JP7565734B2 - Substrate holding member and manufacturing method thereof - Google Patents

Description

The present invention relates to a substrate holding member and a method for manufacturing the same.

Some substrate holding members used in semiconductor manufacturing equipment, such as electrostatic chucks, are equipped with cooling members to keep the substrate at a predetermined temperature during the semiconductor process.

Patent Document 1 discloses an electrostatic chuck in which a metal plate having an insulating film formed on its surface by thermal spraying and a dielectric substrate having electrodes formed on its surface are joined with an insulating adhesive so that the electrodes face each other, the thickness of the insulating film is 0.3 mm or more and 0.6 mm or less, the thermal conductivity of the insulating adhesive is 1 W/mK or more, and the thermal conductivity of the insulating film is greater than that of the insulating adhesive.

Patent Document 2 also discloses a heater unit having a substrate having a cooling flow path, a heater section arranged above the substrate and having a heating element, and a heat insulating layer arranged between the substrate and the heater section. It also describes that the thermal conductivity of the heat insulating layer may be lower than that of the substrate, that the heat insulating layer may be SUS containing pores, that the heater unit further has an insulator covering the heating element, and that the thermal conductivity of the heat insulating layer may be lower than that of the insulator.

JP 2007-243139 A JP 2017-037721 A

Conventionally, metal materials, especially Al alloys, have been used for the cooling plate of an electrostatic chuck because of their workability and cooling effect. Electrostatic chucks have used ceramic sintered bodies made of _Al2O3 or _AlN . To integrate these, organic adhesives have been proposed because of their ease of integration. However, when using an organic adhesive as a bonding layer, its heat resistance becomes an issue, and it was not possible to use an electrostatic chuck in a process at 200°C or higher, because the temperature would reach a point where the organic adhesive layer would decompose.

In addition, with the increasing power of recent processes, there is an increasing demand for uniform temperature distribution on the substrate mounting surface of the electrostatic chuck. However, when using a metal cooling plate, the metal plate itself has good thermal conductivity, and the influence of the coolant flow path provided inside the metal plate appears on the mounting surface of the electrostatic chuck, hindering the uniformity of the temperature distribution on the mounting surface.

However, Patent Document 1 does not take into account the heat resistance of the insulating adhesive layer. Furthermore, Patent Document 2 does not take into account the bonding between the heat insulating layer and the base material or the heat insulating layer and the heater section, and therefore does not take into account the heat resistance when an organic adhesive is used. Furthermore, neither Patent Document 1 nor Patent Document 2 takes into account the uniformity of the temperature distribution when cooling the substrate.

The present invention has been made in consideration of these circumstances, and aims to provide a substrate holding member and a method for manufacturing the same, in which the temperature of the silicone adhesive layer is kept below the heat-resistant temperature even when used in a process in which the temperature of the substrate reaches or exceeds the heat-resistant temperature of the silicone adhesive layer, and in which the temperature distribution of the substrate mounting surface is highly uniform.

(1) In order to achieve the above object, the substrate holding member of the present invention is characterized in that it comprises a ceramic member formed in a flat plate shape from ceramics and having a substrate mounting surface on one main surface, a first sprayed film formed on the other main surface of the ceramic member, a metal cooling member having a refrigerant flow path inside, a second sprayed film formed on the planar main surface of the cooling member, and a silicone adhesive layer bonding the first sprayed film and the second sprayed film. In this way, by providing a sprayed film on each of the bonding surface between the ceramic member and the silicone adhesive layer and the bonding surface between the cooling member and the silicone adhesive layer, even if the substrate holding member is used in a process at a temperature higher than the heat resistance temperature of the silicone adhesive layer, the temperature of the silicone adhesive layer can be kept below the heat resistance temperature, and deterioration of the silicone adhesive layer can be prevented and thermal unevenness on the substrate mounting surface of the substrate holding member can be reduced. At the same time, the flexibility of the silicone adhesive layer can relieve stress generated between the substrate holding member and the cooling member. As a result, it is possible to use the substrate holding member in processes at temperatures higher than the heat resistance temperature of the silicone adhesive layer while equalizing the temperature distribution on the substrate mounting surface of the substrate holding member.

(2) In the substrate holding member of the present invention, the ceramic member is formed of a ceramic containing AlN as a main component, and when the thermal resistance per unit area in the thickness direction of the ceramic member is Re ( ^m2 K/W), the thermal resistance per unit area in the thickness direction of the first sprayed film is Rf1 ( ^m2 K/W), the thermal resistance per unit area in the thickness direction of the silicone adhesive layer is Rb ( ^m2 K/W), the thermal resistance per unit area in the thickness direction of the second sprayed film is Rf2 ( ^m2 K/W), and the thermal resistance per unit area in the thickness direction in the region from the main surface of the cooling member on the silicone adhesive layer side to the coolant flow path is Rm ( ^m2 K/W), 0.75≧(Re+Rf1)/(Re+Rf1+Rb+Rf2+Rm)≧0.24. In this way, by adjusting the thermal resistance per unit area of the ceramic member, first sprayed film, silicone adhesive layer, second sprayed film, and cooling member depending on the ceramic material that forms the ceramic member, the substrate holding member can be used even in high-temperature processes of 250°C or higher.

