Polymer microlens arrays applicable to AlInGaN ultraviolet micro-light-emitting diodes

We report on the fabrication of high-optical-quality microlens arrays based on ultraviolet (UV)-curable polymer adhesive. The lenses are suitable, amongst other applications, for high-transmission and projection of the output of UV micropixellated light-emitting diodes. The microlenses were fabricated using a resist-reflow technique with reactive ion etching. An O₂--CF₄ etch-gas chemistry, where atomic fluorine eliminates the carbon-related polymer residue at the etch front effectively, resulted in etch rates of 1.4 μm per minute for the polymer. Spherical microlenses of root mean square surface roughness 3 nm were obtained.