Electrostatic chuck

Abstract

This electrostatic chuck is provided with: a dielectric substrate; a base plate which is a metal member bonded to the dielectric substrate and in which air holes are formed; and a ventilation insert disposed inside the air hole. The ventilation insert is provided with: a porous part which is a part formed by porous ceramic having air permeability; and a dense part which is a portion formed of a dense ceramic that does not have air permeability and which surrounds the porous part over the entire circumference from the outer circumferential side. The porous part and the dense part are integrated with each other by sintering instead of a bonding material formed of a material other than ceramic.

Description

Technical Field

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

[0002] For example, in semiconductor manufacturing equipment such as CVD equipment, 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 supporting the dielectric substrate, and these have a structure in which they are joined to each other. When a voltage is applied to the adsorption electrode, an electrostatic force is generated to adsorb and hold the substrate placed on the dielectric substrate.

[0003] In order to adjust the temperature of the substrate being processed, an inert gas such as helium is supplied to the space between the dielectric substrate and the substrate. For example, Patent Document 1 below describes that the inert gas is supplied to the space through gas holes formed in the susceptor plate and the dielectric substrate.

[0004] During the processing of the substrate, the potential of the substrate and its surroundings increases with the injection of plasma or the application of voltage to the adsorption electrode. On the other hand, the potential of the base plate is maintained at the same potential as that of the peripheral components constituting the semiconductor manufacturing device (for example, the ground potential). Therefore, in the base plate, especially on the inner surface of the pores, insulation breakdown is likely to occur between high-potential portions. If part of the plasma flows into the inner side of the pores, the insulation breakdown as described above is more likely to occur.

[0005] Therefore, for example, as described in the following patent document 1, a porous plug is arranged inside the pores of the base plate to prevent insulation breakdown. The porous plug is a porous member formed of an insulating material such as ceramic. By arranging the porous plug in the pores, the insulation withstand voltage can be improved while maintaining air permeability.

[0006] Patent Literature Patent Document 1: Japanese Patent Application Publication No. 2020-109806 Summary of the invention

[0007] When the entire porous plug-in is made into a porous member, the inner surface of the pores as metal is exposed to the internal space of the pores by the porous member, so sometimes the insulation withstand voltage cannot be fully ensured. As a countermeasure to prevent insulation damage on the inner surface of the pores, as described in the above-mentioned patent document 1, it is conceivable to cover the outer peripheral side of the porous member with a dense cylindrical member. However, the porous member and the cylindrical member are ceramic members made separately, so it is believed that a gap due to dimensional tolerance, etc. will be formed between the two. Since this gap may become a path for insulation damage to the base plate, it is not preferred.

[0008] In order to eliminate the above-mentioned gap, it is also possible to use an adhesive to bond the outer peripheral surface of the porous member to the inner peripheral surface of the cylindrical member. However, when such a structure is made, a part of the uncured (that is, liquid) adhesive penetrates into the interior of the porous member during bonding and then solidifies. As a result, the cross-sectional area of ​​the flow path inside the porous member becomes smaller and its area is not constant, so a new problem arises that the unevenness of the gas flow supplied to the substrate side through the ventilation plug also increases.

[0009] The present invention is made in view of such problems, and the technical problem to be solved is to provide an electrostatic chuck which can prevent insulation breakdown in air holes through a ventilation plug and can also suppress uneven gas flow.

[0010] In order to solve the above-mentioned problems, the electrostatic chuck involved in the present invention comprises: a dielectric substrate having a first air hole formed therein; a base plate which is a metal member joined to the dielectric substrate and having a second air hole connected to the first air hole formed therein; and a vent plug which is arranged inside the second air hole. The vent plug comprises: a porous portion which is a portion formed of porous ceramic having air permeability; and a dense portion which is a portion formed of dense ceramic not having air permeability, and surrounds the porous portion from the outer peripheral side over the entire span. The porous portion and the dense portion are integrated with each other by sintering, without a bonding material formed of a material other than ceramic being interposed therebetween.

[0011] In the electrostatic chuck constructed in this way, the ventilation plug is not entirely formed of the porous portion, but also includes a dense portion that surrounds the porous portion from the outer peripheral side over the entire circumference. Since the dense portion exists between the inner surface of the second pore and the porous portion, it is possible to prevent insulation breakdown from occurring to the inner surface of the second pore.

[0012] Since the porous part and the dense part are integrated with each other by sintering, there is no gap between them, so there is no insulation breakdown to the base plate through the gap.

[0013] Furthermore, there is no bonding material such as an adhesive between the porous portion and the dense portion, so that the flow path cross-sectional area of ​​the porous portion does not decrease due to the intrusion of the adhesive, and the flow rate of the gas flowing through the ventilation plug does not become uneven.

[0014] Furthermore, although the porous part and the dense part may be directly connected without using a separate bonding material, they may be connected by a bonding material formed of a ceramic material. In either case, the entire porous insert including the porous part and the dense part may be sintered into one piece.

[0015] According to the present invention, it is possible to provide an electrostatic chuck which can prevent insulation breakdown in air holes by means of a vent insert and can also suppress unevenness in gas flow rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a cross-sectional view schematically showing the structure of the electrostatic chuck according to the first embodiment. Figure 2 It is a magnified representation Figure 1 A diagram showing the structure of a vent plug and its vicinity in an electrostatic chuck. Figure 3 It is a diagram showing the structure of the ventilation plug. Figure 4A , Figure 4B It is a diagram for explaining problems when using the ventilation insert according to the comparative example. Figure 5 It is a cross-sectional view schematically showing the structure of an electrostatic chuck according to the second embodiment. Figure 6 is enlarged and detailed Figure 5 Diagram of a portion of the structure of an electrostatic chuck. Fig. 7A , Figure 7B It is a cross-sectional view showing the structure of an electrostatic chuck according to a modification of the second embodiment. Figure 8 This is a diagram showing an enlarged view of a part of the structure of an electrostatic chuck according to a third embodiment. Fig. 9 This is a diagram showing an enlarged view of a part of the structure of an electrostatic chuck according to a fourth embodiment. Fig.10 This is a diagram showing an enlarged view of a part of the structure of an electrostatic chuck according to a fifth embodiment. Explanation of symbols 10-electrostatic suction cup; 100-dielectric substrate; 110, 120, 210-face; 140-pore; 145-ventilation member; 160-pore; 180-protrusion; 181-chamfer; 200-base plate; 211, 404-chamfered portion; 230-insulating film; 240-pore; 310-sealing member; 400-ventilation plug; 403-top end surface; 410-porous portion; 420-dense portion. DETAILED DESCRIPTION

[0017] Hereinafter, the present embodiment will be described with reference to the drawings. In order to facilitate the description, the same components are denoted by the same reference numerals as much as possible in each of the drawings, and repeated descriptions are omitted.

