Total gamma dose characteristics of CMOS devices in SOI structuresbased on oxidized porous silicon

The electrical characteristics of complementary metal-oxide-semiconductor (CMOS) transistors and ring oscillators fabricated in porous silicon silicon-on-insulator (SOI) structures are presented before and after gamma irradiation. P-channel SOI/MOS transistors exhibit a front-gate threshold voltage shift of -0.2 and -0.55 V after exposure to doses of 1 and 10 Mrad(Si), respectively, under floating bias conditions, which are different from worst case conditions. For n-channel transistors the corresponding values are -0.1 and -0.2 V. The additional bottom and sidewall B⁺ ion implants with a dose of 2×10¹³ cm^-2 are found to be effective to prevent leakage current along the n-channel transistor bottom and sidewalls. SOI/CMOS ring oscillators present a 40% higher speed in comparison with the same bulk CMOS devices and continued stable operation under a supply voltage of 3-5.5 V, for gamma irradiation up to 10 Mrad(Si), and an operating temperature ranging from 77 to 400 K