Fundamental Study of the Mask Topography Effect on the Advanced Phase-Shifting Masks for Next-Generation Lithography

摘要

Phase-shifting masks (PSMs) with trench- or mesa-type quartz etched structure are widely known as powerful resolution enhancement technologies for advanced lithography. For advanced PSMs, the feature size on a mask including a phase shifter is beyond the wavelength of the light source, and for such a sub-wavelength phase shifter, the impact of the mask topography effect on the amount of phase shifting and the light transmittance becomes prominent. However, an effective method of measuring the actual phase shifting and transmittance of such a tiny phase shifter has not yet been reported because of the difficulty in measuring the sub-wavelength structure. In this work, we have attempted to measure the actual transmittance and phase shifting using the assembled tiny phase shifter aperture array pattern, and we have successfully revealed the actual transmittance and phase shifting behavior of the tiny phase shifter depending on its feature size and trench depth.