JP2024104939A - Ceramic Susceptor - Google Patents

Abstract

To provide a ceramic susceptor which is available for a semiconductor manufacturing process under a low temperature and with high output.SOLUTION: A ceramic susceptor 100 comprises: a substrate 10 including a mounting surface and formed from a ceramic sintered body containing Sic as a main component; and at least one electrode 20 embedded in the substrate 10. Volume resistivity of the substrate 10 is greater than 108 Ωcm at 20°C and greater than 109 Ωcm at -30°C. Thus, electric insulation property of the substrate under a low temperature can be secured and functions of the susceptor, in which the electrode is embedded, can be presented in a semiconductor manufacturing process under a low temperature with high output.SELECTED DRAWING: Figure 1

Description

The present invention relates to a ceramic susceptor.

As semiconductors have become finer in recent years, there has been an increasing demand for finer processing in semiconductor manufacturing processes. For example, in etching processes, there is an increasing demand for high-definition shallow trench structures with narrow trench widths and deep trench depths. To meet this demand, processes at low temperatures (below 0°C) have been considered that suppress isotropic etching by radicals and focus on anisotropic etching by ions.

Patent Document 1 discloses a method for controlling a low-temperature processing apparatus for plasma processing a workpiece, which is attracted and held by an electrostatic chuck means on a susceptor in a processing chamber and cooled, with a reactive plasma of a predetermined processing gas, by placing the workpiece on the attraction surface of the electrostatic chuck means, supplying a heat transfer gas to the contact surface between the workpiece and the electrostatic chuck means, and then, after a predetermined time has elapsed, converting the processing gas introduced into the processing chamber into plasma.

Japanese Unexamined Patent Publication No. 7-147274

At low temperatures, the etching rate decreases and throughput does not increase, so it was necessary to increase the output (large amount of heat). However, as the output increases, the amount of heat incident on the substrate being processed also increases, making it difficult to absorb this large amount of heat and maintain the substrate at a low temperature.

The heat transferred to the susceptor is conducted inside the susceptor, so the thermal conductivity of the material that makes up the susceptor affects heat absorption. In other words, materials with high thermal conductivity are effective for heat absorption, and for example, SiC and AlN have been considered. However, although SiC has high thermal conductivity, it has a low volume resistivity, making it difficult to use as a material that makes up the base material of a susceptor with an embedded electrode.

Patent Document 1 discloses a method for controlling an electrostatic chuck that can cool a substrate at low power (power of 100 W or less), but it cannot be used in processes that involve a large amount of incident heat. Therefore, there has been a demand for a susceptor that can be used in semiconductor manufacturing processes at low temperatures and with high power.

The present invention was made in consideration of these circumstances, and aims to provide a ceramic susceptor that can be used in low-temperature, high-output semiconductor manufacturing processes.

(1) In order to achieve the above object, the present invention provides the following means: That is, a ceramic susceptor according to an embodiment of the present invention is a ceramic susceptor, which includes a base having a mounting surface and formed of a ceramic sintered body mainly composed of SiC, and at least one electrode embedded in the base, and is characterized in that the volume resistivity of the base is greater than 10 ⁸ Ωcm at 20°C and greater than 10 ⁹ Ωcm at -30°C.

In this manner, by making the volume resistivity of the base material greater than 10 ⁸ Ωcm at 20° C. and greater than 10 ⁹ Ωcm at −30° C., the electrical insulation of the base material at low temperatures can be ensured, and the function of a susceptor with embedded electrodes can be exhibited in a semiconductor manufacturing process at low temperatures and high power.

(2) In addition, in the ceramic susceptor of the application example of (1) above, the electrode is an electrode for electrostatic adsorption.

The ceramic susceptor of the present invention has electrical insulation properties at low temperatures, so this configuration allows the ceramic susceptor to function as an electrostatic chuck that can be used at low temperatures and high output. In particular, it can be suitably used as a Johnsen-Rahbek (JR) type electrostatic chuck that can exert a strong contact pressure (adsorption force).

(3) In addition, in the ceramic susceptor of the application example of (1) above, the electrode is a heater electrode.

The ceramic susceptor of the present invention has electrical insulation properties even at low temperatures, so this configuration allows the ceramic susceptor to function as a heater for regulating substrate temperature and heating, which can be used at low temperatures and with high output.

(4) In addition, in the ceramic susceptor of the application example of (1) above, the electrode is a high-frequency electrode.

The ceramic susceptor of the present invention has electrical insulation properties even at low temperatures, so this configuration allows the ceramic susceptor to function as an RF application base that can be used at low temperatures and high output.

(5) In addition, in the ceramic susceptor of any of the application examples (1) to (4) above, the electrode is characterized in that an insulating layer is provided on the surface.

In this way, by providing an insulating layer on the surface of the electrode, unnecessary leakage current can be suppressed. Furthermore, even if the electrical insulation of the base material becomes insufficient due to the environment in which the ceramic susceptor is used, the risk of malfunction can be reduced.

(6) In addition, in the ceramic susceptor of the application example of (5) above, the electrodes are made of W, Mo or an alloy containing these as main components, and the insulating layer is formed of a nitride or oxide having a melting point of 2200°C or higher.

This makes it possible to specifically construct a ceramic susceptor in which an insulating layer is provided on the electrode.

