Electrostatic chuck and base

Abstract

In an electrostatic chuck which electrostatically adsorbs and fixes a workpiece placed on a placement surface by applying a voltage to an electrode implanted therein, the placement surface has a concavo-convex structure comprising a plurality of convex portions two-dimensionally spaced apart from each other at a predetermined pitch and flat concave portions between the convex portions, and the convex portions comprise: flat portions; the substrate is provided with a flat surface which is vertical to the thickness direction of the electrostatic chuck and is uniform in height; and an inclined portion located around the flat portion, the height of the inclined portion decreasing from the flat portion toward the recessed portion, and the inclination angle of the upper surface of the inclined portion with respect to the thickness direction of the electrostatic chuck being 65-84 degrees.

Description

Technical Field

[0001] This invention relates to an electrostatic chuck for electrostatically adsorbing and fixing workpieces such as wafers, and particularly to the shape of its mounting surface. Background Technology

[0002] In semiconductor manufacturing processes, electrostatic chucks that utilize electrostatic adsorption to hold the workpiece are widely used in etching apparatuses such as plasma etching apparatuses, PVD apparatuses, CVD apparatuses, and ion plating apparatuses. One known electrostatic chuck is configured such that the mounting surface for holding a plate-shaped workpiece, such as a semiconductor wafer, is a concave-convex surface with multiple protrusions (protrusions). The protrusions support the workpiece, and cooling gas can flow through the concave portions (see, for example, Patent Documents 1 and 2).

[0003] Patent document 1 discloses an electrostatic chuck in which the convex part of the placement surface is columnar, frustum conical, or hemispherical.

[0004] In addition, Patent Document 2 discloses the following scheme: the protrusion of the placement surface has: a top part, which includes a top surface located at the top and rising with a gentle curve; a column part, whose cross-sectional diameter decreases as it approaches the top part from the bottom side; and a bottom part, which connects the column part and the bottom surface with a gentle curve.

[0005] In the electrostatic chucks disclosed in Patent Documents 1 and 2, particles are sometimes generated due to friction between the workpiece and the protrusions on the mounting surface. These particles constitute a major cause of defects, and therefore, it is desirable to minimize them. The smaller the contact area between the workpiece and the protrusions, the less likely particles are to be generated; however, if the contact area is too small, the adsorption force is insufficient. If the adsorption force is insufficient, the wafer may sometimes be lifted by, for example, cooling gas flowing through the recess.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2010-123843

[0009] Patent Document 2: Japanese Patent Application Publication No. 2017-191949 Summary of the Invention

[0010] The present invention was made in view of the above-mentioned problems, and its object is to realize an electrostatic chuck that increases the adsorption force with the workpiece without increasing the contact area.

[0011] To address the aforementioned issues, the first aspect of the present invention is an electrostatic chuck that electrostatically attracts and fixes a workpiece placed on a mounting surface by applying a voltage to an internally implanted ESC electrode. The mounting surface is characterized by having a concave-convex structure consisting of a plurality of protrusions arranged two-dimensionally at predetermined intervals and flat recesses between the protrusions. Each protrusion comprises: a flat portion having a flat surface that is perpendicular to the thickness direction of the electrostatic chuck and has a uniform height; and an inclined portion located around the flat portion, the height of which decreases as it approaches the recess from the flat portion, and the inclination angle of the upper surface of the inclined portion relative to the thickness direction of the electrostatic chuck is 65 degrees or more and 84 degrees or less.

[0012] The second aspect of the present invention is based on the electrostatic chuck involved in the first aspect, characterized in that the protrusion is conical in cross-sectional view.

[0013] The third aspect of the present invention is based on the electrostatic chuck involved in the second aspect, characterized in that at least one of the convex portion, the flat portion, and the concave portion is continuous with a curved surface.

[0014] The fourth aspect of the present invention is based on the electrostatic chuck involved in any of the first to third aspects, characterized in that the flat surface is circular when viewed from above, and the inclined portion is annular when viewed from above.

[0015] The fifth aspect of the present invention is based on the electrostatic chuck involved in any of the first to fourth aspects, characterized in that the height of the flat surface measured from the recess is 10μm to 50μm.

[0016] The sixth aspect of the present invention is a base, characterized in that it comprises: an electrostatic chuck as described in any of the first to fifth aspects; a heater electrode embedded inside the electrostatic chuck; and a cooling plate coupled to the electrostatic chuck, which is capable of cooling the workpiece by circulating a refrigerant through a flow path provided inside the chuck.

