Negative resist pattern forming process

Abstract

This invention provides a method for forming a negative resist pattern, which utilizes a non-chemically amplified resist composition with excellent sensitivity and resolution in lithography using high-energy rays. The method includes: (i) forming a resist film on a substrate using a resist composition comprising a high-valent iodine compound, a carboxyl-containing polymer, and a solvent; (ii) exposing the resist film to high-energy rays; and (iii) developing the exposed resist film using a developer that dissolves unexposed portions without dissolving exposed portions.

Description

[Technical Field]

[0001] This invention relates to a method for forming negative resist patterns. [Previous Technology]

[0002] With the expansion of the IoT market, there is a growing demand for higher integration, higher speed, and lower power consumption of LSIs, leading to rapid miniaturization of patterning patterns. In particular, logic devices are driving miniaturization. As the most advanced miniaturization technology, mass production of 10 nm node devices based on ArF immersion lithography with dual, triple, and quadruple patterning is underway, and research on next-generation 7 nm node devices using extreme ultraviolet (EUV) lithography at a wavelength of 135 nm is also in progress.

[0003] As miniaturization progresses, image blurring caused by acid diffusion becomes a problem (Non-Patent Document 1). To ensure the resolution of fine patterns with a size of less than 45 nm, it has been proposed that not only improving the dissolution contrast as proposed in the prior art, but also controlling acid diffusion is important (Non-Patent Document 2). However, since chemical amplification inhibitor compositions improve sensitivity and contrast through acid diffusion, if the post-exposure baking (PEB) temperature is lowered or the PEB time is shortened to suppress acid diffusion to the limit, the sensitivity and contrast will be significantly reduced.

[0004] Adding an acid-generating agent that produces a large volume of acid is effective in suppressing acid diffusion. Therefore, a scheme has been proposed to copolymerize an acid-generating agent containing a polymerizable olefin onium salt in a polymer. However, from the viewpoint of acid diffusion, it is considered that chemically amplified inhibitor compositions cannot form patterns in the patterning of inhibitor films with a size of less than 16 nm, and it is desirable to develop non-chemically amplified inhibitor compositions.

[0005] Materials used in non-chemically amplified inhibitor compositions include polymethyl methacrylate (PMMA). PMMA is a positive inhibitor material whose main chain is cleaved and its molecular weight is reduced by EUV irradiation, thereby increasing its solubility in organic solvents in the developer.

[0006] Hydrosilsesquioxane (HSQ) is a negative resist material that is insoluble in alkaline developing solutions due to the crosslinking reaction of silanol produced by EUV irradiation. Additionally, chlorinated calixarnes also function as negative resist materials. These negative resist materials have small molecular sizes before crosslinking, eliminating blurring caused by acid diffusion, resulting in low edge roughness and very high resolution. They are used as pattern transfer materials to indicate the resolution limits of exposure devices. However, the sensitivity of these materials is insufficient and further improvement is needed.

[0007] One of the main reasons that makes the development of materials for EUV lithography difficult is the low number of photons in EUV exposure. EUV energy is much higher than ArF excimer laser, and the number of photons in EUV exposure is only one-fourteenth of that in ArF exposure. Furthermore, the size of the pattern formed by EUV exposure is less than half that of ArF exposure. Therefore, EUV exposure is susceptible to variations in the number of photons. Variations in the number of photons in the extremely short wavelength radiation range are shot noise, a physical phenomenon that cannot be eliminated. Therefore, so-called stochastics are being studied. While the effects of shot noise cannot be eliminated, methods to reduce this effect are being discussed. Not only do dimensional uniformity (CDU) and linewidth roughness (LWR) increase due to shot noise, but hole blockage is also observed with a probability of one in millions. Therefore, if holes are blocked, conduction failure occurs, and the transistor does not operate, negatively impacting the overall device performance. Considering practical sensitivity, in resistive compositions with PMMA and HSQ as the main components, the evaluation will be significantly affected by probability theory, and the desired resolution performance cannot be obtained.

[0008] As a method to reduce the influence of shot noise on the resist side, the introduction of elements with high EUV light absorption has attracted attention. Patent Document 1 proposes a chemical amplification resist composition containing iodine atoms with high EUV light absorption. However, as mentioned above, chemical amplification resist compositions cannot achieve excellent resolution performance in EUV lithography with increasingly smaller dimensions in the future.

[0009] Patent Document 2 proposes a negative resist composition using tin compounds. Because it has high EUV light absorption and is predominantly composed of tin, its probability theory is improved, enabling high sensitivity / high resolution. However, this type of metal resist suffers from many problems, including insufficient solubility in resist solvents, storage stability issues, and defects caused by etching residues.

[0010] In contrast, Patent Document 3 proposes a positive resist composition using a high-valent iodide. Because it contains iodine, which has high absorption of EUV light, its probability theory is improved, similar to that of metal resists, enabling high sensitivity / high resolution. Furthermore, since it is composed only of organic molecules, it can improve the developer solubility and residue-related defects that are problems with metal resists. However, as resist compositions used in lithography, there are positive types that dissolve the exposed area to form a pattern and positive types that retain the exposed area to form a pattern. The choice depends on the desired resist pattern shape; however, since this resist composition is positive, it cannot be applied when the desired pattern is negative. [Prior Art Documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 2018-5224 [Patent Document 2] Japanese Patent Application Publication No. 2021-503482 [Patent Document 3] Japanese Patent Application Publication No. 2023-167368 [Patent Document 4] Japanese Patent Application Publication No. 2015-180928 [Patent Document 5] Japanese Patent Application Publication No. 2018-95853 [Non-Patent Documents]

[0012] [Non-Patent Literature 1] SPIE Vol. 5039 p1 (2003) [Non-Patent Literature 2] SPIE Vol. 6520 p65203L-1 (2007) [Summary of the Invention]

[0013] [Problem to be Solved by the Invention] The present invention has been made in view of the above-mentioned circumstances, and its object is to provide a method for forming negative resist patterns, using a non-chemically amplified resist composition with excellent sensitivity and resolution in lithography using high-energy rays, particularly electron beam (EB) lithography and EUV lithography. [Means for Solving the Problem]

[0014] In order to achieve the above-mentioned objective, the inventors have repeatedly conducted in-depth research and found that by combining a resist composition mainly composed of a high-valent iodine compound having at least two acetoxy groups and a polymer containing carboxyl groups with a suitable developer, it is possible to obtain a negative resist pattern with extremely high sensitivity and excellent resolution, which is extremely effective for precision micro-processing, thereby completing the present invention.

