JP7657072B2 - Electrode-embedding member, its manufacturing method, and substrate holding member - Google Patents

Description

The present invention relates to an electrode-embedded member, a manufacturing method thereof, and a substrate-holding member.

Heater plates (electrode-embedded components) with electrodes (heat generating resistors) embedded in them have been used as components for semiconductor manufacturing equipment. The heater plate can heat the substrate placed on it.

Patent Document 1 discloses a ceramic heater that includes a ceramic base provided with a heating surface that supports and heats the workpiece, a heating element embedded within the base, and an embossed portion on the heating surface that comes into contact with the workpiece, and that aims to prevent adverse effects on the workpiece from heat spots on the heating surface, and that when the average temperature of the heating surface is raised to a target temperature, there are heat spots on the heating surface where the surface temperature is relatively high, and the number of embossed portions per unit area in the heat spots is smaller than the number of embossed portions per unit area in areas other than the heat spots.

Patent document 2 discloses a hot plate and electrostatic chuck with a holding surface flatness of 1 to 50 μm. It describes how the unevenness of the wafer temperature is caused by surface undulations, and how this is kept within a specified range; how ALN is preferable for the ceramic; how when used as a chuck, the variation in the distance between the wafer and the electrode is reduced, providing sufficient chucking force; and how the undulations are convex.

JP 2002-124367 A International Publication WO 01/13423 A1

Electrode-embedded components such as electrostatic chucks with built-in heaters and ceramic heaters can have abnormal heating points (hot spots). Due to the need for process uniformity in semiconductor processes, there has been a demand for electrode-embedded components that do not cause hot spots.

In Patent Document 1, hot spots (heat spots) are identified in advance and the number of embossed portions per unit area in the hot spots is reduced to reduce their impact, but no consideration is given to reducing the occurrence of localized hot spots. Furthermore, although Patent Document 2 describes application to electrostatic chucks, there is no mention of protruding portions, and no mention of localized hot spots.

The present invention was made in consideration of these circumstances, and aims to provide an electrode embedding member and a substrate holding member that can reduce the occurrence of localized hot spots, suppress particle entrapment, and, if necessary, allow the space under the substrate to serve as a gas flow path.

(1) In order to achieve the above object, the electrode embedding member of the present invention is an electrode embedding member comprising a base formed of a ceramic sintered body, an electrode embedded in the base, and a plurality of pin-shaped protrusions formed by protruding upward from the upper surface of the base, and the cross-sectional curve obtained by cutting the mounting curved surface formed by the upper ends of the plurality of pin-shaped protrusions at a cross section passing through the central axis of the base as the Z axis, is a curve that has a maximum Z value near the central axis and monotonically decreases toward the outer periphery of the base, or a curve that has a minimum Z value near the central axis and monotonically increases toward the outer periphery of the base, when the intersection line between a predetermined reference plane and the cross section is the X axis.

In this way, by having the cross-sectional curve of the mounting surface be a curve that has a maximum Z value near the central axis and monotonically decreases toward the periphery of the base, or a curve that has a minimum Z value near the central axis and monotonically increases toward the periphery of the base, the substrate can better conform to the pin-shaped protrusions than by increasing the flatness of the mounting surface to make it closer to a plane, thereby reducing the occurrence of localized hot spots. In addition, because the substrate is supported by the pin-shaped protrusions, particle entrapment can be suppressed, and the space below the substrate can be used as a gas flow path if necessary.

(2) In addition to the characteristic feature of (1) , the electrode-embedded member of the present invention is characterized in that the cross-sectional curve satisfies ΔZ(X) max - ΔZ(X) min ≦1 (μm), where L (mm) is a reference length in the X-axis direction, Z(X) is a value of Z (mm) for a certain X (mm), and ΔZ(X) = Z(X) _- ((Z(X + L) + Z(X - L))/2), where ΔZ(X) _is the _maximum value of ΔZ(X) and ΔZ(X) is the _minimum value of ΔZ(X).

This helps to reduce localized unevenness, further reducing the occurrence of localized hot spots.

(3) The electrode-embedded member of the present invention is also characterized in that the flatness of the curved surface is 50 μm or less.

This allows the substrate to be placed without wrinkling.

(4) In addition to the feature of (1) , an electrode-embedded member according to another aspect of the present invention is characterized in that, when a curve obtained by cutting the aforementioned placement surface at a second cross section perpendicular to the X-axis and including the Z-axis is defined as a second cross-sectional curve, and an intersection line between the predetermined reference plane and the second cross section is defined as a Y-axis, a coefficient of determination R2 for a first approximation equation when the cross-sectional curve is approximated by a quadratic curve, and a coefficient of determination R2 for a second approximation equation when the second cross-sectional curve is approximated by a quadratic curve are both 0.99 or more.

This allows the cross-sectional curves in the X-axis and Y-axis directions to have a quadratic curve shape, suppressing localized and irregular changes in the height direction of the cross-sectional curve, further reducing the occurrence of localized hot spots.

(5) Furthermore, the electrode-embedded member of the present invention is characterized in that, when the quadratic coefficient of the first approximation formula is a(X) and the quadratic coefficient of the second approximation formula is a(Y), the relationship 2(a(X)-a(Y))/(a(X)+a(Y))≦0.1 is satisfied.

This creates a curved surface that is highly symmetrical with respect to the Z axis, and suppresses localized and irregular changes in the height direction of the cross-sectional curve over the entire surface, thereby preventing the occurrence of hot spots.

(6) Furthermore, in the electrode-embedded member of the present invention, when the quadratic coefficient of the first approximation formula is a(X) and the quadratic coefficient of the second approximation formula is a(Y), the absolute values of a(X) and a(Y) are 4× ^10-4 or more.

