Composite sintered body, electrostatic chuck member, and electrostatic chuck device

Abstract

This ceramic composite sintered body comprises aluminum oxide, which is a main phase, and silicon carbide, which is a sub-phase, wherein: the amount of carbon atoms contained in the composite sintered body is 0.45-1.5 mass%; the proportion of a region other than a composite of the aluminum oxide and the silicon carbide on the surface of the composite sintered body is at most 3%; and when the thickness of the composite sintered body is 0.3 mm, the withstand voltage is at least 15 kV.

Description

Composite sintered body, electrostatic chuck member, and electrostatic chuck device

[0001] The present invention relates to a composite sintered body, an electrostatic chuck member, and an electrostatic chuck device. This application claims priority based on Japanese Patent Application No. 2025-055794, filed in Japan on March 28, 2025, the contents of which are incorporated herein by reference.

[0002] In semiconductor manufacturing equipment that performs plasma processes, an electrostatic chuck device is used that allows for easy attachment and fixing of a plate-shaped sample (wafer) to the sample stage, and also allows the wafer to be maintained at a desired temperature. The electrostatic chuck device comprises a substrate, one of which is a mounting surface on which the wafer is placed, and electrostatic adsorption electrodes that generate an electrostatic force (Coulomb force) between the substrate and the wafer placed on the aforementioned mounting surface (see, for example, Patent Document 1). The substrate is usually formed from a ceramic sintered body.

[0003] Since electrostatic chuck devices are exposed to high-temperature plasma environments during use, they require durability against plasma. In the following description, the "durability against plasma" of an electrostatic chuck device will be referred to as "plasma resistance," and high durability against plasma will be evaluated as "high plasma resistance." As an electrostatic chuck device, it is preferable that it does not generate foreign particles (particles) that detach from the mounting surface in a plasma environment, which can be sources of contamination to plate-shaped samples. An electrostatic chuck device with high plasma resistance can suppress the generation of such particles.

[0004] As a substrate for an electrostatic chuck device with plasma resistance, a composite sintered body has been proposed in which the size of a region with a different composition from other regions is less than 5 μm in volume-based Heywood diameter distribution, and which is composed of two types of insulating particles with different particle sizes and two types of conductive particles with different particle sizes (see, for example, Patent Document 2).

[0005] Furthermore, in electrostatic chuck devices, a configuration is known in which fine grooves are provided on the upper surface of the sample stage, and a gaseous refrigerant (e.g., helium) is supplied to the grooves, causing the refrigerant to flow between the wafer and the sample stage. In such an electrostatic chuck device, it is conceivable to improve cooling efficiency and reduce the in-plane temperature difference of the wafer by increasing the gas pressure (supply pressure) of the refrigerant supplied to the grooves of the sample stage. In an electrostatic chuck device with the above configuration, when the gas pressure of the refrigerant is increased, a high adsorption force is required for the electrostatic chuck device to prevent the wafer from detaching due to the pressure received from the refrigerant. To obtain a high adsorption force, it is preferable that the relative permittivity of the substrate of the electrostatic chuck device is high.

[0006] On the other hand, the electrostatic chuck device is exposed to an alternating electric field used to generate plasma during the plasma process. The substrate is preferably made of a material with a low dielectric loss tangent to suppress heat generation in the alternating electric field.

[0007] As a substrate for an electrostatic chuck device that achieves both a high relative permittivity and a low dielectric loss tangent, a composite sintered ceramic body has been proposed that contains a metal oxide as the main phase and silicon carbide as the secondary phase, wherein a predetermined amount of silicon carbide crystal grains are dispersed within the metal oxide crystal grains and at the grain boundaries of the metal oxide (see, for example, Patent Document 3).

[0008] Japanese Patent Publication No. 2005-210077, Japanese Patent Publication No. 2020-150169, International Publication No. 2018 / 181130

[0009] However, the electrostatic chuck device described in Patent Document 2 had the problem that although its plasma resistance was improved, its voltage resistance characteristics were not sufficient.

[0010] Furthermore, in the composite sintered body described in Patent Document 3, there was a problem that the substrate was easily worn down when an aluminum silicate compound called mullite was formed, resulting in unstable plasma resistance. In the composite sintered body described in Patent Document 3, the wear of the substrate can be suppressed by reducing the silicon carbide content. However, in this case, the relative permittivity of the substrate (composite sintered body) becomes smaller, which leads to a problem of reduced adsorption force of the electrostatic chuck device.

[0011] Therefore, there was a need for composite sintered bodies with excellent plasma resistance, voltage resistance, and dielectric properties.

[0012] This invention has been made in view of these circumstances, and aims to provide a novel composite sintered body with excellent plasma resistance and high voltage resistance. It also aims to provide an electrostatic chuck member and an electrostatic chuck device using such a composite sintered body.

[0013] To solve the above problems, one aspect of the present invention includes the following aspects.

[0014] [1] A composite sintered body of ceramics comprising aluminum oxide as the main phase and silicon carbide as the secondary phase, wherein the amount of carbon atoms contained in the composite sintered body is 0.45% by mass or more and 1.5% by mass or less, the proportion of areas other than the composite of aluminum oxide and silicon carbide on the surface of the composite sintered body is 3% or less, and the withstand voltage measured when the thickness of the composite sintered body is 0.3 mm is 15 kV or more.

[0015] [2] An electrostatic chuck member having a plate-shaped base body formed from the composite sintered body described in [1], one of which is a mounting surface on which a plate-shaped sample is placed, and an electrostatic adsorption electrode provided on the opposite side of the base body from the mounting surface, or inside the base body.

[0016] An electrostatic chuck device comprising the electrostatic chuck member described in [3] and [2]. The composite sintered body described in [1] above preferably has one or more of the following features described in [4] to [6]. [4] The composite sintered body described in [1], wherein the region is a region that appears as a black spot when the surface of the composite sintered body is observed under an optical microscope at 50x magnification and binarized, and the dielectric strength is the voltage at which a current of 1 μA flows through the test piece when a test piece of the composite sintered body with a thickness of 0.3 mm is prepared and the voltage is increased and applied at a rate of 1 kV / second. [5] The composite sintered body described in [1] or [4], wherein the composite sintered body contains 1.0 part by mass or more and 5.0 parts by mass or less of silicon carbide per 100 parts by mass of aluminum oxide, the region contains an aluminum silicate, and the region is a portion on the surface of the composite sintered body where the silicate has been scraped off. [6] The composite sintered body comprises a pre-oxidation step of preparing SiC particles and oxidizing their surface, and the SiC particles treated in the pre-oxidation step and Al ２ O ３ The particles and the dispersion medium are mixed, and the Al ２ O ３ The steps are: to obtain a mixed solution containing 1 to 5 parts by mass of the SiC particles per 100 parts by mass of other particles; to adjust the pH of the mixed solution to 2.6 to 7.5; and to spray the pH-adjusted mixed solution at a rate of 300 ml / min to 1000 ml / min, and the Al ２ O ３ A step of mixing particles and the SiC particles while colliding them with each other to obtain a slurry, and removing the dispersion medium from the slurry, and the Al ２ O ３ A composite sintered body according to [1], [4], or [5], manufactured by a manufacturing method comprising: a step of obtaining granules containing particles and the SiC particles; a step of molding the obtained granules to obtain a molded body; and a step of heating the obtained molded body to 1600°C or higher while compacting it under a non-oxidizing atmosphere at a pressure of 5 MPa or higher to perform pressure sintering.

[0017] According to the present invention, a novel composite sintered body excellent in plasma resistance and having high withstand voltage can be provided. In addition, an electrostatic chuck member and an electrostatic chuck device using such a composite sintered body can be provided.

[0018] Figure 1 is a schematic diagram illustrating the state of a sintered body when measuring volume resistivity. Figure 2 is a schematic cross-sectional view showing an example of the electrostatic chuck member 2 and the electrostatic chuck device 1A described in the present embodiment. Figure 3 is an optical microscope image of a surface of the composite sintered body obtained in Example 1. Figure 4 is an optical microscope image of a surface of the composite sintered body obtained in Example 2. Figure 5 is an optical microscope image of a surface of the composite sintered body obtained in Comparative Example 1. Figure 6 is an optical microscope image of a surface of the composite sintered body obtained in Comparative Example 2.

[0019] Hereinafter, preferred examples of each embodiment of the composite sintered body, the electrostatic chuck member, and the electrostatic chuck device of the present invention will be described. The present embodiment is specifically described to facilitate better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. For example, unless otherwise particularly limited, conditions such as materials, amounts, types, numbers, sizes, ratios, and temperatures may be changed, added, or omitted as necessary. Preferred examples may be exchanged or shared between the embodiments described below.

