Radiation effects in MOS devices caused by x-ray and e -beam lithography

In this study we have found that electron–beam and x-ray irradiations of metal (or polysilicon) -oxide-semiconductor devices performed at typical PBS or PMMA exposure levels create temperature-bias-stress (TBS) instability. Experimental results can be most reasonably explained by assuming that exposure to both of these types of ionizing radiation causes mobilization of positive charge in the insulator. The positive charge is forced closer to the semiconductor–gate-oxide interface during the positive bias phase of the TBS test. This damage mechanism was found in HCl, H2/O2, and dry grown oxides. HCl oxides exhibited the effect the least of the three oxide types studied. N2 anneals performed at 500° and 900°C, and H2 anneals performed at 500°C (all for 30 min) did not substantially reduce TBS instability. A 900°C anneal in H2 for 30 min did create a marked reduction in the TBS-induced instability.