electrostatic chuck

Abstract

The present invention provides an electrostatic chuck capable of ensuring adhesion between a dielectric substrate and a conductive layer. [Solution] The electrostatic chuck 10 comprises a dielectric substrate 100 having a surface 110 which is a mounting surface, a heater 140 provided inside the dielectric substrate 100, and an adsorption electrode 130 provided inside the dielectric substrate 100 at a position closer to the surface 110 than the heater 140. Both the heater 140 and the adsorption electrode 130 have a plurality of ceramic particles CP arranged inside a conductor. The heater 140 is thicker than the adsorption electrode 130. In this electrostatic chuck 10, the average particle diameter of the ceramic particles CP arranged inside the heater 140 is 50% or more and 150% or less of the average particle diameter of the ceramic particles CP arranged inside the adsorption electrode 130.

Description

Technical Field

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

Background Art

[0002] For example, in semiconductor manufacturing equipment such as an etching apparatus, an electrostatic chuck is provided as a device for adsorbing and holding a substrate such as a silicon wafer to be processed. The electrostatic chuck includes a dielectric substrate provided with adsorption electrodes. When a voltage is applied to the adsorption electrodes, an electrostatic force is generated, and the substrate placed on the dielectric substrate is adsorbed and held.

[0003] The above-mentioned adsorption electrodes are often provided as conductive layers embedded inside the dielectric substrate. As such a conductive layer, in addition to the above-mentioned adsorption electrodes, for example, a heater, an RF electrode, etc. may be provided. The thickness of each conductive layer is individually set according to its function. Therefore, it is common for a plurality of conductive layers inside the dielectric substrate to have different thicknesses from each other.

[0004] As described in Patent Document 1 below, a plurality of ceramic particles may be arranged inside the conductive layer. By adopting such a configuration, it is possible to ensure the adhesion between the ceramics constituting the dielectric substrate and the conductive layer inside it.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] During the manufacturing of the electrostatic chuck, the dielectric substrate is formed by laminating multiple green sheets. The conductive layer is formed by printing a paste-like material onto the surface of some of the green sheets before lamination.

[0007] The thickness of the conductive layer is generally adjusted by the particle size of the ceramic particles mixed into the paste. For example, if a paste containing ceramic particles with a relatively small average particle size is used, the conductive layer formed by printing will be thin. On the other hand, if a paste containing ceramic particles with a relatively large average particle size is used, the conductive layer formed by printing will be thick.

[0008] However, if the particle size of the ceramic particles contained in the conductive layer becomes too large, the adhesion between the ceramics constituting the dielectric substrate and the conductive layer will actually decrease.

[0009] This invention has been made in view of these problems, and its objective is to provide an electrostatic chuck that can ensure adhesion between a dielectric substrate and a conductive layer. [Means for solving the problem]

[0010] To solve the above problems, the electrostatic chuck according to the present invention comprises a dielectric substrate having a mounting surface on which an object to be adsorbed is placed, a first conductive layer provided inside the dielectric substrate, and a second conductive layer provided inside the dielectric substrate at a position closer to the mounting surface than the first conductive layer. Both the first conductive layer and the second conductive layer have a plurality of ceramic particles arranged inside a conductor. The first conductive layer is thicker than the second conductive layer. In this electrostatic chuck, the average particle diameter of the ceramic particles arranged inside the first conductive layer is 50% or more and 150% or less of the average particle diameter of the ceramic particles arranged inside the second conductive layer.

[0011] In the electrostatic chuck with the above configuration, the average particle size of the ceramic particles placed inside the relatively thick first conductive layer is smaller than in conventional designs, and is about the same size as the average particle size of the ceramic particles placed inside the relatively thin second conductive layer. This configuration ensures sufficient adhesion between the dielectric substrate and the first conductive layer. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide an electrostatic chuck that can ensure adhesion between a dielectric substrate and a conductive layer. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic cross-sectional view showing the configuration of the electrostatic chuck according to the first embodiment. [Figure 2] This diagram shows cross-sections of the internal electrodes and the heater. [Figure 3] This is a diagram illustrating a method for manufacturing a dielectric substrate. [Figure 4] This is a schematic cross-sectional view showing the configuration of an electrostatic chuck according to the second embodiment. [Figure 5] This is a schematic cross-sectional view showing the configuration of an electrostatic chuck according to the third embodiment. [Modes for carrying out the invention]

[0014] This embodiment will now be described with reference to the attached drawings. To facilitate understanding of the explanation, the same reference numerals are used for identical components in each drawing whenever possible, and redundant explanations are omitted.

