A method to fabricate high-aspect-ratio microstructures using PMMA photoresist

Fabrications of high-aspect-ratio microstructures (HARMS) using negative photoresist have been studied a lot by researchers recently, but the removal of the resist is still a problem. We report a method to fabricate HARMS using PMMA, a positive photoresist. A classical microstructure, densely packed micro square columns, was tried in our study. A top grid made of negative photoresists was employed to join all the separate parts together to prevent them from tilting or clumping. The development and electroplating processes were not influenced by the top grid. Excellent nickel micro-pores-structures were obtained finally, demonstrating that the method is a promising way to fabricate HARMS especially when the resist needs to be removed.