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Jan 2006

Volume 24, Issue 1, pp. 1-177

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Etching of ruthenium coatings in O2- and Cl2-containing plasmas

C. C. Hsu, J. W. Coburn, and D. B. Graves

J. Vac. Sci. Technol. A 24, 1 (2006); http://dx.doi.org/10.1116/1.2121751 (8 pages) | Cited 6 times

Online Publication Date: 9 December 2005

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Ruthenium (Ru) film etching has been studied with O2- and Cl2-containing inductively coupled plasmas to understand the etching mechanism and the relationship between plasma characteristics and the competition between the wall deposition of etch by-products and the creation of volatile etch by-products that flow into the downstream. The ICP was characterized by multiple in situ diagnostic tools. Ru films were etched either from 6-in. wafers placed on a rf-biased substrate or from Ru-coated QCMs without a Ru-coated wafer present. Ru etches readily in O2-containing plasma. Cl2 addition resulted in significant changes in etch rate, wall deposition behavior, and the downstream etch product composition. When Ru was etched by Ar/O2 plasmas, a positive wall deposition rate was observed and no RuO4 was observed in the foreline. The etching rate correlated well with the oxygen radical density. With Cl2 addition, our observations included the significantly increased etching rate, the detection of RuO4 downstream by FTIR, the detection of RuOxCly ions in the plasma, and virtually zero wall deposition. The increased etch rate with Cl2 addition was not solely due to an increase in O atom concentration, plasma density, plasma potential or the electron energy distribution. It is believed that both O- and Cl-containing species (ions and/or neutrals) are necessary to explain the different behavior in Ru etching by using Cl2 and O2-containing plasmas.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
78.30.Er Solid metals and alloys

Free molecular background flow in a vacuum chamber equipped with two-sided pumps

Chunpei Cai, Iain D. Boyd, and Quanhua Sun

J. Vac. Sci. Technol. A 24, 9 (2006); http://dx.doi.org/10.1116/1.2126678 (11 pages) | Cited 2 times

Online Publication Date: 9 December 2005

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Spacecraft propulsion systems, such as Hall thrusters, are designed and tested in large vacuum chambers. The pumping capacity of modern facilities makes it possible to maintain pressures as low as 10−3–10−4 Pa. One fundamental concern for the vacuum chamber is the facility effects on the chamber performance. In this study, several free molecular models are developed to analyze the rarefied background flow inside a vacuum chamber equipped with two-sided vacuum pumps. These models lead to various sets of analytical results including velocity distribution functions for the background flow and formulas to compute the vacuum pump sticking coefficient. These results can be used to evaluate the performance of vacuum chambers and to aid constructing proper background flows for particle simulations of these systems. The results indicate that the background flow conditions can have a significant nonzero mean velocity and cannot be considered to be described by a Maxwellian velocity distribution. The models are applied to analyze the rarefied background flow in a specific vacuum chamber. Calculations of the sticking coefficient for flow of xenon in the vacuum chamber yield values close to 0.40 for cryogenic pumps. Several modifications of the background flow treatment for particle simulations are proposed with the aid of these analytical results.
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47.85.Kn Hydraulic and pneumatic machinery
47.45.Dt Free molecular flows
47.45.Ab Kinetic theory of gases
47.11.-j Computational methods in fluid dynamics
07.30.Cy Vacuum pumps

Investigation of Ni reaction with sputtered amorphous SiGe thin film on SiO2 substrate

Xin-Ping Qu, Peng Duan, Yan-Qing Wu, Tao Chen, Guang-Wei Wang, Guo-Ping Ru, and Bing-Zong Li

J. Vac. Sci. Technol. A 24, 20 (2006); http://dx.doi.org/10.1116/1.2126679 (5 pages)

Online Publication Date: 9 December 2005

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Ni reaction with amorphous SiGe (a-SiGe) thin film on SiO2 substrate through rapid thermal annealing (RTA) was investigated. The amorphous SiGe thin film was deposited by ion beam sputtering. X-ray diffraction (XRD), Auger electron spectroscopy (AES) depth profiling, and four point probe (FPP) were used to check the phase formation, atom distribution, and sheet resistance during the reaction. It was found that the Ni reaction with a-SiGe was different from the Ni reaction with poly-SiGe. Besides an orthorhombic NiSi phase, a tetragonal η-NiSi phase was formed during Ni reaction with an a-SiGe layer and remained stable after 800 °C annealing. A NiSi2 phase was formed at temperature as low as 550 °C along with the crystallization of SiGe.When annealed at a higher temperature, Ge outdiffused to the surface and Ni diffused to the interface of SiGe/SiO2 where it formed a thin layer of Ni silicide. The cause of the reduced temperature for formation of NiSi2 from Ni reaction with amorphous SiGe is discussed.
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68.35.Fx Diffusion; interface formation
68.55.-a Thin film structure and morphology
61.43.Dq Amorphous semiconductors, metals, and alloys
73.61.Jc Amorphous semiconductors; glasses
61.72.Cc Kinetics of defect formation and annealing
79.20.Fv Electron impact: Auger emission

