JP5785489B2 - Pellicle - Google Patents

Description

  The present invention relates to a pellicle for lithography used to prevent foreign matters from adhering to a mask when manufacturing a semiconductor device such as an LSI or a VLSI or a liquid crystal display panel. In particular, the present invention relates to a pellicle useful for lithography using an excimer laser used in exposure requiring high resolution. The present invention particularly preferably relates to a pellicle useful for lithography used for ultraviolet light exposure of 200 nm or less.

  In a photolithography process for manufacturing a semiconductor, a semiconductor manufacturing apparatus such as a stepper (reduced projection exposure apparatus) is used to form a photoresist pattern corresponding to an integrated circuit on a wafer. The pellicle is formed by stretching a transparent thin film on one end face of a pellicle frame having a frame shape, and prevents foreign matter from directly adhering to the mask in order to form a circuit pattern. Therefore, even if foreign matter adheres to the pellicle in the photolithography process, the foreign matter does not form an image on the wafer coated with the photoresist, thereby preventing a short circuit or disconnection of the semiconductor integrated circuit due to the foreign matter image. And the manufacturing yield of the photolithography process can be improved.

  In recent years, with the high integration of semiconductor devices, the wavelength of exposure light used in the photolithography process has been shortened. That is, there is a demand for a technique capable of drawing a fine circuit pattern with a narrower line width when drawing an integrated circuit pattern on a wafer. In order to cope with this, for example, as exposure light of a photolithography stepper, KrF excimer laser (wavelength 248 nm), ArF excimer laser (wavelength 193 nm) proceeding from conventional g-line (wavelength 436 nm) and i-line (wavelength 365 nm). Further, light having a shorter wavelength such as F2 excimer laser (wavelength 157 nm) is about to be used.

  As a method for fixing the pellicle on the mask, a method of fixing with a pressure-sensitive adhesive is usually used, and as the pressure-sensitive adhesive, there are acrylic, rubber-based, polybutene-based, polyurethane-based, silicone-based, and the like. It is known (see Patent Document 1). The pressure-sensitive adhesive layer is formed on the other end surface of the pellicle frame with the pellicle film stretched on one end surface. When the pellicle film or the photomask (hereinafter also referred to as “mask”) becomes dirty, It is necessary to remove the pellicle once to remove the dirt, and to attach the pellicle to the mask again. In addition, the pressure-sensitive adhesive is required to have a load resistance that does not peel even when a certain load is applied, so that there is no problem such as peeling of the pellicle from the mask in the exposure process.

  Further, as the exposure light has a shorter wavelength and higher energy as described above, the frequency of occurrence of contamination of the pellicle film or the mask due to the exposure is increased, so that the frequency of replacement of the pellicle and the mask is increased. Under such circumstances, there is a demand for a pellicle pressure-sensitive adhesive that stably has an appropriate adhesive force and does not leave any adhesive residue on the mask when being replaced. In particular, in a photolithography process using light having a wavelength shorter than 200 nm, fogging called haze is likely to occur. Therefore, there is a demand for the property that the adhesive does not remain on the mask when the pellicle is peeled off from the mask. . On the other hand, the silicone-based adhesive currently used as a pellicle adhesive in the photolithography process using a KrF excimer laser (wavelength 248 nm) tends to cause adhesive residue on the mask and has a load resistance. There was a problem that it was not enough.

  As a method for improving the adhesive residue after peeling off the pellicle, Patent Document 2 discloses a pellicle having an adhesive layer having a cohesive breaking strength of 20 g / mm 2 or more. However, the adhesive residue and load resistance problem of the adhesive are generally in a trade-off relationship, and an adhesive with little adhesive residue has poor load resistance, causing a problem that the pellicle peels off during exposure.

  Therefore, the present applicants disclose the composition and physical properties of an acrylic pressure-sensitive adhesive having improved load resistance and adhesive residue in Patent Documents 3 and 4.

