electrostatic chuck

Abstract

To provide an electrostatic chuck capable of removing the quantity of heat entering a substrate in an early stage, coping with higher power of a conductor process, and suppressing dechucking properties from becoming worse.SOLUTION: The present invention relates to an electrostatic chuck 100, which comprises a base body 110 made of a ceramic sintered compact, an electrode 120 for electrostatic attraction embedded in the base body 110, and a plurality of gas introduction holes 118 open in a top surface 112 of the base body 110, wherein the base body 110 has a surface 130 of 30 to 99.5% in rate of contact with a mounted substrate, the surface 130 has a surface roughness Ra of 0.2 μm or less, and skewness Rsk found from a roughness curve of the surface 130 is minus.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electrostatic chuck.

Background Art

[0002] In a film forming apparatus such as plasma CVD for forming a thin film by installing a substrate (wafer) in a vacuum chamber, supplying a raw material gas onto the substrate, and plasmaizing the raw material gas by a high-frequency current (RF) or the like, and depositing a substance generated by a chemical reaction on the substrate, or in an etching apparatus such as plasma etching for scraping using plasma to form grooves, patterns, etc. on the surface of the substrate, an electrostatic chuck is used as a means for holding the substrate.

[0003] In the plasma treatment process as described above, the temperature of the substrate also rises due to the generated heat. At that time, various methods are taken to adjust the temperature of the substrate so that it becomes a temperature suitable for each treatment temperature. For example, it is joined to a base member formed of a metal such as aluminum having a flow path for circulating a medium such as cooling water on the surface facing the substrate holding surface of the electrostatic chuck, or a heat transfer structure for introducing an inert gas such as He into the space between the back surface of the substrate and the substrate holding surface of the electrostatic chuck is provided to keep the temperature of the substrate constant.

[0004] In recent years, due to the progress of manufacturing process technology, the power density of plasma has increased, and accordingly, the amount of incident heat on the substrate has also increased. Since an increase in the amount of incident heat on the substrate may cause the substrate temperature to rise excessively and affect the manufacturing process of each step such as causing problems in the pattern formation process, it is necessary to enhance the cooling performance of the substrate more than ever. In addition, it is necessary to adjust the temperature of the substrate to an appropriate temperature at an early stage in order to improve the manufacturing yield. For example, although the appropriate process treatment temperature varies depending on the manufacturing process, it is necessary to control it to about 100°C to 400°C (up to about 200°C for an aluminum base).

[0005] Patent Document 1 discloses a substrate cooling device having a substrate contact plate having a protruding portion provided in the peripheral part, a recess that forms a cavity, a central part having a plurality of protrusions, each of which terminates at the contact surface and the surface of the protruding portion provided in the peripheral part and the respective contact surface are provided on the same plane, and at least one gas inlet groove for supplying gas into the cavity, and a cooling plate that is thermally connected to the substrate contact plate and has grooves for passing a cooling liquid.

[0006] Furthermore, Patent Document 2 discloses an electrostatic chuck in which the gas groove of the electrostatic chuck is composed of a plurality of radial grooves arranged at equal intervals, a plurality of annular grooves arranged concentrically and communicating with the radial grooves, and at least one radially extending partition groove that divides each mounting surface surrounded by two adjacent annular grooves and two adjacent radial grooves into two or more sections in the region from the first annular groove from the center, such that the mounting surface surrounded by two adjacent annular grooves and two adjacent radial grooves, the mounting surface surrounded by two adjacent annular grooves, radial grooves and partition grooves, and the mounting surface surrounded by two adjacent annular grooves and two adjacent partition grooves each have approximately equal areas. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 9-232415 [Patent Document 2] Japanese Patent Publication No. 2002-170868 [Overview of the project] [Problems that the invention aims to solve]

[0008] The multiple protrusions described in Patent Document 1 have a roughened contact surface with the substrate with a Ra of approximately 0.35 μm to 3.0 μm, and the contact rate between the substrate and the multiple protrusions is approximately 2 to 20%. The main part of the cooling means described in Patent Document 1 is heat transfer between the substrate and the gas in the cavity, but the contact rate was low and the gas pressure was also low (less than 20 Torr). Therefore, the substrate cooling device of Patent Document 1 was likely to be insufficient for transferring a large amount of heat quickly.

[0009] In the technology described in Patent Document 2, heat transfer gas is introduced from a gas inlet formed only in the center of the substrate, flows radially through radial grooves, and then flows while merging with annular grooves. Because the gas flow path described in Patent Document 2 is complex, there was a risk that it would be insufficient for uniformizing the temperature of the entire substrate or transferring a larger amount of heat due to the non-uniformity of the heat transfer gas flow at the branching points of the flow path and the time lag in the gas flow from the center of the substrate to the outer diameter. In addition, the pressure of the helium gas introduced from the gas inlet was low (approximately 10 Torr).

[0010] This invention has been made in view of these circumstances, and aims to provide an electrostatic chuck that can quickly remove the heat input to the substrate, can handle the increasing power of semiconductor processes, and can suppress deterioration of decuckability. [Means for solving the problem]

[0011] (1) In order to achieve the above objectives, the present invention employs the following means. Specifically, an electrostatic chuck in an application example of the present invention is an electrostatic chuck comprising a substrate made of a ceramic sintered body, an electrostatic adsorption electrode embedded in the substrate, and a plurality of gas introduction holes opening on the upper surface of the substrate, wherein the substrate has a surface with a contact rate of 30% to 99.5% with respect to the substrate on which it is placed, a surface roughness Ra of the surface of 0.2 μm or less, and a negative skewness Rsk obtained from the surface roughness curve.

[0012] In this way, by increasing the contact rate with the substrate and ensuring the surface condition of the surface in contact with the substrate is within the above range, the contact condition between the substrate and the substrate surface is improved, allowing the heat input to the substrate to be removed quickly, thus enabling it to handle the increasing power of semiconductor processes. Furthermore, it is possible to improve heat transfer from the substrate to the electrostatic chuck while suppressing deterioration of de-chuck performance.

[0013] (2) Furthermore, the electrostatic chuck in the application example of (1) above is characterized in that the skewness Rsk is less than -1.0.

[0014] This allows for better suppression of deterioration in de-chuck performance while maintaining heat transfer from the substrate to the electrostatic chuck.

[0015] (3) Furthermore, the electrostatic chuck of the application example of (1) or (2) above is characterized by comprising a base member having a gas flow path that is joined to the lower surface of the substrate opposite to the upper surface and connected to the gas introduction hole.

