JP2916321B2 - Method for detecting internal defects in multilayer semiconductor substrate, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention is a multi the internal defects of the multi-layer semiconductor substrate such as a semiconductor wafer having a multilayer structure, and illuminated with laser light or the like is detected by observing the scattered light, etc.
The present invention relates to a method and an apparatus for detecting an internal defect in a layer semiconductor substrate or the like .

[0002]

2. Description of the Related Art Conventionally, as a method for observing defects in each layer of a semiconductor wafer or the like having a multi-layered structure of Si crystals, a laser beam having a wavelength of 1800 nm is irradiated on the wafer by expanding the beam diameter and scattered light. Method of observing (T. Oga
wa, Lu Taijingand K.C. Toyod
a, Jpn. J. Appl. Phys. 30 (199
1) L1393), a method of irradiating a laser having a fixed wavelength such as an Ar laser on a wafer and observing the reflected light (EF.
Steigmeier and H.S. Auderse
t, Applied Physics A, (199
0) 531) and the like are known.

FIG. 4 of the conventionally known Japanese Patent Laid-Open Publication No. Hei 4-24541 shows that the wavelength of a laser beam to be incident is appropriately selected so that the laser beam is incident on an object made of gallium arsenide. The depth can be controlled, and due to such characteristics, when measuring the internal defect of the test object composed of gallium arsenide,
For example, it is described that when a laser beam having a wavelength of about 900 nm is used, the laser beam incident from the front surface of the test object can be sufficiently attenuated near the rear surface (the sixth column, upper right column, lines 13 to 6). (See the 11th line in the lower left column of the sheet).

Further, JP-A-2-16438, JP-A-4-95861, JP-A-2-190974, JP-A-58-106444, JP-A-63-2
JP-A-12911, JP-A-3-238348, and JP-A-4-26845 also describe techniques substantially similar to the above-mentioned publications.

On the other hand, in an automatic focusing mechanism in a microscope used for observing such a defect, a method of irradiating a laser beam to a wafer from the microscope side and observing a reflected light thereof is used. There is also known a method of projecting a specific pattern and focusing by observing the image.

[0006]

The technique described in the above-mentioned publication is a technique for controlling the depth at which a laser beam is incident on a test object by appropriately selecting the wavelength of the laser beam to be incident. According to this technique, however, as shown in FIG. 4 of JP-A-4-24541, the absorption coefficient k of gallium arsenide hardly changes up to a wavelength of around 870 nm, and sharply decreases to 900 nm exceeding 870 nm. I do. Therefore, it is not possible to observe a defect very close to the surface of the test object, for example, near 1 μm by distinguishing the defect from the surface defect only by selecting the wavelength. In order to detect defects on the surface of a test object, especially near the surface of a multilayer semiconductor substrate , by distinguishing the defects on the surface, instead of applying the absorption characteristics of the incident laser beam, surface defects and internal defects of the laser beam are used. What is necessary is just to apply the change characteristic of the scattered intensity from.

In the focusing method for observing the reflected light, there is a problem that focusing cannot be performed unless the inclination of the wafer normal to the laser optical axis is within about ± 5 °. Further, in the focusing method for observing the projected image, a special mechanism is required to apply the method to a sample that is positively tilted. In other words, if the pattern is projected on the place to be observed, the pattern will interfere with the subsequent measurement after focusing, so that a countermeasure is required.

[0008] The present invention has been made in view of such problems of the prior art, multi-layered half, such as a semiconductor wafer having a multilayer structure
That the detection of internal defects in the conductor substrate or the like, and can be detected by specifying the position and depth of each layer defect exists
It is.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a multi-layer semiconductor substrate having a predetermined laser beam incident thereon, and the resulting optical information from the multi-layer semiconductor substrate obtained by an observation optical system. In a method for detecting a surface defect and an internal defect of a multilayer semiconductor substrate based on information, wavelengths (λ2, λ4,...) At which a large reflectance is generated due to interference of reflected light at the surface and interface and wavelengths at which a small reflectance ( λ
, Λ3,...), The wavelength (λ2, λ
4, ...) using any one of the laser beams of the detected scattered image from dust挨and scratches multilayer semiconductor substrate surface, any of the small wavelength of the reflectance (.lambda.1, [lambda] 3, ...) 1
Detects scattered images from defects inside the multilayer semiconductor substrate using two laser beams, and compares these two scattered images to distinguish between surface defects and internal defects. Method.

