JP6697285B2 - Wafer defect inspection system - Google Patents

Description

  The present invention relates to a wafer defect inspection apparatus for detecting defects such as cracks, slips, dimples, mounds, bumps or grinding marks generated on the surface of a wafer, and defects such as inclusion of foreign matter or voids between facing wafers of a bonded wafer. In particular, the present invention relates to a wafer defect inspection apparatus for detecting cracks generated on the surface of a wafer.

  A conventional inspection apparatus for a silicon wafer generates a parallel light from the light source that emits light and the emitted light, irradiates the surface of the silicon wafer, and reflects the reflected light within the predetermined visual field reflected on the surface of the silicon wafer. The optical device includes a guiding optical device and an imaging unit that captures a surface image of the silicon wafer by the reflected light guided (for example, Patent Document 1).

JP 2005-114587 A

In the conventional silicon wafer inspection device, the optical device consists of an optical fiber, an eyepiece lens, a pinhole member, a half mirror and a collimating lens, and generates parallel light from the light emitted from the light source, and There is a problem that the structure is complicated because the structure is such that it is irradiated vertically.
Further, although the conventional inspection apparatus for a silicon wafer can detect a crack, it has a problem that the position of the crack on the surface of the silicon wafer cannot be specified.

  The present invention has been made to solve the above-mentioned problems, and provides a low-cost wafer defect inspection device that has a simple device configuration, can specify the position of a defect on a wafer, and is inexpensive. ..

  In the wafer defect inspection apparatus according to the present invention, the mounting means for mounting the wafer in the imaging area, the illuminating means for irradiating the surface of the wafer on the mounting means with light, and the light reflected by the surface of the wafer The screen includes a screen on which the surface image of the wafer is projected, a light-shielding unit that prevents the screen from being directly irradiated with the light from the illumination unit, and an imaging unit that captures the surface image of the wafer projected on the screen.

  The wafer defect inspection apparatus according to the present invention has a simple apparatus configuration and can detect a wafer defect in a short time.

It is explanatory drawing for demonstrating the system configuration of the wafer defect inspection apparatus which concerns on this embodiment. It is explanatory drawing for demonstrating the positional relationship of each component of a wafer defect inspection apparatus. (A) is a front view showing a schematic configuration of a wafer defect inspection apparatus according to the present embodiment, and (b) is a side view showing a schematic configuration of the wafer defect inspection apparatus according to the present embodiment. (A) is a plan view showing an example of a calibration jig, (b) is an explanatory view showing an example of a calibration image, and (c) is an explanatory view showing an example of an image including a crack. 4A is an explanatory diagram showing an image obtained by calibrating the image shown in FIG. 4C, and FIG. 5B is an explanatory diagram in which the image shown in FIG. 5A is reflected on the map of the wafer. It is explanatory drawing for demonstrating the system configuration of the wafer defect inspection apparatus which concerns on 2nd Embodiment. FIG. 7A is an explanatory diagram showing an example of a captured image for each predetermined time, and FIG. 7B shows an example of a composite image obtained by extracting a predetermined area from each captured image shown in FIG. FIG. 9C is an explanatory diagram showing an example of a corrected image obtained by correcting the composite image shown in FIG. 7B.

(First Embodiment of the Invention)
The wafer defect inspection apparatus 100 according to the present invention is a semiconductor wafer such as a silicon wafer or a compound wafer such as silicon carbide (SiC), gallium arsenide (GaAs), gallium phosphide (GaP) or gallium nitride (GaN) (hereinafter, simply referred to as “ (Referred to as "wafer 200"), which detects defects such as cracks, slips, dimples, mounds, ridges or grinding marks on the surface of wafer 200), and defects such as foreign matter mixture or voids between bonded wafers 200 facing each other. Yes, the inspection principle for each defect is the same. Therefore, in the following description, the wafer defect inspection apparatus 100 that detects a crack generated on the surface of the wafer 200 will be described as an example.
As shown in FIGS. 1 and 3, the wafer defect inspection apparatus 100 irradiates the mounting means 10 for mounting the wafer 200 to be inspected in the imaging region and the surface of the wafer 200 on the mounting means 10 with light. Illuminating means 20, a screen 30 on which a surface image of the wafer 200 is projected by the light reflected on the surface of the wafer 200, and a light shielding means 40 for preventing direct light from the illuminating means 20 from irradiating the screen 30. A first image pickup means 50 for picking up a surface image of the wafer 200 projected on the screen 30.

