Cross-sectional TEM characterization of low temperature (750-800°C) epitaxial silicon by very low pressure (6 mTorr) chemical vapor deposition with and without plasma enhancement

Abstract

Cross-sectional transmission electron microscopy (XTEM) and high resolution transmission electron microscopy (HRTEM) were used to characterize epitaxial silicon grown by chemical vapor deposition at 750–800° C. Optimum conditions for pre-deposition argon plasma sputter cleaning were found to be -100 V dc substrate bias and 2.5 W rf power for 13 minutes at 4 m Torr and 750–800° C. No dislocations were observed by XTEM in films deposited subsequent to this plasma exposure. Analysis of the epitaxial layer/substrate interface by HRTEM indicates complete lattice registration despite the presence of a discontinuous array of defects or microprecipitates. The strain field associated with these defects is approximately 13Å in width. Annealing the epitaxial layers at 1150° C inN ₂ for 4 hours led to the generation of additional defects believed to be associated with carbon and oxygen clustering. Preliminary results indicate that neither temporary (30 seconds) growth interruptions nor low power (2.5 W) plasma enhancement of thedeposition process lead to the generation of defects observable by XTEM.