WO2014142125A1 - Pellicle film, and pellicle - Google Patents

Abstract

Provided are a pellicle film and a pellicle which exhibit excellent transmittance with respect to extreme ultraviolet (EUV) light, and sufficient physical strength and durability in practical use, and with which film fragments can be easily removed, and excellent productivity can be achieved. A pellicle film (1) is configured using a carbon porous-body film, and has a film thickness (D) in the range of 100 nm - 63 µm.

Description

Pellicle membrane and pellicle

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

Semiconductor integrated circuits have been improved since the start of production in the 1960s, and the degree of integration has been improved. From the beginning of the 1970s to the present, the integration of about 4 times has been achieved in three years. The process continues. A technique that has contributed to the high integration of this semiconductor integrated circuit is an exposure technique called optical lithography. In this exposure technique, the minimum line width of the wiring of the semiconductor integrated circuit is determined by the resolution, and the obtained resolution is in accordance with the Rayleigh equation, the aperture of the exposure optical system, the apparatus constant called the K1 factor of the exposure apparatus, and the exposure wavelength λ ( Hereinafter, it is simply described as λ). As a result, in order to obtain a resolution of 45 nm or less, EUV lithography using λ = 6 to 14 nm of extreme ultraviolet light (hereinafter also referred to as EUV (Extreme Ultra Violet) light) called the EUV region is the most promising. It is thought that.

Current issues in EUV lithography development include output of EUV light source, EUV resist, EUV mask defects, contamination particles, and the like. Among them, the fact that the output of the EUV light source, specifically, the output of the EUV light source cannot be sufficiently increased greatly affects all the problems. For example, in the problem related to the contamination particles of the EUV mask, since EUV light is largely absorbed by almost all substances, the conventional exposure wavelength, 436 nm (g-line), 365 nm (i-line), 248 nm (KrF), 193 nm Unlike the transmission reduction projection exposure technique using (ArF) or the like, the EUV lithography uses the reflection reduction projection exposure technique, and all the components of the exposure apparatus including the EUV mask are arranged in a vacuum.

However, according to recent demonstration tests of EUV lithography, even if the components are placed in a vacuum, contamination particles may be generated in large amounts in the exposure apparatus, and it may be necessary to frequently clean the EUV mask. Is expected. Therefore, if the output (intermediate condensing point value) of the EUV light source can be obtained by several hundred W or more, a pellicle is required as usual.

As pellicle films used for EUV pellicles, those having the following four types of film structures have been proposed. The first film structure is made of an element having a low extinction coefficient k (hereinafter also simply referred to as k) with respect to EUV light, such as carbon nanotubes (Carbon Nano Tube: CNT), etc. It is grown at intervals of several tens of nm and a height of several μm (see, for example, Patent Document 1).

In the second film structure, an extremely thin flat film having a film thickness of 20 to 150 nm is formed using silicon Si as an element having a low k with respect to EUV light with λ = 13.5 nm, and this is used as a pellicle film for EUV. (For example, refer to Patent Document 2).

The third film structure is an element having low k with respect to EUV light (silicon (Si), ruthenium (Ru), iridium (Ir), gold (Au), rhenium (Rh), carbon (C), etc.), or Using a compound (aluminum nitride (AlN), silicon nitride (SiN), silicon carbide (SiC), etc.) and a single-layer or multi-layer flat film having a film thickness of 30 to 300 nm, and openings such as rectangular and honeycomb-shaped A composite membrane in which a so-called grid or mesh membrane (hereinafter also referred to as a support membrane) having a wire diameter of several tens of μm and a cycle of lines of several hundred μm to several mm is joined (hereinafter also referred to as a support membrane) ( For example, see Patent Documents 3 to 5 and Non-Patent Document 2).

In the fourth film structure, an airgel film made of an element (Si, Ru, C, etc.) having a low k for EUV light is used as a pellicle film for EUV. The airgel membrane is a sponge-like porous material containing a large number of micropores, mesopores, and macropores having an apparent density of several tens ^-3 to several tens ^-1 g / cm ³ , including air of 90.0 to 99.8%. It is a membrane. By using an airgel film in which the pore diameter in the airgel film is sufficiently smaller than the wavelength of the incident EUV light and the decrease in transmittance due to Rayleigh scattering is minimized, the film thickness is about 1.0 to 10.0 μm. It is said that a film having sufficient film strength and high transmittance for EUV light can be obtained without a film (see, for example, Patent Documents 6 and 7).

This film structure has the following features: (1) Absorption of substances in the EUV region is highly dependent on the type of element and density of the substance, and (2) a foam structure (porous film) that allows Rayleigh scattering. In this way, attention is paid to securing the film thickness and increasing the film strength. In particular, in Patent Document 6, a pellicle film for EUV light having a high EUV light transmittance is obtained by silicon aerogel (Si airgel) produced by electrochemically dissolving Si using a solution containing hydrogen fluoride HF as a main component. A pellicle film for EUV having high oxidation resistance can be obtained by using a metal foam aerogel prepared by irradiating a hydrogel containing a transition metal ion such as a noble metal or Ru with γ rays to deposit metal nanoparticles. It is said that.

Patent Document 7 shows an attempt to realize this film structure with CNTs. In this structure, the CNT itself is used as a pellicle film for EUV by forming a film having a thickness of 1.0 to 5.0 nm by some method. By setting the apparent density of the CNT film to 1.5 × 10 ⁻³ to 0.5 g / cm ³ , a film structure similar to an airgel can be obtained.

US Patent No. 776394 JP 2009-271262 A Japanese Patent Laying-Open No. 2005-43895 US Pat. No. 7,153,615 JP 2010-256434 A JP 2010-509774 A US Pat. No. 7,767,985

However, although the first film structure uses C as an element having a low k, the dust-proof protective film is in direct contact with the EUV mask surface, and the focus of the mask surface and a part of the pellicle film is Since they overlap, there is a possibility that the performance as a pellicle cannot be exhibited. In addition, the structure control of CNTs is extremely difficult, and the production cost may increase. Therefore, the first film structure is not realistic.

Even if Si with low k is used for the second film structure, if the transmittance when EUV light passes through the pellicle film twice is to be secured 50% or more, the film thickness needs to be 200 nm or less. is there. Therefore, in order to obtain a high transmittance, a flat film having a very thin film thickness is required, and it is difficult to ensure the strength of the film itself. Further, when Si is used as the pellicle film, if the pellicle film is damaged due to impact or the like, the fragments may adhere to the EUV mask surface. In this case, not only does it not function as a pellicle film, but there may arise a problem that it becomes contamination particles that are difficult to remove.

The third film structure is an effective configuration for securing the film strength, and enables the film thickness to be reduced. However, the support film itself acts as an obstacle and a limited visual field for the incident light to the EUV mask and the reflected light from the EUV mask, and the transmittance is reduced by about 30 to 60% compared to the transmittance of the flat film alone. It will be. Further, when a material other than carbon C is used as the material of the pellicle film, there may be a problem of contamination particles at the time of breakage.

The fourth film structure has an advantage in that not only the high transmittance to EUV light is ensured, but also the restrictions on the film thickness are greatly improved as compared with the second film structure and the third film structure. is there. However, the EUV pellicle film disclosed in Patent Document 6 has the following problems. That is, as in the third film structure, when an airgel film made of an element other than C is used as an EUV pellicle film, it is difficult to remove contamination if the EUV pellicle film is damaged for some reason such as impact. The problem of becoming particles can arise.

Moreover, when the CNT film | membrane shown by patent document 7 is used as an airgel film, there exist the following problems. Even if an extremely thin airgel film having a thickness of 1.0 to 5.0 nm is formed using CNTs having a diameter of 1 to 2 nm and a fiber length of several tens of μm, sufficient mechanical film strength cannot be obtained. On the other hand, in order to obtain sufficient mechanical film strength, when the apparent density is increased to a normal carbon density of about 1.5 g / cm ³ , it is possible to obtain a high transmittance as obtained with an original airgel film. Can not.

Furthermore, in general, CNT uses a large amount of a metal catalyst such as iron Fe, cobalt Co, nickel Ni or the like having a high extinction coefficient in the production process. Therefore, the CNT inevitably contains a large amount of impurities. It becomes a large carbon film, and high transmittance cannot be obtained. Further, when the impurities are removed in order to use only a carbon film having a low extinction coefficient, there is a problem that the productivity is lowered and the manufacturing cost is extremely increased.

The present invention provides a pellicle film and a pellicle that have high transparency to EUV light, have practically sufficient physical strength and durability, can easily remove film fragments, and are excellent in productivity. Objective.

As a result of intensive studies to solve the above-mentioned problems, the present inventor made a general-purpose carbon pellicle film material so that part of the film was damaged and adhered to the EUV mask surface. Even in this case, it is possible to easily remove the porous film having a pore diameter / pore diameter distribution and an apparent density that can be used for a pellicle at a low cost with high productivity. I found out that I can do it.

That is, the pellicle film according to one aspect of the present invention is composed of a carbon porous film, and the film thickness D is 100 nm to 63 μm.

In one embodiment, the transmittance T when the extreme ultraviolet light having the wavelength of 13.5 nm passes once is 84% or more, and the fineness of the carbon porous membrane when the extreme ultraviolet light passes once The scattering amount Δ due to the holes may be 10% or less.

In one embodiment, the apparent density obtained by dividing the mass by the volume in the porous carbon membrane may be 1.0 × 10 ⁻³ to 2.1 g / cm ³ .

In one embodiment, the wavelength λ of extreme ultraviolet light is 13.5 nm, the density W of graphite is 2.25 g / cm ³ , the apparent density (g / cm ³ ) of the porous carbon film is ρ, and the film thickness is D ( nm), the carbon porous membrane may have structural parameters satisfying the following formulas (1) to (5).
α ≦ 30 (α: pore size parameter) (1)
0.335 ≦ Nd ≦ 13 (N: number of pores in the film thickness direction (pieces), d: wall thickness of the pores (nm)) (2)
αλ / d ≦ 81 (λ: exposure wavelength (nm)) (3)
However, the above N and d are
N = −1 + {(W−ρ) ^1/3 / W ^1/3 } + {D (W−ρ) ^1/3 / αλW ^1/3 } (4)
d = −αλ + {αλW ^1/3 / (W−ρ) ^1/3 } (5)

In one embodiment, the wavelength λ of extreme ultraviolet light is 13.5 nm, the density W of graphite is 2.25 g / cm ³ , the apparent density (g / cm ³ ) of the porous carbon film is ρ, and the film thickness (nm) Is D, the carbon porous membrane may have structural parameters satisfying the following formulas (6) to (9).
α ≦ 30 (α: pore size parameter) (6)
αλ / d ≦ 81 (λ: exposure wavelength (nm)) (7)
0.08 g / cm ³ ≦ ρ ≦ 0.7 g / cm ³ (8)
D: 100 ≦ D ≦ 850 (9)

A pellicle according to another aspect of the present invention includes the pellicle film described above and a frame to which the pellicle film is attached.

In one embodiment, the frame may be provided with a groove in which a mask adhesive for bonding to the lithography mask is disposed on the surface opposite to the surface to which the pellicle film is attached.

In one embodiment, the frame may be provided with an electromagnet for bonding to the lithography mask on the surface opposite to the surface on which the pellicle film is supported.

According to the present invention, it has high transmittance to EUV light, has practically sufficient physical strength and durability, can easily remove film fragments, and has excellent productivity.

(A) is a graph which shows the relationship between an extinction coefficient, a transmittance | permeability, and a reflectance, (b) is a graph which shows the relationship between a refractive index, a transmittance | permeability, and a reflectance. It is a graph which shows the relationship between a wavelength, a refractive index, and an extinction coefficient. It is a graph which shows the relationship between an apparent density, a refractive index, and an extinction coefficient. It is a schematic diagram which shows the structural model of a carbon porous body film. It is a figure which shows the manufacturing process of a carbon porous body film. It is a perspective view which shows the pellicle which concerns on one Embodiment. It is a figure which shows the cross-sectional structure in the VII-VII line in FIG. It is a figure which shows the cross-sectional structure of a flame | frame. It is a figure which shows the cross-sectional structure of a flame | frame.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.

Hereinafter, after describing “1. Definition or explanation of terms used in this embodiment”, this embodiment will be described in the order of “2. Pellicle film of this embodiment” and “3. Pellicle of this embodiment”. I will explain it.

1. Definition or explanation of terms used in this embodiment [reference value of this embodiment]
The reference value of the present embodiment indicates three physical property values of transmittance, scattering amount, and film thickness of a pellicle film that is preferable for achieving the object of the present embodiment.

The transmittance T of the pellicle film (hereinafter also referred to as T, the unit is%) is preferably 70% or more of the reflectance of a single reflector used in EUV lithography, and is used as a reference value for T. At the time of exposure, EUV (Extreme Ultra Violet) light is generally incident and reflected on the EUV mask surface at an incident angle θ = 6 °, and the pellicle film covering the EUV mask surface is reciprocated twice. Therefore, the preferable T when passing through the pellicle film once is 84% or more (since passing twice, it becomes 84% × 84% = 70%). Similarly, in order to obtain T of 80% or more and 90% or more at the time of two passes, the necessary T at the time of one pass is 89% or more and 95% or more, respectively. The reference value for T is hereinafter referred to as “transmittance reference value”, and the reference values of 84%, 89%, and 95% are set as the first transmittance reference (T1), the second transmittance reference (T2), and the third reference value, respectively. This is referred to as the transmittance standard (T3).