This makes it easier to control the temperature distribution and suppresses the occurrence of hot spots when the electrode-embedded member is used as a two-zone heater in which the electrodes can be controlled separately on the inside and outside of the substrate.

(7) The substrate holding member of the present invention is characterized by comprising an electrode-embedded member according to any one of (1) to (6) above, and a support member joined to the underside of the electrode-embedded member and supporting the electrode-embedded member.

This makes it possible to construct a substrate holding member using an electrode-embedded member that can reduce the occurrence of localized hot spots.

(8) The method for manufacturing an electrode-embedded member of the present invention is characterized in that it includes the steps of: preparing a ceramic base having an electrode embedded therein and having a plurality of pin-shaped protrusions formed on one of its main surfaces; placing or adsorbing a substrate on the pin-shaped protrusions and measuring the curved shape of the surface with a laser interferometer; polishing or grinding the pin-shaped protrusions so that the curved shape becomes a predetermined convex or concave shape that is approximately symmetrical about a central axis; and placing or adsorbing a substrate on the pin-shaped protrusions after polishing or grinding, measuring the curved shape of the surface with a laser interferometer, and verifying that the curved shape becomes the predetermined convex or concave shape.

In this way, by polishing or grinding the multiple pin-shaped protrusions so that the curved shape when the substrate is placed on it has a predetermined convex or concave shape, the substrate can better conform to the pin-shaped protrusions than if the curved shape was made more flat to make it closer to a plane, making it possible to manufacture an electrode-embedded member that can reduce the occurrence of localized hot spots.

(9) The present invention also provides a method for producing an electrode-embedded member, comprising the steps of:
a step of preparing a ceramic base having an electrode embedded therein and a plurality of pin-shaped protrusions formed on one of its principal surfaces; a step of placing or sucking a substrate on the plurality of pin-shaped protrusions and measuring the curved shape of the surface with a laser interferometer; a step of cutting the measured curved shape at a cross section passing through the Z axis with the central axis as the Z axis, a line of intersection between a predetermined reference plane and the cross section is defined as the X axis, a reference length in the X-axis direction is defined as L (mm), a value of Z (mm) for a certain X (mm) is defined as Z(X), and a value of deviation ΔZ(X) is defined as ΔZ(X)=Z(X)-((Z(X+L)+Z(X-L))/2), where ΔZ(X) is the maximum value of ΔZ(X) _max and ΔZ(X) is the _{minimum value} of ΔZ(X) _min, The method is characterized by including the steps of: polishing or grinding the plurality of pin-shaped protrusions so as to satisfy the relationship ≦1 (μm); and placing or adsorbing a substrate on the plurality of pin-shaped protrusions after polishing or grinding, measuring the curved shape of the surface with a laser interferometer, and verifying that the curved shape satisfies the specified relationship.

In this way, by polishing or grinding the multiple pin-shaped protrusions so that the curved shape when the substrate is placed on it satisfies a specified relationship, the substrate can better conform to the pin-shaped protrusions than if the curved shape was made more flat to make it closer to a plane, and an electrode-embedded member can be manufactured that can reduce the occurrence of localized hot spots.

The present invention can reduce the occurrence of localized hot spots. In addition, because the substrate is supported by pin-shaped protrusions, particle entrapment can be suppressed, and the space below the substrate can be used as a gas flow path if necessary.

1 is a schematic cross-sectional view showing an example of an electrode-embedded member according to a first embodiment of the present invention. 3 is a schematic diagram showing an example of an upper surface of an electrode-embedded member according to the first embodiment; FIG. 2 is a schematic partial cross-sectional view showing an example of an electrode-embedded member according to the first embodiment. FIG. FIG. 4 is a schematic partial cross-sectional view for determining a deviation ΔZ(X) at a certain point X in the example of FIG. 3 . 5A to 5C are schematic diagrams showing modified examples of the upper surface of the electrode-embedded member according to the first embodiment. 5 is a schematic partial cross-sectional view showing a modified example of an electrode-embedded member according to the first embodiment. FIG. 5 is a schematic partial cross-sectional view showing a modified example of an electrode-embedded member according to the first embodiment. FIG. 5 is a schematic partial cross-sectional view showing a modified example of an electrode-embedded member according to the first embodiment. FIG. 1 is a schematic cross-sectional view showing an example of a substrate holding member according to a first embodiment. FIG. 6 is a schematic cross-sectional view showing an example of an electrode-embedded member according to a second embodiment of the present invention. 6A and 6B are graphs showing the measurement results in the X-axis direction and the Y-axis direction of the substrate surface of the substrate holding member of Example 1, respectively. 6A and 6B are graphs showing the measurement results in the X-axis direction and the Y-axis direction of the substrate surface of the substrate holding member of Comparative Example 1, respectively. 13A and 13B are graphs showing the deviation ΔZ(X) values for cross-sectional curves in the X-axis direction of Example 1 and Comparative Example 1, respectively. 6A and 6B are graphs showing the temperature distributions of the substrates of Example 1 and Comparative Example 1, respectively. FIG. 11 is a schematic cross-sectional view showing a substrate holding member according to a conventional example.

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.

[First embodiment]
(Configuration of electrode-embedded member)
An electrode-embedded member according to a first embodiment of the present invention will be described with reference to Figs. 1 to 4. Fig. 1 is a schematic cross-sectional view showing an example of an electrode-embedded member according to the first embodiment of the present invention. Fig. 2 is a schematic view showing an example of the upper surface of an electrode-embedded member according to the first embodiment. Fig. 3 is a schematic partial cross-sectional view showing an example of an electrode-embedded member according to the first embodiment. Fig. 4 is a schematic partial cross-sectional view for determining a deviation ΔZ(X) at a certain X in the example of Fig. 3. In the partial cross-sectional view, the terminal 50 and the terminal hole 52 are omitted. The electrode-embedded member 100 according to this embodiment includes a base 10, an electrode 20, and a pin-shaped protrusion 30.

