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Nov 2002

Volume 20, Issue 6, pp. 1835-2139

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Mass spectrometric studies of low pressure CH4, CH4/H2, and H2 plasma beams generated by an inductively coupled radio frequency discharge

Katsuyuki Okada and Shojiro Komatsu

J. Vac. Sci. Technol. A 20, 1835 (2002); http://dx.doi.org/10.1116/1.1506171 (5 pages) | Cited 2 times

Online Publication Date: 6 November 2002

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Low pressure CH4, CH4/H2, and H2 plasma beams were generated by a 13.56 MHz inductively coupled radio frequency (rf) plasma with a magnetic field (∼300 G) to utilize them as radical sources for the epitaxial growth of diamond. The threshold ionization technique using a quadrupole mass spectrometer has been employed to measure the absolute density of CH3 radicals (n) in CH4 and CH4/H2 plasma beams. The ions of CH4 and CH4/H2 plasma beams were composed of CHx, C2Hx, C3Hx, and Hx fragment ions, while Hx fragment ions occupied the H2 plasma beam. When the rf power and the pressure were increased, the n and the relative intensities of H3+, C2Hx, and C3Hx fragment ions were increased. This implies that both the homogeneous secondary ion–molecular reactions and the heterogeneous plasma–surface interactions take place in the plasma generation region of the low pressure plasma beams with an increase in rf power and pressure. The increase of H3+ also induces an increase of atomic hydrogen, which is essential for diamond growth. It is therefore concluded that moderate rf power and higher pressure are favorable for diamond growth. © 2002 American Vacuum Society.
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52.77.Dq Plasma-based ion implantation and deposition
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.70.Nc Particle measurements
82.33.Ya Chemistry of MOCVD and other vapor deposition methods
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
52.40.Hf Plasma-material interactions; boundary layer effects

Investigation of the hydrogenation properties of Zr films under unclean plasma conditions

L. Q. Shi, G. Q. Yan, J. Y. Zhou, S. Z. Luo, S. M. Peng, W. Ding, and X. G. Long

J. Vac. Sci. Technol. A 20, 1840 (2002); http://dx.doi.org/10.1116/1.1506174 (6 pages) | Cited 2 times

Online Publication Date: 6 November 2002

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By the means of non-Rutherford backscattering spectroscopy and elastic recoil detection analysis, the plasma hydrogenation of Zr films with and without a Ni overlayer were investigated. Close to the theoretical maximum hydrogen storage capacity (H/Zr=2) was attained when the sample was exposed to plasma with relative low contamination and a hydrogen pressure of ∼2 Pa and a substrate temperature of 393 K for 10 min. This reaction rate is much higher than obtained for gas hydrogenation. In an unclean plasma condition, the absorption of hydrogen is retarded by C and O contamination occurring on the sample surface. Though the oxide layer does not act as an efficient permeation barrier to atomic hydrogen, the maximum equilibrium hydrogen content dropped drastically with increasing contamination. In contrast to theoretical prediction, the hydrogen capacity for Ti is lower than Zr due to sample contamination. Also, the influence of the Ni overlayer on the plasma hydrogenation is discussed. © 2002 American Vacuum Society.
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68.47.De Metallic surfaces
84.60.-h Direct energy conversion and storage
81.65.-b Surface treatments
52.77.-j Plasma applications
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Bx Metals, semimetals, and alloys
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Electron emission suppression characteristics of molybdenum grids coated with carbon film by ion beam assisted deposition

Xianghuai Liu, Congxin Ren, Bingyao Jiang, Hong Zhu, Yanyuan Liu, and Jingxian Wu

J. Vac. Sci. Technol. A 20, 1846 (2002); http://dx.doi.org/10.1116/1.1506173 (4 pages) | Cited 3 times

Online Publication Date: 6 November 2002

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Carbon was coated on the surface of molybdenum grids by ion beam assisted deposition. The electron emission characteristics from the grids with and without carbon, which were contaminated by an active electron emission substance of the cathode, was measured using an analogous diode method. The results show that electron emission from the carbon-coated Mo grid was much less than that from the Mo grid without carbon. The cathode emission substance deposited on the carbon surface of the grid was analyzed by x-ray photoelectron spectroscopy and electron probes. Analysis results revealed that the carbon-coated Mo grid could effectively reduce the accumulation of the cathode emitting substances Ba and BaO on the grid surface. The reason for the suppression of electron emission of the carbon-coated Mo grid is discussed. The carbon-coated Mo grids were used in pulsed-controlled grid traveling wave tubes and the working lifetime of the tube was increased from tens of hours to over 1000 h. © 2002 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
79.60.Jv Interfaces; heterostructures; nanostructures

Investigation and simulation of XeF2 isotropic etching of silicon

Behraad Bahreyni and C. Shafai

J. Vac. Sci. Technol. A 20, 1850 (2002); http://dx.doi.org/10.1116/1.1506172 (5 pages) | Cited 4 times

Online Publication Date: 6 November 2002

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Trenching and loading phenomena observed on XeF2-etched (100) silicon wafers are explained in this article. Trenching refers to deeper etching at the side of an etch feature with respect to the middle of the feature. Loading is the reduction in etch depth that adjacent etched regions impose on their respective etch profiles. These two phenomena are especially recognized at locations where the substrate is etched through large mask openings. Both phenomena were reported by other groups, but no explanation was given for them. A novel model explaining these phenomena is developed in this article, and the etching process is simulated in software. The results are compared to several etched samples with varying mask aperture size and etch depth. Good agreement is found between simulated profiles and actual measured etch profiles at given mean-free paths. Furthermore, our simulator predicts that the reaction probability between etchant and substrate molecules influences surface roughness of the etched regions. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
68.35.B- Structure of clean surfaces (and surface reconstruction)

Quantitative analysis of annealing-induced structure disordering in ion-implanted amorphous silicon

Ju-Yin Cheng, J. M. Gibson, P. M. Baldo, and B. J. Kestel

J. Vac. Sci. Technol. A 20, 1855 (2002); http://dx.doi.org/10.1116/1.1507331 (5 pages) | Cited 10 times

Online Publication Date: 6 November 2002

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We use fluctuation electron microscopy to characterize medium-range order in ion-implanted amorphous silicon. In fluctuation microscopy, intensity fluctuation in a dark-field image contains the information of high-order atomic correlations in the length scale of 1–3 nm. In this study, we heated as-implanted silicon at 500, 550, and 580 °C for various times. Our results indicate that in the beginning amorphous silicon is a disordered phase with robust medium-range order. Thermal annealing leads to disordering of the structure. Furthermore, we find that the activation energy of the disordering is about 2.7 eV, close to the activation energy for thermal relaxation (about 2.2 eV). Our finding suggests a strong correlation between structure disordering and thermal relaxation. © 2002 American Vacuum Society.
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61.43.Dq Amorphous semiconductors, metals, and alloys
81.05.Gc Amorphous semiconductors
81.05.Cy Elemental semiconductors

Thermal stability of Pr2O3 films grown on Si(100) substrate

A. Goryachko, J. P. Liu, D. Krüger, H. J. Osten, E. Bugiel, R. Kurps, and V. Melnik

J. Vac. Sci. Technol. A 20, 1860 (2002); http://dx.doi.org/10.1116/1.1507332 (7 pages) | Cited 5 times

Online Publication Date: 6 November 2002

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We have investigated the effect of thermal annealing on uncapped and Si-capped Pr2O3 films deposited on Si(100) substrate by Auger electron spectroscopy, x-ray photoelectron spectroscopy, and transmission electron microscopy. A rapid diffusion of Si out of the substrate was found for uncapped films at temperatures starting from 700 °C. The diffused Si is oxidized, forming a Pr2O3–Prx–Oy–Siz mixture. The excess Si diffuses through the film, forming a SiO2 rich layer on the surface. Annealing of uncapped films in vacuum has qualitatively similar effects as annealing in N2, which is not the case for Si-capped films. The latter were transformed into a Pr2O3–Prx–Oy–Siz mixture when annealed in N2 starting from 900 °C and into PrSix when annealed in vacuum starting from 700 °C. Two distinct PrSix phases were found, with Si-richer phases corresponding to higher annealing temperature. © 2002 American Vacuum Society.
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68.60.Dv Thermal stability; thermal effects
68.35.Fx Diffusion; interface formation
66.30.Ny Chemical interdiffusion; diffusion barriers
68.55.Nq Composition and phase identification
79.20.Fv Electron impact: Auger emission
79.60.Dp Adsorbed layers and thin films
68.37.Lp Transmission electron microscopy (TEM)

Angle-resolved x-ray photoelectron spectroscopy of ultrathin Al2O3 films grown by atomic layer deposition

