Substrate holding member and method for manufacturing the same

Abstract

To provide a substrate holding member capable of improving the positioning accuracy of a substrate in a state of low contact with the substrate.SOLUTION: A substrate holding item 100 includes a substrate 10 on a flat plate and a plurality of convex portions 20 formed by protruding upwardly from an upper surface 12 of the substrate 10. An upper-end surface 24 of the convex portions has a narrow groove 26 formed in the circumferential direction of the substrate 10. Thereby, when a substrate W is sucked, a radial expansion or a displacement of the substrate is suppressed, and the positioning accuracy of the substrate W (accuracy of overlay) is improved.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a substrate holding member and a method for manufacturing the same.

Background Art

[0002] Conventionally, in semiconductor manufacturing apparatuses and the like, a substrate holding member for supporting a substrate such as a silicon wafer or a glass wafer has been used. Since such a substrate holding member supports the back surface of the substrate, for example, in the case of a vacuum chuck, the substrate is adsorbed and supported by evacuating the space defined by the surface of the substrate body and the back surface of the substrate through the vent holes formed on the surface of the substrate body.

[0003] In recent years, with the progress of miniaturization and ultra-high precision of semiconductor products, as a substrate holding member, for the purpose of reducing the risk of impairing the planar accuracy of the substrate due to particles biting into between the substrate body and the substrate, in order to reduce the contact area between the substrate and the substrate body, a substrate holding member in which the region for supporting the substrate is composed of a plurality of pin-shaped convex portions is used.

[0004] Further, due to the miniaturization and ultra-high precision of semiconductor products, the wiring patterns formed on the substrate are also miniaturized and multi-layered. In the exposure process, it is necessary to stack a plurality of layers of circuit patterns on the substrate, and the requirement for the positioning accuracy (overlay accuracy) between the layers is also becoming strict.

[0005] Patent Document 1 discloses an article holding device in which an amorphous hard carbon film (for example, a DLC film or the like) is formed on the surface of a substrate holding surface to suppress the generation of particles due to wear of the holding surface, thereby reducing the risk of particles biting into between the holding surface and the substrate.

[0006] In Patent Document 2, scratches extending in the radial direction are formed on the surface of the chuck that supports the wafer. As a result, the frictional force with the wafer in the radial direction is reduced, and by reducing the friction against the lateral movement when the wafer is adsorbed to the chuck, it is disclosed that the wafer can be adsorbed in a flat state.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] With the miniaturization and multi-layer wiring of the wiring pattern formed on the substrate, the positioning accuracy of the substrate adsorbed to the substrate holding member (chuck) during the exposure process is very important. However, the substrate to be adsorbed is not necessarily excellent in flatness and may have concave or convex warps. Since the warp shape of the substrate at this time is not constant, pressure is not always evenly applied to the back surface of the substrate when negative pressure is generated by the suction of the vacuum chuck or when the electrostatic adsorption force is generated by the electrostatic chuck, and slippage, expansion / contraction, displacement, etc. of the substrate may occur.

[0009] The amorphous hard carbon film (DLC film) formed on the surface of the holding surface described in Patent Document 1 has the characteristics of high hardness and high wear resistance, and in addition, has the characteristic of a low friction coefficient, and there are problems such as slippage of the substrate during adsorption and difficulty in positioning.

[0010] When the scratches described in Patent Document 2 are formed, the frictional force with the wafer in the radial direction is reduced, and thus there are problems such as expansion / contraction and displacement of the wafer in the radial direction during wafer adsorption and difficulty in positioning.

[0011] The present invention has been made in view of such circumstances, and an object thereof is to provide a substrate holding member capable of improving the positioning accuracy of a substrate while maintaining a low contact state with the substrate.

Means for Solving the Problems

[0012] (1) To achieve the above object, the substrate holding member of the present invention is a substrate holding member, comprising a base body on a flat plate, and a plurality of Pin-shaped protrusions formed to protrude upward from the upper surface of the base body, wherein the upper end surface of the protrusion has a fine groove formed in the circumferential direction of the base body. having, and the narrow groove has a width of 1 to 10 μm It is characterized by having this.

[0013] In this way, by having a fine groove formed in the circumferential direction on the upper end surface of the protrusion, when the substrate is adsorbed, the expansion, contraction, and displacement of the substrate in the radial direction are suppressed, so that the positioning accuracy (overlay accuracy) of the substrate is improved.

[0014] (2) Further, in the substrate holding member of the present invention, the upper end surface of the protrusion is characterized in that the surface roughness Ra along the radial direction of the base body is larger than the surface roughness Ra along the circumferential direction of the base body.

[0015] In this way, since the surface roughness Ra in the radial direction of the upper end surface of the protrusion is larger than the surface roughness Ra in the circumferential direction, the positioning accuracy of the substrate is further improved.

[0016] (3) Further, in the substrate holding member of the present invention, when the upper surface is divided into four regions by two straight lines passing through the center of the base body and orthogonal to each other, any region includes a protrusion in which the surface roughness Ra along the radial direction of the base body of the upper end surface of the protrusion is larger than the surface roughness Ra along the circumferential direction of the base body.

