Low Cost SOI Wafer Process for MEMS and VLSI Applications

MicSOI (silicon-on-insulator) material is a most promising substrate for military and commercial applications. The SOI process based on hydrogen-implantation, wafer splitting, and wafer bonding is the newest and the cheapest approach to SOI fabrication. We propose to develop hydrogen-implanted SOI wafer process for production with a focus on improving the quality of SOI thus improving radiation hardness of the buried oxide in SOI-based devices. A problem for SOI material as related to radiation hard microelectronics is a positive charge trapping in buried SiO2 layer. The trapping sensitivity is 10 to 100 times higher than in conventional thermal oxide layer. This prevents the use of SOI as a mainstream starting material for military and commercial VLSI. We have already determined that implantation and bonding do not cause quality decreasing of the buried oxide. The charge trapping is caused by two neighboring and opposite internal Si/SiO2 interfaces. Our approach to solve the trapping problem is novel additional step in SOI wafer processing. This is high dose ionizing irradiation of wafers with subsequent annealing. This treatment decreases drastically internal stress in the SOI sandwich thus highly decreasing density of traps for holes in buried oxide and at both toD and bottom Si/SiO2 interfaces. New variations of SOI process also suggested to improve quality of SOI wafers.