JP2018146668A - Pellicle film and method for producing pellicle film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pellicle film having an excellent balance between EUV light transmittance and handleability, and a method for producing the same. A pellicle film is composed of a carbon film, and the in-plane film thickness unevenness, which is the uniformity of the thickness of the carbon film constituting the pellicle film, is 15% or less, and is a film obtained from the external dimensions of the film. The ratio of the volume V (cm3) of the film to the mass G (g) of the film, that is, the density which is a value calculated as G / V is 0.3 to 2.1 g / cm3. Further, the carbon film contains a random layer carbon structure derived from carbon or a compound containing a carbon atom, and the compound containing a carbon atom is one or more selected from the group consisting of a polyimide compound and a polybenzoxazine compound. Is. [Selection diagram] None

Description

  The present invention relates to a pellicle film for lithography using extreme ultraviolet light and a method for manufacturing the pellicle film.

  The degree of integration of semiconductor integrated circuits has been improved, and high integration has continued until now. For high integration of semiconductor integrated circuits, an exposure technique called photolithography is used. In this exposure technique, in order to obtain a resolution with a minimum line width of 45 nm or less of the wiring of a semiconductor integrated circuit, the exposure wavelength is called extreme ultraviolet light (hereinafter referred to as EUV (Extreme Ultra Violet) light) of 6 to 14 nm called the EUV region. It is considered that EUV lithography using (also referred to as) is useful.

  EUV light has the property of being easily absorbed by almost all substances. Therefore, in photolithography using EUV light as exposure light, exposure is performed using a reflective optical system. Specifically, the EUV light as the reflected light is exposed by reflecting the EUV light on the original on which the exposure pattern is reflected. At this time, if a foreign substance adheres to the original plate, EUV light is absorbed by the foreign substance or EUV light is scattered, so that a desired pattern may not be exposed.

  Therefore, it has been studied to protect the EUV light irradiation surface of the original plate with a pellicle. The pellicle has a pellicle film for protecting the EUV light irradiation surface of the original. When the pellicle film is irradiated with EUV light, the pellicle film absorbs the EUV light and a sufficient exposure amount may not be obtained. Since carbon absorbs less EUV light, it has attracted attention as a pellicle film material, and so far, films containing carbon have been proposed (see Patent Documents 1 and 2).

  Patent Document 1 discloses a pellicle film having a film thickness of 100 nm to 63 nm and formed of a carbon porous film. Such a pellicle film has high transparency to EUV light, has physical strength and durability, can easily remove film fragments, and is excellent in productivity.

  Patent Document 2 discloses that a pellicle film can be manufactured by irradiating a film containing an organic material with EUV light so that the organic material is carbonized and converted into an inorganic material. Such a pellicle film is said to be excellent in EUV light transmission and durability, and to be self-supporting.

International Publication 2014/142125 Pamphlet International Publication 2015/178250 Pamphlet

However, paying attention to the relationship between the EUV light transmittance and the film thickness, the pellicle film of Patent Document 2 has a thin film thickness with respect to the EUV light transmittance. Therefore, handling is difficult when performing operations such as attaching the obtained pellicle film to a member or the like. In order to facilitate the handling of the film, a method of increasing the film thickness can be considered, but by increasing the film thickness, the EUV light absorbed by the film increases and the EUV light transmittance decreases. . Therefore, there is a need for a pellicle film that has a constant film thickness and excellent EUV light transmittance in order to improve handling properties.
In view of the above problems, an object of the present invention is to provide a pellicle film excellent in the balance between the transmittance of EUV light and the handling property, and a method for manufacturing such a pellicle film.

As a result of intensive studies to solve the above problems, the present inventors have found that a pellicle film composed of a carbon film having a specific in-plane film thickness unevenness and density has a high EUV light transmittance. However, the present inventors have found that it is excellent in handling properties and completed the present invention.
In addition, the present inventors have found that the pellicle film can be formed as a self-supporting film having no cracks during carbonization and excellent in strength by a specific manufacturing method, and the present invention has been completed.