[0015] That is, the present invention provides the following method for forming a negative resist pattern. 1. A method for forming a negative resist pattern, comprising the following steps: (i) forming a resist film on a substrate using a resist composition comprising a high-valent iodine compound, a carboxyl-containing polymer, and a solvent; (ii) exposing the resist film to high-energy radiation; (iii) developing the exposed resist film using a developer that dissolves unexposed portions without dissolving exposed portions. 2. The method for forming a negative resist pattern as described in 1, wherein the developer is an alkaline developer. 3. The method for forming a negative resist pattern as described in 1 or 2, wherein the high-energy radiation is an electron beam or extreme ultraviolet radiation. 4. A method for forming a negative resist pattern as described in any of 1 to 3, wherein the high-valent iodine compound is represented by the following formula (1): [Chemical 1] where n is an integer from 0 to 5, R1 and R2 are each independently a halogen atom or a hydrocarbon group with 1 to 10 carbon atoms that may contain heteroatoms, and R1 and R2 may be bonded to each other and form a ring together with the carbon atoms they are bonded to and the atoms between the carbon atoms, R3 is a halogen atom or a hydrocarbon group with 1 to 40 carbon atoms that may contain heteroatoms, and when n is 2 to 5, each R3 may be the same or different from each other. 5. A method for forming a negative inhibitor pattern according to any one of 1. to 4., wherein the carboxyl-containing polymer comprises a repeating unit as shown in formula (2) below, [Chemical 2] where RA is a hydrogen atom, a halogen atom, a methyl group or a trifluoromethyl group, XA is a single bond, a phenyl group, a naphthyl group or *-C(=O)-O-XA1-, XA1 is a saturated alkyl group, a phenyl group or a naphthyl group having 1 to 10 carbon atoms, and the saturated alkyl group may also contain at least one selected from hydroxyl, ether bond, ester bond and lactone ring, * represents an atomic bond with a carbon atom of the main chain, except that when RA is a methyl group, XA is not a single bond. 6. A method for forming a negative inhibitor pattern according to any one of 1. to 5., wherein the inhibitor composition further comprises a crosslinking agent. 7. A method for forming a negative inhibitor pattern according to any one of 1. to 6., wherein the inhibitor composition further comprises a free radical scavenger. [Effects of the Invention]

[0016] The negative resist patterning method of the present invention is particularly useful in EB lithography and EUV lithography, taking into account both high sensitivity and high resolution, and is extremely useful in forming fine patterns.

Implementation Method

[0017] [Resistant Composition] The resistant composition used in the negative resist patterning method of the present invention comprises: a high-valent iodine compound with at least two acetoxy groups, a carboxyl-containing polymer, and a solvent.

[0018] [High-valence iodine compounds] High-valence iodides are a general term for iodides that have valence electrons in a form that exceeds the octet rule. As used in this invention, there are no particular limitations as long as the high-valence iodide has at least 2 acetoxy groups. Examples include tricoordinate iodides with an oxidation number of +3 and pentacoordinate iodides with an oxidation number of +5.

[0019] As the aforementioned high-valent iodine compound, the tricoordinate high-valent iodine compound shown in formula (1) below is preferred. [Chemical 3]

[0020] In formula (1), n ​​is an integer from 0 to 5.

[0021] In formula (1), R1 and R2 are each independently a halogen atom, or may contain heteroatoms and are hydrocarbon groups with 1 to 10 carbon atoms. Furthermore, R1 and R2 may also bond to each other and form a ring together with the carbon atoms they are bonded to and the carbon atoms between them. Specific examples of the aforementioned halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc. The aforementioned hydrocarbon groups with 1 to 10 carbon atoms may be saturated or unsaturated, and may be straight-chain, branched, or cyclic. Specific examples include alkyl groups with 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, dibutyl, tributyl, n-pentyl, tripentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclic saturated hydrocarbon groups with 3 to 10 carbon atoms, such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norcamphenyl, tricyclo[5.2.1.02,6]decyl, and adamantyl; alkenyl groups with 2 to 10 carbon atoms, such as vinyl and propenyl; aryl groups with 6 to 10 carbon atoms, such as phenyl and naphthyl; and groups obtained by combining them. Furthermore, some or all of the hydrogen atoms in the aforementioned hydrocarbon group can be replaced by a group containing heteroatoms such as oxygen, sulfur, nitrogen, or halogen atoms. Similarly, a portion of the -CH2- group in the aforementioned hydrocarbon group can be replaced by a group containing heteroatoms such as oxygen, sulfur, or nitrogen atoms. As a result, the group may contain hydroxyl, cyano, halogen, carbonyl, ether, thioether, ester, sulfonate, carbonate, carbamate, lactone ring, sulfonyl lactone ring, or carboxylic anhydride (-C(=O)-OC(=O)-). R1 ​​and R2 are preferably hydrocarbon groups with 1 to 4 carbon atoms.

