Electrostatic chuck

Abstract

To provide an electrostatic chuck capable of sufficiently inhibiting dispersion of in-plane temperature distribution of a substrate.SOLUTION: An electrostatic chuck 10 comprises a dielectric substrate 100, a linear heater 500 built into the dielectric substrate 100, and a base plate 200 bonded to the dielectric substrate 100. An aperture 241 is formed in a face 210 of the base plate 200 on the dielectric substrate 100 side. In view from a direction perpendicular to a face 110 of the dielectric substrate 100, in a portion of the heater 500 that overlaps the aperture 241, a line width W2 of the heater 500 at a position that is the center in an extension direction of the heater 500 is larger than a line width W1 of the heater 500 at a position that is an edge in the direction.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an electrostatic chuck. [Background technology]

[0002] For example, in semiconductor manufacturing equipment such as a CVD device or an etching device, an electrostatic chuck is provided as a device for attracting and holding a substrate such as a silicon wafer to be processed. The electrostatic chuck includes a dielectric substrate provided with an attracting electrode and a base plate supporting the dielectric substrate, which are joined together. The attracting electrode is generally built into the dielectric substrate, but the metal base plate may also be used as the attracting electrode. When a voltage is applied to the attracting electrode, an electrostatic force is generated, and the substrate placed on the dielectric substrate is attracted and held.

[0003] During processing such as etching, it is necessary to maintain the temperature of the substrate at an appropriate temperature. For this reason, as described in Patent Document 1 below, an electrostatic chuck may have a built-in heater for temperature adjustment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7185544 Summary of the Invention [Problem to be solved by the invention]

[0005] An opening is formed on the surface of the base plate that is bonded to the electrostatic chuck, for example, for the purpose of arranging a temperature sensor. In the portion of the dielectric substrate directly above such an opening, heat is not easily transferred to the base plate, and therefore a local temperature rise is likely to occur during processing. Therefore, in the electrostatic chuck described in the above Patent Document 1, the heater line width is made thicker in the portion directly above the opening. Since the amount of heat generated by the heater is small directly above the opening, i.e., in the portion where a local temperature rise is likely to occur, it is possible to suppress the variation in the temperature distribution within the surface of the substrate.

[0006] However, even when limited to the portion of the heater overlapping the opening, the likelihood of temperature rise is not uniform but varies depending on the location. For example, heat is relatively easily dissipated from the portion of the heater overlapping the edge of the opening, while heat is relatively difficult to dissipate from the portion overlapping the center of the opening. In the electrostatic chuck described in the above Patent Document 1, the heater line width is uniform over the entire portion overlapping the opening. For this reason, it is believed that a local temperature rise still occurs directly above the opening.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrostatic chuck that can sufficiently suppress variations in the in-plane temperature distribution of a substrate. [Means for solving the problem]

[0008] In order to solve the above problems, an electrostatic chuck according to the present invention includes a dielectric substrate having a mounting surface on which an object to be attracted is placed, a linear heater built into the dielectric substrate, and a base plate joined to a surface of the dielectric substrate opposite the mounting surface. An opening is formed in the surface of the base plate facing the dielectric substrate. When viewed from a direction perpendicular to the mounting surface, in a portion of the heater overlapping with the opening, the linear width of the heater at a center position along the extension direction is larger than the linear width of the heater at an end position along the same direction.

[0009] In an electrostatic chuck having such a configuration, the line width of the heater overlapping the opening is not uniform, and the line width at the center is locally larger than the line width at the ends of the heater, where heat is relatively easy to dissipate. Compared to the amount of heat generated at the ends, where heat is relatively easy to dissipate, the amount of heat generated at the center, where heat is relatively difficult to dissipate (i.e., where the temperature is easily increased), is suppressed, and the temperature distribution directly above the opening becomes roughly uniform. This makes it possible to sufficiently suppress the variation in the temperature distribution within the surface of the substrate. Note that the "center" here refers to the center of the heater overlapping the opening when viewed from above, and may not coincide with the center of the opening.

