Pellicle film, pellicle, exposure master, and exposure apparatus

Abstract

Provided is a pellicle film that is likely to have uniform in-plane thickness and, as a result, is likely to have uniform transmittance with respect to EUV light.　A pellicle film 12 is used in EUV lithography. The pellicle film 12 has bundles 21 containing a plurality of carbon nanotubes (CNTs) 23. Here, in the pellicle film 12, when the bundles 21 are cut along a plane intersecting the direction in which the CNTs extend, the included bundles 21 have an oblateness {(t1-t2) / t1} of 0.10-0.90 as calculated from the long diameter (t1) and the short diameter (t2) of the bundles wq.

Description

Technical Field

[0001] The present invention relates to a pellicle film, a pellicle, a photomask, and an exposure apparatus.

Background Art

[0002] Semiconductor devices are manufactured through lithography. In lithography, exposure light emitted from an exposure apparatus is irradiated onto a mask on which a circuit pattern is drawn, whereby the circuit pattern is transferred onto a photoresist. At this time, a pellicle is attached to the mask for dust prevention and the like. The pellicle has a frame and a pellicle film provided on the frame so as to close an opening formed by the frame.

[0003] Due to the demand for pattern miniaturization, extreme ultraviolet (EUV) lithography has attracted attention as a next-generation lithography technology. In EUV lithography, EUV light having a shorter wavelength than conventional exposure light (for example, ArF excimer laser light) is used as exposure light. In order to withstand the temperature rise caused by the irradiation of EUV light, a high heat resistance is required for the pellicle film used in EUV lithography.

[0004] Here, a pellicle film containing carbon nanotubes (hereinafter sometimes referred to as "CNT"), which is a material excellent in heat resistance, has been proposed (see Patent Document 1). Patent Document 1 discloses a pellicle film containing CNTs having a diameter of 0.8 to 6 nm, a length of 10 μm to 10 cm, and a carbon content of 98% by mass or more.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Previously, there was room for improvement in providing pellicle films that easily achieve uniformity in EUV light transmittance. Therefore, an object of the present invention is to provide a pellicle film that easily achieves uniform thickness within its surface, and as a result easily achieves uniformity in the transmittance of EUV light. Another object of the present invention is to provide a pellicle, an exposure plate, and an exposure apparatus having such a pellicle film. [Means for solving the problem]

[0007] One embodiment of the present invention is as follows: [1] A pellicle film used in EUV lithography, The pellicle film has a bundle containing multiple carbon nanotubes (CNTs), A pellicle film comprising a bundle, wherein when the bundle is cut at a plane intersecting the extending direction of the CNT, the flattening ratio {(t1-t2) / t1} calculated from the major axis (t1) and minor axis (t2) of the bundle is 0.10 to 0.90. [2] The pellicle film according to item 1, wherein the bundle comprises an inorganic material layer containing an inorganic oxide and / or inorganic nitride. [3] The pellicle film is the pellicle film according to item 2, wherein the pellicle film has the inorganic material layer on the outermost periphery of the bundle. [4] When the bundle is cut at a plane intersecting the extending direction of the CNT, The pellicle film according to item 2 or 3, wherein the inorganic material layer surrounds the entire bundle. [5] When the bundle is cut at a plane intersecting the extending direction of the CNT, A pellicle film according to any one of items 2 to 4, comprising an inorganic material layer having a thickness of 0.5 to 8.0 nm. [6] When the bundle is cut at a plane intersecting the extending direction of the CNT, A pellicle film according to any one of items 1 to 5, wherein the major axis (t1) of the bundle is 5.0 to 40.0 nm and the minor axis (t2) is 2.0 to 20.0 nm. [7] A pellicle film according to any one of items 2 to 6, wherein the ratio (ni / nc) of the refractive index (ni) of the inorganic material layer at an exposure wavelength of 13.5 nm to the refractive index (nc) of the CNT at an exposure wavelength of 13.5 nm is 0.95 to 1.05. [8] A pellicle film according to any one of items 2 to 7, wherein the extinction coefficient (ki) of the inorganic material layer at an exposure wavelength of 13.5 nm is 0.05 or less. [9] The inorganic material constituting the aforementioned inorganic material layer is A pellicle film according to any one of items 2 to 8, comprising at least one oxide and / or nitride selected from the group consisting of zirconium (Zr), niobium (Nb), aluminum (Al), hafnium (Hf), lanthanum (La), molybdenum (Mo), silicon (Si), yttrium (Y), and titanium (Ti).

[10] A pellicle film described in any one of items 1 to 9, having an EUV light transmittance of 90% or more.

