Electrostatic chuck

Abstract

An electrostatic chuck is provided that can suppress deviations in the in-plane temperature distribution of a substrate. The electrostatic chuck comprises: a dielectric substrate having a first portion including a mounting surface (i.e., a surface) and a second portion that protrudes further outward from the outer peripheral end of the first portion and is thinner than the first portion; a base plate bonded to the dielectric substrate; and a bonding layer for bonding the dielectric substrate and the base plate. The bonding layer includes: a first bonding layer; and a second bonding layer that annularly surrounds the first bonding layer from the outer peripheral side. The thermal conductivity of the second bonding layer is higher than that of the first bonding layer. In this electrostatic chuck, when viewed from above, the inner peripheral end of the second bonding layer is located at a position overlapping the first portion.

Description

Technical Field

[0001] This invention relates to an electrostatic chuck. Background Technology

[0002] For example, in semiconductor manufacturing apparatuses such as etching equipment, electrostatic chucks are provided as devices for adsorbing and holding substrates such as silicon wafers that are to be processed. An electrostatic chuck comprises: a dielectric substrate on which adsorption electrodes are provided; and a base plate supporting the dielectric substrate, having a structure in which these are joined together. When a voltage is applied to the adsorption electrodes, an electrostatic force is generated, adsorbing and holding the substrate placed on the dielectric substrate.

[0003] As described in Patent Document 1 below, for example, a bonding layer such as a cured silicone adhesive is used to bond the dielectric substrate and the base plate.

[0004] Patent documents Patent Document 1: Japanese Patent Application Publication No. 2020-23088 Summary of the Invention

[0005] During processing, it is necessary to suppress deviations in the in-plane temperature distribution of the substrate as much as possible. As a countermeasure to suppress deviations in the in-plane temperature distribution, the inventors have studied a technique in which the material of the bonding layer is different in different parts.

[0006] The present invention was made in view of the following problem, and its object is to provide an electrostatic chuck that can suppress deviations in the in-plane temperature distribution of a substrate.

[0007] To address the aforementioned problems, the electrostatic chuck of the present invention comprises: a dielectric substrate having a first portion including a mounting surface for placing an object to be processed and a second portion protruding further outward from the outer peripheral end of the first portion and being thinner than the first portion; a base plate bonded to the dielectric substrate; and a bonding layer for bonding the dielectric substrate and the base plate. The bonding layer includes: a first bonding layer; and a second bonding layer annularly surrounding the first bonding layer from the outer peripheral side. The thermal conductivity of the second bonding layer is higher than that of the first bonding layer. When the electrostatic chuck is viewed from a direction perpendicular to the mounting surface, the inner peripheral end of the second bonding layer is located at a position overlapping with the first portion.

[0008] During substrate processing, the temperature of the outer peripheral portion of the substrate rises more easily than that of the inner peripheral portion. Furthermore, although a ring-shaped member, such as a "focusing ring," is placed directly above the second part, the temperature of this ring-shaped member also tends to rise during processing.

[0009] In the electrostatic chuck with the above-described structure, the portion of the dielectric substrate supporting the aforementioned parts—that is, the portion supporting the components whose temperature is prone to rise during the bottom support process—is bonded to the base plate by a second bonding layer with higher thermal conductivity. By employing this structure, it is possible to suppress the temperature rise of the annular component and simultaneously suppress deviations in the in-plane temperature distribution of the substrate.

[0010] According to the present invention, an electrostatic chuck capable of suppressing deviations in the in-plane temperature distribution of a substrate can be provided. Attached Figure Description

[0011] Figure 1 This is a cross-sectional view that schematically represents the structure of the electrostatic chuck involved in this embodiment. Figure 2 It means Figure 1 A diagram showing the structure of the bonding layer of an electrostatic chuck. Symbol Explanation 10-Electrostatic chuck; 100-Dielectric substrate; 101-Part 1; 102-Part 2; 110-Face; 200-Base plate; 300-Bonding layer; 310-First bonding layer; 320-Second bonding layer; W-Substrate. Detailed Implementation

[0012] Hereinafter, this embodiment will be described with reference to the accompanying drawings. For ease of understanding, the same symbols will be used to label the same components as much as possible in each drawing, and repeated descriptions will be omitted.

