Ceramic susceptor

Abstract

Provided is a ceramic susceptor capable of improving volume resistivity at high temperatures. The ceramic susceptor according to an embodiment of the present invention has a substrate mounting plate. The substrate mounting plate includes aluminum nitride and spinel. The aluminum nitride content in the substrate mounting plate is 95.0 mass% to 99.9 mass%. The spinel content in the substrate mounting plate is 0.1 mass% to 1.0 mass% in terms of oxides. The aluminum nitride has a polycrystalline structure. The spinel is located at the grain boundary between crystal grains of the aluminum nitride. The lattice constant of the spinel is 8.040 Å to 8.110 Å.

Description

Ceramic Susceptor

[0001] The present invention relates to a ceramic susceptor.

[0002] In the manufacture of semiconductor devices such as integrated circuits, it is known to deposit a desired thin film on a semiconductor substrate supported by a ceramic susceptor equipped with a resistance heating element. Such a ceramic susceptor is, for example, a ceramic susceptor containing 90 wt % or more of an aluminum nitride phase, 0.5 to 3.0 wt % of magnesium (calculated as MgO), and TiO ２ A susceptor has been proposed that includes a plate containing a sintered body containing 0.05 to 0.5 wt % titanium (calculated as 0.05 wt %) (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2023-047311

[0004] In recent years, semiconductor devices have become increasingly multilayered, and multiple thin films may be stacked on a semiconductor substrate. In this case, it is desirable to increase the film formation temperature to thin each of the multiple thin films and thereby reduce the total thickness of the stacked structure. However, when such a film formation process is performed using the susceptor described in Patent Document 1, residual stress from the thin films may cause warping of the semiconductor substrate. Therefore, studies have been conducted to further add an electrostatic chuck (ESC) function to the susceptor described in Patent Document 1 to suppress warping of the semiconductor substrate during the film formation process. However, when an ESC electrode is provided on the susceptor described in Patent Document 1 and a film formation process is performed at a high temperature, for example, above 600°C, the volume resistivity of the plate decreases, and current may leak from the ESC electrode to the plate. Current leakage from the ESC electrode to the plate may result in insufficient electrostatic chucking function for the semiconductor substrate, making it impossible to stably support the semiconductor substrate during the film formation process. A primary object of the present invention is to provide a ceramic susceptor that can improve volume resistivity in a high temperature range.

[0005] [1] A ceramic susceptor according to an embodiment of the present invention has a substrate mounting plate. The substrate mounting plate contains aluminum nitride and a spinel. The aluminum nitride content in the substrate mounting plate is 95.0 mass % or more and 99.9 mass % or less. The spinel content in the substrate mounting plate, calculated as oxide, is 0.1 mass % or more and 1.0 mass % or less. The aluminum nitride has a polycrystalline structure. The spinel is located at grain boundaries between crystal grains of the aluminum nitride. The lattice constant of the spinel is 8.040 Å or more and 8.110 Å or less. [2] In the ceramic susceptor described in [1] above, the substrate mounting plate may further contain titanium nitride. [3] In the ceramic susceptor described in [2] above, the titanium nitride content in the substrate mounting plate may be 0.01 mass % or more and 1.0 mass % or less, calculated as oxide. [4] In the ceramic susceptor according to any one of [1] to [3] above, the volume resistivity of the substrate mounting plate at 600°C is 1.0 × 10 ９ [5] In the ceramic susceptor according to any one of [1] to [4] above, the content of α-aluminum oxide in the substrate mounting plate may be 1.0 mass % or less. [6] The ceramic susceptor according to any one of [1] to [5] above may further include an internal electrode embedded in the substrate mounting plate. [7] In the ceramic susceptor according to [6] above, the internal electrode may further include a resistance heating element.

[0006] According to an embodiment of the present invention, a ceramic susceptor having improved volume resistivity in a high temperature range can be realized.

[0007] FIG. 1 is a schematic diagram of a ceramic susceptor according to one embodiment of the present invention.

[0008] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments. In addition, in order to clarify the explanation, the width, thickness, shape, etc. of each part may be shown schematically in the drawings compared to the embodiments, but this is merely an example and does not limit the interpretation of the present invention.

