JP6984860B2 - Defect inspection methods and defect inspection equipment - Google Patents

Description

The present invention relates to a method for inspecting a defect of an inspected object, a defect inspection device, and a light source device.

There are destructive inspection methods and non-destructive inspection methods as methods for inspecting extremely small defects such as wafer defects. However, a destructive inspection method typified by etching has a problem that the inspected object cannot be used after the inspection, and therefore a non-destructive inspection method is preferably used. On the other hand, as a non-destructive inspection method that does not perform such a destructive treatment, there are, for example, an electrical method and a method using light or ultrasonic waves (Patent Documents 1 to 3).

The present inventors apply stress to the inspected object for defect inspection of wafers and the like that have not been sufficiently inspected even by the non-destructive inspection method disclosed in Patent Documents 1 to 3 and the like. We have proposed a method of inspecting minute defects and various defects by obtaining the intensity ratio of scattered light of polarized light applied to the object to be inspected before and after the inspection (Patent Documents 4 to 6). The techniques disclosed in these patent documents have been proposed as techniques suitable for substrates for optical functional elements, superlattice structures, MEMS structures, glass, reticle, etc., particularly centering on the above-mentioned wafers. ..

In Patent Document 4, light polarized by a polarizer is incident on an inspected object, and the presence or absence of defects is determined and detected from the difference in scattered light intensity before and after application of ultrasonic waves to the inspected object for the scattered light. It discloses the method of doing so.

Patent Document 5 discloses a method of incident light polarized by a polarizer and discriminating and detecting the presence or absence of defects from the difference in scattered light intensity before and after applying stress to the object to be inspected. It is something to do. Further, Patent Document 6 discloses a stress due to a mechanical static load such as a tensile static load as an even more preferable method for this stress, and further discloses a quality control method for a wafer or a semiconductor element.

Further, Non-Patent Documents 1 and 2 utilize the techniques of Patent Documents 4 to 6, and further, as the stress applying means, the stress applying means capable of adjusting the stress application to the glass element to be inspected in a non-contact manner is used. It discloses the inspection method.

Japanese Unexamined Patent Publication No. 62-177447 Japanese Unexamined Patent Publication No. 2002-188999 Japanese Patent No. 3664134 Japanese Patent No. 4631002 Japanese Patent No. 5007979 Japanese Patent No. 5713264

Yoshitaro Sakata, 2 others, "Development of a novel non-contact inspection technique to detect microcracks under the surface of a glass substrate by thermal stress-induced lightscattering method", Optics & Laser Technology 90 (2017) 80-83 Yoshitaro Sakata, 2 others, "Microscopic study of stress effects around micro-crack tips using a non-contactstress-induced light scattering method", AIP ADVANCES 6, 095315 (2016)

The present inventors use a device for detecting the difference in scattered light intensity before and after stress application by the defect inspection device 200 as shown in FIG. 11, and the defects whose detection accuracy is lowered when inspecting the inspected object 10 such as glass. I found that there is. This device has a configuration according to Non-Patent Document 2. The defect inspection device 200 reflects the light emitted from the light emitting means 20 toward the direction L1 (the outline is shown by a two-dot broken line in FIG. 11) in the direction L2 by the reflector 221 and is supported by the support portion 11. Irradiate the subject 10 to be inspected. The light emitted from the light emitting means 20 is the light transmitted through the object to be inspected 10. Further, as this light, a laser light source or the like is used as light having high directivity in order to increase the intensity of light for detecting defects and the like.

Further, the presence or absence of stress applied to the object to be inspected 10 can be changed by the contact type stress applying means 40. Since the light emitted to the object 10 to be inspected is directed to the direction L2, the light is not detected by the scattered light detecting means 30 via the objective lens 31 if there is no defect or the like. It has a so-called dark field system. Therefore, no defect is detected even if the image processing is performed by the arithmetic processing means 50 or the magnified observation processing unit 70, and the display unit 60 is also displayed as having no defect. On the other hand, when there is a defect in the observation position of the object to be inspected, light is scattered due to the defect, and the scattering is detected by the scattered light detecting means 30, so that a predetermined process is performed and the defect is detected. At this time, by comparing the results of the presence or absence of stress applied by the stress applying means 40, it is a device that can detect even finer defects.

However, in this defect inspection device 200, since the light from the light emitting means 20 is a laser light source having high directivity, it is incident on the object to be inspected 10 at a single incident angle. It has been newly discovered that when inspecting with such a single angle of incidence, the defect may be overlooked depending on the angle of incidence and the defect. FIG. 12 shows that the defect is detected by the defect inspection device 200 by changing the orientation of the inspected object at the same position of the same inspected object. The inspection of FIG. 12A was performed with the in-plane orientation of the inspected object set to 0 °, and a crack was detected near the center thereof.

On the other hand, in the inspection of FIG. 12 (b), the inspected body 10 is inspected with the in-plane orientation changed by 90 ° with respect to FIG. 12 (a). At this time, the crack as shown in FIG. 12A could not be detected. However, as shown in the lower part of the image, scattered parts at other points were observed. That is, from this result, it was found that the detection accuracy depends on the shape and orientation of the crack when the defect is inspected only by the conventional single incident angle. In order to solve this problem of detection accuracy, it is necessary to perform an inspection in which the direction of the light source or the orientation of the object to be inspected is changed, so that the inspection efficiency is lowered due to an increase in the number of operations.

Under such circumstances, the present inventors have investigated a method for inspecting defects with excellent inspection efficiency, which can eliminate such dependence on the orientation of cracks. That is, an object of the present invention is to provide a method for detecting a defect and a defect inspection apparatus capable of inspecting to eliminate the dependence of the orientation of the defect. Further, it is to provide a light source device suitable for that purpose.

As a result of diligent research to solve the above problems, the present inventor has found that the following invention meets the above object, and has arrived at the present invention.

