Wafer holder

Abstract

To provide a wafer holding body having rigidity difficult to be deflected even in a construction having a cooling mechanism in an inner part.SOLUTION: A wafer holding body comprises: a first plate of which an upper surface is a wafer mounting surface; a second plate; and a heater plate, and provides a coolant flow channel in an inner part of any one of the first plate and the second plate. Each of the first plate, the second plate, and the heater plate has a circle in view of the wafer mounting surface side. The heater plate is arranged so as to be contacted to a lower surface of the first plate and the upper surface of the second plate between the lower surface of the first plate and the upper surface of the second plate, and a value of a product of a value LB (mm) obtained by subtracting a height of the flow channel from a whole thickness of the wafer holding body and a mean Young rate (kN / mm2) of the wafer holding body is 1800kN / mm or larger.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a wafer holder. [Background technology]

[0002] Wafer holders, such as those used in wafer probers, are known that perform testing and the like while controlling the temperature of a semiconductor wafer placed on its upper surface through heating and cooling. Patent Document 1 discloses a configuration in which a highly thermally conductive material is attached to the backside of a chuck top, with the aim of providing a wafer holder for a wafer prober that exhibits excellent uniformity of temperature distribution over a wide temperature range without compromising the high rigidity of the chuck top. Patent Document 2 discloses a wafer holder for a wafer prober that includes a chuck top and a heating element, and that includes a cooling mechanism in which a fluid flows through a gap formed between the chuck top and the heating element. Patent Document 3 discloses a substrate mounting table with a coolant flow path provided inside the chuck top. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-9976 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-27218 [Patent Document 3] Japanese Patent Application Publication No. 2019-212775 Summary of the Invention [Problem to be solved by the invention]

[0004] In a wafer holder, for example, when a wafer prober is used for testing, a large force may be applied to the entire wafer or a portion of it when the probe is pressed against it. The wafer holder must have rigidity to prevent it from deflecting under such forces. If the wafer holder deflects, a gap may form between the wafer and the holder, adversely affecting the temperature uniformity across the wafer surface. Furthermore, depending on the applied force, it may even lead to damage to the wafer holder itself. Means for increasing the rigidity of the entire wafer holder, as in Patent Document 1, are conceivable. However, in a configuration such as Patent Document 3, where a flow path is provided inside the chuck top itself, the thickness of the chuck top varies in parts, making it difficult to ensure overall rigidity. One objective of the present disclosure is to provide a wafer holder that is rigid enough to prevent deflection, even when equipped with an internal cooling mechanism. [Means for solving the problem]

[0005] The wafer holder of the present disclosure comprises a first plate whose upper surface serves as a wafer mounting surface, a second plate, and a heater plate, and is provided with a coolant flow path inside either the first plate or the second plate. The first plate, the second plate, and the heater plate are each circular when viewed from the wafer mounting surface side. The heater plate is disposed between the lower surface of the first plate and the upper surface of the second plate, and is in contact with the lower surface of the first plate and the upper surface of the second plate. The value LB (mm) obtained by subtracting the height of the flow path from the total thickness of the wafer holder and the average Young's modulus (kN / mm) of the wafer holder are used. 2 ) is 1800kN / mm or more. [Effects of the Invention]

[0006] According to the wafer holder of the present disclosure, even if it is configured to include an internal cooling mechanism, it can have rigidity that makes it less likely to bend. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic plan view of a wafer holder according to an embodiment. [Figure 2] FIG. 2 is a schematic vertical cross-sectional view of the wafer holder shown in FIG. 1 taken along line AA. [Figure 3] FIG. 3 is a schematic cross-sectional view taken along line BB of the wafer holder shown in FIG. 2, illustrating the shape of the flow path. [Figure 4] FIG. 4 is a schematic cross-sectional view of a heater plate according to an embodiment. [Figure 5] FIG. 5 is a schematic cross-sectional view showing a modified example of a wafer holder according to the embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view showing a wafer holder according to another embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view showing a wafer holder according to yet another embodiment. [Figure 8] FIG. 8 is a diagram illustrating the relationship between the force applied to the wafer holder and the deflection. [Figure 9] FIG. 9 is a diagram showing symbols used to explain the dimensional relationships of a wafer holder according to an embodiment. [Figure 10] FIG. 10 is a schematic cross-sectional view showing the basic configuration of a semiconductor manufacturing apparatus using a wafer holder according to an embodiment. [Figure 11] FIG. 11 is a schematic cross-sectional view showing the basic configuration of a semiconductor manufacturing device using a wafer holder according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Description of the embodiments of the present disclosure] Embodiments of the present disclosure will be listed and described below.

[0009] (1) The wafer holder of the present disclosure is A wafer holder comprising a first plate having an upper surface serving as a wafer mounting surface, a second plate, and a heater plate, wherein either the first plate or the second plate has a coolant flow path therein, each of the first plate, the second plate, and the heater plate is circular when viewed from the wafer mounting surface side; the heater plate is disposed between the lower surface of the first plate and the upper surface of the second plate so as to be in contact with the lower surface of the first plate and the upper surface of the second plate; The value LB (mm) obtained by subtracting the height of the flow path from the total thickness of the wafer holder and the average Young's modulus (kN / mm 2 ) is 1800kN / mm or more.

