Ceramic plate

Abstract

A ceramic plate with improved adhesion strength between a ceramic substrate and an internal electrode is provided. The ceramic plate includes a ceramic substrate containing aluminum oxide and / or aluminum nitride, and an internal electrode containing an electrode base material, a thermal expansion coefficient adjuster, and Ti, which are embedded in the ceramic substrate, and the ceramic substrate has a Ti-diffused region in which Ti is diffused around the internal electrode.

Description

[Technical field]

[0001] The present invention relates to a ceramic plate. [Background technology]

[0002] In film deposition and etching equipment for semiconductor manufacturing processes, susceptors are used to support wafers. Such susceptors generally have a structure in which internal electrodes such as heater electrodes, electrostatic chuck (ESC) electrodes, and RF electrodes are embedded inside a ceramic substrate.

[0003] Patent Document 1 (WO2019 / 188148) discloses a susceptor having a main body made of a composite sintered body containing aluminum oxide and magnesium aluminum spinel, and an internal electrode disposed inside the main body. Patent Document 2 (JP 2022-48078 A) discloses a composite sintered body having a base material containing aluminum oxide as a main material and an electrode containing ruthenium, zirconium oxide, and aluminum oxide disposed inside or on the surface of the base material. Patent Document 3 (JP 2022-48679 A) discloses a composite sintered body having a base material containing ceramic as a main material and an electrode containing tungsten and zirconium oxide disposed inside or on the surface of the base material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2019 / 188148 [Patent Document 2] Patent Publication No. 2022-48078 [Patent Document 3] JP 2022-48679 A Summary of the Invention

[0005] In applications such as susceptors for semiconductor manufacturing equipment, it is desirable to increase the adhesive strength between the ceramic substrate and the internal electrodes embedded therein in order to ensure high performance.

[0006] The inventors have now discovered that the adhesion strength between the ceramic substrate and the internal electrode can be improved by incorporating Ti into the material constituting the internal electrode and forming a Ti-diffused region in which Ti is diffused around the internal electrode.

[0007] SUMMARY OF THE PRESENT EMBODIMENTS It is therefore an object of the present invention to provide a ceramic plate having improved adhesion strength between a ceramic substrate and an internal electrode.

