JP2005308615A - Surface flaw inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect the surface flaw in the uppermost layer even if a flaw, for example, film thickness irregularity or the like is present in the lower layer of the uppermost layer exposed to the inspection surface of a specimen in the surface flaw inspection device without being affected by the flaw. <P>SOLUTION: A rotary holder 9 for allowing filters 9a and 9b mutually different in a wavelength band to advance and retreat to selectively change over them is provided in the light path between a halogen lamp 6 for emitting white light and a CCD 17. Then, inspection images photographed by illumination lights different in wavelength band are compared with each other to extract only the abnormal part present in the uppermost layer of the specimen 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface defect inspection apparatus. For example, the present invention relates to a surface defect inspection apparatus that inspects a surface defect of a substrate having a regular pattern on the surface, such as a semiconductor wafer or a liquid crystal substrate.

For example, in a photolithography process in which patterns are formed in multiple layers on a substrate such as a semiconductor wafer or a liquid crystal substrate, if there is uneven film thickness or dust adheres to the resist applied to the substrate surface, the line width of the pattern after etching will be poor. This may cause defects such as pinholes in the pattern. Further, if there is a poor focus in pattern exposure, the resist cross-sectional shape after development is different from a normal one, which causes a defect in a subsequent process. Therefore, before etching the substrate, it was necessary to inspect for the presence of surface defects as described above.
Conventionally, as such a surface defect device, the substrate is irradiated with light of an appropriate wavelength, and an image of the substrate surface is obtained by reflected light, scattered light, and diffracted light, and the surface is compared with an image of a normal substrate. Devices for inspecting for defects are known.
For example, in Patent Document 1, a narrow band light source having a central wavelength that can be arbitrarily selected is irradiated with parallel light in a range approximately equal to the observation field of the subject, and the specularly reflected or scattered light is observed. A surface defect inspection apparatus is described.
Patent Document 2 discloses a surface defect that includes a first imaging unit that illuminates a subject in a line at a predetermined angle and images the specularly reflected light, and a second imaging unit that also images diffracted light. An inspection device is described.
JP-A-7-27709 (page 4-6, FIG. 1) JP-A-9-61365 (page 3-6, FIG. 5)

However, the conventional surface defect apparatus as described above has the following problems.
In the techniques described in Patent Documents 1 and 2, since imaging is performed in one wavelength band, information obtained is small and information on a plurality of films is not reflected. In particular, when inspecting the uppermost layer defect exposed on the surface, if there is a defect such as film thickness unevenness in the lower layer, an image affected by the defect is captured, so the uppermost layer defect is accurately identified. There was a problem of being unable to inspect.

  The present invention has been made in view of the above problems, and aims to improve inspection accuracy by obtaining a plurality of film image information. In addition, even if defects such as film thickness unevenness exist in the lower layer of the uppermost layer exposed on the inspection surface of the subject, the surface can detect surface defects in the uppermost layer without being affected by those defects An object is to provide a defect inspection apparatus.

In order to solve the above problems, the present invention is a surface defect inspection apparatus for inspecting a surface defect of a specimen having a layered structure and having at least the uppermost layer and its immediate lower layer exposed on the surface, the light source, Illuminating means for irradiating the subject surface with light from the light source as a substantially parallel light beam; and imaging means for forming an image of light in a predetermined direction emitted from the subject by the light beam emitted from the illuminating means; An image pickup means for picking up an image of light in the predetermined direction, and a light flux wavelength band that is arranged in an optical path between the light source and the image pickup means, and is selective between at least two wavelength bands independent of each other And a wavelength selection means for switching to the image, and an image processing means for extracting a defect on the surface of the object by performing image processing on a plurality of images picked up by light fluxes of respective wavelength bands switched by the wavelength selection means. Features.
According to the surface defect inspection apparatus of the present invention, an image of light emitted from the subject in a predetermined direction is formed by the imaging unit by the substantially parallel light beam irradiated on the subject by the illumination unit, and the imaging unit When imaging, the wavelength selection unit switches the wavelength of the light beam in the optical path between the light source and the imaging unit between at least two wavelength bands to obtain a plurality of images. Then, defect extraction is performed by image processing the plurality of images. Therefore, according to the material of the uppermost layer, a plurality of images are switched to a wavelength band not affected by the lower layer covered by the uppermost layer and a wavelength band affected by the lower layer.

