JP7614770B2 - Substrate holding member - Google Patents

Description

The present invention relates to a substrate holding member.

Conventionally, substrate holding members that support substrates such as silicon wafers and glass have been used in semiconductor manufacturing equipment. The base that constitutes the substrate holding member supports the back side of the substrate, and the substrate is supported by evacuating the air through vent holes formed on the surface of the substrate. In recent years, semiconductor products have become increasingly fine and highly accurate. If particles are present between the substrate and the substrate, localized swelling of the substrate occurs, and in the circuit pattern formation process by exposing the substrate to light, defects such as short circuits in the circuit pattern formed on the substrate occur, resulting in a decrease in the yield of semiconductor products. For this reason, it is necessary to avoid such defects. In order to reduce the risk of such particle bite, and to reduce the contact area between the substrate and the substrate, substrate holding members are used that have a region that supports the substrate as multiple pin-shaped protrusions.

In Patent Document 1, in order to further reduce the risk of particles getting caught, the height of the annular sealing bank portion (annular convex portion) formed to surround the multiple pin-shaped convex portions is formed to be slightly lower than the multiple pin-shaped convex portions so that the degree of vacuum required for correcting the plane of the substrate can be obtained. Furthermore, in Patent Document 1, pin-shaped convex portions (of the same height as the multiple pin-shaped convex portions formed in the negative pressure region) are formed further outboard of the sealing edge bank portion as a support surface for the substrate in order to prevent the outer periphery of the substrate from dropping downward (towards the substrate).

JP 2001-185607 A

The substrate is attracted by reducing the pressure in the space between the back surface of the substrate and the front surface of the substrate due to the negative pressure of a suction pump connected to an air vent formed in the substrate. However, because the height of the annular protrusion is lower than that of the multiple pin-shaped protrusions, air is constantly flowing in from outside the substrate during the substrate attracting operation.

At the same time as this air inflow, if particles are allowed to invade from the outside and become trapped between the rear surface of the substrate and the pin-shaped protrusions, problems such as localized deterioration in flatness may occur. However, Patent Document 1 does not take into account the intrusion of particles from the outside.

The present invention was made in consideration of these circumstances, and aims to provide a substrate holding member that can reduce the contact area between the substrate and the base while suppressing the intrusion of particles from the outside.

(1) In order to achieve the above object, a substrate holding member of the present invention is a substrate holding member comprising a flat base having one or more ventilation holes opening on an upper surface thereof, and a plurality of convex portions formed protruding upward from the upper surface of the base, the convex portions comprising: an annular convex portion formed in a ring shape along the outer periphery of the upper surface of the base; a plurality of inner convex portions formed inside the annular convex portion and having an upper end at a position farther from the upper surface of the base than an upper end of the annular convex portion; and an annular, arc-shaped or line-segment-shaped outer convex portion formed outside the annular convex portion and having an upper end at a position farther from the upper surface of the base than an upper end of the annular convex portion , the outer convex portion being formed by a plurality of partial outer convex portions,
The plurality of partial outer convex portions are characterized by being arranged in a ring shape . In this way, a ring-shaped convex portion lower than the plurality of inner convex portions is provided on the upper surface of the base, and a ring-shaped, arc-shaped or linear outer convex portion higher than the ring-shaped convex portion is provided on the outer side of the ring-shaped convex portion, thereby forming a wall in the outer peripheral region. As a result, the inflow of air during the adsorption operation is restricted, and the intrusion of particles from the outside can be suppressed while reducing the contact area between the substrate and the base.

(2) In addition, in the substrate holding member of the present invention, the outer convex portion is characterized in that it is arranged at a position where the outer convex portion exists on all straight lines passing through the center of the substrate. In this way, by arranging the outer convex portion at a position where the outer convex portion exists on all straight lines passing through the center of the substrate, it is possible to further suppress the intrusion of particles when air flows in.

(3) In addition, in the substrate holding member of the present invention, the outer convex portion is formed in a circular ring shape. This further enhances the effect of suppressing particle intrusion, since the outside of the annular convex portion is entirely covered by the outer convex portion formed in a circular ring shape.