[0008] According to the present invention, the following aspects are provided. [Aspect 1] a ceramic substrate comprising aluminum oxide and / or aluminum nitride; an internal electrode including an electrode base material, a thermal expansion coefficient adjusting material, and Ti, embedded in the ceramic substrate; wherein the ceramic substrate has a Ti-diffused region in which Ti is diffused around the internal electrodes. [Aspect 2] 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. [Aspect 3] 3. The ceramic plate according to claim 1 or 2, wherein the electrode base material is Mo. [Aspect 4] The ceramic plate according to any one of aspects 1 to 3, wherein the thermal expansion coefficient adjuster comprises aluminum oxide and / or aluminum nitride. [Aspect 5] 5. The ceramic plate according to any one of aspects 1 to 4, wherein the content of the electrode base material in the internal electrodes is 40 to 98% by weight. [Aspect 6] 6. The ceramic plate according to any one of aspects 1 to 5, wherein the content of the thermal expansion coefficient adjuster in the internal electrodes is 1 to 40% by weight. [Aspect 7] 7. The ceramic plate according to any one of aspects 1 to 6, wherein the internal electrodes have a Ti content of 1 to 20% by weight. [Aspect 8] The ceramic plate according to any one of aspects 1 to 7, wherein the Ti-diffused regions are present over a predetermined Ti diffusion distance from the surfaces on both sides of the internal electrodes, and the Ti diffusion distance is 20 μm or more. [Aspect 9] The ceramic plate according to any one of aspects 1 to 8, wherein an average grain size of ceramic crystal grains constituting a region near the electrodes of the ceramic substrate within 20 μm from the surface on both sides of the internal electrodes is larger than an average grain size of ceramic crystal grains constituting a region of the ceramic substrate other than the Ti-diffusion region. [Aspect 10] The ceramic plate according to any one of aspects 1 to 9, wherein an average grain size of ceramic crystal grains constituting a region near the electrodes of the ceramic substrate within 20 μm from the surface on both sides of the internal electrodes is at least 2.0 times the average grain size of ceramic crystal grains constituting a region of the ceramic substrate other than the Ti-diffusion region. [Aspect 11] 11. The ceramic plate according to any one of aspects 1 to 10, wherein diffusion of Ti in the Ti-diffused region is brought about by firing an internal electrode containing Ti. [Aspect 12] 12. The ceramic plate according to any one of aspects 1 to 11, wherein the ceramic substrate is a composite sintered body containing aluminum oxide, and magnesium oxide and / or magnesium aluminum spinel. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view showing one embodiment of a ceramic plate according to the present invention. [Figure 2A]1 shows a cross-sectional SEM image of a ceramic plate sample of Example 2. [Figure 2B] 2B shows a Ti mapping image by EPMA of Example 2 measured in a region corresponding to the cross-sectional SEM image of FIG. 2A. [Diagram 3] FIG. 2 is a schematic cross-sectional view showing a jig in which a test piece was incorporated, used when measuring the adhesion strength between a ceramic substrate and an internal electrode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Ceramic plate FIG. 1 shows one embodiment of a ceramic plate according to the present invention. The ceramic plate 10 shown in FIG. 1 includes a ceramic substrate 12 and an internal electrode 14. The ceramic substrate 12 includes aluminum oxide and / or aluminum nitride. The internal electrode 14 is embedded in the ceramic substrate, and includes an electrode base material, a thermal expansion coefficient adjusting material, and Ti. The ceramic substrate 12 has a Ti-diffusion region 12a in which Ti is diffused around the internal electrode 14. By thus including Ti in the material constituting the internal electrode 14 and forming a Ti-diffusion region in which Ti is diffused around the internal electrode 14, the adhesive strength between the ceramic substrate 12 and the internal electrode 14 can be improved.

[0011] As described above, in order to ensure high performance in applications of semiconductor manufacturing equipment such as susceptors, it is desirable to increase the adhesion strength between the ceramic substrate and the internal electrode embedded therein. For example, if the adhesion strength between the ceramic substrate and the internal electrode is weak, peeling or cracks may occur. In this regard, one idea for increasing the adhesion strength between the ceramic substrate and the internal electrode is to add a ceramic material to the internal electrode, but since the resistance of the electrode also increases, it is not possible to add more ceramic material than necessary. In this regard, according to the present invention, the adhesion strength between the ceramic substrate 12 and the internal electrode 14 can be improved by including Ti as a metal additive in the material constituting the internal electrode 14. This is considered to be because a Ti-diffused region 12a in which Ti is diffused is formed around the internal electrode 14 in the ceramic substrate 12. Moreover, since Ti is a metal additive, the resistance of the electrode is less likely to increase compared to the case of adding a ceramic material.

[0012] The ceramic substrate 12 includes aluminum oxide and / or aluminum nitride, and preferably includes aluminum oxide. The ceramic substrate 12 made of such a material has excellent thermal conductivity, high electrical insulation, and thermal expansion characteristics similar to those of silicon. Therefore, the ceramic substrate 12 is made of aluminum oxide and / or aluminum nitride as a main component (for example, 50% by weight). % The content is preferably 90 to 100% by weight, more preferably 95 to 100% by weight, and particularly preferably 99 to 100% by weight.

[0013] When the ceramic substrate 12 contains aluminum oxide, the ceramic substrate 12 may further contain magnesium oxide (MgO) and / or magnesium aluminum spinel (MgAl2O4) as an additive. That is, the ceramic substrate 12 may be a composite sintered body containing aluminum oxide and magnesium oxide and / or magnesium aluminum spinel. Since magnesium oxide reacts with aluminum oxide and changes to magnesium aluminum spinel during firing, a typical composite sintered body contains aluminum oxide and magnesium aluminum spinel. In such a composite sintered body, the average grain size of the ceramic crystal grains around the internal electrode 14 tends to be larger than the average grain size in other places due to the reaction with Ti diffused from the internal electrode 14, which is considered to contribute to improving the adhesion strength between the ceramic substrate 12 and the internal electrode 14.

