Fabrication and Evaluation of the CdZnTe Microlens Arrays

This paper presents a modified thermal reflow process to fabricate CdZnTe (CZT) microlens arrays and a new convenient method to evaluate the quality of the microlens. In the fabrication experiment, square photoresist (PR) isolated-islands with almost zero gap each other were formed on a CdZnTe substrate by the underexposure photolithographic process firstly. Then, high fill-factor (almost 100%) PR microlens arrays were generated via thermal reflow the islands at 110 degrees C for 30 minutes. Finally, through etching the substrate using the PR microlens arrays as the mask by an inductively coupled plasma (ICP) dry etching process with Ar/N-2/CH4 gas, the high fill-factor CdZnTe microlens arrays were achieved. Besides, a new convenient method to evaluate the quality of the microlens was also established in this paper. At the first step of the evaluation, the data of surface topography of the microlens fabricated was recorded by the confocal scanning laser microscope (CSLM). Then, the characteristic of the microlens such as the surface topography, focusing properties, the light intensity distribution of the microlens, etc. was simulated and displayed by the procedure base on the CZT optical parameters and the data of the actual surface topography of the microlens. The results show that the microlens fabricated by the modified thermal reflow process can focus 80% incident light of the pixel on the 30% central region, with only 1.6% optical crosstalk.