Wafer mounting table and method for manufacturing wafer mounting table

Abstract

A wafer placement table on which a wafer is placed and fixed includes: an electrostatic chuck including a ceramic substrate having a wafer placement surface, and an ESC electrode and a heater electrode respectively implanted in the ceramic substrate; a metal cooling plate; and a resin adhesive sheet that adheres the electrostatic chuck and the cooling plate, the electrostatic chuck having a concavo-convex structure comprising one or more types of unit structures with respect to the adhesive surface of the adhesive sheet, and in the concavo-convex structure, protrusions are provided at a pitch of 100 [mu] m or more and 300 [mu] m or less.

Description

Technical Field

[0001] This invention relates to a wafer carrier stage for electrostatically adsorbing and fixing processed objects such as wafers, and particularly to the bonding of its electrostatic chuck. Background Technology

[0002] When performing prescribed processes such as plasma processing on semiconductor wafers (hereinafter referred to as wafers), wafer mounting stages (also called electrostatic chucks, etc.) for electrostatic adsorption and fixation of the wafers are known (see, for example, Patent Document 1 and Patent Document 2).

[0003] In summary, the aforementioned wafer stage has the following configuration: a ceramic substrate (ceramic component) in which ESC electrodes (electrostatic chuck electrodes) for electrostatic adsorption of the wafer and heater electrodes for heating the wafer are embedded, and a cooling plate (also called a stage, etc.) having a flow path for the refrigerant to cool the ceramic substrate is bonded together by an adhesive layer.

[0004] In the aforementioned wafer placement stage, with the wafer placed on the upper surface of the ceramic substrate, i.e., the placement surface, a DC voltage is applied to the ESC electrode to electrostatically adsorb and fix the wafer. Simultaneously, a coolant flows through the flow path inside the cooling plate, and the heater electrode is energized, thereby heating the wafer to a predetermined temperature distribution (heat distribution).

[0005] In the wafer stage described above, the desired temperature distribution is typically ensured by setting the heater electrodes in a manner that achieves a heat density that matches the heat dissipation distribution.

[0006] However, sometimes the desired heat density cannot be achieved due to deviations in the shape (cross-sectional area, width, etc.) of the heater electrodes from the design specifications. For this reason, the temperature distribution on the wafer surface fixed to the wafer stage may vary between individual wafers. Depending on the circumstances, a wafer stage that does not achieve the desired temperature distribution may also be manufactured.

[0007] Furthermore, the heat dissipation distribution in the wafer stage may vary between individual components due to variations in the thickness of the adhesive layer and the processing precision of the cooling plate. In particular, when an adhesive sheet made of sheet-like resin is used as the adhesive layer, uneven thickness of the adhesive sheet may cause distribution of thermal resistance, sometimes deteriorating the heat uniformity of the wafer stage.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2020-53460

[0011] Patent Document 2: Japanese Patent No. 5891332 Summary of the Invention

[0012] The present invention was made in view of the above-mentioned problems, and its object is to realize a wafer stage with better heat uniformity in the mounting surface than in the past.

[0013] To address the aforementioned issues, the first solution of the present invention is a wafer mounting stage for wafer placement and fixation, characterized by comprising an electrostatic chuck, the electrostatic chuck having a ceramic substrate with a wafer mounting surface, and ESC electrodes and heater electrodes respectively embedded within the ceramic substrate; a metal cooling plate; and a resin adhesive sheet that bonds the electrostatic chuck and the cooling plate together. The electrostatic chuck has a concave-convex structure composed of one or more unit structures on the adhesive surface of the adhesive sheet, wherein the protrusions in the concave-convex structure are arranged at a spacing of 100 μm or more and 300 μm or less.

[0014] The second aspect of the present invention is based on the wafer placement stage involved in the first aspect, characterized in that, in each of the one or more unit structures, the distance between the front end of the protrusion and the cooling plate is uniform.

[0015] The third aspect of the present invention is based on the wafer placement stage involved in the first aspect, characterized in that the bonding surface of the electrostatic chuck has the multiple unit structures, and the distance between the front end of the protrusion and the cooling plate is different in each of the multiple unit concave-convex structures.

[0016] The fourth aspect of the present invention is based on the wafer placement stage involved in the first to third aspects, characterized in that, in the concave-convex structure, the convex portion and the concave portion, which are straight in top view, are alternately and periodically arranged.

[0017] The fifth aspect of the present invention, based on the wafer stage involved in the fourth aspect, is characterized in that the bonding surface of the electrostatic chuck is composed of multiple unit regions, the multiple unit structures being: a first unit structure having a first protrusion forming the protrusion; and a second concave-convex structure having a second protrusion forming the protrusion, the distance between the front end of the first protrusion and the cooling plate and the distance between the front end of the second protrusion and the cooling plate are different, in each of the multiple unit regions, the first unit structure and the second unit structure exist mixed in a predetermined ratio, the predetermined ratio of each of the multiple unit regions being determined based on the reference temperature distribution generated on the placement surface when the heater electrode of the wafer stage with the bonding surface of the electrostatic chuck is energized.

[0018] The sixth aspect of the present invention, based on the wafer placement stage involved in the fourth aspect, is characterized in that the bonding surface of the electrostatic chuck is composed of multiple unit regions, the multiple unit structures being: a first unit structure, which is composed of a first protrusion forming the protrusion and a first recess forming the recess; a second unit structure, which is composed of a second protrusion forming the protrusion and having a distance from the cooling plate different from the first protrusion and a second recess forming the recess; and a third unit structure, which is composed of a third protrusion having a distance from the cooling plate the same as the first protrusion and a third protrusion having a depth greater than the first protrusion. The third recess with a large concave portion is formed; and a fourth unit structure is formed by a fourth protrusion at the same distance from the cooling plate as the second protrusion and a fourth recess with a depth greater than the second concave portion. In each of the plurality of unit regions, the first to fourth unit structures are mixed in a predetermined ratio. The predetermined ratio in each of the plurality of unit regions is determined based on the reference temperature distribution generated on the placement surface when the heater electrode of the wafer placement stage with the bonding surface flat of the electrostatic chuck is energized, and the thickness of the bonding sheet at the location corresponding to each of the plurality of unit regions.

[0019] The seventh aspect of the present invention is a method for manufacturing a wafer mounting stage for wafer placement and fixation, characterized by comprising the following steps: a preparation step, wherein an electrostatic chuck is prepared, the electrostatic chuck having a ceramic substrate having a wafer mounting surface, and an ESC electrode and a heater electrode respectively embedded inside the ceramic substrate; and a bonding step, wherein the electrostatic chuck and a metal cooling plate are bonded together with a resin adhesive sheet, the preparation step comprising: a correction step for setting an uneven structure by alternately and periodically setting protrusions and recesses on the adhesive surface of the electrostatic chuck for the adhesive sheet, the correction step being at least one of a first correction step and a second correction step, wherein the first correction step reduces the deviation in the temperature distribution generated on the mounting surface; and the second correction step, wherein if the adhesive sheet has uneven thickness, the recesses absorb the uneven thickness.

[0020] The eighth aspect of the present invention is based on the manufacturing method of the wafer stage involved in the seventh aspect, characterized in that, in the correction process, the concave-convex structure is composed of one or more unit structures, and the distance between the convex part and the concave part is set to be more than 100 μm and less than 300 μm respectively.

[0021] The ninth aspect of the present invention is based on the wafer stage manufacturing method involved in the eighth aspect, characterized in that, in the calibration process, in each of the one or more unit structures, the distance between the front end of the protrusion and the cooling plate is made uniform.

[0022] The tenth aspect of the present invention is based on the wafer stage manufacturing method involved in the eighth aspect, characterized in that, in the calibration process, the plurality of unit structures are provided on the bonding surface of the electrostatic chuck, such that the distance between the front end of the protrusion and the cooling plate is different in each of the plurality of unit structures.

[0023] The eleventh aspect of the present invention is based on the manufacturing method of the wafer stage involved in any of the eighth to tenth aspects, characterized in that, in the correction process, the protrusion and the recess are set as straight lines.

[0024] The twelfth aspect of the present invention, based on the wafer stage manufacturing method of the eleventh aspect, is characterized in that, when the correction process is the first correction process, the bonding surface of the electrostatic chuck is virtually divided into multiple unit regions, and the multiple unit structures are configured as follows: a first unit structure having a first protrusion forming the protrusion; and a second unit structure having a second protrusion forming the protrusion, such that the distance between the front end of the first protrusion and the cooling plate and the distance between the front end of the second protrusion and the cooling plate are different; in each of the multiple unit regions, the first unit structure and the second unit structure are mixed in a predetermined ratio; and the predetermined ratio in each of the multiple unit regions is set such that the temperature deviation in the temperature distribution generated on the placement surface when the heater electrode is energized is reduced compared to the temperature deviation in the reference temperature distribution generated on the placement surface when the heater electrode of the wafer stage with a flat bonding surface of the electrostatic chuck is energized.

[0025] The thirteenth aspect of the present invention, based on the wafer stage manufacturing method of the eleventh aspect, is characterized in that, when the correction process is the first and second correction processes, the bonding surface of the electrostatic chuck is virtually divided into multiple unit regions, and the multiple unit structures are configured as follows: a first unit structure, which is composed of a first protrusion forming the protrusion and a first recess forming the recess; a second unit structure, which is composed of a second protrusion forming the protrusion and having a distance from the cooling plate different from the first protrusion and a second recess forming the recess; and a third unit structure, which is composed of a third protrusion having a distance from the cooling plate the same as the first protrusion and a third recess having a depth greater than the first recess. The structure comprises a fourth unit structure, which consists of a fourth protrusion at the same distance from the cooling plate as the second protrusion and a fourth recess with a depth greater than the second recess. In each of the plurality of unit regions, the first to fourth unit structures are mixed in a predetermined ratio. The predetermined ratio in each of the plurality of unit regions is set such that the temperature deviation in the temperature distribution generated on the placement surface when the heater electrode is energized is reduced compared to the temperature deviation in the reference temperature distribution generated on the placement surface when the heater electrode of the wafer placement stage with the bonding surface of the electrostatic chuck is energized, and is based on the thickness of the bonding sheet at the location corresponding to each of the plurality of unit regions.

