Wafer edge detection device

Abstract

A wafer edge detection device is provided that can easily measure the shape of a wafer side edge by capturing an image of the wafer side edge along the surface based on diffused light irradiated from a point light source. [Solution] The device comprises a point light source consisting of an LED light source 4 and a pinhole member 5 arranged on one side along the tangent 12 direction of the wafer edge at one side end 11 of the wafer 10, and a camera 6 arranged along the tangent 12 direction and on the other side opposite the point light source across the one side end 11.Light is irradiated from the point light source, and the camera 6 captures a side image based on the amount of light irradiated on the front side and back side, including the one side end 11, by the diffused light emitted from the point light source.

Description

[Technical Field]

[0001] The present invention relates to a wafer edge detection device that accurately measures the shape of a wafer edge. [Background technology]

[0002] As a technique for measuring the outer peripheral edge portion of a wafer, for example, the technique shown in Patent Document 1 is disclosed. The technique shown in Patent Document 1 includes a parallel light irradiation system that irradiates a measurement portion, which is the outer peripheral edge portion of a disk-shaped measurement object, with parallel light along the circular surface of the measurement object and so that the measurement portion is disposed in the light beam, and an imaging optical system that includes an image sensor onto which an image of the measurement portion is projected and captures the image of the measurement portion, the parallel light irradiation system includes a point light source, a collimator lens that converts the light from the point light source into parallel light and emits it, and a telecentric lens through which the light from the collimator lens is irradiated through the measurement object, and the point light source includes an LED, an optical fiber as an example of a diffusing member that diffuses and emits the light from the LED, and a pinhole member that forms a pinhole into which the light from the optical fiber is incident. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-47919 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technology disclosed in Patent Document 1 requires that a point light source be converted into parallel light and emitted, which makes the device configuration complicated and increases the difficulty of realization. Also, because imaging is performed based on parallel light, even slight tilt or misalignment of the object being measured makes it difficult to accurately determine the thickness of the object, which requires extremely strict adjustment of the position, etc.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide a wafer edge detection device that can easily measure the shape of a wafer side edge by imaging the wafer side edge along a surface based on diffused light irradiated from a point light source. [Means for solving the problem]

[0006] The wafer edge detection device of the present invention comprises a point light source arranged on one side along the tangent direction of the wafer edge at one side end of the wafer, and a camera arranged along the tangent direction and on the other side opposite the point light source across the one side end, and irradiates light from the point light source, and the camera captures a side image based on the amount of light irradiated onto the front side and back side of the wafer including the one side end by the diffused light emitted from the point light source.

