Substrate holding member

Abstract

To provide a substrate holding member which can prevent enlargement of an area of contact with a substrate while suppressing deformation of a peripheral portion of the substrate.SOLUTION: A substrate holding member 100 comprises a ceramic base material 110. On an upper surface 111 of the ceramic base material 110, there are provided: an annular protrusion 152, with an annular shape, which is located on a peripheral portion of the upper surface 111; a plurality of first protrusions 154 located outside the annular protrusion 152; and a plurality of second protrusions 156 located inside the annular protrusion 152. Inside the ceramic base material 110, there is formed a first gas passage 164 having an opening 164a opened to the inside of the annular protrusion 152. A difference L2-L1 between a height L2 of the first protrusions 154 from the upper surface 111 and a height L1 of the annular protrusion 152 from the upper surface 111 is greater than 1 μm.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. However, depending on the width of the seal ring, the contact area with the substrate can become large, which may cause particles to adhere to the substrate due to contact between the substrate and the seal ring.

[0005] The present invention has been made in consideration of such circumstances, and aims to provide a substrate holding member that can suppress deformation of the outer periphery of the substrate and prevent the contact area with the substrate from becoming too large. [Means for solving the problem]

[0006] According to an aspect of the present invention, a ceramic substrate is provided having an upper surface and a lower surface facing the upper surface in a vertical direction, The ceramic substrate is The ceramic substrate the outer periphery of the upper surface The upper surface of the ceramic base is formed so as to surround the upper surface of the ceramic base from the outermost side. and protruding upward from the upper surface of the ceramic base. outermost an annular protrusion; On the upper surface, outermost a plurality of first protrusions disposed outside the annular protrusion and protruding upward from the upper surface; On the upper surface, outermost a plurality of second protrusions disposed inside the annular protrusion and protruding upward from the upper surface; On the upper surface, outermost a first gas flow path having an opening disposed inside the annular protrusion, a position in the vertical direction of an upper surface of the outermost annular convex portion is lower than a position in the vertical direction of upper surfaces of the plurality of first convex portions; the positions of the upper surfaces of the plurality of first protrusions in the up-down direction; outermost There is provided a substrate holding member characterized in that the difference in the vertical position of the upper surface of the annular protrusion is greater than 1 μm. [Effects of the Invention]

[0007] In the above embodiment, the substrate holding member includes a first gas flow path having an opening that opens to the inside of the annular convex portion. This allows the flow rate and / or pressure of the gas flowing through the first gas flow path to be adjusted. For example, the pressure in the gap surrounded by the upper surface of the substrate holding member, the annular convex portion, and the substrate can be set lower than the pressure outside the gap. This allows the substrate to be held by adsorbing it toward the upper surface of the ceramic base due to the pressure difference. Furthermore, a gas different from the gas in the external environment can be supplied through the first gas flow path to the gap surrounded by the upper surface of the ceramic base, the annular convex portion, and the lower surface of the substrate. Furthermore, a first convex portion is provided on the outer periphery of the ceramic base outside the annular convex portion and abuts against the outer periphery of the substrate when holding the substrate. This prevents deformation of the outer periphery of the substrate when adsorbing it toward the upper surface of the ceramic base. Furthermore, the difference in the vertical direction between the upper surfaces of the multiple first convex portions and the upper surface of the annular convex portion is greater than 1 μm. In other words, the difference (L2-L1) between the vertical length (L2) from the top surface of the ceramic substrate and the vertical length (L1) of the annular protrusion from the top surface of the ceramic substrate is greater than 1 μm. Therefore, even if the outer periphery of the substrate is deformed, there is no risk of the substrate coming into contact with the top surface of the annular protrusion. This prevents particles generated by contact between the substrate and the top surface of the annular protrusion from adhering to the substrate. At the same time, if the substrate holding member includes an electrode as a heating element, heat spots corresponding to the positions of the annular protrusions that occur on the substrate due to heat transfer from contact between the annular protrusions and the substrate can be prevented. [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(d) 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 100A of Comparative Example 1. In FIG. [Figure 7] FIG. 7 is a table summarizing the results of Examples 1 to 5 and Comparative Examples 1 and 2. [Figure 8] FIG. 8 is a schematic explanatory diagram of the electrostatic chucking electrode 124. As shown in FIG. 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 circular plate-shaped member 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 (hereinafter simply referred to as an annular protrusion 152), a plurality of first protrusions 154 arranged outside the annular protrusion 152, and a plurality of second protrusions 156 arranged inside the annular protrusion 152 are provided on the upper surface 111 of the ceramic substrate 110. Note that in FIG. 1, the number of first protrusions 154 and second 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 made of, for example, aluminum nitride, alumina, silicon nitride, or the like.