[0010] The above-mentioned wafer holder has a rigidity that prevents excessive deflection even when a large force is applied to the wafer mounting surface. Even if the wafer holder has a configuration in which a refrigerant flow path is provided as a cooling mechanism inside, it can have a rigidity that makes it difficult to deflect. As will be described in detail later, the inventors of the present application have developed a wafer holder in which a force is applied to the mounting surface, in order to reduce the deflection of the mounting surface to a certain level or less, by using an average Young's modulus (kN / mm 2 By setting the product of the average Young's modulus and LB to 1800 kN / mm or more, the deflection rate when a force of 0.1 MPa is applied to the mounting surface can be reduced to 0.3 × 10 -3 We found that the following can be done. The deflection rate will be explained later.

[0011] (2) A cross section of the flow path in a direction perpendicular to the placement surface is a rectangle having sides parallel to the placement surface, A distance LA (mm) between the placement surface and the flow path and a width W (mm) of the flow path may satisfy the relationship LA / W≧3.0.

[0012] The above configuration makes it possible to make a wafer holder that is even less likely to warp, even when equipped with a flow path. As will be described in more detail below, the inventors investigated the degree to which the flow path affects the amount of warp. As a result, they discovered that the wafer holder is more likely to warp when the distance between the upper edge of the flow path and the mounting surface is short and the width of the flow path is wide. That is, when the distance from the mounting surface to the upper edge of the flow path is LA (mm) and the width of the flow path is W (mm), they found that warp can be further reduced by making LA / W ≥ 3.0.

[0013] (3) The value LB (mm) obtained by subtracting the height of the flow path from the total thickness of the wafer holder and the average Young's modulus (kN / mm 2 ) may be 2700 kN / mm or more.

[0014] According to the above-mentioned configuration, even when a flow path is provided, the wafer holder can be made even less likely to bend. Specifically, by setting the value of the product of the average Young's modulus and LB to 2700 kN / mm or more, the deflection rate when a force of 0.1 MPa is applied to the mounting surface can be reduced to 0.2×10 -3 It can be as follows:

[0015] (4) The material of the first plate may be any one of copper, copper alloy, aluminum, and aluminum alloy.

[0016] If the first plate is made of one of the above metals, a wafer holder with excellent thermal conductivity can be obtained at a practical cost. That is, efficient heating or cooling is possible whether the temperature of the mounting surface is heated by a heater or cooled by a refrigerant.

[0017] (5) The material of the first plate may be ceramic or a ceramic composite.

[0018] If the first plate is made of a material such as ceramic, it is easier to obtain higher rigidity for the same thickness than if it were made of metal. This makes it possible to make the wafer holder less likely to bend, even in a configuration with a flow path. Alternatively, it is possible to construct a wafer holder with the same rigidity with a thinner thickness.

[0019] (6) The second plate may be made of copper, a copper alloy, aluminum, or an aluminum alloy.

[0020] If the second plate is made of one of the above metals, a wafer holder with excellent thermal conductivity can be obtained at a practical cost. In other words, if the second plate has a coolant flow path within it, efficient cooling becomes possible.

[0021] (7) The second plate may be made of a ceramic material or a ceramic composite material.

[0022] If the second plate is made of a material such as ceramic, it is easier to obtain high rigidity for the same thickness compared to metal. This makes it possible to create a wafer holder that is less likely to bend, even in a configuration with a flow path. Alternatively, it is possible to construct a wafer holder with the same rigidity but with a thinner thickness. The second ceramic may be the same material as the first ceramic, or it may be a different material.

[0023] (8) The device may further include a third plate in the form of a circular flat plate so as to be in contact with the lower surface of the second plate.

[0024] Furthermore, by providing a third plate, the rigidity of the entire wafer holder can be increased, making the wafer holder even less likely to bend, even in a configuration that includes a flow path.

[0025] (9) The material of the third plate may be any one of copper, copper alloy, aluminum, and aluminum alloy.

[0026] If the third plate is made of one of the above metals, a wafer holder with excellent thermal conductivity can be obtained at a practical cost.

[0027] (10) The material of the third plate may be ceramic or a ceramic composite.

[0028] If the third plate is made of a material such as ceramic, it is easier to obtain high rigidity for the same thickness compared to metal. This makes it possible to make a wafer holder that is less likely to bend, even when the wafer holder has a flow path inside it. Alternatively, it is possible to construct a wafer holder with the same rigidity but with a thinner thickness. The third ceramic may be the same material as the first and second ceramics, or they may be different materials.

[0029] (11) The heater plate may be a laminate of a first resin layer, a heater circuit layer, and a second resin layer.

[0030] A heater plate with this configuration is thin and flat, and has excellent adhesion to other plates, making it possible to make the overall thickness of the wafer holder thin, and facilitating the manufacture of the wafer holder.

[0031] (12) The material of the first resin layer may be a polyimide resin or a silicone resin filled with a filler.

[0032] Polyimide resin is an insulating material that combines heat resistance and insulating properties. Polyimide resin is suitable for the first resin layer of a heater plate because it is in thin sheet form and can easily support a heater circuit. By using polyimide resin, it is possible to create a heater plate that is thin and can be used up to about 250°C. A thin heater plate can reduce thermal resistance. Low thermal resistance makes it possible to efficiently transfer heat from the heater to the first plate and second plate. Furthermore, low thermal resistance makes it possible to speed up the response of the wafer holder to temperature changes.

