JP7003907B2 - Semiconductor wafer end face evaluation method, semiconductor wafer storage container evaluation method, semiconductor wafer packaging form evaluation method, and semiconductor wafer transport form evaluation method - Google Patents

Description

The present invention relates to an end face evaluation method for a semiconductor wafer, an evaluation method for a semiconductor wafer accommodating container, an evaluation method for a semiconductor wafer packaging form, and an evaluation method for a semiconductor wafer transport form.

Patent Document 1 proposes that a semiconductor wafer is photographed by a camera and an visual inspection is performed using the obtained image data.

Japanese Unexamined Patent Publication No. 2012-204703

In the field of semiconductor wafer manufacturing, the end face of a semiconductor wafer may be subject to visual inspection. This is because foreign matter may adhere to the wafer end face due to friction between the wafer holding member of the semiconductor wafer accommodating container and the wafer end face, for example, due to vibration during transportation. Because. However, the method proposed in Patent Document 1 is specifically a method for evaluating a semiconductor device (chip) formed on a substrate by using image data obtained by camera photography. It is not a method for evaluating wafer end faces.

One aspect of the present invention is to provide a new evaluation method for evaluating the end face of a semiconductor wafer, and more specifically, to provide a new evaluation method capable of evaluating the adhesion of foreign matter on the end face of a semiconductor wafer. The purpose is to do.

One aspect of the present invention is
The semiconductor wafer to be evaluated includes a chamfered surface at the end face of the wafer.
Irradiating at least the end face of the semiconductor wafer to be evaluated with light,
Taking a picture of the wafer end face irradiated with the above light with a camera that selectively detects specularly reflected light.
Creating multiple luminance distribution curves in the wafer thickness direction from the images obtained by the above shooting,
Creating an average curve of the multiple luminance distribution curves created above,
A threshold curve is created by subtracting the luminance value determined as the correction luminance value from each luminance value on the average curve, and the luminance below or below the value on the threshold curve is shown on the image. Judging the area as a foreign matter adhesion area,
(Hereinafter, also referred to simply as "end face evaluation method"),
Regarding.

In the above-mentioned end face evaluation method, the end face of the wafer irradiated with light is photographed by a camera that selectively detects specularly reflected light. Diffuse reflection occurs when light is applied to the region where foreign matter is attached to the end face of the wafer. Therefore, the region to which the foreign matter is attached is displayed dark (that is, with low brightness) in the image taken by the camera that selectively detects the specularly reflected light. On the other hand, the area where no foreign matter adheres is displayed brightly (that is, with high brightness) in the image taken by the camera.
In completing the end face evaluation method, the present inventors set a low-luminance region on an image taken by a camera that selectively detects specularly reflected light as a foreign matter adhesion region as an evaluation regarding the adhesion of foreign matter on the wafer end face. I considered to judge. However, as a result of examination, the captured image has uneven brightness (shading) depending on the position, and if the low-brightness region is simply determined to be the foreign matter adhesion region, the region where the foreign matter does not adhere is regarded as the foreign matter adhesion region. It has been found that there is a possibility that the determination may be made, or vice versa, the region where foreign matter is attached may be determined as the region where no foreign matter is attached. It is presumed that this luminance unevenness is caused by the machining unevenness of the chamfered surface normally formed on the wafer end face, but it is usually considered difficult to completely eliminate such machining unevenness.
In view of the above, as a result of further diligent studies, the present inventors have created an average curve of a plurality of luminance distribution curves as described above, and then subtracted the correction luminance value from this average curve to create a threshold value. The above-mentioned end face evaluation method using the curve for determining the foreign matter adhesion region has been completed. By using the threshold curve created in this way, it is possible to reduce the influence of luminance unevenness in the captured image.

In one aspect, the above-mentioned imaging can be performed in the circumferential direction of the wafer while rotating the semiconductor wafer to be evaluated with the center of rotation as the center of rotation, and after correcting the distortion in the circumferential direction of the wafer of the image obtained by the above-mentioned imaging. The brightness distribution curve can be created.

