Wafer inspection device and wafer inspection method

Abstract

In a wafer inspection device according to the present disclosure, a control device causes a wafer and a wafer back surface non-contact holding mechanism to approach each other while feeding a mounting speed in accordance with the distance therebetween in a state in which the wafer is supported by a support pin, and simultaneously supplies air from a positive pressure air supply port or a central air supply port. When the distance becomes a prescribed value, the control device causes a holding claw to contact and hold the outer peripheral end part of the wafer, and releases the wafer from the support pin. Furthermore, the control device provides one of the positive pressure air supply port and a negative pressure suction port with a design pressure corresponding to a distance (design gap) between the wafer and the wafer back surface non-contact holding mechanism for wafer inspection, and changes the pressure of the other from the higher pressure side relative to the design pressure until the design pressure is achieved, whereby the wafer is held with contact only at the outer peripheral end part and without contact with the back surface.

Description

Wafer inspection device and wafer inspection method

[0001] The present disclosure relates to a wafer inspection apparatus and a wafer inspection method.

[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 or short circuits in wiring. These foreign matter can be present in various forms, such as from moving parts of transport devices, from the human body, reaction products produced by process gases within processing equipment, or contaminated chemicals or materials.

[0003] Therefore, surface inspection equipment is used to detect and manage foreign particles on wafer surfaces. This allows the monitoring and control of the dust generation status of each manufacturing device and the cleanliness of each process, thereby improving product quality and yield. The method of foreign particle inspection involves irradiating light such as laser light onto the wafer surface and detecting the scattered light from foreign particles, thereby inspecting the size and attachment position of the foreign particles, and obtaining information unique to each wafer.

[0004] During wafer inspection, the wafer is fixed to a holding device. Wafer holding methods are broadly divided into backside suction and backside non-contact methods. Backside suction uses an air intake on a flat table to suction the backside of the wafer. This means the backside is fixed in contact with the table. Backside suction is used for patterned wafers and bare wafers before pattern formation. On the other hand, backside non-contact methods hold only the outer periphery of the wafer and fix it to the table. Backside non-contact methods are used for bare wafers before pattern formation. In particular, backside non-contact surface inspection equipment is used for shipping inspections at wafer manufacturers and receiving inspections at process manufacturers. For this reason, there is a demand not only for preventing foreign particle adhesion but also for improving the reproducibility and accuracy of foreign particle detection. One way to achieve this is to improve the flatness of the wafer.

[0005] Patent Document 1 discloses the following technology: "A non-contact wafer chucking apparatus includes a wafer chuck and a gripper assembly coupled to a portion of the wafer chuck. The wafer chuck includes a pressurized gas element configured to generate a pressurized gas region across a surface of the wafer chuck suitable for lifting a wafer above the surface of the wafer chuck. The wafer chuck further includes a vacuum element configured to generate a reduced pressure region across the surface of the wafer chuck, the reduced pressure region having a lower pressure than the pressurized gas region. The reduced pressure region is suitable for holding the wafer above the wafer chuck without contacting the wafer chuck. The chucking apparatus includes a rotational drive unit configured to selectively rotate the wafer chuck. A gripper element is reversibly connectable to an edge portion of the wafer to hold the wafer such that the wafer and the gripper assembly rotate synchronously with the wafer chuck" (see the abstract of Patent Document 1).

[0006] Special table 2017 / 504199 publication

[0007] The wafer chuck in Patent Document 1 holds the wafer's backside without contact, so the process leading up to the wafer's placement, i.e., the mounting method, must also be considered. Regarding this point, the patent document describes a method in which the wafer is positioned above the wafer chuck. When the two come close to each other, pressurized air is applied to the wafer from the wafer chuck alone, correcting deformation due to the wafer's self-weight sinking and preventing the wafer from contacting the wafer chuck. However, the timing and applied pressure are not disclosed. Depending on the applied pressure conditions, the wafer may float and slide sideways. This can result in the wafer being held in an eccentric state from the center of rotation, leading to incorrect recording of coordinate information for foreign objects on the wafer. Furthermore, the wafer may fail to be mounted, causing it to fall off.

[0008] Therefore, the present disclosure provides a wafer inspection device that can prevent the wafer from coming into contact with the wafer chuck and achieve safe wafer loading while maintaining wafer positional accuracy.

[0009] In order to solve the above problems, the wafer inspection device of the present disclosure is a wafer backside non-contact holding mechanism having an air flow path structure in which a positive pressure air supply port and a negative pressure intake port provided in a negative pressure intake groove are paired, and a central air supply port provided in the center, wherein the air flow path structure shares the negative pressure intake groove and the negative pressure intake port with adjacent air flow path structures, and the wafer backside non-contact holding mechanism is arranged evenly in the radial and circumferential directions, a positive pressure air supply circuit that supplies positive pressure air to the positive pressure air supply port, a negative pressure air suction circuit that negatively sucks the positive pressure air from the negative pressure intake port, and a central air supply port that supplies air to the central supply port. The wafer peripheral edge holding mechanism includes an air supply circuit, a rotation mechanism that rotates the wafer backside non-contact holding mechanism, a vertical drive mechanism that drives the wafer backside non-contact holding mechanism and the rotation mechanism up and down, a wafer peripheral edge holding mechanism having holding claws that are arranged on the outer periphery of the wafer backside non-contact holding mechanism and that contact and hold the wafer at the outer edge, and a mechanism that drives the holding claws in a planar direction, support pins that temporarily support the wafer at the outer edge, and a control device that controls the positive pressure air supply circuit, the negative pressure air suction circuit, the center air supply circuit, the rotation mechanism, the vertical drive mechanism, and the wafer peripheral edge holding mechanism. The control device controls the up-and-down drive mechanism so that, with the wafer supported by the support pins at its outer peripheral edge, the wafer and the wafer backside non-contact holding mechanism are brought closer together while applying a mounting speed according to the distance between them, and simultaneously supplies the positive pressure air from the positive pressure air supply port or supplies the central air from the central air supply port, and when the distance reaches a specified value, drives the wafer outer peripheral edge holding mechanism so that the holding claws contact and hold the outer peripheral edge of the wafer, and releases support by the support pins at the outer peripheral edge of the wafer, and then controls the positive pressure air supply circuit and the negative pressure air suction circuit so that a specified design pressure is applied to either the positive pressure air supply port or the negative pressure intake port, and the pressure of the other is changed from a pressure higher than the specified design pressure to finally reach the specified design pressure.

[0010] Further features related to the present disclosure will become apparent from the description of this specification and the accompanying drawings. Also, aspects of the present disclosure are achieved and realized by the elements and combinations of various elements and the aspects of the following detailed description and the appended claims. The description of this specification is merely exemplary and does not limit the scope or application of the claims of the present disclosure in any way.

[0011] According to the technology of the present disclosure, it is possible to prevent the wafer from coming into contact with the wafer chuck and to achieve safe wafer loading while maintaining the wafer positional accuracy. Other problems, configurations, and advantages will become clear from the description of the following embodiments.

[0012] FIG. 1 is a schematic diagram showing the configuration of a wafer inspection apparatus according to a first embodiment. FIG. 2 is a schematic diagram of a peripheral structure and a control circuit of a wafer chuck according to the first embodiment. FIG. 3 is a perspective view of a wafer chuck according to the first embodiment. FIG. 4 is a diagram for explaining an air bearing structure and a graph showing the characteristics of the air bearing structure. FIG. 5 is a perspective view of a clamping mechanism as seen from the outside. FIG. 6 is a perspective view of a wafer chuck as seen from below. FIG. 7 is a diagram for explaining the operation of the clamping mechanism. FIG. 8 is a flowchart of the operation of loading a wafer onto a wafer chuck according to the first embodiment. FIG. 9 is a conceptual diagram for explaining the positional relationship between a wafer and a wafer chuck. FIG. 10 is a conceptual diagram for explaining the positional relationship between a wafer and a wafer chuck in a modified example of the operation of loading a wafer onto a wafer chuck. FIG. 11 is a graph showing the levitation force acting on a wafer relative to a wafer gap h when the wafer approach speed is constant. FIG. 12 is a graph showing an example of a wafer approach speed pattern relative to a wafer gap h that keeps the wafer levitation force constant. FIG. 13 is a graph showing a wafer approach speed pattern relative to the movement time of the wafer chuck that keeps the wafer levitation force constant. FIG. 14 is an example of an adjustment curve when changing the intake pressure from the negative pressure air suction port of the air bearing mechanism when the wafer gap h is within 500 to 100 μm. 10 is a diagram showing an example of an adjustment curve when changing the supply pressure from the positive pressure air supply port of the air bearing mechanism when the wafer gap h is within 500 to 100 μm. FIG. 11 is a schematic diagram of the structure around the wafer chuck and a control circuit according to a second embodiment. FIG. 12 is a schematic diagram for explaining the structure of a wafer support pin according to the second embodiment. FIG. 13 is a schematic diagram for explaining the structure of a wafer support pin according to a modified example of the second embodiment.