Also,The wavelength having a large reflectance (λ2, λ
4,...) And wavelengths with small reflectance (λ1, λ3,...)
Is from a tunable laser devicemultilayer
semiconductor Method for detecting internal defects in substrates, etc.With
is there.

[0011] Further, the incident laser beam is applied to a multilayer semiconductor substrate.
The refracted light in the plate has a predetermined small cross section, and a scattered image generated by the refracted light is placed on an optical axis that substantially intersects the optical axis of the refracted light at a predetermined angle on a microscope. two obtained, that identified based the depth position in the multi-layer semiconductor substrate of a defect image included in the obtained scattering image on the microscope visual field position where the defect image is present, the multi-layer semiconductor substrate with an incident laser beam by Multi-layer semiconductor substrate characterized in that scanning is performed two-dimensionally
And the like for detecting internal defects .

In addition, the optical information generated by the incident light includes not only scattered light but also fluorescent light obtained by dispersing light from a defect .
This is a method for detecting an internal defect .

Further, a predetermined laser beam is incident on the multilayer semiconductor substrate, optical information generated from the multilayer semiconductor substrate by the observation optical system is obtained, and a surface defect or a surface defect of the multilayer semiconductor substrate is obtained based on the obtained optical information. Is a device for detecting internal defects, wherein the illuminating means comprises a wavelength (λ2, λ4, λ2, λ4) of a large reflectance caused by interference of reflected light on the surface and the interface.
...) and the wavelength of a small reflectivity (.lambda.1, having [lambda] 3, ...)
Are those, means for obtaining the image data, a large wavelength (λ2, λ4, ...) of the reflectivity to detect the scattered image data from the surface of the dust挨and scratches by using any one of the A multi-layer semiconductor substrate or the like which obtains and compares scattered image data from internal defects for each wavelength using any one of wavelengths (λ1, λ3,...) having a small reflectance. Of the present invention is a device for detecting an internal defect.

The multi-layer semiconductor substrate is a wafer having a multi-layer structure of Si crystal, and has a wavelength (λ2,
.lambda.4, ...) and a multilayer semiconductor small wavelengths (.lambda.1 reflectance, the wavelength of [lambda] 3, ...) is in the range of 400~2000nm
This is a method for detecting an internal defect in a substrate or the like .

The observation optical system detects internal defects in a multi-layer semiconductor substrate or the like which obtains fluorescence by spectrally dispersing light from defects, in addition to light information based on scattered light.
It is a device .

[0016]

One of the wavelengths (.lambda.2, .lambda.4,...) Having a large reflectivity and relatively small wavelengths (.lambda.1, .lambda.3,. If any are incident one multi <br/> layer semiconductor substrate of a), large wavelength λ of reflectance
The scattered light due to 2, λ4, ... Contains more light information from defects present on the surface than light information from defects inside, and wavelengths with small reflectance (λ1, λ3,.
In the scattered light due to the above, light information from a defect existing inside contains more light information than light information from a defect existing on the surface. Therefore, for each incident light, the optical information generated thereby is obtained, and these two optical information are compared, for example, the wavelength of the large reflectance is obtained from the optical information obtained by the wavelength (λ1, λ3,...) Of the small reflectance. (Λ2, λ4,
..), It is possible to detect only a defect that is truly inside.

In another aspect of the present invention, when the incident an incident laser beam on the multilayer semiconductor substrate, the multilayer semiconductor base
Since the refracted light in the plate has a predetermined small cross section, the area in the multilayer semiconductor substrate illuminated by the refracted light is a linear or planar area along the optical axis. Therefore, when this region is observed by the microscope on an optical axis intersecting the optical axis of the refracted light at a predetermined angle, the depth of each part of the scattered image in the visual field of the microscope is within the visual field. Will correspond to the position in. Therefore, the defect image in the visual field is detected together with the information on the depth as the position in the visual field.

