Electrostatic chuck

Abstract

The invention provides an electrostatic chuck capable of suppressing deviation of in-plane temperature distribution of a substrate during processing. An electrostatic chuck (10) is provided with: a dielectric substrate (100); an adsorption electrode (130) provided inside the dielectric substrate (100); and an RF electrode (140) provided inside the dielectric substrate (100). In a plan view, an outer peripheral end portion of the RF electrode (140) is provided within a range closer to the inside than an outer peripheral end portion of the adsorption electrode (130).

Description

Technical Field

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

[0002] For example, in a semiconductor manufacturing apparatus such as an etching apparatus, an electrostatic chuck is provided as an apparatus for adsorbing and holding a substrate such as a silicon wafer that is an object to be processed. The electrostatic chuck includes: a dielectric substrate provided with an adsorption electrode; and a base plate that supports the dielectric substrate, having a structure in which these are joined to each other. When a voltage is applied to the adsorption electrode, an electrostatic force is generated to adsorb and hold the substrate placed on the dielectric substrate. Although the adsorption electrode is sometimes formed on the surface of the dielectric substrate on the base plate side, it is usually provided inside the dielectric substrate.

[0003] As described in Patent Document 1 below, an RF electrode is sometimes additionally provided inside the dielectric substrate in addition to the adsorption electrode. The RF electrode functions as one of a pair of opposing electrodes for generating plasma in a semiconductor manufacturing apparatus.

[0004] Patent Document Patent Document 1: Japanese Patent Application Laid-Open No. 2011-119654 Summary of the Invention

[0005] When processing a substrate such as etching, Joule heat is generated on the RF electrode, and the temperature of surrounding components may rise. That is, the RF electrode may become a heat source during processing. Regarding how to arrange the heat source, that is, the RF electrode, in order to suppress the deviation of the in-plane temperature distribution of the substrate during processing, no specific research has been conducted in the past.

[0006] The present invention has been made in view of such problems, and the technical problem to be solved is to provide an electrostatic chuck that can suppress the deviation of the in-plane temperature distribution of the substrate during processing.

[0007] To solve the above problems, the electrostatic chuck according to the present invention includes: a dielectric substrate having a placement surface for placing an object to be adsorbed; an adsorption electrode provided inside the dielectric substrate; and an RF electrode provided inside the dielectric substrate. When viewed from a direction perpendicular to the placement surface, the outer peripheral side end of the RF electrode is provided within a range closer to the inside than the outer peripheral side end of the adsorption electrode.

[0008] In processes such as etching, it is well known that the temperature of the portion particularly on the outer peripheral side of the substrate tends to increase. Thus, in the electrostatic chuck having the above structure, by accommodating the outer peripheral side end portion of the heat source, i.e., the RF electrode, within a range closer to the inner side than the outer peripheral side end portion of the adsorption electrode, it is possible to suppress the temperature rise in the portion on the outer peripheral side of the substrate. As a result, it is possible to more effectively suppress the deviation of the in-plane temperature distribution of the substrate during processing as compared with the prior art.

[0009] According to the present invention, it is possible to provide an electrostatic chuck capable of suppressing the deviation of the in-plane temperature distribution of the substrate during processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a cross-sectional view schematically showing the structure of the electrostatic chuck according to the present embodiment. Figure 2 is an enlarged and detailed view showing Figure 1 a part of the structure of. REFERENCE SIGNS 10 - electrostatic chuck; 100 - dielectric substrate; 110 - surface; 111 - sealing ring; 130 - adsorption electrode; 140 - RF electrode. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0011] Hereinafter, the present embodiment will be described with reference to the drawings. For ease of explanation, in each drawing, the same reference signs are used for the same components as much as possible, and repeated explanations are omitted.

[0012] The electrostatic chuck 10 according to the present embodiment adsorbs and holds a substrate W to be processed by electrostatic force inside a semiconductor manufacturing apparatus (not shown) such as an etching apparatus, for example. The substrate W, which is the object to be adsorbed, is, for example, a silicon wafer. The electrostatic chuck 10 can also be used in apparatuses other than semiconductor manufacturing apparatuses.

[0013] Figure 1 shows the structure of the electrostatic chuck 10 in a state of adsorbing and holding the substrate W as a schematic cross-sectional view. The electrostatic chuck 10 includes a dielectric substrate 100 and a base plate 200.