[0026] According to the first to thirteenth embodiments of the present invention, a wafer placement stage with excellent thermal conductivity is achieved compared to the case without a concave-convex structure.

[0027] In particular, according to the first to sixth and eighth to thirteenth schemes, in the heat transfer from the electrostatic chuck to the cooling plate, the heat transfer from the protrusion is dominant, and compared with the case without the concave-convex structure, a wafer stage that can achieve efficient heat transfer from the electrostatic chuck to the cooling plate can be realized.

[0028] In particular, according to the second, third, ninth and tenth embodiments, a wafer placement stage can be realized to achieve uniform heat transfer from the electrostatic chuck through the bonding sheet to the cooling plate.

[0029] In particular, according to the third and tenth embodiments, a wafer stage can be realized in which the degree of heat transfer from the electrostatic chuck through the bonding sheet to the cooling plate varies depending on the position.

[0030] In particular, according to the fifth and sixth schemes, a wafer stage can be realized that improves the temperature deviation in the mounting surface compared with the reference temperature distribution.

[0031] Furthermore, according to the sixth scheme, even when the bonding sheet has uneven thickness, a wafer placement stage can be achieved that improves the temperature deviation in the placement surface compared to the reference temperature distribution.

[0032] In addition, according to the twelfth and thirteenth schemes, by changing the formation method of the concave and convex structure according to the reference temperature distribution, the temperature deviation of the wafer placement surface can be corrected.

[0033] Furthermore, according to the thirteenth scheme, by adjusting the depth of the recess according to the uneven thickness of the adhesive sheet, the temperature deviation of the wafer placement surface can also be corrected even when the adhesive sheet has uneven thickness. Attached Figure Description

[0034] Figure 1 This is a schematic cross-sectional view of the wafer stage 10 along the thickness direction.

[0035] Figure 2 This is a schematic diagram illustrating the detailed structure of the bonding portion of the electrostatic chuck 20 and the adhesive sheet 40.

[0036] Figure 3 This is a diagram illustrating two types of convex-concave structures 25 with different shapes of the convex portion 23 and the concave portion 24.

[0037] Figure 4 This is a graph used to illustrate temperature deviation correction.

[0038] Figure 5 This is a diagram showing the measured cross-sectional shape profile of the electrostatic chuck 20.

[0039] Figure 6 This is a diagram used to illustrate the specific details of temperature deviation correction.

[0040] Figure 7 This is a figure showing the temperature distribution image IM2 in the placement surface 20a of the wafer stage 10, which is constructed using an electrostatic chuck 20 to be calibrated.

[0041] Figure 8 This is a diagram showing the formation of the high-rib structure 25H.

[0042] Figure 9 This is a diagram showing how the low-rib structure 25L is formed.

[0043] Figure 10 This is a schematic diagram showing the appearance of the bonding sheet 40 having a wafer stage 10 with uneven thickness.

[0044] Figure 11 This is a schematic diagram of a wafer stage 10 formed by providing an uneven structure 25 in the electrostatic chuck 20 to accommodate the uneven thickness of the bonding sheet 40.

[0045] Figure 12 This is a diagram used to illustrate the thickness-absorbing high-rib structure 25H.

[0046] Figure 13 This is a diagram used to illustrate the thickness-absorbing low-rib structure 25L. Detailed Implementation

[0047] <Chip Placement Stage>

[0048] Figure 1 This is a schematic cross-sectional view along the thickness direction of the wafer stage 10 according to an embodiment of the present invention. In summary, the wafer stage 10 has the following configuration: an electrostatic chuck 20 and a cooling plate 30 are joined by an adhesive sheet 40, thereby stacking the electrostatic chuck 20 and the cooling plate 30. The wafer stage 10, also referred to as a base, etc., is used to hold a semiconductor wafer (wafer) in place by the electrostatic chuck 20 during prescribed processes such as plasma processing, which are forms of workpieces.

[0049] The electrostatic chuck 20 is obtained by implanting an ESC electrode (electrostatic chuck electrode) 21 for electrostatically adsorbing a wafer into a plate-shaped (e.g., circular) ceramic substrate made of insulating ceramics such as Al2O3 and AlN. Figure 1 The electrostatic chuck 20 shown also incorporates heater electrodes 22 for heating the wafer. Such an electrostatic chuck 20 is also referred to as an electrostatic chuck heater. Figure 1 In the electrostatic chuck 20 shown, the ESC electrode 21 is embedded near the placement surface 20a, compared to the heater electrode 22. In the electrostatic chuck 20, the main surface opposite to the bonding surface 20b of the bonding sheet 40 becomes the placement surface 20a for placing the wafer.

[0050] Examples of materials used for the ESC electrode 21 and the heater electrode 22 include metals such as W, Mo, Ti, Si, and Ru, or their carbides, nitrides, etc.

[0051] The cooling plate 30 is a portion that has an internal flow path 31, through which a coolant (e.g., water) is introduced from the outside into the flow path 31 to cool the electrostatic chuck 20 and the wafer that is electrostatically attracted and fixed to its mounting surface 20a. Regarding the flow path 31, a preferred embodiment is a continuous groove arranged in a vortex shape in plan view to cool approximately the entire area of ​​the electrostatic chuck 20. Alternatively, it can be a configuration of multiple independent open-loop grooves arranged concentrically in plan view.

[0052] The preferred material for the cooling plate 30 is a metal such as aluminum; however, ceramic or a composite material of metal and ceramic may also be used.

[0053] Fins 32 may be provided protrudingly at at least one location in the flow path 31. The fins 32 have the function of increasing the flow rate of the refrigerant at their location, thereby locally improving cooling efficiency. The shape and size of the fins 32 are appropriately determined according to the cooling conditions required at their location. The fins 32 may be made of the same material as the cooling plate 30, or they may be made of a different material. It should be noted that a design without fins 32 is also possible.

[0054] The adhesive sheet 40 is an adhesive sheet made of resin such as thermosetting epoxy resin. The bonding of the electrostatic chuck 20 and the cooling plate 30 using the adhesive sheet 40 can be achieved, for example, by heat-pressurization bonding: the adhesive sheet 40 is sandwiched between the electrostatic chuck 20 and the cooling plate 30 to obtain a laminate, and the laminate is heated and pressurized at a specified temperature. The thickness of the adhesive sheet 40 is preferably at least 100 μm to 300 μm before bonding.

[0055] In addition, the wafer stage 10 also includes a first power supply unit 50 responsible for supplying power to the ESC electrode 21, and a second power supply unit 60 responsible for supplying power to the heater electrode 22.

[0056] A first power supply unit 50 is arranged along the stacking direction of the electrostatic chuck 20 and the cooling plate 30. The first power supply unit 50 includes: a power supply terminal 51; an insulating component (sleeve) 52 surrounding the power supply terminal 51; and a connecting portion 53 disposed at one end of the power supply terminal 51 and connected to the ESC electrode 21. The first power supply unit 50 is inserted into a through hole 33 and protrudes to the outside at the other end. Furthermore, at this other end, the power supply terminal 51 is electrically connected to an externally mounted ESC power supply 70.

[0057] In the wafer placement stage 10, when a wafer is placed on the placement surface 20a of the electrostatic chuck 20, the ESC power supply 70 applies a DC voltage to the ESC electrode 21 through the power supply terminal 51 and the connection part 53, thereby electrostatically adsorbing the wafer onto the placement surface 20a.

[0058] Additionally, the second power supply unit 60 includes: a power supply terminal 61; an insulating component (sleeve) 62 surrounding the power supply terminal 61; and a connecting portion 63 disposed at one end of the power supply terminal 61 and connected to the heater electrode 22. The second power supply unit 60 is inserted into a through hole 34 provided in the cooling plate 30, and protrudes to the outside at the other end. Furthermore, at this other end, the power supply terminal 61 is electrically connected to a heater power supply 80 provided externally.

[0059] In the wafer stage 10, the heater electrode 22 is energized by the heater power supply 80 through the power supply terminal 61 and the connection part 63, thereby heating the wafer stage 10 and the wafer.

[0060] Additionally, a refrigerant inlet / outlet 35, communicating with the flow path 31, is provided through the cooling plate 30. It should be noted that... Figure 1 For the sake of simplicity, only one refrigerant inlet / outlet 35 is shown in the diagram. However, in reality, there is one refrigerant inlet / outlet 35 at each of the two ends of the groove forming the flow path 31. Each refrigerant inlet / outlet 35 is connected to a cooler unit 90 that circulates and supplies refrigerant to the flow path 31.

[0061] In the wafer stage 10 with the above configuration, the wafer placed on the placement surface 20a is electrostatically adsorbed and fixed by applying voltage to the ESC electrode 21. At the same time, the heater electrode 22 is energized to heat the wafer and the coolant is circulated to the flow path 31 to balance the heating and cooling. As a result, the wafer can be heated with a specified temperature distribution.

[0062] The wafer stage 10 can be manufactured in the following order: for example, after preparing an electrostatic chuck 20 with an ESC electrode 21 and a heater electrode 22 implanted therein, and a cooling plate 30, the electrostatic chuck 20 and the cooling plate 30 are bonded together with an adhesive sheet 40, and then the first power supply section 50 and the second power supply section 60 are implanted.

