REDUCTION OF DEFECTS IN SOS MATERIAL BY ION IMPLANTATION OF GERMANIUM FOR APPLICATION TO BIPOLAR TECHNOLOGY

SUBSTANTIAL REDUCTION OF DEFECTS IN SILICON-ON-SAPPHIRE (SOS) MATERIAL IS REQUIRED TO BROADEN THE RANGE OF APPLICATIONS TO INCLUDE BIPOLAR DEVICES. DURING THE PAST FEW YEARS, IT HAS BEEN SHOWN THAT REGIONAL AMORPHIZATION OF THE SILICON LAYER BY IMPLANTATION OF SILICON AND SOLID PHASE EPITAXY REGROWTH CAN REDUCE THE DEFECT DENSITY IN THE SI OVERLAYER OF SOS MATERIAL. HOWEVER, ONE OBSTACLE TO LARGE SCALE USE OF THIS PROCESS IS THAT IT REQUIRES IMPLANTATION OF SI-29 IONS TO AVOID INTRODUCTION OF CONTAMINANTS. ANOTHER OBSTACLE IS THAT THE WAFERS MUST BE COOLED TO LIQUID NITROGEN TEMPERATURE. THE RESEARCHERS PROPOSE A PROGRAM TO STUDY THE EFFECT OF GERMANIUM IMPLANTATION AND SOLID PHASE EPITAXY PROCESS, WHICH COULD BE FEASIBLE FOR LARGE SCALE WAFER IMPROVEMENT. IMPLANTATION OF GE IS ADVANTAGEOUS BECAUSE AMORPHIZATION CAN BE ACHIEVED WITH A DOSE ALMOST AN ORDER OF MAGNITUDE LOWER THAN REQUIRED WITH SI, AND WITHOUT LIQUID NITROGEN COOLING. IN PRELIMINARY WORK AT SPIRE, GE IMPLANTATION APPEARS TO BE VERY EFFECTIVE IN REDUCING THE DENSITY OF DEFECTS IN THE SILICON OVERLAYER OF SEPARATION BY IMPLANTATION OF OXYGEN (SIMOX) WAFERS. THEY BELIEVE THAT A SIMILAR PROCESS COULD REDUCE THE DENSITY OF DEFECTS IN THE SILICON LAYER OF SOS WAFERS. THIS PROGRAM WILL DEMONSTRATE THE EFFECTIVENESS OF GE IMPLANTATION AND SOLID PHASE EPITAXY.