Effects of Repetitive Mechanical Stress on Flexible Oxide Thin-Film Transistors and Stress Reduction via Additional Organic Layer

We investigated the effects of repetitive mechanical bending stress on top-gate amorphous InGaZnO thin-film transistors (TFTs). Electrical parameters were gradually degraded under repetitive tensile bending stress. After 50 000 bending cycles, some TFTs showed gate leakage current increase during positive gate bias thermal stress. After 60 000 bending cycles, conduction path was physically severed to an open state. However, when an additional organic layer was deposited on the TFTs as a stress-reduction layer, device characteristics were unaffected by repetitive mechanical stress up to 100 000 cycles. Finite element structural simulations show the vulnerable stress-concentrated regions that cause leakage current, contact resistance increase, and interface traps. Electrical deterioration under repetitive bending is significantly mitigated by applying a stress-reduction layer.