In one aspect, the end face evaluation method can further include noise removal processing. The noise removal process may be a process of excluding a region having a pixel count less than or less than the number of pixels defined as a noise threshold from the foreign matter adhering region among the regions determined to be foreign matter adhering regions on the image. can.

In one aspect, in the end face evaluation method, one or more selected from the group consisting of the luminance value, the number of pixels, and the size of the region determined to be the foreign matter adhered region is used as an index, and the region determined to be the foreign matter adhered region is used. It can include assessing the adhesion level of foreign matter.

In one aspect, the evaluation of the adhesion level of the foreign matter can be performed on the portion of the wafer end face of the semiconductor wafer to be evaluated that is in contact with the contamination source member.

In one aspect, the foreign matter can be an organic substance.

One aspect of the present invention is
Vibration of the container to be evaluated while accommodating the semiconductor wafer,
The end face of the semiconductor wafer after the vibration is evaluated by the end face evaluation method, and
As a result of the above evaluation, when it is determined that the adhesion of foreign matter on the end face of the semiconductor wafer is at an allowable level, a container having the same specifications as the container to be evaluated is determined as a container used for accommodating and transporting the semiconductor wafer. matter,
(Hereinafter, also simply referred to as "container evaluation method"),
Regarding.
Here, the semiconductor wafer accommodating container having the same specifications means that it is an accommodating container of the same manufacturer and the same model number.

One aspect of the present invention is
Vibration of the semiconductor wafer packed in the packing form to be evaluated,
The end face of the semiconductor wafer after the vibration is evaluated by the end face evaluation method, and
As a result of the above evaluation, when it is determined that the adhesion of foreign matter on the end face of the semiconductor wafer is at an allowable level, the packing form to be evaluated is determined as the packing form when transporting the semiconductor wafer.
(Hereinafter, also referred to simply as "packing form evaluation method"),
Regarding.

One aspect of the present invention is
Transporting semiconductor wafers in the mode of transport to be evaluated,
The semiconductor wafer after transportation is evaluated by the end face evaluation method of the semiconductor wafer, and
As a result of the above evaluation, when it is determined that the adhesion of foreign matter on the end face of the semiconductor wafer is at an allowable level, the transport mode to be evaluated is determined as the transport mode for transporting the product semiconductor wafer.
(Hereinafter, also simply referred to as "transportation form evaluation method"),
Regarding.

According to one aspect of the present invention, it is possible to provide a new evaluation method capable of evaluating the adhesion of foreign matter on the end face of a semiconductor wafer.

This is an example (distortion corrected) of an image obtained by photographing the end face of a wafer. This is an example (before distortion correction) of an image obtained by photographing the end face of a wafer. An example of the average curve and the threshold curve created for the image shown in FIG. 1 is shown. The threshold curve shown in FIG. 3 and the luminance distribution curve created for the I-I'position in FIG. 1 are shown. It is a graph which shows the correlation between the value obtained by the image determination software and the determination result by visual determination about the brightness of the foreign matter adhesion region. It is a graph which shows the correlation between the value obtained by the image determination software and the determination result by visual determination about the area (the number of pixels) of the foreign matter adhesion region. It is a graph which shows the correlation between the value obtained by the image determination software and the determination result by visual determination about the length of the foreign matter adhesion region.

[Semiconductor wafer end face evaluation method]
One aspect of the present invention is that the semiconductor wafer to be evaluated includes a chamfered surface on the end face of the wafer and irradiates at least the end face of the wafer of the semiconductor wafer to be evaluated with light, and the end face of the wafer irradiated with the light is positively reflected light. To take a picture with a camera that selectively detects , The threshold curve is created by subtracting the luminance value determined as the correction luminance value from each luminance value on the average curve, and the luminance below or below the value on the threshold curve is shown on the image. The present invention relates to an end face evaluation method for a semiconductor wafer, which comprises determining a region as a foreign matter adhesion region.
Hereinafter, the end face evaluation method will be described in more detail.

