JP2002139834A - Pattern forming method, method for producing semiconductor device and photosensitive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a negative type pattern free of swelling and excellent in resolution while having a chemical structure transparent in the far UV region including 193 nm wavelength of ArF excimer laser beam and having high dry etching resistance. SOLUTION: A reaction in which part or the whole of a γ- or δ- acetoxycarboxylic acid structure is converted into a lactone structure by an acid catalyzed reaction is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microlithography process using a photosensitive composition, which is a fine processing technique in a manufacturing process of a semiconductor device or the like, and a method of manufacturing a semiconductor device or the like including the microlithography process. More specifically, a negative type suitable for a photolithography process using a deep ultraviolet light having a wavelength of 220 nm or less, such as an ArF excimer laser beam, which is a shorter wavelength light source than a high pressure mercury lamp or a KrF excimer laser, which is a current ultraviolet light source. The present invention relates to a pattern forming method, a method for manufacturing a semiconductor device, and a photosensitive composition used for the method.

[0002]

2. Description of the Related Art A photolithography technique for forming a fine pattern on the order of microns or submicrons in an electronic device such as a semiconductor has played a central role in mass production fine processing technology. The recent demand for higher integration and higher density of semiconductor devices is
Many advances have been made in microfabrication technology. In particular, as the minimum processing size approaches the exposure wavelength, photolithography technology using a KrF excimer laser (248 nm) from g-line (436 nm) and i-line (365 nm) of a high-pressure mercury lamp and a shorter wavelength light source is developed. It has been.

[0003] In response to these changes in the exposure wavelength, photoresists have been developed with materials corresponding to the respective wavelengths. Conventionally, in photoresists suitable for these wavelengths,
Although the sensitizer and the sensitizing mechanism are different from each other, aqueous alkali development utilizing aqueous alkali solubility of a resin or polymer material having a phenol structure has been industrially used. These resins or polymer materials inevitably contain a large amount of aromatic rings, which was also a chemical structural element for improving the etching resistance in a dry etching step after the formation of a resist pattern.

A negative resist using such a resin having a phenol structure is disclosed in JP-A-62-1640.
45 and a cross-linking type such as JP-A-4-165359
And a dissolution inhibiting type such as In any case, a submicron fine pattern can be formed without swelling.

In recent years, expectations for photolithography using an ArF excimer laser (193 nm) as a light source have increased as a lithography technique for a region having a minimum processing dimension smaller than 0.25 μm. However, this wavelength is the absorption maximum due to the aromatic ring, and in a photoresist material mainly containing a phenol structure which has been conventionally industrially used, the range in which an exposure latent image can be formed is limited to the extreme surface of the photoresist film. It was difficult to form a fine resist pattern by aqueous alkali development.

On the other hand, various resist materials having high transmittance in this wavelength region and high dry etching resistance have been proposed. ArF excimer laser wavelength 19
As a chemical structure which is transparent in a far ultraviolet region including 3 nm and can impart dry etching resistance to a resist material, use of an adamantane skeleton has been disclosed in JP-A-4-39665.
Japanese Patent Application Laid-Open Nos. 5-265212 and 5-265212 similarly disclose the use of a norbornane skeleton.
Is disclosed. In addition to these structures, JP-A-7-28237 and JP-A-8-259626 disclose that an alicyclic structure such as a tricyclodecanyl group is generally effective.

A polymer having a transparent chemical structure in a far ultraviolet region including a wavelength of 193 nm of an ArF excimer laser,
With respect to the resist material which enables aqueous alkali development, JP-A-4-39665, JP-A-4-184345,
As disclosed in JP-A-4-226461 and JP-A-5-80515, attempts have been made to utilize the carboxylic acid structure of acrylic acid or methacrylic acid. In these, the solubility of the portion dissolved in the developing solution in aqueous alkali development depends on the carboxylic acid structure of acrylic acid or methacrylic acid. JP-A-8-259626 discloses a polymer compound in which a carboxylic acid group is added to an alicyclic structure introduced into a methacrylic ester side chain.

[0008]

In the phenol structure conventionally used as an alkali-soluble group, pKa =
In contrast to 10.0 (phenol), these carboxylic acid structures have a low value of pKa = 4.8 (acetic acid),
High acidity. Therefore, when they are used as the alkali-soluble groups of the base resin, generally, at the same mole fraction, the resin having a carboxylic acid structure has a higher dissolution rate in an aqueous alkali, and the resin having a carboxylic acid structure is phenol. It dissolves even in a low-concentration alkaline developer in which the resin having the structure does not dissolve.

When a resin having a carboxylic acid as described above is used, if a crosslinking agent as disclosed in JP-A-62-164045 is used, a carboxylic acid having a high acidity remains in a crosslinked portion. There was a drawback that the alkali developer infiltrated there and swelled to make it impossible to form a fine pattern. Further, as disclosed in JP-A-4-165359, when a compound having a dissolution inhibiting action is formed by an acid generated by exposure, a resin having a carboxylic acid does not provide a dissolution contrast, and a negative resist is used. There was a drawback that it did not become.

A first object of the present invention is to provide a negative pattern forming method which can be developed without swelling of a fine pattern in an aqueous alkaline developer and which has excellent resolution performance by esterification of a material having a carboxylic acid. Is to provide. A second object of the present invention is to provide a method for manufacturing a semiconductor device using such a pattern forming method. Further, a third object of the present invention is to provide a photosensitive composition used in such a method for forming a pattern or a method for manufacturing a semiconductor device.

[0011]

In order to achieve the first object, a method for forming a pattern according to the present invention comprises the steps of:
-A step of forming a coating film made of a photosensitive composition containing an acetoxycarboxylic acid structure or a δ-acetoxycarboxylic acid structure, and irradiating the coating film with an actinic radiation of a predetermined pattern to irradiate the actinic radiation. Γ-
Changing to a lactone structure or a δ-lactone structure.

The γ- or δ-acetoxycarboxylic acid structure changes from soluble to insoluble in an aqueous alkaline developer by changing to a γ-lactone or δ-lactone structure by an acid-catalyzed reaction. As a result, a negative pattern is formed by development with an aqueous alkali. The generated γ-lactone or δ-lactone structure is not hydrolyzed by a commonly used aqueous solution of tetraalkylammonium hydroxide and is stable during development. The acid for causing the acid-catalyzed reaction is realized by using an acid generator that generates an acid upon irradiation with actinic radiation.

