Electrostatic chuck

Abstract

To provide an electrostatic chuck capable of suppressing variations in the in-plane temperature distribution of a substrate during processing.SOLUTION: An electrostatic chuck 10 comprises a dielectric substrate 100, a heating section 300 which is a conductor wound in a linear configuration, and receives power from an external source to generate heat and heat the dielectric substrate 100, and a base plate 200 bonded to the dielectric substrate 100, with a refrigerant flow path 250 formed internally through which refrigerant flows. In the top view, the refrigerant flow path 250 includes an arc section 250A, which is the portion extending along an arc-shaped path, and the heating section 300 includes a meandering section 300A, which is a portion that at least partially overlaps the arc section 250A and meanders relative to the arc section 250A.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] For example, semiconductor manufacturing equipment such as etching equipment 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 that supports the dielectric substrate, which are joined together. 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] During substrate processing, 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. Heat from the substrate is transferred to the coolant through the dielectric substrate and the base plate, and is discharged to the outside together with the coolant.

[0004] Furthermore, during substrate processing, it is also necessary to make the temperature distribution within the surface of the substrate as uniform as possible. In order to enable the temperature distribution within the surface of the substrate to be adjusted with high precision, electrostatic chucks equipped with heaters have been developed in recent years and are already in practical use. The heater may be provided inside the dielectric substrate, as described in Patent Document 1 below, for example, or may be provided outside the dielectric substrate as a unit. In either configuration, the heater has a heat-generating portion which is a conductor routed in a linear manner. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-120910 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, the electrostatic chuck is provided with both a coolant flow path and a heat generating portion. When designing such an electrostatic chuck, the routing of the coolant flow path and the heat generating portion is carefully considered so as to achieve a uniform in-plane temperature distribution of the substrate during processing.

[0007] However, during the manufacture of an electrostatic chuck, the respective positions of the coolant flow passage and the heat generating portion may not be as designed and may deviate from the designed positions. If the relative positional relationship between the coolant flow passage and the heat generating portion is deviated, there is a possibility that the in-plane temperature distribution of the substrate during processing may vary greatly.

[0008] 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. [Means for solving the problem]

[0009] 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, a heat generating portion which is a linear conductor and generates heat when supplied with power from an external source to heat the dielectric substrate, and a base plate joined to the dielectric substrate and having a coolant flow path formed therein through which a coolant passes. When viewed from a direction perpendicular to the mounting surface, the coolant flow path has an arc portion which is a portion extending along an arc-shaped path, and the heat generating portion has a serpentine portion which is at least partially overlapping with the arc portion and which meanders relative to the arc portion.

[0010] In an electrostatic chuck having such a configuration, the serpentine portion of the heat generating portion is disposed directly above the arc portion of the coolant flow path. Therefore, compared to a conventional configuration in which the heat generating portion does not have a serpentine portion, even if a misalignment occurs between the coolant flow path and the heat generating portion, the coolant flow path and the heat generating portion are more likely to remain overlapped with each other in a top view. This makes it less likely that a local temperature rise due to a misalignment will occur, thereby suppressing variations in the in-plane temperature distribution of the substrate during processing. [Effects of the Invention]

[0011] 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. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view schematically illustrating a configuration of an electrostatic chuck according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing an example of how to divide the regions in which the heat generating parts are arranged. [Figure 3] FIG. 2 is a diagram showing the configuration of a heat generating unit. [Figure 4] 10A and 10B are diagrams showing the configuration of a coolant flow path formed inside a base plate. [Figure 5] FIG. 4 is a diagram showing the positional relationship between a refrigerant flow path and a heat generating portion when viewed from above. [Figure 6] FIG. 4 is a diagram showing the positional relationship between a refrigerant flow path and a heat generating portion when viewed from above. [Figure 7] FIG. 4 is a diagram showing the positional relationship between a refrigerant flow path and a heat generating portion when viewed from above. [Figure 8] 10 is a diagram showing the relationship between the relative amount of displacement between the refrigerant flow path and the heat generating portion and temperature variation. FIG. [Figure 9] FIG. 4 is a diagram showing the positional relationship between a refrigerant flow path and a heat generating portion when viewed from above. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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.

