Alumina sintered body, method for manufacturing alumina sintered body, and electrostatic chuck

Abstract

To provide a technique for improving at least one of thermal conductivity and volume resistivity of an alumina sintered compact.SOLUTION: The alumina sintered compact containing alumina (Al2O3) as a main component and having a 0mol (MgO) content of 0. 0mol% <MgO ≤ 1. 35W% based on the alumina content has a coefficient of thermal conductivity at 25 °C of ≥ 15W / m * K and a coefficient of thermal conductivity at 300 °C of ≥ magnesia / m * K.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an alumina sintered body, a method for manufacturing an alumina sintered body, and an electrostatic chuck. [Background technology]

[0002] Electrostatic chucks used to attract and hold wafers in semiconductor manufacturing equipment generally use alumina (aluminum oxide: Al2O3) for the plate-shaped portion on which the wafer is placed. A technology has been disclosed for improving the withstand voltage of such electrostatic chuck members primarily composed of alumina by adding magnesia (MgO) (see, for example, Patent Document 1). Furthermore, a technology has been disclosed for improving the volume resistivity at the operating temperature of the electrostatic chuck (e.g., 300°C) (see, for example, Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6373212 [Patent Document 2] Patent No. 4744855 [Patent Document 3] Japanese Patent Publication No. 2023-150882 Summary of the Invention [Problem to be solved by the invention]

[0004] Electrostatic chucks are required to have high clamping force, fast attachment / detachment response, and high temperature rise / fall speeds. However, when using alumina for electrostatic chucks, the low thermal conductivity of alumina poses challenges, such as cracking due to rapid temperature rise / fall and the resulting long processing time.

[0005] In Patent Document 1 mentioned above, the thermal conductivity was not examined, and in the technologies described in Patent Documents 2 and 3, sufficient thermal conductivity and volume resistivity were not obtained. Such problems are not limited to the members for electrostatic chucks, but are common problems for alumina sintered compacts used for various members of semiconductor manufacturing apparatuses.

[0006] The present disclosure has been made to solve the above-described problems, and an object thereof is to provide a technique for improving at least one of the thermal conductivity and the volume resistivity of an alumina sintered compact.

Means for Solving the Problems

[0007] The present disclosure has been made to solve at least one of the above-described problems, and can be realized in the following forms.

[0008] (1) According to one form of the present disclosure, there is provided an alumina sintered compact containing alumina (Al2O3) as a main component, in which the content of magnesia (MgO) with respect to the content of alumina is 0.0 mol% < MgO ≤ 1.0 mol%. This alumina sintered compact has a thermal conductivity of 35 W / m·K or more at 25°C and a thermal conductivity of 15 W / m·K or more at 300°C.

[0009] According to the alumina sintered compact of this form, sufficient thermal conductivity can be obtained both at 25°C (room temperature) and at 300°C (high temperature region used in an electrostatic chuck). Therefore, when the alumina sintered compact of this form is used for, for example, an electrostatic chuck, the rate of temperature increase and decrease can be increased, and thus the lead time can be shortened.

[0010] (2) In the alumina sintered compact of the above form, the abundance of pores may be 0.003 pieces / μm 2 or less. By minimizing the abundance of pores in this way, the thermal conductivity and the volume resistivity of the alumina sintered compact can be improved.

[0011] (3) In the alumina sintered body of the above embodiment, when the pores are divided into first pores, which are pores present at grain boundaries, and second pores, which are pores present within crystal grains, the ratio of the number of second pores to the total number of first pores and second pores may be 20% or less. Whether the conductive path is in the grain, in the grain boundary phase, or at the interface, the alumina sintered body of this embodiment may have a pore number of 0.003 / μm 2 Since the void ratio in the crystal grains is low, the volume resistivity can be further improved.

[0012] (4) In the above-mentioned alumina sintered body, the density is 3.98 g / cm 3 The alumina sintered body has a high density and a reduced amount of voids, and therefore the thermal conductivity can be further improved.

[0013] (5) In the above-mentioned alumina sintered body, the volume resistivity at 300°C is 1.0 × 10 16 The alumina sintered body may have a resistivity of Ω·cm or more. In this way, even when the alumina sintered body is used at a high temperature of about 300°C, the alumina sintered body has a high volume resistivity. Therefore, when the alumina sintered body is used in an electrostatic chuck, for example, the alumina sintered body can uniformly attract and hold a wafer. This makes it possible to provide an electrostatic chuck with high responsiveness for desorption, thereby improving the wafer attraction and desorption performance.