Further, still other or more detailed features, objects, effects, and the like of the present invention will be clarified through the following embodiments.

[0019]

FIG. 1 is a schematic block diagram of a defect detection apparatus according to one embodiment of the present invention. As shown in FIG. 1 , this device is a laser device 10 for outputting a laser beam 101 for observation.
3, the microscope 109 a condenser lens 107 for irradiating the laser beam 101 on the multilayer semiconductor substrate 105 receives the scattered light from the multilayer semiconductor substrate 105 due to the irradiated laser beam 101, to expand its scattering image, the enlarged An image sensor 111 for photoelectrically converting the scattered image to obtain an image signal of the scattered image (fluorescence, specular reflection light) , and a pattern used for focusing the microscope 109 on the multilayer semiconductor substrate 105 are described.
Projection means 113 for projecting onto a multilayer semiconductor substrate 105, a multi
The normal layer semiconductor substrate 105 (multilayer semiconductor substrate 105
Between the optical axis of the microscope 109 and a line perpendicular to the plane of
And a stage 115 that is moved by a driving unit (not shown). Microscope 109
Has an objective lens 117 and an imaging lens 119.
The projection means 113 includes a spatial modulation element pattern 121, a light source 123, a convex lens 125 for irradiating the light emitted from the light source 123 to the spatial modulation element pattern 121, a diffusion plate 127 and a convex lens 129, and a space illuminated thereby.
A light projection lens 131 and a half mirror 133 for forming an image of the modulation element pattern 121 at the focal position of the microscope 109 are provided. The spatial modulation element pattern 121 is arranged on the focal plane of the light projecting lens 131.

FIG. 2 is a principle diagram for explaining the principle of observing the multilayer semiconductor substrate 105 by the apparatus shown in FIG. In the figure, reference numeral 201 denotes a TV camera observation system including the image pickup device 111 and the image forming lens 119, and the TV camera observation system 201 and the objective lens 117.
These form an observation system. The objective lens 117 of FIG.
So that it becomes a parallel beam and enters the imaging lens 119
However, the objective lens 117 shown in FIG.
It is described so as to enter the observation system 201. Multilayer semiconductor base
Normal of the plate 105 surface, the optical axis of the observation system, and the optical axis of the incident laser beam 101 is contained in the same plane, and the multilayer half
Angle β is 10-60 ° formed between the optical axis of the incident laser beam 101 and the conductive substrate 105, the refracted light optical axis and the multilayer semiconductor
The angle α formed by the normal to the body substrate 105 is set to approximately 16 °. The field of view 203 of the TV camera observation system 201 is a multilayer
The measurement areas 1a to 4a are divided according to the depth of each of the layers 1b to 4b of the semiconductor substrate 105.

[0021] In this configuration, in order to detect defects, first, by projecting an image of the spatial modulation element pattern 121 for focusing on the multilayer semiconductor substrate 105, the spatial modulation element Pas
The position of the stage 115 is controlled so that the contrast of the projected image of the turn 121 is maximized between the measurement areas 2a and 3a. Next, the stage 115 is moved by a predetermined distance so that the focal position of the objective lens 117 corresponds to the depth position of the boundary between the layers 2b and 3b. Next, the position of the laser beam 101 is adjusted so that the focal point 205 of the laser beam 101 is located at a position corresponding to the measurement areas 1a, 2a, 3a, and 4a, which are desired detection target layers. As a result, the measurement areas 1a to 4a in the visual field 203 become the layers 1b to
Corresponding to 4b, therefore, the depth of focus of the observation system is multi-layered and a half
As long as the layers 1b to 4b on the conductive substrate 105 are covered, an image of a defect or the like in the visual field 203 can be obtained together with information on the layer where the defect exists. The depth of field in this case is, for example, about 40 μm when the magnification of the observation system is 20 ×, and about 15 μm when the magnification of the observation system is 50 ×. Also,
The projection of the spatial modulation element pattern 121 stops when it becomes unnecessary so as not to hinder observation. Spatial modulation
This is not the case when a pattern having no pattern that hinders observation is used as the element pattern 121 .

