Base plate and substrate fixing device

Abstract

This invention relates to a base plate having one surface and another surface opposite to the first surface. An electrostatic chuck can be mounted on the first surface. The base plate includes a refrigerant flow path disposed therein. The inner wall of the refrigerant flow path has an upper surface that protrudes toward the first surface in a direction intersecting the direction of refrigerant flow in a longitudinal cross-sectional view. An unevenness is formed on the upper surface.

Description

[Technical Field]

[0001] This invention relates to a base plate and a substrate fixing device. [Previous Technology]

[0002] In related technologies, film forming equipment (e.g., CVD equipment, PVD equipment, and the like) and plasma etching equipment used in the manufacture of semiconductor devices such as ICs and LSIs have platforms for accurately holding wafers in a vacuum processing chamber.

[0003] Regarding this platform, for example, a substrate holding device configured to adsorb and hold a wafer as an adsorption target by means of an electrostatic chuck mounted on a substrate is proposed. A coolant flow path for cooling the wafer is provided in the substrate, for example. For example, to improve the cooling efficiency of the wafer, non-uniformity has been provided on the side surface of the coolant flow path (e.g., see PTL 1). [List of References] [Patent Documents]

[0004] PTL 1: JP-A-2008-186856 [Summary of the Invention]

[0005] However, regarding the base plate, the cooling efficiency on the side of the device's electrostatic chuck needs to be further improved.

[0006] The present non-limiting embodiment of the present disclosure is to provide a base plate that can improve the cooling efficiency on the side of the electrostatic chuck of the device.

[0007] According to one aspect of this disclosure, a base plate is provided having one surface and another surface opposite to the first surface. An electrostatic chuck can be mounted on the first surface. The base plate includes a refrigerant flow path disposed therein. The inner wall of the refrigerant flow path has an upper surface that protrudes toward the first surface in a direction intersecting the direction of refrigerant flow in a longitudinal cross-sectional view. An unevenness is formed on the upper surface.

[0008] According to the disclosed technology, a base plate can be provided that can improve the cooling efficiency on the side of the electrostatic chuck of the device.

Implementation Method

[0010] Specific examples of the present invention will now be described with reference to the drawings. Note that in the individual drawings, components with the same configuration are indicated by the same element symbols, and repeated descriptions may be omitted.

[0011] [Overall Structure of Substrate Fixing Device 1] FIG1 is a simplified cross-sectional view illustrating the substrate fixing device according to this specific example. Referring to FIG1, the substrate fixing device 1 has the following main components: substrate 10, adhesive layer 20, and electrostatic clamp 30.

[0012] The base plate 10 has a surface 10a and another surface 10b opposite to the surface 10a, and the electrostatic chuck 30 can be mounted on the side of the surface 10a. The surface 10a and the other surface 10b of the base plate 10 are substantially parallel.

[0013] The thickness of the substrate 10 is, for example, about 20 to 40 mm. The substrate 10 is formed of, for example, aluminum or titanium, and can be used as an electrode or the like for controlling plasma. By supplying a predetermined high-frequency electrical power to the substrate 10, the energy used to cause collisions between ions and the like in the generated plasma state and the wafer adsorbed on the electrostatic chuck 30 can be controlled to effectively perform etching.

[0014] The substrate 10 has a refrigerant flow path 15. The refrigerant flow path 15 has a refrigerant inlet portion 15a at one end and a refrigerant outlet portion 15b at the other end. The refrigerant flow path 15 can be connected to a refrigerant control device (not shown) disposed outside the substrate holding device 1. The refrigerant control device (not shown) can introduce refrigerant (e.g., cooling water, GALDEN, and the like) from the refrigerant inlet portion 15a into the refrigerant flow path 15 and discharge the refrigerant from the refrigerant outlet portion 15b. By circulating the refrigerant in the refrigerant flow path 15 to cool the substrate 10, the wafer adsorbed on the electrostatic chuck 30 can be cooled.

[0015] A gas supply component configured to supply gas for cooling the wafer held and held by the electrostatic chuck 30 may be provided inside the substrate 10. The gas supply component is, for example, a hole formed in the substrate 10. By introducing, for example, an inert gas (e.g., He, Ar, etc.) from outside the substrate holding device 1 into the gas supply component, the wafer held and held by the electrostatic chuck 30 can be cooled.

[0016] The electrostatic chuck 30 is a component configured to adsorb and hold a wafer as the adsorbed object. The planar shape of the electrostatic chuck 30 is, for example, circular. The diameter of the wafer as the adsorbed object of the electrostatic chuck 30 is, for example, 8 inches, 12 inches, or 18 inches. Note that the description "viewed from above" refers to the object viewed from the normal direction of the placement surface 31a of the substrate 31, and the description "planar shape" refers to the shape of the object viewed from the normal direction of the placement surface 31a of the substrate 31.

