High temperature reactive ion etching of indium-tin oxide with HBr and CH4 mixtures
Abstract
Reactive ion etching of indium-tin oxide using HBr/CH4 feed gas at 250°C has been studied in four areas: feed gas composition, power, loading factor, and surface analysis. The result was compared with that using HCl/CH4 as the feed gas. There was no anomalous high rate peak throughout the whole concentration range. Etch rates of HBr and HBr/20% CH4 plasmas increased linearly with the increase of power, which was similar to the HCl etch process but different from the two-stage etch mechanism of the HCl/40% CH4 plasma. The reaction between CH4 and photoresist was non-negligible. It was responsible for the photoresist surface reticulate formation and the loading factor. Surface analysis data showed that when the CH4 concentration increased, the plasma etched tin preferentially over indium, and the metal-bromine peak disappeared gradually. The influence of CH4 on the HBr/indium-tin oxide surface reactions, e.g., the halide removal mechanism, was different from that on the HCl/indium-tin oxide surface reactions. In summary, the indium-tin oxide surface reactions are sensitive not only to the plasma parameters but also to the photoresist pattern under the high temperature process condition.