[0033] Silicone resin filled with filler has excellent flexibility, meaning it is a material that easily deforms elastically. Filling with filler also improves the thermal conductivity of silicone resin. A first resin layer made of silicone resin filled with filler absorbs the irregularities of the heater circuit layer, making it easy to adhere to the first or second plate. Since gaps are less likely to form between the plates, it has excellent thermal conductivity between the plates. Heater plates made of silicone resin filled with filler can be used up to approximately 200°C. Known materials can be used for the filler. Ceramic fillers can be used as fillers that have excellent thermal conductivity and insulating properties. Examples of ceramic filler materials include aluminum nitride, alumina, and boron nitride.

[0034] (13) The material of the second resin layer may be a polyimide resin or a silicone resin filled with a filler.

[0035] The second resin layer can be made of the same material as the first resin layer. By using these resins for the second resin layer, the same effects as when they are used for the first resin layer can be obtained. The second resin layer and the first resin layer can be made of the same material or different materials. For example, the first resin layer can be made of polyimide resin and the second resin layer can be made of silicone resin filled with filler. Both the first resin layer and the second resin layer can be made of polyimide resin. Both the first resin layer and the second resin layer can be made of silicone resin filled with filler. When adhesion with the first plate or the second plate is important, it is recommended to use silicone resin filled with filler on the surface of the heater plate that is to be adhered to the plate.

[0036] (14) In a test in which the underside of the wafer holder, which is the surface opposite to the mounting surface, is supported and a force of 0.1 MPa is applied to the mounting surface, the deflection rate of the mounting surface is 0.3×10 -3 It may be the following:

[0037] The wafer holder described above is extremely resistant to bending even when configured with a flow path. The bending rate will be described later.

[0038] [Details of the embodiments of the present disclosure] A wafer holder according to an embodiment of the present disclosure will be described with reference to the drawings. The wafer holder according to the present disclosure can be used as part of semiconductor manufacturing equipment. The following description will be given taking as an example a wafer holder used in a wafer prober. A wafer prober is an inspection device that measures the electrical performance of a semiconductor wafer with circuits formed thereon while controlling the wafer at a predetermined temperature before cutting the wafer into individual chips. The wafer holder according to an embodiment of the present disclosure is not limited to wafer probers, and can also be used for wafer holders with similar structures for other applications. The same reference numerals in the figures indicate the same objects. The size and positional relationship of components shown in each drawing are depicted for the purpose of clarity and do not necessarily represent the actual dimensional relationships. Furthermore, directions are indicated with the side on which the wafer is placed being the upper side and the opposite side being the lower side.

[0039] [Configuration of the wafer holder] (Embodiment 1) A wafer holder 1 exemplified as this embodiment will be described with reference to the drawings. FIG. 1 is a schematic plan view of a wafer holder according to this embodiment as seen from below, and FIG. 2 is a schematic longitudinal cross-sectional view showing the AA cross section of FIG. 1. Referring to FIGS. 1 and 2, wafer holder 1 comprises a first plate 10, a heater plate 30, and a second plate 20. It may also comprise a third plate 40, which will be described later, but this is not essential. The upper surface 11 of first plate 10 is the mounting surface on which wafer S is placed. Hereinafter, upper surface 11 of first plate 10 may be simply referred to as mounting surface 11.

[0040] In this example, the second plate 20 has a channel 100 therein for circulating a coolant. FIG. 3 is a schematic cross-sectional view showing the cross section BB of FIG. 2 to explain the shape of the channel 100. FIG. 3 shows the portion of the wafer holder 1 where the channel 100 is located, cut along a plane parallel to the mounting surface 11. The channel 100 is formed in a swirling manner within the second plate 20, which is circular in plan view. The coolant flows into the channel 100 from the inlet 101, travels around the channel 100, and is discharged from the outlet 102. The shape of the channel 100 is an example for illustrative purposes and is not limited thereto. In this example, there is only one channel 100, but the number of channels is not limited thereto. Multiple channels may be provided on the same plane, or the channel may be configured to branch or merge internally. FIG. 2 is a schematic cross-sectional view for illustrative purposes, simply showing multiple channel cross sections arranged in a direction perpendicular to the coolant flow direction. The first plate 10, heater plate 30, and second plate 20 are stacked in this order. The heater plate 30 is disposed between the lower surface 12 of the first plate 10 and the upper surface 21 of the second plate 20. The stacked plates are fixed together by fastening members 50 so that their surfaces are in close contact with each other. In this example, the fastening members 50 are bolts inserted from the lower surface 22 of the second plate 20, and are fixed by threads provided inside the first plate 10. As illustrated in FIG. 3, the flow path 100 is provided so as to avoid the fastening members 50.

[0041] <First plate> The first plate 10 is a plate-like member whose upper surface serves as a wafer mounting surface 11. Although not shown in this example, the first plate 10 may be provided with a suction mechanism for the wafer S on the upper surface 11, which serves as the wafer S mounting surface. Specific examples of the suction mechanism include a vacuum chuck having a groove formed in the upper surface 11 of the first plate 10 and an exhaust path for exhausting air from the groove, an electrostatic chuck, a mechanical clamp, and the like. When a vacuum chuck is provided, a suction flow path separate from the coolant flow path 100 may be provided inside the first plate 10. The overall shape of the first plate 10 is shaped to match the shape of the wafer S and is typically circular in top view. The size of the first plate 10 is such that there is some space around the wafer S when it is mounted thereon. Examples of sizes of the wafer S include a diameter of 200 mm, a diameter of 300 mm, and a diameter of 450 mm. For example, if the wafer S has a diameter of 300 mm, the diameter of the first plate 10 can be 310 mm.

