Wafer holder and wafer holding device

Abstract

A wafer holder includes a plate-shaped base body, and an ejector disposed inside the base body. The ejector includes a suction port, an input port, a nozzle, and a diffuser. The base body includes: an upper surface on which a wafer is placed; a lower surface positioned opposite to the upper surface; an outer peripheral surface connecting the upper surface and the lower surface; a suction hole provided on the upper surface; an air supply hole provided on the lower surface or the outer peripheral surface; an exhaust hole provided on the lower surface or the outer peripheral surface; a suction passage connecting the suction port and the suction hole; an air supply passage connecting the input port and the air supply hole; and an exhaust passage connecting the diffuser and the exhaust hole.

Description

Wafer holder and wafer holding device

[0001] The present disclosure relates to a wafer holder and a wafer holding apparatus.

[0002] Patent Document 1 discloses a substrate temperature control device including a mounting table on which a wafer is placed. The device includes a suction force generating unit with a suction pipe that draws in air around the wafer, and a suction force adjusting unit with an adjustment gas pipe that supplies a suction force adjusting gas to the suction pipe to adjust the suction force. The suction force generating unit generates a suction force that sucks the wafer and causes the wafer to adhere to the mounting table. The surface of the mounting table is provided with suction holes that suck the wafer. A flow path communicating with the suction holes is provided inside the mounting table. A suction pipe communicating with the flow path is connected to the mounting table. The suction force generating unit has a vacuum ejector. The suction pipe is connected to a low-pressure port of the vacuum ejector. A supply pipe connected to a compressed air source is connected to a high-pressure port of the vacuum ejector. An exhaust pipe is connected to an outlet of the vacuum ejector. In the suction force generating section, high-speed air is supplied from the supply pipe to the high-pressure port of the vacuum ejector and discharged from the outlet of the vacuum ejector. This high-speed air attracts air, which is sucked from the low-pressure port of the vacuum ejector. As a result, air around the wafer is sucked into the suction pipe through the suction holes, generating a suction force that sucks the wafer. The air sucked from the low-pressure port and the compressed air supplied to the high-pressure port are discharged from the outlet to the exhaust pipe.

[0003] International Publication No. 2020 / 246268

[0004] A wafer holder according to the present disclosure comprises a plate-shaped base and an ejector disposed inside the base. The ejector has a suction port, an input port, a nozzle, and a diffuser. The base has an upper surface on which a wafer is placed, a lower surface opposite the upper surface, an outer circumferential surface connecting the upper surface and the lower surface, suction holes provided in the upper surface, air supply holes provided in the lower surface or the outer circumferential surface, exhaust holes provided in the lower surface or the outer circumferential surface, a suction path connecting the suction port and the suction holes, an air supply path connecting the input port and the air supply hole, and an exhaust path connecting the diffuser and the exhaust hole.

[0005] FIG. 1 is a cross-sectional view showing the configuration of a wafer holding device according to an embodiment. FIG. 2 is a cross-sectional view showing an example of a wafer holder according to an embodiment. FIG. 3 is a plan view showing the upper surface of a base in a wafer holder according to an embodiment. FIG. 4 is a cross-sectional view showing the vicinity of the upper surface of a base in a wafer holder according to an embodiment. FIG. 5 is a cross-sectional view showing another example of a base in a wafer holder according to an embodiment. FIG. 6 is a plan view showing an enlarged view of the configuration of an ejector. FIG. 7 is a cross-sectional view showing another example of an ejector provided inside the base in a wafer holder according to an embodiment. FIG. 8 is a plan view showing an example of the configuration of flow channels provided inside the base in a wafer holder according to Example 1. FIG. 9 is a plan view showing another example of the configuration of flow channels provided inside the base in a wafer holder according to Example 2. FIG. 10 is a plan view showing another example of the configuration of flow channels provided inside the base in a wafer holder according to Example 3. FIG. 11 is a plan view showing another example of the configuration of flow channels provided inside the base in a wafer holder according to Example 4. FIG. 12 is a plan view showing another example of the configuration of flow channels provided inside the base in a wafer holder according to Example 5. 13 and 14 are graphs showing the relationship between the amount of warpage and the pressure of the compressed gas when the wafer is suctioned, with the flow rate of the compressed gas kept constant.

[0006] [Problem to be Solved by the Present Disclosure] In a conventional mounting table, the ejector is provided outside the chamber in which the mounting table is housed. A suction pipe that communicates with a suction hole is connected to the mounting table. The suction pipe is drawn out of the chamber. The suction pipe is connected to an ejector that generates suction force. An exhaust pipe is connected to the outlet of the ejector. Gas discharged from the outlet of the ejector is sent to an exhaust duct through an exhaust pipe provided outside the chamber.

[0007] In such a conventional mounting table, the distance of the flow path from the suction hole to the vacuum ejector is long, making it difficult to ensure sufficient suction force. Furthermore, corrosive gases may be mixed into the gas sucked through the suction hole. Examples of such corrosive gases include reactive gases used in film formation. If corrosive gases are mixed into the gas sucked through the suction hole, the suction and exhaust pipes may corrode.

[0008] An object of the present disclosure is to provide a wafer holder that makes it easy to ensure the suction force that attracts the wafer.

[0009] Effect of the Present Disclosure The wafer holder of the present disclosure makes it easy to ensure the suction force that attracts the wafer.

[0010] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0011] (1) A wafer holder according to the present disclosure includes a plate-shaped base and an ejector disposed inside the base. The ejector has a suction port, an input port, a nozzle, and a diffuser. The base has an upper surface on which a wafer is placed, a lower surface opposite the upper surface, an outer circumferential surface connecting the upper surface and the lower surface, suction holes provided in the upper surface, air supply holes provided in the lower surface or the outer circumferential surface, exhaust holes provided in the lower surface or the outer circumferential surface, a suction path connecting the suction port and the suction holes, an air supply path connecting the input port and the air supply hole, and an exhaust path connecting the diffuser and the exhaust hole.

[0012] The wafer holder of the present disclosure has an ejector inside the base, so the distance between the suction hole and the ejector is shorter than when the ejector is provided outside the base. The suction path is short, so it is easy to ensure the suction force required to suck the wafer. Furthermore, the wafer holder of the present disclosure does not require components equivalent to the suction piping and exhaust piping used in the conventional mounting tables described above. With the wafer holder of the present disclosure, the ejector is provided inside the base, so there is no need for suction piping extending outside the chamber. Furthermore, gas exhausted from the exhaust hole is discharged into the chamber housing the wafer holder, so there is no need for exhaust piping provided outside the chamber.

[0013] (2) In the wafer holder of (1) above, the base may have a first plate and a second plate joined together at their joining surfaces. One or both of the joining surfaces of the first plate and the second plate may have a groove. The ejector may be constituted by the groove.

[0014] In the wafer holder of (2) above, the ejector is formed integrally with the base, so the number of parts required is reduced.

[0015] (3) In the wafer holder of (2) above, the grooves may have a rectangular cross section perpendicular to the direction in which they extend.

[0016] Grooves with rectangular cross sections are easy to form.

[0017] (4) In the wafer holder of (1) above, the ejector may be configured as a component separate from the base.

[0018] The wafer holder of (4) above can be manufactured easily because it can be processed separately from the base. If the ejector is a separate component from the base, a commercially available ejector can be used.

[0019] (5) In the wafer holder of any one of (1) to (4) above, the ejector may include a plurality of ejectors, and the air supply path may branch from the air supply hole to the input port of each of the plurality of ejectors.

[0020] The wafer holder of (5) above has multiple ejectors, which improves suction power. Also, because compressed gas can be supplied to multiple ejectors from a single air supply hole, fewer air supply holes are required.

[0021] (6) In the wafer holder of any one of (1) to (5) above, the suction hole may include a plurality of suction holes, and the suction path may branch from the suction port to each of the plurality of suction holes.

[0022] The wafer holder of (6) above can suck gas from each of a plurality of suction holes with one ejector, thereby reducing the number of ejectors.

