Comparative study on the channel hot-carrier degradation of N- and P-MOSFETs with CVD tungsten polycide gate

Abstract

The channel hot-carrier induced degradation of polysilicon (PolySi) and tungsten polycide (WSix) gate nMOSFETs and pMOSFETs are studied using the charge-pumping (CP) technique. WSix nMOSFETs under maximum substrate current (Isub,max) stress (Vg ≈ Vd/2) are degraded to a smaller extent when compared to the PolySi nMOSFETs. From the CP measurements, it is confirmed that fewer interface traps (Nit) are generated for the WSix devices. However, under maximum gate current (Ig,max) stress (Vg = Vd), the WSix nMOSFETs showed higher degradation than the PolySi devices. In contrast, WSix pMOSFETs showed higher degradation when compared to the PolySi devices under both the Ig,max and Isub,max stresses. The CP results showed that more Nit and Nox (negative oxide trapped charges) are present in the WSix pMOSFETs when compared with the PolySi devices. Finally, the operation of WSix CMOS transistors is found to be limited by the hot-carrier lifetime of WSix pMOSFETs.