[0014] The dielectric substrate 100 is a substantially disk-shaped member made of a ceramic sintered body. Although the dielectric substrate 100 contains, for example, high-purity alumina (Al2O3), it may also contain other materials. Considering the plasma resistance and the like required for the dielectric substrate 100 in a semiconductor manufacturing apparatus, the ceramic purity, type, additives, etc. in the dielectric substrate 100 can be appropriately set. The diameter of the dielectric substrate 100 is, for example, 290 to 300 mm. The thickness of the dielectric substrate 100 is, for example, 0.5 to 3.0 mm.

[0015] In the dielectric substrate 100,Figure 1 The upper side surface 110 in [0] becomes the "placement surface" for placing the substrate W. In addition, in the dielectric substrate 100, Figure 1 The lower side surface 120 in [2] becomes the "surface to be joined" that is joined to the base plate 200 via the joining layer 300. Hereinafter, the viewpoint when observing the electrostatic chuck 10 along the direction perpendicular to the surface 110 from the surface 110 side will also be referred to as "top view observation".

[0016] Inside the dielectric substrate 100, an adsorption electrode 130 is embedded. The adsorption electrode 130 is, for example, a thin plate-like layer formed of a metal material such as tungsten, and is arranged parallel to the surface 110. As the material of the adsorption electrode 130, in addition to tungsten, molybdenum, platinum, palladium, etc. can also be used. If a voltage is externally applied to the adsorption electrode 130 from a power supply circuit (not shown), an electrostatic force is generated between the surface 110 and the substrate W, and thus the substrate W is adsorbed and held. As the structure of the above-mentioned power supply circuit, various known structures can be adopted. The adsorption electrode 130 can be provided as a so-called "single-pole" electrode, that is, only one, as in this embodiment, or can be provided as a so-called "bipolar" electrode, that is, two. The depth of the position where the adsorption electrode 130 is arranged, that is, the distance from the bottom surface 116 (described later) to the adsorption electrode 130 is, for example, 0.1 to 0.5 mm.

[0017] Inside the dielectric substrate 100, on the basis of the above-mentioned adsorption electrode 130, an RF electrode 140 is also embedded. In a semiconductor manufacturing apparatus, the RF electrode 140 is provided as one of a pair of opposing electrodes for generating plasma. The other of the opposing electrodes is provided at a position in the semiconductor manufacturing apparatus that is closer to the upper side than the electrostatic chuck 10. If a high-frequency alternating voltage is externally applied between these opposing electrodes, plasma is generated on the upper side of the substrate W and is used for processes such as film formation or etching of the substrate W.

[0018] Similar to the adsorption electrode 130, the RF electrode 140 is also, for example, a thin 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. can also be used. The RF electrode 140 is embedded at a position closer to the surface 120 side than the adsorption electrode 130. Similar to the adsorption electrode 130, the RF electrode 140 is arranged parallel to the surface 110. When observed from the top view, the RF electrode 140 is a substantially circular single electrode. When observed from the top view, the center of the RF electrode 140 coincides with the center of the dielectric substrate 100. The distance from the adsorption electrode 130 to the RF electrode 140 is, for example, 0.2 to 2 mm. The distance from the RF electrode 140 to the surface 120 is, for example, 0.1 to 2.5 mm.

[0019] As Figure 1As shown, a space SP is formed between the dielectric substrate 100 and the substrate W. When performing processes such as etching in a semiconductor manufacturing apparatus, helium gas for temperature adjustment is supplied from the outside to the space SP through pores (not shown). By having helium gas present between the dielectric substrate 100 and the substrate W, the thermal resistance between the two is adjusted, and thus the temperature of the substrate W is maintained at an appropriate temperature. Also, the gas for temperature adjustment supplied to the space SP can be a gas of a type different from helium.

[0020] A seal ring 111 and dots 112 are provided on the placement surface, i.e., surface 110, and the above-described space SP is formed around these.

[0021] The seal ring 111 is a wall that divides the space SP at the outermost peripheral position. The seal ring 111 is an annular protrusion formed on the surface 110 side. The tip ( Figure 1 the upper end in this case) of the seal ring 111 becomes a part of the surface 110 and abuts against the substrate W. It can be said that the tip of the seal ring 111 is the outermost peripheral side portion of the placement surface, i.e., surface 110.

[0022] Also, a plurality of seal rings 111 can be provided in a manner that divides the space SP. With such a structure, the pressure of the helium gas in each space SP can be adjusted individually, and the surface temperature distribution of the substrate W can be made uniform during the process.

