JP7729764B2 - Substrate holding member - Google Patents

Description

The present invention relates to a substrate holding member for holding a substrate such as a silicon wafer.

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, multiple protrusions (projections) that protrude from the upper surface of the base body to support the substrate, and an annular protrusion (seal ring) that protrudes annularly from the upper surface of the outer periphery of the base body to support the substrate.

JP 2009-111243 A

In the electrostatic chuck described in Patent Document 1, the height of 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 can lead to the risk of particles adhering to the substrate due to contact between the substrate and the seal ring.

The present invention was made in consideration of these 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.

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
an annular protrusion disposed on the outer periphery of the ceramic base and protruding upward from the upper surface of the ceramic base;
a plurality of first protrusions disposed on an upper surface of the annular protrusion and protruding upward from the upper surface of the annular protrusion;
a plurality of second protrusions disposed inside the annular protrusion on the upper surface of the ceramic base and protruding upward from the upper surface of the ceramic base;
a first gas flow path having an opening disposed inside the annular protrusion on the upper surface of the ceramic base;
a heating element embedded in the ceramic base or disposed on the lower surface of the ceramic base ,
a length of the annular protrusion from the upper surface of the ceramic base in the vertical direction is 135 μm or more and 2 mm or less;
The substrate holding member is characterized in that the length of the plurality of first protrusions in the vertical direction from the upper surface of the annular protrusion is greater than 1 μm.

In the above aspect, 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 for adjustment of the flow rate and/or pressure of the gas flowing through the first gas flow path. 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 substrate using a pressure difference. Furthermore, the annular convex portion and the first convex portion are provided on the outer periphery of the ceramic substrate and abut against the outer periphery of the substrate when holding the substrate. This prevents deformation of the outer periphery of the substrate when adsorbed toward the upper surface of the ceramic substrate. Furthermore, because multiple first convex portions are formed on the upper surface of the annular convex portion, when the substrate is adsorbed toward the upper surface of the ceramic substrate, the contact area with the lower surface of the substrate can be reduced compared to when no first convex portions are provided on the upper surface of the annular convex portion. Furthermore, because the height of the first convex portions is greater than 1 μm, even if the outer periphery of the substrate deforms, there is no risk of the substrate abutting against the upper surface of the annular convex portion. This prevents particles generated by contact between the substrate and the upper surface of the annular protrusion from adhering to the substrate. At the same time, if the substrate holding member is equipped with an electrode as a heating element, it can prevent heat spots that occur on the substrate corresponding to the position of the annular protrusion when the annular protrusion comes into contact with the substrate and transfers heat.

FIG. 1 is a perspective view of a substrate holding member 100. FIG. FIG. 2 is a schematic explanatory diagram of the substrate holding member 100. As shown in FIG. FIG. 3 is a schematic diagram illustrating the electrode 120. FIG. 4 is a schematic explanatory diagram of a substrate holding member 100 in which the height position of the first convex portion 154 is higher than the height position of the second convex portion 156. 5(a) to 5(d) are diagrams showing the flow of a method for manufacturing the ceramic base 110. 6(a) to 6(d) are diagrams showing the flow of another method for manufacturing the ceramic substrate 110. FIG. 7 is a view equivalent to FIG. 2 of a substrate holding member 100A of Comparative Example 1. In FIG. FIG. 8 is a table summarizing the results of Examples 1 to 4 and Comparative Examples 1 and 2.

<Substrate holding member 100>
A substrate holding member 100 according to an embodiment of the present invention will be described with reference to Figures 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 Figure 1). As shown in Figure 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.

The ceramic substrate 110 is a circular, plate-like 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 clarity. As shown in FIG. 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 second protrusions 156. Note that in FIG. 1, the number of second protrusions 156 is reduced compared to FIG. 2 for clarity. Also, as shown in FIG. 2, a first gas flow path 164, described below, is formed inside the ceramic substrate 110. The ceramic substrate 110 can be formed, for example, from a sintered ceramic body such as aluminum nitride, alumina, or silicon nitride.

