ETCHING CHARACTERISTICS OF TIN OXIDE THIN-FILMS IN ARGON-CHLORINE RADIO-FREQUENCY PLASMAS

We have developed an etch process suitable for high resolution transpa rent conductive oxide patterning with high etch rates, up to 70 nm/min , and applicability to large area flat panel display substrates. It wa s found that the addition of small amounts of Cl-2 significantly enhan ced the etch rate compared to addition of pure argon but that beyond 2 5% Cl-2 the rate tended to fall. There is a significant loading effect where the etch rate approximately doubled for exposed tin oxide areas between 80% and 10% of the substrate area. This loading sensitivity w as found to increase with increasing power and decreasing Cl-2 concent ration. It was also observed that local changes in pattern dimensions affected the uniformity of the etch rate. A large photoresist etch rat e was observed between one and three times that of the tin oxide and i t decreased as the area of photoresist coverage increased. Linewidth l oss, up to 4 mu m at high powers, was overcome using improved ultravio let exposure, leading to feature resolution capabilities of <5 mu m. E tch rate inhomogeneity was also observed on a local scale, possibly du e to redeposition of sputtered photoresist. Overetching, however, ensu res rapid clearing of tin oxide islands without damage to the underlyi ng SiO2 buffer layer. (C) 1996 American Vacuum Society.