JP2008241662A - Image stabilizing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image stabilizing device capable of preventing image shake arisen in an image in which an object to be inspected is obtained which moves at high speed by a simple structure. <P>SOLUTION: The image stabilizing device comprises a mounting stand 17 movable, having a mounting surface 17a for mounting a wafer 11, an image picking-up unit 13 for capturing the image of the wafer 11, an optical system 14 for introducing the image of the wafer 11 to the image picking-up unit 13, and a control unit 18 for controlling the image capture by the movement of the mounting stand 17 and the image picking-up unit 13. A light path changing member 24 is provided that an optical axis location Lo in a light path deriving section is displaced without displacing an optical axis location Li in a light path introducing section by changing an attitude thereof, and the control unit 18 changes the attitude of the light path changing member 24 so that the light axis location Lo follows the movement of the mounting stand when the image of the wafer 11 is captured by the image picking-up unit 13 while moving the mounting stand 17. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an apparatus for acquiring an image while moving an object to be inspected, such as an appearance inspection apparatus for inspecting the appearance of a semiconductor chip on a wafer by moving the wafer in a semiconductor manufacturing process.

  Conventionally, for example, an appearance inspection apparatus for inspecting the appearance of a semiconductor chip on a wafer by moving the wafer, a circuit pattern on a photosensitive agent (photoresist) formed or coated on the surface of the wafer by irradiating light 2. Description of the Related Art In a semiconductor exposure apparatus or the like that exposes and transfers an image, an image is acquired while moving an object to be inspected, and inspection, exposure, transfer, and the like are performed using this image.

  In the appearance inspection apparatus as an example, an image of a fine electronic circuit pattern formed on a wafer (test surface) as an object to be inspected is acquired, and this acquired image and an image of an electronic circuit pattern in an appropriate state ( Template), a difference between both images is extracted, and whether or not the difference exceeds a set defect tolerance is determined to determine whether the wafer that is the inspection object is good or bad. However, in this appearance inspection apparatus, for example, when the moving speed of the wafer is increased in order to shorten the inspection time, the acquired image of the test surface of the wafer (hereinafter also referred to as an acquired image) is blurred, and the template and Therefore, it is difficult to appropriately extract the difference between the two, which greatly affects the accuracy of the determination of the quality of the inspection object.

Therefore, in order to prevent a reduction in the accuracy of the determination of the inspection object due to the movement of the inspection object with respect to the camera, it is possible to cause a blur in the acquired image by moving the camera in accordance with the movement of the inspection object. An apparatus for preventing this is considered (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2004-340643

  However, in a configuration such as a conventional image blur prevention device, it is necessary to move the camera at a high speed in accordance with the movement of the object to be inspected, which makes the configuration as a device very complicated.

  The present invention has been made in view of the above circumstances, and provides an image blur prevention device capable of preventing the occurrence of blurring in an acquired image of an inspection object that moves at high speed with a simple configuration. is there.

  In order to solve the above-described problem, the image blur prevention device according to claim 1 has a placement surface on which an object to be inspected is placed, and is movable along a plane parallel to the placement surface. A mounting table, an imaging means for acquiring an image of the inspection object placed on the placement surface, and an image of the inspection object placed on the placement surface located in a predetermined area An optical system that guides the imaging means to the imaging means, and a control means that controls movement of the mounting table and image acquisition by the imaging means, and the optical system reaches the imaging means by changing the posture. In the optical path, an optical path changing member that displaces the optical axis position in the optical path deriving unit on the imaging means side without displacing the optical axis position in the optical path introducing unit on the mounting table is provided, and the control means The image of the object to be inspected is taken by the imaging means while moving the table. When to, and changing the posture of the optical path changing member so that the optical axis position in the optical path derivation unit follows the movement of the mounting table.

  According to the configuration described above, even if the position of the object to be inspected changes according to the movement of the mounting table, the optical axis position at the optical path deriving unit in the optical path to the imaging means in the optical system is the movement of the mounting table. Since the image is followed, the image of the inspection object existing at the same position is guided to the imaging unit, so that it is possible to prevent the image acquired by the imaging unit from being blurred. it can.

  In addition, by changing the attitude of the optical path changing member of the optical system, the optical axis position in the optical path deriving unit is made to follow the movement of the mounting table, so that the configuration can be simplified and the mounting table can be moved at high speed. Even if it is moved, it can be easily handled.

  An image blur prevention apparatus according to a second aspect is the image blur prevention apparatus according to the first aspect, wherein the control unit is directed in a direction opposite to the moving direction of the mounting table as viewed from the imaging surface of the imaging unit. By displacing the optical axis center in the optical path deriving unit with a movement amount equal to the movement amount of the mounting table as viewed on the imaging surface, the optical axis center is caused to follow the movement of the mounting table. To do.

  According to the configuration described above, the optical axis position in the optical path deriving unit can follow the movement of the mounting table with a very simple configuration.

  The image blur prevention device according to claim 3 is the image blur prevention device according to claim 2, wherein the optical path changing member is parallel to the imaging surface and the moving direction of the mounting table as viewed on the imaging surface. It is characterized by being a glass plate that can be rotated around an axis perpendicular to the axis.

