‐temperature phase, which is stable at temperatures above 145 °C, (100) surfaces of the Te cubic lattice are observed. In both phases, surface atomic reconstructions are not detected. © 1996 American Vacuum Society
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Emission measurements and simulation of silicon field‐emitter arrays with linear planar lenses

Cha‐Mei Tang, T. A. Swyden, K. A. Thomason, L. N. Yadon, D. Temple, C. A. Ball, W. D. Palmer, J. E. Mancusi, D. Vellenga, and G. E. McGuire

J. Vac. Sci. Technol. B 14, 3455 (1996); http://dx.doi.org/10.1116/1.588779 (5 pages) | Cited 10 times

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Results of beam collimation experiments on linear field‐emitter arrays with linear planar lenses are summarized. The electron beam is imaged on a phosphor screen. In general, as lens voltage is reduced relative to the gate voltage, the elliptically shaped screen images narrow, becoming fine lines with emission currents showing only modest reductions. This reduction of emission current can be overcome by increasing the gate voltage only a few volts without affecting beam collimation. As the lens voltage is reduced, screen current decreases relative to emission current while gate current increases, indicating that some emitted electrons in this linear lens geometry cannot propagate to the anode screen. Experimental data and qualitative modeling are in fair agreement. © 1996 American Vacuum Society
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85.45.Bz Vacuum microelectronic device characterization, design, and modeling

Comparative study of the elastic properties of silicate glass films grown by plasma enhanced chemical vapor deposition

G. Carlotti, L. Doucet, and M. Dupeux

J. Vac. Sci. Technol. B 14, 3460 (1996); http://dx.doi.org/10.1116/1.588780 (5 pages) | Cited 12 times

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The Brillouin light scattering technique has been used to study the elastic properties of a number of silicon dioxide films deposited by plasma‐enhanced chemical vapor deposition on Si substrates. In addition to stoichiometric undoped glass films produced from either silane or tetraethylorthosilicate, we have also studied nonstoichiometric Si‐rich films and P‐doped films. The phase velocity of both the surface Rayleigh mode and the longitudinal bulk wave in the film material has been measured and the two independent elastic constants c11 and c44 have been evaluated. The derived values of the Young modulus and the Poisson ratio show appreciable deviations from the values we measured on thermally grown oxide. Moreover, the evolution of the stress during thermal cycles has been analyzed using the substrate curvature method. This permitted us to estimate the thermal expansion coefficient of the films and to distinguish between the intrinsic and thermal components of the stress. © 1996 American Vacuum Society
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68.60.-p Physical properties of thin films, nonelectronic
78.35.+c Brillouin and Rayleigh scattering; other light scattering
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Ammonia nitridation of thermal polyoxide to eliminate epitaxial ambient induced dielectric pinhole formation

W. W. Fultz and G. W. Neudeck

J. Vac. Sci. Technol. B 14, 3465 (1996); http://dx.doi.org/10.1116/1.588781 (5 pages) | Cited 2 times

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The incorporation and distribution of nitrogen in ammonia nitrided thermal polyoxide (NPOX) dielectric films and their degradation durability to reduced pressure, dichlorosilane (SiH2Cl2)–HCl–H2 ambient during epitaxial lateral overgrowth (ELO) indicated that the surface nitrogen concentration had no effect. However, a bulk nitrogen concentration as low as 8 at. % significantly reduced the formation of ELO ambient induced pinholes in 250 Å polyoxide films. After 40 min of ELO ambient stress the electrical yield was raised from 0%, for the control polyoxide dielectric capacitors, to 84% for NPOX dielectric capacitors. Analyses of the failed devices suggest that active pinhole generation still exists, however, the bulk nitrogen concentration dramatically reduces the frequency and rate at which these dielectric defects are produced. © 1996 American Vacuum Society
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81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
85.30.-z Semiconductor devices
77.55.-g Dielectric thin films
77.22.Jp Dielectric breakdown and space-charge effects

Selective dry etching of oxide films for spacer applications in a high density plasma

Lynn R. Allen, Victoria Yu‐Wang, and Masyuki Sato

J. Vac. Sci. Technol. B 14, 3470 (1996); http://dx.doi.org/10.1116/1.588782 (3 pages)

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The use of a high density plasma to etch oxide side wall spacers was investigated. Process trends and the optimum process conditions required were determined. Oxide and polysilicon etch rates, uniformities, and the selectivity of oxide to polysilicon were all measured. The resulting etch chemistry had an oxide etch rate of 350 nm/min with a selectivity of oxide to polysilicon of 30:1. © 1996 American Vacuum Society
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81.65.Cf Surface cleaning, etching, patterning
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
85.40.Hp Lithography, masks and pattern transfer

Polysilicon gate etching in high density plasmas. IV. Comparison of photoresist and oxide masked polysilicon etching‐thickness determination of gate oxide layers using x‐ray photoelectron spectroscopy

F. H. Bell and O. Joubert

J. Vac. Sci. Technol. B 14, 3473 (1996); http://dx.doi.org/10.1116/1.588783 (10 pages) | Cited 11 times

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The characteristics of oxide and photoresist masked polysilicon trench etching has been studied by real‐time HeNe laser ellipsometry and quasi in situ x‐ray photoelectron spectroscopy (XPS). Poly‐Si films on SiO2‐covered Si (100) substrates were masked either with a 1‐μm‐thick photoresist or a 200‐nm‐thick oxide hard mask. The 200‐mm‐diam wafers were etched downstream in a helicon high density plasma source using a chlorine‐based gas chemistry. When using an oxide hard mask instead of a photoresist mask, the selectivity of polysilicon over oxide was improved by a factor greater than 3. A new approach to the surface characterization of semiconductor submicron structures by XPS is presented. Photoelectron signals originating from the gate oxide film and the underlying silicon substrate were measured in regular arrays of trenches. The ratio between the SiO2 peak area of the gate oxide film and the Si 2p peak area of the silicon substrate was correlated with the thickness of the SiO2 film. The thickness determined was obtained by calibrating peak area ratios with oxide thickness measurements using spectroscopic ellipsometry. Consequently, the gate oxide thicknesses derived from the area ratios were calculated in patterned areas after etching of photoresist and oxide hard masked polysilicon features as a function of the aspect ratio of the features and mask coverage on the wafer. It was found that the gate oxide consumption is enhanced in high aspect ratio features masked with photoresist as well as in areas with high photoresist coverage; the carbon coverage on the gate oxide film was found to scale with the increased gate oxide etching in the small features. Similar effects were not observed with the oxide masked sample. © 1996 American Vacuum Society
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81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors
85.40.Hp Lithography, masks and pattern transfer
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Electron‐beam/ultraviolet hybrid exposure combined with novel bilayer resist system for a 0.15 μm T‐shaped gate fabrication process

H. Takano, H. Nakano, H. Minami, K. Hosogi, N. Yoshida, K. Sato, Y. Hirose, and N. Tsubouchi

J. Vac. Sci. Technol. B 14, 3483 (1996); http://dx.doi.org/10.1116/1.588784 (6 pages) | Cited 4 times

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Electron‐beam/ultraviolet (UV) exposure technology to produce undercut T‐shaped resist cavities with bottom openings as small as 0.15 μm is demonstrated with a novel bilayer resist system for AlInAs/InGaAs high electron mobility transistors operated at the millimeter‐wave band. We employed an image reversal resist (AZ5206E) for the top layer and a polydimethyl glutarimide (PMGI) for the bottom layer. The top layer is delineated by UV exposure and the bottom layer is delineated by electron‐beam direct writing. These resist layers are developed layer by layer in different content aqueous tetramethyl ammonium hydroxide solution. Resist profiles are extremely well controlled because exposure and development of both layers are completely independent. A reliable overhang structure for metal liftoff, with a 0.15 μm footprint, was obtained. Gate length variation of less than ±10% on a 3‐in.‐diam InP substrate was successfully accomplished. In addition, an interesting phenomenon was noted. The combination of these two resists leads to an electron‐beam sensitivity decrease of PMGI. This phenomenon is closely related to the change of molecular weight distribution in PMGI. The novel bilayer resist system also allows the further improvement of resolution. This would provide a practical means for electron‐beam lithography in the nanometer region. © 1996 American Vacuum Society
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
85.30.Tv Field effect devices

Ag2Te/As2S3: A high‐contrast, top‐surface imaging resist for 193 nm lithography

Jerome M. Lavine and Mark J. Buliszak

J. Vac. Sci. Technol. B 14, 3489 (1996); http://dx.doi.org/10.1116/1.588785 (3 pages) | Cited 2 times

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At 193 nm, the Ag2Te/As2S3 inorganic resist system exhibits many of the characteristics previously observed at longer wavelengths, namely, a contrast of the order of 10 and the edge effect, both of which contribute to the printing of narrow linewidths. We have observed 0.3 micron lines limited by the resolution capability of the optical system and not by the resist. Under pulsed excimer laser excitation, this system exhibits a threshold of the order of 3 mJ/cm2/pulse. The system does not exhibit reciprocity. While images were printed with two 17 ns pulses of 4 mJ/cm2/pulse, images could not be printed with a single pulse as large as 50 mJ/cm2/pulse. This behavior is not explained by our previously developed model. © 1996 American Vacuum Society
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Neutral shadowing in circular cylindrical trench holes

