Electrostatic chuck

Abstract

To provide an electrostatic chuck which can ensure plasma uniformity on an upper side of a dielectric substrate even with a configuration in which an outer circumferential edge of the dielectric substrate protrudes.SOLUTION: An electrostatic chuck 10 includes a dielectric substrate 100, an RF electrode 140 provided inside the dielectric substrate 100, and a base plate 200 made of metal and joined to the dielectric substrate 100. The dielectric substrate 100 includes a protrusion section 101 protruding outward beyond a surface 210 of the base plate 200 in top view, and a part of the RF electrode 140 is provided in the protrusion section 101.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] For example, semiconductor manufacturing equipment such as an etching apparatus is provided with an electrostatic chuck 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. When a voltage is applied to the attracting electrode, an electrostatic force is generated, attracting and holding a substrate placed on the dielectric substrate.

[0003] A semiconductor manufacturing apparatus is provided with RF electrodes as a pair of opposing electrodes for generating plasma. As described in Patent Document 1 below, a base plate of an electrostatic chuck may be used as one of the RF electrodes. Alternatively, the RF electrode may be built into a dielectric substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-119654 Summary of the Invention [Problem to be solved by the invention]

[0005] The bonding layer between the dielectric substrate and the base plate is made of, for example, a hardened silicone adhesive. During processing such as etching, the edge of the bonding layer may be exposed to plasma, deteriorate, and fly off, adversely affecting the substrate being processed.

[0006] To prevent this, the inventors have developed an electrostatic chuck in which the dielectric substrate is larger than the bonded surface of the base plate, i.e., the outer edge of the dielectric substrate protrudes outward from the bonded surface. This configuration allows a member covering the periphery of the bonding layer to be positioned below the dielectric substrate. This reduces the influence of the bonding layer on the substrate during processing.

[0007] If the outer edge of the dielectric substrate protrudes outward from the surface to be bonded, the base plate as an RF electrode will not be present directly below the protruding portion of the dielectric substrate, which can cause the plasma directly above the protruding portion to become non-uniform, potentially resulting in uneven etching and other processes.

[0008] 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 ensure uniformity of plasma above the dielectric substrate even when the outer peripheral end of the dielectric substrate is configured to protrude. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides an electrostatic chuck comprising: a dielectric substrate having a mounting surface on which an object to be attracted is placed, an RF electrode provided inside the dielectric substrate, and a base plate which is a metal member and joined to the dielectric substrate. When viewed from a direction perpendicular to the mounting surface, the dielectric substrate has a protruding portion that protrudes outward beyond the joined surface of the base plate, and a part of the RF electrode is provided on the protruding portion.

[0010] By providing a part of the RF electrode on the protrusion, it is possible to sandwich almost the entire space directly above the dielectric substrate (including directly above the protrusion) between a pair of electrodes including the RF electrode, thereby ensuring uniformity of the plasma above the dielectric substrate. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an electrostatic chuck that can ensure uniformity of plasma above the dielectric substrate even when the outer peripheral end of the dielectric substrate is configured to protrude. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view schematically showing the configuration of an electrostatic chuck according to a first embodiment. [Figure 2] FIG. 2 is an enlarged view showing a part of the configuration of FIG. 1 in detail. [Figure 3] FIG. 4 is a cross-sectional view showing a configuration of a part of an electrostatic chuck according to a modified example of the first embodiment. [Figure 4] FIG. 10 is a cross-sectional view showing a configuration of a portion of an electrostatic chuck according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicated descriptions will be omitted.

[0014] A first embodiment will be described. An 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 an etching apparatus. The object to be attracted, that is, the substrate W, is, for example, a silicon wafer. The electrostatic chuck 10 may also be used in apparatuses other than semiconductor manufacturing apparatuses.

[0015] 1 is a schematic cross-sectional view showing the configuration of an electrostatic chuck 10 in a state where the electrostatic chuck 10 attracts and holds a substrate W. The electrostatic chuck 10 includes a dielectric substrate 100 and a base plate 200.