  According to the configuration described above, since the glass plate only needs to be rotated in accordance with the movement of the mounting table, it is possible to reliably follow the movement of the mounting table with the extremely simple configuration of the optical axis position in the optical path deriving unit. Can do.

  The image blur prevention device according to claim 4 is the image blur prevention device according to claim 2, wherein the optical path changing member is parallel to the imaging surface and the moving direction of the mounting table as viewed on the imaging surface. It is a mirror that is rotatable about an axis perpendicular to the axis.

  According to the configuration described above, since the mirror only needs to be rotated according to the movement of the mounting table, it is possible to reliably follow the movement of the mounting table with an extremely simple configuration of the optical axis position in the optical path deriving unit. it can.

  The image blur prevention device according to claim 5 is the image blur prevention device according to claim 2, wherein the optical path changing member includes a surface parallel to the imaging surface, a moving direction of the mounting table, and the imaging surface. The mirror is characterized in that it can be translated along a direction parallel to a line defined by the intersection with the plane including the moving direction of the mounting table as viewed.

  According to the configuration described above, since the mirror only needs to be translated in accordance with the movement of the mounting table, it is possible to reliably follow the movement of the mounting table with the optical axis position in the optical path deriving unit with a very simple configuration. it can.

  An image blur prevention apparatus according to a sixth aspect is the image blur prevention apparatus according to the second aspect, wherein the optical path changing member is a polyhedral prism that is rotatable around an optical axis of an optical path leading to the imaging means. It is characterized by being.

  According to the configuration described above, the polygonal prism only needs to be rotated in accordance with the movement of the mounting table, so that the optical axis position in the optical path deriving unit can be made to follow the movement of the mounting table with an extremely simple configuration. Can do.

  According to the image blur prevention apparatus of the present invention, it is possible to prevent blurring from occurring in an acquired image of an inspection object that moves at high speed with a simple configuration.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram showing an appearance inspection apparatus 10 as an image blur prevention apparatus according to the present invention, and FIG. 2 is a schematic view of a wafer 11 as viewed from above for explaining a scanning state in the appearance inspection apparatus 10. FIG. FIG. 3 is an explanatory diagram for explaining the correlation between the positions of the imaging unit 13 and the optical system 14 with respect to the test surface 12 of the wafer 11 and the timing at which the flash light F is emitted from the flash light source 15. FIG. 2 is a partially enlarged front view of the upper part, and the timing at which the flash F is emitted is made to correspond to the position and time axis on the scanning lines S1 and S2 in the upper partial front view. The graph is shown. FIG. 4 is an explanatory diagram for explaining a basic concept for blur prevention in the image blur prevention apparatus according to the present invention, and FIG. 5 is a diagram for explaining blur prevention in the appearance inspection apparatus 10 of the present embodiment. It is a typical block diagram for demonstrating a structure. FIG. 6 is a graph showing the control method in the appearance inspection apparatus 10 of this embodiment in terms of operation with respect to time, and FIG. 7 is a graph showing a specific example of the control method in the appearance inspection apparatus 10. In the following description, it is assumed that the vertical direction is the Z axis direction when FIG. 1 is viewed from the front, and the plane orthogonal to this is the XY plane (the horizontal direction is the Y axis direction when FIG. 1 is viewed from the front).

  An appearance inspection apparatus 10 as an image blur prevention apparatus according to the present invention acquires an image of a fine electronic circuit pattern formed on a wafer 11 as an object to be inspected, and this acquired image and an electronic circuit pattern in an appropriate state The quality of the wafer 11 that is the object to be inspected is determined by comparing the image (template) with each other, extracting the difference between the two images, and determining whether the difference exceeds the set defect tolerance. To do. The appearance inspection apparatus 10 includes a base 16, a mounting table 17 on which the wafer 11 is placed, an imaging unit 13 for acquiring an image of the inspection object (the wafer 11 in this embodiment), an inspection object ( An optical system 14 that guides the image of the wafer 11) to the imaging unit 13 and a control unit 18 that comprehensively controls the overall operation are provided.

  The mounting table 17 is movable on the base 16 in the X-axis direction and the Y-axis direction, and has a mounting surface 17a parallel to the XY plane. The mounting surface 17a can hold the mounted wafer 11 in a state parallel to the XY plane. Thus, since the mounting table 17 can be appropriately moved in the XY plane while holding the wafer 11 in a state parallel to the XY plane, the appearance inspection apparatus 10 moves the wafer 11 to the X-Y plane. It can be appropriately moved along the -Y plane. An optical system 14 is provided so as to face the test surface 12 of the wafer 11 to be moved (the surface located above when placed on the placement surface 17a).

  Although not shown, the optical system 14 is fixed to the base 16 with the imaging unit 13 as viewed in the XY plane, and is configured by connecting the flash guide path 20 to the image guide path 19. Yes. In the image guide path 19, an objective lens 21, a beam splitter 22, an imaging lens 23, and a glass plate 24 are provided, and the test surface of the wafer 11 placed on the placement surface 17 a of the placement table 17. 12 images are guided to the imaging unit 13. Here, since the size dimension of the test surface 12 of the wafer 11 is very large compared to the details of the electronic circuit pattern on the test surface 12 of the wafer 11, the field of view of the optical system 14 (one image in the image pickup unit 13). An acquisition area 25 (see FIG. 2), which is an area that can be acquired as an image, is extremely smaller than the test surface 12 of the wafer 11. A flash guide path 20 is connected to the image guide path 19 in order to illuminate the visual field (25) of the optical system 14 with the flash F.