O. Renault, L. G. Gosset, D. Rouchon, and A. Ermolieff

J. Vac. Sci. Technol. A 20, 1867 (2002); http://dx.doi.org/10.1116/1.1507330 (10 pages) | Cited 30 times

Online Publication Date: 6 November 2002

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Thin (45 nm) and ultrathin (4.5–1 nm) Al2O3 layers deposited on HF-stripped Si or thin SiO2 surfaces by atomic layer deposition were studied by angle-resolved x-ray photoelectron spectroscopy, before and after rapid thermal annealing (RTA) at 800 °C for 15 min in N2 or annealing in a conventional furnace under ultrahigh vacuum (UHV) (p=10−6 mbar) and N2 at the same temperature. Samples were characterized in terms of chemical defects and interfacial regrowth upon annealing. Chemical defects as Al–OH groups are evidenced from the O 1s spectra even after RTA. Interfacial regrowth, estimated from the Si 2p components intensity, was found (1) to occur upon every kind of annealing, (2) to be dependent on the initial Al2O3 thickness (the thicker the layer the greater the regrowth), and (3) to be significantly reduced on SiO2 surfaces as thin as 0.5 nm. In agreement with previous studies, we also consistently found the presence of an oxidized Si component at the Al2O3/substrate interface centered at 102 eV for which an assignment to silicate groups (Si–O–Al) is proposed, on the basis of other x-ray photoelectron spectroscopy parameters. Given the influence of UHV annealing in interfacial regrowth, Al–OH defects may play an important role in interface oxidation. © 2002 American Vacuum Society.
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79.60.Dp Adsorbed layers and thin films
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Ms Insulators
68.60.Wm Other nonelectronic physical properties
68.35.Ct Interface structure and roughness

Investigation of thermal flux to the substrate during sputter deposition of aluminum

Samuel D. Ekpe and Steven K. Dew

J. Vac. Sci. Technol. A 20, 1877 (2002); http://dx.doi.org/10.1116/1.1507342 (9 pages) | Cited 13 times

Online Publication Date: 6 November 2002

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The transient and steady state thermal flux at the substrate during the deposition of aluminum film in a direct current magnetron sputter system has been determined by measuring the resistance of a complementary metal–oxide–semiconductor (CMOS) sensor. The sensor is calibrated using ohmic self-heating before the plasma is switched on. The steady state thermal flux at the substrate was measured to vary from 9.6 to 46 mW/cm2 at a substrate-target distance of 10.8 cm depending on the magnetron power (75–300 W) and gas pressure. Plasma radiation and electron bombardment are noted to be the most significant sources of the thermal flux to the substrate, each contributing about 36% and 29%, respectively, of the total thermal flux at the substrate for a magnetron power of 200 W and gas pressure of 5 mTorr. Thermal radiation is also an important factor, along with kinetic energy and condensation energy. Total energy per deposited atom is calculated to be in the range of 28–52 eV depending on the magnetron power and gas pressure, and increases with pressure but decreases with magnetron power. The trend seems to suggest that at higher magnetron powers (>300 W for a 3 in. target), a pressure independent total energy per deposited atom may be obtained. © 2002 American Institute of Physics.
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81.15.Cd Deposition by sputtering
68.60.Dv Thermal stability; thermal effects
68.55.A- Nucleation and growth
07.20.-n Thermal instruments and apparatus
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.30.Tv Field effect devices

Structural and luminescent properties of ZnTe film grown on silicon by metalorganic chemical vapor deposition

C. X. Shan, X. W. Fan, J. Y. Zhang, Z. Z. Zhang, X. H. Wang, J. G. Ma, Y. M. Lu,, Y. C. Liu, D. Z. Shen, X. G. Kong, and G. Z. Zhong

J. Vac. Sci. Technol. A 20, 1886 (2002); http://dx.doi.org/10.1116/1.1507344 (5 pages) | Cited 10 times

Online Publication Date: 6 November 2002

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Reported here are the structural and luminescent properties of ZnTe films grown on Si substrates by metalorganic chemical vapor deposition (MOCVD). ZnO intermediate layers annealed at different temperature are employed to buffer the thermal and chemical difference between the ZnTe epilayers and silicon substrates. With increasing the annealing temperature of ZnO buffer layer, the crystallization of ZnTe assessed by x-ray diffraction is improved. Temperature dependent photoluminescence (PL) of the ZnTe epilayer is processed to evaluate the optical properties of our samples. The PL spectra are characterized by an asymmetry line shape labeled E, and it can be dissolved into two Gaussian lines with energy discrepancy of about 18.5 meV. The origins of these two Gaussian lines are thought to be free and bound excitons emission, respectively. The dependence of luminescence on temperature indicates that the emission from bound excitons dominates the spectrum below 157 K. While above 157 K, the bound excitons are detrapped to become free excitons, and free excitons emission becomes dominant. Also, the broadening of the emission line resulting from the ionized impurity scattering cannot be neglected above 157 K. Temperature dependence of the full width at half maximum and peak energy of the spectra can be comprehended well under the framework of the two-dissociation-process theory, which, in turn, further strengthens the validity of the origin of the spectra. © 2002 American Vacuum Society.
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
68.55.-a Thin film structure and morphology
81.05.Dz II-VI semiconductors
71.35.-y Excitons and related phenomena
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Cc Kinetics of defect formation and annealing

Wet chemical etching studies of Zr and Hf-silicate gate dielectrics

M. A. Quevedo-Lopez, M. El-Bouanani, R. M. Wallace, and B. E. Gnade

J. Vac. Sci. Technol. A 20, 1891 (2002); http://dx.doi.org/10.1116/1.1507343 (7 pages) | Cited 21 times

Online Publication Date: 6 November 2002

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The etching properties of alternate gate dielectric candidates Hf and Zr silicate in hydrofluoric acid (HF) solutions are presented. As-deposited Hf silicate films were found to be more difficult to etch when compared with as-deposited Zr silicate films. After annealing, both Hf and Zr silicate are harder to etch than as-deposited films. Annealed Zr silicate films were the most difficult to remove in either concentrated, or diluted HF solutions. Film densification, along with crystallization of the silicate films near the Si interface are thought to be responsible for the etch rate change in these silicate systems. Alternate processes to remove remnant metal from the silicon surface after gate dielectric removal are also discussed. After annealing and dielectric film removal, remnant Zr and Hf concentrations near the Si surface of ∼1019/cm3 and ∼1016/cm3, respectively, were observed. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.20.Pm Rate constants, reaction cross sections, and activation energies
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
81.40.Gh Other heat and thermomechanical treatments
68.35.Dv Composition, segregation; defects and impurities

A biaxial rotation for depositing homogeneous large-area double-sided YBa2Cu3O7−X thin films

B. W. Tao, Y. R. Li, X. Z. Liu, S. M. He, and J. Geerk

J. Vac. Sci. Technol. A 20, 1898 (2002); http://dx.doi.org/10.1116/1.1507341 (5 pages) | Cited 3 times

Online Publication Date: 6 November 2002

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To deposit homogeneous large-area double-sided YBa2Cu3O7–X thin films simultaneously, a single inverted cylindrical target sputtering system with a simple rotation apparatus and a tubelike heater has been developed. The substrate (2 in. LaAlO3) rotated continuously in the heater so that films can be deposited on both sides simultaneously. Three different rotation modes, which are vertical in-plane rotation, out-of-plane rotation, and biaxial rotation (filed as a Chinese patent), have been tried out. The thickness distributions have been measured and compared with theoretical investigation results. While deposited with the subtle biaxial rotation mode, the film shows a much better thickness homogeneity than that with the other two single-axial rotation modes. The measurement result of critical transition temperature (TC) gives the demonstration that the biaxial rotation technique effectively improves the homogeneity of large-area thin films deposited by inverted cylindrical sputtering. Microwave surface resistance (RS), which is the key property for high-temperature superconductivity films used for fabricating microwave devices, ranged from 20 to 50 mΩ (at 75 K, 145 GHz). © 2002 American Vacuum Society.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.25.N- Response to electromagnetic fields
68.55.-a Thin film structure and morphology
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Thermal reaction of nickel and Si0.75Ge0.25 alloy

K. L. Pey, W. K. Choi, S. Chattopadhyay, H. B. Zhao, E. A. Fitzgerald, D. A. Antoniadis, and P. S. Lee

J. Vac. Sci. Technol. A 20, 1903 (2002); http://dx.doi.org/10.1116/1.1507339 (8 pages) | Cited 24 times

Online Publication Date: 6 November 2002

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The interfacial reactions and chemical phase formation between nickel and ultrahigh vacuum chemical vapor deposited Si0.75Ge0.25 alloy have been studied within the temperature range of 300–900 °C for forming low resistive and uniform silicide films for future application in SiGe based metal–oxide–semiconductor field effect transistor devices. The silicided films were characterized by the x-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, transmission electron microscopy, and micro-Raman microscopy techniques. Smooth and uniform nickel monogermanosilicide NiSi0.75Ge0.25 films have been observed for samples annealed at around 400–500 °C. For annealing temperatures of 500 °C and above, Ge-rich Si1−zGez grains where z>0.25 were found among Ge deficient Niy(SiwGe1−w)1−y grains where w<0.25 and the Niy(Si1−wGew)1−y phase is thermally stable up to an annealing temperature of 800 °C. We found that the Ni/SiGe reaction is mainly diffusion controlled with Ge and Ni as the dominant diffusing species compared to Si during the annealing process. In addition, Ge has been found to promote agglomeration especially above 700 °C, leading to an abrupt increase in the sheet resistance. © 2002 American Vacuum Society.
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68.35.Fx Diffusion; interface formation
61.72.Cc Kinetics of defect formation and annealing
85.30.Tv Field effect devices

