Wafer Inspection Equipment

Abstract

A wafer inspection device (10) according to the present invention comprises a wafer chuck (200) on which a wafer (205) can be mounted. The wafer chuck (200) comprises: an air supply port (204) that supplies air to a wafer (205); an air discharge port (203) that discharges the air; a clamp mechanism (206) that holds the wafer (205); and a plurality of annular projections (2011). A distribution of pressure between the wafer chuck (200) and the wafer (205) in the radial direction of the wafer chuck when the wafer chuck (200) is not equipped with the annular projections (2011) and the wafer chuck (200) is rotated is represented by a higher-order function of a position in the radial direction. The annular projections (2011) have a shape where the value of pressure loss caused by the annular projections (2011) when the wafer chuck (200) rotates and air is supplied is at least the value of the pressure in the distribution of pressure represented by the higher-order function at the same position as the position in the radial direction to which the value of the pressure loss was imparted.

Description

[Technical Field]

[0001] The present invention relates to an inspection apparatus for inspecting a wafer. [Background technology]

[0002] In the semiconductor manufacturing process, the presence of foreign matter on a substrate such as a semiconductor wafer can cause defects such as poor insulation of wiring or short circuits. There are various types of foreign matter, including those generated from moving parts such as transport devices, those generated from the human body, those generated by reactions with process gases inside processing equipment, and those that have been mixed in chemicals or materials.

[0003] Therefore, by using wafer inspection equipment to detect and manage foreign matter on the wafer surface, it is possible to monitor and control the dust generation status of each manufacturing device and the cleanliness of each process, thereby improving product quality and yield, etc. The method of foreign matter inspection involves irradiating light such as laser light onto the wafer surface and detecting the light scattered from the foreign matter, thereby detecting the size and attachment position of the foreign matter, and acquiring this as unique information for each wafer.

[0004] During inspection, wafers are fixed to a holding device. Wafer fixing methods can be broadly divided into backside suction and backside non-contact methods. Backside suction is a method in which the backside of the wafer is sucked by an air suction port on a flat table. Therefore, the backside of the wafer is in contact with the table and fixed. On the other hand, backside non-contact is a method in which only the outer periphery of the wafer is held and fixed to the table. Backside suction is mainly used for wafers on which patterns have been formed. Backside non-contact is used for wafers before pattern formation, i.e., bare wafers. Backside non-contact wafer inspection equipment in particular is used for wafer shipping inspections at manufacturing manufacturers and wafer receiving inspections at process manufacturers, so there is a demand for not only preventing foreign matter from adhering to wafers, but also for improved reproducibility and accuracy in foreign matter detection.

[0005] One method for improving the accuracy of detecting foreign particles on a wafer is to improve the flatness of the wafer. When a wafer is fixed flat in an inspection device, the wafer is not significantly deformed (for example, warped), and therefore the accuracy of detecting foreign particles can be improved. An example of a conventional technique for improving the flatness of a wafer is described in Patent Document 1.

[0006] The inspection device described in Patent Document 1 includes a chuck having a ring-shaped rim that conforms to the shape of the wafer and on which the wafer is placed, and a ring-shaped air gap forming portion disposed on the surface of the chuck, and the internal space surrounded by the wafer, chuck, and rim is maintained at a predetermined pressure distribution by gas supplied into the internal space, and a predetermined amount of air gap is constantly formed between the air gap forming portion and the wafer, thereby correcting flexure and warpage of the wafer. The inspection device in Patent Document 1 also includes a height position control portion that detects height information near the corrected inspection point on the wafer and drives an elevation drive mechanism to control the vertical movement position of the inspection point that could not be fully corrected, thereby controlling the inspection surface of the wafer to a predetermined height position. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-168479 Summary of the Invention [Problem to be solved by the invention]

[0008] Conventional wafer inspection devices have not always fully satisfied users in terms of maintaining wafer flatness with a simple configuration. For example, the inspection device described in Patent Document 1 ensures wafer flatness by applying gas pressure to the backside of the wafer and dynamically controlling the wafer surface. Because this control is performed in real time on a wafer rotating at high speed during inspection, the control circuitry becomes large. Furthermore, correcting wafer warpage deviation to zero requires addressing the second- and third-order components of rotation, which requires complex control. Furthermore, the proximity of the correction drive frequency to the wafer's natural frequency can cause self-excited vibration of the wafer, potentially degrading wafer flatness.

[0009] An object of the present invention is to provide a wafer inspection device that can hold a wafer flat with a simple configuration. [Means for solving the problem]

[0010] A wafer inspection device according to the present invention includes a rotatable wafer chuck on which a wafer can be placed. The wafer chuck includes an air supply port for supplying air to the backside of the wafer, an air exhaust port for exhausting the air, a clamping mechanism for holding the wafer, and a plurality of annular protrusions protruding upward. The wafer chuck, assuming that the annular protrusions are not included, has a pressure distribution between the wafer and the wafer in the radial direction of the wafer chuck when the wafer chuck rotates, which is expressed by a high-order function of position in the radial direction. The annular protrusions are shaped so that when the wafer chuck rotates and the air is supplied, the value of the pressure loss caused by the annular protrusions is equal to or greater than the pressure value in the pressure distribution expressed by the high-order function at the same radial position at which the pressure loss value is applied. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a wafer inspection device that can hold a wafer flat with a simple configuration. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing the configuration of a wafer inspection device according to a first embodiment of the present invention. [Figure 2A] FIG. 2 is a perspective view showing a wafer chuck. [Figure 2B] 2B is an enlarged view of the center of the wafer chuck taken along the cross section AA in FIG. 2A. FIG. [Figure 2C] 2B is an enlarged view of the clamp mechanism and its vicinity taken along the line AA in FIG. 2A. FIG. [Figure 3A] FIG. 2 is a view of the wafer chuck on which the wafer is placed, viewed from above the wafer. [Figure 3B] FIG. 3B is a diagram showing a cross section BB in FIG. 3A. [Figure 4A] FIG. 10 is a diagram illustrating the concept of correction pressure. [Figure 4B] 10A and 10B are diagrams illustrating a correction method using a correction pressure when a plurality of ribs are arranged on a wafer chuck. [Figure 5] 10 is a graph showing the change in pressure loss caused by the rib when the distance between the wafer and the rib is changed. [Figure 6A] FIG. 10 is a diagram showing the positional relationship between the wafer chuck and the optical system immediately after the wafer is placed on the wafer chuck. [Figure 6B] FIG. 10 is a diagram showing a state in which the measurement position of the height sensor coincides with the center of the wafer due to linear movement of the wafer chuck. [Figure 6C] FIG. 10 is a diagram showing the wafer chuck moved to a position where the rotation center of the wafer chuck coincides with the geometric center of the optical measurement unit. [Figure 7] 10 is a flowchart showing the operation of the wafer inspection device in the second embodiment. [Figure 8] FIG. 10 is a diagram schematically illustrating the pressure distribution of the correction air when the wafer chuck described in the first embodiment is used and the pressure distribution of the correction air when a conventional wafer chuck is used. [Figure 9] FIG. 10 is a diagram showing the measurement results of the average height in the circumferential direction of the wafer at each position in the radial direction of the wafer. [Figure 10A] FIG. 10 is a diagram showing the analysis results obtained by examining, by fluid-structure coupled analysis, the change in flatness in the radial direction of the wafer relative to the amount of correction air when a downwardly convex deformed wafer is placed on the wafer chuck of Example 1. [Figure 10B] FIG. 10 is a diagram showing the analysis results obtained by examining, by fluid-structure coupled analysis, the change in flatness in the radial direction of the wafer relative to the amount of correction air when an upwardly convex deformed wafer is placed on the wafer chuck of Example 1. [Figure 10C] FIG. 10 shows the results of comparing the radial shape of a wafer with a downward convex deformation obtained by fluid-structure interaction analysis with the shape before the deformation was corrected. [Figure 10D] FIG. 10 shows the results of comparing the radial shape of a wafer with an upward convex deformation obtained by fluid-structure interaction analysis with the shape before the deformation was corrected. DETAILED DESCRIPTION OF THE INVENTION

