Retaining member

Abstract

According to this disclosure, a retaining member is provided that includes a porous material capable of ensuring a sufficient gas flow rate. [Solution] The retaining member 100 of the present disclosure comprises a plate-shaped member 11 having a first surface S1 and a second surface S2 disposed on the opposite side of the first surface S1, and having a gas flow path 12 formed inside that connects a gas outlet 12b opening on the first surface S1 side and a gas inlet 12a opening on the second surface S2 side, and a porous body 70 disposed within the gas flow path 12 of the plate-shaped member 11, wherein the porous body 70 comprises a skeletal base material 71 mainly composed of an insulating material, and gas vents 73 are formed inside the skeletal base material 71 that allow gas to pass through from a second end surface 70b on the side closer to the second surface S2 of the porous body 70 toward the first end surface 70a on the opposite side of the second end surface 70b, and the gas vents 73 are composed of a spherical first pore 72A and an amorphous second pore 72B which has a shape other than spherical.

Description

[Technical Field]

[0001] The present disclosure relates to a holding member. [Background Art]

[0002] As an example of a holding member that holds a wafer during the manufacture of semiconductors, an electrostatic chuck disclosed in Japanese Patent No. 7704335 is known, for example. This type of electrostatic chuck includes a base body made of ceramics (e.g., alumina), and a wafer is held by electrostatic attraction on a mounting surface that is a surface of the base body. The electrostatic attraction is generated when a voltage is applied to an electrostatic electrode provided inside the base body.

[0003] In this type of electrostatic chuck, in processes such as plasma etching, an inert gas (a heat-conductive gas such as helium gas) is supplied between the base body and the wafer to remove heat from the wafer. For this reason, for example, a gas supply portion for flowing an externally supplied inert gas toward the wafer is formed inside the base body of the electrostatic chuck. On the mounting surface of the base body, a gas hole, which is a through hole positioned at an end of the gas supply portion, is provided, and the inert gas is supplied from the gas hole toward the wafer.

[0004] Incidentally, abnormal discharge (arcing) may occur inside the gas supply portion due to high-frequency power applied during the process, and the abnormal discharge may damage the wafer on the base body. Therefore, in order to suppress the occurrence of such abnormal discharge, a gas-permeable porous body has been provided inside the gas hole. The porous body is formed from a ceramic material containing angular ceramic particles. When an inert gas is supplied to such a porous body from the upstream side of the gas supply portion, the inert gas passes through three-dimensional network-shaped pores in the porous body and moves to the downstream side of the gas supply portion. [Prior Art Literature] [Patent Literature]

[0005] [Patent Literature 1] Patent No. 7704335 [Overview of the project] [Problems that the invention aims to solve]

[0006] As described above, one possible approach to counter abnormal discharge is to use angular ceramic materials to form pores in a porous body. However, if pores are formed solely from angular ceramic particles, steric hindrance is likely to occur, causing the angular ceramic particles to bond to each other three-dimensionally. This reduces the likelihood of forming gas-permeable pores that communicate three-dimensionally within the porous body, raising concerns about reduced gas permeability that allows for sufficient gas flow. Therefore, porous bodies used in countermeasures against abnormal discharge as described above require sufficient gas permeability to allow for sufficient gas flow.

[0007] The purpose of this disclosure is to provide a retaining member equipped with a porous material that can ensure a sufficient gas flow rate. [Means for solving the problem]

[0008] The retaining member of this disclosure comprises a plate-shaped member having a first surface and a second surface disposed on the opposite side of the first surface, with a gas passage formed inside that connects a gas outlet opening on the first surface side and a gas inlet opening on the second surface side, and a porous body disposed within the gas passage of the plate-shaped member, wherein the porous body comprises a skeletal base material mainly composed of an insulating material, and gas vents are formed inside the skeletal base material that allow gas to pass through from a second end face on the side of the porous body closer to the second surface toward the first end face opposite to the second end face, and the gas vents are composed of a spherical first pore and an amorphous second pore having a shape other than spherical. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide a retaining member that has a porous body capable of ensuring a sufficient gas flow rate. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic perspective view showing the external configuration of the retaining member according to this embodiment. [Figure 2] Figure 2 is a schematic cross-sectional view showing the internal structure of the retaining member according to this embodiment. [Figure 3] Figure 3 is a cross-sectional view of the holding substrate, showing an enlarged portion of the gas flow path on the substrate side. [Figure 4] Figure 4 is a schematic diagram illustrating the manufacturing method of the retaining substrate. [Figure 5] Figure 5 is a schematic diagram illustrating the manufacturing method of the retaining substrate. [Figure 6] Figure 6 is an SEM image showing a cross-section including the porous material, interface, and plate-like member, magnified near area A in Figure 3 (magnification: 500x). [Figure 7] Figure 7 is an SEM image showing a cross-section including the porous material, interface, and plate-like member, magnified near area A in Figure 3 (magnification: 200x). [Modes for carrying out the invention]

[0011] [Description of Embodiments in this Disclosure] First, embodiments of this disclosure will be listed and described.

[0012] [1] The retaining member of the present disclosure comprises a plate-shaped member having a first surface and a second surface disposed on the opposite side of the first surface, and having a gas flow path formed inside that connects a gas outlet opening on the first surface side and a gas inlet opening on the second surface side, and a porous body disposed within the gas flow path of the plate-shaped member, wherein the porous body comprises a skeletal base material mainly composed of an insulating material, and gas vents are formed inside the skeletal base material that allow gas to pass through from a second end face on the side of the porous body closer to the second surface toward a first end face opposite to the second end face, and the gas vents are composed of a spherical first pore and an amorphous second pore having a shape other than spherical.

[0013] For example, when a porous body is formed using only angular ceramic particles, irregularly shaped second pores are likely to form due to steric hindrance between the angular ceramic particles. At the same time, many closed spaces that do not communicate with the outside are likely to form within the porous body, which is thought to reduce overall gas permeability. Therefore, for example, when spherical pore-forming material is used, spherical first pores are formed, and by connecting the closed spaces with the first pores, an increase in gas permeability can be expected. In this way, by configuring gas vents to include both first and second pores, gas permeability can be improved.

[0014] (2) In the holding member described in (1) above, the ceramic material constituting the skeletal base material includes a first ceramic material having a predetermined particle size and a second ceramic material having a larger particle size than the first ceramic material, wherein the second ceramic material is preferably polyhedral in shape.

[0015] According to the above configuration, the porous body is formed to comprise a relatively large-diameter second ceramic material and a relatively small-diameter first ceramic material. Therefore, particles of adjacent second ceramic materials are connected by the first ceramic material, and second pores are easily formed between particles of adjacent second ceramic materials. When the second pores communicate with the first pores, the flow rate of gas that can circulate through the gas vent holes of the porous body increases. The porous body formed after firing can achieve a balance between voltage resistance and strength retention. Here, by including the first ceramic material with a relatively small diameter, the sinterability during firing can be improved, and the strength of the porous body that is a sintered body can be ensured. Furthermore, by including the second ceramic material with a relatively large diameter, dielectric breakdown at grain boundaries of the porous body that is a sintered body is prevented, and the voltage resistance is improved. In addition, since the second ceramic material contained in the porous body has a polyhedral shape, it is conceivable that the second pores formed between particles of the second ceramic material become larger. When the second pores become larger, particles of the first ceramic material easily enter into the second pores, and sintering is performed in a manner connecting the first ceramic material and the second ceramic material, which is expected to result in improved sinterability. Therefore, the porous body can ensure a sufficient gas flow rate.

[0016] (3) In the holding member according to (1) or (2) above, it is preferable that an average pore diameter of the first pores is larger than an average pore diameter of the second pores.

