TWI797484B - Wafer chuck inspection system - Google Patents

Abstract

The invention discloses a wafer chuck inspection system used for inspecting a wafer chuck. The wafer chuck is defined with a supporting surface, and the supporting surface comprises a first inspection area and a second inspection area. The wafer chuck inspection system comprises a first camera module and a second camera module. The first camera module is disposed on a first side of the wafer chuck for photographing the second inspection area. The second camera module is arranged on a second side of the wafer chuck for photographing the first inspection area. The wafer chuck is defined with a center line, the first side and the second side are located on both sides of the center line, and the first inspection area and the second inspection area are located on both sides of the center line.

Description

Wafer Chuck Inspection System

The invention relates to a wafer chuck detection system, in particular to a wafer chuck detection system utilizing multiple camera modules.

Wafer chucks are used to carry wafers for various processes, and are often used in various semiconductor machines. Since the semiconductor process requires a high degree of precision, if there are foreign objects, contamination or damage on the surface of the wafer chuck, it is likely to affect the yield rate of the subsequent process. Therefore, the industry needs to regularly check the status of the wafer chuck. Compared with manually inspecting the wafer chuck, it is better to use a camera to photograph the surface of the wafer chuck, and judge the status of the wafer chuck through image analysis. However, since existing semiconductor machines have clear functions, such as etching and epitaxy, etc., there is often no extra space to install cameras, so it is difficult to simultaneously detect wafer chucks. It is not practical to disassemble the wafer chuck from the semiconductor machine for inspection, which means that the process will be interrupted and the production efficiency will be reduced.

Following the above, in order to fully capture the surface of the wafer chuck, those with ordinary knowledge in the technical field can understand that the camera is usually set above the wafer chuck. However, the vertical space inside the semiconductor machine is very compact and narrow, especially when other functional modules are often installed directly above the wafer chuck, it is not easy to make room for the camera. In addition, if the camera is to shoot the surface of the wafer chuck obliquely from the side, it will also be impossible to see the whole picture of the surface of the wafer chuck because of the focal length and depth of field. Accordingly, the industry needs a new wafer chuck inspection system, which can not only be integrated in the limited space of semiconductor equipment, but also be able to use cameras to detect wafer chucks.

The invention provides a wafer chuck detection system, which can be arranged in a semiconductor machine, and can use a camera to detect the wafer chuck from the horizontal direction.

The present invention proposes a wafer chuck detection system for detecting wafer chucks. The wafer chuck defines a bearing surface, and the bearing surface includes a first detection area and a second detection area. The wafer chuck detection system includes a first camera module and a second camera module. The first camera module is arranged on the first side of the wafer chuck for taking pictures of the second detection area. The second camera module is arranged on the second side of the wafer chuck for taking pictures of the first detection area. The wafer chuck is defined with a centerline, the first side and the second side are respectively located on both sides of the centerline, and the first detection area and the second detection area are respectively located on both sides of the centerline.

In some embodiments, the first camera module may include a first lens with a first shortest focusing distance, and the second camera module may include a second lens with a second shortest focus distance. The shortest focusing distance may be the same as the second shortest focusing distance. Here, the first shortest focusing distance is not greater than the distance from the first lens to the centerline. In addition, the distance from the first lens to the centerline is the same as the distance from the second lens to the centerline. In addition, the first lens and the second lens may be located on the reference surface, the reference surface is parallel to the carrying surface, and the distance between the reference surface and the carrying surface is smaller than a first threshold value.

In some embodiments, the carrying surface may further include a third detection area and a fourth detection area, the third detection area and the fourth detection area are between the first detection area and the second detection area, the first detection area and the third detection area The detection area is on the same side of the central line, and the second detection area and the fourth detection area are on the same side of the central line. Here, the first camera module can be used to photograph the second inspection area and the fourth inspection area, and the second camera module can be used to photograph the first inspection area and the third inspection area. In addition, the first camera module may include a first lens and a third lens, and the second camera module may include a second lens and a fourth lens, the first lens is used to photograph the second detection area, and the second lens is used to photograph the second detection area. A detection area, the third lens is used to photograph the fourth detection area, and the fourth lens is used to photograph the third detection area. In addition, the first lens has a first shortest focusing distance, the third lens has a third shortest focusing distance, and the third shortest focusing distance may be shorter than the first shortest focusing distance. Alternatively, the pixels of the first shot may be larger than the pixels of the third shot. On the other hand, the first camera module may include a first light source, and the second camera module may include a second light source. The first light source and the second light source are used to illuminate the carrying surface.

