Wafer holding stand

Abstract

To provide a wafer holding stand with less variation in endothermic characteristic between an outer peripheral region and an inner peripheral region in the wafer holding stand.SOLUTION: A wafer holding stand includes a plate having an upper surface on which a wafer is mounted. The plate includes a coolant passage in an interior of the plate. The coolant passage includes a first coolant passage disposed in an outer peripheral region of the plate, and a second coolant passage that is disposed in an inner peripheral region of the plate and connects to the first coolant passage. A cross-sectional area of the first coolant passage is smaller than a cross-sectional area of the second coolant passage.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a wafer holding stage.

Background Art

[0002] Patent Document 1 discloses a substrate mounting stage. The substrate mounting stage corresponds to the wafer holding stage in the present disclosure. The substrate mounting stage is used, for example, in a prober. A prober is an inspection apparatus that measures the electrical performance of each chip before cutting a wafer on which a plurality of circuits are formed into individual chips. The substrate mounting stage of Patent Document 1 includes a chuck top having a disk shape. The chuck top is a plate having an upper surface on which a wafer is placed. Inside the plate, a refrigerant flow path through which a refrigerant flows is provided. The cross-sectional area of the refrigerant flow path is uniform from the inlet to the outlet of the refrigerant flow path.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the cross-sectional area of the refrigerant flow path is uniform from the inlet to the outlet of the refrigerant flow path as in Patent Document 1, the outer peripheral region of the upper surface of the plate is more difficult to cool than the inner peripheral region of the upper surface of the plate.

[0005] One object of the present disclosure is to provide a wafer holding stage in which the variation in heat absorption characteristics between the outer peripheral region and the inner peripheral region in the wafer holding stage is small.

Means for Solving the Problems

[0006] The wafer holding stage of the present disclosure includes a plate having an upper surface on which the wafer is placed. The plate includes a refrigerant flow path inside the plate. The refrigerant flow path includes a first refrigerant flow path disposed in an outer peripheral region of the plate and a second refrigerant flow path disposed in an inner peripheral region of the plate and connected to the first refrigerant flow path. The cross-sectional area of the first refrigerant flow path is smaller than the cross-sectional area of the second refrigerant flow path.

Advantages of the Invention

[0007] The wafer holding stage of the present disclosure has a small variation in heat absorption characteristics between the outer peripheral region and the inner peripheral region in the wafer holding stage.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0009] 《Description of Embodiments of the Present Disclosure》 First, the embodiments of the present disclosure will be listed and described.

[0010] (1) The wafer holding stage according to one aspect of the present disclosure includes a plate having an upper surface on which the wafer is placed. The plate includes a refrigerant flow path inside the plate. The refrigerant flow path includes a first refrigerant flow path disposed in an outer peripheral region of the plate and a second refrigerant flow path disposed in an inner peripheral region of the plate and connected to the first refrigerant flow path. The cross-sectional area of the first refrigerant flow path is smaller than the cross-sectional area of the second refrigerant flow path.

[0011] The wafer holding stage of (1) above has a small variation in heat absorption characteristics between the outer peripheral region and the inner peripheral region. Although details will be described later, generally, the heat transfer region of the chip disposed near the outer peripheral edge of the plate is smaller than the heat transfer region of the chip disposed at the center of the plate. In the case of a conventional configuration where the cross-sectional area of the refrigerant flow path is uniform, that is, in the case of a conventional configuration where the cross-sectional area of the first refrigerant region disposed in the outer peripheral region is the same as the cross-sectional area of the second refrigerant region disposed in the inner peripheral region, the flow velocity of the refrigerant flowing through the first refrigerant region in the outer peripheral region is the same as the flow velocity of the refrigerant flowing through the second refrigerant flow path in the inner peripheral region. Therefore, in the case of the conventional configuration, the chip disposed near the outer peripheral edge of the plate is less likely to dissipate heat compared to the chip disposed at the center of the plate. On the other hand, in the wafer holding stage of (1) above, since the cross-sectional area of the first refrigerant region disposed in the outer peripheral region is smaller than the cross-sectional area of the second refrigerant region disposed in the inner peripheral region, the flow velocity of the refrigerant flowing through the first refrigerant region in the outer peripheral region is faster than the flow velocity of the refrigerant flowing through the second refrigerant flow path in the inner peripheral region. Therefore, the wafer holding stage of (1) above is more likely to dissipate heat from the chip disposed near the outer peripheral edge of the plate and the chip disposed at the center of the plate to the same extent compared to the case of the above conventional configuration.

[0012] Further, in the wafer holding stage of (1) above, since the second refrigerant flow path having a cross-sectional area larger than that of the first refrigerant flow path in the outer peripheral region is disposed in the inner peripheral region, it is easy to suppress an increase in the pressure loss of the entire refrigerant flow path compared to the case where the cross-sectional area of the second refrigerant region disposed in the inner peripheral region is the same as the cross-sectional area of the first refrigerant region disposed in the outer peripheral region.

[0013] (2) In the wafer holding stage of (1) above, the outer peripheral region is an annular region having a predetermined width from the outer peripheral edge of the plate, and the predetermined width may be equal to or greater than the distance between the upper surface and the lower surface of the first refrigerant flow path.

[0014] Although the wafer holding stage of (2) above will be described in detail later, a first refrigerant flow path with a high refrigerant flow rate can be arranged within the heat transfer region of the chip arranged near the outer peripheral edge of the plate. Therefore, the wafer holding stage of (2) above can easily cool the outer peripheral region effectively. Thus, the wafer holding stage of (2) above can reduce the variation in heat absorption characteristics between the outer peripheral region and the inner peripheral region.