[0018] The first embodiment is described. The electrostatic chuck 10 according to the present embodiment, for example, in an etching device or a CVD film forming device (not shown) inside a semiconductor manufacturing device, attracts and holds a substrate W to be processed by electrostatic force. The substrate W is, for example, a silicon wafer. The electrostatic chuck 10 can also be used in devices other than semiconductor manufacturing devices.

[0019] Figure 1 , the structure of the electrostatic chuck 10 in a state of sucking and holding the substrate W is shown as a schematic cross-sectional view. The electrostatic chuck 10 includes a dielectric substrate 100 , a base plate 200 , and a bonding layer 300 .

[0020] The dielectric substrate 100 is a roughly disk-shaped member composed of a ceramic sintered body. The dielectric substrate 100 contains, for example, high-purity aluminum oxide (Al2O3), but may also contain other materials. The purity and type of ceramics in the dielectric substrate 100, additives, etc. may be appropriately set in consideration of the plasma resistance required of the dielectric substrate 100 in the semiconductor manufacturing device.

[0021] In the dielectric substrate 100, Figure 1 The upper surface 110 in the dielectric substrate 100 is a "placing surface" on which the substrate W is placed. Figure 1 The lower surface 120 in the figure becomes a "joined surface" joined to the base plate 200 by the joining layer 300 described later. Hereinafter, the viewpoint when observing the electrostatic chuck 10 from the surface 110 side in a direction perpendicular to the surface 110 is also expressed as "top view".

[0022] An adsorption electrode 130 is embedded inside the dielectric substrate 100. The adsorption electrode 130 is a relatively thin flat plate-shaped layer formed of a metal material such as tungsten, and is arranged parallel to the surface 110. As a material of the adsorption electrode 130, molybdenum, platinum, palladium, etc. can be used in addition to tungsten. If a voltage is applied to the adsorption electrode 130 from the outside through the power supply circuit 13, an electrostatic force is generated between the surface 110 and the substrate W, thereby the substrate W is adsorbed and held. The adsorption electrode 130 can be provided as two so-called "bipolar" electrodes as in the present embodiment, or only one so-called "monopolar" electrode can be provided.

[0023] Figure 1, the entire power supply circuit 13 is simplified. In the power supply circuit 13, the portion inside the dielectric substrate 100 is constituted as, for example, an elongated via (hole) filled with a conductor, and an electrode terminal (not shown) is provided at its lower end. In the power supply circuit 13, the portion that passes through the base plate 200 described later is a conductive metal member (such as a busbar) whose one end is connected to the above-mentioned electrode terminal. In the base plate 200, a through hole (not shown) for passing the power supply circuit 13 is formed. Between the inner surface of the through hole and the power supply circuit 13, for example, a cylindrical insulating member may also be provided.

[0024] like Figure 1 As shown, a space SP1 is formed between the dielectric substrate 100 and the substrate W. When film formation or other processing is performed in the semiconductor manufacturing apparatus, helium gas for temperature adjustment is supplied from the outside to the space SP1 through the gas hole 140 described later. By making the helium gas exist between the dielectric substrate 100 and the substrate W, the thermal resistance between the two is adjusted, so that the temperature of the substrate W is maintained at an appropriate temperature. In addition, the gas for temperature adjustment supplied to the space SP1 may be a gas of a different type from helium.

[0025] A sealing ring 111 and points 112 are provided on the surface 110 which is the adsorption surface, and a space SP1 is formed around them.

[0026] The sealing ring 111 is a wall that divides the space SP1 at the position that becomes the outermost periphery. The upper end of the sealing ring 111 becomes a part of the surface 110 and abuts against the substrate W. In addition, a plurality of sealing rings 111 may be provided in a manner that divides the space SP1. With such a structure, the pressure of the helium gas in each space SP1 can be adjusted separately, and the surface temperature distribution of the substrate W can be made uniform during processing.

[0027] Figure 1 The portion marked with the symbol "116" is the bottom surface of the space SP1. Hereinafter, this portion is also referred to as "bottom surface 116". The sealing ring 111 is formed as a result of digging out a portion of the surface 110 to the position of the bottom surface 116 together with the point 112 described below.

[0028] The dots 112 are circular protrusions protruding from the bottom surface 116. A plurality of dots 112 are provided and are dispersed approximately evenly on the placement surface of the dielectric substrate 100. The upper end of each dot 112 becomes a part of the surface 110 and contacts the substrate W. By providing a plurality of such dots 112, the substrate W is prevented from being bent.

[0029] A groove 113 is formed on the bottom surface 116 of the space SP1. The groove 113 is formed so as to recede from the bottom surface 116 toward the surface 120. The groove 113 is formed for the purpose of rapidly diffusing the helium gas supplied from the air hole 140 in the space SP1 and making the pressure distribution in the space SP1 approximately uniform in a short time.

[0030] The dielectric substrate 100 is provided with a gas hole 140 extending vertically from the surface 120 toward the surface 110. The end of the gas hole 140 on the surface 110 side opens on the bottom surface of the groove 113. The dielectric substrate 100 is provided with a plurality of gas holes 140, which are arranged along the groove 113. The gas hole 140 constitutes a part of a flow path for supplying gas into the space SP1, and is connected to the space SP1 on the bottom surface of the groove 113. When the space SP1 is divided into a plurality of spaces by the sealing ring 111, one or more gas holes 140 are connected to each of the divided spaces SP1. The gas hole 140 corresponds to the "first gas hole" in the present embodiment.

