Wafer mounting table

Abstract

To suppress stress that acts on an electrode due to temperature changes, while suppressing an increase in resistance value of the electrode.SOLUTION: A wafer mounting table 10 comprises: a ceramic substrate 20 having a wafer mounting surface 20a on its upper face; an electrode 22 built in the ceramic substrate 20; and a conductive electrode extraction part 23 which is built in the ceramic substrate 20 so as to be electrically connected to the electrode 22. Compared with the electrode 22, the electrode extraction part 23 has a higher volume content of a ceramic material which is the same as a main component of the ceramic substrate 20.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a wafer mounting table.

Background Art

[0002] Conventionally, a wafer mounting table including a ceramic substrate having a wafer mounting surface, an electrode embedded inside the ceramic substrate, and a power supply member for supplying power to the electrode is known. In Patent Document 1, an electrode terminal, which is a part of the electrode, is provided so as to be exposed on a surface of the ceramic substrate opposite to the wafer mounting surface, and the power supply member and the electrode terminal are electrically connected. Further, it is described that a conductive material or a mixture of a conductive material and the material of the ceramic substrate is used for the electrode.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the difference in the coefficient of thermal expansion between the electrode terminal (electrode extraction portion) and the ceramic substrate is large, stress is applied from the electrode terminal to the electrode due to temperature change, and peeling or cracking of the electrode may occur. As described in Patent Document 1, the difference in the coefficient of thermal expansion from the ceramic substrate can be reduced by including the material of the ceramic substrate in the electrode and the electrode terminal. However, if the electrode contains a large amount of the material of the ceramic substrate, the resistance value of the electrode increases, which is not preferable.

[0005] The present invention has been made to solve such problems, and the main object is to suppress an increase in the resistance value of the electrode and suppress the stress acting on the electrode due to temperature change.

Means for Solving the Problems

[0006] The present invention has adopted the following means to achieve the above-described main object.

[0007] [1] The wafer stage of the present invention includes a ceramic substrate having a wafer placement surface on the upper surface, electrodes built in the ceramic substrate, a conductive electrode extraction part built in the ceramic substrate and electrically connected to the electrodes, and is provided with the electrode extraction part has a high volume content ratio of the same ceramic material as the main component of the ceramic substrate as compared with the electrodes, and is such.

[0008] In this wafer stage, the electrode extraction part has a high volume content ratio of the same ceramic material as the main component of the ceramic substrate as compared with the electrodes. Thereby, the electrode extraction part can reduce the difference in the coefficient of thermal expansion between itself and the ceramic substrate. Therefore, peeling and cracking of the electrodes due to stress acting on the electrodes from the electrode extraction part caused by temperature changes can be suppressed. On the other hand, since the electrodes have a low volume content ratio of the same ceramic material as the main component of the ceramic substrate as compared with the electrode extraction part, problems due to the resistance value of the electrodes becoming too high can be suppressed. From the above, in this wafer stage, while suppressing an increase in the resistance value of the electrodes, the stress acting on the electrodes due to temperature changes can be suppressed.

[0009] [2] In the above-described wafer stage (the wafer stage described in [1] above), a part of the upper surface of the electrode extraction part may be a substrate bonding region bonded to the ceramic substrate. By doing so, since the electrode extraction part is in close contact with the ceramic substrate in the substrate bonding region, even if stress is generated due to the difference in thermal expansion between the electrode extraction part and the ceramic substrate due to temperature changes, it is difficult for the stress to act on the electrodes.

[0010] [3] In the above-described wafer mounting table (the wafer mounting table described in [2] above), the substrate bonding region may include a part of the outer peripheral edge portion of the upper surface of the electrode extraction portion. Here, the stress acting on the electrode due to temperature change tends to be large particularly around the outer peripheral edge portion of the upper surface of the electrode extraction portion. Therefore, by including a part of this outer peripheral edge portion in the substrate bonding region, the stress acting on the electrode due to temperature change can be further reduced.

[0011] [4] In the above-described wafer mounting table (the wafer mounting table described in any one of [1] to [3] above), it includes a power supply member that is arranged to be inserted from the lower surface of the ceramic substrate and is electrically connected to the electrode extraction portion, and a plurality of electrode extraction portions may be provided for one power supply member. In this way, compared with the case of providing one electrode extraction portion having the same volume as the total volume of the plurality of electrode extraction portions, the stress caused by the thermal expansion difference between the electrode extraction portion and the ceramic substrate due to temperature change can be reduced. In this case, a part of the upper surface of each of the plurality of provided electrode extraction portions may have a substrate bonding region joined to the ceramic substrate.

[0012] [5] In the above-described wafer mounting table (the wafer mounting table described in any one of [1] to [4] above), the electrode extraction portion may have a through hole that penetrates the electrode extraction portion in the vertical direction. In this way, since the volume of the electrode extraction portion is reduced by the amount of the through hole, the stress caused by the thermal expansion difference between the electrode extraction portion and the ceramic substrate due to temperature change can be reduced.

[0013] [6] In the above-described wafer mounting table (the wafer mounting table described in any one of [1] to [5] above), the electrode extraction portion may have a greater thickness in the vertical direction compared to the electrode. When the electrode extraction portion has a greater thickness than the electrode, the stress caused by the thermal expansion difference between the electrode extraction portion and the ceramic substrate due to temperature change tends to be large, so the significance of applying the present invention is high.

