US 10,606,172 B2  89  90  exposed to EUV through a patterned mask. The resist film  was baked (PEB) on a hotplate at the temperature shown in  Table 2 for 60 seconds and developed in a 2.38 wt % TMAH  aqueous solution for 30 seconds to form a hole pattern  having a size of 23 nm and a pitch of 46 nm.  The resist pattern was evaluated under CD-SEM (CG- 5000, Hitachi High-Technologies Corp.). The exposure dose  that provides a hole pattern having a size of 23 nm is  reported as sensitivity. The size of 50 holes at that dose was  measured, from which a size variation  (3a)  was computed  and reported as CDU.  The resist composition is shown in Table 2 together with  the sensitivity and CDU of EUV lithography.  The invention claimed is:  1.  A resist composition comprising a base polymer, an  acid generator and a quencher containing an iodonium salt  having the formula (A):  It  is demonstrated in Tables 1 and 2 that resist composi› tions comprising an iodonium salt having formula (A)  within the scope of the invention offer a satisfactory reso› lution and improved LWR and CDU.  Japanese Patent Application No. 2017-052391 1s mcor- porated herein by reference. Although some preferred  embodiments have been described, many modifications and  variations may be made thereto in light of the above teach› ings.  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.  TABLE 2  Acid  Polymer  generator  Quencher  Organic solvent PEB temp. Sensitivity CDU  (pbw)  (pbw)  (pbw)  (pbw)  Example  2-1  Polymer 3  Quencher 7  PGMEA (400)  (100)  (4.00)  CyH (2,000)  PGME (100)  2-2  Polymer 3  Quencher 8  PGMEA (400)  (100)  (4.00)  CyH (2,000)  PGME (100)  2-3  Polymer 3  Quencher 9  PGMEA (400)  (100)  (4.50)  CyH (2,000)  PGME (100)  2-4  Polymer 3  Quencher 10  PGMEA (400)  (100)  (4.50)  CyH (2,000)  PGME (100)  2-5  Polymer 3  Quencher 11  PGMEA (400)  (100)  (4.50)  CyH (2,000)  PGME (100)  2-6  Polymer 3  Quencher 12  PGMEA (400)  (100)  (4.50)  CyH (2,000)  PGME (100)  2-7  Polymer 3  Quencher 13  PGMEA (400)  (100)  (4.50)  CyH (2,000)  PGME (100)  2-8  Polymer 3  Quencher 14 PGMEA (400)  (100)  (5.00)  CyH (2,000)  PGME (100)  2-9  Polymer 3  PAG 2  Quencher 13  PGMEA (400)  (100)  (15)  (4.50)  CyH (2,000)  PGME (100)  2-10  Polymer 3  PAG 3  Quencher 13  PGMEA (400)  (100)  (15)  (4.50)  CyH (2,000)  PGME (100)  2-11  Polymer 3  PAG4  Quencher 13  PGMEA (400)  (100)  (15)  (4.50)  CyH (2,000)  PGME (100)  Comparative  2-1  Polymer 3  Comparative  PGMEA (400)  Example  (100)  Quencher 6  CyH (2,000)  (2.50)  PGME (100)  (" C.)  (mJ/cm 2 )  (nm)  100  26  2.4  100  28  2.3  100  24  2.3  100  25  2.3  100  26  2.1  100  28  2.0  100  24  2.1  100  20  2.2  100  21  2.9  100  16  2.6  100  14  2.9  100  35  4.0  (A)  [  )l_  c~  /_  ~  x2  FP  0  R2  R’,  ,  x•’  ’C~.  I  1+  I  R3  wherein R 1  is a hydroxyl group, C$_{1}$-C$_{6 }$ straight, branched  or cyclic alkyl or alkoxy group, C$_{2}$-C$_{6 }$ straight,  branched or cyclic acyloxy group, fluorine, chlorine,  bromine, amino, -NR$^{5}$-C(=O)-R 6 , or-NR $^{5}$----C  (=O)-O-R 6 , R 5  is hydrogen or a C$_{1}$-C$_{6 }$ straight,  branched or cyclic alkyl group, R  6  is a C$_{1 }$-C$_{6 }$ straight,  branched or cyclic alkyl group or C$_{2}$ -C$_{8 }$ straight,  branched or cyclic alkenyl group; X$^{1 }$is a single bond or  a ( q+ 1 )-valent C$_{1 }$-C$_{20 }$linking group which may contain  at least one moiety selected from ether, carbonyl, ester,  amide, sultone, lactam, carbonate, halogen, hydroxyl  and carboxyl; X 2  is an ether, ester or amide group; R 2  and R 3  are each independently trifluoromethyl or a  CcC$_{10 }$ aryl, C$_{2}$ -C$_{6 }$ alkenyl or C$_{2}$-C$_{6 }$ alkynyl group in 