Ceramic plate

Abstract

Provided is a ceramic plate in which the adhesion strength between a ceramic substrate and an internal electrode is improved. This ceramic plate is provided with: a ceramic substrate containing aluminum oxide and / or aluminum nitride; and an internal electrode that contains an electrode base material, a coefficient of thermal expansion adjusting material, and Ti and is implanted in the ceramic substrate, the ceramic substrate having a Ti diffusion region in which Ti diffuses around the internal electrode.

Description

Technical Field

[0001] This invention relates to ceramic plates. Background Technology

[0002] In semiconductor manufacturing processes, substrates are used in film deposition and etching equipment to support wafers. Such substrates typically have the following configuration: internal electrodes such as heater electrodes, electrostatic chuck (ESC) electrodes, and RF electrodes are embedded inside the ceramic substrate.

[0003] Patent Document 1 (WO2019 / 188148) discloses a base comprising: a main body of a composite sintered structure containing alumina and magnesium aluminum spinel, and an internal electrode disposed within the main body. Patent Document 2 (Japanese Patent Application Publication No. 2022-48078) discloses a composite sintered body comprising: a substrate containing alumina as the main material, and electrodes disposed within or on the surface of the substrate containing ruthenium, zirconium oxide, and alumina. Patent Document 3 (Japanese Patent Application Publication No. 2022-48679) discloses a composite sintered body comprising: a substrate containing ceramic as the main material, and electrodes disposed within or on the surface of the substrate containing tungsten and zirconium oxide.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: WO2019 / 188148

[0007] Patent Document 2: Japanese Patent Application Publication No. 2022-48078

[0008] Patent Document 3: Japanese Patent Application Publication No. 2022-48679 Summary of the Invention

[0009] However, in applications such as semiconductor manufacturing devices like substrates, it is desirable to increase the bonding strength between the ceramic substrate and the internal electrodes embedded therein in order to ensure high performance.

[0010] The inventors of this invention have recently discovered that by containing Ti in the material constituting the internal electrode and forming a Ti diffusion region that diffuses Ti around the internal electrode, the adhesion strength between the ceramic substrate and the internal electrode can be improved.

[0011] Therefore, the object of the present invention is to provide a ceramic plate in which the adhesion strength between the ceramic substrate and the internal electrode is improved.

[0012] According to the present invention, the following solution is provided.

[0013] [Option 1]

[0014] A ceramic slab, wherein:

[0015] A ceramic substrate comprising alumina and / or aluminum nitride; and

[0016] An internal electrode, comprising an electrode matrix, a thermal expansion coefficient adjusting material, and Ti, is embedded within the ceramic substrate.

[0017] The ceramic substrate has a Ti diffusion region formed by Ti diffusing around the internal electrode.

[0018] [Option 2]

[0019] According to the ceramic plate described in Scheme 1, wherein...

[0020] The electrode base material is selected from at least one of the following groups: Mo, W, WC, MoC, Nb, NbC, and Ru.

[0021] [Option 3]

[0022] According to the ceramic plate described in scheme 1 or 2, wherein,

[0023] The electrode substrate is Mo.

[0024] [Option 4]

[0025] The ceramic plate according to any one of Schemes 1 to 3, wherein...

[0026] The thermal expansion coefficient adjusting material comprises alumina and / or aluminum nitride.

[0027] [Option 5]

[0028] The ceramic plate according to any one of Schemes 1 to 4, wherein...

[0029] The content of the electrode matrix in the internal electrode is 40-98% by weight.

[0030] [Option 6]

[0031] The ceramic plate according to any one of Schemes 1 to 5, wherein...

[0032] The content of the thermal expansion rate adjusting material in the internal electrode is 1-40% by weight.

[0033] [Option 7]

[0034] The ceramic plate according to any one of Schemes 1 to 6, wherein,

[0035] The Ti content in the internal electrode is 1-20% by weight.

[0036] [Option 8]

[0037] The ceramic plate according to any one of Schemes 1 to 7, wherein,

[0038] The Ti diffusion region exists within a specified Ti diffusion distance, measured from the surfaces on both sides of the internal electrode, and the Ti diffusion distance is 20 μm or more.