[0014] [7] In the above-described wafer mounting table (the wafer mounting table according to any one of [1] to [6] above), the ceramic material may be alumina or aluminum nitride.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

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Figure 5

Figure 6

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Figure 8

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Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0016] Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of the wafer mounting table 10 of the present embodiment (a cross-sectional view when the wafer mounting table 10 is cut along a plane including the central axis of the wafer mounting table 10), FIG. 2 is a partially enlarged view of FIG. 1 (an enlarged view within the frame indicated by the two-dot chain line in FIG. 1), FIG. 3 is an enlarged view of the periphery of the electrode extraction portion 23 in FIG. 2, and FIG. 4 is a partial top view of the electrodes 22 and the electrode extraction portion 23 (a top view of the periphery of the electrode extraction portion 23). In FIG. 4, the region where the electrode 22 exists is hatched for easy understanding of the positional relationship between the electrode 22 and the electrode extraction portion 23.

[0017] As shown in FIG. 1, the wafer mounting table 10 includes a ceramic substrate 20, a cooling plate 30, a bonding layer 40, and a power supply member 50.

[0018] The ceramic substrate 20 is a disk-shaped member having a wafer mounting surface 20a on its upper surface. The ceramic substrate 20 is formed of a ceramic-containing material. The ceramic-containing material is a material mainly composed of a ceramic material, and may contain components derived from a sintering aid (such as rare earth elements, etc.) and inevitable components in addition to the ceramic material. The main component means that the volume content ratio in the whole is 50% by volume or more. The volume content ratio of the ceramic material, which is the main component of the ceramic substrate 20, may be 80% by volume or more, or 90% by volume or more. Examples of the ceramic material include alumina or aluminum nitride. In the present embodiment, the main component of the ceramic substrate 20 is alumina.

[0019] The ceramic substrate 20 incorporates electrodes 22 and an electrode extraction portion 23. The electrodes 22 and the electrode extraction portion 23 have conductivity. The electrode 22 is a flat single-pole type electrode. In this embodiment, the electrode 22 is a disc-shaped electrode. The electrode extraction portion 23 is a frustum-shaped (a shape obtained by cutting a sphere with two horizontal planes) member. The electrode extraction portion 23 is electrically connected to the electrode 22. The electrode extraction portion 23 is disposed below the electrode 22, and a part of the upper surface is in contact with the lower surface of the electrode 22. The lower surface of the electrode extraction portion 23 is exposed on the bottom surface of the power supply member insertion hole 28 and is in contact with a brazing material layer 29 disposed on the bottom surface of the power supply member insertion hole 28. The electrode extraction portion 23 has a greater thickness in the vertical direction compared to the electrode 22. That is, as shown in FIG. 3, the thickness T2 of the electrode extraction portion 23 is greater than the thickness T1 of the electrode 22. The thickness T2 is, for example, 0.1 mm or more and 1 mm or less. The thickness T1 is, for example, 0.01 mm or more and 0.03 mm or less. The thickness T2 may be 10 times or more, and may be 20 times or more, the thickness T1. The electrode 22 is used as an electrostatic electrode in this embodiment. The layer above the electrode 22 in the ceramic substrate 20 functions as a dielectric layer. A power supply 62, which is a DC power supply for electrostatic adsorption, is connected to the electrode 22 via a power supply member 50.

[0020] A part of the upper surface of the electrode extraction portion 23 forms a substrate bonding region 24 that is bonded to the ceramic substrate 20. In this embodiment, a circular through-hole 22a is formed at a position overlapping the electrode extraction portion 23 when viewed virtually from above through the electrode 22 (FIG. 4), and the portion of the upper surface of the electrode extraction portion 23 located directly below this through-hole 22a is the substrate bonding region 24. When viewed virtually from above, the through-hole 22a overlaps the central portion of the electrode extraction portion 23. In a top view, the through-hole 22a is provided to be concentric with the electrode extraction portion 23, and the diameter of the through-hole 22a is smaller than the diameter of the electrode extraction portion 23. Therefore, when viewed virtually from above, the entire through-hole 22a is included in the electrode extraction portion 23, and the entire through-hole 22a coincides with the substrate bonding region 24. Since the through-hole 22a exists directly above the substrate bonding region 24, the electrode 22 does not exist directly above the substrate bonding region 24.