Control of plasma flux composition incident on TiN films during reactive magnetron sputtering and the effect on film microstructure

C. Muratore, S. G. Walton, D. Leonhardt, and R. F. Fernsler

J. Vac. Sci. Technol. A 24, 25 (2006); http://dx.doi.org/10.1116/1.2134706 (5 pages) | Cited 5 times

Online Publication Date: 9 December 2005

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A hybrid plasma enhanced physical vapor deposition (PEPVD) system consisting of an unbalanced dc magnetron and a pulsed electron beam-produced plasma was used to deposit reactively sputtered titanium nitride thin films. The system allowed for control of the magnitudes of the ion and neutral flux, in addition to the type of nitrogen ions (atomic or molecular) that comprised the flux. For all deposition experiments, the magnitude of the ion flux incident on the substrate was held constant, but the composition of the total flux was varied. X-ray diffraction and atomic force microscopy showed that crystallographic texture and surface morphology of the films were affected by the plasma flux composition during growth.
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81.15.Cd Deposition by sputtering
52.77.Dq Plasma-based ion implantation and deposition
68.55.-a Thin film structure and morphology
68.37.Ps Atomic force microscopy (AFM)

Plasma etching of HfO2 at elevated temperatures in chlorine-based chemistry

M. Hélot, T. Chevolleau, L. Vallier, O. Joubert, E. Blanquet, A. Pisch, P. Mangiagalli, and T. Lill

J. Vac. Sci. Technol. A 24, 30 (2006); http://dx.doi.org/10.1116/1.2134707 (11 pages) | Cited 15 times

Online Publication Date: 9 December 2005

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Plasma etching of HfO2 at an elevated temperature is investigated in chlorine-based plasmas. Thermodynamic studies are performed in order to determine the most appropriate plasma chemistry. The theoretical calculations show that chlorocarbon gas chemistries (such as CCl4 or Cl2–CO) can result in the chemical etching of HfO2 in the 425–625 K temperature range by forming volatile effluents such as HfCl4 and CO2. The etching of HfO2 is first studied on blanket wafers in a high density Cl2–CO plasma under low ion energy bombardment conditions (no bias power). Etch rates are presented and discussed with respect to the plasma parameters. The evolution of the etch rate as function of temperature follows an Arrhenius law indicating that the etching comes from chemical reactions. The etch rate of HfO2 is about 110 Å/min at a temperature of 525 K with a selectivity towards SiO2 of 15. x-ray photoelectron spectroscopy analyses (XPS) reveal that neither carbon nor chlorine is detected on the HfO2 surface, whereas a chlorine-rich carbon layer is formed on top of the SiO2 surface leading to the selectivity between HfO2 and SiO2. A drift of the HfO2 etch process is observed according to the chamber walls conditioning due to chlorine-rich carbon coatings formed on the chamber walls in a Cl2–CO plasma. To get a very reproducible HfO2 etch process, the best conditioning strategy consists in cleaning the chamber walls with an O2 plasma between each wafer. The etching of HfO2 is also performed on patterned wafers using a conventional polysilicon gate. The first result show a slight HfO2 foot at the bottom of the gate and the presence of hafnium oxide-based residues in the active areas.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
61.80.Jh Ion radiation effects
79.60.Bm Clean metal, semiconductor, and insulator surfaces
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

Effectiveness of dilute H2 plasmas in removing boron from Si after etching of HfO2 films in BCl3 plasmas

C. Wang and V. M. Donnelly

J. Vac. Sci. Technol. A 24, 41 (2006); http://dx.doi.org/10.1116/1.2134708 (4 pages) | Cited 6 times

Online Publication Date: 9 December 2005

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BCl3-containing plasmas are used to etch HfO2, a high dielectric constant (“high-k”) material. We have investigated several plasmas for their effectiveness in cleaning boron from the underlying Si surface after BCl3 plasma etching of HfO2, while removing a minimum amount of Si. X-ray photoelectron spectroscopy with vacuum sample transfer was used for surface analysis. B cleaning was optimum in dilute H2 plasmas (in Ar) compared to pure H2 plasmas. Dilute H2 plasmas slowed B cleaning process to a controllable time. In a 1% H2–Ar plasma, 20 s was required to clean ∼ 90% B from the surface after a 60 s overetch of HfO2 in BCl3 plasmas. The Si substrate was etched <3 nm during this cleaning period, which was considerably suppressed comparing pure H2 plasma cleaning. Dilute I2 plasmas (in Ar) can also clean B from the Si surfaces in a short time (10 s) but more Si substrate was etched compared to H2–Ar plasmas. BCl3–H2 plasmas deposited a thick B-containing layer on the Si surface instead of combining etching and cleaning into one step.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
68.47.Fg Semiconductor surfaces
81.05.Cy Elemental semiconductors
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

Ion-surface interactions on c-Si(001) at the radiofrequency-powered electrode in low-pressure plasmas: Ex situ spectroscopic ellipsometry and Monte Carlo simulation study

