Projection Photolithography Technique

One can distinguish between two different techniques for the production of polymer particles with microsystems (a) emulsification of liquid monomers followed by polymerization of the subsequent monomer droplets and (b) direct polymerization through continuous flow projection photolithography. 

The Perkin Elmer projection printer is the tool most currently used in photolithography manufacturing. Because of the interference of photons at the resist-substrate interface and the absorption of the resist, it is always more difficult to develop the bottom of the resist image to size than to obtain a surface image. A double layer technique has been developed to resolve this problem. The top image layer is sensitized DQ and the bottom layer is composed of a DQ derivative. 

Some of these problems can be overcome using a top barrier coating to isolate the resist layer from the immersion medium [21]. Current state-of-the-art immersion photolithography systems utilise a wavelength of 193 nm [22]. Using optical techniques such as off-axis illumination and water immersion projection lenses, these systems can define feature sizes as fine as 38 nm. 

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