## 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- 236571 filed in Japan on Dec. 18, 2018, the entire contents of which are hereby incorporated by reference. 

[0002] This invention relates to a resist composition 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 (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 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 iodine› substituted resins as EUV resist material. Regrettably, it is not true that a higher sensitivity is obtainable merely by incorporating iodine to increase the number of photons absorbed. With respect to the acid generation in EUV exposure, Non-Patent Document 1 reports that the acid generation efficiency of iodized styrene is only 14% of that of hydroxystyrene. 

[0008] The EUV lithography resist must meet high sensi› tivity, high resolution and low LWR at the same time. As the acid diffusion distance is reduced, LWR is reduced, but sensitivity becomes lower. For example, as the PEB tem› perature is lowered, the outcome is a reduced LWR, but a lower sensitivity. As the amount of quencher added is increased, the outcome is a reduced LWR, but a lower sensitivity. It is necessary to overcome the tradeoff relation between sensitivity and LWR. It would be desirable to have 

## TECHNICAL FIELD 

## BACKGROUND ART 

a resist material having a high sensitivity and resolution as well as improved LWR and CDU. 

[0009] 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. 

[0010] Patent Document 1: JP-A 805-204157 

[0011] Patent Document 2: JP-A 2015-161823 

[0012] Patent Document 3: WO 2013/024777 

[0013] Patent Document 4: JP-A 2018-004812 

[0014] Patent Document 5: JP 5852490 (U.S. Pat. No. 9,176,379) 

[0015] Patent Document 6: JP-A 2015-180928 (U.S. Pat. No. 9,563,123) 

[0016] Patent Document 7: JP-A 2015-172746 (U.S. Pat. No. 9,448,475) 

[0017] Patent Document 8: JP-A 2017-219836 

[0018] Non-Patent Document 1: Jpn. J. Appl. Physics, Vol. 46, No. 7, pp. L142-L144, 2007 

[0019] For the acid-catalyzed chemically amplified resist, it is desired to develop a resist composition providing a high sensitivity and reducing LWR or improving CDU of hole patterns. 

[0020] An object of the invention is to provide a resist composition which exhibits a high sensitivity, low LWR and improved CDU independent of whether it is of positive tone or negative tone, and a pattern forming process using the same. 

[0021] The inventors have found that a resist composition comprising an iodized polymer and a quencher selected from a sulfonium or ammonium salt of iodized benzene ring-containing carboxylic acid, a sulfonium or ammonium salt of iodized benzene ring-containing N-carbonylsulfona› mide, an iodized benzene ring-containing amine, and an iodized benzene ring-containing ammonium salt exhibits a high sensitivity, low LWR, improved CDU, and wide pro› cess margin. 

[0022] In one aspect, the invention provides a resist com› position comprising an iodized base polymer, and at least one quencher selected from the group consisting of a sul› fonium or ammonium salt of iodized benzene ring-contain› ing carboxylic acid, a sulfonium or ammonium salt of iodized benzene ring-containing N-carbonylsulfonamide, an iodized benzene ring-containing amine, and an iodized ben› zene ring-containing ammonium salt. 

[0023] Preferably, the sulfonium or ammonium salt of iodized benzene ring-containing carboxylic acid, the sulfo› nium or ammonium salt of iodized benzene ring-containing N-carbonylsulfonamide, the iodized benzene ring-contain› ing amine, and the iodized benzene ring-containing ammo› nium salt have the following formulae (A)-1 to (A)-4, respectively. 

## CITATION LIST 

## SUMMARY OF INVENTION 