[0014] 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 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.

[0015] 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.

[0016] The dielectric substrate 100 is a substantially disk-shaped member made of a sintered ceramic body. The dielectric substrate 100 contains, for example, high-purity aluminum oxide (Al2O3), but may also contain other materials. The purity, type, and additives of the ceramics in the dielectric substrate 100 can be appropriately set in consideration of the plasma resistance and other properties required of the dielectric substrate 100 in semiconductor manufacturing equipment.

[0017] 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 400. 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."

[0018] An attraction electrode 130 is embedded inside the dielectric substrate 100. The attraction electrode 130 is a thin, flat layer made of a metal material such as tungsten, and is disposed parallel to the surface 110. The attraction electrode 130 may be made of a material other than tungsten, such as molybdenum, platinum, or palladium. When a voltage is applied to the attraction 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 attracting and holding the substrate W. The power supply path may be configured in any of various well-known ways. The attraction electrode 130 may be provided as a single so-called "monopolar" electrode as in this embodiment, or as two so-called "bipolar" electrodes.

[0019] In addition to the above-described chucking electrode 130, a heat generating portion 300 is also embedded inside the dielectric substrate 100. The heat generating portion 300 is a conductor that is routed linearly when viewed from above, and functions as a "heater" that generates heat when supplied with power from an external source to heat the dielectric substrate 100.

[0020] The heat generating part 300 is a thin, flat layer made of a metal material such as tungsten, similar to the chucking electrode 130. The heat generating part 300 is embedded in a position closer to the surface 120 than the chucking electrode 130. Similar to the chucking electrode 130, the heat generating part 300 is disposed parallel to the surface 110.

[0021] When viewed from above, the dielectric substrate 100 is divided into three regions HA as shown in Fig. 2. In this embodiment, a heat generating portion 300 is embedded in each region HA individually. This makes it possible to individually adjust the heat generation amount of each heat generating portion 300 and make the in-plane temperature distribution of the substrate W during processing closer to uniform.

[0022] 3 shows an example of the heat generating part 300 routed in one area HA. ​​In each area HA, one linear heat generating part 300 is routed along a path that passes uniformly through almost the entire area.

[0023] Circular pads 301 and 302 are formed on both ends of the heat generating part 300. The heat generating part 300 and pads 301 and 302 are formed, for example, by etching a thin metal foil, and the entire part functions as a single heater. Note that the shapes of the heat generating part 300 and other parts shown in Figure 3 are schematic and differ from the actual shapes. The same applies to the positions of the pads 301 and 302.

[0024] Returning to FIG. 1, the explanation will continue. A space SP is formed between the dielectric substrate 100 and the substrate W. When processing such as etching is performed in the semiconductor manufacturing equipment, helium gas for temperature adjustment is supplied to the space SP from the outside through a gas hole (not shown). 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.

[0025] A seal ring 111 and dots 112 are provided on a surface 110 that is a mounting surface, and the space SP is formed around these.

[0026] 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 multiple 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.

[0027] 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.

[0028] 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.

[0029] 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 surface 210 of the base plate 200 on the upper side in FIG. 1 is a "bonded surface" that is bonded to the dielectric substrate 100 via a bonding layer 400. The outer shape of the base plate 200 and the outer shape of the surface 210 when viewed from above are both circular, and these are concentric circles.

[0030] The bonding layer 400 is a layer provided between the dielectric substrate 100 and the base plate 200, and bonds them together. The bonding layer 400 is formed by curing an adhesive made of an insulating material. In this embodiment, a silicone adhesive is used as the adhesive. However, the bonding layer 400 may be formed by curing 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 400 so as to reduce the thermal resistance between the dielectric substrate 100 and the base plate 200.

[0031] 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 an insulating film, the dielectric strength of the base plate 200 can be increased.

