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Nov 1996

Volume 14, Issue 6, pp. 2983-3291


Current capabilities and limitations of in situ particle monitors in silicon processing equipment

Ken M. Takahashi and John E. Daugherty

J. Vac. Sci. Technol. A 14, 2983 (1996); http://dx.doi.org/10.1116/1.580257 (11 pages) | Cited 7 times

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By enabling real time monitoring and control of particle levels in integrated circuit process equipment, in situ particle monitors (ISPMs) have the potential to reduce dramatically the dominant source of yield‐killing defects, i.e., process induced particles. However, there are also significant limitations to their use for on‐line monitoring. A survey of the ISPM literature shows that the greatest benefit provided by ISPMs for most applications is their immediate indication of high‐particle excursions. In only a few applications described in the literature do the sensor data correlate with wafer surface scans and show enough sensitivity to baseline particle levels to control process maintenance cycles. Scaling arguments show that at gas pressures below about 100 mTorr, gravitational settling and particle inertia typically prevent particles from being carried efficiently to exhaust sensors, in spite of experimental evidence that bouncing significantly aids particle transport. Combined with the low sampling efficiency of most sensors, these limitations make exhaust sensors impractical for many applications including most sputtering and many etching processes, unless chambers are regularly vented to high pressures. The cutoff imposed by particle transport limitations is clearly demarcated in the ISPM literature, which indicates good sensitivity of exhaust sensors to baseline particle levels in high pressure processes such as plasma‐enhanced chemical‐vapor deposition, sensitivity only to high‐particle excursions for processes around 100 mTorr, and insensitivity to particle levels in processes that operate at low pressures, except during gas venting or purging. For many applications, standard sensors are susceptible to false counting due to fouled optics, noise from rf and magnetic fields, and optical emissions. High current ion implanters, with their nearly noise‐free chambers, are the only fully proven application of in‐chamber sensors. To overcome the particle transport limitations in other critical defect‐producing processes that operate at low pressure, in‐chamber sensors that are insensitive to the harsh chemistry and high noise levels of process chambers need to be developed. © 1996 American Vacuum Society
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Reactive ion etching of silica structures for integrated optics applications

M. V. Bazylenko and M. Gross

J. Vac. Sci. Technol. A 14, 2994 (1996); http://dx.doi.org/10.1116/1.580258 (10 pages) | Cited 13 times

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Reactive ion etching of silica in a hollow cathode reactor using a CHF3/Ar gas mixture has been studied as a function of masking material, rf power, sample temperature, and O2 and CF4 additions. Etch rates in excess of 0.5 μm/min are typically obtained with a selectivity over amorphous silicon and photoresist of more than 10. The sidewall roughness for etching with an amorphous silicon mask is of the order of 0.05 μm, whereas for a photoresist mask, under similar etching conditions, the sidewall roughness is up to 0.1 μm. For the a‐Si mask a further improvement in the sidewall roughness down to 0.02 μm can be obtained by adding O2 to the discharge or elevating the sample temperature, however both parameters cause lateral etching of the a‐Si mask and therefore linewidth loss. Nonetheless, when using sample temperature as a control parameter, a process window was found which allows smooth sidewalls to be obtained without dimension loss. In the case of O2 additions such a process window was not found. Possible mechanisms accounting for this difference are discussed. Etching in a CHF3/Ar discharge occurs in competition with simultaneous polymer deposition. The polymer deposition rate was measured in areas shielded from ion bombardment. A phenomenological model describing the effects of polymer deposition on etch rates, sidewall slope, and roughness is proposed. This model assumes that a polymer film with different steady‐state thickness can form on different etched structure surfaces, as a result of a balance between polymer etching and deposition. The model is used to explain the tendencies in etch rates, profile slope, and sidewall roughness obtained in this study. © 1996 American Vacuum Society
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81.65.Cf Surface cleaning, etching, patterning
42.82.Cr Fabrication techniques; lithography, pattern transfer

Effect of supplied substrate bias frequency in ultrahigh‐frequency plasma discharge for precise etching processes

Seiji Samukawa, Hiroto Ohtake, and Tsutomu Tsukada

J. Vac. Sci. Technol. A 14, 3004 (1996); http://dx.doi.org/10.1116/1.580163 (6 pages) | Cited 4 times

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The characteristics of silicon etching using radio‐frequency (rf) substrate biased ultrahigh‐frequency (UHF) plasma determined by using a Cl2 etchant were investigated. The silicon etching rate and the etching profile were improved by decreasing the substrate bias frequency to less than 600 kHz. It is suggested that a large number of negative chlorine ions is generated in the high‐density, low‐pressure UHF plasma because of the extremely low electron temperature. The low‐frequency substrate bias accelerates the negative and positive ions alternately to the substrate surface. As a result, the low‐frequency biased UHF plasma can be used to achieve high‐rate, highly anisotropic, and microloading‐free silicon etching with a 600 kHz rf substrate bias. © 1996 American Vacuum Society
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors

Etching characteristics of tin oxide thin films in argon–chlorine radio frequency plasmas

P. Maguire, J. Molloy, S. J. Laverty, and J. McLaughlin

J. Vac. Sci. Technol. A 14, 3010 (1996); http://dx.doi.org/10.1116/1.580164 (7 pages) | Cited 3 times

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We have developed an etch process suitable for high resolution transparent conductive oxide patterning with high etch rates, up to 70 nm/min, and applicability to large area flat panel display substrates. It was found that the addition of small amounts of Cl2 significantly enhanced the etch rate compared to addition of pure argon but that beyond 25% Cl2 the rate tended to fall. There is a significant loading effect where the etch rate approximately doubled for exposed tin oxide areas between 80% and 10% of the substrate area. This loading sensitivity was found to increase with increasing power and decreasing Cl2 concentration. It was also observed that local changes in pattern dimensions affected the uniformity of the etch rate. A large photoresist etch rate was observed between one and three times that of the tin oxide and it decreased as the area of photoresist coverage increased. Linewidth loss, up to 4 μm at high powers, was overcome using improved ultraviolet exposure, leading to feature resolution capabilities of <5 μm. Etch rate inhomogeneity was also observed on a local scale, possibly due to redeposition of sputtered photoresist. Overetching, however, ensures rapid clearing of tin oxide islands without damage to the underlying SiO2 buffer layer. © 1996 American Vacuum Society
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81.65.Cf Surface cleaning, etching, patterning
81.05.Hd Other semiconductors
85.60.Pg Display systems

Integrated processing of silicon oxynitride films by combined plasma and rapid‐thermal processing

S. V. Hattangady, H. Niimi, and G. Lucovsky

J. Vac. Sci. Technol. A 14, 3017 (1996); http://dx.doi.org/10.1116/1.580165 (7 pages) | Cited 29 times

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Silicon oxynitride (OXN) gate dielectric thin films have been prepared in a cluster tool using a low thermal‐budget process combining plasma and rapid‐thermal step. This N2‐based process has (i) increased process latitude for the formation of N‐rich alloys, and (ii) resulted in lower bonded‐H concentrations, in comparison to NH3‐based processes. On‐line Auger electron spectroscopy and off‐line infrared spectroscopy have been used to characterize chemical bonding, showing that the deposited films are pseudobinary alloys, (SiO2)x(Si3N4)1−x. The processing steps are (i) a 300 °C plasma‐assisted oxidation, (ii) a 300 °C plasma‐assisted chemical vapor deposition of oxynitride films, and (iii) a 30 s, 900 °C postdeposition rapid‐thermal anneal. Electrical characterization of O–OXN–O structures in metal–oxide–semiconductor capacitors was performed using capacitance–voltage techniques to evaluate the effect of alloy composition on midgap interface state density, Dit, and flat‐band voltage, Vfb. © 1996 American Vacuum Society
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Ion–surface interactions in low temperature silicon epitaxy by remote plasma enhanced chemical–vapor deposition

