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

Technical Field

[0001] The present invention relates to an acetal compound, particularly an acetal compound useful for a resist composition. Further, the present invention relates to an additive containing the acetal compound, which is used 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 by the action of an acid.

Background Art

[0002] With the high integration and high speed of LSIs, the miniaturization of pattern rules has been rapidly progressing. Currently, lithography techniques using KrF excimer laser light (wavelength 248 nm) or ArF excimer laser light (wavelength 193 nm) are used in mass production. Further, research and development are also underway on lithography techniques using F2 excimer laser light (wavelength 157 nm) with a shorter wavelength, EUV (extreme ultraviolet rays), X-rays, and electron beams, which have shorter wavelengths than these excimer lasers.

[0003] On the other hand, in memory ICs, in order to increase the memory capacity, the three-dimensionalization of memory layers such as 3D-NAND is becoming the mainstream. Since it is necessary to increase the number of processing steps in the vertical direction for the three-dimensionalization of memory layers, thickening of the resist film is required. For example, Patent Document 1 discloses a chemically amplified positive photoresist composition for thick films used to form a thick film photoresist layer with a film thickness of 5 to 150 μm.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the case of a thick film resist, since the resin is applied thickly, there is a problem that cracks are likely to occur in the resist film after baking. Furthermore, in the etching process of the resist film, minute bubbles are generated in the resist due to the decomposition of the acid generator, and there is also a problem that unevenness derived from the bubbles occurs on the pattern surface when etching is performed.

[0006] Therefore, an object of the present invention is to provide a compound useful for a resist composition capable of suppressing the generation of cracks in a thick film resist and forming a resist pattern having a smooth and good surface state. Furthermore, an object of the present invention is to provide a resist composition containing the compound.

Means for Solving the Problems

[0007] As a result of intensive studies to achieve the above object, the present inventors have found that by incorporating an acetal compound, which is a reaction product of a polyhydric phenol and a vinyl ether having an oxyethylene chain, into a resist composition, it is possible to suppress the generation of cracks even in a thick film resist and form a resist pattern having a smooth and good surface state, and have thus completed the present invention.

[0008] That is, according to the present invention, the following inventions are provided. [1] The following general formula (1):

Chemical formula

Chemical formula

[10] A method for producing the acetal compound according to any one of [1] to [7], comprising a polyhydric phenol having a valence of 2 to 4 and the following general formula (2):

Chemical formula

Advantages of the Invention

[0009] According to the present invention, in a thick film resist, cracks do not occur, and a resist pattern with a smooth pattern surface can be formed.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Modes for Carrying Out the Invention

[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 for a resist composition capable of suppressing the generation of cracks in a thick film resist and forming a resist pattern with a smooth surface state and good quality.

[0012] The acetal compound of the present invention is represented by the following general formula (1). [Chemical formula] 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 subjecting a polyhydric phenol and a vinyl ether having an oxyethylene chain to an acetalization reaction in the coexistence of an acid catalyst. In the reaction of a polyhydric phenol and a vinyl ether having an oxyethylene chain, it is preferable to react an equivalent amount of vinyl ether corresponding to the valence of the phenol so that all phenolic hydroxyl groups are converted into acetals.

[0014] A polyhydric phenol is a phenol having a plurality of phenolic hydroxyl groups. In the present specification, phenol refers to all compounds in which a hydroxyl group is bonded to an aromatic ring. The polyhydric phenol is a dihydric to tetrahydric phenol, preferably a dihydric or trihydric phenol, more preferably a dihydric phenol. The polyhydric phenol preferably has 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 the polyhydric phenol include various bisphenols, naphthalenediol, anthracenediol, pyrenediol, 1,1,1-tris(4-hydroxyphenyl)ethane, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, biphenylenediol and the like. Among these, it is preferable to use at least one compound of 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 the formula (2).

Chemical formula

[0017] Examples of the group represented by the general formula (2) include the following.

