Wafer mounting table

Abstract

The wafer mounting table 10 includes a ceramic base 20 having a wafer mounting surface 20a on its upper surface, an electrode 22 built into the ceramic base 20, and a conductive electrode lead-out portion 23 built into the ceramic base 20 and electrically connected to the electrode 22. The electrode lead-out portion 23 has a higher volumetric content of the same ceramic material as the main component of the ceramic base 20 than the electrode 22.

Description

[Technical field]

[0001] The present invention relates to a wafer stage. [Background technology]

[0002] Conventionally, a wafer mounting table is known that includes a ceramic base having a wafer mounting surface, an electrode embedded in the ceramic base, and a power supply member for supplying power to the electrode. In Patent Document 1, an electrode terminal, which is a part of the electrode, is provided so as to be exposed on the surface of the ceramic base opposite to the wafer mounting surface, and the power supply member and the electrode terminal are electrically connected. It is also described that the electrode is made of a conductive material, or a mixture of a conductive material and the material of the ceramic base is used. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-216786 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the difference in thermal expansion coefficient between the electrode terminal (electrode extraction portion) and the ceramic base is large, stress is applied to the electrode from the electrode terminal due to temperature changes, which may cause the electrode to peel off or crack. As described in Patent Document 1, the difference in thermal expansion coefficient between the ceramic base and the electrode can be reduced by including the material of the ceramic base in the electrode and electrode terminal, but including a large amount of the material of the ceramic base in the electrode undesirably increases the resistance value of the electrode.

[0005] The present invention has been made to solve such problems, and has as its main object to suppress an increase in the resistance value of the electrodes while suppressing the stress acting on the electrodes due to temperature changes. [Means for solving the problem]

[0006] In order to achieve the above-mentioned main object, the present invention adopts the following means.

[0007] [1] The wafer mounting table of the present invention comprises: a ceramic base having a wafer mounting surface on an upper surface thereof; An electrode embedded in the ceramic substrate; a conductive electrode lead-out portion built into the ceramic base and electrically connected to the electrode; Equipped with The electrode extraction portion has a higher volume content of the same ceramic material as the main component of the ceramic base than the electrode. It is something.

[0008] In this wafer mounting table, the electrode lead-out portion has a higher volume content of the ceramic material that is the same as the main component of the ceramic base compared to the electrode. This allows the electrode lead-out portion to reduce the difference in thermal expansion coefficient between the electrode lead-out portion and the ceramic base. This makes it possible to suppress peeling and cracking of the electrode caused by stress acting on the electrode from the electrode lead-out portion due to temperature changes. On the other hand, since the electrode has a lower volume content of the ceramic material that is the same as the main component of the ceramic base compared to the electrode lead-out portion, defects caused by the resistance value of the electrode becoming too high can be suppressed. From the above, in this wafer mounting table, it is possible to suppress the stress acting on the electrode due to temperature changes while suppressing an increase in the resistance value of the electrode.

[0009] [2] In the above-mentioned wafer mounting table (the wafer mounting table described in [1] above), a part of the upper surface of the electrode lead-out portion may be a base bonding region bonded to the ceramic base. In this way, the electrode lead-out portion is in close contact with the ceramic base in the base bonding region, so that even if stress occurs due to a difference in thermal expansion between the electrode lead-out portion and the ceramic base caused by temperature change, the stress is unlikely to act on the electrode.

[0010] [3] In the above-mentioned wafer mounting table (the wafer mounting table described in [2] above), the base bonding region may include a part of the outer periphery of the upper surface of the electrode lead-out portion. Here, the stress acting on the electrode due to temperature change is likely to be large especially around the outer periphery of the upper surface of the electrode lead-out portion. Therefore, by including a part of this outer periphery in the base bonding region, the stress acting on the electrode due to temperature change can be further reduced.

