Holding device and porous body with dense layer

Abstract

To provide a holding device and the like equipped with a porous body that improves a gas flow rate while maintaining strength.SOLUTION: A holding device 100 includes a holding substrate 10 which includes a plate-shaped member 11 that has a first surface S1 and a second surface S2 disposed on the opposite side to the first surface S1, a gas flow path 120 that has a gas outlet 12b opened on the first surface S1 side and a gas inlet 12a opened on the second surface S2 side and is formed inside the plate-shaped member 11, and a porous body 70 that is disposed in the gas flow path 120. In the holding device 100, the porous body 70 includes a skeletal base material 71 made mainly of an insulating material. The skeletal base material 71 has a through-hole group 720 formed of a plurality of through-holes 72. The through-hole group 720 has peaks in a pore size distribution measured by an Hg porosimeter each in a range of less than 5 μm and a range of 5 μm or more and 15 μm or less.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a holding device and a porous body with a dense layer.

Background Art

[0002] As an example of a holding device for holding a wafer (semiconductor wafer) when manufacturing a semiconductor, an electrostatic chuck can be mentioned (see Patent Document 1). The electrostatic chuck includes a holding substrate (ceramic substrate) mainly made of insulating ceramics (for example, alumina), and the wafer is held on the surface of the holding substrate by electrostatic attraction. The electrostatic attraction is generated when a voltage is applied to a chuck electrode provided inside the holding substrate.

[0003] In this type of electrostatic chuck, in plasma processing such as plasma etching, a heat conduction gas such as helium gas is supplied between the holding substrate and the wafer to remove heat from the wafer. Therefore, a gas flow path for flowing the heat conduction gas supplied from the outside toward the wafer is formed inside the holding substrate of the electrostatic chuck. A plurality of gas flow outlets located at the end of the gas flow path are provided on the surface of the holding substrate, and the heat conduction gas is supplied toward the wafer from each gas flow outlet.

[0004] Note that abnormal discharge (arcing) may occur in the gas flow path due to the high-frequency power applied during plasma processing, and the wafer on the holding substrate may be damaged by the abnormal discharge. Therefore, in order to suppress the occurrence of such abnormal discharge, a gas-permeable porous body is provided in the gas flow path. The porous body is composed of a skeletal base material made of an insulating ceramic material and a plurality of three-dimensional network-like communication holes formed inside the skeletal base material. When the heat conduction gas is supplied to such a porous body from the upstream side of the gas flow path, the heat conduction gas passes through the three-dimensional network-like communication holes in the porous body and moves to the downstream side of the gas flow path.

Prior Art Documents

Patent Documents

[0005] Patent Document 1 Japanese Patent No. 4959905 Summary of the Invention Problems to be Solved by the Invention

[0006] There is a so-called trade-off relationship between the strength of the porous body and the gas flow rate that can pass through the porous body, making it difficult to preferably achieve both, which has been a problem.

[0007] An object of the present invention is to provide a holding device or the like including a porous body with improved strength while maintaining a required gas flow rate. Means for Solving the Problems

[0008] The means for solving the above problems are as follows. That is, <1> A holding device including a holding substrate having a plate-like member including a first surface and a second surface disposed on the opposite side of the first surface, a gas outlet opening on the first surface side, a gas inlet opening on the second surface side, a gas flow path formed inside the plate-like member, and a porous body disposed in the gas flow path, wherein the porous body includes a skeletal base material mainly composed of an insulating material, the skeletal base material has a group of communication holes formed of a plurality of communication holes, and the group of communication holes has peaks of pore size distribution measured by an Hg porosimeter, one by one, in a range of less than 5 μm and in a range of 5 μm or more and 15 μm or less.

[0009] <2> The holding device according to <1>, wherein the porosity of the porous body is 70% or more and 90% or less.

