Evaluation method for defect position in depth direction of wafer

Abstract

The present invention is a method for evaluating a defect position in a depth direction of a wafer by using an X-ray topography (XRT), the method comprising: a step for acquiring an XRT image in which the wafer has a front surface and a back surface; x-rays are incident on the front surface from the right direction and the left direction at an incident angle which is a diffraction condition, and two XRT images, namely a right-eye image and a left-eye image, are acquired on the back surface; a positioning step in which, for the two acquired XRT images, positioning is performed at a defect position on either the front surface or the rear surface; and a defect position determination step of determining, on the basis of the deviation between the right-eye image and the left-eye image, other defect positions in which the depth direction of the wafer is different. As a result, it is possible to provide a method for evaluating the position of a defect in the depth direction of a wafer by a simple method using an X-ray topography (XRT).

Description

Technical Field

[0001] The present invention relates to a method for evaluating the position of a defect in the depth direction of a wafer by means of an X-ray topograph (XRT). Background Art

[0002] An X-ray topograph (XRT) is a device widely used for observing defects in crystalline materials, particularly semiconductor device materials typified by silicon wafers. Different from the measurement principle of X-ray CT, the XRT does not detect the difference in transmittance but detects the distortion of a diffraction grating. Therefore, although it is only applicable to single crystals, it can detect very small defects.

[0003] Using the transmission method of the XRT, the position of defects in the entire wafer can be known, but depth information of the defects cannot be obtained. The depth information of defects in semiconductor device materials is very important information for determining whether the defects will affect device failures. In recent years, using the XRT, in order to obtain depth information, sectional topographs and three-dimensional topographs obtained by combining multiple sectional topographs have been obtained. However, in order to obtain a sectional topograph, a very long measurement time is required, and in order to obtain three-dimensional data that requires information of multiple sectional topographs, more time is required. Moreover, this measurement requires synchrotron radiation light from a strong X-ray generating device, etc., and there are many limitations.

[0004] Thus, previously, it was difficult to perform three-dimensional data conversion by overlapping sectional topograph images. However, in recent years, a method capable of realizing three-dimensional data conversion of defects has been developed (for example, Patent Document 1). However, even with this method, obtaining three-dimensional data is still time-consuming, and there is a problem of a narrow measurement area.

[0005] Furthermore, in semiconductor device materials, it is very important whether the defects causing device failures are located in the device layer, i.e., the surface, or the back surface. However, previously, it was not possible to simply evaluate the depth position of defects using the XRT.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-105831 Summary of the Invention

[0009] (I) Technical Problems to be Solved

[0010] The present invention has been developed in view of the above problems, and an object thereof is to provide a method for evaluating the position of a defect in the depth direction of a wafer by a simple method using an X-ray topograph (XRT).

[0011] (II) Technical Solutions

[0012] The present invention is developed to solve the above problems, and provides a method for evaluating the defect position in the depth direction of a wafer, which is a method for evaluating the defect position in the depth direction of a wafer by using an X-ray topographer (XRT), and includes: a process of obtaining an XRT image, wherein the wafer has a front surface and a back surface, and X-rays are incident on the front surface from the right direction and the left direction at an incident angle that satisfies the diffraction condition, and two XRT images, namely a right-eye image and a left-eye image, are obtained on the back surface; a positioning process, in which, for the two obtained XRT images, positioning is performed based on the defect position on either the front surface or the back surface; and a defect position determination process, in which, based on the deviation between the right-eye image and the left-eye image, other defect positions in different depth directions of the wafer are determined.

[0013] In such a method for evaluating the defect position in the depth direction of a wafer, for the defects on the surface where positioning has been performed, the right-eye image and the left-eye image are consistent, but for the defects on the surface different from the surface where positioning has been performed, the right-eye image and the left-eye image deviate. Based on this deviation, it can be determined that the defects are at different positions in the depth direction. If such a method is used, only two images need to be obtained in the normal usage mode of the X-ray topographer (XRT), and the measurement can be performed in a short time. Since special usage modes such as using enhanced radiation light and narrowing the measurement area are not adopted, it is universal. As a result, the defect position in the depth direction of the wafer can be evaluated in a very simple way.