That is, the present invention is as follows.
[1]
Composed of carbon film,
In-plane film thickness unevenness is 15% or less,
The density is 0.3 to 2.1 g / cm ³ ;
Pellicle membrane.
[2]
The pellicle film according to [1], wherein the in-plane film thickness unevenness is 5% or less.
[3]
The pellicle film according to [1] or [2], wherein the density is 0.8 to 2.1 g / cm ³ .
[4]
The carbon film comprises carbon or a turbostratic carbon structure derived from a compound containing carbon atoms;
The pellicle film according to any one of [1] to [3], wherein the compound containing a carbon atom is one or more selected from the group consisting of a polyimide compound and a polybenzoxazine compound.
[5]
A pellicle film manufacturing method comprising a carbon film, wherein the carbon film has a thickness of less than 1500 nm,
Laminating a film containing carbon atoms on a substrate;
Heating the film laminated on the substrate at 800-1400 ° C. in a nitrogen atmosphere to form a carbon film;
Including a step of peeling the carbon film from the substrate,
A method for producing a pellicle film.
[6]
The carbon film comprises carbon or a turbostratic carbon structure derived from a compound containing carbon atoms;
The method for producing a pellicle film according to [5], wherein the compound containing carbon atoms is one or more selected from the group consisting of a polyimide compound and a polybenzoxazine compound.

  The present invention can provide a pellicle film excellent in the balance between EUV light transmittance and handling properties, and a method for producing the pellicle film.

Derived from PI, carbon film heated at 1100 ° C., obtained by APD method, carbon film heated at 1100 ° C., obtained by APD method, obtained by laser Raman measurement using carbon film before heating It is a figure which shows the obtained spectrum.

  Hereinafter, a mode for carrying out the present invention (hereinafter abbreviated as “this embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

[Pellicle membrane]
Pellicle film of the present embodiment is constituted by a carbon film, thickness unevenness in the surface is 15% or less, a density of ^{0.3g / cm 3 ~2.1g / cm 3} .
The fact that the pellicle film is made of a carbon film means that the pellicle film is made of a carbon film.

In general, as the film thickness of the carbon film increases, the transmittance of EUV light decreases. However, since high EUV light transmittance is required, it is necessary to reduce the film thickness. By reducing the film thickness, for example, when the deposited carbon film is attached to a frame or the like, there is a risk of film breakage and handling is difficult.
The carbon film constituting the pellicle film in the present embodiment can increase the transmittance of EUV light when the film thickness unevenness and the density of the inner surface are in the above ranges. As a result, since the EUV light permeability can be maintained even when the carbon film is relatively thick, a pellicle film having an excellent balance between handling properties and high EUV light transmittance can be obtained.

(In-plane film thickness unevenness)
In-plane film thickness unevenness in this embodiment refers to the uniformity of the thickness of the carbon film constituting the pellicle film. The in-plane film thickness unevenness in the present embodiment can be obtained from the following equation (1). As the in-plane film thickness unevenness (%) is smaller, the film thickness is more uniform.

  In-plane film thickness unevenness (%) = Δt / t × 100 Formula (1)

Δt is a difference between the in-plane maximum film thickness and the in-plane minimum film thickness.
t is the film thickness average value of the in-plane film thickness.

The in-plane film thickness unevenness is 15% or less, preferably 5% or less, and more preferably 4% or less. The in-plane film thickness unevenness is ideally 0% from the viewpoint of improving the EUV light transmittance, but may be 0.1% or more, or 0.5% or more. Good.
By setting the in-plane film thickness unevenness to 15% or less, when EUV light passes through the pellicle film, it is possible to prevent the EUV light from diffusing in the pellicle film and to improve the EUV light transmission. it is conceivable that.

In-plane film thickness unevenness is, for example, 15% or less by heating the entire substrate on which films containing carbon atoms are stacked and carbonizing the film containing carbon atoms in a method for manufacturing a pellicle film described later. Can be controlled.
Specifically, the in-plane film thickness unevenness can be measured by the method described in the examples.