[0023] (7) A wafer holding device according to the present disclosure includes the wafer holder according to any one of (1) to (6) above, and a supply device that supplies compressed gas to the gas supply hole.

[0024] The wafer holding device of the present disclosure is equipped with the wafer holder of the present disclosure, and is therefore able to adsorb the wafer to the upper surface of the base with an appropriate suction force.

[0025] (8) In the wafer holding device of (7), the supply device may have a pressure measuring unit that measures the pressure of the compressed gas supplied to the gas inlet. The wafer holding device may detect the suction state of the wafer based on a change in the pressure measured by the pressure measuring unit.

[0026] The wafer holding device (8) above is capable of detecting whether the wafer has been properly attracted to the upper surface of the base.

[0027] (9) In the wafer holding device of (7), the supply device may have a flow rate measuring unit that measures the flow rate of the compressed gas supplied to the gas inlet. The wafer holding device may detect the suction state of the wafer based on a change in the flow rate measured by the flow rate measuring unit.

[0028] The wafer holding device (9) above is capable of detecting whether the wafer has been properly attracted to the upper surface of the base.

[0029] (10) In any one of the wafer holding devices described above in (7) to (9), the supply device may have a valve that adjusts the flow rate of the compressed gas supplied to the gas supply hole. The wafer holding device may control the flow rate with the valve to release the suction of the wafer.

[0030] The wafer holding device (10) above can easily remove the wafer held by suction on the upper surface of the base.

[0031] [Details of the Embodiments of the Present Disclosure] Specific examples of wafer holders and wafer holding devices according to the embodiments of the present disclosure will be described below with reference to the drawings. The same reference numerals in the figures indicate the same or corresponding parts. The shapes, sizes, positional relationships, etc. shown in each figure are depicted for the purpose of clarifying the description and do not necessarily represent the actual shapes, sizes, positional relationships, etc.

[0032] It should be noted that 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 meaning and scope equivalent to the claims.

[0033] [Embodiment] <Overall Configuration> An overview of a wafer holder 1 and a wafer holding device 100 according to an embodiment will be described with reference to FIG. 1 . FIG. 1 is a cross-sectional view that schematically shows the internal configuration of the wafer holding device 100. As shown in FIG. 1 , the wafer holding device 100 includes a wafer holder 1 disposed within a chamber 8. The wafer holding device 100 exemplified in this embodiment is a film formation device that forms a thin film by plasma processing on the surface of a wafer 10 placed on the wafer holder 1. An ambient gas is introduced into the chamber 8. A shower head 81 is disposed on the upper surface of the chamber 8. A reactive gas is supplied onto the wafer 10 from the shower head 81. The ambient gas is, for example, air or an inert gas. Examples of inert gases include nitrogen and argon. The reactive gas is, for example, a halogen-based gas. Examples of halogen-based gases include fluorine-based gas, chlorine-based gas, and bromine-based gas. The halogen-based gas is a corrosive gas. The reactive gas may be mixed with a carrier gas. The carrier gas is a gas that carries the reactive gas to the surface of the wafer 10, and is, for example, nitrogen, argon, or helium.

[0034] <Wafer Holder> The wafer holder 1 comprises a plate-shaped base 2. The base 2 has an upper surface 21 on which the wafer 10 is placed. Here, the side on which the upper surface 21 is located is referred to as "upper," and the opposite side is referred to as "lower." The wafer holder 1 of this embodiment further comprises a heater 4 that heats the wafer 10, and a support body 7 that supports the base 2. The wafer holder 1 has the function of vacuum-adsorbing the wafer 10 to the upper surface 21 of the base 2. By adsorbing the wafer 10 to the upper surface 21, the warpage of the wafer 10 is corrected, even if the wafer 10 had warpage before being placed on the upper surface 21. Furthermore, even if the wafer 10 is likely to warp due to heat or a chemical reaction during film formation on the wafer 10, the warpage of the wafer 10 is corrected. By correcting the warpage of the wafer 10, the wafer 10 can be heated uniformly, for example, when heated by the heater 4.

[0035] One of the features of the wafer holder 1 of this embodiment is that it is provided with an ejector 50 inside the base 2. The configuration of the base 2 will be described in detail below.

[0036] <<Base>> The base 2 is a plate-like member on which the wafer 10 is placed. As shown in FIG. 2, the base 2 has an upper surface 21, a lower surface 22, and an outer peripheral surface 23. FIG. 2 shows a cross section cut along a plane perpendicular to the upper surface 21. The wafer 10 is placed on the upper surface 21. The shape of the base 2 is, for example, a disk or a rectangular plate. That is, the shape of the upper surface 21 is a circle or a polygon. The shape of the upper surface 21 matches the shape of the wafer 10. The size of the base 2 is slightly larger than that of the wafer 10. The material of the wafer 10 is, for example, silicon or a compound semiconductor.

[0037] The base body 2 in this example has a disk-like shape. The upper surface 21 is horizontal. The upper surface 21 and the lower surface 22 are parallel to each other. The outer peripheral surface 23 is perpendicular to the upper surface.

[0038] The material of the substrate 2 is, for example, ceramics. Examples of ceramics include aluminum nitride, aluminum oxide, and silicon carbide. The material of the substrate 2 may be a composite material of the above-mentioned ceramics and a metal. Examples of metals include aluminum, an aluminum alloy, copper, and a copper alloy.

[0039] The base 2 is supported by a support 7, which will be described later. A first end 71 of the support 7 is connected to the lower surface 22.

[0040] The base 2 of this example is formed by joining multiple plates. As shown in FIG. 2, the base 2 has a first plate 2a, a second plate 2b, and a third plate 2c. In other words, the base 2 has three plates. From top to bottom, the first plate 2a, the second plate 2b, and the third plate 2c are arranged. The first plate 2a and the second plate 2b are joined together vertically. The second plate 2b and the third plate 2c are joined together vertically. In FIG. 2, the boundaries between the plates are indicated by dashed lines. This is also true for FIGS. 5 and 7. Each plate is circular. The material of each plate is the ceramic or composite material described above.

[0041] 2, the base 2 of this example includes a heater 4 that heats the wafer 10. The heater 4 is provided inside the base 2. Heat from the heater 4 is transferred from the inside of the base 2 to the upper surface 21, heating the wafer 10. The heater 4 is composed of a sheet-like heating element 40.

[0042] Terminals and power lines (not shown) are connected to the heating element 40. The terminals are embedded inside the base 2 and connected to the heating element 40. Holes (not shown) into which the terminals are fitted are provided in the inner region of the support 7 on the underside 22, and the terminals are drawn out from the underside 22. Power lines are arranged inside the support 7 and connected to the terminals. A power source (not shown) is connected to the power lines. Power is supplied to the heating element 40 from the power source via the power lines. When a current flows through the heating element 40, the heating element 40 generates heat.

[0043] The heater 4 is configured to heat the wafer 10 uniformly to a predetermined temperature. The material of the heating element 40 is a metal suitable for resistance heating. The metal is, for example, one selected from the group consisting of stainless steel, nickel, nickel alloy, silver, silver alloy, tungsten, tungsten alloy, molybdenum, molybdenum alloy, chromium, and chromium alloy. The nickel alloy is, for example, nichrome.

[0044] There are no particular limitations on the method for forming the heating element 40. The heating element 40 can be formed by screen printing a paste containing powder made of the above-mentioned metal, followed by firing. Alternatively, the heating element 40 can be formed by patterning a foil made of the above-mentioned metal.

[0045] In this example, the heater 4 is provided at the boundary between the second plate 2b and the third plate 2c. The heating element 40 is formed on the joining surface of the second plate 2b or the joining surface of the third plate 2c. In Fig. 2, the heating element 40 is shown as being formed on the lower surface of the second plate 2b and the upper surface of the third plate 2c, but in reality, the heating element 40 is formed on the lower surface of the second plate 2b or the upper surface of the third plate 2c.