Also, do not move the multilayer semiconductor substrate 105.
In such a case, the field of view 203 is fixed, and the area beyond the field of view 203 cannot be detected. However, in order to detect the area beyond the field of view 203, the laser beam 101 is applied to the multilayer semiconductor substrate 1.
With reciprocating in a direction perpendicular to the maximum inclination direction of 05, by moving in parallel a multilayer semiconductor substrate 105 at its maximum inclination direction, as shown in FIG. 3, multi
For example, 200 × 200 × 16 of the layer semiconductor substrate 105
A three-dimensional area of about μm is scanned in a raster scan manner.
As a result, a scattered image of a defect in that region can be obtained together with information on the depth position indicating which of the measurement regions 1a to 4a has been detected.

FIG. 4 is an explanatory diagram for explaining the resolution in this detection. As shown in the drawing, the resolution in the surface direction of the multilayer semiconductor substrate 105 defined by the interval between each scanning line in the scanning by the laser beam 101 is about 0.4 μm, and the multilayer semiconductor substrate 10 of the laser beam 101
Assuming that the refraction angle α at 5 is about 16 °, the resolution in the depth direction is about 1.4 μm.

FIG. 5 is a schematic diagram showing a defect detection method according to another embodiment of the present invention. Here, as a laser device,
A tunable laser such as a dye laser or a Ti sapphire laser is used, and a light beam 101 emitted from the laser is expanded via a collimator 301 and irradiated onto a multilayer semiconductor substrate 105. And the division of the measurement area in the visual field of the TV camera observation system 201 cannot be performed because the laser beam is not thin . Also,
Normal direction of the multi-layer semiconductor substrate 105 surface is better-matched with the optical axis of the TV camera observation system 201. Other than that,
The configuration is similar to that of FIG.

FIG. 6 shows an SOI (Sili) which has a multilayer structure of Si crystal and is used as a multilayer semiconductor substrate 105.
FIG. 3 is a cross-sectional view of a wafer having a “con on insulator” structure. This wafer has a Si substrate 401, an oxide film (SiO ₂ ) layer 403 having a thickness of 0.2 μm formed thereon,
And a 1 μm-thick Si layer 405 formed thereon.

In this configuration, when detecting a defect, the focus of the observation system is adjusted to the surface of the wafer in the same manner as described above. However, here, the Si layer 4 within the depth of focus is
Since the defect located in the layer 05 and the SiO ₂ layer 403 is detected, there is no need to further adjust the focal position. And
The observation is performed by irradiating the laser beam 101 such that the irradiation area coincides with the visual field of the TV camera observation system 201.

FIG. 7 is an explanatory view showing a state when a laser beam is irradiated on the wafer. FIG. 7A shows a case where the reflectance on the wafer surface is large, and FIG. 7B shows a case where the reflectance is small. The graphs on the left side of each of FIGS. 7A and 7B show the incident laser beam 101 having an incident intensity I _0.
5 is a graph showing a change in the light intensity I of refracted light with respect to a wafer depth D due to the above. Note that a curve 509 is an attenuation curve due to absorption.

As shown in FIG.
Separates the reflected light 501 and the refracted light 503 from the wafer surface (Si crystal having a refractive index of 3.5) and the SiO ₂ layer 40.
8 (refractive index ≒ 1.5), the reflectivity R on the wafer surface becomes larger in accordance with the wavelength λ of the laser light than in the case of a wafer containing only a Si crystal due to the interference of the reflected light on the surface ( interface ). Fluctuates in a large range as shown in FIG. When the reflectance is large (λ2, λ4, ...) , As shown in FIG.
Defect 5 at the boundary between the Si layer 405 and the SiO ₂ layer 403
In the case where the intensity of the scattered light 507 from the light source 05 is small and the reflectance is small (λ1, λ3, ...) , The intensity increases as shown in FIG.