The base 10 is made of a sintered ceramic body and is formed into a generally flat plate shape. The base 10 may be generally disc-shaped or may have various other shapes such as a polygonal plate or an elliptical plate. Note that a generally flat plate shape includes a convex shape or a concave shape, which will be described later. The base 10 has a shape in which the center 16 of the base is naturally determined.

The electrode 20 is embedded in the base 10. The electrode 20 is used as a heater electrode for heating the substrate (wafer) W. Electrodes used for other purposes, such as an electrostatic adsorption electrode or a high-frequency electrode, may also be embedded.

A plurality of pin-shaped protrusions 30 are formed protruding upward from the upper surface 12 of the base 10. The shape of the pin-shaped protrusions 30 is appropriately selected from among cylindrical shapes such as a cylindrical column, a rectangular column, a cone shape such as a cone, a truncated cone, a truncated pyramid, and a shape with the top of the cone cut off, etc.

The arrangement of the pin-shaped protrusions 30 is not particularly limited. They may be of a known form or a similar form, and may be arranged in a regular manner, such as concentric circles as shown in FIG. 2, a square lattice as shown in FIG. 5, or a triangular lattice, or may be arranged irregularly with localized sparseness and density. FIG. 5 is a schematic diagram showing a modified example of the upper surface of the electrode-embedded member according to the first embodiment.

The upper ends 32 of the pin-shaped protrusions as a whole form a curved surface (curved mounting surface) of a predetermined shape on which the substrate W is placed. As a result, the pin-shaped protrusions 30 support the substrate W. That is, the curved mounting surface formed by the upper ends 32 of the pin-shaped protrusions is determined. As a result, the upper ends 32 of the pin-shaped protrusions come into contact with the substrate W, and the substrate W is supported. Note that some of the pin-shaped protrusions 30 may not have their upper ends in contact with the substrate W. This is because, even if such protrusions exist, the substrate W can be supported depending on the arrangement of the surrounding pin-shaped protrusions 30. Note that in FIG. 3, the entire upper end 32 of the pin-shaped protrusions comes into contact with the substrate W, but only a portion of the upper end 32 of the pin-shaped protrusions may come into contact with the substrate W.

When the central axis of the base 10 (a straight line passing through the center 16 of the base and perpendicular to the reference plane of the base 10) is taken as the Z axis and the cross-sectional curve 42 is cut on the mounting curved surface formed by the upper ends 32 of the multiple pin-shaped protrusions, the cross-sectional curve 42 is a curve that has a maximum value of Z near the central axis and monotonically decreases toward the outer periphery 18 of the base 10 as shown in FIG. 3, or a curve that has a minimum value of Z near the central axis and monotonically increases toward the outer periphery 18 of the base 10 as shown in FIG. 6, when the intersection line between the predetermined reference plane and the cross-section is taken as the X axis. FIG. 6 is a partial cross-sectional view showing a modified example of the electrode-embedded member according to the first embodiment.

The predetermined reference plane may be the upper surface 12 of the base 10 when the upper surface 12 is horizontal when the base 10 is placed on a horizontal surface as shown in FIG. 3 or FIG. 6, or may be a horizontal plane passing through a point on the upper surface 12 of the base 10 that is closest to the horizontal surface when the upper surface 12 is not horizontal when the base 10 is placed on a horizontal surface as shown in FIG. 7 or FIG. 8. The reference plane may also be a plane obtained by translating these horizontal planes upward or downward. FIGS. 7 and 8 are partial cross-sectional views showing modified examples of the electrode-embedded member according to the first embodiment. The vicinity of the central axis refers to a range within 25 mm from the central axis.

In this way, by having the cross-sectional curve 42 of the mounting surface be a curve that has a maximum Z value near the central axis and monotonically decreases toward the outer periphery 18 of the base 10, or a curve that has a minimum Z value near the central axis and monotonically increases toward the outer periphery 18 of the base 10, the substrate W can better conform to the pin-shaped protrusions 30 than by increasing the flatness of the mounting surface to make it closer to a plane, thereby reducing the occurrence of localized hot spots. In addition, because the substrate W is supported by the pin-shaped protrusions 30, particle entrapment can be suppressed, and the space below the substrate W can be used as a gas flow path if necessary.

As shown in FIG. 3, the base 10 and the multiple pin-shaped protrusions 30 are preferably formed such that the base 10 is flat and the multiple pin-shaped protrusions 30 are formed at different heights from the reference plane, and the multiple pin-shaped protrusions 30 form a mounting curved surface. This makes it easier to process the mounting curved surface, and one of the multiple mounting curved surface shapes can be selected when grinding and polishing the pin-shaped protrusions 30.

On the other hand, the shape of the base 10 and the multiple pin-shaped protrusions 30 may be such that the upper surface 12 of the base 10 is formed with substantially the same curved surface as the curved mounting surface, as shown in FIG. 7, and the curved mounting surface is formed by multiple pin-shaped protrusions 30 formed at substantially the same height from the upper surface 12 of the base 10. This makes it possible to make the suction force uniform when the electrode-embedded member 100 is used as a member that adsorbs the substrate W. Note that even with the shape of FIG. 3, the difference in height of the protrusions 30 in the Z-axis direction is slight, so there is no effect on the suction force of the substrate W itself.

The shape of the base 10 may be such that the bottom surface 14 of the base 10 is formed with approximately the same curved surface as the curved surface on which it is placed, as shown in FIG. 8. The electrode 20 embedded in the base 10 may be formed with approximately the same curved surface as the curved surface on which it is placed, as shown in FIG. 8. Therefore, the base 10 being approximately flat includes not only the convex shape shown in FIG. 3 or FIG. 6, but also the convex shape shown in FIG. 7 or FIG. 8, or the concave shape not shown.

