JP6365015B2 - POSITIVE RESIST COMPOSITION AND METHOD FOR PRODUCING THE SAME, AND METHOD FOR PRODUCING RESIST PATTERN USING THE POSITIVE RESIST COMPOSITION - Google Patents

Description

  The present invention relates to a positive resist composition which is a non-chemically amplified resist useful for microfabrication, a method for producing the same, and a method for producing a resist pattern using the resist composition.

2. Description of the Related Art In recent years, in the manufacture of semiconductor elements, pattern miniaturization has rapidly progressed due to advances in lithography technology. For example, semiconductor integrated circuits having a circuit dimension (width) of 30 nm or less are mass-produced.
Conventionally, light exposure is used to form semiconductor devices or integrated circuits. Currently, light exposure is performed using an argon fluoride laser having a wavelength of 195 nm. In order to cope with pattern miniaturization, it is required that light having a shorter wavelength is used.
As a next-generation lithography technique, in addition to EUV lithography technique using extreme ultraviolet light exposure with a wavelength of 13.5 nm as an exposure light source, electron beam direct drawing and imprinting are candidates as new lithography techniques.

In particular, it is desired to develop a resist having a resolution of 20 nm or less as a resist for producing a gate layer of a semiconductor circuit by manufacturing an imprint mold as an original plate of imprint lithography or direct drawing of an electron beam.
In the production of such an ultrafine pattern, as a non-chemically amplified resist in which high resolution is easily obtained, for example, a copolymer of an α-chloroacrylate ester compound and an α-methylstyrene compound is a main component. A main chain cutting type resist such as a resist (for example, ZEP520A manufactured by Nippon Zeon Co., Ltd.) is widely used. This main chain cutting type resist has the property that the polymer main chain is cut by exposure with an electron beam or the like, and only the exposed portion is reduced in molecular weight. Therefore, when this resist is used, a pattern is formed by the difference in dissolution rate with respect to the solvent in each of the exposed area and the unexposed area.

  In developing the resist, a mixed solvent (for example, diethyl ketone and diethyl malonate (trade name: ZED-500 manufactured by Nippon Zeon Co., Ltd.)) was mainly used as a developer. However, when a mixed solvent is used as a developer, there is a difference in the amount of evaporation during development of each organic solvent, resulting in a difference in the progress of development, and there is a problem in in-plane uniformity. In addition, propylene glycol monomethyl ether acetate (PGMEA), 2-pentanone, or ethyl-3-ethoxypropionate (Patent Document 1) is used as a developing solution for the resist. Further, a solvent having at least two chemical structures among an acetic acid group, a ketone group, an ether group and a phenyl group (Patent Document 2), and n-amyl acetate (for example, trade name: ZED-N50 manufactured by Nippon Zeon Co., Ltd.) ) Is known (Patent Document 3).

JP 2001-318472 A JP 2006-525683 A JP 2009-226762 A

  However, in the case where ZEP520A (resist comprising a copolymer of methyl α-chloroacrylate and α-methylstyrene) is developed with the developer as described above, an exposed portion (hereinafter referred to as a resist dissolving portion). ) And a non-exposed portion (hereinafter also referred to as a resist non-dissolved portion) width ratio of 1: 1 to form a line-and-space fine pattern in a resist layer, as shown in a comparative example described later, As the line width of the resist-dissolved portion in the resist layer, the 20 nm scale is the limit of resolution, and it is difficult to further refine the resist pattern. When an ultrafine pattern on the order of 10 nm is formed using ZEP520A, a pattern defect occurs.

  In view of the above circumstances, an object of the present invention is to provide a positive resist composition having a high resolving power so as to be able to form an ultrafine pattern on the order of 10 nm with suppressed pattern defects, a method for producing the same, and the resist composition. An object of the present invention is to provide a method for producing a resist pattern using an object.

  As a result of intensive studies, the present inventors have observed from the electron micrograph of the resist pattern cross section that the ZEP520A resist pattern contains particles of polymer aggregates, and the particle size of the polymer aggregates It was estimated that had an effect on resolution. And a copolymer having a specific repeating unit in which a specific high molecular weight component and a low molecular weight component are reduced, having a specific weight average molecular weight and a specific molecular weight distribution. When it was used, it was found that it was possible to form an ultrafine pattern on the tens of nm scale with improved resolution and suppressed pattern defects, and the present invention was completed.

  That is, the positive resist composition according to the present invention is represented by the following general formula (I), the weight average molecular weight (Mw) is 9,500 to 35,000, and the weight average with respect to the number average molecular weight (Mn). It contains the copolymer (A) whose molecular weight distribution (Mw / Mn) represented by molecular weight (Mw) is 1.05-1.25, and a solvent (B).

(In General Formula (I), L is a direct bond or —COO—. R ¹ represents a hydrocarbon group containing a hydrocarbon ring. R ² represents a hydrocarbon group.)

  The positive resist composition of the present invention is a copolymer having a specific repeating unit, having a specific weight average molecular weight, and having a specific molecular weight distribution. Since the high molecular weight component and the low molecular weight component are reduced, the particle or particle size of the polymer aggregate in the resist pattern is reduced, the resolution is improved, and a specific low molecular weight component that is easily dissolved in the developer is added. The pattern defect of the non-exposed part is suppressed by being reduced, and an ultrafine pattern on the tens of nm scale with the pattern defect suppressed can be formed.

The method for producing a positive resist composition according to the present invention is a method for producing a positive resist composition containing the copolymer (A) and a solvent, and the copolymer represented by the general formula (I). Preparing (P);
By fractionating the copolymer (P) using chromatography, it is represented by the following general formula (I), the weight average molecular weight (Mw) is 9,500 to 35,000, and It has the process of preparing the copolymer (A) whose molecular weight distribution (Mw / Mn) represented by the weight average molecular weight (Mw) with respect to average molecular weight (Mn) is 1.05-1.25. .