[0017] The seventh aspect of the present invention is a base, characterized in that it comprises: an electrostatic chuck as described in any of the first to fifth aspects; a heater electrode embedded inside the electrostatic chuck; and a hollow shaft mounted on the electrostatic chuck.

[0018] According to the first to seventh aspects of the present invention, the electrostatic adsorption force of the electrostatic chuck can be increased without increasing the contact area between the workpiece and the electrostatic chuck. Attached Figure Description

[0019] Figure 1This is a simplified cross-sectional view showing the configuration of the wafer stage 10 equipped with an electrostatic chuck 20.

[0020] Figure 2 This is a simplified cross-sectional view showing the detailed structure of the mounting surface 20a of the electrostatic chuck 20.

[0021] Figure 3 This is an enlarged cross-sectional view of the inclined portion 25 near the embossing 23.

[0022] Figure 4 This is a diagram showing a modified example of embossing 23.

[0023] Figure 5 This is a diagram showing another embodiment of the electrostatic chuck 20. Detailed Implementation

[0024] <Chip Placement Stage>

[0025] Figure 1 This is a simplified cross-sectional view along the thickness direction of the electrostatic chuck 20, showing the configuration of a wafer stage 10 equipped with the electrostatic chuck 20 according to an embodiment of the present invention. The wafer stage 10, also called a base, is used to hold a semiconductor wafer (wafer) in place during prescribed processes such as plasma processing, which is one aspect of the work being processed.

[0026] In summary, the wafer stage 10 has the following configuration: an electrostatic chuck 20 and a cooling plate 30 are bonded together by a bonding layer 40, thereby stacking the electrostatic chuck 20 and the cooling plate 30.

[0027] The electrostatic chuck 20 is configured such that an ESC electrode (electrostatic chuck electrode) 21 for electrostatic adsorption of a wafer is implanted in a plate-shaped (e.g., circular plate-shaped) component 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. This 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 implanted near the placement surface 20a, compared to the heater electrode 22. In the electrostatic chuck 20, the main surface opposite to the bonding surface of the bonding layer 40 becomes the placement surface 20a for placing the wafer.

[0028] 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.

[0029] The cooling plate 30 is a portion having an internal flow path 31, which cools the electrostatic chuck 20 and the wafer electrostatically attached to its mounting surface 20a by introducing a coolant (e.g., water) into the flow path 31 from the outside. Regarding the flow path 31, a preferred example is a continuous groove arranged in a vortex shape when viewed from above, so that approximately the entire area of ​​the electrostatic chuck 20 is cooled. Alternatively, it can be a configuration of multiple independent open-loop grooves arranged concentrically when viewed from above.

[0030] As the material for the cooling plate 30, it is preferable to use a metal material such as aluminum; however, ceramic or a composite material of metal and ceramic may also be used.

[0031] 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 refrigerant flow rate 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.

[0032] The electrostatic chuck 20 and the cooling plate 30 are joined by a heat-pressurization bonding process using a bonding layer 40. This heat-pressurization bonding is as follows: for example, the ceramic plate-shaped component constituting the electrostatic chuck 20 and the component constituting the cooling plate 30 are bonded together using a resin adhesive or adhesive sheet, metal solder, ceramic adhesive, or other adhesive layer to obtain a laminate. The laminate is then heated and pressurized at a specified temperature.

[0033] In addition, the chip stage 10 also includes a first power supply unit 50 that provides power to the ESC electrode 21 and a second power supply unit 60 that provides power to the heater electrode 22.

[0034] The first power supply unit 50 is arranged along the stacking direction of the electrostatic chuck 20 and the cooling plate 30, and includes: a power supply terminal 51; an insulating member (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 the 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 equipped ESC power supply 70.

[0035] 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, so that the wafer is electrostatically attracted to the placement surface 20a.

[0036] 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 an externally provided heater power supply 80.

[0037] 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.

[0038] Furthermore, the refrigerant inlet / outlet 35 passes through a predetermined position on the cover 30b, and this refrigerant inlet / outlet 35 communicates with the flow path 31 while the cover 30b is fixed to the base 30a. It should be noted that... Figure 1 For simplicity, only one refrigerant inlet / outlet 35 is shown in the diagram. However, in reality, one refrigerant inlet / outlet 35 is provided 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 refrigerant to the flow path 31.