That is, the present invention relates to the following invention.

The present invention is a method of inspecting a defect of an inspected object by irradiating the inspected object with light having a wavelength that can be transmitted into the inspected body and detecting the scattered light, and the inspected object is subjected to the above-mentioned. The step of irradiating the inspection position of the object to be inspected with the light condensed by the light condensing means and determining the intensity of the scattered light generated by the light condensing means and detecting the intensity of the scattered light by the scattered light detecting means, and the intensity of the scattered light. The present invention relates to a method for inspecting a defect, which comprises a step of detecting a defect by comparing the intensity of scattered light obtained in the required step with a predetermined threshold value.

Further, in the present invention, the support portion of the inspected object and the inspected object supported by the support portion are irradiated with light having a wavelength that can pass through the inspected object and condensed by a condensing means. The light source device, the scattered light detecting means for detecting the scattered light of the light irradiated to the object to be inspected by the light source device, and the intensity of the light detected by the scattered light detecting means are compared with a predetermined threshold value. The present invention relates to a defect inspection apparatus comprising an arithmetic processing unit for detecting defects in an inspected object.

According to these inventions, since the light to be inspected is simultaneously irradiated with light having various incident angles, it is possible to prevent a decrease in inspection accuracy due to the orientation of defects existing in the inspected object and to be excellent. Defect inspection is possible with the same inspection accuracy.

Further, the present invention irradiates the inspected body with light having a wavelength that can be transmitted into the inspected body in a state where no stress is applied to the inspected object and a state in which the stress is applied, and detects the scattered light. This is a method of inspecting a defect of the inspected object by irradiating the inspection position of the inspected object with light condensed by a condensing means without applying stress to the inspected object. In the step of obtaining the intensity of the first scattered light in which the intensity of the scattered light generated by the above is detected by the scattered light detecting means, and in a state where the stress is applied to the inspection position of the inspected object by the stress applying means, the inspected object is inspected. The step of irradiating the inspection position of the above with the light collected by the condensing means and obtaining the intensity of the second scattered light for detecting the intensity of the scattered light generated by the light condensing means by the scattered light detecting means, and the first scattering. By comparing the intensity of the first scattered light obtained in the step of obtaining the intensity of light with the intensity of the second scattered light obtained in the step of obtaining the intensity of the second scattered light with a predetermined threshold value. The present invention relates to a method for inspecting a defect, which comprises a step of detecting a defect.

Further, in the present invention, the support portion of the inspected object, the stress applying means for applying stress to the inspected object supported by the support portion, and the inspected object supported by the support portion are subjected to the inspected object. A light source device that irradiates light having a wavelength that can pass through the body by condensing means, a scattered light detecting means that detects scattered light of light radiated by the light source device on the object to be inspected, and the subject. An arithmetic processing unit that detects defects in the inspected object by comparing the intensity of light detected by the scattered light detecting means with a predetermined threshold value in a state where stress is applied to the inspected object and a state in which stress is not applied to the inspected object. It relates to a defect inspection device characterized by being provided with.

According to these inventions, since the light to be inspected is simultaneously irradiated with light having various incident angles, it is possible to prevent a decrease in inspection accuracy due to the orientation of defects existing in the inspected object and to be excellent. Defect inspection is possible with the same inspection accuracy. Furthermore, stress can be applied by the stress application unit, and finer defects and the like can be detected with excellent accuracy based on the scattered light with and without stress application.

In the present invention, it is preferable that the light collected by the light collecting means is parallel light. The parallel light is excellent in that high-intensity light can be efficiently incident on the condensing means and the irradiation angle and range thereof can be easily controlled. Further, by using parallel light, it is excellent in that it is easy to adjust the light uniformly irradiated from all directions to the inspection position of the inspected object in combination with the condensing means.

In the present invention, it is preferable that the light collecting means is an axicon lens. When an axicon lens is used, it is easy to irradiate the inspection position of the object to be inspected as light having various irradiation angles without reducing the light intensity of the light incident on the axicon lens. Further, at this time, the use of parallel light is particularly excellent in that it is easy to adjust the light uniformly irradiated from all directions.

In the present invention, it is preferable that the light irradiating the inspection position of the object to be inspected is polarized light, and the scattered light detecting means obtains the scattered light by polarization separation. By separating the polarizations and analyzing them, it is possible to perform more accurate inspections such as defect classification including polarization dependence and noise removal.

In the present invention, it is preferable that the angle at which the condensed light is incident on the scattered light detecting means is blocked by the light blocking means. By having the light-shielding means, it is possible to remove the light incident on the scattered light detecting means even by condensing the light, and it is possible to detect only the scattered light with high accuracy.

In the present invention, it is preferable to adjust the intensity of the parallel light by the parallel light intensity adjusting means for adjusting the intensity of the parallel light. By adjusting the intensity of the parallel light, the intensity of the scattered light can be adjusted so that the amount of light that can be easily analyzed by the scattered light detecting means can be adjusted.

In the present invention, it is preferable that the stress applying means is a non-contact type stress applying means that applies stress to the inspected object in a non-contact manner. Since the stress applying means is a non-contact type, it is possible to suppress noise, abnormal deformation, formation of new defects, etc. due to contact of the stress applying means with the object to be inspected.

In the present invention, it is preferable that the stress applying means is a thermal stress applying means that applies stress by heating and / or cooling the object to be inspected. Since the stress applying means is a thermal stress applying means, it is possible to suppress noise, abnormal deformation, formation of new defects, etc. due to the force of mechanical deformation.

In the present invention, the parallel light is preferably light derived from a laser light source. The laser light source has high directivity, and it is easy to design an optical path so that light does not enter the scattered light detection means when scattering does not occur, and it is easy to design a high light intensity, so the intensity of scattered light is also detected. Easy to adjust to a strength that is easy to do.