To sum up, the wafer chuck detection system provided by the present invention has two camera modules, which are respectively arranged on both sides of the wafer chuck. In addition to not occupying the vertical space above the wafer chuck, it also avoids the single lens focal length Not enough to cover the whole wafer chuck issue.

The features, purpose and functions of the present invention will be further disclosed below. However, what is described below is only an embodiment of the present invention, and should not be used to limit the scope of the present invention, that is, all equivalent changes and modifications made according to the patent scope of the present invention will still be the gist of the present invention. It does not depart from the spirit and scope of the present invention, so it should be regarded as a further embodiment of the present invention.

Please refer to FIG. 1 and FIG. 2 together. FIG. 1 is a schematic top view of a wafer chuck detection system according to an embodiment of the present invention, and FIG. 2 is a schematic side view of a wafer chuck detection system according to an embodiment of the present invention. . As shown in the figure, the wafer chuck detection system 1 is used to detect the wafer chuck 2, the wafer chuck detection system 1 includes a first camera module 10 and a second camera module 12, and the wafer chuck 2 defines a carrying surface 20 , the carrying surface 20 can be used to carry a wafer. Here, if the wafer chuck 2 may be installed in a semiconductor machine, this embodiment does not limit the type of semiconductor machine. In addition, this embodiment does not limit what size wafer the wafer chuck 2 is used to carry, nor does it limit the size of the carrying surface 20 of the wafer chuck 2 . In practice, a centerline 22 may be defined on the bearing surface 20 , and the centerline 22 may divide the bearing surface 20 into a first detection area 200 and a second detection area 202 . Taking the example in FIG. 1 as an example, the first detection area 200 may be the bearing surface 20 on the left side of the central line 22 , and the second detection area 202 may be the bearing surface 20 on the right side of the central line 22 . For convenience of description, in this embodiment, the left side of the center line 22 is defined as the first side of the wafer chuck 2 , and the right side of the center line 22 is defined as the second side of the wafer chuck 2 . That is to say, the first detection area 200 is on the same side of the central line 22 as the first side, and the second detection area 202 is on the same side of the central line 22 as the second side. Each component of the wafer chuck detection system 1 will be described below.

The first camera module 10 is arranged on the first side of the wafer chuck 2, the first camera module 10 may have a first lens 100 and a first light source 102, the first lens 100 is used to photograph the second detection area 202, the first The light source 102 can be used to illuminate the carrying surface 20 . It can be seen from the figure that although the first lens 100 is located on the first side of the wafer chuck 2 , it is not used to photograph the relatively close first inspection area 200 , but to photograph the far second inspection area 202 . In one example, the first lens 100 has a first shortest focusing distance, which may be the distance from the first lens 100 to the central line 22 , that is, the distance D1 shown in FIG. 2 . Of course, the first shortest focusing distance of the first lens 100 may also be smaller than the distance D1, that is, at least the complete second detection area 202 must be covered. Those with ordinary knowledge in the technical field can understand that the lens has a corresponding minimum focusing distance. If the object being photographed is close to the minimum focusing distance, the lens may not be able to focus, and the captured object will be blurred. Accordingly, in order to ensure that the first lens 100 can clearly photograph the bearing surface 20 , in this embodiment, the first lens 100 is only used to photograph the far second detection area 202 , and the second detection area 202 is closest to the first lens 100 The edge of , should also be farther than the first shortest focusing distance of the first lens 100 . In addition, the depth of field of the first lens 100 should at least extend to the second side of the wafer chuck 2 , that is to say, the first lens 100 has at least a depth of field of the distance D4.