[0014] (6) According to another aspect of the present disclosure, there is provided a method for producing an alumina-based sintered body according to the above aspect. This method for producing an alumina-based sintered body includes a powder production step of coating the surfaces of alumina particles with magnesia particles to produce a raw material powder, and a firing step of molding and firing the raw material powder. According to this method for producing an alumina-based sintered body, since the surfaces of the alumina particles are coated with magnesia particles in the powder production step, it is possible to more uniformly suppress the grain growth of alumina compared to a case where alumina particles and magnesia particles are mixed while being pulverized (ball mill mixing), and it is possible to reduce the amount of voids in the alumina-based sintered body.

[0015] (7) According to another aspect of the present disclosure, there is provided an electrostatic chuck. The electrostatic chuck includes a plate-shaped member including the alumina sintered body of the above aspect and an attraction electrode formed on the plate-shaped member. According to this electrostatic chuck, the plate-shaped member has sufficient thermal conductivity both at 25°C (room temperature) and at 300°C (the high-temperature range used in electrostatic chucks). Therefore, the in-plane temperature distribution of a wafer held by this electrostatic chuck can be made more uniform, and variations in etching rate, etc. can be reduced. As a result, yield can be improved. Furthermore, the wafer temperature increase / decrease rate can be increased, thereby shortening lead time.

[0016] The present disclosure can be realized in various forms, for example, in the form of a component for a semiconductor manufacturing apparatus, a semiconductor manufacturing apparatus, a holding device, an electrostatic chuck, an apparatus including these, and a method for manufacturing a component for a semiconductor manufacturing apparatus. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a process diagram showing a method for producing an alumina sintered body. FIG. [Figure 2] FIG. 10 is a diagram showing evaluation results of samples. [Figure 3] FIG. 1 is a schematic cross-sectional view of an electrostatic chuck. [Figure 4] FIG. 1 is a schematic top view of an electrostatic chuck. [Figure 5] FIG. 2 is an enlarged schematic cross-sectional view of an electrostatic chuck. DETAILED DESCRIPTION OF THE INVENTION

[0018] First Embodiment The alumina-based sintered body as the first embodiment of the present disclosure contains alumina (Al2O3) as the main component, and the content of magnesia (MgO) relative to the content of alumina satisfies 0.0 mol% < MgO ≤ 1.0 mol%. The thermal conductivity at 25°C is 35 W / m·K or more, and the thermal conductivity at 300°C is 15 W / m·K or more. Here, the "main component" means the component with the highest content ratio.

[0019] The content of magnesia can be determined as follows. For the alumina-based sintered body, elemental analysis by XRF (X-ray Fluorescence) is performed to quantify the amount of magnesium (Mg). The amount of magnesia is obtained by converting the amount of magnesium in the analysis result into oxides. Similarly, the amount of aluminum (Al) is quantified and converted into oxides to obtain the content of alumina. Then, the ratio of the amount of magnesia (mol) to the amount of alumina (mol) is calculated.

[0020] In the alumina-based sintered body, by adding magnesia, abnormal grain growth of alumina grains can be suppressed.

[0021] The thermal conductivity can be measured by the laser flash method after cutting out and processing a specimen from the alumina-based sintered body in accordance with JIS-R1611.

[0022] The alumina-based sintered body of the present embodiment preferably has the number of pores present less than or equal to 0.003 pores / μm 2 as follows. By minimizing the number of pores in this way, the thermal conductivity and volume resistivity of the alumina-based sintered body can be improved. Also, by reducing the number of pores, the breakdown voltage can be improved. Further, since the number of pores is small, the initiation points of plasma erosion are reduced, and the plasma resistance can be improved.

[0023] The amount of vacancies present can be counted visually using a cross-sectional STEM (Scanning Transmission Electron Microscope) image. The presence of vacancies can be confirmed using a fractured surface SEM image. Although the fractured surface SEM image shows the number of vacancies at the grain boundaries, it does not show the number of vacancies present within the grains, so the total number of vacancies found using the fractured surface SEM image will be greater. Therefore, when the number of vacancies is small in the fractured surface SEM image, it is preferable to confirm the amount of vacancies present using a cross-sectional STEM image.