[0031] like Figure 1 As shown, the portion of the pore 140 on the surface 120 side is enlarged in diameter compared to the portion on the surface 110 side, and a vent plug 145 is arranged inside the pore 140. The vent plug 145 is a porous body formed of, for example, alumina, and has air permeability as a whole. By arranging such a vent plug 145 inside the pore 140, the flow of gas in the pore 140 is ensured, and at the same time, insulation breakdown can be suppressed on the path through the pore 140.

[0032] The base plate 200 is a substantially disk-shaped metal member that supports the dielectric substrate 100. The base plate 200 is formed of a metal material such as aluminum. Figure 1 The upper surface 210 in FIG. 1 becomes a “joined surface” to be joined to the dielectric substrate 100 via the joining layer 300 .

[0033] like Figure 1 As shown, the base plate 200 is formed with air holes 240 extending vertically from the surface 210 toward the surface 220 on the opposite side thereof. When viewed from above, the air holes 240 are respectively formed at positions overlapping with the air holes 140 of the dielectric substrate 100, and are connected to the air holes 140 via the through holes 311 provided in the bonding layer 300. The air holes 240, together with the air holes 140 of the dielectric substrate 100, form a part of the path for supplying helium gas to the space SP1. The air holes 240 correspond to the "second air holes" in this embodiment.

[0034] Furthermore, although the air holes 240 may be formed to extend in a straight line as a whole as in the present embodiment, they may also be formed to bend on the way toward the surface 220. In addition, the plurality of air holes 240 on the surface 210 side may be configured so as to be concentrated into a small number of flow paths inside the base plate 200, and on this basis, the flow paths are extended to the surface 220 side.

[0035] like Figure 1 As shown, the portion of the air hole 240 on the surface 210 side is more enlarged in diameter than the portion on the surface 220 side, and a vent plug 400 is disposed therein. The vent plug 400 is also a member provided to suppress the occurrence of insulation breakdown, similarly to the vent plug 145, but its structure is different from the vent plug 145. The specific structure of the vent plug 400 will be described later.

[0036] A cooling medium flow path 250 for flowing a cooling medium is formed inside the susceptor plate 200. When a process such as film formation is performed in the semiconductor manufacturing apparatus, a cooling medium is supplied from the outside to the cooling medium flow path 250, thereby cooling the susceptor plate 200. During the process, the heat generated on the substrate W is transferred to the cooling medium via the helium gas in the space SP1, the dielectric substrate 100, and the susceptor plate 200, and is discharged to the outside together with the cooling medium.

[0037] An insulating film may also be formed on the surface of the base plate 200. The insulating film may also be formed to cover only a portion of the surface of the base plate 200, rather than the entire surface. For example, the insulating film may also be formed to cover only the side portions except the surface 210 and the surface 220, that is, to cover only the exposed portions that are exposed to plasma, etc. inside the semiconductor manufacturing device. Different from this, the insulating film may also be formed to cover at least the entire range including the surface 210. As the insulating film, for example, a film of aluminum oxide formed by spraying may be used. By covering the surface of the base plate 200 with an insulating film, the insulation withstand voltage of the base plate 200 can be improved.

[0038] The bonding layer 300 is a layer provided between the dielectric substrate 100 and the base plate 200, and the two are bonded. The bonding layer 300 is a layer formed by curing an adhesive material formed by an insulating material. In the present embodiment, a silicone adhesive is used as the above-mentioned adhesive. However, the bonding layer 300 can also be a layer formed by curing other types of adhesives. In either case, it is preferred to use a material with a higher thermal conductivity as much as possible as the material of the bonding layer 300 so that the thermal resistance between the dielectric substrate 100 and the base plate 200 is small.

[0039] The specific structure of the ventilation insert 400 provided in the air hole 240 will be described. Figure 2 In the figure, the enlarged Figure 1 The ventilation plug 400 and the surrounding structures.

[0040] As described above, the portion of the air hole 240 on the surface 210 side is more enlarged than the portion on the surface 220 side, and the ventilation plug 400 is arranged in the enlarged portion. Hereinafter, the enlarged portion of the air hole 240 is also referred to as "enlarged portion 241". The enlarged portion 241 is a space in a substantially cylindrical shape, and its central axis is perpendicular to the surface 210.

[0041] The vent plug 400 is a cylindrical member, and its shape is substantially the same as the shape of the inner space of the enlarged diameter portion 241. That is, the central axis of the vent plug 400 coincides with the central axis of the enlarged diameter portion 241, and the diameter of the outer peripheral surface of the vent plug 400 is substantially equal to the diameter of the inner peripheral surface of the enlarged diameter portion 241.

[0042] The ventilation insert 400 includes a porous portion 410 and a dense portion 420 .

[0043] The porous portion 410 is a part formed of porous ceramics having air permeability. The gas passing through the pores 240 is supplied to the space SP1 after flowing through the porous portion 410 in the ventilation plug 400. The porosity of the porous portion 410 is appropriately set according to the balance between the air permeability required for supplying gas to the space SP1 and the required insulation withstand voltage. In this embodiment, although the porous portion 410 is formed of the same porous alumina as the ventilation plug 145, it can also be formed of other ceramic materials. The porous portion 410 is cylindrical in shape, and its central axis is consistent with the central axis of the ventilation plug 400 as a whole.

[0044] The dense portion 420 is a portion formed of dense ceramic that does not have air permeability. In other words, the dense portion 420 is a portion of the ventilation plug 400 through which gas does not pass. In the present embodiment, the dense portion 420 is formed of alumina, but it can also be formed of other ceramic materials. In addition, the ceramic material constituting the porous portion 410 and the ceramic material constituting the dense portion 420 can be the same type of material as in the present embodiment, but can also be different types of materials.

[0045] The dense portion 420 is cylindrical in shape, and its central axis coincides with the central axis of the entire ventilation plug 400. The porous portion 410 is accommodated inside the dense portion 420. Figure 2 The size of the dense portion 420 in the vertical direction is the same as the size of the porous portion 410 in the vertical direction. In this way, the dense portion 420 surrounds the porous portion 410 from the outer peripheral side over the entire circumference. In addition, as described above, the overall shape of the ventilation plug 400 including the porous portion 410 and the dense portion 420 is a cylindrical shape.