(3) In the substrate holding member of the present invention, the ceramic member is formed of _a ceramic containing _Al2O3 as a main component, and when the thermal resistance per unit area in the thickness direction of the ceramic member is Re ( ^m2 K/W), the thermal resistance per unit area in the thickness direction of the first sprayed film is Rf1 (m2 ^K /W), the thermal resistance per unit area in the thickness direction of the silicone adhesive layer is Rb ( ^m2 K/W), the thermal resistance per unit area in the thickness direction of the second sprayed film is Rf2 ( ^m2 K/W), and the thermal resistance per unit area in the thickness direction in the region from the main surface of the cooling member on the silicone adhesive layer side to the coolant flow path is Rm ( ^m2 K/W), 0.77≧(Re+Rf1)/(Re+Rf1+Rb+Rf2+Rm)≧0.20. In this way, by adjusting the thermal resistance per unit area of the ceramic member, first sprayed film, silicone adhesive layer, second sprayed film, and cooling member depending on the ceramic material that forms the ceramic member, the substrate holding member can be used even in high-temperature processes of 250°C or higher.

(4) Furthermore, the substrate holding member of the present invention is characterized in that, in the substrate holding member, the ceramic member is formed of a ceramic mainly composed of AlN, and (Rf1+Rb+Rf2)/(Re+Rf1+Rb+Rf2+Rm)≧0.83. In this way, by adjusting the thermal resistance per unit area in the thickness direction of the ceramic member, the first sprayed film, the silicone adhesive layer, the second sprayed film, and the cooling member according to the ceramic material forming the ceramic member, the amount of heat supply required to maintain a predetermined process temperature can be reduced.

(5) The substrate holding member of the present invention is characterized in that the ceramic member is formed of a ceramic containing Al ₂ O ₃ as a main component, and (Rf1+Rb+Rf2)/(Re+Rf1+Rb+Rf2+Rm)≧0.63. In this way, the amount of heat supply required to maintain a predetermined process temperature can be reduced by adjusting the thermal resistance per unit area in the thickness direction of the ceramic member, the first sprayed film, the silicone adhesive layer, the second sprayed film, and the cooling member according to the ceramic material forming the ceramic member.

(6) The method for manufacturing a substrate holding member of the present invention is characterized in that it includes the steps of forming and sintering ceramic raw material powder to produce a ceramic member, preparing a plurality of metal members and forming a groove portion that serves as a flow path for a refrigerant, joining the plurality of metal members with the groove portion formed therein to produce a cooling member having the flow path, spraying a first thermal spray raw material powder containing a predetermined ceramic onto a surface of the ceramic member facing the substrate mounting surface to form a first thermal spray film, spraying a second thermal spray raw material powder containing a predetermined ceramic onto one main surface of the cooling member to form a second thermal spray film, applying a silicone adhesive to at least one of the first thermal spray film or the second thermal spray film to bond the ceramic member and the cooling member, and curing the silicone adhesive to form a silicone adhesive layer. In this way, by providing a thermal spray film on the bonding surface between the ceramic member and the silicone adhesive layer and on the bonding surface between the cooling member and the silicone adhesive layer, the temperature of the silicone adhesive layer can be kept below the heat resistance temperature even when the substrate holding member is used in a process at a temperature higher than the heat resistance temperature of the silicone adhesive layer, and deterioration of the silicone adhesive layer can be prevented and thermal unevenness on the substrate mounting surface of the substrate holding member can be reduced. At the same time, the flexibility of the silicone adhesive layer can reduce stress generated between the substrate holding member and the cooling member. As a result, it is possible to use the electrostatic chuck in a process at a temperature higher than the heat resistance temperature of the silicone adhesive layer while uniforming the temperature distribution on the substrate mounting surface of the substrate holding member.

According to the present invention, even if the substrate holding member is used in a process at a temperature higher than the heat resistance temperature of the silicone adhesive layer, the temperature of the silicone adhesive layer can be kept below the heat resistance temperature, preventing deterioration of the silicone adhesive layer and reducing thermal unevenness on the substrate mounting surface of the substrate holding member. As a result, it is possible to stably use the electrostatic chuck in a process at a temperature higher than the heat resistance temperature of the silicone adhesive layer while homogenizing the temperature distribution on the substrate mounting surface of the substrate holding member.

FIG. 2 is a front cross-sectional view showing the substrate holding member of the embodiment. 1 is a table showing the manufacturing conditions and temperature measurements for each sample. 1 is a table showing the manufacturing conditions and temperature measurements for each sample.

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 the substrate holding member]
1 is a front cross-sectional view showing a substrate holding member 10. The substrate holding member 10 includes a ceramic member 12, a first sprayed film 14, a cooling member 16, a second sprayed film 18, and a silicone adhesive layer 20. The substrate holding member 10 may also have one or more electrodes embedded therein as necessary. The substrate holding member 10 can be used, for example, in an electrostatic chuck, a heater, etc.

The ceramic member 12 is formed of ceramics in a flat plate shape, and has a substrate mounting surface 28 on one of its main surfaces. The ceramics constituting the ceramic member 12 are preferably ceramics containing AlN or Al ₂ O ₃ as the main component. The term "main component" means that the weight ratio of the main component to the weight of the ceramic member 12 is 90 wt % or more. In addition to the ceramics as the main component, the ceramic member 12 may contain additives for various purposes, such as increasing thermal conductivity. For example, additives made of oxides of Group 2a elements or Group 3a elements or transition metal oxides may be added to adjust thermal conductivity or volume resistivity.

In general, in the case of ceramics mainly composed of AlN, it is known that the thermal conductivity increases when the amount of additives such as Y ₂ O ₃ is increased, but adding more than a certain amount causes a decrease in thermal conductivity. Therefore, it is desirable to set the content of additives consisting of oxides of 2a group elements and 3a group elements and transition metal oxides to 10 wt% or less. In the case of ceramics mainly composed of Al ₂ O ₃ , it is also desirable to set the content of additives consisting of oxides of 2a group elements and 3a group elements and transition metal oxides to 10 wt% or less. Examples of additives of 2a group elements include Mg, Ca, Sr, Ba, etc., and examples of additives of 3a group elements include Y, La, Sm, Ce, etc. Examples of additives of transition metals include Ti, Cr, Mn, Ni, etc.