When the pellicle film is a porous film, the amount of scattering (hereinafter also referred to as Δ, the unit is%) is not only small when T is small, but also the blur of the circuit image on the EUV mask surface during exposure. Is generated. Therefore, it is desired that the scattering amount is as small as possible, but there is no clear reference value. In the present embodiment, the upper limit of the amount of scattering considered to be a preferable range when passing through the pellicle film once is defined as the “scattering amount reference value”, and the reference values of 10%, 5%, and 1% are respectively used as the first scattering. These are referred to as an amount reference (Δ1), a second scattering amount reference (Δ2), and a third scattering amount reference (Δ3). Regarding the amount of scattering, it is considered that the amount of scattering when the pellicle film covering the EUV mask surface is passed twice in a reciprocating manner is approximately twice the amount of scattering when passing once.

The film thickness of the pellicle film (hereinafter also referred to as D, the unit is nm) has a great influence on the film strength (bending rigidity of the film) and the ease of handling of the film. In a pellicle film using a conventional flat film of Si alone, D is unavoidably set to 50 to 100 nm in order to obtain a T of 70% or more when passing through the pellicle film twice. By using a carbon porous membrane as in this embodiment, D can be made thick while maintaining the transmittance. Therefore, D = 100 nm or more is set as the minimum necessary film thickness of the present embodiment. The film thickness D is preferably 300 nm or more, more preferably 500 nm or more. The reference value for D is hereinafter referred to as “film thickness reference value”, and the standards of 100 nm, 300 nm, and 500 nm are respectively referred to as the first film thickness standard (D1), the second film thickness standard (D2), and the third film thickness standard ( D3).

[Structural model of pellicle film of this embodiment]
The pellicle film of this embodiment is composed of a carbon porous film, and the thickness D of the pellicle film is 100 nm to 63 μm. The pellicle film of this embodiment preferably has a specific structure described later. Hereinafter, the premise, the structural model of the carbon porous film, and each structural parameter used for defining the structure of the pellicle film will be described.

(Assumption 1)
An actual carbon porous membrane has a monodisperse pore structure (a structure model in which the pore diameter, wall thickness or column thickness, shape, etc. of the pores are the same and the aggregate state of such pores is uniform. It has a polydispersed structure in which various pores are mixed. However, in this embodiment, in order to simplify the discussion, the carbon porous film actually obtained is approximated to a carbon porous film composed of monodispersed cubic shell-shaped or cubic frame-shaped pores as described later (hereinafter, respectively). Are sequentially referred to as a cubic wall group pore model and a cubic axis group pore model), and the structure thereof can be defined by structural parameters.

(Assumption 2)
The values of the density W of graphite (gC) and the density of amorphous carbon (aC) at room temperature are 2.25 to 2.26 g / cm ³ (W = 2 in this embodiment), respectively. and .25g / cm ^3), the density of a-C is 1.8 ~ 2.1g / cm ^3. Therefore, the actual density of carbon takes a value within the range of 1.8 to 2.26 g / cm ³ depending on the crystallinity.

As described above, the carbon constituting the pore wall or column of the actual carbon porous film is not all formed of graphite crystals, but in this embodiment, the graphite microcrystals aggregate in a non-oriented manner. It is assumed that it is formed of a polycrystalline body. If the crystallinity of the carbon is low and the density is less than 2.25 g / cm ³ , the wall thickness or column thickness d, or the substantial wall thickness dN or column thickness dN, as will be described later in [Appendix]. ^1/2 can be increased depending on the optical constant (particularly k) of the carbon at that density.

Based on (Premise 1) and (Premise 2), as a pore structure model of the carbon porous membrane of the present embodiment, a cubic shell shape having a wall thickness or a column thickness d as shown in FIG. Alternatively, a structure in which N pieces of cubic frame-shaped pores (pore diameter L) are stacked in the thickness direction is referred to as a cubic wall group pore model and a cubic axis group pore model, respectively. It is assumed that the layers in which the cubes are spread are stacked while being shifted in the thickness direction so that the apexes of the four corners of each cube are located in the center of the surface of the adjacent cube in the thickness direction. Assuming a pore structure model, L0 = L + d (10) between L, L0, d, film thickness D, number N of pores, and pore size parameters α, d.
D = Nαλ + (N + 1) d (11)
The relationship is established.

Furthermore, the structure of the porous membrane of the present embodiment can be defined using first and second structure parameters described later, and between each structure parameter, an equation ( 12) to (14) are related to the cubic axis pore model, and the relationships of (15) to (17) are established.
N = −1 + {(W−ρ) ^1/3 / W ^1/3 } + {D (W−ρ) ^1/3 / αλW ^1/3 } (12)
d = αλ {−1 + W ^1/3 / (W−ρ) ^1/3 } (13)
ρ = W [(L0 ³ −L) / L0 ³ ] = W [{(1 + αλ / d) ³ − (αλ / d) ³ } / (1 + αλ / d) ³ ] (14)
N = 8.32 × 10 ⁻¹ {D / (αλ)}-10.64 {ρ} + 3.54 × 10 ⁻² {D ^1/2 } + 7.65 × 10 ⁻¹ (15)
^{d = 7.90 × 10 -1 {ραλ} } + 8.43 × 10 -1 {(αλ) 1/2} -7.93 × 10 -1 {ρ -1/3} -7.60 × 10 -1 ... (16)
ρ = W [{8 (d / 2) ² · (L + d / 2) +4 (d / 2) ² · L} / L0 ³ ] = W (1 + 3αλ / d) / (1 + αλ / d) ³ (17)

Regarding the cubic wall set pore model, Equations (11) and (14) use the first structure parameter group to represent the second structure parameter group, and Equations (12) and (13) represent the second structure parameter group. Represents the first structural parameter group.

Regarding the cubic axis pore model, Equations (11) and (17) use the first structure parameter group to represent the second structure parameter group, and Equations (15) and (16) represent the second structure parameter group. Represents the first structural parameter group.

[Structural parameters]
The preferred structure of the carbon porous membrane in the present embodiment is determined according to the following three physical property values, T, Δ, and D reference values. And the structure of the carbon porous membrane includes the pore diameter (L) or the pore size parameter (α), the wall thickness or column thickness (d) forming the pores, and the number of pores stacked in the film thickness direction ( N) is defined as the first structural parameter group, and the apparent density of the carbon porous membrane described as L (or α), D, and ρ (ap) or ρ is defined as the second structural parameter group, and these structural parameters are defined. It shall be possible. The first structural parameter group is a microscopic structural parameter, which is convenient for defining the structure of the carbon porous membrane, but it is difficult to measure and observe directly and indirectly, and these are difficult in the manufacturing process. It is difficult to control and define the structure of the film using the value of. The second structural parameter group is a macroscopic structural parameter, and it is relatively easy to measure and observe directly and indirectly, and it is easy to control the structure using these values in the manufacturing process. A microscopic structure cannot be uniquely determined without assuming a pore structure model from the value of.

If a structural model of the carbon porous membrane is assumed between the two structural parameter groups, Equation (12) to Equation (14) are obtained in the cubic wall-assembled pore model, and Equation (15) is obtained in the cubic shaft-assembled pore model. Although a concrete relationship as shown in Equation (17) is established, it is impossible to always take a strict correspondence.

In the present embodiment, the contents are described using both structural parameter groups as appropriate, and when there is a contradiction between the two, the second structure in which the structure of the carbon porous membrane can be easily specified within a range that satisfies the reference value. The parameter group is used with priority.

[Pore diameter L, pore radius r]
The pore diameter (L) is the peak peak radius r (peak) of the peak of the pore distribution curve obtained from the adsorption isotherm of the gas adsorption type pore distribution measurement method, and the maximum peak radius r (max) (pore L (peak) and L (max) are values obtained by doubling the values of the distribution radius and the pore distribution base (pointing to the larger pore radius value) (referred to as double values), respectively. The unit is [nm]. Note that r (max) and L (max) are used when discussing the upper limit of each criterion of Δ, and otherwise L (peak) is L and r (peak) is r unless otherwise specified. Use. Experimentally and empirically, Junichi Hayashi, Toshihide Horikawa, Carbon, No. 236, 15-21 (2009) [hereinafter referred to as Reference A], as shown in FIG. 6 and FIG. 8, r (max) is a logarithmic scale of r on the horizontal axis of the pore distribution diagram. In the pore distribution curve whose axis is dV / d [Log (r)] of the integral pore volume, it is often about 1.5 to 3 times r (peak). Further, when the peak of the pore distribution is low and r (max) is difficult to understand, r (peak) is set as an alternative value for r (max).

In gas adsorption type pore distribution measurement, usually a carbide sample is heated in vacuum at 200-250 ° C for 2-15 hours in advance, then nitrogen adsorption / desorption isothermal measurement at liquid nitrogen temperature is performed, and DH analysis is performed from the adsorption / desorption isotherm. The pore distribution curve is obtained by the method or the BJH analysis method. In this embodiment, this method is used to determine the pore diameter.

[Pore size parameter α]
The pore size parameter (α) means that when the pore diameter is L and the wavelength of EUV light used for exposure is λ,
α = L / λ (18)
The pore diameter is expressed as a multiple of λ. In this case, α is about 1/3 of the size parameter Λ (≡2πγ / λ = πα, where γ is the radius of the spherical scatterer and π is the pi) used in the usual Mie scattering theory. It has become.

In the cubic wall set pore model, the pore diameter can be substantially defined because the individual pores are separated by walls. In the cubic axis set pore model, the individual pores are connected, and as shown in FIG. 4B, the values are strictly classified (virtual).

[Wall Thickness or Column Thickness d]
The pore wall thickness or column thickness (d) in the present embodiment delimits individual pores constituting the carbon porous membrane in the cubic wall set pore model (becomes a pore barrier). It is the average thickness of the carbon wall, and the thickness of the wall of the cubic wall set. In the cubic axis pore model, the average thickness of carbon rods (columns) that formally divide the pores that make up the carbon porous membrane, and the thickness of the cubic frame It is. The unit is [nm].

D can be obtained by taking a cross-sectional photograph of the porous film using a transmission electron microscope (TEM) or a scanning electron microscope (SEM) and processing the photograph. However, since observation at a high magnification itself is extremely difficult, and further, it is doubtful whether the information itself obtained from the cross-sectional photograph is local and the average wall thickness of the porous film is used. The value calculated from α and ρ (ap) by Equation (13) for the cubic wall group pore model and by Equation (16) for the cubic axis group pore model is d.

Considering that the size of carbon atoms is about 0.33 nm and the interlayer distance of graphite (which can be regarded as a laminate of graphene sheets) is 0.335 nm, the value of d is about 0. 335 nm is the lower limit of d. However, in the graphene sheet 1 layer or 2 layers (d = about 0.67 nm), when the pore diameter is large (for example, α> 4) or when a large force is applied to the pellicle film, the wall strength or the column strength (film strength) In reality, a graphene sheet having four layers (d = 1.35 nm) or more is preferable. Of course, when the pore diameter is small (for example, α <1) or when a large force is not applied to the membrane, d can be brought close to 0.335 nm.

[Number of pores N]
The number of pores (N) is the number of pores having a pore diameter L in the film thickness direction. In the present embodiment, N is a value calculated from α, ρ (ap), and D according to Equation (12) in the cubic wall group pore model and according to Equation (15) in the cubic axis group pore model. N should be an integer of N ≧ 1 in the definition of the word, but a positive real value is allowed. The fractional part of the numerical value below the decimal point is considered to reflect the deviation from the pore structure model in which monodispersed cubic shell-like or cubic frame-like pores are neatly stacked.

[Apparent density ρ (ap), Arithmetic apparent density ρ]
The apparent density ρ (ap) is a density using the membrane volume when it is assumed that there are no pores inside the porous membrane, and the ratio between the membrane volume V and the membrane mass G obtained from the outer dimensions of the membrane. , G / V. On the other hand, the arithmetic apparent density ρ is based on the pore structure model, in the present embodiment, according to the equation (14) for the cubic wall assembly pore model and the equation (17) for the cubic axis assembly pore model. A value calculated from α, ρ (ap), and D is ρ. Since (Assumption 1) and (Assumption 2) are assumed, ρ (ap) = ρ is treated without distinction between the two. The unit is [g / cm ³ ].

[Film thickness D]
The film thickness (D) is the thickness of a sheet, film, or film used in the usual sense. The measurement of the thickness of this embodiment can be obtained as a value obtained by averaging 10 or more images of a porous film in a non-contact manner with an interval of 1 mm or more using an electron microscope (SEM). The unit is usually [nm], and [μm] is also used as necessary.

[Pore shape]
The average pore shape of the porous membrane is described in Reference A, Hideki Matsuoka, Journal of Crystallographic Society, No. 41, 213-226 (1999), Keiko Nishikawa, Carbon, No. 191, 71-76 (2000), it can be obtained from the scattering intensity analysis in the Debye-Porod region of small angle X-ray scattering (SAXS). That is, when the logarithmic plot of the X-ray scattering intensity I as a function of the scattering vector s is a logarithmic slope of −4, −2, and −1, the pore shape is spherical, disk-shaped, cylindrical, respectively. Means that

2. 2. Pellicle membrane of this embodiment and method for manufacturing the pellicle membrane 2-1. Pellicle of this embodiment The pellicle film of this embodiment will be described in detail below for each [technical point].