[0022] In formula (1), R3 is a halogen atom or a hydrocarbon group with 1 to 40 carbon atoms that may also contain heteroatoms. When n is 2 to 5, each R3 can be the same as the others, and they can also be different. Specific examples of the aforementioned halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc. The aforementioned hydrocarbon groups with 1 to 40 carbon atoms can be saturated or unsaturated, and can be straight-chain, branched, or cyclic. Specific examples include alkyl groups with 1 to 40 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, dibutyl, tributyl, n-pentyl, tripentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclic saturated hydrocarbon groups with 3 to 40 carbon atoms, such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norcamphenyl, tricyclo[5.2.1.02,6]decyl, adamantyl, and adamantylmethyl; and aryl groups with 6 to 40 carbon atoms, such as phenyl, naphthyl, and anthracene. In addition, some or all of the hydrogen atoms in the above-mentioned hydrocarbon group can be replaced by a group containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, and halogen atoms. A portion of the -CH2- in the above-mentioned hydrocarbon group can be replaced by a group containing heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms. As a result, it can contain hydroxyl groups, cyano groups, halogen atoms, carbonyl groups, ether bonds, thioether bonds, ester bonds, sulfonate bonds, carbonate bonds, carbamate bonds, lactone rings, sulfonolactone rings, carboxylic anhydrides (-C(=O)-OC(=O)-), etc.

[0023] As specific examples of the high-valent iodine compounds shown in formula (1), the following compounds can be cited, but are not limited to these. [Chemistry 4]

[0024] [Chemical 5]

[0025] [Chemical 6]

[0026] [Chemical 7]

[0027] [Chemical 8]

[0028] [Chemical 9]

[0029] [Carboxyl-containing polymers] Preferably, the aforementioned carboxyl-containing polymers comprise repeating units containing carboxyl groups. As the aforementioned repeating units containing carboxyl groups, the repeating units shown in formula (2) below are preferred. [Chemical 10]

[0030] In formula (2), RA is a hydrogen atom, a halogen atom, a methyl group, or a trifluoromethyl group. XA represents a single bond, an phenyl group, a naphthyl group, or *-C(=O)-O-XA1-. XA1 is a saturated alkyl group, an phenyl group, or a naphthyl group with 1 to 10 carbon atoms, which may contain at least one of the following: hydroxyl group, ether bond, ester bond, and lactone ring. * represents an atomic bond with a carbon atom in the main chain. Wherein, when RA is a methyl group, XA is not a single bond.

[0031] Specific examples of the aforementioned repeating units containing carboxyl groups include, but are not limited to, the following examples, in which RA is the same as above. [Chemical 11]

[0032] [Chemical 12]

[0033] The aforementioned carboxyl-containing polymer may further include repeating units other than the aforementioned carboxyl-containing repeating unit (hereinafter also referred to as other repeating units). There are no particular limitations on the aforementioned other repeating units, but they are preferably repeating units that can improve the solubility of polymers that are poorly soluble in solvents solely by means of repeating units containing carboxyl groups. Such repeating units are preferably repeating units having a hydrocarbon group having 1 to 20 carbon atoms, which may include at least one of the following: hydroxyl groups other than fluorine atoms and phenolic hydroxyl groups, cyano groups, carbonyl groups, ester bonds, ether bonds, thioether bonds, carbonate bonds, lactone rings, and sulopentalide rings.

[0034] As specific examples of other repeating units mentioned above, the following repeating units can be listed, but are not limited to these. It should be noted that in the following formulas, RA is the same as above. [Chemistry 13]

[0035] [Chemical 14]

[0036] [Chemical 15]

[0037] [Chemical 16]

[0038] [Chemical 17]

[0039] [Chemical 18]

[0040] [Chemical 19]

[0041] [Chemical 20]

[0042] [Chemical 21]

[0043] [Chemical 22]

[0044] [Chemical 23]

[0045] [Chemical 24]

[0046] [Chemical 25]

[0047] [Chemical 26]

[0048] [Chemical 27]

[0049] In the above-mentioned carboxyl-containing polymer, the ratio (molar ratio) of the repeating unit containing carboxyl groups to other repeating units is preferably 10:90 to 90:10, more preferably 15:85 to 85:15, and even more preferably 20:80 to 80:20.

[0050] The weight-average molecular weight (Mw) of the above-mentioned carboxyl-containing polymer is preferably 1,000 to 500,000, and more preferably 3,000 to 100,000. It should be noted that, in this invention, Mw is the converted value of polystyrene determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

[0051] Furthermore, when the carboxyl-containing polymer has a wide molecular weight distribution (Mw / Mn), impurities may be observed on the pattern or the shape of the pattern may deteriorate after exposure due to the presence of polymers with low and high molecular weights. Therefore, as the pattern regularity becomes finer, the influence of Mw and Mw / Mn tends to increase. Thus, in order to obtain a resist composition suitable for fine pattern sizes, the aforementioned carboxyl-containing polymer preferably has a narrow dispersion of Mw / Mn of 1.0 to 2.0.

[0052] As a method for synthesizing the above-mentioned carboxyl-containing polymer, for example, a method is to polymerize the monomer that provides the above-mentioned repeating unit by adding a free radical polymerization initiator to an organic solvent and heating it.

[0053] Specific examples of organic solvents used in the polymerization reaction include: toluene, benzene, THF, diethyl ether, dialkylene, cyclohexane, cyclopentane, methyl ethyl ketone (MEK), propylene glycol monomethyl ether acetate (PGMEA), γ-butyrolactone (GBL), etc. Specific examples of polymerization initiators include: 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylpentanonitrile), 2,2-azobis(2-methylpropionic acid) dimethyl ester, 1,1'-azobis(1-acetoxy-1-phenylethane), benzoyl peroxide, lauryl peroxide, etc. The amount of the above polymerization initiator added relative to the total monomers being polymerized is preferably 0.01 to 25 mol%. The reaction temperature is preferably 50 to 150°C, more preferably 60 to 100°C. The optimal reaction time is 2 to 24 hours, and from the perspective of production efficiency, 2 to 12 hours is even better.

