CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2018-150158 filed in Japan on Aug. 9, 2018, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to a resist composition and a patterning process using the composition.

BACKGROUND ART

To meet the demand for higher integration density and operating speed of LSIs, the effort to reduce the pattern rule is in rapid progress. The enlargement of the logic memory market in harmony with the wide-spreading of smart phones drives forward the miniaturization technology. As the advanced miniaturization technology, logic devices of 10-nm node are manufactured in a large scale by the double patterning version of ArF immersion lithography. The fabrication of 7-nm node devices of the next generation by the same double patterning process is approaching the mass-scale manufacture stage. EUV lithography is one of the candidates for the fabrication of 5-nm node devices of the next-to-next generation.

Since the wavelength (13.5 nm) of extreme ultraviolet (EUV) is shorter than 1/10 of the wavelength (193 nm) of ArF excimer laser, the EUV lithography achieves a high contrast of image-forming light. Because of an extraordinarily high energy density of EUV, the number of photons sensitive thereto is small. An influence of a variation in number of photons randomly generated in the exposed region is pointed out. Since the size of pattern features resolved by the EUV lithography is less than half of the feature size by the ArF lithography, a dimensional variation (manifesting as CDU or LWR) due to a variation of photon number becomes a serious problem.

For increasing the throughput of EUV lithography, it is desired to endow a photoresist material with a higher sensitivity. However, since the photoresist material having a higher sensitivity produces a smaller number of photons, the dimensional variation becomes more significant. It is thus desired to develop a photoresist material having a high sensitivity while reducing CDU and LWR.

To achieve a high sensitivity, Patent Document 1 discloses a photoresist material comprising an iodized base polymer. Also, Patent Documents 2 and 3 propose iodized compounds as an additive to the photoresist material.

CITATION LIST

Patent Document 1: JP-A 2015-161823

Patent Document 2: WO 2013/024777

Patent Document 3: JP-A 2013-083957

SUMMARY OF INVENTION

The resist materials described in these patent documents, however, are insufficient in sensitivity, CDU and LWR to comply with the EUV lithography. There is a demand for a photoresist material having a high sensitivity and capable forming a line pattern with improved LWR and a hole pattern with improved CDU.

An object of the invention is to provide a resist composition having a high sensitivity, minimal LWR and improved CDU, and a pattern forming process using the same.

The inventors have found that using a carbonyloxyimide compound having an iodized or brominated aromatic ring, a resist composition having a high sensitivity, minimal LWR and improved CDU is obtained.

In one aspect, the invention provides a resist composition comprising a compound having the formula (A).


Herein R1is hydroxyl, carboxyl, amino, nitro, fluorine, chlorine, C1-C20alkyl, C1-C20alkoxy, C2-C20acyloxy, C2-C20alkoxycarbonyl, —NR1A—C(═O)—R1B, or —NR1A—C(═O)—O—R1B, some or all of the hydrogen atoms on the alkyl, alkoxy, acyloxy and alkoxycarbonyl groups may be substituted by fluorine, chlorine, bromine, hydroxyl or C1-C6alkoxy. R1Ais hydrogen or a C1-C6alkyl group, some or all of the hydrogen atoms on the alkyl group may be substituted by halogen, hydroxyl, C1-C6alkoxy, C2-C7acyl or C2-C7acyloxy. R1Bis a C1-C16alkyl, C2-C16alkenyl or C6-C12aryl group, some or all of the hydrogen atoms on these groups may be substituted by halogen, hydroxyl, C1-C6alkoxy, C2-C7acyl or C2-C7acyloxy. R2is a C6-C10arylene, C1-C8alkanediyl or C2-C8alkenediyl group, some or all of the hydrogen atoms on these groups may be substituted by C1-C12straight or branched alkyl, C2-C12straight or branched alkenyl, C2-C12straight or branched alkynyl, C1-C12straight or branched alkoxy, nitro, acetyl, phenyl or halogen, or some carbon on these groups may be replaced by an ether bond. X is bromine or iodine. L is a single bond or a C1-C20divalent hydrocarbon group which may contain an ether bond or ester bond, m and n each are an integer, meeting 1≤m≤5, 0≤n≤4, and 1≤m+n≤5.

Preferably, m is an integer of 2 to 4. Also preferably, X is iodine.

In one preferred embodiment, the resist composition may further comprise a base polymer.

The resist composition may further comprise an acid generator capable of generating sulfonic acid, imidic acid or methide acid, an organic solvent, a quencher, and/or a surfactant.

Preferably the resist composition is a chemically amplified positive resist composition.

In a more preferred embodiment, the base polymer comprises recurring units having the formula (a1) or recurring units having the formula (a2).


Herein RAis each independently hydrogen or methyl, R11and R12are each independently an acid labile group, R13is fluorine, trifluoromethyl, cyano, a C1-C6straight, branched or cyclic alkyl or alkoxy group, or a C2-C7straight, branched or cyclic acyl, acyloxy or alkoxycarbonyl group, R14is a single bond or a C1-C6straight or branched alkanediyl group in which some carbon may be replaced by an ether bond or ester bond, Y1is a single bond, phenylene, naphthylene, or a C1-C12linking group containing an ester bond, ether bond or lactone ring, and Y2is a single bond, —C(═O)—O— or —C(═O)—NH—, p is 1 or 2, and q is an integer of 0 to 4.

The base polymer may comprise recurring units of at least one type selected from recurring units having the formulae (f1) to (f3).


Herein RAis each independently hydrogen or methyl. Z1is a single bond, phenylene, or —O—Z11, —C(═O)—O—Z11—, or —C(═O)—NH—Z11—, Z11is a C1-C6alkanediyl group, C2-C6alkenediyl group or phenylene group, which may contain a carbonyl moiety, ester bond, ether bond or hydroxyl moiety. Z2is a single bond, —Z21—C(═O)—O—, —Z21—O—, or —Z21—O—C(═O)—, Z21is a C1-C12alkanediyl group which may contain a carbonyl moiety, ester bond or ether bond. Z3is a single bond, methylene, ethylene, phenylene, fluorinated phenylene, —O—Z−—, —C(═O)—O—Z31—, or —C(═O)—NH—Z31—, Z31is a C1-C6alkanediyl group, C2-C6alkenediyl group, phenylene, fluorinated phenylene, or trifluoromethyl-substituted phenylene group, which may contain a carbonyl moiety, ester bond, ether bond or hydroxyl moiety. R21to R28are each independently a C1-C20monovalent hydrocarbon group which may contain a heteroatom, any two of R23, R24and R25or any two of R26, R27and R28may bond together to form a ring with the sulfur atom to which they are attached. A1is hydrogen or trifluoromethyl. M−is a non-nucleophilic counter ion.

In another aspect, the invention provides a pattern forming process comprising the steps of coating the resist composition defined above onto a substrate, baking, exposing the resulting resist film to high-energy radiation, and developing the exposed resist film in a developer.

Preferably, the high-energy radiation is ArF excimer laser of wavelength 193 nm, KrF excimer laser of wavelength 248 nm, EB, or EUV of wavelength 3 to 15 nm.

ADVANTAGEOUS EFFECTS OF INVENTION

The compound having formula (A) is a sensitizer because it contains an iodine or to bromine atom which is highly absorptive to EUV and upon exposure, it effectively generates secondary electrons which are transported to an acid generator to increase sensitivity. Also the compound is a contrast enhancer because upon exposure, it generates a carboxyl group to enhance alkaline solubility. These lead to a high sensitivity and reduced values of LWR and CDU. Thus a resist composition having a high sensitivity, minimal LWR and improved CDU is designed.