[0020] <<Composite Sintered Body>> A ceramic composite sintered body is generally a sintered body formed using a plurality of material powders and essentially containing ceramics. Examples thereof include those obtained by mixing and sintering two or more types of ceramic powders and particles, and those obtained by mixing and sintering one or more types of ceramic powders / particles and metal particles. The composite sintered body of the present embodiment contains aluminum oxide (Al ２ O ３ ) as the main phase and silicon carbide (SiC) as the secondary phase, and is a ceramic composite sintered body. The content of carbon atoms contained in the composite sintered body is 0.45 mass% or more and 1.5 mass% or less. On the surface of the composite sintered body, the proportion of regions other than the composite of aluminum oxide and silicon carbide is 3% or less. When the thickness of the sintered body is 0.3 mm, the withstand voltage is 15 kV or more.

[0021] In this specification, "regions other than the composite of aluminum oxide and silicon carbide" refers to regions that appear as black spots when the surface of the composite sintered body is observed under an optical microscope at 50x magnification. The size (actual dimensions) of the black spots may be, for example, about 50 μm.

[0022] "Areas that appear like sunspots," for example, areas that appear as sunspots, may contain aluminum silicates, which have a different composition from the aluminum oxide and silicon carbide composite. Examples of aluminum silicates include Al ８ O １２ Si ２ Yes, Al ７ O １４ Si ２ Examples of mullites include those found on the surface of SiC particles (SiO₂). ２ (Membrane) and Al ２ O ３ It is produced by the reaction of particles.

[0023] Aluminum silicates (mullite) have lower durability when exposed to plasma compared to silicon carbide and aluminum oxide. Therefore, when a composite sintered body containing mullite is exposed to a plasma environment, the mullite is easily selectively eroded from the surface of the composite sintered body, becoming particles that can become a source of contamination for plate-like samples. In addition, the areas in the composite sintered body where the mullite has been eroded can generate pores called "pits."

[0024] Therefore, in this specification, the "areas other than the composite of aluminum oxide and silicon carbide" on the surface of the composite sintered body may be described as "pit areas" as areas where pits may occur. If there are many pit areas in the composite sintered body, there is a risk that the performance of the composite sintered body, such as wear resistance and heat uniformity, will deteriorate.

[0025] On the other hand, previous studies by the inventors have shown that conventional composite sintered bodies of aluminum oxide and silicon carbide have reduced dielectric strength when the number of pit regions is very small. In addition, conventional composite sintered bodies have the problem that when the number of pit regions is very small, the dielectric constant becomes small and the adsorption force decreases.

[0026] The pit regions described above are thought to be caused by the oxidation of silicon carbide during the manufacturing process of the composite sintered body. It is presumed that if the amount of silicon carbide oxidation is high (in other words, if there is a large amount of oxidized silicon carbide), the resulting pit regions will also be larger. On the other hand, if there is no process in which silicon carbide is oxidized, the occurrence of pit regions can be suppressed, but it may not be possible to obtain a composite sintered body with excellent dielectric strength and dielectric properties.

[0027] In response to the aforementioned conflicting requirements, the inventors focused on and investigated factors such as the amount of oxygen contained in the silicon carbide raw material, the silicon carbide content in the composite sintered body, and the process by which silicon carbide is oxidized during the manufacturing of the composite sintered body. As a result of diligent investigation, the inventors discovered that it is possible to obtain a composite sintered body of aluminum oxide and silicon carbide that has a low proportion of pit areas (3% or less), exhibits good plasma resistance, and also has excellent dielectric and dielectric properties, thus completing the invention.

[0028] (Composition) In the composite sintered body, aluminum oxide is Al ２ O ３ Therefore, although the ratio of silicon carbide (SiC) can be arbitrarily selected, in order to obtain the desired pit region ratio, dielectric constant, volume resistivity, and wear resistance, Al ２ O ３ The amount of SiC per 100 parts by mass is preferably 1.0 part by mass or more and 5.0 parts by mass, and more preferably 2.0 parts by mass or more and 4.0 parts by mass. It may also be 1.5 parts by mass or more and 3.5 parts by mass, 2.0 parts by mass or more and 3.5 parts by mass, or 2.5 parts by mass or more and 4.5 parts by mass. The main phase may mean the largest proportion in the sintered body, for example, that it is contained in more than 50% by mass in the composite sintered body. The secondary phase may mean that its proportion is less than that of the main phase. The ratio of SiC contained in the composite sintered body can be calculated, for example, by determining the amount of carbon atoms contained in the composite sintered body using a carbon analyzer and converting it as if all carbon atoms were contained in SiC.

[0029] It is known that SiC has many different crystal structures. Specifically, examples include those with a cubic crystal system and a 3C type (sphalerite type) crystal structure, those with a hexagonal crystal system such as 4H type and 6H type and a wurtzite type crystal structure, and those with a rhombohedral crystal system and a 15R type crystal structure. In this embodiment, those with a 3C type crystal structure are referred to as "β-SiC". All others with different crystal structures are referred to as "α-SiC".

[0030] The SiC contained in the composite sintered body is preferably β-SiC. Furthermore, in the composite sintered body, the crystal grains of β-SiC are made of Al, which is the matrix material. ２ O ３ In a state surrounded by crystal grains of Al ２ O ３ It is preferable that it is dispersed within the crystal grains.

[0031] To achieve the above SiC content in the composite sintered body, the amount of carbon atoms contained in the composite sintered body is 0.45% by mass or more and 1.5% by mass or less. It may also be 0.60% by mass or more and 1.3% by mass or less, 0.70% by mass or more and 1.2% by mass or less, 0.80% by mass or more and 1.1% by mass or less, or 0.90% by mass or more and 1.0% by mass or less. By having the amount of carbon contained in the composite sintered body within the above range, the amount of SiC exposed on the surface of the composite sintered body can be appropriately controlled, and the proportion of pit areas on the surface of the composite sintered body can be kept to 3% or less.

[0032] The amount of nitrogen contained in the composite sintered body of this embodiment can be arbitrarily selected, but it is preferably less than 0.015% by mass, more preferably less than 0.005% by mass, and even more preferably 0% by mass (below the detection limit).

[0033] For reasons unknown, when the composite sintered body contains a large amount of nitrogen, the proportion of pit regions may not be less than 3%. For this reason, it is preferable that the composite sintered body of this embodiment does not contain nitrogen (nitrogen atoms).

[0034] (Pit Regions) On the surface of the composite sintered body of this embodiment, the proportion of regions other than the composite of aluminum oxide particles and silicon carbide (pit regions) is 3% or less, preferably 2.5% or less, more preferably 2% or less, and even more preferably 1.5% or less. It may also be 1.4% or less, 1.3% or less, or 1.1% or less.

[0035] The proportion of pit areas is 3% or less, resulting in excellent wear resistance. Therefore, the generation of particles and pits can be suppressed when exposed to plasma. Here, wear resistance means that the composite sintered body is resistant to abrasion from physical contact. The excellent wear resistance of the composite sintered body suppresses wear due to repeated contact with the wafer, and also suppresses wear when exposed to plasma. As a result, a composite sintered body with excellent wear resistance can extend the service life of electrostatic chuck members and electrostatic chuck devices made from such composite sintered bodies.

[0036] On the other hand, from the viewpoint of dielectric strength and dielectric properties, the proportion of the pit area is preferably 0.1% or more, more preferably 0.3% or more, and even more preferably 0.5% or more. The upper and lower limits of the proportion of the pit area can be arbitrarily combined.

[0037] The proportion of the pit area can be measured by observing the surface with an optical microscope, as described above. For example, the surface of a composite sintered body, such as a plate-shaped composite sintered body, can be observed using an optical microscope (product name: Digital Microscope VHX-900F, lens illumination: brightfield (coaxial reflected light), manufactured by Keyence Corporation) at a desired magnification, for example, 50x. Examples of observation locations include the center and outer periphery of the main surface of the composite sintered body. Using the microscope image obtained in this way, the pit area and the other areas can be binarized, and the area ratio (pit area / entire observation field × 100) can be calculated. It is preferable that the surface observed is a smooth or flat surface.

[0038] When observed with an optical microscope, pit regions appear as black spots of approximately 20-300 μm in size. Therefore, by binarizing the image into areas that appear black under an optical microscope and other areas, the proportion of the surface can be calculated by considering the black areas as pit regions. In this way, the proportion of materials other than the aluminum oxide and silicon carbide composite (the proportion of pit regions) can be calculated. In the binarization process, a threshold is set where there is no substantial difference in the size of the pit regions by comparing the images before and after binarization.

[0039] The size of a single pit region can be arbitrarily selected, but it is preferably 300 μm or less, more preferably 250 μm or less, and even more preferably 200 μm or less. The average size of the pit regions is preferably 300 μm or less, more preferably 250 μm or less, and even more preferably 200 μm or less.

[0040] The size of a single pit region is defined as the length of the longest side of the smallest rectangle circumscribing the pit region. The average value can be calculated using the arithmetic mean. In this embodiment, the composite sintered body has an average pit region size of 300 μm or less, making it less susceptible to localized large plasma erosion (excellent plasma resistance), thus extending the service life of the electrostatic chuck device.

