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, an RF electrode 140 embedded inside the dielectric substrate 100, and an attraction electrode 130 embedded inside the dielectric substrate 100 at a position on a surface 110 side relative to the RF electrode 140. In a case of being viewed from a direction perpendicular to the surface 110, the attraction electrode 130 includes a circular opening 131 that is coaxial with the penetration hole 151 and incorporating the penetration hole 151. The RF electrode 140 includes a circular opening 141 that is coaxial with the penetration hole 151 and incorporating the penetration hole 151. A radius R2 of the opening 141 is larger than a radius R1 of the opening 131.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] For example, in a semiconductor manufacturing apparatus such as a CVD apparatus, an electrostatic chuck is provided as a device for adsorbing and holding a substrate such as a silicon wafer to be processed. The electrostatic chuck includes a dielectric substrate provided with adsorption electrodes. When a voltage is applied to the adsorption electrodes, an electrostatic force is generated, and the substrate placed on the dielectric substrate is adsorbed and held.

[0003] As described in Patent Document 1 below, the dielectric substrate may incorporate an RF electrode, which is one of a pair of opposing electrodes for generating plasma in a semiconductor manufacturing apparatus. In this case, both the adsorption electrode and the RF electrode are incorporated in the dielectric substrate.

[0004] Further, the dielectric substrate often has through-holes formed vertically through the placement surface. Such through-holes are formed for purposes such as supplying an inert gas such as helium between the dielectric substrate and the substrate. Circular openings are formed in each of the adsorption electrode and the RF electrode at a portion that overlaps the through-hole in a top view so that the adsorption electrode or the like does not expose on the inner surface of the through-hole. The opening is formed concentric with the through-hole and encompassing the through-hole.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] During the processing of the substrate, while the adsorption electrode is at a high potential, the RF electrode is maintained at a predetermined low potential (for example, the same ground potential as the base plate supporting the dielectric substrate). At this time, in the through-hole, a strong electric field is generated from the edge of the opening of the adsorption electrode toward the edge of the opening of the RF electrode. Since the direction of such an electric field is the same as the extending direction of the through-hole, there is a possibility that dielectric breakdown may occur through the path of the through-hole.

[0007] The present invention has been made in view of such problems, and an object thereof is to provide an electrostatic chuck capable of suppressing the occurrence of dielectric breakdown through a through-hole.

Means for Solving the Problems

[0008] In order to solve the above problems, the electrostatic chuck according to the present invention includes a dielectric substrate having a mounting surface on which an object to be adsorbed is placed, and a through-hole formed perpendicular to the mounting surface, an RF electrode embedded inside the dielectric substrate, and an adsorption electrode embedded inside the dielectric substrate at a position closer to the mounting surface side than the RF electrode. When viewed from a direction perpendicular to the mounting surface, a circular first opening that is concentric with the through-hole and includes the through-hole is formed in the adsorption electrode, and a circular second opening that is concentric with the through-hole and includes the through-hole is formed in the RF electrode. In this electrostatic chuck, the radius of the second opening is larger than the radius of the first opening.

[0009] In the electrostatic chuck having such a configuration, the edge of the second opening formed in the RF electrode is located farther from the through-hole than the edge of the first opening formed in the adsorption electrode. In the through-hole, among the electric field from the edge of the first opening toward the edge of the second opening, the component along the extending direction of the through-hole becomes smaller, so that the possibility of dielectric breakdown occurring through the through-hole can be suppressed lower than before.

[0010] In addition, in the electrostatic chuck according to the present invention, it is also preferable that the difference between the radius of the second opening and the radius of the first opening is 2.7 mm or less. The larger the radius of the second opening, the farther the edge of the second opening is from the through hole, so the possibility of dielectric breakdown occurring through the through hole is reduced. However, if the radius of the second opening is made too large, the electric field around the adsorption electrode at a high potential may also affect other parts through the second opening, and there is a possibility of causing dielectric breakdown in that part. According to the confirmation by the inventors through experiments and the like, it has been found that if the difference between the radius of the second opening and the radius of the first opening is 2.7 mm or less, such dielectric breakdown can be prevented.

[0011] In addition, in the electrostatic chuck according to the present invention, it is also preferable that the through hole is a hole for gas supply. When the through hole is a hole for gas supply, the pressure inside the through hole becomes 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 great.