  In the positive resist composition and the method for producing the same according to the present invention, the solvent (B) has a solubility of the copolymer (A) at 23 ° C. of 5 g / 100 g of solvent and a boiling point of 60 to 205. C. is preferably from the viewpoint that the uniformity of the resist layer to be produced is improved and the resist pattern shape becomes better.

In addition, the method for producing a resist pattern according to the present invention includes:
A resist layer forming step of forming a resist layer by applying a positive resist composition according to the present invention on a substrate and then heating;
An exposure step of exposing a predetermined pattern by irradiating the resist layer with active energy rays;
And a developing step of developing the exposed resist layer with a developer.

  In the method for producing a resist pattern according to the present invention, a resist test film in which the positive resist composition is coated on a substrate is formed, and a development test at a development temperature of 0.5 to 20 cm / sec at a development temperature. It is preferable to further have a developer selection step of selecting the solution as the developer from the viewpoint of better resist pattern shape.

In the method for producing a resist pattern according to the present invention,
Preparing a copolymer (P) represented by the general formula (I);
By fractionating the copolymer (P) using chromatography, it is represented by the following general formula (I), the weight average molecular weight (Mw) is 9,500 to 35,000, and It further has the process of preparing the copolymer (A) whose molecular weight distribution (Mw / Mn) represented by the weight average molecular weight (Mw) with respect to average molecular weight (Mn) is 1.05-1.25, This is preferable from the viewpoint of forming an ultrafine pattern of a dozen nm scale in which pattern defects are suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the positive resist composition and its manufacturing method which have so high resolution that it can form the ultra fine pattern of a dozen nanometer scale in which the pattern defect | deletion was suppressed, and the resist using the said resist composition A method for manufacturing a pattern can be provided.

FIG. 1 is an SEM photograph of the resist pattern of Example 2. FIG. 2 is an SEM photograph showing an example of a pattern defect portion of a resist pattern.

The present invention is described in detail below.
I. Positive resist composition The positive resist composition of the present invention is represented by the following general formula (I), has a weight average molecular weight (Mw) of 9,500 to 35,000, and a number average molecular weight (Mn ), A copolymer (A) having a molecular weight distribution (Mw / Mn) represented by a weight average molecular weight (Mw) of 1.05 to 1.25, and a solvent (B).

(In General Formula (I), L is a direct bond or —COO—. R ¹ represents a hydrocarbon group containing a hydrocarbon ring. R ² represents a hydrocarbon group.)

  The copolymer (A) used in the present invention has the property that the polymer main chain is cleaved at the repeating unit (i-2) by exposure with an electron beam or the like, and only the exposed portion is reduced in molecular weight. Have Therefore, when the resist containing the copolymer (A) is used, a pattern is formed by the difference in dissolution rate between the exposed portion and the non-exposed portion in the solvent.

  Since the copolymer (A) has the specific repeating unit, it functions as a main-chain-breaking resist material and has a specific weight average molecular weight and a specific molecular weight distribution. The high molecular weight component and the low molecular weight component are reduced. Therefore, in the resist pattern, it is estimated that the polymer aggregate particles or particle diameter due to a specific high molecular weight component is reduced, pattern loss due to peeling of the polymer aggregate is suppressed, and higher resolution can be obtained. Is done. In addition, since specific low molecular weight components are reduced in the resist pattern, it is suppressed that the film thickness of the pattern is reduced or the pattern shape is deteriorated due to a portion that is excessively dissolved during development, and pattern defects or defects are suppressed. Is done. Therefore, in the positive resist composition of the present invention, it is possible to form an ultrafine pattern on the tens of nm scale in which pattern defects are suppressed.

Hereafter, each structure of such a positive resist composition of this invention is demonstrated in detail in order. In the present invention, “active energy rays” mean far ultraviolet rays such as KrF excimer laser, ArF excimer laser, and F ₂ excimer laser, electron beams, ion beams, EUV, X-rays, and the like.
In the present invention, the structure of the resist layer formed by the resist dissolving portion and the resist non-dissolving portion is referred to as “resist pattern”.

  In addition, in the description of the group (atomic group) in this invention, the description which has not described substitution and non-substitution includes what has a substituent with the thing which does not have a substituent. For example, the “alkyl group” includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group). Moreover, an alkyl group and an aliphatic hydrocarbon ring contain unsaturated hydrocarbon which has a double bond, a triple bond, etc. other than saturated hydrocarbon. The aliphatic hydrocarbon ring includes monocyclic and polycyclic hydrocarbons such as bicyclic and tricyclic.

<Copolymer (A)>
(Repeating unit (i-1))
In the repeating unit (i-1) of the general formula (I), L is a direct bond or —COO—. Here, the direct bond means that R ^{1 in the} repeating unit (i-1) is directly bonded to the carbon atom of the main chain of the repeating unit (i-1) without a linking group.
R ¹ represents a hydrocarbon group containing a hydrocarbon ring. Since the repeating unit (i-1) has a hydrocarbon group containing a hydrocarbon ring, a function required for a resist such as dry etching resistance is imparted. Here, examples of the hydrocarbon ring include an aromatic hydrocarbon ring and an aliphatic hydrocarbon ring. The aromatic hydrocarbon ring preferably has 6 to 12 carbon atoms and more preferably 6 to 10 carbon atoms, and examples thereof include a benzene ring, a naphthalene ring, and a biphenyl ring. In addition, the aliphatic hydrocarbon ring preferably has 7 to 12 carbon atoms and more preferably 10 to 12 carbon atoms, and examples thereof include an adamantane ring, a norbornane ring, a dicyclopentane ring, and a dicyclopentene ring.
The hydrocarbon ring may have a substituent, and suitable substituents include alkyl groups and halogens such as chlorine.