The first sprayed film 14 is formed on the surface of the ceramic member 12 facing the substrate mounting surface 28. The first sprayed film 14 is made of ceramics. _The first sprayed film 14 is preferably made of ceramics having low thermal conductivity, such as _Al2O3 , _Y2O3 , or _ZrO2 . The first sprayed film 14 can be produced by a known spraying method, such as a plasma spraying method or a dry plasma spraying method. The thickness of the first _sprayed film 14 is preferably 0.05 mm or more and 2 mm or less.

It is preferable that the first sprayed film 14 has a predetermined porosity. This enhances the heat insulating effect. The porosity is preferably 2% or more, and more preferably 5% or more. The upper limit of the porosity does not need to be particularly limited as long as the thermal conductivity of the first sprayed film 14 is within the predetermined range, but it can be, for example, 10% or less.

The cooling member 16 is made of metal and has a refrigerant flow path 22 inside. The metal that constitutes the cooling member 16 is most preferably an aluminum alloy because of its workability and high thermal conductivity, but alloys containing copper, titanium, nickel, and stainless steel may also be used. The refrigerant may be water, ethylene glycol, or freon, and the refrigerant temperature may be below the boiling point.

The second sprayed film 18 is formed on one of the main surfaces of the cooling member 16. The main surface of the cooling member 16 on which the second sprayed film 18 is formed is a flat surface. The second sprayed film 18 is made of ceramics. The second sprayed film 18 is preferably made of ceramics such as Al ₂ O ₃ , Y ₂ O ₃ , and ZrO _2. The second sprayed film preferably has a relatively high thermal conductivity because the effect of the cooling member is weakened if the thermal conductivity is too low. Therefore, the porosity is preferably 5% or less, and more preferably 2% or less. The thickness of the second sprayed film 18 is preferably 0.05 mm or more and 2 mm or less. The materials and thicknesses of the first sprayed film 14 and the second sprayed film 18 may be the same or different.

The porosity of the first sprayed film 14 and the second sprayed film 18 may be the same value or different values.

The silicone adhesive layer 20 bonds the first sprayed film 14 and the second sprayed film 18. This allows the ceramic member 12 and the cooling member 16 to be bonded. The silicone adhesive layer 20 is formed of a silicone adhesive containing silicone as a main component, such as silicone resin or modified silicone resin. The curing type of the silicone adhesive can be selected from dehydration, dealcoholization, and addition polymerization types. One-component curing, two-component curing, and ultraviolet curing types can also be selected. The silicone adhesive may contain ceramics such as Al ₂ O ₃ and AlN or metal fillers such as Cu to adjust thermal conduction. The thickness of the silicone adhesive layer 20 is preferably 0.1 mm or more and 2.0 mm or less. The silicone adhesive layer has a sufficiently small Young's modulus compared to ceramics and metals, so it can maintain flexibility.

The ceramic member 12 shown in FIG. 1 has two electrodes 24, 26 embedded therein. The electrode 24 in FIG. 1 is an electrode for electrostatic attraction, and the electrode 26 is an electrode that functions as a heating resistor. In this way, the substrate holding member 10 may have one or more electrodes embedded therein as necessary. The substrate holding member 10 shown in FIG. 1 is an electrostatic chuck having a heating resistor.

In this way, by providing the first sprayed film 14 and the second sprayed film 18 on the bonding surface between the ceramic member 12 and the silicone adhesive layer 20 and the bonding surface between the cooling member 16 and the silicone adhesive layer 20, respectively, even if the substrate holding member 10 is used in a process at a temperature higher than the heat resistance temperature of the silicone adhesive layer 20, the temperature of the silicone adhesive layer 20 can be kept below the heat resistance temperature, preventing deterioration of the silicone adhesive layer 20 and reducing thermal unevenness on the substrate mounting surface 28 of the substrate holding member 10. At the same time, the flexibility of the silicone adhesive layer can relieve stress generated between the substrate holding member and the cooling member. As a result, it is possible to use the substrate holding member 10 in a process at a temperature higher than the heat resistance temperature of the silicone adhesive layer 20 while uniformizing the temperature distribution on the substrate mounting surface 28 of the substrate holding member 10.

(Thermal resistance design)
The above configuration allows the substrate holding member 10 to be used in a process at a temperature higher than the heat resistance temperature of the silicone adhesive layer 20. However, when considering use in a process at a higher temperature or reducing the amount of heat supply required to maintain a predetermined process temperature, it is preferable to design the thermal resistance of the substrate holding member 10. The thermal resistance per unit area in the thickness direction of the substrate holding member 10 (m ² K/W) is set by the following calculation (hereinafter, the thermal resistance is a value per unit area). The thermal resistance Re (m ² K/W) per unit area in the thickness direction of the ceramic member 12 is the thickness of the ceramic (m)/thermal conductivity of the ceramic (W/mK). The thermal resistance Rf1 (m ² K/W) per unit area in the thickness direction of the first sprayed film 14 is the thickness of the first sprayed film (m)/thermal conductivity of the first sprayed film (W/mK). The thermal resistance Rm ( ^m2K /W) per unit area in the thickness direction of the cooling member 16 is defined as the distance (m) between the coolant flow path and the cooling member surface/thermal conductivity (W/mK) of the cooling member. The thermal resistance Rb ( ^m2K /W) per unit area in the thickness direction of the silicone adhesive layer is defined as the thickness (m) of the silicone adhesive layer/thermal conductivity (W/mK) of the silicone adhesive layer. The thickness direction is defined as the direction perpendicular to the substrate mounting surface 28 of the substrate holding member 10.