[0013] [First Embodiment] <Configuration Example of Wafer Inspection Apparatus> Fig. 1 is a schematic diagram showing the configuration of a wafer inspection apparatus 10 according to a first embodiment. The wafer inspection apparatus 10 includes a wafer introduction unit 11, a transport mechanism 12, an inspection chamber 13, a control device 15, and a storage device 16. A wafer 100 is loaded into the wafer introduction unit 11 while being stored in a cassette (not shown). The transport mechanism 12 is configured to transport the wafer 100 loaded into the wafer introduction unit 11 to the inspection chamber 13. The inspection chamber 13 is configured to be able to inspect the wafer 100. The wafer inspection apparatus 10 is installed in a space where cleanliness is maintained to prevent foreign matter from adhering to the wafer 100.

[0014] The inspection chamber 13 has an optical measurement unit 131, a motor 132, a base 133, and a wafer chuck 200. The optical measurement unit 131 is fixed in position and optically measures foreign matter on the wafer 100. The wafer 100 is mounted on the wafer chuck 200 so that the position and size of the foreign matter can be measured while the wafer 100 is rotated. The motor 132 supports the rotation of the wafer chuck 200. The base 133 has linear movement means that supports the motor 132 and linearly moves the wafer chuck 200 in the radial direction.

[0015] The control device 15 controls the overall operation of the wafer inspection device 10. The control device 15 also processes the inspection results from the optical measurement unit 131 to inspect the size and attachment position of foreign matter on the wafer 100. Although one control device 15 is shown in FIG. 1 , control may be performed by at least two control devices: one that controls the transport mechanism 12, and one that controls the inspection chamber 13. The storage device 16 stores information required for control, such as programs executed by the control device 15 and a database used for the wafer loading operation described below. The storage device 16 may also be configured using multiple pieces of hardware.

[0016] FIG. 2 is a schematic diagram illustrating the structure and control circuit surrounding the wafer chuck 200. FIG. 2 specifically illustrates the mechanisms within the inspection chamber 13, excluding the optical measurement unit 131. The upper portion of FIG. 2 is a top view of the wafer chuck 200. Below that is a side view of the inspection chamber 13. The wafer chuck 200 is a non-contact wafer backside holding mechanism having a generally circular disk shape, and is attached to a rotationally driven motor 132. The motor 132 may be, for example, a spindle motor. The motor 132 is attached to a base 133 equipped with a mechanism (not shown) that drives the wafer chuck 200 in the radial direction. A vertical drive mechanism 134 is attached to the base 133, which is fixed to a stationary portion. The vertical drive mechanism may be, for example, a vertical drive gear. Thus, the base 133 is configured to be vertically movable. The wafer chuck 200 has a clamping mechanism 300 on its outer periphery. The clamping mechanism 300 has built-in holding claws (described later) that hold the outer peripheral edge 100a of the wafer 100.

[0017] The wafer 100 is detached by vertically moving the base 133, motor 132, and wafer chuck 200 up and down using the vertical drive mechanism 134b, and the holding claws built into the clamping mechanism 300 move toward the inner and outer periphery of the wafer 100 to clamp it. The wafer 100 is transferred from the arm of the transfer mechanism 12 to the wafer chuck 200, and three wafer support pins 135 are provided as a temporary resting place for the wafer 100. The wafer support pins 135 are provided at angular positions that divide the wafer chuck 200 into thirds in the circumferential direction and at radial positions corresponding to the outer periphery of the wafer 100. The number of wafer support pins 135 can be at least three to support the wafer 100 on a surface, but may be more than three. The wafer support pins 135 are mounted on a non-moving component separate from the base 133 so that they can move relative to the wafer chuck 200. Furthermore, wafer support pin through holes 220 for passing through wafer support pins 135 are provided in wafer chuck 200 at positions corresponding to wafer support pins 135. Clamping mechanisms 300 are provided at angular positions that divide wafer chuck 200 equally into six circumferential directions, at positions where they can hold outer peripheral edge 100a of wafer 100. The number of clamping mechanisms 300 can be at least three, but may be more than three, in order to support wafer 100 by outer peripheral edge 100a.

[0018] An air supply pump 136 and a positive pressure air supply circuit 136a are connected to the wafer chuck 200 via a positive pressure air supply system 136b built into the motor 132. In addition, an intake pump 137 and a negative pressure air suction circuit 137a are connected to the wafer chuck 200 via a negative pressure air suction system 137b built into the motor 132. The air supply pump 136 and the positive pressure air supply circuit 136a are used to supply air at positive pressure to an air bearing structure described below. The intake pump 137 and the negative pressure air suction circuit 137a are used to suck air from the air bearing structure using negative pressure.

[0019] Furthermore, a central air supply pump 138 and a central air supply circuit 138a are connected to the wafer chuck 200 via a central air supply system 138b built into the motor 132. The central air supply pump 138 and the central air supply circuit 138a are used when correcting subsidence due to the wafer's own weight by utilizing a central air supply port provided in the center of the wafer chuck 200, which will be described later. The central air supply pump 138, the central air supply circuit 138a, and the central air supply system 138b supply air for correcting subsidence due to the wafer's own weight, and are designed to be able to be controlled with a small air flow rate and good time response compared to the air supply and air suction to the air bearing structure.

[0020] In addition, a clamp mechanism drive pump 139 and a clamp mechanism drive air supply circuit 139a are connected to the wafer chuck 200 via a clamp mechanism drive air supply system 139b built into the motor 132, and are used to operate the clamp mechanism 300.

[0021] The control unit 150 is connected to each pump, the motor 132, and the vertical drive mechanism 134b via a control circuit network 150c, and performs integrated control of these. The control by the control unit 150 may be performed by the control device 15, or the control unit 150 and the control device 15 may be separate pieces of hardware.

[0022] FIG. 3 is a perspective view of the wafer chuck 200. The vertical direction is the Z direction, and the horizontal direction is the XY direction. The wafer chuck 200 has an air bearing structure 201, a central air supply port 210, and a clamping mechanism 300. The air bearing structure 201 is a mechanism that holds the wafer 100 in a non-contact manner in the vertical direction with a certain gap between it and the wafer chuck 200. The air bearing structure 201 has a pressure pocket 203 and a positive pressure air supply port 203a, which supplies positive pressure air bearing air 203b. The air bearing structure 201 also has an air intake groove 204 and a negative pressure air suction port 204a, which suck in and exhaust negative pressure air bearing air 204b. The air intake groove 204 and the negative pressure air suction port 204a are located in positions shared by adjacent air bearing structures 201. A more detailed configuration of the air bearing structure 201 will be described later. The central air supply port 210 is provided in the center of the wafer chuck 200 and supplies central air 210b to correct sinking of the wafer due to its own weight. The clamping mechanism 300 holds the wafer 100 (shown by the dashed line) in the horizontal direction (X and Y directions). The clamping mechanism 300 is configured to be able to contact and hold the outer peripheral edge 100a of the wafer.

[0023] Here, an overview of the operation of the wafer inspection apparatus 10 will be described. As described with reference to FIG. 1 , the wafer 100 loaded into the wafer introduction section 11 is removed from the cassette by the transport mechanism 12 and moved to the inspection chamber 13. The wafer 100 moved to the inspection chamber 13 is placed on the wafer chuck 200, which is the mounting location. In this manner, the wafer 100 is positioned opposite the direction of gravity relative to the wafer chuck 200. Thereafter, the wafer 100 is held at its outer peripheral edge 100 a by a clamping mechanism 300 built into the wafer chuck 200 to prevent it from falling off the wafer chuck 200. During this process, air is discharged onto the backside of the wafer 100 from the central air supply port 210 or the positive pressure air supply port 203 a of the air bearing structure 201 to generate pressure. This compensates for the sinking of the wafer 100 due to gravity, and a levitation force is applied to prevent the backside of the wafer 100 from contacting the surface of the wafer chuck 200, thereby holding the wafer 100 in a non-contact manner. Thereafter, air is supplied from the positive pressure air supply port 203a of the air bearing structure 201 while air is sucked from the negative pressure air supply port 204a, thereby balancing the positive and negative pressures on the backside of the wafer 100. This allows the wafer 100 to be held with high flatness and high support rigidity by the air bearing effect while maintaining non-contact between the backside of the wafer 100 and the wafer chuck 200. After the wafer 100 is held flat and with high rigidity in this manner, the optical measurement unit 131 measures foreign particles on the wafer 100. To this end, the wafer chuck 200 is rotationally driven by the motor 132 and translated horizontally by a linear movement means (not shown) of the base 133. With this movement, the size, position, etc. of foreign particles on the entire surface of the wafer 100 are mapped by the control unit 150, and the mapping is recorded as foreign particle inspection data for the wafer 100. After the measurement, the wafer 100 is released from the wafer chuck 200 and the clamping mechanism 300, and is again transferred from the wafer chuck 200 by the transfer mechanism 12 and returned to the cassette. This process is repeated until all the wafers in the cassette are inspected for foreign matter.