[0021] The electrode 22 and the electrode extraction part 23 contain a conductive material such as W, Mo, WC, MoC, Ru, TiN, etc. As the conductive material used for the electrode 22 and the electrode extraction part 23, those with a coefficient of thermal expansion close to that of the ceramic substrate 20 are preferred. It is preferable that the types of the conductive material contained in the electrode 22 and the conductive material contained in the electrode extraction part 23 are the same. The conductive material contained in the electrode 22 and / or the electrode extraction part 23 may be a plurality of types of materials. The electrode 22 and the electrode extraction part 23 contain the same ceramic material (alumina in this embodiment) as the main component of the ceramic substrate 20. Thereby, the coefficient of thermal expansion of the electrode 22 and the electrode extraction part 23 can be made close to the coefficient of thermal expansion of the ceramic substrate 20. Note that for the electrode 22, it is not necessary to contain the same ceramic material as the main component of the ceramic substrate 20. In addition to the conductive material and the ceramic material, the electrode 22 and the electrode extraction part 23 may contain components derived from a sintering aid (such as rare earth elements, etc.) and unavoidable components. Also, assuming that the volume content ratios of the same ceramic material as the main component of the ceramic substrate 20 in the electrode 22 and the electrode extraction part 23 are C1 and C2 [volume%] respectively, the volume content ratio C2 is higher than the volume content ratio C1. For example, the volume content ratio C1 in the electrode 22 may be 0 volume% or more, 10 volume% or more, or 30 volume% or more. The volume content ratio C1 may be 50 volume% or less. The volume content ratio C2 in the electrode extraction part 23 may be 30 volume% or more, 50 volume% or more, or 70 volume% or more. The volume content ratio C2 may be 90 volume% or less, or 80 volume% or less. The difference D (=C2 - C1) between the volume content ratio C1 and the volume content ratio C2 may be, for example, 5 volume% or more, 10 volume% or more, 20 volume% or more, or 30 volume% or more. The higher the volume content ratio C1, the closer the coefficient of thermal expansion of the electrode 22 is to the coefficient of thermal expansion of the ceramic substrate 20. Similarly, the higher the volume content ratio C2, the closer the coefficient of thermal expansion of the electrode extraction part 23 is to the coefficient of thermal expansion of the ceramic substrate 20. In this embodiment, since C1 < C2, the coefficient of thermal expansion of the electrode extraction part 23 is closer to the coefficient of thermal expansion of the ceramic substrate 20 than that of the electrode 22.In addition, when the conductive material contained in the electrode 22 and the electrode extraction portion 23 has a lower coefficient of thermal expansion than the ceramic material (alumina in this embodiment) which is the main component of the ceramic substrate 20 (for example, any one or more of W, Mo, WC, and MoC), the higher the volume content ratio C1, the higher the coefficient of thermal expansion of the electrode 22, and the higher the volume content ratio C2, the higher the coefficient of thermal expansion of the electrode extraction portion 23. Also, when the conductive material contained in the electrode 22 and the electrode extraction portion 23 has a higher coefficient of thermal expansion than the ceramic material (alumina in this embodiment) which is the main component of the ceramic substrate 20 (for example, any one or more of Ru and TiN), the higher the volume content ratio C1, the lower the coefficient of thermal expansion of the electrode 22, and the higher the volume content ratio C2, the lower the coefficient of thermal expansion of the electrode extraction portion 23. The electrode 22 may contain both a material having a lower coefficient of thermal expansion and a material having a higher coefficient of thermal expansion than the ceramic material which is the main component of the ceramic substrate 20 as the conductive material. Also in this case, if the coefficient of thermal expansion of the entire conductive material (a plurality of types of materials) contained in the electrode 22 is different from the coefficient of thermal expansion of the ceramic material, the coefficient of thermal expansion of the electrode 22 will change depending on the volume content ratio C1. The same applies to the electrode extraction portion 23. If the coefficient of thermal expansion of the entire conductive material (a plurality of types of materials) contained in the electrode extraction portion 23 is different from the coefficient of thermal expansion of the ceramic material, the coefficient of thermal expansion of the electrode extraction portion 23 will change depending on the volume content ratio C2. And if C1 < C2, the coefficient of thermal expansion of the electrode extraction portion 23 is closer to the coefficient of thermal expansion of the ceramic substrate 20 than that of the electrode 22. Also, regardless of whether the conductive material is one type or a plurality of types, it is preferable that the coefficient of thermal expansion of the conductive material (as a whole) contained in the electrode extraction portion 23 is the same as or closer to the coefficient of thermal expansion of the ceramic material which is the main component of the ceramic substrate 20 than the coefficient of thermal expansion of the conductive material (as a whole) contained in the electrode 22.

[0022] The volume content ratio C2 of the electrode extraction portion 23 is a value calculated as the area ratio of the ceramic material confirmed in the observation image when a representative cross-section of the electrode extraction portion 23 is observed at a magnification of 1000 times using a scanning electron microscope (SEM). The volume content ratio C1 of the electrode 22 and the volume content ratio of the main component in the ceramic substrate 20 are also values calculated by the same method.

[0023] The cooling plate 30 is a disk-shaped member having a refrigerant flow path 32 inside which refrigerant can circulate. The refrigerant flow path 32 is formed in one stroke from one end to the other end so as to cover the entire surface of the cooling plate 30 in a plan view. One end and the other end of the refrigerant flow path 32 are connected to a refrigerant circulation pump (not shown) having a function of adjusting the temperature of the refrigerant. The cooling plate 30 is made of a conductive material containing, for example, a metal. Examples of the conductive material include composite materials and metals. Examples of the composite material include metal matrix composites (also referred to as metal matrix composites (MMC)). Examples of MMC include materials containing Si, SiC, and Ti, and materials obtained by impregnating a SiC porous body with Al and / or Si. A material containing Si, SiC, and Ti is referred to as SiSiCTi, a material obtained by impregnating a SiC porous body with Al is referred to as AlSiC, and a material obtained by impregnating a SiC porous body with Si is referred to as SiSiC. Examples of the metal include Al, Ti, Mo, or their alloys. As the conductive material used for the cooling plate 30, those having a coefficient of thermal expansion close to that of the ceramic substrate 20 are preferable.