<Semiconductor wafer to be evaluated>
The semiconductor wafer to be evaluated by the end face evaluation method is a semiconductor wafer having a chamfered surface in the end face of the wafer. The chamfered surface can be formed by subjecting the outer peripheral edge portion of the semiconductor wafer to chamfering and chamfering mirror polishing. The chamfering process and the chamfering mirror surface polishing process can be performed by a known method. The semiconductor wafer to be evaluated can be various semiconductor wafers generally used as a semiconductor substrate. For example, as a specific example of the semiconductor wafer, various silicon wafers can be mentioned. The silicon wafer can be, for example, a silicon single crystal wafer that has been cut out from a silicon single crystal ingot and then subjected to various processing such as chamfering and chamfering mirror polishing. Specific examples of such a silicon single crystal wafer include a polished wafer that has been polished and has a polished surface on the surface. Further, the silicon wafer can be various silicon wafers such as an epitaxial wafer having an epitaxial layer on a silicon single crystal wafer and an annealed wafer in which a modified layer is formed on a silicon single crystal wafer by an annealing treatment. The semiconductor wafer to be evaluated can have a diameter of, for example, 200 mm, 300 mm or 450 mm, and can have a thickness of, for example, 700 to 1000 μm.

<Wafer end face photography>
In the end face evaluation method, an image obtained by photographing the wafer end face of the semiconductor wafer to be evaluated is used. This image can be obtained by irradiating at least the wafer end face of the semiconductor wafer to be evaluated with light and taking a picture of the irradiated wafer end face with a camera that selectively detects specular reflected light. It suffices to irradiate at least the part to be photographed on the end face of the wafer with light. The type of light emitted here is not limited, and may be light of any wavelength, monochromatic light, or light in a wavelength range having a predetermined width may be included. As the camera, a commercially available camera or a camera having a known configuration can be used. As an example, a CCD (Charge Coupled Device) camera can be mentioned, but the present invention is not limited thereto. By adjusting the relative positional relationship between the camera, the light source, and the wafer end face, it is possible to selectively detect the specular reflected light among the reflected light from the wafer end face. The number of cameras used for shooting may be one or two or more. For example, a camera is installed to photograph the upper part, the central part, and the lower part of the wafer end face, and the images are taken by a total of three cameras, and the image taken by each camera is used to create a brightness distribution curve in the wafer thickness direction. Can be used to Further, the imaging can be performed continuously or intermittently in the circumferential direction of the wafer while rotating the semiconductor wafer to be evaluated with the center of the wafer as the center of rotation. A line scan camera can also be used for continuous imaging in the circumferential direction of the wafer. The above imaging can be performed, for example, by using a commercially available semiconductor wafer end face inspection device.

