Effects of furnace annealing and hot pressing on the properties of SZO thin films and on the characteristics of SZO-TFTs

Abstract

Silicon zinc oxide (SZO) thin films were deposited via co-sputtering, while thin-film transistors (TFTfs) with the SZO film as the active layer were fabricated with a bottom gate configuration. Two kinds of post-treatment, furnace annealing and hot pressing, were carried out on the deposited SZO films. The effects of the post-treatment on the crystalline structure, chemical bond, surface roughness, and optical transmittance of the deposited SZO TFTs were analyzed as functions of the post-treatment conditions that were used. It was observed from the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results that the structure of the SZO film became amorphous and the amount of Si-O bonds in the SZO film drastically increased after low-temperature furnace annealing. The on-off current ratio was 1.35× 108 for the TFT after furnace annealing (200°C) and 1.93× 108 for the TFT after hot-pressing (200°C, 2MPa), while that of the as-deposited SZO-TFT was 3.16×106. The experiment results showed that the hot pressing method would be preferable because it could improve the electrical characteristics of the SZO-TFTs, yielding similar results from the case where furnace annealing for about 60min was carried out, in spite of the short process time (about 30s) of the hot pressing method.