[0011] [4] The above-mentioned wafer mounting table (the wafer mounting table according to any one of [1] to [3] above) may further include a power supply member arranged to be inserted from the lower surface of the ceramic base and electrically connected to the electrode lead-out portion, and a plurality of electrode lead-out portions may be provided for one of the power supply members. In this way, stress caused by a difference in thermal expansion between the electrode lead-out portion and the ceramic base due to temperature change can be reduced compared to a case where a single electrode lead-out portion having the same volume as the total volume of the plurality of electrode lead-out portions is provided. In this case, a part of the upper surface of each of the plurality of electrode lead-out portions may have a base bonding region bonded to the ceramic base.

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

[0013] [6] In the above-mentioned wafer mounting table (the wafer mounting table according to any one of [1] to [5] above), the electrode lead-out portion may have a thickness in the vertical direction greater than that of the electrode. If the electrode lead-out portion is thicker than the electrode, stress caused by a difference in thermal expansion between the electrode lead-out portion and the ceramic base due to temperature change is likely to be large, and therefore it is highly meaningful to apply the present invention.

[0014] [7] In the above-mentioned wafer stage (the wafer stage described in any one of [1] to [6] above), the ceramic material may be alumina or aluminum nitride. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is a cross-sectional view showing a schematic configuration of a wafer mounting table 10. [Diagram 2] A partially enlarged view of Figure 1. [Diagram 3] 3 is an enlarged view of the periphery of the electrode lead-out portion 23 in FIG. 2. [Figure 4] FIG. 2 is a partial top view of the electrode 22 and the electrode lead-out portion 23. [Diagram 5] 5A to 5C are explanatory diagrams of a manufacturing process of the ceramic base 20 and a process of joining the power supply member 50 to the electrode extraction portion 23. [Figure 6] FIG. 13 is an enlarged view of the periphery of an electrode lead-out portion 23 of a modified example. [Figure 7] FIG. 13 is an enlarged view of the periphery of an electrode lead-out portion 23 of a modified example. [Figure 8] FIG. 13 is a partial top view of an electrode 22 and an electrode lead-out portion 23 of a modified example. [Figure 9] FIG. 13 is an enlarged view of the periphery of an electrode extraction portion 323 of a modified example. [Figure 10] FIG. 13 is a partial top view of an electrode 22 and an electrode lead-out portion 323 of a modified example. [Figure 11] FIG. 13 is an enlarged view of the periphery of an electrode lead-out portion 423 of a modified example. [Figure 12] FIG. 13 is a partial top view of an electrode 22 and an electrode lead-out portion 423 of a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Next, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing a schematic configuration of a wafer mounting table 10 of this embodiment (a cross-sectional view when the wafer mounting table 10 is cut on a plane including the central axis of the wafer mounting table 10), Fig. 2 is a partial enlarged view of Fig. 1 (an enlarged view of the inside of the frame shown by the two-dot chain line in Fig. 1), Fig. 3 is an enlarged view of the periphery of the electrode extraction part 23 in Fig. 2, and Fig. 4 is a partial top view of the electrode 22 and the electrode extraction part 23 (a top view of the periphery of the electrode extraction part 23). In Fig. 4, the area where the electrode 22 exists is hatched so that the positional relationship between the electrode 22 and the electrode extraction part 23 can be easily understood.

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

[0018] The ceramic base 20 is a disk-shaped member having a wafer mounting surface 20a on the upper surface. The ceramic base 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 sintering aids (e.g., rare earth elements, etc.) and unavoidable components in addition to the ceramic material. The main component means that the volume content of the whole is 50 volume % or more. The volume content of the ceramic material, which is the main component of the ceramic base 20, may be 80 volume % or more, or may be 90 volume % or more. Examples of the ceramic material include alumina and aluminum nitride. In this embodiment, the main component of the ceramic base 20 is alumina.

