Novel model of haze generation on photomask

ArF lithography sometimes generates the haze defects on the photomask substrate, resulting in serious yield deterioration in ULSI production. In order to solve this problem, experimental and theoretical studies have been carried out on the generated haze defects. In characterizing the haze defects, the composition and chemical structure of the haze defects were analyzed by focusing on 1.0 x 0.3μm sizes defects using Raman, ToF-SIMS and AES spectroscopy with their highest spatial and mass resolution level. To confirm the experimental analyses, theoretical ab initio molecular orbital calculations were carried out on the model compounds of the generated haze defects. These experimental and theoretical studies indicate that the haze defects on quartz surface consist of (NH 4 ) 2 SO 4 and that those on half-tone (HT) film surface, on the other hand, consist of (MoO 3 ) x (SO 4 ) y (NH 4 ) z complex including Mo from HT film material. In the latter case, NH 4 ion was observed only in surface region of the haze defects. Based on these results, we have proposed a novel model of haze generation mechanism on quartz and HT film surfaces of photomask substrate.