Electrostatic chuck

Abstract

The invention provides an electrostatic chuck capable of easily realizing a complicated internal structure of a base plate. An electrostatic chuck (10) is provided with: a dielectric substrate (100); and a base plate (200) that is bonded to the dielectric substrate (100). The base plate (200) has: a first portion (201) that is a portion on the dielectric substrate (100) side; and a second portion (202) that is a portion adjacent to the first portion (201) from the opposite side of the dielectric substrate (100) and that has a larger outer shape than the first portion (201) in plan view. The base plate (200) is configured by bonding a plurality of members, and a bonding boundary (B1) closest to the dielectric substrate (100) side is located in the second portion (202).

Description

Technical Field

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

[0002] For example, in a semiconductor manufacturing apparatus such as an etching apparatus, an electrostatic chuck is provided as an apparatus for adsorbing and holding a substrate such as a silicon wafer to be processed. The electrostatic chuck includes: a dielectric substrate provided with an adsorption electrode; and a base plate that supports the dielectric substrate, and has a structure in which these are joined to each other. When a voltage is applied to the adsorption electrode, an electrostatic force is generated to adsorb and hold the substrate placed on the dielectric substrate.

[0003] As described in Patent Document 1 below, a cooling medium flow path for allowing a cooling medium to pass through is formed inside the base plate. In order to easily form the cooling medium flow path, etc., the base plate usually has a structure in which a plurality of members are joined. For example, if a groove is formed on the surface of one member and other members are joined so as to cover the surface, a flow path along the groove can be easily formed inside the base plate.

[0004] Patent Document Patent Document 1: Japanese Patent Application Laid-Open No. 2015-35447 Summary of the Invention

[0005] In the base plate, on the basis of the above-described cooling medium flow path, a supply flow path for guiding gas to the placement surface side of the dielectric substrate is further formed. In addition, a porous member for preventing discharge may be disposed inside the supply flow path. As such, the internal structure in the vicinity of the dielectric substrate in the base plate is usually relatively complicated.

[0006] As described above, the base plate usually has a structure in which a plurality of members are joined to each other. In order to realize the above-described complicated internal structure, there is more room for improvement in the existing electrostatic chucks regarding the position where the joining boundary between the members in the base plate should be set.

[0007] The present invention has been made in view of such problems, and the technical problem to be solved is to provide an electrostatic chuck that can easily realize a complicated internal structure of the base plate.

[0008] To solve the above problems, the electrostatic chuck according to the present invention includes: a dielectric substrate having a placement surface for placing an object to be adsorbed; and a base plate joined to the dielectric substrate. The base plate has: a first portion, which is a portion on the dielectric substrate side; and a second portion, which is a portion adjacent to the first portion from the opposite side of the dielectric substrate and has an outer shape larger than that of the first portion when viewed from a direction perpendicular to the placement surface. The base plate is constituted by joining a plurality of members, and the joining boundary closest to the dielectric substrate side is located in the second portion.

[0009] In the electrostatic chuck having the above structure, a base plate is formed by joining a plurality of members, and the joining boundary closest to the dielectric substrate side is located in the second portion, rather than in the first portion. Compared with the case where the joining boundary is located in the first portion, the member closest to the dielectric substrate side becomes thicker. Therefore, for example, it is possible to easily perform an operation such as arranging a porous member in the gas supply flow path. As a result, a complex internal structure in the base plate can be easily realized.

[0010] According to the present invention, an electrostatic chuck capable of easily realizing a complex internal structure of a base plate can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 FIG. is a cross-sectional view schematically showing the structure of the electrostatic chuck according to the present embodiment. Figure 2 FIG. is a view schematically showing the structure of a distribution flow path or the like inside the base plate. REFERENCE SIGNS 10 - Electrostatic chuck; 100 - Dielectric substrate; 110 - Surface; 200 - Base plate; 201 - First portion; 202 - Second portion; C1 - First member; C2 - Second member; B1 - Joining boundary; 240 - Supply flow path; 250 - Distribution flow path; 260 - Porous member. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0012] Hereinafter, the present embodiment will be described with reference to the drawings. For ease of understanding the description, in each drawing, the same reference signs are given to the same components as much as possible, and redundant description is omitted.

[0013] The electrostatic chuck 10 according to the present embodiment adsorbs and holds a substrate W to be processed by electrostatic force inside a semiconductor manufacturing apparatus (not shown) such as an etching apparatus, for example. The substrate W as the object to be adsorbed is, for example, a silicon wafer. The electrostatic chuck 10 can also be used in apparatuses other than semiconductor manufacturing apparatuses.