[0054] The polymerization initiator described above can be added to the monomer solution and supplied to the reactor, or a starting aqueous solution can be prepared separately from the monomer solution and supplied to the reactor independently. Since polymerization may occur during the standby time due to free radicals generated from the initiator, resulting in ultra-high molecular weight polymers, it is preferable, from a quality management perspective, to prepare the monomer solution and initiator solution independently and add them dropwise. Acid-labile groups can be used directly from the groups introduced into the monomer, or they can be protected or partially protected after polymerization. Furthermore, to adjust the molecular weight, known chain transfer agents such as dodecyl mercaptan and 2-mercaptoethanol can be used in conjunction. In this case, the amount of these chain transfer agents added relative to the total amount of monomers being polymerized is preferably 0.01 to 20 mol%.

[0055] It should be noted that the amount of each monomer in the above monomer solution can be appropriately set, for example, in a manner that makes up the ideal content ratio of the above repeating unit.

[0056] In the above-mentioned inhibitor composition, the high-valent iodine compound and the carboxyl-containing polymer are preferably contained in a molar ratio of 10:90 to 90:10, more preferably in a molar ratio of 20:80 to 80:20, and even more preferably in a molar ratio of 30:70 to 70:30. The aforementioned high-valent iodide can be used alone or in combination of two or more. The aforementioned carboxyl-containing polymer can be used alone or in combination of two or more with different composition ratios, Mw, and / or Mw / Mn.

[0057] [Solvent] The aforementioned inhibitor composition includes a solvent. The solvent is not particularly limited, as long as it can dissolve the high-valent iodine compound, the carboxyl-containing polymer, and the other components listed below to form a film. Such a solvent is preferably an organic solvent; specific examples include ketones such as cyclohexanone, methyl-2-n-pentyl ketone, and methyl isopentyl ketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, diacetone alcohol, 4-methyl-2-pentanol, and methyl 2-hydroxyisobutyrate; and propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, and ethylene glycol monomethyl ether. Ethers such as monoethyl ether of alcohol, dimethyl propylene glycol ether, and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol monotert-butyl ether acetate; carboxylic acids such as formic acid, acetic acid, and propionic acid; lactones such as γ-butyrolactone; and their mixed solvents, etc.

[0058] In the aforementioned inhibitor composition, the content of the solvent is preferably such that the concentration of the solid component in the inhibitor composition is 0.1 to 20% by mass, more preferably 0.1 to 15% by mass, and even more preferably 0.1 to 10% by mass. It should be noted that, in this invention, the solid component refers to the total amount of components in the inhibitor composition excluding the solvent. The solvent may be used alone or in combination of two or more.

[0059] [Other Ingredients] The inhibitor composition may further include a surfactant. Fluorinated and / or polysiloxane-based surfactants are preferred as the surfactants described above. Specific examples of such surfactants include those described in paragraph

[0276] of U.S. Patent Application Publication No. 2008 / 0248425. Furthermore, surfactants other than those described in paragraph

[0280] of U.S. Patent Application Publication No. 2008 / 0248425 may also be used.

[0060] When the above-mentioned inhibitor composition includes the above-mentioned surfactant, its content is preferably 0.0001 to 2% by mass of the total solid components. The above-mentioned surfactant can be used alone or in combination of two or more.

[0061] The above-mentioned inhibitor composition may further include a free radical scavenger. By adding a free radical scavenger, the light reaction in the lithography can be controlled, and the sensitivity can be adjusted.

[0062] Specific examples of the aforementioned free radical scavengers include hindered phenols, quinones, hindered amines, and thiols. Specific examples of hindered phenols include butylated hydroxytoluene (BHT) and 2,2'-methylenebis(4-methyl-6-tert-butylphenol). Specific examples of quinones include 4-methoxyphenol (p-methoxyphenol) and hydroquinone. Specific examples of hindered amines include 2,2,6,6-tetramethylpiperidine and 2,2,6,6-tetramethylpiperidine-N-oxy radical. Specific examples of thiols include dodecyl mercaptan and hexadecyl mercaptan.

[0063] When the above-mentioned inhibitor composition includes the above-mentioned free radical scavenger, its content is preferably 0.01 to 10% by mass of the total solid components. The above-mentioned free radical scavenger can be used alone or in combination of two or more.

[0064] The above-mentioned resist composition may further include a crosslinking agent. By adding a crosslinking agent, the photoreaction in the lithography can be promoted, thereby increasing the sensitivity of the resist.

[0065] Specific examples of the aforementioned crosslinking agents include compounds having carbon-carbon unsaturated groups such as vinyl, (meth)acrylate, allyl, alkynyl, and aromatic rings as functional groups. Specifically, specific examples of compounds having vinyl groups include chain olefins, branched olefins, and cyclic olefins that may have substituents. Specific examples of compounds having (meth)acrylate groups include acrylic acid, methacrylic acid, acrylates, and methacrylates that may have substituents. Specific examples of compounds having allyl groups include allyl alcohol, allyl ether, allyl ester, acrylamide, allylamine, and isocyanurates containing allyl groups. Specific examples of compounds having alkynyl groups include alkynols, alkynyl ethers, alkynyl esters, alkynylamine, alkynylamine, and isocyanurates containing alkynyl groups that may have substituents. Specific examples of compounds having aromatic rings include aromatic hydrocarbons, heteroaromatic hydrocarbons, styrene, stilbene, phenylacetylene, acenaphthene, chalcone, etc., which may have substituents. The crosslinking agent may have only one of the aforementioned functional groups or may have multiple functional groups. The number of the aforementioned functional groups contained in the crosslinking agent is 1 to 10, more preferably 2 to 8.

[0066] When the above-mentioned inhibitor composition includes the above-mentioned crosslinking agent, its content is preferably 0.01 to 50% by mass of the total solid components. The above-mentioned crosslinking agent can be used alone or in combination of two or more.

[0067] The resist composition contains high-valent iodides and carboxyl-containing polymers as main components, but does not contain the acid-inhibiting base polymers or photoacid generators found in conventional chemical amplification resist compositions. However, the aforementioned resist composition, in particular, becomes insoluble in the developer when exposed by EB or EUV exposure, enabling the formation of negative patterns. The mechanism is not fully understood, but it is speculated, for example, as follows.