[0041] There are no particular limitations on the method for evaluating wear resistance, but for example, it can be evaluated by its resistance to machining.

[0042] (Withstand Voltage) The withstand voltage of the composite sintered body of this embodiment is 15 kV or more, as measured when the thickness of the composite sintered body is 0.3 mm. That is, the withstand voltage is the value measured when a test piece of composite sintered body with a thickness of 0.3 mm is prepared. A test piece of composite sintered body with a thickness of 0.3 mm can be obtained, for example, by surface grinding.

[0043] The dielectric strength of a composite sintered body may refer to the voltage at which a current of 1 μA flows through the sintered test piece when a voltage of 1 kV / second is applied to the composite sintered body. A high dielectric strength allows for the application of high voltages, which improves the suction force when used in electrostatic chuck devices. It also improves the durability of the composite sintered body.

[0044] In the composite sintered body of this embodiment, the degree of oxidation of silicon carbide is controlled in the manufacturing process described later to achieve both plasma resistance and dielectric strength. In this embodiment, the appropriate degree of oxidation of silicon carbide is defined using the percentage of the pit region, which is a value correlated with the amount of silicon carbide oxidation, and the dielectric strength.

[0045] (Relative Permittivity) The relative permittivity of the composite sintered body at 200 Hz is preferably 11.0 or higher, more preferably 12.0 or higher, and even more preferably 12.5 or higher. It may also be 13.0 or higher, 13.5 or higher, 14.0 or higher, 15.0 or higher, 17.0 or higher, etc. By having a relative permittivity of 11.0 or higher at 200 Hz of the composite sintered body, sufficient electrostatic adsorption force can be generated to adsorb the wafer to the electrostatic chuck device. The upper limit of the relative permittivity at 200 Hz is not particularly limited and may be 60 or lower, 50 or lower, 25 or lower, 23 or lower, 20 or lower, 18 or lower, or 16 or lower.

[0046] From the viewpoint of improving the dielectric strength of an electrostatic chuck member comprising a composite sintered body, the relative permittivity at 200 Hz is preferably 25 or less, and more preferably 20 or less. The above upper and lower limits of the relative permittivity at 200 Hz can be arbitrarily combined.

[0047] The relative permittivity of the composite sintered body at 1 MHz is preferably 11.0 or higher, and more preferably 12.0 or higher. It may also be 12.5 or higher, 13.0 or higher, 13.5 or higher, 14.0 or higher, 15.0 or higher, 17.0 or higher, etc. The upper limit is preferably 40 or lower, more preferably 35 or lower, and even more preferably 30 or lower. It may also be 25 or lower, 20 or lower, 18 or lower, or 16 or lower. More specifically, it is preferably 11 to 40, and more preferably 12 to 30. By having the relative permittivity of the composite sintered body at 1 MHz within the above range, sufficient electrostatic adsorption force can be generated to adsorb the wafer to the electrostatic chuck device.

[0048] From the viewpoint of improving the dielectric strength of an electrostatic chuck member comprising a composite sintered body, the relative permittivity at 1 MHz is preferably 23 or less, and more preferably 20 or less. The above upper and lower limits of the relative permittivity at 1 MHz can be arbitrarily combined.

[0049] The dielectric loss tangent of the composite sintered body at 1 MHz is preferably 0.035 or less, preferably 0.030 or less, and more preferably 0.029 or less.

[0050] The relative permittivity and dielectric loss tangent of a composite sintered body may be values ​​obtained by measuring the composite sintered body using, for example, the parallel plate method. For example, the relative permittivity and dielectric loss tangent can be measured using any selected apparatus, but may refer to values ​​measured in air at room temperature (25°C) using an impedance analyzer (e.g., model number E4990A, Keysight Technologies) and an LCR meter (e.g., model number 4274A, Keysight Technologies). The relative permittivity and dielectric loss tangent can also be measured, for example, according to JIS C-2139-2-1.

[0051] When measuring the relative permittivity and dielectric loss tangent of a composite sintered body, a test specimen prepared with a constant thickness can be used. For example, a cylindrical (disc-shaped) test specimen with a diameter of 28 mm and a thickness of 1 mm may be used. The main electrode provided on the composite sintered body to be measured has a diameter of φ13 mm, the outer diameter of the guard electrode 120 is φ24 mm, the inner diameter is φ15 mm, and the diameter of the counter electrode 130 is φ24 mm. It is advisable to accurately measure the thickness and diameter of the sintered body and electrodes beforehand. The electrodes can be formed using a method similar to that described later for volume resistivity. The conditions described in the examples below may be used to measure the relative permittivity and dielectric loss tangent. Note that φ represents the diameter.

[0052] (Volume Resistivity) The volume resistivity (Ω·cm) of the composite sintered body is 1.0 × 10⁻⁶ １５ Ω・cm or more 1.0×10 １８ Preferably, it is Ω·cm or less, and 5.0 × 10 １５ Ω・cm or more 5.0×10 １７ It is more preferable that it be Ω·cm or less, and 1.0 × 10 １６ Ω・cm or more 1.0×10 １７ It is even more preferable that the volume resistivity is Ω·cm or less. Having the volume resistivity of the composite sintered body within the above range ensures sufficient insulation as a substrate for the electrostatic chuck device, suppressing an increase in leakage current to the adsorbed wafer and preventing damage to devices formed on the wafer and preventing poor wafer detachment.

[0053] The volume resistivity (Ω·cm) of a composite sintered body may refer to the value obtained by measuring the composite sintered body using, for example, the DC three-terminal method. Figure 1 is a schematic diagram showing an example of the electrodes used for measurement and the appearance of the sintered body when measuring volume resistivity. In the figure, reference numeral 100 indicates the sintered body, reference numeral 110 indicates the main electrode, reference numeral 120 indicates the guard electrode, and reference numeral 130 indicates the counter electrode. The diameter of the composite sintered body 100 to be measured is, for example, φ28 mm and its thickness is 1 mm. The diameter of the main electrode 110 is φ13 mm, the outer diameter of the guard electrode 120 is φ24 mm and its inner diameter is φ15 mm, and the diameter of the counter electrode 130 is φ24 mm. φ represents the diameter. It is advisable to accurately measure the thickness and diameter of the sintered body and electrodes beforehand before measuring the volume resistivity. Volume resistivity can also be measured, for example, based on JIS C2139-3-1.

[0054] In the above method, first, to form each electrode, silver paste (e.g., US-202A, manufactured by Daiken Chemical Manufacturing & Sales Co., Ltd.) is printed onto the upper and lower surfaces of the sintered body 100 using a film-forming device such as a screen printer. Then, for example, it is dried in air at 150°C for 12 hours. In this way, the main electrode 110, guard electrode 120, and counter electrode 130 are formed. The screen printer can be selected arbitrarily, but for example, the MEC-2400 manufactured by Mitani Micronics Co., Ltd. can be used.

[0055] Next, the volume resistance of the sintered body with the three electrodes is measured using an appropriate device, such as an insulation resistance meter. For example, the volume resistance (Rv) is determined by leaving the sintered body at room temperature (24°C) for a predetermined time, applying a DC voltage, and measuring the current after charging for one minute. Specifically, the volume resistance (Rv) of the sintered body is determined by applying a DC voltage to the sintered body and measuring the current after charging for one minute using an insulation resistance meter or similar device. Then, the volume resistivity (ρv) is calculated using the thickness of the sintered body and the electrode area from the following formula (1). ρv = S / t × Rv = S / t × V / I …(1) (S: effective area of ​​the electrode (cm²) ２ ), t: thickness of sintered body (cm), Rv: volume resistivity (Ω), V: DC voltage (V), I: current (A)

[0056] For measuring volume resistivity, a resistivity measuring device or a high-resistivity / micro-current meter can preferably be used. Specifically, for example, a resistivity measuring device manufactured by Nishiyama Seisakusho Co., Ltd. and a digital ultra-high-resistivity / micro-current meter (model 5450) manufactured by ADC Corporation can preferably be used. For example, the measurement atmosphere may be air, and the applied voltage may be, for example, 500V. For measuring volume resistivity, the conditions described in the embodiments below may also be used.

[0057] (Grain size) Al contained in the composite sintered body ２ O ３ The average grain size of the particles can be arbitrarily selected within the range in which the composite sintered body satisfies the aforementioned electrical properties (relative permittivity, volume resistivity, and dielectric strength). ２ O ３ The average grain size of the particles is preferably, for example, 0.1 μm to 10 μm. More preferably, it is 0.5 μm to 5 μm, and even more preferably, 0.7 μm to 3 μm. The average grain size can be obtained by polishing the surface of the sample and measuring it with an electron microscope (SEM).