[0016] This allows heat to be conducted from the substrate to the base component, and heat transfer from the substrate to the substrate can be performed more efficiently.

[0017] (4) Furthermore, in an electrostatic chuck according to any of the application examples (1) to (3) above, the chuck comprises a plurality of pin-shaped protrusions formed projecting upward from the upper surface of the base body, and an annular protrusion formed projecting upward from the upper surface of the base body so as to surround the plurality of pin-shaped protrusions, wherein the surface is composed of the upper end faces of the pin-shaped protrusions and the upper end faces of the annular protrusions.

[0018] This allows the substrate to be uniformly adsorbed even if it is warped or undulating, and the incident heat to the substrate can be uniformly transferred through heat conduction by contact with the pin-shaped protrusions and heat transfer effect by the gas.

[0019] (5) Further, in the electrostatic chuck of any one of the application examples (1) to (3) above, a plurality of island-shaped convex portions formed to protrude upward from the upper surface of the substrate, and an annular convex portion formed to protrude upward from the upper surface of the substrate so as to surround the plurality of island-shaped convex portions, and the surface is composed of the upper end surfaces of the island-shaped convex portions and the upper end surface of the annular convex portion.

[0020] Thereby, even when the substrate has warpage or undulation, the substrate can be evenly adsorbed, and the incident heat to the substrate can be evenly heat-transferred by the heat conduction due to the contact with the island-shaped convex portions and the heat transfer effect by gas.

[0021] (6) Further, in the electrostatic chuck of the application example (4) above, the height of the pin-shaped convex portion is 5 μm or more and 10 μm or less.

[0022] Thereby, the electrostatic adsorption force in the non-contact surface portion that does not contact the substrate can be increased, and the adsorption force of the entire substrate can be improved. Also, the gas can be quickly filled in the space.

[0023] (7) Further, in the electrostatic chuck of the application example (5) above, the height of the island-shaped convex portion is 25 μm or more and 1000 μm or less.

[0024] Thereby, the amount of gas introduced into the space can be increased, and the heat transfer effect by gas can be enhanced.

Advantages of the Invention

[0025] According to the electrostatic chuck of the present invention, the contact state between the substrate and the surface of the substrate becomes good, the amount of heat input to the substrate can be quickly removed, and it can cope with the high power of the semiconductor process. Also, while improving the heat transfer from the substrate to the electrostatic chuck, the deterioration of the de-chucking property can be suppressed.

Brief Description of the Drawings

[0027] Next, embodiments of the present invention will be described with reference to the drawings. To facilitate understanding of the explanation, the same reference numeral is used for identical components in each drawing, and redundant explanations are omitted. Note that the sizes of each component in the configuration diagrams are conceptual representations and do not necessarily represent actual dimensional ratios.

[0028] [Embodiment] (Configuration of an electrostatic chuck) An electrostatic chuck according to an embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a schematic cross-sectional view showing an example of an electrostatic chuck according to an embodiment of the present invention. Figure 2 is a schematic diagram showing an example of the top surface of an electrostatic chuck according to an embodiment of the present invention. Figure 1 shows a cross-section along line AA in Figure 2. The electrostatic chuck 100 according to an embodiment of the present invention comprises a substrate 110 and at least one electrostatic adsorption electrode 120.

[0029] The base body 110 is made of a ceramic sintered body. The base body 110 may be in various shapes, such as a roughly circular disc, a polygonal plate, or an elliptical plate. The base body 110 is flat except for any protrusions formed on the upper surface 112. Aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, etc. can be used as the material for the ceramic sintered body.

[0030] The substrate 110 is provided with a plurality of gas introduction holes 118 opening on the upper surface 112 of the substrate 110. It is preferable that the gas introduction holes 118 be formed in multiple locations in order to introduce heat transfer gas to the back surface of the substrate W at a uniform and high pressure. For example, it is preferable to have a gas introduction hole diameter of 0.05 mm to 3 mm, with one hole positioned at the center 116 of the substrate 110, and to assume one or more concentric circles increasing radially at equal intervals from this center, with multiple holes arranged at equal intervals in this concentric pattern. Alternatively, multiple holes may be arranged regularly at predetermined intervals in a triangular or square shape. To obtain uniform heat transfer, it is preferable to maintain as much symmetry as possible in the arrangement of the gas introduction holes 118.

[0031] However, due to the arrangement of lift pin holes and protrusions, it is not necessary for all gas inlet holes 118 to be in a regular arrangement. Also, when the surface 130 is composed of the upper end surfaces of pin-shaped protrusions or island-shaped protrusions described later, it is preferable to arrange the gas inlet holes 118 in a manner that is as symmetrical as possible, in accordance with the shape of the recesses and grooves.

[0032] The substrate 110 has a surface 130 on which it has a contact rate of 30% to 99.5% with respect to the substrate W on which it is placed. The surface 130 of the substrate 110 refers to the surface that actually contacts the substrate W. By setting the contact rate between the surface 130 of the substrate 110 that actually contacts the substrate W and the substrate W to 30% to 99.5%, thermal conductivity is improved, and heat transfer from the substrate W to the substrate 110 can be performed efficiently, thus improving heat transfer performance. As a result, the contact state between the substrate W and the surface 130 of the substrate 110 is good, the amount of heat that has entered the substrate W can be removed quickly, and it is possible to respond to the increasing power of semiconductor processes.

[0033] The contact rate can be calculated as (surface area of ​​the substrate) / (area of ​​the substrate to be adsorbed) × 100 (%). The area of ​​the surface 130 of the substrate 110 can be calculated by subtracting the area of ​​holes that do not come into contact with the substrate W, such as gas introduction holes 118 and lift pin holes, from the area of ​​the top surface 112 of the substrate 110. If the substrate 110 is located outside the outer periphery of the substrate W, i.e., if the substrate 110 is larger than the substrate W, the area of ​​the top surface 112 of the substrate 110 used to calculate the area of ​​the surface 130 of the substrate 110 shall exclude the top surface 112 of the substrate 110 that is located outside the outer periphery of the substrate W. The area of ​​the surface 130 of the substrate 110 may also be measured using a laser interferometer. The area of ​​the substrate W to be adsorbed shall be a substrate that meets the standards of SEMI (Semiconductor Equipment and Materials International). For example, the area of ​​a substrate W with a diameter Φ of 300 mm can be used as a reference.

