Acetal compound, additive containing said compound, and resist composition containing said compound

Abstract

[Problem] To provide: a composition which is for thick film resist and with which cracks in a resist film are suppressed and a pattern with a favorable surface condition can be formed; and an acetal compound from which the same can be formed. [Solution] Provided are: an acetal compound represented by formula (1) (in the formula, R1 represents a C1-C12 alkyl group, a C5-C12 cycloalkyl group, or a C1-C12 acyl group, n is an integer of 1-5, m represents an integer of 2-4, and Ar is a residue obtained by removing hydrogen atoms from hydroxyl groups in a m-valent polyhydric phenol); and a composition which is for thick film resist and contains the same.

Description

Acetal compound, additive containing said compound, and resist composition containing said compound

[0001] The present invention relates to an acetal compound, particularly an acetal compound useful in a resist composition. The present invention also relates to an additive containing the acetal compound for use in a resist composition. The present invention also relates to a resist composition containing the acetal compound, particularly a thick-film resist composition whose solubility in a developer changes under the action of an acid.

[0002] As LSIs become more highly integrated and faster, pattern rules are becoming increasingly fine. Currently, lithography techniques using KrF excimer laser light (wavelength 248 nm) and ArF excimer laser light (wavelength 193 nm) are used in mass production. Research and development is also underway on lithography techniques using F2 excimer laser light (wavelength 157 nm), which has an even shorter wavelength, as well as EUV (extreme ultraviolet) and X-rays, which have shorter wavelengths than these excimer lasers, and electron beams.

[0003] On the other hand, in memory ICs, three-dimensional memory layers, such as 3D-NAND, are becoming mainstream in order to increase memory capacity. The three-dimensionalization of memory layers requires an increase in the number of vertical processing steps, which calls for thicker resist films. For example, Patent Document 1 discloses a thick-film chemically amplified positive photoresist composition used to form a thick-film photoresist layer with a thickness of 5 to 150 μm.

[0004] JP 2008-191218 A

[0005] However, thick-film resists have the problem that the thick resin coating makes the resist film prone to cracking after baking.Furthermore, during the resist film etching process, the decomposition of the acid generator generates tiny bubbles in the resist, which causes unevenness due to the bubbles on the pattern surface after etching.

[0006] Therefore, an object of the present invention is to provide a compound that is useful for a resist composition that suppresses the occurrence of cracks in a thick-film resist and is capable of forming a resist pattern with a smooth and favorable surface condition.A further object of the present invention is to provide a resist composition containing such a compound.

[0007] As a result of extensive research into achieving the above-mentioned object, the inventors discovered that by incorporating into a resist composition an acetal compound, which is a reaction product of a polyhydric phenol and a vinyl ether having an oxyethylene chain, it is possible to suppress the occurrence of cracks even in thick-film resists and to form resist patterns with a smooth and excellent surface condition, which led to the completion of the present invention.

[0008] That is, according to the present invention, the following inventions are provided: [1] A compound represented by the following general formula (1): (In general formula (1), R １ represents an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an acyl group having 1 to 12 carbon atoms. n is an integer of 1 to 5. m is an integer of 2 to 4. Ar is a residue obtained by removing a hydrogen atom from a hydroxyl group of a polyhydric phenol having a valence of m. [2] An acetal compound represented by the following general formula (2): (In general formula (2), R １ and n is R in general formula (1). １and n are synonymous with each other.) The acetal compound according to [1], wherein the polyhydric phenol is a phenol having 10 to 30 carbon atoms. [4] The acetal compound according to [1] or [2], wherein the polyhydric phenol is a bisphenol-type compound. [5] The acetal compound according to [1] or [2], wherein the polyhydric phenol is a naphthalene diol. [6] The acetal compound according to [1] or [2], wherein the polyhydric phenol is at least one compound selected from the group consisting of bisphenol A, 1,1,1-tris(4-hydroxyphenyl)ethane, and 1,5-dihydroxynaphthalene. [7] The acetal compound according to any one of [1] to [6], which is used in a resist composition. [8] An additive, comprising the acetal compound according to any one of [1] to [7], which is used in a resist composition. [9] A resist composition comprising a polymer whose solubility in a developer changes under the action of an acid, an acid generator, a solvent, and the acetal compound according to any one of [1] to [7].

[10] A method for producing the acetal compound according to any one of [1] to [7], comprising: (In general formula (2), R １ and n is R in general formula (1). １ and n are synonymous with each other.) in the presence of an acid.

[0009] According to the present invention, a good resist pattern can be formed without generating cracks in the thick-film resist and with a smooth pattern surface.