[0024] <Wafer Holding in the Z Direction> FIG. 4 is a diagram illustrating the structure of the air bearing structure 201. The left side of FIG. 4 is an enlarged view of the area indicated by A in FIG. 3. The right side of FIG. 4 is a cross-sectional view taken along the line B-B of the left side of FIG. 4. As shown in FIG. 4, the air bearing structure 201 has, as its basic components, a pressure pocket 203, a positive pressure air supply port 203a, an intake groove 204, and a negative pressure air suction port 204a. The positive pressure air supply port 203a is orifice-shaped. The pressure pocket 203 is a recess provided in the surface of the wafer chuck 200 and is connected to the positive pressure air supply port 203a. The negative pressure air suction port 204a is orifice-shaped. The intake groove 204 is arranged around the periphery of the air bearing structure 201, and the intake groove 204 and the negative pressure air suction port 204a are arranged so as to be shared between adjacent air bearing structures. Air supplied from the air supply pump 136 via the positive pressure air supply circuit 136a is supplied as positive pressure air bearing air 203b from the positive pressure air supply port 203a to the gap between the wafer 100 and the wafer chuck 200. The air is then sucked as negative pressure air bearing air 204b from the air intake grooves 204 and negative pressure air suction ports 204a arranged around the air bearing structure 201, and is sucked by the air intake pump 137 via the negative pressure air suction circuit 137a. The air intake grooves 204 and negative pressure air suction ports 204a are shared with the adjacent air bearing structures 201, and positive pressure air from the adjacent air bearing structures 201 is also sucked.

[0025] Because the wafer 100 is held without contact with the wafer chuck 200, i.e., with a gap between it and the wafer chuck 200, a parallel space (hereinafter referred to as the wafer gap h) exists between the rear surface of the wafer 100 and the front surface of the wafer chuck 200 in this flow path. Air flows through this parallel space to form an air film, generating the wafer gap h. Given constant positive and negative pressure conditions, the wafer gap h remains constant. This effect is called the air bearing effect. For each positive pressure air supply port 203a, the air bearing structure 201 is provided with at least one negative pressure air suction port 204a (intake port) shared between adjacent air bearing structures 201, forming a pair of air supply port and intake port. This configuration achieves a balance between the positive and negative pressures, or a balance between the air supply and intake flow rates, resulting in an air bearing effect due to the action of the positive pressure air bearing air 203b and the negative pressure air bearing air 204b. This makes it possible to hold the wafer 100 with high flatness and high supporting rigidity.

[0026] FIG. 5 is a graph showing the characteristics of the air bearing structure 201. As shown in FIG. 5, by setting the positive pressure of the positive-pressure air supply port 203a and the negative pressure of the negative-pressure air suction port 204a of the air bearing structure 201 to specified values ​​determined by design, the wafer gap h has a single stable value (wafer gap equilibrium distance) at the equilibrium position, which is the design value of the wafer gap h. If the wafer gap h is narrower than the design value, a force pushing up the wafer 100 (repulsive force) acts; if it is wider, a force attracting the wafer (attractive force) acts. This effect is effective when the wafer gap h is in the range of approximately several μm to 100 μm. In particular, when the design wafer gap value is in the range of approximately 30 to 70 μm, a strong air bearing effect causes strong repulsive and attractive forces to return the wafer to the design wafer gap value in response to even a slight change in the wafer gap h. That is, the support rigidity (change in wafer acting force in response to change in wafer gap h) is high, and the wafer is held with high rigidity, so it is possible to hold the wafer flat and to flatten and hold a warped wafer.

[0027] On the other hand, when the wafer gap h is in the range of approximately more than 100 μm to approximately 500 μm, the support stiffness becomes small. In this range, the wafer is flexibly held with low stiffness. Therefore, even for a warped wafer, excessive force is not applied to flatten the wafer, and the wafer can be flexibly held while allowing for the warped shape. Furthermore, even if vertical vibration occurs during wafer holding, because the support stiffness has a positive value, a weak air bearing effect acts on the wafer, suppressing the vibration, making it possible to hold the wafer stably.

[0028] FIG. 3 shows an example of the arrangement of air bearing structures 201 on the surface of the wafer chuck 200. The inventors proposed this structure in Japanese Patent Application No. 2023-005894. The air bearing structures 201 are evenly arranged with a uniform circumferential arrangement density from the inner periphery to the outer periphery. At the outermost periphery, smaller air bearing structures 201 are evenly arranged in the circumferential direction than those on the inner periphery, further improving the arrangement density. This structure allows the Z-direction wafer retention force of the air bearing structures 201 to be constant from the inner periphery to the outer periphery. In other words, a uniform air bearing effect can be generated across the entire surface of the wafer 100. This results in a uniform wafer gap h, enabling flat retention. Furthermore, the support rigidity is uniform, enabling even a warped wafer to be flattened and retained. The arrangement of the air bearing structures 201 is not limited to that shown in FIG. 3 and can be arbitrarily modified as long as the effects of the technology disclosed herein are not impaired.

[0029] <Holding of wafer in XY directions> Figure 6A is a perspective view of clamp mechanism 300 seen from the outside, and is an enlarged view of the area indicated by C in Figure 3. Figure 6B is a perspective view of wafer chuck 200 seen from below. Figure 6C is a diagram for explaining the operation of clamp mechanism 300, and is a cross-sectional view taken along line D-D in Figure 3.

[0030] The clamping mechanism 300 includes holding claws 301, a rotating shaft 302, a flexible support mechanism 303, a rod 304, and a rod driving mechanism 305. The holding claws 301 contact and hold the wafer 100 at a holding claw wafer contact portion 301a and are rotatably supported by the rotating shaft 302. The flexible support mechanism 303 flexibly supports the holding claws 301 so that the holding claws 301 are movable in the axial direction of the rotating shaft 302, i.e., the vertical direction (Z direction). The rod 304 connects the holding claws 301 to the rod driving mechanism 305. The rod driving mechanism 305 drives the rod 304 in the radial direction of the chuck 200. The operation of the rod driving mechanism 305 is controlled by the control unit 150. The details of the operation of holding the wafer 100 will be described later, so a brief explanation will be given here. When the rod driving mechanism 305 moves the rod 304 toward the outer periphery, the connection between the holding claws 301 and the rod 304 also moves toward the outer periphery. This action causes the holding claws 301 to rotate around the rotation axis 302, and the holding claw wafer contact portions 301a move inward. As a result, the holding claws 301 come into contact with the outer peripheral edge 100a of the wafer 100 at the holding claw wafer contact portions 301a, and hold the wafer 100 in the X and Y directions. Holding the wafer 100 in the X and Y directions must be such that it does not shift in position in the circumferential or radial directions due to the effects of centrifugal force caused by the start and stop of rotation and high-speed rotation during wafer inspection. For this reason, the holding claws 301 are configured to be rigidly supported in the X and Y directions by the clamp mechanism 300.

[0031] As will be described later, the timing of the operation of the holding claws 301 to hold the wafer 100 occurs before the wafer 100 approaches the design value of the wafer gap h. After the holding claws 301 hold the outer peripheral edge 100a of the wafer 100, the wafer 100 approaches the chuck 200 together with the holding claws 301. While the air bearing effect acts on the wafer 100, the wafer 100 approaches further together with the holding claws 301 until the design value of the wafer gap h is reached and the wafer 100 is held. At the design value of the wafer gap h, the wafer 100 must be flat for wafer inspection. Therefore, to prevent deformation due to force applied in the Z direction at the outer peripheral portion of the wafer 100, the flexible support mechanism 303 must have a rigidity in the Z direction that is sufficiently flexible relative to the air film rigidity at the design value of the wafer gap h. This allows the holding claws 301 to be flexibly supported and move in the Z direction. While FIG. 6C illustrates the flexible support mechanism 303 having a coil spring structure, a leaf spring or the like may also be used. Alternatively, the holding claw wafer contact portion 301a of the holding claw 301 may be made independent and supported by a soft support member such as a spring.