(7) In addition, in the ceramic susceptor of any of the application examples (1) to (6) above, the substrate is characterized in that a media flow path is provided therein.

This allows the ceramic susceptor to be given the ability to heat and cool using a medium, expanding the functionality of the ceramic susceptor.

(8) In addition, in the ceramic susceptor of any of the application examples (1) to (7) above, the purity of the SiC of the substrate is 99.91 wt% or more.

This makes it easy to specifically configure a ceramic susceptor whose base material has a volume resistivity of more than 10 ⁸ Ωcm at 20°C and more than 10 ⁹ Ωcm at -30°C.

The ceramic susceptor of the present invention can be used in semiconductor manufacturing processes at low temperatures and high power.

1 is a schematic cross-sectional view showing an example of a ceramic susceptor according to an embodiment of the present invention. FIG. 11 is a schematic cross-sectional view showing a modified example of a ceramic susceptor according to an embodiment of the present invention. FIG. 11 is a schematic partial cross-sectional view showing a modified example of a ceramic susceptor according to an embodiment of the present invention. FIG. 11 is a schematic cross-sectional view showing a modified example of a ceramic susceptor according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing an example of the upper surface of a ceramic susceptor according to an embodiment of the present invention. FIG. 11 is a schematic cross-sectional view showing a modified example of a ceramic susceptor according to an embodiment of the present invention. 10A and 10B are schematic diagrams showing modified examples of the upper surface of the ceramic susceptor according to the embodiment of the present invention. 5A to 5D are schematic cross-sectional views each showing a stage of a manufacturing method for a ceramic susceptor. 5A to 5D are schematic cross-sectional views each showing a stage of a manufacturing method for a ceramic susceptor. 2 is a schematic cross-sectional view showing one stage of a method for manufacturing a ceramic susceptor. FIG. 1 is a table showing the production conditions and the results of various tests of Examples and Comparative Examples.

Next, an embodiment of the present invention will be described with reference to the drawings. To facilitate understanding of the description, the same reference numbers are used for the same components in each drawing, and duplicate descriptions will be omitted. Note that in the configuration diagrams, the size of each component is shown conceptually, and does not necessarily represent the actual dimensional ratio.

[Embodiment]
(Configuration of electrode-embedded member)
A ceramic susceptor according to an embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view showing an example of a ceramic susceptor according to an embodiment of the present invention. A ceramic susceptor 100 according to an embodiment of the present invention includes a substrate 10 and at least one electrode 20.

The substrate 10 is formed of a ceramic sintered body whose main component is SiC. The substrate 10 may be in various shapes, such as a substantially circular plate, a polygonal plate, or an elliptical plate. The substrate 10 is flat except for convex portions formed on the upper surface 12. If no pin-shaped convex portions, which will be described later, are formed on the upper surface 12 of the substrate 10, the upper surface 12 of the substrate 10 forms a flat or curved surface (mounting surface) of a predetermined shape on which a substrate is placed.

The volume resistivity of the substrate 10 is greater than 10 ⁸ Ωcm at 20° C. and greater than 10 ⁹ Ωcm at −30° C. This ensures electrical insulation of the substrate 10 at low temperatures (below 0° C.), allowing the substrate 10 to function as a ceramic susceptor with the electrodes 20 embedded therein in a semiconductor manufacturing process at low temperatures and high power.

The heat transferred to the ceramic susceptor 100 is thermally conducted inside the ceramic susceptor 100, so the thermal conductivity of the material that constitutes the ceramic susceptor 100 affects heat absorption. In other words, materials with high thermal conductivity are effective for heat absorption. Therefore, the thermal conductivity of the substrate 10 is preferably 50 W/mK or more, and more preferably 100 W/mK or more.

The ceramic sintered body mainly composed of SiC means that the purity of SiC is 98 wt% or more. The purity of SiC in the base material is preferably 99.91 wt% or more. This makes it easy to specifically configure the ceramic susceptor 100 having a base material volume resistivity of more than 10 ⁸ Ωcm at 20°C and more than 10 ⁹ Ωcm at -30°C.

The electrode 20 is embedded in the substrate 10. The electrode 20 is embedded in a shape that corresponds to the design of the ceramic susceptor 100. The electrode 20 is preferably made of W, Mo, or an alloy containing these as its main components.

The electrode 20 is preferably an electrode for electrostatic adsorption. Since the ceramic susceptor 100 of the present invention has electrical insulation properties at low temperatures, this configuration allows the ceramic susceptor 100 to function as an electrostatic chuck that can be used at low temperatures and high output.

To absorb the large amount of heat incident on the substrate, it is effective to increase the heat transfer caused by contact between the substrate and the ceramic susceptor 100. For this purpose, it is preferable that the ceramic susceptor 100 be a Johnsen-Rahbek (JR) type electrostatic chuck capable of exerting a strong contact pressure (adsorption force).