[0014] In a composite sintered body containing aluminum oxide (Al2O3) and magnesium aluminum spinel (MgAl2O4), the ratio of the amount of crystal phase of MgAl2O4 to Al2O3 (hereinafter also referred to as "MgAl2O4 / Al2O3 crystal phase amount ratio") is preferably within the range of 0.003 to 0.01. In this specification, the ratio of the amount of crystal phase of MgAl2O4 to Al2O3 is defined as a value obtained by dividing the peak intensity of the (311) plane of the MgAl2O4 crystal phase by the peak intensity of the (113) plane of the Al2O3 crystal phase using the results of X-ray diffraction measurement. The content of Mg in the composite sintered body has no particular upper limit, but is preferably 0.35 wt% or less, more preferably 0.07 wt% or less.

[0015] The ceramic substrate 12 has a Ti-diffusion region 12a in which Ti is diffused around the internal electrode 14. The diffusion of Ti in this Ti-diffusion region 12a is brought about by firing the Ti-containing internal electrode. As described above, the adhesion strength between the ceramic substrate 12 and the internal electrode 14 is improved by diffusing Ti around the internal electrode 14 in the ceramic substrate 12. The presence of the Ti-diffusion region 12a can be confirmed by performing elemental analysis with an EPMA (electron probe microanalyzer) on the cross section of the ceramic plate 10 to obtain a Ti mapping image, according to the procedure described in the examples below. The Ti-diffusion region 12a is located a predetermined Ti diffusion distance (L in FIG. 2B) from the surfaces on both sides of the internal electrode 14. Ti The Ti diffusion distance is preferably 20 μm or more, more preferably 20 to 100 μm, and further preferably 50 to 75 μm. The Ti diffusion distance is calculated based on the Ti mapping image by dividing the distance L Ti The outer edge of this Ti diffusion region is determined by drawing a straight line parallel to the internal electrode in a 430 μm × 600 μm viewing area of ​​the Ti mapping image, translating the line in a direction away from the internal electrode, and identifying the line at the position where the ratio of the total length of the line segments that overlap (cross) the Ti-derived pixels to the total length (600 μm) of the line is 50% or less.

[0016] It is preferable that the average grain size of the ceramic crystal grains constituting the electrode vicinity region within 20 μm from the surface on both sides of the internal electrode 14 of the ceramic substrate 12 is larger than the average grain size of the ceramic crystal grains constituting the region other than the Ti-diffused region 12a of the ceramic substrate 12. This can further improve the adhesion strength between the ceramic substrate 12 and the internal electrode 14. Specifically, it is preferable that the average grain size of the ceramic crystal grains constituting the electrode vicinity region within 20 μm from the surface on both sides of the internal electrode 14 of the ceramic substrate 12 is 2.0 times or more, more preferably 2.0 to 10.0 times, and even more preferably 2.0 to 7.0 times, of the ceramic crystal grains constituting the region other than the Ti-diffused region 12a of the ceramic substrate 12.

[0017] The thickness of the ceramic substrate 12 may be the thickness of a general ceramic plate, and is not particularly limited, but may be typically 1 to 10 mm, and more typically 2 to 5 mm.