[0015] (3) In the wafer holding stage of (1) or (2) above, the cross-sectional area of the first refrigerant flow path may be 1 / 5 times or more and 1 / 2 times or less of the cross-sectional area of the second refrigerant flow path.

[0016] The wafer holding stage of (3) above can easily suppress an increase in the pressure loss of the entire refrigerant flow path because the cross-sectional area of the first refrigerant flow path is 1 / 5 times or more of the cross-sectional area of the second refrigerant flow path. The wafer holding stage of (3) above can easily increase the flow rate of the refrigerant flowing through the first refrigerant flow path because the cross-sectional area of the first refrigerant flow path is 1 / 2 times or less of the cross-sectional area of the second refrigerant flow path.

[0017] (4) In the wafer holding stage of any one of (1) to (3) above, the first refrigerant flow path may be one first flow path arranged in a plane parallel to the upper surface, and the second refrigerant flow path may be a second parallel flow path having a plurality of second flow paths arranged in parallel in the plane.

[0018] The wafer holding stage of (4) above can easily increase the flow rate of the refrigerant flowing through the first refrigerant flow path and can easily suppress an increase in the pressure loss of the entire refrigerant flow path.

[0019] (5) In the wafer holding stage of any one of (1) to (3) above, the first refrigerant flow path may be a first parallel flow path, and the second refrigerant flow path may be a second parallel flow path. The first parallel flow path has a plurality of first flow paths arranged in parallel in a plane parallel to the upper surface. The second parallel flow path has a plurality of second flow paths arranged in parallel in the plane. The number of the plurality of second flow paths is larger than the number of the plurality of first flow paths.

[0020] The wafer holding stage of the above (5) is such that the flow velocity of the refrigerant flowing through the first refrigerant flow path tends to be high, and it is easy to suppress an increase in the pressure loss of the entire refrigerant flow path.

[0021] (6) In the wafer holding stage of the above (4) or the above (5), the refrigerant flow path may include an outward path that extends from an inlet disposed on the outer periphery of the plate toward the central portion of the plate, and a return path that extends from the central portion toward an outlet disposed on the outer periphery of the plate. The outward path includes the first refrigerant flow path in which the arc-shaped first flow path extends from the outer peripheral region toward the inner peripheral region while alternately turning back in a first rotation direction and a second rotation direction, and the second refrigerant flow path in which the arc-shaped second flow path extends from a location near the outer peripheral region of the inner peripheral region toward the center of the plate while alternately turning back in the first rotation direction and the second rotation direction. The return path extends from the central portion through between the turning-back locations of the outward path toward the outer peripheral region. The first rotation direction and the second rotation direction are rotation directions centered on the center of the plate and are opposite to each other.

[0022] The wafer holding stage of the above (6) can reduce the variation in heat absorption characteristics between the outer peripheral region and the inner peripheral region.

[0023] 《Details of Embodiments of the Present Disclosure》 Hereinafter, embodiments of the wafer holding stage of the present disclosure will be described with reference to the drawings. The shapes, sizes, positional relationships, etc. shown in each figure are presented for the purpose of clarifying the description and do not necessarily represent the actual shapes, sizes, positional relationships, etc. The same reference numerals in the figures denote the same objects. Note that the present invention is not limited to the configurations shown in the embodiments, but is intended to be defined by the claims and to include all modifications within the meaning and scope equivalent to the claims.

[0024] 《Embodiment》 [Wafer Holding Stage] Referring to FIGS. 1 to 3, the wafer holding stage 1 of the embodiment will be described. As shown in FIG. 1, the wafer holding stage 1 of this embodiment includes a plate 2. The plate 2 has an upper surface 2u on which the wafer is placed. FIG. 1 schematically shows a cross-section of the wafer holding stage 1 cut by a plane orthogonal to the upper surface 2u of the plate 2. Here, the side where the upper surface 2u is located is defined as "upper", and the side where the lower surface 2d on the opposite side is located is defined as "lower". The plate 2 includes a refrigerant flow path 3 through which the refrigerant flows. The wafer holding stage 1 of this embodiment further includes a support structure 5 that supports the plate 2. One of the features of the wafer holding stage 1 of this embodiment is that the plate 2 is provided with a specific refrigerant flow path 3.

[0025] The wafer holding stage 1 of this embodiment is used as part of a semiconductor manufacturing apparatus. The following description will be made taking the case where the wafer holding stage 1 of this embodiment is used in a wafer prober as an example. A wafer prober is an inspection apparatus that measures the electrical performance of each chip of a semiconductor wafer on which a plurality of circuits are formed while controlling the wafer at a predetermined temperature before cutting the wafer into individual chips. The inspection of the wafer is performed, for example, by supplying power from a probe pin of a probe card to the chip while pressing the probe pin from above the chip formed on the wafer, and measuring the electrical performance of the chip. When power is supplied to the chip, the chip generates heat and the temperature of the wafer rises. Also, when the chip is pressed by the probe pin, a downward load is applied to the upper surface 2u of the plate 2. The wafer holding stage 1 is not limited to a wafer prober and can also be used for other wafer holding stages that require temperature adjustment of the wafer.

[0026] [Plate] Plate 2 is a member on which a wafer (not shown) is placed. The wafer is placed on the upper surface 2u of plate 2. Inside plate 2, a refrigerant flow path 3 is provided. When refrigerant flows through the refrigerant flow path 3, plate 2 is cooled, and the wafer can be cooled. The material of the wafer is, for example, silicon or a compound semiconductor. Plate 2 may be provided with a chuck mechanism (not shown) for adsorbing the wafer on the upper surface 2u. When the wafer is adsorbed on the upper surface 2u, the warp of the wafer is corrected, and the entire wafer can be brought into close contact with the upper surface 2u.

