169  US 9,360,753 B2  170  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.  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):  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,  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:  TABLE3  PEB  temperature  Sensitivity  LWR  Resist  (" c.)  (mJ/cm 2 )  (nm)  Example 2-1  Resist 17  95  10.0  3.1  Example 2-2  Resist 18  95  10.0  3.1  Example 2-3  Resist 19  95  9.0  3.3  Example 2-4  Resist 20  95  9.0  3.2  Example 2-5  Resist 21  95  9.0  3.1  Example 2-6  Resist 22  95  10.5  3.3  Example 2-7  Resist 23  95  11.0  3.3  Example 2-8  Resist 24  95  10.0  3.4  Comparative  Comparative  95  13.5  4.3  Example 2-1  Resist 2  (1)  cr’•(R  11 coo-h  Cr 3 •(R 11 coo-h  (Cr 3 •MR $^{13}$Coo-)$_{6 }$ Mn 2 •(R 11 coo-)o  (Mn 3 •MR 12 (Coo-)o)3  Fe 2 •R 12 (COO-)o  Fe 3 •R $^{13}$(Coo-h  ca 2 •(R 11 coo-)o  Ni 2 •cR 11 coo-h  cu•R 11 coo› Cu2•R12(COO-)o  zn•R 11 coo› Ag•R11coo› cd 2 •cR 11 coo-Jo  sn 2 •(R 11 coo-) 2  Sn 4 •(R  $^{12}$(COO-hh  Sb 3 .(R  11 coo-) 3  cr’•R 12 ccoo-h  (Cr 3 •) 2 (R  12 (COO-) 2 ) 3 Cr 3 •(R 11 COO-) 7 (OH)o  Fe 3 •(R 11 coo-h  (Fe 3 •MR $^{12}$(coo-)o)3  Fe 2 •cR  11 coo-Jo  Co 2 •R 12 (COO-h  Ni 2 •R 12 ccoo-h  (Cu•JoR 12 (COO-)o  Cu 2 •(R 11 Coo-) 2  (zn•)2R 12 (COO-) 2  Zn 2 +(R 11 COO-)o  (Ag•J 2 R 12 ccoo-h  cd 2 •R 12 ccoo-Jo  Sn 2 +R 12 (COO-) 2  Sn 4 +(R 11 COO-) 4  Sn 4 •R 1 4(coo-) 4  (Sb 3 .MR 12 ccoo-J  sb 3 •Rll(coo-J 3  2h  Hl"•(R 12 coo-J 2 ) 2  Hf’•R 14 (coo-J 4 