The analysis of radiation effects on combined bipolar-MOS structure

Abstract

A total dose response of pnp Lateral Lambda Bipolar Transistor (L/sup 2/BT) is presented. The fabricated L/sup 2/BT structure is obtained by merging PMOS transistor and PNP lateral bipolar transistor in one device. With 35 nm thin oxide above active channel and base areas, L/sup 2/BT appears as convenient device for simultaneous analysis of radiation induced effects on bipolar and MOS type transistor operation. It was found that near-midgap interface surface recombination velocity affects bipolar operation at much lower total dose before substantial generation of positive trapped oxide charge develops to affect MOS operation. The relative weak sensitivity of L/sup 2/BT current gain on total accumulation dose is identified and explained. Based on this result, a new radiation hardening approach of lateral bipolar transistors is proposed with internal current loop sensing method.