[0014] In addition, preferably, the method of incident X-rays on the front surface from the right direction and the left direction at an incident angle that satisfies the diffraction condition is: fixing the incident angle in either the right direction or the left direction, incident X-rays to obtain an XRT image, and then rotating the wafer by 180 degrees, incident X-rays to obtain another XRT image in the other direction, thereby obtaining the two XRT images, namely the right-eye image and the left-eye image.

[0015] If such a method is used, even if the X-ray generator and the detector are not operated, the XRT images in the right direction and the left direction can be easily obtained, so the defect position in the depth direction of the wafer can be evaluated in a very simple way.

[0016] In addition, preferably, in the defect position determination process, either one of the two obtained XRT images is subjected to white-black inversion and then synthesized for determination.

[0017] In such a defect position determination process, since the defect position can be accurately determined based on the color difference between white and black, it can be suitably applied to the method for evaluating the defect position in the depth direction of a wafer.

[0018] In addition, a method for evaluating the defect position in the depth direction of a wafer is provided, which is a method for evaluating the defect position in the depth direction of a wafer using an X-ray topography (XRT), wherein the wafer has a surface and a back surface, X-rays are incident on the surface from right and left directions at incident angles that become diffraction conditions, two XRT images, a right eye image and a left eye image, are obtained on the back surface, and the two XRT images are captured as one image by visual observation, thereby observing the defect position in the depth direction in a stereoscopic view (Japanese: stereoscopic) (3D image).

[0019] If this is the method for evaluating the defect position in the depth direction of the wafer, if two XRT images are captured as one image by visual observation, if there are defects with different positions in the depth direction, then since the deviation of the two images can be observed in a three-dimensional manner, it can be determined as a defect with different positions in the depth direction by observing in a three-dimensional manner. If this method is used, only two images can be obtained by the usual use of the X-ray profiler (XRT), and the measurement can be performed in a short time. Since special use methods such as enhancing the radiation light and narrowing the measurement area are not used, it is universal. In addition, since the defect position is evaluated visually, there is no need to prepare an evaluation device separately. As a result, the defect position in the depth direction of the wafer can be evaluated in an extremely simple way.

[0020] In addition, the wafer is preferably at least one of a single crystal wafer and a wafer with devices formed thereon.

[0021] If it is such a wafer, it can be suitably applied to the evaluation method of the defect position in the depth direction of the wafer using an X-ray topography (XRT). In particular, if it is a silicon wafer or a SiC wafer, the incident angle that becomes the diffraction condition can be known in advance, so it can be suitably applied to the evaluation method of the defect position in the depth direction of the wafer.

[0022] In addition, in the case of a SiC wafer, there may be a case where crystal defects are intricately distributed inside the crystal, and the present invention can be applied to confirm this situation.

[0023] Furthermore, if the wafer has a device formed thereon, it is possible to simply evaluate whether the defect causing the device failure is located in the device layer, i.e., the surface, or the back surface. In a wafer having a device formed thereon, surface defects directly affect the device yield, and the present invention can help improve the yield even if only surface defects can be evaluated instead of the entire depth direction.

[0024] (III) Beneficial effects

[0025] As described above, in the method for evaluating the defect position in the depth direction of a wafer according to the present invention, only two images need to be obtained in the normal usage mode of an X-ray topograph (XRT). The measurement can be carried out in a short time. Since special usage modes such as using enhanced synchrotron radiation or narrowing the measurement area are not adopted, it is universal. As a result, the defect position in the depth direction of the wafer can be evaluated by an extremely simple method. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FIG. is a schematic diagram of an embodiment of the method for evaluating the defect position in the depth direction of a wafer according to the present invention.

[0027] Figure 2 FIG. is a schematic diagram of the case where two XRT images are obtained by changing the incident angle of X-rays.

[0028] Figure 3 FIG. is a schematic diagram of the case where two XRT images are obtained by rotating the wafer.

[0029] Figure 4 FIG. is a schematic diagram of another embodiment of the present invention.