[0024] In the alumina sintered body of this embodiment, when pores are divided into first pores, which are pores present at grain boundaries, and second pores, which are pores present within crystal grains, it is preferable that the ratio of the number of second pores to the total number of first pores and second pores is 20% or less. When the conductive path is within a crystal grain, the volume resistivity decreases if the number of pores within the crystal grain is large. When the number of pores is 0.003 / μm 2 If the vacancy ratio is extremely low (below 20%) and the ratio of vacancies within the crystal grains is low (below 20%), the volume resistivity can be further improved. The amount of vacancies can be counted using a cross-sectional STEM image, as described above.

[0025] In the alumina sintered body of this embodiment, the density is 3.98 g / cm 3 Preferably, the average grain size of the alumina crystal grains is less than 3.0 μm. Such an alumina sintered body has high density and a reduced amount of voids, which further improves the thermal conductivity.

[0026] The density of the alumina sintered body can be measured by the Archimedes method (JIS R 1634).

[0027] The grain size of alumina crystal grains in an alumina sintered body can be measured by the intercept method. Specifically, the fracture surface of the alumina sintered body is observed using a scanning electron microscope (SEM), and when a line of length L is drawn on the obtained secondary electron image, the number n of grains that the line crosses is measured. Note that grains with both ends of the line inside are counted as 0.5 grains. Then, the average grain size D (μm) is calculated using the following formula (1): D = 1.5 × L / n (1) In this embodiment, an arbitrary number of lines intersecting with the number n of particles of 100 or more are drawn in parallel to determine a plurality of average particle diameters D, and the standard deviation is calculated using the determined plurality of average particle diameters.

[0028] In the alumina sintered body of this embodiment, the volume resistivity at 300°C is 1.0 × 10 16 In this way, the alumina sintered body has a high volume resistivity even when used at a high temperature of about 300°C, and therefore, when the alumina sintered body is used in, for example, an electrostatic chuck, it can uniformly attract a wafer and provide an electrostatic chuck with high responsiveness for desorption, thereby improving the wafer attracting and desorbing performance.

[0029] FIG. 1 is a process diagram showing a method for manufacturing an alumina sintered body. In the method for manufacturing an alumina sintered body of this embodiment, a powder preparation step P1 is first carried out. In the powder preparation step P1, alumina (Al2O3) particles and magnesia (MgO) particles that have been weighed in advance are prepared, and the surfaces of the alumina particles are coated with the magnesia particles to prepare a raw material powder. As a method for coating the surfaces of alumina particles with magnesia particles, various known methods can be used, such as dry particle compounding, wet particle compounding, powder sputtering, etc. The amount of MgO added is 0.00 mol% relative to Al2O3. <MgO≦1.0mol%である。

[0030] Magnesia has the effect of suppressing the grain growth of alumina, and by coating the surfaces of alumina particles with magnesia particles, the grain growth of alumina can be suppressed more uniformly, and the densification of the alumina sintered body can be promoted.

[0031] Next, the sintering process P2 is performed. In this process, the raw material powder obtained in the powder preparation process P1 is molded in a hot press and sintered at a temperature between 1300°C and 1700°C to produce an alumina sintered body. A sintering temperature higher than 1700°C increases the likelihood of abnormal grain growth and a decrease in voltage resistance. Therefore, the sintering temperature should be between 1300°C and 1700°C. The hot press pressure can be set arbitrarily. A low pressure below 10 MPa makes it difficult for the particles to be crushed during hot pressing, preventing densification and increasing the likelihood of air voids remaining at the grain boundaries. Therefore, a pressure between 10 MPa and 40 MPa is recommended. The MgO content in the alumina sintered body can be determined using XRF or ICP (Inductively Coupled Plasma) optical emission spectroscopy. Hot pressing applies pressure during firing, which allows the particles to be crushed during firing compared to air firing, promoting densification and reducing voids at grain boundaries.In addition, the contact area between particles is increased, so the sintering process itself can be completed in a shorter time than air firing.