The curved placement surface can be measured with a three-dimensional measuring device. However, it is important that when the substrate W is placed or adsorbed on the electrode-embedded member 100, the substrate W conforms to the curved placement surface, and that the shape of the surface of the substrate W opposite the curved placement surface (the surface of the substrate W) is an ideal curved surface. For this reason, the curved surface measured by a laser interferometer on the surface opposite the curved placement surface when a silicon wafer with a thickness of 0.775 mm is placed or adsorbed is regarded as the curved placement surface. The same applies to the cross-sectional curve 42.

As shown in FIG. 4, the cross-sectional curve 42 preferably satisfies ΔZ(X) max - ΔZ(X) min ≦1 (μm), and more preferably satisfies ΔZ(X) max - ΔZ(X) min ≦1 (μm), where L (mm) is the reference length in the X-axis direction, Z(X) is the value of Z (mm) for a certain X (mm), and ΔZ(X) = Z(X) _{- (} (Z(X + _L ) + Z(X - L)) / 2), and the maximum value of ΔZ(X) is ΔZ(X) _max and the minimum value of ΔZ(X) is ΔZ(X) _min . Here, X is defined in a region at least L inward from the outer edge of the region where the electrode-embedded member is placed on the substrate, and is preferably calculated in a region 2L inward from the outer edge of the region. This suppresses localized unevenness, and thus the occurrence of localized hot spots can be further reduced. FIG. 4 is a schematic partial cross-sectional view for determining the deviation ΔZ(X) at a certain X in the example of FIG. 3. The reference length L may be the arrangement pitch of the pin-shaped protrusions 30. For example, when the pin-shaped protrusions 30 are arranged in a concentric circle, the difference in the radii of the concentric circles may be applied. When a plurality of pin-shaped protrusions 30 are arranged at regular intervals, the reference length L is preferably set to the interval. Fig. 6 shows such an example.

The flatness of the curved support surface is preferably 50 μm or less. This allows the substrate W to be supported without wrinkling. The flatness of the curved support surface is the difference between the maximum and minimum Z values for all points on the curved support surface. The lower limit of the flatness varies depending on the diameter of the substrate 10 and the shape of the target curved support surface, but is preferably 5 μm or more, for example.

In addition, when the curve obtained by cutting the placement surface at a second cross section perpendicular to the X-axis and including the Z-axis is the second cross section, and the intersection line between a predetermined reference plane and the second cross section is the Y-axis, it is preferable that the coefficient of determination R ² for the first approximation formula when the cross section curve is approximated by a quadratic curve and the coefficient of determination R 2 for the second approximation formula when the second cross section curve is approximated by a ^quadratic curve are both 0.99 or more. This allows the cross section curves in the X-axis and Y-axis directions to have a quadratic curve shape, and local and irregular changes in the height direction of the cross section curve can be suppressed, thereby further reducing the occurrence of local hot spots. Note that the coefficient of determination R ² can be calculated by dividing the regression sum of squares by the total sum of squares. The regression sum of squares is the sum of squares of the deviations of the predicted values of the objective variable, and the total sum of squares is the sum of squares of the deviations of the observed values of the objective variable.

In addition, when the units of Z are μm, X and Y are mm, the quadratic coefficient of the first approximation equation is a(X), and the quadratic coefficient of the second approximation equation is a(Y), it is preferable that 2(a(X) - a(Y))/(a(X) + a(Y))≦0.1 is satisfied. This forms a curved surface with good symmetry with respect to the Z axis, and localized and irregular changes in the height direction of the cross-sectional curve can be suppressed over the entire surface, thereby suppressing the occurrence of hot spots. Note that a(X) and a(Y) have the same positive and negative values.

The height of the pin-shaped protrusion 30 is preferably 50 μm or more and 500 μm or less. The height of the pin-shaped protrusion 30 refers to the distance from the reference surface of the base 10 to the upper end 32 of the pin-shaped protrusion. The upper end 32 of the pin-shaped protrusion is preferably a flat surface of a predetermined size. In this case, the maximum diameter of the flat surface of the upper end 32 of the pin-shaped protrusion is preferably 100 μm or more and 300 μm or less. The surface roughness of the flat surface of the upper end 32 of the pin-shaped protrusion is preferably Ra 0.01 μm or more and 0.50 μm or less.

The electrode-embedded member 100 may also be provided with a terminal 50, a terminal hole 52, a lift pin hole (not shown), and, if used as a vacuum chuck, a vent hole for that purpose, an annular protrusion, etc.

(Configuration of the substrate holding member)
Next, the configuration of the substrate holding member according to the first embodiment will be described. Fig. 9 is a cross-sectional view showing an example of the substrate holding member according to this embodiment. The substrate holding member 150 according to this embodiment includes an electrode embedding member 100 and a support member 110. The basic configuration of the electrode embedding member 100 is as described above.

The support member 110 is made of a ceramic sintered body and supports the electrode-embedded member 100. This allows the substrate holding member 150 to be used in a heater with a shaft, an electrostatic chuck with a shaft, and the like. The support member 110 is joined to a predetermined position on the underside of the electrode-embedded member 100 via a joining surface 112. The joining may be solid-state joining or joining using a joining material. The support member 110 is preferably formed of a ceramic sintered body having the same main component as the base 10 of the electrode-embedded member 100.

Second Embodiment
10 is a cross-sectional view showing an example of an electrode-embedded member according to a second embodiment of the present invention. The electrode-embedded member 200 according to this embodiment has a basic configuration similar to that of the electrode-embedded member 100 according to the first embodiment, and therefore only the differences will be described below.