[0013] The wafer inspection device according to the present invention discharges air onto the back surface (lower surface) of the wafer to generate pressure, and uses this pressure to correct deformation (or flatness) of the wafer, thereby keeping the wafer flat. In the wafer inspection device according to the present invention, the wafer chuck on which the wafer is placed is equipped with an annular protrusion that corrects deformation (or flatness) of the wafer, and the shape of the annular protrusion is determined based on the appropriate distribution of correction pressure generated between the wafer and the wafer chuck by air, so that the wafer can be efficiently kept flat with a simple configuration.

[0014] In the present invention, wafer flatness is an index showing whether a wafer is flat. The wafer flatness is expressed, for example, as the height distance between the top and bottom positions of a wafer that is deformed due to warpage or the like when placed on a wafer inspection device. A wafer being flat means that the flatness of the wafer falls within a predetermined range.

[0015] A wafer inspection device according to an embodiment of the present invention will be described below with reference to the drawings. [Example]

[0016] A wafer inspection device according to a first embodiment of the present invention will be described. In the wafer inspection device according to this embodiment, the shape of annular protrusions (hereinafter referred to as "ribs") that correct wafer deformation (or flatness) is determined based on an appropriate distribution of correction pressure in the radial direction of the wafer chuck. The shape of the ribs includes the size of the ribs (for example, the protruding height and the width, which is the length in the radial direction).

[0017] 1 is a schematic diagram showing the configuration of a wafer inspection apparatus 10 according to this embodiment. The wafer inspection apparatus 10 includes, as its main components, a wafer introduction unit 11 that introduces a wafer 205 from outside, a transport mechanism 12 that transports the wafer 205, an inspection chamber 13 that inspects the wafer 205, and a control unit 14 that controls the entire wafer inspection apparatus 10. The wafer inspection apparatus 10 is installed in a space where cleanliness is maintained to prevent foreign matter from adhering to the wafer 205.

[0018] The inspection chamber 13 includes an optical measurement unit 131 that optically measures foreign particles on a wafer 205, a wafer chuck 200 on which the wafer 205 is placed, a motor 132 that rotates the wafer chuck 200, and a linear movement unit 133 that linearly moves the motor 132 and the wafer chuck 200. The optical measurement unit 131 is fixed in position. Therefore, the wafer 205 placed on the wafer chuck 200 rotates with the rotation of the wafer chuck 200, and changes position with the linear movement of the wafer chuck 200, and the position and size of foreign particles present on the surface are measured by the optical measurement unit 131.

[0019] Hereinafter, the directions along the surface (wafer surface) of the wafer 205 placed on the wafer chuck 200 will be referred to as the XY direction or horizontal direction, and the direction perpendicular to the wafer surface will be referred to as the Z direction or vertical direction. The rotation axis of the motor 132 faces the Z direction. The wafer chuck 200 and the wafer 205 placed on the wafer chuck 200 rotate around the Z direction (vertical direction) as their rotation axis and move linearly in the XY direction (horizontal direction). Furthermore, the radial direction and circumferential direction refer to the radial direction and circumferential direction of the wafer chuck 200 (or the wafer 205 placed on the wafer chuck 200). The inside in the radial direction (center side) will be referred to as the inner circumferential side, and the outside in the radial direction will be referred to as the outer circumferential side. The outer circumferential portion is the part on the outside in the radial direction.

[0020] The wafer 205 is stored in a cassette (not shown) and loaded into the wafer introduction section 11. Thereafter, the wafer 205 is removed from the cassette by the transfer mechanism 12 and moved to the inspection chamber 13. The wafer 205 moved to the inspection chamber 13 by the transfer mechanism 12 is placed on the wafer chuck 200.

[0021] Fig. 2A is a perspective view showing a wafer chuck 200. In Fig. 2A, a wafer 205 placed on the wafer chuck 200 is separated from the wafer chuck 200, and the wafer chuck 200 is depicted in a transparent manner.

[0022] The wafer 205 is placed on the upper part of the wafer chuck 200. That is, the wafer 205 is placed at a position opposite to the direction in which gravity acts on the wafer chuck 200 (gravity direction).

[0023] The wafer chuck 200 includes a wafer chuck base 201, a wafer support 202, an air supply port 204, an air exhaust port 203, a clamping mechanism 206, and a plurality of ribs 2011. The wafer chuck 200 is capable of placing a wafer 205 thereon and is rotatable around the Z direction (vertical direction) as the rotation axis. The wafer chuck 200 may include a plurality of clamping mechanisms 206.

[0024] The wafer chuck base 201 is the main body (base) of the wafer chuck 200.

[0025] The wafer support part 202 is ring-shaped and vertically supports the outer peripheral surface of the wafer 205. As will be described later, the wafer support part 202 includes a plurality of contact parts 202a that are portions that come into contact with the wafer 205, and a plurality of non-contact parts 202b that do not come into contact with the wafer 205 and have a gap between them.

[0026] The air supply port 204 is an opening that supplies air (correction air) to the rear surface (lower surface) of the wafer 205 to correct deformation (or flatness) of the wafer 205, and is provided in the center of the wafer chuck 200.

[0027] The air outlet 203 is formed by the non-contact portion 202 b and discharges the correction air supplied to the rear surface of the wafer chuck 200 to the outside of the wafer chuck 200 .

[0028] The clamping mechanism 206 is a mechanism for holding the wafer 205 .

[0029] The rib 2011 is an annular protrusion provided on the surface of the wafer chuck 200 facing the wafer 205, and protrudes upward from the wafer chuck base 201. The multiple ribs 2011 are arranged concentrically around the rotation axis of the wafer chuck 200.