[0007] In this way, in the wafer edge detection device of the present invention, diffused light is irradiated from a point light source arranged on one side along the tangential direction of the wafer edge at one side end of the wafer, and a side image based on the amount of light irradiated onto the front and back sides of the wafer, including the one side end, is captured by a camera arranged along the tangential direction and on the other side opposite the point light source across the one side end.This makes it easier for the diffused light emitted from the point light source to wrap around to the front and back sides of the wafer, and has the effect of enabling one side end of the wafer to be accurately imaged from the side without the extremely strict adjustments that are required with parallel light. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing the configuration of a wafer edge detection device according to a first embodiment of the present invention. [Figure 2] 3A to 3C are diagrams showing schematic projection images of one side edge of a wafer when the amount of light irradiated varies in the wafer edge detection device according to the first embodiment of the present invention. [Figure 3]FIG. 1 is a first diagram showing a comparison of imaging results when the wafer edge detection device according to the first embodiment of the present invention is not provided with a pinhole member and the diameter of the LED light source is 0.5 mm and when the diameter of the LED light source is 1 mm. [Figure 4] FIG. 2 is a second diagram showing a comparison of imaging results when the wafer edge detection device according to the first embodiment of the present invention does not include a pinhole member and the diameter of the LED light source is 0.5 mm and when the diameter of the LED light source is 1 mm. [Figure 5] FIG. 1 is a first diagram showing a comparison of imaging results when the wafer edge detection device according to the first embodiment of the present invention is not provided with a pinhole member and the diameter of the LED light source is 0.5 mm and when the diameter of the LED light source is 2 mm. [Figure 6] FIG. 2 is a second diagram showing a comparison of imaging results when the wafer edge detection device according to the first embodiment of the present invention does not include a pinhole member and the diameter of the LED light source is 0.5 mm and when the diameter of the LED light source is 2 mm. [Figure 7] FIG. 1 is a first diagram showing a comparison of imaging results when the diameter of the pinhole member is 2 mm and when no pinhole member is provided and the diameter of the LED light source is 2 mm in a wafer edge detection device according to the first embodiment of the present invention. [Figure 8] FIG. 2 is a second diagram showing a comparison of imaging results when the diameter of the pinhole member is 2 mm and when no pinhole member is provided and the diameter of the LED light source is 2 mm in the wafer edge detection device according to the first embodiment of the present invention. [Figure 9] 5A to 5C are diagrams showing imaging results when the positions of the point light source, the wafer, and the camera are changed in the wafer edge detection device according to the first embodiment of the present invention. [Figure 10] FIG. 4 is a diagram showing the imaging results of the exposure time at which the image was most clearly captured for each pinhole size of the point light source in the wafer edge detection device according to the first embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment of the present invention) The wafer edge detection device according to this embodiment will be described with reference to Figures 1 to 9. The wafer edge detection device 1 according to this embodiment accurately captures the shape of one side edge of the wafer as viewed from the side by capturing an image of light from a point light source irradiated from one side along the tangent direction of the wafer edge at one side edge of the wafer (for example, a silicon wafer) with a camera on the other side along the tangent direction of the wafer edge.

[0010] 1 is a schematic diagram showing the configuration of a wafer edge detection device according to this embodiment. As described above, wafer edge detection device 1 includes: an LED light source 4 that is disposed on one side of a tangent line 12 to a wafer edge at one side edge 11 of a wafer 10 to be imaged and that emits light, for example, white light; a pinhole member 5 that is disposed downstream in the optical path of the light emitted from LED light source 4 and that is disposed so that tangent line 12 to the wafer edge passes through a pinhole; and a camera 6 that is disposed on the other side of tangent line 12 to the wafer edge and that images one side edge 11 of wafer 10 from the side using diffused light emitted from the pinhole in pinhole member 5.

[0011] It is not necessary to provide the pinhole member 5. In this embodiment, the point light source may be formed by the LED light source 4 alone, or may be formed by the LED light source 4 and the pinhole member 5.

[0012] In Fig. 1, a portion of the white light emitted from the LED light source 4 is blocked by the pinhole member 5, while a portion of the light is emitted as diffused light from the pinhole. The size of this pinhole, i.e., the size of the point light source, is one of the important parameters for adjusting the amount of light, as will be described later.

[0013] The diffused light emitted from the pinhole diffuses radially at various angles and illuminates one side edge 11 of wafer 10. Camera 6 projects the diffused light onto one side edge 11 of wafer 10, thereby capturing an image of one side edge 11 of wafer 10 as viewed from the side. Here, the diffused light emitted from the pinhole (point light source) is made up of countless light rays that diffuse radially at various angles as described above, and is light that easily wraps around to the front and back sides of one side edge 11 of wafer 10.

[0014] In other words, the image projected by the camera 6 changes depending on the amount of light irradiated onto one side edge 11 of the wafer 10. FIG. 2 is a diagram schematically showing projected images of one side edge of a wafer when different amounts of light are irradiated in the wafer edge detection device according to this embodiment. FIG. 2(A) shows the case when the amount of light is low, and FIG. 2(B) shows the case when the amount of light is high. In the case of FIG. 2(A), at one side edge 11 of the wafer 10, the thickness of the region near the outer edge of the wafer 10 (hereinafter referred to as thickness A) is greater than the thickness of the region near the center of the wafer 10 (hereinafter referred to as thickness B). On the other hand, in the case of FIG. 2(B), even for the same wafer 10, the thickness A and thickness B are greater than the thickness A.