Here, when the ceramic member 12 is formed of a ceramic mainly composed of AlN, it is preferable that 0.75 ≧ (Re + Rf1) / (Re + Rf1 + Rb + Rf2 + Rm) ≧ 0.24. In this way, by adjusting the thermal resistance per unit area in the thickness direction of the ceramic member 12, the first sprayed film 14, the silicone adhesive layer 20, the second sprayed film 18, and the cooling member 16 according to the ceramic material forming the ceramic member 12, the substrate holding member 10 can be used even in a high-temperature process of 250 ° C or more. The value of (Re + Rf1) / (Re + Rf1 + Rb + Rf2 + Rm) is considered to indicate the degree of temperature of the silicone adhesive layer 20. The value of (Re+Rf1)/(Re+Rf1+Rb+Rf2+Rm) is related to the temperature of the interface between the silicone adhesive layer 20 and the first sprayed film 14; if this value is large, the temperature of the silicone adhesive layer 20 tends to be low, and if this value is small, the temperature tends to be high.

Furthermore, when the ceramic member is formed of a ceramic containing Al ₂ O ₃ as a main component, it is preferable that 0.77 ≥ (Re + Rf1) / (Re + Rf1 + Rb + Rf2 + Rm) ≥ 0.20. In this way, by adjusting the thermal resistance per unit area in the thickness direction of the ceramic member 12, the first sprayed film 14, the silicone adhesive layer 20, the second sprayed film 18, and the cooling member 16 according to the ceramic material forming the ceramic member 12, the substrate holding member 10 can be used even in high-temperature processes of 250° C. or more.

In addition, when the ceramic member 12 is formed of a ceramic mainly composed of AlN, it is preferable that (Rf1+Rb+Rf2)/(Re+Rf1+Rb+Rf2+Rm)≧0.83. In this way, by adjusting the thermal resistance per unit area in the thickness direction of the ceramic member 12, the first sprayed film 14, the silicone adhesive layer 20, the second sprayed film 18, and the cooling member 16 according to the ceramic material forming the ceramic member 12, it is possible to reduce the amount of heat supply required to maintain a predetermined process temperature. The value of (Rf1+Rb+Rf2)/(Re+Rf1+Rb+Rf2+Rm) is considered to indicate the degree of ease of application to semiconductor processes. If the value of (Rf1+Rb+Rf2)/(Re+Rf1+Rb+Rf2+Rm) is small, the amount of heat supply required to reach a predetermined substrate processing temperature becomes excessive, and it tends to be difficult to use in semiconductor processes.

Furthermore, when the ceramic member 12 is made of a ceramic mainly composed of Al ₂ O ₃ , it is preferable that (Rf1+Rb+Rf2)/(Re+Rf1+Rb+Rf2+Rm)≧0.63 is satisfied, where Re is the thermal resistance per unit area in the thickness direction of the ceramic member 12, and Rm is the thermal resistance per unit area in the thickness direction in the region from the main surface of the cooling member 16 on the silicone adhesive layer 18 side to the coolant flow path. In this way, by adjusting the thermal resistance per unit area in the thickness direction of the ceramic member 12, the first sprayed film 14, the silicone adhesive layer 20, the second sprayed film 18, and the cooling member 16 according to the ceramic material forming the ceramic member 12, the amount of heat supply required to maintain a predetermined process temperature can be reduced.

In addition, when designing the above thermal resistance, the thickness and thermal conductivity of each member are preferably in the following ranges. The thickness of the ceramic member 12 is preferably 1 mm or more and 30 mm or less, and the thermal conductivity of the ceramic member 12 is preferably 4 W/mK or more and 250 W/mK or less. The thickness of the first ceramic sprayed film 14 is preferably 0.3 mm or more and 2.0 mm or less, and the thermal conductivity of the first ceramic sprayed film 14 is preferably 0.4 W/mK or more and 16.0 W/mK or less. The thickness of the second ceramic sprayed film 18 is preferably 0.1 mm or more and 2.0 mm or less, and the thermal conductivity of the second ceramic sprayed film 18 is preferably 0.4 W/mK or more and 16.0 W/mK or less. The thickness of the silicone adhesive layer 20 is preferably 0.1 mm or more and 2.0 mm or less, and the thermal conductivity of the silicone adhesive layer 20 is preferably 0.1 W/mK or more and 4.0 W/mK or less. The thickness (shortest distance) from the main surface of the cooling member 16 on the silicone adhesive layer side to the refrigerant flow path is preferably 2 mm or more and 30 mm or less, and the thermal conductivity of the cooling member 16 is preferably 10 W/mK or more and 300 W/mK or less. The thermal conductivity of each part is measured at 25°C.

[Method of manufacturing the substrate holding member]
Next, a method for manufacturing the substrate holder configured as described above will be described in the following order: a method for manufacturing the ceramic member, a method for manufacturing the cooling member, a thermal spraying method, and a method for forming the silicone adhesive layer.

(Method of manufacturing ceramic member)
The following method for producing a ceramic member will be described as a method for producing a ceramic member from a raw material mainly composed of AlN by a powder hot pressing method, but the raw material and manufacturing method are not limited to this method, and can also be applied to a ceramic member mainly composed of Al ₂ O _3. In addition to the powder hot pressing method, a green sheet lamination method or other conventional manufacturing methods can be adopted. First, the AlN ceramic raw material powder is granulated. The granulated powder is added with 0.3 wt % to 6 wt % Y ₂ O ₃ in an internal ratio, and a binder is added to granulate the granulated powder. Next, the granulated powder is filled into a bottomed carbon mold (molding die), a punch of the carbon mold is placed on it, and then sintered.

