Aluminum nitride sintered body and electrostatic chuck for semiconductor manufacturing equipment comprising the same

Abstract

The present invention provides an aluminum nitride sintered body having a surface portion with reduced surface resistivity while maintaining a high internal volume resistivity, and an electrostatic chuck for semiconductor manufacturing equipment equipped therewith. [Solution] An aluminum nitride sintered body having a first main surface, Ca 12 Al 14 O 33 The aluminum nitride sintered body has a surface portion sandwiched between a first main surface and a virtual surface P, the distance from the first main surface to the interior side of the aluminum nitride sintered body being 1 mm, and the surface resistivity of the aluminum nitride sintered body at 25°C, measured on the first surface portion which is at least a part of the surface portion, is 2.8 × 10⁻⁶ 7 Ω / □cm or more 1.2×10 9 The resistivity is Ω / □cm or less, the calcium content of the first surface is 3.6% by mass or more and 9.0% by mass or less, and the volume resistivity of the aluminum nitride sintered body at 25°C is 0.36 × 10⁻⁶ 14 Ω cm or more 2.4×10 14 It is an aluminum nitride sintered body with a density of Ω·cm or less.

Description

[Technical Field]

[0001] This disclosure relates to an aluminum nitride sintered body and an electrostatic chuck for semiconductor manufacturing equipment equipped therewith. [Background technology]

[0002] Aluminum nitride (AlN) sintered bodies have high volume resistivity and thermal conductivity, and excellent thermal shock resistance, making them suitable for use in conveying jigs and heat sink components.

[0003] On the other hand, since aluminum nitride sintered bodies are used in semiconductor manufacturing equipment, techniques for reducing the volume resistivity of aluminum nitride sintered bodies are also being considered. For example, Patent Document 1 discloses an aluminum nitride sintered body containing a mayenite phase and calcium, in which the volume resistivity is reduced. In Patent Document 1, the volume resistivity is reduced throughout the entire aluminum nitride sintered body. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2008-74644 [Overview of the project] [Problems that the invention aims to solve]

[0005] Aluminum nitride sintered bodies are also used as insulating materials for electrostatic chucks. In applications of electrostatic chucks, in order to improve the adsorption force, it is desirable to reduce the resistivity of only the surface portion while maintaining a high resistivity inside the aluminum nitride sintered body, rather than reducing the overall volume resistivity of the aluminum nitride sintered body.

[0006] Therefore, the present disclosure aims to provide an aluminum nitride sintered body having a surface portion with reduced surface resistivity while maintaining a high internal volume resistivity, and an electrostatic chuck for semiconductor manufacturing equipment equipped therewith. [Means for solving the problem]

[0007] The aluminum nitride sintered body of this disclosure is an aluminum nitride sintered body having a first main surface, wherein the aluminum nitride sintered body is Ca 12 Al 14 O 33 The aluminum nitride sintered body contains a phase, and the aluminum nitride sintered body has a surface portion sandwiched between the first main surface and a virtual surface P at a distance of 1 mm from the first main surface to the interior side of the aluminum nitride sintered body, and the surface resistivity of the aluminum nitride sintered body at 25°C, measured on the first surface portion which is at least a part of the surface portion, is 2.8 × 10⁻⁶ 7 Ω / □cm or more 1.2×10 9 The resistivity is Ω / □cm or less, the surface resistivity is measured in accordance with JIS C 2139-3-2:2008, the calcium content of the first surface is 3.6% by mass or more and 9.0% by mass or less, and the volume resistivity of the aluminum nitride sintered body at 25°C is 0.36 × 10⁻⁶ 14 Ω cm or more 2.4×10 14 The aluminum nitride sintered body has a volume resistivity of Ω·cm or less, and the volume resistivity is measured in accordance with JIS C 2139-3-1:2008. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide an aluminum nitride sintered body having a surface portion with reduced surface resistivity while maintaining a high internal volume resistivity. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a cross-sectional view of an aluminum nitride sintered body according to Embodiment 1. [Figure 2]Figure 2 is a side view of a test piece used in the method for measuring volume resistivity. [Figure 3] Figure 3 is a side view of a test piece used in the method for measuring surface resistivity. [Figure 4] Figure 4 is a cross-sectional view of an electrostatic chuck for a semiconductor manufacturing apparatus according to Embodiment 2.