[0027] The shape of plate 2 is a shape that matches the shape of the wafer, and is usually disc-shaped. The size of plate 2 is slightly larger than that of the wafer. The size of plate 2 is designed according to the size of the wafer. The diameter of the wafer is, for example, from 2 inches (about 50 mm) to 12 inches (about 300 mm). The diameter of plate 2 is, for example, 100 mm or more and 400 mm or less.

[0028] The thickness of plate 2 is, for example, 15 mm or more and 30 mm or less. The thickness of plate 2 is a dimension along the direction perpendicular to the upper surface 2u. If the thickness of plate 2 is 15 mm or more, it is easy to ensure the rigidity of plate 2 and easy to form the refrigerant flow path 3. If the thickness of plate 2 is 30 mm or less, the wafer holding stage 1 can be made compact. Also, the thinner plate 2 is, the easier it is for the heat capacity of plate 2 to be small. Therefore, the cooling efficiency by the refrigerant flowing through the refrigerant flow path 3 and the responsiveness of heating by a heater (described later) tend to be high. The thickness of plate 2 may be 15 mm or more and 20 mm or less, or 16 mm or more and 18 mm or less. In this example, plate 2 is configured by laminating an upper plate 21 and a lower plate 22 vertically. The lower surface of the upper plate 21 and the upper surface of the lower plate 22 are joined to each other. The thickness of plate 2 is the total thickness of the upper plate 21 and the lower plate 22.

[0029] The plate 2 is made of a material with high thermal conductivity and high rigidity. The material of the plate 2 is, for example, a metal, ceramics, or a composite of ceramics. The metal is, for example, copper, a copper alloy, aluminum, or an aluminum alloy. The ceramics is, for example, silicon carbide or aluminum nitride. The composite of ceramics is, for example, a composite of silicon and silicon carbide, a composite of aluminum and silicon carbide, or a composite of aluminum, silicon, and silicon carbide. The material of the plate 2 in this example is oxygen-free copper.

[0030] The thermal conductivity of the plate 2 is, for example, 100 W / m·K or more. The thermal conductivity of the plate 2 may be 200 W / m·K or more, 300 W / m·K or more, or 400 W / m·K or more. This thermal conductivity is the value at 20°C. The thermal conductivity of copper is about 400 W / m·K, and the thermal conductivity of aluminum is about 230 W / m·K. The thermal conductivity of silicon carbide is about 200 W / m·K, and the thermal conductivity of aluminum nitride is about 150 W / m·K. The thermal conductivity of the composite of silicon and silicon carbide (Si-SiC) is about 170 W / m·K.

[0031] The surface of the plate 2 may be subjected to surface treatment. The surface treatment is, for example, plating. Specific examples of the plating are nickel plating or nickel-phosphorus plating. The method of plating is electroplating or electroless plating. When the material of the plate 2 is copper or a copper alloy, nickel plating or nickel-phosphorus plating may be applied to the upper surface 2u on which the wafer is placed. Copper easily diffuses into silicon, which is a constituent material of the wafer. Therefore, by providing the above plating on the upper surface 2u of the plate 2, the phenomenon of copper contained in the plate 2 diffusing into the wafer can be suppressed.

[0032] (Refrigerant flow path) Refrigerant flows through the refrigerant flow path 3. The state of the refrigerant is, for example, liquid or gas. Specific examples of the liquid are water, oil, ethylene glycol aqueous solution, or fluorine-based liquid. Specific examples of the gas are nitrogen gas or dry air. The refrigerant flow path 3 is formed inside the plate 2. The refrigerant flow path 3 is arranged in a plane parallel to the upper surface 2u. FIG. 2 shows a cross section obtained by cutting the portion of the plate 2 where the refrigerant flow path 3 is formed with a plane parallel to the upper surface 2u.

[0033] As shown in FIG. 1, the refrigerant flow path 3 in this example is constituted by a groove formed on the lower surface of the upper plate 21 and the flat upper surface of the lower plate 22. Specifically, a groove corresponding to the shape of the refrigerant flow path 3 is formed on the lower surface of the upper plate 21, and the refrigerant flow path 3 is constituted by joining the lower surface of the upper plate 21 and the upper surface of the lower plate 22. The above groove may be formed on at least one of the lower surface of the upper plate 21 and the upper surface of the lower plate 22. For example, the above groove may be formed on the upper surface of the lower plate 22, and the lower surface of the upper plate 21 may be flat. In this case, the refrigerant flow path 3 is constituted by the groove formed on the upper surface of the lower plate 22 and the flat lower surface of the upper plate 21. Also, the above groove may be formed on both the lower surface of the upper plate 21 and the upper surface of the lower plate 22. In this case, the refrigerant flow path 3 is constituted by the above grooves formed on the lower surface of the upper plate 21 and the upper surface of the lower plate 22 overlapping vertically.

[0034] As shown in FIG. 2, the refrigerant flow path 3 has an inlet 3i, an outlet 3e, a first refrigerant flow path 31, and a second refrigerant flow path 32.

[0035] 〈Inlet and Outlet〉 The inlet 3i is the part where the refrigerant is introduced into the interior of the plate 2. The outlet 3e is the part where the refrigerant is discharged to the exterior of the plate 2. The inlet 3i and the outlet 3e each open to the outer peripheral surface of the plate 2. There is one inlet 3i and one outlet 3e respectively. The first pipe 41 is connected to the inlet 3i, and the second pipe 42 is connected to the outlet 3e. The first pipe 41 is a pipe that introduces the refrigerant pumped from a pump (not shown) into the inlet 3i. The second pipe 42 is a pipe that sends the refrigerant discharged from the outlet 3e to a tank (not shown). The refrigerant recovered in the tank is sent to a cooler and cooled in the cooler. The refrigerant cooled in the cooler is sent to a pump. The refrigerant circulates in the order of the tank, the cooler, the pump, the refrigerant flow path 3, and the tank. In this example, the inlet 3i and the outlet 3e are arranged adjacent to each other.