<Creation of threshold curve>
By the above imaging, an image of a part or all of the wafer end face of the semiconductor wafer to be evaluated in the wafer thickness direction can be acquired for a part or all of the wafer circumferential direction. If the portion of the wafer end face to be imaged includes a region where foreign matter is attached, diffuse reflection occurs in that region when light is applied. Therefore, the region to which the foreign matter is attached is displayed dark (that is, with low brightness) in the above image. On the other hand, the region where no foreign matter adheres is displayed brightly (that is, with high brightness) in the above image. Therefore, it is conceivable to simply determine the low-luminance region on the image as the foreign matter adhesion region. However, as a result of the studies by the present inventors, it has been found that the image taken as described above has uneven brightness (shading) depending on the position. An example of an image including such uneven brightness is shown in FIG. FIG. 1 is an image in which the distortion of the image shown in FIG. 2 in the circumferential direction of the wafer is corrected. The details of such distortion correction will be described later. In the images shown in FIGS. 1 and 2, the foreign matter adhering region is displayed dark, but in addition to the foreign matter adhering region, the low-luminance band (black band extending from above to below on the image) is displayed darkly. Due to the presence of the above, uneven brightness occurs in the thickness direction of the wafer. Further, although not clearly shown in FIGS. 1 and 2, luminance unevenness also occurs in the circumferential direction of the wafer. It is presumed that such uneven brightness is caused by uneven processing of chamfering, but it is usually considered difficult to completely eliminate such uneven processing. Therefore, in the end face evaluation method, the following (1) and (2) are carried out in order to reduce the influence of the luminance unevenness.
(1) A plurality of luminance distribution curves in the wafer thickness direction are created from the images obtained by the above photographing. Then, an average curve of these plurality of luminance distribution curves is created.
(2) A curve obtained by subtracting the brightness value determined as the correction brightness value from each brightness value on the created average curve is used as the threshold curve.
As described above, by using the average curve of multiple luminance distribution curves instead of one luminance distribution curve for creating the threshold curve, the threshold curve in which the influence of the luminance unevenness at each point on the end face of the wafer is reduced can be obtained. Obtainable. Further, if one value is simply set as the threshold value of the brightness value and the region showing the brightness below or below this threshold value is determined as the foreign matter adhesion region, the determination result is affected by the brightness unevenness in the wafer thickness direction. It ends up. On the other hand, by determining the foreign matter adhering region using the threshold curve created as described above, it is possible to reduce the influence of the luminance unevenness in the wafer thickness direction on the determination result. The above average curve can be created, for example, by calculating the arithmetic mean of each luminance value on a plurality of luminance distribution curves. The luminance distribution curve created to obtain the average curve is a luminance distribution curve of 2 or more, may be a luminance distribution curve of 100 or more, or a luminance distribution curve of 1000 or more, and as an example, a luminance distribution of about 1000 to 30,000. It can also be a curve. However, the number of luminance distribution curves used for creating the average curve can be arbitrarily determined according to the resolution of the captured image and the like, and is not limited to the range exemplified above. Further, the correction luminance value can be set to an arbitrary value according to the type of foreign matter to be detected as a low luminance region and the like. The above average curve and threshold curve can be created, for example, by analysis based on a known method. FIG. 3 shows an example of an average curve and a threshold curve created for the image shown in FIG.

<Distortion correction>
FIG. 2 shows that the semiconductor wafer to be evaluated can be continuously photographed in the circumferential direction of the wafer by an end face inspection device equipped with a CCD camera (line scan camera) while rotating the wafer center as the center of rotation. It is an image. As is clear from FIG. 2, the captured image is distorted in the circumferential direction of the wafer. This is because it is usually difficult for a general wafer rotation mechanism to rotate a wafer horizontally with respect to a fixed CCD camera. When such distortion occurs in the captured image, the above-mentioned luminance distribution curve is created using the distortion-corrected image in which the distortion in the circumferential direction of the wafer is corrected, and the created luminance distribution curve is used. It is preferable to create the above-mentioned average curve and threshold curve. Distortion correction can be performed by aligning the center position in the wafer thickness direction at each position in the wafer circumferential direction of the captured image. Such distortion correction can be performed, for example, by image processing based on a known method.

