Ceramic Susceptor

Abstract

The present invention provides a ceramic susceptor which comprises: a ceramic plate assembly that is composed of a first ceramic plate and a second ceramic plate, which are bonded to each other via a ceramic bonding interface; an internal electrode that is embedded in the first ceramic plate; a terminal hole that is provided so as to pass through the second ceramic plate in the thickness direction from one surface of the second ceramic plate, to cross the ceramic bonding interface, and to reach the internal electrode or the like in the first ceramic plate, and that has a small diameter part having a relatively small hole diameter and constituting a portion close to the bottom of the terminal hole, and a large diameter part having a relatively large hole diameter and constituting a portion far from the bottom of the terminal hole; a metal eyelet that is fitted into the small diameter part of the terminal hole; a terminal rod that is inserted into the terminal hole and the eyelet and that has one end directly or indirectly connected to the internal electrode; and an isolation structure that is composed of a space and / or an insulating material for electrically isolating the terminal rod and the eyelet from the ceramic bonding interface.

Description

[Technical Field]

[0001] The present disclosure relates to ceramic susceptors. [Background technology]

[0002] Susceptors are used to support wafers in film deposition and etching equipment used in semiconductor manufacturing processes. A widely used susceptor includes a ceramic plate on which the wafer is placed and a cylindrical ceramic shaft attached to the ceramic plate. The ceramic plate typically has a ceramic base made of aluminum nitride (AlN) or other materials with excellent heat and corrosion resistance, with internal electrodes embedded inside, such as heater electrodes, RF electrodes, and electrostatic chuck (ESC) electrodes.

[0003] Ceramic susceptors with embedded internal electrodes and internal spaces for gas passages are known. For example, Patent Document 1 (JP 2017-527984 A) describes a substrate support including a first plate having multiple purge gas channels on its backside, a second plate disposed directly below the first plate, and an edge ring surrounding the first plate, in which the multiple purge gas channels extend from a single inlet in the central portion of the first plate to multiple outlets in the peripheral portion. This substrate support includes multiple heating elements embedded in the second plate so that the second plate provides multiple heating zones.

[0004] As disclosed in Patent Document 1, an internal space with a complex shape, such as a gas path, can be formed by bonding multiple ceramic substrates, including ceramic substrates with grooves and holes formed therein. In this regard, bonding agents suitable for bonding ceramic substrates are known. For example, Patent Document 2 (JP 2004-345952 A) discloses a bonding agent for bonding multiple substrates made of aluminum nitride ceramics, which contains a flux consisting of 25 to 45 wt % CaO, 5 to 30 wt % YO, and the remainder AlO, and aluminum nitride ceramics.

[0005] Ceramic susceptors with internal electrodes are provided with terminal holes for connecting terminal rods. Various improvements to such terminal holes have been proposed. For example, Patent Document 3 (JP 2020-516043 A) discloses a ceramic heater including a ceramic plate including an embedded heating element, threads formed on a portion of the inner circumferential surface of an opening, and a connector embedded so as to be partially exposed on the bottom surface of the opening, and a support eyelet connected to an electrode rod fastened via the threads. This document discloses that, from the perspective of stress relaxation, a recess recessed inward is formed at the bottom edge of the inner circumferential surface of the opening, and this recess is machined into a predetermined round shape. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2017-527984 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-345952 [Patent Document 3] Special Publication No. 2020-516043 Summary of the Invention

[0007] As described above, ceramic susceptors are known in which internal paths such as gas paths are formed inside ceramic plates by bonding ceramic substrates together, and internal electrodes (heater electrodes, RF electrodes, ESC electrodes, etc.) are embedded. In manufacturing such ceramic susceptors, after bonding the ceramic substrates together, machining is performed to form terminal holes for electrical connection with the internal electrodes. Terminal rods are then inserted into the terminal holes via metal eyelets and joined to the internal electrodes by brazing or the like, thereby ensuring electrical connection between the terminal rods and the internal electrodes. However, there has been a problem of reduced insulation resistance between the internal electrodes and the terminal rods connected thereto and the ceramic susceptor surface (this insulation resistance is measured in water and may be referred to below as "underwater insulation resistance"). A reduced underwater insulation resistance is undesirable because it increases the risk of abnormalities during semiconductor manufacturing processes using ceramic susceptors, such as film formation, etching, and ion implantation.

[0008] The present inventors have now discovered that in a ceramic susceptor having a terminal rod and an eyelet in a terminal hole, by providing a structure that electrically isolates the terminal rod and the eyelet from the ceramic joint interface, it is possible to achieve high underwater insulation resistance between the ceramic susceptor surface and the internal electrode and the terminal rod connected thereto.

[0009] Therefore, an object of the present invention is to provide a ceramic susceptor that has an eyelet and a terminal rod in a terminal hole, and has an internal electrode within a ceramic plate assembly, yet can achieve high underwater insulation resistance between the ceramic susceptor surface and the internal electrode and the terminal rod connected thereto.