  Also, with the recent trend toward shorter exposure light wavelengths and higher energies, pattern miniaturization has progressed. For this reason, when the flatness of the mask is poor, defocusing occurs during exposure, and the accuracy of the pattern to be printed Is said to cause problems. For this reason, the flatness required for the mask has become stricter than before.

  One of the factors that change the flatness of the mask is said to be affected by the pellicle, and Patent Documents 5 and 6 are disclosed as methods that do not change the flatness with a mask adhesive material.

  In addition, the present inventors disclose Patent Document 7 as a patent that improves load resistance, mask flatness, and adhesive residue.

Japanese Patent Laid-Open No. 05-281711 JP 2006-146085 A JP 2010-002895 A JP 2011-107468 A JP 2009-276504 A JP 2009-025560 A JP 2011-128605 A

  The decrease in load resistance of the pellicle may occur during or after exposure. Therefore, the load resistance during and after exposure to deep ultraviolet (DUV) is particularly important.

  However, when the load resistance of the pellicle is improved, the pressure-sensitive adhesive tends to become hard, and the flatness of the mask often decreases. Therefore, it has been desired to develop a pressure-sensitive adhesive and pellicle that have both.

  Therefore, an object of the present invention is to provide a pellicle that has good load resistance and excellent mask flatness.

  As a result of intensive studies, the present inventors have found that the flatness of the mask can be improved and the load resistance can be improved by setting the stress relaxation property of the adhesive layer of the pellicle to a specific value. It came to complete. If the stress of the adhesive layer is relaxed, the adhesive absorbs the strain caused by the load applied when attaching the pellicle, so that the flatness of the mask can be maintained, and furthermore, the pellicle and mask are not distorted. It has been found that the load resistance is improved because the adhesiveness of the pressure-sensitive adhesive layer is not affected.

That is, the present invention relates to the following.
[1] A pellicle having a pellicle frame having an opening, a pellicle film covering the opening provided on one end surface of the pellicle frame, and an adhesive layer provided on the other end surface of the pellicle frame The pellicle is characterized in that the pressure-sensitive adhesive layer has a stress relaxation rate of 25% or more.
[2] The pellicle according to [1], wherein the pressure-sensitive adhesive layer has a peel strength of 0.45 to 4.0 kgf after the pressure-sensitive adhesive layer is irradiated with deep ultraviolet rays.
[3] The pressure-sensitive adhesive layer contains a reaction product of a (meth) acrylic acid alkyl ester copolymer and a curing material,
The (meth) acrylic acid alkyl ester copolymer comprises a (meth) acrylic acid alkyl ester having a C 1-14 alkyl group and a reactive monomer as monomer units. The pellicle according to [1] or [2], which is a polymer.
[4] The pellicle according to [3], wherein the curing material includes at least one compound selected from the group consisting of a polyfunctional epoxy compound and an isocyanate compound.
[5] The pressure-sensitive adhesive layer is a reaction product of 100 parts by mass of the (meth) acrylic acid alkyl ester copolymer and 0.01 to 3 parts by weight of the curing material [3] or The pellicle according to [4].
[6] The reactive monomer contains acrylic acid, and the amount of the monomer unit derived from the acrylic acid is 2 to 7% by mass with respect to all monomer units constituting the (meth) acrylic acid alkyl ester copolymer. The pellicle according to any one of [3] to [5], wherein
[7]
The (meth) acrylic acid alkyl ester copolymer comprises a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 3 carbon atoms and a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 14 carbon atoms. The pellicle according to any one of [3] to [6], wherein the pellicle is contained.

  The pellicle of the present invention is excellent in both load resistance and mask flatness.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be implemented with appropriate modifications within the scope of the gist thereof.

  The pressure-sensitive adhesive layer of the pellicle of this embodiment has a stress relaxation rate of 25% or more. When the stress relaxation rate is at this value, the force can be relaxed with respect to the load applied to the mask, so that the stress applied to the mask is absorbed by the adhesive layer itself, and the influence of flatness on the mask is mitigated. . The stress relaxation rate of the pressure-sensitive adhesive layer is more preferably 35 to 95%, and even more preferably 40 to 90%. If the stress relaxation rate is 95% or less, the pressure-sensitive adhesive does not become too soft and no problem occurs during handling.

