Low Temperature Selective Si Epitaxy Using Si2H6 and Cl2: Investigations into Selectivity Robustness and Epitaxial Film Quality

Abstract

AbstractIn this paper, we explore selective Si epitaxy by UltraHigh Vacuum Rapid Thermal Chemical Vapor Deposition (UHV-RTCVD) using Si2H6, H2, and C12 with particular emphasis on selectivity robustness. Two key parameters considered in this study were partial pressures of Si2H6 and H2. It was found that excessive increases in either partial pressure could lead to selectivity degradation. The two mechanisms by which the observed selectivity degradation can be explained are as follows: A higher Si2H6 partial pressure provides a larger flux of Si atoms which directly influences the probability of reaching the critical nuclei size for stable nuclei formation while an increase in H2 partial pressure reduces the desorption rate of Si adatoms from the insulator surface by reducing the available Cl in the gas phase for SiC12 formation. The impact of process parameters on epitaxial defect density was also evaluated using darkfield imaging. The results clearly indicate increasing defect density upon increases in both the chlorine flow rate and the level of contamination introduced through the silicon source gas.