JP2024072952A - Pellicle and method for producing pellicle - Google Patents

Abstract

To provide a pellicle capable of suppressing breakage of a pellicle film and a method for producing the pellicle.SOLUTION: A pellicle 1 includes a pellicle film 2 made of SiC, which includes one main surface 2a and the other main surface 2b, a first graphene film 3 formed on one main surface 2a of the pellicle film 2, a second graphene film 4 formed on the other main surface 2b of the pellicle film 2, and a border 5 including holes 51 and supporting the pellicle film 2 from the other main surface 2b side of the pellicle film 2. At least one of the first graphene film 3 and the second graphene film 4 includes a plurality of graphene domains, and at least some of the graphene domains include a first portion and a second portion protruding in a direction away from the pellicle film 2 around the first portion.SELECTED DRAWING: Figure 1

Description

The present invention relates to a pellicle and a method for manufacturing a pellicle. More specifically, the present invention relates to a pellicle that can prevent damage to the pellicle membrane and a method for manufacturing a pellicle.

In photolithography technology used in the manufacturing process of semiconductor devices, a resist is applied to a semiconductor wafer, and exposure light is applied to the required areas of the applied resist using a photomask, creating a resist pattern of the required shape on the semiconductor wafer. When the exposure light is applied to the resist, the photomask is covered with a dustproof cover called a pellicle to prevent foreign matter from adhering to the photomask.

In the manufacturing process of semiconductor devices, the demand for finer photolithography technology is increasing as semiconductor devices become finer. In recent years, it has become mainstream to use light (248 nm) from a KrF (krypton fluoride) excimer laser as a light source or light (193 nm) from an ArF (argon fluoride) excimer laser as a light source as exposure light. In addition, the use of EUV (Extreme Ultra Violet) light (13.5 nm), which has a shorter wavelength than these lights, is also being considered.

When a KrF excimer laser or an ArF excimer laser is used as the light source, an organic thin film is used as the pellicle film. However, when the wavelength of the exposure light is short, such as EUV light, the energy that the pellicle film receives from the exposure light increases. For this reason, in photolithography using EUV light, the use of inorganic thin films with high transmittance and high resistance to EUV light is being considered. This type of inorganic thin film includes Si (silicon), SiN (silicon nitride), C (carbon) (graphite, graphene, diamond-like carbon (DLC), amorphous carbon, carbon nanotubes (CNT), etc.), and SiC (silicon carbide).

Technology relating to pellicles is disclosed, for example, in the following Patent Documents 1 to 4.

The following Patent Document 1 discloses a method for manufacturing a compound semiconductor substrate, which includes a step of forming a SiC film on the front surface of a Si substrate, and a step of removing at least a portion of the rear surface of the Si substrate by wet etching. In the step of removing at least a portion of the rear surface of the Si substrate, the Si substrate and the SiC film are moved relative to the chemical solution used for the wet etching. The following Patent Document 1 also discloses a pellicle that includes a pellicle film made of SiC and a film made of graphene or graphite formed on one main surface of the pellicle film.

The following Patent Document 2 discloses a pellicle that includes a pellicle membrane and a support material that supports the pellicle membrane. The pellicle membrane is made of DLC, amorphous carbon, graphite, carbon nanotubes (CNT), silicon carbide, or the like. The pellicle frame is made of silicon or metal, or the like. This pellicle is manufactured by etching a substrate to form it into a support material, and then forming a pellicle membrane on the substrate.

The following Patent Document 3 discloses a pellicle that includes a pellicle membrane made of a single graphene film or the like.

The following Patent Document 4 discloses a pellicle that includes a main layer made of Si and graphene formed on both sides of the main layer.

JP 2017-218358 A International Publication No. 2014/187710 Japanese Patent No. 6189907 (JP 2016-21078 A) JP 2020-098227 A

In conventional technology, the pellicle film was prone to damage during exposure. For purposes such as achieving high-precision exposure, it is preferable that the irradiation intensity of the exposure light is as high as possible. However, as the irradiation intensity of the exposure light increases, the pellicle film is prone to becoming hot. When the pellicle film becomes hot, the material that constitutes the pellicle film is prone to evaporating, especially when the pellicle film contains SiC. In addition, when the pellicle film becomes hot, hydrogen present in the exposure atmosphere is prone to turning into radicals. These hydrogen radicals etch the pellicle film. As a result, in conventional technology, the pellicle film was prone to being damaged due to the evaporation of the material that constitutes the pellicle film and etching by hydrogen radicals.

The present invention is intended to solve the above problems, and its purpose is to provide a pellicle and a method for manufacturing a pellicle that can prevent damage to the pellicle membrane.

A pellicle according to one aspect of the present invention includes one main surface and the other main surface, a pellicle membrane made of SiC, a first graphene membrane formed on one main surface of the pellicle membrane, a second graphene membrane formed on the other main surface of the pellicle membrane, and a border that includes holes and supports the pellicle membrane from the other main surface side of the pellicle membrane, at least one of the first and second graphene membranes includes a plurality of graphene domains, and at least some of the graphene domains include a first portion and a second portion that protrudes around the first portion in a direction away from the pellicle membrane.

In the above pellicle, preferably, the pellicle membrane includes a plurality of protrusions on the other main surface of the pellicle membrane, each of the plurality of protrusions has a polygonal shape when viewed from the other main surface of the pellicle membrane, and the density of the protrusions on the other main surface of the pellicle membrane is 1 x ¹⁰⁷ /cm2 ^or more and 1 x ¹⁰¹⁰ / ^cm2 or less.