[0017] Thereby, various expansions, contractions, and displacements of the substrate in the radial direction are suppressed, so that the positioning accuracy of the substrate is further improved.

[0018] (4) Further, in the substrate holding member of the present invention, the surface roughness Ra along the radial direction of the base body of the upper end surface of the convex portion is larger than the surface roughness Ra along the circumferential direction of the base body, and the surface roughness Ra along the radial direction of the base body of the convex portion is 0.04 μm or more and less than 0.15 μm.

[0019] Thereby, the effect of improving the positioning accuracy of the substrate can be sufficiently exerted, and the risk of particle generation can be reduced.

[0020] (5) Further, in the substrate holding member of the present invention, at least a part of the upper end surface of the convex portion is formed of a wear-resistant layer.

[0021] Thus, since at least a part of the upper end surface of the convex portion is formed of a wear-resistant layer, the generation of particles in repeated use can be suppressed.

[0022] (6) Further, the manufacturing method of the substrate holding member of the present invention is a manufacturing method of a substrate holding member, including a substrate preparation step of preparing a base body on a flat plate made of a ceramic sintered body, a convex portion forming step of forming a plurality of convex portions protruding from the upper surface of the base body, a lapping step of lapping the upper end surfaces of the plurality of convex portions, and a texturing step of performing texturing on the upper end surfaces of the plurality of convex portions so that the surface roughness Ra in the radial direction is larger than the surface roughness Ra in the circumferential direction.

[0023] Thereby, a substrate holding member with improved positioning accuracy (overlay accuracy) of the substrate can be manufactured.

Effects of the Invention

[0024] According to the present invention, it is possible to improve the positioning accuracy of the substrate while maintaining a low contact state with the substrate.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

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Figure 5

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Figure 7

Figure 8

Figure 9

Figure 10

[0026] Next, embodiments of the present invention will be described with reference to the drawings. For ease of understanding the description, the same reference numerals are given to the same components in each drawing, and overlapping descriptions are omitted. In the configuration diagrams, the sizes of the respective components are conceptually represented and do not necessarily represent actual dimensional ratios.

[0027] [Embodiment] The substrate holding member according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram showing an example of the upper surface of the substrate holding member according to an embodiment of the present invention. Further, FIG. 2 is a schematic cross-sectional view showing an example of the substrate holding member according to an embodiment of the present invention. The substrate holding member 100 according to the present embodiment includes a flat substrate 10 for sucking and holding a substrate (wafer) W.

[0028] The substrate 10 is formed in a flat plate shape by a ceramic sintered body. In addition to a disc shape, the substrate 10 may have various shapes according to the form of the substrate to be adsorbed, such as a polygonal plate shape or an elliptical plate shape. The ceramic sintered body forming the substrate 10 can be made of various materials according to the application. For example, SiC, Al 2 O 3 Si 3 N 4 AlN, cordierite, lithium aluminosilicate, etc. can be used.

[0029] The substrate 10 includes a plurality of convex portions 20 formed to protrude upward from the upper surface 12. The shapes of the plurality of convex portions 20 are appropriately selected from columnar shapes such as cylindrical and prismatic shapes, conical shapes such as conical and pyramidal shapes, and shapes obtained by cutting the upper part of a frustum of a cone or frustum of a pyramid. The shapes of the plurality of convex portions 20 may have a stepped shape in which the cross-sectional area of the upper part is smaller than that of the lower part. That is, the plurality of convex portions 20 are a plurality of pin-shaped convex portions.

[0030] The arrangement of the plurality of convex portions 20 is not particularly limited. It may be a known form or a form similar thereto. For example, in addition to regular arrangements such as concentric circles, square grids, or triangular grids as shown in FIG. 1, an irregular arrangement in which local density variations occur may also be used. It is preferable that the center-to-center distance between adjacent convex portions 20 is 8 mm or less.

[0031] The plurality of convex portions 20 support the substrate W. The upper ends 22 of the plurality of convex portions are formed substantially flush. That is, a plane (reference plane) 30 formed by the upper ends 22 of the plurality of convex portions is determined. Thereby, the upper ends 22 of the plurality of convex portions contact the substrate W, and the substrate W is supported. Note that among the plurality of convex portions 20, there may be those whose upper ends do not contact the substrate W. This is because even if there are such convex portions, depending on the arrangement of the surrounding convex portions 20, it is possible to support the substrate W.

[0032] The height of the convex portion 20 is preferably 50 μm or more and 300 μm or less. Note that the height of the convex portion 20 refers to the distance from the upper surface 12 of the base body 10 to the upper end 22 of the convex portion.

[0033] At least a part of the plurality of convex portions 20 has an upper end 22 of the convex portion formed as a surface (upper end surface). Further, at least a part of the convex portion 20 whose upper end 22 is formed as a surface has a fine groove 26 formed in the circumferential direction of the base body 10 on the upper end surface 24 of the convex portion. In this way, by having the fine groove 26 formed in the circumferential direction of the base body 10 on the upper end surface 24 of the convex portion, when the substrate W is adsorbed, the expansion, contraction, and displacement of the substrate W in the radial direction are suppressed, so the positioning accuracy (overlay accuracy) of the substrate W is improved. For the convex portion 20 whose upper end 22 is formed as a surface, it is preferable that the maximum diameter of the upper end surface 24 of the convex portion is 500 μm or less.

