The effect of solvent water content on the dielectric properties of Al2O3 films grown by atmospheric pressure mist-CVD

Aluminum oxide (Al2O3) dielectric layers were grown by a mist-chemical vapor deposition (mist-CVD) process at 300 °C, using solvent mixtures containing acetone and water. As the acetone to water ratio was varied from 9:1 to 7:3, the leakage current of Al2O3 at an electric field of 7 MV/cm2 decreased from 9.0 × 10−7 to 4.4 × 10−10 A/cm2, and the dielectric constant increased from 6.03 to 6.85 with improved hysteresis during capacitance-voltage measurements. Consequently, the most robust Al2O3 films were obtained at an acetone to water ratio of 7:3, with a dielectric constant (κ) close to the ideal value 7.0, and a breakdown field of approximately 9 MV/cm. Thin film transistors (TFTs) incorporating In-Sn-Zn-O (ITZO) as the semiconductor were fabricated with the Al2O3 (7:3) dielectric onto p++-Si substrates. The devices exhibit high electrical performance, with a high field effect mobility of 42.7 cm2V−1s−1, and a small subthreshold swing (S.S.) value of 0.44 V/decade.