Radiation induced degradation of SOI n-channel LDMOSFETs

SOI laterally diffused MOSFETs (LDMOS) are a promising technology for integrated mixed signal and mixed voltage applications for space. Before these devices can be flown on long term space exploration missions, their radiation response must be understood. Although radiation is expected to produce only a modest shift in the threshold voltage of the thin gate oxides, the thicker buried oxides (BOX) may still be susceptible to radiation degradation. It has been recently shown that the operation and performance of LDMOS devices are strongly influenced by the back gate (substrate) voltage. For these devices. the back gate voltage modifies not only the parasitic back channel, but the series resistance of the drift region as well. We show that the radiation induced degradation of LDMOS device operation involves several mechanisms and is more complex than the usual case of low-voltage SOI CMOS transistors.