[0017] In a three-dimensional network structure of gas vent pores formed in a porous body, gas vent pores formed by communicating first pores and second pores may be formed in some cases. Specifically, in this case, for example, spherical first pores having an average pore diameter larger than that of the second pores and amorphous second pores having an average pore diameter smaller than that of the first pores are formed, and the pores may communicate with each other inside to form gas vent pores. In this way, an increase in gas permeability can be expected. Further, for example, by connecting a closed space with the first pores, gas vent pores are formed, and an increase in gas permeability can be expected. As described above, by providing a difference in the average pore diameter, the closed space serves as a gas vent pore, and the flow rate of gas flowing through the gas vent pores can be further increased as compared with the case where there is no first pore having an average pore diameter larger than that of the second pores.

[0018] (4) In the holding member according to any one of (1) to (3) above, it is preferable that the second pores are constituted by a plurality of angular ceramic particles.

[0019] The amorphous second pores may be formed, for example, by steric hindrance that causes angular ceramic particles to sterically bond to each other.

[0020] (5) In the holding member according to any one of (1) to (4) above, it is preferable that the gas vent pore includes a path in which the first pore, the second pore, and another first pore communicate in this order.

[0021] According to this configuration, in the three-dimensional network structure of gas vent pores formed in the porous body, the first pore, the second pore, and another first pore are arranged in this order, which makes it easier for these pores to communicate with each other, and an increase in gas permeability can be expected. If only the first pores are provided, only voids are formed in the porous body, but by sandwiching the second pore between a plurality of first pores, moderate voids are formed, and excessive voids caused by only the first pores can be avoided. The moderate voids serve as gas vent pores, and an increase in gas permeability can be expected.

[0022] (6) In the holding member described in any of (1) to (5) above, it is preferable that the porosity of the first pores in the porous body is greater than the porosity of the second pores.

[0023] In a porous structure, it is preferable that the porosity of the spherical first pores is greater than that of the amorphous second pores. By making the porosity of the first pores greater than that of the second pores, the probability of closed spaces within the porous structure that do not communicate with the outside being connected via the first pores is increased. This results in the formation of a stronger network of three-dimensionally interconnected gas vents, enabling the stable provision of a sufficient gas flow rate.

[0024] [Details of the embodiments of this disclosure] An embodiment of this disclosure will be described below with reference to Figures 1 to 7. This disclosure is not limited to these examples, and all modifications within the meaning and scope of the claims are intended to be included. Some parts of each drawing show the X, Y, and Z axes of the Cartesian coordinate system XYZ, and each axis is drawn in the same direction in each figure. Here, the Z axis is the axis in the axial direction of the electrostatic chuck 100 (up and down direction in Figure 2), with the upper side of Figure 2 being the top and the lower side of Figure 2 being the bottom. For multiple identical components, one component may be given a reference numeral and the reference numerals of the other components may be omitted. In each drawing, some parts of the configuration may be exaggerated or simplified for ease of explanation. The dimensional ratios of each part may differ in each drawing.

[0025] In this specification, "orthogonal" and "parallel" include not only cases where they are strictly orthogonal or parallel, but also cases where they are approximately orthogonal or parallel within the scope of achieving the function and effect of this embodiment. Furthermore, in this specification, "opposing" refers to the position where two surfaces or members are facing each other, and includes not only cases where they are completely facing each other, but also cases where they are partially facing each other. In addition, in this specification, "opposing" includes both cases where a member other than the two parts is interposed between the two parts, and cases where nothing is interposed between the two parts. Moreover, in this specification, terms such as "first," "second," and "third" are used simply to distinguish things and do not rank them.

[0026] <Electrostatic Chuck> In this embodiment, an electrostatic chuck is given as an example of a holding member 100. The electrostatic chuck 100 is a holding member that holds an object (for example, a wafer W) by attracting it with electrostatic force. The electrostatic chuck 100 is used, for example, as a table on which to place a wafer W in a process of etching using plasma in a reduced-pressure chamber.

[0027] Figure 1 is a schematic diagram illustrating the configuration of the electrostatic chuck 100. As shown in Figure 1, the electrostatic chuck 100 comprises a substantially disc-shaped holding substrate (ceramic substrate) 10, a substantially disc-shaped base member 20 larger than the holding substrate 10, and a bonding material 30 that joins the holding substrate 10 and the base member 20. For example, if the holding substrate 10 is a disc with a diameter of 300 mm and a thickness of 3 mm, the base member 20 is set to be a substantially disc with a diameter of 340 mm and a thickness of 20 mm. Note that the holding substrate 10 and the base member 20 only need to be generally disc-shaped, and they may be provided with positioning parts (such as protrusions and indentations) for aligning them with each other.

[0028] The retaining substrate 10 and the base member 20 are stacked on top of each other in the vertical direction, with the retaining substrate 10 positioned on the upper side in the Z-axis direction and the base member 20 positioned on the lower side in the Z-axis direction. The retaining substrate 10 and the base member 20 are joined to each other by a bonding material 30 interposed between them.

[0029] As shown in Figure 2, the holding substrate 10 has a substantially circular first surface S1 positioned on the upper side, and a substantially circular second surface S2 positioned on the opposite side of the first surface S1 in the Z-axis direction (i.e., the lower side) and facing the base member 20. The first surface S1 is the upper surface of a substantially disc-shaped plate member 11 that constitutes the holding substrate 10, and serves as an adsorption surface for adsorbing and holding the wafer W. The base member 20 has a substantially circular third surface S3 positioned on the upper side and facing the second surface S2 of the holding substrate 10, and a substantially circular fourth surface S4 positioned on the opposite side of the third surface S3 in the Z-axis direction (i.e., the lower side). The bonding material 30 described above is sandwiched between the second surface S2 of the holding substrate 10 and the third surface S3 of the base member 20, and is spread out in layers.

[0030] The retaining substrate 10 comprises a substantially disc-shaped plate member 11. The plate member 11 has a substrate-side gas flow path 12 inside. The lower surface of the plate member 11 becomes the second surface S2 of the retaining substrate 10. The substrate-side gas flow path 12 is an example of a gas flow path in this disclosure.

[0031] The plate-shaped member 11 is an insulating member in the shape of a plate (disc) mainly composed of ceramics. In this specification, "main component" means the component with the highest proportion. In this embodiment, the plate-shaped member 11 is made of alumina (Al2O3). In other embodiments, it may be made of other ceramics such as aluminum nitride (AlN). The alumina in this embodiment includes a third ceramic material 11A that constitutes the skeletal base material of the plate-shaped member 11. For convenience of explanation in this specification, the third ceramic material 11A may also be referred to as the skeletal base material 11A of the plate-shaped member 11.

[0032] The substrate-side gas channel 12 constitutes part of the channel 60 for supplying an inert gas (for example, helium gas, which is a thermal conductive gas) to the electrostatic chuck 100. The substrate-side gas channel 12 is formed inside the plate-shaped member 11 of the holding substrate 10. The substrate-side gas channel 12 consists of a hole that penetrates the holding substrate 10, including a gas inlet 12a opening on the second surface S2 side of the holding substrate 10 and a gas outlet 12b opening on the first surface S1 side. The gas inlet 12a and the gas outlet 12b are in communication within the plate-shaped member 11 via the substrate-side gas channel 12. The gas inlet 12a is in communication with the bonding-side gas channel 31, which will be described later, inside the channel 60. When inert gas is supplied from the gas inlet 12a, the inert gas passes through the substrate-side gas channel 12 and is finally discharged to the outside from the gas outlet 12b.

