In situ infrared spectroscopic study on the role of surface hydrides and fluorides in the silicon chemical vapor deposition process

The role of surface hydrides and fluorides in the Si chemical vapor deposition (CVD) process was studied by in situ Fourier transform infrared spectroscopy using a porous silicon film as the substrate. Hydrides protect the silicon surface from oxidation until they are desorbed at 350–400 °C. However, the hydrides are replaced almost completely by surface fluorides when SiH₂F₂ is used as a reactant in the CVD process at temperatures above 400 °C. The surface is then etched due to a reaction between the fluorides and the surface silicon. When the process temperature is lowered to 250 °C, the surface is covered by both hydrides and fluorides, and a silicon film is deposited.