Time development of microstructure and resistivity for very thin Cu films

S. M. Rossnagel and T. S. Kuan

J. Vac. Sci. Technol. A 20, 1911 (2002); http://dx.doi.org/10.1116/1.1507340 (5 pages) | Cited 12 times

Online Publication Date: 6 November 2002

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The electrical resistance of thin, 4–100 nm sputter-deposited (physical vapor deposition) Cu films was measured in situ in the deposition chamber. The Cu was deposited on silicon dioxide surfaces to reduce surface pinning or adhesion effects and allow high mobility. During, and following the deposition, the electrical resistance was measured under vacuum for periods of up to several thousand minutes, and in each case the electrical resistivity decreased 13%–50% over that time period. This is consistent with reports of room temperature grain growth in electrodeposited thin films. X-ray diffraction data showed significant increases in (111) crystallinity. At very small thicknesses (4.5 nm), it appears that a second mechanism occurs prior to grain growth which may be related to the agglomeration of nearly discontinuous islands on the surface. Similar Cu films deposited on Ta adhesion layers showed little, if any, change in resistance over time, indicating the role of the substrate interface in limiting grain growth. © 2002 American Vacuum Society.
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68.55.-a Thin film structure and morphology
73.61.At Metal and metallic alloys
81.15.Cd Deposition by sputtering
68.35.Np Adhesion

Effects of plasma exposure on structural and optical properties of TiO2 films deposited by off-axis target sputtering

T. Takahashi, H. Nakabayashi, and W. Mizuno

J. Vac. Sci. Technol. A 20, 1916 (2002); http://dx.doi.org/10.1116/1.1510530 (5 pages) | Cited 11 times

Online Publication Date: 6 November 2002

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TiO2 films with thickness of about 800–2300 nm have been reactively deposited on glass-slide substrates at an atmosphere of Ar and O2 mixture, using the off-axis target sputtering method. The maximum deposition rate of the film was 12.8 nm/min. The optical properties and the crystal structure of the films were measured using spectrophotometry, Raman spectroscopy, and x-ray diffractometry, respectively. Most of the films deposited in this study were transparent and had anatase crystal structure, while some of them were semitransparent. The A(101), A(112), A(211) and A(220) peaks were observed in the x-ray diffraction patterns, where A shows the anatase phase of TiO2. With increasing plasma exposure, the x-ray peak intensities IP of A(101) and A(112) gradually decreased, while the IP of A(211) and A(220) gradually increased. The IP depended strongly on the substrate position in this study. Moreover, the A(220) peak was significantly higher than other peaks when the TiO2 crystallites became larger. The anatase phase of the TiO2 films was also revealed in the Raman spectra with a Raman shift of 145 cm−1. With decreasing plasma exposure, the changes in the optical transmittance spectra of TiO2 films were very small at the wavelength of 350–900 nm. However, the transmittance spectra significantly depended on the wavelength with increasing plasma exposure. Consequently, it was found that the crystal structure and the optical properties of as-deposited TiO2 films were strongly affected by plasma exposure during film deposition. © 2002 American Vacuum Society.
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68.55.-a Thin film structure and morphology
78.66.Nk Insulators
81.15.Cd Deposition by sputtering
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.30.Hv Other nonmetallic inorganics

Microstructure and properties of Ti–Si–N nanocomposite films

Xiaoping Hu, Zenghu Han, Geyang Li, and Mingyuan Gu

J. Vac. Sci. Technol. A 20, 1921 (2002); http://dx.doi.org/10.1116/1.1508802 (6 pages) | Cited 26 times

Online Publication Date: 6 November 2002

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Ti–Si–N nanocomposite films were deposited by multitarget reactive magnetron sputtering. Energy dispersive spectroscopy, X-ray diffraction, transmission electron microscopy, and x-ray photoelectron spectroscopy were employed to characterize their microstructure and a microhardness tester was used to measure their hardness. The influence of substrate temperature on these films was investigated, too. The results reveal that the films consist of TiN and Si3N4. Si3N4 exists as amorphous, which strongly prevents the growth of TiN grains and causes TiN to form a nanocrystalline or amorphous phase. The hardness of films deposited at room temperature reaches the peak value of 36 GPa at a Si content of 4.14 at. %, and then decreases gradually with the increase of Si content. The enhancement of the substrate temperature weakens the restraint effect of amorphous Si3N4 on the growth of TiN grains, which results in coarse TiN grains and subsequently leads to a lower peak value and a slower decrease of the hardness of the films. © 2002 American Vacuum Society.
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68.55.-a Thin film structure and morphology
61.46.-w Structure of nanoscale materials
68.60.Bs Mechanical and acoustical properties
62.25.-g Mechanical properties of nanoscale systems
81.07.Bc Nanocrystalline materials
81.15.Cd Deposition by sputtering
62.20.Qp Friction, tribology, and hardness
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
68.37.Lp Transmission electron microscopy (TEM)

Anomalies in modeling of anisotropic etching of silicon: Facet boundary effects

Z. Elalamy, L. M. Landsberger, A. Pandy, M. Kahrizi, I. Stateikina, and S. Michel

J. Vac. Sci. Technol. A 20, 1927 (2002); http://dx.doi.org/10.1116/1.1513790 (7 pages) | Cited 3 times

Online Publication Date: 6 November 2002

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Beginning with an idealized model of anisotropic etching of silicon in which the etch behavior depends only on the crystal features presented to the etchant, this article extends the model to address certain anomalies observed in the data. The idealized model is based on profiles of underetched surfaces and underetch behavior as a function of mask-edge deviation in wagon-wheel experiments on Si{110} and Si{100} at different TMAH concentrations. Underetched surfaces are found to follow a cohesive system composed of planes defined by two types of crystal features: periodic bond chains and rows of kinks. But it is also found that the same crystal planes in the same etchant often exhibit different etch rates. These anomalies are outlined, and interactions at the boundaries between adjacent facets are proposed to explain them. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.20.Pm Rate constants, reaction cross sections, and activation energies
81.05.Cy Elemental semiconductors
85.40.Hp Lithography, masks and pattern transfer

Growth of Be2C(100) films on Be(0001) substrate using C60 as precursor

C.-T. Tzeng, J.-Y. Yuh, W.-S. Lo, R.-Y. Chu, and K.-D. Tsuei

J. Vac. Sci. Technol. A 20, 1934 (2002); http://dx.doi.org/10.1116/1.1513642 (5 pages) | Cited 1 time

Online Publication Date: 6 November 2002

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Highly oriented crystalline beryllium carbide films were grown on Be(0001) substrate using C60 as a carbon source. The films were characterized by low energy electron diffraction, photoemission spectroscopy, and near-edge x-ray absorption fine structure. C60 begins to decompose on Be(0001) at about 250 °C, forming beryllium carbide completely after further annealing to 450 °C. The beryllium carbide film is observed as sets of (100) surfaces, arranged in three domains rotated by 120° from each other. Extra C60 deposited on Be2C(100)/Be(0001) at temperature below 200 °C and heated to 450 °C leads to an increase of the film thickness, indicating the decomposition of C60 on Be2C(100)/Be(0001) at an elevated temperature and formation of new carbide layers on the sample surface. It further implies that the Be2C/Be surface has the ability to supply Be atoms to interact with the new carbon atoms on top, and that Be atoms can diffuse through the beryllium carbide layer at the temperature of 450 °C, possibly involving a vacancy mechanism. © 2002 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
79.60.Dp Adsorbed layers and thin films
68.55.-a Thin film structure and morphology
78.70.Dm X-ray absorption spectra
61.72.Cc Kinetics of defect formation and annealing

Characterization of Pb(Zr, Ti)O3 thin films fabricated by plasma enhanced chemical vapor deposition on Ir-based electrodes

Hee-Chul Lee and Won-Jong Lee

J. Vac. Sci. Technol. A 20, 1939 (2002); http://dx.doi.org/10.1116/1.1513646 (9 pages) | Cited 7 times

Online Publication Date: 6 November 2002

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Structural and electrical characteristics of Pb(Zr, Ti)O3 (PZT) ferroelectric thin films deposited on various Ir-based electrodes (Ir, IrO2, and Pt/IrO2) using electron cyclotron resonance plasma enhanced chemical vapor deposition were investigated. On the Ir electrode, stoichiometric PZT films with pure perovskite phase could be obtained over a very wide range of processing conditions. However, PZT films prepared on the IrO2 electrode contain a large amount of PbOx phases and exhibited high Pb-excess composition. The deposition characteristics were dependent on the behavior of PbO molecules on the electrode surface. The PZT thin film capacitors prepared on the Ir bottom electrode showed different electrical properties depending on top electrode materials. The PZT capacitors with Ir, IrO2, and Pt top electrodes showed good leakage current characteristics, whereas those with the Ru top electrode showed a very high leakage current density. The PZT capacitor exhibited the best fatigue endurance with an IrO2 top electrode. An Ir top electrode provided better fatigue endurance than a Pt top electrode. The PZT capacitor with an Ir-based electrode is thought to be attractive for the application to ferroelectric random access memory devices because of its wide processing window for a high-quality ferroelectric film and good polarization, fatigue, and leakage current characteristics. © 2002 American Vacuum Society.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.66.Bi Elemental solids
61.66.Dk Alloys
77.22.Ej Polarization and depolarization

Correlation of surface chemistry of GaAs substrates with growth mode and stacking fault density in ZnSe epilayers

Soon-Ku Hong, Ji-Ho Chang, Takashi Hanada, Elisabeth Kurtz, Masaoki Oku, and Takafumi Yao

