A new approach to simulating n-MOSFET gate current degradation by including hot-electron induced oxide damage

Abstract

A new gate current model which considers the hot-electron induced oxide damage in n-MOSFET's was developed for the first time. The spatial distributions of oxide damage, including the interface state (N/sub it/) and oxide trapped charge (Q/sub ox/) were characterized by using an improved gated-diode current measurement technique. A numerical model feasible for accurately simulating gate current degradation due to the stress generated N/sub it/ and Q/sub ox/ has thus been proposed. Furthermore, the individual contributions of N/sub it/ and Q/sub ox/ to the degradation of gate current can thus be calculated separately using these oxide damage. For devices stressed under maximum gate current biases, it was found that the interface state will degrade the gate current more seriously than that of the oxide trapped charge. In other words, the interface states will dominate the gate current degradation under I/sub G,max/. Good agreement of the simulated gate current has been achieved by comparing with the measured data for pre-stressed and post-stressed devices. Finally, the proposed degradation model is not only useful for predicting the gate current after the hot-electron stress, but also provides a monitor that is superior to substrate current for submicron device reliability applications, in particular for EPROM and flash EEPROM devices.