  In the repeating unit (i-1), when L is a direct bond, any of an aromatic hydrocarbon ring and an aliphatic hydrocarbon ring can be used because the functions required for the resist such as etching resistance are imparted. However, when L is —COO—, it preferably contains a hydrocarbon ring having 7 or more carbon atoms.

  Examples of the monomer for deriving the repeating unit (i-1) include α-methylstyrene, 4-chloro-α-methylstyrene, 3,5-dichloro-α-methylstyrene, 2-methyl-2-adamantyl methacrylate, Examples include 2-ethyl-2-adamantyl methacrylate and dicyclopentanyl methacrylate.

(Repeating unit (i-2))
The repeating unit (i-2) is a portion where the polymer main chain is cleaved by exposure with an electron beam or the like by being substituted with chlorine. In the repeating unit (i-2) of the general formula (I), R ² represents a hydrocarbon group. Examples of R ² include an alkyl group and a phenyl group. Especially, it is preferable that it is C1-C10, and it is more preferable that it is C1-C6. R ² is preferably an alkyl group from the viewpoint of easy availability and improved polymer solubility. The hydrocarbon group may have a substituent, and suitable substituents include halogen such as chlorine. R ² is preferably an alkyl group or a halogenated alkyl group. Among them, an alkyl group or a halogenated alkyl group having 1 to 10 carbon atoms, further 1 to 6 carbon atoms, and more preferably 1 to 3 carbon atoms. Preferably there is.

  Examples of the monomer that induces the repeating unit (i-2) include methyl α-chloroacrylate, ethyl α-chloroacrylate, propyl α-chloroacrylate, and 2,2,2-trichloroethyl α-chloroacrylate. , Α-chloroacrylate 2,2,3,3,3-pentachloropropyl, α-chloroacrylate pentachlorophenyl and the like.

  Among them, the copolymer (A) is preferably a copolymer of α-methylstyrene and α-chloroacrylic acid alkyl ester from the viewpoint of obtaining high resolution and etching resistance.

  In the copolymer represented by the general formula (I), m / (m + n) where m is the number of repeating units of the repeating unit (i-1) and n is the number of repeating units of the repeating unit (i-2). ) = 0.3 to 0.7 and n / (m + n) = 0.3 to 0.7 are preferable from the viewpoint of a good balance between etching resistance and sensitivity and a good pattern shape. Furthermore, m / (m + n) = 0.4 to 0.6, and n / (m + n) = 0.4 to 0.6, the balance between etching resistance and sensitivity and the pattern shape are improved. To preferred.

The copolymer (A) used in the present invention may contain a repeating unit other than the repeating unit (i-1) and the repeating unit (i-2), but obtains high resolution and etching resistance. From the viewpoint, the total number of moles of the repeating unit (i-1) and the repeating unit (i-2) is preferably 90% or more based on the number of moles of all the repeating units of the copolymer (A). It is preferably 95% or more, more preferably 98% or more, and particularly preferably 100%.
Examples of the repeating unit that may be contained in addition to the repeating unit (i-1) and the repeating unit (i-2) include methyl acrylate, methyl methacrylate, and styrene.

In the copolymer represented by the general formula (I), the weight average molecular weight (Mw) is 9,500 to 35,000, and the weight average molecular weight (Mw) with respect to the number average molecular weight (Mn) is represented. The molecular weight distribution (Mw / Mn) is 1.05 to 1.25. Among them, the copolymer represented by the general formula (I) has a weight average molecular weight (Mw) of 9,500 to 35,000 and a number average molecular weight because the pattern shape becomes good with high resolution. The molecular weight distribution (Mw / Mn) represented by the weight average molecular weight (Mw) relative to (Mn) is preferably 1.05-1.20, and the weight average molecular weight (Mw) is 20,000-30, And the molecular weight distribution (Mw / Mn) represented by the weight average molecular weight (Mw) relative to the number average molecular weight (Mn) is preferably 1.05 to 1.20, and more preferably the weight average molecular weight ( Mw) is 20,000 to 30,000, and the molecular weight distribution (Mw / Mn) represented by the weight average molecular weight (Mw) with respect to the number average molecular weight (Mn) is 1.1 to 1.20. Like .
In addition, in this invention, a weight average molecular weight (Mw) and a number average molecular weight (Mn) can be calculated | required by the polystyrene conversion value using a gel permeation chromatography (GPC). Specifically, for example, it can be determined by the measurement method shown in the examples described later.

The weight average molecular weight (Mw) is 9,500-35,000, and the molecular weight distribution (Mw / Mn) represented by the weight average molecular weight (Mw) with respect to the number average molecular weight (Mn) is 1.05-1.25. As a method for preparing the copolymer (A) represented by the general formula (I), a known polymerization method is used as appropriate, and a known polymerization method in which the molecular weight distribution is likely to be narrowed is used as appropriate. You may prepare by.
However, when the copolymer (A) is prepared simply by polymerization, an ultrahigh molecular weight component having a high degree of polymerization that easily forms a polymer aggregate having a large size that causes pattern defects is completely removed. It is difficult to remove. Therefore, it is preferable to include a step of removing the ultra-high molecular weight component and a low molecular weight component having a low polymerization degree that easily cause film loss by fractionation. Here, examples of the fractionation method include a reprecipitation method and a fractionation method using chromatography.

Among them, the step of preparing the copolymer (P) represented by the general formula (I),
By fractionating the copolymer (P) using chromatography, the copolymer (P) is represented by the general formula (I), the weight average molecular weight (Mw) is 9,500 to 35,000, and several It has the process of preparing the copolymer (A) whose molecular weight distribution (Mw / Mn) represented by the weight average molecular weight (Mw) with respect to average molecular weight (Mn) is 1.05-1.25. The copolymer represented by the general formula (I) having a specific molecular weight and a specific molecular weight distribution is preferable from the viewpoint of easily obtaining.