[0039] [Option 9]

[0040] The ceramic plate according to any one of Schemes 1 to 8, wherein,

[0041] The average particle size of the ceramic crystal particles in the region near the electrodes, measured from the surfaces on both sides of the internal electrodes, is larger than the average particle size of the ceramic crystal particles in the region of the ceramic substrate other than the Ti diffusion region.

[0042] [Option 10]

[0043] The ceramic plate according to any one of schemes 1 to 9, wherein...

[0044] The average particle size of the ceramic crystal particles in the region near the electrodes, within 20 μm from both sides of the internal electrode constituting the ceramic substrate, is more than 2.0 times the average particle size of the ceramic crystal particles in the region constituting the ceramic substrate other than the Ti diffusion region.

[0045] [Option 11]

[0046] The ceramic plate according to any one of Schemes 1 to 10, wherein,

[0047] The diffusion of Ti in the Ti diffusion region is achieved through the sintering of the internal electrode containing Ti.

[0048] [Option 12]

[0049] The ceramic plate according to any one of Schemes 1 to 11, wherein,

[0050] The ceramic substrate is a composite sintered body comprising alumina, magnesium oxide and / or magnesium aluminum spinel. Attached Figure Description

[0051] Figure 1 This is a simplified cross-sectional view illustrating one embodiment of the ceramic plate of the present invention.

[0052] Figure 2A The cross-sectional SEM image of the ceramic plate sample in Example 2 is shown.

[0053] Figure 2B Showing the target and Figure 2AThe Ti mapping image of EPMA in Example 2 was obtained by measuring the region corresponding to the cross-sectional SEM image.

[0054] Figure 3 This is a simplified cross-sectional view of a fixture with an embedded test piece used to determine the adhesion strength between a ceramic substrate and an internal electrode. Detailed Implementation

[0055] Ceramic slab

[0056] Figure 1 The image shows one embodiment of the ceramic plate of the present invention. Figure 1 The ceramic plate 10 shown includes a ceramic substrate 12 and an internal electrode 14. The ceramic substrate 12 comprises alumina and / or aluminum nitride. The internal electrode 14 is embedded within the ceramic substrate, and the internal electrode 14 comprises an electrode matrix, a thermal expansion coefficient adjusting material, and Ti. Furthermore, the ceramic substrate 12 has a Ti diffusion region 12a formed by Ti diffusing to the surrounding area of ​​the internal electrode 14. By including Ti in the material constituting the internal electrode 14 and forming a Ti diffusion region around the internal electrode 14, the adhesion strength between the ceramic substrate 12 and the internal electrode 14 can be improved.

[0057] As described above, in applications such as semiconductor manufacturing apparatuses like substrates, it is desirable to improve the adhesion strength between the ceramic substrate and the internal electrodes embedded therein in order to ensure high performance. For example, if the adhesion strength between the ceramic substrate and the internal electrodes is weak, peeling and cracking may sometimes occur. In this regard, adding ceramic material to the internal electrodes is considered as a method to improve the adhesion strength between the ceramic substrate and the internal electrodes; however, since the resistance of the electrodes also increases, it is not possible to add more than necessary ceramic material. In this regard, according to the present invention, by containing Ti as a metal-based additive in the material constituting the internal electrode 14, the adhesion strength between the ceramic substrate 12 and the internal electrode 14 can be improved. This is believed to be because a Ti diffusion region 12a is formed around the internal electrode 14 in the ceramic substrate 12, where Ti diffuses into the ceramic substrate 12. Furthermore, since Ti is a metal-based additive, the resistance of the electrodes is less likely to increase compared to the case where ceramic material is added.

[0058] The ceramic substrate 12 comprises alumina and / or aluminum nitride, preferably alumina. The ceramic substrate 12 made of such a material exhibits excellent thermal conductivity, high electrical insulation, and thermal expansion characteristics close to those of silicon. Therefore, the ceramic substrate 12 preferably comprises alumina and / or aluminum nitride as a main component (e.g., 50% by weight or more), more preferably 90-100% by weight, further preferably 95-100% by weight, and particularly preferably 99-100% by weight.