Barbara Abraham‐Shrauner and Wenjing Chen

J. Vac. Sci. Technol. B 14, 3492 (1996); http://dx.doi.org/10.1116/1.588786 (5 pages) | Cited 9 times

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The neutral flux in the plasma etching of semiconductor wafers has been derived analytically for a simplified model for a circular cylindrical trench hole (circular via). The neutral molecules obey a Maxwellian distribution function and mutual collisions are neglected in the trench. Scattering of the neutrals with the sidewalls and trench bottom is ignored. The flux vector is given at each point on the etching profile surface. The flux vector reduces to the expression previously determined at the center of the trench. Etching profiles of the trench are displayed for neutral flux‐limited etch rates. © 1996 American Vacuum Society
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81.65.Cf Surface cleaning, etching, patterning
85.40.Hp Lithography, masks and pattern transfer
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Process technology for monolithic high‐speed Schottky/resonant tunneling diode logic integrated circuits

P.‐M. Lei, S. Subramaniam, G. H. Bernstein, W. Williamson, B. K. Gilbert, and D. H. Chow

J. Vac. Sci. Technol. B 14, 3497 (1996); http://dx.doi.org/10.1116/1.588787 (5 pages)

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A seven‐layer process was developed to fabricate monolithic high‐speed logic circuits, requiring integration of Schottky diodes and resistors with interband resonant tunneling diodes (RTDs). With this process technology, we have demonstrated a functionally complete logic family based on RTDs with a maximum operating frequency in excess of 12 GHz and a minimum power dissipation on the order of 0.5 mW per gate. © 1996 American Vacuum Society
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Effect of the Ti/TiN bilayer barrier and its surface treatment on the reliability of a Ti/TiN/AlSiCu/TiN contact metallization

L. Ouellet, Y. Tremblay, G. Gagnon, M. Caron, J. F. Currie, S. C. Gujrathi, and M. Biberger

J. Vac. Sci. Technol. B 14, 3502 (1996); http://dx.doi.org/10.1116/1.588788 (7 pages) | Cited 1 time

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The use of an AlSiCu/TiN bilayer for the metallization of 1.0‐μm‐diam and 1.4‐μm‐deep straight wall contacts to 0.2‐μm‐deep n+ and p+ diffusions, results in a n+/p− and a p+/ṇ− junction leakage lower than 10 pA even after nine heat treatments (60 min each) at 450 °C. However, there is a very important degradation of the contact chain resistance statistics at small contact size. On the other hand, the use of a Ti/TiN bilayer barrier under the AlSiCu/TiN interconnect maintains a n+/p− and a p+/n− junction leakage lower than 20 pA and prevents the degradation of the contact chain resistance statistics after the nine heat treatments. It is finally demonstrated that a vent in nitrogen followed by a momentary air exposure of the Ti/TiN bilayer barrier results in larger contact resistance than a vent in nitrogen followed by a one hour long air exposure of the Ti/TiN bilayer barrier before the deposition of the AlSiCu/TiN interconnect. © 1996 American Vacuum Society
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85.40.Ls Metallization, contacts, interconnects; device isolation
73.40.Cg Contact resistance, contact potential
68.35.Fx Diffusion; interface formation

High stability heterojunction bipolar transistors with carbon‐doped base grown by atomic layer chemical beam epitaxy

R. Driad, F. Alexandre, M. Juhel, and P. Launay

J. Vac. Sci. Technol. B 14, 3509 (1996); http://dx.doi.org/10.1116/1.588789 (5 pages)

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We report the improved thermal stability of heavily C‐doped GaAs layers using atomic layer chemical beam epitaxy (ALCBE). The use of ALCBE improves the crystal quality and reduces hydrogen incorporation in the epilayers by about a factor of 2, resulting in enhanced electrical dopant activity as compared to conventional growth techniques. This process has been successfully applied to the fabrication of InGaP/GaAs heterojunction bipolar transistors (HBTs) with a highly C‐doped base grown by ALCBE and other layers grown by conventional CBE. Dc current gains up to 150, for a base doping layer of 3×1019 cm−3, have been obtained. Moreover, the thermal stability of these devices is increased, as indicated by a post‐growth annealing (650°C, 60 min) which induces only a slight current gain degradation of about 20% at high collector currents, to be compared to a degradation of 60% for HBTs conventionally grown by CBE. © 1996 American Vacuum Society
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85.30.Pq Bipolar transistors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Electrical and microstructure analysis of ohmic contacts to p‐ and n‐type GaSb, grown by molecular beam epitaxy

A. Vogt, H. L. Hartnagel, G. Miehe, H. Fuess, and J. Schmitz

J. Vac. Sci. Technol. B 14, 3514 (1996); http://dx.doi.org/10.1116/1.588790 (6 pages) | Cited 8 times

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Pd based and conventional TiPtAu contacts were realized on GaSb grown by molecular beam epitaxy. For p‐type GaSb, an undoped sample with an acceptor background concentration of 6.6×1016 cm−3 and for n‐type GaSb tellurium‐doped samples with donor concentrations of 7.9×1017 and 1.2×1018 cm−3 were used. Circular transmission line patterns were defined on the samples for determining the specific contact resistivity. On n‐type GaSb, the metallizations consisted of palladium and one of the dopants germanium or sulphur. Rapid thermal annealing lead to values of 4×10−5 Ω cm2. On p‐type GaSb, nonalloyed TiPtAu and alloyed PdGePd contacts were deposited. Values as low as 5.6×10−6 Ω cm2 could be obtained. The interfaces of the TiPtAu, the PdGePd, and PdSPd contacts were studied by high resolution cross‐sectional transmission microscopy. © 1996 American Vacuum Society
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73.40.Cg Contact resistance, contact potential
68.35.Fx Diffusion; interface formation
81.40.Rs Electrical and magnetic properties related to treatment conditions

Thermal stability of W, WSix, and Ti/Al ohmic contacts to InGaN, InN, and InAlN

C. B. Vartuli, S. J. Pearton, C. R. Abernathy, J. D. MacKenzie, R. J. Shul, J. C. Zolper, M. L. Lovejoy, A. G. Baca, and M. Hagerott‐Crawford

J. Vac. Sci. Technol. B 14, 3520 (1996); http://dx.doi.org/10.1116/1.588791 (3 pages) | Cited 5 times

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W, WSi0.44, and Ti/Al contact properties were examined on n+In0.65Ga0.35N, InN, and In0.75Al0.25N. W was found to produce low specific contact resistance (dc∼10−7 Ω cm2) ohmic contacts to InGaN, with significant reaction between metal and semiconductor occurring at 900 °C mainly due to out diffusion of In and N. WSix showed an as‐deposited dc of 4×10−7 Ω cm2 but this degraded significantly with subsequent annealing at ≥600 °C. Ti/Al contacts were stable to ∼600 °C (dc∼4×10−7 Ω cm2 at ≤600 °C). The surfaces of these contacts remained smooth to 800 °C for W and WSix and 650 °C for Ti/Al. InN contacted with W and Ti/Al produced ohmic contacts with dc∼10−7 Ω cm2 and for WSixdc∼10−6 Ω cm2. All remained smooth to ∼600 °C, but exhibited significant interdiffusion of In, N, W, and Ti, respectively, at higher temperatures. The contact resistances for all three metalization schemes were ≥10−4 Ω cm2 on InAlN, and degraded with subsequent annealing. © 1996 American Vacuum Society
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73.40.Cg Contact resistance, contact potential
68.35.Fx Diffusion; interface formation

High temperature surface degradation of III–V nitrides

C. B. Vartuli, S. J. Pearton, C. R. Abernathy, J. D. MacKenzie, E. S. Lambers, and J. C. Zolper

J. Vac. Sci. Technol. B 14, 3523 (1996); http://dx.doi.org/10.1116/1.588792 (9 pages) | Cited 24 times

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The surface stoichiometry, surface morphology, and electrical conductivity of AlN, GaN, InN, InGaN, and InAlN were examined at rapid thermal annealing temperatures up to 1150 °C. The sheet resistance of the AlN dropped steadily with annealing, but the surface showed signs of roughening only above 1000 °C. Auger electron spectroscopy (AES) analysis showed little change in the surface stoichiometry even at 1150 °C. GaN root mean square (rms) surface roughness showed an overall improvement with annealing, but the surface became pitted at 1000 °C, at which point the sheet resistance also dropped by several orders of magnitude, and AES confirmed a loss of N from the surface. The InN surface had roughened considerably even at 650 °C, and scanning electron microscopy showed significant degradation. In contrast to the binary nitrides, the sheet resistance of InAlN was found to increase by ∼102 from the as grown value (3.2×10−3 Ω cm) after annealing at 800 °C and then remain constant up to 1000 °C, while that of InGaN increased by two orders of magnitude between 700 and 900 °C. The rms roughness increased above 800 and 700 °C, respectively, for InAlN and InGaN samples. In droplets began to form on the surface at 900 °C for InAlN and at 800 °C for InGaN, and then evaporate at 1000 °C, leaving pits. AES analysis showed a decrease in the N concentration in the top 500 Å of the sample for annealing ≥800 °C in both materials. © 1996 American Vacuum Society
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
72.80.Ey III-V and II-VI semiconductors
81.40.Rs Electrical and magnetic properties related to treatment conditions