  The flash guide path 20 flashes so that the flash F emitted from the flash light source 15 irradiates the test surface 12 of the wafer 11 within the field of view (25) of the optical system 14 via the beam splitter 22 and the objective lens 21. It is configured to guide F into the image guide path 19. Thereby, the optical system 14 can guide the image of the test surface 12 illuminated by the flash F to the imaging unit 13.

  The imaging unit 13 includes an imaging device 26, acquires an image of the test surface 12 guided by the optical system 14 with the imaging device 26, and transmits the acquired image to the control unit 18 as image data.

  The control unit 18 is electrically connected to the mounting table 17, the imaging unit 13, the flash light source 15, and the optical system 14, and comprehensively controls the entire operation. Here, as described above, the visual field (25) of the optical system 14 has a smaller area than the test surface 12 of the wafer 11, and an image that can be acquired at one time by the imaging unit 13 is also a part of the test surface 12 ( Acquisition area 25 (see FIG. 2)). Therefore, the control unit 18 controls the imaging unit 13 and the optical system 14 so that the plurality of acquisition regions 25 are aligned on the test surface 12 so as to cover the test surface 12 of the wafer 11 that is the test object. While the position of the test surface 12 of the wafer 11 is moved, the flash light F is emitted from the flash light source 15 in accordance with the movement, and the image data is acquired from the imaging unit 13 in accordance with the emission timing of the flash F ( Hereinafter referred to as scanning). In the appearance inspection apparatus 10 of the present embodiment, as shown in FIG. 2, the surface 12 to be tested of the wafer 11 is scanned in the Y-axis direction by the scanning line S along the X-axis direction. 25) is moved along the scanning line S1 to acquire images of the respective acquisition regions 25 serially arranged in the X-axis direction on the scanning line S1 in the test surface 12, and then the visual field (25 of the optical system 14) ) Along the scanning line S2 to acquire images of the acquisition regions 25 serially arranged in the X-axis direction on the scanning line S2 of the test surface 12, and then the scanning lines S3, S4, By scanning in the same manner as the scanning lines S5, S6,..., The test surface 12 of the wafer 11 is covered with the acquired images of the acquisition regions 25. On each scanning line S, as shown in FIG. 3, when viewed from each acquisition region 25 as a reference, the imaging unit 13 and the optical system 14 that move relative to the test surface 12 of the wafer 11 are each acquired region. When it is located at the center of 25 (see symbol d), the flash light F is emitted from the flash light source 15. Thereby, the control unit 18 can acquire an image of the entire test surface 12 of the wafer 11.

  Although not shown, an image (template) of an appropriate shape of a circuit pattern provided on the test surface of the inspection object is formed on the control surface 18 on the test surface 12 of the wafer 11 in this embodiment. An image (template) having an appropriate shape of a fine electronic circuit pattern is stored in advance. The control unit 18 performs shape comparison between the template and the acquired image, extracts a difference between both images, and determines whether the extracted difference exceeds the defect tolerance, thereby obtaining each acquisition. The quality of the electronic circuit pattern formed in the image, that is, the quality of the wafer 11 is determined.

  Here, in the appearance inspection apparatus 10, it is considered to increase the moving speed of the mounting table 17 from the viewpoint of shortening the time required for the inspection of the wafer 11. Then, as shown in FIG. 3, the position of the test surface 12 of the wafer 11 with respect to the imaging unit 13 and the optical system 14 moves even during a short time tp when the flash F is emitted (reference symbol d). Therefore, the acquired image is blurred, and the generated blur is extracted as a difference with respect to the template, which may reduce the accuracy of the inspection object determination. As an element that causes a blur in the acquired image as described above, when the amount of movement of the test surface 12 of the wafer 11 during the emission time of the flash F emitted from the flash light source 15 is large, the wafer with respect to the shutter speed in the imaging unit 13 is used. 11 when the movement amount of the test surface 12 is large, or when the electronic circuit pattern as the test object is extremely fine. The appearance inspection apparatus 10 as an image blur prevention apparatus according to the present invention has the following characteristics in order to prevent a reduction in the accuracy of determination of an inspection object due to such blurring of an acquired image. In the following description, as shown in FIG. 1, in the optical path that guides the image of the test surface 12 formed by the optical system 14 to the image sensor 26, the vicinity of the objective lens 21 that faces the test surface 12 is shown. The optical path introducing unit and the vicinity of the imaging device 26 are used as the optical path deriving unit, and the portion of the optical axis L of the optical system 14 that is located in the optical path introducing unit is the optical axis introducing unit Li and the portion that is located in the optical path deriving unit is light Let it be the axis lead-out part Lo.