[0013] The electrostatic chuck 10 described in this embodiment is used, for example, inside a semiconductor manufacturing apparatus (not shown) such as an etching apparatus, to attract and hold a substrate W, which is the object to be processed, by electrostatic force. The substrate W is equivalent to the "object to be processed," such as a silicon wafer. The electrostatic chuck 10 can also be used in apparatuses other than semiconductor manufacturing apparatuses.

[0014] Figure 1 The diagram shows the structure of an electrostatic chuck 10 in a state of adsorbing and holding a substrate W, as a schematic cross-sectional view. The electrostatic chuck 10 includes a dielectric substrate 100, a base plate 200, and a bonding layer 300.

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

[0016] In dielectric substrate 100, Figure 1 The upper side surface 110 of the dielectric substrate 100 becomes the "mounting surface" of the substrate W. Additionally, in the dielectric substrate 100, Figure 1 The lower side surface 120 becomes the "joined surface" that is joined to the base plate 200 by the joining layer 300 described later. Hereinafter, the perspective when viewing the electrostatic chuck 10 from the side of surface 110 along a direction perpendicular to surface 110 will also be described as "top view".

[0017] The dielectric substrate 100 has a first portion 101 and a second portion 102. The first portion 101 extends from the surface 110 towards... Figure 1 The first portion 101 is a generally cylindrical portion extending from the lower side to the surface 120. It can be said that this first portion 101 is the portion of the dielectric substrate 100 that includes the mounting surface, i.e., the surface 110. When viewed from above, the shape of the mounting surface can be made to match the shape of the first portion 101, but they can also be different.

[0018] Part 2 102 is an annular portion that protrudes further outward from the outer peripheral end of Part 1 101, and is also referred to as the "flange portion" of the dielectric substrate 100. Figure 1 In the diagram, the boundary between part 101 and part 202 is represented by a dashed line DL. Part 202 is thinner than part 101. The previously described surface 120 is... Figure 1 The face located at the bottommost side of part 101 is also the bottommost side of part 202. The topmost side of part 202 is face 160. Figure 1 It is located at a lower position compared to surface 110.

[0019] When substrate W is processed in a semiconductor manufacturing apparatus, an annular member RE, such as a "focusing ring," is arranged around substrate W. Surface 160 of part 2 102 becomes the portion that supports such an annular member RE from below. Surface 160 is parallel to surface 110.

[0020] An adsorption electrode 130 is embedded inside the first portion 101 of the dielectric substrate 100. The adsorption electrode 130 is a thin, flat layer formed of a metal material such as tungsten, and is arranged parallel to the surface 110. In addition to tungsten, molybdenum, platinum, palladium, etc., can also be used as the material for the adsorption electrode 130. When a voltage is applied to the adsorption electrode 130 from the outside via a power supply circuit (not shown), an electrostatic force is generated between the surface 110 and the substrate W, thereby adsorbing and holding the substrate W. The adsorption electrode 130 can be provided as a so-called "monopolar" electrode as in this embodiment, or two can be provided as so-called "bipolar" electrodes.

[0021] Inside part 2 102, an internal electrode different from the adsorption electrode 130 may also be provided. Examples of such internal electrodes include an adsorption electrode or an RF electrode used to generate electrostatic force with the annular member RE.

[0022] like Figure 1 As shown, a space SP is formed between the dielectric substrate 100 and the substrate W. During etching or other processes in a semiconductor manufacturing apparatus, an inert gas for temperature control is supplied to the space SP from the outside through the vent 140 (described later). By having the inert gas present 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. Furthermore, although helium is used in this embodiment as the inert gas for temperature control supplied to the space SP, a gas of a different type than helium can also be used.

[0023] A sealing ring 111 and a point 112 are provided on the mounting surface, i.e., surface 110, and the aforementioned space SP is formed around these.

[0024] The sealing ring 111 is an annular protrusion provided as a wall dividing the space SP at the outermost peripheral position. The upper end of the sealing ring 111 becomes part of the surface 110 and abuts against the substrate W. Furthermore, multiple sealing rings 111 can be provided in a manner that divides the space SP. By adopting such a structure, the pressure of 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. In this embodiment, the outer peripheral end of the sealing ring 111 when viewed from above coincides with the outer peripheral end of the first part 101.

