Microlens arrays formed by melting photoresist and ion beam milling

Microlens array design and fabrication on silicon and quartz substrates for infrared focal plane applications have been described. A 128 x 128 element silicon microlens array with a pixel size of 60 x 45 mu m for 3-5 micron bandwidth was designed using ray tracing and computer simulation program. A photoresist shap with rectangular arch was prepared by milting process and the shap was transferred onto a silicon substrate using ion beam milling. A 2x20 element quartz microlens array has also been fabricated using the same method as the manufacture of silicon microlens array. The microlens array structures were characterized by both the scanning electron microscope and the surface stylus. The experiment results show that the microlens arrays can be effectively formed at the temperature of less than 150 degrees C. The use of the microlenses to improve the performance of IR detector arrays is described. A photocurrent gain in excess of 2 has been achieved.