Substrate holding plate and exposure apparatus

Abstract

The present invention relates to a substrate holding plate and an exposure apparatus. The substrate holding plate has a substrate holding surface. The substrate holding plate includes: a base; and a protrusion provided on the substrate holding surface side with respect to the base and supporting a substrate. At least an uppermost surface of the protrusion is a rough surface. The base or the protrusion has a first portion. The protrusion has a second portion having a higher hardness than that of the first portion. The second portion is provided within a range of a distance D from a top of the rough surface. The distance D is smaller than a height difference H between the top and a bottom adjacent to the top.

Description

Technical Field

[0001] This invention relates to a substrate holding plate and an exposure apparatus. Background Technology

[0002] Substrates such as glass or silicon used in the manufacture of various electronic devices are arranged on the holding surface of a substrate holding plate and held by the substrate holding plate.

[0003] The effective method is to roughen the surface of the substrate holding plate.

[0004] Japanese Patent Application Publication No. 2006-64992 discloses a substrate holding plate in which both the supporting surface that supports the substrate and the non-supporting surface that does not support the substrate are rough surfaces, and these rough surfaces are made of aluminum oxide.

[0005] In the substrate holding plate of Japanese Patent Application Publication No. 2006-64992, there is a problem that the rough surface formed on the support surface of the substrate holding plate is worn and smoothed out due to contact with the substrate.

[0006] The present invention provides a substrate holding plate capable of suppressing wear on rough surfaces.

[0007] The present invention also provides a substrate holding plate capable of reducing light reflection at the surface of the substrate holding plate. Summary of the Invention

[0008] A first aspect provides a substrate holding plate having a substrate holding surface, comprising: a base; and a protrusion disposed relative to the base on the substrate holding surface side and supporting the substrate. The uppermost surface of each of the base and the protrusion is a rough surface with an arithmetic mean roughness Ra of 0.4 μm or greater. The base or the protrusion has a first portion. At least the protrusion has a second portion with a hardness higher than the first portion. The second portion is disposed within a distance D from the top of the rough surface. The distance D is less than the height difference H between the top and the bottom adjacent to the top.

[0009] A second aspect provides a substrate holding plate having a substrate holding surface, comprising: a base member having a first portion; a second portion disposed on the substrate holding surface side relative to the first portion and having a hardness higher than that of the first portion; and a third portion disposed on the substrate holding surface side relative to the second portion and having a refractive index lower than that of the second portion. The difference n2-n1 between the refractive index n2 of the second portion and the refractive index n1 of the first portion is less than the difference n2-n3 between the refractive index n2 of the second portion and the refractive index n3 of the third portion.

[0010] A third aspect provides a substrate holding plate having a substrate holding surface, comprising: a base member having a first portion; a second portion disposed on the substrate holding surface side relative to the first portion and having a hardness higher than that of the first portion; and a third portion made of a porous material and disposed on the substrate holding surface side relative to the second portion.

[0011] A fourth aspect provides a substrate holding plate having a substrate holding surface, comprising: a base member having a first portion; and a second portion disposed on the substrate holding surface side relative to the first portion and having a hardness higher than that of the first portion. The first portion is made of a material with an oxygen content of 25 at% or more. The second portion is made of a material with a carbon or nitrogen content of 25 at% or more. The first portion has a nitrogen-containing region, the nitrogen content of which is 1 at% or more within 100 nm of the second portion.

[0012] Further features of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0013] Figures 1A to 1E This is a perspective view of the substrate holding plate.

[0014] Figures 2A to 2C This is a schematic diagram showing the substrate holding plate.

[0015] Figures 3A to 3C This is a schematic diagram showing the substrate holding plate.

[0016] Figure 4A and 4B This is a schematic diagram showing the substrate holding plate.

[0017] Figure 5A and 5B This is a schematic diagram showing the substrate holding plate.

[0018] Figure 6A and 6B This is a schematic diagram showing the substrate holding plate.

[0019] Figure 7A and 7B This is a schematic diagram showing the substrate holding plate.

[0020] Figures 8A to 8C This is a schematic diagram showing the substrate holding plate.

[0021] Figure 9 This is a schematic diagram of the exposure device. Detailed Implementation

[0022] Embodiments of the present invention will now be described with reference to the accompanying drawings. However, the embodiments described below are merely embodiments of the present invention, and the present invention is not limited thereto. In the following description and drawings, the same parts in the various drawings are referred to by the same reference numerals. The same parts will be described with reference to the various drawings, and descriptions of parts referred to by the same reference numerals will be omitted as appropriate.

[0023] Figure 1A This is a perspective view of a substrate holding plate 1 according to a first example of this embodiment. The substrate holding plate 1 in this embodiment includes a base 2 and a protrusion 3 located above or on the base 2. One of the two main surfaces (front surface and rear surface) of the substrate holding plate 1 (referred to as the front surface for convenience) is the substrate holding surface, and the protrusion 3 is disposed at the substrate holding surface. At least the uppermost surface and side surfaces of the protrusion 3 constitute the substrate holding surface.

[0024] Figure 1B This shows that the substrate 7 is placed Figure 1A A perspective view of the substrate holding plate 1 when it is placed on or above the substrate holding plate 1. The substrate 7 is placed on or above the holding surface of the substrate holding plate 1. The base 2 and the protrusion 3 provided on or above the base 2 hold the substrate 7. In particular, the protrusion 3 located at the holding surface supports the substrate 7. Since the protrusion 3 supports the substrate 7, the contact area between the substrate holding plate 1 and the substrate 7 is reduced, and damage to the substrate 7 can be suppressed compared to the case where the protrusion 3 is not provided. When the substrate 7 is placed on or above the holding surface, the uppermost surface of the protrusion 3 is the contact surface between the substrate holding plate 1 and the substrate 7. When the substrate 7 is not placed on or above the holding surface, the uppermost surface of the protrusion 3 is in contact with the atmosphere (e.g., air or inert gas) of the substrate holding plate 1. In the first example, the substrate 7 placed on the substrate holding plate 1 is a substrate 7 for manufacturing an electronic device. The substrate 7 may be part of the electronic device, or it may be removed during the manufacturing process of the electronic device without constituting an electronic device. For example, the substrate 7 may be a glass substrate, resin substrate, or sapphire substrate for manufacturing organic electroluminescent (EL) displays, liquid crystal displays, solar panels, etc.

[0025] A suction hole 4 is provided in the substrate holding plate 1 of this example. The substrate 7 is evacuated through the suction hole 4. However, the suction hole 4 can be omitted.

[0026] Figure 1C This is a perspective view of the substrate holding plate 1 according to the second example of this embodiment. Figure 1D This shows that the substrate 7 is placed Figure 1C A perspective view of substrate holding plate 1 when it is placed on substrate holding plate 1. The second example of substrate holding plate 1 and... Figure 1AThe difference between the substrate holding plate and the first example is that its external shape is circular; however, the other constructions are the same. The substrate 7 to be placed on the substrate holding plate 1 of the second example can be, for example, a semiconductor substrate such as a Si wafer or a SiC wafer, an insulating substrate such as a glass wafer or a plastic wafer, or a sapphire substrate.