[Technical point 1]
The technical point 1 is that the pellicle membrane is a porous membrane. In Mie's scattering theory (Mie scattering itself is scattering by spherical particles, but qualitatively the shape is not limited), light scattering by spherical particles (spherical pores) is the diameter of the particles (pores). When the pore size is 2γ, the wavelength of incident light is λ, and the particle size parameter Λ (= 2πγ / λ) is used, Rayleigh scattering occurs when Λ is sufficiently smaller than 1 (Λ << 1). , Λ is almost 1 (Λ≈1), Mie scattering occurs, and when Λ is sufficiently larger than 1 (Λ >> 1), geometric scattering occurs. Therefore, when the pore diameter is a porous body (porous film) with Λ ≧ 1, when light is incident upon exposure, the light is scattered at the interface between the pore wall or the column and the pore portion, and sufficient transmittance is obtained. It is considered that the circuit image of the mask cannot be correctly formed on the wafer (see Patent Documents 6 and 7).

However, even in the case of a porous body (porous film) having a pore diameter of Λ ≧ 1 or more, when the refractive index of the pore wall or column is equal to the pore portion, that is, the refractive index of vacuum 1.0, When the difference Δn between the refractive index of the column and the refractive index of the pore (space in the pore) is close to 0, for example, Δn = 0.04 or less, the light is the interface between the pore wall and the pore. It was found that it was possible to go straight with almost no reflection or scattering.

FIG. 1 shows the optical constant and transmittance T at an incident angle θ = 6 ° of a flat film (non-porous film) assuming the values of optical constants (refractive index n, extinction coefficient k) and film thickness D. The graph which showed the relationship with the reflectance R is shown. The graph shown in FIG. 1 is calculated using a “G-Solver grid analysis software tool (G-Solver)” commercially available from “Grating Solver Development Company”. FIG. 1A shows the dependence of T and R on k for a flat film with D = 100 nm and n = 1.0, and FIG. 1B shows the flat film with D = 100 nm and k = 0.0005. Is a graph showing the dependence of T and R on n. In FIG. 1A, a region surrounded by a dotted line indicates a region k that can secure T ≧ 84%. From FIG. 1 (a), when T changes significantly with a slight change of k and the film thickness is about 100 nm with a non-porous film, T ≧ T1 = 84% unless at least k is less than the order of 10 ^−3. It can be seen that cannot be obtained.

Further, in FIG. 1B, the region surrounded by a dotted line indicates an n region where the reflectance R ≦ 0.2%. As can be seen from FIG. 1B, when n = 0.94 to 1.4, that is, Δn ≦ 0.04, reflection from the interface is suppressed and T is maximized.

The first advantage of using a porous film as the pellicle film is that the thickness limitation of the 50 to 100 nm film in the conventional Si single crystal flat film is greatly relaxed, and T is T1 or more and Δ is Δ1 or less as described later. And D can be 100 nm or more (D1 or more), 300 nm or more (D2 or more), or 500 nm or more (D3 or more).

A second advantage of using a porous film as a pellicle film is that a corrugated cardboard-like porous wrapping paper material has a higher bending rigidity than a flat film-like paper board having the same weight and the same area. The film has higher bending rigidity than a flat film (non-porous film) having the same weight and the same area.

Whereas the corrugated cardboard plate is a porous structure having a straw-like one-dimensionally extending hole inside, the porous film of the present embodiment has a three-dimensional porous structure, so that the stress concentration is further increased. It can be said that the bending rigidity of the film is even higher. As a result, when the porous film of the present embodiment is used as a pellicle film, the degree of bending of the film by its own weight is small compared to a flat film of another material having the same area and weight.

[Technical point 2]
Technical point 2 is that the porous film is made of carbon. The first advantage of using carbon as the porous film is the superiority of the carbon in the porous film as an optical constant. In general, when the density depending on the kind of elements constituting the film and the ratio of the crystalline / amorphous structure of the film is determined, the optical constants n and k in the EUV region can be obtained from Non-Patent Document 1. Actually, for the calculation of specific numerical values, the web page of CXRO (The Center for X-ray Optics) <http: // henke. lbl. gov / optical_constants / getdb2. html> was used.

As the density, n and k obtained by using the apparent density ρ of the porous film, which is smaller than the density of the non-porous material (usually simply called the density or the true density), are the crystal / amorphous structure and its ratio. Assuming that does not change, the value can be regarded as the optical constant of the porous film having that ρ. Here, if a flat film (non-porous film) having an apparent density ρ and an optical constant at the ρ is referred to as a porous film alternative flat film, various ρs ignoring scattering by the pores for convenience. The n and k of the porous membrane alternative flat membrane that can be obtained can be obtained from Non-Patent Document 1.

FIG. 2 shows carbon C (density 2.2 g / cm ³ ), silicon Si (density 2.33 g / cm ³ ), silicon carbide SiC (density 3.2 g / cm ³ ), and apparent density ρ = 0.6 g / cm. ³ is a graph showing the dependence of C of ^{3 on} the wavelength λ of n and k. As shown in FIG. 2, the optical constants of Si and SiC change discontinuously due to the L absorption edge of Si near λ = 12 nm, whereas the optical constant of C is continuous, n increases monotonously, and k Decreases monotonously. In particular, when λ ≦ 12 nm, C (ρ = 0.6 g / cm ³ ) is smaller than Si and SiC.

FIG. 3 is a graph showing optical constants n and k at λ = 13.6 nm and λ = 6.7 nm for C at various apparent densities ρ, and the optical constants in the EUV region are In the case of Si (2.33 g / cm ³ ) corresponding to the wavelength range of light to be used and the density of materials, for example, corresponding to the wavelength range of λ = 6.7 to 13.6 nm, k is 9.5. × 10 ⁻³ (λ = 6.7 nm) to 1.8 × 10 ⁻³ (λ = 13.6 nm), n is 0.99 (λ = 6.7 nm) to 1.0 (λ = 13.6 nm) On the other hand, in the case of carbon, in the case of graphite (2.25 g / cm ³ ), k is 7.6 × 10 ⁻⁴ (λ = 6.7 nm) to 7.2 × 10 ⁻³ (λ = 13. 6 nm) and n are 0.99 (λ = 6.7 nm to 0.96 (λ = 13.6 nm).

This indicates that Si is more suitable than graphite in producing a pellicle film in the λ = 13.6 nm region, but graphite is rather superior in the λ = 6.7 nm region.

Further, when carbon is formed into a porous film as in the present embodiment, k is 2.0 × 10 ⁻⁴ (λ = 6.7 nm) to 1.9 × 10 6 for C with ρ = 0.6 g / cm ^{3. -3} (λ = 13.6 nm) and n is 1.0 to 0.99. For C with ρ = 0.4 g / cm ³ , k is 1.4 × 10 ⁻⁴ (λ = 6.7 nm) to 1.3 × 10 ⁻³ (λ = 13.6 nm), and n is 1.0 ( λ = 6.7 nm) to 0.99 (λ = 13.6 nm). For C with ρ = 0.2 g / cm ³ , k is 6.8 × 10 ⁻⁵ (λ = 6.7 nm) to 6.4 × 10 ⁻⁴ (λ = 13.6 nm), and n is 1.0 ( λ = 6.7 nm) to 1.0 (λ = 13.6 nm). For C with ρ = 0.08 g / cm ³ , k is 2.7 × 10 ⁻⁵ (λ = 6.7 nm) to 2.6 × 10 ⁻⁴ (λ = 13.6 nm), and n is 1.0 ( λ = 6.7 nm) to 1.0 (λ = 13.6 nm).

In this way, carbon is converted into a porous film, and the apparent density is lowered, so that not only λ = 6.7 nm region but also λ = 13.6 nm region has a low k equal to or higher than Si and an n close to 1.0. Will have.

A second advantage of using carbon as the porous film is that the pellicle film can be easily removed even if it is damaged and adhered to the mask. For example, Noriaki Takagi et al., Ritsumeikan University research report, Ritsu S22-03, “Carbon deposition experiment on EUV lithography mask: Evaluation of cleaning technology”, Hiroaki Oizumi, Ph.D. As introduced in “Basic Lithography Technology Using Ultraviolet (EUV)” (March 2007), VUV light (λ = 172 nm) and EUV light (λ = 13. 5 nm) itself is used to oxidize with active oxygen to carbon monoxide CO or carbon dioxide CO ₂ (oxidation method), or to reduce with atomic hydrogen to methane hydrocarbon (CH _X ) By the (reduction method), carbon adhering to the EUV mask can be removed.

A third advantage of using carbon as the porous film is that a porous film having a target pore diameter and film thickness can be easily produced by applying an existing carbon porous film manufacturing method. That is, as described in “2.2 Pellicle membrane manufacturing method of this embodiment”, a thin film is formed using a solution of an organic compound that causes a sol-gel transition, and a large amount of solvent is contained by the sol-gel method. By forming a hydrogel state and then drying and removing the solvent so that the structure is not crushed, an airgel film as a porous body containing a large amount of bubbles can be obtained. Finally, the airgel membrane is carbonized to obtain a carbon porous membrane as a carbon aerogel, or a polymer raw material (organic compound) that immobilizes the structure in the molecular structure during the chemical reaction process or carbonization process and generates bubbles. A method for obtaining a carbon porous film having pores or gaps generated in the process after a thin film is formed and then chemical reaction or carbonization reaction, or a combination of these methods. Method.

As a thin film technology, unlike the vapor deposition method, the film thickness can be easily controlled using a wet coating method in a non-vacuum environment such as spin coating, die coating, and gravure coating using a polymer solution, or silicon. As in the wafer manufacturing method, a rod-shaped material is thinly cut and polished to form a thin film, thereby enabling high-productivity manufacturing.

A fourth advantage of using carbon as the porous film is that it has excellent thermal characteristics and bending rigidity. The melting point and thermal expansion coefficient of amorphous carbon (aC), graphite (gC) and Si are as follows. That is, the melting point under normal pressure is the highest among all elements, and a-C and g-C have no melting point, Si has 1414 ° C., and the heat resistance of carbon is excellent. The coefficient of thermal expansion is 3.0 × 10 ⁻⁶ / K for ^aC , 3.2 × 10 ⁻⁶ / K for gC, and 3.9 × 10 ⁻⁶ / K for Si. Excellent dimensional stability.

On the other hand, the bending stiffness corresponding to the hardness (physical strength) of the film is proportional to the product of the Young's modulus and the cube of the film thickness D because the Poisson's ratio of carbon and Si is both about 0.2. The Young's modulus of aC is 30 to 33 GPa and the Young's modulus of gC is 14 GPa, whereas the Young's modulus of Si is 130 to 190 GPa. Si is superior to carbon, but in the present embodiment, it is actually a porous carbon film, and since the film thickness D can be made 2.5 to 5 times thicker than the Si flat film, The carbon porous membrane of this embodiment is considered to be larger.

[Technical point 3]
The technical point 3 is that a carbon porous film that satisfies the problem can be defined using restricted structural parameters.

If the structural parameters of the carbon porous membrane are within a specific range that satisfies the constraints that reflect the actual strength of the carbon membrane and experience values in manufacturing, and the reference values for T, Δ, and D, EUV lithography A pellicle film that is suitably used can be obtained. Hereinafter, steps will be described in order.

[Relationship between structural parameter group and reference values (Ti, Δi, Di, i = 1 to 3)]
(1) Step 1
In the N = 1 to 5 layer cubic wall group pore model and the cubic axis group pore model, models were prepared in which d and α were changed in various ways. The optical constants n and k (λ 9.61 × 10 ⁻¹ and 7.70 × 10 ⁻³ ) and λ, respectively, of λ = 13.5 nm of carbon (2.25 g / cm ³ ) obtained from Non-Patent Document 1. = Optical constants n and k at 6.75 nm (9.91 × 10 ⁻¹ and 7.70 × 10 ⁻⁴ , respectively) and diffractive optical element design / analysis software DiffractMOD by RCWA method manufactured by RSsoft The T, Δ, and D at the incident angle θ = 6 ° of each model were calculated. Note that T is the 0th-order transmittance, and Δ is the value obtained by subtracting the 0th-order transmittance from the total transmittance.

In addition to the above-described method using DiffractMOD, there is a method using G-Solver as described above for calculating T, Δ, and D. The former requires a long calculation time because the calculation is complicated and sophisticated, but can cope with both the cubic wall set pore model and the cube axis pore model. On the other hand, the latter is relatively simple and has a fast calculation time, but corresponds only to the cubic wall-assembled pore model, and the calculation result has a transmittance T of 70 to 100% in a single pass. The value of T becomes larger by about 10% at maximum, and the value of Δ becomes smaller by about 5% at maximum when the scattering amount Δ is in the range of 0 to 10%. In the present embodiment, unless otherwise specified, the former applicable to either pore structure model is preferentially used as a calculation method.

The obtained results were subjected to multiple regression analysis using the EXCEL multivariate analysis software tool (multiple regression software) commercially available from Sumi Co., Ltd., and the first structural parameters in each pore structure model The influence of the group and the second structural parameter group on the T and Δ of the carbon porous membrane was determined.

<Step 1-1>
Influence of T, Δ by the first structural parameter group N, d, α in the cubic wall set pore model

As a result of the multiple regression analysis by the first structural parameter group N, d, α in the cubic wall set pore model, the multiple regression equation for T at λ = 13.5 nm is
T = [− 7.65 × 10 ⁻³ {α} −1.53 × 10 ⁻² {dN} + 9.95 × 10 ⁻¹ ] × 100 (19)
Degree-of-freedom corrected coefficient of determination R ^{* 2} = 0.97
The dependence of each factor obtained using the magnitude relationship of the absolute value of the standard partial regression coefficient (the absolute value of the standard partial regression coefficient of each factor is divided by the sum of the absolute values of the standard partial regression coefficients of all factors. As a percentage, α was 28% and dN was 72%. Note that the multiple regression equation for T is theoretically preferable in order to explain that the transmittance when passing through the pellicle membrane twice needs to be almost squared, etc.
In (T) = [− 1.13 × 10 ⁻² {α} −2.04 × 10 ⁻² {dN} + 2.93 × 10 ⁻² ] (20)
R ^{* 2} = 0.95
However, Equation (19) having a large R ^{* 2} was used in the subsequent calculations.

