Effects of High–Energy Neutrons on Advanced SOI MOSFETs

Abstract

This work discusses the degradations caused by high-energy neutrons in advanced MOSFETs and compares them with damages created by γ-rays reviewing the original researches performed in our laboratory during last years [1-6]. Fully–depleted (FD) Silicon-on-Insulator (SOI) MOSFETs and Multiple-Gate (MuG) FETs with different geometries (notably gate lengths down to 50 nm) have been considered. The impact of radiation on device behavior has been addressed through the variation of threshold voltage (VT), subthreshold slope (S), transconductance maximum (Gmmax) and drain-induced barrier lowering (DIBL). First, it is shown that degradations caused by high-energy neutrons in FD SOI and MuG MOSFETs are largely similar to that caused by γ-rays with similar doses [1,3]. Second, it is revealed that, contrarily to their generally-believed immunity to irradiation [7, 8], very short-channel MuGFETs with thin gate oxide can become extremely sensitive to the total dose effect [2,3]. The possible reason is proposed. Third, a comparative investigation of high-energy neutrons effects on strained and non-strained devices demonstrates a clear difference in their response to high-energy neutrons exposure [6]. Finally, based on simulations and modeling of partially –depleted (PD) SOI CMOS D Flip-Flop, we show how radiation-induced oxide charge and interface states build-up can affect well-known tolerance of SOI devices to transient effects [4,5].