A. Amassian, P. Desjardins, and L. Martinu

J. Vac. Sci. Technol. A 24, 45 (2006); http://dx.doi.org/10.1116/1.2134709 (10 pages) | Cited 5 times

Online Publication Date: 9 December 2005

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We use variable-angle spectroscopic ellipsometry (VASE) to investigate oxide and interface formation during plasma-oxidation of monocrystalline Si(001) at the radiofrequency (rf) powered electrode of a plasma-enhanced chemical vapor deposition reactor. HF-etched c-Si(001) wafers were exposed to an oxygen plasma under conditions similar to those used in optical coatings deposition in order to ascertain the effects of plasma-bulk interactions, and to gauge to what depth O2+ and O+ ions interact with and alter the structure and composition of the target in the presence of negative self-bias, VB. From VASE analyses, modifications are best described using a two-layer model: A top layer consisting of SiO2 and a defective interfacial layer (DL) composed of a mixture of c-Si, a-Si, and SiO2. The saturation value of the modification depth (oxide and DL thickness) increases from 3.4±0.4 to 9.6±0.4 nm, for VB ranging from −60 to −600 V, respectively, and scales with Emax1/2, where Emax is the maximum energy of ions from an rf discharge. These results are in agreement with nuclear ion-bulk interactions leading to atomic displacements and defect accumulation. The interfacial layer broadens with increasing ∣VB∣ while the fraction of a-Si detected increases from ∼ 1% up to ∼ 55% over the investigated VB range, indicative of ballistic and thus depth-dependent oxygen transport to the SiO2–Si interface. Monte Carlo simulations in the binary collision approximation predict significant surface recession due to sputtering, therefore resulting in an apparent self-limiting oxidation mechanism. The surface layers reach their steady-state thicknesses within the first 2 min of plasma exposure and subsequently move into the bulk of the c-Si substrate as a result of oxide sputtering and oxygen transport.
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81.05.Cy Elemental semiconductors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
73.61.Cw Elemental semiconductors
68.47.Fg Semiconductor surfaces
81.65.Mq Oxidation
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Cd Deposition by sputtering
73.23.Ad Ballistic transport
73.50.Fq High-field and nonlinear effects

Optical depth profiling of strontium titanate and electro-optic lanthanum-modified lead zirconium titanate multilayer structures for active waveguide applications

A. Amassian, M. Gaidi, M. Chaker, and L. Martinu

J. Vac. Sci. Technol. A 24, 55 (2006); http://dx.doi.org/10.1116/1.2134710 (10 pages) | Cited 7 times

Online Publication Date: 9 December 2005

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Transparent polycrystalline strontium titanate (STO) and lanthanum-modified lead zirconium titanate (PLZT) thin films were deposited, respectively, on Si and on indium-doped tin oxide (ITO) coated glass by pulsed laser deposition (PLD). PLZT films are shown to exhibit electro-optic properties close to the bulk material when deposited on ITO in specific process conditions. The refractive index depth profile was determined by using a combination of variable angle spectroscopic ellipsometry and spectrophotometry, and the multisample analysis approach. PLZT films deposited at high O2 pressure, PO2, and annealed at 700 °C were found to be more porous and inhomogeneous than low PO2 films. The optical properties of STO films strongly depend on PO2 as well: low PO2 depositions lead to denser film growth with homogeneous, bulk-like refractive index profile, while high PO2 depositions lead to porous and highly inhomogeneous films, exhibiting band-gap variation and formation of a 60-nm-thick interdiffusion layer on Si. We use an optical depth-profiling procedure to investigate the formation of three-layer air/PLZT/STO/ITO/glass stacks, where the PLZT and STO optical properties are optimized by controlling PO2 during STO deposition, in order to form a cladding layer for potential active waveguide applications.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Rm Porous materials; granular materials
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
61.43.Gt Powders, porous materials
78.20.Jq Electro-optical effects
81.15.Fg Pulsed laser ablation deposition
81.40.Gh Other heat and thermomechanical treatments
71.20.Ps Other inorganic compounds
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation

Electrical properties of indium-tin oxide films deposited on nonheated substrates using a planar-magnetron sputtering system and a facing-targets sputtering system

Hideo Iwase, Youichi Hoshi, and Makoto Kameyama

J. Vac. Sci. Technol. A 24, 65 (2006); http://dx.doi.org/10.1116/1.2134711 (5 pages) | Cited 2 times

Online Publication Date: 9 December 2005

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Distribution of the electrical properties of indium-tin oxide (ITO) film prepared by both a planar-magnetron sputtering system (PMSS) and a facing-targets sputtering system (FTSS) at room temperature were investigated. It was found that the outstanding non-uniformities of the electrical properties in noncrystalline ITO films are mainly due to the variation of the oxygen stoichiometry dependent on film positions on substrate surfaces. Furthermore, ITO film with uniform distribution of electrical properties was obtainable using FTSS.
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73.61.-r Electrical properties of specific thin films
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology

