Pre- and Postepitaxial Gettering of Oxidation and Epitaxial Stacking Faults in Silicon

Abstract

Certain gettering treatments on the back sides of wafers have been found to be effective in reducing stacking faults in Si bulk wafers. In this study results are reported for various back side, front side, and combined gettering processes on wafers used to receive epitaxial films. Focus in this investigation was on the effectiveness of gettering measures in removing defects in epitaxial films. Results of POCl3 diffusion, Ar ion implantation (I/I), abrasion, and Si3N4 deposition as back-side treatments are reported as well as As I/I and boron diffusion front-side gettering effects. These treatments were employed either in the pre- or postepitaxial deposition mode. When used in the pre-epitaxial mode all of the back-side gettering techniques were found effective in reducing oxidation stacking faults (OSF) in epi films to levels of ≤10 cm-2 as compared to nongettered levels of 100-1000 cm-2. In the post-epi application, Ar I/I was found to give moderate reduction of CSF defects. The back-side gettering techniques combined with front-side gettering used in a pre-epitaxial mode reduces epitaxial type stacking faults (SFepi) significantly and eliminates oxidation stacking faults (OSF) in the epitaxial films. Counts of SFepi were not reduced using the back-side gettering alone. The two front-side procedures were, however, found to reduce both the OSF and SFepi types. The epitaxial films deposited on the As I/I surfaces showed a factor of ten reduction in SFepi defects and OSF types were reduced even more drastically. Boron diffusions in Si reduced OSF counts to nearly zero and SFepi faults by a factor of four over nongettered samples. Some effects of pre-epitaxial and postepitaxial oxidation treatments on stacking fault counts were also investigated. Results are also reported for effectiveness of stacking fault gettering relative to initial cleaning procedures used and stacking fault counts originating from substrates. © 1981, The Electrochemical Society, Inc. All rights reserved.