JP5418461B2 - Substrate inspection method and substrate inspection apparatus - Google Patents

Description

  The present invention relates to a substrate inspection method and a substrate inspection apparatus, and more particularly, to a substrate inspection method capable of detecting a foreign matter adhering to the surface of a substrate or a defect included in the substrate as an abnormal portion, and this method. The present invention relates to a substrate inspection apparatus used.

  In addition to semiconductor substrates used in semiconductor devices and solar cells, glass substrates used in hard disks and liquid crystal display devices, etc., not only foreign substances attached to the surface, but also scratches and substrates attached by external factors It is inspected for defects such as dislocations. This is extremely important for improving the yield in the manufacture of various devices and equipment, and improving the quality of products, and inspecting the substrate on a daily basis in various manufacturing fields and processes. Has been done.

  As described above, as a method of inspecting the foreign matter attached to the substrate and various defects included in the substrate, the surface of the substrate is irradiated with predetermined light and the obtained reflected light is processed, A method for optically detecting a portion having a defect has been proposed.

  For example, the silicon substrate can be obtained by approximating the shape of the target defect with an ellipsoid so as to obtain a dipole moment generated in an asymmetric defect other than a sphere, and processing scattered light based on Rayleigh scattering. A method of accurately measuring the size and density of defects contained in a crystal forming a crystal (see Patent Document 1), or irradiating a substrate with light of a plurality of wavelengths, and detecting with a signal of one wavelength A method of accurately acquiring information derived from defects by comparing the defect distribution in the substrate surface with the distribution of haze signals due to the influence of the lattice distortion or crystal arrangement on the substrate surface due to other wavelengths (see Patent Document 2) ) Etc. are known. In addition, when irradiating p-polarized light to an X-ray exposure mask with an organic film on the surface, the incident angle is set to Brewster's angle, so that the presence of foreign matter can be detected from the presence or absence of scattered light. A detection method (see Patent Document 3) is also known.

  In any of these methods, an abnormal portion of the substrate is detected by irradiating the surface of the substrate with predetermined light and measuring the obtained reflected light or performing a specific process. . However, if the surface of the substrate to be inspected is perfectly flat and in an ideal state, there is no particular problem with these inspection methods. However, in actual substrates, there are some warping and undulations. In some cases, an abnormal part is erroneously detected or an original abnormal part cannot be detected.

  Therefore, in order to cope with such a problem, the first scattered light is detected by irradiating the surface of the substrate with the first laser light while rotating the substrate and moving the substrate in the horizontal direction. By irradiating the second laser beam and detecting the second scattered light, the scattered light from the substrate and the specularly reflected light are detected at the same time, reducing the influence of undulation and local undulation of the entire substrate. Thus, a method has been proposed in which the signal level of a defect can be detected (see Patent Document 4). However, in this method, for the detected regular reflection light, the average value of the detected light amount with respect to the specific detection angle is obtained, and the signal waveform obtained by the average value processing is further processed to obtain a signal waveform having undulation information. Generates and thresholds the signal waveform with this undulation information and performs waveform division processing in several stages, and it is necessary to move the substrate horizontally while rotating the substrate. Since the entire surface of the substrate is scanned by irradiating each laser beam, a huge amount of data is required to be processed or a long time is required for the inspection.

JP 2001-272340 A JP 2001-91451 A JP-A-1-185434 JP 2008-268189 A

  In recent years, as the size of semiconductor substrates and glass substrates has increased, the effects of warpage and undulation have become more prominent. Even if the substrate has warpage or undulation, it is possible to accurately and easily detect abnormal locations. There is a need for a method for inspecting a substrate that can be used.

  The present invention has been made in view of the above circumstances, and it is possible to accurately and easily detect a place with foreign matter adhesion or a defect as an abnormal place while considering the influence of warpage or swell provided on the substrate. An object of the present invention is to provide a method for inspecting a substrate.

  It is another object of the present invention to provide a substrate inspection apparatus that can detect a part having a foreign substance or a defect as an abnormal part while using the above method.

As a result of earnestly examining the means for solving the above problems, the present inventors have radiated p-polarized light onto the surface of the substrate to obtain a substrate image from the specular reflection light. Incident in-plane scanning that changes the incident angle within a predetermined angle range d including the theoretical Brewster angle θ _B and the substrate tilted within a predetermined inclination angle range φ around the line where the incident surface and the substrate intersect The present inventors have found that an abnormal part of a substrate can be detected accurately and simply by combining it with tilt scanning.
That is, the gist of the present invention is as follows.