[0059] When the ceramic substrate 12 contains alumina, it may further contain magnesium oxide (MgO) and / or magnesium aluminate spinel (MgAl2O4) as additives. That is, the ceramic substrate 12 can be a composite sintered body containing alumina, magnesium oxide, and / or magnesium aluminate spinel. Magnesium oxide reacts with alumina during firing to become magnesium aluminate spinel; therefore, a typical composite sintered body contains both alumina and magnesium aluminate spinel. Such a composite sintered body tends to have a larger average particle size of ceramic crystals around the internal electrode 14 due to the reaction with Ti diffused from the internal electrode 14, which is believed to help improve the adhesion strength between the ceramic substrate 12 and the internal electrode 14.

[0060] The ratio of the amount of MgAl2O4 to Al2O3 crystalline phase in the composite sintered body containing alumina (Al2O3) and magnesium aluminum spinel (MgAl2O4) (hereinafter also referred to as the "MgAl2O4 / Al2O3 crystalline phase ratio") is preferably in the range of 0.003 to 0.01. In this specification, the crystalline phase ratio of MgAl2O4 to Al2O3 is defined as the value obtained by dividing the peak intensity of the (311) plane of the MgAl2O4 crystalline phase by the peak intensity of the (113) plane of the Al2O3 crystalline phase using X-ray diffraction measurements. There is no particular upper limit to the Mg content in the composite sintered body, but it is preferably 0.35% by weight or less, more preferably 0.07% by weight or less.

[0061] The ceramic substrate 12 has a Ti diffusion region 12a, which is formed by Ti diffusion around the internal electrode 14. The diffusion of Ti in this Ti diffusion region 12a is achieved through the firing of the Ti-containing internal electrode. As described above, the adhesion strength between the ceramic substrate 12 and the internal electrode 14 is improved by Ti diffusion around the internal electrode 14 in the ceramic substrate 12. The existence of the Ti diffusion region 12a can be confirmed by performing EPMA (electron probe microanalyzer) elemental analysis on a cross-section of the ceramic plate 10 in the order described in the embodiments described later, to obtain a Ti mapping image. The Ti diffusion region 12a exists at a predetermined Ti diffusion distance (refer to...) measured from the surfaces on both sides of the internal electrode 14. Figure 2B L Ti Within the range of ), the Ti diffusion distance is preferably 20 μm or more, more preferably 20–100 μm, and even more preferably 50–75 μm. The Ti diffusion distance is obtained as follows: based on the Ti mapping image, each distance L from the surfaces on both sides of the internal electrode to the outer edge of each Ti diffusion region is... TiThe Ti diffusion distance was measured. The outer edge of the Ti diffusion region was defined as follows: a straight line parallel to the internal electrode was drawn in a 430μm × 600μm field of view of the Ti mapping image, and the line was moved parallel to the internal electrode in the direction away from the internal electrode. The total length of the (crossing) line segments that overlap with the pixels originating from Ti occupied less than 50% of the total length (600μm) of the straight line.

[0062] The average particle size of the ceramic crystal particles in the electrode vicinity region of the ceramic substrate 12, measured from the surfaces on both sides of the internal electrode 14 within 20 μm, is preferably greater than the average particle size of the ceramic crystal particles in the region of the ceramic substrate 12 excluding the Ti diffusion region 12a. This further improves the adhesion strength between the ceramic substrate 12 and the internal electrode 14. Specifically, the average particle size of the ceramic crystal particles in the electrode vicinity region of the ceramic substrate 12, measured from the surfaces on both sides of the internal electrode 14 within 20 μm, is preferably 2.0 times or more, more preferably 2.0 to 10.0 times, and even more preferably 2.0 to 7.0 times, the average particle size of the ceramic crystal particles in the region of the ceramic substrate 12 excluding the Ti diffusion region 12a.

[0063] The thickness of the ceramic substrate 12 can be the thickness of a typical ceramic plate, without particular limitation, typically 1 to 10 mm, and more typically 2 to 5 mm.

