Production of high-quality amorphous silicon films by evaporative silane surface decomposition

High‐quality hydrogenated amorphous silicon films (a‐Si:H) have been produced by decomposition of low‐pressure silane gas on a very hot surface with deposition on a nearby, typically 210 °C substrate. A high‐temperature tungsten filament provides the surface for heterogeneous thermal decomposition of the low‐pressure silane and subsequent evaporation of atomic silicon and hydrogen. These evaporated species (primarily) induce a‐Si:H growth on nearby substrates which are temperature controlled using a novel substrate holder. The light and dark conductivities, optical band gap, deposition rates, and light‐soaking effects of preliminary films are reported. The decomposition‐evaporation process has been examined using a mass spectrometer to directly detect the decomposition rate and the evaporated radical species. Based on this data and other information, a simplified model for the deposition process is suggested. The excellent film quality and the attributes of the deposition process make this technique, which was originally suggested by Wiessman, viable for the fast rate, large‐area deposition of a‐Si:H for solar cells and other applications.

[1]  R. Robertson,et al.  Reaction mechanism and kinetics of silane pyrolysis on a hydrogenated amorphous silicon surface , 1986 .

[2]  B. A. Scott,et al.  Low defect density amorphous hydrogenated silicon prepared by homogeneous chemical vapor deposition , 1982 .

[3]  Chuang‐Chuang Tsai,et al.  Film formation mechanisms in the plasma deposition of hydrogenated amorphous silicon , 1986 .

[4]  J. Nicholas,et al.  Reactions of carbon atoms and methyne with hydrogen and ethylene , 1967 .

[5]  R. Robertson,et al.  Mono‐ and disilicon radicals in silane and silane‐argon dc discharges , 1986 .

[6]  Michael E. Coltrin,et al.  Theoretical study of the heats of formation of Si2Hn (n = 0-6) compounds and trisilane , 1986 .

[7]  H. Guo,et al.  Properties of hydrogenated amorphous silicon prepared by biased activated reactive evaporation , 1987 .

[8]  P. Gaspar,et al.  REACTIONS OF RECOILING SILICON ATOMS WITH PHOSPHINE‐DIENE MIXTURES AND THE QUESTION OF SILYLENE INTERMEDIATES , 1978 .

[9]  R. Farrow.  The Kinetics of Silicon Deposition on Silicon by Pyrolysis of Silane A Mass Spectrometric Investigation by Molecular Beam Sampling , 1974 .

[10]  T. N. Bell,et al.  An evaluation of the kinetic data for hydrogen abstraction from silanes in the gas phase , 1978 .

[11]  Myron Strongin,et al.  a‐Si : H produced by high‐temperature thermal decomposition of silane , 1979 .

[12]  R. E. Viturro,et al.  Some properties of hydrogenated amorphous silicon produced by direct reaction of silicon and hydrogen atoms , 1986 .

[13]  G. Müller,et al.  The influence of preparation conditions on the hydrogen content of amorphous glow‐discharge silicon , 1979 .

[14]  R. Grigorovici,et al.  Optical Properties and Electronic Structure of Amorphous Germanium , 1966, 1966.

[15]  John D. Joannopoulos,et al.  The Physics of Hydrogenated Amorphous Silicon I , 1984 .

[16]  G. Moddel,et al.  Derivation of the low-energy optical-absorption spectra ofa-Si: H from photoconductivity , 1980 .

[17]  Hideki Matsumura,et al.  Catalytic Chemical Vapor Deposition (CTC–CVD) Method Producing High Quality Hydrogenated Amorphous Silicon , 1986 .

[18]  G. Cody,et al.  Exponential absorption edge in hydrogenated α-Si films , 1980 .

[19]  R. T. White,et al.  Mechanism of the silane decomposition. I. Silane loss kinetics and rate inhibition by hydrogen. II. Modeling of the silane decomposition (all stages of reaction) , 1985 .

[20]  D. Staebler,et al.  Reversible conductivity changes in discharge‐produced amorphous Si , 1977 .

[21]  P. Skell,et al.  Chemistry of atomic silicon. III. Reactions of electron bombardment produced silicon vapor with silanes , 1972 .

[22]  B. Watts,et al.  A study of nucleation in chemically grown epitaxial silicon films using molecular beam techniques , 1969 .

[23]  W. Fite,et al.  Reflection and Dissociation of H2 on Tungsten , 1962 .

[24]  J. R. Pierce,et al.  Scientific foundations of vacuum technique , 1949 .

[25]  H. Matsumura.  High‐quality amorphous silicon germanium produced by catalytic chemical vapor deposition , 1987 .

[26]  D. Adler,et al.  Laser‐induced chemical vapor deposition of hydrogenated amorphous silicon. II. Film properties , 1987 .