[0030] Figure 5 FIG. is a schematic diagram showing the difference between the case where the incident direction of X-rays is one direction and the case where it is two directions.

[0031] Figure 6 FIG. is a schematic diagram of the incident angle and diffraction of the wafer that satisfy the diffraction condition.

[0032] Figure 7 FIG. is a photograph for explaining the effect of Example 1 of the present invention.

[0033] Figure 8 FIG. is a photograph for explaining Example 2 of the present invention.

[0034] Figure 9 FIG. is a schematic diagram of the case where a defect penetrates from the front surface to the back surface of the wafer.

[0035] Figure 10 FIG. is a photograph of the case where there are complex dislocations in the wafer. DETAILED DESCRIPTION OF THE INVENTION

[0036] As described above, for the evaluation method of a wafer using an X-ray topograph (XRT), a method is sought for evaluating the defect position in the depth direction of the wafer in a short time, in a universal manner, and with extremely simple results.

[0037] Then, the present inventors repeatedly studied and found that: by irradiating X-rays onto the surface of a wafer from the left and right directions at an incident angle that satisfies the diffraction condition, two XRT images, namely a right-eye image and a left-eye image, are obtained on the back surface, thereby enabling the evaluation of the defect position in the depth direction of the wafer in a short time, in a general manner, and with extremely simple results, thus completing the present invention.

[0038] That is, the present invention is a method for evaluating the defect position in the depth direction of a wafer, which is a method for evaluating the defect position in the depth direction of a wafer using an X-ray topography (XRT), and is characterized by including: a step of obtaining XRT images, wherein the wafer has a front surface and a back surface, X-rays are irradiated onto the front surface from the right and left directions at an incident angle that satisfies the diffraction condition, and two XRT images, namely a right-eye image and a left-eye image, are obtained on the back surface; a positioning step of positioning the defect position on either the front surface or the back surface for the two obtained XRT images; and a defect position determination step of determining other defect positions in different depth directions of the wafer based on the deviation between the right-eye image and the left-eye image.

[0039] In addition, the present invention is a method for evaluating the defect position in the depth direction of a wafer, which is a method for evaluating the defect position in the depth direction of a wafer using an X-ray topography (XRT), and is characterized in that: the wafer has a front surface and a back surface, X-rays are irradiated onto the front surface from the right and left directions at an incident angle that satisfies the diffraction condition, two XRT images, namely a right-eye image and a left-eye image, are obtained on the back surface, and the two XRT images are captured as one image by visual observation, thereby observing the defect position in the depth direction in a stereoscopic view (3D image).

[0040] Hereinafter, the present invention will be described in detail, but the present invention is not limited to these descriptions.

[0041] First, use Figure 5 to illustrate how defects are observed as images according to different incident directions of X-rays. Figure 5 On the left side of are two wafers with different defect positions. First, the upper wafer has oval and rectangular defects on the lower surface and a circular defect on the upper surface. The lower wafer has oval, rectangular, and circular defects on the lower surface. The difference between the upper and lower wafers is only in the position of the circular defect. The circular defect not only has different positions in the up-down direction but also in the left-right direction. The circular defect of the upper wafer is located slightly to the right. In addition, the arrow from the bottom to the top of this figure indicates the incident direction of X-rays, and irradiation is performed in a first direction from the lower left to the upper right and a second direction from the lower right to the upper left. X-rays in these two directions are independently irradiated, and respective XRT images are obtained above the wafer. At this time, simulating the image observed by a human eye from above, the respective images are called a left-eye image and a right-eye image.

[0042] In Figure 5 at the center, it shows the case of only one direction (XRT image (left-eye image) in only the first direction), but the image in the upper figure is not different from the image in the lower figure. This is because of the deviation pattern of the position of the circular defect (on the left side of the lower surface in the lower figure and on the right side in the upper figure), and the phenomenon that the defect on the lower surface deviates significantly more to the right than the defect on the upper surface due to the incident angle from the lower left to the upper right. As a result, it becomes an image where the positions of the circular defects are the same. That is, in the measurement from only one direction, even if the defect positions are different, there may be a situation where the XRT images are not different.