[0063] The electrostatic chuck 20 can be manufactured as follows: for example, multiple ceramic green sheets, including a ceramic green sheet printed with an electrode pattern for ESC electrode 21 and a ceramic green sheet printed with an electrode pattern for heater electrode 22, are laminated and bonded together to form a green sheet molded body, which is then hot-pressed and fired.

[0064] It should be noted that the loading surface 20a of the electrostatic chuck 20 after hot pressing and firing can be subjected to the molding process (convex-concave processing) described later, and a large number of protrusions (protrusions) are provided.

[0065] In addition, the cooling plate 30 can be manufactured by methods such as machining of bulk metal and casting.

[0066] <Detailed Structure of the Electrostatic Chuck>

[0067] The following describes in detail the bonding structure of the ceramic electrostatic chuck 20 and the resin adhesive sheet 40 in the wafer stage 10 according to this embodiment.

[0068] Figure 2 This is a schematic diagram illustrating the detailed structure of the bonding portion between the electrostatic chuck 20 and the adhesive sheet 40. Figure 2 (a) is a schematic cross-sectional view of the wafer stage 10. Figure 2 (b) in the middle is Figure 2 A schematic enlarged cross-sectional view of part A shown in (a) of the diagram. It should be noted that... Figure 2 The dimensions of the parts shown are different from the actual dimensions, especially the thickness of the adhesive sheet 40 is exaggerated.

[0069] Figure 2 (a) or Figure 1 The interface between the electrostatic chuck 20 and the bonding sheet 40 appears to be flat, but this is merely a simplified illustration. Regarding the electrostatic chuck 20 involved in this embodiment, in reality, as shown... Figure 2 As shown in (b), the interface with the adhesive sheet 40, namely the adhesive surface 20b, has a fine uneven structure 25 with a large number of protrusions 23 and concave portions 24 arranged alternately and periodically.

[0070] More specifically, each protrusion 23 is spaced apart from each other by a predetermined distance p in a first direction within a plane, and extends for a predetermined length in a second direction orthogonal to the first direction within the plane.

[0071] Figure 2 In the following figures, a right-handed xyz coordinate system is used, where the first direction is defined as the x-axis, the second direction as the y-axis, and the direction orthogonal to the x-axis and y-axis as the z-axis. Furthermore, regarding the configuration of the wafer stage 10, the explanation assumes that the cooling plate 30, the bonding sheet 40, and the electrostatic chuck 20 are stacked in this order facing the positive z-axis direction (vertically upwards), and that the plane including the x-axis and y-axis (xy plane) is parallel to the horizontal plane.

[0072] In this case, each protrusion 23 protrudes in the negative z-axis direction, is separated from each other by a predetermined distance p in the x-axis direction, and extends in a straight line with a predetermined length in the y-axis direction, which is orthogonal to the x-axis direction in the horizontal plane.

[0073] Furthermore, adjacent protrusions 23 in the x-axis direction form recesses 24. Similarly to the protrusions 23, each recess 24 is spaced apart from each other at a predetermined distance p in the x-axis direction, and extends in a straight line for a predetermined length in the y-axis direction, which is orthogonal to the x-axis direction in the horizontal plane.

[0074] Hereinafter, the uneven structure 25 of the electrostatic chuck 20 will also be referred to as a rib structure. Furthermore, in Figure 2 In the case shown in (b), the protrusion 23 that constitutes the concave-convex structure (rib structure) 25 is closest to the front end face of the cooling plate 30. Figure 2 (b) The height of the lowest end face 23e is uniform. On the other hand, the bottom surface of each recess 24 that is furthest from the cooling plate 30 is ( Figure 2 In (b) of the diagram, the height of the uppermost surface (24e) is also uniform. It should be noted that in... Figure 2In the case shown in (b), the cross section of the protrusion 23 is trapezoidal and its side portion 23s is inclined. However, this is not a necessary option, and the cross section of the protrusion 23 can also be rectangular.

[0075] When an electrostatic chuck 20 with such an uneven structure 25 at the interface is bonded to a cooling plate 30 using an adhesive sheet 40 made of resin and therefore elastic, the protrusions 23 enter the adhesive sheet 40, and the adhesive sheet 40 deforms and enters the recesses 24. Thus, the recesses 24 are completely filled by the adhesive sheet 40. This bonding of the electrostatic chuck 20 and the cooling plate 30 based on the adhesive sheet 40 can be achieved by heat-pressurization bonding, which involves heating and pressurizing their laminated bodies at a specified temperature.

[0076] It should be explained that Figure 2 In the cross-section of the concave-convex structure 25 shown in (b), there must exist a concave-convex reference line L with the following relationship: That is, there must exist a concave-convex reference line L in which the cross-sectional area of ​​the portion 23a of a convex part 23 located below (negative z-axis direction) of the concave-convex reference line L is equal to the cross-sectional area of ​​the portion 24a of a concave part 24 located next to the convex part 23 located above (positive z-axis direction) the concave-convex reference line L. It should be noted that, considering symmetry, it can also be said that the portion adjacent to the convex part 23 in the horizontal direction of the portion of the concave part 24 located on both sides of the convex part 23 located above (positive z-axis direction) the concave-convex reference line L is the portion 24a.

[0077] It should be noted that the convex-concave reference line L forms a portion of a convex-concave reference surface parallel to the XY plane containing the convex-concave reference line L. The convex-concave reference surface is a surface whose volume is equal to that of a portion 23a of a convex portion 23 located below (negative side in the z-axis direction) of the convex portion 23 and the volume of a portion 24a of a concave portion 24 adjacent to the convex portion 23 located above the convex-concave reference line.

[0078] In other words, the concave-convex structure 25 is set in such a way that there is a concave-convex reference line L. Furthermore, it is further confirmed that the height position of the concave-convex reference line L is not necessarily the same as the midpoint of the distance (hereinafter, the concave-convex height) h between the front end face 23e of the protrusion and the bottom face 24e of the concave portion 24.

[0079] The datum line L represents a line at a height equivalent to the lower surface of the electrostatic chuck 20 when the datum structure 25 is virtually flattened and smoothed. When the protrusions 23 and recesses 24 are formed based on the pre-set datum line L, the resin of the adhesive sheet 40, pushed aside by the entry of the protrusion 23 located below the datum line L, precisely enters the portion of the adjacent recess 24 located above the datum line L. That is, the entry of the protrusion 23 toward the adhesive sheet 40 and the entry of the adhesive sheet 40 toward the recess 24 are balanced above and below the datum line L.

[0080] Therefore, from a macroscopic perspective, the bonding of the electrostatic chuck 20 and cooling plate 30 with the concave-convex structure 25 based on the adhesive sheet 40 in this embodiment is substantially equivalent to the bonding of the electrostatic chuck 20 and cooling plate 30 based on the adhesive sheet 40 without such a concave-convex structure 25 and with the flat surface corresponding to the concave-convex reference line L becoming the adhesive surface 20b.

[0081] On the other hand, in the wafer stage 10 according to this embodiment, compared with the case where the flat surface without the uneven structure 25 becomes the bonding surface 20b, the contact area between the electrostatic chuck 20 and the bonding sheet 40 is increased, and therefore, the bonding strength of the electrostatic chuck 20 is further improved.

[0082] Furthermore, when the electrostatic chuck 20 heats up due to the power supply to the heater electrode 22, such as when heating a wafer placed on the placement surface 20a, the heat is transferred from the electrostatic chuck 20 to the cooling plate 30 via the adhesive sheet 40. However, using... Figure 2 In the case of the uneven structure 25 shown in (b), the thermal conductivity of the ceramic constituting the electrostatic chuck 20 is higher than that of the resin constituting the adhesive sheet 40. Therefore, heat transfer via the protrusion 23 (especially near the front end face 23e) is dominant compared to heat transfer via the portion of the adhesive sheet 40 that enters the recess 24 (especially near the bottom surface 24e). This is because heat transfer is more likely to occur not only at the front end face 23e as indicated by arrow AR1, but also from the side surface 23s near the front end face 23e. For example, Al2O3 (alumina), exemplified as the ceramic material constituting the electrostatic chuck 20, has a thermal conductivity of 35 W / m·K, while the thermal conductivity of thermosetting epoxy resin, exemplified as the resin material constituting the adhesive sheet 40, is 0.2 W / m·K.

[0083] As a result, in an electrostatic chuck 20 having a concave-convex structure 25 along a certain concave-convex reference line L, heat transfer occurs more efficiently than in an electrostatic chuck 20 that simply has a flat bonding surface 20b at a position corresponding to the concave-convex reference line L.

[0084] Furthermore, if the uneven thickness of the adhesive sheet 40 is ignored, the distance between the cooling plate 30 and the front end face 23e of the protrusion 23 that governs heat transfer is uniform within the range of height uniformity, as described above. Therefore, from the perspective of the entire range, the heat transfer from the electrostatic chuck 20 to the cooling plate 30 via the adhesive sheet 40 can be made uniform.

[0085] It should be noted that the superior heat transfer performance of the electrostatic chuck 20 with the uneven structure 25 compared to the electrostatic chuck 20 without the uneven structure 25 means that, under the same conditions of energizing the heater electrode 22, the former method of heating the wafer stage 10 by energizing the heater electrode 22 is more efficient than the latter method, resulting in easier heat transfer from the wafer and easier cooling of the wafer. Therefore, when heating the wafer using the former method to achieve the same temperature as the latter, the wafer stage 10 can be used by increasing the heater power from the heater power supply 80 or by using a thicker bonding sheet 40. In this case, heat transfer can be made more uniform, and the electrostatic chuck 20 can heat the wafer in the same way as the method without the uneven structure 25.

