JVA Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

Mar 1996

Volume 14, Issue 2, pp. 267-665


Dynamic rate and thickness metrology during poly‐Si rapid thermal chemical vapor deposition from SiH4 using real time in situ mass spectrometry

L. L. Tedder, G. W. Rubloff, B. F. Cohaghan, and G. N. Parsons

J. Vac. Sci. Technol. A 14, 267 (1996); http://dx.doi.org/10.1116/1.579887 (4 pages) | Cited 12 times

Full Text: | Download PDF


See Also: Erratum

Show Abstract
Real‐time in situ mass spectrometry has been applied to poly‐Si rapid thermal chemical vapor deposition (RTCVD) (from SiH4) on thermally grown SiO2 as a way to determine film thickness at the end of the process and to infer dynamic deposition rate during the process for run‐to‐run and real‐time control applications. Monitoring process ambient at 5 Torr is achieved using two‐stage differential pumping of a sampling aperture in the exhaust stream, and a rapid response time (∼1 s for a ∼30 s process cycle) allows for real time sensing of reactant input, product generation, and reactant depletion. Active mass spectrometric sampling of the reaction by‐product (H2 generated by SiH4 decomposition) provides a monitor of the total reaction/deposition rate during poly‐Si RTCVD in the range 550–850°C. Product generation as a function of temperature is readily distinguished from reactant cracking fragments by spectral analysis. A well‐defined monotonic correlation between the time‐integrated H+2 product signal and the poly‐Si film thickness, determined ex situ by single‐point interferometry (Nanometrics), demonstrates that the integrated mass spectrometric signal can provide real‐time thickness metrology. In addition, the time‐dependence of product and reactant signals provides a real‐time indication of detailed equipment behavior during the process. © 1996 American Vacuum Society
Show PACS
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Optical temperature measurement by grating expansion for rotating semiconductor wafers

C. Huang, M. Lang, and S. R. J. Brueck

J. Vac. Sci. Technol. A 14, 271 (1996); http://dx.doi.org/10.1116/1.579888 (7 pages)

Full Text: | Download PDF

Show Abstract
A noncontact temperature measurement technique, diffraction‐order analysis, based on monitoring the change in diffraction angle from a grating as a result of thermal expansion, is described and results for both Si and GaAs are presented. Two incident beams are used to provide a differential measurement, independent of wafer tilt. Image processing techniques are used to calculate the relative temperature in near real time from the optical signals. Good agreement between optical and the thermocouple temperature measurements is obtained, with an accuracy and precision of ±0.3 °C demonstrated over a 20–600 °C temperature range for a GaAs sample. Analysis of the effects of all six rigid‐body motions of the wafer on the measurement is presented. The measurement is independent of all translational motions; rotational motions (pitch, roll, and yaw) can all be monitored with the same measurement scheme and the temperature measurement corrected for their effects. In many applications in semiconductor manufacturing, wafers are rotated to ensure uniformity. The diffraction‐order analysis technique is demonstrated for a rotating wafer with a 3σ precision of 1.95 °C. © 1996 American Vacuum Society
Show PACS
07.20.Dt Thermometers
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Adsorption induced gas transport phenomena in narrow air channels recorded with work function detectors

B. Flietner, T. Doll, J. Lechner, and I. Eisele

J. Vac. Sci. Technol. A 14, 278 (1996); http://dx.doi.org/10.1116/1.579889 (8 pages)

Full Text: | Download PDF

Show Abstract
Gas transport in narrow air channels (length‐to‐height ratio 1 mm/1 μm) is characterized by work function detectors like hybrid suspended gate field effect transistors (HSGFETs) with sensitive areas located in the middle of the channel. A thin platinum layer covered one side of the channel. In order to separate the influence of the size of the channel structure on the gas exchange Kelvin probe measurements with platinum coated reference electrodes were carried out simultaneously. For the HSGFET we have observed time lags and suppressions of reactions, which indicate a strong adsorption dependence of gas exchange for the investigated testing gas mixture of hydrogen in nitrogen or synthetic air, respectively. The results are discussed in relation to common models for the flow in thin capillaries. We also point out the special features of narrow air channels for investigating adsorption related phenomena and for improving chemical sensor characteristics by incorporating them into small air gaps. © 1996 American Vacuum Society
Show PACS
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
47.60.-i Flow phenomena in quasi-one-dimensional systems
47.45.Dt Free molecular flows
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Irradiation‐induced decomposition of Al2O3 during Auger electron spectroscopy analysis

Jae‐Won Park, Anthony J. Pedraza, and William R. Allen

J. Vac. Sci. Technol. A 14, 286 (1996); http://dx.doi.org/10.1116/1.579890 (7 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
The effect of electron fluence on the decomposition of sapphire (Al2O3) was studied in situ by Auger electron spectroscopy (AES). The decomposition was primarily detected by monitoring the evolution of the low kinetic energy Auger transitions of aluminum in Al2O3 (54 eV) and in metallic aluminum (68 eV). The decomposition of sputter‐cleaned sapphire started at a fluence of ∼4.9×1019 electrons/cm2 (7.8 C/cm2). This fluence was independent of the electron fluxes used in this work, except the lowest, which indicates that heating due to electron bombardment does not significantly affect the decomposition behavior. Electron‐induced decomposition takes place in a minimum of the first five atomic layers of the substrate, as revealed by the evolution during irradiation of the high energy Al peaks associated with Al2O3 (1388 eV) and metallic aluminum (1396 eV). Comparison of the evolution of low and high kinetic energy Auger transitions demonstrates that the decomposition kinetics are much faster for the first monolayer than for the subjacent atomic layers. The surface condition strongly influences the decomposition kinetics. Thus, a carbon layer adsorbed at the alumina surface significantly increases the threshold dose for decomposition. The carbon layer most probably acts as a diffusion barrier for the oxygen produced during decomposition. An equation for the decomposition rate of the first monolayer of alumina is established. The integral of this equation gives a good fitting to the experimental data. It is found that the Auger signal of aluminum from sapphire does not disappear even if the entire region has been decomposed. This effect is due to backscattered electrons that promote Auger electron excitations outside the irradiated region. © 1996 American Vacuum Society
Show PACS
82.50.Kx Processes caused by X-rays or γ-rays
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Characterization of low‐resistivity indium oxide films by Auger electron spectroscopy, x‐ray photoelectron spectroscopy, and x‐ray diffraction and correlation between their properties, composition, and texture

J. I. Jeong, J. H. Moon, J. H. Hong, J.‐S. Kang, Y. Fukuda, and Y. P. Lee

J. Vac. Sci. Technol. A 14, 293 (1996); http://dx.doi.org/10.1116/1.579891 (6 pages) | Cited 5 times

Full Text: | Download PDF

Show Abstract
Auger electron spectroscopy, x‐ray photoelectron spectroscopy, and x‐ray diffraction (XRD) were employed to investigate the stoichiometry and texture of the indium‐oxide films. The films were prepared by the reactive evaporation and reactive ion plating of pure indium in an oxygen atmosphere of ∼10−4 Torr. Standard In and In2O3 grains were used to estimate the atomic concentration of the indium‐oxide films and to identify the film orientation. We correlated the electrical and optical properties of the films with their atomic concentration and texture. It was found that the films exhibiting low resistivity have atomic ratios of O to In of 1.29–1.31 and full widths at half‐maximum for (222) XRD peaks of 0.32°–0.34°. © 1996 American Vacuum Society
Show PACS
68.55.-a Thin film structure and morphology
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
61.05.cf X-ray scattering (including small-angle scattering)
73.61.Le Other inorganic semiconductors

X‐ray photoelectron spectroscopy studies of alkoxide‐derived lithium niobate

N. Kaufherr, D. J. Eichorst, and D. A. Payne

J. Vac. Sci. Technol. A 14, 299 (1996); http://dx.doi.org/10.1116/1.579892 (7 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
X‐ray photoelectron spectroscopy was used to study the thermal conversion of Li, Nb alkoxide derived thin layers on Si(100). Changes in the surface composition with temperature indicated a decomposition process involving lithium transport to the surface, lithium carbonate or oxycarbonate formation, and subsequent reaction to form lithium niobate. For comparison purposes, spectra were also obtained for a single crystal of lithium niobate and layers prepared from sol‐gel derived lithium ethoxide and niobium ethoxide. Heat treatment of the individual precursors gave lithium carbonate (or oxycarbonate) and niobium oxide, respectively. © 1996 American Vacuum Society
Show PACS
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.70.Jb Chemical composition analysis, chemical depth and dopant profiling
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
42.70.-a Optical materials

Chemical vapor deposition of aluminum and gallium nitride thin films from metalorganic precursors

David M. Hoffman, Sri Prakash Rangarajan, Satish D. Athavale, Demetre J. Economou, Jia‐Rui Liu, Zongshuang Zheng, and Wei‐Kan Chu

J. Vac. Sci. Technol. A 14, 306 (1996); http://dx.doi.org/10.1116/1.579893 (6 pages) | Cited 5 times

Full Text: | Download PDF

Show Abstract
Nearly stoichiometric aluminum and gallium nitride thin films were prepared from hexakis(dimethylamido)dimetal complexes, M2[N(CH3)2]6 (M=Al,Ga), and ammonia at substrate temperatures as low as 200 °C by using low pressure thermal and plasma enhanced chemical vapor deposition (CVD). Both processes gave films that showed little or no carbon (<5 at. %) and no oxygen (<few at. %) contamination, but in all cases there was hydrogen incorporation. The films were highly transparent in the ultraviolet and visible regions. The barrier properties of the aluminum nitride films in a Si/AlN/Au metallization scheme were examined by using backscattering spectrometry. The growth rate of the aluminum nitride films was as high as 1300 Å /min. Overall, the results suggest that M2[N(CH3)2]6 (M=Al,Ga) are promising precursors for low‐temperature/low‐pressure thermal and plasma‐enhanced CVD of group III nitride thin films. © 1996 American Vacuum Society
Show PACS
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Ls Metallization, contacts, interconnects; device isolation

Nucleation behavior in molecular beam and chemical vapor deposition of silicon on Si(111)‐(7×7)

L. Andersohn, Th. Berke, U. Köhler, and B. Voigtländer

J. Vac. Sci. Technol. A 14, 312 (1996); http://dx.doi.org/10.1116/1.579894 (7 pages) | Cited 18 times

Full Text: | Download PDF

Show Abstract
The nucleation behavior during chemical vapor deposition (CVD) of silicon on Si(111)‐(7×7) using disilane (Si2H6) is investigated with a scanning tunneling microscope. In the temperature range from 450 to 540 °C it is compared to molecular beam epitaxy (MBE). Whereas the latter is very well described within the framework of classical rate equation based nucleation theories in the complete condensation regime, the same approach fails for CVD growth. For MBE a critical nucleus i∗=5–7 is found. Although the relationship between island density and growth rate in CVD also follows a power law as does MBE, the exponent is significantly higher than the theoretically expected value. The influence of hydrogen present on the surface during CVD growth is also discussed. © 1996 American Vacuum Society
Show PACS
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Cy Elemental semiconductors

