Fabrication Process Of Metal Micro-grating And Metal Micro-column Array Structure

With the rapid development of MEMS technology, the demands of metal micro devices increase in the fields of military equipment, communication network information industry, bio-medical engineering, automotive industry and so on. Meanwhile, UV-LIGA technology known as the primary means of fabricating metal micro devices in MEMS, has obtained close attention and practical application. The primary work of this study mainly concentrates on the fabrication processes of metal micro-grating and metal micro-column array structure, which is subdivided into three specific parts:fabrication of nickel micro-grating with high aspect ratio, fabrication of metal micro-column array structure and process study of removal of SU-8 photoresist by ashing at high temperature.A metal micro-grating with the high aspect ratio was fabricated on a metal substrate by the UV-LIGA technology. To weaken edge bead phenomenon appeared in the process of fabricating the thick photoresist, the’low speed to high speed’ spin coating method has been put forward.The’ exposure step by step’ and ’development once’ were used to fabricate a SU-8 thick photoresist mold with high aspect ratio to overcome the technologic difficulty in fabricating processing. For the defects of electroforming layer caused by long operation time, the fractional electroforming and other methods were adopted to obtain the electroforming grating structure. Meantime, the line width compensation method was taken to solve the problem that line width of SU-8 photoresist mold was reduced by swelling. In the process of stripping photoresist after electroforming, the ultrasonic method and soaked method were alternately used. Finally, the metal micro-grating with a period of 130μm, and a sizc of 900μm× 65μm×243μm was fabricated. The high aspect ratio of the metal micro-grating reaches 5, and its relative error on overall dimensions is lower than 1%. Moreover, the surface roughness of metal micro-grating is lower than 6.17 nm.A metal micro-column array structure with the high aspect ratio was fabricated on a metal substrate by the UV-LIGA technology. The difficult problem of the micropores’ development was solved by using high-frequency ultrasonic. Meantime, a high-quality SU-8 photoresist mold for electroforming with high bond strength to substrate was fabricated after the development time reduced. The poor thickness uniformity of electroforming layers was encounter at the electroforming of micropores. And the problem was solved through the methods of fractional electroforming, adjusting the concentration of surfactants and electroforming with a low current density. Eventually, the metal micro-column array structure with the diameter 80μm and the height 250μm was obtained after removing the photoresist through the method of fast chemical etching, which had 203×203 micro-column. And every single micro-column’s relative error on its diameter and height is lower than 2.1% and 0.3% respectively.The research on the process of high-temperature ashing to remove SU-8 photoresist was developed. And the process details of high-temperature ashing to remove SU-8 photoresist on etal substrate were explored. And the minimum temperature range of SU-8 photoresist’s ashing was obtained through experiments. Specific solutions were given aimed for the problems which occurred in the process of high-temperature ashing, for example, the great deformation,the oxidation of structure, carburization of metal substrate et al. High-temperature ashing process can not only be used to remove the SU-8 photoresist separately while the aspect ratio of the non-intensive nickel microstructure less than 3, but also can be applied to assist other methods in removing the SU-8 photoresist.