Electrostatic chuck

Abstract

Provided is an electrostatic chuck that can suppress variation in an in-plane temperature distribution of a substrate during processing. An electrostatic chuck 10 includes: a dielectric substrate 100 having a surface 110 that is a mounting surface; and a base plate 200 in which a refrigerant flow path 270 is formed and which is joined to the dielectric substrate 100. When a distance from the surface 110 to a surface 220 of the base plate 200 opposite to the mounting surface is T1 and a distance from the surface 110 to the refrigerant flow path 270 is D1, D1 > T1 / 2 is satisfied in this electrostatic chuck 10.

Description

Electrostatic chuck

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

[0002] For example, semiconductor manufacturing equipment such as an etching apparatus is provided with an electrostatic chuck as a device for attracting and holding a substrate, such as a silicon wafer, to be processed. The electrostatic chuck includes a dielectric substrate provided with an attracting electrode and a base plate supporting the dielectric substrate, which are joined together. When a voltage is applied to the attracting electrode, an electrostatic force is generated, attracting and holding a substrate placed on the dielectric substrate.

[0003] During processing such as etching, it is necessary to maintain the temperature of the substrate at an appropriate temperature. For this reason, as described in Patent Document 1 below, a coolant flow path for passing a coolant is formed inside the base plate.

[0004] Patent No. 7479565

[0005] The coolant flow path is routed along a path that passes through almost the entire base plate when viewed from above, but it cannot be routed to pass through all points. Therefore, on the surface of the base plate facing the dielectric substrate, there are areas where the coolant flow path is routed directly below and areas where it is not routed. The presence or absence of such a coolant flow path can cause variations in the in-plane temperature distribution of the substrate during processing.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an electrostatic chuck that can suppress variations in the in-plane temperature distribution of a substrate during processing.

[0007] 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 placed, and a base plate having a coolant flow path formed therein and joined to the dielectric substrate, where T1 is the distance from the mounting surface to the surface of the base plate opposite the mounting surface, and D1 is the distance from the mounting surface to the coolant flow path, where D1 > T1 / 2 holds true for this electrostatic chuck.

[0008] In an electrostatic chuck having such a configuration, the coolant flow path is located at a position sufficiently far from the mounting surface, which reduces the temperature difference between the area directly above the coolant flow path and the area directly above the area where the coolant flow path is not located, thereby suppressing variations in the temperature distribution within the surface of the substrate during processing.

[0009] According to the present invention, it is possible to provide an electrostatic chuck that can suppress variations in the in-plane temperature distribution of a substrate during processing.

[0010] 1 is a cross-sectional view schematically illustrating the configuration of an electrostatic chuck according to a first embodiment; 2 is a diagram illustrating dimensions of each part of an electrostatic chuck according to a first embodiment; 3 is a diagram illustrating dimensions of each part of an electrostatic chuck according to a second embodiment;

[0011] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicated descriptions will be omitted.

[0012] A first embodiment will be described. An 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 an etching apparatus. The substrate W to be attracted is, for example, a silicon wafer. The electrostatic chuck 10 may also be used in apparatuses other than semiconductor manufacturing apparatuses.

[0013] 1 is a schematic cross-sectional view showing the configuration of an electrostatic chuck 10 in a state where the electrostatic chuck 10 attracts and holds a substrate W. 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 sintered ceramic body. The dielectric substrate 100 is made of, for example, high-purity aluminum oxide (Al ２ O ３ 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.

[0015] 1 of the dielectric substrate 100 is a "mounting surface" on which the substrate W is placed. Also, a lower surface 120 of the dielectric substrate 100 in FIG. 1 is a "bonded surface" that is bonded to the base plate 200 via a bonding layer 300. The viewpoint when the electrostatic chuck 10 is viewed from the side of the surface 110 along a direction perpendicular to the surface 110 will hereinafter also be referred to as a "top view."

[0016] 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 parallel to the surface 110. The adsorption electrode 130 may be made of molybdenum, platinum, palladium, or the like, in addition to tungsten. When a voltage is applied to the adsorption electrode 130 from the outside via a power supply path (not shown), an electrostatic force is generated between the surface 110 and the substrate W, thereby adsorbing and holding the substrate W. Various known configurations can be employed as the configuration of the power supply path. Only one adsorption electrode 130 may be provided as a so-called "monopolar" electrode, as in this embodiment, or two may be provided as so-called "bipolar" electrodes.