[0032] <Mounting of Wafer onto Wafer Chuck> The wafer 100 is required to be handled without contacting either its front or back surface within the wafer inspection device 10. Therefore, even in the process from the cassette within the wafer introduction section 11 to the inspection chamber 13, the wafer 100 is transported while being held by the outer peripheral edge 100a of the wafer 100 using a handling jig within the transport mechanism 12. Furthermore, within the inspection chamber 13, when the wafer 100 is loaded onto the wafer chuck 200 from the handling jig, it is naturally required that the wafer 100 be transported without contacting either its front or back surface.

[0033] When the wafer 100 is held by its outer peripheral edge 100a, gravity causes the center to sink and deform due to its own weight. The amount of deformation is approximately 70 to 100 μm for a φ300 mm wafer. This is uniquely determined by the material and shape of the wafer 100. Furthermore, wafers are not necessarily flat; they exhibit concave, convex, or saddle-shaped warpage. The standard for bare wafers shipped by wafer manufacturers is 100 μm or less, with the range of wafer warpage ranging from several tens of μm to a maximum of 100 μm. Device manufacturers also use recycled wafers, which can have warpage up to several hundred μm. Meanwhile, the design value of the wafer gap h for the air bearing structure 201 is approximately 30 to 70 μm. At this design value of the wafer gap h, the strong air bearing effect ensures that even a warped wafer is flattened and held in a non-contact manner. On the other hand, in the process of loading the wafer 100 onto the wafer chuck 200, the wafer gap h approaches to about 100 to 500 μm, but the air bearing effect obtained at this time is weak, which creates the possibility of the wafer 100 and the wafer chuck 200 coming into contact with each other.

[0034] To avoid contact between the wafer 100 and the wafer chuck 200, the wafer loading operation of this embodiment is divided into a proximity operation (macro region) in which the air bearing effect is weak, and an operation (micro region) in which the air bearing effect is strong. The macro region is a proximity operation in which the air bearing effect is weak between the wafer 100 and the wafer chuck 200 from when the wafer is supported by the outer peripheral edge 100a until the wafer gap h reaches approximately 500 to 100 μm. The micro region is an operation in which the air bearing effect is strong from when the wafer gap h reaches the design gap (100 μm or less, approximately 30 to 70 μm). As a result, the wafer 100 is loaded without contacting the wafer chuck 200 in both the macro and micro regions.

[0035] FIG. 7A is a flowchart of the operation of mounting the wafer 100 onto the wafer chuck 200. FIG. 7B is a conceptual diagram for explaining the positional relationship between the wafer 100 and the wafer chuck 200 in steps S11 to S14, S21, and S31 shown in FIG. 7A. Steps S11 to S14 shown in FIGS. 7A and 7B correspond to the macro region, and step S21 corresponds to the micro region. Step S31 is a wafer inspection process. Note that in the following description of the flowchart, although the control unit 150 or the control device 15 actually controls each component, for the sake of simplicity, each component will be described as the main operator of the operation. First, the operation in the macro region will be described in detail.

[0036] 1, the transfer mechanism 12 moves the wafer 100, while holding it by its outer peripheral edge 100a, to the inspection chamber 13 in which the wafer chuck 200 is located. The transfer position of the wafer 100 is a wafer transfer position, which is a position where the center of rotation of the wafer chuck 200 and the center of the wafer 100 coincide horizontally and a height position where the wafer 100 is several millimeters to several tens of millimeters away from the wafer chuck 200 vertically. The handling jig of the transfer mechanism 12, which holds the wafer 100 by its outer peripheral edge 100a, places the wafer 100 on the wafer support pins 135 so that the wafer 100 is supported by the outer peripheral edge 100a. At this time, the wafer 100 sinks under its own weight, causing deformation of about 70 to 100 μm.

[0037] -Step S12- The wafer chuck 200 moves closer to the wafer 100. At this time, a floating force is applied to the wafer 100 due to the air compression between the wafer chuck 200 and the wafer 100. This force acts in a direction that corrects the deformation of the wafer 100 due to its own weight. In order to further correct the deformation due to its own weight, positive pressure air bearing air 203b is supplied from a number of positive pressure air supply ports 203a arranged within the surface of the wafer chuck 200. The relationship between the speed at which the wafer chuck 200 approaches the wafer and the floating force acting on the wafer 100 will be explained later.

[0038] -Step S13- As described above, when the wafer chuck 200 approaches the wafer 100 to within approximately 500 to 100 μm, the holding claws 301 hold the wafer 100 in the horizontal XY direction while the wafer 100 is supported by the wafer support pins 135 at its outer peripheral edge 100 a. As described with reference to FIG. 6, in order for the holding claws 301 to hold the wafer 100, the rod drive mechanism 305 pulls the rod 304 toward the inner periphery. When the distance between the wafer 100 and the wafer chuck 200 reaches a predetermined distance, i.e., approximately 500 to 100 μm, the rod drive mechanism 305 drives the rod 304 toward the outer periphery, bringing the holding claws 301 into contact with the outer peripheral edge 100 a of the wafer 100 and holding the wafer 100. Because the wafer 100 is supported by the wafer support pins 135 at its outer peripheral edge 100 a, the wafer 100 is held without moving horizontally when the wafer is switched to being held by the holding claws 301. On the other hand, if the speed at which the wafer chuck 200 approaches the wafer 110 is too fast, an excessive lifting force acts on the wafer 110, causing it to lift off the wafer support pins 135, potentially causing the wafer to shift in position in the horizontal X and Y directions. To avoid this, the lifting approach speed of the wafer chuck 200 may be switched to a slower speed. The wafer lifting force and approach speed will be described in detail later.

[0039] In step S13, the wafer 100 is positioned close to the wafer chuck 200 with a gap of approximately 500 to 100 μm, and it is necessary to reliably correct for subsidence due to the wafer's own weight. Furthermore, in addition to the initial warpage, the wafer 100 is also subjected to a pressing force from the outer periphery by the holding jaws 301, which may result in a large amount of wafer deformation. To prevent physical contact between the wafer 100 and the wafer chuck 200 even in such a case, the supply of positive pressure air bearing air 203b from the multiple positive pressure air supply ports 203a disposed within the surface of the wafer chuck 200 continues in step S13, following step S12. The pressure and flow rate of the positive pressure air bearing air 203b may be adjusted at the timing when the holding jaws 301 hold the outer peripheral edge 100a of the wafer 100.

[0040] The contact force of the holding jaws 301 on the wafer 100 at this time provides a minimum holding force that prevents the wafer 100 from shifting in the rotational direction when the rotation of the wafer chuck 200 accelerates in step S31, which will be described later. This holding force is determined taking into consideration the rotational acceleration of the motor 132 on which the wafer chuck 200 is mounted and the frictional force between the holding jaws 301 and the outer peripheral edge 100a of the wafer 100. During steady rotation, eccentricity of the wafer 100 generates a whirling force that is applied to the holding jaws 301, so a holding force that can withstand this force is provided. Since the whirling force of the wafer 100 changes when the rotation speed changes, a mechanism that changes the holding force of the holding jaws 301 depending on the rotation speed or a mechanism that utilizes centrifugal force may be used.

[0041] -Step S14- After this, the wafer chuck 200 moves further upward, and releases the wafer 100 from the wafer support pins 135 on which it was placed. At this point, the wafer 100 is held in the Z direction by the holding claws 301 only at the outer peripheral edge 100a of the wafer 100, with the wafer gap h being approximately 500 to 100 μm. In step S14, the supply of positive pressure air bearing air 203b from the positive pressure air supply port 203a, or the adjustment of the flow rate and pressure, continues as in step S13. This completes the operation in the macro region.

[0042] -Step S21- The operation of the micro region, which is the next stage, will now be described. This is the region where the air bearing structure 201 operates. As described above, the air bearing structure 201 exerts an air bearing effect by balancing the pressure and flow rate between the positive-pressure air bearing air 203b supplied from the positive-pressure air supply port 203a and the negative-pressure air bearing air 204b sucked in by the negative-pressure suction port 204a. When the wafer gap h is approximately 500 to 100 μm, a weak air bearing effect generates a fluid force that pulls the wafer 100 toward the wafer chuck 200. When the wafer gap h is approximately 100 μm or less, a strong air bearing effect operates, and the wafer 100 is held flat with high support rigidity at a design gap set to approximately 30 to 70 μm.