The JR type electrostatic chuck needs to maintain its volume resistivity within a certain range at the temperature at which it is used. If the volume resistivity is too large, the JR effect is not exerted, the electrostatic adsorption force is reduced, and the heat transfer with the substrate is deteriorated. If the volume resistivity is too small, the current consumption is large, the potential difference between the substrate and the electrostatic adsorption electrode built into the electrostatic chuck cannot be maintained, the electrostatic adsorption force is reduced, and the heat transfer with the substrate is deteriorated. Therefore, when the ceramic susceptor 100 is used as a JR type electrostatic chuck, the volume resistivity is preferably 10 ⁹ Ωcm or more and 10 ¹² Ωcm or less at the operating temperature, and more preferably 10 ⁹ Ωcm or more and 10 ¹¹ Ωcm or less. Since the ceramic susceptor 100 of the present invention has a volume resistivity at the operating temperature that is generally within this range, it can be suitably used as a JR type electrostatic chuck.

The electrode 20 is preferably a heater electrode. Since the ceramic susceptor 100 of the present invention has electrical insulation properties at low temperatures, this configuration allows the ceramic susceptor 100 to function as a heater for regulating substrate temperature and heating, which can be used at low temperatures and with high output.

The electrode 20 is preferably a high-frequency electrode. Since the ceramic susceptor 100 of the present invention has electrical insulation properties at low temperatures, this configuration allows the ceramic susceptor 100 to function as an RF application base that can be used at low temperatures and high output.

The substrate 10 may have two or more different types of electrodes 20 embedded therein. FIG. 2 is a schematic cross-sectional view showing a modified example of a ceramic susceptor according to an embodiment of the present invention. As shown in FIG. 2, for example, an electrostatic adsorption electrode 22 and a heater electrode 24 are embedded in the substrate 10, thereby providing the electrostatic adsorption function of the substrate, temperature regulation, and heating functions, thereby making the semiconductor manufacturing process more sophisticated. The substrate 10 may have three different types of electrodes 20 embedded therein.

3 is a schematic partial cross-sectional view showing a modified example of a ceramic susceptor according to an embodiment of the present invention. As shown in FIG. 3, the electrode 20 is preferably provided with an insulating layer 28 on its surface. In this way, by providing the insulating layer 28 on the surface of the electrode 20, unnecessary leakage current can be suppressed. In addition, even if the electrical insulation of the substrate 10 becomes insufficient due to the usage environment of the ceramic susceptor 100, the risk of malfunction can be reduced. The insulating layer 28 is preferably 5 μm or more and 1000 μm or less in thickness. The insulating layer 28 is preferably formed of a nitride or oxide having a melting point of 2200° C. or more. The insulating layer 28 may be provided only on a part of the electrode 20. In addition, when there are multiple electrodes 20, the insulating layer 28 may be provided on all of them, or only on some of the electrodes 20.

The insulating layer 28 can be formed of, for example, Y ₂ O ₃ (melting point 2435° C.), La ₂ O ₃ (melting point 2315° C.), or BN (melting point 2700° C.). The insulating layer 28 formed of Y ₂ O ₃ and La ₂ O ₃ can be formed, for example, by suspending Y ₂ O ₃ or La ₂ O ₃ in a solvent, dipping the electrode 20 before embedding, and performing a heat treatment. The insulating layer 28 formed of BN can be formed, for example, by pyrolysis CVD in which BCl ₄ and NH ₃ are used as raw material gases and pyrolyzed at 2000° C. or higher to coat the electrode 20 before embedding.

Figure 4 is a schematic cross-sectional view showing a modified example of a ceramic susceptor according to an embodiment of the present invention. Figure 5 is a schematic view showing an example of the upper surface of a ceramic susceptor according to an embodiment of the present invention. Figure 4 shows a cross section taken along line AA in Figure 5.

As shown in Figures 4 and 5, the substrate 10 preferably has a media flow path 30 therein. The media flow path 30 is formed, for example, in a tubular shape. In a vertical cross section of the substrate 10, the media flow path 30 is preferably located closer to the bottom surface 14 of the substrate 10 than the layer in which the electrodes 20 are embedded. The width of the media flow path 30 is preferably 1 mm or more and 60 mm or less. The cross-sectional shape of the media flow path 30 is not limited to a rectangle, and may be any shape that can be manufactured, such as a circle, an ellipse, a semicircle, or a stepped shape.

The medium flow path 30 is preferably a system that circulates a low-temperature chiller. Therefore, the medium flow path 30 is preferably formed with an inlet for allowing the chiller to flow in and an outlet for allowing the chiller to flow out.

When the media flow path 30 is formed in the substrate 10, it is preferable that the substrate 10 is integrally formed from a ceramic sintered body. The substrate 10 is integrally formed from a ceramic sintered body means that the ceramic sintered body forming the ceiling of the media flow path 30 and the ceramic sintered body forming the bottom of the media flow path 30 are directly bonded together using a bonding material containing ceramics or without using a bonding material. This increases the mechanical strength of the substrate 10.

The media flow path 30 preferably has an approximately annular shape centered at the center 16 of the substrate 10 when viewed from the top surface 12 of the substrate 10. This allows the temperature distribution in the radial direction of the substrate 10 surface to be adjusted. An approximately annular shape includes a shape in which some of the arcs of the annular shape are not connected, as in Figure 5, and a normal annular shape. The dotted line in Figure 5 indicates the shape of the media flow path 30 when the substrate 10 is viewed from the top surface 12. Structures that are viewed from the perspective other than the media flow path 30 are omitted.