[0030] The wafer 205 placed on the wafer chuck 200 is held by a clamping mechanism 206 so as not to fall off the wafer chuck 200. Furthermore, the wafer 205 placed on the wafer chuck 200 partially sinks due to its own weight due to the action of gravity, causing deformation such as warping and making it non-flat (i.e., reducing flatness). Therefore, in the wafer inspection apparatus 10 according to this embodiment, pressure is generated by air (correction air) discharged from the air supply port 204 onto the back surface of the wafer 205, thereby preventing the wafer 205 from sinking due to its own weight and correcting the deformation (or flatness) of the wafer 205. Correction of the flatness of the wafer 205 will be described later.

[0031] The wafer chuck 200 holding the wafer 205 whose flatness has been improved in the above manner is rotated by the motor 132 and moved linearly by the linear movement part 133 in a direction perpendicular to the rotation axis of the motor 132 so that the optical measurement part 131 can measure foreign matter present on the surface of the wafer 205.

[0032] The control unit 14 rotates and moves the wafer chuck 200 holding the wafer 205 as described above, maps the size and position of foreign particles over the entire surface of the wafer 205, and records the data obtained from this mapping as foreign particle data for the wafer 205.

[0033] After the foreign matter measurement is completed, the wafer 205 is released from the clamping mechanism 206, and is transferred by the transfer mechanism 12 from the wafer chuck 200 to the wafer introduction section 11, where it is housed in a cassette.

[0034] The wafer inspection device 10 repeats the above operations to inspect all the wafers 205 accommodated in the cassettes of the wafer introduction section 11 for foreign matter.

[0035] Next, the clamping mechanism 206 and the operation of the clamping mechanism 206 to hold the wafer 205 will be described.

[0036] 2B is an enlarged view of the center of the wafer chuck 200 taken along the AA cross section in FIG. 2A. FIG. 2C is an enlarged view of the clamping mechanism 206 and its vicinity taken along the AA cross section in FIG. 2A. In FIGS. 2B and 2C, the black and white arrows indicate the movement direction of each component. The black arrow indicates the movement direction of the component when the clamping mechanism 206 holds the wafer 205. The white arrow indicates the movement direction of the component when the clamping mechanism 206 releases the hold on the wafer 205.

[0037] The clamping mechanism 206 is provided on a wafer chuck 200 that rotates the wafer 205 , and includes a cam 211 , a bearing 213 , a bearing holder 214 , a compression spring 215 , a rod 216 , a link 217 , a holder 218 , and a holding claw 219 .

[0038] The cam 211 is installed in the center of the wafer chuck base 201, and is attached to an air cylinder 212 that moves in the vertical direction (Z direction), and moves in the vertical direction.

[0039] The bearing 213 contacts the cam 211 and converts the vertical movement of the cam 211 into radial (XY) movement.

[0040] The bearing holder 214 holds the bearing 213 and is connected to a compression spring 215 .

[0041] The compression spring 215 is connected to the bearing holder 214 and the rod 216 and is radially expandable and contractible.

[0042] The rod 216 is connected to a compression spring 215 and is movable relative to the bearing holder 214 in the radial direction by expansion and contraction of the compression spring 215 .

[0043] The link 217 connects the rod 216 and the holding portion 218, and when the rod 216 moves in the radial direction, the holding portion 218 is displaced in the circumferential direction.

[0044] The holding portion 218 is rotatable around the dashed line in FIG. 2C and holds the holding claws 219. The direction of the rotation axis of the holding portion 218 is the Z direction (the direction perpendicular to the surface of the wafer 205). The link 217 and the holding claws 219 are attached to the holding portion 218 at positions symmetrical with respect to the rotation axis.

[0045] The holding claws 219 are attached to the holding unit 218, and can move as the holding unit 218 rotates, thereby coming into contact with the wafer 205. The movement direction of the holding claws 219 is the XY direction (direction along the surface of the wafer 205). The clamping mechanism 206 holds the wafer 205 when the holding claws 219 come into contact with the wafer 205, and releases the wafer 205 when the holding claws 219 are no longer in contact with the wafer 205. Furthermore, it is preferable that the holding claws 219 be rotatable relative to the holding unit 218. The direction of the rotation axis of the holding claws 219 can be, for example, the Z direction. That is, the holding claws 219 can rotate sideways (rotation in a direction along the surface of the wafer 205).

[0046] The clamping mechanism 206 is operated by the movement of air supplied to the air cylinder 212. For example, when the air cylinder 212 is operated by air and the cam 211 moves upward, the holding claws 219 move in the radial direction and move away from the wafer 205, and are no longer in contact with the wafer 205. In the clamping mechanism 206, the mechanisms excluding the air cylinders 212 and cams 211 are arranged symmetrically with respect to the central axis of the wafer chuck 200. The number of clamping mechanisms 206 excluding the air cylinders 212 and cams 211 is determined taking into consideration the holding force generated by the clamping mechanisms 206 and the holding force required for the clamping mechanisms 206.

[0047] The operation of the clamping mechanism 206 is described below.

[0048] After the wafer 205 is transported to the inspection chamber 13 by the transport mechanism 12, as shown in FIG. 2B, air is supplied to the air cylinder 212, causing the cam 211 to move upward and the rod 216 to move inward (in the direction of the white arrow in FIG. 2B). When the rod 216 moves inward, the link 217 is displaced inward following the movement of the rod 216, as shown in FIG. 2C. This causes the holder 218 to rotate, and the holding claws 219, which are positioned symmetrically to the link 217 about the rotation axis, are displaced outward (in the direction of the white arrow in FIG. 2C). This displacement causes the holding claws 219 to move outward beyond the outer edge of the wafer 205. In this way, the holding claws 219 of the wafer chuck 200 open outward, and the wafer chuck 200 is ready to load the wafer 205.

[0049] Thereafter, the transfer mechanism 12 places the wafer 205 on the wafer support portion 202 arranged on the wafer chuck 200. After the transfer mechanism 12 has placed the wafer 205, it leaves the inspection chamber 13.

[0050] After the transfer mechanism 12 exits, the clamp mechanism 206 stops supplying air to the air cylinder 212. This causes the cam 211 to move downward, causing the rod 216 to move toward the outer periphery (in the direction of the black arrow in FIG. 2B). As the rod 216 moves toward the outer periphery, the holder 218 rotates, causing the holding claws 219 to move toward the inner periphery (in the direction of the black arrow in FIG. 2C). This displacement causes the holding claws 219 to come into contact with the outer periphery of the wafer 205, generating a holding force. During this operation, the bearing holder 214, compression spring 215, and rod 216 move toward the outer periphery together until the holding claws 219 come into contact with the outer periphery of the wafer 205.

[0051] After the holding claws 219 come into contact with the wafer 205, the rod 216 stops moving, but the bearing holder 214 continues to move toward the outer periphery until the movement of the cam 211 finishes. This movement of the bearing holder 214 reduces the relative distance between the bearing holder 214 and the rod 216, causing the compression spring 215 to compress. Then, the compression spring 215 generates a spring force due to a reaction force, and this force is transmitted to the holding claws 219.