  The pressure-sensitive adhesive layer is preferably formed from a pressure-sensitive adhesive comprising a reaction product of a (meth) acrylic acid alkyl ester copolymer and a curing material. The (meth) acrylic acid alkyl ester copolymer contains, as monomer units, a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms and a reactive monomer having a functional group having reactivity with a curing material. Those are preferred.

  Specific examples of the alkyl group having 1 to 14 carbon atoms in the alkyl group include butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, and (meth) acrylic acid. Decyl, (meth) acrylic acid esters of linear aliphatic alcohols such as (meth) acrylate dodecyl, (meth) lauryl acrylate, isobutyl (meth) acrylate, isoamyl (meth) acrylate, (meth) acrylic acid 2 -Ethylhexyl, isooctyl (meth) acrylate, isononyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate and the like. These may be used alone or in combination of two or more. Especially, it is more preferable to use 2 types which have the (meth) acrylic-acid alkylester which has a C1-C3 alkyl group, and the (meth) acrylic-acid alkylester which has a C4-C14 alkyl group. . For example, a combination of butyl (meth) acrylate, octyl (meth) acrylate, and the like with methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, or isopropyl (meth) acrylate is there.

  Examples of the reactive monomer having a functional group having reactivity with the curing material include carboxyl group-containing monomers such as (meth) acrylic acid, itaconic acid, maleic acid, and crotonic acid, and (meth) acrylic acid 2-hydroxy Hydroxyl group-containing monomers such as ethyl, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. These may be used alone or in combination of two or more. Among them, from the viewpoint of copolymerizability, versatility and the like, a hydroxyl group containing a hydroxyalkyl group having 2 to 4 carbon atoms such as 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate ( Carboxyl group-containing monomers such as (meth) acrylate and (meth) acrylic acid are preferably used. In particular, (meth) acrylic acid is preferable from the viewpoint of adhesive residue.

  The (meth) acrylic acid alkyl ester copolymer has a (meth) acrylic acid alkyl ester component of 80 to 99% by mass and the reactive monomer of 1 to 20% by mass based on the total amount of the monomer mixture. It is more preferable that it is a copolymer of a monomer mixture because it can express an appropriate adhesive force to the mask. Especially, it is most preferable that it is a copolymer of the monomer mixture whose (meth) acrylic-acid alkylester component is 93-98 mass% and the said reactive monomer is 2-7 mass%.

  Particularly, the constitution of the (meth) acrylic acid alkyl ester copolymer is preferably 5 to 25% by mass of the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 3 carbon atoms, and more preferably 5 to 20%. It is preferable that it is mass%. Moreover, it is preferable that the (meth) acrylic-acid alkylester which has a C4-C14 alkyl group is 68-93 mass%, and it is further preferable that it is 74-92 mass%. The reactive monomer is more preferably 3 to 6% by mass. When the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 3 carbon atoms is within these ranges, the steric hindrance is reduced with respect to the reactive monomer and the adhesion is improved, thereby increasing the load resistance. Moreover, since the glass transition temperature of a copolymer becomes remarkably low and adhesiveness improves, since it is excellent in load resistance, it is preferable. Further, when the reactive monomer is within these ranges, the hydrogen bond becomes strong and the cohesive force becomes strong, so that the adhesive residue after DUV irradiation and the load resistance during exposure become good.

  When the weight average molecular weight of the (meth) acrylic acid alkyl ester copolymer is 700,000 or more and 2.5 million or less, the cohesive force and adhesive force of the pressure-sensitive adhesive layer become appropriate, and it is difficult for adhesive to remain, and It becomes a pressure-sensitive adhesive having particularly excellent adhesive strength and load resistance, which is preferable. The weight average molecular weight is preferably 750,000 to 2.3 million, more preferably 1 million to 2 million. The weight average molecular weight can be controlled by a usual method. Specifically, the weight average molecular weight tends to increase as the monomer concentration during the polymerization reaction generally increases, and the weight average molecular weight tends to increase as the polymerization initiator amount decreases. It is in.