[0017] 1, a space SP is formed between the dielectric substrate 100 and the substrate W. When a process such as etching is performed in the semiconductor manufacturing apparatus, helium gas for temperature adjustment is supplied to the space SP from the outside via a supply flow path 140, which will be described later. By providing helium gas between the dielectric substrate 100 and the substrate W, the thermal resistance between them is adjusted, thereby maintaining the temperature of the substrate W at an appropriate temperature. Note that the temperature adjustment gas supplied to the space SP may be a type of gas other than helium.

[0018] A seal ring 111 and dots 112 are provided on the surface 110, which is the mounting surface, and the space SP is formed around these.

[0019] 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.

[0020] 1, the portion marked with the reference numeral "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 by digging down a portion of the surface 110 to the position of the bottom surface 116.

[0021] The dots 112 are circular protrusions that protrude from the bottom surface 116. A plurality of dots 112 are provided and are distributed approximately evenly on the mounting surface of the dielectric substrate 100. The upper end of each dot 112 forms part of the surface 110 and comes into contact with the substrate W. By providing a plurality of such dots 112, bending of the substrate W is suppressed.

[0022] A supply flow path 140 is formed in the dielectric substrate 100. The supply flow path 140 is a through-hole formed to extend in a direction perpendicular to the surface 110, which is the mounting surface. The end of the supply flow path 140 on the surface 110 side is connected to the space SP. The supply flow path 140 is part of a flow path for supplying helium gas toward the space SP. A plurality of supply flow paths 140 are formed in the dielectric substrate 100, but only two of them are shown in FIG. 1. The supply flow path 140 corresponds to the "gas hole" in this embodiment.

[0023] A porous member may be disposed inside the supply flow path 140. By disposing a porous member inside the supply flow path 140, it is possible to ensure the flow of helium gas in the supply flow path 140 while suppressing the occurrence of dielectric breakdown in the path through the supply flow path 140.

[0024] 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. The base plate 200 is bonded to the surface 120 of the dielectric substrate 100 via a bonding layer 300. 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 the bonding layer 300.

[0025] 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 hardening an adhesive made of an insulating material. In this embodiment, a silicone adhesive is used as the adhesive. However, the bonding layer 300 may be formed by hardening another type of adhesive. In either case, it is preferable to use a material with as high a thermal conductivity as possible as the material for the bonding layer 300 so as to reduce the thermal resistance between the dielectric substrate 100 and the base plate 200.

[0026] An insulating film may be formed on the surface of the base plate 200. For example, an alumina film formed by thermal spraying can be used as the insulating film. By covering the surface of the base plate 200 with the insulating film, the dielectric strength of the base plate 200 can be increased.

[0027] A coolant flow path 270 for flowing a coolant is formed inside the base plate 200. When a process such as etching is performed in the semiconductor manufacturing equipment, 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. The coolant is supplied to and discharged from the coolant flow path 270 through an opening (not shown) formed in a surface 220 of the base plate 200 opposite the surface 210. The surface 220 can be referred to as the "surface opposite the mounting surface" of the base plate 200.

[0028] A supply flow path 240 is formed in the base plate 200. The supply flow path 240 is a hole formed to extend in a direction perpendicular to the surface 110, which is the mounting surface, and extends from the surface 210 to a distribution flow path 250, which will be described later. The supply flow path 240 is formed at each position overlapping the supply flow path 140 in a top view, and is connected to the supply flow path 140 via a through hole provided in the bonding layer 300. The supply flow path 240, together with the supply flow path 140 of the dielectric substrate 100, forms part of a flow path for supplying helium gas toward the space SP on the mounting surface side.

[0029] A porous member may be disposed inside the supply flow path 240. By disposing a porous member inside the supply flow path 240, it is possible to suppress the occurrence of dielectric breakdown in the path through the supply flow path 240 while ensuring the flow of helium gas in the supply flow path 240.