[0052] In this way, the spring force of the compression spring 215 becomes the holding force with which the holding claws 219 hold the wafer 205 in the X and Y directions (directions along the surface of the wafer 205). The spring force of the compression spring 215 is determined by the ratio of the distance from the center of rotation (fulcrum) of the holder 218 to the joint (point of force) between the link 217 and the rod 216, to the distance from this center of rotation to the holding claws 219 (point of action). In this way, the holding claws 219 of the wafer chuck 200 come into contact with the wafer 205 and hold the wafer 205.

[0053] It is preferable that the holding claws 219 are detachable from the holding portion 218. If the holding claws 219 are detachable, when the holding claws 219 become worn, they can be reattached to the holding portion 218 so that the surfaces of the holding claws 219 that come into contact with the wafer 205 are different from the previous surfaces (so that new surfaces are formed). In this way, the worn holding claws 219 can be reused, thereby extending the life of the holding claws 219.

[0054] The shape of the holding claws 219 can be determined arbitrarily, and can be, for example, cylindrical or rectangular. The holding claws 219 are fitted into, for example, the holding portion 218. If the holding claws 219 are cylindrical, the surfaces of the holding claws 219 that come into contact with the wafer 205 can be set arbitrarily, thereby further extending the life of the holding claws 219. If the holding claws 219 are rectangular, there is an advantage that the holding claws 219 can be prevented from rotating at the fitting portion with the holding portion 218, allowing the clamp mechanism 206 to more securely hold the wafer 205. The shape of the holding claws 219 can be determined, for example, in consideration of the strength of the fitting between the holding claws 219 and the holding portion 218.

[0055] In this embodiment, the holding claw 219 is described as rotating laterally (rotating in the Z direction with the rotation axis in the Z direction), but the holding claw 219 may also rotate vertically (rotating in the direction perpendicular to the Z direction with the rotation axis in the Z direction).

[0056] The holding force of the clamp mechanism 206 will now be described. The functions required for the clamp mechanism 206 to hold the wafer 205 are primarily the alignment function when the wafer 205 is placed, the function to prevent slippage when rotation begins, and the function to resist centrifugal force caused by eccentricity of the wafer 205 during steady rotation. The alignment function when the wafer 205 is placed is achieved by static holding force. This is the holding force generated by the compression spring 215 of the clamp mechanism 206. Regarding the functions to prevent slippage and resist centrifugal force, the centrifugal force generated by each component of the clamp mechanism 206 is added to the holding force, so this centrifugal force must also be taken into consideration. At the start of rotation, a holding force greater than the inertial force that tries to stop the wafer 205 is required. During steady rotation, a holding force greater than the centrifugal force calculated by adding up the eccentricity, mass, and rotation speed of the wafer 205 is required. The holding force that resists these forces can be adjusted by adjusting the shapes and masses of components such as the bearing 213, bearing holder 214, rod 216, and link 217.

[0057] The following describes the multiple ribs 2011 provided on the wafer chuck 200. The ribs 2011 are annular protrusions that correct deformation (or flatness) of the wafer 205.

[0058] Fig. 3A is a view of the wafer chuck 200 with the wafer 205 placed thereon, viewed from above (in the +Z direction) the wafer 205. Fig. 3B is a view showing the cross section BB in Fig. 3A. In Fig. 3B, the flow of correction air (air for correcting deformation (or flatness) of the wafer 205) is indicated by arrows.

[0059] As described above, the wafer chuck 200 on which the wafer 205 is placed supplies corrective air from the air supply port 204 to the rear surface (bottom surface) of the wafer 205 to correct deformation of the wafer 205 and hold the wafer 205 flat. As already described, the wafer 205 is held on the wafer chuck 200 by the holding force of the holding claws 219 of the clamping mechanism 206.

[0060] As shown in FIG. 3A, the wafer support portion 202 of the wafer chuck 200 includes a contact portion 202a, which is the portion that actually comes into contact with the wafer 205, and a non-contact portion 202b, which does not come into contact with the wafer 205 and has a gap between it and the wafer 205.

[0061] 3B, the corrective air flows into wafer chuck 200 through air supply port 204, flows radially outward through the gap between the backside of wafer 205 and wafer chuck base 201, and is discharged to the outside of wafer chuck 200 through non-contact portion 202b (air discharge port 203) of wafer support portion 202. In order to efficiently correct deformation of wafer 205 and ensure flatness using the corrective air, wafer chuck 200 is provided with a plurality of ribs 2011 on the surface facing wafer 205. As described above, ribs 2011 are annular protrusions and are installed on wafer chuck base 201 in a concentric circle around the rotation axis of wafer chuck 200.

[0062] Here, the concept of correcting the deformation (or flatness) of the wafer 205 by the pressure applied to the wafer 205 by the correction air will be described. Hereinafter, the pressure applied to the wafer 205 by the correction air to correct the deformation of the wafer 205 will be referred to as the correction pressure. The correction pressure is the pressure generated between the wafer 205 and the wafer chuck 200 by the correction air.

[0063] FIG. 4A is a diagram illustrating the concept of compensation pressure. FIG. 4A schematically illustrates three types of pressure distributions between the wafer 205 and the wafer chuck 200 in the radial direction when the wafer chuck 200 rotates. The left part of FIG. 4A illustrates the pressure distribution in the wafer chuck 200 when the ribs 2011 are not provided and compensation air is not supplied (pressure distribution without ribs). The center part of FIG. 4A illustrates the compensation pressure distribution generated by the ribs 2011 (pressure distribution with ribs). The right part of FIG. 4A illustrates the pressure distribution (total pressure distribution) obtained by combining the pressure distribution without ribs and the pressure distribution with ribs. The total pressure distribution is the pressure distribution in the wafer chuck 200 when the ribs 2011 are provided and compensation air is supplied. The cross between the left and center diagrams of FIG. 4A represents the combination of the pressure distributions.

[0064] 4A, the idea behind the corrective pressure applied to the wafer 205 is to generate a corrective pressure (pressure due to the rib 2011) by the rib 2011 for the pressure distribution without the rib, and then combine the two to obtain a total pressure distribution that is applied to the wafer 205. In other words, the pressure distribution without the rib is corrected by the pressure distribution due to the rib to obtain the total pressure distribution.

[0065] When a wafer chuck 200 without ribs 2011 rotates with a wafer 205 placed thereon, a centrifugal force of rotation is generated in the space between the wafer 205 and the wafer chuck 200, expelling air from the space. This results in a pressure distribution in which the pressure at the center of the wafer chuck 200 is the maximum negative pressure (a pressure lower than atmospheric pressure) and the pressure at the outermost periphery of the wafer chuck 200 is atmospheric pressure (the pressure distribution without ribs in FIG. 4A). That is, in the pressure distribution without ribs, the pressure increases from the center to the outer periphery of the wafer chuck 200 (as the radial position r of the wafer chuck 200 increases).

[0066] The pressure distribution without ribs is basically a distribution in which the pressure is expressed as the square of the radial position r of the wafer chuck 200 (the radial position r of the wafer chuck 200 has the position of the rotation axis of the wafer chuck 200 as its origin). However, considering that compensation air is supplied to the center of the wafer chuck 200, this pressure distribution is a distribution in which the pressure can be approximated by a function of the cube of the radial position r of the wafer chuck 200. Using a higher-order function allows for a more accurate representation of the pressure distribution.

