Substrate holding member

Abstract

To provide a substrate holding member capable of preventing the peripheral part of a substrate from deforming and preventing a contact area with the substrate from increasing.SOLUTION: A substrate holding member 100 includes a ceramic base material 110. The upper surface 111 of the ceramic base material 110 has an annular projection 152 arranged in the peripheral part of the upper surface 111 and a plurality of projections 156 arranged in the inside of the annular projection 152; the inside of the ceramic base material 110 has a first gas passage 164 having an opening 164a opened in the inside of the annular projection 152; and the annular projection 152 has a groove 153.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a substrate holding member for holding a substrate such as a silicon wafer. [Background technology]

[0002] Patent Document 1 discloses an electrostatic chuck for holding a substrate such as a wafer. The electrostatic chuck described in Patent Document 1 includes a base body on which the substrate is placed, a plurality of convex portions (protrusions) that protrude from the upper surface of the base body to support the substrate, and an annular convex portion (seal ring) that protrudes in an annular shape from the upper surface of the outer periphery of the base body to support the substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-111243 Summary of the Invention [Problem to be solved by the invention]

[0004] In the electrostatic chuck described in Patent Document 1, the height of the multiple protrusions dispersed inside the seal ring is the same as the height of the seal ring. Contact between the substrate and the seal ring can suppress deformation of the outer periphery of the substrate. Furthermore, increasing the width of the seal ring can increase the contact area with the substrate, thereby suppressing gas movement between the substrate and the seal ring. This improves the sealing performance between the substrate and the seal ring. However, increasing the contact area with the substrate increases the likelihood of spots where heat transfer is uneven at the contact surface between the substrate and the seal ring, potentially resulting in the occurrence of hot spots or cold spots.

[0005] The present invention has been made in consideration of the above circumstances, and aims to provide a substrate holding member that can suppress deformation of the outer periphery of the substrate and can suppress the occurrence of heat spots and cold spots on the contact surface with the substrate. [Means for solving the problem]

[0006] According to an aspect of the present invention, there is provided a ceramic substrate having an upper surface and a lower surface facing the upper surface in a vertical direction; an electrode embedded in the ceramic substrate or disposed on the lower surface of the ceramic substrate; The ceramic substrate is an annular protrusion disposed on an outer periphery of the upper surface of the ceramic base and protruding upward from the upper surface of the ceramic base; a plurality of protrusions disposed on the upper surface of the ceramic base in an inner region of the annular protrusion and protruding upward from the upper surface of the ceramic base, The area S1 of the upper surface of the annular convex portion and the minimum value S2 of the cross-sectional area of ​​the cross section parallel to the upper surface of the annular convex portion are 0.3≦S2 / S1 ≦0.832 The present invention provides a substrate holding member characterized by: [Effects of the Invention]

[0007] In the above embodiment, an annular protrusion is provided on the outer periphery of the ceramic substrate, which contacts the outer periphery of the substrate when the substrate is held on the upper surface of the ceramic substrate. This prevents deformation of the outer periphery of the substrate when the substrate is held on the upper surface of the ceramic substrate. The annular protrusion also has a low-cross-sectional area portion such that the ratio S2 / S1, where S1 is the area of ​​the upper surface of the annular protrusion and S2 is the minimum cross-sectional area of ​​a cross section parallel to the upper surface of the annular protrusion, satisfies 0.3≦S2 / S1<1. Such a low-cross-sectional area portion can be formed, for example, by providing a groove on the side surface of the annular protrusion. This increases the thermal resistance of the annular protrusion compared to a case in which such a low-cross-sectional area portion is not provided. This prevents heat transferred from the substrate holder to the substrate from concentrating locally in the annular region contacting the upper surface of the annular protrusion. In particular, when the substrate holder includes an electrode as a heating element, this prevents heat spots on the substrate corresponding to the position of the annular protrusion due to heat transfer from the annular protrusion to the substrate. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of a substrate holding member 100. FIG. [Figure 2] FIG. 2 is a schematic explanatory diagram of the substrate holding member 100. As shown in FIG. [Figure 3] FIG. 3 is a schematic diagram illustrating the electrode 120. As shown in FIG. [Figure 4] 4(a) to 4(e) are diagrams showing the flow of a method for manufacturing the ceramic base 110. [Figure 5] 5(a) to 5(d) are diagrams showing the flow of another method for manufacturing the ceramic base 110. In FIG. [Figure 6] FIG. 6 is a view equivalent to FIG. 2 of a substrate holding member 100 according to a second embodiment. [Figure 7] FIG. 7 is a view equivalent to FIG. 2 of a substrate holding member 100 according to a third embodiment. [Figure 8] FIG. 8 is a schematic external view of a substrate holding member 100 according to a fourth embodiment. [Figure 9]FIG. 9 is a schematic explanatory diagram of the electrostatic attraction electrode 124. As shown in FIG. [Figure 10] FIG. 10 is a view equivalent to FIG. 2 of a substrate holding member 100A of Comparative Example 1. In FIG. [Figure 11] FIG. 11 is a table summarizing the results of Examples 1 to 5. [Figure 12] FIG. 12 is a table summarizing the results of Examples 6 to 8 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Substrate holding member 100> A substrate holding member 100 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. The substrate holding member 100 according to this embodiment is a ceramic heater used to heat semiconductor wafers such as silicon wafers (hereinafter simply referred to as wafers 10). In the following description, the up-down direction 5 is defined based on the state in which the substrate holding member 100 is installed and ready for use (the state shown in FIG. 1). As shown in FIG. 1, the substrate holding member 100 according to this embodiment includes a ceramic base 110, an electrode 120, a shaft 130, and a power supply line 140.

[0010] The ceramic substrate 110 is a member having a circular plate shape with a diameter of 12 inches (approximately 300 mm), and the wafer 10 to be heated is placed on the ceramic substrate 110. Note that in FIG. 1, the wafer 10 and the ceramic substrate 110 are shown separated from each other for ease of viewing. As shown in FIG. 1, an annular protrusion 152 (hereinafter simply referred to as the annular protrusion 152) and a plurality of protrusions 156 are provided on the upper surface 111 of the ceramic substrate 110. Note that in FIG. 1, the number of the plurality of protrusions 156 is reduced compared to FIG. 2 for ease of viewing. Also, as shown in FIG. 2, a first gas flow path 164, which will be described later, is formed inside the ceramic substrate 110. The ceramic substrate 110 can be formed of a ceramic sintered body such as aluminum nitride, silicon carbide, alumina, or silicon nitride.

