AC Bias-Temperature Stress Stability of a-InGaZnO Thin-Film Transistors
Eric K.-H. Yu and Jerzy Kanicki
Bias-temperature stress (BTS) stability is a critical factor for display lifetime and having reliable TFTs will greatly reduce pixel circuit complexity. For the a-IGZO TFT, positive and negative DC BTS (dark or illuminated) are all well documented to be much superior compared to a-Si:H TFTs. However, AC BTS is required to accurately represent common flat-panel display addressing conditions for lifetime estimation.
Our objective is to fabricate highly reliable bottom-gate coplanar homojunction a-IGZO TFTs and evaluate their electrical stability under AC and DC BTS. In this project, we conduct a comprehensive study on the AC electrical stability using various test conditions: polarity, pulse width, and duty cycle. Our devices are all very stable under both AC and DC BTS and we observe no ΔVth greater than -0.35V. We show that AC BTS instability worsens under pulses of higher frequency and higher duty cycle.