S. Habermehl and G. Lucovsky

J. Vac. Sci. Technol. A 14, 3024 (1996); http://dx.doi.org/10.1116/1.580166 (9 pages) | Cited 2 times

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Epitaxial Si thin films have been deposited by remote plasma enhanced chemical–vapor deposition at temperatures below 450 °C and at pressures between 50 and 500 mTorr. Growth rate data reveal the presence of two pressure dependent regimes for deposition process activation. Sampling of the plasma afterglow by mass spectrometry indicates a correlation between enhanced rates for single crystal film formation and the onset of an ion‐induced surface H abstraction processes below pressures of ∼200 mTorr. The role of low energy ions in the abstraction of chemisorbed H and its effects on the growth kinetics are discussed. © 1996 American Vacuum Society
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.05.Cy Elemental semiconductors
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

The radio frequency hollow cathode plasma jet arc for the film deposition

H. Baránková, L. Bárdoš, and S. Berg

J. Vac. Sci. Technol. A 14, 3033 (1996); http://dx.doi.org/10.1116/1.580167 (6 pages) | Cited 4 times

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The radio frequency hollow cathode plasma jet (RPJ or RHCPJ) arc discharge is studied for an activated reactive deposition of TiN films. The presence of low content of nitrogen in argon enables reaching the arc regime at lower powers than in pure argon. The transition into the distributed arc after admission of low content of nitrogen results in an extreme enhancement of TiN deposition rate (20–30× higher than for Ti) and at the same time in an effective incorporation of nitrogen into the film. The spontaneously repeated transitions between the hollow cathode discharge and RHCPJ arc at particular parameters are studied. The time development and the character of these transitions confirm the substantial role of metastable argon atoms in the discharge. The comparison of several cathode materials is presented. The reactive deposition of TiN films at low nitrogen pressure without argon is examined. © 1996 American Vacuum Society
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Generation of an electron cyclotron resonance plasma using coaxial‐type open‐ended dielectric cavity with permanent magnets

Tadashi Kimura and Yasunao Okazaki

J. Vac. Sci. Technol. A 14, 3039 (1996); http://dx.doi.org/10.1116/1.580168 (4 pages) | Cited 1 time

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A high density, uniform, and compact electron cyclotron resonance (ECR) plasma source which utilizes surface‐wave radiation and a near‐surface magnetic field is described. The microwaves propagated through a coaxial waveguide are introduced circularly into the circumferential side of a dielectric Al2O3 disk, which is placed at the open end of a coaxial‐type cavity. The ECR magnetic field is similar to three concentric planar magnetron configurations and is directed away from the dielectric surface by permanent magnets set in the center conductor of the coaxial‐type cavity. A surface wave is launched from the dielectric disk surface and generates an ECR plasma. The plasma density and electron temperature are 2.0×1011 cm−3 and 2.2 eV, respectively, at an Ar gas pressure of 10 mTorr and a microwave power of 700 W. The ion saturation current density (Isat) and its uniformity are 8.2 mA/cm2 and ±5.5% within a radius of 10 cm. © 1996 American Vacuum Society
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52.50.Dg Plasma sources
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

‘‘Self‐thickness‐limited’’ plasma polymerization of an ultrathin antiadhesive film

P. Gröning, A. Schneuwly, L. Schlapbach, and M. T. Gale

J. Vac. Sci. Technol. A 14, 3043 (1996); http://dx.doi.org/10.1116/1.580169 (6 pages) | Cited 5 times

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Ultrathin (<5 nm) fluorinated polymer films of homogeneous thicknesses have been deposited from a CF4/H2 microwave discharge. The films have an extremely low surface energy of 4.2 mJ/m2, which is more than four times lower than that for polytetrafluoroethylene. The deposition was carried out in a type of ‘‘self‐thickness‐limited’’ mode, in which the thickness of the deposited polymer film is limited by the plasma parameters. The deposition can be separated into two phases, a growth and a treatment phase. During the treatment phase, the deposited film is fluorinated, which results in a dramatic decrease of the surface energy. The thickness limiting behavior of the plasma is explained by the dualism of etching and polymerization occurring in fluorocarbon discharges. The film was tested as antiadhesion film for the replication of micro‐optical structures, using a Ni shim with a very fine surface relief grating (400 nm periodicity) to hot emboss (at 180 °C) polycarbonate sheed. The tests demonstrate the excellent antiadhesive property of the film with the polycarbonate and reveal a good adhesion of the film with the Ni substrate. © 1996 American Vacuum Society
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments
42.79.-e Optical elements, devices, and systems

Pulse–time‐modulated electron cyclotron resonance plasma discharge for highly selective, highly anisotropic, and charge‐free etching

Seiji Samukawa, Hiroto Ohtake, and Tetsu Mieno

J. Vac. Sci. Technol. A 14, 3049 (1996); http://dx.doi.org/10.1116/1.580170 (10 pages) | Cited 44 times

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Highly selective, highly anisotropic, notch‐free, and charge‐buildup damage‐free silicon etching is performed using electron cyclotron resonance (ECR) Cl2 plasma modulated at a pulse timing of a few tens of microseconds. A large quantity of negative ions are produced in the afterglow of the pulse‐time‐modulated plasma. The decay times of electron density, electron temperature, and sheath potential are considerably reduced. This is attributable to negative‐ion generation. Furthermore, the pulse‐time‐modulated plasma reduces the time averaged sheath potential. As a result of these effects, charged particles in the sheath are drastically modified from the continuous discharge, and they should improve the selective etching in the pulsed ECR plasma and eliminate charge accumulation on the substrate. Additionally, negative‐ion generation dramatically improves the plasma potential distributions in the nonuniform ECR plasma. This technique is also suitable for large scaled etching processes. © 1996 American Vacuum Society
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors

Electric field control of plasma and macroparticles in cathodic arc deposition as a practical alternative to magnetic fields in ducts

Y. Yin and D. R. McKenzie

J. Vac. Sci. Technol. A 14, 3059 (1996); http://dx.doi.org/10.1116/1.580171 (6 pages) | Cited 2 times

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Plasma transportation and ion losses in a cathodic arc fitted with a curved magnetic macroparticle filter are studied for different magnetic field configurations. A planar Langmuir probe was used to carry out ion saturation current measurements along the axis of the duct, so that the losses of ions could be quantified. The losses of ions were found to depend sensitively on the magnetic field configuration in the prefilter region. The potential of the duct wall was measured as a function of distance to the cathode and the results were used to locate the effective anode of the discharge. The location of the effective anode was determined by the magnetic field configuration and affected the running stability of the arc. The conditions which provided the best efficiency of plasma transport also gave the least stable running conditions. The use of an electric field as a macroparticle filter was studied and higher deposition rates for coatings of comparable quality were found to be deposited onto a substrate held parallel to the drift velocity of the plasma to which a negative bias was applied. © 1996 American Vacuum Society
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Surface wave operation mode of the slot antenna microwave plasma source SLAN

F. Werner, D. Korzec, and J. Engemann

J. Vac. Sci. Technol. A 14, 3065 (1996); http://dx.doi.org/10.1116/1.580172 (6 pages) | Cited 9 times

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A new slot antenna concept allows the generation of large volume 2.45 GHz discharges. The microwave power is coupled from an annular waveguide (ring cavity) through ten equidistantly positioned resonant coupling slots into the quartz plasma chamber. Langmuir double probe axial distribution measurements of the electron density and temperature are performed for argon, helium and nitrogen discharges in a power range from 120 to 1200 W and a pressure range from 10 to 150 Pa. Characteristic differences in the discharge behavior for the various gases are presented. With argon a surface wave at the plasma‐quartz interface can be excited, already at 200 W. The resulting plasma column can extend up to 450 mm in length along the tube with 160 mm diameter. The surface wave mode is identified as a m=5 mode by visual inspection of the plasma formation and by recording the azimuthal electric field distribution. In contrast to argon, for helium and nitrogen no surface wave generation for power levels up to 1200 W are observed. Within the investigated power range both gases show a diffusion controlled variation of the electron density. This is verified by fitting the axial density data to the time‐independent diffusion equation for helium and nitrogen and to a simplified surface wave model for argon. © 1996 American Vacuum Society
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.40.Hf Plasma-material interactions; boundary layer effects
52.70.Ds Electric and magnetic measurements

Measurements of spatial and temporal sheath evolution inside tubular material for inner surface ion implantation

