Regular papers

Microlens array production in a microtechnological dry etch and reflow process for display applications

¹ Fraunhofer Institut für Siliziumtechnologie (ISIT), Fraunhoferstrasse 1, 25524 Itzehoe, Germany
² Institut für Mikrosensoren, -aktuatoren und -systeme (IMSAS), University of Bremen, Otto-Hahn-Allee, 28359 Bremen, Germany

^* thomas.knieling@isit.fraunhofer.de

Received: 31 January 2012

Abstract

The fabrication of arrays consisting of densely ordered circular convex microlenses with diameters of 126 µm made of quartz glass in a photoresist reflow and dry etch structure transition process is demonstrated. The rectangular lens arrays with dimensions of 6 mm × 9 mm were designed for focussing collimated light on the pixel center regions of a translucent interference display, which also was produced in microtechnological process steps. The lenses focus light on pixel centers and thus serve for increasing display brightness and contrast since incoming collimated light is partially blocked by opaque metallic ring contacts at the display pixel edges. The focal lengths of the lenses lie between 0.46 mm and 2.53 mm and were adjusted by varying the ratio of the selective dry etch rate of photoresist and quartz glass. Due to volume shrinking and edge line pinning of the photoresist structures the lenses curvatures emerge hyperbolic, leading to improved focussing performance.