[0032] According to the manufacturing method of this embodiment, since the surfaces of the alumina particles are coated with magnesia particles in the powder preparation step P1, the grain growth of alumina can be more uniformly suppressed and the amount of voids in the alumina sintered body can be reduced compared to when alumina particles and magnesia particles are mixed while being pulverized (ball mill mixing).Furthermore, compared to when an alumina sintered body is produced by the gel casting method, an alumina sintered body with fewer impurities and higher withstand voltage can be obtained.

[0033] The alumina sintered body of this embodiment can be used for semiconductor manufacturing equipment parts, semiconductor manufacturing equipment, holding equipment, electrostatic chucks, and equipment including these. [Example]

[0034] The present disclosure will be explained more specifically with reference to examples. The thermal conductivity and volume resistivity were evaluated using alumina sintered body samples 1 to 7. Samples 1 to 4 are examples of the alumina sintered body of the above embodiment, and samples 5 to 7 are comparative examples.

[0035] Figure 2 is a table showing the specifications and evaluation results of Samples 1 to 7. The evaluation method will be described later. In Figure 2, the amount of MgO added is shown as a ratio to Al2O3. The vacancy ratio is the ratio of the amount (number) of vacancies within crystal grains to the amount (number) of all vacancies. The total amount of vacancies is the total amount of primary vacancies present at grain boundaries and secondary vacancies present within crystal grains.

[0036] 1. Sample Preparation Samples 1 to 4 were manufactured by the manufacturing method of the above embodiment. Sample 5 did not contain magnesia, but the firing step P2 was the same as Samples 1 to 4. Sample 6 contained 1.0 mol% or more of magnesia (1.5 mol%), but the manufacturing method was the same as Samples 1 to 4. Sample 7 contained the same amount of magnesia as Sample 1, but in the powder manufacturing step, alumina particles and magnesia particles were mixed while being pulverized (ball mill mixing). The firing step P2 was the same as Samples 1 to 4.

[0037] In Samples 1 to 7, alumina particles with a purity of 99.9% or higher are used.

[0038] Magnesia particles are added to alumina particles in the ratios shown in Figure 2. Specifically, 0.10 mol% is added to Samples 1 and 7, 0.05 mol% to Sample 2, 0.20 mol% to Sample 3, 1.00 mol to Sample 4, and 1.50 mol to Sample 6. No magnesia particles are added to Sample 6. As will be described later, magnesia can suppress abnormal grain growth of alumina crystal grains.

[0039] In these samples, the amount of magnesia added (mol %) is approximately equal to the magnesia content (mol %) in the alumina sintered body.

[0040] By varying the amount of magnesia added, the density of the alumina sintered body, the average grain size of the alumina crystal grains, the number of voids, and the proportion of voids within the crystal grains are all different for Samples 1 to 6. As mentioned above, Sample 7 has the same amount of magnesia added as Sample 1, but the powder production process is different from Samples 1 to 6, and the surfaces of the alumina particles are not coated with magnesia particles. Samples 1 to 7 do not contain impurities other than magnesia and yttria. Here, "does not contain impurities" means that "process impurities such as Si, Ca, and Fe are 10 ppm or less."

[0041] The density of the alumina sintered body was measured by the Archimedes method (JIS R 1634).

[0042] The particle size of the alumina crystal particles in the alumina sintered body was measured by the intercept method as described above.

[0043] The number of vacancies and the proportion of vacancies were determined using cross-sectional STEM images (magnification: 5000x) as described above. Specifically, four or more arbitrary fields containing vacancies were photographed, and the number of vacancies was counted, and the average was used as the number of vacancies. The proportion of vacancies in Figure 2 is the number of vacancies present within crystal grains relative to the total number of vacancies, which is the sum of the number of vacancies present at grain boundaries and the number of vacancies present within crystal grains. Vacancies present at grain boundaries are also called primary vacancies, and vacancies present within crystal grains are also called secondary vacancies 12.

[0044] 2. Evaluation Method (1) Thermal conductivity The thermal conductivity was measured in accordance with JIS-R1611 by cutting out and processing square plates with a side length of 10 mm and a thickness of 1.5 mm from Samples 1 to 7 and using the laser flash method.

[0045] (2) Volume resistivity The volume resistivity was measured in accordance with JIS-C2141 in a nitrogen atmosphere by a direct current three-terminal method using test pieces cut out from Samples 1 to 7 in the shape of a disk with a diameter of 50 mm and a thickness of 1 mm.

