JP2002257747A - Defect inspection equipment - Google Patents

Abstract

(57) Abstract: The present invention mainly relates to a defect inspection apparatus that can detect both foreign matter and scratches with high sensitivity in a single apparatus in inspecting a substrate to be inspected with a pattern. To provide. An illumination system in which an illumination angle, which is an angle between an optical axis of a beam that becomes S-polarized with respect to an inspection surface of an inspection target and an inspection surface of the inspection target, is set to 2 to 20 °, The difference between the first light receiving system in which the angle of difference between the beam and the optical axis is set to 140 to 160 ° and the light receiving angle between the beam and the inspection plane is set to 25 to 55 °, and the difference between the beam and the optical axis. Angle -140
And a second light receiving system in which the light receiving angle, which is an angle made with the inspection surface, is set to 25 to 55 °, and the difference angle between the optical axis of the beam and the second light receiving system is approximately 0 °. And a third light receiving system which is set so as to pass a component which becomes P-polarized light at a light receiving angle of 20 to 50 °.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection apparatus for detecting foreign matter and scratches generated on the surface of a substrate to be processed, and is characterized mainly by a method for inspecting the appearance of a substrate having a pattern in a semiconductor or liquid crystal manufacturing process. There is.

[0002]

2. Description of the Related Art In recent years, electronic devices such as semiconductors have been rapidly miniaturized, and high-precision processing is required. Therefore, if foreign matter adheres to a substrate to be processed such as a semiconductor wafer in a processing step, the quality of a product such as a semiconductor is greatly affected. Also, CMP (Chemical Mechanical Polishing), which is one of the planarization processing techniques, is used.
g: chemical mechanical polishing), when the surface of the substrate to be processed is polished, dust (dust) adheres to the substrate to be processed, so that a scratch (scratch) may be generated. , Is one of the causes affecting quality. In view of the above, in recent years, there has been a demand for a defect inspection technique for inspecting, with high precision, foreign substances adhering to the surface of a substrate to be processed and scratches generated during polishing or the like.

In order to solve the above-mentioned problems, the prior art 1)
A method for inspecting foreign substances, 2) a method for inspecting scratches,
3) A method for inspecting both foreign matter and scratches is disclosed. Hereinafter, the outline of the three inspection methods will be described in order.

1) Method of inspecting foreign matter A foreign matter inspection method and apparatus described in JP-A-09-015163 will be described as an example and will be described with reference to FIG. The specific specifications are as follows.

[0005] A beam that becomes S-polarized light is emitted from an illumination system to the inspection surface of the inspection object so that an axis substantially parallel to the inspection surface of the inspection object becomes the optical axis. At this time,
At an optical axis where an angle between the beam and the inspection surface is an acute angle and a difference angle between the beam and the optical axis is ± 30 ° or less, P The component that becomes polarized light is detected as a foreign substance.

According to such an inspection method, the light intensity of the detection light from the foreign matter is remarkably improved over the light intensity of the detection light from the pattern and the like, the discrimination ratio between the foreign matter and the noise is improved, and even the minute foreign matter is detected. It is possible.

2) Method for Inspecting Scratch The microcrack inspection apparatus and the inspection method described in Japanese Patent Application Laid-Open No. 05-281149 are taken as an example, and FIG.
This will be described with reference to FIG.

First, the definition of the angle of the scratch will be described with reference to FIG. In FIG. 14A, φ
Is the inclination angle of the scratch, and the smaller the φ, the shallower (that is, the smaller the depth) the inclination. Generally, since there is a correlation between the depth and the inclination of the scratch,
As the smaller φ can be detected, the shallower the scratch can be detected, which means that the detection sensitivity is higher. Also,
In FIG. 14B, η is the substrate 1 to be inspected perpendicular to the optical axis of the light receiving system.
These are the angle at which a scratch exists and the scratch rotation angle when the upper inspection area is 0 °. Since the detection of the scratch depends on the angle, it is desirable to be able to detect a scratch having a rotation angle in a large range as much as possible.

Next, specific operation specifications of the invention described in the above publication will be described.

