In this study, the effects of soft baking temperature on the solution derived ZTO (Zn-Sn-O) TFTs (thin-film transistors) as a In-free oxide semiconductor were investigated. In spite of the same hard baking at high temperature(600℃), the electrical properties of ZTO TFT was greatly changed by a small difference in soft baking temperature(180~250℃). The performance of TFT was deteriorated as the soft baking temperature increased. Therefore, it is important to remove the water-related defects well as organic impurities from the ZTO films during soft baking for fabrication of solution-derived high performance of TFTs.