A two-axis Lloydʹs mirror interferometer for fabrication of two-dimensional diffraction gratings

A new two-axis Lloydʹs mirror interferometer based on multi-beam interference is proposed. A square grating substrate with normal in the Z-axis is placed edge to edge with two rectangular mirrors with normals parallel to the XZ-plane (X-mirror) and the YZ-plane (Y-mirror), respectively. The angle between the substrate and each mirror is set to be larger than 90°, so that the beams reflected by the mirrors can be superimposed with the direct beam at the substrate to produce two-dimensional (2D) diffraction grating structures in a single exposure. Sub-micron pitched 2D hole grating structures were fabricated and evaluated.