[0027] Figures 1A to 1D The substrate holding plate 1 shown can be used in the manufacture of various electronic devices. For example, the substrate holding plate 1 can be used in an exposure apparatus (which exposes photoresist coated on substrate 7) to hold the substrate 7. The substrate holding plate 1 can be used not only in exposure apparatuses, but also in film deposition apparatuses, etching apparatuses, etc.

[0028] like Figure 1E As shown, multiple substrate holding plates 1 can be arranged and used as substrate holding tools 11.

[0029] First Embodiment

[0030] Next, we will refer to Figures 2A to 2C The first embodiment is described.

[0031] Figure 2A yes Figure 1A or Figure 1C An enlarged cross-sectional view of the area enclosed by circle IIA. Figure 2B yes Figure 2A An enlarged view of the area enclosed by circle IIB. Figure 2C yes Figure 2B A magnified view of the area enclosed by the circle IIC.

[0032] For reference Figure 1A As described in 1C, the substrate holding plate 1 of this embodiment includes a base 2 and a protrusion 3. In the holding surface, at least the uppermost surface of the protrusion 3 is a rough surface.

[0033] The term "rough surface" in the following description can refer to a surface with an arithmetic mean roughness Ra greater than 0.4 μm. Each protrusion 3 includes a high-hardness portion 5, which is a portion with a hardness higher than that of the base 2. This applies not only to this embodiment but also to other embodiments. In this embodiment, the uppermost surface of the protrusion 3 in the retaining surface will be described as a rough surface. Furthermore, the high-hardness portion 5 will be described as being disposed at the uppermost surface of the protrusion 3 in the retaining surface.

[0034] Base 2 will be described. Base 2 includes component 21, component 22, and component 23. Components 21, 22, and 23 are made of the same material. Components 21, 22, and 23, which are at least made of the same material, are referred to as base members, and portions made of the same material as components 21, 22, and 23 are also referred to as base members. Components 21, 22, and 23 lie in the same plane. The lower surfaces of components 21, 22, and 23 also lie in the same plane and define a rear surface 24 opposite to the substrate holding surface. Component 22 is located between components 21 and 23.

[0035] Protrusion 3 will be described. Protrusion 3 exists on or above component 22 of base 2. Protrusion 3 does not exist on or above components 21 and 23, and provides space. Protrusion 3 exists between the space above component 21 and the space above component 23. There is space between the two protrusions 3.

[0036] The protrusion 3 is composed of a low-hardness portion 31 (which is made of the same material as the base 2) and a high-hardness portion 5. The low-hardness portion 31 is also a base component.

[0037] Next, the high-hardness portion 5 will be described. The high-hardness portion 5 is the portion whose hardness is higher than that of the base portion 2. The high-hardness portion 5 may be the portion whose hardness is higher than that of the low-hardness portion 31.

[0038] will describe Figure 2C In this embodiment, in the retaining surface, at least the uppermost surface of the protrusion 3 is a rough surface, and the protrusion 3 has a high-hardness portion 5. The high-hardness portion 5 is disposed within a distance D from the top 51 of the rough surface. This distance D is less than the height difference H(D) between the top 51 and the bottom 52 adjacent to the top 51. <H)。

[0039] At least one top 51 of a rough surface is provided at the uppermost surface. Preferably, multiple tops are provided at the uppermost surface. More preferably, five or more tops are provided at the uppermost surface. For each of the five or more tops 51, the range of the high-hardness portion 5 can be less than the height difference H relative to the adjacent bottom 52. Furthermore, the height difference Hmax between the highest top 51 of the rough surface at the uppermost surface and the adjacent bottom 52 can be defined. For each of the five or more tops 51, the high-hardness portion 5 can be provided within a range of a distance Dmax from the top 51 of the rough surface. In this case, the distance Dmax is less than the height difference Hmax. <Hmax)。

[0040] The height difference Hmax can be greater than the distance from the top to the low-hardness section 31.

[0041] In this embodiment, the high-hardness portion 5 is set within a distance D that is smaller than the height difference H from the top of the rough surface to the adjacent bottom. Thus, the rough surface of the uppermost surface is formed by the high-hardness portion 5, and the wear of the rough surface can be suppressed.

[0042] At least a portion of the uppermost surface is a high-hardness portion 5. In one example, the top of the rough surface may be composed of a high-hardness portion 5. With this configuration, wear caused by contact between the substrate 7 and the rough surface of the uppermost surface can be suppressed by the high-hardness portion 5. In this embodiment, only the uppermost surface of the protrusion 3 in the retaining surface is roughened, and the rough surface of the uppermost surface of the protrusion 3 is composed of a high-hardness portion 5. As long as at least the rough surface of the uppermost surface of the protrusion 3 (which is the contact surface with the substrate 7) is composed of a high-hardness portion 5, it is more suitable for suppressing wear on the rough surface than if the rough surface of the uppermost surface is not composed of a high-hardness portion 5.

[0043] By making the uppermost surface of protrusion 3 a rough surface, the reflectivity at the front surface of the substrate holder can be reduced during exposure processing. Therefore, variations in irradiance intensity are reduced, and exposure inhomogeneity can be suppressed.

[0044] Furthermore, compared to the case where the uppermost surface of the protrusion 3 is not a rough surface, it has the effect of improving the adhesion between the base 2 and the high-hardness portion 5, and reducing damage to the substrate by reducing the contact area with the substrate.

[0045] In this embodiment, the material constituting the base member (base 2 and low-hardness portion 31) is black alumina. The hardness of black alumina is, for example, about 1600 Hv. The base member (base 2 and low-hardness portion 31) needs to be thick enough to ensure that the substrate maintains the mechanical strength of the plate 1. For example, the thickness of the base member is 10 to 100 mm, preferably 60 mm or less.

[0046] The thickness of the base components (base 2 and low-hardness portion 31) can be less than 30 mm.

[0047] The material constituting the base component is not limited to black alumina; it can be alumina, ceramics, zirconium oxide, glass, plastics, metals, or similar materials. The hardness of the low-hardness portion 31 can be between 1000 and 2000 Hv.

[0048] In this embodiment, the upper surface of the low-hardness portion 31 of the protrusion 3 is also a rough surface. The rough surface of the upper surface of the low-hardness portion 31 is formed by sandblasting the low-hardness portion 31. The shape of the rough surface of the uppermost surface of the protrusion 3 can reflect the shape of the rough surface of the upper surface of the low-hardness portion 31.

[0049] As the thickness of the high-hardness portion 5 decreases, the correlation between the shape of the rough surface of the upper surface of the low-hardness portion 31 and the shape of the rough surface of the uppermost surface of the protrusion 3 increases.

