Electrostatic chuck

Abstract

To provide an electrostatic chuck that can suppress the occurrence of dielectric breakdown through a penetration hole.SOLUTION: An electrostatic chuck 10 includes a dielectric substrate 100 including a penetration hole 151, and an RF electrode 140 embedded inside the dielectric substrate 100. The RF electrode 140 includes a circular opening 141 that is coaxial with the penetration hole 151 and incorporating the penetration hole 151. The difference ΔR between a radius R2 of the opening 141 and a radius R0 of the penetration hole 151 is 1.6 mm or more.SELECTED DRAWING: Figure 2

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, 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] As described in Patent Document 1 below, the dielectric substrate may have an RF electrode built in, which is one of a pair of opposing electrodes for generating plasma in a semiconductor manufacturing device. In this case, the dielectric substrate has both an attraction electrode and an RF electrode built in.

[0004] Furthermore, a through hole that penetrates vertically through the mounting surface is often formed in the dielectric substrate. Such a through hole is formed, for example, for the purpose of supplying an inert gas such as helium between the dielectric substrate and the substrate. In order to prevent the RF electrode from being exposed on the inner surface of the through hole, a circular opening is formed in the RF electrode at a portion that overlaps with the through hole in a top view. The opening is formed so as to be concentric with the through hole and to include the through hole. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-119654 A Summary of the Invention [Problem to be solved by the invention]

[0006] During substrate processing, the chucking electrode is at a high potential, while the RF electrode is kept at a predetermined low potential (for example, the same ground potential as the base plate that supports the dielectric substrate). At this time, a strong electric field is generated in the through-hole from the chucking electrode toward the edge of the opening of the RF electrode. Since the direction of this electric field is roughly the same as the extension direction of the through-hole, there is a possibility that dielectric breakdown will occur along the path through the through-hole.

[0007] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide an electrostatic chuck that can suppress the occurrence of dielectric breakdown through a through hole. [Means for solving the problem]

[0008] In order to achieve the above object, an electrostatic chuck according to the present invention includes a dielectric substrate having a mounting surface on which an object to be attracted is mounted and in which a through hole is formed perpendicular to the mounting surface, and an RF electrode embedded inside the dielectric substrate. The RF electrode has a circular opening that is concentric with and encompasses the through hole, and the difference between the radius of the opening and the radius of a portion of the through hole closest to the mounting surface is 1.6 mm or more.

[0009] In an electrostatic chuck having such a configuration, the edge of the opening formed in the RF electrode is located at a position 1.6 mm or more away from the inner surface of the through hole. In the through hole, the component of the electric field from the high potential portion toward the edge of the opening along the direction in which the through hole extends is small. This makes it possible to reduce the possibility of dielectric breakdown occurring through the through hole compared to the conventional case. The "high potential portion" mentioned above is, for example, an attraction electrode embedded in a dielectric substrate.

[0010] In addition, in the electrostatic chuck according to the present invention, it is also preferable that the difference between the radius of the opening and the radius of the through hole at the portion closest to the mounting surface side is 5.4 mm or less. The larger the radius of the opening, the farther the edge of the opening is from the inner surface of the through hole, so that the possibility of dielectric breakdown through the through hole is reduced. However, if the radius of the opening is too large, the electric field around the portion (e.g., the chucking electrode) that is at a higher potential on the mounting surface side than the RF electrode may affect other portions through the opening, causing dielectric breakdown in those portions. According to the inventors' confirmation by experiments, etc., it has been found that the occurrence of such dielectric breakdown can be prevented by setting the difference between the radius of the opening and the radius of the through hole at the portion closest to the mounting surface side to 5.4 mm or less.

[0011] In the electrostatic chuck according to the present invention, it is also preferable that the through hole is a gas supply hole. When the through hole is a gas supply hole, the pressure inside the through hole is a pressure range in which dielectric breakdown is relatively likely to occur. In such a case, the effect of applying the present invention as described above is particularly large. Effect of the Invention

[0012] According to the present invention, it is possible to provide an electrostatic chuck capable of suppressing the occurrence of dielectric breakdown through a through hole. [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 an enlarged, detailed cross-sectional view of a portion of the structure shown in FIG. 1. [Diagram 3] 1A to 1C are diagrams for explaining the relationship between the shape of an RF electrode or the like and the likelihood of dielectric breakdown. [Figure 4] 1A to 1C are diagrams for explaining the relationship between the shape of an RF electrode or the like and the likelihood of dielectric breakdown. 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 is made of, for example, high-purity aluminum oxide (Al 2 O 3 ), 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, etc. required for the dielectric substrate 100 in the 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 layer made of a metal material such as tungsten, and is disposed so as to be parallel to the surface 110. The material of the adsorption electrode 130 may be molybdenum, platinum, palladium, or the like, in addition to tungsten. 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. The adsorption electrode 130 may be a so-called "monopolar" electrode, as in this embodiment, and only one electrode 130 may be provided, or two electrodes may be provided as so-called "bipolar" electrodes.