Mu Sun, Si‐ze Yang, and Xi‐chen Chen

J. Vac. Sci. Technol. A 14, 3071 (1996); http://dx.doi.org/10.1116/1.580173 (4 pages) | Cited 9 times

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Tubular target of aluminum (inner radius=5 cm, length=15 cm) was immersed in a nitrogen plasma with plasma densities of 6.8×109–5×1010 cm−3 and biased negatively (10–30 kV). A Langmuir probe was used to detect the propagating sheath edge. A comparison of experiment measurements and numerical calculations of temporal and spatial sheath evolution is presented. Experiment measurements of sheath edge position were in good agreement with those determined by numerical calculations. © 1996 American Vacuum Society
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81.65.-b Surface treatments
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.70.Ds Electric and magnetic measurements

Oxygen plasma asher contamination: An analysis of sources and remedies

R. A. Synowicki, Jeffrey S. Hale, William A. McGahan, N. J. Ianno, and John A. Woollam

J. Vac. Sci. Technol. A 14, 3075 (1996); http://dx.doi.org/10.1116/1.580174 (7 pages)

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The low Earth orbit (LEO) environment is commonly simulated using oxygen plasma ashers to determine the effects of LEO on spacecraft materials. However, plasma ashers can also contaminate samples during plasma exposure, making them less than ideal for space simulation. This study results from attempts to minimize or eliminate contamination. Optical methods of variable angle spectroscopic ellipsometry and reflectance spectrophotometry were used to quantify contaminant stoichiometry and deposition rate. Auger electron spectroscopy identified deposited contaminants and their surface coverage. Contamination results from etching of the rubber chamber seals by the plasma. The deposited contaminant was nearly indistinguishable from fully stoichiometric SiO2. Contaminant deposition rates up to 0.27 nm/min have been observed, and these layers effectively passivate the surface by depositing an overcoat of SiOx. Placing metal into the path of the plasma before it can reach the chamber seals greatly reduces contamination. A newly designed chamber confines the plasma to a small volume away from the chamber seals. For fluences as high as 3.5×1022 atoms/cm2, equivalent to 7.5 years of space exposure for the International Space Station, the redesigned asher showed less than one monolayer of deposited contaminant. © 1996 American Vacuum Society
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68.35.Dv Composition, segregation; defects and impurities
07.87.+v Spaceborne and space research instruments, apparatus, and components (satellites, space vehicles, etc.)
94.90.+m Other topics in space plasma physics, physics of the ionosphere and magnetosphere (restricted to new topics in section 94)

Ashing residues on TiN antireflective coating layers

S. Miyaji, T. Kato, and T. Yamauchi

J. Vac. Sci. Technol. A 14, 3082 (1996); http://dx.doi.org/10.1116/1.580175 (5 pages) | Cited 2 times

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Residues appearing on the surface of the TiN antireflective coating (ARC) layer after a resist ashing process were investigated by transmission electron microscope and field emission Auger electron spectroscopy. These residues tend to appear linearly in the center of Al lines covered with the TiN ARC layer, and are generally called the ‘‘backbone.’’ We found that a triangular product mainly composed of Al atoms appears in the center of the resist surface in the final stage of the ashing process and that a thin layer, about 10 nm thick, including Ti atoms, is formed to cover the triangular product and the resist surface. Due to the small solubility of the thin layer including Ti atoms to the alkaline stripper, the triangular product under the thin layer remains as a backbone residue. We demonstrate that the formation of the backbone depends on the distribution of Al and Ti atoms in the sidewall polymer. © 1996 American Vacuum Society
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85.40.Hp Lithography, masks and pattern transfer
82.20.Hf Product distribution

Sputtering of metallic walls in Ar/H2 direct current glow discharges at room temperature

F. L. Tabarés and D. Tafalla

J. Vac. Sci. Technol. A 14, 3087 (1996); http://dx.doi.org/10.1116/1.580176 (5 pages) | Cited 2 times

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Laser induced fluorescence of Cr atoms in their ground state have been used to characterize metallic sputtering in dc glow discharges (GDs) of hydrogen/argon admixtures in a stainless steel chamber at room temperature. A strong decrease in the sputtering signal was observed upon addition of H2 to the pure Ar GD plasma, at constant pressure and total current conditions, even at low H2 concentrations in the admixture. The plasma microscopic parameters have been determined from actinometry and Langmuir probe data. The H implantation characteristics of the studied plasmas were also determined by pump and release experiments. According to all the experimental evidence, hydrogen implantation in the metal surface is the main process responsible for the observed sputtering suppression. The results are compared to similar sputtering reduction observations previously reported in other light contaminant/metal systems. © 1996 American Vacuum Society
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81.65.Cf Surface cleaning, etching, patterning
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Effect of nonstoichiometry upon optical properties of radio frequency sputtered Al–N thin films formed at various sputtering pressures

Dao‐yuan Wang, Yukio Nagahata, Masataka Masuda, and Yasunori Hayashi

J. Vac. Sci. Technol. A 14, 3092 (1996); http://dx.doi.org/10.1116/1.580177 (8 pages) | Cited 3 times

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Colored Al–N films can be easily made through changing the content of nitrogen gas at various sputtering pressures. For films deposited at 5×10−2 Torr, with only slight change in the proportion of nitrogen gas from 0% to 2.5%, 5%, 7.5%, and 10%, the respective visual appearance changed from silver–gray to gray, gray, green–yellow to transparent. With the further increase in the content of nitrogen gas up to 100%, the obtained films were all transparent. For films formed at 5×10−1 Torr, with the content of nitrogen gas being 0%, 2.5%, 5%, 7.5%, 10%, and 20%, the corresponding visual appearance of the films were silver–gray, black, dark‐green–yellow, green–yellow, light‐yellow and transparent. When the content of nitrogen gas changed from 20% to 100%, there was almost no difference in the visual appearance. For films formed at 1 Torr, when the content of nitrogen gas was only over 2.5%, the film became clear. Measurements of transmittance, reflectance, and thickness, calculations of the absorption coefficient, refractive index, and extinction coefficient, and an x‐ray photoemission spectroscopy analysis show that the coloration is mainly due to the nonstoichiometry induced by lower content of nitrogen gas at various sputtering pressures. Furthermore, the calculated extinction coefficients are found to have a much closer relationship with the coloration than other parameters, such as, refractive index and thickness. The optical band gap of the obtained stoichiometric AlN films is 5.85–5.9 eV. © 1996 American Vacuum Society
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78.66.Fd III-V semiconductors
81.15.Cd Deposition by sputtering

Low‐temperature deposition of cubic BN:C films by unbalanced direct current magnetron sputtering of a B4C target

M. P. Johansson, I. Ivanov, L. Hultman, E. P. Münger, and A. Schütze

J. Vac. Sci. Technol. A 14, 3100 (1996); http://dx.doi.org/10.1116/1.580178 (8 pages) | Cited 11 times

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Controllable‐unbalanced dc magnetron sputtering of a B4C target in mixed Ar–N2 discharges has been used to deposit BN:C thin films with carbon concentrations in the range of 5–21 at. % on Si(001) substrates. The variation of the nitrogen gas consumption with nitrogen partial pressure was used to determine the sorption capacity of the sputtering source and was then correlated to the film elemental composition. An additional axially symmetric magnetic field was used to vary the discharge plasma density near the substrate in a wide range. Hence, the ion flux Ji of primary Ar+ and N+2 ions accelerated to the substrate by an applied negative substrate bias could be varied while keeping the deposition flux Jn (the sum of film building species, B, C, and N atoms) near constant. BN:C films were grown at large ion‐to‐neutral flux ratios 3≤Ji/Jn≤24, ion energies Ei≤500 eV, and substrate temperatures 150≤Ts≤350 °C. The phase and elemental composition of as‐deposited BN:C films were characterized by Fourier transform infrared spectroscopy and wavelength dispersive x‐ray spectroscopy, respectively. Deposition of cubic phase c‐BN:C containing 5–7 at. % of C is demonstrated under conditions of low energy (110 eV) ion bombardment, a high ion‐to‐atom arrival rate ratio (Ji/Jn∼24), and low growth temperatures (∼150 °C). © 1996 American Vacuum Society
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81.15.Cd Deposition by sputtering
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
68.55.-a Thin film structure and morphology