[0010] According to the present disclosure, the following aspects are provided. [Aspect 1] a ceramic plate assembly including a first ceramic plate and a second ceramic plate joined to each other via a ceramic joining interface, the ceramic plate assembly having a first surface facing the first ceramic plate and a second surface facing the second ceramic plate; at least one internal electrode selected from the group consisting of a heater electrode, an RF electrode, and an ESC electrode, which is embedded in the first ceramic plate; a terminal hole provided in the second ceramic plate in a thickness direction from the second surface thereof, penetrating the second ceramic plate, crossing the ceramic joint interface, and reaching the internal electrode in the first ceramic plate or a metal member connected thereto, the terminal hole having a small diameter portion having a relatively small hole diameter constituting a side close to a bottom of the terminal hole and a large diameter portion having a relatively large hole diameter constituting a side farther from the bottom of the terminal hole; a metal eyelet fitted into the small diameter portion of the terminal hole; a terminal rod inserted into the terminal hole and the eyelet therein, one end of which is directly or indirectly connected to the internal electrode, and the other end of which extends from the second surface to the outside of the ceramic plate assembly; an isolation structure formed of space and / or insulating material that electrically isolates the terminal rod and the eyelet from the ceramic joint interface; A ceramic susceptor comprising: [Aspect 2] 10. The ceramic susceptor of claim 1, further comprising an internal passage disposed in the first ceramic plate and / or the second ceramic plate facing the ceramic bond interface. [Aspect 3] 3. The ceramic susceptor according to aspect 2, wherein the internal passage is at least one selected from the group consisting of a gas passage, a cooling medium passage, a vacuum passage, and a thermocouple insertion groove. [Aspect 4] the eyelet extends in the direction of the central axis of the terminal hole beyond the height of the ceramic bonding interface to a height corresponding to the second ceramic plate, and the large diameter portion extends beyond the height of the ceramic bonding interface to the inside of the first ceramic plate, A ceramic susceptor according to any one of aspects 1 to 3, wherein the isolation structure includes a space formed between an inner wall surface of the large diameter portion and the eyelet. [Aspect 5] The ceramic susceptor according to any one of aspects 1 to 4 (particularly aspect 4), further comprising an insulating tube covering the inner wall surface of the large diameter portion, whereby the insulating tube covers the end of the ceramic bonding interface, thereby forming part of the isolation structure. [Aspect 6] the eyelet extends in the direction of the central axis of the terminal hole beyond the height position of the ceramic joint interface to a height corresponding to the second ceramic plate, and the large diameter portion terminates within the second ceramic plate without reaching the ceramic joint interface, Aspect 6. The ceramic susceptor of any one of aspects 1 to 5, wherein the isolation structure includes a space formed between the eyelet and the ceramic bonding interface. [Aspect 7] the eyelet terminates within the first ceramic plate without reaching the height of the ceramic joint interface, and the large diameter portion terminates within the second ceramic plate without reaching the height of the ceramic joint interface; A ceramic susceptor according to any one of aspects 1 to 6, wherein the isolation structure includes a gap formed between the terminal rod and an inner wall of the small diameter portion by the eyelet not reaching the small diameter portion. [Aspect 8] The ceramic susceptor according to any one of aspects 1 to 7 (particularly aspect 7), further comprising an insulating tube covering the inner wall surface of the small diameter portion, whereby the insulating tube covers the end of the ceramic bonding interface, thereby forming part of the isolation structure. [Aspect 9] The ceramic susceptor according to any one of aspects 1 to 8, further comprising an insulating film covering the outer peripheral surface of the eyelet, whereby the insulating film covers the end of the ceramic bonding interface, thereby forming part of the isolation structure. [Aspect 10] The ceramic susceptor according to any one of aspects 1 to 9, further comprising a cylindrical ceramic shaft attached to the second surface and having an internal space. [Aspect 11] 11. The ceramic susceptor according to any one of aspects 1 to 10, wherein the first ceramic plate and the second ceramic plate comprise aluminum nitride or aluminum oxide. [Aspect 12] 12. The ceramic susceptor according to any one of aspects 1 to 11, wherein the first ceramic plate and the second ceramic plate are made of materials having the same physical properties. [Aspect 13] 13. The ceramic susceptor according to any one of aspects 1 to 12, wherein the first ceramic plate and the second ceramic plate are made of materials having different physical properties. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing an example of a ceramic susceptor according to the present invention. [Figure 2] 2 is a schematic cross-sectional view showing an example of the structure in the vicinity of a terminal hole of the ceramic susceptor shown in FIG. 1. FIG. [Figure 3] FIG. 4 is a schematic cross-sectional view showing another example of the structure in the vicinity of the terminal hole of the ceramic susceptor according to the present invention. [Figure 4] FIG. 4 is a schematic cross-sectional view showing another example of the structure in the vicinity of the terminal hole of the ceramic susceptor according to the present invention. [Figure 5] FIG. 4 is a schematic cross-sectional view showing another example of the structure in the vicinity of the terminal hole of the ceramic susceptor according to the present invention. [Figure 6] FIG. 4 is a schematic cross-sectional view showing another example of the structure in the vicinity of the terminal hole of the ceramic susceptor according to the present invention. [Figure 7] FIG. 2 is a schematic cross-sectional view showing another example of a ceramic susceptor according to the present invention. [Figure 8] FIG. 8 is a schematic cross-sectional view showing an example of the structure in the vicinity of a terminal hole of the ceramic susceptor shown in FIG. [Figure 9] FIG. 1 is a conceptual diagram showing a measurement system for measuring the underwater insulation resistance of a ceramic susceptor. [Figure 10]FIG. 10 is a schematic cross-sectional view showing an example of the structure of the vicinity of a terminal hole of a ceramic susceptor according to a comparative embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] The ceramic susceptor according to the present invention is a ceramic platform for supporting a wafer, and is used in a film formation apparatus or etching apparatus, particularly a film formation apparatus or etching apparatus for a semiconductor manufacturing process. For example, the ceramic susceptor according to the present invention may be a ceramic heater for a semiconductor film formation apparatus or an electrostatic chuck for a semiconductor etching apparatus. Alternatively, it may be an electrostatic chuck heater that combines heater and electrostatic chuck functions. Typical examples of film formation apparatuses include CVD (chemical vapor deposition) apparatuses (e.g., thermal CVD apparatuses, plasma CVD apparatuses, photo-CVD apparatuses, and MOCVD apparatuses) and PVD (physical vapor deposition) apparatuses.