(4) As described above , in the substrate holding member of the present invention, the outer convex portion is formed by a plurality of partial outer convex portions, and the plurality of partial outer convex portions are arranged in a ring shape. By arranging the partial outer convex portions in a ring shape, the gaps between adjacent partial outer convex portions become air inlets, and the amount of air flowing in from the outside increases, improving the ease of removal (dechucking) after substrate processing.

According to the present invention, a wall is formed in the outer peripheral region by providing an annular convex portion on the upper surface of the base that is lower than the multiple inner convex portions, and further outside that, an outer convex portion that is higher than the annular convex portion. As a result, the inflow of air during the adsorption operation is restricted, and the intrusion of particles from the outside can be suppressed while reducing the contact area between the substrate and the base.

3 is a schematic diagram showing an example of the upper surface of a substrate holding member according to an embodiment of the present invention. FIG. 1 is a partial cross-sectional view showing an example of a substrate holding member according to an embodiment of the present invention. 11A and 11B are schematic diagrams showing modified examples of the upper surface of the substrate holding member according to the embodiment of the present invention. 11A and 11B are schematic diagrams showing modified examples of the upper surface of the substrate holding member according to the embodiment of the present invention. 11A and 11B are schematic diagrams showing modified examples of the upper surface of the substrate holding member according to the embodiment of the present invention.

Next, an embodiment of the present invention will be described with reference to the drawings. To facilitate understanding of the description, the same reference numbers are used for the same components in each drawing, and duplicate descriptions will be omitted. Note that in the configuration diagrams, the size of each component is shown conceptually and does not necessarily represent the actual dimensional ratio.

[Embodiment]
A 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 a substrate holding member according to an embodiment of the present invention. Fig. 2 is a partial cross-sectional view showing an example of the substrate holding member. The substrate holding member 100 includes a substantially flat base 10 for suction-holding a substrate (wafer) W. The base 10 is formed in a substantially flat plate shape from a ceramic sintered body. The base 10 may have various shapes such as a substantially circular plate shape, a polygonal plate shape, or an elliptical plate shape.

The base 10 has one or more ventilation holes 14 opening on the upper surface 12. When there are multiple ventilation holes 14, the ventilation holes 14 may be connected via an air passage passing through the inside of the base 10. The ventilation holes 14 are connected to a vacuum suction device (not shown). The position, shape, and size of the ventilation holes 14 vary depending on the design of the substrate holding member 100, such as the shape of the suction surface area determined by the annular protrusion 22 described below, the shape and type of the substrate W, and the suction force when vacuum suctioned.

The base 10 has a number of protrusions 20 formed by protruding upward from the upper surface 12. The multiple protrusions 20 include an annular protrusion 22, an inner protrusion 24, and an outer protrusion 26.

The annular protrusion 22 is formed in a ring shape along the outer periphery of the upper surface of the base 10. For example, when the base 10 is formed in a disk shape, the annular protrusion 22 is preferably formed in a continuous ring shape when viewed from above at a position closer to the center, leaving a predetermined range from the outer periphery of the upper surface of the base 10 that forms the outer protrusion 26.

The upper end 22a of the annular convex portion is closer to the upper surface 12 of the base 10 than the upper end 24a of the inner convex portion. That is, the height of the annular convex portion 22 is lower than the height of the inner convex portion 24. As a result, during the suction operation of the substrate W, air always flows in from the outside of the base 10, and the Bernoulli effect is exerted near the annular convex portion 22, thereby suppressing the sinking of the edge of the substrate W. The height of the annular convex portion 22 refers to the distance from the upper surface 12 of the base 10 to the upper end 22a of the annular convex portion. It is preferable that the height of the annular convex portion 22 is lower than the height of the inner convex portion 24 by 1 μm or more and 5 μm or less. For example, when the height of the inner convex portion 24 is 100 μm, the height of the annular convex portion is preferably 95 μm or more and 99 μm or less. It is preferable that the width of the annular convex portion 22 is 0.05 mm or more and 8 mm or less. It is also preferable that the width of the annular convex portion 22 is equal to or less than the distance between the centers of the adjacent inner convex portions 24. Additionally, the upper end 22a of the annular convex portion is preferably formed as a flat surface. In this case, the surface roughness of the flat surface (upper end surface) of the upper end 22a of the annular convex portion is preferably Ra 0.2 μm or less.