[0009] A. Overview of Ceramic Susceptor FIG. 1 is a schematic diagram of a ceramic susceptor according to one embodiment of the present invention. The ceramic susceptor 100 includes a substrate mounting plate 1. The substrate mounting plate 1 may have any appropriate shape. The substrate mounting plate 1 is preferably disk-shaped. The thickness of the substrate mounting plate 1 is, for example, 5 mm to 50 mm. The substrate mounting plate 1 has a mounting surface 1a on which a semiconductor substrate 8 can be placed. The mounting surface 1a is typically one surface of the substrate mounting plate 1 in the thickness direction.

[0010] In one embodiment, the substrate support plate 1 contains aluminum nitride (hereinafter referred to as AlN) and spinel. In other words, the substrate support plate 1 contains an AlN crystalline phase and a spinel crystalline phase. The AlN content in the substrate support plate 1 is 95.0 mass % or more and 99.9 mass % or less. The spinel content in the substrate support plate 1 is 0.1 mass % or more and 1.0 mass % or less, calculated as oxide. The AlN has a polycrystalline structure. The spinel is located at the grain boundaries between AlN crystal grains. The lattice constant of the spinel is 8.040 Å or more and 8.110 Å or less. The inventors discovered that a trace amount of spinel present in a substrate support plate with an AlN content of 95.0 mass % or more affects the volume resistivity of the substrate support plate at high temperatures (e.g., 600°C or higher). Therefore, as a result of extensive research into the arrangement and crystalline state of the spinel, it was found that by having a spinel with a specific lattice constant present at the grain boundaries between AlN crystal grains, the volume resistivity of the substrate mounting plate at high temperatures can be improved. Specifically, by having a spinel with a lattice constant of 8.040 Å or more and 8.110 Å or less present at the grain boundaries between AlN crystal grains, the volume resistivity of the substrate mounting plate at high temperatures can be improved and a decrease in the volume resistivity of the substrate mounting plate at high temperatures can be significantly suppressed.

[0011] A-1. Aluminum nitride (AlN) The substrate mounting plate 1 includes a plurality of AlN crystal grains. Adjacent AlN crystal grains among the plurality of AlN crystal grains are typically bonded together. The average grain size of the plurality of AlN crystal grains is, for example, 1 μm to 5 μm, preferably 1 μm to 3 μm.

[0012] The AlN content in the substrate mounting plate 1 is preferably 97.0 mass% or more, more preferably 98.0 mass% or more. On the other hand, the AlN content in the substrate mounting plate 1 is preferably 99.8 mass% or less, more preferably 99.5 mass% or less, and even more preferably 99.0 mass% or less. When the AlN content in the substrate mounting plate is within this range, high thermal conductivity, high toughness, and high dielectric strength voltage can be achieved. The content of the constituent elements in the substrate mounting plate is measured, for example, by ICP-AES (inductively coupled plasma atomic emission spectroscopy) in accordance with JIS-K0116. The crystalline phase in the substrate mounting plate is measured, for example, by XRD (X-ray diffraction) in accordance with JIS Z2201 and JIS K0114.

[0013] A-2. Spinel Spinel is typically present at grain boundaries or is formed by a reaction between magnesium oxide and aluminum oxide at grain boundaries between AlN crystal grains. The crystal system of spinel is typically a cubic system, more specifically a face-centered cubic system. The lattice constant (a-axis lattice constant) of the spinel is preferably 8.050 Å or more, more preferably 8.060 Å or more, and even more preferably 8.063 Å or more. On the other hand, the lattice constant (a-axis lattice constant) of the spinel is preferably 8.100 Å or less, more preferably 8.090 Å or less. When the lattice constant of the spinel is in this range, the volume resistivity of the substrate mounting plate in the high temperature range can be further improved, and a decrease in the volume resistivity of the substrate mounting plate in the high temperature range can be sufficiently suppressed.

[0014] The spinel content in the substrate mounting plate 1 is preferably 0.2 mass % or more, and more preferably 0.3 mass % or more, calculated as oxide. When the spinel content in the substrate mounting plate is in this range, the volume resistivity of the substrate mounting plate in a high temperature range can be stably improved.

[0015] A-3. Titanium Nitride (TiN) In one embodiment, the substrate mounting plate 1 further contains titanium nitride (hereinafter referred to as TiN). In other words, the substrate mounting plate 1 contains a TiN crystalline phase in addition to the AlN crystalline phase and the spinel crystalline phase. TiN is typically present at the grain boundaries between AlN crystal grains.

