## 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- 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 

## TECHNICAL FIELD 

## BACKGROUND ART 

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 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. 

[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. 

[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. 

[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. 

[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) 

[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. 

[0019] An increase in acid diffusion also causes degrada› tion of resolution, LWR and CDU. 

## CITATION LIST 

## SUMMARY OF INVENTION 