Multiple inner convex portions 24 are formed inside the annular convex portion 22. The multiple inner convex portions 24 support the substrate W. The upper ends 24a of the multiple inner convex portions are formed to be approximately flush. In other words, a plane (reference plane) 30 formed by the upper ends 24a of the multiple inner convex portions is determined. As a result, the upper ends 24a of the multiple inner convex portions abut against the substrate W, supporting the substrate W. Note that some of the multiple inner convex portions 24 may have upper ends that do not abut against the substrate W. This is because, even if such convex portions exist, it is possible to support the substrate W depending on the arrangement of the surrounding inner convex portions 24.

The upper end 24a of the inner convex portion is located farther from the upper surface 12 of the base 10 than the upper end 22a of the annular convex portion. That is, the height of the inner convex portion 24 is higher than the height of the annular convex portion 22. The upper end 24a of the inner convex portion is preferably a flat surface of a predetermined size. In this case, the maximum diameter of the flat surface of the upper end 24a of the inner convex portion is preferably 100 μm or more and 500 μm or less. The surface roughness of the flat surface of the upper end 24a of the inner convex portion is preferably Ra 0.01 μm or more and 0.50 μm or less. The shape of the inner convex portion 24 may be a cylinder, a prism, a truncated cone, a truncated pyramid, or the like, or may be a stepped shape in which the cross-sectional area of the upper portion is smaller than that of the lower portion. The inner convex portion 24 may also be a steep truncated cone shape with a high aspect ratio.

The inner convex portions 24 may be arranged in a regular manner, such as on a triangular lattice, in a square lattice, or in a concentric circle, or may be arranged irregularly with localized variations in density. The height of the inner convex portions 24 is preferably 50 μm or more and 500 μm or less. The height of the inner convex portions 24 refers to the distance from the upper surface 12 of the base 10 to the upper end 24a of the inner convex portions. The distance between adjacent inner convex portions 24 is preferably 1.5 mm or more and 8 mm or less, in terms of the center-to-center distance.

The outer convex portion 26 is formed on the outside of the annular convex portion 22. The upper end 26a of the outer convex portion is located farther from the upper surface 12 of the base 10 than the upper end 22a of the annular convex portion. In other words, the height of the outer convex portion 26 is higher than the height of the annular convex portion 22. This creates a wall in the outer peripheral region of the base 10, restricting the inflow of air during the adsorption operation and suppressing the intrusion of particles. The height of the outer convex portion 26 refers to the distance from the upper surface 12 of the base 10 to the upper end 26a of the outer convex portion. The height of the outer convex portion 26 is preferably 50 μm or more and 1500 μm or less.

The upper end 26a of the outer convex portion may form the same surface as the reference surface 30. This makes it easier to form the outer convex portion. The upper end 26a of the outer convex portion may be located 1.0 mm farther from the upper surface 12 of the substrate 10 than the reference surface 30, or 0.77 mm farther. In other words, the difference between the height of the outer convex portion 26 and the height of the inner convex portion 24 is preferably 0.0 mm or more and 1.0 mm or less, and more preferably 0.0 mm or more and 0.77 mm or less. It is preferable that the surface formed by the upper end 26a of the outer convex portion is not higher than the upper surface of the substrate W to be adsorbed. If the surface formed by the upper end 26a of the outer convex portion is higher than the upper surface of the substrate W to be adsorbed, abnormal convection of the air flowing in is likely to occur on the inner side of the outer convex portion 26 and near the end of the substrate W when the substrate W is adsorbed, causing the end of the substrate W to be warped up or down, which may cause the flatness of the end of the substrate to deteriorate. Therefore, the height of the outer convex portion 26 may be determined according to the thickness of the substrate W to be adsorbed.

The outer convex portion 26 is formed in an annular, arc-shaped, or linear shape. Details of the shape of the outer convex portion 26 will be described later. The width of the outer convex portion 26 is preferably 0.2 mm or more and 2.0 mm or less. For ease of design, the width of the outer convex portion 26 may be the same as that of the annular convex portion 22, or may be different from that of the annular convex portion 22. In addition, the upper end 26a of the outer convex portion is preferably formed as a flat surface. In this case, the surface roughness of the flat surface (upper end surface) of the upper end 26a of the outer convex portion is preferably Ra 0.2 μm or less.