Monte Carlo numerical analysis of target erosion and film growth in a three‐dimensional sputtering chamber

Vladimir V. Serikov and Kenichi Nanbu

J. Vac. Sci. Technol. A 14, 3108 (1996); http://dx.doi.org/10.1116/1.580179 (16 pages) | Cited 26 times

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A combination of two mathematical models for three‐dimensional Monte Carlo particle simulation of a low pressure sputtering environment is proposed. One is intended for the simulation of a discharge gas flow, and the other for the sputtered atom transport. The combination is used to characterize target erosion and film growth. The models are refined with recourse to experimental measurements made in a practical sputtering apparatus (SPF‐210 AS, ANELVA Ltd.) over the range of operating pressures and flow rates of 0.3–10 Pa and 0.5–5 sccm, respectively. A considerable number of numerical analyses are done to find possible reasons for the measured nonuniformity of target erosion and film growth rate distributions. Simulation results show that under the operating and design conditions treated here the nonuniformity of gas flow field appears to be too weak to explain the experimental data. Film growth rates simulated for measured erosion rates show a good agreement with the experimental data for the various operating pressures above. Important features of the present simulation are the inclination of the angular distribution of sputtered atoms, and taking into consideration reemission of sputtered atoms deposited onto the target. The inclination of angular distribution results from the oblique ion incidence onto the target surface. The existence of highly eroded etch track along the target edge is shown to be correlated with the greater sputtering yield for the oblique ion incidence near the edge. Axial asymmetry of the erosion and growth rate distributions may be due to the asymmetry of the electric field lines at the periphery of the target, which leads to a nonuniform incidence angle along the edge. In contrast to erosion and growth rates, the redeposition rate of sputtered atoms onto the target is found to increase considerably with pressure. © 1996 American Vacuum Society
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81.15.Cd Deposition by sputtering
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Reactive magnetron sputter deposition of polycrystalline vanadium nitride films

X. Chu, S. A. Barnett, M. S. Wong, and W. D. Sproul

J. Vac. Sci. Technol. A 14, 3124 (1996); http://dx.doi.org/10.1116/1.580180 (6 pages) | Cited 5 times

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Polycrystalline vanadium nitride films were deposited onto M2 steel substrates using a high‐rate reactive dc magnetron sputtering system by sputtering vanadium metal in an Ar+N2 atmosphere under N2 partial pressure control. The crystal structure, surface morphology, and properties of the films were affected by several process parameters such as nitrogen partial pressure, target power, and negative substrate bias. Analytical techniques including x‐ray diffraction and scanning electron microscopy were used to characterize the structure and morphology of the films, and the mechanical properties of the films were measured by a Vickers microhardness and a scratch adhesion testers. The nitrogen partial pressure was found to be the dominant deposition parameter for the formation of different phases which includes crystalline V metal, hexagonal β‐V2Nx, and cubic δ‐VNx, amorphous V–Nx solid solution, and their mixtures. The film hardness was affected by crystalline phase, and a maximum hardness of 3000 kgf/mm2 Hv0.05 was found at the β‐V2Nx phase. The morphology of the films varied in a wide range from cauliflowerlike rough and porous surface to smooth and dense surface, and can be correlated to deposition parameters. © 1996 American Vacuum Society
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81.15.Cd Deposition by sputtering
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties

Laser desorption study of deuterium implanted in silicon carbide

D. Kéroack and B. Terreault

J. Vac. Sci. Technol. A 14, 3130 (1996); http://dx.doi.org/10.1116/1.580181 (5 pages)

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Laser desorption of deuterium implanted in hot‐pressed silicon carbide samples was performed. The samples had been implanted at ion energies ranging from 1 keV/D to 3 keV/D and at fluences from 0.6×1020 m−2 to 1.8×1021 m−2. For the high fluence samples (≥3×1020 m−2), comparison of the experimental data of desorption rate versus laser energy with the results of computer simulations reveals that second order detrapping is the limiting re‐emission process. The effective trap activation energy decreases from 0.9±0.1 eV/molecule at 1 keV/D to 0.5±0.1 eV/molecule at 3 keV/D. Blister formation and exfoliation or other forms of radiation damage could explain the energy dependence in the high fluence samples. At low fluence (<3×1020 m−2), most of the D2 re‐emission takes place above the melting threshold (12 kJ/m2). Computer simulations, using the thermal properties of the solid phase of SiC extrapolated above the melting point, give information about the nature of the detrapping process. A first order detrapping mechanism with an activation energy of 2.0±0.2 eV was found under those conditions. A comparaison is made with the deuterium laser desorption behaviour in Be, C and Si. © 1996 American Vacuum Society
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79.20.La Photon- and electron-stimulated desorption
61.80.Jh Ion radiation effects
61.82.Ms Insulators
28.52.Fa Materials

Chemical bonding and electronic properties of Se‐rich ZnSe–GaAs(001) interfaces

G. Bratina, T. Ozzello, and A. Franciosi

J. Vac. Sci. Technol. A 14, 3135 (1996); http://dx.doi.org/10.1116/1.580182 (9 pages) | Cited 8 times

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We report synchrotron radiation, soft‐x‐ray photoemission spectroscopy studies of ZnSe–GaAs heterojunctions fabricated by molecular beam epitaxy in situ on GaAs(001)2×4 substrates. Measurements of the band offsets confirm that interfaces grown in Se‐rich conditions exhibit relatively low valence band offsets (as low as 0.5 eV), while interfaces grown in Zn‐rich conditions show relatively high valence band offsets (as high as 1.3 eV). In the Se‐rich case, the improved surface sensitivity of the technique revealed previously unreported contributions to the As 3d and Ga 3d core lineshapes, with substantial (0.8–2 eV) chemical shifts. The shifts, as well as the coverage and escape‐depth dependence of the results suggest enhanced atomic intermixing across Se‐rich interfaces, with the formation of both Se–As and Se–Ga chemical bonds. © 1996 American Vacuum Society
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73.20.At Surface states, band structure, electron density of states
79.60.Jv Interfaces; heterostructures; nanostructures
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Formation of titanium nitride coatings by nitrogen plasma immersion ion implantation of evaporated titanium films

J. Hartmann, W. Ensinger, A. Königer, B. Stritzker, and B. Rauschenbach

J. Vac. Sci. Technol. A 14, 3144 (1996); http://dx.doi.org/10.1116/1.580183 (3 pages)

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Titanium was deposited onto silicon by electron beam evaporation in high vacuum. The Ti films were treated by plasma immersion ion implantation (PIII) with energetic nitrogen ions extracted from a plasma which was generated by electron cyclotron resonance microwave excitation. The elemental composition of the films was measured by Rutherford backscattering spectrometry and the different phases were identified by x‐ray diffraction. The results show that nitrogen PIII treatment leads to nitrogen ion incorporation with nitride phase formation, accompanied by an increase in density. Two mechanisms for the incorporation of nitrogen can be distinguished: implantation and radiation enhanced diffusion. © 1996 American Vacuum Society
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81.40.Wx Radiation treatment (particle and electromagnetic)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Optical emission spectroscopy from arc‐like Ti vapor plasma and effects of self‐ion bombardment on Ti and TiN film deposition

H. Kajioka, K. Higuchi, and Y. Kawashimo

J. Vac. Sci. Technol. A 14, 3147 (1996); http://dx.doi.org/10.1116/1.580184 (9 pages) | Cited 3 times

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Arc‐like Ti vapor plasma is formed on the electron beam evaporation source by applying low dc voltage to the anode near the source in high vacuum. This plasma spectrum consists of Ti I (neutral) and Ti II (Ti+) lines. However no emission lines of nitrogen are observed with nitrogen gas inflow up to 1.3×10–1 Pa. This suggests that the dominant ion species is Ti+. Ti and TiN films are deposited on the water‐cooled and non‐cooled substrates at anode current 60 A. When negative substrate voltage (Vs) increases from 0 to 1000 V, substrate current density at 0.34 m from the source increases from 60 to 90 A/m2. Ion‐to‐Ti impinging flux ratio is estimated to be ∼1.35 at Vs=0 V. Deposition rates of 4 nm/s (Ti film) and 3 nm/s (TiN film) at Vs=0 V decrease largely in the former case and slightly in the latter case with increasing Vs. That is, self‐sputter yield of the former is larger than that of the latter. The former varies with, and the latter is independent of substrate temperature. N/Ti ratio in TiN film is close to unity for the noncooled substrate. On the other hand, N/Ti ratio decreases from 0.9 to 0.7 with δ TiN single phase for the water‐cooled substrate with increasing Vs. These results are different from the reported results from low energy‐ion assisted deposition and reactive bias sputtering. This is attributed to the fact that self‐ion bombardment differs from N+2 and/or Ar+ bombardment. © 1996 American Vacuum Society
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.05.-t Specific materials: fabrication, treatment, testing, and analysis