[0016] 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 also contain other materials. The purity, type, and additives of the ceramics in the dielectric substrate 100 can be appropriately set taking into consideration the plasma resistance and other properties required of the dielectric substrate 100 in semiconductor manufacturing equipment. The diameter of the dielectric substrate 100 is, for example, 290 to 300 mm. The thickness of the dielectric substrate 100 is, for example, 0.5 to 3.0 mm.

[0017] 1 of the dielectric substrate 100 is a "mounting surface" on which the substrate W is placed. Also, a lower surface 120 of the dielectric substrate 100 in FIG. 1 is a "bonded surface" that is bonded to the base plate 200 via a bonding layer 300. The viewpoint when the electrostatic chuck 10 is viewed from the side of the surface 110 along a direction perpendicular to the surface 110 will hereinafter also be referred to as a "top view."

[0018] An adsorption electrode 130 is embedded within the dielectric substrate 100. The adsorption electrode 130 is a thin, flat layer made of a metal material such as tungsten, and is disposed parallel to the surface 110. The adsorption electrode 130 may be made of tungsten or other materials such as molybdenum, platinum, or palladium. When a voltage is applied to the adsorption electrode 130 from the outside via a power supply line (not shown), an electrostatic force is generated between the surface 110 and the substrate W, thereby adsorbing and holding the substrate W. Various known configurations can be employed for the power supply line. As in this embodiment, only one adsorption electrode 130 may be provided as a so-called "monopolar" electrode, or two may be provided as so-called "bipolar" electrodes. The depth at which the adsorption electrode 130 is disposed, i.e., the distance from a bottom surface 116 (described below) to the adsorption electrode 130, is, for example, 0.1 to 0.5 mm.

[0019] In addition to the above-described attracting electrode 130, an RF electrode 140 is also embedded inside the dielectric substrate 100. The RF electrode 140 is provided as one of a pair of opposing electrodes for generating plasma in the semiconductor manufacturing equipment. The other opposing electrode is provided at a position above the electrostatic chuck 10 in the semiconductor manufacturing equipment. When a high-frequency AC voltage is applied between these opposing electrodes, plasma is generated above the substrate W, and is used for processing the substrate W, such as film formation and etching.

[0020] Like the chucking electrode 130, the RF electrode 140 is a thin, flat layer made of a metal material such as tungsten. Other materials that may be used for the RF electrode 140 include molybdenum, platinum, and palladium, in addition to tungsten. The RF electrode 140 is embedded in a position closer to the surface 120 than the chucking electrode 130. Like the chucking electrode 130, the RF electrode 140 is disposed parallel to the surface 110. The RF electrode 140 is a single electrode that is substantially circular in top view. The center of the RF electrode 140 coincides with the center of the dielectric substrate 100 in top view. The distance from the chucking electrode 130 to the RF electrode 140 is, for example, 0.2 to 2 mm. The distance from the RF electrode 140 to the surface 120 is, for example, 0.1 to 2.5 mm.

[0021] As shown in FIG. 1, a power feed line 14 is connected to the RF electrode 140. The power feed line 14 is an electric path provided to match the potential of the RF electrode 140 with the potential of the base plate 200 when a high-frequency AC voltage is applied between the RF electrode 140 and the other opposing electrode. In FIG. 1, the entire power feed line 14 is depicted in a simplified form. The power feed line 14 is configured, for example, as an electrode terminal having one end connected to the RF electrode 140 and the other end formed to protrude downward from the surface 120. The protruding portion of the power feed line 14 as described above is embedded in a recess (not shown) formed in the surface 210 of the base plate 200 and connected to a metal portion of the base plate 200. The number of power feed lines 14 may be two or more.