Figure 6 is a schematic cross-sectional view showing a modified example of a ceramic susceptor according to an embodiment of the present invention. Figure 7 is a schematic view showing a modified example of the upper surface of a ceramic susceptor according to an embodiment of the present invention. Figure 6 shows a cross section taken along line BB in Figure 7.

As shown in FIG. 6 and FIG. 7, the media flow paths 30 are preferably arranged in a concentric shape centered on the center 16 of the substrate 10 in a shape seen through the substrate 10 from the top surface 12. This allows fine adjustment of the radial temperature distribution on the surface of the substrate 10. The substantially annular media flow paths 30 arranged in a concentric shape may be double as shown in FIG. 6 and FIG. 7, or may be triple or more. The substantially annular media flow paths 30 arranged in a concentric shape may be connected inside the substrate 10 as shown in FIG. 7, or each may have an inlet and an outlet. In addition, the width of the gap between adjacent media flow paths 30 (the width of the substrate 10 present in the gap between adjacent media flow paths 30) is preferably 2 mm or more. In addition, the width of the gap between adjacent media flow paths 30 is preferably 25% or more of the width of the media flow path 30. This allows the strength of the substrate 10 to be maintained even if the media flow path 30 is formed inside the substrate 10.

The media flow path 30 may include a linear shape. In addition, a substantially annular media flow path 30 and a linear media flow path 30 may be combined. The substantially annular media flow path 30 and the linear media flow path 30 may be connected to each other.

The ceramic susceptor 100 may have pin-shaped protrusions. In this case, multiple pin-shaped protrusions are formed and protrude upward from the upper surface 12 of the substrate 10. The shape of the pin-shaped protrusions is appropriately selected from among pillar shapes such as a cylindrical shape or a rectangular pillar shape, pyramid shapes such as a cone shape or a pyramid shape, and shapes with the top of a pyramid shape such as a truncated cone shape or a truncated pyramid shape.

The arrangement of the pin-shaped protrusions is not particularly limited. It may be in a known form or a similar form, and may be, for example, a regular arrangement such as concentric circles, a square lattice, or a triangular lattice, or may be an irregular arrangement with localized sparseness and denseness. In addition, annular protrusions may be arranged on the outer periphery of the upper surface 12 of the ceramic susceptor 100 so as to surround the pin-shaped protrusions.

When pin-shaped protrusions are formed on the substrate 10, the upper ends of the multiple pin-shaped protrusions as a whole form a flat or curved surface (mounting surface) of a predetermined shape on which the substrate is placed. As a result, the multiple pin-shaped protrusions support the substrate. That is, the mounting surface formed by the upper ends of the multiple pin-shaped protrusions is determined. As a result, the upper ends of the multiple pin-shaped protrusions come into contact with the substrate, and the substrate is supported. Note that, among the multiple pin-shaped protrusions, there may be some whose upper ends do not come into contact with the substrate. This is because, even if such pin-shaped protrusions exist, it is possible to support the substrate depending on the arrangement of the surrounding pin-shaped protrusions. The upper ends of the pin-shaped protrusions may come into contact with the substrate entirely, or only partially.

The height of the pin-shaped protrusions varies depending on the application of the ceramic susceptor 100. For example, when the ceramic susceptor 100 is used as an electrostatic chuck, it is preferably 5 μm or more and 50 μm or less. Also, for example, when the ceramic susceptor 100 is used as a heater for adjusting the temperature of a substrate or for heating, it is preferably 50 μm or more and 1000 μm or less. The height of the pin-shaped protrusions refers to the distance from the upper surface 12 of the substrate 10 to the upper end of the pin-shaped protrusions. It is preferable that the upper end of the pin-shaped protrusions is a flat surface of a predetermined size. In this case, the maximum diameter of the flat surface at the upper end of the pin-shaped protrusions is preferably 100 μm or more and 5 mm or less. It is preferable that the surface roughness of the flat surface at the upper end of the pin-shaped protrusions is Ra 0.01 μm or more and 1.6 μm or less.

The ceramic susceptor 100 may have terminals 50, 51 and terminal holes 52 as necessary. The ceramic susceptor 100 may also have lift pin holes (not shown) and ventilation holes when used as a vacuum chuck.

[Method of manufacturing ceramic susceptor]
Next, a method for manufacturing a ceramic susceptor according to an embodiment of the present invention will be described. The ceramic susceptor according to an embodiment of the present invention is manufactured, for example, by a molded body hot pressing method described below. The method for manufacturing a ceramic susceptor is not limited to this method, and may be, for example, a powder hot pressing method or a conventional green sheet lamination method. The powder hot pressing method is a method in which ceramic raw material powder and a predetermined heating resistor and electrode are alternately stacked to embed the heating resistor and electrodes inside the ceramic, and then the resulting product is uniaxially hot-pressed and fired.

The manufacturing method for a ceramic susceptor according to an embodiment of the present invention using a molded body hot pressing method includes a ceramic molded body forming process, a ceramic degreased body making process, a laminate forming process, a laminate firing process, and a substrate processing process.

In the ceramic molded body forming process, for example, a plurality of ceramic molded bodies are formed from ceramic raw material powder mainly composed of SiC (silicon carbide). Sintering aids may be added as necessary. For example, additives such as sintering aids _B4C , C, binders, plasticizers, and dispersants are appropriately added to and mixed with SiC ceramic raw material powder to prepare a slurry, and the granulated powder is granulated by a spray drying method or the like. The granulated powder is then pressure-molded to form a plurality of ceramic molded bodies.