In addition, the wafer defect inspection apparatus 100 uses a second image capturing unit 60 that captures a notch (or an orientation flat) of the wafer 200 and a surface image of the wafer 200 captured by the first image capturing unit 50, which will be described later. The image processing means 70 for performing processing to detect cracks generated on the surface of the wafer 200, the mounting means 10, the illumination means 20, the first image pickup means 50, and the second image pickup means 60 are controlled, and image processing is performed. An arithmetic unit 80 for specifying the position of the crack based on the surface image of the wafer 200 image-processed by the unit 70, and a display unit 90 for displaying the detection result of the crack are provided.
In the wafer defect inspection apparatus 100, the illumination unit 20, the screen 30, the light shielding unit 40, and a part of the first imaging unit 50 are included in the dark chamber 101, and the dark chamber 101 corresponding to the wafer 200 on the mounting unit 10 is included. The bottom of is open.

  The mounting unit 10 pulls out one wafer 200 from the cassette 300 in which a plurality of wafers 200 are aligned and stored, moves the pulled-out wafer 200 backward and positions it in the imaging region, and after the crack inspection, moves the wafer 200 forward. It is a stage having a uniaxial drive mechanism that moves to and is stored in the original position of the cassette 300.

The illumination unit 20 is arranged at a position where the optical axis O ₁ intersects the wafer 200 on the mounting unit 10 via the gap between the light shielding unit 40 and the first imaging unit 50.
The illumination means 20 according to the present embodiment is a high-intensity illumination 21 that uses an LED (light-emitting diode) as a point light source as a light source (for example, high-intensity illumination manufactured by Excelitas Technologies Inc. (type name: 0TFI-0275)) and a first lens 22 (for example, CCTV lens (model name: MV0813) manufactured by Muteron Co., Ltd.) that sets the irradiation angle θ _{1 of the} light emitted from the illumination 21 to 60 °. Equipped with.

The illumination 21 is preferably a point light source in order to obtain the contrast and resolution of the surface image (captured image) of the wafer 200 projected on the screen 30, and as the point light source, a xenon mercury lamp other than the LED is used. Conceivable. However, the xenon mercury lamp has a problem that it has a short light emission life, is expensive, and cannot be installed at a tilt, as compared with the LED. Therefore, the illumination 21 according to this embodiment is preferably an LED.
In particular, the LED used for the illumination 21 has a width on the light emitting surface and is not a perfect point light source. Therefore, in order to approximate the LED to a point light source, the illumination 21 is preferably provided with a shield plate 21b having a pinhole with a diameter of about 3 mm immediately before the LED on the base 21a side (for example, several mm before). ..
As a result, the wafer defect inspection apparatus 100 can obtain a surface image (captured image) of the wafer 200 with higher contrast and resolution than in the case where the shielding plate 21b (pinhole) is not provided.

Here, the dimple generated on the surface of the wafer 200 does not have a serious problem as a defect as a crack, and the outer shape in a plan view is a circle or an ellipse. There is a difference in appearance.
However, in the case of a surface image (captured image) of the wafer 200 having a low contrast and a low resolution, the crack may appear rounded with a blurred outer corner, and may not be distinguished from a dimple.
Therefore, the wafer defect inspection apparatus 100 is provided with the shielding plate 21b (pinhole) to enhance the contrast and the resolution, clarify the difference between the crack and the dimple, increase the crack detection power, and improve the inspection sensitivity. can do.

Although the pinhole of the shielding plate 21b has a smaller diameter, the LED becomes closer to a point light source, but the irradiation angle θ ₁ becomes narrower and the entire surface of the wafer 200 cannot be irradiated. I can't get good brightness.
Further, as the distance between the LED and the shield plate 21b (pinhole) becomes smaller, the irradiation angle θ ₁ becomes narrower, and when the distance is too close, the shield plate 21b (pinhole) accumulates heat from the LED, and the heat causes the LED Damage.
Therefore, according to the irradiation intensity of the LED, the magnification of the first lens 22, the distance between the illumination unit 20 and the wafer 200, the size of the wafer 200, and the like, the distance between the LED and the shield plate 21b (pinhole) and the shield are provided. It is preferable to appropriately set the diameter of the pinhole of the plate 21b.

