Ceramic heater

Abstract

To provide a ceramic heater that can realize non-uniform temperature distribution such as outer cool (inner hot) and outer hot.SOLUTION: A ceramic heater 100 includes a disc-shaped ceramic base material 110, and a heater electrode 122 embedded in the ceramic base material 110. An annular convex portion 152 is provided on the outer periphery of the ceramic base material 110, and a plurality of convex portions 156 are provided inside the annular convex portion 152. The center line average roughness Ra1 of the upper surface 152a of the annular convex portion 152 and the center line average roughness Ra2 of the upper surfaces 156a of the plurality of convex portions 156 are different from each other.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a ceramic heater for holding and heating a substrate such as a silicon wafer.

Background Art

[0002] Patent Document 1 discloses a ceramic heater for holding and heating a substrate such as a wafer. The ceramic heater described in Patent Document 1 includes a ceramic base material (first base body) on which the substrate is placed, an annular convex portion (annular support portion) protruding upward from the upper surface of the ceramic base material, and a plurality of protrusions provided inside the annular convex portion. In the ceramic heater of Patent Document 1, the purpose is to realize a flat temperature distribution as the temperature distribution of the wafer to be placed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, in the semiconductor manufacturing process, the temperature distribution of the substrate to be processed is diverse. For example, there is a demand for a ceramic heater that can realize a non-uniform temperature distribution such as outer-cooled (inner-hot) or outer-hot.

[0005] The present invention has been made in view of such circumstances, and an object thereof is to provide a ceramic heater that can realize a non-uniform temperature distribution such as outer-cooled (inner-hot) or outer-hot.

Means for Solving the Problems

[0006] According to an embodiment of the present invention, a disc-shaped ceramic substrate having an upper surface and a lower surface facing the upper surface in the vertical direction, The device comprises a heating element embedded in the ceramic substrate or positioned on the lower surface of the ceramic substrate, The aforementioned ceramic substrate is An annular protrusion is arranged on the outer periphery of the ceramic substrate and protrudes above the upper surface of the ceramic substrate, The ceramic substrate comprises a plurality of protrusions arranged inside the annular protrusion and projecting upward above the upper surface of the ceramic substrate, The centerline average roughness Ra1 of the upper surface of the annular protrusion and the centerline average roughness Ra2 of the upper surfaces of the plurality of protrusions are different from each other. the law of nature, The ratio Ra1 / Ra2 of the centerline average roughness Ra1 of the upper surface of the annular protrusion and the centerline average roughness Ra2 of the upper surfaces of the plurality of protrusions is, 1.3 ≤ Ra1 / Ra2 ≤ 32 satisfies A ceramic heater characterized by the above is provided. [Effects of the Invention]

[0007] According to the above configuration, the centerline average roughness Ra1 of the upper surface of the annular protrusion and the centerline average roughness Ra2 of the upper surfaces of the multiple protrusions are different from each other. This makes it possible to create different conditions for the adhesion between the wafer (substrate) placed on the ceramic heater and the annular protrusion, and for the adhesion between the wafer and the multiple protrusions. As a result, a temperature difference can be created between the inner and outer regions of the wafer, achieving a so-called outer-hot or inner-hot (outer-cool) state. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a perspective view of the ceramic heater 100. [Figure 2] Figure 2 is a schematic diagram of the ceramic heater 100. [Figure 3] Figure 3 is a schematic diagram of electrode 120. [Figure 4]Figure 4 is a schematic diagram of the heater electrode 122. [Figure 5] Figure 5 is a magnified view of a portion of the ceramic heater 100. [Figure 6] Figures (a) to (e) show the flow of the manufacturing method for the ceramic substrate 110. [Figure 7] Figures (a) to (d) show the flow of another method for manufacturing the ceramic substrate 110. [Figure 8] Figure 8 is a table summarizing the results of Examples 1 to 5. [Figure 9] Figure 9 is a table summarizing the results of Examples 6-9 and the comparative examples. [Modes for carrying out the invention]

[0009] <Ceramic Heater 100> A ceramic heater 100 according to an embodiment of the present invention will be described with reference to Figures 1 and 2. The ceramic heater 100 according to this embodiment is a ceramic heater used for heating semiconductor wafers such as silicon wafers (hereinafter simply referred to as wafer 10). In the following description, the vertical direction 5 is defined based on the state in which the ceramic heater 100 is installed for use (the state in Figure 1). As shown in Figure 1, the ceramic heater 100 according to this embodiment comprises a ceramic substrate 110, an electrode 120 (see Figure 2), a shaft 130, and power supply lines 140 and 141 (see Figure 2).

[0010] The ceramic substrate 110 is a circular, plate-shaped component with a diameter of 12 inches (approximately 300 mm), and the wafer 10 to be heated is placed on top of the ceramic substrate 110. In Figure 1, the wafer 10 and the ceramic substrate 110 are shown separated for clarity. As shown in Figure 1, the upper surface 111 of the ceramic substrate 110 is provided with an annular protrusion 152 (hereinafter simply referred to as the annular protrusion 152) and a plurality of protrusions 156. In Figure 1, the number of plurality of protrusions 156 is reduced compared to Figure 2 for clarity. Also, as shown in Figure 2, a first gas channel 164, which will be described later, is formed inside the ceramic substrate 110. The ceramic substrate 110 can be formed from, for example, a ceramic sintered body of aluminum nitride, silicon carbide, alumina, silicon nitride, etc.