[0016] The content of TiN in the substrate mounting plate 1, calculated as oxide, is, for example, 0.01 mass % or more, and preferably 0.3 mass % or more. On the other hand, the content of TiN in the substrate mounting plate 1, calculated as oxide, is, for example, 1.0 mass % or less, and preferably 0.8 mass % or less. When the content of TiN in the substrate mounting plate is in this range, formation of conductive paths in the grain boundary layer is suppressed, and a decrease in the volume resistivity of the substrate mounting plate is suppressed, which is preferable.

[0017] A-4. Other Crystal Phases The substrate mounting plate 1 may further contain other crystal phases. The other crystal phases are crystal phases other than the AlN crystal phase, the spinel crystal phase, and the TiN crystal phase, and examples thereof include α-aluminum oxide (α-alumina). The content of the other crystal phases in the substrate mounting plate 1 is, for example, 1.0 mass % or less. Meanwhile, the lower limit of the content of the other crystal phases in the substrate mounting plate 1 is typically 0 mass %. When the content of the other crystal phases in the substrate mounting plate is within this range, a decrease in the volume resistivity of the substrate mounting plate at high temperatures can be stably suppressed.

[0018] A-5. Physical Properties of the Substrate Mounting Plate Such a substrate mounting plate has a relatively high volume resistivity in the high temperature range. The volume resistivity of the substrate mounting plate 1 at 600°C is, for example, 1.0×10 ９ Ω cm or more, preferably 1.2 × 10 ９ Ω cm or more, more preferably 2.0 × 10 ９ Ω cm or more, more preferably 5.0 × 10 ９ Ω cm or more, particularly preferably 1.0 × 10 １０ Ω cm or more, particularly preferably 7.0 × 10 １０ Ω cm or more, most preferably 8.0 × 10１０ On the other hand, the volume resistivity of the substrate mounting plate 1 at 600° C. is, for example, 1.0×10 １２ Ω cm or less, for example, 1.5 × 10 １１ The volume resistivity of the substrate mounting plate at 600° C. is measured in accordance with, for example, JIS C2141-1992.

[0019] The thermal conductivity of the substrate mounting plate 1 at 600° C. is, for example, 20 W / m·K to 50 W / m·K. The thermal conductivity of the substrate mounting plate at 600° C. is measured in accordance with, for example, the flash method specified in JIS R1611:2010.

[0020] The open porosity of the substrate mounting plate 1 is, for example, 1.0% or less. The open porosity of the substrate mounting plate is measured in accordance with, for example, JIS R1634.

[0021] The relative density of the substrate mounting plate 1 is, for example, 99.0% or more, and preferably 99.5% or more. On the other hand, the upper limit of the relative density of the substrate mounting plate 1 is typically 100%. The relative density of the substrate mounting plate is measured, for example, in accordance with JIS R1634.

[0022] B. Manufacturing Method of Substrate Mounting Plate Next, a manufacturing method of a substrate mounting plate according to one embodiment will be described. The manufacturing method of a substrate mounting plate according to one embodiment includes a mixing step, a molding step, a calcination step, and a firing step, in this order.

[0023] B-1. Mixing Step In the mixing step, at least an AlN raw material and a magnesium oxide raw material (hereinafter referred to as an MgO raw material) are mixed together, or an AlN raw material and a spinel raw material are mixed together to prepare a mixture.

[0024] The AlN raw material contains AlN as a main component. The AlN raw material may contain oxygen and carbon in addition to AlN. The oxygen content in the AlN raw material is, for example, 0.7 mass % to 0.9 mass %. The carbon content in the AlN raw material is, for example, 200 ppm to 400 ppm. The AlN raw material is typically in a powder form. The average particle size D50 of the AlN raw material is, for example, 1 μm.

[0025] The MgO raw material contains MgO as a main component. The MgO raw material is typically in a powder form. The average particle size D50 of the MgO raw material is, for example, 0.5 μm.

[0026] The amount of the MgO raw material added is, for example, 0.1 parts by mass or more, preferably 0.2 parts by mass or more, and more preferably 0.4 parts by mass or more, relative to 100 parts by mass of the AlN raw material. On the other hand, the amount of the MgO raw material added is, for example, 1.1 parts by mass or less, preferably 1.0 part by mass or less, and more preferably 0.9 parts by mass or less, relative to 100 parts by mass of the AlN raw material.