  For the production of such a (meth) acrylic ester copolymer, known production methods such as solution polymerization, bulk polymerization, emulsion polymerization, and various radical polymerizations can be appropriately selected. Further, the obtained (meth) acrylic acid alkyl ester copolymer may be any of a random copolymer, a block copolymer, a graft copolymer, and the like. In solution polymerization, for example, ethyl acetate, toluene or the like is used as a polymerization solvent.

  As a specific example of solution polymerization, the reaction is carried out under an inert gas stream such as nitrogen, as a polymerization initiator, for example, azobisisobutyronitrile 0.01 to 2.0 parts per 100 parts by weight of the total amount of monomers. Addition of parts by weight is usually performed at about 50 to 70 ° C. for about 8 to 30 hours. The polymerization initiator, chain transfer agent, emulsifier and the like used for radical polymerization are not particularly limited and can be appropriately selected and used.

  Preferred polymerization initiators include, for example, azo-based 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis (2-methylpropionic acid) ) Dimethyl, 4,4'-azobis-4-cyanovaleric acid, peroxide-based benzoyl peroxide, and the like.

  The pressure-sensitive adhesive used in the pressure-sensitive adhesive layer of the pellicle of this embodiment is particularly preferably composed of a composition containing a reaction product of the above (meth) acrylic acid alkyl ester copolymer and a curing material.

  The stress relaxation rate of the pressure-sensitive adhesive layer also depends on the degree of crosslinking of the polymer. If the degree of cross-linking is too low, it tends to be too soft and the adhesive residue will be bad. If the degree of crosslinking is too high, it will become too hard and the flatness to the mask will tend to be reduced. In order to control the degree of crosslinking, the amount of the curing material is preferably 0.01 to 3 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid alkyl ester copolymer. The amount of the curing material is more preferably 0.03 parts by mass to 2.5 parts by mass, and still more preferably 0.05 parts by mass to 1.0 parts by mass. If the amount of the curing material is 0.01 parts by mass to 3 parts by mass, the pressure-sensitive adhesive layer has a moderate crosslink density, and thus hardly affects the flatness of the photomask (the deformation of the photomask can be particularly suppressed). Can be formed. Furthermore, an adhesive layer with little adhesive residue can be formed. This is because if the amount of the curing material is 3 parts by mass or less, the crosslinking density does not become too large, so that the pressure-sensitive adhesive absorbs the stress applied to the mask and the effect of flatness on the photomask is alleviated. It is done. On the other hand, if the amount of the curing material is 0.01 parts by mass or more, the crosslinking density does not become too small, so that the handling property in the manufacturing process is maintained, and the adhesive residue that occurs when peeling the pellicle from the mask There seems to be no problem.

  As such a curing material, metal salts, metal alkoxides, aldehyde compounds, non-amino resin amino compounds, urea compounds, isocyanate compounds, metal chelate compounds, melamine compounds, aziridine compounds, etc. The cured material to be used can be mentioned. In view of reactivity with the functional group component of the (meth) acrylic acid alkyl ester copolymer, at least one curing material selected from the group consisting of isocyanate compounds and polyfunctional epoxy compounds is preferred, and polyfunctional epoxy. Compounds are more preferred.

  Specifically, tolylene diisocyanate is mentioned as an isocyanate compound. As polyfunctional epoxy compounds, neopentyl glycol diglycidyl ether, polyethylene glycol diglycidyl ether, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, phthalic acid diglycidyl ester, dimer acid diglycidyl ester, triglycidyl isocyanurate, Diglycerol triglycidyl ether, sorbitol tetraglycidyl ether, N, N, N ′, N′-tetraglycidyl m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N Examples include ', N'-tetraglycidyldiaminodiphenylmethane.