J. Vac. Sci. Technol. A 20, 1948 (2002); http://dx.doi.org/10.1116/1.1513645 (7 pages) | Cited 1 time

Online Publication Date: 6 November 2002

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We report on the correlation of surface chemistry of GaAs substrates with growth mode and stacking fault density in ZnSe epilayers. High quality ZnSe epilayers with low stacking fault density have been directly grown on commercial epiready GaAs (001) substrates without GaAs buffer layer growth. It is found that proper pregrowth treatments of epiready GaAs (001) substrates to obtain clean surfaces are crucial to two-dimensional layer-by-layer growth and suppression of generation of stacking faults. The surface oxide layers of epiready GaAs substrates before and after chemical etching using a NH4OH-based solution are carefully characterized by angle-resolved x-ray photoelectron spectroscopy. The surface oxide layer is composed of Ga2O3 and As2O3. The chemical etching is found to reduce not only the thickness of the oxide layers but also the ratio of Ga2O3 to As2O3 to about half of that before etching. A clean GaAs (001) surface typically characterized by a (4×1) reconstruction is obtained in the present case after thermal cleaning. Prior to ZnSe growth Zn preexposure is carried out. Reflection high-energy electron diffraction intensity oscillations with more than 50 periods are observed even from the beginning of ZnSe growth on such cleaned GaAs substrates. High quality ZnSe layers with a stacking fault density of low-105 cm−2 range are grown. © 2002 American Vacuum Society.
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81.05.Dz II-VI semiconductors
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.Nn Stacking faults and other planar or extended defects
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
79.60.Dp Adsorbed layers and thin films
81.65.Cf Surface cleaning, etching, patterning
68.35.B- Structure of clean surfaces (and surface reconstruction)

Plasma polymerization and deposition of linear, cyclic and aromatic fluorocarbons on (100)-oriented single crystal silicon substrates

G. H. Yang, S. W. Oh, E. T. Kang, and K. G. Neoh

J. Vac. Sci. Technol. A 20, 1955 (2002); http://dx.doi.org/10.1116/1.1513640 (9 pages) | Cited 9 times

Online Publication Date: 6 November 2002

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Fluoropolymer films were deposited on the Ar plasma-pretreated Si(100) surfaces by plasma polymerization of perfluorohexane (PFH, a linear fluorocarbon), perfluoro(methylcyclohexane) (MCH, a cyclic fluorocarbon), and hexafluorobenzene (HFB, an aromatic fluorocarbon) under different glow discharge conditions. The effects of the radio-frequency plasma power on the chemical composition and structure of the plasma-polymerized fluoropolymer films were studied by x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, time-of-flight secondary ion mass spectrometry, and water contact angle measurements. The changes in structure and composition of the three types of the plasma-deposited films from those of the respective fluorocarbons were compared. Under similar glow discharge conditions: (i) the extent of defluorination was highest for the PFH polymer, (ii) the deposition rate was highest for the HFB polymer, (iii) the cyclic structure of MCH was less well preserved than the aromatic structure of HFB, (iv) aliphatic structures appeared in the plasma-deposited MCH polymer, and (v) the plasma-polymerized HFB has the highest thermal stability due to the preservation of the aromatic rings. The adhesive tape peel test results revealed that the plasma-polymerized and deposited fluoropolymer layers were strongly bonded to the Ar plasma-pretreated Si(100) surfaces. © 2002 American Vacuum Society.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
52.77.Dq Plasma-based ion implantation and deposition
82.35.Gh Polymers on surfaces; adhesion
68.55.Nq Composition and phase identification

Studies on electron behaviors at downstream region of a neutral loop discharge plasma

Tatsuya Sakoda and Youl-Moon Sung

J. Vac. Sci. Technol. A 20, 1964 (2002); http://dx.doi.org/10.1116/1.1513644 (5 pages) | Cited 6 times

Online Publication Date: 6 November 2002

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The measurements of electron temperature, electron density, and ion current density at the plasma downstream region in a neutral loop discharge (NLD) plasma were performed using a double probe. Based on these results and the theoretical analyses of electron behaviors, the entire structure of the NLD plasma was discussed. It was concluded that the obtained profiles of the electron temperature, density, and ion current density at the downstream and throughout the intermediate regions were the mirror of profiles at the plasma source region. In addition, laser Thomson scattering measurements of the electron temperature and density at the downstream region were performed in order to include the quantitative evaluation phase. © 2002 American Vacuum Society.
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52.25.-b Plasma properties
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Electron-temperature control in 915 MHz electron cyclotron resonance plasma

N. Itagaki, Y. Kawai, S. Kawakami, and Nobuo Ishii

J. Vac. Sci. Technol. A 20, 1969 (2002); http://dx.doi.org/10.1116/1.1513791 (5 pages) | Cited 4 times

Online Publication Date: 6 November 2002

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The electron temperature of a 915 MHz electron cyclotron resonance (ECR) plasma was controlled in a wide range by adjusting the incident microwave power when the gradient in the magnetic field strength near the resonant zone was gentle. From the numerical simulations of the microwave-power absorption, the electron temperature in an ECR plasma was found to change with changing spatial profiles of the power absorption. It was also suggested from our experimental and numerical results that the electron temperature is controlled by changing the gradient in the magnetic field strength and/or the microwave frequency because the power absorption profile may be changed with changing effective resonance zone width. © 2002 American Vacuum Society.
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52.50.Sw Plasma heating by microwaves; ECR, LH, collisional heating
52.65.-y Plasma simulation
52.25.-b Plasma properties
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma

Integrated AlN/diamond heat spreaders for silicon device processing

S. N. Yoganand, K. Jagannadham, A. Karoui, and H. Wang

J. Vac. Sci. Technol. A 20, 1974 (2002); http://dx.doi.org/10.1116/1.1513643 (9 pages) | Cited 4 times

Online Publication Date: 6 November 2002

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Growth and characterization of AlN and diamond films on the backside of a Si (100) wafer and the integration of AlN/diamond heat spreaders into silicon device technology is investigated. AlN film was deposited by pulsed dc reactive magnetron sputtering at 600 °C and diamond film was deposited by microwave plasma chemical vapor deposition at 900 °C. The films were characterized by x-ray diffraction and transmission electron microscopy for crystalline quality, by scanning electron microscopy for morphology, and by infrared thermography for heat spreading characteristics. The heat spreading characteristics of the silicon wafer with the composite AlN/diamond films were found to be superior to that of wafers with no heat spreaders or to the wafers with either single layer diamond or single layer AlN heat spreaders. Deep level transient spectroscopy and secondary ion mass spectroscopy were performed on the samples with and without the heat spreader to determine the concentration of the impurities that may have been introduced during deposition of AlN or diamond. The results showed that the purity of the wafers is not altered due to the deposition of AlN and diamond and subsequent device processing steps such as high temperature oxidation. The device characteristics were studied by fabrication of Schottky diodes on the wafers with the composite AlN/diamond heat spreader and compared with that of devices on wafers with no heat spreader. The device characteristics were found to be similar and unaffected by integration with an AlN/diamond heat spreader. Integration of AlN/diamond heat spreaders with silicon device processing has been shown to be successful. © 2002 American Vacuum Society.
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85.30.-z Semiconductor devices
81.15.Cd Deposition by sputtering
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
44.00.00 Heat transfer
81.05.Ea III-V semiconductors
52.77.Dq Plasma-based ion implantation and deposition
81.05.U- Carbon/carbon-based materials

Study on the characteristics of alumdinum thin films prepared by atomic layer deposition

Yong Ju Lee and Sang-Won Kang

J. Vac. Sci. Technol. A 20, 1983 (2002); http://dx.doi.org/10.1116/1.1513636 (6 pages) | Cited 13 times

Online Publication Date: 6 November 2002

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The characteristics of aluminum (Al) films prepared by the atomic layer deposition (ALD) technique using trimethylaluminum (TMA) and a hydrogen plasma were examined for use as a wetting layer for the two-step cold/warm Al deposition. The most important role of a hydrogen plasma was to act as a reducing agent for TMA. The growth rate was saturated at 0.15 nm/cycle, demonstrating that the thickness can be precisely controlled by the number of cycles. Initial layer-by-layer growth was observed and this continued for up to 50 cycles (∼7.5 nm). The root-mean-square thickness variation of an Al film deposited in five cycles (∼0.75 nm) was found to be 0.188 nm. As the PH2/PTMA injection ratio was increased to 10 at a buffer line, the carbon concentration decreased to 1–3 at. %. The resistivity of a 100-nm-thick Al film was 10 μΩ  cm and this film was polycrystalline in nature. ALD Al films also had good step coverage on high aspect ratio trenches. © 2002 American Vacuum Society.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
85.40.Ls Metallization, contacts, interconnects; device isolation
73.61.At Metal and metallic alloys
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Low-temperature Ar/N2 remote plasma nitridation of SiO2 thin films