Thermal stability and desorption of Group III nitrides prepared by metal organic chemical vapor deposition

O. Ambacher, M. S. Brandt, R. Dimitrov, T. Metzger, M. Stutzmann, R. A. Fischer, A. Miehr, A. Bergmaier, and G. Dollinger

J. Vac. Sci. Technol. B 14, 3532 (1996); http://dx.doi.org/10.1116/1.588793 (11 pages) | Cited 53 times

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We present results on the thermal stability as well as the thermally induced hydrogen, hydrocarbon, and nitrogen–hydrogen effusion from thin films of Group III nitrides prepared by low‐pressure chemical vapor deposition from organometallic precursors. We have deposited amorphous, polycrystalline, and epitaxial InN, GaN, and AIN films on (0001) Al2O3 substrates using the chemical reaction of azido[bis(3‐dimethylamino)propyl]indium, triethylgallium, and tritertiarybutylaluminium with ammonia. The substrate temperature was varied between 400 °C and 1100 °C. The elemental composition, in particular its dependence on the growth temperature, was investigated by elastic recoil detection analysis (ERDA). The influence of growth rate and crystallite size on the concentration of surface adsorbed hydrocarbons and carbon oxides is determined by a combination of ERDA and thermal desorption measurements. In addition, the stability of and the nitrogen flux from the InN, GaN, and AIN surfaces was determined by x‐ray diffraction and thermal decomposition experiments. © 1996 American Vacuum Society
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68.60.Dv Thermal stability; thermal effects
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Thermally stable InGaP/GaAs Schottky contacts using low N content double layer WSiN

Kenji Shiojima, Kazumi Nishimura, Masami Tokumitsu, Takumi Nittono, Hirohiko Sugawara, and Fumiaki Hyuga

J. Vac. Sci. Technol. B 14, 3543 (1996); http://dx.doi.org/10.1116/1.588794 (7 pages) | Cited 3 times

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This article describes thermally stable Schottky contacts using low N content double layered WSiN for InGaP/(In)GaAs metal–semiconductor field‐effect transistors with self‐aligned ion‐implanted n+ layers. Transmission electron microscopy observations show that the microscopic interfacial reaction between WSiN and GaAs is completely suppressed when N content in the WSiN is 10% or less. As a result, a WSiN/GaAs‐cap/InGaP Schottky contact shows high thermal stability after annealing at 800 °C for 100 min, even though the GaAs cap is as thin as 25 Å. Moreover, the double‐layer WSiN structure suppresses reduction in the carrier concentration in the channel during activation annealing. The carrier concentration of the GaAs‐cap (40 Å)/InGaP (100 Å)/ InGaAs‐channel (100 Å) film, 6.5×1018 cm−3, decreases to less then 2×1018 cm−3 with low N content WSiN (N=10%, 4000 Å) after annealing at 900 °C for 0.1 s, but it remains 3.8×1018 cm−3 with the double layered WSiN (N=37%, 3800 Å/N=10%, 200 Å). © 1996 American Vacuum Society
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73.30.+y Surface double layers, Schottky barriers, and work functions
85.30.Tv Field effect devices
68.35.Fx Diffusion; interface formation

Improved cathodoluminescence properties of GaAs/Al0.3Ga0.7As tilted T‐shaped quantum wires fabricated on (111)B facet by glancing‐angle molecular beam epitaxy

N. Tomita, M. Tanaka, T. Saeki, S. Shimomura, S. Hiyamizu, K. Fujita, T. Watanabe, T. Higuchi, N. Sano, and A. Adachi

J. Vac. Sci. Technol. B 14, 3550 (1996); http://dx.doi.org/10.1116/1.588795 (5 pages) | Cited 4 times

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GaAs/Al0.3Ga0.7As tilted T‐shaped quantum wires (T‐QWRs) were fabricated by growing Al0.3Ga0.7As/GaAs (well thickness of GaAs Lw=4.4 nm) on a (111)B facet plane that was formed when a GaAs/Al0.3Ga0.7As multi‐quantum well (MQW) layer (Lw=4.5 nm) was grown on a reverse‐mesa etched GaAs(100) substrate by glancing‐angle molecular beam epitaxy (GA‐MBE). Growth conditions of the tilted T‐QWR were optimized, and full width at half‐maximum (FWHM) of a cathodoluminescence (CL) peak from the tilted T‐QWRs was reduced down to 19 meV at 78 K, which is about one‐third of that (61 meV) of previous GaAs/Al0.3Ga0.7As tilted T‐QWRs. © 1996 American Vacuum Society
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Fd III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Quasiperiodic microfacets on the surface of AlGaAs/GaAs quantum well structures grown by molecular beam epitaxy on (311)A high‐index substrates

S. L. S. Freire, L. A. Cury, F. M. Matinaga, E. C. Valadares, M. V. B. Moreira, A. G. de Oliveira, A. R. Alves, J. M. C. Vilela, M. S. Andrade, T. M. Lima, and J. A. Sluss

J. Vac. Sci. Technol. B 14, 3555 (1996); http://dx.doi.org/10.1116/1.588796 (4 pages) | Cited 2 times

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Standard molecular beam epitaxy is used to demonstrate the growth feasibility and reproducibility on the formation of microfacet array on the top surface of higher‐index (311)A quantum well structures. The quasiperiodic microfacet array was characterized by atomic force microscopy and was observed to be along the [2̄33] direction, whereas for the (100) reference sample the microscopic surface morphology presented the terraces formation. We have used photoluminescence to characterize the optical properties of the samples. The observed redshift of the luminescence from the (311)A sample, in relation to the (100) reference sample, was correlated with the existence of a lateral confinement potential induced by the period of faceting in this structure. The comparative analysis based on photoluminescence measurements have also shown the higher quality and the lower impurity incorporation for the (311)A oriented samples. © 1996 American Vacuum Society
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Fd III-V semiconductors
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Layer‐by‐layer removal of GaAs(110) by bromine

C. Y. Cha and J. H. Weaver

J. Vac. Sci. Technol. B 14, 3559 (1996); http://dx.doi.org/10.1116/1.588797 (4 pages) | Cited 3 times

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Scanning tunneling microscopy results show that heating a nearly saturated Br–GaAs(110) 2×1/c(2×2) surface to 600 K leads to a random distribution of single‐layer deep vacancy islands. These islands expand via continued etching upon heating to 700 K. Subsequent exposure to Br2 at 625 K results in complete removal of the first layer via step retreat. Accordingly, monolayer etching can be achieved. The different etching pathways of the exposure‐annealing treatment and that of continuous etching are discussed. © 1996 American Vacuum Society
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81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Treatment of InP surfaces in radio frequency H2 and H2/CH4/Ar plasmas: In situ compositional analysis, etch rates, and surface roughness

J. E. Parmeter, R. J. Shul, A. J. Howard, and P. A. Miller

J. Vac. Sci. Technol. B 14, 3563 (1996); http://dx.doi.org/10.1116/1.588798 (12 pages) | Cited 6 times

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The surface composition, etch rates, and surface roughness of indium phosphide (InP) surfaces treated in radio frequency (rf) hydrogen and hydrogen/argon/methane plasmas have been investigated using in situ Auger spectroscopy and ex situ scanning electron microscopy and atomic force microscopy. In agreement with most previous studies, hydrogen plasmas are found to completely remove surface carbon and oxygen impurities, but at the expense of some degree of surface phosphorus depletion. This depletion can be minimized by utilizing brief plasma exposure times and low rf power settings. Oxygen removal is found to be rate limiting in the production of a clean surface. InP etching in hydrogen/argon/methane can be performed either in a low density, capacitively coupled plasma mode, or in a high density, inductively coupled plasma mode. For operation in the low density regime, the etched surfaces have a constant and nearly stoichiometric composition, independent of plasma parameters. Etch rates vary from ∼20–400 Å/min, while the root mean square (rms) surface roughness varies from ∼20 to >400 Å. Both of these quantities show definite trends with changing plasma parameters, and, in particular, high etch rates and low surface roughness are both favored by increasing total plasma pressure and methane flow rate. Within the ranges studied, the etch rate is most strongly affected by the amount of hydrocarbon species reaching the surface, which can remove indium in the form of indium alkyl products. However, sputtering effects are also shown to be significant. Etching InP in the high density plasma mode gives an etch rate of ∼700 Å/min, but only at the expense of severe surface phosphorus depletion and rms surface roughness of ∼2000 Å. The breakdown of methane within the plasma under these conditions may serve to inhibit indium alkyl formation, and hence lead to the observed phosphorus depletion. © 1996 American Vacuum Society
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81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Annihilation of monolayer holes on molecular beam epitaxy grown GaAs surface during annealing as shown by in situ scanning electron microscopy

