Thermal degradation and theoretical analysis of amorphous oxide thin-film transistor

We have investigated the thermal distribution of an InSnZnO TFT under various gate and drain voltages by using an infrared imaging system and device simulation. An asymmetrical thermal distribution was observed at a local drain region in a TFT depending on bias stress. These phenomena were decelerated or accelerated with stress time. We proposed the degradation model combining Joule heating and the hot carrier effect. To validate the model, we performed device simulation to obtain the distribution of electric field and Joule heating. From the rapid band bending at drain edge under high drain voltage, we demonstrated the possibility of impact ionization.