[0019] The ceramic base 20 incorporates an electrode 22 and an electrode lead-out portion 23. The electrode 22 and the electrode lead-out portion 23 are conductive. The electrode 22 is a flat, monopolar electrode. In this embodiment, the electrode 22 is a disk-shaped electrode. The electrode lead-out portion 23 is a member having a spherical trapezoid shape (a shape obtained by cutting a sphere along two horizontal planes). The electrode lead-out portion 23 is electrically connected to the electrode 22. The electrode lead-out portion 23 is disposed below the electrode 22, and a part of the upper surface of the electrode lead-out portion 23 is in contact with the lower surface of the electrode 22. The lower surface of the electrode lead-out portion 23 is exposed to the bottom surface of the power supply member insertion hole 28, and is in contact with the brazing material layer 29 disposed on the bottom surface of the power supply member insertion hole 28. The electrode lead-out portion 23 has a larger thickness in the vertical direction than the electrode 22. That is, as shown in FIG. 3, a thickness T2 of the electrode lead-out portion 23 is larger than a 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, or 20 times or more, the thickness T1. The electrode 22 is used as an electrostatic electrode in this embodiment. The layer of the ceramic base 20 above the electrode 22 functions as a dielectric layer. A power supply 62, which is a DC power supply for electrostatic attraction, 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 is a base bonding region 24 bonded to the ceramic base 20. In this embodiment, a circular through hole 22a is formed at a position of the electrode 22 that overlaps with the electrode extraction portion 23 when viewed virtually from above (FIG. 4), and a part of the upper surface of the electrode extraction portion 23 that is located directly below the through hole 22a is the base bonding region 24. When viewed virtually from above, the through hole 22a overlaps with the center portion of the electrode extraction portion 23. When viewed from above, the through hole 22a is provided so as 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 base bonding region 24. Since the through-hole 22 a 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 preferable. 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 the electrode 22 does not necessarily have to contain the same ceramic material as the main component of the ceramic substrate 20. The electrode 22 and the electrode extraction part 23 may contain, in addition to the conductive material and the ceramic material, components derived from a sintering aid (such as rare earth elements, etc.) and unavoidable components. Also, if 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. Further, 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. Further, regardless of whether the conductive material is one type or a plurality of types, the coefficient of thermal expansion of the conductive material (as a whole) contained in the electrode extraction portion 23 is preferably 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 taken as 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 taken as values calculated by the same method.

[0023] The cooling plate 30 is a disk-shaped member having a refrigerant flow passage 32 inside which a refrigerant can circulate. The refrigerant flow passage 32 is formed in a single 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 passage 32 are connected to a refrigerant circulation pump (not shown) that has 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 composite materials (also called metal matrix composites (MMCs)), and examples of the MMC include materials containing Si, SiC, and Ti, and materials in which a porous SiC body is impregnated with Al and / or Si. A material containing Si, SiC, and Ti is called SiSiCTi, a material in which a porous SiC body is impregnated with Al is called AlSiC, and a material in which a porous SiC body is impregnated with Si is called SiSiC. Examples of the metal include Al, Ti, Mo, and alloys thereof. The conductive material used for the cooling plate 30 is preferably one whose thermal expansion coefficient is close to that of the ceramic base 20 .

[0024] The bonding layer 40 bonds the lower surface of the ceramic base 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 pressurized and bonded while being heated to a temperature equal to or lower than the solidus temperature of the metal bonding material. As the bonding layer 40, an organic adhesive layer may be adopted 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 lead-out portion 23 and the electrode 22. The metal used for the power supply member 50 is, for example, W, Mo, Ni, etc., and the thermal expansion coefficient of the metal is preferably close to that of the ceramic base 20. The power supply member 50 is disposed so as to be inserted from the lower surface of the ceramic base 20 and is electrically connected to the electrode lead-out portion 23. More specifically, the power supply member 50 is inserted from the lower surface side of the cooling plate 30 through the cooling plate through hole 34 that penetrates the cooling plate 30 in the vertical direction and the bonding layer through hole 44 that penetrates the bonding layer 40 in the vertical direction, and is inserted into the power supply member insertion hole 28 provided in the ceramic base 20. 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 an insulating tube 36 arranged in the cooling plate through hole 34, and is inserted with some play into the power supply member insertion hole 28. The outer peripheral surface of the insulating tube 36 is bonded to the inner peripheral surface of the cooling plate through hole 34 via an adhesive layer 35. The upper end surface of the insulating tube 36 is located higher than the upper surface of the cooling plate 30 and below the lower surface of the ceramic base 20. The power supply member insertion hole 28 is a cylindrical hole provided in the ceramic base 20, and is provided so as to reach the electrode extraction portion 23 from the lower surface of the ceramic base 20.