[0017] The electrostatic clamp 30 is attached to one surface 10a of the base plate 10 by an adhesive layer 20. The adhesive layer 20 is, for example, a polysiloxane-based adhesive. The thickness of the adhesive layer 20 is, for example, about 0.1 to 1.0 mm. The adhesive layer 20 has the effect of bonding the base plate 10 and the electrostatic clamp 30 and reducing the stress caused by the difference in the coefficients of thermal expansion between the ceramic electrostatic clamp 30 and the base plate 10 made of aluminum or titanium.

[0018] The electrostatic chuck 30 has a substrate 31 and an electrostatic electrode 32. The upper surface of the substrate 31 is a placement surface 31a on which the object to be adsorbed is placed. The electrostatic chuck 30 is, for example, a Johnsen-Rahbeck type electrostatic chuck. However, the electrostatic chuck 30 may also be a Coulomb force type electrostatic chuck.

[0019] The substrate 31 is a dielectric. For example, ceramics such as alumina (Al2O3) and aluminum nitride (AlN) are used for the substrate 31. The substrate 31 may include oxides of two or more elements selected from silicon (Si), magnesium (Mg), calcium (Ca), aluminum (Al), and yttrium (Y) as additives. The thickness of the substrate 31 is, for example, about 5 to 10 mm, and the relative permittivity (kHz) of the substrate 31 is, for example, about 9 to 10.

[0020] The electrostatic electrode 32 is a thin-film electrode embedded in the substrate 31. The electrostatic electrode 32 is connected to a power source located outside the substrate holding device 1, and when a predetermined voltage is applied from the power source, an attraction force is generated between the electrostatic electrode and the wafer by electrostatic force. This allows the wafer to be adsorbed and held on the placement surface 31a of the substrate 31 of the electrostatic chuck 30. The higher the voltage applied to the electrostatic electrode 32, the stronger the adsorption and holding force. The electrostatic electrode 32 can have a unipolar or bipolar shape. Regarding the material of the electrostatic electrode 32, for example, tungsten, molybdenum, or similar materials may be used.

[0021] The substrate 31 may be provided with a heat-generating body configured to generate heat by applying voltage from outside the substrate fixing device 1 and to heat the placement surface 31a of the substrate 31 to a predetermined temperature.

[0022] [Shape of the inner wall of the refrigerant flow path 15] Figures 2A and 2B are enlarged views of the area near the refrigerant flow path, wherein Figure 2A is an enlarged view of part A of Figure 1 and Figure 2B is an enlarged view of the area near the upper surface of Figure 2A.

[0023] Referring to Figures 1 and 2A, 2B, the inner wall of the refrigerant flow path 15 has, for example, a pentagon in a longitudinal section view in a direction intersecting the refrigerant flow direction. The corners of the inner wall of the refrigerant flow path 15 may have an R-shape, a chamfered shape, or similar features. Note that the longitudinal section view in the direction intersecting the refrigerant flow direction is, for example, a longitudinal section view in a direction orthogonal to the refrigerant flow direction, as shown in Figures 1 and 2A, 2B.

[0024] In the longitudinal cross-sectional views shown in Figures 1 and 2A, 2B, the inner wall of the refrigerant flow path 15 has an upper surface 151 protruding toward one surface 10a of the base plate 10, a bottom surface 152 located closer to the other surface 10b than the upper surface 151, and a pair of side surfaces 153 and 154 connecting the two ends of the upper surface 151 and the two ends of the bottom surface 152. The width of the refrigerant flow path 15, i.e., the spacing between the side surfaces 153 and 154 facing each other, is, for example, about 1 mm to 3 mm. The maximum height of the refrigerant flow path 15 is, for example, about 2 to 3 times the width of the refrigerant flow path 15.

[0025] The upper surface 151 has a first inclined surface 151a that is connected to one end portion of one side surface 153 and inclined to approach one side surface 10a of the base plate 10 and the other side surface 154. In addition, the upper surface 151 has a second inclined surface 151b that is connected to one end portion of the other side surface 154 and inclined to approach one side surface 10a of the base plate 10 and the other side surface 153.

[0026] The second inclined surface 151b intersects with the first inclined surface 151a to form a corner 151c. The corner 151c can be interpreted as a vertex in a cross-sectional view. The pointed portion of the upper surface 151, including the intersection of the first inclined surface 151a and the second inclined surface 151b, is, for example, sharp. However, the pointed portion of the upper surface 151, including the intersection of the first inclined surface 151a and the second inclined surface 151b, does not necessarily have to be sharp like the corner 151c, and may have an R-shape or a chamfered shape in the cross-sectional view. In other words, in the cross-sectional view, the refrigerant flow path 15 may not form a clear vertex.