[0033] Figure 3 is a cross-sectional view of the holding substrate 10, showing an enlarged portion of the substrate-side gas flow path 12. Figure 3 also shows the cross-sectional structure of the holding substrate 10 cut along the Z-axis. As shown in Figures 2 and 3, the substrate-side gas flow path 12 comprises a first vertical flow path section 120, a horizontal flow path section 130, and a second vertical flow path section 140.

[0034] The first longitudinal channel section 120 includes a gas outlet 12b that opens toward the first surface S1, and is a bottomed channel that extends from the gas outlet 12b toward the second surface S2 along the Z-axis direction of the plate-shaped member 11. A porous body 70, which will be described later, is filled into this first longitudinal channel section 120. The first longitudinal channel section 120 is a channel formed extending in a direction perpendicular to the first surface S1.

[0035] The horizontal flow channel 130 is connected to the first vertical flow channel 120 and is a flow channel that extends parallel to the first surface S1. The downstream end of the horizontal flow channel 130 is connected to the upstream end of the first vertical flow channel 120. As a result, the first vertical flow channel 120 is in communication with the horizontal flow channel 130. In the substrate-side gas flow channel 12, the gas inlet 12a is the upstream side and the gas outlet 12b is the downstream side.

[0036] As shown in Figure 2, the second vertical channel section 140 includes a gas inlet 12a that opens into the second surface S2, and is a channel that extends from the gas inlet 12a toward the first surface S1 side along the Z-axis direction of the plate-shaped member 11. The downstream end of the second vertical channel section 140 is connected to the upstream end of the horizontal channel section 130. As a result, the horizontal channel section 130 is in communication with the second vertical channel section 140. The gas inlet 12a serves as the entrance to the substrate-side gas channel 12.

[0037] The holding substrate 10 also includes a plate-shaped member 11 and a chuck electrode 40. The plate-shaped member 11 is filled into a first longitudinal channel section 120, which is part of the substrate-side gas channel 12, and comprises a gas-permeable porous body 70 mainly composed of ceramics. Details of the porous body 70 will be described later.

[0038] As shown in Figures 2 and 3, the holding substrate 10 includes a chuck electrode 40, which is an electrode member. The chuck electrode 40 is generally planar (layered) and substantially parallel to the first surface S1. The chuck electrode 40 is made of a conductive material such as tungsten, molybdenum, or platinum. As shown in Figure 3, the chuck electrode 40 is arranged inside the holding substrate 10 (plate-shaped member 11) on the first surface S1 side. The chuck electrode 40 is connected to an external power source via terminals (not shown), and when power is supplied to the chuck electrode 40, an electrostatic attraction force is generated, and the wafer W is attracted and held to the first surface S1 of the holding substrate 10 by this electrostatic attraction force. The chuck electrode 40 has a through hole 41 that penetrates in the thickness direction (vertical direction). In other embodiments, the electrode member may include a high-frequency electrode or a heater electrode.

[0039] As shown in Figures 1 and 2, the first surface S1 of the holding substrate 10 is provided with a plurality of gas outlets 12b. The outer edge of the first surface S1 is formed in an annular shape, protruding slightly upward compared to the inner portion. Therefore, when a wafer W is adsorbed and held on the first surface S1, a gap G is formed between the wafer W and the inner portion of the first surface S1, as shown in Figure 2. The inert gas flows out through the flow path 60 from the plurality of gas outlets 12b and fills the gap G. This makes it easier for the temperature of the first surface S1 to be transferred to the wafer W, improving the temperature controllability of the wafer W.

[0040] The base member 20 is composed mainly of, for example, metal (aluminum, aluminum alloy, etc.), a composite of metal and ceramics (Al-SiC), or ceramics (SiC).

[0041] As shown in Figure 2, a refrigerant channel 21 is provided inside the base member 20. By flowing a refrigerant (e.g., a fluorine-based inert liquid, water, etc.) through the refrigerant channel 21, the plasma heat is cooled. When the refrigerant flows through the refrigerant channel 21, the base member 20 is cooled, and the holding substrate 10 is cooled by heat transfer (heat dissipation) between the base member 20 and the holding substrate 10 via the bonding material 30. As a result, the wafer W held on the first surface S1 of the holding substrate 10 is cooled. The temperature of the wafer W held on the first surface S1 can be controlled by appropriately adjusting the flow rate of the refrigerant in the refrigerant channel 21.

[0042] Inside the base member 20, a base-side gas passage 22 is provided, which constitutes part of the passage 60. The base-side gas passage 22 is generally a through-hole extending in the vertical direction (thickness direction) of the base member 20, and includes an inlet 22a opening on the fourth surface S4 of the base member 20 and an outlet 22b opening on the third surface S3. The inlet 22a and the outlet 22b are in communication within the base member 20 via the base-side gas passage 22. The outlet 22b is in communication with the joining-side gas passage 31, which will be described later, inside the passage 60. The inlet 22a is the inlet of the base-side gas passage 22 and also the inlet of the entire passage 60 provided in the holding member 100. When inert gas is supplied from the inlet 22a, the inert gas passes through the base-side gas passage 22 and is finally supplied to the joining-side gas passage 31 from the outlet 22b.

[0043] The bonding material 30 is composed of, for example, a bonding sheet containing a silicone-based organic bonding agent, an inorganic bonding agent, or an Al-based metal adhesive. Preferably, the bonding material 30 has high adhesive strength to both the holding substrate 10 and the base member 20, as well as high pressure resistance and thermal conductivity.

[0044] The joining material 30 also has joining-side gas passages 31 that constitute part of the flow path 60. The joining-side gas passages 31 consist of holes that penetrate the layered joining material 30 in the vertical direction (thickness direction).

[0045] The flow path 60 supplies an inert gas (such as helium gas) to the first surface S1 side of the holding member 100. As described above, the first surface S1 is provided with numerous gas outlets 12b, which are the outlets of the flow path 60, and the inert gas is supplied to the first surface S1 side by being discharged from each gas outlet 12b. As described above, such a flow path 60 comprises a base-side gas flow path 22, a bonding-side gas flow path 31, and a substrate-side gas flow path (gas flow path) 12.

[0046] Multiple inlets 22a of the flow path 60 are provided on the fourth surface S4 of the base member 20. When inert gas (arrow H in Figure 2) is supplied from each inlet 22a, the inert gas sequentially passes through the base-side gas flow path 22, the bonding-side gas flow path 31, and the substrate-side gas flow path (gas flow path) 12 connected to each inlet 22a, and is finally discharged from multiple gas outlets 12b provided on the first surface S1.

[0047] The outlet 22b of the base-side gas passage 22 is connected to the first opening 32a on the lower side (base member 20 side) of the joining-side gas passage 31. The second opening 32b on the upper side (holding substrate 10 side) of the joining-side gas passage 31 is connected to the inlet 12a of the substrate-side gas passage (gas passage) 12. Multiple inlets 12a of the substrate-side gas passage (gas passage) 12 are provided on the second surface S2 of the holding substrate 10.

[0048] The second vertical channel section 140, which includes the inlet 12a of the substrate-side gas channel (gas channel) 12, connects to a plurality of horizontal channel sections 130 downstream. Each of the horizontal channel sections 130 is connected to the first vertical channel section 120. In other words, the substrate-side gas channel (gas channel) 12 branches into multiple channels from the upstream side to the downstream side inside the holding substrate 10 (plate-shaped member 11). <Porous material>

[0049] Next, the porous body 70 that fills the substrate-side gas channel 12 will be described in detail. The porous body 70 is mainly composed of insulating ceramics. In this embodiment, the porous body 70 is mainly composed of alumina (Al2O3), similar to the plate-shaped member 11 of the holding substrate 10. By using the same insulating material, alumina (Al2O3), as the main component of the skeletal base material for both the plate-shaped member 11 and the porous body 70, the plate-shaped member 11 and the porous body 70 are fired simultaneously during sintering, causing them to integrate with each other as alumina (Al2O3), and increasing the bonding force at the interface 70c between them. In other embodiments, the porous body 70 may be mainly composed of other ceramics such as aluminum nitride.

