Abstract
A High Aspect Ratio (HAR) electrostatic comb-drive microactuator of polymethyl-methacrylate (PMMA) is designed to deliver nearly 40 µm uniaxial displacement at 25 V DC. The HAR comb-drive microstructures are fabricated via one-step X-ray lithography (OXL). Polyimide-Au X-ray mask is fabricated and used to pattern 200 μm, 500 μm and 800 μm thick PMMA by deep X-ray lithography (DXRL), followed by drying/release and selective metallization for the development of HAR electrostatic microactuator. The release was optimized with the help of various low-surface-tension liquids. 200 μm and 500 μm thick microstructures were successfully released whereas, 800 μm structures could not be released due to the higher depth and associated capillary force. In addition, non-uniform distribution of Au on the side walls of overlapped region of comb fingers, during metallization, resulted in uneven distribution of electrostatic force followed by short-circuiting of HAR (i.e. 40) microactuator. These are the potential issues in the fabrication of HAR microstructures and devices by OXL and discussed in details in this paper.
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Acknowledgement
The authors are thankful to Tapas Ganguli, Head, SUS for providing the necessary support at every stage of the project. RS acknowledges the support of V.P. Dhamgaye at BL-07, Indus-2. PRS is thankful to G.S. Deshmukh and A.P. Singh for support in Au electroplating for the development of X-ray mask. CM acknowledges the support of R. Kamparath in RF sputtering. The support of Computer Division in accessing COMSOL Multiphysics at Kshitij-5 is greatly acknowledged.
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Shukla, R., Kannojia, H.K., Mukherjee, C. et al. Challenges in fabrication of high aspect ratio electrostatic comb-drive microactuator using one-step X-ray lithography. ISSS J Micro Smart Syst 9, 173–180 (2020). https://doi.org/10.1007/s41683-020-00064-z
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DOI: https://doi.org/10.1007/s41683-020-00064-z