[0027] As shown in Figure 2B, the upper surface 151 is formed with an unevenness 15x. The height of the unevenness 15x on the upper surface 151 is, for example, 0.05 mm or more and 0.1 mm or less. Here, it is assumed that the height of the unevenness 15x corresponds to Rz as explicitly described in JIS B 0601 2013. Note that JIS B 0601 2013 defines roughness parameters and corresponds to ISO 4287 1997 / Amendment 1 2009. Rz is the maximum peak-to-valley height, which is the vertical distance between the highest and lowest peaks of the roughness profile within a specified distance.

[0028] The substrate 10 is preferably manufactured using a 3D metal printing machine. Conventionally, refrigerant flow paths are formed in the metal serving as the substrate by machining and cutting metal blocks and joining the cut metals together by welding or similar methods. However, using this method, it is difficult to form an unevenness 15x on the protruding upper surface 151 of the refrigerant flow path 15 having the shape shown in FIG. 2B. By manufacturing the substrate 10 using a 3D metal printing machine, as shown in FIG. 2B, the refrigerant flow path 15 with an unevenness 15x on the protruding upper surface 151 can be easily formed. Note that the substrate 10 manufactured by the 3D metal printing machine is a monolithically formed product, and its difference from conventional substrates is that it does not have interfaces inside.

[0029] In the base plate 10, unevenness is not formed on the bottom surface 152 and the side surfaces 153 and 154, but unevenness may be formed due to manufacturing accuracy. Even in this case, the height of the unevenness formed on the bottom surface 152 and the side surfaces 153 and 154 is generally lower than the height of the unevenness formed on the top surface 151. The height of the unevenness on the bottom surface 152 and the side surfaces 153 and 154 is, for example, 0.04 mm or less. Specifically, since it is difficult to form unevenness on the bottom surface 152, the height of the unevenness formed on the bottom surface 152 is generally lower than the height of the unevenness formed on the side surfaces 153 and 154. In other words, the roughness of the top surface 151 is greater than the roughness of the bottom surface 152 and the roughness of the side surfaces 153 and 154. Furthermore, the roughness of the side surfaces 153 and 154 is greater than the roughness of the bottom surface 152. Here, it is assumed that the roughness values ​​of each surface are compared by Ra as specified in JIS B 0601 2013. Ra is the arithmetic mean roughness value, which is the arithmetic mean of all values ​​of the roughness profile over a specified distance. Note that the bottom surface 152 and the side surfaces 153 and 154 may also be flat surfaces without unevenness.

[0030] When a virtual line segment L1 is defined as shown in FIG2A, connecting one end portion of one side surface 153 to one end portion of the other side surface 154, the figure defined by the first inclined surface 151a, the second inclined surface 151b, and the virtual line segment L1 has three interior angles. The angle of the first interior angle θ1 formed by the virtual line segment L1 and the first inclined surface 151a is preferably 20 degrees or more and 50 degrees or less, and more preferably 25 degrees or more and 45 degrees or less. Furthermore, the angle of the second interior angle θ2 formed by the virtual line segment L1 and the second inclined surface 151b is preferably 20 degrees or more and 50 degrees or less, and more preferably 25 degrees or more and 45 degrees or less. By setting the first interior angle θ1 and the second interior angle θ2 to these angles, the substrate 10 can be easily manufactured by a 3D metal printing machine. The absolute value of the difference between the first interior angle θ1 and the second interior angle θ2 is, for example, 0 degrees or more and 10 degrees or less. Furthermore, the third interior angle θ3 formed by the first inclined surface 151a and the second inclined surface 151b is, for example, an obtuse angle. By setting these angles, the substrate 10 can be easily manufactured using a 3D metal printing machine.

[0031] Note that since the first inclined surface 151a and the second inclined surface 151b have unevenness 15x, it is assumed that the shape of the first inclined surface 151a and the second inclined surface 151b is indicated by the average line used to calculate Ra as specified in JIS B 0601 2013. For example, the average line is used when calculating the angle of each interior angle. Furthermore, when the average line is a curve, it is assumed that the tangents at both ends of the virtual line segment L1 are used.

[0032] The first inclined surface 151a and the second inclined surface 151b can each be a flat surface or a curved surface. That is, when the first inclined surface 151a and the second inclined surface 151b are indicated by the average line used to calculate Ra as specified in JIS B 0601 2013, the average line can be a straight line or a curve in the cross-sectional view. When the first inclined surface 151a and the second inclined surface 151b are close to flat surfaces, it is easier to manufacture the substrate 10 by a 3D metal printing machine. When the first inclined surface 151a and the second inclined surface 151b are planar surfaces, the figure defined by the first inclined surface 151a, the second inclined surface 151b, and the virtual line segment L1 is, for example, an isosceles triangle.

