ガラス基板上に低温成長させた多結晶シリコン薄膜の構造に与えるハロゲンの影響

抄録

Polycrystalline silicon thin films were fabricated by VHF (100-144MHz) plasma enhanced chemical vapor deposition. Three different source materials were used to grow the films on glass substrates: (1) SiH₂Cl₂/H₂, (2) SiF₄/H₂ and (3) SiH₄/H₂ mixing gases. It was found that the gas mixing ratio where crystal silicon grows strongly depends on the selection of source gas: i.e., crystal growth occurred at mixing ratios (SiF₄/H₂) smaller than 30/10 sccm while the crystal growth in SiH₄/H₂ system required much smaller mixing ratios, such as ≤1/50sccm. Microstructures of the films were also strongly influenced by the source material. (220) orientation structures were easily obtained when SiF₄, SiH₂Cl₂ or B₂H₆ were used, compared to SiH₄. In addition, (400) preferentially oriented film grew on glass when the film was grown at a gas mixing ratio of SiF₄/H₂=30/10sccm and a substrate temperature of 200°C. Chlorinated source gases including SiH_nCl_m (n+m=4) are also expected to produce (400) oriented growth.