[11] Frame and, A pellicle membrane according to any one of items 1 to 10, provided on the frame to close the opening formed by the frame, A pellicle equipped with this feature.

[12] An exposure master plate comprising a mask and a pellicle described in item 11 which is attached to the mask.

[13] A light source that emits EUV light, The exposure master plate described in item 12 is irradiated with the aforementioned EUV light, An exposure apparatus equipped with the following features. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a pellicle film that is likely to have a uniform thickness in the plane, and as a result, it is easy to achieve uniformity in the transmittance of EUV light. Further, according to the present invention, it is possible to provide a pellicle, an exposure original plate, and an exposure apparatus having such a pellicle film.

Brief Description of Drawings

[0009] [Figure 1] A schematic diagram showing a configuration example of an exposure apparatus and an exposure original plate in this embodiment. [Figure 2] A schematic diagram showing a configuration example of a pellicle in this embodiment. [Figure 3] A schematic diagram and a SEM photograph showing a configuration example of a bundle in this embodiment. [Figure 4] A TEM photograph showing a configuration example of a bundle in this embodiment. [Figure 5] A TEM photograph showing a measurement method of the major axis (t1) and minor axis (t2) of a bundle in an example.

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention (hereinafter referred to as "embodiments") will be described with reference to the drawings. In this specification, the upper limit value and the lower limit value of each numerical range may be arbitrarily combined, and may be replaced with the values shown in the examples. In this specification, a numerical range indicated by "~" includes the numerical values described before and after "~" within the range, unless otherwise specified. In this specification, the term "step" includes not only an independent step but also the term if the function of the step is achieved even when it cannot be clearly distinguished from other steps. The scales, shapes, lengths, etc. of each part shown in the drawings may be exaggerated for further clarity.

[0011] Embodiment 1 [Exposure Apparatus and Exposure Original Plate] Figure 1 is a schematic diagram showing an example configuration of the exposure apparatus 1 and exposure master 2 in this embodiment. The exposure apparatus 1 comprises a light source 3 that emits EUV light and an exposure master 2 that is irradiated with EUV light. The exposure master 2 comprises a mask 4 and a pellicle 5 that is attached to the mask 4. The exposure apparatus 1 further comprises an illumination optical system 6, a projection optical system 7, and a stage 8.

[0012] Exposure apparatus 1 is a so-called reflective type apparatus, and such apparatus is suitable for EUV lithography. In exposure apparatus 1, EUV light emitted from light source 3 is focused by illumination optical system 6, passes through pellicle 5, and irradiates mask 4. The EUV light reflected by mask 4 then passes through pellicle 5 again and is guided by projection optical system 7 to photoresist (not shown) on stage 8.

[0013] The exposure apparatus 1 and exposure master plate 2 utilize a pellicle 5. Therefore, even when hydrogen radicals are generated by EUV light irradiation, degradation of the pellicle film due to these hydrogen radicals can be effectively suppressed. This allows the pellicle film to maintain various required properties (heat resistance, high EUV light transmittance, etc.) over a long period. For these reasons, the exposure apparatus 1 and exposure master plate 2 can effectively meet the demands for miniaturization of patterns.

[0014] [Pellicle] [Schematic configuration] Figures 2(a) and (b) are schematic diagrams showing an example of the configuration of the pellicle 5 in this embodiment. The pellicle 5 comprises a frame 11 and a pellicle membrane 12 provided on the frame 11 to close the opening Op formed by the frame 11. The pellicle 5 is mounted on the mask 4 so as to cover the circuit pattern (not shown) to be drawn on the mask 4.

[0015] The thickness of the pellicle film 12 is preferably 10 to 200 nm, more preferably 10 to 100 nm, and even more preferably 10 to 50 nm, from the viewpoint of suitability for use in EUV lithography.

[0016] [Frame] The frame 11 comprises a pair of long sides and a pair of short sides, and these long and short sides form a rectangular opening Op. Both the long and short sides are substantially rectangular parallelepipeds, and therefore the frame 11 has four faces (one end face 11A, the other end face 11B opposite to the one end face 11A, an inner circumferential surface 1C, and an outer circumferential surface 1D opposite to the inner circumferential surface 1C). Here, a pellicle film 12 is provided on one end face 11A of the frame 11. In the figure, the one end face 11A and the pellicle film 12 are in direct contact. However, other materials (e.g., an adhesive layer) may be interposed between the one end face 11A and the pellicle film 12, as long as it does not adversely affect EUV lithography.

[0017] The area of ​​the aperture Op can be set appropriately from the viewpoint of suitability for EUV lithography. When the area of ​​the aperture Op is small, it is easier to prevent bending of the pellicle film 12, and when the area of ​​the aperture Op is large, it is easier to surround the circuit pattern drawn on the mask 4.