As shown in Figures 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 on the upper surface 152a of the annular protrusion 152. Each of the plurality of first protrusions 154 has a cylindrical shape. The plurality of first protrusions 154 are arranged circumferentially at equal intervals on the upper surface 152a of the annular protrusion 152. The position and/or number of the first protrusions 154 on the upper surface 152a of the annular protrusion 152 are appropriately determined depending on the application, action, function, etc. As shown in Figure 2, when the wafer 10 is placed on the ceramic substrate 110, the upper surface 154a of the first protrusions 154 abuts the lower surface of the wafer 10. That is, the annular convex portion 152 and the first convex portion 154 are positioned so as to overlap the wafer 10 in the vertical direction 5 when the wafer 10 is placed on the ceramic base 110. A plurality of second convex portions 156 are provided inside the annular convex portion 152 on the upper surface 111 of the ceramic base 110. Each of the second convex portions 156 has a cylindrical shape. One of the second convex portions 156 is positioned approximately in the center of the upper surface 111. The remaining second convex portions 156 are arranged on the circumference of four equally spaced concentric circles. The second convex portions 156 are also arranged at equal intervals on the circumference of each concentric circle. The position and/or number of the second convex portions 156 are appropriately determined depending on the application, action, and function.

The sum (L1 + L2) of the height L1 of the annular protrusion 152 (the length in the vertical direction 5 from the upper surface 111) and the height L2 of the first protrusion 154 (the length in the vertical direction 5 from the upper surface 152a of the annular protrusion 152) can be in the range of 5 μm to 2 mm. Similarly, the height L3 of the multiple second protrusions 156 can be in the range of 5 μm to 2 mm. As shown in FIG. 2, the sum (L1 + L2) of the height L1 of the annular protrusion 152 and the height L2 of the first protrusion 154 can be the same as the height L3 of the multiple second protrusions 156. As shown in FIG. 4, the sum (L1 + L2) of the height L1 of the annular protrusion 152 and the height L2 of the first protrusion 154 can be greater than the height L3 of the multiple second protrusions 156.

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

The upper surfaces 154a of the multiple first protrusions 154 are preferably circular and have a diameter of 0.1 mm to 5 mm. Furthermore, the spacing between each of the multiple first protrusions 154 can be in the range of 1.5 mm to 30 mm. Similarly, the upper surfaces 156a of the multiple second protrusions 156 are preferably circular and have a diameter of 0.1 mm to 5 mm. Furthermore, the spacing between each of the multiple second protrusions 156 can be in the range of 1.5 mm to 30 mm.

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 located 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 an opening 164a, and is formed inside the ceramic substrate 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.

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 substrate 110 and the lower surface of the wafer 10. For example, a heat transfer gas for heat transfer between the wafer 10 and the ceramic substrate 110 can be supplied. Examples of heat transfer gas that can be used 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 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 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 substrate 110.

As shown in Figures 1 and 2, an electrode 120 (an example of a heating element of the present invention) is embedded within the ceramic substrate 110. As shown in Figure 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 298 mm, and the electrode 120 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 1) is provided approximately in 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), or an alloy containing molybdenum and/or tungsten. The purity of the tungsten or 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, and 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 to this and can be modified as appropriate. In addition to or instead of the electrode 120, at least one of an electrostatic chuck electrode for attracting the wafer 10 to the upper surface 111 by Coulomb force and a plasma electrode for generating plasma above the ceramic substrate 110 may be embedded inside the ceramic substrate 110.

As shown in Figures 1 and 2, a shaft 130 is connected to the lower surface 113 of the ceramic base material 110. The shaft 130 has a hollow, approximately cylindrical cylindrical portion 131 and a large-diameter portion 132 (see Figure 1) located 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 Figure 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.

The upper surface of the cylindrical portion 131 is fixed to the lower surface 113 of the ceramic substrate 110. Like the ceramic substrate 110, the shaft 130 may be formed from a sintered ceramic material such as alumina, aluminum nitride, or silicon nitride. Alternatively, to improve thermal insulation, the shaft 130 may be formed from a material with a lower thermal conductivity than the ceramic substrate 110. The upper surface of the cylindrical portion 131 may also be provided with an enlarged diameter portion similar to the large diameter portion 132 provided below the cylindrical portion 131.

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 it (the area inside the inner diameter). A power supply line 140 for supplying power to the electrode 120 is disposed 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) disposed 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.

Furthermore, as shown in FIG. 2, a second gas flow path 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 flow path 168 is connected to the lower end of the first gas flow path 164.

