Wafer inspection apparatus

Abstract

A wafer inspection apparatus is provided, which moves a macro camera and a micro camera to respective shooting positions with minimum moving units. The micro camera is arranged at an appropriate shooting position of the micro camera in accordance with a center-to-center distance corresponding to a rotation angle of a holding stage. Even in a case where a center (C0) of a holding surface and a center (C1) of a wafer are misaligned and a position of an outer periphery of the wafer in an X-axis direction varies with rotation of the holding stage, a shooting range of the micro camera can be caused to follow the position of the outer periphery of the wafer. Therefore, the shooting range of the micro camera can be easily determined. In addition, by moving both cameras in the X-axis direction with one X-axis moving mechanism, both front surface inspection of the wafer and outer periphery inspection of the wafer can be performed.

Description

Technical Field

[0001] The present invention relates to a wafer inspection device. Background Art

[0002] There is a technique for inspecting the state of a wafer ground by a grinding tool by photographing the ground surface (see Patent Documents 1 and 2). There is also a technique for inspecting whether a defect has occurred on the edge by photographing the edge with an imaging unit.

[0003] When inspecting the ground surface of a wafer, a camera with a wide field of view (imaging range) (macro camera) is used to shorten inspection time. On the other hand, when inspecting the edge of a wafer, a camera with a narrow field of view (imaging range) (micro camera) is used to measure the size of defects along the edge. In other words, by capturing a narrow imaging range with high resolution, measurement accuracy is improved.

[0004] In this way, in order to capture images of both the ground surface and the edge of the wafer, two cameras, a macro camera and a micro camera, are used.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-049581

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2016-075554

[0007] When using a macro camera and a micro camera, the two cameras capture different images of the wafer front and wafer edge. In this regard, if each camera has a moving unit that moves the camera to each imaging location, the device becomes larger. Summary of the Invention

[0008] Therefore, an object of the present invention is to provide a wafer inspection apparatus capable of moving a macro camera and a micro camera to respective imaging locations with minimal moving means to inspect a ground surface and an edge.

[0009] According to the present application, there is provided a wafer inspection apparatus which performs inspection by photographing a front surface of a wafer and a periphery of the wafer, the wafer inspection apparatus including: a macro camera which photographs the front surface of the wafer; a micro camera which photographs the periphery of the wafer, the micro camera having a narrower photographing range and a higher magnification than the macro camera; a holding stage which has a holding surface which holds the wafer; a motor which rotates the holding stage about a center of the holding surface; an angle recognition section which recognizes a rotation angle of the holding stage which is rotated by the motor; a support section which supports the macro camera and the micro camera; an X-axis moving mechanism which moves the support section in an X-axis direction which is parallel to the holding surface; and a control unit which includes: a center calculation section which moves the macro camera to a position at which the periphery of the wafer can be photographed, recognizes coordinates of at least three points on the periphery of the wafer from an image photographed by the macro camera, and calculates a center coordinate of the wafer from the coordinates of the three points; and a distance calculation section which acquires a relationship between an inter-center distance and a rotation angle of the holding stage, rotates the holding stage, and calculates the inter-center distance which corresponds to the rotation angle of the holding stage recognized by the angle recognition section, the inter-center distance being a distance in the X-axis direction between the center coordinate of the holding surface which is recognized in advance and the center coordinate of the wafer calculated by the center calculation section, the micro camera being moved in the X-axis direction by the X-axis moving mechanism based on a distance in the X-axis direction between a photographing range center of the micro camera and the center of the holding surface and the inter-center distance calculated by the distance calculation section, so that the micro camera is disposed at a photographing position which is a position in the X-axis direction at which the photographing range of the micro camera is disposed on the periphery of the wafer, and the periphery of the wafer is photographed by the micro camera, and the state of the periphery of the wafer is inspected.

[0010] According to the present application, even in a case where the center coordinate of the holding surface and the center coordinate of the wafer are misaligned and the position of the periphery of the wafer in the X-axis direction varies with rotation of the holding stage, the control unit can cause the photographing range of the micro camera to follow the varying position of the periphery of the wafer. Therefore, even if the center coordinate of the holding surface and the center coordinate of the wafer are misaligned, the periphery of the wafer can be easily photographed by the micro camera.

[0011] In addition, both the photographing and inspection of the front surface of the wafer and the photographing and inspection of the periphery of the wafer can be performed by moving the macro camera and the micro camera in the X-axis direction by one X-axis moving mechanism. Thus, the wafer inspection apparatus can be easily made compact. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a perspective view showing a wafer inspection apparatus according to an embodiment of the present application.