[0032] A coolant flow path 250 for passing 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 250 from the outside, thereby cooling the base plate 200. Heat generated in the substrate W during the process is transferred to the coolant via the helium gas in the space SP, the dielectric substrate 100, and the base plate 200, and is discharged to the outside together with the coolant. The coolant is supplied to and discharged from the coolant flow path 250 through openings 251 and 252 (not shown in FIG. 1, see FIG. 4) formed on a surface 220 of the base plate 200 opposite to the surface 210.

[0033] 4 is a schematic top view of the configuration of refrigerant flow path 250 formed inside base plate 200. As described above, openings 251 and 252 are provided on surface 220 of base plate 200. Refrigerant flow path 250 connects opening 251 and opening 252, and is formed along a path that passes through substantially the entire base plate 200 in top view. Most of refrigerant flow path 250 is formed to extend along an arc-shaped path that is concentric with base plate 200, which is circular.

[0034] In the coolant flow path 250, the portion that extends along an arc-shaped path in a top view is also referred to as an "arc portion 250A" below. In this embodiment, the center of curvature of the arc portion 250A in a top view is concentric with the base plate 200. However, the two do not necessarily have to be concentric.

[0035] Both openings 251 and 252 are circular openings when viewed from above, and are formed to extend perpendicularly to surface 220 from surface 220 toward coolant flow path 250. The internal spaces of openings 251 and 252 can also be considered to be part of coolant flow path 250. In this embodiment, a coolant is supplied to opening 251 from the outside. The coolant that has passed through coolant flow path 250 and is used to cool the substrate W is discharged from opening 252 to the outside.

[0036] The specific configuration of the heat generating portion 300 will be described. FIG. 5(A) schematically illustrates, in a top view, the configuration of the arc portion 250A of the refrigerant flow path 250 and the heat generating portion 300 located directly above it. As shown in the figure, the portion of the heat generating portion 300 located directly above the arc portion 250A extends along a path that meanders relative to the arc portion 250A. This portion of the heat generating portion 300 that extends along such a meandering path will hereinafter also be referred to as the "serpentine portion 300A." In a top view, at least a portion of the serpentine portion 300A overlaps with the arc portion 250A.

[0037] Note that "meandering relative to the arc portion 250A" means that when tracing along the flow direction of the refrigerant in the arc portion 250A, the relative distance between the arc portion 250A and the serpentine portion 300A along a direction perpendicular to the flow direction fluctuates so as to alternately increase and decrease. In this embodiment, the serpentine portion 300A is routed so that the "distance" fluctuates around zero. However, the center of variation of the "distance" does not have to be zero.

[0038] In this way, the serpentine portion 300A of the heat generating portion 300 is a portion that at least partially overlaps with the arc portion 250A in a top view, and is a portion that snakes relatively to the arc portion 250A. The serpentine portion 250A may be provided in the entire portion of the heat generating portion 300 that overlaps with the arc portion 250A in a top view, or may be provided in only a portion of the portion that overlaps with the arc portion 250A.

[0039] The reason for providing the heat generating unit 300 with the serpentine portion 300A as described above will be explained below. FIG. 5(B) shows a configuration of a comparative example of this embodiment in a manner similar to that of FIG. 5(A). In this comparative example, the heat generating unit 300 does not have the serpentine portion 300A. Directly above the arc portion 250A, the heat generating unit 300 extends along an arc-shaped path such that the entire heat generating unit 300 overlaps with the arc portion 250A. In this comparative example, the heat generating unit 300 is routed along a path such that the center of the width of the heat generating unit 300 and the center of the width of the arc portion 250A overlap each other in a top view.

[0040] The electrostatic chuck 10 according to this embodiment is designed so that the relative positional relationship between the heat generating portion 300 and the arc portion 250A is as shown in FIG. 5A when viewed from above. Similarly, the electrostatic chuck 10 according to the comparative example is designed so that the relative positional relationship between the heat generating portion 300 and the arc portion 250A is as shown in FIG. 5B when viewed from above. In either configuration, at least a portion of the heat generating portion 300 overlaps with the arc portion 250A when viewed from above.

