EFFECT OF N2O NITRIDATION ON THE ELECTRICAL-PROPERTIES OF MOS GATE OXIDES

Furnace annealing in N2O is a convenient technique for improving the r eliability of thermal oxides without significant modifications of the process flow. We investigate the impact of N2O nitridation on MOSFET d evice performance, assessing the various factors contributing to the o bserved degradation of electron mobility. Estimates based on low-frequ ency C-V and charge pumping measurements show that nitridation causes a significant increase of the interface trap density in the vicinity o f the conduction band. Interface traps contribute a parasitic componen t to the gate-channel capacitance, thus leading to an overestimate of the inversion charge. This effect accounts for a substantial fraction of the mobility degradation which is observed for the nitrided devices . The remaining degradation can be ascribed to an enhancement of Coulo mb scattering, maybe due to differences in dopant segregation,and to a change of the surface roughness characteristics. (C) 1998 Elsevier Sc ience Ltd.