(density)
The density is a ratio between the film volume V (cm ³ ) and the film mass G (g) obtained from the outer dimensions of the film, that is, a value calculated as G / V.
Density, from the viewpoint of improving the permeability of the EUV light is ^{0.3g / cm 3 ~2.1g / cm 3} , preferably ^{0.8g / cm 3 ~2.1g / cm 3} , more preferably is ^{0.9g / cm 3 ~1.9g / cm 3} .
Density, by the carbon film containing turbostratic carbon structure, it is possible to ^{0.3g / cm 3 ~2.1g / cm 3} . Further, the density is increased by lowering the density of the carbon film obtained by the method for producing the pellicle film described later by further activating carbon dioxide gas or by heat treatment in a high-temperature inert atmosphere. it performs, it can be controlled in the range of ^{0.3g / cm 3 ~2.1g / cm 3} .
Specifically, the density can be measured by the method described in Examples.

(Carbon film thickness)
The thickness of the carbon film constituting the pellicle film of this embodiment is preferably less than 1500 nm. The thickness of a carbon film is the thickness of a film | membrane used by the normal meaning. The upper limit value of the thickness of the carbon film is more preferably 1200 nm or less, still more preferably 1000 nm or less, and still more preferably 500 nm or less.
By setting the thickness of the carbon film to less than 1500 nm, it is possible to obtain a carbon film that is free from cracks during manufacturing.
Further, the lower limit value of the thickness of the carbon film is not particularly limited as long as it is larger than 0 nm.

The thickness of the carbon film can be controlled, for example, by adjusting the thickness of the film when a film containing carbon atoms is stacked on the substrate in a method for manufacturing a pellicle film described later.
The thickness of the carbon film can be measured with an atomic force microscope (AFM), an electron microscope (SEM), or the like. Specifically, the thickness of the carbon film can be measured by the method described in Examples.

[Method for producing pellicle film]
The method for manufacturing a pellicle film according to the present embodiment is a method for manufacturing a pellicle film, which is formed of a carbon film, and the thickness of the carbon film is less than 1500 nm. In addition, the method for manufacturing a pellicle film according to this embodiment includes a step of laminating a film containing carbon atoms on a substrate (step I), and heating the film laminated on the substrate at 800 to 1400 ° C. in a nitrogen atmosphere. Step (step II), and step (III) of peeling the carbon film from the substrate.

(Process I)
The step of laminating a film containing carbon atoms on a substrate refers to forming a compound containing carbon or carbon atoms on the substrate into a film shape.

The substrate is not particularly limited as long as the substrate has a melting point higher than 800 to 1400 ° C. which is a heating temperature when forming a carbon film. For example, a substrate containing silicon carbide, a substrate containing silicon dioxide, silicon Examples include a substrate. As the substrate, a silicon substrate (hereinafter also referred to as Si substrate) whose surface layer contains silicon dioxide (SiO ₂ ) is preferable.
By producing a carbon film on a Si substrate, a carbon film having excellent in-plane film thickness uniformity can be produced without breaking the film.

As a method for forming carbon or a compound containing carbon atoms into a film, known techniques can be applied, for example, sputtering, electron beam evaporation, ion plating, molecular beam epitaxy, ionization evaporation, laser ablation. Method, arc plasma deposition method, thermal chemical vapor deposition method, plasma chemical vapor deposition method, metal organic chemical vapor deposition method, spray pyrolysis method, electroless plating method, electroplating method, coating firing method, aerosol deposition method, fine particle coating method, And a spin coat method etc. are mentioned.
Among them, as a method for forming carbon into a film on a substrate, an arc plasma deposition method (also referred to as an APD method) is preferable, and as a method for forming a compound containing a carbon atom on a substrate, a spin coating method is used. Is preferred.
By applying the arc plasma deposition method and the spin coating method, a carbon film having excellent in-plane film thickness uniformity can be manufactured.