(1) A substrate image having pixels corresponding to divided small regions obtained by dividing the surface of the substrate into a plurality of small regions is obtained from specular reflection light obtained by irradiating the surface of the substrate with p-polarized light. And, based on the substrate image, is a method for inspecting a substrate for detecting a location having a foreign matter adhesion or a defect as an abnormal location,
i) In the plane of incidence of p-polarized light including the diameter of the substrate, the angle of incidence of p-polarized light relative to the surface of the substrate is relative within a predetermined angle range d including the theoretical Brewster angle θ _B of the substrate. In-plane scanning to be changed automatically,
ii) tilt scanning in which the substrate is relatively tilted within a predetermined tilt angle range φ around the line where the incident surface and the substrate intersect as a central axis;
In combination with each other, changing the incident angle of the p-polarized light to the surface of the substrate and the incident direction of the p-polarized light to the surface of the substrate, respectively,
When p-polarized light is actually incident on the divided small area of the substrate surface at the Brewster angle θ _B and the corresponding pixel light amount is zero, the pixel light amount is once in the entire substrate image obtained above. A method for inspecting a substrate, comprising detecting a divided small region that does not become zero as an abnormal portion of the substrate.

(2) The angle range d of the in-plane scanning is at least d = θ _B ± α on the basis of the theoretical Brewster angle θ _B in consideration of the maximum inclination angle α due to warpage and swell of the substrate. The method for inspecting a substrate as described in (1) above, wherein the range is included.

(3) The tilt scanning is performed in a tilt angle range φ of −0.5 ° or more and + 0.5 ° or less, where the tilt angle when the incident surface and the substrate intersect perpendicularly is 0 °. (1) The inspection method of the board | substrate as described in (2).

(4) The in-plane scanning is performed at an angular interval of 0.01 ° to 0.5 °, and the inclined scanning is performed at an inclination angle interval of 0.01 ° to 0.5 °. The substrate inspection method according to any one of (1) to (3) above.

(5) Irradiation means for irradiating the surface of the substrate with p-polarized light and the substrate are mounted, and the incident angle of the p-polarized light and the incident direction of the p-polarized light are relatively changed. A substrate holding means capable of acquiring the substrate image having pixels corresponding to the divided small areas obtained by dividing the surface of the substrate into a plurality of small areas from the obtained specular reflection light, and A substrate inspection apparatus comprising an image processing means capable of processing a substrate image and detecting a portion having a foreign matter adhesion or a defect as an abnormal portion of the substrate,
By changing the incident angle of the p-polarized light irradiated from the irradiation means and the incident direction of the p-polarized light by the substrate holding means,
i) The incident angle of the p-polarized light with respect to the surface of the substrate within a predetermined angle range d including the theoretical Brewster angle θ _B of the substrate within the plane of incidence of the p-polarized light including the diameter of the substrate. Changing incident in-plane scanning;
ii) tilt scanning in which the substrate is tilted within a predetermined tilt angle range φ around a line where the incident surface and the substrate intersect as a central axis;
Each board image is acquired by the image acquisition means,
When the p-polarized light is actually incident at the Brewster angle θ _B on the divided small areas on the substrate surface by the image processing means, the light quantity of the corresponding pixels is processed as zero, and all the obtained above are obtained. A substrate inspection apparatus for detecting a divided small region in which a light amount of a pixel never becomes zero in a substrate image as an abnormal portion of the substrate.

(6) The substrate holder is a substrate holder capable of tilting the placed substrate in an arbitrary direction so as to rotate around two orthogonal axes forming xy orthogonal coordinates. The substrate inspection apparatus according to (5) above.

According to the present invention, when the light of p-polarized light is incident at Brewster angle theta _B, by utilizing the fact that reflected light from the substrate is zero, while considering warpage or waviness included in the substrate, theoretically a scanning plane of incidence of changing the incident angle in an angular range including the Brewster angle theta _B of inclination scanning and for in the central axis line entrance surface and the substrate intersects tilting the substrate at a predetermined inclination angle range φ By combining these, even if the substrate has warpage or undulation, an abnormal portion of the substrate can be detected accurately and simply.