The present invention has a parallel light irradiating means for irradiating parallel light having a wavelength that can pass through the inspected object, and a condensing means for condensing the light radiated by the parallel light irradiating means on the inspected object. It can be a light source device for inspection. By irradiating the light collecting means with parallel light and condensing the light, the light to be inspected can be uniformly irradiated from all directions (circumferential direction with respect to the inspection position). Therefore, it is possible to efficiently irradiate the object to be inspected with high-intensity light from various incident angles. As a result, it is possible to carry out an inspection in which irradiation is performed from substantially all directions, and it is possible to carry out an inspection in which there are few shadows and the dependence of the inspection light on the incident direction is small.

According to the method for inspecting defects and the defect inspection apparatus of the present invention, defects can be detected with excellent inspection accuracy regardless of the orientation of the defects existing in the inspected object. Further, the light source device of the present invention is a light source device suitable for defect inspection of the present invention, and can efficiently irradiate an object to be inspected with high-intensity light from various incident angles.

It is a schematic diagram which shows the defect inspection apparatus which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the defect inspection apparatus which concerns on the 2nd Embodiment of this invention. It is a schematic diagram which shows the light source apparatus which concerns on 3rd Embodiment of this invention. It is a schematic diagram which shows the light source apparatus which concerns on 4th Embodiment of this invention. It is a schematic diagram which shows the light source apparatus which concerns on 5th Embodiment of this invention. It is a schematic diagram which shows the flow of the defect inspection method S1 of this invention. It is a figure of the defect observed by the defect inspection which concerns on Example 1 of this invention. It is a figure of the defect observed by the defect inspection which concerns on Example 2 of this invention. It is another figure of the defect observed by the defect inspection which concerns on Example 2 of this invention. It is another figure of the defect observed by the defect inspection which concerns on Example 2 of this invention. It is a schematic diagram which shows the defect inspection apparatus 200 of the structure based on the conventional defect inspection apparatus. It is a figure of the defect observed by the defect inspection apparatus 200.

Hereinafter, embodiments of the present invention will be described in detail, but the description of the constituent elements described below is an example (representative example) of the embodiments of the present invention, and the present invention is described below unless the gist thereof is changed. It is not limited to the contents of.

[First Embodiment]
FIG. 1 shows a defect inspection device according to the first embodiment of the present invention. The defect inspection device 101 shown in FIG. 1 is an apparatus for inspecting defects of the inspected body 10 supported by the support portion 11. The defect inspection device 101 includes a light emitting means 20, a beam expander 21, a reflecting mirror 22, a light shielding portion 24, a condenser lens 231, a stress applying means 41, an objective lens 31, and a scattered light detecting means 30. Have. The scattered light detected by the scattered light detecting means 30 is processed by the arithmetic processing unit 50 and displayed on the display unit 60 as appropriate. Further, the image detected by the scattered light detecting means can be observed via the magnified observation processing unit 70 for the purpose of specifying the inspection position and the like.

The defect inspection device 101 irradiates the inspected body 10 with light having a wavelength that can be transmitted into the inspected body 10 in a state where stress is not applied to the inspected body 10 and a state in which stress is applied, and the scattered light thereof. By detecting the above, the defect of the inspected body 10 can be inspected.

In the defect inspection device 101, the inspection position of the inspected object 10 is irradiated with the light transmitted through the inspected object 10 emitted from the light emitting means 20 as follows. First, the light emitted from the light emitting means 20 to the beam expander 21 is irradiated to the reflector 22 side as parallel light (the direction is indicated by the arrow P1 in FIG. 1) by the beam expander 21. Then, the light reflected from the reflecting mirror 22 is condensed by the condenser lens 231 and irradiates the inspected position of the inspected body 10. The condenser lens 231 serves as a means for collecting parallel light derived from the beam expander 21. When irradiating from the condenser lens 231, a light-shielding portion 24 which is a light-shielding means is provided so that light having an incident angle directly transmitted from the reflecting mirror 22 to the scattered light detecting means 30 side is not provided. This optical system is a so-called dark field system irradiation system. The two-dot broken line in the figure shows the concept of the direction of the parallel light and the focused light.

Stress can be applied to the inspected object 10 by the stress applying means 41, and depending on whether or not the stress applying means 41 is used, a state in which stress is applied to the inspected object and a state in which no stress is applied. And can be achieved.

First, without using the stress applying means 41, the light focused through the condenser lens 231 is irradiated to the inspected position of the inspected object 10 as described above, and the first scattered light generated by the light is irradiated to the inspected position. Perform the process of determining the strength. The intensity of the first scattered light is detected by the scattered light detecting means 30, appropriately stored in a memory (not shown), and becomes data to be arithmetically processed by the arithmetic processing unit 50.

Next, in a state where stress is applied to the inspected position of the inspected object 10 by the stress applying means 41, the inspected position of the inspected object 10 is irradiated with light focused through the condenser lens 231 to obtain the same. The intensity of the second scattered light generated by the above is obtained. The intensity of the second scattered light is detected by the scattered light detecting means 30 and appropriately stored in a memory (not shown), and is subjected to arithmetic processing by the arithmetic processing unit 50, similarly to the intensity of the first scattered light described above. It becomes the data to be done.

The intensity of the first scattered light and the intensity of the second scattered light obtained in this way are arithmetically processed by the arithmetic processing unit 50, and defects are detected by comparing them with a predetermined threshold value. be able to. In this defect detection, the parallel light derived from the beam expander 21 is focused by the condenser lens 231, and the light having various incident angles irradiates the inspected object 10 with the scattered light. Therefore, the defect can be detected without depending on the incident angle with respect to the object to be inspected 10, and the defect detection accuracy can be improved.