Enhanced adherence of area‐selective electroless metal plating on insulators

G. A. Shafeev, J.‐M. Themlin, L. Bellard, W. Marine, and A. Cros

J. Vac. Sci. Technol. A 14, 319 (1996); http://dx.doi.org/10.1116/1.579895 (8 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
We describe a simple way of producing adherent metal films (Cu or Ni) on insulator surfaces [SiO2, glass, or polyphenylquinoxaline (PPQ), an insulating polymer] by electroless growth on a thermally activated palladium acetylacetonate [Pd(acac)2] seeding layer. Using this process, we produced tiny metal patterns on insulators by localized laser pyrolysis (using either a pulsed Cu vapor or a cw Ar+ laser) of the spun‐on seeding layer. A tensile stress test applied to a Ni deposit on SiO2 reveals bonding strengths as high as 2 N/mm2. The mechanisms of such an increased adherence have been studied using x‐ray photoemission spectroscopy (XPS). The critical role of the chemical environment of the Pd clusters obtained by pyrolytic decomposition of the Pd(acac)2 seeding layer is shown. In particular, XPS reveals that most of the Pd atoms left at the surface after thermal decomposition still remain bonded to an organic aromatic species identified as one of the two acetylacetonate ‘‘wings’’ of the parent molecule. A wear‐resistant metal deposit on insulators can only be formed when these remaining ligands are removed by an additional acetic acid treatment. © 1996 American Vacuum Society
Show PACS
68.35.Gy Mechanical properties; surface strains
81.15.Fg Pulsed laser ablation deposition
81.05.Bx Metals, semimetals, and alloys

Role of chemical bonding in the epitaxial growth of noble metals on ionic crystal substrates

K. Yamamoto, Y. Kasukabe, R. Takeishi, and T. Osaka

J. Vac. Sci. Technol. A 14, 327 (1996); http://dx.doi.org/10.1116/1.579896 (5 pages) | Cited 6 times

Full Text: | Download PDF

Show Abstract
Thin films of Au were deposited onto MgO substrates cleaved in ultrahigh vacuum. The films, which were examined by transmission electron microscopy and electron diffraction, did not grow with a (111) orientation observed in a Au/NaCl system but with a (100) orientation which had been observed in a Pd/MgO system. In order to obtain some insight into the differences in the epitaxial orientations, we studied interfacial chemical bonding states in Au/MgO(100), Pd/MgO(100), and Au/NaCl(100) systems using total pair‐potential calculations and discrete variational Xα calculations. The results show that interfacial interaction in both the Au/MgO and the Pd/MgO system is stronger than that in the Au/NaCl system. The relation between the strength of the interfacial chemical bond and the epitaxial orientation in the above systems is discussed. © 1996 American Vacuum Society
Show PACS
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.Fx Diffusion; interface formation
81.05.Bx Metals, semimetals, and alloys

Fabrication and characterization of extremely smooth large area gold surfaces

Nathan G. Woodard and Gregory P. Lafyatis

J. Vac. Sci. Technol. A 14, 332 (1996); http://dx.doi.org/10.1116/1.579897 (4 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
We describe our work on gold surfaces that are made by peeling gold films off various smooth glass substrates. We find that we are able to routinely and reliably produce extremely smooth, large area gold surfaces: typically, for areas ≤40 μm square we find the residual roughness of our samples is an order of magnitude less than that of surfaces produced using conventional techniques. While we intend to use these to measure the van der Waals force between alkali atoms and gold surfaces, other potential uses include samples for fundamental surface physics investigations, scanning tunneling microscopy substrates, and reflective optics. We provide details as to how we make these extremely smooth samples and discuss our activities to characterize them. © 1996 American Vacuum Society
Show PACS
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.Bx Metals, semimetals, and alloys

Pure and fluorine‐doped silica films deposited in a hollow cathode reactor for integrated optic applications

M. V. Bazylenko, M. Gross, A. Simonian, and P. L. Chu

J. Vac. Sci. Technol. A 14, 336 (1996); http://dx.doi.org/10.1116/1.579898 (10 pages) | Cited 9 times

Full Text: | Download PDF

Show Abstract
Silica films have been deposited in a high density hollow cathode plasma deposition system from silane and oxygen gas mixtures. Additions of carbon tetrafluoride (CF4) were used to fluorine dope the silica. The deposited films were characterized by means of Fourier transform infrared (FTIR) spectroscopy, wavelength dispersive x‐ray spectroscopy, chemical etch rate (P etch), stress and refractive index measurements. The pure silica films, though deposited at a high rate (over 1500 Å/min), exhibit a P‐etch rate only 1.3 times that of thermal oxide. The refractive index of the as‐deposited silica is higher than that of thermal oxide, but reduces to the thermal oxide value after high‐temperature (1000 °C) annealing. Based on the thickness change measurements, the higher refractive index was attributed to a higher density of the deposited silica due to a smaller Si–O–Si bond angle, as supported by FTIR data. Fluorine doping results in a reduction in film stress by a factor of 4 over pure silica, as well as a reduction in OH content from about 1 at. % in pure silica to below the FTIR detection limit (0.1 at. %). The refractive index initially decreases with CF4 flow rate, concomitant with an increase in fluorine content, but then rises above the refractive index of pure silica. This increase has been found to be due to the deposition of silicon‐rich oxide at the higher CF4 flow rates, which is attributed to an increasingly oxygen deficient discharge resulting from oxygen consumption by the dissociation products of CF4. © 1996 American Vacuum Society
Show PACS
42.70.Ce Glasses, quartz
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.66.Jg Amorphous semiconductors; glasses
42.82.Cr Fabrication techniques; lithography, pattern transfer

Development of 111 texture in Al films grown on SiO2/Si(001) by ultrahigh‐vacuum primary‐ion deposition

Y. W. Kim, I. Petrov, J. E. Greene, and S. M. Rossnagel

J. Vac. Sci. Technol. A 14, 346 (1996); http://dx.doi.org/10.1116/1.579899 (6 pages) | Cited 9 times

Full Text: | Download PDF

Show Abstract
A high degree of 111 preferred orientation with minimal mosaic spread has been shown by many researchers to be essential for electromigration resistance in Al‐based interconnects. We have found that 111 texture can be greatly enhanced through the use of low‐energy self‐ion irradiation during deposition. In these experiments, 300‐nm‐thick Al layers were grown on SiO2 at 65 °C from highly ionized beams provided by an ultrahigh‐vacuum primary‐ion deposition (PID) source. Al+ ion energies EAl+ and ion/neutral ratios JAl+/JAl were independently varied from 10 to 120 eV and from 0% to 68%, respectively. All PID Al films exhibited very strong 111 preferred orientations, which increased with increasing EAl+ and/or JAl+/JAl, and azimuthally symmetric x‐ray diffraction pole figures with no measurable tilt. The full width at half‐maximum intensity Δω of 111 ω‐rocking curves decreased continuously from 9.6° with EAl+=10 eV and JAl+/JAl=68% to 2.2° with JAl+/JAl=120 eV compared to 10.6° for films deposited by thermal evaporation. This was accompanied by a continuous decrease in the average grain size from 370 nm for thermal deposition to 90 nm with EAl+=120 eV. The PID Al films exhibited a columnar microstructure with weak competitive column growth. Changing the beam energy after the formation of a continuous layer had only a minor effect on film texture, indicating that the degree of ion‐irradiation‐induced preferred orientation is controlled during nucleation and/or coalescence while local pseudomorphic forces dominate thereafter. ω‐rocking curves from a bilayer film consisting of a 20‐nm‐thick Al buffer layer grown by PID followed by a 280‐nm‐thick thermally evaporated Al overlayer were essentially identical to those obtained from 300‐nm‐thick single‐layer PID Al films. © 1996 American Vacuum Society
Show PACS
68.55.-a Thin film structure and morphology
81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.05.Bx Metals, semimetals, and alloys
85.40.Ls Metallization, contacts, interconnects; device isolation

Effects of oblique energetic bombardment on the morphology and microstructure of triode ion plated titanium films

K. R. Gunasekhar, M. Ghanashyam Krishna, A. R. Raju, K. N. Krishna, and S. Mohan

J. Vac. Sci. Technol. A 14, 352 (1996); http://dx.doi.org/10.1116/1.579900 (7 pages)

Full Text: | Download PDF

Show Abstract
The effect of angle of incidence of ions, varied between 45° and 90°, generated in a triode ion plating system on the morphology and microstructure of titanium films, has been investigated. It has been found that intensity of reflections, lattice parameters, stress, and grain size are strong functions of the angle of incidence of the ions. The same properties were studied for their variation with bias voltage between 0 and 2 kV at a constant substrate bias current of 10 mA. It was found that the intensity of the (002) reflection increases with an increase in angle of ion incidence up to 60°. The lattice parameter and stress reach a minimum while the grain size goes through a maximum at this value. All the films show a tensile stress independent of deposition parameters. To isolate the effects due to ion bombardment the films have been coated in high vacuum, in a diode mode, and finally the triode configuration. It has been conclusively found that the angle of incidence of ions is very important in controlling properties and growth of the films. © 1996 American Vacuum Society
Show PACS
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
81.05.Bx Metals, semimetals, and alloys
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Chemical shifts and optical properties of tin oxide films grown by a reactive ion assisted deposition

Won‐Kook Choi, Hyung‐Jin Jung, and Seok‐Keun Koh

J. Vac. Sci. Technol. A 14, 359 (1996); http://dx.doi.org/10.1116/1.579901 (8 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
Highly oriented nonstoichiometric tin oxide thin films were grown by a reactive ion assisted deposition onto Si(100) and glass substrates at room temperature as a function of relative ion (O)/atom (Sn metal) arrival ratio, and concurrently the deposited ion energy per atom (eV/atom) were changed from 10 to 100 eV/atom. As‐deposited tin oxide films show preferred orientation along the SnO2〈101〉 axis and the x‐ray diffraction peak intensity appears maximum at an average energy of about 50 eV/atom. From quantitative Auger electron spectroscopy, characteristic transitional Auger peaks of Sn metal MNN transitions were shifted to lower kinetic energies by 4–6±1.0 eV as the Sn4+ component becomes dominant in the deposited tin oxide films and the position of O KL1,2L2,3 transition line was also shifted to lower kinetic energy by 1–2±1.0 eV as the composition of deposited tin oxide films were changed from SnO to SnO2, respectively. On the basis of a tin 3d core level and O 1s spectra analysis by x‐ray photoelectron spectroscopy, the sizable chemical shift of different valencies between stannous tin (Sn2+:SnO) and stannic tin (Sn4+:SnO2) was 1.0±0.02 eV and that of O 1s was 0.87±0.02 eV, and those values show larger shifts than previously reported ones. The refractive index n of as‐deposited tin oxide films was evaluated from an ellipsometer, and spectrophotometric transmittances were measured in the wavelength range of 200–800 nm. In the luminous range, the refractive index varied from n=2.36 to 2.04 as oxygen contents increased. © 1996 American Vacuum Society
Show PACS
78.66.Li Other semiconductors
79.60.Dp Adsorbed layers and thin films
81.05.Hd Other semiconductors
81.15.Jj Ion and electron beam-assisted deposition; ion plating

New method of tubular material inner surface modification by plasma source ion implantation