[0068] The aforementioned high-valent iodide is an iodide having at least two acetylation groups. It is believed that by mixing such a high-valent iodide with a carboxylic acid, an exchange of carboxylate ligands occurs in an equilibrium reaction. If the original carboxylate ligands can be removed by some method, a high-valent iodide with new ligands is generated. For example, by mixing diacetylbenzene, a relatively readily available high-valent iodide, with a high-molecular-weight carboxylic acid, and removing the resulting low-boiling-point acetic acid, the ligand exchange is completed. Here, in the case where the carboxylic acid compound is a polymer, it becomes a high-molecular-weight high-valent iodide compound that is cross-linked between polymers by the high-valent iodide compound.

[0069] The polymer crosslinked with high-valent iodides is formed during film formation. Because even if such crosslinked polymers are synthesized beforehand, they are not soluble in most organic solvents, thus solutions cannot be prepared. This is presumably because the high-valent iodides, which originally have low solubility due to high polarization, become even less soluble when using a carboxylic acid-containing polymer as a ligand, which is a high molecular weight component. Therefore, it is ideal to remove the original low-molecular-weight carboxylic acid components during film formation and the subsequent baking step, thereby completing the ligand exchange reaction and simultaneously forming a resistive film.

[0070] The resist film obtained from the above-described resist composition comprises a polymer cross-linked by high-valent iodides generated during film formation. These polymers typically have low solubility, but when using specific solvents such as alkaline aqueous solutions, they exhibit very high solubility due to ligand exchange reactions of the high-valent iodides. However, they decompose under light, transforming into chemical substances with low solubility in these solvents. As a result, the exposure portion becomes insoluble in the developer, presumably functioning as a negative resist composition.

[0071] Based on the above speculation, the aforementioned inhibitor composition is a non-chemical amplification inhibitor composition, which does not require polymers containing acid-instable groups or photoacid generators like conventional chemical amplification inhibitor compositions. Therefore, it will not produce adverse effects caused by acid diffusion (e.g., image blurring), and can distinguish fine patterns.

[0072] The above-mentioned resist composition is particularly effective in EUV lithography. This is due to the presence of iodine atoms with high absorption capacity for EUV light. That is, it can reduce shot noise, achieve higher resolution and lower LWR.

[0073] As EUV resist compositions capable of forming fine patterns, it has been reported that metal resists, using metallic tin compounds with high absorption capacity for EUV light as the main component, are used in the same way as iodine atoms (e.g., Patent Document 2). However, as mentioned above, such metal resists have many problems, such as insufficient solubility in solvents, storage stability, and defects caused by residues after etching due to the inclusion of metal elements. On the other hand, since the aforementioned resist composition does not use metal elements, it is more advantageous than metal resists in terms of defects and has no problems with solubility in solvents. For these reasons, the aforementioned resist composition is more advantageous than metallic resists.

[0074] Patent documents 4 and 5 describe resistive compositions containing high-valent iodine compounds as additives, and resistive compositions that introduce high-valent iodine compounds into the polymer backbone of a base polymer. However, in these patent documents, the characteristics of the aforementioned resistive compositions are only described as improving line edge roughness, and the possibility of photolysis of high-valent iodine compounds is not mentioned at all, nor is the possibility of the non-chemically amplified resistive composition functioning. Furthermore, according to the descriptions and specific examples regarding the doping amount, high-valent iodide is not a main component. In addition, Patent document 3 proposes a positive resistive composition using high-valent iodide, but does not mention the possibility that this resistive composition, combined with a suitable developer, can function as a negative resist. Therefore, based on these documents, it is unlikely that a negative resistive patterning method, as described in this invention, could be conceived that can reduce shot noise in EUV lithography and form fine patterns as a non-chemically amplified resist. That is, this invention explicitly provides a novel negative resistive patterning method.

[0075] [Negative Resistor Pattern Forming Method] The negative resistor pattern forming method of the present invention includes: (i) a step of forming a resist film on a substrate using the aforementioned resist composition; (ii) a step of exposing the aforementioned resist film with high-energy rays; and (iii) a step of developing the aforementioned exposed resist film by dissolving the unexposed portions without dissolving the exposed portions using a developing solution.

[0076] [Step (i)] Step (i) is the step of forming a resist film on a substrate using the aforementioned resist composition. Specifically, the aforementioned resist composition is coated onto a substrate for integrated circuit manufacturing (Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflective film, etc.) or a substrate for mask circuit manufacturing (Cr, CrO, CrON, MoSi2, SiO2) by an appropriate coating method such as spin coating, roll coating, flow coating, dip coating, spray coating, or blade coating, with a coating thickness of 0.01 to 2 μm. The resist film is then pre-baked on a hot plate, preferably at 60 to 200°C for 10 seconds to 30 minutes, more preferably at 80 to 180°C for 30 seconds to 20 minutes, to form the resist film.

[0077] [Step (ii)] Step (ii) is a step of exposing the resist film to high-energy rays. Specific examples of the high-energy rays include ultraviolet rays, far-ultraviolet rays, EB, EUV, X-rays, soft X-rays, excimer lasers, gamma rays, synchrotron radiation, etc. When using ultraviolet rays, far-ultraviolet rays, EUV, X-rays, soft X-rays, excimer lasers, gamma rays, synchrotron radiation, etc., as the high-energy rays, irradiation is performed directly or using a mask for forming the target pattern, with an exposure dose preferably around 1 to 300 mJ / cm², more preferably around 10 to 200 mJ / cm². When using EB as a high-energy ray, irradiation is performed directly or using a mask for forming the target pattern, with an exposure dose preferably around 0.1 to 2000 μC / cm², more preferably around 0.5 to 1500 μC / cm². It should be noted that the above-mentioned resist composition is particularly suitable for fine patterning using EB or EUV in high-energy rays.