Therefore, the wavelengths λ1, λ with low reflectivity
3, ... with a laser beam 101 layers effectively detect and 405,403 scattered images from internal defects, high wavelength λ2 reflectance, .lambda.4, ... dust挨and scratches on the wafer surface by using a laser beam The scattered image from is mainly detected. Then, by comparing these scattered images, surface defects and internal defects are clearly distinguished. Further, as shown in FIG. 8, the oscillation of the reflection intensity due to the interference is observed at a wavelength of 400 nm or more. Therefore, a wavelength of 400 to 200 is provided inside the layer.
Since the light having a wavelength of 0 nm is sufficiently incident, the internal defect is observed using a laser beam in this wavelength range. On the other hand, the light having a wavelength of less than 400 nm does not enter the inside of the layer.
Surface defects may be observed using laser light of m or ordinary light, and internal defects and surface defects may be distinguished.

Instead of changing the wavelength of the laser beam, as shown in FIG.
The wavelength λ / via the second harmonic generation element (KDP) 803
2 (= 400 to 1300 nm) as a mixed light 805 of the fundamental wave and the second harmonic of the wavelength, which is incident on the wafer,
The scattered light from the surface defect and the internal defect may be imaged using another observation system as scattered light of the fundamental wave and the second harmonic, respectively.

FIG. 10 shows an example of a scattered image obtained in this manner. However, for the wafer that is the multilayer semiconductor substrate 105, the thickness of the Si layer 405 is 1 μm, and the thickness of the SiO ₂ layer 403 is 0.4 to 0.5 μm. As shown in FIG. The unetched surface 11 as it is, but the other half is the etched surface 14 exposing the bit 13 of the internal defect by etching.
Is used. FIG. 10A shows a wavelength of 940n.
500 μm in which an internal scattered image due to the laser light of m
The figure shows the state of a visual field of m squares, and FIG.
The view of the field of view of the same portion where the surface scattered image by the laser light of nm is remarkably appeared is shown. Portion 11a corresponds to unetched surface 11, and portion 14a corresponds to etched surface 14. In FIG. 10 (b), an image of dust on the unetched surface 11 appears in the portion 11a, and countless minute bit images on the etched surface 11 appear in the portion 14a. In the portions 11a and 14a of FIG. 10A, a minute bit image of the surface does not appear, and a large number of large dusts, scratches and internal defects on the surface appear.

FIG. 12 is a graph showing changes in the reflectance R and the scattering intensity S with respect to the wavelength λ of the incident light on the wafer. In the figure, a curve 151 indicates a change in reflectance R by calculation, a curve 153 indicates a change in reflectance R by actual measurement, and a curve 1
Numeral 55 indicates a change in the scattering intensity S from the surface defect by actual measurement, and a curve 157 indicates a change in the scattering intensity S from the internal defect by actual measurement. From FIG. 12, it can be seen that the laser near the wavelength of 940 nm
Using the light, internal defects can be detected without being affected by the surface.
When laser light with a wavelength of around 1000 nm is used,
It can be seen that a surface defect is detected without being affected by the above .

FIGS. 13A and 13B show another multilayer semiconductor device.
A 500 μm square view when observing the same place on the body substrate 105 with a laser beam having a wavelength of 1000 nm reaching the inside thereof and a laser beam having a wavelength of 451 nm is shown. By comparing the two, a scattered image from an internal defect can be recognized.

As shown in FIG. 14, the multilayer semiconductor substrate 10
5, when a wafer such that it has a fine Yokozo on the surface, portions thereof microstructure is present therewith as a layer of equivalent thickness is present, internal defects and surface in the same manner Defects can be observed. However, in this case, in order to prevent the diffracted light due to the fine structure from entering the observation optical system and making the internal defect 505 unobservable, an empty space for blocking the diffracted light 183 is provided in the observation optical system.
An intermediate filter (mask) 181 is provided. Specular reflection 1
85 does not cause any problem.

FIGS. 15 to 17 are schematic diagrams each showing a configuration of a defect detection apparatus according to still another embodiment of the present invention. These apparatuses detect defects inside and on the surface of the multilayer semiconductor substrate 105 using laser light having a wavelength of 400 to 2000 nm, and detect surface defects using laser light having a wavelength of 200 to 650 nm.