[0024] The bonding layer 40 bonds the lower surface of the ceramic substrate 20 and the upper surface of the cooling plate 30. The bonding layer 40 may be, for example, a metal bonding layer formed of solder or a metal brazing material. The metal bonding layer may be formed, for example, by TCB (Thermal compression bonding). TCB refers to a known method in which a metal bonding material is sandwiched between two members to be bonded, and the two members are pressure-bonded in a state of being heated to a temperature below the solidus temperature of the metal bonding material. As the bonding layer 40, an organic adhesive layer may be employed instead of the metal bonding layer.

[0025] The power supply member 50 is a metal member for supplying power to the electrode 22. The power supply member 50 is, for example, a metal rod. The power supply member 50 is electrically connected to the electrode extraction part 23 and the electrode 22. The metal used for the power supply member 50 is, for example, W, Mo, Ni, etc., and it is preferable that the thermal expansion coefficient of the metal is close to the thermal expansion coefficient of the ceramic substrate 20. The power supply member 50 is arranged to be inserted from the lower surface of the ceramic substrate 20 and is electrically connected to the electrode extraction part 23. More specifically, the power supply member 50 passes through the inside of the insulating tube 36 arranged in the cooling plate through hole 34 and is inserted into the power supply member insertion hole 28 provided in the ceramic substrate 20 via the cooling plate through hole 34 penetrating the cooling plate 30 in the vertical direction and the bonding layer through hole 44 penetrating the bonding layer 40 in the vertical direction. The diameter of the bonding layer through hole 44 is the same as the diameter of the cooling plate through hole 34. The power supply member 50 passes through the inside of the insulating tube 36 arranged in the cooling plate through hole 34 and is inserted into the power supply member insertion hole 28 with play. The outer peripheral surface of the insulating tube 36 is adhered to the inner peripheral surface of the cooling plate through hole 34 via the adhesive layer 35. The upper end surface of the insulating tube 36 is higher than the upper surface of the cooling plate 30 and is located below the lower surface of the ceramic substrate 20. The power supply member insertion hole 28 is a cylindrical hole provided in the ceramic substrate 20 and is provided so as to reach the electrode extraction part 23 from the lower surface of the ceramic substrate 20.

[0026] The power supply member 50 is electrically connected to the electrode extraction part 23 via the brazing material layer 29. The power supply member 50 is joined to the ceramic substrate 20 and the electrode extraction part 23 by the brazing material layer 29. The brazing material layer 29 is provided in the gap between the bottom surface of the power supply member insertion hole 28 and the tip surface (upper end surface) of the power supply member 50 and in the gap between the side surface of the power supply member insertion hole 28 and the side surface of the power supply member 50. The brazing material layer 29 is formed of, for example, a brazing material such as Au - Ge, Al, Ag, Ag - Cu - Ti, etc.

[0027] Next, an example of using the wafer stage 10 will be described. First, the wafer stage 10 is installed in a vacuum chamber (not shown), and the wafer W is placed on the wafer placement surface 20a of the wafer stage 10. Then, a voltage is applied to the electrode 22 from the power supply 62 via the power supply member 50. Then, the wafer W is adsorbed and fixed to the wafer placement surface 20a. Then, the inside of the vacuum chamber is set to a vacuum atmosphere or a reduced pressure atmosphere, and the wafer W is processed in the vacuum chamber. For example, when processing the wafer W with plasma, an upper electrode equipped with a shower head is arranged on the ceiling inside the vacuum chamber, and a reaction gas is supplied from the shower head to the space between the wafer W and the upper electrode while applying a high-frequency voltage between the upper electrode and the cooling plate 30 to generate plasma. After the processing of the wafer W is completed, the application of the voltage to the electrode 22 is released. Then, the adsorption and fixation of the wafer W to the wafer placement surface 20a are released. Note that a refrigerant is flowed through the refrigerant flow path 32 when it is necessary to lower the temperature of the wafer W.

[0028] Next, among the manufacturing methods of the wafer stage 10, particularly the manufacturing process of the ceramic substrate 20 and the process of joining the power supply member 50 to the electrode extraction portion 23 will be described with reference to FIG. 5. FIG. 5 is an explanatory diagram of these processes.

[0029] First, disk-shaped first and second ceramic compacts 120a and 120b, which are ceramic powder compacts, are produced using a tape casting method, and a hole 121 having a spherical segment shape (a shape obtained by cutting a sphere with a horizontal plane) is formed by cutting on the upper surface of the second ceramic compact 120b (FIG. 5A). The second ceramic compact 120b may be produced by dividing it into a plurality of layers of compacts.