[0010] Compound A synthesized in Example 1 １ 1H-NMR spectrum of Compound A synthesized in Example 1. １３ 1 is a C-NMR spectrum of Compound B synthesized in Example 2. １ 1H-NMR spectrum of Compound B synthesized in Example 2. １３ 1 is a C-NMR spectrum of Compound C synthesized in Example 3. １ 1H-NMR spectrum of Compound C synthesized in Example 3.１３ 1 is a C-NMR spectrum of Compound D synthesized in Example 4. １ 1H-NMR spectrum of Compound D synthesized in Example 4. １３ 1 is a C-NMR spectrum of Compound E synthesized in Example 5. １ 1H-NMR spectrum of Compound E synthesized in Example 5. １３ 1 is a C-NMR spectrum of Compound F synthesized in Comparative Example 1. １ 1H-NMR spectrum of Compound F synthesized in Comparative Example 1. １３ 1 is a C-NMR spectrum of Compound G synthesized in Comparative Example 2. １ 1H-NMR spectrum of Compound G synthesized in Comparative Example 2. １３ This is a C-NMR spectrum.

[0011] [Acetal Compound] The acetal compound of the present invention is a reaction product of a polyhydric phenol and a vinyl ether having an oxyethylene chain. Such an acetal compound can be used as a useful additive in a resist composition, which can suppress the occurrence of cracks in a thick-film resist and enable the formation of a resist pattern with a smooth and excellent surface condition.

[0012] The acetal compound of the present invention is represented by the following general formula (1): In general formula (1), R １ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or an acyl group having 1 to 12 carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an acyl group having 1 to 12 carbon atoms, and more preferably an alkyl group having 1 to 4 carbon atoms or an acyl group having 1 to 12 carbon atoms. n is an integer of 1 to 5, preferably an integer of 1 to 3, and more preferably 1 or 2. m is an integer of 2 to 4. Ar is a residue obtained by removing a hydrogen atom from a hydroxyl group of a polyhydric phenol having a valence of m.

[0013] The acetal compound of the present invention can be obtained by acetalization of a polyhydric phenol with a vinyl ether having an oxyethylene chain in the presence of an acid catalyst. In the reaction of a polyhydric phenol with a vinyl ether having an oxyethylene chain, it is preferable to react an equivalent amount of vinyl ether according to the valence of the phenol, so that all phenolic hydroxyl groups are converted to acetals.

[0014] A polyhydric phenol is a phenol having multiple phenolic hydroxyl groups. In this specification, phenol refers to all compounds in which hydroxyl groups are bonded to an aromatic ring. The polyhydric phenol is a dihydric to tetrahydric phenol, preferably a dihydric or trihydric phenol, and more preferably a dihydric phenol. The polyhydric phenol is preferably a phenol having 10 to 30 carbon atoms, more preferably 10 to 26 carbon atoms, and even more preferably 12 to 20 carbon atoms.

[0015] Specific examples of polyhydric phenols include various bisphenols, naphthalenediol, anthracenediol, pyrenediol, 1,1,1-tris(4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, biphenylenediol, etc. Among these, it is preferable to use at least one compound selected from bisphenol A, 1,1,1-tris(4-hydroxyphenyl)ethane, and 1,5-dihydroxynaphthalene.

[0016] The vinyl ether having an oxyethylene chain is preferably a compound represented by formula (2). R in general formula (2) １ and n is R in general formula (1). １ and n.

[0017] Examples of the group represented by formula (2) include the following. *n in the formula represents the number of repeating oxyethylene chains.

[0018] Examples of the acid catalyst used in the acetalization reaction include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid; carboxylic acids such as formic acid, acetic acid, butyric acid, and trifluoroacetic acid; sulfonic acids such as methanesulfonic acid, benzenesulfonic acid, and toluenesulfonic acid; and phosphonic acids such as methanephosphonic acid and benzenephosphonic acid. Among these, carboxylic acids or sulfonic acids are preferred from the viewpoint of inhibiting the polymerization reaction of vinyl ether.

[0019] The amount of the acid catalyst used cannot be generally specified because it varies depending on the type of acid used, but it is usually 1 to 5000 ppm, and preferably 1 to 2000 ppm, based on the entire reaction system. When the amount of the acid catalyst used is within the above range, side reactions such as a polymerization reaction of the vinyl ether are unlikely to occur, and a sufficient reaction rate is likely to be obtained.

[0020] The solvent used in the acetalization reaction may be any solvent capable of stably dissolving the raw material polymer having a phenolic hydroxyl group, the vinyl ether, the acid catalyst, and the product obtained by the acetalization reaction. Specific examples of the solvent include esters such as methyl acetate, ethyl acetate, isopropyl acetate, propyl acetate, butyl acetate, methyl propionate, methyl lactate, and ethyl lactate; glycol ether esters such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; ethers such as tetrahydrofuran, 1,4-dioxane, and ethylene glycol dimethyl ether; and aromatic hydrocarbons such as toluene and xylene. These may be used alone or in combination of two or more.

[0021] The temperature for the acetalization reaction is preferably 25 to 120°C, more preferably 30 to 100°C, and even more preferably 30 to 80°C.