Advantages 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

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0014] Hereinafter, this embodiment will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same reference numerals are attached to the same components in each drawing as much as possible, and redundant descriptions are omitted.

[0015] The electrostatic chuck 10 according to this embodiment adsorbs and holds a substrate W to be processed by electrostatic force 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] FIG. 1 schematically shows a cross-sectional view of the configuration of the electrostatic chuck 10 in a state where the substrate W is adsorbed and held. 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 ceramic sintered body. The dielectric substrate 100 contains, for example, high-purity aluminum oxide (Al2O3), but may contain other materials. The purity, type, additives, etc. of the ceramics in the dielectric substrate 100 can be appropriately set in consideration of the plasma resistance required for the dielectric substrate 100 in a semiconductor manufacturing apparatus.

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

[0019] An adsorption electrode 130 is embedded inside the dielectric substrate 100. The adsorption electrode 130 is a thin flat plate-like layer formed of a metal material such as tungsten, for example, and is arranged to be parallel to the surface 110. As the material of the adsorption electrode 130, in addition to tungsten, molybdenum, platinum, palladium, etc. may also be used. When a voltage is applied to the adsorption electrode 130 from the outside through the power supply path 13, an electrostatic force is generated between the surface 110 and the substrate W, whereby the substrate W is adsorbed and held. The adsorption electrode 130 may be provided only one as the so-called "unipolar" electrode as in this embodiment, or may be provided two as the so-called "bipolar" electrodes.

[0020] In FIG. 1, the entire power supply path 13 is drawn in a simplified manner. The portion inside the dielectric substrate 100 of the power supply path 13 is configured as, for example, an elongated 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 path 13 that penetrates the base plate 200 is a conductive metal member (for example, a bus bar) having one end connected to the above electrode terminal. A through hole (not shown) for inserting the power supply path 13 is formed in the base plate 200. A cylindrical insulating member may be provided, for example, between the inner surface of the through hole and the power supply path 13.

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

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

[0023] In the RF electrode 140, an opening 143 is formed in the portion that overlaps with the power supply path 13 in top view. By forming the opening 143, insulation between the power supply path 13 and the RF electrode 140 is ensured.

[0024] As shown in FIG. 1, a power supply path 14 is connected to the RF electrode 140. The power supply path 14 is a circuit provided to make the potential of the RF electrode 140 coincide with the potential of the base plate 200 when applying a high-frequency alternating voltage between the RF electrode 140 and the other opposing electrode. In FIG. 1, the entire power supply path 14 is drawn in a simplified manner. The power supply path 14 is configured, for example, such that one end is connected to the RF electrode 140 and the other end is formed as an electrode terminal that protrudes downward from the surface 120. The protruding portion of the power supply path 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 the metal portion of the base plate 200.

[0025] A space SP is formed between the dielectric substrate 100 and the substrate W. When processes such as film formation are 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 later. By interposing helium gas between the dielectric substrate 100 and the substrate W, the thermal resistance between the two is adjusted, and thereby the temperature of the substrate W is maintained at an appropriate temperature. Note that the gas for temperature adjustment supplied to the space SP may be a gas of a type different from helium.

[0026] On the surface 110 which is the suction surface, a seal ring 111 and dots 112 are provided, and the space SP is formed around these.

[0027] The seal ring 111 is a wall that partitions the space SP at the outermost peripheral position. The upper end of the seal ring 111 is part of the surface 110 and abuts against the substrate W. Incidentally, a plurality of seal rings 111 may be provided so as to divide the space SP. With such a configuration, the pressure of the helium gas in each space SP can be individually adjusted, and the surface temperature distribution of the substrate W during processing can be made closer to uniform.

[0028] The portion marked with the reference numeral "116" in FIG. 1 etc. 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 arranged substantially evenly dispersed on the suction surface of the dielectric substrate 100. The upper end of each dot 112 is part of the surface 110 and abuts against the substrate W. By providing a plurality of such dots 112, the deflection of the substrate W is suppressed.

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

[0031] The dielectric substrate 100 is formed with gas holes 150 that extend vertically from the surface 120 toward the surface 110 side, and the gas holes 150 are connected to the space SP through the 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, for example. Among the base plate 200, the upper surface 210 in FIG. 1 serves as a "surface to be joined" that is joined to the dielectric substrate 100 via the joining layer 300.