[0011] As shown in FIGS. 1 and 2, the annular protrusion 152 is an annular protrusion disposed on the outer periphery (outer edge) of the upper surface 111 of the ceramic base 110 and protrudes upward from the upper surface 111. As shown in FIG. 2, when the wafer 10 is placed on the ceramic base 110, the upper surface 152a of the annular protrusion 152 abuts against the lower surface of the wafer 10. In other words, when the wafer 10 is placed on the ceramic base 110, the annular protrusion 152 is disposed at a position that overlaps with the wafer 10 in the up-down direction 5. A groove 153 extending in the circumferential direction is formed on the outer periphery 152P of the annular protrusion 152. The groove 153 has a rectangular cross-sectional shape and is formed around the outer periphery 152P of the annular protrusion 152. The cross-sectional area of ​​the annular protrusion 152, parallel to the upper surface 152a, is smaller in the portion where the groove 153 is formed than in the portion where the groove 153 is not formed. That is, the portion of the annular protrusion 152 where the groove 153 is formed is a low cross-sectional area portion where the cross-sectional area of ​​the cross section parallel to the upper surface 152a is smaller than the other portions.

[0012] A plurality of protrusions 156 are provided on the upper surface 111 of the ceramic base material 110 inside the annular protrusion 152. Each of the plurality of protrusions 156 has a cylindrical shape. One of the plurality of protrusions 156 is disposed approximately at the center of the upper surface 111. The remaining protrusions 156 are arranged on the circumference of four equally spaced concentric circles. Furthermore, on the circumference of each concentric circle, the protrusions 156 are arranged at equally spaced intervals. The position and / or number of the protrusions 156 are appropriately determined depending on the application, action, and function.

[0013] The height of the annular protrusion 152 (the length in the vertical direction 5 from the upper surface 111) can be set in the range of 5 μm to 2 mm. Similarly, the height of the plurality of protrusions 156 can also be set in the range of 5 μm to 2 mm. Note that, as shown in FIG. 2, the height of the annular protrusion 152 can be set to the same height as the plurality of protrusions 156.

[0014] The width of the upper surface 152a of the annular protrusion 152 is preferably constant and can be set to 0.1 mm to 10 mm. The surface roughness Ra of the upper surface 152a of the annular protrusion 152 can be 1.6 μm or less. The surface roughness Ra of the upper surfaces 156a of the multiple protrusions 156 can be 1.6 μm or less. The surface roughness Ra of the upper surface 152a of the annular protrusion 152 and the upper surfaces 156a of the multiple protrusions 156 is preferably 0.4 μm or less, more preferably 0.2 μm or less, and even more preferably 0.1 μm or less.

[0015] The upper surfaces 156a of the plurality of protrusions 156 are preferably circular with a diameter of 0.1 mm to 5 mm. The distance between each of the plurality of protrusions 156 can be set within a range of 1.5 mm to 30 mm.

[0016] As described above, on the upper surface 111, the plurality of protrusions 156 are arranged on the circumference of four concentric circles. As shown in FIG. 2, an opening 164a of a first gas flow path 164 is formed between the innermost concentric circle on which the plurality of protrusions 156 are arranged and the second innermost concentric circle on the upper surface 111. The first gas flow path 164 is a gas flow path having the opening 164a, and is formed inside the ceramic base 110. The first gas flow path 164 extends downward from the opening 164a. As described below, the lower end of the first gas flow path 164 is joined to the upper end of a second gas flow path 168 formed inside the shaft 130.

[0017] The first gas flow path 164 can be used as a flow path for supplying gas to the space (gap) defined by the upper surface 111 of the ceramic base 110 and the lower surface of the wafer 10. For example, a heat transfer gas for heat transfer between the wafer 10 and the ceramic base 110 can be supplied. Examples of the heat transfer gas include an inert gas such as helium or argon, or nitrogen gas. The heat transfer gas is supplied through the first gas flow path 164 at a pressure set within a range of 100 Pa to 40,000 Pa. Furthermore, if process gas infiltrates into the gap inside the annular protrusion 152 through the gap between the upper surface 152a of the annular protrusion 152 and the lower surface of the wafer 10, the gas can be exhausted through the first gas flow path 164. In this case, the differential pressure between the pressure outside the gap and the pressure inside the gap can be adjusted by adjusting the exhaust pressure. This allows the wafer 10 to be adsorbed toward the upper surface of the ceramic base 110.

[0018] As shown in FIGS. 1 and 2, an electrode 120 (one example of a heating element of the present invention) is embedded inside the ceramic substrate 110. As shown in FIG. 3, the electrode 120 is a metal mesh or foil cut into a strip shape. The outer diameter of the electrode 120 is 298 mm. The electrode 120 is not exposed from the side surfaces of the ceramic substrate 110. A terminal portion 121 connected to a power supply line 140 (see FIG. 1) is provided at approximately the center of the electrode 120. The electrode 120 is formed of a heat-resistant metal (high-melting-point metal) such as a mesh or foil woven with wires of tungsten (W), molybdenum (Mo), molybdenum and / or an alloy containing tungsten. The purity of the tungsten and molybdenum is preferably 99% or higher. The thickness of the electrode 120 is 0.15 mm or less. From the viewpoint of increasing the resistance value of the electrode 120 and reducing the current consumption of the substrate holding member 100, it is preferable that the wire diameter be 0.1 mm or less and the thickness of the electrode 120 be 0.1 mm or less. Furthermore, the width of the strip-shaped electrode 120 is preferably 2.5 mm to 20 mm, more preferably 5 mm to 15 mm. In this embodiment, the electrode 120 is cut into the shape shown in FIG. 3 , but the shape of the electrode 120 is not limited thereto and can be modified as appropriate. In addition to or instead of the electrode 120, at least one of an electrostatic chuck electrode for attracting the wafer 10 to the upper surface 111 by Coulomb force and a plasma electrode for generating plasma above the ceramic base 110 may be embedded inside the ceramic base 110.

[0019] 1 and 2, a shaft 130 is connected to the lower surface 113 of the ceramic base 110. The shaft 130 has a hollow, approximately cylindrical cylindrical portion 131 and a large-diameter portion 132 (see FIG. 1) provided below the cylindrical portion 131. The large-diameter portion 132 has a diameter larger than that of the cylindrical portion 131. In the following description, the longitudinal direction of the cylindrical portion 131 is defined as the longitudinal direction 6 of the shaft 130. As shown in FIG. 1, when the substrate holding member 100 is in use, the longitudinal direction 6 of the shaft 130 is parallel to the up-down direction 5.

[0020] The lower surface 113 of the ceramic base 110 may be provided with a protrusion 114 (hereinafter referred to as the joining protrusion 114) for joining to the shaft 130 (see FIG. 9). The shape of the joining protrusion 114 is preferably the same as the shape of the upper surface of the shaft 130 to be joined, and the diameter of the joining protrusion 114 is preferably 100 mm or less. The height of the joining protrusion 114 (height from the lower surface 113) may be 2 mm or more, preferably 5 mm or more. There is no particular upper limit on the height, but considering ease of manufacture, the height of the joining protrusion 114 is preferably 20 mm or less. The lower surface of the joining protrusion 114 is preferably parallel to the lower surface 113 of the ceramic base 100. The surface roughness Ra of the lower surface of the joining protrusion 114 may be 1.6 μm or less. The surface roughness Ra of the lower surface of the joining protrusion 114 is preferably 0.4 μm or less, more preferably 0.2 μm or less.