<Determination of foreign matter adhesion position>
FIG. 4 shows the threshold curve shown in FIG. 3 and the luminance distribution curve created for the I'I'position in FIG. In FIG. 4, the luminance distribution curve includes a low luminance region equal to or less than the luminance value on the threshold curve or less than the luminance value on the threshold curve. Since such a low-luminance region can be said to be a region where the brightness is reduced due to diffused reflection due to the adhesion of foreign matter, the low-luminance region can be determined to be a foreign matter adhesion region. As described above, in the above-mentioned end face evaluation method, in the captured image or the distortion-corrected image, the region showing the brightness equal to or less than the brightness value on the threshold curve or less than the brightness value on the threshold curve is determined to be a foreign matter adhesion region. can do. Further, in one embodiment, among the regions determined to be foreign matter adhering regions, the regions having or less than the number of pixels defined as the noise threshold are excluded from the foreign matter adhering regions (that is, they are not regarded as foreign matter adhering regions). ) Further noise removal processing can be performed. This is because the low-luminance region with a small number of pixels may be a noise component. The number of pixels defined as the noise threshold value can be arbitrarily set according to the required determination accuracy in consideration of the resolution of the captured image and the like. The larger the amount of foreign matter adhered, the lower the brightness of the foreign matter adhered region tends to be. Further, since the number of pixels in the region determined to be the foreign matter adhering region corresponds to the area, it means that the larger the number of pixels in the foreign matter adhering region, the wider the foreign matter is adhering. Therefore, the brightness value and the number of pixels in the region determined to be the foreign matter adhesion region can be used as an index for evaluating the foreign matter adhesion level. Further, the size (for example, length or width) of the foreign matter adhesion region can also be used as an index for evaluating the foreign matter adhesion level. The determination of the foreign matter adhesion level can be performed at least on the portion of the wafer end face of the semiconductor wafer to be evaluated that is in contact with the contamination source member, can also be performed on the peripheral portion of such a portion, or the entire wafer end face. You can also do it with. For example, the above-mentioned foreign matter adhesion level can be selectively determined for the portion that was in contact with the contamination source member or the portion that is in contact with the contamination source member and the peripheral portion thereof. Further, in one aspect, the number of regions determined to be foreign matter adhesion regions can be used as an index for evaluating the foreign matter adhesion level on the wafer end face.

Semiconductor wafers are generally housed in a storage container such as a FOSB (Front Opening Shipping Box) and transported (also referred to as transport) in a manufacturing plant, or are housed in a storage container and shipped from the manufacturing plant for transportation. .. At this time, vibration may be unintentionally applied (vibrated) to the semiconductor wafer. Due to such vibration, the wafer end face and a part of the accommodation container (for example, a wafer holding member) rub against each other, so that the constituent components of the accommodation container may adhere to the wafer end face. The susceptibility to adhesion differs depending on the shape of the contact portion of the container with the wafer, the type of the component constituting the contact portion with the wafer, and the like. Therefore, when determining whether or not a storage container having a certain specification is suitable as a storage container to be used for actual transportation within the manufacturing plant or shipping from the manufacturing factory, the container is stored in the storage container having this specification. The level of adhesion of foreign matter on the wafer end face of the semiconductor wafer can be used as an index for determination. As a method for obtaining an index for such determination, the above-mentioned end face evaluation method can be used. Since a resin container is widely used as a container for a semiconductor wafer, the deposit derived from the container is usually an organic substance in many cases.

It is also possible to create image determination software that implements a program for implementing the end face evaluation method described above. An example of a specific aspect of the image determination software will be described below. However, the present invention is not limited to the following example. Other processes may be further optionally performed before and / or after the various processes described below.

First, in the image determination software, a folder in which images taken about the semiconductor wafer to be evaluated are saved is selected.

After that, in the image determination software, the type (specification) of the storage container in which the semiconductor wafer to be evaluated is stored is selected. The position, size, number, etc. of the semiconductor wafer holding members arranged in the storage container may differ depending on the specifications of the storage container. Therefore, in the image determination software, position information for evaluating the adhesion level of foreign matter is set for each type of storage container. As a result, the adhesion level of foreign matter can be selectively evaluated for the portion of the wafer end face of the semiconductor wafer to be evaluated that has been in contact with the contamination source member.

From the images in the selected folder, use the image judgment software to select the image at the position where the foreign matter adhesion level is evaluated (analysis target position), create the above-mentioned luminance distribution curve, create the average curve, and threshold the value. Create a curve. The analysis target position may be one place or two or more places. The luminance distribution curve is preferably created for the distortion-corrected image to which the above-mentioned distortion correction has been performed.

Further, the image determination software excludes the area of the number of pixels or less or less than the number of pixels defined as the noise threshold value from the area of the brightness value or less or less than the brightness value on the threshold curve on the image at the position where the adhesion level of the foreign matter is evaluated. The area not excluded here is determined as a "foreign matter adhering area" and displayed in different colors. Evaluating the adhesion level of foreign matter on the semiconductor wafer to be evaluated using one or more selected from the group consisting of the luminance value, the number of pixels, and the size (for example, length or width) of the foreign matter adhesion region displayed in different colors in this way as an index. Can be done.