Chemical formula

[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; phosphonic acids such as methanephosphonic acid and benzenephosphonic acid, and the like. Among these, from the viewpoint of suppressing the polymerization reaction of vinyl ether, carboxylic acid or sulfonic acid is preferred.

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

[0020] The solvent used in the acetalization reaction may be any solvent that can stably dissolve the polymer having a phenolic hydroxyl group as a raw material, vinyl ether, 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; aromatic hydrocarbons such as toluene and xylene, and these can be used alone or in a mixture of two or more.

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

[0022] After the acetalization reaction, it is preferable to add a basic compound to the reaction solution to neutralize the acid catalyst or remove the acid catalyst with an anion exchange resin. Specific examples of the basic compound include hydroxides of alkali metals such as sodium and potassium, alkali metal compounds such as carbonates and bicarbonates; 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. Preferably, neutralization with amines or quaternary ammonium compounds and removal of the acid catalyst with an anion exchange resin are used.

[0023] <Composition for resist> The composition for resist of the present invention contains at least a polymer whose solubility in a developer changes by the action of an 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 can be suitably used for a composition for thick film resist 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 the composition for thick film resist, the content of the acetal compound of the present invention in the composition is preferably 1 to 50% by mass, more preferably 1 to 30% by mass, still more preferably 1 to 20% by mass, and particularly preferably 1 to 15% by mass. Also, the content of the polymer is preferably 10 to 80% by mass, more preferably 20 to 60% by mass, still more preferably 25 to 50% by mass.

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

[0026] In particular, a polymer containing a unit derived from hydroxystyrene or a repeating unit having a structure in which the hydroxyl group of hydroxystyrene is protected with a group capable of being eliminated by the action of an acid (hereinafter referred to as an acid dissociable group) is preferable.

[0027] 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] Acid dissociable groups are known to have various structures and are not particularly limited. Specifically, tert-butyl group, tert-amyl group, 1-methyl-1-cyclopentyl group, 1-ethyl-1-cyclopentyl group, 1-methyl-1-cyclohexyl group, 1-ethyl-1-cyclohexyl group, 2-methyl-2-adamantyl group, 2-ethyl-2-adamantyl group, 2-propyl-2-adamantyl group, 2-(1-adamantyl)-2-propyl group, 8-methyl-8-tricyclo[5.2.1.0 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 decanyloxymethyl group, tetrahydropyranyl group, tert-butoxycarbonyl group and other oxygen-containing hydrocarbon groups, etc. can be mentioned.

[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. for the purpose of improving substrate adhesion. As an example of a monomer that provides such a repeating unit, 2-hydroxyethyl (meth)acrylate, 3-hydroxy-1-adamantyl methacrylate, γ-butyrolactone-α-(meth)acrylate, norbornane lactone (meth)acrylate, 2-methacryloyloxyacetoxy-4,5-oxathiatricyclo[4.2.1.03,7]nonane = 5,5-dioxide, etc. can be mentioned.

[0030] Further, the polymer may contain other repeating units that do not have acid-dissociable groups. As an example of a monomer that provides such a repeating unit, styrene, 2-vinylnaphthalene, methyl (meth)acrylate, 1-adamantyl (meth)acrylate, etc. can be mentioned.

[0031] The acid generator can be appropriately selected from those proposed as acid generators for chemically amplified resists. Examples of such include onium salts such as iodonium salts and sulfonium salts, oxime sulfonates, diazomethanes such as bisalkyl or bisaryl sulfonyldiazomethanes, nitrobenzyl sulfonates, imino sulfonates, disulfones, etc. Among these, onium salts are preferred. These can be used alone or in combination of two or more.