  In the image blur prevention apparatus according to the present invention, blurring is prevented from occurring in an image acquired by the concept shown in FIG. For example, it is assumed that the wafer 11 moves to the right (indicated by a two-dot chain line) as indicated by an arrow A1 in FIG. At this time, as shown in FIG. 4B, the optical axis deriving portion Lo is in the direction opposite to the moving direction of the wafer 11 without changing the position of the optical axis introducing portion Li in the optical axis L of the optical system. The optical axis L is moved to the optical axis L ′ by moving it to the left at a speed that matches the moving speed of the wafer 11 (an amount that matches the moving amount of the wafer 11 (see symbol d in FIG. 3)). And change. Here, the moving direction of the wafer 11 is based on the moving direction of the wafer 11 viewed on the imaging surface of the imaging element 26 of the imaging unit 13. Further, the speed that matches the moving speed of the wafer 11 (the amount that matches the moving amount of the wafer 11) is the moving speed (moving amount) of the wafer 11 as viewed on the imaging surface of the image sensor 26, that is, the actual wafer 11. This is obtained by multiplying the moving speed (moving amount (see reference symbol d in FIG. 3)) by the magnification in the optical system.

  Here, in the optical path of the optical system 14, a process in which the image of the center position 11 a of the wafer 11 is guided to the imaging surface of the imaging element 26 is defined as a virtual optical axis IL, and the optical path IL is located in the optical path introducing portion. The location is defined as a virtual introduction unit ILi and a location located in the optical path deriving unit is defined as a virtual deriving unit ILo. As described above, when the optical axis L is changed to the optical axis L ′, as shown in FIG. 4C, even if the wafer 11 moves (see the wafer 11 indicated by the arrow A1 and a two-dot chain line), Since the optical axis L is changed to the optical axis L ′ so as to follow this movement (see FIG. 4B), the virtual introduction part ILi is located at the center position 11a of the wafer 11 when viewed from the virtual optical axis IL. In spite of following the movement (see arrow A3), the virtual deriving portion ILo is positioned at the same location on the imaging surface of the image sensor 26, and the image of the center position 11a of the wafer 11 is always on the image sensor 26. It will be guided to the same location on the imaging surface. In other words, the image of the wafer 11 that is always stationary at the same position is guided to the image sensor 26 regardless of the movement of the wafer 11. For this reason, in the image blur prevention apparatus according to the present invention (the appearance inspection apparatus 10 in the present embodiment), the image of the wafer 11 can be acquired without causing the image sensor 26 (imaging unit 13) to blur. In this way, in the optical axis L of the optical system, the speed at which the optical axis deriving unit Lo is adapted to the moving speed of the wafer 11 in the direction opposite to the moving direction of the wafer 11 without changing the position of the optical axis introducing unit Li. In the appearance inspection apparatus 10 of this embodiment, a glass plate 24 is provided in the optical system 14 (see FIG. 1).

  As shown in FIG. 1, the appearance inspection apparatus 10 is configured to move only the optical axis derivation unit Lo on the optical axis L in the optical system 14 by changing the posture of the glass plate 24. In the appearance inspection apparatus 10 of the present embodiment, the glass plate 24 is fixed to a rotating shaft 24a that extends in the Y-axis direction and is rotatable (see arrow A4). As described above, since the direction in which the scanning line S (see FIG. 2) is formed is configured along the X-axis direction, the test of the wafer 11 with respect to the optical axis L of the optical system 14 is performed. This is because the surface 12 relatively moves in the X-axis direction, and blurring that may occur in the acquired image (acquisition region 25) is formed in the X-axis direction. Although not shown, the rotation shaft 24 a can be controlled by the control unit 18 via a rotation drive control mechanism (for example, a stepping motor) connected to the control unit 18. For this reason, the control part 18 can control the rotation attitude | position around the rotation axis 24a of the glass plate 24 (refer arrow A4 and FIG. 5).

  In the optical system 14, as shown in FIG. 5, the glass plate 24 is appropriately rotated around the rotation axis 24a from a state where the glass plate 24 is parallel to the XY plane (see FIG. 5A). The optical axis L can be changed so that the optical axis deriving unit Lo is moved without changing the optical axis introducing unit Li. Specifically, when the test surface 12 of the wafer 11 moves to the right side, that is, the positive side in the X-axis direction when viewed from the front in FIG. 5 (see the scanning line S1, the scanning line S3, the scanning line S5, etc. in FIG. 2), As shown in FIG.5 (b), the glass plate 24 is rotated counterclockwise (refer arrow A5). Then, the optical axis so that the optical axis deriving portion Lo moves to the left side (negative side in the X-axis direction) with respect to the optical axis introducing portion Li by the glass plate 24 inclined with respect to the optical axis direction (see La). L will change.

  On the other hand, when the test surface 12 of the wafer 11 moves to the left side, that is, the negative side in the X-axis direction when viewed from the front in FIG. 5 (see the scanning line S2, scanning line S4, scanning line S6, etc. in FIG. 2). As shown in FIG. 5C, the glass plate 24 is rotated clockwise (see arrow A6). Then, the optical axis so that the optical axis deriving portion Lo moves to the right side (positive side in the X-axis direction) with respect to the optical axis introducing portion Li by the glass plate 24 inclined with respect to the optical axis direction (see La). L will change. Such control of the rotation posture of the glass plate 24 can be performed as shown in the graph of FIG. 6 to correspond to scanning of the surface 12 to be measured of the wafer 11 (see FIG. 2).