[0022] As shown in Fig. 1, a space SP is formed between the dielectric substrate 100 and the substrate W. When a process such as etching is performed in the semiconductor manufacturing equipment, helium gas for temperature adjustment is supplied to the space SP from the outside through a gas hole (not shown). By providing helium gas between the dielectric substrate 100 and the substrate W, the thermal resistance between them is adjusted, thereby maintaining the temperature of the substrate W at an appropriate temperature. Note that the temperature adjustment gas supplied to the space SP may be a gas other than helium.

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

[0024] The seal ring 111 is a wall that partitions the space SP at the outermost position. The seal ring 111 is an annular protrusion formed on the surface 110. The tip (the upper end in FIG. 1) of the seal ring 111 is part of the surface 110 and abuts against the substrate W. The tip of the seal ring 111 can be said to be the outermost part of the surface 110, which is the mounting surface.

[0025] It should be noted that a plurality of seal rings 111 may be provided to divide the space SP. With such a configuration, the pressure of the helium gas in each space SP can be adjusted individually, and the surface temperature distribution of the substrate W during processing can be made more uniform.

[0026] 1, the portion marked with the reference numeral "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 by digging down a portion of the surface 110 to the position of the bottom surface 116.

[0027] The dots 112 are circular protrusions that protrude from the bottom surface 116. A plurality of dots 112 are provided, and are distributed approximately evenly on the mounting surface of the dielectric substrate 100. The tip of each dot 112 forms part of the surface 110 and comes into contact with the substrate W. By providing a plurality of such dots 112, bending of the substrate W is suppressed.

[0028] The base plate 200 is a substantially disk-shaped member that supports the dielectric substrate 100. The base plate 200 is formed of a metal material such as aluminum. The base plate 200 is bonded to the surface 120 of the dielectric substrate 100 via a bonding layer 300. The surface 210 of the base plate 200, which is on the upper side in FIG. 1, is the "bonded surface" that is bonded to the dielectric substrate 100.

[0029] 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. In this embodiment, a silicone adhesive is used as the adhesive. However, the bonding layer 300 may be formed by curing another type of adhesive. In either case, it is preferable to use a material with as high a thermal conductivity as possible as the material for the bonding layer 300 so as to reduce the thermal resistance between the dielectric substrate 100 and the base plate 200.

[0030] The base plate 200 has a support portion 201 and a flange portion 202. The support portion 201 is the upper portion of the base plate 200 in FIG. 1 and is a generally cylindrical portion that directly supports the dielectric substrate 100 from below. The diameter of the support portion 201, i.e., the diameter of the surface 210, is, for example, 290 to 300 mm, similar to that of the dielectric substrate 100, but is slightly smaller than the diameter of the dielectric substrate 100. The thickness of the support portion 201, i.e., the amount by which the support portion 201 protrudes upward in FIG. 1 (the amount by which it protrudes from the flange portion 202), is, for example, 3 to 15 mm.

[0031] The flange 202 is the lower part of the base plate 200 in FIG. 1. The flange 202 is substantially cylindrical, and its central axis coincides with the central axis of the support portion 201. The diameter of the flange 202 is larger than the diameter of the support portion 201. The amount of protrusion of the flange 202 from the outer surface of the support portion 201 (i.e., the amount of protrusion in the radial direction) is, for example, 20 to 30 mm. The thickness of the flange 202 is, for example, 25 to 40 mm. The overall thickness of the base plate 200, including the support portion 201 and the flange 202, is, for example, 30 to 40 mm.

[0032] When processing a substrate W in a semiconductor manufacturing apparatus, a focus ring (not shown) is installed on the upper surface 203 of the flange portion 202. The focus ring is an annular, plate-shaped member made of an insulating material such as quartz, and is installed for the purpose of adjusting the distribution of plasma during processing. The dielectric substrate 100 and the support portion 201 are substantially entirely surrounded by the focus ring from the outer periphery.

