Edge chipping detection device

Abstract

To provide a chipping detection device for an edge portion that detects chipping for the edge portion of a wafer 2 or truing whetstone with high accuracy.SOLUTION: A chipping detection device for detecting chipping of a chamfered surface C formed on an outer peripheral edge of a wafer 2 and inclined with respect to a main surface thereof includes: an LED lighting device 4 that irradiates the chamfered surface C with light from a direction parallel to the main surface of the wafer 2; imaging means 5 and 6 that image the chamfered surface C illuminated by the light emitted from the LED lighting device 4 and the main surface from a direction orthogonal to the main surface; and a reflector 1 provided so as to cover the LED lighting device 4 from the center direction of the wafer 2. Chipping is detected from images captured by the imaging means 5 and 6.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the shape measurement of the edge portion of a semiconductor wafer, and particularly to a chipping detection device for an edge portion that detects chipping of the edge portion of a wafer or a truing grinding wheel based on a captured image of its end portion.

Background Art

[0002] During the manufacture of a semiconductor wafer, the end portion (edge portion) of the wafer may be damaged or chipped when it comes into contact with other components or a wafer holding member. Furthermore, the wafer may crack due to such damage or chipping. Therefore, in the manufacturing process of the wafer, it is necessary to accurately detect the damage generated at its end portion.

[0003] For example, Patent Document 1 projects a light beam with an irradiation width larger than the thickness width of the wafer from directions parallel to the front and back surfaces of the end portion of the measurement object in order to measure the shape (chamfer shape: angle and chamfer width) of the chamfered edge portion, and images it with two cameras from directions perpendicular to the surface on each of the front and back surface sides. Then, it describes detecting the width of the bright portion image in the captured image as the width of the chamfered end surface.

[0004] In addition, Patent Document 2 describes blocking light rays among the light rays incident on an arbitrary point of the straight portion of the notch portion from the illumination means, where the incident angle of the light ray with respect to the normal of the straight portion is greater than or equal to a reference incident angle, in order to visually recognize the grinding streaks of the notch portion of the wafer.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the above-mentioned prior art, Patent Document 1 merely measures the width of the chamfered end face, regardless of whether the surface other than the chamfered end face is mirror-finished or not, and simultaneously measures each side of the front and back surfaces. Therefore, it is not possible to detect the chipping state of the wafer edge.

[0007] Similarly, while Patent Document 2 allows for the visual identification of grinding marks formed on the chamfered surface of the notch portion of the wafer, it was not possible to evaluate the wafer quality based on the chipping condition of the wafer edge. Furthermore, the detection accuracy was low due to insufficient light intensity irradiating the chipping, the light not irradiating the chipping in the depth direction, and the fact that the chipping is formed by chipping away from the surface width.

[0008] The object of the present invention is to solve the problems of the prior art described above and to provide an edge chipping detection device that can detect chipping at the wafer edge with high accuracy. [Means for solving the problem]

[0009] To achieve the above objective, the present invention provides a chipping detection device for detecting chipping on a chamfered surface formed on the outer edge of a wafer and inclined with respect to the main surface of the wafer, comprising: an LED lighting device that irradiates the chamfered surface with light from a direction parallel to the main surface of the wafer; an imaging means that images the chamfered surface and the main surface illuminated by the light irradiated from the LED lighting device from a direction perpendicular to the main surface; and a reflector provided to cover the LED lighting device from the direction of the center of the wafer, wherein the chipping is detected from the image captured by the imaging means.

[0010] Furthermore, in the chipping detection device described above, it is desirable that the reflector is installed in a position where the LED lighting device side extends beyond the chamfered surface toward the center of the wafer.

[0011] Furthermore, in the chipping detection device described above, it is desirable that the reflector has a U-shape or arc shape when viewed from above, and that a slit is provided in the center in the height direction.

[0012] Furthermore, in the chipping detection device described above, it is desirable that the LED lighting device side of the reflector be painted with white paint with Munsell values ​​N9.5 and RGB (245, 246, 242).

[0013] Furthermore, in the chipping detection device described above, it is desirable that the reflector has an inclined surface that is tilted at 30 to 60 degrees with respect to a plane parallel to the LED lighting device.

[0014] Furthermore, in the chipping detection device described above, it is desirable that the wavelength of the light emitted from the LED lighting device be 570 nm or less.

[0015] Furthermore, in the chipping detection device described above, it is desirable to provide a diffuser between the LED lighting device and the reflector, on the side of the chamfered surface that is closer to the LED lighting device.