[0067] In this embodiment, a pressure distribution without ribs when the wafer chuck 200 rotates is obtained in advance using fluid analysis, and an approximate curve representing this pressure distribution is prepared. The approximate curve representing the pressure distribution without ribs is a curve expressed as a high-order function of the radial position r of the wafer chuck 200, and is obtained by performing fluid analysis on a model of the wafer chuck 200 on which the wafer 205 is placed, under the conditions that no compensation air is supplied to the wafer chuck 200 and the wafer chuck 200 does not have ribs 2011. Any existing method can be used for the fluid analysis.

[0068] In this embodiment, the approximate curve thus obtained, that is, the curve expressed by a high-order function of the radial position r of the wafer chuck 200, is treated as a pressure distribution without ribs.

[0069] In this embodiment, the shape of the ribs 2011 is determined so that when the wafer chuck 200 rotates and correction air is supplied, the pressure loss caused by the ribs 2011 can cancel out the pressure in the pressure distribution without the ribs. Specifically, the shape of the ribs 2011 is determined so that the shape of the distribution of pressure loss caused by the ribs 2011 when correction air is supplied is approximately the same as the shape of the pressure distribution without the ribs ( FIG. 4A ). In other words, the shape of the ribs 2011 is determined so that the increase in pressure loss (increase in the amount of pressure decrease) in the pressure distribution with the ribs ( FIG. 4A ) is approximately the same as the increase in pressure in the pressure distribution without the ribs.

[0070] As shown in the left diagram of Fig. 4A, in the pressure distribution without ribs, the pressure increases from the center of the wafer chuck 200 toward the outer periphery (as the radial position r of the wafer chuck 200 increases). Also, as shown in the central diagram of Fig. 4A, in the pressure distribution with ribs, the pressure loss caused by the ribs 2011 increases from the center of the wafer chuck 200 toward the outer periphery. The pressure loss caused by the ribs 2011 is pressure for correcting deformation of the wafer 205. The shape of the ribs 2011 is determined so that the pressure distribution caused by the ribs cancels out the pressure distribution without the ribs.

[0071] As described above, the shape of the rib 2011 is such that, in the pressure distribution in the radial direction of the wafer chuck 200, the pressure loss caused by the rib 2011 is substantially equal to the pressure in the wafer chuck 200 that does not include the rib 2011. However, the shape of the rib 2011 may be such that, in the pressure distribution in the radial direction of the wafer chuck 200, the magnitude of the pressure loss caused by the rib 2011 is equal to or greater than the pressure in the wafer chuck 200 that does not include the rib 2011. In other words, the shape of the rib 2011 may be such that the value (magnitude) of the pressure loss caused by the rib 2011 is equal to or greater than the value of the pressure in the wafer chuck 200 that does not include the rib 2011 at the same radial position where this pressure loss value was applied (equal to or greater than the pressure value in the pressure distribution expressed as a high-order function of the radial position r). When the pressure loss caused by the rib 2011 is equal to or greater than the pressure in the wafer chuck 200 that does not include the rib 2011, sinking of the wafer 205 due to its own weight can be more effectively prevented.

[0072] First, we will explain the shape and pressure loss of one rib 2011. The pressure loss ΔP caused by the rib 2011 is expressed by known formulas (1) to (3).

[0073]

number

[0074]

number

[0075]

number

[0076] where ξ is the pressure loss coefficient, l is the width of the rib 2011, h is the distance between the wafer 205 and the rib 2011, ρ is the density of the correction air, v is the flow velocity of the correction air between the wafer 205 and the rib 2011, Re is the Reynolds number, and ν is the dynamic viscosity coefficient of the correction air. The width of the rib 2011 is the length of the rib 2011 in the radial direction.

[0077] As shown in Equation 1, when a narrow portion, i.e., a rib 2011, is provided between the wafer chuck 200 and the wafer 205, a pressure loss ΔP is generated by the rib 2011. From the relationships shown in Equations (1) to (3), the smaller the Reynolds number Re, i.e., the smaller the gap h between the wafer 205 and the rib 2011, or the smaller the flow velocity v of the correction air, the larger the pressure loss ΔP generated by the rib 2011. Furthermore, from Equation (1), the larger the width l of the rib 2011, the larger the pressure loss ΔP. ​​Therefore, the gap h between the wafer 205 and the rib 2011, the flow velocity v of the correction air between the wafer 205 and the rib 2011, and the width l of the rib 2011 are parameters that determine the magnitude of the pressure loss ΔP.

[0078] Fig. 5 is a graph showing the change in pressure loss ΔP caused by the rib 2011 when the distance h between the wafer 205 and the rib 2011 is changed. The graph of Fig. 5 can be obtained from equations (1) to (3).

[0079] As can be seen from equation (2), the pressure loss ΔP changes significantly at the boundary of the distance h where the Reynolds number Re is 2000. That is, by setting the distance h so that the correction air becomes a laminar flow when the Reynolds number Re is 2000 or less, the pressure loss ΔP due to the rib 2011, i.e., the pressure for correcting deformation of the wafer 205, can be effectively generated. As can be seen from FIG. 5, when the distance h is equal to or less than a predetermined value h0, the pressure loss ΔP can be increased. That is, when the protruding height of the rib 2011 is greater than a predetermined value, the pressure loss ΔP can be increased.

[0080] Furthermore, since the correction air is a laminar flow between the wafer 205 and the rib 2011, it rotates together with the wafer chuck 200 and flows in the radial direction at a speed according to the pressure of the correction air flowing in from the air supply port 204. Therefore, the correction air is not affected by the centrifugal force caused by the rotation of the wafer chuck 200. Therefore, there is no need to consider negative pressure where the rib 2011 is installed.

[0081] The results of a detailed study of the relationship between pressure loss ΔP and the spacing h are described below. The spacing h at which the Reynolds number Re is 2000 or less was determined, assuming that the wafer 205 has a radius of 150 mm and a rotation speed of 50 Hz. The relationship between pressure loss ΔP and the spacing h is shown in FIG. 5 . It was found that if the spacing h is 0.5 mm or less, the correction air becomes a laminar flow over the entire area of ​​the wafer 205. In other words, the spacing h (predetermined value h0) at which the Reynolds number Re is 2000 or less is 0.5 mm or less. On the other hand, to prevent the wafer 205 from contacting the rib 2011, the minimum value of the spacing h must be 0.1 mm. From the above, it is preferable that the spacing h between the wafer 205 and the rib 2011 be 0.1 mm or more and 0.5 mm or less.

[0082] Next, the concept of the distance h between the wafer 205 and the ribs 2011 will be described for the case where the wafer chuck 200 is provided with a plurality of ribs 2011.