[0046] The porous part 410 and the dense part 420 are not separate components that can be separated from each other, but are integrated into one. The porous part 410 and the dense part 420 are manufactured by a method described later, and are integrated into one by sintering.

[0047] and Figure 2 Likewise, Figure 3 2 shows a cross section of the ventilation plug 400 cut along a plane passing through the central axis thereof. Figure 3 2 shows an example of an image obtained by observing a part of the cross section using an electron microscope, specifically, an image of a boundary portion between the porous portion 410 and the dense portion 420 . Figure 3 The portion denoted by the reference numeral “ 411 ” is a cross section of a pore formed in the porous portion 410 .

[0048] In this specification, "to be integrated with each other by sintering" means that Figure 3 As shown in the example, the ceramic particles constituting the dense portion 420 are bonded to the ceramic particles contained in the porous portion 410 directly or through the grain boundaries. Specifically, at the boundary portion between the porous portion 410 and the dense portion 420, there are only the ceramic materials constituting each other, namely Al2O3 or other impurities (SiO2), and there is no bonding layer formed by materials other than ceramics (such as silicone adhesives, etc.). The porous portion 410 and the dense portion 420 as a whole become a ceramic sintered body. For example, using a scanning electron microscope, observing the cross-section of the ventilation plug 400 at a magnification of 500 times, it can be confirmed that they are integrated with each other through sintering. The observation conditions can be the usual observation conditions for ceramic sintered bodies, and thermal etching can be performed as needed.

[0049] The vent plug 400 is a member for suppressing insulation breakdown in the pore 240. Assuming that the vent plug 400 is configured such that the dense portion 420 is not provided on the outer peripheral side of the vent plug 400 and the vent plug 400 is formed as a porous portion 410, the inner surface of the expanded diameter portion 241, which is metal, is exposed to the inner space of the pore 240 through the porous portion 410. Figure 2 As shown by arrow AR, the possibility of insulation breakdown on the path from the dielectric substrate 100 side toward the outer periphery of the ventilation plug 400 increases. Therefore, in this embodiment, a dense portion 420 is provided on the outer periphery of the ventilation plug 400 to prevent insulation breakdown on the path.

[0050] As a structure of the ventilation plug 400 for preventing insulation breakdown, for example Figure 4AAs in the comparative example shown in FIG. 2 , it is also possible to consider a structure in which the porous portion 410 and the dense portion 420 are pre-formed as separate sintered bodies, and the two are arranged in parallel inside the expanded diameter portion 241. However, in such a structure, a small gap G is formed between the porous portion 410 and the dense portion 420 due to the dimensional tolerance of the two members, and insulation breakdown may occur on the path along the gap G. In contrast, in the present embodiment, the porous portion 410 and the dense portion 420 are formed into an integral sintered body, and no gap is formed between the two, so insulation breakdown does not occur on the above path.

[0051] Furthermore, if the porous portion 410 and the dense portion 420 are preliminarily formed as separate sintered bodies and the two are bonded together using, for example, a silicone adhesive, the above-mentioned gap G will not be formed. However, when bonding is performed using an adhesive, a portion of the uncured (that is, liquid) adhesive intrudes from the outer peripheral surface of the porous portion 410 to the inside and then cures. Figure 4B In FIG. 4 , a region 425 into which the adhesive has penetrated is schematically shown.

[0052] In this state, the cross-sectional area of ​​the flow path inside the porous part 410 is reduced by the area 425, and the area is not constant. Therefore, a new problem occurs that the flow rate of the gas supplied to the space SP1 through the ventilation plug 400 becomes uneven. In contrast, in this embodiment, there is no adhesive or the like between the porous part 410 and the dense part 420, so the porous part 410 as a whole can always function as a gas flow path, and the above-mentioned flow rate unevenness does not occur.

[0053] As described above, in the electrostatic chuck 10 of the present embodiment, the vent plug 400 can prevent insulation breakdown in the air hole 240 and suppress unevenness in the flow rate of gas supplied to the space SP1.

[0054] In place of the dense portion 420 being provided on the outer peripheral side of the porous portion 410, it is also possible to form a sprayed film of aluminum oxide or the like in a manner covering the outer side of the porous portion 410. However, a part of the sprayed film will enter the porous portion 410, so that Figure 4B The comparative example of may cause the problem of reduction or unevenness of the flow path cross-sectional area. In addition, it is sometimes difficult to fully ensure the thickness of the thermal spraying film to fully exert the insulation withstand voltage. Therefore, even if compared with the structure of providing the thermal spraying film, this embodiment is still preferred.

[0055] In this embodiment, the porous portion 410 and the dense portion 420 are each formed of a high-purity alumina ceramic having a purity of 92% or more. By increasing the purity of the materials constituting each, the integrity of the ventilation plug 400 as a whole can be further improved. The purity of the material can be measured by mass spectrometry based on ICP or elemental analysis based on XRF.

[0056] By selecting the material, the average particle size of the ceramic in the porous part 410 and the dense part 420 can be arbitrarily set. However, it is preferred that the average particle size of the ceramic in the dense part 420 is smaller than the average particle size of the ceramic in the porous part 410. By reducing the average particle size of the dense part 420, the insulation performance of the dense part 420 can be fully ensured. In addition, since the dense part 420 can be thinned, the diameter of the porous part 410 can also be increased to ensure the flow rate of the gas.

[0057] The thickness of the dense portion 420 is uniform over the entire circumference. The "thickness" mentioned here refers to the dimension of the dense portion 420 in a direction perpendicular to the central axis of the ventilation plug 400. Figure 3 By making the thickness of the dense portion 420 uniform over the entire circumference, the dielectric strength voltage is not reduced locally in a portion along the circumferential direction, and a sufficient dielectric strength voltage can be ensured over the entire circumference.

[0058] Sometimes, a voltage of 3 kV or more is applied to the pores 240. Even in this case, in order to reliably prevent insulation breakdown, it is preferable to ensure that the thickness of the dense portion 420 is 0.1 mm or more, and more preferably 0.3 mm or more. Figure 3 The thickness T of the dense portion 420 shown can also be ensured to be 30% or more of the diameter D of the inner surface of the dense portion 420 (which can also be referred to as the diameter of the outer surface of the porous portion 410 ).