In the above pellicle, preferably, at least a portion of the surface of each of the multiple protrusions includes a (111) plane, and the border is made of a single crystal material containing Si.

In the above pellicle, preferably, the particle size of each of the multiple graphene domains in the second graphene film is 1 nm or more and 1 μm or less, and more preferably 3 nm or more and 50 nm or less.

In the above pellicle, preferably, the density of the second portion of at least a part of the graphene domains in the second graphene film is not less than 1 x 10 ⁶ particles/cm ² and not more than 1 x 10 ¹⁴ particles/cm ² .

In the above pellicle, the pellicle membrane preferably has a thickness of 5 nm or more and 100 nm or less, and more preferably has a thickness of 5 nm or more and 30 nm or less.

A pellicle according to another aspect of the present invention includes one main surface and the other main surface, and comprises a pellicle membrane made of SiC, and a border including holes and made of Si, the border supports the pellicle membrane from the other main surface side of the pellicle membrane, the pellicle membrane includes a plurality of protrusions on the other main surface, when viewed from the other main surface side of the pellicle membrane, the plurality of protrusions have a polygonal shape, and the density of the protrusions on the other main surface of the pellicle membrane is 1 x ¹⁰⁷ /cm2 ^or more and 1 x ¹⁰¹⁰ / ^cm2 or less.

A method for manufacturing a pellicle according to yet another aspect of the present invention includes a step of forming a pellicle film made of SiC on a substrate, the substrate supporting the pellicle film from the other main surface side of the pellicle film, and further includes a step of forming a hole in the substrate, a step of forming a first graphene film on one main surface of the pellicle film, and a step of forming a second graphene film on the other main surface of the pellicle film, and in the step of forming the second graphene film, a gas containing a carbon precursor and hydrogen molecules is supplied to the other main surface of the pellicle film while the pellicle film is heated to a temperature of 1000°C or higher and lower than the melting point of the material constituting the substrate.

In the above manufacturing method, preferably, the step of forming the pellicle film includes a step of carbonizing the substrate by supplying a gas containing hydrocarbon molecules and hydrogen molecules to the substrate while the substrate is heated to a temperature of 1000°C or higher and lower than the melting point of the material constituting the substrate, and a step of epitaxially growing SiC after the step of carbonizing the substrate, and in the step of carbonizing the substrate, the molar ratio of hydrocarbon molecules to hydrogen molecules in the gas containing hydrocarbon molecules and hydrogen molecules is greater than 0 and less than or equal to 10%.

In the above manufacturing method, preferably, in the step of carbonizing the substrate, the molar ratio of hydrocarbon molecules to hydrogen molecules in the gas containing hydrocarbon molecules and hydrogen molecules is greater than 0 and less than or equal to 10%.

In the above manufacturing method, preferably, in the step of carbonizing the substrate, the substrate is heated to a temperature of 1100°C or higher and 1300°C or lower.

In the above manufacturing method, preferably, the step of forming the first graphene film and the step of forming the second graphene film are performed in parallel, and in the steps of forming the first and second graphene films, a gas containing a carbon precursor and hydrogen molecules is supplied to each of one and the other main surfaces of the pellicle film while the pellicle film is heated to a temperature of 1000°C or higher and lower than the melting point of the material constituting the substrate.

In the above manufacturing method, preferably, in the step of forming the second graphene film, a gas containing a carbon precursor and hydrogen molecules is supplied in a state in which the pellicle film is heated to a temperature of 1100° C. or more and 1200° C. or less in an atmosphere with a pressure of ¹ ×10 3 Pa or more and 2×10 ⁵ Pa or less, and the molar ratio of the carbon precursor to the hydrogen molecules in the gas containing the carbon precursor and the hydrogen molecules is 0.01% or more and 0.5% or less, more preferably 0.1% or more and 0.2% or less.

A method for manufacturing a pellicle according to yet another aspect of the present invention includes a step of forming a pellicle film made of SiC on a substrate made of Si, the substrate supporting the pellicle film from the other main surface side of the pellicle film, and further includes a step of forming holes in the substrate, the step of forming the pellicle film includes a step of carbonizing the substrate by supplying a gas containing hydrocarbon molecules and hydrogen molecules to the substrate while the substrate is heated to a temperature of 1000°C or higher and lower than the melting point of the material constituting the substrate, and a step of epitaxially growing SiC after the step of carbonizing the substrate, and in the step of carbonizing the substrate, the molar ratio of hydrocarbon molecules to hydrogen molecules in the gas containing hydrocarbon molecules and hydrogen molecules is greater than 0 and less than or equal to 10%.

The present invention provides a pellicle that can prevent damage to the pellicle membrane and a method for manufacturing the pellicle.