[0041] However, in an actual electrostatic chuck 10, the relative positional relationship between the heat generating portion 300 and the arc portion 250A often does not conform to the strict design. For example, the position of the heat generating portion 300 inside the dielectric substrate 100 may deviate from the designed position. Similarly, the position of the coolant flow path 250 inside the base plate 200 may deviate from the designed position. Furthermore, the relative positional relationship between the dielectric substrate 100 and the base plate 200 may deviate during bonding.

[0042] FIG. 6(A) shows a state in which the heat generating unit 300 of this embodiment has shifted a predetermined distance to the left relative to the arc portion 250A from the state shown in FIG. 5(A) (i.e., the designed position). FIG. 6(B) shows a state in which the heat generating unit 300 of the comparative example has shifted a predetermined distance to the left relative to the arc portion 250A from the state shown in FIG. 5(B) (i.e., the designed position). The respective amounts of shift (the "predetermined distance" described above) are the same. Thus, FIG. 6 shows an example in which the heat generating unit 300 has shifted slightly to the left from the state shown in FIG. 5.

[0043] In the state of Fig. 6, in either configuration, at least a portion of the heat generating portion 300 overlaps with the arc portion 250A in top view. However, in the comparative example of Fig. 6(B), the area of ​​the portion of the heat generating portion 300 that overlaps with the arc portion 250A is reduced to half compared to the state of Fig. 5(B).

[0044] 7(A) shows a state in which the heat generating portion 300 of this embodiment has been further displaced a predetermined distance to the left relative to the arc portion 250A from the state shown in FIG. 6(A). FIG. 7(B) shows a state in which the heat generating portion 300 of the comparative example has been further displaced a predetermined distance to the left relative to the arc portion 250A from the state shown in FIG. 6(B). The respective amounts of displacement (the "predetermined distance" described above) are the same. Thus, FIG. 7 shows an example in which the heat generating portion 300 has been significantly displaced to the left from the state shown in FIG. 5.

[0045] As shown in Fig. 7(A), the heat generating portion 300 (serpentine portion 300A) according to this embodiment remains partially overlapped with the arc portion 250A even after the large positional deviation described above occurs. On the other hand, as shown in Fig. 7(B), the heat generating portion 300 according to the comparative example does not overlap with the arc portion 250A at all after the large positional deviation described above occurs.

[0046] 7(B), the portion of the substrate W directly above the heat generating portion 300 is directly heated by the heat generating portion 300, but is not directly cooled by the coolant flow path 250, so the temperature of this portion is relatively likely to rise. Also, the portion of the substrate W directly above the coolant flow path 250 is directly cooled by the coolant flow path 250, but is not directly heated by the heat generating portion 300, so the temperature of this portion is relatively likely to drop. For the reasons described above, in the configuration according to the comparative example, the variation in the in-plane temperature distribution of the substrate W in the state of FIG. 7(B) is likely to be large.

[0047] In contrast, in this embodiment, even after a positional shift of the same magnitude as in the comparative example of Fig. 7(B) occurs, a portion of the heat generating portion 300 overlaps with the arc portion 250A, as shown in Fig. 7(A). In other words, compared to the configuration of the comparative example, even when a shift occurs in the positional relationship between the coolant flow path 250 and the heat generating portion 300, the coolant flow path 250 and the heat generating portion 300 are more likely to maintain a state in which they overlap with each other in a top view. Therefore, the temperature difference between the portion of the substrate W directly above the heat generating portion 300 and the portion directly above the coolant flow path 250 is kept smaller than in the state of Fig. 7(B).

[0048] Figure 8(A) shows a schematic graph of the relationship between the positional deviation (horizontal axis) between the heat generating portion 300 and the arc portion 250A in the electrostatic chuck 10 according to this embodiment and the magnitude of variation in the in-plane temperature distribution of the substrate W (vertical axis).