FIG. 1 is a schematic perspective view showing a relationship between irradiation of p-polarized light and a substrate in the inspection method of the present invention. FIG. 2 is a substrate side view for schematically explaining the relationship between the incident angle of p-polarized light and the Brewster angle θ _{B on} the surface of the substrate. FIG. 3 is a plan view schematically illustrating the state of the substrate image. FIG. 4 is a side view schematically illustrating the inspection apparatus of the present invention. FIG. 5 is a schematic plan view for explaining the operation of inclining the substrate in the substrate holding means of the inspection apparatus.

Hereinafter, the present invention will be described in detail.
In the present invention, the surface of the substrate is irradiated with p-polarized light, and the substrate image is acquired from the specular reflection light (regular reflection light). In order to irradiate the surface of the substrate with p-polarized light, for example, a known light source and a polarizer may be used. In this case, the light source is not particularly limited, but preferably the entire surface of the substrate to be inspected. It is preferable to use one that can emit p-polarized light at a time.

In the present invention, as shown in FIG. 1, a predetermined value including the theoretical Brewster angle θ _B of the substrate 1 to be inspected in the incident surface 4 of the p-polarized light 2 including the diameter 1 a of the substrate 1. In this angle range d, “i) In-plane scanning” is performed to change the incident angle θ of the p-polarized light 2. Normally, the reflectance of p-polarized light decreases as the incident angle increases, eventually becoming 0 (zero), and then increasing again. The incident angle of Brewster's angle (Brewster's angle) θ _B when this reflectance is zero, Brewster angle theta _B is refraction of the material of the incidence side index n ₁ and the permeate side material refractive index of n ₂ From the above, it can be obtained by the following equation (1). In the present invention, the Brewster angle θ _B obtained from the equation (1) is referred to as a theoretical Brewster angle θ _B of the substrate to be inspected. As shown in Table 1, for example, the refractive index of quartz is 1.54, and if p-polarized light is incident on the quartz substrate from the atmospheric pressure air (refractive index 1.0) side, it is theoretical. The Brewster angle θ _B is 57.00 °. Similarly, the refractive index of silicon carbide (SiC) is 2.65, and when the p-polarized light is incident on the SiC substrate from the air side, the theoretical Brewster angle θ _B is 69.33 °. Become.

  By the way, for example, a substrate that is cut out from an ingot and finished by mirror finishing, such as a SiC substrate, is generally accompanied by warpage or undulation due to internal stress, processing stress, or the like that the ingot has. The same applies to other substrates such as glass substrates, and it is practically difficult to finish the entire surface of the substrate to a completely flat surface, and due to processing stress etc., the substrate is warped or wavy. Will exist. In particular, in recent years, since various substrates have been increased in size, it is difficult to produce a completely flat substrate without warping or undulation.

Therefore, in the present invention, the in-plane scanning is performed to relatively change the incident angle of the p-polarized light with respect to the surface of the substrate. Preferably, the predetermined angle range d to be changed by this in-plane scanning is preferably It is preferable to include a maximum inclination angle α formed on the surface of the substrate by warping or undulation, and more preferably, the angle range d is at least based on the theoretical Brewster angle θ _B (center). It is preferable to include a range of d = θ _B ± α. This point will be described with reference to the schematic diagram shown in FIG. 2. The p-polarized light 2 incident at the theoretical Brewster angle θ _B is not reflected on an ideal flat surface, but is warped or waved. In some places, this relationship does not hold, and a part of the incident light 2 is reflected. Therefore, with respect to an ideal flat surface, the angle α having the largest inclination angle among the inclinations formed by warping and undulation is used, and at least in the range of d = θ _B ± α. By performing scanning, it is possible to prevent erroneous detection of abnormal parts on the entire surface of the substrate.

  Further, in the present invention, as shown in FIG. 1, "ii) tilt scanning" in which the substrate is relatively tilted within a predetermined tilt angle range φ with the line where the incident surface 4 and the substrate 1 intersect as the central axis 1b. (That is, scanning that rotates around a line (axis) formed by the incident surface and the substrate surface). Formed on the substrate by performing “i) In-plane scanning” with the tilt angle range φ of “ii) tilt scan” centered on the central axis 1b including the maximum tilt angle α formed by warping and undulation. The entire surface of the substrate can be inspected while taking into account all warpage and undulations, including local irregularities.