  In FIG. 6, the horizontal axis is the time axis, the vertical axis in (a) is the ON state when the flash F is emitted from the flash light source 15, and the OFF state when it is not emitted, (b) and (c) Is the inclination angle of the glass plate 24 on the basis of the state in which the glass plate 24 is parallel to the XY plane (the counterclockwise direction is positive when viewed from the front in FIG. 5). In FIG. 6, the time during which the flash F is in the ON state (may be the shutter speed in the imaging unit 13) is tp, and the amount of movement of the test surface 12 of the wafer 11 at the time tp (symbol d in FIG. 3). Let D be the absolute value of the angle of inclination of the glass plate 24 required to move the optical axis deriving portion Lo by an amount suitable for the reference).

Control unit 18, as shown in (a) in the graph of FIG. 6, _{'between, t} from _{n + 1 t n + 1'} from between _{(t n t n} flash F is ON _{during, t n + 2} from _{t n + 2} In the scene (refer to scanning line S1, scanning line S3, scanning line S5, etc. in FIG. 2) that moves to the positive side in the X-axis direction (see “between”), the inclination angle of the glass plate 24 as shown in FIG. In a scene where the glass plate 24 is rotated so as to continuously change between 0 ° and D ° and moved to the negative side in the X-axis direction (see scanning line S2, scanning line S4, scanning line S6, etc.) (C), the glass plate 24 is rotated so that the inclination angle of the glass plate 24 continuously changes between 0 ° and −D °. In other words, the control unit 18 appropriately rotates the glass plate 24 in accordance with the movement of the mounting table 17 set in advance. As described above, in the scene where the image capturing unit 13 acquires the image of the test surface 12 of the wafer 11, the control unit 18 causes the optical axis deriving unit Lo of the optical axis L in the optical system 14 of the image sensor 26 of the image capturing unit 13. Since the optical axis L is changed so as to follow the movement of the test surface 12 of the wafer 11 on the imaging surface, an image of the test surface 12 of the wafer 11 guided from the optical system 14 is captured. When viewed with the element 26 (imaging unit 13), it is stationary, and it is possible to prevent the obtained image of the test surface 12 from blurring.

  A specific example of the control method as shown in FIG. 6 is shown in FIG. In FIG. 7, the horizontal axis indicates time, and in a scene of moving to the positive side in the X-axis direction (see scanning line S1, scanning line S3, scanning line S5, etc. in FIG. 2), the time progresses in the right direction when viewed from the front. Direction, and in the scene of moving to the negative side in the X-axis direction (see scanning line S2, scanning line S4, scanning line S6, etc. in FIG. 2), the leftward direction in front view is the time progression direction. In the graph of FIG. 7, the upper stage shows the ON / OFF state of the flash F, and the lower stage shows the state in which the glass plate 24 is tilted with reference to the state of the upper flash F as a broken line R. .

  In the appearance inspection apparatus 10 of this embodiment, although not shown, the moving speed of the test surface 12 of the wafer 11 along the scanning line S is constant. Further, each acquisition region 25 appears on the scanning line S at the moving speed so that the acquisition regions 25 are adjacent to each other at equal intervals on the same scanning line S with the movement speed as a reference. The polygonal line R is set so that the time required to travel the interval l (see FIG. 3) is one cycle, that is, the glass plate 24 is rotated periodically so that the inclination angle satisfies the polygonal line R. Has been moved. In this broken line R, the flash F is in an ON state so as to correspond to the time position at which the inclination angle of the glass plate 24 changes from −D / 2 to D / 2 when the time axis is viewed in the direction toward the right side of the front view. Is set. That is, in a scene where the test surface 12 of the wafer 11 moves relatively to the positive side in the X-axis direction, the inclination angle of the glass plate 24 is changed from −D / 2 to D / 2, and the test of the wafer 11 is performed. In a scene where the surface 12 moves relatively to the negative side in the X-axis direction, the inclination angle of the glass plate 24 is changed from D / 2 to -D / 2. With such a control method, even if the tilt angle of the glass plate 24 (D / 2 and -D / 2 in the above example) does not completely match the ON state of the flash F, it is constant before and after that. Since the inclination angle of the glass plate 24 is changed so as to be a straight line of inclination, it is possible to prevent the obtained image of the test surface 12 from being blurred. Further, in the control method of FIG. 7, by setting the state where the inclination angle is 0 ° as the center position of the flash F in the ON state (intermediate time of the ON state), the test surface 12 of the wafer 11 is relatively In general, the inclination angle of the glass plate 24 changes in the same broken line in a scene where the glass plate 24 moves to the positive side in the X-axis direction and a scene where the test surface 12 of the wafer 11 moves relatively to the negative side in the X-axis direction. R, in other words, the attitude control of the glass plate 24 can be made the same. If the relative moving speed of the imaging unit 13 and the optical system 14 and the test surface 12 of the wafer 11 is not completely constant, the period of the polygonal line R and the change in the moving speed are matched. By appropriately changing the ON state timing of the flash F corresponding thereto, it is possible to more appropriately prevent the obtained image from blurring.