Mode for Carrying Out the Invention

[0010] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (1) The aluminum nitride sintered body of the present disclosure is an aluminum nitride sintered body having a first main surface, and the aluminum nitride sintered body contains a Ca 12 Al 14 O 33 phase. The aluminum nitride sintered body has a surface portion sandwiched between the first main surface and a virtual surface P whose distance from the first main surface to the inner side of the aluminum nitride sintered body is 1 mm. The surface resistivity of the aluminum nitride sintered body at 25°C, measured on at least a part of the surface portion, which is the first surface portion, is 2.8×10 7 Ω / □cm or more and 1.2×10 9 Ω / □cm or less. The surface resistivity is measured in accordance with JIS C 2139-3-2:2008. The calcium content of the first surface portion is 3.6 mass% or more and 9.0 mass% or less. The volume resistivity of the aluminum nitride sintered body at 25°C is 0.36×10 14 Ω·cm or more and 2.4×10 14 Ω·cm or less. The volume resistivity is measured in accordance with JIS C 2139-3-1:2008. It is an aluminum nitride sintered body.

[0011] In the surface portion of the aluminum nitride sintered body of the present disclosure, the surface resistivity at 25°C measured on the first surface portion is 2.8×10 7 Ω / □cm or more and 1.2×10 9 Ω / □cm or less. This indicates that the surface resistivity of the surface portion of the aluminum nitride sintered body is reduced.

[0012] The aluminum nitride sintered body of this disclosure has a surface portion with reduced surface resistivity. The reason for this is presumed to be as follows: In the manufacturing process of the aluminum nitride sintered body of this disclosure, AlN powder is sintered by adding a Ca compound and an Al oxide. As a result, conductive Ca compounds are added to the AlN sintered body. 12 Al 14 O 33 A phase is formed. The aluminum nitride sintered body of this disclosure is conductive Ca 12 Al 14 O 33 It contains a phase and the calcium content of the first surface is 3.6% by mass or more and 9.0% by mass or less. In the aluminum nitride sintered body, conductive Ca is present on the first surface. 12 Al 14 O 33 A phase exists, and the surface resistivity of the first surface is reduced.

[0013] The aluminum nitride sintered body of this disclosure has a surface portion with reduced surface resistivity as described above, while having a volume resistivity of 0.36 × 10⁻¹⁶ at 25°C. 14 Ω cm or more 2.4×10 14 It is less than Ω·cm. This indicates that the volume resistivity of the internal region of the aluminum nitride sintered body is high.

[0014] As described above, this disclosure makes it possible to provide an aluminum nitride sintered body having a surface portion with reduced surface resistivity while maintaining a high internal volume resistivity.

[0015] (2) In (1) above, the aluminum nitride sintered body has an internal region where the distance from the surface to the inside of the aluminum nitride sintered body is more than 1 mm, and the calcium content of the internal region may be 0.1% by mass or less. According to this, conductive Ca is present in the internal region of the aluminum nitride sintered body. 12 Al 14 O 33 Because the phase is less likely to exist, the internal region of the aluminum nitride sintered body tends to have a higher volume resistivity.

[0016] (3) In (1) or (2) above, the aluminum nitride sintered body has an internal region where the distance from the surface to the interior of the aluminum nitride sintered body is more than 1 mm, and the silicon content of the internal region may be 0.21% by mass or more and 0.24% by mass or less. The silicon is derived from SiO2, which is used as a sintering aid when the aluminum nitride sintered body is made. When the silicon content of the internal region is 0.21% by mass or more, the sinterability of the aluminum nitride sintered body is improved, and the bonding between the internal region and the surface is easily improved. When the silicon content of the internal region is 0.25% by mass or less, the internal region can have good thermal conductivity. In addition, a glass phase is less likely to form in the internal region, and the aluminum nitride sintered body can have good heat resistance.

[0017] (4) In any of (1) to (3) above, the silicon content of the first surface portion may be 0.05 mass% or less. This allows the first surface portion to have good thermal conductivity. Furthermore, the formation of a glass phase on the first surface portion is less likely to occur, and the aluminum nitride sintered body can have good heat resistance. Moreover, when manufacturing the aluminum nitride sintered body, it is possible to suppress the sintering of the first surface portion in relation to the internal region.