[0059] In this embodiment, the ventilation plug 400 is only embedded in the enlarged diameter portion 241. That is, the outer side surface of the dense portion 420 and the inner side surface of the enlarged diameter portion 241 are not bonded by adhesive or the like, but a small gap (not shown) is formed between the two. Figure 2 As shown, the end of the dielectric substrate 100 side in the gap is blocked by the bonding layer 300. Therefore, insulation breakdown does not occur through the gap. In order to realize such a structure, the diameter of the through hole 311 provided in the bonding layer 300 is larger than the diameter of the inner side surface of the dense portion 420 and smaller than the diameter of the outer side surface of the dense portion 420.

[0060] The method for manufacturing the ventilation plug 400 is described below. First, a porous member and a cylindrical molded body are prepared. The porous member is a porous ceramic sintered body, and its shape is a cylindrical shape. The porous member is the part that eventually becomes the porous portion 410.

[0061] The cylindrical molded body is a dense ceramic molded body, and its shape is cylindrical. That is, a cylindrical hole is formed in the cylindrical molded body. The cylindrical molded body is the part that eventually becomes the dense portion 420. When the porous member and the cylindrical molded body are prepared separately, the porous member has become a sintered body, and on the other hand, the cylindrical molded body has become an unsintered molded body. At this time, the diameter of the inner side of the cylindrical molded body is slightly larger than the diameter of the outer side of the porous member.

[0062] Next, a porous member is arranged inside the hole of the cylindrical molded body. That is, the porous member is covered by the cylindrical molded body from the outer circumference over the entire circumference. Thus, the porous member and the cylindrical molded body are formed into a generally cylindrical shape as a whole. The entire inner side surface of the cylindrical molded body and the entire outer side surface of the porous member are opposite to each other, and a gap (not shown) is formed between the two.

[0063] While maintaining this state, the porous member and the cylindrical molded body are fired simultaneously. At this time, the cylindrical molded body gradually shrinks due to firing, and the gap between the two becomes zero. In other words, the inner side surface of the cylindrical molded body and the outer side surface of the porous member are in a state of being closely attached to each other without a gap. As a result of firing in such a state, the porous member and the cylindrical molded body are joined to each other and become a whole sintered body.

[0064] Hereinafter, the contents different from the first embodiment will be mainly described, and the description of the same contents as the first embodiment will be appropriately omitted.

[0065] Figure 5 In, as Figure 1 The structure of the electrostatic chuck 10 according to the present embodiment is shown in the same schematic cross-sectional view. In the present embodiment as well, the electrostatic chuck 10 includes a dielectric substrate 100 , a base plate 200 , and a bonding layer 300 .

[0066] An adsorption electrode 130 is embedded in the dielectric substrate 100. In the present embodiment, only one adsorption electrode 130 is provided as a so-called "monopole" electrode. Figure 1 Similar to the first embodiment, two adsorption electrodes 130 may be provided as so-called “bipolar” electrodes. Figure 5 In the figure, the power supply circuit 13 for applying a voltage to the adsorption electrode 130 is omitted.

[0067] In the present embodiment, helium gas is supplied to the space SP1 through the air hole 160. The air hole 160 is a through hole formed in a manner of penetrating the dielectric substrate 100. The air hole 160 is formed to extend vertically from the bottom surface 116 toward the surface 120 side. Although the air hole 160 can be formed to extend in a straight line as in the present embodiment, it can also be formed to bend on the way from the bottom surface 116 toward the surface 120. When a plurality of sealing rings 111 are provided in a manner of dividing the space SP1, the air hole 160 can be formed at positions corresponding to the plurality of spaces SP1, respectively.

[0068] In this embodiment, the groove 113 is not formed on the bottom surface 116. Similar to the first embodiment, after the groove 113 is formed on the bottom surface 116, the air hole 160 may be formed so as to open on the bottom surface of the groove 113.

[0069] In the present embodiment, a pair of air holes 160 formed at positions close to each other are formed in a plurality of groups so as to penetrate through each portion of the dielectric substrate 100 . Figure 5 , only one group of pores 160 is shown. The pores 160 correspond to the "first pores" in this embodiment. The specific structure of the pores 160 and its vicinity will be described later.

[0070] As in the first embodiment, the base plate 200 is provided with a gas hole 240. The gas hole 240 is a hole connected to the gas hole 160 described above, and forms a part of a path for supplying helium gas to the space SP1.

[0071] The air hole 240 is formed to extend vertically from the surface 210 toward the surface 220 side opposite to the surface 210. A plurality of air holes 240 are formed, and one air hole 240 is formed at each position corresponding to each pair of air holes 160. That is, two air holes 160 are connected to one air hole 240. In this embodiment, the air hole 240 corresponds to the "second air hole".

[0072] Although the pore 240 may be formed to extend in a straight line as in the present embodiment, it may also be formed to bend on the way from the surface 210 toward the surface 220. In either case, the opening of the end of the pore 160 on the surface 120 side and the opening of the end of the pore 240 on the surface 210 side may overlap each other when viewed from above.

[0073] like Figure 5As shown in the figure, the portion near the end of the surface 210 side in the air hole 240 is an expanded diameter portion 241 whose diameter is expanded more than other portions. Inside the expanded diameter portion 241, a vent plug 400 having the same structure as that described in the first embodiment is arranged. By arranging the vent plug 400 inside the air hole 240, the flow of helium gas in the air hole 240 is ensured, and at the same time, the occurrence of insulation breakdown on the path passing through the air hole 240 can be suppressed.

[0074] The ventilation plug 400 is a substantially cylindrical member, and is arranged inside the enlarged diameter portion 241 in a state where the central axis thereof coincides with the central axis of the enlarged diameter portion 241. The outer diameter of the ventilation plug 400 is substantially equal to the inner diameter of the enlarged diameter portion 241. For example, the ventilation plug 400 is pressed into the enlarged diameter portion 241. In the present embodiment, the end surface of the ventilation plug 400 on the dielectric substrate 100 side is located in the same plane as the surface 210.

[0075] Figure 6 , the structure of the pore 160 and its vicinity is shown in an enlarged manner. In addition, in this figure, the dots 112 formed on the surface 110 side are omitted.