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

[0027] Next, an example of use of the wafer mounting table 10 will be described. First, the wafer mounting table 10 is installed in a vacuum chamber (not shown), and the wafer W is mounted on the wafer mounting surface 20a of the wafer mounting table 10. Then, a voltage is applied from the power source 62 to the electrode 22 via the power supply member 50. Then, the wafer W is adsorbed and fixed to the wafer mounting 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 placed on the ceiling of the vacuum chamber, and a high frequency voltage is applied between the upper electrode and the cooling plate 30 while a reactive gas is supplied from the shower head to the space between the wafer W and the upper electrode 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 mounting surface 20a is released. Incidentally, a coolant is passed through the coolant flow passage 32 when it is necessary to lower the temperature of the wafer W.

[0028] Next, the manufacturing method of the wafer mounting table 10, particularly the manufacturing process of the ceramic base 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, the first and second ceramic compacts 120a and 120b are formed from ceramic powder in a disk shape by tape casting, and a hole 121 having a spherical notch shape (a shape obtained by cutting a sphere along one horizontal plane) is formed on the upper surface of the second ceramic compact 120b by cutting (FIG. 5A). The second ceramic compact 120b may be formed by dividing it into multiple layers of compacts.

[0030] Next, a conductive paste is printed on the upper surface of the second ceramic compact 120b in 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, thereby forming an electrode extraction portion precursor 123 that will eventually become the electrode extraction portion 23. Next, the conductive paste is printed on the upper surface of the second ceramic compact 120b to form an electrode precursor 122 that will eventually become the electrode 22. The electrode precursor 122 is printed in a pattern having a through hole 122a that will eventually become the through hole 22a. As a result, the lower surface of the electrode precursor 122 and the upper surface of the electrode extraction portion precursor 123 come into contact with each other, and the portion of the upper surface of the electrode extraction portion precursor 123 that is located directly below the through hole 122a becomes the base bonding region 124. The base bonding region 124 is a region that will eventually become the base bonding region 24. The conductive paste may be, for example, a paste containing particles of the conductive material used for the electrodes 22 and the electrode lead-out portions 23 described above and particles of the same ceramic material as the main component of the ceramic base 20. The conductive paste may contain a sintering aid. The volume contents C1 and C2 described above can be adjusted by adjusting the content ratio of the ceramic material in the conductive paste.

[0031] Next, the first and second ceramic molded bodies 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 molded body 120a enters the through hole 122a and contacts the base bonding region 124 of the electrode extraction portion precursor 123. This laminate 120 is hot-press fired and then cooled to room temperature, and the power supply member insertion hole 28 is formed by cutting, and the outer shape and thickness are appropriately processed to obtain a ceramic base 20 (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 portion precursor 123 having the base bonding region 124 becomes the electrode extraction portion 23 having the base bonding region 24 after hot-press firing and after the power supply member insertion hole 28 is formed. The power supply member insertion hole 28 can be formed, for example, by countersinking. The power supply member insertion hole 28 is formed to a depth such that the electrode extraction portion precursor 123 is exposed at the bottom surface of the power supply member insertion hole 28. A part of the lower side of the electrode extraction portion precursor 123 is cut away by the countersinking at this time to form the electrode extraction portion 23. The electrode extraction portion 23 and the ceramic particles of the ceramic base 20 surrounding the electrode extraction portion 23 are bonded in close contact with each other by the hot press firing. Therefore, the base bonding region 24 of the electrode extraction portion 23 is bonded to the ceramic base 20 in close contact with the ceramic particles (here, the ceramic particles in the through holes 122a) present directly above the base bonding region 24 of the ceramic base 20.