[0021] The upper surface of the cylindrical portion 131 is fixed to the lower surface 113 of the ceramic base 110 (or to the lower surface of the bonding protrusion 114 if the bonding protrusion 114 is provided). The shaft 130 may be formed of a ceramic sintered body such as aluminum nitride, silicon carbide, alumina, or silicon nitride, just like the ceramic base 110. Alternatively, to improve heat insulation, the shaft 130 may be formed of a material with a lower thermal conductivity than the ceramic base 110. An enlarged diameter portion similar to the large diameter portion 132 provided below the cylindrical portion 131 may be provided on the upper surface of the cylindrical portion 131.

[0022] As shown in FIG. 2, the shaft 130 has a hollow cylindrical shape, and a through-hole extending in the longitudinal direction 6 is formed inside the shaft 130 (the region inside the inner diameter). A power supply line 140 for supplying power to the electrode 120 is arranged in the hollow portion (through-hole) of the shaft 130. The upper end of the power supply line 140 is electrically connected to a terminal portion 121 (see FIG. 3) arranged in the center of the electrode 120. The power supply line 140 is connected to a heater power supply (not shown). As a result, power is supplied to the electrode 120 via the power supply line 140.

[0023] 2, the cylindrical portion 131 of the shaft 130 is formed with a second gas flow path 168 extending in the vertical direction 5. As described above, the upper end of the second gas flow path 168 is connected to the lower end of the first gas flow path 164.

[0024] Next, a description will be given of a method for manufacturing the substrate holding member 100. In the following, an example will be described in which the ceramic base 110 and the shaft 130 are made of aluminum nitride.

[0025] First, a method for manufacturing the ceramic substrate 110 will be described. As shown in FIG. 4(a), granulated powder P, primarily composed of aluminum nitride (AlN) powder, is placed in a carbon mold with a bed 501 and pre-pressed with a punch 502. The granulated powder P preferably contains 5 wt% or less of a sintering aid (e.g., Y2O3). Next, as shown in FIG. 4(b), an electrode 120 cut to a predetermined shape is placed on the pre-pressed granulated powder P. The electrode 120 is placed parallel to a plane perpendicular to the pressure direction (the bottom surface of the mold with a bed 501). At this time, a W pellet or a Mo pellet may be embedded at the position of the terminal 121 (see FIG. 3) of the electrode 120.

[0026] As shown in FIG. 4(c), granulated powder P is further poured into the bed-type mold 501 so as to cover the electrode 120, and pressed with a punch 502 to form a mold. Next, as shown in FIG. 4(d), the granulated powder P with the electrode 120 embedded therein is fired in a pressed state. The pressure applied during firing is preferably 1 MPa or more. Furthermore, firing is preferably performed at a temperature of 1800°C or more. Next, as shown in FIG. 4(e), blind holes are drilled to the electrode 120 to form the terminals 121. If a pellet is embedded, blind holes are drilled to the pellets. Furthermore, through holes that become part of the first gas flow paths 164 are formed. This allows the production of a ceramic base 110 with the first gas flow paths 164 formed therein. In this case, it is preferable to provide a predetermined opening in the electrode 120 in advance so that the electrode 120 is not exposed from the first gas flow paths 164.

[0027] The ceramic base material 110 can also be manufactured by the following method. As shown in Fig. 5(a), a binder is added to aluminum nitride granulated powder P, which is then CIP molded and processed into a disk shape to produce an aluminum nitride compact 510. Next, as shown in Fig. 5(b), the compact 510 is degreased to remove the binder.

[0028] As shown in FIG. 5(c), a recess 511 for embedding the electrode 120 is formed in the degreased compact 510. The electrode 120 is placed in the recess 511 of the compact 510, and another compact 510 is stacked on top of it. The recess 511 may be formed in the compact 510 in advance. Next, as shown in FIG. 5(d), the stacked compacts 510 sandwiching the electrode 120 are fired in a pressed state to produce a fired body. The pressure applied during firing is preferably 1 MPa or more. Furthermore, firing is preferably performed at a temperature of 1800°C or more. The steps after producing the fired body are the same as those described above, and therefore will not be described here.

[0029] The upper surface 111 of the ceramic base material 110 thus formed is ground and subjected to lapping (polishing). Furthermore, the upper surface 111 is sandblasted to form a plurality of convex portions 156 and annular convex portion 152 on the upper surface 111. Furthermore, the annular convex portion 152 is ground to form grooves 153 in the annular convex portion 152. Note that sandblasting is a suitable method for forming the plurality of convex portions 156 and the annular convex portion 152, and grinding is a suitable method for forming grooves 153, but other processing methods may also be used for either.

[0030] Next, a method for manufacturing the shaft 130 and a method for bonding the shaft 130 to the ceramic base 110 will be described. First, granulated powder P of aluminum nitride to which several wt % of binder has been added is formed under hydrostatic pressure (approximately 1 MPa), and the compact is processed into a predetermined shape. The outer diameter of the shaft 130 is approximately 30 mm to 100 mm, and a flange portion 133 (see FIG. 8) having a diameter larger than the outer diameter of the cylindrical portion may be provided on the end surface of the cylindrical portion. The length of the cylindrical portion 131 can be, for example, 50 mm to 500 mm. At this time, through holes that become the second gas flow paths 168 are formed in the compact. Thereafter, the compact is fired in a nitrogen atmosphere. For example, the compact is fired at a temperature of 1900°C for two hours. After firing, the sintered body is processed into a predetermined shape to form the shaft 130. The upper surface of the cylindrical portion 131 and the lower surface 113 of the ceramic base 110 can be fixed by diffusion bonding at 1600°C or higher and under a uniaxial pressure of 1 MPa or higher. In this case, the surface roughness Ra of the lower surface 113 of the ceramic substrate 110 is preferably 0.4 μm or less, and more preferably 0.2 μm or less. The upper surface of the cylindrical portion 131 and the lower surface 113 of the ceramic substrate 110 can also be bonded using a bonding agent. For example, an AlN bonding material paste containing 10 wt% Y2O3 can be used as the bonding agent. For example, the AlN bonding material paste can be applied to the interface between the upper surface of the cylindrical portion 131 and the lower surface 113 of the ceramic substrate 110 to a thickness of 15 μm, and then heated at 1700°C for 1 hour while applying a force of 5 kPa in a direction perpendicular to the upper surface 111 (the longitudinal direction 6 of the shaft 130). Alternatively, the upper surface of the cylindrical portion 131 and the lower surface 113 of the ceramic substrate 110 can be fixed together by screwing, brazing, or the like. [Example]

[0031] The present invention will be further described below using examples and comparative examples, but the present invention is not limited to the examples and comparative examples described below.

[0032] [Comparative Example 1] A substrate holding member 100A of Comparative Example 1 (see FIG. 10 ) will be described. In Comparative Example 1, a ceramic substrate 110 having a diameter of 310 mm and a thickness of 25 mm was fabricated by the above-described fabrication method using aluminum nitride (AlN) to which 5 wt % of a sintering aid (YO) was added. The electrode 120 was fabricated by cutting a molybdenum mesh (wire diameter 0.1 mm, mesh size #50, plain weave) into the shape shown in FIG. 3 , and embedded in the ceramic substrate 110. An annular protrusion 152 having an inner diameter of 292 mm, an outer diameter of 298 mm, a width of 3 mm, and a height of 2000 μm from the upper surface 111 was formed on the upper surface 111 of the ceramic substrate 110. As shown in FIG. 10 , in the substrate holding member 100A of Comparative Example 1, no groove 153 was formed on the outer peripheral surface 152P of the annular protrusion 152. Furthermore, a plurality of cylindrical protrusions 156 each having a diameter of 2 mm and a height of 2000 μm from the upper surface 111 were formed on the upper surface 111 of the ceramic base 110. As described above, the plurality of protrusions 156 were arranged concentrically, with the distance between each protrusion being in the range of 10 to 20 mm. As described above, in the substrate holding member 100A of Comparative Example 1, the height of the annular protrusion 152 was 2000 μm, and the height of the plurality of protrusions 156 was also 2000 μm. That is, the height of the annular protrusion 152 and the height of the plurality of protrusions 156 were the same. In other words, the position (height position) of the upper surface 152a of the annular protrusion 152 in the vertical direction 5 was the same as the height position of the upper surface 156a of the protrusions 156 in the vertical direction 5. The surface roughness Ra of the upper surface 152a of the annular protrusion 152 and the upper surface 156a of the protrusions 156 was both 0.4 μm.

[0033] The diameter of the opening 164a of the first gas flow path 164 is 3 mm. The center of the opening 164a is located 30 mm from the center of the ceramic base 110.

[0034] The substrate holding member 100A having such a shape was placed in a process chamber. Argon gas was supplied as a process gas into the process chamber at a pressure of 26,600 Pa (200 Torr). Furthermore, the argon gas was supplied through the first gas passage 164 to a pressure of 6,650 Pa (50 Torr).

[0035] The temperature of the substrate holding member 100A was evaluated using the following procedure. First, a silicon wafer for temperature evaluation was placed on the ceramic substrate 110, and an external power supply (not shown) was connected to the electrode 120 of the substrate holding member 100. The output power of the external power supply was adjusted to 650 W. The pressures of the process gas and argon gas (heat transfer gas) were then adjusted to the above pressure. The temperature distribution in a 298 mm diameter area of ​​the silicon wafer for temperature evaluation, excluding a 1 mm area from the outer edge, was then measured using an infrared camera. The difference between the maximum and minimum temperatures in the 298 mm diameter area of ​​the silicon wafer for temperature evaluation was defined as the temperature difference Δ. The silicon wafer for temperature evaluation was also evaluated for the occurrence of localized high-temperature areas (heat spots) at positions vertically overlapping the annular protrusion 152. A heat spot was determined to have occurred if there was a region 3.0°C or higher than the average temperature of the silicon wafer for temperature evaluation. The silicon wafer for temperature evaluation was a 300 mm diameter silicon wafer with a 30 μm-thick blackbody film coated on its top surface. A blackbody film is a film with an emissivity (radiation rate) of 90% or more, and can be formed, for example, by coating a blackbody paint whose main ingredient is carbon nanotubes. In Comparative Example 1, the gas flow rate of argon gas flowing through the first gas flow path 164 was 0.8 sccm. The gas flow rate of argon gas was adjusted using a mass flow meter. When the temperature distribution of the silicon wafer for temperature evaluation was evaluated, the temperature difference Δ was 5.2°C. Furthermore, a heat spot occurred in part of the annular region of the silicon wafer for temperature evaluation that overlaps with the annular protrusion 152 in the vertical direction.

[0036] [Example 1] As shown in FIG. 2, the substrate holding member 100 of Example 1 has the same shape as the substrate holding member 100A of Comparative Example 1, except that a groove 153 is formed in the outer peripheral surface 152P of the annular convex portion 152. The groove 153 extends around the outer peripheral surface 152P of the annular convex portion 152 in the circumferential direction. The groove 153 is 1 mm wide and 1.5 mm deep, and has a rectangular cross-sectional shape. The upper end of the groove 153 is located 1000 μm below the upper surface 152a of the annular convex portion 152. The cross-sectional area of ​​the cross section of the annular convex portion 152 parallel to the upper surface 152a is minimum over the entire width of the groove 153 (the range from the upper end to the lower end of the groove 153). In Example 1, the area S1 of the upper surface 152a of the annular convex portion 152 is 2778.9 mm 2 On the other hand, the cross-sectional area S2 of the groove 153 parallel to the upper surface 152a is 1382.4 mm 2 In Example 1, the ratio S2 / S1 of the minimum value S2 of the cross-sectional area of ​​the cross section parallel to the upper surface 152a of the annular protrusion 152 to the area S1 of the upper surface 152a is 0.497.

[0037] In Example 1, the argon gas was adjusted to the same pressure as in the comparative example. In Example 1, the gas flow rate of the argon gas flowing through the first gas flow path 164 was 0.8 sccm, which was a flow rate that did not pose a problem in pressure control. The gas flow rate of the argon gas was adjusted using a mass flow meter. When the temperature distribution of the silicon wafer for temperature evaluation was evaluated, the temperature difference Δ was 2.6°C. Furthermore, no heat spots were observed in the annular region of the silicon wafer for temperature evaluation that overlapped with the annular protrusion 152 in the vertical direction.

[0038] [Example 2] The substrate holding member 100 of Example 2 is similar to the substrate holding member 100 of Example 1, except for the width of the groove 153. A groove 153 having a width of 5 mm and a depth of 1.5 mm extends circumferentially around the outer peripheral surface 152P of the annular protrusion 152 and the outer peripheral surface 110P of the ceramic substrate 110 of the substrate holding member 100 of Example 2. The groove 153 has a rectangular cross-sectional shape. As in Example 1, the upper end of the groove 153 is located 1000 μm below the upper surface 152 a of the annular protrusion 152. Because the width of the groove 153 is 5 mm and the height of the annular protrusion 152 (the vertical distance from the upper surface 110 a of the ceramic substrate 110 to the upper surface 152 a of the annular protrusion 152) is 2 mm, the lower end of the groove 153 is located 4 mm below the upper surface 110 a of the ceramic substrate 110, as shown in FIG. 6 . In the range from the upper end of the groove 153 to a position 1 mm below it, the cross-sectional area of ​​the cross section of the annular protrusion 152 parallel to the upper surface 152a is smallest. The range from the upper end of the groove 153 to a position 1 mm below it is a groove formed on the outer circumferential surface 152P of the annular protrusion 152, and is an example of the first groove of the present invention. Furthermore, the range from a position 1 mm below the upper end of the groove 153 to the lower end of the groove 153 is a groove formed on the outer circumferential surface 110P of the ceramic base 110, and is an example of the second groove of the present invention. In Example 2, the area S1 of the upper surface 152a of the annular protrusion 152 is 2778.9 mm 2 The minimum value S2 of the cross-sectional area of ​​the annular protrusion 152 parallel to the upper surface 152a is 1382.4 mm 2 In Example 2, too, the ratio S2 / S1 of the minimum cross-sectional area S2 of the cross section parallel to the upper surface 152a of the annular protrusion 152 to the area S1 of the upper surface 152a of the annular protrusion 152 was 0.497. The argon gas was adjusted to the same pressure as in Example 1. In Example 2, the gas flow rate of the argon gas flowing through the first gas flow path 164 was 0.8 sccm. When the temperature distribution of the temperature-evaluation silicon wafer was evaluated, the temperature difference Δ was 1.9°C. Furthermore, no heat spots were observed in the annular region of the temperature-evaluation silicon wafer that overlaps with the annular protrusion 152 in the vertical direction.

