JP3190157B2 - Crystal defect inspection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal defect inspection method for inspecting crystal defects and the like in a crystal substrate, and more particularly to a method for detecting the presence or absence of crystal defects, precipitates or foreign matter in a semiconductor substrate using a light beam. The present invention relates to a crystal defect inspection method for inspection.

[0002]

2. Description of the Related Art Conventionally, there are various methods for observing crystal defects and the like, and in particular, a method for detecting crystal defects and the like using a light beam has the advantage of being nondestructive and simple and has been widely used.

[0003] When foreign matter is present on the path of the light beam, the light beam is scattered, and the existence of minute foreign matter having a wavelength equal to or less than the wavelength of the light beam is known as a chindal phenomenon.

In a semiconductor crystal, when a light beam having a wavelength component of energy lower than the band gap is incident, the light beam travels through the crystal without being absorbed,
The light is scattered by a portion having a different refractive index from the surrounding semiconductor crystal, such as a crystal defect, a precipitate, or a foreign substance. Since the scattered light intensity increases as the intensity of the incident light increases, laser light, particularly infrared laser light, is usually used as a light source.
In addition, the distribution of scatterers that scatter light can be observed by scanning the incident light beam.

In a silicon semiconductor crystal, YAG
1.12 μm infrared light from a laser is used as a light source, and scattered light is detected by an infrared vidicon. As a scatterer that scatters light, a BMD (Bulk Micro) such as an oxygen precipitate is used.
Defect) and stacking faults are known.

FIGS. 5 to 7 schematically show the structure of a conventional crystal defect inspection method. A light beam 4 is incident on the cleavage plane 2 on the side of the silicon crystal substrate 1, and the scattered light 5 scattered by the crystal defects 4 is illuminated by the observation lens 6 of the TV camera placed above the silicon crystal substrate 1. To detect. The observation lens 6 is focused on the position of a crystal defect or the like 4 to be observed near the inside of the upper surface 7 of the silicon crystal substrate 1. The image from the observation lens 6 is captured by an image pickup tube 8 of a TV camera.
The image is formed on the image pickup surface, subjected to signal processing such as binarization and stored by the signal processor 9, and then displayed on the TV monitor 10 for observation.

Further, as shown in FIG. 6, a light beam 3 is incident on the upper surface 7 of the silicon crystal substrate 1 to
The scattered light 5 scattered by and emitted from the cleavage plane 2 is detected by the observation lens 6 of the TV camera placed above the cleavage plane 2. The observation lens 6 includes a crystal defect 4 to be observed near the inside of the cleavage plane 2 of the silicon crystal substrate 1.
The focus is on the position. Then, as in the case of FIG. 5, the image is displayed on the TV monitor 10 via the signal processor 9 and observed.

Recently, as shown in FIG. 7, a light beam 3 having a polarization plane perpendicular to the upper surface 7 of the silicon crystal substrate 1 is formed.
Is incident at a Brewster angle, and all the light beams 3 enter the crystal without causing reflection on the upper surface 7, and an infrared tomograph is reported.

[0009]

It is desirable that a silicon crystal substrate for an VLSI has no residual crystal defects which adversely affect device characteristics. At least in a range of several μm from the upper surface serving as the device active region, it is necessary to have no defect. The range of the device active region differs depending on the type of the VLSI, but is at most about 10 μm. In this range, there are some problems when trying to detect crystal defects by detecting scattered light emitted from the silicon crystal substrate.

First, in the conventional case shown in FIG. 5, there is a problem that it is extremely difficult to make the light beam 3 enter the silicon crystal substrate 1 within 10 μm from the upper surface 7 very parallel to the upper surface 7. For example, if the incident light beam is 100
It is difficult to adjust the angle between the silicon crystal substrate 1 as a sample and the light beam 3 so that the change in the distance between the upper surface 7 and the light beam 3 is made within 1 μm during the travel of 0 μm on a normal sample stage. is there. In addition, the edge portion of the cleavage plane 2 of the silicon crystal substrate 1 is not usually cleaved finely, and it is difficult for the light beam passing through this portion to bend and travel extremely parallel to the upper surface 7.