[0011] As shown in FIGS. 1 and 2 , the annular protrusion 152 is a circular protrusion arranged on the outer periphery (outer edge) of the upper surface 111 of the ceramic substrate 110 and protrudes upward from the upper surface 111. A plurality of first protrusions 154 are provided in a region outside the annular protrusion 152 on the outer periphery (outer edge) of the upper surface 111 of the ceramic substrate 110. Each of the first protrusions 154 has a cylindrical shape. The first protrusions 154 are arranged circumferentially at equal intervals outside the annular protrusion 152. The positions and / or number of the first protrusions 154 outside the annular protrusion 152 are appropriately determined depending on the application, action, function, etc. As shown in FIG. 2 , when the wafer 10 is placed on the ceramic substrate 110, the upper surfaces 154 a of the first protrusions 154 abut against the lower surface of the wafer 10. That is, the first protrusion 154 is disposed at a position that overlaps with the wafer 10 in the up-down direction 5 when the wafer 10 is placed on the ceramic base 110. A plurality of second protrusions 156 are provided inside the annular protrusion 152 on the upper surface 111 of the ceramic base 110. Each of the plurality of second protrusions 156 has a cylindrical shape. One of the plurality of second protrusions 156 is disposed approximately at the center of the upper surface 111. The remaining second protrusions 156 are arranged on the circumference of four equally spaced concentric circles. Furthermore, the second protrusions 156 are arranged at equally spaced intervals on the circumference of each concentric circle. The position and / or number of the plurality of second protrusions 156 are appropriately determined depending on the application, action, and function.

[0012] The height L1 of the annular convex portion 152 (the vertical length from the upper surface 111 of the ceramic substrate 110) can be selected from the range of 5 μm to 2 mm. Similarly, the height L2 of the plurality of first convex portions 154 and the height L3 of the plurality of second convex portions 156 can also be selected from the range of 5 μm to 2 mm. As shown in FIG. 2, the height L2 of the first convex portion 154 can be the same as the height L3 of the plurality of second convex portions 156 (L2 = L3). Also, as shown in FIG. 2, the height L1 of the annular convex portion 152 is lower than the height L2 of the first convex portion 154 and the height L3 of the plurality of second convex portions 156 (L1 < L2, L1 < L3). Therefore, L1, L2, and L3 are selected from the above range, and values that satisfy the conditions of L2 - L1 > 1 μm and L2 = L3 are chosen.

[0013] The width of the annular convex portion 152 is preferably a constant width and can be set to 0.1 mm to 10 mm. The surface roughness Ra of the upper surface 152a of the annular convex portion 152 can be 1.6 μm or less. The surface roughness Ra of the upper surfaces 154a of the plurality of first convex portions 154 and the upper surfaces 156a of the plurality of second convex portions 156 can be 1.6 μm or less. Note that the surface roughness Ra of the upper surfaces 154a of the first convex portions 154 and the upper surfaces 156a of the plurality of second convex portions 156 is preferably 0.4 μm or less, and more preferably 0.2 μm or less.

[0014] The upper surfaces 154a of the plurality of first convex portions 154 are preferably circular with a diameter of 0.1 mm to 5 mm. Also, the spacing distance between the respective convex portions of the plurality of first convex portions 154 can be in the range of 1.5 mm to 30 mm. Similarly, the upper surfaces 156a of the plurality of second convex portions 156 are preferably circular with a diameter of 0.1 mm to 5 mm. Also, the spacing distance between the respective convex portions of the plurality of second convex portions 156 can be in the range of 1.5 mm to 30 mm.

[0015] As described above, on the upper surface 111, the multiple second 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 the upper surface 111 where the multiple second protrusions 156 are arranged and the second innermost concentric circle. 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.

[0016] 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 can be supplied between the wafer 10 and the ceramic base 110. 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.

[0017] As shown in FIGS. 1 and 2, an electrode 120 (an 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 and has a bilaterally symmetrical shape. The outer diameter of the electrode 120 is approximately 298 mm, and the electrode 120 is not exposed from the side 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 attraction electrode 124 (see FIG. 8 ) 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.