Further, in the illuminating means 20 according to the present embodiment, the illumination 21 is screwed on the outer periphery of the base 21a of the emission light port, and the lens mount of the first lens 22 is the C mount, as shown in FIG. As described above, the screw portion of the first lens 22 and the first lens 22 are connected via the adapter (not shown) so that the distance d ₁ between the exit light port of the illumination 21 and the C-mount side lens end surface of the first lens 22 is set to 5 mm. The C mount of the lens 22 of No. 1 is connected. The first lens 22 is not always necessary and may be removed as necessary.

Further, in the illumination 21 according to the present embodiment, the distance d ₂ between the vertical reference passing through the center of the emission light port and the vertical reference passing through the center of the wafer 200 on the mounting means 10 is 350 mm, The distance d ₃ between the horizontal reference passing through the center and the horizontal reference passing through the center of the wafer 200 on the mounting means 10 is 400 mm, and the inclination angle θ ₂ is 45 ° with respect to the horizontal reference passing through the center of the emission light port. It is installed as follows.
In this embodiment, since the wafer 200 of 8 inches (diameter 200 mm) is the inspection target, the distance d ₂ is 350 mm and the distance d ₃ is 400 mm, but the size of the wafer 200 (for example, 4 inches It is preferable to appropriately set the distance d ₂ and the distance d ₃ according to (diameter 100 mm) to 12 inches (diameter 300 mm).

The screen 30 has a lower side 31 disposed near one end 11 of the mounting means 10 and is inclined inward with respect to the mounting means 10.
The screen 30 according to the present embodiment is a square plate-shaped body having a side of 300 mm or more (for example, 400 mm), and the projection surface has fine irregularities on the surface and is matte white.
Further, in the screen 30 according to the present embodiment, as shown in FIG. 2, the distance d ₄ between the vertical reference passing through the center of the lower side 31 and the vicinity of the notch of the wafer 200 on the mounting means 10 is set to 30 mm, and the lower side The distance d ₅ between 31 and the horizontal reference passing through the center of the wafer 200 on the mounting means 10 is set to 10 mm to 20 mm (for example, 12.06 mm), and the inclination angle θ is set with respect to the vertical reference passing through the center of the lower side 31. ₃ is set to 28 °.
As the wafer 200 on the mounting means 10 is separated from the screen 30, the surface image itself of the wafer 200 projected on the screen 30 becomes more blurred (blurred) at the peripheral edge of the wafer 200. The wafer 200 on the placing means 10 and the screen 30 should be brought close to each other.
Further, the lower side 31 of the screen 30 is installed at a height (distance d ₅ ) where the wafer 200 does not pass under the screen 30 and interfere with it.

The light shielding means 40 is intended to prevent the light of the illumination means 20 from directly hitting the screen 30, and the lower side 41 is arranged above the other end 12 of the mounting means 10 and spaced upward from the mounting means 10. It is provided and is inclined substantially outwardly with respect to the mounting means 10 substantially parallel to the screen 30.
The light shielding unit 40 according to the present embodiment is a square plate-shaped body having a side of 350 mm, and as shown in FIG. 2, a vertical reference passing through the center of the lower side 41 and the center of the wafer 200 on the mounting unit 10. and 150mm distance _{d 6} between the vertical reference through a distance _{d 7} between the horizontal reference passing through the center of the wafer 200 on the lower side 41 and mounting means 10 and 200 mm, a vertical passing through the center of the lower side 41 The tilt angle θ ₄ is set to 30 ° with respect to the reference.
Note that the distance d ₄ , the distance d _{5, the} inclination angle θ ₃ , and the dimensions of the light shielding unit 40 described above are set with a margin, but the dimensions are not limited to these values.

The first imaging unit 50 is arranged to face the inclined surface of the screen 30 with a gap between the other end 12 of the mounting unit 10 and the lower side 41 of the light shielding unit 40.
The first imaging unit 50 according to the present embodiment includes an inspection camera 51 (for example, an area scan camera manufactured by Basler (type name: acA2500-14gm)) and a second lens 52 (for example, a stock company). CCTV lens (type name: HF0818J) manufactured by MUTERON Co., Ltd.
Further, the first image pickup means 50 is an area scan camera (type name: acA2500-14gm) made by Basler or CCTV made by Mutlon Co., Ltd. if it is a high-resolution camera and lens having a resolution of 5M class or higher. It is not limited to the lens (type name: HF0818J).

