US 10,802,400 B2  161  162  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 may  be blended. The quencher is typically selected from con› ventional basic compounds. Conventional basic compounds  include primary, secondary, and tertiary aliphatic amines,  mixed amines, aromatic amines, heterocyclic amines, nitro› gen-containing compounds with carboxyl group, nitrogen› containing compounds with sulfonyl group, nitrogen-con› taining  compounds  with  hydroxyl  group,  nitrogen› containing compounds with hydroxyphenyl group, alcoholic  nitrogen-containing compounds, amide derivatives, imide  derivatives, and carbamate derivatives. Also included are  primary, secondary, and tertiary amine compounds, specifi› cally 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 com› pounds having a carbamate group as described in JP  3 790649. 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 may also be used as the quencher. While an  a-fluorinated 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 or a carboxylic  acid is released by salt exchange with an a-non-fluorinated  onium salt. An a-non-fluorinated sulfonic acid and a car› boxylic acid function as a quencher because they do not  induce deprotection reaction.  Another useful quencher is an onium salt of carboxylic  acid having the formula ( 4):  wherein R 4 " is a C $_{1 }$-C$_{40 }$ straight, branched or cyclic mon› ovalent hydrocarbon group which may contain a heteroa› tom, and  MA+  is an onium ion which is typically a sulfo› nium, iodonium or ammonium ion.  The preferred anion moiety of the carboxylic acid onium  salt has the formula (5):  wherein R 402  and R 403  are each independently hydrogen,  fluorine or trifluoromethyl, and R$^{404 }$is hydrogen, hydroxyl,  a C$_{1 }$-C$_{35 }$ straight, branched or cyclic monovalent hydrocar› bon group which may contain a heteroatom, or a substituted  or unsubstituted  CcC$_{30 }$ aryl group.  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 quencher is preferably added in an amount of 0 to 5  parts, more preferably Oto 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  The resist composition is used in the fabrication of  various integrated circuits. Pattern formation using the resist  composition may be performed by well-known lithography  processes. The process generally involves coating, prebak› ing, exposure, post-exposure baking (PEB), and develop- ment.  If necessary, any additional steps may be added.  For example, the resist composition is first applied onto a  substrate on which an integrated circuit is to be formed ( e.g.,  Si, SiO$_{2}$ ,  SiN, SiON, TiN, WSi, BPSG, SOG, or organic  antireflective coating) or a substrate on which a mask circuit  is to be formed (e.g., Cr, CrO, CrON, M0Si$_{2}$ ,  or SiO$_{2}$ )  by a  suitable coating technique such as spin coating, roll coating,  flow coating, dipping, spraying or doctor coating. The  coating is prebaked on a hot plate at a temperature of 60 to  150°  C. for 10 seconds to 30 minutes, preferably at 80 to  120°  C. for 30 seconds to 20 minutes. The resulting resist  film is generally 0.01 to 2.0 µm  thick.  The resist film is then exposed to a desired pattern of  high-energy radiation such as UV, deep-UV, EB, EUV, x-ray,  soft x-ray, excimer laser light, y-ray or synchrotron radia› tion, directly or through a mask. The exposure dose is  preferably about 1 to 200 mJ/cm 2 ,  more preferably about 10  to 100 mJ/cm 2 ,  or about 0.1 to 100 µC/cm 2 ,  more preferably  about 0.5 to 50 µC/cm 2 .  The resist film is further baked  (5) 