SiC formation by C60 molecules as a precursor: A synchrotron-radiation photoemission study of the carbonization process

C.-P. Cheng, T.-W. Pi, C.-P. Ouyang, and J.-F. Wen

J. Vac. Sci. Technol. A 24, 70 (2006); http://dx.doi.org/10.1116/1.2134712 (4 pages) | Cited 3 times

Online Publication Date: 9 December 2005

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Formation of SiC upon annealing an atomically clean Si(001)-2×1 surface covered with half a monolayer of C60 molecules has been investigated by a synchrotron-radiation photoemission. C60 molecules are chemisorbed at room temperature on the silicon surface via Si–C60 hybridization to form covalent bonds. During annealing of the film at 700 °C, Si atoms in the first layer below the surface move upward to bond with C60 molecules, enhancing the formation of SixC60 and resulting in weakened C–C bonds within C60 molecules. Upon further annealing to 750 °C, most C60 molecules decompose and formation of the SiC film begins. Total decomposition of C60 molecules occurs at 800 °C, and only a SiC film is then found.
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73.90.+f Other topics in electronic structure and electrical properties of surfaces, interfaces, thin films, and low-dimensional structures (Restricted to new topics in section 73)
79.60.Jv Interfaces; heterostructures; nanostructures

Study of annealed Co thin films deposited by ion beam sputtering

A. Sharma, R. Brajpuriya, S. Tripathi, and S. M. Chaudhari

J. Vac. Sci. Technol. A 24, 74 (2006); http://dx.doi.org/10.1116/1.2135292 (4 pages) | Cited 7 times

Online Publication Date: 15 December 2005

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This paper presents structural, magnetic and transport property measurements carried out on as deposited as well as annealed Co (400 Å) thin films. The magnetization measurements carried out using a magneto-optical Kerr effect (MOKE) technique show large increases in coercivity and saturation field values with annealing of the samples at higher temperatures. However, corresponding resistivity measurements show a gradual decrease in resistivity and drops to minimum at 500 °C. Observed magnetization and resistivity behavior is mainly attributed to (i) change in crystal structure from hcp to fcc; (ii) increase in grain size; and (iii) stress relaxation due to the annealing treatment as revealed by x-ray diffraction measurements.
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75.50.Cc Other ferromagnetic metals and alloys
81.40.Gh Other heat and thermomechanical treatments
73.61.At Metal and metallic alloys
75.70.Ak Magnetic properties of monolayers and thin films
78.20.Ls Magneto-optical effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
64.70.K- Solid-solid transitions
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
68.55.-a Thin film structure and morphology

Ge interactions on HfO2 surfaces and kinetically driven patterning of Ge nanocrystals on HfO2

Scott K. Stanley, Sachin V. Joshi, Sanjay K. Banerjee, and John G. Ekerdt

J. Vac. Sci. Technol. A 24, 78 (2006); http://dx.doi.org/10.1116/1.2137328 (6 pages) | Cited 5 times

Online Publication Date: 15 December 2005

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Germanium interactions are studied on HfO2 surfaces, which are prepared through physical vapor deposition (PVD) and by atomic layer deposition. X-ray photoelectron spectroscopy and temperature-programed desorption are used to follow the reactions of germanium on HfO2. Germanium chemical vapor deposition at 870 K on HfO2 produces a GeOx adhesion layer, followed by growth of semiconducting Ge0. PVD of 0.7 ML Ge (accomplished by thermally cracking GeH4 over a hot filament) also produces an initial GeOx layer, which is stable up to 800 K. PVD above 2.0 ML deposits semiconducting Ge0. Temperature programed desorption experiments of ∼ 1.0 ML Ge from HfO2 at 400–1100 K show GeH4 desorption below 600 K and GeO desorption above 850 K. These results are compared to Ge on SiO2 where GeO desorption is seen at 550 K. Exploiting the different reactivity of Ge on HfO2 and SiO2 allows a kinetically driven patterning scheme for high-density Ge nanoparticle growth on HfO2 surfaces that is demonstrated.
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81.16.Rf Micro- and nanoscale pattern formation
68.43.Vx Thermal desorption
79.60.Dp Adsorbed layers and thin films
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
61.46.Hk Nanocrystals

Rapid thermal oxidation of Ge-rich Si1−xGex heterolayers

M. K. Bera, S. Chakraborty, R. Das, G. K. Dalapati, S. Chattopadhyay, S. K. Samanta, W. J. Yoo, A. K. Chakraborty, Y. Butenko, L. Šiller, M. R. C. Hunt, S. Saha, and C. K. Maiti

J. Vac. Sci. Technol. A 24, 84 (2006); http://dx.doi.org/10.1116/1.2137329 (7 pages) | Cited 3 times

Online Publication Date: 15 December 2005

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Rapid thermal oxidation (RTO) of the Ge-rich (x = 0.7)Si1−xGex heterolayer is reported. In particular, the structural modifications of SiGe films during oxidation process and the dependence of the oxidation kinetics on Ge content, oxidation temperature, and oxide thickness have been studied. The segregation mechanism of Ge at the oxide/SiGe interface is discussed. Interface properties of the RTO-grown oxides studied using high-frequency capacitance-voltage (C-V) characteristics of metal-oxide-semiconductor capacitors are also reported.
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81.65.Mq Oxidation
64.75.-g Phase equilibria