[0018] 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.

[0019] The upper surface of the cylindrical portion 131 is fixed to the lower surface 113 of the ceramic base 110. The shaft 130 may be made of a ceramic sintered body such as alumina, aluminum nitride, or silicon nitride, like the ceramic base 110. Alternatively, in order to improve heat insulation, the shaft 130 may be made 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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 of the electrode 120.

[0024] 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 is pressed and molded with a punch 502. 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. Firing is also preferably performed at a temperature of 1800°C or more. Next, to form the terminal 121, a blind hole is drilled down to the electrode 120. Note that if a pellet is embedded, it is sufficient to drill a blind hole down to the pellet. Furthermore, a through hole that becomes part of the first gas flow path 164 is formed. This allows the production of a ceramic base material 110 having the first gas flow path 164 formed therein.

[0025] 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.

[0026] 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.

[0027] The upper surface 111 of the ceramic base material 110 thus formed is ground and then subjected to lapping (mirror polishing). Furthermore, the upper surface 111 is subjected to sandblasting, thereby forming a plurality of second protrusions 156 and annular protrusions 152 on the upper surface 111, and forming a plurality of first protrusions 154 on the upper surface 152a of the annular protrusions 152. Note that sandblasting is a suitable processing method for forming the plurality of second protrusions 156, annular protrusions 152, and plurality of first protrusions 154, but other processing methods may also be used.

[0028] 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 aluminum nitride powder P containing several wt % of binder is molded under hydrostatic pressure (approximately 1 MPa) to form a molded body into a predetermined shape. The length of the cylindrical portion 131 of the shaft 130 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 molded body. The molded body is then fired in a nitrogen atmosphere. For example, the firing is performed 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 base 110 is preferably 0.4 μm or less, and more preferably 0.2 μm or less. Alternatively, the upper surface of the cylindrical portion 131 and the lower surface 113 of the ceramic base 110 can be bonded together 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 a thickness of 15 μm at the interface between the upper surface of the cylindrical portion 131 and the lower surface 113 of the ceramic base 110, and the bonding can be achieved by applying a force of 5 kPa in a direction perpendicular to the upper surface 111 (the longitudinal direction 6 of the shaft 130) and heating at a temperature of 1700°C for one hour. Alternatively, the upper surface of the cylindrical portion 131 and the lower surface 113 of the ceramic base 110 can be fixed together by screwing, brazing, or the like. [Example]

[0029] 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.

[0030] [Example 1] Although not shown in FIG. 2, a molybdenum mesh (wire diameter 0.1 mm, mesh size #50, plain weave) cut into the shape shown in FIG. 3 was fabricated as the electrode 120. Then, a ceramic substrate 110 having a diameter of 310 mm and a thickness of 25 mm was fabricated with this electrode 120 embedded therein. An annular protrusion 152 having an inner diameter of 280 mm, an outer diameter of 286 mm, a width of 3 mm, and a height of 147 μm from the upper surface 111 was formed on the upper surface 111 of the ceramic substrate 110. A plurality of cylindrical first protrusions 154 having a PCD of 0.296 mm, a diameter of 2 mm, and a height of 150 μm from the upper surface 111 were formed at equal intervals in the region outside the annular protrusion 152 on the upper surface 111 of the ceramic substrate 110. Furthermore, a plurality of cylindrical second protrusions 156 each having a diameter of 2 mm and a height of 150 μm from the upper surface 111 were formed in an area inside the annular protrusion 152 on the upper surface 111 of the ceramic base 110. Thus, in the substrate holding member 100 of Example 1, the height L1 of the annular protrusion 152 is 147 μm, and the height L2 of the first protrusion 154 and the height L3 of the plurality of second protrusions 156 are 150 μm. In other words, the height L1 of the annular protrusion 152 is 3 μm shorter than the height L2 of the plurality of first protrusions 154 and the height L3 of the plurality of second protrusions 156. In other words, the position (height position) of the upper surface 154a of the first convex portion 154 in the up-down direction 5 is the same as the height position of the upper surface 156a of the second convex portion 156, and the height position of the upper surface 152a of the annular convex portion 152 is 3 μm lower than the height positions of the upper surface 154a of the first convex portion 154 and the upper surface 156a of the second convex portion 156. The surface roughness Ra of the upper surface 152a of the annular convex portion 152, the upper surface 154a of the first convex portion 154, and the upper surface 156a of the second convex portion 156 was all 0.4 μm.