[0011] As shown in Figures 1 and 2, the annular projection 152 is an annular projection located on the outer periphery (outer edge) of the upper surface 111 of the ceramic substrate 110, and protrudes upward from the upper surface 111. As shown in Figure 2, when the wafer 10 is placed on the ceramic substrate 110, the upper surface 152a of the annular projection 152 abuts against the lower surface of the wafer 10. In other words, the annular projection 152 is positioned so as to overlap with the wafer 10 in the vertical direction 5 when the wafer 10 is placed on the ceramic substrate 110. On the upper surface 111 of the ceramic substrate 110, inside the annular projection 152, there are multiple projections 156. All of the multiple projections 156 have a cylindrical shape. One of the multiple projections 156 is located approximately in the center of the upper surface 111. The remaining projections 156 are arranged on the circumference of four concentric circles arranged at equal intervals. Furthermore, the protrusions 156 are arranged at equal intervals along the circumference of each concentric circle. The positions and / or number of the protrusions 156 are set appropriately according to the application, function, and purpose.

[0012] The height of the annular convex portion 152 can be in the range of 5 μm to 2 mm. Similarly, the height of the plurality of convex portions 156 can also be in the range of 5 μm to 2 mm. In the present embodiment, the height of the annular convex portion 152 and the height of the plurality of convex portions 156 are the same. In this specification, the height of the annular convex portion 152 and the height of the plurality of convex portions 156 are defined as the vertical length from the upper surface 111 of the ceramic substrate 110. When the upper surface 111 of the ceramic substrate 110 is not flat, for example, has a step, it is defined as the vertical length from the highest position among the upper surfaces 111 of the ceramic substrate 110.

[0013] The width of the upper surface 152a of the annular convex portion 152 is preferably a constant width and can be 0.1 mm to 10 mm. The upper surfaces 156a of the plurality of convex portions 156 are preferably circular with a diameter of 0.1 mm to 5 mm. Further, the separation distance between the respective convex portions of the plurality of convex portions 156 can be in the range of 1.5 mm to 30 mm.

[0014] The center line average roughness Ra1 of the upper surface 152a of the annular convex portion 152 can be 0.001 μm or more and 1.6 μm or less. The center line average roughness represents the unevenness of the surface as the average of the absolute values of the deviations from its center line. Similarly, the center line average roughness Ra2 of the upper surfaces 156a of the plurality of convex portions 156 can be 0.001 μm or more and 1.6 μm or less. From the viewpoint of gas tightness, the center line average roughness Ra1 of the upper surface 152a of the annular convex portion 152 is preferably 0.4 μm or less. Also, from the viewpoint of suppressing the adhesion of particles to the wafer 10, the center line average roughness Ra2 of the upper surfaces 156a of the plurality of convex portions 156 is preferably 0.4 μm or less. The center line average roughness Ra1 of the upper surface 152a of the annular convex portion 152 and the center line average roughness Ra2 of the upper surfaces 156a of the plurality of convex portions 156 are more preferably 0.2 μm or less, and even more preferably 0.1 μm or less. Since it is difficult to make the center line average roughness Ra1 and Ra2 less than 0.0001 μm in manufacturing, the center line average roughness Ra1 and Ra2 are usually set to 0.0001 μm or more.

[0015] For measuring the center line average roughness Ra1 of the annular convex portion 152, a stylus-type or optical surface roughness meter is used. The measurement locations are positions (4 locations) equally spaced every 90 degrees in the circumferential direction on the upper surface 152a of the annular convex portion 152. And the average value of the center line average roughness when scanning in the circumferential direction is defined as Ra1. For measuring the center line average roughness Ra2 of the plurality of convex portions 156, the same surface roughness meter is used. As the measurement locations, 4 convex portions 156 that are close to half of the radius with respect to the outer diameter of the ceramic base material or the outer diameter of the annular convex portion and are close to positions equally spaced every 90 degrees in the circumferential direction are selected. And the average value of the center line average roughness when scanning the upper surface 156a of the corresponding convex portion 156 in an arbitrary direction is defined as Ra2. When the diameter of the convex portion 156 is extremely small, it is substituted with the center line average roughness of the upper surface 111 of the ceramic base material 110 corresponding to the above 4 locations before forming the convex portion 156.

[0016] By appropriately changing the grinding wheel, the mesh number of the abrasive grains, the processing conditions, and the blasting conditions, it can be adjusted to a desired center line average roughness. Also, the process of adjusting to the desired center line roughness may be before or after the blasting process for forming the convex portion.

[0017] In this embodiment, the center line average roughness Ra1 of the upper surface 152a of the annular convex portion 152 is 0.2 μm, and the center line average roughness Ra2 of the upper surfaces 156a of the plurality of convex portions 156 is 0.1 μm. The ratio Ra1 / Ra2 of the center line average roughness Ra1 of the upper surface 152a of the annular convex portion 152 to the center line average roughness Ra2 of the upper surfaces 156a of the plurality of convex portions 156 is 2.