[0032] Next, the power supply member 50 and the electrode extraction portion 23 are joined together to electrically connect them. Specifically, a brazing sheet that will eventually become the brazing layer 29 is placed on the bottom surface of the power supply member insertion hole 28, and the power supply member 50 is inserted from the bottom surface of the ceramic base 20. That is, the brazing sheet is sandwiched between the bottom surface of the power supply member insertion hole 28 (including the part of the electrode extraction portion 23 that is exposed on the bottom surface) 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 layer 29 (FIG. 5E). As a result, the power supply member 50 and the electrode extraction portion 23 are joined together and electrically connected via the brazing layer 29.

[0033] In parallel with these steps, the cooling plate 30 is prepared by a known method, and the insulating tube 36 is attached to the cooling plate 30 via an adhesive layer 35. Then, the cooling plate 30 is bonded to the ceramic base 20 after the above-mentioned steps are performed via a bonding layer 40 to obtain the wafer mounting table 10. The step of bonding the power supply member 50 to the electrode extraction portion 23 (FIG. 5E) may be performed before or after bonding the cooling plate 30 to the ceramic base 20.

[0034] In the wafer mounting table 10 of the present embodiment described above, the electrode lead-out portion 23 has a higher volume content of the ceramic material, which is the same as the main component of the ceramic base 20, compared to the electrode 22. That is, the volume content C2 is higher than the volume content C1. This allows the electrode lead-out portion 23 to have a smaller thermal expansion coefficient difference with the ceramic base 20. Therefore, peeling or cracking of the electrode 22 caused by stress acting on the electrode 22 from the electrode lead-out portion 23 due to temperature change can be suppressed. For example, if the electrode lead-out portion 23 has a lower thermal expansion coefficient than the ceramic base 20, if the difference between the thermal expansion coefficients is large, when the laminate 120 is hot-press fired and then cooled to room temperature in the manufacturing process of the ceramic base 20, the electrode lead-out portion 23 (more precisely, the electrode lead-out portion precursor 123) will shrink less due to temperature change during cooling compared to the ceramic base 20. In addition, when the electrode lead-out portion 23 has a higher thermal expansion coefficient than the ceramic base 20, if the difference between the thermal expansion coefficients is large, the electrode lead-out portion 23 (more precisely, the electrode lead-out portion precursor 123) contracts more due to temperature changes during cooling than the ceramic base 20. As a result, stress is generated from the electrode lead-out portion 23 to the electrode lead-out portion 23, which applies stress to the electrode 22 directly above the electrode lead-out portion 23, and the electrode 22 may peel off or crack. This stress is particularly likely to be large around the outer periphery of the upper surface of the electrode lead-out portion 23, and for example, the electrode 22 is likely to peel off or crack in the area indicated by the two dashed circles in FIG. 3. In addition, the electrode 22 may be stressed not only during cooling after firing the laminate 120, but also during cooling after use of the wafer mounting table 10. In contrast, in this embodiment, the volume content C2 is higher than the volume content C1, so that the stress acting on the electrode 22 from the electrode lead-out portion 23 can be suppressed, and peeling or cracking of the electrode 22 can be suppressed. Furthermore, if not only the volume content C2 in the electrode lead-out portion 23 but also the volume content C1 in the electrode 22 is increased, there is a concern that the resistance value of the electrode 22 will become too high, resulting in problems (e.g., a decrease in function as an electrostatic electrode). In contrast, in this embodiment, the volume content C1 is lower than the volume content C2, so that problems caused by the resistance value of the electrode 22 becoming too high can be suppressed.In addition, since the electrode extraction part 23 does not need to function as an electrostatic electrode like the electrode 22, even if the resistance value becomes high, it is less likely to cause a problem compared to the electrode 22. From the above, in the wafer mounting table 10 of this embodiment, it is possible to suppress an increase in the resistance value of the electrode 22 while suppressing the stress acting on the electrode 22 due to temperature change.