[0016] Furthermore, in the chipping detection apparatus described above, it is preferable that the imaging means comprises a top camera positioned on one side of the wafer and a bottom camera positioned on the other side of the wafer.

[0017] Furthermore, in the chipping detection device described above, it is desirable that the LED lighting device be a panel-type surface light source with multiple blue light-emitting LEDs arranged therein. [Effects of the Invention]

[0018] According to the present invention, a reflector is provided so as to cover the LED lighting device from the direction of the center of the wafer, and the LED lighting device illuminates the wafer from a direction parallel to the wafer. Chipping is detected from an image taken from a direction perpendicular to the main surface of the wafer. As a result, the light diffusely reflected by the reflector is also illuminated in the depth direction of the chipping, allowing for high-precision detection of the chipping state.

Brief Description of the Drawings

[0019] [Figure 1] Side view showing the main part of the chipping detection device according to an embodiment of the present invention [Figure 2] Plan view of FIG. 1 [Figure 3] Enlarged cross-sectional view showing the irradiation of light in the chamfered portion (chamfered edge portion) according to an embodiment [Figure 4] Perspective view of the reflector 1 according to an embodiment [Figure 5] Enlarged cross-sectional view showing the irradiation of light in the conventional chamfered portion (chamfered edge portion) [Figure 6] Figure comparing the captured image of an embodiment in which chipping 8 is detected by the imaging means with the prior art

Modes for Carrying Out the Invention

[0020] FIG. 1 is a side view showing the main part of the chipping detection device, FIG. 2 is a plan view, and FIG. 3 is an enlarged cross-sectional view showing the irradiation of light in the chamfered portion (chamfered edge portion). The shape measurement of the semiconductor wafer edge portion measures the chamfer angle, face width, etc. using a camera and a lighting device. The device installs the camera vertically with respect to the measurement location of the wafer 2, and the lighting equipment is installed orthogonally thereto. Chipping detection is an example of shape measurement, and is particularly important as shape measurement and is performed in the same manner as the measurement of the face width.

[0021] The shape measurement device, or the chipping detection device, includes a rotatable turntable 3 that adsorbs and holds the main surface P of the wafer 2 in a horizontal posture, an LED lighting device 4 as lighting means, an upper surface camera 6 disposed on one side sandwiching the wafer 2 as imaging means, and a lower surface camera 5 disposed on the other side sandwiching the wafer. Although not shown in the figure, the chipping detection device has an image processing device, a monitor, etc. The turntable 3 is placed with the wafer 2 that has been cleaned after the chamfering process. The chamfered surface C is formed at the outer peripheral edge of the wafer 2 and is inclined with respect to the main surface P of the wafer 2.

[0022] The LED lighting device 4 is positioned to the side of the rotating table 3 and illuminates the edge of the wafer 2 with light from a direction parallel to the wafer 2, as shown by arrow A. The light is also reflected by the reflector 1, as shown by arrow B. The LED lighting device 4 is rectangular in shape with a height H and width L of the illumination light so that the illumination light becomes a surface light source. In other words, the LED lighting device 4 has a diffuser plate 7 that diffuses the light.

[0023] The top camera 6 is positioned opposite the outer periphery of the top surface of the wafer 2 and captures the shape of the top edge portion of the wafer 2. The bottom camera 5 is positioned opposite the outer periphery of the bottom surface of the wafer 2 and captures the shape of the bottom edge portion of the wafer 2. The top camera 6 and the bottom camera 5 capture the chamfered surface C and the main surface P of the wafer 2, which are illuminated by light emitted from the LED lighting device 4, from a direction perpendicular to the main surface P of the wafer 2.

[0024] Of the light irradiated onto the wafer 2 from the LED lighting device 4, only the light reflected from the chamfered surface C is captured by the top camera 6 and the bottom camera 5. As a result, the image showing the chamfered surface C of the wafer 2 is displayed in white, and the image showing the main surface P is displayed in black, and these images are displayed on the monitor.

[0025] The image processing device measures the width of the chamfered surface C and detects chipping 8 from the captured image. The image processing device also has the function of extracting an image of the chamfered surface C from the images captured by the top camera 6 and the bottom camera 5, and performing image processing such as edge detection.