[0014] Figure 1 FIG. shows the structure of the electrostatic chuck 10 in a state of adsorbing and holding the substrate W as a schematic cross-sectional view. The electrostatic chuck 10 includes a dielectric substrate 100 and a base plate 200.

[0015] The dielectric substrate 100 is a substantially disk-shaped member made of a ceramic sintered body. Although the dielectric substrate 100 contains, for example, high-purity alumina (Al2O3), it may also contain other materials. Considering the plasma resistance and the like required for the dielectric substrate 100 in a semiconductor manufacturing apparatus, the ceramic purity, type, additives, etc. in the dielectric substrate 100 can be appropriately set. 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.

[0016] In the dielectric substrate 100, Figure 1 the upper-side surface 110 therein becomes the "placement surface" for placing the substrate W. Further, in the dielectric substrate 100, Figure 1 the lower-side surface 120 therein becomes the "surface to be joined" that is joined to the base plate 200 via the joining layer 300. Hereinafter, the viewpoint when observing the electrostatic chuck 10 in the direction perpendicular to the surface 110 from the surface 110 side will also be described as "top view observation".

[0017] An adsorption electrode 130 is embedded inside the dielectric substrate 100. The adsorption electrode 130 is, for example, a thin plate-shaped layer formed of a metal material such as tungsten and is arranged parallel to the surface 110. As the material of the adsorption electrode 130, in addition to tungsten, molybdenum, platinum, palladium, etc. can also be used. If a voltage is externally applied to the adsorption electrode 130 through a power supply circuit (not shown), an electrostatic force is generated between the surface 110 and the substrate W, and thereby the substrate W is adsorbed and held. As the structure of the above-mentioned power supply circuit, various known structures can be adopted. The adsorption electrode 130 can be provided as a so-called "single-pole" electrode, i.e., only one, as in the present embodiment, or can be provided as a so-called "bipolar" electrode, i.e., two. The depth of the position where the adsorption electrode 130 is arranged, that is, the distance from the bottom surface 116 (described later) to the adsorption electrode 130 is, for example, 0.1 to 0.5 mm.

[0018] As Figure 1 shown, a space SP is formed between the dielectric substrate 100 and the substrate W. When performing a process such as etching in a semiconductor manufacturing apparatus, helium for temperature adjustment is supplied from the outside to the space SP through a supply flow path 140 (described later). By making helium exist between the dielectric substrate 100 and the substrate W, the thermal resistance between the two is adjusted, and thereby the temperature of the substrate W is maintained at an appropriate temperature. And the gas for temperature adjustment supplied to the space SP can also be a gas of a type different from helium.

[0019] A seal ring 111 and dots 112 are provided on the placement surface, i.e., the surface 110, and the above-mentioned space SP is formed around these.

[0020] The sealing ring 111 is a wall that divides the space SP at the outermost peripheral position. The sealing ring 111 is an annular protrusion formed on the surface 110 side. The tip ( Figure 1 the upper end in) of the sealing ring 111 becomes a part of the surface 110 and abuts against the substrate W. It can be said that the tip of the sealing ring 111 is the placement surface, that is, the outermost peripheral side portion of the surface 110.

[0021] Moreover, a plurality of sealing rings 111 can also be provided in a manner that divides the space SP. With such a structure, it is possible to individually adjust the pressure of helium gas in each space SP, and the surface temperature distribution of the substrate W can be made uniform during processing.

[0022] Figure 1 In, the portion marked with the symbol "116" is the bottom surface of the space SP. Hereinafter, this portion will also be referred to as the "bottom surface 116". The sealing ring 111, together with the point 112 described below, is formed as a result of digging a part of the surface 110 to the position of the bottom surface 116.

[0023] The point 112 is a circular protrusion protruding from the bottom surface 116. A plurality of points 112 are provided and are disposed approximately evenly on the placement surface of the dielectric substrate 100. The tip of each point 112 becomes a part of the surface 110 and abuts against the substrate W. By providing a plurality of such points 112, the warping of the substrate W is suppressed.

[0024] A supply flow path 140 is formed in the dielectric substrate 100. The supply flow path 140 is a through hole formed so as to extend in a direction perpendicular to the placement surface, that is, the surface 110. The end portion on the surface 110 side in the supply flow path 140 is connected to the space SP. The supply flow path 140 is a part of the flow path for supplying helium gas to the space SP. Although a plurality of supply flow paths 140 are formed in the dielectric substrate 100, Figure 1 only one of them is shown in.

