Hideki Matsumura

Study on catalytic chemical vapor deposition method to prepare hydrogenated amorphous silicon

A new type of thermal chemical vapor deposition (CVD) method is presented. In the method, material gases are decomposed by catalytic or pyrolytic reaction with a heated catalyzer, so that films can be deposited at temperatures less than 300u2009°C without any plasma or photochemical excitation, and the method is particularly called ‘‘Catalytic‐CVD.’’ Hydrogenated amorphous silicon films are deposited by this method, and the deposition mechanism is also investigated. It is found that device‐quality amorphous silicon films can be obtained and that inactive species, which are generated at the catalyzer and transported without gas‐phase reactions, are key species to make a high‐quality film by this method.

Silicon nitride produced by catalytic chemical vapor deposition method

The catalytic chemical vapor deposition method is applied to obtain silicon nitride insulating films usable in large‐scale integrated circuits. A N2 H4, N2 , and SiH4 gas mixture is decomposed by the catalytic or pyrolytic reaction with a heated catalyzer placed near substrates, and thus silicon nitride films are deposited at low temperatures around 300u2009°C with deposition rates higher than several hundreds A/min, without any help from plasma and photochemical excitation. It is found that the resistivity, the breakdown electric field, and also the hydrogen content of the films can be almost equivalent to those of the films deposited by the thermal chemical vapor deposition at 700u2009°C or more, and that their step coverage appears sufficient to apply them on device fabrication.

High‐quality amorphous silicon germanium produced by catalytic chemical vapor deposition

High‐quality amorphous silicon germanium (a‐SiGe:H) films are produced by a new ‘‘catalytic chemical vapor deposition (CTLu2009CVD)’’ method. In the method, a SiH4, GeH4, and H2 gas mixture is decomposed without using any plasmas or photochemical excitation, but using only the thermal or the catalytic reaction with a heated tungsten catalyzer. Photoconductive properties of CTLu2009CVD a‐SiGe:H are apparently not degraded as the Ge content increases. The photoconductivity and the photosensitivity for AM‐1 of 100 mW/cm2 are 10−5–10−4 (Ω cm)−1 and 104, respectively, even for the sample of optical band gap of 1.40–1.45 eV.

Catalytic chemical vapor deposition method to prepare high quality hydro‐fluorinated amorphous silicon

A new type of chemical vapor deposition method, named ‘‘Catalytic‐CVD’’ method, is presented. In the method, deposition gases are decomposed by catalytic or pyrolytic reaction between deposition gases and a heated catalyzer, and films are thermally grown on a substrate at temperatures lower than 300u2009°C without any help from glow discharge plasma. Hydro‐fluorinated amorphous silicon (a‐Si:F:H) films are deposited by this method using both a SiF2 and H2 gas mixture and a SiH2F2 and H2 mixture. It is found that a very high quality a‐Si:F:H film can be obtained, and for instance, that the photosensitivity for AM‐1 of 100 mW/cm2 exceeds 106 and the spin density is as low as 6×1015 cm−3.

Study on impurity diffusion in the glow-discharged hydrogenated amorphous silicon

Abstract Diffusion coefficients of impurities such as boron and antimony in hydrogenated amorphous silicon are estimated by observing the change of impurity profiles after annealing. Diffusion of electrically activated boron atoms is also experimentally studied. It is found that the diffusion coefficient of impurity depends only weakly on impurity itself, and that the diffusion coefficient and its activation energy are nearly equal to those of hydrogen. It is also suggested that electrically activated imurities diffuse as easily as non-activated ones.

Measurement of boron diffusivity in hydrogenated amorphous silicon by using nuclear reaction 10B(n,α)7Li

The method to measure boron profile by using the nuclear reaction 10B(n,α)7Li is applied to estimate the diffusivity of boron in the glow‐discharged hydrogenated amorphous–silicon (a–Si:H). It is found that the diffusivity of boron in a–Si:H is much larger than that in crystalline silicon (c–Si). For instance, it is about 2×1016 cm2/s at 330u2009°C and larger than in c–Si by twelve orders of magnitude. The activation energy of the diffusivity is also estimated to be 1.5 eV. These values are nearly equal to those of hydrogen in a–Si:H. The minimum duration, in which the characteristics of p–i–n type a–Si:H solar cells may start to change due to this boron diffusion, is roughly estimated using both boron diffusivity and its activation energy.

A new hydro-fluorinated amorphous silicon produced by using intermediate species SiF2

Abstract Intermediate species SiF 2 , mixed with H 2 , is used instead of SiF 4 as the material gas for a hydro-fluorinated amorphous silicon (a-Si:F:H). The deposition rate can be easily increased up to about 20 A/sec without apparent degradation of photo-conductive property by using intermediate species, and also, Si-F or Si-H single bond configuration becomes dominant although there apparently exist Si-H 2 or Si-F 2 higher order bonds in the film produced by using SiF 4 .

Demagnified projection printing by a new x‐ray lithographic technique using no thin‐film masks

A new x‐ray lithographic technique using no thin‐film pattern masks is presented. A pattern image is projected by utilizing the total reflection of the x ray from a pattern plate, in which a pattern picture is drawn on a thick and hard substrate. The projected image is geometrically demagnified by the sine of incident angle of the x ray. And we actually succeeded in obtaining the demagnified line and space patterns of 1.9‐μm width from the similar patterns of 210 μm by using copper Kα x ray.

High Quality Amorphous Silicon Prepared by Catalytic Chemical Vapor Deposition (CTL-CVD) Method

A new method of producing high quality hydrogenated amorphous silicon (a-Si:H) and its compound films is presented. An SiH 4 and H 2 gas mixture is decomposed without using any plasmas or photochemical excitation, but using only thermal and catalytic reactions between deposition gas and a heated tungsten catalyzer. Photoconductivity of a-Si:H films produced by, this method reaches 10 −3 (Ωcm) −1 and photosensitivity exceeds 10 5 for illumination of AM-1 light of 100 mW/cm 2 , highly efficient boron- or phosphorus-doping into the films is achieved, and also the optical band gap of the films is easily controlled without apparent degradation of the properties by adding GeH 4 gas to the deposition gas.

Catalytic chemical vapor deposition method to obtain high quality amorphous silicon and silicon-germanium

Abstract A new method to deposit amorphous films, named “Catalytic Chemical Vapor Deposition (CTL-CVD)” method, is presented. In the method, the catalytic or pyrolytic reactions between deposition gases and a heated tungsten catalyzer are utilized to lower the deposition temperatures of thermal CVD. It is found that high quality amorphous silicon and silicon-germanium films can be deposited at the substrate temperatures lower than 300 °C and with a deposition rate higher than several A/sec by this method.