Improved performance and stability of In-Sn-Zn-O thin film transistor by introducing a meso-crystalline ZrO2 high-k gate insulator

Abstract

Electrical characteristics and reliability of an In-Sn-Zn-O (ITZO) thin film transistor (TFT) using ZrO2 as a high-k gate insulator were investigated. Varying the atomic layer deposition process temperature caused differences in the ZrO2 thin film chemical state and microstructure. Corresponding changes in the electrical properties of the thin film were evaluated. While the ZrO2 thin film deposited at 300 degrees C exhibited an excellent thin film property, the best TFT performance as measured by subthreshold swing, effective mobility, and on/off ratio was achieved with deposition at 250 degrees C. The formation of meso-crystalline structure and subsequent low leakage current density enhanced the TFT performance along with the suppression of Coulombic scattering and interface defect formation. Moreover, the reliability of the TFT was demonstrated using both positive and negative bias temperature stress measurements.