The ceramic raw material powder used may be raw material powder produced by the Acheson method or raw material powder produced by the CVD method. Of these, it is preferable to use raw material powder produced by the CVD method, which tends to increase the volume resistivity.

The ceramic raw material powder is preferably of high purity, preferably 99% or more, more preferably 99.9% or more. The average particle size of the ceramic raw material powder is preferably 0.1 μm or more and 1.0 μm or less.

The mixing method may be either wet or dry, and a mixer such as a ball mill or a vibration mill may be used. The molding method may be a known method such as uniaxial pressing or cold isostatic pressing (CIP). The method for forming the ceramic molded body is not limited to pressing, and may be, for example, green sheet lamination or casting, which may be appropriately degreased or further calcined to produce the ceramic molded body.

After molding, the ceramic molded body may be machined to adjust the shape of the molded body. In addition, grooves may be formed on one or both sides of the ceramic molded body (the bonding surface with another ceramic molded body) to match the shapes of electrodes, vias, wiring, etc. Machining may be performed after degreasing.

In the ceramic degreased body production process, multiple ceramic molded bodies are degreased at a predetermined temperature or higher for a predetermined period of time or longer to produce multiple ceramic degreased bodies.

The ceramic molded body is heat-treated, for example, at a temperature of 500°C to 900°C to become a ceramic degreased body. The degreasing time is preferably 1 hour to 120 hours. An atmospheric furnace or a nitrogen atmosphere furnace can be used for degreasing, but an atmospheric furnace is preferred to remove the organic components of the binder.

In the laminate formation process, one or more electrodes and, if necessary, via material and wiring are prepared, and these are combined with multiple ceramic degreased bodies to form a laminate formed in a flat plate shape. Figures 8(a) to (d) are schematic cross-sectional views each showing one stage of the manufacturing process of a ceramic susceptor. Figure 8(a) shows a cross-section of a ceramic degreased body 101 whose upper surface is the mounting surface, an electrode 20, and a ceramic degreased body 102 in which a recess in which the electrode 20 is placed is formed. Figure 8(b) shows a laminate 110 formed by combining the ceramic degreased body 101, the electrode 20, and the ceramic degreased body 102. In Figure 8, the laminate 110 is made using two ceramic degreased bodies, but the number of ceramic degreased bodies may be three or more depending on the design of the ceramic susceptor. The electrodes, via material, and wiring are formed by foil, thin plate, wire, mesh, or porous body of these materials such as molybdenum or tungsten, or by filling with paste or printing.

The electrode 20 is prepared by machining it into a shape that corresponds to the design of the ceramic susceptor. The electrode can be in a variety of shapes, such as mesh or foil. It can also be made of a variety of materials, such as molybdenum or tungsten.

In the laminate firing process, the laminate 110 is uniaxially pressurized and fired in the lamination direction to form a substrate. Among the firing conditions, the pressure is preferably 4 MPa or more. The firing temperature is preferably 2000°C or more and 2200°C or less. The firing time is preferably 1 hour or more and 12 hours or less, and more preferably 1 hour or more and 5 hours or less. The firing atmosphere is, for example, a nitrogen or inert gas atmosphere, but may also be a vacuum atmosphere. The vacuum atmosphere may be followed by an inert gas atmosphere. As a result, one or more ceramic degreased bodies are sintered in each laminate to become ceramic sintered bodies, which are integrated to obtain a substrate. Figure 8 (c) shows a cross section of the substrate before substrate processing.

In the substrate processing process, the outer shape of the substrate is processed. If necessary, pin-shaped protrusions, etc. are formed. Terminal holes for connecting terminals are also drilled at specified positions on the underside.

Then, a terminal is connected to the terminal hole using solder or the like. The terminal can be made of Ni or the like. The solder can be made of Au or the like. Figure 8(d) shows a cross section of the substrate with the terminal connected.

A ceramic calcined body preparation process may be provided between the ceramic degreased body preparation process and the laminate formation process. When the ceramic calcined body preparation process is provided, the ceramic degreased body is calcined at a predetermined temperature to prepare a ceramic calcined body. This allows the dimensional accuracy of the ceramic susceptor to be improved. The calcination temperature is preferably 1200°C or higher and 1900°C or lower. The calcination time is preferably 0.5 hours or higher and 12 hours or lower. The calcination atmosphere is preferably a nitrogen or inert gas atmosphere, but may be a vacuum atmosphere or the like. When the calcined body preparation process is provided, machining may be performed after the calcined body preparation process.

In this way, it is possible to produce ceramic susceptors with embedded electrodes that can be used in semiconductor manufacturing processes at low temperatures and high power.

[Modification of the method for manufacturing a ceramic susceptor]
Next, a modified example of the method for manufacturing a ceramic susceptor according to the present invention will be described. The method for manufacturing a ceramic susceptor having a media flow path according to the embodiment of the present invention by a molded body hot pressing method includes a ceramic molded body forming step, a ceramic degreased body fabricating step, a laminate forming step, a laminate firing step, a substrate precursor processing step, a substrate precursor bonding step, and a substrate processing step. The ceramic molded body forming step, the ceramic degreased body fabricating step, and the substrate processing step are the same as those described above, and therefore will not be described.