[0018] (5) The electrostatic chuck for semiconductor manufacturing equipment of the present disclosure is an electrostatic chuck for semiconductor manufacturing equipment comprising the aluminum nitride sintered body described in (1) to (4) above. According to the present disclosure, it is possible to provide an electrostatic chuck for semiconductor manufacturing equipment comprising an aluminum nitride sintered body having a surface portion with reduced surface resistivity while maintaining a high internal volume resistivity of the aluminum nitride sintered body.

[0019] [Details of the embodiments of this disclosure] Specific examples of the aluminum nitride sintered body and electrostatic chuck for semiconductor manufacturing equipment described herein will be explained below with reference to the drawings. In the drawings of this disclosure, the same reference numerals indicate the same or equivalent parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately modified for clarity and simplification of the drawings and do not necessarily represent actual dimensional relationships.

[0020] In this specification, the notation "A~B" means A or greater and B or less. If no unit is specified for A, but a unit is specified only for B, then the unit for A and the unit for B are the same.

[0021] In this specification, when compounds and the like are represented by chemical formulas, unless otherwise specified, the atomic ratios should include all conventionally known atomic ratios and should not necessarily be limited to those within the stoichiometric range.

[0022] In this disclosure, if one or more numerical values ​​are listed as the lower and upper limits of a numerical range, any combination of any one numerical value listed as the lower limit and any one numerical value listed as the upper limit shall also be disclosed.

[0023] In this disclosure, “equipment,” “includes,” “possesses,” and variations thereof are open-ended terms. Open-ended terms may or may not include additional elements in addition to the essential elements. The statement “consists of” is a closed term. However, even a configuration expressed in closed terms may include additional elements that are usually incidental or irrelevant to the subject technology.

[0024] [Embodiment 1: Aluminum nitride sintered body] An aluminum nitride sintered body of one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") will be described with reference to Figure 1. The aluminum nitride sintered body 1 of Embodiment 1 is an aluminum nitride sintered body 1 having a first main surface S1. The aluminum nitride sintered body 1 is Ca 12 Al 14 O 33 The aluminum nitride sintered body 1 includes a phase. The aluminum nitride sintered body 1 has a surface A1 sandwiched between a first main surface S1 and a virtual surface P at a distance of 1 mm from the first main surface S1 to the interior side of the aluminum nitride sintered body. The surface resistivity of the aluminum nitride sintered body at 25°C, measured on the first surface which is at least a part of surface A1, is 2.8 × 10⁻⁶. 7 Ω / □cm or more 1.2×109 The resistivity is less than or equal to Ω / □cm. Surface resistivity is measured in accordance with JIS C 2139-3-2:2008. The calcium content of the first surface is 3.6% by mass or more and 9.0% by mass or less. The volume resistivity of aluminum nitride sintered body 1 at 25°C is 0.36 × 10⁻⁶. 14 Ω cm or more 2.4×10 14 The resistivity is less than or equal to Ω·cm. Volume resistivity is measured in accordance with JIS C 2139-3-1:2008.

[0025] <shape> The shape of the aluminum nitride in Embodiment 1 is not particularly limited, as long as it has a first principal surface. The shape of the aluminum nitride in Embodiment 1 may be, for example, plate-like. In this disclosure, the first principal surface means the surface that defines the outer edge of the aluminum nitride sintered body and has a larger area than the other surfaces.

[0026] The shape of the first main surface can be set as appropriate depending on the application. For example, the shape of the first main surface may be circular or rectangular. The area of ​​the first main surface can be set as appropriate depending on the application. The area of ​​the first main surface is 2400 mm². 2 More than 35000mm 2 The following is also acceptable.

[0027] The average thickness of the aluminum nitride sintered body of Embodiment 1 can be set appropriately depending on the application. The average thickness may be 4 mm or more and 15 mm or less. In this disclosure, the average thickness of the aluminum nitride sintered body means the average of the thicknesses measured at five locations along the normal to the first main surface of the aluminum nitride sintered body.

[0028] <Ca 12 Al 14 O 33 phase> The aluminum nitride sintered body of Embodiment 1 is Ca 12 Al 14 O 33 Includes a phase. In the aluminum nitride sintered body of Embodiment 1, Ca 12 Al 14 O 33The phase may be present on the first surface. In the aluminum nitride sintered body of Embodiment 1, Ca 12 Al 14 O 33 The phase does not necessarily have to exist in the internal domain.