[0042] The material of the first plate 10 can be a metal, a nonmetal, or a composite of a metal and a nonmetal, which have excellent thermal conductivity. The higher the thermal conductivity of the material of the first plate 10, the more preferable it is. Examples of metals include copper, copper alloys, silver, silver alloys, aluminum, and aluminum alloys. Examples of nonmetals include silicon and ceramics. Examples of ceramics include aluminum nitride and silicon carbide. Examples of ceramic composites include a composite of silicon and silicon carbide, a composite of aluminum and silicon carbide, and a composite of aluminum, silicon, and silicon carbide. The material of the first plate 10 in this example is an aluminum alloy.

[0043] The thermal conductivity of the material making up the first plate 10 is preferably 100 W / m·K or higher. This thermal conductivity is more preferably 200 W / m·K or higher, 300 W / m·K or higher, and particularly preferably 400 W / m·K or higher. Typical values for the thermal conductivity of aluminum are approximately 230 W / m·K, that of copper is approximately 400 W / m·K, and that of silver is approximately 420 W / m·K. The thermal conductivity of silicon carbide is approximately 200 W / m·K, and that of aluminum nitride is approximately 150 W / m·K.

[0044] The surface of the first plate 10 may be subjected to a surface treatment. Examples of this surface treatment include plating. Specific examples of plating include Ni plating and Ni-P plating. Plating techniques include electrolytic plating and electroless plating. In this example, the surface treatment is Ni-P plating by electroless plating. When copper containing oxygen-free copper is used for the first plate 10, Ni plating or Ni-P plating is preferable. Copper easily diffuses into silicon, which is the constituent material of the wafer, so Ni plating or Ni-P plating can suppress this diffusion. As a result, the reliability of devices obtained from the wafer can be ensured.

[0045] <Heater plate> The heater plate 30 is a heating element for heating or cooling a wafer to a predetermined temperature. The heater plate 30 is a flat heater. FIG. 4 shows a schematic cross-sectional view of the heater plate 30 according to this embodiment. The heater plate 30 of this embodiment is a laminate of a first resin layer 31, a heater circuit layer 32, and a second resin layer 33. The heater circuit layer 32 is a metal circuit pattern serving as a resistance heating element and generates heat when electricity is applied. In this embodiment, the heater circuit layer 32 is made of a thin stainless steel film. Other metals may also be used for the heater circuit layer 32, and this is not a limitation. While FIG. 4 illustrates a schematic laminated structure, it is preferable that the first resin layer 31 and the second resin layer 33 fill gaps in the heater circuit layer 32. Furthermore, the surfaces of the first resin layer 31 and the second resin layer 33 may not be flat but may have an uneven shape corresponding to the arrangement of the heater circuit layer 32.

[0046] The first resin layer 31 and the second resin layer 33 are resin sheets used to insulate the heater circuit layer 32 and maintain its pattern shape. In this example, the first resin layer 31 is made of polyimide resin, and the second resin layer 33 is made of silicone resin filled with filler. The first resin layer 31 made of polyimide resin has a thermal conductivity of 0.3 W / m·K and a thickness of 0.05 mm, for example. The second resin layer 33 made of silicone resin filled with filler has a thermal conductivity of 5 W / m·K and a thickness of 0.5 mm, for example. In this example, the heater plate 30 is provided on the underside of the first plate 10. The heater plate 30 is held so as to be mechanically sandwiched between the first plate 10 and the second plate 20. The first resin layer 31 is in contact with the first plate 10, and the second resin layer 33 is in contact with the second plate 20. The heater plate 30 is preferably in the shape of a disk, and may have a diameter equal to or slightly smaller than that of the second plate 20 .

[0047] <Second plate> The second plate 20 is a member that supports the first plate 10 from the underside. The overall shape of the second plate 20 is a shape that matches the shape of the wafer S and is usually circular in a top view. The size of the second plate 20 may be the same as or smaller than the first plate 10. The first plate 10 and the second plate 20 are arranged so that their centers are common in a plan view. When the first plate 10 and the second plate 20 are circular and have the same diameter, the entire underside 12 of the first plate 10 is covered by the second plate 20. When the diameter of the first plate 10 is larger than the diameter of the second plate 20, the circular second underside 12b, which is the central portion of the underside of the first plate 10, overlaps with the second plate 20 via the heater plate 30, and the annular first underside 12a, which is the outer periphery of the second underside 12b, is exposed.

[0048] The second plate 20 can be made of a metal, nonmetal, or metal-nonmetal composite with excellent thermal conductivity. Metals include copper, copper alloys, silver, silver alloys, aluminum, and aluminum alloys. Nonmetals include silicon and ceramics. Ceramics include aluminum nitride and silicon carbide. Ceramic composites include silicon-silicon carbide composites, aluminum-silicon carbide composites, and aluminum-silicon-silicon carbide composites. Because the second plate 20 supports the first plate 10, highly rigid ceramics or composites thereof are preferably used. In this example, the second plate 20 is an aluminum alloy. The thermal conductivity of the material of the second plate 20 is preferably 100 W / m·K or higher. This thermal conductivity is preferably 200 W / m·K or higher, 300 W / m·K or higher, and particularly preferably 400 W / m·K or higher.