[0010] In the electrostatic chuck according to the present invention, when viewed from a direction perpendicular to the mounting surface, it is also preferable that the heater line width is largest at the center of the heater along the extending direction in the portion overlapping the opening. Since the amount of heat generated by the heater is smallest at the center where heat transfer to the base plate is least difficult (i.e., where the temperature is most likely to rise), the temperature distribution directly above the opening can be made even more uniform.

[0011] In the electrostatic chuck according to the present invention, it is also preferable that, when viewed from a direction perpendicular to the mounting surface, the heater has a line width that gradually increases toward the center of the heater in the extension direction in the portion overlapping the opening. The amount of heat generated by the heater in the portion overlapping the opening in the top view gradually decreases from the end side toward the center. In the electrostatic chuck having the above configuration, the distribution of the amount of heat generated by the heater is appropriately adjusted in accordance with the distribution of heat transfer inside the opening, so that the temperature distribution directly above the opening can be made even more uniform.

[0012] In the electrostatic chuck according to the present invention, it is also preferable that, when viewed from a direction perpendicular to the mounting surface, the heater has a line width that gradually increases toward the center of the heater in the extending direction, in a portion of the heater that overlaps with the opening. By adopting such a configuration, it is possible to easily form a heater having a line width that is larger at the center than at the ends. Effect of the Invention

[0013] According to the present invention, it is possible to provide an electrostatic chuck capable of sufficiently suppressing variations in the in-plane temperature distribution of a substrate. [Brief description of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view illustrating a schematic configuration of an electrostatic chuck according to an embodiment of the present invention. [Diagram 2] 3A to 3C are diagrams for explaining examples of the arrangement of multiple heaters built into the dielectric substrate according to the present embodiment. [Diagram 3] 3A to 3C are diagrams illustrating an example of the configuration of a heater built into the dielectric substrate according to the present embodiment. [Figure 4] 13A to 13C are diagrams illustrating other examples of the arrangement of multiple heaters built into a dielectric substrate. [Diagram 5] 13A and 13B are diagrams showing other examples of the configuration of a heater built into a dielectric substrate. [Figure 6] 5A to 5C are diagrams illustrating examples of the shape of a heater in a portion of the electrostatic chuck according to the embodiment that overlaps with an opening when viewed from above. [Figure 7] 10A and 10B are diagrams illustrating other examples of the shape of the heater in the portion overlapping with the opening in a top view of the electrostatic chuck according to the embodiment. [Figure 8] 10A and 10B are diagrams illustrating other examples of the shape of the heater in the portion overlapping with the opening in a top view of the electrostatic chuck according to the embodiment. [Figure 9] 10A and 10B are diagrams illustrating other examples of the shape of the heater in the portion overlapping with the opening in a top view of the electrostatic chuck according to the embodiment. [Figure 10] FIG. 13 is a diagram showing the shape of a heater in a portion of an electrostatic chuck according to a comparative example that overlaps with an opening when viewed from above. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components in each drawing are denoted by the same reference numerals as much as possible, and duplicated description will be omitted.

[0016] The electrostatic chuck 10 according to this embodiment is configured to electrostatically attract and hold a substrate W to be processed inside a semiconductor manufacturing apparatus (not shown), such as a CVD film forming apparatus. The substrate W is, for example, a silicon wafer. The electrostatic chuck 10 may be used in an apparatus other than a semiconductor manufacturing apparatus.

[0017] 1 shows, in a schematic cross-sectional view, the configuration of an electrostatic chuck 10 in a state in which the electrostatic chuck 10 attracts and holds a substrate W. The electrostatic chuck 10 includes a dielectric substrate 100, a base plate 200, and a bonding layer 300.

[0018] The dielectric substrate 100 is a substantially disk-shaped member made of a sintered ceramic body. The dielectric substrate 100 contains, for example, high-purity aluminum oxide (Al2O3), but may contain other materials. The purity, type, and additives of the ceramics in the dielectric substrate 100 can be appropriately set in consideration of the plasma resistance and other properties required of the dielectric substrate 100 in semiconductor manufacturing equipment.