[0020] 1, the entire power supply line 13 is depicted in a simplified manner. The 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. The 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. The base plate 200 is formed with a through hole (not shown) for inserting the metal therethrough. For example, a cylindrical insulating member may be provided between the inner surface of the through hole and the power supply line 13.

[0021] In addition to the above-mentioned attraction electrode 130, an RF electrode 140 is also embedded inside the dielectric substrate 100. The RF electrode 140 is provided as one of a pair of opposing electrodes for generating plasma in the semiconductor manufacturing equipment. The other of the opposing electrodes is provided at a position above the electrostatic chuck 10 in the semiconductor manufacturing equipment. When a high-frequency AC voltage is applied between these opposing electrodes, plasma is generated above the substrate W, and is used for processing the substrate W, such as film formation and etching.

[0022] The RF electrode 140, like the adsorption electrode 130, is a thin flat layer made of a metal material such as tungsten. In addition to tungsten, molybdenum, platinum, palladium, etc. may be used as the material of the RF electrode 140. The RF electrode 140 is embedded at a position closer to the surface 120 than the adsorption electrode 130. In other words, the adsorption electrode 130 is embedded at a position closer to the surface 110 than the RF electrode 140. Like the adsorption electrode 130, the RF electrode 140 is arranged parallel to the surface 110 and the adsorption electrode 130. The RF electrode 140 is a single electrode that is substantially circular in top view.

[0023] An opening 143 is formed in a portion of the RF electrode 140 that overlaps with the power feed line 13 in top view. By forming the opening 143, insulation between the power feed line 13 and the RF electrode 140 is ensured.

[0024] As shown in Fig. 1, the RF electrode 140 is connected to the power feed line 14. The power feed line 14 is an electric path provided to make the potential of the RF electrode 140 equal to the potential of the base plate 200 when a high-frequency AC voltage is applied between the RF electrode 140 and the other counter electrode. In Fig. 1, the entire power feed line 14 is illustrated in a simplified manner. The power feed line 14 is configured as an electrode terminal having, for example, one end connected to the RF electrode 140 and the other end formed to protrude downward from the surface 120. The protruding portion of the power feed line 14 as described above is embedded in a recess (not shown) formed in the surface 120 of the base plate 200 and is connected to a metal portion of the base plate 200.

[0025] A space SP is formed between the dielectric substrate 100 and the substrate W. When a process such as film formation is performed in the semiconductor manufacturing apparatus, helium gas for temperature adjustment is supplied from the outside to the space SP through a gas hole 150 described below. By providing 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.

[0026] A seal ring 111 and dots 112 are provided on a surface 110 which is an adsorption surface, and a space SP is formed around these.

[0027] The seal ring 111 is a wall that divides the space SP at the outermost position. The upper end of the seal ring 111 forms part of the surface 110 and abuts against the substrate W. Note that a plurality of seal rings 111 may be provided to divide the space SP. 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 more uniform.

[0028] 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.

[0029] 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.

[0030] Groove 113 is formed in bottom surface 116 of space SP. Groove 113 is formed so as to recede further from bottom surface 116 toward surface 120. Groove 113 is formed for the purpose of quickly diffusing helium gas supplied from gas hole 150 into space SP and making the pressure distribution in space SP approximately uniform within a short period of time.

[0031] Gas holes 150 are formed in the dielectric substrate 100, extending vertically from the surface 120 toward the surface 110, and the gas holes 150 are connected to the space SP via through holes 151 shown in Fig. 2. A plurality of gas holes 150 are formed, but only one of them is shown in Fig. 1.

[0032] 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 such as aluminum. The upper surface 210 of the base plate 200 in FIG. 1 is a "bonded surface" that is bonded to the dielectric substrate 100 via a bonding layer 300.

[0033] An insulating film 230 is formed on almost the entire surface of the base plate 200 except for the surface 220 on the lower side in FIG. 1. The insulating film 230 is a film made of an insulating material such as alumina, and is formed by, for example, thermal spraying. The surface 210 described above is entirely on the insulating film 230. The range of the base plate 200 on which the insulating film 230 is formed may be a range different from that shown in FIG. 1. For example, the insulating film 230 may be formed only on the surface 210, which is the surface to be joined.

[0034] A coolant flow path 270 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 270 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.

[0035] Gas holes 250 are formed in the base plate 200, extending vertically from the surface 210 toward the surface 220. The gas holes 250 are formed at positions overlapping with the gas holes 150 of the dielectric substrate 100 in a top view, and communicate with the gas holes 150 via through holes provided in the bonding layer 300. The gas holes 250, together with the gas holes 150 of the dielectric substrate 100, form part of a path for supplying helium gas toward the space SP.