Amit Khandelwal, Hiro Niimi, Gerald Lucovsky, and H. Henry Lamb

J. Vac. Sci. Technol. A 20, 1989 (2002); http://dx.doi.org/10.1116/1.1513635 (8 pages) | Cited 13 times

Online Publication Date: 6 November 2002

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Low-temperature nitridation of SiO2 thin films by Ar/N2 remote plasma processing was investigated using on-line Auger electron spectroscopy, angle-resolved x-ray photoelectron spectroscopy (ARXPS), and optical emission spectroscopy (OES). Nitridation experiments were performed at 300 °C using 30 W Ar/N2 remote plasmas at 0.1 and 0.3 Torr. Ar/N2 remote plasma exposure of 5 nm SiO2 films for 30 min results in nitrogen incorporation throughout the films, independent of process pressure and plasma reactor configuration (i.e., upstream versus downstream N2 injection). ARXPS indicates a N–Si3 local bonding configuration with second nearest neighbor oxygen atoms. Ar/N2 remote plasma exposure at 0.1 Torr results in higher nitrogen concentrations (8–10 at. %). Reactor configuration has a negligible effect at 0.1 Torr; conversely, downstream N2 injection results in higher nitrogen concentrations (5–6 at. %) than upstream injection (3–4 at. %) at 0.3 Torr. OES indicates that the Ar/N2 remote plasmas contain N2 triplet excited states and ground-state N atoms. The Ar emission intensities and the saturation N concentrations in the resultant films follow similar trends with processing pressure and reactor configuration; the N2 first positive emission intensities run counter to these trends. We infer that low-temperature SiO2 nitridation by Ar/N2 remote plasmas is a two-step process: O removal by Ar+ ion bombardment and N insertion by plasma-generated active N species. Moreover, the first step appears to be rate limiting under the conditions employed in this study. Annealing the oxynitride films in N2 at 900 °C decreases the N concentration and results in a more uniform nitrogen distribution. © 2002 American Vacuum Society.
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52.77.-j Plasma applications
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Subsurface interstitials as promoters of three-dimensional growth of Ti on Si(111): An x-ray standing wave, x-ray photoelectron spectroscopy, and atomic force microscopy investigation

G. Kuri, Th. Schmidt, V. Hagen, G. Materlik, R. Wiesendanger, and J. Falta

J. Vac. Sci. Technol. A 20, 1997 (2002); http://dx.doi.org/10.1116/1.1513638 (7 pages) | Cited 1 time

Online Publication Date: 6 November 2002

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The adsorption and growth of Ti on Si(111)-7×7 surface at room temperature was studied with x-ray standing waves and high energy x-ray photoelectron spectroscopy. The surface morphology of the specimens was analyzed using atomic force microscopy. We observed that at the submonolayer (0.08–0.24 ML) coverage a significant fraction of the metal atoms are coherently located in the near-surface interstitial positions of the Si lattice. For a higher Ti coverage (1.8 ML), the coherently ordered fraction almost vanishes and the surface is covered with three-dimensional islands. The Ti-coverage results are interpreted in terms of an interfacial transition layer containing Ti interstitials below the Si surface at low coverage, and a disordered mixed Ti–Si phase at higher Ti concentration. © 2002 American Vacuum Society.
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68.43.Fg Adsorbate structure (binding sites, geometry)
61.72.J- Point defects and defect clusters
68.43.Mn Adsorption kinetics
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.49.Uv X-ray standing waves
68.37.Xy Scanning Auger microscopy, photoelectron microscopy
79.60.Dp Adsorbed layers and thin films
68.37.Ps Atomic force microscopy (AFM)
68.35.Dv Composition, segregation; defects and impurities
68.55.Nq Composition and phase identification

Highly 〈100〉-oriented growth of polycrystalline silicon films on glass by pulsed magnetron sputtering

P. Reinig, B. Selle, F. Fenske, W. Fuhs, V. Alex, and M. Birkholz

J. Vac. Sci. Technol. A 20, 2004 (2002); http://dx.doi.org/10.1116/1.1513634 (3 pages) | Cited 3 times

Online Publication Date: 6 November 2002

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Nominally undoped polycrystalline silicon (poly-Si) thin films were deposited on glass at 450 °C at high deposition rate (>100 nm/min) by pulsed dc magnetron sputtering. The pulse frequency was found to have a significant influence on the preferred grain orientation. The x-ray diffraction pattern exhibits a strong enhancement of the (400) reflex with increasing pulse frequency. The quantitative evaluation reveals that over 90% of the grains are 〈100〉 oriented. The observed change in preferred grain orientation in poly-Si films at low temperatures is associated with concurrent ion bombardment of the growing film. © 2002 American Vacuum Society.
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81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
81.05.Cy Elemental semiconductors

Epitaxial growth of metastable δ-TaN layers on MgO(001) using low-energy, high-flux ion irradiation during ultrahigh vacuum reactive magnetron sputtering

C.-S. Shin, Y.-W. Kim, N. Hellgren, D. Gall, I. Petrov, and J. E. Greene

J. Vac. Sci. Technol. A 20, 2007 (2002); http://dx.doi.org/10.1116/1.1513639 (11 pages) | Cited 13 times

Online Publication Date: 6 November 2002

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We report on the microstructural evolution and physical properties of epitaxial δ-TaN layers grown on MgO(001) at 600 °C by ultrahigh vacuum reactive magnetron sputtering of Ta in mixed Ar/N2 discharges as a function of the N2 fraction fN2 (0.100⩽fN2⩽0.275) and the incident ion energy Ei (8.4⩽Ei⩽65eV). The ratio of the ion-to-Ta fluxes Ji/JTa incident at the growing film was maintained at 11±0.5 with 0.100⩽fN2⩽0.200 and 15±0.3 with 0.250⩽fN2⩽0.275. High-resolution x-ray diffraction, transmission electron microscopy, and Rutherford backscattering spectrometry results show that films grown with Ei≲40eV are single-phase δ-TaNx(001), with x increasing from 0.94 with fN2=0.100 to 1.37 with fN2=0.275, exhibiting a cube-on-cube epitaxial relationship with the substrate: (001)δ-TaN‖(001)MgO and [100]δ-TaN‖[100]MgO. However, the use of Ei≲20 eV leads to δ- TaNx(001) layers which are underdense with a self-organized array of 1-nm-wide nanopipes oriented predominantly along orthogonal 〈100〉 directions. The nanopipes, which are first observed at film thicknesses of ≃5 nm and extend to the surface, form due to the combination of low adatom surface diffusivities, leading to kinetic roughening, and atomic shadowing. Fully dense stoichiometric epitaxial δ-TaN(001) films were obtained with Ei=30 eV and fN2=0.125. Increasing Ei to 40 eV results in a high density of {111} stacking faults. Films grown with even higher ion energies, 40<Ei⩽65 eV, contain large concentrations of residual extended defects as well as hexagonal γ-Ta2N second-phase inclusions. The room-temperature resistivity, hardness, elastic modulus, and relaxed lattice constant of fully dense stoichiometric δ-TaN(001) are 185±15 μΩ cm, 32.9±0.9 GPa, 435±15 GPa, and 0.4351±0.0002 nm, respectively. © 2002 American Vacuum Society.
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81.15.Cd Deposition by sputtering
68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Ng Insulators
61.72.Nn Stacking faults and other planar or extended defects
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
61.80.Jh Ion radiation effects
61.66.Bi Elemental solids
61.66.Dk Alloys
61.82.Ms Insulators
68.37.Lp Transmission electron microscopy (TEM)
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
68.35.Fx Diffusion; interface formation
68.35.B- Structure of clean surfaces (and surface reconstruction)
62.20.Qp Friction, tribology, and hardness
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

In situ pressure measurements in small gettered volumes

Vincenc Nemanič, Marko Žumer, and Bojan Zajec

J. Vac. Sci. Technol. A 20, 2018 (2002); http://dx.doi.org/10.1116/1.1515802 (5 pages)

Online Publication Date: 6 November 2002

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In modern small optoelectronic devices like field emitter displays, miniature cathode ray tubes (CRTs), channel photomultipliers, etc., the vacuum requirements are much more stringent than in conventional electron beam devices. As there should be a pressure in the ultrahigh vacuum region and the volume is only a few cm3, a direct measurement is not feasible and is often estimated on the basis of the expected pumping speed of the getter. The present study was arranged to investigate the pressure in small CRTs (25 cm3) during a period of several months, namely after the conventional pumping and bakeout procedure, immediately after the activation of Ba getters and after the accumulation of some months. All the CRTs were equipped by a spinning rotor gauge ball. Two barium getter sizes were studied: St15/AM/O/9.5 and St15/AM/O/5, both made by SAES. After the evaporation by the prescribed procedure the pressure did not drop, but increased from p∼1×10−5 mbar up to p∼1×10−3 mbar, showing that the pumping speed was completely suppressed by forming of a nongetterable gas. When the same experiments were repeated inside identical glass bulbs connected with a valve to a quadrupole mass spectrometer, a formation of methane was observed. The initial rate just after the activation was Q∼10−8 mbar l s−1, but even after several hours it was still as high as Q∼10−9 mbar l s−1. By switching-on the cathode heater, methane was pumped by the getter after a precedent cracking procedure. The virtual pumping speed was directly related to the heater power, but independent of the getter area. Therefore, within the cathode warm-up period, methane was “pumped” and did not represent a harmful gaseous contaminant in a small electron beam device with a thermionic cathode. © 2002 American Vacuum Society.
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85.45.Bz Vacuum microelectronic device characterization, design, and modeling
84.47.+w Vacuum tubes
07.30.Dz Vacuum gauges
07.30.Cy Vacuum pumps
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Structural, electronic and magnetic properties of chalcopyrite magnetic semiconductors: A first-principles study

Silvia Picozzi, Alessandra Continenza, Yu-Jun Zhao, Wen-Tong Geng, and Arthur J. Freeman