[0022] After the acetalization reaction, it is preferable to neutralize the acid catalyst by adding a basic compound to the reaction solution or to remove the acid catalyst with an anion exchange resin. Specific examples of basic compounds include alkali metal compounds such as hydroxides, carbonates, and hydrogen carbonates of alkali metals such as sodium and potassium; aqueous ammonia and ammonia gas; amines such as trimethylamine and triethylamine; pyridines such as pyridine and methylpyridine; and quaternary ammonium compounds such as tetraalkylammonium hydroxide. Neutralization with amines or quaternary ammonium compounds and removal of the acid catalyst with an anion exchange resin are preferred.

[0023] <Resist Composition> The resist composition of the present invention contains at least a polymer whose solubility in a developer changes under the action of acid, an acid generator, a solvent, and the acetal compound of the present invention, and may further contain other additives such as an acid diffusion inhibitor. In particular, the acetal compound of the present invention is suitable for use in a thick-film resist composition used to form a thick-film resist having a film thickness of 1 μm or more, preferably 1 μm or more and 100 μm or less.

[0024] In the case of a thick-film resist composition, the content of the acetal compound of the present invention in the composition is preferably 1 to 50 mass%, more preferably 1 to 30 mass%, even more preferably 1 to 20 mass%, and particularly preferably 1 to 15 mass%, and the content of the polymer is preferably 10 to 80 mass%, more preferably 20 to 60 mass%, and even more preferably 25 to 50 mass%.

[0025] The polymer used in the resist composition of the present invention is a polymer whose solubility in a developer changes under the action of an acid, and can be arbitrarily selected from those generally used for chemically amplified resists.

[0026] In particular, polymers containing repeating units derived from hydroxystyrene or having a structure in which the hydroxyl group of hydroxystyrene is protected with a group that can be dissociated by the action of acid (hereinafter referred to as an acid-dissociable group) are preferred.

[0027] Furthermore, it may also contain a repeating unit having a structure in which the carboxyl group of acrylic acid or methacrylic acid is protected with an acid-dissociable group.

[0028] The acid-dissociable group has a variety of known structures and is not particularly limited. Specific examples include a tert-butyl group, a tert-amyl group, a 1-methyl-1-cyclopentyl group, a 1-ethyl-1-cyclopentyl group, a 1-methyl-1-cyclohexyl group, a 1-ethyl-1-cyclohexyl group, a 2-methyl-2-adamantyl group, a 2-ethyl-2-adamantyl group, a 2-propyl-2-adamantyl group, a 2-(1-adamantyl)-2-propyl group, an 8-methyl-8-tricyclo[5.2.1.0]diene, an 8-methyl-1-cyclopentyl group, an 8-methyl-1-cyclopentyl group, an 8-methyl-1-cyclopentyl group, an 8-methyl-1-cyclohex ... 2,6 ] decanyl group, 8-ethyl-8-tricyclo[5.2.1.0 2,6 ] decanyl group, 8-methyl-8-tetracyclo[4.4.0.1 2,5 .1 7,10 ] dodecanyl group, 8-ethyl-8-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodecanyl group and other saturated hydrocarbon groups; 1-methoxyethyl group, 1-ethoxyethyl group, 1-iso-propoxyethyl group, 1-n-butoxyethyl group, 1-tert-butoxyethyl group, 1-cyclopentyloxyethyl group, 1-cyclohexyloxyethyl group, 1-tricyclo[5.2.1.0 2,6 ]decanyloxyethyl group, methoxymethyl group, ethoxymethyl group, iso-propoxymethyl group, n-butoxymethyl group, tert-butoxymethyl group, cyclopentyloxymethyl group, cyclohexyloxymethyl group, tricyclo[5.2.1.0 2,6 ] Examples include oxygen-containing hydrocarbon groups such as decanyloxymethyl group, tetrahydropyranyl group, and tert-butoxycarbonyl group.

[0029] In addition to the above repeating units, the polymer may contain repeating units containing polar groups such as alcoholic hydroxyl groups, lactones, sultones, etc., in order to improve substrate adhesion. Examples of monomers that provide such repeating units include 2-hydroxyethyl(meth)acrylate, 3-hydroxy-1-adamantyl methacrylate, γ-butyrolactone-α-(meth)acrylate, norbornane lactone (meth)acrylate, and 2-methacryloyloxyacetoxy-4,5-oxathiatricyclo[4.2.1.03,7]nonane=5,5-dioxide.

[0030] The polymer may also contain other repeating units that do not have an acid-dissociable group. Examples of monomers that provide such repeating units include styrene, 2-vinylnaphthalene, methyl (meth)acrylate, and 1-adamantyl (meth)acrylate.

[0031] The acid generator can be appropriately selected from those proposed as acid generators for chemically amplified resists. Examples of such acid generators include onium salts such as iodonium salts and sulfonium salts, oximesulfonates, diazomethanes such as bisalkyl or bisarylsulfonyldiazomethanes, nitrobenzylsulfonates, iminosulfonates, and disulfones. Among these, onium salts are preferred. These may be used alone or in combination of two or more.