[0023] Figure 1 In, the portion marked with the 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 and the dots 112 described next are formed as a result of digging a part of the surface 110 to the position of the bottom surface 116.

[0024] The dot 112 is a circular protrusion protruding from the bottom surface 116. A plurality of dots 112 are provided and are disposed approximately evenly on the placement surface of the dielectric substrate 100. The tip of each dot 112 becomes a part of the surface 110 and abuts against the substrate W. By providing a plurality of such dots 112, warping of the substrate W is suppressed.

[0025] 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 material such as aluminum, for example. The base plate 200 is joined to the surface 120 of the dielectric substrate 100 by a joining layer 300. In the base plate 200, Figure 1 the upper side surface 210 therein becomes the "surface to be joined" that is joined to the dielectric substrate 100.

[0026] The bonding layer 300 is a layer provided between the dielectric substrate 100 and the base plate 200 to bond the two. The bonding layer 300 is a layer formed by curing an adhesive made of an insulating material. In the present embodiment, a silicone adhesive is used as the above-mentioned 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 a relatively high thermal conductivity as the material of the bonding layer 300 so that the thermal resistance between the dielectric substrate 100 and the base plate 200 is small.

[0027] An insulating film may also be formed on the surface of the base plate 200. As the insulating film, for example, a film of alumina formed by sputtering can be used. By covering the surface of the base plate 200 with the insulating film, the withstand voltage of the base plate 200 can be improved.

[0028] The base plate 200 has a support portion 201 and a flange portion 202. The support portion 201 is the Figure 1 upper side portion in the base plate 200 and is a substantially cylindrical portion that directly supports the dielectric substrate 100 from below. Although the diameter of the support portion 201, i.e., the diameter of the surface 210, can be the same as the diameter of the dielectric substrate 100, it can also be slightly smaller than the diameter of the dielectric substrate 100. The diameter of the support portion 201 is, for example, 290 to 300 mm. In addition, the thickness of the support portion 201, i.e., the protruding amount of the support portion 201 toward the Figure 1 upper side (the protruding amount from the flange portion 202) is, for example, 3 to 15 mm.

[0029] The flange portion 202 is the Figure 1 lower side portion in the base plate 200. The shape of the flange portion 202 is substantially cylindrical, and its central axis coincides with the central axis of the support portion 201. The diameter of the flange portion 202 is larger than the diameter of the support portion 201. The protruding amount of the flange portion 202 starting from the outer side surface of the support portion 201 (that is, the protruding amount in the radial direction) is, for example, 20 to 30 mm. The thickness of the flange portion 202 is, for example, 25 to 40 mm. The overall thickness of the base plate 200 including the support portion 201 and the flange portion 202 is, for example, 30 to 40 mm.

[0030] When processing the substrate W in the semiconductor manufacturing apparatus, a focus ring (not shown) is provided on the upper surface 203 of the flange portion 202. The focus ring is a circular and plate-like member formed of an insulating material such as quartz, and is provided for the purpose of adjusting the distribution of the plasma during processing. Substantially the entire dielectric substrate 100 and the support portion 201 are in a state of being surrounded by the focus ring from the outer peripheral side.

[0031] Inside the base plate 200, a coolant flow path 250 for allowing a coolant to pass through is formed. When performing a process such as etching in a semiconductor manufacturing apparatus, the coolant is supplied from the outside to the coolant flow path 250, thereby cooling the base plate 200. During the process, the heat generated on the substrate W is transferred to the coolant 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 coolant.

[0032] However, in a process such as etching, it is well known that the temperature of the portion particularly on the outer peripheral side of the substrate W tends to increase. Thus, in the electrostatic chuck 10 of the present embodiment, in order to suppress the above-described local temperature rise and make the in-plane temperature distribution of the substrate W during the process as uniform as possible, various improvements described below are implemented.

[0033] As Figure 1 shown, the coolant flow path 250 not only surrounds the portion directly below the substrate W disposed in the base plate 200, but also surrounds the portion disposed closer to the outside than directly below the substrate W. By the coolant flowing through the outer portion, a focus ring (not shown) and the like directly above the upper surface 203 are cooled, and thereby the outer peripheral side portion of the substrate W is also cooled.

[0034] In the present embodiment, the diameter of the flange portion 202 is large. By increasing the flange portion 202 and circulating the coolant on the basis of forming the coolant flow path 250 over substantially the entire span thereof, it is possible to suppress the temperature rise of the outer peripheral side portion of the substrate W.