As described above, the defect inspection device 101 has a support portion 11 of the inspected body 10. Further, it has a stress applying means 41 for applying stress to the object to be inspected supported by the support portion 11. Further, a light emitting means 20 having a wavelength capable of passing through the inspected body 10 and a beam expander 21 in which the light derived from the light emitting means 20 is parallel light to the inspected body 10 supported by the support portion 11. The light collected by the condenser lens 231 that collects the parallel light is irradiated. Therefore, with these configurations, a light source device for irradiating the object 10 to be inspected with light collected by condensing parallel light is formed. Further, the scattered light of the light irradiated to the inspected object 10 through the condenser lens 231 is detected by the scattered light detecting means 30. Therefore, the scattered light detecting means 30 is a light receiving means for detecting the scattered light of the light irradiated to the inspected object 10 by the above-mentioned light source device. Further, a defect in the inspected object 10 is obtained by comparing the intensity of the light detected by the light receiving means (scattered light detecting means 30) with a predetermined threshold value in the state where the stress is applied to the inspected object 10 and the state where the stress is not applied to the inspected object 10. It has an arithmetic processing unit 50 that detects the above.

[Light emitting means (light source)]
In the present invention, the light irradiating the object to be inspected is light having a wavelength that can pass through the object to be inspected. This light is irradiated by using a light emitting means that emits light having a wavelength that can be transmitted to the object to be inspected. If there is a portion such as a defect that is the starting point of scattering, the scattered light is widely scattered in various directions from that portion. When examining this scattering direction, the forward scattering that scatters in the direction in which the incident light travels is often the strongest scattering. In the present invention, in order to improve the detection accuracy including the scattering property due to the size and the like in addition to the dependence of the defect direction, the forward scattering or the scattering close to the forward scattering is detected. Therefore, the light irradiating the object to be inspected is light having a wavelength that can pass through the object to be inspected. Further, the surface (side) to irradiate the light to the object to be inspected and the surface (side) to which the means for detecting the scattered light is provided are configured to detect the transmitted light side instead of the reflected light. ) Is preferable.
The light irradiated in the present invention includes light having a wavelength of 400 to 800 nm, as well as light having a wavelength in the ultraviolet region to a wavelength in the near infrared region. The light to be irradiated is appropriately selected from the wavelengths in this range in consideration of each object to be inspected, the measurement environment, transparency, ease of detection, and the like.

As the light to be irradiated, various types of light that can determine the scattered light intensity of the object to be inspected can be selected and used. For example, as the light to irradiate, the light having a specific wavelength dispersed may be used. If the light is spectroscopic, it is easy to detect the penetration / transmission and scattering intensity of the light of that wavelength with respect to the inspected object, and on the other hand, the characteristics of the inspected object such as the influence of absorption / reflection are examined. Therefore, there is an advantage that the measurement can be easily performed at the optimum wavelength.

Further, it is preferable to use laser light as the light to be irradiated. The higher the intensity of the irradiated light, the higher the intensity of the scattered light and the light intensity that is easier to detect, and the laser light easily achieves the light intensity suitable for such detection.

Further, as the light to be irradiated, an LED may be used, or a monochromatic light emitting LED may be used. Furthermore, it is even better to use a high-luminance one. As for this LED, the higher the intensity of the irradiated light, the higher the intensity of the scattered light and the easier it is to detect. Therefore, it is preferable to set the intensity of the irradiated light to be high.

In the present invention, the scattered light intensity may become too strong and difficult to detect due to a configuration such as detecting forward scattering. Therefore, it is preferable to have a step of adjusting the intensity of the parallel light by the parallel light intensity adjusting means for adjusting the intensity of the parallel light. The most straightforward method for achieving this is that the light emitting means can adjust the amount of light. In addition to this, it is possible to adjust the amount of light shielding by the light-shielding portion, the magnification of the objective lens, the presence / absence of a polarizing filter (polarization separation means), its arrangement, and the like.

[Parallel light (parallel light irradiation means)]
In the present invention, the light applied to the object to be inspected is preferably light in which parallel light is condensed. This parallel light refers to light that is line-irradiated or surface-irradiated in parallel with light having strong directivity with respect to the condensing means. When such parallel light is applied to the condensing means, the directivity is strong and the light is widely incident on the condensing means, so that the directing derived from the parallel light is directed to a predetermined focal point at various incident angles. It can irradiate strong light.

As the parallel light, for example, laser light is used as a light emitting means, and a known optical element such as a collimator lens is combined to perform line irradiation of pseudo-parallel irradiation light or area irradiation of pseudo-plane irradiation light. be able to.

The parallel light can also be irradiated by a beam expander capable of irradiating the laser light source as light equivalent to an appropriate parallel light at a distance to the condensing means. Furthermore, it is also possible to irradiate light equivalent to parallel light by a combination of a concave lens and a convex lens, which will be described later.

[Reflector]
In the present invention, the optical path may be controlled by a reflecting mirror or the like arranged at an appropriate position for irradiation, detection, and the like of various types of light. For example, in the embodiment of the present invention, a reflecting mirror is mainly provided before irradiating the condensing means with the light irradiated by the parallel light irradiating means (beam expander or combination of concave lens and convex lens). This reflector may be appropriately used according to the specifications of each means and the like as long as the present invention can be achieved by utilizing the characteristics of light.

[Condensing means]
In the present invention, light having strong directivity is incident on the condensing means, and light having strong directivity can be irradiated to a predetermined focal point at various incident angles. This condensing means, for example, a condenser lens or an axicon lens, condenses the light at a predetermined focal position depending on the incident position of the light incident on the optical element. Defect detection is performed by arranging the inspection position of the object to be inspected at the position of the focal point of the light collecting means.