Ultrasensitive leak detection during ultrahigh vacuum evacuation by quadrupole mass spectrometer

Xu Chen, Tianbin Huang, Ligong Wang, Qiji Jin, and Liangzhen Cha

J. Vac. Sci. Technol. A 24, 91 (2006); http://dx.doi.org/10.1116/1.2137330 (4 pages) | Cited 1 time

Online Publication Date: 15 December 2005

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One must do ultrasensitive leak detection during ultrahigh-vacuum (UHV) evacuation, especially just before the device is sealed off from the vacuum system, to guarantee the longevity of the sealed high-vacuum or even UHV devices with small volume. A quadrupole mass spectrometer (QMS) with an UHV evacuation system can be used under accumulation mode to do the testing. Possible accumulate modes, as well as their advantages and shortcomings, are studied experimentally and discussed in this paper. We found that the opening action of the metal valve during accumulation mode always severely affects the height of the peak indicated by QMS and causes considerable errors. If we determine the leak rate by the peak area instead of the peak height, the situation is much improved. This method has proven quite useful in ensuring the tightness quality for complex sealed UHV devices with small volumes. Ultrasensitive leak detection has been carried out for such real evacuating devices, and a leak rate of 2×10−14 Pa∙m3/s was detected, which is far lower than its dynamic mode and the detection limit of the current advanced commercial leak detectors.
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07.30.Hd Vacuum testing methods; leak detectors
07.75.+h Mass spectrometers

How deposition parameters control growth dynamics of nc-Si deposited by hot-wire chemical vapor deposition

H. R. Moutinho, B. To, C.-S. Jiang, Y. Xu, B. P. Nelson, C. W. Teplin, K. M. Jones, J. Perkins, and M. M. Al-Jassim

J. Vac. Sci. Technol. A 24, 95 (2006); http://dx.doi.org/10.1116/1.2137331 (8 pages) | Cited 5 times

Online Publication Date: 15 December 2005

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We studied the growth of silicon films deposited by hot-wire chemical vapor deposition under different values of filament current, substrate temperature, and hydrogen dilution ratio. The physical and electrical properties of the films were studied by Raman spectroscopy, x-ray diffraction, atomic force microscopy, conductive-atomic force microscopy, and transmission electron microscopy. There is an interdependence of the growth parameters, and films grown with different parameters can have similar structures. We discuss why this interdependence occurs and how it influences the properties of the deposited films, as well as the deposition rate. In general, the films have a complex structure, with a mixture of amorphous, (220)-oriented crystalline and nanocrystalline phases present in most cases. The amount of each phase can be controlled by the variation of one or more of the growth parameters at a time.
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81.05.Cy Elemental semiconductors
73.61.Cw Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.10.Bk Growth from vapor
81.07.Bc Nanocrystalline materials
68.55.A- Nucleation and growth
61.46.Hk Nanocrystals
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.05.cp X-ray diffraction
68.37.Ps Atomic force microscopy (AFM)
68.37.Lp Transmission electron microscopy (TEM)

Low-resistivity atomic-layer-deposited-TaN with atomic-layer-deposited-TaN/physical-vapor-deposited-Ta multilayer structure for multilevel Cu damascene interconnect

Akira Furuya, Nobuyuki Ohtsuka, Naofumi Ohashi, Seiichi Kondo, and Shinichi Ogawa

J. Vac. Sci. Technol. A 24, 103 (2006); http://dx.doi.org/10.1116/1.2137332 (3 pages) | Cited 1 time

Online Publication Date: 19 December 2005

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One important issue for integrating atomic-layer-deposited (ALD) TaN barrier metal into Cu interconnects is a low thickness margin due to high electrical resistivity ( ∼ 50 mΩ cm) of ALD-TaN. In investigating this issue, the median via resistance (0.16 μm diameter vias) was found to increase from 0.5 to 26 Ω/via as the ALD-TaN thickness was increased from 1 to 2 nm. To reduce the resistivity of ALD-TaN, its atomic concentration on various substrates was investigated. The N/Ta ratio of ALD-TaN was found to be about 4/5 on a SiO2 substrate but about 1/2 on a Ta substrate. We also confirmed that the Ta-rich ALD-TaN film on the Ta substrate had low electrical resistivity ( ∼ 2 mΩ cm). We could thus successfully obtain low via resistance (5.4 Ω/via) with thick ALD-TaN (5 nm) by using a PVD-Ta/ALD-TaN/PVD-Ta multilayer structure.
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81.05.Bx Metals, semimetals, and alloys
81.07.-b Nanoscale materials and structures: fabrication and characterization
73.61.At Metal and metallic alloys
68.55.A- Nucleation and growth
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
85.40.Ls Metallization, contacts, interconnects; device isolation
68.65.Ac Multilayers