Naohisa Inoue, Keizo Morimoto, Tsutomi Araki, Taichiro Ito, Yoshikazu Homma, and Jiro Osaka

J. Vac. Sci. Technol. B 14, 3575 (1996); http://dx.doi.org/10.1116/1.588545 (7 pages)

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The behavior of monolayer‐deep holes on the surface of (001) GaAs grown by molecular beam epitaxy during post‐growth annealing is observed by in situ scanning electron microscopy. Most small holes disappear immediately after growth in the same way as the islands. However, it is found that some are left for a long time and form big holes with each other. These residual big holes are elongated in the [110] direction initially. They extend in the [110] direction and coalesce with each other, but, at the same time, they shrink in the [1–10] direction and become elongated in the [110] direction. Finally they shrink in both directions and disappear. It takes about 10 min for all the holes to disappear, which is much longer than the growth interruption period usually employed to smooth heterointerfaces. The anisotropic behavior of big holes are discussed in relation to the reported growth anisotropy. © 1996 American Vacuum Society
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68.35.Dv Composition, segregation; defects and impurities
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Antimony doped GaAs: A model of dominant current transport mechanism

E. Valcheva, T. Paskova, and R. Yakimova

J. Vac. Sci. Technol. B 14, 3582 (1996); http://dx.doi.org/10.1116/1.588546 (6 pages)

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Schottky barrier structures formed on epitaxial GaAs:Sb have been studied at different Sb concentrations (0–1×1020 cm−3) and different temperatures (80–300 K). Current–voltage (I–V) characteristics have been numerically simulated and compared with the experimental measurements in an attempt to reveal the dominant current transport mechanism. Since Sb is a nonelectrically active dopant in GaAs but efficiently influences defect ensemble, the role of the defects on the electrical characteristics of the device structures could be investigated. Three different regions of Sb doping have been considered in accordance with a previous study of the structural and electronic properties of metal organic vapor phase epitaxy‐grown GaAs:Sb. The current transport in the samples containing an optimum amount of Sb (respectively, minimum defects) is dominated by a thermionic field emission in the main operation bias range, although indications of Poole–Frenkel effect are observed, related to the intrinsic near mid‐gap electron levels. In the undoped and highly doped samples the current is mainly due to a carrier diffusion mechanism. In addition, the large amount of defects in these samples results in an electron tunneling component which is present in the I–V characteristics. © 1996 American Vacuum Society
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85.30.De Semiconductor-device characterization, design, and modeling
73.30.+y Surface double layers, Schottky barriers, and work functions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Misfit dislocations in strained InxGa1−xAs heterostructure on patterned GaAs (001) substrate

W. Zeng, S. S. Jiang, C. Ferrari, S. Gennari, G. Salviati, and J. H. Jiang

J. Vac. Sci. Technol. B 14, 3588 (1996); http://dx.doi.org/10.1116/1.588730 (5 pages)

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〈110〉 60° and 〈100〉 edge misfit dislocations in In0.06Ga0.94As heterostructures grown on patterned GaAs (001) substrates with relatively low misfit f(f=0.0043) have been investigated. The reduction of 〈110〉 misfit dislocation density on mesas is observed by cathodoluminescence, while the 〈100〉 misfit dislocation density on mesas observed by synchrotron radiation double crystal topography remains unchanged. The critical thickness is calculated by modifying the Matthews mechanical equilibrium theory introduced by Chidambarrao et al. The calculated results can be applied to both the nonpatterned area and the sidewalls of the mesa. The critical thickness of one side of the mesa is larger than that of nonpatterned areas. The critical thickness of both sides of mesas is dependent on the angle between the sidewall and (001) GaAs. This is likely due to different values of cos ϕ/sin ψ, which determines the values of the friction force FF with different sidewall angles. It is suggested that the 〈100〉 misfit dislocations are generated by climb and they can cross mesas by climbing along 〈100〉 directions. © 1996 American Vacuum Society
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.Ct Interface structure and roughness
78.66.Fd III-V semiconductors
61.05.C- X-ray diffraction and scattering

Surface roughness‐induced artifacts in secondary ion mass spectrometry depth profiling and a simple technique to smooth the surface

S. B. Herner, B. P. Gila, K. S. Jones, H.‐J. Gossmann, J. M. Poate, and H. S. Luftman

J. Vac. Sci. Technol. B 14, 3593 (1996); http://dx.doi.org/10.1116/1.588731 (3 pages) | Cited 7 times

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We report on secondary ion mass spectrometry (SIMS) depth profile artifacts induced by surface roughness. The formation of a TiSi2 film at 800 °C on a boron doping superlattice (DSL) of Si results in a rough (22.0 nm root mean square) interface between the film and Si DSL. After chemically etching off the TiSi2 film, SIMS information is collected while sputtering through the surface of the Si DSL. The resulting depth profiles are irreproducible due to the initial surface roughness. By chemo‐mechanically polishing the Si prior to SIMS analysis, we smooth the surface and the resulting depth profiles are then consistent and easily explained by current diffusion theory. © 1996 American Vacuum Society
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81.70.Jb Chemical composition analysis, chemical depth and dopant profiling
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Ps Polishing, grinding, surface finishing

Rh/n‐GaAs contacts with and without sulfur passivation

G. Eftekhari

J. Vac. Sci. Technol. B 14, 3596 (1996); http://dx.doi.org/10.1116/1.588732 (3 pages)

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The Rh/n‐GaAs contacts with and without sulfur passivation were examined. It was demonstrated that passivation results in contacts of better quality and improved thermal stability. The passivated contacts had higher barrier height, lower reverse current, and lower ideality factor. The formation of thermally stable S–S, S–Ga, and S–As bonds at the GaAs surface, suppression of thermally generated defects, and possible modification in the charge and structure of native oxide were used to explain the observations. © 1996 American Vacuum Society
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73.40.Cg Contact resistance, contact potential
68.35.Fx Diffusion; interface formation
81.65.Rv Passivation

Hydrogen‐induced reconstruction of the GaP(001) surface studied by scanning tunneling microscopy

A. Watanabe, H. Shimaya, M. Naitoh, and S. Nishigaki

J. Vac. Sci. Technol. B 14, 3599 (1996); http://dx.doi.org/10.1116/1.588733 (4 pages) | Cited 2 times

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We report results of a scanning tunneling microscopy investigation on the reconstruction of GaP(001) surfaces. We have observed a 4×2 structure, accompanied locally with c(8×2) domains, at a surface prepared by using ion sputtering and annealing method. On the contrary, both 2×4 [with local c(2×8)] and 4×2 [with local c(8×2)] structures are obtained by hydrogenation followed by annealing. The former consists of a unit structure of three P dimers plus one dimer vacancy, whereas the latter is a parallel arrangement of zig–zag‐chained structures along the [110] direction. It has been shown that the surface hydrogenation before annealing induces new types of reconstruction. © 1996 American Vacuum Society
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68.35.Rh Phase transitions and critical phenomena
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Erratum: Selective wet etching of lattice‐matched InGaAs/InAlAs on InP and metamorphic InGaAs/InAlAs on GaAs using succinic acid/hydrogen peroxide solution [J. Vac. Sci. Technol. B 14, 3400 (1996)]

Hervé Fourre, Frédéric Diette, and Alain Cappy

J. Vac. Sci. Technol. B 14, 3603 (1996); http://dx.doi.org/10.1116/1.588734 (1 page) | Cited 1 time

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Abstract Unavailable
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81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors
99.10.Cd Errata

Erratum: Surface reaction of trimethylgallium on GaAs [J. Vac. Sci. Technol. B 14, 136 (1996)]

Jun‐ichi Nishizawa, Hiroshi Sakuraba, and Toru Kurabayashi

J. Vac. Sci. Technol. B 14, 3604 (1996); http://dx.doi.org/10.1116/1.588735 (1 page) | Cited 1 time

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Abstract Unavailable
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Erratum: Deep‐etch silicon mm‐waveguide structure for the relativistic acceleration of electrons [J. Vac. Sci. Technol. B 14, 2524 (1996)]

T. L. Willke and A. D. Feinerman

J. Vac. Sci. Technol. B 14, 3605 (1996); http://dx.doi.org/10.1116/1.588736 (1 page)

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41.75.Lx Other advanced accelerator concepts
81.05.Cy Elemental semiconductors