The copolymer (P) may be appropriately polymerized using a known polymerization method, and a commercially available copolymer represented by the general formula (I) may be used. By fractionating and fractionating at an arbitrary timing during fractionation using chromatography, the weight average molecular weight and molecular weight distribution of the copolymer after fractionation can be controlled. The weight average molecular weight of the copolymer (P) is not particularly limited.
From the viewpoint of more efficiently preparing the copolymer (A) used in the present invention by fractional fractionation using chromatography, the weight average molecular weight of the copolymer (P) before fractionation is: It is preferably about 5,000 to 50,000.

Examples of a method for fractionating and fractionating the copolymer (P) using chromatography include fractional fractionation methods using various chromatographies such as gel permeation chromatography (GPC). .
As a method of fractionation using chromatography, fractionation is performed at an arbitrary timing so that a copolymer (A) having a target weight average molecular weight and molecular weight distribution is obtained, and appropriate fractionation is performed. There is no particular limitation. Usually, fractionation is performed so as to remove higher molecular weight components and lower molecular weight components, and a portion having a molecular weight between them is appropriately fractionated and fractionated.

In the positive resist composition according to the present invention, the copolymer (A) may be used alone or in combination of two or more.
The content of the copolymer (A) is preferably 80% by weight or more, preferably 90% by weight or more, and more preferably 95% by weight or more based on the total solid content of the positive resist composition. It is preferable that In addition, in this invention, solid content means things other than a solvent among the components contained in a positive resist composition.

<Solvent (B)>
The positive resist composition of the present invention further includes a solvent (B) in which the copolymer (A) is dissolved.
The solvent (B) is an organic solvent capable of dissolving the copolymer (A), and can be appropriately selected from those generally used as a solvent for resist compositions. Examples of the solvent (B) include ketones such as diethyl ketone, cyclohexanone, and cyclopentanone; ethers such as ethylene glycol dimethyl ether and tetrahydrofuran; alcohol ethers such as propylene glycol monomethyl ether; butyl formate, butyl acetate, and butyric acid Esters such as ethyl, ethyl lactate and diethyl malonate; oxycarboxylic acid esters such as methyl 2-methoxypropionate; cellosolv esters such as methyl cellosolve acetate and ethyl cellosolve acetate; propylene glycols such as propylene glycol monomethyl ether acetate Diethylene glycols such as diethylene glycol monomethyl ether and diethylene glycol dimethyl ether; trichlorethylene Any halogenated hydrocarbons; aromatic compounds such as toluene, xylene, anisole, o-dichlorobenzene, nitrobenzene, ethyl benzoate; N, N-dimethylformamide, N, N-dimethylacetamide, N-methylacetamide, N -Examples include, but are not limited to, polar solvents such as methylpyrrolidone.

  Among them, as the solvent (B), it is preferable to select and use a solvent in which the copolymer (A) has a solubility at 23 ° C. of 5 g of the copolymer (A) / 100 g or more of the solvent. In this case, since the solubility of the copolymer (A) in the solvent (B) is sufficiently high, a resist layer is formed by heating the coating film of the resist composition to volatilize the solvent (B). In this case, the aggregate of the copolymer (A) is difficult to precipitate, and it is preferable from the viewpoint that a uniform resist layer is formed and the pattern shape tends to be good.

  Especially, as a solvent (B), it is preferable to use the solvent whose boiling point is 60-205 degreeC. When a solvent having a low boiling point is used, it is difficult to obtain a uniform film by rapidly drying the resist composition coating. However, in the case of the solvent having the above boiling point, the resist composition coating is heated to remove the solvent (B ) Is volatilized to form a resist layer, which is preferable because a more uniform resist layer can be formed. The boiling point of the solvent (B) is preferably 100 to 200 ° C.

  The content of the solvent (B) in the positive resist composition according to the present invention is not particularly limited, and is appropriately set according to the coating film thickness at a concentration that can be applied to a substrate or the like. In general, the solvent is used so that the solid content concentration of the resist composition is preferably in the range of 0.1 to 20% by weight, more preferably 0.2 to 15% by weight.

<Other ingredients>
In the positive resist composition of the present invention, a miscible additive, for example, a surfactant or a sensitizer for improving the coating property is optionally added as long as the effect of the present invention is not impaired. Can be contained.

<Manufacture of positive resist composition>
The positive resist composition according to the present invention is usually produced by uniformly mixing the copolymer (A) and, if necessary, other additives into the solvent (B).
Especially, as mentioned above, it is preferable to have the process of preparing the said copolymer (A) by fractionating the said copolymer (P) with a gel permeation chromatography (GPC).

II. Method for Producing Resist Pattern The method for producing a resist pattern according to the present invention includes:
A resist layer forming step of forming a resist layer by applying a positive resist composition according to the present invention on a substrate and then heating;
An exposure step of exposing a predetermined pattern by irradiating the resist layer with active energy rays;
A developing step of developing the exposed resist layer with a developer;
It is characterized by including.

  According to the method for producing a resist pattern according to the present invention, a fine pattern having a good pattern shape can be formed with a high resolving power, and in particular, an ultrafine pattern of a dozen nm scale in which pattern defects are suppressed is formed. be able to.

Hereinafter, each step will be described.
(I) Resist Layer Formation Step In this step, first, the positive resist composition according to the present invention is applied onto a substrate.
The material for the substrate is not particularly limited, and for example, silicon, silicon oxide, quartz, or the like can be used. For example, a silicon wafer or a quartz substrate with a hard mask such as chromium can be used as the substrate.
The coating method is not particularly limited as long as it is a method capable of uniformly coating the positive resist composition on the substrate surface, and various methods such as a spray method, a roll coating method, a slit coating method, and a spin coating method. Can be used.