[Evaluation method for semiconductor wafer storage container]
One aspect of the present invention is to vibrate the container to be evaluated in a state of accommodating the semiconductor wafer, to evaluate the end face of the semiconductor wafer after the vibration by the end face evaluation method, and the result of the evaluation. When it is determined that the adhesion of foreign matter on the end face of the semiconductor wafer is at an acceptable level, the semiconductor wafer including determining a container having the same specifications as the container to be evaluated as a container used for accommodating and transporting the semiconductor wafer. Regarding the evaluation method of the storage container.

According to the above-mentioned container evaluation method, it can be determined that a container in which foreign matter derived from the container is likely to adhere to the end face of the wafer due to vibration is not suitable for actual use, and a container in which foreign matter is unlikely to adhere can be determined. It can be determined as a storage container to be used when actually transporting a semiconductor wafer. The vibration can be performed by a known method such as using a commercially available vibration tester, and the magnitude of the vibration to be applied and the time to apply the vibration can be arbitrarily set. This point is the same for the following packing form evaluation method. Further, the above allowable level can be arbitrarily set according to the degree of foreign matter adhesion permitted to the product wafer. This point is the same for the following packing form evaluation method and transportation form evaluation method.

[Evaluation method of packing form of semiconductor wafer]
One aspect of the present invention is to vibrate a semiconductor wafer packed in a packaging form to be evaluated, to evaluate the end face of the semiconductor wafer after the vibration by the end face evaluation method, and as a result of the evaluation. The present invention relates to a semiconductor wafer packing form evaluation method including determining a packing form to be evaluated as a packing form when transporting a semiconductor wafer when it is determined that adhesion of foreign matter on the end face of the semiconductor wafer is at an allowable level.

The above-mentioned packing form includes the type of packing material used at the time of transportation, the type of cushioning material, and the like. As described above, the semiconductor wafer may be unintentionally vibrated during transportation, but the tendency of foreign matter to adhere to the end face of the wafer due to such vibration is determined by the semiconductor wafer housed in the container. It also depends on the packing form such as what kind of packing material is used for packing and what kind of cushioning material is used. Therefore, when determining whether or not a certain packing form is suitable as a packing form when actually shipping and transporting a product wafer, foreign matter on the wafer end face of the semiconductor wafer packed and vibrated in this packing form is used. The level of adhesion can be used as an index for determination. As a method for obtaining an index for such determination, the above-mentioned end face evaluation method can be used.

[Evaluation method of transport form of semiconductor wafer]
One aspect of the present invention is to transport a semiconductor wafer in a transport mode to be evaluated, to evaluate the transported semiconductor wafer by the end face evaluation method, and as a result of the evaluation, to the end face of the semiconductor wafer. The present invention relates to a method for evaluating a semiconductor wafer transport mode, which comprises determining a transport mode to be evaluated as a transport mode for transporting a product semiconductor wafer when the adhesion of foreign matter is determined to be an acceptable level.

The above-mentioned transportation form includes the type of transportation means (aircraft, ship, truck, etc.) used at the time of transportation, the transportation route used at the time of transportation to the destination, and the like. When the semiconductor wafer is housed in the storage container and transported, the magnitude of the vibration applied to the semiconductor wafer and the time during which the vibration is applied differ depending on the transportation mode. Therefore, when determining whether or not a certain transport mode is suitable as a transport mode when actually transporting a product wafer, the level of foreign matter adhesion on the wafer end face of the semiconductor wafer transported in this transport mode is used as an index for determination. Can be. As a method for obtaining an index for such determination, the above-mentioned end face evaluation method can be used.

Hereinafter, the present invention will be further described based on examples. However, the present invention is not limited to the embodiments shown in the examples.