In one embodiment of the present invention, this is a cross-sectional view showing the configuration of a pellicle 1 when cut along a plane perpendicular to a main surface 2a of a pellicle membrane 2. 1 is a plan view showing the configuration of a pellicle 1 when viewed from the main surface 2a side of a pellicle membrane 2 in a first embodiment of the present invention. FIG. FIG. 2 is an enlarged view of part A in FIG. A diagram showing a schematic diagram of the state of the main surface 2b of the pellicle membrane 2. 2 is a cross-sectional view showing the configuration of a graphene domain 41 constituting each of the graphene films 3 and 4. FIG. FIG. 2 is a diagram illustrating a Raman spectrum of a graphene film. 1 is a cross-sectional view showing a first step of a method for manufacturing a pellicle 1 in one embodiment of the present invention. A cross-sectional view showing a second step of the method for manufacturing the pellicle 1 in one embodiment of the present invention. A cross-sectional view showing a third step of the method for manufacturing the pellicle 1 in one embodiment of the present invention. A cross-sectional view showing a fourth step of the method for manufacturing a pellicle 1 in one embodiment of the present invention. FIG. 8 is an enlarged view of part B in FIG. FIG. 9 is an enlarged view of part C in FIG. 8 . FIG. 11 is an enlarged view of part D in FIG. FIG. 2 is a plan view showing an example of a method for holding a pellicle film 2 in a CVD apparatus in one embodiment of the present invention. FIG. 1 is a diagram showing the observation results and test results of samples 1 to 5. 1 is an SEM image of a principal surface of the graphene film on the border side in Sample 1. 1 is an SEM image of a cross section of Sample 1.

One embodiment of the present invention will be described below with reference to the drawings. In this specification, the expression "formed on a surface" means that it is formed in contact with that surface. The expression "formed on the surface side" means both that it is formed in contact with that surface and that it is formed without contacting that surface (at a distance from that surface). The size of each component shown in the drawings is a conceptual size and may differ from the actual dimensions of each component.

Figure 1 is a cross-sectional view showing the configuration of a pellicle 1 when cut along a plane perpendicular to the main surface 2a of the pellicle membrane 2 in one embodiment of the present invention.

Referring to FIG. 1, pellicle 1 (an example of a pellicle) in this embodiment includes pellicle film 2 (an example of pellicle film 2), graphene film 3 (an example of a first graphene film), graphene film 4 (an example of a second graphene film), and border 5 (an example of a border). In the following description, the stacking direction of pellicle film 2 relative to border 5 (the vertical direction in FIG. 1) may be referred to as the thickness direction.

The pellicle film 2 transmits the exposure light and prevents foreign matter from adhering to the photomask. The pellicle film 2 is made of SiC. The pellicle film 2 includes a main surface 2a and a main surface 2b. From the viewpoint of ensuring the transmittance of EUV light and the mechanical strength of the pellicle film 2, it is preferable that the pellicle film 2 has a thickness w of 5 nm or more and 100 nm or less. It is more preferable that the pellicle film 2 has a thickness w of 5 nm or more and 30 nm or less. The pellicle film 2 is made of single crystal 3C-SiC, polycrystalline SiC, amorphous SiC, or the like. In particular, when the pellicle film 2 is epitaxially grown on the main surface 5a of the border 5, the pellicle film 2 is generally made of 3C-SiC.

Each of the graphene films 3 and 4 promotes heat dissipation from the pellicle film 2 and protects the pellicle film 2. The graphene film 3 is formed on the main surface 2a of the pellicle film 2 and is in contact with the main surface 2a of the pellicle film 2. The graphene film 4 is formed on the main surface 2b of the pellicle film 2 and is in contact with the main surface 2b of the pellicle film 2.

The border 5 supports the pellicle film 2 from the main surface 2b side of the pellicle film 2. In other words, the pellicle film 2 is formed on the main surface 5a side of the border 5. The border 5 includes a hole 51 (an example of a hole). The main surface 4a of the graphene film 4 is exposed at the bottom of the hole 51. The border 5 is made of a single crystal material containing, for example, Si. The border 5 may be made of Si. The border 5 has a planar shape of a closed curve. The border 5 includes a main surface 5a and a main surface 5b. When the border 5 is made of Si, the (100) plane is exposed on the main surface 5a of the border 5. When the border 5 is made of Si, the (111) plane or the (110) plane may be exposed on the main surface 5a of the border 5.

Here, the graphene film 4 is formed only at the bottom of the hole 51, and is not formed between the pellicle film 2 and the border 5. The main surface 2b of the pellicle film 2 and the main surface 5a of the border 5 are in contact with each other. The graphene film 4 may be formed over the entire main surface 2b of the pellicle film 2. In this case, the main surface 2b of the pellicle film 2 and the main surface 5a of the border 5 are separated by the graphene film 4.

Figure 2 is a plan view showing the configuration of the pellicle 1 when viewed from the main surface 2a side of the pellicle film 2 in the first embodiment of the present invention. Figure 1 corresponds to a cross-sectional view taken along line I-I in Figure 2. In Figure 2, the border 5 is shown by a dotted line in order to show the shape of the border 5, but in reality the border 5 is not directly visible.

2, the pellicle film 2, the graphene films 3 and 4, the border 5, and the hole 51 each have an arbitrary planar shape. The pellicle film 2 is supported at its outer peripheral end by the border 5 having a closed curve shape. As a result, the mechanical strength of the pellicle film 2 is reinforced by the border 5. The pellicle film 2 and the graphene films 3 and 4 may each have a circular planar shape, for example, as shown in FIG. 2(a) and FIG. 2(c), or a rectangular planar shape as shown in FIG. 2(b). The border 5 may have a square planar shape as shown in FIG. 2(b), or a circular planar shape as shown in FIG. 2(a) and FIG. 2(c). The hole 51 may have a square planar shape as shown in FIG. 2(b) and FIG. 2(c), or a circular planar shape as shown in FIG. 2(a).

Figure 3 is an enlarged view of part A in Figure 1. Figure 4 is a schematic diagram showing the state of the main surface 2b of the pellicle membrane 2.

