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 mum/min (623- 723 K, 0.9x10(5) Pa, 3.3- 10 mol% HCl/H-2). Si growth rate by CVD was also in the same order (1323- 1473 K, 0.1- 1x10(5) Pa, 0.1- 9 mol% SiHCl3/H-2 or SiCl4/H-2), which was quantitatively explained by kinetic simulations. This process can be combined with layer transfer processes to form crystalline Si thin films.