[0031] 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.

[0032] The substrate holding member 100 having such a shape was placed in a process chamber. Argon 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 and adjusted to a pressure of 6,650 Pa (50 Torr).

[0033] The temperature of the substrate holding member 100 was evaluated using the following procedure. First, a silicon wafer for temperature evaluation was placed on the ceramic substrate 110, and 650 W of heater power was supplied to the substrate holding member 100 from an external power source (not shown). The pressures of the process gas and the argon gas as the heat transfer gas were adjusted to the above pressure. The temperature distribution in a 298 mm diameter area of ​​the silicon wafer for temperature evaluation was then measured using an infrared camera. The temperature distribution was measured when the argon gas pressure adjustment in the first gas flow path 164 began (first measurement) and 10 minutes later (second measurement). The silicon wafer for temperature evaluation was a 300 mm diameter silicon wafer coated with a 30 μm thick blackbody film on its top surface. The blackbody film is a film with an emissivity (radiation rate) of 90% or higher, and can be formed by coating it with a blackbody paint whose main ingredient is carbon nanotubes, for example. In Example 1, the flow rate of the argon gas flowing through the first gas flow path 164 was 39 sccm. The average value of the temperature distribution in the first temperature measurement was 377.0° C., and the average value of the temperature distribution in the second temperature measurement was 377.8° C. When the temperature distribution of the silicon wafer for temperature evaluation was evaluated, no heat spot region was generated in the position overlapping with the annular convex portion 152.

[0034] [Example 2] The substrate holding member 100 of Example 2 is similar to the substrate holding member 100 of Example 1, except that the height L1 of the annular protrusion 152 is 145 μm. In the substrate holding member 100 of Example 2, the height L2 of the first protrusion 154 and the height L3 of the multiple second protrusions 156 are the same. 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 103 sccm. The average value of the temperature distribution in the first temperature measurement was 376.7°C, and the average value of the temperature distribution in the second temperature measurement was 378.0°C. When the temperature distribution of the silicon wafer used for temperature evaluation was evaluated, no heat spot regions were generated at the positions overlapping with the annular protrusion 152.

[0035] [Example 3] The substrate holding member 100 of Example 3 is similar to the substrate holding member 100 of Example 1, except that the height L1 of the annular protrusion 152 is 140 μm. In the substrate holding member 100 of Example 3, the height L2 of the first protrusion 154 and the height L3 of the multiple second protrusions 156 are the same. 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 380 sccm. The average value of the temperature distribution in the first temperature measurement was 377.4°C, and the average value of the temperature distribution in the second temperature measurement was 379.2°C. When the temperature distribution of the silicon wafer used for temperature evaluation was evaluated, no heat spot regions were generated at the positions overlapping with the annular protrusion 152.

[0036] [Example 4] The substrate holding member 100 of Example 4 is similar to the substrate holding member 100 of Example 1, except that the height L1 of the annular protrusion 152 is 148.5 μm and an electrostatic attraction electrode 124 (shown in FIG. 8 ) is embedded in the substrate holding member 100 instead of the electrode 120. As shown in FIG. 8 , the electrostatic attraction electrode 124 has two semicircular electrodes 152a and 152b arranged facing each other at a predetermined distance, resulting in a generally circular shape. In Example 4, a voltage of +500 V was applied to the electrode 152a and a voltage of −500 V was applied to the electrode 152b to electrostatically attract the wafer 10. In the substrate holding member 100 of Example 4, the height L2 of the first protrusion 154 and the height L3 of the multiple second protrusions 156 are the same. In Example 4, nitrogen gas was supplied as a process gas into the process chamber at a pressure of 10 Pa (0.075 Torr). Furthermore, helium gas was supplied through the first gas flow path 164 at a pressure of 665 Pa (5 Torr). In Example 4, the gas flow rate of the helium gas supplied to the first gas flow path 164 was 2 sccm. In Example 4, 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. The average value of the temperature distribution in the first temperature measurement was 57.0°C, and the average value of the temperature distribution in the second temperature measurement was 57.1°C. When the temperature distribution of the silicon wafer for temperature evaluation was evaluated, no heat spot region was generated at the position overlapping with the annular protrusion 152.