[0018] As described above, on the upper surface 111 of the ceramic substrate 110, the multiple protrusions 156 are arranged on the circumference of four concentric circles. As shown in Figure 2, an opening 164a of the first gas channel 164 is formed between the innermost concentric circle on the upper surface 111 where the multiple protrusions 156 are arranged and the second concentric circle from the inside. The first gas channel 164 is a gas channel with an opening 164a and is formed inside the ceramic substrate 110. The first gas channel 164 extends downward from the opening 164a. As will be described later, the lower end of the first gas channel 164 is joined to the upper end of the second gas channel 168 formed inside the shaft 130.

[0019] The first gas channel 164 can be used as a channel for supplying gas to the space (gap) defined by the upper surface 111 of the ceramic substrate 110 and the lower surface of the wafer 10. For example, it can supply heat transfer gas for heat transfer between the wafer 10 and the ceramic substrate 110. As the heat transfer gas, for example, an inert gas such as helium or argon, or nitrogen gas can be used. The heat transfer gas is supplied through the first gas channel 164 at a pressure set within the range of 100 Pa to 40000 Pa. In addition, if process gas enters the gap inside the annular protrusion 152 from 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 channel 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 makes it possible to adsorb the wafer 10 toward the upper surface of the ceramic substrate 110.

[0020] As shown in Figure 2, an electrode 120 is embedded inside the ceramic substrate 110. The electrode 120 includes a heater electrode 122 and an electrostatic adsorption electrode 124. The electrostatic adsorption electrode 124 is embedded above the heater electrode 122.

[0021] As shown in Figure 3, the electrostatic adsorption electrode 124 consists of two semicircular electrodes 124a and 124b arranged facing each other at a predetermined distance apart, and has an overall substantially circular shape. In this embodiment, the outer diameter of the electrostatic adsorption electrode 124 is 292 mm. By applying a predetermined voltage (for example, ±500 V) to electrodes 124a and 124b, the wafer 10 can be electrostatically adsorbed.

[0022] As shown in Figure 4, the heater electrode 122 is a metal mesh or foil cut into strips. The outer diameter of the heater electrode 122 is 298 mm. The heater electrode 122 is not exposed from the side of the ceramic substrate 110. A terminal portion 121 for connection to the power supply line 140 (see Figure 2) is provided approximately in the center of the heater electrode 120. The heater electrode 122 is formed from a heat-resistant metal (high melting point metal) such as a mesh or foil woven from wire of tungsten (W), molybdenum (Mo), or an alloy containing molybdenum and / or tungsten. The purity of the tungsten and molybdenum is preferably 99% or higher. The thickness of the heater electrode 122 is 0.15 mm or less. From the viewpoint of increasing the resistance value of the heater electrode 122 and reducing the current consumption of the ceramic heater 100, it is preferable to make the wire diameter 0.1 mm or less and the thickness of the heater electrode 122 0.1 mm or less. Furthermore, the width of the strip-shaped heater electrode 122 is preferably 2.5 mm to 20 mm, and more preferably 5 mm to 15 mm. In this embodiment, the heater electrode 122 is cut into the shape shown in Figure 4, but the shape of the heater electrode 122 is not limited to this and can be changed as appropriate. In addition to the heater electrode 122, or in place of the heater electrode 122, a plasma electrode for generating plasma may be embedded above the ceramic substrate 110.

[0023] As shown in Figures 1 and 2, a shaft 130 is connected to the lower surface 113 of the ceramic substrate 110. The shaft 130 has a hollow, substantially cylindrical cylindrical portion 131 and two large-diameter portions 132 and 133. The large-diameter portion 132 is located above the cylindrical portion 131 (see Figure 2), and the large-diameter portion 133 is located below the cylindrical portion 131 (see Figure 1). The large-diameter portions 132 and 133 have larger diameters than the diameter 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 Figure 1, in the operating state of the ceramic heater 100, the longitudinal direction 6 of the shaft 130 is parallel to the vertical direction 5.

[0024] As shown in Figure 2, a protrusion 114 (hereinafter referred to as the joining protrusion 114; corresponding to the protrusion of the present invention) for joining with the shaft 130 is provided on the lower surface 113 of the ceramic substrate 110. 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 0.2 mm or more, and preferably 5 mm or more. There is no particular upper limit on the height, but considering the ease of manufacturing, the height of the joining protrusion 114 is preferably 20 mm or less. In addition, the lower surface 114B of the joining protrusion 114 is preferably parallel to the lower surface 113 of the ceramic substrate 100. The centerline average roughness Ra of the lower surface 114B of the joining protrusion 114 may be 1.6 μm or less. Furthermore, the centerline average roughness Ra of the lower surface 114B of the joining protrusion 114 is preferably 0.4 μm or less, and more preferably 0.2 μm or less.

[0025] The upper surface of the cylindrical portion 131 is fixed to the lower surface 114B of the joining projection 114 of the ceramic base material 110. The shaft 130 may be formed from a ceramic sintered body such as aluminum nitride, silicon carbide, alumina, or silicon nitride, similar to the ceramic base material 110. Alternatively, to improve heat insulation, it may be formed from a material with lower thermal conductivity than the ceramic base material 110.