[0013] FIGS. 1 and 2 show one embodiment of a ceramic susceptor. For ease of explanation, in all drawings, including FIGS. 1 and 2, the ceramic susceptor 10 is shown in the orientation during manufacturing or the orientation during underwater insulation resistance measurement (see FIG. 9), and is shown upside down, opposite to the orientation during use in a semiconductor manufacturing device. The ceramic susceptor 10 shown in FIGS. 1 and 2 includes a ceramic plate assembly 12, an internal electrode 14, a terminal hole 16, an eyelet 18, a terminal rod 20, and an isolation structure 30. The ceramic plate assembly 12 includes a first ceramic plate 12a and a second ceramic plate 12b bonded to each other via a ceramic bonding interface 12c. The ceramic plate assembly 12 has a first surface 12d on the first ceramic plate 12a side and a second surface 12e on the second ceramic plate 12b side. An internal electrode 14 is embedded in the first ceramic plate 12a. The internal electrode 14 includes at least one electrode selected from the group consisting of a heater electrode, an RF electrode, and an ESC electrode. The terminal hole 16 extends from the second surface 12e of the second ceramic plate 12b in the thickness direction, penetrates the second ceramic plate 12b, crosses the ceramic joint interface 12c, and reaches the internal electrode 14 in the first ceramic plate 12a or a metal member 24 connected thereto. As shown in FIG. 2 , the terminal hole 16 has a small-diameter portion 16a having a relatively small diameter that forms the side closer to the bottom (i.e., the closed end of the hole) of the terminal hole, and a large-diameter portion 16b having a relatively large diameter that forms the side farther from the bottom. The eyelet 18 is a cylindrical metal member that fits into the small-diameter portion 16a of the terminal hole 16. A terminal rod 20 is inserted into the terminal hole 16 and the eyelet 18 therein. One end of the terminal rod 20 is directly or indirectly connected to the internal electrode 14, and the other end of the terminal rod 20 extends from the second surface 12e to the outside of the ceramic plate assembly 12. Isolation structure 30 comprises space and / or insulating material that electrically isolates terminal rod 20 and eyelet 18 from ceramic bond interface 12c.In this way, in a ceramic susceptor 10 having a terminal rod 20 and an eyelet 18 in the terminal hole 16, by providing a structure that electrically isolates the terminal rod 20 and the eyelet 18 from the ceramic joint interface 12c, it is possible to achieve high underwater insulation resistance between the surface of the ceramic susceptor 10 and the internal electrode 14 and the terminal rod 20 connected thereto.