Examples of the compound capable of generating an acid upon irradiation with the actinic radiation include onium salts such as triphenylsulfonium triflate, sulfonyloxyimides such as trifluoromethanesulfonyloxynaphthylimide, and sulfonate esters. Any material that generates an acid by irradiation with actinic radiation, for example, an ArF excimer laser or the like may be used.

The above-mentioned γ-acetoxycarboxylic acid structure or δ-acetoxycarboxylic acid structure can be used alone or in a mixed state of both. In a γ-acetoxycarboxylic acid structure or a δ-acetoxycarboxylic acid structure, a deacetic acid reaction is caused by an acid catalyst, and esterification is performed intramolecularly to form a 5- or 6-membered lactone. The acetic acid generated by this reaction is low molecular and volatilizes out of the system. as a result,
The number of carboxylic acids is greatly reduced. Therefore, unlike the cross-linking reaction in which the reaction occurs between molecules and the number of carboxylic acids hardly changes between the exposed and unexposed parts, the penetration of the developer hardly occurs in the exposed and insolubilized parts, which is a problem of the prior art. There is no swelling of the pattern after development which was a point.

As a similar structure, a γ-hydroxy acid or δ-hydroxy acid structure also generates γ-lactone or δ-lactone by an acid-catalyzed reaction. However, the γ-hydroxy acid or δ-hydroxy acid structure has a drawback that when it is made into a solution, it has low stability, especially at room temperature, and gradually changes to a γ-lactone or δ-lactone structure.
On the other hand, γ-acetoxycarboxylic acid structure or δ
The acetoxycarboxylic acid structure is stably present in solution.

The carboxylic acid structure used in the pattern forming method of the present invention has the following chemical formula (1) or (2)
It is desirable that the chemical structure represented by Here, in the formula, R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , and R ⁸ represent hydrogen or an alkyl group having 1 to 10 carbon atoms, and the alkyl groups are connected to each other. May form a cyclic alkyl group. In the formula, R ⁹ , R ¹⁰ , and R ¹¹ represent hydrogen, an alkyl group having 1 to 3 carbon atoms, or halogen. Particularly, R ¹ and R ³ , or R ³ and R ⁵ , or R ⁵
It is more preferable that any one of R ⁷ and R ⁷ form a cyclic alkyl group because a structurally easy formation of a 5- or 6-membered ring of γ-lactone or δ-lactone is possible.

[0017]

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[0018]

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Further, it is desirable that at least the carboxylic acid structure represented by the chemical formula (1) or (2) is contained in the film-forming component constituting the photosensitive composition. The film-forming component generally has a weight average molecular weight of 1,000.
A polymer compound having a molecular weight of about 0 to 300,000 may be mentioned. However, even if it is not a polymer compound, any solvent can be used as long as a coating film can be formed with a solvent, and an oligomer or a low molecular compound capable of forming a film may be used. Good. The number of the carboxylic acid structures contained in the film-forming component may be at least the amount at which the film-forming component becomes soluble in the developer used.

Here, when the carboxylic acid structure represented by the chemical formula (1) or (2) is contained in the polymer compound and is directly contained in the main chain, the chemical formula (1) or (2) In some cases, the carboxylic acid portion and the acetoxy group portion are sterically distant from each other, and the lactonization reaction may not easily occur. On the other hand, when the carboxylic acid structure represented by the chemical formula (1) or (2) is contained in the side chain, the carboxylic acid portion and the acetoxy group portion are hardly distant from each other. This is more preferable because it easily occurs and a pattern can be formed with high sensitivity.

The above-mentioned film-forming component or the photosensitive composition containing the same preferably further contains an alicyclic structure.
Examples of the alicyclic structure include adamantyl, norbornane, tricyclodecane, and androstane structures. Since these structures have high dry etching resistance and are transparent in the wavelength region of far ultraviolet light, particularly ArF excimer laser light, by including such a structure,
Dry etching resistance can be improved without lowering the transmittance.

The active actinic radiation used in the present invention includes far ultraviolet light having a wavelength of 250 nm or less and vacuum ultraviolet light such as ArF excimer laser light, but electron beams, EUV, X-rays and the like can also be used. Then, these radiations are called active actinic radiation.

In the present invention, when irradiating a predetermined pattern of actinic radiation, vacuum ultraviolet light such as ArF excimer laser light is usually formed into a predetermined pattern through a mask or a reticle. At this time, it is desirable to use a super-resolution technique typified by a modified illumination method or a phase shift mask because a pattern with higher resolution can be obtained.

The aqueous alkaline developer used in the present invention is desirably an aqueous solution of a tetraalkylammonium hydroxide having 1 to 5 carbon atoms. Also suitable are general-purpose 2.38% tetramethylammonium hydroxide aqueous solutions used for developing i-line and g-line resists and KrF excimer laser resists, and those appropriately diluted.

The pattern forming method of the present invention desirably includes a step of heating the coating film after the step of irradiating with actinic radiation and before the step of developing with an aqueous alkaline developer. By this heating step, the acid-catalyzed deacetic acid reaction producing lactone proceeds more efficiently.

In order to achieve the second object, a method of manufacturing a semiconductor device according to the present invention comprises forming a resist pattern on a semiconductor substrate by any one of the above-described pattern forming methods, Process of etching
Alternatively, the method includes a step of implanting ions into the substrate.

Examples of the etching method used in the semiconductor manufacturing method of the present invention include dry etching methods such as plasma etching, reactive ion etching, and reactive ion beam etching, and wet etching methods.

The substrate to be processed in the semiconductor device manufacturing method of the present invention is an oxide film such as a silicon dioxide film or a coating glass film formed by a CVD method or a thermal oxidation method, or a nitride film such as a silicon nitride film. Is mentioned. In addition, various metal films such as aluminum and its alloys, tungsten, and polycrystalline silicon can be used.