[0015] This is caused by the difference in the amount of diffused light that exits the pinhole and wraps around to the front and back sides of the wafer 10. That is, when the amount of light irradiated is small, as in Fig. 2(A), the amount of diffused light that wraps around to the front and back sides of the wafer 10 is small, and the projected area of ​​the wafer 10 is captured larger. Conversely, when the amount of light irradiated is large, as in Fig. 2(B), the amount of diffused light that wraps around to the front and back sides of the wafer 10 is large, and the projected area of ​​the wafer 10 is captured smaller.

[0016] In the wafer edge detection device 1 of this embodiment, when one side edge 11 of the wafer 10 is viewed from the side, the boundary line in the projected image on the front side of the wafer 10 and the boundary line in the projected image on the back side are approximately parallel, that is, the state imaged at thickness A ≒ thickness B shown in Figure 2 is detected as the side image of one side edge 11 of the wafer 10.

[0017] Specifically, the side image of one side edge 11 of wafer 10 is detected by adjusting the exposure time when camera 6 captures an image and / or the size of the pinhole (the size of the point light source, i.e., the amount of light emitted from the point light source) as described above. In other words, if the exposure time of camera 6 is controlled to be longer, the amount of light received by camera 6 increases accordingly, and if the exposure time of camera 6 is controlled to be shorter, the amount of light received by camera 6 decreases accordingly. Therefore, by controlling the exposure time of camera 6, it is possible to capture an image so that thickness A is approximately equal to thickness B.

[0018] Furthermore, instead of or in addition to controlling the exposure time of the camera 6, the diameter of the pinhole in the pinhole member 5 (or the diameter of the LED light source 4 itself if the pinhole member 5 is not provided) is adjusted. That is, if the diameter of the pinhole is increased, the amount of light received by the camera 6 increases accordingly, and if the diameter of the pinhole is decreased, the amount of light received by the camera 6 decreases accordingly. Therefore, by adjusting the diameter of the pinhole, it becomes possible to capture an image so that thickness A is approximately equal to thickness B.

[0019] The following shows the imaging results of the camera 6 when the exposure time of the camera 6 is changed for several different light source diameters. FIGS. 3 and 4 are diagrams showing a comparison of imaging results when the wafer edge detection device according to this embodiment is not equipped with a pinhole member and the LED light source diameter is 0.5 mm and when the LED light source diameter is 1 mm. FIG. 3 shows the imaging results when the exposure time of the camera 6 is gradually changed from 100 μs to 500 μs, and FIG. 4 shows the imaging results when the exposure time of the camera 6 is gradually changed from 1000 μs to 10,000 μs. Both FIGS. 3(A) and 4(A) show the imaging results when the diameter of the LED light source 4 is 0.5 mm, and both FIGS. 3(B) and 4(B) show the imaging results when the diameter of the LED light source 4 is 1 mm.

[0020] 3 and 4, the difference d between thickness A and thickness B generally tends to gradually decrease as the exposure time increases, with the exception of the 5000 μs exposure time with a light source diameter of 0.5 mm and the 300 μs exposure time with a light source diameter of 1 mm. Furthermore, comparing the values ​​of difference d, the difference is generally smaller with a light source diameter of 1 mm. With a light source diameter of 1 mm, thickness A equals thickness B at the 3000 μs exposure time, i.e., the projected images on the front side and the back side at one edge 11 of the wafer 10 are parallel. With a light source diameter of 0.5 mm, thickness A does not equal thickness B even with an exposure time of 10000 μs, but it is estimated that thickness A will eventually equal thickness B if the exposure time is further increased.

