Thermal recovery process of electron irradiated Si1-xCx source/drain n-MOSFETs

In this study, the performance degradation by electron irradiation and the thermal recovery process of Si0.99C0.01 source/drain (S/D) n-MOSFETs are reported. The electron mobility is 15% enhanced by 1%-C doping in the S/D stressor region. The electron mobility is degraded by 2-MeV electron irradiation, but the relative change was the same irrespective of C doping and electron fluence. This fact indicates that tensile-strain relaxation by displacement damage in the Si:C stressors is not significantly impacting the mobility degradation by electron irradiation. Evidence is given that increased scattering in the channel is the main cause of mobility degradation by 2-MeV electron irradiation. In addition, it is shown that for a fluence of 5x10(17) e/cm(2), the electrical performance is recovered by thermal annealing. After 323 K for 15 min annealing, the mobility amounts to 95% of the preirradiation value. In the case of Si0.7Ge0.3 S/D p-MOSFETs, it has been shown before that the device performance is recovered to the same degree for the same irradiation/thermal annealing conditions of this study. CMOS circuits are fabricated by a combination of n-MOSFETs and p-MOSFETs, therefore, it can be confirmed that strained CMOS devices using Si: C S/D n-MOSFETs and SiGe S/D p-MOSFETs, respectively, can operate in the radiation environment studied here. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim