Electrostatic chuck

Abstract

The present invention aims to provide an electrostatic chuck in which the resistance to arc discharge and the flow rate of the flowing gas can be ensured while the mechanical strength (rigidity) of the porous portion is improved. An electrostatic chuck is provided, characterized in that a first porous portion has: a loose portion having a plurality of pores; and a dense portion having a higher density than the density of the loose portion, the plurality of loose portions each extend in a first direction from a base plate toward a ceramic dielectric substrate, the dense portion is located between the plurality of loose portions, the loose portion has a wall portion provided between the pores, and in a second direction that is substantially orthogonal to the first direction, the minimum value of the size of the wall portion is smaller than the minimum value of the size of the dense portion.

Description

[0001] This application is a divisional application of the invention patent application filed on February 28, 2019, entitled "Electrostatic Chuck" and with application number "201910149338.6". Technical Field

[0002] The present invention relates to an electrostatic chuck. Background Technology

[0003] A ceramic electrostatic chuck, manufactured by sandwiching electrodes between ceramic dielectric substrates such as alumina and then firing them, applies electrostatic power to the built-in electrodes and uses electrostatic force to attract substrates such as silicon wafers. In such an electrostatic chuck, an inert gas such as helium (He) flows between the surface of the ceramic dielectric substrate and the back of the substrate to be attracted, thereby controlling the temperature of the substrate.

[0004] For example, in apparatuses that process substrates, such as chemical vapor deposition (CVD) devices, sputtering devices, ion implantation devices, and etching devices, there are components that cause the substrate temperature to rise during processing. In electrostatic chucks used in such devices, an inert gas, such as he, flows between the ceramic dielectric substrate and the substrate to be adsorbed, thereby suppressing the temperature rise of the substrate by bringing the inert gas into contact with the substrate.

[0005] In an electrostatic chuck that controls substrate temperature using an inert gas such as He, holes (gas introduction paths) for introducing the inert gas such as He are provided in a ceramic dielectric substrate and a base plate supporting the ceramic dielectric substrate. Furthermore, through holes communicating with the gas introduction path in the base plate are provided on the ceramic dielectric substrate. Thus, the inert gas introduced from the gas introduction path in the base plate is guided to the back side of the substrate through the through holes in the ceramic dielectric substrate.

[0006] Here, when processing a substrate within a device, discharges (arc discharges) sometimes occur from plasma within the device toward a metal base plate. The gas inlet path of the base plate and the through-holes of the ceramic dielectric substrate can easily become discharge paths. Therefore, there are techniques that improve resistance to arc discharges (insulation strength, etc.) by providing porous portions in the gas inlet path of the base plate and the through-holes of the ceramic dielectric substrate. For example, Patent Document 1 discloses an electrostatic chuck that improves insulation within the gas inlet path by providing a sintered ceramic porous body within the gas inlet path, using the structure and pores of the sintered ceramic porous body as a gas flow path. Patent Document 2 discloses an electrostatic chuck that provides a discharge prevention member, constructed of a ceramic porous body, within the gas diffusion gap for preventing discharge in the processing gas flow path. Patent Document 3 discloses an electrostatic chuck that reduces arc discharge by providing a dielectric insert as a porous dielectric such as alumina. In such an electrostatic chuck with a porous structure, it is necessary to ensure resistance to arc discharge and the flow rate of gas, while improving the mechanical strength (rigidity) of the porous structure.

[0007] Patent Document 1: Japanese Patent Application Publication No. 2010-123712

[0008] Patent Document 2: Japanese Patent Application Publication No. 2003-338492

[0009] Patent Document 3: Japanese Patent Application Publication No. 10-50813 Summary of the Invention

[0010] This invention is based on the understanding of such a problem, and the technical problem to be solved is to provide an electrostatic chuck that, in an electrostatic chuck with a porous part, can ensure resistance to arc discharge and flow of gas, while improving the mechanical strength (rigidity) of the porous part.

[0011] The first invention is an electrostatic chuck, characterized by comprising: a ceramic dielectric substrate having a first main surface for placing an object to be adsorbed, a second main surface opposite to the first main surface, and an electrode disposed between the first main surface and the second main surface; a base plate supporting the ceramic dielectric substrate and having a gas inlet path; a first porous portion disposed between the base plate and the first main surface of the ceramic dielectric substrate and at a position opposite to the gas inlet path; and a second porous portion disposed between the first porous portion and the gas inlet path, wherein a first direction is defined as the direction from the base plate toward the ceramic dielectric substrate, and when projected onto a plane perpendicular to the first direction, the electrode and the gas inlet path do not coincide.

[0012] According to this electrostatic chuck, since the first porous part is provided with a loose portion and a dense portion extending in the first direction, it is possible to ensure resistance to electric arc discharge and gas flow, while also improving the mechanical strength (rigidity) of the first porous part.

[0013] The second invention is an electrostatic chuck, characterized in that, in the first invention, the size of the plurality of holes respectively provided in the plurality of loose portions in the second direction is smaller than the size of the dense portions.

[0014] According to this electrostatic chuck, the resistance to arc discharge can be further improved because the size of multiple holes can be significantly reduced.

[0015] The third invention is an electrostatic chuck, characterized in that, in the first or second invention, the aspect ratio of the plurality of holes respectively provided in the plurality of loose portions is 30 or more and 10000 or less.

[0016] Based on this electrostatic chuck, resistance to arc discharge can be further improved.

[0017] The fourth invention is an electrostatic chuck, characterized in that, in any one of the first to third inventions, in the second direction, the size of the plurality of holes respectively provided in the plurality of loose portions is 1 micrometer or more and 20 micrometers or less.

[0018] According to this electrostatic chuck, since it is possible to arrange holes with a size of 1 to 20 micrometers extending in one direction, it is possible to achieve high resistance to electric arc discharge.

[0019] The fifth invention is an electrostatic chuck, characterized in that, in any one of the first to fourth inventions, when viewed along the first direction, the first hole is located at the center of the loose portion, and among the plurality of holes, the number of holes adjacent to and surrounding the first hole is six.

[0020] According to this electrostatic chuck, when viewed from above, multiple holes can be arranged with high isotropy and high density. This ensures resistance to arc discharge and adequate gas flow, while also improving the rigidity of the first porous section.

[0021] The sixth invention is an electrostatic chuck, characterized in that, in any one of the first to fifth inventions, it further comprises an electrode disposed between the first main surface and the second main surface, and the distance in a second direction between the porous region of the first porous part and the electrode is longer than the distance in a first direction between the first main surface and the electrode.

[0022] According to this electrostatic chuck, by further increasing the distance in the second direction between the porous region of the first porous portion and the electrode, discharge in the first porous portion can be suppressed. Furthermore, by further shortening the distance in the first direction between the first main surface and the electrode, the force for adsorbing objects placed on the first main surface can be increased.

[0023] The seventh invention is an electrostatic chuck, characterized in that, in any one of the first to sixth inventions, it further comprises a second porous portion disposed between the first porous portion and the gas inlet path, wherein, in the second direction, the size of the second porous portion is larger than the size of the first porous portion.

[0024] According to this electrostatic chuck, since a higher insulation strength can be obtained by setting a second porous part, the occurrence of arc discharge can be suppressed more effectively.

[0025] The eighth invention is an electrostatic chuck, characterized in that, in any one of the first to seventh inventions, it further comprises a second porous part having a plurality of holes disposed between the first porous part and the gas inlet path, wherein the average diameter of the plurality of holes disposed in the second porous part is larger than the average diameter of the plurality of holes disposed in the first porous part.

[0026] According to this electrostatic chuck, the presence of a second porous section with a larger diameter pore facilitates smooth gas flow. Furthermore, the smaller diameter first porous section, located on the object being adsorbed, more effectively suppresses arc discharge.

[0027] The ninth invention is an electrostatic chuck, characterized in that, in any one of the inventions from the first to the seventh, it further comprises a second porous part having a plurality of holes disposed between the first porous part and the gas inlet path, wherein the diameter deviation of the plurality of holes disposed in the first porous part is smaller than the diameter deviation of the plurality of holes disposed in the second porous part.

[0028] According to this electrostatic chuck, since the diameter deviation of the multiple holes provided in the first porous part is smaller than the diameter deviation of the multiple holes provided in the second porous part, the occurrence of arc discharge can be suppressed more effectively.

[0029] The tenth invention is an electrostatic chuck, characterized in that, in the eighth or ninth invention, the size of the second porous portion is larger than the size of the first porous portion in the first direction.

[0030] According to this electrostatic chuck, since higher insulation strength can be obtained, the occurrence of arc discharge can be suppressed more effectively.

[0031] The 11th invention is an electrostatic chuck, characterized in that, in any one of the 8th to 10th inventions, the plurality of holes provided in the second porous part are more dispersed in three dimensions than the plurality of holes provided in the first porous part, and the proportion of holes penetrating in the first direction is greater in the first porous part than in the second porous part.

[0032] Furthermore, referring to Figure 10 An example of pores dispersed in 3D will be discussed later.

[0033] According to this electrostatic chuck, higher insulation strength can be obtained by providing a second porous section with multiple holes dispersed in three dimensions, thus more effectively suppressing the occurrence of arc discharge. Furthermore, by providing a first porous section with a higher proportion of holes penetrating in the first direction, smoother gas flow can be achieved.

