OPTIMIZATION OF PROCESS CONDITIONS FOR SELECTIVE SILICON EPITAXY USING DISILANE, HYDROGEN, AND CHLORINE

We have previously reported a process for low temperature selective si licon epitaxy using Si2H6, H-2, and Cl-2 in an ultrahigh vacuum rapid thermal chemical vapor deposition reactor.(1) Selective deposition imp lies that growth occurs on the Si surface but not on any of the surrou nding insulator surfaces. Using this method and process chemistry, the level of Cl species required to maintain adequate selectivity has bee n greatly reduced in comparison to SiH2Cl2-based, conventional CVD app roaches.(2,3) In this report, we have extended upon the previous work and provide information regarding the selectivity of the silicon depos ition process to variations in the growth conditions. We have investig ated the selectivity of the process to variations in disilane flow/par tial pressure, growth temperature, and system contamination. We demons trate that increases in either the Si2H6 partial pressure or flow rate , the process temperature, pr the source contamination levels can lead to selectivity degradation. In regard to the structural quality of th e selective epitaxial layers, we have observed epitaxial defects that have appeared to be a strong function of two basic conditions: the con tamination level of the process and the chlorine flow rate or chlorine partial pressure. Overall, the results in this study indicate several process conditions that can inhibit the quality of a selective silico n deposition process developed for single-wafer manufacturing.