  According to the surface defect apparatus of the present invention, the image picked up by the image pickup means can be obtained as a plurality of images picked up by switching between at least two wavelength bands. A lot of information can be obtained, and the inspection accuracy can be improved. In addition, according to the material of the uppermost layer, a plurality of images are switched between a wavelength band that is not affected by the lower layer covered by the uppermost layer and a wavelength band that is affected by the lower layer, and the lower layer is processed by image processing. It is possible to remove the influence of the above and to extract the surface defect of the uppermost layer.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In all the drawings, even if the embodiments are different, the same or corresponding members are denoted by the same reference numerals, and redundant description is omitted.
A surface defect inspection apparatus according to an embodiment of the present invention will be described.
FIG. 1 is a front explanatory view for explaining a schematic configuration of a surface defect inspection apparatus according to an embodiment of the present invention. FIG. 2 is a functional block diagram for explaining a configuration of a control system in the surface defect inspection apparatus according to the embodiment of the present invention.

The surface defect inspection apparatus 1 according to the present embodiment uses a photolithography process, such as a semiconductor wafer or a liquid crystal substrate, to form a layered structure in the thickness direction and to form a regular pattern in the plane direction. The object 4 to be formed can be inspected for surface defects as needed during the manufacturing process. The placement direction of the subject 4 is not particularly limited, but for the sake of convenience, the following description will be made assuming that the surface of the examination target is placed vertically upward.
The schematic configuration of the surface defect inspection apparatus 1 includes a stage (not shown) that holds a subject 4 and moves to a predetermined inspection position, a lamp house 5, a rotary holder 9 (wavelength selection means), a condensing lens 10, and a fiber bundle. 11, a half mirror 15, a collimating lens 14 (illuminating means, imaging means), an imaging lens 16, a CCD 17 (imaging means), and the control unit 2.

The lamp house 5 includes a halogen lamp 6 (light source) that emits white light, a heat ray absorption filter 8 that cuts a wavelength band in the infrared region from the white light, and light that has passed through the heat ray absorption filter 8 to a substantially parallel light flux. The condenser lens 7 is provided.
As the light source, other light sources that generate white light, for example, a metal halide lamp, a xenon lamp, and the like can be suitably employed.

  The rotary holder 9 can selectively advance and retreat a plurality of filters 9a and 9b having different wavelength characteristics and a transmission unit (not shown) that transmits all wavelengths into the optical path of the light emitted from the condenser lens 7. This is a moving mechanism. For example, the filters 9a and 9b and the transmission part are arranged on a rotating disk rotated by a motor (not shown).

A large number of filters 9a and 9b can be provided by changing the wavelength characteristics according to the material and thickness of the film layer provided on the subject 4, but since there is essentially no change, in the following, one filter is each provided. The case will be explained.
The filters 9a and 9b are narrowband transmission filters having wavelengths λ ₁ and λ ₂ as center wavelengths and full widths at half maximum and wavelength widths of Δλ ₁ and Δλ ₂ , respectively, and wavelength bands λ _A having different center wavelengths. (First wavelength band) and λ _B (second wavelength band) light are transmitted. Such a narrow band transmission filter can be constituted by, for example, an interference filter.
The wavelength band λ _A has a wavelength that is absorbed by the uppermost layer of the subject 4 at or near the center wavelength λ ₁ , and the wavelength band λ _B is a wavelength region that transmits the other uppermost layer.
As a top layer, since it is often inspected in a state where the resist layer is provided, in the present embodiment, to include a wavelength that is absorbed in the resist according to the wavelength lambda _A. The resist generally has an absorption band that significantly absorbs a predetermined wavelength in addition to the exposure wavelength. Since the specific wavelength varies depending on the type of resist, it is selected based on the manufacturer's information. On the other hand, the wavelength band λ _B may be other than the image picked up in the wavelength band λ _A as an image because the rate of absorption by the resist is less than that of the wavelength band λ _A. However, as an example, λ ₂ = 550 A wavelength band of ˜600 nm can be suitably employed.
Here, the wavelength widths Δλ ₁ and Δλ ₂ are set so that interference fringes and diffracted light for inspection can be appropriately observed. For example, in order to observe the interference fringes, the coherence length is so narrow that the interference fringes appear clearly, and in the optical system inside the apparatus, for example, noise such as speckle noise does not affect the observation. preferable. As an example, when the center wavelength is 550 to 600 nm, the wavelength width is preferably about 10 to 30 nm.