Further, a conical mirror having a reflecting mirror portion on the outside and a truncated cone-shaped mirror having a reflecting mirror portion on the inside can be combined as a light collecting means. In this case, a conical mirror is placed inside the conical mirror, light is incident from the apex side of the conical mirror, the incident light is reflected on the outer surface of the conical mirror, and the conical mirror is reflected in the reflecting direction. By arranging the inner side surface of the mirror, the light reflected by the conical trapezoidal mirror irradiates the bottom side of the inner conical mirror with the condensed and diffused light. By arranging the inspected object near the focal point for condensing light, this configuration also serves as condensing means. This configuration shows an example with reference to the fifth embodiment described later.

Depending on the incident position of parallel light or the like with respect to the condensing means, the irradiation direction of a part of the light emitted so as to be condensed from the condensing means may be the position of the scattered light detecting means. In this case, the scattered light detecting means is directly irradiated with the light, and the emitted light is generally stronger than the scattered light, so that the scattered light detecting means is directly irradiated from the condensing means. The detection of the intensity of the incident light becomes noise, and there is a possibility that the scattered light cannot be detected. Therefore, it is preferable to provide a light-shielding portion that shields the direction of the light directly incident from the light-collecting means to the scattered light detecting means, depending on the light-collecting means.

Although it depends on the type of the light collecting means and the arrangement of the scattered light detecting means, the light incident in the direction perpendicular to the center of the light collecting means is generally regarded as the scattered light detecting means arranged near the center. On the other hand, it is often configured to be directly incident. This is because the arrangement of the scattered light detecting means is suitable for detecting scattered light having many incident angles having a large inclination angle. Therefore, it is preferable that the light-shielding portion is provided only in the center of the range where the parallel light or the like is irradiated to the condensing means. This range can be designed to block an area of about 5 to 30% with respect to the irradiation area of parallel light or the like for the condensing means. The light-shielding portion can be simply provided by a method such as attaching a sticker having light absorption (black or the like) used for inspection to the target position of the light collecting means.

[Support]
In carrying out the present invention, the entire body to be inspected is supported by a support portion by, for example, gripping both ends of the body to be inspected with fasteners. This support portion may simply support the object to be inspected, but is preferably connected to a position changing means such as a so-called XY stage so that the inspection position can be easily changed.

[Inspected body]
The inspected object to be inspected by the present invention may be an inspected object capable of transmitting light adopted in the present invention. For example, a member using a glass material that is almost transparent to general light (400 to 800 nm) and transmits those light, a member using a transparent resin, SiC (silicon carbide, silicon carbide) or GaN ( Members using gallium nitride, gallium nitride) can be mentioned. Further, since a silicon wafer also transmits near infrared rays, it can be an inspected object by selecting light having a wavelength that can be transmitted as a light source. In the present invention, since the defect is detected by detecting the scattered light, it is easy to distinguish the irregular scattered light derived from the defect from the other ones by easily grasping the one having high smoothness and the pattern. It is preferable to target things.

[Stress applying means]
In the present invention, since it is necessary to compare the presence or absence of stress applied to the object to be inspected, the stress applying means is used. In order to apply stress, the method of directly contacting the part to be inspected by applying a force such as pressing or pulling is easier to make a more straightforward structure and it is easier to apply stress, so such a stress applying means is adopted. You may. On the other hand, such a method may cause disturbance, and in this case, it is preferable to apply stress by a stress applying means that does not contact the inspected object. Examples of the non-contact stress applying means include a stress applying means by thermal stress and a means by sound wave.

As the stress applying means adopted in the present invention, a thermal stress applying means for applying stress by heating and / or cooling the object to be inspected is preferable. As the specific thermal stress applying means, it is preferable that the heated and / or cooled gas is applied to the object to be heated and / or cooled. That is, it is preferable to apply stress to the object to be inspected by applying a gas having a temperature higher than that of the object to be inspected or a gas having a temperature colder than that of the object to be inspected. The gas applied to the inspected object can be easily adjusted so that the position and shape of the inspected object do not fluctuate by applying the gas to the inspected object, and is suitable as the stress applying means by the thermal stress of the present invention. Alternatively, an infrared heat beam may be used, or a Pelche element may be partially attached to generate a temperature difference in the body to be inspected to apply stress.

[Scattered light detection means (light receiving means)]
In the present invention, the scattered light scattered from the object to be inspected is detected by a configuration capable of detecting the light. The intensity of the scattered light is detected by the light receiving means, and is appropriately stored in a storage unit (memory) or the like in order to distinguish the presence or absence of stress application and compare the scattered light intensity. This scattered light is detected by a line sensor as one-dimensional linear information or an area as two-dimensional planar information so that the position of the scattered light of the inspected object can be specified. It may be detected by a sensor. For example, when the scattered light is in the range of visible light or the like, it can be detected by a CCD camera or the like as planar information. In addition, in order to reduce the variation in the detection sensitivity of the scattered light intensity, it is better to detect the scattered light intensity a plurality of times and obtain the scattered light intensity as an integral value thereof.

[Arithmetic processing unit]
In the present invention, with respect to the inspected portion of the same inspected object, the irradiation light is obliquely directed to the inspected portion in a state where stress is applied to the inspected object and in a state where the stress is not applied. Irradiate from, and measure the scattered light intensity. As a result, the intensity of the scattered light (intensity of the first scattered light) obtained in the state where the stress is not applied to the inspected object and the scattered light obtained in the state where the stress is applied to the inspected object are obtained. Since the intensity of (second scattered light intensity) can be obtained, defects can be detected by comparing with a predetermined threshold value based on these ratios. The contrast of this predetermined threshold value is performed by the arithmetic processing unit.