[0039] In the wafer stage 10 with the above configuration, while the wafer placed on the placement surface 20a is electrostatically adsorbed and fixed by applying voltage to the ESC electrode 21, the heater electrode 22 is energized to heat the wafer and the coolant is circulated to the flow path 31, thereby balancing heating and cooling and enabling the wafer to be heated with a specified temperature distribution.

[0040] The wafer stage 10 can be manufactured in the following order: for example, an electrostatic chuck 20 with an ESC electrode 21 and a heater electrode 22 implanted, and a cooling plate 30 are prepared respectively. The electrostatic chuck 20 and the cooling plate 30 are joined together using a bonding layer 40. Next, a first power supply unit 50 and a second power supply unit 60 are implanted, thereby manufacturing the wafer stage 10.

[0041] The electrostatic chuck 20 can be manufactured as follows: for example, multiple ceramic green sheets, including ceramic green sheets printed with electrode patterns for ESC electrode 21 and ceramic green sheets printed with electrode patterns for heater electrode 22, are stacked and bonded together to form a green sheet molded body, and the green sheet molded body is hot-pressed and fired to produce the electrostatic chuck 20.

[0042] However, in this embodiment, the mounting surface 20a of the electrostatic chuck 20 after hot pressing and firing is subjected to the embossing process (convex-concave processing) described later, and a large number of protrusions are provided.

[0043] In addition, the cooling plate 30 can be manufactured using methods such as machining of bulk metal and casting, gel casting, etc.

[0044] <Details of the placement surface>

[0045] Figure 2 This is a simplified cross-sectional view along the thickness direction of the electrostatic chuck 20, showing the detailed structure of the mounting surface 20a of the electrostatic chuck 20. It should be noted that... Figure 2 The image also shows the appearance of the chip 100 placed on the placement surface 20a.

[0046] Figure 1 For simplification, the mounting surface 20a is shown as uniformly flat. However, in reality, the mounting surface 20a of the electrostatic chuck 20 of the embodiment of the present invention has an uneven structure consisting of a large number of protrusions 23 arranged two-dimensionally at a predetermined spacing p and recesses 26 between these protrusions 23. Hereinafter, the protrusions 23 will also be referred to as embossing 23, and the surface of the recesses 26 will also be referred to as the bottom surface 26a. It should be noted that the spacing p is set to approximately 2 mm to 20 mm.

[0047] The embossing 23 has a flat portion 24 and an inclined portion 25. The flat portion 24 is a part having a flat surface 24a. The flat surface 24a is substantially perpendicular to the thickness direction of the electrostatic chuck 20, flat, and has a uniform height (vertical distance measured from the bottom surface 26a of the recess 26) h. The flat surface 24a and the bottom surface 26a of the recess 26 may include micro-undulations unavoidably generated during manufacturing. Therefore, the height h can be, for example, the difference between the roughness center lines of the flat surface 24a and the bottom surface 26a. The roughness center lines of the flat surface 24a and the bottom surface 26a can be the average of multiple measurements obtained using the methods specified in JIS B 0601:1994 and JIS B 0031:1994. The height h is approximately 10 μm to 50 μm.

[0048] The inclined portion 25 is a portion located around the flat portion 24 when viewed from above the loading surface 20a, where the height (vertical distance measured from the bottom surface 26a of the recess 26) decreases continuously or intermittently as it moves from the flat portion 24 toward the recess 26.

[0049] In a preferred embodiment, the flat surface 24a of each embossed 23, when viewed from above, is a circle with a diameter d1 at its center, and each embossed 23 itself is also a circle with a diameter d2 when viewed from above. Consequently, the inclined portion 25 is an annular shape with a width w when viewed from above. Furthermore, the upper surface 25a of the inclined portion 25 appears as a straight cone in a cross-sectional view. Sometimes, the inclined portion 25, in which the upper surface 25a appears as a straight cone in a cross-sectional view, is specifically referred to as a cone portion 25. The diameter d1 is approximately 0.5 mm to 3 mm, similar to that of conventional embossed embossings without the inclined portion 25.

[0050] Because the mounting surface 20a has such an uneven structure, only the flat portion 24 of the embossing 23 actually contacts the wafer 100 and directly supports it from below when the wafer 100 is mounted on the electrostatic chuck 20. It should be noted that cooling gas for cooling the wafer 100 sometimes flows between the inclined portion 25 and the recessed portion 26, which do not contact the wafer 100, and the wafer 100.