The condensing lens 10 is an optical element that condenses the light transmitted through the rotary holder 9 on the end face of the fiber bundle 11.
The fiber bundle 11 is for transmitting the light condensed on one end face by the condensing lens 10 and emitting it to the other end face. Near the other end face of the fiber bundle 11, there are provided a diffusion plate 12 for diffusing the outgoing light and averaging the intensity distribution, and a diaphragm 13 for shaping the outgoing light into an appropriate beam diameter. Thus, the diffusion plate 12 and the diaphragm 13 form a secondary light source that illuminates the subject 4 with uniform intensity.

The half mirror 15 reflects the divergent light beam that has passed through the aperture 13 and reflects it toward the subject 4, and also transmits the light emitted from the subject 4 and traveling backward in the same optical path, and the illumination optical system. It is an optical element for branching the optical path with the imaging optical system.
The collimating lens 14 is an optical element that guides the illumination light to the subject 4 using the diffused light reflected by the half mirror 15 as a parallel light beam. In this embodiment, the collimating lens 14 is arranged so that the optical axis 18 is along the normal line of the surface of the subject 4.
The imaging lens 16 is provided with the half mirror 15 sandwiched between the optical axis 18, and the light that is emitted from the subject 4 by the illumination light incident on the subject 4 and travels backward along the optical axis 18. This is an optical element for forming an image of the subject 4 on the imaging surface of the CCD 17.
The CCD 17 is an area sensor for imaging a range illuminated with illumination light, photoelectrically converting the image and sending it as an image signal.

  In addition, in order to implement | achieve the optical performance demonstrated above, the optical elements which have power, such as the condenser lens 7, the condensing lens 10, the collimating lens 14, and the image formation lens 16, for example, a spherical surface, an aspherical surface, a free-form surface, An appropriate optical surface such as a Fresnel lens surface is provided. Further, in FIG. 1, although illustrated as one element, a lens group in which these optical surfaces are combined may be used. If necessary, not only the lens but also other optical elements having power, such as curved mirrors, prisms having power, DOE (Diffractive Optical Element), hologram elements, etc. may be employed.

The control unit 2 is connected to a halogen lamp 6, a rotary holder 9, a CCD 17, and a stage (not shown) that holds and moves the subject 4, and transmits a drive voltage and a control signal for controlling the operation to each. Is.
As shown in FIG. 2, the schematic configuration of the control unit 2 includes a computer 31 that controls the entire apparatus, a keyboard 32 connected to the computer 31, a memory 33, a monitor TV 30, an image processing unit 35 (image processing means), And a sequencer 37.

The keyboard 32 and the monitor TV 30 are input / output means of the computer 31, and perform operations of the surface defect inspection apparatus 1 and input / output of inspection conditions through the computer 31. It goes without saying that other means may be used as long as such input / output can be performed. For example, instead of the keyboard 32, a device such as a mouse or a joystick may be used, and the output means may be a printer.
The memory 33 is a means for storing an OS for operating the computer 31, a control program for executing a control operation, and various data, for example, examination conditions for each type of the subject 4, examination data, and the like. The inspection conditions include optical system settings and image processing conditions.
The control program built in the memory 33 sends a control signal to the image processing unit 35 and the sequencer 37, and controls each unit via the control signal.

The image processing unit 35 is an image pickup device, a CCD 17, an image storage unit 36 that stores image signals and image data during image processing, and stores read-only image data that is referred to in image processing as necessary, and the CCD 17. Are connected to a monitor TV 34 that displays images picked up in step 1 and images after image processing. Then, an inspection image on the surface of the subject 4 is taken from the CCD 17 and an appropriate image processing is performed on the inspection image, so that an abnormal portion of the inspection image is compared with a normal image stored in the image storage unit 36 in advance. It is extracted so that it can be determined whether the abnormal part is an image defect.
When the abnormal part is determined as a defect, information such as the type, number, position, and area of the defect is sent to the computer 31 and a defect image can be output to the monitor TV 34 as necessary.

The sequencer 37 controls the operation of the halogen lamp 6, the rotary holder 9, and the CCD 17, and controls the suction mechanism, positioning mechanism, moving mechanism, and the like provided on the stage to suck and hold the subject 4. Then, the stage control unit 39 that moves the predetermined examination range so as to be within the predetermined visual field, and the subject 4 is taken out from the stocker and placed on the stage, and the subject 4 that has finished the examination is ejected from the stage and stored. Are connected to a substrate transfer control unit 40 for controlling a transfer unit (not shown) to be stored in the control unit, and each operation can be controlled via these control units in accordance with respective control signals sent from the computer 31. Yes.
The operation control of the halogen lamp 6 by the optical system control unit 38 includes lighting / extinguishing and variable light amount control. The operation control of the rotary holder 9 is control for changing the angular position of the rotary disk and selectively switching one of the filters 9a and 9b and the transmission part in the optical path. The operation control of the CCD 17 is control for changing imaging conditions such as exposure time control according to the amount of received light.