[0050] The porous body 70 is a gas-permeable member containing gas vents 73 made up of numerous pores 72. Inert gas can pass through the gas vents 73 of the porous body 70. The porous body 70 is filled into each of the multiple first vertical channel sections 120 in the substrate-side gas channel 12. The porous body 70 is arranged without gaps in the internal space of the substrate-side gas channel 12. In this way, the area of ​​the substrate-side gas channel 12 where the porous body 70 is arranged in the first vertical channel section 120 is called the "porous region R". The holding substrate 10 has a porous region R consisting of the area where the porous body 70 is arranged. The porous body 70 as a whole has a cylindrical shape extending in the vertical direction (the thickness direction of the holding substrate 10).

[0051] As shown in Figure 3, the porous body 70 is filled into the first vertical channel section 120 such that a space V is formed on its lower side. In plan view, the porous body 70 is filled into the cylindrical first vertical channel section 120 such that its circular upper end surface 70a is exposed from the gas outlet 12b and its circular lower end surface 70b is exposed from the opening 12c toward the space V. In this embodiment, the first surface S1 and the upper end surface 70a are arranged to be on the same plane. The upper end surface 70a corresponds to the first end surface of this disclosure and is an example of the first end surface of this disclosure. The lower end surface 70b corresponds to the second end surface of this disclosure and is an example of the second end surface of this disclosure.

[0052] The lower end surface 70b of the porous body 70 faces the space V within the lateral flow channel 130, and the inert gas supplied from the upstream side of the substrate-side gas flow channel (gas flow channel) 12 is supplied into the porous body 70 from this lower end surface 70b. The lower end surface 70b is porous, and this lower end surface 70b serves as the inlet for the inert gas.

[0053] Furthermore, the interface 70c between the porous body 70 and the plate-shaped member 11 is composed of the outer circumferential portion of the porous body 70 and the inner circumferential portion of the first longitudinal channel 120 in a plan view, and has a cylindrical shape that extends straight in a linear fashion in the vertical direction. The first longitudinal channel 120 is formed of alumina, which is the third ceramic material 11A that constitutes the plate-shaped member 11. The porous body 70 and the peripheral wall portion 111 that constitutes the first longitudinal channel 120 are joined together by sintering.

[0054] As shown in Figures 6 and 7, the porous body 70 is equipped with a skeletal base material 71 mainly composed of insulating ceramics. Gas vents 73 are formed inside the skeletal base material 71, with a plurality of pores 72 communicating with each other. The gas vents 73 form a ventilation path for inert gas to pass through inside the porous body 70. The gas vents 73 are interconnected holes that allow gas to pass from the lower end surface 70b on the side closer to the second surface S2 of the porous body 70 to the upper end surface 70a on the opposite side in the vertical direction from the lower end surface 70b. That is, when inert gas is supplied to the porous body 70 from the upstream lower end surface 70b, the inert gas moves through the three-dimensional network of pores 72 (gas vents 73) inside the porous body 70 to the upper end surface 70a downstream of the gas supply section.

[0055] Each pore 72 constituting the gas vent 73 consists of, for example, traces of burnt carbon powder or other materials used as pore-forming material during the manufacture of the porous body 70, or areas where powdered ceramic material (e.g., alumina powder) 75, 76 for forming the skeletal base material 71 of the porous body 70 is absent. The pores 72 are formed as traces of oxidation and disappearance of the pore-forming material during the manufacture of the porous body 70 by firing. As the pore-forming material, synthetic resin beads, carbon powder, carbon fibers, etc., which can be oxidized and disappear during the manufacture of the porous body 70 by firing, are used. The gas vent 73, as a whole, forms a three-dimensional network as the pores 72 are interconnected. In this specification, the skeletal portion of the porous body 70 other than the pores 72 is referred to as the skeletal base material 71.

[0056] Part A in Figure 3 includes a portion of the porous body 70, a portion of the plate-like member 11, and the interface 70c between the porous body 70 and the plate-like member 11. Figures 6 and 7 show SEM images of part A in Figure 3. These SEM images were taken by cutting part A along the Z-axis, polishing the cut surface, and then using a scanning electron microscope (SEM) (magnifications: 500x and 200x). As shown on the left side of Figure 6, the skeletal base material 71 of the porous body 70 contains the first ceramic material 75 (described later) and numerous pores 72. As shown on the left side of Figure 7, the skeletal base material 71 of the porous body 70 contains the first ceramic material 75 (described later), the second ceramic material 76, and numerous pores 72. Also, as shown on the right side of Figures 6 and 7, the third ceramic material 11A is shown inside the plate-like member 11. In Figures 6 and 7, the interface 70c is shown in the center. The interface 70c contains the pores 72 of the porous body 70, the first ceramic material 75, and the third ceramic material 11A of the plate-shaped member 11.

[0057] As shown in Figures 6 and 7, the porous body 70 includes spherical first pores 72A and irregularly shaped second pores 72B as pores 72. That is, the gas vents 73 include spherical first pores 72A and irregularly shaped second pores 72B. As shown in Figures 6 and 7, the pores 72 arranged in three-dimensional space are shown as cross-sectional views showing the two-dimensional arrangement. In particular, the spherical shape of the first pores 72A is shown as circular or approximately circular in any selected cross-section, and the irregular shape of the second pores 72B is shown as circular or an irregular shape other than approximately circular in any selected cross-section.

[0058] A first pore 72A is a pore 72 whose appearance or outline has a spherical shape. A first pore 72A having a spherical shape is a pore that is three-dimensionally isotropic and approximates a circle in any cross-section. The spherical shape of the first pore 72A includes not only a perfect sphere but also a roughly spherical shape that approximates a perfect sphere, an ellipsoid, etc. Furthermore, the spherical shape of the first pore 72A also includes shapes in which a part or the whole of a perfect sphere, roughly spherical shape, ellipsoid, etc., is irregular. In other words, the first pore 72A may have a shape that is substantially recognized as spherical. The spherical outline of the first pore 72A makes dielectric breakdown less likely to occur in the void. The circularity of the pores 72A contained in the porous body 70 may be calculated from the cross-sectional area of ​​the SEM image of the porous body 70. Spherical first pores 72A are determined by the following criterion A. <Judgment Criteria A> 1. Calculate the area of ​​the stomata. The area of ​​a pore is the area of ​​a circle calculated using the equivalent diameter. The equivalent diameter is the diameter of a perfect circle that has the same area as the projected area of ​​an irregularly shaped particle. 2. The stomata have a surface area of ​​100 μm². 2 The following judgment will be made based on whether the above conditions apply or not. (a) Stomatal area of ​​100 μm 2 In the above cases A stomata is considered spherical if its circularity is 0.5 or greater and its needle-like aspect ratio is 1.5 or less. (b) Stomatal area of ​​100 μm 2 If less than A stomata is considered spherical if its circularity is 0.9 or greater and its needle-like aspect ratio is 1.2 or less.