[0037] [Example 5] The substrate holding member 100 of Example 5 is similar to the substrate holding member 100 of Example 1, except that the height L1 of the annular protrusion 152 is 135 μm. In the substrate holding member 100 of Example 5, the height L2 of the first protrusion 154 and the height L3 of the multiple second protrusions 156 are the same. 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 840 sccm. The gas flow rate was excessive, making it difficult to adequately control the pressure. The average value of the temperature distribution in the first temperature measurement was 377.1°C, and the average value of the temperature distribution in the second temperature measurement was 379.0°C. When the temperature distribution of the silicon wafer used for temperature evaluation was evaluated, no heat spot regions were observed where the annular protrusion 152 overlapped.

[0038] [Comparative Example 1] As shown in FIG. 6 , the substrate holding member 100A of Comparative Example 1 differs from the substrate holding member 100 of Example 1 in that the height L1 of the annular protrusion 152 is 150 μm and that the first protrusion 154 is not provided outside the annular protrusion 152. In the substrate holding member 100A of Comparative Example 1, the height L1 of the annular protrusion 152 is the same as the height L3 of the multiple second protrusions 156. In Comparative Example 1, the argon gas was adjusted to the same pressure as in Example 1. In Comparative Example 1, the average temperature distribution in the first temperature measurement was 377.0°C, and the average temperature distribution in the second temperature measurement was 381.5°C. 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 used for temperature evaluation was evaluated, a heat spot region was generated at the position overlapping the annular protrusion 152.

[0039] Comparative Example 2 The substrate holding member 100 of Comparative Example 2 is similar to the substrate holding member 100 of Example 1, except that the height L1 of the annular protrusion 152 is 149 μm. In the substrate holding member 100 of Comparative Example 2, the height L2 of the first protrusion 154 and the height L3 of the multiple second protrusions 156 are also the same. In Comparative Example 2, the argon gas was adjusted to the same pressure as in Example 1. In Comparative Example 2, the average value of the temperature distribution in the first temperature measurement was 376.8°C, and the average value of the temperature distribution in the second temperature measurement was 380.5°C. The gas flow rate of the argon gas flowing through the first gas flow path 164 was 4.6 sccm. When the temperature distribution of the silicon wafer used for temperature evaluation was evaluated, a heat spot region was generated at the position overlapping with the annular protrusion 152.

[0040] <Summary of Examples and Comparative Examples> FIG. 7 shows a table summarizing the results of Examples 1 to 5 and Comparative Examples 1 and 2 described above.

[0041] As shown in FIG. 2 , the substrate holding member 100 of Examples 1 to 5 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 3 and 5, 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 3 and 5) can be set lower than the pressure of the process gas in the process chamber (26,600 Pa in Examples 1 to 3 and 5). Because the pressure of the gap surrounded by the upper surface 111 of the ceramic base 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. In the substrate holding member 100 of Example 4, the electrostatic attraction electrode 124 is embedded, and therefore the wafer 10 can be electrostatically attracted and held by applying a predetermined voltage to the electrostatic attraction electrode 124. In this case as well, the substrate holding member 100 is provided with the first gas flow path 164, and therefore a gas different from the process gas in the process chamber can be supplied at an appropriate flow rate through the first gas flow path 164 to the gap surrounded by the upper surface 111 of the ceramic base 110, the annular convex portion 152, and the wafer 10.

[0042] In the substrate holding member 100 of Examples 1 to 5, a plurality of first protrusions 154 are formed on the outer side of the annular protrusion 152. As described above, the height position of the upper surface 152a of the annular protrusion 152 is lower than the height positions of the upper surfaces 154a of the first protrusions 154 and the upper surfaces 156a of the second protrusions 156, and the difference is greater than 1 μm. As a result, when the wafer 10 is attracted toward the upper surface 111 of the substrate holding member 100, the upper surface 152a of the annular protrusion 152 does not come into contact with the lower surface of the wafer 10. This prevents the generation of heat spot regions on the wafer 10 at positions that overlap with the annular protrusions 152 in the vertical direction 5. Note that, because the first protrusions 154 are provided on the outer side of the annular protrusions 152, the outer peripheral portion of the lower surface of the wafer 10 can be supported by the first protrusions 154. This allows the wafer 10 to be stably supported.