In the APD method, carbon is deposited on a substrate to form a film.
Since the thickness of the formed carbon film is reduced by heating in the step II, the thickness of the film formed by the APD method is preferably 1900 nm or less, more preferably 1500 nm or less, and further preferably It is 630 nm or less.
The lower limit of the thickness of the film formed by the APD method is not particularly limited as long as the thickness of the carbon film can be larger than 0 nm, and exceeds 0 nm.

In the arc plasma deposition method, for example, a carbon film can be produced by using an arc plasma deposition apparatus. Specifically, a carbon film can be obtained by discharging the cathode containing graphite to evaporate carbon and depositing the carbon on a Si substrate. When depositing, the Si substrate may be rotated to increase the uniformity of the carbon film.
Examples of the arc plasma vapor deposition apparatus include a vapor deposition apparatus APD-1P-GB manufactured by Advance Riko Co., Ltd.

In the spin coating method, a compound containing carbon atoms is applied on a substrate to form a film.
Since the thickness of the formed carbon film is reduced by heating in the step II, the thickness of the film formed by the APD method is preferably 3000 nm or less, more preferably 2400 nm or less, and further preferably It is 2000 nm or less.
The lower limit of the thickness of the film formed by the APD method is not particularly limited as long as the thickness of the obtained carbon film can be larger than 0 nm, and exceeds 0 nm.

The compound containing a carbon atom is not particularly limited as long as it is carbonized by heating, and is preferably an organic material.
More preferably, the compound containing a carbon atom is a polyimide compound, polybenzoxazine compound, polyacrylonitrile compound, polyisocyanate compound, polyamide compound, heteroaromatic ring compound, polyphenylene resin, polyether resin, liquid crystal polymer resin, polyparaxylylene. It is 1 or more types selected from the group which consists of a len resin, a phenol resin, an epoxy resin, and a furan resin.
More preferably, the compound containing a carbon atom is one or more selected from the group consisting of a polyimide compound and a polybenzoxazine compound.

The polyimide compound is not particularly limited as long as it is a polymer having an imide bond, but is preferably a reaction product of an acid anhydride and a diamine.
Examples of the acid anhydride include pyromellitic anhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), 2,3,3 ′, 4-biphenyltetracarboxylic dianhydride. Product (BPDA), 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 4,4′-oxydiphthalic dianhydride (ODPA), 3,3 ′, 4,4′- And diphenylsulfotetracarboxylic dianhydride (DSDA).
Examples of the diamine include p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, and 3,3′-. Diaminobenzophenone, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 1,3-bis (4-aminophenoxy) benzene, Examples include 1,3-bis (3-aminophenoxy) benzene and 4,4′-bis (3-aminophenoxy) biphenyl.
Among these polyimide compounds, a polymer that is a reaction product of BPDA and diaminodiphenyl ether is preferable.

The polybenzoxazine compound is preferably a reaction product of a phenol compound, a diamine and formaldehyde.
Examples of the phenol compound include 4,4′-dihydroxybiphenyl, 1,4-dihydroxybenzene, and the like.
Examples of the diamine include p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, and 3,3′-. Diaminobenzophenone, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 1,3-bis (4-aminophenoxy) benzene, Examples include 1,3-bis (3-aminophenoxy) benzene and 4,4′-bis (3-aminophenoxy) biphenyl.
Among these polybenzoxazine compounds, a polymer that is a reaction product of 4,4′-dihydroxydiphenylmethane and diaminodiphenyl ether is preferable.

  When the polyimide compound and the polybenzoxazine compound are coated on the substrate, the polyimide compound and the polybenzoxazine compound may be directly coated on the substrate, and the above-mentioned compound, which is a raw material of the polyimide compound and the polybenzoxazine compound, is applied to the substrate. It is good also as a polyimide compound and a polybenzoxazine compound by apply | coating and polymerizing this compound on a board | substrate by heating.