[0015] A first embodiment will be described. The electrostatic chuck 10 according to this embodiment adsorbs and holds a substrate W to be processed by electrostatic force inside a semiconductor manufacturing apparatus (not shown) such as an etching apparatus. The substrate W corresponds to an "object to be adsorbed", and is, for example, a silicon wafer. The electrostatic chuck 10 may be used in an apparatus other than a semiconductor manufacturing apparatus.

[0016] FIG. 1 schematically shows a cross-sectional view of the configuration of the electrostatic chuck 10 in a state where the substrate W is adsorbed and held. The electrostatic chuck 10 includes a dielectric substrate 100 and a base plate 200.

[0017] The dielectric substrate 100 is a substantially disk-shaped member made of a ceramic sintered body. The dielectric substrate 100 contains, for example, high-purity aluminum oxide (Al2O3), but may contain other materials. The purity, type, additives, etc. of the ceramics in the dielectric substrate 100 can be appropriately set in consideration of the plasma resistance required for the dielectric substrate 100 in a semiconductor manufacturing apparatus.

[0018] The dielectric substrate 100 of this embodiment contains high-purity alumina having a purity of 99.5% or more as a main component. The purity of the high-purity alumina contained in the dielectric substrate 100 as its main component is more preferably 99.9% or more, and still more preferably 99.99% or more.

[0019] Incidentally, the "main component" refers to the compound most contained in the object (here, the dielectric substrate 100). Specifically, the "main component" refers to a compound that is confirmed to be relatively more contained in terms of volume ratio or mass ratio than any other compound contained in the object when quantitative analysis or semi-quantitative analysis using X-ray diffraction (XRD) is performed on the object.

[0020] Of the dielectric substrate 100, the upper surface 110 in FIG. 1 is the "placement surface" on which the substrate W is placed. Also, the lower surface 120 of the dielectric substrate 100 in FIG. 1 is the "surface to be joined" that is joined to the base plate 200 via the joining layer 300 described later. Along the direction perpendicular to the surface 110, the viewpoint when looking at the electrostatic chuck 10 from the surface 110 side will also be referred to as the "top view" hereinafter.

[0021] The dielectric substrate 100 is provided with a flange portion 101. The flange portion 101 is a portion that protrudes further to the outer peripheral side than the surface 110 which is the placement surface. In the top view, the flange portion 101 surrounds the entire surface 110 from the outside. The surface of the flange portion 101 on the side of the substrate W (the upper surface in FIG. 1) is at a position closer to the base plate 200 side (the lower side in FIG. 1) than the surface 110. When processing the substrate W, an annular member (not shown) called a "focus ring" or the like is placed on the flange portion 101.

[0022] A heater 140 is provided inside the dielectric substrate 100. The heater 140 is a conductor wound in a line shape, which receives power supply from the outside and generates heat to heat the dielectric substrate 100. The heater 140 is, for example, a thin flat plate-like layer formed of a metal material such as palladium, and is arranged parallel to the surface 110. As the material of the heater 140, in addition to palladium, molybdenum, platinum, tungsten, etc. may also be used. The power supply to the heater 140 is performed, for example, via a power supply terminal (not shown) embedded on the surface 120 side of the dielectric substrate 100.

[0023] The heater 140 is routed along a path that passes through almost the entire dielectric substrate 100 when viewed from above, but in Figure 1, the cross-section of the heater 140 is schematically depicted as a single straight line. The dielectric substrate 100 may be divided into multiple regions when viewed from above, and the heater 140 may be individually arranged in each region. This configuration makes it possible to individually adjust the amount of heat generated by the heater 140 in each region. The heater 140 corresponds to the "first conductive layer" in this embodiment.