[0018] The frame 11 is composed of, for example, titanium, β-type titanium alloy, and carbon material. Among these, titanium alloy is preferred, and β-type titanium alloy is more preferred. This makes it easier to impart flexibility to the frame 11, thus making it easier to suppress distortion of the mask 4 when the pellicle 5 is attached to the mask 4. It also makes it easier to increase the strength of the frame 11.

[0019] [Mask adhesive layer and release film] The frame 11 may be provided with an adhesive layer (mask adhesive layer) for attaching the frame 11 to the mask 5. In the figure, the frame 11 has a mask adhesive layer 13 on the side opposite to the side on which the pellicle film 12 is provided (one end face 11A) (the other end face 11B). The mask adhesive layer 13 is composed of an adhesive such as an acrylic, rubber, vinyl, epoxy, or silicone adhesive. Among these, an acrylic or silicone adhesive is preferred. The thickness of the mask adhesive layer 13 is, for example, 0.1 to 1.0 mm.

[0020] If the pellicle 5 includes a mask adhesive layer 13, it may further include a release film 14 (liner) laminated on the adhesive surface of the mask adhesive layer 13. The release film 14 suppresses deterioration of the adhesive strength of the mask adhesive layer 13 during storage or transportation of the pellicle 5. When attaching the pellicle 5 to the mask 4, the release film 14 can be peeled off from the mask adhesive layer 13, thereby exposing the adhesive surface of the mask adhesive layer 13.

[0021] The thickness of the release film 14 is, for example, 30 to 200 μm, and it is made of a resin such as polyester. To improve release properties, the surface of the release film 14 may be subjected to a release treatment (for example, a treatment to provide a silicone layer or a fluorine layer).

[0022] [Pellicle membrane] [Schematic configuration] Figures 3(a)-(b) and 4(a)-(b) show examples of the configuration of bundles 21 that constitute the pellicle film 12. Of these, Figure 3(a) is a schematic perspective view showing an example of the configuration of bundles 21, in which an inorganic material layer 22 is arranged around bundles 21 containing multiple CNTs 23. Figure 3(b) is an SEM image showing an example of a network structure formed by bundles 21, and Figures 4(a)-(b) are TEM images showing an example of a cross-sectional structure of bundles 21.

[0023] One aspect of this embodiment is a pellicle film 12 used in EUV lithography, wherein the pellicle film 12 has a bundle 21 containing a plurality of CNTs 23, and the bundle 21 comprises an inorganic material layer 22 containing an inorganic oxide and / or inorganic nitride (see, for example, Figure 3(a)). According to the above-described pellicle film 12, even when hydrogen radicals are generated by irradiation with EUV light, the degradation of CNT 23 due to these hydrogen radicals can be suitably suppressed. As a result, various properties required of the pellicle film 12 (heat resistance, high transmittance to EUV light, etc.) can be maintained over a long period of time, and it is easy to provide a pellicle film with high transmittance and high transmittance uniformity.

[0024] [For EUV lithography applications] EUV lithography is a type of lithography that uses EUV light as the exposure light, and is performed, for example, by an exposure apparatus 1. In EUV lithography, EUV light, which has a shorter wavelength than conventional exposure light, is irradiated onto the pellicle film 12, for example, under a hydrogen atmosphere. The pellicle film 12 has an EUV light transmittance of preferably 90% or more, more preferably 93% or more, and even more preferably 95% or more. This makes it easier to perform EUV lithography.

[0025] 〔bundle〕 (CNT) Bundle 21 is, for example, a bundle containing multiple CNTs 23. The outer surface of bundle 21 is formed by the connection of the outer surfaces of the CNTs 23 located on the outermost edge of the bundle. The CNTs 23 that make up bundle 21 are, CNTs (single-walled nanotubes; SWCNTs) having a single-layer structure, CNTs (double-walled nanotubes; DWCNTs) having a two-layer structure, or CNTs (multiwalled nanotubes; MWCNTs) have a multilayer structure of three or more layers. Either method is acceptable. If the number of layers in the layer structure is small, it is easier to thin the pellicle film 12.

[0026] The length of the CNT23 is preferably less than 10 μm. Including relatively short CNT23s increases the number of ends of the CNT23s in the pellicle film 12. In this case, it is possible to suitably obtain a configuration in which the ends of the CNT23s are wrapped around other CNT23s, thereby making it easier to improve the film strength of the pellicle film 12. Furthermore, it is preferable that the carbon purity of the CNTs is 99.5% or higher. This makes it easier to suppress the adverse effects of impurities, and thus makes it easier to improve the transmittance to EUV light.

