Electrostatic chuck
By employing a high thermal conductivity outer peripheral bonding layer and a double-layer bonding layer structure with optimized pore positions in the electrostatic chuck, the problem of uneven temperature distribution within the substrate surface is solved, achieving uniformity and stability of substrate temperature.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TOTO LTD
- Filing Date
- 2025-11-18
- Publication Date
- 2026-06-19
Smart Images
Figure CN122249017A_ABST
Abstract
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 mounting surface for placing an object to be processed and having formed a plurality of pores; a base plate supporting 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 its outer periphery. 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, if the pore formed closest to the outer periphery among the plurality of pores formed at a position closer to the inner periphery than the outer periphery of the mounting surface is considered as the outermost pore, the outer periphery of the first bonding layer is located closer to the outer periphery than the center of the outermost pore.
[0008] In substrate processing, the temperature rises more easily on the outer peripheral side of the substrate compared to the inner peripheral side. However, depending on the structure of the electrostatic chuck, the temperature of the substrate may locally decrease in the area directly above the outermost vent.
[0009] In the electrostatic chuck with the above structure, the portion near the outermost peripheral pores of the dielectric substrate is bonded to the base plate by a first bonding layer with low thermal conductivity. Since this portion is difficult to cool by the base plate, localized temperature drops directly above the outermost peripheral pores can be suppressed, and deviations in the in-plane temperature distribution of the substrate can be suppressed.
[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 showing the structure of the electrostatic chuck according to the first embodiment. Figure 2 It means Figure 1 A diagram showing the structure of the dielectric substrate of the electrostatic chuck. Figure 3 It means Figure 1 A diagram showing the structure of the bonding layer of an electrostatic chuck. Figure 4 This is a cross-sectional view showing the structure of the electrostatic chuck according to the second embodiment. Symbol Explanation 10-Electrostatic chuck; 100-Dielectric substrate; 110-Face; 140-Vacuum; 140A-Outermost peripheral vent; 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 first embodiment will be described. The electrostatic chuck 10 of this embodiment, for example, inside a semiconductor manufacturing apparatus (not shown) such as an etching apparatus, uses electrostatic force to attract and hold a substrate W that is to be processed. The substrate W corresponds 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] An adsorption electrode 130 is embedded inside 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.
[0018] 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.
[0019] Figure 2 This is a top-view drawing of the dielectric substrate 100. As shown in the figure, sealing rings 111, 112 and point 113 are provided on the mounting surface, i.e., surface 110, and the aforementioned space SP is formed around these.
[0020] The sealing ring 111 is an annular protrusion provided as a wall dividing the space SP at the outermost peripheral position. The top end (upper end) of the sealing ring 111 becomes part of the surface 110 and abuts against the substrate W. The sealing ring 111 is positioned at the outermost peripheral end of the mounting surface, which corresponds to the "outer sealing ring" in this embodiment.
[0021] The sealing ring 112 is a circular protrusion located closer to the inner circumference than the sealing ring 111. The top end (upper end) of the sealing ring 112 also becomes part of the surface 110 and abuts against the substrate W. The sealing ring 112 divides the space SP into two spaces. By adopting this 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. The sealing ring 112 is equivalent to the "inner sealing ring" in this embodiment. In addition to the sealing rings 111 and 112, other sealing rings may be provided on the dielectric substrate 100.
[0022] Figure 1 and Figure 2 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 rings 111 and 112, together with point 113 described below, are formed as a result of excavating a portion of surface 110 to the position of bottom surface 116.
[0023] Point 113 is a circular protrusion projecting from the bottom surface 116. (Example) Figure 2 As shown, a plurality of points 113 are provided and are distributed approximately evenly on the mounting surface of the dielectric substrate 100. The upper end surface of each point 113 becomes part of a surface 110 and abuts against the substrate W. By providing a plurality of such points 113, bending of the substrate W is suppressed.
[0024] A vent 140 is formed on the dielectric substrate 100. The vent 140 is a through hole formed in a direction perpendicular to the mounting surface, i.e., surface 110. The end of the vent 140 on the surface 110 side is connected to the space SP. The vent 140 is part of a flow path for supplying helium gas to the space SP.
