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-en hanced chemical vapor deposition (CVD) using SiF4, SiH4 and H-2 gases at a substrate temperature of 300 degrees C. Growth of the films has b een monitored by spectroscopic ellipsometry, and time resolved film co mpositions have been investigated. The film deposited with SiH4 dilute d by H-2 at a power level of 500 mW/cm(2) showed crystal fraction of 5 0%, and it increased up to 80% with addition of SiF4, although the dep osition rate decreased and the surface roughness was enhanced. These r esults suggest that preferential etching of amorphous tissue brings ab out the increase of crystalline fraction. Crystallization of the film was verified by transmission electron microscopy along with the decrea se in hydrogen content shown by the infrared absorption spectrum.