[0010] <3> A porous body with a dense layer including a columnar porous body having a group of communication holes having peaks of pore size distribution measured by an Hg porosimeter, one by one, in a range of less than 5 μm and in a range of 5 μm or more and 15 μm or less, and a cylindrical dense layer disposed around the porous body and having a smaller porosity than the porous body.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a holding device or the like including a porous body with improved strength while maintaining a required gas flow rate.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0013] <Embodiment 1> Hereinafter, the holding device 100 according to Embodiment 1 will be described with reference to FIGS. 1 to 5. The holding device 100 is an electrostatic chuck that adsorbs and holds an object (for example, a wafer W) by electrostatic attraction. The electrostatic chuck is used, for example, as a table for placing the wafer W in a process of performing etching using plasma in a decompressed chamber.

[0014] FIG. 1 is a perspective view schematically showing the external configuration of the holding device 100 according to Embodiment 1, and FIG. 2 is a cross-sectional view schematically showing the internal structure of the holding device 100 according to Embodiment 1. The holding device 100 includes a disk-shaped holding substrate (ceramic substrate) 10 and a disk-shaped base member 20 larger than the holding substrate 10. For example, when the holding substrate 10 has a disk shape with a diameter of 300 mm and a thickness of 3 mm, the base member 20 is set to have a disk shape with a diameter of 340 mm and a thickness of 20 mm. Note that the holding substrate 10 and the base member 20 may be provided with positioning portions (such as irregularities) for aligning their positions with each other, respectively.

[0015] The holding substrate 10 and the base member 20 are stacked on top of each other in the vertical direction with the holding substrate 10 disposed on the upper side and the base member 20 disposed on the lower side. The holding substrate 10 and the base member 20 are joined to each other by a bonding material 30 interposed therebetween.

[0016] The holding substrate 10 has a substantially circular first surface S1 disposed on the upper side and a substantially circular second surface S2 disposed on the opposite side (i.e., the lower side) of the first surface S1 and facing the base member 20. The base member 20 has a substantially circular third surface S3 disposed on the upper side and facing the second surface S2 of the holding substrate 10, and a substantially circular fourth surface S4 disposed on the opposite side (i.e., the lower side) of the third surface S3. The above-described bonding material 30 is sandwiched between the second surface S2 of the holding substrate 10 and the third surface S3 of the base member 20 and is in a state of spreading in a layer.

[0017] The holding 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 becomes the first surface S1 of the holding substrate 10. Also, the lower surface of the plate member 11 becomes the second surface S2 of the holding substrate 10.

[0018] The plate-shaped member 11 is an insulating member having a plate shape (disc shape) mainly composed of ceramics. In this specification, the "main component" means the component with the highest content ratio. The plate-shaped member 11 of the present embodiment is made of alumina (Al2O3). In other embodiments, it may be made of other ceramics such as aluminum nitride (AlN).

[0019] The substrate-side gas flow path (an example of a gas flow path) 12 constitutes a part of the flow path 60 for flowing an inert gas (for example, helium gas which is a heat-conducting gas) provided in the holding device 100. The substrate-side gas flow path 12 is formed inside the plate-shaped member 11 of the holding substrate 10. The substrate-side gas flow path 12 is composed of a hole penetrating through the holding substrate 10, including an inlet 12a opening to the second surface S2 of the holding substrate 10 and a gas flow outlet 12b opening to the first surface S1. When an 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 gas flow outlet 12b.

[0020] FIG. 3 is a cross-sectional view of the holding substrate 10 with a part of the substrate-side gas flow path 12 enlarged. FIG. 3 shows a cross-sectional structure of the holding substrate 10 cut along the thickness direction. As shown in FIGS. 2 and 3, the substrate-side gas flow path 12 includes a first vertical flow path portion 120, a horizontal flow path portion 130, and a second vertical flow path portion 140.

[0021] The first vertical flow path portion 120 includes a gas flow outlet 12b opening to the first surface S1 side, and is a bottomed flow path extending along the thickness direction of the plate-shaped member 11 from the gas flow outlet 12b to the second surface S2 side. A porous body 70 described later is filled in the first vertical flow path portion 120.