[0036] 〈First Refrigerant Flow Path · Second Refrigerant Flow Path〉 As shown in FIG. 2, the first refrigerant flow path 31 is arranged in the outer peripheral region of the plate 2. The outer peripheral region is a region including the outer peripheral edge of the plate 2 and is an annular region concentric with the center 2a of the plate 2. The second refrigerant flow path 32 is arranged in the inner peripheral region of the plate 2. The inner peripheral region is a circular region surrounded by the outer peripheral region. The inner peripheral region is a circular region concentric with the center 2a of the plate 2. As shown in FIGS. 1 to 3, the first refrigerant flow path 31 and the second refrigerant flow path 32 are arranged in the same plane parallel to the upper surface 2u. That is, the distances from the upper surface 2u to the upper surfaces of the first refrigerant flow path 31 and the second refrigerant flow path 32 are equal. As shown in FIG. 2, the first refrigerant flow path 31 and the second refrigerant flow path 32 are continuous. That is, the number of refrigerant flow paths 3 is one. As will be described later, the cross-sectional area of the first refrigerant flow path 31 is smaller than the cross-sectional area of the second refrigerant flow path 32.

[0037] The width w of the outer peripheral region, which is an annular region in this example, is equal to or greater than the distance y between the upper surface 2u and the lower surface of the first refrigerant flow path 31, as shown in FIG. 3. The distance y is the largest distance between the upper surface 2u and the lower surface of the first refrigerant flow path 31 along the direction orthogonal to the upper surface 2u. The width w of the outer peripheral region is equal to or greater than 1 times the distance y. In this example, the distance y corresponds to the thickness of the upper plate 21. In FIG. 2, a third virtual circle C3 is shown that is concentric with the center 2a of the plate 2 and has a radius equal to the difference between the radius r of the plate 2 and the distance y.

[0038] The inner peripheral region may be an area that is equal to or greater than the area enclosed by the first virtual circle C1 and equal to or less than the area enclosed by the fourth virtual circle C4. The first virtual circle C1 and the fourth virtual circle C4 are determined using the diameter x, the distance y, and the distance z of the chip 100 that is the object of electrical performance inspection. The distance z is the distance between the center 2a of the plate 2 and the center of the second chip 102. The second chip 102 is four chips 100 that are arranged at equal intervals around the central axis of the plate 2 near the outer peripheral edge of the plate 2. In FIG. 2, the contours of the five chips 100 are shown as a rectangle of a two-dot chain line. The five chips 100 are one first chip 101 arranged at the center 2a of the plate 2 and the four second chips 102 described above. The diameter x of the chip 100 is the diameter of the inscribed circle of the chip 100. The center of the chip 100 is the center of the inscribed circle of the chip 100. The first virtual circle C1 is a circle that surrounds each chip 100 and indicates the region where the heat of the chip 100 is transferred on the lower surface of the refrigerant flow path 3. The first virtual circle C1 is a circle with a radius of (x + 2y) / 2. The fourth virtual circle C4 is a circle with a radius of z - {(x + 2y) / 2}. That is, the outer peripheral region may be the region between the second virtual circle C2 and the fourth virtual circle C4, or the region between the second virtual circle C2 and a fifth virtual circle (not shown), or the region between the second virtual circle C2 and the central first virtual circle C1. The second virtual circle C2 is a circle along the outer peripheral edge of the plate 2. In FIG. 2, for convenience of explanation, it is drawn slightly larger than the outer peripheral edge of the plate 2. The fifth virtual circle is a virtual circle between the fourth virtual circle C4 and the central first virtual circle C1. The fifth virtual circle may be a circle passing through a position that is 1 / 3 times the distance between the fourth virtual circle C4 and the central first virtual circle C1, a circle passing through a position that is 1 / 2 times the distance, or a circle passing through a position that is 2 / 3 times the distance. In this example, the outer peripheral region is the region between the second virtual circle C2 and the fourth virtual circle C4, and the inner peripheral region is the region enclosed by the fourth virtual circle C4.

[0039] The refrigerant flow path 3 in this example has an outward path that extends from the inlet 3i disposed on the outer periphery of the upper plate 21 toward the central portion of the upper plate 21, and a return path that extends from the central portion toward the outlet 3e disposed on the outer periphery. A wall is provided between each flow path that constitutes the outward path and the return path. The outward path includes a first refrigerant flow path 31 in which an arc-shaped first flow path 311 connected to the inlet 3i extends from the outer peripheral edge of the upper plate 21 toward the inner peripheral region while alternately turning back in a first rotation direction and a second rotation direction, and an arc-shaped second flow path 321 connected to the first refrigerant flow path 31 extends from a location near the outer peripheral region of the inner peripheral region toward the central portion of the inner peripheral region while alternately turning back in the first rotation direction and the second rotation direction. The first rotation direction and the second rotation direction are rotation directions centered on the center of the upper plate 21 and are opposite to each other. The return path is connected to the outward path and extends from the central portion of the upper plate 21 toward the outer periphery of the upper plate 21 through between the turning-back locations of the outward path. The return path extends linearly from the central portion toward the outer peripheral region. The return path is connected to the outlet 3e. The cross-sectional area of the flow path that constitutes the return path is the same in the inner peripheral region and the outer peripheral region. The cross-sectional area of the flow path that constitutes the return path may be equal to or greater than the cross-sectional area of the first refrigerant flow path 31 and equal to or less than the cross-sectional area of the second refrigerant flow path 32. Different from this example, the return path may be constituted by a second refrigerant flow path 32 that extends linearly from the central portion toward the outer peripheral region and a first refrigerant flow path 31 that extends linearly from the second refrigerant flow path 32 toward the outlet 3e.