[0086] Preferably, the spacing p of the protrusions 23 is set to be 100 μm or more and 300 μm or less. Furthermore, Figure 2 In the case of the rib structure 25 shown in (b), the recesses 24 also have the same spacing p. When the spacing p of the protrusions 23 is less than 100 μm, it is not easy to ensure the processing accuracy, including the formation of the recesses 24, and it is not easy to obtain the desired concave-convex structure 25, so it is not preferred. In addition, when the spacing p of the protrusions 23 exceeds 300 μm, in order for the adhesive sheet 40 to enter the recesses 24 during bonding, the resin constituting the adhesive sheet 40 needs to move (displace, deform) significantly, and residual stress remains after bonding, so it is not preferred.

[0087] More preferably, the spacing p of the protrusions 23 is set to 150 μm or more. In this case, the desired uneven structure 25 can be formed relatively easily and reliably, and the heat transfer efficiency can also be well achieved.

[0088] However, the shapes of the convex part 23 and concave part 24 corresponding to a certain convex or concave reference line L are not limited to one type. Figure 3 This is a diagram illustrating two types of concave-convex structures 25 (25H, 25L) where the concave-convex reference line L is universal, but the shapes of the convex part 23 and the concave part 24 are different.

[0089] Figure 3In the concave-convex structure 25H shown on the left, the cross-section of the convex portion 23 (23H) is narrower in the horizontal direction (x-axis direction) and longer in the figure. On the other hand, the cross-section of the concave portion 24 (24H) is wider in the horizontal direction than that of the convex portion 23 (23H). The distance from the concave-convex reference line L to the front end face 23e of the convex portion 23 is greater than the distance from the concave-convex reference line L to the bottom face 24e of the concave portion 24. However, the cross-sectional areas of the portion 23a below the concave-convex reference line L and the portion 24a above the concave-convex reference line L are equal.

[0090] In contrast, Figure 3 In the concave-convex structure 25L shown on the right, the cross-section of the convex portion 23 (23L) and the cross-section of the concave portion 24 (24L) have the same shape. Similarly, the cross-sectional areas of the portion 23a below the concave-convex reference line L and the portion 24a above it are equal.

[0091] When comparing the concave-convex structure 25H and the concave-convex structure 25L, the concave-convex reference line L is the same, and within the scope of each structure, the distance from the front end face 23e of the protrusion 23 to the cooling plate 30 is constant. On the other hand, the distance from the concave-convex reference line L to the front end face 23e of the protrusion 23H in the concave-convex structure 25H is greater than the distance from the concave-convex reference line L to the front end face 23e of the protrusion 23L in the concave-convex structure 25L. Therefore, the distance from the protrusion 23H to the cooling plate 30 is smaller compared to the protrusion 23L.

[0092] Hereinafter, the front end face 23e of the protrusion 23 relative to the concave-convex structure 25H that is far from the concave-convex reference line L will be referred to as a high rib structure (or H rib) 25H, and the front end face 23e of the protrusion 23 relative to the concave-convex structure 25L that is close to the concave-convex reference line L will be referred to as a low rib structure (or L rib) 25L. It should be noted that... Figure 3 The high-rib structure 25H and low-rib structure 25L shown are merely illustrative examples, and their specific shapes are not limited to these.

[0093] The difference in the uneven structure 25 is related to the amount of heat transfer from the electrostatic chuck 20 to the cooling plate 30 via the adhesive sheet 40.

[0094] That is, the smaller the distance from the front end face 23e to the cooling plate 30, the smaller the thermal resistance of the adhesive sheet 40 and the greater the heat transfer. Conversely, the larger the distance from the front end face 23e to the cooling plate 30, the greater the thermal resistance of the adhesive sheet 40 and the smaller the heat transfer. Therefore, if Figure 3 In the case shown, the heat transfer from the front end face 23e of the protrusion 23 to the high-rib structure 25H is greater than that to the low-rib structure 25L shown on the right. That is, under the same conditions of energizing and heating with the heater electrode 22, the part where the high-rib structure 25H is located is easier to cool than the part where the low-rib structure 25L is located.

[0095] In this embodiment, the relationship between the distance from the front end face 23e of the protrusion 23 to the cooling plate 30 and the thermal resistance of the adhesive sheet 40, as described above, is used to correct the deviation in the heat distribution in the mounting surface 20a of the electrostatic chuck 20. In principle, the higher the temperature of a region is compared to a certain reference temperature, the closer the front end face 23e of the protrusion 23 is to the cooling plate 125 in the concave-convex structure 25 located on its opposite side; conversely, the lower the temperature of a region is compared to the reference temperature, the further the front end face 23e of the protrusion 23 is from the cooling plate 125. Therefore, compared to the case where no correction is performed, the deviation in temperature (or heat density) in the mounting surface 20a can be reduced (resulting in homogenization of the mounting surface 20a).

[0096] It should be noted that the above correction is only intended to reduce the temperature deviation relative to a certain reference temperature, and to make the temperature of a certain part of the placement surface 20a consistent with the reference temperature. The absolute temperature adjustment is carried out as follows: when the wafer placement stage 10 is used, the heater power input to the heater power supply 80 is adjusted, and the thickness of the bonding sheet 40 to be used is adjusted in advance.

[0097] Figure 4 This diagram illustrates the temperature (or heat density) deviation correction performed in this embodiment. In this embodiment, the electrostatic chuck 20 is divided into multiple unit regions RE in a top view. The mixing ratio (planar area ratio) of the high-rib structure 25H and the low-rib structure 25L in each unit region RE varies according to the temperature before correction, thereby performing temperature (or heat density) correction for each unit region RE. Hereinafter, the region in unit region RE where the high-rib structure 25H is provided is referred to as sub-region RE1, and the region where the low-rib structure 25L is provided is referred to as sub-region RE2.

[0098] More specifically, the more high-rib structures 25H there are, the easier it is for temperature to drop; the more low-rib structures 25L there are, the less likely it is for temperature to drop. Using this relationship, the correspondence between the planar area ratio of sub-regions RE1 and RE2 and the correction amount for temperature (or heat density) is determined in advance through experiments. Furthermore, based on the actual heat distribution, the area ratio applied in each unit region RE is set, and concave-convex structures 25 corresponding to this area ratio are set in each unit region. This combination of high-rib structures 25H and low-rib structures 25L that provides the planar area ratio of sub-regions RE1 and RE2 is also called a rib pattern.

[0099] The high-rib structure 25H and the low-rib structure 25L are referred to as the first unit structure and the second unit structure, respectively. In other words, the rib pattern is a pattern in which one or more unit structures are mixed in a prescribed ratio. In addition, the convex portion 23H and the concave portion 24H of the high-rib structure 25H are referred to as the first convex portion and the first concave portion, respectively, and the convex portion 23L and the concave portion 24L of the low-rib structure 25L are referred to as the second convex portion and the second concave portion, respectively.

[0100] Figure 4 In the illustrated case, the area ratio of sub-region RE1 of the high-rib structure 25H, which consists of two partial sub-regions RE1a and RE1b, to sub-region RE2 of the low-rib structure 25L between the two sub-regions is 2:1. It should be noted that sub-region RE2 may also have partial sub-regions, and the number of partial sub-regions in sub-regions RE1 and RE2 is not particularly limited. However, it is preferable that sub-regions RE1 and RE2 are periodically arranged at least within the unit region RE.

[0101] in addition, Figure 5 This diagram shows the measured cross-sectional shape profile of the electrostatic chuck 20 when set in a unit region RE with planar dimensions of 37.5 mm × 37.5 mm, with four different ratios of a high-rib structure 25H with a spacing p of 150 μm and a convex-concave height h of 50 μm, and a low-rib structure 25L with a spacing p of 150 μm and a convex-concave height h of 20 μm. It should be noted that the reference temperature is set to 97.7 °C.

[0102] Figure 5 (a) shows the outline of the rib pattern with only the high-rib structure 25H. Experiments have confirmed that this rib pattern allows for temperature correction that reduces the temperature difference between the placement surface 20a (which is hotter than the reference temperature) and the reference temperature by 1°C. This is because during bonding, at the location of the high-rib structure 25H, its protrusion 23H enters the bonding sheet 40. Consequently, the front end face 23e of the protrusion 23H is closer to the cooling plate 30 than in the case without correction (where bonding is performed with a flat bonding surface 20b), thus increasing the heat transfer from the placement surface 20a.

[0103] on the other hand, Figure 5 (d) in the figure shows the outline of the rib pattern with only the low rib structure 25L. Regarding this rib pattern, experiments confirmed that temperature correction can be performed to reduce the temperature difference between the placement surface 20a (which is lower than the reference temperature) and the reference temperature by 1°C. This is because, during bonding, even at the location of the low rib structure 25L, its protrusion 23L enters the bonding sheet 40. However, the distance between the front end face 23e of the protrusion 23L and the cooling plate 30 is actually greater than in the case without correction (when bonding is performed with a flat bonding surface 20b), thereby reducing the heat transfer from the placement surface 20a.

[0104] Hereinafter, the correction based on the former rib pattern will be referred to as the correction with a temperature correction amount of -1℃, and the correction based on the latter rib pattern will be referred to as the correction with a temperature correction amount of +1℃.

[0105] also, Figure 5 (b) shows the outline of a rib pattern in which the high-rib structure 25H and the low-rib structure 25L are set at a ratio of 2:1. On the other hand, Figure 5 (c) shows the outline of the rib pattern in which the high rib structure 25H and the low rib structure 25L are set at a ratio of 1:2. When using these rib patterns, it was also confirmed that the temperature correction values ​​at the mounting surface 20a are -0.33°C and +0.33°C, respectively. This means that the temperature correction value when using a rib pattern that allows both the high rib structure 25H and the low rib structure 25L to coexist is the intermediate value of the temperature correction value when only one of the ribs is used.