In the apparatus shown in FIG.
Numeral 01 has a beam diameter enlarged by a concave lens 163, is converted into parallel light by a collimator lens 161 and is introduced into an optical path of an observation system via a half mirror 171 to irradiate the multilayer semiconductor substrate 105 via an objective lens 117. As described above, the specular reflection image of the surface defect and the specular reflection image of the internal defect are changed by changing the wavelength of the laser beam 101, and the objective lens 117, the imaging lens 119, and the image sensor 111
, And as an electric signal.

In the apparatus shown in FIG. 16, the wavelengths λ1 and λ2
The multilayer semiconductor substrate 105 is illuminated with the laser beam 101 obtained by mixing the laser light of the above through a half mirror 169, and the specularly reflected light is divided into a wavelength λ1 component and a λ2 component by a dichroic mirror 173, and is divided by the wavelength λ1 component. While observing the surface of the multilayer semiconductor substrate 105 through the imaging lens 119 and the image sensor 111, the wavelength λ2
The specular reflection image from the inside of the multilayer semiconductor substrate 105 is observed through the imaging lens 165 and the image sensor 167 according to the components.

In the apparatus shown in FIG.
01 is blocked by the mask 175, and only the light beam in the peripheral portion is reflected by the mirror 177 and the objective lens 11.
Irradiation is performed on the multilayer semiconductor substrate 105 through the peripheral portion 7, and a regular reflection image is obtained through the central portion of the objective lens 117. Others are the same as the case of FIG.

[0039]

According to the present invention, a predetermined laser beam is incident on a multi-layer semiconductor substrate, optical information generated from the multi-layer semiconductor substrate is obtained by an observation optical system, and the multi-layer semiconductor substrate is obtained based on the obtained optical information. small a method for detecting surface defects and internal defects, the wavelength resulting large reflectance by the interference of the reflected light on the surface and interface (λ2, λ4, ...) and
Out of the wavelengths (λ1, λ3,...) That produce a small reflectance , one of the wavelengths (λ2, λ4,.
Scattered images from dust and scratches on the surface of the multilayer semiconductor substrate are detected using two laser beams, and wavelengths having small reflectance (λ1, λ
The scattering image from the defect inside the multilayer semiconductor substrate is detected by using any one of the laser lights of (3,...), And by comparing the two scattering images, the surface defect and the internal defect are distinguished. As shown in FIGS. 7A and 7B, the incident laser light 101 is reflected light 501 and refracted light 503 as shown in FIGS.
However, in the case of a multi-layer semiconductor substrate, the reflectance R fluctuates in a large width as shown in FIG. 8 according to the wavelength λ of the laser light due to interference of the reflected light at the wafer surface and the interface. When the reflectance is large (λ2, λ4, ...),
As shown in FIG. 7A, when the intensity of the scattered light 507 from the defect 505 at the interface is small and the reflectance is small (λ
1), the intensity of the scattered light 507 from the defect 505 at the interface increases as shown in FIG. 7B, so that the wavelength (λ1, λ3,. Scattered images from internal defects are effectively detected by any one of the laser beams 101, and wavelengths (λ2, λ4,
…)) Can be used to effectively detect scattered images from dust and scratches on the wafer surface using any one of the laser beams. By comparing these two scattered images, surface defects and internal defects can be determined. Can be clearly distinguished. Further, the wavelengths with large reflectance (λ2, λ4,...) And the wavelengths with small reflectance (λ1, λ4,.
3,...) Are emitted from the wavelength tunable laser device and can be easily obtained. In addition, the incident laser beam is formed so that the refracted light in the multilayer semiconductor substrate has a predetermined small cross section, and a scattered image generated by the refracted light has a predetermined angle with the optical axis of the refracted light. Obtained by a microscope on an optical axis substantially intersecting
Specifying the depth position of the defect image included in the obtained scattered image on the multilayer semiconductor substrate based on the position in the microscope field of view where the defect image exists is two-dimensionally scanning the multilayer semiconductor substrate with the incident laser beam. Since the method is a method for detecting an internal defect in a multi-layer semiconductor substrate or the like, which is performed while scanning, a depth position indicating in which of the measurement areas 1a to 4a the scattered image of the defect in that area is detected. Information can be obtained. Also, a predetermined laser beam is incident on the multilayer semiconductor substrate,
In an apparatus that obtains optical information generated from the multilayer semiconductor substrate by an observation optical system and detects a surface defect or an internal defect of the multilayer semiconductor substrate based on the obtained optical information, an illuminating unit includes a surface and an interface. Are the reflection intensities that oscillate at wavelengths (λ2, λ4,...) Having a large reflectance and wavelengths (λ1, λ3,...) Having a small reflectance caused by the interference of the reflected light. Large wavelength (λ
2, .lambda.4,...), A scattered image from dust or scratches on the surface of the multi-layer semiconductor substrate is detected by using one of the laser beams, and the wavelength (λ1, .lambda.3,. Since the present invention is a device for detecting an internal defect in a multilayer semiconductor substrate or the like which detects a scattered image from a defect inside the multilayer semiconductor substrate using any one of the laser beams, the same effect as in the above-described method is obtained. In addition, it is possible to detect surface and internal defects in a multilayer semiconductor substrate or the like with a relatively simple device.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a defect detection device according to an embodiment of the present invention.

