Determining Emission Lines for <i>in situ</i> Compositional Analysis of Sputter-deposited MgO Films Using Optical Emission Spectroscopy

In situ elemental analysis is required to improve the yield and quality of sputter-deposited metal oxide films by detecting the films whose compositions are deviated from the required compositions. In this study, the author proposed a method to determine the MgO film composition by measuring the intensities of the Mg emission lines and O I 777.3 nm line during sputter deposition. Linearity (R2 value) between the emission intensity ratios of the Mg lines to the O I 777.3 nm line and Mg/O atomic ratio in the films was investigated. The Mg I 518.4 and 517.3 nm lines exhibited R2 values higher than 0.80, and showed the properties that (1) they did not overlap with other emission lines and (2) their intensities exhibited a dependence on the input power to the MgO target and chamber pressure, similar to that of the O I 777.3 nm line, which were consistent with the properties of the Zn emission lines that can accurately determine the ZnO films compositions. Therefore, searching emission lines that satisfy the two properties is a powerful approach for the in situ elemental analysis of sputter-deposited metal oxide films.