A novel nondestructive testing method for amorphous Si–Sn–O films

Traditional methods to evaluate the quality of amorphous silicon-substituted tin oxide (a-STO) semiconductor film are destructive and time-consuming. Here, a novel non-destructive, quick, and facile method named microwave photoconductivity decay (μ-PCD) is utilized to evaluate the quality of a-STO film for back channel etch (BCE) thin-film transistors (TFTs) by simply measuring the D value and peak reflectivity signal. Through the μ-PCD method, both optimum deposition procedure and optimal annealing temperature are attained to prepare a-STO film with superior quality. The a-STO TFTs are fabricated by the obtained optimum procedure that exhibits a mobility of 8.14 cm2 V−1 s−1, a I on/I off ratio of 6.07 × 109, a V on of -1.2 V, a steep subthreshold swing of 0.21 V/decade, a low trap density (D t) of 1.68 × 1012 eV−1 cm−2, and good stability under the positive/negative gate-bias stress. Moreover, the validity of the μ-PCD measurement for a-STO films is verified by x-ray photoelectron spectroscopy, Hall effect measurement, and the performance of STO TFTs measured by traditional methods. The non-destructive μ-PCD method sheds light on the fast optimization of the deposition procedure for amorphous oxide semiconductor films with excellent quality.