[0034] The 12th invention is an electrostatic chuck, characterized in that, in any one of the inventions from the 1st to the 11th, the first porous portion and the ceramic dielectric substrate contain alumina as main components, and the purity of the alumina in the ceramic dielectric substrate is higher than the purity of the alumina in the first porous portion.

[0035] This electrostatic chuck ensures properties such as plasma resistance and guarantees the mechanical strength of the first porous section. As an example, by including trace amounts of additives in the first porous section, sintering of the first porous section is promoted, ensuring control of porosity and mechanical strength.

[0036] According to the present invention, an electrostatic chuck is provided, which, in the case of an electrostatic chuck with a porous portion, can ensure resistance to electric arc discharge and flow of gas, while improving the mechanical strength (rigidity) of the porous portion. Attached Figure Description

[0037] Figure 1 This is a schematic cross-sectional view illustrating the electrostatic chuck involved in this embodiment.

[0038] Figure 2 (a) and Figure 2 (b) is a schematic diagram illustrating the electrostatic chuck involved in the embodiment. Figure 2 (c) and (d) are schematic cross-sectional views illustrating the hole 15c involved in other embodiments.

[0039] Figure 3 (a) and Figure 3 (b) is a schematic diagram illustrating the first porous part of the electrostatic chuck according to the illustrative embodiment.

[0040] Figure 4This is a schematic top view of the first porous part of the electrostatic chuck according to the illustrated embodiment.

[0041] Figure 5 This is a schematic top view of the first porous part of the electrostatic chuck according to the illustrated embodiment.

[0042] Figure 6 (a) and Figure 6 (b) is a schematic top view of the first porous part of the electrostatic chuck according to the illustrative embodiment.

[0043] Figure 7 (a) and Figure 7 (b) is a schematic diagram illustrating another first porous material part involved in the embodiment.

[0044] Figure 8 This is a schematic cross-sectional view of the electrostatic chuck involved in the illustrative embodiment.

[0045] Figure 9 (a) and Figure 9 (b) is a schematic cross-sectional view of the electrostatic chuck involved in the illustrative embodiment.

[0046] Figure 10 This is a schematic cross-sectional view of the second porous part of the electrostatic chuck according to the illustrated embodiment.

[0047] Figure 11 This is a schematic cross-sectional view illustrating other electrostatic chucks involved in the illustrative embodiments.

[0048] Figure 12 This is a schematic cross-sectional view illustrating other electrostatic chucks involved in the illustrative embodiments.

[0049] Symbol Explanation

[0050] 11-Ceramic dielectric substrate; 11a-First main surface; 11b-Second main surface; 11p-First substrate region; 12-Electrode; 13-Point; 14-Groove; 15-Through hole; 15a-Hole; 15b-Hole (First hole); 15c-Hole (Second hole); 15w-Inner wall; 20-Connecting part; 50-Base plate; 50U-Top; 50a-Upper part; 50b-Lower part; 51-Input path; 52-Output path; 53-Gas introduction path; 55-Connecting path; 60-Adhesive part; 70-Second porous part; 70U-Top; 71- Ceramic porous body; 71p - pore; 72 - ceramic insulating film; 80 - adsorption and retention voltage; 90 - first porous part; 90L - bottom; 90U - top; 90p - first region; 91 - porous region; 91s - side; 93 - dense region, 93s - side; 94 - loose part; 94a~94g - first to seventh loose parts; 95 - dense part; 96 - pore; 96a~96g - first to seventh pore; 97 - wall; 110 - electrostatic chuck; W - object; SP - space; ROI1 - evaluation range; ROI2 - evaluation range. Detailed Implementation

[0051] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, in each drawing, the same reference numerals are used to denote the same constituent elements, and detailed descriptions are omitted where appropriate.

[0052] Figure 1 This is a schematic cross-sectional view illustrating the electrostatic chuck involved in this embodiment.

[0053] like Figure 1 As shown, the electrostatic chuck 110 according to this embodiment includes a ceramic dielectric substrate 11, a base plate 50, and a first porous portion 90.

[0054] The ceramic dielectric substrate 11 is, for example, a flat substrate material formed from sintered ceramic. For example, the ceramic dielectric substrate 11 contains alumina (Al₂O₃). For example, the ceramic dielectric substrate 11 is formed from high-purity alumina. The concentration of alumina in the ceramic dielectric substrate 11 is, for example, 99 atomic% or more and 100 atomic% or less. By using high-purity alumina, the plasma resistance of the ceramic dielectric substrate 11 can be improved. The ceramic dielectric substrate 11 has: a first main surface 11a on which the adsorbate W is placed; and a second main surface 11b located opposite to the first main surface 11a. The adsorbate W is, for example, a semiconductor substrate such as a silicon wafer.

[0055] An electrode 12 is disposed in a ceramic dielectric substrate 11. The electrode 12 is disposed between a first main surface 11a and a second main surface 11b of the ceramic dielectric substrate 11. The electrode 12 is formed by being inserted into the ceramic dielectric substrate 11. The electrostatic chuck 110 is as follows: by applying an adsorption and holding voltage 80 to the electrode 12, a charge is generated on the first main surface 11a side of the electrode 12, and the object W is adsorbed and held by electrostatic force.

[0056] In this embodiment, the direction from the base plate 50 toward the ceramic dielectric substrate 11 is referred to as the Z direction (an example of the first direction), one of the directions that is approximately orthogonal to the Z direction is referred to as the Y direction (an example of the second direction), and the direction that is approximately orthogonal to the Z and Y directions is referred to as the X direction (an example of the second direction).

[0057] The electrode 12 is a thin film extending along the first main surface 11a and the second main surface 11b of the ceramic dielectric substrate 11. The electrode 12 is an adsorption electrode used to adsorb and hold the object W. The electrode 12 can be either unipolar or bipolar. Figure 1 The electrode 12 shown is bipolar, with two electrodes 12 disposed on the same surface.

[0058] The electrode 12 is provided with a connecting portion 20 extending toward the second main surface 11b of the ceramic dielectric substrate 11. The connecting portion 20 is, for example, a via (solid type) or a via hole (hollow type) that communicates with the electrode 12. The connecting portion 20 can also be a metal terminal that is connected by a suitable method such as brazing.

[0059] The base plate 50 is a component that supports the ceramic dielectric substrate 11. The ceramic dielectric substrate 11 is mediated by... Figure 2 The adhesive portion 60 shown in (a) is fixed to the base plate 50. For example, the portion of the silicone adhesive that has hardened can be used as the adhesive portion 60.

[0060] The base plate 50 is, for example, made of metal. The base plate 50 is, for example, divided into an upper part 50a and a lower part 50b made of aluminum, and a connecting passage 55 is provided between the upper part 50a and the lower part 50b. One end of the connecting passage 55 is connected to the input passage 51, and the other end of the connecting passage 55 is connected to the output passage 52.

[0061] The base plate 50 also functions as a temperature regulator for the electrostatic chuck 110. For example, when cooling the electrostatic chuck 110, a cooling medium flows in from the input path 51 and out from the output path 52 through the connecting path 55. Thus, by absorbing heat from the base plate 50, the cooling medium can cool the ceramic dielectric substrate 11 mounted thereon. On the other hand, when heat preservation is needed for the electrostatic chuck 110, a heat preservation medium can be placed in the connecting path 55. A heating element can also be placed within the ceramic dielectric substrate 11 and the base plate 50. By adjusting the temperature of the base plate 50 and the ceramic dielectric substrate 11, the temperature of the object W held and held by the electrostatic chuck 110 can be adjusted.

[0062] Furthermore, on the first main surface 11a side of the ceramic dielectric substrate 11, dots 13 are provided as needed, and grooves 14 are provided between the dots 13. That is, the first main surface 11a is a concave-convex surface, having concave portions and convex portions. The convex portions of the first main surface 11a correspond to the dots 13, and the concave portions of the first main surface 11a correspond to the grooves 14. The grooves 14 extend continuously in the XY plane. A space is formed between the back side of the object W placed on the electrostatic chuck 110 and the first main surface 11a containing the grooves 14.

[0063] The ceramic dielectric substrate 11 has a through hole 15 connected to the groove 14. The through hole 15 is provided across the span from the second main surface 11b to the first main surface 11a. That is, the through hole 15 extends in the Z direction from the second main surface 11b to the first main surface 11a and passes through the ceramic dielectric substrate 11.

[0064] By appropriately selecting the height of point 13 (depth of groove 14) and the area ratio and shape of point 13 to groove 14, the temperature of object W and the particles attached to object W can be controlled in an optimal state.

[0065] A gas inlet path 53 is provided on the base plate 50. The gas inlet path 53 may be provided, for example, by passing through the base plate 50. Alternatively, the gas inlet path 53 may not pass through the base plate 50 and may branch off from other gas inlet paths 53 to the ceramic dielectric substrate 11 side. In addition, the gas inlet path 53 may be provided at multiple locations on the base plate 50.

[0066] Gas inlet path 53 is connected to through hole 15. That is, gas (helium (He) etc.) flowing into gas inlet path 53 flows into through hole 15 after passing through gas inlet path 53.

[0067] Gas flowing into the through-hole 15 flows into the space between the object W and the first main surface 11a of the containing groove 14 after passing through the through-hole 15. Thus, the object W can be directly cooled by gas.

