electrostatic chuck

Abstract

To provide an electrostatic chuck that can suppress dielectric breakdown in through-holes of heater units. [Solution] The electrostatic chuck 10 comprises a dielectric substrate 100 and a heater unit 300 for heating the dielectric substrate 100. The heater unit 300 includes a heating layer that generates heat when power is supplied from an external source, an insulating layer 320 that houses the heating layer, a first conductor plate 310A that is in contact with the insulating layer 320 from the dielectric substrate 100 side, and a second conductor plate 310B that is in contact with the insulating layer 320 from the side opposite to the dielectric substrate 100. A through hole 304 is formed in the heater unit 300. In this electrostatic chuck 10, the diameter D2 of the through hole 304 formed in the second conductor plate 310B is larger than the diameter D3 of the through hole 304 formed in the insulating layer 320.

Description

Technical Field

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

Background Art

[0002] For example, in semiconductor manufacturing equipment such as an etching 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 an adsorption electrode and a base plate for supporting the dielectric substrate. When a voltage is applied to the adsorption electrode, an electrostatic force is generated, and the substrate placed on the dielectric substrate is adsorbed and held.

[0003] During the processing of the substrate, it is required to make the in-plane temperature distribution of the substrate as uniform as possible. In order to be able to adjust the in-plane temperature distribution of the substrate with high accuracy, in recent years, an electrostatic chuck equipped with a heater has also been developed and is already in practical use. The heater may be provided inside the dielectric substrate, but as described in Patent Document 1 below, for example, it may also be provided between the dielectric substrate and the base plate as a heater unit.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The inventors of the present invention are considering a configuration of a heater unit for heating a dielectric substrate, which includes an insulating layer that houses a heat generating layer inside and a pair of conductor plates that sandwich the insulating layer from above and below.

[0006] The heater unit needs to have through-holes that penetrate the entire unit, such as lift pin holes and gas supply holes. In a heater unit with the above configuration, there is a possibility of dielectric breakdown occurring inside the through-hole, along the path from one conductor plate to the other.

[0007] This invention has been made in view of these problems, and its objective is to provide an electrostatic chuck that can suppress dielectric breakdown in through holes of a heater unit. [Means for solving the problem]

[0008] To solve the above problems, the electrostatic chuck according to the present invention comprises a dielectric substrate having a mounting surface on which an object to be adsorbed is placed, and a heater unit bonded to the dielectric substrate and heating the dielectric substrate. The heater unit has a heating layer that generates heat when power is supplied from the outside, an insulating layer that houses the heating layer, a first conductor plate arranged to contact the insulating layer from the dielectric substrate side, and a second conductor plate arranged to contact the insulating layer from the opposite side of the dielectric substrate. The heater unit has a through hole formed in a direction perpendicular to the mounting surface that penetrates the entire heater unit. In this electrostatic chuck, the diameter of the through hole formed in the second conductor plate is larger than the diameter of the through hole formed in the insulating layer.

[0009] In the electrostatic chuck with the above configuration, a portion of the insulating layer protrudes so as to obstruct the path from the edge of the through-hole formed in the first conductor plate to the edge of the through-hole formed in the second conductor plate. Since dielectric breakdown from the first conductor plate to the second conductor plate inside the through-hole can only occur through a path that bypasses the protruding insulating layer, the occurrence of such dielectric breakdown can be suppressed. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an electrostatic chuck that can suppress dielectric breakdown in through holes of a heater unit. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing the configuration of the electrostatic chuck according to the first embodiment. [Figure 2] This is a schematic exploded assembly diagram showing the configuration of the heater unit. [Figure 3] This figure shows an example of the arrangement of sub-heater layers in a heater unit. [Figure 4] This diagram shows the configuration of one subheater layer. [Figure 5] This figure shows an example of the arrangement of the main heater layer in a heater unit. [Figure 6] This diagram shows the configuration of one main heater layer. [Figure 7] This is a diagram to explain the role of the bypass layer, etc. [Figure 8] This is a schematic cross-sectional view showing a part of the configuration of the heater unit according to the first embodiment. [Figure 9] This is a schematic cross-sectional view showing a part of the configuration of the heater unit according to the second embodiment. [Figure 10] This is a schematic cross-sectional view showing a part of the configuration of a heater unit related to a comparative example. [Modes for carrying out the invention]

[0012] This embodiment will be described below with reference to the attached drawings. To facilitate understanding of the explanation, the same reference numerals are used for identical components in each drawing whenever possible, and redundant explanations are omitted.