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

[0034] A refrigerant flow path 270 for flowing refrigerant is formed inside the base plate 200. When a process such as film formation is performed in the semiconductor manufacturing apparatus, refrigerant is supplied from the outside to the refrigerant flow path 270, whereby the base plate 200 is cooled. The heat generated in the substrate W during the process is transmitted to the refrigerant through the helium gas in the space SP, the dielectric substrate 100, and the base plate 200, and is discharged to the outside together with the refrigerant.

[0035] The base plate 200 is formed with gas holes 250 extending vertically from the surface 210 toward the surface 220 side. The gas holes 250 are formed at positions overlapping the gas holes 150 of the dielectric substrate 100 in a top view, and are communicated with the gas holes 150 through 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] Incidentally, the gas holes 250 may be formed to extend linearly as a whole as in the present embodiment, or may be formed to bend on the way toward the surface 220. Further, a plurality of gas holes 250 on the surface 210 side may be aggregated into a small number of flow paths inside the base plate 200, and then the flow paths may be extended 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 joins the two. The bonding layer 300 is obtained by curing an adhesive made of an insulating material. As such an adhesive, for example, a silicone-based adhesive can be used.

[0038] A specific configuration of the upper end portion of the gas hole 150 and its vicinity will be described. FIG. 2 shows a schematic cross-sectional view of the configuration of this portion. As shown in the figure, the gas hole 150 is formed 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 of the groove 113. The gas hole 150 and the space SP are communicated with each other through a 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. Also, the central axis AX of the through-hole 151 coincides with the central axis of the gas hole 150. That is, the through-hole 151 extends in a direction perpendicular to the surface 110. The helium gas passing 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 that is closest to the surface 110 among the through-holes, 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. Alternatively, in such a manner, the gas hole 150 may extend all the way to the bottom surface of the groove 113 as it is.

[0041] As shown in FIG. 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 air permeability. A space PN is formed between the upper end of the porous plug 155 and the upper end of the gas hole 150. By disposing the porous plug 155, it is possible to further make it difficult for dielectric breakdown to occur 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 near the bonding layer 300.

[0042] In the adsorption electrode 130, an opening 131 is formed in a portion that overlaps the through-hole 151 and the gas hole 150 in a top view. In the top view, the opening 131 is a circular opening, and its center is on the central axis AX. Also, the radius R1 of the opening 131 is larger than the radius R0 of the through-hole 151. That is, the opening 131 is concentric with the through-hole 151 in the top view and is a circular opening that includes the through-hole 151.

[0043] Among the RF electrodes 140, openings 141 are formed in portions that overlap the through holes 151 and gas holes 150 in a top view. In the top view, the opening 141 is a circular opening, and its center is on the central axis AX. Also, the radius R2 of the opening 141 is larger than the radius R0 of the through hole 151. That is, the opening 141 is concentric with the through hole 151 in the top view and is a circular opening that encompasses the through hole 151.

[0044] The opening 131 corresponds to the "first opening" in the present embodiment. The opening 141 corresponds to the "second opening" in the present embodiment. By forming the opening 131 and the opening 141, it is prevented that the adsorption electrode 130 and the RF electrode 140 are exposed on the inner surface of the through hole 151.

[0045] In the present embodiment, the radius R2 of the opening 141, which is the second opening, is larger than the radius R1 of the opening 131, which is the first opening.

[0046] The reason for such a configuration will be explained. FIG. 3(B) shows the configuration of a portion corresponding to FIG. 2 of the electrostatic chuck according to the comparative example. 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 (about the same as the radius R1 in FIG. 3).

[0047] During the processing of the substrate W, while the adsorption electrode 130 is at a high potential, the RF electrode 140 is maintained at a predetermined low potential (the same potential as the base plate 200, for example, the ground potential). Each arrow shown in FIG. 3(B) schematically represents the electric field lines in the vicinity of the edges of the opening 141 and the opening 131. Each electric field line extends from the edge of the opening 131 toward the edge of the opening 141. When the radius R1 of the opening 131 and the radius R2 of the opening 141 are equal to each other as in this comparative example, the direction of the electric field in the through hole 151 (that is, the direction of the above-mentioned electric field lines) is substantially the same as the extending direction of the through hole 151. For this reason, in the configuration of this comparative example, there is a possibility that dielectric breakdown may occur through the path of the through hole 151.