[0068] The first porous portion 90 can be disposed in the Z direction between the base plate 50 and the first main surface 11a of the ceramic dielectric substrate 11, and at a position opposite to the gas inlet path 53. For example, the first porous portion 90 can be disposed in the through hole 15 of the ceramic dielectric substrate 11. For example, the first porous portion 90 can be inserted into the through hole 15.

[0069] Figure 2 (a) and Figure 2 (b) is a schematic diagram illustrating the electrostatic chuck involved in the embodiment. Figure 2 (a) Example of the periphery of the first porous part 90. Figure 2 (a) is equivalent to Figure 1 An enlarged view of region A shown. Figure 2 (b) is a top view illustrating the first porous section 90.

[0070] in addition, Figure 2 (c) and (d) are schematic cross-sectional views illustrating the hole 15c involved in other embodiments.

[0071] Furthermore, in order to avoid becoming complicated, Figure 2 Point 13 is omitted in (a), (c), and (d) (for example, refer to...). Figure 1 It was described in this way.

[0072] In this example, the through hole 15 has a hole portion 15a and a hole portion 15b (equivalent to an example of the first hole portion). One end of the hole portion 15a is located on the second main surface 11b of the ceramic dielectric substrate 11.

[0073] Furthermore, the ceramic dielectric substrate 11 can have a hole 15b located in the Z direction between the first main surface 11a and the first porous portion 90. The hole 15b communicates with the hole 15a and extends to the first main surface 11a of the ceramic dielectric substrate 11. That is, one end of the hole 15b is located on the first main surface 11a (groove 14). The hole 15b is a connecting hole connecting the first porous portion 90 and the groove 14. The diameter (length in the X direction) of the hole 15b is smaller than the diameter (length in the X direction) of the hole 15a. By providing a hole 15b with a smaller diameter, the design freedom of the space (e.g., the first main surface 11a including the groove 14) between the ceramic dielectric substrate 11 and the object W can be increased. For example, as Figure 2 As shown in (a), the width (length in the X direction) of the groove 14 can be made smaller than the width (length in the X direction) of the first porous portion 90. As a result, for example, discharge can be suppressed in the space provided between the ceramic dielectric substrate 11 and the object W.

[0074] The diameter of hole 15b is, for example, 0.05 mm or more and 0.5 mm or less. The diameter of hole 15a is, for example, 1 mm or more and 5 mm or less. Furthermore, hole 15b can also be indirectly connected to hole 15a. That is, hole 15c (an example relative to the second hole) can also be provided to connect hole 15a and hole 15b. Figure 2 As shown in (a), a hole 15c can be provided on the ceramic dielectric substrate 11. Figure 2 As shown in (c), the pore portion 15c can also be provided in the first porous portion 90. For example... Figure 2 As shown in (d), the hole 15c can also be provided in both the ceramic dielectric substrate 11 and the first porous portion 90. That is, at least one of the ceramic dielectric substrate 11 and the first porous portion 90 can have a hole 15c located between the hole 15b and the first porous portion 90. In this case, if the hole 15c is provided in the ceramic dielectric substrate 11, the strength around the hole 15c can be improved, and tilting around the hole 15c can be suppressed. Therefore, the occurrence of arc discharge can be suppressed more effectively. If the hole 15c is provided in the first porous portion 90, it is easier to align the hole 15c with the first porous portion 90. Therefore, it is easier to simultaneously reduce arc discharge and smooth gas flow. The holes 15a, 15b, and 15c are, for example, cylindrical shapes extending in the Z direction.

[0075] At this time, in the X or Y direction, the size of the orifice 15c can be smaller than the size of the first porous portion 90 and larger than the size of the orifice 15b. According to the electrostatic chuck 110 of this embodiment, by providing the first porous portion 90 at a position opposite to the gas inlet path 53, the flow rate of gas flowing in the orifice 15b can be ensured, while simultaneously improving resistance to arc discharge. Furthermore, since the size of the orifice 15c in the X or Y direction is larger than that of the orifice 15b, most of the gas introduced into the larger first porous portion 90 can be introduced into the smaller orifice 15b via the orifice 15c. That is, arc discharge reduction and smooth gas flow can be achieved.

[0076] As described above, the ceramic dielectric substrate 11 has at least one groove 14 that opens into the first main surface 11a and communicates with the first aperture 15. In the Z direction, the size of the aperture 15c can be smaller than the size of the groove 14. This allows gas to be supplied to the first main surface 11a via the groove 14. Therefore, it is easier to supply gas to a larger area of ​​the first main surface 11a. Furthermore, since the size of the aperture 15c in the X or Y direction is smaller than the size of the groove 14, the time for gas to pass through the aperture 15c can be shortened. That is, while achieving smooth gas flow, the occurrence of arc discharge can be suppressed more effectively.

[0077] As described above, an adhesive portion 60 can be provided between the ceramic dielectric substrate 11 and the base plate 50. In the Z-direction, the size of the hole 15c can be smaller than the size of the adhesive portion 60. This improves the bonding strength between the ceramic dielectric substrate 11 and the base plate 50. Furthermore, since the size of the hole 15c in the Z-direction is smaller than the size of the adhesive portion 60, it is possible to more effectively suppress arc discharge while simultaneously ensuring smooth gas flow.

[0078] Furthermore, the size of the hole 15c in the X or Y direction can be made larger than the size of the groove 14 in the X or Y direction. This allows for smoother gas flow while more effectively suppressing arc discharge.

[0079] In this example, the first porous portion 90 is disposed in the hole portion 15a. Therefore, the upper surface 90U of the first porous portion 90 does not expose to the first main surface 11a. That is, the upper surface 90U of the first porous portion 90 is located between the first main surface 11a and the second main surface 11b. On the other hand, the lower surface 90L of the first porous portion 90 exposes to the second main surface 11b.

[0080] The first porous portion 90 comprises: a porous region 91 having multiple pores; and a dense region 93, which is denser than the porous region 91. The dense region 93 is a region with fewer pores than the porous region 91 or a region that is substantially pore-free. The porosity (percentage: %) of the dense region 93 is lower than that of the porous region 91. Therefore, the density (g / cm³) of the dense region 93 is lower. 3 The density (g / cm³) of the porous region 91 3 The dense region 93 is denser than the porous region 91, therefore, the rigidity (mechanical strength) of the dense region 93 is higher than that of the porous region 91.

[0081] The porosity of the dense region 93 is, for example, the volume ratio of the space (pores) contained in the dense region 93 to the total volume of the dense region 93. The porosity of the porous region 91 is, for example, the volume ratio of the space (pores) contained in the porous region 91 to the total volume of the porous region 91. For example, the porosity of the porous region 91 is 5% or more and 40% or less, preferably 10% or more and 30% or less, and the porosity of the dense region 93 is 0% or more and 5% or less.

[0082] The first porous portion 90 is columnar (e.g., cylindrical). Additionally, the porous region 91 is columnar (e.g., cylindrical). The dense region 93 contacts or continues the porous region 91. Figure 2As shown in (b), when viewed along the Z direction, the dense region 93 surrounds the outer periphery of the porous region 91. The dense region 93 is cylindrical (e.g., cylindrical) surrounding the side surface 91s of the porous region 91. In other words, the porous region 91 is configured to penetrate the dense region 93 in the Z direction. Gas flowing into the through-hole 15 from the gas inlet 53 is fed into the groove 14 through the plurality of holes provided in the porous region 91.

[0083] By providing a first porous portion 90 with such a porous region 91, the gas flow rate in the through hole 15 can be ensured, while resistance to arc discharge can be improved. In addition, since the first porous portion 90 has a dense region 93, the rigidity (mechanical strength) of the first porous portion 90 can be improved.

[0084] For example, the first porous portion 90 is integrated with the ceramic dielectric substrate 11. The integration of the two components refers to a state where the two components are chemically bonded, for example, through sintering. No material (e.g., adhesive) is provided between the two components to fix one component to the other. That is, the first porous portion 90 and the ceramic dielectric substrate 11 are integrated without any other components such as adhesives provided between them.

[0085] More specifically, when the first porous portion 90 is integrated with the ceramic dielectric substrate 11, the side surface of the first porous portion 90 (the side surface 93s of the dense region 93) contacts the inner wall 15w of the through hole 15, and the first porous portion 90 is supported and fixed to the ceramic dielectric substrate 11 by the inner wall 15w in contact with the first porous portion 90.

[0086] For example, through holes are provided on the substrate material before sintering to become the ceramic dielectric substrate 11, and the first porous portion 90 is embedded in the through holes. By sintering the ceramic dielectric substrate 11 (and the embedded first porous portion 90) in this state, the first porous portion 90 and the ceramic dielectric substrate 11 can be integrated.

[0087] In this way, by integrating with the ceramic dielectric substrate 11, the first porous portion 90 is fixed to the ceramic dielectric substrate 11. As a result, the strength of the electrostatic chuck 110 can be improved compared to fixing the first porous portion 90 to the ceramic dielectric substrate 11 with adhesives or the like. For example, the electrostatic chuck will not age due to corrosion, ablation, or other causes of adhesives.