Also, the multiple regression equation for Δ at λ = 13.5 nm is
Δ = [5.05 × 10 ⁻⁴ {dNα} + 3.66 × 10 ⁻³ ] × 100 (21)
R ^{* 2} = 0.92
It became.

On the other hand, the multiple regression equation for T at λ = 6.75 nm is
T = [− 1.98 × 10 ⁻³ {α} −4.68 × 10 ⁻³ {dN} +1.01] × 100 (22)
R ^{* 2} = 0.91
Thus, the dependency rate of each factor was 34% for α and 66% for dN. The multiple regression equation for T is
In (T) = [- 2.16 × 10 -3 {α} -5.05 × 10 -3 {dN} + 1.24 × 10 -2] ... (23)
R ^{* 2} = 0.90
However, equation (22) having a large R ^{* 2} was used in the subsequent calculations.

Also, the multiple regression equation for Δ at λ = 6.75 nm is
Δ = [1.49 × 10 ⁻⁴ {dNα} −1.47 × 10 ⁻⁴ ] × 100 (24)
R ^{* 2} = 0.94
It became.

From these results, in the cubic wall set pore model, T is the product of the pore wall thickness and the number of laminated pores, that is, the material of the film constituting Nd in the film thickness direction. It can be seen that a large thickness (corresponding to the thickness of the flat membrane) has a great influence, and α corresponding to the size of the pores has no influence as much as the former factor. On the other hand, since Δ is in the form of a product of αNd, it can be seen that α and Nd affect the same extent. α physically corresponds to the pore diameter L (= λα), meaning that Δ is easily affected by the pore diameter.

<Step 1-2>
Influence of T, Δ by the first structural parameter group N, d, α in the cubic frame pore model

As a result of the multiple regression analysis by the first structural parameter group N, d, α in the cubic axis pore model, the multiple regression equation for T at λ = 13.5 nm is
T = [6.02 × 10 ⁻³ {α} −8.69 × 10 ⁻³ {dN ^1/2 } +1.00] × 100 (25)
R ^{* 2} = 0.86
Thus, the dependency rate of each factor was 33% for α and 67% for dN ^1/2 . The multiple regression equation for T is
In (T) = [6.86 × 10 ⁻³ {α} −5.01 × 10 ⁻³ {dN} −1.34 × 10 ⁻² ] (26)
R ^{* 2} = 0.79
However, equation (25) having a large R ^{* 2} was used in the subsequent calculations.

Also, the multiple regression equation for Δ at λ = 13.5 nm is
Δ = [1.99 × 10 ⁻³ {dN ^1/2 } −1.25 × 10 ⁻² ] × 100 (27)
R ^{* 2} = 0.71
It became. It should be noted that the multiple regression equation for Δ is theoretically preferable in order to explain that it is necessary to almost double the value when the scattering rate when passing through the pellicle film twice passes,
Δ = [9.14 × 10 ⁻⁴ {dN} −7.55 × 10 ⁻³ ] × 100 (28)
R ^{* 2} = 0.66
However, Equation (27) having a large R ^{* 2} was used in the subsequent calculations.

On the other hand, the multiple regression equation for T at λ = 6.75 nm is
T = [1.07 × 10 ⁻³ {α} −2.95 × 10 ⁻³ {dN ^1/2 } +1.00] × 100 (29)
R ^{* 2} = 0.91
Thus, the dependency rate of each factor was 22% for α and 78% for dN ^1/2 . The multiple regression equation for T is
In (T) = [1.06 × 10 ⁻³ {α} −1.51 × 10 ⁻³ {dN} + 2.84 × 10 ⁻⁴ ] (30)
R ^{* 2} = 0.91
Although both could be approximated, Equation (29) was used in the subsequent calculations because of its consistency with Equation (25).

Also, the multiple regression equation for Δ at λ = 6.75 nm is
Δ = [9.06 × 10 ⁻⁴ {dN ^1/2 } −5.50 × 10 ⁻³ ] × 100 (31)
R ^{* 2} = 0.63
It became. The multiple regression equation for Δ is
Δ = [4.34 × 10 ⁻⁴ {dN} −3.85 × 10 ⁻³ ] × 100 (32)
R ^{* 2} = 0.62
However, Equation (31) having a large R ^{* 2} was used in the subsequent calculations.

From these results, in the cubic axis set pore model, T is a value of dN ^1/2 which is considered to correspond to a substantial thickness in the film thickness direction corresponding to dN of the cube wall set pore model. Has a great influence, and it can be seen that α corresponding to the size of the pore does not influence as much as the former factor. On the other hand, Δ is a connected pore in the cubic axis pore model, and since α has only a formal meaning, α is regarded as 1 and has an influence in the form of dN ^1/2 . That is, it means that there is no influence of the pore diameter.

<Step 1-3>
Influence on T and Δ by the second structural parameter group ρ, D, α in the cubic wall group pore model and the cubic axis group pore model

Subsequently, the influence of the second structural parameter group ρ, D, α on T, Δ is examined. As a result of the multiple regression analysis using the second structural parameter group ρ, D, α in the cubic wall set pore model, the multiple regression equation for T at λ = 13.5 nm is
T = [− 1.26 × 10 ⁻³ {Dρ (λα) ^1/2 } −9.52 × 10 ⁻³ {ρD} + 9.60 × 10 ⁻¹ ] × 100 (33)
R ^{* 2} = 0.98
Thus, the dependency ratio of each factor was 60% for Dρ (λα) ^1/2 and 40% for ρD. Also, the multiple regression equation for Δ at λ = 13.5 nm is
Δ = [9.72 × 10 ⁻⁴ {Dρ (λα) ^1/2 } −3.75 × 10 ⁻³ (ρD) + 3.16 × 10 ⁻³ ] × 100 (34)
R ^{* 2} = 0.93
Thus, the dependency rate of each factor was 74% for Dρ (λα) ^1/2 and 26% for ρD.

On the other hand, the multiple regression equation for T at λ = 6.75 nm is
T = [− 6.62 × 10 ⁻⁴ {Dρ (λα) ^1/2 } −1.41 × 10 ⁻³ (ρD) + 9.96 × 10 ⁻¹ ] × 100 (35)
R ^{* 2} = 0.99
Thus, the dependency ratio of each factor was 81% for Dρ (λα) ^1/2 and 19% for ρD.

Also, the multiple regression equation for Δ at λ = 6.75 nm is
Δ = [4.49 × 10 ⁻⁴ {Dρ (λα) ^1/2 } −1.11 × 10 ⁻³ {ρD} −1.84 × 10 ⁻³ ] × 100 (36)
R ^{* 2} = 0.95
Thus, the dependency rate of each factor was 78% for Dρ (λα) ^1/2 and 22% for ρD.

On the other hand, as a result of the multiple regression analysis using the second structural parameter groups ρ, D, and α in the cubic frame pore model, the multiple regression equation for T at λ = 13.5 nm is
T = [− 1.59 × 10 ⁻⁴ {Dρ (λα) ^1/2 } −1.59 × 10 ⁻³ {ρD} + 9.66 × 10 ⁻¹ ] × 100 (37)
R ^{* 2} = 0.99
Thus, the dependency ratio of each factor was 35% for Dρ (λα) ^1/2 and 65% for ρD.

Also, the multiple regression equation for Δ at λ = 13.5 nm is
Δ = [1.59 × 10 ⁻⁴ {Dρ (λα) ^1/2 } −3.57 × 10 ⁻⁴ (ρD) −2.41 × 10 ⁻³ ] × 100 (38)
R ^{* 2} = 0.91
Thus, the dependency ratio of each factor was 70% for Dρ (λα) ^1/2 and 30% for ρD.

On the other hand, the multiple regression equation for T at λ = 6.75 nm is
T = [− 8.20 × 10 ⁻⁵ {Dρ (λα) ^1/2 } −3.27 × 10 ⁻⁴ (ρD) +1.00] × 100 (39)
R ^{* 2} = 0.99
Thus, the dependency rate of each factor was 54% for Dρ (λα) ^1/2 and 46% for ρD.

Also, the multiple regression equation for Δ at λ = 6.75 nm is
Δ = [7.60 × 10 ⁻⁵ {Dρ (λα) ^1/2 } −1.66 × 10 ⁻⁴ {ρD} −1.31 × 10 ⁻³ ] × 100 (40)
R ^{* 2} = 0.93
Thus, the dependency rate of each factor was 68% for Dρ (λα) ^1/2 and 32% for ρD.

In these results, the explanatory variables {Dρ (λα) ^1/2 } and {ρD} of T and Δ have a large R ^{* 2 in the} form that the product ρD of the apparent density ρ and the film thickness D is included as a common factor. Is obtained, it can be seen that ρD has a great influence on both T and Δ. Since ρD corresponds to the film weight per unit area in the film thickness direction, it is related to the substantial amount of substance in the film thickness direction, and if ρ is large, D needs to be thinned. If is small, it can be seen that D can be increased.

(2) Step 2
From the multiple regression equation shown in Step 1, qualitatively, it was possible to know the influence of each structural parameter group on T and Δ. In step 1, N ≦ 5 for the sake of calculation, but the first structural parameter group (N, d, α) and the second structural parameter satisfying the respective reference values (Ti, Δi, Di; i = 1 to 3). In order to know the values of the group (ρ, D, α), the values of N satisfying the reference values of Ti and Δi at each α, d, N (Ti), N (Δi) are estimated, and further the formula (2 ) To obtain D values D (Ti) and D (Δi) that satisfy the respective reference values of T and Δ. However, with respect to Δi, since R ^{* 2} in Equation (27) and Equation (31) is somewhat smaller, it was expected that the error would be larger than Ti. Therefore, for Δi, ½ of the value of the scattering amount by definition is set as the upper limit value of each Δi (for example, according to the definition, 10% of the scattering amount should be Δ1, but 5% is the upper limit of Δ1). . As a result, the amount of scattering when passing through the pellicle film twice was 10%, 5%, and 1%, corresponding to Δ1, Δ2, and Δ3, respectively. N (Ti), N (Δi), D (Ti), and D (Δi) mean the upper limit number of layers N _max and the upper limit film thickness D _max that satisfy the reference values of T and Δ, respectively. To do.

From Step 2, under the first structural parameters α and d, the upper limit number of layers N _max satisfying the respective reference values of T and Δ, and under the second structural parameters α and ρ, each of T and Δ It is possible to quantitatively know the upper limit film thickness _Dmax that satisfies the reference value, that is, the range of D.

As a result, with respect to ρ, as ρ becomes smaller, the upper limit film thickness _Dmax that satisfies the respective reference values of T and Δ tended to increase (particularly, T increases exponentially). On the other hand, with respect to α, since the value of D _max varies greatly with respect to the value of ρ, it cannot be said as clearly as the tendency with respect to ρ. However, with respect to T, D _max increases as α increases, and Δ On the other hand, D _max tended to decrease as α increased.

(3) Step 3
From step 2, the ranges of the structural parameters α, N, d, ρ, D required to satisfy the respective reference values Ti, Δi, Di (i = 1 to 3) can be obtained. However, in the present embodiment, in addition to the above, the ranges of the structural parameters α, N, d, ρ, and D satisfying the constraint conditions 1 to 4 as a carbon porous membrane that can be actually obtained are set in the present embodiment. A porous carbon membrane satisfying the problems is obtained.
Restriction 1: 0.335 nm ≦ d (41)
Restriction condition 2: 1 ≦ N (42)
Restriction condition 3: 0.5 ≦ α (43)
Restriction condition 4: 1.0 × 10 ⁻³ g / cm ³ ≦ ρ ≦ 2.25 g / cm ³ (44)

Constraint conditions 1 and 2 are related to the microstructure parameters described in the definition of d and N, and are the premise of the calculation. Note that d is preferably 1.35 nm or more. N is preferably 2 or more, and if the value is large, the cubic shell-like or cubic frame-like pores having different microstructure parameters in each pore structure model are within the range satisfying each reference value. A laminated film structure in the film thickness direction can be considered.

Constraint condition 3 is a structural parameter common to both micro and macro, and the α value here indicates a value corresponding to L (peak) of the pore distribution. From the significance of this embodiment, the lower limit is set to 0.5. The carbon porous membrane actually obtained contains pores having pore diameters smaller than the α value, and it is difficult to eliminate them. However, pores with small pore diameters are not preferable because they hardly contribute to the improvement of the film thickness of the carbon porous membrane, and only reduce the transmittance due to the lamination of the wall thickness. Therefore, it is preferable that the pore distribution has a sharp shape centered on L (peak). The upper limit of α is obtained from step 2, but empirically L (max) ≈1.5 × L (peak) to 3 × L (peak), corresponding to the average pore diameter in the carbon porous membrane If the upper limit [L (peak) / λ] of α is set to 1 / 1.5 to 1/3 of the upper limit of α obtained from step 2, the maximum pore diameter in the carbon porous membrane actually obtained is It is considered that it can be suppressed to the upper limit of α obtained from Step 2, and is preferable.