[0014] As mentioned above, ceramic susceptors are known in which internal paths, such as gas paths, are formed inside the ceramic plates by bonding ceramic substrates together. However, such conventional configurations suffer from a problem of reduced underwater insulation resistance between the ceramic susceptor surface and the internal electrodes and terminal rods connected thereto. Reduced underwater insulation resistance is undesirable because it increases the risk of abnormalities during semiconductor manufacturing processes using ceramic susceptors, such as film formation, etching, and ion implantation. Research by the present inventors has revealed that reduced underwater insulation resistance occurs at the interface between the ceramic plates and the electrode terminal structure (metal components such as eyelets and terminal rods). In particular, the ceramic bonding interface 12c envisioned in this invention is not a metal interface, and therefore exposure of this interface would not normally be expected to impair insulation properties. However, the present inventors unexpectedly discovered that the ceramic bonding interface 12c reduces insulation resistance. Although the mechanism underlying the reduced insulation resistance at the ceramic bond is unclear, the ceramic bonding agent disclosed in Patent Document 2 is thought to be involved. Specifically, when a ceramic plate assembly 12 having a ceramic bonding interface 12c derived from a ceramic bonding agent, such as the ceramic susceptor 110 of the comparative embodiment shown in FIG. 10, is processed to form a terminal hole 16 for electrical connection, the ceramic bonding interface 12c is exposed in the processed terminal hole 16, and components derived from the ceramic bonding agent after firing are presumably responsible for impairing the insulating properties. Specifically, components of the bonding agent exposed at the ceramic bonding interface 12c are incorporated into the terminal hole 16 and come into contact with metal parts (e.g., eyelets 18, terminal rods 20, and metal members 24) directly or indirectly brazed to the internal electrode 14, resulting in a significant decrease in insulation resistance. Therefore, as shown in FIG. 2, by providing a structure (i.e., an isolation structure 30) that prevents direct contact between the ceramic bonding interface 12c, which is the joint between the ceramic plates 12a and 12b, and the internal electrode 14 and the terminal rod 20 connected thereto, the above-mentioned decrease in underwater insulation resistance can be prevented. In this way, a ceramic susceptor with high underwater insulation resistance can be provided.

[0015] The ceramic plate assembly 12 includes a first ceramic plate 12a and a second ceramic plate 12b. The first ceramic plate 12a and the second ceramic plate 12b may be made of materials having the same physical properties or different physical properties (e.g., volume resistivity and thermal expansion coefficient). In the latter case, for example, the volume resistivity of the first ceramic plate 12a may be relatively higher than that of the second ceramic plate 12b, or the volume resistivity of the second ceramic plate 12b may be relatively higher than that of the first ceramic plate 12a. In either case, the first ceramic plate 12a and the second ceramic plate 12b are not particularly limited except for the configuration of the isolation structure 30 and may have a configuration similar to that of ceramic plates used in known ceramic susceptors or ceramic heaters. Therefore, the first ceramic plate 12a and the second ceramic plate 12b preferably contain aluminum nitride or aluminum oxide, more preferably aluminum nitride, from the viewpoints of excellent thermal conductivity, high electrical insulation, and thermal expansion characteristics similar to those of silicon.

[0016] The ceramic plate assembly 12 further includes a ceramic bonding interface 12c between the first ceramic plate 12a and the second ceramic plate 12b, bonding them together. The ceramic bonding interface 12c is an interface layer that is derived from the ceramic bonding agent used to bond the first ceramic plate 12a and the second ceramic plate 12b and remains after firing. The ceramic bonding agent is not particularly limited as long as it is a bonding agent that can be used to bond ceramic plates together, and can be a known ceramic bonding agent such as that disclosed in Patent Document 2. A preferred ceramic bonding agent can be one that contains a flux consisting of 25 to 45 wt% CaO, 5 to 30 wt% YO, and the remainder AlO, and 10 to 90 wt% aluminum nitride ceramic relative to the bonding agent (see Patent Document 2).

[0017] The ceramic plate assembly 12 preferably has a disk-like shape. However, the planar shape of the disk-like ceramic plate assembly 12 does not need to be a perfect circle; for example, it may be an incomplete circle with a missing portion, such as an orientation flat. The size of the ceramic plate assembly 12 is not particularly limited and may be determined appropriately depending on the diameter of the wafer to be used. In the case of a circular shape, the diameter is typically 150 to 450 mm, for example, about 300 mm. Furthermore, as shown in FIG. 1, the diameter of the first ceramic plate 12a and the diameter of the second ceramic plate 12b may be different.

[0018] If desired, a ceramic shaft 26 may be attached to the second surface 12e of the ceramic plate assembly 12. The ceramic shaft 26 is a cylindrical member with an internal space S and may have a configuration similar to that of ceramic shafts used in known ceramic susceptors or ceramic heaters. The internal space S is configured to allow the terminal rod 20 to pass therethrough. The ceramic shaft 26 is preferably made of the same ceramic material as the ceramic plate assembly 12. Therefore, the ceramic shaft 26 preferably contains aluminum nitride or aluminum oxide, more preferably aluminum nitride. The upper end surface of the ceramic shaft 26 is preferably bonded to the second surface 12e of the ceramic plate assembly 12 by solid-state bonding or diffusion bonding. The outer diameter of the ceramic shaft 26 is not particularly limited and may be, for example, approximately 40 mm. The inner diameter of the ceramic shaft 26 (the diameter of the internal space S) is also not particularly limited and may be, for example, approximately 36 mm.

