Plasma etch effects on low-temperature selective epitaxial growth of silicon

Abstract

The quality of epitaxial silicon grown on regions exposed to plasma etching using He, CHF3, and CF4 etching gases has been studied. Plasma-etch-induced surface damage leads to defects in the epilayers. Dislocation loops and precipitates at the epi/substrate interface are always observed. High-temperature prebake can further lead to microtwins and threading dislocations. The formation of defects in epilayers is attributed to the ion bombardment induced surface/subsurface defects and the reactive-ion-induced contaminants on exposed Si areas. A 900 °C grown sacrificial oxide film can efficiently remove both near-surface defects and contaminants to get a clean SiO2/Si interface, resulting in high quality Si epilayers. A 5-nm sacrificial oxide is adequate. An air exposure between several plasma etch cycles is also important in suppressing polymer accumulation on substrates.