Next, a method for manufacturing the substrate holding member 100 will be described. Below, we will explain an example in which the ceramic base 110 and shaft 130 are made of aluminum nitride.

First, a method for manufacturing the ceramic substrate 110 will be described. As shown in FIG. 5( 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., Y ₂ O ₃ ). Next, as shown in FIG. 5( b), an electrode 120 cut into 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.

As shown in FIG. 5(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 using a punch 502. Next, as shown in FIG. 5(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 higher. Next, a blind hole is drilled down to the electrode 120 to form the terminal 121. 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 substrate 110 with the first gas flow path 164 formed therein.

The ceramic substrate 110 can also be manufactured by the following method. As shown in Figure 6(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 Figure 6(b), the compact 510 is degreased to remove the binder.

As shown in FIG. 6(c), a recess 511 for embedding an 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. Note that the recess 511 may be formed in the compact 510 beforehand. Next, as shown in FIG. 6(d), the stacked compacts 510, sandwiching the electrode 120 between them, are fired in a pressed state to produce a fired body. The pressure applied during firing is preferably 1 MPa or more. Firing is also preferably performed at a temperature of 1800°C or higher. The steps after producing the fired body are the same as those described above, so a description thereof will be omitted.

The upper surface 111 of the ceramic substrate 110 thus formed is ground and then subjected to lapping (mirror polishing). Furthermore, the upper surface 111 is sandblasted to form a plurality of second protrusions 156 and annular protrusions 152 on the upper surface 111, and a plurality of first protrusions 154 on the upper surface 152a of the annular protrusions 152. Sandblasting is a suitable method for forming the plurality of second protrusions 156, annular protrusions 152, and a plurality of first protrusions 154, although other processing methods can also be used.

Next, a method for manufacturing the shaft 130 and a method for bonding the shaft 130 to the ceramic substrate 110 will be described. First, aluminum nitride granulated powder P containing a few wt % of binder is molded under hydrostatic pressure (approximately 1 MPa) and processed 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 serve as 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. The sintered body is then 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 substrate 110 can be fixed by diffusion bonding at 1600°C or higher and under a uniaxial pressure of 1 MPa or higher. In this case, the surface roughness Ra of the lower surface 113 of the ceramic substrate 110 is preferably 0.4 μm or less, and more preferably 0.2 μm or less. The upper surface of the cylindrical portion 131 and the lower surface 113 of the ceramic substrate 110 can also be bonded using a bonding agent. For example, an AlN bonding material paste containing 10 wt % Y ₂ O ₃ can be used as the bonding agent. For example, the AlN bonding material paste can be applied to the interface between the upper surface of the cylindrical portion 131 and the lower surface 113 of the ceramic substrate 110 to a thickness of 15 μm, and then heated at 1700° C. for 1 hour while applying a force of 5 kPa in a direction perpendicular to the upper surface 111 (the longitudinal direction 6 of the shaft 130). Alternatively, the upper surface of the cylindrical portion 131 and the lower surface 113 of the ceramic substrate 110 can be fixed together by screwing, brazing, or the like.

The present invention will be further explained below using examples and comparative examples. However, the present invention is not limited to the examples and comparative examples described below.

[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 such an electrode 120 embedded therein. An annular convex portion 152 having an inner diameter of 292 mm, an outer diameter of 298 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 convex portions 154 having a diameter of 2 mm and a height of 3 μm from the upper surface 152 a of the annular convex portion 152 were formed on the upper surface 152 a of the annular convex portion 152. Furthermore, a plurality of cylindrical second convex portions 156 having a diameter of 2 mm and a height of 150 μm from the upper surface 111 were formed on the upper surface 111 of the ceramic substrate 110. As described above, in the substrate holding member 100 of Example 1, the height L1 of the annular convex portion 152 is 147 μm, the height L2 of the first convex portion 154 is 3 μm, and the height L3 of the multiple second convex portions 156 is 150 μm. In other words, the sum (L1 + L2) of the height L1 of the annular convex portion 152 and the height L2 of the first convex portion 154 is the same as the height L3 of the multiple second convex portions 156. In other words, the vertical position (height position) of the upper surface 154a of the first convex portion 154 is the same as the vertical position (height position) of 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.

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.