[0088] When the first porous portion 90 is integrated with the ceramic dielectric substrate, the outer periphery of the first porous portion 90 is subjected to forces from the ceramic dielectric substrate. On the other hand, when multiple holes are provided in the first porous portion 90 to ensure gas flow, the mechanical strength of the first porous portion 90 is reduced. Therefore, when the first porous portion is integrated with the ceramic dielectric substrate, the first porous portion may break due to the forces applied to it from the ceramic dielectric substrate.

[0089] In contrast, since the first porous portion 90 has a dense region 93, the rigidity (mechanical strength) of the first porous portion 90 can be improved, and the first porous portion 90 can be integrated into the ceramic dielectric substrate 11.

[0090] Furthermore, in this embodiment, the first porous portion 90 may not necessarily be integrally formed with the ceramic dielectric substrate 11. For example, as... Figure 12 As shown, the first porous portion 90 can also be mounted on a ceramic dielectric substrate using an adhesive.

[0091] Furthermore, the dense region 93 is located between the inner wall 15w of the ceramic dielectric substrate 11 where the through-hole 15 is formed and the porous region 91. That is, the porous region 91 is provided on the inner side of the first porous portion 90, and the dense region 93 is provided on the outer side. By providing the dense region 93 on the outer side of the first porous portion 90, the rigidity against the force applied to the first porous portion 90 from the ceramic dielectric substrate 11 can be improved. As a result, the first porous portion 90 and the ceramic dielectric substrate 11 can be easily integrated. In addition, for example, an adhesive member 61 is provided between the first porous portion 90 and the ceramic dielectric substrate 11 (see reference). Figure 12 When the dense region 93 is used, it is possible to suppress gas from contacting the adhesive member 61 through the interior of the first porous portion 90. This suppresses aging of the adhesive member 61. Furthermore, by providing the porous region 91 inside the first porous portion 90, the through-holes 15 of the ceramic dielectric substrate 11 are prevented from being blocked by the dense region 93, ensuring gas flow.

[0092] The thickness of the dense region 93 (the length L0 between the side 91s of the porous region 91 and the side 93s of the dense region 93) is, for example, more than 100 μm and less than 1000 μm.

[0093] The first porous portion 90 is made of an insulating ceramic. The first porous portion 90 (each porous region 91 and dense region 93) contains at least one of alumina (Al2O3), titanium oxide (TiO2), and yttrium oxide (Y2O3). As a result, the first porous portion 90 has high insulation strength and high rigidity.

[0094] For example, the first porous part 90 may use any one of alumina, titanium dioxide and yttrium oxide as the main component.

[0095] At this point, the purity of the alumina in the ceramic dielectric substrate 11 can be higher than the purity of the alumina in the first porous portion 90. This ensures the plasma resistance and other properties of the electrostatic chuck 110, and also ensures the mechanical strength of the first porous portion 90. As an example, by including trace amounts of additives in the first porous portion 90, sintering of the first porous portion 90 is promoted, ensuring control over porosity and mechanical strength.

[0096] This specification allows for the determination of the ceramic purity of alumina and other materials in the ceramic dielectric substrate 11 using methods such as fluorescence X-ray analysis and ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry).

[0097] For example, the material of porous region 91 is the same as the material of dense region 93. However, the material of porous region 91 and dense region 93 can also be different. The composition of the material of porous region 91 can also be different from the composition of the material of dense region 93.

[0098] In addition, such as Figure 2 As shown in (a), the distance D1 in the X or Y direction between the porous region 91 (the plurality of loose portions 94 described later) and the electrode 12 is longer than the distance D2 in the Z direction between the first main surface 11a and the electrode 12. By further increasing the distance D1 in the X or Y direction between the porous region 91 provided in the first porous portion 90 and the electrode 12, discharge in the first porous portion 90 can be suppressed. In addition, by further shortening the distance D2 in the Z direction between the first main surface 11a and the electrode 12, the force for adsorbing the object W placed on the first main surface 11a can be increased.

[0099] Figure 3 (a) and Figure 3 (b) is a schematic diagram illustrating the first porous part of the electrostatic chuck according to the illustrative embodiment.

[0100] Figure 3 (a) is a top view of the first porous section 90 viewed along the Z direction. Figure 3 (b) is a cross-sectional view of the first porous section 90 on the ZY plane.

[0101] like Figure 3 (a) and Figure 3As shown in (b), in this example, the porous region 91 has multiple loose portions 94 and dense portions 95. Each of the loose portions 94 has multiple pores. The dense portions 95 are more compact than the loose portions 94. That is, the dense portions 95 are portions with fewer pores than the loose portions 94, or portions that are substantially pore-free. The porosity of the dense portions 95 is lower than that of the loose portions 94. Therefore, the density of the dense portions 95 is higher than that of the loose portions 94. The porosity of the dense portions 95 can also be the same as that of the dense region 93. Because the dense portions 95 are more compact than the loose portions 94, the rigidity of the dense portions 95 is higher than that of the loose portions 94.

[0102] The porosity of a loose portion 94 is, for example, the volume ratio of the spaces (pores) contained in the loose portion 94 to the total volume of the loose portion 94. The porosity of a compact portion 95 is, for example, the volume ratio of the spaces (pores) contained in the compact portion 95 to the total volume of the compact portion 95. For example, the porosity of the loose portion 94 is 20% or more and 60% or less, preferably 30% or more and 50% or less, and the porosity of the compact portion 95 is 0% or more and 5% or less.

[0103] Multiple loose portions 94 extend in the Z direction. For example, the multiple loose portions 94 are each columnar (cylindrical or polygonal) and are configured to penetrate the porous region 91 in the Z direction. Compact portions 95 are located between the multiple loose portions 94. The compact portions 95 are walls that separate adjacent loose portions 94. Figure 3 As shown in (a), when viewed along the Z direction, the compact portion 95 is configured to surround the respective outer periphery of the plurality of loose portions 94. The compact portion 95 is continuous with the dense region 93 at the outer periphery of the porous region 91.

[0104] The number of loose portions 94 disposed within the porous region 91 is, for example, 50 or more and less than 1000. Figure 3 As shown in (a), when viewed along the Z direction, the multiple loose portions 94 are approximately the same size as each other. For example, when viewed along the Z direction, the multiple loose portions 94 are isotropically and equally distributed within the porous region 91. For example, the distance between adjacent loose portions 94 (i.e., the thickness of the compact portion 95) is approximately constant.

[0105] For example, when viewed along the Z direction, the distance L11 between the side 93s of the dense region 93 and the loose portion 94 closest to the side 93s among the multiple loose portions 94 is more than 100 μm and less than 1000 μm.

[0106] In this way, by providing multiple loose portions 94 and denser portions 95 in the porous region 91, compared with the case where multiple pores are randomly distributed in 3 dimensions in the porous region, it is possible to ensure resistance to electric arc discharge and gas flow in the through hole 15, while improving the rigidity of the first porous part 90.

[0107] For example, if the porosity of the porous region increases, the gas flow rate increases, while the resistance to arc discharge and rigidity decrease. In contrast, by providing a tight section 95, the decrease in resistance to arc discharge and rigidity can be suppressed even with increased porosity.

[0108] For example, when viewed along the Z direction, imagine the smallest circle, ellipse, or polygon comprising all the multiple loose portions 94. The inner side of this circle, ellipse, or polygon can be considered as a porous region 91, while the outer side of the circle, ellipse, or polygon can be considered as a dense region 93.

[0109] As explained above, the first porous portion 90 can have: a plurality of loose portions 94 having a plurality of holes 96 including a first hole and a second hole; and a compact portion 95 having a density higher than that of the loose portions 94. The plurality of loose portions 94 extend in the Z direction. The compact portion 95 is located between the plurality of loose portions 94. Each loose portion 94 has a wall portion 97 provided between holes 96 (first hole) and holes 96 (second hole). In the X or Y direction, the minimum size of the wall portion 97 can be smaller than the minimum size of the compact portion 95. Thus, since the first porous portion 90 has loose portions 94 and compact portions 95 extending in the Z direction, resistance to arc discharge and gas flow can be ensured, while the mechanical strength (rigidity) of the first porous portion 90 can be improved.

[0110] In the X or Y direction, the size of the plurality of holes 96 respectively provided in the plurality of loose portions 94 can be made smaller than the size of the dense portions 95. In this way, since the size of the plurality of holes 96 can be sufficiently reduced, the resistance to arc discharge can be further improved.

[0111] Furthermore, the aspect ratio (dimension ratio) of the plurality of holes 96 respectively provided in the plurality of loose portions 94 can be 30 or more and 10,000 or less. This can further improve the resistance to arc discharge. More preferably, the lower limit of the aspect ratio (dimension ratio) of the plurality of holes 96 is 100 or more and the upper limit is 1600 or less.

[0112] Furthermore, in the X or Y direction, the size of the multiple holes 96 respectively provided in the multiple loose portions 94 can be 1 micrometer or more and 20 micrometers or less. In this way, since holes 96 with a size of 1 to 20 micrometers extending in one direction can be arranged, a high resistance to arc discharge can be achieved.

[0113] In addition, as will be discussed later Figure 6 As shown in (a) and (b), when viewed along the Z-direction, the first hole 96a is located at the center of the porous portion 94. Among the multiple holes 96, the number of holes 96b to 96g adjacent to and surrounding the first hole 96a can be six. In this way, when viewed along the Z-direction, the multiple holes 96 can be arranged with high isotropy and high density. As a result, resistance to arc discharge and flow of gas can be ensured, while the rigidity of the first porous portion 90 can be improved.