[0022] The horizontal flow path portion 130 is a flow path that connects to the first vertical flow path portion 120 and extends parallel to the first surface S1. The downstream end of the horizontal flow path portion 130 is connected to the upstream end of the first vertical flow path portion 120. In the substrate-side gas flow path 12, the inlet 12a side is the upstream side, and the gas flow outlet 12b is the downstream side.

[0023] As shown in FIG. 2, the second vertical flow path portion 140 includes an inlet 12a that opens to the second surface S2, and is a flow path that extends from the inlet 12a toward the first surface S1 side along the thickness direction of the plate-like member 11. The downstream end of the second vertical flow path portion 140 is connected to the upstream end of the horizontal flow path portion 130. Note that the inlet 12a forms an inlet of the substrate-side gas flow path 12.

[0024] Further, the holding substrate 10 is filled with a gas-permeable porous body 70 mainly composed of ceramics in a first vertical flow path portion 120 that is a part of the substrate-side gas flow path 12. Details of the porous body 70 will be described later.

[0025] The holding substrate 10 further includes a chuck electrode 40 that is an electrode member. As a whole, the chuck electrode 40 has a substantially planar (layered) shape parallel to the first surface S1. The chuck electrode 40 is formed of a conductive material such as tungsten, molybdenum, or platinum, for example. As shown in FIG. 2, the chuck electrode 40 is disposed on the first surface S1 side inside the holding substrate 10 (plate-like member 11). The chuck electrode 40 is connected to an external power source via a terminal or the like. When power is supplied to the chuck electrode 40, an electrostatic attraction force is generated, and the wafer W is attracted and held on the first surface S1 of the holding substrate 10 by this electrostatic attraction force. A through hole 41 that penetrates in the thickness direction (vertical direction) is formed in the chuck electrode 40. Note that in other embodiments, a high-frequency electrode or a heater electrode may be provided as the electrode member.

[0026] As shown in FIGS. 1 and 2, a plurality of gas outlets 12b are provided on the first surface S1 of the holding substrate 10. The outer peripheral edge portion of the first surface S1 is formed in an annular shape while protruding slightly upward compared to the inner portion thereof. Therefore, when the wafer W is attracted 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 FIG. 2.

[0027] 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).

[0028] A refrigerant flow path 21 is provided inside the base member 20. When a refrigerant (for example, a fluorine-based inert liquid, water, etc.) flows through the refrigerant flow path 21, cooling of the plasma heat is performed. Further, when the refrigerant flows through the refrigerant flow path 21, the base member 20 is cooled, and the holding substrate 10 is cooled by heat transfer (heat extraction) 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. Note that 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 flow path 21.

[0029] A base-side gas flow path 22 that forms part of the flow path 60 is provided inside the base member 20. The base-side gas flow path 22 generally has a shape of a through hole extending in the thickness direction of the base member 20, and includes an inlet 22a that opens to the fourth surface S4 of the base member 20 and an outlet 22b that opens to the third surface S3. The inlet 22a serves as an inlet of the base-side gas flow path 22 and also serves as an inlet of the entire flow path 60 provided in the holding device 100.

[0030] 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. As the bonding material 30, those having high adhesive strength with respect to both the holding substrate 10 and the base member 20 and having high pressure resistance and thermal conductivity are preferable.

[0031] A bonding-side gas flow path 31 that forms part of the flow path 60 is also formed in the bonding material 30. The bonding-side gas flow path 31 is composed of holes penetrating the layered bonding material 30 in the thickness direction.

[0032] The flow path 60 supplies an inert gas (such as helium gas) to the first surface S1 side of the holding device 100. As described above, a large number of gas outlets 12b, which are the outlets 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 such a manner that the inert gas is discharged from each gas outlet 12b. As described above, such a flow path 60 includes a base-side gas flow path 22, a joining-side gas flow path 31, and a substrate-side gas flow path (gas flow path) 12.

[0033] 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 (arrow H in FIG. 2) is supplied from each inlet 22a, the inert gas sequentially passes through the base-side gas flow path 22, the joining-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 a plurality of gas outlets 12b provided on the first surface S1.

