A Novel Method for Fabrication of Plastic Microlens Array with Aperture Stops for Projection Photolithography

Abstract

Microlens projection lithography is a new lithography method that uses a microlens array with aperture stops to image a single pattern on a mask onto a resist layer, forming an array of the miniaturized pattern. However, the fabrication of a microlens array with aperture stops is complicated, time-consuming and requires expensive facilities. In this paper, we report a single-step fabrication method of plastic microlens arrays with aperture stops. By using gas pressure to hot press a stainless-steel shadow mask with a microhole array onto a thermoplastic film, the softened polymer material is partially filled into the holes of the shadow mask, and forms a convex surface due to surface tension. After cooling, while keeping the microlens array and shadow mask attached, a plastic microlens array with aperture stops is obtained. To verify its capacity, a microlens projection lithography facility has been designed, constructed, and tested. Arrays of µm-sized patterns have been successfully fabricated using transparency masks of a mm-sized pattern.