J. Vac. Sci. Technol. A 20, 2023 (2002); http://dx.doi.org/10.1116/1.1515801 (4 pages) | Cited 2 times

Online Publication Date: 6 November 2002

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Stimulated by recent experimental observations of room-temperature ferromagnetism of MnxCd1−xGeP2 and MnxZn1−xGeP2, we investigate the structural, electronic, and magnetic properties of this class of systems (II–Ge–V2, II=Zn, Cd, and V=As, P) as a function of Mn concentration and chemical constituents by means of first-principles density-functional- theory-based codes. Our calculations indicate that, for Mn substituting the II element, the antiferromagnetic alignment is the most stable ordering for all the systems studied. For Zn- and Cd-rich systems, the total magnetic moments per Mn atom of the ferromagnetic phase is very close to the ideal value of 5 μB, since the Mn 3d states in the minority spin channel are nearly empty; on the other hand, for Mn rich compounds, the stronger p–d hybridization lowers the total magnetic moment to about 4.4 μB. © 2002 American Vacuum Society.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.40.Mg Numerical simulation studies
61.66.Fn Inorganic compounds
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling
71.20.Nr Semiconductor compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
75.30.Cr Saturation moments and magnetic susceptibilities

Temperature effect on growth of well-ordered thin Al2O3 film on NiAl(110)

Thi Thi Lay, M. Yoshitake, and B. Mebarki

J. Vac. Sci. Technol. A 20, 2027 (2002); http://dx.doi.org/10.1116/1.1515907 (5 pages) | Cited 9 times

Online Publication Date: 6 November 2002

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We have investigated the effect of temperature on the growth of thin Al2O3 film on NiAl(110) surface. 1200 L oxygen was adsorbed at temperatures 570, 620, 670, 700, and 720 K while the pressure was kept constant at 6.6×10−5 Pa. After oxygen absorption the specimen was subsequently annealed at 1070 K for epitaxial growth of crystalline oxide. Low energy electron diffraction (LEED) and Auger electron spectroscopy were used to characterize oxide formation and surface composition. LEED patterns showed that the crystallinity depended on temperature and the brightest crystalline oxide spots were obtained at temperature between 620 and 670 K. Temperature has little effect on film thickness. The average film thickness estimated was around 4 Å. Stoichiometry of O–Al bonds during oxygen absorption and realignment during annealing is important in epitaxial growth of well-ordered crystalline oxide. © 2002 American Vacuum Society.
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68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.Nq Composition and phase identification
68.43.Mn Adsorption kinetics
81.65.Mq Oxidation
68.49.Jk Electron scattering from surfaces
68.35.Dv Composition, segregation; defects and impurities
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.20.Fv Electron impact: Auger emission

Spatial survey of a magnetron plasma sputtering system using a Langmuir probe

D. J. Field, S. K. Dew, and R. E. Burrell

J. Vac. Sci. Technol. A 20, 2032 (2002); http://dx.doi.org/10.1116/1.1515800 (10 pages) | Cited 24 times

Online Publication Date: 6 November 2002

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A two-dimensional spatial survey is conducted for a magnetron sputtering plasma at two pressures (40 and 5 mTorr) using a Langmuir probe. The plasma density is found to be highest (up to 6.0×1010 cm−3) above the etch region of the cathode, near the magnetic trap. The density drops between the etch regions, near the edges of the cathode and also at distances farther away from the cathode. The floating potential was found to be most negative (down to −12 V) in regions where the highest electron temperatures were observed (up to almost 4 eV) and became less negative (near 0 V) in regions where the electron temperature was lowest (less than 0.5 eV). This complementary trend was consistent in all spatial locations and at both pressures. The plasma potential was found to have very weak dependence, if any, on spatial location and pressure. The relationship between electron transport processes, collision processes and electron temperatures is discussed. Electron energy distribution functions were found to be either Maxwellian or bi-Maxwellian in nature, depending on pressure and spatial location. Maxwellian distributions were found near the magnetic trap or source of the plasma. Bi-Maxwellian distributions were found further away from the source, and it appears they result from Maxwellian distributions bifurcating as they diffuse away from the source. The suitability of the popular models for this bifurcation is discussed. © 2002 American Vacuum Society.
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52.77.Dq Plasma-based ion implantation and deposition
81.15.Cd Deposition by sputtering
52.25.Fi Transport properties
52.70.Ds Electric and magnetic measurements

Effect of carbon enrichment induced by photoresist on highly selective SiO2 etching

Changwoong Chu, Kyeong-Koo Chi, and Joo-Tae Moon

J. Vac. Sci. Technol. A 20, 2042 (2002); http://dx.doi.org/10.1116/1.1517255 (7 pages) | Cited 2 times

Online Publication Date: 6 November 2002

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We propose two models to discuss the behavior of the selective etching of SiO2 to the underlying Si3N4 with changing wafer surface temperatures. For this investigation, three specimens, SiO2, Si3N4, and poly-Si, which are nonpatterned, photoresist-patterned, and poly-silicon-patterned, respectively, have been etched in a surface wave plasma system equipped with an electrostatic chuck for wafer temperature control. The coolant temperature, which controls the wafer temperature, has been changed from −20 to 50 °C. For the nonpatterned wafer, the etch rates of SiO2, Si3N4, and poly-Si increase and the selectivities decreases with wafer temperature. However, for the samples patterned with either photoresist or poly-Si, the etch rates of SiO2 decrease with wafer temperature. The temperature rise also leads to an enhancement of selectivity of SiO2/Si3N4, and the steeper profile angles. The presence of a masking layer, even for the poly-Si-patterned samples, results in a different etching behavior. This is because the sticking probability of the polymer precursor becomes smaller on the sidewall of the profile with the temperature increase. Therefore the thickness of polymer on the sidewall of the contact hole decreases, and the thickness of polymer on the bottom increases as the wafer temperature goes up. Comparing photoresist-patterned samples with poly-Si-patterned ones, we can corroborate the role of the photoresist mask layer, which provides a higher carbon-to-fluorine ratio at the near surface. The carbon enrichment accelerates more steeply the etch rate decrement of the substrate layer. In summary, there are two main contributions attributed by the substrate temperature: changing the sticking coefficient of the fluorocarbon precursor and enhancing the photoresist erosion. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
85.40.Hp Lithography, masks and pattern transfer
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Creation of stable, low work function surfaces on Si by implantation of 3 keV Cs+

R. G. Musket and M. Balooch

J. Vac. Sci. Technol. A 20, 2049 (2002); http://dx.doi.org/10.1116/1.1517259 (3 pages) | Cited 2 times

Online Publication Date: 6 November 2002

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Silicon surfaces having native oxides were implanted with 3 keV Cs+ ions and annealed. Implanted doses of 1, 1.7, and 3×1016 Cs/cm2 led to room-temperature work functions with stable, reproducible values of 2.3±0.15 eV after vacuum annealing at 100–560 °C. The resulting surfaces have been characterized with regard to the amount of Cs retained, the thermal and environmental stability of the work function, and the composition and chemistry of the implanted layer. The surface layers consisted of a compound of Si–Cs–O, which is compositionally stable to temperatures of ∼400 °C in vacuum. In addition, we found that these surfaces are stable with regard to exposures to background gases and ambient air. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors
61.72.uf Ge and Si
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
73.30.+y Surface double layers, Schottky barriers, and work functions
61.82.Fk Semiconductors
61.72.Cc Kinetics of defect formation and annealing
68.35.Dv Composition, segregation; defects and impurities

Fluorocarbon-based plasma etching of SiO2: Comparison of C4F6/Ar and C4F8/Ar discharges

Xi Li, Xuefeng Hua, Li Ling, Gottlieb S. Oehrlein, Marcos Barela, and Harold M. Anderson

J. Vac. Sci. Technol. A 20, 2052 (2002); http://dx.doi.org/10.1116/1.1517256 (10 pages) | Cited 42 times

Online Publication Date: 6 November 2002

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A gas phase and surface chemistry study of inductively coupled plasmas fed with C4F6/Ar and C4F8/Ar intended for SiO2 etching processes was performed. Adding Ar to those fluorocarbon gases results in a strong increase of the ion current, by up to a factor of 5 at 90% Ar relative to the pure fluorocarbon gases. The fluorocarbon deposition rate is higher for C4F6/Ar than for C4F8/Ar, whereas the fluorocarbon etching rate is lower, and both quantities decrease as the amount of Ar is increased. For both C4F6/Ar and C4F8/Ar, the CF2 density is more than an order of magnitude greater than the CF density. The CF2 partial pressure decreases as more Ar is added to the C4F6/Ar plasmas. A comparison of these data with corresponding results obtained with C4F8/Ar shows that the CF2 partial pressure in C4F6 is higher for Ar-lean gas mixture than for C4F8/Ar. This remains true up to 40% Ar. Above 40% Ar the CF2 partial pressure in C4F8 is higher than for C4F6. The CF and COF2 partial pressures in C4F8 are higher than for C4F6. The SiO2 etch rate is higher for C4F8/Ar than for C4F6/Ar. This may be attributed in part to the higher F/C ratio of the steady-state fluorocarbon film formed on SiO2 surfaces for C4F8/Ar which was determined by x-ray photoemission spectroscopy (XPS). The etching selectivity of SiO2 over resist and silicon is increased by the addition of Ar to the fluorocarbon gases. Overall, the SiO2/resist and SiO2/Si etching selectivity are higher for C4F6/Ar (i.e., 4 and 9, respectively) at 90% Ar than for C4F8/Ar (i.e., 2 and 5, respectively) at 90% Ar and otherwise identical conditions. Both ellipsometry and XPS measurements show that the steady-state fluorocarbon layer thickness is greater for C4F6/Ar (∼4 nm) than for C4F8/Ar (∼2.8 nm). Argon addition leads to a strong decrease of the fluorine content of the steady-state fluorocarbon layers on both Si and SiO2 surfaces relative to films produced in pure fluorocarbon discharges, and this effect is related to the increase of the SiO2/Si and SiO2/resist etching selectivity. © 2002 American Vacuum Society.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Column angle variations in porous chevron thin films