[0043] In contrast, as shown in FIG. 6 , the substrate holding member 100A of Comparative Example 1 does not have a first protrusion 154 outside the annular protrusion 152. The height position of the upper surface 152a of the annular protrusion 152 is the same as the height position of the upper surface 156a of the second protrusion 156. Therefore, when the wafer 10 is attracted toward the upper surface 111 of the ceramic base 110 as described above, the entire upper surface 152a of the annular protrusion 152 abuts against the lower surface of the wafer 10. The lower surface of the wafer 10 also abuts against the upper surfaces 156a of the multiple second protrusions 156, but the upper surfaces 156a of the multiple second protrusions 156 are spaced apart from one another. Therefore, heat transferred from the upper surfaces 156a of the multiple second protrusions 156 to the wafer 10 does not concentrate locally. In contrast, the upper surface 152a of the annular protrusion 152 is a continuous annular surface. Therefore, when the entire upper surface 152a of the annular protrusion 152 abuts against the lower surface of the wafer 10, heat transferred from the upper surface 152a of the annular protrusion 152 to the wafer 10 may locally concentrate in the annular region abutting the upper surface 152a of the annular protrusion 152. Therefore, in Comparative Example 1, when the temperature distribution of the silicon wafer for temperature evaluation was evaluated, it was considered that a heat spot region occurred at the position of the wafer 10 that overlapped with the annular protrusion 152 in the vertical direction 5. Furthermore, when the difference in height between the upper surface 152a of the annular protrusion 152 and the upper surfaces 154a of the first protrusion 154 and the second protrusion 156 was 1 μm or less, as in Comparative Example 2, the distance between the upper surface 152a of the annular protrusion 152 and the wafer 10 was 1 μm or less. Even in such a case, when the temperature distribution of the silicon wafer for temperature evaluation was evaluated, it was found that a heat spot region occurred at the position of the wafer 10 that overlapped with the annular protrusion 152 in the vertical direction 5. This is thought to be because the wafer 10 bends downward between the first convex portion 154 and the second convex portion 156 due to the suction force and comes into contact with the upper surface 152 a of the annular convex portion 152 .

[0044] Comparing Examples 1 to 3 and 5, it was found that the flow rate of gas flowing through the first gas flow path 164 increased as the height L1 of the annular convex portion 152 decreased. This is because the gap between the upper surface 152a of the annular convex portion 152 and the wafer 10 increased as the height L1 of the annular convex portion 152 decreased. As the gap between the upper surface 152a of the annular convex portion 152 and the wafer 10 increased, the movement of gas increased between the inside and outside of the gap surrounded by the upper surface 111 of the ceramic base 110, the annular convex portion 152, and the wafer 10. Therefore, the flow rate of gas increases to maintain a constant pressure in the gap surrounded by the upper surface 111 of the ceramic base 110, the annular convex portion 152, and the wafer 10. Comparing Examples 1 to 3 and 5 revealed that, from the perspective of suppressing the gas flow rate, it is preferable to set the height of the first convex portion 154 to 10 μm or less, as in Examples 1 to 3. Furthermore, it has been found that in order to suppress the flow rate of gas, it is preferable to set the height of the first convex portion 154 to 5 μm or less.

[0045] <Effects of the embodiment> In the above embodiment and Examples 1 to 5, 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 protrudes upward from the upper surface 111, a plurality of first convex portions 154 that are disposed outside the annular convex portion 152 and protrude upward from the upper surface 111, and a plurality of second convex portions 156 that are disposed inside the annular convex portion 152 and 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. Furthermore, the difference L2-L1 between the height L2 of the multiple first protrusions 154 (the length in the vertical direction 5 from the upper surface 111 of the ceramic base 110) and the height L1 of the annular protrusion 152 (the length in the vertical direction 5 from the upper surface 111 of the ceramic base 110) is greater than 1 μm. In other words, the difference between the height position (position in the vertical direction 5) of the upper surfaces 154a of the multiple first protrusions 154 and the height position of the upper surface 152a of the annular protrusion 152 is greater than 1 μm.

[0046] The substrate holding member 100 is provided with a first gas flow path 164, which allows adjustment of the flow rate and / or pressure of the gas flowing through the first gas flow path 164. For example, the pressure in the gap surrounded by the upper surface 111 of the ceramic base 110, the annular convex portion 152, and the wafer 10 can be set lower than the pressure outside the annular convex portion 152 (external environment). At this time, the wafer 10 can be held by being attracted toward the upper surface 111 of the ceramic base 110 due to the pressure difference. Note that gas flows from outside the annular convex portion 152 into the gap surrounded by the upper surface 111 of the ceramic base 110, the annular convex portion 152, and the wafer 10, but can be exhausted via the first gas flow path 164.

