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A novel approach to integrate densely packed CMOS devices with three-dimensional (3-D) microfluidic systems created at the wafer level using low temperature processes is introduced. The approach is based on low temperature (<50 °C) bonding and releasing of non-UV-exposed SU-8 films onto a SU-8 structured Si wafer bearing CMOS devices and multilayered lithography in the non-UV-exposed SU-8 films to form 3-D microfluidic structures. The fabrication process assures compatibility with CMOS electronics and has the advantage in realizing complex microfluidic systems comparable in size to CMOS devices, hence holding great promise for large-scale integration between the two. We demonstrate in this paper the integration of more than 800 3-D microchannel systems with giant magnetoresistive (GMR) sensors prefabricated on a 4″ Si wafer. [ABSTRACT FROM AUTHOR]

This paper describes a process to fabricate monolithic multilevel high-aspect-ratio microstructures (HARMs) for ferromagnetic devices built on silicon wafers using aligned X-ray lithography in conjunction with electrodeposition. Two X-ray masks were fabricated, each consisting of gold (Au) absorber structures on a transparent polyimide membrane. One mask was used to print a polymethyl methacrylate (PMMA) resist layer. Then, a second PMMA layer was applied to the same wafer, and the second mask was used to pattern it. Transparent alignment windows in the second mask, combined with a piezoelectrically controlled X-ray aligner, allowed for high alignment accuracy between the two print patterns over large areas (>4 inch in diameter). Au circuits were electroplated into first PMMA layer from a sulfite-based electrolyte, and nickel-iron (NiFe) ferromagnetic HARMs were formed in second PMMA resist from a sulfate-based bath. The deposition resulted in well-defined NiFe structures with aspect-ratios up to 67:1 as well as smooth sidewalls and top surfaces. Chemical composition measurements with energy X-ray dispersive spectroscopy (EDS) and wavelength X-ray dispersive spectroscopy (WDS) showed that Fe content increased during the electrodeposition process. To electrically isolate the NiFe posts and Au circuits, both wet chemical etching and sputter etching were explored to remove the exposed seed layer, and the latter approach completely removed the seed layers without damaging the electroplated features. [ABSTRACT FROM AUTHOR]

The concentration of photoacidgenerator (PAG) in SU-8 determines the UV absorption and, therefore, is a limiting factor of the applicable SU-8 thickness. The motivation of this work is to improve SU-8 process control and expand the application scope of SU-8 by modifying its PAG concentration. In this paper we present the experimental results on lithographic properties of SU-8 as the function of PAG concentration (varying up to 2 orders of magnitude). It includes determining the minimum bottom dose and minimum effective energy density for x-ray and UV lithography of SU-8, respectively, and the UV absorption spectra of SU-8. It is fund that as the PAG concentration reduced, SU-8 has lower sensitivities in UV and x-ray lithography, and lower UV absorption coefficients. By using PAG diluted SU-8 taller microstructures with vertical sidewall can be obtained with UV lithography. Based on the large difference in lithographic sensitivities between normal and PAG diluted SU-8, we have developed a new process concept for making 3D microstructures. The 3D microstructures fabricated based on this new process, including microcantilever and microchannel, will be presented. [ABSTRACT FROM AUTHOR]