As shown in FIG. 6, when light is incident on the upper surface 3 of the silicon crystal substrate 1 and scattered light is to be observed from the cleavage plane 2, the light beam 3 is scattered on the upper surface 3 and
There is a problem that it is difficult to detect a nearby defect. Further, the disorder of the edge of the cleavage plane 2 also makes it difficult to detect a defect near the upper surface 7.

On the other hand, as shown in FIG. 7, a light beam 3 having a deflection surface perpendicular to the upper surface 3 of the silicon crystal substrate 1 is shown.
Is incident at a Brewster angle, reflection on the upper surface 7 can be eliminated, and in principle, crystal defects can be detected by detecting scattered light from near the upper surface 7.

In this case, the intensity of the light beam 3 traveling inside the silicon crystal substrate 1 propagates while attenuating according to exp (-αt), where α is the absorption coefficient and t is the traveling distance of the light beam 3. And it is scattered by a scatterer such as BMD. The scattered light is emitted from the upper surface 7 after attenuating to exp (−αt ′), where t ′ is the distance from the scatterer to the upper surface 7. When the detector has high sensitivity or when the incident light beam is sufficiently strong, all the scatterers existing within a predetermined depth can be conveniently detected. Especially super L
In SI, the presence or absence of a crystal defect in a region several μm from the upper surface 7 becomes a problem, and only the defect in the immediate vicinity of the upper surface 7 needs to be detected with high sensitivity. This can be achieved by selecting a light beam having a wavelength component having a large absorption coefficient, as described in another embodiment of the present invention.

However, if fine particles such as dust adhere to the upper surface 7 of the silicon crystal substrate 1, both the dust on the upper surface 7 and the scatterers near the upper surface 7 are within the depth of focus of the observation lens 6. In such a case, there is a problem that it cannot be determined. In this case, when the size of the dust and the like is considerably large, the intensity of the scattered light becomes strong and can be distinguished from others. Have difficulty. In addition, the incident light beam is scattered similarly to dust or the like due to scratches or irregularities on the upper surface of the silicon crystal substrate 1 and hinders detection of crystal defects near the upper surface 7.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to eliminate the influence of dust or the like adhering to the upper surface of the crystal to be inspected and to prevent the crystal existing in the crystal to be inspected near the upper surface from being affected. An object of the present invention is to provide a method for inspecting for the presence or absence of a defect or the like.

Another object of the present invention is to provide a method for inspecting the presence or absence of a crystal defect existing in a crystal to be inspected near the upper surface easily and with high accuracy without forming a reflection surface on the crystal to be inspected. To provide.

[0017]

According to a first aspect of the present invention, there is provided a crystal defect inspection method according to the present invention, wherein a reflection surface having a predetermined inclination angle with respect to an upper surface is provided on a side of a crystal to be inspected. Is formed, the surface of the crystal to be inspected is polished, and an observation lens mounted above the upper surface of the crystal to be inspected is focused near the upper surface of the crystal to be inspected, and is reflected by the reflection surface. A light beam is incident from the lower surface of the crystal to be inspected so that the light beam propagates inside the crystal to be inspected substantially parallel to the upper surface, and the image is inspected by observing an image by scattered light detected through the observation lens. It is characterized in that the presence or absence of a crystal defect, a precipitate, a foreign substance or the like in the crystal is inspected.

In the invention according to claim 3,
When the wavelength component of the light beam has an absorption coefficient of about 10
0 cm ⁻¹ or more, and the observation lens placed above the upper surface of the crystal to be inspected is focused on the vicinity of the upper surface of the crystal to be inspected, and the light beam is irradiated at a substantially Brewster angle. It is characterized in that it is made incident on the upper surface of the test crystal, and an image based on the scattered light detected through the observation lens is observed to check for the presence of crystal defects, precipitates, foreign substances, and the like in the target crystal.

[0019]

Next, the operation of the present invention will be described. Claim 1
In the invention described in the above, the light beam incident from the lower surface of the crystal to be inspected is reflected by the reflecting surface and propagates inside the crystal to be inspected substantially in parallel with the upper surface of the crystal to be inspected, and crystal defects, If a precipitate or a foreign substance is present, it is scattered, and the scattered light is detected by an observation lens focused near the upper surface of the crystal to be inspected. A reflection surface having a predetermined inclination angle with respect to the upper surface is formed on the side of the crystal to be inspected, and the light beam is made to enter from the lower surface of the crystal to be inspected. Even if there is a defect, the presence or absence of crystal defects, precipitates, foreign matter, etc. can be inspected with high accuracy without being directly affected.

