Formation of interface traps in MOSFETs during annealing following low temperature irradiation

The formation of interface traps, N/sub it/, was studied in MOSFETs during isochronal annealing up to 350 K, following exposure to ionizing radiation at 78 K. Two distinct N/sub it/ formation processes are observed. A small (1-10% of total) process occurs at 100-150 K, which is caused by neutral atomic hydrogen, and a second, higher-temperature (200-300 K) process that accounts for most ( >90%) of the N/sub it/ formation also occurs. The characteristics of the high-temperature process support the proton (H/sup +/) model of N/sub it/ formation and are not in agreement with several other common models. Charge pumping and inversion layer mobility techniques for determining N/sub it/ are compared. It is found that the mobility cannot be used to determine N/sub it/ at 78 K (in contrast to its successful use at 295 K), probably because of lateral uniformities in the large radiation-induced fixed oxide charge.<
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