[0035] In addition, a part of the upper surface of the electrode lead-out portion 23 is a base bonding region 24 bonded to the ceramic base 20. As a result, the electrode lead-out portion 23 is in close contact with the ceramic base 20 in the base bonding region 24, so that the above-mentioned stress generated in the electrode lead-out portion 23 can be suppressed by the adhesion force between the base bonding region 24 and the ceramic base 20. As a result, even if stress is generated due to a difference in thermal expansion between the electrode lead-out portion 23 and the ceramic base 20 caused by a temperature change, the stress is unlikely to act on the electrode 22.

[0036] Furthermore, the electrode lead-out portion 23 has a greater thickness in the up-down direction than the electrode 22. When the electrode lead-out portion 23 is thicker than the electrode 22, that is, when the volume of the electrode lead-out portion 23 is greater than when the electrode lead-out portion 23 has the same thickness as the electrode 22, stress caused by the difference in thermal expansion between the electrode lead-out portion 23 and the ceramic base 20 due to temperature change tends to be large, and therefore it is highly meaningful to apply the present invention. In addition, since the electrode lead-out portion 23 is thicker than the electrode 22, it is possible to prevent not only the electrode lead-out portion 23 but also the electrode 22 from being cut when the power supply member insertion hole 28 is formed.

[0037] It goes without saying that the present invention is not limited to the above-described embodiment, and can be embodied in various forms within the technical scope of the present invention.

[0038] For example, in the above-described embodiment, the electrode lead-out portion 23 has the base bonding region 24, but it may not have the base bonding region 24 as shown in Fig. 6. In Fig. 6, the electrode 22 does not have a through-hole 22a, and the electrode 22 is present directly above the entire upper surface of the electrode lead-out portion 23, so that the upper surface of the electrode lead-out portion 23 does not have the base bonding region 24. Even in this case, since the volume content C2 is higher than the volume content C1, it is possible to suppress an increase in the resistance value of the electrode 22 and to 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 is the base bonding region 24, but the position of the base bonding region 24 is not limited thereto. For example, as shown in Figs. 7 and 8, the base 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 AA in Fig. 8. In Figs. 7 and 8, the base bonding region 24 of the electrode 22 has a region 224a and a plurality of (here, six) regions 224b. The region 224a is provided in 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 base 20. Further, the electrode 22 is provided with a plurality of (here, six) trapezoidal through holes 222b provided so as to straddle the outer peripheral edge portion (the circular outline portion of the electrode lead-out portion 23 shown in FIG. 8) of the electrode lead-out portion 23 from the inside to the outside in the radial direction of the electrode lead-out portion 23 in a top view. As a result, a region 224b including a part of the outer peripheral edge portion of the upper surface of the electrode lead-out portion 23 (the part shown by the solid line among the outlines of the electrode lead-out portion 23 shown in FIG. 8) is not in contact with the electrode 22, and is a part of the base bonding region 24 that is bonded to the ceramic base 20. The part of the upper surface of the electrode lead-out portion 23 other than the base bonding region 24 (regions 224a, 224b) 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 is likely to be large, particularly around the outer peripheral edge portion of the upper surface of the electrode lead-out portion 23. Therefore, by including a part of this outer peripheral edge in the region 224b of the base bonding region 24, the stress acting on the electrode 22 due to temperature changes can be further reduced. If the entire outer peripheral edge of the upper surface of the electrode extraction part 23 is made the base bonding region 24, the electrode extraction part 23 and the electrode 22 will not be electrically connected to each other. Therefore, in Figs. 7 and 8, not the entire outer peripheral edge of the upper surface of the electrode extraction part 23 but a part of it is included in the base bonding region 24. In Figs. 7 and 8, the number of regions 224b may be one. In Figs. 7 and 8, the base bonding region 24 may not include the region 224a. In other words, the electrode 22 may not have a through hole 222a.