[0058] In a composite sintered body, Al ２ O ３ The average particle size is 0.1 μm or larger, Al ２ O ３ It is possible to achieve a sufficient insulating effect without the resistivity of the particles themselves decreasing too much. ２ O ３ Because the average grain size is 10 μm or less, the resulting sintered body has sufficiently high mechanical strength and is less prone to chipping.

[0059] In a composite sintered body, Al ２ O ３ The average grain size of Al can be adjusted by controlling the sintering temperature. When the sintering temperature is high, ２ O ３ The average grain size of Al tends to increase, and as the sintering temperature decreases, ２ O ３ The average grain size tends to be smaller.

[0060] (Metallic Impurities) In composite sintered bodies, it is preferable that the content of metallic impurities other than aluminum and silicon is 100 ppm or less. The content of metallic impurities is preferably 50 ppm or less, and more preferably 25 ppm or less. It may also be 10 ppm or less, 5 ppm or less, or 1 ppm or less.

[0061] 《Method for Manufacturing a Composite Sintered Body》 An example of a preferred method for manufacturing the composite sintered body of this embodiment will be described. The method for manufacturing the composite sintered body of this embodiment is: (a) a pre-oxidation step in which the surface of the SiC particles is oxidized, and (b) the SiC particles treated in the pre-oxidation step and Al ２ O ３ (c) A step of obtaining a mixture of particles and a dispersion medium, and (c) Al in the mixture ２ O ３ (d) Adjusting the pH of the mixture so that the surface charge of the particles is positive and the surface charge of the SiC particles in the mixture is negative, and (d) spraying the pH-adjusted mixture at high speed using a grinding and mixing device, Al ２ O ３ (e) A step of mixing particles and SiC particles while colliding them with each other to obtain a slurry, and (f) removing the dispersion medium from the slurry, Al ２ O ３ The process preferably includes the steps of: (f) obtaining granules containing particles and SiC particles; (g) molding the obtained granules to obtain a molded body; and (g) heating the obtained molded body to 1600°C or higher while compacting it under a non-oxidizing atmosphere at a pressure of 5 MPa or higher to perform pressure sintering.

[0062] The "non-oxidizing atmosphere" can be selected arbitrarily, but preferred examples include an inert gas atmosphere or a vacuum atmosphere.

[0063] The inert gas can be selected arbitrarily; for example, nitrogen or argon can be preferably used.

[0064] "Vacuum" means "a state in a space filled with a gas at a pressure lower than atmospheric pressure," and may also refer to the state defined in JIS standards as a pressure that can be used industrially. A vacuum atmosphere refers to an atmosphere where the pressure of the atmospheric gas is the above-mentioned "vacuum." In this embodiment, the vacuum atmosphere may be a low vacuum (100 Pa or more), but is preferably a medium vacuum (0.1 Pa to 100 Pa), and a high vacuum (10 －５ It is more preferable that the pressure is Pa to 0.1 Pa.

[0065] An oxidizing atmosphere means that the atmospheric gas contains oxygen. Examples of oxidizing atmospheres include not only air but also a mixed gas atmosphere of an inert gas and oxygen.

[0066] In the manufacturing method of the composite sintered body of this embodiment, the Al used ２ O ３ The particle is Al ２ O ３ It is preferable that the content of is 99.99% or more. ２ O ３ The particles can be prepared using the alum method. ２ O ３ The particles are Al prepared using, for example, the Bayer method. ２ O ３ Compared to particles, it is possible to significantly reduce the content of sodium atoms, which are metal impurities. Furthermore, Al of the desired purity can be achieved. ２ O ３ If particles can be obtained, various other methods can be employed.

[0067] (a) Pre-oxidation process In the pre-oxidation process, the SiC particles to be used as raw materials are first subjected to a heat treatment in an oxidizing atmosphere to pre-oxidize the surface of the SiC particles. Hereinafter, the above oxidation treatment may be referred to as "pre-oxidation".

[0068] The average particle size of the SiC particles used can be arbitrarily selected as long as it can be processed by the grinding and mixing apparatus described later. For example, it is preferably 20 to 100 nm, more preferably 25 to 90 nm, and even more preferably 35 to 80 nm. It may also be 30 to 60 nm, 40 to 70 nm, or 60 to 90 nm. The upper and lower limits of the average particle size of the SiC particles can be arbitrarily combined from the above ranges. However, it is not limited to these examples. The average particle size may be the average diameter of the particle lengths. That is, the average particle size of SiC particles may be the arithmetic mean of the lengths of the longest sides of the smallest rectangle circumscribing the SiC particles. The average particle size of SiC can be calculated from electron microscope images such as those obtained with a scanning electron microscope (SEM).

[0069] The oxygen content in the SiC particles used is not particularly limited as long as the effects of the present invention are obtained. For example, it is preferably 3.0% by mass or less, more preferably 2.0% by mass or less, and even more preferably 1.8% by mass or less. It may also be 1.5% by mass or less, or 1.0% by mass or less. The lower limit can be arbitrarily selected as needed, but for example, it may be 0.0% by mass or more, 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, or 0.8% by mass or more. The oxygen content can be measured, for example, by an oxygen-nitrogen analyzer. By reducing the amount of oxygen contained in the SiC particles used as raw materials, the proportion of pit regions can be reduced. Note that "oxygen contained in SiC particles" refers to oxygen atoms contained when the SiC particles are partially oxidized.

[0070] The temperature and time of pre-oxidation are not particularly limited and can be arbitrarily selected as long as the effects of the present invention are obtained. The temperature is preferably 200 to 400°C, more preferably 250 to 350°C. It may also be 230 to 300°C, 280 to 350°C, 320 to 400°C, etc. The upper and lower limits of the pre-oxidation temperature can be arbitrarily combined from the above range. The pre-oxidation time can also be arbitrarily selected, for example 1 to 24 hours, more preferably 6 to 12 hours. It may also be 1 to 3 hours, 2 to 10 hours, 8 to 15 hours, 10 to 20 hours, etc. The upper and lower limits of the pre-oxidation time can be arbitrarily combined from the above range. However, it is not limited to these examples only.

[0071] In the pre-oxidation process, for example, the surface of the SiC particles can be oxidized by heating at 300°C for 12 hours. When the amount of SiC particles is large, the pre-oxidation temperature is preferably between 200°C and 350°C, and more preferably between 250°C and 320°C. By lowering the pre-oxidation temperature, a composite sintered body with excellent wear resistance can be obtained.

[0072] By pre-oxidizing SiC particles, silicon dioxide (SiO₂) is formed on the surface of the SiC particles. ２ A film is formed, which increases the hydrophilicity of the SiC particles. This improves the dispersibility of SiC particles in the slurry.

[0073] (b) Step to obtain the mixed solution) In the step to obtain the mixed solution, the Al used as a raw material ２ O ３ The particles and SiC particles are mixed with an organic dispersant and a dispersion medium to obtain a mixture. The mixing method is not particularly limited as long as these materials can be mixed uniformly, and known mixing devices such as stirrers and ultrasonic devices can be used.

[0074] Al used as a raw material ２ O ３The average particle size can be arbitrarily selected as long as it can be processed by the grinding and mixing apparatus described later. For example, it is preferably 0.05 to 0.3 μm, more preferably 0.07 to 0.27 μm, and even more preferably 0.1 to 0.25 μm. It may also be 0.13 to 0.23 μm or 0.15 to 0.20 μm. Al ２ O ３ The upper and lower limits of the average particle diameter can be any combination from the above range. ２ O ３ The average particle diameter may be the volume-average particle diameter.

[0075] The amount of SiC particles used, that is, the SiC particle content in the resulting slurry, is Al ２ O ３ The amount of SiC particles is preferably 1 to 5 parts by mass, and more preferably 2 to 4 parts by mass, per 100 parts by mass of particles. It may also be 1.5 to 3.5 parts by mass, or 2.5 to 4.5 parts by mass, etc. The upper and lower limits of the amount of SiC particles can be any combination from the above range. However, it is not limited to these examples.

[0076] The dispersion medium used is Al ２ O ３ Any solvent capable of dispersing the particles and SiC particles can be selected. For example, water and alcohols such as methanol and ethanol can be used. One of these dispersion media may be used alone, or two or more may be used in combination. The amount of dispersion media can be selected as needed.

[0077] The dispersant used can be a known dispersant, such as a polycarboxylic acid-based dispersant. A commercially available dispersant can preferably be used; for example, Aron A6114 (manufactured by Toagosei Co., Ltd.) can be used.

[0078] (c) Step to adjust pH In the step to adjust pH, Al in the mixed solution ２ O ３pH adjustment of the mixed liquid is performed in consideration of the surface charges of the particles and the SiC particles. The mixed liquid obtained in the above mixing step (the mixed liquid before pH adjustment) usually exhibits basicity of about pH 11. The pH adjustment may be performed while stirring.