[0030] Next, a conductive paste is printed on the upper surface of the second ceramic compact 120b so as to form a predetermined pattern (Fig. 5B). Specifically, first, the conductive paste is printed so as to fill the holes 121 of the second ceramic compact 120b, and an electrode extraction part precursor 123 that finally becomes the electrode extraction part 23 is formed. Subsequently, the conductive paste is printed on the upper surface of the second ceramic compact 120b, and an electrode precursor 122 that finally becomes the electrode 22 is formed. The electrode precursor 122 is printed so as to form a pattern having a shape with a through-hole 122a that finally becomes the through-hole 22a. As a result, the lower surface of the electrode precursor 122 and the upper surface of the electrode extraction part precursor 123 come into contact with each other, and a portion of the upper surface of the electrode extraction part precursor 123 that is located directly below the through-hole 122a becomes the substrate bonding region 124. The substrate bonding region 124 is a region that finally becomes the substrate bonding region 24. As the conductive paste, for example, a paste containing particles of the conductive material used for the above-described electrode 22 and electrode extraction part 23 and particles of a ceramic material the same as the main component of the ceramic substrate 20 can be used. The conductive paste may contain a sintering aid. By adjusting the content ratio of the ceramic material in the conductive paste, the above-described volume content ratios C1 and C2 can be adjusted.

[0031] Subsequently, the first and second ceramic compacts 120a and 120b are stacked and pressure is applied from above and below to obtain a laminate 120 (FIG. 5C). Due to the pressure from above and below, a part of the first ceramic compact 120a enters into the through-hole 122a and contacts the substrate bonding region 124 of the electrode extraction part precursor 123. After hot press firing this laminate 120 and cooling it to room temperature, the power supply member insertion hole 28 is formed by cutting, and the ceramic substrate 20 is obtained by appropriately performing outer shape processing and thickness processing (FIG. 5D). The electrode precursor 122 having the through-hole 122a becomes the electrode 22 having the through-hole 22a after hot press firing. The electrode extraction part precursor 123 having the substrate bonding region 124 becomes the electrode extraction part 23 having the substrate bonding region 24 after hot press firing and after the formation of the power supply member insertion hole 28. The power supply member insertion hole 28 can be formed, for example, by counterboring. The power supply member insertion hole 28 is formed to a depth at which the electrode extraction part precursor 123 is exposed on the bottom surface of the power supply member insertion hole 28. Along with the counterboring at this time, a part of the lower side of the electrode extraction part precursor 123 is cut to become the electrode extraction part 23. By hot press firing, the electrode extraction part 23 and the ceramic particles around the electrode extraction part 23 in the ceramic substrate 20 are closely adhered and joined. Therefore, regarding the substrate bonding region 24 of the electrode extraction part 23, it is closely adhered to the ceramic particles (here, the ceramic particles in the through-hole 122a) existing directly above the substrate bonding region 24 in the ceramic substrate 20 and is joined to the ceramic substrate 20.

[0032] Subsequently, the power supply member 50 and the electrode extraction part 23 are joined and electrically connected. Specifically, a sheet of brazing material that will ultimately become the brazing material layer 29 is disposed on the bottom surface of the power supply member insertion hole 28, and the power supply member 50 is inserted from the lower surface of the ceramic substrate 20. That is, the sheet of brazing material is sandwiched between the bottom surface of the power supply member insertion hole 28 (including the portion exposed on the bottom surface of the electrode extraction part 23) and the tip surface of the power supply member 50. In this state, the brazing material is heated and melted and then cooled and solidified to form the brazing material layer 29 (FIG. 5E). Thereby, the power supply member 50 and the electrode extraction part 23 are joined and electrically connected via the brazing material layer 29.

[0033] In parallel with these steps, the cooling plate 30 is fabricated by a known method, and the insulating tube 36 is attached to the cooling plate 30 via the adhesive layer 35. Then, after performing the above-described steps, the cooling plate 30 is joined to the ceramic substrate 20 via the joining layer 40 to obtain the wafer mounting table 10. Note that the step of joining the power supply member 50 to the electrode extraction portion 23 (FIG. 5E) may be performed before joining the cooling plate 30 to the ceramic substrate 20, or may be performed after joining the cooling plate 30 to the ceramic substrate 20.

