JP2022158147A - holding device - Google Patents

Abstract

To make the in-plane temperature distribution uniform in a holding device equipped with a heater.SOLUTION: A holding device that holds a target object includes a ceramic portion that is mainly composed of ceramic and is formed into a plate shape, a heater electrode portion that heats the ceramic portion, and an adhesive layer formed so as to spread in a plane direction perpendicular to a thickness direction of the ceramic portion, contacting both the ceramic portion and the heater electrode portion, and containing an adhesive and an inorganic filler, and the inorganic filler contains, as a part of the inorganic filler, a fine particle filler having an equivalent sphere diameter smaller than the maximum height of an unevenness formed on the surface of the heater electrode portion.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to retention devices.

2. Description of the Related Art Conventionally, as a holding device for holding an object, for example, an electrostatic chuck for holding an object such as a wafer when manufacturing a semiconductor is known. The electrostatic chuck includes a ceramic portion on which an object is placed, a base portion in which a coolant channel is formed, and a joining portion that joins the ceramic portion and the base portion. Further, such an electrostatic chuck generally includes a heater for heating the wafer, which is an object to be held, and performs temperature control. For example, Japanese Unexamined Patent Application Publication No. 2002-200001 discloses a configuration in which a joint is formed by sandwiching a heater between layers of an organic adhesive agent mixed with a filler for enhancing thermal conductivity.

Japanese Patent Application Laid-Open No. 2013-009001

However, when a heater is placed through an adhesive to heat a ceramic portion on which an object is placed, the in-plane temperature distribution may become uneven locally regardless of the heater placement pattern. The inventors of the present application have found a new problem that there is. Such a problem is not limited to electrostatic chucks, but is common to holding devices in which a heater that heats the ceramic part is arranged via an adhesive agent. rice field.

The present disclosure can be implemented as the following forms.
(1) According to one aspect of the present disclosure, a holding device for holding an object is provided. This holding device is mainly made of ceramic, and includes a plate-shaped ceramic portion, a heater electrode portion for heating the ceramic portion, and a planar direction perpendicular to the thickness direction of the ceramic portion. and an adhesive layer that is in contact with both the ceramic portion and the heater electrode portion and contains an adhesive and an inorganic filler, the inorganic filler being a part of the inorganic filler, the It contains a fine particle filler having an equivalent sphere diameter smaller than the maximum height of the unevenness formed on the surface in contact with the adhesive layer.
According to the holding device of this aspect, since the adhesive layer contains, as part of the inorganic filler, the fine particle filler having an equivalent spherical diameter smaller than the maximum height of the unevenness on the surface of the heater electrode portion, the surface of the heater electrode portion The fine particle filler enters into the recesses of the unevenness. Therefore, in the vicinity of the interface with the heater electrode portion in the adhesive layer, it is possible to increase the thermal conductivity and suppress the thermal resistance, thereby making the heat conduction efficiency uniform in the plane. As a result, the in-plane temperature distribution in the ceramic portion can be made uniform.
(2) In the holding device of the above aspect, the content ratio of the fine particle filler in the inorganic filler may be 1% by volume or more and 30% by volume or less. With such a configuration, the effect of uniforming the in-plane temperature distribution in the ceramic portion is enhanced, and the operability in forming the adhesive layer is improved due to the increased viscosity of the adhesive layer before curing. decline can be prevented.
(3) In the holding device of the above aspect, the fine particle filler may have an aspect ratio of 1.5 or less. With such a configuration, the fine particle filler can easily enter the irregularities on the surface of the heater electrode portion, so that the effect of making the in-plane temperature distribution in the ceramic portion uniform can be enhanced.
(4) In the holding device of the above aspect, the aspect ratio of the filler other than the fine particle filler in the inorganic filler may be 1.5 or less. With such a configuration, it becomes difficult for the adhesive layer to have a region where the inorganic filler is small and the adhesive is large, and the effect of uniforming the in-plane temperature distribution in the ceramic portion can be enhanced.
(5) In the holding device of the above aspect, in the cross section of the adhesive layer, the area ratio of the inorganic filler in a region in contact with the interface with the heater electrode portion, and the above-mentioned The difference from the area ratio of the inorganic filler may be 1% or less. With such a configuration, the inorganic filler is uniformly contained in the adhesive layer, so that variations in heat conduction efficiency in the adhesive layer can be suppressed, and the effect of making the in-plane temperature distribution uniform can be enhanced. can.
(6) In the holding device of the above aspect, the average particle size of the inorganic filler may be 200 μm or less. With such a configuration, the sedimentation rate of the inorganic filler in the adhesive layer before curing can be reduced, and the dispersed state of the inorganic filler in the adhesive layer can be improved. As a result, the effect of uniforming the in-plane temperature distribution can be enhanced.
(7) In the holding device of the above aspect, the inorganic filler may have a true density of 2.0 g/cm ³ or more and 6.5 g/cm ³ or less. With such a configuration, the sedimentation rate of the inorganic filler in the adhesive layer before curing can be reduced, and the dispersed state of the inorganic filler in the adhesive layer can be improved. As a result, the effect of uniforming the in-plane temperature distribution can be enhanced.
(8) The holding device of the above aspect further includes a plate-shaped base portion containing metal, wherein the adhesive layer is disposed between the ceramic portion and the base portion, and the ceramic portion and the base portion, and at least a portion of the heater electrode portion may be arranged inside the adhesive layer. With such a configuration, variations in heat conduction efficiency from the heater electrode portion disposed between the ceramic portion and the base portion to the ceramic portion can be suppressed, and the in-plane temperature distribution in the ceramic portion can be made uniform. .
(9) In the holding device of the above aspect, the ceramic portion includes an upper layer portion having a mounting surface on which an object to be placed of the holding device is placed, and a lower layer portion having the heater electrode portion formed on one surface thereof. , and the adhesive layer is arranged between the back surface of the mounting surface of the upper layer portion and the one surface of the lower layer portion to separate the upper layer portion and the lower layer portion. It is good also as joining. With such a configuration, variations in the heat conduction efficiency from the heater electrode portion disposed between the upper layer portion and the lower layer portion constituting the ceramic portion to the upper layer portion can be suppressed, and the in-plane temperature distribution in the upper layer portion can be made uniform. can be
(10) In the holding device of the above aspect, the ceramic portion includes an upper layer portion having a mounting surface on which an object to be placed of the holding device is placed, a lower layer portion in which the heater electrode portion is formed, The heater electrode portion has a heater electrode exposed portion exposed from the ceramic portion, the adhesive layer is disposed between the upper layer portion and the lower layer portion, and is separated from the upper layer portion. The lower layer portion may be joined to contact the surface of the heater electrode exposed portion. With such a configuration, it is possible to suppress variation in heat conduction efficiency from the heater electrode portion arranged in the lower layer portion constituting the ceramic portion to the upper layer portion, and to make the in-plane temperature distribution uniform in the upper layer portion.
The present disclosure can be implemented in various forms other than those described above, such as a method for manufacturing a holding device and a method for forming a joint.

1 is a perspective view showing the outline of the appearance of an electrostatic chuck according to a first embodiment; FIG. FIG. 2 is a cross-sectional view schematically showing the configuration of an electrostatic chuck; Explanatory drawing which shows how to obtain|require the maximum height of the surface of a heater electrode part. FIG. 4 is a cross-sectional view schematically showing a state of a boundary between a heater electrode portion and an adhesive layer; FIG. 4 is a cross-sectional view schematically showing a state of a boundary between a heater electrode portion and an adhesive layer; FIG. 4 is a cross-sectional view schematically showing a state of a boundary between a heater electrode portion and an adhesive layer; Explanatory drawing which shows the SEM image of the cross section of an adhesive bond layer. Explanatory drawing which shows the SEM image of the cross section of an adhesive bond layer. FIG. 4 is a cross-sectional view schematically showing a state of a boundary between a heater electrode portion and an adhesive layer; FIG. 4 is a cross-sectional view schematically showing a state of a boundary between a heater electrode portion and an adhesive layer; FIG. 4 is a cross-sectional view schematically showing the state of the middle region of the adhesive layer; FIG. 4 is a cross-sectional view that virtually represents how the inorganic filler settles during the formation of the adhesive layer. FIG. 4 is a cross-sectional view that virtually represents how the inorganic filler settles during the formation of the adhesive layer. Sectional drawing which represents typically the structure of the electrostatic chuck of 2nd Embodiment. Sectional drawing which represents typically the structure of the electrostatic chuck of 3rd Embodiment. Sectional drawing which represents typically the structure of the electrostatic chuck of 4th Embodiment. Explanatory drawing collectively showing the conditions and evaluation results of each sample.