[0040] The shape of the refrigerant flow path 3 shown in FIG. 2 is an example, and the shape of the refrigerant flow path 3 is not limited. For example, the shape of the refrigerant flow path 3 may be a form in which a spiral forward path from the outer periphery toward the center and a spiral return path from the center toward the outer periphery are alternately arranged in the radial direction by being folded back at the center. The forward path includes a first refrigerant flow path 31 in which an arc-shaped or spiral first flow path 311 connected to the inlet 3i extends in a first rotational direction from the outer peripheral edge of the upper plate 21 toward the inner peripheral region, and an arc-shaped or spiral second flow path 321 connected to the first refrigerant flow path 31 extends in the first rotational direction from a location near the outer peripheral region of the inner peripheral region toward the center of the inner peripheral region. The return path includes a second refrigerant flow path 32 in which an arc-shaped or spiral second flow path 321 connected to the second refrigerant flow path 32 of the forward path extends in a second rotational direction from the center of the inner peripheral region toward a location near the outer peripheral region of the inner peripheral region, and a first refrigerant flow path 31 in which an arc-shaped or spiral first flow path 311 connected to the second refrigerant flow path 32 of the return path extends in the second rotational direction from the inner peripheral region of the upper plate 21 toward the outer peripheral edge. The first refrigerant flow path 31 of the return path is connected to the outlet 3e. The cross-sectional areas and numbers of the first flow path 311 of the first refrigerant flow path 31 of the forward path and the first flow path 311 of the first refrigerant flow path 31 of the return path are the same. The cross-sectional areas and numbers of the second flow path 321 of the second refrigerant flow path 32 of the forward path and the second flow path 321 of the second refrigerant flow path 32 of the return path are the same.

[0041] Unlike this example, the inlet 3i and the outlet 3e may be provided at different positions. For example, the inlet 3i and the outlet 3e may be provided at positions facing each other on the outer peripheral surface of the plate 2.

[0042] In this example, the first refrigerant flow path 31 is a single first flow path 311, and the second refrigerant flow path 32 is a second parallel flow path 32a having a plurality of second flow paths 321. The adjacent second flow paths 321 are separated by a wall 35. The wall 35 is arranged over the entire length of the second flow path 321. The number of the second flow paths 321 in this example is 2. That is, the number of the walls 35 arranged between the adjacent second flow paths 321 is 1. The number of the second flow paths 321 may be 3 or more. However, in terms of ensuring the cross-sectional area of the second refrigerant flow path 32 and suppressing the deformation of the plate 2 when the above-described load is applied to the upper surface 2u, the number of the second flow paths 321 is preferably 2 or 3.

[0043] Different from this example, the first refrigerant flow path 31 may be a single first flow path 311, and the second refrigerant flow path 32 may be a single second flow path 321. Different from this example, the first refrigerant flow path 31 may be a first parallel flow path having a plurality of first flow paths 311, and the second refrigerant flow path 32 may be a second parallel flow path 32a having a plurality of second flow paths 321. In this case, the adjacent first flow paths 311 are also separated by a wall 35. The number of the second flow paths 321 is larger than the number of the first flow paths 311. For example, the number of the first flow paths 311 is 2, and the number of the second flow paths 321 is 3. In this case, the number of the walls 35 arranged between the adjacent first flow paths 311 is 1, and the number of the walls 35 arranged between the adjacent second flow paths 321 is 2. The number of the first flow paths 311 may be 3 or more, and the number of the second flow paths 321 may be 4 or more. However, in terms of ensuring the cross-sectional areas and lengths of the first refrigerant flow path 31 and the second refrigerant flow path 32, the number of the first flow paths 311 is preferably 2 or 3, and the number of the second flow paths 321 is preferably 3 or 4.

[0044] The cross-sectional shapes of the first refrigerant flow path 31 and the second refrigerant flow path 32 in this example are the same as each other. The cross-sections of the first refrigerant flow path 31 and the second refrigerant flow path 32 are cross-sections orthogonal to the direction in which the refrigerant flows. When the second refrigerant flow path 32 has a plurality of second flow paths 321 as in this example, the cross-sectional shapes of the second flow paths 321 are the same as each other. Different from this example, the cross-sectional shapes of the second flow paths 321 may be different from each other. Different from this example, the cross-sectional shapes of the first refrigerant flow path 31 and the second refrigerant flow path 32 may be different from each other. Different from this example, when the first refrigerant flow path 31 is a first parallel flow path having a plurality of first flow paths 311, the cross-sectional shapes of the first flow paths 311 may be the same as each other or may be different from each other.

[0045] As shown in FIG. 3, the cross-sectional shapes of the first refrigerant flow path 31 and the second refrigerant flow path 32 in this example are rectangular. The rectangular shape includes a square shape. The rectangular shape referred to here is not limited to a geometric rectangle, and includes, for example, a shape in which at least one of the four corners is rounded, etc., in which details are changed. The cross-sectional shapes of the first refrigerant flow path 31 and the second refrigerant flow path 32 are not limited to a rectangular shape. The cross-sectional shapes of the first refrigerant flow path 31 and the second refrigerant flow path 32 may be, for example, triangular, trapezoidal, pentagonal, circular, or semi-circular.