[0027] In the mixing step, a titanium oxide raw material (hereinafter referred to as TiO ) is added to the AlN raw material and the MgO raw material (or the spinel raw material) as needed. ２ The raw material is further mixed. ２ The raw material is TiO as the main component. ２ Contains TiO ２ The raw material is typically in powder form. ２ The average particle size D50 of the raw material is, for example, 0.3 μm.

[0028] TiO ２ The amount of the raw material added is, for example, 0.1 parts by mass or more, preferably 0.3 parts by mass or more, relative to 100 parts by mass of the AlN raw material. ２ The amount of the raw material added is, for example, 1.0 part by mass or less with respect to 100 parts by mass of the AlN raw material.

[0029] In one embodiment, in the mixing step, a binder is added to the AlN raw material and the MgO raw material. Examples of binders include polyvinyl acetal resins, cellulose ether resins, (meth)acrylic resins, and paraffin wax. Note that the (meth)acrylic resin includes acrylic resins and / or methacrylic resins. The binders may be used alone or in combination. Among such binders, (meth)acrylic resins are preferred.

[0030] In the mixing step, any suitable mixing device can be used, such as a ball mill, a bead mill, a vibration mill, a rocking mixer, a blender, a homogenizer, or the like.

[0031] The mixing method may be dry mixing or wet mixing. In one embodiment, wet mixing is performed in the mixing step. In the wet mixing, any appropriate solvent is used. Examples of the solvent include alcohols such as isopropyl alcohol and ethanol; and aromatic hydrocarbons such as toluene and xylene.

[0032] The environmental conditions in the mixing step are not particularly limited. The mixing step is typically carried out at room temperature (23°C) and atmospheric pressure (0.1 MPa). The mixing time is set arbitrarily and appropriately. The mixing time is, for example, 1 hour to 24 hours.

[0033] In this way, a mixture containing at least the AlN raw material and the MgO raw material (or the spinel raw material) is prepared. When the mixing step is dry mixing, the mixture is in a powder state, and when the mixing step is wet mixing, the mixture is in a slurry state.

[0034] B-2. Granulation Step In one embodiment, the method for manufacturing a substrate mounting plate includes a granulation step after the mixing step and before the molding step. In the granulation step, the mixture obtained in the mixing step is granulated by any appropriate granulation method. Examples of the granulation method include spray granulation and tumble granulation, and spray granulation is preferred. This prepares a granulated product of the mixture (hereinafter referred to as raw material granules).

[0035] B-3. ​​Molding Step Next, in the molding step, the mixture (preferably raw material granules) is molded into a desired shape by any appropriate molding method. Examples of molding methods include press molding, sheet molding, and cold isostatic pressing (CIP) molding, and press molding is preferred. The pressure in press molding is, for example, 10 kgf / cm. ２ ~500kgf / cm ２ In this way, a molded body having a desired shape is prepared.

[0036] B-4. Firing Step Next, in the firing step, the molded body is typically fired in a vacuum or a non-oxidizing atmosphere. More specifically, the temperature is raised from room temperature (23°C) to a predetermined firing temperature, and then the firing temperature is maintained for a predetermined firing time. If necessary, a degreasing step may be provided before the firing step.

[0037] The firing temperature is, for example, 1600° C. to 1900° C., preferably 1650° C. to 1850° C. The firing time is, for example, 0.5 hours to 100 hours. The environmental pressure in the firing step is, for example, 100 kPa to 900 kPa.

[0038] Examples of the sintering method include hot pressing and hot isostatic pressing (HIP), with hot pressing being preferred. In hot pressing, the compact is typically placed in a hot press die (e.g., a carbon jig), heated to the sintering temperature as described above, and pressed at a predetermined pressure. The pressure in hot pressing is, for example, 5 MPa to 50 MPa.

[0039] The temperature is then lowered from the firing temperature to room temperature (23°C). The temperature lowering rate is adjusted arbitrarily and appropriately depending on the amount of MgO raw material added. The temperature lowering rate is, for example, 250°C / hr or less, preferably 150°C / hr or less, and more preferably 120°C / hr or less. When the temperature lowering rate is below this upper limit, the lattice constant of the spinel produced in the firing process can be stably adjusted to within the above range. On the other hand, the temperature lowering rate is, for example, 50°C / hr or more, preferably 80°C / hr or more. In this firing process, the raw materials are sintered and reacted to produce a composite sintered body containing AlN and spinel. As a result, a substrate support plate having a desired shape is prepared. The substrate support plate is typically made of a composite sintered body.