(Process II)
The step of heating the film laminated on the substrate at 800 to 1400 ° C. in an inert gas atmosphere to form a carbon film is the heating of the film containing carbon atoms obtained in Step I at 800 to 1400 ° C. This refers to conversion into a carbon film containing a carbon structure.
Since the carbon film includes a turbulent carbon structure obtained by heating carbon or a compound containing carbon atoms, the carbon film in the pellicle film of this embodiment is derived from carbon or a compound containing carbon atoms. It preferably contains a turbulent carbon structure.

  The inert gas is not particularly limited as long as the carbon atoms contained in the film obtained in Step I do not affect the reaction of forming a turbostratic carbon structure, and examples thereof include nitrogen and argon. Among these, nitrogen is preferable.

A heating temperature is 800-1400 degreeC, Preferably it is 900-1300 degreeC, More preferably, it is 1000-1200 degreeC. By setting the heating temperature to 800 to 1400 ° C., carbon atoms contained in the film obtained in Step I can be converted into a turbulent carbon structure, and a carbon film can be obtained. Heating can be performed in a heat treatment furnace or the like.
The heating time is preferably from 1 minute to 10 hours, more preferably from 10 minutes to 3 hours, and even more preferably from 30 minutes to 2 hours, from the viewpoint of sufficiently converting the carbon atom to the disordered carbon structure. It is.

Moreover, it is confirmed by observing sp ² carbon by laser Raman measurement that the conversion from carbon atoms to the turbulent carbon structure has progressed by heating, and the carbon film containing the turbulent carbon structure has been obtained. it can.
Specifically, the observation of sp ² carbon by laser Raman measurement can be performed by the method described in Examples.

(Process III)
A specific method in the step of peeling the carbon film from the substrate is not particularly limited, and for example, a step of spin-coating a composition containing an acrylic resin or the like on the carbon film obtained by heating to form a support film. A step of peeling the substrate by hydrofluoric acid treatment or the like; a step of attaching a support frame to the peripheral edge of the carbon film of the structure composed of the carbon film and the support film; a method of removing the support film by etching or the like; Is mentioned.

[Application of pellicle film]
The pellicle film of this embodiment can be used for a pellicle. The pellicle can be used as a member for preventing foreign matter from adhering to an original plate having an exposure pattern in an EUV exposure apparatus.

  Hereinafter, the present embodiment will be described in more detail using examples and the like, but the present embodiment is not limited to these examples.

(Measurement of EUV light transmittance)
The EUV light transmittance of the pellicle membrane was measured using BL12 held by Kyushu Synchrotron Light Research Center. Specifically, a sample of several mm is attached to an EM Japan Si substrate (SiN film having a thickness of 50 nm only at the central portion of the substrate 500 μm), the substrate is fixed to the side of the dent of the dedicated holder, and 92 eV (λ = 13.5 nm) was irradiated with soft X-rays (EUV light). Then, the transmittance I / I ₀ of EUV light was determined from the transmission intensity ratio with and without the sample.
I ₀ is the incident light intensity detected with no pellicle film installed, and I is the transmitted light intensity detected with the pellicle film installed. The EUV light transmittance I / I ₀ has the following relational expression.

ρ is the density (g / cm ³ ).
mu _m is the mass absorption coefficient (cm ² / g).
d is a film thickness (cm).
μ is a linear absorption coefficient.

(Measurement of in-plane film thickness unevenness)
In-plane film thickness unevenness was measured using an atomic force microscope (AFM) after EUV measurement. About the measuring method of a film thickness, you may measure except AFM, and it does not specifically limit.
The value calculated by the equation (1) from the film thickness value measured by AFM was used as an index of in-plane film thickness unevenness.

  In-plane film thickness unevenness (%) = Δt / t × 100 Formula (1)

Δt is the difference between the film thickness of the thickest part and the thinnest part among the film thicknesses obtained by measurement.
t is the average film thickness obtained by measurement.