[0078] After exposure, PEB needs to be performed. At this time, after exposure, it is better to perform the process on a hot plate or in an oven at 30-150°C for 10 seconds to 30 minutes, preferably at 60-120°C for 30 seconds to 20 minutes.

[0079] [Step (iii)] Step (iii) is a step of developing the exposed resist film after exposure or PEB using a developer that dissolves the unexposed portions but not the exposed portions. In this invention, a negative resist pattern can be obtained by development. There is no particular limitation on the developer used at this time, as long as it dissolves the unexposed portions but not the exposed portions. An alkaline developer is preferred as such a solvent; specific examples include aqueous solutions of fourth-order ammonium salts, ammonia, first-order amines, second-order amines, third-order amines, and inorganic bases. An aqueous solution of a fourth-order ammonium salt, represented by tetramethylammonium hydroxide, is preferred as the alkaline developer, and an aqueous solution with an alkalinity of 0.1 to 20% by mass is even more preferred. An appropriate amount of surfactant or alcohol may also be added to the aforementioned developer. Furthermore, one of these developers may be used alone, or two or more may be used in combination.

[0080] After development, rinsing is performed as needed. The rinsing solution is preferably a solvent that is miscible with the developer and does not dissolve the resist film. Alcohols with 3 to 10 carbon atoms, ether compounds with 8 to 12 carbon atoms, alkanes with 6 to 12 carbon atoms, alkenes, alkynes, and aromatic solvents are preferred as such solvents.

[0081] Rinsing can reduce the collapse of resist patterns and the generation of defects. Furthermore, rinsing is not necessary; by not rinsing, the amount of solvent used can be reduced. [Example]

[0082] Hereinafter, synthetic examples, embodiments and comparative examples are shown to specifically describe the present invention, but the present invention is not limited to the following embodiments.

[0083] [1] Polymer Synthesis The monomers used in the synthesis of the polymer are as described above. [Chemistry 28]

[0084] [Chemical 29]

[0085] [Chemical 30]

[0086] [Synthesis Example 1] Synthesis of Polymer P-1: Under a nitrogen atmosphere, monomer a-1 (47g), monomer b-1 (105g), V-601 (manufactured by Fujifilm and Koimitsu Chemical Co., Ltd.) 5.4g and MEK 180g were weighed in a flask to prepare a monomer-polymerization initiator solution. Under a nitrogen atmosphere, 55g of MEK was placed in another flask and heated to 80°C while stirring. Then, the aforementioned monomer-polymerization initiator solution was added dropwise over 4 hours. After the addition was completed, the polymerization solution was stirred for 2 hours while maintaining the temperature at 80°C, and then cooled to room temperature. The obtained polymerization solution was added dropwise to 4000g of hexane under vigorous stirring, and the precipitated polymer was separated by filtration. The obtained polymer was washed twice with hexane (1200g) and dried under vacuum at 50°C for 20 hours to obtain a white powder of polymer P-1 (yield 146g, yield 96%). The Mw of polymer P-1 is 6600, and the Mw / Mn ratio is 1.80. It should be noted that Mw is a polystyrene conversion value obtained through GPC using THF as a solvent. [Chem. 31]

[0087] [Synthesis Examples 2 to 10] The polymers P-2 to P-10 were synthesized using the same method as in Synthesis Example 1, except that the types and proportions of each monomer were changed.

[0088] [Table 1] polymer Unit 1 Import ratio (mol%) Unit 2 Import ratio (mol%) Mw Mw / Mn P-1 a-1 65 b-1 35 6600 1.80 P-2 a-1 50 b-2 50 6800 1.82 P-3 a-1 60 b-3 40 6700 1.84 P-4 a-2 65 b-1 35 7900 1.79 P-5 a-2 50 b-2 50 8300 1.83 P-6 a-2 60 b-3 40 8200 1.82 P-7 a-3 65 b-1 35 7500 1.80 P-8 a-3 50 b-2 50 7700 1.81 P-9 a-3 60 b-3 40 7600 1.84 P-10 c-1 60 c-2 40 9800 1.82

[0089] [2] Preparation of inhibitor compositions [Examples 1-1 to 1-15, Comparative Examples 1-1 to 1-2] Using the compositions shown in Table 2 below, high-valent iodine compounds, polymers, free radical scavengers, and crosslinking agents were dissolved in a solvent containing 0.01% by mass of a surfactant (PF-636, manufactured by Omnova Corporation). The resulting solution was filtered through a 0.2 μm Teflon (registered trademark) filter, thereby preparing inhibitor compositions (R-01 to R-15). In addition, using the compositions shown in Table 3 below, polymers, photoacid generators, and sensitivity modifiers were dissolved in a solvent containing 0.01% by mass of a surfactant (PF-636, manufactured by Omnova Corporation). The resulting solution was filtered through a 0.2 μm Teflon (registered trademark) filter, thereby preparing comparative inhibitor compositions (CR-01 to CR-02).

[0090] [Table 2] inhibitor Composition High price Iodine compounds (parts by weight) polymer (parts by weight) free radicals Capture agent (parts by weight) Crosslinking agent (parts by weight) Solvent 1 (parts by weight) Solvent 2 (parts by weight) Example 1-1 R-01 I-1(10) P-1(15) - - PGMEA(800) AcOH(200) Examples 1-2 R-02 I-2(14) P-1(15) - - PGMEA(800) AcOH(200) Examples 1-3 R-03 I-3(12) P-1(15) - - PGMEA(800) AcOH(200) Examples 1-4 R-04 I-1(10) P-2(18) - - PGMEA(800) AcOH(200) Examples 1-5 R-05 I-1(10) P-3(17) - - PGMEA(800) AcOH(200) Examples 1-6 R-06 I-1(10) P-4(26) - - PGMEA(800) AcOH(200) Examples 1-7 R-07 I-1(10) P-5(29) - - PGMEA(800) AcOH(200) Examples 1-8 R-08 I-1(10) P-6(28) - - PGMEA(800) AcOH(200) Examples 1-9 R-09 I-1(10) P-7(19) - - PGMEA(800) AcOH(200) Examples 1-10 R-10 I-1(10) P-8(23) - - PGMEA(800) AcOH(200) Examples 1-11 R-11 I-1(10) P-9(21) - - PGMEA(800) AcOH(200) Examples 1-12 R-12 I-1(10) P-1(15) - - HBM(800) AcOH(200) Examples 1-13 R-13 I-1(10) P-1(15) - - PGMEA(800) PA(200) Examples 1-14 R-14 I-1(10) P-1(15) T-1(1) - PGMEA(800) AcOH(200) Examples 1-15 R-15 I-1(10) P-1(15) - L-1(1) PGMEA(800) AcOH(200)

