Impact of proton-radiation-induced spacer damage on the dc characteristics degradation in deep-submicron metal-oxide-semiconductor field effect transistors

The dc characteristics degradation of $0.18μm$ metal-oxide-semiconductor field effect transistors (MOSFETs) after 10 MeV proton irradiation is comprehensively investigated in this paper. The measured results show that the off-state drain current is increased in $N$-channel MOSFETs, which is due to the turn on of the parasitic transistors induced by the shallow trench isolation regions. While in $P$-channel MOSFETs, the threshold voltage increase (absolute value), the transconductance degradation, and the saturation drain current decrease are observed. From the analysis, it is concluded that the basic damage mechanism is not ascribed to the gate oxide and the isolation region. The origin of the observed changes may be mainly due to the damage in the spacer oxides of the transistors. In order to verify the assumption, the leakage current passing through the spacer between the gate and the drain is measured before and after irradiation with floated source/substrate and grounded drain. We find that the leakage current is two to three times larger after irradiation. Finally, in order to confirm the extrapolation, 2-dimension (2D) simulation has been performed with Synopsys TCAD (technical computer-aided design) Sentaurus Device Simulation tools (ISE 10.0). The behavior of the simulated charges trapped in the spacers is qualitatively consistent with the experimental results.