The electrode-embedded member 200 according to this embodiment is a so-called two-zone heater in which different inner electrodes 22 and outer electrodes 24 are embedded in two regions: an inner region including at least the center 16 of the base body, and an outer region on the top surface 12 of the base body 10 excluding the inner region, and the electrodes can be controlled for each region. The number of regions may be three or more.

In this case, when the unit of Z is μm, and the unit of X and Y is mm, the second-order coefficient of the first approximation formula described in the first embodiment is a(X), and the second-order coefficient of the second approximation formula is a(Y), the absolute values of a(X) and a(Y) are preferably 4×10 ⁻⁴ or more. This makes it easier to control the temperature distribution and suppress the occurrence of hot spots when the electrode-embedded member 200 is applied as a two-zone heater in which the electrodes can be controlled separately inside and outside the base. The upper limit of the absolute values of a(X) and a(Y) varies depending on the diameter of the base 10 and the target flatness, but is preferably 2.2×10 ⁻³ or less, for example.

(Configuration of the substrate holding member)
Next, the configuration of the substrate holding member according to the second embodiment will be described. The substrate holding member according to this embodiment has the same configuration as the substrate holding member according to the first embodiment, except that the electrode-embedded member joined to the support member is the above-mentioned two-zone heater. Therefore, the description will be omitted.

[Method of manufacturing electrode-embedded member]
Next, a method for manufacturing the electrode-embedded member according to the first and second embodiments will be described. The electrode-embedded member according to the embodiment is manufactured, for example, by a powder hot pressing method. The powder hot pressing method is a method in which ceramic raw material powder and a predetermined electrode are alternately stacked to embed the electrodes inside the ceramic, and then uniaxial hot pressing and firing the resulting material. By employing the powder hot pressing method, the member can be manufactured in a short period of time. Note that the manufacturing method is not limited to this method, and may be, for example, a molded body hot pressing method disclosed in Japanese Patent No. 6148845, a conventional green sheet lamination method, or the like.

For example, ceramic powder is mixed with additives such as sintering aids, binders, plasticizers, and dispersants to produce ceramic raw material powder (slurry), and the powder is granulated by a spray-drying method or the like. The mixing method may be either wet or dry, and a mixer such as a ball mill or a vibration mill may be used. Examples of ceramic powder that can be used as raw material include silicon carbide, aluminum oxide, aluminum nitride, and silicon nitride.

The ceramic powder is preferably of high purity, preferably 96% or more, more preferably 98% or more. The average particle size of the ceramic powder varies depending on the type of ceramic powder used as the raw material, but is preferably 0.1 μm or more and 1.0 μm or less, and more preferably 0.3 μm or more and 0.8 μm or less.

The material of the electrodes embedded in the ceramic sintered body is preferably Mo or W.

For sintering, uniaxial hot press sintering or atmospheric sintering can be used. In uniaxial hot press sintering, a bottomed carbon mold is filled with granulated powder that will form the base, and after uniaxial pressing, an electrode cut to a specified shape is placed on the compact. The same granulated powder is filled on top of it, a carbon punch is placed on top of it, and after molding, it is preferably hot press sintered at a temperature of 1700°C to 2000°C and a pressure of 1 MPa to 20 MPa for 0.1 hours to 20 hours.

After firing, multiple pin-shaped protrusions are formed, the back surface is processed, terminal holes are formed, and grinding and polishing are performed to the specified shape. Forming methods include blasting, milling, laser processing, etc. If necessary, ventilation holes, annular protrusions, etc. may be formed. This makes it possible to prepare a ceramic base with electrodes embedded inside and multiple pin-shaped protrusions formed on one main surface.

Next, a substrate W is placed or sucked onto the multiple pin-shaped protrusions, and the curved shape of the surface (mounted curved shape) is measured by a laser interferometer. If the measurement shows that the curved shape is a predetermined convex or concave shape that is approximately symmetrical about the central axis, processing is terminated. If the measurement shows that the curved shape is not a predetermined convex or concave shape that is approximately symmetrical about the central axis, the multiple pin-shaped protrusions are polished or ground so that the curved shape becomes a predetermined convex or concave shape that is approximately symmetrical about the central axis. Then, a substrate is placed or sucked onto the multiple pin-shaped protrusions after polishing or grinding, and the curved shape of the surface is measured by a laser interferometer to confirm that the curved shape is the predetermined convex or concave shape. By repeating these steps, the curved shape is processed into the desired shape. A curved surface shape being a predetermined convex or concave shape that is approximately symmetrical about the central axis means that any cross-sectional curve of the measured curved surface shape is a curve that has a maximum Z value near the central axis and monotonically decreases toward the periphery of the base, or a curve that has a minimum Z value near the central axis and monotonically increases toward the periphery of the base.

The target curved shape when the substrate W is placed or sucked onto the multiple pin-shaped protrusions and the curved shape of the surface (mounted curved shape) is measured by a laser interferometer may be a shape that satisfies ΔZ(X) max - ΔZ(X) min ≦ 1 (μm) for a cross-sectional curve cut at a cross section passing through the Z axis with the central axis as the Z axis, where the intersection line between a predetermined reference plane and the cross section is the X axis, the reference length in the X-axis direction is L (mm), the value of Z (mm) for a certain X (mm) is Z(X), the value of deviation ΔZ(X) is ΔZ(X) = Z(X) _- ((Z(X + L) ₊ Z(X - L)) / 2), the maximum value of ΔZ(X) is ΔZ(X) _max and the minimum value of ΔZ(X) is ΔZ(X) _min . In this case, the step of polishing or grinding the multiple pin-shaped protrusions is also performed with that shape as a target. Also, a shape that includes both features or other features may be targeted.

Finally, the terminals are connected to the terminal holes using solder or similar material. The terminals can be made of Ni or similar material. The solder can be made of Au or similar material.