[0013] A first embodiment will be described. The electrostatic chuck 10 according to this embodiment is used to attract and hold a substrate W to be processed by electrostatic force 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 apparatus other than semiconductor manufacturing apparatus.

[0014] FIG. 1 shows a schematic 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 heater unit 300.

[0015] The dielectric substrate 100 is a substantially disk-shaped member made of a ceramic sintered body. The dielectric substrate 100 includes, for example, high-purity aluminum oxide (Al2O3), but may include other materials. The purity, type, additives, etc. of the ceramic in the dielectric substrate 100 can be appropriately set in consideration of the plasma resistance, etc. required for the dielectric substrate 100 in a semiconductor manufacturing apparatus.

[0016] The upper surface 110 of the dielectric substrate 100 in FIG. 1 is the "placement surface" on which the substrate W is placed. Also, the lower surface 120 of the dielectric substrate 100 in FIG. 1 (that is, the side opposite to the placement surface) is the "bonding surface" that is bonded to the heater unit 300 via the bonding layer 410. The direction along the direction perpendicular to the surface 110 and the perspective when viewing the electrostatic chuck 10 from the surface 110 side will also be referred to as "top view" hereinafter.

[0017] An adsorption electrode 130 is embedded inside the dielectric substrate 100. The adsorption electrode 130 is a thin flat plate-shaped layer formed of a metal material such as palladium, and is arranged to be parallel to the surface 110. As the material of the adsorption electrode 130, in addition to palladium, molybdenum, platinum, tungsten, etc. may also be used. 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, and thereby the substrate W is adsorbed and held. As the configuration of the power supply path, various known configurations can be adopted. The adsorption electrode 130 may be provided only one as a so-called "unipolar" electrode as in this embodiment, or may be provided two as a so-called "bipolar" electrode.

[0018] As shown in FIG. 1, a space SP is formed between the dielectric substrate 100 and the substrate W. When a process such as etching is performed in a semiconductor manufacturing apparatus, helium gas for temperature adjustment is supplied from the outside to the space SP through a gas hole 140 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.

[0019] A seal ring 111 and dots 112 are provided on the surface 110 which is a mounting surface, and the above-described space SP is formed around these.

[0020] 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 on the substrate W. Note that 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.

[0021] In FIG. 1, the portion marked with 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 as a result of digging down a part of the surface 110 to the position of the bottom surface 116.

[0022] The dots 112 are circular protrusions protruding from the bottom surface 116. A plurality of dots 112 are provided and are arranged substantially evenly and dispersedly on the mounting surface of the dielectric substrate 100. The upper end of each dot 112 is part of the surface 110 and abuts on the substrate W. By providing a plurality of such dots 112, the deflection of the substrate W is suppressed.

[0023] Gas holes 140 are formed in the dielectric substrate 100. The gas holes 140 are holes for supplying helium gas to the space SP, and are circular through holes formed perpendicular to the surface 110. Multiple gas holes 140 are formed, but only one is shown in Figure 1. The helium gas supplied from the outside passes sequentially through the gas holes 240 formed in the base plate 200 (described later) and the through holes 304 formed in the heater unit 300 (described later), and then is supplied to the space SP through the gas holes 140.

[0024] A porous material, such as alumina, may be placed inside the gas hole 140. This configuration makes it possible to ensure gas flow through the gas hole 140 while suppressing dielectric breakdown along the path through the gas hole 140.

[0025] The base plate 200 is a roughly disc-shaped member that supports the dielectric substrate 100 and the heater unit 300. The base plate 200 is made of a metallic material such as aluminum. Of the base plate 200, the upper surface 210 in Figure 1 is the "bonded surface" which is bonded to the heater unit 300 via the bonding layer 420. The base plate 200 is bonded to the side of the heater unit 300 opposite to the dielectric substrate 100 side.

[0026] A refrigerant channel 250 for circulating refrigerant is formed inside the base plate 200. When etching or other processes are performed in the semiconductor manufacturing equipment, refrigerant is supplied from the outside to the refrigerant channel 250, thereby cooling the base plate 200. During processing, the heat generated in the substrate W is transferred to the refrigerant 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 refrigerant. The supply and discharge of refrigerant to and from the refrigerant channel 250 is performed through an opening (not shown) formed on the surface 220 of the base plate 200 opposite to the surface 210.

