Random telegraph signals in small MOSFETs after X-ray irradiation

The random telegraph signals (RTSs) in small MOSFETs before and after X-ray irradiation and after annealing have been studied. It is believed that the RTSs arise from the trapping/detrapping of individual defect(s) near the SiO/sub 2//Si interface. The key results from this study are: (1) RTSs existed prior to X-ray irradiation in both weak inversion and strong inversion due to process-induced defects, (2) X-ray irradiation causes the disappearance of the original RTS and the appearance of new RTS with different emission time constants, (3) X-ray irradiation also causes high frequency current fluctuations with much more irregular amplitude distribution than the slower RTSs, (4) annealing at 200-300 degrees C in nitrogen removes most of the high frequency component and reveals more clearly some of the radiation-induced RTSs, and (5) annealing at 400 degrees C essentially removes all of the radiation-induced RTSs, but causes the reappearance of one set of the original RTS traces in strong inversion.<
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