[0036] The gas holes 250 may be formed so as to extend linearly as in this embodiment, but may be formed so as to bend on the way to the surface 220. Also, the gas holes 250 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 configured to extend to the surface 220 side.

[0037] 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.

[0038] The specific configuration of the upper end of gas hole 150 and its vicinity will be described. Fig. 2 shows the configuration of this portion as a schematic cross-sectional view. As shown in the figure, gas hole 150 is formed at a position directly below groove 113 so as to extend from surface 120 toward groove 113, but does not reach the bottom surface of groove 113. Gas hole 150 and space SP are connected by through hole 151.

[0039] The through hole 151 is a circular through hole formed to extend linearly from the upper end of the gas hole 150 to the bottom surface of the groove 113. The radius of the through hole 151 is smaller than the radius of the gas hole 150. The central axis AX of the through hole 151 coincides with the central axis of the gas hole 150. In other words, the through hole 151 extends in a direction perpendicular to the surface 110. The helium gas that has passed through the gas hole 150 is supplied from the through hole 151 to the space SP. The through hole 151 can also be said to be the portion of the gas hole 150, which is a through hole, closest to the surface 110, that is, the gas outlet portion.

[0040] As described above, by making the radius of the gas outlet portion of the gas hole 150 small, it is possible to make it difficult for dielectric breakdown to occur through the gas hole 150. Instead of this embodiment, the gas hole 150 may extend directly to the bottom surface of the groove 113.

[0041] 2, a porous plug 155 is disposed inside the gas hole 150. The porous plug 155 is a substantially cylindrical member formed of a porous member having gas permeability. A space PN is formed between the upper end of the porous plug 155 and the upper end of the gas hole 150. The arrangement of the porous plug 155 can further reduce the occurrence of dielectric breakdown between the substrate W and the base plate 200. Similarly, a porous plug for preventing dielectric breakdown may also be disposed in a portion of the gas hole 250 that is in the vicinity of the bonding layer 300.

[0042] An opening 131 is formed in the chucking electrode 130 at a portion that overlaps with the through hole 151 and the gas hole 150 in a top view. In a top view, the opening 131 is a circular opening, and its center is on the central axis AX. Moreover, a radius R1 of the opening 131 is larger than a radius R0 of the through hole 151. That is, the opening 131 is a circular opening that is concentric with the through hole 151 in a top view and includes the through hole 151. The radius R0 of the through hole 151 is, for example, 0.15 mm or less.

[0043] An opening 141 is formed in a portion of the RF electrode 140 that overlaps with the through hole 151 and the gas hole 150 in a top view. In a top view, the opening 141 is a circular opening, and its center is on the central axis AX. Moreover, a radius R2 of the opening 141 is larger than a radius R0 of the through hole 151. That is, the opening 141 is a circular opening that is concentric with the through hole 151 in a top view and includes the through hole 151. In this embodiment, the radius R2 of the opening 141 is larger than a radius R1 of the opening 131.

[0044] By forming the openings 131 and 141, the chucking electrode 130 and the RF electrode 140 are prevented from being exposed on the inner surface of the through-hole 151.

[0045] In this embodiment, the radius R2 of the opening 141 is sufficiently larger than the radius R0 of the through-hole 151, and the difference (ΔR) between the radius R2 and the radius R0 is ensured to be 1.6 mm or more.

[0046] The reason for adopting such a configuration will be explained. Fig. 3(B) shows the configuration of a portion of an electrostatic chuck according to a comparative example, which corresponds to Fig. 2. In this comparative example, the radius R1 of the opening 131 and the radius R2 of the opening 141 are the same as each other (approximately the same as the radius R1 in Fig. 2). As a result, the above ΔR is smaller than 1.6 mm, and is approximately 1.0 mm.

[0047] During processing of the substrate W, the chucking electrode 130 is at a high potential, while the RF electrode 140 is maintained at a predetermined low potential (the same potential as the base plate 200, for example, ground potential). The arrows shown in Fig. 3(B) typically represent electric field lines in the vicinity of the opening 141 and the edge of the opening 131. In Fig. 3(B), the electric field lines extend from the edge of the opening 131 toward the edge of the opening 141. Depending on the size of the opening 131, the electric field lines toward the edge of the opening 141 may extend from the substrate W being processed.

[0048] When the edge of opening 141 is close to through hole 151 and ΔR is smaller than 1.6 mm as in this comparative example, the direction of the electric field in through hole 151 (i.e., the direction of the electric field lines) becomes approximately the same as the extension direction of through hole 151. For this reason, in the configuration of this comparative example, there is a possibility that dielectric breakdown may occur in the path through through hole 151.

