3-indenecarboxylic acid

A 0.3 fin thick SPP layer was exposed to a 20 kV electron beam followed by a flood exposure using near UV radiation with an integrated dose of over 500 mJ/cm2. Such a dose was sufficient to convert the remaining DNQ to indenecarboxylic acid. The resist was then dip-developed In an aqueous TMAH solution for 60 s at 25°C. 

Figure 18. Diazonaphthoquinone-novolac resist. The novolac (Novolak) matrix resin is prepared by acid catalyzed copolymerization of cresol and formaldehyde. The base insoluble sensitizer, a diazohaphthoquinone, undergoes photolysis to produce a carbene which then undergoes Wolff rearrangement to form a ketene. The ketene adds water which is present in, the film, to form a base soluble, indenecarboxylic acid photoproduct.

Indanone was first prepared by distillation of the calcium salt of o-phenylenediacetic acid2 3 and, more recently, by the action of acetic anhydride on its potassium salt.4 It has been obtained by the dilute sulfuric acid-catalyzed hydrolysis and decarboxylation of 2-iminoindan-l-carboxylate6 and ethyl 2-indanone-l-carboxylate.6 2-Indanone is commonly obtained by acid-catalyzed dehydration of an indene glycol,7 8 as illustrated in this preparation. Indene glycol has been obtained from indene via the bromohydrin.9-12 The most recent preparation of 2-indanont is by Curtius degradation of 2-indenecarboxylic acid.13... 

Scheme I. Photolysis of a diazonaphthoquinone (DNQ) positive-resist sensitizer. The reaction leads to a carbene (1), which undergoes a Wolff rearrangement to give a ketene (2). Finally, this ketene can react with water present in the resin to give an indenecarboxylic acid (ICA) (3).

Scheme HI. Decarboxylation of indenecarboxylic acid (ICA) photoproducts during image reversal. The process involves treatment with base to form a carboxylate salt, followed by baking to generate ultimately a base-insoluble...

Knowledge that silyl substituents may be incorporated into standard resist chemistry to effect etching resistance has prompted several workers to evaluate silylated novolacs as matrix resins for conventional positive-photoresist formulations. Typically, these resists operate via a dissolution inhibition mechanism whereby the matrix material is rendered insoluble in aqueous base through addition of a diazonaphthoquinone. Irradiation of the composite induces a Wolff rearrangement to yield an indenecarboxylic acid (Figure 4), which allows dissolution of the exposed areas in an aqueous-base developer (35). 

Figure 2.3. The base-catalyzed image-reversal process involves a patternwise exposure that converts the diazoquinone to the corresponding indenecarboxylic acid, follotved by a bake step that causes base-catalyzed decarboxylation that produces the nonphotosensitive indene derivative. Subsequent flood exposure converts the diazoquinone in the previously unexposed areas of the film into the indenecarboxylic acid. Development then yields a negative image of the mask because the originally patterned areas containing the lipophilic indene derivative are less soluble in base than those containing the...

Willson et al. (30) and Miller et al. (31) described a new mid-UV resist based on diazonaphthoquinone and a novolac resin speciScally designed for use in the mid-UV region. The novolac resin was chosen to be transparent above 300 nm. The structure of the naphthoquinone was designed with the aid of semiempirical molecular orbital calculations to provide increased optical absorbance at the 313-nm emission line. They found that 5-alkylsulfo-nates of diazonaphthoquinone exhibit a greatly improved extinction at both 313 and 334 nm over their aryl counterparts. Furthermore, these compounds photolyze to give substituted indenecarboxylic acids that are transparent above 300 nm, whereas the photoproducts of all of the corresponding aryl derivatives studied retain residual absorbance at 313 nm. They chose a mixed 4,5-disulfonate of an aliphatic diol (structure 3.4) as a spectrally matched sensitizer for the mid-UV resist. 

Similar ring contractions have been observed in 1,2-guinone diazides which have commercial Importance as photoresists. The indenecarboxylic acids (69), for example, are the major products of irradiation of the l-oxo-2-diazo-l,2-dihydronaphthal-enes (70) in aqueous dioxcuie. Related sulphonates have been shown to undergo the same ring contractions. 

A.D. Erlikh, N.P. Protsenko, L.N. Kurovkaja, and G.N. Rodionova, Zh. Vses. Khim. Obua., Pho tolysis of onaphthoquinonediazides Structure of substituted indenecarboxylic acids, 20, 593 (1975) [cited in A. Reiser, Photoreactive Polymers The Science and Technology of Resists, p. 187, John Wiley Sons, Hoboken, NJ (1989) R. Dammel, Diazonaphthoquinone based Resists, pp. 13 15, SPIE Press, Bellingham, WA (1993)]. 

Formation of the resist pattern is due to the solubility change of the exposed part of the resist which results from the photochemical reaction of NQD. Figure 3 shows a change of the dissolution rate of the resist. The dissolutjon rate of a novolak film itself in an alkaline developer is approximately lOOA/sec. Once NQD is added to the novolak resin, the rate decreases drastically by the order of one thousand, which means the unexposed part scarcely dissolves in the alkaline developer. This is called the "dissolution inhibition effect" of NQD (1). And then upon exposure NQD decomposes to produce indenecarboxylic acid which makes the exposed region even more soluble than the novolak itself. 

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