In situ study of processes taking place on silicon surface during its bombardment by CFx/Ar ions: Etching versus polymerization

T. Šikola, D. G. Armour, and J. A. Van den Berg

J. Vac. Sci. Technol. A 14, 3156 (1996); http://dx.doi.org/10.1116/1.580206 (8 pages) | Cited 3 times

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The application of a Kaufman ion source in the study of the etching/polymerization processes taking place at the surface of a silicon substrate being exposed to ion beams generated from CF4/Ar gas mixtures is reported. The processes were analyzed by means of in situ mass and energy spectroscopy of the secondary ions sputtered from the substrate surface and the charge‐exchange ions, respectively. These analytical methods confirmed the growth of the polymer C–F thin films on the silicon surface at higher concentrations of CF4 in the mixture. It was found that there existed a primary beam threshold energy above which the polymer thin film stopped growing and the etch yield of silicon atoms was increased. The simplified activated growth model presented here describes this behavior qualitatively as a competition between creative and destructive processes leading to deposition and removal of the thin polymer film, respectively. © 1996 American Vacuum Society
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81.65.-b Surface treatments
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

Influence of surface oxygen on chemoresistance of tin oxide film

S. Kac̆iulis, G. Mattogno, A. Galdikas, A. Mironas, and A. S̆etkus

J. Vac. Sci. Technol. A 14, 3164 (1996); http://dx.doi.org/10.1116/1.580207 (5 pages) | Cited 2 times

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The oxygen controlled chemoresistance of tin oxide based gas sensors was investigated in the temperature range from 20 to 320 °C. Polycrystalline thin film gas sensors were fabricated by the reactive dc‐magnetron sputtering. The parameters of the sensors were also modified by additional Pt or Sb doping. The effect of surface oxygen species on the chemoresistance was studied by x‐ray photoelectron spectroscopic (XPS) analysis of the surface chemical composition before and after different sample treatments. The oxygen peak at a binding energy 531.8 eV in the XPS core level spectrum was found to be related to the chemisorbed molecular oxygen O−2. The variation of an amount of the O−2 species is found to be the main cause of gas sensitivity of tin oxide films at temperatures from 20 to 230 °C. © 1996 American Vacuum Society
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Study on the interfaces of Cu/PA‐N and PA‐N/Si by secondary ion mass spectroscopy and scanning electron microscopy

G.‐R. Yang, D. Mathur, J. F. McDonald, and T.‐M. Lu

J. Vac. Sci. Technol. A 14, 3169 (1996); http://dx.doi.org/10.1116/1.580208 (5 pages) | Cited 2 times

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For microelectronics applications, it is important to have good interfacial properties between copper and parylene‐N (Cu/ PA‐N), and parylene‐N and silicon (PA‐N/ Si). Two of the relevant interfacial properties studied in this article are diffusion of the individual layers into the other layer at application temperatures and adhesion between these layers. The interface between copper and parylene‐N, and parylene‐N and silicon has been studied using secondary ion mass spectroscopy (SIMS). Scanning electron microscopy (SEM) has also been used to study the PA‐N/Si interface. SEM revealed the microstructure at the interface. SIMS was used to tunnel through the composite film in the cross section and get the various elemental concentrations. This gave the average concentrations prevailing, at a particular depth. It was observed that copper diffuses, from the top, through the PA‐N film to the silicon substrate at 350 °C. Gettering of copper was observed, leading to high concentration of copper at the Cu/PA‐N and PA‐N/Si interface. A high distribution of silicon was observed in PA‐N at the PA‐N/Si interface. X‐ray photoelectron spectroscopy studies showed that no new chemical bonds were formed. Thus, diffusion resulted in a mixing layer which led to good interfacial adhesion. © 1996 American Vacuum Society
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68.35.Fx Diffusion; interface formation
85.40.Ls Metallization, contacts, interconnects; device isolation
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

High resolution electron energy loss spectroscopy study of vapor deposited pyromellitic dianhydride and oxydianiline films on Cu(110)

R. V. Plank, N. J. DiNardo, and J. M. Vohs

J. Vac. Sci. Technol. A 14, 3174 (1996); http://dx.doi.org/10.1116/1.580209 (7 pages) | Cited 2 times

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The reaction of pyromellitic dianhydride (PMDA) and oxydianiline (ODA) on Cu(110) was studied using high resolution electron energy loss spectroscopy (HREELS). The interaction of the individual monomers with Cu(110) was also studied. PMDA dissociated on Cu(110) at 300 K forming a carboxylate link to the surface, releasing CO into the gas phase. ODA was also found to adsorb dissociatively on Cu(110) at 300 K via cleavage of one of the amine NH bonds. Vapor‐deposited PMDA/ODA films on Cu(110) reacted at 300 K to form polyamic acid. Heating a polyamic acid film to 450 K was sufficient to induce imidization and form polyimide. HREELS results indicated that the resulting polyimide chains were both bonded to the surface and terminated with PMDA monomer units. The polyimide film was stable up to 500 K, consistent with the thermal stability of PMDA on Cu(110). © 1996 American Vacuum Society
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68.35.Fx Diffusion; interface formation
68.60.Dv Thermal stability; thermal effects
82.35.-x Polymers: properties; reactions; polymerization
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Dielectric properties of Zr, ZrN, Zr3N4, and ZrO2 determined by quantitative analysis of electron energy loss spectra

P. Prieto, F. Yubero, E. Elizalde, and J. M. Sanz

J. Vac. Sci. Technol. A 14, 3181 (1996); http://dx.doi.org/10.1116/1.580210 (8 pages) | Cited 17 times

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The dielectric properties of Zr, ZrN, Zr3N4, and ZrO2 in the energy range from 1 to 80 eV were determined by quantitative analysis of electron energy loss spectroscopy in the reflection mode (REELS) using a recently proposed model. Collective excitations and electronic transitions are well characterized in the REELS spectra after analysis of the respective energy loss function, real and imaginary parts of the dielectric constant, and the optical joint density of states for the four compounds studied here. © 1996 American Vacuum Society
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
79.20.-m Impact phenomena (including electron spectra and sputtering)

Effect of a vacuum ion gauge on the contamination of a hydrogen‐passivated silicon surface

Sun Jin Yun, Seung‐Chang Lee, Jae‐Jin Lee, and Jeong Yong Lee

J. Vac. Sci. Technol. A 14, 3189 (1996); http://dx.doi.org/10.1116/1.580211 (5 pages) | Cited 1 time

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The effect of operating a vacuum ion gauge on carbonaceous (C) contamination of a hydrogen (H)‐passivated Si surface before epitaxial growth was investigated. The dependence of C contamination on the residence time in the loading chamber, tlc, was determined with or without operating a vacuum ion gauge. The results showed that C contamination of a H‐passivated surface was greatly increased by use of the ion gauge. With ion gauge operation in a vacuum of 1×10−6–1×10−7 Torr in the loading chamber, the configuration of the ion gauge and upside down‐stacked wafers is shown to be a dominant factor of C contamination of the Si surface. The presence of C contaminants could be determined by observing SiC diffraction patterns using in situ reflection high energy electron diffraction (RHEED), since the C contaminants reacted with Si to produce single crystalline SiC at a temperature as high as 850 °C. The RHEED patterns demonstrated that the single crystalline SiC had a zinc‐blende structure. Single crystalline SiC islands with an ellipsoidal cross section were observed by high resolution transmission electron microscopy. In the subsequent epitaxial growth of Si, a well oriented single crystalline Si layer could be grown over the SiC islands although the effect of C contamination on the electrical characteristics of the interface was not clarified. Longer tlc with the ion gauge also required a higher temperature to achieve a 2×1 reconstructed surface structure from the H‐passivated Si surface. © 1996 American Vacuum Society
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81.65.-b Surface treatments
68.35.Dv Composition, segregation; defects and impurities
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
07.30.Dz Vacuum gauges