Further, in the first image pickup means 50 according to the present embodiment, the inspection camera 51 has the inner periphery of the base 51a of the emission light port, and the lens mount of the second lens 52 is a C mount. Yes, the screw portion of the second lens 52 and the C mount of the second lens 52 are connected.
In addition, the first imaging unit 50 (inspection camera 51) according to the present embodiment is fixed to the camera mounting plate 53 with a screw by using a tap attached to the inspection camera 51, and the camera mounting plate 53 is used. Attached to the support body 102 (for example, an aluminum frame).

Further, in the first imaging means 50 according to the present embodiment, as shown in FIG. 2, the distance d ₈ between the projection surface of the screen 30 and the second lens 52 is 410 mm, and the first imaging means 50 is placed on the mounting means 10. The tilt angle θ ₅ is set to 10 ° with respect to a horizontal reference passing through the center of the wafer 200.
The second lens 52 according to the present embodiment uses the lens having the focal length f = 8 mm, and thus the distance d _{8 is set} to 410 mm. However, the distance d ₈ is changed according to the focal length of the lens. It is preferable to set it appropriately.
Further, the tilt angle θ ₅ of the first imaging unit 50 (inspection camera 51) can be varied within a range of ± 5 ° (5 ° to 15 °) and can be fixed at any position. Further, the first image pickup means 50 (second lens 52) can use the focus and aperture adjustment mechanism of the lens itself.
The optical axis O ₂ of the first imaging unit 50 (inspection camera 51) forms an angle θ ₆ with the screen 30 of 108 ° ± 5 ° (103 ° to 113 °) due to the structure of the wafer defect inspection apparatus 100. ), The angle θ ₆ with the screen 30 is preferably 90 °.

The second image pickup means 60 is arranged downward from the vicinity of the one end 11 of the mounting means 10.
The second image pickup means 60 according to the present embodiment includes an inspection camera 61 (for example, an area scan camera manufactured by Basler (type name: acA640-100gm)) and a third lens 62 (for example, Shot Moritex). Anti-vibration megapixel macro lens (model name: ML-MC50HR) manufactured by Co., Ltd. The third lens 62 is not limited to the vibration-resistant megapixel macro lens (model name: ML-MC50HR) manufactured by Shot Moritex Co., Ltd.

Further, in the second image pickup means 60 according to the present embodiment, the inspection camera 61 has the inner periphery of the base 61a of the emission light port, and the inner periphery of the base 61a is screwed, and the lens mount of the third lens 62 is a C mount. Yes, the screw portion of the third lens 62 and the C mount of the third lens 62 are connected.
Further, the second image pickup means 60 (inspection camera 61) according to the present embodiment is fixed to the camera mounting plate 63 with a screw by using a tap attached to the inspection camera 61.

Further, the second image pickup means 60 (inspection camera 61) according to the present embodiment passes through a vertical reference passing through the center of the emission light port and the center of the wafer 200 on the mounting means 10, as shown in FIG. The distance d ₉ from the vertical reference is 100 mm, and the distance d ₁₀ between the horizontal reference passing through the center of the emission light port and the horizontal reference passing through the center of the wafer 200 on the mounting means ₁₀ is 205 mm. Is installed so that the notch of is located at the center of the image.
The distance d ₁₀ of the second image pickup means 60 (inspection camera 61) can be varied within a range of ± 10 mm (195 mm to 215 mm) and can be fixed at any position.

  The image processing unit 70 determines an inspection range by the smoothing process and the binarization process on the surface image of the wafer 200 imaged by the first imaging unit 50, detects a crack by the local threshold method, and Detect cracks within the inspection range by the quantity extraction method.

The calculation means 80 is a calibration image (FIG. 4 (b)) in which the calibration jig 400 (FIG. 4A) in which the dots 402 are mapped in a grid pattern on the substrate 401 corresponding to the wafer 200 is imaged by the first imaging means 50 (FIG. 4B). )) And the surface image of the wafer 200 image-processed by the image processing means 70, the position of the crack is specified.
The calibration jig 400 according to the present embodiment uses a glass substrate having substantially the same shape as the wafer 200 as the substrate 401, and chromium is vapor-deposited on the substrate 401 as the dots 402.

  As shown in FIG. 3B, the display means 90 is arranged on the upper front surface of the wafer defect inspection apparatus 100 and displays the presence or absence of the crack of the wafer 200 detected by the image processing means 70 or the position thereof. Is the display.

