Jul.  30,  2020  1  US 2020/0241418 Al  POSITIVE 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- 012712 filed in Japan on Jan. 29, 2019, the entire contents  of which are hereby incorporated by reference.  [0002]  This invention relates to a positive resist compo› sition and a patterning process using the composition.  [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. The logic devices used in smart  phones or the like drive forward the miniaturization tech› nology. Logic devices of 10-nm node are manufactured in a  large scale using a multi-patterning lithography process  based on ArF lithography.  [0004]  In the application of lithography to next 7-nm or  5-nm node devices, the increased expense and overlay  accuracy of multi-patterning lithography become tangible.  The advent of EUV lithography capable of reducing the  number of exposures is desired.  [0005]  Since the wavelength (13.5 nm) of extreme ultra› violet (EUV) is shorter than ‰o of the wavelength (193 nm)  of ArF excimer laser, the EUV lithography achieves a high  light contrast, from which a high resolution is expectable.  Because of the short wavelength and high energy density of  EUV, an acid generator is sensitive to a small dose of  photons.  It  is believed that the number of photons available  with EUV exposure is  ‰4 of that of ArF exposure. In the  EUV lithography, the phenomenon that the edge roughness  (LER, LWR) of line patterns or the critical dimension  uniformity (CDU) of hole patterns is degraded by a variation  of photon number is considered a problem.  [0006]  Aiming to reduce a photon number variation, an  attempt was made to render the resist more absorptive so that  the number of photons absorbed in the resist film is  increased.  [0007]  Patent Document 1 discloses a halogen-substituted  styrene base resin. Among the halogen atoms, iodine is  highly absorptive to EUV radiation of wavelength 13.5 nm.  Recently Patent Documents 2 to 4 propose to use iodized  resins as EUV resist material.  [0008]  Patent Document 5 proposes a quencher of iodo› nium carboxylate type having a carboxylate ion bonded to  an iodonium cation. Patent Documents 6 and 7 propose the  use of hypervalent iodine compounds as the quencher.  Patent Document 8 discloses a sulfonium salt of iodized  benzoic acid. Since iodine has a large atomic weight,  quenchers in the form of iodized compounds are fully  effective for suppressing acid diffusion.  [0009]  For the purpose of suppressing acid diffusion,  Patent Documents 9 and 10 disclose resist compositions  comprising a polymer comprising amino-containing recur› ring units. The polymeric amine is effective for suppressing  acid diffusion. Moreover, Patent Document 11 proposes a  resist composition comprising a polymer comprising recur› ring units of both acid generator and amine as the base  [0026]  Further, for improving the dissolution contrast,  recurring units having a carboxyl or phenolic hydroxyl  group in which the hydrogen is substituted by an acid labile  group are incorporated into the base polymer. There is  obtained a positive resist composition having a high sensi› tivity, a significantly increased contrast of alkali dissolution  [0025]  Making extensive investigations in search for a  positive resist material capable of meeting the current  requirements including high resolution, low edge roughness  and small size variation, the inventors have found the  following. To meet the requirements, the acid diffusion  distance should be minimized. This invites a lowering of  sensitivity and a drop of dissolution contrast, raising the  problem that the resolution of a two-dimensional pattern  such as hole pattern is reduced. Unexpectedly, when a  polymer comprising recurring units having the structure of  an ammonium salt of a carboxylic acid having an iodine or  bromine-substituted aromatic ring is used as a base polymer,  the efficiency of acid generation is increased by the further› ance of absorption and at the same time, the acid diffusion  distance is minimized. Better results are obtainable using the  polymer as a base polymer in a chemically amplified posi› tive resist composition.  [0024]  An object of the present invention is to provide a  positive resist composition which exhibits a higher sensi› tivity and resolution than conventional positive resist com› positions, low edge roughness and small size variation, and  forms a pattern of good profile after exposure and develop› ment, and a patterning process using the resist composition.  [0023]  Patent Document 13: JP-A 2006-178317  [0022]  Patent Document 12: JP-A 2006-045311 (U.S. Pat.  No. 7,482,108)  [0021]  Patent Document 11: JP-A 2011-039266  [0020]  Patent Document 10: JP-A 2009-181062  [0019]  Patent Document 9: JP-A 2008-133312  [0018]  Patent Document 8: JP-A 2017-219836  [0017]  Patent Document 7: JP-A 2015-172746 (U.S. Pat.  No. 9,448,475)  [0016]  Patent Document 6: JP-A 2015-180928 (U.S. Pat.  No. 9,563,123)  [0015]  Patent Document 5: JP 5852490 (U.S. Pat. No.  9,176,379)  [0014]  Patent Document 4: JP-A 2018-004812  [0013]  Patent Document 3: WO 2013/024777  [0012]  Patent Document 2: JP-A 2015-161823  [0011]  Patent Document  1:  JP-A 805-204157  [0010]  The addition of an acid generator capable of gen› erating a bulky acid is an effective means for suppressing  acid diffusion.  It  was then proposed to incorporate in a  polymer an acid generator of an onium salt having a polym› erizable unsaturated bond. Patent Document 12 discloses a  sulfonium salt having a polymerizable unsaturated bond  capable of generating a specific sulfonic acid and a similar  iodonium salt. Patent Document 13 discloses a sulfonium  salt having sulfonic acid directly attached to the backbone.  polymer.  It  is a single component resist material in the sense  that both acid generator and quencher are allocated to a  common polymer and successful in minimizing the influ› ence of acid diffusion. 