Study On Total Ionizing Dose Effects Of SOI NMOSFETs

With more and more application of silicon-on-insulator (SOI) technology inradiation environment, research on how to improve its performance of anti-radiationbecomes an important topic both in our country and abroad.First, bias dependence of the total ionizing dose (TID) effects for partially depleted(PD) SOI n-channel metal oxide semiconductor (NMOS) is studied by technologycomputer aided design (TCAD) simulation. The results suggest that OFF state is theworst bias during the irradiation. Then, TID effects of0.5μm SOI NMOS devices withelectron and hole traps are analyzed by TCAD three-dimensional simulation. It is foundthat injection of the electron traps in the buried oxide can reduce the off-state leakagecurrent, and the injection of electron traps with different concentrations is compared, theresults show concentration of electron traps should be equal to or greater than that ofhole traps for a good performance of anti-radiation. As the device size decreases,performance of anti-radiation can be significantly improved for thin buried oxide andhigh doping concentration of top silicon layer. From the comparison between the90nmSOI NMOS devices without isolation region and that with the shallow-trench isolation(STI) region, it is found that there is no obvious change in the off-state leakage current,however, the90nm SOI NMOS devices with the STI region show significant thresholdvoltage shift.Finally, a0.35μm PD SOI NMOSFET structure of H-gate and asymmetric source&drain with body ties is presented for radiation-hardened application. The resultssuggest that this structure can not only improve TID but also single-event effects (SEE)hardness. So it could be an ideal radiation-hardened device.