JP7565735B2 - Substrate holding member, manufacturing method thereof, and electrostatic chuck member - Google Patents

Description

The present invention relates to a substrate holding member, a manufacturing method thereof, and an electrostatic chuck member.

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 semiconductor processing.

Patent Document 1 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.

Patent Document 2 also discloses a method for manufacturing a dissimilar material joint, which is characterized by disposing a third member having a Young's modulus of 150 GPa or less and a melting point of 1500 K or less between a first member and a second member having a thermal expansion coefficient different from that of the first member, via a metal brazing material, and brazing the first member to the second member.

Patent Document 3 also discloses a heat dissipation component having a three-layer structure formed by bonding a flat aluminum-ceramic composite made by impregnating a ceramic porous body with an aluminum alloy, the heat dissipation component being characterized in that a cooling groove penetrating the front and back is provided in the middle layer by water jet machining or electric discharge machining, the heat dissipation component being characterized in that the aluminum-ceramic composite is manufactured by high-pressure forging, and the ceramic porous body is characterized in that it is made of at least one material selected from the group consisting of silicon carbide, silicon nitride, aluminum nitride, and alumina.

Patent Document 4 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.

JP 2017-037721 A JP 2010-052011 A JP 2008-071845 A JP 2007-243139 A

Conventionally, metal materials, especially Al _alloys , have been used for cooling plates for cooling substrate holding members such as electrostatic chucks because of their workability and cooling effect. In addition, ceramic sintered bodies made of _Al2O3 or AlN have been used for substrate holding members. To integrate these members, organic adhesives have been proposed because of their ease of integration. However, when using organic adhesives as a bonding layer, their heat resistance becomes an issue, and they could not be used, especially when using electrostatic chucks in processes at 200°C or higher, because the organic adhesive layer reaches a temperature at which it decomposes.

However, Patent Document 1 does not take into account the bonding between the insulating layer and the base material or between the insulating layer and the heater section, and therefore does not take into account the heat resistance when an organic adhesive is used. Patent Document 2 uses a metal brazing material for bonding, and therefore does not take into account the heat resistance when an organic adhesive is used. Patent Document 3 focuses on the thermal expansion coefficient of the heat dissipation component, but does not take into account the heat resistance when an organic adhesive is used. Patent Document 4 does not take into account the heat resistance of the insulating adhesive layer.

The present invention has been made in consideration of these circumstances, and aims to provide a substrate holding member, a manufacturing method thereof, and an electrostatic chuck member, which, even when used in a process in which the temperature of the substrate reaches or exceeds the heat resistance temperature of the organic adhesive in the adhesive layer, keeps the temperature of the adhesive layer below the heat resistance temperature of the organic adhesive.

(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 thermal spray film formed on the other main surface of the ceramic member, a metal cooling member having a refrigerant flow path inside, and a silicone adhesive layer that bonds the thermal spray film and the cooling member. As a result, 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 the flexibility of the silicone adhesive layer can relieve stress generated between the substrate holding member and the cooling member. As a result, it becomes possible to use the substrate holding member in a process at a temperature higher than the heat resistance temperature of the silicone adhesive layer.

(2) In addition, in the substrate holding member of the present invention, the ceramic member is formed of a ceramic mainly composed of AlN, and is characterized in that, when the thermal resistance per unit area in the thickness direction of the sprayed film is Rf and the thermal resistance per unit area in the thickness direction of the silicone adhesive layer is Rb, Rf/Rb is ≧0.32. In this way, by adjusting the ratio of the thermal resistance per unit area of the sprayed film to the thermal resistance per unit area of the silicone adhesive layer according to the ceramic material forming the ceramic member, the substrate holding member can be used even in high-temperature processes of 250°C or more.

(3) In the substrate holding member of the present invention, the ceramic member is formed of _a ceramic mainly composed of _Al2O3 , and when the thermal resistance per unit area in the thickness direction of the sprayed film is Rf and the thermal resistance per unit area in the thickness direction of the silicone adhesive layer is Rb, Rf/Rb ≥ 0.25. In this way, by adjusting the ratio of the thermal resistance per unit area of the sprayed film to the thermal resistance per unit area of the silicone adhesive layer according to the ceramic material forming the ceramic member, the substrate holding member can be used even in high temperature processes of 250°C or higher.