Persistence pays off: Sir Charles Oatley and the scanning electron microscope

T. E. Everhart

J. Vac. Sci. Technol. B 14, 3620 (1996); http://dx.doi.org/10.1116/1.588737 (5 pages) | Cited 2 times

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Shortly after World War II, Sir Charles Oatley initiated research at the Cambridge University engineering laboratories on what has evolved into the modern scanning electron microscope. While much of the research was actually conducted by research students under Oatley’s supervision, he continually provided ideas, resources, and encouragement. He then was instrumental in having this instrument commercialized. His students often continued in the field for some time, making contributions both to the instrument and to its applications that led to improved performance and wider acceptance. This article attempts to capture some of the accomplishments of Sir Charles Oatley as seen by those who worked closely with him. The author believes that Sir Charles deserves the title: ‘‘Father of the Modern Scanning Electron Microscope.’’ © 1996 American Vacuum Society
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01.60.+q Biographies, tributes, personal notes, and obituaries
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Application of scanning probe methods for electronic and magnetic device fabrication, characterization, and testing

A. Born, C. Hahn, M. Löhndorf, A. Wadas, Ch. Witt, and R. Wiesendanger

J. Vac. Sci. Technol. B 14, 3625 (1996); http://dx.doi.org/10.1116/1.588738 (7 pages) | Cited 3 times

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Selected examples of the application of scanning probe methods for the fabrication, characterization, and testing of electronic and magnetic devices are presented. In particular, promising combinations of conventional photolithography or e‐beam lithography with scanning probe methods are described. The combination of atomic‐scale self‐organization processes with scanning probe microscopy and manipulation experiments possibly can lead to a novel class of atomic‐scale devices which could be fabricated on a reasonable time scale. © 1996 American Vacuum Society
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07.79.-v Scanning probe microscopes and components
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
85.30.De Semiconductor-device characterization, design, and modeling
85.70.Ay Magnetic device characterization, design, and modeling

Low‐energy ion damage in semiconductors: A progress report

Evelyn L. Hu, Ching‐Hui Chen, and Debora L. Green

J. Vac. Sci. Technol. B 14, 3632 (1996); http://dx.doi.org/10.1116/1.588739 (5 pages) | Cited 25 times

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There has been steady progress in understanding the propagation of low‐energy, ion‐induced damage into semiconductor substrates. The availability of specifically designed heterostructure substrates allows us to trace the profile of damage into the material. A number of experiments, together with theoretical simulations, have confirmed the important role played by fortuitous channeling of ions, deep into the material (e.g., >1000 Å deep for incident ions energies ∼300 eV). Recent experiments have also shown the importance of rapid diffusion of ion‐created defects. Using a model that includes the effects of both channeling and defect diffusion, channeling and diffusion in ion damage (CHANDID), we have deduced a room‐temperature diffusion constant of D∼1×10−15 cm2/s. This is an extremely high value for diffusion at room temperature, and is more characteristic of diffusion taking place at temperatures of a few hundred to a few thousand degrees centigrade. One cause of this high value of D may be attributed to radiation enhanced diffusion: the creation of excess electrons and holes during the etch process whose subsequent nonradiative recombination transfers momentum to the defects. Preliminary experiments, which monitor the effects of above band‐gap illumination during ion bombardment, validate this picture. Such understanding, of intrinsic importance, can be used to design material and device structures in which the effects of ion damage may be mitigated. © 1996 American Vacuum Society
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61.82.Fk Semiconductors
61.80.Jh Ion radiation effects
85.30.De Semiconductor-device characterization, design, and modeling

Etching processes for fabrication of GaN/InGaN/AlN microdisk laser structures

J. W. Lee, C. B. Vartuli, C. R. Abernathy, J. D. MacKenzie, J. R. Mileham, S. J. Pearton, R. J. Shul, J. C. Zolper, M. Hagerott‐Crawford, J. M. Zavada, R. G. Wilson, and R. N. Schwartz

J. Vac. Sci. Technol. B 14, 3637 (1996); http://dx.doi.org/10.1116/1.588740 (4 pages) | Cited 6 times

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Several new wet and dry etch processes required for fabrication of microdisk lasers in the III nitrides have been developed. ICl/Ar electron cyclotron resonance plasmas produce etch rates of 1.3 μm/min for GaN and 1.15 μm/min for InN at 1000 W microwave power and 250 W of rf power. These rates are substantially faster than previously investigated Cl2/Ar or CH4/H2 plasma chemistries. Selectivities of 5–6 over AlN are obtained for these materials. Wet chemical etching of AlN and InXAl1−XN in KOH‐based solutions was found to be a strong function of etch temperature and material quality. The activation energy for these materials was in the range 2–6 kcal/mol, typical of diffusion‐controlled processes. The KOH solutions did not etch GaN or InN at temperature as high as 80 °C. © 1996 American Vacuum Society
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81.65.Cf Surface cleaning, etching, patterning
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.55.Px Semiconductor lasers; laser diodes

Quantum dots fabricated in InP/InGaAs by free Cl2 gas etching and metalorganic chemical vapor deposition regrowth

R. Panepucci, E. Reuter, P. Fay, C. Youtsey, J. Kluender, C. Caneau, J. J. Coleman, S. G. Bishop, and I. Adesida

J. Vac. Sci. Technol. B 14, 3641 (1996); http://dx.doi.org/10.1116/1.588741 (5 pages)

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The free Cl2 thermal etching of InGaAs/InP was characterized for the fabrication of quantum well dots (QDs). The effects of mask shape on the three‐dimensional structure of the dot was investigated. Quantum dots with dimensions as small as 56 nm were fabricated using electron beam lithography and free Cl2 etching. The dots were characterized using scanning electron microscopy and low temperature photoluminescence (PL). Metalorganic chemical vapor deposition (MOCVD) regrowth of InP on quantum dots of different mask shapes was investigated. The effect of non‐radiative recombination at the etched sidewall was evaluated through the normalized intensity of the PL. A red shift of the PL peak with decreasing dot sizes was observed for the as‐etched structures and attributed to the effect of residual compressive biaxial strain on the InGaAs layer. Free Cl2 etching is an important etch technique for in situ etch and regrowth processes due to the high quality of the etched interface and the ability to perform selective area regrowth with a SiO2 mask still present. © 1996 American Vacuum Society
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
78.66.Fd III-V semiconductors

Reduced nonradiative recombination in etched/regrown AlGaAs/GaAs structures fabricated by in situ processing

S. Kohmoto, Y. Nambu, K. Asakawa, and T. Ishikawa

J. Vac. Sci. Technol. B 14, 3646 (1996); http://dx.doi.org/10.1116/1.588742 (4 pages)

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Effectiveness of in situ processing, which combines Cl2 gas etching with subsequent molecular beam epitaxy regrowth in an ultrahigh vacuum environment, is quantitatively evaluated with nonradiative carrier recombination velocity, S, of etched/regrown AlGaAs/GaAs heterointerfaces. When AlGaAs is in situ regrown on Cl2 gas‐etched flat GaAs surface, the S value is as low as 1.3×103 cm/s. This value is lower than that of air‐exposed/regrown (or ex situ processed) interfaces, thus representing the essential superiority of in situ processing over ex situ. Buried GaAs/AlGaAs multiquantum‐well (MQW) mesa‐stripes are also fabricated by in situ Cl2 gas‐etching/regrowth. The S value at the MQW mesa‐sidewall regrown with AlGaAs is 6.0×103 cm/s, which is reduced by more than one order of magnitude from that of a nonburied case. © 1996 American Vacuum Society
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.65.Cf Surface cleaning, etching, patterning

Etch‐mask of pyrolytic‐photoresist thin‐film for self‐aligned fabrication of smooth and deep faceted three‐dimensional microstructures

G. A. Porkolab, Shih‐Hsiang Hsu, John V. Hryniewicz, Wenhua Lin, Y. J. Chen, Sambhu Agarwala, F. G. Johnson, Oliver King, M. Dagenais, and D. R. Stone

J. Vac. Sci. Technol. B 14, 3650 (1996); http://dx.doi.org/10.1116/1.588743 (4 pages) | Cited 3 times

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Etch‐mask thin‐film material that is particulate‐free and topographically smooth has been created from a standard photoresist spun onto standard semiconductor substrates such as gallium arsenide, indium phosphide, and silicon, and then pyrolyzed by exposing to a temperature of 300 °C in air atmosphere for 1 min on a standard laboratory hot‐plate. The resulting pyrolytic‐photoresist thin‐film is chemically inert to many standard organic solvents including the solvent of photoresist itself and to many inorganic reagents used in semiconductor processing. Therefore the pyrolytic‐photoresist can be patterned by sulfur hexafluoride reactive ion etching via a standard photoresist mask. Upon stripping the standard photoresist in a mixture of 1:1/acetone:developer agitated ultrasonically, the remaining patterned pyrolytic‐photoresist performs as an excellent etch‐mask in chemically assisted ion beam etching and reactive ion etching systems. Thus it can be a key material in the multilayer masking technique used to sculpt self‐aligned three‐dimensional microstructures with deep and smooth facets which are needed for example for photonic integrated circuits and micro‐electro‐mechanical systems. © 1996 American Vacuum Society
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42.82.Cr Fabrication techniques; lithography, pattern transfer
07.10.Cm Micromechanical devices and systems