At this time, an electrode for electrostatic attraction or an electrode serving as a heating resistor may be embedded in the ceramic member. Heat-resistant metals such as tungsten and molybdenum can be used as the electrode for electrostatic attraction or the heating resistor. For example, an electrode for electrostatic attraction or a heating resistor formed of a plate, foil, wire, mesh, or the like is embedded during molding and sintered. For example, when embedding one layer of electrodes, the mold is filled with granulated powder corresponding to the insulating layer of the ceramic member, and the electrode is placed on the molded body after uniaxial pressing. The same granulated powder is filled on top of that, a carbon punch is placed on top, and then sintered. When embedding two or more layers of electrodes, the process of filling with granulated powder and placing the electrode on the molded body after uniaxial pressing is repeated.

Preferably, the firing process is atmospheric firing or uniaxial hot press firing. Normal pressure firing is performed at 1800°C or higher, and uniaxial hot press firing is performed at 1700°C or higher, with pressure and temperature conditions of 1 MPa or higher. However, the firing method is not limited to these. After firing, the substrate mounting surface on which the substrate is to be placed and the back surface on which the first sprayed film is to be provided are formed, and the substrate is processed into a predetermined shape. The external shape of the ceramic member can be selected according to the shape of the substrate to be mounted, such as circular or rectangular.

(Method of manufacturing cooling member)
First, a plurality of metal members are prepared, and a groove portion that serves as a flow path for the refrigerant is formed. Next, the plurality of metal members with the groove portion formed therein are joined to prepare a cooling member having a flow path. The flow path is formed by performing a predetermined machining process on the plurality of metal members, and then using a conventional metal joining method such as brazing, electron beam welding, or diffusion bonding. The metal is most preferably an Al alloy because of its workability and high thermal conductivity, but alloys containing copper, titanium, and nickel, SUS, etc. can also be used. A flow path for the refrigerant is formed inside the metal cooling member. The size and shape of the flow path for the refrigerant may be any size and shape that can uniformly cool the ceramic member.

(Thermal spraying method)
A first sprayed raw material powder containing a predetermined ceramic is sprayed on the surface of the ceramic member facing the substrate mounting surface to form a first sprayed film. Separately, a second sprayed raw material powder containing a predetermined ceramic is sprayed on one main surface of the cooling member to form a second sprayed film. The sprayed film can be produced by a known spraying method, such as an air plasma spraying method using a slurry containing a ceramic raw material powder, or a dry plasma spraying method in which the raw material powder is granulated and fed. The film type of the first sprayed film and the second sprayed film is preferably Al ₂ O ₃ , Y ₂ O ₃ , ZrO _2, etc. The sprayed film has a certain porosity, and the pores exert a heat insulating effect. Therefore, the porosity of the first sprayed film in particular is preferably 2% or more, and more preferably 5% or more. The thermal conductivity of the first sprayed film and the second sprayed film can be adjusted to 0.4 to 16 W/mK depending on these raw materials and porosity. The thickness of the sprayed film is preferably 0.05 mm or more and 2 mm or less.

(Method of forming silicone adhesive layer)
The curing type of the silicone adhesive can be selected from dehydration, dealcoholization, addition polymerization, etc. Also, one-component curing, two-component curing, ultraviolet curing, etc. can be selected. Of these, the silicone adhesive forming the silicone adhesive layer is preferably a heat-curing one. The following description will explain a method of forming a silicone adhesive layer using a heat-curing silicone adhesive.

After weighing and stirring an appropriate amount of silicone adhesive, it is applied to at least one of the first ceramic sprayed film or the second ceramic sprayed film, and after degassing, the two are stacked and heat-cured in an oven under a load in air, nitrogen atmosphere, or reduced pressure. In order to suppress outgassing of siloxane components from the silicone adhesive, it is preferable to cure at 100°C or higher and then treat at 200°C or higher for a certain period of time. In addition, a spacer of a specified thickness may be placed at the same time to adjust the thickness of the silicone adhesive layer. By the above treatment, the ceramic member coated with the first ceramic sprayed film on the back side and the metal cooling member coated with the second ceramic sprayed film on the front side are bonded with the silicone adhesive to form a silicone adhesive layer. Note that if the center line average roughness Ra of the sprayed film is 1 μm or more, the silicone adhesive can penetrate into the gaps in the roughness curve of the sprayed film and adhere well.

This method allows the production of a substrate holder.

[Examples and Comparative Examples]
[Samples a1 to a15]
Next, examples and comparative examples will be described. First, as a sample using AlN as the material of the ceramic member, an electrostatic chuck was produced in which a ceramic member mainly composed of AlN in which an electrostatic chuck electrode was embedded and a cooling member made of an Al alloy were bonded with a silicone adhesive layer. Samples a1 to a15 were produced by varying the presence or absence of the first sprayed film or the second sprayed film, the material, the thickness, the thermal conductivity of the silicone adhesive layer, and the thickness. Hereinafter, samples a1 to a15 are collectively referred to as sample a. FIG. 2 is a table showing the manufacturing conditions and temperature measurements for each sample of samples a1 to a15.

(Preparation of ceramic member used for sample a)
A raw material containing 5 wt% Y ₂ O ₃ added as an additive to AlN was used, and an electrode made by cutting a mesh of Mo (wire diameter 0.1 mm, mesh size #50) was embedded as an electrode. After uniaxial hot press sintering, it was machined into a predetermined shape, and a substrate mounting surface was provided on the front surface, and a flat surface on which a thermal spray film was sprayed was provided on the back surface opposite the front surface, to produce a ceramic member with a diameter of 300 mm and a thickness of 15 mm. The surface roughness Ra of the substrate mounting surface was 0.5 μm, and the surface roughness Ra of the sprayed surface was 1.5 μm. These were measured in accordance with JIS B 0601 and ISO25178. The thermal conductivity measured for the ceramic member alone was 160 W/mK at 25°C. The thermal conductivity was measured using a laser flash method in accordance with JIS R 1611-1997.