[0048] Therefore, in the electrostatic chuck 10 according to the present embodiment, as described above, by making the radius R2 of the opening 141 larger than the radius R1 of the opening 131, the above-described dielectric breakdown is prevented.

[0049] In FIG. 3(A), the same cross-section of the present embodiment as in FIG. 2 shows arrows indicating the electric lines of force in the same manner as in FIG. 3(B). In the present embodiment, by increasing the radius R2 of the opening 141, only the edge of the opening 141 is moved away from the through-hole 151. As a result, in the through-hole 151, among the electric fields from the edge of the opening 131 toward the opening 141, the component along the extending direction of the through-hole 151 becomes smaller, so that the possibility of dielectric breakdown occurring through the through-hole 151 can be suppressed lower than before.

[0050] The larger the radius R2 of the opening 141 is, the lower the possibility of dielectric breakdown occurring in the through-hole 151 becomes. FIG. 4(B) shows a comparative example in the case where the radius R2 is extremely large. FIG. 4(A) represents the same embodiment as in FIG. 3(A).

[0051] As in the comparative example of FIG. 4(B), when the radius R2 is made too large, a part of the electric lines of force extending from the adsorption electrode 130 at a high potential may affect the lower part through the opening 141. For example, in FIG. 4(B), the electric line of force indicated by the arrow AR1 causes a potential difference also in the vicinity of the bonding layer 300 without being shielded by the RF electrode 140. As a result, there is a possibility of causing dielectric breakdown along the inner surface of the through-hole formed in the bonding layer 300 (the portion marked with the symbol "301" in FIG. 4(B)).

[0052] According to what the inventors have confirmed through experiments and the like, it has been found that if the difference between the radius R2 of the opening 141 and the radius R1 of the opening 131 is 2.7 mm or less, such occurrence of dielectric breakdown can be sufficiently prevented. Therefore, it is preferable to set the radius R2 to be R1 + 2.7 mm or less without making the radius R2 too large.

[0053] The difference between the radius R2 and the radius R0 is preferably within the range of 1.6 mm or more and 5.4 mm or less. Further, the radius R2 is preferably within the range of 1.75 mm or more and 5.35 mm or less.

[0054] The openings 141 and 131 as described above may be formed at positions that overlap in a top view with through-holes provided for purposes other than the through-hole 151 in the dielectric substrate 100. For example, the dielectric substrate 100 may be formed with lift pin holes for inserting lift pins (not shown) provided in a semiconductor manufacturing apparatus. Forming the openings 141 and 131 similar to those in the present embodiment at respective positions that overlap with the lift pin holes in a top view can achieve the same effects as those described above.

[0055] However, in the through-hole 151 which is a hole for gas supply, the pressure inside it tends to be in a pressure range where dielectric breakdown is relatively likely to occur. Therefore, at the position of the through-hole 151, the effect of applying the shapes of the openings 141 and 131 as described above is particularly great.

[0056] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Those obtained by appropriately making design changes by those skilled in the art to these specific examples are also included in the scope of the present disclosure as long as they have the features of the present disclosure. Each element, its arrangement, conditions, shape, etc. included in each of the above-described specific examples are not limited to those illustrated and can be changed as appropriate. Each element included in each of the above-described specific examples can be changed in combination as appropriate as long as no technical contradiction occurs.

Explanation of Reference Numerals

[0057] W: Substrate 10: Electrostatic chuck 100: Dielectric substrate 110: Surface 130: Suction electrode 131: Opening 140: RF electrode 141: Opening 151: Through-hole

Claims

1. A dielectric substrate having a placement surface on which an object to be adsorbed is placed, and a through hole formed perpendicularly to the placement surface; An RF electrode embedded inside the dielectric substrate; An adsorption electrode embedded inside the dielectric substrate at a position closer to the placement surface side than the RF electrode, comprising: When viewed from a direction perpendicular to the placement surface, A circular first opening that is concentric with the through hole and includes the through hole is formed in the adsorption electrode; A circular second opening that is concentric with the through hole and includes the through hole is formed in the RF electrode; An electrostatic chuck, wherein a radius of the second opening is larger than a radius of the first opening.

2. The electrostatic chuck according to claim 1, wherein a difference between the radius of the second opening and the radius of the first opening is 2.7 mm or less.

3. The electrostatic chuck according to claim 1 or 2, wherein the through hole is a hole for gas supply.

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