Next, the operation of the surface defect inspection apparatus 1 will be described.
When the inspection start is instructed by the keyboard 32, a control signal is transmitted to the substrate transfer control unit 40 and the stage control unit 39 via the sequencer 37, and the transfer unit and the stage are controlled. As a result, the subject 4 is sucked and held on the stage and positioned at the examination position.
On the other hand, information specifying the type of the subject 4 is input to the computer 31, and the examination conditions stored in advance in the memory 33 are called according to this information.
The inspection conditions are such that the inspection range, the inspection magnification, the illumination conditions, the imaging conditions, and the like can be set according to the material and pattern shape of the inspection surface of each manufacturing process of the subject 4. Although not varied in the present embodiment, if the illumination direction and the imaging direction are varied, information for setting such a direction is also included.
When data related to the illumination condition is read out of the inspection conditions, a control signal corresponding to the optical system control unit 38 is transmitted via the sequencer 37, the conditions of the halogen lamp 6, the rotary holder 9, and the CCD 17 are initialized, and the inspection is performed. The preparation process ends.

Hereinafter, the inspection process following the preparation process will be described with reference to FIGS.
FIG. 3 is a flowchart for explaining a partial operation of the inspection process of the surface defect inspection apparatus according to the embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of the specimen in the thickness direction for explaining the principle of surface defect inspection according to the embodiment of the present invention. FIGS. 5A and 5B are schematic explanatory diagrams schematically showing an image of an abnormal part extracted by image processing according to the embodiment of the present invention. FIG. 5C is a schematic explanatory diagram of the abnormal part image extracted from the images of FIGS. 5A and 5B by the image processing according to the embodiment of the present invention.

In step 501, the rotation holder 9 is rotated by the optical system control unit 38, and the filter 9b is advanced into the optical path.
As a result, white light is emitted is transmitted through the heat ray absorption filter 8 from the halogen lamp 6 is the central wavelength becomes lambda ₂ of the narrow band light. And it inject | emits from the other end surface of the fiber bundle 11, is diffused with the diffusion plate 12, and intensity distribution is averaged. By passing through the diaphragm 13, the light beam is shaped into a predetermined beam diameter, then enters the half mirror 15 while diverging, is reflected by the half mirror surface, travels along the optical axis 18, and enters the collimating lens 14. The incident light is incident on the subject 4 from above along the normal line.
Accordingly, the object 4 is illuminated with parallel light flux of the wavelength band lambda _B.

The illumination light is reflected on the surface of the subject 4, and the regular reflection light, that is, the light reflected vertically upward, travels backward along the optical path of the incident light and converges along the optical axis 18. To do.
Then, the light passes through the half mirror 15 and forms an image at a position conjugate with the diaphragm 13.

In step 502, an image of light by the wavelength band lambda _B is, through an imaging lens 16, is focused on the light receiving surface of the CCD 17. Therefore, imaging is performed under imaging conditions set in advance by inspection conditions, and this image is sent to the image processing unit 35 as an image signal photoelectrically converted by the CCD 17. The image processing unit 35 stores these image signals in an array and stores them in the image storage unit 36. This image is called an inspection image B.
The inspection image B can be displayed on the monitor TV 34 as necessary, and display control processing such as range selection, reduction / enlargement, and display brightness level change can be performed via the computer 31. ing.

Here, the inspection image B imaged in step 502 will be described.
For example, a layered structure as shown in FIG. 4 is formed on the cross section in the thickness direction of the subject 4 after the application, exposure, and development of the photoresist. That is, a resist layer 303 having a predetermined thickness is formed as the uppermost layer on the lower layer 302 provided in the preceding process for etching. The resist layer 303 is patterned according to a predetermined exposure pattern. It should be noted that the wafer substrate 301 is present in the lower layer of the lower layer 302 in an early example of the manufacturing process, and it goes without saying that it is another lower layer formed in the preceding process when the manufacturing process has advanced. .