[0051] When the wafer 100 is adsorbed and fixed to the electrostatic chuck 20, as shown above, a DC voltage is applied to the ESC electrode 21 from the ESC power supply 70. Accordingly, a Johansen-Labeck force (hereinafter referred to as JR force) Fj is generated between the wafer 100 and the flat portion 24 of all the indentations 23 in contact with the wafer 100.

[0052] However, the force contributing to the adsorption and fixation of the wafer 100 is not only the JR force Fj, but also the spatial coulomb force Fc from the portion that is close to but not in contact with the wafer 100. Specifically, the spatial coulomb force Fc includes: the inclined portion spatial coulomb force Ft acting between the entire inclined portion 25 (the upper surface 25a) and the wafer 100, and the bottom surface spatial coulomb force Fb acting between the recess 26 (the entire bottom surface 26a) and the wafer 100. Hereinafter, the spatial coulomb force Fc will also be referred to as the total spatial coulomb force Fc.

[0053] That is, the overall adsorption force F when the chip 100 is adsorbed and fixed on the electrostatic chuck 20 is expressed as F=Fj+Fc=Fj+Ft+Fb.

[0054] In this case, the spatial Coulomb force Ft of the inclined portion is inversely proportional to the distance between the inclined portion 25 and the wafer 100, and the spatial Coulomb force Fb of the bottom surface is inversely proportional to the distance between the bottom surface 26a and the wafer 100. Therefore, when the spacing p of the embossing 23, the planar dimension (diameter) d1 of the flat portion 24, and the height h are all constant, and the deflection of the wafer 100 can be ignored, as long as there is a recess 26 between adjacent embossing 23, the larger the width w of the inclined portion 25, the more significantly the value of the spatial Coulomb force Ft of the inclined portion increases compared to the spatial Coulomb force Fb of the bottom surface. As a result, the relationship that the total spatial Coulomb force Fc and the overall adsorption force F increase holds true.

[0055] This means that by setting inclined portions 25 in each embossing 23, the spatial Coulomb force Ft of the inclined portion is made to play a role, instead of increasing the plane size (diameter) d1 of the flat portion 24 of each embossing 23 to increase the JR force Fj, and the overall adsorption force F can also be increased.

[0056] Furthermore, when the planar dimension d1 of the flat portion 24 is increased, the contact area between the wafer 100 and the electrostatic chuck 20 increases, making it easier for particles to be generated. However, since the inclined portion 25 does not contact the wafer 100, it is not easy for particles to be generated even if the inclined portion 25 is provided.

[0057] In other words, by providing the inclined portion 25 in the embossing 23, the electrostatic adsorption force between the wafer 100 and the electrostatic chuck 20 can be increased without making it easier to generate particles.

[0058] When the upper surface 25a of the inclined portion 25 is conical, the effect of setting the inclined portion 25 on the embossing 23 can be evaluated by the size of the angle (hereinafter, the inclination angle) α formed by the upper surface 25a and the thickness direction of the electrostatic chuck 20.

[0059] Taking an electrostatic chuck 20 with a cone-shaped inclined portion 25 as an example, the inclination angle α (also called cone angle α) is varied, and the Coulomb force Fb in the bottom space and the Coulomb force Ft in the inclined portion space are simulated. The results at this time are presented in Table 1 in conjunction with the JR force Fj obtained in advance through experiments, the total Coulomb force Fc obtained from the simulation results, the sum of the JR force Fj and the total Coulomb force Fc, i.e., the overall adsorption force F, the increase rate of the overall adsorption force F, and the aspect ratio w / h.

[0060] Table 1

[0061]

[0062] It should be noted that during the simulation, the planar dimension (diameter) d1 of the embossing 23 is set to 0.5 mm, the height h of the flat portion 24 of the embossing 23 is set to 20 μm, the ratio of the total area of ​​the flat surface 24a of the flat portion 24 of the embossing 23 to the entire planar area of ​​the placement surface 20a, i.e., the contact area ratio of the wafer 100, is set to 3%, and the DC voltage applied by the ESC power supply 70 to the ESC electrode 21 during electrostatic adsorption is set to 500 V.