[0034] The surface roughness (centerline average roughness) Ra of surface 130 is 0.2 μm or less. By making the surface roughness Ra of surface 130 close to a mirror finish of 0.2 μm or less, the contact condition with the substrate W is improved and the adsorption force is increased. As a result, a heat transfer gas such as He gas at a higher pressure can be introduced from the multiple gas introduction holes 118, improving the heat transfer performance of the substrate W by gas heat transfer. In addition, the improved adsorption force can suppress the unexpected detachment of the substrate W from the electrostatic chuck 100 under high gas pressure. For example, even under a pressure of 100 Torr, the detachment of the substrate W from the base body 110 can be suppressed, and the heat of the substrate W can be cooled quickly. The lower limit of the surface roughness Ra of surface 130 does not need to be particularly limited, but it is preferable to be 0.01 μm or more considering the processing time, etc.

[0035] The skewness Rsk, determined from the roughness curve of surface 130, is negative. By increasing the contact rate with the substrate W and making the skewness Rsk determined from the roughness curve of surface 130 negative, it is possible to improve heat transfer from the substrate W to the base body 110 while suppressing deterioration of the dechuckability of the substrate W. It is preferable that the skewness Rsk is less than -1.0. By making the skewness Rsk less than -1.0, it is possible to further suppress deterioration of dechuckability while maintaining heat transfer from the substrate to the electrostatic chuck.

[0036] Skewness Rsk is an index that indicates the symmetry of the height distribution. It represents the ratio of peaks to valleys relative to the average height of the roughness curve, with the average height being the center line, and is defined in JIS B 0601. A negative skewness Rsk indicates a surface condition with many fine valleys. When skewness Rsk is negative, heat transfer gases can enter through these valleys, resulting in better gas heat transfer. It also helps to prevent the adsorption force from becoming too large due to improved contact coefficient, which can worsen dechuck properties. There is no particular lower limit to the skewness Rsk, but for example, it is preferable to have a value of -5.0 or higher.

[0037] Surface roughness Ra and skewness Rsk can be measured using a commercially available non-contact surface roughness meter in accordance with JIS B 0601. A method to bring skewness Rsk and surface roughness Ra within the scope of the present invention involves manufacturing a ceramic sintered body (substrate 110) using a known manufacturing method, followed by sandblasting and grinding with a coarse-mesh (small particle size) grinding wheel, and then polishing the top surface. A method to make skewness Rsk less than 0 (i.e., negative) can be, for example, as follows: After shaping the substrate 110, the surface that will become surface 130 is ground with a grinding wheel of a grit higher than #170. Then, polishing is performed using free abrasive particles (diamond slurry) with a particle size greater than 3 μm, and finally, finish polishing is performed using small free abrasive particles with a particle size of 3 μm or less. The polishing is performed for a total of 3 hours or more. Furthermore, by shortening the finish polishing time, skewness Rsk can be reduced to less than -1.0.

[0038] From the viewpoint of suppressing grain shedding in the valleys of the surface 130 and ensuring adsorption capacity, it is preferable that the maximum valley depth Rv in the standard length of the surface 130 be designed to be between 2 μm and 8 μm. The maximum valley depth Rv can also be measured by a measurement method compliant with JIS B 0601.

[0039] The electrostatic adsorption electrode 120 is embedded in the substrate 110. The electrostatic adsorption electrode 120 is embedded in a shape that matches the design of the electrostatic chuck 100. Preferably, the electrostatic adsorption electrode 120 is made of W, Mo, or an alloy mainly composed of these.

[0040] The substrate 110 may have electrodes other than the electrostatic adsorption electrode 120 embedded in it. For example, by embedding both the electrostatic adsorption electrode 120 and a heater electrode in the substrate 110, the substrate can exhibit electrostatic adsorption, temperature control, and heating functions, thereby making the semiconductor manufacturing process more functional.

[0041] Figure 3 is a schematic cross-sectional view showing a modified example of the electrostatic chuck 100 according to an embodiment of the present invention. Figure 4 is a schematic diagram showing a modified example of the upper surface of the electrostatic chuck 100 according to an embodiment of the present invention. Figure 3 shows a cross-section along the line BB in Figure 4. As shown in Figure 3 or Figure 4, the electrostatic chuck 100 preferably comprises a plurality of pin-shaped protrusions 140 and an annular protrusion 150. In this case, the surface 130 is composed of the upper end surfaces 142 of the pin-shaped protrusions and the upper end surfaces 152 of the annular protrusions.

[0042] When pin-shaped protrusions 140 are formed on the base body 110, multiple pin-shaped protrusions 140 are formed, projecting upward from the upper surface 112 of the base body 110. The pin-shaped protrusions 140 are formed surrounded by recesses 144. That is, the bottom surface of the recesses 144 becomes the upper surface 112 of the base body 110. The shape of the pin-shaped protrusions 140 can be appropriately selected from shapes such as cylindrical, prismatic, conical, pyramidal, or truncated cone or truncated pyramidal shapes with the upper part of the cone cut off.

[0043] The arrangement of the pin-shaped protrusions 140 is not particularly limited. Any known or similar form is acceptable. For example, in addition to the triangular lattice shape shown in Figure 4, it is preferable to arrange them regularly in a concentric circle or square lattice shape. The distance (pitch) between the centers of adjacent pin-shaped protrusions 140 is preferably 4 mm or more and 20 mm or less. The maximum diameter of the upper end surface 142 of the pin-shaped protrusion is preferably 0.1 mm or more and 5 mm or less. The surface roughness Ra of the upper end surface 142 of the pin-shaped protrusion is preferably 0.2 μm or less. The surface roughness Ra of the upper end surface 142 of the pin-shaped protrusion is preferably 0.01 μm or more.

[0044] The height of the pin-shaped protrusion 140 is preferably 5 μm or more and 10 μm or less. This allows for increased electrostatic adsorption force in the non-contact surface portion that does not come into contact with the substrate W, thereby improving the overall adsorption force of the substrate W. It also allows for faster filling of the space with gas. Pin-shaped protrusions 140 with a height of less than 5 μm are difficult to form. Furthermore, if the height of the pin-shaped protrusion 140 exceeds 10 μm, an excessive voltage is required to obtain sufficient adsorption force, which is industrially undesirable. The height of the pin-shaped protrusion 140 is defined as the distance between the upper surface 112 of the base body 110 and the upper end surface 142 of the pin-shaped protrusion.

