Photoresist latent acids

T. Asakura etal, US Patent 6,512,020 (January 28, 2003) Assignee Ciba Specialty Chemicals Utility Photoresist Latent Acid for Acid-Curable Resins... 

Photosensitive onium salts provide the means for the development of novel positive and negative photoresists based on the concepts advanced in this paper. Work is currently proceeding both at this laboratory and in others to explore the unique opportunities for photoresists based on these materials as latent photochemical sources of strong protonic acids. 

ImRe makes use of another possibility to manipulate the latent image in the photoresist. After imagewise exposure, the indene carboxylic acid in the exposed areas is converted into indene by a base-catalyzed decarboxylation reaction (see Sect. 2.2). Then a flood exposure to near UV is applied to convert all residual diazo-oxide into indene carboxylic acid (see Fig. 5). Because of the decarboxylation reaction in the imagewise exposed areas, these areas now have a low dissolution rate as compared to the masked areas, which contain mainly indene carboxylic acid. Thus, upon... 

Exposure of a dassical chemically amplified photoresist to ultraviolet light as shown in Hgure 15 first causes the generation of a strong acid from the PAG to form a so-called latent ima in the resist. At this stage, in many cases, very litde else happens during exposure itself in terms of reaction within the photoresist... 

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