[0027] Gas holes 240 are formed in each of the base plate 200 at positions that overlap with the gas holes 140 when viewed from above. The gas holes 240 are circular through holes formed to extend perpendicularly from surface 210 to surface 220. The central axis of the gas holes 240 coincides with the central axis of the gas holes 140. As mentioned earlier, the gas holes 140 are part of the path for supplying helium gas to the space SP.

[0028] Furthermore, the gas holes 240 may be formed to extend in a straight line as in this embodiment, but they may also be formed to bend midway from surface 210 to surface 220. Alternatively, the multiple gas holes 240 on surface 210 may be consolidated into a few flow paths inside the base plate 200, and these flow paths may be extended to surface 220.

[0029] A porous material, such as alumina, may be placed inside the gas hole 240. This configuration makes it possible to ensure gas flow through the gas hole 240 while suppressing dielectric breakdown along the path through the gas hole 240.

[0030] An insulating film may be formed on the surface of the base plate 200. As the insulating film, for example, an alumina film formed by thermal spraying can be used. By covering the surface of the base plate 200 with an insulating film, the dielectric strength of the base plate 200 can be increased.

[0031] The heater unit 300 receives power from an external source to generate heat and heat the dielectric substrate 100. As will be explained later, the heater unit 300 is provided with multiple heat-generating parts 331, etc., and the amount of heat generated in each heat-generating part 331, etc. can be individually adjusted. By individually adjusting the amount of heat generated in each part, the in-plane temperature distribution of the substrate W during processing can be made more uniform.

[0032] The heater unit 300 is sandwiched between the dielectric substrate 100 and the base plate 200, and is bonded to each of them. The heater unit 300 is bonded to the dielectric substrate 100 via a bonding layer 410, and the heater unit 300 is bonded to the base plate 200 via a bonding layer 420. The bonding layers 410 and 420 are layers formed by curing, for example, a silicone adhesive. Multiple particulate fillers are arranged inside each to increase thermal conductivity. As the filler, for example, particles mainly composed of alumina can be used.

[0033] In the heater unit 300, through-holes 304 are formed at positions that overlap with the gas holes 140 when viewed from above. The through-holes 304 are circular through-holes formed to extend in a direction perpendicular to the surface 110, and penetrate the entire heater unit 300. The central axis of the through-holes 304 coincides with the central axis of the gas holes 140. As mentioned earlier, the through-holes 304 are part of the path for supplying helium gas to the space SP.

[0034] Note that in Figure 1, the shape of the through-hole 304 is depicted in a simplified manner. The inner diameter of the through-hole 304 is not uniform throughout, but varies depending on its height. The shape of the through-hole 304 will be explained later.

[0035] The specific configuration of the heater unit 300 will now be described. Figure 2 shows the configuration of the heater unit 300 as a schematic exploded assembly diagram. As shown in the figure, the heater unit 300 includes a first conductor plate 310A, a second conductor plate 310B, an insulating layer 320A, a sub-heater layer 330, an insulating layer 320B, a main heater layer 350, an insulating layer 320C, a bypass layer 370, an insulating layer 320D, and a power supply terminal 390. In this embodiment, the sub-heater layer 330, the main heater layer 350, and the bypass layer 370 are arranged from top to bottom in Figure 2, but the order of arrangement may differ from that of this embodiment.

[0036] The first conductor plate 310A is a substantially disc-shaped member and is provided at the upper end of the heater unit 300 in Figure 2. The first conductor plate 310A is the portion that is bonded to the surface 120 of the dielectric substrate 100 via the bonding layer 410.

[0037] The second conductor plate 310B is a substantially disc-shaped member and is provided at the lower end of the heater unit 300 in Figure 2. The second conductor plate 310B is the part that is joined to the surface 210 of the base plate 200 via the bonding layer 420.

[0038] The first conductor plate 310A and the second conductor plate 310B are members that reinforce the entire heater unit 300 by sandwiching the entire sub-heater layer 330, main heater layer 350, and bypass layer 370 between them. In this embodiment, both the first conductor plate 310A and the second conductor plate 310B are made of metal, but they may be made of other conductive materials. Each of the members constituting the heater unit 300, such as the first conductor plate 310A, has the aforementioned through-holes 304 formed therein, but these are not shown in Figure 2.