[0046] The cross-sectional area of the first refrigerant flow path 31 is smaller than the cross-sectional area of the second refrigerant flow path 32. Each cross-sectional area is the sum of the cross-sectional areas of the flow paths constituting each refrigerant flow path. When the first refrigerant flow path 31 is one first flow path 311 as in this example, the cross-sectional area of the first refrigerant flow path 31 is the cross-sectional area of the first flow path 311. Different from this example, when the first refrigerant flow path 31 is a first parallel flow path having a plurality of first flow paths 311, the cross-sectional area of the first refrigerant flow path 31 is the sum of the cross-sectional areas of the plurality of first flow paths 311. That is, the cross-sectional area of the first refrigerant flow path 31 is obtained by the product of the cross-sectional area of each first flow path 311 and the number of first flow paths 311. When the second refrigerant flow path 32 is a second parallel flow path 32a having a plurality of second flow paths 321 as in this example, the cross-sectional area of the second refrigerant flow path 32 is the sum of the cross-sectional areas of the plurality of second flow paths 321. That is, the cross-sectional area of the second refrigerant flow path 32 is obtained by the product of the cross-sectional area of each second flow path 321 and the number of second flow paths 321.

[0047] The wafer holding stage 1 in which the cross-sectional area of the first refrigerant flow path 31 is smaller than the cross-sectional area of the second refrigerant flow path 32 can reduce the variation in heat absorption characteristics between the outer peripheral region and the inner peripheral region. As shown in FIG. 2, a part of the first virtual circle C1 surrounding each of the four second chips 102 arranged near the outer peripheral edge of the plate 2 protrudes outside the outer peripheral edge of the plate 2, that is, outside the second virtual circle C2. That is, the protruding region among the regions surrounded by the first virtual circle C1 is a region that does not overlap with the plate 2. Therefore, the heat transfer region of each second chip 102 is a region excluding the protruding region, that is, a region overlapping with the plate 2. The heat transfer region of each second chip 102 is smaller than the region surrounded by the first virtual circle C1. On the other hand, the first virtual circle C1 surrounding the first chip 101 arranged at the center 2a of the plate 2 overlaps with the plate 2 over all regions. Therefore, the heat transfer region of the first chip 101 is the entire region of the first virtual circle C1. That is, the heat transfer region of the second chip 102 is smaller than the heat transfer region of the first chip 101.

[0048] In the case of a conventional configuration where the cross-sectional area of the refrigerant flow path 3 is uniform, that is, in the case of a conventional configuration where the cross-sectional area of the first refrigerant flow path 31 arranged in the outer peripheral region is the same as the cross-sectional area of the second refrigerant flow path 32 arranged in the inner peripheral region, the flow velocity of the refrigerant flowing through the first refrigerant flow path 31 in the outer peripheral region is the same as the flow velocity of the refrigerant flowing through the second refrigerant flow path 32 in the inner peripheral region. In this case, since the heat transfer region of the second chip 102 is smaller than the heat transfer region of the first chip 101, the second chip 102 is more difficult to dissipate heat than the first chip 101. On the other hand, in the wafer holding stage 1 of this example, since the cross-sectional area of the first refrigerant flow path 31 arranged in the outer peripheral region is smaller than the cross-sectional area of the second refrigerant flow path 32 arranged in the inner peripheral region, the flow velocity of the refrigerant flowing through the first refrigerant flow path 31 in the outer peripheral region is faster than the flow velocity of the refrigerant flowing through the second refrigerant flow path 32 in the inner peripheral region. Therefore, even if the heat transfer region of the second chip 102 is smaller than the heat transfer region of the first chip 101, the wafer holding stage 1 is more likely to dissipate heat from the second chip 102 and the first chip 101 to the same extent as in the case of the above conventional configuration. In particular, since the width w of the outer peripheral region of the wafer holding stage 1 is greater than or equal to the distance y, it is easy to effectively cool the outer peripheral region, so it is easy to dissipate heat from the second chip 102 and the first chip 101 to the same extent.

[0049] Since the cross-sectional area of the second refrigerant flow path 32 of the wafer holding stage 1 is larger than the cross-sectional area of the first refrigerant flow path 31, it is easy to suppress an increase in the pressure loss of the entire refrigerant flow path 3. In particular, in the wafer holding stage 1 of this example, since the inner peripheral region is a region surrounded by the fourth virtual circle C4, the inner peripheral region is relatively wide. That is, since the second refrigerant flow path 32 having a large cross-sectional area of the wafer holding stage 1 is relatively long, it is particularly easy to suppress an increase in the pressure loss of the entire refrigerant flow path 3.

[0050] The cross-sectional area of the first refrigerant flow path 31 is, for example, not less than 1 / 5 times and not more than 1 / 2 times the cross-sectional area of the second refrigerant flow path 32. Since the cross-sectional area of the first refrigerant flow path 31 is not less than 1 / 5 times the cross-sectional area of the second refrigerant flow path 32, the pressure loss of the entire refrigerant flow path 3 is likely to be small. Since the cross-sectional area of the first refrigerant flow path 31 is not more than 1 / 2 times the cross-sectional area of the second refrigerant flow path 32, the flow velocity of the refrigerant flowing through the first refrigerant flow path 31 is likely to be high.

[0051] [Support structure] As shown in FIG. 1, the support structure 5 supports the plate 2. The support structure 5 includes, in order from above, a support 50, a heater unit 51, a support column 52, and a pedestal 53.

[0052] (Support) The support 50 is a member for suppressing warping of the plate 2 due to heat during wafer inspection. The support 50 may be provided as needed and is not an essential member. When there is no support 50, the support column 52 described later supports the plate 2. If the support 50 is provided, when the above-described load is applied to the upper surface 2u, deformation of the plate 2 can be more effectively suppressed. The shape of the support 50 is a shape adapted to the shape of the plate 2. The support 50 in this example is disk-shaped.