[Samples b1 to b6]
In addition, as a sample using Al ₂ O ₃ as the material of the ceramic member, an electrostatic chuck was produced in which a ceramic member mainly composed of Al ₂ O ₃ in which an electrostatic chuck electrode is embedded is bonded to an Al alloy cooling member by a silicone adhesive layer. Samples b1 to b6 were produced by varying the material and thickness of the first sprayed film or the second sprayed film, and the thermal conductivity and thickness of the silicone adhesive layer. Hereinafter, samples b1 to b6 will be collectively referred to as sample b. Figure 3 is a table showing the manufacturing conditions and measured temperatures for each of samples b1 to b6.

(Preparation of ceramic member used for sample b)
A raw material containing 0.05 wt% _MgO added to _Al2O3 was used, and an electrode made of cut Mo mesh (wire diameter 0.1 mm, mesh size #50) was embedded as an electrode. After uniaxial hot press sintering, it was machined into a predetermined shape, and a substrate mounting surface was provided on the front surface, and a flat surface on which a thermal spray film was sprayed was provided on the back surface opposite the front surface, to produce a ceramic member with a diameter of 300 mm and a thickness of 15 mm. The surface roughness Ra of the substrate mounting surface was 0.4 μm, and the surface roughness Ra of the sprayed surface was 1.2 μm. The thermal conductivity measured for the ceramic member alone was 30 W/mK at 25°C.

(Preparation of cooling member)
An Al alloy (6061T6) was used as the metal. The coolant flow passages had a rectangular cross section with a width of 10 mm and a height of 5 mm, and were arranged at a distance of 20 mm in the radial direction. The shortest vertical distance from the surface of the cooling member to the flow passages was 15 mm. The surface roughness Ra of the sprayed surface of the cooling member was 1.6 μm. The cooling member was common to sample a and sample b. The thermal conductivity of the cooling member was 138 W/mK at 25° C.

(Formation of sprayed film)
Al ₂ O ₃ , Y 2 O 3 , or ZrO ₂ was used as a slurry raw material for forming a first sprayed film or a second sprayed film on the surface of the ceramic member facing the substrate mounting surface and the main surface formed by the flat surface of _the cooling _member . The porosity was adjusted so that the thermal conductivity of the ZrO ₂ sprayed film was 0.8 (W/mK), the thermal conductivity of the Y ₂ O ₃ sprayed film was 2 (W/mK), and the thermal conductivity of the Al ₂ O ₃ sprayed film was 4 (W/mK). The above thermal conductivities were measured at 25°C for a single sprayed film produced under the same conditions. The thickness of the sprayed film was 300 μm to 2000 μm.

The manufacturing method of the sprayed film of the sample will be described in detail. A non-oxidizing gas plasma was irradiated or sprayed onto the back surface of the ceramic electrostatic chuck using a high-speed plasma spraying machine, and the surface to be sprayed was preheated. A mixed gas of Ar gas, _N2 gas, and _H2 gas was used as the non-oxidizing gas. The supply rate of Ar gas to the nozzle constituting the spraying machine was controlled to 100 l/min, the supply rate of _N2 gas was controlled to 70 l/min, and the supply rate of _H2 gas was controlled to 60 l/min. The current applied to the nozzle constituting the high-speed plasma spraying machine was controlled to 250 A, so that the power supplied to the nozzle was adjusted to 65 kW. The distance between the tip of the nozzle and the surface to be sprayed of the ceramic member or cooling member was adjusted to 75 mm. The scanning speed or displacement speed of the nozzle with respect to the ceramic member or cooling member was adjusted to 850 mm/s. This generated plasma of a mixed gas of Ar gas, _N2 gas, and _H2 gas, and the plasma was irradiated or sprayed from the tip of the nozzle onto the surface to be sprayed of the ceramic member or cooling member. The preheating of the surface to be sprayed by the plasma irradiation or spraying was carried out for 10 minutes.

Then, the high-speed plasma spraying machine was used as it was, and the ceramic slurry containing the spraying raw material powder was plasma sprayed onto the sprayed surface on the back surface of the ceramic electrostatic chuck using a non-oxidizing gas. The slurry was prepared by mixing 300 g of ceramic raw material powder with a purity of 99.9% or more and an average particle diameter D50 of 0.5 μm with 700 g of water. As the non-oxidizing gas, a mixed gas of Ar gas, N ₂ gas, and H ₂ gas was used. The supply amount of Ar gas to the nozzle constituting the spraying machine was controlled to 100 l/min, the supply amount of N ₂ gas was controlled to 70 l/min, and the supply amount of H ₂ gas was controlled to 60 l/min. As a result, the spraying speed was controlled to 600 to 700 mm/s. The applied current to the nozzle constituting the high-speed plasma spraying machine was controlled to 250 A, and the power supplied to the nozzle was adjusted to 65 kW. The distance between the tip of the nozzle and the surface of the ceramic member or cooling member to be sprayed was adjusted to 75 mm. The scanning speed or displacement speed of the nozzle relative to the ceramic member or cooling member was adjusted to 850 mm/s. This generated a plasma of a mixed gas of Ar gas, _N2 gas, and _H2 gas, and the raw material powder melted by the plasma was sprayed from the tip of the nozzle onto the surface of the ceramic member or cooling member to be sprayed. In this way, a ceramic member and a cooling member were formed in which one surface of the ceramic member or cooling member was covered with a ceramic sprayed film.

(Silicone adhesive layer)
A general silicone resin was used with fillers such as alumina and metal dispersed therein to increase the thermal conductivity. The thermal conductivity of the silicone adhesive layer was 0.9 W/mK to 2.0 W/mK, and the thickness of the silicone adhesive layer was 500 μm to 2000 μm.