[0032] The acid diffusion inhibitor can be appropriately selected from those that have been proposed as acid diffusion inhibitors for chemically amplified resists. Examples of such compounds include nitrogen-containing organic compounds, with primary to tertiary alkylamines or hydroxyalkylamines being preferred. Tertiary alkylamines and tertiary hydroxyalkylamines being particularly preferred. Among these, triethanolamine and triisopropanolamine are particularly preferred. These compounds may be used alone or in combination of two or more.

[0033] The solvent may be any solvent capable of dissolving each component constituting the resist composition to form a homogeneous solution. For example, any of known solvents for forming coating films can be used as a single solvent or a mixture of two or more solvents. Due to their excellent solubility, solvents having at least one polar group selected from a ketone bond, an ester bond, an ether bond, and a hydroxy group are preferred. Among these, solvents with a boiling point of 110 to 220°C at atmospheric pressure are particularly preferred because they have a moderate evaporation rate during baking after spin coating and excellent film-forming properties. Specific examples of such solvents include solvents having a ketone bond such as methyl isobutyl ketone, methyl isoamyl ketone, methyl amyl ketone, and cyclohexanone, solvents having an ether bond and a hydroxy group such as propylene glycol monomethyl ether (PGME) and propylene glycol monoethyl ether, solvents having an ether bond and an ester bond such as propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate, and ethyl 3-ethoxypropionate, solvents having an ester bond and a hydroxy group such as methyl lactate and ethyl lactate, and solvents having an ester bond such as γ-butyrolactone. Of these, PGMEA, PGME, γ-butyrolactone, and ethyl lactate are preferred.

[0034] The resist composition can further contain, as desired, compounds commonly used as resist additives, such as organic carboxylic acids or phosphorus oxoacids for the purposes of preventing deterioration in the sensitivity of the acid generator or improving the shape of the resist pattern and deposition stability, additional resins for improving the performance of the resist film, surfactants for improving coatability, dissolution inhibitors, plasticizers, stabilizers, colorants, antihalation agents, dyes, etc.

[0035] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. In the following examples, parts are by mass unless otherwise specified.

[0036] The analyses in this example were carried out as follows. [Identification of Compounds] The compounds synthesized below were identified as follows:１ H-NMR and １３ C-NMR was used for each compound. １ H-NMR spectrum and １３ The C-NMR spectra are shown in Figures 1 to 14. Note that the synthesized compounds were not isolated but analyzed as solutions containing the solvent, so the NMR spectra contain peaks of the solvent, propylene glycol monomethyl ether acetate. １ The peaks of propylene glycol monomethyl ether acetate in H-NMR were ppm = 1.16 (d), 1.95, 3.27, 3.32-3.38 (dd), 4.98 (m), １３ The peaks of propylene glycol monomethyl ether acetate in the C-NMR spectrum are ppm = 16.86, 21.03, 58.91, 69.52, 75.42, and 170.23. Apparatus: AVANCE manufactured by Bruker Corporation Frequency: 500 MHz Deuterium solvent: acetone-d6 Internal standard: TMS Measurement temperature: 30°C

[0037] [Weight-average molecular weight and dispersity of polymer] The weight-average molecular weight (Mw) and dispersity (Mw / Mn) of the polymers synthesized below were measured by gel permeation chromatography (GPC) using polystyrene as a standard. Measuring device: HPLC-8220GPC manufactured by Tosoh Corporation Detector: Differential refractive index (RI) detector Column: Shodex GPC KF804 x 3 (manufactured by Showa Denko KK) Eluent: Tetrahydrofuran Flow rate: 1.0 mL / min Temperature: 40°C Calibration curve: Prepared using a polystyrene standard sample (manufactured by Tosoh Corporation)

[0038] [Polymer composition] The composition ratio of each monomer in the synthesized polymer is １３ The resultant was analyzed by C-NMR. 2.0 g of the polymer solution after the concentration adjustment and 0.1 g of Cr(III) acetylacetonate were dissolved in 1.0 g of deuterated acetone to prepare a sample for analysis. Apparatus: AVANCE 400 manufactured by Bruker Corporation. Nuclide: １３ C Measurement method: Inverse gate decoupling

[0039] [Synthesis of Resist Additives] [Example 1] Synthesis of Compound A Bisphenol A and propylene glycol monomethyl ether acetate (PGMEA) were placed in a recovery flask and concentrated under reduced pressure at 40°C to prepare a solution with a water content of 500 ppm or less and a Bis-A concentration of 40% by mass. A reaction vessel equipped with a thermometer, a condenser, and a stirrer was charged with 2680.0 g of the Bis-A / PGMEA solution and 63.8 g of a 20% by mass trifluoroacetic acid / PGMEA solution, and heated to 60°C with stirring in a nitrogen stream. A mixed solution of 1055.4 g of 2-methoxyethyl vinyl ether (MOVE) and 468.2 g of PGMEA was added dropwise over 60 minutes, and the reaction was continued for an additional 4 hours after the completion of the dropwise addition. After the reaction was completed, the reaction mixture was passed through 243.5 g of Amberlyst B20-HG DRY packed in a column over 6 hours to remove the catalyst trifluoroacetic acid. Thereafter, the mixture was concentrated under reduced pressure at 40°C to obtain a PGMEA solution containing Compound A at a concentration of 50% by mass.

