Apr. 18,  2019  83  US 2019/0113844 Al  diffusion. By virtue of these advantages, the composition is  fully useful in commercial application and suited as a  pattern-forming material for the fabrication of VLSis.  [0137]  Examples of the organic solvent used herein are  described in JP-A 2008-111103, paragraphs [0144]-[0145]  (U.S. Pat. No. 7,537,880). Exemplary solvents include  ketones such as cyclohexanone, cyclopentanone and methyl- 2-n-pentyl ketone; alcohols such as 3-methoxybutanol,  3-methyl-3-methoxybutanol,  l-methoxy-2-propanol,  and  l-ethoxy-2-propanol; ethers such as propylene glycol  monomethyl ether, ethylene glycol monomethyl ether, pro› pylene glycol monoethyl ether, ethylene glycol monoethyl  ether, propylene glycol dimethyl ether, and diethylene glycol  dimethyl ether; esters such as propylene glycol monomethyl  ether acetate (PGMEA), propylene glycol monoethyl ether  acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl  3-methoxypropionate, ethyl 3-ethoxypropionate, t-butyl  acetate, t-butyl propionate, and propylene glycol mono-t› butyl ether acetate; and lactones such as y-butyrolactone,  which may be used alone or in admixture.  [0138]  The organic solvent is preferably added in an  amount of 100 to 10,000 parts, and more preferably 200 to  8,000 parts by weight per 100 parts by weight of the base  polymer.  [0139]  Exemplary surfactants are described in JP-A 2008- 111103, paragraphs [0165]-[0166]. Inclusion of a surfactant  may improve or control the coating characteristics of the  resist composition. The surfactant is preferably added in an  amount of 0.0001 to 10 parts by weight per 100 parts by  weight of the base polymer.  [0140]  In the case of positive resist compositions, inclu› sion of a dissolution inhibitor may lead to an increased  difference in dissolution rate between exposed and unex› posed areas and a further improvement in resolution. In the  case of negative resist compositions, a negative pattern may  be formed by adding a crosslinker to reduce the dissolution  rate of exposed area.  [0141]  The dissolution inhibitor which can be used herein  is a compound having at least two phenolic hydroxyl groups  on the molecule, in which an average of from  O  to 100 mo!  % of all the hydrogen atoms on the phenolic hydroxyl  groups are replaced by acid labile groups or a compound  having at least one carboxyl group on the molecule, in which  an average of 50 to 100 mo! % of all the hydrogen atoms on  the carboxyl groups are replaced by acid labile groups, both  the compounds having a molecular weight of 100 to 1,000,  and preferably 150 to 800. Typical are bisphenol A, trisphe› nol, phenolphthalein, cresol novolac, naphthalenecarboxylic  acid, adamantanecarboxylic acid, and cholic acid derivatives  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]).  [0142]  In the positive resist composition, the dissolution  inhibitor is preferably added in an amount of  O  to 50 parts,  more preferably 5 to 40 parts by weight per 100 parts by  weight of the base polymer.  [0143]  Suitable crosslinkers which can be used herein  include epoxy compounds, melamine compounds, guan› amine compounds, glycoluril compounds and urea com› pounds having substituted thereon at least one group  selected from among methylol, alkoxymethyl and acy› loxymethyl groups, isocyanate compounds, azide com› pounds, and compounds having a double bond such as an  [0133]  Further, a sulfonium or iodonium salt having a  brominated anion may be used as the PAG. Examples of the  brominated anion are those having formulae (3-1) to (3-4)  wherein iodine is replaced by bromine. Examples of the  brominated anion are the same as examples of the iodized  anion except that iodine is replaced by bromine.  [0134]  When the resist composition contains the acid  generator of addition type, an appropriate amount of the  generator added is 0.1 to 50 parts, more preferably 1 to 40  parts by weight per 100 parts by weight of the base resin.  [0135]  Other Components  [0136]  With the base polymer and sulfonium salt as  described above, other components such as an organic  solvent, surfactant, dissolution inhibitor, and crosslinker  may be blended in any desired combination to formulate a  chemically amplified positive or negative resist composi› tion. This positive or negative resist composition has a very  high sensitivity in that the dissolution rate in developer of  the base polymer in exposed areas is accelerated by catalytic  reaction. In addition, the resist film has a high dissolution  contrast, resolution, exposure latitude, and process adapt› ability, and provides a good pattern profile after exposure,  and minimal proximity bias because of restrained acid  j  0  ____r{O_z_~F3  0~  ’  ~S03- 0  Q_>--o-<:t:~ 