[0076] like Figure 6 As shown, a protrusion 180 is formed on the surface 120 on the base plate 200 side of the dielectric substrate 100. In the protrusion 180, a part of the surface 120 protrudes toward the base plate 200. The protrusion 180 has a circular shape when viewed from above. A pair of air holes 160 formed at positions close to each other are each formed to penetrate one protrusion 180.

[0077] The protrusion 180 is integrated with other portions (portions other than the protrusion 180) of the dielectric substrate 100. For example, the protrusion 180 can be formed by subjecting the surface 120 of the dielectric substrate 100 to a process such as sandblasting.

[0078] The central axis of the protrusion 180 coincides with the central axis of the entire ventilation plug 400. The outer diameter of the protrusion 180 is substantially equal to the outer diameter of the porous portion 410.

[0079] An annular sealing member 310 is arranged between the dielectric substrate 100 and the ventilation plug 400. The sealing member 310 is a member formed by curing a silicone adhesive, for example. The inner diameter of the sealing member 310 is substantially equal to the outer diameter of the protrusion 180. The thickness of the sealing member 310 (the dimension in the direction perpendicular to the placement surface) is the same as the thickness of the bonding layer 300. The sealing member 310 is arranged to surround the entire periphery of the protrusion 180 from the outer peripheral side. When the electrostatic suction cup 10 is manufactured, the sealing member 310 is arranged as a member for preventing the uncured adhesive that becomes the bonding layer 300 from entering the inside. Although the sealing member 310 can be a member formed of the same material as the bonding layer 300, it can also be a member formed of a different material.

[0080] The protrusion amount of the protrusion 180 toward the base plate 200 is slightly smaller than the thickness of the bonding layer 300. Therefore, a small gap, namely a space SP2, is formed between the top surface of the protrusion 180 and the ventilation plug 400. The space SP2 corresponds to the internal space of the through hole 311 in the first embodiment.

[0081] As described above, in the electrostatic chuck 10 of the present embodiment, the protrusion 180 is formed on the dielectric substrate 100 , and the air hole 160 is formed so as to penetrate the protrusion 180 .

[0082] The reason for such a structure is described below. During the processing of the substrate W, the potential of the substrate W and its surroundings increases due to the injection of plasma or the application of voltage to the adsorption electrode 130. On the other hand, the potential of the base plate 200 is maintained at the same potential as that of the surrounding components constituting the semiconductor manufacturing apparatus (for example, the ground potential). Therefore, insulation breakdown is likely to occur in the air hole 160 and on the path passing through the air hole 240.

[0083] Assuming that the protrusion 180 is not formed on the dielectric substrate 100, the thickness of the space SP2 is equal to the thickness of the bonding layer 300. That is, in the vicinity of the pores 160 and the like, in the portion where the dielectric substrate 100 and the base plate 200 face each other, a space SP2 having a thickness equal to the thickness of the bonding layer 300 is formed between the two members. This thickness is, for example, about 250 μm. According to Paschen's law, in the space of the above thickness, the pressure of the helium gas inside the pores 160 and the like is always in a pressure region where insulation breakdown is more likely to occur.

[0084] Therefore, in this embodiment, the protrusion 180 is formed on the dielectric substrate 100, so that the thickness of the space SP2 is smaller than the thickness of the bonding layer 300. That is, the distance between the dielectric substrate 100 and the base plate 200 (the ventilation plug 400 in this embodiment) facing each other at the position of the air hole 160 is smaller than the thickness of the bonding layer 300. By making the distance between the two members small to a degree that insulation breakdown does not occur, it is possible to fully suppress insulation breakdown caused by the air hole 160 and the space SP2.

[0085] Furthermore, as a structure for narrowing the space SP2, it is also possible to reduce the thickness of the entire bonding layer 300 instead of forming the protrusion 180. However, if the thickness of the bonding layer 300 is changed, it may be impossible to absorb the difference in thermal expansion between the dielectric substrate 100 and the base plate 200 by the bonding layer 300. Therefore, as in the present embodiment, it is preferable to form the protrusion 180 instead of changing the thickness of the bonding layer 300.

[0086] It is also possible to have a configuration in which the vent plug 400 is not disposed inside the air hole 240, but the protrusion 180 is directly opposite to the surface 210 of the base plate 200. Even in such a configuration, the protrusion 180 is formed and the space SP2 is narrowed, thereby preventing insulation breakdown. However, in order to make insulation breakdown more difficult to occur, it is preferable to dispose the vent plug 400 as in the present embodiment.

[0087] The ventilation plug 400 may also be entirely a porous portion 410. However, when a dense portion 420 is provided on the outer periphery of the porous portion 410 as in the present embodiment, the inner surface (that is, metal) of the pores 240 is covered by the dense portion 420, thereby more reliably preventing insulation breakdown.

[0088] As described above, the outer diameter of the protrusion 180 is substantially equal to the outer diameter of the porous portion 410. As a result, in a plan view, the porous portion 410 overlaps with the pores 160 formed in the protrusion 180. Since the porous portion 410 is disposed directly below the pores 160, the supply of helium gas to the space SP1 is not unnecessarily hindered.

[0089] When viewed from above, the entire dense portion 420 is located closer to the outside than the protruding portion 180. In such a structure, the sealing member 310 surrounding the protruding portion 180 from the outer peripheral side can be in contact with the dense portion 420 over the entire span. As a result, it is possible to prevent the uncured adhesive that becomes the bonding layer 300 from invading the inside of the porous portion 410. In addition, when viewed from above, only a part of the dense portion 420 can be arranged at a position closer to the outside than the protruding portion 180, rather than the entire dense portion 420. In other words, the inner diameter of the dense portion 420 can also be slightly smaller than the outer diameter of the protruding portion 180.

[0090] like Figure 6 As shown, the portion near the end of the pore 160 on the base plate 200 side is an expanded diameter portion 161 that is expanded more than the other portions. That is, the inner diameter at the end of the pore 160 on the base plate 200 side is larger than the inner diameter at the end of the pore 160 on the placement surface side. By enlarging the inner diameter of the inlet portion of the helium gas in the pore 160, even when the thickness of the space SP2 is very narrow, the flow rate of the helium gas flowing into the pore 160 can be ensured. For example, it is preferable to make the length of the expanded diameter portion 161 to be approximately the same as the thickness of the bonding layer 300.

