Distribution phenomena of charged defects and neutral electron traps in process-induced radiation-damaged IGFETs with gate insulators grown at 1000 degrees C and 800 degrees C

Gate oxide defects, in the form of trapped charges and neutral electron traps, were measured before and after irradiation using optically assisted electron injection. Following irradiation and injection, the measured voltage shifts ( Delta V/sub T/) indicate that radiation-induced extrinsic defects are localized near, but not exactly at the Si-SiO/sub 2/ interface. Delta V/sub T/ is found to be linear with respect to the gate oxide thickness when the top electrode resides above the defect region, and quadratic with respect to the thickness when the top electrode encroaches on the defect region. For very thin gate oxides, Delta V/sub T/ approaches zero. Application of a defect distribution model based on this behavior reveals that the gate oxidation temperature does not influence the distribution of radiation-induced defects, but does influence their concentration; with the 800 degrees C oxides always containing more defects than the 1000 degrees C oxides. A gate oxide thickness regime of less than 5-6 nm in which radiation-induced threshold voltage shifts approach zero is identified.<
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