Mu Sun, Si‐ze Yang, and Bing Li

J. Vac. Sci. Technol. A 14, 367 (1996); http://dx.doi.org/10.1116/1.579902 (3 pages) | Cited 19 times

Full Text: | Download PDF

Show Abstract
Plasma source ion implantation is a non‐line‐of‐sight ion implantation technique for surface modification of materials, but that technique is only suitable for outer surface modification of hollow targets, not for inner surface modification. In this article we present a new method that applies to inner surface implantation. Preliminary experimental results show that this new method increases plasma density and uniformity inside the tubular target with the inner surface, generates a plasma sheath between the inner surface of the target and the plasma to implant the inner surface of the target effectively, and achieves a dose uniformity that is acceptable for industrial applications. © 1996 American Vacuum Society
Show PACS
81.65.-b Surface treatments
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Ion deposition by inductively coupled plasma mass spectrometry

Ke Hu and R. S. Houk

J. Vac. Sci. Technol. A 14, 370 (1996); http://dx.doi.org/10.1116/1.579903 (4 pages)

Full Text: | Download PDF

Show Abstract
An atmospheric pressure inductively coupled plasma (ICP) is used with a quadrupole mass spectrometer (MS) for ion deposition. The deposited element is introduced as a nebulized aqueous solution. Modifications to the ICP‐MS device allow generation and deposition of a mass‐resolved beam of 165Ho+ at 5×1012 ions s−1. The ICP is a universal, multielement ion source that can potentially be used for applications such as deposition of mixtures of widely varying stoichiometry or of alternating layers of different elements. © 1996 American Vacuum Society
Show PACS
81.15.Jj Ion and electron beam-assisted deposition; ion plating
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Pulsed plasma deposition of chromium oxide/chromium‐cermet coatings

D. Gall, R. Gampp, H. P. Lang, and P. Oelhafen

J. Vac. Sci. Technol. A 14, 374 (1996); http://dx.doi.org/10.1116/1.580092 (6 pages) | Cited 7 times

Full Text: | Download PDF

Show Abstract
A novel radio frequency magnetron sputtering method for the deposition of composite films which consist of chromium oxide and chromium (Cr2O3/Cr‐cermet) is presented. As an extension to conventional reactive sputtering of a Cr target in an argon and oxygen atmosphere the oxygen flow into the process chamber is switched periodically on and off. This leads to an oscillating oxygen partial pressure during the sputtering process and an alternating deposition of metallic chromium and chromium oxide. In situ x‐ray and ultraviolet photoelectron spectroscopy are used to monitor the oxidation state of chromium at the film surface and to study the chemical interactions between adjacent layers. Ex situ x‐ray diffraction analysis reveals the multilayered and nanocrystalline structure of the deposited films. The overall chromium and chromium oxide concentration is estimated from the optical constants n and k determined by reflectance and transmission measurements in the wavelength range between 400 and 2200 nm. © 1996 American Vacuum Society
Show PACS
81.15.Cd Deposition by sputtering
81.05.Mh Cermets, ceramic and refractory composites
78.66.Sq Composite materials
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Measurement of the gas temperature in fluorocarbon radio frequency discharges using infrared absorption spectroscopy

M. Haverlag, E. Stoffels, W. W. Stoffels, G. M. W. Kroesen, and F. J. de Hoog

J. Vac. Sci. Technol. A 14, 380 (1996); http://dx.doi.org/10.1116/1.580093 (4 pages) | Cited 27 times

Full Text: | Download PDF

Show Abstract
The translational gas temperature was measured in 13.56 MHz radio‐frequency (rf) discharges in CF4 and CHF3. Infrared absorption spectra of CF4 and CF2 were recorded using a tunable diode laser and the gas temperature was deduced from the linewidths of the absorption lines of these molecules. It is shown that linewidth measurements yield a simple and direct method to determine the gas temperature, with an accuracy up to ∼10 K. The results obtained in CF4 and CHF3 plasmas indicate that the translational temperatures of all particles investigated in these plasmas are, at most, 50 K above the room temperature. The temperature increases with increasing gas pressure and rf power, but it is independent of the flow rate. This is attributed to an increased heating rate of the gas. Moreover, it was found that the temperature rise is significantly smaller in CHF3 than in CF4, under the same plasma conditions. This can be attributed to a higher power dissipation by chemical conversion of the parent gas in a CHF3 discharge, as compared with a CF4  plasma. © 1996 American Vacuum Society
Show PACS
52.25.Kn Thermodynamics of plasmas
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Pi High-frequency and RF discharges

Production and destruction of CFx radicals in radio‐frequency fluorocarbon plasmas

M. Haverlag, W. W. Stoffels, E. Stoffels, G. M. W. Kroesen, and F. J. de Hoog

J. Vac. Sci. Technol. A 14, 384 (1996); http://dx.doi.org/10.1116/1.580094 (7 pages) | Cited 44 times

Full Text: | Download PDF

Show Abstract
Spacially resolved densities of CF, CF2, and CF3  radicals in capacitively coupled 13.56 MHz radio‐frequency (rf) discharges in CF4 and CHF3 were determined by means of infrared absorption spectroscopy employing a tunable diode laser spectrometer. It was established that the stationary CF2 density and density profile in a CF4 plasma depend strongly on the electrode material. This is attributed to different sticking coefficients of CF2 on different surfaces. Furthermore, it was found that the densities of all CFx radicals increase near the electrodes at high gas pressures and rf powers in a CHF3 plasma. This leads to the conclusion that production of CFx radicals takes place in the sheath region close to the electrodes. It is proposed that collisions between ions and source gas molecules are responsible for this production of CFx radicals. In the presence of a destruction process in the plasma glow (e.g., by three‐body recombination with other radicals) and the absence of a fast surface loss process this results in the observed increase of CFx densities near the electrodes. In order to study the radical kinetics time dependent measurements were performed during power modulation of the plasma. It was found that the decay time of the CF2 density in the afterglow of a CF4 plasma is much shorter than the corresponding decay time in a CHF3 discharge. This suggests that the surface loss is relatively less important in the latter case, in agreement with measurements of spatial density distributions. This is explained by the presence of a (CFx)n layer, which is readily deposited on the electrodes in a CHF3 discharge, and by low sticking probabilities of CF and CF2 radicals on such a layer. © 1996 American Vacuum Society
Show PACS
52.25.Ya Neutrals in plasmas
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Pi High-frequency and RF discharges

Measurements of pulsed‐power modulated argon plasmas in an inductively coupled plasma source

Sumio Ashida, M. R. Shim, and M. A. Lieberman

J. Vac. Sci. Technol. A 14, 391 (1996); http://dx.doi.org/10.1116/1.580095 (7 pages) | Cited 38 times

Full Text: | Download PDF

Show Abstract
The behavior of pulsed‐power (square wave) modulated argon plasmas generated by an inductively coupled plasma (ICP) source is experimentally investigated. The apparatus is an ICP source with a flat coil geometry equipped with a cylindrical Langmuir probe on the axis of the cylindrical chamber. The evolution of the plasma density is determined from the wave forms of ion saturation currents. The rise and fall of the density had a time scale of a few tens of microseconds. The time average plasma density is also measured as a function of pulse frequency and duty ratio, holding the average absorbed power constant. When the plasma is modulated, the density is larger than that for a continuous wave excitation of the same average power. Larger densities are obtained for smaller duty ratios. The density increases monotonically as the period is decreased down to 100 μs. This agrees qualitatively with the modeling result, which accounts for the higher density by the difference of time scales for the generation and the loss of charged particles. The results for electron temperature measurements also show good agreement with the model quantitatively during the pulse ‘‘on’’ times. If the period is long enough, it is found that the electron temperature rises abruptly at the initial stage of power application, in agreement with the calculation. © 1996 American Vacuum Society
Show PACS
52.80.Pi High-frequency and RF discharges
52.70.Ds Electric and magnetic measurements
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Simulation of microloading in aluminum etching

Masahiko Aoki and Yoshitaka Sasamura

J. Vac. Sci. Technol. A 14, 398 (1996); http://dx.doi.org/10.1116/1.580096 (6 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
A simulator for aluminum etching was developed in order to analyze the microloading effect. We have adopted the procedure that the flux rates (gas particles, ions, and sputtered mask fragments) are calculated independently as a function of trench aspect ratio; then the etching rate is calculated with these flux rates at each aspect ratio. The simulator can be operated on a personal computer by this simple procedure and the characteristics of aluminum etching can be obtained quickly. The surface reaction parameters were determined by fitting the calculated result to the basic experimental etching rate data. By using these surface reaction parameters the simulator can predict the characteristics of aluminum etching such as etching rate, selectivity, etc. The difference of the microloading effect between photoresist and oxide mask was also analyzed. It was confirmed by this simulator that the microloading effect was affected by the sputtered photoresist fragments. © 1996 American Vacuum Society
Show PACS
81.65.Cf Surface cleaning, etching, patterning
85.40.Bh Computer-aided design of microcircuits; layout and modeling

H2O pumping by sputter discharge with a LaB6 cathode

Y. Funato, M. Miyoshi, K. Akaishi, Y. Kubota, and M. Mushiaki

J. Vac. Sci. Technol. A 14, 404 (1996); http://dx.doi.org/10.1116/1.580097 (4 pages)

Full Text: | Download PDF

Show Abstract
Properties of H2O water vapor pumping by glow discharge sputtering with a LaB6 cold cathode are studied experimentally. For the purpose of developing a new type of sputter ion pump, lanthanum hexaboride (LaB6) is applied as the cathode material on the basis of a preliminary study. The application of LaB6 as the cathode of sputter discharge was proposed at first to obtain a low outgassing wall for a plasma vacuum chamber. The experiments showed that the vacuum chamber with the LaB6 sputter coating reached a lower ultimate pressure than that without the coating. LaB6 coating by glow discharge on a stainless steel wall is effective to reduce the H2O outgassing rate of a vacuum wall as shown by mass spectrometric analysis. The pumping speed of H2O by the coated wall is estimated experimentally. Characterization of the LaB6 coated films is also made by x‐ray photoelectron spectroscopy measurements. © 1996 American Vacuum Society
Show PACS
07.30.Cy Vacuum pumps

Extraction of oxygen from CO2 using glow‐discharge and permeation techniques

D. Wu, R. A. Outlaw, and R. L. Ash

J. Vac. Sci. Technol. A 14, 408 (1996); http://dx.doi.org/10.1116/1.580098 (7 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
A promising method to extract oxygen from CO2, which constitutes more than 95% of the Mars atmosphere, is by using glow‐discharge dissociation of CO2 combined with the permeation of the generated oxygen through a Ag membrane. Quadrupole mass spectrometry was utilized to measure the oxygen flux through a 0.35‐mm‐thick, 2.01 cm2 area membrane separating a two‐chamber system. On the upstream side of the membrane, a dc glow discharge was established with 350 V and 5 mA current. It was found that as much as 75% of the CO2 was dissociated to form CO and O (part of which recombined to form O2). The atomic and molecular oxygen generated were adsorbed on the membrane surface, subsequently dissolved into the Ag, and diffused through the membrane thickness to the downstream surface where it desorbed as molecular oxygen. The resulting oxygen flux was studied as a function of upstream CO2 pressure, discharge current, discharge probe to membrane distance, and membrane temperature. It was found that the atomic oxygen generated a much higher concentration gradient across the membrane than did the molecular oxygen which resulted in a correspondingly higher oxygen flux through the membrane. The total oxygen flux through the membrane with a CO2 glow‐discharge pressure of 5 Torr and a membrane temperature of 450 °C was found to be greater than 1014 cm−2 s−1. This method can be used to continuously and efficiently supply oxygen for astronauts in a future manned mission to Mars. © 1996 American Vacuum Society
Show PACS
07.87.+v Spaceborne and space research instruments, apparatus, and components (satellites, space vehicles, etc.)
52.75.-d Plasma devices

