High Dose-Rate SIMOX Synthesis by Plasma Implantation

Using a Separation by Plasma IMplantation of OXygen (SPIMOX) technique, we have recently achieved a breakthrough in high-dose rate SIMOX synthesis using an oxygen plasma. We succeeded in maintaining high voltages (>50kV) across the plasma sheath by using extremely low gas pressure (<0.1mTorr) but efficient ionisation plasma sources (ECR). An oxygen dose of 3×10¹⁷ cm^-2 is accomplished within 3 minutes as compared to hours when using conventional ion implantation. By implanting with a bias of 50kV to substrate, an oxygen plasma excited by ECR source in the low sub-mTorr pressure range, and post-implantation annealing at 1300^oC for 2 hours, a continuous buried SiO₂ layer is formed underneath a single-crystalline silicon overlayer of about 30nm. By tuning the ration O₂⁺:O⁺ ion concentrations in the plasma to approximately 1:2., we also obtain a double SIMOX structure with one implantation step. These results suggest plasma implantation can synthesise SIMOX with very high throughput and with the implantation time independent of wafer size.