[0021] 5 and 6 are diagrams showing a comparison of imaging results when the wafer edge detection device according to this embodiment is not equipped with a pinhole member and the LED light source diameter is 0.5 mm and when the LED light source diameter is 2 mm. FIG. 5 shows imaging results when the exposure time of the camera 6 is gradually changed from 100 μs to 500 μs, and FIG. 6 shows imaging results when the exposure time of the camera 6 is gradually changed from 1000 μs to 10,000 μs. Both FIGS. 5(A) and 6(A) show imaging results when the diameter of the LED light source 4 is 0.5 mm, and both FIGS. 5(B) and 6(B) show imaging results when the diameter of the LED light source 4 is 2 mm.

[0022] 5 and 6, as in the cases of Figures 3 and 4, the difference d between thickness A and thickness B generally tends to gradually decrease as the exposure time increases, with the exception of the cases where the light source diameter is 0.5 mm and the exposure time is 5000 μs, and where the light source diameter is 2 mm and the exposure time is 200 μs. Furthermore, comparing the values ​​of difference d, the difference is generally smaller for the light source diameter of 2 mm, and with the light source diameter of 2 mm, thickness A > thickness B at the point where the projection image of the front side and the projection image of the back side at one side edge 11 of wafer 10 are no longer parallel, and thickness A increases.

[0023] 7 and 8 show a comparison of imaging results when the pinhole diameter is 2 mm and when no pinhole member is provided and the LED light source diameter is 2 mm in the wafer edge detection device according to this embodiment. Fig. 7 shows imaging results when the exposure time of the camera 6 is gradually changed from 200 μs to 400 μs, and Fig. 8 shows imaging results when the exposure time of the camera 6 is gradually changed from 500 μs to 2000 μs. Figs. 7(A) and 8(A) both show imaging results when the pinhole diameter is 2 mm, while Figs. 7(B) and 8(B) both show imaging results when the pinhole member 5 is not provided and the LED light source 4 diameter is 2 mm.

[0024] 3 and 4 and 5 and 6, the results shown in Figures 7 and 8 show that the difference d between thickness A and thickness B generally tends to gradually decrease as the exposure time increases, with the exception of the 200 μs exposure time when the LED light source diameter is 2 mm in Figure 7(B). Furthermore, when comparing the values ​​of difference d, the difference is generally smaller when pinhole member 5 is provided (Figures 7(A) and 8(A)), and when pinhole member 5 is provided, thickness A = thickness B, i.e., the projected image on the front side and the projected image on the back side at one side edge 11 of wafer 10 are parallel at the time of exposure time of 500 μs.

[0025] 3 to 8, by controlling the exposure time of camera 6 and the size of the point light source (amount of light emitted), it is possible to adjust the amount of diffused light that wraps around to the front and back sides of wafer 10, and it is possible to capture images so that the projected image on the front side and the projected image on the back side at one side edge 11 of wafer 10 are parallel to each other. The above results show that the larger the diameter of the point light source, the shorter the exposure time, and it is particularly clear that when pinhole member 5 is used and diffused light is emitted from a pinhole, it is possible to capture an image of thickness A = thickness B most efficiently in the shortest time.

[0026] Here, in order to make the projected image on the front side and the projected image on the back side of one side edge 11 of wafer 10 parallel, it is extremely important to adjust the position of the point light source, the position and tilt of wafer 10, and the position and imaging direction of camera 6. For example, when the irradiated light is parallel, the above parameters are particularly important, and even a slight deviation from the linearity will make it impossible to capture an accurate image. In other words, extremely strict mechanical adjustments are required, which increases manufacturing costs and labor.

[0027] In contrast to this, in this embodiment, as described above, irradiating diffused light from a point light source enables the light to wrap around to the front and back sides of the wafer 10, and the amount of light that wraps around can be precisely adjusted by appropriately setting the exposure time of the camera 6 and the size of the point light source. Therefore, by making not only mechanical adjustments of the position of the point light source, the position and tilt of the wafer 10, and the position and imaging direction of the camera 6, but also adjustments based on the setting values ​​of the point light source and the camera 6, it is possible to accurately image the side surface of the wafer 10 without requiring strict mechanical adjustments as with parallel light.