  Among these, a nitrogen-containing epoxy compound having 2 to 4 epoxy groups is preferable, and a nitrogen-containing epoxy compound having 4 epoxy groups is preferably used from the viewpoint of reactivity. If the reactivity is good, the cross-linking reaction is completed quickly after coating with the pressure-sensitive adhesive, so that the characteristics are stabilized in a short time and the productivity is excellent.

  In the case of the pressure-sensitive adhesive containing the (meth) acrylic acid alkyl ester copolymer and the polyfunctional epoxy compound, the stress relaxation rate can be adjusted by appropriately controlling the degree of crosslinking of the polymer.

  The reaction for obtaining the reaction product of the (meth) acrylic acid alkyl ester copolymer and the polyfunctional epoxy compound is carried out by weighing the (meth) acrylic acid alkyl ester copolymer solution and the polyfunctional epoxy compound solution, After mixing and stirring so as to mix uniformly, the solvent is removed by heating and drying, and then it is rapidly heated by heating.

  The pressure-sensitive adhesive layer preferably has a peel strength of 0.45 to 4 kgf after being irradiated with DUV. If it is this range, it will become easy to peel at the time of re-covering after exposure, and there will also be little adhesive residue. Furthermore, since the load resistance is good during exposure, there is no problem that the pellicle falls. Furthermore, it is preferable that it is 0.7-3.5 kgf, and it is more preferable that it is 0.75-3.0 kgf.

  Furthermore, preferably, the peel strength of the pressure-sensitive adhesive layer after DUV irradiation is in the range of 0.7 to 3.5 kgf. If it is this range, it will become easy to peel at the time of re-covering after exposure, and there will be little adhesive residue to a mask. Furthermore, since the load resistance is good, the pellicle does not fall during exposure, and the peel strength after DUV irradiation is preferably in the range of 0.75 to 3.0 kgf.

  The pellicle of this embodiment includes a pellicle frame having an opening, a pellicle film supported on one end surface of the pellicle frame and covering the opening, and the above-described pressure-sensitive adhesive layer provided on the other end surface of the pellicle film Composed. The pellicle of this embodiment can be suitably manufactured by the following method, for example.

  First, the above-mentioned (meth) acrylic acid alkyl ester copolymer solution and the curing material solution are mixed to obtain an adhesive precursor composition. In this case, in order to apply a pressure-sensitive adhesive layer having a predetermined thickness and width, the pressure-sensitive adhesive precursor composition is further diluted with a solvent to adjust the solution concentration (viscosity). The solvent for dilution is selected from the viewpoints of solubility, evaporation rate and the like. Specific examples of preferred solvents include, but are not limited to, acetone, ethyl acetate, and toluene.

  Second, the pressure-sensitive adhesive precursor composition is applied to the other end surface of the pellicle frame having a pellicle film bonded to one end surface. The application method is not particularly limited, but it is preferable to apply using a dispenser. The viscosity of the acrylic copolymer solution in the pressure-sensitive adhesive precursor composition (referred to as a solution consisting of a solvent and a (meth) acrylic acid alkyl ester copolymer) is not particularly limited, but is preferably 50 P or less, more preferably Is a viscosity of about 10 to 40 P, more preferably about 20 to 30 P (B-type viscometer, 25 ° C.). By diluting with a solvent in application with a dispenser, there is little stringing of the coating liquid, and it becomes easy to adjust to a stable width and thickness.

  Thirdly, the solvent and / or residual monomer can be removed by heating and drying the applied pressure-sensitive adhesive layer. Further, when the functional group of the (meth) acrylic acid alkyl ester copolymer and the curing material are reacted by heating to form a cross-linked structure, the pellicle frame pressure-sensitive adhesive composition is integrated and is in close contact with the pellicle frame surface.

  The drying temperature is preferably 50 to 200 ° C., and preferably 60 to 190 ° C. in consideration of the boiling point of the solvent and the remaining monomer and the decomposition temperature of the (meth) acrylic acid alkyl ester copolymer. Moreover, it is preferable to use an adhesive for a pellicle in the state dried enough so that the solvent contained in an adhesive may be 50 ppb or less by the following outgas test.