[0034] FIGS. 3(a) and 3(b) are schematic perspective views showing a convex portion 20 in which no fine groove 26 is formed on the upper end surface 24 of the convex portion and a convex portion 20 in which a fine groove 26 is formed in the circumferential direction, respectively. The fine groove 26 may or may not be continuous from one end to the other end of the upper end surface 24 of the convex portion. The width of the fine groove 26 is preferably 1 μm or more and 10 μm or less. The depth of the fine groove 26 is preferably 0.2 μm or more and 2 μm or less.

[0035] The substrate holding member 100 of the present invention preferably has the fine grooves 26 as shown in FIG. 4 as a whole by the convex portions 20 in which the fine grooves 26 are formed in the circumferential direction. FIG. 4 is a schematic diagram showing the concept of the upper surface of the substrate holding member 100 in which the convex portions 20 with the fine grooves 26 formed in the circumferential direction are arranged entirely. FIG. 5 is a schematic diagram showing the concept of the upper surface of the substrate holding member in which the convex portions with the fine grooves formed in one direction are arranged entirely. Note that the convex portions 20 are omitted in FIGS. 4 and 5.

[0036] As shown in FIG. 4, the substrate holding member 100 in which the convex portions 20 with the fine grooves 26 formed in the circumferential direction are arranged entirely can suppress the sliding, expansion / contraction, and displacement of the substrate W in all radial directions from the center of the substrate W. On the other hand, as shown in FIG. 5, the substrate holding member in which the convex portions with the fine grooves formed in one direction are arranged entirely can suppress the sliding, expansion / contraction, and displacement of the substrate W in a certain radial direction from the center of the substrate W, but cannot suppress the sliding, expansion / contraction, and displacement in a radial direction different from that. Therefore, in the substrate holding member of the present invention, it is preferable that there are a plurality of the convex portions 20 with the fine grooves 26 formed in the circumferential direction, and it is more preferable that they are arranged entirely.

[0037] However, since the convex portions 20 with the fine grooves 26 formed in the circumferential direction can suppress the sliding, expansion / contraction, and displacement of the substrate W in the radial direction at the locations where they are arranged, even if some of the convex portions 20 are the convex portions 20 with the fine grooves 26 formed in the circumferential direction and the other convex portions 20 are the convex portions 20 without the fine grooves 26 formed, they are included in the scope of the present invention.

[0038] It is preferable that the surface roughness Ra along the radial direction of the base body 10 of the upper end surface 24 of the convex portion is larger than the surface roughness Ra along the circumferential direction of the base body 10. In this way, since the surface roughness Ra in the radial direction of the upper end surface 24 of the convex portion is larger than the surface roughness Ra in the circumferential direction, the positioning accuracy of the substrate W is further improved. Note that the radial direction and the circumferential direction of the base body 10 are the radial direction and the circumferential direction of a circle having the center 16 of the base body as the center of the circle when the center 16 of the base body is set on the upper surface 12 of the base body 10. The center 16 of the base body is preferably set in the vicinity of the center of the substrate W when the substrate W having the maximum diameter that can be placed on the substrate holding member 100 is placed. The vicinity of the center is a range within 0.2 mm from the center of the substrate W having the maximum diameter.

[0039] The surface roughness Ra along the radial direction of the base body 10 of the convex portion 20, where the surface roughness Ra along the radial direction of the upper end surface 24 of the convex portion is larger than the surface roughness Ra along the circumferential direction of the base body 10, is preferably 0.04 μm or more. If the surface roughness Ra along the radial direction is too small, the effect of suppressing the expansion, contraction, and displacement of the substrate W in the radial direction when the substrate W is adsorbed becomes small. Also, the surface roughness Ra along the radial direction of the base body 10 of the convex portion 20, where the surface roughness Ra along the radial direction of the upper end surface 24 of the convex portion is larger than the surface roughness Ra along the circumferential direction of the base body 10, is preferably less than 0.15 μm, and more preferably 0.1 μm or less. If the surface roughness Ra along the radial direction is too large, the risk of particle generation increases.

[0040] The surface roughness Ra along the circumferential direction of the base body 10 of the convex portion 20, where the surface roughness Ra along the radial direction of the upper end surface 24 of the convex portion is larger than the surface roughness Ra along the circumferential direction of the base body 10, is preferably 0.001 μm or more and 0.08 μm or less.

[0041] Incidentally, the surface roughness Ra along the radial direction of the substrate 10 on the upper end surface 24 of the convex portion, and the surface roughness Ra along the circumferential direction of the substrate 10 can be obtained by three-dimensionally scanning the unevenness amount of the upper end surface 24 of the convex portion non-contact with a white interferometer, creating a 2D chart on a straight line in the radial direction or a curve in the circumferential direction on the scanned 3D height map, and obtaining it from the created 2D chart. The surface roughness Ra is preferably the average value of the upper end surfaces 24 of a plurality of convex portions.