[0034] In the wafer mounting stage 10 of the present embodiment described in detail above, the electrode extraction portion 23 has a higher volume content ratio of the ceramic material that is the same as the main component of the ceramic substrate 20 than the electrode 22. That is, the volume content ratio C2 is higher than the volume content ratio C1. Thereby, the difference in the coefficient of thermal expansion between the electrode extraction portion 23 and the ceramic substrate 20 can be reduced. Therefore, it is possible to suppress peeling and cracking of the electrode 22 due to the stress acting on the electrode 22 from the electrode extraction portion 23 due to temperature changes. For example, when the coefficient of thermal expansion of the electrode extraction portion 23 is lower than that of the ceramic substrate 20, if the difference in the coefficient of thermal expansion between the two is large, when the laminate 120 is hot press fired and then cooled to room temperature in the manufacturing process of the ceramic substrate 20, the electrode extraction portion 23 (accurately, the electrode extraction portion precursor 123) has a smaller shrinkage amount due to the temperature change during cooling than the ceramic substrate 20. Further, when the coefficient of thermal expansion of the electrode extraction portion 23 is higher than that of the ceramic substrate 20, if the difference in the coefficient of thermal expansion between the two is large, the electrode extraction portion 23 (accurately, the electrode extraction portion precursor 123) has a larger shrinkage amount due to the temperature change during cooling than the ceramic substrate 20. As a result, stress is generated from the electrode extraction portion 23 to the electrode extraction portion 23, and stress is applied to the electrode 22 directly above the electrode extraction portion 23, and peeling and cracking may occur in the electrode 22. This stress tends to increase particularly around the outer peripheral edge portion of the upper surface of the electrode extraction portion 23. For example, peeling and cracking of the electrode 22 are likely to occur in the regions indicated by the two broken-line circles in FIG. 3. Further, not only during cooling after firing of the laminate 120, but also during cooling after use of the wafer mounting stage 10, stress may be applied to the electrode 22 in the same manner. On the other hand, in the present embodiment, since the volume content ratio C2 is higher than the volume content ratio C1, the stress acting on the electrode 22 from the electrode extraction portion 23 can be suppressed, and peeling and cracking of the electrode 22 can be suppressed. Further, if not only the volume content ratio C2 in the electrode extraction portion 23 but also the volume content ratio C1 in the electrode 22 is increased, there is a concern that problems (for example, a decrease in the function as an electrostatic electrode) may occur due to the resistance value of the electrode 22 becoming too high. On the other hand, in the present embodiment, since the volume content ratio C1 is lower than the volume content ratio C2, problems due to the resistance value of the electrode 22 becoming too high can be suppressed.Note that since the electrode extraction portion 23 does not need to function as an electrostatic electrode like the electrode 22, even if the resistance value increases, it is less likely to cause problems compared to the electrode 22. From the above, in the wafer mounting stage 10 of the present embodiment, it is possible to suppress the increase in the resistance value of the electrode 22 and suppress the stress acting on the electrode 22 due to temperature changes.

[0035] Also, a part of the upper surface of the electrode extraction portion 23 is a substrate bonding region 24 joined to the ceramic substrate 20. As a result, the electrode extraction portion 23 is in close contact with the ceramic substrate 20 in the substrate bonding region 24, so the stress generated in the electrode extraction portion 23 described above can be suppressed by the adhesion force between the substrate bonding region 24 and the ceramic substrate 20. Thereby, even if stress is generated due to the thermal expansion difference between the electrode extraction portion 23 and the ceramic substrate 20 due to temperature changes, it is difficult for the stress to act on the electrode 22.

[0036] Furthermore, the electrode extraction portion 23 has a greater thickness in the vertical direction compared to the electrode 22. When the electrode extraction portion 23 is thicker than the electrode 22, that is, when the volume of the electrode extraction portion 23 is larger compared to the case where the electrode extraction portion 23 has the same thickness as the electrode 22, the stress caused by the thermal expansion difference between the electrode extraction portion 23 and the ceramic substrate 20 due to temperature changes is likely to increase. Therefore, the significance of applying the present invention is high. Note that since the electrode extraction portion 23 is thicker than the electrode 22, it is possible to suppress not only the electrode extraction portion 23 but also the electrode 22 from being cut during the formation of the power supply member insertion hole 28.

[0037] Note that the present invention is not limited to the above-described embodiments, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

[0038] For example, in the above-described embodiment, the electrode extraction portion 23 had the substrate bonding region 24, but as shown in FIG. 6, it may not have the substrate bonding region 24. In FIG. 6, the electrode 22 does not have the through-hole 22a, and the electrode 22 exists directly above the entire upper surface of the electrode extraction portion 23. Therefore, the upper surface of the electrode extraction portion 23 does not have the substrate bonding region 24. Even in this case, since the volume content ratio C2 is higher than the volume content ratio C1, it is possible to suppress an increase in the resistance value of the electrode 22 and suppress the stress acting on the electrode 22 due to temperature changes.

[0039] In the above-described embodiment, the central portion of the upper surface of the electrode extraction portion 23 was the substrate bonding region 24, but the position of the substrate bonding region 24 is not limited to this. For example, as shown in FIGS. 7 and 8, the substrate bonding region 24 may include a part of the outer peripheral edge portion of the upper surface of the electrode extraction portion 23. FIG. 7 is a cross-sectional view taken along line A-A of FIG. 8. In FIGS. 7 and 8, the substrate bonding region 24 of the electrode 22 has a region 224a and a plurality (here, six) of regions 224b. The region 224a is provided at the central portion of the upper surface of the electrode extraction portion 23 as in the above-described embodiment, and is a region located directly below the through-hole 222a provided in the electrode 22. Therefore, the region 224a is not in contact with the electrode 22 and is bonded to the ceramic substrate 20. Further, the electrode 22 is provided with a plurality (here, six) of trapezoidal through-holes 222b provided so as to straddle the inner and outer sides in the radial direction of the electrode extraction portion 23 across the outer peripheral edge portion of the electrode extraction portion 23 (the circular contour line portion of the electrode extraction portion 23 shown in FIG. 8) in a top view. As a result, the region 224b including a part of the outer peripheral edge portion of the upper surface of the electrode extraction portion 23 (the portion indicated by the solid line in the contour line of the electrode extraction portion 23 shown in FIG. 8) is not in contact with the electrode 22 and is a part of the substrate bonding region 24 bonded to the ceramic substrate 20. The portion other than the substrate bonding region 24 (regions 224a and 224b) of the upper surface of the electrode extraction portion 23 is in contact with the lower surface of the electrode 22 and is electrically connected. As described above, the stress acting on the electrode 22 due to temperature change tends to be large particularly around the outer peripheral edge portion of the upper surface of the electrode extraction portion 23. Therefore, by including a part of this outer peripheral edge portion in the region 224b of the substrate bonding region 24, the stress acting on the electrode 22 due to temperature change can be further reduced. If the entire outer peripheral edge portion of the upper surface of the electrode extraction portion 23 is made the substrate bonding region 24, the electrode extraction portion 23 and the electrode 22 will not be electrically connected. Therefore, in FIGS. 7 and 8, not the entire outer peripheral edge portion of the upper surface of the electrode extraction portion 23 but a part thereof is included in the substrate bonding region 24. In FIGS. 7 and 8, the number of regions 224b may be one. In FIGS. 7 and 8, the substrate bonding region 24 may not include the region 224a. That is, the electrode 22 may not have the through-hole 222a.