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

[0033] The solvent may be any substance that can dissolve each component constituting the resist composition to form a uniform solution. For example, any known solvent for forming a coating film can be used as a single solvent or a mixed solvent of two or more solvents. Solvents having at least one polar group selected from a ketone bond, an ester bond, an ether bond, and a hydroxy group are preferred because of their excellent solubility. Among these, solvents having a boiling point of 110 to 220 °C at normal pressure are particularly preferred because they have an appropriate 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, cyclohexanone, etc., solvents having an ether bond and a hydroxy group such as propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether, etc., solvents having an ether bond and an ester bond such as propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate, ethyl 3-ethoxypropionate, etc., solvents having an ester bond and a hydroxy group such as methyl lactate, ethyl lactate, etc., solvents having an ester bond such as γ-butyrolactone, etc. Among these, PGMEA, PGME, γ-butyrolactone, and ethyl lactate are preferred.

[0034] If desired, the resist composition may further contain organic carboxylic acids and oxoacids of phosphorus for preventing the sensitivity deterioration of the acid generator, improving the shape of the resist pattern, standing stability, etc., additional resins for improving the performance of the resist film, surfactants for improving coatability, dissolution inhibitors, plasticizers, stabilizers, colorants, antihalation agents, dyes, etc., and compounds commonly used as resist additives as appropriate according to need.

Examples

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

[0036] The analysis in this example was conducted as follows. [Identification of Compounds] The identification of the compounds synthesized below was 1 performed by 1H-NMR and 13 13C-NMR. The 1H-NMR spectra and 1 13C-NMR spectra of each compound are shown in Figures 1 to 14. Since the synthesized compounds were not isolated and analyzed as solutions containing solvents, the NMR spectra contain peaks of propylene glycol monomethyl ether acetate as the solvent. Note that 13 the peaks of propylene glycol monomethyl ether acetate in 1H-NMR are at ppm = 1.16 (d), 1.95, 3.27, 3.32 - 3.38 (dd), 4.98 (m), and 1 the peaks of propylene glycol monomethyl ether acetate in 13C-NMR spectra are at ppm = 16.86, 21.03, 58.91, 69.52, 75.42, 170.23. 13 Apparatus: AVANCE manufactured by Bruker Frequency: 500 MHz Deuterated 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 GPC (gel permeation chromatography) using polystyrene as a standard. Measurement apparatus: HPLC-8220GPC manufactured by Tosoh Corporation Detector: Differential refractive index (RI) detector Column: Shodex GPC KF804 × 3 columns (manufactured by Showa Denko) Eluent: Tetrahydrofuran Flow rate: 1.0 mL / min Temperature: 40 °C Calibration curve: Prepared using a polystyrene standard sample (manufactured by Tosoh)

[0038] [Polymer Composition] The monomer composition ratio of the synthesized polymer was 13 analyzed by C-NMR. A sample for analysis was prepared by dissolving 2.0 g of the polymer solution after concentration adjustment and 0.1 g of Cr(III) acetylacetonate in 1.0 g of deuterated acetone. Apparatus: AVANCE400 manufactured by Bruker Nucleus: 13 C Measurement method: Inverse gated decoupling

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

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

Chemical formula

[0041] The results of the NMR analysis of compound A are as follows. 11H-NMR (500 MHz, acetone-d6): δ ppm = 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 13C-NMR (500 MHz, acetone-d6): δ ppm = 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 referred to as THPE) and PGMEA were placed in a eggplant-shaped flask and concentrated under reduced pressure at 40 °C to prepare a solution with a water content of 500 ppm or less in the solution and a THPE concentration of 20% by mass. 2966.5 g of the aforementioned THPE / PGMEA solution and 4.2 g of a 1% by mass methanesulfonic acid / PGMEA solution were charged into a reaction vessel equipped with a thermometer, a condenser, and a stirrer, and heated to 60 °C with stirring in a nitrogen stream. Here, a mixed solution of 672.5 g of 2-methoxyethyl vinyl ether (hereinafter referred to as MOVE) and 552.4 g of PGMEA was added dropwise over 120 minutes, and the reaction was continued for another 2 hours after the addition was completed. After the reaction was completed, the reaction solution was passed through 243.5 g of Amberlyst B20-HG·DRY packed in a column for 6 hours to remove methanesulfonic acid as a catalyst. Thereafter, it was concentrated under reduced pressure at 40 °C to obtain a PGMEA solution with a compound B 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:

Chemical formula

[0044] The results of the NMR analysis of Compound B are as follows. 11H-NMR (400 MHz, acetone-d6): δ ppm = 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 13C-NMR (400 MHz, acetone-d6): δ ppm = 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 eggplant-shaped 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 in the solution. 200.8 g of the aforementioned 40% by mass bisphenol A / PGMEA solution and 6.8 g of a 20% by mass trifluoroacetic acid / PGMEA solution were charged into a reaction vessel equipped with a thermometer, a condenser, and a stirrer, and heated to 60°C with stirring in a nitrogen stream. Here, 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 over 60 minutes, and the reaction was continued for another 6 hours after the addition was completed. After the reaction was completed, the reaction solution was passed through 26.1 g of Amberlyst B20-HG·DRY packed in a column for 6 hours to remove trifluoroacetic acid as a catalyst. Then, it was concentrated under reduced pressure at 40°C to obtain a PGMEA solution with a compound C concentration of 50% by mass.

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

[0047] The results of the NMR analysis of compound C are as follows. 11H-NMR (400 MHz, acetone-d6): δ ppm = 1.41 (6H), 1.62 (6H), 3.24 (6H), 3.44 - 3.78 (24H), 5.42 (2H), 6.92 (4H), 7.12 (4H) 13 13C-NMR (400 MHz, acetone-d6): δ ppm = 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 referred to as ACVE), and PGMEA were placed in an eggplant flask, concentrated under reduced pressure at 40 °C to obtain a PGMEA solution in which the water content in the solution was 500 ppm or less and the total concentration of bisphenol A and ACVE was 55% by mass. 906.8 g of the aforementioned solution and 112.4 g of a 20% by mass trifluoroacetic acid / PGMEA solution were charged into an eggplant flask equipped with a thermometer, a condenser, and a stirrer, heated to 50 °C with stirring in a nitrogen stream, and then 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 for 6 hours to remove trifluoroacetic acid as a catalyst. Then, it was concentrated under reduced pressure at 40 °C to obtain a PGMEA solution having a concentration of Compound D of 50% by mass.

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

[0050] The results of NMR analysis of Compound D are as follows. 1H-NMR (400 MHz, acetone-d6): δ ppm = 1.43 (6H), 1.61 (6H), 1.67 - 1.70 (12H), 1.85 (12H), near 1.96 (6H), 3.69 (2H), 3.85 (2H), 4.14 (4H), 5.41 (2H), 6.93 (4H), 7.13 (4H) 13 C-NMR (400 MHz, acetone-d6): δ ppm = 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 Put 1,5-dihydroxynaphthalene and PGMEA into an eggplant flask, concentrate under reduced pressure at 40 °C to prepare a solution with a water content of 500 ppm or less in the solution and a 1,5-dihydroxynaphthalene concentration of 40% by mass. Charge 243.8 g of the aforementioned 1,5-dihydroxynaphthalene / PGMEA solution and 0.5 g of a 1% by mass methanesulfonic acid / PGMEA solution into an eggplant flask equipped with a thermometer, a condenser, and a stirrer, and heat to 60 °C with stirring in a nitrogen stream. Here, 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 another 6 hours after the addition was complete. After the reaction was completed, the reaction solution was passed through 10.7 g of Amberlyst B20-HG·DRY packed in a column for 6 hours to remove methanesulfonic acid as the catalyst. Then, it was concentrated under reduced pressure at 40 °C to obtain a solution with a compound E concentration of 50% by mass.