[0042] For example, when the convex portions 20 where the surface roughness Ra along the radial direction of the substrate 10 on the upper end surface 24 of the convex portion is larger than the surface roughness Ra along the circumferential direction of the substrate 10 are on the entire upper surface 12 of the substrate 10, four circles with an arbitrary radius centered on the center 16 of the substrate are set, and a total of 12 convex portions in three directions at equal intervals of 120° in the rotation direction are selected as the observation positions. The surface roughness Ra along the radial direction of the substrate 10 and the surface roughness Ra along the circumferential direction of the substrate 10 of all the selected convex portions 20 are obtained, and the average values can be used as the surface roughness Ra along the radial direction of the substrate 10 and the surface roughness Ra along the circumferential direction of the substrate, respectively.

[0043] Also, when the upper surface 12 is divided into four regions by two straight lines passing through the center 16 of the substrate and orthogonal to each other, it is preferable that each region includes convex portions 20 where the surface roughness Ra along the radial direction of the substrate 10 on the upper end surface 24 of the convex portion is larger than the surface roughness Ra along the circumferential direction of the substrate 10. Thereby, since the expansion, contraction, and displacement of the substrate in various radial directions are suppressed, the positioning accuracy of the substrate is further improved.

[0044] For example, it is sufficient that all the convex portions 20 in the region inside a circle with a predetermined radius centered on the center 16 of the substrate have a surface roughness Ra along the radial direction of the substrate 10 on the upper end surface 24 of the convex portion that is larger than the surface roughness Ra along the circumferential direction of the substrate 10. Also, for example, it is sufficient that all the convex portions 20 in a donut-shaped region surrounded by two circles with different predetermined radii centered on the center 16 of the substrate have a surface roughness Ra along the radial direction of the substrate 10 on the upper end surface 24 of the convex portion that is larger than the surface roughness Ra along the circumferential direction of the substrate 10.

[0045] As described above, it is preferable that all of the convex portions 20 formed on the base 10 have the fine grooves 26 formed in the circumferential direction. Further, it is preferable that all of the convex portions 20 formed on the base 10 are convex portions 20 in which the surface roughness Ra along the radial direction of the base 10 of the upper end surface 24 of the convex portion is larger than the surface roughness Ra along the circumferential direction of the base 10.

[0046] At least a part of the upper end 22 of the convex portion, or at least a part of the upper end surface 24 of the convex portion is preferably formed of the wear-resistant layer 28. By forming at least a part of the upper end surface 24 of the convex portion with the wear-resistant layer 28, generation of particles during repeated use can be suppressed. FIGS. 6(a) and (b) are schematic cross-sectional views showing the convex portion 20 on which the wear-resistant layer 28 is formed. As shown in FIG. 6(a), the wear-resistant layer 28 may be formed on all or at least a part of the upper end 22 or the upper end surface 24 of the convex portion. Further, as shown in FIG. 6(b), it may be formed on the upper end 22 or the upper end surface 24 of the convex portion, its side surface, and the upper surface 12 of the base 10.

[0047] The wear-resistant layer 28 can be formed of a DLC film (diamond-like carbon), a SiC film, etc. formed by physical vapor deposition (PVD method), chemical vapor deposition (CVD method), ionized vapor deposition method, etc.

[0048] The convex portion 20 in which at least a part of the upper end surface 24 of the convex portion is formed of the wear-resistant layer 28 preferably has the fine groove 26 formed in the circumferential direction. Further, the convex portion 20 in which at least a part of the upper end surface 24 of the convex portion is formed of the wear-resistant layer 28 preferably has a surface roughness Ra along the radial direction of the base 10 of the upper end surface 24 of the convex portion larger than the surface roughness Ra along the circumferential direction of the base 10. This is because when at least a part of the upper end surface 24 of the convex portion is formed of the wear-resistant layer 28, slipping, expansion and contraction, displacement, etc. of the substrate are likely to occur.

[0049] The substrate holding member 100 may be provided with electrodes, terminals, terminal holes, lift pin holes, etc. (not shown). Further, when used as a vacuum chuck, it may be provided with vent holes, annular protrusions, etc. for that purpose. Further, when used as an electrostatic chuck, it may be provided with electrodes for electrostatic adsorption, etc.

[0050] FIG. 7 is a schematic diagram showing a modification of the upper surface of the substrate holding member according to an embodiment of the present invention. Further, FIG. 8 is a schematic cross-sectional view showing a modification of the substrate holding member according to an embodiment of the present invention. FIGS. 7 and 8 assume the case where the substrate holding member 100 is used as a vacuum chuck.

[0051] The annular protrusion 40 is formed in an annular shape along the outer periphery of the upper surface 12 of the base body 10. For example, when the base body 10 is formed in a disc shape, the annular protrusion 40 is preferably formed continuously in an annular shape when viewed from above at a position along the outer periphery of the upper surface of the base body 10 or at a position closer to the center side with a predetermined width from the outer periphery. When the annular protrusion 40 is formed in an annular shape, its center preferably coincides with the center 16 of the base body.