[0019] The internal electrode 14 is an electrode embedded in the first ceramic plate 12a and includes at least one selected from the group consisting of a heater electrode, an RF electrode, and an ESC electrode. The heater electrode is not particularly limited, but may be, for example, a conductive coil wired in a single stroke across the entire surface of the first ceramic plate 12a. Terminal rods 20 for power supply are connected to both ends of the heater electrode, and the terminal rods 20 are connected to a heater power supply (not shown). When power is supplied from the heater power supply, the heater electrode generates heat and heats a wafer placed on the surface of the first ceramic plate 12a. The heater electrode is not limited to a coil and may be, for example, a ribbon (a thin, elongated plate), a mesh, or a print. The RF electrode enables film formation by a plasma CVD process when high frequency is applied. The ESC electrode is an abbreviation for an electrostatic chuck (ESC) electrode and is also called an electrostatic electrode. The ESC electrodes are preferably circular thin-layer electrodes with a diameter slightly smaller than that of the ceramic plate assembly 12. For example, they may be mesh electrodes formed by weaving thin metal wires into a net shape. The ESC electrodes may also be used as plasma electrodes. That is, by applying high frequency to the ESC electrodes, the ESC electrodes can also be used as RF electrodes, enabling film formation by a plasma CVD process. Terminal rods 20 are connected to the ESC electrodes for power supply, and the terminal rods 20 are connected to an external power supply (not shown). When a voltage is applied from the external power supply, the ESC electrodes chuck a wafer placed on the surface of the ceramic plate assembly 12 by the Johnsen-Rahbek force. Preferably, the internal electrode 14 includes a heater electrode and an RF or ESC electrode. An internal electrode 14 may also be embedded in the second ceramic plate 12b.

[0020] Optionally, internal passages 28 may be provided in the first ceramic plate 12a and / or the second ceramic plate 12b, facing the ceramic bonding interface 12c. The internal passages 28 may be at least one selected from the group consisting of gas passages, cooling medium passages, vacuum passages, and thermocouple insertion grooves. Because such internal passages 28 tend to have complex shapes, it is preferable to form groove- or channel-shaped recesses in the first ceramic plate 12a (in combination with the second ceramic plate 12b) to form the internal passages 28, and then bond the second ceramic plate 12b to the recessed surface of the first ceramic plate 12a using a ceramic bonding agent to form the internal passages 28. To form the internal passages 28 in the second ceramic plate 12b, the first ceramic plate 12a may be bonded to the recessed surface of the second ceramic plate 12b using a ceramic bonding agent. When forming the internal vias 28 in each of the first ceramic plate 12a and the second ceramic plate 12b, the recessed surface of the first ceramic plate 12a and the recessed surface of the second ceramic plate 12b can be bonded to each other using a ceramic bonding agent. Therefore, the internal vias 28 typically face the ceramic bonding interface 12c, as shown in Figures 1 and 2. The presence of the internal vias 28 facing the ceramic bonding interface 12c exposes the ceramic bonding interface 12c, which can lead to a decrease in underwater insulation resistance through the ceramic bonding interface 12c. However, the present invention effectively prevents such a decrease in underwater insulation resistance.

[0021] The terminal hole 16 extends from the second surface 12e through the second ceramic plate 12b in the thickness direction, crosses the ceramic joint interface 12c, and reaches the internal electrode 14 in the first ceramic plate 12a or the metal member 24 connected thereto. The terminal hole 16 has a small-diameter portion 16a with a relatively small diameter that forms the side closest to the bottom (i.e., the closed end) of the terminal hole 16, and a large-diameter portion 16b with a relatively large diameter that forms the side farther from the bottom. The small-diameter portion 16a has a diameter that fits the eyelet 18 or the terminal rod 20 inserted therein. The large-diameter portion 16b is designed to have a larger diameter than the small-diameter portion 16a, allowing the protrusion 20a on the terminal rod 20 to penetrate into the large-diameter portion 16b. Therefore, the diameter of the large-diameter portion 16b is preferably larger than the diameter of the protrusion 20a. For example, the diameter of the small-diameter portion 16a is 6 to 8 mm, and the diameter of the large-diameter portion 16b is 10 to 15 mm. Furthermore, the small diameter portion 16a may be threaded.

[0022] The eyelet 18 is a metallic cylindrical member that fits into the small diameter portion 16a of the terminal hole 16. The eyelet 18 serves to guide the terminal rod 20 for smooth insertion into the terminal hole 16. The eyelet 18 may be threaded. In this case, the terminal rod 20 may also be threaded so that the terminal rod 20 can be inserted while threaded into the eyelet 18. The metal constituting the eyelet 18 is not particularly limited, but preferred examples include Ni, W, Mo, and W-Mo alloys, with Ni being preferred. The eyelet 18 may also have a male thread on its outer periphery. By providing a threaded portion, the small diameter portion 16a and the eyelet 18 can be threaded together.