[0043] Therefore, in step S21 of the micro region, the operation of the negative pressure air bearing air 204b sucked by the negative pressure suction port 204a is added to the positive pressure air bearing air 203b from the positive pressure air supply port 203a, and the wafer gap h is narrowed while controlling these pressures and flow rates in a time series, so that the wafer 100 is held flat with high support rigidity at the design value of the wafer gap h for wafer inspection. This time series control of the pressure and flow rate will be described in detail later.

[0044] In the operation of step S21, the holding jaws 301 of the clamping mechanism 300 follow the movement of the wafer 100 in the Z direction, i.e., the change in the wafer gap h, and move together with the wafer 100 toward the wafer chuck 200. The flexible support mechanism 303 built into the holding jaws 301 has a rigidity in the Z direction that is sufficiently flexible compared to the air film rigidity generated by the air bearing structure 201, and therefore does not affect the movement of the wafer 100 toward the wafer chuck 200.

[0045] During step S21, the wafer chuck 200 moves in the Z direction to the inspection height position. At this time, the wafer support pins 135 pass through the wafer support pin through holes 220 formed in the wafer chuck 200. This completes step S21, with the wafer chuck 200 being prepared for the rotational inspection.

[0046] -Step S31- Wafer chuck 200, which holds wafer 100 in the above manner, is rotated and translated by motor 132, and the entire surface of wafer 100 is inspected for foreign matter by optical measurement unit 131 installed above wafer 100. Even during the rotational and translational movements, wafer 100 is held flat on wafer chuck 200 with high support rigidity at the designed gap due to the strong air bearing effect. Therefore, the entire surface of wafer 100 is within the focal range of the inspection position height of optical measurement unit 131, making it possible to inspect wafer 100 with high sensitivity.

[0047] After the foreign particle inspection is completed, the above steps are followed in reverse. That is, upon completion of the foreign particle inspection, the suction operation of the negative pressure air bearing air 204b sucked through the negative pressure suction port 204a is stopped. At this time, the suction operation is stopped in stages in a time series manner to prevent the wafer gap h from suddenly increasing. Next, to release the wafer 100 from the wafer chuck 200, the wafer chuck 200 moves downward, causing the wafer support pins 135 to relatively approach the outer peripheral edge 100a of the wafer 100 (step S14). As the wafer chuck 200 further moves downward, the wafer support pins 135 contact and hold the outer peripheral edge 100a of the wafer (step S13). At the same time, the rod drive mechanism 305 drives the holding claws 301 to move away from the wafer 100, releasing the holding in the X and Y directions. This releases the wafer 100 from the wafer chuck 200 (step S12). At this time, if air does not flow between the wafer 100 and the wafer chuck 200, the two will not be able to be separated smoothly. Forcing the separation will cause the wafer 100 to bend significantly, potentially causing it to fall off or become damaged. Slower separation reduces this possibility, but increases the operating time. To avoid this, air is supplied from the positive pressure air supply port 203a of the air bearing structure 201 when the wafer 100 is released from the wafer chuck 200. Of course, even in this case, it is important to select a supply pressure that will prevent the wafer 100 from falling off the wafer support pins 135. This shortens the wafer 100 release time while reducing the possibility of the wafer 100 falling off or becoming damaged. The wafer chuck 200 then moves further downward, and at the wafer transfer position height, the air supply 203b from the positive pressure air supply port 203a is stopped (step S11). The transfer mechanism 12 shown in FIG. 1 then moves the wafer 100 to the wafer loading chamber 11, completing the wafer inspection sequence.

[0048] 7B, in steps S12 to S14 of the operation of mounting the wafer 100 on the wafer chuck 200, positive pressure air bearing air 203b is supplied from a number of positive pressure air supply ports 203a arranged within the surface of the wafer chuck 200 in order to correct deformation due to sinking of the wafer 100 due to its own weight. On the other hand, a central air supply port 210 arranged in the center of the wafer chuck 200 can also be used to correct deformation due to sinking of the wafer 100 due to its own weight.

[0049] 7C is a conceptual diagram for explaining the positional relationship in the mounting operation of the wafer 100 onto the wafer chuck 200 when correcting deformation due to sinking of the wafer 100 due to its own weight using the central air supply port 210. The difference from FIG. 7B is that in order to correct deformation due to sinking of the wafer 100 due to its own weight in steps S12 to S14, central air 210b arranged at the center of the wafer chuck 200 is used in FIG. 7C instead of the positive pressure air bearing air 203b in FIG. 7B.

[0050] As described in FIG. 2, the supply of central air 210b from the central air supply port 210 is designed to be controlled with good time response at a lower air flow rate than the positive pressure air bearing air 203b from the positive pressure air supply port 203a of the air bearing structure. For example, the flow rate of the positive pressure air bearing air 203b is approximately 100 to 200 L / min, while the flow rate of the central air 210b is approximately 10 to 20 L / min, which is about 1 / 10 of the flow rate. This allows for more accurate time-series control of the levitation force acting on the wafer 100 and correction for self-gravity subsidence. This allows for more stable mounting of the wafer 100 onto the wafer chuck 200.

[0051] <Regarding Wafer Levitation Force and Approach Speed> In the series of wafer inspections described above, in steps S12 to S14 in the macro region, the wafer chuck 200 moves closer to the wafer 100. That is, the wafer 100 approaches the wafer chuck 200 relatively. At this time, a levitation force is applied to the wafer 100 due to the air compression between the wafer chuck 200 and the wafer 100. This force acts in a direction that corrects the wafer 100's self-weight subsidence deformation. However, if the wafer approach speed is too fast, the levitation force may be excessively applied to the wafer 100, causing the wafer 100 to lift off the wafer support pins 135, for example, in step S12, potentially resulting in horizontal positional deviation. In other words, when the wafer 100's self-weight subsidence correction is performed using the wafer levitation force generated by the wafer approach speed, there is a trade-off between the two. Therefore, the inventors calculated the levitation force of the wafer 100 when the wafer 100 approaches the wafer chuck 200 at a constant speed. The results are shown in FIG. 8.

[0052] 8 is a graph showing the levitation force acting on the wafer 100 versus the wafer gap h when the approach speed of the wafer 100 is constant. According to this graph, the curve of the wafer levitation force generation increases rapidly as the wafer gap h becomes smaller, and depending on the approach speed conditions, a levitation force greater than the weight of the wafer 100 itself is generated. From this result, the approach speed at which the wafer levitation force becomes equivalent to the wafer's own weight was calculated. The results are shown in FIG. 9.

[0053] FIG. 9 is a graph showing an example of a wafer approach speed pattern relative to the wafer gap h, which maintains a constant wafer levitation force. This graph shows that the characteristics of the wafer approach speed relative to the wafer gap can be expressed by a quadratic function. When a levitation force close to the wafer's own weight is set as the criterion, the wafer's self-weight sinking deformation is eliminated, and the wafer moves while maintaining a horizontal shape. If the approach speed is faster than this, the wafer will experience a levitation force greater than the support force from the wafer support pins 135, which may cause the wafer 100 to float when placed on the wafer chuck 200, resulting in horizontal displacement. Therefore, the fastest approach time in this range satisfies this condition. Approach speed control using this function allows the wafer 100 to approach the wafer chuck 200 without floating. The wafer approach speed patterns relative to the wafer gap h shown in FIG. 9 are compiled into a database and stored in advance in the storage device 16. By controlling the Z-direction speed of the wafer chuck 200 in accordance with this database of wafer approach speed patterns (wafer approach speed database), a feedback circuit is not required, and a simple control system can be configured.

[0054] 9, a distance sensor (not shown) is provided to measure the wafer gap h. The control unit 150 controls the speed at which the wafer chuck 200 approaches the wafer 100 based on the detection signal of the distance sensor.

[0055] Fig. 10 is a graph showing a wafer approach speed pattern versus wafer chuck movement time that maintains a constant wafer levitation force. Fig. 10 shows a wafer approach speed pattern when the approach operation time of wafer chuck 200 (the drive time of vertical drive mechanism 134b) is a variable. The approach speed between wafer 100 and wafer chuck 200 can be controlled based on the wafer approach speed pattern versus wafer chuck movement time in Fig. 10 instead of the wafer approach speed pattern versus wafer gap h in Fig. 9. The wafer approach speed pattern shown in Fig. 10 is effective in that it does not require a distance sensor to measure wafer gap h and allows time control, making processing simpler.