[0049] The second plate 20 has a flow path 100 for the coolant. The cross-sectional shape of the flow path 100 is not limited, but considering the cooling efficiency of the wafer and the ease of manufacturing the wafer holder, it is preferable that the cross-section of the flow path 100 is rectangular. The rectangle should have two opposing sides parallel to the mounting surface 11 and the other two sides perpendicular to the mounting surface 11. This is because the distance between the coolant flowing through the flow path 100 and the mounting surface 11 is short and constant, making it easy to maintain a uniform temperature distribution on the mounting surface 11. The flow path 100 must have a cross-sectional area sufficient to allow the coolant to flow at the desired flow rate. The cross-sectional area of the flow path 100 in the direction perpendicular to the flow of the coolant is 5 mm, although this depends on the type of coolant used and the temperature used. 2 The cross-sectional area of the flow path 100 is 10 mm 2 More preferably, 15 mm or more 2 That's all.

[0050] (Variation 1) FIG. 5 is a diagram showing a modified example of the wafer holder 1 according to embodiment 1. In the wafer holder 1 of FIG. 5, the first plate 10 is a plate-like body with a flange. The underside 12 of the first plate is composed of a circular second underside 12b, which is the portion that overlaps with the second plate 20, and an annular first underside 12a, which is the outer periphery of the second underside 12b. The distance between the mounting surface 11 and the first underside 12a is different from the distance between the mounting surface 11 and the second underside 12b. In other words, the first plate 10 has a structure in which a central portion of constant thickness is surrounded by a flange that is thinner than the central portion. The flange, or first underside 12a, is used as a portion for providing a support that supports the entire wafer holder from below. With this structure, the thickness of the first plate can be designed arbitrarily, regardless of the thickness of the flange.

[0051] (Embodiment 2) FIG. 6 is a diagram illustrating another embodiment of the wafer holder 1. In the wafer holder 1 of FIG. 6, the first plate 10 is provided with a flow path 100. The shape of the flow path 100 is the same as when the second plate 20 is provided with the flow path 100. When the flow path 100 is provided in the first plate 10 in this way, it is easier to shorten the distance between the refrigerant flowing through the flow path 100 and the mounting surface 11 compared to embodiment 1. Therefore, the mounting surface 11 and the wafer S can be quickly cooled by the refrigerant. This is effective in a design that emphasizes the cooling performance of the refrigerant over heating by a heater on the mounting surface 11.

[0052] (Embodiment 3) FIG. 7 is a diagram illustrating yet another embodiment of the wafer holder 1. In addition to the configuration of embodiment 1, the wafer holder 1 of FIG. 7 further includes a third plate 40 in contact with the underside 22 of the second plate 20. By using the third plate 40 in this manner, the overall rigidity of the wafer holder 1 can be increased. This also increases the degree of freedom in combining the materials and thicknesses of the first plate 10, second plate 20, and third plate 40. As will be described later, it becomes easier to design the relationship between the average Young's modulus and thickness of the entire wafer holder, which in turn makes it easier to design the flow path structure.

[0053] The first plate 10, heater plate 30, second plate 20, and third plate 40 are fixed together by fastening members 50 so that their surfaces are in close contact with each other. In this example, the fastening members 50 are bolts inserted from the underside of the third plate 40, and are fixed by threads provided inside the first plate 10. In FIG. 7, the heater plate 30 is disposed between the first plate 10 and the second plate 20. The heater plate 30 may also be disposed between the second plate 20 and the third plate 40. Furthermore, although the second plate 20 is provided with the flow path 100 in FIG. 8, the flow path 100 may also be provided in the first plate 10.

[0054] <Third Plate> The third plate 40 is a member that supports the first plate 10 and the second plate 20 from the underside. The overall shape of the third plate 40 is a shape that matches the shape of the wafer S, and is usually circular when viewed from above. The size of the third plate 40 may be the same as or smaller than the second plate 20. The second plate 20 and the third plate 40 are arranged so that they share a common center when viewed from above. When the heater plate 30 is sandwiched between the second plate 20 and the third plate 40, it is preferable that the third plate 40 be circular and have the same diameter as the second plate 20.

[0055] The third plate 40 can be made of a metal, nonmetal, or composite of a metal and a nonmetal, which have excellent thermal conductivity. Examples of metals include copper, copper alloys, silver, silver alloys, aluminum, and aluminum alloys. Examples of nonmetals include silicon and ceramics. Examples of ceramics include aluminum nitride and silicon carbide. Examples of ceramic composites include a silicon-silicon carbide composite, an aluminum-silicon carbide composite, and an aluminum-silicon-silicon carbide composite. Because the third plate 40 has the function of supporting the first plate 10 and the second plate 20, highly rigid ceramics or composites thereof are preferably used. Using a highly rigid material for the third plate 40 allows the overall thickness of the wafer holder to be reduced.

[0056] [Wafer holder deflection] <Deflection rate> The deflection and deflection rate of the wafer holder 1 will now be explained. Force can act on the mounting surface 11 side of the wafer holder 1. When an inspection prober is pressed against the wafer S while it is mounted, a downward force is applied to the wafer holder 1. Additionally, when inspecting or processing the wafer S in a pressurized or reduced-pressure environment, a force is applied due to the pressure difference between the mounting surface side and the underside of the wafer holder 1.