Next, the processing operation of the wafer defect inspection apparatus 100 according to this embodiment will be described.
In the wafer defect inspection apparatus 100, when the cassette 300 is loaded onto the vertically moving elevator 103, the vertically moving elevator 103 places the wafer 200 to be inspected in the cassette 300 on the basis of the control signal of the arithmetic means 80. The cassette 300 is moved up and down so as to match the height of the stage of the means 10.
Then, the mounting means 10 pulls out one wafer 200 from the cassette 300 based on the control signal of the arithmetic means 80, moves the wafer 200 backward, and conveys it to the imaging region.

  Then, the second imaging unit 60 images the peripheral portion (the notch at the left end in FIG. 1) of the wafer 200 based on the control signal of the arithmetic unit 80, and outputs the image data to the arithmetic unit 80.

Then, the illumination unit 20 irradiates the wafer 200 on the mounting unit 10 with light based on the control signal of the calculation unit 80.
The light applied to the wafer 200 on the mounting means 10 is reflected by the surface of the wafer 200, reaches the screen 30, and projects a surface image of the wafer 200 on the screen 30.
In this case, the direct light of the illumination means 20 is blocked by the light blocking means 40 and does not reach the screen 30, but reaches the screen 30 as indirect light.

  Then, the first image pickup means 50 picks up the surface image of the wafer 200 projected on the screen 30 based on the control signal of the calculation means 80, and outputs the image data to the image processing means 70.

When the image processing unit 70 acquires the captured image data (hereinafter referred to as original image data), the image processing unit 70 performs smoothing processing such as a moving average filter (averaging filter) or a Gaussian filter on the original image data to obtain the original image data. Smooth the image.
Further, the image processing means 70 performs a binarization process on the original image data after smoothing (hereinafter, referred to as smoothed image data) based on a threshold value of brightness for distinguishing the wafer 200 and the screen 30, The inspection range (the surface of the wafer 200) is determined from the smoothed image.
In addition, the image processing unit 70 detects a crack in the original image data by using a local threshold method based on a threshold value of the brightness that distinguishes the crack from the other area, with respect to the original image data.
Further, the image processing means 70 performs SIFT (Scale Invaliant Feature Transform) or SURF (Speeded Up Robust Features) on the original image based on the inspection range determined by the binarization process and the crack detected by the local threshold method. A crack in the inspection range is detected from the original image by using a feature amount extraction method such as the above, and the image data after the image processing is output to the calculation unit 80.

Then, the mounting means 10 moves the wafer 200 having undergone the crack inspection forward based on the control signal of the arithmetic means 80 and stores the wafer 200 in the original position of the cassette 300.
Further, the vertical movement elevator 103 moves the cassette 300 in the vertical direction based on the control signal of the arithmetic means 80 so that the position of the next wafer 200 to be inspected in the cassette 300 matches the height of the stage of the mounting means 10. To move.
Hereinafter, similar to the above-mentioned processing operation, the wafer defect inspection apparatus 100 performs the same crack inspection on all the wafers in the cassette 300.

  Then, when the wafer defect inspection apparatus 100 finishes the crack inspection on all the wafers in the cassette 300, the calculation unit 80 outputs the inspection result to the display unit 90, and the display unit 90 detects the crack of the wafer 200. The number (the image of the wafer 200 after the image processing, if necessary) is displayed, and the inspection processing ends.

  Note that the wafer defect inspection apparatus 100 performs the following processing when detecting not only the presence or absence of a crack but also the position of the crack.

The calculation unit 80 acquires a calibration image (FIG. 4B) using the calibration jig 400 in advance, calculates the distortion amount of the image based on the calibration image, and detects it using the feature amount extraction method. The image including the crack (FIG. 4C) is calibrated with the distortion amount.
Further, the calculation means 80 reflects the image calibrated with the distortion amount (FIG. 5A) on the map of the wafer 200 from which the distortion is removed (the map data of the wafer 200 acquired in advance) (FIG. 5 ( b)), the coordinate position (x, y) of the crack with respect to the notch (origin 0) on the wafer 200 is detected.
In this case, the calculation unit 80 detects the rotation amount of the wafer 200 based on the image of the peripheral edge (notch) of the wafer 200 imaged by the second imaging unit 60, and the wafer 200 is set as the coordinate position of the crack on the map. It reflects the rotation amount of.