[0040] In the above-described embodiment, one electrode extraction portion 23 was provided for one power supply member 50, but the present invention is not limited to this. A plurality of electrode extraction portions 23 may be provided for one power supply member 50. For example, as shown in FIGS. 9 and 10, three electrode extraction portions 323a to 323c may be provided as the electrode extraction portion 323 for one power supply member 50. FIG. 9 is a cross-sectional view taken along line B-B of FIG. 10. In FIGS. 9 and 10, the electrode extraction portion 323 has three electrode extraction portions 323a to 323c that are spaced apart from each other. The substrate bonding region 324 has regions 324a to 324c that are part of the upper surfaces of the respective three electrode extraction portions 323a to 323c. Each of the electrode extraction portions 323a to 323c is a frustum-shaped member, and the lower surface is joined to the power supply member 50 via the brazing material layer 29 and is electrically connected. The electrode 22 is formed with a through hole 322a similar to the through hole 22a. The through hole 322a is provided so as to straddle the inner and outer sides in the radial direction of the outer peripheral edge portions of the respective electrode extraction portions 323a to 323c in a top view. Thereby, regions 324a to 324c including a part of the outer peripheral edge portion of each of the electrode extraction portions 323a to 323c (the portions indicated by solid lines in the contour lines of the electrode extraction portions 323a to 323c shown in FIG. 10) are not in contact with the electrode 22 and are the substrate bonding region 324 joined to the ceramic substrate 20. The portions of the upper surface of the electrode extraction portion 323 other than the substrate bonding region 324 (regions 324a to 324c) are in contact with the lower surface of the electrode 22 and are electrically connected. Since this electrode extraction portion 323 is divided into a plurality of electrode extraction portions 323a to 323c, compared with the case of providing one electrode extraction portion 23 having the same volume as the total volume of the plurality of electrode extraction portions 323a to 323c, the stress caused by the thermal expansion difference between the electrode extraction portion 323 and the ceramic substrate 20 due to temperature change can be reduced. Further, for each of the plurality of electrode extraction portions 323a to 323c, a part of the outer peripheral edge portion of the upper surface is included in the substrate bonding region 324 (regions 324a to 324c). Therefore, similar to the electrode extraction portion 23 shown in FIGS. 7 and 8, the stress acting from the electrode extraction portion 323 on the electrode 22 due to temperature change can be further reduced. In FIGS. 9 and 10, the electrode 22 may not have the through hole 322a and the substrate bonding region 324 may not exist.Further, one or more of the regions 324a to 324c of the electrode extraction portions 323a to 323c may not include a part of the outer peripheral edge portion of the upper surface of the corresponding electrode extraction portions 323a to 323c, such as being located at the center of the corresponding electrode extraction portions 323a to 323c. Even in these cases, the above-described effects due to the electrode extraction portion 323 being divided into a plurality of electrode extraction portions 323a to 323c can be obtained.

[0041] In the above-described embodiment, the electrode extraction portion 23 may have a through-hole that penetrates the electrode extraction portion 23 in the vertical direction. For example, as shown in FIGS. 11 and 12, the electrode extraction portion 423 may have a through-hole 425. FIG. 11 is a cross-sectional view taken along line C-C of FIG. 12. In FIGS. 11 and 12, since the electrode extraction portion 423 has a through-hole 425 that penetrates the electrode extraction portion 423 in the vertical direction, a ring-shaped region located directly below the through-hole 22a on the upper surface of the electrode extraction portion 423 becomes the substrate bonding region 424. Since the volume of this electrode extraction portion 423 is reduced by the amount of the through-hole 425, the stress caused by the thermal expansion difference between the electrode extraction portion 423 and the ceramic substrate 20 due to temperature changes can be reduced. In FIGS. 11 and 12, the electrode 22 may not have the through-hole 22a and the substrate bonding region 424 may not exist. Even in this case, the above-described effects due to the electrode extraction portion 423 having the through-hole 425 can be obtained. Alternatively, in FIGS. 11 and 12, the through-hole 222b shown in FIGS. 7 and 8 may be added to the electrode 22, and the region 224b shown in FIGS. 7 and 8 may be added as a part of the substrate bonding region 424.

