Observation of radiation induced changes in stress and electrical properties in MOS devices

Strain measurements using X-ray diffraction were performed on irradiated commercial and radiation-hardened metal gate CMOS devices in addition to polysilicon gate NMOS devices. I-V curves were taken and V_ot and V_it were separated using the subthreshold slope method for all devices. A correlation has been shown to exist between physical strain relaxation and the electrical properties as a function of radiation dose and recovery. Data shown suggest that the physical response (strain relaxation) in the silicon at the oxide interface is a measure of the type of damage induced and the recovery mechanism. Postradiation measurements of ▵V_it and ▵V_ot taken immediately after irradiation support the conclusions of V. Zekeriya and T.-P. Ma (1983) and K. Kasama et al. (1986,1987); compressive stress at the silicon/SiO₂ interface does reduce radiation damage in the device