| A range of materials are tested and compared as sacrificial layers for releasing SU-8 structures from the substrate following their manufacture. Four metals (chromium, chromiun/gold, copper and aluminium) and three polymers (polymethylmethacrylate, polyimide and polystyrene) were investigated. Factors assessed included; quality of the SU-8 structures (by SEM examination before and after release), effect of changing etchant concentrations, monitoring of the undercutting process (through depth measurement with time), and the time taken for the successful release process. Overall, it was found that the metals were the best choice as sacrificial layers under SU-8 for structures up to 200 µm, whereas polymers were the better for larger structures (up to 600 µm in this work). |
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