[0047] An annular protrusion 152 is provided on the outer periphery of the ceramic base 110, and a first protrusion 154 is provided further outside the annular protrusion 152. The first protrusion 154 provided outside the annular protrusion 152 abuts against the outer periphery of the wafer 10 when the wafer 10 is held. This prevents the outer periphery of the wafer 10 from being deformed when the wafer 10 is attracted toward the upper surface 111 of the ceramic base 110. Furthermore, the difference L2-L1 between the height L2 of the plurality of first protrusions 154 (the length in the vertical direction 5 from the upper surface 111 of the ceramic base 110) and the height L1 of the annular protrusion 152 (the length in the vertical direction 5 from the upper surface 111 of the ceramic base 110) is greater than 1 μm. In other words, the difference in height between the upper surfaces 154a of the plurality of first protrusions 154 (the position in the vertical direction 5) and the upper surface 152a of the annular protrusion 152 is greater than 1 μm. Therefore, even if the outer periphery of the wafer 10 is slightly deformed, there is no risk of the wafer 10 coming into contact with the upper surface 152a of the annular protrusion 152. This makes it possible to prevent particles generated due to contact between the wafer 10 and the upper surface 152a of the annular protrusion 152 from adhering to the wafer 10. Furthermore, since the annular protrusion 152 is provided on the outer periphery of the ceramic base 110, it is possible to prevent gas from entering the gap surrounded by the upper surface 111 of the ceramic base 110, the annular protrusion 152, and the wafer 10 from outside the annular protrusion 152.

[0048] In the above embodiment and Examples 1 to 5, the substrate holding member 100 includes an electrode 120 as a heating element and functions as a ceramic heater. As described above, a plurality of first protrusions 154 are formed on the outer side of the annular protrusion 152. Therefore, when the wafer 10 is attracted toward the upper surface 111 of the substrate holding member 100, the upper surface 152a of the annular protrusion 152 does not abut the lower surface of the wafer 10, but the upper surface 154a of the first protrusion 154 contacts the lower surface of the wafer 10. Furthermore, because the difference L2-L1 between the height L2 of the first protrusion 154 and the height L1 of the annular protrusion 152 is greater than 1 μm, a gap greater than 1 μm can be provided between the upper surface 152a of the annular protrusion 152 and the lower surface of the wafer 10. This prevents heat from being directly transferred from the upper surface 152a of the annular protrusion 152 to the wafer 10. This makes it possible to prevent a heat spot area from occurring at a position on the wafer 10 that overlaps with the annular protrusion 152 in the vertical direction 5, compared to when the difference L2-L1 between the height L2 of the first protrusion 154 and the height L1 of the annular protrusion 152 is 1 μm or less.

[0049] In the above embodiment and Examples 1 to 5, the height position in the vertical direction 5 of the upper surfaces 154a of the multiple first protrusions 154 and the height position in the vertical direction 5 of the upper surfaces 156a of the multiple second protrusions 156 are the same. In this case, when the wafer 10 is attracted and held toward the upper surface 111 of the substrate holding member 100, the upper surfaces 154a of the multiple first protrusions 154 and the upper surfaces 156a of the multiple second protrusions 156 abut against the lower surface of the wafer 10. This prevents the wafer 10 from being deformed, and the wafer 10 can be held stably.

[0050] In the above-described embodiment and Examples 1 to 3, the difference L2-L1 between the height L2 (length in the vertical direction 5 from the upper surface 111) of the plurality of first protrusions 154 and the height L1 (length in the vertical direction 5 from the upper surface 111 of the ceramic base 110) of the annular protrusion 152 is 10 μm or less. In other words, the difference in height between the height position (position in the vertical direction 5) of the upper surfaces 154a of the plurality of first protrusions 154 and the height position of the upper surface 152a of the annular protrusion 152 is 10 μm or less. As the height L1 of the annular protrusion 152 is reduced, the gap between the upper surface 152a of the annular protrusion 152 and the wafer 10 increases. Accordingly, the movement of gas between the inside and outside of the gap surrounded by the upper surface 111 of the ceramic base 110, the annular protrusion 152, and the wafer 10 increases. Therefore, the gas flow rate required to maintain constant pressure in the gap surrounded by the upper surface 111 of the ceramic base 110, the annular convex portion 152, and the wafer 10 increases. In contrast, by setting the height of the first convex portion 154 to 10 μm or less, the gas flow rate required to maintain constant pressure in the gap surrounded by the upper surface 111 of the ceramic base 110, the annular convex portion 152, and the wafer 10 can be reduced. Furthermore, by setting the height of the first convex portion 154 to 5 μm or less, the gas flow rate can be further reduced.