[0043] In Figure 5 on the right side, it shows the case of two directions (both the XRT image (left-eye image) in the first direction and the XRT image (right-eye image) in the second direction). The left-eye image is the same as before, but for the right-eye image, the difference in the positions of the circular defects between the image in the upper figure and the image in the lower figure is large. That is, by measuring from two directions, at least in the image of one direction, the difference in the defect positions is shown. Conversely, this means that in the case where the difference in the defect positions is shown in the image, if the lower surface is used as a reference, it can be known that there are defects on different surfaces in the upper direction, and thus the defect positions in different depth directions can be determined.

[0044] The method of this time is a method that utilizes the following phenomenon: If images from different directions such as the left-eye image and the right-eye image are overlapped, the defect positions will change according to the different depth positions. In the XRT image from one direction that is usually performed, the difference caused by the different depths cannot be obtained.

[0045] Hereinafter, regarding an embodiment of the present invention, reference is made to Figure 1 and Figure 2 for explanation.

[0046] The wafer is configured such that the surface of the wafer becomes the lower surface and the back surface becomes the upper surface, and two conventional transmission XRT measurements are performed. At this time, as shown in the upper figure of Figure 1 , for the same diffraction plane, X-rays are incident obliquely from the left direction and the right direction for measurement respectively. Since the X-rays are incident obliquely with respect to the sample, the images obtained from the defects are shifted in position according to the different depths of the defects, and as a result, the left-eye image and the right-eye image are obtained respectively, and these images are compared, thereby enabling the evaluation of the position in the depth direction according to the difference in the defect positions.

[0047] Figure 1Among them, the positions of the defects (oval, rectangular) near the surface (lower surface) do not change in the right-eye image and the left-eye image, but the positions of the images of the defects (circular) near the back surface (upper surface) change. If only the defects whose positions change in the right-eye image and the left-eye image are extracted, it is possible to determine that the defects are near the back surface.

[0048] The right-eye image of the obtained X-ray topography image is inverted from white to black, and while positioning it so that the positions of the defects (oval, rectangular) near the surface (lower surface) coincide, it is overlapped with the left-eye image. Thus, it is possible to make only the places where the defect positions deviate, that is, the circular defects located on the back surface (upper surface) appear.

[0049] In addition, Figure 2 is a schematic diagram of the positional relationship among the generator, the detector, and the sample when obtaining the right-eye image and the left-eye image in the case where the X-ray generator and the detector are devices that can move freely. When obtaining the right-eye image, it is only necessary to arrange the generator on the right side, and when obtaining the left-eye image, it is only necessary to arrange the generator on the left side.

[0050] In this way, measurements are performed by irradiating X-rays from the left and right, but the irradiation from the left and right is preferably set so that the same diffraction plane can be measured. Specifically, in the measurement of a (100) silicon wafer, in most cases, measurements are performed using (400) diffraction or (220) diffraction. Among them, for the case of using (400) diffraction, the incident angle from the right direction is 74.86°, and the incident angle from the left direction is 105.15°; for the case of using (220) diffraction, the incident angle from the right direction is 79.36°, and the incident angle from the left direction is 100.64°. However, there is an off-angle (in Japanese: OFF angle) in the wafer, and diffraction occurs rarely at the above incident angles. In most cases, it deviates by several degrees to several minutes.

[0051] In addition, in the case of a SiC wafer, in most cases, measurements are performed using the (11-20) diffraction plane. For the incident angle in this case, the incident angle from the right direction is 76.66°, and the incident angle from the left direction is 103.34°.

[0052] Most conventional XRT measurements are performed using monochromatic X-rays. In this case, the diffraction angle must be strictly determined. However, recently, there is also XRT using non-monochromatic X-rays. Therefore, in this case, the diffraction angle does not have to be so strict. Specifically, as long as it is within the range where an XRT image can be obtained, even if the diffraction angle deviates, it is not a problem.

[0053] In addition, when performing two measurements once from the left and once from the right, if the measurements are performed on the same diffraction plane, stereoscopic observation can also be performed visually, but images obtained under other diffraction conditions can also be used for comparison.