[0025] Figure 1 In the diagram, the portion marked with the symbol "116" is the bottom surface of space SP. Hereinafter, this portion will also be referred to as "bottom surface 116". The sealing ring 111, together with point 112 described below, is formed as a result of excavating a portion of surface 110 up to the position of bottom surface 116.

[0026] Point 112 is a circular protrusion extending from the bottom surface 116. Multiple points 112 are provided and are distributed approximately evenly on the mounting surface of the dielectric substrate 100. The upper end surface of each point 112 becomes part of surface 110 and abuts against the substrate W. By providing multiple such points 112, bending of the substrate W is suppressed.

[0027] A via 140 is formed on the dielectric substrate 100. The via 140 is a through-hole formed in a direction perpendicular to the mounting surface, i.e., surface 110. The end of the via 140 on the surface 110 side is connected to the space SP. The via 140 is part of a flow path for supplying helium gas to the space SP. Although multiple vias 140 are formed on the dielectric substrate 100, in… Figure 1 Only two of them are shown in the illustration.

[0028] like Figure 1As shown, the portion of the vent 140 on the side of surface 120 is enlarged compared to the portion on the side of surface 110. Hereinafter, this enlarged portion will also be referred to as the "enlarged portion 141". A vent plug 150 is disposed inside the enlarged portion 141. The vent plug 150 is, for example, a porous material formed of alumina, and is permeable overall. By disposing such a vent plug 150 inside the vent 140, the flow of gas in the vent 140 is ensured, while insulation breakdown along the path through the vent 140 is also suppressed. Furthermore, the permeable portion of the vent plug 150 may be only a part of it, rather than the entire plug. For example, only the central portion of the vent plug 150 may be permeable, while the outer peripheral portion may not be permeable.

[0029] The base plate 200 is a generally disk-shaped component that supports the dielectric substrate 100. The base plate 200 is formed, for example, of a metallic material such as aluminum. The base plate 200... Figure 1 The upper side surface 210 becomes the "bonded surface" that is bonded to the dielectric substrate 100 by means of the bonding layer 300.

[0030] Inside the base plate 200, a cooling medium flow path 260 is formed for through which a cooling medium flows. During processes such as etching in the semiconductor manufacturing apparatus, a cooling medium is supplied from the outside to the cooling medium flow path 260, thereby cooling the base plate 200. During processing, heat generated on the substrate W is transferred to the cooling medium via helium gas in the space SP, the dielectric substrate 100, and the base plate 200, and is discharged to the outside along with the cooling medium. In the base plate 200, the cooling medium for the cooling medium flow path 260 is supplied and discharged through an opening (not shown) formed on the surface 220 opposite to surface 210.

[0031] A perforation 240 is formed on the base plate 200. The perforation 240 is a through hole formed in a manner that extends vertically from the surface 210 to the opposite surface 220. When viewed from above, the perforations 240 are formed at positions that overlap with the perforations 140 of the dielectric substrate 100, and are connected to the perforations 140 by through holes provided on the bonding layer 300. The perforations 240 and the perforations 140 of the dielectric substrate 100 together constitute part of a flow path for supplying helium gas to the space SP.

[0032] like Figure 1As shown, in this embodiment, the portion of the vent 240 on the side of surface 210 is enlarged compared to the portion on the side of surface 220. Hereinafter, this enlarged portion will also be referred to as the "enlarged diameter portion 241". A vent plug 250 is disposed inside the enlarged diameter portion 241. The vent plug 250 is, for example, a porous material formed of alumina, and is generally breathable. By disposing such a vent plug 250 inside the vent 240, the flow of gas in the vent 240 is ensured, while insulation breakdown along the path through the vent 240 can be suppressed. Furthermore, the breathable portion of the vent plug 250 may be only a part of it, rather than the entire vent plug. For example, only the central portion of the vent plug 250 may be breathable, while the outer peripheral portion may not be breathable.

[0033] Furthermore, the vents 240 can be formed as a single unit extending in a straight line, as in this embodiment, but they can also be formed to bend along the path from surface 210 to surface 220. Alternatively, a structure can be adopted in which multiple vents 240 on the surface 210 side are combined into a few flow paths inside the base plate 200, and these flow paths are extended to the surface 220 side.