Constraint condition 4 is determined from the lower limit of the apparent density ρ actually obtained as carbon aerogel. The reciprocals of ρ and αλ / d are related to the equation (5) in the cubic wall set pore model and the equation (8) in the cube axis set pore model. αλ / d is an index of the strength of the individual pores by the structure of the term. Specifically, if the value is small (ρ is large), the pores themselves are strong.

The structural parameter D necessary for satisfying the respective reference values Ti, Δi, Di (i = 1 to 3) from step 2 under the constraint conditions 1 to 4 as the carbon porous membrane that can be obtained in practice. , Ρ, α, d were determined as follows.

In the cubic axis pore model, the range of the film thickness D was D = 100 nm to 23881 nm (23 μm) at λ = 13.5 nm, and D = 100 nm to 63850 nm (63 μm) at λ = 6.75 nm. In the cubic wall set pore model, D = 100 nm to 517 nm at λ = 13.5 nm, D = 100 nm to 1711 nm at λ = 6.75 nm, and the upper limit value of D is the smallest in each pore structure model It was realized with ρ and the maximum αλ / d.

The range of the apparent density ρ is ρ = 1.0 × 10 ⁻³ to 9.4 × 10 ⁻¹ g / cm ^{3 at} λ = 13.5 nm and λ = 6.75 nm in the cubic axial pore model. Was ρ = 1.2 × 10 ⁻³ to 2.1 g / cm ³ . In the cubic wall set pore model, ρ = 18.2 × 10 ⁻² to 5.6 × 10 ⁻¹ g / cm ^{3 at} λ = 13.5 nm, and ρ = 8.8 × at λ = 6.75 nm. 10 ⁻² to 1.7 g / cm ³ . On the other hand, the range of αλ / d serving as an index of the strength of individual pores is such that the upper limit of ρ is the minimum αλ / d in each pore structure model and the corresponding λ, and the lower limit of ρ is the maximum Of αλ / d. That is, when the range of αλ / d is expressed in a form corresponding to the above range of ρ, αλ / d = 81 to 1.25 at λ = 13.5 nm and λ = 6. At 75 nm, αλ / d = 75 to 0.16. In the cubic wall set pore model, αλ / d = 81 to 10 at λ = 13.5 nm, and αλ / d = 75 to 1.7 at λ = 6.75 nm.

The range of the pore size parameter α is α = 0.5 to 181 at λ = 13.5 nm and α = 0.5 to 726 at λ = 6.75 nm in the cubic axis pore model. In the cubic wall set pore model, α = 0.5 to 20 at λ = 13.5 nm and α = 0.5 to 86 at λ = 6.75 nm under 0.335 nm ≦ d. . Under 1.35 nm ≦ d, α = 0.5 to 18 at λ = 13.5 nm, and α = 0.5 to 84 at λ = 6.75 nm.

The range of the pore wall thickness or the column thickness d is, in the cubic axis pore model, d = 0.335 nm to 30.5 nm at λ = 13.5 nm and d = 0.0.3 nm at λ = 6.75 nm. 335 to 60.6 nm. In the cubic wall set pore model, d = 0.335 nm to 6.74 nm at λ = 13.5 nm, and α = 0.335 nm to 32.2 nm at λ = 6.75 nm.

Hereinafter, in Step 3, an example of a characteristic structure preferable as a pellicle film (provided that d ≧ 1.35 nm) is shown. In addition, each pore structure model is represented in the form of {α, d [unit nm], D [unit nm], ρ [unit g / cm ³ ], αλ / d} in the ranges of the structural parameter group and the constraint condition values. An example of the structure is described for each wavelength of EUV light. Note that {A1, B1, C11-C12, D1, E1}-{A2, B1, C21-C22, D2, E2} are the pore size parameters with the wall thickness or the column thickness d being the same B1 value. It means that the reference value of the present embodiment can be taken when α is in the range of A1 to A2 and the film thickness D is in the range of C11-C22 and C21-C22 corresponding to each α.

<Step 3-1>
Ideal structure for pellicle film-T3 ・ δ3 ・ D3

The characteristic structure 1 is an ideal structure as a pellicle film. At λ = 13.5 nm in the cubic axis pore model,
{Α, d, D, ρ, αλ / d} = { ² , 1.35, 500-835, 1.5 × 10 ⁻² , 20} − {8, 1.35, 500-4659, 1.0 × 10 ⁻³ , 80}, { ³ , 2.01, 500-677, 1.5 × 10 ⁻² , 20}-{10, 2.01, 500-2635, 1.4 × 10 ⁻³ , 67 }, {4, 2.7, 500-592, 1.5 × 10 ⁻² , 20}-{15, 2.70, 500-2188, 1.6 × 10 ⁻³ , 75}, {6, 3 .35, 500-587, 1.0 × 10 ⁻² , 24}-{20, 3.35, 500-1894, 1.0 × 10 ⁻³ , 81}, {8, 4.02, 500-542 ^{, 8.5 × 10 -3, 27}} - {20,4.02,500-1320,1.4 × 10 -3, 67}, {15,4.69,500-736,3 ^{4 × 10 -3, 43} -} {25,4.69,500-1212,1.3 × 10 -3, 72}, {15,5.40,500-559,4.5 × 10 -3, 38}-{30, 5.40, 500-1098, 1.2 × 10 ⁻³ , 75}
A porous carbon membrane having the following structural parameters.

A carbon porous membrane having these structural parameters is the most suitable structure as a pellicle membrane because it can obtain physical property values of T = T3, Δ = Δ3, and D = D3. In particular,
{ ² , 1.35, 500-835, 1.5 × 10 ⁻² , 20}, {3, 2.01, 500-677, 1.5 × 10 ⁻² , 20}, {4, 2.7 , 500-592, 1.5 × 10 ⁻² , 20}, {6, 3.35, 500-587, 1.0 × 10 ⁻² , 24}
A carbon porous membrane having the following structural parameters satisfies ρ ≧ 1.0 × 10 ⁻² g / cm ³ , and is more preferable from the viewpoint of membrane strength.

In the cubic wall set pore model, there are no carbon porous membranes having structural parameters for obtaining physical properties of T = T3, Δ = Δ3, and D = D3 at λ = 13.5 nm and 6.75 nm.

<Step 3-2>
Structure with priority on transmittance in the cubic wall-set pore model-T2, δ2, D1

As characteristic structure 2, at λ = 13.5 nm of the cubic wall set pore model, a carbon porous material having a structural parameter for obtaining physical property values of T = T2, Δ = Δ2, and D = D1 as a structure with high transmittance priority. A membrane is present. That is,
{Α, d, D, ρ, αλ / d} = {2, 1.35, 100-119, 3.1 × 10 ⁻¹ , 20} − {8, 1.35, 111-210, 8.2 × 10 ⁻² , 80}, {3, 2.01, 100-110, 3.0 × 10 ⁻¹ , 20}-{8, 2.01, 112-143, 1.2 × 10 ⁻¹ , 54 }, {6, 2.70, 100-114, 2.1 × 10 ⁻¹ , 30}
A porous carbon film having the following structural parameters, ρ ≧ 1.0 × 10 ⁻² g / cm ^3, which is preferable from the viewpoint of film strength.

<Step 3-3>
Thickness priority structure-T1, Δ1, D3

As the characteristic structure 3, there is a porous film having a structure parameter that obtains physical properties of T = T1, Δ = Δ1, and D = D3. At λ = 13.5 nm of the cubic axis pore model,
{Α, d, D, ρ, αλ / d} = {0.5, 1.35, 1588-1636, 1.7 × 10 ⁻¹ , 5}-{8, 1.35, 21402-35650, 1 0.0 × 10 ⁻³ , 80}, {0.5, 2.01, 776-799, 3.0 × 10 ⁻¹ , 3.4}-{10, 2.01, 12388-22508, 1.4 × 10 ⁻³ , 67}, { ¹ , 2.70, 796-850, 1.7 × 10 ⁻¹ , 5}-{15, 2.70, 14350-24047, 1.2 × 10 ⁻³ , 75 }, {1, 3.35, 540-578, 2.3, 4}-{20, 3.35, 16523-24140, 1.0 × 10 ⁻³ , 81}, {2, 4.02, 690 ^{-789,1.0 × 10 -1, 67} -} {20,4.02,11504-16806,1.4 × 10 -3, 67}, {2, ^{.69,520-594,1.3 × 10 -1, 5.8} -} {25,4.69,13551-15420,1.3 × 10 -3, 72}, {3,5.40,568 -694, 8.6 × 10 ⁻² , 7.5}-{25, 5.40, 10245-11658, 1.7 × 10 ⁻³ , 63}, {6, 8.1, 500-726, 5 .2 × 10 ⁻² , 10}-{25, 8.1, 4595-5228, 3.7 × 10 ⁻³ , 42}, {8, 10.8, 500-618, 5.2 × 10 ⁻² 10}-{25, 10.8, 2612-2970, 6.4 × 10 ⁻³ , 31}, {10, 13.5, 500-554, 5.2 × 10 ⁻² , 10}-{25 ^{, 13.5,1691-1922,9.7 × 10 -3, 25}} , {15,16.2,500-728,3.5 × 10 ^{2, 13} - {25,16.2,1191-1352,1.4 ×} 10 -2, 21}, {20,21.6,500-641,3.5 × 10 -2, 12.5} − {25, 21.6, 693-784, 2.3 × 10 ⁻² , 15.6}
A porous carbon membrane having the following structural parameters.

In particular,
{Α, d, D, ρ, αλ / d} = {0.5, 1.35, 1588-1636, 1.7 × 10 ⁻¹ , 5}-{2, 1.35, 5550-6359, 1 .5 × 10 ⁻² , 20}, {0.5, 2.01, 776-799, 3.0 × 10 ⁻¹ , 3.4}-{2, 2.01, 2564-2937, 3.1 × 10 ⁻² , 13}, { ¹ , 2.70, 796-850, 1.7 × 10 ⁻¹ , 5}-{4, 2.70, 2778-3632, 1.9 × 10 ⁻² , 20 }, {1, 3.35, 540-578, 2.3, 4}-{6, 3.35, 2687-3976, 1.0 × 10 ⁻² , 24}, { ² , 4.02, 690 ^{-789,1.0 × 10 -1, 67} -} {6,4.02,1881-2784,1.5 × 10 -3, 20}, {2,4.69,520-594,1 ^{3 × 10 -1, 5.8} -} {8,4.69,1833-3049,1.1 × 10 -2, 23}, {3,5.40,568-694,8.6 × 10 - ² , 7.5}-{8, 5.40, 1393-2316, 1.5 × 10 ⁻² , 20}, {6, 8.1, 500-726, 5.2 × 10 ⁻² , 10} -{10, 8.1, 806-1456, 2.1 × 10 ⁻² , 8.1}, {8, 10.8, 500-618, 5.2 × 10 ⁻² , 10}-{15, 10.8, 944-1573, 1.7 × 10 ⁻² , 19}, {10, 13.5, 500-554, 5.2 × 10 ⁻² , 10}-{20, 13.5, 1069− ^{1555,1.5 × 10 -2, 20},} {15,16.2,500-728,3.5 × 10 -2, 13} - {25,16.2,1191- ^{352,1.4 × 10 -2, 21},} {20,21.6,500-641,3.5 × 10 -2, 12.5} - {25,21.6,693-784,2. 3 × 10 ⁻² , 15.6}
A carbon porous membrane having the following structural parameters satisfies ρ ≧ 1.0 × 10 ⁻² g / cm ³ , and is more preferable from the viewpoint of membrane strength.

At λ = 13.5 nm of the cubic wall set pore model,
{Α, d, D, ρ, αλ / d} = {8, 1.35, 500-517, 8.2 × 10 ⁻² , 80}
A porous carbon membrane having the following structural parameters.

The above shows an example of a characteristic structure preferable as a pellicle film, using each range of the value of the structural parameter group and the constraint condition. However, when EUV light passes through the carbon porous film once even using mathematical formulas. An EUV pellicle film having a transmittance T of 84% or more, a scattering amount Δ of 10% or less, and a film thickness D of 100 nm or more can be shown. For example, when calculating using the above G-Solver, the wavelength λ of EUV light is 13.5 nm, the density W of graphite is 2.25 g / cm ³ , and the apparent density (g / cm ³ ) of the porous carbon film is When ρ and the film thickness are D (nm), using the first structural parameter, in the cubic wall set pore model, the carbon porous body film has the structural parameters of the following equations (1) to (5). A pellicle film for EUV that satisfies the range may be preferable.
α ≦ 30 (α: pore size parameter) (1)
0.335 ≦ Nd ≦ 13 (N: number of pores in the film thickness direction (pieces), d: wall thickness of the pores (nm)) (2)
αλ / d ≦ 81 (λ: exposure wavelength (nm)) (3)
However, the above N and d are
N = −1 + {(W−ρ) ^1/3 / W ^1/3 } + {D (W−ρ) ^1/3 / αλW ^1/3 } (4)
d = −αλ + {αλW ^1/3 / (W−ρ) ^1/3 } (5)

Similarly, in the cubic wall set pore model using the second structural parameter, it is preferable that the pellicle membrane for EUV satisfies the range of the structural parameters of the following formulas (6) to (9) in the carbon porous membrane can do.
α ≦ 30 (α: pore size parameter) (6)
αλ / d ≦ 81 (λ: exposure wavelength (nm)) (7)
0.08 g / cm ³ ≦ ρ ≦ 0.7 g / cm ³ (8)
D: 100 nm ≦ D ≦ 850 nm (9)

As described above, a characteristic structure preferable as a pellicle film for EUV can be shown using mathematical formulas corresponding to the exposure wavelength λ and the approximate pore structure model under an appropriate calculation method.