[0046] 3. Evaluation Results The alumina sintered bodies of Samples 1 to 4 (Examples) satisfy all of the following requirements [1] to [6]. [1] Magnesia (MgO) content is 0.0 mol% <MgO≦1.0mol%である。 [2] The thermal conductivity at 25°C is 35 W / m·K or more, and the thermal conductivity at 300°C is 15 W / m·K or more. [3] The number of vacancies is 0.003 / μm 2 The following is the result. [4] When vacancies are divided into first vacancies, which are vacancies present at grain boundaries, and second vacancies, which are vacancies present within crystal grains, the ratio of the amount of the second vacancies to the total amount of the first vacancies and the second vacancies is 20% or less. [5] Density is 3.98 g / cm 3 or more, and the average particle size of the alumina crystal particles is smaller than 3.0 μm. 〔6〕The volume resistivity at 300 °C is 1.0×10 16 Ω·cm or more.

[0047] In contrast, Sample 5 (comparative example) does not satisfy all the requirements of the above [1] to [6]. That is, Sample 5 (comparative example) has a lower density, the particle size of alumina crystal grains is more than twice as large, the number of pores is much larger by orders of magnitude, the proportion of pores existing in the alumina crystal grains is more than three times as high, the thermal conductivity is low, and the volume resistivity is much lower compared to the examples. From these results, it was confirmed that since Sample 5 does not contain magnesia, the growth of alumina crystal grains is not suppressed, and it becomes an alumina sintered body having more pores compared to the examples, and as a result, the thermal conductivity and volume resistivity are low.

[0048] Although Sample 6 (comparative example) satisfies the requirement of the above [4], it does not satisfy the requirements of the above [1] to [3], [5], and [6]. As described above, the addition amount of magnesia in Sample 6 (comparative example) is 1.5 mol%, which is more than that of Samples 1 to 4, but the manufacturing method is the same as that of Samples 1 to 4. From this, it was confirmed that in the alumina sintered body, the content of magnesia of 0.0 mol% < MgO ≦ 1.0 mol% is appropriate. This is because magnesia has a low volume resistivity, and if the content is too much, it will lower the volume resistivity of the alumina sintered body. Also, if the addition amount of magnesia is too much, a large amount of magnesia (spinel MgAl2O4) phase is generated, and pores remain at the grain boundaries. Therefore, even if the particle size of the alumina crystal grains can be reduced, the number of pores cannot be sufficiently reduced, resulting in a decrease in both the thermal conductivity and the volume resistivity.

[0049] Although Sample 7 satisfies the above requirement [1], it does not satisfy the above requirements [2] to [6]. As mentioned above, Sample 7 differs from Samples 1 to 6 in the manufacturing process, in that the surfaces of the alumina particles are not coated with magnesia particles during the powder manufacturing process. Although Sample 7 differs from Sample 1 in the powder manufacturing process, the magnesia content is the same as Sample 1, and the firing process is also the same as Sample 1. However, Sample 7 has 25 times the number of voids as Sample 1, and its thermal conductivity and volume resistivity are both orders of magnitude lower than Sample 1. This confirms that coating the surfaces of alumina particles with magnesia particles can reduce the voids in alumina-based sintered bodies.

[0050] Second Embodiment FIG. 3 is a schematic cross-sectional view of an electrostatic chuck 100 according to a second embodiment of the present disclosure. The electrostatic chuck 100 of this embodiment uses the alumina sintered body of the first embodiment and is part of a semiconductor manufacturing apparatus that performs plasma etching, ion implantation, electron beam exposure, and the like. The electrostatic chuck 100 is used to fix, correct the flatness of, and transport a semiconductor wafer W (hereinafter simply referred to as a "wafer W"), as well as to cool the wafer W. FIG. 3 shows X, Y, and Z axes that are orthogonal to each other to identify directions. For convenience, the positive direction of the Z axis is referred to as the stacking direction in this specification.