The second camera module 12 is arranged on the second side of the wafer chuck 2, the second camera module 12 can also have a second lens 120 and a second light source 122, the second lens 120 is used to photograph the first detection area 200, and The second light source 122 can also be used to illuminate the carrying surface 20 . In one example, the second lens 120 also has a second shortest focusing distance, which may be the distance from the second lens 120 to the central line 22 , that is, the distance D2 shown in FIG. 2 . Certainly, the second shortest focusing distance of the second lens 120 may also be smaller than the distance D2, that is, at least the entire first detection area 200 must be covered. Similarly, in order to ensure that the second lens 120 can clearly photograph the carrying surface 20 , in this embodiment, the second lens 120 is set only to photograph the far first detection area 200 , and the first detection area 200 is closest to the second lens 120 The edge of , should also be farther than the second shortest focusing distance of the second lens 120 . In addition, the depth of field of the second lens 120 should at least extend to the first side of the wafer chuck 2 , that is to say, the second lens 120 has at least a depth of field of the distance D3. In practice, the specification of the first lens 100 may be the same as that of the second lens 120 , for example, the first shortest focusing distance may be the same as the second shortest focusing distance. In addition, the first camera module 10 and the second camera module 12 can be arranged at symmetrical positions, that is, the distance from the first lens 100 to the centerline 22 is the same as the distance from the second lens 120 to the centerline 22 .

In addition, the first lens 100 and the second lens 120 are located on the same reference surface ref, the reference surface ref is parallel to the carrying surface 20 , and the distance H between the reference surface ref and the carrying surface 20 is smaller than the first threshold value. In practice, the distance H is related to the semiconductor machine. If there is sufficient vertical space inside the semiconductor machine, the distance H can be larger. On the contrary, if the vertical space inside the semiconductor machine is insufficient, the distance H will be smaller. In an example, the first threshold value may be 170mm, preferably, the distance H may be between 50mm and 200mm. It can be seen from the above that, unlike the detection method of using a single lens to shoot wafer chucks, this embodiment allocates one carrying surface 20 to two lenses for shooting. Since the area of each lens is responsible for shooting is small, it can have a higher , more consistent resolution. On the other hand, since each lens in this embodiment only needs to capture part of the bearing surface 20 , the problem that the depth of field of a single lens is not enough to cover the entire bearing surface 20 is solved, and it is also possible to avoid photographing a partially blurred bearing surface 20 . Moreover, since the lens of the wafer chuck detection system 1 of this embodiment is arranged on the side of the wafer chuck 2 , the wafer chuck detection system 1 can complete detection when the vertical space of the semiconductor machine is limited.

In one example, the first lens 100 and the first light source 102 in the first camera module 10 are not necessarily on the same reference surface ref, as long as the first light source 102 can illuminate the carrying surface 20 of the wafer chuck 2, in this embodiment The type of light source of the first light source 102 is not limited. Likewise, the second lens 120 and the second light source 122 in the second camera module 12 are not necessarily on the same reference surface ref, and the embodiment does not limit the type of light source of the second light source 122 . In addition, the first light source 102 and the second light source 122 may each have a set (multiple) of lighting units capable of projecting evenly diffused light. In addition, each lighting unit may be independently driven, and the user can selectively turn on or off different numbers of lighting units in the first light source 102 and the second light source 122 according to the size of the carrying surface 20 or the characteristics of the carrying surface 20 . Taking the example shown in FIG. 1 , for example, the first light source 102 may include but not limited to four lighting units, and the plurality of lighting units may be dispersed around the first lens 100 . On the other hand, in order to make the light irradiated on the carrying surface 20 more uniform, the first light source 102 and the second light source 122 should be arranged at symmetrical positions of the wafer chuck 2 and illuminate the carrying surface 20 at the same angle. In practice, the first light source 102 and the second light source 122 can also be responsible for illuminating a part of the bearing surface 20, for example, the first light source 102 can be responsible for illuminating the first detection area 200 that is closer, and the second light source 122 can be responsible for illuminating the nearer detection area 200. The second detection area 202 is not limited in this embodiment.