As described above, from [Technical Point 1] and [Technical Point 2], the present embodiment is a pellicle film, which is composed of a porous carbon film, and from [Technical Point 3], the film thickness D of the pellicle film is A pellicle film having a thickness of 100 nm to 63 μm.

In addition, what combined the well-known technique can also be mentioned as the further improvement plan [supplementary process] of the carbon porous membrane of this embodiment.

As described in Patent Document 2, the first example is to prevent oxidation / reduction of the porous carbon film by light from a high-power EUV light source on one or both surfaces of the porous carbon film of the present embodiment. In addition, Si, SiC, SiO ₂ , Si ₃ N ₄ , Yttrium Y, Molybdenum Mo, Ru, Rhodium Rh, etc., within a range satisfying the target value of the subject of the present invention, such as a known sputtering method, vacuum deposition method, etc. The method is to coat several nm. Si is particularly preferred because it has a low extinction coefficient of EUV light, a refractive index close to 1.0, and reacts with carbon to form a SiC film having a few nm with excellent strength on the carbon film surface.

In the second example, the carbon porous film of the present embodiment has a film thickness having high transparency and practically sufficient durability for EUV light, but when further film strength is required. As long as the target value of the problem of the present invention is satisfied, the mesh is used as a supporting film as in Patent Document 3, Patent Document 4, Patent Document 5, and Non-Patent Document 2 (materials are Si, Zr, Mo, titanium Ti Nickel nickel, aluminum Al, copper Cu, and their carbides are preferable from the viewpoint of having a small extinction coefficient and Δn, and being easily available as a general-purpose product). In this case, the transmittance is lowered by 10% or more by the support membrane (mesh having a mesh thickness of several tens of μm, a wire diameter constituting the mesh of several tens of μm, and a pore size of several hundred μm to several mm), The transmittance T of the carbon porous membrane alone of the present invention is T2, T3. Note that the support film hardly affects the scattering amount Δ.

As [Additional Notes], a method for correcting the structure parameter will be described. The transmittance T and scattering amount Δ of the present embodiment represented by the equations (19) to (40), the equations (1) to (5), and the equations (6) to (9) in [Technical Point 3]. The relational expression between the structural parameter group of the carbon porous membrane and the structural parameter group for obtaining the reference values of T, Δ, and D are EUV under (Premise 1) and (Premise 2). Using the values of optical constants n and k of graphite with a density W = 2.25 g / cm ³ when light wavelengths λ = 13.5 and λ = 6.75 nm, transmittance T and scattering amount Δ are calculated. , Calculated. Therefore, when the assumption value of the density W of graphite is changed, T and Δ are recalculated in the same manner as in Step 1 to Step 3 using the corresponding new optical constant, and the carbon porous film of this embodiment is What is necessary is just to recalculate the restriction range of structure parameters, Ti, Δi, and Di. For example, when the premise value of the density W of graphite decreases, the extinction coefficient k of carbon decreases and the refractive index n approaches 1, so this embodiment of the thickness D, the apparent density ρ, and the pore size parameter α of the structural parameters The range of restrictions will be expanded.

2-2. Method for Producing Pellicle Membrane According to this Embodiment A method for producing a pellicle membrane according to this embodiment will be introduced below. The porous carbon film as the pellicle membrane according to this embodiment is limited to this production method and its examples. is not. FIG. 5 is a diagram showing a method for manufacturing a pellicle film.

There are the following methods for obtaining a carbon porous membrane. The first method is to add a binder to fine carbon precursor particles or carbon particles that are about the same size to several tens of times the target pore size and do not melt or break during sintering and carbonization. This is a method of obtaining a porous carbon film having pores between the particles by sintering and carbonizing after film formation.

In the second method (Method A), a solvated gel film (for example, hydrogel) containing a large amount of solvent is formed by using a raw material that first undergoes sol-gel transition by a sol-gel method. A method of obtaining a carbon porous film as a carbon aerogel by obtaining aerogel film containing a large amount of bubbles by drying and removing only the solvent so that the solvation structure does not collapse, and finally carbonizing the aerogel film It is.

In the third method (Method B), a chemical reaction or a carbonization reaction is performed using a raw material in which a structure is fixed in a molecular structure in a chemical reaction process or a carbonization process and bubbles are generated. This is a method for obtaining a carbon porous membrane having pores of air bubbles or gaps. From the first method, it is relatively easy to control the particle size and produce a porous carbon membrane having a pore diameter of about 0.5 to 10 times the wavelength of EUV light, compared to other methods. It is difficult to obtain a low-density carbon porous film having an apparent density of 1.0 g / cm ³ or less. The porous carbon membrane of this embodiment can be obtained by the second and third methods.

The carbon porous membrane of this embodiment applies the existing carbon porous membrane manufacturing technology as mentioned in the second advantage of [Technical Point 2]. However, these manufacturing techniques differ in two points, [Technical Point 4] and [Technical Point 5].

[Technical point 4]
Technology point 4 is to introduce thin film deposition technology. Technical point 4 is that the use of the porous carbon membrane of the present embodiment is a pellicle membrane that was not considered at all as an application of the existing porous carbon membrane, so that a film forming technology for obtaining a thin film is added. It is. That is, in the manufacturing method of the carbon porous membrane of this embodiment described later, a film forming step suitable for thinning (step A2, step B2, step AB2) and a coating liquid preparation step for obtaining a thin film (step) A1, process B1, and process AB1) are important technical points.

In the blending process, the composition, molecular weight, and temperature of the coating liquid are adjusted, the viscosity of the coating liquid is lowered, and the film thickness after film formation / drying can be applied to a film thickness of several tens to several hundreds of micrometers. Is preferred. Film thickness after the carbonization is about 0.5 to 3 times the coating thickness in the fixing / drying process (process A3, process B3, process AB3) and carbonization process (process A4, process B4, process AB4) This is because the thickness becomes 100 nm to 63 μm. In order to reduce the viscosity of the coating solution, the concentration of the solute that finally becomes carbonaceous in the coating solution may be reduced within the range of the manufacturing parameters described in Technical Point 5. In particular, when the coating solution is a polymer solution, it is preferable to lower the molecular weight to such an extent that the coating film does not break when it is peeled off from the base material at the time of coating after drying.

Further, as a coating method for obtaining a thin film, it is preferable to use a wet coating method capable of thinly coating a low-viscosity coating solution, not a dry coating method typified by a vapor deposition method. Specifically, coating methods that are low in productivity, such as spin coating, nozzle scan coating, and ink jet coating, but thin films such as bar coating, gravure coating, die coating, doctor coating, and kiss coating are advantageous. Although there is a limit, a coating method with high productivity can be used by continuous coating called roll-to-roll. Furthermore, it is possible to obtain a uniform thin film by adjusting the coating conditions such as coating speed, coating temperature, and coating time as well as adjusting and selecting the coating solution viscosity, composition and coating method appropriately. be able to.

[Technical point 5]
In order to obtain a carbon porous membrane having the structural parameters described in [Technical Point 3], the technical point 5 is a manufacturing parameter (the kind and molecular weight of the carbonaceous solute, the solution composition, the solution concentration) according to each manufacturing method. The crosslinking catalyst species / dehalogenation species and their concentrations, drying conditions, carbonization conditions, etc.) are adjusted, and the details will be described below.

2-2-1. Method for Producing Carbon Airgel-Based Carbon Porous Membrane Method A (the second method described above) for obtaining the carbon porous membrane of this embodiment includes Reference A, US Pat. No. 4,873,218 [hereinafter referred to as Reference B], Monden, Surface, 38 (1), 1-9 (2000) [hereinafter referred to as Reference C], JP-T 8-508535 [hereinafter referred to as Reference D]; Saliger et al. The method introduced in Non-Crystalline Solids, 221, 144-150 (1997) [hereinafter referred to as Reference E] is applied. In these documents, a carbon material having mesopores used for a heat insulating material, a battery, a capacitor, or the like is introduced, and the application of this embodiment is not considered at all. However, it can be applied to the application of the present embodiment by adding a thin film forming technique and adjusting manufacturing parameters so as to obtain a thin hydrogel film.

That is, as shown in FIG. 5, in step A1, as the carbonaceous raw material, one or more monomers consisting of resorcinol (R), phenol, catechol, phloroglucinol and other polyhydroxy-benzene compounds, and formaldehyde ( F) and one or more monomers of furfural, and also as an alkali catalyst (Ca) for gelation (polymerization), potassium carbonate (K ₂ CO ₃ ), sodium carbonate (Na ₂ CO ₃ ), potassium hydrogen carbonate ( Any one or more of alkali metal carbonates such as KHCO ₃ ) and sodium hydrogen carbonate (NaHCO ₃ ) and alkali metal hydrogen carbonate are dissolved in water (Wa), and these are mixed to form coating solution A (RF viscosity). Liquid).

As step A2, following step A1, the coating liquid A is coated on a release film or release substrate so that the film thickness after carbonization becomes 100 to 850 nm so that it can be easily peeled later (as described above). Bar coating, spin coating, etc.) / Film formation. At this time, the surroundings of the release film and the release substrate are hermetically sealed, the coating film does not flow out of the release film and the release substrate, and the solvent (water) evaporates and the composition of the coating liquid It is preferable to seal so that the region which becomes the membrane pores is not crushed.

As step A3, subsequent to step A2, the temperature is raised stepwise from room temperature (20 ° C.) to 100 ° C. or allowed to stand for several days (1 to 14 days) to sufficiently gel (polymerize), A thin-film hydrogel film is obtained. In order to obtain a solid hydrogel membrane quickly, as shown in Reference Document D, heating (50 to 100 ° C.) can be performed during standing, but to obtain a hydrogel membrane having a large pore diameter. The heating temperature is preferably low.

Subsequently, the hydrogel film is peeled off from the release film or release substrate, and dried so that the pore diameter and shape can be more maintained, so that the solvent (water) in the hydrogel film is replaced with acetone or cyclohexane. Carbon dioxide supercritical drying (CO ₂ supercritical drying), [Drying method 1], freeze-drying (after replacement with t-butanol if necessary) [Drying method 2], hot air drying at room temperature to 100 ° C. Or, drying under reduced pressure (hot air / vacuum drying) (after replacement with the treatment liquid used in drying method 1 or drying method 2 if necessary) or [drying method 3] to disperse the water in the hydrogel film and make it porous RF-based airgel membrane is obtained. In substitution, in order to suppress changes in pore diameter and pore shape due to contact with the substitution liquid, the substitution concentration from water in the hydrogel membrane to acetone, cyclohexane, t-butanol, etc. is gradually increased or the number of substitutions is increased. Is preferable.

Also, as the drying method, [Drying method 1] is most preferable in order to suppress capillary contraction due to the interfacial tension of the solvent during drying as much as possible. However, instead of supercritical drying, [Drying Method 2] shown in Reference C, Reference D, and [Drying Method 3] shown in Reference E also sacrifice some pore diameter and pore shape. However, it is advantageous to keep the manufacturing cost low and can be used in this embodiment.

As step A4, subsequent to step A3, the RF airgel film is carbonized at 600 to 3000 ° C. for 10 minutes to 20 hours in an inert atmosphere or nitrogen atmosphere, and carbon as the RF carbon aerogel of this embodiment is obtained. A porous membrane is obtained. The carbonization treatment can use a carbonization / activation production method such as a fixed bed method, a moving bed method, and a tunnel kiln used for carbonization / activation treatment of solid films and sheets without crushing the carbon precursor.

With the carbonization, the pore diameter of the RF airgel shrinks, and the rate of shrinkage decreases as the carbonization temperature increases, but the pore diameter and pore distribution tend to be smaller. Therefore, the carbonization temperature can be adjusted according to the target pore diameter. Usually, the carbonization temperature is 700 to 1500 ° C., and when it is necessary to further increase the film strength, conductivity and thermal conductivity, the treatment can be performed at 2000 to 3000 ° C. In addition, the pore structure can be adjusted by subjecting the obtained carbon porous membrane to an activation treatment as necessary to increase the pore diameter and pore distribution. As the activation method, it is preferable to use a gas activation method in which firing is performed using an activation gas such as water vapor, hydrogen chloride, carbon monoxide, carbon dioxide, oxygen, or the like.

In addition, during the carbonization treatment, the airgel film shrinks greatly, and if carbonized in a non-tensioned state, the film tends to wrinkle, so it is fixed with a frame or sandwiched between two graphite plates or graphite sheets, It is preferable to carbonize the airgel membrane under tension, or to thermally stabilize the structure in advance at 150 ° C. to 250 ° C. in air or iodine (I ₂ ) vapor.

Figure 1 in Reference C and R. W. Pekala, FM. FIG. 2 in Kong, Polym., Prep, 30, 221-223 (1989) [hereinafter referred to as Reference Document F] shows a schematic diagram of the formation mechanism of RF airgel, RF airgel and RF as a carbide thereof. Electron micrographs of carbon-based carbon aerogels are described.

An aggregate of beaded fine particles forms a carbon porous film as an RF carbon aerogel. An actual carbon porous membrane is considered to have an intermediate structure between a cubic axial pore structure model and a cubic wall porous structure model. It can be seen that the structure is similar to the assembled pore structure model.

