Immersion interference lithography for realizing a large slant angle beyond the limit

In holographic systems such as AR and VR devices, the holographic grating is known to increase the efficiency by providing a slant angle. The Interference lithography system is essential for the high-quality production of slant gratings. However, there is a restriction on the angle of the slant structure fabricated by conventional dry interference lithography. Interference lithography with a pitch of 300nm cannot achieve a slant angle of more than 22 degrees due to the geometrical limit of rays. We report on a novel system which combines a prism and immersion lithography to achieve a larger slant angle. A slant angle of 40 degrees can be realized with interference lithography at a pitch of 300nm. We will present its mechanism and processing examples.