[0027] (Mesh structure) The bundles 21 extend in a predetermined direction, and these multiple bundles 21 form a network structure in the pellicle film 12. In Figure 3(b), gaps are formed between the network. In Figure 3(b), the white areas correspond to the bundles 21 and the inorganic material layer 22, and the black areas correspond to the gaps between the bundles 21.

[0028] (Inorganic material layer) The inorganic material layer 22 is provided so as to cover the outer surface of the bundle 21. The inorganic material layer 22 preferably acts as a barrier to the CNTs 23 located inside the inorganic material layer 22. Therefore, it is preferable to have the inorganic material layer 22 on the outermost periphery of the bundle 21 in the pellicle film 12. This makes it easier to suppress the degradation of the CNTs 23 by hydrogen radicals.

[0029] The inorganic material layer 22 may be arranged on the outermost periphery of the bundle 21, in contact with the outermost periphery, may be arranged via any other layer, or may be arranged with a predetermined gap between them. The inorganic material layer 22 may be a single layer or multiple layers. The inorganic material layer 22 is easily realized by exposing the inorganic material to the outer surface of the bundle 21 based on atomic layer deposition (ALD).

[0030] The inorganic material layer 22 may have a single-layer structure or a multi-layer structure of two or more layers. A single-layer structure makes it easier to reduce the density of the network structure. On the other hand, a multi-layer structure of two or more layers makes it easier to obtain an inorganic material layer 22 with excellent properties by allowing each layer to perform its function. A multi-layer structure of two or more layers can be obtained, for example, by applying different inorganic materials to ALD.

[0031] (Refractive index) It is preferable that the ratio (ni / nc) of the refractive index (ni) of the inorganic material layer 22 at an exposure wavelength of 13.5 nm to the refractive index (nc) of the CNT 23 at an exposure wavelength of 13.5 nm is 0.95 to 1.05. This allows the refractive index of the inorganic material to be close to that of the CNT 23 to EUV light, and in this case, scattering of EUV light in the inorganic material layer 22 can be suitably suppressed, making it easier to achieve high transmittance to EUV light.

[0032] (Extinction coefficient) It is preferable that the extinction coefficient (ki) of the inorganic material layer 22 at an exposure wavelength of 13.5 nm is 0.05 or less. This allows for effective suppression of the absorption of EUV light energy by the inorganic material, making it easier to achieve degradation resistance to EUV light.

[0033] (Inorganic materials) The inorganic material layer 22 contains inorganic oxides and / or inorganic nitrides. Such an inorganic material layer 22 barriers the CNTs 23 inside from hydrogen radicals that may be generated by irradiation with EUV light. This allows the pellicle film 12 to maintain various properties (heat resistance, transmittance to EUV light, etc.) over a long period of time. Furthermore, these inorganic materials have better resistance to degradation from EUV light than CNTs 23, making it easier to suitably barrier the bundle 21 from EUV light. Therefore, in this case, it is also easier to achieve resistance to degradation from EUV light.

[0034] The inorganic material is preferably a material containing an oxide and / or nitride selected from the group consisting of zirconium (Zr), niobium (Nb), aluminum (Al), hafnium (Hf), lanthanum (La), molybdenum (Mo), silicon (Si), yttrium (Y), and titanium (Ti). This makes it easier to achieve both degradation resistance to EUV light and high transmittance to EUV light. Furthermore, these materials are easy to surface-treated using known thin-film formation techniques. Examples of thin-film formation techniques include atomic layer deposition (ALD).

[0035] Examples of preferred inorganic materials mentioned above are as follows: Zirconium oxide (ZrO2), zirconium nitride (ZrN and / or Zr3N4), Niobium oxide (Nb2O5), niobium nitride (NbN), Aluminum oxide (Al2O3), aluminum nitride (AlN), Hafnium oxide (HfO2), hafnium nitride (HfN), Lanthanum oxide (La2O3), lanthanum nitride (LaN), Molybdenum oxide (MoO3), molybdenum nitride (MoN), Silicon oxide (SiO2), silicon nitride (SiN), Yttrium oxide (Y2O3), yttrium nitride (YN) Titanium oxide (TiO2), titanium nitride (TiN)

[0036] Since ALD is a method of alternately reacting an organometallic material gas with an oxidizing gas or a reactive nitrogen gas, the inorganic material is preferably a metal oxide or nitride from the viewpoint of suitably realizing ALD. Furthermore, the inorganic material is preferably an oxide or nitride from the viewpoint of resistance to hydrogen radicals generated by irradiation with EUV light in a hydrogen atmosphere.