High-rate deposition of MgO by reactive ac pulsed magnetron sputtering in the transition mode

H. Kupfer, R. Kleinhempel, F. Richter, C. Peters, U. Krause, T. Kopte, and Y. Cheng

J. Vac. Sci. Technol. A 24, 106 (2006); http://dx.doi.org/10.1116/1.2138717 (8 pages) | Cited 5 times

Online Publication Date: 19 December 2005

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A reactive ac pulsed dual magnetron sputtering process for MgO thin-film deposition was equipped with a closed-loop control of the oxygen flow rate (FO2) using the 285 nm magnesium radiation as input. Owing to this control, most of the unstable part of the partial pressure versus flowrate curve became accessible. The process worked steadily and reproducible without arcing. A dynamic deposition rate of up to 35 nm m/min could be achieved, which was higher than in the oxide mode by about a factor of 18. Both process characteristics and film properties were investigated in this work in dependence on the oxygen flow, i.e., in dependence on the particular point within the transition region where the process is operated. The films had very low extinction coefficients (<5×10−5) and refractive indices close to the bulk value. They were nearly stoichiometric with a slight oxygen surplus (Mg/O = 48/52) which was independent of the oxygen flow. X-ray diffraction revealed a prevailing (111) orientation. Provided that appropriate rf plasma etching was performed prior to deposition, no other than the (111) peak could be detected. The intensity of this peak increased with increasing FO2, indicating an even more pronounced (111) texture. The ion-induced secondary electron emission coefficient (iSEEC) was distinctly correlated with the markedness of the (111) preferential orientation. Both refractive index and (111) preferred orientation (which determines the iSEEC) were found to be improved in comparison with the MgO growth in the fully oxide mode. Consequently, working in the transition mode is superior to the oxide mode not only with respect to the growth rate, but also to most important film properties.
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81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
78.66.Nk Insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
61.66.Bi Elemental solids
61.66.Dk Alloys
79.20.Hx Electron impact: secondary emission

Spectroscopic study of gas and surface phase chemistries of CF4 plasmas in an inductively coupled modified gaseous electronics conference reactor

Baosuo Zhou, Eric A. Joseph, Lawrence J. Overzet, and Matthew J. Goeckner

J. Vac. Sci. Technol. A 24, 114 (2006); http://dx.doi.org/10.1116/1.2138718 (12 pages) | Cited 11 times

Online Publication Date: 19 December 2005

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Gas and surface phase chemistries of CF4 plasma were studied in an inductively coupled modified gaseous electronics conference reference cell, using in situ Fourier transform infrared spectroscopy enhanced by a multipass White cell and in situ spectroscopic ellipsometry. The self-bias dc voltage, densities of gaseous species, fluorocarbon film thickness on Si substrate, as well as etch rates of SiO2 and Si were measured during plasma processing as functions of the pressure, CF4 gas flow rate, rf source power, platen bias power, and source-platen gap. The gaseous molecules and radicals monitored included CF4, CF3, CF2, SiF4, and COF2, among which CF4 and SiF4 were found to be the two dominant species, combining for about 80% of the total concentration. The density ratio of SiF4 and COF2 was about 2:1 with no bias on the substrate and increased up to ∼ 8:1 when Si substrate etching took place. Specifically, as the Si etch rate increased, the COF2 density dropped, likely due to suppressed etching of the quartz source window, while the density of SiF4 increased. Comparisons between the gas phase data and etch rate results of Si and SiO2 indicate that the gas phase chemistry is strongly influenced by surface reactions on the substrate, wall, and quartz source window. The thickness of fluorocarbon reaction layer on Si substrate is mainly determined by densities of fluorocarbon radicals and fluorine atoms in the bulk plasma as well as the self-bias voltage on the substrate, and a thicker film is usually associated with a lower etch rate.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.-b Plasma properties

In situ Fourier transform infrared characterization of the plasma chemistry in varying pulsed cycles of a 1,3-butadiene discharge in an inductively coupled gaseous electronics conference cell

A. K. Jindal, A. J. Prengler, L. J. Overzet, and M. J. Goeckner

J. Vac. Sci. Technol. A 24, 126 (2006); http://dx.doi.org/10.1116/1.2141618 (7 pages) | Cited 2 times

Online Publication Date: 19 December 2005

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In situ Fourier transform infrared spectroscopy is used to characterize the plasma chemistry of pulsed 1,3-butadiene (H2CCHCHCH2) discharges subject to varying percentages of the duty cycle in a gaseous electronics conference cell. Variations in densities associated with the major observed spectral bands are closely examined as a function of duty cycle. The possible dissociation mechanisms responsible for all observed vibrations are investigated. For example, the data show that about 44% of CH2 stretching vibrations during continuous wave biasing are due to free CH2 daughter species, while only bound CH2 are observed during pulsing of the discharge. This indicates that only the π bond of the CC bond is cleaved during pulsed mode operation, with the σ being cleaved during cw biasing.
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82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.80.-s Electric discharges
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Effects of N2, O2, and Ar plasma treatments on the removal of crystallized HfO2 film