Mechanistic studies of the thermal decomposition of metal carbonyls on Ni(100) surfaces in connection with chemical vapor deposition processes

Mingde Xu and Francisco Zaera

J. Vac. Sci. Technol. A 14, 415 (1996); http://dx.doi.org/10.1116/1.580099 (10 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
The thermal decomposition of Fe(CO)5, Cr(CO)6, Mo(CO)6, and W(CO)6 on Ni(100) surfaces and under ultrahigh vacuum conditions was studied by using temperature programmed desorption and x‐ray photoelectron spectroscopies. The initial adsorption of those metal carbonyls is mostly molecular at low temperatures, but complete decarbonylation to the naked metal takes place in all cases upon thermal activation. Experiments with coadsorbed isotopically labeled 13CO provided indirect evidence for a stepwise mechanism for Fe(CO)5 which may include the formation of tetra‐ and tricarbonyl intermediates on the surface. For Cr(CO)6, Mo(CO)6, and W(CO)6, on the other hand, complete decomposition occurs in a narrow range of temperature, and no intermediate could be isolated on the surface. The deposition of metal films via metal carbonyl activation was studied under steady state conditions as well. Continuous deposition was seen at substrate temperatures as low as 300 K, but the grown films were found to incorporate both carbon and oxygen under most conditions tested and to change their morphology depending on the substrate temperature during deposition. © 1996 American Vacuum Society
Show PACS
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.05.Bx Metals, semimetals, and alloys

Crystallographic tilting in high‐misfit (100) semiconductor heteroepitaxial systems

Ferenc Riesz

J. Vac. Sci. Technol. A 14, 425 (1996); http://dx.doi.org/10.1116/1.580100 (6 pages) | Cited 12 times

Full Text: | Download PDF

Show Abstract
A model is presented for the formation of crystallographic tilting (misorientation) in highly mismatched (100) oriented zinc‐blende semiconductor heteroepitaxial layers grown on vicinal substrates. The model is based on the asymmetric generation of 60° misfit dislocations upon island coalescence in the initial growth process and the asymmetric strain release at substrate steps, and predicts a correlation between tilt angle and initial growth planarity. Good agreement is found between model and experimental data on the GaAs/Si and other systems. It is also shown that, if the net tilt is small, an azimuthal rotation of the tilt axis may occur, even if the system symmetry would hinder it. The influence of thermal annealing and thermal mismatch on the tilt is discussed as well. © 1996 American Vacuum Society
Show PACS
68.35.Ct Interface structure and roughness
68.60.Bs Mechanical and acoustical properties

Characterization of amorphous carbon thin films

M. A. Capano, N. T. McDevitt, R. K. Singh, and F. Qian

J. Vac. Sci. Technol. A 14, 431 (1996); http://dx.doi.org/10.1116/1.580101 (5 pages) | Cited 11 times

Full Text: | Download PDF

Show Abstract
The objective of this study is to develop improved procedures for characterizing amorphous carbon films. Raman spectroscopy is used to characterize amorphous carbon thin films grown by pulsed laser deposition at temperatures between 293 and 873 K. The amount of bond‐angle disorder is shown to decrease with increasing substrate temperature. However, a shift of the Raman D peak to higher wave numbers is not observed to coincide with the presumed decrease in sp3 bonding as the deposition temperature increases. The graphitic domain size is shown to initially decrease, pass through a minimum, and then increase as temperature increases. Mass densities, measured independently by x‐ray specular reflectometry, are seen to decrease from a maximum of 2.4 g/cm−3 as deposition temperature increases. The trend in the observed density measurements correlates well with the Raman spectroscopy data. The importance of x‐ray specular reflectometry as part of a strategy to completely characterize amorphous carbon films is discussed in terms of these data. © 1996 American Vacuum Society
Show PACS
68.55.-a Thin film structure and morphology
78.30.Am Elemental semiconductors and insulators
61.05.cm X-ray reflectometry (surfaces, interfaces, films)

Aging of photochemical vapor deposited silicon oxide thin films

E. G. Parada, P. González, J. Pou, J. Serra, D. Fernández, B. León, and M. Pérez‐Amor

J. Vac. Sci. Technol. A 14, 436 (1996); http://dx.doi.org/10.1116/1.580102 (5 pages) | Cited 6 times

Full Text: | Download PDF

Show Abstract
Further development of the microelectronic technology requires the growing of stable and passivated dielectric thin films. Photochemical processes are very promising methods to obtain silicon dioxide films for microelectronic purposes. In this article, the aging of silicon oxide films obtained by ArF laser chemical vapor deposition at low temperature is studied. The evolution of the properties of films has been followed up using infrared spectroscopy and ellipsometry, and compared with aging of thermally oxidized silica films. The role of moisture in film aging is also clarified by comparing films exposed to humid and to dry atmospheres. Si–OH groups are incorporated into the film in a specific local bonding environment and relaxation in the film structure takes place while new Si–O groups can be created. Moreover, the dependence of the stability of film properties on the processing parameters is analyzed. © 1996 American Vacuum Society
Show PACS
68.60.Dv Thermal stability; thermal effects
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Strain measurements of SiGeC heteroepitaxial layers on Si(001) using ion beam analysis

S. Sego, R. J. Culbertson, David J. Smith, Z. Atzmon, and A. E. Bair

J. Vac. Sci. Technol. A 14, 441 (1996); http://dx.doi.org/10.1116/1.580103 (6 pages) | Cited 5 times

Full Text: | Download PDF

Show Abstract
The strain in SiGeC heteroepitaxial films grown on Si(001) substrates by chemical vapor deposition is quantified using ion channeling. Rutherford backscattering spectrometry was used to quantify the Ge concentration as well as the film thickness, nuclear resonance elastic ion scattering was used to quantify the C concentration, and ion channeling was utilized to measure film quality and C substitutionality. Channeling angular scans across an off‐normal major axis were used to quantify the strain. The results confirm that addition of C compensates for the strain introduced by Ge. © 1996 American Vacuum Society
Show PACS
68.60.Bs Mechanical and acoustical properties
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.80.-d Chemical analysis and related physical methods of analysis

Healing of surface defects in hard materials by thin coatings

I. Yu. Konyashin

J. Vac. Sci. Technol. A 14, 447 (1996); http://dx.doi.org/10.1116/1.580104 (6 pages)

Full Text: | Download PDF

Show Abstract
Results on improvements in the transverse rupture strength of WC‐based cemented carbides, TiCN‐based cermets, and Al2O3‐based ceramics by the physical vapor deposition of thin coatings are presented. Evaluation of strength decreases in cemented carbides versus the length of half‐elliptic cracks in the near‐surface layer reveals enhancement of the cracks’ influence of the rupture stress value with decreasing fracture toughness of the cemented carbides. TiCN coatings obtained when simultaneous surface ion etching and depositing lead to healing Palmquist cracks formed near corners of Vickers indentations. The coatings are assumed to heal various defects present at the surface of hard materials, which result in an increase in transverse rupture strength of cemented carbides, cermets, and ceramics. Tool lifetime of Al2O3‐based ceramic cutting inserts can be improved by depositing the coatings due to the healing surface defects resulting in retardation of cracks’ initiation and propagation in interrupted cutting. © 1996 American Vacuum Society
Show PACS
81.65.-b Surface treatments
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Mh Cermets, ceramic and refractory composites

Evaluation of the dispersive nature of meshes used for the spherical aberration correction of electrostatic lenses

M. Kato and T. Sekine

J. Vac. Sci. Technol. A 14, 453 (1996); http://dx.doi.org/10.1116/1.580105 (9 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
Although spherical aberration of electrostatic lenses can be corrected in principle by employing meshes, the holes in meshes give rise to local disturbances in the electric field and the performance of mesh lenses deteriorates somewhat due to this effect. The disturbed electric field around mesh holes has a lens action, so a mesh can be regarded as a set of single‐aperture lenses. It is shown that the optical properties of single‐aperture lenses can be approximated to high precision by means of a transfer matrix. Using this formulation, the lens effect added by the presence of holes is extracted without ambiguity from the action of the total lens field. Moreover, the condition where a single‐aperture lens can be regarded as a thin lens with a certain focal length is clarified. An image of a point source is blurred by mesh holes, and the amount of blurring is explained to high precision by their first‐order defocusing action as single‐aperture lenses; calculations using ray tracing have confirmed this. It is shown that the blurring can be suppressed to an acceptable level in applications such as transfer optics for electron spectrometers. © 1996 American Vacuum Society
Show PACS
41.85.Gy Chromatic and geometrical aberrations

Effects of surface oxide on the rapid thermal nitridation of Si(001)

M. Copel, R. M. Tromp, H.‐J. Timme, K. Penner, and T. Nakao

J. Vac. Sci. Technol. A 14, 462 (1996); http://dx.doi.org/10.1116/1.580106 (3 pages) | Cited 5 times

Full Text: | Download PDF

Show Abstract
We have investigated the role of surface oxygen on the rapid thermal nitridation of Si(001) by NH3 using medium energy ion scattering. For short times, typical of rapid thermal processing, monolayer quantities of oxygen are sufficient to reduce nitridation. The oxide remains on the surface after nitridation, which may adversely influence subsequent nitride chemical vapor deposition. © 1996 American Vacuum Society
Show PACS
81.05.Cy Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation

Thermal stability of silver in ion‐exchanged soda lime glasses

Paul W. Wang

J. Vac. Sci. Technol. A 14, 465 (1996); http://dx.doi.org/10.1116/1.580107 (6 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
X‐ray photoelectron spectroscopy was used to study the thermal stability of silver in ion‐exchanged sodium calcium silicate glasses during heat treatment in ultrahigh vacuum. The changes in concentration, in line shape, and in binding energy as functions of sample temperature show that silver diffuses toward the surface and the chemical structure of the sample surface changes. Judging from a comparison of the line shapes and the binding energies of the samples to those of pure silver and silica, the concentration variations in bridging and nonbridging oxygens, and the binding energy shifts of nonbridging oxygens, it is concluded that the SiO2 glass network starts breaking up during Ag+ diffusion at sample temperatures below 200 °C, metallic silver clusters form, and nonbridging oxygens originally surrounded by silver atoms reconnect to silicon atoms at sample temperatures above 200 °C. The relaxation of surface stress introduced by the exchange process and the net reduction of Gibbs free energy cause the surface diffusion and segregation of silver and the reconnection between oxygen and silicon. The estimated activation energy of the silver surface diffusion is 0.16 eV. © 1996 American Vacuum Society
Show PACS
42.70.Ce Glasses, quartz
64.75.-g Phase equilibria
66.30.J- Diffusion of impurities
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Plasma‐enhanced chemical vapor deposition of thick silicon nitride films with low stress on InP