[0035] Figure 2 In, it is enlarged and shown in detail Figure 1 the structure of the outer peripheral side end portion and the vicinity thereof of the dielectric substrate 100 in the electrostatic chuck 10. Figure 2 The dashed line DL1 shown indicates the position of the outer peripheral side end portion of the adsorption electrode 130. The dashed line DL2 indicates the position of the outer peripheral side end portion of the RF electrode 140. And the "outer peripheral side end portion" of the adsorption electrode 130 refers to the portion where the smallest circle including the entire adsorption electrode 130 overlaps with the adsorption electrode 130 when viewed from above. The "outer peripheral side end portion" of the RF electrode 140 is also defined in the same manner.

[0036] In order to prevent insulation breakdown, it is preferable to ensure that the distance from the outer peripheral side end portion (dotted line DL1) of the adsorption electrode 130 to the outer side surface of the dielectric substrate 100 is about 0.1 mm to 3 mm. In addition, it is preferable to ensure that the distance from the outer peripheral side end portion (dotted line DL2) of the RF electrode 140 to the outer side surface of the dielectric substrate 100 is about 0.1 mm to 5 mm. Within the range of satisfying the above conditions, it is preferable that the diameter of the outer peripheral side end portion of the RF electrode 140 is smaller than the diameter of the outer peripheral side end portion of the adsorption electrode 130. In other words, when viewed from above, it is preferable that the outer peripheral side end portion (dotted line DL1) of the RF electrode 140 is disposed within a range closer to the inside than the outer peripheral side end portion (dotted line DL2) of the adsorption electrode 130.

[0037] When processing the substrate W, Joule heat is generated on the RF electrode 140 and the temperature of surrounding components may rise. That is, the RF electrode 140 may become a heat source during processing. Thus, in the present embodiment, as described above, the outer peripheral side end portion of the RF electrode 140 is housed within a range closer to the inside than the outer peripheral side end portion of the adsorption electrode 130. By housing the heat source, i.e., the RF electrode 140, within the above range, it is possible to suppress the temperature rise in the portion on the outer peripheral side of the substrate W. As a result, the deviation of the in-plane temperature distribution of the substrate W during processing can be suppressed more than in the past.

[0038] The diameter of the outer peripheral side end portion of the adsorption electrode 130 is larger than the inner peripheral side diameter of the seal ring 111 and smaller than the outer peripheral side diameter of the seal ring 111. Therefore, when viewed from above, a part of the seal ring 111 overlaps with the adsorption electrode 130. When the seal ring 111 and the adsorption electrode 130 overlap each other when viewed from above, the adsorption force on the seal ring 111 increases, and the seal ring 111 and the substrate W are pressed against each other with a stronger force. As a result, the thermal resistance between the seal ring 111 and the substrate W decreases, and thus the temperature rise of the substrate W directly above the seal ring 111 can be suppressed. As a result, the deviation of the in-plane temperature distribution of the substrate W during processing can be further suppressed.

[0039] Moreover, it may also be configured such that when viewed from above, not a part but the entire seal ring 111 overlaps with the adsorption electrode 130. In this case, it is only necessary to make the outer peripheral side diameter of the seal ring 111 smaller than the diameter of the dielectric substrate 100 and smaller than the outer peripheral side end portion diameter of the adsorption electrode 130.

[0040] As described above, the present embodiment has been described with reference to specific examples. However, the present invention is not limited to these specific examples. Regarding these specific examples, as long as they have the features of the present invention, the techniques appropriately designed and modified by those skilled in the art are also included in the scope of the present invention. The elements, their configurations, conditions, shapes, etc. possessed by each of the foregoing specific examples are not limited to the illustrated content, but can be appropriately changed. As long as there is no technical contradiction, the elements possessed by each of the foregoing specific examples can be appropriately changed in combination.

Claims

1. An electrostatic chuck, characterized in that, it includes: a dielectric substrate having a placement surface for placing an object to be adsorbed; an adsorption electrode disposed inside the dielectric substrate; and an RF electrode disposed inside the dielectric substrate, when viewed from a direction perpendicular to the placement surface, an outer peripheral side end portion of the RF electrode is disposed within a range closer to the inside than an outer peripheral side end portion of the adsorption electrode.

2. The electrostatic chuck according to claim 1, characterized in that, a ring-shaped protrusion, i.e., a sealing ring, whose tip forms a part of the placement surface, is formed on the dielectric substrate, when viewed from a direction perpendicular to the placement surface, at least a part of the sealing ring overlaps with the adsorption electrode.

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