Impact of Elongation Stress on Island-Bridge Shaped Oxide Thin-Film Transistors with Metal Interconnects for Stretchable Electronics Applications

This study presents a comprehensive examination of the degradation mechanisms affecting oxide thin-film transistors (TFTs) with rigid islands and serpentine bridge structures under mechanical elongation stress. Assessments were conducted along the uniaxial direction at 10%, 20%, and 30% strain. To assess the influence of bridge interconnections to the source/drain/gate (S/D/G) electrodes on the TFT performance, measurements were performed using four distinct methods: IG-IC (no connected bridge considered), IG-SC (only S/D-connected bridge considered), SG-IC (only G-connected bridge considered), and SG-SC (all S/D/G-connected bridges considered). IG-IC showed no changes in the elongation state (ΔVth: 0.15 V, ΔμFE: 0.32 cm2/(V s), ΔVhys: 0.01 V, and ΔS.S: 0.00 V/decade). Conversely, the other three measurements show characteristic degradation and abnormal behavior at the 20% elongation. In the stretching assessment considering only S/D bridge stretching, a decrease in mobility, attributed to on-current reduction, was observed (ΔμFE: 18.05 → 3.58 cm2/(V s)). Furthermore, in the stretching assessment considering only G bridge stretching, counterclockwise hysteresis was observed rather than clockwise hysteresis owing to typical charge trapping (ΔVhys: 0.02 → −2.48 V). Therefore, we would like to explain the origin of the degradation in both the contact and gating aspects owing to the elongation stress. Finally, subsequent 20% elongation in the biaxial direction confirmed both the decrease in on-current and the counterclockwise hysteresis.