Next, the positive resist composition applied onto the substrate is heated (prebaked) to remove the solvent (B), thereby forming a resist layer.
The prebaking heating temperature may be appropriately determined depending on the components of the composition, the use ratio, the type of the solvent (B), and the like, but is usually 80 to 200 ° C, preferably 90 to 180 ° C. The pre-bake time is usually about 30 seconds to 15 minutes.

  Although the thickness of a resist layer is not specifically limited, For example, it is suitably adjusted in 15-100 nm, More preferably in the range of 20-50 nm according to the conditions of exposure and image development.

(Ii) Exposure Step In this step, the resist layer is exposed through a mask having a predetermined pattern shape, for example, using an active energy ray exposure device such as an electron beam drawing device or an EUV exposure device, or Exposure is selectively performed by drawing or the like by direct irradiation of an electron beam without passing through the mask.
The exposure light source is not particularly limited, and is performed using an ArF excimer laser, a KrF excimer laser, an F ₂ excimer laser, EUV (Extreme Ultraviolet), an electron beam, an X-ray, an ion beam such as helium or hydrogen. Can do.
Next, after the exposure, the sensitivity may be improved by heating. Therefore, post-exposure bake (PEB) may be performed. The PEB treatment is usually performed at a temperature of 50 to 160 ° C. for a time of about 0.1 to 15 minutes.

(Iii) Development Step Next, the exposed resist layer is developed with a developer, and the exposed portion is removed as a resist dissolving portion.
In the development process of the present invention, it is preferable to include the following developer selection process. By selecting an appropriate developer in the developer selection step, the sensitivity can be improved and the pattern shape can be further improved.

<Developer selection process>
In the developing solution selection step used in the present invention, a resist test film in which the positive resist composition is applied on a substrate is formed, and a developing test solution having a developing speed of 0.5 to 20 cm / sec at a developing temperature is prepared. This is a step of selecting as a developing solution.
Specifically, for example, the positive resist composition is applied on a silicon wafer and then heated at 180 ° C. for 2 minutes to form a resist test film having a thickness of 50 nm after drying. On the other hand, a solvent is prepared as a development test solution. Next, the resist test film is immersed in the development test solution at a development temperature (for example, 23 ° C.) for 10 seconds and rinsed with a poor solvent (for example, hexane) of the positive resist composition. The development speed can be calculated from the amount of film loss of the resist test film after the rinsing.

  When a developing test solution with a developing speed of 0.5 to 20 liters / sec after the rinsing is selected as the developing solution, a developing solution in which the non-exposed portion is hardly dissolved but the exposed portion is appropriately dissolved is selected. can do. Therefore, problems such as excessive dissolution of the non-exposed area during development and rounding of the top of the pattern or reduction in height due to film reduction are suppressed, and the exposed area is removed by dissolution, and the pattern shape is excellent. A resist pattern can be obtained.

  From the viewpoint of obtaining a resist pattern having an excellent pattern shape, it is more preferable to select a developing test solution having a developing speed of 1.0 to 15 cm / sec as the developing solution in the developer selecting step, and the developing speed is 2 It is even more preferable to select a developing test solution having a viscosity of 0.0 to 10 liters / sec as the developing solution.

In the present invention, the developer may be appropriately selected in the developer selection step, and specific examples include, but are not limited to, the following.
For example, when the weight average molecular weight of the copolymer (A) represented by the general formula (I) is about 9,500 to 25,000, for example, ethyl lactate, propyl lactate, butyl lactate, 4-hydroxy-4 One or more selected from the group consisting of -methyl-2-pentanone, 1-butoxy-2-propanol, 3-methoxy-1-butanol, 2-butoxyethanol, propylene glycol monomethyl ether, and o-xylene Further, one or more selected from the group consisting of ethyl lactate, propyl lactate, butyl lactate, and 4-hydroxy-4-methyl-2-pentanone is preferably used from the viewpoint of good sensitivity and sensitivity margin. Among them, ethyl lactate, propyl lactate, butyl lactate, or 4-hydroxy-4-methyl-2-pentanone is preferably used because the sensitivity and sensitivity margin are good and the pattern shape is good.
When the weight average molecular weight of the copolymer (A) represented by the general formula (I) is about 25,000 to 35,000, for example, 4-hydroxy-4-methyl-2-pentanone and propylene One or more selected from the group consisting of glycol monomethyl ether is preferably used.
The developer may be a mixed solvent, but it is preferable that the developer is composed of only one kind of solvent from the standpoint that in-plane uniformity is less likely to cause a problem and the pattern shape tends to be better.

  The development time is appropriately adjusted in the range of, for example, 5 to 200 seconds, more preferably 20 to 90 seconds. The development temperature is appropriately adjusted within a range of, for example, 0 to 30 ° C., more preferably around 0 to 23 ° C.

After development, a rinsing process is usually performed. As a rinse liquid, it selects from the poor solvent of the said positive resist composition suitably, and is used, for example, 2-propanol, hexane, a cyclohexane etc. can be used, or those liquid mixture can also be used. By using a rinse liquid having a lower surface tension, pattern collapse caused by the surface tension during drying can be suppressed.
After the rinsing process, a drying process is performed using, for example, a spin dry apparatus. Thus, a resist pattern composed of a desired resist-dissolved portion and a resist non-dissolved portion is formed. In addition, a baking process is performed after the drying process as necessary for the purpose of removing the developer or rinse agent remaining in the formed resist pattern and improving the adhesion of the resist pattern to the substrate. May be performed.

The method for producing a resist pattern of the present invention is suitably applied to a method for producing a mold.
That is, the method for producing a mold of the present invention is a method for producing a mold having a fine concavo-convex pattern on the surface,
A resist layer forming step of forming a resist layer by applying a positive resist composition according to the present invention on a substrate and then heating;
An exposure step of exposing a predetermined pattern by irradiating the resist layer with active energy rays;
A developing step of developing the exposed resist layer with a developer;
And an etching step of etching using the resist layer after development as a mask.