[0025] As Figure 1 shown, the portion on the surface 120 side in the supply flow path 140 has a larger diameter than the portion on the surface 110 side, and a porous member 160 is disposed inside thereof. The porous member 160 is, for example, a porous body formed of alumina and has air permeability as a whole. By disposing such a porous member 160 inside the supply flow path 140, while ensuring the flow of helium gas in the porous member 160, it is possible to suppress dielectric breakdown from occurring in the path through the supply flow path 140.

[0026] 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, for example. The base plate 200 is joined to the surface 120 of the dielectric substrate 100 by a joining layer 300. In the base plate 200,Figure 1 The upper side surface 210 in becomes the "surface to be joined" joined to the dielectric substrate 100.

[0027] The joining layer 300 is a layer provided between the dielectric substrate 100 and the base plate 200 and joins the two. The joining layer 300 is a layer formed by curing an adhesive made of an insulating material. In the present embodiment, a silicone adhesive is used as the above-mentioned adhesive. However, the joining layer 300 may also be a layer formed by curing other types of adhesives. In any case, it is preferable to use a material with a relatively high thermal conductivity as the material of the joining layer 300 so that the thermal resistance between the dielectric substrate 100 and the base plate 200 is small.

[0028] An insulating film may also be formed on the surface of the base plate 200. As the insulating film, for example, a film of alumina formed by sputtering can be used. By covering the surface of the base plate 200 with the insulating film, the dielectric breakdown voltage of the base plate 200 can be improved.

[0029] The base plate 200 has a first portion 201 and a second portion 202. The first portion 201 is the portion of the base plate 200 on the side of the dielectric substrate 100 ( Figure 1 the upper side in ), and is a substantially cylindrical portion that directly supports the dielectric substrate 100 from below. Although the diameter of the first portion 201, that is, the diameter of the surface 210, may be the same as the diameter of the dielectric substrate 100, it may also be slightly smaller than the diameter of the dielectric substrate 100. The diameter of the first portion 201 is, for example, 290 to 300 mm. In addition, the thickness of the first portion 201, that is, the protruding amount of the first portion 201 toward Figure 1 the upper side (the protruding amount from the second portion 202) is, for example, 3 to 15 mm.

[0030] The second portion 202 is the portion of the base plate 200 adjacent to the first portion 201 from the opposite side of the dielectric substrate 100 ( Figure 1 the lower side in ). In the present embodiment, the entire portion of the base plate 200 other than the first portion 201 becomes the second portion 202. The shape of the second portion 202 is substantially cylindrical, and its central axis coincides with the central axis of the first portion 201. The thickness of the second portion 202 is, for example, 25 to 40 mm. The diameter of the second portion 202 is larger than the diameter of the first portion 201. The protruding amount of the second portion 202 from the outer side surface of the first portion 201 (that is, the protruding amount in the radial direction) is, for example, 20 to 30 mm. Thus, the outer shape of the first portion 201 when viewed from above is larger than the outer shape of the second portion 202 when viewed from above.

[0031] When processing the substrate W in a semiconductor manufacturing apparatus, a focus ring (not shown) is provided on the upper surface 203 of the second part 202. The focus ring is a circular and plate-like member formed of an insulating material such as quartz, and is provided for the purpose of adjusting the distribution of plasma during processing. Substantially the entire dielectric substrate 100 and the first part 201 are in a state of being surrounded by the focus ring from the outer peripheral side.

[0032] Inside the base plate 200, a coolant flow path 270 for allowing a coolant to pass through is formed. When performing processing such as etching in a semiconductor manufacturing apparatus, the coolant is supplied from the outside to the coolant flow path 270, thereby cooling the base plate 200. During processing, the heat generated on the substrate W is transferred to the coolant through 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.

[0033] As Figure 1 shown, the coolant flow path 270 is disposed not only around the portion directly below the substrate W disposed in the base plate 200, but also around the portion closer to the outside than directly below the substrate W. The coolant flowing through the outer portion cools a focus ring (not shown) and the like located directly above the upper surface 203, and thereby the outer peripheral side portion of the substrate W is also cooled.

[0034] In the present embodiment, the diameter of the second part 202 is relatively large. By increasing the second part 202 and forming the coolant flow path 270 over substantially the entire span thereof, and further circulating the coolant, it is possible to suppress the temperature rise of the outer peripheral side portion of the substrate W.