The substrate holding member 100 having this 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 adjusted to a pressure of 6,650 Pa (50 Torr) through the first gas flow path 164.

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 argon gas (heat transfer gas) were then adjusted to the above pressure. The temperature distribution in a 298 mm diameter area of the silicon wafer for temperature evaluation was then measured using an infrared camera. The temperature distribution was measured the first time when the argon gas pressure adjustment in the first gas flow path 164 began (the first measurement) and 10 minutes later (the 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. A blackbody film is a film with an emissivity (radiation rate) of 90% or higher. For example, it can be formed by coating a blackbody paint primarily made of carbon nanotubes. In Example 1, the flow rate of argon gas flowing through the first gas flow path 164 was 36 sccm. The average temperature distribution in the first temperature measurement was 377.1°C, and the average temperature distribution in the second temperature measurement was 378.1°C. When the temperature distribution of the temperature evaluation silicon wafer was evaluated, no heat spot regions were found along the annular protrusion 152.

[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 convex portion 152 is 145 μm and the height L2 of the first convex portion 154 is 5 μm. In the substrate holding member 100 of Example 2, the sum (L1 + L2) of the height L1 of the annular convex portion 152 and the height L2 of the first convex portion 154 is the same as the height L3 of the multiple second convex portions 156. 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 97 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 378.7°C. When the temperature distribution of the silicon wafer used for temperature evaluation was evaluated, no heat spot regions were observed along the annular convex portion 152.

[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 convex portion 152 is 140 μm and the height L2 of the first convex portion 154 is 10 μm. In the substrate holding member 100 of Example 3, the sum (L1 + L2) of the height L1 of the annular convex portion 152 and the height L2 of the first convex portion 154 is the same as the height L3 of the multiple second convex portions 156. 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 361 sccm. 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 378.9°C. When the temperature distribution of the temperature evaluation silicon wafer was evaluated, no heat spot regions were found along the annular convex portion 152.

[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 convex portion 152 is 148.5 μm and the height L2 of the first convex portion 154 is 1.5 μm. In the substrate holding member 100 of Example 4, the sum (L1 + L2) of the height L1 of the annular convex portion 152 and the height L2 of the first convex portion 154 is the same as the height L3 of the multiple second convex portions 156. The argon gas was adjusted to the same pressure as in Example 1. In Example 4, the gas flow rate of the argon gas flowing into the first gas flow path 164 was 9 sccm. 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 378.0°C. When the temperature distribution of the temperature evaluation silicon wafer was evaluated, no heat spot regions were observed along the annular convex portion 152.

[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 convex portion 152 is 135 μm and the height L2 of the first convex portion 154 is 15 μm. In the substrate holding member 100 of Example 4, the sum (L1 + L2) of the height L1 of the annular convex portion 152 and the height L2 of the first convex portion 154 is the same as the height L3 of the multiple second convex portions 156. 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 790 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 378.9°C. When the temperature distribution of the silicon wafer used for temperature evaluation was evaluated, no heat spot regions were observed along the annular convex portion 152.

[Comparative Example 1]
As shown in FIG. 8 , 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 convex portion 152 is 150 μm and the first convex portion 154 is not provided on the upper surface 152a of the annular convex portion 152. In the substrate holding member 100A of Comparative Example 1, the height L1 of the annular convex portion 152 is the same as the height L3 of the multiple second convex portions 156. In Comparative Example 1, argon gas was supplied as a process gas into the process chamber at a pressure of 26,600 Pa (200 Torr). Furthermore, the pressure of the argon gas was adjusted to 6,650 Pa (50 Torr) through the first gas flow path 164. In Comparative Example 1, the average temperature distribution in the first temperature measurement was 376.5°C, and the average temperature distribution in the second temperature measurement was 381.5°C. The flow rate of the argon gas flowing through the first gas flow passage 164 was 0.8 sccm. When the temperature distribution of the silicon wafer for temperature evaluation was evaluated, a heat spot region was found to have occurred along the annular convex portion 152.