[0040] The obtained compound A was confirmed to have the structure of the following formula (3) by NMR analysis. The HPLC purity of the obtained compound was 98.7%. Compound A:

[0041] The results of NMR analysis of Compound A are as follows: １ H-NMR (500MHz, acetone-d6): δppm = 1.41 (6H), 1.61 (6H), 3.24 (6H), 3.45 (4H), 3.60 (2H), 3.77 (2H), 5.40 (2H), 6.91 (4H), 7.11 (4H) １３ C-NMR (500MHz, acetone-d6): δppm = 20.49, 31.33, 42.24, 58.91, 65.52, 72.29, 100.31, 117.53, 128.26, 144.78, 155.67

[0042] Example 2 Synthesis of Compound B 1,1,1-tris(4-hydroxyphenyl)ethane (hereinafter, THPE) and PGMEA were placed in a recovery flask and concentrated under reduced pressure at 40°C to prepare a solution with a water content of 500 ppm or less and a THPE concentration of 20% by mass. A reaction vessel equipped with a thermometer, a condenser, and a stirrer was charged with 2966.5 g of the aforementioned THPE / PGMEA solution and 4.2 g of a 1% by mass methanesulfonic acid / PGMEA solution, and heated to 60°C with stirring in a nitrogen stream. A mixed solution of 672.5 g of 2-methoxyethyl vinyl ether (hereinafter, MOVE) and 552.4 g of PGMEA was added dropwise over 120 minutes, and the reaction was continued for an additional 2 hours after the completion of the dropwise addition. After the reaction was completed, the reaction mixture was passed through 243.5 g of Amberlyst B20-HG DRY packed in a column over 6 hours to remove the catalyst methanesulfonic acid.The mixture was then concentrated under reduced pressure at 40°C to obtain a PGMEA solution containing Compound B at a concentration of 50% by mass.

[0043] The obtained compound B was confirmed to have the structure of the following formula (4) by NMR analysis. The HPLC purity of the obtained compound was 94.2%. Compound B:

[0044] The results of NMR analysis of Compound B are as follows: １ H-NMR (400MHz, acetone-d6): δppm = 1.41 (9H), 2.08 (3H), 3.24 (9H), 3.46 (6H), 3.61 (3H), 3.77 (3H), 5.42 (3H), 6.91 (6H), 6.97 (6H) １３ C-NMR (400MHz, acetone-d6): δppm = 20.47, 31.04, 51.40, 58.90, 63.56, 72.28, 100.26, 117.26, 130.18, 143.49, 155.88

[0045] Example 3 Synthesis of Compound C Bisphenol A and PGMEA were placed in a recovery flask and concentrated under reduced pressure at 40°C to obtain a solution with a water content of 500 ppm or less and a Bis-A concentration of 40% by mass. 200.8 g of the 40% by mass bisphenol A / PGMEA solution and 6.8 g of the 20% by mass trifluoroacetic acid / PGMEA solution were placed in a reaction vessel equipped with a thermometer, a condenser, and a stirrer, and the mixture was heated to 60°C with stirring in a nitrogen stream. A mixed solution of 147.2 g of 2-(2-(2-methoxyethoxy)ethoxy)ethyl vinyl ether (hereinafter referred to as TEGVE) and 101.6 g of PGMEA was added dropwise to the mixture over 60 minutes, and the reaction was continued for an additional 6 hours after the completion of the dropwise addition. After the reaction was completed, the reaction mixture was passed through a column packed with 26.1 g of Amberlyst B20-HG DRY for 6 hours to remove the catalyst trifluoroacetic acid. The mixture was then concentrated under reduced pressure at 40°C to obtain a PGMEA solution containing Compound C at a concentration of 50% by mass.