The outer convex portion 26 is preferably arranged at a position where the outer convex portion 26 exists on all straight lines passing through the center 16 of the base. Usually, the ventilation holes 14 are arranged in a balanced manner to uniformly adsorb the substrate W, and in that case, it can be assumed that the gas flowing into the interior beyond the annular convex portion 22 flows generally toward the center. Therefore, by arranging the outer convex portion 26 in this manner, the intrusion of particles when air flows in can be further suppressed. Note that the center 16 of the base is the center of the circle when the shape of the top surface of the base 10 is a circle, the center of the circle in which they are inscribed when the shape is a rectangle or regular polygon, and the midpoint of the major axis when the shape is an ellipse. Also, when the shape is a cut part of a circle, etc., the center of the base 10 is the center of the original shape.

The outer convex portion 26 is preferably formed in an annular shape. Formed in an annular shape means that the outer convex portion 26 forms a continuous circumference when viewed from above. This further enhances the effect of suppressing particle intrusion, since the outside of the annular convex portion 22 is entirely covered by the outer convex portion 26 formed in an annular shape. For example, when the base body 10 is formed in a disk shape, the outer convex portion 26 is preferably formed in a continuous annular shape when viewed from above, at a position a certain distance toward the center from the outer periphery of the upper surface of the base body 10.

The outer convex portion 26 is formed by a plurality of partial outer convex portions 28, and the plurality of partial outer convex portions 28 are preferably arranged in a ring shape. In this way, by arranging the partial outer convex portions 28 in a ring shape, the gaps between adjacent partial outer convex portions 28 become air inlets, and the amount of air flowing in from the outside increases, improving the ease of removal (dechucking) after substrate processing. The length along the center line of the upper end of the partial outer convex portion 28 is preferably three times or more the width. Each of the partial outer convex portions 28 is preferably formed in an arc shape or a line segment shape. The arrangement of the plurality of partial outer convex portions 28 in a ring shape refers to an arrangement in which the plurality of partial outer convex portions 28 form part of the circumference of a continuous ring-shaped convex portion. For example, the arrangement of the partial outer convex portions in the case where a continuous ring-shaped convex portion is separated into a plurality of partial outer convex portions by slits is included in the case of annular arrangement. In addition, an arrangement in which some or all of the plurality of partial outer convex portions are replaced with line-shaped partial outer convex portions having the same length is also included in the case of annular arrangement.

Figures 3 to 5 are schematic diagrams showing modified examples of the upper surface of the substrate holding member according to the embodiment of the present invention. In all of the modified examples shown in Figures 3 to 5, the outer convex portion 26 is formed by a plurality of partial outer convex portions 28. As shown in Figure 3, the annular outer convex portion 26 may be formed as a plurality of partial outer convex portions 28 by slits. In this way, when the partial outer convex portions 28 are arranged in a single ring, as the width and the total of the slits increase, the dechucking performance improves, but the effect of suppressing particle intrusion decreases, so it is preferable that the total width of the slits is 30% or less of the length of the outer convex portion 26 when a continuous annular outer convex portion 26 without slits is formed at the same position. In addition, when the annular outer convex portion 26 is formed as a plurality of partial outer convex portions 28 by slits, the slits are preferably evenly arranged over the entire outer convex portion 26 when a continuous annular outer convex portion 26 without slits is formed at the same position. The width of each slit is preferably 0.05 mm or more and 8 mm or less.

As shown in FIG. 4, the double annular outer convex portion 26 may be formed as a plurality of partial outer convex portions 28 by slits. In this case, it is preferable that the slits of the inner outer convex portion 26 and the slits of the outer outer convex portion 26 are arranged so as not to overlap. FIG. 4 shows an example of such an arrangement. Also, the example of FIG. 4 shows an example in which the outer convex portion 26 is arranged at a position where it exists on all straight lines passing through the center 16 of the base body. In this arrangement, even if the width and the total width of the slits are increased, the effect of suppressing particle intrusion is maintained, so it is preferable that the total width of the inner and outer slits is 50% or less of the length of each outer convex portion 26 when continuous annular outer convex portions 26 without slits are formed at the same position. This is because, when the partial outer convex portions 28 are arranged in a double annular shape, the risk of particle intrusion can be reduced and dechucking performance can be improved even if the total slit width is increased compared to the case of a single annular shape. Also, the outer convex portions 26 of three or more annular shapes may be formed as a plurality of partial outer convex portions 28 by slits.

