Improvement in radiation hardness of oxide by successive irradiation-then-anneal treatments

Abstract

It was experimentally observed that MOS devices prepared by repeated irradiation-then-anneal treatments were more radiation hard than those without such treatments. A modified isochronal annealing method based on the newly reported flat-band-condition annealing approximation was used in this work to examine the activation energy distribution of the radiation-induced positive charges. It was found that an MOS device after X-ray irradiation with a dose rate of 200 k rads (SiO 2)/min for 5 min exhibited a distribution of activation energy ranging from 1.2 to 1.8 eV. A sample which was subjected to a repeated irradiation-then-anneal treatments exhibited a significant reduction in the distribution of activation energy in the low energy region of 1.2–1.5 eV, but not in the high energy region of 1.5–1.8 eV. The activation energy distribution for samples prepared under various postoxidation treatments are discussed.