[0034] The outlet 22b of the base-side gas flow path 22 is connected to an opening on the lower side (base member 20 side) of the joining-side gas flow path 31. Further, the opening on the upper side (holding substrate 10 side) of the joining-side gas flow path 31 is connected to the inlet 12a of the substrate-side gas flow path (gas flow path) 12. A plurality of inlets 12a of the substrate-side gas flow path (gas flow path) 12 are provided on the second surface S2 of the holding substrate 10.

[0035] The second longitudinal flow path portion 140 including the inlet 12a of such a substrate-side gas flow path (gas flow path) 12 is connected to a plurality of transverse flow path portions 130 on the downstream side thereof. And each transverse flow path portion 130 is connected to a first longitudinal flow path portion 120, respectively. That is, the substrate-side gas flow path (gas flow path) 12 is branched into a plurality of branches from the upstream side to the downstream side inside the holding substrate 10 (plate-like member 11).

[0036] Next, the porous body 70 filled in the substrate-side gas flow path 12 will be described in detail. The porous body 70 is a gas-permeable member containing communication holes composed of a large number of pores, mainly made of insulating ceramics. The porous body 70 is filled in each of the plurality of first vertical flow path portions 120 in the substrate-side gas flow path 12. As a whole, the porous body 70 has a columnar shape extending in the vertical direction (the thickness direction of the holding substrate 10). Such a porous body 70 includes a skeletal base material mainly made of insulating ceramics, and a communication hole group composed of a plurality of communication holes is formed inside the skeletal base material.

[0037] The communication hole group includes a plurality of small-diameter communication holes and a plurality of large-diameter communication holes. The communication hole group forms a three-dimensional network as a whole by the communication holes being connected to each other. Each communication hole constituting the communication hole group is composed of, for example, a burned-out trace such as carbon powder used as a pore-forming material during the production of the porous body 70, or a portion where there is no powdery ceramic material (for example, alumina powder) for forming the skeletal base material described later.

[0038] The skeletal base material constituting the porous body 70 is composed of, for example, a sintered body of a powdery ceramic material such as alumina powder. As the powdery ceramic material used for the porous body 70, it is preferable to use those having different center particle sizes from each other. For example, when mixing and using a large-diameter ceramic material and a small-diameter ceramic material, it is preferable to adjust so that the proportion of the large-diameter ceramic material is larger than that of the small-diameter ceramic material.

[0039] The large-diameter ceramic material (for example, large-diameter alumina powder) is not particularly limited as long as the object of the present invention is not impaired. For example, those having a center particle size in the range of 1.0 μm or more and 5.0 μm or less are preferable.

[0040] The small-diameter ceramic material (for example, small-diameter alumina powder) is not particularly limited as long as the object of the present invention is not impaired. For example, those having a center particle size in the range of 0.1 μm or more and 0.8 μm or less are preferable.

[0041] The porous body 70 of this embodiment includes a group of communication pores having peaks (peak tops, maximum values) of pore size distributions measured by an Hg porosimeter (mercury intrusion porosimeter) one by one in a range of less than 5 μm and a range of 5 μm or more and 15 μm or less (preferably, a range of 5 μm or more and 10 μm or less). The method for measuring the pore distribution of the porous body 70 by the Hg porosimeter will be described later.

[0042] Note that the small-diameter communication pores formed in the porous body 70 (skeletal base material) are defined as communication pores having a peak (peak top, maximum value) in a range of less than 5 μm in the pore size distribution measured by the Hg porosimeter. Further, the large-diameter communication pores formed in the skeletal base material are defined as communication pores having a peak (peak top, maximum value) in a range of 5 μm or more and 15 μm or less (preferably, a range of 5 μm or more and 10 μm or less) in the pore size distribution measured by the Hg porosimeter.

[0043] The porosity of the porous body 70 is not particularly limited as long as the object of the present invention is not impaired, but for example, it is preferably 70% or more and 90% or less. Further, it is preferable that no excessive space in which the pores are connected with a length of 120 μm or more is included in a direction substantially orthogonal to the first surface S1 of the holding device 100.

