US 10,606,172 B2  76  75  in which the hydrogen atom on the hydroxyl or carboxyl  group is replaced by an acid labile group, as described in  U.S. Pat. No. 7,771,914 (JP-A 2008-122932, paragraphs  [0155]-[0178]).  In the positive resist composition, the dissolution inhibitor  is preferably added in an amount of 0 to 50 parts, more  preferably 5 to 40 parts by weight per 100 parts by weight  of the base polymer.  Suitable crosslinkers which can be used herein include  epoxy compounds, melamine compounds, guanamine com› pounds, glycoluril compounds and urea compounds having  substituted thereon at least one group selected from among  methylol, alkoxymethyl and acyloxymethyl groups, isocya› nate compounds, azide compounds, and compounds having  a double bond such as an alkenyl ether group. These  compounds may be used as an additive or introduced into a  polymer side chain as a pendant. Hydroxy-containing com› pounds may also be used as the crosslinker.  Of the foregoing crosslinkers, examples of suitable epoxy  compounds  include tris(2,3-epoxypropyl)  isocyanurate,  trimethylolmethane triglycidyl ether, trimethylolpropane tri› glycidyl  ether,  and triethylolethane  triglycidyl  ether.  Examples of the melamine compound include hexamethylol  melamine, hexamethoxymethyl melamine, hexamethylol  melamine compounds having 1 to 6 methylol groups  methoxymethylated and mixtures thereof, hexamethoxy› ethyl melamine, hexaacyloxymethyl melamine, hexameth› ylol melamine compounds having 1 to 6 methylol groups  acyloxymethylated and mixtures thereof. Examples of the  guanamine compound include tetramethylol guanamine,  tetramethoxymethyl guanamine, tetramethylol guanamine  compounds having 1 to 4 methylol groups methoxymethyl› ated and mixtures thereof, tetramethoxyethyl guanamine,  tetraacyloxyguanamine,  tetramethylol  guanamine  com› pounds having 1 to 4 methylol groups acyloxymethylated  and mixtures thereof. Examples of the glycoluril compound  include tetramethylol glycoluril, tetramethoxyglycoluril,  tetramethoxymethyl  glycoluril,  tetramethylol  glycoluril  compounds having 1 to 4 methylol groups methoxymethyl› ated and mixtures thereof, tetramethylol glycoluril com- pounds having 1 to 4 methylol groups acyloxymethylated  and mixtures thereof. Examples of the urea compound  include  tetramethylol  urea,  tetramethoxymethyl  urea,  tetramethylol urea compounds having 1 to 4 methylol  groups methoxymethylated and mixtures thereof, and  tetramethoxyethyl urea.  Suitable isocyanate compounds include tolylene diisocya› nate, diphenylmethane diisocyanate, hexamethylene diiso› cyanate and cyclohexane diisocyanate. Suitable azide com- pounds  include  1,1’-biphenyl-4,4’-bisazide,  4,4’- methylidenebisazide, and 4,4’-oxybisazide. Examples of the  alkenyl ether group-containing compound include ethylene  glycol divinyl ether, triethylene glycol divinyl ether, 1,2- propanediol divinyl ether, 1,4-butanediol divinyl ether,  tetramethylene glycol divinyl ether, neopentyl glycol divinyl  ether, trimethylol propane trivinyl ether, hexanediol divinyl  ether, 1,4-cyclohexanediol divinyl ether, pentaerythritol  trivinyl ether, pentaerythritol tetravinyl ether, sorbitol tet› ravinyl ether, sorbitol pentavinyl ether, and trimethylol  propane trivinyl ether.  In the negative resist composition, the crosslinker is  preferably added in an amount of 0.1 to 50 parts, more  preferably 1 to 40 parts by weight per 100 parts by weight  of the base polymer.  In the resist composition of the invention, a quencher 65  other than the iodonium salt having formula (A) may be  blended. The other quencher is typically selected from  conventional basic compounds. Conventional basic com› pounds include primary, secondary, and tertiary aliphatic  amines, mixed amines, aromatic amines, heterocyclic  amines, nitrogen-containing compounds with carboxyl  group, nitrogen-containing compounds with sulfonyl group,  nitrogen-containing compounds with hydroxyl group, nitro- gen-containing compounds with hydroxyphenyl group,  alcoholic nitrogen-containing compounds, amide deriva› tives, imide derivatives, and carbamate derivatives. Also  included are primary, secondary, and tertiary amine com› pounds, specifically amine compounds having a hydroxyl,  ether, ester, lactone ring, cyano, or sulfonic acid ester group  as described in JP-A 2008-111103, paragraphs [0146]› [0164], and compounds having a carbamate group as  described in JP 3790649. Addition of a basic compound may  be effective for further suppressing the diffusion rate of acid  in the resist film or correcting the pattern profile.  Onium salts such as sulfonium salts, iodonium salts and  ammonium salts of sulfonic acids which are not fluorinated  at a-position as described in U.S. Pat. No. 8,795,942 (JP-A  2008-158339) and similar onium salts of carboxylic acid  may also be used as the other quencher. While an a-fluo› rinated sulfonic acid, imide acid, and methide acid are  necessary to deprotect the acid labile group of carboxylic  acid ester, an a-non-fluorinated sulfonic acid and a carbox› ylic acid are released by salt exchange with an a-non› fluorinated onium salt.  An  a-non-fluorinated sulfonic acid  and a carboxylic acid function as a quencher because they do  not induce deprotection reaction.  Also useful are quenchers of polymer type as described in  U.S. Pat. No. 7,598,016 (JP-A2008-239918). The polymeric  quencher segregates at the resist surface after coating and  thus enhances the rectangularity of resist pattern. When a  protective film is applied as is often the case in the immer› sion lithography, the polymeric quencher is also effective for  preventing a film thickness loss of resist pattern or rounding  of pattern top.  The other quencher is preferably added in an amount of0  to 5 parts, more preferably 0 to 4 parts by weight per 100  parts by weight of the base polymer.  To the resist composition, a polymeric additive (or water  repellency improver) may also be added for improving the  water repellency on surface of a resist film as spin coated.  The water repellency improver may be used in the topcoat› less immersion lithography. Suitable water repellency  improvers include polymers having a fluoroalkyl group and  polymers having a specific structure with a 1,1,1,3,3,3- hexafluoro-2-propanol residue and are described in JP-A  2007-297590 and JP-A 2008-111103, for example. The  water repellency improver to be added to the resist compo› sition should be soluble in the organic solvent as the  developer. The water repellency improver of specific struc› ture with a 1,1,1,3,3,3-hexafluoro-2-propanol residue is well  soluble in the developer. A polymer having an amino group  or amine salt copolymerized as recurring units may serve as  the water repellent additive and is effective for preventing  evaporation of acid during PEB, thus preventing any hole  pattern opening failure after development.  An  appropriate  amount of the water repellency improver is 0 to 20 parts,  preferably 0.5 to 10 parts by weight per 100 parts by weight  of the base polymer.  Also, an acetylene alcohol may be blended in the resist  composition. Suitable acetylene alcohols are described in  JP-A 2008-122932, paragraphs [0179]-[0182].  An  appropri› ate amount of the acetylene alcohol blended is 0 to 5 parts  by weight per 100 parts by weight of the base polymer.  Process 