DEVELOPMENT OF MOS-TRANSISTORS FOR RADIATION-HARDENED LARGE-SCALE INTEGRATED-CIRCUITS AND ANALYSIS OF RADIATION-INDUCED DEGRADATION

Radiation-hardened MOSFETs were developed. and experimental results on their total dose degradation were collected to evaluate effects of th ree techniques for radiation hardening. The three techniques are; (1) adding a silicon-nitride layer onto the phospho-silicate glass passiva tion layer, (2) thinning of the field oxide by increasing resistance o f the channel stopper, and (3) annealing the gate oxide at lower tempe rature. Technique (1) suppressed the leakage current generated by the parasitic MOSFET, because the negative threshold voltage shift of the parasitic MOSFET was compensated by the positive shift due to the inte rface states generated by hydrogen trapped in the oxide by the silicon nitride deposition. Furthermore, leakage current decreased with techn ique (2) as well. Technique (3) was not effective because the gate oxi de is inherently thin. Results gotten using a linear model for the thr eshold voltage shift represented well the measured data up to 1.5 kGy( Si) at a dose rate of 5 Gy(Si)/h.