[0029] Aluminum nitride sintered body Ca 12 Al 14 O 33 The presence of the phase is confirmed by X-ray diffraction. In the XRD pattern of the aluminum nitride sintered body, Ca is present at 2θ = 20° to 80°. 12 Al 14 O 33 If a peak attributable to Ca exists, the aluminum nitride sintered body is Ca 12 Al 14 O 33 The presence of a phase is confirmed. For X-ray diffraction, for example, "EMPYREAN" (trademark) from Malvern Panalytical may be used.

[0030] <Volume resistivity> The volume resistivity of the aluminum nitride sintered body of Embodiment 1 at 25°C is 0.36 × 10⁻⁶. 14 Ω cm or more 2.4×10 14 The resistivity is less than or equal to Ω·cm. Here, the volume resistivity is measured in accordance with JIS C 2139-3-1:2008. The specific measurement method will be explained using Figure 2. A test piece 21 made of an aluminum nitride sintered body is prepared. The shape of the test piece 21 is a disc with a main surface diameter of 20 mm and a thickness of 5 mm. A main electrode 22 (diameter 14.5 mm) made of a silver electrode and an annular guard electrode 23 (inner diameter 16 mm and outer diameter 18 mm) are formed on one main surface of the test piece (hereinafter also referred to as "main surface A"). An applied electrode 24 (diameter 19 mm) made of a silver electrode is formed on the main surface of the test piece opposite to main surface A. A voltage of 50 V / mm is applied to the test piece with the electrodes formed on it using an ultra-high resistance / microcurrent meter (model 5450, manufactured by ADC Corporation), and the current value after 1 minute is read to calculate the volume resistivity.

[0031] The volume resistivity of the aluminum nitride sintered body at 25°C is 0.36 × 10⁻⁶. 14 When the volume resistivity is Ω·cm or higher, the electrical resistance in the thickness direction of the electrostatic chuck, which is made of an aluminum nitride sintered body, is maintained while the suction force of the electrostatic chuck is further improved. 14 When the volume resistivity is less than or equal to Ω·cm, the electrical resistance in the thickness direction of the electrostatic chuck is maintained while the suction force of the electrostatic chuck is further improved. The volume resistivity is 2.1 × 10⁻⁶. 14 Ω cm or more 2.4×10 14 It is also acceptable if it is less than Ω·cm.

[0032] <Surface resistivity> The aluminum nitride sintered body of Embodiment 1 has a surface portion sandwiched between a first main surface and a virtual surface P at a distance of 1 mm from the first main surface to the interior side of the aluminum nitride sintered body. The surface resistivity of the aluminum nitride sintered body at 25°C, measured on the first surface portion which is at least a part of the surface portion, is 2.8 × 10⁻⁶. 7 Ω / □cm or more 1.2×10 9 The surface resistivity is less than or equal to Ω / □cm. Here, the surface resistivity is measured in accordance with JIS C 2139-3-2:2008. The specific measurement method will be explained using Figure 3. The shape of the test piece 21 is a disc with a main surface diameter of 20 mm and a thickness of 5 mm. On one main surface of the test piece 21 (hereinafter also referred to as "main surface A"), a first main electrode (diameter 14.5 mm) made of silver electrode is formed, and a second annular main electrode (inner diameter 16 mm, outer diameter 18 mm) is formed concentrically with the first main electrode, surrounding the first main electrode. On the main surface of the test piece opposite to main surface A, a guard electrode (diameter 19 mm) made of silver electrode is formed. Using an ultra-high resistance / microcurrent meter (model 5450, manufactured by ADC Corporation), a voltage of 50 V / mm is applied to the test piece, and the current value after 1 minute is read to calculate the surface resistivity.

[0033] The above surface resistivity is 2.8 × 10⁻⁶. 7 When the surface resistivity is Ω / □cm or higher, the suction force as an electrostatic chuck improves. 9When the surface resistivity is Ω / □cm or less, the adsorption force of the electrostatic chuck equipped with an aluminum nitride sintered body is improved. The surface resistivity is 4.6 × 10⁻⁶ 8 Ω / □cm or more 1.2×10 9 It is also acceptable if it is less than or equal to Ω / □cm.

