Fabrication of high quality microlens arrays based on AZ5214 photoresist by laser direct writing and thermal reflow

Microlens arrays (MLAs) are widely used in imaging, display, and micro-optical applications. However, it remains challenging to achieve a high fill factor together with good dimensional uniformity and morphological consistency during fabrication. In this study, dome-shaped MLAs were fabricated on quartz substrates using AZ5214 positive photoresist. The process combined ultraviolet (UV) laser direct writing with thermal reflow, and the key steps, including spin coating, prebaking, exposure, development, and thermal reflow, were optimized. The results show that the fabricated MLAs have a period of about 16.5 μm, an average diameter of about 15.1 μm, an average height of about 2.82 μm, and a radius of curvature of about 11.6 μm. The resulting structures exhibit relatively smooth surfaces and regular profiles. The average volumetric shrinkage is about 8.98%. The maximum relative deviations in diameter and height are approximately 1.7% and 1.5%, respectively. These results demonstrate that dome-shaped MLAs can be fabricated by combining UV laser direct writing with thermal reflow under the present process conditions.