Defect Reduction and Back Channel Degradation in SIMOX

Because of potential back channel leakage problems and parasitic bipolar effects in silicon-on-insulator SOI metal-oxide-semiconductor MOS devices, especially n-channel MOS devices which must operate in an ionizing radiation environment, it is desirable to produce SIMOX wafers which have a layer of poor quality silicon near the Siburied SiO2 interface. Also, for device fabrication these wafers must have low defect, high quality silicon near the wafer surface. In this program we have demonstrated, for the first time, that by Ge implantation and solid phase epitaxy regrowth, the surface region of the Si top layer of the SIMOX wafer is improved and the region adjacent to the buried SiO2 is degraded. N-MOSFETs with and without Ge implantation, were fabricated on SIMOX and Si wafers. Our results show that Ge implantation into SIMOX significantly reduced off-state leakage and parasitic bipolar effects. In addition, gate-induced drain leakage of n-MOSFETs was greatly suppressed and the source-to-drain breakdown voltage was improved. All devices were irradiated with 100 krad x-ray at RADC. Our measurements show that for devices fabricated on SIMOX with Ge implantation the off-state leakage current was up to 1000 times less than for devices fabricated on SIMOX without Ge implantation. Ge Implantation, SOI Devices, Solid phase epitaxy, MOS Devices, SIMOX Wafers.