Referring to Figures 3 and 4, the pellicle film 2 includes a plurality of protrusions 22 (an example of a protrusion) formed on the main surface 2b of the pellicle film 2. When viewed from the main surface 2b side of the pellicle film 2, each of the plurality of protrusions 22 has a polygonal shape. Each side constituting the plurality of protrusions 22 is formed by a crystal plane having a specific orientation. Here, when viewed from the main surface 2b side of the pellicle film 2, each of the plurality of protrusions 22 has a quadrangular shape.

At least a portion of the surface of each of the plurality of protrusions 22 includes, for example, a (111) plane. Specifically, when the protrusions 22 are rectangular, one side of one protrusion 22 includes two crystal faces 221 and 222. One protrusion 22 includes eight crystal faces 221 and 222 of SiC. The crystal face 221 is an outer crystal face of one protrusion 22. The crystal face 222 is an inner crystal face of one protrusion 22. Each of the crystal faces 221 is, for example, composed of a (111) plane. The density of the protrusions 22 on the main surface 2a of the pellicle film 2 is 1×10 ⁷ /cm ² or more and 1×10 ¹⁰ /cm ² or less.

The density of protrusions on the main surface of the pellicle membrane is measured by taking a planar SEM (Scanning Electron Microscope) image or a bird's-eye SEM image of the main surface of the pellicle membrane and counting the number of protrusions present in a specified area (e.g., a square area with a side of 1 μm).

The above-mentioned configuration of the pellicle film 2 is realized by adopting a method for forming the pellicle film 2 described below. The pellicle film 2 in the pellicle 1 does not need to include the protrusions 22.

Figure 5 is a cross-sectional view showing the configuration of the graphene domains 41 that make up each of the graphene films 3 and 4.

3 to 5, each of the graphene films 3 and 4 includes a plurality of graphene domains 41 (an example of a graphene domain). Each of the plurality of graphene domains 41 is stacked in the thickness direction. One layer of graphene domains 41 and a layer of graphene domains 41 thereon are formed at intervals of 0.345 nm by van der Waals forces. A plurality of graphene domains 41 are laid out in a multi-layer on each of the main surfaces 2a and 2b of the pellicle film 2. Each of the main surfaces 2a and 2b of the pellicle film 2 is covered with a plurality of graphene domains 41. Each of the plurality of graphene domains 41 constituting each of the graphene films 3 and 4 is single crystal or polycrystalline. At least a portion of the graphene domains 41 among the plurality of graphene domains 41 constituting each of the graphene films 3 and 4 (more specifically, the plurality of graphene domains 41 constituting the vicinity of the surface of each of the graphene films 3 and 4) includes a central portion 411 (an example of a first portion) and a peripheral portion 412 (an example of a second portion). The central portion 411 extends along the main surface 2a or 2b of the pellicle film 2. The central portion 411 is in contact with the pellicle film 2 or the underlying graphene domain 41. The peripheral portion 412 protrudes in a direction away from the pellicle film 2 around the central portion 411. The peripheral portion 412 is an end of the graphene domain 41, and is turned up in a direction away from the pellicle film 2.

In addition, only one of the graphene films 3 and 4 (for example, only the graphene film 4) may include multiple graphene domains 41.

The density of outer circumferential portions 412 which are protruding portions of graphene domains 41 in each of graphene films 3 and 4 is 1× ¹⁰ particles/cm ^or more and 1× ¹⁰ particles/cm ^or less. The grain size of each of the plurality of graphene domains 41 in each of graphene films 3 and 4 is preferably 1 nm or more and 1 μm or less, and more preferably 3 nm or more and 50 nm or less.

The particle size of the graphene domains in the graphene film is measured by the following method based on the Raman spectrum of the graphene film.

Figure 6 is a schematic diagram showing the Raman spectrum of a graphene film.

6, the Raman spectrum of the graphene film has a D band (near 1350 cm ^-1 ), a G band (near 1582 cm ^-1 ), and a 2D band (near 2685 cm ^-1 ) as main peaks. The D band is a peak derived from an irregular structure or defects. The G band is a peak derived from the in-plane motion of sp2 bonded carbon constituting graphene. When the ratio of the height ID of the D peak to the height IG of the G peak is the ratio ID/IG and the wavelength of the incident light during the Raman spectrum measurement is the wavelength λ, the particle size GD of the graphene domain is calculated using the following formula (1).

Grain size GD=(2.4×10 ⁻¹⁰ (nm ⁻³ ))×λ ⁴ /(ratio ID/IG) (1)

According to the above formula (1), when the wavelength λ is 532 nm and the ratio ID/IG is 1, the particle size GD is 19.2 nm.

The configuration of the graphene films 3 and 4 including the graphene domains 41 described above is realized by employing a method for forming the graphene films 3 and 4 described below.

Next, we will explain the manufacturing method of the pellicle 1 in this embodiment.

Figures 7 to 10 are cross-sectional views showing the process steps of a method for manufacturing a pellicle 1 in one embodiment of the present invention. Figure 11 is an enlarged view of part B in Figure 7. Figure 12 is an enlarged view of part C in Figure 8. Figure 13 is an enlarged view of part D in Figure 10.

Referring to Figures 7 and 11, a plate-shaped substrate 5 (an example of a substrate) is prepared. The substrate 5 corresponds to the border before the holes are formed. Next, the pellicle film 2 is formed on the main surface 5a of the substrate 5.