[0039] [Example 3] The substrate holding member 100 of Example 3 is similar to the substrate holding member 100 of Example 2, except that an inner circumferential groove 154 is formed along the inner circumference of the annular convex portion 152. As shown in FIG. 7 , the ceramic base 110 of the substrate holding member 100 of Example 3 has an inner circumferential groove 154 with a width of 1 mm and a depth of 4 mm formed along the inner circumferential surface 152S (inner side surface 152S) of the annular convex portion 152. The shape of the groove 153 is similar to the groove 153 of Example 2. As in Examples 1 and 2, the upper end of the groove 153 is located 1000 μm below the upper surface 152a of the annular convex portion 152. As in Example 2, the width of the groove 153 is 5 mm, and therefore the lower end of the groove 153 is located 4 mm below the upper surface 110a of the ceramic substrate 110. The area S1 of the upper surface 152a of the annular convex portion 152 is 2778.9 mm 2 In Example 3, an inner circumferential groove 154 is formed along the inner periphery of the annular protrusion 152, and the lower end (bottom) of the inner circumferential groove 154 is located 4 mm below the upper surface 110a of the ceramic substrate 110. Therefore, the cross-sectional area of ​​the annular protrusion 152 parallel to the upper surface 152a is minimum across the entire width of the groove 153 (the range from the upper end to the lower end of the groove 153). The minimum value S2 of the cross-sectional area of ​​the annular protrusion 152 parallel to the upper surface 152a is 1382.4 mm 2 In Example 3, the ratio S2 / S1 of the minimum value S2 of the cross-sectional area of ​​the cross section parallel to the upper surface 152a of the annular protrusion 152 to the area S1 of the upper surface 152a is also 0.497.

[0040] In Example 3, the argon gas was adjusted to the same pressure as in Example 1. In Example 3, the gas flow rate of the argon gas flowing through the first gas flow path 164 was 0.8 sccm. When the temperature distribution of the silicon wafer for temperature evaluation was evaluated, the temperature difference Δ was 1.6°C. Furthermore, no heat spots were observed in the annular region of the silicon wafer for temperature evaluation that overlaps with the annular protrusion 152 in the vertical direction.

[0041] [Example 4] The substrate holding member 100 of Example 4 is similar to the substrate holding member 100 of Example 1, except that the depth of the groove 153 is different. In Example 4, the groove 153 is 1 mm wide, 2 mm deep, and has a rectangular cross-sectional shape. As in Example 1, the upper end of the groove 153 in Example 4 is located 1000 μm below the upper surface 152 a of the annular protrusion 152. Over the entire width of the groove 153 (the range from the upper end to the lower end of the groove 153), the cross-sectional area of ​​the cross section of the annular protrusion 152 parallel to the upper surface 152 a is minimum. In Example 4, the area S1 of the upper surface 152 a of the annular protrusion 152 is 2778.9 mm 2 In contrast, the cross-sectional area S2 of the groove 153 parallel to the upper surface 152a is 920.0 mm 2 In Example 4, the ratio S2 / S1 of the minimum cross-sectional area S2 of the cross section parallel to the upper surface 152a of the annular protrusion 152 to the area S1 of the upper surface 152a of the annular protrusion 152 was 0.331. The argon gas was adjusted to the same pressure as in Example 1. In Example 4, the gas flow rate of the argon gas flowing through the first gas flow path 164 was 0.8 sccm. When the temperature distribution of the temperature evaluation silicon wafer was evaluated, the temperature difference Δ was 2.2°C. Furthermore, no heat spots were observed in the annular region of the temperature evaluation silicon wafer that overlaps with the annular protrusion 152 in the vertical direction.

[0042] [Example 5] The substrate holding member 100 of Example 5 is similar to the substrate holding member 100 of Example 1, except that the depth of the groove 153 is different. In Example 5, the groove 153 is 1 mm wide and 1 mm deep, and has a rectangular cross-sectional shape. As in Example 1, the upper end of the groove 153 in Example 5 is located 1000 μm below the upper surface 152 a of the annular protrusion 152. Over the entire width of the groove 153 (the range from the upper end to the lower end of the groove 153), the cross-sectional area of ​​the cross section of the annular protrusion 152 parallel to the upper surface 152 a is minimum. In Example 5, the area S1 of the upper surface 152 a of the annular protrusion 152 is 2778.9 mm 2 In contrast, the cross-sectional area S2 of the groove 153 parallel to the upper surface 152a is 1846.3 mm 2In Example 5, the ratio S2 / S1 of the minimum cross-sectional area S2 of the cross section parallel to the upper surface 152a of the annular protrusion 152 to the area S1 of the upper surface 152a of the annular protrusion 152 was 0.664. The argon gas was adjusted to the same pressure as in Example 1. In Example 5, the gas flow rate of the argon gas flowing through the first gas flow path 164 was 0.8 sccm. When the temperature distribution of the temperature evaluation silicon wafer was evaluated, the temperature difference Δ was 2.0°C. Furthermore, no heat spots were observed in the annular region of the temperature evaluation silicon wafer that overlaps with the annular protrusion 152 in the vertical direction.

[0043] [Example 6] The substrate holding member 100 of Example 6 is similar to the substrate holding member 100 of Example 1, except that the depth of the groove 153 is different. In Example 6, the groove 153 is 1 mm wide, 0.5 mm deep, and has a rectangular cross-sectional shape. As in Example 1, the upper end of the groove 153 in Example 6 is located 1000 μm below the upper surface 152 a of the annular protrusion 152. Over the entire width of the groove 153 (the range from the upper end to the lower end of the groove 153), the cross-sectional area of ​​the cross section of the annular protrusion 152 parallel to the upper surface 152 a is minimum. In Example 6, the area S1 of the upper surface 152 a of the annular protrusion 152 is 2778.9 mm 2 In contrast, the cross-sectional area S2 of the groove 153 parallel to the upper surface 152a is 2311.8 mm 2 In Example 6, the ratio S2 / S1 of the minimum cross-sectional area S2 of the cross section parallel to the upper surface 152a of the annular protrusion 152 to the area S1 of the upper surface 152a of the annular protrusion 152 was 0.832. The argon gas was adjusted to the same pressure as in Example 1. In Example 6, the gas flow rate of the argon gas flowing through the first gas flow path 164 was 0.8 sccm. When the temperature distribution of the temperature evaluation silicon wafer was evaluated, the temperature difference Δ was 2.9°C. Furthermore, no heat spots were observed in the annular region of the temperature evaluation silicon wafer that overlaps with the annular protrusion 152 in the vertical direction.