A. First embodiment:
(A-1) Structure of electrostatic chuck:
FIG. 1 is a perspective view showing a schematic appearance of an electrostatic chuck 10 according to the first embodiment. FIG. 2 is a cross-sectional view schematically showing the configuration of the electrostatic chuck 10. As shown in FIG. In FIG. 1, a portion of the electrostatic chuck 10 is shown broken. 1 and 2 also show XYZ axes that are orthogonal to each other in order to specify directions. The X-axis, Y-axis, and Z-axis shown in each figure are oriented in the same direction. In this specification, the Z-axis indicates the vertical direction, and the X-axis and the Y-axis indicate the horizontal direction. 1 and 2 schematically show the arrangement of each part, and do not accurately show the ratio of the dimensions of each part.

The electrostatic chuck 10 is a device that attracts and holds an object by electrostatic attraction, and is used, for example, to fix a wafer W as an object in a vacuum chamber of a semiconductor manufacturing apparatus. The electrostatic chuck 10 includes a ceramic portion 20 , a base portion 30 and a joint portion 40 . These are laminated in the order of the ceramic portion 20, the joint portion 40, and the base portion 30 in the -Z-axis direction (vertically downward). The electrostatic chuck 10 in this embodiment is also called a "holding device".

The ceramic part 20 is a substantially circular plate-like member, and is made mainly of ceramic (for example, aluminum oxide, aluminum nitride, etc.). In the specification of the present application, the specific component being "the main component" means that the content of the specific component is 50% by volume or more. The diameter of the ceramic portion 20 may be, for example, about 50 mm to 500 mm, and usually about 200 mm to 350 mm. The thickness of the ceramic portion 20 may be, for example, about 1 mm to 10 mm.

As shown in FIG. 2, a chuck electrode 23 is arranged inside the ceramic portion 20 . The chuck electrode 23 is made of a conductive material such as tungsten or molybdenum. When a voltage is applied to the chuck electrode 23 from a power source (not shown), electrostatic attraction is generated, and the wafer W is attracted and fixed to the mounting surface 24 of the ceramic part 20 by this electrostatic attraction. The chuck electrode 23 may be of a bipolar type or of a unipolar type.

The base portion 30 is a plate-like member containing metal and having a substantially circular shape. The base portion 30 may contain, for example, at least one metal selected from aluminum, magnesium, molybdenum, titanium, tungsten, and nickel. From the viewpoint of suppressing the manufacturing cost while increasing the cooling efficiency of the base portion 30, it is desirable that the metal content in the base portion 30 is high. For example, it is desirable to contain 90% by mass or more of highly versatile aluminum (for example, to use an aluminum alloy such as A6061 or A5052). However, the base portion 30 may contain a component other than metal, such as ceramic. The diameter of the base portion 30 may be, for example, approximately 220 mm to 550 mm, and usually 220 mm to 350 mm. The thickness of the base portion 30 may be, for example, approximately 20 mm to 40 mm.

Inside the base portion 30, a plurality of coolant channels 32 are formed along the XY plane. The base portion 30 is cooled by flowing a coolant such as fluorine-based inert liquid, water, or liquid nitrogen through the coolant channel 32 . The ceramic portion 20 is cooled by heat transfer between the base portion 30 and the ceramic portion 20 via the joint portion 40, and the wafer W held on the mounting surface 24 of the ceramic portion 20 is cooled. Thereby, the temperature control of the wafer W is realized. In addition to the configuration in which the coolant flow path 32 is provided inside the base portion 30 , the base portion 30 may be cooled from the outside of the base portion 30 so that the base portion 30 has a cooling function. It should be noted that illustration of the coolant channel 32 is omitted in FIG. 2 .

The joining portion 40 is arranged between the ceramic portion 20 and the base portion 30 to join the ceramic portion 20 and the base portion 30 together. The joint portion 40 includes an adhesive layer 45 containing an adhesive made of a resin material such as a silicone resin, an acrylic resin, or an epoxy resin, and an inorganic filler made of an inorganic material. Furthermore, the joint portion 40 is made of a conductive material (for example, tungsten, molybdenum, etc.), and is a resistance heating element that heats the wafer W attracted and fixed to the mounting surface 24 by heating the ceramic portion 20. A heater electrode portion 60 is provided as (see FIG. 2). The heater electrode part 60 extends in the direction parallel to the XY plane in a predetermined pattern so as to be able to heat the entire wafer W inside the adhesive layer 45, specifically, the adhesive layer. 45 in the middle of the thickness direction. Therefore, the adhesive layer 45 is formed so as to spread in a plane direction (direction parallel to the XY plane) perpendicular to the thickness direction of the ceramic portion 20 and is in contact with both the ceramic portion 20 and the heater electrode portion 60. there is The thickness of the joint portion 40 can be, for example, about 0.1 mm to 1.0 mm. The configuration of the joint portion 40 will be described later in detail.

A plurality of gas supply paths 50 are further formed in the electrostatic chuck 10 . The gas supply path 50 is provided so as to penetrate the ceramic portion 20, the joint portion 40, and the base portion 30 in the Z direction, and opens at a gas discharge port 52 formed in the mounting surface 24 (see FIG. 1). reference). The gas supply path 50 is supplied with an inert gas such as helium gas from a gas supply device (not shown), and the inert gas is supplied from the gas outlet 52 to the space between the mounting surface 24 and the wafer W. supply. As a result, the heat transfer between the ceramic portion 20 and the wafer W is enhanced, and the controllability of the temperature distribution of the wafer W is further enhanced. Note that the gas supply path 50 is not essential, and the electrostatic chuck 10 may not be provided with the gas supply path 50 .

(A-2) Structure of joint:
The configuration of the joint 40 will be described below. The joint portion 40 includes the adhesive layer 45 containing the adhesive made of resin and the inorganic filler, and the heater electrode portion 60, as described above.

As the inorganic filler, it is possible to use granular or powdery substances composed of various inorganic materials including ceramics, metal oxides, metals, and other inorganic compounds. Specifically, examples of inorganic fillers include aluminum oxide (alumina: Al ₂ O ₃ ), zirconium oxide (zirconia: ZrO ₂ ), yttrium oxide (yttria: Y ₂ O ₃ ), and yttrium fluoride (YF ₃ ). , aluminum nitride (AlN), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), silicon dioxide (silica: SiO ₂ ), iron oxide, barium sulfate, calcium carbonate, and the like. The inorganic filler as described above is, for example, in the form of powder and is dispersed in the adhesive layer 45 for use. Inorganic materials such as those described above that make up the inorganic filler generally have a higher thermal conductivity than the resin that is the adhesive. can be enhanced. In particular, aluminum oxide, aluminum nitride, and silicon carbide are desirable due to their higher thermal conductivity.

The inorganic filler, as a part of the inorganic filler, is a sphere smaller than the maximum height Ry of the irregularities formed on the surface in contact with the adhesive layer 45 of the heater electrode portion 60 (hereinafter also simply referred to as the maximum height Ry). Contains "particulate fillers" with equivalent diameters. In inorganic fillers, fillers other than fine particle fillers, that is, fillers having an equivalent sphere diameter equal to or greater than the maximum height Ry are also referred to as "large-diameter fillers." The “equivalent sphere diameter” is the diameter when a distorted particle is assumed to be a sphere, and is a value converted from the volume of the particle.

The equivalent sphere diameter of the inorganic filler can be determined using the results of particle size distribution analysis of the inorganic filler. The particle size distribution of the inorganic filler can be measured using a laser diffraction particle size distribution analyzer. Inorganic fillers do not change physically or chemically under conditions such as temperature and pressure in the manufacturing process of electrostatic chucks using inorganic fillers. It is considered that the equivalent sphere diameter and volume do not substantially change between the states dispersed in the agent. Therefore, if the equivalent sphere diameter is measured for the inorganic filler before being mixed with the adhesive, the obtained equivalent sphere diameter is substantially the same as the value in the adhesive layer of the manufactured electrostatic chuck. it is conceivable that. In addition, the equivalent sphere diameter of the inorganic filler in the adhesive layer included in the manufactured electrostatic chuck can be measured by removing the inorganic filler from the adhesive layer. Specifically, the adhesive layer of the electrostatic chuck is coated with a dissolving agent appropriately selected according to the adhesive (for example, when using a silicone resin, a silicone resin dissolving agent KSR-2 (manufactured by Kanto Kagaku) ), and the inorganic filler contained in the solution is collected by centrifugation. Then, the particle size distribution of the obtained inorganic filler may be measured using a laser diffraction particle size distribution analyzer. Since the inorganic filler does not change physically or chemically even in the process of recovery from the adhesive layer as described above, the particle size distribution of the inorganic filler recovered from the adhesive layer is The particle size distribution becomes equivalent to that before mixing.