[0037] From the viewpoint of refractive index, the inorganic material layer 22 is preferably zinc oxide, zirconium oxide, yttrium oxide, niobium oxide, or molybdenum oxide. Furthermore, from the viewpoint of the extinction coefficient, the inorganic material layer 22 is preferably made of lanthanum oxide, niobium oxide, silicon oxide, yttrium oxide, or zirconium oxide.

[0038] One or more types of inorganic materials may be used. The inorganic materials may include other inorganic materials (other inorganic materials) other than those mentioned above. The other inorganic materials do not have to be oxides or nitrides. Examples of such other inorganic materials include ruthenium (Ru) and platinum (Pt). The amount of other inorganic materials relative to the total amount of inorganic materials may be 10% by mass or less, 5% by mass or less, 1% by mass or less, or 0% by mass.

[0039] (cross section) A predetermined cross-section is obtained by cutting the bundle 21 at a plane intersecting the extending direction of the CNT 23 (see, for example, Figures 4(a) to (b)). This bundle 21 includes one in which the flattening ratio {(t1-t2) / t1} calculated from the major axis (t1) and minor axis (t2) of the bundle 21 is 0.10 to 0.90. This makes it easier to maintain various properties required of the pellicle film 12 (heat resistance, high transmittance to EUV light, etc.) over a long period of time.

[0040] The major axis (t1) and minor axis (t2) are mathematically derived major and minor axes, respectively, assuming that the bundle in the cross-section is elliptical. The major axis (t1) and minor axis (t2) are orthogonal at the intersection point P. The major axis (t1) and minor axis (t2) are measured based on the method described in the examples.

[0041] The lower limit of the flattening ratio is preferably 0.20 or higher, more preferably 0.35 or higher, even more preferably 0.45 or higher, and particularly preferably 0.60 or higher. The upper limit of the flattening ratio is preferably 0.90 or lower, more preferably 0.85 or lower, and particularly preferably 0.80 or lower. A larger flattening ratio means a greater degree of flattening of the cross-section. In this embodiment, many of the bundles obtained by predetermined image observation (for example, 80% or more) have an elliptical shape in which the major axis (t1) is aligned with the plane direction of the pellicle film 12 and the minor axis (t2) is aligned with the thickness direction of the pellicle film 12. This shape makes it easier to achieve uniform thickness within the plane, and therefore easier to achieve uniformity of transmittance.

[0042] The major axis (t1) and minor axis (t2) can be adjusted by the application conditions of the CNT dispersion during the pellicle film 12 fabrication process, the drying conditions of the coating film containing the CNT dispersion, the degree of tension applied to the pellicle film 12, etc. To obtain a bundle 11 with a large flattening ratio (elliptical cross-sectional shape), it is preferable, for example, to select the type and amount of dispersant in the wet process.

[0043] When the bundle 21 is cut at a plane intersecting the extending direction of the CNT 23, the major axis (t1) of the bundle 21 is preferably 5.0 to 40.0 nm, with the lower limit of the major axis (t1) being preferably 10.0 nm or more, more preferably 13.0 nm or more, even more preferably 15.0 nm or more, and particularly preferably 20.0 nm or more. The upper limit of the major axis (t1) is preferably 40.0 nm or less, more preferably 35.0 nm or less, even more preferably 30.0 nm or less, and particularly preferably 28.0 nm or less. The minor axis (t2) is preferably 2.0 to 20.0 nm, with the lower limit of the minor axis (t2) being preferably 2.0 nm or more, more preferably 5.0 nm or more, even more preferably 6.0 nm or more, and particularly preferably 8.0 nm or more. The upper limit of the minor axis (t2) is preferably 20.0 nm or less, more preferably 18.0 nm or less, even more preferably 16.0 nm or less, and particularly preferably 14.0 nm or less. According to this, the effects of the present invention are easily obtained, the strength of the mesh structure is easily ensured, and the thinning of the pellicle film is also easily achieved.

[0044] When the bundle 21 is cut at a plane intersecting the extending direction of the CNT 23, it is preferable that the inorganic material layer 22 surrounds the entire bundle 21. This makes it easier for the inorganic material layer 22 to barrier the bundle 21 from all directions. From a similar viewpoint, in one embodiment, it is preferable that the inorganic material layer 22 surrounds the entire bundle 21 at at least one of the cut surfaces obtained by cutting the bundle 21 at a plane intersecting the extending direction of the bundle 21.

