Introduction to Photolithography: Preparation of Microscale Polymer Silhouettes
Kimberly L. Berkowski, Kyle N. Plunkett, Qing Yu, and Jeffrey S. Moore
The Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana–Champaign, Urbana, IL 61801
The concepts behind microchip construction via photolithography are demonstrated by a simple laboratory experiment for junior high or high school students using polymer chemistry. In this experiment, a glass microscope slide acts as the microchip. Students can pattern this ?microchip? by layering negative photoresist on the slide using a solution containing monomer, crosslinker, photoinitiator, and dye. The students then cover the photoresist with a photomask, which is the negative of a computer-generated image or text printed on transparency film, and illuminate it with UV light. The photoresist in the exposed area polymerizes into a polymer network with a shape dictated by the photomask. The versatility of this technique is exemplified by allowing each student to fabricate virtually any shape imaginable, including his or her silhouette. This laboratory experiment allows students to visualize the concepts behind the lithography of microchip construction using analogous polymerization techniques. It promotes understanding of photolithography, crosslinking density, and the process of photopolymerization, while demonstrating the power of rapid prototyping used to fabricate microscale devices. The demonstration was used at the University of Illinois Beckman Institute Open House in 2001 and 2002 to process hundreds of polymer silhouettes for visitors.
Supplement
Instructor notes, chemical information, hazards, experiment overview, student procedure, photomask template, troubleshooting tips, suggested questions with answers, and a glossary for this article are available.
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