  As described above, in the appearance inspection apparatus 10, the position of the optical axis deriving unit Lo is not changed without changing the position of the optical axis introducing unit Li even if the presence position of the wafer 11 is changed according to the movement of the mounting table 17. The optical axis L of the optical system 14 is changed so as to follow the movement of the mounting table 17, that is, the optical axis position (optical axis deriving unit Lo) in the optical path deriving unit of the optical path of the optical system 14 is moved. Therefore, the image of the wafer 11 existing at the same position is guided to the imaging unit 13. In other words, when viewed from the virtual optical axis IL with reference to the center position of the moving object to be inspected (see FIG. 4C) 11a, the virtual derivation unit ILo located at the same location on the imaging surface of the imaging element 26 On the other hand, since the optical axis L of the optical system 14 is changed so that the virtual introduction part ILi follows the movement of the center position 11 a of the wafer 11, the imaging part 13 has the wafer 11 existing at the same position. The image will be guided. For this reason, it can prevent that blurring arises in the acquisition image (each acquisition area | region 25) of the to-be-examined surface 12 of the wafer 11 which the imaging part 13 acquires.

  Further, in the appearance inspection apparatus 10, the position of the optical axis in the optical path deriving portion (optical axis deriving portion Lo) of the optical path is detected by changing the posture of the glass plate 24 (optical path changing member) of the optical system 14. Since the movement of the surface 12 (mounting table 17) is followed, the configuration is simple, and even when the mounting table 17 is moved at high speed, it can be easily handled. This is because it is extremely easy to control the rotation posture of the glass plate 24 as compared with the conventional case in which the imaging unit itself follows the movement of the inspection object.

  Furthermore, in the appearance inspection apparatus 10, in the optical system 14, the moving speed of the test surface 12 of the wafer 11 is changed in the direction opposite to the moving direction of the wafer 11, without changing the position of the optical axis introducing portion Li. The acquired image (each acquired region 25) is blurred with a very simple configuration in which the optical axis L is changed to the optical axis L ′ so as to move at a speed suitable for Can be prevented. For example, when the glass plate 24 having a thickness of 0.5 mm is used, if the amount by which the position of the optical axis deriving portion Lo is displaced is 1 to 10 μm, the glass plate 24 is tilted by about ± 1 ° (that is, the book) In the embodiment, it can be changed from the optical axis L to the optical axis L ′ by D = 2 °.

  In the appearance inspection apparatus 10, the wafer 11 acquired by the imaging unit 13 is controlled by controlling the rotation posture of the glass plate 24 so as to match the movement direction and movement speed of the surface 12 of the wafer 11 set in advance. Since it prevents that the acquisition image (each acquisition area | region 25) of the to-be-tested surface 12 of this has a blurring, the external appearance which inspects the external appearance of the semiconductor chip on a wafer like the above-mentioned Example is moved. It is suitable for an inspection apparatus or a semiconductor exposure apparatus that exposes and transfers a circuit pattern to a photosensitizer (photoresist) formed or coated on the surface of a wafer by irradiating light. This is because, in the above-described appearance inspection apparatus, semiconductor exposure apparatus, or the like, the moving speed of the mounting table 17 that is increased from the viewpoint of shortening the time required for the inspection of the wafer 11 is extremely high. This is because the method of correcting the blur by detecting the movement of the inspection surface 12 and reflecting the detection result on the acquired image cannot cope.

  In the appearance inspection apparatus 10, the optical axis deriving unit is appropriately controlled by controlling the posture of the optical path changing member (the glass plate 24 in this embodiment) provided in the optical system 14 in accordance with the timing of image acquisition by the imaging unit 13. Compared with the use of an image processing filter or the like, since Lo is configured to optically prevent blur by changing the optical axis L in the optical system 14 so that Lo follows the movement of the test surface 12 of the wafer 11. Thus, an inexpensive and simple configuration can be obtained.

  Since the appearance inspection apparatus 10 employs a control method as shown in FIG. 7, posture control of the glass plate 24 is performed regardless of the relative movement direction of the test surface 12 of the wafer 11 with respect to the optical system 14 and the imaging unit 13. Can be the same.

  Therefore, in the appearance inspection apparatus 10 according to the present invention, it is possible to prevent the acquisition image (each acquisition region 25) of the wafer 11 (inspection object) moving at high speed with a simple configuration from being blurred.

  In the above embodiment, the glass plate 24 is used as the optical path changing member. However, if the material is transparent (allows light transmission) and has a desired refractive index, for example, plastic (resin Material) or the like may be used, and is not limited to the above-described embodiments.

  In the above-described embodiment, the glass plate 24 is used as the optical path changing member. However, in the optical system 14, the optical axis lead-out portion Lo is placed on the object to be inspected without changing the position of the optical axis introducing portion Li. In the embodiment described above, any method can be used as long as it can be changed from the optical axis L to the optical axis L ′ by following the movement of the wafer 11), and is not limited to the above-described embodiment. For example, a mirror 27 (see FIG. 8) can be used as the optical path changing member. The optical system 14 ′ as an example will be described below.