Argon plasma treatment of polycarbonate: In situ spectroellipsometry study and polymer characterizations

S. Vallon, B. Drévillon, F. Poncin‐Epaillard, J. E. Klemberg‐Sapieha, and L. Martinu

J. Vac. Sci. Technol. A 14, 3194 (1996); http://dx.doi.org/10.1116/1.580212 (8 pages) | Cited 7 times

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The influence of argon plasma on polycarbonate (PC) was studied in terms of structural changes, reaction mechanisms, and adhesion. In situ ultraviolet‐visible ellipsometry reveals formation of a surface layer with a higher refractive index than the untreated polymer. The increase in the refractive index is attributed to polymer densification, which in turn is attributed to crosslinking. However a decrease in the average molecular weight is also observed, and two populations of macromolecules of different sizes are detected by light scattering measurements, revealing a competition between crosslinking and degradation. The reaction mechanisms are investigated using nuclear magnetic resonance and in situ infrared ellipsometry. Degradation is caused by carbonate bond breaking, whereas crosslinking seems to be related to a decrease in methyl groups. In addition, an increase in surface acidity is detected by contact angle measurements and is attributed to photo‐Fries rearrangements producing phenolic groups. The adhesion of a 1‐μm‐thick silica layer on PC is evaluated by the microscratch test, and its enhancement by argon plasma pretreatment is analyzed. © 1996 American Vacuum Society
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81.65.-b Surface treatments
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
78.66.Qn Polymers; organic compounds
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

In situ composition monitoring of InGaAs/InP using quadrupole mass spectrometry

F. G. Celii, Y.‐C. Kao, and H.‐Y. Liu

J. Vac. Sci. Technol. A 14, 3202 (1996); http://dx.doi.org/10.1116/1.580213 (6 pages) | Cited 1 time

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The use of in situ quadrupole mass spectrometry (QMS) provides the precision necessary for many molecular beam epitaxy (MBE) applications in which the composition of ternary or quaternary epitaxial layers must be controlled. Here we show that the composition of InxGa1−xAs, nearly lattice‐matched to InP, can be determined with an uncertainty of Δx∼0.005 in real time (∼4 s averaging time) using QMS in a flux‐monitoring mode. Use of an unapertured mass spectrometer extends the range of reflection mass spectrometry into low substrate temperature growth regimes. We also examined system calibration and drift issues. QMS combines routine data acquisition with simple data analysis, and can be easily retrofit on existing MBE systems. © 1996 American Vacuum Society
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81.70.Jb Chemical composition analysis, chemical depth and dopant profiling
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
07.75.+h Mass spectrometers

Schiff base precursor compounds for the chemical beam epitaxy of oxide thin films. I. Deposition of CuO on MgO[001] using copper (II) bis(benzoylacetone)‐ethylendiimine

E. Fritsch, E. Mächler, F. Arrouy, H. Berke, I. Povey, P. R. Willmott, and J.‐P. Locquet

J. Vac. Sci. Technol. A 14, 3208 (1996); http://dx.doi.org/10.1116/1.580214 (6 pages) | Cited 1 time

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A new precursor compound for the deposition of copper oxide thin films under molecular beam conditions, copper bis(benzoylacetone)‐ethylenediimine, has been characterized by thermal analysis and in situ mass spectrometry. Its stability and decomposition behavior are reported as well as its use for the deposition of epitaxial copper oxide thin films on MgO. © 1996 American Vacuum Society
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.-t Specific materials: fabrication, treatment, testing, and analysis
82.80.-d Chemical analysis and related physical methods of analysis

Growth behavior of copper metalorganic chemical vapor deposition using the (hfac)Cu(VTMOS) precursor on titanium nitride substrates

Chi‐Hoon Jun, Youn Tae Kim, Jong‐Tae Baek, Hyung Joun Yoo, and Dai‐Ryong Kim

J. Vac. Sci. Technol. A 14, 3214 (1996); http://dx.doi.org/10.1116/1.580215 (6 pages) | Cited 3 times

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Metalorganic chemical vapor deposition of copper using the thermally stable (hfac)Cu(VTMOS) [C10H13O5CuF6Si: 1,1,1,5,5,5‐hexafluoro‐2,4 pentadionato(vinyltrimethoxysilane) copper (I)] precursor has been carried out on TiN substrates prepared by physical vapor deposition (PVD) and rapid thermal processing (RTP). The apparent activation energies over substrate temperatures ranging from 160 to 220 °C were about 7.5 kcal/mol on the PVD‐TiN and 9.7 kcal/mol on the RTP‐TiN. The higher growth rate of the copper deposit on the RTP‐TiN could be ascribed to the increase in nucleation sites and the higher electron catalytic reactivity, resulting in enhancement of copper nucleation density in the initial stages of film growth. The copper deposits revealed polycrystalline phases with a preferred orientation of (111), and impurities within the films were below the detection limit of Auger electron spectroscopy. As substrate temperature increased, the copper films on the PVD‐TiN developed as a columnar structure according to the Volmer–Weber growth mode, and on the RTP‐TiN a nearly equiaxed structure was formed presumably by Stranski–Krastanov grain growth. The electrical resistivity of the deposits on the PVD‐TiN and the RTP‐TiN was in the range 2.8–5.4 μΩ cm for 1500–3100 Å film thicknesses and 4.4–6.2 μΩ cm for 2300–4300 Å film thicknesses, respectively. With increasing film thickness, the electrical resistivity of the copper layers linearly increased on the PVD‐TiN, while it gradually decreased on the RTP‐TiN. Consequently, the variations in the electrical resistivity of the deposits could be explained by changes in microstructures of the copper films, due to different growth behavior of copper on the two types of substrates. © 1996 American Vacuum Society
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Bx Metals, semimetals, and alloys
73.61.At Metal and metallic alloys

Molecular beam epitaxy growth of CdTe on (211)A GaAs

Jingjiang Yin, Qi Huang, Junming Zhou, and Jingou Yin

J. Vac. Sci. Technol. A 14, 3220 (1996); http://dx.doi.org/10.1116/1.580216 (4 pages) | Cited 2 times

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CdTe has been grown on (211)A GaAs for the first time in the growth temperature range of 240–310 °C by molecular beam epitaxy. The quality and characteristics of the epitaxial film were studied by photoluminescence spectra, an x‐ray double crystal rocking curve, a Nomarski interference microscope, and etching. High quality CdTe films were obtained. For our best film the full width at half maximum of the x‐ray double crystal rocking curve was 126 arcsecond, and that of photoluminescence at 77 K was 8.9 meV. The epilayer was always (211)A CdTe with a tilted angle of about 2° around CdTe[01̄1]∥GaAs[01̄1] with respect to the substrate. A model of the initial growth stage of CdTe on (211)A GaAs is presented. © 1996 American Vacuum Society
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Dz II-VI semiconductors
68.55.-a Thin film structure and morphology
78.66.Hf II-VI semiconductors

Process–property relationships between silicon selective epitaxial growth ambients and degradation of insulators

W. Gaynor, C. G. Takoudis, and G. W. Neudeck

J. Vac. Sci. Technol. A 14, 3224 (1996); http://dx.doi.org/10.1116/1.580217 (4 pages) | Cited 2 times

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Comprehensive thermodynamic analyses of the effects of silicon selective epitaxial growth (SEG) environments and low temperature substrate pretreatments on insulator degradation are presented. Silicon nitride is predicted to degrade at about 150 °C higher than silicon dioxide of the same thickness in DCS/H2 ambients at 40 Torr, in agreement with experimental data. Hydrogen/HCl and hydrogen/HCl/dichlorosilane substrate treatments are shown to result in more extensive insulator degradation than a hydrogen bake at the same conditions (e.g., 40–150 Torr, 0.001–1 ppm H2O), also in agreement with experimental data. In low temperature silicon SEG, the addition of ppm levels of a chlorosilane to H2 is predicted to lower the temperature at which substrate surfaces are cleaned in situ by about 150–200 °C, at 0.1–100 Torr, in agreement with experimental observations. Because these thermodynamic analyses take a short computation time (e.g., typically on the order of a few seconds), such results can serve as effective guidelines for substrate surface cleaning and insulator degradation during silicon SEG. Further, these results effectively yield basic process–property relationships between silicon SEG ambients and degradation of insulators with a minimal amount of experimentation. © 1996 American Vacuum Society
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65.20.-w Thermal properties of liquids
65.40.gd Entropy
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Aspects of nitrogen surface chemistry relevant to TiN chemical vapor deposition

