Closed recycle CVD process for mass production of SOG-Si from MG-Si

"CVD Process with Closed Gas Recycling" is proposed for mass production of SOG-Si from MG-Si. By combining chlorosilane synthesis in the reaction of MG-Si and HCl and Si-CVD from chlorosilanes, a closed system with ideal Si conversion ratio of 100 % can be realized with little emission of chloride pollutants. Based on thermodynamic investigation, operating temperatures were set below 900 K for Si etching and above 1200 K for Si-CVD. Si etching showed time dependent natures due to the activation of Si surface, and the rate of activated surfaces was in the order of 1 /spl mu/m/min (623- 723 K. 0.9/spl times/10/sup 5/ Pa, 3.3- 10 mol% HCl/H/sub 2/). Si growth rate by CVD was also in the same order (1323- 1473 K, 0.1- 1/spl times/10/sup 5/ Pa, 0.1- 9 mol% SiHCl/sub 3//H/sub 2/ or SiCl/sub 4//H/sub 2/), which was quantitatively explained by kinetic simulations. This process can be combined with layer transfer processes to form crystalline Si thin films.