An illumination system in which an illumination angle .beta., Which is an angle formed between the beam optical axis and the inspection surface of the object to be inspected with respect to the inspection surface of the object to be inspected, is set to an acute angle, and an optical axis of the beam. The difference angle is set to 180 °, and the light receiving angle, which is the angle formed with the inspection surface, is set to a slightly shifted angle that does not receive the regular reflection light of the illumination angle β of the illumination optical system.

With this setting, due to the inclination of the scratch, the specular reflection is received in the direction slightly shifted, and the angle of the minute scratch is detected. According to such an inspection method, it is possible to detect a small angle of inclination of the scratch that can be detected, and the range of the rotation angle of the scratch that can be detected is wide.

3) Method for inspecting both foreign matter and scratches The technical document described in "Technical Data on Wafer Defect Inspection System EAGLE: Hamamatsu Photonics Co., Ltd." And the detection sensitivity is significantly reduced.

Hereinafter, a specific inspection method will be described with reference to FIG.

The above inspection method has three features. 1) The illumination azimuth α of the illumination system 2 is set to about 35 °, and 2) The light reception angle γ of the light receiving system is set to 90 °. 3) that two illumination optical systems are provided.

First, detection of a scratch will be described. Due to the features 1) and 2), it is possible to prevent the diffracted light from the wiring pattern composed of 0 ° and 90 ° from entering the light receiving system, thereby preventing a decrease in the detection sensitivity in the wiring pattern. Also, due to the feature of 3), the range of the detectable rotation angle η of the scratch is twice as large as that in the case of one illumination system.

FIG. 14 shows the result of an independent optical analysis simulation. In this simulation, the illumination light is specularly reflected (= Fresnel reflection) due to the inclination of the scratch.
Then, a scratch inclination angle φ and a scratch rotation angle η under conditions that light enters a light receiving system having a predetermined aperture angle are calculated.

FIG. 14A shows one of the two illumination systems.
It shows the detection capability of the illumination system 1 of the machine. The detectable inclination angle φ is a minimum of 25 °. At this time, the detectable rotation angle η is from 90 ° to 110 °, and the difference is only in the range of 20 °. FIG. 14B shows the sum of the effects of the second illumination system, and the detectable rotation angle is doubled.

Generally, the inclination angle is required to be at least about 5 ° from the depth of the scratch to be detected, but can be detected only from 25 °. Furthermore, assuming that the rotation angle can be detected only at 40 ° out of 180 ° which may exist and that the rotation angle occurs evenly, 78% (= (180 ° −4)
0 °) / 180 °).

Regarding the detection of foreign matter, it is easy to judge that the detection sensitivity is poor from FIG. 10 showing the amount of foreign matter and the pattern using the light receiving angle of the above-described foreign matter detection method as a parameter. That is, since the light receiving angle is 90 °, the light amount from the pattern is stronger than the light amount from the foreign matter, and the S / N is 1
As a result, the detection sensitivity deteriorates.

[0020]

However, each of the above three inspection methods has the following problems.

1) This is a method of inspecting an optical system specialized for a foreign substance. The ability to detect a foreign substance on a patterned substrate is excellent, but the ability to detect a scratch is low.

2) This method is an inspection method specialized for scratches, and has an excellent ability to inspect scratches on a substrate with a pattern. However, the sensitivity of foreign matter inspection is extremely low and cannot be put to practical use.

3) Since the inspection method is not specialized for both foreign matter and scratch, the inspection ability is very low as compared with the case where the detection sensitivity for foreign matter and scratch is specialized.

The present invention has been made in view of the above-mentioned conventional problems, and provides a defect inspection apparatus capable of detecting both a foreign substance and a scratch with high sensitivity using a single apparatus mainly for inspecting a substrate with a pattern. The purpose is to:

[0025]

According to a first aspect of the present invention, there is provided a defect inspection apparatus, wherein an optical axis of an S-polarized beam is applied to an inspection surface to be inspected. An illumination system in which the angle between the inspection surface and the inspection surface to be inspected is set to 2 ° to 20 °, and a difference angle between the optical axis of the beam and the optical axis of the first light receiving system is 140 ° to 160 °; And the difference angle between the optical axis of the beam and the optical axis of the second light receiving system is -140 ° to -1.
The angle between the second light receiving system, which is set to 60 ° and the angle formed with the inspection surface at 25 ° to 55 °, and the difference angle between the inspection surface and the optical axis of the beam is approximately 0 °, 20 ° angle
The third light receiving system is set to be up to 50 ° and set so as to pass a component serving as P-polarized light.