As shown in FIG. 5, when the outer convex portion 26 is formed by a plurality of partial outer convex portions 28, each partial outer convex portion 28 may have a convex portion extending in the circumferential direction of the base body 10 inclined at a predetermined angle. By adopting such a configuration, in addition to the effect of improving the dechucking property, a flow path for free abrasive grains input from the outer periphery is secured during polishing of the surface of the inner convex portion 24, and polishing efficiency is improved. As shown in FIG. 5, the arrangement in which each partial outer convex portion 28 has a convex portion extending in the circumferential direction of the base body 10 inclined at a predetermined angle is also included in the case of being arranged in a ring shape. This is because the effect of the present invention can be obtained even with such an arrangement. The predetermined angle is preferably greater than 0° and less than or equal to 60°. Note that the example of FIG. 5 shows an example in which the outer convex portion 26 is arranged at a position where it exists on all straight lines passing through the center 16 of the base body, but such a characteristic does not have to be satisfied. In addition, when two or more outer convex portions 26 are formed concentrically, a hybrid structure may be formed in which a convex portion with a circumferentially extending slit is formed on the outside and a convex portion with a constant inclination is formed on the inside, or vice versa.

In this way, the outer convex portion 26 being annular, arc-shaped, or linear includes the case where the outer convex portion 26 is a continuous ring, and the case where the outer convex portion 26 is composed of multiple partial outer convex portions 28 formed in an arc-shaped or linear shape, and the partial outer convex portions 28 are arranged in a ring shape.

If the distance between the outer convex portion 26 closest to the annular convex portion 22 and the annular convex portion 22 is too close, the risk of the substrate W coming into contact with the outer convex portion 26 increases. Therefore, it is preferable that the shortest distance between a point on the circumference of the upper end 26a of the outer convex portion (the upper end point if the upper end is not a surface) and a point on the circumference of the upper end 22a of the annular convex portion (the upper end point if the upper end is not a surface) in a direction parallel to the reference plane 30 is 1 mm or more. In addition, since the outer convex portion 26 exerts an effect of suppressing particle intrusion from the lateral direction even if the distance from the annular convex portion 22 is large, there is no need to set an upper limit. However, considering ease of manufacture, etc., it is preferable that the shortest distance between the outer convex portion 26 closest to the annular convex portion 22 and the annular convex portion 22 in a direction parallel to the reference plane 30 between a point on the circumference of the upper end 26a of the outer convex portion and a point on the circumference of the upper end 22a of the annular convex portion is 15 mm or less.

Note that the substrate holding member 10 shown in Figures 1 to 5 does not include lift pin holes or surrounding protrusions.

[Method of manufacturing the substrate holding member]
A plate-shaped compact is made from raw material powder by a well-known method, and this compact is fired to obtain a plate-shaped ceramic sintered body. Although a disk-shaped substrate holder is shown in Fig. 1, any shape such as a polygonal shape or an elliptical shape may be used. Silicon carbide, aluminum oxide, aluminum nitride, etc. are used as the ceramic sintered body.

Next, vent holes, annular convex portions, inner convex portions, outer convex portions, etc. are formed on the surface that will become the upper surface of the ceramic sintered body. Forming methods that can be used include blasting, milling, laser processing, etc. After forming multiple convex portions, the upper end surface of each convex portion may be polished, etc.

The upper ends of the multiple inner convex portions are formed to be approximately flush with each other, with their upper ends located farther from the top surface of the base than the upper end of the annular convex portion. The upper ends of the outer convex portions are formed to be farther from the top surface of the base than the upper end of the annular convex portion.

The annular convex portion is formed in a ring shape along the outer periphery of the upper surface of the base. The amount by which the annular convex portion protrudes from the upper surface of the base is preferably determined according to the amount by which the inner convex portion protrudes from the upper surface of the base. For example, it is preferably formed to be 1 μm or more and 5 μm or less lower than the height of the inner convex portion. The width of the annular convex portion is preferably formed in the range of 0.05 mm or more and 8 mm or less.