[0026] As shown in Figure 2, the shaft 130 has a hollow cylindrical shape, and a through hole extending in the longitudinal direction 6 (see Figure 1) is formed inside it (the region inside the inner diameter). A power supply line 140 for supplying power to the heater electrode 122 and a power supply line 141 for supplying power to the electrostatic adsorption electrode 124 are arranged in the hollow portion (through hole) of the shaft 130. In Figure 2, only one power supply line 140 and one power supply line 141 are shown, but in reality, multiple power supply lines 140 and multiple power supply lines 141 are arranged. The upper end of the power supply line 140 is electrically connected to a terminal portion 121 (see Figure 3) located in the center of the heater electrode 122. The power supply line 140 is connected to a heater power supply (not shown). As a result, power is supplied to the heater electrode 122 via the power supply line 140. Similarly, power is supplied to the electrostatic adsorption electrode 124 via the power supply line 141.

[0027] Furthermore, as shown in Figure 2, a second gas passage 168 extending in the vertical direction 5 is formed in the cylindrical portion 131 of the shaft 130. As described above, the upper end of the second gas passage 168 is connected to the lower end of the first gas passage 164.

[0028] Next, the manufacturing method of the ceramic heater 100 will be described. In the following explanation, the case in which the ceramic substrate 110 and shaft 130 are formed from aluminum nitride will be used as an example.

[0029] First, the method for manufacturing the ceramic substrate 110 will be described. For the sake of simplicity, it will be assumed that only a heater electrode 122 is embedded inside the ceramic substrate 110 as an electrode 120. As shown in Figure 6(a), granulated powder P, mainly composed of aluminum nitride (AlN) powder, is placed into a carbon bed mold 501 and pre-pressed with a punch 502. It is preferable that the granulated powder P contains 5 wt% or less of a sintering aid (for example, Y2O3). Next, as shown in Figure 6(b), the heater electrode 122, cut to a predetermined shape, is placed on top of the pre-pressed granulated powder P. The heater electrode 122 is positioned parallel to the surface perpendicular to the pressurizing direction (the bottom surface of the bed mold 501). At this time, pellets of W or Mo may be embedded at the terminal 121 (see Figure 4) of the heater electrode 122.

[0030] As shown in Figure 6(c), granulated powder P is further added to the bed mold 501 so as to cover the heater electrode 122, and then pressed and molded with a punch 502. Next, as shown in Figure 6(d), the granulated powder P with the embedded heater electrode 122 is fired in the pressed state. The pressure applied during firing is preferably 1 MPa or more. It is also preferable to fire at a temperature of 1800°C or higher. Next, as shown in Figure 6(e), a blind hole is drilled up to the heater electrode 122 in order to form the terminal 121. If a pellet is embedded, a blind hole drilling up to the pellet is sufficient. Furthermore, a through hole is formed which will become part of the first gas flow path 164. This makes it possible to produce a ceramic substrate 110 with the first gas flow path 164 formed inside. In this case, it is preferable to provide a predetermined opening in the heater electrode 122 in advance so that the heater electrode 122 is not exposed from the first gas flow path 164.

[0031] Furthermore, the ceramic substrate 110 can also be manufactured by the following method. As shown in Figure 7(a), a binder is added to granulated aluminum nitride powder P and CIP molding is performed, and the resulting disc is processed to produce an aluminum nitride molded body 510. Next, as shown in Figure 7(b), the molded body 510 is degreased to remove the binder.

[0032] As shown in Figure 7(c), a recess 511 for embedding the heater electrode 122 is formed in the degreased molded body 510. The heater electrode 122 is placed in the recess 511 of the molded body 510, and another molded body 510 is stacked on top. The recess 511 may be formed in the molded body 510 in advance. Next, as shown in Figure 7(d), the molded bodies 510 stacked with the heater electrode 122 sandwiched in between are fired while pressed to produce a fired body. The pressure applied during firing is preferably 1 MPa or more. It is also preferable to fire at a temperature of 1800°C or higher. The process after producing the fired body is the same as the process described above, so the explanation is omitted.

[0033] The upper surface 111 of the ceramic substrate 110 formed in this manner is ground and lapped. Furthermore, sandblasting is performed on the upper surface 111 to form a plurality of protrusions 156 and an annular protrusion 152 on the upper surface 111. At this time, the multiple protrusions 156 are processed to have the same height. The upper surface 152a of the annular protrusion 152 is also processed to a predetermined shape. Although sandblasting is preferred as the processing method for forming the multiple protrusions 156 and annular protrusion 152, other processing methods can also be used. Furthermore, cylindrical processing is performed on the lower surface 113 of the ceramic substrate 110 to form a joining protrusion 114 that protrudes from the lower surface 113.

[0034] Next, the manufacturing method of the shaft 130 and the method of joining the shaft 130 to the ceramic substrate 110 will be described. First, granulated aluminum nitride powder P with several wt% binder added is molded under hydrostatic pressure (approximately 1 MPa) to process the molded body into a predetermined shape. At this time, a through hole that will become the second gas passage 168 is formed in the molded body. The outer diameter of the shaft 130 is approximately 30 mm to 100 mm. The end face of the cylindrical portion 131 of the shaft 130 does not necessarily have to have a flange portion 133 (see Figure 5). The length of the cylindrical portion 131 can be, for example, 50 mm to 500 mm. After processing the molded body into a predetermined shape, the molded body is fired in a nitrogen atmosphere. For example, it is fired at a temperature of 1900°C for 2 hours. Then, the shaft 130 is formed by processing the sintered body into a predetermined shape after firing. The upper surface of the cylindrical portion 131 and the joining projection 114 of the ceramic substrate 110 can be fixed by diffusion bonding at a temperature of 1600°C or higher and a uniaxial pressure of 1 MPa or higher. In this case, the centerline average roughness Ra of the lower surface 114B of the joining projection 114 of the ceramic substrate 110 is preferably 0.4 μm or less, and more preferably 0.2 μm or less. Alternatively, the upper surface of the flange portion 133 and the lower surface 114B of the joining projection 114 can be joined using a bonding agent. As a bonding agent, for example, an AlN bonding paste with 10 wt% Y2O3 added can be used. For example, the above AlN bonding paste can be applied to the interface between the upper surface of the flange portion 133 and the lower surface 114B of the joining projection 114 to a thickness of 15 μm, and the two can be joined by heating at a temperature of 1700°C for 1 hour while applying a force of 5 kPa in a direction perpendicular to the upper surface 111 (longitudinal direction 6 of the shaft 130). Alternatively, the upper surface of the cylindrical portion 131 and the lower surface 114B of the joining projection 114 can be fixed together by screwing, brazing, or the like. [Examples]