In this way, the electrode-embedded member according to the embodiment of the present invention can be manufactured.

[Method of manufacturing the substrate holding member]
The ceramic powder is granulated to form a ceramic molded body that will become the support member after firing. The ceramic powder preferably has the same main component as the ceramic powder used in the electrode-embedded member.

Next, the ceramic molded body is degreased at a predetermined temperature or higher for a predetermined time or longer to produce a ceramic degreased body. For example, it is heat treated at a temperature of 400°C or higher and 800°C or lower to produce a ceramic degreased body. The degreasing time is preferably 1 hour or longer and 120 hours or shorter. For degreasing, an atmospheric furnace or a nitrogen atmosphere furnace can be used, but an atmospheric furnace is preferred.

Next, the ceramic degreased body is fired to fire the support member that supports the electrode-embedded member. The firing of the support member is preferably performed at normal pressure. The firing temperature is preferably 1500°C or higher and 2000°C or lower. The firing time is preferably 1 hour or higher and 12 hours or lower. The firing atmosphere is, for example, a nitrogen or inert gas atmosphere, but may also be a vacuum atmosphere.

Then, a support member is placed at a predetermined position on the underside of the electrode-embedded member, and the electrode-embedded member and the support member are joined by applying pressure perpendicular to the joining surface while heating. The pressure is preferably 1 MPa or more. The heating temperature is preferably 1500°C or more and 2000°C or less. The heating time is preferably 0.5 hours or more and 5 hours or less. The heating atmosphere is, for example, a nitrogen or inert gas atmosphere, but may also be a vacuum atmosphere. This results in a solid-state bond between the substrate holding member body and the support member. The joining means is not limited to solid-state bonding, and may also be a means that involves an inorganic bonding material.

It is preferable to perform the formation of the pin-shaped protrusions of the electrode-embedded member, polishing or grinding the pin-shaped protrusions, brazing the terminals, etc. after joining the electrode-embedded member and the support member.

In this way, it is possible to manufacture a substrate holding member according to an embodiment of the present invention in which an electrode-embedded member and a support member are joined.

[Examples and Comparative Examples]
Example 1
Example 1 is a substrate holding member having a convex curved mounting surface as shown in FIG. 9. The material of the base and the support member is a sintered body mainly composed of aluminum nitride (AlN). A base (electrode-embedded member) in which a substantially disk-shaped electrode having a diameter of φ300 mm and a thickness of t25 mm is embedded and a support member are prepared, and after joining with the support member, multiple pin-shaped protrusions are formed by blasting. The multiple pin-shaped protrusions are formed in a concentric shape of φ1 mm in an area within φ298 mm from the center of the base, with a height of 50 μm from the reference plane.

Then, the pin-shaped protrusions were polished to create a convex mounting surface. Starting from the outer periphery of the pin-shaped protrusions, the protrusions were polished with loose abrasive grains, and the height was reduced by a maximum of about 10 μm, creating a convex mounting surface. The surface roughness Ra of the multiple pin-shaped protrusions was set to 0.05 μm.

In other words, the substrate holding member of Example 1 is a substrate holding member that has been processed so that the cross-sectional curve obtained by cutting the curved mounting surface formed by the upper ends of the pin-shaped convex portions at a cross section passing through the central axis of the base body, with the Z axis being the Z axis, is a curve that has a maximum Z value near the central axis and monotonically decreases toward the outer periphery of the base body when the intersection line between the cross section and a predetermined reference plane is the X axis.

(Comparative Example 1)
Comparative Example 1 is a conventional substrate holding member having a flat curved mounting surface as shown in Fig. 15. The substrate holding member was produced under the same conditions as in Example 1, and the polishing of the pin-shaped convex portion was adjusted to increase the flatness of the curved mounting surface (mounting plane). Fig. 15 is a schematic cross-sectional view showing the conventional substrate holding member.

(Method of measuring the curved surface)
The surface (surface of the substrate) opposite to the curved surface when a substrate (silicon wafer) having a diameter of 300 mm and a thickness of 0.775 mm was placed on the substrate holding member obtained in Example 1 and Comparative Example 1 was measured by a laser interferometer. Figures 11(a) and (b) are graphs showing the measurement results in the X-axis direction and the Y-axis direction of the substrate surface of the substrate holding member of Example 1, respectively. Also, Figures 12(a) and (b) are graphs showing the measurement results in the X-axis direction and the Y-axis direction of the substrate surface of the substrate holding member of Comparative Example 1, respectively. Note that the predetermined reference plane in the examples and comparative examples is the predetermined reference plane in Figure 1 translated upward. Therefore, there is a range in which the value of Z is negative. These graphs can be interpreted as showing the cross-sectional curves in the X-axis direction and the Y-axis direction of the curved surface of the substrate holding member of Example 1 and Comparative Example 1, respectively.

The flatness of the curved mounting surface in Example 1 was 10 μm, while the flatness of the curved mounting surface in Comparative Example 1 was 3.5 μm. On the other hand, as can be seen by comparing the graphs in FIG. 11 and FIG. 12, Example 1 had a greater flatness than Comparative Example 1, but the local unevenness was smaller. This is thought to be because, when processing is performed with the aim of reducing the overall flatness as in Comparative Example 1, the parts with poor flatness are polished intensively, and the boundary between the parts that have been polished intensively and the parts that have not been polished much is not polished any further as long as it is within a specified range. It is also presumed that further polishing to reduce the unevenness at this boundary would result in a worsening of the overall flatness.

On the other hand, when machining is performed with the aim of smoothing the mounting surface to a convex or concave shape, without placing emphasis on overall flatness, as in the present invention, polishing is performed continuously from the outer circumference to the inner circumference or from the inner circumference to the outer circumference, so it is thought that there is almost no boundary between the areas that have been polished intensively and the areas that have not been polished much.