However, in the case of a substrate cut out from an ingot such as a SiC substrate or a Si substrate, since the surface is cut out to be flat, the degree of local unevenness is small, and the surface becomes a mirror surface after cutting out. Since the polishing is performed, the inclination angle formed by warping or waviness is also about ± 0.5 ° at the maximum. Furthermore, in the inspection of these semiconductor substrates, the abnormality that should actually be detected is mainly crystal defects such as pits and micropipe defects, and adhesion of foreign matters such as particles, and the crystal defects are minute. In addition, the size of particles and the like is about several microns at most. In addition, when the theoretical Brewster angle θ _B is taken into consideration, the above-described inclined scanning is centered on the central axis 1b in detecting microscopic abnormal portions of the semiconductor substrate. It is preferable to perform the inclination angle range φ within a range of about ± 2 °, and more preferably, the inclination angle range φ is within a range of ± 0.5 °. Note that the tilt angle range φ of this tilt scan is such that the tilt angle when the incident surface 4 and the substrate 1 intersect perpendicularly is 0 °.

In the present invention, the above-mentioned “i) In-plane scanning” and “ii) Inclined scanning” are combined, and the incident angle θ of the p-polarized light 2 with respect to the surface of the substrate 1 and the p-polarized light with respect to the surface of the substrate. The substrate image is acquired from each specular reflection light while changing the incident direction of the light 2. At this time, as shown in FIG. 3A, the surface of the substrate to be inspected is divided into a plurality of small regions, and a substrate image 5n having pixels corresponding to the divided small regions 1c is obtained. . Here, the light of p-polarized light incident at the Brewster angle theta _B of theoretical, if equivalent to the actual Brewster angle theta _B, in principle, since the reflection is eliminated at the divided small regions 1c, the substrate image In 5n, the light quantity of the pixel corresponding to the divided small area is regarded as zero (1c-1 in FIG. 3A). However, if a foreign substance such as a particle adheres to the divided small area or has a defect such as a pit, reflected light is observed, and the light quantity of the corresponding pixel does not become zero (FIG. 3). (a) 1c-2). On the other hand, if it is a portion corresponding to warping or undulation, the Brewster angle θ _B is not actually reached, so that the reflected light is also observed, and the light quantity of the pixel corresponding to the divided small area does not become zero.

  Therefore, in all the substrate images obtained by combining “i) In-plane scanning” and “ii) Inclined scanning, a divided small region where the light quantity of the pixel never becomes zero is detected as an abnormal portion of the substrate. . For example, FIG. 3B is an example of another inspection image 5n on the same inspection board as the substrate image 5n shown in FIG. 3A (the direction of the image is the same), and the reflected light in FIG. Since the amount of light is zero in some of the pixels in which detection is detected, it can be determined that the divided small areas corresponding to these pixels correspond to the portions of warpage and swell provided in the substrate. Then, in all the substrate images, a pixel whose light amount never becomes zero is determined as a divided small region having a foreign matter attached or a defect such as a pit. In the substrate image 5n shown in FIG. 3, for the sake of convenience, a pixel having no reflection from the divided small area of the substrate and having a light quantity of zero is represented by a white cell 1c-1, and the reflected light is observed and the light quantity is observed. Pixels that do not become zero are represented by black cells 1c-2.

The total number of substrate images is determined by a combination of “i) In-plane scanning” and “ii) Inclined scanning”. Specifically, it is determined by the angle interval and angle range d of the in-plane scanning and the inclination angle interval and inclination angle range φ of the inclined scanning. Here, the angle interval of the in-plane scanning and the inclination angle interval of the inclined scanning are not particularly limited, and are determined by the accuracy required for detecting the abnormal part, the capacity of the image acquiring means for acquiring the substrate image, and the like. However, it is preferable that the angle interval of the in-plane scanning and the inclination angle interval of the inclined scanning are each preferably 0.01 ° to 0.5 °. For example, when inspecting a SiC substrate having warpage or undulation with a maximum inclination angle α = 0.5 °, an angular range of ± 0.5 ° centered on the theoretical Brewster angle θ _B = 69.33 ° In-plane scanning of all 101 stages of d is performed at an angular interval of 0.01 °, and from −0.5 ° at an inclination angle interval of 0.01 ° with the line intersecting the incident surface and the substrate as the central axis. A total of 101 × 101 substrate images can be obtained by combining the in-plane scanning and the tilt scanning by performing 101 tilt scans in the tilt angle range φ up to + 0.5 °.