K. D. Harris, D. Vick, T. Smy, and M. J. Brett

J. Vac. Sci. Technol. A 20, 2062 (2002); http://dx.doi.org/10.1116/1.1517258 (6 pages) | Cited 10 times

Online Publication Date: 6 November 2002

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We describe the fabrication of porous chevron thin films deposited at glancing incidence and report some common growth peculiarities of the microstructure. In particular, the second (and additional) chevron arms of porous chevron thin films are consistently inclined at angles significantly greater than the corresponding first arms. This effect is observed in both real and simulated films and has important implications in the fabrication of optical coatings. A simple theoretical model is developed to describe this effect, and a technique for achieving consistent column angles is presented. © 2002 American Vacuum Society.
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81.05.Rm Porous materials; granular materials
42.79.Wc Optical coatings
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
42.82.Cr Fabrication techniques; lithography, pattern transfer

Observation of step-flow growth in femtosecond pulsed laser deposition of Si on Si(100)-2×1

M. S. Hegazy and H. E. Elsayed-Ali

J. Vac. Sci. Technol. A 20, 2068 (2002); http://dx.doi.org/10.1116/1.1517257 (4 pages) | Cited 5 times

Online Publication Date: 6 November 2002

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Step-flow growth mode is observed for 100 fs pulsed laser deposition (fsPLD) of Si on vicinal Si(100)-2×1, while the Volmer–Weber mode is observed for fsPLD of Si on Si(100)-1×1. Reflection high-energy electron diffraction (RHEED) is used to in situ monitor the dynamics of the film growth while ex situ atomic force microscopy (AFM) is used to observe the morphology of the grown film. For Si on Si(100)-2×1, the diffraction pattern’s basic features remain unchanged during deposition, indicating step-flow growth. AFM shows smooth growth on flat terraces. However, for Si on Si(100)-1×1 two growth behaviors are observed. For a laser fluence of 1.9 J/cm2 and a substrate temperature below ∼400 °C, we observe a decay of the RHEED peaks until they completely disappear, indicating the loss of the long-range order in the grown film. Postdeposition analysis shows three-dimensional (3D) clusters associated with the Volmer–Weber growth mode. On the other hand, deposition above ∼400 °C at the same laser fluence results in the decay and eventual disappearance of the reflection diffraction peaks accompanied by the evolution of a transmission pattern instead. Transmission patterns appear when the electrons are diffracted in a transmission mode through 3D crystallites. These crystallites are observed in the AFM images. © 2002 American Vacuum Society.
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81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.A- Nucleation and growth

Surface morphology of ion-beam deposited carbon films under high temperature

Meiyong Liao, Chunlin Chai, Shaoyan Yang, Zhikai Liu, Fuguang Qin, and Zhanguo Wang

J. Vac. Sci. Technol. A 20, 2072 (2002); http://dx.doi.org/10.1116/1.1517996 (3 pages)

Online Publication Date: 6 November 2002

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Carbon films with an open-ended structure were obtained by mass-selected ion-beam deposition technique at 800 °C. Raman spectra show that these films are mainly sp2-bonded. In our case, threshold ion energy of 140 eV was found for the formation of such surface morphology. High deposition temperature and ion-beam current density are also responsible for the growth of this structure. Additionally, the growth mechanism of the carbon films is discussed in this article. It was found that the ions sputtered pits on the substrate in the initial stage play a key role in the tubular surface morphology. © 2002 American Vacuum Society.
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68.55.-a Thin film structure and morphology
81.05.U- Carbon/carbon-based materials
81.15.Jj Ion and electron beam-assisted deposition; ion plating
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators

Study on time of flight property of uniform magnetic sector field analyzers up to the third-order approximation

Min Cheng, Tiantong Tang, Zhenhua Yao, and Zhenhua Wang

J. Vac. Sci. Technol. A 20, 2075 (2002); http://dx.doi.org/10.1116/1.1517999 (4 pages)

Online Publication Date: 6 November 2002

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Time of flight (TOF) is an important concept in many electron optical instruments including TOF analyzers and streak camera image tubes. In this article, successive approximation approach is applied to study the TOF properties of uniform magnetic sector field analyzers. The charged particle trajectories in the magnetic field analyzers are calculated up to the third-order approximation and the corresponding solutions are obtained. Therefore, the TOF properties of the uniform magnetic sector field analyzers are analytically derived up to the third-order approximation. © 2002 American Vacuum Society.
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41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
41.85.Qg Particle beam analyzers, beam monitors, and Faraday cups
41.75.Fr Electron and positron beams

Multiple cavity modes in the helicon plasma generated at very high radio frequency

G. S. Eom and W. Choe

J. Vac. Sci. Technol. A 20, 2079 (2002); http://dx.doi.org/10.1116/1.1517994 (5 pages) | Cited 2 times

Online Publication Date: 6 November 2002

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Helicon plasma generated at very high radio frequency has almost the same properties as common high frequency helicon plasmas. By measurements of wave number and plasma potential, additional mode changes inside the helicon plasma were observed with increasing magnetic field. It was also observed that the wavelength of the helicon wave changes discretely with respect to the plasma length indicating strong restriction of the parallel wavelength to the plasma dimension. The dependence of plasma potential on magnetic field indicates that its change is not entirely due to capacitive coupling. The corresponding mode transition is related to the cavity modes driven by a helicon wave. © 2002 American Vacuum Society.
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52.50.Dg Plasma sources
52.80.Pi High-frequency and RF discharges
52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
52.25.Fi Transport properties
52.70.Ds Electric and magnetic measurements

Correlation between structure, stress and deposition parameters in direct current sputtered zinc oxide films

O. Kappertz, R. Drese, and M. Wuttig

J. Vac. Sci. Technol. A 20, 2084 (2002); http://dx.doi.org/10.1116/1.1517997 (12 pages) | Cited 28 times

Online Publication Date: 6 November 2002

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Thin ZnO and ZnO:Al films have been prepared by reactive dc magnetron sputtering, using both metallic and ceramic targets. The influence of oxygen flow and total pressure on film stress, structure, texture, and surface roughness has been examined. The properties of the films strongly depend on the deposition conditions, in particular the total pressure. Increasing the pressure from 0.5 to 2 Pa resulted in rougher, and less strained films. Increasing the oxygen flow at a constant total pressure led to a slight increase in stress, but had no visible effect on the surface roughness. Structural investigations by x-ray diffraction (XRD) showed that polycrystalline films with pronounced preferential orientation were formed. Most XRD-spectra showed a coexistence of strained and unstrained ZnO in wurtzite structure. The relative abundance of the relaxed phase is a function of the intrinsic stress only, and does not directly depend on deposition parameters. However, the deposition parameters determine the stress within the film, and thus influence the amount of the relaxed grains. © 2002 American Vacuum Society.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
81.05.Dz II-VI semiconductors
68.60.Bs Mechanical and acoustical properties
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.47.Gh Oxide surfaces

Atomic layer deposition of zirconium silicate films using zirconium tetrachloride and tetra-n-butyl orthosilicate

Won-Kyu Kim, Sang-Woo Kang, Shi-Woo Rhee, Nae-In Lee, Jong-Ho Lee, and Ho-Kyu Kang

J. Vac. Sci. Technol. A 20, 2096 (2002); http://dx.doi.org/10.1116/1.1517998 (5 pages) | Cited 16 times

Online Publication Date: 6 November 2002

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Atomic layer chemical vapor deposition of zirconium silicate films with a precursor combination of ZrCl4 and tetra-n-butyl orthosilicate (TBOS) was studied for high dielectric gate insulators. The effect of deposition conditions, such as deposition temperature, pulse time for purge and precursor injection on the deposition rate per cycle, and composition of the film were studied. At 400 °C, the growth rate saturated to 1.35 Å/cycle above 500 sccm of the argon purge flow rate. The growth rate, composition ratio ((Zr/Zr+Si)), and impurity contents (carbon and chlorine) saturated with the increase of the injection time of ZrCl4 and TBOS and decreased with the increased deposition temperature from 300 to 500 °C. The growth rate, composition ratio, carbon, and chlorine contents of the Zr silicate thin films deposited at 500 °C were 1.05 Å/cycle, 0.23, 1.1 at. %, and 2.1 at. %, respectively. It appeared that by using only zirconium chloride and silicon alkoxide sources, the content of carbon and chlorine impurities could not be lowered below 1%. It was also found that the incorporation rate of metal from halide source was lower than alkoxide source. © 2002 American Vacuum Society.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Photoelastic modulation-reflection absorption infrared spectroscopy of CO on Pd(111)