Figures 13(a) and (b) are graphs showing the deviation ΔZ(X) values for the cross-sectional curves in the X-axis direction of Example 1 and Comparative Example 1, respectively. Each shows values calculated in the range of -139.5 (mm) ≦ X ≦ 139.5 (mm) with the reference length in the X-axis direction being L = 9.5 mm, the value of Z (mm) for a certain X (mm) being Z(X), and the value of deviation ΔZ(X) being ΔZ(X) = Z(X) - ((Z(X + L) + Z(X - L))/2).

According to this graph, it was found that the deviation ΔZ(X), which indicates local unevenness, was smaller in Example 1 than in Comparative Example 1. In addition, when the maximum value of ΔZ(X) is ΔZ(X) _max and the minimum value of ΔZ(X) is ΔZ(X) _min , it was confirmed that Example 1 satisfied ΔZ(X) _max - ΔZ(X) _min ≦1 (μm), but Comparative Example 1 did not.

(Evaluation Method)
The substrate was placed on the substrate holding member of Example 1 and Comparative Example 1, and a voltage was applied to the internal electrode to set the temperature of the center of the substrate to 400°C and control the temperature. At this time, the temperature distribution of the substrate was measured along the X-axis using an infrared camera. Figures 14(a) and (b) are graphs showing the temperature distribution of the substrate of Example 1 and Comparative Example 1, respectively. When the graphs show a peak-shaped portion, it was determined that a hot spot occurred according to the size of the peak. The graph of Figure 14 shows the temperature distribution in the range of -100 mm to +100 mm. This is because the influence of scattering, etc. is large in the outer periphery, which is far from the infrared camera, and the deviation between the measured temperature of the infrared camera and the actual temperature may become large.

(Evaluation Results)
A relatively small peak was observed near the center in Example 1. On the other hand, a large hot spot occurred near the center in Comparative Example 1. In other words, it was confirmed that the substrate holding member of the present invention suppresses the occurrence of hot spots.

Next, the approximation formulas were calculated when the cross-sectional curves of Example 1 and Comparative Example 1 were approximated by a quadratic curve when the unit of Z was μm, and the units of X and Y were mm. The first approximation formula when the cross-sectional curve in the X-axis direction of the example was approximated by a quadratic curve was Z = (4.598E-04) X ² + (2.416E-03) X - (3.403E + 00), and the coefficient of determination R ² for this was 0.9983. The second approximation formula when the cross-sectional curve in the Y-axis direction (second cross-sectional curve) was approximated by a quadratic curve was Z = (4.453E-04) Y ² - (1.526E-03) Y + (3.296E + 00), and the coefficient of determination R ² for this was 0.9972. That is, it was confirmed that the coefficient of determination R ² of each of the examples was 0.99 or more.

On the other hand, the first approximation equation when the cross-sectional curve in the X-axis direction of Comparative Example 1 was approximated by a quadratic curve was Z = (9.232E-05) ^X2 + (2.354E-04)X-(6.858E-01), and the coefficient of determination ^R2 for this was 0.8910. Also, the second approximation equation when the cross-sectional curve in the Y-axis direction (second cross-sectional curve) was approximated by a quadratic curve was Z = (1.146E-04) ^Y2 + (3.055E-04)Y-(8.462E-01), and the coefficient of determination ^R2 for this was 0.8715. That is, the coefficients of determination ^R2 for Comparative Example 1 were all below 0.99.

In addition, for Example 1, when the quadratic coefficient of the first approximation equation is a(X) and the quadratic coefficient of the second approximation equation is a(Y), it was confirmed that 2(a(X)-a(Y))/(a(X)+a(Y))≦0.1. This confirmed that the substrate holding member of the example has a curved surface that is symmetrical with respect to the Z axis. With this characteristic, it is believed that localized and irregular changes in the height direction of the cross-sectional curve can be suppressed over the entire surface, thereby suppressing the occurrence of hot spots.

Moreover, the absolute values of a(X) and a(Y) in Example 1 were 4×10 ⁻⁴ or more, whereas those in Comparative Example 1 were less than 4×10 ⁻⁴ .

Example 2
In Example 2, a substrate holding member was produced under the same conditions as in Example 1, except that the electrodes of the electrode-embedded member of Example 1 were a circular inner electrode having a diameter of 200 mm or less and a donut-shaped outer electrode having a diameter of 200 mm or more and 298 mm or less, forming a two-zone heater in which each electrode could be controlled separately.

(Comparative Example 2)
In Comparative Example 2, a substrate holding member was produced under the same conditions as in Comparative Example 1, except that the electrodes of the electrode-embedded member in Comparative Example 1 were replaced with two-zone heaters similar to those in Example 2.

In Example 2, by separately controlling the inner electrode and the outer electrode, it was possible to control the temperature distribution so that the surface temperature of the substrate gradually decreased from the inside to the outside of the substrate. In contrast, in Comparative Example 2, it was attempted to control the temperature distribution so that the surface temperature of the substrate gradually decreased from the inside to the outside of the substrate by separately controlling the inner electrode and the outer electrode, but it was only possible to control the temperature to decrease sharply at the boundary between the inner electrode and the outer electrode.

In Example 2, the absolute values of a(X) and a(Y) were 4×10 ⁻⁴ or more, whereas they were less than 4×10 ⁻⁴ in Comparative Example 2. In this way, it is considered that by having the absolute values of a(X) and a(Y) of the cross-sectional curves be a predetermined value or more, i.e., the radius of curvature of the mounting curved surface be a predetermined value or less, when the electrode-embedded member is used as a two-zone heater in which the electrodes can be controlled separately on the inside and outside of the base, it becomes easier to control the temperature distribution and the occurrence of hot spots can be suppressed.

