## POSITIVE 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. 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 

## TECHNICAL FIELD 

## BACKGROUND ART 

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. 

[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. 

[0011] Patent Document 1: JP-A 805-204157 

[0012] Patent Document 2: JP-A 2015-161823 

[0013] Patent Document 3: WO 2013/024777 

[0014] Patent Document 4: JP-A 2018-004812 

[0015] Patent Document 5: JP 5852490 (U.S. Pat. No. 9,176,379) 

[0016] Patent Document 6: JP-A 2015-180928 (U.S. Pat. No. 9,563,123) 

[0017] Patent Document 7: JP-A 2015-172746 (U.S. Pat. No. 9,448,475) 

[0018] Patent Document 8: JP-A 2017-219836 

[0019] Patent Document 9: JP-A 2008-133312 

[0020] Patent Document 10: JP-A 2009-181062 

[0021] Patent Document 11: JP-A 2011-039266 

[0022] Patent Document 12: JP-A 2006-045311 (U.S. Pat. No. 7,482,108) 

[0023] Patent Document 13: JP-A 2006-178317 

[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. 

[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. 

[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 

## CITATION LIST 

## SUMMARY OF INVENTION 