[0063] Furthermore, the overall adsorption force F (26.2 Torr) and JR force Fj (18 Torr) of the electrostatic chuck 20 with the embossed 23 not having the inclined portion 25, i.e., the inclined angle α = 0 degrees, were used in advance through experiments. Therefore, strictly speaking, the values ​​of each force at the inclined angle α = 0 degrees in Table 1 are experimental values. Moreover, the increase rate of the overall adsorption force F is shown as the increase rate based on the overall adsorption force F at the inclined angle α = 0 degrees.

[0064] As shown in Table 1, the following trend exists: the larger the tilt angle α, the greater the increase rate of the overall adsorption force F.

[0065] In this embodiment, the preferred range for the tilt angle α when the tilt portion 25 is provided on the embossing 23 is 65 degrees or more, which increases the overall adsorption force by more than 1% compared to the case where the tilt portion 25 is not provided. This is believed to be because the overall adsorption force F is significantly increased compared to the case where the tilt portion 25 is not provided. It should be noted that Table 1 also shows that even when the tilt angle α is set at, for example, about 30 degrees, the effect of increasing the adsorption force is hardly obtained.

[0066] However, the tilt angle α is set to 84 degrees or less. This is because if the tilt angle α exceeds 84 degrees, the possibility of the wafer 100 still contacting the tilted portion 25 due to the deflection of the wafer 100 during adsorption and fixation increases, which is not preferable.

[0067] That is, in this embodiment, when the surface of the electrostatic chuck 20 is given an uneven surface by a large number of embossings 23, by providing inclined portions 25 around the flat portions 24 of each embossing 23 at an angle α of 65 degrees or more and 84 degrees or less relative to the thickness direction of the electrostatic chuck 20, the electrostatic attraction force of the wafer 100 relative to the electrostatic chuck 20 is increased without increasing the contact area with the wafer 100. It should be noted that the range of this angle α of 65 degrees or more and 84 degrees or less roughly corresponds to the range of the aspect ratio w / h of 2.1 or more and 9.5 or less, which is equivalent to the tangent (tan) of the angle α.

[0068] This effect of increasing electrostatic adsorption force by using the electrostatic chuck 20 can also be achieved when a workpiece other than the wafer 100 is placed on the chuck.

[0069] It should be noted that by providing the inclined portion 25 in the embossing 23, the area of ​​the flat surface 24a of the flat portion 24 is not increased. In other words, the contact area with the wafer 100 is not increased compared to the case where the inclined portion 25 is not provided, and the adsorption force can be increased. In other words, by reducing the area of ​​the flat surface 24a and providing the inclined portion 25, the contact area with the wafer 100 can be reduced, and the same level of adsorption force as the case where the inclined portion 25 is not provided can be obtained.

[0070] <Example of the fine shape of the inclined part>

[0071] Figure 3 It is a schematic enlarged cross-sectional view along the thickness direction of the electrostatic chuck 20 near the inclined portion 25 of a certain embossing 23.

[0072] Figure 2 The image shows the upper surface 25a of the inclined portion 25, which appears as a straight line in a cross-sectional view, continuous with the flat surface 24a of the flat portion 24 and the bottom surface 26a of the recess 26. However, when observing the actual inclined portion 25 from a microscopic perspective, as... Figure 3 As shown, its upper surface 25a is composed of a flat inclined surface, i.e., a straight central portion 250 in the cross-sectional view, and curved (curved in the cross-sectional view) curved portions 251 and 252 at both ends. The curved portion 251 can be smoothly continuous with the bottom surface 26a of the recess 26, and the curved portion 252 can be smoothly continuous with the flat surface 24a of the flat portion 24.

[0073] When the curved surface 251 is formed, particles are less likely to remain at the boundary between the embossing 23 and the recess 26. In addition, when the curved surface 252 is formed, the embossing 23 is less likely to be rubbed off when the wafer 100 comes into contact.

[0074] The curved surfaces 251 and 252 are typically formed within a very small area at both ends of the inclined portion 25. Therefore, the virtual extension surfaces of the central portion 250 of the upper surface 25a, the bottom surface 26a of the concave portion 26, and the flat surface 24a of the flat portion 24 can be considered as... Figure 2 The upper surface 25a of the inclined portion 25, the bottom surface 26a of the recessed portion 26, and the flat surface 24a of the flat portion 24.