[0051] In FIG. 3 , the wafer W held by the electrostatic chuck 100 is indicated by a dashed line. As shown in FIG. 3 , the electrostatic chuck 100 includes a plate-shaped member 20 on which the wafer W, which is an object to be chucked, is held, and a base member 30 bonded to the plate-shaped member 20 and having a cooling function. The plate-shaped member 20 includes a first surface 23 on which the wafer W is held, a second surface 24 that is the backside of the first surface 23, and an attraction electrode 21 formed inside the plate-shaped member 20. As shown in the figure, the base member 30 is bonded to the second surface 24 of the plate-shaped member 20 via a bonding layer 40. Note that, although the first surface 23 of the plate-shaped member 20 that holds the wafer W is shown simply in FIG. 3 , it is formed with a seal band portion 26 and multiple embossments 27, which will be described later.

[0052] The plate-shaped member 20 is an alumina sintered body whose main component is alumina (Al2O3), and satisfies at least the requirements [1] and [2] described in the first embodiment. A plurality of chucking electrodes 21 serving as conductors are embedded inside the plate-shaped member 20. When a voltage is applied to the chucking electrodes 21 with the wafer W placed on the first surface 23, an electrostatic force is generated, and the wafer W is fixed to the first surface 23.

[0053] A gas flow path 22, which is a through-hole that penetrates the second surface 24 and the first surface 23 of the plate-shaped member 20 in the stacking direction, is provided inside the plate-shaped member 20. The gas flow path 22 supplies an inert gas (e.g., helium gas) for cooling the wafer W, which is supplied from a gas supply hole 32 of the base member 30 (described later), onto the first surface 23. As shown in FIG. 3 , the gas flow path 22 opens onto the first surface 23.

[0054] The base member 30 is made of a metal with excellent thermal conductivity, such as aluminum or stainless steel. Gas supply holes 32 are formed inside the base member 30 so as to penetrate in the stacking direction. An inert gas supplied by a device such as a pump is supplied to the gas flow path 22 of the plate-like member 20 through the gas supply holes 32.

[0055] FIG. 4 is a schematic top view of the electrostatic chuck 100. FIG. 5 is an enlarged schematic cross-sectional view of the electrostatic chuck 100. FIG. 5 illustrates a cross section taken along line AA in FIG. 4. As shown in FIG. 4, the plate-shaped member 20 and the base member 30 have a substantially disk-like shape centered at a center O. A first surface 23 of the plate-shaped member 20 has outlets (openings) for a plurality of gas flow paths 22 formed therein. As shown in FIGS. 4 and 5, the first surface 23 also has a flat surface 25, a convex seal band portion 26 formed continuously along the outer edge of the flat surface 25, and a plurality of cylindrical embossments 27 protruding from the flat surface 25 inside the seal band portion 26. When the wafer W is held by the plate-shaped member 20, it is attracted to the surfaces of the seal band portion 26 and the embossments 27.

[0056] The raw material powder, which is the raw material of the alumina sintered body of the first embodiment, is pre-formed by pre-pressing. With the metal mesh or metal foil for the adsorption electrode 21 of the plate-like member 20 arranged, the pre-pressed raw material powder is arranged between the press-molded bodies and fired by hot pressing. After firing, it is processed by grinding to produce the plate-like member 20 in which the seal band portion 26 and the emboss 27 are formed. That is, the surfaces of the seal band portion 26 and the emboss 27 are formed of the alumina sintered body of the first embodiment.

[0057] As described above, the electrostatic chuck 100 includes a plate-like member 20 and a base member 30 joined to the plate-like member 20. The plate-like member 20 has an adsorption electrode 21 formed inside and a seal band portion 26 continuously formed along the outer edge of the first surface 23. The surface of the first surface 23 that holds the wafer W is an alumina sintered body mainly composed of alumina (Al2O3), in which the content of magnesia (MgO) relative to the content of alumina is 0.0 mol% <MgO ≤ 1.0 mol%, and the thermal conductivity at 25°C is 35 W / m·K or more, and the thermal conductivity at 300°C is 15 W / m·K or more. That is, since the surface of the first surface 23 that holds the wafer W is formed of an alumina sintered body with few pores and high thermal conductivity, the in-plane temperature distribution uniformity of the wafer W held by the electrostatic chuck 100 can be increased, and variations such as etching rate can be reduced. As a result, the yield can be improved. In addition, since the rate of temperature increase and decrease of the wafer can be increased, the lead time of semiconductor manufacturing can be shortened. Therefore, by using the electrostatic chuck 100 of the present embodiment, the yield of wafer semiconductors can be improved, and the lead time of semiconductor manufacturing can be shortened.