FIG. 2 is a principle diagram for explaining a principle of observing a multilayer semiconductor substrate by the apparatus of FIG. 1;

FIG. 3 is an explanatory diagram showing a state in which a multilayer semiconductor substrate is scanned in a raster scan manner in the apparatus of FIG. 1;

FIG. 4 is an explanatory diagram for explaining resolution in detection by the device of FIG. 1;

FIG. 5 is a schematic diagram showing a defect detection method according to another embodiment of the present invention.

6 is a cross-sectional view of an SOI structure wafer having a multilayer structure of a Si crystal, which is used as a multilayer semiconductor substrate in the apparatus of FIG.

FIG. 7 is an explanatory view showing a state when a laser beam is irradiated on a wafer in the apparatus shown in FIG. 5;

FIG. 8 is a graph showing that the reflectance on the surface of the wafer as shown in FIG. 6 fluctuates in a larger range according to the wavelength λ of the laser beam than in the case of a wafer containing only Si crystals.

FIG. 9 is an explanatory diagram showing how laser light having a wavelength is mixed light of a fundamental wave having a wavelength of λ / 2 and a second harmonic having a wavelength of λ via a second harmonic generation element.

10 is a schematic diagram showing an example of a scattered image obtained when observing the wafer of FIG. 11 in the apparatus of FIG.

FIG. 11 is a schematic view showing a wafer on which the scattered image of FIG. 10 is obtained.

12 is a graph showing changes in reflectance R and scattering intensity S with respect to the wavelength λ of incident light on the wafer of FIG.

FIG. 13 is a schematic view showing a state when another multilayer semiconductor substrate is observed in the apparatus of FIG. 5;

FIG. 14 is a schematic diagram showing a state in which defects are observed when the multilayer semiconductor substrate is a wafer having a fine structure on the surface.

FIGS. 15 and 17 are schematic views showing a configuration of a defect detection apparatus according to still another embodiment of the present invention.

[Explanation of symbols]

101 laser light, 103 laser device, 105 multilayer
Semiconductor substrate , 107: condenser lens, 109: microscope, 1
11 image pickup device, 113 projecting means, 115 stage, 117 objective lens, 119 imaging lens, 121
... spatial modulation element pattern, 123 ... light source, 125, 12
9: convex lens, 127: diffusion plate, 131: light projecting lens, 133: half mirror, 163: concave lens, 161
... Collimator lens, 167 ... Imaging element, 169 ... Half mirror, 171 ... Half mirror, 173 ... Dichroic mirror, 175 ... Mask, 177 ... Mirror, 183
... Diffraction light, 181 ... Filter (mask), 185 ... Specular reflection light, 201 ... TV camera observation system, 203 ... Field of view, 1b
４4b layer, 1a〜4a measurement area, 301 collimator, 401 Si substrate, 403 oxide film (SiO 2)
Layer: 405: Si layer, 501: Reflected light, 503: Refracted light, 505: Defect, 507: Scattered light, 801: Laser light of wavelength λ, 803: Second harmonic generation element, 805: Mixed light