[0023] The terminal rod 20 is a rod-shaped power supply member inserted into the terminal hole 16 and the eyelet 18 therein. One end of the terminal rod 20 is directly or indirectly connected to the internal electrode 14, and the other end extends from the second surface 12e to the outside of the ceramic plate assembly 12. The term "directly or indirectly connected to the internal electrode 14" refers to the fact that the terminal rod 20 may be directly connected to the internal electrode 14 or indirectly connected to the internal electrode 14 via a metal member 24. The tip of the terminal rod 20 is preferably connected to the internal electrode 14 and / or the metal member 24 by brazing. The metal constituting the terminal rod 20 is not particularly limited, but preferred examples include Ni, W, Mo, and a joint structure of Ni and W, with Ni being preferred. The terminal rod 20 may have a flange-shaped protrusion 20a along the outer periphery of the terminal rod 20 at a predetermined longitudinal position (excluding the portion inserted into the small-diameter portion 16a). This protrusion 20a is used as a portion against which the tip of a loading jig (e.g., a ceramic tube) abuts when the terminal rod 20 is inserted into the terminal hole 16 and pushed toward the internal electrode 14 with a load applied. The tip of the terminal rod 20 is brazed to the internal electrode 14 and / or the metal member 24, and by applying a load to the terminal rod 20 with a loading jig via the protrusion 20a, the brazed joint portion can be pressed by the tip of the terminal rod 20. By raising the temperature to a brazing temperature (e.g., approximately 1000°C) in this state, the terminal rod 20 and the metal member 24 (the terminal rod 20, buffer material 24b, and tablet 24a in the illustrated example) can be tightly brazed together.

[0024] An insulating tube 22 is preferably provided around the terminal rod 20 so as to surround the outer circumferential surface of the terminal rod 20. That is, the terminal rod 20 is preferably provided so as to pass through the hollow portion of the insulating tube 22. This ensures insulation around the terminal rod 20. Therefore, when there are multiple terminal rods 20, the terminal rods 20 can be prevented from coming into electrical contact with each other.

[0025] The metal member 24 is a member interposed between the internal electrode 14 and the terminal rod 20 to assist in ensuring electrical connection, and its configuration is not particularly limited. A preferred metal member 24 includes tablets 24a and / or buffer material 24b, and more preferably includes both tablets 24a and buffer material 24b. The tablets 24a are massive metal members (e.g., configured in a mesh shape) that facilitate electrical connection with the internal electrode 14 and are provided on the internal electrode 14 side. This ensures a sufficient contact area for soldering the terminal rod 20 or the buffer material 24b. Preferred examples of metals constituting the tablets 24a include Mo, W, and W-Mo alloys, with Mo being preferred. The buffer material 24b is a metal member provided as a buffer to reduce the thermal expansion difference between the tablets 24a and the terminal rod 20 and is provided between the tablets 24a and the terminal rod 20. Preferred examples of metals constituting the buffer material 24b include alloys such as Kovar (registered trademark) (Fe-Ni-Co alloy). When the metal member 24 includes the tablet 24a and the buffer material 24b, the terminal rod 20, the buffer material 24b, and the tablet 24a are preferably brazed together.

[0026] As shown in Figures 2 to 6 and 8, the isolation structure 30 is composed of a space 32 (see Figures 2 to 5 and 8) and / or an insulating material 34 (see Figures 5 and 6) that electrically isolates the terminal rod 20 and the eyelet 18 from the ceramic joint interface 12c. By providing the isolation structure 30 that electrically isolates the terminal rod 20 and the eyelet 18 from the ceramic joint interface 12c in this manner, high underwater insulation resistance can be achieved between the surface of the ceramic susceptor 10 and the internal electrode 14 and the terminal rod 20 connected thereto. Therefore, the isolation structure 30 is not particularly limited as long as it has a structure that prevents direct contact between the end of the ceramic joint interface 12c facing the terminal hole 16 and the terminal rod 20 or the eyelet 18 provided around it.

[0027] According to a preferred embodiment of the present invention, as shown in FIG. 2, the eyelet 18 extends in the direction of the central axis C of the terminal hole 16 beyond the height of the ceramic bonding interface 12c to a height corresponding to the second ceramic plate 12b, and the large-diameter portion 16b extends beyond the height of the ceramic bonding interface 12c into the interior of the first ceramic plate 12a. As a result, the isolation structure 30 includes a space 32 formed between the inner wall surface of the large-diameter portion 16b and the eyelet 18. This prevents direct contact between the end of the ceramic bonding interface 12c and the eyelet 18 (and the terminal rod 20 therein). In this embodiment, the space 32 can be considered a part of the large-diameter portion 16b of the terminal hole 16.

[0028] According to another preferred embodiment of the present invention, as shown in FIG. 3, the eyelet 18 extends in the direction of the central axis C of the terminal hole 16 beyond the height of the ceramic bonding interface 12c to a height corresponding to the second ceramic plate 12b, and the large-diameter portion 16b terminates within the second ceramic plate 12b without reaching the ceramic bonding interface 12c. As a result, the isolation structure 30 includes a space 32 formed between the eyelet 18 and the ceramic bonding interface 12c. This prevents direct contact between the end of the ceramic bonding interface 12c and the eyelet 18 (and the terminal rod 20 therein). In this embodiment, the space 32 can be considered an annular internal space disposed around the annular eyelet 18.