[0059] Second pores 72B are pores 72 that have an irregular shape other than spherical in their three-dimensional appearance or contour. In contrast to first pores 72A, which have a specific geometric shape (spherical, ellipsoidal, cylindrical, etc.) in their three-dimensional appearance or contour, the irregular shape of second pores 72B refers to a complex shape that cannot be approximated as a specific geometric shape (spherical, ellipsoidal, cylindrical, etc.), such as a crack-like or angular shape, and the curvature of the contour is non-uniform depending on the position. Furthermore, irregular pores 72B have a shape that cannot be approximated as spherical or ellipsoidal in their three-dimensional appearance or contour. Irregular pores 72B are determined by the following criterion B. <Judgment Criteria B> 1. Calculate the area of ​​the stomata. The area of ​​a pore is the area of ​​a circle calculated using the equivalent diameter. The equivalent diameter is the diameter of a perfect circle that has the same area as the projected area of ​​an irregularly shaped particle. 2. The stomata have a surface area of ​​100 μm². 2 The following judgment will be made based on whether the above conditions apply or not. (a) Stomatal area of ​​100 μm 2 In the above cases A stomata is considered irregular in shape if its circularity is less than 0.5 and its needle-like ratio is greater than 1.5. (b) Stomatal area of ​​100 μm 2 If less than A stomata is considered irregular in shape if its circularity is less than 0.9 and its needle-like ratio is greater than 1.2.

[0060] As the pore-forming material for forming the spherical first pores 72A, particulate materials such as synthetic resin beads or carbon powder are used. The shape of the particulate pore-forming material for forming the spherical first pores 72A may be a perfect sphere, a nearly spherical shape, an ellipsoid, etc. The particle size of the pore-forming material for forming the first pores 72A is determined as the central particle size assuming that the pore-forming material for forming the spherical first pores 72A is a perfect sphere. The central particle size is sometimes called the median particle size and includes indices such as D50 and D90.

[0061] For example, synthetic resin fibers or carbon fibers can be used as pore-forming materials for forming the irregularly shaped second pores 72B. The shape of the pore-forming material for forming the second pores 72B may be irregular, needle-shaped, etc. In this embodiment, the needle-shape ratio of the pore-forming material for forming the second pores 72B is used, and the aspect ratio of the pore-forming material for forming the second pores 72B is obtained by dividing the maximum diameter by the maximum width perpendicular to the maximum diameter. The material and size of the pore-forming material for forming the first pores 72A and second pores 72B are not limited to those described above. On the other hand, as shown in Figure 7, the first pores 72A are traces of spherical resin beads that have burned out (disappeared) inside the skeletal substrate 71 of the porous body 70. The gas vents 73 through which each pore 72B is connected are smaller than the first pores 72A. The needle-shape ratio of the pores 72B contained in the porous body 70 may be calculated from the cross-sectional area of ​​the SEM image of the porous body 70. Furthermore, the formation of the second pore 72B is not limited to cases where a pore-forming material is used.

[0062] The gas vents 73 contain two types of pores 72A and 72B. For example, if the porous body 70 is formed using only angular ceramic particles of the second ceramic material 76 described later, irregularly shaped second pores 72B are likely to be formed due to steric hindrance between the angular ceramic particles. At the same time, many closed spaces that do not communicate with the outside are likely to be formed within the porous body 70, so the overall gas permeability is likely to decrease. Therefore, for example, if spherical pore-forming material is used, spherical first pores 72A will be formed, and by connecting the closed spaces with the first pores 72A, an increase in gas permeability can be expected. In this way, by configuring the gas vents to include both first pores 72A and second pores 72B, gas permeability can be improved.

[0063] As shown in Figure 7, the skeletal base material 71 constituting the porous body 70 is made of a sintered body of powdered ceramic material such as alumina powder. The powdered ceramic materials 75 and 76 used in the porous body 70 have different particle sizes. The skeletal base material 71 includes a small-diameter first ceramic material 75 (see Figures 6 and 7) having a predetermined particle size, and a large-diameter second ceramic material 76 (see Figure 7) having a larger particle size than the first ceramic material 75. The third ceramic material 11A of the plate-shaped member 11 has a particle size smaller than the particle size of the second ceramic material 76.

[0064] In this embodiment, particle size includes the central particle size. The central particle size is sometimes called the median particle size and includes indices such as D50 and D90. In this embodiment, the central particle size is expressed using the D50 index. In this embodiment, particle size includes the central particle size, but it is not limited to the central particle size and may also include the average particle size. The method for measuring the central particle size was to use the laser diffraction / scattering method in accordance with JIS R1629, and the central particle size of the first ceramic material 75 and the second ceramic material 76 of the porous body 70 and the third ceramic material 11A of the plate-like member 11 were measured. In this embodiment, the average particle size is expressed using the index of the average particle size (catalog value) of the ceramic material, but the average particle size may also be expressed using the manufacturer's nominal value of the compounded ceramic material as the index.

[0065] In this embodiment, the small-diameter first ceramic material 75 (for example, small-diameter alumina powder 1) that constitutes the skeletal base material of the porous body 70 has a median particle size of 2.0 μm. The large-diameter second ceramic material 76 (for example, large-diameter alumina powder 2) has a median particle size of 20.0 μm. For example, the first ceramic material 75 has a median particle size in the range of 3.0 μm or less. Alternatively, the first ceramic material 75 may have a median particle size in the range of 0.1 μm to 3.0 μm.

[0066] For example, the central particle size of the large-diameter second ceramic material 76 (e.g., large-diameter alumina powder 2) is five times or more than that of the first ceramic material 75. The central particle size of the second ceramic material 76 is approximately 20.0 μm. In this embodiment, the central particle sizes of the first ceramic material 75 and the second ceramic material 76 are set at 2.0 μm and 20.0 μm, respectively, but the size is not limited to these values.

[0067] The skeletal substrate 71, which includes the first ceramic material 75 and the second ceramic material 76, forms a three-dimensional network structure overall within the porous body 70. In this embodiment, since the porous body 70 is formed by including the second ceramic material 76, which has a relatively large central particle diameter, and the first ceramic material 75, which has a relatively small central particle diameter, adjacent particles of the second ceramic material 76 are connected by the first ceramic material 75, and second pores 72B are more easily formed between adjacent particles of the second ceramic material 76. The gas vents 73 have two types of pores, and when these second pores 72B communicate with the first pores 72A, the closed space becomes the gas vent 73, and the flow rate of inert gas that can circulate inside the porous body 70 increases compared to the case where there are no first pores 72A, which have a larger average pore diameter than the second pores 72B. Therefore, the porous body 70 formed after firing can balance its dielectric strength and strength. Here, by including a relatively small-diameter first ceramic material 75, the sinterability during firing is improved, and the strength of the porous body 70, which is the sintered body, can be ensured. Furthermore, by including a relatively large-diameter second ceramic material 76, dielectric breakdown at the grain boundaries of the porous body 70, which is the sintered body, is prevented, and the dielectric strength is improved. Specifically, by including a second ceramic material 76 having a relatively large particle size, the grain boundary area per unit volume is reduced. Since grain boundaries are areas where impurities and fine voids are likely to exist and electric field concentration is likely to occur, reducing the grain boundary area per unit volume mitigates local electric field concentration. As a result, the occurrence of dielectric breakdown originating from grain boundaries is suppressed, and the dielectric strength of the porous body 70 is improved. In addition, at the interface 70c between the porous body 70 and the plate-shaped member 11, the first ceramic material 75 is more likely to be arranged than the second ceramic material 76, and when the first ceramic material 75 and the third ceramic material 11A are fired simultaneously, the sinterability is improved. Furthermore, within the porous body 70, the second ceramic material 76 forming the skeletal base material 71 of the porous body 70 has an extra-large central particle size that is even larger than the central particle size of the relatively large-diameter third ceramic material 11A, which makes it easier for pores 72 to form between the particles of the second ceramic material 76, and also improves the dielectric strength.Therefore, it is possible to provide an electrostatic chuck 100 equipped with a porous body 70 that maintains the required gas flow rate while improving strength and voltage resistance.