[0045] When pin-shaped protrusions 140 are formed on the base body 110, an annular protrusion 150 is formed. The annular protrusion 150 is formed to protrude upward from the upper surface 112 of the base body 110 so as to surround the multiple pin-shaped protrusions 140. The outer diameter of the annular protrusion 150 is set to be the same as or smaller than the outer diameter of the base body 110. The width of the annular protrusion 150 is preferably 0.3 mm or more and 5 mm or less in order to function as a sealing part. In addition, as a countermeasure against gas leakage due to high gas pressure, the annular protrusion 150 may be formed in multiple layers (for example, double).

[0046] The height of the annular protrusion 150 is preferably the same as the height of the multiple pin-shaped protrusions 140. This allows for gas sealing. However, if the amount of gas escaping from the gap between the upper end surface 152 of the annular protrusion and the substrate W does not affect heat transfer by the gas, the height of the annular protrusion 150 may be lower than the height of the pin-shaped protrusions 140. Specifically, a height of about 1 μm to 3 μm lower is acceptable. The height of the annular protrusion 150 is the distance between the upper surface 112 (bottom surface of the recess) of the base body 110 and the upper end surface 152 of the annular protrusion. The surface roughness Ra of the upper end surface 152 of the annular protrusion is 0.2 μm or less. Preferably, the surface roughness Ra of the upper end surface 152 of the annular protrusion is 0.01 μm or more.

[0047] The upper end surfaces 142 of the multiple pin-shaped protrusions and the upper end surface 152 of the annular protrusion define a predetermined shape of plane or curved surface (substrate mounting surface 132) on which the substrate W is placed. In this way, the multiple pin-shaped protrusions 140 and the annular protrusions 150 support the substrate W. In other words, in this modified example, the upper end surfaces 142 of the pin-shaped protrusions and the upper end surfaces 152 of the annular protrusions that actually contact the substrate W are the surface 130 of the substrate mounting surface 132. Note that some of the multiple pin-shaped protrusions 140 may have upper end surfaces that do not contact the substrate W. This is because even if such pin-shaped protrusions 140 are present, the substrate W can still be supported depending on the arrangement of the surrounding pin-shaped protrusions 140. In Figure 3, the entire upper end surface 142 of the pin-shaped protrusion and the upper end surface 152 of the annular protrusion are in contact with the substrate W. However, only a portion of the upper end surface 142 of the pin-shaped protrusion or the upper end surface 152 of the annular protrusion may be in contact with the substrate W. In such a case, the area of ​​the surface 130 is the area of ​​the upper end surface 142 of the pin-shaped protrusion and the upper end surface 152 of the annular protrusion that actually contacts the substrate W.

[0048] Figure 5 is a schematic cross-sectional view showing a modified example of the electrostatic chuck 100 according to an embodiment of the present invention. Figure 6 is a schematic diagram showing a modified example of the upper surface of the electrostatic chuck according to an embodiment of the present invention. Figure 5 shows a cross-section along the CC line in Figure 6. As shown in Figure 5 or Figure 6, the electrostatic chuck 100 preferably comprises an island-shaped projection 160 and an annular projection 150. In this case, the surface 130 is composed of the upper end surface 162 of the island-shaped projection and the upper end surface 152 of the annular projection.

[0049] When island-shaped protrusions 160 are formed on the base body 110, multiple island-shaped protrusions 160 are formed, projecting upward from the upper surface 112 of the base body 110. The island-shaped protrusions 160 are formed surrounded by grooves 164. That is, the bottom surface of the grooves 164 becomes the upper surface 112 of the base body 110. The shape and arrangement of the island-shaped protrusions 160 are not particularly limited. The shape of the grooves 164 is preferably linear, combining straight lines and arcs, or broad, without any parts that narrow abruptly, in order to quickly distribute the heat transfer gas within the grooves 164. When the grooves 164 are formed linearly, for example, they can be grid-like grooves made by combining straight grooves, radial grooves passing through the center, or donut-shaped grooves made by combining annular grooves. Alternatively, a combination of these shapes is also acceptable. When the grooves 164 are formed linearly, the width of the grooves 164 is preferably 0.5 mm or more and 5.0 mm or less. A gas introduction hole 118 may be formed on the upper end surface 162 of the island-shaped protrusion.

[0050] In this specification, a protrusion whose upper end surface has an area less than or equal to the area of ​​a circle with a diameter of 5000 μm is referred to as a pin-shaped protrusion 140, and a protrusion whose upper end surface has an area greater than the area of ​​a circle with a diameter of 5000 μm is referred to as an island-shaped protrusion 160. It is preferable that the area of ​​each island-shaped protrusion 160 be approximately the same for the purpose of uniformizing the amount of heat transferred. The surface roughness Ra of the upper end surface 162 of the island-shaped protrusion is 0.2 μm or less. It is preferable that the surface roughness Ra of the upper end surface 162 of the island-shaped protrusion is 0.01 μm or more.

[0051] The height of the island-shaped protrusions 160 is preferably 25 μm or more and 1000 μm or less. In the case of island-shaped protrusions 160, the flow path for the heat transfer gas becomes the groove 164, so the volume is smaller compared to the recess 144 of the pin-shaped protrusions 140. Therefore, by increasing the height of the island-shaped protrusions 160, that is, by deepening the groove 164, the amount of gas introduced into the space can be increased, and the incident heat to the substrate W can be uniformly transferred by the solid heat transfer and gas heat transfer effects. To ensure electrostatic adsorption force, a multi-layer configuration may be used in which electrostatic adsorption electrodes 120 are also placed inside the island-shaped protrusions 160.

[0052] When island-shaped protrusions 160 are formed on the base body 110, an annular protrusion 150 is formed. The annular protrusion 150 is formed to protrude upward from the upper surface 112 of the base body 110 so as to surround the multiple island-shaped protrusions 160. The outer diameter of the annular protrusion 150 is set to be the same as or smaller than the outer diameter of the base body 110. The width of the annular protrusion 150 is preferably 0.3 mm or more and 5 mm or less in order to function as a sealing part. In addition, as a countermeasure against gas leakage due to high gas pressure, the annular protrusion 150 may be formed in multiple layers (for example, double).