[0050] The arithmetic mean roughness Ra of the uppermost surface of the protrusion 3 is, for example, in the range of 0.4 to 10 μm. The arithmetic mean roughness Ra of the uppermost surface of the protrusion 3 can be 0.6 μm or more, 0.8 μm or more, or 1.0 μm or more. The arithmetic mean roughness Ra of the uppermost surface of the protrusion 3 can be 8.0 μm or less, 6.0 μm or less, 4.0 μm or less, or 2.0 μm or less. In order to set the arithmetic mean roughness Ra of the uppermost surface of the protrusion 3, which reflects the rough surface shape of the upper surface of the low-hardness portion 31, to 0.4 μm or more, the arithmetic mean roughness Ra of the upper surface of the low-hardness portion 31 can exceed 0.4 μm, and can be set, for example, to 0.6 μm or more. The arithmetic mean roughness Ra of the uppermost surfaces of the base 2 and the protrusion 3 can be in the range of 0.4 to 4.0 μm.

[0051] As long as the protrusions 3 can support the substrate 7, the shape and array spacing of the protrusions 3 can be arbitrary. In this example, each protrusion 3 has a truncated conical or cylindrical shape. The spacing of the protrusions 3 is, for example, 1 mm or more and 100 mm or less, preferably 10 mm or more and 30 mm or less. The spacing of the protrusions 3 can be 1 mm or more and 10 mm or less. The height of the protrusions 3 is, for example, 10 μm or more and 1 mm or less, preferably 0.2 mm or more and 0.8 mm or less. The height of the protrusions 3 can be, for example, 50 μm or more and 0.5 mm or less, or 0.3 mm or less.

[0052] As the material for the high-hardness portion 5, diamond-like carbon (DLC) formed into a film by plasma chemical vapor deposition (CVD) is used to improve wear suppression. DLC may contain hydrogen. The lower the hydrogen content in DLC, the higher the hardness and brittleness tend to be. Conversely, the higher the hydrogen content in DLC, the lower the hardness tends to be, and the higher the toughness tends to be. For example, the hardness of DLC can be 6 to 16 GPa; however, by adjusting the hydrogen content, it can be 9 to 13 GPa. For example, when the hydrogen content in DLC is 21 to 26 at%, good film quality (high hardness and high toughness) can be obtained when forming the high-hardness portion 5 with a rough surface. The hydrogen content in DLC can be 23 to 26 at%. The hydrogen content in DLC can be controlled by film formation conditions (e.g., source gas flow rate and substrate bias). The hydrogen content in DLC can be analyzed by elastic recoil detection analysis (ERDA). DLC may contain argon. The higher the argon content in DLC, the lower the refractive index of DLC, which is effective in suppressing reflection. The argon content in DLC can be below 10 at%. Note that "at%" indicating elemental content represents "atomic %" or "percentage of atoms". In addition to the analytical methods described in this specification, elemental content (concentration) can also be analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS).

[0053] The material of the high-hardness portion 5 is not limited to diamond-like carbon (DLC), but can be silicon carbide (SiC), titanium nitride (TiN), titanium carbide (TiC), ceramics, or cemented carbide. When the hardness of the base component is about 1600 Hv, the hardness of the high-hardness portion 5 can be between 2000 and 4000 Hv.

[0054] By using the high-hardness part 5 to form the rough surface of the uppermost surface, wear on the rough surface can be suppressed.

[0055] The thickness of the high-hardness portion 5 needs to be sufficient to suppress rough surface wear caused by contact with the substrate 7. The thickness of the high-hardness portion 5 is, for example, 0.4 μm or more, preferably 1 μm or more. However, when the thickness of the high-hardness portion 5 is 10 μm or more, cracks are likely to occur in the high-hardness portion 5. Therefore, the thickness of the high-hardness portion 5 can be less than 10 μm.

[0056] The film thickness of the high-hardness portion 5 can be greater than the height difference H of the rough surface of the uppermost surface of the protrusion 3.

[0057] Furthermore, the range of the high-hardness portion 5 can be less than the height difference H between it and the bottom portion 52.

[0058] The height difference H from the top 51 of the rough surface to the adjacent bottom 52 of the rough surface can be greater than 0.1 μm and less than 1.2 μm.

[0059] The low-hardness portion 31 can be referred to as the first portion, and the high-hardness portion 5 can be referred to as the second portion.

[0060] The thickness of the high-hardness portion 5 can be relatively small so that the shape of the rough surface of the upper surface of the low-hardness portion 31 is reflected in the shape of the rough surface of the uppermost surface of the protrusion 3. Specifically, the thickness μm of the high-hardness portion 5 is preferably 4 times or less than the arithmetic mean roughness Ra of the rough surface of the upper surface of the low-hardness portion 31, more preferably 2 times or less. It can be approximately considered that the arithmetic mean roughness Ra of the rough surface of the upper surface of the low-hardness portion 31 is equal to the arithmetic mean roughness Ra of the rough surface of the uppermost surface of the protrusion 3. In this case, it can be said that the thickness of the high-hardness portion 5 is preferably 4 times or less than the arithmetic mean roughness Ra of the rough surface of the uppermost surface of the protrusion 3, more preferably 2 times or less. The height difference H of the rough surface of the uppermost surface of the protrusion 3 can be approximately twice the arithmetic mean roughness Ra of the rough surface of the uppermost surface of the protrusion 3. Therefore, it can be said that the thickness of the high-hardness portion 5 is preferably 2 times or less than the height difference H of the rough surface of the uppermost surface of the protrusion 3, more preferably 1 time or less. Furthermore, as long as the arithmetic mean roughness Ra of the uppermost surface of the protrusion 3 is 0.4 μm or more, the height difference H can be 0.8 μm or more. When the thickness of the high-hardness portion 5 is equal to or less than twice the arithmetic mean roughness Ra of the rough surface of the uppermost surface of the protrusion 3, the bottom 52 of the rough surface of the uppermost surface of the protrusion 3 is easily located at a position lower than the top of the rough surface of the upper surface of the low-hardness portion 31 (which corresponds to the top 51 of the rough surface of the uppermost surface of the protrusion 3). This is advantageous for controlling the shape of the rough surface of the uppermost surface of the protrusion 3 by utilizing the shape of the rough surface of the upper surface of the low-hardness portion 31, which serves as the base of the bottom layer of the high-hardness portion 5. As the roughness of the rough surface of the upper surface of the low-hardness portion 31 decreases, the thickness of the high-hardness portion 5 decreases. As the roughness of the rough surface of the upper surface of the low-hardness portion 31 increases, the thickness of the high-hardness portion 5 increases.

[0061] Next, the suction holes 4 according to this embodiment will be described. To hold and retain the substrate 7 placed on the protrusion 3, the lower opening of each suction hole 4 is connected to a vacuum pump (not shown), thereby allowing the air around the protrusion 3 to be suctioned and depressurized. By providing the protrusion 3, more air can be suctioned compared to the case where the protrusion 3 is not provided. Although the side surface of the suction hole 4 in this embodiment is coated with a high-hardness portion 5, since this side surface is not the surface facing the substrate 7, it is not necessary to coat this side surface with the high-hardness portion 5. Similarly, the high-hardness portion 5 does not need to be applied to the rear surface 24 of the base 2 and the side surface of the base 2.

[0062] Second Embodiment

[0063] Next, we will refer to Figure 3A , 3B The second embodiment is described in conjunction with 3C.

