Off-state gate current in n-channel MOSFETs with nitrided oxidegate dielectrics

The authors report on the off-state gate current (I_g ) characteristics of n-channel MOSFETs using thin nitrided oxide (NO) gate dielectrics prepared by rapid thermal nitridation at 1150°C for 10-300 s. New phenomena observed in NO devices are a significant I_g at drain voltages as low as 4 V and an I_g injection efficiency reaching 0.8, as compared to 8.5 V and 10^-7 in SiO₂ devices with gate dielectrics of the same thickness. Based on the drain bias and temperature dependence, it is proposed that I_g in MOSFETs with heavily nitrided oxide gate dielectrics arises from hot-hole injection, and the enhancement of gate current injection is due to the lowering of valence-band barrier height for hole emission at the NO/Si interface. The enhanced gate current injection may cause accelerated device degradation in MOSFETs. However, it also presents potential for device applications such as EPROM erasure