[0054] The image obtained when X-rays are incident from the left is set as the left-eye image, and the image obtained when X-rays are incident from the right is set as the right-eye image. However, even if the right-eye image and the left-eye image are swapped, as long as the two XRT images can be compared, it is no problem even if the right-eye image and the left-eye image are swapped. When the device is restricted and the X-ray generator and detector cannot be operated to the inverted position, the sample can also be rotated 180 degrees and measured at the same angle, and the measured result can be rotated 180 degrees.

[0055] As described above, one embodiment of the present invention is a method for evaluating the defect position in the depth direction of a wafer using an X-ray topograph (XRT), including: a step of obtaining an XRT image, wherein the wafer has a surface (lower surface) and a back surface (upper surface), X-rays are incident on the surface (lower surface) from the right and left directions at an incident angle that becomes a diffraction condition, and two XRT images, a right-eye image and a left-eye image, are obtained on the back surface (upper surface); a positioning step of performing positioning on the two obtained XRT images with respect to the defect position on the surface of the surface; and a defect position determination step of determining other defect positions in different depth directions of the wafer based on the deviation between the right-eye image and the left-eye image. Thus, the defect positions on the back surface (upper surface) in different depth directions of the wafer can be determined.

[0056] If it is such a method for evaluating the defect position in the depth direction of a wafer, for the defects on the surface where positioning has been performed, the right-eye image and the left-eye image are the same, but for the defects on the back surface different from the surface where positioning has been performed, the right-eye image and the left-eye image deviate. Based on this deviation, defects with different positions in the depth direction can be determined. If it is such a method, only two images need to be obtained in the normal usage mode of the X-ray topograph (XRT), and the measurement can be performed in a short time. Since special usage modes such as enhanced synchrotron radiation and narrowed measurement regions are not adopted, it is universal. As a result, the defect position in the depth direction of the wafer can be evaluated by a very simple method.

[0057] In addition, regarding the defect position in the depth direction of the wafer, the surface and the back surface have been described, but the inside of the wafer can also be observed.

[0058] In addition, as a defect position judgment step, the right-eye image in the two obtained XRT images is subjected to black-and-white inversion and synthesized with the left-eye image, and the circular defect position on the back surface (upper surface) can be determined.

[0059] In the case of such a defect position determination process, since the defect position can be accurately determined based on the difference in the color of white or black, it can be suitably applied to the evaluation method of the defect position in the depth direction of the wafer.

[0060] Hereinafter, regarding other embodiments of the present invention, reference will be made to Figure 3 for description.

[0061] In the case where the device is restricted and the X-ray generator and detector cannot be operated to the inverted position, as Figure 3 shown, the right-eye image and the left-eye image can be obtained.

[0062] 1. Irradiate X-rays from the right direction to obtain a right-eye image.

[0063] 2. Rotate the wafer 180 degrees and irradiate X-rays from the right direction at the same angle to obtain an image. In Figure 3 it shows the case where when the wafer marked with A and B is rotated 180 degrees, it becomes left-right inverted.

[0064] 3. Acquisition of the left-eye image.

[0065] By rotating the image obtained in the above step 2 by 180 degrees, it becomes the same as the X-ray topography image obtained by irradiating from the left direction without rotating the wafer.

[0066] In this embodiment, either the X-ray topography images of the obtained right-eye image and left-eye image are subjected to white-black inversion and overlapped, whereby the deviation of the defect position, that is, the defect located on the surface, can be made to appear.

[0067] As described above, in the evaluation method of the defect position in the depth direction of the wafer according to this embodiment, in the method of irradiating X-rays from the right direction and the left direction to the surface at an incident angle that becomes the diffraction condition, the following steps are shown: fixing the incident angle to the right direction, irradiating X-rays to obtain an XRT image (right-eye image), then rotating the wafer 180 degrees, irradiating X-rays to obtain an XRT image in the other direction, and rotating the obtained image by 180 degrees, thereby obtaining two XRT images, namely the right-eye image and the left-eye image.

