Different Crystal Growth Mechanisms of Si(001)-(2 x 1):H during Plasma-Enhanced Chemical Vapor Deposition of SiH3 and SiH2 Radicals: Tight-Binding Quantum Chemical Molecular Dynamics Simulations

作者：Kuwahara Takuya; Ito Hiroshi; Kawaguchi Kentaro; Higuchi Yuji; Ozawa Nobuld; Kubo Momoji^*

来源：Journal of Physical Chemistry C, 2013, 117(30): 15602-15614.

DOI：10.1021/jp4021504

We use tight-binding quantum chemical molecular dynamics to investigate the crystal growth mechanisms of H-terminated Si(001)-(2 x 1) during plasma-enhanced chemical vapor deposition of SiH3 and Sill, radicals. We find that crystal growth by SiH3 radical deposition consists of two stages: (1) the first SiH3 radical abstracts a surface-terminating H atom and produces a dangling bond, and (2) a second SiH3 radical is adsorbed on the dangling bond. Thus, at least two SiH3 radicals are required for generating a new Si Si bond. Interestingly, during SiH2 deposition, a SiH2 radical can be directly adsorbed onto a H-terminated site without H abstraction by another SiH2 radical. Thus, one SiH2 radical is sufficient for generating a new Si Si bond. This SiH2 radical crystal growth mechanism is different from the SiH3 radical mechanism. The direct adsorption process consists of a two-step chemical reaction: (1) the SiH2 radical abstracts a surface-terminating H atom and produces a dangling bond and a SiH3 radical, and (2) the SiH3 radical is adsorbed on the dangling bond. In addition, the crystal growth rate for SiH2 radicals is higher than that for SiH3 radicals, because generating one new Si Si bond requires either a single SiH2 radical or two SiH3 radicals. However, our simulations reveal that SiH2 deposition produces defective Si thin films because many dangling bonds are formed during crystal growth. Compared with SiH2 deposition, SiH3 deposition should therefore produce Si thin films of higher quality.

• 出版日期2013-8-1