[0030] Distribution channels 250 are formed inside the base plate 200. The distribution channels 250 are channels for distributing helium gas to each of the supply channels 240 (and the supply channels 140 connected thereto). The distribution channels 250 are provided at a position closer to the mounting surface (upper side in FIG. 2 ) than the refrigerant channels 270, i.e., at a position inside the base plate 200 near the surface 210. The distribution channels 250 are routed parallel to the surface 210 and connected to the lower ends of each of the supply channels 240. The base plate 200 is formed with supply channels (not shown) that extend from the surface 220 to the distribution channels 250. Helium gas supplied from the outside is supplied to the distribution channels 250 via the supply channels and distributed from the distribution channels 250 to each of the supply channels 240.

[0031] As described above, the base plate 200 has a relatively complex internal structure, with the refrigerant flow paths 270, distribution flow paths 250, supply flow paths 240, and the like formed therein. To facilitate the formation of the refrigerant flow paths 270 and the like, the base plate 200 of this embodiment is formed by joining multiple members. Specifically, the base plate 200 is formed by joining together three members, namely, a first member 201, a second member 202, and a third member 203, into an integrated unit. The members are joined by welding, but may also be joined by methods such as brazing or fastening. The number of members constituting the base plate 200 may be four or more, or two or less.

[0032] The first member 201, the second member 202, and the third member 203 are arranged in this order along a direction perpendicular to the surface 110, which is the mounting surface. The first member 201 is the part of the members constituting the base plate 200 that is closest to the dielectric substrate 100. The surface 210 mentioned above is a part of the first member 201. The third member 203 is the part of the members constituting the base plate 200 that is on the opposite side from the dielectric substrate 100. The surface 220 mentioned above is a part of the third member 203. The second member 202 is a member that is between the first member 201 and the third member 203.

[0033] A joint boundary B1 between the first member 201 and the second member 202 is parallel to the surface 110 and the surface 210. A joint boundary B2 between the second member 202 and the third member 203 is also parallel to the surface 110 and the surface 210.

[0034] In this embodiment, the entire distribution channels 250 and the supply channels 240 are both formed in the first member 201. The distribution channels 250 are grooves that are formed in advance along the surface of the first member 201 that will become the joining boundary B1 before the respective members are joined. In this way, by forming the grooves in advance on the surface of the first member 201 and then joining the second member 202 so as to cover the surface, the distribution channels 250 that follow the grooves can be easily formed inside the base plate 200. Note that the grooves that will become the distribution channels 250 may be formed not on the surface of the first member 201 but on the surface of the second member 202 that will become the joining boundary B1.

[0035] In this embodiment, the coolant flow path 270 is entirely formed in the second member 202. The coolant flow path 270 is a groove that is formed in advance along the surface of the second member 202 that will become the joining boundary B2 before the respective members are joined. In this way, by forming a groove in advance on the surface of the second member 202 and then joining the third member 203 so as to cover this surface, the coolant flow path 270 that follows the groove can be easily formed inside the base plate 200. Note that the groove that will become the coolant flow path 270 may also be formed on the surface of the second member 202 that will become the joining boundary B1.

[0036] Fig. 2 shows a simplified cross section of the electrostatic chuck 10 shown in Fig. 1. For convenience of illustration, hatching of each cross section is omitted in Fig. 2. Also, the bond boundary B1 and the bond boundary B2 of the base plate 200 are omitted from the illustration.

[0037] 2 represents the distance from the surface 110, which is the mounting surface, to the surface 220 of the base plate 200 opposite to the mounting surface. The surfaces 110 and 220 are parallel to each other. Therefore, the above-mentioned "distance" refers to the distance along a direction perpendicular to the surface 110. The distance from the surface 110 to the surface 220 will also be referred to as "distance T1" hereinafter. The distance T1 can also be referred to as the overall thickness of the electrostatic chuck 10.

[0038] The dashed-dotted line DL1 shown in Fig. 2 is a line representing a height position where the distance from the surface 110 is T1 / 2, that is, a center position in the thickness direction of the electrostatic chuck 10. "D1" shown in Fig. 2 is the distance from the surface 110, which is the mounting surface, to the coolant flow path 270. As described above, these "distances" also refer to distances along a direction perpendicular to the surface 110. The distance from the surface 110 to the coolant flow path 270 will hereinafter also be referred to as "distance D1."

[0039] The coolant flow path 270 is routed along a path that passes through almost the entire base plate 200 when viewed from above, but it cannot be routed so as to pass through all positions. Therefore, on the surface 210 of the base plate 200 on the mounting surface side (the upper side in FIG. 2 ), there are parts directly below which the coolant flow path 270 is routed and parts below which the coolant flow path 270 is not routed. The presence or absence of such a coolant flow path 270 may cause variations in the in-plane temperature distribution of the substrate W during processing.