[0049] The "positional deviation" shown on the horizontal axis of FIG. 8(A) is a parameter that indicates, for example, in units of "mm," how much the relative positional relationship between the heat generating portion 300 and the arc portion 250A deviates from the design. When the positional relationship is as designed, the positional deviation is 0. The "ΔT" shown on the vertical axis of the same figure is a parameter that indicates the magnitude of variation in the in-plane temperature distribution of the substrate W during processing. For example, an example of such a parameter that can be used is the difference in temperature between the hottest and coldest portions of the substrate W.

[0050] 8A, in the electrostatic chuck 10 according to this embodiment, ΔT is smallest when the positional misalignment is 0. As the absolute value of the positional misalignment increases, ΔT gradually increases, and when the absolute value of the positional misalignment reaches x1, ΔT reaches its maximum. x1 represents the positional misalignment at the time when the heat generating portion 300 and the arc portion 250A no longer overlap each other in top view. In this embodiment, x1 can also be said to be the magnitude of the positional misalignment required to maximize ΔT.

[0051] Figure 8(B) shows, in a manner similar to Figure 8(A), the relationship between the positional deviation (horizontal axis) between the heat generating portion 300 and the arc portion 250A in the electrostatic chuck 10 according to the comparative example such as Figure 5(B) and the magnitude of variation in the in-plane temperature distribution of the substrate W (vertical axis).

[0052] 8B, in the electrostatic chuck 10 according to the comparative example, ΔT is smallest when the positional misalignment is 0. As the absolute value of the positional misalignment increases, ΔT gradually increases, and when the absolute value of the positional misalignment reaches x2, ΔT reaches its maximum. x2 represents the positional misalignment at the time when the heat generating portion 300 and the arc portion 250A no longer overlap each other in top view. It can also be said that x2 is the magnitude of the positional misalignment required to maximize ΔT in the comparative example.

[0053] The magnitude of the misalignment required to maximize ΔT is larger in this embodiment (x1) than in the comparative example (x2). This is because the heat generating unit 300 of this embodiment has a serpentine portion 300A located directly above the arc portion 250A. In this embodiment, because the heat generating unit 300 is provided with the serpentine portion 300A, the slope of the increase in ΔT when misalignment occurs is smaller than in the comparative example. That is, in this embodiment, a local temperature rise of the substrate W due to misalignment is less likely to occur, making it possible to suppress variations in the in-plane temperature distribution of the substrate W during processing more effectively than in the past.

[0054] The shape of the serpentine portion 300A is not limited to the shape of this embodiment. For example, as shown in the modified example of Fig. 9, when the positional deviation is zero, the entire serpentine portion 300A, not just a part of it, may overlap with the arc portion 250A in top view.

[0055] In this embodiment, a heater for heating the dielectric substrate 100 is provided inside the dielectric substrate 100 as the heat generating portion 300. Instead of this configuration, a configuration may be adopted in which the heater for heating the dielectric substrate 100 is provided outside the dielectric substrate 100 (for example, between the dielectric substrate 100 and the base plate 200) as a heater unit. In this case, the heat generating portion 300 having the serpentine portion 300A is provided inside the heater unit.

[0056] 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. [Explanation of symbols]

[0057] 10: Electrostatic chuck 100: Dielectric substrate 110: Face 200: Base plate 250: Refrigerant flow path 250A: Arc section 300: Heat generating part 300A: Serpentine section W: Substrate

Claims

1. a dielectric substrate having a mounting surface on which an object to be attracted is placed; a heat generating portion which is a linear conductor and receives power from an external source to generate heat and heat the dielectric substrate; a base plate joined to the dielectric substrate and having a coolant flow path formed therein through which a coolant passes; When viewed from a direction perpendicular to the placement surface, The refrigerant flow path has an arc portion that extends along an arc-shaped path, The electrostatic chuck according to claim 1, wherein the heat generating portion has a serpentine portion that is at least partially overlapping with the arc portion and that serpentines relative to the arc portion.

2. When viewed from a direction perpendicular to the placement surface, 2. The electrostatic chuck according to claim 1, wherein the center of curvature of the arcuate portion coincides with the center of the base plate.

Images