[0045] When the bundle 21 is cut at a plane intersecting the extending direction of the CNT 23, it is preferable that the inorganic material layer 22 has a thickness of 0.5 to 8.0 nm. More preferably, it is preferable that it has a thickness of 0.5 to 5.0 nm, and more preferably 1.0 to 3.5 nm. This makes it easier to obtain the effects of the present invention, and furthermore, it is easier to ensure the strength of the network structure and to achieve thinning of the pellicle film. The thickness of such an inorganic material layer 22 corresponds to the thickness of the portion that can perform the function of the inorganic material layer 22, and can be analyzed, for example, by images acquired by a transmission electron microscope (TEM).

[0046] [Method for manufacturing pellicle membrane] There are two processes for depositing carbon nanotube (CNT) films: the wet process and the dry process. The "wet process" refers to a process that utilizes a CNT dispersion, while the dry process does not. Here, we will explain using the wet process as an example.

[0047] In one embodiment, the method for producing a pellicle film is as follows: Step 1 involves applying a dispersion containing CNTs to a substrate to create a coating film, Step 2 involves drying the coating to create a film containing CNTs on the substrate, Step 3 involves immersing a substrate on which a film containing CNTs has been fabricated in water to recover the film containing CNTs, A step of heating the film containing CNTs (step 4), The process includes a step (step 5) of surface-treating a film containing CNTs to arrange an inorganic material layer 22 on a bundle 21 containing multiple CNTs.

[0048] (Process 1) In step 1, a dispersion containing CNTs is applied to a substrate to create a coating film. The dispersion containing CNTs can be prepared by dispersing CNTs synthesized by a predetermined method in a solution of a solvent and a dispersant. Preferably, the solvent has a surface tension of 50.00 mN / m or higher, more preferably 60.00 mN / m or higher, and even more preferably 70.00 mN / m or higher. Preferably, the solvent is an aqueous solution {a solution containing water and a solvent other than water (other solvents)}, or water (surface tension: 72.75 mN / m), with water being particularly preferred. The flatness of the bundle is thought to be influenced by the surface tension of the solvent in the dispersion containing CNTs. Specifically, during the drying of the coating film, as described later, stress is generated due to the surface tension of the solvent, which is thought to increase the flatness of the bundle. When the solvent is an aqueous solution containing water and other solvents, the water content in the aqueous solution is preferably 50% by volume or more, more preferably 70% by volume or more, even more preferably 80% by volume or more, and particularly preferably 90% by volume or more. Examples of dispersants include sodium dodecyl sulfate, flavin derivatives, sodium cholate, and sodium dodecylbenzenesulfonate. A glass substrate or the like can be used as the substrate. As a method for coating the dispersion containing CNTs, spin coating can be used, and the rotation speed of the spin coating can be typically 300 rpm or more, preferably 600 rpm or more, and more preferably 1000 rpm or more. The rotation time of the spin coating can be typically 3 seconds or more, preferably 5 seconds or more, and more preferably 15 seconds or more.

[0049] (Process 2) In step 2, a film containing CNTs is fabricated on the substrate by drying the coating obtained in step 1. Drying can be carried out, for example, in a nitrogen atmosphere using a heat treatment furnace. The drying temperature is, for example, 800-1400°C, 900-1300°C, or 1000-1200°C.

[0050] (Step 3) In step 3, the substrate after step 2 (the substrate on which a film containing CNTs has been fabricated) is immersed in water to recover the film containing CNTs. Recovery can be carried out by scooping up the film containing CNTs from the water using a predetermined frame.

[0051] (Step 4) In step 4, the film containing CNTs recovered in step 3 is heated. This can be done, for example, under reduced pressure or a vacuum atmosphere using a vacuum furnace. The drying temperature is, for example, 200-600°C, 300-500°C, or 350-450°C. If a dispersion containing a dispersant is used in step S1, the dispersant may remain in the film containing CNTs recovered in this step, but the amount of such dispersant can be reduced by heating in this step.

[0052] (Step 5) In step 5, an inorganic material layer 22 is placed on the bundle 21 by surface treatment of the film containing CNTs after step 4 (i.e., the outer periphery of the bundle of the film). As a surface treatment, for example, a method is used in which the outer surface of the bundle 21 is exposed to inorganic material raw materials based on atomic layer deposition (ALD). The type of inorganic material and the thickness of the inorganic material can be controlled by adjusting the type of inorganic material applied to ALD and the amount deposited by ALD.

[0053] [How to manufacture pellicle] The pellicle can be obtained by a conventional method using the above-mentioned pellicle film 12. In other words, A step of preparing the pellicle film 12 (step 11), and The process includes a step (step 12) of attaching the prepared pellicle membrane 12 to the frame 11 so as to close the opening Op formed by the frame 11.

