Holding device

Abstract

This holding device (100) is provided with a ceramic substrate (10) having a plate-shaped member (11) that includes a first surface (S1) of an object to be held (W) and is mainly composed of ceramic, and a gas flow path (12) formed inside the plate-shaped member (11), the gas flow path (12) has, in a portion thereof, a porous region (R) configured from a site in which a gas-permeable porous body (70) containing a plurality of pores (71) and containing a ceramic as a main component is disposed, the porous body (70) including, as the pores (71), a plurality of large-diameter pores (71a) having a central particle diameter of more than 20 [mu] m and 55 [mu] m or less, and a plurality of small-diameter pores (71b) having a central particle diameter of 3 [mu] m or more and 20 [mu] m or less. The volume ratio of the large-diameter pores (71a) included in the porous body (70) is greater than the volume ratio of the small-diameter pores (71b) included in the porous body (70).

Description

Technical Field

[0001] The invention relates to a retaining device. Background Art

[0002] As an example of a holding device for holding a wafer during semiconductor manufacturing, there is an electrostatic chuck as shown in Patent Document 1. This electrostatic chuck includes a ceramic substrate (chuck body) mainly made of insulating ceramic (e.g., alumina), and holds the wafer on the surface of the ceramic substrate by electrostatic attraction. The electrostatic attraction is generated by applying a voltage to a chuck electrode provided inside the ceramic substrate.

[0003] In this electrostatic chuck, helium is supplied between the ceramic substrate and the wafer to remove heat from the wafer during a plasma process such as plasma etching. Therefore, a flow path (pipeline) is formed inside the ceramic substrate of the electrostatic chuck for flowing a heat-conducting gas supplied from the outside toward the wafer. The flow path extends from the back side of the ceramic substrate to the surface side on which the wafer is mounted. Furthermore, a porous region composed of a porous body of an insulating ceramic material (such as alumina) is provided inside the flow path. The porous region is provided to allow helium to pass through and suppress the generation of abnormal discharge (plasma passing through the flow path) in the plasma process. Inside the porous body, a ventilation path for helium to pass through is formed in a mesh shape. The ventilation path is formed by pores, which are traces of burnt (disappeared) pore-forming materials (beads made of synthetic resin, carbon powder, etc.) in the form of particles during the manufacture (firing) of the porous body. That is, in the porous body, a plurality of pores are connected in a mesh shape, thereby forming a ventilation path.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 4959905

[0007] (Problems to be solved by the invention)

[0008] In recent years, in plasma processes, there is a demand for increasing plasma power for reasons such as increasing etching speed. Therefore, high plasma resistance is required for porous bodies in the flow path. However, depending on the configuration of pores in the porous body, the insulation of the porous body may be reduced, which becomes a problem. Summary of the invention

[0009] An object of the present invention is to provide a porous body holding device having a porous region constituting a gas flow path and having excellent plasma resistance.

[0010] (Methods for solving problems)

[0011] The means for solving the above-mentioned problems are as follows. <1> A holding device comprises a ceramic substrate, the ceramic substrate having a plate-like member with ceramic as a main component and a first surface including a holding object, and a gas flow path formed inside the plate-like member, wherein the gas flow path has a porous region in a portion thereof, the porous region is composed of a portion configured with a gas-permeable porous body with ceramic as a main component and including a plurality of pores, the porous body including a plurality of large-diameter pores with a central particle diameter greater than 20 μm and less than 55 μm and a plurality of small-diameter pores with a central particle diameter greater than 3 μm and less than 20 μm as the pores, and the volume ratio of the large-diameter pores contained in the porous body is greater than the volume ratio of the small-diameter pores contained in the porous body.

[0012] <2> According to the above <1> In the retaining device, the porosity of the porous body is greater than 60%.

[0013] <3> According to the above <1> or <2> In the above-mentioned retaining device, the porous body does not include an excessively large space formed by connecting the pores in one direction with a length of 120 μm or more.

[0014] (Effects of the Invention)

[0015] According to the present invention, it is possible to provide a holding device for a porous body having excellent plasma resistance and including a porous region constituting a gas flow path. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is an explanatory diagram schematically showing the general structure of the holding device according to the first embodiment.

[0017] Figure 2 This is a cross-sectional view schematically showing the internal structure of the holding device according to the first embodiment.

[0018] Figure 3 This is a cross-sectional view of the holding device in which a portion of the substrate-side gas flow path is enlarged.

[0019] Figure 4 This is an explanatory diagram schematically showing a part of the internal structure of a porous body.

[0020] Figure 5 This is a binary image of the cross section of the porous body.