[0056] As described above, the approach speed pattern in this embodiment has been described as the maximum value at which the wafer 100 does not shift in position. Alternatively, if a wafer floating margin is required, an approach speed can be set at which a floating force equal to or less than the wafer's own weight, for example, half the wafer's own weight, is applied. In this case, some degree of deformation due to the wafer's own weight will occur, and this deformation can be corrected. Specifically, air can be supplied between the wafer 100 and the wafer chuck 200 during the approach operation from the positive pressure air supply port 203 a of the air bearing structure 201 or the central air supply port 210 provided in the center, thereby assisting in the correction of deformation due to the wafer's own weight. The amount of air supplied must be reduced as the wafer gap narrows.

[0057] When priority is given to the responsiveness and flow rate accuracy of the supplied air, the central air supply port 210 may be used. The central air supply port 210 illustrated in FIG. 3 is connected to the central air supply pump 138, central air supply circuit 138a, and central air supply system 138b illustrated in FIG. 2. Furthermore, the central air 210b is designed to be controlled with good time response at a lower air flow rate than the supply of positive pressure air bearing air 203b to the air bearing structure and the suction of negative pressure air bearing air 204b. Therefore, using the central air 210b can assist in self-weight subsidence deformation correction with good precision and response at a small flow rate. When the central air supply port 210 is used, a self-weight subsidence correction force acts on the center of the wafer 100, and the wafer is subjected to a lifting force due to the approach speed and an air lifting force at the center. A force is applied to the wafer 100 in a direction that lifts it at the center, leaving it slightly deformed in the direction of gravity. On the other hand, the force for correcting subsidence due to gravity is weaker near the wafer support pins 135 (rod-shaped members) on which the wafer 100 rests, so a downward force in the direction of gravity remains on the wafer 100. This reduces the possibility that the wafer 100 will float up and separate from the wafer support pins 135.

[0058] Next, the time-series control of pressure and flow rate in step S21 of the micro region will be described. This is the region where the air bearing structure 201 is operated. As described above, the air bearing structure 201 exerts an air bearing effect by balancing the pressure and flow rate of the positive-pressure air bearing air 203b supplied from the positive-pressure air supply port 203a and the negative-pressure air bearing air 204b sucked in by the negative-pressure suction port 204a. In step S21 of the micro region, the wafer gap h is narrowed by controlling the pressure and flow rate of the positive-pressure air bearing air 203b from the positive-pressure air supply port 203a and the negative-pressure air bearing air 204b sucked in by the negative-pressure suction port 204a in a time-series manner. If the positive-pressure air bearing air 203b or the negative-pressure air bearing air 204b is applied to the air bearing structure 201 with a sudden, step-like change, the fluid force also acts suddenly on the wafer 100, which may cause vibration of the wafer 100 or the wafer 100 to come into contact with the wafer chuck 200. To avoid such a phenomenon, in this embodiment, a fluid force that attracts the wafer 100 to the wafer chuck 200 is gradually applied.

[0059] Specifically, first, either the positive pressure air supply port 203a (positive pressure side) or the negative pressure air exhaust port 204a (negative pressure side) of the air bearing mechanism 201 is set to the design pressure for air bearing operation, and the other is set in a direction higher than the design pressure for air bearing operation. The design pressure refers to the positive pressure of the positive pressure air bearing air 203b and the negative pressure of the negative pressure air bearing air 204b, which correspond to the design value (design gap) of the wafer gap h during wafer inspection. The pressure direction refers to the direction of increasing pressure in the case of the positive pressure air bearing air 203b, and the direction of approaching atmospheric pressure in the case of the negative pressure air bearing air 204b. As a result, the pressure balance between the positive pressure air bearing air 203b and the negative pressure air bearing air 204b acts in a direction that increases the wafer gap h generated by the air bearing structure 201. Therefore, the pressure setting on the positive pressure side or negative pressure side is set to approximately 500 to 100 μm, which is higher than the design value (design gap) of the wafer gap h and close to the wafer gap h at the end of macro-region operation. Thereafter, the pressure on the positive pressure side or negative pressure side set on the pressurizing side is gradually shifted toward the design pressure so that the wafer gap h is set to the design value (design gap).

[0060] When changing the intake pressure of negative pressure air suction port 204a of air bearing mechanism 201, positive pressure air supply port 203a (positive pressure side) of air bearing mechanism 201 is set to the design value for air bearing operation, and negative pressure air suction port 204a (negative pressure side) is set to a value closer to atmospheric pressure than the design pressure for air bearing operation, so that wafer gap h is approximately 500 to 100 μm. After this, the pressure on the negative pressure side is gradually changed to the design pressure, and wafer gap h is set to the design value (design gap).

[0061] FIG. 11 shows an example of an adjustment curve when the negative pressure side pressure is gradually shifted to the design pressure to adjust the wafer gap h to the design value. The adjustment curve exhibits a characteristic in which the wafer gap h narrows significantly as the suction pressure decreases from atmospheric pressure (0 Pa) to a slightly negative pressure. Then, by adjusting the suction pressure in the negative pressure direction, the wafer gap h approaches the design gap. Therefore, the supply pressure from the positive pressure air supply port 203a is set to the design pressure, and the suction pressure from the negative pressure air suction port 204a is set to a starting pressure close to atmospheric pressure. The wafer gap h at this time, i.e., the starting gap in step S21, is set to approximately 500 to 100 μm, which is close to the wafer gap h at the end of step S14. The suction pressure from the negative pressure air suction port 204a is then reduced and finally adjusted to the set pressure (design value). This allows the wafer gap h to reach the design value (design gap).

[0062] Next, when changing the supply pressure of positive pressure air suction port 203a of air bearing mechanism 201, negative pressure air suction port 204a (negative pressure side) of air bearing mechanism 201 is set to the design pressure for air bearing operation, and positive pressure air supply port 203a (positive pressure side) is set in the direction of increasing pressure above the design pressure for air bearing operation. That is, the wafer gap h (starting gap in step S21) created by air bearing structure 201 is set to approximately 500 to 100 μm, which is larger than the design value (design gap) and close to the wafer gap h at the end of macro region operation. Thereafter, in order to set wafer gap h to the design value (design gap), the pressure on the positive pressure side set on the increasing pressure side is gradually reduced to transition to the design pressure.

[0063] 12 shows an example of an adjustment curve when the pressure on the positive pressure side is gradually reduced to transition to the design pressure, and the wafer gap h is set to the design value. The negative pressure air suction port 204a is set to a constant design pressure. The air supply pressure from the positive pressure air supply port 203a is set to a pressure higher than the design pressure. This air supply pressure can be set to, for example, a value several tens of percent higher or several tenths higher than the design pressure. Thereafter, the air supply pressure from the positive pressure air supply port 203a is reduced and finally adjusted to the design pressure. This allows the wafer gap h to be set to the design value.

[0064] Summary of First Embodiment As described above, the wafer inspection apparatus 10 according to the first embodiment includes a wafer chuck 200 (wafer backside non-contact holding mechanism), a clamping mechanism 300 (wafer outer peripheral edge holding mechanism), wafer support pins 135, and a control unit 150 (control device). The wafer chuck 200 is provided with an air bearing structure 201 having a positive pressure air supply port 203a, an air intake groove 204, and a negative pressure air suction port 204a. The air intake groove 204 and the negative pressure air suction port 204a are shared between adjacent air bearing structures 201. A plurality of air bearing structures 201 are uniformly arranged in the radial and circumferential directions, and the air bearing effect allows the wafer 100 to be uniformly held without contacting the backside of the wafer. The wafer chuck 200 also includes a central air supply port 210 to compensate for sinking of the wafer due to its own weight.

[0065] With the wafer 100 supported by the support pins 135, the control unit 150 controls the vertical drive mechanism 134 to bring the wafer 100 and the wafer chuck 200 closer to each other while applying a wafer approaching speed according to the distance between them. At the same time, the control unit 150 corrects the sinking of the wafer 100 due to its own weight by time-series control of the positive pressure air bearing air 203b by the positive pressure air supply circuit 136a or time-series control of the center air 210b by the center air supply circuit 138a. The wafer approaching speed is set based on the wafer approaching speed pattern relative to the wafer gap or the wafer approaching speed pattern relative to the wafer chuck movement time.