FIG. 3 is an explanatory diagram showing how to obtain the maximum height Ry of the irregularities formed on the surface of the heater electrode portion 60. As shown in FIG. In order to obtain the maximum height Ry, the cross section of the heater electrode portion 60 of the electrostatic chuck 10 is observed with a scanning electron microscope (SEM), and cut in a field of view of 50 μm×50 μm. A straight line A is formed by connecting two points that are the most convex (the height of the convex portion in the unevenness is the highest) on the surface of the heater electrode portion 60 that is in contact with the adhesive layer 45 . A straight line B, which is parallel to the straight line A and passes through the most concave point toward the inside of the heater electrode portion 60, is taken. Let the distance between the straight lines A and B be the maximum height Ry. In this embodiment, since both surfaces of the heater electrode portion 60 are in contact with the adhesive layer 45, the maximum height of each surface of the heater electrode portion 60 is obtained as described above, and the average value thereof is used as the heater The maximum height of the electrode portion 60 is Ry. In the heater electrode portion 60, if the unevenness formed on each surface has different heights, the maximum height Ry obtained separately for each surface may be used.

The heater electrode portion 60 of the present embodiment is produced by cutting a metal foil (plate) made of tungsten or molybdenum into a predetermined pattern for heating the ceramic portion 20 . The heater electrode portion 60 of the present embodiment has unevenness with a height of about 1 to several tens of μm on the surface in contact with the adhesive layer 45 . The surface of the heater electrode portion 60 may be processed, for example, by etching or polishing. The height of the irregularities formed on the surface of the heater electrode portion 60 is sufficiently small relative to the thickness of the heater electrode portion 60 and is a value that reflects the surface roughness of the entire surface of the heater electrode portion 60 .

FIG. 4 is a cross-sectional view schematically showing the state of the boundary between the heater electrode portion 60 and the adhesive layer 45. As shown in FIG. In this embodiment, the adhesive layer includes fine particle filler 41A and large diameter filler 41B as inorganic fillers. Since the fine particle filler 41A has an equivalent sphere diameter smaller than the maximum height Ry of the surface of the heater electrode portion 60, part of the fine particle filler 41A enters the recesses in the unevenness of the heater electrode portion 60 surface.

(A-3) Electrostatic chuck manufacturing method:
Next, a method for manufacturing the electrostatic chuck 10 according to this embodiment will be described. First, the plate-shaped ceramic part 20 in which the chuck electrode 23 is arranged is manufactured. The ceramic part 20 having the chuck electrode 23 inside can be produced by, for example, a known sheet lamination method or press molding method. At this time, the ceramic portion 20 is formed with an electrical via and a ventilation port such as the gas supply path 50 . Further, the base portion 30, the adhesive sheet for forming the joint portion 40, and the heater electrode portion 60 are prepared.

For the adhesive sheet, an adhesive paste is prepared by stirring the constituent materials of the adhesive layer 45 under vacuum, and the prepared adhesive paste is formed into a sheet using a roll coater or the like. It is made by heating and semi-curing under conditions of time. The constituent material of the adhesive layer 45 includes an adhesive before curing, an inorganic filler, and further includes a coupling agent, a curing catalyst, a cross-linking agent, and the like selected as necessary.

The adhesive sheet described above is pasted on the surface of the ceramic portion 20 opposite to the mounting surface 24, and after removing the portions of the adhesive sheet above the conductive vias and air vents, the heater electrode portion 60 is formed on the adhesive sheet. to place. Also, the above uncured adhesive sheet is adhered onto the base portion 30, and the adhesive sheet is removed from portions above the conductive vias and vent holes. After that, the ceramic part 20 and the base part 30 are superimposed and attached in a vacuum so that the surfaces to which the adhesive sheets are attached face each other, and the adhesive sheets are cured by heating to form the ceramic part 20 and the base part 30 . are joined by the joining portion 40 . After that, the electrostatic chuck 10 is manufactured by performing post-processing such as polishing of the outer circumference as necessary.

As described above, when the ceramic portion 20 and the base portion 30 are laminated and adhered so that the surfaces to which the uncured adhesive sheets are attached face each other, the ceramic portion disposed above the laminated structure The adhesive sheet is pressurized by the mass of 20 and the pressure generated in the lamination process, and the adhesive penetrates into the irregularities on the surface of the heater electrode portion 60 . At this time, the fine particle filler 41A among the inorganic fillers penetrates into the irregularities together with the adhesive, and an adhesive layer 45 as shown in FIG. 4 can be obtained.

According to the electrostatic chuck of the present embodiment configured as described above, the adhesive layer 45, as a part of the inorganic filler, has an equivalent sphere diameter smaller than the maximum height Ry of the irregularities on the surface of the heater electrode portion 60. , the fine particle filler 41A enters into the concave portions of the unevenness of the surface of the heater electrode portion 60 . Therefore, in the vicinity of the interface between the adhesive layer 45 and the heater electrode portion 60, the thermal conductivity can be enhanced, the thermal resistance can be suppressed, and the thermal conduction efficiency can be made uniform over the entire interface. As a result, the in-plane temperature distribution in the ceramic portion 20 heated by the heater electrode portion 60 can be made uniform. If the in-plane temperature distribution becomes non-uniform, for example, in the electrostatic chuck 10, the etching speed that progresses in the vacuum chamber of the semiconductor manufacturing apparatus will vary, and the quality of the wafer W may vary. According to this embodiment, by suppressing the variation in the in-plane temperature distribution, it is possible to suppress the inconvenience caused by the variation in the in-plane temperature distribution.

FIG. 5 is a cross-sectional view schematically showing the state of the boundary between the heater electrode portion 60 and the adhesive layer 45 when the inorganic filler does not contain the fine particle filler 41A but contains only the large diameter filler 41B. As shown in FIG. 5, when the inorganic filler does not contain the fine particle filler 41A, the inorganic filler cannot enter the concave portions of the uneven surface of the heater electrode portion 60. As shown in FIG. Therefore, in the vicinity of the interface with the heater electrode portion 60 in the adhesive layer 45, there is generated a region (resin-rich region) where the inorganic filler is small and the adhesive is abundant, as shown as region R in FIG. In such a resin-rich region, the efficiency of heat conduction from the heater electrode portion 60 to the adhesive layer 45 is locally reduced, causing non-uniform in-plane temperature distribution.

Moreover, in this embodiment, both the fine particle filler 41A and the large-diameter filler 41B are provided as inorganic fillers, so that the heat conduction efficiency of the adhesive layer 45 as a whole can be enhanced. The reason why the heat conduction efficiency of the adhesive layer 45 is improved by providing both the fine particle filler 41A and the large diameter filler 41B is considered as follows.

FIG. 6 is a cross-sectional view schematically showing the state of the boundary between the heater electrode portion 60 and the adhesive layer 45 when the adhesive layer 45 contains only the fine particle filler 41A as the inorganic filler. Even if the amount of the inorganic filler contained in the adhesive layer 45 is about the same, as shown in FIG. Compared to the case where the large-diameter filler 41B exists, the proportion of the adhesive existing between the particles of the filler is increased. That is, the heat conduction path (heat transfer path) formed in the adhesive layer 45 by the inorganic filler increases the amount of intervening adhesive, and the effect of improving the heat conduction efficiency of the adhesive layer 45 by the inorganic filler. is suppressed. The large-diameter filler 41B can ensure a longer heat transfer distance without being interposed by the adhesive. can be enhanced. In the present embodiment, by including both the large-diameter filler 41B and the fine particle filler 41A, the heat transfer path formed by the fine particle filler 41A can connect the large-diameter filler 41B, which efficiently conducts heat, thereby providing adhesion. The heat transfer performance of the entire agent layer 45 can be enhanced.