In the invention according to claim 3,
When the wavelength component of the light beam has an absorption coefficient of about 10
Since the light beam was selected so as to be 0 cm ⁻¹ or more and was incident on the upper surface of the crystal to be inspected at a substantially Brewster angle, the light beam entered only near the upper surface inside the crystal to be inspected, Without being affected by being reflected by the lower surface of the crystal to be inspected, and without forming a reflection surface on the crystal to be inspected, the crystal defects existing in the crystal to be inspected near the upper surface can be easily detected with high accuracy. The presence can be checked.

[0021]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a crystal defect inspection method according to the present invention. 1 to 3
A first embodiment of the present invention will be described with reference to FIG. 15 commercially available
A silicon crystal substrate having a diameter of 0 mm is used as a sample. This is an N-type (100) substrate having a resistivity of 2 to 3 ohm cm.
The oxygen concentration is 1.6 × 10 ¹⁸ / cm ³ (old AST). A 15 mm × 15 mm observation sample is cut out from such a substrate. As shown in FIG. 3A, the upper surface 7 of the cut silicon crystal substrate 1 is mirror-polished, while the lower surface 12 is an etched surface and has a glossy but rough surface.

The lower surface 12 which is such a rough surface
Is polished with # 2000 alumina abrasive, and then 0.05
Mirror finishing was performed using a μm alumina suspension to form a mirror surface parallel to the upper surface 7 (FIG. 3B).

Next, the silicon crystal substrate 1 shown in FIG.
Is adhered to a sample holder inclined at 45 degrees, and the sides are polished using # 800 alumina abrasive grains.
The reflecting surface 13 was formed so as to have a degree angle. Further, the reflecting surface 13 was polished with # 2000 alumina abrasive grains, and then mirror-finished using a 0.05 μm alumina suspension.

Also, in this embodiment, an observation lens 6 is provided above the upper surface 7 of the silicon crystal substrate 1 as in the case shown in FIG. The observation lens 6 is focused on the position of a crystal defect 4 to be observed near the upper surface 7 inside the silicon crystal substrate 1. The depth of focus of the observation lens 6 is about 2 μm.

Next, as shown in FIG. 1, the light beam 3 is incident on the lower surface 12 of the silicon crystal substrate 1 vertically from below the lower surface 12 through the slit 14. The light beam 3 is Nd: Y
It is supplied from an AG laser and has a wavelength component of 1.24 μm. The width of the slit 14 is 10 μm. This 1.24
The light beam 3 having a wavelength component of μm is sufficiently transparent to the silicon crystal substrate 1.

In FIG. 1, the incident position of the light beam 15 passing through the slit 14 on the lower surface 12 is moved as a, b, and c to make the light beam 15 incident. The light beam 15 incident at the incident position a is transmitted through the silicon crystal substrate 1 (a
′), The entire light beam 15 is emitted through the upper surface 7 of the silicon crystal substrate 1 (a ″).

The light beam 15 incident at the incident position b passes through the inside of the silicon crystal substrate 1 (b '), and a part of the light beam 15 is reflected by the reflecting surface 13 and the other passes through the upper surface 7 and exits. I do. The light beam reflected by the reflecting surface 13 propagates along the upper surface 7 near the upper surface 7 inside the silicon crystal substrate 1 (b
´´). When a crystal defect 4 such as a BMD, which is a scatterer, is present in this optical path, the light beam is scattered and scattered light 5 is emitted to the upper surface 7.

The light beam 15 incident at the incident position c passes through the silicon crystal substrate 1 (c '), and the entire light beam 15
The light is reflected at 3 (c ″) and propagates through a relatively deep region inside the silicon crystal substrate 1. If a crystal defect 4 exists in this optical path, the light beam is scattered. Since the wavelength of the scattered light 5 is the same as the wavelength of the light beam 3 and is sufficiently transparent to the silicon crystal substrate 1, the scattered light 5 is emitted to the upper surface 7 without much attenuation. Therefore, by changing the incident position of the light beam 3, it is possible to observe crystal defects 4 at various depths from the upper surface 7.

