Electrostatic chuck

Abstract

To provide an electrostatic chuck capable of preventing breakage of a dielectric substrate due to thermal stress.SOLUTION: An electrostatic chuck 10 comprises a dielectric substrate 100. A face 110 of the dielectric substrate 100 has a groove 113, and apertures 151 penetrating a bottom surface BS of the groove 113. In view from a direction perpendicular to the face 110, if a portion of the bottom surface BS including the apertures 151 is designated as a first portion BS1 and a portion of the bottom surface BS adjacent to the first portion BS1 from the outside is designated as a second portion BS2, then the surface roughness of the first portion BS1 is less than that of the second portion BS2.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] For example, in semiconductor manufacturing equipment such as CVD equipment and etching equipment, an electrostatic chuck is provided as a device for attracting and holding a substrate such as a silicon wafer to be processed. The electrostatic chuck includes a dielectric substrate on which an attracting electrode is provided. When a voltage is applied to the attracting electrode, an electrostatic force is generated, and the substrate placed on the dielectric substrate is attracted and held.

[0003] In order to adjust the temperature of the substrate during processing, an inert gas such as helium is often supplied to the space between the dielectric substrate and the substrate. For example, as described in Patent Document 1 below, an opening serving as a gas supply port is formed on the surface of the dielectric substrate on which the substrate is placed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-218592 A Summary of the Invention [Problem to be solved by the invention]

[0005] In order to secure a space between the substrate and the dielectric substrate, a recess is formed on the surface of the dielectric substrate on which the substrate is placed, and an opening serving as a gas supply port is formed so as to penetrate the bottom surface of the recess.

[0006] The recess is formed by subjecting the dielectric substrate to processing such as sandblasting, etc. As a result, the surface roughness of the bottom surface of the recess is relatively large. Since the opening is formed so as to penetrate through the rough bottom surface, the unevenness along the ridge line of the opening edge is large.

[0007] During substrate processing, thermal stress is applied to each part of the dielectric substrate, including the opening. Therefore, if the edge of the opening is significantly uneven, a large thermal stress is locally applied to that part, which may cause the dielectric substrate to break starting from the edge of the opening.

[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 prevent damage to a dielectric substrate due to thermal stress. [Means for solving the problem]

[0009] In order to solve the above problems, the electrostatic chuck according to the present invention is an electrostatic chuck including a dielectric substrate, in which a mounting surface on which an object to be attracted is mounted is formed with a recess and an opening penetrating a bottom surface of the recess. When viewed from a direction perpendicular to the mounting surface, a portion of the bottom surface including the opening is defined as a first portion, and a portion of the bottom surface adjacent to the first portion from the outside is defined as a second portion, the surface roughness of the first portion is smaller than the surface roughness of the second portion.

[0010] In an electrostatic chuck having such a configuration, the surface roughness of the bottom surface of the recess is not uniform throughout, and a first portion having a small surface roughness and a second portion having a large surface roughness are adjacent to each other. Since the opening is formed to penetrate the first portion, which has the small surface roughness, the unevenness of the edge of the opening is small, and the stress applied locally to the edge of the opening is also small. As a result, damage to the dielectric substrate originating from the edge of the opening can be prevented.

[0011] In the electrostatic chuck according to the present invention, it is also preferable that the first portion includes a plurality of openings. Even when a plurality of small-diameter openings are formed to ensure a sufficient gas flow rate, it is not necessary to provide a first portion for each opening. This makes it possible to easily form the first portion, etc. Effect of the Invention

[0012] According to the present invention, it is possible to provide an electrostatic chuck capable of preventing damage to a dielectric substrate due to thermal stress. [Brief description of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view illustrating a schematic configuration of an electrostatic chuck according to an embodiment of the present invention. [Diagram 2] 2 is a diagram showing a configuration of a dielectric substrate provided in the electrostatic chuck of FIG. 1. [Diagram 3] 2 is an enlarged, detailed cross-sectional view of a portion of the structure shown in FIG. 1. [Figure 4] 2 is a diagram showing a configuration of a dielectric substrate provided in the electrostatic chuck of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components in each drawing are denoted by the same reference numerals as much as possible, and duplicated description will be omitted.

[0015] The electrostatic chuck 10 according to this embodiment is configured to electrostatically attract and hold a substrate W to be processed inside a semiconductor manufacturing apparatus (not shown), such as a CVD film forming apparatus. The substrate W is, for example, a silicon wafer. The electrostatic chuck 10 may be used in an apparatus other than a semiconductor manufacturing apparatus.