[0029] Since elements formed by the method of manufacturing a semiconductor device of the present invention, particularly memory elements, can be formed with a fine pattern, the degree of integration can be increased. Therefore, since the elements can be made small, the number of elements that can be obtained from one wafer increases, and the yield improves.
Also, the bit cost can be reduced. Therefore, a flash memory, which is a nonvolatile semiconductor storage device, or a DR
It is suitable for manufacturing an AM (Dynamic Random Access Memory).

In order to achieve the third object, the photosensitive composition of the present invention comprises a compound having a γ-acetoxycarboxylic acid structure or a δ-acetoxycarboxylic acid structure as an alkali-soluble group, and irradiation with active actinic radiation. At least contains a compound that generates an acid.

Γ-acetoxycarboxylic acid structure or δ-
The acetoxycarboxylic acid structures can be used alone or in a mixed state. γ-
The acetoxycarboxylic acid structure or δ-acetoxycarboxylic acid structure causes an intramolecular esterification reaction using an acid generated from a compound that generates an acid upon irradiation with active actinic radiation as a catalyst to form a 5- or 6-membered lactone. I do. This reaction is an intramolecular esterification reaction, and the produced acetic acid volatilizes out of the system due to its low molecular weight. As a result, the number of carboxylic acids is greatly reduced.

Therefore, unlike the cross-linking reaction in which the reaction occurs between the molecules and the amount of the carboxylic acid hardly changes between the exposed and unexposed parts, the developer hardly penetrates into the exposed and insolubilized parts. As a result, it is possible to provide a photosensitive composition having no pattern swelling after development, which is a problem of the prior art.

The above-mentioned γ-acetoxycarboxylic acid structure or δ-acetoxycarboxylic acid structure used in the photosensitive composition of the present invention is preferably a chemical structure represented by the above chemical formula (1) or (2). .

The carboxylic acid structure represented by the chemical formula (1) or (2) is desirably contained in the film forming component constituting the photosensitive composition as described above. The film-forming component generally has a weight average molecular weight of 1,000 to 30.
Although a high molecular compound of about 000 is exemplified, an oligomer or a low molecular compound that can form a film may be used as long as it can be applied with a solvent, without being a high molecular compound. The number of the carboxylic acid structures contained in the film-forming component may be at least the amount at which the film-forming component becomes soluble in the developer used.

The above-mentioned film-forming component or the photosensitive composition containing the same preferably further contains an alicyclic structure. Examples of the alicyclic structure include adamantyl, norbornane, tricyclodecane and androstane structures. These structures have high dry etching resistance,
Since it is transparent in the wavelength region of far ultraviolet light, particularly ArF excimer laser light, by including such a structure, dry etching resistance can be improved without reducing transmittance.

Examples of the compound capable of generating an acid upon irradiation with actinic radiation include onium salts such as triphenylsulfonium triflate, dimethylphenylsulfonium triflate and dimethyl-4-hydroxynaphthyl triflate, and N-trifluoromethanesulfonyloxy. Examples include sulfonyloxyimides such as naphthylimide, N-methanesulfonyloxynaphthylimide, N-trifluoromethanesulfonyloxysuccinimide, N-perfluorooctanesulfonyloxysuccinimide, and sulfonic acid esters. An excimer laser or the like may be used as long as it generates an acid by irradiation with actinic radiation, and is not limited thereto. These acid generators may be used in combination of two or more.

The acid generator is preferably used in an amount of 0.1 to 50 parts by weight, more preferably 0.5 to 20 parts by weight, based on 100 parts by weight of the film-forming component of the photosensitive composition. It is more preferable to use it.

Further, the photosensitive composition of the present invention has two components for improving resolution, process stability and storage stability.
-Basic compounds such as benzylpyridine, phenylpyridine, tripentylamine, triethanolamine,
Salts such as tetramethylammonium iodide, tetrapentylammonium chloride and tetraethylphosphonium iodide may be added. It is desirable to add 0.01 to 100 parts by weight of these basic compounds and salts to the acid generator used.

The photosensitive composition of the present invention contains hexamethoxymethyl melamine, 1,3,4,6-tetrakis (methoxymethyl) glucoururil as a crosslinking agent in order to enhance the heat resistance of the formed pattern. , 4-dioxane-2,3-diol and the like.
These crosslinking agents are desirably used in an amount of 0.1 to 50 parts by weight based on 100 parts by weight of the film forming component of the photosensitive composition.

The photosensitive composition of the present invention is used by dissolving it in a solvent and spin-coating it on a substrate as a solution. At this time, any solvent may be used as long as the above components are sufficiently dissolved and a uniform coating film can be formed by spin coating. Moreover, you may use individually or in mixture of 2 or more types.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. First, prior to the examples, synthetic examples of the materials used in the present invention will be described.

<Synthesis Example 1> Synthesis of polymer (3c) having γ-acetoxy acid structure In a 500 ml three-necked flask equipped with a thermometer, a cooling tube, and a nitrogen inlet tube, 5-methylenebicyclo [2.2. 1] 26.4 g of hept-2-ene and 2 parts of citraconic anhydride
5.2 g, 2,2'-azobis (isobutyronitrile)
Was added, and 300 g of tetrahydrofuran was added. The mixture was refluxed at 70 ° C. while introducing nitrogen, and polymerization was carried out for 8 hours. After the polymerization, the above reaction product was poured into 1000 ml of n-hexane to precipitate a polymer, which was then dried and dried to obtain 5-methylenebicyclo [2.2.1] hept-2-ene-citraconic anhydride copolymer (3a) 19. 0.4 g (yield 38)
%).

The structure of the obtained polymer was found to be mainly represented by the following chemical formula (3a) from various analytical methods (in the formula, n represents an integer).

[0044]

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When the molecular weight of this polymer in terms of polystyrene was examined in tetrahydrofuran by gel permeation chromatography (GPC), the weight average molecular weight was 2,200 and the number average molecular weight was 1,600.
Met.

In a 500 ml three-necked flask, 3.0 g of sodium borohydride and 100 g of tetrahydrofuran were placed, cooled to 0 ° C. in an ice bath, and stirred under nitrogen to obtain 5-methylenebicyclo [synthesized as described above. 2.
2.1] A solution of 17.4 g of hept-2-ene-citraconic anhydride copolymer in 120 g of tetrahydrofuran was added dropwise over about 1 hour. After the dropwise addition, the mixture was stirred for several hours and left overnight.

