Development of beam splitter using multilayer membrane for extreme ultraviolet phase-shift microscopes

The realization of a defect-free mask is a technical problem in extreme ultraviolet lithography (EUVL) technology, which is expected as a next-generation lithography technology. We are therefore proposing and developing the EUV phase-shift microscope for phase-defect inspection. The beam splitter is the key element in this microscope. In this paper, we describe the present situation on the development of the beam splitter. The most inportant issue in beam splitter development is controlling stress. By controlling At gas pressure, we controlled stress and thereby successfully developed the beam splitter.