Characterization of plasma damage in plasma nitrided gate dielectrics for advanced CMOS dual gate oxide process

A comprehensive study on plasma induced degradation of gate oxide integrity (GOI) in remote plasma nitridation (RPN) process for advanced CMOS technology is presented. It is observed that device performance degradation caused by plasma nitridation will limit further reduction of gate leakage, albeit more than one order gate leakage current reduction can be achieved. NFETs, compared with pFETs, exhibit more Ig reduction while they also suffer more severely in Idsat degradation. Such phenomenon is ascribed to plasma induced damage since it is controversial to general characteristics of nitrided oxides. Evidence reveals that nitrogen radical indeed penetrates to Si/SiO₂ interface and causes "radical-induced re-oxidation". Consequently, GOI of heavily nitrided oxides is degraded and such degradation is polarity dependent. Excessive electron trapping caused by plasma nitridation is believed to be responsible for the degradation. Therefore, plasma nitridation should be carefully treated for its further application in advanced CMOS technology.