[0035] The present invention will be further described below using Examples 1 to 9. However, the present invention is not limited to the examples described below. Figures 8 and 9 show tables summarizing the results of Examples 1 to 9 and comparative examples.

[0036] [Example 1] The ceramic heater 100 of Example 1 (see Figure 2) will now be described. In Example 1, a ceramic substrate 110 with a diameter of 300 mm and a thickness of 25 mm was fabricated using the above-described method, with aluminum nitride (AlN) to which 5 wt% of a sintering aid (Y2O3) had been added as the raw material. A heater electrode 122 was prepared by cutting a molybdenum mesh (wire diameter 0.1 mm, mesh size #50, plain weave) into the shape shown in Figure 4, and this heater electrode 122 was embedded in the ceramic substrate 110. Similarly, an electrostatic adsorption electrode 124 with the shape shown in Figure 3 was embedded in the ceramic substrate 110.

[0037] An annular projection 152 with an inner diameter of 292 mm, an outer diameter of 298 mm, and a width of 3 mm was formed on the upper surface 111 of the ceramic substrate 110. The vertical length 5 between the upper surface 152a of the annular projection 152 and the upper surface 111 of the ceramic substrate 110 (height of the annular projection 152) is 150 μm. Furthermore, a plurality of cylindrical projections 156 with a diameter of 2 mm were formed on the upper surface 111 of the ceramic substrate 110. The vertical length 5 between the upper surface 156a of the plurality of projections 156 and the upper surface 111 of the ceramic substrate 110 (height of the plurality of projections 156) is 150 μm. As described above, the plurality of projections 156 are arranged concentrically, and the distance between each projection is in the range of 10 mm to 20 mm.

[0038] 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 substrate 110.

[0039] In Example 1, the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 was set to 0.2 μm, and the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 was set to 0.1 μm. In this case, the ratio Ra1 / Ra2 of the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 to the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 is 2.

[0040] A ceramic heater 100 of this shape was installed in a process chamber, and the temperature of the ceramic heater 100 was evaluated using the following procedure. A silicon wafer with a diameter of 300 mm for temperature evaluation was placed on the ceramic heater 100, and an external power supply (not shown) was connected to the heater electrode 122 of the ceramic heater 100. After reducing the pressure inside the process chamber to 1 Pa or less, nitrogen gas was supplied to the process chamber as the process gas at a pressure of 10 Pa. Helium gas was flowed through the first gas channel 164. The pressure of the helium gas flowing through the first gas channel 164 was adjusted to 1333 Pa (10 Torr). In Example 1, the gas flow rate of the helium gas flowing through the first gas channel 164 was less than 0.1 sccm. Then, the output power of the external power supply was adjusted so that the temperature of the top surface of the silicon wafer was 500°C in a steady state. Subsequently, the temperature distribution of the silicon wafer used for temperature evaluation was measured using an infrared camera, and the temperature difference Δ between the average temperature of the inner region (region with a diameter of 250 mm or less) and the average temperature of the outer region (region with a diameter of 250 mm to 300 mm) was evaluated. The silicon wafer used for temperature evaluation was a 300 mm diameter silicon wafer with a 30 μm thick blackbody film coated on its upper surface. A blackbody film is a film with an emissivity (radiative efficiency) of 90% or more, and can be formed, for example, by coating with a blackbody paint mainly composed of carbon nanotubes.

[0041] In Example 1, the average temperature of the inner region was 500°C, and the average temperature of the outer region was 498.5°C. The temperature difference Δ between the average temperature of the inner region and the average temperature of the outer region was 1.5°C. In Example 1, an inner-hot state was achieved in which the average temperature of the inner region was higher than the average temperature of the outer region.

[0042] [Example 2] The ceramic heater 100 of Example 2 is the same as the ceramic heater 100 of Example 1, except that the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 is 1.6 μm, and the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 is 0.4 μm. In Example 2, the ratio Ra1 / Ra2 of the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 to the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 was 4.

[0043] A ceramic heater 100 of this shape was installed in a process chamber, and a silicon wafer for temperature evaluation, similar to that in Example 1, was placed on the ceramic heater 100. The temperature of the ceramic heater 100 was then evaluated using the same procedure as in Example 1. In Example 2, the gas flow rate of helium gas flowing through the first gas channel 164 was 1.0 sccm. The average temperature of the inner region was 500°C, and the average temperature of the outer region was 497.0°C. The temperature difference Δ between the average temperature of the inner region and the average temperature of the outer region was 3.0°C. In Example 2, an inner-hot state was achieved in which the average temperature of the inner region was higher than the average temperature of the outer region.