[0040] In the above-described embodiment, one electrode lead-out portion 23 is provided for one power supply member 50, but this is not limited thereto. A plurality of electrode lead-out portions 23 may be provided for one power supply member 50. For example, as shown in Figs. 9 and 10, three electrode lead-out portions 323a to 323c may be provided as electrode lead-out portions 323 for one power supply member 50. Fig. 9 is a BB cross-sectional view of Fig. 10. In Figs. 9 and 10, the electrode lead-out portion 323 has three electrode lead-out portions 323a to 323c arranged at a distance from each other. The base bonding region 324 has regions 324a to 324c which are parts of the upper surfaces of the three electrode lead-out portions 323a to 323c. Each of the electrode lead-out portions 323a to 323c is a member having a spherical trapezoid shape, and the lower surface is bonded to the power supply member 50 via the brazing material layer 29 and electrically connected. The electrode 22 is provided with a through hole 322a similar to the through hole 22a. The through hole 322a is provided so as to straddle the outer peripheral edge of each of the electrode extraction parts 323a to 323c from the inside to the outside in the radial direction when viewed from above. As a result, regions 324a to 324c including a part of the outer peripheral edge of each of the electrode extraction parts 323a to 323c (portions indicated by solid lines among the contours of the electrode extraction parts 323a to 323c shown in FIG. 10) are not in contact with the electrode 22 and serve as a base bonding region 324 bonded to the ceramic base 20. The portion of the upper surface of the electrode extraction part 323 other than the base bonding region 324 (regions 324a to 324c) is in contact with the lower surface of the electrode 22 and is electrically connected thereto. Since the electrode lead-out portion 323 is divided into a plurality of electrode lead-out portions 323a to 323c, the stress caused by the difference in thermal expansion between the electrode lead-out portion 323 and the ceramic base 20 due to temperature change can be reduced compared to the case where one electrode lead-out portion 23 having the same volume as the total volume of the plurality of electrode lead-out portions 323a to 323c is provided. In addition, a part of the outer periphery of the upper surface of each of the plurality of electrode lead-out portions 323a to 323c is included in the base bonding region 324 (regions 324a to 324c). Therefore, similar to the electrode lead-out portion 23 shown in FIG. 7 and FIG. 8, the stress acting on the electrode 22 from the electrode lead-out portion 323 due to temperature change can be further reduced. In FIG. 9 and FIG. 10, the electrode 22 may not have the through hole 322a and the base bonding region 324 may not exist.Furthermore, one or more of the regions 324a-324c of the electrode extracting portions 323a-323c may not include part of the outer periphery of the upper surface of the corresponding electrode extracting portion 323a-323c, for example, one or more of the regions 324a-324c of the electrode extracting portions 323a-323c may be located in the center of the corresponding electrode extracting portion 323a-323c. Even in these cases, the above-mentioned effect obtained by dividing the electrode extracting portion 323 into the multiple electrode extracting portions 323a-323c can be obtained.

[0041] In the above-mentioned embodiment, the electrode extraction part 23 may have a through hole penetrating the electrode extraction part 23 in the vertical direction. For example, as shown in FIG. 11 and FIG. 12, the electrode extraction part 423 may have a through hole 425. FIG. 11 is a cross-sectional view taken along CC in FIG. 12. In FIG. 11 and FIG. 12, the electrode extraction part 423 has a through hole 425 penetrating the electrode extraction part 423 in the vertical direction, so that the ring-shaped region located directly below the through hole 22a on the upper surface of the electrode extraction part 423 is the base bonding region 424. Since the volume of the electrode extraction part 423 is reduced by the amount of the through hole 425, the stress caused by the thermal expansion difference between the electrode extraction part 423 and the ceramic base 20 due to temperature change can be reduced. In FIG. 11 and FIG. 12, the electrode 22 may not have the through hole 22a and the base bonding region 424 may not exist. Even in this case, the above-mentioned effect due to the electrode extraction part 423 having the through hole 425 can be obtained. 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.