[0019] 1 of the dielectric substrate 100 is a "mounting surface" on which a substrate W, which is an object to be attracted, is placed. Also, a lower surface 120 of the dielectric substrate 100 in FIG. 1 (i.e., the surface 120 opposite to the surface 110) is a "bonded surface" that is bonded to a base plate 200 via a bonding layer 300 described below. The viewpoint when the electrostatic chuck 10 is viewed from the surface 110 side along a direction perpendicular to the surface 110 is hereinafter also referred to as a "top view".

[0020] An adsorption electrode 130 is embedded inside the dielectric substrate 100. The adsorption electrode 130 is a thin, flat layer made of a metal material such as tungsten, and is disposed so as to be parallel to the surface 110. The material of the adsorption electrode 130 may be molybdenum, platinum, palladium, or the like, in addition to tungsten. When a voltage is applied to the adsorption electrode 130 from the outside via the power supply path 13, an electrostatic force is generated between the surface 110 and the substrate W, thereby adsorbing and holding the substrate W. The adsorption electrode 130 may be provided in twos as a so-called "bipolar" electrode as in this embodiment, or may be provided in only ones as a so-called "monopolar" electrode.

[0021] 1, the entire power supply line 13 is depicted in a simplified manner. A portion of the power supply line 13 inside the dielectric substrate 100 is configured as, for example, a long and narrow via (hole) filled with a conductor, and an electrode terminal (not shown) is provided at the lower end thereof. A portion of the power supply line 13 penetrating the base plate 200 is a conductive metal member (for example, a bus bar) having one end connected to the electrode terminal. A through hole (not shown) for inserting the power supply line 13 is formed in the base plate 200. For example, a cylindrical insulating member may be provided between the inner surface of the through hole and the power supply line 13.

[0022] A space SP is formed between the dielectric substrate 100 and the substrate W. When a process such as film formation is performed in the semiconductor manufacturing apparatus, helium gas for temperature adjustment is supplied from the outside to the space SP through a gas hole (not shown) formed in the dielectric substrate 100. By providing helium gas between the dielectric substrate 100 and the substrate W, the thermal resistance between them is adjusted, and the temperature of the substrate W is thereby maintained at an appropriate temperature. The temperature adjustment gas supplied to the space SP may be a type of gas other than helium.

[0023] A seal ring 111 and dots 112 are provided on a surface 110 which is an attraction surface, and a space SP is formed around these.

[0024] The seal ring 111 is a wall that divides the space SP at the outermost position. The upper end of each seal ring 111 forms part of the surface 110 and abuts against the substrate W. Note that a plurality of seal rings 111 may be provided to divide the space SP. With this configuration, it is possible to individually adjust the pressure of the helium gas in each space SP and make the surface temperature distribution of the substrate W during processing more uniform.

[0025] 1 and the like, the portion marked with the reference symbol "116" is the bottom surface of the space SP. Hereinafter, this portion will also be referred to as the "bottom surface 116." The seal ring 111, together with the dots 112 described below, is formed as a result of digging down a part of the surface 110 to the position of the bottom surface 116. The bottom surface 116 may have grooves formed therein to quickly diffuse the helium gas within the space SP.

[0026] The dots 112 are circular protrusions protruding from the bottom surface 116. A plurality of dots 112 are provided and are distributed approximately evenly on the attraction surface of the dielectric substrate 100. The upper end of each dot 112 forms part of the surface 110 and abuts against the substrate W. By providing a plurality of such dots 112, bending of the substrate W is suppressed.

[0027] The dielectric substrate 100 includes a built-in heater 500. The heater 500 is an electric heater that generates heat when power is supplied from an external source. The heater 500 is a thin, flat layer made of a metal material such as tungsten, and is embedded between the chucking electrode 130 and the surface 120. The material of the heater 500 is not limited to tungsten, and other materials may be used. The heater 500 is routed in a linear pattern parallel to the surface 110. The specific shape of the heater 500 will be described later.