[0106] By changing the rib pattern in each unit region RE of the mounting surface 20a according to its temperature before correction, an electrostatic chuck 20 with improved heat uniformity can be obtained compared to the case without correction.

[0107] <Specific examples of temperature deviation correction>

[0108] Next, a specific example of temperature deviation correction at the loading surface 20a by changing the rib pattern, or in other words, changing the area ratio of sub-region RE1 and sub-region RE2, will be explained. Figure 6 This is a diagram used to illustrate the specific details of temperature deviation correction.

[0109] It should be noted that, in the case of deviation correction, the wafer stage 10 should ideally be temporarily constructed using an electrostatic chuck 20 without the raised / lowered structure 25 (hereinafter referred to as an electrostatic chuck without raised / lowered structure 25), and the electrostatic chuck 20 should be heated by energizing the heater electrode 22. Based on the temperature distribution of the resulting placement surface 20a, the raised / lowered structure 25 should be provided on the electrostatic chuck 20. However, in this case, it is necessary to separate the electrostatic chuck 20 without raised / lowered structure 25, which is temporarily bonded to the cooling plate 30 with the adhesive sheet 40, and then provide the raised / lowered structure 25. However, it is not easy to separate it again, and if the electrostatic chuck 20 obtained after separation is formed with raised / lowered structure 25 and then bonded again, the bonding state may change. Therefore, such a solution is not necessarily practical.

[0110] On the other hand, for example, if a large number of smooth electrostatic chucks are manufactured under the same manufacturing conditions, the probability that the temperature distribution in each smooth electrostatic chuck is approximately the same is relatively high. Therefore, in this embodiment, under this premise, for a wafer stage 10 constructed using one of such a large number of smooth electrostatic chucks, Figure 6 The temperature distribution of the mounting surface 20a shown in (a) is measured, and the result is regarded as the temperature distribution before correction. The temperature deviation in other electrostatic chucks 20 manufactured under the same conditions is corrected as part of the preparation process before bonding. That is, for each unit area RE of the electrostatic chuck 20 from the same manufacturing batch as the electrostatic chuck 20 for which the temperature distribution measurement was performed, a concave-convex structure 25 is set with a general rib pattern based on the temperature distribution before correction.

[0111] It should be noted that in this case, the electrostatic chuck 20 without any irregularities that provides the temperature distribution before correction of the placement surface 20a is called the reference electrostatic chuck 20, and the electrostatic chuck 20 that performs temperature deviation correction by setting the irregularity structure 25 based on the temperature distribution before correction is called the electrostatic chuck 20 to be corrected.

[0112] Figure 6 Figure (a) shows a temperature distribution image (thermal imaging image) IM1 on the placement surface 20a of the reference electrostatic chuck 20 when the heater electrode 22 of the reference electrostatic chuck 20 is energized on the wafer placement stage 10, where the ceramic component of the electrostatic chuck 20 is made of alumina (Al2O3) and the bonding sheet 40 is made of thermosetting epoxy resin. It should be noted that in the temperature distribution image IM1, the closer the area is to white, the higher the relative temperature; the closer the area is to black, the lower the relative temperature. In the temperature distribution image IM1, there are high-temperature regions on the upper left and right sides, while low-temperature regions are distributed over a wider area in the lower half, excluding the area near the center. It should be noted that the difference between the highest and lowest temperatures is 3.1°C.

[0113] in addition, Figure 6 In (a), for a temperature distribution image IM1 like this, a grid M of squares with a side length of 37.5 mm is virtually superimposed. Grid M consists of all 64 (8 × 8) square unit grids Mu. Each unit grid Mu corresponds to the aforementioned unit region RE. Based on the temperature distribution within each unit grid Mu in the temperature distribution image IM1, the temperature correction amount in the unit region RE corresponding to the unit grid Mu of the electrostatic chuck 20 to be calibrated is determined. In the bonding surface 20b of the electrostatic chuck 20 to be calibrated, a concave-convex structure 25 (rib pattern) corresponding to the determined temperature correction amount is formed for each unit region RE.

[0114] In this calibration example, any one of the five rib patterns A to E shown in Table 1 is used for temperature calibration in each unit region RE. Calibration is performed in such a way that the intermediate temperature between the highest and lowest temperatures reaches the reference temperature. It should be noted that in Table 1, an area ratio of 0 for L-ribs or H-ribs means that only H-ribs (high rib structure 25H) or L-ribs (low rib structure 25L) are formed.

[0115] Table 1

[0116]

[0117] Table 1 shows, for example, the application of rib pattern A consisting only of high rib structure 25H to the cell region RE in which the temperature of the loading surface 20a should be reduced by 1°C compared with the temperature distribution in the cell grid Mu. Similarly, in the unit region RE where it is determined that the temperature of the loading surface 20a should be reduced by 0.33°C compared to before correction, a rib pattern B with a high rib structure 25H and a low rib structure 25L set at a ratio of 4:2 (=2:1) ​​is applied; in the unit region RE where it is determined that the temperature should be close to the reference temperature and maintained at the temperature before correction, a rib pattern C with a high rib structure 25H and a low rib structure 25L set at a ratio of 3:3 (=1:1) is applied; in the unit region RE where it is determined that the temperature of the loading surface 20a should be increased by 0.33°C compared to before correction, a rib pattern D with a high rib structure 25H and a low rib structure 25L set at a ratio of 2:4 (=1:2) is applied; and in the unit region RE where it is determined that the temperature of the loading surface 20a should be increased by 1°C compared to before correction, a rib pattern E consisting only of the low rib structure 25L is applied. It should be noted that the rib pattern settings are not limited to the cases given in Table 1 and can be appropriately set according to the obtained temperature distribution image.

[0118] and, Figure 6 (b) in the diagram refers to the rib pattern applied to the cell region RE corresponding to each cell grid Mu, based on the temperature distribution image IM1. Figure 6 The grid M in (a) is shown in the diagram. Based on this rib pattern, a raised / recessed structure 25 is provided in each unit region RE of the electrostatic chuck 20 to be calibrated.

[0119] also, Figure 7 It shows the adoption and acquisition Figure 6 The temperature distribution image IM1 in (a) is a diagram of the temperature distribution image IM2 on the placement surface 20a of the wafer stage 10, which is constructed from the same manufacturing batch of reference electrostatic chuck 20 and is an electrostatic chuck 20 to be calibrated. It should be noted that the temperature scale is consistent with the temperature distribution image IM1 based on the depth of the temperature scale.

[0120] Comparing temperature distribution image IM2 with temperature distribution image IM1, it can be seen that in temperature distribution image IM2, the significant high-temperature region has been eliminated, and the low-temperature region has also been reduced. It should be noted that the difference between the highest and lowest temperatures is 2.2℃.

[0121] The results demonstrate that the temperature deviation correction involved in this embodiment is an effective solution.

[0122] <Methods for forming concave and convex structures>

[0123] Next, one method for forming the concave-convex structure 25 as a preparatory step before bonding will be described. Specifically, a method for forming a rib structure with a trapezoidal cross-section for the protrusions 23 and concave portions 24 using laser processing will be described. Figure 8 This is a diagram showing the formation of the high-rib structure 25H. Figure 9 This diagram shows the formation of the low-rib structure 25L. It should be noted that... Figure 8 and Figure 9 In, with Figure 2 Compared to the above, the electrostatic chuck 20 is flipped up and down.

[0124] In the formation of any rib structure, it is common to repeatedly irradiate the surface of the object to be processed (the opposite side of the placement surface 20a) in the electrostatic chuck 20 before processing (before correction) with laser LB along the y-axis direction to form a recess 24 at the irradiation position of laser LB, but the specific irradiation method is different.

[0125] Now, as Figure 8 (a) and Figure 9 As shown in (a), the width of the front end face 23e of the protrusion 23 in the concave-convex structure 25 (high rib structure 25H or low rib structure 25L) with spacing p to be formed is set to w1, the width of the bottom face 24e of the concave part 24 is set to w2, the concave-convex height (the distance between the front end face 23e of the protrusion 23 and the bottom face 24e of the concave part 24) is set to h, and the maximum opening width of the concave part 24 (the width at the same height as the front end face 23e of the protrusion 23) is set to w0. In addition, the concave part 24 is formed such that the zx section orthogonal to its extension direction, i.e., the y-axis direction, is symmetrical with respect to the central axis C extending in the vertical direction (z-axis direction).

[0126] In this case, although the specific values ​​are different, however, Figure 8 (a) and Figure 9 The high rib structure 25H and low rib structure 25L shown in (a) both have the following structure: the front end face 23e has a width of w1 and a height of h; the convex part 23 extending along the y-axis direction and the bottom face 24e have a width of w2 and a maximum opening width of w0; and the concave parts 24 extending along the y-axis direction are alternately adjacent in the x-axis direction.

[0127] It should be noted that, from the viewpoint of ensuring good heat transfer from the electrostatic chuck 20 to the adhesive sheet 40, the width w1 of the front end face 23e of the protrusion 23 is preferably 40 μm or more. From the viewpoint of minimizing the influence of processing deviations, the width w1 of the front end face 23e of the protrusion 23 is also preferably 40 μm or more. Furthermore, if the inclination of the side portion 23s of the protrusion 23 relative to the horizontal plane (xy plane) is 45° or less, and the width w2 of the bottom surface 24e of the recess 24 is 10 μm or more, the adhesion of the adhesive sheet 40 can be more sufficiently ensured.

