In situ ellipsometric monitoring of the growth of polycrystalline silicon thin films by RF plasma chemical vapor deposition

Polycrystalline silicon thin films have been deposited by RF plasma-enhanced chemical vapor deposition (CVD) using SiF4, SiH4 and H2 gases at a substrate temperature of 300 °C. Growth of the films has been monitored by spectroscopic ellipsometry, and time resolved film compositions have been investigated. The film deposited with SiH4 diluted by H2 at a power level of 500 mW/cm2 showed crystal fraction of 50%, and it increased up to 80% with addition of SiF4, although the deposition rate decreased and the surface roughness was enhanced. These results suggest that preferential etching of amorphous tissue brings about the increase of crystalline fraction. Crystallization of the film was verified by transmission electron microscopy along with the decrease in hydrogen content shown by the infrared absorption spectrum.