[0044] [Example 3] The ceramic heater 100 of Example 3 is the same as the ceramic heater 100 of Example 1, except that the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 is 1.6 μm, and the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 is 0.05 μm. In Example 3, the ratio Ra1 / Ra2 of the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 to the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 was 32.

[0045] A ceramic heater 100 of this shape was installed in a process chamber, and a silicon wafer for temperature evaluation, similar to that in Example 1, was placed on the ceramic heater 100. The temperature of the ceramic heater 100 was then evaluated using the same procedure as in Example 1. In Example 3, the gas flow rate of helium gas flowing through the first gas channel 164 was 1.0 sccm. The average temperature of the inner region was 500°C, and the average temperature of the outer region was 495.0°C. The temperature difference Δ between the average temperature of the inner region and the average temperature of the outer region was 5.0°C. In Example 3, an inner-hot state was achieved in which the average temperature of the inner region was higher than the average temperature of the outer region.

[0046] [Example 4] The ceramic heater 100 of Example 4 is the same as the ceramic heater 100 of Example 1, except that the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 is 1.6 μm, and the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 is 1.2 μm. In Example 4, the ratio Ra1 / Ra2 of the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 to the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 was 1.3.

[0047] A ceramic heater 100 of this shape was installed in a process chamber, and a silicon wafer for temperature evaluation, similar to that in Example 1, was placed on the ceramic heater 100. The temperature of the ceramic heater 100 was then evaluated using the same procedure as in Example 1. In Example 3, the gas flow rate of helium gas flowing through the first gas channel 164 was 1.0 sccm. The average temperature of the inner region was 500°C, and the average temperature of the outer region was 499.0°C. The temperature difference Δ between the average temperature of the inner region and the average temperature of the outer region was 1.0°C. In Example 4, an inner-hot state was achieved in which the average temperature of the inner region was higher than the average temperature of the outer region.

[0048] [Example 5] The ceramic heater 100 of Example 5 is the same as the ceramic heater 100 of Example 1, except that the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 is 2.4 μm, and the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 is 0.4 μm. In Example 5, the ratio Ra1 / Ra2 of the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 to the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 was 6.

[0049] A ceramic heater 100 of this shape was installed in a process chamber, and a silicon wafer for temperature evaluation, similar to that in Example 1, was placed on the ceramic heater 100. The temperature of the ceramic heater 100 was then evaluated using the same procedure as in Example 1. In Example 5, the gas flow rate of helium gas flowing through the first gas channel 164 was 2.1 sccm. The average temperature of the inner region was 500°C, and the average temperature of the outer region was 496.5°C. The temperature difference Δ between the average temperature of the inner region and the average temperature of the outer region was 3.5°C. In Example 5, an inner-hot state was achieved in which the average temperature of the inner region was higher than the average temperature of the outer region.

[0050] [Example 6] The ceramic heater 100 of Example 6 is the same as the ceramic heater 100 of Example 1, except that the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 is 0.1 μm, and the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 is 0.2 μm. In Example 6, the ratio Ra1 / Ra2 of the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 to the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 was 0.5.

[0051] A ceramic heater 100 of this shape was installed in a process chamber, and a silicon wafer for temperature evaluation, similar to that in Example 1, was placed on the ceramic heater 100. The temperature of the ceramic heater 100 was then evaluated using the same procedure as in Example 1. In Example 6, the gas flow rate of helium gas flowing through the first gas channel 164 was less than 0.1 sccm. The average temperature of the inner region was 500°C, and the average temperature of the outer region was 502.0°C. The temperature difference Δ between the average temperature of the inner region and the average temperature of the outer region was 2.0°C. In Example 6, an outer-hot state was achieved in which the average temperature of the outer region was higher than the average temperature of the inner region.

[0052] [Example 7] The ceramic heater 100 of Example 7 is the same as the ceramic heater 100 of Example 1, except that the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 is 0.4 μm, and the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 is 1.6 μm. In Example 7, the ratio Ra1 / Ra2 of the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 to the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 was 0.25.

[0053] A ceramic heater 100 of this shape was installed in a process chamber, and a silicon wafer for temperature evaluation, similar to that in Example 1, was placed on the ceramic heater 100. The temperature of the ceramic heater 100 was then evaluated using the same procedure as in Example 1. In Example 7, the gas flow rate of helium gas flowing through the first gas channel 164 was less than 0.1 sccm. The average temperature of the inner region was 500°C, and the average temperature of the outer region was 503.0°C. The temperature difference Δ between the average temperature of the inner region and the average temperature of the outer region was 3.0°C. In Example 7, an outer-hot state was achieved in which the average temperature of the outer region was higher than the average temperature of the inner region.

[0054] [Example 8] The ceramic heater 100 of Example 8 is the same as the ceramic heater 100 of Example 1, except that the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 is 0.05 μm, and the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 is 1.6 μm. In Example 8, the ratio Ra1 / Ra2 of the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 to the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 was 0.03.