As described above, from the viewpoint of ensuring the heat conduction efficiency of the adhesive layer 45 as a whole, the spread of the particle size of the inorganic filler contained in the adhesive layer 45 is desirably about 0.01 to 300 μm. In particular, the spread of particle size of the fine particle filler 41A is preferably about 0.01 to 5 μm. Moreover, since the thickness of the joint portion 40 is preferably about 0.1 mm to 1.0 mm, the average particle size of the inorganic filler is preferably about 20 to 200 μm.

In addition, from the viewpoint of securing the effect of increasing the thermal conductivity by entering the concave portions of the surface of the heater electrode portion 60 while the fine particle filler 41A forms a heat transfer path between the large-diameter fillers 41B, the inorganic The content of the fine particle filler 41A in the filler is desirably 1% by volume or more. However, if the inorganic filler contains the fine particle filler 41A and the thermal conductivity is increased to a desired level, the content ratio of the fine particle filler 41A in the inorganic filler may be less than 1% by volume. In addition, while the heat transfer efficiency of the entire adhesive layer 45 is secured by the large-diameter filler 41B, the viscosity of the adhesive layer before curing increases due to the increase in the content of the fine particle filler 41A. From the viewpoint of suppressing deterioration of operability when forming the , the content ratio of the fine particle filler 41A in the inorganic filler is preferably 30% by volume or less. However, if the heat transfer performance of the adhesive layer 45 as a whole and the increase in viscosity of the adhesive layer before curing are permissible, the content of the fine particle filler 41A in the inorganic filler may exceed 30% by volume.

The content ratio (% by volume) of the fine particle filler 41A in the inorganic filler can be obtained using the result of the particle size distribution analysis of the inorganic filler described above. Particle size distribution analysis determines the volume of each particle. As a result of the particle size distribution analysis, particles having an equivalent sphere diameter smaller than the maximum height Ry are regarded as fine particle fillers, and the ratio of the total volume of the fine particle fillers to the total volume of the inorganic fillers is determined as the content of the fine particle fillers 41A in the inorganic fillers. A ratio (% by volume) may be used.

In the inorganic filler of the present embodiment, the fine particle filler 41A preferably has an aspect ratio of 1.5 or less. Moreover, in the inorganic filler of the present embodiment, the aspect ratio of the large-diameter filler 41B is desirably 1.5 or less. Here, the "aspect ratio" means a value (L/W) obtained by dividing the length of the major axis (major axis L) of the filler particles by the length of the minor axis (minor axis W). "Long axis L" refers to the longest linear distance between two points on the outer periphery of the filler particles when observing the cross section of the filler particles. The term "minor axis W" refers to the maximum value of the distance between two points on the outer circumference of the filler particles in the direction perpendicular to the straight line connecting the two points, which is the longest straight distance, in the cross section.

The method for obtaining the aspect ratio will be described in more detail below. When obtaining the aspect ratio of the fine particle filler 41A in the inorganic filler, the cross section of the adhesive layer 45 of the electrostatic chuck 10 is observed with a scanning electron microscope (SEM) at a magnification of 3000, for example, and a field of view of 10 μm×10 μm is cut out. The major axis L and the minor axis W are measured for 50 fine particle fillers 41A observed in the field of view, and the length ratio L/W is calculated. Let the average value of the obtained values be the aspect ratio of the fine particle filler 41A. When obtaining the aspect ratio of the filler other than the fine particles of the inorganic filler, that is, the large-diameter filler 41B, the cross section of the adhesive layer 45 of the electrostatic chuck 10 is observed with a scanning electron microscope (SEM) at a magnification of, for example, 500 to 1000. , a 200 μm × 200 μm field. The major axis L and the minor axis W are measured for ten large-diameter fillers 41B observed in the field of view, and the length ratio L/W is calculated. Let the average value of the obtained values be the aspect ratio of the large-diameter filler 41B.

7 and 8 are explanatory diagrams showing SEM images of the cross section of the adhesive layer 45. FIG. FIG. 7 shows how the fine particle filler 41A is dispersed in the field of view of 10 μm×10 μm. In the electrostatic chuck 10 of the present embodiment, as described above, since the height of the unevenness on the surface of the heater electrode portion 60 is about 10 to several tens of μm, most of the filler particles are A state of being the fine particle filler 41A is observed. In addition, in FIG. 8, it appears that the filler particles including the large-diameter filler 41B are dispersed in the field of view of 200 μm×200 μm.

FIG. 9 is a cross-sectional view schematically showing the state of the boundary between the heater electrode portion 60 and the adhesive layer 45 when the aspect ratio of the fine particle filler 41A is greater than 1.5. FIG. 10 is a cross-sectional view schematically showing the state of the boundary between the heater electrode portion 60 and the adhesive layer 45 when the aspect ratio of the large-diameter filler 41B is greater than 1.5.

The closer the aspect ratio of the fine particle filler 41A is to 1 and the closer the shape of the fine particle filler 41A is to a sphere, the easier it is for the fine particle filler 41A to enter the irregularities on the surface of the heater electrode portion 60, thereby enhancing the heat transfer performance. On the other hand, as shown in FIG. 9, when the aspect ratio of the fine particle filler 41A is greater than 1.5 and has an elongated shape, when the fine particle filler having the same equivalent sphere diameter and the aspect ratio closer to 1 is used, Compared to , the fine particle filler 41A is less likely to enter the unevenness of the surface of the heater electrode portion 60, and the heat conduction efficiency may be locally reduced, resulting in an uneven in-plane temperature distribution. Therefore, by setting the aspect ratio of the fine particle filler 41A to 1.5 or less, the in-plane temperature distribution can be made more uniform. However, if the degree of variation in in-plane temperature distribution on the mounting surface 24 of the electrostatic chuck 10 is within an allowable range, the aspect ratio of the fine particle filler 41A may exceed 1.5.

Also, the closer the aspect ratio of the large-diameter filler 41B is to 1 and the closer the shape of the large-diameter filler 41B is to a sphere, the less resin-rich portions are generated in the adhesive layer 45, and the more uniform the in-plane temperature distribution is. On the other hand, as shown in FIG. 10, when the aspect ratio of the large-diameter filler 41B is greater than 1.5 and has an elongated shape, a large-diameter filler having the same equivalent sphere diameter and an aspect ratio closer to 1 is used. As compared with the case of using the adhesive layer 45, a resin-rich region such as the region R shown in FIG. 5 is likely to occur. In such a resin-rich region, the heat conduction efficiency is locally lowered, so that the in-plane temperature distribution may become non-uniform. Therefore, by setting the aspect ratio of the large-diameter filler 41B to 1.5 or less, the in-plane temperature distribution can be made more uniform. However, the aspect ratio of the large-diameter filler 41B may exceed 1.5 as long as the degree of variation in the in-plane temperature distribution on the mounting surface 24 of the electrostatic chuck 10 is within the allowable range.

In this embodiment, in any cross section of the adhesive layer 45, the ratio of the area occupied by the inorganic filler is the area near the heater electrode portion 60 and the middle area of the adhesive layer 45 separated from the heater electrode portion 60. , and it is desirable that the inorganic filler be uniformly contained in the entire adhesive layer 45 . Specifically, for example, when the cross section of the adhesive layer 45 is observed, the area ratio of the inorganic filler in the region in contact with the interface with the heater electrode portion 60 and the inorganic filler in the region including the center in the thickness direction of the adhesive layer 45 The difference from the area ratio of the filler is desirably 1% or less. Furthermore, in order for the inorganic filler to be contained uniformly in the entire adhesive layer 45, when comparing the area ratio of the inorganic filler in two arbitrary regions in an arbitrary cross section of the adhesive layer 45, the difference between the two is 1% or less is more desirable.

FIG. 11 is a cross-sectional view schematically showing the central portion in the thickness direction of the adhesive layer 45 away from the heater electrode portion 60 when the content of the fine particle filler 41A in the adhesive layer 45 is the same as in FIG. It is a diagram. As shown in FIGS. 4 and 11, if the inorganic filler is uniformly contained in the entire adhesive layer 45, variations in heat transfer efficiency can be suppressed and the in-plane temperature distribution can be uniform. can be

Below, how to obtain the area ratio of the inorganic filler for each location in the cross section of the adhesive layer 45 will be described. In order to obtain the area ratio of the inorganic filler, the adhesive layer 45 is cut out from the electrostatic chuck 10 so as to include the portion where the heater electrode portion 60 and the adhesive layer 45 are in contact with each other, and is polished so that a cross-sectional view can be made. . Polishing may be performed, for example, by CP (cross-section polisher) processing using an ion milling method so that the inorganic filler in the adhesive layer 45 does not shed. The adhesive layer 45 of the sample obtained in this way was observed with a scanning electron microscope (SEM). The image is cut out in an area of 200 μm×200 μm. At this time, the heater electrode portion 60 may be in the field of view. From the obtained image, the area occupied by the inorganic filler is Sa, the area occupied by the inorganic filler and the adhesive (the area of the entire cut-out image) is Sb, and "Sa/Sb × 100" is calculated to obtain the inorganic filler. Calculate the area ratio occupied by Such analysis can be performed using image processing software such as WinROOF (manufactured by Mitani Shoji Co., Ltd.) and ImageJ.