[0040] C. Details of the Ceramic Susceptor The ceramic susceptor 100 may be composed of only the substrate mounting plate 1, or may further include other members in addition to the substrate mounting plate 1.

[0041] As shown in FIG. 1, the ceramic susceptor further includes an internal electrode 2 in addition to the substrate mounting plate 1 described above.

[0042] The internal electrodes 2 are embedded in the substrate mounting plate 1. To embed the internal electrodes 2 in the substrate mounting plate 1, for example, in the above-described molding step, the mixture is molded in a state in which the internal electrodes 2 are embedded in the mixture at desired positions, and then the calcination step and the firing step are carried out.

[0043] The internal electrode 2 is positioned at a predetermined distance from the mounting surface 1a in the thickness direction of the substrate mounting plate 1. The distance between the mounting surface 1a and the internal electrode 2 in the thickness direction of the substrate mounting plate 1 is, for example, 0.1 mm to 3.0 mm.

[0044] The internal electrode 2 may be, for example, an ESC electrode, an RF electrode, or a resistance heating element.

[0045] In the illustrated example, the ceramic susceptor 100 includes an ESC electrode 21 as the internal electrode 2. When the internal electrode 2 includes the ESC electrode 21, when a voltage is applied to the ESC electrode 21 with the semiconductor substrate 8 placed on the mounting surface 1 a, the ESC electrode 21 becomes charged with either a positive or negative charge, and the other of the positive and negative charges present in the semiconductor substrate 8 moves toward the mounting surface 1 a of the semiconductor substrate 8. As a result, a Coulomb force is generated between the semiconductor substrate 8 and the ESC electrode 21, and the semiconductor substrate 8 is chucked to the substrate mounting plate 1.

[0046] Although not shown, the ceramic susceptor 100 may include a plurality of ESC electrodes 21. The plurality of ESC electrodes 21 are embedded in the substrate mounting plate 1 and are spaced apart from one another in a plane direction perpendicular to the thickness direction of the substrate mounting plate 1. When the ceramic susceptor 100 includes a plurality of ESC electrodes 21, when a voltage is applied to the plurality of ESC electrodes 21, some of the plurality of ESC electrodes 21 can be positively charged and the remaining portions of the plurality of ESC electrodes 21 can be negatively charged. Therefore, the semiconductor substrate 8 can be chucked to the substrate mounting plate 1 in multiple zones.

[0047] In one embodiment, the internal electrode 2 functions as an RF electrode (i.e., a radio frequency electrode) for plasma processing. In the illustrated example, the ESC electrode 21 also functions as an RF electrode. That is, the ESC electrode 21 preferably functions as an RF / ESC electrode. Examples of plasma processing include film formation processing and etching processing. When such plasma processing is performed on a semiconductor substrate 8 on the mounting surface 1a, an upper electrode is disposed on the opposite side of the RF electrode from the semiconductor substrate 8. In this state, when radio frequency power is supplied to the RF electrode, a processing gas can be excited in the space between the substrate mounting plate 1 and the upper electrode to generate plasma. The plasma processing is performed on the semiconductor substrate 8 using this plasma.

[0048] The ESC electrode 21 may have any appropriate shape. The ESC electrode 21 typically has a plate shape. In one embodiment, the ESC electrode 21 has a shape similar to the outer shape of the substrate mounting plate 1 when viewed in the thickness direction of the substrate mounting plate 1. In the illustrated example, the center of the ESC electrode 21 and the center of the substrate mounting plate 1 substantially coincide with each other when viewed in the thickness direction of the substrate mounting plate 1. The thickness of the ESC electrode 21 is, for example, 0.1 mm to 1.0 mm.

[0049] The ESC electrode 21 is made of any suitable conductive material. A typical conductive material is a metal having a relatively high melting point. Examples of such metals include tantalum (Ta), tungsten (W), molybdenum (Mo), platinum (Pt), rhenium (Re), hafnium (Hf), and alloys thereof. These metals may be used alone or in combination.

[0050] In the illustrated example, the ESC electrode 21 is electrically connected to the first power supply rod 6. The above-described voltage (or high-frequency power) can be applied to the ESC electrode 21 via the first power supply rod 6. The first power supply rod 6 is typically made of the same metal as the ESC electrode 21.