  That is, in the mold manufacturing method, the substrate is etched using the resist layer on which the predetermined uneven pattern is formed by the above-described resist pattern manufacturing method as a mask. As a result, a concavo-convex pattern corresponding to the resist pattern is formed on the surface of the substrate. According to the present invention, by forming an ultrafine resist pattern manufactured by the above-described resist pattern manufacturing method as a mask, an ultrafine uneven pattern can be formed in the manufacture of a mold. For example, such a mold is itself used as a mold for nanoimprinting, or used as a master for replicating such a mold, for example, by electroforming.

  The etching is not particularly limited as long as it can form a concavo-convex pattern on the substrate, and can be appropriately selected according to the purpose. For example, reactive ion etching (RIE), ion milling, sputter etching, and the like can be given. Among these, RIE and ion milling are particularly preferable. The RIE etchant is appropriately selected according to the substrate material. For example, when the substrate is a silicon wafer, fluorine-based gas or chlorine-based gas can be used.

  Moreover, the positive resist composition and the method for producing a resist pattern according to the present invention can be suitably applied to the following uses other than the above-described mold production. For example, photomasks for semiconductor devices, semiconductor manufacturing, microelectromechanical systems (MEMS), sensor elements, optical disks, optical components such as diffraction gratings and polarizing elements, nanodevices, organic transistors, color filters, microlens arrays, immunoassay chips It can be widely applied to the production of DNA separation chips, microreactors, nanobiodevices, optical waveguides, optical filters, photonic crystals, and the like.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

Hereinafter, the present invention will be specifically described with reference to examples. These descriptions do not limit the present invention.
In the synthesis examples and examples, the structures and physical properties were confirmed using the following apparatuses.
¹ H-NMR: JEOL JNM-LA400WB, manufactured by JEOL Ltd.
Weight average molecular weight and molecular weight distribution: “Waters, Water 2695 apparatus” was used as a gel permeation chromatography (GPC) measurement, and three columns of “Shodex GPC LF-804 (Showa Denko, 8.0 mm ID × 300 mm)” were used as columns. And measured using THF (tetrahydrofuran) as the eluent. The experimental conditions were as follows: sample concentration 0.5%, flow rate 1.0 ml / min, sample injection volume 50 μl, measurement temperature 40 ° C., RI detector. The calibration curve was prepared from “polystylen standard sample TSK standard” manufactured by Tosoh Corporation.

[Synthesis Example 1] Synthesis of copolymer (P-1) 85 mL of dioxane was added to the flask, and the mixture was stirred at 80 ° C for about 30 minutes in a nitrogen atmosphere. A solution of 35.5 g (0.3 mol) of α-methylstyrene, 24.1 g (0.2 mol) of methyl α-chloroacrylate, and 85 mL of dioxane (0.82 g, 5 mmol) was added dropwise over about 30 minutes. After dropping, the reaction solution was kept at 80 ° C. under a nitrogen atmosphere and stirred for about 15 hours. After completion of the reaction, the reaction solution was poured into methanol to obtain a white precipitate. Further, the precipitate was dissolved again in dioxane, and reprecipitation with methanol was repeated twice. The re-precipitate was filtered off and dried at about 80 ° C. in a vacuum dryer to obtain 29.2 g (yield: 49%) of a white solid.
The structure of the polymer was confirmed to be a random copolymer of α-methylstyrene and methyl α-chloroacrylate by 1H-NMR spectrum. The copolymerization ratio (molar ratio) was α-methylstyrene: α-methyl chloroacrylate = 50: 50.
The weight average molecular weight (Mw) was 15,400, and the molecular weight distribution (Mw / Mn) was 1.8.

[Synthesis Examples 2-3] Synthesis of Copolymers (P-2) to (P-3) The amount of AIBN added was 1.97 g (12 mmol) in Synthesis Example 2 and 0.25 g (1. The α-methylstyrene / α-chloroacrylate methyl copolymer (P-2) and the copolymer (P-3) having different molecular weights were synthesized in the same manner as in Synthesis Example 1 except for changing to 5 mmol). . It is confirmed by 1H-NMR spectrum that the structures of the copolymer (P-2) and the copolymer (P-3) are both random copolymers of α-methylstyrene and methyl α-chloroacrylate. did. The copolymerization ratio (molar ratio) was α-methylstyrene: methyl α-chloroacrylate = 50: 50.
The copolymer (P-2) had a weight average molecular weight (Mw) of 7,700 and a molecular weight distribution (Mw / Mn) of 1.6. The copolymer (P-3) had a weight average molecular weight (Mw) of 22,800 and a molecular weight distribution (Mw / Mn) of 1.8.

[Synthesis Example 4] Synthesis of Copolymer (P-4) A copolymer was prepared in the same manner as in Synthesis Example 1 except that an equimolar amount of 2-methyl-2-adamantyl methacrylate was used instead of α-methylstyrene. (P-4) was synthesized.
The structure of the polymer was confirmed by 1H-NMR spectrum to be a random copolymer of 2-methyl-2-adamantyl methacrylate and methyl α-chloroacrylate. The copolymerization ratio (molar ratio) was 2-methyl-2-adamantyl methacrylate: methyl α-chloroacrylate = 50: 50.
The weight average molecular weight (Mw) was 23,800, and the molecular weight distribution (Mw / Mn) was 1.9.