The pellicle membrane 2 is formed in a two-step process as follows:

In the first step, the main surface 5a of the substrate 5 is carbonized. Specifically, the substrate 5 is heated to a temperature of 1000°C or higher but lower than the melting point of the material (here, Si) that constitutes the substrate 5, and a mixed gas containing hydrocarbon molecules and H (hydrogen) molecules is supplied to the main surface 5a of the substrate 5. This carbonizes the main surface 5a of the substrate 5, and a SiC film 23 is formed. The heating temperature of the substrate 5 is preferably 1100°C or higher but lower than 1300°C.

Under the above conditions, C atoms in the mixed gas react with Si on the main surface 5a of the substrate 5 to form the SiC film 23. In parallel with the formation of the SiC film 23, H atoms in the mixed gas are converted into radicals, which selectively etch away the Si on the main surface 5a of the substrate 5 that is not covered by the SiC film 23. This forms a depression 53 on the main surface 5a of the substrate 5. The crystal plane 531 of the Si that constitutes the depression 53 is a specific plane, such as a (111) plane, and depends on the crystal plane orientation of the main surface 5a of the substrate 5.

The molar ratio of hydrocarbon molecules to H molecules in the above mixed gas is greater than 0 and less than or equal to 10%. This makes the concentration of hydrocarbon molecules in the mixed gas low enough not to reach the concentration required to form a dense SiC film, so that the SiC film 23 has a mesh-like structure. As a result, depressions 53 can be formed in the gaps in the mesh-like SiC film 23.

8 and 12, in the second step, the SiC film 24 is epitaxially grown on the main surface 23a of the SiC film 23. The SiC film 24 is also formed in the gaps and recesses 53 of the mesh-like SiC film 23. The SiC films 23 and 24 become the pellicle film 2. As a result, the pellicle film 2 including the main surfaces 2a and 2b is formed on the main surface 5a of the substrate 5. The substrate 5 supports the pellicle film 2 from the main surface 2b side of the pellicle film 2. The portion of the SiC film 24 filling the recess 53 becomes the protrusion 22. The protrusion 22 protrudes toward the substrate 5 more than the SiC film 23 and constitutes a part of the main surface 2b of the pellicle film 2. The crystal surface of the protrusion 22 that contacts the substrate 5 becomes the crystal surface 221, and has the same plane orientation as the Si crystal surface 531 that constitutes the recess 53. When the crystal face 531 of the recess 53 includes a (111) plane, the crystal face 221 of the protrusion 22 also includes a (111) plane. The density of the protrusions 22 on the main surface 2a of the pellicle film 2 is 1×10 ⁷ /cm ² or more and 1×10 ¹⁰ /cm ² or less.

It should be noted that the smaller the molar ratio of hydrocarbon molecules to H molecules in the mixed gas used in the first step, the more the number of depressions 53 on the main surface 5a of the substrate 5 and the more the number of protrusions 22 on the pellicle film 2. Specifically, when the molar ratio of hydrocarbon molecules to H molecules in the mixed gas is greater than 0 and less than or equal to 10%, the density of the protrusions 22 on the main surface 2a of the pellicle film 2 is greater than or equal to 1 x ¹⁰⁷ /cm2 ^{and less} than or equal to 1 x ¹⁰¹⁰ /cm2.

Referring to FIG. 9, a mask layer 91 made of SiC or the like is formed on the outer peripheral edge of the main surface 5b of the substrate 5. Using the mask layer 91 as a mask, the central portion RG1 of the main surface 5b of the substrate 5 is removed. The central portion RG1 is removed by any method, for example, mechanical polishing such as sandblasting.

As a result of removing the central portion RG1, a groove 52 is formed on the main surface 5b of the substrate 5, with the material constituting the substrate 5 as its bottom surface. The groove 52 has a depth that does not penetrate the substrate 5. Due to the presence of the groove 52, the thickness of the central portion of the substrate 5 is thinner than the thickness of the outer peripheral edge portion of the substrate 5.

In addition, after forming the grooves 52 in the substrate 5, the pellicle film 2 may be formed on the main surface 5a of the substrate 5.

10 and 13, after the formation of the pellicle film 2, the bottom surface RG2 of the groove 52, which is a part of the substrate 5, is removed by wet etching. As a result of removing the bottom surface RG2, the groove 52 becomes a hole 51 penetrating the substrate 5, and the substrate 5 becomes a border 5. The main surface 2b of the pellicle film 2 is exposed at the bottom surface of the hole 51. By adopting wet etching as a method for removing the bottom surface RG2, damage to the pellicle film 2 when removing the bottom surface RG2 can be suppressed. Note that the hole 51 may be formed in the plate-shaped substrate 5 using only wet etching without forming the groove 52 by any method. After the hole 51 is formed, the mask layer 91 is removed. This results in the structure 1a. Note that the mask layer 91 does not have to be removed in the structure 1a.

The chemical used in wet etching the bottom surface RG2 may be, for example, a mixed acid containing an oxidizing acid such as hydrofluoric acid and nitric acid, or an aqueous solution of potassium hydroxide (KOH). In order to prevent the pellicle film 2 from being etched and to improve the quality of the pellicle film 2, it is preferable to use a mixed acid made of hydrofluoric acid and nitric acid as the chemical for wet etching the substrate 5.