Moreover, in the present embodiment, the average particle size of the inorganic filler is desirably 200 μm or less. The average particle size of the inorganic filler can be determined using the results of the particle size distribution analysis of the inorganic filler described above. Moreover, in the present embodiment, the true density of the inorganic filler is desirably 2.0 g/cm ³ or more and 6.5 g/cm ³ or less. The true density of the inorganic filler can be calculated from the chemical composition of the material used as the inorganic filler. When at least one of the average particle diameter of the inorganic filler and the true density of the inorganic filler satisfies the above conditions, the sedimentation speed of the inorganic filler in the adhesive layer 45 before curing can be sufficiently reduced. can.

12 and 13 are cross-sectional views that virtually represent how the inorganic filler settles in the adhesive layer 45 before curing when the adhesive layer 45 is formed. FIG. 12 shows the state of the adhesive layer 45 in the middle in the thickness direction, and FIG. 13 shows the state of the adhesive layer 45 near the boundary with the lower surface of the heater electrode portion 60 . In FIG. 12 and FIG. 13, the manner in which the inorganic filler settles is indicated by broken line arrows. As shown in FIGS. 12 and 13, if the settling speed of the inorganic filler is high, the inorganic filler may settle in the adhesive layer 45 until the adhesive layer 45 is cured. As described above, in the process of manufacturing the joint portion 40, when pressure is applied to the uncured adhesive layer 45 between the ceramic portion 20 and the base portion 30, the fine particle filler 41A dispersed in the adhesive is generated. It enters into the irregularities on the surface of the heater electrode portion 60 together with the adhesive. However, when the sedimentation speed of the inorganic filler is large with respect to the time required for curing the adhesive, as shown in FIG. .

When the inorganic filler settles in the adhesive layer 45 before curing as described above, the distribution of the inorganic filler forming the heat transfer paths in the adhesive layer 45 becomes uneven, and the in-plane temperature distribution may become uneven. . By reducing the sedimentation speed of the inorganic filler so as to suppress the sedimentation of the inorganic filler until the adhesive layer 45 is cured, the in-plane temperature distribution can be made more uniform. The terminal sedimentation velocity u _t of the inorganic filler can be expressed by the following formula (1).

（式中、ρ_ｓは、無機フィラーの密度であり、ρは、溶媒（硬化前の接着剤）の密度であり、ｇは、重力加速度であり、ｄ_ｐは、無機フィラーの粒子径であり、μは、溶媒（硬化前の接着剤）の粘度である。）

(Wherein, _ρs is the density of the inorganic filler, ρ is the density of the solvent (adhesive before curing), g is the gravitational acceleration, and _dp is the particle size of the inorganic filler. , μ is the viscosity of the solvent (adhesive before curing).)

From the formula (1), it is understood that the lower the density of the inorganic filler and the smaller the particle size of the inorganic filler, the smaller the terminal sedimentation velocity. Therefore, when forming the adhesive layer 45 using a silicone-based resin, an acrylic-based resin, an epoxy-based resin, or the like, which are widely used as adhesives for forming the adhesive layer, the general density and Considering the viscosity, the average particle diameter of the inorganic filler is 200 μm or less, or the true density of the inorganic filler is 2.0 g/cm ³ or more and 6.5 g/cm ³ or less. can be sufficiently small. By sufficiently reducing the sedimentation speed of the inorganic filler, the inorganic filler can be sufficiently uniformly dispersed in the entire adhesive layer 45 after curing. By sufficiently uniformly dispersing the inorganic filler, in the cross section of the adhesive layer 45, the area ratio of the inorganic filler in the region in contact with the interface with the heater electrode portion 60 and the area including the center of the thickness direction of the adhesive layer 45 It becomes easy to make the difference from the area ratio of the inorganic filler 1% or less.

However, if the in-plane temperature distribution can be made uniform as desired by including fine particle fillers and large-diameter fillers in the inorganic filler, the average particle size of the inorganic filler and the true density of the inorganic filler satisfy the conditions described above. It is also possible not to do so. Even if the average particle size of the inorganic filler and the true density of the inorganic filler do not satisfy the above conditions, for example, when adjusting the adhesive layer before curing, the inorganic filler and the adhesive can be mixed more sufficiently. It is also possible to improve the dispersed state of the inorganic filler in the adhesive layer after curing.

In addition, in the conditions related to the inorganic filler described above, the lower limit of the true density is a value for ensuring the ease of handling of the inorganic filler in the manufacturing process of the electrostatic chuck 10 . Further, the viscosity of the resin used as the adhesive constituting the adhesive layer 45 is preferably 3 to 50 Pa·s, and the density of the resin is preferably 0.9 to 1.0 g/cm ³ . preferable. If the viscosity of the resin is too low, the sedimentation speed of the inorganic filler particles increases, and the inorganic filler sediments due to gravity during curing of the adhesive. On the other hand, if the viscosity of the resin is too high, it may become difficult to mix the inorganic filler and the adhesive.

An example of the terminal sedimentation velocity obtained using the formula (1) is shown below. Here, the density of the solvent (adhesive before curing) is 1×10 ³ kg/m ³ and the viscosity of the solvent (adhesive before curing) is 100 Pa·S.

When aluminum oxide having a particle diameter of 150 μm (alumina: Al ₂ O ₃ , true density of 3.9×10 ³ kg/m ³ ) is used as the inorganic filler, the terminal sedimentation velocity is 3.68×10 ⁻⁷ . m/s. Also, considering the interference sedimentation corrected with the void ratio of the inorganic filler as 0.56, the interference sedimentation velocity when using alumina with a particle diameter of 150 μm as the inorganic filler is 2.44 × 10 ^-8 m / s. . The results show a sedimentation of 8.8×10 ⁻² m in 1 hour.

On the other hand, when zirconium oxide having a particle size of 300 μm (zirconia: ZrO ₂ , true density of 5.7×10 ³ kg/m ³ ) is used as the inorganic filler, the terminal sedimentation velocity is 2.45× 10 ⁻⁶ m/s. In addition, considering the interference sedimentation corrected with the void ratio of the inorganic filler as 0.56, the interference sedimentation velocity when using zirconia with a particle size of 300 μm as the inorganic filler is 1.63 × 10 ^-7 m / s. . The results show a sedimentation of 5.87×10 ⁻¹ mm in 1 hour.

B. Second embodiment:
FIG. 14 is a cross-sectional view schematically showing the configuration of the electrostatic chuck 110 of the second embodiment, similar to FIG. The electrostatic chuck 110 of the second embodiment has the same configuration as that of the first embodiment, except for the arrangement of the heater electrode section 60 . In the electrostatic chuck 110 of the second embodiment, parts common to those of the electrostatic chuck 10 of the first embodiment are given the same reference numerals.

The heater electrode portion 60 of the electrostatic chuck 110 of the second embodiment is provided on the lower surface (the surface in the −Z-axis direction) of the ceramic portion 20 . Such a heater electrode portion 60 can be formed, for example, as follows. That is, a heater paste is produced by mixing tungsten particles or platinum particles (for example, particle size of 10 μm to several tens of μm) with an adhesive before curing and an organic solvent. A heater pattern is formed by screen-printing or coating the heater paste on the lower surface of the ceramic part 20 . The heater electrode portion 60 is formed on the ceramic portion 20 by degreasing and firing the formed heater pattern. Here, the heater electrode portion 60 is formed with unevenness having a height of about 1 to several tens of μm. After that, the above-described adhesive sheet is pasted on the base portion 30, and after removing the portions of the adhesive sheet above the conductive vias and vents, the ceramic portion is placed so that the adhesive sheet and the heater electrode portion 60 face each other. 20 and the base portion 30 are overlapped and attached in a vacuum. The ceramic portion 20 and the base portion 30 are joined by the joint portion 40 by curing the adhesive sheet by heating.