[0083] The wafer 205 is held by the wafer chuck 200 with its outer periphery supported by the wafer support portion 202. Therefore, when the wafer 205 is initially placed on the wafer chuck 200, the center of the wafer 205 sinks under its own weight, causing the center to be deformed and concave. For this reason, the rib 2011 must be shaped so as not to come into contact with the wafer 205. The sinking of the wafer 205 under its own weight reaches a maximum value of about 0.1 mm at the center of the wafer 205. Considering variations in deformation of the wafer 205, it is desirable that the distance h at the center of the wafer 205 be about 0.5 mm.

[0084] In order to efficiently obtain the pressure loss ΔP due to the ribs 2011, it is desirable that the spacing h be smaller at the outer periphery of the wafer chuck 200 than at the center, i.e., that the protruding heights of the multiple ribs 2011 are different from one another and greater at the outer periphery than at the center of the wafer chuck 200. Furthermore, it is more desirable that the spacing h become smaller from the center to the outer periphery of the wafer chuck 200, i.e., that the protruding height of the ribs 2011 become greater from the center to the outer periphery of the wafer chuck 200.

[0085] The pressure distribution to be corrected (the pressure distribution without ribs shown in FIG. 4A ) is a distribution in which the pressure at the center of the wafer chuck 200 is the maximum negative pressure and the pressure at the outermost periphery of the wafer chuck 200 is atmospheric pressure, and is a curve expressed by a high-order function of the radial position r of the wafer chuck 200. Therefore, in order for the pressure distribution with the ribs ( FIG. 4 ) to cancel out the pressure distribution without the ribs (i.e., for the value (magnitude) of the pressure loss caused by the ribs 2011 to be equal to or greater than the pressure value in the wafer chuck 200 without the ribs 2011 at the same radial position where this pressure loss value was applied), the pressure loss must be greater at the outer periphery of the wafer chuck 200 than at the center. For this reason, it is desirable that the protruding height of the ribs 2011 be greater at the outer periphery of the wafer chuck 200 than at the center. It is even more desirable that the protruding height of the ribs 2011 increase from the center to the outer periphery of the wafer chuck 200.

[0086] The protruding height of the ribs 2011 does not have to increase monotonically from the center to the outer periphery of the wafer chuck 200. In other words, among the multiple ribs 2011 arranged in the radial direction, there may be a rib 2011 that protrudes higher than two adjacent ribs 2011 on the inner and outer periphery sides. Of course, the protruding height of the rib 2011 is a height that prevents the rib 2011 from contacting the wafer 205.

[0087] The flow velocity v of the correction air between the wafer 205 and the rib 2011 is the flow velocity at the center in the radial direction of the rib 2011. The flow rate of the correction air (the product of the area of ​​the air supply port 204 and the flow velocity v) is constant. Therefore, the flow rate of the correction air is determined in advance as a constant, and the flow area of ​​the correction air at the center in the radial direction of the rib 2011 is determined from the interval h, so that the flow velocity v can be determined.

[0088] Next, a method for setting the pressure distribution when a plurality of ribs 2011 are arranged on the wafer chuck 200 will be described.

[0089] 4B is a diagram illustrating a correction method using a correction pressure when multiple ribs 2011 are arranged on the wafer chuck 200. Fig. 4B shows the pressure distribution without ribs and the distribution of the correction pressure (pressure distribution with ribs) in the radial direction of the wafer chuck 200. As an example, the pressure distribution without ribs is expressed by a cubic function of the radial position r.

[0090] The number of ribs 2011 is M, and each rib 2011 is identified by a subscript n (n = 1 to M) that increases from the outer periphery toward the center. The pressure loss value due to each rib 2011 is ΔPxn, and the pressure loss value at the radial position xn of the nth rib 2011 counting from the outer periphery is P(xn).

[0091] When multiple ribs 2011 are arranged on the wafer chuck 200, the pressure at a target radial position xn increases by the sum of the pressure losses caused by the ribs 2011 located on the outer periphery of the position xn. That is, the distribution of the corrected pressure is expressed by Equation (4).

[0092]

number

[0093] Here, P(xN) is the pressure loss value at the radial position xN of the Nth rib 2011 counting from the outer periphery, and N is the order of the rib 2011 counting from the outer periphery.

[0094] After the distance h between the wafer 205 and the ribs 2011 is determined to some extent, the ribs 2011 are arranged on the outermost periphery of the wafer chuck 200 to determine the pressure loss ΔPx1. Then, the pressure loss ΔPxn of each rib 2011 is adjusted sequentially from the outer periphery toward the center by changing the radial position xn of each rib 2011. Then, the width l of each rib 2011 and the number of ribs 2011 are adjusted so that the shape of the compensation pressure distribution (the distribution of pressure loss caused by the ribs 2011) approximately matches the shape of the pressure distribution without the ribs. If these shapes do not match sufficiently, the distance h between the wafer 205 and the ribs 2011 is adjusted. By adjusting the ribs 2011 from the outer periphery toward the center of the wafer chuck 200 in this manner and adding up the pressure losses caused by the ribs 2011, the compensation pressure distribution can be obtained.

[0095] The pressure distribution without ribs is corrected using the compensation pressure distribution obtained in this manner. During this adjustment routine, the compensation pressure distribution must be constantly referenced so that the pressure curve without ribs and the compensation pressure curve roughly match. After the wafer 205 is placed on the wafer chuck 200 configured in this manner, the flatness of the wafer 205 is finally adjusted using compensation air.

[0096] As described above, the wafer inspection apparatus 10 according to this embodiment can hold the wafer 205 flat with a simple configuration, and can improve the accuracy of detecting foreign matter present on the surface of the wafer 205. [Example]

[0097] A second embodiment of the present invention will be described. In this embodiment, the wafer inspection device 10 according to the first embodiment is used to measure the flatness of the wafer 205 with a sensor, and corrective air is supplied based on the measured flatness, thereby making it possible to keep the wafer 205 flat.

[0098] 6A is a diagram showing the positional relationship between the wafer chuck 200 and the optical system immediately after the wafer 205 is placed on the wafer chuck 200. The wafer chuck 200 is positioned at the wafer receiving position.

[0099] The wafer inspection device 10 includes a height sensor 301 , an amplifier 302 , a data processing unit 303 , and an air control unit 304 .

[0100] The height sensor 301 measures the height position of the wafer 205 placed on the wafer chuck 200. Hereinafter, the height position of the wafer 205 will be referred to as the height of the wafer 205. The installation position of the height sensor 301 is directly above a line that passes through the center of the wafer 205 and extends in the direction of linear movement of the wafer chuck 200 when the transfer mechanism 12 places the wafer 205 on the wafer chuck 200 (i.e., when the position of the wafer chuck 200 is the wafer receiving position), and is directly above the outer periphery of the wafer 205.

[0101] The amplifier 302 amplifies the signal output by the height sensor 301 .

[0102] The data processing unit 303 receives the signal output by the height sensor 301 from the amplifier 302, processes this signal (measurement value of the height sensor 301), and outputs the processed result to the air control unit 304. Through such processing, the data processing unit 303 supplies corrective air to the wafer chuck 200 using the air control unit 304.

[0103] The air control unit 304 is provided in the wafer chuck 200 and supplies corrective air to the wafer chuck 200 based on instructions from the data processing unit 303 .