[0034] <Calcium content> ≪Calcium content of the first surface≫ In the aluminum nitride sintered body of Embodiment 1, the calcium content of the first surface is 3.6% by mass or more and 9.0% by mass or less. When the calcium content of the first surface is 3.6% by mass or more, conductive Ca is present on the first surface. 12 Al 14 O 33 Phase formation is facilitated, and the surface resistivity measured on the first surface is reduced. Ca 12 Al 14 O 33 The phase improves the conductivity of the aluminum nitride sintered body, but its thermal conductivity and strength are low. If the calcium content of the first surface is 9.0 mass% or less, Ca 12 Al 14 O 33 The decrease in the overall thermal conductivity and mechanical strength of the aluminum nitride sintered body due to the presence of an excess phase is suppressed.

[0035] The calcium content of the first surface mentioned above may be 5.4% by mass or more and 9.0% by mass or less.

[0036] The calcium content of the first surface is measured by ICP emission spectroscopy. Specifically, the surface resistivity is first measured on the first main surface of the aluminum nitride sintered body, and if the surface resistivity is 2.8 × 10⁻⁶ 7 Ω / □cm or more 1.2×10 9Identify the first region with a capacitance of Ω / □cm or less. Cut the aluminum nitride sintered body with a plane parallel to the normal to the first principal surface, crossing the first region, to expose the cross-section. In the cross-section, identify the surface portion sandwiched between the first principal surface within the first region and a virtual surface P at a distance of 1 mm from the first principal surface to the interior of the aluminum nitride sintered body. Cut out the surface portion from the aluminum nitride sintered body and crush it to obtain a powder. After melting the powder in an alkaline solution, neutralize it with acid, and measure the calcium content by ICP emission spectroscopy. For ICP emission spectroscopy, for example, Shimadzu Corporation's "ICP-7510" may be used.

[0037] ≪Calcium content in the internal region≫ As shown in Figure 1, the aluminum nitride sintered body 1 of Embodiment 1 has an internal region A2 at a distance of more than 1 mm from the surface to the interior of the aluminum nitride sintered body 1, and the calcium content of the internal region A2 may be 0.1% by mass or less. The lower limit of the calcium content of the internal region is not particularly limited, but from the viewpoint of raw material impurities, it may be 0.01% by mass or more. The calcium content of the internal region may be 0.01% by mass or more and 0.1% by mass or less, or 0.01% by mass or more and 0.02% by mass or less.

[0038] The calcium content of the above-mentioned internal region is measured by ICP emission spectroscopy. Specifically, first, the aluminum nitride sintered body is cut with a plane parallel to the normal to the first main surface to expose the cross-section. In the cross-section, the internal region where the distance from the surface to the interior of the aluminum nitride sintered body is more than 1 mm is identified. This internal region is cut out from the aluminum nitride sintered body and crushed to obtain powder. After melting the powder in an alkaline solution, it is neutralized with acid, and the calcium content is measured by ICP emission spectroscopy.

[0039] <Silicon content> <<Silicon content in the internal region>> The aluminum nitride sintered body of Embodiment 1 has an internal region where the distance from the surface to the interior of the aluminum nitride sintered body is more than 1 mm, and the silicon content of the internal region may be 0.21% by mass or more and 0.24% by mass or less, or 0.21% by mass or more and 0.23% by mass or less. The silicon content of the internal region is measured using ICP emission spectrometry in the same manner as the method for measuring the calcium content of the internal region described above.

[0040] <<Silicon content of the first surface>> In the aluminum nitride sintered body of Embodiment 1, the silicon content of the first surface may be 0.05 mass% or less. The lower limit of the silicon content of the first surface is not particularly limited, but from the viewpoint of raw material impurities, it may be 0.02 mass% or more. The silicon content of the internal region may be 0.02 mass% or more and 0.05 mass% or less, or 0.02 mass% or more and 0.04 mass% or less. The silicon content of the first surface is measured using ICP emission spectrometry in the same manner as the method for measuring the calcium content of the first surface described above.

[0041] In the aluminum nitride sintered body of Embodiment 1, the ranges of the surface resistivity, calcium content, and volume resistivity may be combined in any way.