Since the element active region important for the VLSI is within a few μm from the upper surface 7, it is important to inspect for crystal defects 4 in this range. In order to cope with this, as shown in FIG. 2, by adjusting the width of the slit 14 and the incident position of the light beam 3, the light beam reflected by the reflection surface 13 can be used only in the vicinity of the upper surface 7. Propagate. For this purpose, the incident position of the light beam 16 is adjusted so as to irradiate the light beam 16 to the vicinity of the corner 20 of the upper surface 7 and the reflection surface 13, and then the light beam 17 transmitted from the upper surface 7
What is necessary is just to adjust the width of the slit 14 so that there may be no.

The scattered light 5 scattered by the crystal defects 4 and emitted to the upper surface 7 is similar to the case shown in FIG.
An image is formed on the imaging surface of the imaging tube 8 of the TV camera by the observation lens 6. Then, the image formed on the imaging surface of the imaging tube 8 is subjected to signal processing such as binarization and storage processing by the signal processor 9 and then displayed on the TV monitor 10 for observation.

As shown in FIG. 2, the width of the slit 14 and the incident position of the light beam 3 are adjusted to observe the crystal defect 4 three-dimensionally, and the light beam reflected by the reflecting surface 13 is adjusted. Is incident on the incident position such that the light beam 19 propagates parallel to the upper surface 7 at a depth h from the upper surface 7. And
The depth h is changed by changing the incident position of the light beam 19, and crystal defects 4 are observed at each depth h. The image of the crystal defect 4 at each depth h is processed by the signal processor 9 and image-analyzed by a computer, and displayed on the TV monitor 10 as a three-dimensionally synthesized image.

According to the configuration of the present embodiment, the lower surface 12 of the silicon crystal substrate 1 is so arranged that the light beam reflected by the reflection surface 13 propagates inside the silicon crystal substrate 1 substantially parallel to the upper surface 7.
Since the light beam 3 is incident from above, the crystal defects 4 and the like 4 in the silicon crystal substrate 1 can be inspected with high accuracy without being affected by dust or the like attached to the upper surface 7.

Since the depth h from the upper surface 7 can be easily changed by changing the incident position of the light beam 19, three-dimensional characteristics such as the distribution of crystal defects 4 in the silicon crystal substrate 1 can be easily improved. Can be observed.

Next, an embodiment of the present invention will be described with reference to FIG.

First, general contents relating to the third aspect of the invention will be described. As shown in FIG. 7, when a crystal defect or the like 4 is detected by an infrared tomography method, conventionally, the wavelength component of the light beam 3 to be used is selected so that the absorption coefficient of the silicon crystal substrate 1 is not so large. Was. This is because when the wavelength component of the light beam 3 to be used gives a large absorption coefficient, the wavelength of the scattered light due to the crystal defect 4 is the same as the wavelength of the incident light beam 3 and the scattered light is generated in the silicon crystal substrate 1. This is to prevent the scattered light from being absorbed and not being detected.

On the other hand, the lower surface 1 of the commercially available silicon crystal substrate 1
2 is usually a rough surface. When the light beam 3 having the wavelength component whose absorption coefficient of the silicon crystal substrate 1 is not so large is used, the light beam 3 reaches the lower surface 12 and is scattered on the rough lower surface 12. Then, as shown in FIG. 9, non-uniform background noise is given to prevent the detection of scattered light due to crystal defects or the like 4 which should be detected. The non-uniform background noise can be removed to some extent by polishing the lower surface 12 with a mirror surface. But in this case,
A step of mirror-polishing the lower surface 12 is further required, and there is a problem that it cannot be easily performed in a normal inspection step or a laboratory.

The third aspect of the present invention is different from the conventional idea in which the wavelength component of the light beam 3 to be used is selected so that the absorption coefficient of the silicon crystal substrate 1 is not so large. In other words, the element active region important for the VLSI or the like is within a few μm from the upper surface 7, and it is important to inspect the presence or absence of crystal defects 4 in this range. This means that the absorption coefficient of the silicon crystal substrate 1 was selected so as not to be too small.