[0044] The porous body 70 is filled in the first vertical flow path portion 120 so that a space V is formed below it. The porous body 70 is filled in the cylindrical first vertical flow path portion 120 in such a manner that the circular upper end surface 70a is exposed from the gas outlet 12b and the circular lower end surface 70b is exposed to the space V side from the opening 12c. In the case of this embodiment, the first surface S1 and the upper end surface 70a are arranged to be in the same plane with each other.

[0045] The lower end surface 70b of the porous body 70 faces the space V in the horizontal flow path portion 130, and the inert gas supplied from the upstream side of the substrate-side gas flow path (gas flow path) 12 is supplied into the porous body 70 from this lower end surface 70b. The lower end surface 70b is porous, and the lower end surface 70b serves as an inlet for the inert gas.

[0046] Further, the peripheral surface 70c of the porous body 70 forms a cylindrical shape that extends straight in the vertical direction. The porous body 70 and the peripheral wall portion 111 constituting the first longitudinal flow path portion 120 are sintered and joined to each other.

[0047] Subsequently, an example of the manufacturing method of the holding device 100 of the present embodiment will be described. Here, first, while referring to FIGS. 4 and 5, the manufacturing method of the holding substrate 10 constituting the holding device 100 will be described. FIGS. 4 and 5 are explanatory diagrams schematically showing the manufacturing method of the holding substrate 10. The manufacturing method of this holding substrate 10 applies a sheet lamination method using a green sheet (ceramic green sheet). In FIGS. 4 and 5, the lower side (second surface S2 side) of the holding substrate 10 corresponds to the upper side of each figure, and the upper side (first surface S1 side) of the holding substrate 10 corresponds to the lower side of each figure.

[0048] First, as shown in FIG. 4(A), a plurality of green sheets for forming the plate-like member 11 of the holding substrate 10 are laminated to form a first laminate 80a. A conductor layer 9 is formed on a predetermined green sheet constituting the first laminate 80a, and such a green sheet is laminated on other green sheets.

[0049] The slurry for the green sheet is obtained, for example, by adding an organic solvent to a mixture containing alumina powder, an acrylic binder, a dispersant, a plasticizer, etc., and mixing it using a ball mill. This slurry is formed into a sheet shape by a casting device, and then the obtained molded product is dried to obtain a plurality of green sheets.

[0050] Also, the metallizing paste for forming the conductor layer 9 is obtained, for example, by adding conductive powder such as tungsten or molybdenum to a mixture of alumina powder, an acrylic binder, and an organic solvent and kneading them. By printing this metallizing paste using, for example, a screen printing device, the conductor layer 9 is formed on a specific green sheet.

[0051] Next, as shown in FIG. 4(B), a hole 81 for forming the first longitudinal flow path portion 120 is formed at a predetermined position of the first laminate 80a. The hole 81 is provided in a cylindrical shape so as to penetrate the first laminate 80a in the thickness direction. The hole 81 is formed at a predetermined position of the first laminate 80a using a known processing device (such as a router).

[0052] Next, as shown in FIG. 4(C), the hole 81 of the first laminate 80a is filled with a porous body paste 7 for forming the porous body 70. The porous body paste 7 is obtained, for example, by kneading a mixture containing alumina powder, two types of pore formers (carbon powder, resin beads), a binder, an organic solvent, and the like. Details of the porous body paste 7 will be described in the examples described later.

[0053] Examples of the method for filling the porous body paste 7 into the hole 81 include a method using an injection molding device and a method using a screen printing device. The first laminate 80a filled with the porous body paste 7 in the hole 81 is appropriately dried.

[0054] Thereafter, as shown in FIG. 5(D), the first laminate 80a and the second laminate 80b are laminated. The second laminate 80b is composed of a plurality of laminated green sheets. Note that, at a predetermined position of the second laminate 80b, a hole 82 for forming the second longitudinal flow path portion 140 and a groove 83 for forming the transverse flow path portion 130 are provided. The laminate composed of the first laminate 80a and the second laminate 80b is composed of, for example, a laminate of 20 green sheets, and they are thermocompression-bonded to each other. The outer periphery of the laminate may be appropriately cut. Then, the laminate is machined by cutting to produce a disk-shaped molded body. Thereafter, the obtained molded body is degreased and sintered, and further, the molded body after degreasing and sintering is sintered (main sintering) to obtain a sintered body.