[0021] Figure 6 This is an enlarged cross-sectional view of a portion of a substrate-side gas flow path of a holding device according to a second embodiment. DETAILED DESCRIPTION

[0022] <Implementation Method 1>

[0023] Below, refer to Figure 1 to Figure 5The holding device 100 of Embodiment 1 is described. The holding device 100 is an electrostatic chuck that absorbs and holds an object (e.g., a wafer W) by electrostatic attraction while heating the object (e.g., a wafer W) to a predetermined processing temperature (e.g., 50° C. to 400° C.). The electrostatic chuck is used as a workbench for mounting the wafer W in a process of etching using plasma in a decompressed chamber, for example.

[0024] Figure 1 1 is an explanatory diagram schematically showing the general structure of the holding device 100 according to the first embodiment. Figure 2 1 is a cross-sectional view schematically showing the internal structure of the holding device 100 of the first embodiment. The holding device 100 includes a disc-shaped ceramic substrate 10 and a disc-shaped base member 20 larger than the ceramic substrate 10. For example, when the ceramic substrate 10 is in the shape of a disc with a diameter of 300 mm and a thickness of 3 mm, the base member 20 is set to be in the shape of a disc with a diameter of 340 mm and a thickness of 20 mm. In addition, positioning portions (concave and convex, etc.) for mutual alignment can also be provided on the ceramic substrate 10 and the base member 20, respectively.

[0025] The ceramic substrate 10 and the base member 20 are stacked on each other in the vertical direction, with the ceramic substrate 10 arranged on the upper side and the base member 20 arranged on the lower side. The ceramic substrate 10 and the base member 20 are bonded to each other with a bonding material 30 interposed therebetween.

[0026] The ceramic substrate 10 has: a first surface S1 of a substantially circular shape, which is arranged on the upper side; a second surface S2 of a substantially circular shape, which is arranged on the opposite side (i.e., the lower side) of the first surface S1 and is opposite to the base member 20. The base member 20 has: a third surface S3 of a substantially circular shape, which is arranged on the upper side and is opposite to the second surface S2 of the ceramic substrate 10; and a fourth surface S4 of a substantially circular shape, which is arranged on the opposite side (i.e., the lower side) of the third surface S3. The above-mentioned bonding material 30 is sandwiched between the second surface of the ceramic substrate 10 and the third surface S3 of the base member 20, and is in a state of spreading in layers.

[0027] The ceramic substrate 10 includes a disk-shaped plate member 11 and a substrate-side gas flow path 12 formed inside the plate member 11. The upper surface of the plate member 11 is a first surface S1 of the ceramic substrate 10. The lower surface of the plate member 11 is a second surface S2 of the ceramic substrate 10.

[0028] The plate-shaped member 11 is a plate-shaped (disk-shaped) insulating member whose main component is ceramic. In this specification, "main component" refers to the component with the largest content. The plate-shaped member 11 of this embodiment is made of aluminum oxide (Al 2 O 3) In addition, in other embodiments, the plate-shaped member 11 may also be composed of other ceramics such as aluminum nitride (AlN).

[0029] The substrate-side gas flow path (an example of a gas flow path) 12 constitutes a part of the flow path 60 for flowing the inert gas (for example, helium as a heat transfer fluid) provided by the retaining device 100. The substrate-side gas flow path 12 is formed inside the plate-like member 11 of the ceramic substrate 10. The substrate-side gas flow path 12 includes an inlet 12a opened on the second surface S2 of the ceramic substrate 10 and an outlet 12b opened on the first surface S1. The substrate-side gas flow path 12 is arranged as a whole in the form of passing through the interior of the plate-like member 11 from the inlet 12a toward the outlet 12b. Therefore, when the inert gas is supplied from the inlet 12a, the inert gas passes through the substrate-side gas flow path 12 and is finally discharged to the outside from the outlet 12b. Such a substrate-side gas flow path 12 includes a transverse flow path 121, a first longitudinal flow path 122, and a second longitudinal flow path 123.

[0030] The lateral flow path 121 is formed inside the plate-like member 11 along a direction perpendicular to the thickness direction of the plate-like member 11 (ie, along the first surface S1, etc., Figure 2 left and right direction) extending flow path.

[0031] The first longitudinal flow path 122 is a flow path that extends in the thickness direction of the plate-like member 11 inside the plate-like member 11 and connects the inlet 12 a and the lateral flow path 121 .

[0032] The second longitudinal flow path 123 is a flow path extending in the thickness direction of the plate-shaped member 11 inside the plate-shaped member 11 and connecting the outlet 12b to the transverse flow path 121. In the case of this embodiment, a plurality of second longitudinal flow paths 123 are connected to one transverse flow path 121. As described later, the second flow path 123 includes a receiving chamber 123a for receiving a porous body and a discharge path 123b connected to the receiving chamber 123a and including the outlet 12b.

[0033] The ceramic substrate 10 further includes a chuck electrode 40 and a heater electrode 50 .