[0053] The height of the annular protrusion 150 is preferably the same as the height of the multiple island-shaped protrusions 160. This allows for gas sealing. However, if the amount of gas escaping from the gap between the upper end surface 152 of the annular protrusion and the substrate W does not affect heat transfer by the gas, the height of the annular protrusion 150 may be lower than the height of the island-shaped protrusions 160. Specifically, a height of about 1 μm to 3 μm lower is acceptable. The height of the annular protrusion 150 is the distance between the upper surface 112 of the base body 110 (the bottom surface of the groove 164) and the upper end surface 152 of the annular protrusion. The surface roughness Ra of the upper end surface 152 of the annular protrusion is 0.2 μm or less. Preferably, the surface roughness Ra of the upper end surface 152 of the annular protrusion is 0.01 μm or more.

[0054] The upper end surfaces 162 of the multiple island-shaped protrusions and the upper end surface 152 of the annular protrusions define a predetermined shape of plane or curved surface (substrate mounting surface 132) on which the substrate W is placed. As a result, the multiple island-shaped protrusions 160 and the annular protrusions 150 support the substrate W. In other words, in this modified example, the upper end surfaces 162 of the island-shaped protrusions and the upper end surfaces 152 of the annular protrusions that actually contact the substrate W are the surface 130 of the substrate mounting surface 132. Note that in Figure 5, the entire upper end surfaces 162 of the island-shaped protrusions and the upper end surfaces 152 of the annular protrusions are in contact with the substrate W, but only a part of the upper end surface 162 of the island-shaped protrusions or the upper end surface 152 of the annular protrusions may be in contact with the substrate W. In such a case, the area of ​​the surface 130 is the area of ​​the upper end surfaces 162 of the island-shaped protrusions and the upper end surfaces 152 of the annular protrusions that actually contact the substrate W. In a modified example in which a pin-shaped protrusion 140 or an island-shaped protrusion 160 is formed, the area of ​​the surface 130 can be calculated by subtracting the area of ​​the gas introduction hole 118 and lift pin hole located inside the substrate W, the recess 144 that forms the pin-shaped protrusion 140 or annular protrusion 150, and the groove 164 that forms the island-shaped protrusion 160 or annular protrusion 150 from the area of ​​the substrate W.

[0055] The height of the pin-shaped protrusion 140, the island-shaped protrusion 160, or the annular protrusion 150, and the three-dimensional position of the upper end surface 142 of the pin-shaped protrusion, the upper end surface 162 of the island-shaped protrusion, or the upper end surface 152 of the annular protrusion can be measured using a three-dimensional measuring instrument or a laser interferometer.

[0056] The base body 110 may have both pin-shaped protrusions 140 and island-shaped protrusions 160. This improves the suction force in the areas where the island-shaped protrusions 160 are formed, while reducing the risk of particle trapping in the areas where the pin-shaped protrusions 140 are formed, allowing for appropriate adsorption of a warped substrate W according to its warp. When the base body 110 has both pin-shaped protrusions 140 and island-shaped protrusions 160, the depths of the recesses 144 and grooves 164 may differ; that is, the upper surface 112 of the base body 110 may vary depending on its position.

[0057] Figure 7 is a schematic cross-sectional view showing a modified example of the electrostatic chuck 100 according to an embodiment of the present invention. As shown in Figure 7, it is preferable that the electrostatic chuck 100 includes a base member 170 which is joined to the lower surface 114 facing the upper surface 112 of the substrate 110 and has a gas flow path 172 connected to a gas introduction hole 118. This allows heat conduction from the substrate 110 to the base member 170, and enables more efficient heat transfer from the substrate W to the substrate 110.

[0058] The base member 170 functions as a cooling member used to maintain the substrate W at a predetermined temperature by transferring the heat input to the substrate W during the semiconductor process through the base body 110. The base member 170 is formed from a metal or ceramic. As such a metal, Al and Al alloys, which have workability and high thermal conductivity, are most preferred, but other materials such as copper, titanium, nickel-containing alloys, and SUS may also be used. As for the ceramic, it is particularly preferable that the ceramic has a thermal conductivity of 100 W / m·K or higher, for example, aluminum nitride.

[0059] The base member 170 preferably has a refrigerant channel 174 inside. The refrigerant channel 174 is formed, for example, in a tubular shape. This further enhances the heat transfer performance from the substrate W. As the refrigerant, water, ethylene glycol, fluorocarbons, etc., can be used. The width of the refrigerant channel 174 is preferably 1 mm or more and 60 mm or less. The cross-sectional shape of the refrigerant channel 174 is not limited to a rectangle, but can be any shape that is manufacturable, such as a circle, ellipse, semicircle, or stepped shape.

[0060] The substrate 110 and the base member 170 are preferably joined by adhesive bonding for simplicity. The bonding method can be selected according to the operating temperature of the semiconductor process used; for example, silicone resin bonding, In bonding, or bonding with Al foil can be used. A stress-relieving structure may be provided between the substrate 110 and the base member 170. Since the substrate 110 and the base member 170 generally have different coefficients of thermal expansion, there is a risk of delamination between the substrate 110 and the base member 170 due to warping or deformation caused by thermal stress during use, but the stress-relieving layer can suppress the risk of delamination.

[0061] The electrostatic chuck 100 may be provided with terminals 180 and terminal holes 182 as needed. The electrostatic chuck 100 may also be provided with lift pin holes or the like (not shown).

[0062] [Manufacturing method for electrostatic chucks] Next, a method for manufacturing an electrostatic chuck according to an embodiment of the present invention will be described. An electrostatic chuck according to an embodiment of the present invention is manufactured, for example, by a powder hot-pressing method. The powder hot-pressing method is a method in which electrodes are embedded inside ceramics by alternately stacking ceramic raw material powder and predetermined electrodes, and then firing the mixture using a single-axis hot-pressing method. By employing the powder hot-pressing method, the product can be manufactured in a short period of time. The manufacturing method is not limited to this method, and may also be, for example, the molded body hot-pressing method disclosed in Japanese Patent No. 6148845, the green sheet lamination method, the CIP molding method, or other conventional manufacturing methods.

[0063] For example, ceramic raw material powder (slurry) is prepared by adding appropriate additives such as sintering aids, binders, plasticizers, and dispersants to ceramic powder and mixing, and then granulated powder is produced by a spray-drying method or the like. For example, when AlN is used as the raw material, 0.3 to 6 wt% of Y2O3 is added as a sintering aid to the AlN ceramic raw material powder to produce granulated powder. The mixing method can be either wet or dry, and mixers such as ball mills and vibration mills can be used. Aluminum nitride, aluminum oxide, silicon carbide, and silicon nitride can be used as raw material ceramic powders.