[0091] For example, another disc-shaped member may be joined to the surface 120 of the dielectric substrate 100 to form the protrusion 180. However, in view of the possibility of the protrusion 180 falling off, it is preferred that the protrusion 180 be formed integrally with other parts of the dielectric substrate 100 as in the present embodiment. In either case, like other parts of the dielectric substrate 100, the protrusion 180 is preferably formed as a dense body that does not have air permeability.

[0092] The number of pores 160 penetrating one protrusion 180 may be only one or more than three. If a plurality of pores 160 are formed in one protrusion 180 as in the present embodiment, each pore 160 can be made small in diameter while the flow rate of helium gas can be sufficiently ensured. As a result, the occurrence of insulation breakdown can be further suppressed.

[0093] A chamfer 181 may be formed at the outer peripheral end of the protrusion 180 to prevent chipping. For example, the chamfer 181 may be Fig. 7A The R chamfer shown can also be Figure 7B C chamfer shown.

[0094] As in the first embodiment, the ventilation plug 400 of this embodiment has a porous portion 410 and a dense portion 420, which are integrated with each other by sintering. Instead of such a form, the porous portion 410 and the dense portion 420 can be integrated by bonding the separable components with an adhesive or the like.

[0095] Hereinafter, the contents different from the above-mentioned second embodiment will be mainly described, and the description of the same contents as the second embodiment will be appropriately omitted.

[0096] Figure 8 In Figure 6 The structure of the electrostatic chuck 10 according to the present embodiment is depicted from the same viewpoint. Figure 8 As shown, the ventilation insert 400 of this embodiment extends to Figure 6 The second embodiment shown is closer to the dielectric substrate 100 than the second embodiment shown.

[0097] For convenience of explanation, the surface of the base plate 200 facing the dielectric substrate 100 via the bonding layer 300 is also referred to as the “opposing surface”. In this embodiment, the surface 210 corresponds to the “opposing surface”. Hereinafter, the surface 210 is also referred to as the “opposing surface 210”.

[0098] Furthermore, even when the surface of the base plate 200 including the surface 210 is covered with an insulating film, the surface 210 is the "opposing surface" as described above, not the surface of the insulating film. In any case, the "opposing surface" is the surface of the base plate 200 which is metal and is opposed to the dielectric substrate 100 through the bonding layer 300.

[0099] like Figure 8 As shown, a portion of the ventilation plug 400 of this embodiment protrudes from the opposing surface 210 toward the dielectric substrate 100. That is, the protrusion 180 protrudes from the dielectric substrate 100 toward the space SP2, while the ventilation plug 400 protrudes from the base plate 200 toward the space SP2. The protrusion amount of the ventilation plug 400 toward the dielectric substrate 100 side is smaller than the thickness of the bonding layer 300.

[0100] As described above, by making the mutually opposed protrusion 180 and the ventilation plug 400 protrude toward the space SP2, the thickness of the space SP2 is further reduced, thereby making it more difficult for insulation breakdown to occur in the space SP2.

[0101] The other structures are described below. A chamfered portion 211 is formed at the boundary portion between the inner surface of the enlarged diameter portion 241 in the air hole 240 and the opposite surface 210. The chamfered portion 211 is a surface that is inclined so that its inner diameter increases as it moves toward the dielectric substrate 100. A portion of the bonding layer 300 also enters between the chamfered portion 211 and the dense portion 420.

[0102] Hereinafter, the top end surface of the ventilation plug 400 on the dielectric substrate 100 side is also referred to as "top end surface 403". A chamfered portion 404 is formed on the outer peripheral side portion of the top end surface 403, that is, on the boundary portion between the outer side surface of the dense portion 420 and the top end surface 403. The chamfered portion 404 is a surface that is inclined so that its diameter decreases as it goes toward the dielectric substrate 100 side. The chamfered portion 404 may be a C chamfer, but may also be an R chamfer.

[0103] Even in the present embodiment, between the ventilation plug 400 and the dielectric substrate 100, an annular sealing member 310 is also configured that surrounds the protrusion 180 from the outside. Most of the sealing member 310 of the present embodiment is sandwiched between the top face 403 and the face 120. Therefore, the thickness (dimension along the direction perpendicular to the placement surface) of the sealing member 310 is less than the thickness of the bonding layer 300. By configuring such a sealing member 310, the bonding layer 300 is prevented from intruding into the inner side of the sealing member 310. That is, the uncured adhesive that becomes the bonding layer 300 is prevented from intruding and blocking the pores 160 during manufacturing.

[0104] like Figure 8 As shown in FIG. 1 , the outer peripheral end of the sealing member 310 extends to a position directly above the chamfered portion 404. In other words, the sealing member 310 is arranged so as to straddle both the top end surface 403 and the chamfered portion 404 in a plan view.

[0105] Assuming that the sealing member 310 overlaps only the top surface 403 in a plan view, the entire sealing member 310 is compressed by the top surface 403 when the electrostatic chuck 10 is assembled. As a result, the force applied from the sealing member 310 to the dielectric substrate 100 is too large, and the dielectric substrate 100 may be damaged.

[0106] Therefore, in the present embodiment, as described above, when viewed from above, the sealing member 310 is configured to span both the top end surface 403 and the chamfered portion 404. In such a structure, a portion of the sealing member 310 compressed during assembly has room to escape to a relatively large space, that is, right above the chamfered portion 404. Compared to a case where the entire sealing member 310 is compressed by the top end surface 403, the force borne by the dielectric substrate 100 becomes smaller, so that damage to the dielectric substrate 100 can be suppressed.

[0107] Hereinafter, the contents different from the above-mentioned third embodiment will be mainly described, and the description of the same contents as the third embodiment will be appropriately omitted.

[0108] Fig. 9 In Figure 6 and Figure 8 The structure of the electrostatic chuck 10 according to the present embodiment is depicted from the same viewpoint. Fig. 9 As shown, in this embodiment, the surface of the base plate 200 is covered with an insulating film 230. The insulating film 230 is a film formed of an insulating material such as aluminum oxide, for example, and is formed by spraying. The insulating film 230 of this embodiment is formed to cover the opposing surface 210 and the chamfered portion 211. The range of the base plate 200 covered by the insulating film 230 may also be a range different from the above content.