[0034] The chuck electrode 40 is formed of a conductive material (such as tungsten, molybdenum, platinum, etc.) in a layered (planar) shape. Figure 2 As shown, the chuck electrode 40 is arranged on the first surface S1 side inside the ceramic substrate 10 (plate-shaped member 11). The chuck electrode 40 is generally circular when viewed from the top and bottom directions. When a DC high voltage is applied to the chuck electrode 40 from a power source (not shown), an electrostatic attraction is generated, and the wafer W is adsorbed and fixed to the first surface S1 of the ceramic substrate 10 by the electrostatic attraction. In addition, a known power supply terminal (not shown) is electrically connected to the chuck electrode 40.

[0035] When a voltage is applied to the heater electrode 50 and a current flows, the heater electrode 50 generates heat, thereby heating the wafer W held on the first surface S1 of the ceramic substrate 10. Figure 2 As shown, the heating electrode 50 is arranged inside the ceramic substrate 10 (plate-like member 11) at a position lower than the chuck electrode 40 (i.e., the second surface S2 side). The heating electrode 50 is composed of a plurality of electrodes, and when viewed from the top and bottom directions, a concentric or spiral pattern is formed as a whole. The heater electrode 50 is formed into a layer (planar shape) of a conductive material (aluminum, nickel, copper, stainless steel, etc.). A well-known power supply terminal (not shown) is electrically connected to each heater electrode 50. By appropriately adjusting the current supplied to each heating electrode 50, the temperature of the semiconductor wafer W held by the first surface S1 can be controlled. In addition, the ceramic substrate 10 may also have a temperature measuring element (such as a thermistor) and the like.

[0036] like Figure 1 and Figure 2 As shown in FIG. 1 , a plurality of outlets 12 b are provided on the first surface S1 of the ceramic substrate 10. The outer peripheral edge of the first surface S1 protrudes slightly upward compared to the inner portion thereof and is formed into a circular ring shape. Therefore, when the wafer W is adsorbed and held on the first surface S1, as shown in FIG. Figure 2 As shown, a gap G is formed between the semiconductor wafer W and a portion inside the first surface S1 .

[0037] The base member 20 is mainly composed of, for example, metal (aluminum, aluminum alloy, etc.), a composite of metal and ceramic (Al—SiC), or ceramic (SiC).

[0038] A cooling medium flow path 21 is provided inside the base member 20. The plasma heat is cooled by flowing a cooling medium (e.g., a fluorine-based inert liquid, water, etc.) in the cooling medium flow path 21. In addition, when the cooling medium flows in the cooling medium flow path 21, the base member 20 is cooled, and the ceramic substrate 10 is cooled by heat transfer (heat dissipation) between the base member 20 and the ceramic substrate 10 via the bonding material 30. As a result, the wafer W held on the first surface S1 of the ceramic substrate 10 is cooled. By appropriately adjusting the flow rate of the cooling medium in the cooling medium flow path 21, the temperature of the semiconductor wafer W held on the first surface S1 can be controlled.

[0039] A base-side gas flow path 22 constituting a part of the flow path 60 is provided inside the base member 20. The base-side gas flow path 22 is in the form of a through hole extending in the thickness direction of the base member 20 as a whole, and includes an inlet 20a opened at the fourth surface S4 of the base member 20 and an outlet 20b opened at the third surface S3. The inlet 20a constitutes the inlet of the base-side gas flow path 22, and constitutes the inlet of the entire flow path 60 provided in the holding device 100.

[0040] 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 bonding agent. The bonding material 30 preferably has high adhesion to both the ceramic substrate 10 and the base member 20 and has high heat resistance and thermal conductivity.

[0041] The bonding-side gas flow path 31 constituting a part of the flow path 60 is also formed in the bonding material 30. The bonding-side gas flow path 31 is constituted by a hole penetrating the layered bonding material 30 in the thickness direction.

[0042] The flow path 60 supplies an inert gas (helium or the like) to the first surface S1 side of the holding device 100. A plurality of outlets 12b of the flow path 60 are provided on the first surface S1, and the inert gas is supplied to the first surface S1 side in the form of discharging the inert gas from each outlet 12b. As described above, such a flow path 60 includes a susceptor-side gas flow path 22, a bonding-side gas flow path 31, and a substrate-side gas flow path 12.

[0043] A plurality of inlets 22a of the flow path 60 are provided on the fourth surface S4 of the base member 20. When an inert gas ( Figure 2 When the inert gas is directed to the substrate, as shown by the arrow H in the figure, it passes through the base side gas flow path 22, the bonding side gas flow path 31 and the substrate side gas flow path 12 connected to each inlet 22a in sequence, and is finally discharged from a plurality of outlets 12b provided on the first surface S1.