[0064] The ceramic powder is preferably of high purity, preferably 96% or higher, and more preferably 98% or higher. The average particle size of the ceramic powder also varies depending on the type of ceramic powder used as the raw material, but for example, when AlN is used as the raw material, it is preferably 0.1 μm to 1.0 μm, and more preferably 0.3 μm to 0.8 μm.

[0065] The material used for the electrostatic adsorption electrodes embedded in the ceramic sintered body is preferably Mo, W, or an alloy thereof. Electrostatic adsorption electrodes can be formed from meshes, foils, coils, or thin films of these materials. For example, a Mo mesh (wire diameter 0.1 mm, 50 mesh, plain weave) can be cut into a predetermined shape to form the electrostatic adsorption electrode. The outer diameter is smaller than the outer diameter of the substrate so as not to be exposed from the outer surface of the substrate. Terminals for connection to an external power source may also be embedded simultaneously. Furthermore, heater electrodes may be embedded for purposes such as localized temperature control.

[0066] Sintering can be carried out using either uniaxial hot press firing or atmospheric pressure firing. In uniaxial hot press firing, granulated powder to form the base body is filled into a bottomed carbon mold, and after uniaxial pressing, electrostatic adsorption electrodes cut to a predetermined shape are placed on the molded body. The same granulated powder is then filled on top, a punch of the carbon mold is placed on top, and after molding, firing is carried out under predetermined firing conditions. For example, when using AlN as the raw material, it is preferable to perform hot press firing for 0.1 hours to 20 hours at a temperature of 1700°C to 2000°C and a pressure of 1 MPa to 20 MPa.

[0067] After firing, gas inlet holes are formed, the surface and back surface are processed, terminal holes are formed, and the material is ground or polished to a predetermined shape. Formation methods include blasting, milling, laser processing, etc. Depending on the design of the electrostatic chuck, multiple pin-shaped protrusions, multiple island-shaped protrusions, annular protrusions, etc. may also be formed. At this time, the gas inlet holes, multiple pin-shaped protrusions, multiple island-shaped protrusions, annular protrusions, etc. are formed so that the surface contact rate is within a predetermined range.

[0068] The surface on which the substrate will be mounted is processed to achieve a predetermined surface condition. First, laser processing, sandblasting, or grinding with a grinding wheel is performed to shape the surface (formation of flat surfaces, pin-shaped protrusions, or island-shaped protrusions). This makes it possible to make the skewness Rsk of the surface after polishing, as described later, negative. Subsequently, the top surface that will be the substrate mounting surface is processed by polishing to achieve a surface roughness Ra within a predetermined range.

[0069] After polishing, the terminals are connected to the terminal holes using brazing material. The terminals can be made of materials such as nickel (Ni). The brazing material can be made of materials such as Au (Gold) brazing material.

[0070] In this way, the heat input to the substrate can be removed quickly, enabling the manufacture of an electrostatic chuck that can handle the increasing power of semiconductor processes and suppress deterioration of detachability.

[0071] [Examples and Comparative Examples] (Example 1) Example 1 describes an example of an electrostatic chuck with a flat surface. 5 wt% Y2O3 was added as a sintering aid to AlN raw material powder, and a binder, dispersant, etc. were added as appropriate and mixed to prepare a slurry. Granulated powder was then produced by spray drying. An electrode for electrostatic adsorption was prepared by cutting Mo mesh to a wire diameter of 0.1 mm and mesh size #50. Next, the granulated powder was filled into a carbon mold, the electrode was embedded, and uniaxial hot pressing was performed in a nitrogen atmosphere at a firing temperature of 1800°C and a hot pressing pressure of 5 MPa. The firing time was 6 hours. The resulting ceramic sintered body was machined to obtain a ceramic sintered body with a diameter of 310 mm and a thickness of 25 mm.

[0072] Multiple Φ0.5 mm gas introduction holes were formed on the surface of the ceramic sintered body, whose outer shape had been processed, so that the contact rate with the substrate on which it would be placed was 99.4%. Subsequently, the surface was ground and polished with free abrasive grains to achieve the desired surface condition. Then, a cooling member (base member) made of Al alloy was prepared on the surface opposite to the surface (bottom surface), formed to the same diameter and thickness as the ceramic sintered body, and containing a rectangular refrigerant channel with a width of 10 mm and a height of 10 mm in cross-section. This was bonded with silicone adhesive to fabricate the electrostatic chuck of Example 1. The surface roughness Ra confirmed after fabrication was 0.18 μm, and the skewness Rsk, determined from the surface roughness curve, was -1.2.

[0073] (Example 2) Examples 2 to 6 are examples of electrostatic chucks with pin-shaped protrusions and annular protrusions on the surface. In Example 2, the surface of a ceramic sintered body with a machined outer shape, manufactured in the same manner as in Example 1, was blast-blasted to form multiple pin-shaped protrusions and annular protrusions so that the contact rate between the polished surface and the substrate on which it would be placed was 30%. Multiple gas introduction holes of Φ0.5 mm were also formed in the recesses. Subsequently, the upper end surfaces (surfaces) of the pin-shaped protrusions and annular protrusions were ground and polished with free abrasive grains to achieve a predetermined surface condition, thereby manufacturing the electrostatic chuck of Example 2. After polishing, the diameter of the multiple pin-shaped protrusions was Φ1.0 mm and the height was 10 μm, and the width of the annular protrusions was 1.0 mm and the height was 10 μm. The surface roughness Ra confirmed after manufacturing was 0.08 μm, and the skewness Rsk determined from the surface roughness curve was -2.5.

[0074] (Example 3) In Example 3, multiple pin-shaped protrusions and annular protrusions were formed so that the contact rate between the polished surface and the substrate on which it was placed was 45%. Otherwise, the electrostatic chuck of Example 3 was manufactured under the same conditions as in Example 2. The surface roughness Ra confirmed after manufacturing was 0.11 μm, and the skewness Rsk determined from the surface roughness curve was -1.8.

[0075] (Example 4) In Example 4, the height of the multiple pin-shaped protrusions and annular protrusions was set to 5 μm. Otherwise, the electrostatic chuck of Example 4 was fabricated under the same conditions as in Example 2. The surface roughness Ra confirmed after fabrication was 0.08 μm, and the skewness Rsk determined from the surface roughness curve was -2.1.

[0076] (Example 5) In Example 5, the height of the multiple pin-shaped protrusions and annular protrusions was set to 20 μm. Otherwise, the electrostatic chuck of Example 5 was fabricated under the same conditions as in Example 2. The surface roughness Ra confirmed after fabrication was 0.08 μm, and the skewness Rsk determined from the surface roughness curve was -1.9.