In the laminate formation process, one or more electrodes and, if necessary, via material and wiring are prepared, and these are combined with multiple ceramic degreased bodies to form one or more laminates formed in a flat plate shape. Figures 9(a) to (d) and Figure 10 are schematic cross-sectional views each showing one stage of the manufacturing process of a ceramic susceptor. Figure 9(a) shows a cross-section of a ceramic degreased body 101, the upper surface of which serves as a mounting surface, an electrode 20, a ceramic degreased body 102, in which a recess in which the electrode 20 is placed is formed and the lower surface of which serves as the ceiling of the media flow path, and a ceramic degreased body 103, in which a groove 105, which serves as part of the media flow path, is formed. Figure 9(b) shows a laminate 110 formed by combining the ceramic degreased body 101, the electrode 20, and the ceramic degreased body 102. Also, one laminate 110 is formed only from the ceramic degreased body 103. The laminate 110 may be made of one ceramic degreased body.

In the laminate firing process, the formed laminate is uniaxially pressurized and fired in the stacking direction to form one or more substrate precursors. The firing conditions are the same as above. The multiple substrate precursors include, for example, a substrate precursor in which an electrode is embedded, a substrate precursor that serves as a cover for a media flow path, and a substrate precursor in which part of a media flow path is formed.

In the substrate precursor processing step, one or more substrate precursors are each subjected to the necessary processing. For example, a groove that will become the media flow path after bonding is formed. Figure 9 (c) shows a cross section of a substrate precursor 122 in which a groove 105 that will become the media flow path after bonding is formed. In Figure 9, the media flow path is formed by covering the groove 105 with another substrate precursor 121, but the media flow path may also be formed by combining grooves formed in two substrate precursors. Using this method, media flow paths of various shapes can be formed.

In the substrate precursor bonding process, multiple substrate precursors are bonded to produce a substrate. Bonding can be performed using either a bonding method that uses a bonding material or a bonding method that does not use a bonding material. Figure 9(d) shows the substrate after bonding.

First, a bonding method using a bonding material will be described. First, a bonding material is prepared and applied to at least one of the end faces of the substrate precursor on the bonding side. The end face of the substrate precursor on the bonding side is preferably polished to a surface roughness Ra of 1.6 μm or less, and more preferably to 0.4 μm or less. The thickness of the applied bonding material is preferably 5 μm or more and 30 μm or less.

Next, multiple substrate precursors are placed and heated while being pressed in a direction perpendicular to the substrate placement surface. Of the bonding conditions, the pressure is preferably 5 kPa or more. The heating temperature is preferably 1500°C or more and 1800°C or less. The heating time is preferably 0.5 hours or more and 5 hours or less. The heating atmosphere is, for example, a nitrogen or inert gas atmosphere, but may also be a vacuum atmosphere. This allows multiple substrate precursors to be bonded.

The bonding material may be any material capable of bonding the substrate precursors together. For example, it may be a paste of mixed powder containing at least B ₄ C powder in SiC powder, which is the same main component as the substrate precursor. It may also be a paste containing 90 wt % or more of SiC and, if necessary, containing Si or B to adjust the temperature at which the substrate precursors become molten during bonding.

Next, a bonding method that does not use a bonding material will be described. First, multiple substrate precursors are arranged. The end faces of the substrate precursors on the bonding side are preferably polished to a surface roughness Ra of 0.1 μm or less. Next, the substrate precursors are heated while being pressed in a direction perpendicular to the substrate mounting surface. Among the bonding conditions, the pressure is preferably 4 MPa or more. The heating temperature is preferably 1600°C or more and 2000°C or less. The heating time is preferably 0.5 hours or more and 6 hours or less. The heating atmosphere is, for example, a nitrogen or inert gas atmosphere, but may also be a vacuum atmosphere. This allows multiple substrate precursors to be bonded.

In the above-mentioned method, the substrate precursor is formed from a ceramic sintered body and then bonded to form the substrate, but the substrate precursor may be formed from a ceramic calcined body and then bonded and sintered to form the substrate. In addition, when the structure of the media flow path is simple, the substrate can be made by processing a ceramic degreased body, laminating and sintering it. When the structure of the media flow path is complex, when a flow path that communicates with the outside is provided to the media flow path, or when the dimensional accuracy of the media flow path is to be high, the method of bonding ceramic sintered bodies is preferable.

In this way, it is possible to manufacture ceramic susceptors with embedded electrodes and media flow paths that can be used in semiconductor manufacturing processes at low temperatures and high power.

[Examples and Comparative Examples]
Example 1
Example 1 is an example of a ceramic susceptor in which an electrostatic attraction electrode is embedded. The raw material of the substrate was SiC raw material powder (purity 99.9 wt%) produced by the Acheson method. 0.1 wt% of _B4C was added as a sintering aid to the SiC raw material powder, and binders, dispersants, etc. were appropriately added and mixed to produce a slurry, which was then granulated by a spray-drying method.

Next, the granulated powder was isostatically molded, and after molding, it was processed into a disk-shaped compact with a diameter of 320 mm and a thickness of 10 mm, and a disk-shaped compact with a diameter of 320 mm and a thickness of 20 mm. In addition, a recess with a diameter of 294 mm and a depth of 0.15 mm was formed on one side of the compact with a thickness of 20 mm. The electrodes were made by combining two Mo meshes (wire diameter 0.1 mm, #50 mesh, plain weave) processed into a semicircular shape with a radius of 146 mm. The electrodes were shaped so that the outer diameter fell within the range of approximately Φ294 mm.