[0068] The powdered ceramic materials 75 and 76 used in the porous body 70 have different shapes from each other. The second ceramic material 76 contains coarse-grained angular ceramic particles. These angular ceramic particles have a polyhedral shape. Specifically, unlike spherical ceramics, these angular ceramic particles have at least one corner. Furthermore, these angular ceramic particles refer to particles having multiple planes or edges, and include, for example, polyhedral particles having crystal faces, crushed particles obtained by grinding, amorphous particles, etc. In this embodiment, these angular ceramic particles are polyhedra with an overall angular shape having multiple faces or edges. As shown in Figure 7, the second ceramic material 76 has a polyhedral shape. In this embodiment, a polyhedral shape refers to a shape other than a sphere, such as a perfect sphere, a nearly spherical shape, or an ellipsoidal shape. The first ceramic material 75 is composed of spherical ceramic particles. Spherical ceramic particles are ceramic particles whose outer shape is spherical, nearly spherical, or ellipsoidal, or have a rounded shape close to a sphere, and which have fewer corners and edges compared to angular ceramic particles. Because the second ceramic material 76 contained in the porous body 70 has a polyhedral shape, it is thought that the pores 72 formed between the particles of the second ceramic material 76 become larger. As the pores 72 become larger, the particles of the first ceramic material 75 can more easily enter these pores 72, and as a result of sintering in a way that connects the first ceramic material 75 and the second ceramic material 76, improved sinterability is expected. As shown in Figure 7, the particle shape can be confirmed, for example, by observation using a scanning electron microscope (SEM).

[0069] The plurality of pores 72 include two types of pores 72 having different average pore diameters. The plurality of pores 72 include a first pore 72A and a second pore 72B which is smaller in diameter than the first pore 72A. The average pore diameter of the first pore 72A is larger than the average pore diameter of the second pore 72B. The average pore diameter of the first pore 72A is 40.0 μm. The average pore diameter of the second pore 72B is 5.0 μm. In this embodiment, the average pore diameters of the first pore 72A and the second pore 72B are 40.0 μm and 5.0 μm, respectively, but are not limited to these sizes. In this embodiment, the first pore 72A has an average pore diameter in the range of 10.0 μm or more. In this embodiment, the second pore 72B has an average pore diameter in the range of 1.0 μm or more. When pores 72 are formed by a pore-forming material, the average pore diameter of the pores 72 depends on the central particle size of the pore-forming material. In this embodiment, the average pore diameter includes the average inner diameter and the average pore diameter. The shape of the pores specified by the average pore diameter is not limited to circular shapes, but also includes irregular shapes such as connecting holes and branched holes. In this embodiment, the average pore diameter calculated by the equivalent circle diameter obtained by image analysis is shown. Alternatively, the average pore diameter may be shown using the average particle size (catalog value) of the pore-forming material as an index, or the average pore diameter may be shown using the manufacturer's nominal value of the compounded pore-forming material as an index.

[0070] In the three-dimensional network structure of the gas vents 73 formed within the porous body 70, gas vents may be formed in which first pores 72A and second pores 72B are interconnected. More specifically, in this case, for example, a spherical first pore 72A with an average pore diameter larger than that of the second pore 72B and an amorphous second pore 72B with an average pore diameter smaller than that of the first pore 72A may be formed, and these pores 72A and 72B may be interconnected internally to form a group of gas vents. In this way, an increase in gas permeability can be expected. Furthermore, for example, by connecting a closed space with the first pore 72A or the second pore 72B, a gas vent 73 can be formed, and an increase in gas permeability can be expected. In this way, by creating a difference in the average pore diameter, the enclosed space becomes a gas vent 73, and the gas flow rate through the gas vent can be further increased compared to the case where there are no two types of pores 72A and 72B with different average pore diameters.

[0071] Pores 72 may consist of areas where powdered ceramic material (e.g., alumina powder) 75,76 for forming the skeletal base material 71 of the porous body 70 is absent. The porous body 70 contains relatively large-diameter ceramic material 76, and adjacent particles of the second ceramic material 76 are connected by the first ceramic material 75. In the three-dimensional network inside the porous body 70, irregularly shaped second pores 72B are arranged between multiple angular ceramic particles contained in the second ceramic material 76. Irregularly shaped second pores 72B are formed, for example, by steric hindrance such that two or more angular ceramic particles are three-dimensionally bound to each other. The communication of these second pores with the first pores increases the flow rate of gas that can flow through the gas vents 73 of the porous body 70.

[0072] As shown in Figures 6 and 7, the gas vents 73 include a path in which a first pore 72A, a second pore 72B, and another first pore 72A are connected in this order. Alternatively, the gas vents 73 may also include a path in which a first pore 72A, a second pore 72B, another second pore 72B, and another first pore 72A are connected in this order. In the three-dimensional network structure of the gas vents 73 formed in the porous body 70, the arrangement of the first pore 72A, the second pore 72B, and the first pore 72A in this order facilitates communication between these pores 72, and an increase in gas permeability can be expected. If only the first pores 72A, which are larger in diameter than the second pores 72B, are present, only voids will be created within the porous body 70 with multiple first pores 72A in point contact with each other. However, by inserting one or more second pores 72B, which are smaller in diameter than the first pores 72A, between multiple first pores 72A, an appropriate amount of void is created, avoiding excessive voids consisting only of first pores 72A. These appropriate voids act as gas vents, and an increase in gas permeability can be expected.

[0073] In this embodiment, when the overall porosity of the porous body 70 is set to 100%, the porosity of the spherical first pores 72A is 71.7%. The porosity of the irregularly shaped second pores 72B is 28.3%.

[0074] The porosity of the porous material 70 can be determined using the Archimedes method. Alternatively, the porosity of the porous material 70 can also be measured based on SEM images. Specifically, the porous material 70 is cut along an arbitrary direction, and the resulting cross-section is photographed with a scanning electron microscope. The resulting binarized image, obtained by binarizing the SEM image, can be analyzed using predetermined material development simulation software to determine the porosity of the porous material 70. When using the simulation software, the circular black areas scattered within the binarized image can be extracted as first pores 72A, thereby measuring the "area ratio of first pores 72A to the total area of ​​pores 72 contained in the porous material 70." Furthermore, the irregularly shaped black areas other than circular ones scattered within the binarized image can be extracted as second pores 72B, thereby measuring the "area ratio of irregularly shaped second pores 72B to the total area of ​​pores 72 contained in the porous material 70." Furthermore, regarding the method for measuring porosity, the porosity of the porous body 70 provided in the electrostatic chuck 100 of this embodiment may be measured using a mercury porosimeter. In that case, the porous body 70 to be measured is set in a He gas introduction unit, and the amount of He gas permeate under a pressure of 50 Torr is measured.

[0075] In the porous body 70, the porosity of the first pores 72A is greater than that of the second pores 72B. Of all the pores 72 formed in the porous body 70, it is preferable that the porosity of the spherical first pores 72A is greater than that of the amorphous second pores 72B. This increases the probability that closed spaces within the porous body 70 that do not communicate with the outside are connected via the first pores 72A. As a result, a stronger network of three-dimensionally interconnected gas vents 73 is formed, and a sufficient gas flow rate can be stably secured.

[0076] Next, an example of a manufacturing method for the electrostatic chuck 100 of this embodiment will be described. First, the manufacturing method for the holding substrate 10 that constitutes the electrostatic chuck 100 will be described with reference to Figures 4 and 5. Figures 4 and 5 are schematic explanatory diagrams showing the manufacturing method of the holding substrate 10. This manufacturing method for the holding substrate 10 applies a sheet lamination method using a green sheet (ceramic green sheet). In Figures 4 and 5, the lower side of the holding substrate 10 (second surface S2 side) corresponds to the upper side of each figure, and the upper side of the holding substrate 10 (first surface S1 side) corresponds to the lower side of each figure.

