Analysis of Mechanical and Electrical Origins of Degradations in Device Durability of Flexible InGaZnO Thin-Film Transistors
Hye‐Won Jang, Gi‐Heon Kim, Sung‐Min Yoon
Abstract
Mechanically flexible In–Ga–Zn-O (IGZO) thin-film transistors (TFTs) were fabricated and characterized on poly(ethylene naphthalate) (PEN) with various film thicknesses. The physical origins of mechanical and electrical degradations in device characteristics were extensively and systematically investigated under various mechanical strain conditions to improve the device operational reliabilities. To investigate the mechanical durability of the IGZO TFTs, the effects of PEN thickness on the variations in critical radius of bending curvature were analyzed, which were estimated to be 3, 7, and 14 mm, when the PEN thickness was 25, 50, and 125 μm, respectively. During the cyclic bending tests for the TFTs fabricated on 25 μm thick PEN, the operation cycles were estimated to be markedly reduced from 10 000 to 150 when the applied strain increased from 0.3 to 0.45% (critical strain), respectively. It was clearly suggested that the main origin for the device degradation under bending deformation could be altered from electrical to mechanical ones in the vicinity of the critical strain determined by critical radius of curvature. In other words, the evolution of microcracks and the variations in the density of states within the IGZO channel were found to have critical impacts on the device characteristics of the flexible IGZO TFTs above and below the critical strain, respectively. Consequently, the systematic analysis and the obtained results provided design guidelines and insights for implementing more mechanically robust devices in flexible electronics.