A predetermined threshold value used for determining the defect is set by the size of the defect to be detected, the material of the object to be inspected, the intensity of the irradiated / scattered light, and the like. The subject to be inspected, which is the main object of the present invention, has high homogeneity. Scattering is unlikely to occur even if light is irradiated to such an object to be inspected without applying stress, and scattering occurs only when a foreign substance or the like is present. Also, defects such as micron-sized cracks often have little scattering when no stress is applied. However, when stress is applied in the presence of micron-sized cracks, large scattering occurs. Therefore, if the scattered light intensity ratio is within the range of the scattered light intensity expected as noise when the scattered light is detected, or when there is clearly a foreign substance, and the scattered light intensity ratio is taken before and after the stress is applied, the ratio is centered on about 1. It becomes the range that was done. On the other hand, if there are micron-sized cracks, large scattering occurs when stress is applied, so the scattered light intensity ratio before and after stress application is set to "scattered light intensity after stress application / scattered light intensity before stress application". Then, it exceeds 1 and becomes a large value. Therefore, the range in which this ratio is assumed by the noise level may be set as the threshold value.

[Magnified observation processing unit]
In the present invention, observation using a microscope may be performed. For this purpose, it is possible to use a method of inspecting the inspected portion of the inspected body having an enlarged observation step of magnifying and observing the inspected portion. Further, the inspection device can be provided with a microscope for observing the inspected portion of the inspected object. Here, the microscope is a configuration in which a minute object can be visually magnified and observed by using an optical or electronic technique. For example, the information of scattered light may be observed with the naked eye through a magnifying lens or the like, or it may be detected by a CCD camera or the like and used as an image. The present invention relates to a technique capable of providing such a microscope, and it is possible to observe a portion determined to be a defect by having a microscope as appropriate and promptly, and only as information on scattered light intensity. Instead, the defect can be discriminated from the magnified observation image.

[Display]
The result of inspecting the defect according to the present invention can be output as appropriate so that the result can be easily recognized, and can be displayed on a monitor or the like as a display unit.

[Second embodiment]
FIG. 2 shows a defect inspection device according to a second embodiment of the present invention. Since the defect inspection device 102 shown in FIG. 2 has a configuration similar to that of the inspection device 101 according to the first embodiment, the differences will be mainly described below. The defect inspection device 102 has a concave lens 211 and a convex lens 212 instead of the beam expander 21. Further, it has an axicon lens 232 instead of the condenser lens 231. By using the axicon lens 232 and providing the objective lens 31 and the scattered light detecting means 30 in an appropriate arrangement (distance), there is no light directly incident on the scattered light detecting means 30. The configuration is such that 24 can be omitted. Further, in the second embodiment, it has a polarizing filter 251 and a polarizing filter 252.

In the second embodiment, the light emitted from the light emitting means 20 is spread by the concave lens 211, and then the parallel light (outlined by P2 in FIG. 2) in which the irradiation directions of the spread light are aligned by the convex lens 212. Shows). This parallel light is reflected by the reflecting mirror 22 and irradiates the axicon lens 232. The light incident on the axicon lens 232 is condensed and irradiated on the object to be inspected. Therefore, with these configurations, a light source device for irradiating the object 10 to be inspected with light collected by condensing parallel light is formed.

In the second embodiment, the axicon lens 232 is used as the condensing means. This axicon lens is an optical element having a conical portion. Light incident from the bottom surface side of the conical portion is linearly focused at a plurality of positions centered on the optical axis in the direction of the apex of the cone. For this focusing, for example, the light incident on the left side of the axicon lens 232 in FIG. 2 is focused as light having a width as shown by a two-dot broken line parallel to the direction C1 side. Similarly, the light incident on the right side is focused as light having a width shown by a two-dot broken line parallel to the direction C2 side. Here, for convenience of the figure, the direction C1 and the direction C2 are shown, but these are shown in cross section, and this light collection is at a position extending from the surface of the inspected object 10. It becomes a ring shape. According to this axicon lens, if the inspected object is placed at an appropriate position in the ring-shaped optical path, the inspected position of the inspected object is substantially irradiated with light having a circumferential tilt angle. It becomes. Further, in principle, since the noise of the high-intensity light transmitted through the center is small even if the light-shielding portion is not provided, the total intensity of the light used for the inspection is strong, and the scattered light intensity is likely to be generated accordingly.

Further, in the second embodiment, the polarizing filter 251 for polarizing the light irradiating the inspection position of the inspected object 10 and the scattered light detecting means 30 can obtain the scattered light by polarization separation. Has a polarizing filter 252. As both the polarizing filter 251 and the polarizing filter 252, a linear polarizing filter, a circular polarizing filter, or the like can be adopted. For example, by using both the polarizing filter 251 and the polarizing filter 252 as linear polarizing filters in the arrangement of the cross Nicol, it is possible to detect that the scattering from the inspected object 10 changes the degree of polarization of the linearly polarized light. , Only defects can be detected efficiently. In particular, in the present invention, defects that cause significant scattering after stress application are often scattered to change the degree of polarization as compared before and after stress application, so such defects are detected with higher detection accuracy. can do.

[Detection of polarized light component]
As disclosed in the second embodiment, the polarizing component may be detected by the polarizing filters 251 and 252. As the polarization component, a means capable of adjusting linearly polarized light, elliptically polarized light, and circularly polarized light can be appropriately adopted. Typical examples are polarizing plates and polarized lenses, but optical elements other than these may be used. By making it possible to analyze the polarization component, it is possible to improve the accuracy of defect detection and contribute to the classification of the type of defect.

[Third embodiment]
FIG. 3 shows a light source device 103 of the defect inspection device according to the third embodiment of the present invention. Since the light source device 103 shown in FIG. 3 has a configuration in which a part of the defect inspection device 102 according to the second embodiment can be modified and used, the differences will be mainly described below. The light source device 103 has a parallel light irradiating means 213, and irradiates the parallel light (the outline is shown by P3 in FIG. 3) toward the reflecting mirror 22. Then, the parallel light reflected by the reflector 22 is incident on the axicon lens 232 as in the second embodiment. Further, the third embodiment is configured not to include the polarizing filter 251 and the polarizing filter 252. In the second embodiment of FIG. 2, a configuration is disclosed in which the polarizing filters 251 and 252 are combined, but the polarizing filters 251 and 252 can be omitted in this way.