[0052] The upper end 42 of the annular protrusion is preferably at a position closer to the upper surface 12 of the base body 10 than the upper ends 22 of the plurality of protrusions. That is, the height of the annular protrusion 40 is preferably lower than the height of the plurality of protrusions 20. Thereby, during the adsorption operation of the substrate W, air always flows in from the outside of the base body 10, and the Bernoulli effect is exerted in the vicinity of the annular protrusion 40 to suppress the sinking of the edge of the substrate W. Further, the contact area with the substrate W can be reduced, and the risk of particle generation is reduced. Note that although the annular protrusion 40 is formed to be lower than the upper ends of the plurality of protrusions 20 by a certain amount, there is no problem as long as the interval is such that sufficient vacuum is obtained for the adsorption of the substrate W due to the generation of a pressure gradient and outside air is always introduced from the outer periphery during the adsorption of the substrate W.

[0053] The height of the annular convex portion 40 refers to the distance from the upper surface 12 of the base body 10 to the upper end 42 of the annular convex portion. The height of the annular convex portion 40 is preferably 1 μm or more and 10 μm or less lower than the height of the plurality of convex portions 20. For example, when the height of the plurality of convex portions 20 is 100 μm, the height of the annular convex portion 40 is preferably 90 μm or more and 99 μm or less.

[0054] The width of the annular convex portion 40 is preferably 0.1 μm or more and 8 mm or less. Also, the width of the annular convex portion 40 is preferably equal to or less than the distance between the centers of the adjacent plurality of convex portions 20. The annular convex portion 40 may have various shapes such as a trapezoidal shape or a hemispherical shape in addition to a rectangular cross-sectional shape, but the upper end 42 of the annular convex portion is preferably formed as a flat surface. In that case, the surface roughness of the flat surface (the upper end surface 44 of the annular convex portion) of the upper end 42 of the annular convex portion is preferably Ra 0.20 μm or less.

[0055] In the case of a so-called Bernoulli type vacuum chuck where the upper end 42 of the annular convex portion is closer to the upper surface 12 of the base body 10 than the upper ends 22 of the plurality of convex portions, since the upper end surface 44 of the annular convex portion does not contact the substrate W, it is not necessary to form a fine groove in the upper end surface 44 of the annular convex portion. On the other hand, in the case of a vacuum chuck where the upper end 42 of the annular convex portion is formed flush with the upper ends 22 of the plurality of convex portions, since the upper end surface 44 of the annular convex portion contacts the substrate W, a fine groove 26 may be formed in the upper end surface 44 of the annular convex portion.

[0056] One or a plurality of vent holes 50 that open to the upper surface 12 are formed in the base body 10. When a plurality of vent holes 50 are formed, the plurality of vent holes 50 may communicate with each other through a ventilation path passing through the inside of the base body 10. The vent hole 50 is connected to a vacuum suction device (not shown). The position, shape, and size of the vent hole 50 vary according to the design of the substrate holding device, such as the shape of the region of the suction surface, the shape and type of the substrate W, and the suction force when vacuum suction is performed.

[0057] [Manufacturing method of substrate holding member] Next, a method for manufacturing a substrate holding member according to an embodiment of the present invention will be described. The method for manufacturing a substrate holding member according to an embodiment of the present invention includes a substrate preparation step, a convex portion forming step, a lapping process step, and a texturing process step. Each step will be described below.

[0058] In the substrate preparation step, a substrate on a flat plate made of a ceramic sintered body is prepared. By a well-known method, a flat molded body is produced from raw material powder, and this molded body is fired to obtain a flat ceramic sintered body. The ceramic sintered body is SiC, Al 2 O 3 、Si 3 N 4 、AlN, cordierite, lithium aluminosilicate, or the like. The raw material powder may contain a sintering aid. Although a disc-shaped substrate holding member is illustrated in FIG. 1 and the like, any shape such as a polygonal shape or an elliptical shape may be used.

[0059] In the convex portion forming step, a plurality of convex portions protruding from the upper surface of the substrate are formed. That is, a plurality of convex portions are formed on the surface that becomes the upper surface of the ceramic sintered body. Further, if necessary, ventilation holes, annular convex portions, and the like are formed. As a forming method, it is possible to form by blasting, milling, laser processing, or the like.

[0060] The arrangement of the plurality of convex portions is not particularly limited. It may be a known form or a form similar thereto. For example, the arrangement may be an irregular arrangement in which local density occurs in addition to a regular arrangement such as a triangular lattice, a square lattice, or a concentric circle.

[0061] The shapes of the plurality of convex portions are appropriately selected from columnar shapes such as cylindrical and prismatic, conical shapes such as conical and pyramidal, and shapes obtained by cutting the upper part of a frustum of a cone or a frustum of a pyramid. The shape of the plurality of convex portions 20 may be a stepped shape in which the cross-sectional area of the upper part is smaller than that of the lower part. At least a part of the convex portions is formed with the upper end of the convex portion as a surface. That is, it is preferable that the shape of at least a part of the convex portions is a columnar shape such as a cylindrical or prismatic shape, or a shape obtained by cutting the upper part of a frustum of a cone or a frustum of a pyramid.