[0016] 1 shows, in a schematic cross-sectional view, the configuration of an electrostatic chuck 10 in a state in which the electrostatic chuck 10 attracts and holds a substrate W. The electrostatic chuck 10 includes a dielectric substrate 100, a base plate 200, and a bonding layer 300.

[0017] The dielectric substrate 100 is a substantially disk-shaped member made of a sintered ceramic body. The dielectric substrate 100 contains, for example, high-purity aluminum oxide (Al2O3), but may contain other materials. The purity, type, and additives of the ceramics in the dielectric substrate 100 can be appropriately set in consideration of the plasma resistance and other properties required of the dielectric substrate 100 in semiconductor manufacturing equipment.

[0018] 1 of the dielectric substrate 100 is a "mounting surface" on which a substrate W, which is an object to be attracted, is placed. Also, a lower surface 120 of the dielectric substrate 100 in FIG. 1 is a "bonding surface" that is bonded to a base plate 200 via a bonding layer 300 described below. The viewpoint when the electrostatic chuck 10 is viewed from the side of the surface 110 along a direction perpendicular to the surface 110 is hereinafter also referred to as a "top view".

[0019] An adsorption electrode 130 is embedded inside the dielectric substrate 100. The adsorption electrode 130 is a thin, flat conductive layer made of a metal material such as tungsten. In addition to tungsten, the adsorption electrode 130 may be made of molybdenum, platinum, palladium, or the like. When a voltage is applied to the adsorption electrode 130 from the outside via the power supply path 13, an electrostatic force is generated between the surface 110 and the substrate W, thereby adsorbing and holding the substrate W. Two adsorption electrodes 130 may be provided as so-called "bipolar" electrodes, or only one may be provided as so-called "monopolar" electrode.

[0020] 1, the entire power supply line 13 is depicted in a simplified manner. A portion of the power supply line 13 inside the dielectric substrate 100 is configured as, for example, a long and narrow via (hole) filled with a conductor, and an electrode terminal (not shown) is provided at the lower end thereof. A portion of the power supply line 13 penetrating the base plate 200 is a conductive metal member (for example, a bus bar) having one end connected to the electrode terminal. A through hole (not shown) for inserting the power supply line 13 is formed in the base plate 200. For example, a cylindrical insulating member may be provided between the inner surface of the through hole and the power supply line 13.

[0021] A space SP is formed between the dielectric substrate 100 and the substrate W. In addition, the dielectric substrate 100 is formed with gas holes 140 extending from the surface 120 toward the surface 110, and the gas holes 140 are connected to the space SP via through holes 150 (see FIG. 3) described later. When a process such as film formation is performed in the semiconductor manufacturing device, helium gas for temperature adjustment is supplied to the space SP from the outside through the gas holes 140. By interposing helium gas between the dielectric substrate 100 and the substrate W, the thermal resistance between them is adjusted, and the temperature of the substrate W is thereby maintained at an appropriate temperature. The gas for temperature adjustment supplied to the space SP may be a type of gas other than helium. In addition, the configuration of the gas holes 140 is depicted in a simplified manner in FIG. 1. The specific configuration of the gas holes 140 will be described later.

[0022] Fig. 2 is a top view of the dielectric substrate 100. As shown in Fig. 2, a seal ring 111 and dots 112 are provided on a surface 110 that is a mounting surface, and the above-mentioned space SP is formed around these.

[0023] The seal rings 111 are walls that divide the space SP, and a plurality of seal rings 111 are provided so as to be arranged concentrically when viewed from above. The upper end of each seal ring 111 forms part of the surface 110 and abuts against the substrate W. In this embodiment, a total of four seal rings 111 are provided, thereby dividing the space SP into four. With this configuration, it is possible to individually adjust the pressure of the helium gas in each space SP and make the surface temperature distribution of the substrate W during processing closer to uniform.

[0024] 1 and the like, the portion marked with the reference symbol "116" is the bottom surface of the space SP. Hereinafter, this portion will also be referred to as the "bottom surface 116." The seal ring 111, together with the dots 112 described below, is formed as a result of digging down a part of the surface 110 to the position of the bottom surface 116. The space SP corresponds to a "recess" formed in the surface 110 of the dielectric substrate 100.