[0044] The outlet 22b of the base-side gas flow path 22 is connected to the opening on the lower side (base member 20 side) of the bonding-side gas flow path 31. In addition, the opening on the upper side (ceramic substrate 10 side) of the bonding-side gas flow path 31 is connected to the inlet 12a of the substrate-side gas flow path 12. A plurality of inlets 12a of the substrate-side gas flow path 12 are provided on the second surface S2 of the ceramic substrate 10.

[0045] The first longitudinal flow path 122 having the inlet 12a of the substrate-side gas flow path 12 on the upstream side is connected to the transverse flow path 121 on the downstream side. In addition, a plurality of second longitudinal flow paths 123 are connected to the transverse flow path 121. That is, the substrate-side gas flow path 12 is formed in a shape that branches into a plurality of gas flow paths from the upstream side toward the downstream side inside the ceramic substrate 10 (plate-shaped member 11).

[0046] Figure 3 FIG. 1 is a cross-sectional view of the holding device 100 in which a portion of the substrate-side gas flow path 12 is enlarged. Figure 3 As shown, the second vertical flow channel 123 of the substrate-side gas flow channel 12 includes a storage chamber 123 a and a discharge channel 123 b .

[0047] The receiving chamber 123a is a part of the second longitudinal flow path 123, and its inner diameter is set larger than that of the second longitudinal flow path 123 located on its upstream side. The receiving chamber 123a is formed inside the plate-like member 11 of the ceramic substrate 10. That is, the receiving chamber 123a is formed by alumina (ceramic) constituting the plate-like member 11. The receiving chamber 123a has a roughly cylindrical space inside it. And, it is shaped so that the porous body 70 is arranged without gaps in the space (that is, in the receiving chamber 123a). In this way, the portion of the substrate-side gas flow path 12 where the porous body 70 is arranged in the receiving chamber 123a of the second longitudinal flow path 123 is called the "porous region R".

[0048] The discharge path 123b is a flow path connected to the downstream side of the receiving chamber 123a, and is in the form of a through hole extending in the thickness direction of the ceramic substrate 10 (plate-like member 11). A plurality of discharge paths 123b are connected to one receiving chamber 123a. Each discharge path 123b is of a smaller diameter (smaller diameter) than the receiving chamber 123a and the second longitudinal flow path 123 located on its upstream side. The open end on the downstream side of each such discharge path 123b becomes the outlet 12b of the flow path 60. The porous region R is formed on the first surface S1 side, so when the first surface S1 is viewed from above, the porous body 70 is exposed from each outlet 12b.

[0049] The porous body 70 is a gas-permeable member mainly composed of insulating ceramics and including a plurality of pores 71 . Figure 4 : is an explanatory diagram schematically showing a part of the internal structure of the porous body 70. The porous body 70 is cylindrical as a whole, and a ventilation path for passing an inert gas is formed in a mesh shape inside. The ventilation path is composed of a member formed by connecting a plurality of pores 71 to each other in the porous body 70. The pores 71 are formed as traces of burning (disappearance) of a pore-forming material in a particle shape during the manufacture (firing) of the porous body 70. In addition, in this specification, the skeleton part other than the pores 71 in the porous body 70 is referred to as aggregate 72.

[0050] In the present embodiment, the porous body 70 is made of aluminum oxide (Al 2 O 3 ) as a main component. In other embodiments, the porous body 70 may also be mainly composed of other ceramics such as aluminum nitride (AlN).

[0051] The porous body 70 includes a plurality of large-diameter pores 71a having a central particle diameter greater than 20 μm and less than 55 μm and a plurality of small-diameter pores 71b having a central particle diameter greater than 3 μm and less than 20 μm as pores 71. In addition, the central particle diameter of the large-diameter pores 71a is preferably greater than 25 μm and less than 55 μm. In addition, the central particle diameter of the small-diameter pores 71b is preferably greater than 10 μm and less than 20 μm.

[0052] In this specification, the center particle diameter of the pores 71 is obtained as a value obtained by dividing the "center particle diameter of the pore-forming material" by the cut rate. The cut rate is the ratio of shrinkage during firing of the ceramic molded body (unsintered molded product described later) used to manufacture the porous body 70. The center particle diameter of the pore-forming material is the particle diameter at which the cumulative degree of the particle size distribution measured by the light scattering method is 50% in terms of volume percentage.

[0053] As the pore-forming material, for example, beads made of synthetic resin, carbon powder, etc. are used. In addition, as a particle-shaped pore-forming material, for example, it can be spherical (perfect spherical) or polygonal. It should be noted that the center particle diameter of the pore-forming material is calculated assuming that the pore-forming material is a perfect spherical material.

[0054] In the present embodiment, the volume ratio of the large-diameter pores 71a included in the porous body 70 is set to be larger than the volume ratio of the small-diameter pores 71b included in the porous body 70. If set in this way, when the holding device 100 is used (for example, when a plasma process such as plasma etching is performed on an object while the object is held), the air permeability in the porous region R of the substrate-side gas flow path (gas flow path) 12 can be ensured, and the insulation of the porous region R can be ensured.