[0077] (Example 6) In Example 6, the polishing method was changed. Otherwise, the electrostatic chuck of Example 6 was fabricated under the same conditions as in Example 2. The surface roughness Ra confirmed after fabrication was 0.15 μm, and the skewness Rsk, determined from the surface roughness curve, was -0.33.

[0078] (Example 7) Examples 7 to 12 are examples of electrostatic chucks with island-shaped protrusions and annular protrusions on the surface. In Example 7, the surface of a ceramic sintered body with a processed outer shape, manufactured in the same manner as in Example 1, was blast-blasted to form multiple island-shaped protrusions and annular protrusions so that the contact rate between the polished surface and the substrate on which it would be placed was 60%. At this time, the area of ​​the multiple island-shaped protrusions was made to be approximately the same, and grooves with a width of 3.0 mm were formed. In addition, multiple gas introduction holes with a diameter of Φ0.5 mm were formed in the grooves. Subsequently, the upper end surfaces (surfaces) of the island-shaped protrusions and annular protrusions were ground and polished with free abrasive grains to achieve a predetermined surface condition, thereby manufacturing the electrostatic chuck of Example 7. After polishing, the height of the multiple island-shaped protrusions was 500 μm, and the width of the annular protrusions was 1.0 mm and the height was 500 μm. The surface roughness Ra, confirmed after fabrication, was 0.12 μm, and the skewness Rsk, determined from the surface roughness curve, was -2.1.

[0079] (Example 8) In Example 8, multiple island-shaped protrusions and annular protrusions were formed so that the contact rate between the polished surface and the substrate on which it was placed was 75%. Otherwise, the electrostatic chuck of Example 8 was fabricated under the same conditions as in Example 7. The surface roughness Ra confirmed after fabrication was 0.15 μm, and the skewness Rsk determined from the surface roughness curve was -3.0.

[0080] (Example 9) In Example 9, the height of the multiple island-shaped protrusions and annular protrusions was set to 50 μm. Otherwise, the electrostatic chuck of Example 9 was fabricated under the same conditions as in Example 7. The surface roughness Ra confirmed after fabrication was 0.13 μm, and the skewness Rsk determined from the surface roughness curve was -1.8.

[0081] (Example 10) In Example 10, the height of the multiple island-shaped protrusions and annular protrusions was set to 950 μm. Otherwise, the electrostatic chuck of Example 10 was fabricated under the same conditions as in Example 7. The surface roughness Ra confirmed after fabrication was 0.11 μm, and the skewness Rsk determined from the surface roughness curve was -1.5.

[0082] (Example 11) In Example 11, the height of the multiple island-shaped protrusions and annular protrusions was set to 20 μm. Otherwise, the electrostatic chuck of Example 9 was fabricated under the same conditions as in Example 7. The surface roughness Ra confirmed after fabrication was 0.12 μm, and the skewness Rsk determined from the surface roughness curve was -2.6.

[0083] (Example 12) In Example 12, the height of the multiple island-shaped protrusions and annular protrusions was set to 1100 μm. Otherwise, the electrostatic chuck of Example 12 was fabricated under the same conditions as in Example 7. The surface roughness Ra confirmed after fabrication was 0.12 μm, and the skewness Rsk determined from the surface roughness curve was -1.5.

[0084] (Comparative Example 1) Comparative Example 1 is a comparative example of an electrostatic chuck with a flat surface. In Comparative Example 1, multiple gas introduction holes were formed so that the contact rate between the surface and the substrate on which it is placed after polishing was 99.6%. In addition, the grinding and polishing method of the surface was changed. Otherwise, the electrostatic chuck of Comparative Example 1 was manufactured under the same conditions as in Example 1. The surface roughness Ra confirmed after manufacturing was 0.17 μm, and the skewness Rsk determined from the surface roughness curve was -1.3.

[0085] (Comparative Example 2) Comparative Examples 2 and 3 are comparative examples of electrostatic chucks with pin-shaped and annular protrusions on the surface. Comparative Example 2 had a modified polishing method. Otherwise, the electrostatic chuck of Comparative Example 2 was manufactured under the same conditions as in Example 2. The surface roughness Ra confirmed after manufacturing was 0.24 μm, and the skewness Rsk determined from the surface roughness curve was -1.1.

[0086] (Comparative Example 3) Comparative Example 3 had multiple pin-shaped protrusions and annular protrusions formed on the surface so that the contact rate between the polished surface and the substrate on which it was placed was 20%. Otherwise, the electrostatic chuck of Example 3 was manufactured under the same conditions as in Example 2. The surface roughness Ra confirmed after manufacturing was 0.10 μm, and the skewness Rsk determined from the surface roughness curve was -1.9.

[0087] (Preparation for temperature measurement) The electrostatic chucks of the examples and comparative examples were installed in the chamber, a silicon wafer was placed on the surface as a measurement substrate, and a voltage of ±1.0kV was applied to the electrostatic adsorption electrode to adsorb and fix the silicon wafer. In addition, He gas was introduced through multiple gas introduction holes and filled between the substrate mounting surface and the silicon wafer. At this time, the He gas pressure was adjusted to 100 Torr. A mixture of water and ethylene glycol was prepared for the refrigerant flow path, the refrigerant temperature was set to 20°C, and it was circulated at a flow rate of 3 L / min.

[0088] (Surface temperature measurement) Next, heat was applied by irradiating a silicon wafer with plasma at an output of 3 kW. The silicon wafer used was a TC-equipped wafer with thermocouples (TC) at 17 points (1 at the center, 8 at the intermediate radius, and 8 on the outer edge), and the temperature at the measurement points was measured.

[0089] (Temperature difference measurement) Furthermore, to evaluate temperature uniformity, the temperature difference ΔT was defined as the difference between the highest and lowest temperatures at each measurement point. A temperature difference ΔT of 5.0°C or less was considered particularly good (○), a temperature difference ΔT between 5.0°C and 7.0°C was considered good (△), and a temperature difference ΔT greater than that was considered poor (×).

[0090] Figure 8 is a table showing the manufacturing conditions and test results for the examples and comparative examples. Note that the asterisks (*) in the columns for substrate surface temperature and temperature difference in the table in Figure 8 indicate that the temperature measurement conditions were different. The electrostatic chucks of Examples 1-4 and 6-10 were found to exhibit excellent heat transfer efficiency and temperature distribution uniformity, with the surface temperature controlled to 100°C or less at all measurement points under the preparation conditions for temperature measurement, and the temperature difference ΔT also controlled to 5°C or less.

