Microlens beam homogenizer for excimer laser processing

Abstract

This paper reports the results of developed microlens beam homogenizer for the 248 nm excimer laser. Excimer laser has a complex irradiance profile, and it is difficult to design a homogenizer for this kind of light source. We present a method to design microlens beam homogenizer according to the propagation properties of the irradiance profile. Since the intensity distribution image of excimer laser raw beam can be photographed by the laser beam analyzer, we use matlab to analyze the image and extract relevant information to calculate. With the calculated data, we simulate a virtual excimer laser source which has the same irradiance profile as the initial beam. According to the energy spatial distribution characteristics of the virtual excimer laser source, a microlens beam homogenizer is designed. The designed microlens homogenizer has been fabricated and tested. Measurements of the irradiance profile is presented and compared to the ideal design. After shaping and homogenization, a highly uniform beam spot is obtained finally. The profile of this beam spot is a square flat-top with dimensions of approximately 17 × 17 mm2. This optical system can transform approximately 80% of the total input beam power into the work plane of output beam, and beam uniformity of better than ±3% is realized. The successful development of this optical system can provide a technical support for the excimer laser processing with high quality and efficiency.