[0055] The volume ratio of the large-diameter pores 71a contained in the porous body 70 is preferably 60% by volume or more and 90% by volume or less, and more preferably 65% ​​by volume or more and 80% by volume or less. The volume ratio of the large-diameter pores 71a contained in the porous body 70 can be set to a desired value by appropriately adjusting the amount of pore-forming material used to form the large-diameter pores 71a when manufacturing the porous body 70.

[0056] The volume ratio of the small-diameter pores 71b contained in the porous body 70 is preferably 10% by volume or more and 40% by volume or less, and more preferably 20% by volume or more and 35% by volume or less. The volume ratio of the small-diameter pores 71b contained in the porous body 70 can be set to a desired value by appropriately adjusting the amount of pore-forming material used to form the small-diameter pores 71b when manufacturing the porous body 70.

[0057] If the volume ratio of the large-diameter pores 71a and the small-diameter pores 71b included in the porous body 70 is within the above range, the small-diameter pores 71a are easy to enter between the adjacent large-diameter pores 71a in the porous body 70, and as a result, it is possible to suppress the excessive connection of the plurality of large-diameter pores 71a in a straight line in one direction. If the volume ratio of the large-diameter pores 71a included in the porous body 70 is too large, the possibility that the plurality of large-diameter pores 71a are continuously adjacent in a straight line in the porous body 70 increases. In addition, if the volume ratio of the small-diameter pores 71b included in the porous body 70 is too large, a sufficient ventilation path cannot be formed in the porous body 70, and the air permeability decreases.

[0058] The “volume ratio of the large-diameter pores 71a included in the porous body 70” is the ratio of the volume of all the large-diameter pores 71a to the volume of all the pores of the porous body 70 (100%). In addition, the “volume ratio of the small-diameter pores 71b included in the porous body 70” is the ratio of the volume of all the small-diameter pores 71b to the volume of all the pores of the porous body 70 (100%). It should be noted that the volume of the total pores of the porous body 70 is calculated from the porosity of the porous body 70 and the volume of the porous body 70.

[0059] In the present embodiment, the porosity of the porous body 70 is not particularly limited as long as the purpose of the present invention is not impaired, and is preferably 60% or more, for example. The porosity of the porous body 70 is obtained using the Archimedean method. If the porosity of the porous body 70 is within such a range, when the holding device 100 is used (during plasma processing), the air permeability in the porous region R of the substrate-side gas flow path (gas flow path) 12 can be ensured, and the insulation of the porous region R can be ensured.

[0060] In addition, in the present embodiment, the porous body 70 preferably does not include an excessive space formed by connecting the pores 71 in one direction with a length of 120 μm or more. The "one direction" mentioned here is an arbitrarily determined direction in the porous body 70. Since the porous body 70 does not include such an excessive space, the insulation of the porous body 70 is improved, and as a result, when the holding device 100 is used (during plasma treatment), the insulation breakdown of the porous body 70 caused by the excessive space is suppressed.

[0061] In addition, the one direction is preferably a direction substantially perpendicular to the first surface S1 of the holder 100 (i.e., a thickness direction of the holder 100). If the porous body 70 is set to not include an excessively large space formed by the pores 71 being connected to each other for a length of 120 μm or more in the direction substantially perpendicular to the first surface S1 of the holder 100 (one direction), insulation breakdown of the porous body 70 during use of the holder 100 (during a plasma process) can be more effectively suppressed.

[0062] Here, refer to Figure 5 A method for confirming the presence or absence of an excessive space in the porous body 70 will be described. Figure 5 This is a binary image of the cross section of the porous body 70. First, the porous body 70 is cut in an arbitrary direction, and the obtained cross section is photographed using a scanning electron microscope (SEM: Scanning Electron Microscope) (magnification: 200 times). The obtained SEM image is binarized using commercially available material development simulation software, and the excessively large spaces formed by the pores 71 connected in one direction with a length of more than 120 μm are extracted from the obtained binary image. Figure 5 In the binary image shown, there is no excessive space, and the maximum stays in one direction ( Figure 5 A space X with a length of 111 μm was observed in the vertical direction. Figure 5 The binary image shown corresponds to a SEM image of a cross-section obtained by cutting the porous body 70 in the holding device 100 in a direction substantially perpendicular to the first surface S1. Figure 5 The up-down direction corresponds to a direction substantially orthogonal to the first surface S1.

[0063] In the present embodiment, a ventilation path is formed in the porous body 70 by combining the large-diameter pores 71 a and the small-diameter pores 71 b so as not to form a space (excessive space) extending long in a specific direction.

