The role of electron traps on the post-stress interface trap generation in hot-carrier stressed p-MOSFET's

Abstract

The generation of interface traps in p-MOSFET's subjected to hot-electron injection is found to proceed even after the stress has been terminated. The extent of post-stress interface trap generation is strongly dependent on the magnitude of the preceding hot-electron stress, as well as the magnitude and polarity of the gate voltage during relaxation. Trap generation is enhanced for negative gate voltage anneal, but suppressed for positive gate voltage anneal. For a given stress-induced damage, the corresponding trap generation kinetics can be completely described by a single characteristic, which is shifted in time according to the magnitude of the applied gate voltage. Existing interface trap generation models are discussed in the light of the experimental results. A new model involving the tunneling of holes from the inversion layer to deep-level electron traps is proposed. Similar post-stress effect observed for hot-electron stressed n-MOSFET's provides additional support for the model. Our work suggests that near-interface electron traps, apart from the well-known hole traps, may also significantly affect the longterm stability of the Si-SiO2 interface. © 1999 IEEE.