[0046] The obtained compound C was confirmed to have the structure of the following formula (5) by NMR analysis. The HPLC purity of the obtained compound was 94.9%. Compound C:

[0047] The results of NMR analysis of Compound C are as follows: １ H-NMR (400MHz, acetone-d6): δppm = 1.41 (6H), 1.62 (6H), 3.24 (6H), 3.44-3.78 (24H), 5.42 (2H), 6.92 (4H), 7.12 (4H) １３ C-NMR (400MHz, acetone-d6): δppm = 20.50, 31.33, 42.24, 58.90, 65.65, 70.94-71.12, 72.54, 100.28, 117.56, 128.24, 144.75, 155.68

[0048] Example 4 Synthesis of Compound D 750.0 g of bisphenol A, 1768.4 g of 2-(vinyloxy)ethyl 1-adamantanecarboxylate (hereinafter, ACVE), and PGMEA were placed in a recovery flask and concentrated under reduced pressure at 40°C to obtain a PGMEA solution with a water content of 500 ppm or less and a combined concentration of bisphenol A and ACVE of 55% by mass. 906.8 g of the aforementioned solution and 112.4 g of a 20% by mass trifluoroacetic acid / PGMEA solution were placed in a recovery flask equipped with a thermometer, a condenser, and a stirrer. The mixture was heated to 50°C with stirring in a nitrogen stream, and the reaction was continued for 8 hours. After completion of the reaction, the reaction solution was passed through 430.0 g of Amberlyst B20-HG DRY packed in a column over 6 hours to remove the catalyst trifluoroacetic acid. Thereafter, the mixture was concentrated under reduced pressure at 40° C. to obtain a PGMEA solution containing Compound D at a concentration of 50% by mass.

[0049] The obtained compound D was confirmed to have the structure of the following formula (6) by NMR analysis. The HPLC purity of the obtained compound was 98.5%. Compound D:

[0050] The results of NMR analysis of Compound D are as follows: １ H-NMR (400MHz, acetone-d6): δppm = 1.43 (6H), 1.61 (6H), 1.67-1.70 (12H), 1.85 ( 12H), around 1,96 (6H), 3.69 (2H), 3.85 (2H), 4.14 (4H), 5.41 (2H), 6.93 (4H), 7.13 (4H) １３ C-NMR (400MHz, acetone-d6): δppm=20.24, 28.70, 31.35, 37.09, 39.46, 41 .12, 42.27, 63.71, 63.78, 99.99, 117.54, 128.25, 144.82, 155.60, 177.04

[0051] Example 5 Synthesis of Compound E 1,5-dihydroxynaphthalene and PGMEA were placed in a recovery flask and concentrated under reduced pressure at 40°C to prepare a solution with a water content of 500 ppm or less and a 1,5-dihydroxynaphthalene concentration of 40% by mass. 243.8 g of the aforementioned 1,5-dihydroxynaphthalene / PGMEA solution and 0.5 g of a 1% by mass methanesulfonic acid / PGMEA solution were placed in a recovery flask equipped with a thermometer, a condenser, and a stirrer, and the mixture was heated to 60°C while stirring in a nitrogen stream. A mixed solution of 138.1 g of 2-methoxyethyl vinyl ether and 88.5 g of PGMEA was added dropwise over 60 minutes, and the reaction was continued for an additional 6 hours after the completion of the addition. After the reaction was completed, the reaction solution was passed through 10.7 g of Amberlyst B20-HG DRY packed in a column over 6 hours to remove the catalyst methanesulfonic acid. Thereafter, the mixture was concentrated under reduced pressure at 40° C. to obtain a solution having a compound E concentration of 50% by mass.

[0052] The obtained compound E was confirmed by NMR analysis to have the structure of the following formula (7): The HPLC purity of compound E was 88.8%.

[0053] Compound E:

[0054] The results of NMR analysis of Compound E are as follows: １ H-NMR (400MHz, acetone-d6): δppm = 1.56 (6H), 3.24 (6H), 3.4-3.9 (8H), 5.66 (2H), 7.12 (2H), 7.36 (2H), 7.88 (2H) １３ C-NMR (400MHz, acetone-d6): δppm = 20.57, 58.72, 66.02, 72.31, 101.04, 110.45, 115.99, 126.07, 128.42, 153.45

[0055] [Comparative Example 1] Synthesis of Compound F Bisphenol A and PGMEA were placed in a recovery flask and concentrated under reduced pressure at 40 °C to obtain a solution with a water content of 500 ppm or less and a Bis-A concentration of 40% by mass. 337.6 g of the aforementioned bisphenol A / PGMEA solution and 7.0 g of a 20% by mass trifluoroacetic acid / PGMEA solution were charged into a recovery flask equipped with a thermometer, a condenser, and a stirrer, and the mixture was heated to 40 °C while stirring in a nitrogen stream. A mixed solution of 98.1 g of ethyl vinyl ether and 25.0 g of PGMEA was added dropwise to the mixture over 60 minutes, and the reaction was continued for another 4 hours after the completion of the dropwise addition. After the completion of the reaction, the reaction solution was passed through 26.7 g of Amberlyst B20-HG DRY packed in a column over 6 hours, and the catalyst trifluoroacetic acid was removed. The mixture was then concentrated under reduced pressure at 40 °C to obtain a solution with a compound F concentration of 50% by mass.