[0054] After steps 11 and 12 described above, or between steps 11 and 12 described above, if necessary, for example, Steps to provide the frame 11 with the mask adhesive layer 13 and the release film 14, The process may include the step of providing a filter in the ventilation holes of the frame 11.

[0055] Other Embodiments The present invention is not limited to Embodiments 1 and 2, and can be implemented with various modifications within the scope of its gist.

[0056] The frame may have any external and internal shapes for attaching the pellicle film and for enclosing the circuit pattern depicted on the mask 4. The frame is constructed as a single unit, but may be constructed to be separable.

[0057] The pellicle film may be pressed onto the frame, or it may be attached to the frame via a predetermined adhesive layer (film adhesive layer). The pellicle 11 may have a predetermined adhesive layer on the inner circumferential surface 11C of the frame. The pellicle 11 may have mechanical means such as a jig for attaching the pellicle 11 to the mask 4, in which case the mask adhesive layer 13 and the release film 14 can be omitted. [Examples]

[0058] This embodiment will be described in more detail with reference to examples and comparative examples.

[0059] [Fabrication of pellicle membrane] [Example 1] 1 g of CNTs and 1 g of sodium dodecyl sulfate as a dispersant were added to 500 mL of water and stirred with a magnetic stirrer at 300 rpm for 1.5 hours to obtain a suspension. The suspension was then subjected to ultrasonic dispersion for 2 hours. During the process, the suspension was cooled with water as needed to prevent the liquid temperature from exceeding 30°C. A CNT dispersion was then obtained. The obtained CNT dispersion was degassed to obtain a dispersion liquid.

[0060] The obtained dispersion was spin-coated onto a glass substrate (rotation speed 1200 rpm for 15 seconds) and dried. This resulted in a CNT film with a thickness of 80 nm on the glass substrate. The CNT film was peeled off the glass substrate by immersing it in water, and the CNT film was scooped up with a frame to obtain a self-supporting CNT film.

[0061] The obtained CNT self-supporting film was heated in a vacuum furnace at 400°C to reduce the amount of sodium dodecyl sulfate. Subsequently, based on ALD, the CNT self-supporting film was exposed to silicon dioxide (SiO2). This yielded the pellicle film of Example 1.

[0062] [Examples 2] to [Examples 7] A pellicle film was obtained using the same method as in Example 1, except that the various raw materials and physical properties were changed as shown in the table. In Example 7, ALD was not performed.

[0063] [Comparative Example 1] A pellicle film was obtained using the same method as in Example 1, except that ZEONANO® 03DS-NP-RD (a 0.3% N-methylmethylpyrrolidone dispersion of ZEONANO® SG101, manufactured by Nippon Zeon Co., Ltd.) was used as the CNT dispersion. The surface tension of N-methylpyrrolidone is 41 mN / m.

[0064] [Making pellicles, etc.] A pellicle was fabricated by heat-pressing the pellicle films of the examples and comparative examples onto one end face of a Ti frame, and by providing an acrylic-based mask adhesive layer on the other end face. Furthermore, an exposure master and exposure apparatus were suitably obtained using the pellicle of the example by conventional methods. The Ti frame used had external dimensions of 40mm x 35mm, internal dimensions of 30mm x 25mm, and a height of 3mm.

[0065] [Material property evaluation] [EUV transmittance] EUV transmittance was measured at NewSUBARU BL-10 (on the University of Hyogo campus) by irradiating with EUV light at a wavelength of 13.5 nm. The beam size was 1.0 mm × 0.06 mm. Transmittance of 90% or more was evaluated as ○, and less than 90% as ×.

[0066] [Transmittance uniformity] The method described above under [EUV Transmittance] was used to scan the central part of the sample in the direction of the shorter side. The difference between the highest and lowest transmittance points was evaluated as follows: less than 0.8% was rated as ○, 0.8-1.2% as △, and greater than 1.2% as ×.

[0067] 〔scattering〕 At NewSUBARU BL-10 (on the University of Hyogo campus), EUV light with a wavelength of 13.5 nm was irradiated, and the resulting scattered light was acquired as a CCD image and analyzed. Scattered light within ±6° was calculated. Scattered light was evaluated as ○ if less than 0.4%, and × if 0.4% or more.

[0068] [EUV hydrogen resistant] The experiment was conducted at NewSUBARU BL-9 (on the University of Hyogo campus). The sample was placed in a chamber, vacuumed, and then hydrogen at 20 Pa was introduced. EUV light with a wavelength of 13.5 nm was irradiated at an intensity of 14 W / cm² and an integrated light dose of 140 kJ / cm². After the irradiation test, the samples were visually inspected and evaluated as follows: ○ if the film shape was maintained without wrinkles, △ if wrinkles were present, and × if damage occurred.