[0026] Figure 4 is a perspective view of the reflector 1, which is installed to cover the LED lighting device 4 from the center of the wafer 2. However, it does not obstruct the field of view of the top camera 6 and the bottom camera 5. As shown in Figures 2 and 4, the shape of the reflector 1, when viewed from above, is U-shaped or arc-shaped with slopes 1-2 and 1-3, and a slit 1-1 is provided in the center in the height direction.

[0027] Slit 1-1 is larger than the thickness of wafer 2, and the chamfered surface C of wafer 2 is inserted into it. The reflector 1 is installed so that the side of the reflector 1 facing the LED lighting device 4 is beyond the chamfered surface C, that is, the width of the reflector 1 extends beyond the center of wafer 2. The diffuser 7 should be placed between the LED lighting device 4 and the reflector 1, on the side of the chamfered surface C that is facing the LED lighting device 4.

[0028] The slopes 1-2 and 1-3 should be inclined at an angle of 30 to 60°, preferably about 45°, with respect to the plane 1-4 parallel to the LED lighting device 4 and the diffuser plate 7. The height direction of the reflector plate 1 may also be similarly sloped. The material of the reflector plate 1 is a metal plate, which is formed by bending.

[0029] The inside of the reflector 1, on the side facing the LED lighting device 4, has a rough finish with a Ra of 10-40 μm, preferably around 25 μm, and is coated with melamine baked paint in white with Munsell values ​​N9.5 and RGB (245, 246, 242). Alternatively, the reflector 1 can be improved by using a white, arc-shaped piece of paper with the concave side facing the LED lighting device 4. The paint color may also be ivory.

[0030] Figure 5 is an enlarged cross-sectional view of a chamfered portion (chamfered edge portion) measured by a conventional edge shape measuring device without a reflector 1. Figure 5 shows the relationship between light irradiated onto the wafer 2 from the LED lighting device 4 and typical light reflected by the chamfered surface C and chipping 8.

[0031] As shown in Figure 5, light from the LED lighting device 4 shines onto the chamfered surface C as indicated by arrow A, and is reflected as indicated by arrow F to be captured by the top camera 6 and the bottom camera 5. However, since the chipping 8 is a situation where the chamfered surface C is missing, its inclination is different from that of the chamfered surface C. In addition, the amount of light reaching the chipping 8 is also affected by the shadow cast by the LED lighting device 4.

[0032] Therefore, the amount of light reaching the top camera 6 and bottom camera 5 from the chipping 8 is significantly insufficient. As a result, although the conventional technology improves somewhat by diffusing the light from the LED lighting device 4 with the diffuser plate 7, the detection accuracy of the chipping 8 is still insufficient.

[0033] In contrast to the conventional technology, the embodiment includes a reflector 1 as shown in Figure 3. Light from the LED lighting device 4 not only shines on the chamfered surface C from arrow A, but is also reflected by the reflector 1 as shown by arrows G and F before reaching the chamfered surface C. The light from the LED lighting device 4 also reaches the chipping 8, which has a different inclination than the chamfered surface C, increasing the amount of light illuminating the chipping 8. In other words, the light diffusely reflected by the reflector 1 is also illuminating the chipping 8 in the depth direction, allowing for high-precision detection of the state of the chipping 8.

[0034] Furthermore, the reflector 1 has slopes 1-2 and 1-3, and the inside of the reflector 1, the side facing the LED lighting device 4, is a rough-finished surface and painted in a neutral color, so that the light from the LED lighting device 4 is scattered, further enhancing the effect. Since light scattering is more pronounced the shorter the wavelength of light, it is preferable to set the wavelength of the light emitted from the LED lighting device 4 to a short wavelength of 570 nm or less.

[0035] Note that the light with a wavelength of 570 nm or less may include wavelengths within the visible light region or wavelengths including the ultraviolet light region. For example, it is preferable to use a blue light-emitting LED that can stably emit single-wavelength light and utilize light with a wavelength of 450 nm to 495 nm in order to improve measurement accuracy. Furthermore, the LED lighting device 4 is preferably a panel-type surface light source with multiple blue light-emitting LEDs arranged on it.

[0036] Figure 6 is a comparison of an image captured by the top camera 6 (imaging means) detecting chipping 8 with the conventional technology. The same applies to images captured by the bottom camera 5. (a) shows the case without the reflector 1, (b) shows the case where the LED lighting device 4 is surrounded by white arc-shaped paper instead of the metal plate reflector 1 shown in Figure 4, and (c) shows the case with the metal plate reflector 1 shown in Figure 4.