[0057] FIG. 8 is a diagram illustrating the relationship between force and deflection applied to wafer holder 1. FIG. 8 shows force F applied to mounting surface 11 from above. Support bodies 60 are provided to support the entire wafer holder. Support bodies 60 are, for example, cylindrical pillars. Support bodies 60 are positioned so that the annular end faces of support bodies 60 contact the outer periphery of first lower surface 12a of first plate 10. When force F is applied to mounting surface 11, first plate 10 and second plate 20 deflect so that their centers bulge downward. When a negative force is applied due to usage, that is, when force F is applied upward in the figure, the deflection results in an upward bulge. The absolute value of the amount of displacement occurring between the center and peripheral edge of mounting surface 11 in the direction perpendicular to mounting surface 11 is defined as deflection amount D. The amount of deflection D varies depending on the size of wafer holder 1 supported by support bodies 60. In other words, even if the same force F is applied to wafer holders 1 made of the same material, the amount of deflection D will differ if the size of the wafer holder 1 is different. Therefore, the value obtained by dividing the amount of deflection D by the diameter of the portion supported by support body 60 is defined as the deflection rate, and the following evaluation is performed using this value. The deflection rate is a dimensionless quantity.

[0058] FIG. 9 is a diagram showing reference numerals used to explain the dimensional relationships of the wafer holder 1 according to this embodiment. The configuration of the wafer holder 1 shown in FIG. 2 will be used as an example for the explanation. For ease of viewing, the reference numerals for each component will be omitted. The thickness of the first plate 10 is L1, the thickness of the heater plate 30 is L2, and the thickness of the second plate 20 is L3. The second plate 20 has a flow path 100 therein. The cross section of the flow path 100 is rectangular with a height H and a width W. The top view of each plate is circular, and the diameter of the first plate 10 is D1, and the diameter of the second plate 20 is D2.

[0059] The rigidity of the wafer holder 1 is affected by the Young's modulus of the entire wafer holder and the thickness of each plate. If a channel 100 is provided inside, the portion where the channel 100 is present is more likely to bend than other portions, so it is advisable to exclude the channel 100 from the rigidity design. LB is the thickness of the entire wafer holder minus the height of the channel. In FIG. 9, the thickness of the entire wafer holder is L1 + L2 + L3, where LB = L1 + L2 + L3 − H. In a configuration using a third plate 40 as in FIG. 7, if the thickness of the third plate 40 is represented as L4 (not shown), the thickness of the entire wafer holder is L1 + L2 + L3 + L4, where LB = L1 + L2 + L3 + L4 − H. Here, if the heater plate 30 is made of a resin sheet and a heating element circuit, and the thickness L2 of the heater plate 30 is thinner than the other plates, the thickness L2 of the heater plate 30 may be ignored. In other words, it may be considered as L2 = 0. This is because the contribution of heater plate 30 to the rigidity of wafer holder 1 is extremely small. Consider, for example, a case where heater plate 30 is 1 mm thick and the total thickness of the other plates is 20 mm. Because the Young's modulus of resin is an order of magnitude smaller than that of metal or ceramics, its contribution to rigidity is one order of magnitude smaller than 1 / 20, or less than 1%.

[0060] <Average Young's modulus> The average Young's modulus of the wafer holder 1 is defined as follows: If the wafer holder 1 is a stack of N layers of plates, and the Young's modulus of the nth layer is Yn and the thickness of the nth layer is Ln, then the value defined by the following equation (1) is taken to be the average Young's modulus of the wafer holder 1. Average Young's modulus = Σ(Yn × Ln) / ΣLn (1) Here, Σ is the sum of n=1 to N.

[0061] The value of LB explained above with reference to FIG. 9, that is, the thickness of the wafer holder excluding the height of the flow path, can be written in a similar manner as in the following equation (2). LB=ΣLn―H (2) Here, Σ is the sum of n=1 to N.

[0062] In order to reduce the deflection of the mounting surface 11 to a certain level, the average Young's modulus (kN / mm 2 The value of the product of the average Young's modulus and the thickness LB (mm) should be 1800 kN / mm or more. By setting the value of the product of the average Young's modulus and LB to 1800 kN / mm or more, the deflection rate when a force F of 0.1 MPa is applied to the mounting surface 11 can be reduced to 0.3 × 10 -3 Furthermore, by setting the value of the product of the average Young's modulus and LB to 2700 kN / mm or more, the deflection rate when a force F of 0.1 MPa is applied to the mounting surface 11 can be set to 0.2×10 -3 There is no upper limit to the value of the product of the average Young's modulus and LB, but when considering that the thickness of the entire wafer holder must be kept below a certain level and the Young's modulus of usable materials is taken into account, the upper limit is 10,000 kN / mm or less, and preferably approximately 8,000 kN / mm or less.

[0063] <Effect of flow path width> Furthermore, when the distance between the upper edge of the flow channel 100 and the mounting surface 11 is short and the width of the flow channel 100 is wide, the wafer holder 1 is prone to bending. The reason for this tendency is the presence of a wide space immediately below the mounting surface 11. If the distance from the mounting surface 11 to the upper edge of the flow channel 100 is LA (mm) and the width of the flow channel 100 is W (mm), bending can be further reduced by making LA / W ≥ 3.0. To reduce the amount of bending, it is more preferable that LA / W ≥ 5.0, and even more preferable that LA / W ≥ 6.0. To increase LA / W, it is effective to increase LA or decrease W. However, if LA is made too large, the distance between the flow channel 100 and the mounting surface 11 increases, reducing cooling efficiency. Furthermore, if W is made too small, the cross-sectional area of the flow channel 100 decreases, increasing the resistance to the refrigerant flow and reducing cooling efficiency. Therefore, the upper limit of LA / W is preferably 30, more preferably 20, and even more preferably LA / W≦10.