[0024] An adsorption electrode 130 is provided inside the dielectric substrate 100 at a height position on the surface 110 side of the heater 140. The adsorption electrode 130 is a thin, flat layer formed of a metallic material such as palladium, and is arranged parallel to the surface 110. In addition to palladium, molybdenum, platinum, tungsten, etc. may be used as the material for the adsorption electrode 130. When a voltage is applied to the adsorption electrode 130 from the outside via a power supply path (not shown), an electrostatic force is generated between the surface 110 and the substrate W, thereby adsorbing and holding the substrate W. The adsorption electrode 130 may be provided as a so-called "monopolar" electrode, as in this embodiment, or as a so-called "bipolar" electrode, with two electrodes provided. Power is supplied to the adsorption electrode 130, for example, via a power supply terminal (not shown) embedded on the surface 120 side of the dielectric substrate 100. The adsorption electrode 130 corresponds to the "second conductive layer" in this embodiment.

[0025] As shown in Figure 1, a space SP is formed between the dielectric substrate 100 and the substrate W. When etching or other processes are performed in the semiconductor manufacturing apparatus, an inert gas for temperature control is supplied to the space SP from the outside through a gas hole (not shown). By interposing an inert gas between the dielectric substrate 100 and the substrate W, the thermal resistance between them is adjusted, thereby maintaining the temperature of the substrate W at an appropriate temperature. In this embodiment, helium gas is used as the inert gas for temperature control supplied to the space SP, but a different type of gas may be used.

[0026] A sealing ring 111 and dots 112 are provided on the mounting surface 110, and the above-mentioned space SP is formed around them.

[0027] The seal ring 111 is an annular projection provided as a wall that partitions the space SP at the outermost position. The upper end of the seal ring 111 is part of the surface 110 and contacts the substrate W. Multiple seal rings 111 may be provided to divide the space SP. This configuration allows for individual adjustment of the helium gas pressure in each space SP, making the surface temperature distribution of the substrate W more uniform during processing.

[0028] In Figure 1, the portion labeled "116" is the bottom surface of the space SP. Hereafter, this portion will also be referred to as "bottom surface 116". The seal ring 111, along with the dot 112 described below, is formed as a result of excavating a portion of the surface 110 down to the position of the bottom surface 116.

[0029] The dots 112 are circular protrusions that extend from the bottom surface 116. Multiple dots 112 are provided and are distributed approximately evenly on the mounting surface of the dielectric substrate 100. The upper end surface of each dot 112 is part of the surface 110 and contacts the substrate W. By providing multiple such dots 112, the bending of the substrate W is suppressed.

[0030] The base plate 200 is a roughly disc-shaped member that supports the dielectric substrate 100. The base plate 200 is made of a metallic material such as aluminum. Of the base plate 200, the upper surface 210 in Figure 1 is the "bonded surface" which is bonded to the dielectric substrate 100 via the bonding layer 300.

[0031] The bonding layer 300 is a layer provided between the dielectric substrate 100 and the base plate 200, and it bonds the two together. The bonding layer 300 is made by curing an adhesive made of an insulating material. In this embodiment, a silicone adhesive is used as the adhesive. However, the bonding layer 300 may be made by curing another type of adhesive. In any case, it is preferable to use a material with the highest possible thermal conductivity for the bonding layer 300 so that the thermal resistance between the dielectric substrate 100 and the base plate 200 is reduced.

[0032] A refrigerant channel 250 for circulating refrigerant is formed inside the base plate 200. When etching or other processes are performed in the semiconductor manufacturing equipment, refrigerant is supplied from the outside to the refrigerant channel 250, thereby cooling the base plate 200. During processing, the heat generated in the substrate W is transferred to the refrigerant via the helium gas in the space SP, the dielectric substrate 100, and the base plate 200, and is discharged to the outside together with the refrigerant. The supply and discharge of refrigerant to and from the refrigerant channel 250 is performed through an opening (not shown) formed on the surface 220 of the base plate 200 opposite to the surface 210.