[0064] Figure 3A This is a cross-sectional view showing an example of a substrate holding plate 1 according to this embodiment. Figure 3B yes Figure 3A An enlarged view of the area enclosed by circle IIIB. Figure 3C yes Figure 3A A magnified view of the area enclosed by circle IIIC. Note that... Figure 3B The structure of the uppermost surface of protrusion 3 in the region surrounded by circle IIC can be compared with the reference. Figure 2C (that is) Figure 2B The structure described in the enlarged view of the area surrounded by circle IIC is the same, so its description is omitted.

[0065] The difference between the substrate holding plate 1 of this embodiment and the first embodiment is that the rough surface composed of the high hardness portion 5 is not only provided on the uppermost surface of the protrusion 3, but also on the side surface of the protrusion 3 and on the components 21 and 23 (the first section, which is a section without protrusions above or above the section) provided on the holding surface of the substrate holding plate 1.

[0066] In the substrate holding plate 1, the base 2 can represent the entire portion excluding the protrusion 3. The uppermost surface of the base 2 is in spatial contact with both sides of the protrusion 3. Similar to the first embodiment where the protrusion 3 includes a high-hardness portion 5 and a low-hardness portion 31, in the second embodiment, the base 2 can include a high-hardness portion 5 and a low-hardness portion 31. In the first embodiment, the base 2 can be equivalent to components 21 to 23. However, in the second embodiment, the base 2 may also include high-hardness and low-hardness portions in addition to components 21 to 23. Therefore, the high-hardness and low-hardness portions of the base 2 other than components 21 to 23 are specifically referred to as transition portions 9. Transition portions 9 are a part of the base 2.

[0067] In the substrate holding plate 1 of this embodiment, the base 2 includes a transition portion 9 in addition to components 21 to 23. The transition portion 9 will be described. The transition portion 9 is either the portion of the base 2 that transitions from component 22 to the protrusion 3, or the portion of the base 2 that transitions from component 21 or 23 to the space provided above component 21 or 23. In this embodiment, the transition portion 9 is composed of a portion (low-hardness portion) made of the same material as components 21 to 23 (base member) and a high-hardness portion 5.

[0068] The transition portion 9 exists at a location where the transition portion 9 transitions from component 22 to protrusion 3 via a low-hardness portion or from component 21 or 23 to a space disposed above component 21 or 23 via a high-hardness portion 5. Specifically, the transition portion 9 between component 22 and protrusion 3 includes a portion composed of a low-hardness portion (base member) and a portion composed of high-hardness portions 5 located on both sides of the low-hardness portion.

[0069] will describe Figure 3C . Figure 3C yes Figure 3A An enlarged view of the area surrounded by circle IIIC. In this embodiment, as... Figure 3B As shown, the side surface of the protrusion 3 in the retaining surface is a rough surface. The upper surfaces of components 21 and 23, which are base members, are also rough surfaces. Furthermore, a second section 55 composed of a high-hardness portion 5 is provided on each component 21 and 23. The upper surface of the second section 55 composed of the high-hardness portion 5 on the substrate retaining surface side is a rough surface. The construction in which the upper surface of the second section 55 on the substrate retaining surface side (which is a surface that does not contact the substrate) is a rough surface is suitable for reducing reflectivity.

[0070] Furthermore, since the side surface of the protrusion 3 and the portion above or above the components 21 and 23 are made of the high-hardness portion 5, the contact area between the substrate holding plate 1 and the high-hardness portion 5 is increased, and film separation between the substrate holding plate 1 and the high-hardness portion 5 can be suppressed.

[0071] In this embodiment, Figure 3C The distance D shown exists within a range less than the height difference H. However, it is sufficient that the distance D at least at the uppermost surface of protrusion 3 falls within a range less than the height difference H.

[0072] The surface shape of the high-hardness portion 5 (second section 55) and the surface shape of the low-hardness portion (components 21 and 23) serving as the bottom base of the high-hardness portion 5 can be the same as the surface shapes of the high-hardness portion 5 and the low-hardness portion 31 in the first embodiment. The arithmetic mean roughness Ra of the uppermost surface of the base 2 is, for example, in the range of 0.4 to 10 μm. The arithmetic mean roughness Ra of the uppermost surface of the base 2 can be 0.6 μm or more, 0.8 μm or more, or 1.0 μm or more. The arithmetic mean roughness Ra of the uppermost surface of the base 2 can be 8.0 μm or less, 6.0 μm or less, 4.0 μm or less, or 2.0 μm or less. In order to set the arithmetic mean roughness Ra of the uppermost surface of the base 2, which reflects the rough surface shape of the upper surfaces of components 21 and 23, to 0.4 μm or more, the arithmetic mean roughness Ra of the upper surfaces of components 21 and 23 can be greater than 0.4 μm, and can be set, for example, to 0.6 μm or more. The arithmetic mean roughness Ra of the uppermost surface of the base 2 and the protrusion 3 can be in the range of 0.4 to 4.0 μm.

[0073] Third Embodiment

[0074] Next, we will refer to Figure 4A and 4B The third embodiment is described below. This embodiment differs from the second embodiment in that the upper surface of the low-hardness portion 31 is flat compared to the rough surface of the uppermost surface of the protrusion 3. In this example, as with the first and second embodiments, since the high-hardness portion 5 is included within the rough surface of the uppermost surface of the protrusion 3, wear on the rough surface can be suppressed.

[0075] Fourth embodiment

[0076] Next, we will refer to Figure 5A and 5B The fourth embodiment is described. This embodiment provides a form similar to the second embodiment; however, the difference is that the protrusion 3 is composed only of the high-hardness portion 5.

[0077] In this example, since the high-hardness portion 5 is included within the rough surface used to reduce reflectivity, wear on the rough surface can be suppressed. In this embodiment, the transition portion 9 is composed of the high-hardness portion 5.

[0078] Fifth Embodiment

[0079] Next, we will refer to Figure 6A and 6BThe fifth embodiment is described. In this embodiment, the base 2 is composed of a portion 50 that is different from the high-hardness portion 5 and the low-hardness portion 31, the upper part of the protrusion 3 is composed of the high-hardness portion 5, and the lower part of the protrusion 3 is composed of the low-hardness portion 31. In this example, since the rough surface of the uppermost surface is composed of the high-hardness portion 5, wear on the rough surface can be suppressed.

[0080] In this embodiment, the low-hardness portion 31 can be referred to as the first portion, while the high-hardness portion 5 can be referred to as the second portion.

[0081] Sixth Embodiment

[0082] Next, we will refer to Figure 7A and 7B The sixth embodiment is described.

[0083] Figure 7A This is a cross-sectional view showing an example of a substrate holding plate 1 according to this embodiment. Figure 7B yes Figure 7A An enlarged view of the area enclosed by circle VIIB.

[0084] The difference between the construction of this embodiment and that of the second embodiment is that at least a portion of the portion above components 21 and 23, the uppermost surface of protrusion 3, and the side surface of protrusion 3 are composed of a low refractive index portion 6, which has a lower refractive index than the high hardness portion 5.