[0079] When the pH of the mixed liquid is on the acidic side (pH < 7), Al ２ O ３ particles have a positive zeta potential for Al ２ O ３ particles. This is because when the pH of the mixed liquid is on the acidic side, hydroxyl groups on the surface of Al ２ O ３ particles are protonated (H ＋ ), that is, protons (H ＋ ) are added, which is considered to cause the surface to become positively charged.

[0080] On the other hand, when the pH of the mixed liquid is on the basic side (pH > 7), Al ２ O ３ particles have a negative zeta potential. This is considered to be because when the pH of the mixed liquid is on the basic side, protons dissociate from hydroxyl groups on the surface of Al ２ O ３ particles, causing the surface to become negatively charged. The zeta potential may refer to the potential difference generated between the surface of particles dispersed in a liquid, specifically a layer called the slipping plane near the surface, and the surrounding liquid.

[0081] Al ２ O ３ compared with the above behavior of particles, the behavior of the zeta potential of SiC particles is different. For SiC particles, when the pH of the mixed liquid is in the range up to around 2 to 3, the zeta potential of SiC particles becomes zero. And the zeta potential of SiC particles becomes negative in a wide range from the acidic region where the pH of the mixed liquid is around 3 to the basic region.

[0082] When two particles having such a relationship coexist in the same mixed liquid, when the pH of the mixed liquid is in a range where "the surface charge of Al ２ O ３ particles in the mixed liquid is positive" and "the surface charge of SiC particles in the mixed liquid is negative", the two particles preferably aggregate, so-called hetero-aggregation occurs. In this step, the pH of the slurry is adjusted to about 2.6 to 7.5, and Al ２O ３ The particles and SiC particles are heteroaggregated.

[0083] At this time, Al ２ O ３ To prevent the particles and SiC particles from precipitating, it is preferable to add a dispersant to the mixture as appropriate. As the dispersant, known dispersants, such as polycarboxylic acid-based dispersants, can be used. Commercially available dispersants can preferably be used; for example, Aron A6114 (manufactured by Toagosei Co., Ltd.) can be used.

[0084] The pH of the mixed solution used for heteroaggregation is preferably 3 to 7, more preferably 4 to 7, even more preferably 5 to 7, and particularly preferably 6 to 7. When comparing the absolute values ​​of the zeta potentials of both particles after pH adjustment, the closer the absolute values ​​of the zeta potentials are to each other, the more likely heteroaggregation is to occur, resulting in the desired aggregated state.

[0085] pH adjustment can be performed by adding the desired amount of acid to the mixture and mixing. While any acid can be used, inorganic acids such as nitric acid, phosphoric acid, hydrochloric acid, and sulfuric acid, and organic acids such as acetic acid are preferred. Of these, hydrochloric acid and sulfuric acid may generate chlorine and sulfur in the sintering process described later, potentially causing equipment deterioration. Therefore, it is preferable to use nitric acid, phosphoric acid, and organic acids for pH adjustment.

[0086] (d) Step to obtain slurry In the step to obtain slurry, a pH-adjusted mixture is sprayed at high speed using a grinding and mixing device (for example, a two-flow particle impact type grinding and mixing device), and Al ２ O ３ A slurry is obtained by mixing particles and SiC particles while colliding them with each other. By performing this mixing, Al ２ O ３ The particles and SiC particles are pulverized, and a slurry containing these pulverized particles is obtained. The injection speed can be arbitrarily selected, but is preferably, for example, 300 ml / min to 1000 ml / min. It may also be 400 ml / min to 800 ml / min or 500 ml / min to 700 ml / min.

[0087] Al ２ O ３ When particles collide with SiC particles, larger particles have greater kinetic energy during the collision and are easily pulverized. On the other hand, smaller particles have less kinetic energy during the collision and are less easily pulverized. Therefore, the pulverized Al obtained using the above-mentioned pulverization and mixing apparatus is difficult to pulverize. ２ O ３ The particles and SiC particles will have a narrow particle size distribution with few coarse or over-ground particles. Therefore, using mixed particles ground and mixed using a two-flow particle impact type grinding and mixing apparatus can suppress abnormal grain growth nucleated by coarse particles during the pressure sintering process described later.

[0088] Furthermore, when grinding and mixing using such a grinding and mixing device, it is possible to suppress the inclusion of impurities caused by damage to each medium, compared to methods that use media such as ball mills or bead mills.

[0089] (e) Step to obtain granules In the step to obtain granules, the dispersion medium is removed from the slurry, and Al ２ O ３ Granules containing particles and SiC particles are obtained. The method for removing the dispersion medium can be arbitrarily selected. For example, a known spray drying method can be suitably used. The size of the granules can be arbitrarily selected, but generally, they may be, for example, 30 to 100 μm or 50 to 85 μm.

[0090] In the spray-drying method, minute droplets of slurry are sprayed. By spraying, the surface area per unit volume of the slurry is increased, and by continuously exposing the minute droplets to hot air, instantaneous drying and granulation can be achieved. Granules produced by the spray-drying method tend to be spherical, reflecting the shape of the minute droplets.

[0091] (e-1) Oxidation treatment step) After step (e) obtaining granules, an oxidation treatment step may be performed on the obtained granules. If you want to improve the dielectric strength characteristics, it is preferable to perform the oxidation treatment. If you want to reduce the proportion of pit areas, it is preferable not to perform this step.

[0092] In the oxidation treatment process, for example, the obtained granules are first heated in a non-oxidizing atmosphere at a temperature between 100°C and 700°C, and then heated in an oxidizing atmosphere to oxidize the surface of the granules. In the oxidation treatment process, the treatment is carried out sequentially under the two different atmospheres.

[0093] First, the obtained granules are heated to a temperature of 100°C to 700°C (for example, 500°C) under normal pressure (without pressing) in a non-oxidizing atmosphere. This removes impurities such as water, dispersion medium, and dispersant contained in the granules. The above temperature may be 300 to 700°C, 300 to 650°C, 400 to 550°C, 500 to 600°C, etc., as needed. It may also be 150°C to 400°C, 200°C to 450°C, etc. The heating time can be arbitrarily selected, but for example, it may be 3 to 8 hours, 8 to 10 hours, or 10 to 15 hours. These atmospheres and temperatures are sometimes referred to as the degreasing atmosphere and degreasing temperature.

[0094] As a non-oxidizing atmosphere, an inert gas atmosphere using nitrogen or argon is preferred. Furthermore, when performing the above heating under an inert gas atmosphere, in order to efficiently remove the generated impurities from the system, a heating treatment using so-called gas flow, where the atmospheric gas is flowed, is preferred.

[0095] Next, the granules from which impurities have been removed are oxidized by heating them to an arbitrarily selected temperature (e.g., 380°C or lower) under an oxidizing atmosphere. The atmosphere for the oxidation treatment can be arbitrarily selected, but an air atmosphere is preferred. The above temperature can be selected as needed, and may be 100 to 370°C, 150 to 350°C, 200 to 400°C, 180 to 300°C, etc. The heating time can be arbitrarily selected, and may be 1 to 5 hours, 5 to 12 hours, or 12 to 24 hours, for example.

[0096] According to this procedure, an oxide film (SiO₂) is formed on the surface of the SiC particles contained in the granules during the oxidation treatment. ２ This can suppress the formation of a film.

[0097] (f) Step to obtain a molded body Next, the obtained granules are molded, preferably by uniaxial molding (uniaxial press molding), according to the desired shape of the sintered body, to obtain a molded body.

[0098] (g) Pressure sintering step In the pressure sintering step, the molded body obtained in step (f) obtaining the molded body is compressed in a non-oxidizing atmosphere at a pressure of an arbitrarily selected pressure, for example, 5 MPa or more, preferably 15 MPa or more, more preferably 25 MPa or more, and heated to an arbitrarily selected temperature, for example, 1600°C or higher, to perform pressure sintering. Through this operation, the Al contained in the molded body ２ O ３ The sintering of the particles and SiC particles proceeds, resulting in a dense sintered body with few pores. The above temperature can be selected as needed, and may be 1700-1800°C or 1800-1900°C, etc. The heating time can be selected arbitrarily, for example, 1-5 hours, 3-8 hours, or 6-12 hours.

[0099] According to the manufacturing method described above, a composite sintered body of this embodiment can be obtained in which the degree of oxidation of silicon carbide is appropriately controlled.

[0100] 《Electrostatic Chuck Member, Electrostatic Chuck Device》 Figure 2 is a schematic cross-sectional view showing the electrostatic chuck member 2 and electrostatic chuck device 1A of this embodiment. The electrostatic chuck device 1A includes the electrostatic chuck member 2.

[0101] In this specification, the side on which the electrostatic chuck member 2 is positioned relative to the base 3 may be referred to as "upper," and the opposite side as "lower." Furthermore, in the following description, the vertical direction will be used as the stacking direction when describing the parts of the electrostatic chuck device 1A. However, the vertical direction here is merely used for the sake of simplicity in explanation and does not limit the orientation of the electrostatic chuck device 1A when it is in use.

