Sep. 10,2020  1  US 2020/0285149 Al  RESIST COMPOSITION AND PATTERNING  PROCESS  CROSS-REFERENCE TO RELATED  APPLICATION  TECHNICAL FIELD  BACKGROUND ART  CITATION LIST  SUMMARY OF INVENTION  [0001]  This non-provisional application claims pnonty  under 35 U.S.C. § 119(a) on Patent Application No. 2019- 040730 filed in Japan on Mar. 6, 2019, the entire contents of  which are hereby incorporated by reference.  [0002]  This invention relates to a resist composition and a  pattern forming process.  [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  smartphones 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 preventing the reduction of resolution of  resist pattern due to a lowering of light contrast, 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  (meth)acrylate 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  [0019]  An increase in acid diffusion also causes degrada› tion of resolution, LWR and CDU.  [0018]  As the wavelength of light becomes shorter, the  energy density thereof becomes higher and hence, the num› ber of photons generated upon exposure becomes smaller. A  variation in photon number causes variations in the LWR of  line patterns and the CDU of hole patterns. As the exposure  dose increases, the number of photons increases, leading to  a less variation of photon number. Thus there is a tradeoff  relationship between sensitivity and resolution, LWR and  CDU. In particular, the EUV lithography resist materials  have the tendency that a lower sensitivity leads to better  LWR and CDU.  [0010]  Patent Document 7 discloses a resist composition  comprising a 2,5,8,9-tetraaza-l-phosphabicyclo[3.3.3]unde› cane salt, biguanide salt, and phosphazene salt of an iodized  aromatic carboxylic acid. A sensitizing effect due to the high  absorption of iodine is expectable as well as a high sensi› tivity and low acid diffusion assigned to a salt of a strong  base with a 2,5,8,9-tetraaza-l-phosphabicyclo[3.3.3]unde› cane, biguanide or phosphazene. Nevertheless, there is the  demand for a resist material of new concept which exhibits  a higher sensitivity and lower acid diffusion.  [0009]  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.  [0008]  Patent Document 6 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.  [0007]  Patent Document 5 discloses a resist composition  comprising a sulfonium salt of iodized aromatic carboxylic  acid as a quencher. The quencher is readily decomposed  upon EUV exposure due to the substantial EUV absorption  of iodine, and is quite effective for controlling acid diffusion  by virtue of the large atomic weight of iodine. Thus a high  sensitivity and an improved dimension uniformity due to  low acid diffusion are expectable.  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.  [0011]  Patent Document  1:  JP-A 2001-194776  [0012]  Patent Document 2: JP-A 2002-226470  [0013]  Patent Document 3: JP-A 2002-363148  [0014]  Patent Document 4: WO 2008/066011  [0015]  Patent Document 5: JP-A 2017-219836  [0016]  Patent Document 6: JP-A 2018-097356  [0017]  Patent Document 7: JP-A 2018-049264 (U.S. Pat.  No. 10,101,654) 