[0018] Preferable examples of the internal electrode 14 include an ESC electrode, a heater electrode, and an RF electrode. Two types of internal electrodes 13 may be provided in the ceramic substrate 12. The ESC electrode is an abbreviation of an electrostatic chuck (ESC) electrode, and is also called an electrostatic electrode. The ESC electrode is preferably a circular thin-layer electrode having a diameter slightly smaller than that of the ceramic plate 10, and may be, for example, a mesh-like electrode formed by weaving thin metal wires into a net shape and forming a sheet. The ESC electrode may be used as a plasma electrode. That is, by applying a high frequency to the ESC electrode, the ESC electrode can also be used as a plasma electrode, and film formation can also be performed by a plasma CVD process. An ESC rod (not shown) is connected to the ESC electrode for power supply, and the ESC rod is connected to an external power source (not shown). When a voltage is applied to the ESC electrode by the external power source, the ESC electrode chucks a wafer placed on the surface of the ceramic plate 10 by the Johnsen-Rahbek force. The heater electrode is not particularly limited, and may be, for example, a conductive coil wired in a single stroke across the entire surface of the ceramic substrate 12. A heater rod (not shown) is connected to both ends of the heater electrode for power supply, and the heater rod is connected to a heater power supply (not shown). When power is supplied from the heater power supply, the heater electrode generates heat and heats the wafer placed on the surface of the ceramic plate 10. The heater electrode is not limited to a coil, and may be, for example, a ribbon (a long, thin plate) or a mesh. The ribbon-shaped heater electrode may be formed by a printing method. The internal electrode 14 is preferably used as an ESC electrode.

[0019] The internal electrode 14 includes an electrode base material, a thermal expansion coefficient adjusting material, and Ti. The electrode base material is not particularly limited as long as it is a general electrode material having a high melting point, such as a high melting point metal and / or metal carbide. Preferable examples of the electrode base material include Mo, W, WC, MoC, Nb, NbC, Ru, and alloys thereof, more preferably Mo, W or WC, and further preferably Mo. The content of the electrode base material in the internal electrode 14 is not particularly limited, but is preferably 40 to 98% by weight, more preferably 50 to 93% by weight. % It is.

[0020] The Ti content in the internal electrode 14 is not particularly limited as long as the desired adhesive strength is ensured without impairing the function of the internal electrode 14, but is preferably 1 to 20 wt %, and more preferably 3 to 20 wt %.

[0021] The thermal expansion coefficient adjusting material is a material for reducing the difference in thermal expansion coefficient between the internal electrode 14 and the ceramic substrate 12, and contributes to improving the adhesive 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 aluminum oxide 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 the desired adhesive strength can be secured without impairing the function of the internal electrode 14, but is preferably 1 to 40% by weight, and more preferably 4 to 35% by weight.

[0022] The thickness of the internal electrode 14 may be the thickness of an internal electrode embedded in a general ceramic plate, and is not particularly limited, but is preferably 1 to 50 μm, and more preferably 5 to 30 μm.

[0023] Manufacturing method The ceramic plate of the present invention can be produced by disposing a Ti-containing electrode or a Ti-containing electrode paste inside a precursor member (a compact, a calcined body, or a sintered body) of a ceramic substrate, and firing the electrode or the electrode paste by a known method. In this way, Ti is diffused from the Ti-containing internal electrode to its periphery, and a Ti-diffused region is formed around the internal electrode in the ceramic substrate. Therefore, the ceramic plate of the present invention can be produced in the same manner as the known production methods disclosed in Patent Documents 1 to 3, except that Ti is contained in the internal electrode. For example, the ceramic plate of the present invention can be produced by preparing two precursor members (a compact, a calcined body, or a sintered body) of a ceramic substrate, applying the above-mentioned electrode base material, the thermal expansion coefficient adjuster, and an electrode paste containing Ti to one of the precursor members, laminating the other precursor member on the precursor member to which the electrode paste has been applied, and firing the resulting laminate by hot pressing or the like. EXAMPLES

[0024] The present invention will now be further illustrated by the following examples.

[0025] Examples 1-4 (1) Preparation of ceramic plate A ceramic plate having internal electrodes embedded in a ceramic substrate was fabricated by the following procedure.