[0046] (Protrusions / Ribs) As shown in FIGS. 3 and 4, the base 2 may have multiple protrusions 21a and one rib 21b. The protrusions 21a and rib 21b prevent the wafer 10 from coming into surface contact with the upper surface 21. Because the wafer 10 does not come into contact with the suction holes 31 (described later), gas can be easily sucked through the suction holes 31. FIG. 4 shows the vicinity of the upper surface 21 in a cross section taken along line IV-IV in FIG. 3. The protrusions 21a and rib 21b are provided on the upper surface 21. The protrusions 21a are provided inside the area where the wafer 10 overlaps. The shape of the protrusions 21a is columnar. The number and arrangement of the protrusions 21a are not particularly limited and may be determined as appropriate. In this example, the protrusions 21a are evenly distributed over substantially the entire surface of the upper surface 21 to correspond to the intersections of the lattice. The ribs 21b are provided so as to overlap the peripheral edge of the wafer 10. The ribs 21b are annular. The height of the protrusions 21a and the height of the ribs 21b are the same. The heights of the protrusions 21a and the ribs 21b are, for example, not less than 2 μm and not more than 100 μm. The wafer 10 is supported by the multiple protrusions 21a and the ribs 21b.

[0047] In the following description, "holes" such as suction hole 31, air supply hole 32, and exhaust hole 33, and "paths" such as suction path 61, air supply path 62, and exhaust path 63 are generally defined as follows: A "hole" is a space that opens to upper surface 21 or lower surface 22 and extends along outer peripheral surface 23, or a space that opens to outer peripheral surface 23 and extends along upper surface 21 or lower surface 22. A "path" is a space that communicates with the end of the "hole" opposite to its opening and extends in a direction intersecting the "hole." However, if the end of the hole opposite to its opening is connected to ejector 50, the space from the opening of the hole to ejector 50 may also be referred to as a path.

[0048] (Suction Hole, Air Supply Hole, Exhaust Hole) As shown in FIG. 2 , the base 2 has a suction hole 31, an air supply hole 32, and an exhaust hole 33. The suction hole 31 has an opening provided in the upper surface 21. More specifically, the suction hole 31 is provided in the region where the wafer 10 overlaps. The suction hole 31 extends from the upper surface 21 toward the inside of the base 2 to the boundary between the first plate 2a and the second plate 2b. The suction hole 31 is a linear flow path that opens in the upper surface 21. In this example, the suction hole 31 extends in a direction perpendicular to the upper surface 21. The suction hole 31 is connected to a suction path 61 shown in FIG. 6 , which will be described later. The suction path 61 in FIG. 6 is a flow path that extends horizontally along the boundary between the first plate 2a and the second plate 2b. 2, the suction path 61 is not shown, but in reality, the suction hole 31 communicates with a suction port 51 of the ejector 50 (described later) through the suction path 61, as shown in FIG. 6. When the end of the suction hole 31 opposite to the opening is connected to the suction port 51, the suction hole 31 also serves as the suction path.

[0049] The cross-sectional shape of the suction hole 31 is not particularly limited. The cross-sectional shape of the suction hole 31 refers to the shape of a cross section perpendicular to the direction in which the suction hole 31 extends. The cross-sectional shape of the suction hole 31 is, for example, circular, polygonal, semicircular, or elliptical. Examples of polygonal shapes include quadrilaterals, hexagons, and octagons. Quadrilaterals include rectangles. Rectangles include squares. In this example, the cross-sectional shape of the suction hole 31 is circular. The diameter of the suction hole 31 is, for example, 1 mm or more and 10 mm or less. The diameter of the suction hole 31 may further be 1 mm or more and 4 mm or less.

[0050] As shown in FIG. 3 , the base 2 of this example has a plurality of suction holes 31. Although FIG. 3 illustrates eight suction holes 31, the number of suction holes 31 is not particularly limited. The plurality of suction holes 31 may be arranged on a single circumference centered on the central axis of the base 2. The plurality of suction holes 31 may also be arranged on a plurality of circumferences having different radii from the central axis of the base 2. The plurality of suction holes 31 arranged on a circumference concentric with the center of the base 2 may be equally spaced around the central axis of the base 2. Arranging the plurality of suction holes 31 at equal intervals facilitates uniform suction of the wafer 10. From the viewpoint of uniformly suctioning the entire surface of the wafer 10, the suction holes 31 may be arranged in a peripheral region closer to the outer periphery than the bisector between the center and the outer periphery of the base 2. Furthermore, in this peripheral region, the suction holes 31 are preferably equally spaced around the central axis of the base 2.

[0051] As shown in FIG. 2 , the air supply hole 32 has an opening provided in the lower surface 22 or the outer peripheral surface 23. In this example, the air supply hole 32 is provided in the lower surface 22. More specifically, the air supply hole 32 is provided in an area of ​​the lower surface 22 inside the support 7. In this example, there is one air supply hole 32. The air supply hole 32 extends from the lower surface 22 toward the inside of the base 2 to the boundary between the first plate 2a and the second plate 2b. The air supply hole 32 is a linear flow path that opens to the lower surface 22. In this example, the air supply hole 32 extends in a direction perpendicular to the lower surface 22. The air supply hole 32 penetrates the second plate 2b and the third plate 2c. The air supply hole 32 is connected to an air supply path 62 shown in FIG. 6 , which will be described later. The air supply passage 62 is a flow path that is connected to the upper end of the air supply hole 32 and extends horizontally along the boundary between the first plate 2 a and the second plate 2 b. The air supply hole 32 is connected to an input port 52 of the ejector 50, which will be described later, through the air supply passage 62.

[0052] There may be a plurality of air supply holes 32. The air supply holes 32 may be provided on the outer peripheral surface 23. The air supply holes 32 may be provided on both the lower surface 22 and the outer peripheral surface 23.

[0053] The cross-sectional shape of the air supply hole 32 is not particularly limited. The cross-sectional shape of the air supply hole 32 refers to the shape of a cross section perpendicular to the direction in which the air supply hole 32 extends. The cross-sectional shape of the air supply hole 32 is, for example, circular, polygonal, semicircular, or elliptical. In this example, the cross-sectional shape of the air supply hole 32 is circular. The diameter of the air supply hole 32 is, for example, 1 mm or more and 10 mm or less. The diameter of the air supply hole 32 may also be 2 mm or more and 6 mm or less.

[0054] Compressed gas is supplied to the air inlet 32. A supply pipe 90 is connected to the opening of the air inlet 32. The supply pipe 90 is arranged inside the support body 7, which will be described later. The supply pipe 90 passes through the inside of the support body 7 and is led out to the outside of the chamber 8 shown in FIG. 1. A supply source 91, shown in FIG. 1, is connected to the supply pipe 90. The supply source 91 is a device that sends compressed gas to the supply pipe 90. The supply source 91 is arranged outside the chamber 8. The compressed gas sent out from the supply source 91 is supplied to the air inlet 32 ​​through the supply pipe 90. The supply source 91 is, for example, a compressor.

[0055] The compressed gas is the above-mentioned atmospheric gas or carrier gas introduced into the chamber 8. As will be described later, the compressed gas is exhausted into the chamber 8 through the exhaust hole 33. Therefore, if the compressed gas is the same as the gas introduced into the chamber 8, it is unlikely to affect film formation.

[0056] As shown in FIG. 2 , the exhaust hole 33 has an opening provided in the lower surface 22 or the outer peripheral surface 23. In this example, the exhaust hole 33 is provided in the lower surface 22. More specifically, the exhaust hole 33 is provided in a region of the lower surface 22 outside the support 7. The exhaust hole 33 extends from the lower surface 22 toward the inside of the base 2 to the boundary between the first plate 2a and the second plate 2b. The exhaust hole 33 is a linear flow path that opens to the lower surface 22. In this example, the exhaust hole 33 extends in a direction perpendicular to the lower surface 22. The exhaust hole 33 penetrates the second plate 2b and the third plate 2c. The exhaust hole 33 is connected to an exhaust path 63 shown in FIG. 6 , which will be described later. The exhaust path 63 is a flow path that is connected to the upper end of the exhaust hole 33 and extends horizontally along the boundary between the first plate 2a and the second plate 2b. The exhaust hole 33 communicates with a diffuser 53 of the ejector 50 (described later) through an exhaust path 63. At least one exhaust hole 33 is sufficient.