L. Shi, C. A. M. Steenbergen, A. H. de Vreede, M. K. Smit, T. L. M. Scholtes, F. H. Groen, and J. W. Pedersen

J. Vac. Sci. Technol. A 14, 471 (1996); http://dx.doi.org/10.1116/1.580108 (3 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
We have developed a low‐temperature plasma‐enhanced chemical vapor deposition process that facilitates the deposition of silicon nitride films with controlled stress by using periodically alternating high‐ and low‐frequency power sources. Very thick films of 3 μm with low stress were deposited on InP substrates. Suitable sidewall profiles for metallization are obtained at 250 °C deposition temperature. A 3‐μm‐thick low‐stress nitride film was successfully applied to reduce the capacitance of bond pad for an array of four InP based photodetectors, that were integrated with a four channel phased‐array wavelength demultiplexer. The capacitance of the detectors was below 0.5 pF at −5 V bias. © 1996 American Vacuum Society
Show PACS
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)
68.60.Bs Mechanical and acoustical properties
81.65.Cf Surface cleaning, etching, patterning

Microwave surfatron system for plasma processing

L. Bárdoš, H. Baránková, and S. Berg

J. Vac. Sci. Technol. A 14, 474 (1996); http://dx.doi.org/10.1116/1.580109 (4 pages) | Cited 1 time

Full Text: | Download PDF

Abstract Unavailable
Show PACS
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.ub Fullerenes and related materials

Particle formation in the remote plasma enhanced chemical vapor deposition of Si films from Si2H6–SiF4–H2

Dong‐Hwan Kim and Shi‐Woo Rhee

J. Vac. Sci. Technol. A 14, 478 (1996); http://dx.doi.org/10.1116/1.580110 (3 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
SiF4 was added to Si2H6–H2 to enhance the crystallinity of Si films deposited at low temperatures around 400 °C in a remote plasma enhanced chemical vapor deposition reactor. A grid was inserted to detect the extent of powder formation as a function of operating variables. It was found that the fluorine chemistry reduced the amount of powder formation in the gas phase and helped crystallization at low temperatures. © 1996 American Vacuum Society
Show PACS
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Cy Elemental semiconductors
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

Use of a Cu/Ag/Au alloy as a reference material for the calibration of x‐ray photoelectron spectrometers

Brian R. Strohmeier

J. Vac. Sci. Technol. A 14, 481 (1996); http://dx.doi.org/10.1116/1.580111 (4 pages)

Full Text: | Download PDF

Show Abstract
The use of a sputter‐cleaned copper/silver/gold (Cu/Ag/Au) alloy for calibrating the energy scale and instrument resolution as full width at half‐maximum (FWHM) of x‐ray photoelectron spectrometers is described. The Cu 3p3/2, Cu 2p3/2, Cu L3M4,5M4,5, Ag 3d5/2, Ag M4NN, and Au 4f7/2 lines have been recommended in the literature for calibrating x‐ray photoelectron spectroscopy (XPS) instruments. The three‐component alloy material is a convenient alternative to the common practice of using three separate sputter‐cleaned reference materials (i.e., Cu, Ag, and Au foils) to obtain these measurements. Results indicate that the Cu/Ag/Au alloy yields XPS binding energies within reasonable experimental error (i.e., ±0.2 eV or less) of the values obtained for pure Cu, Ag, and Au materials. In addition, the FWHM values obtained for the major XPS peaks of the Cu/Ag/Au alloy were essentially equivalent (i.e., within ±0.03 eV or less) to the values obtained for pure Cu, Ag, and Au metal foils. This material, however, is not suitable as a standard reference material for calibrating the intensity scale of XPS instruments because of localized variations in composition across the alloy surface. © 1996 American Vacuum Society
Show PACS
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
07.81.+a Electron and ion spectrometers

A novel tilt assembly for ultrahigh vacuum XYZ‐rotary manipulators

J. G. C. Labanda and S. A. Barnett

J. Vac. Sci. Technol. A 14, 485 (1996); http://dx.doi.org/10.1116/1.580112 (2 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
A novel sample tilt assembly was developed for ultrahigh vacuum XYZ‐rotary manipulators which have the sample surface normal on the manipulator rotation axis. With conventional tilt mechanisms, sample azimuth and tilt angle cannot be varied independently since the rotation motion is about the manipulator axis, not the tilted sample normal. The present design allows sample tilt of ±10° and independent 360° rotation about the tilted sample surface normal. © 1996 American Vacuum Society  
Show PACS
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
06.60.Sx Positioning and alignment; manipulating, remote handling

Plasma crystal

G. E. Morfill and H. Thomas

J. Vac. Sci. Technol. A 14, 490 (1996); http://dx.doi.org/10.1116/1.580113 (6 pages) | Cited 43 times

Full Text: | Download PDF

Show Abstract
Plasma crystal is the term used to describe the recently discovered ordered state that a colloidal plasma may assume under certain conditions. This state resembles metals, to some extent, with the ‘‘atoms’’ represented by the highly negatively charged and highly ordered colloidal particles and the ‘‘electrons’’ by the mobile plasma ions and electrons—perhaps ‘‘heavy metal’’ might be an appropriate description. Plasma crystals are formed in a colloidal plasma if two conditions are met: (1) The Coulomb coupling parameter (the ratio of the Coulomb energy between neighboring particles to their kinetic energy) exceeds a certain threshold and (2) the lattice parameter (the ratio of the particle separation to the Debye length) is smaller than unity. These conditions are easy to generate in rf discharge plasmas and plasma crystallization then proceeds spontaneously. Plasma crystals have some unique properties, which make them exciting systems to study. (1) In their own right, as a hitherto unknown form of condensed plasma, they may provide many insights into basic plasma physical processes and transport effects. (2) As model systems for the detailed investigation of phase transitions, lattice defects, annealing, doping, etc., they may provide new information for a better understanding of solid state physics. (3) As test systems they may be useful for investigating nonlinear effects in ‘‘nanocrystals’’ (crystals with less than approximately 100 lattice planes).
The unique properties, which enable these investigations and possibly many more, are (1) global charge neutrality, (2) very fast response, (3) very little damping, and (4) easy experimental control and diagnostics, i.e., detailed imaging and high temporal resolution of the dynamics of individual particles (‘‘atoms’’). We present here an overview of recent developments in this new research field. © 1996 American Vacuum Society
Show PACS
52.25.-b Plasma properties

Wave propagation and damping in plasma crystals

Milenko Zuzic, Hubertus M. Thomas, and Gregor E. Morfill

J. Vac. Sci. Technol. A 14, 496 (1996); http://dx.doi.org/10.1116/1.580114 (5 pages) | Cited 46 times

Full Text: | Download PDF

Show Abstract
Wave propagation through plasma crystals provides an interesting experimental approach towards understanding strongly coupled plasmas as well as certain solid state properties of crystals. In order to build up our basic understanding of conditions and processes, oscillation modes of one‐ and two‐particle systems are investigated first, and the damping process is identified by studying the amplitude variations of the oscillations as a function of the excitation frequency. Next, single layer plasma crystals are investigated using the same techniques. An induced spontaneous transition from the solid to the gas phase is observed, and its possible origin is discussed. © 1996 American Vacuum Society
Show PACS
52.35.Dm Sound waves
52.25.Vy Impurities in plasmas
52.40.Hf Plasma-material interactions; boundary layer effects

Solid/liquid/gaseous phase transitions in plasma crystals

Hubertus M. Thomas and Gregor E. Morfill

J. Vac. Sci. Technol. A 14, 501 (1996); http://dx.doi.org/10.1116/1.580115 (5 pages) | Cited 28 times

Full Text: | Download PDF

Show Abstract
We present further observations of the solid/liquid and liquid/gaseous phase transition in plasma crystals. Plasma crystal is the term used to describe the recently discovered ‘‘state’’ that a colloidal plasma may assume under certain conditions—a state which has properties resembling those of metals. During the melting transition from solid to liquid the system passes through an intermediate ‘‘flow and floe’’ stage that has not been observed in other model crystals before. It may well be that this intermediate stage is a general feature of the solid/liquid phase transition in crystals. In this case it is clearly important. The fact that this stage could be detected for the first time is a consequence of the unique properties of plasma crystals: global charge neutrality, very fast response and little damping, easy experimental control, detailed imaging, and fine time resolution of the dynamics of individual particles (‘‘atoms’’). © 1996 American Vacuum Society
Show PACS
52.25.-b Plasma properties

Coulomb crystal formation from growing particles in a plasma and the analysis

Y. Hayashi and K. Tachibana

J. Vac. Sci. Technol. A 14, 506 (1996); http://dx.doi.org/10.1116/1.580116 (5 pages) | Cited 19 times

Full Text: | Download PDF

Show Abstract
A Coulomb crystal formation process from growing particles in an ethylene plasma was analyzed simultaneously by Mie‐scattering ellipsometry and charge‐coupled device video images. It was confirmed that the phase transition of Coulomb liquid to Coulomb solid occurred after around 20 min of particle growth. The Coulomb crystal formed a body‐centered‐cubic (bcc) structure at the first stage, while it changed to a hexagonal pole structure after more than 40 min. Particles are collectively bound by cohesion forming a bcc structure. They are closely packed in lateral layers and aligned in the vertical direction when an attractive force between dipoles, which consists of negative particles and the polarized surrounding positive ions, becomes strong. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Particle simulation of two dimensional dust crystal formation in a mesothermal plasma flow

F. Melandsø and J. Goree

J. Vac. Sci. Technol. A 14, 511 (1996); http://dx.doi.org/10.1116/1.580117 (8 pages) | Cited 41 times

Full Text: | Download PDF

Show Abstract
A two‐dimensional simulation is used to study the crystallization of strongly coupled dusty plasmas. The dust grains are simulated as particles, while the electrons and ion solutions are obtained from fluid equations. We model gas discharges with dust particles confined in the sheath and at the sheath edge. In these regions the ions flow past the dust grains at a velocity v0 that typically is mesothermal, vTi≪v0≪vTe. A negative charged dust particle will under these conditions focus the ions, creating a local maximum in the plasma potential on the downstream side of the particle. This maximum means that there is an anisotropic interparticle interaction, which can be manifested as an attractive interparticle force along the axis of the plasma flow. Our simulation shows that the equilibrium configuration of a dust crystal structure can be profoundly influenced by this asymmetry in the ion flow and plasma potential for certain charge to mass ratios for the dust particles. We initially distribute dust particles randomly in space with zero velocity and integrate their equations of motion, tracking their orbits as they settle into equilibrium positions. We show that there are several stable final equilibria, although they do not all have the same potential energy or probability of occurring. The most likely crystal configuration depends on the charge‐to‐mass ratio and the horizontal particle spacing of the grains. The vertically aligned columns of particles that have been observed in plasma crystal experiments are shown to be most likely for large dust charge‐to‐mass ratios. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.40.Hf Plasma-material interactions; boundary layer effects
52.65.-y Plasma simulation

Experimental studies of two‐dimensional and three‐dimensional structure in a crystallized dusty plasma

