Optical System Research Of Excimer Laser Micro-Machining

Excimer lasers are intense sources in ultraviolet range with suitable properties for microfabrication applications, short laser pulse are used for 'no-thermal'ablative material removal of different material like polymers, glasses and ceramics. But excimer laser beam quality is low, multimode and non-uniform energy distribution, which influences machining quality. Especially for mask projecting micro-machining method, which method can machine whole picture by a single exposure, high efficiency and 0.5um limiting resolution, but because of non-uniform energy distribution, the fabrication picture depth is different, which influence finished quality. This work designs a mask projecting micro-machining system of excimer laser, including homogenizer, projecting image system and locating monitor system. The 248nm excimer laser beam characteristic is discussed. Based on the integral principle, by extending and splitting beam, a lenslet array homogenizer for excimer laser is designed. a high uniformity of the output beam within 13×13mm is obtained. The intensity variation coefficient is under ±5%. which make it is adapt to mask projecting micro-machining of excimer laser and irradiation. A higher resolution image lens is needed for micro-machining system, based on least-squares, using refracting system, a 15 ratio 1 projecting image lens is designed, by rectifying spherical aberration, coma and distortion. It caters mask projecting micro-machining. Micro-device size is very small, it is difficult for locating it during machining. Based on coaxial principle, by fitting CMOS sensor with zoom lens, a coaxial monitor system is designed. It can locate precise micro-device by cross curve.