[0013] Figure 2 is a plan view showing a wafer placed on a holding surface of a holding stage.

[0014] Figure 3 is a schematic view showing a relationship between a rotation angle of a holding stage and a center-to-center distance.

[0015] Figure 4 is a plan view showing a photographing range of a microscopic camera arranged on an outer periphery of a wafer.

[0016] Explanation of Reference Numerals

[0017] 1: wafer inspection apparatus; W: wafer; 11: holding stage; 12: holding surface; 21: motor; 22: encoder; 31: macroscopic camera; 33: microscopic camera; 41: support portion; 42: support portion main body; 43: first support column; 44: second support column; 51: X-axis moving mechanism; 61: control unit; 62: center calculating portion; 63: distance calculating portion; C0: center of holding surface; C1: center of wafer; MA: photographing range of microscopic camera. DETAILED DESCRIPTION

[0018] Figure 1 The wafer inspection apparatus 1 of the embodiment of the present application shown is an apparatus for performing inspection by photographing a front surface of a wafer W and an outer periphery of the wafer W. In particular, in the wafer inspection apparatus 1, a ground surface and an outer periphery of a ground wafer W are photographed and inspected.

[0019] As shown in Figure 1 , the wafer inspection apparatus 1 has a holding stage 11 that holds a wafer W, a motor 21 that rotates the holding stage 11, and an encoder 22.

[0020] The holding stage 11 has a holding surface 12 that holds the wafer W. The holding surface 12 contains, for example, a porous ceramic material, and holds the wafer W by being communicated with a suction source (not shown) to adsorb the wafer W.

[0021] The motor 21 rotates the holding stage 11 with an axis L that passes through the center of the holding surface 12 of the holding stage 11 and extends in the Z-axis direction as a center axis. The encoder 22 has a function of recognizing a rotation angle of the holding stage 11 that is rotated by the motor 21, and is an example of an angle recognition portion.

[0022] The wafer inspection apparatus 1 further has a macroscopic camera 31 and a microscopic camera 33, a support portion 41 that supports these macroscopic camera 31 and microscopic camera 33, and an X-axis moving mechanism 51 that moves the support portion 41 in the X-axis direction.

[0023] The support portion 41 has a support portion main body 42, and a first support column 43 and a second support column 44 extending in the horizontal direction. The first support column 43 and the second support column 44 extend from the side surface of the +Y side of the support portion main body 42 in the +Y direction. The first support column 43 supports the macro camera 31, and the second support column 44 supports the micro camera 33.

[0024] The support portion main body 42 is disposed in such a manner that a part thereof is positioned inside the X-axis moving mechanism 51. The X-axis moving mechanism 51 moves the support portion 41 including the support portion main body 42 together with the macro camera 31 and the micro camera 33 in the X-axis direction by a not-shown driving mechanism built therein. The X-axis moving mechanism 51 moves the macro camera 31 and the micro camera 33, for example, in such a manner that the center thereof passes above the holding surface 12 in the X-axis direction.

[0025] The macro camera 31 has a relatively wide field of view (imaging range) and is provided so as to image the front surface (polished surface) of the wafer W held on the holding stage 11. On the other hand, the micro camera 33 has a relatively narrow field of view (imaging range) and is provided so as to image the outer periphery (edge) of the wafer W held on the holding stage 11.

[0026] The imaging range of the macro camera 31 is 15 μm x 15 μm, for example, and the imaging range of the micro camera 33 is 2 μm x 2 μm. In addition, the imaging magnification of the micro camera 33 is set to be higher than that of the macro camera 31.

[0027] In addition, the wafer inspection device 1 has a control unit 61 that controls each component of the wafer inspection device 1. The control unit 61 has a center calculating portion 62 and a distance calculating portion 63, controls each component of the wafer inspection device 1, and performs the inspection of the wafer W performed by the wafer inspection device 1.

[0028] Hereinafter, the inspection operation of the wafer W based on the control of the control unit 61 will be described.

[0029] In the inspection of the wafer W, first, the operator or a not-shown conveyance mechanism places the wafer W on the holding surface 12 of the holding stage 11 in such a manner that the polished surface faces upward. Then, the control unit 61 causes the holding surface 12 to communicate with the suction source, whereby the wafer W is held by the holding surface 12. Figure 2 A wafer W placed on the holding surface 12 of the holding stage 11 is shown in the drawing. In the example shown in the drawing, the wafer W is placed on the holding surface 12 in such a manner that the center CI thereof is offset from the center CO of the holding surface 12.