[0039] The insulating layer 320A is provided between the first conductor plate 310A and the sub-heater layer 330, and is a layer for electrically insulating the two. The insulating layer 320A also plays a role in physically joining the two. In this embodiment, the insulating layer 320A is a polyimide film, but it may contain components other than polyimide, and may be formed from a material different from polyimide.

[0040] The subheater layer 330 is the part that generates heat by receiving power from an external source. The subheater layer 330 corresponds to the "heat-generating layer" in this embodiment. In Figure 2, the subheater layer 330 is schematically depicted as a single disc, but in reality, the subheater layer 330 is divided into multiple regions, and each region can be heated individually. The specific configuration of the subheater layer 330 will be described later.

[0041] The insulating layer 320B is provided between the sub-heater layer 330 and the main heater layer 350, and serves to electrically insulate them from each other. The insulating layer 320B also plays a role in physically joining the two layers. In this embodiment, the insulating layer 320B is a polyimide film, but it may contain components other than polyimide, and may be formed from a material different from polyimide.

[0042] The main heater layer 350 is the part that generates heat by receiving power from an external source. The main heater layer 350, along with the sub-heater layer 330 mentioned earlier, corresponds to the "heat-generating layer" in this embodiment. In Figure 2, the main heater layer 350 is schematically depicted as a single disc, but in reality, the main heater layer 350 is divided into multiple regions, and each region can be heated individually. The specific configuration of the main heater layer 350 will be explained later.

[0043] The main heater layer 350 generates more heat per unit area compared to the sub-heater layer 330 mentioned earlier. The main heater layer 350 is intended to raise the overall temperature of the dielectric substrate 100 in a short time. The sub-heater layer 330 is intended to adjust the temperature of each part of the dielectric substrate 100 and to make the in-plane temperature distribution of the substrate W more uniform. Thus, in this embodiment, two heater layers are provided separately, each according to its respective role.

[0044] The insulating layer 320C is provided between the main heater layer 350 and the bypass layer 370, and serves to electrically insulate them from each other. The insulating layer 320C also plays a role in physically joining the two layers. In this embodiment, the insulating layer 320C is a polyimide film, but it may contain components other than polyimide, and may be formed from a material different from polyimide.

[0045] The bypass layer 370 is a layer for electrically connecting the power supply terminal 390 (described later) to the sub-heater layer 330 or the main heater layer 350. In Figure 2, the bypass layer 370 is schematically depicted as a single disc, but in reality, the bypass layer 370 is divided into multiple parts. By providing the bypass layer 370 in the middle of the electrical circuit connected to the sub-heater layer 330, etc., it becomes possible to adjust the position of the power supply terminal 390. Each of the divided bypass layers 370 is electrically connected to either the sub-heater layer 330 or the main heater layer 350 in part.

[0046] The insulating layer 320D is provided between the bypass layer 370 and the second conductor plate 310B, and is a layer for electrically insulating the two. The insulating layer 320D also plays a role in physically joining the two. In this embodiment, the insulating layer 320D is a polyimide film, but it may contain components other than polyimide, and may be formed from a material different from polyimide.

[0047] During the manufacturing of the heater unit 300, the layers shown in Figure 2 are stacked and the entire assembly is pressurized and heated. As a result, the entire assembly is bonded together as a single unit via the insulating layer 320A, which is a polyimide film.

[0048] Once the above bonding is complete, insulating layers 320A, 320B, 320C, and 320D are bonded together and become a single unit. The entire integrated insulating layer in this manner will hereafter be referred to as "insulating layer 320". Inside insulating layer 320 are a sub-heater layer 330, which is a heating layer, a main heater layer 350, which is also a heating layer, and a bypass layer 370. The first conductor plate 310A is in contact with insulating layer 320 from the dielectric substrate 100 side, and the second conductor plate 310B is in contact with insulating layer 320 from the opposite side of the dielectric substrate 100.

[0049] The power supply terminal 390 is the part that receives power from the outside to generate the necessary electricity for heating the subheater layer 330 and the like. In this embodiment, the power supply terminal 390 is formed as an elongated rod-shaped plug, with one end joined to the bypass layer 370. Multiple power supply terminals 390 are provided according to the number of bypass layers 370, but only two of them are shown in Figure 2. Through holes (not shown) are formed in the base plate 200 at positions corresponding to the power supply terminals 390, and the power supply terminals 390 are inserted through these through holes.