[0064] Preferred examples of internal electrodes 14 include: ESC electrodes, heater electrodes, and RF electrodes. Two types of internal electrodes 13 can be provided within the ceramic substrate 12. An ESC electrode is short for electrostatic chuck (ESC) electrode, also known as an electrostatic electrode. The ESC electrode is preferably a thin, circular electrode with a diameter slightly smaller than that of the ceramic plate 10; for example, it can be a mesh electrode made by weaving fine metal wires into a mesh and forming a sheet. The ESC electrode can be used as a plasma electrode. That is, by applying a high frequency to the ESC electrode, it can also be used as a plasma electrode, and a film can be formed using a plasma CVD process. An ESC rod (not shown) is connected to the ESC electrode for power supply; the ESC rod is connected to an external power source (not shown). Regarding the ESC electrode, when a voltage is applied by an external power source, the wafer placed on the surface of the ceramic plate 10 is held in place by the Johansen-Label force. The heater electrode is not particularly limited; for example, a conductive coil can be wired across the entire surface of the ceramic substrate 12 in a single-stroke manner. Heater rods (not shown) are connected to both ends of the heater electrode for power supply; the heater rods are connected to a heater power supply (not shown). The heater electrode heats up when powered by the heater power supply, heating the wafer placed on the surface of the ceramic plate 10. The heater electrode is not limited to a coil; for example, it can be a strip (a thin, elongated plate) or a mesh. The strip-shaped heater electrode can be formed by printing. The internal electrode 14 is preferably used as an ESC electrode.

[0065] The internal electrode 14 comprises an electrode base material, a thermal expansion coefficient adjusting material, and Ti. The electrode base material is not particularly limited; it can be any common electrode material with a high melting point, such as a high-melting-point metal and / or metal carbide. Preferred examples of the electrode base material include Mo, W, WC, MoC, Nb, NbC, Ru, and alloys thereof, more preferably Mo, W, or WC, and even more preferably Mo. The content of the electrode base material in the internal electrode 14 is not particularly limited, but is preferably 40–98% by weight, more preferably 50–93% by weight.

[0066] The Ti content in the internal electrode 14 is not particularly limited as long as it can ensure the desired sealing force without compromising the function of the internal electrode 14. It is preferably 1 to 20% by weight, and more preferably 3 to 20% by weight.

[0067] The thermal expansion coefficient adjusting material is used to reduce the difference in thermal expansion coefficients between the internal electrode 14 and the ceramic substrate 12, which helps to improve the adhesion strength between the ceramic substrate and the internal electrode. Therefore, the thermal expansion coefficient adjusting material can be the same ceramic material as the ceramic substrate 12. Therefore, the thermal expansion coefficient adjusting material preferably contains alumina and / or aluminum nitride. The content of the thermal expansion coefficient adjusting material in the internal electrode 14 is not particularly limited as long as it can ensure the desired adhesion force without impairing the function of the internal electrode 14, and is preferably 1 to 40% by weight, more preferably 4 to 35% by weight.

[0068] The thickness of the internal electrode 14 can be the same as that of an internal electrode implanted in a typical ceramic plate, without particular limitation, preferably 1 to 50 μm, more preferably 5 to 30 μm.

[0069] Manufacturing method

[0070] The ceramic plate of the present invention can be manufactured by placing a Ti-containing electrode or a Ti-containing electrode paste inside a precursor component (molded body, pre-fired body, or sintered body) of a ceramic substrate, and firing it using a known method. Accordingly, Ti diffuses from the Ti-containing internal electrode to its surroundings, thereby forming a Ti diffusion region around the internal electrode in the ceramic substrate. Therefore, the ceramic plate of the present invention can be manufactured in the same manner as the known manufacturing methods disclosed in Patent Documents 1-3, except that the internal electrode contains Ti. For example, regarding the ceramic plate of the present invention, two precursor components (molded bodies, pre-fired bodies, or sintered bodies) of a ceramic substrate are prepared; the aforementioned electrode paste containing electrode base material, thermal expansion adjustment material, and Ti is coated onto one precursor component; another precursor component is stacked on the precursor component coated with electrode paste; and the resulting laminate is fired using hot pressing or the like.

[0071] Example

[0072] The invention will be further illustrated by the following examples.

[0073] Examples 1 to 4

[0074] (1) Production of ceramic slabs

[0075] Ceramic plates with internal electrodes embedded in a ceramic substrate are fabricated in the following order.