Michelle T. Schulberg, Mark D. Allendorf, and Duane A. Outka

J. Vac. Sci. Technol. A 14, 3228 (1996); http://dx.doi.org/10.1116/1.580218 (8 pages) | Cited 3 times

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NH3 is an important component of many chemical vapor deposition (CVD) processes for TiN films, which are used for diffusion barriers and other applications in microelectronic circuits. In this study, the interaction of NH3 with TiN surfaces is examined with temperature programmed desorption (TPD) and Auger electron spectroscopy. NH3 has two adsorption states on TiN: a chemisorbed state and a multilayer state. A new method for analyzing TPD spectra in systems with slow pumping speeds yields activation energies for desorption for the two states of 24 kcal/mol and 7.3 kcal/mol, respectively. The sticking probability into the chemisorption state is ∼0.06. These results are discussed in the context of TiN CVD. In addition, the high temperature stability of TiN is investigated. TiN decomposes to its elements only after heating to 1300 K, showing that decomposition is unlikely to occur under CVD conditions. © 1996 American Vacuum Society
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Formation of metastable epitaxial CoSix (x<2) layers by reactive codeposition on CoSi2(111)

S. Hong, P. Wetzel, G. Gewinner, and C. Pirri

J. Vac. Sci. Technol. A 14, 3236 (1996); http://dx.doi.org/10.1116/1.580219 (9 pages) | Cited 5 times

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The reaction of Co deposited at 350 °C on epitaxial CoSi2 is investigated by means of low‐energy electron diffraction, core‐level and angle‐resolved valence‐band photoemission, and ion scattering spectroscopy. Co is deposited onto ∼100‐Å‐thick CoSi2(111) films epitaxially grown on Si(111) which exhibit a Si‐rich surface. For one Co monolayer equivalent, the Si‐rich surface labeled CoSi2(111)–Si is converted into a bulklike terminated one, labeled CoSi2(111). The latter is characterized by a specific surface state located at ∼2.8 eV binding energy at the center of the surface Brillouin zone, which derives from dangling bonds on Co and Si in the topmost planes. Upon increasing the amount of Co, the latter is found to react with the silicide layer up to much larger depths comparable to the photoelectron mean free path (15–20 Å). A thin metastable epitaxial CoSix (x≤2) overlayer with a cubic structure is formed for Co amounts up to the equivalent of 15 monolayers, typically. The electronic as well as crystallographic structure of this thin metastable CoSix layer is compared to that of recently discovered metastable CoSix layers, epitaxially grown on Si(111) by codeposition and found to be closely related. The data strongly suggest a simple picture where the additional Co merely diffuses into the initial CaF2‐type CoSi2 layer and occupies part of the interstitial octahedral sites of the face centered cubic Co sublattice. Moreover, it is shown that upon reaction of 6–8 Co monolayers the surface state observed on the ideal‐bulk–CoSi2(111) termination still persists but is shifted toward higher binding energies due to changes in the composition of the silicide underneath. This indicates that the surface structure of the CoSix (x≤2) layer is also similar to that of bulk‐terminated CoSi2(111). For higher Co coverages, an epitaxial ϵ‐CoSi layer with the stable B20 type structure is achieved, as attested by a √3×√3 R30° low‐energy electron diffraction pattern and specific valence‐band features. © 1996 American Vacuum Society
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.Fx Diffusion; interface formation
85.40.Sz Deposition technology

TiN barrier layer formation by the two‐step rapid thermal conversion process

Youn Tae Kim, Chi‐Hoon Jun, Jin Ho Lee, Jong Tae Baek, and Hyung Joun Yoo

J. Vac. Sci. Technol. A 14, 3245 (1996); http://dx.doi.org/10.1116/1.580220 (7 pages) | Cited 1 time

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We formed TiN barrier layers on single‐crystalline silicon substrates by thermal conversion of Ti films at various temperatures in an ammonia ambient using a rapid thermal process with a sequential two‐step temperature cycle. The first‐step temperatures were held in the low‐temperature range of 400–450 °C for 60–300 s to minimize Ti/Si interaction while keeping reasonable interaction of Ti/NH3 and nitrogen diffusion through the Ti layer to maximize the thickness of the TiN layer. Then, the second‐step was carried out at relatively high temperatures, 700–1000 °C, for 5–90 s to reduce Ti/Si interaction during the silicidation process. By the first steps of the low temperature process, sheet resistances increased with annealing time up to 60 s due to the deep penetration and high concentration of nitrogen in the Ti film, followed by saturation at 60–120 s; they steadily decreased beyond 120 s. Sheet resistance increases were dominated by the nitrogen‐rich Ti layer formed during the first steps of long‐time nitrogen diffusion. With the second steps of the high temperature process, nitrogen enriched Ti layers were converted to Ti‐rich TiN layers, resulting in abrupt decreases in the sheet resistance due to silicidation, densification of TiN, and conversion of the remaining Ti to TiN layers. By means of a two‐step rapid thermal conversion process of the 1000 Å Ti layer under long‐time nitridation cycle conditions with optimal thermal conversion conditions (first step: 400 °C/90 s; second step: 700 °C/60 s), we obtained TiN/TiSi2 bilayers of 700/1500 Å thicknesses with the TiN thickness ratio relative to the totally converted layer in excess of 30%. These results indicate that the thickness ratio of the TiN layer prepared by a two‐step process relative to the totally converted layer is double that obtained by a one‐step process, while it also provides reduced total thickness of the thermally converted layer. © 1996 American Vacuum Society
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81.65.-b Surface treatments
85.40.Ls Metallization, contacts, interconnects; device isolation
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Vacuum arc deposition of Mo films

Nikolay Vershinin, Boris Straumal, and Wolfgang Gust

J. Vac. Sci. Technol. A 14, 3252 (1996); http://dx.doi.org/10.1116/1.580221 (4 pages)

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Mo coatings on Cu substrates were deposited with the aid of an unfiltered vacuum arc at a deposition voltage of 31 V. Dependencies of the deposition rate Rd on the discharge current I (in the interval from 80 to 180 A) and the distance L between the cathode and substrate were investigated. Rd increases monotonically with increasing I and decreases with increasing L. If the substrate is parallel to the cathode surface, Rd is much higher than it is for substrates which are perpendicular to the cathode surface. Rd values as high as 15 nm/s were reached. The reasons for this behavior are analyzed. It is also shown that Mo macroparticles are well incorporated into the coating building an integral part of it. © 1996 American Vacuum Society
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Bx Metals, semimetals, and alloys
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Simulation model to very low pressure chemical vapor deposition of SiGe alloy

Shulin Gu, Ronghua Wang, Rong Zhang, and Youdou Zheng

J. Vac. Sci. Technol. A 14, 3256 (1996); http://dx.doi.org/10.1116/1.580222 (5 pages) | Cited 4 times

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Kinetics study of very low pressure chemical vapor deposition (VLPCVD) of SiGe alloys has been reported in this article. In this kinetics model, the SiGe alloy deposition process has been treated as three steps: SiH4 and GeH4 adsorption on Si and Ge vacancy sites, hydrogen exchange between silicon and germanium hydrides, and hydrogen desorption from growing surface. The kinetics model is fit to the data of SiGe layers deposited from decomposition of SiH4 and GeH4 by the VLPCVD method. The model agrees well with experimental data. © 1996 American Vacuum Society
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Hd Other semiconductors
82.20.Wt Computational modeling; simulation
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Reduction of outgassing rate from residual gas analyzers for extreme high vacuum measurements

