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EUV Exposure Test 

The positive resist composition was spin coated onto a silicon substrate ( diameter 4 inches, vapor primed with hex› amethyldisilazane (HMDS)) and pre-baked on a hot plate at 105° C. for 60 seconds to form a resist film of 50 nm thick. The resist film was exposed imagewise to EUV under condi› tions: NA 0.3 and dipole illumination. 

Immediately after the imagewise exposure, the resist film was baked (PEB) on a hot plate at the temperature shown in Table 3 for 60 seconds and puddle developed in a 2.38 wt% TMAH aqueous solution for 30 seconds to form a positive pattern. 

Sensitivity was an exposure dose that provided a 1: 1 reso› lution of a 35-nm line-and-space pattern. The 35-nm line- and-space pattern at that dose was measured for LWR under SEM. 

The resist composition is shown in Table 3 along with the sensitivity and resolution of EUV lithography. 

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It is evident from Tables 2 and 3 that the resist compositions of Examples have a sufficient resolution and a high sensitivity and are fully reduced in edge roughness. The resist composi› tions of Comparative Examples have a sufficient resolution, but their sensitivity and LWR values are noticeably inferior to those of Examples. 

It is demonstrated that the resist composition comprising a polymer comprising acid labile group-substituted recurring units and preferably acid generator-bearing recurring units, to which a salt of mono- to tetra-functional C$_{1}$-C$_{20 }$carboxylic acid or complex of ~-diketone with a metal selected from among sodium, magnesium, chromium, manganese, iron, cobalt, nickel, copper, zinc, silver, cadmium, indium, tin, antimony, cesium, zirconium, and hafnium is added, exhibits a high resolution, a high sensitivity, and a minimal LER. The resist composition is best suited as the resist material for VLSis and patterning material for masks. 

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents 55 may be substituted for elements thereof without departing from the scope of the invention. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments 60 falling within the scope of the appended claims. 

Japanese Patent Application No. 2011-161640 is incorpo› rated herein by reference. 

Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise 

than as specifically described without departing from the scope of the appended claims. 

The invention claimed is: 

1. A chemically amplified resist composition comprising a polymer comprising recurring units (al) of acid labile group› substituted (meth)acrylic acid, styrenecarboxylic acid or vinylnaphthalenecarboxylic acid, recurring units (a2) having an acid labile group-substituted phenolic hydroxyl group rep› resented by the following formula ( 1) or both recurring units (al) and recurring units (a2): 

<img src='content_image/904935.jpg'>

wherein R 1 and R 3 are each independently hydrogen or methyl, R$^{2 }$and R 4 each are an acid labile group, X$_{1 }$ is a single bond, a C$_{1 }$-C$_{12 }$linking group having at least one of ester moiety, lactone ring, phenylene moiety or naph› thylene moiety, a phenylene group, or a naphthylene group, X$_{2 }$ is a single bond or an ester or amide group, al and a2 are numbers in the range: 0sals0.9, 0sa2s0.9, and 0sal+a2<1, and an acid generator, 

said resist composition further comprising a metal salt selected from the group consisting of the following gen› eral formulae: 

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wherein R 11 is each independently hydrogen, or a straight, branched or cyclic C $_{1 }$-C$_{20 }$alky 1, C$_{2}$ -C$_{20 }$alkeny 1, C$_{2}$ -C$_{20 }$alky› ny l, or C$_{6}$-C$_{20 }$aryl group which may have a hydroxyl, ether, ester, amino, amide, sulfonic acid ester, halogen, cyano, nitro, carbonate, carbamate, thiol, sulfide, thioketone radical or het› ero-aromatic ring; R $^{12 }$is a single bond, or a straight, branched or cyclic C$_{1 }$-C$_{20 }$alkylene, alkenylene, alkynylene, or CcC$_{20 }$ arylene group which may have a hydroxyl, ether, ester, amino, amide, sulfonic acid ester, halogen, cyano, nitro, carbonate, carbamate, thiol, sulfide, thioketone radical or hetero-aro› matic ring; R$^{13 }$and R$^{14 }$each are an alkylene, arylene, alk› enylene or alkynylene group as defined for R 12 , in which one or two hydrogen atoms are substituted by one or two carboxyl groups, 