Jinghao Chen, Won Jong Yoo, and Daniel S. H. Chan

J. Vac. Sci. Technol. A 24, 133 (2006); http://dx.doi.org/10.1116/1.2141619 (8 pages) | Cited 4 times

Online Publication Date: 19 December 2005

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The effects of plasma treatment using Ar, N2, and O2 on the removal of crystallized HfO2 films in a dilute HF solution were studied. The resulting damage in source and drain regions, and recess in isolation regions were also investigated. It was found that plasma nitridation with an ion energy of several hundred electron volts can lower the wet etch resistance of crystallized HfO2 films up to 70 Å thick through the generation of Hf–N bonds. However, thermal nitridation did not introduce sufficient nitrogen into bulk crystallized HfO2 films to lower wet etch resistance. Plasma nitridation without bias power introduced nitrogen to the crystallized HfO2 in the region only within 10 Å of the surface. The enhancement of the etch rate of crystallized HfO2 in dilute HF and the amount of recess in the active and isolation regions using N2, O2, and Ar plasma treatment have been evaluated. Results show that N2 plasma treatment is the most effective in enhancing the removal rate of crystallized HfO2 in dilute HF and minimizing recess on substrate among the plasmas studied.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
52.77.Bn Etching and cleaning

Influence of excitonic singlet-triplet splitting on the photoluminescence of Si/SiO2 multiple quantum wells fabricated by remote plasma-enhanced chemical-vapor deposition

R. Rölver, M. Först, O. Winkler, B. Spangenberg, and H. Kurz

J. Vac. Sci. Technol. A 24, 141 (2006); http://dx.doi.org/10.1116/1.2141620 (5 pages) | Cited 16 times

Online Publication Date: 19 December 2005

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Excitonic effects in the photoluminescence (PL) of Si/SiO2 multiple quantum wells are investigated. The structures were fabricated by remote plasma-enhanced chemical-vapor deposition and subsequent rapid thermal annealing which leads to the formation of nanocrystalline Si well layers. In addition to distinct confinement features, the energy splitting between excitonic singlet and triplet states is derived as a function of the Si layer thickness. Anomalous temperature dependence and sublinear dependence of the PL intensity on optical excitation power are observed. These effects result from the interplay between the occupation of dark triplet states and thermal activation of excitons into optically active singlet states.
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78.55.Ap Elemental semiconductors
78.67.De Quantum wells
71.35.-y Excitons and related phenomena
61.72.Cc Kinetics of defect formation and annealing

Optimization of multilayer wear-resistant thin films using finite element analysis on stiff and compliant substrates

R. K. Lakkaraju, F. Bobaru, and S. L. Rohde

J. Vac. Sci. Technol. A 24, 146 (2006); http://dx.doi.org/10.1116/1.2121750 (10 pages) | Cited 1 time

Online Publication Date: 23 December 2005

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Extensive research has been carried out by researchers on the growth and characterization of multilayer protective coatings, but the design of these coatings still remains largely empirical. In this regard, recent progress has been made in developing a design approach for optimizing a multilayer coating structure before deposition, which would help save time and material. In pursuit of an optimal design, finite element analysis using a plane strain Hertzian contact model was developed to investigate the stress/strain behavior within the layers of the system. The present study looks to find the optimal thicknesses of individual layers in a multilayer coating/substrate system that can reduce stresses and/or strains in the system. Multilayer Cr/CrN thin films were modeled and optimized to have effective “load support” by the films on stiff A2 steel and compliant 2024-Al substrates. Optimization was carried out using both multiobjective and single-objective procedures for the models of eight-layer film on substrates. For the multilayer on A2 steel substrate, the first test case is a multiobjective optimization performed by minimizing the strain discontinuities at the coating/substrate interface and the stresses developed in the uppermost layer under combined normal and tangential load conditions. Another option is a single-objective optimization (minimizing the strain discontinuity) and constraining the stress to values below the yield stress. The same two test cases were employed on the 2024-Al model, but the stresses considered were those in the substrate in order to keep the model within the elastic regime. Efficiency of several optimization algorithms, such as genetic algorithms and gradient based routines are discussed and the preliminary results are compared to experimental pin-on-disk wear results of empirically designed coatings. Architectures were found with improvements in the elastic measures employed here.
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81.40.Pq Friction, lubrication, and wear
68.60.Bs Mechanical and acoustical properties
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
81.65.-b Surface treatments
62.20.Qp Friction, tribology, and hardness
62.20.F- Deformation and plasticity
62.20.D- Elasticity

