MODELING OF OUTPUT SNAPBACK CHARACTERISTICS IN N-CHANNEL SOI MOSFETS

The snapback effect is usually observed in the output characteristics of an n-channel SOI MOSFET with zero gate voltage in which the drain-to-source breakdown voltage is less than the drain-to-body avalanche voltage. It can be attributed to parasitic lateral bipolar actions as well as the MOS feedback mode of operation-a point often overlooked in the literature. An analytical model is developed in this paper for predicting the observed output characteristics taking into account both the bipolar and the MOS mechanisms. Results obtained from this model agree well with the experimental I-V curves, and show that, with continuing scaling of device geometries and improvement in SOI materials, the bipolar-induced snapback will become dominant in the future.