Even with such a configuration, the adhesive layer 45 in contact with both the ceramic portion 20 and the heater electrode portion 60 contains the large-diameter filler and the fine particle filler together with the adhesive, so that the unevenness of the surface of the heater electrode portion 60 is reduced. into which the particulate filler penetrates. Therefore, as in the first embodiment, the effect of uniforming the in-plane temperature distribution in the electrostatic chuck 110 can be obtained. In the above-described manufacturing method, the firing process is performed at a temperature below the melting point of tungsten or platinum that constitutes the heater pattern. is uneven. Therefore, the fine particle filler penetrates into the irregularities of the surface of the heater electrode portion 60, thereby suppressing the formation of a resin-rich region in the vicinity of the interface with the heater electrode portion 60 in the adhesive layer 45, thereby improving the heat transfer performance. can be enhanced.

C. Third embodiment:
FIG. 15 is a cross-sectional view schematically showing the structure of the electrostatic chuck 210 of the third embodiment, similar to FIG. The electrostatic chuck 210 of the third embodiment differs from that of the first embodiment in that a ceramic portion 220 is provided instead of the ceramic portion 20 and the heater electrode portion 60 is arranged inside the ceramic portion 220 . In the electrostatic chuck 210 of the third embodiment, parts common to those of the electrostatic chuck 10 of the first embodiment are given the same reference numerals.

The ceramic part 220 of the third embodiment includes an upper layer part 21 and a lower layer part 22 which are plate-like members formed mainly of ceramic. The upper layer portion 21 has a mounting surface 24 on its upper surface, and a chuck electrode 23 is provided inside. The lower layer portion 22 is arranged between the upper layer portion 21 and the base portion 30, and has a heater electrode portion 60 formed on the upper surface thereof, and a first joint portion 240 containing an adhesive on the lower surface side. It is joined to the base portion 30 . A second joint portion including an adhesive layer 245 containing an adhesive and an inorganic filler and the above-described heater electrode portion 60 between the rear surface of the mounting surface 24 of the upper layer portion 21 and the upper surface of the lower layer portion 22. 242 is arranged to join the upper layer portion 21 and the lower layer portion 22 .

A method for manufacturing the ceramic portion 220 of the third embodiment will be described. The upper layer portion 21 and the lower layer portion 22 having the chuck electrode 23 therein can be produced by, for example, a known sheet lamination method or press molding method. At this time, the upper layer portion 21 and the lower layer portion 22 are formed with electrical vias, gas supply paths 50, and other vent holes. The heater electrode portion 60 is fabricated by forming a heater pattern on the upper surface of the lower layer portion 22 using heater paste in the same manner as the heater electrode portion 60 formed on the lower surface of the ceramic portion 20 in the second embodiment. can be done. Then, an uncured adhesive layer containing an inorganic filler is formed on the lower surface of the upper layer portion 21 by, for example, screen printing. The part 21 and the lower layer part 22 are overlapped and attached in a vacuum. After that, by curing the adhesive by heating, the upper layer portion 21 and the lower layer portion 22 are joined by the second joining portion 242, and the ceramic portion 220 is obtained. After providing the heater electrode portion 60 on the upper surface of the lower layer portion 22 , prior to bonding with the upper layer portion 21 , the heater electrode portion 60 was energized to measure the heat generation state, and the heat generation was locally generated in the heater electrode portion 60 . The temperature distribution during the heat generation of the heater electrode portion 60 may be made uniform by cutting away the portion where the amount is small to increase the resistance.

Even with such a configuration, the adhesive layer 245 that is in contact with both the upper layer portion 21 of the ceramic portion 220 and the heater electrode portion 60 contains the large-diameter filler and the fine particle filler together with the adhesive. The fine particle filler penetrates into the unevenness of the surface. Therefore, as in the first embodiment, the effect of uniforming the in-plane temperature distribution in the electrostatic chuck 210 can be obtained.

D. Fourth embodiment:
FIG. 16 is a cross-sectional view schematically showing the configuration of the electrostatic chuck 310 of the fourth embodiment, similar to FIG. The electrostatic chuck 310 of the fourth embodiment is different from the first embodiment in that a ceramic portion 320 is provided in place of the ceramic portion 20 and the heater electrode portion 60 is arranged inside the ceramic portion 320 . In the electrostatic chuck 310 of the fourth embodiment, parts common to those of the electrostatic chuck 10 of the first embodiment are given the same reference numerals.

The ceramic part 320 of the fourth embodiment includes an upper layer part 21 and a lower layer part 322 which are plate-like members formed mainly of ceramic. The upper layer portion 21 has a mounting surface 24 on its upper surface, and a chuck electrode 23 is provided inside. The lower layer portion 322 is arranged between the upper layer portion 21 and the base portion 30, and has the heater electrode portion 60 formed therein. It is joined to the portion 30 . A second joint portion 342 having an adhesive layer 345 containing an adhesive and an inorganic filler is disposed between the back surface of the mounting surface 24 of the upper layer portion 21 and the upper surface of the lower layer portion 322 . It joins with the lower layer part 322 .

A groove 327 is formed in the lower layer portion 322 downward (in the −Z-axis direction) from the upper surface. The groove 327 is provided to reach the heater electrode portion 60 , and the heater electrode portion 60 is exposed from the ceramic portion 320 (lower layer portion 322 ) at the groove 327 . A portion of the heater electrode portion 60 exposed from the ceramic portion 320 through the groove 327 is called a "heater electrode exposed portion 64". The adhesive layer 345 forming the second joint portion 342 contacts the heater electrode exposed portion in the groove 327 .

A method for manufacturing the ceramic portion 320 of the fourth embodiment will be described. The upper layer portion 21 having the chuck electrode 23 inside and the lower layer portion 322 having the heater electrode portion 60 inside can be produced by, for example, a known sheet lamination method or press molding method. At this time, conductive vias and vent holes are formed in the upper layer portion 21 and the lower layer portion 322 . On the upper surface of the lower layer portion 322, the surface layer of the lower layer portion 322 is removed by blasting or the like directly above a specific portion of the heater electrode portion 60 to form a heater electrode exposed portion 64 where a part of the heater electrode portion 60 is exposed. A formed groove 327 is provided. During processing, the surface of the heater electrode exposed portion 64 is formed with unevenness having a height of about 1 to several tens of μm. In addition, from the viewpoint of forming a good heat transfer path, it is preferable that the large-diameter filler 41B enters the groove 327, and the diameter of the outer periphery and the height of the groove 327 when viewed from above are 100 μm or more. is preferred. Then, the previously described adhesive sheet in an uncured state is attached to the lower surface of the upper layer portion 21, and the portions of the adhesive sheet above the conductive vias and the air vents are removed. Thereafter, the upper layer portion 21 and the lower layer portion 322 are overlapped and adhered in a vacuum such that the surface of the lower layer portion 322 on which the grooves 327 are formed faces the adhesive sheet. After that, by curing the adhesive by heating, the upper layer portion 21 and the lower layer portion 322 are bonded together by the second bonding portion 342, and the ceramic portion 320 is obtained. At this time, the adhesive containing the inorganic filler enters the grooves 327 as it deforms.

Even with such a configuration, the adhesive layer 345 that contacts both the upper layer portion 21 and the lower layer portion 322 of the ceramic portion 320 and the heater electrode portion 60 contains the large-diameter filler and the fine particle filler together with the adhesive. The fine particle filler penetrates into the irregularities on the surface of the heater electrode portion 60 . Therefore, as in the first embodiment, the effect of uniforming the in-plane temperature distribution in the electrostatic chuck 310 can be obtained.

E. Other embodiments:
The present disclosure may be applied to holding devices other than electrostatic chucks that hold the wafer W using electrostatic attraction. That is, another holding device that includes a ceramic part, a heater electrode part that heats the ceramic part, and an adhesive layer that contacts both the ceramic part and the heater electrode part, and holds an object on the surface of the ceramic part. For example, the present invention can be similarly applied to heater devices for vacuum devices such as CVD, PVD, and PLD, vacuum chucks, and the like.

Below, the holding device of the present disclosure will be described based on examples. Here, as with the electrostatic chuck 10 shown in FIG. 2, eight kinds of electrostatic chucks, samples S1 to S8, were manufactured and mounted as electrostatic chucks having heater electrode portions 60 arranged inside the bonding portions 40. The temperature variation on the placement surface was evaluated.