[0091] In Example 5, the electrostatic chuck with a high pin-shaped protrusion could not obtain sufficient suction force at the voltage conditions for preparing for temperature measurement, and the substrate detached due to a gas pressure of 100 Torr, making measurement impossible. However, by increasing the suction voltage, it was possible to prevent the substrate from detaching due to a gas pressure of 100 Torr. At this time, the surface temperature was controlled to 100°C or less at all measurement points, and the temperature difference ΔT could also be controlled to 5°C or less.

[0092] In Example 11, the electrostatic chuck with a low island-shaped protrusion had a smaller amount of gas introduced into the space, resulting in some measurement points with higher surface temperatures compared to the above examples, and a slight temperature difference was observed.

[0093] Furthermore, in the electrostatic chuck of Example 12, which had a high island-shaped protrusion, the surface temperature was similar to that of the other examples, but the risk of discharge between the groove bottom and the substrate increased, leading to challenges in process stability. This is presumed to be because the groove depth is too deep, and conditions such as gas pressure and temperature increase the probability of gas molecules in the groove colliding with other molecules.

[0094] The electrostatic chuck in Comparative Example 1, which had a high contact rate with the substrate, exhibited excellent solid heat transfer, and its surface temperature was controlled to below 100°C. However, the temperature difference ΔT was higher than 7.0°C. This is presumed to be due to the small number of gas introduction holes formed, which resulted in inadequate gas heat transfer in some areas, and the fact that the chuck could not be uniformly adsorbed across the entire substrate mounting surface due to the warping of the substrate.

[0095] Furthermore, in Comparative Example 2, where the surface roughness Ra of the substrate mounting surface was high, sufficient suction force could not be obtained with the voltage conditions for preparing for temperature measurement, and the substrate detached due to the gas pressure of 100 Torr, making measurement impossible. By increasing the suction voltage, it was possible to prevent the substrate from detaching due to the gas pressure of 100 Torr. At this time, suction of the substrate was possible, but the contact with the substrate was poor, and although the surface temperature was controlled to below 100°C, the temperature difference ΔT was higher than 7.0°C.

[0096] Furthermore, the electrostatic chuck in Comparative Example 3, which had a low contact rate with the substrate, was unable to exhibit sufficient solid thermal conductivity and could not control the surface temperature to below 100°C. The temperature difference ΔT also exceeded 7.0°C.

[0097] Furthermore, in Example 6, where the skewness Rsk was negative but greater than -1.0, the surface temperature was controlled to 100°C or less at all measurement points, and the temperature difference ΔT was also controlled to 5°C or less, demonstrating excellent heat transfer efficiency and temperature distribution uniformity. However, the dechuckability was slightly worse compared to Example 2. This is presumed to be because Example 2 has a smaller skewness value and a surface state with more fine grooves than Example 6, allowing gas to enter the substrate mounting surface, thus improving the detachment between the substrate mounting surface and the substrate. In contrast, Example 6 has fewer fine grooves, reducing the area where gas can enter, thus maintaining a high adsorption force and resulting in worse detachment than Example 2. Therefore, it was confirmed that a skewness Rsk of less than -1.0 is preferable in order to further suppress the deterioration of dechuckability while maintaining heat transfer from the substrate to the electrostatic chuck.

[0098] From the above results, it was confirmed that the electrostatic chuck of the present invention provides good contact between the substrate and the surface of the substrate, allowing for the early removal of heat input to the substrate, and thus enabling it to handle the increasing power of semiconductor processes. Furthermore, it was confirmed that it is possible to improve heat transfer from the substrate to the electrostatic chuck while suppressing deterioration of de-chuck performance.

[0099] The present invention is not limited to the embodiments described above, and it goes without saying that it extends to 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 illustrative purposes only and may be modified as appropriate. [Explanation of Symbols]

[0100] 100 electrostatic chucks 110 Base 112 Top surface 114 Bottom surface 116 center 118 Gas inlet hole 120 Electrodes for electrostatic adsorption 130 Surface 132 Substrate mounting surface 140 Pin-shaped protrusion 142 Upper end surface of pin-shaped protrusion 144 recess 150 Annular protrusion 152 Upper end surface of the annular protrusion 160 Island-shaped protrusions 162 Upper end surface of island-shaped protrusion 164 Groove 170 Base member 172 Gas flow path 174 Refrigerant flow path 180 terminals 182 terminal holes

Claims

1. It is an electrostatic chuck, A substrate made of a ceramic sintered body, An electrostatic adsorption electrode embedded in the substrate, The substrate comprises a plurality of gas introduction holes opening on the upper surface, The substrate has a surface with a contact rate of 30% to 99.5% with the substrate on which it is placed. The surface roughness Ra of the aforementioned surface is 0.2 μm or less. An electrostatic chuck characterized in that the skewness Rsk, determined from the surface roughness curve, is negative.

2. The electrostatic chuck according to claim 1, characterized in that the skewness Rsk is less than -1.

0.

3. The electrostatic chuck according to claim 1, further comprising a base member having a gas flow path connected to the gas introduction hole and joined to the lower surface of the substrate opposite to the upper surface.

4. The electrostatic chuck according to claim 2, further comprising a base member having a gas flow path connected to the gas introduction hole and joined to the lower surface of the substrate opposite to the upper surface.

5. A plurality of pin-shaped protrusions are formed projecting upward from the upper surface of the base, It comprises an annular projection formed to protrude upward from the upper surface of the base so as to surround the plurality of pin-shaped projections, The electrostatic chuck according to any one of claims 1 to 4, characterized in that the surface is composed of the upper end surface of the pin-shaped projection and the upper end surface of the annular projection.

6. A plurality of island-shaped protrusions are formed projecting upward from the upper surface of the base, It comprises an annular projection formed to protrude upward from the upper surface of the base so as to surround the plurality of island-shaped projections, The electrostatic chuck according to any one of claims 1 to 4, characterized in that the surface is composed of the upper end surface of the island-shaped protrusion and the upper end surface of the annular protrusion.

7. The electrostatic chuck according to claim 5, characterized in that the height of the pin-shaped protrusion is 5 μm or more and 10 μm or less.

8. The electrostatic chuck according to claim 6, characterized in that the height of the island-shaped protrusions is 25 μm or more and 1000 μm or less.

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