Also, FIGS. 10 to 13 in Reference Document A contain graphs of the pore distribution of RF-based carbon airgel and graphs of SAXS Debye-Porod analysis. From FIG. 10 of the same document, as the dependence of the catalyst species on the pore distribution of the RF carbon aerogel, the peak pore radius r (peak) and the pore diameter of the alkali metal bicarbonate are larger than those of the alkali metal carbonate. From FIG. 12 of the same document, L is obtained as the dependency of R / C. As R / C increases, the pore diameter L increases, but the pore distribution becomes broad, and the peak of the peak of the pore distribution curve It can be seen that the height also decreases.

From FIG. 13 of the same document, the pore shape is spherical regardless of the catalyst type because the slope of the Debye-Porod plot is close to −4 when the R / C is several hundred (eg, 200) or less. You can see that they are close.

In the following, from typical experimental values described in Reference A, Reference B, and Reference C, R and F are used as raw materials that become carbonaceous as Step A1, and Na ₂ CO ₃ is used as various composition ratios as Ca. In Step A2, the coating liquid A was prepared as a thin film by spin coating to obtain a hydrogel film, and then in Step A3, the hydrogel film was gelled (polymerized) at room temperature to 100 ° C. , CO ₂ supercritical drying or freeze drying or hot air drying to obtain an airgel membrane, and then the airgel membrane is carbonized at 1000 ° C. as step A4, and finally the carbon porous membrane of this embodiment is obtained The multiple regression equations of the composition ratio and the obtained structural parameters, Equation (36) and Equation (37) were obtained. Apparent density is
ρ = −1.27 × 10 ⁻¹ · ln (R / Ca) + 7.07 · (R / Wa) + 7.24 × 10 ⁻¹ (45)
R ^{* 2} = 0.92
Thus, the dependency rate of each factor was 36% for ln (R / Ca) and 64% for R / Wa.

The pore radius r is
ln (r) = 2.41 × 10 ⁻¹ · ln (R / Ca) −5.23 × 10 ⁻¹ · ln (R / Wa) + 5.36 × 10 ⁻¹ · ln (R / F) −9 .69 × 10 ⁻¹ (46)
R ^{* 2} = 0.79
Thus, the dependency rate of each factor was 39% for ln (R / Ca), 37% for ln (R / Wa), and 25% for ln (R / F). Note that α corresponding to the pore radius r is obtained by doubling r and dividing by λ according to the equation (18).

From the equations (45) and (46), the following can be understood. As the molar ratio R / Ca between R and Ca increases, the apparent density ρ decreases and α corresponding to the pore radius r increases. Further, according to the above cited reference 4, the influence of the type of Ca is such that K ₂ CO ₃ ≈Na ₂ CO ₃ <NaHCO ₃ <KHCO _{3 in} order, α increases, and when R / Ca decreases, the pore distribution becomes sharper. Thus, when 0 <R / Ca ≦ 200, spherical pores are obtained, and when R / Ca> 800, disk-like pores are obtained. Therefore, in order to obtain a sharp pore distribution with large spherical pores, it is preferable to use an alkali metal hydrogen carbonate and make R / Ca as small as possible.

On the other hand, as the molar ratio R / Wa between R and Wa increases, ρ increases and α decreases. As the molar ratio R / F between R and F increases, α increases. Therefore, in order to obtain large pores, it is preferable to make R / Wa as small as possible and R / F as large as possible.

Furthermore, when approximated by a multiple regression equation of the second structural parameter group and T, Δ, that is, a cubic wall set pore model, at λ = 13.5 nm, using Equations (33) and (34), When λ = 6.75 nm is approximated by the cubic axis assembly pore model using Equations (35) and (36), when λ = 13.5 nm, Equations (37) and (38) are used. When λ = 6.75 nm, the composition range of Ti, Δi, and Di that satisfies the problems of the present embodiment can be known by using the equations (39) and (40).

As described above, a solvated gel film (for example, hydrogel) containing a large amount of a solvent is formed by using a raw material that first undergoes a sol-gel transition by the sol-gel method. It is possible to obtain an airgel film containing a large amount of bubbles by drying and removing only the solvent so as not to be crushed, and finally carbonizing the airgel film to obtain the carbon porous film of this embodiment as a carbon airgel. it can.

2-2-2. Method for Producing Carbon Halogen Vinyl Resin-Based or Vinylidene Halide Resin Carbon Porous Membrane Method B (the third method described above) for obtaining the carbon porous membrane of the present embodiment is disclosed in Japanese Patent No. 4871319 [hereinafter referred to as reference]. Reference G], Junya Yamashita, Masatoshi Shiotani, Carbon, No. 204, 182-191 (2002) [referred to as Reference H] is applied. These references G and H are introduced as relating to a method for producing a carbon material having mesopores used for a catalyst support material, a gas storage material, a gas separation material, an electrode material, etc. It is not considered at all. However, it can be applied to the use of this embodiment by adding a thin film forming technique and adjusting the manufacturing parameters so that a thin vinyl halide resin film or vinylidene halide resin film can be obtained. .

That is, as shown in FIG. 5, as step B1, a carbonaceous raw material is a vinyl halide resin or vinyl halide copolymer resin having a vinyl halide composition of 60 mol% or more (generically referred to as a vinyl halide resin). Highly halogenated vinyl resin having a halogen weight ratio of 60 wt% or more, or a vinylidene halide or vinylidene halide copolymer resin having a vinylidene halide composition of 60 mol% or more (collectively referred to as vinylidene halide resin) (Hereinafter, the high-halogenated vinyl resin and the vinylidene halide resin are treated in the same manner, and unless otherwise specified, simply referred to as the vinylidene halide resin). A solution in which these resins are dissolved in a good solvent or a latex in which fine particles of a vinylidene halide resin are dispersed in water is prepared. These solutions and latex are collectively referred to as a coating solution B.

As step B2, following step B1, this coating solution B is applied and formed on a release film or release substrate so that the film thickness after carbonization is 100 nm to 63 μm. A solvent or water is scattered by drying with hot air and reduced pressure at the following temperature to obtain a thin film resin film of vinylidene halide resin (vinylidene halide resin film).

As step B3, subsequent to step B2, the vinylidene halide resin film is changed to an aqueous solution of a dehydrohalogenating agent (base) of an alkali metal hydroxide [potassium hydroxide (KOH), sodium hydroxide (NaOH), etc.] and / or Or a solution of a dehydrohalogenating agent (base) in an amine solution [ammonia water (NH ₃ water), 1,8-diazabicyclo [5,4,0] -7-undecene (DBU), etc.] and tetrahydrofuran (THF) Using a mixed solution of a good solvent for partially or entirely dissolving vinylidene halide resins such as dimethylformamide (DMF) and a poor solvent for vinylidene halide resins such as water, alcohol and / or ether, and mixing at room temperature to A dehydrohalogenation reaction treatment is performed at a temperature below the boiling point of the solution for 1 second to 2 weeks to obtain a vinylidene halide resin-based carbon precursor film. The mixed solution may undergo phase separation depending on the composition. The mixed solution used in the present embodiment has a composition that does not cause phase separation, and is essential for causing the dehydrohalogenation reaction of the carbon precursor with good reproducibility.

In step B2 and step B3, unlike step A2 and step A3, it takes time to gel the release film or the coating film on the release substrate, or it is peeled off after the coating film is dried with hot air. It is also possible to immerse the coating film directly in the mixed solution without any operation. Contact with the mixed solution causes cross-linking (fixation of structure) of the coating film by dehalogenation, and at the same time, the generated dehydrohalogen gas causes the vinylidene halide resin film from the release film or release substrate. It is because it peels naturally. Therefore, a vinylidene halide resin film can be obtained in an extremely short time compared with Method A.

Further, in the dehydrohalogenation of the coating film in the step B3, a crosslinked structure called a polyene structure (meaning a molecular skeleton structure having —C═C— or C≡C—) in the vinylidene halide resin film is removed. Bubbles generated by the hydrogen halide are generated, and a large number of the bubbles remain in the vinylidene halide resin-based carbon precursor film remaining in the film. This carbon precursor film has a number of cross-linked structures, so that the dehydrohalogenation reaction and carbonization (non-destructive carbonization, graphitization) can proceed without melting even in the subsequent step B4.

As step B4, following step B3, the vinylidene halide resin-based carbon precursor film is heated under tension at 600 to 3000 ° C. for 10 minutes to 20 hours in an inert atmosphere or nitrogen atmosphere as in step A4. In this method, carbonization is performed to obtain the vinylidene halide resin-based carbon porous film of the present embodiment.

Control of pore diameter and pore distribution by Method B is determined in Step B1 by the composition mol% of high vinyl halide and vinylidene halide in the resin, the molecular weight of the resin, and the resin concentration in the coating liquid B. The higher the value, the smaller the pore size. In Step B2, the pore distribution in the film can be sharpened by reducing the film thickness. Furthermore, in step B3, the higher the concentration of the base (dehydrohalogenating agent) such as alkali metal hydroxide and amine in the mixed solution, the higher the concentration of the good solvent of the vinylidene halide resin in the mixed solution, the larger the pore size. Becomes larger. In step B4, as in step A4, the pore diameter tends to decrease as the carbonization temperature increases. However, depending on the amount of residual halogen in the carbon precursor, the pore diameter / pore distribution can be increased at 600 ° C. to 1200 ° C. . Furthermore, the pore structure can also be adjusted by enlarging the pore diameter and the pore distribution by the activation treatment as in step A4. As examples of Method B, examples of Reference G and Reference H are described below.

As Step B1, a vinylidene chloride resin or vinylidene chloride copolymer resin (collectively PVDC resin) having a vinylidene chloride (VDC) composition of 60 mol% or more is dissolved in a carbonaceous raw material using THF as a good solvent for the PVDC resin. To make coating solution B.

As step B2, the coating liquid B is spin-coated on a glass release substrate so that the film thickness after carbonization becomes 100 to 850 nm, and dried with hot air at 80 ° C. to obtain a thin PVDC resin film.

In step B3, the PVDC resin film is subjected to dehydrochlorination reaction treatment (deHCl treatment) using a mixed solution of an alkali metal hydroxide KOH aqueous solution, a good solvent THF, and a poor solvent methanol, and a PVDC carbon precursor film. Get.

Finally, as step B4, this PVDC-based carbon precursor film is subjected to tension heating carbonization at 600 to 3000 ° C. in a nitrogen atmosphere to obtain the PVDC-based carbon porous film of the present embodiment.

As the PVDC resin, those described in [0011] to [0012] of Reference G can be used. As the molar content of the VDC component in the PVDC resin is higher, the polyene structure generated in one molecule is increased by the de-HCl reaction in Step B3, and a cross-linked structure between a plurality of molecules is easily generated. This is preferable because it can be carbonized in a solid state without melting.

However, a PVDC resin having a VDC composition of 100 mol% is difficult to be uniformly dissolved, and the PVDC film is hard and brittle, so that it is difficult to handle, and a vinylidene chloride copolymer (VDC copolymer) is preferable. The molar composition ratio of VDC in the VDC copolymer is 0.6 (60 mol%), preferably 0.8 (80 mol%) or more, more preferably 0.9 (90 mol%) or more. preferable.

_{Incidentally, (- CH 2 -CHCl-) n} , with respect to conventional PVC resin given by the structural formula [Cl content of 57 wt%], the structural formula _{[(-CH 2 -CHCl-) 4 -CHCl} -CHCl -] _N , a chlorinated PVC resin having a [Cl content of 61 wt%], a chlorinated rubber having [(—CHCl—C (CH ₃ ) Cl—CHCl—CHCl—) _n , and a [Cl content of 68 wt%], etc. Even in a highly chlorinated PVC resin having a chlorine content (Cl content) exceeding about 60 wt%, the same as the PVDC resin having (—CH ₂ —CCl ₂ —) _n and [Cl content 73 wt%] in Step B3 Can be used as a carbonaceous raw material of the present embodiment because it can be carbonized without melting even during carbonization in step B4.

As the coating liquid B, an aqueous dispersion of PVDC resin called latex or THF, 1,4-dioxane, cyclohexane, cyclopentanone, chlorobenzene, dichlorobenzene shown in [0014] of Reference G is used as the PVDC resin. PVDC resin solution dissolved in a good solvent of PVDC resin such as DMF, methyl ethyl ketone, and ethyl acetate can be used. Preferred good solvents are THF and DMF.

The PVDC-based carbon precursor film is subjected to deHCl treatment using the composition and processing conditions of the alkaline processing liquid shown in [0014] to [0015] of Reference G as a mixed solution, and the PVDC-based carbon porous film is It can be carried out under the carbonization conditions shown in [0017] of Reference G. Since the PVDC resin film and PVDC-based carbon precursor film of this embodiment are thin films, the alkali (base) concentration, good solvent concentration, deHCl treatment temperature, and deHCl treatment and carbonization treatment time are described in the same patent document. In comparison, it can be kept low and short.

FIG. 3 in Reference G shows a TEM photograph of the PVDC carbon porous membrane. FIG. 2 of the same document is a graph of the pore distribution of the PVDC carbon porous membrane. From FIG. 3 of the same document, a large number of spherical pores surrounded by the pore walls form a PVDC-based carbon porous film. From FIG. 2 of the same document, L≈13 nm (α≈1). It can be seen that a large number of .0) pores are formed. Thus, the vinylidene halide-based carbon porous film tends to be a strong carbon porous film with a thicker pore wall thickness than the carbon airgel-based carbon porous film. An actual carbon porous membrane is considered to have an intermediate structure between a cubic axial structure pore structure model and a cubic wall structure pore structure model, but speakingly, the pore structure of the vinylidene halide carbon porous film is It can be seen that the structure is similar to the cubic wall-set pore structure model.