[0114] Figure 4 This is a schematic top view of the first porous part of the electrostatic chuck according to the illustrated embodiment.

[0115] Figure 4 This represents a portion of the first porous section 90 as viewed along the Z direction, equivalent to Figure 3 (a) Enlarged view.

[0116] When viewed along the Z direction, the multiple loose portions 94 are approximately hexagonal (approximately regular hexagonal). When viewed along the Z direction, the multiple loose portions 94 have: a first loose portion 94a, located at the center of the porous region 91; and six loose portions 94 (the second to the seventh loose portions 94b to 94g) surrounding the first loose portion 94a.

[0117] Loose portions 94b to 94g, numbered 2 to 7, are adjacent to loose portion 94a, numbered 1 to 7. Loose portions 94b to 94g are the loose portions 94 that are closest to loose portion 94a among the loose portions 94.

[0118] The second loose portion 94b and the third loose portion 94c are arranged side by side with the first loose portion 94a in the X direction. That is, the first loose portion 94a is located between the second loose portion 94b and the third loose portion 94c.

[0119] The length L1 (diameter of the first loose portion 94a) in the X direction of the first loose portion 94a is longer than the length L2 in the X direction between the first loose portion 94a and the second loose portion 94b, and longer than the length L3 in the X direction between the first loose portion 94a and the third loose portion 94c.

[0120] Furthermore, lengths L2 and L3 are respectively equivalent to the thickness of the compact portion 95. That is, length L2 is the length of the compact portion 95 between the first loose portion 94a and the second loose portion 94b in the X direction. Length L3 is the length of the compact portion 95 between the first loose portion 94a and the third loose portion 94c in the X direction. Lengths L2 and L3 are approximately equal. For example, length L2 is more than 0.5 times and less than 2.0 times the length L3.

[0121] Furthermore, the length L1 is approximately equal to the length L4 (diameter of the second loose portion 94b) in the X direction, and approximately equal to the length L5 (diameter of the third loose portion 95c) in the X direction of the third loose portion 94c. For example, the lengths L4 and L5 are more than 0.5 times and less than 2.0 times the length L1, respectively.

[0122] Thus, the first porous portion 94a is adjacent to and surrounded by six of the plurality of porous portions 94. That is, when viewed along the Z direction, at the center of the porous region 91, there are six porous portions 94 adjacent to each porous portion 94. As a result, when viewed from above, the plurality of porous portions 94 can be arranged with higher isotropy and higher density. This ensures resistance to arc discharge and gas flow rate in the through-hole 15, while also improving the rigidity of the first porous portion 90. Furthermore, deviations in resistance to arc discharge, gas flow rate in the through-hole 15, and rigidity of the first porous portion 90 can be suppressed.

[0123] The diameter (length L1, L4, or L5, etc.) of the loose portion 94 is, for example, 50 μm or more and 500 μm or less. The thickness (length L2 or L3, etc.) of the dense portion 95 is, for example, 10 μm or more and 100 μm or less. The diameter of the loose portion 94 is larger than the thickness of the dense portion 95. In addition, the thickness of the dense portion 95 is thinner than the thickness of the dense region 93.

[0124] Figure 5 This is a schematic top view of the first porous part of the electrostatic chuck according to the illustrated embodiment.

[0125] Figure 5 This indicates a portion of the first porous section 90 as viewed along the Z direction. Figure 5 It is an enlarged view of the periphery of a loose section 94.

[0126] like Figure 5 As shown, in this example, the loose portion 94 has: a plurality of holes 96; and a wall portion 97 disposed between the plurality of holes 96.

[0127] Multiple pores 96 extend in the Z direction. Each pore 96 is a capillary-like structure extending in one direction (one-dimensional capillary structure), penetrating the loose portion 94 in the Z direction. Wall portions 97 form walls that separate adjacent pores 96. Figure 5 As shown, when viewed along the Z direction, the wall portion 97 is configured to surround the respective outer periphery of the plurality of holes 96. The wall portion 97 continues from the compact portion 95 at the outer periphery of the loose portion 94.

[0128] The number of holes 96 provided within a single loose section 94 is, for example, 50 or more and less than 1000. Figure 5 As shown, when viewed along the Z-direction, the plurality of holes 96 are approximately the same size as each other. For example, when viewed along the Z-direction, the plurality of holes 96 are isotropically and equally distributed within the loose portion 94. For example, the distance between adjacent holes 96 (i.e., the thickness of the wall portion 97) is approximately constant.

[0129] In this way, by arranging holes 96 extending in one direction within the loose portion 94, a higher resistance to arc discharge can be achieved with a smaller deviation compared to the case where multiple holes are randomly distributed in three dimensions within the loose portion.

[0130] Here, the "capillary structure" of the multiple pores 96 will be further explained.

[0131] In recent years, there has been further progress in reducing circuit linewidth and minimizing circuit spacing to achieve high integration of semiconductors. Applying greater power to electrostatic chucks requires a higher level of temperature control over the adsorbed object. In this context, it is necessary to reliably suppress arcing even under high-power conditions, while ensuring sufficient gas flow and controlling that flow with high precision. In the electrostatic chuck 110 of this embodiment, the ceramic plug (first porous part 90), which is conventionally provided to prevent arcing in the helium supply orifice (gas inlet path 53), has had its orifice diameter (diameter of orifice 96) reduced to, for example, a level of several micrometers to tens of micrometers (the diameter of orifice 96 will be described in detail later). If the diameter is reduced to this level, it may be difficult to control the gas flow. Therefore, in this invention, for example, the shape of orifice 96 has been further studied to make it along the Z-direction. Specifically, conventionally, flow is ensured by using a larger orifice, and arcing is prevented by making its shape more complex in three dimensions. On the other hand, in this invention, for example, the diameter of the orifice 96 is made as small as a few micrometers to tens of micrometers to prevent arc discharge, while the flow rate is ensured by simplifying its shape. That is, this invention was developed based on a completely different way of thinking than before.

[0132] Furthermore, the shape of the loose portion 94 is not limited to a hexagon; it can also be a circle (or ellipse) or other polygons. For example, when viewed along the Z direction, one can imagine the smallest circle, ellipse, or polygon comprising all the multiple holes 96 arranged at intervals of less than 10 μm. The inner side of this circle, ellipse, or polygon can be considered the loose portion 94, while the outer side can be considered the compact portion 95.

[0133] Figure 6 (a) and Figure 6 (b) is a schematic top view of the first porous part of the electrostatic chuck according to the illustrative embodiment.

[0134] Figure 6 (a) and Figure 6 (b) shows a portion of the first porous part 90 as viewed along the Z direction, and is an enlarged view of the pores 96 within a loose part 94.

[0135] like Figure 6 As shown in (a), when viewed along the Z direction, the plurality of holes 96 have: a first hole 96a, located at the center of the loose portion 94; and six holes 96 (holes 2 to 7, 96b to 96g), surrounding the first hole 96a. Holes 2 to 7, 96b to 96g, are adjacent to the first hole 96a. Holes 2 to 7, 96b to 96g, are the holes 96 closest to the first hole 96a among the plurality of holes 96.

[0136] Holes 2 (96b) and 3 (96c) are arranged side-by-side with hole 1 (96a) in the X direction. That is, hole 1 (96a) is located between hole 2 (96b) and hole 3 (96c).

[0137] For example, the length L6 (diameter of the first hole 96a) along the X direction of the first hole 96a is longer than the length L7 along the X direction between the first hole 96a and the second hole 96b, and longer than the length L8 along the X direction between the first hole 96a and the third hole 96c.

[0138] Furthermore, lengths L7 and L8 are respectively equivalent to the thickness of the wall portion 97. That is, length L7 is the length of the wall portion 97 between the first hole 96a and the second hole 96b in the X direction. Length L8 is the length of the wall portion 97 between the first hole 96a and the third hole 96c in the X direction. Lengths L7 and L8 are approximately equal. For example, length L7 is more than 0.5 times and less than 2.0 times the length L8.

[0139] Furthermore, the length L6 is approximately equal to the length L9 (diameter of the second hole 96b) along the X direction, and approximately equal to the length L10 (diameter of the third hole 96c) along the X direction. For example, the lengths L9 and L10 are more than 0.5 times and less than 2.0 times the length L6, respectively.

[0140] For example, a smaller orifice diameter improves resistance to arc discharge and rigidity. Conversely, a larger orifice diameter increases gas flow rate. The diameter of the orifice 96 (length L6, L9, or L10, etc.) is, for example, 1 micrometer (μm) or more and 20 μm or less. By arranging orifices with diameters of 1 to 20 μm extending in one direction, higher resistance to arc discharge can be achieved with smaller deviations. More preferably, the diameter of the orifice 96 is 3 μm or more and 10 μm or less.

[0141] Here, the method for determining the diameter of hole 96 is explained. An image is obtained using a scanning electron microscope (e.g., Hitachi High-Tech S-3000) at a magnification of 1000x or higher. Using commercially available image analysis software, the diameter of hole 96 is calculated to be equivalent to the diameter of 100 circles, and this average value is taken as the diameter of hole 96.

