193nm EAPSM Inspection Comparison: Commercial versus Alternative Absorber Material

摘要

Current commercially available 193nm Embedded Attenuated Phase Shift Mask (EAPSM) blanks are MoSiON-based. In order to obtain the appropriate optical properties of 6% transmission and 180-degree phase shift at 193nm wavelength, these films are built very thin and subsequently have very high transmission at longer wavelengths. Current inspection tools use 365nm as the inspection wavelength; therefore the high transmission of the commercial blanks (>50% at 365nm) causes sensitivity problems in current high-end inspection tools. This problem is only fixed by costly upgrades to the current inspection tools, resulting in much higher mask costs. Pholronics, Inc. has developed an alternative film slack mat obtains the appropriate optical properties at 193nm (6%T and 180-degree phase shift). This film stack has a relatively low transmission (<15%) at the inspection tool wavelength in comparison to the commercial blanks enabling improved inspection performance with the current tool set. This paper outlines the development of new 193nm EAPSM blanks, the processing of these masks, and the resulting inspection performance in comparison to the commercial EAPSM blanks.