[0085] will describe Figure 7B .like Figure 7B As shown, in this embodiment, the bottom of the rough surface of the uppermost surface is composed of a low refractive index portion 6. The rough surface of the uppermost surface is composed of a high hardness portion 5 and a low refractive index portion 6.

[0086] In this configuration, light incident on the bottom of the rough surface of the uppermost surface is incident on the high-hardness portion 5 via the low-refractive-index portion 6. Therefore, the reflectivity on the holding surface of the substrate holding plate 1 can be reduced.

[0087] In this embodiment, since the rough surface of the uppermost surface is composed of a high-hardness portion 5 and maintains a height difference H from the top 51 to the bottom 62, wear of the rough surface due to contact with the substrate 7 can be suppressed.

[0088] The low-refractive-index portion 6 will be described. The refractive index of the low-refractive-index portion 6 is lower than that of the high-hardness portion 5. Therefore, by providing the low-refractive-index portion 6 on the substrate holding surface side of the high-hardness portion 5, the refractive index relative to air is reduced and the reflectivity is decreased. The low-refractive-index portion 6 has a lower refractive index and hardness than the high-hardness portion 5.

[0089] The reflection at the front surface of the substrate holder will be described. The exposure apparatus for forming fine patterns uses light beams with wavelengths of 365 nm (i-line), 405 nm (h-line), and 436 nm (g-line). The reflection at the front surface of the substrate holder is primarily Fresnel reflection, which can be obtained using the following formula.

[0090] R = {(N0-N1) / (N0+N1)} 2 +{(N1-N2) / (N1+N2)} 2

[0091] Where R is reflectivity,

[0092] N0 is the refractive index of air.

[0093] N1 is the refractive index of the lower refractive index portion, and

[0094] N2 is the refractive index of the high-hardness portion.

[0095] By using a porous material made of inorganic oxides as the low-refractive-index portion 6 on the holding surface of the substrate holding plate, a low reflectivity can be provided compared to the case of using a non-porous antireflective material. This is because the surface of the porous material made of inorganic oxides has subtle irregularities, and a refractive index gradient is formed at the interface with air.

[0096] Since the low-refractive-index portion 6 forms part of the holding surface of the substrate holding plate 1, the refractive index change between air and the high-hardness portion 5 is slowed down, and the reflectivity on the holding surface can be reduced. Even without the high-hardness portion 5, the reflectivity on the holding surface can be reduced by slowing down the refractive index change between air and the low-hardness portion 31.

[0097] The low-refractive-index portion 6, by using a material with a lower refractive index than the high-hardness portion 5, has the effect of reducing the reflectivity on the front surface of the substrate holding plate 1. The inorganic oxide can be aluminum oxide or silicon dioxide, but cannot be a resin material.

[0098] The low-refractive-index portion 6 is composed of chain-like particles, hollow particles, or solid particles. The low-refractive-index portion 6 can be formed to have a thickness of, for example, 0.1 to 1.0 μm, preferably 0.1 to 0.4 μm.

[0099] The low refractive index portion 6 exists either in a uniformly formed state or in a dispersed state.

[0100] In this embodiment, the substrate 8 is used to ensure a stronger and closer contact between the high-hardness portion 5 and the low-refractive-index portion 6. The substrate 8 is present at the interface between the high-hardness portion 5 and the low-refractive-index portion 6. The substrate 8 may be present in a uniformly formed state or in a dispersed state. In this example, a silane coupling agent is used as the substrate 8; however, the substrate 8 is not limited to this. Any material can be used as long as it improves the adhesion between the high-hardness portion 5 and the low-refractive-index portion 6.

[0101] In the first to fifth embodiments, the uppermost surface of the substrate holding plate 1 is a rough surface, which can scatter incident light and reduce reflectivity. However, in the first to fifth embodiments, due to the large difference in refractive index between the high-hardness portion 5 and air, scattered light is easily generated. In this embodiment, the uppermost surface of the substrate holding plate 1 is a rough surface, and a low-refractive-index portion 6 is provided. Therefore, a refractive index gradient is formed at the interface with air. Compared with the case where the low-refractive-index portion 6 is not provided, the reflectivity can be further reduced.

[0102] In this embodiment, the distance D from the top of the rough surface to the high-hardness portion 5 is less than the height difference H from the top of the rough surface to the bottom of the rough surface adjacent to that top. It is not necessary to provide this configuration for all bottoms adjacent to a given top; providing such a bottom for one top is sufficient.

[0103] The high-hardness portion 5 is disposed within a distance D from the top 51. In this embodiment, the top 51 is formed by the high-hardness portion 5. However, the top can also be formed by the low-refractive-index portion 6. When the top 51 is formed by the low-refractive-index portion 6, the low-refractive-index portion 6 is worn away within a distance D due to contact with the substrate. However, thereafter, the high-hardness portion 5 forms the top 51, and the high-hardness portion 5 constitutes the rough surface of the uppermost surface of the protrusion 3, thereby suppressing wear on the rough surface.

[0104] The substrate holding plate 1 of this embodiment is intended to be used not only under light of wavelengths that are impermeable to the high-hardness portion 5, but also under light of wavelengths that are permeable to the high-hardness portion 5. For example, when the high-hardness portion 5 is DLC, ultraviolet light cannot pass through the DLC, but infrared light can. Therefore, the difference n2-n1 between the refractive index n2 of the high-hardness portion 5 and the refractive index n1 of the base member having the first portion is less than the difference n2-n3 between the refractive index n2 of the high-hardness portion 5 and the refractive index n3 of the low-refractive-index portion 6.

[0105] This structure prevents light passing through the high-hardness part 5 from being reflected by the base component.

[0106] Each of n1, n2, and n3 is the refractive index of light of a wavelength that can pass through the high-hardness portion 5. The refractive index n2 of the high-hardness portion 5 is higher than the refractive index n1 of the low-hardness portion 31.

[0107] With this structure, even when using light that can pass through the high-hardness part 5, light reflection at the interface between the high-hardness part 5 and the base member can be suppressed.

[0108] The suction hole 4 in this embodiment will be described. Since the side surface of the suction hole 4 in this embodiment is not the surface facing the substrate 7, the low refractive index portion 6 does not need to be provided on the side surface of the suction hole 4.

[0109] In this embodiment, the low-hardness portion 31 can be referred to as the first portion, the high-hardness portion 5 can be referred to as the second portion, and the low-refractive-index portion 6 can be referred to as the third portion.

[0110] Seventh Embodiment

[0111] Next, we will refer to Figure 8A , 8B The seventh embodiment is described in 8C.

[0112] The difference between this embodiment and the sixth embodiment is that the rough surface of the uppermost surface is composed only of the low refractive index portion 6 instead of the high hardness portion 5. This embodiment provides a form in which the distance D from the top 61 of the rough surface composed of the low refractive index portion 6 to the top 51 of the rough surface composed of the high hardness portion 5 is less than the height difference H from the top 61 to the bottom 62 of the rough surface.