[0053] The support 50 is in close contact with the lower surface 2d of the plate 2. By bringing the plate 2 and the support 50 into close contact, the rigidity of the entire wafer holding stage 1 can be increased. The support 50 and the plate 2 are brought into close contact by, for example, vacuum suction, bolt tightening, or adhesion. Vacuum suction is performed by a vacuum suction mechanism. The vacuum suction mechanism includes, for example, a vacuum flow path 50a provided on at least one of the lower surface 2d of the plate 2 and the upper surface of the support 50.

[0054] The vacuum flow path 50a is, for example, at least one of a groove and a hole provided on at least one of the lower surface 2d of the plate 2 and the upper surface of the support 50. The vacuum flow path 50a in this example is a groove provided on the upper surface of the support 50. A vacuum pump (not shown) is connected to the vacuum flow path 50a. By driving the vacuum pump, the inside of the vacuum flow path 50a becomes a vacuum state, and the plate 2 and the support 50 are adsorbed. By using the vacuum suction mechanism, the support 50 and the plate 2 can be easily attached and detached.

[0055] The material of the support 50 is, for example, ceramics or a composite of ceramics. The ceramics that make up the support 50 are, for example, alumina, mullite alumina, mullite, cordierite, steatite, silicon nitride, silicon carbide. The composite of ceramics that makes up the support 50 is, for example, a composite of silicon and silicon carbide, a composite of aluminum and silicon carbide, or a composite of aluminum, silicon, and silicon carbide.

[0056] (Heater unit) The heater unit 51 is a device for heating the wafer to a predetermined temperature. The heater unit 51 can adjust the temperature of the wafer. The heater unit 51 is disposed on the lower surface of the support 50. The heater unit 51 includes a disc-shaped heater. The heater is constituted by, for example, a resistance heating element.

[0057] Alternatively, instead of the heater unit 51, the support structure 5 may include a temperature adjustment unit having a wafer heating function and a wafer cooling function. The temperature adjustment unit has, for example, a structure in which a heating body and a cooling body are integrally laminated. The heating body includes the heater described above. A refrigerant flow path is formed in the cooling body. As the refrigerant flowing through the cooling body, a refrigerant different from the refrigerant flowing through the refrigerant flow path 3 can be used, but the same refrigerant may be used. Thus, by having both a heating function and a cooling function, the degree of freedom in adjusting the temperature of the wafer can be increased.

[0058] (Support column) The support column 52 is a member that supports the plate 2 on the pedestal 53. When there is a support 50, the support column 52 supports the support 50 on the pedestal 53. The shape of the support column 52 is, for example, columnar or tubular. The support column 52 supports the support 50 or the plate 2 through a through-hole formed in the heater unit 51. The outer diameter of the support column 52 is sufficiently smaller than the outer diameter of the support 50 or the outer diameter of the plate 2. The contact area between the support column 52 and the support 50, or the contact area between the support column 52 and the plate 2 is small. Thereby, the heat conduction from the plate 2 to the pedestal 53 via the support column 52 is suppressed, and the heat absorption characteristics of the plate 2 are maintained. The support column 52 can form a space between the heater unit 51 and the pedestal 53. This space contributes to the heat insulation between the plate 2 and the pedestal 53. The support column 52 in this example is tubular. In this example, the number of the support columns 52 is plural so that the plate 2 or the support 50 can be supported well in balance. The material of the support column 52 is ceramics such as alumina, mullite alumina, mullite, cordierite, steatite, or silicon nitride.

[0059] (Pedestal) The pedestal 53 is a member that supports the support 50, the heater unit 51, and the support column 52. The material of the pedestal 53 is ceramics such as alumina, aluminum nitride, silicon carbide, a composite of silicon and silicon carbide, a composite of aluminum and silicon carbide, or a composite of aluminum, silicon, and silicon carbide.

[0060] 《Test Example》 In the test example, a plurality of trial calculation models were designed, and the heat absorption characteristics of the outer peripheral region and the inner peripheral region of the plate provided with the refrigerant flow path were evaluated by experiments.

[0061] 〔Trial Calculation Model 1〕 As described with reference to FIG. 2, the trial calculation model 1 is a refrigerant flow path in which the cross-sectional area of the first refrigerant flow path arranged in the outer peripheral region is smaller than the cross-sectional area of the second refrigerant flow path arranged in the inner peripheral region. In the trial calculation model 1, the first refrigerant flow path is one first flow path, and the second refrigerant flow path is a second parallel flow path having two second flow paths. The cross-sectional area of the first refrigerant flow path is set to 1 / 3 times the cross-sectional area of the second refrigerant flow path.

[0062] Calculation Model 2 The Calculation Model 2 is different from the Calculation Model 1 in that the secondary refrigerant flow path is one secondary flow path. The cross-sectional area of the primary refrigerant flow path was set to 1 / 3 times the cross-sectional area of the secondary refrigerant flow path.

[0063] Calculation Model 3 The Calculation Model 3 is different from the Calculation Model 1 in that the cross-sectional area of the primary refrigerant flow path and the cross-sectional area of the secondary refrigerant flow path are the same, and the secondary refrigerant flow path is one secondary flow path. That is, the refrigerant flow path of the Calculation Model 3 is one flow path with a uniform cross-sectional area. The cross-sectional area of the primary refrigerant flow path is 1 times the cross-sectional area of the secondary refrigerant flow path.

