Investigations on proton-irradiation-induced spacer damage in deep-submicron MOSFETs

In this paper, we have focused our attention on DC characteristics degradation of 0.18 ¿m MOSFETs after 10-MeV proton irradiation. It is shown that the threshold voltage shift, the transconductance degradation and the saturation drain current decrease are lager in PMOSFETs, while small effects are exhibited in NMOSFETs. From the analysis, it is concluded that the basic damage mechanism is not ascribed to the gate oxide and the isolation. The origin of the observed changes is due to the damage in spacer oxides of the MOSFETs. The mechanism involved is that the energetic protons incident on the spacer region lose their energy to displace the atoms, give rise to many defects, and create a disordered region (displacement damage region), where many defects and traps can capture positive charges to make the static characteristics degraded. Therefore, it is pointed out that the sidewalls are one of sensitive regions for irradiation hardness.