[0050] The configuration of the subheater layer 330 will now be described. As mentioned earlier, the subheater layer 330 is divided into multiple regions, and each region can be heated individually. Figure 3 shows an example of how the subheater layer 330 is divided, viewed from above. In this example, the subheater layer 330 is divided into a total of 24 regions HA.

[0051] The subheater layer 330 is configured as linear heating elements 331, which are individually routed within each region HA. In other words, a total of 24 heating elements 331 are provided in this embodiment.

[0052] Figure 4 shows an example of a heat-generating element 331 routed within a single region HA. In each region HA, a single linear heat-generating element 331 is routed along a path that passes through almost the entire area equally. The heat-generating element 331 is the part that generates heat when power is supplied from an external source. Although not shown in the figure, in areas where through-holes 304 are formed, the heat-generating element 331 is routed along a path that avoids the through-holes 304.

[0053] Circular pad portions 332 and 333 are formed at each end of the heating element 331. The heating element 331 and the pad portions 332 and 333 are formed, for example, by etching a thin metal foil, and the whole structure functions as a single subheater layer 330. In other words, one subheater layer 330 is provided for each of the 24 regions HA.

[0054] Note that the shape of the heating element 331 shown in Figure 4 is schematic and differs from the actual shape. The same applies to the positions of the pads 332 and 333.

[0055] The configuration of the main heater layer 350 will now be described. Similar to the sub-heater layer 330, the main heater layer 350 is also divided into multiple regions, and each region can be heated individually. Figure 5 shows an example of how the main heater layer 350 is divided, viewed from above. In this example, the main heater layer 350 is divided into a total of three regions HB.

[0056] The main heater layer 350 is configured as linear heating elements 351, which are routed individually within each region HB. In other words, in this embodiment, a total of three heating elements 351 are provided.

[0057] Figure 6 shows an example of a heat-generating element 351 routed within one region HB. In each region HB, a single linear heat-generating element 351 is routed along a path that passes through almost the entire area equally. The heat-generating element 351 is the part that generates heat when power is supplied from an external source. Although not shown in the figure, in areas where through-holes 304 are formed, the heat-generating element 351 is routed along a path that avoids the through-holes 304. The number of heat-generating elements 351 (3 in total) is less than the number of heat-generating elements 331 (24 in total).

[0058] Circular pad portions 352 and 353 are formed at each end of the heating element 351. The heating element 351 and the pad portions 352 and 353 are formed, for example, by etching a thin metal foil, and the whole structure functions as a single main heater layer 350. In other words, one main heater layer 350 is provided for each of the three regions HB.

[0059] Note that the shape of the heating element 351 shown in Figure 6 is schematic and differs from the actual shape. The same applies to the positions of the pads 352 and 353.

[0060] Figure 7 shows a schematic perspective view of the configuration of two regions HA, two sub-heater layers 330 arranged within them, and bypass layers 370 connected to the sub-heater layers 330. One of the two regions HA shown in Figure 7 will be referred to as "region HA1" below. The other region HA will be referred to as "region HA2" below. Note that the shape of the heating element 331 etc. shown in Figure 7 is schematic and differs from the actual shape.

[0061] As mentioned earlier, the bypass layer 370 is divided into multiple parts. In Figure 7, only three of the divided bypass layer 370 are shown. Of the three divided bypass layer 370, the one labeled "371" in Figure 7 is positioned so as to overlap with only one region HA in a top view. In other words, it is individually positioned directly beneath each region HA. The portion of the bypass layer 370 that is positioned in this manner will also be referred to as "bypass layer 371" below.

[0062] Of the divided bypass layers 370, the one labeled "372" in Figure 7 is positioned to overlap with both region HA1 and region HA2 in a top view. This portion of the bypass layer 370 will also be referred to as "bypass layer 372" below.

[0063] In the subheater layer 330 located in region HA1, a pad portion 332 at one end of the heating element 331 is electrically connected to the bypass layer 371 directly below it. A pad portion 333 at the other end of the heating element 331 is electrically connected to the bypass layer 372.

[0064] The same applies to the subheater layer 330 located in region HA2, where a pad portion 332 at one end of the heating element 331 is electrically connected to the bypass layer 371 directly below it. A pad portion 333 at the other end of the heating element 331 is electrically connected to the bypass layer 372.