[0044] [Example 7] As shown in FIG. 8 , the substrate holding member 100 of Example 7 is similar to the substrate holding member 100 of Example 1, except that a bonding protrusion 114 having a diameter of 80 mm and a height of 3 mm is provided at the center of the lower surface 113 of the ceramic base 110. The cylindrical portion 131 of the shaft 130 has an outer diameter of 70 mm, an inner diameter of 50 mm, and a longitudinal length of 170 mm. A flange portion 133 having a diameter of 80 mm and a thickness of 15 mm is provided on the upper end surface of the cylindrical portion 131. The bonding protrusion 114 and the flange portion 133 are then diffusion bonded. In Example 7, the argon gas pressure was adjusted to the same level as in Example 1.

[0045] In Example 7, the shape of the groove 153 is the same as in Example 1. Therefore, as in Example 1, the area S1 of the upper surface 152a of the annular protrusion 152 is 2778.9 mm 2 The cross-sectional area S2 of the groove 153 parallel to the upper surface 152a is 1382.4 mm 2 As in the first embodiment, the ratio S2 / S1 of the minimum value S2 of the cross-sectional area of ​​the cross section parallel to the upper surface 152a of the annular protrusion 152 to the area S1 of the upper surface 152a is 0.497.

[0046] In Example 7, the flow rate of argon gas flowing through the first gas flow path 164 was 0.8 sccm. When the temperature distribution of the silicon wafer for temperature evaluation was evaluated, the temperature difference Δ was 2.8°C. Furthermore, no heat spots were observed in the annular region of the silicon wafer for temperature evaluation that overlapped with the annular protrusion 152 in the vertical direction 5. Furthermore, a leak check was performed using a helium leak detector. In the leak check, the lower opening of the shaft 130 was connected to the helium leak detector, and then helium gas was sprayed from the outside of the shaft 130 to evaluate whether or not there was a helium leak from the joint between the joining protrusion 114 and the shaft 130. 10 -8 Pa·m 3 / s or more was observed, it was determined that a leak had occurred. In Example 7, no leak was observed even after 10 temperature cycles.

[0047] [Example 8] The substrate holding member 100 of Example 8 is similar to the substrate holding member 100 of Example 1, except that the width of the groove 153 is different and an electrostatic attraction electrode 124 shown in FIG. 9 is embedded in the ceramic base 110 instead of the electrode 120 shown in FIG. 3. As shown in FIG. 9, the electrostatic attraction electrode 124 has two semicircular electrodes 124a and 124b arranged facing each other at a predetermined distance, and has a generally circular shape overall. The outer diameter of the electrostatic attraction electrode 124 is 292 mm. In Example 7, a voltage of +500 V was applied to electrode 124a and a voltage of −500 V was applied to electrode 124b to electrostatically attract the wafer 10.

[0048] In Example 8, a groove 153 having a width of 2 mm and a depth of 1.5 mm extends around the circumference of the outer peripheral surface 152P of the annular protrusion 152 of the substrate holding member 100. The cross-sectional shape of the groove 153 is rectangular. As in Example 1, the upper end of the groove 153 is located 1000 μm below the upper surface 152a of the annular protrusion 152. In Example 8, the width of the groove 153 is 2 mm, and therefore the lower end of the groove 153 is located 1 mm below the upper surface 110a of the ceramic substrate 110. In the range from the upper end of the groove 153 to a position 1 mm below, the cross-sectional area of ​​the annular protrusion 152, parallel to the upper surface 152a, is smallest. In Example 8, the area S1 of the upper surface 152a of the annular protrusion 152 is 2778.9 mm 2 The minimum value S2 of the cross-sectional area of ​​the annular protrusion 152 parallel to the upper surface 152a is 1382.4 mm 2 In Example 7, the ratio S2 / S1 of the minimum value S2 of the cross-sectional area of ​​the cross section parallel to the upper surface 152a of the annular protrusion 152 to the area S1 of the upper surface 152a is 0.497.

[0049] In the substrate holding member 100 of Example 8, a heat quantity of approximately 500 W was supplied from plasma formed above the substrate holding member 100 by a high-frequency power supply (not shown), and the heat was absorbed by a cooling plate installed on the back surface 113 of the substrate holding member 100. In Example 8, the pressure inside the process chamber was evacuated to 1 Pa or less, and helium gas was flowed through the first gas flow path 164. The pressure of the helium gas flowing through the first gas flow path 164 was adjusted to 1330 Pa (10 Torr). In Example 8, the gas flow rate of the helium gas flowing through the first gas flow path 164 was 0.2 sccm. When the temperature distribution of the silicon wafer for temperature evaluation was evaluated, the temperature difference Δ was 1.4°C. Furthermore, no heat spots were observed in the annular region of the silicon wafer for temperature evaluation that overlapped with the annular protrusion 152 in the vertical direction.

[0050] Comparative Example 2 The substrate holding member 100 of Comparative Example 2 differs from the substrate holding member 100 of Example 1 in the depth of the groove 153. In Comparative Example 2, the groove 153 is 1 mm wide, 2.5 mm deep, and has a rectangular cross-sectional shape. As in Example 1, in Comparative Example 2, the upper end of the groove 153 is located 1000 μm below the upper surface 152 a of the annular protrusion 152. Over the entire width of the groove 153 (the range from the upper end to the lower end of the groove 153), the cross-sectional area of ​​the cross section of the annular protrusion 152 parallel to the upper surface 152 a is smallest. In Comparative Example 2, the area S1 of the upper surface 152 a of the annular protrusion 152 is 2778.9 mm 2 In contrast, the cross-sectional area S2 of the groove 153 parallel to the upper surface 152a is 459.2 mm 2In Comparative Example 2, the ratio S2 / S1 of the minimum cross-sectional area S2 of the cross section parallel to the upper surface 152a of the annular protrusion 152 to the area S1 of the upper surface 152a of the annular protrusion 152 was 0.165. The argon gas was adjusted at the same pressure as in Example 1. In Comparative Example 2, the gas flow rate of the argon gas flowing through the first gas flow path 164 was greater than 1000 sccm. Observation of the portion (low cross-sectional area portion) of the annular protrusion 152 where the groove 153 was formed revealed cracks. It is believed that the groove 153 was too deep, causing insufficient strength in the low cross-sectional area portion. The temperature distribution of the silicon wafer for temperature evaluation was evaluated, revealing a temperature difference Δ of 6.5°C. Heat spots were observed in the annular region of the silicon wafer for temperature evaluation that overlapped with the annular protrusion 152 in the vertical direction. As described above, it is believed that gas leaked from the cracks that occurred in the low cross-sectional area portion, which increased the flow rate of argon gas flowing through the first gas flow path 164 and made it impossible to obtain a sufficient differential pressure. This caused the adhesion of the temperature evaluation silicon wafer to become unstable, resulting in some areas being strongly and weakly adhered, and thus creating heat spots.