After the solution was poured into about 300 ml of water and stirred, about 1N aqueous hydrochloric acid was gradually added to the solution to make it weakly acidic at about pH 4. About 200 ml of ethyl acetate
Was added and extraction was performed twice, and the obtained organic layer was added to 150 ml.
Of water three times. After washing, the organic layer was dried over anhydrous sodium sulfate, and after drying, the solvent was removed by distillation under reduced pressure.
The mixture was poured into 800 ml of n-hexane, and the precipitated polymer was dried to obtain 13.8 g of a white powdery polymer.

According to various analytical methods, the structure of the obtained polymer was a structure in which the anhydride portion of (3a) was reduced to form a lactone, and a ring-opened structure was obtained by the following chemical formula (3)
It was found to be a polymer (3b) having at least a γ-hydroxy acid structure as shown in b1) or (3b2). Here, in the formula, l and m represent integers.

[0049]

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[0050]

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Next, 8.8 g of the polymer (3b) was dissolved in 50 ml of tetrahydrofuran, 5.2 g of acetic anhydride and 1.0 g of N, N-dimethylaminepyridine were added thereto at room temperature, and 10.2 g of triethylamine was further added. It was added dropwise at room temperature. After the dropwise addition, stirring was continued at room temperature to cause a reaction for 5 hours.

After the reaction, 200 ml of water was added to the solution, and about 0.5N aqueous hydrochloric acid was gradually added to the solution to make it weakly acidic at about pH 4. 100 ml of ethyl acetate and 50 ml of tetrahydrofuran were added to this solution, and extraction was performed twice, and the obtained organic layer was washed three times with 100 ml of water. After washing, the organic layer was dried over anhydrous sodium sulfate. After drying, the solvent was distilled off under reduced pressure, and the mixture was poured into 700 ml of n-hexane. The precipitated polymer was dried to obtain 6.0 g of a milky white powdery polymer. Was. The structure of the obtained polymer was determined by the following chemical formulas (3c1) and (3c2) from various analytical methods.
Polymer having a γ-acetoxy acid structure shown in (3c)
It turned out to be. Here, in the formula, l and m represent integers.

[0053]

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[0054]

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100 parts by weight of the obtained polymer (3c) was dissolved in 600 parts by weight of diacetone alcohol, and the pore size was adjusted to 0.
Filtered with a 2 μm filter. Spin it on, 10
Baking was performed at 0 ° C. for 2 minutes to obtain a polymer film. A film (thickness: 420 nm) applied on a silicon substrate is coated with an aqueous tetramethylammonium hydroxide solution (concentration: 2.38% by weight).
When it was immersed in, it melted in 6.0 seconds while the interference color changed, and the residual film became zero. In addition, when the dissolution was examined using a dissolution rate monitor, it was found that the dissolution occurred sequentially from the surface formation without swelling. When immersed in a diluted aqueous solution of tetramethylammonium hydroxide (concentration: 0.113% by weight), no dissolution occurred.

When the absorption spectrum of the film coated on the lithium fluoride substrate was measured by a vacuum ultraviolet spectrometer (manufactured by ARC), the absorbance at 193 nm was 0.73 at a film thickness of 1.0 μm. It turned out to be small.

<Synthesis Example 2> Synthesis of polymer (4c) having γ-ethylcarbonyloxy acid structure Polymerization was performed using maleic anhydride instead of citraconic anhydride used in Synthesis Example 1. Take 21.2 g of 5-methylenebicyclo [2.2.1] hept-2-ene and 19.6 g of maleic anhydride and polymerize with 2.56 g of 2,2′-azobis (isobutyronitrile). 5
-Methylenebicyclo [2.2.1] hept-2-ene-
37.5 g of maleic anhydride copolymer (4a) was obtained (92% yield). It was found from various analytical methods that the structure of the obtained polymer was mainly the structure of the chemical formula (4a).
Here, in the formula, n represents an integer. When the molecular weight of this polymer in terms of polystyrene was examined, the weight average molecular weight was 5,800 and the number average molecular weight was 2,500.

[0058]

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When the anhydride portion was reduced and hydrolyzed with sodium borohydride in the same manner as in Synthesis Example 1, the structure of the obtained polymer was determined by various analytical methods to be the anhydride portion of the chemical formula (4a). Represented by the formulas (4b1) and (4b2) having at least a reduced lactonized structure and a further opened γ-hydroxy acid structure
(4b). Here, in the formula, l and m represent integers.

[0060]

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[0061]

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Next, in the same manner as in Synthesis Example 1, the reaction was carried out using propanoic anhydride instead of acetic anhydride, and the yield was 58%.
Thus, a milky white powdery polymer was obtained. The structure of the obtained polymer was found to be a polymer (4c) represented by chemical formulas (4c1) and (4c2) having a γ-ethylcarbonyloxy acid structure by various analytical methods (wherein l
And m represent an integer).

[0063]

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[0064]

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100 parts by weight of the obtained polymer (4c) was dissolved in 600 parts by weight of diacetone alcohol, and the pore size was adjusted to 0.
Filtered with a 2 μm filter. It was spin-coated on a silicon substrate and baked at 100 ° C. for 2 minutes to obtain a polymer film. When the coating film (thickness: 470 nm) was immersed in an aqueous solution of tetramethylammonium hydroxide (concentration: 0.113% by weight), it melted in 6.2 seconds while the interference color changed.
The remaining film became zero. Next, when the film was immersed in a 2.38% by weight aqueous solution of tetramethylammonium hydroxide, the film was instantaneously dissolved, and the dissolution rate could not be measured.

When the absorption spectrum of the film coated on the lithium fluoride substrate was measured with a vacuum ultraviolet spectrometer (manufactured by ARC), the absorbance at 193 nm was 0.1 μm at a film thickness of 1.0 μm.
82, indicating that the absorption was small.