  The inspection method of the present invention is not limited by the type or shape of the material constituting the substrate, and as the substrate to be inspected, for example, SiC, Si, quartz, single crystal including sapphire, polycrystal, In addition to an amorphous semiconductor substrate, a glass substrate, various plastic substrates, and the like can be given, and other materials can also be applied. However, a substrate made of a material having a single refractive index is desirable because it may not be detected correctly if materials having different refractive indexes are mixed or bonded together. In addition, examples of abnormalities that can be detected by the inspection method of the present invention include adhesion of foreign matters such as particles, scratches caused by external factors, and defects such as pits included in the substrate itself. It is done. For example, in the case of a SiC single crystal substrate, it is possible to detect micropipes, polishing flaws, scratches, voids, triangular defects caused by crystal defects included in the substrate itself, and the like.

  In order to inspect a substrate using the substrate inspection method of the present invention, for example, an inspection apparatus having the following configuration example can be used. That is, as shown in FIG. 4, the irradiation means 8 for irradiating the surface of the substrate 1 with the p-polarized light 2 and the substrate 1 are mounted, and the incident angle of the p-polarized light 2 and the incident direction thereof. The substrate holding means 10 capable of relatively changing the image, the image obtaining means 9 for obtaining a substrate image from the obtained specular reflected light 3, and processing the obtained substrate image The substrate inspection apparatus includes the image processing unit 11 that can detect the detected portion as an abnormal portion of the substrate.

  Here, as the irradiation means 8 for irradiating the p-polarized light 2, as described above, a known light source 6 and polarizer 7 can be used. The image acquisition means 9 preferably includes a device that can capture a substrate image, such as a CCD (Charge Coupled Device) camera, and a device that can store the captured substrate image, such as a hard disk or memory. It is. At that time, since the number of pixels of the CCD camera or the like determines the number and size of the divided small areas on the substrate surface, it is preferable to use a photographing apparatus having at least 1,000 × 1,000 pixels.

Further, the substrate holding means 10 changes the incident angle and the incident direction of the p-polarized light so that the in-plane scanning (rotational scanning around the y axis) of the mounted substrate intersects the incident surface and the substrate. Can be used as long as it can perform tilt scanning (rotational scanning around the x-axis) that tilts the substrate around the center axis, and preferably tilts the entire substrate mounted on the mounting surface. A substrate holder provided with a mechanism or a substrate holder provided with a rotation mechanism capable of rotating the substrate is desirable. In particular, a semiconductor substrate cut out from an ingot, such as a SiC substrate or a Si substrate, can be sufficiently inspected even when the tilt angle range φ in tilt scan is within ± 0.5 ° as described above. When inspecting these semiconductor substrates, as shown in FIG. 4 and FIG. 5, each of the two predetermined axes around two orthogonal axes (x, y) forming xy orthogonal coordinates on the substrate surface is predetermined. It is preferable to use a substrate holder that can be rotated within the range of 2 and can tilt the mounted substrate arbitrarily. That is, in the substrate holder 10 shown in these drawings, the in-plane scanning is performed by inclining the substrate 1 within a predetermined angle range d including the theoretical Brewster angle θ _B around the y-axis, By tilting the substrate 1 with the x axis as the rotation axis, tilt scanning can be performed at a tilt angle range φ of at least ± 0.5 °.

Then, the substrate images obtained by the image acquisition means by combining the in-plane scanning and the inclination scanning are processed by the image processing means composed of arithmetic processing equipment such as a computer, and the portion having the adhesion of foreign matter or a defect is substrate. Detect as an abnormal part of That is, when p-polarized light is actually incident at a Brewster angle θ _B on a divided small region of the substrate surface, the light amount of the corresponding pixel in the substrate image is processed as zero, and A divided small area where the light intensity never becomes zero is detected as an abnormal part. At this time, every time the substrate image is taken by the image acquisition means, the light amount of the pixel corresponding to each divided small region is assigned with the minimum value, and the light amount is finally determined in the reconstructed substrate image. A location other than zero may be detected as an abnormal location.