(4) In addition, in the substrate holding member of the present invention, when the thermal resistance per unit area in the thickness direction of the ceramic member is Re, 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 refrigerant flow path is Rm, (Rf + Rb) / (Re + Rf + Rb + Rm) ≧ 0.84 is satisfied. In this way, by adjusting the thermal resistance per unit area of the ceramic member, the sprayed film, the silicone adhesive layer, and the cooling member according to the ceramic material that forms the ceramic member, the amount of heat supply required to maintain a predetermined process temperature can be reduced.

(5) In addition, in the substrate holding member of the present invention, when the thermal resistance per unit area in the thickness direction of the ceramic member is Re, 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 refrigerant flow path is Rm, (Rf + Rb) / (Re + Rf + Rb + Rm) ≧ 0.71. In this way, by adjusting the thermal resistance per unit area of the ceramic member, the sprayed film, the silicone adhesive layer, and the cooling member according to the ceramic material that forms the ceramic member, the amount of heat supply required to maintain a predetermined process temperature can be reduced.

(6) The electrostatic chuck member of the present invention is an electrostatic chuck member, which is formed in a flat shape from ceramics mainly composed of AlN, has a substrate mounting surface on one main surface, and is characterized in that it comprises a ceramic member with an electrode embedded therein, and a thermal spray film formed on the other main surface of the ceramic member, and is characterized in that, when the thermal resistance per unit area in the thickness direction of the ceramic member is Re and the thermal resistance per unit area in the thickness direction of the thermal spray film is Rf, 0.38 ≧ Re / Rf ≧ 0.03. In such an electrostatic chuck member with a thermal spray film on the back surface, by adjusting the thermal resistance per unit area of the ceramic member and the thermal spray film according to the ceramic material forming the ceramic member, the temperature difference (temperature gradient) between the front and back of the thermal spray film can be increased when the heat input to the electrostatic chuck surface is transferred to the cooling member. As a result, when the electrostatic chuck member is attached to the cooling member with a heat-resistant adhesive, the temperature of the underside (adhesive side) of the sprayed film can be made lower than the heat resistance temperature of the heat-resistant adhesive.

(7) The present invention also provides an electrostatic chuck member, comprising a ceramic member formed in a flat plate shape from ceramics mainly composed of Al ₂ O ₃ , having a substrate mounting surface on one main surface, and having an electrode embedded therein, and a thermal sprayed film formed on the other main surface of the ceramic member, wherein Re is the thermal resistance per unit area in the thickness direction of the ceramic member, and Rf is the thermal resistance per unit area in the thickness direction of the thermal sprayed film, and the relationship is 1.33 ≧ Re/Rf ≧ 0.13. In such an electrostatic chuck member having a thermal sprayed film on its back surface, by adjusting the thermal resistances per unit area of the ceramic member and the thermal sprayed film according to the ceramic material forming the ceramic member, it is possible to increase the temperature difference (temperature gradient) between the front and back of the thermal sprayed film when the amount of heat input to the electrostatic chuck surface is transferred to the cooling member. As a result, when the electrostatic chuck member is bonded to the cooling member by a heat-resistant adhesive, the temperature of the lower surface (adhesive side) of the sprayed film can be made lower than the heat resistance temperature of the heat-resistant adhesive.

(8) 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 spray raw material powder containing a predetermined ceramic on a surface facing the substrate mounting surface of the ceramic member to form a sprayed film, applying a silicone adhesive to at least one of the sprayed film or the joining surface of the cooling member to bond the ceramic member and the cooling member, and curing the silicone adhesive to form a silicone adhesive layer. As a result, 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, deterioration of the silicone adhesive layer can be prevented, and the flexibility of the silicone adhesive layer can alleviate stress generated between the substrate holding member and the cooling member. As a result, it becomes possible to use the substrate holding member in a process at a temperature higher than the heat resistance temperature of the silicone adhesive layer.

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, and deterioration of the silicone adhesive layer can be prevented. As a result, it becomes possible to use the substrate holding member in a process at a temperature higher than the heat resistance temperature of the silicone adhesive layer.

FIG. 2 is a front cross-sectional view showing the substrate holding member of the embodiment. FIG. 2 is a front cross-sectional view showing the electrostatic chuck 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 sprayed film 14, a cooling member 16, and a silicone adhesive layer 18. 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 26 on one of its main surfaces. The ceramics constituting the ceramic member 12 are preferably ceramics mainly composed of AlN or Al ₂ O _3. The term "mainly composed" means that the weight ratio of the main component to the weight of the ceramic member 12 is 90 wt % or more. The ceramic member 12 may contain additives for various purposes, such as increasing thermal conductivity, in addition to the ceramics mainly composed of ceramics. 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 sprayed film 14 is formed on the surface of the ceramic member 12 facing the substrate mounting surface _26. The sprayed film 14 is made of ceramics. The sprayed film 14 is preferably made of ceramics having low thermal conductivity, such as _Al2O3 , _Y2O3 , _{or ZrO2} . The 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 sprayed film 14 is preferably 0.3 mm or more and 3 mm or less.