  After drying and crosslinking, a release sheet for protecting the pressure-sensitive adhesive surface may be attached to the pressure-sensitive adhesive layer. As the release sheet, a film having a thickness of about 30 to 200 μm such as polyester is generally used. Also, if the release force when peeling the release sheet from the pressure-sensitive adhesive layer is large, the pressure-sensitive adhesive may be deformed when peeled off. A mold release treatment such as fluorine may be performed.

  After a release sheet for protecting the adhesive surface is applied, a load may be applied to mold the adhesive surface substantially flat.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited at all by these.

<Example 1>
(Adjustment of adhesive composition)
The (meth) acrylic acid alkyl ester copolymer 1 was prepared by a usual method. Specifically, ethyl acetate (30 parts by mass) is placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, and butyl acrylate (BA) / methyl acrylate (MA) / acrylic acid. A mixture of (AA) / 2,2′-azobisisobutyronitrile (32 parts by mass) was charged at a mass ratio of 77/19/4 / 0.3 to prepare a reaction solution. The reaction was carried out by refluxing the reaction solution for 8 hours in a nitrogen atmosphere. After completion of the reaction, toluene (38 parts by mass) was added to obtain a solution (acrylic copolymer solution) of acrylic acid alkyl ester copolymer 1 having a nonvolatile content concentration of 32% by mass (weight average molecular weight 800,000). 0.1 mass of polyfunctional epoxy compound (1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, nonvolatile concentration 5%, toluene solution) is added to 100 mass parts of the obtained acrylic copolymer. Part of the mixture was added and stirred and mixed to obtain a solution of the pressure-sensitive adhesive precursor composition.

(Preparation of pellicle with adhesive layer)
Then, the above-mentioned pressure-sensitive adhesive precursor composition prepared on the entire other end surface of an aluminum alloy pellicle frame (outer diameter 113 mm × 149 mm, inner diameter 109 mm × 145 mm, height 4.8 mm) having a pellicle film bonded to one end surface The solution was applied with a dispenser. The applied solution was dried and cured by heating in two steps (1 step: 100 ° C., 8 minutes; 2 steps: 180 ° C., 8 minutes), and the pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition for pellicle of Example 1 A pellicle of Example 1 having a thickness of 0.3 mm was obtained. Next, a polyester protective film having a thickness of 100 μm subjected to silicone release treatment was bonded to the pressure-sensitive adhesive layer. In this state, the adhesive strength was stabilized by curing at room temperature (20 ± 3 ° C.) for 3 days, and a pellicle with an adhesive layer was produced. The obtained pellicle with an adhesive layer was evaluated by the following method.

(Molecular weight measurement)
A sample of the pressure-sensitive adhesive composition collected from the pressure-sensitive adhesive layer of the pellicle was vacuum-dried to remove the solvent. The eluent was added to the remaining sample to adjust the concentration to 1.0 mg / mL. This was filtered with a 0.5 micron filter, and the filtrate was used as a GPC sample. The measurement conditions of GPC are as follows.
Data processing: Tosoh GPC-8020
Equipment: Tosoh HLC-8220GPC
Column: TSKgel SuperHZN-M (4.6mmI.D. × 15cm) 1+
TSKgel SuperHZ2000 (4.6mmI.D. × 15cm) 1 oven: 40 ℃
Eluent: 0.35mL / min CHCl ₃
Sample volume: 50μl (1.0mg / mL)
Detector: RI
Calibration curve: polystyrene

(Evaluation of stress relaxation)
A sample of an adhesive layer having a thickness of 0.3 mm, a width of 1.5 mm, and a length of 30 mm was prepared from the pellicle. A tensile stress was applied to the sample of the adhesive layer using an autograph at a chuck interval of 10 mm and a tensile speed of 30 mm / min, and the sample was held as it was when a load of 100 mN was applied to the adhesive layer. The remaining load f was measured, and the stress relaxation rate was calculated by the following formula.
Stress relaxation rate (%) = (100−f) × 100/100