When wet etching the bottom surface RG2, it is preferable to perform the wet etching by moving the pellicle film 2 and the substrate 5 relative to the chemical solution used for the wet etching. In particular, in order to avoid a situation in which the pellicle film 2 is damaged due to the pressure from the chemical solution while the pellicle film 2 and the substrate 5 are being moved, it is preferable to move the pellicle film 2 and the substrate 5 in a direction within a plane parallel to the main surface 2a of the pellicle film 2. As such wet etching, spin etching is most preferable.

The mask layer 91 may be made of a material that is insoluble in at least one of a chemical solution containing an acid that has an oxidizing effect on Si and hydrofluoric acid, and an alkaline aqueous solution composed only of components that have no oxidizing effect on Si. The mask layer 91 may be made of, for example, SiC, SiN, _SiO2 (silicon oxide), photoresist, or the like.

The structure 1a shown in FIG. 10 has a structure in which the graphene films 3 and 4 are omitted from the pellicle 1 in FIG. 1. It is also possible to use the structure 1a in which the graphene films 3 and 4 are omitted as a pellicle.

Referring to FIG. 1, a graphene film 3 is then formed on the main surface 2a of the pellicle film 2 by using a CVD (chemical vapor deposition) method or the like, and a graphene film 4 is formed on the main surface 2b of the pellicle film 2. The graphene films 3 and 4 are preferably formed in parallel. When forming the graphene films 3 and 4, a mixed gas containing a carbon precursor and H molecules is supplied to each of the main surfaces 2a and 2b of the pellicle film 2 while the pellicle film 2 is heated to a temperature of 1000° C. or higher and lower than the melting point of the material (here, Si) constituting the substrate 5.

The pressure of the atmosphere when the graphene films 3 and 4 are formed may be any of reduced pressure, normal pressure, and increased pressure. However, from the viewpoint of forming the graphene films 3 and 4 using a film forming device for the pellicle film 2, the pressure of the atmosphere when the graphene films 3 and 4 are formed is preferably 1×10 ⁻⁴ Pa or more and 2×10 ⁵ Pa or less, and more preferably 1×10 ³ Pa or more and 2×10 ⁵ Pa or less. From the viewpoint of suppressing deformation of the substrate 5 due to heat, the temperature of the pellicle film 2 when each of the graphene films 3 and 4 is formed is preferably 1100° C. or more and 1200° C. or less.

The molar ratio of carbon precursor to H molecules in a mixed gas containing carbon precursor and H molecules is, for example, 0.01% or more and 100% or less. The molar ratio of carbon precursor to H molecules in a mixed gas containing carbon precursor and H molecules is preferably 0.01% or more and 1% or less, and more preferably 0.1% or more and 0.2% or less.

As the carbon precursor, a hydrocarbon such as methane, ethane, propane, butane, pentane, hexane, heptane, octane, ethylene, propylene, butene, pentene, hexene, heptene, octene, acetylene, propyne, butyne, pentyne, hexyne, heptyne, or octyne is used. As the carbon precursor, it is particularly preferable to use methane, ethane, or propane.

The lower the temperature of the pellicle film 2 when the graphene film is formed, the higher the density of the graphene domains in the graphene film and the smaller the particle size of the graphene domains in the graphene film. When the temperature of the pellicle film 2 when each of the graphene films 3 and 4 is formed is 1100°C or higher and 1200°C or lower, the particle size of each of the multiple graphene domains 41 in each of the graphene films 3 and 4 is 3 nm or higher and 50 nm or lower.

In order to form the graphene films 3 and 4 in parallel, it is preferable that the pellicle film 2 is held in the following manner during the formation of the graphene films 3 and 4.

Figure 14 is a plan view showing an example of a method for holding the pellicle film 2 in a CVD device in one embodiment of the present invention.

Referring to FIG. 14, the CVD apparatus includes a holding portion 81 for holding the pellicle film 2. The holding portion 81 includes an annular outer peripheral portion 81a and a plurality of (three in this example) protruding portions 81b provided at equal intervals on the inner peripheral end of the outer peripheral portion 81a. Each of the plurality of protruding portions 81b is linear and protrudes toward the center of the outer peripheral portion 81a. The pellicle film 2 is placed on the tip of each of the plurality of protruding portions 81b so that the main surface 2a faces upward. A mixed gas containing carbon precursors and H molecules is caused to flow in the direction indicated by the arrow AR1 on the main surface 2a of the pellicle film 2. A portion of the mixed gas containing carbon precursors and H molecules flows around to the main surface 2b of the pellicle film 2 through the space SP between the outer peripheral portion 81a and the plurality of protruding portions 81b.

By using the above-mentioned method, a mixed gas containing a carbon precursor and hydrogen molecules is supplied to each of the main surfaces 2a and 2b of the pellicle film 2. Both the main surfaces 2a and 2b of the pellicle film 2 are in contact with the carbon precursor. As a result, the graphene films 3 and 4 can be formed in parallel on each of the main surfaces 2a and 2b of the pellicle film 2.

[Effects of the embodiment]

In the above-described embodiment, each of the main surfaces 2a and 2b of the pellicle film 2 is covered by each of the graphene films 3 and 4. Compared to the interatomic bonding force of the SiC that constitutes the pellicle film 2, the interatomic bonding force of the graphene that constitutes the graphene films 3 and 4 is stronger. This makes it possible to prevent evaporation of the SiC that constitutes the pellicle film and etching of the pellicle film by hydrogen radicals. As a result, damage to the pellicle film 2 can be suppressed.