<Sample S1>
A ceramic granule containing alumina as a main component was produced by a known method. Ceramic granules were press-molded, and the resulting ceramic press-molded body was placed in a mold. A chuck electrode 23 is placed on the placed ceramic press-formed body, and a compact obtained by press-molding ceramic granules is further placed on the chuck electrode 23, and then hot-pressed at high temperature and high pressure. to obtain a sintered body. Conductive vias and vent holes were formed in the obtained fired body to obtain the ceramic part 20 . An uncured adhesive sheet containing a silicone adhesive was attached to the surface of the ceramic part 20 opposite to the mounting surface 24 . After removing the silicone adhesive on the conductive vias and vents, the heater electrode portion 60 processed into a predetermined pattern shape was placed on the adhesive sheet. Similarly, an uncured adhesive sheet was attached to the upper surface of the base portion 30, and the silicone adhesive on the conductive vias and vent holes was removed. The ceramic part 20 and the base part 30 were laminated in a vacuum so that the adhesive sheets faced each other, and the silicone adhesive was cured by heating to obtain an electrostatic chuck.

The silicone adhesive used to make sample S1 was prepared as follows. That is, alumina powder having an average particle size of 311 μm was added as an inorganic filler to polydimethylsiloxane having a viscosity of 10 Pa·s and mixed to obtain a main agent. Here, the alumina powder used contained alumina having a particle size corresponding to the fine particle filler. A coupling agent, a curing catalyst, and a cross-linking agent were added to and mixed with the resulting main agent to obtain a silicone adhesive. Here, the proportion of alumina in the silicone adhesive was 75% by mass. The resulting silicone adhesive was molded into a sheet and partially cured by heating to obtain an adhesive sheet for sample S1.

<Sample S2>
It was produced in the same manner as sample S1, except that the adhesive sheet used was different. The silicone adhesive used to make sample S2 was prepared as follows. Specifically, silica powder having an average particle size of 291 μm was added as an inorganic filler to polydimethylsiloxane having a viscosity of 10 Pa·s, and mixed to obtain a main agent. Here, fine particle silica powder with a particle size of 1.5 μm was added so as to be 15% by volume of the total inorganic filler. A coupling agent, a curing catalyst, and a cross-linking agent were added to and mixed with the resulting main agent to obtain a silicone adhesive. Here, the proportion of silica in the silicone adhesive was 75% by mass. The resulting silicone adhesive was molded into a sheet and partially cured by heating to obtain an adhesive sheet for sample S2.

<Sample S3>
It was produced in the same manner as sample S1, except that the adhesive sheet used was different. The silicone adhesive used to make sample S3 was prepared as follows. That is, alumina powder having an average particle size of 254 μm was added as an inorganic filler to polydimethylsiloxane having a viscosity of 10 Pa·s and mixed to obtain a main agent. Here, the alumina powder used contained alumina having a particle size corresponding to the fine particle filler. A coupling agent, a curing catalyst, and a cross-linking agent were added to and mixed with the resulting main agent to obtain a silicone adhesive. Here, the proportion of silica in the silicone adhesive was 75% by mass. The resulting silicone adhesive was molded into a sheet and partially cured by heating to obtain an adhesive sheet for sample S3.

<Sample S4>
It was produced in the same manner as sample S1, except that the adhesive sheet used was different. The silicone adhesive used to make sample S4 was prepared as follows. That is, alumina powder having an average particle size of 120 μm was added as an inorganic filler to polydimethylsiloxane having a viscosity of 10 Pa·s, and mixed to obtain a main agent. Here, the alumina powder used contained alumina having a particle size corresponding to the fine particle filler. A coupling agent, a curing catalyst, and a cross-linking agent were added to and mixed with the resulting main agent to obtain a silicone adhesive. Here, the proportion of alumina in the silicone adhesive was 75% by mass. The resulting silicone adhesive was molded into a sheet and partially cured by heating to obtain an adhesive sheet for sample S4.

<Sample S5>
It was produced in the same manner as sample S1, except that the adhesive sheet used was different. The silicone adhesive used to make sample S5 was prepared as follows. Specifically, Fe—Si alloy powder having an average particle size of 155 μm was added as an inorganic filler to polydimethylsiloxane having a viscosity of 10 Pa·s, and mixed to obtain a main agent. The alloy powder used here had a substantially uniform particle size and did not contain particles having a particle size corresponding to the fine particle filler. A coupling agent, a curing catalyst, and a cross-linking agent were added to and mixed with the resulting main agent to obtain a silicone adhesive. The proportion of the alloy in the silicone adhesive was 75% by mass. The resulting silicone adhesive was molded into a sheet and partially cured by heating to obtain an adhesive sheet for sample S5.

<Sample S6>
It was produced in the same manner as sample S1, except that the adhesive sheet used was different. The silicone adhesive used to make sample S6 was prepared as follows. Specifically, silica powder having an average particle size of 50 μm was added as an inorganic filler to polydimethylsiloxane having a viscosity of 10 Pa·s, and mixed to obtain a main agent. The silica powder used here had a substantially uniform particle size and did not contain particles having a particle size corresponding to the fine particle filler. A coupling agent, a curing catalyst, and a cross-linking agent were added to and mixed with the resulting main agent to obtain a silicone adhesive. The proportion of the alloy in the silicone adhesive was 75% by mass. The resulting silicone adhesive was molded into a sheet and partially cured by heating to obtain an adhesive sheet for sample S6.

<Sample S7>
It was produced in the same manner as sample S1, except that the adhesive sheet used was different. The silicone adhesive used to make sample S7 was prepared as follows. That is, alumina powder having an average particle size of 180 μm was added as an inorganic filler to polydimethylsiloxane having a viscosity of 10 Pa·s, and mixed to obtain a main agent. The alumina powder used here had a substantially uniform particle size and did not contain particles having a particle size corresponding to the fine particle filler. A coupling agent, a curing catalyst, and a cross-linking agent were added to and mixed with the resulting main agent to obtain a silicone adhesive. The proportion of the alloy in the silicone adhesive was 75% by mass. The resulting silicone adhesive was molded into a sheet and partially cured by heating to obtain an adhesive sheet for sample S7.

<Sample S8>
It was produced in the same manner as sample S1, except that the adhesive sheet used was different. The silicone adhesive used to make sample S8 was prepared as follows. That is, alumina powder having an average particle size of 150 μm was added as an inorganic filler to polydimethylsiloxane having a viscosity of 10 Pa·s and mixed to obtain a main agent. The alumina powder used here had a substantially uniform particle size and did not contain particles having a particle size corresponding to the fine particle filler. A coupling agent, a curing catalyst, and a cross-linking agent were added to and mixed with the resulting main agent to obtain a silicone adhesive. The proportion of the alloy in the silicone adhesive was 75% by mass. The resulting silicone adhesive was molded into a sheet and partially cured by heating to obtain an adhesive sheet for sample S8.

Regarding the electrostatic chucks of the manufactured samples S1 to S8, the "maximum height Ry of the unevenness formed on the surface of the heater electrode portion 60", the "equivalent sphere diameter α of the inorganic filler", and the "content ratio of the fine particle filler in the inorganic filler" (% by volume)", "Aspect ratio of inorganic filler", "In the cross section of the adhesive layer, the area ratio of the inorganic filler in the area in contact with the interface with the heater electrode part, and the area including the center in the thickness direction of the adhesive layer Difference from the area ratio of the inorganic filler (hereinafter also referred to as area ratio difference)”, “true density”, and “average particle size” are obtained, and the placement surface when heating is performed using the heater electrode unit 60 24 was evaluated for in-plane temperature distribution (temperature variation).

The "maximum height Ry" was measured by the method described above with reference to FIG. The "equivalent sphere diameter α of the inorganic filler" was obtained by converting the volume of the particles using the results of the particle size distribution analysis of the inorganic filler. The particle size distribution of the inorganic filler was measured using a laser diffraction particle size distribution analyzer (Partica-LA-500, manufactured by Horiba, Ltd.). The "content ratio (% by volume) of the fine particle filler in the inorganic filler" was also determined using the results of the particle size distribution analysis of the inorganic filler described above. As a result of particle size distribution analysis, particles having an equivalent spherical diameter smaller than the maximum height Ry were defined as fine particle fillers, and the content ratio (% by volume) of the fine particle fillers was determined.