[0042] <Area percentage of the first surface on the first main surface> The area percentage of the first surface portion on the first main surface of the aluminum nitride sintered body of Embodiment 1 can be appropriately set depending on the application of the aluminum nitride sintered body. For example, from the viewpoint of improving the adsorption force when the aluminum nitride sintered body is used as a material for an electrostatic chuck, the area percentage of the first surface on the first main surface may be 50% to 100%, or 80% to 100%.

[0043] <Volume percentage of the first surface of the aluminum nitride sintered body> The volume percentage of the first surface portion of the aluminum sintered body in Embodiment 1 can be appropriately set depending on the application of the aluminum nitride sintered body. For example, from the viewpoint of thermal conductivity and volume resistivity, the volume percentage of the first surface portion of the aluminum sintered body may be 24% by volume or more and 68% by volume or less.

[0044] <Other areas> The aluminum nitride sintered body of Embodiment 1 may consist of a first surface portion and an internal region. Alternatively, the aluminum nitride sintered body of Embodiment 1 may consist of other regions other than the first surface portion and the internal region. The other regions correspond to the surface portion other than the first surface portion. The surface resistivity measured on the other regions, the calcium content of the other regions, and the silicon content of the other regions are not particularly limited, as long as the effects of this disclosure are not impaired.

[0045] For example, the surface resistivity measured at 25°C on other regions is 1.4 × 10⁻⁶. 8 Ω / □cm or more 4.8×10 13 It is also acceptable if it is less than or equal to Ω / □cm.

[0046] For example, the calcium content in other regions may be between 0.01% by mass and 9.0% by mass.

[0047] For example, the silicon content in other regions may be between 0.02% by mass and 0.24% by mass.

[0048] <Method for manufacturing aluminum nitride sintered bodies> An example of a method for manufacturing an aluminum nitride sintered body according to Embodiment 1 will be described. The method for manufacturing an aluminum nitride sintered body may include a step for producing Ca-containing AlN powder, a step for producing Ca-free AlN powder, and a step for producing an aluminum nitride sintered body.

[0049] ≪Process for producing Ca-containing AlN powder≫ AlN powder, Al2O3 powder, and CaCO3 powder are mixed to obtain a first mixed powder. The first mixed powder may also contain polycarboxylic acid as a dispersant, polyvinyl butyral as a binder, and phenolic resin.

[0050] The first mixed powder is wet-mixed in a ball mill with ethanol as the solvent for 24 hours. The resulting slurry is thoroughly dried to obtain Ca-containing AlN powder (hereinafter also referred to as "Ca-AlN powder").

[0051] ≪Process for producing Ca-free AlN powder≫ A second mixed powder is obtained by mixing AlN powder with Y2O3 powder and SiO2 powder as sintering aids. The second mixed powder may also contain polycarboxylic acid as a dispersant, polyvinyl butyral as a binder, and phenolic resin. The mixing ratio of Y2O3 powder to SiO2 powder is set to Y2O3 powder:SiO2 powder = 10:1. The mixing ratio of AlN powder, Y2O3 powder, and SiO2 powder is adjusted so that the silicon content in the second mixed powder is 0.21% by mass or more and 0.24% by mass or less.

[0052] The second mixed powder is wet-mixed in a ball mill with ethanol as the solvent for 24 hours. The resulting slurry is thoroughly dried to obtain Ca-free AlN powder (hereinafter also referred to as "Y-AlN powder").

[0053] <<Aluminum Nitride Sintered Body Fabrication Process>> Ca-AlN powder and Y-AlN powder are individually filled into molds and molded using a uniaxial molding machine to obtain a molded body. During filling, the powders are arranged such that the region of the molded body corresponding to the first surface of the aluminum nitride sintered body obtained by sintering the molded body consists of Ca-AlN powder, and the region of the molded body corresponding to the internal region of the aluminum nitride sintered body consists of Y-AlN powder.

[0054] The obtained molded body is degreased in a nitrogen atmosphere at 500°C for 2 hours to obtain a degreased body. The degreased body is placed in a carbon mold with an inner wall coated with boron nitride (BN), and sintered in a nitrogen atmosphere at 1 atmosphere at 1650°C for 25 hours to obtain an aluminum nitride sintered body.