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

[0053] Compound E:

Chemical formula

[0054] The results of the NMR analysis of Compound E are as follows. 1 1H-NMR (400 MHz, acetone-d6): δ ppm = 1.56 (6H), 3.24 (6H), 3.4 - 3.9 (8H), 5.66 (2H), 7.12 (2H), 7.36 (2H), 7.88 (2H) 13 13C-NMR (400 MHz, acetone-d6): δ ppm = 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 an eggplant 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 in the solution. 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 an eggplant flask equipped with a thermometer, a condenser, and a stirrer, and heated to 40 °C with stirring in a nitrogen stream. Here, a mixed solution of 98.1 g of ethyl vinyl ether and 25.0 g of PGMEA was added dropwise over 60 minutes, and the reaction was continued for another 4 hours after the addition was complete. After the reaction was completed, the reaction solution was passed through 26.7 g of Amberlyst B20-HG·DRY packed in a column for 6 hours to remove trifluoroacetic acid as the catalyst. Then, it was concentrated under reduced pressure at 40 °C to obtain a solution with a concentration of Compound F of 50% by mass.

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

Chemical formula

[0057] The results of the NMR analysis of Compound F are as follows. 11H-NMR (400 MHz, acetone-d6): δ ppm = 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 13C-NMR (400 MHz, acetone-d6): δ ppm = 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 an eggplant flask and concentrated under reduced pressure at 40 °C to prepare a PGMEA solution with a water content of 500 ppm or less in the solution 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 an eggplant flask equipped with a thermometer, a condenser, and a stirrer, and heated to 60 °C with 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 thereto over 60 minutes, and the reaction was continued for another 6 hours after the addition was completed. After the reaction was completed, the reaction solution was passed through 243.7 g of Amberlyst B20-HG·DRY packed in a column for 6 hours to remove trifluoroacetic acid as a catalyst. Then, it was concentrated under reduced pressure at 40 °C to obtain a solution with 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:

Chemical formula

[0060] The results of NMR analysis of compound G are as follows. 11H-NMR (400 MHz, acetone-d6): δ ppm = 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 13C-NMR (400 MHz, acetone-d6): δ ppm = 21.47, 24.48, 24.65, 26.31, 31.34, 32.96, 34.17, 42.26, 74.76, 98.95, 117.67, 128.29, 144.63, 155.74

[0061] [Synthesis of Polymer for Resist] [Synthesis Example 1] Synthesis of p-Hydroxystyrene / Styrene / t-Butyl Methacrylate Copolymer Into an eggplant flask equipped with a thermometer, a condenser, and a stirrer, 900.0 g of a p-ethylphenol solution (hereinafter referred to as PHS monomer solution) containing 24% by mass of p-hydroxystyrene, 23% by mass of methanol, and 10% by mass of water was charged and heated to 80 °C. In another 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 put and stirred to form a uniform solution. This solution was dropped into the above-mentioned eggplant flask over 2 hours, and the polymerization reaction was continued with stirring for another 1 hour. Then, the polymerization solution was cooled to room temperature, and this was dropped into a mixed solution of 4023 g of methylcyclohexane and 603 g of 2-propanol to precipitate the polymer, and the supernatant was removed. Further, for purification, 2-propanol was added to the polymer to redissolve it, and it was dropped into methylcyclohexane to precipitate the polymer, and the operation of removing the supernatant was repeated 5 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 having a polymer concentration of 50% by mass. The obtained polymer had a composition ratio of p-hydroxystyrene:styrene:t-butyl methacrylate of 59.1:20.6:20.3, Mw = 19,000, and Mw / Mn = 1.83.

[0063] [Preparation of Resist Composition] A PGMEA solution containing 50% by mass of Compound A obtained in Example 1 was 60 parts by mass (30 parts by mass in terms of Compound A), 140 parts by mass of the polymer solution for resist 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 and adjusted to a solid content concentration of 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 - G obtained in Examples 2 - 5 and Comparative Examples 1 and 2 were blended at the ratios shown in Table 1, and resist compositions were prepared respectively.

[0065] Also, as Comparative Example 3, a resist composition not containing Compounds A - G was prepared.