As mentioned above, the inorganic filler does not change physically or chemically under the conditions such as temperature and pressure in the manufacturing process of the electrostatic chuck using the inorganic filler. It is considered that the equivalent sphere diameter and volume do not substantially change between the state of being dispersed in the adhesive after production and the state of being dispersed in the adhesive after production. Therefore, the equivalent sphere diameter α of the inorganic filler included in each sample, the content ratio (% by volume) of the fine particle filler in the inorganic filler, and the average particle diameter can be determined by analyzing the particle size distribution of the inorganic filler before it is mixed with the adhesive. It was measured.

As the "aspect ratio of the inorganic filler", the aspect ratio of the fine particle filler and the aspect ratio of the large-diameter filler were determined separately, and the average value of both was determined. To obtain the aspect ratio of the particulate filler, the cross section of the adhesive layer 45 was observed with a scanning electron microscope (SEM) at a magnification of 3000, and a 10 μm×10 μm field of view was cut out as shown in FIG. Then, for 50 fine particle fillers observed in the field of view, the major axis L and the minor axis W were measured, the length ratio L/W was calculated, and the average value of the obtained values was taken as the aspect ratio of the fine particle filler. . To obtain the aspect ratio of the large-diameter filler, the cross section of the adhesive layer 45 was observed with a scanning electron microscope (SEM) at a magnification of 500 to 1000, and a field of view of 200 μm×200 μm was cut out. Then, the major diameter L and minor diameter W of 10 large-diameter fillers observed in the field of view are measured, the length ratio L/W is calculated, and the average value of the obtained values is taken as the aspect ratio of the large-diameter filler. did. In all samples, the aspect ratio of the fine particle filler and the aspect ratio of the large diameter filler were almost the same.

The "area ratio difference" was measured as follows. First, from each sample electrostatic chuck, the adhesive layer 45 was cut out so as to include the portion where the heater electrode portion 60 and the adhesive layer 45 were in contact, and was polished so as to be cross-sectional. Polishing was performed by CP (cross-section polisher) processing using an ion milling method so that the inorganic filler in the adhesive layer 45 would not shed. The adhesive layer 45 of the sample obtained in this way was observed with a scanning electron microscope (SEM). The image was cut out in an area of 200 μm×200 μm. At this time, the heater electrode portion 60 may be in the field of view. From the obtained image, the area occupied by the inorganic filler is Sa, the area occupied by the inorganic filler and the adhesive (the area of the entire cut-out image) is Sb, and "Sa/Sb × 100" is calculated to obtain the inorganic filler. The area ratio occupied by was calculated. Such analyzes were performed using the image processing software ImageJ. After the above analysis, the difference between the area ratio of the inorganic filler obtained for the region in contact with the interface with the heater electrode portion and the area ratio of the inorganic filler obtained for the region including the center in the thickness direction of the adhesive layer is calculated, It was referred to as "area ratio difference".

"True density" was calculated from the material chemical composition of each inorganic filler used. The "average particle size" was obtained using the results of the particle size distribution analysis of the inorganic filler described above.

The temperature variation for evaluating the in-plane temperature distribution is obtained by operating each electrostatic chuck so that the ceramic portion 20 of the electrostatic chuck reaches 150° C., and measuring the temperature of the mounting surface 24 with an infrared radiation thermometer. It was obtained by measuring using The difference between the temperature of the highest temperature location on the mounting surface 24 and the temperature of the lowest temperature location was defined as "temperature variation".

FIG. 17 is an explanatory diagram collectively showing the conditions and evaluation results of each sample. In FIG. 17 , “YES” is written in the “Ry>α” column for samples containing fine particle fillers as part of the inorganic filler among the samples. Samples S5 to S8 do not contain a particulate filler (“Ry>α” is “NO”) and correspond to comparative examples.

As shown in FIG. 17, samples S1 to S4 containing fine particle fillers as part of the inorganic filler have smaller temperature variations than samples S5 to S8 that do not contain fine particle fillers, and have the effect of making the in-plane temperature distribution uniform. was confirmed to be obtained. In addition, among the samples S1 to S4, "the content ratio of the fine particle filler is 1 volume% or more and 30 volume% or less", "the aspect ratio of the fine particle filler or the large diameter filler is 1.5 or less", and "the area ratio difference is 1% or less", "the true density of the inorganic filler is 2.0 g/cm ³ or more and 6.5 g/cm ³ or less", and "the average particle size of the inorganic filler is 200 μm or less" Sample S2 that satisfies at least one condition. ˜S4 have smaller temperature variations than sample S1, which satisfies none of the conditions, and it was confirmed that the effect of making the in-plane temperature distribution uniform is enhanced. In particular, sample S4, which satisfies all of the above conditions, had the smallest temperature variation.

The present disclosure is not limited to the above-described embodiments and the like, and can be implemented in various configurations without departing from the scope of the present disclosure. For example, the technical features in the embodiments corresponding to the technical features in the respective modes described in the Summary of the Invention column may be used to solve some or all of the above problems, or Substitutions and combinations may be made as appropriate to achieve part or all. Also, if the technical features are not described as essential in this specification, they can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10, 110, 210, 310... Electrostatic chuck 20, 220, 320... Ceramic part 21... Upper layer part 22, 322... Lower layer part 23... Chuck electrode 24... Mounting surface 26... Terminal 30... Base part 32... Coolant flow path DESCRIPTION OF SYMBOLS 40... Joining part 41A... Fine particle filler 41B... Large diameter filler 45, 245, 345... Adhesive layer 50... Gas supply path 52... Gas discharge port 60... Heater electrode part 62... Terminal 64... Heater electrode exposure part 240... 1st Joining portions 242, 342... Second joining portion 327... Groove

Claims (10)

A holding device for holding an object,
a ceramic portion that is mainly composed of ceramic and is formed into a plate shape;
a heater electrode portion for heating the ceramic portion;
an adhesive layer formed so as to extend in a plane direction perpendicular to the thickness direction of the ceramic portion, contacting both the ceramic portion and the heater electrode portion, and containing an adhesive and an inorganic filler;
with
The inorganic filler is characterized by containing, as a part of the inorganic filler, a fine particle filler having an equivalent sphere diameter smaller than the maximum height of the unevenness formed on the surface of the heater electrode portion in contact with the adhesive layer. holding device. A holding device according to claim 1, wherein
A holding device, wherein a content ratio of the fine particle filler in the inorganic filler is 1% by volume or more and 30% by volume or less. A holding device according to claim 1 or 2,
A holding device, wherein the fine particle filler has an aspect ratio of 1.5 or less. A holding device according to any one of claims 1 to 3,
The holding device, wherein the aspect ratio of the filler other than the fine particle filler in the inorganic filler is 1.5 or less. A holding device according to any one of claims 1 to 4,
In the cross section of the adhesive layer, the difference between the area ratio of the inorganic filler in the region in contact with the interface with the heater electrode portion and the area ratio of the inorganic filler in the region including the center in the thickness direction of the adhesive layer is A holding device characterized by being 1% or less. A holding device according to any one of claims 1 to 5,
A holding device, wherein the inorganic filler has an average particle size of 200 µm or less. A holding device according to any one of claims 1 to 6,
A holding device, wherein the inorganic filler has a true density of 2.0 g/cm ³ or more and 6.5 g/cm ³ or less. A holding device according to any one of claims 1 to 7, further comprising:
A base portion that includes a metal and is formed into a plate shape,
the adhesive layer is disposed between the ceramic portion and the base portion to bond the ceramic portion and the base portion;
The holding device, wherein at least part of the heater electrode portion is arranged inside the adhesive layer. A holding device according to any one of claims 1 to 7,
The ceramic portion is divided into an upper layer portion having a mounting surface on which an object to be placed of the holding device is placed, and a lower layer portion having the heater electrode portion formed on one surface,
The adhesive layer is arranged between the rear surface of the mounting surface of the upper layer portion and the one surface of the lower layer portion, and bonds the upper layer portion and the lower layer portion. holding device. A holding device according to any one of claims 1 to 7,
The ceramic portion is divided into an upper layer portion having a mounting surface on which an object to be placed of the holding device is placed, and a lower layer portion having the heater electrode portion formed therein,
The heater electrode portion has a heater electrode exposed portion exposed from the ceramic portion,
The adhesive layer is disposed between the upper layer portion and the lower layer portion, joins the upper layer portion and the lower layer portion, and contacts the surface of the heater electrode exposed portion.

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