[0057] A mixed gas of compressed gas supplied from the gas inlet 32 ​​and suction gas sucked through the suction hole 31 is discharged from the opening of the exhaust hole 33. The exhaust hole 33 may be provided so as to communicate with the space within the chamber 8 so that the mixed gas is discharged into the chamber 8. Because the mixed gas is discharged from the exhaust hole 33 into the chamber 8, an exhaust pipe for sending the mixed gas from the exhaust hole 33 to an exhaust duct provided outside the chamber 8 is not required. The exhaust hole 33 may be provided on the outer peripheral surface 23, as shown in FIG. 5. The exhaust hole 33 in FIG. 5 opens on the outer peripheral surface 23 and extends from the outer peripheral surface 23 toward the inside of the base 2 to the diffuser 53. The exhaust hole 33 in FIG. 5 extends in a direction perpendicular to the outer peripheral surface 23. The extension direction of the exhaust hole 33 in FIG. 5 is parallel to the top surface 21. As shown in FIG. 5, when the end opposite the opening of the exhaust hole 33 is connected to the diffuser 53, the exhaust hole 33 also serves as an exhaust path. Therefore, the reference numeral for the exhaust path 63 is omitted in FIG.

[0058] By providing exhaust holes 33 on the lower surface 22 or the outer peripheral surface 23, the atmosphere around wafers 10 is less likely to be disturbed by the airflow generated by the mixed gas discharged from exhaust holes 33. Therefore, film formation is less likely to be affected. In particular, when exhaust holes 33 are provided on the lower surface 22, the atmosphere around wafers 10 is less susceptible to the airflow, and therefore film formation is less likely to be affected.

[0059] The cross-sectional shape of the exhaust hole 33 is not particularly limited. The cross-sectional shape of the exhaust hole 33 refers to the shape of a cross section perpendicular to the direction in which the exhaust hole 33 extends. The cross-sectional shape of the exhaust hole 33 is, for example, circular, polygonal, semicircular, or elliptical. In this example, the cross-sectional shape of the exhaust hole 33 is circular. The diameter of the exhaust hole 33 is, for example, 2 mm or more and 20 mm or less. The diameter of the exhaust hole 33 may further be 4 mm or more and 12 mm or less.

[0060] (Ejector) An ejector 50 is provided inside the base body 2. In this example, the ejector 50 is provided at the boundary between the first plate 2a and the second plate 2b, as shown in Fig. 2. In Fig. 2, the ejector 50 is shown schematically for ease of understanding.

[0061] The configuration of the ejector 50 of this example will be described in detail with reference to Figure 6. Figure 6 shows the right-hand ejector 50 in Figure 2. Figure 6 shows the ejector 50 in a perspective view of the substrate 2 from the top surface 21. The ejector 50 has a suction port 51, an input port 52, a nozzle 52a, and a diffuser 53. For ease of understanding, Figure 6 uses different hatching to indicate the parts corresponding to the suction port 51, the input port 52, the nozzle 52a, and the diffuser 53. The ejector 50 injects compressed gas introduced from the input port 52 at high speed from the nozzle 52a to the diffuser 53, generating a vacuum that sucks the gas from the suction port 51.

[0062] (Input Port) The input port 52 is connected to the air inlet 32. An air inlet passage 62 is connected to the input port 52. Compressed gas supplied from the air inlet 32 ​​passes through the input port 52 and is sprayed from the nozzle 52a. The nozzle 52a converts the pressure of the compressed gas into kinetic energy, increasing the flow velocity of the compressed gas. The compressed gas accelerated by the nozzle 52a is sent to the inlet 531 of the diffuser 53. The narrower the nozzle opening of the nozzle 52a, the faster the flow velocity of the compressed gas. The higher the supply pressure of the compressed gas, the faster the flow velocity of the compressed gas.

[0063] (Suction Port) The suction port 51 is connected to the suction hole 31. A suction path 61 is connected to the suction port 51. The high-speed compressed gas injected from the nozzle 52a expands and is decompressed at the inlet 531 of the diffuser 53. The reduction in pressure at the inlet 531 enables suction through the suction port 51, and gas is sucked in through the suction hole 31. The suction gas sucked in through the suction hole 31 merges with and is mixed with the high-speed compressed gas at the inlet 531. The faster the flow velocity of the compressed gas, the greater the suction force generated at the suction port 51. The suction gas is gas present in the chamber 8.

[0064] (Diffuser) The diffuser 53 is in communication with the exhaust hole 33. An exhaust path 63 is connected to the diffuser 53. The diffuser 53 is a flow path that diffuses high-speed compressed gas. The diffuser 53 decelerates and pressurizes the high-speed compressed gas and suction gas mixed at the inlet 531. The mixed gas of the high-speed compressed gas and suction gas passes through the diffuser 53 and is discharged from the outlet 532. The mixed gas discharged from the diffuser 53 is sent to the exhaust hole 33 through the exhaust path 63.

[0065] The diffuser 53 has a cross-sectional area larger than the cross-sectional area of ​​the injection port of the nozzle 52a. The cross-sectional area of ​​the diffuser 53 increases from the inlet portion 531 toward the outlet portion 532. The larger the length and cross-sectional area of ​​the diffuser 53, the easier it is to diffuse the high-speed compressed gas, and the greater the suction force generated at the suction port 51. The length of the diffuser 53 is, for example, 10 mm or more and 40 mm or less. The length of the diffuser 53 may further be 15 mm or more and 30 mm or less. The cross-sectional area of ​​the diffuser 53 is, for example, 10 mm or more and 40 mm or less. ２ More than 100 mm ２ The cross-sectional area of ​​the diffuser 53 is further increased to 15 mm ２ More than 50 mm ２ The cross-sectional area of ​​the nozzle 52a may be, for example, 0.2 mm ２ More than 5 mm ２ The cross-sectional area of ​​the nozzle 52a is 0.3 mm ２ 4mm or more ２ The following is also acceptable.

[0066] The ejector 50 of this example is configured with grooves 5 formed in one or both of the joining surfaces of the first plate 2a and the second plate 2b shown in FIG. 2 . That is, the grooves 5 may be formed in at least one of the lower surface of the first plate 2a and the upper surface of the second plate 2b. The cross-sectional shape of the grooves 5 may be, for example, circular, polygonal, semicircular, or elliptical. The cross-sectional shape of the grooves 5 refers to the shape of a cross section perpendicular to the extension direction of the grooves 5. The cross-sectional shape of the grooves 5 refers to the cross-sectional shape of the space formed between the joined first plate 2a and second plate 2b. If grooves having semicircular or semi-elliptical cross-sectional shapes are provided on both the lower surface of the first plate 2a and the upper surface of the second plate 2b, the cross-sectional shape of the grooves 5 becomes circular or elliptical when the two plates are combined. The cross-sectional shape of the grooves 5 in this example is rectangular. That is, the cross-sectional shapes of the suction port 51, the input port 52, the nozzle 52a, and the diffuser 53 are each rectangular. The extension direction of the grooves 5 is the same as the gas flow direction.

[0067] (Suction Passage, Air Supply Passage, and Exhaust Passage) As shown in Fig. 6, the base 2 has a suction passage 61, an air supply passage 62, and an exhaust passage 63. The suction passage 61 is a flow path connecting the suction port 51 and the suction hole 31. The suction gas sucked in from the suction hole 31 is sent to the suction port 51 through the suction passage 61. The air supply passage 62 is a flow path connecting the input port 52 and the air supply hole 32. The compressed gas supplied from the air supply hole 32 is sent to the input port 52 through the air supply passage 62. The exhaust passage 63 is a flow path connecting the diffuser 53 and the exhaust hole 33. The mixed gas discharged from the diffuser 53 is sent to the exhaust hole 33 through the exhaust passage 63.