[0113] Since the low-refractive-index portion 6 at the uppermost surface is in contact with the substrate 7, the low-refractive-index portion 6 is immediately worn after the substrate 7 is placed. However, as the wear of the low-refractive-index portion 6 progresses, the high-hardness portion 5 becomes the top of the rough surface of the protrusion 3, and maintains the distance HD from the top 51 to the bottom 62. Therefore, the wear of the rough surface can be suppressed.

[0114] will describe Figure 8C . Figure 8C It shows the relationship with Figure 8B The different views differ in that the distance D is greater than the height difference H. In this example, the low-refractive-index portion 6 is worn down due to contact with the substrate 7. Since the low-refractive-index portion 6 is worn down from the top 61 to the top 51 composed of the high-hardness portion 5, the bottom 62 is similarly worn down to the top 61. Therefore, since the uppermost surface of the protrusion 3 is composed of the low-refractive-index portion 6, the reflectivity at the surface is reduced by the low-refractive-index portion 6. However, the rough surface in the uppermost surface of the protrusion 3 is likely to be worn down.

[0115] Eighth embodiment

[0116] In this embodiment, the base component (low-hardness portion 31 and components 21 and 23) has a nitrogen-containing region. The nitrogen-containing region may exist near the high-hardness portion 5, for example, within a range of 100 nm from the high-hardness portion 5. The nitrogen content of the nitrogen-containing region may be 1 at% or more.

[0117] The maximum nitrogen content in the nitrogen-containing region is preferably 5 at% or more, more preferably 10 at% or more. The maximum nitrogen content in the nitrogen-containing region can be less than 25 at%. In the base member, at locations separated from the high-hardness portion 5, for example, at locations sufficiently separated from the high-hardness portion 5, for example, at a distance of 100 μm from the high-hardness portion 5, the nitrogen content can be less than 1 at%. Since nitrogen has a high diffusion inhibition function relative to other elements, the diffusion of impurities between the base member (low-hardness portion) and the high-hardness portion 5 can be suppressed by providing a nitrogen-containing region. Furthermore, when the oxygen content in the base member is 25 at% or more and the carbon or nitrogen content in the inorganic material film (high-hardness portion 5) provided on the base member is 25 at% or more, the adhesion between the base member and the inorganic material film is improved when a nitrogen-containing region is provided in the base member. Typical examples of base members with an oxygen content of 25 at% or more include oxides, such as silicon oxide (silicon dioxide), aluminum oxide (alumina), and zirconium oxide (zirconia).

[0118] Inorganic material films with a carbon or nitrogen content of 25 at% or more are carbon films such as DLC, carbide films such as silicon carbide (SiC) or titanium carbide (TiC), or nitride films such as silicon nitride (SiN) or titanium nitride (TiN). Inorganic material films contain, in addition to nitrogen or carbon, 25 at% or more of an element that forms a compound with nitrogen or carbon (e.g., a metallic titanium or a semi-metal such as silicon). Carbon films, carbide films, and nitride films generally have low adhesion to oxides. In particular, DLC hardly adheres to or chemically reacts with the underlying substrate, thus exhibiting low adhesion to metals or oxides. However, when nitrogen-containing regions are formed within the oxide, the adhesion between the nitrogen-containing regions and the carbon film, carbide film, or nitride film is improved. Nitrogen-containing regions can be formed by embedding nitrogen into the surface of the substrate before the inorganic material film is formed on the substrate. Therefore, the nitrogen-containing region may contain 1 at% or more (more specifically, 5 at% or more) of nitrogen generated due to the implanted nitrogen, and 25 at% or more of oxygen already present in the base component before the nitrogen implantation. In addition, the nitrogen-containing region contains 25 at% or more of an element (such as a metal like aluminum or a half-metal like silicon) that forms a compound with the oxygen already present in the base component before the nitrogen implantation.

[0119] Instead of embedding nitrogen into a base component such as alumina, a SiC layer can be deposited on the base component as an adhesion layer, and a DLC film can be deposited on the SiC layer. When comparing the adhesion of the two films in a scratch test, the adhesion of the DLC film with only nitrogen embedding is higher than that with only a SiC layer. Embedding nitrogen into the base component below the SiC layer can increase the adhesion between the SiC layer and the alumina substrate.

[0120] When a DLC film is formed on the base member of a substrate holder, if film formation fails, the DLC film needs to be removed. Since DLC evaporates upon reaction with oxygen, it can be removed, for example, by heating the film in the atmosphere or exposing it to an oxygen plasma. When the adhesion layer is a SiC layer, the surface of the SiC is oxidized to form SiO or SiO2 due to the DLC film removal step. When a DLC film is formed on it, the DLC may peel off easily due to the low adhesion between SiO or SiO2 and the DLC. On the other hand, when a nitrogen-containing region obtained by nitriding the base member of the substrate holder is used as the adhesion layer, the adhesion layer is less likely to be oxidized by the DLC film removal step. Therefore, even if a DLC film is re-formed after removal, the DLC has sufficient adhesion.

[0121] Here, the case where the base component is an oxide is described as an example; however, even when the base component is metal, the adhesion between the carbide or nitride film and the metal is low. Therefore, when a nitrogen-containing region is formed on the surface of the metal base component, the adhesion between the metal base component and the carbide or nitride film is improved.

[0122] The present invention is not limited to the above embodiments, and many modifications can be made within the scope of the technical concept of the present invention.

[0123] Figure 9This is a schematic diagram of an exposure apparatus. The optical device EQP, serving as the exposure apparatus, includes a light source 14 and mirrors 16 and 17 constituting an illumination optical system. The optical device EQP includes a mask stage 19 supporting a mask 18, which serves as a pattern forming unit, a projection optical system 25 projecting a pattern formed on the mask 18, and a substrate holding plate 1 supporting a substrate 7. Exposure light 15 from the light source 14 is reflected by mirrors 16 and 17 of the illumination optical system and guided to the mask 18. The exposure light 15 carrying the pattern formed on the mask 18 is focused by the projection optical system 25 and projected onto the substrate 7. The substrate 7 and the substrate holding plate 1 are moved by a substrate moving unit 26. The light source 14 projects the pattern formed on the mask 18 onto the substrate 7. Photoresist is applied to the substrate 7. The photoresist is exposed to the exposure light 15. The substrate 7 can be a semiconductor wafer or a glass substrate for a flat panel display (FPD). The exposure light used in the exposure apparatus is typically ultraviolet light. The wavelength of the exposure light is 436 nm for g-line sources and approximately 365 nm for i-line sources. The wavelength of the exposure light is approximately 248 nm for KrF excimer laser sources, approximately 193 nm for ArF excimer laser sources, and approximately 10 to 20 nm for extreme ultraviolet (EUV) sources.

[0124] The projection optical system can be a reduced projection type, a constant magnification projection type, or a magnified projection type. Although a transmissive mask 18 is shown here, a reflective mask 18 can also be used. The projection optical system can be a refractive type using lenses or a reflective type using mirrors.

[0125] Example

[0126] Next, we will refer to Figure 7A and 7B Describe a specific example.

[0127] In this example, a substrate with a length of 200mm to 1500mm and a width of 800mm to 1500mm is used.