[0076] (1a) Production of ceramic pre-fired body

[0077] Weigh 99.9 parts by weight of commercially available Al2O3 powder (purity: ≥99.99%, average particle size D50: 0.4–0.6 μm) and 0.1 parts by weight of commercially available MgO powder (purity: ≥99.9%, average particle size D50: ≤1 μm), and mix them to obtain ceramic raw material powder. Add binder (polyvinyl alcohol (PVA)), water, dispersant, etc., to this ceramic raw material powder, and mix using a rotary drum for a specified time (e.g., 16 hours) to prepare a slurry. Spray dry the obtained slurry using a spray dryer to obtain granulated alumina powder. The granulated alumina powder is then subjected to a temperature range of 25–500 kgf / cm³. 2 Under pressure, uniaxial compression molding is performed to produce a disc-shaped molded body with a diameter of 350 mm and a thickness of 5 mm. This disc-shaped molded body is then degreased and pre-fired at 750–900°C for approximately 1–4 hours to produce a ceramic pre-fired body. Thus, for each example, two ceramic pre-fired bodies are produced.

[0078] (1b) Formation of the stacked body

[0079] According to the mixing ratios given in Table 1, commercially available Mo powder (purity: 99.9%, average particle size D50: 1–2 μm), commercially available Ti powder (purity: 99.9%, average particle size D50: 3–4 μm), and commercially available Al2O3 powder (purity: 99.99%, average particle size D50: 0.4–0.6 μm) were weighed and wet-mixed using a ball mill. Then, the mixture was kneaded with a solvent (terpineol) and a binder (polyisobutyl methacrylate) to form an electrode paste. The obtained electrode paste was screen-printed onto the upper surface of a ceramic pre-fired body and allowed to dry. Then, another ceramic pre-fired body was stacked on top of the dried ceramic pre-fired body coated with the electrode paste, forming a laminate with an electrode paste layer sandwiched between the two ceramic pre-fired bodies.

[0080] (1c) Firing of the laminate

[0081] The resulting laminate is placed inside a hot press mold. The laminate within the hot press mold is then fired under vacuum using hot pressing at 250 kgf / cm². 2 The hot pressing is performed by holding the pressure at a maximum temperature of 1600°C for 8 hours. This results in a ceramic plate with internal electrodes embedded within a ceramic substrate.

[0082] (2) Evaluation of ceramic slabs

[0083] The following evaluations were conducted on the produced ceramic slabs.

[0084] <Obtaining Ti-mapped images using EPMA>

[0085] After cutting out the cross-section of the ceramic plate and performing mirror polishing, planar ion milling using Ar ions was performed to obtain the observation cross-section. The obtained observation cross-section was observed using a scanning electron microscope (SEM), and elemental analysis was performed on the cross-section using an EPMA (electron probe microanalyzer, product name: JXA-8530FPlus, manufactured by Nippon Electron Ltd.) under a measurement condition of 15 kV accelerating voltage, obtaining a Ti mapping image. By comparing the obtained cross-sectional SEM image and the Ti mapping image, a Ti diffusion region was confirmed in each of the samples in Examples 2-4, indicating that Ti had diffused into the vicinity of the internal electrode. On the other hand, no such Ti diffusion region was confirmed in the sample of Example 1 (Comparative Example). Figure 2A The cross-sectional SEM image of Example 2 is shown in the figure. On the other hand, Figure 2B The text shows: targeting and Figure 2A The Ti mapping image of EPMA in Example 2 was obtained by measuring the region corresponding to the cross-sectional SEM image. Furthermore, for each sample from Examples 2 to 4, based on the Ti mapping image, the distance L from the surfaces on both sides of the internal electrode to the outer edge of each Ti diffusion region was measured. Ti (Ti diffusion distance L) Ti The measurements were performed. In the Ti mapping image, two Ti diffusion distances L were obtained, one above and one below the internal electrode. Ti However, they are roughly the same value. One of the obtained values ​​is shown in Table 1. It should be noted that the outer edge of the Ti diffusion region in the Ti mapping image is defined as: a straight line drawn parallel to the internal electrode within a 430 μm × 600 μm field of view of the Ti mapping image, such that the line is moved parallel to the direction away from the internal electrode, and the total length of the (cross-cutting) line segments overlapping with the pixels originating from Ti occupies less than 50% of the total length (600 μm) of the straight line.