(Evaluation of photomask deformation)
Evaluation of deformation of the photomask was performed using a FlatMaster 200 manufactured by Tropel. After measuring the flatness of the photomask (6025 quartz), a pellicle was attached to the photomask, and the flatness of the photomask after the pellicle was attached was measured (measurement range: 135 mm × 110 mm). The difference in flatness before and after attachment was calculated as the amount of deformation of the photomask caused by attaching the pellicle. The pellicle was attached to quartz with a simple mounter (load: 30 kgf, 60 seconds). The degree of deformation of the photomask was evaluated according to the following criteria.
○: Deformation amount of photomask due to pasting of pellicle is smaller than 100 nm x: Deformation amount of photomask due to pasting of pellicle is 100 nm or more

(Load resistance test under deep ultraviolet (DUV) environment)
The protective film was peeled off from the pellicle with the pellicle pressure-sensitive adhesive layer, and the pellicle was affixed to the 6025 quartz blank base material and the 6025 chrome mask blank base material by applying a load of 30 kgf for 60 seconds using a simple mounter.

A 1 kg weight was attached to the base material to which the pellicle had been attached, and was left in that state under deep ultraviolet (DUV) irradiation. The load resistance was evaluated according to the following criteria according to the time until the pellicle peeled from the substrate.
○: No air pass even after 3 days Δ: Pellicle falls from substrate after 1 day ×: Pellicle falls from substrate after 3 hours

(Peeling strength after deep ultraviolet (DUV) irradiation)
The pellicle with the pressure-sensitive adhesive layer was cut after peeling off the protective film to prepare a pellicle piece having a width of 1.5 mm and a length of 5 cm. This pellicle piece was affixed to a 6012 quartz blank substrate.

A deep ultraviolet ray with an integrated irradiation amount of 40 J / cm ² was irradiated with an illuminance of 15 mW / cm ² to the pressure-sensitive adhesive layer of the pellicle piece attached to the base material using a Deep UV lamp. The pellicle piece after irradiation was pulled at a pulling speed of 5 mm / min using an autograph, and the maximum peeling force at that time was evaluated.

<Example 2>
Example 1 except that the amount of the polyfunctional epoxy compound (1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, nonvolatile content concentration 5%, toluene solution) was changed to 0.3 parts by mass A pellicle was produced in the same manner and evaluated.

<Example 3>
A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube is charged with ethyl acetate (30 parts by mass), and a mixture of butyl acrylate / acrylic acid / 2,2′-azobisisobutyronitrile. (32 parts by mass) was charged at a mass ratio of 96/4 / 1.0 to prepare a reaction solution. In a nitrogen atmosphere, the reaction solution was heated at 60 ° C. for 8 hours to carry out the reaction. After completion of the reaction, toluene (38 parts by mass) was added to obtain a solution (acrylic copolymer solution) of acrylic acid alkyl ester copolymer 2 having a nonvolatile content concentration of 32% by mass (weight average molecular weight 800,000). 0.1 mass of polyfunctional epoxy compound (1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, nonvolatile concentration 5%, toluene solution) is added to 100 mass parts of the obtained acrylic copolymer. Part of the mixture was added and stirred and mixed to obtain a solution of the pressure-sensitive adhesive precursor composition. A pellicle was prepared in the same manner as in Example 1 and evaluated.

<Example 4>
Example 1 except that the amount of the polyfunctional epoxy compound (1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, non-volatile content 5%, toluene solution) was changed to 0.03 parts by mass. A pellicle was produced in the same manner and evaluated.

<Example 5>
Example 1 except that the amount of the polyfunctional epoxy compound (1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, nonvolatile content concentration 5%, toluene solution) was changed to 0.6 parts by mass A pellicle was produced in the same manner and evaluated.

<Comparative Example 1>
Example 1 except that the amount of the polyfunctional epoxy compound (1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, nonvolatile content concentration 5%, toluene solution) was changed to 3.0 parts by mass A pellicle was produced in the same manner and evaluated.