(Measurement of carbon film thickness)
The thickness of the carbon film was measured using AFM after EUV measurement.

(Density measurement)
The density was calculated as the ratio between the volume V (cm ³ ) of the film and the mass G (g) of the film obtained from the outer dimensions of the film, that is, G / V.

(Evaluation of membrane strength (liquid pulling up))
In the following examples, the carbon film is immersed in isopropyl alcohol, and the carbon film is pulled up from the liquid using a silicon substrate (center part: SiN film) used for EUV measurement. It was evaluated by whether or not. In the table, ◯ represents that the film did not break when the film was pulled up, and x represents that the film was broken when the film was pulled up.

(Observation of sp ² carbon by laser Raman measurement)
Observation of sp ² carbon by laser Raman measurement was performed using a Raman microscope (inVia Reflex manufactured by Renishaw). The Raman measurement, measurement conditions, environmental atmosphere: in the atmosphere, the excitation light: 532 nm, excitation light intensity: 1%, the objective lens: 100 times, grating: 1800gr / mm, measurement area: and 165cm ^-1 ~1920cm ^-1 did.
A spectrum obtained using the carbon film obtained in Example 1 below, the carbon film obtained by the arc plasma deposition method of Example 8, and the film obtained by the arc plasma deposition method before heating is shown in FIG. .

[Example 1]
A polyimide precursor (BPDA-ODA) synthesized from 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-diaminodiphenyl ether (ODA) is dissolved in N-methylpyrrolidone. A 15 wt% solution was applied onto the Si substrate by spin coating. A polyimide film having a film thickness of 400 nm was obtained by imidization on a substrate in a nitrogen atmosphere at 300 ° C. for 1 hour. The film thickness was obtained as an average value of 10 or more points taken at intervals of 1 mm or more with a cross-sectional SEM.
Subsequently, this substrate was placed in a heat treatment furnace and carbonized by heating at 1100 ° C. for 1 hour under N ₂ flow to obtain a carbon film. The film thickness of the carbon film was determined by measuring the difference between the carbon film and the substrate with a contact step meter after making scratch marks on the carbon film with tweezers, and setting the carbon film thickness to 200 nm. Met. When the surface of the carbon film was observed with an optical microscope at 1000 times, no cracks were observed.
Thereafter, an acetone solution of polymethyl methacrylate resin (PMMA) 15 wt% was spin coated on the substrate at 500 rpm to form a support film. The substrate was immersed in a 40 wt% hydrogen fluoride (HF) aqueous solution, and the carbon film with the PMMA film was peeled off from the substrate and washed with water. Then, the carbon film with the PMMA film was immersed in an acetone: isopropyl alcohol = 1: 1 (weight ratio) solution to dissolve the PMMA, and then the carbon film was transferred to the isopropyl alcohol liquid using a glass substrate. Furthermore, according to the SiN window part of the center of the Si substrate made from EM Japan, the carbon film was pulled up and isopropyl alcohol was dried to obtain a carbon film for EUV measurement. When the EUV transmittance of this carbon film was measured, the transmittance was 41%.

[Example 2]
The same procedure as in Example 1 was performed except that the concentration of the BPDA-ODA solution in N-methylpyrrolidone was 10 wt%. The carbon film thickness was 140 nm and the film thickness unevenness was 2.9%. Further, the EUV transmittance was 56%.

[Example 3]
The same operation as in Example 1 was carried out except that the concentration of the BPDA-ODA in N-methylpyrrolidone was 8 wt%. The carbon film thickness was 100 nm, and the film thickness unevenness was 2.6%. Further, the EUV transmittance was 60%.

[Example 4]
The same operation as in Example 1 was performed except that the concentration of the BPDA-ODA in N-methylpyrrolidone solution was 5.5 wt%. The carbon film thickness was 80 nm, and the film thickness unevenness was 3.0%. Further, the EUV transmittance was 70%.