[0033] A coolant flow path 250 for passing a coolant is formed inside the base plate 200. When a process such as etching is performed in the semiconductor manufacturing equipment, 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.

[0034] As described above, in the electrostatic chuck 10 according to this embodiment, the diameter of the support portion 201, which is the portion of the base plate 200 that directly supports the dielectric substrate 100, is smaller than the diameter of the dielectric substrate 100. As a result, the dielectric substrate 100 protrudes outward from the surface 210, which is the surface to be joined. Such a protruding portion of the dielectric substrate 100 will also be referred to as the "protruding portion 101" hereinafter. The protruding amount of the protruding portion 101, i.e., the protruding amount of the dielectric substrate 100 from the outer surface of the support portion 201 (protruding amount in the radial direction), is, for example, 1 mm to 3 mm.

[0035] During processing such as etching, the end of the bonding layer 300 may be exposed to plasma, deteriorate, and fly off, which may adversely affect the substrate W during processing. When the protrusion 101 is provided on the dielectric substrate 100 as in this embodiment, a member that covers the exposed portion of the bonding layer 300 from the periphery can be disposed below the dielectric substrate 100. In FIG. 2, an example of the location of such a member is indicated by a dashed line labeled "400." By disposing this member, the influence of the bonding layer 300 on the substrate W during processing can be suppressed.

[0036] During processing such as etching, it is necessary to ensure uniformity of plasma above the dielectric substrate 100 so that processing can be performed uniformly. When the dielectric substrate 100 does not have the protruding portion 101 and the entire surface 120 of the dielectric substrate 100 is supported from below by the base plate 200, for example, the base plate 200 can function as an RF electrode to ensure uniformity of plasma over the entire area directly above the surface 110. However, when the dielectric substrate 100 has the protruding portion 101 as in this embodiment, the base plate 200 as an RF electrode does not exist directly below the protruding portion 101. This can cause the plasma to become non-uniform directly above the protruding portion 101, which can result in processing such as etching not being performed uniformly.

[0037] Therefore, in the electrostatic chuck 10 according to this embodiment, an RF electrode 140 is provided inside the dielectric substrate 100, and the arrangement of the RF electrode 140 is devised to ensure uniformity of the plasma during processing.

[0038] Fig. 2 shows an enlarged detailed view of the configuration of the protrusion 101 and its vicinity of the electrostatic chuck 10 shown in Fig. 1. The dotted line DL1 shown in Fig. 2 indicates the position of the outer peripheral edge of the surface 210 to be joined. The dotted line DL2 indicates the position of the outer peripheral edge of the attraction electrode 130. The dotted line DL3 indicates the position of the outer peripheral edge of the RF electrode 140.

[0039] The "outer peripheral end" of the RF electrode 140 refers to the portion where the RF electrode 140 overlaps with the smallest circle among the circles that encompass the entire RF electrode 140 when viewed from above. The "outer peripheral end" of the chucking electrode 130 is defined in the same way.

[0040] The diameter of the outer peripheral end of the RF electrode 140 is larger than the diameter of the surface 210 of the base plate 200. Therefore, the outer peripheral end (dotted line DL3) of the RF electrode 140 extends into the inside of the protruding portion 101 of the dielectric substrate 100.

[0041] In a configuration in which a part of the RF electrode 140 is provided on the protruding portion 101 as in this embodiment, substantially the entire space directly above the dielectric substrate 100 (including the area directly above the protruding portion 101) can be sandwiched between a pair of electrodes including the RF electrode 140. In other words, even in a configuration in which the protruding portion 101 is provided on the dielectric substrate 100, the RF electrode 140 can be expanded to an area wider than the surface 210 of the base plate 200. This makes it possible to ensure uniformity of plasma above the dielectric substrate 100.

[0042] Furthermore, in this embodiment, the diameter of the outer peripheral end of the chucking electrode 130 is larger than the diameter of the surface 210 of the base plate 200. In other words, not only the RF electrode 140 but also the chucking electrode 130 are partially embedded in the protruding portion 101 in top view.