[0062] The upper ends of the plurality of convex portions are formed substantially flush. The plurality of convex portions are preferably designed according to conditions such as the substrate to be adsorbed, for example, with a protrusion amount of 50 μm or more and 500 μm or less, and an interval between the plurality of convex portions of 1.5 mm or more and 8 mm or less. Further, the diameter of the upper end surface of the convex portion formed as a surface is preferably 100 μm or more and 500 μm or less.

[0063] In the lapping process, the upper end surfaces of the plurality of convex portions are lapped. The surface of the convex portion is lapped and polished with free abrasive grains, and the surface roughness Ra is preferably 0.05 μm or less, more preferably 0.04 μm or less.

[0064] In the texturing process, the upper end surfaces of the plurality of convex portions are textured so that the surface roughness Ra in the radial direction is larger than the surface roughness Ra in the circumferential direction. Specifically, fine grooves along the circumferential direction are formed on the surface of the convex portion by surface texturing. At this time, the surface roughness Ra along the radial direction of the substrate is preferably 0.04 μm or more and less than 0.15 μm. The texturing process is performed, for example, as follows. FIGS. 9(a) and (b) are a schematic perspective view and a plan view showing the process of the texturing process, respectively.

[0065] The texturing process is performed, for example, by scanning a piece of a dense ceramic sintered body on the surfaces of the plurality of convex portions. The ceramic piece is made of, for example, Al 2 O 3 or ZrO 2 oxide ceramics, is disk-shaped or square-shaped, and the surface roughness Ra of the surface in contact with the substrate holding member (the plurality of convex portions) is preferably 0.1 μm or more and 0.5 μm or less. If Ra exceeds 0.5 μm, there is a risk of generation of particles due to wear of the plurality of convex portions and deterioration of the flatness of the substrate holding member. If it is less than 0.1 μm, adsorption to the plurality of convex portions occurs, making it difficult to scan the ceramic piece, and there is a risk of damaging the convex portions due to excessive force being applied.

[0066] In order to suppress dust generation from the ceramic piece itself, the purity of the ceramic piece is preferably high purity. For example, it is preferably 95% or more, and more preferably 99% or more.

[0067] Diamond paste is thinly and uniformly applied to the surface of the ceramic piece, placed on the surfaces of the plurality of convex portions, and scanned in the circumferential direction of the substrate holding member at a pressure of 1 kPa or less (the self-weight level of the piece). At this time, for the purpose of forming fine grooves along the circumferential direction, the ceramic piece is scanned only in a certain direction. For example, after scanning the outer peripheral portion of the substrate holding member about 1 to 3 turns, the ceramic piece is offset inward and scanned about 1 to 3 turns in the same manner. Then, the surface roughness is measured, and if the value is not satisfactory, the surface texturing process is performed by repeating the same scanning.

[0068] The surface roughness Ra along the radial direction of the base body of the upper end surface of the convex portion and the surface roughness Ra along the circumferential direction of the base body are obtained by three-dimensionally scanning the unevenness amount of the upper end surface of the convex portion non-contact with a white interferometer, creating a 2D chart on a straight line in the radial direction or a curve in the circumferential direction on the scanned 3D height map, and can be obtained by the created 2D chart. The surface roughness Ra is preferably the average value of the upper end surfaces of the plurality of convex portions.

[0069] Note that, before or after the texturing process, a wear-resistant layer forming step of forming a wear-resistant layer on at least a part of the upper end surfaces of the plurality of convex portions may be provided. The wear-resistant layer forming step can form a wear-resistant layer by forming a DLC film (diamond-like carbon), a SiC film, etc. on the substrate holding member on which the plurality of convex portions are formed and lapping is performed, by physical vapor deposition (PVD method), chemical vapor deposition (CVD method), ionized vapor deposition method, etc.

[0070] When the thickness of the wear-resistant layer to be formed is thinner than the depth of the fine grooves formed in the texturing process, it may be performed either before or after the texturing process. When the thickness of the wear-resistant layer to be formed is equal to or greater than the depth of the fine grooves formed in the texturing process, it is preferably performed after the texturing process.

[0071] By the above-described process, the substrate holding member of the present invention can be manufactured.

[0072] [Examples and Comparative Examples] (Example 1) A substantially disc-shaped substrate having a diameter of φ310 mm and a thickness of t1.5 mm, made of a sintered body of silicon carbide, was prepared, and air holes, a plurality of convex portions, and an annular convex portion were formed by blasting. The plurality of convex portions had a height of 150 μm and a diameter of φ300 μm, and were formed in a triangular lattice pattern with a center-to-center distance of 4 mm between the convex portions. The annular convex portion had a width of 200 μm and was formed to be 3 μm lower than the plurality of convex portions by additional processing.

[0073] Subsequently, lapping and polishing were performed with free abrasive grains, and finishing was performed so that the surface roughness Ra of the plurality of convex portions was about 0.03 μm.