[0104] The operation of the wafer inspection device 10 in this embodiment will now be described.

[0105] FIG. 7 is a flowchart showing the operation of the wafer inspection apparatus 10 in this embodiment.

[0106] In step S71, the wafer chuck 200 places the wafer 205 at the wafer receiving position, and holds the wafer 205 with the clamping mechanism 206 (FIG. 6A).

[0107] In step S72, wafer chuck 200 starts to rotate. At this time, the geometric center of optical measurement unit 131, which optically measures foreign matter on wafer 205, is separated from the center of rotation of wafer chuck 200, as shown in FIG.

[0108] In step S73, height sensor 301 measures the height of the outer periphery of wafer 205 while wafer 205 makes one rotation. Data processing unit 303 averages the heights of the outer periphery of wafer 205 measured by height sensor 301 while wafer 205 makes one rotation, and calculates the average value of the height of the outer periphery of wafer 205. This average value becomes the reference value.

[0109] In step S74, while rotating the wafer 205, the wafer chuck 200 moves linearly to a position where the rotation center of the wafer chuck 200 coincides with the geometric center of the optical measurement unit 131. During this linear movement, the measurement position of the height sensor 301 coincides with the center of the wafer 205.

[0110] FIG. 6B is a diagram showing a state in which the measurement position of the height sensor 301 coincides with the center of the wafer 205 due to linear movement of the wafer chuck 200.

[0111] 7, the height sensor 301 measures the height of the wafer 205 when the measurement position of the height sensor 301 coincides with the center of the wafer 205 while the wafer chuck 200 is moving. That is, the height sensor 301 measures the height of the center of the wafer 205 while the wafer 205 is rotating.

[0112] In step S76, the data processing unit 303 calculates the difference between the reference value, which is the average value of the height of the outer periphery of the wafer 205, and the height of the center of the wafer 205.

[0113] In step S77, the data processing unit 303 supplies, via the air control unit 304, an amount of compensation air corresponding to the calculated height difference to the wafer chuck 200. Specifically, the data processing unit 303 supplies an amount of compensation air to the wafer chuck 200 that reduces the height difference (preferably, reduces the height difference to zero) so that the wafer 205 is held flat. The data processing unit 303 can determine, for example, by feedback processing, the amount of compensation air that reduces (or reduces the height difference to zero).

[0114] The operations from step S73 to step S77 are performed while the wafer chuck 200 is rotating, before the wafer inspection device 10 starts inspecting the wafer 205. Since the response delay when supplying the correction air is less than one second, the correction air can be supplied in step S77 almost immediately after the height of the wafer 205 is measured in step S75.

[0115] In step S78, wafer inspection device 10 starts inspecting the surface of wafer 205 using optical measurement unit 131. When the supply of correction air in step S77 ends and wafer chuck 200 moves linearly to a position where the center of rotation of wafer chuck 200 coincides with the geometric center of optical measurement unit 131, wafer inspection device 10 starts inspecting the surface of wafer 205.

[0116] 6C is a diagram showing wafer chuck 200 that has moved to a position where the center of rotation of wafer chuck 200 coincides with the geometric center of optical measurement unit 131. In the state shown in FIG. 6C, wafer inspection device 10 inspects the surface of wafer 205.

[0117] 7, the wafer inspection apparatus 10 determines the amount of correction air to be supplied while the wafer chuck 200 is rotating, using the difference between two values: the average height of the outer periphery of the wafer 205 and the height of the center of the wafer 205. This allows the configuration of the data processing unit 303 to be simplified, and the response speed is fast, making it possible to keep the wafer 205 flat without affecting throughput.

[0118] Furthermore, the relationship between the amount of compensation air and the difference between the height of the outer periphery and the height of the center of the wafer 205 can be determined by experiment or the like and recorded in advance in a table. The data processing unit 303 can store this table, and in step S77 of FIG. 7, the amount of compensation air that reduces (or makes zero) the height difference can be determined from this table. The data processing unit 303 supplies the amount of compensation air determined from the table to the wafer chuck 200. Using such a table allows the wafer 205 to be held flat more quickly.

[0119] Next, to evaluate the validity of the method of measuring the height of the wafer 205 and supplying corrective air, corrective air was manually supplied using this method, and the radial flatness of the wafer 205 was evaluated. The flatness of the wafer 205 was compared between the case where the wafer chuck 200 described in Example 1 was used and the case where a conventional wafer chuck was used. Note that in the conventional wafer chuck, the protruding height of the rib (the distance h between the wafer 205 and the rib) and the width l of the rib are constant.

[0120] 8 is a diagram schematically showing the pressure distribution of the correction air when the wafer chuck 200 described in Example 1 is used (pressure distribution of the example) and the pressure distribution of the correction air when a conventional wafer chuck is used (conventional pressure distribution). The left diagram of FIG. 8 shows the pressure distribution of the example, and the right diagram of FIG. 8 shows the conventional pressure distribution. The pressure distribution of the correction air corresponds to the total pressure distribution shown on the right side of FIG. 4A.

[0121] In the conventional pressure distribution, the pressure drops at the center in the radial direction. In the pressure distribution of the embodiment, the pressure drop at the center in the radial direction seen in the conventional pressure distribution is eliminated, and the effect of improving the pressure distribution by the rib 2011 can be confirmed.

[0122] In addition, as a pre-adjustment of the wafer chuck, the variation in height of the multiple contact portions 202a of the wafer support portion 202 was adjusted to about 8 μm, and the circumferential flatness of the outermost portion of the wafer 205 (the distance between the top and bottom positions of the wafer 205) was adjusted to 11 μm. The rib 2011 described in Example 1 was provided on the thus-adjusted wafer chuck to form the wafer chuck 200 described in Example 1, and a conventional rib was provided to form a conventional wafer chuck. The adjustment of the compensation air was performed according to the flowchart shown in FIG. 7. That is, the height of the outer periphery of the wafer 205 was measured and the average value was calculated, and then the height at the center of the wafer 205 was measured. The amount of compensation air was manually adjusted so that the difference between these values ​​became as small as possible and as close to zero as possible.

[0123] 9 is a diagram showing the measurement results of the average height (displacement in the height direction) in the circumferential direction of wafer 205 at each position in the radial direction of wafer 205. Fig. 9 shows the measurement results when wafer chuck 200 described in Example 1 was used (Example) and when a conventional wafer chuck was used (Conventional).

[0124] The curve obtained from the measurement results in FIG. 9 is a curve representing the height of the wafer 205 in the radial direction, i.e., a curve representing the deformation of the wafer 205, and is influenced by the structure of the rib 2011. The overall trends of these curves are the same between the Example and the conventional example. However, the maximum difference in height, which indicates the flatness of the wafer 205, is 25.5 μm for the conventional example and 12.5 μm for the Example. That is, the flatness of the wafer 205 in the Example is improved to about half that of the conventional example.