Next, the absorption coefficient when a silicon crystal substrate is used as a sample will be examined numerically. The wavelength at which the absorption coefficient of the silicon crystal substrate is 100 cm ⁻¹ or more is 0.98 μm or less. In addition, the Brewster angle in this wavelength range is 74 degrees to 79 degrees, and therefore, the optical path length of the incident light beam is 2.5% to 3.5 compared to the normal incidence.
%, And the optical path length of the scattered light is also increased by about 3%.

As the silicon crystal substrate 1, commercially available 625 μm
When a wafer having a thickness of m is used, the light beam incident at the Brewster angle is scattered or reflected on the lower surface 12 of the wafer, and the optical path length until reaching the upper surface 7 again is 0.0625x.
2 × 1.03 = 0.1288 cm. Also, YAG
The absorption coefficient of the laser at 1.06 μm wavelength is 10 cm
^{-1 so} that the intensity of the light beam 3 is
2-Decrease to 28% via upper surface 7 The absorption coefficient is 1
In the case of a wavelength component of 0.98 μm, which becomes 00 cm ⁻¹ , 2.
Attenuates to 5 × 10 ⁻⁴ %. Absorption coefficient is 300 cm ^-1
2.1 × 10 ^{−15 for a} wavelength component of 0.9 μm
% Attenuated, absorption coefficient 1000 cm ^{- 1} If the wavelength component 0.8μm made is attenuated to 1.2x10 ^-54%.

From the above, the absorption coefficient is 100 cm
^{If the} light beam 3 having a wavelength component of ^-1 or more is used, it is considered that the influence of the scattering from the lower surface 12 can be ignored for the detection of crystal defects 4 and the like in the vicinity of the upper surface 7 of the silicon crystal substrate 1.

In general, when detecting scattered light from a crystal substrate having a large absorption coefficient, approximately (1 / absorption coefficient)
It is considered that scattered light from the depth range is mainly detected. Therefore, the absorption coefficient is from about 100 cm ⁻¹ or more to about 5
When the wavelength component is selected to be less than 000 cm ⁻¹ , scattered light from a depth range of approximately 100 μm to approximately 5 μm from the upper surface 7 is mainly detected.

Next, one embodiment of the third aspect of the present invention will be specifically described. In FIG. 4, a silicon crystal substrate 1 is a commercially available silicon wafer having a diameter of 150 mm.
It is mounted on the Y stage. An observation lens 6 is provided above the upper surface 7 of the silicon crystal substrate 1 as in the case shown in FIG. 5 and the like. The observation lens 6 is a crystal to be observed near the upper surface 7 inside the silicon crystal substrate 1. It is focused on the position of the defect 4 or the like.

The light beam 3 propagated from the laser light source 25 by the fiber 26 irradiates the upper surface 7 of the silicon crystal substrate 1 at Brewster's angle. Assuming that n is a wavelength-dependent refractive index, the Brewster angle θ _B is given by the following equation (1): θ _B = tan ⁻¹ n When the absorption coefficient is 1000 cm ^-1 or more, the following is determined in consideration of the influence of absorption. That is, assuming that the reflectance is R, R is given by equation (2). Is Brewster angle theta _B obtained as theta is the R minimized.

[0044]

(Equation 1) Here, n and k are the real part and the imaginary part of the complex refractive index (n + ik), respectively. Brewster angle θ _B has wavelength of 1.0μ
74 degrees to 79 degrees in the range of m to 0.47 μm.

As the laser light source 25, in addition to a Nd: YAG laser (wavelength 1.06 μm), a Kr laser (wavelength 0.
78 μm, 0.66 μm, 0.54 μm) and a Ti sapphire laser. 0.66 for Ti sapphire laser
0.69 out of the wavelength tunable range of μm to 1.10 μm.
It can be used with a large output in the range of μm to 0.95 μm.

