Transient Response of 0.18-μm SOI MOSFETs and SRAM Bit-Cells to Heavy-Ion Irradiation for Variable SOI Film Thickness

In this paper, the effect of silicon-on-insulator (SOI) thickness scaling in fully and partially depleted SOI (FD-SOI and PD-SOI) devices is analyzed for their transient response to heavy-ion irradiation. We have analyzed radiation performance of FD-/PD-SOI MOSFETs and 6-T SRAM bit-cells, conforming to 0.18-mu m technology node, using calibrated 2-D TCAD simulations. We, for the first time, report here that while SRAMs designed with FD-SOI devices have superior hardness to heavy-ion radiation, they are also more sensitive to SOI film thickness than the SRAMs designed with PD-SOI devices. The slopes of the critical linear energy transfer (LETC) to SOI film thickness curves are +1000 and -950,000 MeV . cm/mg for PD-SOI and FD-SOI devices at 1.8V supply voltage (V-DD), respectively. The negative slope for FD-SOI device indicates better radiation performance for thinner silicon films, while a positive slope in PD-SOI device indicates better radiation performance with thicker silicon films. We further investigated the effect of ambient temperature and supply voltage (V-DD) on SOI thickness scaled FD-/PD-SOI devices. We show that increasing V-DD results in increased generated charge due to the heavy-ion at transistor level, whereas LETC of the SRAM bit-cell improves with increasing V-DD. We further highlight that the heavy-ion radiation response as a function of ambient temperature depends not only on the thickness of the SOI film but also on the LET of the impinging heavy-ion.