In2O3 film prepared by a PEALD process with balanced oxygen radical supply and ion bombardment damage

Abstract

The growth rate of In2O3 thin film prepared by atomic layer deposition (ALD) is usually low when using conventional oxidants, such as water vapor and oxygen gas, due to the low reactivity and thermal stability of most available In-precursors. In this work, In2O3 film was prepared by a remote O2 plasma enhanced ALD process with reasonable growth rate. The O2 plasma duration was tuned taking not only the oxidizing effects but also the ion bombardment effects that have received little attention into consideration. The results show that the film growth was dominated by the oxidizing process manifested by the increase of film growth rate with increasing plasma duration in the early stage of the O2 plasma pulse. In this stage, the optical properties were rarely influenced by the plasma duration, whereas the carrier mobility significantly increased with increasing plasma duration. However, the ion bombardment effects became dominant in the later stage of the O2 plasma pulse symbolized by the saturation of the growth rate. Accordingly, more oxygen vacancy defects were created in the film by ion bombardment, leading to the increase of carrier concentration and decrease of refractive index, optical band gap and carrier mobility.