[0040] Therefore, in the electrostatic chuck 10 according to this embodiment, the coolant flow path 270 is located sufficiently far from the surface 110. Specifically, the coolant flow path 270 is located at a position where the relationship "D1>T1 / 2" holds between a distance D1 from the surface 110 to the coolant flow path 270 and a distance T1 from the surface 110 to the surface 220. In other words, the coolant flow path 270 is located so that the upper end of the coolant flow path 270 is located below a position (dashed line DL1) that is the center of the electrostatic chuck 10 in the thickness direction.

[0041] By arranging the coolant flow path 270 at a position sufficiently far from the mounting surface, the temperature difference between the area directly above the area through which the coolant flow path 270 is routed and the area directly above the area through which the coolant flow path 270 is not routed can be reduced, thereby making it possible to suppress the variation in the in-plane temperature distribution of the substrate W during processing more effectively than ever before.

[0042] In addition, when the distance D1 from the surface 110 to the refrigerant flow path 270 varies depending on the position along the refrigerant flow direction, it is sufficient to configure the refrigerant flow path 270 so that "D1 > T1 / 2" is satisfied for the smallest distance D1. In other words, it is sufficient that "D1 > T1 / 2" is satisfied for the refrigerant flow path 270 closest to the surface 110.

[0043] "T2" shown in FIG. 2 represents the distance from surface 210 of base plate 200 on the mounting surface side to surface 220 of base plate 200 on the opposite side to the mounting surface. Surface 210 and surface 220 are parallel to each other. Therefore, the above "distance" refers to the distance along a direction perpendicular to surface 110 and surface 210. The distance from surface 210 to surface 220 will also be referred to as "distance T2" ​​below. Distance T2 can also be referred to as the overall thickness of base plate 200.

[0044] The dashed-dotted line DL2 shown in Fig. 2 is a line representing the height position where the distance from the surface 210 is T2 / 2, i.e., the center position in the thickness direction of the base plate 200. "D2" shown in Fig. 2 is the distance from the surface 210 on the mounting surface side of the base plate 200 to the refrigerant flow path 270. As above, these "distances" also refer to distances along a direction perpendicular to the surface 110, etc. The distance from the surface 210 to the refrigerant flow path 270 will hereinafter also be referred to as "distance D2."

[0045] In this embodiment, the refrigerant flow path 270 is disposed at a position where "D2>T2 / 2" holds true between a distance D2 from the surface 210 to the refrigerant flow path 270 and a distance T2 that is the overall thickness of the base plate 200. In other words, the refrigerant flow path 270 is disposed so that the upper end of the refrigerant flow path 270 is below a position (dashed dotted line DL2) that is the center of the base plate 200 in the thickness direction.

[0046] That is, in this embodiment, the coolant flow path 270 is disposed at a position where "D1 > T1 / 2" and "D2 > T2 / 2" are both satisfied. Since the coolant flow path 270 is disposed at a position sufficiently lower, it is possible to sufficiently suppress variations in the in-plane temperature distribution of the substrate W during processing.

[0047] As described above, the distribution flow path 250 is provided at a position inside the base plate 200 near the surface 210. The distribution flow path 250 is a portion that can become a "thermal resistance" that hinders the flow of heat when cooling the dielectric substrate 100. Therefore, if there is a large variation in the in-plane temperature distribution in each part of the surface 210, arranging the distribution flow path 250 near the surface 210 is likely to further increase the variation in the in-plane temperature distribution.

[0048] However, in this embodiment, the coolant flow path 270 is disposed below and away from the surface 110 and the surface 210, so that the in-plane temperature distribution at each portion of the surface 210 is generally uniform during processing of the substrate W. Therefore, even if the distribution flow path 250 is disposed near the surface 210, the effect is small, and the variation in the in-plane temperature distribution can be suppressed to a negligible level.

[0049] 2 indicates the distance from the surface 210 of the base plate 200 on the mounting surface side to the distribution channel 250 in a direction perpendicular to the surface 110. This distance will also be referred to as "distance D3" hereinafter. To achieve the above-described effect, it is preferable that the distance D3 is 5 mm.