[0055] Thereafter, a mask that shields a portion corresponding to the convex outer peripheral edge portion is disposed on the surface of the fired body, and shot blasting is performed to project particles such as ceramics, thereby forming a convex outer peripheral edge portion on the surface of the fired body. Thereafter, by polishing the surface of this fired body or the like, a holding substrate 10 having a plate-like member 11 as shown in FIG. 5(E) is obtained.

[0056] Note that the above-described debinding firing and main firing are performed by disposing the laminate of the first laminate 80a and the second laminate 80b 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 debinding firing and main firing, the porous body paste 7 (unfired composition) filled in the hole portion 81 and the laminate of the green sheets for forming the plate-like member 11 and the like are fired simultaneously.

[0057] The manufacturing method of the base member 20 is basically the same as that of the conventional product. Therefore, a detailed description thereof is omitted.

[0058] After the holding substrate 10 and the base member 20 are each manufactured, they are joined using the joining material 30. The joining of the holding substrate 10 and the base member 20 by the joining material 30 is basically the same as the joining in the conventional product. Therefore, a detailed description thereof is omitted. In this way, the holding device 100 is manufactured.

[0059] The porous body 70 used in the holding device 100 of the present embodiment as described above has improved gas flow while maintaining its strength.

[0060] <Embodiment 2> Next, the holding substrate 10A included in the holding device according to Embodiment 2 will be described with reference to FIG. 6. FIG. 6 is an enlarged cross-sectional view of a part of the substrate-side gas flow path 12A of the holding substrate 10A according to Embodiment 2. The basic configuration of the holding substrate 10A of the present embodiment is the same as that of Embodiment 1. Therefore, in FIG. 6, for the portions corresponding to those in Embodiment 1, reference numerals obtained by adding the symbol "A" to the same reference numerals as those in Embodiment 1 are used, and detailed descriptions thereof are omitted.

[0061] The holding substrate 10A includes a disk-shaped plate member 11A and a substrate-side gas flow path 12A formed inside thereof. As shown in FIG. 6, the substrate-side gas flow path 12A includes a first vertical flow path portion 120A, a horizontal flow path portion 130A, and a second vertical flow path portion 140A. And the first vertical flow path portion 120A is filled with a gas-permeable porous body 70A mainly composed of ceramics. The configuration of the porous body 70A is the same as that of the porous body 70 in Embodiment 1. The porous body 70A has a columnar shape including a group of communication holes having peaks (peak tops, maximum values) of pore size distribution measured by a Hg porosimeter, one each in a range of less than 5 μm and a range of 5 μm or more and 15 μm or less (preferably, 5 μm or more and 10 μm or less).

[0062] The upper surface of the plate member 11A is the first surface SA1 of the holding substrate 10A, and the lower surface of the plate member 11A is the second surface SA2 of the holding substrate 10A. A chuck electrode 40A is provided inside the holding substrate 10A.

[0063] The plate member 11A of the present embodiment is provided with a plurality of mounting hole portions 150A, and a mounting body (porous body with a dense layer) 90A is fixed to each mounting hole portion 150A using an adhesive. In FIG. 6, for convenience of explanation, one mounting hole portion 150A and one mounting body (porous body with a dense layer) 90A fixed thereto are shown. The mounting hole portion 150A has a cylindrical shape extending straight from the first opening portion (mounting port) 151A side to the second surface SA2 side.

[0064] The mounting body (porous body with a dense layer) 90A is composed of a columnar (column-shaped) porous body 70A extending in the vertical direction and a cylindrical (tubular) mounting frame portion (dense layer) 50A extending in the vertical direction disposed around the porous body 70A. The porous body 70A and the mounting frame portion (dense layer) 50A are integrally joined to each other by solid-phase bonding through co-firing. The porosity of the porous body 70A is higher than the porosity of the mounting frame portion (dense layer) 50A. The mounting frame portion (dense layer) 50A is gas-impermeable (for example, the porosity is 5% or less and the relative density is 95% or more).