[0064] [Simulation Results] To verify the difference in the amount of deflection due to differences in the structure of the wafer holder 1, simulation experiments were conducted by changing the materials and thicknesses of the first plate 10, second plate 20, and third plate 40, as well as the arrangement of the flow path 100. Here, to simplify the structure, the presence of the heater plate 30, which has little effect, was ignored. That is, in Figure 9, L2 = 0 was assumed. The flow path 100 had a uniform shape. The cross section of the flow path 100 was a rectangle with a height H = 3 mm and a width W = 3 mm. Furthermore, the first plate 10 and the second plate 20 were assumed to be made of the same material, and the thickness from the mounting surface was used as a parameter to express the differences in structure, regardless of whether the flow path 100 was provided on the first plate 10 or the second plate 20. In the following data, the total thickness (mm) of the wafer holder is the sum of the distance LA (mm) from the mounting surface 11 to the flow path 100, the height H (mm) of the flow path 100, and the thickness LC (mm) of the lower part of the flow path. LC is the distance between the lower edge of flow channel 100 and lower surface 22 of second plate 20. Furthermore, when third plate 40 is provided so as to contact lower surface 22 of second plate 20, the thickness of third plate 40 is L4 (mm), and the value of LA+H+LC+L4 is the total thickness (mm) of wafer holder 1.

[0065] The first material is a material commonly used for the first plate 10 and the second plate 20. In this evaluation, an aluminum alloy (alloy symbol A5052: Japan Industrial Standards) was used as the metal material for the first material, and a silicon silicon carbide composite (Si-SiC) was used as the ceramic material. The second material is a material used for the third plate 40, and in this case, an aluminum alloy (A5052), alumina (Al2O3), or a silicon silicon carbide composite (Si-SiC) was used. The Young's modulus of A5052 is 75 kN / mm 2 , and the Young's modulus of alumina is 370 kN / mm 2 , Young's modulus of Si-SiC is 280kN / mm 2 Let's say.

[0066] Table 1 shows the evaluation results when both the first and second materials were A5052. The symbols and definitions for each dimension in the table are as described above. LB is the total thickness minus the channel height H. For each sample, the deflection amount and deflection rate, as defined above, were determined. The first plate 10, second plate 20, and third plate 40 all had the same diameter, which in this case was 310 mm. The evaluation was performed under the condition that the outermost periphery of the lowermost surface was supported by the support 60 in a circular ring shape, and a force F of 0.1 MPa was applied to the entire mounting surface 11. In calculating the deflection rate, the diameter of the portion supported by the support 60 was set to 310 mm.

[0067] Table 2 shows the results when the first material was A5052 and the second material was alumina or Si-SiC. The definitions of each value for the samples used and the conditions for calculating the amount of deflection are the same as in Table 1. Table 3 shows the results when both the first and second materials were Si-SiC. The definitions of each value for the samples used and the conditions for calculating the amount of deflection are the same as in Table 1.

[0068] [Table 1]

[0069] [Table 2]

[0070] [Table 3]

[0071] The standard for determining whether the wafer S is acceptable or not was determined based on the degree to which the gap between the wafer S and the mounting surface 11 affects the temperature uniformity within the wafer surface. -3 The following is considered to be a non-defective product. This deflection rate corresponds to a deflection of 100 μm or less at a diameter of 310 mm on the mounting surface. Referring to samples A01 to A25 in Table 1, if the value of the product of the wafer holder thickness LB excluding the flow path and the average Young's modulus is 1800 kN / mm or more, the deflection rate is 0.3×10 -3 It can be seen that the following is satisfied. Within this range, the rigidity required for a wafer holder can be ensured. Furthermore, when focusing on samples A02, A03, and A10, if the value of the product of thickness LB and average Young's modulus is 2700 kN / mm or more, the deflection ratio is 0.2 x 10 -3 It is found that the following is satisfied.

[0072] Furthermore, when we look at the arrangement of the flow channels, we can see from comparisons of samples A02, A09, and A14 that the amount of deflection is particularly small in samples that satisfy LA / W ≥ 3.0. A comparison of samples A15 and A18, and A16 and A17, which have the same value for the product of LB and average Young's modulus, shows that the larger the LA / W, the smaller the deflection rate.

[0073] The deflection rate can be further reduced by providing the third plate 40. Samples A05, A19, and A22 have the same structure from the mounting surface to the flow channel and the same overall thickness, but differ in whether or not they have the third plate 40. From these data, it can be seen that the deflection rate can be reduced by providing the third plate 40.

[0074] Table 2 confirms the effect of using a ceramic material as the second material. Samples B01 to B06 and samples C01 to C06 all have a third plate made of ceramic as the second material. Using a ceramic material increases the average Young's modulus. As a result, the product of the wafer holder thickness LB (excluding the flow path) and the average Young's modulus is greater than 1800 kN / mm, and the wafer holder deflection rates all meet the evaluation criteria. Furthermore, when the LA / W value is 3.0 or greater, the deflection rate is even smaller. From this data, it can be seen that if the product of LB and the average Young's modulus is 7000 kN / mm or greater, the deflection rate can be kept below 0.1. In other words, for the 310 mm diameter used in this experiment, the deflection amount can be kept below 32 μm.