[0042] In the above-described embodiment, the electrode extraction portion 23 has a frustum shape, but it is not limited to this. For example, the electrode extraction portion 23 may have a cylindrical shape.

[0043] In the above-described embodiment, the electrode 22 is an electrostatic electrode, but it is not limited thereto and may be a heater electrode or an RF electrode (a high-frequency electrode for plasma generation). Even when the electrode 22 is a heater electrode or an RF electrode, there is a concern that problems may occur due to the resistance value of the electrode 22 becoming too high, so the significance of applying the present invention is high. For example, when the electrode 22 is a heater electrode, if the resistance value of the electrode 22 becomes too high, there is a concern that problems such as the voltage of the power supply to be applied becoming too large to obtain the required amount of heat generation may occur. When the electrode 22 is an RF electrode, if the resistance value of the electrode 22 becomes too high, there is a concern that the electrode 22 itself may generate heat and be damaged when RF is applied, or the amount of plasma generated may decrease because the power consumed by the electrode 22 increases. By applying the present invention, such problems can be suppressed while suppressing peeling and cracking of the electrode 22. In the above-described embodiment, the wafer mounting table 10 may incorporate two or more of an electrostatic electrode, a heater electrode, and an RF electrode in the ceramic substrate 20. In this case, the present invention may be applied to one or more of the incorporated electrodes.

[0044] In the above-described embodiment, the electrode 22 is a flat electrode, but it is not limited thereto and may be, for example, a mesh electrode. In this case, if a part of the upper surface of the electrode extraction portion 23 is a region where the mesh opening of the electrode 22 exists directly above (that is, it is not in contact with the electrode 22) and is joined to the ceramic substrate 20, that region can be said to be a substrate joining region.

[0045] Although not particularly described in the above-described embodiment, the area of the substrate joining region 24 may be 1.2 mm 2 or more. As shown in FIGS. 7 to 10, when the substrate joining region has a plurality of regions, the area of each of the plurality of regions may be 1.2 mm 2 or more. Also, not limited to the case where the area of each of the plurality of regions is 1.2 mm 2 or more, one or more regions having an area of 1.2 mm 2 or more may be included in the plurality of regions.

[0046] In the above-described embodiment, a metal rod is exemplified as the power supply member 50, but it is not particularly limited thereto, and for example, a metal cable may be used.

Industrial Applicability

[0047] The present invention can be used in an apparatus for processing a wafer.

Explanation of Signs

[0048] 10 Wafer stage, 20 Ceramic substrate, 20a Wafer placement surface, 22 Electrode, 22a, 122a, 222a, 222b, 322a Through hole, 23, 123, 323, 323a to 323c, 423 Electrode extraction part, 24, 124, 324, 424 Substrate bonding region, 28 Power supply member insertion hole, 29 Brazing material layer, 30 Cooling plate, 32 Refrigerant flow path, 34 Cooling plate through hole, 35 Adhesive layer, 36 Insulating tube, 40 Bonding layer, 44 Bonding layer through hole, 50 Power supply member, 62 Power supply, 120 Laminate, 120a, 120b First and second ceramic molded bodies, 121 Hole, 122 Electrode precursor, 123 Electrode extraction part precursor, 224a, 224b, 324a to 324c Regions, 425 Through hole.

Claims

1. A ceramic substrate having a wafer mounting surface on its upper surface, The electrode embedded in the ceramic substrate, A conductive electrode extraction section is embedded in the ceramic substrate and electrically connected to the electrode, Equipped with, The electrode and the electrode extraction section contain the same ceramic material as the main component of the ceramic substrate. The electrode extraction section has a higher volume content of the ceramic material compared to the electrode. The volume content C1 of the ceramic material in the electrode is 10 volume percent or more, and the volume content C2 of the ceramic material in the electrode extraction section is 30 volume percent or more. Wafer mounting stand.

2. A portion of the upper surface of the electrode extraction portion is a substrate bonding region that is bonded to the ceramic substrate. The wafer mounting platform according to claim 1.

3. The area of ​​the substrate bonding region is 1.2 mm² or more. The wafer mounting platform according to claim 2.

4. The electrode extraction section has an upper surface area that is larger than the lower surface area. A wafer mounting platform according to any one of claims 1 to 3.

5. The substrate bonding region includes a part of the outer peripheral edge of the upper surface of the electrode extraction portion. The wafer mounting platform according to claim 2 or 3.

6. A power supply member is positioned to be inserted from the bottom surface of the ceramic substrate and electrically connected to the electrode extraction portion. Equipped with, Multiple electrode extraction sections are provided for each power supply member. A wafer mounting platform according to any one of claims 1 to 3.

7. The electrode extraction section has a through hole that penetrates the electrode extraction section in the vertical direction. A wafer mounting platform according to any one of claims 1 to 3.

8. The electrode extraction section has a greater thickness in the vertical direction compared to the electrode. A wafer mounting platform according to any one of claims 1 to 3.

9. The ceramic material is alumina or aluminum nitride. A wafer mounting platform according to any one of claims 1 to 3.

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