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

[0043] In the above-mentioned embodiment, the electrode 22 is an electrostatic electrode, but it may be a heater electrode or an RF electrode (a high-frequency electrode for generating plasma). Even when the electrode 22 is a heater electrode or an RF electrode, there is a concern that a malfunction 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 a malfunction may occur, such as the voltage of the power supply to be applied to obtain the required amount of heat being too high. 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 when RF is applied and be damaged, or the amount of plasma generated may decrease due to the increase in power consumed by the electrode 22. By applying the present invention, it is possible to suppress such malfunctions while suppressing peeling and cracking of the electrode 22. Note that in the above-mentioned embodiment, the wafer mounting table 10 may have two or more of the electrostatic electrode, the heater electrode, and the RF electrode built into the ceramic base 20. In this case, the present invention may be applied to one or more of the built-in electrodes.

[0044] In the above embodiment, the electrode 22 is a flat electrode, but 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 part 23 is a region directly above which the mesh openings of the electrode 22 are present (i.e., not in contact with the electrode 22) and which is bonded to the ceramic base 20, that region can be called a base bonding region.

[0045] Although not specifically described in the above embodiment, the area of ​​the substrate bonding region 24 is 1.2 mm 2 In the case where the base bonding region has a plurality of regions as shown in Figs. 7 to 10, the area of ​​each of the plurality of regions is 1.2 mm 2 In addition, each of the multiple regions may have an area of ​​1.2 mm or more. 2 Not limited to cases where the area is 1.2 mm or more, but 2 It may contain one or more regions where the number is equal to or greater than 1.

[0046] In the above embodiment, a metal rod is used as the power supply member 50, but the power supply member 50 is not limited to this and may be, for example, a metal cable. [Industrial Applicability]

[0047] The present invention can be used in an apparatus for processing wafers. [Explanation of symbols]

[0048] 10 wafer mounting table, 20 ceramic base, 20a wafer mounting surface, 22 electrode, 22a, 122a, 222a, 222b, 322a through hole, 23, 123, 323, 323a to 323c, 423 electrode lead-out portion, 24, 124, 324, 424 base bonding area, 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 source, 120 laminate, 120a, 120b first and second ceramic molded bodies, 121 hole, 122 electrode precursor, 123 Electrode extraction portion precursor, 224a, 224b, 324a to 324c regions, 425 through hole.

Claims

1. a ceramic base having a wafer mounting surface on an upper surface thereof; An electrode embedded in the ceramic substrate; a conductive electrode lead-out portion built into the ceramic base and electrically connected to the electrode; Equipped with the electrode extraction portion has a higher volume content of the same ceramic material as the main component of the ceramic base than the electrode; a part of an upper surface of the electrode extraction portion is a base bonding region that is bonded to the ceramic base, The base bonding region includes a part of an outer periphery of an upper surface of the electrode extraction portion. Wafer placement stage.

2. a ceramic base having a wafer mounting surface on an upper surface thereof; An electrode embedded in the ceramic substrate; a conductive electrode lead-out portion built into the ceramic base and electrically connected to the electrode; a power supply member disposed so as to be inserted from a lower surface of the ceramic base and electrically connected to the electrode lead-out portion; Equipped with the electrode extraction portion has a higher volume content of the same ceramic material as the main component of the ceramic base than the electrode; A plurality of the electrode extraction portions are provided for one of the power supply members. Wafer placement stage.

3. A part of the upper surface of the electrode extraction portion is a base bonding region that is bonded to the ceramic base. The wafer stage according to claim 2 .

4. The base bonding region includes a part of an outer periphery of an upper surface of the electrode extraction portion. The wafer stage according to claim 3 .

5. The electrode lead-out portion has a through hole that penetrates the electrode lead-out portion in the vertical direction. The wafer mounting table according to any one of claims 1 to 4.

6. The electrode extraction portion has a thickness in the up-down direction greater than that of the electrode. The wafer mounting table according to any one of claims 1 to 4.

7. The ceramic material is alumina or aluminum nitride; The wafer mounting table according to any one of claims 1 to 4.

Images