Moving mask UV lithography for three-dimensional structuring

Abstract

This paper presents a systematic study on a novel 3D (three-dimensional) UV (ultraviolet) lithography apparatus for thick photoresist and a UV lithography process simulation for 3D microstructuring. In order to realize a wide variety of 3D microstructures, the developed proximity 3D UV lithography apparatus adopts the ‘moving mask lithography’ concept which was originally proposed by the authors for deep x-ray lithography. Furthermore, the authors propose a new practical photoresist profile simulation approach adopting the ‘fast marching method’ to consider the photoresist dissolution vector in the development process. A series of moving mask UV lithography experiments using a positive-tone photoresist (50 µm thickness) successfully confirmed (1) the capability of the moving mask UV exposure technique for 3D microstructuring and (2) the validity of the proposed photoresist profile simulation.

SU-8 Photolithography as a Toolbox for Carbon MEMS

“…Yet another approach is the use of colored masks as demonstrated by Taff and colleagues [36], where they first characterized the UV absorption of different colors and then printed them on transparent film using a standard laser color printer. Other approaches include moving mask lithography [37], tilting and rotation of the substrate stage [38]; holography [39,40] and stereolithography [41].…”

Rapid Fabrication of Hydrogel Microstructures Using UV-Induced Projection Printing

“…The steps involved in this process are: preparing the wafer, coating with photoresist, soft baking, alignment and exposure, post-exposure bake, and strip resist. This technique, however, faces a lot of limitations when it comes to microfabrication, most notable being the fact that photomasks play a critical role in the pattern definition process [22,23]. Although fabrication of photomasks has been commercialized, the time and cost of their fabrication process presents a main obstacle to the application of photolithography to the rapid and inexpensive prototyping of patterns.…”

Moving-mask Lithography for 3D Microstructure Molding

“…Such microneedles have been formed by molding, in which control of the sidewall inclination angle of the microstructures is very important. For this purpose, techniques such as inclined deep X-ray lithography [3], double-exposure deep X-ray lithography [4], moving mask X-ray lithography [5][6][7], gray-scale lithography [8], inclined UV lithography [9], moving-mask UV lithography [10][11][12], backside lithography [13,14] and deep UV lithography using diffraction [15][16][17][18] have been investigated. X-ray lithography requires a synchrotron, which is prohibitively expensive for many microsystem laboratories [3][4][5][6][7]9,10].…”

“…However, conventional UV exposure from the surface side of the photoresist can only be adopted for positive tone resists to produce inclined microstructures. The thickness of the positive tone resist restricts the microstructure height to less than 50 µm [10], which is too thin for microneedle applications. Therefore, backside lithography using a thick negative-tone photoresist is a more promising technique.…”