IGZO TFT의 어닐링 조건에 따른 특성과 안정성에 관한 연구

Abstract

Recently, display technology has made remarkable progress over the last few year. But low electrical mobility(<) and opaque nature of a-Si:H and bad uniformity of LTPS are running into limitation to drive next-generation display with large, high-frequency, high-resolution. So amorphous InGaZnO thin film transistor have attracted considerable interest due to their good uniformity, high field effect mobility, transparency and low process temperature. In this paper, to improve a-IGZO thin film transistor characteristic, annealing conditions were investigated. With a-IGZO thin film deposited by DC sputtering, the roughness and the amorphous state according to the annealing temperature were analyzed. And the effect of thermal environment, annealing temperature, and the pre / post heat treatment on the characteristics of the TFT were examined. And with the heat treatment conditions, the instability of a-IGZO TFTs according to the driving conditions were examined. As a result, TFT with heat treatment in air environment showed excellent properties of a field-effect mobility () 5.76cm/Vs, subthreshold swing 0.652V/decade and ON / OFF current ratio of ~. In addition, annealing temperature 400 ℃ , pre / post heat treatment made the biggest improvement and it was confirmed by AFM and XRD analysis. The instability of a-IGZO TFT with the driving voltage, driving temperature were investigated. The VTH shift increased with voltage bias stress time and driving temperature. And with pre / before heat treatment, improvement of stability of a-IGZO TFT could be confirmed. According to the test results, to obtain the most excellent characteristics and stability, pre / post annealing and minimum temperatures over 300 ℃ annealing in air condition is demanded. For a long time driving under bias stress and heat, sufficient stability of the TFT is the most important task. So research about improvement of interfacial properties of channel layer, the channel layer / gate insulator and the improvement of the passivation material in various directions are required.