[0064] Here, a method for manufacturing the holding device 100 of the present embodiment will be described. The method for manufacturing the holding device 100 is, for example, as follows. First, the ceramic substrate 10 and the base member 20 are prepared.

[0065] The method for producing the ceramic substrate 10 is as follows. First, a mixture of alumina powder, an acrylic binder, an appropriate amount of a dispersant and a plasticizer, and an organic solvent is further added to the mixture by a ball mill to produce a green sheet slurry. The green sheet slurry is formed into a sheet by a casting device, and then the obtained molded product is dried to produce a plurality of green sheets.

[0066] In addition, conductive powders such as tungsten and molybdenum are added to a mixture of alumina powder, acrylic binder, and organic solvent and kneaded to prepare a metallization paste. The metallization paste is printed using, for example, a screen printing device to form an unsintered conductor layer that will later become a heater electrode, a clamping electrode, etc. on each specific green sheet.

[0067] Furthermore, holes and grooves that become the substrate-side gas flow path 12 and the like are formed on each specific green sheet. At this time, holes for forming the storage chamber 123a are formed on specific green sheets.

[0068] In addition, a mixture of alumina powder, a pore-forming material, and a binder is molded to obtain an unsintered molded product for a porous body 70 of a predetermined size. As a pore-forming material, beads made of synthetic resin, carbon powder, etc. are used. The particle size of the alumina powder (ceramic powder) is appropriately adjusted. Then, the unsintered molded product is filled into a hole portion provided in a specific green sheet for forming the receiving chamber 123a. At this time, the unsintered molded product for the porous body 70 can also be installed in the hole portion of the green sheet using an adhesive or the like.

[0069] Next, multiple sheets (e.g., 20 sheets) of the green sheets are heat-pressed in an overlapping state, and the outer periphery is cut as needed to produce a stack of green sheets. A disc-shaped molded body is produced by cutting the green sheet stack, and the molded body is degreased, and then the degreased molded body is fired to produce a fired body. When such a molded body is fired, the unsintered molded article used for the porous body 70 is also fired to form the porous body 70. The pore-forming material in the unsintered molded article is burned (disappeared) during firing, thereby forming a ventilation path that is three-dimensionally connected in a mesh shape inside the porous body 70.

[0070] Next, a mask is placed on the surface of the obtained sintered body to cover the portion corresponding to the convex outer peripheral edge, and shot peening of ceramic particles is performed, thereby forming a convex outer peripheral edge on the surface of the sintered body. Then, the surface of the sintered body is ground to obtain a ceramic substrate 10.

[0071] The method for manufacturing the base member 20 is basically the same as the method for manufacturing a conventional product, and therefore, a detailed description thereof will be omitted.

[0072] After the ceramic substrate 10 and the base member 20 are separately manufactured, they are bonded together using the bonding material 30. The bonding of the ceramic substrate 10 and the base member 20 using the bonding material 30 is basically the same as that in the conventional product. Therefore, the holding device 100 is manufactured in a manner that omits detailed description thereof.

[0073] As described above, in the holding device 100 of the present embodiment, the volume ratio of the large-diameter pores 71a included in the porous body 70 is set to be larger than the volume ratio of the small-diameter pores 71b included in the porous body 70. If set in this way, when the holding device 100 is used (for example, when a plasma process such as plasma etching is performed on an object while the object is held), the air permeability in the porous region R of the substrate-side gas flow path (gas flow path) 12 can be ensured, and the insulation of the porous region R can be ensured. Such a holding device 100 includes the porous body 70 having excellent plasma resistance, which constitutes the porous region R of the substrate-side gas flow path (gas flow path) 12.

[0074] In addition, in this embodiment, if the porosity of the porous body 70 is greater than 60%, when using the holding device 100 (during plasma processing), the permeability in the porous region R of the substrate side gas flow path (gas flow path) 12 is ensured, and the insulation of the porous region R is ensured.

[0075] In addition, in the present embodiment, the porous body 70 preferably does not include an excessive space formed by connecting the pores 71 in one direction with a length of 120 μm or more. Since the porous body 70 does not include such an excessive space, the insulation of the porous body 70 is improved, and as a result, when the holding device 100 is used (during plasma treatment), the insulation breakdown of the porous body 70 caused by the excessive space is suppressed.

[0076] <Implementation Method 2>

[0077] Next, refer to Figure 6 A holding device 100B according to the second embodiment will be described. Figure 6 FIG. 1 is a cross-sectional view of a portion of the substrate-side gas flow path 12B of the holding device 100B of the second embodiment, which is enlarged. The basic structure of the holding device 100B of the present embodiment is the same as that of the first embodiment. Figure 6 In the present invention, for the parts corresponding to the first embodiment, the same reference numerals as those in the first embodiment are further denoted by reference numerals with reference numerals "B" added thereto, and detailed descriptions thereof are omitted.