[0034] An insulating film may also be formed on the surface of the base plate 200. The insulating film may be formed to cover only a portion of the surface of the base plate 200, rather than the entire surface. For example, the insulating film may be formed to cover only the side portions other than surfaces 210 and 220, i.e., the exposed portions inside the semiconductor manufacturing apparatus exposed to plasma, etc. Conversely, the insulating film may be formed to cover at least the entire area including surface 210. For example, an alumina film formed by thermal spraying may be used as the insulating film. By covering the surface of the base plate 200 with an insulating film, the insulation withstand voltage of the base plate 200 can be improved.

[0035] The bonding layer 300 is a layer disposed between the dielectric substrate 100 and the base plate 200, bonding the two together. The bonding layer 300 is a layer formed by curing an adhesive material made of an insulating material. In this embodiment, a silicone adhesive is used as the adhesive. However, the bonding layer 300 can also be a layer formed by curing other types of adhesives. In any case, it is preferable to use a material with the highest possible thermal conductivity as the material for the bonding layer 300, so as to minimize the thermal resistance between the dielectric substrate 100 and the base plate 200.

[0036] Figure 2 The structure of the bonding layer 300 as viewed from above is shown in a stylized diagram. Furthermore, through holes are formed in portions of the bonding layer 300 that overlap with the pores 140 or with pin holes (not shown), etc. Figure 2 The diagram of the through hole is omitted.

[0037] The bonding layer 300 in this embodiment includes a first bonding layer 310 and a second bonding layer 320. When viewed from above, the first bonding layer 310 is circular in shape. When viewed from above, the center of the first bonding layer 310 coincides with the center of the dielectric substrate 100. The second bonding layer 320 surrounds the first bonding layer 310 in a ring shape from its outer periphery. When viewed from above, the outer periphery ends of the first bonding layer 310, the inner periphery ends of the second bonding layer 320, and the outer periphery ends of the second bonding layer 320 are all circular, and these are arranged in a concentric circle.

[0038] The materials of the first bonding layer 310 and the second bonding layer 320 are different. Specifically, the materials of the two layers are selected such that the thermal conductivity of the second bonding layer 320 is higher than that of the first bonding layer 310. For example, such a difference in thermal conductivity is achieved by making the amount of filler added to the adhesive before the silicone adhesive that becomes the bonding layer 300 is cured different.

[0039] However, when processing the substrate W in a semiconductor manufacturing apparatus, it is preferable that the deviation in the in-plane temperature distribution of the substrate W be as small as possible. However, the temperature of the substrate W during processing tends to locally increase in the peripheral portion. Furthermore, the temperature of the annular member RE, which is arranged to surround the substrate W from the peripheral side, often rises, potentially causing the temperature of the peripheral portion of the substrate W to rise further. Therefore, in the electrostatic chuck according to this embodiment, by studying the arrangement of the first bonding layer 310 and the second bonding layer 320, the aforementioned localized temperature rise is suppressed.

[0040] Figure 1 The dashed line DL1 indicates the end position of the outer periphery of the first bonding layer 310. The dashed line DL2 indicates the end position of the inner periphery of the second bonding layer 320. The dashed line DL3 indicates the end position of the outer periphery of the first part 101. The "end position of the outer periphery of the first part 101" can also be understood as the "end position of the inner periphery of the second part 102".

[0041] In this embodiment, the shape of the second bonding layer 320 is configured such that, when viewed from above, the inner peripheral end (dotted line DL2) of the second bonding layer 320 is located closer to the inner peripheral side than the outer peripheral end (dotted line DL3) of the first portion 101. As a result, when viewed from above, the inner peripheral end of the second bonding layer 320 is located at a position that overlaps with the first portion 101.

[0042] The reasons are as follows. As previously described, during the processing of substrate W, the temperature of the outer peripheral portion of substrate W rises more easily than that of the inner peripheral portion, and the temperature of the annular member RE surrounding substrate W from the outer peripheral side also rises more easily.

[0043] Therefore, in the electrostatic chuck 10 according to this embodiment, as described above, the inner peripheral end (dotted line DL2) of the second bonding layer 320 is positioned at a location that overlaps with the first portion 101 when viewed from above. Furthermore, "the location that overlaps with the first portion 101" is a position closer to the inner peripheral side than the outer peripheral end of the first portion 101.

