Comparison between ZnO films grown by atomic layer deposition using H ₂O or O₃ as oxidant

This study investigated the atomic layer deposition (ALD) behavior of zinc oxide (ZnO) films on SiO₂/Si substrates using Zn(C₂H ₅)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.