Conduction anisotropy in porous thin films with chevron microstructures

D. Vick and M. J. Brett

J. Vac. Sci. Technol. A 24, 156 (2006); http://dx.doi.org/10.1116/1.2148413 (9 pages) | Cited 8 times

Online Publication Date: 23 December 2005

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Electrical conductivity measurements were performed on structurally anisotropic thin films deposited using the glancing angle deposition apparatus [ K. Robbie and M. J. Brett, J. Vac. Sci. Technol. A 15, 1460 (1997) ; K. Robbie, J. Sit, and M. J. Brett, J. Vac. Sci. Technol. B 16, 1115 (1998) ; K. Robbie and M. J. Brett, US Patent No. 5,866,204 (2 February 1999) ]. The films were comprised of bilayers of titanium over silica, engineered as a chevron morphology. Samples were evaporated at various incident vapor deposition angles α, in order to investigate the effects of morphology and voiding on the behavior of conductivity. A rapid decline in the conductivity, accompanied by an increase in conduction anisotropy in the plane of the substrate, was observed with increasing α. A random walk model was developed to model the transport properties of the films, and applied to microstructures predicted by a three-dimensional ballistic thin film simulator. In order to generate reasonable agreement between the modeling and measurement, it was necessary to incorporate the effect of native oxide formation on the exposed surfaces of the titanium layer.
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73.61.Ng Insulators
68.55.-a Thin film structure and morphology
61.43.Gt Powders, porous materials

Characterization of low dielectric constant plasma polymer films deposited by plasma-enhanced chemical vapor deposition using decamethyl-cyclopentasiloxane and cyclohexane as the precursors

Jaeyoung Yang, Sungwoo Lee, Hyoungsun Park, Donggeun Jung, and Heeyeop Chae

J. Vac. Sci. Technol. A 24, 165 (2006); http://dx.doi.org/10.1116/1.2148414 (5 pages) | Cited 7 times

Online Publication Date: 23 December 2005

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We investigated the properties of plasma polymer films deposited by plasma-enhanced chemical vapor deposition using a mixture of decamethyl-cyclopentasiloxane (C10H30O5Si5) and cyclohexane (C6H12) as the precursors, which we refer to as plasma polymerized decamethyl-cyclopentasiloxane: cyclohexane (PPDMCPSO:CHex) films. The relative dielectric constants, k, of the plasma polymer films were correlated with the Fourier transform infrared absorption peaks of the C–Hx, Si–CH3, and Si–O related groups. As the amount of the CHx species in the as-deposited plasma polymer films increased, the k value and the leakage current density of the thin films decreased. The subsequent annealing of the PPDMCPSO:CHex film at 400 °C for 1 h further reduced the k value to as low as k = 2.05. This annealed PPDMCPSO:CHex thin film showed a leakage current density of the order of 4×10−7 A/cm2 at 1 MV/cm and a breakdown field of 6.5 MV/cm. Through the bias-temperature stress test, it was estimated that the PPDMCPSO:CHex film with a k value of 2.05 would retain its insulating properties for ten years at 167 °C under an electrical field of 1 MV/cm, when it is presented as a layer adjacent to Cu/TaN(10 nm).
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77.84.Jd Polymers; organic compounds
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
78.66.Qn Polymers; organic compounds

Effect of assistant rf field on phase composition of iron nitride film prepared by magnetron sputtering process

W. L. Li, F. Zheng, and W. D. Fei

J. Vac. Sci. Technol. A 24, 170 (2006); http://dx.doi.org/10.1116/1.2148415 (4 pages)

Online Publication Date: 23 December 2005

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Fe–N thin films were fabricated using a direct current magnetron sputtering process assisted by a radio-frequency (rf) field. The effect of the rf field on the phase composition of the films was investigated. The results indicate that with the assistance of the rf field, various kinds of iron nitrides can be obtained in the films, including α′-Fe–N, α″-Fe16N2, ξ-Fe2N, ε-Fe3N, and γ″-FeN with ZnS structure. It was found that the rf field greatly benefits the formation of iron nitrides in the Fe–N films.
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81.05.-t Specific materials: fabrication, treatment, testing, and analysis
81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth

Effects of Al content on grain growth of solid solution (Ti,Al)N films

Z.-J. Liu and Y. G. Shen

J. Vac. Sci. Technol. A 24, 174 (2006); http://dx.doi.org/10.1116/1.2148416 (4 pages) | Cited 1 time

Online Publication Date: 23 December 2005

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Substitutional solid solution (Ti1−xAlx)N films with different Al contents (0 ⩽ x ⩽ 0.41) were deposited onto unheated Si(100) substrates by reactive unbalanced close-field magnetron sputtering in an Ar–N2 gas mixture. The effect of Al atomic concentration on the sizes of crystal grains during deposition was investigated. X-ray diffraction analysis revealed that the incorporated Al atoms had an obvious impact on the grain growth of (Ti1−xAlx)N films and the average crystal grain size showed an exponential decay with Al atomic concentration. A phenomenological model was proposed to analyze this solute-drag effect occurring during film deposition. It was found that the presence of solute drag in normal grain growth resulted in a low kinetic growth exponent, and the exponential decay in average grain size with solute atomic concentration could be reproduced in our calculations.
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81.05.-t Specific materials: fabrication, treatment, testing, and analysis
81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth
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