[0033] An insulating film may be formed on the surface of the base plate 200. The insulating film may be formed to cover only a portion of the surface of the base plate 200, rather than the entire surface. For example, the insulating film may be formed to cover only the side portions excluding surfaces 210 and 220, i.e., the exposed portions that are exposed to plasma or the like inside the semiconductor manufacturing equipment. Alternatively, the insulating film may be formed to cover an area that includes at least the entire surface 210. As the insulating film, for example, an alumina film formed by thermal spraying can be used. By covering the surface of the base plate 200 with an insulating film, the dielectric strength of the base plate 200 can be increased.

[0034] The specific configurations of the heater 140 (first conductive layer) and the adsorption electrode 130 (second conductive layer) will now be described. Both the heater 140 and the adsorption electrode 130 are conductive layers provided inside the dielectric substrate 100, but their entirety is not formed of conductors. The heater 140 and the adsorption electrode 130 contain multiple ceramic particles CP inside, and the area surrounding the ceramic particles CP is almost entirely filled with conductors. In other words, multiple ceramic particles CP are arranged inside a conductor. Note that the ceramic particles CP are primary particles.

[0035] Figure 2(A) shows an example of an image obtained by observing the portion of the adsorption electrode 130 in the cross-section of a sample of the electrostatic chuck 10 that was cut perpendicular to the mounting surface, using a scanning electron microscope. The upper end of the image roughly coincides with the upper end of the adsorption electrode 130. Similarly, the lower end of the image roughly coincides with the lower end of the adsorption electrode 130. Prior to the observation with the scanning electron microscope, the portion of the conductor contained in the adsorption electrode 130 that was near the cross-section was removed. Therefore, Figure 2(A) shows the three-dimensional arrangement of ceramic particles CP that were located inside the adsorption electrode 130. In other words, not only the ceramic particles CP located at the cross-sectional position but also the ceramic particles CP located further inside the cross-section are shown.

[0036] Figure 2(B) shows an example of an image obtained by observing the portion of the cross-section containing the heater 140 using a scanning electron microscope. The upper edge of the image roughly coincides with the upper edge of the heater 140. Similarly, the lower edge of the image roughly coincides with the lower edge of the heater 140. Before performing the scanning electron microscope observation, the portion of the conductor contained in the heater 140 that was near the cross-section was removed. Therefore, Figure 2(B), like Figure 2(A), shows the three-dimensional arrangement of the ceramic particles CP that were arranged inside the heater 140. The magnification of the image in Figure 2(B) is the same as the magnification of the image in Figure 2(A).

[0037] As is clear from comparing the two images, the thickness T1 of the heater 140 is greater than the thickness T2 of the adsorption electrode 130. This difference in the thickness of each conductive layer is set according to the magnitude of the current flowing through them. The adsorption electrode 130 has a relatively small thickness T2 because almost no current flows through it even when a high voltage is applied. The heater 140 needs to have a large current flow through it to generate Joule heat, so its thickness T1 is set relatively large to reduce its electrical resistance. In this embodiment, the thickness T2 of the adsorption electrode 130 is about 4 μm, and the thickness T1 of the heater 140 is about 9 μm.

[0038] In Figure 2(B), the particle size of the ceramic particles CP arranged inside the heater 140 is shown as "D1". In the following explanation, the average particle size of the multiple ceramic particles CP arranged inside the heater 140 (first conductive layer) will also be referred to as "average particle size D1".

[0039] In Figure 2(A), the particle size of the ceramic particles CP arranged inside the adsorption electrode 130 is shown as "D2". In the following explanation, the average particle size of the multiple ceramic particles CP arranged inside the adsorption electrode 130 (second conductive layer) will also be referred to as "average particle size D1".

[0040] Furthermore, "average particle diameter" refers to the average value of the diameters of each ceramic particle CP placed within the same conductive layer. "Diameter of ceramic particle CP" refers to the diameter of a sphere when the ceramic particle CP is considered to be a sphere of the same volume.

[0041] In the electrostatic chuck 10 of this embodiment, the average particle diameter D1 of the ceramic particles CP arranged inside the heater 140 is 50% or more and 150% or less of the average particle diameter D2 of the ceramic particles CP arranged inside the adsorption electrode 130. In other words, while the heater 140 and the adsorption electrode 130 differ in thickness, the average particle diameter of the ceramic particles CP arranged inside them is approximately the same. In this embodiment, the average particle diameters D1 and D2 are both about 1 μm.