Synthesis Example 3 Synthesis of Polymer (5e) Having δ-Acetoxy Acid Structure 5.0 g of androsterone and 1.5 g of pyridine were dissolved in 200 ml of tetrahydrofuran, and 1.6 g of acrylic acid chloride was added thereto. Tetrahydrofuran 30m
The solution dissolved in 1 was added dropwise at 0 ° C. After the dropwise addition, the mixture was further stirred at room temperature for several hours, and the precipitated hydrochloride of pyridine was separated by filtration. 150 ml of ethyl acetate was added to the filtrate, and 100 m of water was added.
Washed 4 times with l. After washing with water, the organic layer was dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure. The residue crystallized. This was recrystallized from a mixed solvent of ethanol / tetrahydrofuran to obtain a white compound represented by the following chemical formula (5a).

[0068]

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4.0 g of the obtained monomer (5a)
And dissolved in 40 ml of THF.
0.19 g of 2′-azobis (isobutyronitrile) was added, and the mixture was heated at 70 ° C. and refluxed for polymerization for 6 hours. After the polymerization, the solution was poured into 500 ml of n-hexane, and the polymer was precipitated and dried to obtain a polymer of the formula (5b) as a polymer of the monomer (5a) (where n represents an integer).

[0070]

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When the molecular weight of this polymer in tetrahydrofuran was determined by gel permeation chromatography (GPC), the weight average molecular weight was 2,800 and the number average molecular weight was 2,300.

The polymer (5b) synthesized as described above
3.0 g was dissolved in 100 ml of tetrahydrofuran, and 100 ml of acetic acid and 50 ml of hydrogen peroxide were added thereto.
Stirred at 0 ° C. for several hours. After the reaction, the solvent was removed by distillation under reduced pressure, and the mixture was poured into 500 ml of water. The precipitate was separated by filtration and dried to obtain a polymer having a δ-lactone structure and represented by the chemical formula (5c) (in the formula, n represents an integer).

[0073]

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2.5 g of the polymer (5c) synthesized as described above was dissolved in 100 ml of tetrahydrofuran,
150 ml of 0.5N aqueous sodium hydroxide solution was added, and 2
Stirred for hours. An aqueous solution of hydrochloric acid was gradually added thereto to make it weakly acidic. About 150 ml of ethyl acetate was added to this solution and extraction was performed twice, and the obtained organic layer was washed twice with 100 ml of water. After washing, the organic layer was dried over anhydrous sodium sulfate.
The mixture was poured into 00 ml, and the polymer was precipitated and dried to obtain 2.3 g of a white powdery polymer. The structure of the obtained polymer was found to be mainly the structure of the following chemical formula (5d) from various analytical methods (wherein, l and m represent integers).

[0075]

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Next, 2.1 g of the obtained polymer (5d)
And acetic anhydride, N, N-
Acetylation was performed using dimethylaminopyridine and triethylamine to obtain 1.8 g of a polymer having a δ-acetoxy acid structure. It was found from various analytical methods that the structure of the obtained polymer was mainly the structure of the following chemical formula (5e) (wherein, l and m represent integers).

[0077]

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100 parts by weight of the obtained polymer (5e) was dissolved in 1000 parts by weight of 1-methoxy-2-propanol and filtered with a filter having a pore size of 0.2 μm. It was spin-coated on a silicon substrate and baked at 100 ° C. for 2 minutes to obtain a thin film. Apply the coating film (300 nm) to a tetramethylammonium hydroxide aqueous solution (concentration: 0.113% by weight)
When it was immersed, it melted in 5 seconds while the interference color changed, and the residual film became 0. When the absorption spectrum of the film applied on the lithium fluoride substrate was measured by a vacuum ultraviolet spectrometer (manufactured by ARC), the absorbance at a wavelength of 193 nm was 1.
It was 0.27 at 0 μm, indicating that the absorption was small.

Example 1 100 parts by weight of the polymer (3c) having a γ-acetoxy acid structure synthesized in Synthesis Example 1
3 parts by weight of an acid generator triphenylsulfonium nonaflate and 0.01 parts by weight of 2-benzylpyridine are dissolved in 600 parts by weight of diacetone alcohol, and the solution is filtered using a Teflon (registered trademark) filter having a pore size of 0.20 μm to obtain a resist. The solution was used.

The above resist solution was spin-coated on a silicon substrate treated with hexamethyldisilazane, and heated at 100 ° C. for 2 minutes to form a resist film having a thickness of 0.35 μm.

ArF excimer laser stepper (ISI Mic
rostep, NA = 0.60), the resist film was exposed through a Levenson-type phase shift mask. After exposure, baking was performed at 100 ° C. for 2 minutes. An aqueous solution of tetramethylammonium hydroxide at 2.degree.
% By weight), the unexposed portion of the film dissolved in 9 seconds. Therefore, development takes twice as long as 1
This was performed for 8 seconds, followed by rinsing with pure water for 15 seconds.

As a result, a negative type 0.12 μm line and space pattern was obtained at an exposure amount of 30 mJ / cm ² . At this time, no swelling of the pattern was observed. In addition,
When the obtained substrate having the pattern was immersed in tetrahydrofuran, the pattern was instantaneously dissolved, and it was found that no cross-linking had occurred. This resist solution showed no change in sensitivity and resolution even when stored in a refrigerator (6 ° C.) for 14 days, indicating that storage stability was good.

Further, regarding the above resist film, CHF
Etching was performed using a parallel plate type reactive ion etching apparatus using _three gases. The conditions were a CHF ₃ flow rate of 35 sccm, a gas pressure of 10 mTorr, and an RF bias power of 150 W. As a result, the etch rate of this resist was 1.22 when the commercially available novolak resin was 1.0, indicating that the resist had sufficiently practical dry etching resistance.

The above resist applied on the NaCl plate was
Similarly, ArF excimer light was irradiated at 30 mJ / cm ² , and infrared absorption spectra before and after baking after exposure were measured by FT-1720X manufactured by Perkin Elmer. As a result, after the post-exposure bake, 34
It was found that the peak near 66 cm ^-1 was greatly reduced. It was also found that the peak at 1712 cm ^-1 due to lactone had increased.

