Phase Mask Pinholes as Spatial Filters for Laser Interference Lithography

Abstract

Laser resonators have outputs with Gaussian spatial beam profiles. In laser interference lithography (LIL), using such Gaussian‐shaped beams leads to an inhomogeneous exposure of the substrate. As a result, dimensions of lithography‐defined features vary significantly across the substrate. In most LIL setups, pinholes are used as filters to remove optical noise. Following a concept proposed by Hariharan et al., a phase mask can be added to these pinholes. In theory, this modification results in a more uniform beam profile, and, if applied as spatial filters in LIL, in improved exposure and hence feature size uniformity. Here, the first successful fabrication of such elements is reported on and their use in an LIL setup is demonstrated to reduce feature dimension variations in fabricated devices.

Keywords

• laser interference lithography
• nanolithography
• phase mask
• pinholes