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X-ray absorption gratings are the heart of coded-aperture and Talbot-Lau x-ray phase-contrast imaging (XPCi) techniques. The quality of imaging – visibility – in the aforementioned techniques is highly dependent on the quality of gratings. SU-8, an epoxy-based photoresist, is valued in Micro-Electro-Mechanical-Systems (MEMS) fabrication due to its excellent mechanical and optical properties. For fabricating x-ray absorption grating following the MEMS process, gold is the material most widely used to stop incident x-rays. One of the main challenges in fabricating a quality x-ray absorption grating is the adhesion between SU-8 molds and gold thin film, where due to poor adhesion of SU-8 to gold thin films and SU-8’s internal high level of stress, SU-8 molds delaminate, crack, or peel off during developing or electroplating steps. This problem becomes more challenging when a greater field of view gratings are required. Employing SU-8 on a gold substrate requires an adhesion layer to assure SU-8’s mechanical stability during fabrication steps. Without this layer, realizing a high-quality grating is challenging. In this work, we have investigated the adhesion quality of SU-8 to gold thin films for different adhesion promoter layers. We have employed a combination of a SU-8 thin film and a metallic-silane-based nanometer-thin film to improve the adhesion quality between SU-8 photoresist and a gold thin film substrate. We have tested the quality of adhesion using tape test and through a harsh (highly acidic) electroplating solution.
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