[0068] In this example, the suction path 61, the air supply path 62, and the exhaust path 63 are formed by the above-mentioned grooves 5. That is, the cross-sectional shape of each of the suction path 61, the air supply path 62, and the exhaust path 63 is rectangular.

[0069] 2, the ejector 50 of this example has an input port 52 and a diffuser 53 arranged on a straight line. Alternatively, the ejector 50 may have a suction port 51 and a diffuser 53 arranged on a straight line, and the input port 52 may be arranged perpendicular to the diffuser 53, as shown in FIG.

[0070] The ejector 50 may be composed of components independent of the base 2. The components constituting the ejector 50 can be fabricated by processing a ceramic material such as aluminum nitride. For example, in the case of the base 2 shown in FIG. 2 or FIG. 5, the components constituting the ejector 50 are attached to the base 2 as follows: Before stacking the first plate 2a on the second plate 2b, the components constituting the ejector 50 are placed on the second plate 2b. Then, the first plate 2a, which has suction holes 31, is stacked on the second plate 2b. At this time, the suction ports 51 are inserted into the suction holes 31. Also, in the case of the base 2 shown in FIG. 7, the components constituting the ejector 50 are attached to the base 2 as follows: Before stacking the first plate 2a on the second plate 2b, the diffuser 53 is inserted into the exhaust hole 33. Then, when stacking the first plate 2a on the second plate 2b, the suction ports 51 are inserted into the suction holes 31. In the case of the base 2 of Figure 7, exhaust holes 33 that also serve as exhaust paths are provided on the lower surface 22, which increases the bonding area between the first plate 2a and the second plate 2b compared to the case where the exhaust holes 33 are provided on the outer peripheral surface 23 as in the base 2 of Figure 5.

[0071] <<Support>> As shown in Figures 1 and 2, the support 7 supports the base 2. The support 7 has a cylindrical shape. In this example, the support 7 is cylindrical. The support 7 is arranged roughly concentrically with the base 2. In this example, the base 2 is arranged on the support 7 so that the central axis of the cylindrical support 7 and the central axis of the disk-shaped base 2 are coaxial. Inside the support 7, power lines (not shown) connected to the heating element 40, a supply pipe 90, and the like are arranged.

[0072] The support 7 has a first end 71 and a second end 72. Each of the first end 71 and the second end 72 has a flange-like shape. The first end 71 is connected to the lower surface 22 of the base 2. A seal member (not shown) is disposed between the first end 71 and the lower surface 22. The second end 72 is connected to the bottom surface of the chamber 8. A seal member (not shown) is disposed between the second end 72 and the bottom surface of the chamber 8. These seal members maintain airtightness within the support 7. At least one of the first end 71 and the lower surface 22 and the second end 72 and the bottom surface of the chamber 8 may be directly bonded without a seal member. When a corrosive gas is supplied into the chamber 8 in which the wafer holder 1 is disposed, maintaining airtightness within the support 7 allows the power lines and supply pipes 90 disposed within the support 7 to be isolated from the corrosive gas. A through-hole 80 is provided in an area inside the support 7 at the bottom surface of the chamber 8. The power lines and supply pipes 90 are led out of the chamber 8 through the through-holes 80 .

[0073] The material of the support 7 is, for example, ceramics. The material of the support 7 may be the same as or different from the material of the base 2.

[0074] 8 to 12, an embodiment of the arrangement of the ejector 50 and the configuration of the flow path provided inside the base 2 will be described. Figures 8 to 12 show the base 2 as seen through from the top surface 21.

[0075] Example 1 In Example 1 shown in Figure 8, there is one ejector 50. The air supply hole 32 is provided at a position overlapping with the center of the base 2 or near the center of the base 2. The air supply hole 32 and the input port 52 are connected by an air supply path 62. The air supply path 62 is a linear flow path. One exhaust hole 33 is provided for each ejector 50. The exhaust hole 33 and the diffuser 53 are connected by an exhaust path 63. The exhaust path 63 is a linear flow path.

[0076] The suction holes 31 are provided on two circles with different radii centered on the central axis of the base 2. In Fig. 8, these two circles are indicated by two-dot chain lines. This is also true in Figs. 9 to 12. The suction holes 31 have a plurality of first suction holes 31a arranged on the circumference of the smaller diameter circle and a plurality of second suction holes 31b arranged on the circumference of the larger diameter circle. There are four first suction holes 31a. There are sixteen second suction holes 31b. The suction holes 31 and the suction port 51 are connected by a suction path 61. The suction path 61 branches from the suction port 51 to each of the plurality of suction holes 31.

[0077] The suction path 61 includes a first suction path 611, a second suction path 612, and a third suction path 613. The first suction path 611, the second suction path 612, and the third suction path 613 are all arc-shaped. The first suction path 611, the second suction path 612, and the third suction path 613 are arranged concentrically around the central axis of the base 2. The first suction path 611, the second suction path 612, and the third suction path 613 are arranged in order from closest to the center of the base 2. The first suction path 611 is a flow path connected to the suction port 51. The second suction path 612 is two flow paths branching off from an end of the first suction path 611. The third suction path 613 is two flow paths branching off from an end of one second suction path 612.

[0078] The second suction path 612 is arranged on the same circumference as the first suction hole 31a. The first suction hole 31a is connected to the second suction path 612. The third suction path 613 is arranged on the same circumference as the second suction hole 31b. The second suction hole 31b is connected to the third suction path 613.

[0079] In the first embodiment, one ejector 50 can suck from a plurality of suction holes 31 .

[0080] 9, the number of ejectors 50 is two. The arrangement of the suction holes 31 is the same as in Example 1. That is, the suction holes 31 include four first suction holes 31a and sixteen second suction holes 31b.

[0081] The air supply path 62 includes a first air supply path 621 and a second air supply path 622. The first air supply path 621 is a linear flow path connected to the air supply hole 32. The second air supply path 622 is two flow paths branching off from the first air supply path 621. Both ends of the second air supply path 622 are connected to the respective input ports 52. The second air supply path 622 is a combination of a semicircular arc flow path connected to the first air supply path 621 and a linear flow path connecting from the end of the semicircular arc flow path to the input port 52. The air supply path 62 branches off from one air supply hole 32 to the input ports 52 of each ejector 50.

[0082] The suction path 61 includes a first suction path 611, a third suction path 613, and a fourth suction path 614. The third suction path 613 is arranged on the same circumference as the second suction hole 31b. The fourth suction path 614 is a linear flow path connecting the first suction path 611 and the third suction path 613. The fourth suction path 614 extends along the diameter of the base 2. The fourth suction path 614 is arranged at a position overlapping with the first suction hole 31a. The fourth suction path 614 is arranged on the same circumference as the second suction hole 31b. The first suction hole 31a is connected to the fourth suction path 614. The second suction hole 31b is connected to the third suction path 613.

[0083] In the second embodiment, the two ejectors 50 are provided, and thus the suction force is improved compared to the first embodiment.

[0084] 10 , the number of ejectors 50 is three or more. The arrangement of the suction holes 31 is the same as in Example 1. That is, the suction holes 31 have four first suction holes 31 a and sixteen second suction holes 31 b.

[0085] One ejector 50 is provided for every two suction holes 31. There are a total of 10 ejectors 50. Each ejector 50 is located midway between two adjacent suction holes 31. Each suction hole 31 is connected to a suction port 51 by a suction path 61.

[0086] The air supply path 62 branches from one air supply hole 32 to the input ports 52 of each ejector 50. The air supply path 62 includes a first air supply path 621, a second air supply path 622, a third air supply path 623, and a fourth air supply path 624. The third air supply path 623 is a circular flow path located between a small circle where the first suction hole 31a is located and a large circle where the second suction hole 31b is located. The second air supply path 622 is a combination of a semicircular flow path connected to the first air supply path 621 and a linear flow path connected to the third air supply path 623. The linear flow path extends along the diameter of the base 2, away from the center of the base 2.