[Comparative Example 2]
The substrate holding member 100A of Comparative Example 2 differs from the substrate holding member 100 of Example 1 in that the height L1 of the annular convex portion 152 is 149 μm and the height L2 of the first convex portion 154 provided on the upper surface 152a of the annular convex portion 152 is 1 μm. In the substrate holding member 100A of Comparative Example 2, the sum (L1 + L2) of the height L1 of the annular convex portion 152 and the height L2 of the first convex portion 154 is the same as the height L3 of the multiple second convex portions 156. In Comparative Example 2, argon gas was introduced into the process chamber as a process gas at a pressure of 26,600 Pa (200 Torr). Furthermore, the argon gas was supplied through the first gas flow path 164 at a pressure of 6,650 Pa (50 Torr). In Comparative Example 2, the average temperature distribution in the first temperature measurement was 376.0°C, and the average temperature distribution in the second temperature measurement was 381.4°C. The flow rate of the argon gas flowing through the first gas flow passage 164 was 4.3 sccm. When the temperature distribution of the silicon wafer for temperature evaluation was evaluated, a heat spot region was found to have occurred along the annular convex portion 152.

<Summary of Examples and Comparative Examples>
FIG. 8 shows a table summarizing the results of Examples 1 to 5 and Comparative Examples 1 and 2 described above.

As shown in Figures 2 and 4, 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 5, the pressure in the gap surrounded by the upper surface 111 of the substrate holding member 110, the annular protrusion 152, and the wafer 10 (6,650 Pa in Examples 1 to 5) can be set lower than the process gas pressure in the process chamber (26,600 Pa in Examples 1 to 5). Because the pressure in the gap surrounded by the upper surface 111 of the substrate holding member 110, the annular protrusion 152, and the wafer 10 can be set lower than the process gas pressure in the process chamber, the differential pressure allows the wafer 10 to be attracted toward the upper surface 111 of the ceramic base 110, thereby holding the wafer 10.

In the substrate holding member 100 of Examples 1 to 5, multiple first protrusions 154 are formed on the upper surface 152a of the annular protrusion 152. As described above, when the wafer 10 is attracted toward the upper surface 111 of the substrate holding member 100, the entire upper surface 152a of the annular protrusion 152 does not abut the underside of the wafer 10, but rather the upper surfaces 154a of the first protrusions 154 come into contact with the underside of the wafer 10. Therefore, the contact area with the underside of the wafer 10 can be reduced compared to when the first protrusions 154 are not provided on the upper surface 152a of the annular protrusion 152. This makes it possible to prevent heat spot regions from occurring on the wafer 10 along the annular protrusions 152.

In contrast, as shown in FIG. 7 , in the substrate holding member 100A of Comparative Example 1, the first convex portion 154 is not provided on the upper surface 152a of the annular convex portion 152. 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 convex portion 152 abuts against the lower surface of the wafer 10. Note that the lower surface of the wafer 10 also abuts against the upper surfaces 156a of the multiple second convex portions 156, but the upper surfaces 156a of the multiple second convex portions 156 are dispersed at a distance from each other. Therefore, heat transferred from the upper surfaces 156a of the multiple second convex portions 156 to the wafer 10 does not concentrate locally. In contrast, the upper surface 152a of the annular convex portion 152 is a continuous circular surface. Therefore, when the entire upper surface 152a of the annular convex portion 152 abuts against the lower surface of the wafer 10, heat transferred from the upper surface 152a of the annular convex portion 152 to the wafer 10 may locally concentrate in the annular region abutting the upper surface 152a of the annular convex portion 152. Therefore, in Comparative Example 1, when the temperature distribution of the temperature-evaluation silicon wafer was evaluated, it is believed that a heat spot region occurred along the annular convex portion 152. Furthermore, even when the first convex portion 154 is provided on the upper surface 152a of the annular convex portion 152, if the height of the first convex portion 154 is 1 μm or less, as in Comparative Example 2, the distance between the upper surface 152a of the annular convex portion 152 and the wafer 10 is 1 μm or less. Even in such a case, when the temperature distribution of the temperature-evaluation silicon wafer was evaluated, it was found that a heat spot region occurred along the annular convex portion 152.