[0033] As described above, in the substrate 10 of the substrate fixing device 1, the upper surface 151 (which is the surface closest to the wafer to be cooled) has a convex shape toward one of the surfaces 10a of the substrate 10, and the unevenness 15x is provided on the upper surface 151 in the inner wall of the coolant flow path 15. This increases the contact area between the inner wall of the coolant flow path 15 and the coolant on the side closest to the wafer to be cooled, thereby improving the cooling efficiency of the wafer. Furthermore, the first inclined surface 151a and the second inclined surface 151b are inclined at a predetermined angle, making it easier to manufacture the substrate 10 using a 3D metal printing machine.

[0034] Although preferred embodiments and similar examples have been described in detail, the present invention is not limited to the foregoing embodiments and similar examples, and various changes and substitutions can be made to the foregoing embodiments and similar examples without departing from the scope defined in the claims.

[0035] For example, in addition to semiconductor wafers (silicon wafers and the like), glass substrates and the like used in the manufacturing process of liquid crystal panels and the like can be used as examples of objects to be adsorbed by the substrate fixing device of the present invention.

[0036] For example, as shown in Figures 3 and 4A, 4B, the inner wall of the refrigerant flow path 15A may have a curved upper surface 151A protruding toward one of the surfaces 10a of the base plate 10. As shown in Figure 4B, the upper surface 151A is formed with an unevenness 15xA. The height of the unevenness 15xA on the upper surface 151A is, for example, 0.05 mm or more and 0.1 mm or less. [Simplified Explanation of the Diagram]

[0009] FIG1 is a simplified cross-sectional view illustrating the substrate fixing device according to this embodiment. FIG2A and 2B are enlarged views of the portion near the refrigerant flow path in FIG1. ​​FIG3 is a simplified cross-sectional view illustrating a modified embodiment of the substrate fixing device according to this embodiment. FIG4A and 4B are enlarged views of the portion near the refrigerant flow path in FIG3.

Claims

1. A base plate having a surface and another surface opposite to the surface, wherein an electrostatic chuck is mountable on the surface, the base plate comprising: a refrigerant flow path disposed therein, wherein the inner wall of the refrigerant flow path has an upper surface protruding toward the surface in a direction intersecting the direction of refrigerant flow in a longitudinal section, and wherein an unevenness is formed on the upper surface.

2. The base plate as requested in item 1, wherein, In the longitudinal cross-sectional view, the inner wall of the refrigerant flow path has a bottom surface located closer to the other surface than the upper surface, and a first side surface and a second side surface connecting the two ends of the upper surface and the two ends of the bottom surface to each other, wherein the roughness of the upper surface is greater than the roughness of the bottom surface and the roughness of the first and second side surfaces.

3. The base plate as requested in item 2, wherein, The roughness of the first and second side surfaces is greater than the roughness of the bottom surface.

4. The base plate as requested in item 2 or 3, wherein, In the longitudinal cross-sectional view, the upper surface has a first inclined surface that is connected to one end portion of the first side surface and is inclined to approach the first surface and the second side surface, and a second inclined surface that is connected to one end portion of the second side surface, is inclined to approach the first surface and the first side surface, and is connected to the first inclined surface. When a virtual line segment is defined to connect one end portion of the first side surface and one end portion of the second side surface, the diagram defined by the first inclined surface, the second inclined surface, and the virtual line segment has three interior angles, including a first interior angle formed by the virtual line segment and the first inclined surface, a second interior angle formed by the virtual line segment and the second inclined surface, and a third interior angle formed by the first inclined surface and the second inclined surface. The angle of the first interior angle is greater than 20 degrees and less than 50 degrees, and the angle of the second interior angle is greater than 20 degrees and less than 50 degrees.

5. The base plate as requested in item 4, wherein, In this longitudinal section, the absolute value of the difference between the angle of the first interior angle and the angle of the second interior angle is greater than 0 degrees and less than 10 degrees.

6. The base plate as requested in item 4, wherein, In this longitudinal section, the third interior angle is an obtuse angle.

7. The base plate as requested in item 4, wherein, The first inclined surface and the second inclined surface are flat surfaces.

8. The base plate as requested in item 4, wherein, In the longitudinal cross-sectional view, the pointed portion of the upper surface, including the intersection of the first inclined surface and the second inclined surface, is sharp.

9. The base plate of any one of requests 1 to 3, wherein, The base plate is a monolithically molded product and has no internal interfaces.

10. A substrate fixing device, comprising: The base plate for any one of items 1 to 3; and an electrostatic chuck mounted on one surface of the base plate.

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