[0050] The cross-sectional shape of the distribution channel 250 shown in Figures 1 and 2 is the cross-sectional shape when the distribution channel 250 is cut perpendicular to the gas flow direction. The dimension of this cross-sectional shape in the up-down direction in Figure 2 etc. is defined as the "height dimension" of the distribution channel 250. The dimension of the same cross-sectional shape in the left-right direction in Figure 2 etc. is defined as the "width dimension" of the distribution channel 250. As shown in Figure 2 etc., the height dimension of the distribution channel 250 is smaller than the width dimension of the distribution channel 250.

[0051] By forming the distribution channels 250 so that the height dimension is smaller than the width dimension, the thickness of the portion of the base plate 200 near the distribution channels 250 can be reduced, and the thermal resistance of that portion can be suppressed. In other words, it is possible to suppress deterioration of heat dissipation due to the provision of the distribution channels 250. This makes it possible to increase the cooling efficiency of the dielectric substrate 100 by the base plate 200 and further uniformize the in-plane temperature distribution of the substrate W.

[0052] A second embodiment will be described below. Differences from the first embodiment will be mainly described below, and descriptions of commonalities with the first embodiment will be omitted as appropriate.

[0053] 3 is a schematic diagram of the configuration of the electrostatic chuck 10 according to this embodiment, drawn in the same manner as in FIG. 2. In this embodiment, as in the first embodiment, the coolant flow path 270 is disposed at a position where "D1 > T1 / 2" is satisfied. However, the coolant flow path 270 is disposed at a position where "D2 < T2 / 2" is satisfied, rather than at a position where "D2 > T2 / 2" is satisfied, which is different from the first embodiment. That is, in this embodiment, the coolant flow path 270 is disposed so that the upper end of the coolant flow path 270 is located above the center of the base plate 200 in the thickness direction (dash-dotted line DL2).

[0054] When such a configuration is adopted, the base plate 200 can be made thinner than in the first embodiment while ensuring a sufficient distance D1 from the surface 110, which is the mounting surface, to the coolant flow path 270. This allows the weight of the base plate 200 to be reduced. In addition, the reduced heat capacity of the base plate 200 provides the advantages of improved temperature responsiveness and facilitating adjustment of the height position of the mounting surface when attaching the electrostatic chuck 10 to a semiconductor manufacturing apparatus.

[0055] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Design modifications to these specific examples made by a person skilled in the art as appropriate are also included within the scope of the present disclosure as long as they comprise the features of the present disclosure. The elements of the above-described specific examples, as well as their arrangement, conditions, shape, etc., are not limited to those exemplified and can be modified as appropriate. The elements of the above-described specific examples can be combined in various ways as appropriate, as long as no technical contradictions arise.

[0056] 10: Electrostatic chuck 100: Dielectric substrate 110: Surface 140: Supply flow path 200: Base plate 210, 220: Surface 250: Distribution flow path 270: Coolant flow path W: Substrate

Claims

1. An electrostatic chuck comprising: a dielectric substrate having a mounting surface on which an object to be attracted is placed; and a base plate having a coolant flow path formed therein and joined to the dielectric substrate, wherein when the distance from the mounting surface to the surface of the base plate opposite the mounting surface is T1 and the distance from the mounting surface to the coolant flow path is D1, the relationship D1 > T1 / 2 holds.

2. The electrostatic chuck according to claim 1, wherein when the distance from the surface of the base plate facing the mounting surface to the surface of the base plate opposite the mounting surface is T2, and the distance from the surface of the base plate facing the mounting surface to the coolant flow path is D2, the following relationship holds: D2 > T2 / 2.

3. The electrostatic chuck according to claim 1, wherein when the distance from the surface of the base plate facing the mounting surface to the surface of the base plate opposite the mounting surface is T2, and the distance from the surface of the base plate facing the mounting surface to the coolant flow path is D2, the following relationship holds: D2 < T2 / 2.

4. The electrostatic chuck according to claim 1, wherein a plurality of gas holes are formed in the dielectric substrate, and a distribution flow path for distributing gas to each of the gas holes is formed inside the base plate at a position closer to the mounting surface than the coolant flow path.

5. The electrostatic chuck according to claim 4, wherein the distance from the surface of the base plate on the mounting surface side to the distribution flow path is within 5 mm.

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