[0037] In (a), since there is no reflector 1, the chamfered surface C of the wafer 2 is shown in white, and the main surface P is shown in black, with shading. However, the chipping area 8 (center of the figure) does not have shading from the main surface P (right side of the figure), making it difficult to distinguish.

[0038] In (b), the reflector 1 uses a white, arc-shaped piece of paper with the concave side facing the LED lighting device 4, so the chamfered surface C of the wafer 2 is shown in white. However, the difference in shading between the main surface P and the chamfered surface is small. Also, the difference in shading between the main surface P and the chipping 8 is larger than in (a), showing some improvement. However, the positional relationship between the chipping 8 and the chamfered surface is difficult to discern.

[0039] (c) shows the chamfered surface C of wafer 2, with the width displayed in white, allowing for clear identification of the difference in shading between the main surface P and the width. Furthermore, the difference in shading between the main surface P and the width improves the detection accuracy of chipping 8.

[0040] Furthermore, the experimental results showed that when wafer 2 was a silicon wafer and the detection results of chipping 8 were expressed as an evaluation index, the score was 67 for (a) without reflector 1, 815 for (b) with reflector 1 made of paper, and 940 for (c) with reflector 1 made of the metal plate shown in Figure 4.

[0041] However, the evaluation index is a cumulative value that assigns points to the difference in contrast within the measured range. For example, when there is no chipping 8, the evaluation index is 0, with the face width being white and the wafer 2 surface being black. If chipping 8 is present in the face width, black appears in the white areas, creating a contrast difference which is then assigned a score. Similarly, if chipping 8 is present in the wafer 2 surface, white areas appear in the solid black areas, creating contrast which is then assigned a score.

[0042] The above explanation applies to wafer 2, but the same principles apply to truing wheels (GC wheels), and it is possible to detect chipping 8 at the edges. Furthermore, since truing requires transferring the shape to the grinding wheel, greater precision in shape is required, and minimizing damage such as chipping 8 is strongly desired, similar to wafer 2. [Explanation of symbols]

[0043] 1...Reflector 1-1…Slit 1-2…Slope 1-4... side 2… Wafer 3… Rotating table 4...LED lighting device 5…Underside camera 6…Top-mounted camera 7…Diffuser 8…Chipping A...Arrow C... chamfered surface G... arrow H...height P…principal surface

Claims

1. In a chipping detection device for detecting chipping on the chamfered surface of a wafer, It comprises a surface light source, an imaging means, and a diffuse reflector. The surface light source irradiates light so that it is incident directly on the chamfered surface and the reflective surface of the diffuse reflector, respectively, from the side of the wafer toward the center of the wafer. The imaging means captures and images the reflected light from the chamfered surface. A chipping detection device wherein the diffuse reflector is positioned opposite the surface light source and located on the central side of the wafer relative to the surface light source and the imaging means, and is configured to reflect light incident from the surface light source and irradiate the chamfered surface.

2. A chipping detection device for detecting chipping on the chamfered surface of a wafer, A surface light source that irradiates light onto the chamfered surface from the side of the wafer, An imaging means for capturing reflected light from the chamfered surface and imaging it, The system comprises a diffuse reflector facing the surface light source and provided on the wafer side of the surface light source and the imaging means, The chipping detection apparatus according to claim 1, wherein the surface light source is arranged spaced apart from the wafer in a direction parallel to the main surface of the wafer.

3. A chipping detection device for detecting chipping on the chamfered surface of a wafer, A surface light source that irradiates light onto the chamfered surface from the side of the wafer, An imaging means for capturing reflected light from the chamfered surface and imaging it, The system comprises a diffuse reflector facing the surface light source and provided on the wafer side of the surface light source and the imaging means, The chipping detection apparatus according to claim 1, wherein the diffuse reflector, the imaging means, and the surface light source are arranged in order from the center of the wafer along the radial direction of the wafer.

4. The chipping detection device according to claim 1, wherein the imaging means is positioned so as not to be incident on the light from the surface light source or the specularly reflected light of the light from the diffuse reflector.

5. A chipping detection device for detecting chipping on the chamfered surface of a wafer, A surface light source that irradiates light onto the chamfered surface from the side of the wafer, An imaging means for capturing reflected light from the chamfered surface and imaging it, The system comprises a diffuse reflector facing the surface light source and provided on the wafer side of the surface light source and the imaging means, The chipping detection device according to claim 1, wherein the diffuse reflector is formed in a U-shape or arc shape in a plan view and is arranged to open toward the surface light source.

Images