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Silica films with various types of alkyl groups were grown from the liquid phase, at room temperature, using alkyl tri-alkoxy silane compounds. From Fourier transform infrared (FTIR) absorption measurements, a majority of Si-alkyl bonds in the source molecules were found to remain in the grown film, while Si-alkoxy bonds were completely removed. Electrical and thermal properties have been measured comparatively for various films having dense alkyl groups. The films with the methyl group are promising for silicon production in ultra large-scale integrated circuits (Si-ULSIs) and the film having the vinyl group for non-heat-tolerant compound-semiconductor large-scale integrated circuits (LSIs).

Based on the first result of the layer-by-layer deposition of silicon dioxide films by a cyclic exposure of water and tetra isocyanate silane, Si(NCO) 4 , new isocyanate compounds preferable to Si(NCO) 4 have been proposed for ideal layer-by-layer deposition characteristics. Preliminary results are also presented for one of the substances.

The characteristics of amorphous silicon thin-film transistors fabricated by chemical vapor deposition method is discussed in detail in conjunction with posthydrogenation. As the hydrogenation around an active interface starts, the transistor performance is abruptly improved and then does not change with further hydrogenation. A critical condition for hydrogenation for such an abrupt improvement may be accounted for based on a simple formula using a transit time of hydrogen atoms. A desirable thickness of amorphous silicon films for high performance TFT is thicker than 100 nm. In addition, it is recommended that hydrogenation is to be made at a temperature as low as possible as long as it can be possible.

Low-K silica films were grown from the liquid phase using methyl-triethoxy-silane. Physical and chemical properties were investigated together with electronic properties. The film had dense methyl groups and showed insulating characteristics even under as-grown conditions. The dielectric constant, low-field resistivity and breakdown field-strength were 3.6, 1013 Ωcm and IMV/cm, respectively, for the as-grown film. They were improved to 2.6, more than 1015 Ωcm and more than 3MV/cm, respectively, after 300°C vacuum annealing

We have successfully demonstrated chemical vapor deposition of a silica film in which some of oxygen atoms of the pure silica network are replaced to methylene (-CH 2 ,) groups. The as-deposited film was thermally unstable owing to the unwanted decomposition reaction of the methylene group with the dense H 2 O in the film. It was found that the film could be dehydrated without decomposition of the methylene group by low temperature anncaling in a XeF 2 ambient. The dehydrated film showed not only good insulating and low-k characteristics (resistivity of 10 15 Ω cm, breakdown field of 3.3 MV/cm, and k of 2.8), but also good thermal properties, such as good thermal stability and high thermal conductivity.

An organic-silica film has been proposed, where a short alkylene group is substituted for an oxygen atom in the silicon-dioxide matrix structure. This film is expected to have not only low dielectric constant but also good thermal conductivity and adhesion strength. The ab-initio molecular orbital calculation reveals that oxidation resistance is improved in the film. Preliminary experimental results are also presented.

We have studied post-hydrogenation characteristics and photo-absorption characteristics of amorphous-silicon films thermally deposited from disilane at 500°C. There is a critical post-hydrogenation temperature of about 400°C, below which both the density of hydrogen (deuterium) atoms on the surface and the activation energy of their diffusion constants are constant. Post-hydrogenation drastically enhances the decrease of the photo-absorption coefficient for photon energies less than the optical bandgap. The optimum density of hydrogen atoms introduced by post-hydrogenation was between 3 at% and 3.5 at%. The Urbach tail slope E 0 was 42 meV, i.e., about 8 meV lower than the typical value of the film deposited by plasma enhanced chemical vapor deposition (PECVD) method.