[0125] Furthermore, the time required for manual adjustment of the compensation air was less than one minute. When the compensation air is adjusted automatically as described in Example 1, the adjustment of the compensation air can be completed within the time required to start up the rotation of the wafer chuck 200 (approximately several seconds).

[0126] From the measurement results shown in FIG. 9, it was confirmed that the flatness of the wafer 205 was improved by the structure of the rib 2011 in the example, and it was found that the wafer 205 could be held efficiently.

[0127] In the wafer chuck 200 described in the first embodiment, the pressure distribution of the correction air is symmetrical with respect to the rotation axis of the wafer chuck 200. Therefore, in the wafer chuck 200 of the first embodiment, even for a wafer 205 that is deformed symmetrically with respect to the axis, for example, a wafer 205 whose central portion has been deformed into a concave or convex shape before inspection, improvement in flatness can be expected when the wafer chuck 200 holds the wafer 205.

[0128] Therefore, a coupled analysis of fluid and structure was performed to study how to improve (correct) the flatness of the deformed wafer 205. The deformation of the wafer 205 used in the study simulated deformation due to sinking under its own weight, with the deformation being greatest at the center, and the maximum deformation amount was 73 μm at the center. The deformed wafer 205 has a downwardly convex shape. This model of the wafer 205 was turned upside down, and a model of the wafer 205 with an upwardly convex shape was also created. In other words, two types of deformed wafer 205 models were created: one with a downwardly convex shape and one with an upwardly convex shape.

[0129] For the analysis system in which these wafers 205 were placed on the wafer chuck 200, the pressure on the backside of the wafer 205 due to the compensation air was first obtained by fluid analysis, and this pressure was reflected in the boundary conditions of the structural analysis to determine the radial shape of the wafer 205 by structural analysis, and the maximum value of the deformation of the wafer 205 in the radial direction (the distance between the top position and the bottom position) was evaluated as the flatness.

[0130] Hereinafter, the wafer 205 deformed into a downwardly convex shape will be referred to as a downwardly convex deformed wafer, and the wafer 205 deformed into an upwardly convex shape will be referred to as an upwardly convex deformed wafer.

[0131] 10A and 10B are diagrams showing the analysis results obtained by fluid-structure coupled analysis of the change in the radial flatness of the wafer relative to the amount of correction air when a downwardly convexly deformed wafer is placed on the wafer chuck 200 of Example 1 and when a upwardly convexly deformed wafer is placed on the wafer chuck 200. Fig. 10A shows the results for the downwardly convexly deformed wafer, and Fig. 10B shows the results for the upwardly convexly deformed wafer.

[0132] The flatness of the downward convex deformed wafer and the upward convex deformed wafer changed depending on the amount of correction air, and a minimum value for flatness was obtained for each. The minimum deformation amount (flatness) was 10 μm for the downward convex deformed wafer and 5 μm for the upward convex deformed wafer, indicating that deformation could be corrected for both types of deformed wafer.

[0133] Figures 10C and 10D show the results of comparing the radial shape of the wafer obtained by the fluid-structure interaction analysis with the shape before the deformation was corrected (before the correction air was supplied). Figure 10C shows the results for a downward-convex deformed wafer, and Figure 10D shows the results for an upward-convex deformed wafer. In Figures 10C and 10D, the wafer height (height position) relative to the wafer's radial position is shown as the wafer's radial shape, with the wafer height obtained by the fluid-structure interaction analysis shown by the solid line and the wafer height before the deformation was corrected shown by the dashed line.

[0134] The results obtained from the fluid-structure interaction analysis showed that for both the downward convex deformed wafer and the upward convex deformed wafer, the wafer height was approximately equal at the center (where the radius is 0 mm) and the outer periphery (where the radius is 150 mm). This indicates that the wafer height adjustment method in this example made the wafer flat, and therefore this method is valid.

[0135] From the above, it can be seen that, as long as the deformation of the wafer 205 is axially symmetric, it is possible to ensure a certain degree of flatness even for a wafer 205 that has been deformed before inspection, by using the wafer chuck 200 described in Example 1. From the above, as also described in Example 1, the wafer inspection apparatus 10 according to this example can hold the wafer 205 flat with a simple configuration, and can also improve the accuracy of detecting foreign matter present on the surface of the wafer 205.

[0136] The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to embodiments including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to delete part of the configuration of each embodiment, or to add or replace other configurations. [Explanation of symbols]

[0137] 10...wafer inspection device, 11...wafer introduction section, 12...transport mechanism, 13...inspection chamber, 14...control section, 131...optical measurement section, 132...motor, 133...linear movement section, 200...wafer chuck, 201...wafer chuck base, 202...wafer support section, 202a...contact section, 202b...non-contact section, 203...air exhaust port, 204...air supply port, 205...wafer, 206...clamping mechanism, 211...cam, 212...air cylinder, 213...bearing, 214...bearing holding section, 215...compression spring, 216...rod, 217...link, 218...holding section, 219...holding claws, 301...height sensor, 302...amplifier, 303...data processing section, 304...air control section, 2011...rib.

Claims

1. a rotatable wafer chuck on which a wafer can be placed, the wafer chuck includes an air supply port that supplies air to the back surface of the wafer, an air discharge port that discharges the air, a clamping mechanism that holds the wafer, and a plurality of annular protrusions that protrude upward; the wafer chuck does not include the annular protrusion, and when the wafer chuck rotates, a pressure distribution between the wafer and the wafer in a radial direction of the wafer chuck is expressed by a high-order function of position in the radial direction; the annular protrusion has a shape such that a value of pressure loss caused by the annular protrusion when the wafer chuck is rotated and the air is supplied is equal to or greater than a value of the pressure in the pressure distribution expressed by the higher-order function at the same position in the radial direction as the position at which the value of the pressure loss was given. A wafer inspection device characterized by:

2. The plurality of annular protrusions have different heights. The wafer inspection device according to claim 1 .

3. the height of the plurality of annular protrusions increases from the center of the wafer chuck toward the outer periphery thereof; The wafer inspection device according to claim 1 .

4. The plurality of annular protrusions include an annular protrusion having a height greater than that of the annular protrusions adjacent to each other in both radial directions. The wafer inspection device according to claim 1 .

5. a height sensor for measuring the position of the wafer placed on the wafer chuck in the height direction; a data processing unit; an air control unit for supplying the air to the wafer chuck; the height sensor measures the height of the outer periphery of the wafer while the wafer makes one rotation, and measures the height of the center of the wafer while the wafer is rotating; the data processing unit calculates an average value by averaging the heights of the outer periphery of the wafer measured by the height sensor, and calculates a difference between the average value and the height of the center of the wafer measured by the height sensor; the data processing unit supplies the amount of air corresponding to the difference to the wafer chuck by the air control unit; The wafer inspection device according to claim 1 .

6. the data processing unit stores a table recording the relationship between the amount of air to be supplied to the wafer chuck and the difference between the height of the outer periphery of the wafer and the height of the center, and obtains from the table the amount of air that reduces the difference between the average value and the height of the center of the wafer, and supplies the obtained amount of air to the wafer chuck.

6. The wafer inspection device according to claim 5.

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