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-2684 (JP, A) JP-A-3-238348 (JP, A) JP-A-4-24541 (JP, A) JP-A-2- 16438 (JP, A) JP-A-63-213810 (JP, A) JP-A-2-109749 (JP, A) (58) Fields studied (Int. Cl. ⁶ , DB name) G01N 21/84-21 / 90

Claims (7)

(57) [Claims] 1. A predetermined laser beam is made incident on a multilayer semiconductor substrate, optical information generated from the multilayer semiconductor substrate is obtained by an observation optical system, and surface defects and surface defects of the multilayer semiconductor substrate are determined based on the obtained optical information. In the method of detecting internal defects, large interference is caused by interference of reflected light on the surface and interface.
Wavelengths (λ2, λ4, ...) that produce reflectance and small reflectance
The resulting wavelength (λ1, λ3, ...) of the scattering image from dust挨and scratches multilayer semiconductor substrate surface using any one of a laser beam of a large wave reflectivity (λ2, λ4, ...) detecting the small wavelength (λ1, λ3, ...) of the reflectivity to detect the scattered image of the interior of the defective multilayer semiconductor substrate using any one of a laser beam of, comparing these two scattering image A method for detecting internal defects in a multi-layer semiconductor substrate or the like that distinguishes between surface defects and internal defects. 2. The method according to claim 1, wherein the reflectance is large.
Wavelength ( λ2, λ4,... ) And wavelength ( λ
1, λ3, ... ) is a method for detecting internal defects in a multilayer semiconductor substrate or the like emitted from a wavelength tunable laser device.
Law . 3. The method according to claim 1, wherein the incident laser beam is formed such that the refracted light in the multilayer semiconductor substrate has a predetermined small cross section, and a scattered image generated by the refracted light is converted into light of the refracted light. Obtained by a microscope on an optical axis substantially intersecting with the axis at a predetermined angle, and the depth position of the defect image included in the obtained scattered image in the multilayer semiconductor substrate in the field of view of the microscope where the defect image exists that identified based on a multilayer semiconductor at incident laser beam
It is performed while scanning the body substrate two-dimensionally
A method for detecting internal defects in a multilayer semiconductor substrate or the like . 4. The multilayer semiconductor substrate according to claim 1, wherein the optical information generated by the incident light includes not only scattered light but also fluorescent light obtained by dispersing light from a defect.
A method for detecting internal defects in plates and the like . 5. A multi-layer semiconductor substrate is irradiated with a predetermined laser beam, optical information generated from the multi-layer semiconductor substrate is obtained by an observation optical system, and a surface defect or a surface defect of the multi-layer semiconductor substrate is obtained based on the obtained optical information. Is a device for detecting an internal defect, wherein the illuminating means is provided with wavelengths (λ2, λ4,...) Of large reflectivity caused by interference of reflected light on the surface and the interface.
Wavelength of small reflectivity (λ1, λ3, ...) those having a
There, means for obtaining the image data, a large wavelength (λ2, λ4, ...) of the reflectance by using any one of detecting the scattered image data from dust挨and scratches on the surface, the reflectance For detecting internal defects in a multi-layer semiconductor substrate or the like, which obtains and compares scattered image data from internal defects for each wavelength using one of the smaller wavelengths (λ1, λ3,...). . 6. The multilayer semiconductor substrate according to claim 1, wherein
A wafer having a multi-layer structure of i-crystals and having a large reflectance
Wavelengths (λ2, λ4,...) And wavelengths (λ
1, [lambda] 3, ... method of detecting internal defects in a multilayer semiconductor substrate such as a wavelength in the range of 400~2000nm of). 7. The multi-layer semiconductor substrate or the like according to claim 5, wherein the observation optical system obtains fluorescence by dispersing light from a defect as well as scattered light as optical information .
Internal defect detection device .