Self-Limiting Film Growth of Transparent Conducting In2O3 by Atomic Layer Deposition using Trimethylindium and Water Vapor

Conformal and self-limiting film growth of transparent conducting In2O3 is demonstrated with atomic layer deposition (ALD) using trimethylindium (TMIn) and water vapor. Various parameters, including pulsing times of TMIn and H2O and deposition temperature, are varied to confirm the ALD processing window of In2O3. It is found that an extremely large Langmuir exposure of H2O (∼2 Torr s) is required to fully react the surface-adsorbed In-(CH3)* groups with H2O. Self-limiting film growth is obtainable at the deposition temperatures between 200 and 251 °C where the film growth is controlled by surface adsorption of TMIn molecules. Within the ALD window, ALD-In2O3 exhibits a film growth rate of ∼0.039 nm/cycle at 217 °C. In addition, the film exhibits an excellent step coverage of ∼97% on a high-aspect-ratio (∼11) nanostructure. The resistivity of the ALD-In2O3 film deposited at 200 °C is about 2.8 × 10–3 Ω cm, and this is attributed to the high Hall mobility of 84 cm2/(V s). Finally, the reduction of the Hall mobility of the films with respect to increases in the deposition temperature is correlated to the evolution of microstructures.