[0042] To explain the reason for setting the average particle diameters D1 and D2 as described above, we will briefly explain the manufacturing process of the dielectric substrate 100.

[0043] The dielectric substrate 100 of this embodiment is manufactured by laminating a plurality of green sheets and firing the resulting laminate. A green sheet is formed from a slurry containing ceramic raw material powder into a sheet shape.

[0044] As shown in Figure 3(A), a conductive layer 500 made of a paste-like material is printed on the surface of some of the green sheets 410. The conductive layer 500 is the part that will become the adsorption electrode 130 and heater 140 after firing. The material of the conductive layer 500 is, for example, a mixture of a resin-based binder with palladium powder and a powder made of multiple ceramic particles CP. By mixing ceramic particles CP into the material of the conductive layer 500, adhesion between the ceramics constituting the dielectric substrate 100 and the heater 140 etc. located inside it can be ensured.

[0045] As shown in Figure 3(B), a green sheet 410 with a conductive layer 500 printed on it is laminated with several other green sheets 420. Although only one green sheet 410 with the conductive layer 500 printed on it is shown in Figure 3(B), in the configuration of this embodiment, two green sheets 410 with the conductive layer 500 printed on them are arranged. When the resulting laminate is fired, one conductive layer 500 becomes an adsorption electrode 130, and the other conductive layer 500 becomes a heater 140. After that, the dielectric substrate 100 according to this embodiment is completed through processes such as polishing.

[0046] During screen printing, the thickness of the conductive layer 500 immediately after printing (i.e., at the time shown in Figure 3(A)) is adjusted as appropriate so that it corresponds to the thickness of the adsorption electrode 130 after firing. Conventionally, the thickness of the conductive layer 500 has generally been adjusted by the particle size of the ceramic particles CP mixed into the material of the conductive layer 500. For example, as in this embodiment, if the thickness T1 of the heater 140 is to be greater than the thickness T2 of the adsorption electrode 130, the particle size of the ceramic particles CP mixed into the conductive layer 500 that becomes the heater 140 should be made greater than the particle size of the ceramic particles CP mixed into the conductive layer 500 that becomes the adsorption electrode 130.

[0047] However, if the particle size of the ceramic particles CP contained in the heater 140 etc. becomes too large, the adhesion between the ceramics constituting the dielectric substrate 100 and the heater 140 etc. will actually decrease. In addition, the conductive path in the heater 140 etc. will become narrower, which may cause its electrical resistance to deviate from the design value. Conversely, if the particle size of the ceramic particles CP contained in the heater 140 etc. becomes too small, the adhesion of the heater 140 will also decrease.

[0048] Therefore, in the electrostatic chuck 10 according to this embodiment, the ceramic particles CP arranged inside the heater 140 and the ceramic particles CP arranged inside the adsorption electrode 130 are adjusted so that their average particle diameters are approximately the same. By making the thickness T1 of the heater 140 thicker than the thickness T2 of the adsorption electrode 130, while reducing the average particle diameter of the ceramic particles CP arranged inside the adsorption electrode 130 compared to conventional methods, sufficient adhesion of the heater 140 can be ensured.

[0049] In the electrostatic chuck 10 of this embodiment, the average particle diameter D1 of the ceramic particles CP arranged inside the heater 140 is 50% or more and 150% or less of the average particle diameter D2 of the ceramic particles CP arranged inside the adsorption electrode 130. The range of the average particle diameter D1 may be set to a narrower range centered around 100%. For example, if the average particle diameter D1 is set to a range of 90% or more and 110% or less of the average particle diameter D2, an even more favorable effect can be obtained.

[0050] Furthermore, it is preferable that the average particle size D1 of the ceramic particles CP arranged inside the heater 140 be smaller than 20% of the thickness T1 of the heater 140. By keeping the average particle size D1 to this size, the adhesion of the heater 140 can be further improved.

[0051] Furthermore, in order to ensure sufficient thickness of the conductive layer 500, which will become the heater 140, after printing as shown in Figure 3(A), instead of increasing the particle size of the ceramic particles CP mixed into the material of the conductive layer 500, for example, the particle size of the palladium powder mixed into the same material can be increased.