[0142] Further optimization is made to minimize the diameter deviation of the multiple orifices 96. By reducing the diameter deviation, the flow rate of the flowing gas and the insulation strength can be more precisely suppressed. The diameter deviation of the multiple orifices 96 can be calculated using the cumulative distribution equivalent to the diameters of 100 circles obtained from the calculation of the orifice diameters 96. Specifically, using the concepts of particle size distribution at 50 vol% (median diameter) and particle size distribution at 90 vol% (dip diameter), which are commonly used in particle size distribution measurement, the cumulative distribution curve of orifices 96 with the horizontal axis representing the orifice diameter (μm) and the vertical axis representing the relative porosity (%) is used to determine the orifice diameter at 50 vol% (equivalent to the D50 diameter) and the orifice diameter at 90 vol% (equivalent to the D90 diameter). Preferably, the diameter deviation of the multiple orifices 96 is suppressed to a degree that satisfies the relationship D50:D90 ≤ 1:2.

[0143] The thickness of the wall portion 97 (lengths L7, L8, etc.) is, for example, 1 μm or more and 10 μm or less. The thickness of the wall portion 97 is thinner than the thickness of the compact portion 95.

[0144] Thus, the first hole 96a is adjacent to and surrounded by six holes 96 among the plurality of holes 96. That is, when viewed along the Z direction, there are six holes 96 adjacent to one hole 96 at the center of the loose portion 94. As a result, when viewed from above, the plurality of holes 96 can be arranged with higher isotropy and higher density. This ensures resistance to arc discharge and gas flow rate in the through hole 15, while also improving the rigidity of the first porous portion 90. In addition, deviations in resistance to arc discharge, deviations in gas flow rate in the through hole 15, and deviations in the rigidity of the first porous portion 90 can be suppressed.

[0145] Figure 6(b) Other examples showing the configuration of multiple holes 96 within the loose portion 94. For example... Figure 6 As shown in (b), in this example, multiple holes 96 are arranged in a concentric circle with the first hole 96a as the center. Thus, when viewed from above, multiple holes can be arranged with high isotropy and high density.

[0146] Furthermore, for example, the first porous portion 90 with the structure described above can be manufactured by extrusion molding. In addition, the lengths L0 to L10 can be measured separately by observation using a microscope such as a scanning electron microscope.

[0147] The evaluation of porosity in this specification will be explained. Here, the evaluation of porosity in the first porous section 90 will be used as an example.

[0148] Obtain as Figure 3 (a) A top view image is used to calculate the proportion R1 of multiple loose portions 94 in the porous region 91 through image analysis. Images are obtained using a scanning electron microscope (e.g., Hitachi High Technology Corporation, S-3000). A BSE image is obtained by setting the accelerating voltage to 15 kV and the magnification to 30x. For example, the image size is 1280 × 960 pixels, and the image grayscale is 256 levels.

[0149] The proportion R1 of multiple loose portions 94 in the porous region 91 was calculated using image analysis software (such as Win-ROOF Ver6.5 (Mitani Shoji Co., Ltd.)).

[0150] The ratio R1 can be calculated using Win-ROOF Ver6.5 as described below.

[0151] The evaluation scope ROI1 (refer to) Figure 3 (a) is the smallest circle (or ellipse) containing all the loose portion 94.

[0152] Binarization based on a single threshold (e.g., 0) is performed to calculate the area S1 of the evaluation range ROI1.

[0153] Binarization is performed based on two thresholds (e.g., 0 and 136) to calculate the total area S2 of multiple loose portions 94 within the evaluation range ROI1. Then, hole filling is performed within the loose portions 94, and smaller areas considered interference are removed (threshold: below 0.002). Additionally, the two thresholds are appropriately adjusted based on the image's brightness and contrast.

[0154] As a proportion of area S2 to area S1, calculate the ratio R1. That is, ratio R1 (%) = (area S2) / (area S1) × 100.

[0155] In this embodiment, the proportion R1 of the plurality of loose portions 94 in the porous region 91 is, for example, 40% or more and 70% or less, preferably 50% or more and 70% or less. The proportion R1 is, for example, about 60%.

[0156] Obtain as Figure 5 An image resembling a top view is used, and the proportion R2 of the multiple pores 96 in the loose portion 94 is calculated through image analysis. The proportion R2 corresponds, for example, to the porosity of the loose portion 94. Images are obtained using a scanning electron microscope (e.g., Hitachi High Technology Corporation, S-3000). A BSE image is obtained by setting the accelerating voltage to 15 kV and the magnification to 600x. For example, the image size is 1280 × 960 pixels, and the image grayscale is 256 levels.

[0157] The proportion R2 of multiple holes 96 in the loose portion 94 is calculated using image analysis software (such as Win-ROOF Ver6.5 (Mitani Shoji Co., Ltd.)).

[0158] The ratio R1 can be calculated using Win-ROOF Ver6.5 as described below.

[0159] The evaluation scope ROI2 (refer to) Figure 5 The loose portion 94 is shaped to approximately hexagonal. The evaluation area ROI2 includes all the holes 96 located in one loose portion 94.

[0160] Binarization based on a single threshold (e.g., 0) is performed to calculate the area S3 of the evaluation range ROI2.

[0161] Binarization is performed based on two thresholds (e.g., 0 and 96) to calculate the total area S4 of multiple holes 96 within the evaluation range ROI2. Then, hole filling is performed within the holes 96, and smaller areas considered interference are removed (threshold: below 1). Additionally, the two thresholds are adjusted appropriately based on the image's brightness and contrast.

[0162] As a proportion of area S4 to area S3, the ratio R2 is calculated. That is, ratio R2 (%) = (area S4) / (area S3) × 100.

[0163] In this embodiment, the proportion R2 (porosity of the loose portion 94) of the plurality of pores 96 in the loose portion 94 is, for example, 20% or more and 60% or less, preferably 30% or more and 50% or less. The proportion R2 is, for example, about 40%.

[0164] The porosity of the porous region 91 is, for example, the product of the proportion R1 of the multiple loose portions 94 in the porous region 91 and the proportion R2 of the multiple pores 96 in the loose portions 94. For example, when the proportion R1 is 60% and the proportion R2 is 40%, the porosity of the porous region 91 can be calculated to be about 24%.

[0165] By using the first porous portion 90 with such porosity of the porous region 91, the gas flow rate in the through hole 15 can be ensured, while the insulation strength can be improved.

[0166] Similarly, the porosity of the ceramic dielectric substrate and the second porous portion 70 can be calculated. Furthermore, it is preferable to appropriately select the magnification of the scanning electron microscope, for example, in the range of tens to thousands of times, depending on the object being observed.

[0167] Figure 7 (a) and Figure 7 (b) is a schematic diagram illustrating another first porous material part involved in the embodiment.

[0168] Figure 7 (a) is a top view of the first porous section 90 viewed along the Z direction. Figure 7 (b) is equivalent to Figure 7 (a) Enlarged view of a portion thereof.

[0169] like Figure 7 (a) and Figure 7 As shown in (b), in this example, the planar shape of the loose portion 94 is circular. However, the planar shape of the loose portion 94 can also be non-hexagonal.

[0170] Figure 8 This is a schematic cross-sectional view of the electrostatic chuck involved in the illustrative embodiment.

[0171] Figure 8 Equivalent to Figure 2 The image shows an enlarged view of region B. That is, Figure 8 This indicates the vicinity of the interface F1 between the first porous portion 90 (dense region 93) and the ceramic dielectric substrate 11. Furthermore, in this example, both the first porous portion 90 and the ceramic dielectric substrate 11 are made of alumina.

[0172] like Figure 8 As shown, the first porous portion 90 has: a first region 90p, located on the ceramic dielectric substrate 11 side in the X or Y direction; and a second region 90q, continuous with the first region 90p in the X or Y direction. The first region 90p and the second region 90q are part of the dense region 93 of the first porous portion 90.

[0173] The first region 90p is located between the second region 90q and the ceramic dielectric substrate 11 in the X or Y direction. The first region 90p is a region approximately 40 to 60 μm away from the interface F1 in the X or Y direction. That is, the width W1 of the first region 90p in the X or Y direction (the length of the first region 90p in the direction perpendicular to the interface F1) is, for example, more than 40 μm and less than 60 μm.

[0174] Furthermore, the ceramic dielectric substrate 11 includes: a first substrate region 11p, located on the side of the first porous portion 90 (first region 90p) in the X or Y direction; and a second substrate region 11q, continuous with the first substrate region 11p in the X or Y direction. The first region 90p and the first substrate region 11p are arranged in contact. The first substrate region 11p is located between the second substrate region 11q and the first porous portion 90 in the X or Y direction. The first substrate region 11p is a region approximately 40 to 60 μm away from the interface F1 in the X or Y direction. That is, the width W2 of the first substrate region 11p in the X or Y direction (the length of the first substrate region 11p in the direction perpendicular to the interface F1) is, for example, 40 μm or more and 60 μm or less.

[0175] Figure 9 (a) and Figure 9 (b) is a schematic cross-sectional view of the electrostatic chuck involved in the illustrative embodiment.

[0176] Figure 9 (a) is Figure 8 An enlarged view of a portion of region 90p shown in Figure 1. Figure 9 (b) is Figure 8 An enlarged view of a portion of the first substrate region 11p shown.