[0028] The inventors conducted the following experiments on the position (height) of the point light source, the position (height) of the wafer 10, and the position (height) of the camera 6. Images were taken while changing the height of the wafer 10 and the imaging direction of the camera 6, assuming that they were completely aligned horizontally. FIG. 9 shows imaging results obtained when the positions of the point light source, wafer, and camera were changed in the wafer edge detection device according to this embodiment. FIG. 9(A) shows the imaging results and thickness A values ​​obtained when the height of the camera 6 was changed in 0.5 mm increments from −1 mm to +1 mm. FIG. 9(B) shows the imaging results and thickness A values ​​obtained when the height of the stage on which the wafer 10 is placed was changed in 0.5 mm increments from −1 mm to +1 mm. FIG. 9(C) shows the imaging results and thickness A values ​​obtained when the height of the point light source was changed in 0.5 mm increments from −1 mm to +1 mm.

[0029] 9, changes in the height of camera 6 have little effect on the imaging results, whereas changes in the height of the stage or the height of the illumination have a large effect on the imaging results (the difference between thickness A and thickness B is large). Therefore, rough horizontal adjustments may be made by adjusting the height of the stage or the illumination (point light source), and fine horizontal adjustments may be made by adjusting the height of camera 6. After making these horizontal adjustments, by further adjusting the exposure time of camera 6 and the size of the point light source as described above, it becomes possible to capture an extremely accurate image of the side surface at one edge of wafer 10.

[0030] The position of the point light source, the position and inclination of the wafer 10, the position and imaging direction of the camera 6, the exposure time of the camera 6, and / or the pinhole diameter of the pinhole member 5 may be automatically adjusted. That is, although the above parameters are initially set to optimal values, slight variations or changes may occur during use. In such cases, all or some of the above parameters are automatically adjusted to their initial states. A determination of whether a variation or change has occurred in the above parameters can be made, for example, when wafers 10 with a larger difference between thickness A and thickness B than before are consecutively detected. Specifically, for example, if the number of wafers 10 with a difference between thickness A and thickness B equal to or greater than a predetermined value has previously been about one in 100, but several wafers (e.g., about three) are consecutively detected, it may be determined that there is a possibility of a malfunction in the wafer edge detection device 1, and the above parameters may be reset or readjusted. In this case, the optimal values ​​may be determined by arbitrarily changing the parameters, or an alert may be output to prompt the operator to readjust.

[0031] The inventors also performed imaging by varying the exposure time for each pinhole size. FIG. 10 shows the imaging results for the exposure time that produced the clearest image for each pinhole size of the point light source in the wafer edge detection device according to this embodiment. The results in FIG. 10 indicate that by increasing the exposure time as the pinhole size becomes smaller, it becomes possible to image minute irregularities on the surface of the wafer 10. (Although the difference is difficult to discern in FIG. 10 due to resolution limitations, in reality, the fine irregularities are more clearly imaged when the pinhole is smaller and the exposure time is longer.) That is, when adjusting the light intensity for imaging using the diffusion of light onto the front and back sides of the wafer 10, the longer the exposure time with a smaller pinhole, the more detailed the image can be captured. The shorter the exposure time with a larger pinhole, the higher the imaging efficiency.

[0032] As described above, the wafer edge detection device of this embodiment comprises a point light source consisting of an LED light source 4 (or consisting of an LED light source 4 and a pinhole member 5 installed downstream thereof) arranged on one side along the tangent 12 of the wafer edge at one side end 11 of the wafer 10, and a camera 6 arranged along the tangent 12 and on the other side opposite the point light source across the one side end 11.Light is irradiated from the point light source, and the camera 6 captures a side image based on the amount of light irradiated onto the front and back sides, including the one side end 11, by the diffused light emitted from the point light source.This means that the diffused light emitted from the point light source is more likely to wrap around to the front and back sides of the wafer, and one side end of the wafer can be accurately imaged from the side without the need for extremely severe mechanical adjustments (such as adjusting the positioning of the point light source, camera 6, and wafer 10) as is done with parallel light.

