An optical setup for doing photolithography on microscopic samples of arbitrary shape and size

What is it about?

Photolithography is a technique for printing very fine features onto materials and is used extensively in the semiconductor chip industry. Typically, UV light is passed through a patterned mask which exposes parts of a photo-sensitive chemical coated surface, thereby generating a pattern that mimics the mask. But it is challenge to do this on microscopic samples because one has to first find the sample and thereafter the mask has to suit the sample's shape and size. We achieve this instead by building a microscope based setup wherein the sample is moved across the demagnified image of a simple masks to write the required pattern. As an example we show how to print thin metallic electrodes on a tiny flake of a semiconductor material of arbitrary shape and size.

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Photo by Photo Boards on Unsplash

Photo by Photo Boards on Unsplash

Why is it important?

This is a relatively more efficient (needs fewer steps and much less time) and extremely low cost approach that can be used in place of more involved and expensive techniques like electron-beam lithography, when say one is trying to make electrodes on microscopic flakes of graphene or similar 2D materials. One can make electrode structures with thin parts having widths as small a 2.5 micron using only two simple masks. The same two masks can be used for flakes of different shape and size.

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