[Fourth Embodiment]
FIG. 4 shows a light source device 104 of the defect inspection device according to the fourth embodiment of the present invention. Similar to the light source device 103, the light source device 104 shown in FIG. 4 has a configuration in which a part of the defect inspection device 102 according to the second embodiment can be modified and used. Here, similarly to the light source device 103, the polarizing filters 251 and 252 are omitted, but the light-shielding portion 241 is attached to the center of the axicon lens 232. As described above, the axicon lens 232 has a small amount of light transmitted through its center and detected by the scattered light detecting means 30, but it depends on the incident angle of parallel light (derived from the parallel light irradiating means 213) and the like. Noise may be detected. By providing the light-shielding portion 241, it is possible to perform a highly stable inspection by further eliminating the concern about noise.

[Fifth Embodiment]
FIG. 5 shows a light source device 105 of the defect inspection device according to the fifth embodiment of the present invention. Similar to the light source device 103, the light source device 105 shown in FIG. 5 has a configuration in which a part of the defect inspection device 102 according to the second embodiment can be modified and used. The light source device 105 has a light irradiating means 214, and the light radiated from the light irradiating means 214 (the outline is shown by P4 in FIG. 5) is reflected by the reflecting mirror 22 toward the apex side of the conical mirror 233. Be irradiated. The conical mirror 233 is a conical mirror having a reflecting mirror portion on the outside. The light emitted to the apex side of the conical mirror 233 is reflected to the truncated cone mirror 234 and further reflected inside the truncated cone mirror 234 to irradiate the object 10 to be inspected from various angles. It becomes a composition. Therefore, the conical mirror 233 and the truncated cone mirror 234 function as condensing means for the object 10 to be inspected. In this fifth embodiment, by adjusting the reflection angle between the conical mirror and the truncated cone mirror, irradiation from various angles is achieved even if the irradiation area of the light incident on the conical mirror is small. You can also do it. Therefore, the light emitted from the light irradiating means 214 may be narrower than the parallel light (P1 to P3) of the first to fourth embodiments.

[Sixth Embodiment]
FIG. 6 is a diagram for explaining in more detail the flow of the defect inspection method S1 using the defect inspection apparatus 1 and the like of FIG. The defect inspection method S1 includes a step S10 for obtaining the scattered light intensity (intensity of the first scattered light) of the inspected portion of the inspected object without applying stress and a stress applied state (a state in which stress is applied to the inspected object). This is an inspection method including a step S20 for obtaining the scattered light intensity (second scattered light intensity) of the inspected portion of the inspected object, and a step S30 for detecting defects from the results of the steps S10 and S20. This defect inspection method S1 can be performed using the defect inspection device 1 or the like, which is the first embodiment.

The step S10 includes a step S11 of condensing and irradiating the surface with light at the inspection position of the inspected object without applying stress to the inspected object, and the intensity of the scattered light generated thereby. This is a step including the step S12 for obtaining (the intensity of the first scattered light).

Step S20 includes a step S21 in which light is focused and irradiated at the same inspection position of the inspected object as in which light was irradiated in step S11 with stress applied to the inspected object. This is a step including the step S22 for obtaining the intensity of the scattered light (second scattered light intensity) generated by the above.

Then, in step S30, the intensity of the scattered light (intensity of the first scattered light) obtained in the state where the stress was not applied to the inspected object in step S10 and the stress were applied to the inspected object in step S20. It has a step S31 for comparing the intensity of the scattered light (intensity of the second scattered light) obtained in the state, and a step S32 for comparing the contrasted value obtained by the step S31 with a predetermined threshold value. This is a step including a step S33 for determining a defect from the result of S32. As a result, defects that are difficult to detect without applying stress, such as micron-sized cracks, can be detected separately from noise and foreign matter.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is changed.

[Example 1]
Based on the inspection device 101 according to the first embodiment, the experiment of Example 1 was carried out by the design showing the main configurations below.

Light emitting means 20: Laser (OBIS manufactured by Coherent, wavelength 532 nm, 50 mW)
Beam Expander 21: Beam Expander (Edmond Optics Japan, 20x)
Light-shielding part 24: Light-shielding plate (φ15 mm)
Condenser lens 231: Condenser lens (φ30mm, focal point f = 50mm)
Subject 10: Glass substrate (length 76 mm, width 25 mm, thickness 1 mm), placed 50 mm above the condenser lens according to the focal length of the condenser lens Support portion 11: Both ends of the glass substrate (about 2 mm at each end) Clamp that grips each), connected to a rotating stage (Sigma Kouki Co., Ltd.) Stress application means 41: Dryer that adjusts the air outlet to Φ3 mm to blow hot air with high directional lens 31: Objective lens (5x)
Scattered light detection means 30: Camera (cooled CCD camera manufactured by BITRAN, 772 x 580 pxel)
Calculation processing unit 50: The ratio of scattered light intensity (scattered light intensity after stress application / scattered light intensity before stress application) was used as surface image information. A point having a scattered light intensity ratio of 1.2 or more was emphasized (displayed in gray) as a portion having a possibility of a defect, and a point having a ratio of scattered light intensity exceeding 1.5 was particularly emphasized (displayed in white).
Display unit 60: The calculation result of the calculation processing unit is displayed on the monitor.

With this configuration, the detection inspection was performed while changing the orientation of the object to be inspected using the rotating stage. In addition, in the defect inspection apparatus 200 shown in FIG. 11, this inspected object is a target in which a remarkable orientation dependency was observed at the time of defect detection, as shown in FIG.

FIG. 7 shows the results of defect detection when the object to be inspected was rotated 90 °, 180 °, and 270 ° with the orientation of the object to be inspected at the time of initial installation as a reference of 0 °. 7 (a) is an observation image when rotated by 0 °, (b) is 90 °, (c) is 180 °, and (d) is 270 °.