  In the optical system 14 ′, as shown in FIG. 8, the image guide path 19 ′ is configured differently from the optical system 14. The image guide path 19 ′ is configured such that an optical path from the objective lens 21 to the imaging lens 23 is bent at a right angle by a mirror 27. In the optical system 14 ′, as shown in FIG. 9A, the optical axis L is changed by translating the mirror 27 in the vertical direction along the Z-axis direction (see arrow A7). Specifically, the mirror 27 is translated from the position indicated by the alternate long and short dash line downward (the negative side in the Z-axis direction), thereby imaging the optical axis deriving unit Lo without changing the position of the optical axis introducing unit Li. The optical axis L is moved to the optical axis L ′ so as to move downward (see arrow A8 and the optical axis deriving unit Lo ′), which is the direction opposite to the moving direction of the wafer 11 as viewed on the imaging surface of the imaging device 26 of the unit 13. To change. Then, as shown in FIG. 9B, when the test surface 12 of the wafer 11 moves to the right side, that is, the positive side in the X-axis direction when the front view of FIG. 9 is viewed (see the wafer 11 indicated by a two-dot chain line) When viewed from the virtual axis IL with reference to the center position 11a of the test surface of the wafer 11, the virtual introduction part ILi follows the movement of the center position 11a of the wafer 11 (see the arrow A9 and the virtual introduction part ILi ′) and is virtually derived. The part ILo is located at the same position on the image pickup surface of the image pickup device 26, and the image of the moved wafer 11 is present at the same position on the image pickup surface of the image pickup device 26, that is, at the same position when viewed from the image pickup unit 13. An image of the wafer 11 is guided. When the test surface 12 of the wafer 11 moves to the negative side in the X-axis direction, although not shown, the mirror 27 may be translated upward. Even in the case of this optical system 14 ', the acquired image (each acquisition region 25) of the wafer 11 (inspection object) is controlled by controlling the height position of the mirror 27 in the same manner as the optical system 14 of the above-described embodiment. ) Can be prevented from blurring. In FIG. 9, the optical axis L is changed to the optical axis L ′ and the virtual optical axis IL is changed to the virtual optical axis IL ′. These changes are conceptually shown for easy understanding. It does not always coincide with the actual change in the optical axis.

  Further, similarly to the optical system 14 ′ shown in FIG. 8, the optical system 14 ″ (see FIG. 10) may be configured using a mirror 27 ′. As shown in FIG. 10, the optical system 14 ″ has the same configuration as the optical system 14 ′, but the mirror 27 ′ is extended in the Y axis direction instead of being translated in the Z axis direction. It is set as the structure rotated around a rotating shaft. Even in the case of this optical system 14 ″, the optical axis deriving portion Lo is covered in the direction opposite to the moving direction of the wafer 11 without changing the position of the optical axis introducing portion Li due to the rotational posture of the mirror 27 ′. The inspection object (wafer 11 in the above-described embodiment) is moved at a speed that matches the movement speed (an amount that matches the movement amount) (see the arrow A10 and the optical axis deriving section Lo ′), and the optical axis L to the optical axis L. It is the same as the optical system 14 ′ except that it is displaced to ′ (see FIG. 10A). In the case of this optical system 14 ″, as shown in FIG. 10B, the test surface 12 of the wafer 11 moves to the right side, that is, the positive side in the X-axis direction when the front surface of FIG. 10 is viewed (two-dot chain line). ), The mirror 27 ′ is rotated clockwise (rotation from the mirror 27 ′ indicated by the two-dot chain line to the mirror 27 ′ indicated by the solid line), and the virtual optical axis IL becomes the virtual optical axis IL ′. (See arrow A11). In FIG. 10, the optical axis L is changed to the optical axis L ′ and the virtual optical axis IL is changed to the virtual optical axis IL ′. These changes are conceptually shown for easy understanding. It does not always coincide with the actual change in the optical axis.

  Further, in addition to the glass plate 24, the mirror 27, and the mirror 27 ′, as the optical path changing member, a wedge prism 2 is provided between the objective lens 21 and the imaging lens 23 in the optical system 14 of FIG. The angle may be changed by appropriately rotating the optical member formed by stacking the sheets. In the optical system 14 ′ of FIG. 8, a polygon mirror is provided instead of the mirror 27 and the rotation is appropriately driven. May be.

  In the above-described embodiment, as illustrated in FIG. 2, the test surface 12 of the wafer 11 is configured to scan in the Y-axis direction with the scanning line S along the X-axis direction. The movement is performed while moving the position of the test surface 12 of the wafer 11 with respect to the imaging unit 13 and the optical system 14 so as to align the plurality of acquisition regions 25 on the test surface 12 so as to cover the test surface 12. As long as the flash light F is emitted from the flash light source 15 and the image data is acquired from the imaging unit 13 in accordance with the emission timing of the flash F, the invention is not limited to the above-described embodiment. Absent. For example, as shown in FIG. 11, the scanning surface 12 of the wafer 11 may be configured to scan so as to align a plurality of acquisition regions 25 spirally from the peripheral edge toward the center. In this case, it is necessary to appropriately move the optical axis introducing portion Li in the X axis direction and the Y axis direction so that the optical axis introducing portion Li follows the movement of the test surface 12 of the wafer 11 with reference to the optical axis deriving portion Lo. For this reason, the optical path changing member also needs to be configured so that the posture can be changed in the X-axis direction and the Y-axis direction. For example, when the glass plate 24 of the optical system 14 is used as the optical path changing member, in addition to the rotating shaft 24a (see FIGS. 1 and 5) extending in the Y-axis direction, although not shown, the glass plate 24 extends in the X-axis direction. It is conceivable that an existing rotation shaft is provided and the rotation shaft can be driven and controlled by the control unit 18 in the same manner as the rotation shaft 24a. Further, when the mirror 27 'is used as shown in FIGS. 10A and 10B, it is configured to be rotatable around the X axis and rotatable around the Y axis. For example, around the X axis. It is conceivable that the mirror 27 ′ is supported on a rotatable frame so as to be rotatable about the Y axis, and the attitude of the mirror 27 ′ can be driven and controlled by the control unit 18.

