Impact of stress induced by stressors on hot carrier reliability of strained nMOSFETs

In this study, the nMOSFETs with contact-etch-stop-layer (CESL) stressor and SiGe channel have been fabricated with a modified 90 nm technology. The performance of nMOSFETs has been measured. And the hot carrier reliability of the SiGe-channeled nMOSFETs with various CESL nitride layers has also been extensively studied. In addition, the impact of stress induced by CESL stressor and SiGe-channel on hot-carrier reliability of the strained nMOSFETs has been analysed through experimental investigation. The shift in threshold voltage (?Vth) vs. stress time (t) under different stress temperatures was measured. Furthermore, according to the reliability results, both the interface states (Nit) and oxide trapped charges (Not) increased after hot-carrier stress. With regard to the hot-carrier reliability, for all stress conditions the degradation of strained nMOSFETs with compressive CESL stressor is more serious than the degradation of those with tensile CESL stressors. The nMOSFET devices with tensile CESL have better performance and hot-carrier reliability than those with compressive CESL. Moreover, it is suggested that the CESL-induced damages (Nit) located at the interface between gate dielectric and underlying channel be responsible for the hot-carrier reliability.