It is worth mentioning that traditionally, when a single light source is used to illuminate the bearing surface, it is easy to have abnormal bright or dark bands on the image of the bearing surface, because there are special fine cutting lines on the bearing surface that cause stray light. In contrast, since the present embodiment illuminates different areas of the carrying surface 20 in sections, and the light sources (more than two) are more dispersed, the influence of stray light can be effectively reduced. In this way, this embodiment can avoid abnormal bright bands or dark bands in the image, that is, improve the signal-to-noise ratio of foreign objects or defects in the image on the bearing surface 20 . In practice, when the wafer chuck detection system 1 detects foreign objects or defects in the image of the carrying surface 20, the first light source 102 and the second light source 122 will set multiple brightness levels so that the first lens 100 and the second lens 120 can be respectively The images of the first detection area 200 and the second detection area 202 under different brightness are captured. Next, the processing unit (not shown) in the wafer chuck inspection system 1 will then analyze whether there are abnormal features over a certain area in the images of the first inspection area 200 and the second inspection area 202 . After obtaining the location of the abnormal feature, the processing unit can draw a distribution map of foreign objects or defects on the bearing surface 20 .

In addition, with the advancement of semiconductor technology, the size of the wafer chuck 2 may become larger and larger. The depth of field of the first lens 100 may not extend to the second side of the wafer chuck 2 , and the depth of field of the second lens 120 may not extend to the first side of the wafer chuck 2 . Or, the images captured by the first lens 100 and the second lens 120 may have insufficient resolution. At this time, the camera module of this embodiment can be improved, so that the camera module is provided with more than one lens corresponding to different areas on the carrying surface 20 to solve the above problems. Please refer to FIG. 1, FIG. 3 and FIG. 4 together. FIG. 3 is a schematic top view of a wafer chuck detection system according to another embodiment of the present invention, and FIG. 4 is a schematic diagram of a wafer chuck detection system according to another embodiment of the present invention. Schematic side view of the system. 3 and the embodiment shown in FIG. 1 are similar in that the wafer chuck detection system 3 also includes a first camera module 30 and a second camera module 32, and the wafer chuck 2 defines a carrying surface 20 for carrying Face 20 may be used to carry a wafer. The difference between the embodiments of FIG. 3 and FIG. 1 is that, in addition to a centerline 22 that can be defined on the carrying surface 20, an auxiliary line 24a can also be defined between the centerline 22 and the first side of the wafer chuck 2, the center An auxiliary line 24b may also be defined between the line 22 and the second side of the wafer chuck 2 . Thereby, the carrying surface 20 can be divided into a first detection area 200 , a second detection area 202 , a third detection area 204 and a fourth detection area 206 by the center line 22 , the auxiliary line 24 a and the auxiliary line 24 b.

As shown in the figure, the left side of the auxiliary line 24a is the first detection area 200, the third detection area 204 is between the auxiliary line 24a and the center line 22, and the fourth detection area 206 is between the center line 22 and the auxiliary line 24b. The right side of the line 24b is the second detection area 202 . In other words, the third detection area 204 and the fourth detection area 206 are between the first detection area 200 and the second detection area 202, on the bearing surface 20, from left to right are the first detection area 200, the third detection area The detection area 204 , the fourth detection area 206 and the second detection area 202 .

In addition, the first camera module 30 of the wafer chuck detection system 3 has a first lens 300, a third lens 302 and a first light source 304. The lens 302 is used to photograph the fourth detection area 206 which is relatively close, and the first light source 304 is used to illuminate the carrying surface 20 . As mentioned above, due to the large size of the wafer chuck 2 in this embodiment, the first lens 300 may not be enough to capture half of the carrying surface 20, so the first lens 300 is only used to capture the far second detection area 202 , and the second detection area 202 is closest to the edge of the first lens 300 and should be farther than the first shortest focusing distance of the first lens 300 . In other words, the first shortest focusing distance of the first lens 300 may be the distance D1 plus the distance D5. Likewise, the third shortest focusing distance of the third lens 302 may be the distance D1. In addition, as described in the previous embodiment, the first lens 300 has at least the depth of field of the distance D6, and the third lens 302 has at least the depth of field of the distance D5.