[0087] The fourth air supply passage 624 is a flow path that branches off from the third air supply passage 623 and is connected to the input port 52 of each ejector 50. The fourth air supply passage 624, which is provided in the inner circumferential region of the third air supply passage 623, is connected to the input port 52 of each ejector 50 provided in the inner circumferential region. The fourth air supply passage 624, which is provided in this inner circumferential region, is a linear flow path that extends from the third air supply passage 623 toward the input port 52. The fourth air supply passage 624, which is provided in the outer circumferential region of the third air supply passage 623, is connected to the input port 52 of each ejector 50 provided in the outer circumferential region. The fourth air supply passage 624, which is provided in this outer circumferential region, is a combination of a linear flow path that branches off from the third air supply passage 623 and an arc-shaped flow path that branches off from this linear flow path to the input port 52.

[0088] In the third embodiment, the suction force is improved by providing a plurality of ejectors 50. In addition, the distances from the suction holes 31 to the suction port 51 can be made equal. Therefore, the suction force of each suction hole 31 varies little.

[0089] <Example 4> In Example 4 shown in Figure 11, similar to Example 3, one ejector 50 is provided for two suction holes 31. Unlike Example 3, Example 4 has eight first suction holes 31a. The number of second suction holes 31b is the same as Example 3, that is, 16. There are a total of 12 ejectors 50. Each ejector 50 is located midway between two adjacent suction holes 31. Each suction hole 31 is connected to a suction port 51 by a suction path 61.

[0090] The air supply path 62 includes a first air supply path 621, a second air supply path 622, and a fifth air supply path 625. The fifth air supply path 625 is two flow paths branching off from the second air supply path 622. The fifth air supply path 625 is an arc-shaped flow path having a length corresponding to approximately one-quarter of the circumference of a circle concentric with the base 2. Ends of the fifth air supply path 625 branch off to connect to the input ports 52 of the three ejectors 50. The air supply path 62 branches off from one air supply hole 32 to the input ports 52 of each ejector 50.

[0091] In the fourth embodiment, the suction force is improved by providing a plurality of ejectors 50. In addition, the distances from the suction holes 31 to the suction port 51 can be made equal. Therefore, the suction force of each suction hole 31 varies little.

[0092] 12 , the number of ejectors 50 is one, similar to that of Example 1. The arrangement of the suction holes 31 is the same as that of Example 4. Example 5 differs from Example 1 in that the first suction path 611 connected to the suction port 51 has a circular shape.

[0093] The suction path 61 branches from the suction port 51 to each of the multiple suction holes 31. The suction path 61 includes a first suction path 611, a second suction path 612, a third suction path 613, a fifth suction path 615, a sixth suction path 616, a seventh suction path 617, an eighth suction path 618, and a ninth suction path 619. The fifth suction path 615 is located 180° opposite the position of the circular first suction path 611 where it is connected to the ejector 50. The sixth suction path 616 is a semicircular arc-shaped flow path branching off from the fifth suction path 615. The seventh suction path 617 is a linear flow path extending from the end of the sixth suction path 616. The seventh suction path 617 extends along the diameter of the base 2, away from the center of the base 2. The eighth suction path 618 and the ninth suction path 619 are flow paths branching off from the seventh suction path 617. The eighth suction path 618 connects the seventh suction path 617 and the second suction path 612. The eighth suction path 618 is a combination of an arc-shaped flow path having a length corresponding to approximately one-quarter of the circumference of a circle concentric with the base 2 and a linear flow path that connects from the end of this arc-shaped flow path to the second suction path 612. The ninth suction path 619 connects the seventh suction path 617 and the third suction path 613. The ninth suction path 619 is a combination of an arc-shaped flow path having a length corresponding to approximately one-quarter of the circumference of a circle concentric with the base 2 and an arc-shaped flow path that branches from the end of this arc-shaped flow path to the third suction path 613.

[0094] The actual shape of the ejector 50 may have a slight error from the designed shape. For example, in the configuration of Example 1 shown in FIG. 8 , this error causes a difference in the suction force between the suction holes 31 provided on the upper side and the suction holes 31 provided on the lower side. That is, the suction force becomes asymmetrical between the upper and lower sides. In Example 5, as shown in FIG. 12 , the first suction path 611 is configured to be circular, and the suction path 61 is configured so that the suction gas sucked from the suction holes 31 is temporarily collected in the fifth suction path 615, thereby minimizing the asymmetry of the suction force.

[0095] <Wafer Holding Device> The configuration of a wafer holding device 100 according to an embodiment will be described with reference to FIG. 1 . The wafer holding device 100 includes the wafer holder 1 according to the embodiment described above and a supply device 9. The supply device 9 supplies compressed gas to the gas inlet 32. In this embodiment, the supply device 9 includes the supply pipe 90 described above and a supply source 91 formed of a compressor. The supply source 91 is a device that generates compressed gas. The supply pipe 90 is a flow path that sends compressed gas from the supply source 91 to the gas inlet 32. In this example, the compressed gas is sent from the supply source 91 to the supply pipe 90 at a constant flow rate or constant pressure. The supply device 9 according to this example includes a pressure measurement unit 92, a valve 93, and a flow rate measurement unit 94. The wafer holding device 100 according to this example further includes a controller 110 that includes a first control unit 111 and a second control unit 112.

[0096] The controller 110 controls the operation of the wafer holding device 100. Each process performed by the first control unit 111 and the second control unit 112 is realized by a processing circuit including one or more processors. The processing circuit may be configured with an integrated circuit that combines one or more memories, various analog circuits, and various digital circuits in addition to the one or more processors. The processing circuit may also include an input / output I / F (Interface). The one or more memories store programs that cause the one or more processors to execute each of the processes. The one or more memories are typically ROM (Read-Only Memory) or RAM (Random Access Memory). The one or more processors may execute each of the processes according to the program read from the one or more memories, or according to a logic circuit designed in advance to execute each of the processes. The processor may be any of various processors suitable for computer control, such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Integrated Circuit). Note that the physically separated processors may cooperate with each other to execute the processes. For example, the processors installed in the physically separated computers may cooperate with each other via a network such as a LAN (Local Area Network), a WAN (Wide Area Network), or the Internet to execute the processes. The program may be installed into the memory from an external server device or the like via the network, or may be distributed in a state stored on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a semiconductor memory, and then installed into the memory from the recording medium.

[0097] As described above, when the wafer 10 is to be sucked onto the upper surface 21 of the base 2, compressed gas is supplied to the gas supply hole 32. The compressed gas supplied from the gas supply hole 32 is introduced through the input port 52 of the ejector 50 shown in FIG. 6, generating a suction force at the suction port 51. As a result, gas in the chamber 8 is sucked through the suction hole 31, creating a negative pressure between the wafer 10 and the upper surface 21, and the wafer 10 is sucked onto the upper surface 21. The flow rate of the compressed gas when the wafer 10 is being sucked is set so as to generate a predetermined suction force.

[0098] (Pressure Measurement Unit) The pressure measurement unit 92 measures the pressure of the compressed gas supplied to the air inlet 32. In this example, the pressure measurement unit 92 is provided in the supply pipe 90. The pressure measurement unit 92 measures the pressure of the compressed gas flowing through the supply pipe 90. The pressure measurement unit 92 is disposed downstream of the valve 93. "Downstream" means downstream in the direction in which the compressed gas flows. The pressure measurement unit 92 is configured by, for example, a pressure gauge.

[0099] (Detection 1 of Wafer Suction State) The wafer holding device 100 is configured to detect the suction state of the wafer 10 based on a change in pressure measured by the pressure measurement unit 92. The wafer holding device 100 can detect that the wafer 10 has been sucked onto the upper surface 21 of the base 2.