[0177] like Figure 9 As shown in (a), region 90p contains multiple particles g1 (grains). Additionally, as... Figure 9 As shown in (b), the first substrate region 11p contains a plurality of particles g2 (grains).

[0178] The average particle size (the average diameter of multiple particles g1) in region 90p of the first substrate is different from the average particle size (the average diameter of multiple particles g2) in region 11p of the first substrate.

[0179] Since the average particle size in the first region 90p is different from the average particle size in the first substrate region 11p, the bonding strength (interface strength) between the grains of the first porous portion 90 and the grains of the ceramic dielectric substrate 11 can be improved at the interface F1. For example, it is possible to suppress the peeling of the first porous portion 90 from the ceramic dielectric substrate 11 and the detachment of grains.

[0180] Furthermore, the average particle size can be used as follows: Figure 9 (a) and Figure 9 (b) The average equivalent circle diameter of grains in such a cross-sectional image. The equivalent circle diameter is the diameter of a circle having the same area as the area of ​​the planar shape of the object.

[0181] It is also preferable to integrate the ceramic dielectric substrate 11 with the first porous portion 90. By integrating the first porous portion 90 into the ceramic dielectric substrate 11, it can be fixed to the ceramic dielectric substrate 11. As a result, compared with fixing the first porous portion 90 to the ceramic dielectric substrate 11 by means of adhesives, the strength of the electrostatic chuck can be improved. For example, corrosion and ablation of adhesives can be suppressed, thus preventing the electrostatic chuck from aging.

[0182] In this example, the average particle size in the first substrate region 11p is smaller than the average particle size in the first region 90p. Because the particle size in the first substrate region 11p is smaller, the bonding strength between the first porous portion and the ceramic dielectric substrate can be improved at the interface. Furthermore, because the particle size in the first substrate region is smaller, the strength of the ceramic dielectric substrate 11 can be improved, suppressing the risk of cracking due to stress occurring during manufacturing or processes. For example, the average particle size in the first region 90p is 3 μm or more and 5 μm or less. For example, the average particle size in the first substrate region 11p is 0.5 μm or more and 2 μm or less. The average particle size in the first substrate region 11p is 1.1 times or more and 5 times or less than the average particle size in the first region 90p.

[0183] Furthermore, for example, the average particle size in the first substrate region 11p is smaller than the average particle size in the second substrate region 11q. In the first substrate region 11p, which is disposed in contact with the first region 90p, for example during sintering in the manufacturing process, the interface strength with the first region 90p is preferably improved through interactions such as diffusion. On the other hand, in the second substrate region 11q, the inherent material properties of the ceramic dielectric substrate 11 are preferably utilized. By making the average particle size in the first substrate region 11p smaller than the average particle size in the second substrate region 11q, it is possible to simultaneously ensure the interface strength in the first substrate region 11p and the properties of the ceramic dielectric substrate 11 in the second substrate region 11q.

[0184] The average particle size in the first region 90p can be smaller than the average particle size in the first substrate region 11p. Therefore, the bonding strength between the first porous portion 90 and the ceramic dielectric substrate 11 can be improved at the interface. Furthermore, since the average particle size in the first region 90p is smaller, the strength of the first porous portion 90 is increased, thus suppressing particle shedding during the process and reducing particle size.

[0185] For example, in both the first porous section 90 and the ceramic dielectric substrate 11, the average particle size can be adjusted by modifying the sintering conditions, such as the material composition and temperature. For instance, the amount and concentration of sintering aids added during the sintering of the ceramic material can be adjusted. For example, magnesium oxide (MgO) used as a sintering aid can suppress abnormal grain growth.

[0186] Furthermore, similar to the aforementioned, the average particle size in the first region 90p can be made smaller than the average particle size in the second substrate region 11q. This improves the mechanical strength of the first region 90p.

[0187] Refer again Figure 2 (a) The structure of the electrostatic chuck 110 will continue to be described. The electrostatic chuck 110 may also have a second porous portion 70. The second porous portion 70 can be disposed in the Z direction between the first porous portion 90 and the gas inlet path 53. For example, the second porous portion 70 is embedded in the ceramic dielectric substrate 11 side of the base plate 50. Figure 2 As shown in (a), for example, a countersunk portion 53a is provided on the ceramic dielectric substrate 11 side of the base plate 50. The countersunk portion 53a is provided in a cylindrical shape. By appropriately designing the inner diameter of the countersunk portion 53a, the second porous portion 70 is fitted into the countersunk portion 53a.

[0188] The upper surface 70U of the second porous portion 70 protrudes towards the upper surface 50U of the base plate 50. The upper surface 70U of the second porous portion 70 is opposite to the lower surface 90L of the first porous portion 90. In this example, a space SP is formed between the upper surface 70U of the second porous portion 70 and the lower surface 90L of the first porous portion 90. The space SP can also be filled by at least one of the second porous portion 70 and the first porous portion 90. That is, the second porous portion 70 and the first porous portion 90 may not be in contact.

[0189] The second porous portion 70 includes: a ceramic porous body 71 having multiple pores; and a ceramic insulating film 72. The ceramic porous body 71 is provided in a cylindrical shape (e.g., cylindrical) and fitted into the countersunk portion 53a. Although the shape of the second porous portion 70 is preferably cylindrical, it is not limited to a cylindrical shape. The ceramic porous body 71 is made of an insulating material. The material of the ceramic porous body 71 can be, for example, Al2O3, Y2O3, ZrO2, MgO, SiC, AlN, Si3N4. The material of the ceramic porous body 71 can also be glass such as SiO2. The material of the ceramic porous body 71 can also be Al2O3-TiO2, Al2O3-MgO, Al2O3-SiO2, Al6O3, etc. 13 Si2, YAG, ZrSiO4, etc.

[0190] The porosity of the ceramic porous body 71 is, for example, 20% or more and 60% or less. The density of the ceramic porous body 71 is, for example, 1.5 g / cm³. 3 Above, 3.0g / cm 3 The following describes how He and other gases flowing in the gas inlet path 53 are delivered to the tank 14 through the through holes 15 provided on the ceramic dielectric substrate 11 via multiple holes in the ceramic porous body 71.

[0191] A ceramic insulating membrane 72 is disposed between the ceramic porous body 71 and the gas inlet path 53. The ceramic insulating membrane 72 is denser than the ceramic porous body 71. The porosity of the ceramic insulating membrane 72 is, for example, less than 10%. The density of the ceramic insulating membrane 72 is, for example, 3.0 g / cm³. 3 Above, 4.0 g / cm 3 The ceramic insulating film 72 is disposed on the side of the ceramic porous body 71.

[0192] Materials used for the ceramic insulating film 72 include, for example, Al2O3, Y2O3, ZrO2, and MgO. Other materials used for the ceramic insulating film 72 include Al2O3-TiO2, Al2O3-MgO, Al2O3-SiO2, and Al6O3. 13 Si2, YAG, ZrSiO4, etc.

[0193] The ceramic insulating film 72 is formed on the side of the ceramic porous body 71 by spraying. Spraying refers to a method in which a coating material is melted or softened by heating, and accelerated into microparticles, which are then impacted against the side of the ceramic porous body 71 to solidify and accumulate the flattened particles to form a film. For example, the ceramic insulating film 72 can also be fabricated by physical vapor deposition (PVD), chemical vapor deposition (CVD), sol-gel method, aerosol deposition method, etc. When the ceramic insulating film 72 is formed by spraying, the film thickness is, for example, 0.05 mm or more and 0.5 mm or less.

[0194] The porosity of the ceramic dielectric substrate 11 is, for example, 1% or less. The density of the ceramic dielectric substrate 11 is, for example, 4.2 g / cm³. 3 .

[0195] As previously described, the porosity of the ceramic dielectric substrate 11 and the second porous portion 70 was measured using a scanning electron microscope. Density was measured according to JIS (Japanese Industrial Standard) C 2141 5.4.3.

[0196] When the second porous portion 70 is fitted into the countersunk portion 53a of the gas inlet passage 53, the ceramic insulating film 72 is in contact with the base plate 50. That is, between the through hole 15 that guides gas such as He to the groove 14 and the metal base plate 50, there is a ceramic porous body 71 and a ceramic insulating film 72 with high insulation properties. By using such a second porous portion 70, higher insulation can be achieved compared to simply providing the ceramic porous body 71 in the gas inlet passage 53.

[0197] Furthermore, the size of the second porous portion 70 can be larger than the size of the first porous portion 90 in either the X or Y direction. Since a higher insulation strength can be obtained by providing such a second porous portion 70, the occurrence of arc discharge can be suppressed more effectively.

[0198] Furthermore, the multiple holes provided in the second porous section 70 are more dispersed in three dimensions compared to the multiple holes provided in the first porous section 90, allowing the proportion of holes penetrating in the Z-direction in the first porous section 90 to be greater than that in the second porous section 70. Since higher insulation strength can be obtained by providing the second porous section 70 with multiple holes dispersed in three dimensions, the occurrence of arc discharge can be suppressed more effectively. Additionally, the first porous section 90, with its higher proportion of holes penetrating in the Z-direction, facilitates smoother gas flow.

[0199] Furthermore, the size of the second porous portion 70 can be made larger than the size of the first porous portion 90 in the Z direction. This allows for higher insulation strength and thus more effective suppression of arc discharge.