Photoluminescence blueshift induced by reactive ion etching of strained CdZnSe/ZnSe quantum well structures

L. M. Sparing, P. D. Wang, S. H. Xin, S. W. Short, S. S. Shi, J. K. Furdyna, J. L. Merz, and G. L. Snider

J. Vac. Sci. Technol. B 14, 3654 (1996); http://dx.doi.org/10.1116/1.588744 (4 pages) | Cited 3 times

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A study of the effects of reactive ion etching (RIE) on molecular beam epitaxy‐grown Zn1−xCdxSe/ZnSe strained multiple quantum well samples using low temperature photoluminescence reveals a blueshift in the characteristic peak positions of the wells when etched with CH4/H2. Based on the experimental results, we suggest that the blueshift is not a result of hydrogen incorporation, but that etch induced damage relaxes the compressive strain present in the as‐grown quantum well, producing the observed blueshift. After thermal annealing the energy of the photoluminescence signal returns to its original value, suggesting a restoration of the strain by elimination of the structural damage induced by RIE. However, the original photoluminescence intensity is not recovered by annealing. © 1996 American Vacuum Society
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78.66.Hf II-VI semiconductors
81.65.Cf Surface cleaning, etching, patterning
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Dry etching damage in III–V semiconductors

S. Murad, M. Rahman, N. Johnson, S. Thoms, S. P. Beaumont, and C. D. W. Wilkinson

J. Vac. Sci. Technol. B 14, 3658 (1996); http://dx.doi.org/10.1116/1.588745 (5 pages) | Cited 20 times

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Dry etching using ions can cause damage to the underlying semiconductor. This paper discusses damage in III–V semiconductors and presents examples of etching conditions under which it can be effectively eliminated. A distinction between surface and sidewall damage is made and methods of measuring both parameters are reviewed. It is noted that the noble gases cause relatively deep damage, while under the correct circumstances, etchants that have a marked chemical effect can cause much less damage. The present state of understanding of the mechanisms for the damage is discussed. © 1996 American Vacuum Society
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81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors
61.80.Jh Ion radiation effects
85.30.-z Semiconductor devices

Effects of etch‐induced damage on the electrical characteristics of in‐plane gated quantum wire transistors

K. K. Ko, E. W. Berg, and S. W. Pang

J. Vac. Sci. Technol. B 14, 3663 (1996); http://dx.doi.org/10.1116/1.588746 (5 pages) | Cited 3 times

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In‐plane gated (IPG) quantum wire transistors were fabricated using dry etching in a Cl2/Ar plasma generated with an electron cyclotron resonance source. The electrical characteristics of the IPG transistors were correlated with the geometrical dimensions as well as the dry etching and passivation conditions. In‐plane gates with the width of the channel (Wc) and the width of the gate isolation (Wg) ranging from 100 to 850 nm were studied. Good field‐effect transistor characteristics with transconductances up to 371 mS/mm were obtained on these devices. At a gate‐source voltage (VGS) of 2 V, the saturated drain‐source current (IDSAT) increased from 68 to 153 μA as Wc increased from 440 to 800 nm. No current was measured on IPG transistors with Wc ≤−130 nm. The quasi‐one‐dimensional channel can be completely pinched off with VGS ≤−1 V. It was found that the gate leakage current decreased with a wider Wg and a deeper depth for the gate isolation. The leakage current at VGS=2 V decreased significantly from 250 to <0.1 pA when the etch depth increased from 320 to 440 nm. The gate leakage current and IDS were also found to increase with rf power used for etching due to additional defects generated at higher ion energy. These defects, however, can be passivated with low energy chlorine species, and reduction of the gate leakage current from 40 to 4.4 nA was observed after a 1 min Cl2 plasma passivation. © 1996 American Vacuum Society
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.65.Cf Surface cleaning, etching, patterning

Effects of O2 addition to SiCl4/SiF4 and the thickness of the capping layer on gate recess etching of GaAs‐pseudomorphic high electron mobility transistors

S. K. Murad, N. I. Cameron, S. P. Beaumont, and C. D. W. Wilkinson

J. Vac. Sci. Technol. B 14, 3668 (1996); http://dx.doi.org/10.1116/1.588747 (6 pages) | Cited 5 times

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The effects of the addition of a small amount of O2 to SiCl4/SiF4 plasma and the thickness of the GaAs capping layer on gate recess etching of GaAs pseudomorphic high electron mobility transistor (p‐HEMT) devices have been studied. During gate recessing of GaAs/AlGaAs p‐HEMTs using a selective reactive ion etching (RIE) process in SiCl4/SiF4 plasma [see S. K. Murad, N. I. Cameron, P. D. Wang, S. P. Beaumont, and C. D. W. Wilkinson, Microelectron. Eng. 27, 439 (1995)], it was found that the profile of the gate changes dramatically from undercut to nearly vertical with no lateral etching when the thickness of the capping layer was reduced below 40 nm. This vertical profile puts the gate metal too close to the recess edges in devices with a ≤30 nm capping layer. The addition of a very small amount of O2 to SiCl4/SiF4 plasma was seen to increase GaAs etch rates remarkably, while maintaining the high selectivity over AlGaAs. This increase in the etch rate agrees well with optical emission spectroscopic observations which indicate that the Cl emission has increased by more than an order of magnitude for the addition of only 1.5% of O2 to SiCl4/SiF4 plasma. This selective RIE process of SiCl4/SiF4/O2 was applied to gate recess etching of GaAs/AlGaAs/InGaAs p‐HEMTs with various capping layer thicknesses. The profile of the T gates changed from nearly vertical (with no undercut or gate offset) to undercut with a lateral etch rate depending on the thickness of the capping layer. The lateral etching rate also strongly depends on the O2 flow. The p‐HEMT devices gate recessed using this process (SiCl4/SiF4/O2) exhibited an ft of 120 GHz, gm of 700 mS/mm and a gain of 9.5 dB at 94 GHz. © 1996 American Vacuum Society
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81.65.Cf Surface cleaning, etching, patterning
85.30.Tv Field effect devices

Investigation of improved regrown material on InP surfaces etched with methane/hydrogen/argon

D. G. Yu, C.‐H. Chen, B. P. Keller, A. L. Holmes, E. L. Hu, and S. P. Den Baars

J. Vac. Sci. Technol. B 14, 3674 (1996); http://dx.doi.org/10.1116/1.588748 (5 pages) | Cited 1 time

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In this work, we study the hydrogen introduced into InP during methane/hydrogen/argon reactive ion etching (RIE) to determine its effect on metalorganic chemical vapor deposition regrowth. We replace hydrogen with deuterium and confirm that deuterium is introduced into the substrate during methane/deuterium/argon RIE with secondary ion mass spectrometry. During regrowth, the deuterium diffuses from deep within the material and clusters at the regrowth interface, strongly indicating the presence of defects. To further understand the role of hydrogen, we investigate the separate effects of ion damage and hydrogenation on subsequent regrowth. We find that photoluminescence of regrown quantum wells is greatly improved on argon ion damaged substrates which have been additionally exposed to hydrogen at −150 V for 3 min. These experiments illustrate that hydrogen interacts with defects in InP, preventing their propagation during regrowth, and improving the photoluminescence quality of regrown quantum wells. © 1996 American Vacuum Society  
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81.65.Cf Surface cleaning, etching, patterning
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors

Reactive ion etch‐induced effects on 0.2 μm T‐gate In0.52Al0.48As/In0.53Ga0.47As/InP high electron mobility transistors

R. Cheung, W. Patrick, I. Pfund, and G. Hähner

J. Vac. Sci. Technol. B 14, 3679 (1996); http://dx.doi.org/10.1116/1.588749 (5 pages) | Cited 3 times

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The effect of CH4/H2 reactive ion etching on In0.52Al0.48As surfaces and In0.52Al0.48As/ In0.53Ga0.47As/InP heterostructure have been studied using Schottky diode, x‐ray photoelectron spectroscopy, and room temperature transport experiments. The application of CH4/H2 as a dry etch gas for the gate recess step in the fabrication of 0.2 μm T‐gate In0.52Al0.48As/In0.53Ga0.47As/InP high electron mobility transistor has been explored. We show that while the room temperature mobility and the dc and high frequency performance of the dry etched devices are at least comparable to the wet etched ones, their microwave noise behaviours are extremely sensitive to dry etch‐induced defects. © 1996 American Vacuum Society
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85.30.Tv Field effect devices
81.65.Cf Surface cleaning, etching, patterning
84.40.Lj Microwave integrated electronics

Photoluminescence studies on radiation enhanced diffusion of dry‐etch damage in GaAs and InP materials