[0075] Figure 3In the cross-sectional view, line L0 corresponds to the virtual extension surface of the central portion 250, line L1 corresponds to the virtual extension surface of the bottom surface 26a, and line L2 corresponds to the virtual extension surface of the flat surface 24a. Furthermore, the vertical and horizontal distances between the intersection point P1 of lines L0 and L1 and the intersection point P2 of lines L0 and L2 can be considered as the height h and width w, respectively. More specifically, intersection point P1 corresponds to the cross-section of the intersection line of the virtual extension surface of the central portion 250 and the virtual extension surface of the bottom surface 26a, and intersection point P2 corresponds to the cross-section of the intersection line of the virtual extension surface of the central portion 250 and the virtual extension surface of the flat surface 24a. Additionally, the angle between the thickness direction of the electrostatic chuck 20 and line L0 can be considered as the tilt angle α.

[0076] The embossing 23 of the electrostatic chuck 20, in whole or in part, can be [features such as] Figure 3 The shape of the inclined portion 25 is shown. Alternatively, there may be an embossed portion 23 having only one of the curved portion 251 or the curved portion 252.

[0077] The formation of the uneven structure, consisting of embossed (convex) 23 and concave 26 with inclined portions 25 having cone-shaped or similar forms, can be performed as follows: for example, before joining the ceramic plate-shaped component constituting the electrostatic chuck 20 and the component constituting the cooling plate 30, the flat surface of the former ceramic component is processed in an appropriate combination using various known processing methods such as sandblasting, machining, ultrasonic processing, laser processing, and grinding, thereby forming the uneven structure.

[0078] As explained above, according to this embodiment, when the surface of an electrostatic chuck used for electrostatic adsorption and fixation of a workpiece such as a semiconductor wafer is given with a large number of embossings to reduce the contact area, by providing inclined portions with an angle of 65 degrees or more and 84 degrees or less relative to the thickness direction of the electrostatic chuck around the flat portions of each embossing, the electrostatic adsorption force of the electrostatic chuck can be increased without increasing the contact area between the workpiece and the electrostatic chuck.

[0079] <Variation Example>

[0080] The tilt angle α of the tilted portion 25 of each embossed 23 provided on the mounting surface 20a of the electrostatic chuck 20 does not need to be the same, and can vary depending on the position of each embossed 23 when the electrostatic chuck 20 is viewed from above.

[0081] For example, the tilt angle α of the embossing 23 located on the outer periphery can be greater than the tilt angle α of the embossing 23 located in the center. In this case, the adsorption force of the embossing 23 on the outer periphery is greater than the adsorption force of the embossing 23 in the center. Therefore, even if the adsorbed object, i.e., the wafer, warps, it is possible to prevent the wafer from leaving the mounting surface 20a on the outer periphery and to fix the wafer well.

[0082] In the above embodiments, the description mainly focuses on the configuration in which the height of the inclined portion 25 continuously decreases as it approaches the concave portion 26 from the flat portion 24. More specifically, the configuration in which the inclined portion 25 is conical is illustrated. However, as mentioned above, the height of the inclined portion 25 may also be a form that changes discontinuously.

[0083] Figure 4 This is a diagram showing a modified example of an embossed 23 having such a shape as an inclined portion 25. More specifically, Figure 4 This is a schematic enlarged cross-sectional view of the area near the inclined portion 25 along the thickness direction of the electrostatic chuck 20. Figure 4 In the embossing 23 shown, the inclined portion 25 is configured as a multi-level shape comprising multiple steps 25s. That is, the height of the inclined portion 25 changes discontinuously as it moves from the flat portion 24 toward the concave portion 26. In this case, the inclined line 25b passing through the edge portion of each step 25s in the cross section can be compared with, for example, Figure 2 The same applies to the straight line formed by the cross section of the upper surface 25a of the tapered inclined portion 25 shown. That is, the angle formed by the inclined line 25b and the thickness direction of the electrostatic chuck 20 corresponds to the inclination angle α.

[0084] Such embossing 23 having a multi-level inclined portion 25 including multiple steps 25s can be achieved, for example, by laser processing.

[0085] Even with the embossing 23 of the multi-level inclined portion 25 forming an uneven structure on the placement surface 20a, the electrostatic chuck 20 can still achieve the effect of increasing the electrostatic adsorption force of the electrostatic chuck 20 without increasing the contact area between the workpiece and the electrostatic chuck 20.

[0086] <Another solution for electrostatic chucks>

[0087] Figure 5 It is different from Figure 1 A simplified cross-sectional view along the thickness direction of the electrostatic chuck 20 of another embodiment of the shown scheme. In summary, Figure 5 The electrostatic chuck 20 shown is composed of and Figure 1 The electrostatic chuck 20 shown is composed of a plate-shaped (e.g., circular) ceramic plate 12 formed of the same insulating ceramic, and a hollow ceramic shaft 14 joined to the ceramic plate 12.