From the above, it has been confirmed that the electrode embedding member and substrate holding member of the present invention can reduce the occurrence of localized hot spots, suppress particle entrapment, and, if necessary, can use the space under the substrate as a gas flow path.

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 Base 12 Upper surface 14 Lower surface 16 Center of base 18 Outer periphery 20 Electrode 22 Inner electrode 24 Outer electrode 30 Pin-shaped protrusion 32 Upper end of pin-shaped protrusion 42 Cross-sectional curve 50 Terminal 52 Terminal hole 100, 200 Electrode embedding member 110 Support member 112 Bonding surface 150 Substrate holding member W Substrate

Claims (8)

An electrode embedding member,
A base body formed of a ceramic sintered body;
an electrode embedded in the substrate;
a plurality of pin-shaped protrusions formed to protrude upward from the upper surface of the base,
a cross-sectional curve obtained by cutting the mounting surface formed by the upper ends of the multiple pin-shaped convex portions at a cross section passing through the central axis of the base body as the Z-axis, is a curve that has a maximum Z value near the central axis and monotonically decreases toward the outer periphery of the base body, or a curve that has a minimum Z value near the central axis and monotonically increases toward the outer periphery of the base body, when an intersection line between a predetermined reference plane and the cross section is set as the X-axis;
The cross-sectional curve is expressed by the following equation: the reference length in the X-axis direction is L (mm), the value of Z (mm) for a certain X (mm) is Z(X), and the value of deviation ΔZ(X) is
ΔZ(X)=Z(X)-((Z(X+L)+Z(XL))/2)
With the maximum value of ΔZ(X) being ΔZ(X) _max and the minimum value of ΔZ(X) being ΔZ(X) _min ,
ΔZ(X) _max - ΔZ(X) _min ≦1(μm)
An electrode-embedded member, comprising : 2. The electrode-embedded member according to claim 1, wherein the flatness of the curved mounting surface is 50 [mu]m or less. An electrode embedding member,
A base body formed of a ceramic sintered body;
An electrode embedded in the substrate;
a plurality of pin-shaped protrusions formed to protrude upward from the upper surface of the base,
a cross-sectional curve obtained by cutting the mounting surface formed by the upper ends of the multiple pin-shaped convex portions at a cross section passing through the central axis of the base body as the Z-axis, is a curve that has a maximum Z value near the central axis and monotonically decreases toward the outer periphery of the base body, or a curve that has a minimum Z value near the central axis and monotonically increases toward the outer periphery of the base body, when an intersection line between a predetermined reference plane and the cross section is set as the X-axis;
an electrode-embedded member, characterized in that, when a curve obtained by cutting the mounting surface at a second cross section perpendicular to the X-axis and including the Z-axis is defined as a second cross-sectional curve, and an intersection line between the predetermined reference plane and the second cross section is defined as a Y-axis, a coefficient of determination R2 for a first approximation equation when the cross-sectional curve is approximated by a quadratic curve, and a coefficient of determination R2 for a second approximation equation when the second cross-sectional curve is approximated by a quadratic curve are both 0.99 or more. When the quadratic coefficient of the first approximation equation is a(X) and the quadratic coefficient of the second approximation equation is a(Y),
2(a(X)-a(Y))/(a(X)+a(Y))≦0.1
4. The electrode-embedding member according to claim 3, wherein the above-mentioned condition is satisfied. When the quadratic coefficient of the first approximation formula is a(X) and the quadratic coefficient of the second approximation formula is a(Y), the absolute values of a(X) and a(Y) are 4×10 ^-4 5. The electrode-embedding member according to claim 3 or 4, characterized in that: An electrode-embedded member according to any one of claims 1 to 5,
a support member joined to a lower surface of the electrode-embedded member and supporting the electrode-embedded member. A method for manufacturing an electrode-embedded member, comprising the steps of:
preparing a ceramic base having an electrode embedded therein and a plurality of pin-shaped protrusions formed on one of its main surfaces;
a step of placing or sucking a substrate on the plurality of pin-shaped protrusions and measuring the curved surface shape of the substrate by a laser interferometer;
a step of polishing or grinding the plurality of pin-shaped protrusions so that the curved surface shape has a predetermined convex or concave shape that is substantially symmetrical with respect to a central axis;
a step of placing or sucking a substrate onto the plurality of pin-shaped convex portions after polishing or grinding, measuring the curved shape of the surface with a laser interferometer, and confirming that the curved shape is the specified convex shape or concave shape. A method for manufacturing an electrode-embedded member, comprising the steps of:
preparing a ceramic base having an electrode embedded therein and a plurality of pin-shaped protrusions formed on one of its main surfaces;
a step of placing or sucking a substrate on the plurality of pin-shaped protrusions and measuring the curved surface shape of the substrate by a laser interferometer;
The measured curved surface shape is cut at a cross section passing through the Z axis with the central axis as the Z axis, the intersection line between a predetermined reference plane and the cross section is the X axis, the reference length in the X axis direction is L (mm), the value of Z (mm) for a certain X (mm) is Z(X), and the value of deviation ΔZ(X) is
ΔZ(X)=Z(X)-((Z(X+L)+Z(XL))/2)
Then, the maximum value of ΔZ(X) is ΔZ(X). _max , the minimum value of ΔZ(X) is ΔZ(X) _min When
ΔZ(X) _max −ΔZ(X) _min ≦1 (μm)
a step of polishing or grinding the plurality of pin-shaped protrusions so as to satisfy
a step of placing or sucking a substrate onto the plurality of pin-shaped convex portions after polishing or grinding, measuring the curved shape of the surface with a laser interferometer, and verifying that the curved shape satisfies the specified relationship.