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Published March 2012 | public
Journal Article

Ultradeep fused silica glass etching with an HF-resistant photosensitive resist for optical imaging applications


Microfluidic and optical sensing platforms are commonly fabricated in glass and fused silica (quartz) because of their optical transparency and chemical inertness. Hydrofluoric acid (HF) solutions are the etching media of choice for deep etching into silicon dioxide substrates, but processing schemes become complicated and expensive for etching times greater than 1 h due to the aggressiveness of HF migration through most masking materials. We present here etching into fused silica more than 600 µm deep while keeping the substrate free of pits and maintaining a polished etched surface suitable for biological imaging. We utilize an HF-resistant photosensitive resist (HFPR) which is not attacked in 49% HF solution. Etching characteristics are compared for substrates masked with the HFPR alone and the HFPR patterned on top of Cr/Au and polysilicon masks. We used this etching process to fabricate suspended fused silica membranes, 8–16 µm thick, and show that imaging through the membranes does not negatively affect image quality of fluorescence microscopy of biological tissue. Finally, we realize small through-pore arrays in the suspended membranes. Such devices will have applications in planar electrophysiology platforms, especially where optical imaging is required.

Additional Information

© 2012 IOP Publishing Ltd. Received 8 October 2011, in final form 7 January 2012. Published 14 February 2012. Funding for this work was provided by The Broad Foundations. DAW is the recipient of a Career Award at the Scientific Interface from the Burroughs Wellcome Fund. We thank James R. Heath for granting us use of his clean room facility and Habib Ahmad for contributions in creating figures in this manuscript. We also thank Jen-Kan Yu, Slobodan Mitrovic and the UCLA Nanoelectronics Research Facility staff, especially Joe Zendejas and Tom Lee, for their support in device fabrication.

Additional details

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