US 2020/0050105 Al  1  Feb. 13, 2020  RESIST COMPOSITION AND PATTERNING  PROCESS  CROSS-REFERENCE TO RELATED  APPLICATION  [0001]  This non-provisional application claims pnonty  under 35 U.S.C. § 119(a) on Patent Application No. 2018- 150050 filed in Japan on Aug. 9, 2018, the entire contents of  which are hereby incorporated by reference.  [0002]  This invention relates to a resist composition and a  pattern forming process.  TECHNICAL FIELD  BACKGROUND ART  [0003]  To meet the demand for higher integration density  and operating speed of LS Is, the effort to reduce the pattern  rule is in rapid progress. In particular, the enlargement of the  logic memory market to comply with the wide-spread use of  smart phones drives forward the miniaturization technology.  As the advanced miniaturization technology, manufacturing  of microelectronic devices at the 10-nm node by double  patterning of the ArF immersion lithography has been imple› mented in a mass scale. Manufacturing of 7-nm node  devices as the next generation by the double patterning  technology is approaching to the verge of high-volume  application. The candidate for 5-nm node devices as the next  generation but one is EUV lithography.  [0004]  As the pattern feature size is reduced, approaching  to the diffraction limit of light, light contrast lowers. In the  case of positive resist film, a lowering of light contrast leads  to reductions of resolution and focus margin of hole and  trench patterns. For mitigating the influence of reduced  resolution of resist pattern due to a lowering of light con› trast, an attempt is made to enhance the dissolution contrast  of resist film.  [0005]  Chemically amplified resist compositions compris› ing an acid generator capable of generating an acid upon  exposure to light or EB include chemically amplified posi› tive resist compositions wherein deprotection reaction takes  place under the action of acid and chemically amplified  negative resist compositions wherein polarity switch or  crosslinking reaction takes place under the action of acid.  Quenchers are often added to these resist compositions for  the purpose of controlling the diffusion of the acid to  unexposed region to improve the contrast. The addition of  quenchers is fully effective to this purpose. A number of  amine quenchers were proposed as disclosed in Patent  Documents 1 to 3.  [0006]  With respect to the acid labile group used in  methacrylate polymers for the ArF lithography resist mate› rial, deprotection reaction takes place when a photoacid  generator capable of generating a sulfonic acid having  fluorine substituted at a-position (referred to "a-fluorinated  sulfonic acid") is used, but not when an acid generator  capable of generating a sulfonic acid not having fluorine  substituted at a-position (referred to "a-non-fluorinated  sulfonic acid") or carboxylic acid is used. If a sulfonium or  iodonium salt capable of generating an a-fluorinated sulfo› nic acid is combined with a sulfonium or iodonium salt  capable of generating an a-non-fluorinated sulfonic acid, the  sulfonium or iodonium salt capable of generating an a-non› fluorinated sulfonic acid undergoes ion exchange with the  a-fluorinated sulfonic acid. Through the ion exchange, the  a-fluorinated sulfonic acid thus generated by light exposure  is converted back to the sulfonium or iodonium salt while  the sulfonium or iodonium salt of an a-non-fluorinated  sulfonic acid or carboxylic acid functions as a quencher.  Patent Document 4 discloses a resist composition compris› ing a sulfonium or iodonium salt capable of generating  carboxylic acid as a quencher.  [0007]  Patent Document 5 discloses a resist composition  comprising an iodized aniline as a quencher. The aniline has  a low basicity which is insufficient to suppress acid diffu› s10n.  [0008]  Sulfonium and iodonium salt type quenchers are  photo-decomposable like photoacid generators. That is, the  amount of quencher in the exposed region is reduced. Since  acid is generated in the exposed region, the reduced amount  of quencher leads to a relatively increased concentration of  acid and hence, an improved contrast. However, the acid  diffusion in the exposed region is not suppressed, indicating  the difficulty of acid diffusion control.  CITATION LIST  DISCLOSURE OF INVENTION  [0009]  Patent Document  1:  JP-A 2001-194776  [0010]  Patent Document 2: JP-A 2002-226470  [0011]  Patent Document 3: JP-A 2002-363148  [0012]  Patent Document 4: WO 2008/066011  [0013]  Patent Document 5: JP-A 2018-097356  [0014]  For the acid-catalyzed chemically amplified resist,  it is desired to develop a quencher capable of reducing the  LWR of line patterns or the CDU of hole patterns and  improving sensitivity.  [0015]  An object of the invention is to provide a resist  composition which exhibits a high sensitivity and a reduced  LWR or improved CDU, independent of whether it is of  positive tone or negative tone; and a pattern forming process  using the same.  [0016]  The inventors have found that using an amine  compound having an iodine-substituted aromatic ring (also  referred to as iodized aromatic ring-containing amine com› pound, hereinafter) as the quencher, a resist material having  a reduced LWR, improved CDU, high contrast, improved  resolution, and wide process margin is obtainable.  [0017]  In one aspect, the invention provides a resist com› position comprising a base polymer and a quencher, the  quencher being an amine compound having an iodine› substituted aromatic ring bonded to the nitrogen atom via a  C$_{1 }$-C$_{20 }$ divalent hydrocarbon group which may contain at  least one moiety selected from ester bond and ether bond.  [0018]  Specifically, the amine compound has the formula  (A).  (A) 