Shu Watanabe, Masakazu Aono, and Shigeki Kato

J. Vac. Sci. Technol. A 14, 3261 (1996); http://dx.doi.org/10.1116/1.580223 (6 pages) | Cited 2 times

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One problem associated with partial pressure measurement in an extreme high vacuum region is outgassing from the residual gas analyzer (RGA) itself. In order to reduce the outgassing rate from the RGA, the temperature of the filament should be lowered, and the heat generated around the ion source of the RGA should be dissipated in the atmosphere. We modified a RGA and reduced its outgassing rate to 1.5×10−12 Pa m3/s. We also determined the partial outgassing rate from the ion source and chamber quantitatively and found that hydrogen constituted more than 99% of the outgassing from the stainless steel. © 1996 American Vacuum Society
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07.30.Bx Degasification, residual gas
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
79.20.La Photon- and electron-stimulated desorption

Measurements of tritium retention and removal on the Tokamak Fusion Test Reactor

C. H. Skinner, W. Blanchard, J. Kamperschroer, P. LaMarche, D. Mueller, A. Nagy, S. Scott, G. Ascione, E. Amarescu, R. Camp, M. Casey, J. Collins, M. Cropper, C. Gentile, M. Gibson, et al.

J. Vac. Sci. Technol. A 14, 3267 (1996); http://dx.doi.org/10.1116/1.580224 (8 pages) | Cited 7 times

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Recent experiments on the Tokamak Fusion Test Reactor have afforded an opportunity to measure the retention of tritium in a graphite limiter that is subject to erosion, codeposition, and high neutron flux. The tritium was injected by both gas puff and neutral beams. The isotopic mix of hydrogenic recycling was measured spectroscopically and the tritium fraction T/(H+D+T) transiently increased to as high as 75%. Some tritium was pumped out during the experimental run and some removed in a subsequent campaign using various clean‐up techniques. While the short term retention of tritium was high, various conditioning techniques were successful in removing ≊8000 Ci and restoring the tritium inventory to a level well below the administrative limit. © 1996 American Vacuum Society
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28.52.Fa Materials

Vacuum performance of the Synchroton Radiation Research Center 1.3 GeV synchrotron light source

G. Y. Hsiung, J. R. Huang, J. G. Shyy, D. J. Wang, J. R. Chen, and Y. C. Liu

J. Vac. Sci. Technol. A 14, 3275 (1996); http://dx.doi.org/10.1116/1.580225 (3 pages)

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The operation of the Synchrotron Radiation Research Center 1.3 GeV synchrotron light source vacuum system shows good features of quick beam self‐cleaning, low carbonaceous gas desorption, and less dust. The phenomenon of the photon induced desorption (PID) has been studied. Recently, a set of new vacuum chambers for wiggler were installed, and the commissioning of the storage ring was restarted. The pressure rise and the PID coefficients during the beam running both in the straight and bending chambers were compared. The performance of the overall vacuum system is to be described. © 1996 American Vacuum Society
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07.85.Qe Synchrotron radiation instrumentation
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
79.20.La Photon- and electron-stimulated desorption

Pumping characteristics of the St707 nonevaporable getter (Zr 70 V 24.6‐Fe 5.4 wt %)

C. Benvenuti and P. Chiggiato

J. Vac. Sci. Technol. A 14, 3278 (1996); http://dx.doi.org/10.1116/1.580226 (5 pages) | Cited 11 times

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The room temperature pumping speeds of the St707 nonevaporable getter (NEG) have been measured both for individual gases and for gas mixtures as a function of the quantities of gas pumped. The interesting feature of this NEG consists in its moderately low activation temperature. Therefore particular attention has been devoted to defining the optimum temperature and duration of the activation process to obtain the highest possible pumping speed in a given practical situation. It has been found that heating at 400 °C for about 1 h, or at 350 °C for one day, results in pumping speeds of about 1000 l s−1 m−1 for H2, 2000 l s−1 m−1 for CO, and 450 l s−1 m−1 for N2, values very close to those obtained after activation at the higher temperature of 740 °C. The St707 NEG is therefore particularly suitable for passive activation during bakeout of stainless steel vacuum systems, avoiding the need for electrical insulation and feedthroughs which are mandatory when activation is carried out by resistive heating. © 1996 American Vacuum Society
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07.30.Bx Degasification, residual gas

Improved substrate temperature stability during molecular beam epitaxy growth using indium free mounting of small substrates of various shapes

R. M. Sieg, R. N. Sacks, P. N. Grillot, and S. A. Ringel

J. Vac. Sci. Technol. A 14, 3283 (1996); http://dx.doi.org/10.1116/1.580227 (5 pages)

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Large substrate surface temperature decreases are observed during molecular beam epitaxy growth onto small indium bonded substrates, due to coating of the molybdenum block. These large temperature transients, along with other difficulties associated with indium bonding (e.g., potential substrate surface damage, unwanted indium on the back of the substrate) make indium free substrate mounting desirable, however, indium free mounting systems have previously been restricted to whole standard‐sized round wafers. In this study we compare the temperature characteristics of new indium free modular substrate mounting blocks, which can accommodate substrates of various sizes (up to 3 inch diameter) and shapes, with traditional indium mounting of small substrates. Although the new modular indium free holders have a large molybdenum surface area exposed to the molecular beams, we find that the substrate surface temperature transients during growth are reduced to nearly negligible levels versus similar growth on indium bonded substrates, due to the effective thermal isolation of the substrate from the molybdenum. The real effects of these temperature differences observed by in situ pyrometry were confirmed by ex situ deep level transient spectroscopy (DLTS) measurements of homoepitaxial GaAs films, which show a two‐to‐three order of magnitude trap density increase in films grown on indium bonded substrates versus films grown on substrates mounted without indium bonding. This DLTS result is consistent with a real growth temperature difference between the two mounting techniques as was measured in situ by pyrometry. © 1996 American Vacuum Society
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
06.60.Ei Sample preparation (including design of sample holders)

Simple setup combining ferromagnetic resonance and surface magneto‐optic Kerr effect for measurements of magnetic properties of ultrathin films in ultrahigh vacuum

M. Li and G.‐C. Wang

J. Vac. Sci. Technol. A 14, 3288 (1996); http://dx.doi.org/10.1116/1.580228 (3 pages) | Cited 3 times

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We describe a setup consisting of a ferromagnetic resonance (FMR) cavity and an ultrahigh vacuum (UHV) chamber. The magnetic sample under UHV can be moved into a quartz tube finger which is an integral part of the UHV chamber. This 2‐cm‐o.d. finger can be inserted with a small clearance into the entrance hole of a cylindrical microwave cavity. The FMR absorption versus applied magnetic field spectra were measured at various angles θ between the applied magnetic field and the sample plane for Co films deposited in situ on a Si(111) surface. When the finger is withdrawn from the cavity, the hysteresis loop of the magnetic sample can be measured using the surface magneto‐optic Kerr effect. © 1996 American Vacuum Society
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
75.70.Ak Magnetic properties of monolayers and thin films
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
78.20.Ls Magneto-optical effects

Erratum: Fluorocarbon high density plasmas. VII. Investigation of selective SiO2‐to‐Si3N4 high density plasma etch processes [J. Vac. Sci. Technol. A 14, 2127 (1996)]

Ying Zhang, Gottlieb S. Oehrlein, and Ferdinand H. Bell

J. Vac. Sci. Technol. A 14, 3291 (1996); http://dx.doi.org/10.1116/1.580229 (1 page)

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81.65.Cf Surface cleaning, etching, patterning
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
99.10.Cd Errata

Erratum: Scanning force microscopy and polymerization studies on cast thin films of hectorite and montmorillonite [J. Vac. Sci. Technol. A 14, 1488 (1996)]

Timothy L. Porter, Michael P. Eastman, Michael E. Hagerman, Jennifer L. Attuso, and Edlin D. Bain

J. Vac. Sci. Technol. A 14, 3291 (1996); http://dx.doi.org/10.1116/1.580230 (1 page)

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Abstract Unavailable
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
82.35.-x Polymers: properties; reactions; polymerization
99.10.Cd Errata
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