The resist film initially had a structure of the polymer (3c) having a γ-acetoxy acid structure, and was alkali-soluble by the carboxylic acid. ArF excimer laser exposure generates trifluoromethanesulfonic acid from the acid generator triphenylsulfonium triflate, and the bake after exposure uses the acid as a catalyst to convert the structure of γ-acetoxy acid in the polymer into deacetic acid in the molecule. Followed by esterification to give the structure of γ-lactone. as a result,
The exposed portion became insoluble in the alkali developing solution, and a negative pattern was formed. The mechanism of the negative conversion at this time was not a crosslinking reaction but a large decrease in the amount of carboxylic acid due to lactonization, so that swelling was avoided, and a fine pattern with high precision was formed.

<Example 2> In place of the polymer (3c) having a γ-acetoxy acid structure used in Example 1, the compound (4c) having a γ-ethylcarbonyloxy acid structure synthesized in Synthesis Example 2 was used in 100 parts. Parts by weight, 3 parts by weight of an acid generator, triphenylsulfonium triflate, and 0.01 parts by weight of tetrapentylammonium chloride were dissolved in 600 parts by weight of cyclohexanone, and filtered using a Teflon filter having a pore size of 0.20 μm to obtain a resist solution. .

The resist solution was spin-coated on a silicon substrate treated with hexamethyldisilazane in the same manner as in Example 1, and then heated at 100 ° C. for 2 minutes to form a resist film having a thickness of 0.30 μm. Formed.

Exposure was performed through a chromium mask using an ArF excimer laser stepper in the same manner as in Example 1, and then baking was performed at 100 ° C. for 2 minutes. 23 ° C. tetramethylammonium hydroxide aqueous solution (0.11
(3% by weight), the unexposed portion of the film dissolved in 12 seconds. Therefore, the development was performed for about 24 times, which is about twice the time, and then rinsed with pure water for 15 seconds.
As a result, at an exposure dose of 20 mJ / cm2, a negative type 0.1
A 6 μm line and space pattern was obtained. At this time, no swelling of the pattern was observed. It was also found that this resist solution had no change in sensitivity and resolution even when stored in a refrigerator (6 ° C.) for 14 days, and had good storage stability.

Further, with respect to the above resist film, Example 1
Etching was performed under the following conditions. As a result, the etch rate of this resist was 1.30 when the etching rate of a coating film of a commercially available novolak resin was 1.0, indicating that the dry etching resistance was high.

Example 3 100 parts by weight of the polymer (5e) having a δ-acetoxy acid structure synthesized in Synthesis Example 3 was used, and the acid generator triphenylsulfonium nonaflate 3 was used.
Parts by weight and 0.015 parts by weight of phenylpyridine were dissolved in 600 parts by weight of 1-methoxy-2-propanol, and filtered using a Teflon filter having a pore size of 0.20 μm to obtain a resist solution.

The above-mentioned resist solution was spin-coated on a silicon substrate treated with hexamethyldisilazane in the same manner as in Example 1, and then heated at 100 ° C. for 2 minutes to form a resist film having a thickness of 0.35 μm. Was formed.

As in the case of the first embodiment, exposure is performed by an ArF excimer laser stepper through a phase shift mask.
A post-exposure bake was performed at 0 ° C. for 2 minutes. 23 ° C aqueous solution of tetramethylammonium hydroxide (0.048%)
When the resist film was immersed, the unexposed portion of the film was 5.0
Dissolved in seconds. Therefore, the development was performed twice as long as that for 10 seconds, followed by rinsing with pure water for 15 seconds. as a result,
At an exposure of 26 mJ / cm ² , a negative 0.12 μm line and space pattern was obtained. At this time, no swelling of the pattern was observed. It was also found that this resist solution had no change in sensitivity and resolution even when stored in a refrigerator (6 ° C.) for 14 days, and had good storage stability.

The resist film was exposed through a Levenson-type phase shift mask using a KrF excimer laser stepper (NA = 0.45). After baking at 120 ° C. for 2 minutes after exposure, the resist film was immersed in an aqueous solution of tetramethylammonium hydroxide (2.38% by weight) at 23 ° C., and the unexposed portion of the film was dissolved in 5.0 seconds. . Therefore, the development was performed twice as long as that for 10 seconds, followed by rinsing with pure water for 15 seconds.

As a result, a negative 0.18 μm line and space pattern was obtained at an exposure amount of 50 mJ / cm ² . At this time, no swelling of the pattern was observed. This resist solution showed no change in sensitivity and resolution even when stored at room temperature (23 ° C.) for 7 days, indicating that storage stability was good.

Further, with respect to the above resist film, Example 1
Etching was performed under the following conditions. As a result, the etching rate of this resist is 1.25, when the etching rate of a coating film of a commercially available novolak resin is 1.0.
It was found that the film had sufficient dry etching resistance for practical use.

Example 4 100 g of the polymer (3c) having a γ-methoxycarboxylic acid structure synthesized in Synthesis Example 1 was used.
Parts by weight, 3 parts by weight of an acid generator, trifluoromethanesulfonyloxysuccinimide, and 10 parts by weight of 1,3,4,6-tetrakis (methoxymethyl) glucoururil are dissolved in 600 parts by weight of diacetone alcohol, and the pore size is 0.20 μm.
The resultant was filtered using a Teflon filter of m to obtain a resist solution.

The above resist solution was spin-coated on a silicon substrate treated with hexamethyldisilazane in the same manner as in Example 1, and then heated at 100 ° C. for 2 minutes to form a resist film having a thickness of 0.30 μm. Was formed. Exposure was performed with an ArF excimer laser stepper through a phase shift mask in the same manner as in Example 1, followed by baking after exposure at 100 ° C. for 2 minutes. When the resist film was immersed in an aqueous solution of tetramethylammonium hydroxide (2.38% by weight) at 23 ° C., the unexposed portion of the film dissolved in 5.0 seconds. Therefore, the development was performed twice as long as that for 10 seconds, followed by rinsing with pure water for 10 seconds. As a result, the exposure amount was 35 mJ / cm
^In Step ² , a negative 0.13 μm line and space pattern was obtained. At this time, no swelling of the pattern was observed. It was also found that this resist solution had no change in sensitivity and resolution even when stored in a refrigerator (6 ° C.) for 14 days, and had good storage stability.