[0102] <Electrostatic Chuck Member> The electrostatic chuck member 2 comprises a base body 11 and an electrostatic adsorption electrode 13. The electrostatic chuck member 2 has a first adsorption portion 21 that adsorbs and holds the wafer W on its upper surface, and a second adsorption portion 22 that adsorbs and holds the focus ring FR on its upper surface. The base body 11 is formed from the composite sintered body described above.

[0103] The first suction portion 21 is formed in a cylindrical shape in plan view, and its upper surface is provided with a plurality of upwardly projecting protrusions 211. In addition, a closed annular protrusion 212 is provided along the edge of the upper surface of the first suction portion 21. In this specification, "plan view" refers to the field of view from the thickness direction of the electrostatic chuck member 2.

[0104] The electrostatic chuck device 1A supports the wafer W with the tips (upper surfaces) of the multiple protrusions 211 and the upper surface of the annular protrusion 212. In other words, in the electrostatic chuck device 1A, the virtual surface connecting the upper surface of the annular protrusion 212 and the upper surfaces of the multiple protrusions 211 corresponds to the mounting surface 21a of the wafer W.

[0105] When a wafer W is placed on the mounting surface 21a, the space on the lower surface of the wafer W, surrounded by the multiple protrusions 211 and the annular protrusion 212, functions as a flow channel 21x for the cooling gas to flow. The electrostatic chuck device 1A is provided with a gas supply hole (not shown) that penetrates the electrostatic chuck device 1A in the thickness direction, and cooling gas is supplied from the gas supply hole to the flow channel 21x. The cooling gas flowing through the flow channel 21x cools the wafer W, which is heated during plasma processing.

[0106] The second suction portion 22 is a concentric cylindrical (donut-shaped) form with a larger radius than the first suction portion 21 in a plan view, and the second suction portion 22 is integrally formed with the first suction portion 21. The upper surface 22a of the second suction portion 22 is exposed in a plan view, surrounding the periphery of the first suction portion 21. The upper surface 22a corresponds to the mounting surface that holds the focus ring FR by suction.

[0107] An annular groove 22x is formed on the upper surface 22a in plan view. When the focus ring FR is placed on the upper surface 22a, the space surrounded by the lower surface of the focus ring FR and the groove 22x functions as a flow path for the cooling gas. The electrostatic chuck device 1A is provided with a gas supply hole (not shown) that penetrates the electrostatic chuck device 1A in the thickness direction, and cooling gas is supplied from the gas supply hole to the flow path (groove 22x). The cooling gas flowing through the flow path cools the focus ring FR, which is heated during plasma processing.

[0108] (Electrostatic Adsorption Electrode) The electrostatic adsorption electrode 13 is positioned inside the substrate 11. The electrostatic adsorption electrode 13 extends along the mounting surface 21a of the substrate 11. When a voltage is applied to the electrostatic adsorption electrode 13, it generates an electrostatic adsorption force to hold the wafer W on the mounting surface 21a. In Figure 2, the electrostatic adsorption electrode 13 is provided inside the substrate 11, but the electrostatic adsorption electrode 13 may also be provided on the surface of the substrate 11 opposite to the mounting surface (i.e., the lower surface 2a of the electrostatic chuck member 2).

[0109] The adsorption electrode 15 is positioned inside the substrate 11. The adsorption electrode 15 extends in an annular shape in plan view along the upper surface 22a of the second adsorption portion 22. When a voltage is applied, the adsorption electrode 15 generates an electrostatic adsorption force to hold the focus ring FR to the upper surface 22a.

[0110] The electrostatic adsorption electrode 13 and the adsorption electrode 15 are each connected to a power supply terminal (not shown) for applying a DC voltage to the electrostatic adsorption electrode 13 and the adsorption electrode 15, respectively.

[0111] The electrostatic adsorption electrodes 13 and 15 are preferably composed of a composite material of an insulating material and a conductive material. The insulating material contained in the electrostatic adsorption electrodes 13 and 15 is not particularly limited, but for example, aluminum oxide (Al ２ O ３ ), aluminum nitride (AlN), silicon nitride (Si ３ N ４ ), yttrium(III) oxide (Y ２ O ３ ), yttrium aluminum garnet (YAG) and SmAlO ３ It is preferable that it be at least one selected from the group consisting of the following:

[0112] The conductive material contained in the electrostatic adsorption electrode 13 is molybdenum carbide (Mo ２ Preferably, it is at least one selected from the group consisting of C), molybdenum (Mo), tungsten carbide (WC), tungsten (W), tantalum carbide (TaC), tantalum (Ta), silicon carbide (SiC), carbon black, carbon nanotubes, and carbon nanofibers.

[0113] The thickness of the electrostatic chuck member 2 can be arbitrarily selected, but it is preferably 0.5 mm or more and 5 mm or less. For example, it may be 1.0 mm or more or 3 mm or less. When the thickness of the electrostatic chuck member 2 is 0.5 mm or more, the dielectric strength of the electrostatic chuck member 2 is high. Also, when the thickness of the electrostatic chuck member 2 is 5 mm or less, the heat capacity of the electrostatic chuck member 2 is reduced, making it easier to maintain a uniform temperature of the plate-shaped sample being processed during plasma processing.

[0114] <Base> The base 3 is a disc-shaped member in plan view and supports the electrostatic chuck member 2 from below (the other side in the stacking direction). The upper surface (support surface) 3a of the base 3 faces the lower surface 2a of the electrostatic chuck member 2 in the vertical direction (stacking direction) via the bonding layer 4. The base 3 supports the electrostatic chuck member 2 at its support surface 3a.

[0115] A flow path 31 for circulating a refrigerant may be provided inside the base 3. The refrigerant flowing through the flow path 31 can be arbitrarily selected, but examples include a fluorine-based inert liquid, water, He gas, N2. ２ Gases or the like are used. The flow path 31 extends along the support surface 3a. The refrigerant in the flow path 31 cools the entire base 3 and also cools the electrostatic chuck member 2 via the support surface 3a. In other words, the base 3 functions as a temperature control member for the electrostatic chuck member 2.

[0116] The base 3 is connected to an external high-frequency power supply 5 via a matching circuit (not shown) and may also serve as an internal electrode for plasma generation.

[0117] The material of the base 3 can be arbitrarily selected and is not limited to metals with excellent thermal conductivity, electrical conductivity, and workability, composite materials containing these metals, ceramics with high thermal conductivity, conductive ceramics, or metal-ceramic composite materials (MMC: Metal Matrix Composition). For example, aluminum (Al), aluminum alloys, copper (Cu), copper alloys, stainless steel (SUS), and ceramics composed of a high thermal conductivity material and a conductive material are preferably used. The ceramics preferably have a volume ratio of 10:90 to 90:10 between the high thermal conductivity material and the conductive material, and may be composed of AlN and TiN, AlN and Mo, or AlN, TiN, and Mo. At least the surface of the base 3 exposed to the plasma is preferably anodized or has an insulating film such as alumina deposited on it. The size of the base 3 can be arbitrarily selected as needed.

[0118] <Bonding Layer> The bonding layer 4 can be made of known bonding materials, and may be formed of organic adhesives such as polyimide resin, silicone resin, and epoxy resin. These organic adhesives are required to have heat resistance and insulating properties after bonding and curing. Among organic adhesives, the bonding layer 4 is preferably formed of a silicone adhesive. Silicone adhesives have a low glass transition temperature, a high heat resistance temperature, and rubber elasticity. It is preferable that insulating ceramic powder (aluminum oxide, aluminum nitride, etc.) is added to this silicone adhesive as a thermally conductive filler.

[0119] Furthermore, the material of the bonding layer 4 may be a metal brazing material or a ceramic.

[0120] The materials for the base 3 and bonding layer 4 described above are merely examples. Any base and bonding layer used in known electrostatic chuck devices can be appropriately adopted.

[0121] Furthermore, the electrostatic chuck device 1A may appropriately adopt known configurations as components of the electrostatic chuck device, as long as they do not impair the effects of the invention.

[0122] With the electrostatic chuck section and electrostatic chuck apparatus configured as described above, since the composite sintered body mentioned above is used as the base, wafer fixation for long periods of time is possible under various temperature conditions.

[0123] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but the present invention is not limited to these examples. The shapes and combinations of the constituent members shown in the above examples are merely examples, and can be modified in various ways based on design requirements, etc., without departing from the spirit of the present invention.

[0124] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0125] (Evaluation Method) The evaluation method used in the examples is described below.

[0126] 1. <Relative Permittivity> In this embodiment, the relative permittivity of the composite sintered body was measured using the parallel plate method.