[0068] If it is such a method, even without operating the X-ray generator and detector, the XRT images in the right direction and the left direction can be easily obtained, so the defect position in the depth direction of the wafer can be evaluated by a very simple method.

[0069] In addition, in the present embodiment, the acquired right-eye image and left-eye image are captured as one image, so that observation can also be performed in a stereoscopic view (3D image), and thus it is possible to easily distinguish surface defects and backside defects.

[0070] In addition, in principle, the defect positions on the irradiation surface of the X-ray are made to coincide, and only the surface defects on the opposite side of the irradiation surface of the X-ray are evaluated based on the deviation of the positions of the surface defects on the opposite side of the irradiation surface of the X-ray. Moreover, if the defect positions on the surface on the opposite side of the irradiation surface of the X-ray are made to coincide, then due to the deviation of the defect positions on the irradiation surface of the X-ray, it is also possible to evaluate only the defects on the irradiation surface of the X-ray.

[0071] Hereinafter, regarding other embodiments of the present invention, reference is made to Figure 4 for description.

[0072] As another method, by stereoscopically observing the two images, a stereoscopic image of the defect can also be obtained. The right-eye image and left-eye image obtained by the same method as in the foregoing embodiment (X-rays are incident on the surface from the right and left directions at incident angles that satisfy the diffraction condition, and two XRT images, namely the right-eye image and left-eye image, are acquired on the backside) are observed with the right eye and left eye respectively, and by means of stereoscopic observation, methods such as 3D glasses, it is possible to see the defects located on the surface emerging. Figure 4 In this case, circular defects on the backside (upper surface) of the wafer can be seen emerging.

[0073] As described above, the method for evaluating the defect position in the depth direction of the wafer according to the present embodiment discloses a method for evaluating the defect position in the depth direction of a wafer, wherein the wafer has a surface and a backside, X-rays are incident on the surface from the right and left directions at incident angles that satisfy the diffraction condition, two XRT images, namely the right-eye image and left-eye image, are acquired on the backside, and the two XRT images are captured as one image by visual observation, so as to observe the defect position in the depth direction in a stereoscopic view (3D image).

[0074] If it is a method for evaluating the defect position in the depth direction of such a wafer, when visually capturing two XRT images as one image, if there are defects with different positions in the depth direction, since the deviation between the two images allows for a three-dimensional observation, it is possible to determine, based on this three-dimensional observation, defects with different positions in the depth direction (circular defects on the back surface (upper surface)). If it is such a method, it is only necessary to obtain two images in the normal usage mode of an X-ray topographer (XRT), and the measurement can be carried out in a short time. Since it does not adopt special usage modes such as enhanced synchrotron radiation and narrowed measurement areas, it is universal. Moreover, since the evaluation of the defect position is carried out visually, there is no need to separately prepare an evaluation device, etc. As a result, it is possible to evaluate the defect position in the depth direction of the wafer in an extremely simple method.

[0075] In addition, the present invention is not limited to silicon wafers, and can also be applied to SiC wafers and silicon wafers on which devices are formed.

[0076] In the case of SiC wafers, there may be a situation where the crystal defects are intricate inside the crystal, and the present invention can confirm this situation. In addition, in a silicon wafer on which devices are formed, surface defects directly affect the device yield, so it is possible to use XRT to evaluate only the surface defects rather than the entire depth direction.

[0077] Furthermore, regarding these wafers, it is effective when wanting to know the three-dimensional structure of the defects in the wafer.

[0078] Examples

[0079] Hereinafter, regarding the results after actually carrying out the trial production evaluation, it will be specifically described using photos, drawings, etc.

[0080] (Example 1)

[0081] First, a carbon film was grown by vapor phase on the upper surface of a silicon wafer with a plane orientation of (100). The damage formed on the back side due to this operation was evaluated.

[0082] Taking the surface side as the X-ray irradiation surface, XRT measurement was carried out by incident X-rays from the Figure 6 direction shown in (1). At this time, in order to carry out the measurement under the (400) diffraction condition, the incident angle was set to 74.86°.