[Comparative Synthesis Examples 1 and 2] Synthesis of Comparative Copolymers (CP-1) to (CP-2) The amount of AIBN added was 2.46 g (15 mmol) in Comparative Synthesis Example 1 and 0.2 in Comparative Synthesis Example 2. Comparative copolymers (CP-1) to (CP-2) were synthesized in the same manner as in Synthesis Example 1 except that the amount was changed to 16 g (1 mmol).
It is confirmed by 1H-NMR spectrum that the structures of copolymer (CP-1) and copolymer (CP-2) are both random copolymers of α-methylstyrene and methyl α-chloroacrylate. did. The copolymerization ratio (molar ratio) was α-methylstyrene: methyl α-chloroacrylate = 50: 50.
The weight average molecular weight (Mw) of the copolymer (CP-1) was 6,100, and the molecular weight distribution (Mw / Mn) was 1.6. The copolymer (CP-2) had a weight average molecular weight (Mw) of 34,700 and a molecular weight distribution (Mw / Mn) of 1.9.

[Production Examples 1-6] Preparation of Copolymers (A-1) to (A-7) Using the copolymers (P-1) to (P-4) obtained in Synthesis Examples 1 to 4, Fraction fractionation was performed using a GPC fractionation system (LC-20AD manufactured by Shimadzu Corporation) to prepare copolymers (A-1) to (A-7). As conditions for the preparative GPC, one column is “Shodex GPC K-2002 (made by Showa Denko, 20.0 mm ID × 300 mm)” and “Shodex GPC K-2003 (made by Showa Denko, 20.0 mm ID × 300 mm)”. One is used, chloroform is used as an eluent, a sample is a 10 wt% chloroform solution, a flow rate is 3 ml / min, a sample injection amount is 500 μl, a column oven temperature is 50 ° C., and an RI detector (detector temperature is 40 ° C.). Sorting was performed.
The fractionated chloroform solution was concentrated and reprecipitated in methanol to obtain copolymers (A-1) to (A-7) having respective molecular weight distributions. Table 1 shows the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) after fractionation.

[Comparative Production Examples 1 to 3] Preparation of Comparative Copolymers (CA-1) to (CA-3) The comparative copolymers (CP-1) and comparative copolymers (CP-1) obtained in Comparative Synthesis Examples 1 and 2 ( Using CP-2) and the copolymer (P-1) obtained in Synthesis Example 1, fractionation was performed by a GPC fractionation system (LC-20AD manufactured by Shimadzu Corporation) in the same manner as in the above production example. Comparative copolymers (CA-1) to (CA-3) were prepared. Table 1 shows the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) after fractionation.

[Examples 1 to 15] Production of Positive Resist Composition Each of the copolymers (A-1) to (A-7) obtained by fractionation was added to the solvent described in Table 2 at a concentration of 1.5 wt%. Then, it was filtered through a 10 nm filter (manufactured by Nihon Entegris) made of UPE (ultra high molecular weight polyethylene) to prepare positive resist compositions of Examples 1 to 15.
The boiling point of each solvent when a positive resist composition is prepared is shown.
Anisole: boiling point 153.8 ° C., toluene: boiling point 110.6 ° C., nitrobenzene: boiling point 210.9 ° C., THF (tetrahydrofuran): boiling point 66 ° C., NMP (N-methylpyrrolidone): boiling point 202 ° C.
Each of the above solvents had a solubility at 23 ° C. of each copolymer used in combination of 5 g / 100 g or more of the solvent.

[Comparative Examples 1 to 6] Production of comparative positive resist composition Copolymer (P-1) before fractionation, comparative copolymers (CA-1) to (CA-3) obtained by fractionation, And ZEP520A (manufactured by Nippon Zeon Co., Ltd.) in the solvent shown in Table 2 at a concentration of 1.5 wt%, the positive resist compositions of Comparative Examples 1 to 6 were prepared in the same manner as in the above Examples. Prepared.

<Manufacture and evaluation method of resist pattern>
Using the positive resist compositions obtained in Examples 1 to 15 and Comparative Examples 1 to 6, resist patterns were prepared by the following methods and evaluated. The results are also shown in Table 2.

(1) Manufacture of resist pattern Each positive resist composition is uniformly applied onto a 6-inch silicon substrate using a spinner, pre-baked (PAB) at 180 ° C. for 120 seconds, and a resist layer having a thickness of 30 nm Formed.
Drawing was performed on each of the resist layers using an electron beam drawing apparatus (acceleration voltage: 100 KV). After the drawing was completed, the film was developed with a developer shown in Table 2 at 5 ° C. for 30 seconds, and further rinsed with 2-propanol for 30 seconds to produce a line and space (L / S) resist pattern.
A developer was selected according to the following procedure. The resulting development speed is also shown in Table 2.
<Developer selection process>
The positive resist composition was uniformly applied on a 6-inch silicon substrate using a spinner, heated at 180 ° C. for 2 minutes, and a resist test film having a thickness of 50 nm after drying was formed. On the other hand, the solvent used as a developing test solution was prepared. Next, the resist test film was immersed in the development test solution at a development temperature (5 ° C.) for 10 seconds and rinsed with 2-propanol for 30 seconds. The developing speed was calculated from the amount of film loss of the resist test film after rinsing, and a solvent having a developing speed of 0.5 to 20 kg / sec was selected and used as a developer.

(3) Evaluation (3-1) Sensitivity and resolving power Sensitivity and resolving power were measured with a scanning electron microscope (SEM) (manufactured by Holon). The sensitivity was measured in units of μC / cm ² with the minimum dose at which a 30 nm L / S pattern was formed 1: 1 (when drawn with a design line width of 30 nm) as sensitivity. Further, the limit resolution (the line and space are separated and resolved) at the irradiation amount was defined as the resolution. An SEM photograph of the 14 nm L / S resist pattern obtained in Example 2 is shown in FIG.

(3-2) Evaluation Method of Sensitivity Margin A 10 when the width of the dose that forms a 20 nm L / S pattern when drawn with a design line width of 20 nm is 20% or more with reference to the optimum dose. % Is less than 20% and B is less than 10% (or unresolvable).