  The display unit 90 displays the position coordinates of the crack along with the number of the wafer 200 in which the crack is detected (if necessary, the image of the wafer 200 after image processing) based on the inspection result input from the calculation unit 80. Display in map and coordinate position (x, y).

  As described above, in the wafer defect inspection apparatus 100 according to the present embodiment, the mounting unit 10 that mounts the wafer 200 on the imaging region, and the illumination unit that irradiates the surface of the wafer 200 on the mounting unit 10 with light. 50, a screen 30 on which the surface image of the wafer 200 is projected by the light reflected on the surface of the wafer 200, a light blocking means 40 for preventing the direct light from the illumination means 50 from irradiating the screen 30, and a screen 30. By providing the image pickup means 50 for picking up the surface image of the wafer 200 projected onto the wafer 200, the device configuration is simple, and the cracks on the surface of the wafer 200 can be detected in a short time. ..

(Second Embodiment of the Invention)
FIG. 6 is an explanatory diagram for explaining the system configuration of the wafer defect inspection apparatus according to the second embodiment. FIG. 7A is an explanatory diagram showing an example of captured images at predetermined time intervals, and FIG. 7B is a composite image in which a predetermined area is extracted from each captured image shown in FIG. 7C is an explanatory diagram showing an example, and FIG. 7C is an explanatory diagram showing an example of a corrected image obtained by correcting the composite image shown in FIG. 7B. 6 and 7, the same reference numerals as those in FIGS. 1 to 5 indicate the same or corresponding parts, and the description thereof will be omitted.

As described above in the first embodiment, the farther the wafer 200 on the mounting means 10 is from the screen 30, the more the surface image itself of the wafer 200 projected on the screen 30 becomes blurred (out of focus) at the peripheral edge of the wafer 200. ).
That is, in the surface image of the wafer 200 projected on the screen 30, the peripheral portion of the wafer 200 projected on the upper side 32 side of the screen 30 is the peripheral portion (notch) of the wafer 200 projected on the lower side 31 side of the screen 30. (Oriental flat part) is out of focus.

  Therefore, the wafer defect inspection apparatus 100 according to the present embodiment, as a crack and dimple inspection apparatus, selects a part of the surface image of the wafer 200 projected on the screen 30 from the lower side 31 of the screen 30. , Which is what you use.

  The mounting means 10 according to the present embodiment has a mechanism for horizontally moving the wafer 200 in the vertical direction with respect to the lower side 31 of the screen 30. In particular, the mounting means 10 according to the present embodiment moves the wafer 200 in the direction away from the first imaging means 50 (the lower side 31 of the screen 30) with respect to the initial position set in the dark room 101. Have.

  Further, the wafer defect inspection apparatus 100 according to the present embodiment is attached to the arm drive shaft of the mounting means 10, detects the position of the linear axis, and outputs a pulse signal as position information. (Shown) and a counter unit 13 that counts output pulses from the linear encoder and outputs the count information to the arithmetic means 80.

  Further, in the present embodiment, the calculation means 80 outputs a control signal to the illumination means 20 and the first image pickup means 50 at predetermined time intervals based on the count information of the counter unit 13.

  Further, the illumination unit 20 according to the present embodiment has a mechanism that emits light at predetermined time intervals based on the control signal of the calculation unit 80.

  Further, the first image pickup means 50 according to the present embodiment has a mechanism for picking up an image pickup area on the screen 30 at predetermined time intervals based on the control signal of the calculation means 80.

  In addition, the image processing unit 70 according to the present embodiment extracts striped imaged images of the wafer 200 in a predetermined region of the imaged region from the imaged images of the plurality of wafers 200 imaged at predetermined time intervals, The striped captured images are combined, and the combined elliptical image of the wafer 200 is corrected to a circular shape.

Next, the processing operation of the wafer defect inspection apparatus 100 according to this embodiment will be described.
It should be noted that the same process as that of the above-described first embodiment is performed until one wafer 200 is taken out from the cassette 300, the wafer 200 is set at the initial position in the dark room 101, and before the image is taken by the first imaging means 50. Since this is an operation, the description is omitted.

  The first image pickup means 50 picks up a surface image of the wafer 200 projected on the screen 30 based on the control signal of the calculation means 80, and outputs image data to the image processing means 70.