[Example 5]
The same procedure as in Example 1 was performed except that the concentration of the BPDA-ODA in N-methylpyrrolidone solution was 4 wt%. The carbon film thickness was 50 nm and the film thickness unevenness was 2.0%. Further, the EUV transmittance was 79%.

[Example 6]
The same operation as in Example 1 was performed except that the concentration of the BPDA-ODA in N-methylpyrrolidone solution was 0.5 wt%. The carbon film thickness was 5 nm. However, the carbon film was broken when the carbon film with the PMMA film was immersed in an acetone: isopropyl alcohol = 1: 1 (weight ratio) solution and then pulled up using a glass substrate.

[Example 7]
The BPDA-ODA in Example 1 was changed to polybenzoxazine (PBO) synthesized from 4,4′-dihydroxydiphenylmethane and 4,4′-diaminodiphenyl ether, and 15 wt% polydissolved in 1,4-dioxane. The benzoxazine solution was applied onto the Si substrate by spin coating. Ring-opening polymerization was performed at 250 ° C. in a nitrogen atmosphere on the substrate to obtain a film thickness of 320 nm. The film thickness was obtained as an average value of 10 or more points taken at intervals of 1 mm or more with a cross-sectional SEM.
Subsequently, this substrate was placed in a heat treatment furnace and carbonized by heating at 1100 ° C. for 1 hour under N ₂ flow to obtain a carbon film. The film thickness of the carbon film was determined by measuring the level difference between the carbon film and the substrate with a contact level meter after making scratch marks on the carbon film with tweezers to obtain a carbon film thickness of 150 nm, and film thickness unevenness of 3.3%. Met. When the surface of the carbon film was observed with an optical microscope at 1000 times, no cracks were observed.
Thereafter, a PMMA 15 wt% acetone solution was spin-coated on the substrate at 500 rpm to form a support film. The substrate was immersed in a 40 wt% HF aqueous solution, and the carbon film with the PMMA film was peeled off from the substrate and washed with water. Then, the carbon film with the PMMA film was immersed in an acetone: isopropyl alcohol = 1: 1 (weight ratio) solution to dissolve the PMMA, and then the carbon film was transferred to the isopropyl alcohol liquid using a glass substrate. Furthermore, according to the SiN window part of the center of the Si substrate made from EM Japan, the carbon film was pulled up and isopropyl alcohol was dried to obtain a carbon film for EUV measurement. When the EUV transmittance of the carbon film was measured, the transmittance was 50%.

[Example 8]
Preparation of the carbon film by the arc plasma deposition method was performed using a vapor deposition apparatus APD-1P-GB manufactured by Advance Riko Co., Ltd. Specifically, high-purity artificial graphite as a cathode was discharged at a voltage of 100 V, a capacitor capacity of 720 F, and a frequency of 10 Hz to evaporate carbon. The evaporated carbon was deposited on a Si substrate placed at a distance of 15 mm from the cathode. The thickness of the carbon film was 100 nm. In order to improve the uniformity of the carbon film, the Si substrate was rotated at 30 rpm. The substrate on which the carbon film was formed was placed in a heat treatment furnace and carbonized by heating at 1100 ° C. for 1 hour under N ₂ flow to obtain a carbon film. The subsequent operations were all performed in the same manner as in Example 1. The carbon film thickness was 80 nm, and the film thickness unevenness was 3.1%. The EUV transmittance was 71%.

[Example 9]
The carbon film produced in Example 1 was made porous, that is, reduced in density by activating carbon dioxide gas.
Specifically, the carbon film produced in Example 1 was heat-treated at 800 ° C. for 5 minutes in a carbon dioxide gas stream having a flow rate of 100 ml / min. The mass loss due to the heat treatment was 48%. The obtained porous carbon film were measured physical property values in the same manner as in Example 1, a density 0.82 g / cm ^3, carbon film thickness 200 nm, a film thickness non-uniformity of 2.5%. The EUV transmittance was 62%.

