Irradiation-then-anneal processing to improve BSIT performance

Experimental data on the effect of irradiation-then-anneal treatments on the electrical characteristics of high voltage power static induction transistors (BSIT´s) are given. The above treatments include bombardment of chips by high energy, high flux electrons, and a subsequent isothermal treatment. The effect of different irradiation dose and annealing temperature combinations on a number of BSIT characteristics are explored. A qualitative model explaining experimental results is given. Production and annealing behavior of radiation-induced defects in the active region of BSIT´s are discussed. The relation of static and dynamic characteristics of BSIT´s with radiation-induced defect contamination is examined. A criterion of preference of the recombination center as a means to control BSIT characteristics is proposed. On the basis of a comparison of radiation-induced defect parameters a conclusion that the criterion of preference fits the A-center is made. Taking into account the proposed criterion the design rules (concerning the choice of irradiation-then-anneal processing conditions and the choice of initial wafer) to develop the best tradeoff between on-state and turn-off losses of BSIT´s are given