[0043] In this configuration in which part of the attraction electrode 130 is provided on the protrusion 101, the attraction force of the protrusion 101 to the substrate W increases, and the two are tightly attached to each other with strong force. Although the base plate 200, which serves as a coolant, is not present directly below the protrusion 101, the thermal resistance between the protrusion 101 and the substrate W is reduced, so that the temperature rise of the substrate W directly above the protrusion 101 can be suppressed to some extent. As a result, the variation in the in-plane temperature distribution of the substrate W during processing can be suppressed.

[0044] The diameter of the outer peripheral end of the chucking electrode 130 is larger than the diameter of the inner peripheral side of the seal ring 111 and smaller than the diameter of the outer peripheral side of the seal ring 111. Furthermore, the diameter of the outer peripheral side of the seal ring 111 is larger than the diameter of the surface 210 of the base plate 200. In top view, a portion of the seal ring 111 overlaps with both the protrusion 101 and the chucking electrode 130. By overlapping the seal ring 111, the protrusion 101, and the chucking electrode 130 in top view, cooling of the substrate W in this portion can be further enhanced. As a result, variation in the in-plane temperature distribution of the substrate W can be further suppressed.

[0045] The entire seal ring 111, rather than just a part of it, may overlap both the protrusion 101 and the chucking electrode 130 in top view. In this case, the diameter of the inner periphery of the seal ring 111 may be made larger than the diameter of the support portion 201. The diameter of the outer periphery of the seal ring 111 may be made smaller than the diameter of the dielectric substrate 100 and also smaller than the diameter of the outer periphery end of the chucking electrode 130.

[0046] In either case, it is preferable to ensure a distance of approximately 0.1 mm to 3 mm from the outer peripheral end (dotted line DL2) of the chucking electrode 130 to the outer surface of the dielectric substrate 100. By ensuring such a distance, it is possible to prevent dielectric breakdown between the chucking electrode 130 and the outside.

[0047] The diameter of the outer peripheral end (dotted line DL3) of the RF electrode 140 is larger than the diameter of the outer peripheral end (dotted line DL1) of the chucking electrode 130. That is, the RF electrode 140 is provided in a range where its outer peripheral end is further outward than the outer peripheral end of the chucking electrode 130 in a top view. It is preferable to secure a distance of approximately 0.1 mm to 2 mm from the outer peripheral end (dotted line DL3) of the RF electrode 140 to the outer surface of the dielectric substrate 100.

[0048] During processing, the potential of the RF electrode 140 is generally set to be smaller than the potential of the chucking electrode 130. In this embodiment, by extending the outer peripheral end of the RF electrode 140 beyond the outer peripheral end of the chucking electrode 130, the RF electrode 140 can be provided over as wide an area as possible while still ensuring a sufficient dielectric strength. As a result, plasma uniformity can be ensured.

[0049] As described above, it is preferable that the diameter of the outer peripheral end of the RF electrode 140 is larger than the diameter of the surface to be joined (surface 210) of the base plate 200. The "surface to be joined" here refers to the surface of the metal part of the base plate 200 that faces the dielectric substrate via the bonding layer 300. The "surface to be joined" can be defined in the same way as above even when the surface 210 is covered with an insulating film.

[0050] 3, an insulating film 230 is formed to cover the surface of the base plate 200, including the surface 210. The insulating film 230 is an alumina film formed by thermal spraying, for example. The thickness of the insulating film is, for example, 1 mm or less.

[0051] 3, the portion of surface 210 near the outer peripheral edge is not flat but curved in an arc. This curved portion of surface 210 will be referred to as "surface 210A" below. In this modification, the entire surface 210, including surface 210A, is defined as the "bonded surface" that is bonded to dielectric substrate 100 via insulating film 230 and bonding layer 300.