[0026] (1a) Preparation of ceramic calcined body A ceramic raw material powder was obtained by weighing and mixing 99.9 parts by weight of commercially available Al2O3 powder (purity: 99.99% or more, average particle size D50: 0.4 to 0.6 μm) and 0.1 parts by weight of commercially available MgO powder (purity: 99.9% or more, average particle size D50: 1 μm or less). A binder (polyvinyl alcohol (PVA)), water, a dispersant, etc. were added to this ceramic raw material powder, and the mixture was mixed in a trommel for a predetermined time (for example, 16 hours) to prepare a slurry. The obtained slurry was spray-dried in a spray dryer to obtain a granulated alumina powder. The granulated alumina powder was then subjected to a pressure of 25 to 500 kgf / cm. 2Under pressure, it was uniaxially press-formed into a disk-shaped formed body with a diameter of 350 mm and a thickness of 5 mm. This disk-shaped formed body was degreased and then calcined at 750 to 900 °C for about 1 to 4 hours to obtain a ceramic calcined body. Thus, two ceramic calcined bodies were produced for each example.

[0027] (1b) Formation of laminate Commercially available Mo powder (purity: 99.9%, average particle size D50: 1 to 2 μm), commercially available Ti powder (purity: 99.9%, average particle size D50: 3 to 4 μm), and commercially available Al2O3 powder (purity: 99.99%, average particle size D50: 0.4 to 0.6 μm) were weighed so as to have the blending ratios shown in Table 1, wet-mixed in a ball mill, and then kneaded together with a solvent (terpineol) and a binder (poly(methacrylic acid i-butyl)) to form an electrode paste. The obtained electrode paste was applied by screen printing onto the upper surface of one ceramic calcined body and dried. Thereafter, another ceramic calcined body was laminated on the ceramic calcined body coated with the dried electrode paste to form a laminate in which an electrode paste layer was sandwiched between the two ceramic calcined bodies.

[0028] (1c) Firing of laminate The laminate thus formed was placed in a hot press die. The laminate in this hot press die was fired by hot pressing in a vacuum atmosphere. This hot pressing was performed by holding at the highest temperature of 1600 °C for 8 hours at a press pressure of 250 kgf / cm 2 Thus, a ceramic plate with internal electrodes embedded therein was obtained.

[0029] (2) Evaluation of ceramic plate The following various evaluations were performed on the produced ceramic plates.

[0030] <Acquisition of Ti mapping image by EPMA> A cross section of the ceramic plate was cut out and mirror-polished, and then flat ion milling was performed with Ar ions to obtain an observation cross section. The obtained observation cross section was observed with a SEM (scanning electron microscope), and an elemental analysis was performed on the cross section with an EPMA (electron probe microanalyzer, product name: JXA-8530FPlus, manufactured by JEOL Ltd.) under a measurement condition of an acceleration voltage of 15 kV to obtain a Ti mapping image. By comparing the obtained cross-sectional SEM image with the Ti mapping image, it was confirmed that a Ti diffusion region in which Ti was diffused around the internal electrode was present in each sample of Examples 2 to 4. On the other hand, such a Ti diffusion region was not confirmed in the sample of Example 1 (comparative example). FIG. 2A shows a cross-sectional SEM image of Example 2, while FIG. 2B shows an EPMA Ti mapping image of Example 2 measured in the region corresponding to the cross-sectional SEM image of FIG. 2A. In addition, for each sample of Examples 2 to 4, the distances L from the surfaces on both sides of the internal electrode to the outer edges of the Ti diffusion region were calculated based on the Ti mapping image. Ti (Ti diffusion distance L Ti In the Ti mapping image, a total of two Ti diffusion lengths L Ti were obtained, but they were roughly the same value. One of the obtained values ​​is shown in Table 1. The outer edge of the Ti diffusion region in the Ti mapping image was determined by drawing a straight line parallel to the internal electrode in the viewing area of ​​430 μm × 600 μm of the Ti mapping image, translating the line in a direction away from the internal electrode, and identifying the line at a position where the proportion of the total length of the line segments overlapping (crossing) the Ti-derived pixels to the total length (600 μm) of the line was 50% or less.