<Comparative Example 2>
Except for changing the mass ratio of butyl acrylate / methyl acrylate / acrylic acid / 2,2′-azobisisobutyronitrile to 77/15/8 / 0.3, the pellicle was prepared in the same manner as in Example 1. I tried to make it, but I couldn't make it.

<Comparative Example 3>
A rubber-based hot-melt adhesive (SEBS) of styrene ethylene butylene styrene is attached to the other end surface of an aluminum alloy pellicle frame (outer diameter 113 mm × 149 mm, inner diameter 109 mm × 145 mm, height 4.8 mm) having a pellicle film bonded to one end surface. Polymer rubber adhesive) was applied. A pellicle was prepared in the same manner as in Example 1 and evaluated.

  Since the pellicle of the present invention is a pellicle that generates a small amount of outgas and has excellent organic gas adsorption performance, an IC (integrated circuit), an LSI (large scale integrated circuit), a TFT type LCD (thin film transistor liquid crystal display), etc. It can be suitably used in the lithography process.

Claims (7)

A pellicle having a pellicle frame having an opening, a pellicle film covering the opening provided on one end surface of the pellicle frame, and an adhesive layer provided on the other end surface of the pellicle frame, ,
The pressure-sensitive adhesive layer contains a reaction product of a (meth) acrylic acid alkyl ester copolymer and a curing material,
The (meth) acrylic acid alkyl ester copolymer is reactive with 93 to 98% by mass of (meth) acrylic acid alkyl ester component with respect to all monomer units constituting the (meth) acrylic acid alkyl ester copolymer. Including 2 to 7% by mass of monomer as a monomer unit,
The (meth) acrylic acid alkyl ester component is butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, (meth) acrylic Lauryl acid, isobutyl (meth) acrylate, isoamyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, methyl (meth) acrylate, (meth) At least one compound selected from the group consisting of ethyl acrylate, propyl (meth) acrylate and isopropyl (meth) acrylate,
A pellicle, wherein the pressure-sensitive adhesive layer has a stress relaxation rate of 25% or more.   The pellicle according to claim 1, wherein the pressure-sensitive adhesive layer has a peel strength of 0.45 to 4.0 kgf after the pressure-sensitive adhesive layer is irradiated with deep ultraviolet rays. The pellicle according to claim 1 or 2 , wherein the curing material contains at least one compound selected from the group consisting of a polyfunctional epoxy compound and an isocyanate compound. Claims 1 to 3, wherein the pressure-sensitive adhesive layer, wherein the (meth) which is a reaction product of the hardener from 0.01 to 1.0 part by weight acrylic acid alkyl ester copolymer 100 parts by weight The pellicle according to any one of the above. The reactive monomer contains acrylic acid, and the amount of monomer units derived from the acrylic acid is 2 to 7% by mass with respect to all monomer units constituting the (meth) acrylic acid alkyl ester copolymer. The pellicle according to any one of claims 1 to 4 , wherein the pellicle is characterized. The (meth) acrylic acid alkyl ester copolymer comprises a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 3 carbon atoms and a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 14 carbon atoms. The pellicle according to any one of claims 1 to 5 , wherein the pellicle is contained. The amount of monomer units derived from the (meth) acrylic acid alkyl ester having an alkyl group having 4 to 14 carbon atoms is 68 to 93 with respect to all monomer units constituting the (meth) acrylic acid alkyl ester copolymer. Mass%,
  The amount of the monomer unit of the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 3 carbon atoms is 5 to 25% by mass with respect to all the monomer units constituting the (meth) acrylic acid alkyl ester copolymer. And
The (meth) acrylic acid alkyl ester having an alkyl group having 4 to 14 carbon atoms is at least one compound selected from the group consisting of butyl (meth) acrylate and octyl (meth) acrylate,
The (meth) acrylic acid alkyl ester having an alkyl group having 1 to 3 carbon atoms is composed of methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate and isopropyl (meth) acrylate. The pellicle according to claim 6, wherein the pellicle is at least one kind of compound selected from the above.