Defect Reduction at the Silicon (112) Wafer Surface by Amorphization and Recrystallization

Silicon wafers oriented on (112) are the preferred substrates for deposition of mercury cadmium telluride layers by molecular beam epitaxy. Surface defects introduced during polishing of the wafers degrade the quality of the epitaxy and the performance of infrared detectors fabricated within these materials. We propose a process for reducing the density of the defects that are inherent in the silicon and induced during wafer-polishing. The new process begins by ion implantation to render the region near the wafer surface amorphous. Industry-standard chemical-mechanical polishing of the amorphous surface will yield a surface that is smooth. This layer will then be recrystallized by a high-temperature anneal. Prior to annealing, hydrogenation of the wafer will be done to suppress defect formation during recrystallization. We anticipate that improvements in the quality of the (112) silicon surface will lead to higher operability values for LWIR focal plane arrays.