[0077] First, as shown in Figure 4(A), a first laminate 80a is formed by stacking multiple green sheets to form the plate-shaped member 11 of the holding substrate 10. A conductive layer 9 is formed on a predetermined green sheet that makes up the first laminate 80a, and such a green sheet is stacked on other green sheets.

[0078] The slurry for green sheets is obtained by mixing a mixture containing, for example, alumina powder, an acrylic binder, a dispersant, and a plasticizer, with an organic solvent, using a ball mill. This slurry is then formed into sheets using a casting device, and the resulting molded products are dried to obtain multiple green sheets.

[0079] Furthermore, the metallized paste for forming the conductive layer 9 is obtained, for example, by adding conductive powders such as tungsten or molybdenum to a mixture of alumina powder, an acrylic binder, and an organic solvent and kneading it. The conductive layer 9 is formed on a specific green sheet by printing this metallized paste, for example, using a screen printing device.

[0080] Next, as shown in Figure 4(B), a hole 81 for forming the first longitudinal channel 120 is formed at a predetermined location in the first laminate 80a. The hole 81 is cylindrical in shape and penetrates the first laminate 80a in the thickness direction (vertical direction). The hole 81 is formed at a predetermined location in the first laminate 80a using a known processing device (router, etc.). The hole 81 is a hole with a diameter of approximately 4 mm and a depth of approximately 5 mm processed on the green sheet. In this embodiment, the hole 81 is a circular hole with a diameter of approximately 4 mm and a depth of approximately 5 mm, but it is not limited to this size or shape.

[0081] Next, as shown in Figure 4(C), a porous paste 7 for forming a porous body 70 is filled into the pores 81 of the first laminate 80a. The porous paste 7 is obtained, for example, by kneading a mixture containing alumina powder, two types of pore-forming materials (carbon powder and resin beads), a binder, an organic solvent, etc. Since the porous paste 7 is more fluid than the second ceramic material 76, it spreads evenly throughout the pores 81, and the first ceramic material 75 is also placed near the interface 70c together with the porous paste 7. The fluidity of the porous paste 7 and each of the ceramic materials 75 and 76 is thought to be due to their shape, diameter, and the amount they are mixed in.

[0082] Mixed alumina powder 3 was obtained by preparing alumina powder 1 with a median particle size of 2.0 μm and alumina powder 2 with a median particle size of 20.0 μm, and mixing them in a ratio of 75:25 (volume ratio). Mixed pore-forming material 4 was obtained by preparing resin beads with a median particle size of 40.0 μm and carbon powder with a median particle size of 5.0 μm, and mixing them in a ratio of 70:30 (volume ratio). Mixed alumina powder 3 and mixed pore-forming material 4 were then mixed in a ratio of 20:80 (volume ratio) to obtain mixed powder 5. Furthermore, the obtained mixed powder and a commercially available binder for injection molding were mixed in a ratio of 78:22 (volume ratio) to obtain a paste-like unfired composition for porous materials (porous material paste 7).

[0083] The materials, sizes, and mixing ratios of alumina powder 1, alumina powder 2, mixed alumina powder 3, mixed pore-forming material 4, mixed powder 5, and the two types of pore-forming materials (carbon powder, resin beads) are not limited to those described above.

[0084] Methods for filling the porous material paste 7 into the pores 81 include, for example, using an injection molding apparatus or a screen printing apparatus. The first laminate 80a, in which the porous material paste 7 has been filled into the pores 81, is dried as appropriate.

[0085] Subsequently, as shown in Figure 5(D), the first laminate 80a and the second laminate 80b are stacked. The second laminate 80b consists of multiple green sheets stacked together. The second laminate 80b is provided with holes 82 for forming the second vertical channel 140 and grooves 83 for forming the horizontal channel 130 at predetermined locations. The laminate consisting of the first laminate 80a and the second laminate 80b consists of, for example, 20 green sheets stacked together, which are heat-pressed together. The outer circumference of the laminate may be cut as appropriate. The laminate is then machined to produce a disc-shaped molded body. The resulting molded body is then degreased and fired, and the degreased and fired molded body is further fired (final firing) to obtain a fired body.

[0086] Subsequently, a mask is placed on the surface of the fired body to shield the portion corresponding to the convex outer edge, and a shot blast is performed by projecting granular material such as ceramics, thereby forming a convex outer edge on the surface of the fired body. After that, the surface of the fired body is polished or otherwise processed to obtain a holding substrate 10 having a plate-like member 11, as shown in Figure 5(E).

[0087] The degreasing and main firing described above are carried out with the first laminate 80a and the second laminate 80b arranged such that the first surface S1 side of the holding substrate 10 is on the upper side and the second surface S2 side is on the lower side. In such degreasing and main firing, the porous paste 7 (unfired composition) filled in the holes 81 and the laminate of green sheets for forming plate-like members 11, etc., are fired simultaneously.

[0088] The manufacturing method for the base component 20 is basically the same as that for conventional products. Therefore, a detailed explanation will be omitted.

[0089] After the holding substrate 10 and the base member 20 are manufactured, they are joined together using the bonding material 30. The joining of the holding substrate 10 and the base member 20 using the bonding material 30 is basically the same as the joining in conventional products. Therefore, a detailed explanation is omitted. In this way, the electrostatic chuck 100 is manufactured.

[0090] The porous body 70 used in the electrostatic chuck 100 of this embodiment is designed to maintain the necessary gas flow rate while improving strength and voltage resistance.

[0091] <Effects of this embodiment> As described above, the electrostatic chuck 100 of this embodiment is a holding member 100 having a plate-shaped member 11 having a first surface S1 and a second surface S2 located on the opposite side of the first surface S1, and a gas passage 12 formed inside that connects a gas outlet 12b opening on the first surface S1 side and a gas inlet 12a opening on the second surface S2 side, and a porous body 70 disposed within the gas passage 12 of the plate-shaped member 11, wherein the porous body 70 is equipped with a skeletal base material 71 whose main component is an insulating material (alumina), and gas vents 73 are formed inside the skeletal base material 71 that allow gas to pass through from a second end face 70b on the side closer to the second surface S2 of the porous body 70 toward the first end face 70a on the opposite side of the second end face 70b, and the gas vents 73 are composed of a spherical first pore 72A and an amorphous second pore 72B which has a shape other than spherical.

[0092] For example, if a porous body 70 is formed using only angular ceramic particles, irregularly shaped second pores 72B are likely to be formed due to steric hindrance between the angular ceramic particles. At the same time, many closed spaces that do not communicate with the outside are likely to be formed within the porous body 70, which is thought to reduce the overall gas permeability. Therefore, for example, if a spherical pore-forming material is used, spherical first pores 72A will be formed, and by connecting the closed spaces with the first pores 72A, an increase in gas permeability can be expected. In this way, by configuring the gas vents 73 to include both first pores 72A and second pores 72B, gas permeability can be improved.

[0093] In the holding member 100 of this embodiment, the ceramic materials 75 and 76 constituting the skeletal base material 71 include a first ceramic material 75 having a predetermined particle size and a second ceramic material 76 having a larger particle size than the first ceramic material 75, wherein the second ceramic material 76 preferably has a polyhedral shape.

