Avalanche‐Induced Hot Electron Injection and Trapping in Gate Oxides on p‐Si

Abstract

Hot electron trapping in gate oxides can lead to threshold drifts in short channel MOSFET's. Therefore, factors affecting the efficiency of hot electron trapping have been investigated by rf‐bias aging of MOS capacitors followed by flatband voltage measurements. It was found that avalanche‐injection electron current levels of >5 μA cm−2 produce excessive amounts of hot electron trapping; currents of <4 μA cm−2 were preferred for oxide characterization. A relatively small amount of hot electron trapping produced an enormous density of fast surface states. The observed flatband shifts would, therefore, contain significant contributions from surface states. The total flatband shift due to hot electron injection and trapping increased with higher p‐Si substrate doping levels and with increasing oxide thickness . Eectron beam irradiation (5–30 μC cm−2) followed by a 450°C, anneal did not significantly change the hot electron trapping behavior of the gate oxide. Possible implications of these results on the generic reliability of VLSI devices are discussed.