[0200] Furthermore, the average diameter of the plurality of pores provided in the second porous portion 70 can be made larger than the average diameter of the plurality of pores provided in the first porous portion 90. Thus, since the second porous portion 70 has larger pore diameters, smoother gas flow can be achieved. Conversely, since the first porous portion 90 has smaller pore diameters on the adsorption target side, the occurrence of arc discharge is more effectively suppressed.

[0201] In addition, because it can reduce the deviation in the diameter of multiple holes, it can more effectively suppress arc discharge.

[0202] Figure 10 This is a schematic cross-sectional view of the second porous portion 70 of the electrostatic chuck according to the illustrated embodiment.

[0203] Figure 10 This is an enlarged view of a portion of the cross-section of the ceramic porous body 71.

[0204] Inside the ceramic porous body 71, multiple pores 71p disposed in the ceramic porous body 71 are dispersed in three dimensions in the X, Y, and Z directions. In other words, the ceramic porous body 71 has a three-dimensional network structure diffused in the X, Y, and Z directions. The multiple pores 71p are, for example, randomly dispersed in the ceramic porous body 71.

[0205] Since the multiple pores 71p are dispersed in three dimensions, a portion of each pore 71p will also be exposed to the surface of the ceramic porous body 71. Therefore, fine irregularities are formed on the surface of the ceramic porous body 71. That is, the surface of the ceramic porous body 71 is relatively rough. Due to the surface roughness of the ceramic porous body 71, a sprayed film, i.e., a ceramic insulating film 72, can be easily formed on the surface of the ceramic porous body 71. For example, the contact between the sprayed film and the ceramic porous body 71 is improved. Furthermore, peeling of the ceramic insulating film 72 can be suppressed.

[0206] The average diameter of the plurality of pores 71p provided in the porous ceramic body 71 is larger than the average diameter of the plurality of pores 96 provided in the porous region 91. The diameter of the pores 71p is, for example, 10 μm or more and 50 μm or less. Through the porous region 91 with smaller pore diameters, the gas flow rate flowing in the through-holes 15 can be controlled (limited). As a result, deviations in the gas flow rate caused by the porous ceramic body 71 can be suppressed. As mentioned above, the diameters of the pores 71p and pores 96 are measured using a scanning electron microscope.

[0207] Figure 11 This is a schematic cross-sectional view illustrating other electrostatic chucks involved in the illustrative embodiments.

[0208] and Figure 2 (a) Similarly, Figure 11 Example of the periphery of the first porous section 90.

[0209] In this example, the through-hole 15 provided in the ceramic dielectric substrate 11 does not have a hole portion 15b (the connecting hole connecting the first porous part 90 and the groove 14). For example, the diameter (length along the X direction) of the through-hole 15 does not change in the Z direction and is approximately constant.

[0210] like Figure 11As shown, at least a portion of the upper surface 90U of the first porous portion 90 is exposed toward the first main surface 11a of the ceramic dielectric substrate 11. For example, the upper surface 90U of the first porous portion 90 is positioned in the Z direction at the same position as the bottom of the groove 14 in the Z direction.

[0211] In this way, the first porous portion 90 can be disposed over almost the entire through-hole 15. Since no small-diameter connecting holes are provided in the through-hole 15, the gas flow rate flowing in the through-hole 15 can be increased. In addition, since the first porous portion 90 with high insulation can be disposed in most of the through-hole 15, higher resistance to arc discharge can be obtained.

[0212] Figure 12 This is a schematic cross-sectional view illustrating other electrostatic chucks involved in the illustrative embodiments.

[0213] and Figure 2 (a) Similarly, Figure 12 Example of the periphery of the first porous section 90.

[0214] In this example, the first porous portion 90 is not integrated into the ceramic dielectric substrate 11.

[0215] An adhesive member 61 (adhesive) is provided between the first porous portion 90 and the ceramic dielectric substrate 11. The first porous portion 90 is bonded to the ceramic dielectric substrate 11 by the adhesive member 61. For example, the adhesive member 61 is provided between the side surface of the first porous portion 90 (the side surface 93s of the dense region 93) and the inner wall 15w of the through hole 15. The first porous portion 90 and the ceramic dielectric substrate 11 may not be in contact.

[0216] The adhesive member 61 is, for example, made of silicone adhesive. The adhesive member 61 is, for example, an elastic member with elasticity. The elastic modulus of the adhesive member 61 is, for example, lower than that of the dense region 93 of the first porous portion 90, and lower than that of the ceramic dielectric substrate 11.

[0217] In the structure in which the first porous portion 90 and the ceramic dielectric substrate 11 are bonded by the adhesive member 61, the adhesive member 61 can be used as a buffer material to absorb the difference between the thermal shrinkage of the first porous portion 90 and the thermal shrinkage of the ceramic dielectric substrate 11.

[0218] The embodiments of the present invention have been described above. However, the present invention is not limited to the above description. For example, although a structure utilizing Coulomb force is illustrated as the electrostatic chuck 110, a structure utilizing Johnson-Rabec force can also be applied. Furthermore, regarding the foregoing embodiments, techniques that can be appropriately modified by those skilled in the art to incorporate the features of the present invention are also included within the scope of the present invention. In addition, as long as it is technically feasible, the elements of the foregoing embodiments can be combined, and such combined techniques, as long as they incorporate the features of the present invention, are also included within the scope of the present invention.

Claims

1. An electrostatic chuck, characterized in that, have: A ceramic dielectric substrate has a first main surface on which an adsorbed object is placed, a second main surface opposite to the first main surface, and an electrode disposed between the first main surface and the second main surface; The base plate supports the ceramic dielectric substrate and has a gas inlet path; The first porous portion is disposed between the base plate and the first main surface of the ceramic dielectric substrate and at a position opposite to the gas inlet path; as well as The second porous section is disposed between the first porous section and the gas inlet path. The direction from the base plate toward the ceramic dielectric substrate is defined as the first direction. When projected onto a plane perpendicular to the first direction, the electrode does not coincide with the gas inlet path. The first porous portion comprises: a plurality of loose portions, each of the plurality of loose portions having a plurality of pores; and a dense portion having a higher density than the loose portions. The plurality of loose portions extend in a first direction from the base plate toward the ceramic dielectric substrate. The dense portion is located between the plurality of loose portions. The loose portion has a wall portion disposed between the holes. In a second direction that is substantially orthogonal to the first direction, the minimum size of the wall portion is smaller than the minimum size of the compact portion.

2. The electrostatic chuck according to claim 1, characterized in that, The base plate has a countersunk hole portion disposed on the ceramic dielectric substrate side of the base plate, and the second porous portion is disposed in the countersunk hole portion. When projected onto a plane perpendicular to the first direction, the electrode does not coincide with the countersunk portion.

3. The electrostatic chuck according to claim 1 or 2, characterized in that, It also has an adhesive portion disposed between the ceramic dielectric substrate and the base plate. The first porous portion has a first upper surface on the first main surface side and a first lower surface on the second main surface side. The second porous portion has a second upper surface on the side of the first porous portion and a second lower surface on the opposite side of the second upper surface. A space is provided between the first lower part and the second upper part. Viewed from a direction perpendicular to the first direction, the space coincides with the adhesive portion. When projected onto a plane perpendicular to the first direction, the electrode does not coincide with the space.

4. The electrostatic chuck according to claim 1, characterized in that, In the second direction, the size of the plurality of holes respectively provided in the plurality of loose portions is smaller than the size of the dense portions.

5. The electrostatic chuck according to claim 1 or 4, characterized in that, The aspect ratio of the plurality of holes respectively provided in the plurality of loose portions is 30 or more.

6. The electrostatic chuck according to claim 1 or 4, characterized in that, In the second direction, the size of the plurality of pores respectively provided in the plurality of loose portions is 1 micrometer or more and 20 micrometers or less.

7. The electrostatic chuck according to claim 1 or 4, characterized in that, When viewed along the first direction, the plurality of holes includes a first hole located at the center of the loose portion. Of the plurality of holes, there are 6 holes that are adjacent to and surround the first hole.

8. The electrostatic chuck according to claim 1 or 4, characterized in that, The average diameter of the plurality of pores provided in the second porous part is larger than the average diameter of the plurality of pores provided in the first porous part.

9. The electrostatic chuck according to claim 1 or 4, characterized in that, The diameter deviation of the plurality of holes provided in the first porous part is smaller than the diameter deviation of the plurality of holes provided in the second porous part.

10. The electrostatic chuck according to claim 8, characterized in that, The pores disposed in the second porous part are more dispersed in three dimensions than the pores disposed in the first porous part. The proportion of holes penetrating in the first direction is greater in the first porous portion than in the second porous portion.

11. The electrostatic chuck according to claim 1 or 4, characterized in that, The first porous portion and the ceramic dielectric substrate contain alumina as the main components. The purity of the alumina in the ceramic dielectric substrate is higher than that of the alumina in the first porous portion.

12. The electrostatic chuck according to claim 1 or 4, characterized in that, The ceramic dielectric substrate has a first hole located between the first main surface and the first porous portion. At least one of the ceramic dielectric substrate and the first porous portion has a second porous portion located between the first porous portion and the first porous portion. In a second direction that is substantially orthogonal to a first direction from the base plate toward the ceramic dielectric substrate, the size of the second hole is smaller than the size of the first porous portion and larger than the size of the first hole.

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