[0100] Detection method 1 for detecting the suction state of the wafer 10 from pressure changes of the compressed gas supplied to the gas supply hole 32 will be described below. The mechanism for detecting the suction state of the wafer 10 is as follows. The inventors discovered that when compressed gas is supplied at a constant flow rate, the pressure of the compressed gas flowing through the supply pipe 90 changes depending on the suction state of the wafer 10. When suction of the wafer 10 begins with the compressed gas flow rate kept constant, the pressure of the compressed gas gradually decreases as the wafer 10 approaches the top surface 21. When the wafer 10 approaches the top surface 21 to a certain extent, the pressure begins to decrease suddenly. When the wafer 10 is suctioned to the top surface 21, the pressure becomes approximately constant. In other words, the pressure changes between the start of suction of the wafer 10 and the end of suction of the wafer 10. If the pressure suddenly decreases and then becomes constant, it can be determined that the wafer 10 has been suctioned. Therefore, by measuring the pressure of the compressed gas using the pressure measurement unit 92 and monitoring the change in the pressure, it is possible to detect whether the wafer 10 has been properly suctioned. "The wafer 10 is properly adsorbed" means that the warpage of the wafer is corrected and the wafer is adsorbed onto the upper surface 21 of the base 2. More specifically, in this example, the wafer 10 is adsorbed while in contact with the protrusions 21 a and the ribs 21 b.

[0101] The inventors conducted a simulation experiment and obtained the following results. In this experiment, the relationship between the amount of warpage of the wafer 10 and the pressure of the compressed gas was investigated. The amount of warpage of the wafer 10 refers to the distance between the upper surface of the rib 21b and the lower surface of the peripheral edge of the wafer 10, as shown in FIGS. 3 and 4. Before the start of suction of the wafer 10, the amount of warpage of the wafer 10 is 1 mm. The flow rate of the compressed gas is constant during suction of the wafer 10. The relationship between the amount of warpage and the pressure during suction of the wafer 10 is shown in Table 1, and a graph of Table 1 is shown in FIG. 13. In Table 1, the pressure at each amount of warpage is expressed as 100%, with the pressure at a warpage of 1 mm being set as 100%. The pressure at zero amount of warpage indicates the pressure when the peripheral edge of the wafer 10 contacts the rib 21b. The horizontal axis of the graph in FIG. 13 represents the amount of warpage (mm), and the vertical axis represents the pressure (%).

[0102]

[0103] As shown in Table 1, the smaller the amount of warpage, i.e., the closer the wafer 10 is to the top surface 21, the lower the pressure. In this experiment, the pressure remained almost unchanged within the range of warpage from 1 mm to 0.2 mm. For example, the difference between the pressure when the amount of warpage was 1 mm and the pressure when the amount of warpage was 0.2 mm was less than 1%. Furthermore, when the amount of warpage was less than 0.2 mm, the pressure suddenly decreased. For example, the difference between the pressure when the amount of warpage was 0.2 mm and the pressure when the amount of warpage was zero was approximately 4%.

[0104] As can be seen from the above results, when the flow rate of the compressed gas is controlled to a constant value, a change in pressure occurs between the start of suction of the wafer 10 and the end of suction of the wafer 10. It is possible to determine whether the wafer 10 has been suctioned based on the change in pressure measured by the pressure measurement unit 92, i.e., the pressure difference per unit time. For example, by displaying the pressure measured by the pressure measurement unit 92 on a monitor (not shown), an operator can determine whether the wafer 10 has been properly suctioned based on the change in pressure. Furthermore, as will be described later, it is also possible for the first control unit 111 to determine whether the wafer 10 has been properly suctioned. Based on the determination result that the wafer 10 has been suctioned, for example, film formation on the wafer 10 is started.

[0105] (First Control Unit) The wafer holding device 100 of this example has a first control unit 111 that detects the suction state of the wafer 10. When compressed gas is supplied at a constant flow rate, the first control unit 111 calculates a change in pressure measured by the pressure measurement unit 92 and determines that the wafer 10 has been suctioned based on the change in pressure. Specifically, the first control unit 111 executes control to detect the suction state of the wafer 10 based on the pressure measured by the pressure measurement unit 92. The first control unit 111 calculates a pressure difference per unit time, which is the change in pressure, from the measurement result of the pressure measurement unit 92. The first control unit 111 determines that the wafer 10 has been properly suctioned when the pressure difference increases from the start of suction of the wafer 10, exceeds a predetermined first threshold, and then decreases to a predetermined second threshold or less.

[0106] (Valve) The valve 93 adjusts the flow rate of compressed gas supplied to the air inlet 32. In this example, the valve 93 is provided in the supply pipe 90. By adjusting the opening degree of the valve 93, the flow rate of compressed gas flowing through the supply pipe 90 is adjusted.

[0107] (Flow Rate Measuring Unit) The flow rate measuring unit 94 measures the flow rate of compressed gas supplied to the air inlet 32. In this example, the flow rate measuring unit 94 is provided in the supply pipe 90. The flow rate measuring unit 94 measures the flow rate of compressed gas flowing through the supply pipe 90. The flow rate measuring unit 94 is disposed downstream of the valve 93. The flow rate measuring unit 94 is configured by, for example, a flow meter.

[0108] (Detection of Wafer Suction State 2) The wafer holding device 100 may be configured to detect the suction state of the wafer 10 based on a change in the flow rate measured by the flow rate measuring unit 94 .

[0109] Detection Method 2, which is different from Detection Method 1 described above, will now be described. In Detection Method 2, the suction state of the wafer 10 is detected from changes in the flow rate of compressed gas supplied to the gas inlet 32. The inventors discovered that when compressed gas is supplied at a constant pressure, the flow rate of compressed gas flowing through the supply pipe 90 changes depending on the suction state of the wafer 10. When suction of the wafer 10 begins with the compressed gas pressure kept constant, the flow rate of the compressed gas gradually increases as the wafer 10 approaches the upper surface 21. When the wafer 10 approaches the upper surface 21 to a certain extent, the flow rate begins to increase suddenly. Once the wafer 10 is suctioned to the upper surface 21, the flow rate becomes approximately constant. In other words, the flow rate changes between the start of suction of the wafer 10 and the end of suction of the wafer 10. If the flow rate suddenly increases and then becomes constant, it can be determined that the wafer 10 has been suctioned. Therefore, by measuring the flow rate of the compressed gas using the flow rate measuring unit 94 and monitoring changes in the flow rate, it is possible to detect whether the wafer 10 has been properly suctioned.

[0110] The inventors conducted a simulation experiment and obtained the following results. In this experiment, the relationship between the amount of warpage of the wafer 10 and the flow rate of compressed gas was investigated. Before the start of suction of the wafer 10, the amount of warpage of the wafer 10 was 1 mm. The pressure of the compressed gas was constant during suction of the wafer 10. The relationship between the amount of warpage during suction of the wafer 10 and the flow rate is shown in Table 2, and a graph of Table 2 is shown in FIG. 14. In Table 2, the flow rate when the amount of warpage is 1 mm is set to 100%, and the flow rate for each amount of warpage is shown. The flow rate when the amount of warpage is zero indicates the flow rate when the peripheral edge of the wafer 10 contacts the rib 21b. The horizontal axis of the graph in FIG. 14 represents the amount of warpage (mm), and the vertical axis represents the flow rate (%).

[0111]

[0112] As shown in Table 2, the smaller the amount of warpage, i.e., the closer the wafer 10 is to the top surface 21, the greater the flow rate. In this experiment, the flow rate remained almost unchanged within the range of warpage from 1 mm to 0.1 mm. For example, the difference in flow rate between when the amount of warpage was 1 mm and when the amount of warpage was 0.1 mm was less than 1%. Furthermore, when the amount of warpage was less than 0.1 mm, the flow rate suddenly increased. For example, the difference in flow rate between when the amount of warpage was 0.1 mm and when the amount of warpage was zero was approximately 2%.

[0113] As can be seen from the above results, when the pressure of the compressed gas is controlled to a constant value, a change in the flow rate occurs between the start and end of suction of the wafer 10. It is possible to determine whether the wafer 10 has been suctioned based on the change in the flow rate measured by the flow rate measurement unit 94, i.e., the difference in flow rate per unit time. For example, by displaying the flow rate measured by the flow rate measurement unit 94 on a monitor (not shown), an operator can determine whether the wafer 10 has been properly suctioned based on the change in the flow rate. Furthermore, as will be described later, it is also possible for the first control unit 111 to determine whether the wafer 10 has been properly suctioned. Based on the determination result that the wafer 10 has been suctioned, for example, film formation on the wafer 10 is started.