[0056] The obtained compound F was confirmed to have the structure of the following formula (8) by NMR analysis. The HPLC purity of the obtained compound was 96.6%. Compound F:

[0057] The results of NMR analysis of Compound F are as follows: １ H-NMR (400MHz, acetone-d6): δppm = 1.11 (6H), 1.40 (6H), 1.61 (6H), 3.49 (2H), 3.71 (2H), 5.35 (2H), 6.89 (4H), 7.12 (4H) １３ C-NMR (400MHz, acetone-d6): δppm = 15.52, 20.61, 31.34, 42.24, 61.55, 100.01, 117.38, 128.26, 144.63, 155.80

[0058] [Comparative Example 2] Synthesis of Compound G Bisphenol A and PGMEA were placed in a recovery flask and concentrated under reduced pressure at 40 °C to prepare a PGMEA solution with a water content of 500 ppm or less and a bisphenol A concentration of 40% by mass. 2401.9 g of the aforementioned bisphenol A / PGMEA solution and 63.9 g of a 20% by mass trifluoroacetic acid / PGMEA solution were charged into a recovery flask equipped with a thermometer, a condenser, and a stirrer, and the mixture was heated to 60 °C while stirring in a nitrogen stream. A mixed solution of 1168.4 g of cyclohexyl vinyl ether and 637.0 g of PGMEA was added dropwise over 60 minutes, and the reaction was continued for another 6 hours after the completion of the addition. After the reaction was completed, the reaction solution was passed through 243.7 g of Amberlyst B20-HG DRY packed in a column over 6 hours, and the catalyst trifluoroacetic acid was removed. Thereafter, the mixture was concentrated under reduced pressure at 40° C. to obtain a solution having a compound G concentration of 50% by mass.

[0059] The obtained compound G was confirmed to have the structure of the following formula (9) by NMR analysis. The HPLC purity of the obtained compound was 97.8%. Compound G:

[0060] The results of NMR analysis of Compound G are as follows: １ H-NMR (400MHz, acetone-d6): δppm=1.18-1.50 (12H), 1.39 (6H), 1.61 (6H), 1.65 (4H), 1.81 (4H), 3.64 (2H), 5.49 (2H), 6.89 (4H), 7.12 (4H) １３ C-NMR (400MHz, acetone-d6): δppm = 21.47, 24.48, 24.65, 26, 31, 31.3 4, 32.96, 34.17, 42.26, 74.76, 98.95, 117.67, 128.29, 144.63, 155.74

[0061] [Synthesis of Resist Polymers] [Synthesis Example 1] Synthesis of p-hydroxystyrene / styrene / t-butyl methacrylate copolymer 900.0 g of a p-ethylphenol solution (hereinafter referred to as "PHS monomer solution") containing 24% by weight of p-hydroxystyrene, 23% by weight of methanol, and 10% by weight of water was charged into a recovery flask equipped with a thermometer, a condenser, and a stirrer, and heated to 80°C. In a separate container, 1350.0 g of a PHS monomer solution having the same composition as described above, 184.6 g of styrene, 182.2 g of t-butyl acrylate, and 39.1 g of dimethyl 2,2'-azobis(2-methylpropionate) were added and stirred to form a homogeneous solution. This solution was added dropwise to the recovery flask over 2 hours, and stirring was continued for another hour to carry out the polymerization reaction. The polymerization solution was then cooled to room temperature and added dropwise to a mixed solution of 4023 g of methylcyclohexane and 603 g of 2-propanol to precipitate a polymer, and the supernatant was removed. For further purification, the polymer was redissolved in 2-propanol, and the polymer was precipitated by adding dropwise to methylcyclohexane, followed by removal of the supernatant liquid. This procedure was repeated five times.

[0062] The recovered polymer was dissolved in 2600 g of PGMEA and concentrated under reduced pressure at 40°C to prepare a PGMEA solution with a polymer concentration of 50% by mass. The obtained polymer had a p-hydroxystyrene:styrene:t-butyl methacrylate composition ratio of 59.1:20.6:20.3, Mw=19,000, and Mw / Mn=1.83.

[0063] [Preparation of Resist Composition] 60 parts by mass of the PGMEA solution containing 50% by mass of Compound A obtained in Example 1 (30 parts by mass in terms of Compound A), 140 parts by mass of the resist polymer solution obtained in Synthesis Example 1 (70 parts by mass in terms of polymer), 1 part by mass of an acid generator (SP140 manufactured by ADEKA), and 0.1 part by mass of a surfactant (F447 manufactured by DIC) were dissolved in PGMEA to adjust the solids concentration to 40% by mass, and then filtered through a membrane filter with a pore size of 0.45 μm to prepare a resist composition.

[0064] Similarly, compounds B to G obtained in Examples 2 to 5 and Comparative Examples 1 and 2 were mixed in the proportions shown in Table 1 to prepare resist compositions.

[0065] Furthermore, as Comparative Example 3, a resist composition that did not contain any of Compounds A to G was prepared.

[0066] Using the above resist compositions, the physical properties of the resist compositions were evaluated according to the following methods.

