Investigation of emission lines for in-situ elemental analysis of Cu–Zn films deposited by sputtering

Abstract

Sputter deposition is the most widely used technique to obtain thin films for industrial products. However, the conventional method for achieving the desired composition for films comprising multiple elements is time-consuming because the deposition conditions to obtain the desired film composition are determined by repeating post-deposition elemental analysis of the films under different deposition conditions. In this paper, we focus on optical emission spectroscopy during sputter deposition for in situ elemental analysis of films and report a method for selecting emission lines to determine the film composition. We investigated the linearity between the emission intensity ratio of Cu I lines to Zn I lines for Cu–Zn targets and the atomic ratio of Cu/Zn in the deposited films. The results indicated that the conventional method of selecting emission lines with the highest intensity did not produce the highest R2 value because the intensity of the Cu I 296.1 nm line, which produced the highest R2 value (0.986) with the Zn I 307.6 nm line, was 1% of the intensity of the Cu I 324.8 nm line, which had the highest intensity. The linearity remained almost unchanged at any fixed chamber pressures; however, it decreased at different chamber pressures. Therefore, the composition of Cu–Zn films deposited by sputtering can be determined in situ from the emission intensity ratios at a fixed chamber pressure using the intensity ratio of Cu I lines to Zn I lines with high R2 values.