[0083] Since the X-ray generator of the device used this time could not be moved to the position in the (2) direction, the wafer was rotated 180 degrees, and XRT measurement was carried out again by incident X-rays from the (1) direction. Then, the second measurement result was rotated 180 degrees to set it to the same positional relationship as the first measurement. The image obtained from the (1) direction was set as the right-eye image, and the image obtained from the (2) direction was set as the left-eye image.Figure 7 This shows an example of an overlapping image obtained by reversing the black and white of one of the two sides. In this case, the positions of the surface defects are made to coincide. The linear crack defects visible as surface defects cancel each other out and become invisible, and it can be shown that only the contact damage on the back surface remains.

[0084] (Example 2)

[0085] In addition, as Figure 8 shown, by capturing the left-eye image and the right-eye image with the dots overlapping as one image, it is also possible to observe visually based on a stereoscopic view (3D image). By this method, the depth information of the defect can also be obtained.

[0086] Figure 8 The image of Figure 7 is the same as the image shown, but by attempting to overlap the dots on the image, stereoscopic observation can be performed. This data is the result of the case where there are defects on the front and back surfaces of a silicon wafer. However, like the slip in silicon crystals and the defects in SiC, not only on the front and back surfaces of the crystal, but also when defects occur inside, by this method based on a stereoscopic view (3D image), since the intermediate defects in the bulk crystal can also be known, it is more effective.

[0087] Furthermore, examples considered effective for stereoscopic observation are supplemented.

[0088] Figure 9 A schematic diagram showing the case where the defect penetrates from the wafer surface to the back surface and an example of stereoscopic observation.

[0089] Figure 10 This is an example of the case where there are complex dislocations inside the crystal. For Figure 9 , Figure 10 such cases, by the method of confirming through stereoscopic observation, it is easier to grasp the overall image of the defect.

[0090] In addition, the present invention is not limited to the above-described embodiments. The above-described embodiments are illustrative, and any solution having a structure substantially the same as the technical idea described in the claims of the present invention and achieving the same effects is included in the technical scope of the present invention.

Claims

1. A method for evaluating the defect position in the depth direction of a wafer, which is a method for evaluating the defect position in the depth direction of a wafer by using an X-ray topographer (XRT). Characterized in that it includes a process of obtaining XRT images, wherein the wafer has a front surface and a back surface, X-rays are incident on the front surface from the right direction and the left direction at an incident angle that satisfies the diffraction condition, and two XRT images, namely a right-eye image and a left-eye image, are obtained on the back surface; a positioning process, in which, for the two obtained XRT images, positioning is performed based on the defect position on either the front surface or the back surface; and a defect position determination process, in which other defect positions in different depth directions of the wafer are determined based on the deviation between the right-eye image and the left-eye image.

2. The method for evaluating the defect position in the depth direction of a wafer according to claim 1, characterized in that the method of incident X-rays on the front surface from the right direction and the left direction at an incident angle that satisfies the diffraction condition is: fixing the incident angle in either the right direction or the left direction, incident X-rays to obtain an XRT image, then rotating the wafer by 180 degrees, and incident X-rays to obtain an XRT image in the other direction, thereby obtaining the two XRT images, namely the right-eye image and the left-eye image.

3. The method for evaluating the defect position in the depth direction of a wafer according to claim 1 or 2, characterized in that in the defect position determination process, determination is performed by performing black-and-white inversion on any one of the two obtained XRT images and then synthesizing them.

4. A method for evaluating the defect position in the depth direction of a wafer, which is a method for evaluating the defect position in the depth direction of a wafer by using an X-ray topographer (XRT). Characterized in that the wafer has a front surface and a back surface, X-rays are incident on the front surface from the right direction and the left direction at an incident angle that satisfies the diffraction condition, two XRT images, namely a right-eye image and a left-eye image, are obtained on the back surface, and the two XRT images are captured as one image by visual inspection, so as to observe the defect position in the depth direction in a stereoscopic view (3D image).

5. The method for evaluating the defect position in the depth direction of a wafer according to claim 1 or 4, characterized in that the wafer is at least one of a single-crystal wafer and a wafer formed with devices.

Images