[0094] According to the above configuration, the porous body 70 is formed by including a relatively large-diameter second ceramic material 76 and a relatively small-diameter first ceramic material 75. As a result, adjacent particles of the second ceramic material 76 are connected by the first ceramic material 75, and second pores 72B are more easily formed between adjacent particles of the second ceramic material 76. When these second pores 72B communicate with the first pores 72A, the flow rate of gas that can circulate through the gas vents 73 of the porous body 70 increases. The porous body 70 formed after firing can balance dielectric strength and strength. Here, by including the relatively small-diameter first ceramic material 75, the sinterability during firing is improved, and the strength of the sintered porous body 70 can be ensured. Furthermore, by including the relatively large-diameter second ceramic material 76, dielectric breakdown at the grain boundaries of the sintered porous body 70 is prevented, and the dielectric strength is improved. Furthermore, because the second ceramic material 76 contained in the porous body 70 has a polyhedral shape, it is conceivable that the second pores 72B formed between the particles of the second ceramic material 76 become larger. When the second pores 72B become larger, the particles of the first ceramic material 75 can more easily enter the second pores 72B, and as a result of sintering in a way that connects the first ceramic material 75 and the second ceramic material 76, it is expected that the sinterability will improve. Therefore, the porous body 70 can ensure a sufficient gas flow rate.

[0095] In the holding member 100 of this embodiment, it is preferable that the average pore diameter of the first pore 72A is larger than the average pore diameter of the second pore 72B.

[0096] In the three-dimensional network structure of the gas vents 73 formed within the porous body 70, there are cases where gas vents 73 are formed by the communication of first pores 72A and second pores 72B. More specifically, in this case, for example, a spherical first pore 72A with an average pore diameter larger than the second pore 72B and an amorphous second pore 72B with an average pore diameter smaller than the first pore 72A may be formed, and these pores 72A and 72B may communicate with each other internally to form a gas vent 73. In this way, an increase in gas permeability can be expected. Furthermore, for example, by connecting a closed space with the first pore 72A, a gas vent can be formed, and an increase in gas permeability can be expected. In this way, by creating a difference in the average pore diameter, the enclosed space becomes the gas vent 73, and the gas flow rate through the gas vent 73 can be further increased compared to the case where there is no first pore 72A with an average pore diameter larger than the second pore 72B.

[0097] In the holding member 100 of this embodiment, it is preferable that the second pore 72B is composed of a plurality of angular ceramic particles.

[0098] The amorphous second pores 72B may be formed, for example, by steric hindrance such that angular ceramic particles are three-dimensionally bound to one another.

[0099] In the holding member 100 of this embodiment, it is preferable that the gas vent hole 73 includes a path in which the first hole 72A, the second hole 72B, and another first hole 72A are connected in this order.

[0100] With this configuration, in the three-dimensional network structure of gas vents 73 formed within the porous body 70, the arrangement of first pores 72A, second pores 72B, and other first pores 72A in this order facilitates communication between these pores 72A and 72B, and an increase in gas permeability can be expected. If only first pores 72A are present, only voids will be created within the porous body 70, but by sandwiching second pores 72B between multiple first pores 72A, an appropriate amount of void is created, avoiding excessive voids consisting only of first pores 72A. This appropriate amount of void becomes gas vents, and an increase in gas permeability can be expected.

[0101] In the holding member 100 of this embodiment, it is preferable that the porosity of the first pore 72A in the porous body 70 is greater than the porosity of the second pore 72B.

[0102] In the porous body 70, it is preferable that the porosity of the spherical first pores 72A is greater than that of the amorphous second pores 72B. By making the porosity of the first pores 72A greater than that of the second pores 72B, the probability that closed spaces within the porous body 70 that do not communicate with the outside are connected via the first pores 72A is increased. As a result, a stronger network of three-dimensionally interconnected gas vents 73 is formed, and a sufficient gas flow rate can be stably secured.

[0103] <Other Embodiments> (1) In the above embodiment, an example was given in which the gas outlet 12b and the gas inlet 12a are located at different positions in a plan view and communicate internally, but it is also possible to have a configuration in which the gas outlet 12b and the gas inlet 12a are located at the same position in a plan view and communicate internally.

[0104] (2) In the above embodiment, Figure 2 shows two gas inlets 12a and eight gas outlets 12b, but this is just an example, and the arrangement, size, number, and shape of the gas inlets 12a and gas outlets 12b of the electrostatic chuck 100 are not limited to the above embodiment.

[0105] (3) In the above embodiment, a holding member 100 having only a chuck electrode 40 as an electrode member has been described, but it is not limited to a chuck electrode 40 and may have multiple electrode members.

[0106] (4) The gas passage 60 for passing the inert gas does not have to be formed in the base member, and may be formed only in the holding substrate.

[0107] (5) The method for manufacturing the retaining member shown in the above embodiments is just one example, and it may be manufactured by other methods as long as it does not impair the purpose of the present invention.

[0108] (6) In the porous region R of this embodiment, the porous body 70 is arranged to fill each of the multiple first longitudinal channel sections 120 in the substrate-side gas channel 12. However, the arrangement position, size, number, and shape of the porous body 70 in the porous region R are examples only and are not limited to the above embodiment.

[0109] (7) In this embodiment, the porous body 70 is shown in which porous bodies 70 are arranged in all of the first vertical channel sections 120. However, the number of first vertical channel sections 120 and the number of porous bodies 70 arranged in the first vertical channel sections 120 may be different.

[0110] (8) In this embodiment, the position, range, and size of part A in Figure 3 are examples only and are not limited thereto. As long as the porous body 70 has a configuration that includes an interface with the porous body and a plate-like member, it is acceptable as long as it does not impair the purpose of the present invention. [Explanation of Symbols]

[0111] 7…Paste for porous materials, 9…Conductive layer, 10…Retaining substrate, 11…Plate-shaped member, 11A...Third ceramic material (skeleton base material), 12...Substrate-side gas channel (gas channel), 12a...Gas inlet, 12b...Gas outlet, 12c...Opening 20...Base member, 22...Base-side gas passage, 22a...Inlet, 22b...Outlet, 30...Jointing material, 31...Gas passage on the joining side, 32a...First opening, 32b...Second opening 40...Chuck electrode, 41...Through hole, 60...flow channel, 70... Porous body, 70a... Upper end surface (first end surface), 70b... Lower end surface (second end surface), 70c…interface 71... Skeleton base material, 72... Stomata, 72A... First stomata, 72B... Second stomata 73... Gas vent 75...First ceramic material, 76...Second ceramic material 80a...First layer, 80b...Second layer, 81...Hole, 82...Hole, 83...Groove 100...Electrostatic chuck (holding member), 111...peripheral wall part, 120...first vertical flow path section, 130...horizontal flow path section, 140...second vertical flow path section, V...space, S1...first surface, S2...second surface, S3...third surface, S4...fourth surface, W...wafer (object), R...porous region, G...gap

Claims

1. A plate-shaped member having a first surface and a second surface located on the opposite side of the first surface, with a gas flow path formed inside that connects a gas outlet opening on the first surface side and a gas inlet opening on the second surface side, A holding member having a porous body disposed within the gas flow path of the plate-shaped member, The porous body comprises a skeletal base material mainly composed of an insulating material, Gas vents are formed inside the skeletal substrate, allowing gas to pass through from the second end face on the side closer to the second surface of the porous body toward the first end face on the opposite side of the second end face. The holding member comprises a gas vent hole comprising a spherical first pore and an irregularly shaped second pore having a shape other than spherical.

2. The ceramic material constituting the skeletal substrate includes a first ceramic material having a predetermined particle size and a second ceramic material having a larger particle size than the first ceramic material. The holding member according to claim 1, wherein the second ceramic material has a polyhedral shape.

3. The holding member according to claim 1 or claim 2, wherein the average pore diameter of the first pore is greater than the average pore diameter of the second pore.

4. The retaining member according to claim 1 or claim 2, wherein the second pore is composed of a plurality of angular ceramic particles.

5. The holding member according to claim 1 or claim 2, wherein the gas vent includes a path through which the first vent, the second vent, and another first vent are connected in this order.

6. The retaining member according to claim 1, wherein the porosity of the first pore is greater than the porosity of the second pore in the porous body.

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