[0028] A plurality of heaters 500 are provided, and are arranged at different positions from each other when viewed from above. This makes it possible to individually adjust the heat generation amount of each heater 500 and suppress variations in the in-plane temperature distribution of the substrate W. Each heater 500 has the same distance from the surface 110 (i.e., the embedded depth).

[0029] A pair of power supply paths 51, 52 are connected to each heater 500. The power supply paths 51, 52 constitute an electric path for supplying power to the heater 500, and are connected to both ends of the heater 500, which is linear. In Fig. 1, only some of the multiple power supply paths 51, 52 are shown.

[0030] As with the previously described power feed line 13, the power feed lines 51 and 52 are illustrated in a simplified manner in Fig. 1. The portions of the power feed lines 51 and 52 inside the dielectric substrate 100 are configured as elongated vias (holes) filled with a conductor, for example, and an electrode terminal (not shown) is provided at the lower end thereof. The portions of the power feed lines 51 and 52 penetrating the base plate 200 are rod-shaped metal pieces (bus bars) having one end connected to the electrode terminal. The base plate 200 has through holes (not shown) for inserting the metal pieces therethrough.

[0031] The power supply paths 51, 52 are provided individually corresponding to the respective heaters 500. That is, the number of the power supply paths 51, 52 is equal to the number of the heaters 500. However, of the power supply paths 51, 52, for example, the one that is set to the ground potential may be shared among a plurality of heaters 500. In this case, the number of electrode terminals provided for supplying power to the heaters 500 is smaller than the total number of the power supply paths 51, 52.

[0032] The base plate 200 is a substantially disk-shaped member that is bonded to the surface 120 of the dielectric substrate 100 in order to support the dielectric substrate 100. The base plate 200 is formed of a metal such as aluminum. A surface 210 of the base plate 200 on the upper side in FIG. 1 is a "bonded surface" that is bonded to the dielectric substrate 100 via a bonding layer 300. The surface of the base plate 200 including the surface 210 may be covered with an insulating film such as an alumina sprayed film.

[0033] The bonding layer 300 is a layer provided between the dielectric substrate 100 and the base plate 200, and bonds them together. The bonding layer 300 is formed by curing an adhesive made of an insulating material. For example, a silicone-based adhesive can be used as such an adhesive.

[0034] 1 is formed in the base plate 200. An opening 241, which is the upper end of the through hole 240, is formed in the surface 210. The through hole 240 and the opening 241 are formed for the purpose of attaching a temperature sensor TC to the surface 120 of the dielectric substrate 100.

[0035] The temperature sensor TC is a sensor, such as a thermocouple, for measuring the temperature of each portion of the dielectric substrate 100 during processing. A signal line 14 extending from the temperature sensor TC is led out through a through hole 240 to the outside.

[0036] The temperature sensors TC are attached to a plurality of locations on the surface 120. Correspondingly, a plurality of through holes 240 and openings 241 are formed in the base plate 200. However, only one each of the temperature sensors TC, through holes 240, and openings 241 are shown in FIG.

[0037] In addition to the opening 241, other openings may be formed on the surface 210 of the base plate 200. Such openings may include, for example, an opening for supplying helium gas to the dielectric substrate 100, and openings for passing the power feed paths 13, 51, and 52. The holes extending from the respective openings into the inside of the base plate 200 may be formed so as to extend linearly as a whole like the through-hole 240, but may also be formed so as to bend midway toward the surface 220.

[0038] A coolant flow path 250 for flowing a coolant is formed inside the base plate 200. When a process such as film formation is performed in the semiconductor manufacturing apparatus, a coolant is supplied to the coolant flow path 250 from the outside, thereby cooling the base plate 200. Heat generated in the substrate W during the process is transferred to the coolant via the helium gas in the space SP, the dielectric substrate 100, and the base plate 200, and is discharged to the outside together with the coolant.