[0055] A ceramic heater 100 of this shape was installed in a process chamber, and a silicon wafer for temperature evaluation, similar to that in Example 1, was placed on the ceramic heater 100. The temperature of the ceramic heater 100 was then evaluated using the same procedure as in Example 1. In Example 8, the gas flow rate of helium gas flowing through the first gas channel 164 was less than 0.1 sccm. The average temperature of the inner region was 500°C, and the average temperature of the outer region was 505.0°C. The temperature difference Δ between the average temperature of the inner region and the average temperature of the outer region was 5.0°C. In Example 8, an outer-hot state was achieved in which the average temperature of the outer region was higher than the average temperature of the inner region.

[0056] [Example 9] The ceramic heater 100 of Example 9 is the same as the ceramic heater 100 of Example 1, except that the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 is 1.2 μm, and the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 is 1.6 μm. In Example 9, the ratio Ra1 / Ra2 of the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 to the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 was 0.75.

[0057] A ceramic heater 100 of this shape was installed in a process chamber, and a silicon wafer for temperature evaluation, similar to that in Example 1, was placed on the ceramic heater 100. The temperature of the ceramic heater 100 was then evaluated using the same procedure as in Example 1. In Example 9, the gas flow rate of helium gas flowing through the first gas channel 164 was 0.6 sccm. The average temperature of the inner region was 500°C, and the average temperature of the outer region was 501.0°C. The temperature difference Δ between the average temperature of the inner region and the average temperature of the outer region was 1.0°C. In Example 9, an outer-hot state was achieved in which the average temperature of the outer region was higher than the average temperature of the inner region.

[0058] [Comparative Example] In the comparative example ceramic heater, the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 is 0.4 μm, and the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 is 0.4 μm. Thus, in the comparative example, unlike Examples 1 to 9, the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 and the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 are the same. In the comparative example, the ratio Ra1 / Ra2 of the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 to the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156 is 1.

[0059] A ceramic heater of this shape was installed in a process chamber, and a silicon wafer for temperature evaluation, similar to that in Example 1, was placed on the comparative ceramic heater. The temperature of the comparative ceramic heater was then evaluated using the same procedure as in Example 1. In the comparative example, the gas flow rate of helium gas flowing through the first gas channel 164 was less than 0.1 sccm. The average temperature of the inner region was 500°C, and the average temperature of the outer region was also 500°C. The temperature difference Δ between the average temperature of the inner region and the average temperature of the outer region was 0°C. In the comparative example, the average temperature of the inner region and the average temperature of the outer region were the same, and it was not possible to achieve an inner-hot or outer-hot state.

[0060] <Effects of the Embodiment> In the above embodiments and Examples 1 to 9, the ceramic heater 100 comprises a disc-shaped ceramic substrate 110 and a heater electrode 122 embedded in the ceramic substrate 110. The outer periphery of the ceramic substrate 110 is provided with an annular projection 152 that protrudes above the upper surface 111 of the ceramic substrate 110, and the inside of the annular projection 152 of the ceramic substrate 110 is provided with a plurality of projections 156 that protrude above the upper surface 111 of the ceramic substrate 110. In the comparative example, the centerline average roughness Ra1 of the upper surface 152a of the annular projection 152 and the centerline average roughness Ra2 of the upper surface 156a of the plurality of projections 156 were the same. Therefore, it is considered that there was no difference in the adhesion between the wafer 10 and the annular projection 152 and the adhesion between the wafer 10 and the plurality of projections 156. As a result, in the comparative example, there was no temperature difference between the inner and outer regions of the wafer 10, and it was not possible to achieve a so-called outer-hot or inner-hot state. In contrast, in the above embodiments and examples 1 to 9, the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 and the centerline average roughness Ra2 of the upper surface 156a of the multiple protrusions 156 are different from each other. As a result, it is thought that the adhesion between the wafer 10 and the annular protrusion 152 and the adhesion between the wafer 10 and the multiple protrusions 156 were different. As a result, a temperature difference could be created between the inner and outer regions of the wafer 10, making it possible to achieve a so-called outer-hot or inner-hot state.

[0061] Comparing Examples 1-5 with Examples 6-9, by making the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 greater than the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156, the average temperature of the inner region of the wafer 10 can be made higher than the average temperature of the outer region of the wafer 10, thus achieving a so-called inner-hot state. Furthermore, by making the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 smaller than the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156, the average temperature of the outer region of the wafer 10 can be made higher than the average temperature of the inner region of the wafer 10, thus achieving a so-called outer-hot state.

[0062] As shown in Examples 1 to 5, the ratio Ra1 / Ra2 of the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 to the centerline average roughness Ra2 of the upper surface 156a of the multiple protrusions 156 can be set to 1.3 ≤ Ra1 / Ra2 ≤ 32. In this case, when the average temperature of the inner region of the wafer 10 is set to 500.0°C, the average temperature of the outer region can be set to 495.0°C to 499.0°C, and an inner-hot state can be reliably achieved.

[0063] As shown in Examples 6 to 9, the ratio Ra1 / Ra2 of the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 to the centerline average roughness Ra2 of the upper surface 156a of the multiple protrusions 156 can be set to 0.03 ≤ Ra1 / Ra2 ≤ 0.8. In this case, when the average temperature of the inner region of the wafer 10 is set to 500.0°C, the average temperature of the outer region can be set to 501.0°C to 505.0°C, and an outer-hot state can be reliably achieved.