[0065] The first vertical flow path portion 120A includes a gas outlet 12Ab that opens to the first surface SA1 side, and extends from the gas outlet 12Ab to the second surface SA2 side along the thickness direction of the plate member 11A. The first vertical flow path portion 120A has a substantially cylindrical shape extending in the vertical direction, and on the opposite side of the gas outlet 12Ab, there is an opening 12Ac that is the inlet of the first vertical flow path portion 120A and has substantially the same diameter as the gas outlet 12Ab. From this opening 12Ac, the lower end surface 70Ab of the porous body 70A is exposed to the space VA side.

[0066] The porous body 70A is filled in the first vertical flow path portion 120A so that the space VA is formed below it. The upper end surface 70Aa of the porous body 70A is flat and circular in plan view. This upper end surface 70Aa is exposed from the gas outlet 12Ab. In the case of this embodiment, the first surface SA1 and the upper end surface 70Aa are arranged to be in the same plane as each other.

[0067] As described above, in the holding device of this embodiment, the mounting body (porous body with a dense layer) 90A is mounted in the mounting hole portion 150A using an adhesive. Therefore, in the holding device of this embodiment, the structure is such that the repair of the porous body 70A in the substrate-side gas flow path 12A in the holding substrate 10A is easy.

[0068] Hereinafter, the present invention will be described in more detail based on examples. Note that the present invention is not limited by these examples in any way.

[0069] [Example 1] Alumina powder 1 with a median particle size of 2.2 μm and alumina powder 2 with a median particle size of 0.4 μm were prepared, and they were mixed at a ratio of 75:25 (volume ratio) to obtain a mixed alumina powder. Also, as a pore former, resin beads with a median particle size of 40 μm and carbon powder with a median particle size of 5 μm were prepared, and they were mixed at a ratio of 70:30 (volume ratio) to obtain a mixed pore former. Then, the mixed alumina powder and the mixed pore former were mixed at a ratio of 20:80 (volume ratio) to obtain a mixed powder. Further, the obtained mixed powder and a binder (commercially available product) for injection molding were mixed at a ratio of 78:22 (volume ratio) to obtain a paste-like unfired composition for a porous body (porous body paste).

[0070] The obtained unfired composition for a porous body was injection molded into a hole with a diameter of about 4 mm and a depth of about 5 mm processed on a green sheet, cut to a predetermined size, and then degreased and fired to obtain a sample containing the porous body of Example 1.

[0071] 〔Example 2, Example 3, and Comparative Example 1〕 Samples of Example 2, Example 3, and Comparative Example 1 were prepared in the same manner as in Example 1, except that the mixing ratio (volume ratio) of each material was changed to the values shown in Table 1.

[0072]

Table 1

[0073] 〔Pore distribution〕 In accordance with JIS R1655-2003, the pore size distribution of the porous body in each sample such as Example 1 was measured using a Hg porosimeter (mercury intrusion porosimeter). The results are shown in Fig. 7. Fig. 7 is a graph showing the pore size distribution of the porous body in each sample such as Example 1. The vertical axis of the graph shown in Fig. 7 represents Log Differential Intrusion (mL / g), and the horizontal axis represents the pore size (nm).

[0074] As shown in Fig. 7, the graphs of the pore size distributions of Examples 1 to 3 each had one peak (peak top, maximum value) in the range of less than 5 μm and in the range of 5 μm or more and 15 μm or less, respectively. Thus, it was confirmed that the porous bodies of Examples 1 to 3 each had a group of communication pores having peaks (peak tops, maximum values) of the pore size distribution measured with a Hg porosimeter in the range of less than 5 μm and in the range of 5 μm or more and 15 μm or less, respectively.