[0128] In the case of forming a high-ribbed structure of 25H, such as Figure 8 As shown in (b), within a specified width w3 along the x-axis of the machining target surface (opposite to the placement surface 20a) 20s of the electrostatic chuck 20 before processing (before calibration), laser LB is sequentially irradiated at positions spaced apart by a specified irradiation interval Δwa in the x-axis direction. The width w3 is set such that its center position in the x-axis direction becomes the position of the central axis C of the ultimately desired recess 24. Furthermore, the following settings are made... Figure 8 In the case of the convex portion 23 and concave portion 24 with a trapezoidal cross-section shown in (a), the width w3 can be smaller than the maximum opening width w0 of the concave portion 24 to be formed. The irradiation by the laser LB can be repeated a specified number of times.

[0129] For example, if a laser LB with an output power of 20W, a wavelength of 1030nm, and a frequency of 200kHz is used to form a high rib structure 25H with a spacing p of 150μm, a width w1 of the front end face 23e of the protrusion 23 of 40μm, a width w2 of the bottom face 24e of the concave part 24 of 10μm, a maximum opening width w0 of the concave part 24 of 140μm, a concave-convex height h of 45μm, and a distance of 15μm between the front end face 23e of the protrusion 23 and the concave-convex reference line L, then the laser LB with a width w3 of 29μm and an irradiation spacing Δwa of 1μm is repeatedly irradiated 3 times (that is, irradiated at position 30) with the position of the central axis C of the concave part 24 to be formed as the center.

[0130] On the other hand, in the case of forming a low-ribbed structure of 25L, firstly, as Figure 9 As shown in (b), within the entire forming range of the low rib structure 25L on the object surface (opposite to the placement surface 20a) 20s of the electrostatic chuck 20 before processing (before correction), laser LB is sequentially irradiated at positions spaced apart by a predetermined irradiation interval Δwb in the x-axis direction. As a result, the ceramic component constituting the electrostatic chuck 20 is removed to a predetermined depth d on the object surface 20s side. This irradiation by laser LB is referred to as one irradiation. One irradiation can be repeated a predetermined number of times.

[0131] Next, as Figure 9 As described in (c), in the newly formed surface 20t through this removal, laser LB is sequentially irradiated at each position spaced apart by a distance p. The irradiation position in the x-axis direction is set to the position of the central axis C of the ultimately desired recess 24. This irradiation by laser LB is referred to as a double irradiation. The double irradiation can be repeated a predetermined number of times.

[0132] For example, if a laser LB with an output power of 20W, a wavelength of 1030nm, and a frequency of 200kHz is used to form a low-rib structure 25L with a spacing p of 150μm, a width w1 of the front end face 23e of the protrusion 23 of 40μm, a width w2 of the bottom face 24e of the concave part 24 of 10μm, a maximum opening width w0 of the concave part 24 of 140μm, a height h of convexity and concaveness of 15μm, and a distance of 15μm between the front end face 23e of the protrusion 23 and the concaveity and concaveness reference line L, then after one irradiation with the laser LB with an irradiation spacing Δwb of 15μm, it is sufficient to repeat 10 irradiations with a spacing of 150μm.

[0133] It should be explained that Figure 8 and Figure 9 In order to simplify the illustration, the side portion 23s of the protrusion 23 is shown to have a straight cross section. However, depending on the processing conditions, it may sometimes be stepped or curved.

[0134] Furthermore, as described above, temperature deviation correction is performed for each unit region RE. However, the scanning distance of the laser LB in a known laser irradiation apparatus capable of performing high-precision laser LB irradiation at intervals of several μm to tens of μm is at most about 70 mm. Therefore, the size of the unit region RE is preferably at least 70 mm or less in the scanning direction (y-axis direction).

[0135] Furthermore, when correcting for temperature deviations, the rib patterns in each element region (RE) are typically different; therefore... Figure 8 and Figure 9 The combination of high-rib structure 25H and low-rib structure 25L formed by laser LB irradiation shown also corresponds to the rib pattern applied in each unit region RE. Therefore, although high-rib structure 25H and low-rib structure 25L are provided in multiple unit regions RE, when forming the desired rib pattern in each unit region RE, it is possible to form all high-rib structure 25H and low-rib structure 25L on the entire workpiece surface 20s, or to form high-rib structure 25H and low-rib structure 25L sequentially for each unit region RE in accordance with the applied rib pattern.

[0136] <Addressing Uneven Thickness of Adhesive Sheets>

[0137] like Figure 2 As shown in (b) of this embodiment, in the wafer stage 10, by providing the uneven structure 25, heat transfer from the electrostatic chuck 20 to the cooling plate 30 via the bonding sheet 40 can be homogenized at the same height as the front end face 23e of the protrusion 23. Furthermore, as... Figure 3 , Figure 4 As shown, taking advantage of the fact that the amount of heat transfer varies depending on the distance between the front end face 23e of the protrusion 23 and the cooling plate 30, and based on the rib pattern shown in Table 1, for each unit region RE, the temperature deviation in the mounting surface 20a of the electrostatic chuck 20 when energizing the heater electrode 22 is corrected.

[0138] However, such a correction effect should theoretically achieve the desired result if, before bonding, the bonding sheet 40 has no substantial thickness unevenness or if the thickness unevenness is substantially negligible. For example... Figure 4 The balance shown in the upper and lower convex portions 23 of the convex and concave reference line L towards the adhesive sheet 40 and towards the concave portion 24 is based on the premise that the thickness of the adhesive sheet 40 is uniform.

[0139] However, in actual adhesive sheets 40, for example, when the target thickness is 200 μm, there is sometimes a thickness unevenness of up to about 2 μm (a deviation from the specified thickness) that is localized or global.

[0140] Figure 10 This is a schematic diagram showing the appearance of the bonding sheet 40 having a wafer stage 10 with uneven thickness.

[0141] More specifically, Figure 10 Image (a) shows a wafer stage 10 formed by bonding an electrostatic chuck 20 and a cooling plate 30 together using an adhesive sheet 40 having an upwardly convex shape on the upper surface 40a of the adhesive surface to the electrostatic chuck 20. The thickness of this adhesive sheet 40 increases by a maximum of Δt relative to a reference thickness t. It should be noted that in this embodiment, the reference thickness t is not the thickness that the adhesive sheet 40 should ideally have (the thickness envisioned during the design of the wafer stage 10), but rather refers to the minimum thickness. Therefore, in this embodiment, the uneven thickness of the adhesive sheet 40 refers to areas with relatively larger thicknesses compared to other areas. Furthermore, for the electrostatic chuck 20, a depth-cutting process corresponding to the shape of the upper surface 40a of the adhesive sheet is performed to ensure the flatness of the loading surface 20a.

[0142] Figure 10 Figure (b) shows a schematic curve of the thermal resistance in the x-axis direction in an adhesive sheet 40 like this. It should be noted that... Figure 10(b) in the figure also corresponds to the temperature distribution curve in the mounting surface 20a when the heater electrode 22 is used for uniform heating.

[0143] The greater the thickness of the bonded sheet 40, the greater the thermal resistance; therefore, the less heat is transferred from the electrostatic chuck 20 to the cooling plate 30. That is, Figure 10 In the configuration shown in (a), the thickness difference of the adhesive sheet 40 is dominant for heat transfer from the electrostatic chuck 20 to the cooling plate 30, which affects the heat uniformity.

[0144] It should be explained that Figure 10 In (a) of the illustration, a case is shown where there is a protrusion throughout the adhesive sheet 40 for the sake of simplicity. However, in reality, there are also cases where there are one or more local thickness irregularities, and the electrostatic chuck 20 is deep-cut to address these thickness irregularities. In this case, the same applies to the fact that the thickness irregularities directly affect heat transfer from the electrostatic chuck 20 to the cooling plate 30.

[0145] on the other hand, Figure 11 This is a schematic diagram of a wafer stage 10 formed by providing an uneven structure 25 in the electrostatic chuck 20 to accommodate the uneven thickness of the bonding sheet 40.

[0146] More specifically, Figure 11 Image (a) shows an electrostatic chuck 20 with a concave-convex structure 25 and a cooling plate 30 having a concave-convex structure 25. Figure 10 (a) A wafer stage 10 is formed by bonding adhesive sheets 40 of the same uneven thickness. Additionally, Figure 11 In (a), the surface shape of the adhesive sheet 40 before bonding is shown by dashed lines. Figure 10 The position of the upper surface 40a in (a) of the diagram.

[0147] exist Figure 11 In the anti-corrosion structure 25 of the electrostatic chuck 20 shown in (a), the front end face 23e of the protrusion 23 is in contact with... Figure 3 Similarly, the height is uniform, but the height of the bottom surface 24e of the recess 24 varies depending on its position. More specifically, the degree of unevenness is smaller where the thickness unevenness is smaller, and the degree of unevenness is larger where the thickness unevenness is larger. As a result, the uneven structure 25 extends along the position of the upper surface 40a.

[0148] In this case, although it is impossible to imagine the overall convex and concave reference line L of the electrostatic chuck 20, it can be said locally that the entry of the convex portion 23 at the top and bottom of the upper surface 40a toward the adhesive sheet 40 and the entry of the adhesive sheet 40 toward the concave portion 24 are roughly balanced.

[0149] Figure 11 (b) shows the following: Figure 11 The schematic curve of the thermal resistance of the adhesive sheet 40 in the x-axis direction when the bonding scheme shown in (a) is applied is provided. It should be noted that... Figure 11 (b) in the figure also corresponds to the temperature distribution curve in the mounting surface 20a when the heater electrode 22 is used for uniform heating.