[0064] Evaluation of Heat Absorption Characteristics The following experiment was conducted using each calculation model to evaluate the heat absorption characteristics. Five heating elements were arranged on the upper surface of the plate. As shown in FIG. 2, one heating element was arranged at the center of the plate, and four heating elements were arranged near the outer peripheral edge of the plate at equal intervals around the central axis of the plate. Each heating element is a rectangular plate having a thermal conductivity equivalent to that of a silicon wafer. The heat generation density of each heating element is 30 W / cm 2 . The sides and the upper surface of each heating element are assumed to be insulated. While flowing the refrigerant through the refrigerant flow path, power was supplied to each heating element in a state where a downward load was applied to the upper surface of each heating element. The supplied power was 100 W. The temperature of the refrigerant introduced into the refrigerant flow path was 23°C. The load was 100 kgf = 980 N. Power was supplied until the temperature of each heating element became stable, and the temperature difference ΔT (°C) between the temperature of the lower surface of each heating element when the temperature was stable and the temperature of the lower surface of each heating element before power supply was obtained. By dividing the temperature difference ΔT of each heating element by the supplied power, the thermal resistance at the location where each heating element was arranged was obtained. The closer the ratio of the maximum value of the central thermal resistance to the outer peripheral thermal resistance is to 1, the smaller the difference in heat absorption characteristics between the outer peripheral region and the inner peripheral region.

[0065] Figure 4 graphically shows the relationship between the cross-sectional area ratio and the thermal resistance ratio of each trial model. The cross-sectional area ratio on the horizontal axis is the ratio of the cross-sectional area of the first refrigerant flow path to the cross-sectional area of the second refrigerant flow path. The thermal resistance ratio on the vertical axis is the ratio of the central thermal resistance to the maximum value of the outer peripheral thermal resistance. The black circles in Figure 4 indicate Trial Model 1, the black filled squares indicate Trial Model 2, and the cross marks indicate Trial Model 3. In Figure 4, a straight line connecting Trial Model 1 and Trial Model 3 is shown.

[0066] The thermal resistance ratio of Trial Model 1 was 0.966. The thermal resistance ratio of Trial Model 2 was 0.930. The thermal resistance ratio of Trial Model 3 was 0.834. From these results, it was found that by using a plate having a refrigerant flow path in which the cross-sectional area of the first refrigerant flow path arranged in the outer peripheral region is smaller than the cross-sectional area of the second refrigerant flow path arranged in the inner peripheral region, the variation in the heat absorption characteristics between the outer peripheral region and the inner peripheral region can be reduced. In particular, it was found that Trial Model 1 in which the second refrigerant flow path is a second parallel flow path having two second flow paths can reduce the variation in the heat absorption characteristics between the outer peripheral region and the inner peripheral region more than Trial Model 2 in which the second refrigerant flow path is a single second flow path.

[0067] From the graph of Figure 4, it was found that when the second refrigerant flow path is a second parallel flow path having two second flow paths, the thermal resistance ratio satisfies 0.9 or more and 1.1 or less when the ratio of the cross-sectional area of the first refrigerant flow path to the cross-sectional area of the second refrigerant flow path is 2 or more and 5 or less.

Explanation of Signs

[0068] 1 Wafer holding stage 2 Plate 2a Center 2u Upper surface 2d Lower surface 21 Upper plate 22 Lower plate 3 Refrigerant flow path 3i Inlet 3e Outlet 31 First refrigerant flow path 311 First flow path 32 Second refrigerant flow path 32a Second parallel flow path 321 Second flow path 35 Wall 41 First pipe 42 Second pipe 5 Support structure 50 Support body 50a Vacuum flow path 51 Heater unit 52 Support pillar 53 Pedestal 100 Chip 101 First chip 102 Second chip C1 First virtual circle C2 Second virtual circle C3 Third virtual circle C4 Fourth virtual circle r Radius y, z distance w Width

Claims

1. A wafer holding stage comprising a plate having an upper surface on which a wafer is placed, wherein the plate has a refrigerant flow path inside the plate, the refrigerant flow path includes: a first refrigerant flow path disposed in an outer peripheral region of the plate; and a second refrigerant flow path disposed in an inner peripheral region of the plate and connected to the first refrigerant flow path, wherein a cross-sectional area of the first refrigerant flow path is smaller than a cross-sectional area of the second refrigerant flow path. Wafer holding stage.

2. The outer peripheral region is an annular region having a predetermined width from an outer peripheral edge of the plate, wherein the predetermined width is equal to or greater than a distance between the upper surface and a lower surface of the first refrigerant flow path. The wafer holding stage according to claim 1.

3. The cross-sectional area of the first refrigerant flow path is equal to or greater than 1 / 5 times and equal to or less than 1 / 2 times the cross-sectional area of the second refrigerant flow path. The wafer holding stage according to claim 1 or claim 2.

4. The first refrigerant flow path is one first flow path disposed in a plane parallel to the upper surface, and the second refrigerant flow path is a second parallel flow path having a plurality of second flow paths arranged in parallel in the plane. The wafer holding stage according to claim 3.

5. The first refrigerant flow path is a first parallel flow path having a plurality of first flow paths arranged in parallel in a plane parallel to the upper surface, the second refrigerant flow path is a second parallel flow path having a plurality of second flow paths arranged in parallel in the plane, wherein the number of the plurality of second flow paths is greater than the number of the plurality of first flow paths. The wafer holding stage according to claim 3.

6. The refrigerant flow path includes: a forward path extending from an inlet disposed on an outer periphery of the plate toward a central portion of the plate; and a return path extending from the central portion toward an outlet disposed on the outer periphery of the plate, wherein the forward path includes: the first refrigerant flow path in which the arc-shaped first flow path extends from the outer peripheral region toward the inner peripheral region while alternately turning back in a first rotation direction and a second rotation direction; and the second refrigerant flow path in which the arc-shaped second flow path extends from a location near the outer peripheral region of the inner peripheral region toward the center of the plate while alternately turning back in the first rotation direction and the second rotation direction, the return path extends from the central portion through between turning-back locations of the forward path toward the outer peripheral region, wherein the first rotation direction and the second rotation direction are rotation directions centered on the center of the plate and are opposite to each other. The wafer holding stage according to claim 4.

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