Ching‐Hui Chen, D. Ginger Yu, Evelyn L. Hu, and Pierre M. Petroff

J. Vac. Sci. Technol. B 14, 3684 (1996); http://dx.doi.org/10.1116/1.588750 (4 pages) | Cited 13 times

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We have investigated the radiation enhanced diffusion of ion defects during reactive ion beam etching of GaAs and InP, using the multiple quantum well (MQW) probe technique. During low energy (sub‐keV) Ar+ ion exposure, illumination with light of energy above the band gap can substantially reduce the photoluminescence efficiency of MQW samples, relative to those which were not laser illuminated; the degradation of luminescence efficiency increases with the intensity of the light. Illumination with light of energy below the band gap produces a slight increase in the damage profiles. The observation of enhanced defect diffusion due to optical radiation in our studies suggests that in ion‐assisted etching of semiconductors, the generation of excess electron‐hole pairs and their subsequent recombination can play an important role in the propagation of defects into the substrate. © 1996 American Vacuum Society
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66.30.Lw Diffusion of other defects
61.80.Jh Ion radiation effects
81.65.Cf Surface cleaning, etching, patterning
78.66.Fd III-V semiconductors

Suppression of electron shading effect by a counter radio frequency bias in plasma etching

T. Kamata and H. Arimoto

J. Vac. Sci. Technol. B 14, 3688 (1996); http://dx.doi.org/10.1116/1.588648 (4 pages) | Cited 4 times

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We investigated the suppression of the charge buildup caused by the electron shading effect using a counter rf bias, which produces high energy electrons reflected from the counter electrode. We expected that these high energy electrons could overcome the potential barrier formed at the entrance of high aspect‐ratio hole patterns and to decrease the charge buildup at the bottom of these patterns. We directly investigated the charge buildup by measuring dc self‐bias potential differences between high aspect‐ratio hole patterns and open‐space pattern. The dc self‐bias potential difference increased, independent of the hole pattern aspect ratio, at the lower substrate rf bias voltage and they tended to saturate at the following higher substrate rf bias voltage. The dc self‐bias potential difference reached about 100 V with a substrate rf bias voltage of 400 V for an aspect ratio of 2. The dc self‐bias potential difference dramatically decreased from 100 to 20 V by increasing the counter rf bias voltage. In addition, we investigated this suppression effect by changing the phase difference between counter and substrate bias voltages when both bias frequencies were set to 13.56 MHz. We found that there is a variation of the suppression effect with respect to the phase difference. This indicates that high energy electrons, which were accelerated in an oscillation sheath, could reach the bottom of the holes. © 1996 American Vacuum Society
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
85.40.Hp Lithography, masks and pattern transfer

Fabrication of micromechanical switches for routing radio frequency signals

John N. Randall, Chuck Goldsmith, David Denniston, and Tsen‐Hwang Lin

J. Vac. Sci. Technol. B 14, 3692 (1996); http://dx.doi.org/10.1116/1.588649 (5 pages) | Cited 8 times

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Micromechanical switches have several advantages over other switch technologies for the routing of microwave and mm‐wave signals. They offer low loss, low switching power, very low standby power, and are extremely linear. The switching speeds are very slow compared to solid state switches; however, for a number of applications, their specifications appear attractive. For instance, electronically steerable antenna arrays operating at 10, 20, and 30 GHz need phase shifters for each antenna element. Micromechanical RF switches that offered lower losses could find significant applications as phase shifters for telecommunications applications. We describe the fabrication of membrane micromechanical RF switches that switch signals of 10 GHz and higher. Dry etching plays a critical role in fabrication. In particular the isotropic removal of a sacrificial polymer layer between the bottom electrode and the membrane is a critical process. Reasonable rates must be obtained at moderate temperatures and there must be as little residue as possible. A high degree of selectivity over that of the capacitor dielectric is also a requirement. Our process should be compatible with microwave monolithic integrated circuit (MMIC) processing technology allowing integration with RF amplifiers and other components. © 1996 American Vacuum Society
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84.40.-x Radiowave and microwave (including millimeter wave) technology
07.10.Cm Micromechanical devices and systems

Sharpening Si field emitter tips by dry etching and low temperature plasma oxidation

M. R. Rakhshandehroo and S. W. Pang

J. Vac. Sci. Technol. B 14, 3697 (1996); http://dx.doi.org/10.1116/1.588650 (5 pages) | Cited 4 times

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Dry etching and low temperature plasma oxidation were used to sharpen Si field emitter tips. Si emitters with tip radii of 67 nm were formed by dry etching in a Cl2 plasma at 5 mTorr. An electron cyclotron resonance (ECR) source was used to generate the plasma and erosion of a SiO2 mask was employed to control the Si emitter geometry. The Si emitters were sharpened by dry etching in the Cl2 plasma generated at 0.7 and 5 mTorr after the SiO2 mask was completely eroded. After etching the emitters for 7 min at 0.7 mTorr, the tip radius decreased from 67 to 22 nm. The sharpening effect could be attributed to enhanced sputtering yield at sloped surfaces. At higher pressure of 5 mTorr, the sharpening effect was reduced and the tip radius only decreased from 67 to 62 nm. Optical emission spectroscopy and mass spectrometry were used to monitor the etching and sharpening of Si emitter tips. Sharp increases in the Si emission signal at 288.1 nm and mass spectrometric signal for 63SiCl+ were observed once the SiO2 mask was completely eroded and the sharpening of Si emitters had started. Plasma oxidation was also used to sharpen the emitter tips. With the stage at room temperature, up to 257 nm of plasma oxide was grown in an O2 plasma generated at 0.3 mTorr by the ECR source. After oxide removal, the emitters tip radius was found to decrease from 67 to 8 nm. In comparison, the same amount of oxide grown by thermal dry oxidation at 950 and 1100 °C only reduced the tip radius to 32 and 50 nm, respectively. Sharper emitter tips and faster oxidation rate can be obtained by plasma oxidation. © 1996 American Vacuum Society
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85.45.Db Field emitters and arrays, cold electron emitters
81.65.-b Surface treatments

Realization of atomic layer etching of silicon

Satish D. Athavale and Demetre J. Economou

J. Vac. Sci. Technol. B 14, 3702 (1996); http://dx.doi.org/10.1116/1.588651 (4 pages) | Cited 11 times

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An experimental system and methodology were developed to realize dry etching of single crystal silicon with monolayer accuracy. Atomic layer etching of silicon is a cyclic process composed of four consecutive steps: reactant adsorption, excess reactant evacuation, ion irradiation, and product evacuation. When successful, completion of one cycle results in removal of one monolayer of silicon. The process was self‐limiting with respect to both reactant and ion dose. Control of the ion energy was the most important factor in realizing etching of one monolayer per cycle. © 1996 American Vacuum Society
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81.65.Cf Surface cleaning, etching, patterning
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
81.05.Cy Elemental semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)

Precision optical aspheres for extreme ultraviolet lithography

D. R. Kania, D. P. Gaines, D. S. Sweeney, G. E. Sommargren, B. La Fontaine, S. P. Vernon, D. A. Tichenor, J. E. Bjorkholm, F. Zernike, and R. N. Kestner

J. Vac. Sci. Technol. B 14, 3706 (1996); http://dx.doi.org/10.1116/1.588652 (3 pages) | Cited 1 time

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We have demonstrated significant advances in the production of aspheric optics for extreme ultraviolet lithography. An optic has been fabricated with an aspheric departure of 1.5 μm, a figure error of 0.7 nm rms, and a nanoroughness of 0.25 nm rms. Further improvements are required in the figure and nanoroughness to reach high throughput and near diffraction limited performance in an extreme ultraviolet lithography system. © 1996 American Vacuum Society
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42.79.-e Optical elements, devices, and systems
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Effects of compaction on 193 nm lithographic system performance

Richard Schenker and William Oldham

J. Vac. Sci. Technol. B 14, 3709 (1996); http://dx.doi.org/10.1116/1.588653 (5 pages) | Cited 1 time

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Ultraviolet radiation induces compaction in fused silica. Using stress‐induced birefringence as a dosimeter, we are able to measure refractive index changes over the range of 20 ppb–1.5 ppm and have found a general description of compaction versus 193 nm dose valid for a wide range of intensities, pulse rates, and fused silicas. Using the experimental data, we evaluate the effect of compaction damage on a model 193 nm optic. Zernike phase aberration terms from compaction in elements near the pupil plane of the system are calculated using Fourier optics while aberrations from other elements are estimated using ray‐tracing. Aerial image simulations show significant distortion and focal shifts occur at the edge of the image field for only a 0.05λ total rms compaction‐induced wave front aberration. The useful life of the model system depends strongly on the throughput, resist sensitivity, and partial coherence. For a system operating at 10 million pulses per day with a 70% clear field mask and sigma of 0.5, we predict a life range of 6 months to 12 years for resist sensitivities ranging from 50 mJ/cm2 to 10 mJ/cm2. This life prediction increases by over factor of 2 for sigma of 0.7. © 1996 American Vacuum Society
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
42.30.Va Image forming and processing
42.70.-a Optical materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Merit functions for lithographic lens design