[0065] Furthermore, the electrical connections of each part as described above are achieved, for example, by welding the upper and lower layers together. To make the configuration easier to understand, in Figure 7, each welded part is schematically depicted as a rod-shaped member extending in a straight line (the part labeled 301). In the parts that overlap with each welded part in the top view, openings are formed in each of the layers between the subheater layer 330 and the bypass layer 370 (insulating layer 320B, main heater layer 350, and insulating layer 320C), and the subheater layer 330 and the bypass layer 370 are directly connected through these openings.

[0066] The subheater layer 330 and the bypass layer 370 may be electrically connected by welding, as in this embodiment, but they may also be electrically connected by other means. For example, they may be electrically connected via a conductive member extending vertically. In either configuration, the subheater layer 330 and the bypass layer 370 are connected via an electrical circuit labeled 301 in Figure 7. This electrical circuit will also be referred to as "connection section 301" below.

[0067] One end of a power supply terminal 390 is connected to each bypass layer 371 from below in Figure 7. A voltage is individually applied to each of these power supply terminals 390 from an external DC power supply. Similarly, one end of a power supply terminal 390 is also connected to the bypass layer 372 from below in Figure 7. This power supply terminal 390 is grounded.

[0068] As described above, each subheater layer 330 provided in each region HA has one pad portion 332 connected to an individual DC power supply via a bypass layer 371, and the other pad portion 333 is grounded via a common bypass layer 372. Other subheater layers 330 not shown in Figure 7 are also connected to a DC power supply in a similar configuration. This configuration makes it possible to supply power individually to each of the multiple subheater layers 330 and adjust the amount of heat generated in each part.

[0069] It is also possible to supply power to the subheater layer 330 directly from the power supply terminal 390 without going through the bypass layer 370. However, by configuring the power supply to go through the bypass layer 370 as in this embodiment, it becomes possible to increase the flexibility of the placement of the power supply terminal 390 and to consolidate the grounded power supply terminal 390 into one.

[0070] The power supply to each main heater layer 350 is also achieved by the same configuration as described above. The specific configuration is the same as that shown in Figure 7, so its explanation and illustration are omitted.

[0071] The configuration of the heater unit 300 near the through-hole 304 will now be described. Figure 8 shows a schematic cross-sectional view of a portion of the heater unit 300 when it is cut by a plane passing through the central axis of the through-hole 304. In this figure, the entire insulating layer 320 is depicted as a single block, and the heat-generating parts 331 and 351 housed inside the insulating layer 320 are not shown. The heat-generating parts 331 and 351 are routed along paths that avoid the through-hole 304 when viewed from above. Therefore, the heat-generating parts 331 and 351 are not exposed on the inner surface of the through-hole 304.

[0072] The portion of the through-hole 304 formed in the first conductor plate 310A will also be referred to as "through-hole 314A" below. The portion of the through-hole 304 formed in the insulating layer 320 will also be referred to as "through-hole 324" below. Furthermore, the portion of the through-hole 304 formed in the second conductor plate 310B will also be referred to as "through-hole 314B" below.

[0073] As mentioned earlier, the inner diameter of the through-holes 304 is not uniform throughout. As shown in Figure 8, the diameter D2 of the through-hole 304 (through-hole 314B) formed in the second conductor plate 310B is larger than the diameter D3 of the through-hole 304 (through-hole 324) formed in the insulating layer 320. Similarly, the diameter D1 of the through-hole 304 (through-hole 314A) formed in the first conductor plate 310A is also larger than the diameter D3 of the through-hole 304 (through-hole 324) formed in the insulating layer 320.

[0074] To clarify the reason for this configuration, the configuration of the electrostatic chuck 10 in the comparative example will be described. In the configuration of the comparative example shown in Figure 10, the inner diameter of the through hole 304 is uniform throughout. That is, the diameter D1 of the through hole 314A, the diameter D2 of the through hole 314B, and the diameter D3 of the through hole 324 are all the same size.

[0075] When substrate W is being processed in semiconductor manufacturing equipment, substrate W and electrostatic chuck 10 are exposed to plasma. Due to the effects of the plasma, a potential difference may occur between the first conductor plate 310A and the second conductor plate 310B. If this potential difference becomes large, dielectric breakdown will occur inside the through hole 304 along the path from the first conductor plate 310A to the second conductor plate 310B. Specifically, dielectric breakdown occurs along the path indicated by arrow AR, from the edge of the through hole 314A in the first conductor plate 310A to the edge of the through hole 314B in the second conductor plate 310B.