[0127] (Equipment used) Equipment used: Impedance analyzer (model number E4990A, manufactured by Keysight Technologies), LCR meter (model number 4274A, manufactured by Keysight Technologies)

[0128] (Measurement conditions) Measurement atmosphere: Air Measurement temperature: 25°C Measurement frequency: 200 Hz, 1 MHz

[0129] 2. <Volume Resistivity (Ω·cm)> In this embodiment, the volume resistivity (Ω·cm) of the composite sintered body was measured using the DC three-terminal method.

[0130] (Equipment used) Screen printing machine: MODEL MEC-2400, manufactured by Mitani Micronics Co., Ltd. Resistivity measuring device: Nishiyama Seisakusho Co., Ltd. Digital ultra-high resistance / micro current meter (Model 5450, manufactured by ADC Corporation)

[0131] (Measurement conditions) Measurement temperature: Room temperature (24°C) Measurement atmosphere: Air (flow rate 200 ml / min) Applied voltage: 500 V

[0132] (Measurement Method) Using a screen printing machine, silver paste (US-202A, manufactured by Daiken Chemical Manufacturing and Sales Co., Ltd.) was printed onto the top and bottom surfaces of the sintered body, and dried in air at 150°C for 12 hours to form the main electrode 110, guard electrode 120, and counter electrode 130 as shown in Figure 1.

[0133] At this time, the diameter of the main electrode 110 was 1.45 cm, and the inner diameter of the guard electrode 120 was 1.60 cm.

[0134] A DC voltage was applied to a sintered body formed with a main electrode 110, a guard electrode 120, and a counter electrode 130. The current after charging for 1 minute was measured to determine the volume resistivity (Rv) of the sintered body. Next, the volume resistivity (ρv) was calculated using the thickness of the sintered body and the electrode area from the following formula (1): ρv = S / t × Rv = S / t × V / I …(1) (S: effective area of ​​the electrode (cm²) ２ ), t: thickness of sintered body (cm), Rv: volume resistivity (Ω), V: DC voltage (V), I: current (A)

[0135] 3. <Withstand Voltage> In this embodiment, the withstand voltage of the composite sintered body was measured by the following method.

[0136] <Measurement Method> A 0.3 mm thick composite sintered body test specimen was prepared and sandwiched between cylindrical electrodes with a diameter of 20 mm. The composite sintered body was then immersed in silicone oil at room temperature, and a high-voltage power supply (Matsusada Precision Co., Ltd., model number HGR10-20P) connected to the cylindrical electrodes was applied while increasing the voltage at a rate of 1 kV / second. The voltage at which a current of 1 μA flowed through the test specimen was measured as the withstand voltage value.

[0137] 4. <Amount of oxygen contained in the raw material silicon carbide particles> The amount of oxygen contained in the raw material silicon carbide particles was measured using an oxygen-nitrogen analyzer (LECO, model number: ON836) by melt extraction-non-dispersive infrared absorption method. Specifically, 0.01 g of raw material silicon carbide particles and 0.05 g of fuel graphite powder were placed in a graphite crucible and melted and decomposed by resistance heating in a helium stream using the aforementioned apparatus. Then, CO and CO2 were generated by the reaction of the oxygen in the graphite and silicon carbide. ２The oxygen content of the silicon carbide particles was analyzed and quantified using the non-dispersive infrared detector of the aforementioned apparatus. The amount of oxygen contained in the silicon carbide particles was calculated using the values ​​obtained from the above analysis and quantification.

[0138] 5. <Amount of carbon atoms contained in the composite sintered body> The amount of carbon atoms contained in the composite sintered body was measured using a carbon analyzer (LECO, model number: C744) by combustion-nondispersive infrared absorption spectroscopy. Specifically, the composite sintered body was pulverized, and 0.1 g of the pulverized composite sintered body was placed in a graphite crucible together with 1 g of a tungsten-tin mixture, which is a combustion aid, and burned in the aforementioned apparatus in a helium stream and oxygen gas. The generated CO and CO ２ The carbon atoms were analyzed and quantified using the non-dispersive infrared detector of the aforementioned apparatus. Using the values ​​obtained from the above analysis and quantification, the amount of silicon carbide contained in the composite sintered body was calculated from its atomic weight, assuming that the amount of carbon atoms contained in the composite sintered body was derived from the silicon carbide contained in the composite sintered body.

[0139] 6. <Percentage of Pit Areas> "Observation with Optical Microscope" The surface of the composite sintered body was observed at 50x magnification using an optical microscope (product name: Digital Microscope VHX-900F, lens illumination: brightfield (coaxial incident light), manufactured by Keyence Corporation) for the central and outer parts of the composite sintered body. The two obtained optical microscope images were binarized, and the area ratio of areas with different compositions (areas with different compositions / total observation field × 100) was calculated.

[0140] When observed with an optical microscope, pit regions appear as black spots. Therefore, the image was binarized, separating the areas that appeared black under an optical microscope from the rest of the image. The black areas were treated as pit regions, and the rest were treated as non-pit regions. The proportion of pit regions (excluding composites of aluminum oxide and silicon carbide) was then calculated. In the binarization process, a threshold was set where there was no substantial difference in the size of the pit regions by comparing the images before and after binarization. The values ​​shown in Table 2 are the average values ​​of the proportion of pit regions in the central area and the proportion of pit regions in the outer periphery.

[0141] 7. <Blasting Amount> The blasting conditions that create protrusions of approximately 35 μm when using the sintered body of Comparative Example 1 (described later) were confirmed. Then, under these conditions, samples of Examples 1-3 and Comparative Examples 1-3 were blasted to form protrusions, and the height of these protrusions (the depth removed by blasting) was measured. The higher the height of the protrusions, the more easily the sintered body is worn. Therefore, sintered bodies with smaller protrusion heights have superior wear resistance. Note that in Table 2, the result for Comparative Example 1 is 39 mm, but the value obtained from the measurement is listed as is.

[0142] [Example 1] "Preparation of Slurry" As starting materials, β-SiC type silicon carbide (β-SiC) particles synthesized by thermal plasma CVD with an average particle size of 0.03 μm (oxygen content 1.5 mass%) and aluminum oxide (Al) with an average particle size of 0.1 μm ２ O ３ ) Particles were used.

[0143] For the β-SiC particles, we used those that had been heat-treated at 280°C for 12 hours in an atmospheric environment to oxidize the particle surface. This operation corresponds to the "pre-oxidation process" described above.

[0144] β-SiC particles and Al ２ O ３ The particle, Al ２ O ３ β-SiC particles make up 3.0% by mass of the total amount of particles (Al ２ O ３ The β-SiC particles were weighed out in an amount of 3.0 parts by mass per 100 parts by mass of other particles, added to distilled water containing a polycarboxylic acid-based dispersant, and mixed using an ultrasonic dispersion device to obtain a mixed solution. This operation corresponds to the "step of obtaining a mixed solution" described above.

[0145] Nitric acid was added to the resulting mixture to adjust the pH of the slurry to 6.5. This operation corresponds to the "pH adjustment step" described above.

[0146] This pH-adjusted mixture was then ground and mixed using a two-flow particle impact grinding and mixing apparatus. This operation corresponds to the "step for obtaining slurry" described above.

[0147] The resulting slurry is spray-dried using a spray-drying apparatus to separate β-SiC and Al ２ O ３ The granules contained in the granules were obtained. This operation corresponds to the "step of obtaining granules" in the present invention.

[0148] Next, the granules were heated to 520°C under a nitrogen atmosphere to remove moisture and dispersants (impurities). After that, the granules were heated at 250°C for 12 hours under an air atmosphere. This operation corresponds to the "oxidation treatment step" described above.

[0149] Next, the granules were uniaxially pressed at a press pressure of 8 MPa to form a molded body with a diameter of 320 mm and a thickness of 15 mm. This operation corresponds to the "molding process" described above.

[0150] The resulting molded body was placed in a graphite mold and sintered under an argon atmosphere at a press pressure of 40 MPa and 1750°C to obtain the composite sintered body of Example 1. This operation corresponds to the "pressure sintering process" described above.

[0151] (Example 2) A composite sintered body of Example 2 was obtained in the same manner as in Example 1, except that the oxidation treatment step was omitted.

[0152] (Example 3) A composite sintered body of Example 3 was obtained in the same manner as in Example 1, except that silicon carbide with an oxygen content of 1.9% by mass was used as the raw material.

[0153] (Comparative Example 1) A composite sintered body was prepared as follows, according to the method described in Patent Document 2 (Japanese Patent Application Publication No. 2020-150169).

[0154] "Preparation of Ceramic Dielectric Materials" <Preparation of First Granules> The first silicon carbide dispersion was prepared as follows: Silicon carbide (SiC) powder with an average particle size of 0.11 μm and an oxygen content of 0.6 mass% was weighed so that it amounted to 8.5 mass% of the total amount of this silicon carbide powder and the aluminum oxide powder described later. The silicon carbide powder was dispersed using water to prepare a slurry containing silicon carbide (SiC) powder whose particle size (D50) at which the cumulative volume percentage of the particle size distribution of the silicon carbide powder reaches 50% is between 0.1 μm and 0.2 μm. This slurry was dispersed using a sand mill to prepare the first silicon carbide dispersion, in which silicon carbide powder was dispersed in water.