Comparing Examples 1 to 5, it was found that the flow rate of gas flowing through the first gas flow path 164 increases as the height of the first convex portion 154 increases. This is because the gap between the upper surface 152a of the annular convex portion 152 and the wafer 10 increases as the height of the first convex portion 154 increases. As the gap between the upper surface 152a of the annular convex portion 152 and the wafer 10 increases, the movement of gas between the inside and outside of the gap surrounded by the upper surface 111 of the substrate holding member 110, the annular convex portion 152, and the wafer 10 increases. Therefore, the gas flow rate increases to maintain the pressure within the gap surrounded by the upper surface 111 of the substrate holding member 110, the annular convex portion 152, and the wafer 10. From the perspective of suppressing the gas flow rate, it was found that it is preferable to set the height of the first convex portion 154 to 10 μm or less, as in Examples 1 to 4. Furthermore, it was found that it is preferable to set the height of the first convex portion 154 to 5 μm or less in order to suppress the gas flow rate.

<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 disposed on the outer periphery of the upper surface 111 and protruding upward from the upper surface 111, a plurality of first convex portions 154 disposed on the upper surface 152a of the annular convex portion 152 and protruding upward from the upper surface 152a, and a plurality of second convex portions 156 disposed inside the annular convex portion 152 and protruding upward from the upper surface 111. Furthermore, a first gas flow path 164 having an opening 164a opening to the inside of the annular convex portion 152 is formed inside the ceramic base 110. The height of the first convex portion 154 from the upper surface 152a of the annular convex portion 152 (length in the vertical direction 5) is greater than 1 μm.

By individually adjusting 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 substrate holding member 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, this pressure difference allows the wafer 10 to be adsorbed toward the upper surface 111 of the ceramic substrate 110, thereby holding the wafer 10. The annular convex portion 152 and the first convex portion 154 are provided on the outer periphery of the ceramic substrate 110, and abut against the outer periphery of the wafer 10 when holding the wafer 10. This prevents the outer periphery of the wafer 10 from deforming when the wafer 10 is adsorbed toward the upper surface 111 of the ceramic substrate 110. Furthermore, because multiple first protrusions 154 are formed on the upper surface 152a of the annular protrusion 152, when the wafer 10 is attracted toward the upper surface 111 of the substrate holding member 100, the contact area with the lower surface of the wafer 10 can be reduced compared to when the first protrusions 154 are not provided on the upper surface 152a of the annular protrusion 152. Furthermore, because the height of the first protrusions 154 is greater than 1 μm, even if the outer periphery of the wafer 10 is deformed, there is no risk of the wafer 10 coming into contact with the upper surface 152a of the annular protrusion 152. This prevents particles generated by contact between the wafer 10 and the upper surface 152a of the annular protrusion 152 from adhering to the wafer 10. Furthermore, because 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 substrate holding member 110, the annular protrusion 152, and the wafer 10 from outside the annular protrusion 152.

In the above embodiment and Examples 1 to 5, the substrate holding member 100 is a ceramic heater equipped with an electrode 120 as a heating element. Furthermore, as described above, multiple first protrusions 154 are formed on the upper surface 152a of the annular protrusion 152. Therefore, when the wafer 10 is attracted toward the upper surface 111 of the substrate holding member 100, the entire upper surface 152a of the annular protrusion 152 does not abut against the lower surface of the wafer 10, but rather the upper surfaces 154a of the first protrusions 154 contact the lower surface of the wafer 10. Furthermore, because the height of the first protrusions 154 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 the occurrence of heat spot regions along the annular protrusion 152 on the wafer 10 compared to when the first protrusion 154 is not provided on the upper surface 152a of the annular protrusion 152, or compared to when the first protrusion 154 with a height of 1 μm or less is provided on the upper surface 152a of the annular protrusion 152.

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 convex portions 154 and the height position in the vertical direction 5 of the upper surfaces 156a of the multiple second convex portions 156 are the same. In this case, when the wafer 10 is held by suction toward the upper surface 111 of the substrate holding member 100, the upper surfaces 154a of the multiple first convex portions 154 and the upper surfaces 156a of the multiple second convex portions 156 abut against the lower surface of the wafer 10. This prevents the wafer 10 from deforming, enabling the wafer 10 to be held stably.

In the above embodiment and Examples 1 to 4, the length L2 (height L2) of the multiple first protrusions 154 in the vertical direction 5 from the upper surface 152a of the annular protrusion 152 is 10 μm or less. As the height L2 of the first protrusions 154 increases, the gap between the upper surface 152a of the annular protrusion 152 and the wafer 10 increases. This increases the movement of gas between the inside and outside of the gap surrounded by the upper surface 111 of the substrate holding member 110, the annular protrusions 152, and the wafer 10. Therefore, the gas flow rate increases to maintain the pressure within the gap surrounded by the upper surface 111 of the substrate holding member 110, the annular protrusions 152, and the wafer 10. In contrast, by setting the height of the first protrusions 154 to 10 μm or less, the gas flow rate can be suppressed. Furthermore, by setting the height of the first protrusions 154 to 5 μm or less, the gas flow rate can be further suppressed.