Next, an electrode was placed in the recess of the molded body with a thickness of t20 mm, and combined with a molded body with a thickness of t10 mm to form a laminate. Next, the laminate was heat treated at 1500°C in a vacuum atmosphere for 2 hours, and then hot-pressed in an Ar atmosphere at a firing temperature of 2050°C and a hot-press pressure of 4 MPa. The firing time was 3 hours. After firing, the outer diameter was set to Φ300 mm, the distance (thickness) from the upper surface to the electrode was set to 1 mm, and the upper surface was polished to Ra 0.2 μm. In addition, a blind hole was formed to the electrode, and a Kovar terminal was brazed in a vacuum at 850°C with Bag-8 brazing material. In this way, the ceramic susceptor of Example 1 was produced. In addition, using the same granulated powder, a disk-shaped test sample of Example 1 with a diameter of Φ60 mm and a thickness of t10 mm was produced under the same firing conditions.

Example 2
In Example 2, the firing atmosphere was an _N2 -added Ar atmosphere ( _N2 /Ar flow ratio = 0.03). Except for that, the ceramic susceptor of Example 2 was produced under the same conditions as those of Example 1. In addition, the same granulated powder was used to produce a test sample of Example 2 under the same firing conditions.

Example 3
In Example 3, the granulated powder was granulated using a sintering aid of 0.1 wt % _B4C + 1 wt % C. The firing temperature was 2000°C, and the hot press pressure was 15 MPa. Except for this, the ceramic susceptor of Example 3 was produced under the same conditions as those of Example 1. In addition, a test sample of Example 3 was produced using the same granulated powder and under the same firing conditions.

Example 4
In Example 4, the granulated powder was granulated using a sintering aid of 0.3 wt % _B4C + 2 wt % C. The firing temperature was 2100°C, and the hot press pressure was 15 MPa. Other than that, the ceramic susceptor of Example 4 was produced under the same conditions as Example 1. Also, a test sample of Example 4 was produced using the same granulated powder and under the same firing conditions.

Example 5
In Example 5, the raw material of the substrate was changed to SiC raw material powder (purity 99.9 wt%) produced by the CVD method. The sintering aid was 0.1 wt% _B4C + 1 wt% C, and the granulated powder was granulated. The hot press pressure was 15 MPa. A ceramic susceptor of Example 5 was produced under the same conditions as Example 1 except for the above. A test sample of Example 5 was produced using the same granulated powder and under the same firing conditions.

(Comparative Example 1)
In Comparative Example 1, the granulated powder was granulated using a sintering aid of 0.1 wt% _B4C + 5 wt% C. Except for that, the ceramic susceptor of Comparative Example 1 was produced under the same conditions as those of Example 1. In addition, a test sample of Comparative Example 1 was produced using the same granulated powder under the same firing conditions.

(Comparative Example 2)
In Comparative Example 2, the granulated powder was granulated using 0.3 wt % B ₄ C as the sintering aid. Otherwise, the ceramic susceptor of Comparative Example 2 was produced under the same conditions as those of Example 1. In addition, a test sample of Comparative Example 2 was produced using the same granulated powder and under the same firing conditions.

(Comparative Example 3)
In Comparative Example 3, the firing temperature was set to 2200° C. Except for this, the ceramic susceptor of Comparative Example 3 was produced under the same conditions as those of Example 1. In addition, a test sample of Comparative Example 3 was produced using the same granulated powder under the same firing conditions.

(Measurement of volume resistivity)
The volume resistivity of the test samples of the examples and comparative examples was measured by the three-terminal method (JIS C 2139-3). The thickness of the test sample was processed to 2 mm, and a measurement object of Φ60 mm x 2 mmt was prepared. The electrodes were formed by printing Ag paste. Using a measuring device (Advantest R8340 (ultra-high resistance meter)), the volume resistivity was measured 1 minute after the test voltage of 500 VDC was applied. The measurement temperatures were 20°C (room temperature), -20°C, -30°C, and -50°C. For measurements below 0°C, the measurement object was placed in a vacuum chamber equipped with a cooling plate, and after evacuation, it was cooled by the cooling plate to a specified temperature and then measurement was started.

(Component analysis after firing)
For the test samples of the examples and comparative examples, trace element analysis by GDMS and free carbon analysis were performed in accordance with JIS G 1211-3 (combustion-infrared absorption method), JIS R 1616 (chemical analysis method for silicon carbide fine powder for fine ceramics), and JIS R 6124 (chemical analysis method for silicon carbide abrasives). The total of trace elements other than Si and C and free carbon was subtracted from 100% to obtain the purity of SiC for each test sample.

(Adsorption force test)
The ceramic susceptors of the examples and comparative examples were placed on a cooling plate in a vacuum chamber, and a substrate (silicon wafer) was placed on the top surface. The ceramic susceptors were cooled to a predetermined temperature (-20°C, -30°C, -50°C) after evacuation, and a voltage of ±500V was applied between the terminals from an external power source. A load cell was pressed against the substrate from the side to measure the load at which the substrate began to move. If the load at which the substrate began to move was 3000 gf or more, it was evaluated that a sufficient suction force was exerted.

