RADIATION-INDUCED INCREASE IN THE INVERSION LAYER MOBILITY OF REOXIDIZED NITRIDED OXIDE MOSFETS

The inversion layer mobility of reoxidized nitrided oxide (RNO) n-MOSFET's (and, to a lesser degree, p-MOSFET's) is found to increase after irradiation and subsequent low-temperature anneal, a process sequence which occurs in X-ray or electron-beam lithography fabrication of CMOS circuits. 1/f noise measurements indicate that the irradiation and anneal reduce the density of near-interface electron traps. Thus our findings support the model which invokes nitridation-induced near-interface electron traps as part of the explanation for reduced low-field electron mobility in RNO versus conventional oxide MOSFET's. Our data for p-channel devices suggest that the near-interface trap is amphoteric in nature, but much less efficient at trapping holes.