[0029] According to another preferred embodiment of the present invention, as shown in FIG. 4 , the eyelet 18 terminates within the first ceramic plate 12a without reaching the ceramic bonding interface 12c, and the large-diameter portion 16b terminates within the second ceramic plate 12b without reaching the ceramic bonding interface 12c. As a result, the standoff structure 30 includes a gap 32a formed between the terminal rod 20 and the inner wall of the small-diameter portion 16a due to the eyelet 18 not reaching the small-diameter portion 16a. This prevents direct contact between the end of the ceramic bonding interface 12c and the eyelet 18 (and the terminal rod 20 therein). In this embodiment, the gap 32a (as the space 32) can be considered a part of the small-diameter portion 16a of the terminal hole 16.

[0030] According to another preferred embodiment of the present invention, as shown in FIG. 5, an insulating tube 34a may be further provided to cover the inner wall surface of the large-diameter portion 16b. The insulating tube 34a can form part of the isolation structure 30 by covering the end of the ceramic bonding interface 12c. This more effectively prevents direct contact between the end of the ceramic bonding interface 12c and the eyelet 18 (and the terminal rod 20 therein), thereby stably ensuring high underwater insulation resistance. The embodiment shown in FIG. 5 is an embodiment in which the insulating tube 34a is further provided in addition to the embodiment shown in FIG. 2, but this embodiment is not limited to this. That is, the insulating tube 34a covering the inner wall surface of the large-diameter portion 16b may be arbitrarily combined with other embodiments disclosed herein.

[0031] According to another preferred embodiment of the present invention, although not shown, an insulating tube (not shown) covering the inner wall surface of the small diameter portion 16a may be further provided in the embodiment shown in FIG. 4. The insulating tube covers the end of the ceramic bonding interface 12c, thereby forming part of the isolation structure 30. This more effectively prevents direct contact between the end of the ceramic bonding interface 12c and the terminal rod 20, thereby ensuring high underwater insulation resistance. This embodiment corresponds to the embodiment shown in FIG. 4 in which an insulating tube is further provided, but this embodiment is not limited thereto. In other words, the insulating tube covering the inner wall surface of the small diameter portion 16a may be combined with any of the other embodiments disclosed herein.

[0032] According to a preferred embodiment of the present invention, as shown in Fig. 6, an insulating film 34b may be further provided to cover the outer peripheral surface of the eyelet 18. The insulating film 34b can form part of the isolation structure 30 by covering the end of the ceramic bonding interface 12c. This prevents the end of the ceramic bonding interface 12c from coming into direct contact with the eyelet 18 (and the terminal rod 20 therein). There are no particular limitations on the material that can be used for the insulating film 34b as long as it is an insulating material, but preferred examples include nitrides such as aluminum nitride and oxides such as yttrium oxide.

[0033] Although the various embodiments described above (see FIGS. 1 to 6 ) all have internal passages 28, the ceramic susceptor of the present invention may not have internal passages 28. FIGS. 7 and 8 show one embodiment of such a ceramic susceptor 10. The ceramic susceptor 10 shown in FIGS. 7 and 8 has the same structure as FIG. 2 except that it does not have internal passages 28. Even a ceramic susceptor without internal passages 28 can suffer from the problem of reduced underwater insulation resistance through the ceramic bonding interface 12 c. However, this problem can be solved by providing an isolation structure 30 (e.g., a space 32 formed between the inner wall surface of the large-diameter portion 16 b and the eyelet 18 in the embodiment of FIGS. 7 and 8 ). Furthermore, even in these ceramic susceptors 10 without internal passages, the first ceramic plate 12 a and the second ceramic plate 12 b may be made of materials having the same physical properties or different physical properties (e.g., volume resistivity and thermal expansion coefficient). In the latter case, for example, the volume resistivity of the first ceramic plate 12a may be relatively higher than that of the second ceramic plate 12b, or the volume resistivity of the second ceramic plate 12b may be relatively higher than that of the first ceramic plate 12a.

[0034] Various embodiments have been described above, but the components described with respect to the embodiment shown in Figures 1 and 2 also apply to the corresponding components with the same symbols in the embodiments shown in Figures 3 to 8, except for changes specific to each embodiment. [Example]

[0035] The present invention will be explained in more detail by the following examples, but the present invention is not limited to the following examples.

[0036] Examples 1-8 (1) Fabrication of ceramic susceptor For each example, various components were prepared as shown in Table 1. Using these components, ceramic susceptors 10 and 110 having the specifications shown in Table 1 and various embodiments shown in Table 2 and Figures 1 to 8 and 10 referred to therein were fabricated by known procedures.