J. B. Pieper, J. Goree, and R. A. Quinn

J. Vac. Sci. Technol. A 14, 519 (1996); http://dx.doi.org/10.1116/1.580118 (6 pages) | Cited 57 times

Full Text: | Download PDF

Show Abstract
Coulomb crystallization of monodisperse 9.4‐μm‐diam spheres confined in a plasma is investigated in a modified GEC rf Reference Cell using various gases and electrode topographies. For some plasma conditions, planar electrodes confine particles radially in a few horizontal layers due to the curvature of the sheath boundary, and a two‐dimensional (2D) hexagonal lattice is observed which structural analysis shows to be consistent with the intermediate ‘‘hexatic’’ phase of KTHNY 2D melting theory. A depression in the electrode surface causes a corresponding depression in the sheath and allows trapping of more layers in a three‐dimensional (3D) structure, which is viewed in cross section by video imaging of a plane illuminated by a horizontal laser sheet. To synthesize 3D images, a stack of 2D images is made by moving the laser sheet and camera focal plane vertically through the particle cloud. This reveals regions of two stable 3D configurations within the cloud: body‐centered‐cubic and simple hexagonal with vertically aligned particles. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.80.Pi High-frequency and RF discharges
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.40.Hf Plasma-material interactions; boundary layer effects

Diagnostic of dusty plasma conditions by the observation of Mach cones caused by dust acoustic waves

O. Havnes, F. Li, F. Melandsø, T. Aslaksen, T. W. Hartquist, G. E. Morfill, T. Nitter, and V. Tsytovich

J. Vac. Sci. Technol. A 14, 525 (1996); http://dx.doi.org/10.1116/1.580119 (4 pages) | Cited 21 times

Full Text: | Download PDF

Show Abstract
The theory of dust acoustic waves in dusty plasmas is well developed for conditions with monosized dust particles. It was proposed [O. Havnes et al., J. Geophys. Res. 100, 1731 (1995)] that such waves may be generated in planetary dust rings by boulders moving through the dust at a velocity that is somewhat higher than the dust acoustic velocity. In this manner Mach cones can form with an opening angle that is dependent on the boulder velocity and the local dust acoustic velocity. Measurements of this opening angle will therefore provide additional information on dusty plasma conditions since the dust acoustic velocity can be determined when the boulder velocity is known. We suggest that this method may also be applied under laboratory conditions if a suitable controlled disturbance can be made and we discuss how the dust acoustic velocity and resulting Mach cones are affected if the dusty plasma have a distribution of dust sizes. © 1996 American Vacuum Society
Show PACS
52.70.-m Plasma diagnostic techniques and instrumentation
52.25.Vy Impurities in plasmas
52.35.Tc Shock waves and discontinuities

Model for ion‐induced nucleation based on properties of small ionic clusters

S. L. Girshick, N. P. Rao, and M. Kelkar

J. Vac. Sci. Technol. A 14, 529 (1996); http://dx.doi.org/10.1116/1.580139 (6 pages) | Cited 5 times

Full Text: | Download PDF

Show Abstract
A method is presented for calculating ion‐induced nucleation rates. Whereas classical ion‐induced nucleation theory makes the approximation that small ionic clusters are charged droplets whose properties equal their values for the bulk liquid, the method presented gives a nucleation rate in the form of a summation over discrete cluster properties. The summation converges rapidly around the critical cluster size, which is often as small as a few atoms. This approach allows the direct utilization of experimental and/or computational data for cluster properties. Sample calculations are presented for nucleation of silicon particles via condensation of neutral silicon vapor onto silicon anions for conditions representative of microelectronics processing plasmas. As the temperature increases the predicted nucleation rates show a transition from the collision‐limited regime to the condensation–evaporation regime, where nucleation rates drop sharply with temperature. The value of the temperature where this occurs depends on the condensible vapor concentration. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Anionic clusters in dusty hydrocarbon and silane plasmas

Ch. Hollenstein, W. Schwarzenbach, A. A. Howling, C. Courteille, J.‐L. Dorier, and L. Sansonnens

J. Vac. Sci. Technol. A 14, 535 (1996); http://dx.doi.org/10.1116/1.580140 (5 pages) | Cited 34 times

Full Text: | Download PDF

Show Abstract
Measurements of anions and cations are reported for hydrocarbon and silane radio frequency capacitive glow discharges. Series of anions were observed by quadrupole mass spectrometry using power‐modulated plasmas, and their structures are interpreted from the form of the mass spectra. Various experiments in silane plasmas show that anion confinement results in particles and conversely, anion detrapping can inhibit particle formation. In contrast, the polymerized neutral flux magnitudes, mass spectra and dynamics are independent of the powder formation. Powder is known to form readily in deposition plasmas containing electronegative free radicals, and the general role of anions in particle formation is discussed in the light of these experiments. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.80.Pi High-frequency and RF discharges
52.70.Nc Particle measurements
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Growth processes of particles in high frequency silane plasmas

Yukio Watanabe, Masaharu Shiratani, Hiroharu Kawasaki, Sanjay Singh, Tsuyoshi Fukuzawa, Yoshio Ueda, and Hiroshi Ohkura

J. Vac. Sci. Technol. A 14, 540 (1996); http://dx.doi.org/10.1116/1.580141 (6 pages) | Cited 26 times

Full Text: | Download PDF

Show Abstract
Growth processes of particles in high frequency silane plasmas are studied as a parameter of discharge frequency (3.5–28 MHz) or by modulating the amplitude of discharge voltage (125–275 V). Except for the 28 MHz case, particles tend to grow through three phases of nucleation and subsequent initial growth, rapid growth, and growth saturation. A detailed study for 6.5 MHz explains the following features: morphology of particles shows that coagulation of particles plays a crucial role in the rapid growth phase; a coagulation rate of 200 s−1 observed in the rapid growth phase is extremely high compared to a thermal collision rate of 5 s−1 between particles; coagulation almost stops when decreasing the discharge power by about one‐fourth at the middle of the rapid growth phase; two size groups of particles with narrow size dispersions coexist during and after the rapid growth phase. For 28 MHz, while, as compared to 6.5 MHz, particles appear early after the initiation of discharge and their density is high by about two orders, their growth rate in the subsequent phase is quite low. To properly explain most rapid growth features, a model, taking into account coagulation between oppositely charged particles, is proposed. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.80.Pi High-frequency and RF discharges

In situ infrared absorption spectroscopy of dusty plasmas

G. M. W. Kroesen, J. H. W. G. den Boer, L. Boufendi, F. Vivet, M. Khouli, A. Bouchoule, and F. J. de Hoog

J. Vac. Sci. Technol. A 14, 546 (1996); http://dx.doi.org/10.1116/1.580142 (4 pages) | Cited 10 times

Full Text: | Download PDF

Show Abstract
In situ, time‐resolved Fourier transform infrared spectroscopy was used to study particulate formation in rf discharges in mixtures of silane, argon, and nitrogen. The spectra were taken at a maximum rate of 20 Hz. The discharge conditions were chosen such that previous calibrations of the time evolutions of particle size and density could be used. The measurements indicate that the onset of the solid‐state vibrational absorptions of the SiH and SiH2 bands only takes place after the nucleation and coagulation phase have finished; it coincides with the previously predicted start of the deposition of amorphous hydrogenated silicon on the particles. The dissociation of the silane feed gas is found to be in the range of 30%, and its time development suggests that also the large‐scale dissociation of silane only starts after the coagulation phase. This is in agreement with previously observed trends for the electron temperature. If silicon partilces are grown in the plasma, and the silane flow is stopped, the Si particles stay trapped in the glow. The infrared measurements, however, show that they almost completely oxidize: the SiH/SiH2 vibrations disappear and a strong SiO vibration appears. If nitrogen gas is allowed into the plasma, the SiO vibration is replaced by a SiN vibration. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Pi High-frequency and RF discharges

Particle formation rates in sulfur hexafluoride plasma etching of silicon

Mary P. Garrity, Thomas W. Peterson, and John F. O’Hanlon

J. Vac. Sci. Technol. A 14, 550 (1996); http://dx.doi.org/10.1116/1.580143 (6 pages) | Cited 6 times

Full Text: | Download PDF

Show Abstract
Particle formation during low pressure SF6/argon etching of silicon in a single wafer parallel plate reactor is studied. Particles are extracted from the exhaust and collected on the wafer. Particle composition and morphology depend on plasma power, etch time, gas composition, and pressure. Primary particles of tens of nm in diameter and spherical and chain aggregates as large as 5 μm are observed. Critical powers and etch times are required for the formation of these aggregates. The presence of major gas phase species is determined using mass spectrometry and optical emission spectroscopy. Mechanisms for describing the formation processes of particles are presented, including gas phase precursor formation, nucleation, and coagulation. Precursor formation is determined from plasma‐dependent, homogeneous, gas‐phase reactions and etch product distributions predicted from electrical and etch rate measurements of the plasma. Dissociation of SF6 into lower molecular weight SFx species and unsaturated SiFex species is primarily responsible for initial particle formation. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
81.65.Cf Surface cleaning, etching, patterning

Dust formation and charging in an Ar/SiH4 radio‐frequency discharge

E. Stoffels, W. W. Stoffels, G. M. W. Kroesen, and F. J. de Hoog

J. Vac. Sci. Technol. A 14, 556 (1996); http://dx.doi.org/10.1116/1.580144 (6 pages) | Cited 20 times

Full Text: | Download PDF

Show Abstract
The formation and charging of submicrometer dust particles in a low pressure argon/silane radio‐frequency (rf) discharge was studied using laser‐induced photodetachment in combination with a microwave resonance technique. This method allows a measurement of the spatially averaged electron density, the spatially resolved negative ion density, and/or the charge on small clusters in the plasma as a function of time during particle formation. The loss frequency of photodetached electrons yields information about the recharging of small clusters. During the first second after plasma ignition dust particles are formed. Simultaneously, the electron density decreases from about 2×1015 m−3 to about 4×1014 m−3. In the first 10 ms after discharge ignition, charged particles are not present in the plasma and the photodetachment experiment gives a negative ion density of 4×1015 m−3. During the first 50 ms after plasma ignition, nanocrystallites are formed, which is reflected by a strong increase of the loss frequency of photodetached electrons. After 50 ms the particles start to coalesce and acquire a negative charge, which results in a strong increase of the photodetachment signal. After 1 s of plasma operation, the charge density on particles is about 8×1016 m−3. The photodetachment signal decreases with the gas flow rate, indicating that the clusters are expelled from the plasma by the gas flow. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.80.Pi High-frequency and RF discharges
52.70.-m Plasma diagnostic techniques and instrumentation

A model for transport and agglomeration of particles in reactive ion etching plasma reactors

Fred Y. Huang, Helen H. Hwang, and Mark J. Kushner

J. Vac. Sci. Technol. A 14, 562 (1996); http://dx.doi.org/10.1116/1.580145 (5 pages) | Cited 12 times

Full Text: | Download PDF

Show Abstract
Dust particle contamination of wafers in reactive ion etching (RIE) plasma tools is a continuing concern in the microelectronics industry. It is common to find that particles collected on surfaces or downstream of the etch chamber are agglomerates of smaller monodisperse spherical particles. These observations, and the fact that the forces which govern the transport and trapping of particles are partly determined by their size, place importance on understanding particle growth and agglomeration mechanisms. Since individual particles in plasma etching tools are negatively charged, their agglomeration is problematic since the particles must obtain sufficient kinetic energy to overcome their mutual electrostatic repulsion. In this article, we discuss results from a model for particle agglomeration in RIE plasma tools with which we address the transport of particles and interparticle collisions resulting in agglomeration. These results indicate that the rate and extent of particle agglomeration depend on the particle density, plasma power deposition, and, to a lesser degree, gas flow. The dependence of agglomeration on rf power results from the fact that the kinetic energy of a dust particle is largely determined by its acceleration by ion drag forces. Significant agglomeration may occur in particle traps where the particle density is large. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Production of nanometric particles in radio frequency glow discharges in mixtures of silane and methane