Christopher J. Progler and Dale M. Byrne

J. Vac. Sci. Technol. B 14, 3714 (1996); http://dx.doi.org/10.1116/1.588654 (5 pages) | Cited 2 times

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We describe a new approach to the optimization of lithography lenses where lithographic quality factors are enclosed inside the optimization loop. These quality factors are derived from an image simulation program which calculates the relevant lithography metrics each time an optimization cycle is attempted. We find lithographic merit functions strongly impact the final lens performance, and superior lithographic imaging is possible when they are employed. We also show that lens users benefit by understanding the aberration balance inherent in each lithography lens. © 1996 American Vacuum Society
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42.15.Eq Optical system design
85.40.Hp Lithography, masks and pattern transfer
42.79.Bh Lenses, prisms and mirrors

Attenuated phase shift mask materials for 248 and 193 nm lithography

B. W. Smith, S. Butt, Z. Alam, S. Kurinec, and R. L. Lane

J. Vac. Sci. Technol. B 14, 3719 (1996); http://dx.doi.org/10.1116/1.588655 (5 pages) | Cited 6 times

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In order to push resolution toward diffraction limits for 248 and 193 nm lithography, it is likely that some combination of optical enhancement may be needed. The attenuated phase shift mask approach may prove to be one of the less complex techniques available. Four materials are presented which may meet optical and process requirements for use as attenuated phase shift mask films: a molybdenum silicon oxide composite, an aluminum/aluminum nitride cermet, an understoichiometric silicon nitride, and a tantalum silicon oxide composite. All of these materials are shown to be capable of 4%–15% transmission at 193 nm with thicknesses that produce a π phase shift. Evaluation of addition film properties including plasma reactive ion etch and long wavelength transmission helps in establishing materials which may be most production worthy. © 1996 American Vacuum Society
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85.40.Hp Lithography, masks and pattern transfer
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Propagation effects of partial coherence in optical lithography

R. J. Socha and A. R. Neureuther

J. Vac. Sci. Technol. B 14, 3724 (1996); http://dx.doi.org/10.1116/1.588656 (6 pages) | Cited 5 times

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A method based on optimal expansions is described for making an order of magnitude speed up in the analysis of partial coherence effects of scattering in optical lithography, inspection, and alignment. This method expands the incident mutual intensity from the illumination into coherent nonuniform plane waves whose effects can be added incoherently. For three‐dimensional structures, the CPU time is reduced by an order of magnitude over the uniform plane wave approach of Abbe. For two‐dimensional structures, the number of simulations with the decomposition technique has been found to be about three times smaller than with Abbe’s approach. The method has been incorporated into TEMPEST and shown to give accurate results and reduced CPU time in applications of imaging an attenuated phase shift mask, patterning of gates over an active area well in silicon, and inspection of a trench in silicon dioxide, where the CPU time savings are most significant due to large NA’s and high σ’s. Results for an embedded phase shift mask show the need to generalize Hopkin’s method to include effects of the dependence of the diffraction efficiencies on the angle of incidence. The inclusion of partial coherence in regions of topography scattering show beneficial imaging effects in that reflective notching is reduced as σ is increased. © 1996 American Vacuum Society
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85.40.Hp Lithography, masks and pattern transfer
42.25.-p Wave optics

General aspheric refractive micro‐optics fabricated by optical lithography using a high energy beam sensitive glass gray‐level mask

Walter Däschner, Pin Long, Robert Stein, Chuck Wu, and S. H. Lee

J. Vac. Sci. Technol. B 14, 3730 (1996); http://dx.doi.org/10.1116/1.588657 (4 pages) | Cited 9 times

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General aspheric refractive microlens arrays with an almost 100% fill factor are useful in a wide range of applications ranging from display, optoelectronic interconnections, or improving the efficiency of detector arrays to lithography techniques utilizing microlens arrays. In this article a technique will be discussed which allows the microlithographic fabrication of general aspheric non rotationally symmetric refractive lenses with a 100% fill factor. A gray‐level mask based on high energy beam sensitive (HEBS) glass is used to pattern a thick (4–5 micron) photoresist layer. After development, the refractive structure is transferred into the substrate material using a chemically assisted ion beam etching (CAIBE) process. The HEBS‐glass gray‐level mask is generated by a electron‐beam writer, allowing for complete freedom in terms of the shape and location of the lenses. © 1996 American Vacuum Society
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.-e Optical elements, devices, and systems

Simulation of light propagation in optical linear and nonlinear resist layers by finite difference beam propagation and other methods

A. Erdmann and W. Henke

J. Vac. Sci. Technol. B 14, 3734 (1996); http://dx.doi.org/10.1116/1.588658 (4 pages) | Cited 2 times

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This article presents a new method for the calculation of light propagation in resist layers and compares it with scaled defocus and transfer matrix algorithms. Our method is not restricted to homogeneous resist and substrate layers. For the first time, a simulation of focus drilling is presented. © 1996 American Vacuum Society
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42.25.Bs Wave propagation, transmission and absorption
85.40.Hp Lithography, masks and pattern transfer

Micro‐objective lens with compact secondary electron detector for miniature low voltage electron beam systems

W. Liu, T. Ambe, and R. F. Pease

J. Vac. Sci. Technol. B 14, 3738 (1996); http://dx.doi.org/10.1116/1.588659 (4 pages) | Cited 3 times

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The low voltage scanning electron microscope appears to be attractive for the examination of ultrathin film such as surface contamination. However, achieving high resolution and high secondary electron detection efficiency at, say 100 eV landing energy, meets serious electron optical challenges. We describe a very low aberration micro‐objective lens that is combined with an efficient secondary electron detector to address this issue. The objective lens comprises a mirco‐einzel lens followed by a retarding region (from 10 000 to 100 V) and a final electrode just above the sample to minimize the electric field at the sample surface. The retarding field (a) lowers aberration of the objective lens and (b) accelerates the secondary electrons to improve the detection. Using computer modeling we have optimized the design to minimize the primary beam diameter and maximize secondary electron collection. For a landing energy of 100 eV the minimum beam diameter is about 10 nm at 96 μm working distance when the beam energy spread is 0.1 eV. About 50% of secondary electrons can be collected by the compact p‐n junction detector micromachined to serve also as the bottom electrode of the einzel lens. The depletion region extends from 0.25 to 5 μm at zero bias and experimental results indicate a current gain of more than 2000. © 1996 American Vacuum Society
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41.85.Ne Electrostatic lenses, septa
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Triangular‐variable‐shaped beams using the cell projection method

Yasuhiro Someda, Yasunari Shoda, and Norio Saitou

J. Vac. Sci. Technol. B 14, 3742 (1996); http://dx.doi.org/10.1116/1.588660 (5 pages) | Cited 1 time

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A triangular variable shaped electron beam lithography method using the cell projection method is proposed. The shaped beams are formed by a conventional rectangular beam method and variable triangular apertures. This method has three significant characteristics: The plural kind of triangles can be made. This increases the pattern flexibility and decreases the number of shots. The position of one corner of the triangles is automatically determined. Therefore, there is no fluctuation of the triangular beam position and the size of the triangle can be varied with high precision. The triangular apertures are located such as to minimize the deflection distance. This realizes high speed and high precision beam formation. With these characteristics, this method is expected to be used for high speed and high precision mask fabrication. © 1996 American Vacuum Society
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85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
41.85.Ew Particle beam profile, beam intensity

Combined calculation of lens aberrations, space charge aberrations, and statistical Coulomb effects in charged particle optical columns

X. R. Jiang, J. E. Barth, and P. Kruit

J. Vac. Sci. Technol. B 14, 3747 (1996); http://dx.doi.org/10.1116/1.588661 (6 pages) | Cited 4 times

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Optimizing a charged particle optical system utilizing a high brightness source requires the inclusion of the effect of Coulomb interactions in the evaluations. A new computer program package, named ANALIC, has been developed to perform the combined calculation of lens aberrations, space charge aberrations, and statistical Coulomb effects in a complete instrument. By making use of an analytical slice method, valid for weak/incomplete collisions, to calculate the Coulomb interactions, the program combines reasonable accuracy with high speed. Using ANALIC, an optical system with an arbitrary number of lenses and apertures, an arbitrary mode of imaging, and an arbitrary distribution of the beam energy can be analyzed directly. The functions, features, organization, and calculation approach of the program are reported. As an example of the use of the program, a four lens electron probe instrument is analyzed for the demonstration of the combined calculation and optimization process of a particle optical system. © 1996 American Vacuum Society
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41.85.-p Beam optics

Optical design of a combined ion and electron beam system for nanotechnology

P. W. H. de Jager and P. Kruit

J. Vac. Sci. Technol. B 14, 3753 (1996); http://dx.doi.org/10.1116/1.588662 (6 pages)

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