[0031] <Composition analysis of ceramic substrate> The ceramic substrate was pulverized in a mortar to obtain a powder. The crystalline phase of this powder was identified by an X-ray diffraction (XRD) device. The measurement conditions were CuKα, 40 kV, 40 mA, 2θ = 10 to 70°, and a sealed tube type X-ray diffraction device (D8-ADVANCE, manufactured by Bruker AXS Co., Ltd.) was used. The measurement step width was 0.02°. In addition, when the content of the constituent phase was small and no peaks could be detected by X-ray diffraction, the presence of the constituent phase was confirmed by microstructural observation using SEM (scanning electron microscope) or EDX (energy dispersive X-ray analysis). As a result, it was found that in all of Examples 1 to 4, the ceramic substrate was composed of Al2O3 crystalline phase and MgAlO4 crystalline phase. The MgAl2O4 / Al2O3 crystal phase ratio in the ceramic substrate was calculated as 0.004 by dividing the peak intensity of the (311) plane of the MgAl2O4 crystal phase by the peak intensity of the (113) plane of the Al2O3 crystal phase. The Mg content in the ceramic substrate was calculated as 0.07% by weight by an analysis method based on JIS R1649.

[0032] <Average particle size> The average particle size of ceramic crystal particles such as Al2O3 crystal particles was measured by the intercept method for the electrode vicinity region within 20 μm from the surface on both sides of the internal electrode of the ceramic substrate and the region other than the Ti diffusion region of the ceramic substrate. Specifically, the ceramic substrate was polished with a cross-section polisher (CP) (IB-15000CP, manufactured by JEOL Ltd.), and the obtained polished cross section (cross section perpendicular to the main surface of the internal electrode) was photographed with a 500x field of view (190 μm × 250 μm). An arbitrary number of line segments were drawn in the electrode vicinity region in the SEM image of the polished cross section, and the number n of crystal particles crossed by the line segments of length L was calculated. Note that when the end of the line segment was located within a crystal particle, the crystal particle was counted as 1 / 2. The value obtained by dividing the length L of the line segment by n was taken as the average intercept length l, and the average particle size A of the ceramic crystal particles was determined by multiplying the l by a coefficient of 1.5. The average grain size B of the ceramic crystal grains was also determined in the same manner as above for the region other than the Ti-diffused region in the SEM image of the polished cross section of the ceramic substrate. The results are shown in Table 1, which also shows the A / B ratio.

[0033] <Adhesion strength> A ceramic plate similar to the ceramic plate prepared in (1) above was prepared, except for the thickness of the ceramic plate and the shape of the electrode paste application, and the adhesion strength between the ceramic substrate and the internal electrodes was measured.

[0034] (i) Preparation of ceramic plates Two ceramic calcined bodies with a diameter of 350 mm and a thickness of 20 mm were prepared in the same manner as in (1a) above except for the thickness. The electrode paste prepared in (1b) above was applied to one of the ceramic calcined bodies in a circular shape with a diameter slightly smaller than that of the ceramic calcined body to a thickness of 10 μm. Another ceramic calcined body was laminated on the ceramic calcined body to which the electrode paste was applied, to obtain a disk-shaped laminate with a diameter of 350 mm and a thickness of 40 mm. The laminate thus obtained was fired in the same manner as in (1c) above to obtain a disk-shaped ceramic plate. Five cylindrical test pieces with a diameter of 9.9 mm and a central axis in the thickness direction of the ceramic plate were cut out from the obtained ceramic plate. At this time, the reference position for cutting out each cylindrical test piece in the ceramic plate (i.e., the position of the central axis of each cylindrical test piece) was set to the center of the disk-shaped ceramic plate and four positions arranged at equal angular intervals in the circumferential direction on the same circumference around this center. 3, each cylindrical test piece 10' has a disk-shaped internal electrode 14 in the 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 over the entire surface of one surface of each ceramic substrate 12.

