Diazonaphthoquinone-5-sulfonate

The photoactive compounds, or sensitizers, that are used in the formulation of positive photoresists, are substituted diazonaphthoquinones shown in Figure 17. The substituent, shown as R in Figure 17, is generally an aryl sulfonate. The nature of the substituent influences the solubility characteristics of the sensitizer molecule and also influences the absorption characteristics of the chromophor (79). The diazonaphthoquinone sulfonates are soluble in common organic solvents but are insoluble in aqueous base. Upon exposure to light, these substances undergo a series of reactions that culminate in the formation of an indene carboxylic acid as depicted in Figure 17. The photoproduct, unlike its precursor, is extremely soluble in aqueous base by virtue of the carboxylic acid functionality. 

FIGURE 5.43 Photolysis of diazonaphthoquinone sulfonate esters (DNS) followed by (a) Wolff rearrangement to a ketene intermediate, which (b) reacts with water to form an indene carboxylic acid or (c) reacts with phenolic hydroxyl groups (in absence of water) to form ester linkages. 

FIGURE 5.44 Typical examples of multifunctional diazonaphthoquinone sulfonate esters used in photoresists. 

Evidence for the existence of a ketene intermediate was first obtained by Nakamura et al. (1972) in a study of the photolysis of 2,1-diazonaphthoquinone-5-sulfonic acid by flash photolysis in aqueous solution. An intermediate with a strong absorption at 350 nm and a lifetime of approximately 2 ms was found. 

Diazonaphthoquinone (DNQ) Compounds Preparation. 2.3,4,4 -tetrahydroxy-benzophenone-l,2-diazonaphthoquinone-5-sulfonate (average esterification ratio is 75%) (TBP-DNQ) was purchased from Tokyo Gosei Kogyo Co. Ltd. 4,4 -bis(l,2-diazonaphthoquinone-5-sulfonamino)diphenyl ether (DDE-Q) To a solution of 4,4-... 

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