Behavior of the molybdenum silicide thin film by 193 nm exposure

Abstract

In order to embody high resolution at 32 nm and below, molybdenum silicide (MoSi) phase shift mask (PSM) is essential material in the ArF lithography process, generally. But some problems reported from for the variation of PSM characteristics like transmittance variation and chemical durability. This change in characteristics is an issue for the yield drop in the semiconductor device manufacturing. So we study the behavior of MoSi PSM thin film in the view point of the ArF laser exposure in this paper. Firstly, the problems of MoSi thin film by the 193 nm exposure are observed. From the result, 0.36 % of the transmittance was changed by 193 nm irradiation with 10 kJ of energy. Accordingly, MoSi thin film characteristics were degraded by the ArF laser irradiation. The reason for the transmittance degradation by irradiation for MoSi thin film was analyzed. Also, we found that the oxygen was activated by the ArF laser and this activated oxygen penetrated to MoSi thin film. Consequently, the transmittance increased by the penetrated oxygen. Then we investigated the improvement scheme for MoSi thin film's irradiation characteristic. First, the transmittance of the thin film was changed by the reactive gas ratio change. Also, the Si ratio in the MoSi thin film was changed. Lastly, densification process was applied. Consequently, the densification process for the MoSi thin film improved the irradiation characteristics.