| Summary: | 碩士 === 國立交通大學 === 工學院碩士在職專班精密與自動化工程組 === 99 === Here a novel process is proposed to fabricate sealed micro channels by using negative photoresist SU-8. In previous studies, fabricating sealed micro channels needs either wafer bonding or multiple photoresist coating. The proposed method needs only SU-8 single-layer coating and double-side partial exposure, without wafer bonding, to fabricate not just sealed micro channels, but also sealed micro channels with non-uniform inside cross section.
It is a common technique to fabricate negative photoresist structures having different thickness from the top by various front-side exposure dosages. Here, by further combining back-side exposure, plating Cr pattern on glass substrate to act as the mask for back-side exposure, negative photoresist structures with different thickness, either from the top or the bottom, can be fabricated. From experimental results, it is found that thickness uniformity can be greatly improved when soft bake is conducted before edge bead removal. Also, soft bake at 95℃ for 30 minutes can avoid stickiness between the mask and photoresist. Furthermore, reflection effect during exposure is found to be a critical factor on developed photoresist thickness. Using injection mold instead of conventional spin coating method, thickness of SU-8 2075 can be coated above 200 μm easily. It is shown that for front-side exposure dosage of 78 mJ/cm2, the reflection effect can be effectively reduced while coated SU-8 thickness is above 380μm. In combining front-side and back-side exposure, it is also found that, without coating sufficient SU-8 thickness, cross-link effect from double-side exposure will happen to result in over exposure. Finally, while coating SU-8 above 380μm, a feasible recipe is established to successfully fabricate sealed micro channels with variable inside cross section.
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