[0078] The holding device 100B of this embodiment is similar to the first embodiment and includes a disc-shaped ceramic substrate 10B, a disc-shaped base member 20B, and a layered bonding material 30B interposed therebetween. The ceramic substrate 10B includes a plate-shaped member 11B, a substrate-side gas flow path 12B formed therein, a chuck electrode 40B, and a heater electrode 50B.

[0079] The substrate-side gas flow path 12B constitutes a part of a flow path 60B through which an inert gas (helium gas) flows. Figure 6 Horizontal flow channel 121B, first vertical flow channel 122B and second vertical flow channel 123B are shown in FIG.

[0080] The second longitudinal flow path 123AB is provided with a receiving chamber 123Ba for receiving the porous body 70B and a discharge path 123Bb connected to the receiving chamber 123Ba and including an outlet 12Bb. The outlet 12Bb is arranged on the first surface SAB of the ceramic substrate 10B. In addition, the portion where the porous body 70B is arranged in the receiving chamber 123Ba becomes a porous region RB.

[0081] In the case of this embodiment, a porous region RB is also provided in the first longitudinal flow path 122B. The porous region RB is provided near the inlet 12Ba opened on the second surface SB2. A receiving chamber 122Ba for receiving the porous body 70B is provided in the first longitudinal flow path 122B, and the portion where the porous body 70B is arranged in the receiving chamber 122Ba becomes the porous region RB in the first longitudinal flow path 122B.

[0082] The porous body 70B of this embodiment is the same as that of Embodiment 1. Therefore, in this embodiment, the volume ratio of large-diameter pores included in the porous body 70B is also set to be larger than the volume ratio of small-diameter pores included in the porous body 70B. In addition, the porosity of the porous body 70B is set to be 60% or more.

[0083] In the present embodiment, the porous body 70B is set to include no excessively large space therein in which pores are connected in one direction with a length of 120 μm or more.

[0084] As described above, in the holding device 100B of the present embodiment, the porous region 70B for plasma countermeasures may be provided in a part of the substrate-side gas flow path 12B arranged near the second surface SB2 side.

[0085] The holding device 100B of the present embodiment, similarly to the first embodiment, includes a porous body 70B having excellent plasma resistance and constituting a porous region RB of a substrate-side gas flow path (gas flow path) 12B.

[0086] <Other Implementation Methods>

[0087] The present invention is not limited to the embodiments described in the above description and drawings, and for example, the following embodiments are also included in the technical scope of the present invention.

[0088] (1) In the above embodiment, the ceramic of the porous body and the ceramic of the plate-like member in the ceramic substrate are composed of the same type of ceramic, but as long as the purpose of the present invention is not impaired, for example, the ceramic of the porous body and the ceramic of the plate-like member may be composed of different types of ceramic. For example, the porous body may be composed of aluminum oxide and the plate-like member may be composed of aluminum nitride, or the porous body may be composed of aluminum nitride and the plate-like member may be composed of aluminum oxide.

[0089] (2) In the above embodiment, the flow path for passing the inert gas is also formed in the base member. However, in other embodiments, the flow path may not be formed in the base member, but may be formed only in the ceramic substrate.

[0090] (3) The method for manufacturing the holding device shown in the above embodiment is an example, and the holding device may be manufactured by other methods as long as the purpose of the present invention is not impaired.

[0091] Hereinafter, the present invention will be further described based on examples. However, the present invention is not limited to these examples at all.

[0092] [Example 1]

[0093] The ceramic substrate of Example 1 was produced by basically the same method as in the above-mentioned Embodiment 1 except that the green molded product for the porous body was formed under the following conditions.

[0094] Alumina powder, a pore-forming material and a binder are mixed, and the mixture is formed by a predetermined forming device to obtain an unsintered molded product for a cylindrical porous body. The pore-forming material is composed of a pore-forming material for large-diameter pores (average particle size 40 μm) and a pore-forming material for small-diameter pores (average particle size 5 μm). The pore-forming material for large-diameter pores is mixed with 280 parts by volume relative to 100 parts by volume of alumina powder. In addition, the pore-forming material for small-diameter pores is mixed with 120 parts by volume relative to 100 parts by volume of alumina powder. The obtained unsintered molded product for a porous body is filled into the above-mentioned hole portion of the green sheet having a hole portion for forming a receiving chamber in the same manner as in the above-mentioned embodiment 1.

[0095] [Example 2]

[0096] As pore-forming materials, pore-forming material for large-diameter pores (average particle size 27 μm) and pore-forming material for small-diameter pores (average particle size 20 μm) are used, and the amount of pore-forming material for large-diameter pores is 280 parts by volume, and the amount of pore-forming material for small-diameter pores is 120 parts by volume. Except for this, the ceramic substrate of Example 2 is prepared in the same manner as Example 1.