[0051] In the above-described embodiment and examples, a second gas flow path 168 extending in the up-down direction 5 can be formed in the cylindrical portion 131 of the shaft 130. The upper end of the second gas flow path 168 is connected to the lower end of the first gas flow path 164. Since the second gas flow path 168 connected to the first gas flow path 164 is formed in the cylindrical portion 131 of the shaft 130, gas (e.g., heat transfer gas) can be easily supplied to and exhausted from the first gas flow path 164 through this second gas flow path 168.

[0052] <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. For example, in the above-described embodiments and examples, the upper surface 111 of the ceramic base 110 is flat. However, the present invention is not limited to such an embodiment. For example, the upper surface 111 may have a step. In such a case, the height L1 of the annular protrusion 152, the height L2 of the multiple first protrusions 154, and the height L3 of the multiple second protrusions 156 are defined as lengths in the vertical direction 5 from the same height position on the upper surface 111, rather than as lengths from different height positions on the upper surface 111. Furthermore, the dimensions, such as the height and width, shapes, and surface roughness Ra of the annular protrusion 152 and the first protrusion 154 may be modified as appropriate. Furthermore, the height of the multiple second protrusions 156, the shape of the upper surface 156a, and the surface roughness Ra of the upper surface 156a may be modified as appropriate.

[0053] For example, the shape of the upper surfaces 154a of the multiple first protrusions 154 and the upper surfaces 156a of the multiple second protrusions 156 does not necessarily have to be circular and can be any shape. Even in this case, it is preferable that the upper surfaces 154a and 156a have an area approximately equal to that of a circle with a diameter of 1 mm to 5 mm. In the above description, the multiple second protrusions 156 are arranged so as to be distributed concentrically, but the present invention is not limited to this configuration. For example, the multiple second 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 multiple second protrusions 156 is in the range of 1.5 mm to 30 mm.

[0054] 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, in the above embodiment, the electrode 120, which is a heater electrode serving as a heating element, is embedded in the ceramic substrate 110. The electrode embedded in the ceramic substrate 110 does not necessarily have to be a heater electrode serving as a heating element like the electrode 120. For example, it may be an electrostatic attraction electrode or a high-frequency electrode.

[0055] 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.

[0056] 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).

[0057] 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.

[0058] 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]

[0059] 100 Substrate holding member 110 Ceramic substrate 120 electrodes 130 shaft 140 Feed line 152 Annular convex part 154 First convex part 156 Multiple protrusions

Claims

1. a ceramic substrate having an upper surface and a lower surface facing the upper surface in the vertical direction; The ceramic substrate is an outermost annular protrusion disposed on the upper surface of the ceramic base so as to surround an outer periphery of the upper surface of the ceramic base from the outermost side and protruding upward from the upper surface of the ceramic base; a plurality of first protrusions disposed on the upper surface outside the outermost annular protrusion and protruding upward from the upper surface; a plurality of second protrusions disposed on the upper surface inside the outermost annular protrusion and protruding upward from the upper surface; a first gas flow path having an opening disposed inside the outermost annular protrusion on the upper surface, a position of an upper surface of the outermost annular convex portion in the vertical direction is lower than positions of upper surfaces of the plurality of first convex portions in the vertical direction; a difference between the vertical position of the upper surfaces of the plurality of first convex portions and the vertical position of the upper surface of the outermost annular convex portion being greater than 1 μm;

2. The substrate holder according to claim 1 , further comprising a heating element embedded in the ceramic base or disposed on the lower surface of the ceramic base.

3. 3. The substrate holding member according to claim 1, wherein the difference between the vertical position of the upper surfaces of the plurality of first convex portions and the vertical position of the upper surface of the outermost annular convex portion is 10 μm or less.

4. Further, a cylindrical shaft is joined to the lower surface of the ceramic base, The substrate holding member according to any one of claims 1 to 3, wherein the shaft comprises a second gas flow path disposed between an inner surface of the shaft and an outer surface of the shaft and connected to the first gas flow path.

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