In the above embodiments and examples, a second gas flow path 168 extending in the vertical 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.

<Modifications>
The above-described embodiment is merely illustrative and may be modified as appropriate. For example, the shapes and dimensions of the ceramic substrate 110 and the shaft 130 are not limited to those of the above-described embodiment and may be modified as appropriate. The height, width, and other dimensions, shapes, and surface roughness Ra of the upper surfaces of the annular protrusion 152 and the first protrusion 154 may be modified as appropriate. Furthermore, the height, shape, and surface roughness Ra of the upper surfaces 156a of the multiple second protrusions 156 may be modified as appropriate.

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 do not necessarily have to be circular and can be any shape. Even in this case, it is preferable that they have an area approximately equal to that of a circle with a diameter of 1 mm to 5 mm. Also, in the above explanation, the multiple second protrusions 156 are arranged so as to be distributed concentrically, but the present invention is not limited to such an embodiment. For example, the multiple second protrusions 156 may be arranged so as to be distributed in 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.

In the above embodiment, molybdenum, tungsten, or an alloy containing molybdenum and/or tungsten was 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 can also be used. Also, while the electrode 120 is a heater electrode that functions as a heat generating element, the electrode 120 does not necessarily have to be a heater electrode that functions as a heat generating element; for example, it may be an electrostatic attraction electrode or a high-frequency electrode.

In the above embodiment, the substrate holding member 100 is provided with an electrode 120, but the present invention is not limited to such an embodiment, and the substrate holding member 100 does not necessarily have to be provided with an electrode 120. Furthermore, even if the substrate holding member 100 is provided with an 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.

In the above embodiment, the substrate holding member 100 includes a shaft 130, but the present invention is not limited to such an embodiment, and the substrate holding member 100 does not necessarily include a shaft 130. Furthermore, even if the substrate holding member 100 includes a shaft 130, the second gas flow path 168 extending in the vertical 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).

The above describes the invention using embodiments and modifications thereof, but the technical scope of the present invention is not limited to the scope of the above description. It will be obvious 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.

The order in which each process in the manufacturing method shown in the specification and drawings is performed is not specifically stated, and processes can be performed in any order unless the output of a previous process is used in a subsequent process. For convenience, descriptions using "first," "next," etc. do not imply that the processes must be performed in that order.

REFERENCE SIGNS LIST 100 Substrate holding member 110 Ceramic base material 120 Electrode 130 Shaft 140 Power supply line 152 Annular convex portion 154 First convex portion 156 Multiple convex portions

Claims (4)

a ceramic substrate having an upper surface and a lower surface facing the upper surface in the vertical direction;
The ceramic substrate is
an annular protrusion disposed on the outer periphery of the ceramic base and protruding upward from the upper surface of the ceramic base;
a plurality of first protrusions disposed on an upper surface of the annular protrusion and protruding upward from the upper surface of the annular protrusion;
a plurality of second protrusions disposed inside the annular protrusion on the upper surface of the ceramic base and protruding upward from the upper surface of the ceramic base;
a first gas flow path having an opening disposed inside the annular protrusion on the upper surface of the ceramic substrate;
a heating element embedded in the ceramic base or disposed on the lower surface of the ceramic base ,
a length of the annular protrusion from the upper surface of the ceramic base in the vertical direction is 135 μm or more and 2 mm or less;
A substrate holding member, wherein the length of the plurality of first protrusions in the vertical direction from the top surface of the annular protrusion is greater than 1 μm. The substrate holding member according to claim 1 , wherein the height positions of the upper surfaces of the plurality of first protrusions in the vertical direction are the same as the height positions of the upper surfaces of the plurality of second protrusions in the vertical direction . 3. The substrate holding member according to claim 1 , wherein the length of the plurality of first protrusions in the vertical direction from the upper surface of the annular protrusion is 10 [mu]m or less . 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 .