Dose Rate Effects in MOS Transistors

Enhanced low dose rate sensitivity (ELDRS) has been a subject as well as a concern for radiation hardness assurance
testing over several decades, in particular because of the underestimation of the effects in the accelerated testing [1].
ELDRS is prominent in bipolar transistors, where more pronounced gain reduction is observed at low dose rate. This
phenomenon is related to thick layers of soft oxides [1]. Such oxides are also used in modern CMOS process nodes as
shallow trench insulation. Thus the differences in oxide space charge build-up at low and high dose rates are worth
considering also for the MOS transistors [2]. In this context, the to-date reported results on dose rate effects in MOS
transistors over several CMOS process nodes will be reviewed [2, 3]. Also, our recent experimental results will be
presented. The considerations for TID testing of MOS transistors will be discussed on an example of MOS transistor
characteristics irradiated under two different dose rates.
References
[1] Pease, R. L., et al. (2008, September). ELDRS in bipolar linear circuits: A review. In 2008 European Conference on
Radiation and Its Effects on Components and Systems (pp. 18-32). IEEE.
[2] Witczak, S. C., et al. (2005). Dose-rate sensitivity of modern nMOSFETs. IEEE transactions on nuclear science,
52(6), 2602-2608.
[3] Borghello, G., et al. (2018). Dose-rate sensitivity of 65-nm MOSFETs exposed to ultrahigh doses. IEEE
Transactions on Nuclear Science, 65(8), 1482-1487.