As is clear from these figures, obvious defects were detected at any angle. Therefore, according to the present invention, defects can be detected with high detection accuracy without changing the orientation of the object to be inspected.

[Example 2]
Based on the defect inspection apparatus 102 according to the second embodiment, the experiment of Example 2 was carried out by the design showing the main configurations below. The objective lens 31 is omitted from the second embodiment. Further, the description of the configuration of the light emitting means 20, the object to be inspected 10, the support portion 11, and the scattered light detecting means 30 common to those of the first embodiment will be omitted.

Concave lens 211: Concave lens (φ6 mm, focal length f = 6 mm)
Convex lens 212: Convex lens (φ25 mm, focal length f = 120 mm)
Polarizing filters 251, 252: Polarizing filters (linearly polarized light manufactured by Sigma Kogyo), and polarizing filters 251,252 were arranged so as to be cross Nicols.
Axicon lens 232: Axicon lens (SIGMA KOKI, Inc., apex angle 155 degrees)
Display unit 60: The calculation result of the calculation processing unit is displayed on the monitor.

With this configuration, the detection inspection was performed while changing the orientation of the object to be inspected using the rotating stage.

FIG. 8 shows the result of defect detection when the object to be inspected is moved to 90 ° with the orientation of the object to be inspected at the time of initial installation as a reference of 0 °. FIG. 8A is an observation image when rotated by 0 °, and FIG. 8B is an observation image when rotated by 90 °. Since the objective lens is not used, the edge corresponding to the circumference of the lens is displayed at the same time.

As is clear from these figures, a clear defect was detected in the center of the image at any angle. Therefore, according to the present invention, defects can be detected with high detection accuracy without changing the orientation of the object to be inspected.

Further, FIG. 9 is a diagram in which the amount of light of the light emitting means 20 is adjusted and the image is taken again at 0 ° corresponding to FIG. 8 (a), and an enlarged view (right side) of the defect corresponding portion. Similarly, FIG. 10 is a diagram in which the amount of light of the light emitting means 20 is adjusted and re-imaged at 90 ° corresponding to FIG. 8 (b), and an enlarged view (right side) of the defect corresponding portion. By adjusting the amount of light in this way, it was possible to detect defects more clearly.

According to the present invention, defects such as glass and wafers can be detected with higher accuracy, which is industrially useful. The present invention also contributes to improving the defect detection speed.

10 Inspected object 101, 102, 200 Defect inspection device 103, 104, 105 Light source device 11 Support part 20 Light emitting means 21 Beam expander 211 Concave lens 212 Convex lens 213 Parallel light irradiation means 214 Light irradiation means 22, 221 Reflector 231 Condenser lens 232 Axicon lens 233 Conical mirror 234 Conical trapezoidal mirror 24,241 Shading unit 251,252 Polarizing filter 30 Scattered light detection means 31 Objective lens 40, 41 Stress application means 50 Calculation processing unit 60 Display unit 70 Magnifying observation processing unit S1 Defect inspection Method

Claims (8)

By irradiating the inspected body with light having a wavelength that can be transmitted into the inspected body in a state where stress is not applied to the inspected body and in a state where stress is applied, and detecting the scattered light of the inspected body, the inspected body is subjected to light. It ’s a method of inspecting defects.
With no stress applied to the object to be inspected, the inspection position of the object to be inspected is irradiated with light collected by condensing parallel light, and the intensity of the scattered light generated thereby is detected. The process of determining the intensity of the first scattered light detected by means,
In a state where stress is applied to the inspection position of the inspected object by the stress applying means, the inspected position of the inspected object is irradiated with the condensed light of parallel light by the condensing means, and the scattered light generated by the light is irradiated. The step of obtaining the intensity of the second scattered light, in which the intensity is detected by the scattered light detecting means, and
A step of blocking light at an angle directly incident on the scattered light detection means by the light blocking means, which is collected by the light collecting means.
A predetermined threshold value is the intensity of the first scattered light obtained in the step of obtaining the intensity of the first scattered light and the intensity of the second scattered light obtained in the step of obtaining the intensity of the second scattered light. A method for inspecting a defect, which comprises a step of detecting a defect by contrasting with. The method for inspecting a defect according to claim 1, wherein the light collecting means is an axicon lens. The method according to claim 1 or 2, wherein the light irradiating the inspection position of the object to be inspected is polarized light, and the scattered light detecting means has a step of obtaining the scattered light by polarization separation. The method for inspecting a defect according to any one of claims 1 to 3, further comprising a step of adjusting the intensity of parallel light by the parallel light intensity adjusting means for adjusting the intensity of parallel light. The method for inspecting a defect according to any one of claims 1 to 4, wherein the stress applying means is a non-contact type stress applying means for applying stress to the object to be inspected in a non-contact manner. The method for inspecting a defect according to any one of claims 1 to 5, wherein the stress applying means is a thermal stress applying means for applying stress by heating and / or cooling the object to be inspected. The method for inspecting a defect according to any one of claims 1 to 6, wherein the light collected by the light collecting means is light derived from a laser light source. The support of the object to be inspected and
A stress applying means for applying stress to the object to be inspected supported by the support portion, and
A parallel light irradiating means for irradiating the parallel light of a wavelength that can penetrate the previous SL inspection object,
The light emitted by the parallel light irradiating means, and focusing means for irradiating converged light toward the object to be inspected,
A scattered light detector for detecting the scattered light of the light irradiation shines the test subject,
A light- shielding means that blocks light at an angle that is collected by the light-collecting means and directly incident on the scattered light detecting means.
Arithmetic processing for detecting defects in the inspected object by comparing the intensity of light detected by the scattered light detecting means with a predetermined threshold value in a state where stress is applied to the inspected object and a state where stress is not applied to the inspected object. Department and
A defect inspection device characterized by being equipped with.

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