[0091] [Table 3] inhibitor Composition polymer (parts by weight) Photoacid generator (parts by weight) Sensitivity modifier (parts by weight) Solvent 1 (parts by weight) Solvent 2 (parts by weight) Comparative Example 1-1 CR-01 P-10(80) PAG-1(19) Q-1(6) PGMEA (1890) GBL(210) Comparative Examples 1-2 CR-02 P-10(80) PAG-1(19) I-1(5) PGMEA (1890) GBL(210)

[0092] In Tables 2 and 3, the high-valent iodine compounds (I-1 to I-3), photoacid generator PAG-1, sensitivity modifier Q-1, free radical scavenger T-1, crosslinking agent L-1, and solvent are as described above. [Chemical 32]

[0093] [Chemical 33]

[0094] [Chemical 34]

[0095] [Chemical 35]

[0096] [Chemical 36]

[0097] • Solvents: PGMEA (propylene glycol monomethyl ether acetate), AcOH (acetic acid), HBM (methyl 2-hydroxyisobutyrate), PA (propionic acid), GBL (γ-butyrolactone)

[0098] [3] EUV lithography evaluation (line and spacing pattern) [Examples 2-1 to 2-15, Comparative Examples 2-1 to 2-2] Each resist composition (R-01 to R-15, CR-01 to CR-02) was spin-coated onto a Si substrate with a film thickness of 20 nm, which was formed with a silicon spin-coated hard mask SHB-A940 (silicon content of 43% by mass) manufactured by Shin-Etsu Chemical Industry Co., Ltd., and pre-baked (PAB) for 60 seconds at the temperature recorded in Table 4 using a heating plate to produce a resist film with a film thickness of 40 nm. The aforementioned resist film was exposed using an ASML NXE3400 EUV scanner (NA 0.33, σ 0.9, 90° dipole illumination) to a 36 nm line-to-spacing (LS) 1:1 pattern. The pattern was then subjected to PEB for 60 seconds at the temperature described in Table 4 on a heated plate, followed by 30 seconds of development using the developer described in Table 4, to form a negative LS pattern with a spacing width of 18 nm and a pitch of 36 nm.

[0099] The obtained resist pattern was evaluated as follows. The results are shown in Table 4.

[0100] [Sensitivity Evaluation] The above LS pattern was observed using a Hitachi Advanced Technology Co., Ltd. measuring SEM (CG-6300). The optimal exposure Eop (mJ / cm2) of the LS pattern with a spacing width of 18 nm and a pitch of 36 nm was determined and used as the sensitivity.

[0101] [LWR Evaluation] For an LS pattern obtained by irradiation with optimal exposure, the dimensions at 10 points along the length of the spacing width were measured using a Hitachi Advanced Technology Co., Ltd. length-measuring SEM (CG-6300). The LWR (nm) was calculated as three times the standard deviation (σ). The smaller this value, the smaller the roughness and the more uniform the spacing width of the pattern.

[0102] [Evaluation of Limiting Resolution] Using a Hitachi Advanced Technology Co., Ltd. measuring SEM (CG-6300), the linewidth (nm) that limits the resolution when gradually increasing the exposure from the optimal exposure for forming the aforementioned LS pattern was determined, and this value was taken as the limiting resolution (nm). The smaller this value, the better the limiting resolution, and the more fine the pattern can be formed.

[0103] [Table 4] inhibitor Composition PAB / PEB (°C) Developer Eop (mJ / cm 2 ) LWR (nm) Limiting resolution (nm) Example 2-1 R-01 100 / 90 TMAH 38 3.5 15 Example 2-2 R-02 100 / 90 TMAH 38 3.5 15 Example 2-3 R-03 100 / 90 TMAH 35 3.3 17 Examples 2-4 R-04 100 / 90 TMAH 41 3.7 14 Examples 2-5 R-05 100 / 90 TMAH 43 3.4 14 Examples 2-6 R-06 100 / 90 TMAH 44 3.6 17 Examples 2-7 R-07 100 / 90 TMAH 43 3.7 17 Examples 2-8 R-08 100 / 90 TMAH 44 3.5 17 Examples 2-9 R-09 100 / 90 TMAH 39 3.4 17 Example 2-10 R-10 100 / 90 TMAH 41 3.6 15 Example 2-11 R-11 100 / 90 TMAH 41 3.3 17 Example 2-12 R-12 100 / 90 TMAH 37 3.3 14 Example 2-13 R-13 100 / 90 TMAH 36 3.4 14 Example 2-14 R-14 100 / 90 TMAH 42 3.2 13 Example 2-15 R-15 100 / 90 TMAH 34 3.3 12 Comparative Example 2-1 CR-01 105 / 90 nBA 80 4.6 19 Comparative Example 2-2 CR-02 105 / 90 nBA 85 4.9 19

[0104] Developer: nBA (butyl acetate) TMAH (2.38% by mass tetramethylammonium hydroxide aqueous solution)

[0105] According to the results shown in Table 4, it can be seen that the negative resist patterning method of the present invention can form a negative resist pattern with excellent sensitivity, LWR and resolution in LS patterning based on EUV exposure.