[0155] The aluminum oxide dispersion was prepared as follows: Aluminum oxide (Al) with an average particle size of 0.15 μm ２ O ３ The aluminum oxide powder was weighed so that it constituted 91.5% by mass of the total amount of the silicon carbide powder and the aluminum oxide powder. The aluminum oxide powder was dispersed using water to prepare a slurry containing aluminum oxide powder, in which the particle size (D50) at which the cumulative volume percentage of the particle size distribution of the aluminum oxide powder reached 50% was 0.1 μm or more and 0.5 μm or less. This slurry was dispersed using a sand mill to prepare a first aluminum oxide dispersion in which aluminum oxide powder was dispersed in water.

[0156] Next, the first silicon carbide dispersion and the first aluminum oxide dispersion were mixed using an ultrasonic disperser to prepare the first mixture.

[0157] This first mixture was dried at 200°C using a spray dryer to form the first granules.

[0158] <Preparation of the second granule> Silicon carbide powder with an average particle size of 0.03 μm was weighed so that it accounted for 8.5% by mass of the total amount of the silicon carbide powder and the aluminum oxide powder described later. The silicon carbide powder was dispersed using water to prepare a slurry containing silicon carbide powder whose particle size (D50) at which the cumulative volume percentage of the particle size distribution of the silicon carbide powder reaches 50% is between 0.03 μm and 0.1 μm. This slurry was dispersed using a sand mill to prepare a second silicon carbide dispersion in which silicon carbide powder was dispersed in water.

[0159] Aluminum oxide powder with an average particle size of 0.1 μm was weighed so that it accounted for 91.5% by mass of the total amount of silicon carbide powder and this aluminum oxide powder. This aluminum oxide powder was dispersed using water to prepare a slurry containing aluminum oxide powder whose particle size (D50) at which the cumulative volume percentage of the particle size distribution of the aluminum oxide powder reached 50% was between 0.1 μm and 0.3 μm. This slurry was dispersed using a sand mill to prepare a second aluminum oxide dispersion in which aluminum oxide powder was dispersed in water.

[0160] Next, the second silicon carbide dispersion and the second aluminum oxide dispersion were mixed using an ultrasonic disperser to prepare a second mixture.

[0161] This second mixture was dried at 200°C using a spray dryer to form the second granules.

[0162] <Preparation of composite sintered body> Next, the first granules and the second granules are mixed using a dry stirring and mixing vessel, and the mixture of the first granules and the second granules (Al ２ O ３ A SiC composite powder was prepared. The mixing ratio of the first granules to the second granules was set to 93:7 by mass.

[0163] Next, the mixture of the first granules and the second granules was molded into a predetermined shape using a known molding method.

[0164] Next, the molded body was sandwiched between carbon plates having a flatness of 0.1 mm with a surface roughness Ra, and fired using a hot press under an argon atmosphere at 1750°C and a pressure of 40 MPa for 2 hours to produce the composite sintered body of Comparative Example 1.

[0165] (Comparative Example 2) A composite sintered body of Comparative Example 2 was obtained in the same manner as in Example 1, except that the heating temperature in the pre-oxidation step was changed from 280°C to 500°C, the SiC addition amount was changed from 3.0% by mass to 5% by mass, and the oxidation treatment step was omitted. The oxygen content in the silicon carbide particles after the pre-oxidation step was 5.2% by mass.

[0166] (Comparative Example 3) A composite sintered body of Comparative Example 3 was obtained in the same manner as in Example 2, except that silicon carbide with an oxygen content of 1.9% by mass was used as the raw material.

[0167] <Evaluation> For the composite sintered bodies of Examples 1-3 and Comparative Examples 1-3, the oxygen content of silicon carbide particles, the amount of carbon contained in the sintered body, the amount of SiC contained in the sintered body, the percentage of pitted areas, the dielectric strength, the dielectric properties at 1 MHz, the volume resistivity, and the amount of blast abrasion were measured.

[0168] The results are shown in Tables 1 and 2. Table 1 summarizes the conditions for each example and comparative example, and Table 2 summarizes the evaluation results. Note that the "@" symbol in Table 2 has no particular meaning.

[0169] Furthermore, Figure 3 shows an optical microscope image of the composite sintered body obtained in Example 1, Figure 4 shows an optical microscope image of the composite sintered body obtained in Example 2, Figure 5 shows an optical microscope image of the composite sintered body obtained in Comparative Example 1, and Figure 6 shows an optical microscope image of the composite sintered body obtained in Comparative Example 2. The black dots that appear in the photographs of Figures 3 to 6 correspond to the "regions other than the silicon carbide composite (pit regions)" in this embodiment.

[0170]

[0171]

[0172] In the examples, the pit area was 3% or less in the central and peripheral regions of the composite sintered body. In Comparative Examples 1 and 3, the pit area was also 3% or less in the central and peripheral regions of the composite sintered body. The composite sintered bodies of Examples 1 to 3, which were manufactured by focusing on factors that oxidize silicon carbide, were confirmed to have a pit area ratio of 3% by mass or less and a dielectric strength of 15kV or more. By comparing Examples 1 to 3 with Comparative Examples 1 and 3, it was confirmed that composite sintered bodies manufactured under conditions in which SiC is less likely to oxidize during the manufacturing process have a smaller pit area ratio but a lower dielectric strength.

[0173] In Comparative Example 2, the pit area was 3% or more in both the central and peripheral parts of the composite sintered body. By comparing Examples 1-3 with Comparative Example 2, it was confirmed that a smaller proportion of the pit area resulted in less blast collapse and superior wear resistance.

[0174] Based on the above results, it has been confirmed that the present invention is useful.

[0175] 1A Electrostatic chuck device 2 Electrostatic chuck member 2a Bottom surface 3 Base 3a Top surface 4 Bonding layer 5 High-frequency power supply 11 Substrate 13, 15 Electrostatic adsorption electrodes 21 First adsorption part 21a Mounting surface 21x Flow channel 22 Second adsorption part 22a Top surface of second adsorption part 22x Groove 31 Flow channel 100 Sintered body 110 Main electrode 120 Guard electrode 130 Counter electrode 211 Protrusion 212 Annular protrusion FR Focus ring W Wafer

Claims

1. A composite sintered ceramic body comprising aluminum oxide as the main phase and silicon carbide as the secondary phase, wherein the amount of carbon atoms contained in the composite sintered body is 0.45% by mass or more and 1.5% by mass or less, the proportion of areas other than the composite of aluminum oxide and silicon carbide on the surface of the composite sintered body is 3% or less, and the withstand voltage measured when the thickness of the composite sintered body is 0.3 mm is 15 kV or more.

2. An electrostatic chuck member comprising a plate-shaped base body formed from the composite sintered body described in claim 1, the base body having one main surface which is a mounting surface on which a plate-shaped sample is placed, and an electrostatic adsorption electrode provided on the side of the base body opposite to the aforementioned mounting surface, or inside the base body.

3. An electrostatic chuck device comprising the electrostatic chuck member described in claim 2.

4. The composite sintered body according to claim 1, wherein the region is the region that appears as a black spot when the surface of the composite sintered body is observed under an optical microscope at 50x magnification and binarized, and the dielectric strength means the voltage at which a current of 1 μA flows through the test piece when a test piece of the composite sintered body with a thickness of 0.3 mm is prepared and the voltage is increased and applied at a rate of 1 kV / second.

5. The composite sintered body according to claim 1, wherein the composite sintered body contains 1.0 part by mass or more and 5.0 parts by mass of silicon carbide per 100 parts by mass of aluminum oxide, the region contains an aluminum silicate, and the region is a portion on the surface of the composite sintered body where the silicate has been removed.

6. The composite sintered body comprises a pre-oxidation step in which SiC particles are prepared and their surface is oxidized, and Al ２ O ３ The particles and the dispersion medium are mixed, and the Al ２ O ３ The steps are: to obtain a mixed solution containing 1 to 5 parts by mass of the SiC particles per 100 parts by mass of other particles; to adjust the pH of the mixed solution to 2.6 to 7.5; and to spray the pH-adjusted mixed solution at a rate of 300 ml / min to 1000 ml / min, and the Al ２ O ３ A step of mixing particles and the SiC particles while colliding them with each other to obtain a slurry, and removing the dispersion medium from the slurry, and the Al ２ O ３ A composite sintered body according to claim 1, manufactured by a manufacturing method comprising the steps of: obtaining granules containing particles and SiC particles; molding the obtained granules to obtain a molded body; and heating the obtained molded body to 1600°C or higher while compacting it under a non-oxidizing atmosphere at a pressure of 5 MPa or higher to perform pressure sintering.

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