[0097] [Example 3]

[0098] As pore-forming materials, pore-forming material for large-diameter pores (average particle size 240 μm) and pore-forming material for small-diameter pores (average particle size 20 μm) are used, and the amount of pore-forming material for large-diameter pores is 280 parts by volume, and the amount of pore-forming material for small-diameter pores is 120 parts by volume. Except for this, the ceramic substrate of Example 3 is prepared in the same manner as Example 1.

[0099] 〔Measurement of transmittance〕

[0100] The transmittance (air permeability) of each porous body included in the ceramic substrates of Examples 1 to 3 was measured by the method described below.

[0101] The unsintered molded product for the porous body was injection molded in a hole with a diameter of about 3.5 mm and a depth of about 5 mm processed on the green sheet, cut into a predetermined bracket size, degreased, and sintered to obtain a sample. Then, the sample was placed in a He gas introduction unit and the He gas permeability at a pressure of 50 Torr was measured.

[0102] The results of the measurements showed that the transmittance of Example 1 was 3.9 sccm, the transmittance of Example 2 was 10.1 sccm (relative to Example 1, the transmittance increased by 159%), and the transmittance of Example 3 was 8.1 sccm (relative to Example 1, the transmittance increased by 109%).

[0103] 〔Determination of porosity〕

[0104] The porosity in the porous bodies of Examples 1 to 3 was measured. Specifically, the porosity was measured based on the SEM images (binarized images) of the cut surfaces obtained by cutting the porous bodies of each Example in the up-down direction using commercially available material development simulation software. As a result, the porosity of the porous body of Example 1 was 72%, the porosity of the porous body of Example 2 was 70%, and the porosity of the porous body of Example 3 was 71%.

[0105] 〔Volume ratio of pores〕

[0106] In the porous bodies of Examples 1 to 3, “the volume ratio of large-diameter pores included in the porous body” and “the volume ratio of small-diameter pores included in the porous body” are as follows.

[0107] In the case of Example 1, the volume ratio of large-diameter pores is 44 volume %, and the volume ratio of small-diameter pores is 19 volume %.

[0108] In the case of Example 2, the volume ratio of large-diameter pores is 39 volume %, and the volume ratio of small-diameter pores is 16 volume %.

[0109] In the case of Example 3, the volume ratio of large-diameter pores is 45 volume %, and the volume ratio of small-diameter pores is 19 volume %.

[0110] 〔Confirmation of whether there is too much space〕

[0111] The presence or absence of excessive spaces in the porous bodies of Examples 1 to 3 was confirmed by using the method using the above-mentioned SEM images. Excessive spaces were extracted based on the SEM images (binarized images) of the cut surfaces obtained by cutting the porous bodies of each Example in the up-down direction. As a result, in Examples 1 to 3, no excessive spaces were detected in which pores were connected in one direction with a length of 120 μm or more.

[0112] Description of Reference Numerals

[0113] 100 ... holding device, 10 ... ceramic substrate, 11 ... plate-shaped member, 12 ... substrate-side gas flow path (gas flow path), 12a ... inlet, 12b ... outlet, 121 ... lateral flow path, 122 ... first longitudinal flow path, 123 ... second longitudinal flow path, 20 ... base member, 21 ... cooling medium flow path, 22 ... base-side gas flow path, 22a ... inlet, 22b ... outlet, 30 ... bonding material, 31 ... bonding-side gas flow path, 40 ... chuck electrode, 50 ... heater electrode, 60 ... flow path, 70 ... porous body, 71 ... pores, 71a ... large-diameter pores, 71b ... small-diameter pores, 72 ... aggregate, G ... gap, W ... object (wafer), R ... porous region, S1 ... first surface, S2 ... second surface, S3 ... third surface, S4 ... fourth surface

Claims

1. A holding device, comprising a ceramic substrate, the ceramic substrate comprising: a plate-shaped member including a first surface of a holding object and having ceramic as a main component; and a gas flow path formed inside the plate-shaped member, wherein: The gas flow path has a porous region in a part thereof, and the porous region is composed of a portion where a gas-permeable porous body having a ceramic as a main component and a plurality of pores is arranged. The porous body includes, as the pores, a plurality of large-diameter pores having a center particle diameter greater than 20 μm and less than 55 μm and a plurality of small-diameter pores having a center particle diameter greater than 3 μm and less than 20 μm. The volume ratio of the large-diameter pores contained in the porous body is greater than the volume ratio of the small-diameter pores contained in the porous body.

2. The holding device according to claim 1, wherein: The porous body has a porosity of 60% or more.

3. The holding device according to claim 1 or 2, wherein: The porous body does not include an excessively large space in which the pores are connected in one direction with a length of 120 μm or more.

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