  Hereinafter, the present invention will be described in more detail based on examples and the like. The present invention is not limited to the following contents.

  A 4H polytype SiC single crystal substrate having a diameter of 100 mm was evaluated by the method of the present invention using an apparatus as shown in FIG. The light source 6 was a light source in which a sodium lamp was collimated by a collimator, and the SiC substrate was irradiated with light that was made p-polarized by the polarizer 7. The SiC substrate was placed on the sample table 10 and fixed so as not to move on the sample table 10 by a vacuum chuck from the back surface.

The SiC substrate is a substrate that is cut out from a 4H single crystal ingot using a wire saw to a thickness of 1 mm and then polished using diamond abrasive grains until the surface becomes a mirror surface. Therefore, the surface looks completely flat by visual observation, but there is a warp / swell of about 9 μm over the entire 100 mm diameter. The reflected image data is obtained while changing the incident angle by rotating the substrate about the y-axis on the sample stage 10 which can be rotated together with the respective substrates about two orthogonal axes (x, y). I got it. The incident angle was changed from 68.83 ° to 69.93 ° in 0.01 ° increments (“i) In-plane scanning”). This corresponds to the meaning of correcting the fine warp / waviness in the x-axis direction of the substrate and obtaining the reflection image data corresponding to the Brewster angle θ _B. In addition to the rotational scanning around the y-axis, the measurement was performed while rotating around the x-axis in the range of -0.5 ° to + 0.5 ° in increments of 0.01 ° (“ii) Inclined scanning”) . This corresponds to absorbing a measurement error from the Brewster angle θ _B due to fine warping and waviness in the y-axis direction of the substrate. The rotational scanning around the x axis was centered at the position (0 °) where the incident surface of the p-polarized light and the SiC substrate intersect perpendicularly. In this substrate, there is a warp / swell of about 9 μm over the entire diameter of 100 mm, but the slope is greater than (9 μm) / (100 mm) where the slope is maximum. However, with this substrate that has been mirror-polished, the inclination is not so great and is at most (9 μm) / (10 mm), so the maximum inclination angle α is about arctan (9 μ / 10 mm) = 0.052 °. . Therefore, if i) In-plane scanning and ii) Inclined scanning are performed within the range of ± 0.5 °, which is one digit higher than that, it is possible to correct warpage and undulation of the entire substrate with a margin.

  As described above, 101 × 101 pieces of data were acquired around the x axis and the y axis, respectively. Each piece of data was captured and recorded by the image acquisition means 9. The image acquisition means 9 includes a 10 million pixel CCD camera, and 10 million pixel data can be obtained. For each pixel, 101 × 101 pieces of data are captured while scanning around the x axis and the y axis, but the pixel data is rewritten only when the amount of light is smaller than the pixel data during the scanning process. Employs logic. The purpose of this is to prevent the harmful effects of recording a large amount of storage capacity when 101 × 101 data is recorded for all 10 million pixels.

  Using the acquired image data of 10 million pixels, the image processing means 11 was used to evaluate the surface state of the entire SiC substrate having a diameter of 100 mm. Here, one pixel corresponds to an area of 0.3 mm × 0.3 mm on the substrate surface. There was no reflected light in almost the entire area of the SiC substrate, and no foreign matter or defect was detected in most areas with a spatial resolution of 0.3 mm × 0.3 mm. However, in the region 2 mm from the edge of the peripheral part of the substrate, a large number of pixels in which reflected light is recognized were detected. Since a total of 23 foreign matters or defects were detected, micropipe defects were observed when the corresponding portions were observed with an optical microscope after the main measurement.

  In this measurement, in order to improve the spatial resolution, a part of a SiC substrate having a diameter of 100 mm was enlarged, and image data was acquired by the image acquisition means 9. Specifically, the image acquisition means 9 acquired data by enlarging a central 5 mm square area of a SiC substrate having a diameter of 100 mm. At that time, since a region of 0.0016 mm × 0.0016 mm corresponds to one pixel, the spatial resolution is 2 μm (˜0.0016 mm). When data of a 5 mm square area was analyzed using the image processing means 11, 14 foreign matters or defects were detected. After this measurement, when the corresponding part was observed with an optical microscope, no defect could be observed, but foreign matter (dust) was observed.