E. Bertran, J. Costa, G. Viera, and R. Q. Zhang

J. Vac. Sci. Technol. A 14, 567 (1996); http://dx.doi.org/10.1116/1.580146 (5 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
The formation of silicon particles in rf glow discharges has attracted attention due to their effect as a contaminant during film deposition or etching. However, silicon and silicon alloy powders produced by plasma‐enhanced chemical vapor deposition (PECVD) are promising new materials for sintering ceramics, for making nanoscale filters, or for supporting catalytic surfaces. Common characteristics of these powders are their high purity and the easy control of their stoichiometry through the composition of the precursor gas mixture. Plasma parameters also influence their structure. Nanometric powders of silicon–carbon alloys exhibiting microstructural properties such as large hydrogen content and high surface/volume ratio have been produced in a PECVD reactor using mixtures of silane and methane at low pressure (<1 Torr) and low frequency square‐wave modulated rf power (13.56 MHz). The a‐Si1−xCx:H powders were obtained from different precursor gas mixtures, from R=0.05 to R=9, where R=[SiH4]/([SiH4]+[CH4]). The structure of the a‐Si1−xCx:H powder was analyzed by several techniques. The particles appeared agglomerated, with a wide size distribution between 5 and 100 nm. The silane/methane gas mixture determined the vibrational features of these powders in the infrared. Silicon–hydrogen groups were present for every gas composition, whereas carbon–hydrogen and silicon–carbon bonds appeared in methane‐rich mixtures (R<0.6). The thermal desorption of hydrogen revealed two main evolutions at about 375 and 660 °C that were ascribed to hydrogen bonded to silicon and carbon, respectively. The estimated hydrogen atom concentration in the sample was about 50%. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.80.Pi High-frequency and RF discharges
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Electrical characterization and modeling of a dust forming plasma in a radio frequency discharge

L. Boufendi, A. Bouchoule, and T. Hbid

J. Vac. Sci. Technol. A 14, 572 (1996); http://dx.doi.org/10.1116/1.580147 (5 pages) | Cited 27 times

Full Text: | Download PDF

Show Abstract
In this article we focus on the time evolution of macroscopic and microscopic properties of a dust forming plasma in a silane–argon low pressure radio frequency (rf) discharge. The time evolution of electron density, ion density, dust particle concentration, and the current density were recorded in a low pressure (0.1 Torr) rf Ar–SiH4 discharge. From these data and optical emission spectroscopy simultaneous measurements, the time evolution of the electron mean energy and the particle mean charge are determined. Together with previous experimental data concerning the nucleation and growth of dust particles, a complete experimental set of microscopic and macroscopic data is available and it is compared to a theoretical model including both particle growth and dusty discharge parameters. A clear representation of this closely coupled time evolution of the particles’ formation and plasma properties is given. It includes the nucleation and coagulation phenomena for particles, and the strong increase of the rf electric field in the plasma volume and the increase of the excitation rates of electrons. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.80.Pi High-frequency and RF discharges
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Synthesis of silicon nitride particles in pulsed radio frequency plasmas

R. J. Buss and S. V. Babu

J. Vac. Sci. Technol. A 14, 577 (1996); http://dx.doi.org/10.1116/1.580148 (5 pages) | Cited 9 times

Full Text: | Download PDF

Show Abstract
Silicon nitride (hydrogenated) particles are synthesized using a pulsed 13.56 MHz glow discharge. The plasma is modulated with a square‐wave on/off cycle of varying period to study the growth kinetics. In situ laser light scattering and ex situ particle analysis are used to study the nucleation and growth. For SiH4/Ar and SiH4/NH 3 plasmas, an initial very rapid growth phase is followed by slower growth, approaching the rate of thin film deposition on adjacent flat surfaces. The average particle size can be controlled in the 10–100 nm range by adjusting the plasma‐on time. The size dispersion of the particles is large and is consistent with a process of continuous nucleation during the plasma‐on period. The large polydispersity is also reported for silicon particles from silane and differs from that reported in other laboratories. The silicon nitride particle morphology is compared to that of silicon and silicon carbide particles generated by the same technique. Whereas Si particles appear as rough clusters of smaller subunits, the SiC particles are smooth spheres, and the Si 3N4 particles are smooth but nonspherical. Postplasma oxidation kinetics of the particles are studied with Fourier transform infrared spectra and are consistent with a hydrolysis mechanism proposed in earlier work with continuous plasmas. Heat treatment of the powder in an ammonia atmosphere results in the elimination of hydrogen, rendering the silicon nitride resistant to atmospheric oxidation. © 1996 American Vacuum Society
Show PACS
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.25.Vy Impurities in plasmas
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.20.-n Methods of materials synthesis and materials processing

Particle beam mass spectrometer measurements of particle formation during low pressure chemical vapor deposition of polysilicon and SiO2 films

Peter H. McMurry, Sandeep Nijhawan, Nagaraja Rao, Paul Ziemann, David B. Kittelson, and Stephen Campbell

J. Vac. Sci. Technol. A 14, 582 (1996); http://dx.doi.org/10.1116/1.580149 (6 pages) | Cited 5 times

Full Text: | Download PDF

Show Abstract
We have recently built a particle beam mass spectrometer (PBMS) for measuring ultrafine particle size distributions (0.005–0.25 μm) at low pressures (≳100 mTorr). The PBMS is being used to study nucleation and growth in low pressure chemical vapor deposition processes relevant to the production of semiconductor devices. In this article, the function and performance of the PBMS is summarized, and results of measurements made while depositing polysilicon and silicon dioxide films in tube furnaces are discussed. Measurements made during deposition of polysilicon films showed that there was a critical reactor pressure below which particles were not present; this critical pressure varied in proportion to the residence time in the reactor, and was insensitive to reactor temperature. Above the critical pressure, however, the concentration of particles produced was sensitive to reactor temperature. The average particle size was in the 0.003–0.03‐μm‐diam range, with concentrations of ∼104 cm−3. In contrast, particles produced during the deposition of oxide films in a low‐temperature oxide (LTO) furnace were considerably larger (0.1–0.3 μm) and were present at lower concentrations (∼103 cm−3). These differences suggest that the chemical mechanisms of particle formation and growth in the two systems are quite different. Simultaneous measurements of particle accumulation on witness wafers during the LTO experiments showed a reasonable correlation with PBMS data, thereby illustrating the relevance of PBMS measurements to device fabrication. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.70.Nc Particle measurements
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Sz Deposition technology

Detection of dust particles in the plasma by laser‐induced heating

W. W. Stoffels, E. Stoffels, G. M. W. Kroesen, and F. J. de Hoog

J. Vac. Sci. Technol. A 14, 588 (1996); http://dx.doi.org/10.1116/1.580150 (7 pages) | Cited 12 times

Full Text: | Download PDF

Show Abstract
Heating of dust particles suspended in a low pressure discharge by means of a high power pulsed laser was analyzed. A detailed model of particle heating and thermal decomposition was developed and experimentally verified using 1 μm Teflon‐like particles in a radio‐frequency argon discharge. Laser‐induced heating results in blackbody‐like emission from the particles. This radiation can be easily recorded and a particle temperature of about 3500 K is determined by fitting the emission spectra. From the model it follows that the time resolved emission intensity gives valuable information about the particles: the time delay between the onset of the laser pulse and the blackbody‐like emission corresponds to the heating time of the clusters and is dependent on their size. Moreover, the absolute emission intensity is proportional to the particle density. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Pi High-frequency and RF discharges

In situ characterization of the transient behavior of particles in low pressure plasmas

Ursula I. Schmidt and David B. Graves

J. Vac. Sci. Technol. A 14, 595 (1996); http://dx.doi.org/10.1116/1.580151 (8 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
Contamination due to plasma‐generated particles is one of the major issues affecting the yield loss in microelectronics fabrication. Laser light scattering performed in situ during the process provides important information about particle distributions both spatially resolved and as a function of time. It is therefore well suited for the investigation of the transient behavior of process‐generated particles that can influence the performance of etching or deposition plasmas. The present light scattering system allows the quantitative determination of particle size and number density by detecting the scattering intensity at two separate angles (angular dissymmetry) and/or at two different polarization states (polarization dissymmetry), respectively. A special calibration procedure is required in order to obtain quantitative results for particle size and number density. Based on this analysis, we report the temporal evolution of the spatial distribution of aluminum particles in an argon discharge. We examine the transition from a continuous cloud of particles filling the entire interelectrode gap to a narrow band of intense scattering near the grounded electrode. Other changes of light scattering patterns with time have been observed under other conditions. The implications of these observations in terms of particle generation and evolution in gas discharge plasmas are discussed. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.-s Electric discharges
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

In situ polarization‐sensitive laser‐light‐scattering method for simultaneous measurements of two‐dimensional spatial size and density distributions of particles in plasmas

Masaharu Shiratani, Hiroharu Kawasaki, Tsuyoshi Fukuzawa, and Yukio Watanabe

J. Vac. Sci. Technol. A 14, 603 (1996); http://dx.doi.org/10.1116/1.580152 (5 pages) | Cited 14 times

Full Text: | Download PDF

Show Abstract
An in situ polarization‐sensitive laser‐light‐scattering (PSLLS) method is developed to measure simultaneously two‐dimensional spatial distributions of size and density of particles in plasmas, in order to reveal growth processes and behavior of particles over a discharge space. The system developed can view the whole discharge area of 50×200 mm2 illuminated by a sheet laser beam with a spatial resolution of 2×2×2 mm3 and a time resolution of 33 ms, and measure particles larger than 50 nm in size and greater than 106 cm−3 in density. Using the PSLLS method, it is found that particles formed in radio frequency silane plasmas initially appear principally in an annular region around the plasma/sheath boundary near the powered electrode. Moreover, larger particles tend to reside nearer to the powered electrode about 10 mm off the discharge‐column axis. The region occupied by particles spreads axially toward the grounded electrode (downstream region) and also radially toward both the discharge‐column axis and the discharge wall, and then particles flow out of the discharge space with a gas flow. © 1996 American Vacuum Society
Show PACS
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Vy Impurities in plasmas
52.80.Hc Glow; corona

Dynamic laser light scattering studies of dusty plasmas in the Gaseous Electronics Conference Reference Cell

H. M. Anderson and S. B. Radovanov

J. Vac. Sci. Technol. A 14, 608 (1996); http://dx.doi.org/10.1116/1.580153 (7 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
Particle generation has been studied during reactive ion etching of oxide wafers in CF4/CHF3 plasmas using the Gaseous Electronics Conference Reference Cell. Under certain discharge process conditions, copious amounts of submicron particles form due to plasma interactions with the oxide substrate. Particles were observed in situ by laser light scattering and dynamic laser light scattering (DLLS). DLLS can be used to determine information about particle size, motion, and growth dynamics. DLSS measurements show process‐induced dust particles confined in an electrostatic trap exhibit low‐frequency oscillatory motion consistent with charge‐density‐wave motion. These results are also consistent with the plasma dust particles forming a strongly coupled Coulomb liquid phase. © 1996 American Vacuum Society
Show PACS
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Vy Impurities in plasmas
81.65.Cf Surface cleaning, etching, patterning