[0055] [Embodiment 2: Electrostatic Chuck for Semiconductor Manufacturing Equipment] An electrostatic chuck for semiconductor manufacturing equipment according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") will be described with reference to Figure 4. The electrostatic chuck 10 for semiconductor manufacturing equipment of Embodiment 2 comprises the aluminum nitride sintered body of Embodiment 1.

[0056] The electrostatic chuck 10 for semiconductor manufacturing equipment of Embodiment 2 includes a first member 11 made of the aluminum nitride sintered body of Embodiment 1, and one main surface of the first member 11 corresponds to the first main surface of Embodiment 1. The first member 11 may be, for example, plate-shaped. The shape of the first main surface S1 of the first member 11 can be appropriately set depending on the application. The shape of the first main surface S1 may be, for example, circular or rectangular.

[0057] An internal electrode 13 is provided inside the first member 11. By placing a wafer on the first main surface S1 of the first member 11 and applying a current to the internal electrode, the wafer can be electrically attracted and fixed to the first main surface S1 in a vacuum. [Examples]

[0058] This embodiment will be described in more detail by reference to examples. However, this embodiment is not limited by these examples.

[0059] [Fabrication of aluminum nitride sintered bodies] Aluminum nitride sintered bodies were prepared for each sample using the following procedure. The details of the raw materials are as follows. AlN powder: Tokuyama Corporation "H grade", CaCO3 powder: Shiraishi Industries Co., Ltd. "Brilliant-1500" (trademark), Y2O3 powder: Shin-Etsu Chemical Co., Ltd. "RU-P", SiO2 powder: Kojunsei Kagaku Co., Ltd. "SIO14PB"

[0060] <Process for producing Ca-containing AlN powder> AlN powder, Al2O3 powder, CaCO3 powder, polycarboxylic acid, polyvinyl butyral, and phenolic resin were mixed to obtain a first mixed powder. The mixing ratios of AlN powder, Al2O3 powder, and CaCO3 powder in each sample were as shown in Table 1. In all samples, the amount of polycarboxylic acid was 1 part by mass, the amount of polyvinyl butyral was 2 parts by mass, and the amount of phenolic resin was 0.1 part by mass with respect to 100 parts by mass of the first mixed powder.

[0061] The first mixed powder was wet-mixed in a ball mill for 24 hours using ethanol as a solvent. The obtained slurry was sufficiently dried to obtain Ca-containing AlN powder (Ca-AlN powder).

[0062] <Process for producing Ca-free AlN powder> AlN powder, Y2O3 powder, SiO2 powder, polycarboxylic acid, and polyvinyl butyral were mixed to obtain a second mixed powder. The mixing ratios of AlN powder, Y2O3 powder, and SiO2 powder in each sample were as shown in Table 1. The amount of polycarboxylic acid was 1 part by mass, the amount of polyvinyl butyral was 2 parts by mass, and the amount of phenolic resin was 0.1 part by mass with respect to 100 parts by mass of the second mixed powder.

[0063] The second mixed powder was wet-mixed in a ball mill for 24 hours using ethanol as a solvent. The obtained slurry was sufficiently dried to obtain Ca-free AlN powder (Y-AlN powder).

[0064] <Process for producing aluminum nitride sintered body> A mold was prepared, and the powders described in the "surface part" and "other than surface part" columns of the "formed body" in Table 1 were filled in order, and formed into a φ30 mm × 4 mm thickness by a uniaxial molding machine to obtain a formed body. In the formed body, the region sandwiched between one main surface and a virtual surface whose distance along the thickness direction from the main surface is 1 mm was composed of the powder described in the "surface part" column, and the other regions were composed of the powder described in the "other than surface part" column.

[0065] The obtained formed body was degreased at 500 °C for 2 hours in a nitrogen atmosphere to obtain a degreased body. The degreased body was placed in a carbon mold with its inner wall coated with boron nitride (BN), and sintering was performed at 1650 °C for 25 hours in a nitrogen atmosphere of 1 atm to obtain aluminum nitride sintered bodies of each sample.

[0066]

Table 1

[0067] [Evaluation] Whether the aluminum nitride sintered body of each sample contains the Ca 12 Al 14 O 33 phase was confirmed by X-ray diffraction. In all samples, the aluminum nitride sintered body was confirmed to contain the Ca 12 Al 14 O 33 phase.