[0066] Then, when the distance between wafer 100 and wafer chuck 200 reaches a specified value (approximately 500 to 100 μm), control unit 150 drives rod drive mechanism 305 (mechanism that drives the claws) of clamp mechanism 300 (wafer outer peripheral edge holding mechanism) so that holding claws 301 hold outer peripheral edge 100 a of wafer 100 at holding claw wafer contact portion 301 a. Wafer 100 is released from support pins 135, and wafer 100 is held on wafer chuck 200 with its own weight sinking corrected so that its back surface is not in contact and only its outer peripheral edge 100 a is in contact with the wafer.

[0067] Thereafter, the control unit 150 controls the pressure of the positive pressure air bearing air 203b by the positive pressure air supply circuit 136a and the negative pressure air bearing air 204b by the negative pressure air suction circuit 137a in a time series manner. A set pressure corresponding to the design gap is applied to either the positive pressure air bearing air 203b or the negative pressure air bearing air 204b, and the pressure of the other is set to the pressurized side higher than the set pressure. As a result, the wafer 100 is held in a non-contact state on the wafer chuck 200 by a weak air bearing effect, with a gap wider than the design gap.

[0068] Furthermore, the control unit 150 changes the pressure set on the pressurizing side so that it approaches the set pressure corresponding to the design gap. At the set pressure of the positive pressure air bearing air 203b and the set pressure of the negative pressure air bearing air 204b, the wafer 100 is held flat on the wafer chuck 200 with high support rigidity even for a warped wafer due to the strong air bearing effect at the design gap.

[0069] In this manner, the following operations are performed: a macro operation of bringing wafer 100 and wafer chuck 200 close to each other without contacting the backside of wafer 100; an operation of holding claws 301 that holds wafer 100 horizontally at outer peripheral edge 100a at the end of the macro operation; and a micro operation of applying a strong air bearing effect by air bearing structure 201 of wafer chuck 200. This allows wafer chuck 200 to hold wafer 100 in contact only at the outer peripheral edge without contacting the backside of wafer 100, and enables a mounting operation that ensures horizontal positional accuracy of wafer 100, and a non-contact wafer holding operation and optical inspection operation that ensure wafer flatness. As a result, a wafer inspection device with high sensitivity, accuracy, and reliability can be realized.

[0070] Second Embodiment When wafers are shipped from wafer manufacturers, their weight, thickness, and warpage are controlled within standard ranges. However, when device manufacturers use reclaimed wafers, variations in wafer weight, thickness, warpage, or rigidity may occur. This causes variations in the amount of wafer sinking due to its own weight, which may change the optimal value for the approach speed to the wafer chuck, which affects wafer floating, during the wafer approach operation described with reference to Figures 8 to 10. To solve this problem, a second embodiment describes a configuration in which a load sensor or suction mechanism is provided on the wafer support pins.

[0071] <Configuration Example of Wafer Inspection Apparatus> Fig. 13 is a schematic diagram of the mechanisms and control circuit around the wafer chuck 200 according to the second embodiment. Fig. 13 is similar to Fig. 2 (first embodiment), but differs in that wafer support pins 140 are provided instead of wafer support pins 135. In addition, each wafer support pin 140 is connected to a control unit 150.

[0072] FIG. 14 is a schematic diagram illustrating the structure of a wafer support pin 140 according to the second embodiment. As shown in FIG. 14, the wafer support pin 140 is composed of a wafer placement portion 140a, a load detection portion 140b, and a base portion 140c. The load detection portion 140b is connected to the control unit 150. The outer peripheral edge 100a of the wafer 100 is chamfered and rounded, and the upper surface of the wafer placement portion 140a of the wafer support pin 140 is tapered. The wafer support pin 140 does not contact the backside of the wafer 100, but only contacts the outer peripheral edge 100a at this tapered portion. By configuring all of the multiple wafer support pins 140 in FIG. 13 to have the structure shown in FIG. 14, it is possible to control the wafer 100 to prevent misalignment due to floating.

[0073] FIG. 15 is a schematic diagram illustrating the structure of a wafer support pin 141 according to a modified example of the second embodiment. The wafer support pin 140 may have the configuration of the wafer support pin 141 shown in FIG. The wafer support pin 141 is provided with a mechanism for suction-holding the outer peripheral edge 100a of the wafer 100 using wafer support pin suction holes 141a and wafer support pin suction hole suction mechanisms 141b provided near the contact position with the outer peripheral edge 100a of the wafer 100. The wafer support pin suction hole suction mechanism 141b is connected to the control unit 150. The outer peripheral edge 100a of the wafer 100 is chamfered and rounded, and the tapered portion of the upper surface of the wafer support pin 141 contacts only the outer peripheral edge 100a of the wafer 100 without contacting the backside of the wafer 100. By providing the wafer support pin suction holes 141b near this contact portion, the outer peripheral edge 100a of the wafer 100 can be suction-held. By replacing all of the wafer support pins 140 in FIG. 13 with the wafer support pins 141 shown in FIG. 15, it becomes possible to control the wafer 100 to prevent displacement due to floating.

[0074] <Wafer Mounting Operation onto Wafer Chuck> The wafer mounting operation onto the wafer chuck according to the second embodiment will now be described. The control unit 150 performs overall control while detecting the load of the wafer 100 using the load detection portion 140b of the wafer support pin 140 shown in FIG. 14 . The basic flow of the wafer mounting operation is as shown in FIG. 7A , except for the speed control method in step S12. In step S12, the control unit 150 controls the speed at which the wafer chuck 200 approaches the wafer 100 based on the load of the wafer 100 input from the load detection portion 140b, so that the load is always greater than zero, i.e., so that the load does not become zero. This allows the wafer 100 to always be in contact with the wafer support pin 140, thereby preventing misalignment due to the wafer 100 floating. The subsequent operations from steps S13 to S31 are the same as those in the first embodiment.

[0075] 15, the basic flow of the wafer loading operation is the same as that shown in FIG. 7A, but the method of controlling support of the wafer edge 100a by the wafer support pins in steps S11 to S13 is different. That is, in step S11, the wafer 100 is placed so as to be supported by the outer circumferential edge 100a, and simultaneously, the control unit 150 suction-holds the wafer 100 at the outer circumferential edge 100a using the suction ports 141a of the support pins 141. Next, in step S12, the control unit 150 continues suction-holding the wafer 100 at the outer circumferential edge 100a. Furthermore, in step S13, simultaneously, when the wafer 100 is switched to being held at the outer circumferential edge 100a by the holding claws 301, the control unit 150 ends suction-holding of the wafer 100 at the outer circumferential edge 100a using the suction ports 141a of the support pins 141. In steps S11 to S13, by suction-holding the outer peripheral edge 100a of the wafer 100 with the wafer support pin suction holes 141a, the contact force of the wafer 100 with the wafer support pins 141 can be compensated for, and misalignment of the wafer 100 due to floating can be prevented even if the speed at which the wafer chuck 200 approaches the wafer 100 is increased. Furthermore, even if the wafer 100 is significantly warped, especially at its periphery, by suction-holding the outer peripheral edge 100a of the wafer 100 with the wafer support pins 141, the wafer 100 can be kept stably held.

[0076] Summary of the Second Embodiment According to the wafer loading operation of the second embodiment described above, it is possible to stably hold wafers without misalignment in the horizontal direction, even when the wafers have large variations in weight and shape. As a result, it is possible to realize a wafer inspection device with high measurement accuracy and high reliability in wafer transport.

[0077] [Modifications] The present disclosure is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present disclosure, and it is not necessary to include all of the described configurations. Furthermore, a part of one embodiment can be replaced with a configuration of another embodiment. Furthermore, a configuration of another embodiment can be added to a configuration of one embodiment. Furthermore, a part of the configuration of each embodiment can be added to, deleted from, or substituted for a part of the configuration of another embodiment.