[0069] [The major axis (t1) and minor axis (t2) of the bundle] The pellicle films of the examples and comparative examples were bonded to silicon dummy substrates, and then subjected to FIB processing to prepare samples for cross-sectional observation. The prepared samples were observed using a JEOL JEM-F200 transmission electron microscope (TEM). The acceleration voltage was set to 200kV. In the images obtained by TEM, the inorganic material portion is captured as a dark area, so the darker areas were identified as the inorganic material layer. In cases where the boundary of the inorganic material layer was ambiguous, the image was binarized using image processing software to clarify the boundary line.

[0070] Figures 5(a) and 5(b) are TEM images showing the measurement method for the major axis (t1) and minor axis (t2) of the bundle 21 in the cross-section shown in Figures 4(a) and 4(b). In Figure 5, the cross-sectional image has been binarized, with the inorganic material layer 22 shown in black and the CNT 23 inside it shown in white. The longest distance between boundaries of a line crossing bundle 21 is defined as the major axis, and this length is defined as the major axis (t1). When the perpendicular bisector of the major axis is drawn inside bundle 21, the length of this line segment is defined as the minor axis (t2). Using the obtained major axis (t1) and minor axis (t2), the flattening ratio {(t1-t2) / t1} is calculated.

[0071] [Table 1] [Industrial applicability]

[0072] This invention can be used in the fields of pellicle films, pellicles, exposure plates, and exposure apparatus. [Explanation of symbols]

[0073] 1: Exposure device 2: Exposure master plate 3:Light source 4: Mask 5: Pellicle 6: Illumination optical system 7: Projection optical system 8: Stage 11: Frame 11A: One end surface 11B: Other end surface 11C: Inner surface 11D: Outer surface 12: Pellicle membrane 21: Bundle 22: Inorganic material layer 23: Carbon nanotubes (CNTs) t1: Major axis t2: Short diameter P: Intersection of the major and minor axes

Claims

1. A pellicle film used in EUV lithography, The pellicle film has a bundle containing multiple carbon nanotubes (CNTs), A pellicle film comprising a bundle, wherein when the bundle is cut at a plane intersecting the extending direction of the CNT, the major axis (t1) of the bundle is 5.0 to 40.0 nm, and the flattening ratio {(t1-t2) / t1} calculated from the minor axis (t2) is 0.10 to 0.

80.

2. The pellicle film according to claim 1, wherein the bundle comprises an inorganic material layer containing an inorganic oxide and / or inorganic nitride.

3. The pellicle film according to claim 2, wherein the pellicle film has the inorganic material layer on the outermost periphery of the bundle.

4. When the bundle is cut at a plane that intersects the extending direction of the CNT, The pellicle film according to claim 2, wherein the inorganic material layer surrounds the entire bundle.

5. When the bundle is cut at a plane that intersects the extending direction of the CNT, The pellicle film according to claim 2, comprising an inorganic material layer having a thickness of 0.5 to 8.0 nm.

6. When the bundle is cut at a plane that intersects the extending direction of the CNT, The pellicle film according to claim 1 or 2, wherein the major axis (t1) of the bundle is 5.0 to 30.0 nm and the minor axis (t2) is 2.0 to 20.0 nm.

7. The pellicle film according to claim 2, wherein the ratio (ni / nc) of the refractive index (ni) of the inorganic material layer at an exposure wavelength of 13.5 nm to the refractive index (nc) of the CNT at an exposure wavelength of 13.5 nm is 0.95 to 1.

05.

8. The pellicle film according to claim 2, wherein the extinction coefficient (ki) of the inorganic material layer at an exposure wavelength of 13.5 nm is 0.05 or less.

9. The inorganic material constituting the aforementioned inorganic material layer is The pellicle film according to claim 2, comprising at least one oxide and / or nitride selected from the group consisting of zirconium (Zr), niobium (Nb), aluminum (Al), hafnium (Hf), lanthanum (La), molybdenum (Mo), silicon (Si), yttrium (Y), and titanium (Ti).

10. The pellicle film according to claim 1 or 2, wherein the transmittance of EUV light is 90% or more.

11. Frame and, A pellicle membrane according to claim 1 or 2, provided on the frame so as to close an opening formed by the frame, A pellicle equipped with this feature.

12. An exposure master plate comprising a mask and a pellicle according to claim 11 that is attached to the mask.

13. A light source that emits EUV light, An exposure apparatus comprising: an exposure master plate according to claim 12, which is irradiated with the aforementioned EUV light.

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