NFET effective work function improvement via stress memorization technique in replacement metal gate technology

In this paper, for the first time we investigate and report the effective workfunction (eWF) modulation arising from stress memorization technique (SMT) in advanced replacement metal gate (RMG) CMOS technology. Our SMT data show a strong improvement in NFET short channel effect (SCE) besides a typical strain-induced mobility enhancement, suggesting better eWF. Further investigation proves that the eWF improvement is due to the electron affinity increase at silicon conduction band caused by the uniaxial channel strain from SMT. The impact of the electron affinity change on device performance and reliability has been evaluated.