[0044] In this structure, the portion of the dielectric substrate 100 that overlaps with the second bonding layer 320 when viewed from above becomes the outer peripheral portion supporting the substrate W from below and the portion of the annular member RE. That is, the portion of the dielectric substrate 100 that supports the member whose temperature is prone to rise from below, as described above, is bonded to the base plate 200 by the second bonding layer 320, which has a higher thermal conductivity. By adopting this structure, the temperature rise of the annular member RE can be suppressed, as can the temperature rise of the outer peripheral portion of the substrate W, and the in-plane temperature distribution of the substrate W can be made more uniform.

[0045] Furthermore, the positional relationship between the second bonding layer 320 and the first portion 101, as described above, can be maintained in any cross-section that includes at least the central axis of the dielectric substrate 100 (i.e., such as...). Figure 1 This can be achieved on any cross section containing the central axis of the dielectric substrate 100. In other words, when viewed from above, although the entire end of the inner circumferential side of the second bonding layer 320 may be located in a position that overlaps with the first portion 101, a portion of that end may also be located in a position that does not overlap with the first portion 101.

[0046] Hereinafter, the distance from the inner peripheral end (dotted line DL2) of the second bonding layer 320 to the outer peripheral end (dotted line DL3) of the first part 101 when viewed from above will also be referred to as "distance D2". When the distance D2 is too small, the outer peripheral portion of the substrate W cannot be cooled efficiently. On the other hand, when the distance D2 is too large, not only the outer peripheral portion of the substrate W is cooled, but also its inner portion is over-cooled. According to experiments conducted by the inventors, it has been confirmed that if the distance D2 is controlled within the range of 1 mm or more and 30 mm or less, the deviation of the in-plane temperature distribution of the substrate W can be sufficiently suppressed.

[0047] In this embodiment, the outer peripheral end (dotted line DL1) of the first bonding layer 310 and the inner peripheral end (dotted line DL2) of the second bonding layer 320 are separated, and a space is formed between them. By adopting such a structure, when the dielectric substrate 100 and the base plate 200 are bonded, it is possible to prevent the different types of adhesives, namely the first bonding layer 310 and the second bonding layer 320, from mixing and changing their respective physical properties.

[0048] Hereinafter, the distance from the outer peripheral end (dotted line DL1) of the first bonding layer 310 to the inner peripheral end (dotted line DL2) of the second bonding layer 320 will also be referred to as "distance D1". It is preferable to control the distance D1 to 2 mm or less in order to avoid excessive thermal resistance between the dielectric substrate 100 and the base plate 200. If mixing of the first bonding layer 310 and the second bonding layer 320 during bonding will not be a problem, the distance D1 can also be made to 0 mm. In addition, a bonding layer 300 made of other materials may be disposed between the first bonding layer 310 and the second bonding layer 320.

[0049] The present embodiment has been described above with reference to specific examples. However, the present invention is not limited to these specific examples. Regarding these specific examples, any design modifications made by those skilled in the art that possess the features of the present invention are also included within the scope of the present invention. The elements, their configurations, conditions, shapes, etc., of the foregoing specific examples are not limited to the illustrated content, but can be appropriately modified. As long as there is no technical contradiction, the elements of the foregoing specific examples can be appropriately changed and combined.

Claims

1. An electrostatic chuck, characterized in that, It comprises: a dielectric substrate having a first portion including a mounting surface for placing an object to be processed and a second portion that protrudes further outward from the outer peripheral end of the first portion and is thinner than the first portion; The base plate is bonded to the dielectric substrate; A bonding layer is used to bond the dielectric substrate and the base plate. The bonding layer includes: a first bonding layer; and a second bonding layer, which surrounds the first bonding layer in a ring shape from the outer periphery. The thermal conductivity of the second bonding layer is higher than that of the first bonding layer. When viewed from a direction perpendicular to the mounting surface, The end of the inner circumferential side of the second bonding layer is located at a position that overlaps with the first part.

2. The electrostatic chuck according to claim 1, characterized in that, The first bonding layer is separated from the second bonding layer.

3. The electrostatic chuck according to claim 1, characterized in that, When viewed from a direction perpendicular to the mounting surface, The distance from the end of the inner peripheral side of the second bonding layer to the end of the outer peripheral side of the first part is more than 1 mm and less than 30 mm.

4. The electrostatic chuck according to claim 1, characterized in that, When viewed from a direction perpendicular to the mounting surface, The distance from the end of the outer periphery of the first bonding layer to the end of the inner periphery of the second bonding layer is less than 2 mm.

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