Temperature- and Field-Dependent Charge Relaxation in SiO2 Gate Insulators

Experimental results are presented for the time dependence of the relaxation of flat-band voltage shift (ΔVFB) induced by ionizing radiation in metaloxide-semiconductor (MOS) capacitors incorporating radiation-hard wet (pyrogenic H20) thermally-grown SiO2 gate insulators. ΔVFB was observed from 0.4 ms to 800 s following short-pulse sample irradiation at temperatures from 79 to 295 K and with applied fields from -6 to + 6 MV/cm. The results illustrate the strong temperature and field dependences of hole transport in the SiO2 which is responsible for the early annealing of the radiation-induced ΔVFB. Examples are given of the manner in which these data may be applied to estimate the response of radiation-hard MOS devices at various times after irradiation, particularly in the potentially troublesome low temperature (80-150 K) regime.