Analysis of Thermal Degradation in Oxide Thin Film Transistors

We have investigated the thermal degradation of oxide TFT with various gate length and width under various gate and drain voltages by using an infrared imaging system. An asymmetrical thermal distribution was observed at a local drain region in a TFT depending on bias stress. Threshold voltage shift was observed with stress time depending on the gate width. We discussed the degradation mechanism by analyzing the electrical properties and thermal distribution. We considered that the degradation phenomena are caused by a combination of Joule heating and the hot carrier effect. This model was confirmed by theoretical device simulation.