The second camera module 32 of the wafer chuck detection system 3 has a second lens 320, a fourth lens 322 and a second light source 324. The second lens 320 is used to photograph the farthest first detection area 200. The fourth lens 322 The second light source 324 is used to illuminate the carrying surface 20 for photographing the third detection area 204 at a relatively short distance. Similar to the first camera module 30, the second lens 320 is only used to photograph the far first detection area 200, and the first detection area 200 is closest to the edge of the second lens 320, and should be farther than the second lens 320 The second shortest focusing distance. In other words, the second shortest focusing distance of the second lens 320 may be the distance D2 plus the distance D4. Likewise, the fourth shortest focusing distance of the fourth lens 322 may be the distance D2. In addition, the second lens 320 has at least a depth of field of the distance D3, and the fourth lens 322 has at least a depth of field of the distance D4. In practice, the specification of the first lens 300 may be the same as that of the second lens 320 , for example, the first shortest focusing distance may be the same as the second shortest focusing distance. Moreover, the specification of the third lens 302 may be the same as that of the fourth lens 322 , for example, the third shortest focusing distance may be the same as the fourth shortest focusing distance. In addition, the first camera module 30 and the second camera module 32 can be arranged at symmetrical positions, and the first lens 300 and the second lens 320 can be arranged on the same reference plane ref.

In one example, the specification of the first lens 300 is different from that of the third lens 302 . Assuming that the pixels corresponding to the first lens 300 and the third lens 302 are the same, the focal lengths of the first lens 300 and the third lens 302 may be different. For example, the first lens 300 may be a long-focus lens for photographing the far first detection area 200 , and the third lens 302 may be a short-focus lens for photographing the relatively close third detection area 204 . In addition, assuming that the focal lengths of the first lens 300 and the third lens 302 are the same, the first lens 300 should correspond to a larger photosensitive element, or the first lens 300 should have more pixels than the third lens 302 . Those with ordinary knowledge in the technical field can freely select the focal lengths and pixels corresponding to the first lens 300 and the third lens 302, as long as the images captured by the first lens 300 and the third lens 302 should have similar resolution and magnification, All should belong to the category of the first lens 300 and the third lens 302 of this embodiment. In practice, the images captured by the first lens 300 and the third lens 302 have similar resolution and magnification, which can avoid edge discontinuity when the processing unit in the wafer chuck inspection system 3 combines images.

It is worth mentioning that the horizontal heights of the third lens 302 and the fourth lens 322 should be the same and symmetrical, but they are not limited to be arranged on the same reference surface ref. For the convenience of description, in this embodiment, the first lens 300 , the second lens 320 , the third lens 302 and the fourth lens 322 have the same horizontal height and are all arranged on the reference surface ref as an example. Same as the previous embodiment, the distance H between the reference surface ref and the carrying surface 20 is smaller than the first threshold value, and the distance H may be between 50 mm and 200 mm, which is not limited in this embodiment. As described in the previous embodiment, in this embodiment, one carrying surface 20 is assigned to four lenses for shooting, and since the area of each lens is responsible for shooting is further reduced, compared with the example in FIG. 1 , the one shown in FIG. 3 Examples should have a higher, more consistent resolution. In addition, since each lens in this embodiment also only needs to capture part of the bearing surface 20 , it can also solve the problem that the depth of field of a single lens is not enough to cover the entire bearing surface 20 , and can also avoid photographing a partially blurred bearing surface 20 . Moreover, since the lens of the wafer chuck detection system 3 in this embodiment is also arranged on the side of the wafer chuck 2, the wafer chuck detection system 3 can also complete the detection when the vertical space of the semiconductor machine is limited.

In one example, although the first light source 304 and the second light source 324 may also be responsible for illuminating a part of the carrying surface 20 respectively, the illumination areas of the first light source 304 and the second light source 324 may be different from those of the first lens 300 and the second lens. 320 , shooting areas corresponding to the third lens 302 and the fourth lens 322 . Taking the first light source 304 as an example, a part of the lighting units in the first light source 304 can be responsible for illuminating the relatively close first detection area 200, and another part of the lighting units in the first light source 304 can be responsible for illuminating the far third detection area 204 . Alternatively, each lighting unit of the first light source 304 may also illuminate the first detection area 200 and the third detection area 204 at the same time, which is not limited in this embodiment.

