Evidence of Radiation-Induced Dopant Neutralization in Partially-Depleted SOI NMOSFETs

Radiation-induced dopant passivation is evidenced for the first time in partially-depleted SOI n-channel MOSFETs. Isochronal annealing experiments following 10 Mrad(SiO₂) irradiation demonstrate that the neutralization of boron atoms in the NMOSFET body is most pronounced in the 125degC-150degC temperature range. This results in an abrupt decrease of the threshold voltage and the subthreshold swing, due to the transition of the body from partial to full depletion. The SOI four-gate transistor, inherently present in the partially-depleted MOSFET structure, is demonstrated to be a very efficient tool for monitoring dopant neutralization through irradiation and annealing. Radiation-induced dopant passivation has important consequences regarding the reliability of short-channel partially-depleted NMOSFETs.