The Surface Chemistry of Si/Ge Deposition

Abstract

ABSTRACTReaction processes leading to the deposition of Si and Ge epilayers have been delineated using a combination of surface spectroscopies. The dissociative adsorption of disilane and digermane has been investigated on the Ge(111) surface using multiple internal reflection infrared spectroscopy (MIRIRS). Molecular adsorption of Si2H6 and Ge2H6 occurs for adsorption below 150K. Molecular and dissociative adsorption are competitive processes at 110-140K. Dissociative adsorption of Si2H6 and Ge2H6 occurs above 150K. Trihydride formation (SiH3 and GeH3) is favored near 150-200K, while Si-H and Ge-H bond scission becomes significant above 200K. Di- and trihydrides are dominant below 300K, while the monohydrides are most prevalent above 300K. Decomposition of all surface hydrides occurs by 600K. On the Si(100) surface, digermane adsorption leads to the deposition of a Ge overlayer. Hydrogen desorption from the Ge/Si(100) surface is strongly altered with respect to the clean Si surface. The observed desorption behavior has important consequence on the low temperature deposition of Sil-xGex by thermal CVD.