High temperature failure modes of In2O3 thin films and improved thermal stability using Al2O3/ZrO2 protective layers

The limiting temperature of an In₂O₃ thin film sensor is much lower than its melting point. Herein, the failure modes of In₂O₃ thin films at high temperatures, including sublimation and changes in composition, have been studied. The edge and surface layer sublimation rates increased dramatically at 1350 °C, indicating that it is the limiting temperature of no-protection In₂O₃ films. In addition, oxygen atoms will escape from In₂O₃ thin films at high temperatures, forming oxygen vacancies. As the main current carrier type in In₂O₃, the increasing number of oxygen vacancies affects the resistance of In₂O₃ thin film sensors. To solve these problems and promote the high temperature performance of In₂O₃ thin films, protection methods based on Al₂O₃ and ZrO₂ layers have been investigated. The ZrO₂ protective layer alleviated the serious considerable sublimation of In₂O₃ thin films at high temperatures, and the Al₂O₃ protective layer was beneficial for reduction the escape of oxygen atoms. Finally, different protection layers were evaluated by in-situ resistivity measurements of In₂O₃ thin films at high temperatures. The resistance of the In₂O₃ thin film resistor with a protective multilayer consisting of Al₂O₃ and ZrO₂ remained stable at 1360 °C, verifying the protection method effectively increased the thermal stability of In₂O₃ thin films.