It is preferable that the 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 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 20 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, freon, etc., and the refrigerant temperature may be below the boiling point.

The silicone adhesive layer 18 bonds the sprayed film 14 and the cooling member 16. This allows the ceramic member 12 and the cooling member 16 to be bonded. The silicone adhesive layer 18 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 18 is preferably 0.1 mm or more and 2.0 mm or less. The silicone adhesive layer 18 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 22, 24 embedded therein. The electrode 22 in FIG. 1 is an electrode for electrostatic attraction, and the electrode 24 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 a sprayed film 14 on the bonding surface between the ceramic member 12 and the silicone adhesive layer 18, 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 18, the temperature of the silicone adhesive layer 18 can be kept below the heat resistance temperature, and deterioration of the silicone adhesive layer 18 can be prevented. 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 substrate holding member 10 in a process at a temperature higher than the heat resistance temperature of the silicone adhesive layer 18 while homogenizing the temperature distribution of the substrate mounting surface 26 of the substrate holding member 10.

(Thermal resistance design)
The above configuration allows the substrate holding member 10 to be used in processes at temperatures higher than the heat resistance temperature of the silicone adhesive layer 18. However, when considering use in processes at higher temperatures or reducing the amount of heat 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, 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 Rf (m ² K/W) per unit area in the thickness direction of the thermal spray film 14 is the thickness of the thermal spray film (m)/thermal conductivity of the thermal spray 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 18 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 26 of the substrate holding member 10.

When the ceramic member 12 is mainly composed of AlN, the substrate holding member 10 preferably has an Rf/Rb of 0.32 or more. In this way, by adjusting the ratio of the thermal resistance per unit area of the sprayed film 14 to the thermal resistance per unit area of the silicone adhesive layer 18 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. The value of Rf/Rb is considered to indicate the temperature of the silicone adhesive layer 18. The value of Rf/Rb is related to the temperature of the interface between the silicone adhesive layer 18 and the sprayed film 14; a large value of Rf/Rb tends to lower the temperature of the silicone adhesive layer 18, and a small value tends to raise the temperature.

When the ceramic member of the substrate holding member 10 is mainly composed of Al ₂ O ₃ , it is preferable that Rf/Rb ≧ 0.25. In this way, by adjusting the ratio of the thermal resistance per unit area of the thermal sprayed film 14 to the thermal resistance per unit area of the silicone adhesive layer 18 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, the substrate holding member 10 preferably has (Rf+Rb)/(Re+Rf+Rb+Rm)≧0.84. In this way, by adjusting the thermal resistance per unit area of the ceramic member 12, the sprayed film 14, the silicone adhesive layer 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. The value of (Rf+Rb)/(Re+Rf+Rb+Rm) is considered to indicate the degree of ease of application to semiconductor processes. If the value of (Rf+Rb)/(Re+Rf+Rb+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 of the substrate holding member 10 is formed of a ceramic containing Al ₂ O ₃ as a main component, it is preferable that (Rf+Rb)/(Re+Rf+Rb+Rm)≧0.71. In this manner, by adjusting the thermal resistance per unit area of the ceramic member 12, the sprayed film 14, the silicone adhesive layer 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 sprayed film 14 is preferably 0.3 mm or more and 3.0 mm or less, and the thermal conductivity of the sprayed film 14 is preferably 0.4 W/mK or more and 16.0 W/mK or less. The thickness of the silicone adhesive layer 18 is preferably 0.1 mm or more and 2.0 mm or less, and the thermal conductivity of the silicone adhesive layer 18 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 the method can also be applied to a ceramic member mainly composed of Al ₂ O _3. In addition to the powder hot pressing method, it is also possible to adopt a green sheet lamination method or other conventional manufacturing methods. 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 placed and the back surface on which the sprayed film is provided are formed, and the substrate is processed into a specified 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 sprayed film is formed by spraying a sprayed raw material powder containing a predetermined ceramic on the surface of the ceramic member facing the substrate mounting surface. The sprayed film can be produced by a known spraying method, such as a plasma spraying method using a slurry containing ceramic raw material powder, a dry plasma spraying method in which raw material powder is granulated and fed, or other known spraying methods. The film type of the 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 sprayed film is preferably 2% or more, and more preferably 5% or more. The thermal conductivity of the 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 0.3 mm or more and 3.0 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 joint surfaces of the sprayed film or the cooling member, and after degassing, the two are stacked and a load is applied to heat cure in an oven in air, nitrogen atmosphere, or under 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 on the back side with the sprayed film and the metal cooling member 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.

