Chemistry of Materials

Synthesis and Properties of Diazopiperidiones for Use in Nonchemically Amplified Deep UV Photoresists

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3-Diazopiperi-2,4-diones have been prepared and explored as photoactive substrates for microlithography. Michael addition of primary amines to methyl acrylate, followed by amidation with methyl malonate yielded amides that underwent base-catalyzed cyclization to the corresponding piperi-2,4-diones. The pendant esters of the resultant piperidiones were removed by hydrolysis and decarboxylation and diazotization was carried out by treatment with tosyl azide. The resulting 3-diazopiperi-2,4-diones absorb in the 240-260-nm spectral range, are readily soluble in common solvents, and undergo the Wolff rearrangement with high quantum yield upon exposure in the deep ultraviolet (DUV) (248-257 nm), affording ketenes that react with adventitious water to provide transparent, base soluble photoproducts. These characteristics make them ideal chromophores for the design of nonchemically amplified photoresists for use in the DUV. Bis-diazopiperidione derivatives prepared from 4,8-bis(chlorosulfonylmethyl)tricyclo[,6]decane and a hydroxyl-functionalized 3-diazopiperi-2,4-dione yielded products that efficiently inhibit novolac dissolution in aqueous tetramethylammonium hydroxide and are therefore useful for formulating advanced resist materials.