D. Stacchiola, A. W. Thompson, M. Kaltchev, and W. T. Tysoe

J. Vac. Sci. Technol. A 20, 2101 (2002); http://dx.doi.org/10.1116/1.1517995 (5 pages) | Cited 2 times

Online Publication Date: 6 November 2002

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The photoelastic modulation-reflection absorption infrared spectrum (PEM-RAIRS) of CO on single crystal Pd(111) is measured for CO pressures up to ∼150 Torr. The ac component of the signal, corresponding to the infrared signal of the surface, is measured using a synchronous demodulator circuit rather than using a lock-in amplifier as used in previous experiments to measure the infrared spectra of model catalysts surfaces. This allows the spectra to be collected at almost the same speed as RAIRS spectra performed in ultrahigh vacuum. A simplified synchronous demodulator circuit is described consisting of two sample-and-hold circuits operating at 100 kHz. Spectra are obtained that are in excellent agreement with previous results showing that a combination of hcp and fcc threefold sites are occupied by CO at 300 K. Atop sites become occupied as the CO pressure increases. Heating the Pd(111) sample to ∼500 K removes all adsorbed CO. © 2002 American Vacuum Society.
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78.30.-j Infrared and Raman spectra
33.20.Ea Infrared spectra
68.43.Fg Adsorbate structure (binding sites, geometry)
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Plasma–surface kinetics and simulation of feature profile evolution in Cl2+HBr etching of polysilicon

Weidong Jin, Steven A. Vitale, and Herbert H. Sawin

J. Vac. Sci. Technol. A 20, 2106 (2002); http://dx.doi.org/10.1116/1.1517993 (9 pages) | Cited 39 times

Online Publication Date: 6 November 2002

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The etching of polysilicon by low energy Cl2+HBr plasma beam was studied, and the etching yield as a function of composition, ion impingement energy and ion incident angle was measured. The etching yield by HBr plasma beam is slightly lower than Cl2 plasma beam. The angular dependence of etching yield by both Cl2 and HBr beam strongly suggests the mechanism of ion induced chemical etching, with highest etching yield at normal incident angle. For Cl2 beam, the etching yield almost keeps constant until the off-normal incident angle of ions increased to 45°, while for HBr beam, the etching yield starts dropping even with small off-normal angle. The angular dependence of etching yield by Cl2+HBr plasma at different composition exhibits similar trend as pure HBr. Using x-ray photoelectron spectroscopy, the coverage of Cl and Br on polysilicon surfaces after etching in Cl2+HBr plasmas was measured. The Cl coverage after etching with pure Cl2 plasma beam is about 1.4 times higher than the Br coverage after etching with pure HBr plasma beam, due to the larger size of Br atom. The instantaneous sputtering yields of polysilicon by Ar+ ions after Cl2 and HBr plasma etching are similar, indicating that the lower Br coverage is not responsible for the lower etching rate in HBr plasma. The effect of the angular dependent etching yield difference between Cl2 and HBr on feature profile evolution, as identified with Monte Carlo simulation, might contribute to the more anisotropic etching in HBr plasma. © 2002 American Vacuum Society.
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81.05.Cy Elemental semiconductors
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
79.60.Bm Clean metal, semiconductor, and insulator surfaces
02.70.Uu Applications of Monte Carlo methods

Dramatic change of electrical properties in La–Ba–Mn–O thin films prepared using bias sputtering

Jong Cheol Lee, Sang Yub Ie, Seung Iel Park, Yeonjin Yi, Gyu In Jang, Ho Shik Song, Dong Gyun You, and Kwangho Jeong

J. Vac. Sci. Technol. A 20, 2115 (2002); http://dx.doi.org/10.1116/1.1519866 (4 pages)

Online Publication Date: 6 November 2002

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Polycrystalline La–Ba–Mn–O thin films have been grown using rf magnetron sputtering on Si(100) substrates from a stoichiometric La0.7Ba0.3MnO3 target. Four films were grown with substrate biased such as −5, −10, −15, and −25 V and compared with the film grown with grounded substrate. Bias effects on the stoichiometry and physical properties of the films are studied. The dc resistivity was measured in the temperature range from 85 to 300 K for the films with substrate bias of 0, −5, −10, −15, and −25 V. The magnetoresistance was measured in the magnetic field of 0–10 000 Oe and at 77 K. The film with grounded substrate showed semiconductor behavior (dρ/dT<0) over the whole temperature range. The films with biased substrate, however, showed the maximum resistance at each metal–insulator transition temperature TMI. In order to find out the origin of the extreme change of electrical resistivity, x-ray photoemission spectroscopy (XPS) and x-ray diffraction (XRD) measurements were carried out. From the analysis of XPS and XRD data, bias sputtering increased La and Ba concentration in the La–Ba–Mn–O thin film and led to an increase of Mn–O–Mn bond angle. It changed films from semiconductor behavior to metal–insulator transition behavior. © 2002 American Vacuum Society.
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73.61.Le Other inorganic semiconductors
81.15.Cd Deposition by sputtering
72.60.+g Mixed conductivity and conductivity transitions
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.55.-a Thin film structure and morphology

Conductance calculation of a long tube with equilateral triangle cross section

Ping Fan, Ji-Guo Chu, and Jian-Da Shao

J. Vac. Sci. Technol. A 20, 2119 (2002); http://dx.doi.org/10.1116/1.1519864 (4 pages)

Online Publication Date: 6 November 2002

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Using the stratified gas flow model for calculating the conductance of long tubes with constant cross section, an analytical expression for calculating the conductance of a long tube with equilateral triangle cross section has been derived. The formula given is applicable to the full pressure range. A minimum in the conductance in the intermediate flow state is shown. © 2002 American Vacuum Society.
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47.60.-i Flow phenomena in quasi-one-dimensional systems
47.55.Hd Stratified flows
47.45.-n Rarefied gas dynamics
07.30.Bx Degasification, residual gas

Effect of surface polymerization on plasma and process stability in polycrystalline-silicon etching

Songlin Xu, Thorsten Lill, Shashank Deshmukh, and Olivier Joubert

J. Vac. Sci. Technol. A 20, 2123 (2002); http://dx.doi.org/10.1116/1.1519865 (8 pages) | Cited 10 times

Online Publication Date: 6 November 2002

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Properties of the plasma containing Cl2, HBr, and O2 species used for polysilicon etching change when the chamber wall is coated with organic polymer, causing the etch performance to drift. In this work, the plasma instability due to surface polymerization has been characterized through the comparison of free radical densities in an etch chamber coated with fluorocarbon polymer and other materials such as silicon oxide and anodized aluminum. The results of plasma diagnostics show that chlorine, bromine, and oxygen densities decrease after a polymer film is deposited onto the chamber wall. The root cause for the decrease in halogen radical densities has been attributed to the higher surface recombination rate of these free radicals on polymer surface, while the decrease in oxygen radical density is mainly caused by the consumption of oxygen in the cleaning of the polymer deposition. The impact of the plasma property change on etch performance has also been analyzed through etch rate and critical dimension (CD) evaluation. The lower free radical density in polymer-coated chamber generally lowers the etch rate and generates CD gain but the sensitivity of the process drift to the plasma property variation depends on process conditions. Approaches to reduce the effect of surface polymerization have been discussed. © 2002 American Vacuum Society.
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81.05.Cy Elemental semiconductors
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.70.-m Plasma diagnostic techniques and instrumentation
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High-sensitivity x-ray photoelectron spectroscopy characterization of a quantum device structure

M. Wintrebert-Fouquet and K. S. A. Butcher

J. Vac. Sci. Technol. A 20, 2131 (2002); http://dx.doi.org/10.1116/1.1508801 (3 pages)

Online Publication Date: 6 November 2002

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A high-resolution, high-sensitivity VG x-ray photoelectron spectrometer was used to study a semiconductor layer structure grown for the fabrication of resonant tunneling bipolar transistor devices. Depth profiling using argon ion milling, at a rate of 50 Å/min, has allowed the device layers to be identified on the basis of their elemental composition. The measurement system sensitivity was sufficient to identify the elemental components of the 11 Å AlAs barrier layer in quantum tunneling InGaAs/AlAs device layers. © 2002 American Vacuum Society.
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79.60.Jv Interfaces; heterostructures; nanostructures
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
73.23.Hk Coulomb blockade; single-electron tunneling
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
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Low temperature deposition of α-Al2O3 thin films by sputtering using a Cr2O3 template

P. Jin, G. Xu, M. Tazawa, K. Yoshimura, D. Music, J. Alami, and U. Helmersson

J. Vac. Sci. Technol. A 20, 2134 (2002); http://dx.doi.org/10.1116/1.1513641 (3 pages) | Cited 25 times

Online Publication Date: 6 November 2002

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© 2002 American Vacuum Society.
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81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth

Refractive index control of silicon nitride films prepared by radio-frequency reactive sputtering

P. S. Nayar

J. Vac. Sci. Technol. A 20, 2137 (2002); http://dx.doi.org/10.1116/1.1513637 (3 pages) | Cited 5 times

Online Publication Date: 6 November 2002

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Silicon nitride films were prepared on polished silicon wafers by radio-frequency reactive sputtering using a silicon target in nitrogen–argon plasma. The deposition rate was controlled from 2 to 7 nm/minute. The refractive index of the film decreased continuously and was varied from 2.8 to 1.96. The process described here is simple and does not require knowledge of the absolute magnitudes of partial pressures of the gases used. This method is well suited for fabricating multilayer structures of silicon nitride films with different refractive indices. © 2002 American Vacuum Society.
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78.66.Nk Insulators
81.15.Cd Deposition by sputtering
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.55.-a Thin film structure and morphology
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