US 9,869,931 B2  168  167  TABLE 4  said resist composition further comprising a complex of a  metal with an acid, the metal being selected from the  group consisting of cerium, copper, zinc, iron, indium,  yttrium, ytterbium, tin, thulium, scandium, nickel, neo› dymium, hafnium, zirconium, titanium, lanthanum, sil› ver, barium, holmium, terbium, lutetium, europium,  dysprosium, gadolinium, rubidium, strontium, and  cesium, and the acid being selected from the group  consisting of a C$_{1 }$-C$_{4 }$ fluoroalkylsulfonic acid, CcC$_{12 }$ arylsulfonic acid having at least one fluorine atom  which may be substituted with hydroxy group, C$_{1 }$-C$_{12 }$ alkoxy group or acyloxy group, or sulfonyl group,  tetraphenylboric acid having at least one fluorine atom,  C$_{1 }$-C$_{4 }$ fluoroalkylsulfonimidic acid, and C$_{1 }$-C$_{4 }$ fluoro› alkylsulfonemethide acid.  2.  The resist composition of claim  1  wherein the polymer  comprising recurring units of acid labile group-substituted  (meth)acrylic acid, styrenecarboxylic acid or vinylnaphtha› lenecarboxylic acid and/or recurring units having an acid  labile group-substituted phenolic hydroxyl group has recur› ring units (al) and/or (a2), as represented by the general  formula (1 ):  It  is evident from Tables 3 and 4 that the resist compo- sitions of Examples have a high sensitivity and reduced  LWR. The resist compositions of Comparative Examples  have sensitivity and LWR values which are inferior to those  of Examples.  It  is demonstrated that the resist composition comprising  a polymer comprising acid labile group-substituted recur› ring units and preferably acid generator-bearing recurring  units, to which a specific metal-acid complex is added,  exhibits a high resolution, a high sensitivity, and a minimal  LWR. 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 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 falling within the scope of the  appended claims.  Japanese Patent Application Nos. 2015-023149 and 2015- 15 9402 are incorporated 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 resist composition comprising a polymer comprising  recurring units of acid labile group-substituted (meth)acrylic  acid, styrenecarboxylic acid or vinylnaphthalenecarboxylic 60  acid and/or recurring units having an acid labile group› substituted phenolic hydroxyl group, and an acid generator,  or a copolymer comprising recurring units of acid labile  group-substituted (meth)acrylic acid, styrenecarboxylic acid  or vinylnaphthalenecarboxylic acid and/or recurring units 65  having an acid labile group-substituted phenolic hydroxyl  group and recurring units having an acid generator,  8.  A resist composition comprising a polymer comprising  recurring units of acid labile group-substituted (meth)acrylic  acid, styrenecarboxylic acid or vinylnaphthalenecarboxylic  acid and/or recurring units having an acid labile group› substituted phenolic hydroxyl group, and an acid generator,  or a copolymer comprising recurring units of acid labile  group-substituted (meth)acrylic acid, styrenecarboxylic acid  or vinylnaphthalenecarboxylic acid and/or recurring units  7.  The process of claim  5  wherein the high-energy radia› tion is an electron beam at an accelerating voltage of 1 to 150  keV.  6.  The process of claim  5  wherein the high-energy radia› tion is EUV radiation having a wavelength of 3 to 15  nm.  5.  A pattern forming process comprising the steps of  coating the resist composition of claim  1  onto a substrate,  baking, exposing the resulting resist film to high-energy  radiation, and developing with a developer.  4.  The resist composition of claim  1,  further comprising  at least one component selected from among an organic  solvent, a dissolution inhibitor, an acid generator, a basic  compound, and a surfactant.  3.  The resist composition of claim  1  which is a chemically  amplified positive resist composition.  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 and  naphthylene moiety, a phenylene group, or a naphth- ylene 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 0<al+a2<1.  (1)  PEB temp.  Resist  (" C.)  Example  21  Resist 21  85  22  Resist 22  85  23  Resist 23  75  24  Resist 24  75  25  Resist 25  80  26  Resist 26  80  27  Resist 27  80  28  Resist 28  80  29  Resist 29  80  30  Resist 30  80  31  Resist 31  80  32  Resist 32  80  33  Resist 33  80  34  Resist 34  80  35  Resist 35  80  36  Resist 36  80  37  Resist 37  80  Comparative  85  Resist 1  Sensitivity LWR  (µC/cm 2 )  (nm)  24.0  5.9  26.0  5.8  22.0  4.8  23.5  4.9  19.0  4.4  18.0  4.1  27.0  3.9  28.0  3.8  24.0  3.7  22.0  3.6  23.0  3.4  22.0  3.4  24.0  3.6  25.0  3.6  23.0  3.3  25.0  3.2  23.0  3.1  35.5  7.2  Comparative  Example  2  3  Comparative  Resist 2  Comparative  Resist 3  85  21.5  9.2  85  36.5  7.2 