[0049] Therefore, in the electrostatic chuck 10 according to this embodiment, the radius R2 of the opening 141 is increased so as to ensure that ΔR is 1.6 mm or more, as described above, thereby preventing the above-mentioned dielectric breakdown.

[0050] In Fig. 3(A), arrows indicating electric field lines are shown in the same cross section of this embodiment as in Fig. 2, as in Fig. 3(B). In this embodiment, the radius R2 of the opening 141 is increased, so that the edge of the opening 141 is moved away from the through-hole 151. As a result, in the through-hole 151, of the electric field from the high-potential portion toward the edge of the opening 141, the component along the extension direction of the through-hole 151 becomes smaller. The "high-potential portion" is, for example, the chucking electrode 130, but it may also be the substrate W being processed.

[0051] In the present embodiment of FIG. 3(A), the component of the electric field toward the opening 141 that is along the extension direction of the through hole 151 is reduced, so that it is possible to reduce the possibility of dielectric breakdown occurring through the through hole 151 to a lower level than in the past.

[0052] According to the findings of the present inventors through experiments and the like, it has been found that if ΔR is ensured to be 1.6 mm or more, the occurrence of dielectric breakdown through the through hole 151 can be sufficiently prevented.

[0053] It has been confirmed that the above-mentioned effect of setting ΔR to 1.6 mm or more is achieved to some extent even when the radius R2 and the radius R1 are the same. That is, even when not only the radius R2 but also the radius R1 are increased, it is possible to prevent the occurrence of dielectric breakdown through the through-hole 151. However, if the opening 131 of the chucking electrode 130 is made too large, the chucking force may become insufficient, and the substrate W may not be held sufficiently. For this reason, it is preferable to make only the opening 141 of the RF electrode 140 large, as in this embodiment.

[0054] The larger the radius R2 of the opening 141, i.e., the larger ΔR, the lower the possibility of dielectric breakdown occurring in the through hole 151. Fig. 4(B) shows a comparative example in which the radius R2 is extremely large. Fig. 4(A) shows the same embodiment as Fig. 3(A).

[0055] 4(B), when the radius R2 or ΔR is too large, some of the electric field lines extending from the part with high potential (the chucking electrode 130 in this example) may affect the lower part through the opening 141. For example, the electric field lines indicated by the arrow AR1 in FIG. 4(B) are not blocked by the RF electrode 140 and generate a potential difference in the vicinity of the bonding layer 300. As a result, there is a possibility that a dielectric breakdown may occur along the inner surface of the through-hole formed in the bonding layer 300 (the part marked with the reference symbol "301" in FIG. 4(B)).

[0056] According to the findings of the inventors of the present invention through experiments, etc., it has been found that if ΔR is set to 5.4 mm or less, the occurrence of such dielectric breakdown can be sufficiently prevented. Therefore, it is preferable to not make the radius R2 too large, but to set it to radius R0 + 5.4 mm or less.

[0057] It is preferable that the radius R2 is in the range of 1.75 mm or more and 5.35 mm or less. Furthermore, when the radius R2 is made larger than the radius R1 as in this embodiment, it is preferable that the difference between the radius R2 and the radius R1 is set to 2.7 mm or less.

[0058] The openings 141 and 131 as described above may be formed in the dielectric substrate 100 at positions overlapping with through holes provided for a purpose other than the through hole 151 in a top view. For example, the dielectric substrate 100 may be formed with lift pin holes for inserting lift pins (not shown) provided in a semiconductor manufacturing device. Even if the openings 141 and 131 similar to those of this embodiment are formed at positions overlapping with the lift pin holes in a top view, the same effects as those described above can be achieved.

[0059] However, the pressure inside through hole 151, which is a gas supply hole, tends to be a pressure range where dielectric breakdown is relatively likely to occur. For this reason, the application of the shapes of opening 141 and opening 131 as described above to the position of through hole 151 is particularly effective.

[0060] 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]

[0061] W: Substrate 10: Electrostatic chuck 100: Dielectric substrate 110: Face 140:RF electrode 141:Aperture 151:Through hole

Claims

1. A dielectric substrate having a mounting surface on which an object to be adsorbed is placed, and having through holes formed perpendicular to the mounting surface, Adsorption electrodes embedded inside the dielectric substrate, The RF electrode is embedded inside the dielectric substrate at a position different from that of the adsorption electrode, The RF electrode has a circular opening that is concentric with the through hole and encloses the through hole. The difference between the radius of the opening and the radius of the through hole at the part closest to the mounting surface described above is 1.6 mm or more. An electrostatic chuck characterized in that a porous plug is placed inside the through hole.

2. The electrostatic chuck according to claim 1, characterized in that the difference between the radius of the opening and the radius of the portion of the through hole closest to the mounting surface is 5.4 mm or less.

3. The electrostatic chuck according to claim 1 or 2, characterized in that the through hole is a hole for supplying gas.

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