The method using Reference H is described below. Reference H uses a vinylidene fluoride resin (PVDF resin) film instead of PVDC resin, and a mixed solution of organic strong base DBU, PVDF good solvent DMF, and PVDF poor solvent ethanol. A method for obtaining a PVDF carbon porous film having a large number of mesopores after carbonization treatment after obtaining a PVDF carbon precursor film by hydrogenation treatment has been introduced. Can be used.

Furthermore, in Reference Document H, an eclectic method (Method AB) of Method A and Method B is introduced, and this method can also be applied to this embodiment. That is, like the manufacturing process of the carbon porous membrane shown in FIG. 5, a vinyl chloride resin (PVC resin) having a different number average molecular weight M is used as the carbonaceous raw material as the process AB1, and the PVC resin powder is dissolved in DMF. DBU is dropped into the solution at room temperature, and a part of the PVC resin is deHCled to prepare a viscous coating liquid AB composed of three components of PVC, DMF and DBU.

Subsequently, as step AB2, the coating liquid AB is applied and formed on the release film or release substrate so that the film thickness after carbonization becomes 100 nm to 63 μm. At this time, the surroundings of the release film and the release substrate are hermetically sealed, the coating film does not flow out of the release film and the release substrate, and the solvent (water) evaporates and the composition of the coating liquid After sealing so as not to change or the region that becomes the membrane pores is not crushed, it is heated at room temperature to 70 ° C. to be sufficiently gelled to obtain a PVC gel membrane.

As step AB3, after peeling the PVC gel film from the release film or release substrate, the DMF in the gel is directly replaced with liquid CO ₂ , and then CO ₂ supercritical drying is performed to disperse the solvent and make it porous. A PVC airgel membrane is obtained.

Finally, as step AB4, the PVC-based airgel membrane is heat-stabilized by stepwise heating in air (under O ₂ ) at 150 to 250 ° C., or the PVC-based gel membrane is heated with iodine (I ₂ ) vapor. After heat stabilization at 150 to 250 ° C., heat to 700 ° C. to 3500 ° C. (here 1000 ° C.) in an inert atmosphere or nitrogen atmosphere in the same manner as PVDC carbon porous membrane and PVDF carbon porous membrane. Carbonization can be performed to obtain a porous carbon film made of PVC-based carbon airgel.

If the PVC airgel film is heated as it is in step AB4, the PVC airgel film melts and its pore structure collapses. Therefore, unlike the case where chlorinated PVC resin or PVDC resin is used as a carbonaceous raw material, the pore structure by thermal stabilization Immobilization is essential.

FIG. 8 in Reference H shows the pore distribution of the PVC-based carbon airgel. FIG. 8 shows the dependency of the molecular weight M on the pore distribution and the dependency of the PVC concentration.

Below, from typical experimental values described in Reference H, it is assumed that the porous carbon membrane of the present embodiment is obtained according to the method AB, and the PVC in the solution consisting of three components of PVC, DMF, and DBU Weight percent concentration (wt% concentration, [PVC]), number average molecular weight of PVC (M), weight ratio of DBU molecule to chlorine atom (Cl) in PVC molecule (DBU / Cl) The regression equation, equation (47), and equation (48) were obtained. The apparent density ρ is
ρ = 2.15 × 10 ⁻¹ · ([PVC]) + 4.64 × 10 ⁻² · (M × 10 ⁴ ) + 5.52 × 10 ⁻² · (DBU / Cl) −2.87 × 10 ⁻¹ ... (47)
R ^{* 2} = 0.86
Thus, the dependence rates of the factors were 66% for [PVC], 27% for M, and 7% for DBU / Cl.

The pore radius r is
r = −4.31 · ([PVC]) − 1.12 · (M × 10 ⁴ ) + 1.83 · (DBU / Cl) + 2.74 × 10 ¹ (48)
R ^{* 2} = 0.74
Thus, the dependence rate of each factor was 58% for [PVC], 32% for M, and 10% for DBU / Cl. Α corresponding to the pore radius r is obtained by doubling r and dividing by λ according to Equation 2.

From the equations (47) and (48), the following can be understood. As [PVC] increases, the apparent density ρ increases and α corresponding to the pore radius r decreases. On the other hand, as M increases, ρ increases and α decreases, and as DBU / Cl increases, ρ and α increase. Therefore, in order to obtain large pores, [PVC] and M are preferably as small as possible and DBU / Cl as large as possible.

Furthermore, when approximated by a multiple regression equation of the second structural parameter group and T, Δ, that is, a cubic wall set pore model, at λ = 13.5 nm, using Equations (33) and (34), When λ = 6.75 nm is approximated by the cubic axis assembly pore model using Equations (35) and (36), when λ = 13.5 nm, Equations (37) and (38) are used. When λ = 6.75 nm, the composition range of Ti, Δi, and Di that satisfies the problems of the present embodiment can be known by using the equations (39) and (40).

As described above, a chemical reaction or carbonization reaction is performed using a raw material in which bubbles are generated while the structure is fixed in a chemical reaction process or carbonization process in the molecular structure, and bubbles or gaps generated in those processes are narrowed. By setting it as a hole, the carbon porous film of this embodiment can be obtained as a halogenated vinyl resin-based or halogenated vinylidene resin-based carbon porous film.

2-2-3. Supplementary Processing As a supplementary processing shown in FIG. 5, after obtaining the carbon porous membrane of the present embodiment, oxidation or reduction of the carbon porous membrane by light from a high-power EUV light source is applied to one or both surfaces of the surface of the carbon porous membrane. In order to prevent Si, SiC, SiO ₂ , Si ₃ N ₄ , Y, Mo, Ru, Rh, etc. within the range satisfying the target values of the problems of this embodiment, a known sputtering method, vacuum deposition method, etc. By this method, it is possible to coat several nm. Si is particularly preferable because it has a low extinction coefficient of EUV light, a refractive index close to 1.0, and further reacts with carbon to form a SiC film having a few nm with excellent strength on the carbon film surface.

3. Pellicle of this Embodiment FIG. 6 is a perspective view showing a pellicle. FIG. 7 is a diagram showing a cross-sectional configuration along the line VII-VII in FIG. As shown in FIG. 6, the pellicle 10 of the present embodiment is obtained by bonding the above-described carbon porous film to the frame 3 using the film adhesive 2 as the pellicle film 1. Further, a bonding mechanism 4 with a mask adhesive (including its protective film) or a frame is provided on the side of the pellicle that is bonded to the mask.

As the frame 3 used in the present embodiment, a frame having one or more vent holes 5 provided on the side surface, which is used in a normal pellicle, can be used. The frame material is preferably an Al—Zn-based aluminum alloy frame (7000-based aluminum alloy frame) in which Zn and Mg are added to increase the strength among aluminum alloys. More preferably, in order to suppress stray light when the EUV light is irradiated onto the frame, elements Mg and Si having a refractive index of EUV light close to a vacuum refractive index of 1.0 and a large extinction coefficient k are added to provide strength and corrosion resistance. An Al—Mg—Si-based aluminum alloy frame (6000-based aluminum alloy frame) with improved resistance is preferable. Or the frame which vapor-deposited the surface of the aluminum alloy flame | frame with these elements Si, SiC, Mg, Zn can also be used.

As the mask adhesive 4, for example, an adhesive containing a reaction product of a (meth) acrylic acid alkyl ester and a polyfunctional epoxy compound used in an ArF pellicle introduced in JP 2011-107488 A is used. Can be used. When EUV light is applied to the adhesive, decomposition gas may be generated from the components of the adhesive. Therefore, when the frame is bonded to the mask, the frame adhesive should not protrude from the edge of the frame width. It can be applied narrower than the width of 3. Moreover, as an arrangement | positioning form of the mask adhesive 4, as one form, as shown to Fig.8 (a), the mask adhesive 4 can be arrange | positioned to the groove | channel 6 provided in the flame | frame 3. As shown in FIG. At this time, the mask adhesive 4 is applied in the groove 6 slightly thicker than the depth of the groove 6. Further, as shown in FIG. 8B, grooves 7 and 8 may be further provided on both sides of the groove 6 where the mask adhesive 4 is disposed so that the mask adhesive does not protrude from the width of the frame.

However, the EUV mask usually peels off the pellicle and is often used again. In this case, the adhesive residue of the mask adhesive on the EUV mask sometimes becomes a problem. Therefore, as a bonding mechanism between the pellicle 10 and the EUV mask, instead of the mask adhesive, as shown in FIG. 9, the conductive coil 12 is attached to the wire core 11 of a ferromagnetic material such as iron Fe, cobalt Co, nickel Ni or the like. Electromagnets 13 wound with metal nanowires, carbon nanowires, etc. are embedded in the grooves 6 of the frame 3 or joined with an adhesive or the like, and on the other hand, a ferromagnetic surface is provided on the EUV mask side as well. It is more preferable to join to. Instead of installing the electromagnet 13 on the frame 3, an electromagnet can be installed on the EUV mask side, and a ferromagnetic wire or the like can be provided in the groove of the frame.

In addition, as a method of setting a ferromagnetic surface on a mask for EUV made of a multilayer film in which Si and molybdenum (Mo) are alternately deposited on 40 layers of zero expansion glass (LTE glass) alternately, a mask that adheres to a frame is used. A frame or seal made of ferromagnetism such as permalloy thin film or amorphous rare earth iron alloy film in advance is affixed to these areas, or these ferromagnetic thin films are produced by vacuum deposition, sputter deposition, or electrodeposition. You just have to.

As the film adhesive 2, it is preferable to use an inorganic adhesive that has adhesive force and generates little decomposition gas even when irradiated with EUV light and does not affect the exposure. For example, an epoxy resin adhesive mixed with an inorganic substance, for example, A-3 / C-3 (epoxy resin adhesive using carbon black as a filler) manufactured by Fujikura Kasei Co., Ltd., a phenolic adhesive mixed with an inorganic substance, for example, FC-403R / XC-223 manufactured by Fujikura Kasei Co., Ltd. (phenolic resin adhesive using graphite as a filler) or inorganic reactive adhesives such as silicate, phosphate, and colloidal silica can be used.

Subsequently, a method for manufacturing the pellicle 10 will be described. First, when the mask adhesive 4 is used after the frame 3 previously coated with the film adhesive 2 and the pellicle film 1 of the present embodiment are bonded, the mask adhesive on the bonding surface side of the frame 3 with the EUV mask is used. The pellicle 10 of this embodiment can be obtained by applying 4 and then attaching a protective film.

Note that this operation is not required when the frame 3 is bonded to the EUV mask such as an electromagnetic type without using an adhesive. It is possible to use the frame 3 in which the electromagnet 13 or the like is bonded to the bonding surface side of the frame 3 with the EUV mask in advance.

The present invention can be suitably used in the field of EUV lithography as a pellicle film and a pellicle for protecting a lithography mask from contamination.

1 ... pellicle film, 3 ... frame, 4 ... mask adhesive, 13 ... electromagnet.

Claims (9)

1. A pellicle membrane made of a porous carbon membrane and having a thickness D of 100 nm to 63 μm
2. The transmittance T when the extreme ultraviolet light having a wavelength of 13.5 nm passes once is 84% or more, and the amount of scattering by the pores of the carbon porous membrane when the extreme ultraviolet light passes once The pellicle film according to claim 1, wherein Δ is 10% or less.
3. The pellicle membrane according to claim 1 or 2, wherein a pore diameter of the carbon porous membrane is 6.75 nm or more and 2430 nm or less.
4. The pellicle membrane according to any one of claims 1 to 3, wherein an apparent density obtained by dividing mass by volume in the carbon porous membrane is 1.0 × 10 ^-3 to 2.1 g / cm ^3. .
5. When the wavelength λ of extreme ultraviolet light is 13.5 nm, the density W of graphite is 2.25 g / cm ³ , the apparent density (g / cm ³ ) of the carbon porous film is ρ, and the film thickness (nm) is D The pellicle membrane according to any one of claims 1 to 4, wherein the carbon porous membrane has structural parameters satisfying the following expressions:
   α ≦ 30 (α: pore size parameter)
   0.335 ≦ Nd ≦ 13 (N: number of pores in the film thickness direction (pieces), d: wall thickness of the pores (nm))
   αλ / d ≦ 81 (λ: exposure wavelength (nm))
   However, N and d are
   N = −1 + {(W−ρ) ^1/3 / W ^1/3 } + {D (W−ρ) ^1/3 / αλW ^1/3 }
   d = −αλ + {αλW ^1/3 / (W−ρ) ^1/3 }
6. When the wavelength λ of extreme ultraviolet light is 13.5 nm, the density W of graphite is 2.25 g / cm ³ , the apparent density (g / cm ³ ) of the carbon porous film is ρ, and the film thickness (nm) is D The pellicle membrane according to any one of claims 1 to 4, wherein the carbon porous membrane has structural parameters satisfying the following expressions:
   α ≦ 30 (α: pore size parameter)
   αλ / d ≦ 81 (λ: exposure wavelength (nm))
   0.08 g / cm ³ ≦ ρ ≦ 0.7 g / cm ³
   D: 100 ≦ D ≦ 850
7. A pellicle film according to any one of claims 1 to 6,
   A pellicle comprising a frame to which the pellicle film is attached.
8. The pellicle according to claim 7, wherein the frame is provided with a groove on a surface opposite to a surface to which the pellicle film is attached, in which a mask adhesive for bonding to a lithography mask is disposed.
9. The pellicle according to claim 7, wherein the frame is provided with an electromagnet for bonding to a lithography mask on a surface opposite to a surface on which the pellicle film is supported.

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