[0025] Multiple vents 140 are provided and distributed to allow helium gas to be supplied to various parts of the space SP. The actual configuration of the vents 140 in the structure is as follows: Figure 2 As shown, but in Figure 1 Only four of the vents 140 are shown in the schematic diagram. Multiple vents 140 are provided at positions closer to the outer periphery than the sealing ring 112 and at positions closer to the inner periphery than the sealing ring 112.
[0026] Among the multiple pores 140, the pore 140 formed closest to the outer periphery when viewed from above is hereinafter referred to as the "outermost peripheral pore 140A". It can also be said that the outermost peripheral pore 140A is the pore 140 located at the end closest to the outer periphery of the mounting surface, i.e., surface 110, from the inner periphery. Figure 2As shown, in this embodiment, there are a plurality of outermost vents 140A, which are arranged in a circular pattern along the sealing ring 111. When viewed from above, these plurality of outermost vents 140A are positioned between the sealing ring 111 and the sealing ring 112.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] Figure 3 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 3 The diagram of the through hole is omitted.
[0034] 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.
[0035] 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.
[0036] However, when the substrate W is processed 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 rise in the outer peripheral portion. Therefore, in this embodiment, as described above, the thermal conductivity of the second bonding layer 320 disposed on the outer peripheral side is made higher than the thermal conductivity of the first bonding layer 310 disposed on the inner peripheral side. Since the outer peripheral portion of the dielectric substrate 100 (that is, the portion supporting the outer peripheral side of the substrate W) is more easily cooled by the base plate 200, the local temperature rise on the outer peripheral side of the substrate W can be suppressed.
[0037] In this embodiment, in order to further suppress the deviation of the in-plane temperature distribution of the substrate W, the relative positional relationship between the first bonding layer 310 and the outermost peripheral pore 140A was also studied.
[0038] Figure 1 The dashed line DL1 indicates the center position of the outermost pore 140A. Furthermore, the "center position of the outermost pore 140A" refers to the central axis position of the outermost pore 140A when viewed from above. The dashed line DL2 indicates the end position of the outer periphery of the first bonding layer 310. The dashed line DL3 indicates the end position of the inner periphery of the second bonding layer 320.
[0039] In this embodiment, the shape of the first bonding layer 310 is set such that, when viewed from above, the end of the outer peripheral side of the first bonding layer 310 (dotted line DL2) is located closer to the outer peripheral side than the center (dotted line DL1) of the outermost peripheral pore 140A.
[0040] The reason is as follows. As previously described, during the processing of substrate W, the temperature rises more easily on the outer peripheral side of substrate W compared to the inner peripheral side. However, depending on the different structures of the electrostatic chuck 10, the temperature of substrate W may locally decrease in the area directly above the outermost peripheral vent 140A. For example, when the outermost peripheral vent 140A is positioned near the sealing ring 112, the temperature directly above the outermost peripheral vent 140A may locally decrease.
[0041] Therefore, in the electrostatic chuck 10 according to this embodiment, as described above, the end of the outer peripheral side of the first bonding layer 310 (dotted line DL2) is positioned closer to the outer peripheral side than the center (dotted line DL1) of the outermost peripheral vent 140A. In this structure, the portion near the outermost peripheral vent 140A of the dielectric substrate 100 is bonded to the base plate 200 by means of the first bonding layer 310, which has a lower thermal conductivity. Since this portion is difficult to cool by the base plate 200, local temperature drop directly above the outermost peripheral vent 140A can be suppressed, and deviations in the in-plane temperature distribution of the substrate W can be suppressed.
[0042] Furthermore, the positional relationship between the first bonding layer 310 and the outermost peripheral vent 140A as described above is such that, in a cross-section that includes at least the central axis of the dielectric substrate 100 and the central axis of the outermost peripheral vent 140A (that is, as... Figure 1 It is valid on such a cross section.