Further, this resist film is subjected to an acceleration voltage of 50 k
A line and space pattern was exposed using a V electron beam lithography system. Baking and development after exposure were performed under the same conditions as in the ArF excimer laser exposure.
At μC / cm ² , a negative 0.13 μm line and space pattern was obtained. At this time, no swelling of the pattern was observed.

Further, with respect to the above resist film, Example 1
Etching was performed under the following conditions. As a result, the etch rate of this resist was 1.20 when the etching rate of a coating film of a commercially available novolak resin was 1.0, indicating that the dry etching resistance was high.

<Embodiment 5> FIG. 1 shows a well-known MOS (metal-
1 shows a cross-sectional view of an (oxide-semiconductor) transistor. This transistor has a structure in which a drain current flowing between the source electrode 16 and the drain electrode 17 is controlled by a voltage applied to the gate electrode 18.

The steps for fabricating such a structure consist of dozens of steps, which can be broadly divided into three groups: steps up to the formation of a field oxide film, steps up to the formation of a gate, and final steps.

The steps up to the formation of the first field oxide film (FIG. 2) include a step of forming a resist pattern on the silicon nitride film. This field oxide film was formed as in the following examples.

By a known method, as shown in FIG.
A 50 nm oxide film 22 is formed on a mold silicon wafer 21, and a 200 nm silicon nitride film 23 is formed thereon by plasma CVD to form a substrate. A resist pattern 24 having a 0.30 μm line is formed on this substrate by the material and method described in the first embodiment (FIG. 2B). After the silicon nitride film 23 is etched by a known method using the resist pattern as a mask (FIG. 2C), boron ions for channel stopper are implanted using the resist as a mask again. After removing the resist 24 (FIG. 2D), a 1.2 μm field oxide film 25 is formed in the element isolation region by selective oxidation using the silicon nitride film 23 as a mask (FIG. 2E).

Thereafter, a gate forming step and a final step were performed according to a known method. That is, the silicon nitride film 2
3 is etched, the gate is oxidized, and the polysilicon 2
6 is grown (FIG. 2F). Example 3
The resist pattern 27 of the 0.12 μm line is formed by using the pattern forming method shown in FIG. Using this resist pattern 27 as a mask, the polycrystalline silicon 26 is etched by a known method to form a gate 28 (FIG. 2 (h)).

Although the following steps are not shown, the source,
The thin oxide film of the drain is etched, and then arsenic is diffused in the polysilicon gate, source and drain, and an oxide film is formed in the polysilicon gate, source and drain regions. Open contacts for aluminum wiring to the gate, source, and drain, perform aluminum deposition and patterning, further form a protective film, and form pads for bonding. Thus, a MOS transistor as shown in FIG. 1 is formed.

Here, regarding the MOS transistor,
In particular, a method for forming a field oxide film has been described. However, it is needless to say that the present invention is not limited to this, but can be applied to other semiconductor device manufacturing methods and processes.

Embodiment 6 A semiconductor memory device was manufactured by using the pattern forming method described in any one of Embodiments 1 to 4 of the present invention. FIG. 3 is a cross-sectional view partially showing the main steps of element production. As shown in FIG.
An i-semiconductor 31 is used as a substrate, and an element isolation region 32 is formed on the surface thereof using a known element isolation technique. Next, for example, polycrystalline Si having a thickness of 150 nm and SiO having a thickness of 200 nm
A word line 33 having a structure in which _two word lines are stacked is further formed, for example, 150 nm of SiO ₂ is deposited by using a chemical vapor deposition method, and is processed anisotropically to form a side spacer 34 of SiO _{2 on} the side wall of the word line. To form

Next, an n diffusion layer 35 is formed by a usual method. Next, as shown in FIG. 3B, a data line 36 made of polycrystalline Si, a high melting point metal silicide, or a laminated film of these is formed through a normal process. Next, FIG.
As shown in (c), a storage electrode 38 made of polycrystalline Si is formed through a normal process. Then, Ta ₂ O ₅ , Si
_{One of 3} N ₄ , SiO ₂ , BST, PZT, a ferroelectric material, or a composite film thereof is applied to form an insulating film 39 for a capacitor. Subsequently, a low-resistance conductor such as polycrystalline Si, high-melting-point metal, high-melting-point metal silicide, or Al or Cu is applied to form the plate electrode 40.

Next, as shown in FIG. 3D, a wiring 41 is formed through a normal process. Next, a memory element was manufactured through a normal wiring forming step and a passivation step. Note that, here, only typical manufacturing steps have been described, but other than this, ordinary manufacturing steps were used. Further, the present invention can be applied even if the order of each step is changed.

In the lithography process in the device manufacturing process, the pattern forming method described in any one of the first to fourth embodiments of the present invention is applied to most of the lithography processes. In the present invention, the pattern is formed using a negative resist. It is not always necessary to apply the present invention to a process that is not suitable or a process having a large pattern size. For example, the present invention was not applied to a conduction hole forming step in a passivation step or a pattern formation in an ion implantation mask forming step.

Next, a pattern formed by lithography will be described. FIG. 4 shows a typical pattern arrangement of the manufactured memory element. 42 is a word line, 43 is a data line, 4
4 is an active region, 45 is a storage electrode, and 46 is a pattern of an electrode extraction hole. Also in this example, the pattern formation of Examples 1 to 4 of the present invention was used for all except the 46 electrode extraction holes shown here. The present invention is used in the process using the minimum design rule other than the pattern formation shown here.

In the device manufactured by using the present invention, the size between the patterns could be reduced as compared with the device manufactured by using the conventional method. Therefore, the device area of the same structure could be reduced.
When manufacturing semiconductor elements, the number of semiconductor elements that can be manufactured from one wafer has increased, and the yield has improved.

Comparative Example 1 100 parts by weight of the polymer (3b) having a γ-hydroxy acid structure synthesized in Synthesis Example 1,
2 parts by weight of an acid generator, triphenylsulfonium triflate, and 0.01 parts by weight of 2-benzylpyridine were dissolved in 600 parts by weight of diacetone alcohol, and filtered using a Teflon filter having a pore size of 0.20 μm to obtain a resist solution.