Production and control of K–C60 plasma for material processing

T. Hirata, R. Hatakeyama, T. Mieno, and N. Sato

J. Vac. Sci. Technol. A 14, 615 (1996); http://dx.doi.org/10.1116/1.580154 (4 pages) | Cited 6 times

Full Text: | Download PDF

Show Abstract
An ultrafine‐particle plasma including large negative fullerene ions is produced by introducing fullerene particles into a low‐temperature (≊0.2 eV) potassium plasma column confined by a strong axial magnetic field. The density ratio of the negative fullerene to positive potassium ions is controlled by changing the oven temperature for fullerene sublimation and the plasma density being varied in the range from 0 to 0.97 in the central region of the plasma cross section. Since the electrons are well confined in the central region, the ratio increases radially and is more than 0.9999 in the radial edge region. A thin film consisting of the potassium and fullerene particles is formed on a metal end plate which terminates the plasma column. Depending on the end plate potential and radial position, the film is verified to contain metal‐doped fullerenes with the potassium atom in the endohedral cavity, which are formed as a result of the potassium‐atom insertion into the stable cage of fullerene particles. © 1996 American Vacuum Society
Show PACS
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.ub Fullerenes and related materials
52.80.-s Electric discharges

The dust direct current self‐bias potential in a time varying plasma sheath

Frank Melandsø, Tore Nitter, Torsten Aslaksen, and Ove Havnes

J. Vac. Sci. Technol. A 14, 619 (1996); http://dx.doi.org/10.1116/1.580155 (5 pages) | Cited 9 times

Full Text: | Download PDF

Show Abstract
We introduce an important physical effect, namely, the response of the dust particle charge to an oscillating electric field in a plasma sheath. The ac field may lower the average dust potential well below the corresponding floating potential Uf in a dc sheath. The resulting dust potential will be called the dust dc self‐bias potential Udc and is generally a sensitive function of the ac potential amplitude and of the ratio ωch/ω between the so‐called dust charging frequency ωch and the ac frequency ω. The difference between Udc and Uf maximizes for ωch≪ω and approaches 0 for ωch≫ω. We propose that the dust dc self‐bias effect is important in all plasmas having a rapid potential variation and always has to be taken into account when calculating the charge and the force on dust particles in such plasmas. Since levitation of dust particles above surfaces normally requires negative dust particles, the dust dc self‐bias effect may explain why some experiments indicate that levitation of dust particles is easier in rf discharges than in dc discharges. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.40.Hf Plasma-material interactions; boundary layer effects
52.80.-s Electric discharges

Stochastic charge fluctuations in dusty plasmas

Themis Matsoukas, Marc Russell, and Matthew Smith

J. Vac. Sci. Technol. A 14, 624 (1996); http://dx.doi.org/10.1116/1.580156 (7 pages) | Cited 41 times

Full Text: | Download PDF

Show Abstract
We consider the stochastic properties of charge fluctuations of noninteracting particles surrounded by a stationary, undisturbed plasma of electrons and singly charged positive ions. For unscreened Coulomb interaction in the orbit–motion limit the mean particle charge and the variance of the fluctuations are proportional to the particle size. The result applies to both Maxwellian and non‐Maxwellian electrons as well as to charging by ion winds. When the polarizability of the particle is included in the electrostatic interaction, both the ion and electron currents to the particle increase and the mean particle charge becomes more negative. Except for particles in the low nanometer range, the effect of the polarizability can be neglected at the electron temperatures encountered in typical plasmas. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.25.Gj Fluctuation and chaos phenomena

Ion‐dust streaming instability in processing plasmas

M. Rosenberg

J. Vac. Sci. Technol. A 14, 631 (1996); http://dx.doi.org/10.1116/1.580157 (3 pages) | Cited 41 times

Full Text: | Download PDF

Show Abstract
An ion‐dust streaming instability is investigated for conditions representative of plasma sheath interface regions where dust grains are observed to be present in processing plasmas. Kinetic theory is used, and the effects of collisions of charged particles with neutrals is retained. It is found that an instability with growth rate of the order of the dust plasma frequency may be driven by the drift of ions relative to charged dust. Possible implication for plasma etching is briefly discussed. © 1996 American Vacuum Society
Show PACS
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.25.Vy Impurities in plasmas
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.40.Hf Plasma-material interactions; boundary layer effects

Particle trapping, transport, and charge in capacitively and inductively coupled argon plasmas in a Gaseous Electronics Conference Reference Cell

S. M. Collins, D. A. Brown, J. F. O’Hanlon, and R. N. Carlile

J. Vac. Sci. Technol. A 14, 634 (1996); http://dx.doi.org/10.1116/1.580158 (5 pages) | Cited 6 times

Full Text: | Download PDF

Show Abstract
Particle trapping has been observed for both a capacitively coupled and an inductively coupled Gaseous Electronics Conference Reference Cell. Particles in the system were formed by introducing 10% CCl2F2 into an argon discharge for 5–10 min and sputtering the resulting film during argon‐only experiments. The particles generated were 200–600 nm in diameter. Particle transport was observed in the postplasma regime for both capacitively and inductively coupled cases. For the capacitively coupled plasma, particles of positive, negative and neutral charge were found during the postplasma and shown to be affected by the presence of a dc field during the postplasma period. The charge on these particles was determined to be between 1.4 and 12.4 electron charges based on a study of particle motion. This compares to a theoretical value of 800–2600 while the plasma is ignited. For the inductively coupled plasma both a low density mode and a high density mode were observed, being distinguished by a sudden increase in the emission from the plasma as rf power to the inductive coil was increased. In the high density mode of the inductively coupled plasma, the particle cloud was observed to reside less than a millimeter from the powered electrode as the high density plasma mode was established. This was distinguished from a trap height of 4–7 mm for the capacitively coupled plasma which corresponds to the sheath thickness. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.80.Pi High-frequency and RF discharges
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.40.Hf Plasma-material interactions; boundary layer effects

Mapping of radio frequency plasma potential throughout a particle trapping region using an emissive probe

Jungwon Kang, Robert N. Carlile, John F. O’Hanlon, and Sean M. Collins

J. Vac. Sci. Technol. A 14, 639 (1996); http://dx.doi.org/10.1116/1.580159 (5 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
This article describes the use of an emissive probe to map the time‐invariant plasma potential in a rf generated plasma in a GEC Reference Cell. The mapping has been done throughout a region expected to trap contamination particles for four different geometric configurations of materials on the powered electrode of the GEC Cell. For one case, there is a potential maximum which is a trap for negatively charged particles. For the other three cases, trapping can occur if a second force besides the electrostatic force is present. We postulate that this is the ion drag force. When particles are present in the system, the resulting particle clouds are observed using laser light scattering, and are superimposed of the maps. These clouds occur just where one would expect them to, given the electromagnetic force configuration exhibited by the maps plus the supposition of the existence of an ion drag force. It is shown that, at the location of a cloud, the ion drag force is of the right magnitude relative to the electrostatic force to permit trapping of particles. © 1996 American Vacuum Society
Show PACS
52.70.Ds Electric and magnetic measurements
52.25.Vy Impurities in plasmas
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.40.Hf Plasma-material interactions; boundary layer effects

Cooling by dust in levitation experiments and its effect on dust cloud equilibrium profiles

A. Brattli and O. Havnes

J. Vac. Sci. Technol. A 14, 644 (1996); http://dx.doi.org/10.1116/1.580160 (5 pages) | Cited 5 times

Full Text: | Download PDF

Show Abstract
The thermophoretic force on dust particles is caused by a temperature gradient in the background gas. This force can be important in experiments or production processes and in other environments where dust occurs. We discuss the local cooling of the neutral gas by levitated dust clouds and how this affects the temperature gradient and the equilibrium dust density profile. Dust is heated through neutral gas particle impacts while it loses energy by either reemitting impacting particles or by thermal radiation at the particle temperature. The dust particle temperature can be considerably lower than that of the ambient gas and can therefore lead to a local cooling of the gas. Changes in the temperature gradient and the thermophoretic force can be large enough to affect the equilibrium density profile of levitated dust. We find that the equilibrium profile with the thermophoretic force calculated from the temperature profile without dust cooling is closer to the electrode but with much the same shape as the profile calculated without the thermophoretic force. The profile where local cooling is included in the thermophoretic force is more compressed compared to the profile without local cooling and it often has a pronounced peak closest to the electrode. Since radiation cooling of a dust particle is proportional to the fourth power of its temperature, the cooling effect is largest at comparatively high gas (and dust) temperatures. We show examples of levitated dust layer profiles with and without the dust cooling effect. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.40.Hf Plasma-material interactions; boundary layer effects
51.10.+y Kinetic and transport theory of gases

Particle contamination characterization in a helicon plasma etching tool

Gary S. Selwyn and Andrew D. Bailey

J. Vac. Sci. Technol. A 14, 649 (1996); http://dx.doi.org/10.1116/1.580161 (6 pages) | Cited 5 times

Full Text: | Download PDF

Show Abstract
There is much current interest regarding the formation, transport, charging, and behavior of particulate contamination in high density plasma tools, as these tools are generally regarded as the future of plasma processing for the semiconductor industry due to the need to obtain greater anisotropy and faster process rates concurrently with reduced surface damage. Because of the low pressures in which these tools typically operate (<5 mTorr), the likelihood of homogeneous nucleation processes leading to particle contamination problems is low. Similarly, the effect of ion drag is also expected to be greater, possibly leading to reduced particle trapping effects. Yet, few laser light scatter studies have been performed in high density plasma tools.
This study is the first in situ characterization of particle contamination in a plasma etching tool using a helicon source. It was performed during normal process conditions for poly‐Si etching and also under intentionally altered process conditions designed to produce particles. The effect of a bipolar, electrostatic chuck on wafer particle deposition was also investigated. Results showed that under normal process conditions, few particles were deposited onto the wafer; those that were observed were attributed to thermal stress effects resulting in flaking of deposition films, probably on the quartz bell jar of the source. Results also suggest that the electrostatic chuck increased particle deposition when the clamping voltage was applied. No trapping was observed over the wafer or near the source. However, some trapped particles were observed below the wafer platform. These particles showed unusual motion, but probably have minimal effect on wafer contamination. The issues pertaining to particle contamination formation and transport in this high density plasma tool are discussed. © 1996 American Vacuum Society
Show PACS
52.25.Vy Impurities in plasmas
52.80.Pi High-frequency and RF discharges
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning

Experimental evidence for nanoparticle deposition in continuous argon–silane plasmas: Effects of silicon nanoparticles on film properties

Pere Roca i Cabarrocas, Patrick Gay, and Aomar Hadjadj

J. Vac. Sci. Technol. A 14, 655 (1996); http://dx.doi.org/10.1116/1.580162 (5 pages) | Cited 29 times

Full Text: | Download PDF