[0033] Furthermore, if necessary, the exposure time when the camera 6 takes an image is controlled so that the boundary line on the front side and the boundary line on the back side in the side image of the wafer 10 are approximately parallel. Therefore, by simply setting the exposure time of the camera 6 to an optimum value, it is possible to capture an extremely accurate side image in which the boundary line on the front side and the boundary line on the back side of the wafer 10 are approximately parallel.

[0034] Furthermore, if necessary, the point light source comprises an LED light source 4 that emits a predetermined light and a pinhole member 5 that is arranged in front of the LED light source 4, and the diameter of the pinhole in the pinhole member 5 is adjusted so that the boundary line on the front side and the boundary line on the back side in the side image of the wafer 10 are approximately parallel.Therefore, by simply setting the pinhole diameter to an optimal value, it is possible to capture an extremely accurate side image in which the boundary line on the front side and the boundary line on the back side of the wafer 10 are approximately parallel.

[0035] Furthermore, if necessary, an adjustment mechanism is provided for adjusting the height position of the stage supporting the wafer 10, the height position of the point light source, and / or the height position of the camera 6, so that the imaging environment can be optimally adjusted using the exposure time of the camera 6 and the size of the point light source as parameters in addition to the height position of the stage, the height position of the point light source, and the height position of the camera 6.

[0036] Furthermore, if necessary, the imaging arrangement is fine-tuned by adjusting the height position of the camera 6 after adjusting the height position of the stage or the height position of the light source, so that optimal values ​​can be set in stages, starting with the parameters that have the greatest impact on imaging.

[0037] Furthermore, if necessary, the adjustment mechanism readjusts the multiple wafers 10 to be detected in accordance with changes in the degree of parallelism between the boundary line on the front side and the boundary line on the back side in the side image of the wafer 10, so that if parameter readjustment is required depending on the use of the wafer edge detection device 1, it can be done immediately, either automatically or manually. [Explanation of symbols]

[0038] 1. Wafer edge detection device 4 LED light source 5 Pinhole member 6. Camera 10 wafers 11 One end 12 tangent

Claims

1. a point light source disposed on one side of one end of the wafer along a tangential direction of the wafer edge; a camera disposed along the tangential direction and on the other side opposite the point light source across the one side end, A wafer edge detection device characterized by irradiating light from the point light source and using the camera to capture side images based on the amount of light irradiated onto the front and back sides of the wafer, including the one side edge, by the diffused light emitted from the point light source.

2. 2. The wafer edge detection device according to claim 1, A wafer edge detection device characterized in that the exposure time when the camera captures an image is controlled so that the boundary line on the front side and the boundary line on the back side in the side image of the wafer are approximately parallel.

3. 3. The wafer edge detection device according to claim 1, the point light source includes a light source that emits a predetermined light and a pinhole disposed in front of the light source, A wafer edge detection device, characterized in that the diameter of the pinhole is adjusted so that the boundary line on the front side and the boundary line on the back side of the wafer in the side image are approximately parallel.

4. 3. The wafer edge detection device according to claim 1, A wafer edge detection device comprising an adjustment mechanism for adjusting the height position of a stage that supports the wafer, the height position of the point light source, and / or the height position of the camera.

5. 5. The wafer edge detection device according to claim 4, A wafer edge detection device, characterized in that after adjusting the height position of the stage or the height position of the light source, fine adjustment of the image pickup arrangement is performed by adjusting the height position of the camera.

6. 5. The wafer edge detection device according to claim 4, A wafer edge detection device characterized in that, for multiple wafers to be detected, readjustment is performed by the adjustment mechanism in accordance with changes in the degree of parallelism between the boundary line on the front side and the boundary line on the back side in the side image of the wafer.

Images