Defect generation in gate oxides during the polysilicon doping and activation process

Abstract

Doped polysilicon films have become a very important part of semiconductor technology. Defect generation in the polysilicon doping/activation process, as shown in this report, can severely reduce gate oxide quality. Whether the doping process is by ion implantation, in-situ dopant deposition with polysilicon, or, spin-on dopant diffusion into polysilicon, capacitor yields with thin gate oxide are increasingly degraded by increasing dopant concentration, increasing activation temperature and increasing activation time. In highly doped polysilicon gate processing for submicron CMOS, defect densities in the gate oxide are shown to be near 10 cm -2, after BF + 2 or As + self aligned, source/drain implant and activation. After a low dose implant and activation however, such as used in a silicided polygate process, the defect density is only 0.002 cm -2. These phenomena can have a large effect on megabit memory yields.