Comparison between ZnO films grown by plasma-assisted atomic layer deposition using H2O plasma and O2 plasma as oxidant

Zinc oxide (ZnO) thin films have attracted significant attention for application in thin film transistors (TFTs) due to their specific characteristics, such as high mobility and transparency. In this paper, the authors fabricated TFTs with ZnO thin films as channel layers deposited by plasma-assisted atomic layer deposition (PAALD) at 100 °C using two different plasma sources, water (H2O-plasma) and oxygen gas (O2-plasma), as oxidants, and investigated the effects of the plasma sources on TFT performances. The TFT with ZnO channel layer deposited with H2O-plasma indicated higher performances such as a field effect mobility (μ) of 1.1 cm²/Vs. Analysis of the ZnO films revealed that the residual carbon in the film deposited with H2O-plasma was lower than that of O2-plasma. In addition, the c-axis preferred orientation was obtained in the case of the ZnO film deposited with H2O-plasma. These results suggest that it is possible to fabricate high-performance ZnO TFTs at low temperatures by PAALD with H2O-plasma.