[Configuration of electrostatic chuck member]
2 is a front cross-sectional view showing the electrostatic chuck member 30. The electrostatic chuck member 30 includes a ceramic member 12 in which an electrode 22 is embedded, and a thermal sprayed film 14. Details of the ceramic member 12 and the thermal sprayed film 14 are similar to those of the above-described substrate holding member 10. The electrode 22 is an electrode for electrostatic attraction. In addition, the electrostatic chuck member 30 may have other electrodes, such as a heater electrode, embedded therein as necessary.

When the electrostatic chuck member 30 of the present invention is attached to a general cooling member using a heat-resistant adhesive, not limited to silicone adhesive, it is possible to use the electrostatic chuck member 30 in processes above the heat resistance temperature of the heat-resistant adhesive. Therefore, the thermal resistance of the ceramic member 12 and the sprayed film 14 is designed according to the ceramic material that forms the ceramic member 12. The thermal resistance Re per unit area in the thickness direction of the ceramic member 12 and the thermal resistance Rf per unit area in the thickness direction of the sprayed film 14 are the same as those of the substrate holding member 10 described above.

(Thermal resistance design)
When the ceramic member 12 is formed of a ceramic containing AlN as a main component, the electrostatic chuck member 30 satisfies 0.38≧Re/Rf≧0.03. In this manner, by adjusting the thermal resistance per unit area in the thickness direction of the ceramic member 12 and the sprayed film 14 in accordance with the ceramic material forming the ceramic member 12, the ceramic member 12 can be bonded and integrated with a general cooling plate using any adhesive having a heat resistance temperature of 200° C. or higher, not limited to silicone adhesive, and can be used in processes at or above the heat resistance temperature.

Furthermore, when the ceramic member 12 is formed of a ceramic containing Al ₂ O ₃ as a main component, the electrostatic chuck member 30 satisfies 1.33≧Re/Rf≧0.13. In this manner, by adjusting the thermal resistance per unit area in the thickness direction of the ceramic member 12 and the sprayed film 14 in accordance with the ceramic material forming the ceramic member 12, the electrostatic chuck member 30 can be bonded and integrated with a general cooling plate using any adhesive having a heat resistance temperature of 200° C. or higher, not limited to silicone adhesive, and can be used in processes at or above the heat resistance temperature.

When the electrostatic chuck member 30 is bonded with a silicone adhesive, a polyimide-based varnish adhesive, or a heat-resistant inorganic adhesive whose main components are fire-resistant ceramics and an inorganic polymer, it can be used in processes at 250°C or higher. In addition, while an Al alloy is often used for the cooling member, other metals such as SUS, Ti, Cu, brass, and ceramics may also be used. Regardless of which of these materials is used, the electrostatic chuck member 30 of the present invention has a large temperature difference between the front and back of the sprayed film, so the temperature of the adhesive can be kept below the heat-resistant temperature.

[Examples and Comparative Examples]
[Samples a1 to a14]
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 a14 were produced by varying the presence or absence of a sprayed film, the material, the thickness, the thermal conductivity and the thickness of the silicone adhesive layer. Hereinafter, samples a1 to a14 are collectively referred to as sample a. FIG. 3 is a table showing the manufacturing conditions and the measured temperature values of each sample of samples a1 to a14.

(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 b13]
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 with a silicone adhesive layer. Samples b1 to b13 were produced by varying the presence or absence of a sprayed film, the material, thickness, and the thermal conductivity and thickness of the silicone adhesive layer. Hereinafter, samples b1 to b13 will be collectively referred to as sample b. Figure 4 is a table showing the manufacturing conditions and measured temperatures for each of samples b1 to b13.

