Process Steps for High Quality Si-Based Epitaxial Growth at Low Temperature via RPCVD

Abstract

The key process steps for growing high-quality Si-based epitaxial films via reduced pressure chemical vapor deposition (RPCVD) are investigated herein. The quality of the epitaxial films is largely affected by the following steps in the epitaxy process: ex-situ cleaning, in-situ bake, and loading conditions such as the temperature and gaseous environment. With respect to ex-situ cleaning, dry cleaning is found to be more effective than wet cleaning in 1:200 dilute hydrofluoric acid (DHF), while wet cleaning in 1:30 DHF is the least effective. However, the best results of all are obtained via a combination of wet and dry cleaning. With respect to in-situ hydrogen bake in the presence of H-2 gas, the level of impurities is gradually decreased as the temperature increases from 700 degrees C to a maximum of 850 degrees C, at which no peaks of O and F are observed. Further, the addition of a hydrogen chloride (HCl) bake step after the H-2 bake results in effective in-situ bake even at temperatures as low as 700 degrees C. In addition, the effects of temperature and environment (vacuum or gas) at the time of loading the wafers into the process chamber are compared. Better quality epitaxial films are obtained when the samples are loaded into the process chamber at low temperature in a gaseous environment. These results indicate that the epitaxial conditions must be carefully tuned and controlled in order to achieve high-quality epitaxial growth.