[0067] [Crack Resistance and Surface Roughness] Hexamethyldisilazane was applied to a 6-inch silicon wafer and then heat-treated at 100° C. for 60 seconds. The resist composition described above was spin-coated onto the treated silicon wafer and pre-baked on a hot plate at 100° C. for 60 seconds to form a resist layer with a thickness of 8 μm.

[0068] The obtained resist layer was etched under the following conditions. The surface of the resist layer after etching was visually observed to evaluate the crack resistance. If no cracks were observed, it was evaluated as ◯, and if cracks were observed, it was evaluated as ×. The evaluation results are shown in Table 1. <Etching conditions> Output: 180 W Chamber pressure: 18 Pa Gas type: O ２ Gas flow rate: 100 mL / min Etching time: 10 minutes

[0069] The surface roughness was measured by measuring the resist layer surface after etching with an atomic force microscope (Dimension Icon, manufactured by BRUKER), and the average surface roughness Ra within a 5 μm square area was calculated. Ra is the arithmetic average roughness as defined in JIS B 0601:2013. Using the Ra value of a resist composition (Comparative Example 3) that did not contain compounds A to G as the standard, an Ra value of 60% or less of the Ra value of Comparative Example 3 was evaluated as ◯, a value of more than 60% but less than 100% was evaluated as △, and a value of 100% or more was evaluated as ×. The evaluation results are shown in Table 1.

[0070] [Sensitivity Evaluation of Resist Composition] Hexamethyldisilazane was applied to a 6-inch silicon wafer and then heat-treated at 100° C. for 60 seconds. The resist composition was spin-coated onto the treated silicon wafer and dried on a hot plate at 100° C. for 60 seconds to form a resist layer with a thickness of 8 μm.

[0071] The formed resist layer was exposed to light with a wavelength of 248 nm using an open frame exposure device (light source: Hg-Xe lamp, UVS-2000 manufactured by Litho Tech Japan) for 10 mm at different exposure doses. ２ ×10mm ２ After irradiating 18 shots of 10 ... ２ )

[0072] Using the Eth value of a resist composition (Comparative Example 3) that did not contain compounds A to G as the standard, if the Eth value was 80% or less of the Eth value of Comparative Example 3, it was evaluated as ◯, and if it was over 80%, it was evaluated as △. The evaluation results are shown in Table 1.

[0073]

[0074] In Example 5, because Compound E contains a naphthalene ring, it has a strong absorption of light with a wavelength of 248 nm, and the sensitivity is inferior to that of Example 2. However, it is presumed that when exposed to i-line (365 nm), EUV, or the like, the sensitivity is maintained while cracks and unevenness on the resist film surface can be suppressed.

[0075] When used as a thick resist, the resist composition containing the acetal compound of the present invention was able to suppress cracks from occurring in the resist film after etching, and also suppress unevenness on the resist film surface caused by the generation of bubbles.

[0076] The acetal compound of the present invention can be used in resist compositions, particularly thick-film resist compositions.

Claims

1. The following general formula (1): 【Chemistry 1】 (In general formula (1), R １ represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 12 carbon atoms. n is an integer from 1 to 3. m is an integer from 2 to 4. Ar is a residue obtained by removing a hydrogen atom from a hydroxyl group of a polyhydric phenol having a valence of m. An acetal compound represented by the formula:

2. A polyhydric phenol having a valence of 2 to 4 and a compound represented by the following general formula (2): 【Chemistry 2】 (In general formula (2), R １ and n is R in general formula (1). １ and n are synonymous.) The acetal compound according to claim 1, which is a reaction product with a vinyl ether having an oxyethylene chain represented by the formula:

3. The acetal compound according to claim 1 or 2, wherein the polyhydric phenol is a phenol having 10 to 30 carbon atoms.

4. The acetal compound according to claim 1 or 2, wherein the polyhydric phenol is at least one compound selected from the group consisting of bisphenols, naphthalenediol, anthracenediol, pyrenediol, 1,1,1-tris(4-hydroxyphenyl)ethane, and 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane.

5. 3. The acetal compound according to claim 1, wherein the polyhydric phenol is at least one compound selected from the group consisting of bisphenol A, 1,1,1-tris(4-hydroxyphenyl)ethane, and 1,5-dihydroxynaphthalene.

6. The acetal compound according to any one of claims 1 to 5, which is used in a resist composition.

7. An additive for use in a resist composition, comprising the acetal compound according to any one of claims 1 to 6.

8. A resist composition comprising: a polymer whose solubility in a developer changes under the action of an acid; an acid generator; a solvent; and the acetal compound according to any one of claims 1 to 6.

9. A method for producing the acetal compound according to any one of claims 1 to 6, comprising the steps of: A divalent to tetravalent polyphenol and a compound represented by the following general formula (2): 【Chemistry 3】 (In general formula (2), R １ and n is R in general formula (1). １ and n are synonymous.) The production method comprises reacting a vinyl ether represented by the formula:

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