[0150] like Figure 11 As shown in (b) in the figure, Figure 11 In the scheme shown in (a), when the electrostatic chuck 20 has a raised / lowered structure 25, the thermal resistance in the adhesive sheet 40 is approximately uniform regardless of its location. This is because: Figure 2 Similarly, in the case shown in (b), heat transfer from the protrusion 23, which is set at a uniform height, is dominant.

[0151] This suggests that if the height of the front end face 23e of the protrusion 23 is made uniform, and the degree of unevenness in the concave-convex structure 25 is adjusted according to the unevenness of the thickness of the adhesive sheet 40, then even if there is unevenness in the thickness of the adhesive sheet 40, the temperature deviation in the placement surface 20a of the electrostatic chuck 20 can be well corrected.

[0152] However, as mentioned above, in reality, temperature (or heat density) deviations occur randomly and quantitatively depending on location, so it is unrealistic to have a different height of the front end face 23e that faithfully corresponds to this deviation. Furthermore, the degree of thickness unevenness in the adhesive sheet 40 varies from individual to individual, and it is also unrealistic to have a faithful correspondence to this thickness unevenness.

[0153] Therefore, before bonding, the thickness distribution of the bonding sheet 40 is measured in advance. If the bonding sheet 40 has uneven thickness, in order to correct the temperature deviation in the mounting surface 20a, when setting the rib pattern in each unit region RE according to the above scheme based on the temperature distribution of the mounting surface 20a in the reference electrostatic chuck 20, in addition to the usual high rib structure 25H and low rib structure 25L, high rib structures 25H and low rib structures 25L, which are obtained by making the recess 24 deeper than the depth determined by the relationship with the concave-convex reference line L, are also used as constituent units of the rib pattern. Hereinafter, the high rib structure 25H and low rib structure 25L obtained by making the recess 24 deeper in this way will be referred to as the thickness-absorbing high rib structure 25H and the thickness-absorbing low rib structure 25L, respectively.

[0154] It should be noted that, while the high-rib structure 25H and low-rib structure 25L are typically referred to as the first unit structure and the second unit structure, respectively, the thickness-absorbing high-rib structure 25H and the thickness-absorbing low-rib structure 25L are also referred to as the third unit structure and the fourth unit structure, respectively. In other words, in addition to correcting for temperature deviations, when absorbing uneven thickness of the bonded sheet 40, one or more of these four unit structures are mixed in a specified ratio in the rib pattern. Furthermore, the protrusions 23H and concave portions 24H of the thickness-absorbing high-rib structure 25H are also referred to as the third protrusion and the third concave portion, respectively, and the protrusions 23L and concave portions 24L of the thickness-absorbing low-rib structure 25L are also referred to as the fourth protrusion and the fourth concave portion, respectively.

[0155] Figure 12 This diagram is used to illustrate the thickness-absorbing high-rib structure 25H. Figure 13 This diagram illustrates the thickness-absorbing low-rib structure 25L. (Example) Figure 12 (a) and Figure 13 As shown in (a), in the thickness-absorbing high-rib structure 25H and the thickness-absorbing low-rib structure 25L, the convex portion 23 is formed to be the same as that of the usual high-rib structure 25H and low-rib structure 25L, and is also the same as the original (without considering thickness unevenness) convex portion 23. On the other hand, the concave portion 24 is formed such that its bottom surface 24f is deeper than the bottom surface 24e of the concave portion 24 in the usual high-rib structure 25H and low-rib structure 25L, which is determined according to the position of the concave-convex reference line L. This can be achieved by appropriately adjusting the processing conditions during the laser processing described above.

[0156] Therefore, as Figure 12 (b) and Figure 13 As shown in (b), in the thickness absorption high rib structure 25H and the thickness absorption low rib structure 25L, the area deeper than the recess 24 in the typical high rib structure 25H and low rib structure 25L becomes the thickness absorption region 24α.

[0157] Furthermore, when correcting the temperature deviation in the placement surface 20a, based on the temperature correction amount in each unit region RE determined by the temperature distribution of the placement surface 20a in the reference electrostatic chuck and the predetermined degree of thickness unevenness of the adhesive sheet 40 at the location corresponding to each unit region RE, the area ratio of the usual high rib structure 25H, the usual low rib structure 25L, the thickness-absorbing high rib structure 25H, and the thickness-absorbing low rib structure 25L in the rib pattern applied in the unit region RE is changed.

[0158] Right now, Figure 12 and Figure 13In order to simplify the illustration, a scheme is shown in which a bottom surface 24f is formed at a position deeper than the usual bottom surface 24e in a recess 24 and a thickness absorption region 24α is provided. However, in reality, the area ratio of the thickness absorption high rib structure 25H and the thickness absorption low rib structure 25L in each unit region RE is set according to the degree of thickness unevenness at the location corresponding to each unit region RE, in other words, the size of the thickness unevenness that should be absorbed in each unit region RE.

[0159] In this case, the uneven structure 25 in each unit region RE does not necessarily correspond to the actual thickness unevenness shape of the adhesive sheet 40 at the location corresponding to that unit region RE. However, the greater the thickness unevenness, the larger the area ratio of the high-thickness-absorbing rib structure 25H to the low-thickness-absorbing rib structure 25L. That is, a large number of thickness-absorbing regions 24α are provided. The adhesive sheet 40 is elastic, so the location with uneven thickness is deformed by the insertion of the protrusion 23 and fits well into the recess 24 with the thickness-absorbing region 24α.

[0160] It should be noted that the maximum thickness adjustment of the adhesive sheet 40 resulting from the provision of the thickness-absorbing high-rib structure 25H and the thickness-absorbing low-rib structure 25L is set to 2 μm or more. This means that the absorption of thickness unevenness is at least 2 μm when at least one of the thickness-absorbing high-rib structure 25H and the thickness-absorbing low-rib structure 25L is provided in the unit region RE. In this case, thickness unevenness can be effectively absorbed through the thickness-absorbing region 24α.

[0161] In Table 2, when simultaneously correcting for temperature deviations and absorbing thickness unevenness in the mounting surface 20a, examples of rib patterns set in each unit region RE are represented by the area ratios of a typical high-rib structure 25H (H-rib), a typical low-rib structure 25L (L-rib), a thickness-absorbing high-rib structure 25H (thickness-absorbing H-rib), and a thickness-absorbing low-rib structure 25L (thickness-absorbing L-rib). In Table 2, the area ratios of each rib structure are set as A, B, C, and D, respectively. It should be noted that an area ratio of 0 means that the rib structure is not set.

[0162] Table 2

[0163]

[0164] In the examples shown in Table 2, the thermal resistance adjustment is set to five stages for temperature deviation correction: +1.0℃, +0.5℃, ±0℃, -0.5℃, and -1.0℃. For example, a thermal resistance adjustment of +1.0℃ is equivalent to performing a temperature correction that reduces the temperature difference between the loading surface 20a (which is lower than the reference temperature) and the reference temperature by 1.0℃.

[0165] In the example shown in Table 2, the thermal resistance adjustment is adjusted according to five levels: 8:0, 6:2, 4:4, 2:6, and 0:8, by changing the ratio of the total ratio of the typical high-rib structure 25H and the thickness-absorbing high-rib structure 25H (A+B) to the total ratio of the typical low-rib structure 25L and the thickness-absorbing low-rib structure 25L (C+D). This means that, regarding the correction of temperature deviation on the mounting surface 20a, the thickness-absorbing high-rib structure 25H and the thickness-absorbing low-rib structure 25L function in the same way as the typical high-rib structure 25H and the low-rib structure 25L.

[0166] On the other hand, by changing the ratio of the total ratio of the usual high-rib structure 25H and the usual low-rib structure 25L (A+C) to the total ratio of the thickness-absorbing high-rib structure 25 and the thickness-absorbing low-rib structure 25L (B+D) to 8:0, 4:4, and 0:8, the sheet thickness adjustment amount is changed in three levels: 0μm, 1μm, and 2μm.

[0167] Therefore, by applying any of the 15 rib patterns to each unit region RE based on the temperature distribution of the placement surface 20a in the reference electrostatic chuck 20 and the predetermined distribution of thickness unevenness in the adhesive sheet 40, the temperature deviation in the placement surface 20a can be corrected even when there is thickness unevenness in the adhesive sheet 40.

[0168] It should be noted that if the temperature at the corresponding part of the placement surface 20a increases by 1℃ when the rib pattern of A:B:C:D=8:0:0:0 is applied, the temperature increase in the unit region RE is only 0.1℃ when the rib pattern of A:B:C:D=0:8:0:0 is applied, compared with the case without thickness unevenness.

[0169] Furthermore, it was confirmed that when the rib pattern A:B:C:D = 0:0:8:0 is applied, the temperature at the corresponding part of the placement surface 20a increases by 1°C compared to the case without thickness unevenness. However, when the rib pattern A:B:C:D = 0:0:0:8 is applied, the temperature increase is only 0.4°C.

[0170] As explained above, according to this embodiment, in a wafer stage in which an electrostatic chuck and a cooling plate are bonded together with an adhesive sheet, a wafer stage with excellent heat transfer can be achieved by providing a concave-convex structure on the bonding surface of the adhesive sheet for the electrostatic chuck, compared to a case without such a concave-convex structure.

[0171] That is, in the heat transfer from the electrostatic chuck to the cooling plate, the heat transfer from the convex part is dominant. Therefore, compared with the case without the concave-convex structure, it is possible to make the heat transfer from the electrostatic chuck to the cooling plate more efficient.

[0172] Furthermore, by making the distance between the front end face of the protrusion and the cooling plate uniform at least within the range of the concave-convex structure, the heat transfer from the electrostatic chuck to the cooling plate via the adhesive sheet can be made uniform.