[0051] <Summary of Examples and Comparative Examples> 11 and 12 show tables summarizing the results of Examples 1 to 8 and Comparative Examples 1 and 2 described above.

[0052] As shown in FIGS. 2, 6, and 7, the substrate holding member 100 of Examples 1 to 8 includes a first gas flow path 164 having an opening 164a that opens to the inside of the annular protrusion 152. This allows the flow rate and / or pressure of the gas flowing through the first gas flow path 164 to be adjusted. For example, as in Examples 1 to 7, the pressure of the gap surrounded by the upper surface 111 of the ceramic base 110, the annular protrusion 152, and the wafer 10 (6,650 Pa in Examples 1 to 8) can be set lower than the pressure of the process gas in the process chamber (26,600 Pa in Examples 1 to 8). Because the pressure of the gap surrounded by the upper surface 111 of the substrate holding member 110, the annular protrusion 152, and the wafer 10 can be set lower than the pressure of the process gas in the process chamber, the wafer 10 can be held by being attracted toward the upper surface 111 of the ceramic base 110 due to the pressure difference. Alternatively, as in Example 8, when the substrate holding member 100 is equipped with an electrostatic adsorption electrode 124, the wafer 10 can be held by adsorbing it toward the upper surface 111 of the ceramic base material 110 using electrostatic force.

[0053] Here, when the groove 153 is not formed in the annular protrusion 152, as in Comparative Example 1, the thermal resistance of the annular protrusion 152 is smaller than when the groove 153 is formed, and heat is more easily transferred to the upper surface 152a of the annular protrusion 152 via the annular protrusion 152. Accordingly, more heat is transferred from the substrate holding member 100 to the wafer 10, and the heat may be locally concentrated in the annular region of the wafer 10 that abuts the upper surface 152a of the annular protrusion 152. Therefore, in Comparative Example 1, when the temperature distribution of the temperature-evaluation silicon wafer was evaluated, it is believed that a heat spot region occurred along the annular protrusion 152. In contrast, in Examples 1 to 8, the groove 153 was formed in the outer peripheral surface 152P of the annular protrusion 152. As a result, the portion of the annular protrusion 152 where the groove 153 is formed is a low-cross-sectional area portion in which the cross-sectional area of ​​the cross section parallel to the upper surface 152a is smaller than the other portions. This increases the thermal resistance of the annular protrusion 152, suppressing the heat transferred to the wafer 10 and preventing the occurrence of heat spots. At the same time, the ratio of heat transferred from the upper surface 152a of the annular protrusion 152 to the wafer 10 and heat transferred from the upper surfaces 156a of the multiple protrusions 156 to the wafer 10 is adjusted, thereby relatively reducing heat spots on the upper surface of the annular protrusion 152.

[0054] Comparing Examples 1 to 3, it was found that the temperature difference Δ could be reduced by increasing the width of the groove 153 or by forming an inner circumferential groove 154 along the inner circumference of the annular convex portion 152. The length of the low cross-sectional area portion provided in the annular convex portion 152 could be increased by increasing the width of the groove 153 or by forming an inner circumferential groove 154 along the inner circumference of the annular convex portion 152. Increasing the length of the low cross-sectional area portion could increase the thermal resistance of the annular convex portion 152. Thus, it was found that increasing the thermal resistance of the annular convex portion 152 could suppress the heat transfer to the wafer 10 and prevent the occurrence of heat spots.

[0055] A comparison between Examples 1 and 4 revealed that the temperature difference Δ can be reduced as the depth of the groove 153 is increased. This is thought to be because the thermal resistance of the annular protrusion 152 increases as the depth of the groove 153 is increased, thereby suppressing heat transfer to the wafer 10. However, it was found that if the depth of the groove 153 is made too deep, as in Comparative Example 2, the strength of the low cross-sectional area portion is insufficient and cracks are more likely to occur. Furthermore, a comparison between Examples 1, 5, and 6 revealed that the temperature difference Δ increases as the depth of the groove 153 is made shallower. This is thought to be because the thermal resistance of the annular protrusion 152 decreases as the depth of the groove 153 is made shallower, making it more difficult to suppress heat transfer to the wafer 10.

[0056] Comparing Examples 1 to 8 with Comparative Example 2, it was found that the occurrence of heat spots can be suppressed when the ratio S2 / S1 of the minimum value S2 of the cross-sectional area of ​​the cross section parallel to the upper surface 152a to the area S1 of the upper surface 152a of the annular protrusion 152 is 0.3 or more. Furthermore, comparing Examples 1 to 5, 7, and 8 with Example 6, it was found that the occurrence of heat spots can be suppressed and the temperature difference Δ can be kept to 3.0°C or less when the ratio S2 / S1 of the minimum value S2 of the cross-sectional area of ​​the cross section parallel to the upper surface 152a to the area S1 of the upper surface 152a of the annular protrusion 152 is 0.7 or less.

[0057] <Effects of the embodiment> In the above embodiment and Examples 1 to 8, the substrate holding member 100 includes a ceramic base 110. The upper surface 111 of the ceramic base 110 is provided with an annular convex portion 152 that is disposed on the outer periphery of the upper surface 111 and that protrudes upward from the upper surface 111, and a plurality of convex portions 156 that are disposed inside the annular convex portion 152 and that protrude upward from the upper surface 111. Furthermore, a first gas flow path 164 having an opening 164a that opens to the inside of the annular convex portion 152 is formed inside the ceramic base 110.

[0058] The annular protrusion 152 is provided on the outer periphery of the ceramic base 110, which can prevent deformation of the outer periphery of the wafer 10 when the wafer 10 is attracted toward the upper surface of the ceramic base 110. Furthermore, the annular protrusion 152 can prevent gas from entering the gap surrounded by the upper surface 111 of the substrate holding member 110, the annular protrusion 152, and the wafer 10 from the outside. Alternatively, the annular protrusion 152 can prevent gas from leaking from the inside to the outside. When the annular protrusion 152 functions as a barrier to prevent gas from leaking or flowing in, it is more effective to have a larger contact area between the upper surface 152a of the annular protrusion 152 and the lower surface of the wafer 10. However, if the contact area between the upper surface 152a of the annular protrusion 152 and the lower surface of the wafer 10 is large, heat transferred from the substrate holding member 110 to the wafer 10 may be locally concentrated in the annular region abutting the upper surface 152a of the annular protrusion 152, as described above. Therefore, in the substrate holding member 100 of the above embodiment and Examples 1 to 8, grooves 153 are formed in the annular protrusion 152 to form a low-cross-sectional area portion in the annular protrusion 152, where the cross-sectional area of ​​the annular protrusion 152 parallel to the upper surface 152a is smaller than that of other portions. In the above embodiment and Examples 1 to 8, the ratio S2 / S1 of the minimum cross-sectional area S2 of the annular protrusion 152 parallel to the upper surface 152a to the area S1 of the upper surface 152a is set to 0.3 or more and less than 1. In this case, the strength of the annular protrusion 152 is maintained, cracks are prevented from occurring in the grooves 153 of the annular protrusion 152, and the thermal resistance of the annular protrusion 152 can be increased. This prevents excessive heat from being transferred to the wafer 10, suppresses the occurrence of heat spots, and ensures a uniform temperature distribution on the wafer 10.

