In situ compositional analysis of ZnO films deposited using sputtering

Abstract

Metal oxide films are widely used in various industrial products, such as solar cell electrodes and flat panel displays, and they are typically produced using sputter deposition. In situ elemental analysis of metal oxide films improves their reliability because a slight difference in the film compositions affects their properties. Herein, an in situ elemental analysis method of sputter-deposited metal oxide films was developed based on optical emission spectroscopy. The possibility of determining the compositions of the ZnO films based on the emission intensities of the Zn and O I lines during sputter deposition was investigated, and the selection procedures of the emission lines suitable for determining the film composition were proposed. This was achieved by evaluating the linearity (R2 value) between the emission intensity ratio of the Zn I lines to the O I line and the Zn/O atomic ratio in the films. The Zn I lines with R2 values higher than 0.950 did not virtually overlap with other emission lines, and their emission intensity exhibited a dependence on the chamber pressure and the input power to the target similar to that of the O I 777.3 nm line. The highest R2 value (0.992) was obtained for a combination of the Zn I 481.1 nm and O I 777.3 nm lines. The results indicate that obtaining emission spectra during the sputtering of a ZnO target can improve the reliability of ZnO films.