The inner convex portions are formed in multiple numbers inside the annular convex portion. The arrangement, shape, protruding height, etc. of the inner convex portions are not particularly limited. They may be in a known form or a form similar thereto. For example, the arrangement may be a regular arrangement such as a triangular lattice, a square lattice, or a concentric circle, or may be an irregular arrangement with localized sparseness and density. The shape may be a columnar or cone shape, and may further be a stepped shape in which the cross-sectional area of the upper part is smaller than that of the lower part. In addition, it is preferable to design the inner convex portions according to the conditions of the substrate to be adsorbed, for example, with a protrusion amount of 50 μm to 500 μm, a convex portion diameter of 100 μm to 2 mm, and a convex portion interval of 1.5 mm to 8 mm.

The outer convex portion is formed on the outside of the annular convex portion. Depending on the design, the outer convex portion may be formed as a continuous annular convex portion or as a collection of partial outer convex portions. It is preferable to design the outer convex portion according to the conditions of the substrate to be adsorbed, for example, within the range of 50 μm to 1500 μm protruding from the upper surface of the base and 0.2 mm to 2.0 mm wide.

In this manner, the substrate holding member of the present invention can be manufactured.

[Examples and Comparative Examples]
Example 1
Example 1 is a substrate holding member in which an outer convex portion is formed in a circular ring shape as shown in FIG. 1. A substantially disk-shaped base body made of sintered silicon carbide with a diameter of φ310 mm and a thickness of t1.5 mm was prepared, and an air passage, a plurality of inner convex portions, an annular convex portion, and an outer convex portion were formed by blast processing. The plurality of inner convex portions were formed so as to have a height of 150 μm, a diameter of φ300 μm at the upper end surface of the convex portion, and a triangular lattice shape with a center-to-center distance of 3 mm between each convex portion. Subsequently, lapping was performed using free abrasive grains, and finishing processing was performed so that the surface roughness Ra of the plurality of inner convex portions was 0.03 μm.

The annular convex portion was formed with an outermost diameter of φ296 mm and a width of 0.5 mm, and was formed by additional processing so that it was 3 μm lower than the multiple inner convex portions. The outer convex portion was formed in a ring shape with an outermost diameter of φ305 mm and a width of 0.5 mm, and a substrate holding member was produced with the same height as the multiple inner convex portions. The shortest distance in the direction parallel to the reference plane between a point on the circumference of the upper end of the annular convex portion and a point on the circumference of the upper end of the outer convex portion was 4 mm.

Example 2
Example 2 is a substrate holding member in which the outer convex portion is formed in an annular shape and divided into a plurality of partial outer convex portions by slits, as shown in Fig. 3. A substrate holding member having the same configuration as Example 1 was produced, except that a plurality of slits were formed to divide the outer convex portion of Example 1 at predetermined intervals.

In Example 1, 64 slits of approximately 3 mm each were formed at equal intervals in a circumferential length of approximately 960 mm in the outer convex portion. The total width of the slits relative to the entire circumference of the annular outer convex portion before the slits were formed was approximately 20%. The shortest distance in a direction parallel to the reference plane between a point on the circumference of the upper end of the annular convex portion and a point on the circumference of the upper end of the outer convex portion was 4 mm. Note that FIG. 3 only shows a schematic view of the shape of Example 2, and the details of the shape, such as the width and number of slits, are different.

Example 3
Example 3 is a substrate holding member in which the outer convex portion is formed in a double ring shape, and each outer convex portion is divided into a plurality of partial outer convex portions by slits, as shown in Fig. 4. The outer convex portions are formed with outermost diameters of φ305 mm and φ308 mm, and widths of 0.5 mm, respectively, and a plurality of slits are formed dividing the outer convex portion at a predetermined interval. A substrate holding member having the same configuration as Example 1 was produced. Note that in this case, the inner slit and the outer slit were formed at positions that did not overlap in adjacent concentric circles.