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

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

[0068] Etching was performed on the obtained resist layer under the following conditions. For crack resistance, the surface of the resist layer after etching was visually observed. If no crack was observed, it was evaluated as ○, and if a crack was observed, it was evaluated as ×. The evaluation results are shown in Table 1. <Etching Conditions> Output: 180 W Chamber pressure: 18 Pa Gas species: O2 Gas flow rate: 100 mL / min Etching time: 10 minutes

[0069] In addition, the surface roughness was measured by an atomic force microscope (Dimension Icon manufactured by BRUKER) on the surface of the resist layer after etching, and the surface average roughness Ra in a 5 μm square range was calculated. Note that Ra is the arithmetic average roughness defined in JIS B 0601:2013. Based on the Ra value of the resist composition (Comparative Example 3) not containing Compounds A to G, when the Ra value was 60% or less of the Ra value of Comparative Example 3, it was evaluated as ○, when it was more than 60% and less than 100%, it was evaluated as △, and when it was 100% or more, it 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 heat-treated at 100 °C for 60 seconds. The above resist composition was spin-coated on the treated silicon wafer and dried on a hot plate at 100 °C for 60 seconds to form a resist layer with a film thickness of 8 μm.

[0071] The formed resist layer was exposed to light with a wavelength of 248 nm using an open-frame exposure apparatus (light source: Hg-Xe lamp, UVS-2000 manufactured by Lithotech Japan) with varying exposure amounts for 18 shots of 10 mm 2 ×10 mm 2 . After that, it was heat-treated at 100 °C for 60 seconds. Next, the exposed and heat-treated silicon wafer was developed with a 2.38 mass% aqueous solution of tetramethylammonium hydroxide at 23 °C using a resist development rate measuring apparatus (RDA-790 manufactured by Lithotech Japan), and the change in the resist film thickness over time at each exposure amount was measured. This data was analyzed to obtain the sensitivity Eth of the resist. The smaller the value of Eth, the higher the sensitivity. Eth: An approximate straight line was drawn in the range of 10% to 70% of the residual film rate of the residual film rate curve, and the exposure amount (mJ / cm 2 )

[0072] Based on the Eth value in the case of the resist composition (Comparative Example 3) not containing Compounds A to G, when the Eth value was 80% or less of the Eth value of Comparative Example 3, it was evaluated as ○, and when it was more than 80%, it was evaluated as △. The evaluation results are shown in Table 1.

[0073]

Table 1

[0074] In Example 5, since compound E contains a naphthalene ring, it strongly absorbs light with a wavelength of 248 nm, and the sensitivity was inferior compared to Example 2. However, it is presumed that exposure with i-line (365 nm), EUV, etc. can suppress cracks and irregularities on the surface of the resist film while maintaining the sensitivity.

[0075] When the resist composition containing the acetal compound of the present invention was used as a film-thickness resist, it was possible to suppress cracks from occurring in the resist film after etching, and further suppress irregularities on the surface of the resist film caused by the generation of bubbles.

Industrial Applicability

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

Claims

1. An acetal compound represented by the following general formula (1): 【Chemical 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 of 1 to 3. m represents 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, and the polyhydric phenol is a phenol having 10 to 30 carbon atoms.)

2. The acetal compound according to claim 1, which is a reaction product of a polyhydric phenol having a valence of 2 to 4 and a vinyl ether having an oxyethylene chain represented by the following general formula (2):

3. [Chemical Formula 2] (In general formula (2), R １ and n are synonymous with R １ and n in general formula (1).) The acetal compound according to claim 1 or 2, wherein the polyhydric phenol is a phenol having 10 to 20 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 bisphenol, naphthalenediol, anthracenediol, pyrenediol, 1,1,1-tris(4-hydroxyphenyl)ethane, and 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane.

5. The acetal compound according to claim 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.

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

7. An additive containing the acetal compound according to any one of claims 1 to 6, which is used in a resist composition.

8. A resist composition containing a polymer whose solubility in a developer changes by 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: reacting a polyhydric phenol having a valence of 2 to 4 with a vinyl ether represented by the following general formula (2) in the presence of an acid. ​ ​ 【Chemical Formula 3】 (In general formula (2), R １ and n have the same meanings as R １ and n in general formula (1).) ​

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