[0035] A supply flow path 240 is formed in the base plate 200. The supply flow path 240 is a hole formed to extend in a direction perpendicular to the placement surface, i.e., surface 110, and extends from surface 210 to a distribution flow path 250 described later. The supply flow paths 240 are respectively formed at positions that overlap with the supply flow path 140 in a top view, and are connected to the supply flow path 140 through through holes 310 provided in the bonding layer 300. The supply flow path 240 becomes a part of the flow path for supplying helium gas to the space SP on the placement surface side together with the supply flow path 140 of the dielectric substrate 100.

[0036] As Figure 1As shown, the portion on the surface 210 side in the supply flow path 240 has a larger diameter than the portion on the distribution flow path 250 side, and a porous member 260 is disposed inside thereof. The porous member 260 is, for example, a porous body formed of alumina and has air permeability as a whole. By disposing such a porous member 260 inside the supply flow path 240, while ensuring the flow of helium in the supply flow path 240, it is possible to suppress dielectric breakdown from occurring on the path through the supply flow path 240.

[0037] A distribution flow path 250 is formed inside the base plate 200. The distribution flow path 250 is a flow path for distributing helium to the respective supply flow paths 240. The distribution flow path 250 is arranged around in parallel with the surface 210 and is connected to the lower ends of the respective supply flow paths 240.

[0038] Figure 2 In, the structure of the distribution flow path 250 inside the base plate 200 and the supply flow path 240 connected thereto is schematically depicted. Figure 2 The arrows in indicate the flow of helium. Figure 2 In, the portion marked with the symbol "251" indicates the flow path of helium formed in the base plate 200 for guiding the helium supplied from the outside to the distribution flow path 250. Hereinafter, this flow path will also be referred to as "flow path 251". One end of the flow path 251 is connected to the distribution flow path 250. The other end of the flow path 251 opens on the surface 220 on the opposite side of the surface 210 in the base plate 200.

[0039] As Figure 2 shown, in the present embodiment, a plurality of supply flow paths 240 are arranged in a circular pattern when viewed from above. The distribution flow path 250 is arranged around in a circular shape so as to pass directly below the respective supply flow paths 240 when viewed from above. The lower ends of the respective supply flow paths 240 are connected to the distribution flow path 250. Therefore, the helium supplied from the outside flows through the flow path 251 and is supplied to the distribution flow path 250, and is distributed from the distribution flow path 250 to the respective supply flow paths 240. Thereafter, it flows from the respective supply flow paths 240 through the supply flow path 140 located directly above it and is supplied to the space SP. By forming the distribution flow path 250 inside the base plate 200, it is possible to reduce the number of portions (that is, the flow path 251) that receive helium supply from the outside.

[0040] In this way, a cooling medium flow path 270, a distribution flow path 250, a supply flow path 240, etc. are formed inside the base plate 200, and it has a relatively complex internal structure. Moreover, since the porous member 260 is disposed in each supply flow path 240, the internal structure on the dielectric substrate 100 side in the base plate 200 becomes even more complex.

[0041] In order to easily form a cooling medium flow path 270 or the like, the base plate 200 of the present embodiment is formed by joining a plurality of members. Specifically, three members composed of a first member C1, a second member C2, and a third member C3 are joined to each other to form a single body, thereby forming the base plate 200. Although the members are joined by welding, for example, they can also be joined by methods such as brazing or connection fixing. The number of members constituting the base plate 200 can be four or more, or can also be two.

[0042] The first member C1, the second member C2, and the third member C3 are arranged in this order along a direction perpendicular to the placement surface, that is, the surface 110. The first member C1 is the part closest to the dielectric substrate 100 side among the members constituting the base plate 200. The surface 210 described above is a part of the first member C1. The third member C3 is the part located on the opposite side of the dielectric substrate 100 among the members constituting the base plate 200. The surface 220 described above is a part of the third member C3. The second member C2 is a member located between the first member C1 and the third member C3.

[0043] The joining boundary B1 between the first member C1 and the second member C2 is parallel to the surface 110 and the surface 210. The joining boundary B2 between the second member C2 and the third member C3 is also parallel to the surface 110 and the surface 210.

[0044] The joining boundary B1 is the joining boundary closest to the dielectric substrate 100 side among the plurality of joining boundaries. The first member C1 is a member closer to the dielectric substrate 100 side than the joining boundary B1. The second member C2 is a member joined to the first member C1 across the joining boundary B1.