According to a second aspect of the present invention, in the defect inspection apparatus, the illumination angle, which is an angle between the optical axis of the S-polarized beam and the inspection surface of the inspection target, is 2 angles.
The difference between the illumination system set to ° to 20 ° and the optical axis of the beam is set to 140 ° to 160 °, and the light receiving angle, which is the angle formed with the inspection surface, is set to 25 ° to 55 °. 1 and the difference angle between the optical axis of the beam and -140 to -160.
° and set the light reception angle, which is the angle
The difference angle between the second light receiving system set to 55 ° and the optical axis of the beam is almost 0 °, the light receiving angle between the inspection surface and the light receiving angle is 20 to 50 °, and the component that becomes P-polarized light is passed. A third light receiving system set so as to cause the illumination system to be a spot scanning mechanism, and all or a part of the first to third light receiving systems to be optical systems constituted by mirrors. The light receiving element of the system is constituted by an element having a light receiving area.

According to a third aspect of the present invention, in the defect inspecting apparatus of the second aspect, the first to third light receiving systems constituted by mirrors are constituted by two mirrors of an objective mirror and an image forming mirror. The mirror between the objective mirror and the image forming mirror is constituted by a mirror optical system that forms a parallel light beam.

According to a fourth aspect of the present invention, there is provided a defect inspection apparatus, comprising: means for determining a defect detected by the first light receiving system or the second light receiving system but not detected by the third light receiving system as a scratch; And means for judging other defects as foreign matter.

A defect inspection apparatus according to a fifth aspect of the present invention is the defect inspection apparatus according to the first to fourth aspects, and includes means for switching the third light receiving system.

[0030]

(First Embodiment) FIG. 1 is a schematic diagram for realizing a defect inspection apparatus according to the present embodiment. Figure 1
(A) and (b) are views when the defect inspection apparatus is viewed from the side and top, respectively.

First, the basic configuration of the defect inspection apparatus shown in FIG. 1 will be described.

In the defect inspection apparatus according to this embodiment, 1 is a substrate to be inspected, 2 is a defect, 3 is an illumination system, 4 is a first light receiving system, 5 is a second light receiving system, and 6 is a third light receiving system. , 7 are light receivers of the first light receiving system, 8 is light receiver of the second light receiving system, and 9 is the third light receiver.
The receiver of the light receiving system of 10 is configured with a polarizing filter,
These components make it possible to detect foreign substances attached to the substrate and scratches generated in the polishing step with high accuracy.

Hereinafter, the operation specifications in this embodiment will be described.

The defect 2 existing in the inspection area on the substrate 1 to be inspected is illuminated by the illumination system 3 composed of laser illumination or the like. The first light receiving system 4, the second light receiving system 5, and the third light receiving system 6 receive reflected light, scattered light, and diffracted light emitted from the defect 2, respectively. , The second light receiving system 8 and the third light receiving system 9 receive light.

Subsequently, the light beams received by the three photodetectors are A / D converted by a photodetector A / D converter (not shown), and preset by a signal processor (not shown). Compared to the value, if the value is larger than the set threshold value, it is determined as a defect. As described above, the detection optical system performs the defect inspection by scanning the required area or the entire surface of the substrate 1 to be inspected.

The positional relationship of the components in the defect inspection apparatus is as follows (Table 1).

[0037]

[Table 1]

When the components have the positional relationship shown in Table 1, the illumination system 3 irradiates the foreign substance 2 on the substrate 1 to be inspected with a beam that becomes S-polarized light. At this time, the third light receiving system 6
A polarizing filter 10 is provided on the front surface of the light-emitting device, and it is possible to detect only P-polarized light components among reflected light, scattered light, and diffracted light depending on the characteristics of the polarizing filter 10. At this time, γ in FIG. 1B is set to 160 ° as a difference angle between the first light receiving system 4 and the second light receiving system 5 with respect to the optical axis of the illumination system 3. The difference angle of the third light receiving system 6 is set to 0 °.

