Silicon tetrachloride, SiCl4, is a key chemical in the silicon chemical vapor deposition. It is used in the production of silane, SiH4. The purity of SiCl4 is essential to the production of high-quality silicon films. To eliminate trichlorosilane, SiHCl3, within the high-purity silicon tetrachloride, chlorine gas is bubbled through the liquid SiCl4
at 298 K to promote the following reaction:
SiHCl3 + Cl2 = SiCl4 + HCl
The HCl is then easily removed in a stripper, using nitrogen as the stripping gas.
To determine the mass-transfer coefficient of chlorine in liquid SiCl4, a Schmidt number is needed. Evaluate the Schmidt number for chlorine in liquid silicon tetrachloride at 298 K. Following information is available for SiCl4 at 298 K:
density = 1.47 gm/cm^3 mew = 5.2*10^-4
The diffusivity for chlorine in silicon tetrachloride can be evaluated using the Wilke-Chang equation.