[0078] DESCRIPTION OF SYMBOLS 10: Wafer inspection device 11: Wafer introduction section 12: Transfer mechanism 13: Inspection chamber 15: Control device 16: Storage device 100: Wafer 100a: Outer periphery 131: Optical measurement section 132: Motor 133: Base 134a: Vertical drive gear 134b: Vertical drive mechanism 135: Wafer support pin 136: Air supply pump 136a: Positive pressure air supply circuit 136b: Positive pressure air supply system 137: Suction pump 137a: Negative pressure air suction circuit 137b: Negative pressure air supply system 138: Central air supply pump 138a: Central air supply circuit 138b: Central air supply system 139: Clamping mechanism drive pump 139a: Clamping mechanism drive air supply circuit 139b: Clamping mechanism drive air supply system 140: Wafer support pin 140a: Wafer placement section 140b: Load detection section 141a: Wafer support pin suction hole 141b: Wafer support pin suction hole suction mechanism 150: Control unit 200: Wafer chuck (wafer back surface non-contact holding mechanism) 201: Air bearing structure 203a: Positive pressure air supply port 203b: Positive pressure air bearing air 204: Air intake groove 204a: Negative pressure air suction port 204b: Negative pressure air bearing air 210: Center air supply port 210b: Center air 220: Wafer support pin through hole 300: Clamping mechanism (wafer outer edge holding mechanism) 301: Holding claw 301a: Holding claw wafer contact part 302: Rotating shaft 303: Flexible support mechanism 304: Rod 305: Rod driving mechanism

Claims

1. A wafer inspection device for inspecting wafers, comprising: a wafer backside non-contact holding mechanism having an air flow path structure in which a positive pressure air supply port and a negative pressure intake port provided in a negative pressure intake groove are paired, and a central air supply port provided in the center, wherein the air flow path structure shares the negative pressure intake groove and the negative pressure intake port with adjacent air flow path structures and is evenly arranged in the radial and circumferential directions; a positive pressure air supply circuit that supplies positive pressure air to the positive pressure air supply port; a negative pressure air suction circuit that negatively pressure sucks the positive pressure air from the negative pressure intake port; a central air supply circuit that supplies air to the central supply port; a rotation mechanism that rotates and drives the wafer backside non-contact holding mechanism; a vertical drive mechanism that drives the wafer backside non-contact holding mechanism and the rotation mechanism up and down; a wafer outer edge holding mechanism having holding claws that are arranged on the outer periphery of the wafer backside non-contact holding mechanism and contact and hold the wafer at the outer edge, and a mechanism that drives the holding claws in a planar direction; support pins that temporarily support the wafer at the outer circumferential edge; and a control device that controls the positive pressure air supply circuit, the negative pressure air suction circuit, the central air supply circuit, the rotation mechanism, the vertical drive mechanism, and the wafer outer circumferential edge holding mechanism, wherein the control device controls the vertical drive mechanism so that, with the wafer supported by the support pins at the outer circumferential edge, the wafer and the wafer backside non-contact holding mechanism are brought closer together while imparting a mounting speed according to the distance between them, and simultaneously supplies the positive pressure air from the positive pressure air supply port or supplies the central air from the central air supply port, and when the distance reaches a specified value, drives the wafer outer circumferential edge holding mechanism so that the holding claws contact and hold the outer circumferential edge of the wafer, and releases support by the support pins at the outer circumferential edge of the wafer, and then A wafer inspection device characterized in that the positive pressure air supply circuit and the negative pressure air suction circuit are controlled so that a specified design pressure is applied to either the positive pressure air supply port or the negative pressure air intake port, and the pressure of the other port is changed from a pressure higher than the specified design pressure to finally reach the specified design pressure.

2. A wafer inspection device as described in claim 1, further comprising a memory device that stores a first relationship between the distance between the wafer and the wafer backside non-contact holding mechanism and the mounting speed, which results in a constant levitation force for the wafer, and the control device controls the vertical drive mechanism so that the mounting speed conforms to the first relationship.

3. A wafer inspection device as described in claim 1, further comprising a storage device that stores a second relationship between the drive time of the drive mechanism and the mounting speed, which results in a constant levitation force for the wafer, and the control device controls the vertical drive mechanism so that the mounting speed conforms to the second relationship.

4. The wafer inspection device described in claim 1, characterized in that the control device controls the positive pressure air supply circuit and the negative pressure air suction circuit so as to apply the specified design pressure to the positive pressure air supply port side, apply a pressure closer to atmospheric pressure than the specified design pressure to the negative pressure intake port side, and then finally bring the negative pressure intake port side to the specified design pressure.

5. The wafer inspection device described in claim 1, characterized in that the control device controls the negative pressure air suction circuit and the positive pressure air supply circuit so as to apply the specified design pressure to the negative pressure intake port side, apply a pressure higher than the specified design pressure to the positive pressure air supply port side, and then finally bring the positive pressure air supply port side to the specified design pressure.

6. The wafer inspection device described in claim 1, characterized in that the control device drives the wafer outer edge holding mechanism so that the claws support the outer edge of the wafer, and then drives the up-and-down drive mechanism to move the wafer away from the support pins before controlling the positive pressure air supply circuit and the negative pressure air suction circuit.

7. The wafer inspection device according to claim 1, characterized in that it comprises at least three of said support pins.

8. A wafer inspection device for inspecting wafers, comprising: a wafer backside non-contact holding mechanism having an air flow path structure in which a positive pressure air supply port and a negative pressure intake port provided in a negative pressure intake groove are paired, and a central air supply port provided in the center, the air flow path structure having a structure in which the negative pressure intake groove and the negative pressure intake port are shared with adjacent air flow path structures, and the wafer backside non-contact holding mechanism is evenly arranged in the radial and circumferential directions; a positive pressure air supply circuit that supplies positive pressure air to the positive pressure air supply port; a negative pressure air suction circuit that negatively pressure sucks the positive pressure air from the negative pressure intake port; a central air supply circuit that supplies air to the central supply port; a rotation mechanism that rotates and drives the wafer backside non-contact holding mechanism; a vertical drive mechanism that drives the wafer backside non-contact holding mechanism and the rotation mechanism up and down; a wafer outer edge holding mechanism having holding claws that are arranged on the outer periphery of the wafer backside non-contact holding mechanism and contact and hold the wafer at the outer edge, and a mechanism that drives the holding claws in a planar direction; a control device that controls the positive pressure air supply circuit, the negative pressure air suction circuit, the central air supply circuit, the rotation mechanism, the up and down drive mechanism, and the wafer outer edge holding mechanism, wherein the support pins have load sensors that detect the load of the wafer, and the control device controls the speed at which the wafer is loaded onto the wafer backside non-contact holding mechanism based on the value of the load sensor.

9. The wafer inspection device according to claim 8, wherein the control device controls the speed at which the wafer is placed on the wafer backside non-contact holding mechanism so that the value of the load sensor is always greater than zero.

10. A wafer inspection device as described in claim 8, wherein the support pins have suction holes that suction-hold the outer peripheral edge of the wafer and a suction mechanism that communicates with the suction holes, and the control device operates the suction mechanism to suction-hold the outer peripheral edge of the wafer while the support pins temporarily support the wafer at the outer peripheral edge.

11. A wafer inspection method executed by a control device of a wafer inspection device that inspects wafers, the wafer inspection device comprising: a wafer backside non-contact holding mechanism having an air flow path structure in which a positive pressure air supply port and a negative pressure intake port provided in a negative pressure intake groove are paired, and a central air supply port provided in the center, the air flow path structure having the negative pressure intake groove and the negative pressure intake port shared with adjacent air flow path structures, the wafer backside non-contact holding mechanism being evenly arranged in the radial and circumferential directions; a positive pressure air supply circuit that supplies positive pressure air to the positive pressure air supply port; a negative pressure air suction circuit that negatively sucks the positive pressure air from the negative pressure intake port; a central air supply circuit that supplies air to the central supply port; a rotation mechanism that rotates and drives the wafer backside non-contact holding mechanism; and a vertical drive mechanism that vertically drives the wafer backside non-contact holding mechanism and the rotation mechanism. a wafer outer edge holding mechanism having holding claws arranged on the outer periphery of the wafer backside non-contact holding mechanism for contacting and holding the wafer at the outer edge, and a mechanism for driving the holding claws in a planar direction; and support pins for temporarily supporting the wafer at the outer edge, wherein the wafer inspection method includes, using the control device, controlling the vertical drive mechanism to bring the wafer and the wafer backside non-contact holding mechanism close to each other while applying a loading speed according to the distance between them, with the wafer being supported by the support pins at the outer edge; and simultaneously controlling the positive pressure air supply circuit or the central air supply circuit to supply the positive pressure air from the positive pressure air supply port or the central air from the central air supply port; and when the distance reaches a specified value, driving the wafer holding mechanism to contact and hold the outer edge of the wafer with the holding claws, and controlling the vertical drive mechanism to release support by the support pins at the outer edge of the wafer. Thereafter, the positive pressure air supply circuit and the negative pressure air suction circuit are controlled to apply a specified design pressure to one of the positive pressure air supply port and the negative pressure air suction port, and the pressure of the other is changed from a pressure higher than the specified design pressure to finally reach the specified design pressure.

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