content_image/937437.jpg content_image/937438.jpg
A further preferred optional additive is one or more surfactants, which can promote formation of a substantially uniform coating layer of the overcoated composition. A variety of surfactants may be employed. Suitable surfactants may exhibit an amphiphilic nature, meaning that they can be both hydrophilic and hydrophobic at the same time. Amphi› philic surfactants possess a hydrophilic head group or groups, which have a strong affinity for water and a long hydrophobic tail, which is organophilic and repels water. Suitable surfactants may be ionic (i.e., anionic, cationic) or nonionic. Further examples of surfactants include silicone surfactants, poly(alkylene oxide) surfactants, and fluoro› chemical surfactants. Suitable non-ionic surfactants for use in the aqueous solution include, but are not limited to, octyl and nonyl phenol ethoxylates such as TRITONfi X-114, X-102, X-45, X-15 and alcohol ethoxylates such as BRIJfi 56 (C$_{16}$H$_{33 }$ (OCH$_{2}$CH$_{2}$ ) $_{10}$OH)(ICl), BRIJfi 58 (C$_{16}$H$_{33 }$ (OCH$_{2}$CH$_{2}$ ) 20OH)(IC1). Still further exemplary surfac› tants include alcohol (primary and secondary) ethoxylates, amine ethoxylates, glucosides, glucamine, polyethylene gly› cols, poly(ethylene glycol-co-propylene glycol), or other surfactants disclosed in McCutcheon ’s Emulsifiers and Detergents, North American Edition for the Year 2000 published by Manufacturers Confectioners Publishing Co. of Glen Rock, N.J. 

Nonionic surfactants that are acetylenic dial derivatives also can be suitable, including such surfactants of the following Formulae IV and V: 

<img src='content_image/937437.jpg'>

<img src='content_image/937438.jpg'>

wherein in those Formulae IV and V R$_{1 }$ and R$_{4 }$ are a straight or a branched alkyl chain suitably having from 3 to 10 carbon atoms; R$_{2 }$ and R$_{3 }$ are either Hor an alkyl chain suitably having from 1 to 5 carbon atoms; and m, n, p, and q are numbers that range from 0 to 20. Such surfactants are commercially available from Air Products and Chemicals, Inc. of Allentown, Pa. trade names of SURFYNOLfi and DYNOLfi. 

Additional suitable surfactants for use in coating compo› sitions of the invention include other polymeric compounds such as the tri-block EO-PO-EO co-polymers PLURONICfi 25R2, L121, L123, L31, LSI, Ll0l and P123 (BASF, Inc.). 

For at least certain applications, coating compositions that contain one or more zwitterion surfactants also will be suitable. 

Additional optional additives for the coating composi› tions may include stabilizing agents which can promote enhanced shelf life of the prepared composition. Suitable stabilizing agents may include poly-acids such as diacids and triacids e.g. citric acid, malonic acid. Additional stabi› lizing agents that may be suitable for coating compositions of the invention may be a peroxide materials such as reported in U.S. Pat. No. 6,750,257 and Japanese Patent JP200204568681, which discloses use of hydrogen peroxide as a stabilizing agent in an amount of 5 to 100 ppm in a colloidal silica composition. 

A yet further optional additive for coating compositions of the invention will be one or more acids and/or acid generator compounds. As discussed above, inclusion of an acid source in a coating composition of the invention can provide enhanced resolution of an image patterned in an underlying photoresist layer, including to control the profile of devel› oped photoresist image. As shown in Example 14 which follows, it has been found that the absence of an acid in an overcoated coating composition of the invention can result in undesired T-topping of developed resist image whereas the inclusion of an acid source in an overcoated coating composition of the invention can provide a desired rounded profile of the imaged resist layer. 

Suitable acid additives can be both organic and inorganic acids. Exemplary acid additives include e.g. nitric acid, sulfuric acid, trichloroacetic acid, trifluoroacetic acid, oxalic acid, maleic acid, malonic acid, succinic acid, maleic acid, citric acid, tartaric acid, para toluene sulfonic acid, trifluo- romethylbenzenesulfonic acid, camphor sulfonic acid, and trifluoromethane sulfonic acid. 

Suitable amounts of one or more acids in a coating composition of the invention may vary within a wide range and may be readily optimized for any particular composition by simple testing (e.g. by evaluating resolution of under› coated imaged photoresist) and consideration of factors such as acid pKa, mobility and size. Suitable acid loading levels may include less than 5 weight percent of the fluid coating composition, more preferably less than 1 weight percent of the fluid coating composition, and even more preferably less than 0.5% by weight of fluid coating composition, such as within a range of from 0.1 to 0.4 weight percent of the fluid coating composition. 

II 

Suitable acid generator compounds include photoacid generator compounds and thermal acid generator com› pounds. Exemplary thermal acid generator compounds include both ionic as well as substantially neutral thermal acid generators, e.g. an ammonium arenesulfonate salt. Suitable thermal acid generator compounds are commer- cially available such as from King Industries. Suitable photoacid generator compounds to employ in a coating composition include onium salts, particularly iodonium and sulfonium compounds such as those discussed below with respect to photoresists. Exemplary acid generator com- pounds that may be employed in a coating composition of the invention include triphenyl sulfonium camphor sul› fonate, triphenyl sulfonium trifluormethane sulfonate, triph› enyl sulfonium trifluorooctane sulfonate, triphenyl sulfo› nium trifluorobutane sulfonate, triphenyl sulfonium trifluormethylbenzene sulfonate, triphenyl sulfonium para› toluene sulfonate, ammonium camphor sulfonate, ammo› nium trifluormethane sulfonate, ammonium trifluorooctane sulfonate, ammoniumtrifluorobutane sulfonate, ammonium trifluormethylbenzene sulfonate, and ammonium para-tolu- ene sulfonate. Other photoacid generator compounds iden› tified below for use in connection with photoresists can be employed in an overcoated coating composition of the 