11 is a table showing the manufacturing conditions and the results of various tests for the examples and comparative examples. It was confirmed that the volume resistivity of Examples 1 to 5 was greater than 10 ⁸ Ωcm at 20° C. and greater than 10 ⁹ Ωcm at −30° C. On the other hand, it was confirmed that the volume resistivity of Comparative Examples 1 to 3 was less than 10 ⁸ Ωcm at 20° C. and less than 10 ⁹ Ωcm at −30° C.

From the examples and comparative examples, it was found that the lower the amount of boron added, the higher the volume resistivity, and that to increase the resistance, it is better to add less boron. This is related to the solid solution of boron in the SiC lattice, and is presumed to be due to the formation of an acceptor level in the SiC band. In addition, an increase in volume resistivity was observed by sintering in an Ar atmosphere containing _N2 . This is presumed to be due to the influence of N penetrating into the SiC lattice.

When using SiC powder produced by the Acheson method as the raw material and SiC powder produced by the CVD method as the raw material, it is assumed that the raw powder produced by the CVD method is finer and a relatively fine structure remains even after sintering, and many grain boundaries are formed, resulting in a higher volume resistivity. Furthermore, even if the purity is the same (99.9 wt%), the powder produced by the Acheson method may contain a relatively large amount of impurities, which is also assumed to be the reason why the powder produced by the CVD method has a relatively higher volume resistivity.

In both the Examples and Comparative Examples, the purity of SiC was 98 wt% or more, but the Examples tended to show slightly higher values. In Examples 1 to 5, in which the purity of SiC was 99.85 wt% or more, the volume resistivity met the standard, but in Comparative Examples 2 and 3, in which the purity of SiC was also 99.85 wt% or more, the volume resistivity did not meet the standard. From this, it was confirmed that the volume resistivity is not determined by the purity of SiC alone, and it is not clear whether the performance as a ceramic susceptor is satisfied. On the other hand, Example 4, in which the purity of SiC was less than 99.91 wt%, tended to show lower volume resistivity values at each temperature compared to Examples 1 to 3 and 5, in which the purity of SiC was 99.91 wt% or more. From this, it was confirmed that when the volume resistivity meets the standard, the purity of SiC is preferably 99.91 wt% or more.

In Examples 1 to 5, sufficient adsorptive power was exhibited at all temperatures, −20° C., −30° C., and −50° C., but in Comparative Example 1, sufficient adsorptive power was not exhibited at all temperatures, and in Comparative Examples 2 and 3, sufficient adsorptive power was not exhibited at −20° C. and −30° C. This is presumably because in Examples 1 to 5, the volume resistivities at −20° C., −30° C., and −50° C. were greater than 10 ⁹ Ωcm.

The ceramic susceptor of the embodiment showed a large volume resistivity even at -20°C, so when the ceramic susceptor of the present invention is used as an electrostatic chuck at low temperatures (below 0°C), it is expected that current consumption will be suppressed, a sufficient potential difference will be generated between the substrate and the electrode, and a strong adsorption force will be generated due to the Johnsen-Rahbek effect.

The above confirmed that the ceramic susceptor of the present invention can be used in low-temperature, high-output processes.

The present invention is not limited to the above-described embodiment, and it goes without saying that it covers various modifications and equivalents that fall within the spirit and scope of the present invention. Furthermore, the structure, shape, number, position, size, etc. of the components shown in each drawing are for convenience of explanation and may be changed as appropriate.

REFERENCE SIGNS LIST 10 Substrate 12 Upper surface 14 Lower surface 16 Center 20 Electrode 22 Electrode for electrostatic attraction 24 Electrode for heater 28 Insulating layer 30 Media flow path 50, 51 Terminal 52 Terminal hole 100 Ceramic susceptor 101, 102, 103 Ceramic degreased body 105 Groove 110 Laminate 121, 122 Substrate precursor

Claims (9)

A ceramic susceptor,
A substrate having a mounting surface and formed of a ceramic sintered body mainly composed of SiC;
at least one electrode embedded in the substrate;
The ceramic susceptor is characterized in that the volume resistivity of the substrate is greater than 10 ⁸ Ωcm at 20°C and greater than 10 ⁹ Ωcm at -30°C. The ceramic susceptor according to claim 1, characterized in that the electrode is an electrostatic adsorption electrode. The ceramic susceptor according to claim 1, characterized in that the electrode is a heater electrode. The ceramic susceptor according to claim 1, characterized in that the electrode is a high-frequency electrode. The ceramic susceptor according to claim 1, characterized in that the electrode has an insulating layer on its surface. The electrode is made of W, Mo, or an alloy containing W or Mo as a main component,
6. The ceramic susceptor according to claim 5, wherein the insulating layer is made of a nitride or oxide having a melting point of 2200[deg.] C. or higher. The ceramic susceptor according to any one of claims 1 to 6, characterized in that the substrate has a media flow path provided therein. The ceramic susceptor according to any one of claims 1 to 6, characterized in that the purity of the SiC of the substrate is 99.91 wt% or more. 8. The ceramic susceptor according to claim 7, wherein the purity of the SiC of the substrate is 99.91 wt % or more.