  Then, the mounting means 10 moves the wafer 200 at a constant speed in the horizontal plane in the direction away from the first imaging means 50 with respect to the initial position (on the lower side 31 side of the screen 30).

  The linear encoder detects the position of the linear axis and outputs a pulse signal as position information. Further, the counter unit 13 counts the output pulses from the linear encoder and outputs the count information to the calculating means 80.

  Then, the calculation means 80 outputs a control signal to the illumination means 20 and the first image pickup means 50 at a predetermined time interval (for example, every 100 pulses) based on the count information of the counter unit 13.

The illumination unit 20 irradiates light at a predetermined time interval (for example, every 100 pulses) based on the control signal of the calculation unit 80.
Further, the first image pickup means 50 takes an image of the image pickup area on the screen 30 at predetermined time intervals (for example, every 100 pulses) in synchronization with the illumination means 20 based on the control signal of the calculation means 80, and an image is obtained. The image data is output to the processing means 70.

Then, when the image processing unit 70 acquires a plurality of original image data, the image processing unit 70 captures a plurality of images of the wafers 200 (FIG. 7A) captured at a predetermined time interval (for example, every 100 pulses) from the captured area. The captured images of the wafer 200 in a predetermined area (the rectangular area 1 projected on the lower side 31 side of the screen 30) are extracted in strips.
Further, the image processing means 70 combines the striped imaged images so that they are adjacent to each other in the order of image pickup, and obtains a composite image of the elliptical wafer 200 (FIG. 7B).

  Then, the image processing means 70 performs smoothing processing such as a moving average filter (averaging filter) or a Gaussian filter on the composite image data to smooth the composite image. Since the processing operation is similar to that of the embodiment, the description is omitted.

  The wafer defect inspection apparatus 100 performs the following processing when detecting not only the presence or absence of a defect (crack, dimple) but also the position of the defect.

The image processing means 70 corrects an elliptical image including a defect detected by using the feature amount extraction method described above in the first embodiment in a direction in which the length of the major axis of the ellipse is reduced, and A corrected image (FIG. 7C) of the wafer 200 having a circular shape is obtained.
Then, the calculation means 80 reflects the corrected image (FIG. 7C) on the map of the wafer 200 from which the distortion has been removed (the map data of the wafer 200 acquired in advance), so that the notch (origin of the wafer 200). The coordinate position (x, y) of the defect with respect to 0) is detected.
In this case, the calculation unit 80 detects the rotation amount of the wafer 200 based on the image of the peripheral edge (notch) of the wafer 200 picked up by the second image pickup unit 60, and sets the wafer 200 as the coordinate position of the defect on the map. It reflects the rotation amount of.

  Based on the inspection result input from the computing unit 80, the display unit 90 displays the defect position coordinates of the wafer 200 together with the number of the wafer 200 in which the defect is detected (if necessary, an image of the wafer 200 after image processing). Display in map and coordinate position (x, y).

  Note that the wafer defect inspection apparatus 100 according to the present embodiment uses the predetermined area of the imaging area of the wafer 200, so that the striped captured images to be combined have the same magnification, less distortion, and the first area. Obtaining a corrected image of the circular wafer 200 by simple image processing (correction in the direction of reducing the length of the major axis of the ellipse) as compared with the case of performing calibration using the calibration jig 400 described in the embodiment. You can However, the wafer defect inspection apparatus 100 according to the present embodiment may be calibrated using the calibration jig 400 described in the first embodiment.

  As described above, the wafer defect inspection apparatus 100 according to the present embodiment uses the predetermined area (the rectangular area 1 projected on the lower side 31 side of the screen 30) of the imaging area from the captured image of the wafer 200, There is an effect that it is possible to improve the detection power and the contrast of defects (in particular, cracks and dimples) of the wafer 200 caused by the position of the wafer 200 with respect to the screen 30.

  The wafer defect inspection apparatus 100 according to the present embodiment has described the case where the linear encoder and the counter unit 13 are used to capture an image while moving the wafer 200. However, the movement, stop, and imaging are repeated to capture an image of the wafer 200. You may. However, in this case, the imaging time of one wafer 200 becomes long. Therefore, in order to shorten the imaging time, the shutter operation of the inspection camera 51 of the first imaging unit 50 is accelerated while the wafer 200 is moved without stopping using the linear encoder and counter unit 13. Therefore, it is preferable to repeat the imaging.

