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SUMMARY We have investigated the microwave-detected photoconductivity responses from the amorphous In–Ga–Zn–O (a-IGZO) thin films. The time constant extracted by the slope of the slow part of the reflectivity signals are correlated with TFT performances. We have evaluated the influences of the sputtering conditions on the quality of a-IGZO thin film, as well as the influences of gate insulation films and annealing conditions, by comparing the TFT characteristics with the microwave photoconductivity decay ( -PCD). It is concluded that the -PCD is a promising method for in-line process monitoring for the IGZO-TFTs fabrication.

SUMMARY Microwave photoconductivity decay (μ-PCD) method was applied to evaluate the effects of chemical composition and Ar + plasma induced damage on the bulk and the surface states in amorphous In-Ga-ZnO (a-IGZO) films. It was found that the peak reflectivity signal in the photoconductivity response increased with decreasing the Ga content, and had a strong correlation with the a-IGZO transistor performances. In addition, the peak reflectivity signals obtained after various Ar + plasma treatment duration were well correlated with the transistor characteristics. With Ar + plasma treatment, the peak reflectivity signal decreased in accordance with degradation of transistor characteristics. The μ-PCD method was found to be a very useful tool not only to evaluate the bulk and the surface states, but also to predict the performance of a-IGZO transistors subjected to various plasma processes in the production.