[0039] The configuration of the heater 500 will be described. In Fig. 2, the dielectric substrate 100 is illustrated in a schematic top view. Each region HA shown in the figure represents a region in which a single heater 500 is routed. In the example of Fig. 2, three regions HA are arranged concentrically, and a heater 500 is individually routed in each region HA. That is, in this example, three heaters 500 are provided.

[0040] 3 shows a schematic top view of an area HA indicated by the symbol "HA1" in FIG. 2 and the shape of the heater 500 routed in the area HA1. As shown in FIG. 3, a pair of power supply paths 51, 52 are arranged in the area HA1, and a single linear heater 500 is routed to connect between them. Note that in FIG. 3, the heater 500 is drawn so that its line width is uniform regardless of location, but as will be described later, the line width of the heater 500 is locally larger in some areas. Note that the "line width" here refers to the dimension of the heater 500 along a direction perpendicular to the direction in which the heater 500 extends in a top view.

[0041] The above-mentioned configuration of the heater 500 is merely an example, and the number, arrangement, shape, etc. of the heater 500 may be changed as appropriate. FIG. 4 shows an example in which a plurality of regions HA are arranged differently from that in FIG. 2. In this example, a total of 16 regions HA are arranged, and the heater 500 is routed individually in each region HA. FIG. 5 shows a region HA marked with the symbol "HA2" in FIG. 4 and the shape of the heater 500 routed in the region HA2, as viewed from above. The shape of the heater 500 described below can be adopted regardless of the number and arrangement of the heaters 500 in the dielectric substrate 100.

[0042] As described above, the opening 241 is formed in the surface 210 of the base plate 200 facing the dielectric substrate 100. As shown in Figures 3 and 5, in each region HA, the linear heater 500 is densely routed, so that a part of the heater 500 overlaps with the opening 241 in top view. In Figure 6, the part of the heater 500 directly above the opening 241 is depicted in top view.

[0043] Of the heater 500 located inside the opening 241 in top view, an end portion along the extension direction of the heater 500 (left-right direction in FIG. 6) is hereinafter also referred to as "end portion 510." Also, of the heater 500 located inside the opening 241 in top view, a central portion along the extension direction of the heater 500 is hereinafter also referred to as "central portion 520."

[0044] As shown in FIG. 6, in a portion of the heater 500 overlapping with the opening 241 in a top view, the line width W2 of the heater 500 at the center portion 520 is greater than the line width W1 of the heater 500 at the end portion 510.

[0045] The reason for adopting such a configuration will be described below. In the portion of the dielectric substrate 100 that overlaps with the opening 241 in a top view, heat is not easily transferred to the base plate 200, and a local temperature rise tends to occur easily during processing of the substrate W. Such a local temperature rise is unlikely to occur near the edge of the opening 241, but is more likely to occur the farther away from the edge (i.e., the closer to the center of the opening 241).

[0046] Therefore, when the line width W1 at the end portion 510 and the line width W2 at the central portion 520 are equal to each other, that is, when the line width of the heater 500 is uniform over the entire portion overlapping with the opening 241, as in the comparative example shown in FIG. 10, a local temperature rise may occur at a position directly above the center of the opening 241.

[0047] 6, in the electrostatic chuck 10 according to this embodiment, the line width of the heater 500 is locally increased directly above the opening 241. Since the amount of heat generated by the heater 500 is small directly above the opening 241, i.e., in the portion where a local temperature increase is likely to occur, it is possible to suppress the variation in the in-plane temperature distribution of the substrate W.

[0048] Furthermore, in this embodiment, the line width of the portion of the heater 500 overlapping with the opening 241 is not uniform, and the line width W2 at the center 520 is locally larger than the line width W1 at the end 510. Compared to the amount of heat generated at the end 510 where heat is relatively easy to dissipate, the amount of heat generated at the center 520 where heat is relatively hard to dissipate (i.e. where the temperature is easily increased) is suppressed, so that the temperature distribution directly above the opening 241 becomes roughly uniform. This makes it possible to sufficiently suppress the variation in the in-plane temperature distribution of the substrate W.