Further, for the detection of cracks and dimples, the inventor of the present application can easily obtain the contrast when the distance between the screen 30 and the wafer 200 is short, and thus the area projected onto the lower side 31 of the screen 30 can be used. It is effective, and in detecting slip and mound defects, it is effective to use a region projected on the upper side 32 of the screen 30 when the distance between the screen 30 and the wafer 200 is longer, because it is easier to obtain contrast. I found that.
That is, when the wafer defect inspection apparatus 100 according to the present embodiment is used as a slip and mound inspection apparatus, the surface image of the wafer 200 projected on the screen 30 is projected on the upper side 32 side of the screen 30. You will be using a part of it.
In this case, the mounting means 10 moves the wafer 200 in a direction approaching the first imaging means 50 with respect to the initial position set in the dark room 101.
In particular, the wafer defect inspection apparatus 100 according to the present embodiment detects a crack and dimple defect by extracting a part of the surface image of the wafer 200 projected on the screen 30 which is projected on the lower side 31 side of the screen 30. It is also possible to employ a configuration in which a part projected on the upper side 32 of the screen 30 is extracted and used for slip and mound defect detection to detect cracks and dimples and slip and mound defects.

1 rectangular area 10 mounting means 11 one end 12 other end 13 counter unit 20 illumination means 21 illumination 21a base 21b shielding plate 22 first lens 30 screen 31 lower side 32 upper side 40 light shielding means 41 lower side 50 first imaging means 51 for inspection Camera 51a Base 52 Second lens 53 Camera mounting plate 60 Second imaging means 61 Inspection camera 61a Base 62 Third lens 63 Camera mounting plate 70 Image processing means 80 Computing means 90 Display means 100 Wafer defect inspection device 101 Dark room 102 Support 103 Vertical movement elevator 200 Wafer 300 Cassette 400 Calibration jig 401 Substrate 402 Dot

Claims (5)

In a wafer defect inspection device that detects wafer defects,
Mounting means for mounting the wafer on the imaging region;
Illuminating means having an illumination for irradiating the surface of the wafer on the placing means with light, and a shield plate having a pinhole for approximating the light emitted from the illumination to a point light source ,
A projection surface within the irradiation range of the direct light from the illuminating means, arranged near one end of the placing means, and a screen on which a surface image of the wafer is projected by the light reflected on the surface of the wafer; ,
Light blocking means for preventing direct light from the lighting means from being applied to the screen,
Image pickup means for picking up a surface image of the wafer projected on the screen;
A wafer defect inspection apparatus comprising: The wafer defect inspection apparatus according to claim 1,
The screen, the lower side is disposed in the vicinity of one end of the placing means, inclined inward with respect to the placing means,
The light-shielding means is arranged such that the lower side is apart from the vicinity of the other end of the placing means above and is spaced apart from the placing means, and is inclined substantially outward in parallel to the screen, with respect to the placing means.
The image pickup means is disposed so as to face the inclined surface of the screen through a gap between the other end of the placing means and the lower side of the light shielding means,
The wafer defect inspection apparatus, wherein the illuminating means is arranged at a position where the optical axis intersects with the wafer on the placing means, with a gap between the light shielding means and the imaging means. The wafer defect inspection apparatus according to claim 1 or 2,
For the surface image of the wafer imaged by the imaging means, an inspection range is determined by smoothing processing and binarization processing, defects of the wafer are detected by a local threshold method, and an inspection range is detected by a feature amount extraction method. A wafer defect inspection apparatus comprising image processing means for detecting defects of the wafer inside. The wafer defect inspection apparatus according to claim 3,
The placing means has a mechanism for horizontally moving the wafer in a vertical direction with respect to the lower side of the screen,
The image pickup means has a mechanism for picking up an image pickup area on the screen at predetermined time intervals,
The image processing means respectively extracts, from the imaged images of the plurality of wafers imaged at the predetermined time interval, the imaged images of the wafer in a predetermined region of the imaged region into strips, and captures each striped image. A wafer defect inspection apparatus characterized by synthesizing images. The wafer defect inspection apparatus according to claim 3 or 4,
A defect of the wafer based on a calibration image captured by the image capturing unit and a surface image of the wafer image-processed by the image capturing unit of a calibration jig in which dots are mapped in a grid pattern on a substrate corresponding to the wafer. A wafer defect inspecting apparatus, which is provided with a calculating means for specifying the position of

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