[0059] As shown in FIG. 2, grooves 153 can be formed in the outer peripheral surface 152P of the annular protrusion 152. In this case, since the grooves 153 are provided in the outer peripheral surface 152P, processing is easy and the cross-sectional shape of the annular protrusion 152 can be formed precisely. Furthermore, as in the grooves 153 shown in FIGS. 6 and 7, a groove formed in the outer peripheral surface 152P of the annular protrusion 152 and a groove formed in the outer peripheral surface 110P of the ceramic substrate 110 may form a continuous groove portion. In this case, by also forming grooves in the outer peripheral surface 152P of the annular protrusion 152, it is possible to increase the thermal resistance while avoiding the electrode 120 built into the ceramic substrate 110.

[0060] 6 and 7, by increasing the width of the groove 153 or forming an inner circumferential groove 154 along the inner periphery of the annular protrusion 152, the vertical position of the outer peripheral portion of the upper surface 111a of the ceramic base 110 where the annular protrusion 152 is formed can be made lower than the vertical position of the upper surface 111a of the inner region where the multiple protrusions 156 are formed. In this case, the vertical length of the low cross-sectional area portion provided in the annular protrusion 152 can be increased, and the thermal resistance of the annular protrusion 152 can be increased. This makes it possible to suppress excessive heat transfer to the wafer 10 and prevent the occurrence of heat spots.

[0061] <Modification form> The above-described embodiments are merely illustrative and may be modified as appropriate. For example, the shapes and dimensions of the ceramic base 110 and the shaft 130 are not limited to those of the above-described embodiments and may be modified as appropriate. The dimensions, such as the height and width, of the annular protrusion 152, the shape, and the surface roughness Ra of the upper surface may be modified as appropriate. The height of the multiple protrusions 156, the shape of the upper surface 156a, and the surface roughness Ra of the upper surface 156a may be modified as appropriate. Furthermore, the position, number, shape (longitudinal cross-sectional shape, circumferential length, etc.), and surface roughness Ra of the grooves 153 in the annular protrusion 152 may be modified as appropriate. For example, in the above-described embodiments and examples, the grooves 153 are provided on the outer peripheral surface 152P of the annular protrusion 152. However, the present invention is not limited to such an embodiment. For example, the grooves 153 may be provided on the inner peripheral surface 152S of the annular protrusion 152. Furthermore, the cross-sectional shape of the groove 153 is not limited to a rectangular shape, but may be a curved shape such as a semicircular shape, or may be a shape with a partially inclined portion.

[0062] Furthermore, the shape of the upper surfaces 156a of the plurality of protrusions 156 does not necessarily have to be circular, and can be any shape. Even in this case, it is preferable that the surface area is approximately the same as that of a circle with a diameter of 0.1 mm to 5 mm. Furthermore, in the above description, the plurality of protrusions 156 are arranged so as to be distributed concentrically, but the present invention is not limited to such an embodiment. For example, the plurality of protrusions 156 may be arranged so as to be distributed at random positions. Even in this case, it is preferable that the distance between each of the plurality of protrusions 156 is in the range of 1.5 mm to 30 mm.

[0063] In the above embodiment, molybdenum, tungsten, or an alloy containing molybdenum and / or tungsten is used as the electrode 120, but the present invention is not limited to such an embodiment. For example, metals or alloys other than molybdenum and tungsten may also be used. Furthermore, while the electrode 120 is a heater electrode that functions as a heat source, the electrode 120 does not necessarily have to be a heater electrode that functions as a heat source and may be, for example, an electrostatic attraction electrode or a high-frequency electrode.

[0064] In the above embodiment, the substrate holding member 100 includes the electrode 120, but the present invention is not limited to such an embodiment, and the substrate holding member 100 does not necessarily include the electrode 120. Furthermore, even if the substrate holding member 100 includes the electrode 120, the electrode 120 does not have to be embedded in the ceramic base 110 of the substrate holding member 100. For example, the electrode 120 may be attached to the back surface 113 of the ceramic base 110.

[0065] In the above embodiment, the substrate holding member 100 includes the shaft 130, but the present invention is not limited to such an embodiment, and the substrate holding member 100 does not necessarily include the shaft 130. Furthermore, even if the substrate holding member 100 includes the shaft 130, the second gas flow path 168 extending in the up-down direction 5 does not have to be formed in the cylindrical portion 131 of the shaft 130. For example, instead of the second gas flow path 168, a separate gas pipe can be provided in the hollow region of the cylindrical portion 131 (the region where the power supply line 140 is provided).

[0066] Although the present invention has been described above using embodiments and modifications thereof, the technical scope of the present invention is not limited to the scope of the above description. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0067] The order of execution of each process in the manufacturing method shown in the specification and drawings is not particularly specified, and the processes may be executed in any order unless the output of a previous process is used in a subsequent process. For convenience, even if a description is made using "first," "next," etc., it does not mean that the processes must be executed in this order. [Explanation of symbols]

[0068] 100 Substrate holding member 110 Ceramic substrate 120 electrodes 130 shaft 140 Feed line 152 Annular convex part 152P outer surface 152S Inner surface 153 Groove 154 Inner groove 156 Multiple protrusions

Claims

1. a ceramic substrate having an upper surface and a lower surface facing the upper surface in the vertical direction; an electrode embedded in the ceramic substrate or disposed on the lower surface of the ceramic substrate; The ceramic substrate is an annular protrusion disposed on an outer periphery of the upper surface of the ceramic base and protruding upward from the upper surface of the ceramic base; a plurality of protrusions disposed on the upper surface of the ceramic base in an inner region of the annular protrusion and protruding upward from the upper surface of the ceramic base, The area S1 of the upper surface of the annular convex portion and the minimum value S2 of the cross-sectional area of ​​the cross section parallel to the upper surface of the annular convex portion are 0.3≦S2 / S1≦0.832 A substrate holding member characterized by:

2. The area S1 of the upper surface of the annular convex portion and the minimum value S2 of the cross-sectional area of ​​the cross section parallel to the upper surface of the annular convex portion are 0.3≦S2 / S1≦0.7 2. The substrate holding member according to claim 1, wherein:

3. 3. The substrate holding member according to claim 1, wherein a first groove is formed in the outer peripheral surface of the annular convex portion.

4. 4. The substrate holding member according to claim 3, wherein a second groove is formed on the outer peripheral surface of the ceramic base, and the second groove forms a groove portion continuous with the first groove.

5. 5. The substrate holding member according to claim 1, wherein the vertical position of the outer circumferential portion on the upper surface of the ceramic substrate, where the annular protrusion is arranged, is lower than the vertical position of the inner region on which the plurality of protrusions are arranged.

6. Further, a cylindrical shaft is joined to the lower surface of the ceramic base, 6. The substrate holding member according to claim 1, wherein the electrode embedded in the ceramic base or disposed on the lower surface of the ceramic base is a heating element.

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