The above resist solution was spin-coated on a silicon substrate treated with hexamethyldisilazane, and heated at 100 ° C. for 2 minutes to form a resist film having a thickness of 0.35 μm. This resist film was exposed through an Levenson-type phase shift mask using an ArF excimer laser stepper (ISI Microstep, NA = 0.60). After exposure, baking was performed at 100 ° C. for 2 minutes. When the resist film was immersed in an aqueous solution of tetramethylammonium hydroxide (2.38% by weight) at 23 ° C., the unexposed portion of the film dissolved in 12 seconds. Therefore, development was performed twice as much for 24 seconds, followed by rinsing with pure water for 15 seconds. As a result, a negative type 0.13 μm line and space pattern was obtained at an exposure amount of 20 mJ / cm ² . At this time, no swelling of the pattern was observed.

When this resist solution was stored in a freezer (-8 ° C.), the dissolution rate of the unexposed portion did not change for 7 days, and there was almost no change in sensitivity and resolution. However, when stored in a refrigerator (6 ° C.), the time for dissolving the unexposed portion increased to 23 seconds in 3 days, making the whole less soluble, resulting in an increase in sensitivity to 15 mJ / cm ² . However, it was found that the resolution was reduced to 0.20 μm (line and space) and the storage stability was poor at 6 ° C.

[0116]

By using lactonization of a resin having an acetoxycarboxylic acid structure, a fine pattern can be developed without swelling in an aqueous alkaline developer, and a negative pattern forming method excellent in resolution performance can be stably performed. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a MOS transistor.

FIG. 2 is a sectional view showing a step of forming a field oxide film and a gate using the method of the present invention.

FIG. 3 is a sectional view showing a manufacturing process of a semiconductor memory device using the method of the present invention.

FIG. 4 is a plan view showing an arrangement of typical patterns constituting a memory element.

[Explanation of symbols]

12 ... field oxide film, 13 ... source contact, 1
4 ... Drain contact, 15 ... Polycrystalline silicon, 16
... source electrode, 17 ... drain electrode, 18 ... gate electrode, 19 ... protective film, 22 ... oxide film, 24 ... resist pattern, 25 ... field oxide film, 26 ... polycrystalline silicon film, 27 ... resist pattern, 28 ... multiple Crystalline silicon gate, 31: P-type Si semiconductor substrate, 32: element isolation region,
33, 42: word line, 34: side spacer, 35
... N-diffusion layer, 36, 43 ... data line, 38, 45 ... storage electrode, 39 ... capacitor insulating film, 40 ... plate electrode, 41 ... wiring, 44 ... active area, 46 ... electrode extraction hole.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03F 7/38 511 G03F 7/38 511 7/40 521 7/40 521 H01L 21/027 H01L 21/30 502R (72) Inventor Hiroshi Shiraishi 1-280, Higashi-Koigakubo, Kokubunji-shi, Tokyo F-term in the Central Research Laboratory, Hitachi, Ltd. EV296 FD206 GP03 HA05 4J100 AK31P AL08P BA11P BC12P CA01 HA17 HE22 JA38

Claims (13)

[Claims] 1. A step of forming a coating film comprising a photosensitive composition containing a γ-acetoxycarboxylic acid structure or a δ-acetoxycarboxylic acid structure on a substrate, and irradiating the coating film with actinic radiation of a predetermined pattern. Changing the carboxylic acid structure of the irradiated portion of the actinic radiation to a γ-lactone structure or a δ-lactone structure. 2. The method for forming a pattern according to claim 1, wherein the γ-acetoxycarboxylic acid or δ-acetoxycarboxylic acid structure is represented by the following chemical formula (1) or (2):
A pattern formation method characterized by having a chemical structure represented by: Embedded image Embedded image Where R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸
Represents hydrogen or an alkyl group having 1 to 10 carbon atoms;
These alkyl groups may be connected to each other to form a cyclic alkyl group. In the formula, R ⁹ , R ¹⁰ , R
¹¹ represents hydrogen, an alkyl group having 1 to 3 carbon atoms, or halogen. 3. The pattern forming method according to claim 2, wherein the photosensitive composition contains a polymer compound, and at least the polymer compound has a carboxylic acid structure represented by the formula (1) or (2). A pattern forming method comprising: 4. The pattern forming method according to claim 1, wherein the photosensitive composition containing a carboxylic acid structure further contains an alicyclic structure. 5. The pattern forming method according to claim 1, wherein said active actinic ray is far ultraviolet light having a wavelength of 250 nm or less. 6. The pattern forming method according to claim 1, wherein the actinic radiation is ArF excimer laser light. 7. The pattern forming method according to claim 1, wherein the active actinic radiation of the predetermined pattern is ArF excimer laser light through a phase shift mask. . 8. The pattern forming method according to claim 1, further comprising, after the step of irradiating the active actinic ray, a step of developing a pattern on the coating film using an aqueous alkaline developer. A method for forming a pattern, wherein the aqueous alkaline developer is an aqueous solution of tetraalkylammonium hydroxide. 9. The method for forming a pattern according to claim 8, wherein after the step of irradiating the active actinic ray, before the step of developing the pattern on the coating film using the aqueous alkaline developer, A method for forming a pattern, comprising a step of heating a coating film. 10. A step of forming a resist pattern on a semiconductor substrate by the pattern forming method according to any one of claims 1 to 9, a step of etching the semiconductor substrate based on the resist pattern, or a step of ion etching. A method of manufacturing a semiconductor device, the method including: 11. A photosensitive composition comprising at least a compound having a γ-acetoxycarboxylic acid structure or a δ-acetoxycarboxylic acid structure as an alkali-soluble group, and a compound capable of generating an acid upon irradiation with actinic radiation. . 12. The photosensitive composition according to claim 11, wherein the compound having a γ-acetoxycarboxylic acid structure or a δ-acetoxycarboxylic acid structure as the alkali-soluble group further contains an alicyclic structure. Photosensitive composition. 13. The photosensitive composition according to claim 11, wherein the compound having a γ-acetoxycarboxylic acid structure or a δ-acetoxycarboxylic acid structure as the alkali-soluble group is a high molecular compound. Photosensitive composition.