  Therefore, the SiC substrate was washed again, and the central 5 mm square region of the substrate was evaluated again in this measurement. Although the same part is not measured before and after cleaning, it can be estimated that the measurement part is close by the data at the center of the substrate twice. As a result of the evaluation by this measurement after cleaning, the number of foreign matters or defects was reduced to three, so that it was estimated that there was a cleaning effect.

1: substrate 2: p-polarized light 3: reflected light 4: incident surface 5 n: substrate image 6: light source 7: polarizer 8: irradiation means 9: image acquisition means 10: substrate holding means 11: image processing means

Claims (6)

A substrate image having pixels corresponding to divided small regions obtained by dividing the surface of the substrate into a plurality of small regions is obtained from specular reflection light obtained by irradiating the surface of the substrate with p-polarized light; Based on the substrate image, it is a method for inspecting a substrate for detecting a part having a foreign matter adhesion or a defect as an abnormal part,
i) In the plane of incidence of p-polarized light including the diameter of the substrate, the angle of incidence of p-polarized light relative to the surface of the substrate is relative within a predetermined angle range d including the theoretical Brewster angle θ _B of the substrate. In-plane scanning to be changed automatically,
ii) tilt scanning in which the substrate is relatively tilted within a predetermined tilt angle range φ around the line where the incident surface and the substrate intersect as a central axis;
In combination with each other, changing the incident angle of the p-polarized light to the surface of the substrate and the incident direction of the p-polarized light to the surface of the substrate, respectively,
When p-polarized light is actually incident on the divided small area of the substrate surface at the Brewster angle θ _B and the corresponding pixel light amount is zero, the pixel light amount is once in the entire substrate image obtained above. A method for inspecting a substrate, comprising detecting a divided small region that does not become zero as an abnormal portion of the substrate. The angle range d of the in-plane scanning is at least d = θ _B ± α with respect to the theoretical Brewster angle θ _B in consideration of the maximum inclination angle α due to warpage and undulation provided on the substrate. The substrate inspection method according to claim 1, wherein the substrate inspection method is included.   2. The tilt scan is performed in a tilt angle range φ of −0.5 ° or more and + 0.5 ° or less, where the tilt angle when the incident surface and the substrate intersect perpendicularly is 0 °. 3. The substrate inspection method according to 2.   The in-plane scanning is performed at an angular interval of 0.01 ° to 0.5 °, and the inclined scanning is performed at an inclination angle interval of 0.01 ° to 0.5 °. The inspection method of the board | substrate in any one of 1-3. An irradiation means for irradiating the surface of the substrate with p-polarized light and the substrate can be placed, and the incident angle of the p-polarized light and the incident direction of the p-polarized light can be relatively changed. A substrate holding means, an image acquisition means for acquiring a substrate image having pixels corresponding to the divided small areas obtained by dividing the surface of the substrate into a plurality of small areas from the obtained specular reflection light, and the acquired substrate image An inspection apparatus for a substrate provided with image processing means capable of detecting and detecting a place having a foreign substance adhesion or a defect as an abnormal portion of the substrate,
By changing the incident angle of the p-polarized light irradiated from the irradiation means and the incident direction of the p-polarized light by the substrate holding means,
i) The incident angle of the p-polarized light with respect to the surface of the substrate within a predetermined angle range d including the theoretical Brewster angle θ _B of the substrate within the plane of incidence of the p-polarized light including the diameter of the substrate. Changing incident in-plane scanning;
ii) tilt scanning in which the substrate is tilted within a predetermined tilt angle range φ around a line where the incident surface and the substrate intersect as a central axis;
Each board image is acquired by the image acquisition means,
When the p-polarized light is actually incident at the Brewster angle θ _B on the divided small areas on the substrate surface by the image processing means, the light quantity of the corresponding pixels is processed as zero, and all the obtained above are obtained. A substrate inspection apparatus for detecting a divided small region in which a light amount of a pixel never becomes zero in a substrate image as an abnormal portion of the substrate.   6. The substrate holder, wherein the substrate holding means is capable of tilting the placed substrate in an arbitrary direction so as to rotate around two orthogonal axes forming xy orthogonal coordinates. Inspection apparatus for substrates as described in 1.

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