[0074] Subsequently, as surface texturing, a ceramic piece (φ130 mm × t15 mm) made of aluminum oxide having a relative density of 99% and a surface roughness Ra of 0.3 μm was coated with diamond paste having a particle size of 0.5 μm and scanned in the circumferential direction to manufacture the substrate holding member of Example 1. After the texturing process, the surface roughness Ra along the radial direction of the substrate at the 12 convex portions measured was 0.04 μm. Also, the surface roughness Ra along the circumferential direction of the substrate at the same 12 convex portions was 0.03 μm.

[0075] The surface roughness Ra of the convex portions before the texturing process in the examples and comparative examples was measured as follows. Four circles with arbitrary radii centered on the center of the substrate were set (in this example, φ20 mm, φ110 mm, φ200 mm, φ298 mm), and a total of 12 convex portions in three directions equally spaced at 120° in the rotational direction were selected as the observation positions. Next, the unevenness amount of the upper end surface of the selected convex portions was three-dimensionally scanned non-contact using a white light interferometer (manufactured by AMETEK Talor Hobson: CCI-HD). Next, a 2D chart was created on an arbitrary straight line on the scanned 3D height map, and the surface roughness Ra of each convex portion was determined from the created 2D chart. Then, the surface roughness Ra of the substrate holding member was determined by obtaining the average value of the surface roughness Ra of the 12 convex portions.

[0076] Also, the surface roughness Ra along the radial direction of the substrate of the convex portions after the texturing process in the examples and the surface roughness Ra along the circumferential direction of the substrate were measured as follows. Four circles with arbitrary radii centered on the center of the substrate were set (in this example, φ20 mm, φ110 mm, φ200 mm, φ298 mm), and a total of 12 convex portions in three directions equally spaced at 120° in the rotational direction were selected as the observation positions. Next, the unevenness amount of the upper end surface of the selected convex portions was three-dimensionally scanned non-contact using a white light interferometer (manufactured by AMETEK Talor Hobson: CCI-HD). Next, a 2D chart was created on a straight line in the radial direction or a curve in the circumferential direction on the scanned 3D height map, and the surface roughness Ra along the radial direction of the substrate of each convex portion and the surface roughness Ra along the circumferential direction of the substrate were determined from the created 2D chart. Then, the average value of the surface roughness Ra along the radial direction of the substrate of the 12 convex portions and the average value of the surface roughness Ra along the circumferential direction of the substrate were obtained to determine the surface roughness Ra along the radial direction of the substrate and the surface roughness Ra along the circumferential direction of the substrate of each substrate holding member. Comparative Example 2 determined only the surface roughness along the X direction.

[0077] (Example 2) Example 2 manufactured a substrate holding member under the same conditions as Example 1, except that the number of circumferential scans in the texturing process was increased compared to Example 1. After the texturing process, the surface roughness Ra along the radial direction of the substrate in the measured 12 protrusions was 0.10 μm. Also, the surface roughness Ra along the circumferential direction of the substrate in the same 12 protrusions was 0.03 μm.

[0078] (Example 3) Example 3 manufactured a substrate holding member under the same conditions as Example 1, except that the number of circumferential scans in the texturing process was further increased compared to Example 2. After the texturing process, the surface roughness Ra along the radial direction of the substrate in the measured 12 protrusions was 0.15 μm. Also, the surface roughness Ra along the circumferential direction of the substrate in the same 12 protrusions was 0.03 μm.

[0079] (Example 4) Example 4 manufactured a substrate holding member under the same conditions as Example 1, except that a wear-resistant layer made of a DLC film with a thickness of 0.5 μm was formed on the surfaces of the plurality of protrusions after lapping and polishing, and then texturing was performed. After the texturing process, the surface roughness Ra along the radial direction of the substrate in the measured 12 protrusions was 0.06 μm. Also, the surface roughness Ra along the circumferential direction of the substrate in the same 12 protrusions was 0.03 μm.

[0080] (Comparative Example 1) Comparative Example 1 manufactured a substrate holding member by performing lapping and polishing with free abrasive grains, finishing so that the surface roughness Ra of the plurality of protrusions was about 0.03 μm, and not performing surface texturing.

[0081] (Comparative Example 2) In Comparative Example 2, lapping and polishing was performed using free abrasive grains, and finishing was carried out so that the surface roughness Ra of a plurality of convex portions was about 0.03 μm. As a texturing process, the substrate holding member was manufactured by scanning the ceramic piece only in the Y direction. After the texturing process, the surface roughness Ra along the X direction in the 12 convex portions measured was 0.10 μm.

[0082] (Comparative Example 3) In Comparative Example 3, lapping and polishing was performed using free abrasive grains, and finishing was carried out so that the surface roughness Ra of a plurality of convex portions was about 0.03 μm. A wear-resistant layer made of a DLC film with a thickness of 0.5 μm was formed on the surfaces of the plurality of convex portions after lapping and polishing by PVD method, thereby manufacturing the substrate holding member.