In addition, the peripheral portion 412 of each of the multiple graphene domains 41 constituting each of the graphene films 3 and 4 protrudes in a direction away from the pellicle film 2. The presence of the protruding peripheral portion 412 increases the surface area of the graphene films 3 and 4, improving the heat dissipation efficiency of the pellicle film 2. As a result, the pellicle film 2 is less likely to become hot, and damage to the pellicle film 2 can be suppressed.

Furthermore, there are multiple protrusions 22 on the main surface 2b of the pellicle film 2. The presence of the protrusions 22 increases the surface area of the pellicle film 2, improving the heat dissipation efficiency of the pellicle film 2. As a result, the pellicle film 2 is less likely to become hot, and damage to the pellicle film 2 can be suppressed.

[Example]

The inventors prepared the following samples 1 to 5.

Sample 1 (Example of the present invention): The pellicle 1 shown in FIG. 1 was manufactured using the manufacturing method described in the above embodiment. A pellicle film was formed on the main surface of the substrate in a two-step process including a process of forming a first SiC film by carbonizing the main surface of the substrate and a process of epitaxially growing a second SiC film on the main surface of the first SiC film. When forming the first SiC film, a mixed gas containing hydrocarbon molecules and hydrogen molecules was supplied to the substrate while the substrate was heated to 1175° C. The molar ratio of the hydrocarbon molecules to the hydrogen molecules in the mixed gas was 1%. When forming a graphene film on each of the two main surfaces of the pellicle film, a mixed gas containing a carbon precursor and hydrogen molecules (H ₂ molecules) was supplied to each of the two main surfaces of the pellicle film. The molar ratio of the carbon precursor to the hydrogen molecules in the mixed gas was 0.15%. When forming the graphene film on each of the two main surfaces of the pellicle film, the temperature of the pellicle film was set to 1200° C., and the pressure of the atmosphere was set to 1×10 ⁵ Pa.

Sample 2 (Example of the present invention): Structure 1a (pellicle without graphene film) shown in FIG. 10 was manufactured. The pellicle was manufactured using the same method as the pellicle manufacturing method for sample 1, except that the graphene film was not formed.

Sample 3 (example of the present invention): When forming the first SiC film, a gas containing hydrocarbon molecules but not hydrogen molecules was supplied to the substrate. Other than this, the pellicle was manufactured using the same method as the pellicle manufacturing method for sample 1.

Sample 4 (Comparative Example): A pellicle without a graphene film was manufactured. When forming the first SiC film, a gas containing hydrocarbon molecules but not hydrogen molecules was supplied to the substrate. Other than this, the pellicle was manufactured in the same manner as sample 2.

Sample 5 (Comparative Example): When forming a graphene film on each of the two main surfaces of the pellicle film, a mixed gas containing a carbon precursor and hydrogen molecules was supplied to the substrate. The molar ratio of carbon precursor to hydrogen molecules in the mixed gas was 0.005%. Other than this, the pellicle was manufactured in the same manner as sample 3.

Figure 15 shows the observation and test results of samples 1 to 5. Figure 16 is an SEM image of the main surface of the graphene film on the border side of sample 1. Figure 17 is an SEM image of the cross section of sample 1. In Figure 17, the shape of the graphene domains in the graphene film on the border side is shown by a dotted line.

Referring to Figures 15 to 17, the inventors of the present application next observed each of Samples 1 to 5 using an SEM. For Samples 1, 3, and 5, which contained a graphene film, the main surface of the graphene film on the border side was observed. For Samples 2 and 4, which did not contain a graphene film, the main surface of the pellicle film on the border side was observed. As the SEM, a field emission scanning electron microscope (FE-SEM: JSM-6700F, JEOL Ltd., Japan) was used. The acceleration voltage was set to 5 kV.

As a result of the observation, a plurality of rectangular protrusions were generated on the main surface of the pellicle membrane on the border side in samples 1 and 2. The density of the protrusions was 1×10 ⁷ /cm ² or more and 1×10 ¹⁰ /cm ² or less. On the other hand, no protrusions were generated in samples 3 to 5.

Of the graphene film-containing samples 1, 3, and 5, samples 1 and 3 had peripheral portions (white string-like portions in Figure 16) protruding from the graphene domains throughout the entire graphene film. Sample 5 had no peripheral portions protruding from the graphene domains.

Next, the inventors of the present application measured Raman spectra of the graphene films on the border sides of each of Samples 1 and 3. Based on the ratio ID/IG of the height ID of the D peak to the height IG of the G peak, the particle size of each of the multiple graphene domains in the graphene film and the density of the graphene domains were calculated. As a result, the particle size of each of the multiple graphene domains in the graphene film was 3 nm or more and 50 nm or less. The density of the graphene domains in the graphene film was 1×10 ⁶ domains/cm ² or more and 3×10 ⁷ domains/cm ² or less.

Next, the inventors of the present application evaluated the durability of each of Samples 1 to 5. With each of Samples 1 to 5 placed in a hydrogen atmosphere at a pressure of 5 Pa, the pellicle film was irradiated with EUV light having an illuminance of 27.6 W/ ^cm2 for 2.5 hours.

As a result of irradiation with EUV light, the pellicle film of sample 1 was not damaged. The pellicle film of sample 2 was damaged 2.1 hours after the start of irradiation. The pellicle film of sample 3 was damaged 2.4 hours after the start of irradiation. The pellicle film of sample 4 was damaged 24 minutes after the start of irradiation. The pellicle film of sample 5 was damaged 1.1 hours after the start of irradiation.

[others]

The above-mentioned embodiments and examples can be combined as appropriate.