[0052] 3, the reference numeral "211" is given to the outer surface of the support part 201. Hereinafter, this outer surface will also be referred to as the "outer surface 211." When viewed from above, the position of the outer peripheral end of the surface to be joined (dotted line DL1) and the position of the outer surface 211 are the same.

[0053] When the surface of the base plate 200 is covered with the insulating film 230 as in this modification, the portion of the dielectric substrate 100 that is outside the dotted line DL1 in top view corresponds to the protrusion 101. In addition, the chucking electrode 130 and the RF electrode 140 are formed to extend to positions that are outside the dotted line DL1.

[0054] The second embodiment will be described below. Differences from the first embodiment will be mainly described below, and descriptions of commonalities with the first embodiment will be omitted as appropriate.

[0055] Fig. 4 illustrates the configuration of the electrostatic chuck 10 according to this embodiment from the same perspective as Fig. 2. As shown in Fig. 4, in this embodiment, the diameter of the outer circumferential end (dotted line DL3) of the RF electrode 140 is smaller than the diameter of the outer circumferential end (dotted line DL2) of the attraction electrode 130. In other words, the RF electrode 140 is provided in a range where its outer circumferential end is more inward than the outer circumferential end of the attraction electrode 130 in a top view.

[0056] When the substrate W is being processed, Joule heat is generated in the RF electrode 140, which may increase the temperature of surrounding components. In other words, the RF electrode 140 can become a heat source during processing. Therefore, in this embodiment, as described above, the RF electrode 140 is provided in a range where its outer circumferential end is more inward than the outer circumferential end of the attraction electrode 130. By keeping the RF electrode 140, which is a heat source, within the above range, it is possible to suppress a temperature increase in the outer circumferential portion of the substrate W.

[0057] The outer peripheral edge of the RF electrode 140 may overlap the outer peripheral edge of the chucking electrode 130 in top view. In other words, it is sufficient that the outer peripheral edge of the RF electrode 140 is provided in a range that does not protrude beyond the outer peripheral edge of the chucking electrode 130.

[0058] In a configuration in which the outer peripheral end of the RF electrode 140 is recessed into the protruding portion 101, if heat generation from the RF electrode 140 becomes a problem, the configuration of this embodiment may be adopted instead of the first embodiment.

[0059] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Design modifications to these specific examples made by a person skilled in the art as appropriate are also included within the scope of the present disclosure as long as they comprise the features of the present disclosure. The elements of the above-described specific examples, as well as their arrangement, conditions, shape, etc., are not limited to those exemplified and can be modified as appropriate. The elements of the above-described specific examples can be combined in various ways as appropriate, as long as no technical contradictions arise. [Explanation of symbols]

[0060] 10: Electrostatic chuck 100: Dielectric substrate 101:Protrusion 110: Face 130: Adsorption electrode 140:RF electrode 200: Base plate 210: Face

Claims

1. a dielectric substrate having a mounting surface on which an object to be attracted is placed; an RF electrode provided inside the dielectric substrate; a base plate made of metal and joined to the dielectric substrate; When viewed from a direction perpendicular to the placement surface, the dielectric substrate has a protruding portion that protrudes outward beyond the surface to be joined of the base plate, a protrusion provided on the RF electrode;

2. The dielectric substrate further includes an adsorption electrode provided inside the dielectric substrate, When viewed from a direction perpendicular to the placement surface, 2. The electrostatic chuck according to claim 1, wherein a part of said attracting electrode is provided on said protruding portion.

3. When viewed from a direction perpendicular to the placement surface, 3. The electrostatic chuck according to claim 2, wherein the RF electrode has an outer circumferential end portion located in a range that is more outer than the outer circumferential end portion of the attracting electrode.

4. When viewed from a direction perpendicular to the placement surface, 3. The electrostatic chuck according to claim 2, wherein the RF electrode is provided in a range such that an outer peripheral edge thereof does not extend beyond the outer peripheral edge of the attraction electrode.

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