In this paper, we present a quasi-three-dimensional micro-fluidic device that has been constructed using the LIGA technology at CAMD. The idea is centered in the modular construction of molded plastic devices. A primary master template was patterned into SU-8 and PMMA, from which we made a reversed insertion mold by electroplating Nickel on it. Chips were patterned by hot embossing and the complex structure was obtained by stacking one layer on top of the other. Alignment marks were placed in each different layer to allow the accurate positioning of the structures. Each layer is a 2-dimensional micro-fluidic system and liquids can go from one level to another level, back and forth, producing this almost three-dimensional behavior. This work aims to introduce concepts and features that will be a step towards a complete modularization of micro-fluidic devices.
X-ray lithography is commonly used to build high aspect ratio microstructures (HARMS) in a 1:1 proximity printing process. HARMS fabrication requires high energy X-rays to pattern thick resist layers; therefore the absorber thickness of the working X-ray mask needs to be 10-50 μm in order to provide high contrast. To realize high resolution working X ray masks, it is necessary to use intermediate X-ray masks which have been fabricated using e beam or laser lithographic techniques. The intermediate masks are characterized by submicron resolution critical dimensions (CD) but comparatively lower structural heights (~2 μm). This paper mainly focuses on the fabrication of high resolution X-ray intermediate masks. A three-step approach is used to build the high resolution X-ray masks. First, a so called initial mask with sub-micron absorber thickness is fabricated on a 1 μm thick silicon nitride membrane using a 50KeV e beam writer and gold electroplating. The initial X-ray mask has a gold thickness of 0.56 μm and a maximum aspect ratio of 4:1. Soft X-ray lithography and gold electroplating processes are used to copy the initial mask to form an intermediate mask with 1 μm of gold. The intermediate mask can be used to fabricate a working X-ray mask by following a similar set of procedures outlined above.