[0128] The substrate in this example is a glass substrate; however, it can be a SiC wafer or a liquid crystal panel substrate. The substrate in this example can be a transparent substrate. The transparent substrate in this example is a substrate that can transmit any wavelength of light.

[0129] First, base 2 will be described. Base 2 can have any properties, as long as it does not cause exposure failure due to defocusing. Base 2 is made of black aluminum oxide with a thickness of 60 mm. In this example, the surface is roughened by sandblasting. The Ra value is approximately 0.8 μm, and the Rz value is approximately 5.0 μm. The surface roughness is measured using a Surftest SJ-210 surface roughness meter (Mitutoyo). The evaluation length is 5 mm, and the measurement speed is 0.5 mm / s.

[0130] Next, the protrusions 3 will be described. The shape and array spacing of the protrusions 3 can be arbitrary, as long as they can support the substrate 7. In this example, each protrusion 3 is a truncated cone or cylinder with a diameter of 0.8 mm and a height of 0.5 mm. Furthermore, the spacing between adjacent protrusions 3 is set to 20 mm. Since the protrusions 3 and the base 2 are sandblasted simultaneously, it can be assumed that the surface roughness of the base component at the protrusions 3 is substantially the same as the surface roughness of the base component at the base 2 (within 10%).

[0131] Next, the high-hardness portion 5 will be described. In this example, DLC is used to improve wear suppression. A DLC film is formed by plasma CVD, with at least the surface of the protrusions 3 coated with DLC. The thickness of the DLC film needs to be sufficient for wear suppression, and can be greater than 1 μm. However, when the thickness of the DLC film is greater than 10 μm, the possibility of cracking is high. Therefore, in this example, the thickness of the DLC film is set to 2 μm. The film formation conditions in this example are as follows: argon gas flow rate of 50 sccm, toluene gas flow rate of 2.5 sccm, pressure of 5 Pa, RF power of 500 W / 13.56 MHz, and film formation time of 2 hours. When the formed DLC film is measured with an ellipsometry, the refractive index of the DLC film is 2.1. When the formed DLC film is measured with a nanoindenter, the hardness of the DLC film is approximately 15 GPa. In this example, the hardness of the DLC is obtained by forming a 100 nm thick DLC film on a Si wafer under the same film formation conditions as described above, measuring the DLC film with a nanoindenter, and calculating the hardness of the DLC based on the stress at a depth of 30 nm. Since the DLC film is uniformly formed on the substrate, the surface roughness of the upper surface of the DLC film can be considered to be substantially the same as the surface roughness of the substrate formed by sandblasting (within 10%).

[0132] Next, the low-refractive-index portion 6 will be described. A porous material made of inorganic oxide is used for the low-refractive-index portion 6. In this example, the inorganic oxide is a silicon oxide material with a thickness of 300 nm. In this example, a substrate 8 is used to make the high-hardness portion 5 and the low-refractive-index portion 6 more firmly and tightly contact each other. The substrate 8 is disposed at the interface between the high-hardness portion 5 and the low-refractive-index portion 6. The substrate 8 is provided in a uniformly formed state or in a dispersed state. In this example, a silane coupling agent is used as the substrate material. However, the substrate material is not limited to this. Any material can be used as long as it can improve the adhesion between the high-hardness portion 5 and the low-refractive-index portion 6.

[0133] The low refractive index portion 6 and the base material 8 are formed by spraying using an inorganic particulate dispersion. The spraying conditions in this example are as follows: the liquid supply rate for both the base material 8 and the low refractive index portion 6 is 7 g / min, the spray gun movement speed is 20 m / min, and the atomization pressure is 0.1 MPa.

[0134] The concentration of inorganic particles in the coating liquid is 0.1 wt% for the substrate 8 and 2 wt% for the low-refractive-index portion 6. When the low-refractive-index portion 6 is formed, its refractive index is 1.2 when measured with an ellipsometry. Since the thickness of the low-refractive-index portion 6 is sufficiently smaller than the surface roughness of the base component, the surface roughness of the uppermost surface of the low-refractive-index portion 6 and the substrate 8 of the substrate holding plate 1 can be considered to be substantially the same as (within 10%) the surface roughness of the substrate formed by sandblasting.

[0135] When the substrate holding plate 1 in this example was measured using a spectrochromometer (CM-26d manufactured by Konica Minolta), the effect of reducing reflectivity by 4.5% by forming the low-refractive-index portion 6 was confirmed. Furthermore, roughening the uppermost surface of the protrusion 3 enhanced the adhesion between the protrusion 3 and the high-hardness portion 5, and significantly reduced orthogonal reflection through scattering.

[0136] An example of setting up the nitrogen-containing region as described in the eighth embodiment will be described. A base member of a substrate holding plate, comprising alumina as a primary component, is mounted in a plasma processing apparatus. The plasma processing apparatus can be a plasma CVD apparatus. More specifically, the plasma processing apparatus can be a plasma source ion implantation (PSII) apparatus, an ionization vapor deposition apparatus, or an RF plasma CVD apparatus. After the plasma processing apparatus is evacuated to a predetermined pressure, nitrogen gas is introduced and plasma is generated by a plasma generator to produce nitrogen ions. A negative potential can be applied to the base member of the substrate holding plate by a DC pulse power supply or a DC power supply, or by applying a self-bias voltage generated by RF to the substrate holding member. Nitrogen ions are accelerated by the negative potential applied to the base member of the substrate holding plate and are incident on the base member of the substrate holding plate to perform nitrogen ion implantation into the surface of the base member of the substrate holding plate.

[0137] Analysis of the substrate holding plate's base member in this manner using X-ray photoelectron spectroscopy (XPS) along the depth direction confirmed the presence of nitrogen from the uppermost surface of the base member to a depth of 20 nm. Specifically, the nitrogen content is very high (above 5 at%) from the uppermost surface to a depth of 2.5 nm. For example, 15 at% nitrogen was found at the uppermost surface where the nitrogen content is highest, while 5 at% nitrogen was found at a depth of 2.5 nm. Nitrogen can be distributed substantially uniformly across the entire surface of the substrate holding plate's base member. When a DLC film is formed on the substrate holding plate with the aforementioned nitrogen-containing region, the adhesion between the DLC film and the alumina base member is improved.

[0138] Furthermore, it is also appropriate to reform the membrane after the DLC membrane has been removed.

[0139] According to the present invention, a technique that is advantageous in suppressing wear on the rough surface of a substrate holding plate can be provided.

[0140] The above embodiments can be modified as appropriate without departing from the technical concept. The disclosure of this specification includes not only what is described herein, but also all matters that can be grasped from this specification and the accompanying drawings.

[0141] It should be noted that, regarding the specific numerical ranges listed, the description of "e to f" (where e and f are numbers) indicates above e and / or below f. Furthermore, when describing the ranges "i to j" and "m to n" (where i, j, m, and n are numbers) together, the lower and upper limits of the listed numerical ranges are not limited to the i and j group or the m and n group.

