The effects of ionizing radiation on the breakdown voltage of p-channel power MOSFETs

The effects of ionizing radiation on the breakdown voltage of p-channel power MOSFETs were examined through two-dimension simulation. The breakdown-voltage performance of p-channel power MOSFETs was found to be very different from that of corresponding n-channel power MOSFETs. In p-channel devices, simulation showed breakdown-voltage enhancement for low values of positive oxide-trapped charge, N/sub ot/, whereas for high values of N/sub ot/, the breakdown voltage may or may not continue to increase, and may actually decrease in some topologies. For comparison, in n-channel devices, increases in N/sub ot/ always cause breakdown-voltage degradation. The uncertainties stem from the interaction of the depletion region of the device (which is a function of its termination method) with its isolation technology, making it difficult to predict breakdown voltage for large N/sub ot/. However, insights gained through analysis of depletion-region spreading in p-channel devices suggest a termination/isolation scheme, the VLD-FRR, that will enhance p-channel device reliability in radiation environments.<
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