Photoresists thin layer imaging

Contrast-Enhanced Lithography. Contrast-enhanced lithography is a clever technique that uses a thin layer of a bleachable contrast-enhancing layer coated over a conventional photoresist to sharpen the mask image. 

Figure 12 shows images created in a bilayer composed of a thin layer of a typical polysilane coated over a thick, hard-baked layer of a typical AZ-type photoresist. After solvent development of the imaged layer, the pattern... 

Chemical nature of photoresists, the chemistries involved in the photolithography, the properties of photoresists are briefly described. The discussion includes diazonaphthoquinone/novolac positive photoresists, polymer-aromatic diazide negative photoresists, photopolymerizable compositions, chalcogenide glass using systems, chemically amplified photoresists, and photoresists with an image formation in a thin layer. 

The second productive idea useful in designing of modern photoresists is based upon thin film imaging (TFI). The thin uppermost layer of a photoresist... 

Figure 3.3 Photoresist profiles. (A) Positive resist (a) desired resist profile for lift-off i.e. exposure-controlled profile, also called overcut (b) perfect image transfer by applying a normal exposure dose and relying moderately on the developer (c) receding photoresist structure with thinning of the resist layer i.e. developer control, also called undercut. (B) Negative resist the profile is mainly determined by the exposure. Development swells the resist a little but has otherwise no influence on the wall profile.

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