[0051] In one embodiment, the ceramic susceptor 100 further includes a resistance heating element 22 as the internal electrode 2. In the illustrated example, the resistance heating element 22 is located on the opposite side of the ESC electrode 21 from the mounting surface 1 a of the substrate mounting plate 1. To embed the resistance heating element 22 in the substrate mounting plate 1, for example, in the above-described molding step, the mixture is molded with the resistance heating element 22 embedded in the mixture at a desired position, and then a firing step is performed.

[0052] The resistance heating element 22 is configured to generate heat when a voltage is applied thereto. The resistance heating element 22 may have any suitable shape. Examples of the shape of the resistance heating element 22 include a coil shape, a zigzag shape, and a mesh shape. In the illustrated example, the resistance heating element 22 has a coil shape. The resistance heating element 22 may be formed by printing.

[0053] The resistance heating element 22 is made of any suitable conductive material. Typical conductive materials include metals with relatively high melting points. Examples of such metals include tantalum (Ta), tungsten (W), molybdenum (Mo), tungsten carbide (WC), titanium nitride (TiN), platinum (Pt), rhenium (Re), hafnium (Hf), and alloys thereof. Such conductive materials may be used alone or in combination. Among the conductive materials, preferred are W, Mo, W-Mo alloys, WC, and WC-TiN alloys.

[0054] In the illustrated example, the resistance heating element 22 is electrically connected to the second power feed rod 7. The above-described voltage can be applied to the resistance heating element 22 via the second power feed rod 7. The second power feed rod 7 is typically made of the same conductive material as the resistance heating element 22.

[0055] The ceramic susceptor 100 may further include a ceramic shaft 5. The ceramic shaft 5 is capable of supporting the substrate mounting plate 1. The ceramic shaft 5 is connected to the surface of the substrate mounting plate 1 opposite to the mounting surface 1a.

[0056] The ceramic shaft 5 has any appropriate shape. In one embodiment, the ceramic shaft 5 has a cylindrical shape extending in the thickness direction of the substrate mounting plate 1. In the illustrated example, the axis of the ceramic shaft 5 and the center of the substrate mounting plate 1 substantially coincide with each other when viewed in the thickness direction of the substrate mounting plate 1. The first power feed rod 6 passes through the internal space of the ceramic shaft 5 and is connected to the internal electrode 2. The second power feed rod 7 passes through the internal space of the ceramic shaft 5 and is connected to the resistance heating element 22. The ceramic shaft 5 is made of any appropriate ceramic material. The ceramic shaft 5 is made of, for example, aluminum nitride, and is preferably made of the same material as the substrate mounting plate 1.

[0057] Such a ceramic susceptor can be applied to any appropriate industrial product. Examples of uses of the ceramic susceptor include susceptors, ceramic heaters, and electrostatic chucks. In such a ceramic susceptor 100, the lattice constant of the spinel contained in the substrate mounting plate 1 is within the above-described range, thereby improving the volume resistivity of the substrate mounting plate at high temperatures, for example, at 600°C or higher. Therefore, in plasma processing such as film formation processing, current leakage from the internal electrode 2 can be significantly suppressed, and the electrostatic chuck function for the semiconductor substrate 8 can be fully exhibited.

[0058] The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these examples. The methods for measuring each property are as follows.

[0059] (1) Measurement of Volume Resistivity of Substrate Mounting Plate The volume resistivity at 600°C of the substrate mounting plates manufactured in the Examples and Comparative Examples was measured in a vacuum atmosphere in accordance with JIS C2141-1992. More specifically, a disc-shaped test piece was prepared from the substrate mounting plate. The test piece had a diameter of 50 mm and a thickness of 1 mm. Next, a main electrode and a guard electrode were provided on the upper surface of the test piece, and an application electrode was provided on the lower surface of the test piece. The main electrode, guard electrode, and application electrode were each made of silver (Ag). The diameter of the main electrode was 20 mm. The inner diameter of the guard electrode was 30 mm, and the outer diameter of the guard electrode was 40 mm. The diameter of the application electrode was 45 mm. Next, a voltage of 500 V / mm was applied to the test piece, and the current value was read 1 minute after voltage application. The volume resistivity was calculated from the current value and evaluated according to the following criteria. The results are shown in Table 1. ○: The volume resistivity of the substrate mounting plate at 600°C is 1×10 ９ Ω cm or more ×: The volume resistivity of the substrate mounting plate at 600°C is 1×10 ９ Less than Ω cm