[0049] Furthermore, in this embodiment, in the portion of the heater 500 that overlaps with the opening 241 in a top view, the line width of the heater 500 is largest at the position of the central portion 520. Since the amount of heat generated by the heater 500 is smallest in the central portion 520, which is the portion of the heater 500 where heat transfer to the base plate 200 is least likely to occur (i.e., where the temperature is most likely to increase), the temperature distribution directly above the opening 241 can be made even more uniform.

[0050] 6, in the portion of the heater 500 overlapping with the opening 241 in top view, the line width of the heater 500 gradually increases toward the center portion 520 along the extension direction of the heater 500. With this configuration, the heat generation amount of the heater 500 in the portion overlapping with the opening 241 gradually decreases from the end portion 510 toward the center portion 520. Since the distribution of the heat generation amount of the heater 500 is appropriately adjusted in accordance with the distribution of heat transfer inside the opening 241, the temperature distribution directly above the opening 241 can be made more uniform.

[0051] In the example of Fig. 6, the heater 500 is routed along a path that passes through the center of the opening 241 when viewed from above. In contrast, in the modified example of Fig. 7, the heater 500 is routed along a path that does not pass through the center of the opening 241 when viewed from above. In the modified example of Fig. 7, similar to Fig. 6, the line width W2 of the central portion 520 is larger than the line width W1 of the end portion 510. Even with the configuration of such a modified example, it is possible to achieve the same effects as those described above for the configuration of Fig. 6.

[0052] Another modified example is shown in Fig. 8. In this modified example, a part of the heater 500 is formed so as to be concentric with the opening 241 and have a circular shape with a diameter of W2. The heater 500 has a constant line width of W1 in other parts. Even with the configuration of this modified example, it is possible to achieve the same effects as those described above for the configuration of Fig. 6.

[0053] FIG. 9 shows yet another modified example. In this modified example, the line width of the heater 500 increases stepwise from the end portion 510 side toward the center portion 520. The number of stages of the heater 500 is three in this modified example, but it may be two or one stage, or may be four or more stages. Even with the configuration of such a modified example, it is possible to obtain the same effect as the above-described effect described for the configuration of FIG. 6. With the configuration of this modified example, it is also possible to obtain an advantage that the heater 500 having a shape in which the line width of the center portion 520 is larger than that of the end portion 510 can be easily formed.

[0054] In the above, an example has been described in which the line width of the heater 500 is locally increased directly above the opening 241 for attaching the temperature sensor TC. However, the heater 500 may have a similar configuration to that described above directly above other openings formed on the surface 210.

[0055] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Any design modifications made by a person skilled in the art to these specific examples are also included within the scope of the present disclosure as long as they have the features of the present disclosure. The elements of each of the above-mentioned specific examples and their arrangements, conditions, shapes, etc. are not limited to those exemplified and can be changed as appropriate. The combination of each of the elements of each of the above-mentioned specific examples can be changed as appropriate as long as no technical contradiction occurs. [Explanation of symbols]

[0056] 10: Electrostatic chuck 100: Dielectric substrate 110,120: face 200: Base plate 210,220: Surface 241:Aperture 500:Heater 510: End 520: Central part W1, W2: Line width

Claims

[Claim 1] A dielectric substrate having a mounting surface on which an object to be adsorbed is placed, A linear heater embedded in the dielectric substrate, The dielectric substrate comprises a base plate bonded to the surface opposite to the mounting surface described above, An opening is formed on the surface of the base plate facing the dielectric substrate for attaching a temperature measuring sensor to the dielectric substrate. When viewed from a direction perpendicular to the mounting surface, In the portion of the heater that overlaps with the opening, The wire width of the heater at the central position along the direction in which it extends is greater than the wire width of the heater at the end position along the direction in which it extends. When viewed from a direction perpendicular to the mounting surface, In the portion of the heater that overlaps with the opening, The wire width of the heater is largest at the center along the direction in which the heater extends. The wire width of the aforementioned heater is An electrostatic chuck characterized in that it gradually increases in size as it approaches the central position along the direction in which the heater extends.

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