[0173] Furthermore, by changing the distance between the front end face of the protrusion and the cooling plate, the degree of heat transfer from the electrostatic chuck through the adhesive sheet to the cooling plate can be adjusted according to the position. Utilizing this, by changing the formation scheme of the concave-convex structure based on the temperature distribution of the mounting surface without the concave-convex structure, temperature deviations on the mounting surface can be corrected. By adjusting the depth of the concave portion according to the uneven thickness of the adhesive sheet, temperature deviations on the mounting surface can also be corrected even in the presence of such uneven thickness.

[0174] <Variation Example>

[0175] In the above embodiments, as a concave-convex structure, it is assumed that the convex and concave portions are linear and alternate in plan view. However, the concave-convex structure for homogenization is not limited to this.

[0176] For example, one could design the protrusions to appear as a grid when viewed from above, with the grids formed by the protrusions creating recesses, or one could design the protrusions and recesses of the same scheme interchanged.

[0177] Alternatively, a scheme could be proposed where convex parts, which appear as points when viewed from above (e.g., circular, rectangular, and other polygonal shapes), are periodically and discretely located at grid points, with their surroundings forming concave parts.

[0178] In any of the embodiments, as long as the convex and concave portions are configured with the aforementioned convex and concave reference surfaces, the same effect as the above-described implementation can be obtained.

[0179] It should be noted that in the above embodiment, the uneven structure is provided to correct for temperature deviations across the entire circular loading surface 20a in plan view. Therefore, it is a prerequisite that the height of the front end face of the protrusion within the range of each high rib structure and low rib structure is uniformized; however, the area of ​​10% of the outer periphery of the loading surface can be excluded from this uniformization process.

[0180] Furthermore, from the perspective of ensuring reliable heat transfer uniformity, it is preferable that the height of the front end face of the protrusions within the range of each high-rib structure and low-rib structure is the same. However, from a practical point of view, as long as the balance between the entry of the protrusions relative to the adhesive sheet and the entry of the adhesive sheet relative to the concave portion is ensured, a scheme in which the height of the front end face of the protrusions has a deviation of less than 5 μm is also permissible.

[0181] Furthermore, in the above embodiments, by combining high-rib structures and low-rib structures with different concave-convex heights in the concave-convex structure, the temperature deviation of the loading surface is corrected. However, instead, a scheme can be implemented by combining two types of rib structures with the same distance between the front end face of the protrusion and the cooling plate and different widths of the front end face to achieve different heat transfer in the bonded sheet. However, in this case, for the same reasons as in the above embodiments, the spacing between the protrusions is preferably set to 300 μm or less.

[0182] Furthermore, in the above embodiments, the uneven thickness of the adhesive sheet is addressed by correcting the temperature deviation of the placement surface. However, if it is not necessary to correct the temperature deviation of the placement surface, the uneven thickness of the adhesive sheet can be addressed solely. For example, a scheme could be considered where the ordinary low-rib structure 25L and the thickness-absorbing low-rib structure 25L are mixed in a predetermined ratio according to the uneven thickness of the adhesive sheet 40. It should be noted that the temperature of the placement surface itself can be adjusted by adjusting the heater power.

Claims

1. A wafer mounting stage for mounting and fixing wafers. The wafer stage is characterized by having: An electrostatic chuck comprising a ceramic substrate having a wafer placement surface, and an ESC electrode and a heater electrode respectively embedded within the ceramic substrate; Metal cooling plate; and A resin-based adhesive sheet bonds the electrostatic chuck and the cooling plate together. The electrostatic chuck has a concave-convex structure composed of one or more unit structures on the bonding surface of the adhesive sheet, wherein the protrusions are arranged at a spacing of more than 100 μm and less than 300 μm.

2. The wafer stage according to claim 1, characterized in that, In each of the one or more unit structures, the distance between the front end of the protrusion and the cooling plate is uniform.

3. The wafer stage according to claim 1, characterized in that, The bonding surface of the electrostatic chuck has the aforementioned multiple unit structures. The distance between the front end of the protrusion and the cooling plate is different in each of the various unit concave-convex structures.

4. The wafer stage according to any one of claims 1 to 3, characterized in that, In the concave-convex structure, the convex portions, which appear as straight lines when viewed from above, and the concave portions, which also appear as straight lines when viewed from above, are alternately and periodically arranged.

5. The wafer stage according to claim 4, characterized in that, The bonding surface of the electrostatic chuck is composed of multiple unit areas. The various unit structures are as follows: A first unit structure having a first protrusion forming the protrusion; as well as The second unit structure has a second protrusion forming the protrusion. The distance between the front end of the first protrusion and the cooling plate is different from the distance between the front end of the second protrusion and the cooling plate. In each of the plurality of unit regions, the first unit structure and the second unit structure exist mixed in a predetermined ratio. The specified ratios in each of the plurality of unit regions are determined based on a reference temperature distribution generated on the placement surface when the heater electrodes of the wafer placement stage, whose bonding surface is flat, are energized.

6. The wafer stage according to claim 4, characterized in that, The bonding surface of the electrostatic chuck is composed of multiple unit areas. The various unit structures are as follows: The first unit structure is composed of a first protrusion forming the protrusion and a first recess forming the recess; The second unit structure is composed of a second protrusion forming the protrusion and a distance from the cooling plate different from that of the first protrusion, and a second recess forming the recess. The third unit structure consists of a third protrusion that is at the same distance from the cooling plate as the first protrusion and a third recess that has a greater depth than the first recess. as well as The fourth unit structure consists of a fourth protrusion at the same distance from the cooling plate as the second protrusion and a fourth recess with a depth greater than the second recess. In each of the plurality of unit regions, the first unit structure to the fourth unit structure are mixed in a predetermined ratio. The specified ratios in each of the plurality of unit regions are determined based on the reference temperature distribution generated on the placement surface when the heater electrode of the wafer placement stage, whose bonding surface is flat, is energized, and the thickness of the bonding sheet at the location corresponding to each of the plurality of unit regions.

7. A method for manufacturing a wafer mounting stage, comprising a method for manufacturing a wafer mounting stage for mounting and fixing wafers. The method is characterized by including the following steps: Preparation steps include preparing an electrostatic chuck, which comprises a ceramic substrate with a wafer placement surface, and ESC electrodes and heater electrodes respectively embedded within the ceramic substrate; and In the bonding process, the electrostatic chuck and the metal cooling plate are bonded together using a resin-based adhesive sheet. The preparation process includes: A correction process for the uneven structure is performed by alternately and periodically setting protrusions and concave portions on the bonding surface of the adhesive sheet using the electrostatic chuck. The calibration process is at least one of the following first calibration process and second calibration process. The first calibration process reduces the deviation in the temperature distribution generated on the placement surface; In the second correction process, if the adhesive sheet has uneven thickness, the recess absorbs the uneven thickness.

8. The method for manufacturing a wafer stage according to claim 7, characterized in that, In the correction process, the concave-convex structure is composed of one or more unit structures, and the distance between the convex part and the concave part is set to be more than 100μm and less than 300μm respectively.

9. The method for manufacturing a wafer stage according to claim 8, characterized in that, In the correction process, in each of the one or more unit structures, the distance between the front end of the protrusion and the cooling plate is made uniform.

10. The method for manufacturing a wafer stage according to claim 8, characterized in that, In the calibration process, the various unit structures are provided on the bonding surface of the electrostatic chuck. The distance between the front end of the protrusion and the cooling plate varies in each of the various unit structures.

11. The method for manufacturing a wafer stage according to any one of claims 8 to 10, characterized in that, In the correction process, the convex part and the concave part are set to be straight.

12. The method for manufacturing a wafer stage according to claim 11, characterized in that, When the correction process is the first correction process... The bonding surface of the electrostatic chuck is virtually divided into multiple unit regions. The various unit structures are set as follows: A first unit structure having a first protrusion forming the protrusion; as well as The second unit structure has a second protrusion forming the protrusion. The distance between the front end of the first protrusion and the cooling plate is different from the distance between the front end of the second protrusion and the cooling plate. In each of the plurality of unit regions, the first unit structure and the second unit structure are mixed in a predetermined ratio. The specified ratio in each of the plurality of unit regions is set such that the temperature deviation in the temperature distribution generated on the placement surface when the heater electrode is energized is reduced compared to the temperature deviation in the reference temperature distribution generated on the placement surface when the heater electrode of the wafer placement stage with the bonding surface of the electrostatic chuck is energized.

13. The method for manufacturing a wafer stage according to claim 11, characterized in that, When the correction process consists of the first correction process and the second correction process. The bonding surface of the electrostatic chuck is virtually divided into multiple unit regions. The various unit structures are set as follows: The first unit structure is composed of a first protrusion forming the protrusion and a first recess forming the recess; The second unit structure is composed of a second protrusion forming the protrusion and a distance from the cooling plate different from that of the first protrusion, and a second recess forming the recess. The third unit structure consists of a third protrusion that is at the same distance from the cooling plate as the first protrusion and a third recess that has a greater depth than the first recess. The fourth unit structure consists of a fourth protrusion at the same distance from the cooling plate as the second protrusion and a fourth recess with a depth greater than the second recess. In each of the plurality of unit regions, the first unit structure to the fourth unit structure are mixed in a predetermined ratio. The predetermined ratio in each of the plurality of unit regions is set in such a way that the temperature deviation in the temperature distribution generated on the placement surface when the heater electrode is energized is reduced compared to the temperature deviation in the reference temperature distribution generated on the placement surface when the heater electrode of the wafer placement stage with the bonding surface flat to the electrostatic chuck is energized, and is based on the thickness of the bonding sheet at the location corresponding to each of the plurality of unit regions.

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