[0075] On the other hand, the graph of the pore size distribution of Comparative Example 1 had only one peak in the range of 5 μm or more and 15 μm or less. In the case of Comparative Example 1, it is presumed that such a result was obtained because only resin beads were used as the pore-forming material and carbon powder was not used during the production of the porous body.

[0076] 〔SEM Image〕 The porous body included in the sample of Example 1 was cut, and the cut surface was photographed with a scanning electron microscope (SEM) (magnification: 1000 times). The obtained SEM image is shown in Fig. 8. Fig. 8 is an SEM image of the cut surface of the porous body of Example 1. As shown in Fig. 8, a group of communication pores 720 composed of a large number of communication pores 72 is formed inside the skeleton base material 71 of the porous body 70. In Fig. 8, small-diameter communication pores 72a with a small pore size and large-diameter communication pores 72b with a large pore size are shown. Further, traces 73 where spherical resin beads have burned out (disappeared) are also formed in the skeleton base material 71 of the porous body 70. As shown in Fig. 8, each communication pore 72 is smaller than the trace 73 of the resin bead.

[0077] 〔Permeation Amount〕 For the porous bodies included in the samples such as Example 1, the gas permeation amount was measured by the method shown below. The sample was set in a He gas introduction unit, and the permeation amount of He gas under a pressure of 50 Torr was measured. The results are shown in Table 1. Note that the permeation amount results of Examples 1 to 3 in Table 1 are shown as multiples with respect to the result of Comparative Example 1.

[0078] 〔Strength〕 For the porous bodies included in each sample such as Example 1, the Martens hardness was measured in accordance with ISO14577. The results are shown in Table 1. Note that the strength results of Examples 1 to 3 in Table 1 are shown as multiples of the result of Comparative Example 1.

[0079] As shown in Table 1, although Example 1 sacrificed the permeation amount compared to Comparative Example 1, the strength could be improved by 3.72 times. Note that the permeation amount of Example 1 was sufficient to ensure the required flow rate in the product.

[0080] Also, Example 2 is the case where resin beads and carbon powder are blended at a ratio of 7:3 as the pore-forming material. Such Example 2 resulted in a 10% decrease in the permeation amount compared to Comparative Example 1 that used only resin beads as the pore-forming material, but the strength was improved by 1.71 times.

[0081] Note that in Example 1, since the ratio of the pore-forming material was smaller than that in Example 2, the permeation amount decreased, but the strength increased.

[0082] Also, in the case of Example 3, compared to Comparative Example 1, by reducing the ratio of the small-diameter alumina powder 1 among the alumina powders, the strength decreased, but the permeation amount increased.

Explanation of Signs

[0083] 100... Holding device, 10... Holding substrate, 11... Plate-shaped member, 12... Substrate-side gas flow path (gas flow path), 12b... Gas outlet, 120... First vertical flow path portion, 130... Horizontal flow path portion, 140... Second vertical flow path portion, 70... Porous body, 71... Skeleton base material, 72... Communication hole, 72a... Small-diameter communication hole, 72b... Large-diameter communication hole, 720... Communication hole group, V... Space, S1... First surface, S2... Second surface, W... Wafer (object)

Claims

1. A holding device comprising a plate-like member including a first surface and a second surface disposed on the opposite side of the first surface, a gas outlet opening on the first surface side, a gas inlet opening on the second surface side, a gas flow path formed inside the plate-like member, and a porous body disposed in the gas flow path, wherein the porous body includes a skeletal base material mainly composed of an insulating material, and the skeletal base material has a group of communication holes formed of a plurality of communication holes, the group of communication holes having peaks of pore size distribution measured by an Hg porosimeter, one each, in a range of less than 5 μm and in a range of 5 μm or more and 15 μm or less.

2. The holding device according to claim 1, wherein the porosity of the porous body is 70% or more and 90% or less.

3. A porous body with a dense layer, comprising a columnar porous body including a group of communication holes having peaks of pore size distribution measured by an Hg porosimeter, one each, in a range of less than 5 μm and in a range of 5 μm or more and 15 μm or less, and a cylindrical dense layer disposed around the porous body and having a smaller porosity than the porous body.

Images