In this embodiment, the case where the first light receiving system 4 and the second light receiving system 5 mainly detect a scratch is shown. With this configuration, it is possible to prevent the diffracted light from the wiring pattern composed of 0 ° and 90 ° from entering the light receiving system, thereby preventing the detection sensitivity of the wiring pattern from lowering.

Based on the above-described operation specifications and the positional relationship between the components in the apparatus, the defect 2 on the inspected substrate 1 can be detected with high sensitivity.
It is proved that it is possible to detect by showing an original optical analysis simulation result.

FIG. 2 is a diagram showing the relationship between the scratch rotation angle η and the scratch inclination angle φ. This clarifies the detection capability of the first light receiving system 4 and the second light receiving system 5 using the defect inspection device in FIG. The unique optical analysis simulation calculates the scratch inclination angle φ and the scratch rotation angle η under the condition that the illumination light is specularly reflected (= Fresnel reflection) by the inclination of the scratch and enters the light receiving system with a predetermined aperture angle. Is what you do. In this case, the aperture angle (NA) of the light receiving system is set to 0.3.

As is apparent from FIG. 2, the minimum detectable inclination angle φ is 5 °, and the result is that the inclination angle φ is generally required to have a minimum value of about 5 °. . The detectable rotation angle η is from 65 ° to 115 °.
The difference is about 50 °, and it is possible to detect a range 2.5 times as large as 20 ° which is conventionally known. Further, the detection sensitivity of foreign matter by the third light receiving system 6 is close to the configuration described in the conventional example, and high sensitivity can be realized.

(Second Embodiment) FIG. 3 is a schematic diagram for realizing a defect inspection apparatus according to the present embodiment. FIG. 3 (a)
(B) is a figure when the defect inspection apparatus is seen from the side surface and the upper surface, respectively. The basic configuration and operation specifications of the defect inspection apparatus shown in FIG. 3 are the same as those of the first embodiment. The second embodiment differs from the first embodiment in the following set values (Table 2). That is, the setting position of each component in the defect inspection apparatus is different.

[0044]

[Table 2]

As in the first embodiment, a polarizing filter 10 is provided on the front surface of the third light receiving system 6. It becomes possible to detect only a component that becomes P-polarized light among reflected light, scattered light, and diffracted light. At that time, FIG.
(B) is the first γ with respect to the optical axis of the illumination system 3.
The difference angle between the light receiving system 4 and the second light receiving system 5 is set to 142 °. The difference angle of the third light receiving system 6 is set to 0 °.

In the light receiving optical system using the lens as described in the first embodiment, it is difficult to increase the aperture angle (NA), and reflected light, scattered light, In some cases, the amount of diffracted light cannot be sufficiently detected.
Therefore, in the present embodiment, the aperture angle (N) is replaced by a mirror system instead of the light receiving optical system using a lens.
The difference from the first embodiment is that A) is increased, the detected light amount of the light receiving system is increased, and the detection sensitivity is improved.

When the light receiving system is a mirror optical system,
As compared with a lens optical system, the imaging characteristics are poor, and a line sensor or an area sensor cannot be used as a light receiver. Therefore, by using a photomultiplier or the like having a large area for the light receiver and providing a laser scanning mechanism, the problem of the deterioration of the imaging characteristics due to the substitution of the mirror optical system is solved.

(Third Embodiment) In the first and second embodiments, the device configuration is the same, the arrangement position of the components in the device is changed, and the light receiving optical system and the mirror light receiving system are different. The case where it is performed has been described. In the present embodiment, an example will be described in which an effective inspection method can be performed with a simple mirror light receiving system configuration using a mirror light receiving system.

FIG. 4 shows a method using a conventional mirror light receiving system. The outline will be described below.