(Evaluation Method)
The obtained electrostatic chuck was subjected to a predetermined evaluation process. At this time, a mixture of water and ethylene glycol was used as the coolant, and the heat transfer coefficient was adjusted to 2500 W/mK. The coolant temperature was set to 20° C., and the flow rate of the coolant was set to 3 L/min. Then, the following evaluations were performed.

The electrostatic chuck mounting surface was heated by placing another plate-shaped external heater made of AlN ceramics for supplying heat. In the samples a1 to a7, a11 to a13, a15 and the samples b1, b2, b4, and b6, the average temperature of the substrate mounting surface of the electrostatic chuck was controlled to be in a steady state of 250°C. In the samples a8, a9, and a14, the amount of heat supplied was 10,000 (W/m ² ). In the sample a10, the average temperature of the substrate mounting surface of the electrostatic chuck was controlled to be in a steady state of 300°C. In the sample b3, the average temperature of the substrate mounting surface of the electrostatic chuck was controlled to be in a steady state of 240°C. In the sample b3, when the temperature of the substrate mounting surface of the electrostatic chuck was 250°C, the temperature of the silicone adhesive layer exceeded 200°C. In the sample b5, the average temperature of the substrate mounting surface of the electrostatic chuck was controlled to be in a steady state of 400°C. The temperature of each part exposed on the side surface of the electrostatic chuck and the temperature of the silicone adhesive layer were measured by directly contacting the electrostatic chuck with a thermocouple, or by measuring the temperature of each part on the side surface with an optical thermometer, as appropriate.

(Evaluation Results)
Sample a8 is an electrostatic chuck without the first sprayed film. When the temperature of the substrate mounting surface of the electrostatic chuck of sample 8 reached 232°C, the temperature of the silicone adhesive layer reached 206°C, exceeding the heat resistance temperature of the silicone adhesive layer. In contrast, in samples a1 to a6, a9 to a15, and b1 to b6 on which the first and second sprayed films were formed, the temperature of the silicone adhesive layer could be kept below 200°C when the temperature of the substrate mounting surface of the electrostatic chuck was set to 240°C or higher. In sample a6, the temperature of the silicone adhesive layer exceeded 200°C when the temperature of the substrate mounting surface of the electrostatic chuck was 250°C, but the temperature of the silicone adhesive layer was below 200°C when the temperature of the substrate mounting surface was 240°C. In other words, it was found that for samples a1 to a6, a9 to a15 and samples b1 to b6 on which a first and second sprayed films were formed, the temperature of the silicone adhesive layer could be kept below the heat-resistant temperature even when an electrostatic chuck (substrate holding member) was used in a process at a temperature higher than the heat-resistant temperature of the silicone adhesive layer, and deterioration of the silicone adhesive layer could be prevented.

Sample a7 is an electrostatic chuck without the second sprayed film. Samples a1 and b1 with the first and second sprayed films had a temperature distribution ΔT of 1.2°C and 1.0°C, respectively, on the substrate mounting surface, whereas sample a7 had a temperature distribution ΔT of 2.1°C. This is presumed to be because the heat flow from the electrostatic chuck toward the refrigerant flow path of the cooling member was affected by the second ceramic sprayed film formed on the surface of the cooling member, and this effect was also seen on the substrate mounting surface of the electrostatic chuck. As a result, it was found that samples a1 and b1 with the first and second sprayed films were able to reduce the thermal unevenness on the substrate mounting surface of the electrostatic chuck. It is presumed that samples a2 to a6, a9 to a15, and samples b2 to b6 with the first and second sprayed films have the same effect. The temperature distribution ΔT on the substrate placement surface was measured using an infrared (IR) camera as the maximum value minus the minimum value in the area inside the 290 mm diameter.

In addition, in the samples a1 to a5 and a9 to a15, the temperature of the substrate mounting surface of the electrostatic chuck could be set to 250°C by adjusting the amount of heat supplied, and the temperature of the silicone adhesive layer at that time could be set to 200°C or less. In this case, the ceramic members of the samples a1 to a5 and a11 to a13 were formed of ceramics mainly composed of AlN, and satisfied 0.75 ≧ (Re + Rf1) / (Re + Rf1 + Rb + Rf2 + Rm) ≧ 0.24. This confirmed that the substrate holding member, whose ceramic member is formed of ceramics mainly composed of AlN and satisfies 0.75 ≧ (Re + Rf1) / (Re + Rf1 + Rb + Rf2 + Rm) ≧ 0.24, can be used in processes at least at 250°C or higher. In addition, since the amount of heat supplied was fixed at 10,000 (W/m ² ) in samples a9 and a14, which satisfied the above condition, the temperature of the substrate mounting surface could not be raised to 250° C., but samples a11 and a15, which were produced by increasing the amount of heat supplied using the same electrostatic chucks as samples a9 and a14, respectively, were able to raise the temperature of the substrate mounting surface to 250° C. Furthermore, sample a10, which satisfied the above condition, was able to lower the temperature of the silicone adhesive layer to 200° C. or lower even when the temperature of the substrate mounting surface was set to 300° C.

In addition, in the samples b1, b2, and b4 to b6, the temperature of the substrate mounting surface of the electrostatic chuck could be set to 250° C. by adjusting the amount of heat supplied, and the temperature of the silicone adhesive layer at that time could be set to 200° C. or less. In this case, the ceramic members of the samples b1, b2, and b4 to b6 were formed of ceramics containing Al ₂ O ₃ as the main component, and satisfied 0.77≧(Re+Rf1)/(Re+Rf1+Rb+Rf2+Rm)≧0.20. This confirmed that a substrate holding member whose ceramic member is formed of ceramics containing Al ₂ O ₃ as the main component and satisfies 0.77≧(Re+Rf1)/(Re+Rf1+Rb+Rf2+Rm)≧0.20 can be used in processes at least at 250° C. or more. In addition, in the case of sample b5 which satisfied this condition, even when the temperature of the substrate mounting surface was set to 400°C, the temperature of the silicone adhesive layer could be kept at 200°C or less.