[0083] The upper end surfaces of the convex portions of Example 1 and the upper end surfaces of the convex portions of Comparative Example 1 were observed with an optical microscope. Figures 10(a) and (b) are optical microscope photographs of the upper end surfaces of the convex portions of Example 1 and Comparative Example 1, respectively. As shown in Fig. 10, a large number of fine grooves along the radial direction were formed on the upper end surface of the convex portion of Example 1.

[0084] (Evaluation method) The substrate holding members obtained in the examples and comparative examples were installed in an exposure apparatus, and evaluation was performed by adsorbing a plurality of silicon wafers (substrates) with a diameter of 300 mm and a thickness of 0.7 mm. The overall shape of the silicon wafer was compared before and after adsorption using a Fizeau type laser interferometer (manufactured by Apre Instruments Inc.: S300HR(SCI)), and the presence or absence of expansion, contraction, and displacement in the X direction and Y direction was confirmed.

[0085] (Evaluation results) It was confirmed that the substrate holding members of Example 1 to Example 4 had high positioning accuracy with the slippage, expansion, and displacement of the substrate suppressed throughout the in-plane directions with respect to the X direction and Y direction.

[0086] On the other hand, in Comparative Example 1 where no surface texturing process was performed, there were variations in suppressing the slippage, expansion / contraction, and displacement of the substrate, lacking stability in positioning accuracy. Furthermore, the substrate separation property after the adsorption operation release was worse compared to the examples, also affecting throughput reduction.

[0087] Also, in Comparative Example 2 where the scanning direction of the ceramic piece for the surface texturing process was scanned only in the Y direction, slippage, expansion / contraction, and displacement of the substrate were observed only in the Y direction, and high positioning accuracy could not be obtained.

[0088] In addition, in Comparative Example 3 where a wear-resistant layer was formed and no surface texturing process was performed, there were variations in suppressing the slippage, expansion / contraction, and displacement of the substrate, lacking stability in positioning accuracy. Also, no directivity was confirmed in the slipping direction, and there was a tendency to have a large positional deviation compared to the examples.

[0089] In Example 3 where the surface roughness Ra in the radial direction of the plurality of convex portions was set to 0.15 μm by the surface texturing process, the effect of suppressing the slippage, expansion / contraction, and displacement of the substrate was obtained, but particle generation was observed over time, and it was confirmed that the planar accuracy of the substrate deteriorated. That is, it is estimated that the life as a substrate holding member is shorter compared to Examples 1 and 2.

[0090] From the above, it was confirmed that the substrate holding member of the present invention can improve the positioning accuracy of the substrate while maintaining a low-contact state with the substrate. Also, it was confirmed that the manufacturing method of the substrate holding member of the present invention can manufacture such a substrate holding member.

[0091] The present invention is not limited to the above-described embodiments, and it goes without saying that it extends to various modifications and equivalents included in the spirit and scope of the present invention. Also, the structure, shape, number, position, size, etc. of the components shown in each drawing are for convenience of explanation and can be changed as appropriate.

Explanation of Reference Numerals

[0092] 10 Base body 12 Above 16 Center of the substrate 20 Convex part 22 Upper end of the convex part 24 Upper end face of the convex part 30 Reference plane 40 Annular convex part 42 Upper end of the annular convex part 44 Upper end face of the annular convex part 50 Vent hole 100 Substrate holding member W Substrate

Claims

1. A substrate holding member, comprising: a substrate on a flat plate; and a plurality of pin-shaped convex portions formed to protrude upward from the upper surface of the substrate, wherein an upper end surface of the convex portion has a narrow groove formed in a circumferential direction of the substrate, and the narrow groove has a width of 1 to 10 μm. The substrate holding member is characterized by this.

2. The substrate holding member according to claim 1, wherein a surface roughness Ra along a radial direction of the substrate of the upper end surface of the convex portion is larger than a surface roughness Ra along a circumferential direction of the substrate.

3. When the upper surface is divided into four regions by two straight lines passing through the center of the substrate and orthogonal to each other, each region includes a convex portion in which a surface roughness Ra along a radial direction of the substrate of the upper end surface of the convex portion is larger than a surface roughness Ra along a circumferential direction of the substrate. The substrate holding member according to claim 2 is characterized by this.

4. The surface roughness Ra along a radial direction of the substrate of the convex portion, in which the surface roughness Ra along a radial direction of the substrate of the upper end surface of the convex portion is larger than a surface roughness Ra along a circumferential direction of the substrate, is 0.04 μm or more and less than 0.15 μm. The substrate holding member according to claim 2 or claim 3 is characterized by this.

5. The substrate holding member according to any one of claims 1 to 4, wherein at least a part of the upper end surface of the convex portion is formed of a wear-resistant layer.

6. A method for manufacturing a substrate holding member, comprising: a substrate preparation step of preparing a substrate on a flat plate made of a ceramic sintered body; a convex portion forming step of forming a plurality of convex portions protruding from the upper surface of the substrate; a lapping step of lapping the upper end surfaces of the plurality of convex portions; and a texturing step of performing texturing on the upper end surfaces of the plurality of convex portions so that a surface roughness Ra in a radial direction is larger than a surface roughness Ra in a circumferential direction. The method for manufacturing a substrate holding member is characterized by including these steps.

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