[0068] In the aluminum nitride sintered body of each sample, the volume resistivity at 25 °C, the calcium content rate of the first surface part, the silicon content rate of the first surface part, the surface resistivity on the first surface part, the calcium content rate of the internal region, and the silicon content rate of the internal region were measured by the method described in Embodiment 1. The results are shown in Table 2.

[0069]

Table 2

[0070] [Discussion] The aluminum nitride sintered bodies of Samples 1 to 3 correspond to the examples. These aluminum nitride sintered bodies have a surface part with a reduced surface resistivity while maintaining a high volume resistivity inside the aluminum nitride sintered body.

[0071] The aluminum nitride sintered body of Sample 1-1 has a low calcium content in the first surface portion and a high resistivity in the first surface portion, corresponding to a comparative example. This is because the calcium content in the first surface portion is low, so the conductive Ca 12 Al 14 O 33 phase is insufficient in amount, which is presumably the reason.

[0072] The aluminum nitride sintered body of Sample 1-2 has a calcium content of 18% by mass in the first surface portion and a resistivity of 7.8×10 3 Ω / □cm in the first surface portion, corresponding to a comparative example. This is because the calcium content in the first surface portion is high, and the conductive Ca 12 Al 14 O 33 phase is excessive in amount, which is presumably the reason.

[0073] The aluminum nitride sintered body of Sample 1-3 has no difference in composition between the internal region and the first surface portion and has a low volume resistivity, corresponding to a comparative example. Since a conductive Ca 12 Al 14 O 33 phase is formed in the aluminum nitride sintered body, it is presumed that the volume resistivity is low.

[0074] As described above, the embodiments and examples of the present disclosure have been explained. However, it has been planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples or to variously modify them. The embodiments and examples disclosed this time should be considered as illustrative in all respects and not restrictive ones. The scope of the present invention is shown not by the above-described embodiments and examples but by the claims, and it is intended that all meanings equivalent to the claims and all modifications within the scope are included.

Explanation of Reference Numerals

[0075] 1 Aluminum nitride sintered body 10 Electrostatic chuck for semiconductor manufacturing apparatus 11 First member 13 Internal electrode 21 Test specimens 22 Main electrode 23 Guard electrode 24 Applied electrode 25 First main electrode 26 Second main electrode A Main surface A A1 Surface area A2 internal area P Virtual Surface S1 First principal surface S2 Second principal surface

Claims

1. An aluminum nitride sintered body having a first main surface, The aluminum nitride sintered body is Ca １２ Al １４ O ３３ Including the aspect, The aluminum nitride sintered body has a surface portion sandwiched between the first main surface and a virtual surface P at a distance of 1 mm from the first main surface to the interior side of the aluminum nitride sintered body. The surface resistivity of the aluminum nitride sintered body at 25°C, measured on the first surface portion which is at least a part of the aforementioned surface portion, is 2.8 × 10⁻⁶. ７ Ω / □cm or more 1.2×10 ９ It is less than or equal to Ω / □ cm, The aforementioned surface resistivity was measured in accordance with JIS C 2139-3-2:2008. The calcium content of the first surface portion is 3.6% by mass or more and 9.0% by mass or less. The volume resistivity of the aluminum nitride sintered body at 25°C is 0.36 × 10⁻⁶. １４ Ω・cm or more 2.4×10 １４ It is less than or equal to Ω·cm, The aforementioned volume resistivity is measured in accordance with JIS C 2139-3-1:2008 for an aluminum nitride sintered body.

2. The aluminum nitride sintered body has an internal region that is more than 1 mm away from the surface to the interior side of the aluminum nitride sintered body. The aluminum nitride sintered body according to claim 1, wherein the calcium content of the internal region is 0.1% by mass or less.

3. The aluminum nitride sintered body has an internal region that is more than 1 mm away from the surface to the interior side of the aluminum nitride sintered body. The aluminum nitride sintered body according to claim 1 or claim 2, wherein the silicon content of the internal region is 0.21% by mass or more and 0.24% by mass or less.

4. The aluminum nitride sintered body according to claim 1 or claim 2, wherein the silicon content of the first surface portion is 0.05% by mass or less.

5. An electrostatic chuck for semiconductor manufacturing equipment comprising an aluminum nitride sintered body according to claim 1 or claim 2.

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