[0114] When the compressed gas is supplied at a constant pressure, the first control unit 111 calculates a change in the flow rate measured by the flow rate measurement unit 94 and determines that the wafer 10 has been adsorbed based on the change in the flow rate. Specifically, the first control unit 111 executes control to detect the adsorption state of the wafer 10 based on the flow rate measured by the flow rate measurement unit 94. The first control unit 111 calculates a flow rate difference per unit time, which is a change in the flow rate, from the measurement result of the flow rate measurement unit 94. The first control unit 111 determines that the wafer 10 has been properly adsorbed when the flow rate difference increases from the start of adsorption of the wafer 10 to exceed a predetermined first threshold, and then decreases to a predetermined second threshold or less.

[0115] (Control of Wafer Suction State) The wafer holding device 100 is configured to control the suction state of the wafer 10 to be released by controlling the flow rate of the compressed gas with the valve 93. This control allows the wafer 10 that has been sucked onto the upper surface 21 of the base 2 to be easily removed.

[0116] The mechanism for easily removing the wafer 10 is as follows. The inventors discovered that by reducing the flow rate of the compressed gas when the wafer 10 is adsorbed, the compressed gas introduced from the input port 52 can flow to the suction port 51 of the ejector 50 shown in FIG. 6 without generating a suction force at the suction port 51. The compressed gas flows from the input port 52 to the suction port 51 and flows out through the suction holes 31. This creates a positive pressure between the wafer 10 and the upper surface 21, causing the wafer 10 to detach from the upper surface 21. In other words, the wafer 10 is released from adsorption, allowing the wafer 10 to be easily removed. Therefore, by controlling the flow rate of the compressed gas with the valve 93, it is possible to control the adsorption state of the wafer 10. Specifically, by controlling the flow rate, it is possible to control the adsorption and release of the wafer 10. The flow rate of the compressed gas when releasing the adsorption of the wafer 10 may be set so as not to generate a suction force.

[0117] The inventors conducted a simulation experiment and obtained the following results. In this experiment, the change in pressure at the suction port 51 was investigated when the flow rate of the compressed gas was reduced from a state in which the wafer 10 was suctioned. Based on the operating principle of the ejector 50 described with reference to FIG. 6 , it was generally believed that a reduction in the flow rate of the compressed gas would simply result in a decrease in suction force. However, this experiment revealed that the pressure at the suction port 51 changed from negative to positive by reducing the flow rate of the compressed gas to a very small amount. In this experiment, for example, when the flow rate of the compressed gas became 0.3 liters / minute or less, the pressure at the suction port 51 changed from negative to positive.

[0118] The flow rate of compressed gas when releasing suction of wafer 10 can be determined in advance as a flow rate at which negative pressure changes to positive pressure, depending on the configuration of wafer holder 1, for example, the configuration of each hole, such as suction hole 31, air supply hole 32, and exhaust hole 33, the configuration of each path, such as suction path 61, air supply path 62, and exhaust path 63, and the number of ejectors 50. The configuration of each hole and path refers to, for example, the cross-sectional size and flow path length of each hole and path. This determined flow rate can be used as a threshold value to determine whether suction of wafer 10 has been released.

[0119] As can be seen from the above results, when removing the wafer 10, the suction of the wafer 10 can be released by controlling the flow rate of the compressed gas to a predetermined value or less. In other words, it is possible to determine whether the wafer 10 is ready for removal based on the flow rate. For example, the flow rate measured by the flow rate measuring unit 94 can be displayed on a monitor (not shown), and an operator can adjust the opening of the valve 93 to control the flow rate of the compressed gas, thereby controlling the suction of the wafer 10 to a released state. Furthermore, as will be described later, the suction of the wafer 10 can also be controlled to a released state by controlling the flow rate of the compressed gas using the second control unit 112. For example, after film formation on the wafer 10 is completed, the suction of the wafer 10 is released, and the wafer 10 is automatically replaced.

[0120] (Second Control Unit) The wafer holding device 100 of this example has a second control unit 112 that adjusts the aperture of the valve 93 to control the flow rate of the compressed gas. The second control unit 112 can control the valve 93 so that the flow rate of the compressed gas is constant. Furthermore, by controlling the flow rate, the second control unit 112 can control the wafer 10 to a state in which the suction of the wafer 10 is released. Specifically, the second control unit 112 adjusts the aperture of the valve 93 to control the flow rate to a predetermined threshold or less, thereby controlling the wafer 10 to a state in which it can be removed.

[0121] REFERENCE SIGNS LIST 1 wafer holder 2 base 21 upper surface, 22 lower surface, 23 outer peripheral surface 2a first plate, 2b second plate, 2c third plate 21a convex portion, 21b rib 31 suction hole, 32 air supply hole, 33 exhaust hole 31a first suction hole, 31b second suction hole 4 heater 40 heating element 5 groove 50 ejector 51 suction port 52 input port, 52a nozzle 53 diffuser 531 inlet portion, 532 outlet portion 61 suction path 611 first suction path, 612 second suction path, 613 third suction path 614 fourth suction path, 615 fifth suction path, 616 sixth suction path 617 seventh suction path, 618 eighth suction path, 619 ninth suction path 62 air supply path 621 First gas supply passage 622 Second gas supply passage 623 Third gas supply passage 624 Fourth gas supply passage 625 Fifth gas supply passage 63 Exhaust passage 7 Support 71 First end 72 Second end 8 Chamber 80 Through hole 81 Shower head 9 Supply device 90 Supply pipe 91 Supply source 92 Pressure measurement unit 93 Valve 94 Flow rate measurement unit 10 Wafer 100 Wafer holding device 110 Controller 111 First control unit 112 Second control unit

Claims

1. A wafer holder comprising a plate-shaped substrate and an ejector disposed inside the substrate, the ejector having a suction port, an input port, a nozzle, and a diffuser, the substrate having an upper surface on which a wafer is placed, a lower surface located opposite to the upper surface, an outer peripheral surface connecting the upper surface and the lower surface, a suction hole provided in the upper surface, an air supply hole provided in the lower surface or the outer peripheral surface, an exhaust hole provided in the lower surface or the outer peripheral surface, a suction passage connecting the suction port and the suction hole, an air supply passage connecting the input port and the air supply hole, and an exhaust passage connecting the diffuser and the exhaust hole.

2. The wafer holder according to claim 1, wherein the substrate has a first plate and a second plate joined to each other vertically at a joint surface, and one or both of the joint surface of the first plate and the joint surface of the second plate have grooves, and the ejector is constituted by the grooves.

3. The wafer holder according to claim 2, wherein a cross-sectional shape of the groove perpendicular to a direction in which the groove extends is rectangular.

4. The wafer holder according to claim 1, wherein the ejector is constituted by components independent of the substrate.

5. The wafer holder according to any one of claims 1 to 4, wherein the ejector has a plurality of ejectors, and the air supply passage branches from the air supply hole to each of the input ports of the plurality of ejectors.

6. The wafer holder according to any one of claims 1 to 5, wherein the suction hole has a plurality of suction holes, and the suction passage branches from the suction port to each of the plurality of suction holes.

7. A wafer holding device comprising the wafer holder according to any one of claims 1 to 6 and a supply device for supplying compressed gas to the air supply hole.

8. The wafer holding device according to claim 7, wherein the supply device has a pressure measurement unit for measuring a pressure of the compressed gas supplied to the air supply hole, and detects an adsorption state of the wafer based on a change in the pressure measured by the pressure measurement unit.

9. The wafer holding device according to claim 7, wherein the supply device has a flow rate measurement unit for measuring a flow rate of the compressed gas supplied to the air supply hole, and detects an adsorption state of the wafer based on a change in the flow rate measured by the flow rate measurement unit.

10. The supply device has a valve for adjusting the flow rate of the compressed gas supplied to the air supply hole, and controls the flow rate by the valve to control the state in which the adsorption of the wafer is released. The wafer holding device according to any one of claims 7 to 9.

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