[0086] <Compositional Analysis of Ceramic Substrates>

[0087] The ceramic substrate was pulverized using a mortar and pestle to obtain powder. The crystalline phase of this powder was identified using X-ray diffraction (XRD). The measurement conditions were as follows: CuKα, 40 kV, 40 mA, 2θ = 10–70°, using a sealed tube X-ray diffractometer (Bruker AXS Co., Ltd., D8-ADVANCE). The measurement step width was 0.02°. Furthermore, when the content of the constituent phase was low and peaks could not be detected by X-ray diffraction, the microstructure was observed using SEM (scanning electron microscopy) or EDX (energy-dispersive X-ray diffraction) to confirm the presence of the constituent phase. The results show that even in Examples 1–4, the ceramic substrate was composed of Al₂O₃ and MgAlO₄ crystalline phases. Furthermore, the MgAl2O4 / Al2O3 crystalline phase ratio in the ceramic substrate was determined by dividing the peak intensity of the (311) plane of the MgAl2O4 crystalline phase by the peak intensity of the (113) plane of the Al2O3 crystalline phase, and the result was 0.004. Additionally, the Mg content in the ceramic substrate was determined using the analytical method according to JIS R1649, and the result was 0.07% by weight.

[0088] <Average Particle Size>

[0089] The average particle size of ceramic crystalline particles, including Al2O3 crystalline particles, was determined using the intercept method in the region near the electrodes within 20 μm from both sides of the internal electrode, and in all regions of the ceramic substrate except for the Ti diffusion region. Specifically, the ceramic substrate was polished using a cross-section polisher (CP) (Nippon Electron Ltd., IB-15000CP), and the resulting polished cross-section (a cross-section perpendicular to the main surface of the internal electrode) was photographed at 500x magnification (190 μm × 250 μm). An arbitrary number of line segments were drawn in the region near the electrodes in the SEM image obtained from observing this polished cross-section, and the number of crystalline particles n traversed by a line segment of length L was determined. It should be noted that if the end of the line segment is within a crystalline particle, the crystalline particle is counted as half a particle. The average intercept length l was obtained by dividing the length L of the line segment by n, and this l was multiplied by a coefficient of 1.5 to determine the average particle size A of the ceramic crystalline particles. In addition, the average particle size B of the ceramic crystal particles was determined in the same manner as above for the regions other than the Ti diffusion region in the SEM images obtained from the polished cross-section of the ceramic substrate. The results are shown in Table 1, which also shows the A / B ratio.

[0090] <Seam strength>

[0091] Apart from the difference in the thickness of the ceramic plate and the coating shape of the electrode paste, a ceramic plate identical to the one prepared in (1) above was made, and the adhesion strength between the ceramic substrate and the internal electrode was measured. The details are as follows.

[0092] (i) Production of ceramic slabs

[0093] Except for the thickness, the same procedure as described in (1a) is followed to prepare two ceramic pre-fired bodies with a diameter of 350 mm and a thickness of 20 mm. On one ceramic pre-fired body, the electrode paste prepared in (1b) is applied in a circular pattern with a diameter slightly smaller than that of the ceramic pre-fired body and a thickness of 10 μm. Another ceramic pre-fired body is then stacked on top of the ceramic pre-fired body coated with the electrode paste, thereby obtaining a circular plate-shaped laminate with a diameter of 350 mm and a thickness of 40 mm. This laminate is then fired in the same manner as described in (1c), thereby obtaining a circular plate-shaped ceramic plate. Five cylindrical test pieces with a diameter of 9.9 mm, centered on the thickness direction of the ceramic plate, are cut from the obtained ceramic plate. The cutting reference positions (i.e., the positions of the central axes of each cylindrical test piece) in the ceramic plate are set as follows: the center of the circular ceramic plate, and four positions arranged at equal angular intervals along the circumferential direction around that center. Figure 3 As shown, each cylindrical test piece 10' has a circular internal electrode 14 at its center in the central axis direction C, and the internal electrode 14 is sandwiched between two ceramic substrates 12. In this cylindrical test piece 10', the internal electrode 14 is formed on the entire surface of one side of each ceramic substrate 12.