[0045] As Figure 1 shown, the entire distribution flow path 250 and supply flow path 240 in the present embodiment are formed in the first member C1. The distribution flow path 250 is an annular groove, which is pre-formed along the surface of the first member C1 that becomes the joining boundary B1 before joining the members. In this way, by pre-forming a groove on the surface of the first member C1 and joining the second member C2 so as to cover this surface, it is easy to form the distribution flow path 250 along the groove inside the base plate 200. And the groove that becomes the distribution flow path 250 can also be formed on the surface of the second member C2 that becomes the joining boundary B1, rather than on the surface of the first member C1.

[0046] As Figure 1As shown, the entire cooling medium flow path 270 in this embodiment is formed on the second member C2. The cooling medium flow path 270 is a groove pre-formed along the surface that becomes the joint boundary B2 on the second member C2 before joining the respective members. In this way, by pre-forming a groove on the surface of the second member C2 and joining the third member C3 so as to cover this surface, the cooling medium flow path 270 along the groove can be easily formed inside the base plate 200. Further, the groove that becomes the cooling medium flow path 270 can also be formed on the surface that becomes the joint boundary B1 on the second member C2.

[0047] However, assuming that the joint boundary B1 closest to the dielectric substrate 100 side is located in the first portion 201, the first member C1 becomes thinner compared to this embodiment. As a result, it is necessary to dispose the respective porous members 260 over the spans of both the first portion 201 and the second portion 202. For example, the porous members 260 are respectively inserted into the recesses of the second member C2, and the respective porous members 260 protrude from the surface of the second member C2. In this state, the first member C1 is joined so as to cover the surface of the second member C2. At this time, it is necessary to join the respective porous members 260 protruding from the surface of the second member C2 while aligning them so as to be received in the recesses of the first portion 201. However, the porous members 260 are very small and brittle members, and the number of them is also large. Thus, it is very difficult to perform operations such as the above-mentioned alignment without damaging the porous members 260.

[0048] Therefore, the base plate 200 of this embodiment has a structure in which the joint boundary B1 closest to the dielectric substrate 100 side is located in the second portion 202, rather than a structure in which it is located in the first portion 201. That is, a structure is adopted in which a part of the first portion 201 and the second portion 202 are integrated into one member (the first member C1) without a joint boundary. In such a structure, the first member C1 closest to the dielectric substrate 100 side becomes thicker compared to when the joint boundary B1 is located in the first portion 201. Therefore, as in this embodiment, the entire porous member 260 can be disposed inside the first portion 201. When joining the first member C1 and the second member C2, there is no possibility of damaging the porous member 260, so operations such as the above-mentioned alignment or joining can be easily performed. Thus, the complex internal structure of the base plate 200 can be easily realized.

[0049] As described above, the present embodiment has been described with reference to specific examples. However, the present invention is not limited to these specific examples. Regarding these specific examples, as long as they have the features of the present invention, the techniques in which those skilled in the art make appropriate design changes are also included in the scope of the present invention. The elements, their configurations, conditions, shapes, etc. possessed by each of the foregoing specific examples are not limited to the illustrated content, but can be appropriately changed. As long as there is no technical contradiction, the elements possessed by each of the foregoing specific examples can be appropriately changed in combination.

Claims

1. An electrostatic chuck, characterized in that it includes: a dielectric substrate having a placement surface for placing an object to be adsorbed; and a base plate joined to the dielectric substrate, the base plate having: a first portion, which is the portion on the dielectric substrate side; and a second portion, which is the portion adjacent to the first portion from the opposite side of the dielectric substrate and has an outer shape larger than that of the first portion when viewed from a direction perpendicular to the placement surface, the base plate is constituted by the joining of a plurality of members, and the joining boundary closest to the dielectric substrate side is located in the second portion.

2. The electrostatic chuck according to claim 1, characterized in that among the plurality of members constituting the base plate, when the member closer to the dielectric substrate side than the joining boundary is regarded as the first member, and the member joined to the first member across the joining boundary is regarded as the second member, a supply flow path for supplying gas to the placement surface side is formed on the first member in a manner extending in a direction perpendicular to the placement surface, and a porous member is disposed inside the supply flow path.

3. The electrostatic chuck according to claim 2, characterized in that a plurality of the supply flow paths are formed, and a distribution flow path for distributing gas to the plurality of supply flow paths is further formed in the base plate.

4. The electrostatic chuck according to claim 3, characterized in that, in In either the first member or the second member, the distribution flow path is a groove formed in a manner extending along the joining boundary.

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