(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 thermal sprayed film on the surface of the ceramic member opposite to the substrate mounting surface. The porosity was adjusted so that the thermal conductivity of the ZrO ₂ thermal sprayed film was 0.8 (W/mK), the thermal conductivity of the Y ₂ O ₃ thermal sprayed film was 2 (W/mK), and the thermal conductivity of the Al ₂ O ₃ thermal sprayed film was 4 (W/mK). The above thermal conductivities were measured at 25°C for a single thermal sprayed film produced under the same conditions. The thickness of the thermal sprayed film was 300 μm to 3000 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 applied current 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 was adjusted to 75 mm. The scanning speed or displacement speed of the nozzle with respect to the ceramic 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 of the ceramic member to be sprayed. 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 resulted in the generation of 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 to be sprayed. In this way, a ceramic member was formed in which one surface of the ceramic 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 2000 to 3000 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 samples a1 to a8, a11 to a14 and samples b1 to b8, b10 to b12, the average temperature of the electrostatic chuck substrate mounting surface was controlled to be in a steady state of 250°C. In samples a9 and b9, the amount of heat supplied was 10,000 (W/m ² ). In sample a10, the average temperature of the electrostatic chuck substrate mounting surface was controlled to be in a steady state of 300°C. The temperature of each part exposed on the side surface of the electrostatic chuck at that time was measured by directly contacting the silicone adhesive layer with a thermocouple, or by measuring the temperature of each part on the side surface with an optical thermometer, as appropriate.

(Evaluation Results)
In samples a1 to a13 and samples b1 to b12 in which a sprayed film was formed on the ceramic member, the temperature of the silicone adhesive layer could be kept at 200° C. or less when the temperature of the substrate mounting surface of the electrostatic chuck was set at 220° C. or more. That is, it was found that, in samples a1 to a13 and samples b1 to b12 in which a sprayed film was formed, the temperature of the silicone adhesive layer could be kept at or below the heat-resistant temperature even when the electrostatic chuck (substrate holding member) was used in a process in which the temperature was higher than the heat-resistant temperature of the silicone adhesive layer, and deterioration of the silicone adhesive layer could be prevented.

On the other hand, in samples a14 and b13, in which no sprayed film was formed on the ceramic member, the temperature of the silicone adhesive layer could not be reduced to below 200°C when the temperature of the substrate mounting surface of the electrostatic chuck was set to 250°C.

In addition, in samples a1 to a8 and a10 to a13, 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 kept below 200°C. In samples a1 to a5 and a11 to a13, the ceramic member was made of ceramics mainly composed of AlN, and Rf/Rb ≧ 0.32 was satisfied. Sample a9 satisfied Rf/Rb ≧ 0.32, and in sample a11, which had the same thermal resistance design as sample a9 but had an increased amount of heat supplied, the temperature of the substrate mounting surface of the electrostatic chuck could be set to 250°C, and the temperature of the silicone adhesive layer at that time could be kept below 200°C. This shows that electrostatic chucks whose ceramic members are made of ceramics mainly composed of AlN and which satisfy Rf/Rb ≧ 0.32 can be used as substrate holders even in high-temperature processes at 250°C or higher.

In addition, in the samples b1 to b8 and b10 to b12, 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 the samples b1 to b8 and b10 to b12, the ceramic member was formed of ceramics mainly composed of Al ₂ O ₃ , and Rf/Rb ≧ 0.25 was satisfied. In addition, the sample b9 satisfied Rf/Rb ≧ 0.25, and in the sample b10, which had the same thermal resistance design as the sample b9 but had an increased amount of heat supplied, the temperature of the substrate mounting surface of the electrostatic chuck could be set to 250°C, and the temperature of the silicone adhesive layer at that time could be set to 200°C or less. This shows that the electrostatic chuck, in which the ceramic member is formed of ceramics mainly composed of Al ₂ O ₃ and Rf/Rb ≧ 0.25 is capable of using the substrate holding member even in a high-temperature process of 250°C or more.

Furthermore, in the case of samples a1 to a8, 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 samples a1 to a8, a10, a12, and a13 were formed of ceramics containing AlN as the main component, and satisfied (Rf+Rb)/(Re+Rf+Rb+Rm)≧0.84. This confirmed that an electrostatic chuck whose ceramic member is formed of ceramics containing AlN as the main component and which satisfies (Rf+Rb)/(Re+Rf+Rb+Rm)≧0.84 can reduce the amount of heat supplied necessary to maintain a predetermined process temperature.