At first, it was difficult to predict how large the absorption coefficient would be if the scattered light from the lower surface 12 of the silicon crystal substrate 1 could be neglected. Oscillation was applied to the upper surface 7. In this case, the absorption coefficient is about 300 cm ⁻¹ ,
It is considered that the light beam 3 has entered from the upper surface 7 to a depth of about 30 μm. When the photographing was performed by focusing the observation lens 6 at about 30 μm from the upper surface 7, a photograph as shown in FIG. 8 was obtained. In FIG. 8, 27a, 2
7b, 27c,... Are images corresponding to crystal defects 4 and the like. Reference numeral 28 is considered to be scattered light due to dust on the upper surface 7, judging from its shape. As is clear from FIG. 8, there was no non-uniform background noise formed from the images 29a, 29b, 29c,... Considered to be caused by the scattered light on the lower surface 12 as shown in FIG.

Kr laser (wavelength 0.78 μm, etc.)
Similarly, crystal defect 4 and the like could be detected in the case of using. When the wavelength is 0.66 μm, the absorption coefficient is 3000 cm ⁻¹ ,
It is considered that the light beam 3 has penetrated to a depth of μm, but in addition to crystal defects 4 and the like very near the upper surface 7, scattering by fine particles attached to the upper surface 7 as indicated by reference numeral 28 in FIG. was detected. In order to distinguish between scattering by these fine particles and scattering by crystal defects 4 etc.,
It was possible to change the image when the focusing of the observation lens 6 was shifted.

The wavelength component of the light beam 3 is changed from the absorption coefficient of the silicon crystal substrate 1 of about 100 cm ⁻¹ or more to about 50
It is continuously selected so as to be between 00 cm ^-1 or less, and refocusing of the observation lens 6 is performed at each wavelength.
An image of a crystal defect 4 at each depth h can be obtained. These results are processed by the signal processor 9, image-analyzed by a computer, and displayed on the TV monitor 10 as a three-dimensionally synthesized image. This allows
It is possible to three-dimensionally inspect a crystal defect 4 or the like of the silicon crystal substrate 1.

The laser light source 25 has a wavelength of 0.48.
When an 8 μm Ar laser is used, the absorption coefficient is 200
00 cm ⁻¹ , and travels only a depth of about 0.5 μm from the upper surface 7. The depth of focus of the observation lens 6 was about 2 μm, and the fine particles attached to the upper surface 7 could not be distinguished from the crystal defects 4 near the upper surface 7.

According to the structure of the present embodiment, the wavelength component of the light beam 3 is set so that the absorption coefficient of the silicon crystal substrate 1 is approximately 100 cm.
With the above selection, the presence or absence of crystal defects or the like 4 near the upper surface 7 can be easily inspected with high accuracy without forming a reflective surface without being affected by scattering from the lower surface 12 of the silicon crystal substrate 1. can do.

The wavelength component of the light beam 3 is changed from the absorption coefficient of the silicon crystal substrate 1 of about 100 cm ⁻¹ or more to about 50
By selecting so as to be not more than 00 cm ⁻¹ , it is possible to three-dimensionally inspect the crystal defects 4 etc. of the silicon crystal substrate 1.

[0052]

As described above, according to the present invention,
A reflection surface having a predetermined inclination angle with respect to the upper surface is formed on the side of the crystal to be inspected, and the light beam is made to enter from the lower surface of the crystal to be inspected. Even if there is a defect, the presence or absence of crystal defects, precipitates, foreign matter, etc. can be inspected with high accuracy without being directly affected.

The wavelength component of the light beam is selected so that the absorption coefficient of the non-inspection crystal is approximately 100 cm ^-1 or more, and the light beam is incident on the upper surface of the crystal to be inspected at a substantially Brewster angle. The light beam only enters the vicinity of the upper surface inside the crystal to be inspected, without being affected by the light beam being reflected by the lower surface of the crystal to be inspected, and without forming a reflection surface on the crystal to be inspected. In both cases, the presence / absence of a crystal defect existing in the crystal to be inspected near the upper surface can be easily inspected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a view showing a method of irradiating a light beam in one embodiment of a crystal defect inspection method according to the present invention.

FIG. 2 is a view showing a method of irradiating a light beam to different depths h in the same silicon crystal substrate.