  In the above-described embodiment, the appearance inspection apparatus is shown as the image blur prevention apparatus. However, if the image is acquired while moving the inspection object, for example, the surface of the wafer is irradiated by irradiating light. It may be a semiconductor exposure apparatus that exposes and transfers a circuit pattern to a photosensitizer (photoresist) formed or applied, and is not limited to the above-described embodiments.

It is a block diagram which shows typically the structure of the external appearance inspection apparatus as an image blur prevention apparatus which concerns on this invention. It is the typical front view which looked at the wafer from the upper part in order to demonstrate the mode of scanning in an appearance inspection device. It is explanatory drawing for demonstrating the correlation of the position of the imaging part and optical system with respect to the to-be-tested surface of a wafer, and the timing which flash light is emitted from a flash light source, and shows FIG. 2 partially expanded on the upper part. A partial front view is shown, and a graph in which the timing at which the flashlight is emitted at the lower part is shown in correspondence with the upper partial front view and the time axis. It is explanatory drawing for demonstrating the basic concept for the blurring prevention in the image blurring prevention apparatus which concerns on this invention, (a) shows a mode that a to-be-inspected object moves, (b) is a change of an optical axis. (C) shows how the virtual optical axis is changed. It is a typical block diagram for demonstrating the structure for blurring prevention in the external appearance inspection apparatus 10 of a present Example, (a) shows the state which the glass plate is not rotated, (b) is to be examined. The optical axis deriving unit is displaced to the left to correspond to the scene where the object has moved to the right, and (c) shows the optical axis deriving unit being displaced to the right to accommodate the scene where the object has moved to the left. It shows the state that was done. It is a graph which shows the control method in the appearance inspection apparatus 10 of a present Example by the operation | movement with respect to time, (a) shows the ON / OFF state of a flash, (b) moves a to-be-inspected object to the positive side in the X-axis direction. (C) shows the control of the inclination angle of the glass plate when the inspection object moves to the negative side in the X-axis direction. 5 is a graph showing an example of a control method in the appearance inspection apparatus 10. It is a block diagram which shows typically the optical system of the external appearance inspection apparatus of the example different from FIG. It is explanatory drawing for demonstrating operation | movement of the optical system of FIG. 8, (a) shows a mode that an optical axis is changed, (b) has shown a mode that a virtual optical axis is changed. FIG. 10 is an explanatory diagram for explaining an operation different from the example of FIG. 9 in the optical system of FIG. 8, in which (a) shows how the optical axis is changed, and (b) shows that the virtual optical axis is changed. It shows a state. FIG. 3 is a schematic front view of a wafer as viewed from above in order to explain the scanning of an example different from FIG. 2 in the appearance inspection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Appearance inspection apparatus 11 Wafer (as to-be-inspected object) 13 Imaging part (as imaging means) 14 Optical system 17 Mounting base 17a Mounting surface 18 Control part 24 (As control means) Glass (As optical path changing member) Plate 27 Mirror (as optical path changing member) L Optical axis

Claims (6)

A mounting table having a mounting surface on which an object to be inspected is mounted and movable along a plane parallel to the mounting surface, and an image of the inspection object mounted on the mounting surface are acquired. Imaging means for performing, an optical system for guiding the image of the inspection object placed on the placement surface located in a predetermined area to the imaging means, movement of the placement table, and the imaging means Control means for controlling image acquisition,
In the optical system, by changing the posture, the light in the optical path deriving unit on the imaging unit side is displaced in the optical path to the imaging unit without displacing the optical axis position in the optical path introducing unit on the mounting table. An optical path changing member for displacing the axis position is provided,
The control means changes the optical path so that the optical axis position in the optical path deriving unit follows the movement of the mounting table when the imaging unit acquires the image of the inspection object while moving the mounting table. An image blur prevention apparatus characterized by changing a posture of a member.   The control means is a movement amount equal to the movement amount of the mounting table viewed from the imaging surface in a direction opposite to the moving direction of the mounting table viewed from the imaging surface in the imaging device, and 2. The image blur prevention apparatus according to claim 1, wherein the center of the optical axis is displaced to follow the movement of the mounting table.   The optical path changing member is a glass plate that is parallel to the imaging surface and is rotatable about an axis perpendicular to the moving direction of the mounting table as viewed from the imaging surface. An image blur prevention device as described in 1.   3. The mirror according to claim 2, wherein the optical path changing member is a mirror that is parallel to the imaging surface and is rotatable about an axis perpendicular to the moving direction of the mounting table as viewed on the imaging surface. The image blur prevention apparatus as described.   The optical path changing member is parallel to a line defined by an intersection of a plane parallel to the imaging surface and a plane including the moving direction of the mounting table and the moving direction of the mounting table as viewed on the imaging surface. The image blur prevention apparatus according to claim 2, wherein the image blur prevention apparatus is a mirror that can be translated along. 3. The image blur prevention apparatus according to claim 2, wherein the optical path changing member is a multi-faceted prism that is rotatable around an optical axis of an optical path that reaches the imaging unit.

Images