Furthermore, in the samples a1 to a5, a10, a12, and a13, the temperature of the substrate mounting surface of the electrostatic chuck could be raised to 250° C. even when the amount of heat supplied was less than 10,000 (W/m ² ). In this case, the ceramic members of the samples a1 to a5, a10, a12, and a13 were formed of ceramics containing AlN as the main component, and satisfied (Rf1+Rb+Rf2)/(Re+Rf1+Rb+Rf2+Rm)≧0.83. This confirmed that an electrostatic chuck in which the ceramic member is formed of ceramics containing AlN as the main component and which satisfies (Rf1+Rb+Rf2)/(Re+Rf1+Rb+Rf2+Rm)≧0.83 can reduce the amount of heat supplied necessary to maintain a predetermined process temperature.

Furthermore, in samples b1, b2, and b4 to b6, the temperature of the substrate mounting surface of the electrostatic chuck could be raised to 250° C. even when the amount of heat supplied was less than 10,000 (W/m ² ). In this case, samples b1, b2, and b4 to b6 had ceramic members formed of ceramics containing Al ₂ O ₃ as a main component, and satisfied (Rf1+Rb+Rf2)/(Re+Rf1+Rb+Rf2+Rm)≧0.63. This confirmed that an electrostatic chuck whose ceramic member is formed of ceramics containing Al ₂ O ₃ as a main component and satisfies (Rf1+Rb+Rf2)/(Re+Rf1+Rb+Rf2+Rm)≧0.63 can reduce the amount of heat supplied necessary to maintain a predetermined process temperature.

From the above, it was confirmed that the substrate holding member of the present invention, even when used in a process in which the temperature of the substrate reaches or exceeds the heat resistance temperature of the silicone adhesive layer, keeps the temperature of the silicone adhesive layer below the heat resistance temperature and has a high degree of uniformity in the temperature distribution on the substrate mounting surface. It was also confirmed that the manufacturing method of the present invention can manufacture such a substrate holding member.

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 holding member 12: Ceramic member 14: First sprayed film 16: Cooling member 18: Second sprayed film 20: Silicone adhesive layer 22: Flow passages 24, 26: Electrode 28: Substrate mounting surface

Claims (6)

A substrate holding member,
a ceramic member formed in a flat plate shape from ceramics, having a substrate mounting surface on one main surface thereof and having an electrode embedded therein ;
a first thermal spray coating formed on the other main surface of the ceramic member;
A metal cooling member having a coolant flow path therein;
a second sprayed film formed on the planar main surface of the cooling member;
a silicone adhesive layer that bonds the first sprayed film and the second sprayed film. The ceramic member is formed of a ceramic mainly composed of AlN,
When the thermal resistance per unit area in the thickness direction of the ceramic member is Re (m ² K/W), the thermal resistance per unit area in the thickness direction of the first sprayed coating is Rf1 (m ² K/W), the thermal resistance per unit area in the thickness direction of the silicone adhesive layer is Rb (m ² K/W), the thermal resistance per unit area in the thickness direction of the second sprayed coating is Rf2 (m ² K/W), and the thermal resistance per unit area in the thickness direction in the region from the main surface of the cooling member on the silicone adhesive layer side to the coolant flow path is Rm (m ² K/W),
0.75≧(Re+Rf1)/(Re+Rf1+Rb+Rf2+Rm)≧0.24
2. The substrate holding member according to claim 1, The ceramic member is formed of a _ceramic mainly composed of _Al2O3 ,
When the thermal resistance per unit area in the thickness direction of the ceramic member is Re (m ² K/W), the thermal resistance per unit area in the thickness direction of the first sprayed coating is Rf1 (m ² K/W), the thermal resistance per unit area in the thickness direction of the silicone adhesive layer is Rb (m ² K/W), the thermal resistance per unit area in the thickness direction of the second sprayed coating is Rf2 (m ² K/W), and the thermal resistance per unit area in the thickness direction in the region from the main surface of the cooling member on the silicone adhesive layer side to the coolant flow path is Rm (m ² K/W),
0.77≧(Re+Rf1)/(Re+Rf1+Rb+Rf2+Rm)≧0.20
2. The substrate holding member according to claim 1, In the substrate holding member,
(Rf1+Rb+Rf2)/(Re+Rf1+Rb+Rf2+Rm)≧0.83
3. The substrate holding member according to claim 2, wherein In the substrate holding member,
(Rf1+Rb+Rf2)/(Re+Rf1+Rb+Rf2+Rm)≧0.63
4. The substrate holding member according to claim 3, wherein A method for manufacturing a substrate holding member, comprising the steps of:
A step of forming and firing a ceramic raw material powder to produce a ceramic member having an electrode embedded therein ;
A step of preparing a plurality of metal members and forming grooves that serve as a flow path for a coolant;
a step of joining the plurality of metal members having the grooves formed therein to fabricate a cooling member having the flow passage;
a step of spraying a first thermal spraying raw material powder containing a predetermined ceramic onto a surface of the ceramic member facing the substrate mounting surface to form a first thermal sprayed film;
spraying a second thermal spraying raw material powder containing a predetermined ceramic onto one main surface of the cooling member to form a second thermal sprayed film;
applying a silicone adhesive to at least one of the first sprayed film and the second sprayed film to bond the ceramic member and the cooling member;
and curing the silicone adhesive to form a silicone adhesive layer.