Channel-Length Dependent Performance Degradation of Thermally Stressed IGZO TFTs

摘要： The focus of this work is on the performance degradation of thermally stressed IGZO TFTs with SiO2 for both the gate dielectric and back-channel passivation material. I-V characteristics of TFTs with bottom-gate (BG) and double-gate (DG) electrode configurations were observed to left-shift and degrade with thermal stress. Experimental results indicate the instability occurs either directly or indirectly due to the influence of H2O within the passivation oxide above the IGZO channel region. An atomic layer deposition (ALD) alumina capping layer applied immediately following the passivation oxide anneal was successful in improving thermal stability. Channel length dependence was observed where longer channel DG devices were more prone to degradation. A hypothesis has been developed with H2O as the expected origin of this phenomenon. Experiments have been specifically designed to establish the feasibility of the proposed mechanism. Furthermore, DG devices which exhibit enhanced thermal stability are presented.