[0058] <Modification Example of the Present Embodiment> The present invention is not limited to the above-described embodiment, and can be implemented in various aspects without departing from the gist thereof. For example, the following modifications are possible.

[0059] · The method for manufacturing the alumina sintered body is not limited to the above embodiment. By appropriately changing the type of sintering aid, the addition amount of the sintering aid, the firing method, the firing atmosphere, the firing temperature, the hot press pressure, etc., the content of magnesia (MgO) with respect to the content of alumina is 0.0 mol% < MgO ≤ 1.0 mol%, the thermal conductivity at 25 °C is 35 W / m·K or more, and the thermal conductivity at 300 °C is 15 W / m·K or more, an alumina sintered body can be manufactured. Also, it may be manufactured by other known methods such as the gel casting method.

[0060] · In the above embodiment, an alumina sintered body containing no impurities other than magnesia and yttria was exemplified, but it may contain other impurities. However, it is preferable not to contain other impurities because the withstand voltage can be further improved.

[0061] · In the above second embodiment, an example in which the plate-like member 20 of the electrostatic chuck 100 has the gas flow path 22, the seal band portion 26, and the emboss 27 was shown, but the electrostatic chuck may not include at least one of them.

[0062] · In the above second embodiment, all of the plate-like member 20 was made of the alumina sintered body of the first embodiment, but it is sufficient that at least the surface of the first surface 23 for holding the wafer W is applied with the alumina sintered body of the first embodiment. For example, the surface of the first surface 23 may be formed of the alumina sintered body of the first embodiment, and the second surface 24 may be formed of another alumina sintered body different from the alumina sintered body of the first embodiment. Also, a different member (for example, another alumina sintered body different from the alumina sintered body of the first embodiment) may be disposed or joined between the plate-like member 20 and the base member 30.

[0063] Although an electrostatic chuck is exemplified in the second embodiment, the alumina sintered body of the first embodiment can be used in various holding devices such as heater devices for vacuum devices, susceptors, and mounting tables for CVD (chemical vapor deposition), PVD (physical vapor deposition), PLD (pulsed laser deposition), etc.

[0064] The present disclosure has been described above based on embodiments, examples, and modifications. However, the above-described embodiments are intended to facilitate understanding of the present disclosure and are not intended to limit the present disclosure. The present disclosure may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in the present disclosure. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate. [Explanation of symbols]

[0065] 20...Plate-shaped member 21...Adsorption electrode 22...Gas flow path 23...First side 24...Second Side 25…Plane 26...Seal band part 27...Emboss 30...Base member 32...Gas supply hole 40...Joining layer 100...Electrostatic chuck W...wafer

Claims

1. Alumina (Al 2 O 3 ) as a main component, and the content of magnesia (MgO) relative to the content of alumina is 0.0 mol% < MgO ≦ 1.0 mol%, The thermal conductivity at 25°C is 35 W / m K or more, and The thermal conductivity at 300°C is 15 W / m K or more. Alumina sintered body.

2. The alumina sintered body according to claim 1, The number of voids is 0.003 / μm 2 characterized in that: Alumina sintered body.

3. The alumina sintered body according to claim 2, When the vacancies are divided into first vacancies which are vacancies existing at grain boundaries and second vacancies which are vacancies existing within crystal grains, the ratio of the amount of the second vacancies to the total amount of the first vacancies and the second vacancies is 20% or less. Alumina sintered body.

4. The alumina sintered body according to claim 1, Density is 3.98 g / cm 3 And, The average particle size of the alumina crystal particles is less than 3.0 μm. Alumina sintered body.

5. The alumina sintered body according to claim 1, Volume resistivity at 300°C is 1.0 x 10 16 Ω cm or more, Alumina sintered body.

6. 6. A method for producing an alumina sintered body according to claim 1, comprising: a powder preparation step of preparing a raw material powder by coating surfaces of alumina particles with magnesia particles; a firing step of molding and firing the raw material powder; characterized in that it comprises A method for manufacturing an alumina sintered body.

7. A plate-shaped member comprising the alumina sintered body according to any one of claims 1 to 5; an adsorption electrode formed on the plate-like member; characterized in that it comprises Electrostatic chuck.

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