[0025] The dots 112 are circular protrusions protruding from the bottom surface 116. A plurality of dots 112 are provided and are distributed approximately evenly on the attraction surface of the dielectric substrate 100. The upper end of each dot 112 forms part of the surface 110 and abuts against the substrate W. By providing a plurality of such dots 112, bending of the substrate W is suppressed.

[0026] A groove 113 is formed in the bottom surface 116 of each space SP. The groove 113 is formed so as to recede from the bottom surface 116 further toward the surface 120. The groove 113 is formed for the purpose of quickly diffusing the helium gas supplied from the gas holes 140 into the space SP and making the pressure distribution in the space SP approximately uniform within a short period of time. The bottom surface BS (see FIG. 1) of the groove 113 corresponds to the "bottom surface" of the recess (i.e., the space SP) formed in the surface 110, similar to the bottom surface 116. The bottom surface BS is formed with an opening 151 which serves as an exit for the helium gas that has passed through the gas holes 140. The configuration of the opening 151 and its vicinity will be described later.

[0027] Returning to FIG. 1, the explanation will be continued. The base plate 200 is a substantially disk-shaped member that is bonded to the surface 120 of the dielectric substrate 100 in order to support the dielectric substrate 100. The base plate 200 is formed of a metal such as aluminum. Of the base plate 200, a surface 210 on the upper side in FIG. 1 is a "bonded surface" that is bonded to the dielectric substrate 100 via a bonding layer 300. The surface of the base plate 200 including the surface 210 may be covered with an insulating film such as an alumina sprayed film.

[0028] The bonding layer 300 is a layer provided between the dielectric substrate 100 and the base plate 200, and bonds them together. The bonding layer 300 is formed by curing an adhesive made of an insulating material. For example, a silicone-based adhesive can be used as such an adhesive.

[0029] A coolant flow path 250 for flowing a coolant is formed inside the base plate 200. When a process such as film formation is performed in the semiconductor manufacturing apparatus, a coolant is supplied to the coolant flow path 250 from the outside, thereby cooling the base plate 200. Heat generated in the substrate W during the process is transferred to the coolant via the helium gas in the space SP, the dielectric substrate 100, and the base plate 200, and is discharged to the outside together with the coolant.

[0030] The base plate 200 has gas holes 240 extending vertically from the surface 210 toward the surface 220 on the lower side in FIG. 1. The gas holes 240 are provided at a position overlapping the gas holes 140 in a top view. The gas holes 240 are connected to the gas holes 140 via through holes formed in the bonding layer 300. The gas holes 240, together with the gas holes 140, are part of a path for supplying helium gas toward the space SP. The gas holes 240 may be formed so as to extend linearly as a whole as in this embodiment, but may be formed so as to bend on the way toward the surface 220. In addition, the gas holes 240 on the surface 210 side may be aggregated into a small number of flow paths inside the base plate 200, and the flow paths may be extended to the surface 220 side.

[0031] The specific configuration of the upper end of the gas hole 140 and its vicinity will be described. FIG. 3 shows the configuration of the relevant portion as a schematic cross-sectional view. As shown in the figure, the gas hole 140 is formed so as to extend from the surface 120 toward the groove 113 at a position directly below the groove 113, but does not reach the bottom surface BS of the groove 113. The gas hole 140 and the space SP are communicated with each other by a through hole 150. The through hole 150 is a circular through hole formed so as to extend linearly from the upper end of the gas hole 140 to the bottom surface BS of the groove 113. In this embodiment, a plurality of through holes 150 are formed for one gas hole 140. The upper end of the through hole 150 is an opening 151 that penetrates the bottom surface BS of the groove 113. The helium gas that has passed through the gas hole 140 is supplied to the space SP from each opening 151.

[0032] A porous plug for preventing discharge may be disposed inside the gas hole 140. Similarly, a porous plug for preventing discharge may be disposed in the portion of the gas hole 240 that is adjacent to the bonding layer 300.

[0033] 4 shows the configuration of a portion of the groove 113 where the openings 151 are formed, as viewed from above. A circular portion of the bottom surface BS surrounded by a dotted line DL is hereinafter also referred to as a "first portion BS1." A portion of the bottom surface BS outside the dotted line DL, i.e., a portion adjacent to the first portion BS1 from the outside, is hereinafter also referred to as a "second portion BS2." The first portion BS1 includes all of the multiple openings 151 connected to one gas hole 140. No openings 151 are provided in the second portion BS2.

