Highly Stable Atomic Layer Deposited Zinc Oxide Thin-Film Transistors Incorporating Triple O2 Annealing

Top-gate zinc oxide thin-film transistors have been fabricated by thermal atomic layer deposition, and the effective process steps to improve the device stability have been investigated in detail. In particular, the incorporation of triple rapid thermal annealing steps in oxygen ambient has been proposed to shift the turn-ON voltage toward the positive direction, reduce interface defects, and suppress gate leakage current. Such devices exhibited near zero turn-ON voltage and significantly enhanced electrical and environmental stability. Repeated I
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sweeping over 900 times in air ambient only caused a shift of the transfer characteristics as low as 0.08 V. Both positive and negative gate bias stress tests on such devices exhibited superior stability performance. Furthermore, ring oscillators based on these devices were found to be capable of highly stable continuous operation over 10 000 s, indicating the devices' suitability for practical circuits-on-glass applications.