[0076] Therefore, in the electrostatic chuck 10 according to this embodiment, in order to suppress the occurrence of dielectric breakdown along such a path, the diameter D2 of the through hole 314B is made larger than the diameter D3 of the through hole 324. As shown in Figure 8, in the configuration where D2 > D1 as in this embodiment, a part of the insulating layer 320 protrudes so as to obstruct the path from the edge of the through hole 314A in the first conductor plate 310A to the edge of the through hole 314B in the second conductor plate 310B. Since dielectric breakdown from the first conductor plate 310A to the second conductor plate 310B inside the through hole 304 can only occur in a path that greatly bypasses the protruding insulating layer 320, the occurrence of dielectric breakdown as shown in Figure 10 can be suppressed.

[0077] In the heater unit 300, a through hole for inserting a lift pin, for example, is also formed at a location other than directly below the gas hole 140. The configuration of the through hole 304 and its vicinity as shown in Figure 8 can also be adopted for other through holes and their vicinity formed in the heater unit 300.

[0078] The second embodiment will now be described. The following will primarily focus on the differences from the first embodiment, while common points will be omitted as appropriate.

[0079] Figure 9 schematically shows a part of the configuration of the heater unit 300 according to this embodiment as a cross-sectional view similar to that in Figure 8. As shown in Figure 9, in this embodiment as well, the diameter D2 of the through hole 304 (through hole 314B) formed in the second conductor plate 310B is larger than the diameter D3 of the through hole 304 (through hole 324) formed in the insulating layer 320. Furthermore, in this embodiment, the diameter D1 of the through hole 304 (through hole 314A) formed in the first conductor plate 310A is smaller than the diameter D2 of the through hole 304 (through hole 314B) formed in the second conductor plate 310B, and is the same size as the diameter D3 of the through hole 304 (through hole 324) formed in the insulating layer 320.

[0080] The first conductor plate 310A is the portion that is joined to the dielectric substrate 100. If the diameter D1 of the through hole 314A formed in the first conductor plate 310A becomes too large, the heat transfer path between the heater unit 300 and the dielectric substrate 100 will be narrowed by the amount of the through hole 314A. As a result, there is a possibility that the temperature of the substrate W may rise or fall locally at the position directly above the through hole 304. In order to suppress such temperature changes, it is preferable to reduce the diameter D1 of the through hole 314A formed in the first conductor plate 310A, as in this embodiment, to ensure that the heat transfer path between the heater unit 300 and the dielectric substrate 100 is sufficiently wide.

[0081] The embodiments have been described above with reference to specific examples. However, this disclosure is not limited to these specific examples. Modifications made to these specific examples by those skilled in the art are also included within the scope of this disclosure, as long as they retain the features of this disclosure. The elements, their arrangement, conditions, shapes, etc., of each of the aforementioned specific examples are not limited to those illustrated and can be modified as appropriate. The elements of each of the aforementioned specific examples can be combined in different ways as appropriate, as long as no technical inconsistencies arise. [Explanation of symbols]

[0082] 10: Electrostatic Chuck 100: Dielectric substrate 110: Face 300: Heater unit 304: Through hole 330: Subheater layer 310A: First conductor plate 310B: Second conductor plate 320: Insulating layer 350: Main heater layer D1,D2,D3:Diameter W: Circuit board

Claims

1. A dielectric substrate having a mounting surface on which an object to be adsorbed is placed, The system comprises a heater unit bonded to the dielectric substrate and used to heat the dielectric substrate, The aforementioned heater unit is A heating layer that generates heat when power is supplied from an external source, An insulating layer housing the aforementioned heating layer, A first conductor plate is arranged so as to be in contact with the insulating layer from the dielectric substrate side, The device comprises a second conductive plate arranged to contact the insulating layer from the side opposite to the dielectric substrate, The heater unit has a through hole formed in a direction perpendicular to the mounting surface described above, which penetrates the entire heater unit. An electrostatic chuck characterized in that the diameter of the through hole formed in the second conductor plate is larger than the diameter of the through hole formed in the insulating layer.

2. The electrostatic chuck according to claim 1, characterized in that the diameter of the through hole formed in the first conductor plate is smaller than the diameter of the through hole formed in the second conductor plate.

3. The electrostatic chuck according to claim 2, characterized in that the diameter of the through hole formed in the first conductor plate is the same as the diameter of the through hole formed in the insulating layer.

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