Approximately 100 semiconductor wafers (diameter 300 mm, thickness 775 μm) are placed in a vibration tester (IMV VS-300-2) in a state of being housed in a resin FOSB, and vibrated to force the wafer end face. Resin adhesion was generated.

Using a wafer end face inspection machine (SEMD-300) manufactured by NED, shooting was performed at a total of five shooting positions at 72 ° intervals over the entire circumference of the wafer end face of each semiconductor wafer in the circumferential direction. By shooting at these five shooting positions, images were acquired for the entire circumference of the wafer end face of each semiconductor wafer at 360 ° in the circumferential direction (the number of pixels in the entire circumference in the circumferential direction: 30,000 pixels). The wafer end face inspection machine used here has a light source for irradiating the wafer end face with light and a rotation mechanism for rotating the wafer to be photographed about the center of rotation of the wafer, and three fixed line scan cameras. (CCD camera) photographs the upper part, the central part, and the lower part of the end face of the wafer at each imaging position. Each camera is positioned and fixed to selectively detect specularly reflected light from the wafer end face. By combining the images taken by the three cameras (the number of pixels in the wafer thickness direction of each image: 300 pixels), an image (300 pixels × 3) of the entire wafer end face in the wafer thickness direction can be obtained. The image data thus obtained is stored in a folder with a predetermined folder name for each wafer.

As software for performing image judgment, we have prepared image judgment software that implements the program described above as an example of a specific embodiment.

The following process was executed by the above image judgment software.
(1) Select the folder to be analyzed.
(2) Select the type of FOSB that contained the semiconductor wafer to be analyzed. The FOSB information selected here includes contact position information between the wafer end face and the wafer holding member of the FOSB. The image determination software specifies the contact positions (total of 4 locations) of the wafer end faces with the wafer holding member as analysis target positions.
(3) According to the contact position information set in the type of FOSB selected in (2) above, the image data of the analysis target position in the folder selected in (1) above is selected.
(4) Distortion correction is performed on the image data of each analysis target position selected in (3) above, and the distortion-corrected image has brightness in the wafer thickness direction for each of 3000 pixels continuous in the circumferential direction of the wafer. Create a distribution curve. Therefore, 3000 luminance distribution curves are created for one analysis target position. In this way, an average curve of a total of 12000 luminance distribution curves created for a total of four analysis target positions is created. Further, a threshold curve is created from this average curve. The threshold curve is created by subtracting a preset correction luminance value from each luminance value on the average curve.
(5) With respect to the image data at the analysis target position, a region having a brightness equal to or less than the brightness value on the threshold curve is specified, and a region having a number of pixels or less specified as a noise threshold in advance is excluded from the specified region. The area not excluded is determined to be a foreign matter adhering area and displayed in different colors on the image.
(6) For each area displayed in different colors according to (5) above, the luminance value, the number of pixels (that is, the area) and the length are obtained by the image determination software, and these data are saved in the analysis target folder. The length is obtained as a linear distance between two points farthest on the contour of the region determined to be the foreign matter adhesion region.

The image judged by the above image judgment software was visually observed, and the degree of brightness, area, and length of each foreign substance adhering to the wafer end face at the analysis target position was judged in four stages of 1 to 4. .. Regarding the luminance, the determination result 1 means that the luminance is the lowest level, the larger the determination number is, the higher the luminance is, and the determination result 4 means that the luminance is the highest level. Regarding the area, the determination result 1 means that the area is the smallest level, the larger the determination number, the larger the area, and the determination result 4 means that the area is the largest level. Regarding the length, the determination result 1 means that the length is the shortest level, the larger the determination number is, the longer the length is, and the determination result 4 is the longest level.