[0030] Next, the control unit 61 performs the use of the macro camera 31 and the micro camera 33. Figure 1The wafer W is inspected by the macro camera 31. That is, the control unit 61 controls the X-axis moving mechanism 51 to move the macro camera 31 to a position where the front surface (ground surface) of the wafer W can be imaged, and the wafer W is imaged while the macro camera 31 is scanned on the wafer W in the X-axis direction.

[0031] Next, the control unit 61 performs inspection of the state of the outer periphery of the wafer W (for example, inspection of the presence or absence of defects on the outer periphery) using the micro camera 33. In this inspection, first, the center calculating section 62 of the control unit 61 calculates the coordinates of the center Cl of the wafer W placed on the holding surface 12.

[0032] That is, the center calculating section 62 first controls the X-axis moving mechanism 51 to move the macro camera 31 to a position where the outer periphery of the wafer W can be imaged. Then, the center calculating section 62 identifies the coordinates (outer periphery coordinates) of at least three points on the outer periphery of the wafer W from the image imaged by the macro camera 31. Further, the center calculating section 62 calculates the coordinates (wafer center coordinates) of the center Cl of the wafer W from the outer periphery coordinates of the three points identified.

[0033] As the method of calculating the wafer center coordinates, any known method can be used. For example, the center calculating section 62 generates two straight lines connecting adjacent two points of the outer periphery coordinates of the three points identified, and calculates perpendicular bisectors of the two straight lines, respectively. Then, the center calculating section 62 can calculate the intersection of the two perpendicular bisectors as the center of the wafer W.

[0034] Next, as shown in Figure 2 The distance calculating section 63 of the control unit 61 calculates the center-to-center distance r, which is the distance in the X-axis direction between the coordinates (holding surface center coordinates) of the center Co of the holding surface 12 identified in advance and the wafer center coordinates calculated by the center calculating section 62.

[0035] Then, the distance calculating section 63 calculates the relationship between the center-to-center distance r, which is the distance in the X-axis direction between the holding surface center coordinates and the wafer center coordinates, and the rotation angle of the holding table 11 identified by the encoder 22.

[0036] At this time, for example, the distance calculating section 63 calculates the maximum value of the center-to-center distance r. Then, the distance calculating section 63, for example, obtains the relationship between the rotation angle of the holding table 11 and the center-to-center distance r in the case where the rotation angle of the holding table 11 is set to zero degrees when the center-to-center distance r is the maximum value.

[0037] Figure 3shows an example of the relationship between the rotation angle θ of the holding table 11 and the center-to-center distance r. As shown in the figure, the center-to-center distance r varies in a cosine curve depending on the rotation angle θ of the holding table 11. A negative center-to-center distance r indicates that the center C1 of the wafer W at the start of measurement is located on the -X side relative to the center C0 of the holding surface 12.

[0038] The distance calculator 63 controls the motor 21 to rotate the holding table 11. The distance calculator 63 obtains the rotation angle of the rotating holding table 11 recognized by the encoder 22. The distance calculator 63 calculates the center-to-center distance r for each rotation angle of the holding table 11.

[0039] On the other hand, the control unit 61 identifies the distance in the X-axis direction between the center C1 of the holding surface 12 of the rotating holding table 11 and the center of the imaging range of the micro camera 33. The control unit 61 can calculate this distance based on the position of the X-axis moving mechanism 51, that is, the position of the micro camera 33.

[0040] Then, based on this distance and the center-to-center distance r calculated by the distance calculation unit 63, the control unit 61 moves the micro camera 33 along the X-axis direction via the X-axis movement mechanism 51 to position the micro camera 33 at a photographing position corresponding to the rotation angle of the holding stage 11. This photographing position is the position of the micro camera 33 in the X-axis direction for placing the photographing range of the micro camera 33 on the outer periphery of the wafer W.

[0041] For example, the control unit 61 obtains the imaging position of the micro camera 33 in the X-axis direction, based on the calculated center-to-center distance r and the radius of the wafer W, for arranging the imaging range of the micro camera 33 on the outer periphery of the wafer W. Furthermore, based on the distance in the X-axis direction between the center C1 of the holding surface 12 and the center of the imaging range of the micro camera 33, the control unit 61 calculates the movement distance of the micro camera 33, for arranging the micro camera 33 at the calculated imaging position. The control unit 61 controls the X-axis movement mechanism 51 to move the micro camera 33 in the X-axis direction by the movement distance.