[0052] When the amount of impurities in the ceramics constituting the dielectric substrate 100 decreases, the adhesion between the ceramics and the heater 140 tends to decrease. For this reason, in the case where the dielectric substrate 100 mainly contains high-purity alumina, as in this embodiment, if the particle size of the ceramic particles CP is increased as in the conventional method, the adhesion to the heater 140 may decrease significantly. Therefore, when using high-purity alumina as the material for the dielectric substrate 100, the need to adopt a configuration like that of this embodiment becomes particularly important.

[0053] The second embodiment will be described with reference to Figure 4. Below, we will mainly describe the differences from the first embodiment, and will omit explanations of points common to both embodiments as appropriate. In this embodiment, the configuration of the conductive layer arranged inside the dielectric substrate 100 differs from that of the first embodiment.

[0054] Inside the dielectric substrate 100 of this embodiment, an adsorption electrode 130, a heater 141, a heater 142, and a bypass 143 are provided in order from the mounting surface side. The configuration of the adsorption electrode 130 in this embodiment is the same as the configuration of the adsorption electrode 130 in the first embodiment.

[0055] Heaters 141 and 142, like heater 140 in the first embodiment, receive power from an external source to generate heat and heat the dielectric substrate 100.

[0056] Heater 141 is routed individually within each of the multiple regions divided in a top view. Similarly, heater 142 is also routed individually within each of the multiple regions divided in a top view. Each region for housing heater 141 is more finely subdivided than each region for housing heater 142.

[0057] On the other hand, the amount of heat generated by heater 141 per unit area is less than the amount of heat generated by heater 142 per unit area. Heater 142 is for rapidly raising the temperature of the entire substrate W. Heater 141 is for individually adjusting the temperature of each part to make the in-plane temperature distribution of the substrate W more uniform. The materials of heaters 141 and 142 are the same as the material of heater 140 in the first embodiment, but they may be different materials in terms of electrical resistance, etc.

[0058] The bypass 143 is a conductive layer provided as an electrical circuit for supplying power to each of the multiple heaters 141 and 142. The bypass 143 is a thin, flat layer made of a metallic material and is arranged parallel to the surface 110. Multiple bypasses 143 are provided, corresponding to the number of heaters 141 and 142. The bypass 143 electrically connects the heaters 141, etc., to a power supply terminal (not shown) embedded on the surface 120 side of the dielectric substrate 100. By providing such a bypass 143, it becomes possible to increase the degree of freedom in the arrangement of the power supply terminal. The material of the bypass 143 is the same as the material of the heaters 141 and 142, but it may be a different material in terms of its electrical resistance, etc.

[0059] In this embodiment, the thicknesses of the heaters 141, 142, and bypass 143 are approximately the same as the thickness T1 in the first embodiment, and are greater than the thickness T2 of the adsorption electrode 130. However, the thicknesses of the heaters 141, 142, and bypass 143 may differ from each other within a range greater than the thickness T2 of the adsorption electrode 130.

[0060] The heaters 141, 142, and bypass 143 contain a plurality of ceramic particles CP inside, similar to the heater 140 of the first embodiment. The average particle diameter of the ceramic particles CP located inside each of the heaters 141, 142, and bypass 143 is 50% or more and 150% or less of the average particle diameter of the ceramic particles CP located inside the adsorption electrode 130.

[0061] In other words, in this embodiment, the heaters 141 and 142 and the bypass 143 each correspond to the "first conductive layer," and the adsorption electrode 130 corresponds to the "second conductive layer." This configuration also produces the same effects as those described in the first embodiment.

[0062] The third embodiment will be described with reference to Figure 5. Below, we will mainly describe the differences from the first embodiment, and will omit explanations of points common to the first embodiment as appropriate. In this embodiment as well, the configuration of the conductive layer arranged inside the dielectric substrate 100 differs from the first embodiment.

[0063] The dielectric substrate 100 of this embodiment is provided with an adsorption electrode 130, an RF electrode 151, and an RF electrode 152 inside. The configuration of the adsorption electrode 130 in this embodiment is the same as the configuration of the adsorption electrode 130 in the first embodiment.