The outer convex portion with an outermost diameter of φ305 mm had 64 equally spaced slits of about 3 mm in the outer convex portion of about 960 mm, as in Example 2. The total width of the slits relative to the entire circumference of the annular outer convex portion before the slits were formed was about 20%. The outer convex portion with an outermost diameter of φ308 mm had 64 equally spaced slits of about 3 mm in the outer convex portion of about 968 mm. The total width of the slits relative to the entire circumference of the annular outer convex portion before the slits were formed was about 19.8%. The shortest distance between the circumferential point of the upper end of the inner outer convex portion and the circumferential point of the upper end of the outer outer convex portion in the direction parallel to the reference plane was 1 mm. Note that FIG. 4 only shows a schematic view of the shape of Example 3, and the details of the shape, such as the width and number of slits, are different.

(Comparative Example 1)
In Comparative Example 1, a substrate holding member was produced that had the same structure as in Example 1, except that no outer convex portion was formed.

(Comparative Example 2)
In Comparative Example 2, a substrate holding member was produced that had the same configuration as in Example 1, except that the height of the outer convex portion was 100 μm (47 μm lower than the annular convex portion).

(Evaluation Method)
A substrate with a diameter of 300 mm and a thickness of 0.7 mm was adsorbed on the obtained substrate holding member, and the flatness of the substrate was measured. The measurement was performed by dividing the entire upper surface of the held substrate into squares with sides of 20 mm using a non-contact laser interferometer, measuring the PV values of all the areas within the squares with sides of 20 mm, and taking the maximum value of these PV values as the local flatness (LF) of the substrate holding member. The evaluation was performed as follows: if LF was 0.1 μm or less, it was judged to have particularly good flatness; if LF was greater than 0.1 μm and less than 0.3 μm, it was judged to have good flatness; and if LF was greater than 0.3 μm, it was judged to have poor flatness.

In Examples 1 and 3, LF was 0.1 μm or less, and particularly good flatness was obtained. In Example 2, LF did not reach 0.1 μm or less, but was kept at 0.3 μm or less, and good flatness was obtained.

In Comparative Example 1 and Comparative Example 2, there were some areas in the outer periphery of the substrate where the LF exceeded 0.3 μm. In Comparative Example 1, this is presumably due to the fact that the second annular convex portion was not formed. In Comparative Example 2, the height of the outer convex portion was lower than the height of the annular convex portion, and therefore it is presumed that the effect of suppressing the intrusion of particles from the outside was not obtained.

From the above, it has been confirmed that the substrate holding member of the present invention can reduce the contact area between the substrate and the base while suppressing the intrusion of particles from the outside.

The present invention is not limited to the above-described embodiment, and it goes without saying that it covers various modifications and equivalents that fall within the spirit and scope of the present invention. Furthermore, the structure, shape, number, position, size, etc. of the components shown in each drawing are for convenience of explanation and may be changed as appropriate.

REFERENCE SIGNS LIST 10 Base body 12 Upper surface 14 Vent 16 Center of base body 20 Convex portion 22 Annular convex portion 22a Upper end of annular convex portion 24 Inner convex portion 24a Upper end of inner convex portion 26 Outer convex portion 26a Upper end of outer convex portion 28 Partial outer convex portion 30 Reference surface 100 Substrate holding member W Substrate

Claims (3)

A substrate holding member,
A flat plate-like base having one or more ventilation holes opening on an upper surface thereof;
a plurality of protrusions formed to protrude upward from the upper surface of the base,
The protrusion is
an annular protrusion formed annularly along the outer periphery of the upper surface of the base;
a plurality of inner convex portions formed inside the annular convex portion and having upper ends at positions farther from the upper surface of the base than the upper end of the annular convex portion;
an outer convex portion having an annular, arc-shaped or linear shape, the outer convex portion being formed outside the substrate and outside the annular convex portion when the substrate is held on the base, and having an upper end at a position farther from the upper surface of the base than an upper end of the annular convex portion ;
The outer convex portion is formed by a plurality of partial outer convex portions,
A substrate holding member , wherein the plurality of partial outer convex portions are arranged in an annular shape . The substrate holding member according to claim 1, characterized in that the outer convex portion is arranged at a position where the outer convex portion exists on all straight lines passing through the center of the substrate. The substrate holding member according to claim 2, characterized in that the outer convex portion is formed in a circular ring shape.