[0034] In the dielectric substrate 100 of this embodiment, the surface roughness of the first portion BS1 is smaller than the surface roughness of the second portion BS2. The "surface roughness" referred to here is, for example, the arithmetic mean roughness (Ra), but may also be the maximum height (Rmax), the ten-point mean height (Rz), the root mean square height (Rms), or other surface roughnesses.

[0035] The reason for adopting such a configuration will be explained. In general, recesses such as groove 113 are formed by performing processing such as sandblasting on surface 110 of dielectric substrate 100. For this reason, the surface roughness of bottom surface BS is often relatively large. Since opening 151 is formed so as to penetrate such rough bottom surface BS, unevenness along the ridge line of the edge of opening 151 is likely to be large.

[0036] During processing of the substrate W, thermal stress is applied to each portion of the dielectric substrate 100. For this reason, if the edge of the opening 151 is significantly uneven, a large thermal stress is applied locally to that portion, and there is a possibility that the dielectric substrate 100 will be damaged starting from the edge of the opening 151.

[0037] Therefore, in the electrostatic chuck 10 according to this embodiment, as described above, the surface roughness of the first portion BS1 of the bottom surface BS where the openings 151 are formed is made smaller than the surface roughness of the surrounding second portion BS2. Since each of the openings 151 is formed to penetrate the first portion BS1 having a small surface roughness, the unevenness of the edge of the opening 151 is reduced, and the stress locally applied to the edge of the opening is reduced. As a result, damage to the dielectric substrate 100 originating from the edge of the opening 151 can be prevented.

[0038] A method for reducing the surface roughness of the first portion BS1 may be, for example, to locally polish the portion inside the dotted line DL in FIG. 4 after the formation of the groove 113 by sandblasting is completed.

[0039] Alternatively, after the entire groove 113 is formed to a certain depth by sandblasting with a fine abrasive, the inside portion of the dotted line DL in FIG. 4 may be covered with a mask, and then the entire groove 113 may be further dug down by sandblasting with a coarse abrasive. Since the first portion BS1 is only sandblasted with a fine abrasive, its surface roughness remains small. On the other hand, since the second portion BS2 is sandblasted with a coarse abrasive, its surface roughness increases. In this case, the second portion BS2 will be formed slightly deeper than the first portion BS1.

[0040] In this embodiment, the through holes 150 are small in diameter so that discharge does not occur through the through holes 150 between the substrate W and the base plate 200. In addition, in order to ensure the flow rate of helium gas while making the through holes 150 small in diameter, a plurality of through holes 150 are formed for one gas hole 140. In such a configuration, it is also conceivable to form the first portions BS1 including the respective openings 151 in the same number as the openings 151. However, it is difficult to form the first portions BS1 individually corresponding to the respective openings 151 that are close to each other. For this reason, in this embodiment, the formation of the first portions BS1 is made easy by including a plurality of openings 151 in one first portion BS1.

[0041] The above-mentioned configuration can also be applied to a dielectric substrate 100 that does not have grooves 113. In such a configuration, the surface roughness of the portion of bottom surface 116 where opening 151 is formed may be made small, and the surface roughness of the outer portion thereof may be made large. In this case, the former portion corresponds to first portion BS1, and the latter portion corresponds to second portion BS2.

[0042] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Any design modifications made by a person skilled in the art to these specific examples are also included within the scope of the present disclosure as long as they have the features of the present disclosure. The elements of each of the above-mentioned specific examples and their arrangements, conditions, shapes, etc. are not limited to those exemplified and can be changed as appropriate. The combination of each of the elements of each of the above-mentioned specific examples can be changed as appropriate as long as no technical contradiction occurs. [Explanation of symbols]

[0043] W: Substrate 10: Electrostatic chuck 100: Dielectric substrate 110: Face 113: Groove 151:Aperture SP: Space BS: Bottom BS1: Part 1 BS2: 2nd part

Claims

1. An electrostatic chuck comprising a dielectric substrate, Of the dielectric substrate, the mounting surface on which the object to be adsorbed is placed is: recessed and An opening is formed that penetrates the bottom surface of the recess, When viewed from a direction perpendicular to the mounting surface, Of the bottom surface, the portion that includes the opening is designated as the first portion. When the portion of the bottom surface adjacent to the first portion from the outside is designated as the second portion, The surface roughness of the first portion is smaller than that of the second portion. The electrostatic chuck is characterized in that the dielectric substrate has gas holes formed therein that connect to the openings, and a porous plug is arranged inside the gas holes.

2. The electrostatic chuck according to claim 1, characterized in that the first portion encompasses a plurality of the openings.

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