[0088] One of the main surfaces 12a of the ceramic plate 12 becomes having the same as Figure 2 The same numerous raised (embossed) 23 are placed on the mounting surface 20a. Figure 5 The illustration is simplified, but the embossing 23 on the main surface 12a is also present. Figure 2The flat portion 24 and the inclined portion 25 are shown. That is, an inclined portion 25, forming an angle of 65 degrees or more and 84 degrees or less relative to the thickness direction of the electrostatic chuck, is provided around the flat portion 24 of each embossing 23. It should be noted that... Figure 5 The image also shows the appearance of the chip 100 placed on the placement surface 20a.

[0089] The ceramic shaft 14 is preferably made of the same insulating ceramic as the ceramic plate 12 and is bonded to another main surface 12b of the ceramic plate 12 by solid-phase bonding or diffusion bonding.

[0090] In addition, in ceramic plate 12 and Figure 1 The electrostatic chuck 20 shown also incorporates an ESC electrode 21 for electrostatically attracting the wafer and a heater electrode 22 for heating the wafer. The ESC electrode 21 and heater electrode 22 are energized via rod-shaped power supply terminals 51 and 61 inserted into the internal space of the hollow ceramic shaft 14. It should be noted that... Figure 5 The illustrations of sleeves 52 and 62 and connecting parts 53 and 63 are omitted. Power supply terminal 51 is also referred to as ESC rod 51, and power supply terminal 61 is also referred to as heater rod 61.

[0091] The electrostatic chuck 20 with the above configuration is also... Figure 1 The electrostatic chuck 20 also utilizes Figure 5 The bonding layer 40 (not shown) is bonded to the cooling plate 30 to form the wafer stage 10.

[0092] In addition, multiple lifting pin holes 16 penetrate along the thickness direction. Figure 5 The ceramic plate 12 is shown. More specifically, the lifting pin hole 16 is a hole provided in a form that also penetrates the bonding layer 40 and the cooling plate 30, and is used to allow a lifting pin (not shown) for lifting the wafer 100 placed on the placement surface 20a from below to pass through from below the wafer placement stage 10. It should be noted that... Figure 1 The illustration is omitted, however, Figure 1 The wafer stage 10 shown also has multiple lifting pin holes.

[0093] have Figure 5 In the wafer stage of the electrostatic chuck configured as shown, the electrostatic adsorption force of the electrostatic chuck can be increased without increasing the contact area between the workpiece and the electrostatic chuck.

Claims

1. An electrostatic chuck that electrostatically attracts and holds a workpiece placed on a placement surface by applying a voltage to an ESC electrode implanted inside. The electrostatic chuck is characterized in that: the placement surface has a concave-convex structure composed of a plurality of convex portions arranged two-dimensionally at a prescribed pitch and flat concave portions between the convex portions, the convex portion has: a flat portion having a flat surface that is perpendicular to a thickness direction of the electrostatic chuck and has a uniform height; and a sloped portion that is located around the flat portion and has a height that decreases as it approaches the concave portion from the flat portion, an upper surface of the sloped portion has a slope angle of 65 degrees or more and 84 degrees or less with respect to the thickness direction of the electrostatic chuck.

2. The electrostatic chuck according to claim 1, characterized in that: the convex portion is conical in a cross-sectional view.

3. The electrostatic chuck according to claim 2, characterized in that: the convex portion is continuous with at least one of the flat portion and the concave portion in a curved surface.

4. The electrostatic chuck according to any one of claims 1 to 3, characterized in that: the flat surface is circular when viewed from above, the sloped portion is annular when viewed from above.

5. The electrostatic chuck according to any one of claims 1 to 3, characterized in that: the flat surface has a height of 10 μm to 50 μm from the concave portion.

6. A susceptor, characterized by, comprise: the electrostatic chuck according to any one of claims 1 to 3; a heater electrode implanted inside the electrostatic chuck; and a cooling plate joined to the electrostatic chuck and capable of cooling the workpiece by circulating a refrigerant through a flow path provided inside.

7. A susceptor, characterized by, comprise: the electrostatic chuck according to any one of claims 1 to 3; a heater electrode implanted inside the electrostatic chuck; and a hollow shaft installed to the electrostatic chuck. ​

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