[0042] Therefore, if Figure 4 As shown, the imaging range MA of the micro camera 33 is arranged on the outer periphery of the wafer W. The control unit 61 images the outer periphery of the wafer W through the micro camera 33 and inspects the outer periphery of the wafer W.

[0043] As described above, in the present embodiment, the distance calculating section 63 of the control unit 61 calculates the center-to-center distance r in the X-axis direction corresponding to the rotation angle of the rotated holding stage 11. Then, the control unit 61 configures the micro camera 33 at an appropriate shooting position capable of shooting the outer periphery of the wafer W, based on the calculated center-to-center distance r and the distance in the X-axis direction between the center Cl of the holding surface 12 and the center of the shooting range of the micro camera 33.

[0044] That is, in the present embodiment, even in the case where the holding surface center coordinates and the wafer center coordinates are misaligned and the position of the outer periphery of the wafer W in the X-axis direction varies with the rotation of the holding stage 11, the control unit 61 is able to cause the shooting range of the micro camera 33 to follow the varying outer periphery position of the wafer W.

[0045] Therefore, in the present embodiment, even if the holding surface center coordinates and the wafer center coordinates are misaligned, it is possible to easily shoot the outer periphery of the wafer W by the micro camera 33.

[0046] In addition, by moving the macro camera 31 and the micro camera 33 in the X-axis direction by only one X-axis moving mechanism 51, it is possible to implement both the shooting and inspection of the front surface of the wafer W and the shooting and inspection of the outer periphery of the wafer W. Thus, it is possible to realize the compactness of the wafer inspection device 1.

[0047] In addition, in the present embodiment, the wafer inspection device 1 shoots and inspects the ground surface of the wafer W after the grinding process and the outer periphery thereof. Not limited thereto, the wafer inspection device 1 can also shoot and inspect the polished surface of the wafer W and the outer periphery thereof.

[0048] In addition, the wafer inspection device 1 can also be configured to be provided in a grinding device or a polishing device to shoot and inspect the wafer W after the grinding or polishing. In this case, the grinding device or the polishing device can also have a plurality of cassettes for housing the processed wafers W, and the cassettes housing the processed wafers W are distinguished according to the inspection results of the wafer inspection device 1.

[0049] Alternatively, the wafer inspection device 1 can also be provided in a cutting device that cuts the wafer W. In this case, the wafer inspection device 1 can also be used for the kerf inspection of the cut wafer W.

Claims

1. A wafer inspection device that performs inspection by photographing the front surface and the periphery of a wafer, wherein: The wafer inspection device has: a macro camera that photographs the front side of the wafer; a microscopic camera for photographing the periphery of the wafer, wherein the photographing range of the microscopic camera is narrower and the magnification is higher than that of the macroscopic camera; a holding table having a holding surface for holding a wafer; a motor that rotates the holding table about the center of the holding surface; an angle recognition unit that recognizes a rotation angle of the holding table rotated by the motor; a support portion that supports the macro camera and the micro camera; an X-axis moving mechanism that moves the support portion in an X-axis direction parallel to the holding surface; and control unit, The control unit contains: a center calculation unit that moves the macro camera to a position capable of imaging the periphery of the wafer, identifies coordinates of at least three points on the periphery of the wafer based on the image captured by the macro camera, and calculates the center coordinates of the wafer based on the coordinates of the three points; and a distance calculation unit that obtains a relationship between the center-to-center distance and the rotation angle of the holding table, rotates the holding table, and calculates the center-to-center distance corresponding to the rotation angle of the holding table identified by the angle identification unit, wherein the center-to-center distance is the distance in the X-axis direction between the pre-identified center coordinates of the holding surface and the center coordinates of the wafer calculated by the center calculation unit, and the distance in the X-axis direction is the projection distance in the X-axis direction of the straight-line distance between the center of the holding surface and the center of the wafer. The micro camera is moved only in the X-axis direction by the X-axis moving mechanism based on the distance in the X-axis direction between the center of the imaging range of the micro camera and the center of the holding surface and the distance between the centers calculated by the distance calculating unit, thereby arranging the micro camera at an imaging position for arranging the imaging range of the micro camera at a position in the X-axis direction on the periphery of the wafer. The periphery of the wafer is photographed using the micro camera to inspect the condition of the periphery of the wafer.

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