[0064] The RF electrodes 151 and 152 are provided as one of a pair of counter electrodes for generating plasma in the semiconductor manufacturing apparatus. The other counter electrode is positioned above the electrostatic chuck 10 in the semiconductor manufacturing apparatus. When a high-frequency AC voltage is applied between these counter electrodes, plasma is generated above the substrate W, which is then used for processes such as film deposition and etching on the substrate W.

[0065] The RF electrode 151 is positioned inside the dielectric substrate 100, directly below the mounting surface. In a top view, the RF electrode 151 is approximately circular in shape. The RF electrode 152 is positioned inside the flange portion 101 of the dielectric substrate 100. In a top view, the RF electrode 152 is approximately annular in shape. Both RF electrodes 151 and 152 are thin, flat layers made of a metallic material such as palladium, and are positioned parallel to the surface 110.

[0066] The RF electrodes 151 and 152 are electrically connected to the base plate 200 via a component not shown. Alternatively, the RF electrodes 151 and 152 may be electrically connected to an external power source through a through-hole (not shown) provided in the base plate 200.

[0067] In this embodiment, the thickness of each RF electrode 151 and 152 is greater than the thickness T2 of the adsorption electrode 130. However, the thicknesses of each RF electrode 151 and 152 may differ from each other within a range greater than the thickness T2 of the adsorption electrode 130.

[0068] The RF electrodes 151 and 152, like the heater 140 in the first embodiment, contain a plurality of ceramic particles CP inside. The average particle diameter of the ceramic particles CP arranged inside each of the RF electrodes 151 and 152 is 50% or more and 150% or less of the average particle diameter of the ceramic particles CP arranged inside the adsorption electrode 130.

[0069] In other words, in this embodiment, the RF electrodes 151 and 152 each correspond to the "first conductive layer," and the adsorption electrode 130 corresponds to the "second conductive layer." This configuration also produces the same effects as those described in the first embodiment.

[0070] Furthermore, the dielectric substrate 100 may contain only the adsorption electrode 130 and the RF electrode 151, without the RF electrode 152.

[0071] The embodiments have been described above with reference to specific examples. However, this disclosure is not limited to these specific examples. Modifications made to these specific examples by those skilled in the art are also included within the scope of this disclosure, as long as they retain the features of this disclosure. The elements, their arrangement, conditions, shapes, etc., of each of the aforementioned specific examples are not limited to those illustrated and can be modified as appropriate. The elements of each of the aforementioned specific examples can be combined in different ways as appropriate, as long as no technical inconsistencies arise. [Explanation of Symbols]

[0072] 10: Electrostatic Chuck 100: Dielectric substrate 110: Face 130: Adsorption electrode 140,141,142: Heater 151,152:RF electrode CP: Ceramic particles W: Circuit board

Claims

1. A dielectric substrate having a mounting surface on which an object to be adsorbed is placed, A first conductive layer provided inside the dielectric substrate, The dielectric substrate comprises a second conductive layer provided at a position on the surface side described above, which is closer to the surface side than the first conductive layer, Both the first conductive layer and the second conductive layer have a plurality of ceramic particles arranged inside the conductor. The first conductive layer is thicker than the second conductive layer. The average particle size of the ceramic particles arranged inside the first conductive layer is An electrostatic chuck characterized in that the average particle diameter of the ceramic particles arranged inside the second conductive layer is 50% or more and 150% or less.

2. The average particle size of the ceramic particles arranged inside the first conductive layer is The electrostatic chuck according to claim 1, characterized in that the average particle diameter of the ceramic particles arranged inside the second conductive layer is 90% or more and 110% or less.

3. The electrostatic chuck according to claim 1, characterized in that the average particle diameter of the ceramic particles arranged inside the first conductive layer is less than 20% of the thickness of the first conductive layer.

4. The electrostatic chuck according to claim 1, characterized in that the dielectric substrate contains high-purity alumina with a purity of 99.5% or higher as its main component.

5. The electrostatic chuck according to claim 1, characterized in that the second conductive layer is an adsorption electrode.

6. The electrostatic chuck according to claim 1, characterized in that the first conductive layer is a heater.

7. The electrostatic chuck according to claim 1, characterized in that the first conductive layer is an RF electrode.

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