[0142] For example, combinations of lower and upper bounds can be considered. That is, when describing the range "i to j" and the range "m to n" together, either the range "i to n" or the range "m to j" can be examined, as long as there is no contradiction. Furthermore, "equal to or greater than e" means equal to or greater than e (exceeding e), and values ​​greater than e can be used instead of e. Additionally, "below f" means f or less than f (less than f). Values ​​less than f can be used instead of f.

[0143] The disclosure in this specification also includes supplements to the various concepts described herein. That is, when this specification contains a description of "A is greater than B," for example, even without a description of "B is not greater than A," this specification can be said to disclose that "B is not greater than A." This is because the description of "A is greater than B" is based on the premise that "B is not greater than A."

[0144] While the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims should be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

[0145] This application claims the benefit of Japanese Patent Application No. 2020-196852, filed on November 27, 2020, and No. 2021-065237, filed on April 7, 2021, which are incorporated herein by reference in their entirety.

Claims

1. A substrate holding plate having a substrate holding surface, comprising: a base portion; and a protrusion provided on a substrate holding surface side with respect to the base portion and supporting a substrate, wherein an uppermost surface of each of the base portion and the protrusion is a rough surface having an arithmetic average roughness Ra of 0.4 μm or more, wherein the base portion or the protrusion has a first portion, wherein at least the protrusion has a second portion having a hardness higher than that of the first portion, wherein the second portion is provided within a range of a distance D from a top of the rough surface, and wherein the distance D is smaller than a height difference H between the top and a bottom portion adjacent to the top.

2. The substrate holding plate according to claim 1, wherein The second portion is provided within a range smaller than the height difference H from the bottom portion.

3. The substrate holding plate according to claim 1 or 2, wherein At least a part of the uppermost surface is constituted by the second portion.

4. The substrate holding plate according to claim 1 or 2, wherein The protrusion has the first portion, and a height difference Hmax between a highest top of the rough surface and an adjacent bottom portion is larger than a distance from the highest top of the rough surface to the first portion.

5. The substrate holding plate according to claim 1 or 2, wherein The protrusion has the first portion, an upper surface on a substrate holding surface side of the first portion is a rough surface, and a thickness of the second portion is 4 times or less of an arithmetic average roughness Ra of an uppermost surface of the protrusion.

6. The substrate holding plate according to claim 1 or 2, wherein A second section made of the same material as that of the second portion is provided on a substrate holding surface side with respect to a first section made of the same material as that of the first portion of the substrate.

7. The substrate holding plate according to claim 1 or 2, wherein An upper surface of a first section of the base portion is a rough surface, the first section is made of the same material as that of the first portion, and the upper surface is on a substrate holding surface side.

8. The substrate holding plate of claim 7, wherein, The arithmetic average roughness Ra of the upper surface is 0.4 to 4.0 μm.

9. The substrate holding plate according to claim 1 or 2, wherein The protrusion has a truncated conical shape or a cylindrical shape.

10. The substrate holding plate according to claim 1 or 2, wherein The protrusion includes a plurality of protrusions provided at a pitch of 30 mm or less.

11. The substrate retainer plate of claim 1, wherein, A third portion having a hardness lower than that of the second portion is provided on a substrate holding surface side with respect to the second portion.

12. The substrate holding plate according to claim 1 or 2, wherein The bottom portion is constituted by a third portion having a hardness lower than that of the second portion.

13. The substrate holding plate according to claim 1, wherein: the base portion includes a base member having the first portion; the second portion is provided on a substrate holding surface side with respect to the first portion; and the substrate holding plate includes a third portion provided on a substrate holding surface side with respect to the second portion and having a refractive index lower than that of the second portion, wherein a difference n2-n1 between a refractive index n2 of the second portion and a refractive index nl of the first portion is smaller than a difference n2-n3 between the refractive index n2 of the second portion and a refractive index n3 of the third portion. The third portion is made of a porous material.

14. The substrate holding plate according to claim 11 or 13, wherein, 15. A substrate holding plate having a substrate holding surface, comprising: a base member having a first portion; a second portion provided on a substrate holding surface side with respect to the first portion and having a hardness higher than that of the first portion; and a third portion made of a porous material and provided on a substrate holding surface side with respect to the second portion. ​ ​ The second portion has a higher refractive index than the first portion.

16. The substrate holding plate according to any one of claims 11, 13 and 15, wherein, The third portion is made of aluminum oxide or silicon dioxide.

17. The substrate retainer plate of any of claims 11, 13, and 15, wherein, The third portion is made of chain-shaped particles, hollow particles, or solid particles.

18. The substrate retainer plate of any of claims 11, 13, and 15, wherein, The third portion has a thickness of 0.1 μm to 1.0 μm.

19. The substrate retainer plate of any of claims 11, 13, and 15, wherein, The third portion includes an inorganic material and a silane coupling agent provided between the inorganic material and the second portion.

20. The substrate retainer plate of any of claims 11, 13, and 15, wherein, The third portion does not include a resin material.

21. The substrate retainer plate of any of claims 1 and 13, wherein, The second portion has a higher refractive index than the first portion.

22. The substrate retainer plate of any of claims 1, 13, and 15, wherein, The second portion has a thickness of 0.4 μm to 10 μm.

23. The substrate retainer plate of claim 13 or 15, wherein, The substrate holding plate has a suction hole whose side surface is not coated with a porous material.

24. The substrate retainer plate of any of claims 1, 13, and 15, wherein, The substrate holding plate has a suction hole whose side surface is coated with a portion made of the same material as that of the second portion.

25. The substrate retainer plate of any of claims 1, 13, and 15, wherein, The material of the first portion is black aluminum oxide and the material of the second portion is diamond-like carbon.

26. The substrate retainer plate of any of claims 1, 13, and 15, wherein, A portion made of the same material as that of the second portion is not provided on a back surface opposite to the substrate holding surface.

27. The substrate retainer plate of any of claims 1, 13, and 15, wherein, The first portion has a nitrogen-containing region having a nitrogen content of 1 at% or more within a range of 100 nm or less from the second portion.

28. The substrate retainer plate of claim 27, wherein, The nitrogen-containing region has a maximum nitrogen content of 10 at% or more.

29. A substrate holding plate having a substrate holding surface, comprising: a base member having a first portion; and a second portion provided on a substrate holding surface side with respect to the first portion and having a higher hardness than the first portion, wherein the material of the first portion has an oxygen content of 25 at% or more, wherein the material of the second portion has a carbon content or a nitrogen content of 25 at% or more, and wherein the first portion has a nitrogen-containing region having a nitrogen content of 1 at% or more within a range of 100 nm or less from the second portion.

30. The substrate retainer plate of claim 29, wherein, The nitrogen-containing region has a maximum nitrogen content of 10 at% or more.

31. The substrate retainer plate of any of claims 1, 13, 15, and 29, wherein, The material of the second portion is diamond-like carbon having a hydrogen content of 21 at% to 26 at%.

32. An exposure apparatus, comprising: a substrate holding plate according to any one of claims 1 to 31; a light source; an optical system configured to irradiate a substrate with light emitted from the light source; and a moving unit configured to move the substrate holding plate. ​

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