Furthermore, in samples b1 to b8, b11, and b12, 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 to b8, b11, and b12 had ceramic members formed of ceramics containing Al ₂ O ₃ as a main component, and satisfied (Rf+Rb)/(Re+Rf+Rb+Rm)≧0.71. This confirmed that an electrostatic chuck whose ceramic member is formed of ceramics containing Al ₂ O ₃ as a main component and satisfies (Rf+Rb)/(Re+Rf+Rb+Rm)≧0.71 can reduce the amount of heat supplied necessary to maintain a predetermined process temperature.

In addition, for samples a1 to a13, the ceramic member in which the electrodes are embedded is made of ceramics whose main component is AlN, and the relationship 0.38 ≧ Re/Rf ≧ 0.03 is satisfied. It was found that such electrostatic chuck members are optimal for integrating with cooling members using various types of heat-resistant adhesives.

In addition, in samples b1 to b12, the ceramic members in which the electrodes are embedded are formed of ceramics containing Al ₂ O ₃ as a main component, and satisfy 1.33 ≧ Re/Rf ≧ 0.13. It was found that such electrostatic chuck members are optimal for integration with a cooling member using various types of heat-resistant adhesives.

From the above, it was confirmed that the substrate holding member of the present invention maintains a temperature of the silicone adhesive layer below its heat-resistant temperature even when used in a process in which the substrate temperature exceeds the heat-resistant temperature of the silicone adhesive layer. It was also confirmed that the manufacturing method of the present invention can produce such a substrate holding member. It was also found that the electrostatic chuck member of the present invention is an optimal electrostatic chuck member for integration with a cooling member using various types of heat-resistant adhesives.

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: Thermally sprayed film 16: Cooling member 18: Silicone adhesive layer 20: Flow path 22, 24: Electrode 26: Substrate mounting surface 30: Electrostatic chuck member

Claims (8)

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 thermal spray coating formed on the other main surface of the ceramic member;
A metal cooling member having a coolant flow path therein;
a silicone adhesive layer that bonds the thermal sprayed film and the cooling member. 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 sprayed coating is Rf (m ² K/W) and the thermal resistance per unit area in the thickness direction of the silicone adhesive layer is Rb (m ² K/W),
Rf/Rb≧0.32
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 sprayed coating is Rf (m ² K/W) and the thermal resistance per unit area in the thickness direction of the silicone adhesive layer is Rb (m ² K/W),
Rf/Rb≧0.25
2. The substrate holding member according to claim 1, When the thermal resistance per unit area in the thickness direction of the ceramic member is Re (m ² K/W) and the thermal resistance per unit area in the thickness direction in a region from the main surface of the cooling member on the silicone adhesive layer side to the flow path of the refrigerant is Rm (m ² K/W),
(Rf+Rb)/(Re+Rf+Rb+Rm)≧0.84
3. The substrate holding member according to claim 2, wherein When the thermal resistance per unit area in the thickness direction of the ceramic member is Re (m ² K/W) and the thermal resistance per unit area in the thickness direction in a region from the main surface of the cooling member on the silicone adhesive layer side to the flow path of the refrigerant is Rm (m ² K/W),
(Rf+Rb)/(Re+Rf+Rb+Rm)≧0.71
4. The substrate holding member according to claim 3 , wherein An electrostatic chuck member,
a ceramic member formed in a flat plate shape from a ceramic mainly composed of AlN, having a substrate mounting surface on one main surface thereof, and having an electrode embedded therein;
a thermal spray coating formed on the other main surface of the ceramic member,
When the thermal resistance per unit area in the thickness direction of the ceramic member is Re (m ² K/W) and the thermal resistance per unit area in the thickness direction of the sprayed coating is Rf (m ² K/W),
0.38≧Re/Rf≧0.03
Electrostatic chuck member characterized by: An electrostatic chuck member,
a ceramic member formed in a flat plate shape from a ceramic mainly composed of Al ₂ O ₃ , having a substrate mounting surface on one of its main surfaces, and having an electrode embedded therein;
a thermal spray coating formed on the other main surface of the ceramic member,
When the thermal resistance per unit area in the thickness direction of the ceramic member is Re (m ² K/W) and the thermal resistance per unit area in the thickness direction of the sprayed coating is Rf (m ² K/W),
1.33≧Re/Rf≧0.13
Electrostatic chuck member characterized by: 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 thermal spray raw material powder containing a predetermined ceramic onto a surface of the ceramic member facing the substrate mounting surface to form a thermal sprayed film;
applying a silicone adhesive to at least one of the joining surfaces of the thermal sprayed film and the cooling member to bond the ceramic member and the cooling member;
and curing the silicone adhesive to form a silicone adhesive layer.