Defect 2 existing at inspection point on substrate 1 to be inspected
Is formed by a mirror light receiving system. The mirror light receiving system corresponds to, for example, the first light receiving system 4 in FIG. The reflected light, scattered light and diffracted light from the defect 2 pass through the objective lens 3, the first imaging lens 4 and the second imaging lens 5, and are imaged on a photomultiplier 6 as a light receiver. is there. As described above, the conventional mirror light receiving system has a complicated mirror configuration, and causes the following problems. 1) When three light receiving systems having the same inspection point as an object point are arranged, the optical systems interfere with each other, making the device configuration difficult. 2) Even if interference can be avoided, there is a high possibility that light outside the principal ray will be reflected on a mirror of the component and become noise light which will interfere with detection.

Therefore, as shown in FIG.
In the case where the defect 2 existing at the inspection point above is imaged by the mirror optical system, an example of a method for simplifying the configuration of the mirror optical system will be described, and its effect will be described below.

The mirror light receiving system as shown in FIG. 5 corresponds to, for example, the first light receiving system 4 in FIG. 3A and a light receiver not shown. The reflected light, scattered light, and diffracted light from defect 2
The light is condensed or reflected by the objective lens 3 to become a parallel light beam, and is condensed / reflected by the imaging lens 4 to form an image on a photomultiplier 6 as a light receiver. In the present embodiment, the distance between the objective lens and the imaging lens can be freely set by making the parallel light between the objective mirror and the imaging mirror, the degree of freedom of the configuration is increased, and the above problem is solved. Can be solved.

(Fourth Embodiment) Next, this embodiment will be described with reference to FIGS.

FIG. 6 shows a processing procedure in this embodiment.

First, a defect detected by the first light receiving system 4 and a defect detected by the second light receiving system 5 are combined (this is referred to as A).
I do. Thereafter, the result of the third light receiving system 6 is compared with the above-mentioned A, and if only A is detected, it is determined to be a scratch. The principle described above will be described below.

The first light receiving system 4 and the second light receiving system 5 can detect foreign matter and scratches. Since the detection of the scratch depends on the angle, there may be a scratch that can be detected by the first light receiving system 4 and cannot be detected by the second light receiving system 5. Of course, the opposite is also true. Therefore, if the results of the first light receiving system 4 and the second light receiving system 5 are combined (A), scratches can be detected by these optical systems. Further, the third light receiving system 6 can detect only foreign matters, and cannot detect scratches. Therefore, it can be said that what exists only in A is a scratch. FIG. 7 shows an example of the processing method described above.

With the spread of the CMP process, it is necessary to detect a scratch defect in order to grasp and solve a problem in the CMP process. In the CMP process, the only problematic defect is the scratch, and there is no need to make foreign matter such as the remainder of the slurry a defect, and it is necessary to distinguish and detect the scratch and the foreign matter. In order to realize this discrimination, scratches are effectively used in such a manner that the scratches extend linearly, or a defect is input by a microscope with a higher magnification and determined manually or by an image processing method. In either case, there is a problem that 1) the function exists but the accuracy of discrimination is low, and 2) it takes time because another process is required. For example, in the third embodiment, discrimination was difficult because a single light receiving system was used. However, in the present embodiment, in order to optically discriminate a defect,
Discrimination is completed when the scanning for one inspection is completed, so that high-speed and reliable discrimination can be performed.

(Fifth Embodiment) This embodiment has the same components as those of the defect inspection apparatus described with reference to FIG. 1 except that a mechanism 11 for turning on and off the polarizing filter 10 is added. .

In the first embodiment, the third light receiving system 6 allows only the P-polarized light to pass through the polarizing filter 10.
It arises from the purpose of removing noise from the pattern. Inspection substrate 1 without pattern
When the inspection is performed, it is possible to increase the amount of detected light and to improve the detection sensitivity by passing all the polarized light components. Therefore, in the case of the substrate 1 to be inspected without a pattern, it is possible to improve the detection sensitivity by removing all the polarization components and increasing the amount of detection light by pulling out the polarization filter 10 by the cut-off mechanism 11 with the polarization filter. it can.

[0060]

According to the present invention, a single defect inspection apparatus can detect foreign matter and scratches on a patterned inspection substrate with high sensitivity.