[0060] (2) Identification of Crystalline Phases Contained in the Substrate Mounting Plate and Calculation of the Content Ratio of Each Crystalline Phase The substrate mounting plates manufactured in the Examples and Comparative Examples were pulverized in a mortar, and then silicon (Si) powder, an internal standard sample, was added and mixed. The resulting mixed powder was analyzed using an X-ray diffraction (XRD) device to identify the crystalline phases of the substrate mounting plate. The results are shown in Table 1. The measurement conditions were CuKα, 40 kV, 40 mA, 2θ = 20 to 80°, and a sealed tube X-ray diffractometer (D8-ADVANCE, manufactured by Bruker AXS) was used. The measurement step width was 0.02°. The content ratio of each crystalline phase in the substrate mounting plate was calculated by XRD. The results are shown in Table 1.

[0061] (3) Calculation of lattice constant of spinel contained in substrate mounting plate The lattice constant of the spinel contained in the substrate mounting plate manufactured in the examples and comparative examples was calculated by the WPPD method (powder pattern fitting method) using software (TOPAS manufactured by Bruker AXS). The results are shown in Table 1.

[0062] <<Example 1>> AlN raw material powder (average particle size D50: 1.2 μm, oxygen content: 0.8 mass %), MgO raw material powder (average particle size D50: 0.5 μm), and TiO ２ The raw material powder (average particle size D50: 0.3 μm) was charged into a ball mill according to the formulation shown in Table 1, and then an acrylic resin (binder) and isopropyl alcohol (IPA) were charged into the ball mill and wet-mixed for 2 hours. The resulting slurry was then dried and granulated using a spray granulator to obtain raw material granules. The particle size of the raw material granules was 80 μm. The raw material granules were then uniaxially pressed to obtain a disk-shaped compact. The pressure in the uniaxial pressing was 100 kgf / cm. ２ Next, the compact was subjected to a degreasing process and then fired by a hot press method. More specifically, the compact was fired at 1800°C for 2 hours in a nitrogen atmosphere, and the temperature was decreased at a rate of 100°C / hr. In this way, a substrate mounting plate was obtained.

[0063] <<Examples 2 to 4, Comparative Examples 1 and 2>> AlN raw material powder, MgO raw material powder and TiO２ A substrate mounting plate was obtained in the same manner as in Example 1, except that the amount of raw material powder added was changed to the formulation shown in Table 1 and the temperature drop rate was changed to the formulation shown in Table 1.

[0064]

[0065] [Evaluation] As is clear from Table 1, when a spinel having a lattice constant of 8.060 Å to 8.100 Å is present at the grain boundaries of a substrate mounting plate having an aluminum nitride (AlN) content of 95.0% or more, the volume resistivity of the substrate mounting plate at 600°C can be improved.

[0066] The ceramic susceptor according to the embodiment of the present invention can be used in various industrial products, and can be particularly suitably used as a ceramic susceptor provided in semiconductor device manufacturing equipment.

[0067] REFERENCE SIGNS LIST 1 substrate mounting plate 2 internal electrode 22 resistance heating element 100 ceramic susceptor

Claims

1. A ceramic susceptor having a substrate mounting plate containing aluminum nitride and spinel, wherein the aluminum nitride content in the substrate mounting plate is 95.0 mass % or more and 99.9 mass % or less, and the spinel content in the substrate mounting plate is 0.1 mass % or more and 1.0 mass % or less, calculated as oxide, the aluminum nitride has a polycrystalline structure, the spinel is located at grain boundaries between crystal grains of the aluminum nitride, and the lattice constant of the spinel is 8.040 Å or more and 8.110 Å or less.

2. The ceramic susceptor of claim 1, wherein the substrate mounting plate further comprises titanium nitride.

3. The ceramic susceptor according to claim 2, wherein the content of titanium nitride in the substrate mounting plate is 0.01 mass % or more and 1.0 mass % or less in terms of oxide.

4. The volume resistivity of the substrate mounting plate at 600°C is 1.0 x 10 ９ 4. The ceramic susceptor according to claim 1, wherein the resistivity is Ω·cm or more.

5. A ceramic susceptor according to any one of claims 1 to 3, wherein the content of α-aluminum oxide in the substrate mounting plate is 1.0 mass % or less.

6. The ceramic susceptor according to claim 1 , further comprising an internal electrode embedded in the substrate mounting plate.

7. The ceramic susceptor of claim 6 , wherein the internal electrode further comprises a resistive heating element.

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