[0037] [Table 1]

[0038] (2) Underwater insulation resistance measurement A measurement system 40 shown in FIG. 9 was assembled to measure the underwater insulation resistance of the ceramic susceptors 10 and 110 fabricated in each example. The measurement system 40 included an insulating stand 42 made of an insulating material, a stainless steel water tank 44 placed on the insulating stand 42, an ammeter 46 (manufactured by Keithley) connected to the water tank 44, and a high-voltage power supply 48 (manufactured by Matsusada Precision Co., Ltd.), with the ammeter 46 and the high-voltage power supply 48 both grounded. Ion-exchanged water W was poured into the water tank 44, and the ceramic susceptor 10 was placed in the water tank 44, as shown in FIG. 9, so that the first ceramic plate 12a was completely immersed in the ion-exchanged water W and the water level was higher than the ceramic bonding interface 12c. The distal end of the terminal rod 20 was connected to the high-voltage power supply 48 via a connector 48a. In this state, a voltage of 1 kV was applied to the terminal rod 20 by the high-voltage power supply 48, and the current value was measured with the ammeter 46. The applied voltage (1 kV) was divided by the current value to calculate the underwater insulation resistance between the surface of the ceramic susceptor 10 and the terminal rod 20 connected to the internal electrode 14. The results are shown in Table 2.

[0039] [Table 2]

Claims

1. a ceramic plate assembly including a first ceramic plate and a second ceramic plate joined to each other via a ceramic joining interface, the ceramic plate assembly having a first surface facing the first ceramic plate and a second surface facing the second ceramic plate; at least one internal electrode selected from the group consisting of a heater electrode, an RF electrode, and an ESC electrode, embedded in the first ceramic plate; a terminal hole provided in the second ceramic plate in a thickness direction from the second surface thereof, penetrating the second ceramic plate, crossing the ceramic joint interface, and reaching the internal electrode in the first ceramic plate or a metal member connected thereto, the terminal hole having a small diameter portion having a relatively small hole diameter constituting a side close to a bottom of the terminal hole and a large diameter portion having a relatively large hole diameter constituting a side farther from the bottom of the terminal hole; a metal eyelet fitted into the small diameter portion of the terminal hole; a terminal rod inserted into the terminal hole and the eyelet therein, one end of which is directly or indirectly connected to the internal electrode, and the other end of which extends from the second surface to the outside of the ceramic plate assembly; an internal passage in the first ceramic plate and / or the second ceramic plate facing the ceramic joint interface; an isolation structure formed of space and / or insulating material that electrically isolates the terminal rod and the eyelet from the ceramic joint interface; A ceramic susceptor comprising:

2. 2. The ceramic susceptor according to claim 1, wherein the internal passage is at least one selected from the group consisting of a gas passage, a cooling medium passage, a vacuum passage, and a thermocouple insertion groove.

3. the eyelet extends in the direction of the central axis of the terminal hole beyond the height of the ceramic bonding interface to a height corresponding to the second ceramic plate, and the large diameter portion extends beyond the height of the ceramic bonding interface to the inside of the first ceramic plate, The ceramic susceptor according to claim 1 or 2, wherein the isolation structure includes a space formed between an inner wall surface of the large diameter portion and the eyelet.

4. The ceramic susceptor according to claim 3 , further comprising an insulating tube covering an inner wall surface of the large diameter portion, whereby the insulating tube covers an end of the ceramic bonding interface, thereby forming a part of the isolation structure.

5. the eyelet extends in the direction of the central axis of the terminal hole beyond the height position of the ceramic joint interface to a height corresponding to the second ceramic plate, and the large diameter portion terminates within the second ceramic plate without reaching the ceramic joint interface, The ceramic susceptor of claim 1 or 2, wherein the isolation structure includes a space formed between the eyelet and the ceramic bonding interface.

6. the eyelet terminates within the first ceramic plate without reaching the height of the ceramic joint interface, and the large diameter portion terminates within the second ceramic plate without reaching the height of the ceramic joint interface; The ceramic susceptor according to claim 1 or 2, wherein the isolation structure includes a gap formed between the terminal rod and an inner wall of the small diameter portion by the eyelet not reaching the small diameter portion.

7. The ceramic susceptor of claim 6 , further comprising an insulating tube covering an inner wall surface of the small diameter portion, whereby the insulating tube covers an end of the ceramic bonding interface and thereby forms part of the isolation structure.

8. 3. The ceramic susceptor according to claim 1, further comprising an insulating film covering an outer peripheral surface of the eyelet, whereby the insulating film covers an edge of the ceramic bonding interface and thereby forms part of the isolation structure.

9. The ceramic susceptor according to claim 1 or 2, further comprising a cylindrical ceramic shaft attached to the second surface and having an internal space.

10. The ceramic susceptor of claim 1 or 2, wherein the first ceramic plate and the second ceramic plate comprise aluminum nitride or aluminum oxide.

11. 3. The ceramic susceptor according to claim 1, wherein the first ceramic plate and the second ceramic plate are made of materials having the same physical properties.

12. The ceramic susceptor according to claim 1 or 2, wherein the first ceramic plate and the second ceramic plate are made of materials having different physical properties.

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