[0043] Hereinafter, the distance from the center of the outermost peripheral vent 140A (dotted line DL1) to the end of the outer periphery of the first bonding layer 310 (dotted line DL2) when viewed from above will also be referred to as "distance D1". When the distance D1 is too small, the temperature drop in the portion directly above the outermost peripheral vent 140A cannot be sufficiently suppressed. On the other hand, when the distance D1 is too large, not only is the cooling of the portion directly above the outermost peripheral vent 140A suppressed, but the cooling of other portions nearby is also suppressed, and the temperature of some portions rises excessively. According to experiments conducted by the inventors, it has been confirmed that if the distance D1 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.
[0044] In this embodiment, the outer peripheral end (dotted line DL2) of the first bonding layer 310 and the inner peripheral end (dotted line DL3) 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.
[0045] Hereinafter, the distance from the outer peripheral end (dotted line DL2) of the first bonding layer 310 to the inner peripheral end (dotted line DL3) of the second bonding layer 320 will also be referred to as "distance D2". It is preferable to control the distance D2 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 D2 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.
[0046] Reference Figure 4 The second embodiment will be described below. Hereinafter, the parts that differ from the first embodiment will be described in detail, and the parts that are the same as those in the first embodiment will be omitted as appropriate.
[0047] In this embodiment, a flange portion 101 is provided on the dielectric substrate 100. The flange portion 101 is a portion that protrudes further outward from the mounting surface, i.e., surface 110. When viewed from above, the flange portion 101 surrounds the entire surface 110 from the outside. The surface of the flange portion 101 on the substrate W side ( Figure 4The upper side of the surface), located closer to the base plate 200 side than surface 110 ( Figure 4 The position is located on the lower side of the middle. When processing the substrate W, an annular member (not shown) such as a "focusing ring" is placed on the flange portion 101.
[0048] A perforation can also be formed on the flange portion 101 so that helium can also be supplied directly below the annular member. Such a perforation is located closer to the outer periphery than the outermost peripheral perforation 140A in the first embodiment. However, the "outermost peripheral perforation" is defined as the perforation 140 located closest to the outer periphery among a plurality of perforations 140 formed at a position closer to the inner periphery than the end of the mounting surface (surface 110) on which the workpiece (substrate W) is placed. Therefore, even when a perforation is formed on the flange portion 101, this perforation is not equivalent to the "outermost peripheral perforation".
[0049] like Figure 4 As shown, in this embodiment, 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 diameter portion 141". A vent plug 150 is disposed inside the enlarged diameter portion 141. The vent plug 150 is, for example, a porous material formed of alumina, and is generally breathable. 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 can be suppressed. Furthermore, the breathable 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 breathable, while the outer peripheral portion may not be breathable.
[0050] like Figure 4 As 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.
[0051] Even in the structure described above, the same effects as those explained in the first embodiment are achieved.
[0052] Furthermore, even in a structure where a flange portion 101 is provided on the dielectric substrate 100 as in this embodiment, it is preferable that the second bonding layer 320 is provided at a position where a portion of it overlaps with the mounting surface (surface 110) when viewed from above.
[0053] 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 includes: a dielectric substrate having a mounting surface for placing the object to be processed and having multiple pores formed thereon; Base plate, supporting 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, When the pore formed at the position closest to the outer periphery among a plurality of pores formed at a position closer to the inner periphery than the outer periphery of the mounting surface is taken as the outermost pore, The end of the outer peripheral side of the first bonding layer is located closer to the outer peripheral side than the center of the outermost peripheral pore.
2. The electrostatic chuck according to claim 1, characterized in that, It also features multiple sealing rings, which are annular protrusions formed on the dielectric substrate, with their tips becoming part of the mounting surface. The plurality of sealing rings includes: an outer sealing ring disposed at the outermost peripheral end of the mounting surface; The inner sealing ring is positioned closer to the inner circumference than the outer sealing ring. When viewed from a direction perpendicular to the mounting surface, The outermost pore is formed between the outer sealing ring and the inner sealing ring.
3. The electrostatic chuck according to claim 1, characterized in that, The first bonding layer is separated from the second bonding layer.
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 center of the outermost peripheral pore to the end of the outer peripheral side of the first bonding layer is more than 1 mm and less than 30 mm.
5. 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.