[0035] (ii) Measurement of adhesion strength As shown in FIG. 3, a jig 20 was prepared that had two horizontally adjacent jig elements 22, 24 and an internal space with approximately the same shape and dimensions as the cylindrical test piece 10'. This jig 20 is configured so that the lower surface of the jig element 22 protrudes downward from the lower surface of the jig element 24, and the upper surface of the jig element 24 protrudes upward from the upper surface of the jig element 22. Next, the cylindrical test piece 10' arranged so that the central axis direction C is horizontal was accommodated in the internal space of the jig 20. At this time, the part of the cylindrical test piece 10' to the left of the internal electrode 14 was accommodated inside the jig element 22, and the part of the cylindrical test piece 10' to the right of the internal electrode 14 was accommodated inside the jig element 24. In this way, the boundary surface (contact surface) between the jig element 22 and the jig element 24, which are in surface contact with each other, was positioned at the same position in the central axis direction C as the internal electrode 14 of the cylindrical test piece 10'. The jig 20 thus containing the cylindrical test piece 10' was set in a material testing machine (Autograph AG-10TD, manufactured by Shimadzu Corporation) so as to be sandwiched from above and below, and upward and downward loads were applied to the jig element 22 and the jig element 24, respectively. In this way, a shear load was applied to the internal electrode 14. This shear load was gradually increased until the internal electrode 14 or its left and right parts (i.e., the ceramic substrate 12) of the cylindrical test piece 10' broke. The adhesion strength of the internal electrode 14 was calculated by dividing the maximum load measured at this time by the cross-sectional area perpendicular to the central axis direction C of the internal electrode 14. The results are shown in Table 1.

[0036] [Table 1]

Claims

1. A ceramic substrate containing aluminum oxide and / or aluminum nitride, and an internal electrode embedded in the ceramic substrate and containing an electrode base material, a thermal expansion coefficient adjusting material, and Ti. The ceramic plate is provided with: the ceramic substrate has a Ti diffusion region where Ti is diffused around the internal electrode; the electrode base material is at least one selected from the group consisting of Mo, W, WC, MoC, Nb, and NbC; the ceramic plate, wherein the content of the electrode base material in the internal electrode is 40 to 98% by weight.

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

3. The ceramic plate according to claim 1 or 2, wherein the thermal expansion coefficient adjusting material contains aluminum oxide and / or aluminum nitride.

4. The ceramic plate according to claim 1 or 2, wherein the content of the thermal expansion coefficient adjusting material in the internal electrode is 1 to 40% by weight.

5. The ceramic plate according to claim 1 or 2, wherein the content of Ti in the internal electrode is 1 to 20% by weight.

6. The ceramic plate according to claim 1 or 2, wherein the Ti diffusion region exists over a predetermined Ti diffusion distance from the surfaces on both sides of the internal electrode, and the Ti diffusion distance is 20 μm or more.

7. The ceramic plate according to claim 1 or 2, wherein the average particle size of the ceramic crystal particles constituting the electrode vicinity region within 20 μm from the surfaces on both sides of the internal electrode of the ceramic substrate is larger than the average particle size of the ceramic crystal particles constituting the region other than the Ti diffusion region of the ceramic substrate.

8. The ceramic plate according to claim 1 or 2, wherein the average particle size of the ceramic crystal particles constituting the electrode vicinity region within 20 μm from the surfaces on both sides of the internal electrode of the ceramic substrate is 2.0 times or more the average particle size of the ceramic crystal particles constituting the region other than the Ti diffusion region of the ceramic substrate.

9. The ceramic plate according to claim 1 or 2, wherein the diffusion of Ti in the Ti diffusion region is caused by firing of the internal electrode containing Ti.

10. The ceramic plate according to claim 1 or 2, wherein the ceramic substrate is a composite sintered body containing aluminum oxide, and magnesium oxide and / or magnesium aluminum spinel.

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

Images