[0064] In the above embodiments and examples 1 to 9, the shaft 130 is bonded to the lower surface 113 of the ceramic substrate 110. This improves the heat insulation performance of the ceramic heater 100.

[0065] Another effect of the present invention is the suppression of residual adsorption of the electrostatically adsorbed wafer 10 after electrostatic adsorption. Generally, the area of ​​the upper surface 152a of the annular protrusion 152 is relatively larger than the area of ​​the upper surfaces 156a of the multiple protrusions 156, and residual adsorption occurs on the annular protrusion 152. By increasing the centerline average roughness of the upper surface 152a of the annular protrusion 152, residual adsorption can be suppressed. In the above examples 1 to 5, the centerline average roughness Ra1 of the upper surface 152a of the annular protrusion 152 is larger than the centerline average roughness Ra2 of the upper surfaces 156a of the multiple protrusions 156. Therefore, it is possible to exert both a temperature distribution adjustment effect and a substrate residual adsorption force suppression effect.

[0066] <Change form> The embodiments described above are merely illustrative and can be modified as appropriate. For example, the shape and dimensions of the ceramic substrate 110 and the shaft 130 are not limited to those of the embodiments described above and can be modified as appropriate. The height, width, and other dimensions of the annular projection 152, and the cross-sectional shape of the upper surface 152a of the annular projection 152 can be modified as appropriate.

[0067] The height of the multiple protrusions 156 and the shape of the upper surface 156a can be changed as appropriate. For example, the shape of the upper surface 156a of the multiple protrusions 156 does not necessarily have to be circular and can be any shape. In that case, however, it is preferable that it has an area equivalent to that of a circle with a diameter of 0.1 mm to 5 mm. Furthermore, although the multiple protrusions 156 were arranged to be distributed in a concentric pattern in the above description, the present invention is not limited to such an embodiment. For example, the multiple protrusions 156 may be arranged continuously in a grid pattern so as to be distributed at the vertices of an equilateral triangle or a regular square, or the multiple protrusions 156 may be arranged to be distributed at random positions. In that case as well, it is preferable that the spacing between the multiple protrusions 156 is in the range of 1.5 mm to 30 mm.

[0068] In the above embodiment, molybdenum, tungsten, or an alloy containing molybdenum and / or tungsten was used as the heater electrode 122, but the present invention is not limited to such embodiments. For example, metals or alloys other than molybdenum and tungsten can also be used. Furthermore, the electrode 120 included the heater electrode 122 as a heating element. However, the electrode 120 does not necessarily have to include the heater electrode 122 as a heating element; for example, it may include a high-frequency electrode as a heating element.

[0069] In the above embodiment, the ceramic heater 100 was equipped with a heater electrode 122 embedded in the ceramic substrate 110. However, the present invention is not limited to such an embodiment, and the heater electrode 122 does not have to be embedded in the ceramic substrate 110 of the ceramic heater 100. For example, the heater electrode 122 or the high-frequency electrode may be attached to the back surface 113 of the ceramic substrate 110.

[0070] In the above embodiment, the shaft 130 was provided with large-diameter sections 132 and 133, but the present invention is not limited to such an embodiment, and the shaft 130 does not necessarily have to be provided with large-diameter sections 132 and 133. Also, a second gas passage 168 extending in the vertical direction 5 is not required to be formed in the cylindrical section 131 of the shaft 130. For example, instead of the second gas passage 168, a separate gas pipe can be provided in the hollow region of the cylindrical section 131 (the region where the power supply line 140 is provided).

[0071] Although embodiments and modified versions of the invention have been described above, the technical scope of the present invention is not limited to the scope described above. It will be obvious to those skilled in the art that various modifications or improvements can be made to the above embodiments. It is also clear from the claims that such modified or improved forms may be included in the technical scope of the present invention.

[0072] The order in which each process in the manufacturing method shown in the specification and drawings is executed is not specifically defined, and unless the output of a previous process is used in a later process, the processes can be executed in any order. Even if phrases such as "first," and "next," are used for convenience, this does not mean that the processes must be performed in that order. [Explanation of Symbols]

[0073] 100 Substrate holding member 110 Ceramic substrate 120 electrodes 130 shaft 140 Feed line 152 Annular protrusion 156 Multiple protrusions

Claims

1. A disc-shaped ceramic substrate having an upper surface and a lower surface that is opposite to the upper surface in the vertical direction, The device comprises a heating element embedded in the ceramic substrate or positioned on the lower surface of the ceramic substrate, The aforementioned ceramic substrate is An annular protrusion is arranged on the outer periphery of the ceramic substrate and protrudes above the upper surface of the ceramic substrate, The ceramic substrate comprises a plurality of protrusions arranged inside the annular protrusion and projecting upward above the upper surface of the ceramic substrate, The average centerline roughness Ra1 of the upper surface of the annular protrusion and the average centerline roughness Ra2 of the upper surfaces of the plurality of protrusions are different from each other. The ratio Ra1 / Ra2 of the centerline average roughness Ra1 of the upper surface of the annular protrusion and the centerline average roughness Ra2 of the upper surfaces of the plurality of protrusions is, 1.3 ≤ Ra1 / Ra2 ≤ 32 A ceramic heater characterized by satisfying the following conditions.

2. Furthermore, the ceramic heater according to claim 1, further comprising a cylindrical shaft joined to the lower surface of the ceramic substrate.

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