5 to 7 show the values obtained by the image judgment software and the judgment result by visual judgment regarding the brightness, the number of pixels (area) or the length of the area determined to be the foreign matter adhesion area by the image judgment software. It is a graph which shows the correlation. In FIGS. 5 to 7, the unit on the vertical axis is an arbitrary unit (au). From these graphs, it can be confirmed that the judgment result of the image judgment and the judgment result of the visual judgment are generally correlated. In each graph, numerical values are also plotted on the vertical axis in the judgment result 0 of the visual judgment on the horizontal axis. This indicates that a foreign substance that cannot be visually confirmed can be confirmed by image determination. According to the image determination, objective evaluation based on numerical values such as luminance, number of pixels, and size (for example, length) is also possible.

The present invention is useful for various evaluations in the field of manufacturing semiconductor wafers.

Claims (9)

The semiconductor wafer to be evaluated includes a chamfered surface at the end face of the wafer.
Irradiating at least the end face of the semiconductor wafer to be evaluated with light,
Taking a picture of the end face of the wafer irradiated with the light by a camera that selectively detects specularly reflected light.
Creating a plurality of luminance distribution curves in the wafer thickness direction from the images obtained by the above photographing,
Creating an average curve of the plurality of luminance distribution curves created above,
A threshold curve is created by subtracting a brightness value determined as a correction brightness value from each brightness value on the average curve, and brightness equal to or less than or less than the value on the threshold curve is shown on the image. Judging the area as a foreign matter adhesion area,
A method for evaluating the end face of a semiconductor wafer, including. The above shooting was performed in the circumferential direction of the wafer while rotating the semiconductor wafer to be evaluated with the center of rotation as the center of rotation.
The end face evaluation method for a semiconductor wafer according to claim 1, wherein the luminance distribution curve is created after correcting the distortion of the image obtained by the photographing in the circumferential direction of the wafer. A claim including further performing a noise removing process for excluding a region having a pixel number equal to or less than the number of pixels defined as a noise threshold from the foreign matter adhering region in the region determined to be the foreign matter adhering region on the image. Item 2. The method for evaluating an end face of a semiconductor wafer according to Item 1 or 2. It includes evaluating the adhesion level of foreign matter in the region determined to be the foreign matter adhesion region by using one or more selected from the group consisting of the brightness value, the number of pixels and the size of the region determined to be the foreign matter adhesion region as an index. , The method for evaluating an end face of a semiconductor wafer according to any one of claims 1 to 3. The method for evaluating an end face of a semiconductor wafer according to claim 4, wherein the evaluation of the adhesion level of foreign matter is performed on a portion of the wafer end face of the semiconductor wafer to be evaluated that is in contact with a contamination source member. The method for evaluating an end face of a semiconductor wafer according to any one of claims 1 to 5, wherein the foreign matter is an organic substance. Vibration of the container to be evaluated while accommodating the semiconductor wafer,
The end face of the semiconductor wafer after vibration is evaluated by the end face evaluation method of the semiconductor wafer according to any one of claims 1 to 6, and
As a result of the evaluation, when it is determined that the adhesion of foreign matter on the end face of the semiconductor wafer is at an allowable level, a container having the same specifications as the container to be evaluated is determined as a container used for accommodating and transporting the semiconductor wafer. matter,
A method for evaluating a semiconductor wafer container, including. Vibration of the semiconductor wafer packed in the packing form to be evaluated,
The end face of the semiconductor wafer after vibration is evaluated by the end face evaluation method of the semiconductor wafer according to any one of claims 1 to 6, and
As a result of the evaluation, when it is determined that the adhesion of foreign matter on the end face of the semiconductor wafer is at an allowable level, the packing form to be evaluated is determined as the packing form when transporting the semiconductor wafer.
A method for evaluating a semiconductor wafer packaging form, including. Transporting semiconductor wafers in the mode of transport to be evaluated,
The semiconductor wafer after transportation is evaluated by the method for evaluating the end face of the semiconductor wafer according to any one of claims 1 to 6, and the semiconductor wafer is evaluated.
As a result of the evaluation, when it is determined that the adhesion of foreign matter on the end face of the semiconductor wafer is at an allowable level, the transport mode to be evaluated is determined as the transport mode for transporting the product semiconductor wafer.
A method for evaluating a semiconductor wafer transport mode, including.

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