[0106] [4] EUV lithography evaluation (pillar pattern) [Examples 3-1 to 3-15, Comparative Examples 3-1 to 3-2] Each resist composition (R-01 to R-15, CR-01 to CR-02) was spin-coated onto a Si substrate with a silicon spin-coated hard mask SHB-A940 (Si content of 43% by mass) manufactured by Shin-Etsu Chemical Industry Co., Ltd. with a film thickness of 20 nm. PAB was performed for 60 seconds at the temperature listed in Table 5 using a hot plate to produce a resist film with a film thickness of 50 nm. Next, the aforementioned resist film was exposed using an ASML EUV scanner NXE3400 (NA 0.33, σ 0.9 / 0.6, quadrupole illumination, a mask for a column pattern with a pitch of 64 nm and a +20% bias on the wafer). The film was then subjected to PEB for 60 seconds on a hot plate at the temperature described in Table 5, followed by development for 30 seconds using the developer described in Table 5, resulting in a column pattern with a size of 32 nm.

[0107] The obtained resist pattern was evaluated as follows. The results are shown in Table 5.

[0108] [Sensitivity Evaluation] The aforementioned column pattern was observed using a Hitachi Advanced Technology Co., Ltd. (CG-6300) measuring SEM. The optimal exposure Eop (mJ / cm2) for a column pattern with a size of 22 nm was determined and used as the sensitivity.

[0109] [CDU Evaluation] The dimensions of 50 column patterns obtained by irradiation with the optimal exposure were measured, and the CDU (nm) was taken as three times the standard deviation (σ) calculated from the results (3σ). The smaller this value, the more uniform the column diameter of the pattern can be obtained.

[0110] [Evaluation of Limiting Resolution] Using a Hitachi Advanced Technology Co., Ltd. measuring SEM (CG-6300), the column diameter (nm) that limits resolution when gradually decreasing the exposure from the optimal exposure for forming the aforementioned column pattern was determined, and this value was taken as the limiting resolution (nm). The smaller this value, the better the limiting resolution, and the more finer the column diameter pattern can be formed.

[0111] [Table 5] inhibitor Composition PAB / PEB (°C) Developer Eop (mJ / cm 2 ) CDU (nm) Limiting resolution (nm) Example 3-1 R-01 100 / 90 TMAH 25 2.8 27 Example 3-2 R-02 100 / 90 TMAH 27 2.8 27 Example 3-3 R-03 100 / 90 TMAH 27 2.9 29 Examples 3-4 R-04 100 / 90 TMAH 29 2.9 25 Examples 3-5 R-05 100 / 90 TMAH 29 2.8 27 Examples 3-6 R-06 100 / 90 TMAH 27 3.0 29 Examples 3-7 R-07 100 / 90 TMAH 26 3.0 27 Examples 3-8 R-08 100 / 90 TMAH 28 2.8 27 Examples 3-9 R-09 100 / 90 TMAH 29 2.7 29 Examples 3-10 R-10 100 / 90 TMAH 30 2.9 29 Example 3-11 R-11 100 / 90 TMAH 29 2.7 27 Example 3-12 R-12 100 / 90 TMAH twenty four 2.6 26 Example 3-13 R-13 100 / 90 TMAH twenty three 2.7 26 Example 3-14 R-14 100 / 90 TMAH 28 2.6 twenty four Example 3-15 R-15 100 / 90 TMAH twenty two 2.5 twenty three Comparative Example 3-1 CR-01 105 / 90 nBA 43 3.8 33 Comparative Example 3-2 CR-02 105 / 90 nBA 41 4.0 33

[0112] As can be seen from the results shown in Table 5, the negative resist pattern forming method of the present invention can form a negative resist pattern with excellent sensitivity, CDU and resolution in the column pattern forming based on EUV exposure.

Claims

1. A method for forming a negative resist pattern, comprising the following steps: (i) forming a resist film on a substrate using a resist composition comprising a high-valent iodine compound, a carboxyl-containing polymer and a solvent but not containing a photoacid generator; (ii) exposing the resist film to high-energy rays; (iii) developing the exposed resist film using a developer that dissolves the unexposed portions but not the exposed portions; wherein the high-valent iodine compound is represented by the following formula (1), wherein n is an integer from 0 to 5, R1 and R2 are each independently a halogen atom or a hydrocarbon group having 1 to 10 carbon atoms that may contain heteroatoms, and R1 and R2 may be bonded to each other and form a ring together with the carbon atoms they are bonded to and the atoms between the carbon atoms, R3 is a halogen atom or a hydrocarbon group having 1 to 40 carbon atoms that may contain heteroatoms, and when n is 2 to 5, each R3 may be the same or different from each other.

2. The method for forming a negative resist pattern as described in claim 1, wherein, The developer is an alkaline developer.

3. The method for forming a negative resist pattern as described in claim 1, wherein, The high-energy rays are either electron beams or extreme ultraviolet rays.

4. The method for forming a negative resist pattern as described in any of claims 1 to 3, wherein, The carboxyl-containing polymer contains repeating units as shown in the following formula (2), where RA is a hydrogen atom, a halogen atom, a methyl or trifluoromethyl atom, XA is a single bond, an phenyl group, an naphthyl group or *-C(=O)-O-XA1-, XA1 is a saturated alkyl group, an phenyl group or an naphthyl group with 1 to 10 carbon atoms, and the saturated alkyl group may also contain at least one of the following: hydroxyl group, ether bond, ester bond and lactone ring, * indicates an atomic bond with a carbon atom of the main chain, except that when RA is methyl, XA is not a single bond.

5. The method for forming a negative resist pattern as described in any of claims 1 to 3, wherein, The inhibitor composition also includes a crosslinking agent.

6. The method for forming a negative resist pattern as described in any of claims 1 to 3, wherein, The inhibitor composition also contains a free radical scavenger.