(3-3) Pattern Defect Evaluation Method When a 20 nm L / S pattern (1: 1) was observed 5 times in a 2 μm region with a scanning electron microscope (SEM) (manufactured by Holon), in the resist pattern, A case where there is no pattern defect such as the SEM photograph shown in FIG. 2 (the pattern width is reduced by 30% or more and there is a portion having a lower height as the color of the photograph is clearly darker), and a case where there is a pattern defect X. In FIG. 2, a portion surrounded by an ellipse is a pattern defect portion.

<Summary of results>
A molecular weight distribution (Mw / Mw) represented by the general formula (I), having a weight average molecular weight (Mw) of 9,500 to 35,000 and a weight average molecular weight (Mw) with respect to the number average molecular weight (Mn). In the positive resist compositions of Examples 1 to 15 using the copolymer (A) having a Mn) of 1.05 to 1.25, an ultrafine pattern on the order of tens of nanometers with suppressed pattern defects was formed. It was possible and was shown to have high resolution. Among them, the weight average molecular weight (Mw) is about 9500 to 31,000, and the molecular weight distribution (Mw / Mn) represented by the weight average molecular weight (Mw) with respect to the number average molecular weight (Mn) is 1.20 or less. It was revealed that particularly high resolving power was achieved when the copolymer (A) was used.
The positive resist composition of the present invention is also found to have an improved sensitivity margin, and is useful in the production process when the positive resist composition of the present invention is applied to various pattern manufacturing methods. It was shown that.
On the other hand, when Comparative Example 1 or Comparative Example 4 is compared with Examples 1, 2, and 9 in which the solvent (B) and the developer of the resist composition are the same, the weight average molecular weight (Mw) is 9,500 to 35,000. Even when the molecular weight distribution does not fall within the scope of the present application, it has been clarified that the resolution is inferior and the sensitivity margin is narrow and inferior compared with the case of using the copolymer (A) used in the present invention. It was. Furthermore, it was clarified that when the molecular weight distribution is wide as in Comparative Example 1, a defective portion of the pattern is also generated.
Further, Comparative Example 2 in which the molecular weight distribution is narrow as in the present application but the weight average molecular weight (Mw) is smaller than the range specified in the present application is the same as in Examples 1 and 2 in which the solvent (B) and the developer of the resist composition are the same. Compared with 9 and 9, it was revealed that the resolving power is inferior and the sensitivity margin is narrow and inferior.
Further, Comparative Example 3 in which the molecular weight distribution is narrow as in the present application but the weight average molecular weight (Mw) is larger than the range specified in the present application is the same as in Examples 1 and 2 in which the solvent (B) and the developer of the resist composition are the same. Compared with 9 and 9, it was clarified that the resolving power is inferior, the sensitivity margin is narrow and inferior, and further, a defective portion of the pattern is generated.
In Comparative Examples 5 and 6 using a commercially available ZEP520A having a weight average molecular weight and molecular weight distribution larger than those of the present application, o-xylene has an appropriate development speed of 9.3 kg / sec by the developer selection process of the present application. , Development was performed using n-amyl acetate with an appropriate development speed of 5.6 Å / sec. However, all of them were inferior in resolution, narrow in sensitivity margin and inferior in pattern compared to the examples. It was clarified that a part was also generated.

Claims (6)

A molecular weight distribution (Mw / Mw) represented by the following general formula (I), having a weight average molecular weight (Mw) of 9,500 to 35,000 and a weight average molecular weight (Mw) with respect to the number average molecular weight (Mn) A main chain decomposition type positive resist composition containing a copolymer (A) having a Mn) of 1.05 to 1.25 and a solvent (B).
(In General Formula (I), L is a direct bond or —COO—. R ¹ represents a hydrocarbon group containing a hydrocarbon ring. R ² represents a hydrocarbon group.) The main chain decomposition type positive type according to claim 1, wherein the solvent (B) has a solubility of the copolymer (A) at 23 ° C of 5 g / 100 g or more of the solvent and a boiling point of 60 to 205 ° C. Resist composition. A step of preparing a copolymer (P) represented by the following general formula (I):
By fractionating the copolymer (P) using chromatography, it is represented by the following general formula (I), the weight average molecular weight (Mw) is 9,500 to 35,000, and Having a step of preparing a copolymer (A) having a molecular weight distribution (Mw / Mn) represented by a weight average molecular weight (Mw) with respect to an average molecular weight (Mn) of 1.05 to 1.25,
A method for producing a main chain decomposition type positive resist composition comprising the copolymer (A) and a solvent.
(In General Formula (I), L is a direct bond or —COO—. R ¹ represents a hydrocarbon group containing a hydrocarbon ring. R ² represents a hydrocarbon group.) A resist layer forming step of forming a resist layer by applying the main chain decomposition type positive resist composition according to claim 1 or 2 on a substrate and then heating;
An exposure step of exposing a predetermined pattern by irradiating the resist layer with active energy rays;
A developing step of developing the exposed resist layer with a developer;
A method for producing a resist pattern, comprising:   A developer selection step of forming a resist test film in which the positive resist composition is coated on a substrate and selecting a development test solution having a development rate of 0.5 to 20 liters / sec as a developer at the development temperature. The method for producing a resist pattern according to claim 4, further comprising: Preparing a copolymer (P) represented by the general formula (I);
By fractionating the copolymer (P) using chromatography, it is represented by the following general formula (I), the weight average molecular weight (Mw) is 9,500 to 35,000, and The method further comprises the step of preparing a copolymer (A) having a molecular weight distribution (Mw / Mn) represented by a weight average molecular weight (Mw) with respect to an average molecular weight (Mn) of 1.05 to 1.25. Or the manufacturing method of the resist pattern of 5.