Comparison between ZnO films grown by atomic layer deposition using H2O or O3 as oxidant

Abstract

This study investigated the atomic layer deposition (ALD) behavior of zinc oxide (ZnO) films on SiO2/Si substrates using Zn(C2H5)2 and O3 as the precursor and oxidant, respectively, at substrate temperatures ranging from 230 to 300 °C, and the electrical properties of the thin films. The self-limiting ALD mechanism of ZnO thin film growth was confirmed in the whole temperature region, and the growth rate decreased from 0.19 nm/cycle at 230 °C to 0.16 nm/cycle at 300 °C. ZnO films with a c-axis preferential orientation were obtained at these relatively low temperatures. The films contained a lower oxygen concentration compared to the films grown with the same precursor and H2O oxidant. However, the ZnO film grown with the O3 oxidant at 300 °C showed approximately a resistivity three orders of magnitude higher than that of the ZnO film using the H2O oxidant, due to higher Si impurity concentration in the ZnO films. Si diffusion into the ZnO films must be due to the stronger oxidation power of O3 compared to H2O.