[Example 10]
The carbon film produced in Example 2 was further graphitized, that is, densified by heat treatment in a high-temperature inert atmosphere.
Specifically, the carbon film produced in Example 2 was heat-treated at 3000 ° C. under a stream of argon gas using a small super high temperature furnace SCC-30 / 220 manufactured by Kurata Giken Co., Ltd. The argon gas flow rate was 500 ml / min. The mass reduction by this heat treatment was 1% or less. The physical properties of the graphitized carbon film obtained were measured in the same manner as in Example 1. The density was 2.10 g / cm ³ , the carbon film thickness was 100 nm, and the film thickness unevenness was 2.7%. The EUV transmittance was 54%.

[Comparative Example 1]
The same procedure as in Example 1 was conducted except that the N-methylpyrrolidone solution concentration of BPDA-ODA was 20%, and coating was performed on a Si substrate with a blade coater, and the carbon film thickness was 1500 nm. When the surface of the carbon film was observed with an optical microscope, a plurality of cracks were confirmed.

[Comparative Example 2]
Similar to Example 1, a polyimide film having a film thickness of 400 nm was formed on a Si substrate. Thereafter, the substrate was immersed in a 40 wt% HF aqueous solution, and the polyimide film was peeled off from the substrate and washed with water. The polyimide film was set on a tenter clip, placed in a heat treatment furnace, and carbonized by heating at 1100 ° C. for 1 hour under N ₂ flow while maintaining the tension. However, the film was broken during heating, and a carbon film could not be obtained.

The carbon film obtained by irradiating the polyimide film with EUV light (hereinafter referred to as the carbon film of Comparative Reference Example 1) disclosed in International Publication No. 2015/178250 pamphlet is shown in FIG. It can be read that the rate is 53%.
At this time, the carbon film before carbonization of the carbon film of Comparative Reference Example 1 is expected to be 110 nm, and the carbon film after carbonization of Comparative Reference Example 1 is expected to be around 60 nm. In addition, the carbon film of Comparative Reference Example 1 does not show a band corresponding to sp ² carbon by laser Raman measurement from FIG. 9 of the pamphlet, and contains graphite (density: 2.26 g / cm ³ ) as a main component. It is expected to be.
Since the film thickness of the carbon film of Example 2 was 140 nm when the EUV light transmittance was 56%, the film thickness was larger than that of the carbon film of Comparative Reference Example 1. EUV light transmittance is high. This is because the carbon film of the present embodiment is formed by heating the entire film containing carbon atoms on the substrate, and the film thickness unevenness is suppressed. It is considered that spot exposure by beam scanning causes unevenness due to the scanning pattern and the film thickness is not uniform.

  The pellicle film of the present invention has industrial applicability in the field of EUV lithography as a pellicle film for protecting a lithography mask from contamination.

Claims (6)

Composed of carbon film,
In-plane film thickness unevenness is 15% or less,
The density is 0.3 to 2.1 g / cm ³ ;
Pellicle membrane.   The pellicle film according to claim 1, wherein the in-plane film thickness unevenness is 5% or less. The pellicle film according to claim 1 or 2, wherein the density is 0.8 to 2.1 g / cm ³ . The carbon film comprises carbon or a turbostratic carbon structure derived from a compound containing carbon atoms;
The pellicle film according to any one of claims 1 to 3, wherein the carbon atom-containing compound is at least one selected from the group consisting of a polyimide compound and a polybenzoxazine compound. A pellicle film manufacturing method comprising a carbon film, wherein the carbon film has a thickness of less than 1500 nm,
Laminating a film containing carbon atoms on a substrate;
Heating the film laminated on the substrate at 800-1400 ° C. in a nitrogen atmosphere to form a carbon film;
Including a step of peeling the carbon film from the substrate,
A method for producing a pellicle film. The carbon film comprises carbon or a turbostratic carbon structure derived from a compound containing carbon atoms;
The method for producing a pellicle film according to claim 5, wherein the compound containing a carbon atom is one or more selected from the group consisting of a polyimide compound and a polybenzoxazine compound.