[0109] The ventilation plug 400 of this embodiment is arranged so that a part thereof protrudes from the surface of the insulating film 230 toward the dielectric substrate 100. By arranging the ventilation plug 400 so as to protrude not only from the opposing surface 210 but also from the surface of the insulating film 230, the thickness of the space SP2 can be further reduced.

[0110] Furthermore, depending on the thickness of the insulating film 230 or the bonding layer 300 , the vent plug 400 may be configured to protrude from the opposing surface 210 while not protruding from the surface of the insulating film 230 .

[0111] The fifth embodiment will be described. Figure 8 ) are described, and descriptions of contents that are the same as those in the third embodiment are appropriately omitted.

[0112] Fig.10 In Figure 8 The structure of the electrostatic chuck 10 according to the present embodiment is depicted from the same viewpoint. Figure 8 ) Similarly, a portion of the ventilation plug 400 protrudes from the opposing surface 210 toward the dielectric substrate 100. On the other hand, the dielectric substrate 100 of this embodiment is not provided with the protruding portion 180. Even in such a structure, the thickness of the space SP2 can be reduced to prevent insulation breakdown.

[0113] The structure of the ventilation insert 400 may be different from that described in the first embodiment. For example, the entire ventilation insert 400 may be formed as the porous portion 410. This also applies to the other embodiments described above.

[0114] Above, the present embodiment has been described with reference to specific examples. However, the present invention is not limited to these specific examples. With regard to these specific examples, as long as they have the characteristics of the present invention, the technology that is appropriately designed and changed by those skilled in the art is also included in the scope of the present invention. The various elements and their configurations, conditions, shapes, etc. possessed by the aforementioned specific examples are not limited to the illustrated contents, but can be appropriately changed. As long as there is no technical contradiction, the various elements possessed by the aforementioned specific examples can be appropriately changed and combined.

Claims

1. An electrostatic chuck, characterized in that: The invention comprises: a dielectric substrate having a placement surface for placing an adsorbent and having a first air hole formed thereon; a base plate, which is a metal member supporting the dielectric substrate and has a second air hole formed at a position corresponding to the first air hole; and a ventilation plug, which is arranged inside the second air hole, The ventilation plug includes: a porous portion formed of porous ceramic having air permeability; and a dense portion, which is a portion formed of dense ceramics that does not have air permeability and surrounds the porous portion from the outer peripheral side over the entire circumference, The porous portion and the dense portion are integrated with each other by sintering without interposing a bonding material formed of a material other than ceramics.

2. The electrostatic chuck according to claim 1, characterized in that: The purity of the ceramic in the porous portion and the purity of the ceramic in the dense portion are both 92% or more.

3. The electrostatic chuck according to claim 1, wherein: An average particle size of the ceramic in the dense portion is smaller than an average particle size of the ceramic in the porous portion.

4. The electrostatic chuck according to claim 1, wherein: The dense portion is cylindrical in shape, and its thickness is uniform over the entire circumference.

5. The electrostatic chuck according to claim 4, characterized in that: The thickness of the dense portion is greater than 0.1 mm.

6. The electrostatic chuck according to claim 1, wherein: A bonding layer is further provided for bonding the dielectric substrate and the base plate. A protrusion protruding toward the base plate is formed on a surface of the dielectric substrate on the base plate side. The first air hole is formed to penetrate the protrusion.

7. The electrostatic chuck according to claim 6, characterized in that: When viewed from a direction perpendicular to the placement surface, the porous portion overlaps with the first air hole.

8. The electrostatic chuck according to claim 7, characterized in that: When viewed from a direction perpendicular to the placement surface, At least a portion of the dense portion is located further outward than the protruding portion.

9. The electrostatic chuck according to claim 6, wherein: The plurality of first air holes are formed to penetrate through one protrusion.

10. The electrostatic chuck according to claim 6, wherein An inner diameter of an end portion of the first air hole on the base plate side is larger than an inner diameter of an end portion of the first air hole on the placement surface side.

11. The electrostatic chuck according to claim 6, wherein: The protrusion is formed integrally with other portions of the dielectric substrate.

12. The electrostatic chuck according to claim 6, wherein: When the surface of the base plate facing the dielectric substrate via the bonding layer is regarded as the facing surface, A portion of the ventilation insert protrudes from the opposing surface toward the dielectric substrate.

13. The electrostatic chuck according to claim 12, wherein: The opposite surface is covered by an insulating film, A portion of the ventilation plug protrudes from a surface of the insulating film toward the dielectric substrate.

14. The electrostatic chuck according to claim 12, wherein: An annular sealing member is arranged between the ventilation plug and the dielectric substrate. The bonding layer is prevented from invading the inner side of the sealing member.

15. The electrostatic chuck according to claim 1, wherein: A bonding layer is further provided for bonding the dielectric substrate and the base plate. When the surface of the base plate facing the dielectric substrate via the bonding layer is regarded as the facing surface, A portion of the ventilation insert protrudes from the opposing surface toward the dielectric substrate.

16. An electrostatic chuck, characterized in that: The invention comprises: a dielectric substrate having a placement surface for placing an adsorbent and having a first air hole formed thereon; A base plate, which is a metal member supporting the dielectric substrate and has a second air hole formed at a position corresponding to the first air hole; and a bonding layer for bonding the dielectric substrate and the base plate, A protrusion protruding toward the base plate is formed on a surface of the dielectric substrate on the base plate side. The first air hole is formed to penetrate the protrusion.

17. The electrostatic chuck according to claim 16, wherein: A ventilation plug is disposed inside the second air hole.

18. The electrostatic chuck according to claim 17, wherein: When the surface of the base plate facing the dielectric substrate via the bonding layer is regarded as the facing surface, A portion of the ventilation insert protrudes from the opposing surface toward the dielectric substrate.

19. The electrostatic chuck according to claim 18, wherein: The opposite surface is covered by an insulating film, A portion of the ventilation plug protrudes from a surface of the insulating film toward the dielectric substrate.

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