In the light-receiving optical system using a lens, the method of increasing the aperture angle, which has been difficult, is to use a mirror system to increase the aperture angle, thereby increasing the amount of light detected by the light-receiving system. And the detection sensitivity can be improved.

Further, since a normal light receiving optical system using a mirror has a complicated mirror configuration, the degree of freedom of the configuration can be increased by using a mirror optical system and making parallel rays between the objective mirror and the imaging mirror. As a result, the above problems can be solved.

In addition, it is possible to quickly and accurately discriminate foreign matter from scratches.

In addition, all the polarized light components can pass through the inspection on the inspection target substrate without a pattern, so that the amount of detected light increases and the detection sensitivity can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a detection capability according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram illustrating a conventional mirror light receiving system.

FIG. 5 is a configuration diagram according to a third embodiment of the present invention.

FIG. 6 is a diagram illustrating a detection process according to a fourth embodiment of the present invention.

FIG. 7 is a diagram illustrating an operation according to a fourth embodiment of the present invention.

FIG. 8 is a configuration diagram according to a fifth embodiment of the present invention.

FIG. 9 is a view for explaining an embodiment of Conventional Example 1;

FIG. 10 is a view for explaining the difference between the light emission of the foreign matter and the scratch.

FIG. 11 is a view for explaining an embodiment of Conventional Example 2;

FIG. 12 is a view for explaining an embodiment of Conventional Example 3;

FIG. 13 is a diagram for explaining a tilt angle and a rotation angle of a scratch.

FIG. 14 is a view for explaining a detection capability according to the embodiment of the conventional example 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inspection board 2 Defect 3 Illumination system 4 First light receiving system 5 Second light receiving system 6 Third light receiving system 7 Light receiver of first light receiving system 8 Light receiver of second light receiving system 9 Third light receiving Optical receiver 10 polarizing filter α illumination angle β1 light receiving angle of the first and second light receiving systems β2 light receiving angle of the third light receiving system θ1 aperture angle of the first and second light receiving systems θ2 of the third light receiving system Aperture angle γ Difference angle between first and second light receiving systems

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kenichiro Mase 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Terms (reference) 2F065 AA49 AA61 BB02 CC17 CC25 FF44 GG04 HH04 HH08 HH12 JJ05 JJ08 JJ17 LL21 LL31 MM16 QQ03 QQ25 2G051 AA51 AB01 AB07 AC15 BA10 BA11 BB01 BB07 CA02 CA07 CB05 CC07 CB11 CC11 EB05

Claims (5)

[The claims] 1. An illumination system in which an angle between an optical axis of a beam serving as S-polarized light and an inspection surface to be inspected is set to 2 ° to 20 °, and an angle between the illumination surface and the inspection surface is 25 to 55 °. A first light receiving system and a second light receiving system that are set, and a third light receiving system that is set at an angle of 20 ° to 50 ° with the inspection surface, and an optical axis of the first light receiving system. The difference between the optical axis of the beam and the optical axis of the beam is 140 ° to 160 °, the difference between the optical axis of the second light receiving system and the optical axis of the beam is −140 ° to -160 °, and the light of the first light receiving system A defect inspection apparatus, wherein a difference angle between an axis and an optical axis of the beam is set to approximately 0 °. 2. The defect inspection apparatus according to claim 1, wherein the illumination system is a spot scanning mechanism, and at least one of the first to third light receiving systems is an optical system including a mirror. A defect inspection apparatus characterized in that the light-receiving elements have a light-receiving area. 3. The defect inspection apparatus according to claim 2, wherein the first to third light receiving systems constituted by mirrors are constituted by two mirrors, an objective mirror and an image forming mirror, and between the objective mirror and the image forming mirror. A defect inspection apparatus comprising: a mirror optical system that forms a parallel light beam. 4. A means for judging a defect detected by the first light receiving system or the second light receiving system and not detected by the third light receiving system as a scratch, and a means for judging other defects as foreign matters. A defect inspection device, comprising: 5. The defect inspection apparatus according to claim 1, wherein the third light receiving system includes a moving mechanism.