[0094] (ii) Determination of sealing strength

[0095] like Figure 3As shown, a fixture 20 is prepared, which includes two horizontally adjacent fixture elements 22 and 24, and an internal space with a shape and size approximately the same as that of the cylindrical test piece 10'. The fixture 20 is configured such that the lower surface of fixture element 22 protrudes below the lower surface of fixture element 24, and the upper surface of fixture element 24 protrudes above the upper surface of fixture element 22. Next, the cylindrical test piece 10', arranged horizontally along the central axis C, is housed within the internal space of the fixture 20. At this time, the portion of the cylindrical test piece 10' to the left of the internal electrode 14 is housed within the fixture element 22, and the portion to the right of the internal electrode 14 is housed within the fixture element 24. Thus, the boundary surface (contact surface) of the fixture elements 22 and 24, which are in surface contact, is located at the same position along the central axis C as the internal electrode 14 of the cylindrical test piece 10'. The fixture 20, which houses the cylindrical test piece 10', is mounted on a material testing machine (Autograph AG-10TD, manufactured by Shimadzu Corporation) with the cylindrical test piece 10' clamped from top to bottom. Upward and downward loads are applied to fixture elements 22 and 24, respectively. This applies a shear load to the internal electrode 14. The shear load is gradually increased until the internal electrode 14 of the cylindrical test piece 10', and even its adjacent portions (i.e., the ceramic substrate 12), fracture. The adhesion strength of the internal electrode 14 is determined by dividing the maximum load measured at this point by the cross-sectional area of ​​the internal electrode 14 perpendicular to the central axis C. The results are shown in Table 1.

[0096] Table 1

[0097]

Claims

1. A ceramic plate, wherein, Possessing: a ceramic substrate containing alumina and / or aluminum nitride; and an internal electrode containing an electrode base material, a thermal expansion rate adjustment material, and Ti, and implanted in the ceramic substrate, the ceramic substrate has a Ti diffusion region in which Ti diffuses to the periphery of the internal electrode.

2. The ceramic plate according to claim 1, wherein the electrode base material is at least one selected from the group consisting of Mo, W, WC, MoC, Nb, NbC, and Ru.

3. The ceramic plate according to claim 1, wherein the electrode base material is Mo.

4. The ceramic plate according to any one of claims 1 to 3, wherein the thermal expansion rate adjustment material contains alumina and / or aluminum nitride.

5. The ceramic plate according to any one of claims 1 to 3, wherein the content of the electrode base material in the internal electrode is 40 to 98% by weight.

6. The ceramic plate according to any one of claims 1 to 3, wherein the content of the thermal expansion rate adjustment material in the internal electrode is 1 to 40% by weight.

7. The ceramic plate according to any one of claims 1 to 3, wherein the content of Ti in the internal electrode is 1 to 20% by weight.

8. The ceramic plate according to any one of claims 1 to 3, wherein the Ti diffusion region exists in a range of a prescribed Ti diffusion distance from the surface on both sides of the internal electrode, the Ti diffusion distance being 20 μm or more.

9. The ceramic plate according to any one of claims 1 to 3, wherein the average grain size of ceramic crystal grains constituting an electrode vicinity region of the ceramic substrate within 20 μm from the surface on both sides of the internal electrode is larger than the average grain size of ceramic crystal grains constituting a region other than the Ti diffusion region of the ceramic substrate.

10. The ceramic plate according to any one of claims 1 to 3, wherein the average grain size of ceramic crystal grains constituting an electrode vicinity region of the ceramic substrate within 20 μm from the surface on both sides of the internal electrode is 2.0 times or more of the average grain size of ceramic crystal grains constituting a region other than the Ti diffusion region of the ceramic substrate.

11. The ceramic plate according to any one of claims 1 to 3, wherein the diffusion of Ti in the Ti diffusion region is caused by firing of the internal electrode containing Ti.

12. The ceramic plate according to any one of claims 1 to 3, wherein the ceramic substrate is a composite sintered body containing alumina, and magnesium oxide and / or magnesium aluminate spinel.

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