[0075] Table 3 confirms the effectiveness of using ceramic materials for both the first and second materials. Samples D01 to D16 all have the first plate 10, second plate 20, and third plate 40 constructed of Si-SiC. Using ceramic materials increases the average Young's modulus. As a result, the product of the wafer holder thickness LB (excluding the flow path) and the average Young's modulus is greater than 1800 kN / mm, and the wafer holder deflection rates all meet the evaluation criteria. Furthermore, when the LA / W value is 3.0 or greater, the deflection rate is even smaller. From these data, it can be seen that if the product of LB and the average Young's modulus is 7000 kN / mm or greater, the deflection rate can be reduced to 0.1 or less. In other words, for this 310 mm diameter sample, the deflection amount can be reduced to 32 μm or less. Furthermore, comparing the data in Table 2 with the data in Table 3, it can be confirmed that the sample in Table 3 has a thinner overall thickness than the other samples with the same amount of deflection. That is, by using a ceramic material for the first material as well, the thickness of the wafer holder 1 can be made thin.

[0076] [Semiconductor manufacturing equipment] The basic configuration of a semiconductor manufacturing apparatus using the wafer holder 1 of the above embodiment is shown schematically in FIGS. 10 and 11. The wafer holder 1 is placed in a chamber 70. The wafer holder 1 is supported from below by a support 60 provided in the chamber 70. The support 60 and the wafer holder 1 are hermetically joined. This hermetically joining may be achieved via a sealing member 61 such as an O-ring, as shown in the figure, or by direct joining. FIG. 10 shows an example in which the underside of the first plate 10 of the wafer holder 1 is supported by the support 60. FIG. 11 shows an example in which the underside of the second plate 20, which forms the lowermost surface of the wafer holder 1, is supported by the support 60. The structure of the wafer holder 1 is not limited to that shown in the figure, and other configurations described in this disclosure can be applied. Although not shown, the semiconductor manufacturing apparatus can also be equipped with other structures used in semiconductor wafer processing. These structures include structures related to the introduction and exhaust of gases into the chamber 70, a showerhead, and structures related to plasma generation.

[0077] In this example, support body 60 is cylindrical in shape. The outer diameter of support body 60 is preferably the same as or slightly smaller than the outer diameter of wafer holder 1. As with the other plates, support body 60 is preferably made of a highly rigid ceramic or ceramic composite material.

[0078] In the semiconductor manufacturing equipment shown in FIG. 10 or 11, necessary gases are introduced into chamber 70, or gases are discharged to maintain a vacuum. The underside of wafer holder 1, the portion surrounded by support 60, is normally at atmospheric pressure. For example, when chamber 70 is maintained at a vacuum, a pressure difference equivalent to atmospheric pressure occurs between the top and bottom surfaces of wafer holder 1. In this case, too, as explained in this disclosure, deflection may occur in wafer holder 1. Therefore, as described above, it is effective to use a wafer holder 1 that is rigid enough to resist deflection, even in a configuration equipped with an internal cooling mechanism.

[0079] It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be considered restrictive. The present invention is not limited to these examples, but is defined by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0080] 1 Wafer holder 10 First Plate 11 Mounting surface (top surface of first plate) 12 Underside of first plate 12a 1st bottom surface 12b 2nd bottom surface 20 Second Plate 21 Top surface of second plate 22 Underside of second plate 30 Heater Plate 31 1st resin layer 32 Heater Circuit Layer 33 Second resin layer 40 Third Plate 50 Fastening members 60 Support 61 Sealing member 70 Chambers 100 flow channels 101 Inlet 102 Outlet S wafer

Claims

1. A wafer holder comprising a first plate having an upper surface serving as a wafer mounting surface, a second plate, and a heater plate, wherein either the first plate or the second plate has a coolant flow path therein, each of the first plate, the second plate, and the heater plate has a circular shape when viewed from the wafer mounting surface side; the heater plate is disposed between the lower surface of the first plate and the upper surface of the second plate so as to be in contact with the lower surface of the first plate and the upper surface of the second plate; The value LB (mm) obtained by subtracting the height of the flow path from the total thickness of the wafer holder and the average Young's modulus (kN / mm ２ ) is 3000 kN / mm or more, the material of the first plate or the second plate that includes the flow path is copper, a copper alloy, aluminum, or an aluminum alloy; In a test in which the underside of the wafer holder, which is the surface opposite the mounting surface, is supported by cylindrical supports and a force of 0.1 MPa is applied to the mounting surface, the deflection rate obtained by dividing the amount of deflection of the mounting surface by the diameter of the wafer holder at the portion supported by the supports is 0.16×10 −3 or less. Wafer holder.

2. The material of the first plate is any one of copper, copper alloy, aluminum, or aluminum alloy, The material of the second plate is copper, a copper alloy, aluminum, or an aluminum alloy.

2. The wafer holder of claim 1.

3. a cross section of the flow path in a direction perpendicular to the placement surface is a rectangle having sides parallel to the placement surface; a distance LA (mm) between the placement surface and the flow path and a width W (mm) of the flow path satisfy the relationship LA / W≧3.0, and the deflection rate is less than 0.10×10 −3 ; 3. The wafer holder according to claim 1.

4. Further provided is a third plate having a circular flat plate shape so as to be in contact with a lower surface of the second plate. The wafer holder according to any one of claims 1 to 3.

5. The material of the third plate is copper, a copper alloy, aluminum, or an aluminum alloy.

5. The wafer holder according to claim 4.

6. The material of the third plate is ceramic or a ceramic composite.

5. The wafer holder according to claim 4.

7. the heater plate is a laminate of a first resin layer, a heater circuit layer, and a second resin layer; The wafer holder according to any one of claims 1 to 6.

8. The material of the first resin layer is a polyimide resin or a silicone resin filled with a filler.

8. The wafer holder according to claim 7.

9. The material of the second resin layer is a polyimide resin or a silicone resin filled with a filler.

9. The wafer holder according to claim 7 or 8.

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