To sum up, the wafer chuck detection system provided by the present invention has two camera modules, which are respectively arranged on both sides of the wafer chuck. In addition to not occupying the vertical space above the wafer chuck, it also avoids the single lens focal length Not enough to cover the whole wafer chuck issue.

1: Wafer chuck detection system 10: The first camera module 100: first shot 102: The first light source 12: Second camera module 120:Second shot 122: Second light source 2: wafer suction cup 20: bearing surface 200: The first detection area 202: Second detection area 204: The third detection area 206: The fourth detection area 22: Centerline 24a: Auxiliary line 24b: Auxiliary line 3: Wafer chuck detection system 30: The first camera module 300: first shot 302: The third lens 304: The first light source 32:Second camera module 320: second shot 322: Fourth shot 324: Second light source D1~D6: Distance H: distance ref: reference surface

FIG. 1 is a schematic top view of a wafer chuck detection system according to an embodiment of the present invention.

FIG. 2 is a schematic side view of a wafer chuck detection system according to an embodiment of the present invention.

FIG. 3 is a schematic top view of a wafer chuck detection system according to another embodiment of the present invention.

FIG. 4 is a schematic side view of a wafer chuck detection system according to another embodiment of the present invention.

none

1: Wafer chuck detection system

10: The first camera module

100: first shot

102: The first light source

12: Second camera module

120:Second shot

122: Second light source

2: wafer suction cup

20: bearing surface

200: The first detection area

202: Second detection area

22: Centerline

Claims (11)

A wafer chuck detection system for detecting a wafer chuck, the wafer chuck defines a bearing surface, the bearing surface includes a first detection area and a second detection area, the wafer chuck detection system includes: a A first camera module, arranged on a first side of the wafer chuck, for photographing the second detection area; and a second camera module, arranged on a second side of the wafer chuck, for photographing The first detection area; wherein the wafer chuck defines a center line, the first side and the second side are respectively located on both sides of the center line, and the first detection area and the second detection area are respectively located at the center Two sides of the line; wherein in a vertical direction, the first camera module and the second camera module are located on the side of the wafer chuck. The wafer chuck detection system as described in claim 1, wherein the first camera module includes a first lens, the first lens has a first shortest focusing distance, and the second camera module includes a second lens, The second lens has a second shortest focusing distance, and the first shortest focusing distance is the same as the second shortest focusing distance. The wafer chuck detection system according to claim 2, wherein the first shortest focusing distance is not greater than the distance from the first lens to the centerline. The wafer chuck detection system according to claim 2, wherein the distance from the first lens to the centerline is the same as the distance from the second lens to the centerline. The wafer chuck detection system according to claim 2, wherein the first lens and the second lens are located on a reference plane, the reference plane is parallel to the carrying surface, and the distance between the reference surface and the carrying surface is smaller than a first a threshold value. The wafer chuck detection system as described in claim 1, wherein the carrying surface further includes a third detection area and a fourth detection area, the third detection area and the fourth detection area are between the first detection area and the Between the second detection areas, the first detection area and the third detection area are on the same side of the center line, and the second detection area and the fourth detection area are on the same side of the center line. The wafer chuck detection system according to claim 6, wherein the first camera module is used to photograph the second detection area and the fourth detection area, and the second camera module is used to photograph the first detection area and the fourth detection area The third detection area. The wafer chuck detection system as described in claim 7, wherein the first camera module includes a first lens and a third lens, the second camera module includes a second lens and a fourth lens, and the first camera module includes a second lens and a fourth lens. A lens is used to photograph the second detection area, the second lens is used to photograph the first detection area, the third lens is used to photograph the fourth detection area, and the fourth lens is used to photograph the third detection area. The wafer chuck detection system as described in claim 8, wherein the first lens has a first shortest focusing distance, the third lens has a third shortest focusing distance, and the third shortest focusing distance is shorter than the first shortest focusing distance Focus distance. The wafer chuck inspection system as claimed in claim 8, wherein the pixels of the first lens are larger than the pixels of the third lens. The wafer chuck detection system as described in claim 1, wherein the first camera module includes a first light source, the second camera module includes a second light source, and the first light source and the second light source are used to illuminate Light up the bearing surface.

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