FIG. 3 is a diagram showing polishing of the silicon crystal substrate and formation of a reflection surface 13;

FIG. 4 is a schematic configuration diagram showing another embodiment of the crystal defect inspection method according to the present invention.

FIG. 5 is a schematic configuration diagram showing a configuration of a conventional crystal defect inspection method.

FIG. 6 is a schematic configuration diagram showing the configuration of another conventional crystal defect inspection method.

FIG. 7 is a schematic configuration diagram showing the configuration of still another conventional crystal defect inspection method.

FIG. 8 is a view showing an image due to a crystal defect or the like near the upper surface 7 of the silicon crystal substrate 1 obtained in one embodiment of the crystal defect inspection method according to the present invention.

FIG. 9 is a view showing an image obtained by scattering by a lower surface 12 of a silicon crystal substrate 1 obtained by a conventional crystal defect inspection method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon crystal substrate 2 Cleavage surface 3 Light beam 4 Crystal defect etc. 5 Scattered light 6 Observation lens 7 Top surface 8 Imaging tube of TV camera 9 Signal processor 10 TV monitor 12 Lower surface 13 Reflection surface 14 Slit 15 Light beam 27a Crystal defect etc. 4 image 28 image by fine particles on upper surface 7 29 image by scattered light on lower surface 12

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 21/84-21/958 H01L 21/64-21/66

Claims (4)

(57) [Claims] 1. A reflection surface having a predetermined inclination angle with respect to an upper surface is formed on a side portion of a crystal to be inspected, the surface of the crystal to be inspected is polished, and is mounted above the upper surface of the crystal to be inspected. The observation lens is focused near the upper surface of the crystal to be inspected, and the light beam is reflected from the lower surface of the crystal to be inspected so that the light beam reflected by the reflection surface propagates inside the crystal to be inspected substantially parallel to the upper surface. And inspecting the presence or absence of a crystal defect, a precipitate, a foreign substance, or the like in the crystal to be inspected by observing an image by scattered light detected through the observation lens. A reflection surface having a predetermined inclination angle with respect to the upper surface is formed on a side portion of the crystal to be inspected, the surface of the crystal to be inspected is polished, and is placed above the upper surface of the crystal to be inspected. The observation lens is focused near the upper surface of the crystal to be inspected, and the light beam is reflected from the lower surface of the crystal to be inspected so that the light beam reflected by the reflection surface propagates inside the crystal to be inspected substantially parallel to the upper surface. And observe the image by the scattered light detected through the observation lens, and then the light beam reflected by the reflection surface passes through the inside of the crystal to be inspected substantially parallel to the upper surface at a different depth from before. By reflecting the light beam at different positions on the reflection surface so as to propagate and comparing an image detected through the observation lens with a previous image, crystal defects, precipitates, foreign matter, or the like in the crystal to be inspected. Inspection for the presence of defects Method. 3. The wavelength component of the light beam is selected such that the absorption coefficient of the non-inspection crystal is approximately 100 cm ^-1 or more, and the observation lens placed above the upper surface of the inspection target crystal is inspected. Focus on the vicinity of the upper surface of the crystal, make the light beam incident on the upper surface of the crystal to be inspected at a substantially Brewster angle, observe an image by scattered light detected through the observation lens, and observe the image of the crystal to be inspected. A crystal defect inspection method for inspecting the presence or absence of crystal defects, precipitates, foreign matter, or the like. 4. Select the wavelength components of the light beam so that the absorption coefficient of the non-test crystal is between about 5000 cm ^-1 or less from approximately 100 cm ^-1 or more, placed above the upper surface of the inspection crystals The observed observation lens is focused near the upper surface of the crystal to be inspected, and then the light beam is incident on the upper surface of the crystal to be inspected at a substantially Brewster angle, and the scattered light detected through the observation lens Is observed, and then the wavelength component of the light beam is converted to an absorption coefficient of the non-inspection crystal of about 100 cm ^−1.
From the above, a difference between about 5,000 cm ⁻¹ or less is selected as different from the previous one, and an image due to the scattered light detected through the observation lens is compared with the previous image to obtain crystal defects and precipitates in the crystal to be inspected. Or a crystal defect inspection method characterized by inspecting the presence or absence of foreign matter.