The above-described embodiments and examples should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

1 Pellicle (an example of a pellicle)
1a Structure (an example of a pellicle)
2. Pellicle membrane (an example of a pellicle membrane)
2a, 2b: Main surface of pellicle film 3, 4: Graphene film (examples of first and second graphene films)
3a, 4a Principal surface of graphene film 5 Border or substrate (an example of a border and substrate)
5a, 5b Main surface of border 22 Protrusion of pellicle film (an example of a protrusion)
23, 24 SiC film of pellicle film 23a, 23b Main surface of SiC film 41 Graphene domain (an example of a graphene domain)
51 Border hole (example of hole)
52 Border groove 53 Border depression 81 Holding portion 81a Outer periphery of holding portion 81b Protrusion of holding portion 91 Mask layer 221, 222 Crystal plane of SiC constituting protrusion of pellicle film 411 Central portion of graphene domain (an example of a first portion)
412: Outer periphery of graphene domain (an example of a second portion)
531: Si crystal plane forming the border depression RG1: Center of the border main surface RG2: Bottom surface of the hole

Claims (9)

A pellicle membrane including one principal surface and another principal surface and made of SiC;
A first graphene film formed on the one main surface of the pellicle film;
A second graphene film formed on the other main surface of the pellicle film;
a border including a hole and supporting the pellicle membrane from the other main surface side of the pellicle membrane;
At least one of the first and second graphene films includes a plurality of graphene domains;
At least a portion of the graphene domains among the plurality of graphene domains
A first portion; and
and a second portion protruding in a direction away from the pellicle membrane around the periphery of the first portion. The pellicle membrane includes a plurality of protrusions on the other main surface of the pellicle membrane,
When viewed from the other main surface side of the pellicle membrane, each of the plurality of protrusions has a polygonal shape,
2. The pellicle according to claim 1, wherein the density of protrusions on the other main surface of the pellicle membrane is 1×10 ⁷ /cm ² or more and 1×10 ¹⁰ /cm ² or less. At least a portion of a surface of each of the plurality of protrusions includes a (111) plane;
The pellicle of claim 2 , wherein the border is made of a single crystal material including Si. A pellicle membrane including one principal surface and another principal surface and made of SiC;
a border comprising a hole and made of Si;
The border supports the pellicle membrane from the other main surface side of the pellicle membrane,
The pellicle membrane includes a plurality of protrusions on the other main surface,
When viewed from the other main surface side of the pellicle membrane, the plurality of protrusions have a polygonal shape,
A pellicle, wherein the density of protrusions on the other main surface of the pellicle membrane is 1×10 ⁷ /cm ² or more and 1×10 ¹⁰ /cm ² or less. The method includes forming a pellicle film made of SiC on a substrate, the pellicle film including one main surface and the other main surface, the substrate supporting the pellicle film from the other main surface side of the pellicle film;
forming a hole in the substrate;
forming a first graphene film on the one main surface of the pellicle film;
and forming a second graphene film on the other main surface of the pellicle film,
A method for manufacturing a pellicle, in which, in the step of forming the second graphene film, a gas containing a carbon precursor and hydrogen molecules is supplied to the other main surface of the pellicle film while the pellicle film is heated to a temperature of 1000° C. or higher and lower than the melting point of a material constituting the substrate. The step of forming the pellicle membrane includes:
a step of carbonizing the substrate made of Si by supplying a gas containing hydrocarbon molecules and hydrogen molecules to the substrate while the substrate is heated to a temperature of 1000° C. or higher and lower than the melting point of a material constituting the substrate;
and epitaxially growing SiC after the step of carbonizing the substrate;
The method for manufacturing a pellicle according to claim 5 , wherein in the step of carbonizing the substrate, a molar ratio of hydrocarbon molecules to hydrogen molecules in a gas containing hydrocarbon molecules and hydrogen molecules is greater than 0 and less than or equal to 10%. The method for manufacturing a pellicle according to claim 6, wherein in the step of carbonizing the substrate, the molar ratio of hydrocarbon molecules to hydrogen molecules in the gas containing hydrocarbon molecules and hydrogen molecules is greater than 0 and less than or equal to 10%. In the step of forming the second graphene film, a gas containing the ^{carbon precursor} and hydrogen molecules is supplied in a state in which the pellicle film is heated to a temperature of 1100° C. or more and ¹³⁰⁰ ° C. or less in an atmosphere with a pressure of 1×10 3 Pa or more and 2×10 5 Pa or less;
The method for manufacturing a pellicle according to claim 5 , wherein a molar ratio of the carbon precursor to the hydrogen molecules in the gas containing the carbon precursor and the hydrogen molecules is 0.1% or more and 0.2% or less. The method includes forming a pellicle film made of SiC on a substrate made of Si, the substrate supporting the pellicle film from the other main surface side of the pellicle film;
forming a hole in the substrate;
The step of forming the pellicle membrane includes:
a step of carbonizing the substrate by supplying a gas containing hydrocarbon molecules and hydrogen molecules to the substrate while the substrate is heated to a temperature of 1000° C. or higher and lower than the melting point of a material constituting the substrate;
and epitaxially growing SiC after the step of carbonizing the substrate;
A method for manufacturing a pellicle, wherein in the step of carbonizing the substrate, a molar ratio of hydrocarbon molecules to hydrogen molecules in a gas containing hydrocarbon molecules and hydrogen molecules is greater than 0 and less than or equal to 10%.

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