30 January 1989 Advanced Image Reversal Techniques
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Abstract
Image reversal of a positive photoresist is capable of improving resolution, sidewall angles, and process latitude. Another advantage of an image reversible system is that it produces a negative image by aqueous development. Using novolac resists, we have developed new chemistry which is based on "blocked" reactive agents. The reactive agent can be thermally liberated from the resin, or it can be photochemically generated. After generation, it reacts with the indene carboxylic acid groups in the exposed area to render this area insoluble. After postbake, the resist is flood exposed to convert the remaining photoactive compound in the resist layer; development then gives a negative image of the mask. In one practice of this chemistry, the reactive agent and indene carboxylic acids groups are co-photogenerated. As a result of crosslinking between these two species during processing, the contrast of the photoresist is improved. We call this concept Dual-PAC imaging. Because the crosslinking is a second order reaction based on two photogenerated species, the concentration gradients in the film are sharper than a single-PAC system which follows first order kinetics. The result is an improvement in resolution, cleanout and process latitude as well as contrast.
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James W. Taylor, Thomas L. Brown, David R. Bassett, "Advanced Image Reversal Techniques", Proc. SPIE 1086, Advances in Resist Technology and Processing VI, (30 January 1989); doi: 10.1117/12.953070; https://doi.org/10.1117/12.953070
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KEYWORDS
Photoresist materials

Image processing

Photoresist developing

Chemistry

Floods

Image resolution

Thin film coatings

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