1-micron MOSFET VLSI technology. VIII - Radiation effects

The effect of electron-beam radiation on polysilicon-gate MOSFETs is examined. The irradiations were performed at 25 kV in a vector scan electron-beam lithography system at dosages typical of those used in electron-beam resists. Two types of studies were performed: (1) devices fabricated with optical lithography were exposed to blanket electron-beam radiation after fabrication, and (2) discrete devices from a test chip, fabricated entirely with electron-beam lithography, were used. It is shown that in addition to the threshold voltage shift caused by the accumulation of radiation-induced positive charge in the gate oxides these charged centers and additional uncharged electrons lead to an increase in the electron trapping in irradiated oxides.