In such a subject 4, the lower layer 302 not covered with the resist layer 303 is etched in the next manufacturing process. If the resist layer 303 has defects such as film thickness unevenness and dust adhesion, defects such as defective line width of patterns after etching and difficult to repair such as pinholes may occur. In addition, if there is an in-focus failure during pattern exposure, for example, the edge portion of the resist layer 303 is blurred and an inclined surface is formed, resulting in an abnormality in the cross-sectional shape of the resist after development, resulting in a failure in the next process. Cause.
If there is a defect in the resist layer 303, it is relatively easy to remove the defective resist layer 303 and reprocess it, so that a surface defect inspection is usually performed after resist development.

In FIG. 4, the illumination light can be divided into incident light 304 incident from the upper surface of the resist layer 303 and incident light 305 incident from the upper surface of the lower layer 302 exposed on the surface. In FIG. 4, the incident lights 304 and 305 are drawn so as to be incident from an oblique direction for easy viewing, but this also includes a case where the incident angle is 0 ° as in the present embodiment.
The incident light 304 is reflected as reflected light 304 c on the upper surface of the resist layer 303, reflected light 304 b on the boundary surface between the resist layer 303 and the lower layer 302, and reflected light 304 a on the boundary surface between the lower layer 302 and the wafer substrate 301. .
Incident light 305 is reflected as reflected light 305 b on the upper surface of the lower layer 302 and reflected light 305 a on the boundary surface between the lower layer 302 and the wafer substrate 301.
Therefore, in the light emitted from the upper surface of the resist layer 303, the reflected lights 304c, 304b, and 304a have optical path differences corresponding to the film thicknesses of the resist layer 303 and the lower layer 302, respectively. Occur.
Similarly, in the light emitted from the upper surface of the lower layer 302 exposed on the surface, the reflected lights 305b and 305a have an optical path difference corresponding to the lower layer 302, so that interference fringes occur similarly, and an image having a light-dark distribution is generated. .

These light and dark distributions are constant if the film thickness of each layer film and the exposure pattern of the resist layer 303 are determined. In that case, an image of a normal pattern is stored in the image storage unit 36, and a defect is extracted by comparing with the inspection image B.
However, if there is a film thickness unevenness due to manufacturing errors in the lower layer 302 (see FIG. 4), an optical path difference due to the film thickness unevenness is added and an interference fringe different from the normal pattern is imaged, and an image that can be regarded as an abnormal part appears. .

Next, in step 503, the rotation holder 9 is rotated by the optical system control unit 38 to advance the filter 9a into the optical path. Therefore, in the same manner as in step 501, the subject 4 is illuminated with a parallel light flux in the wavelength band λ _A having the center wavelength λ ₁ .
In step 504, an image is captured in the same manner as in step 502. The image signal is stored in an array and stored in the image storage unit 36. This image is called an inspection image A.

In the wavelength band λ _A , the wavelength absorbed by the resist layer 303 is the center wavelength λ ₁ or a wavelength in the vicinity thereof, so the incident light 304 is absorbed by the resist layer 303, and the intensity of the reflected light 304a, 304b in FIG. , It decreases relative to the reflected light 304c. Therefore, the intensity of the interference component decreases in the region covered with the resist layer 303.
On the other hand, the incident light 305 incident from the surface of the lower layer 302 not covered with the resist layer 303 shows the same light / dark distribution as the inspection image B.

Next, in step 505, the inspection image B is subjected to image processing by the image processing unit 35, and a defect distribution b (abnormal portion distribution) is extracted.
For this image processing, various algorithms for extracting defects by determining film thickness unevenness or foreign matter from the light / dark distribution can be adopted. For example, it is possible to employ image processing that obtains a film thickness distribution of a predetermined region from a light / dark distribution, determines a region different from a predetermined normal range as an abnormal portion, and extracts the region range.
The defect distribution b includes apparent defects that are not included in the resist layer 303 because abnormal portions due to film thickness unevenness of the lower layer 302 are also extracted.
FIG. 5A schematically shows an example of the defect distribution b after processing as a region 401. Here, it is assumed that the abnormal portion 404a is a defect in the resist layer 303 and the abnormal portions 402a and 403a are defects in the lower layer 302.

Next, in step 506, as in step 505, the inspection image A is subjected to image processing by the image processing unit 35, and a defect distribution a (abnormal portion distribution) is extracted.
At that time, image processing is performed in consideration that the inspection image A is an image of incident light in the wavelength band λ _A. Therefore, if the light and dark distribution is an interference fringe due to the same film thickness unevenness, it looks like the inspection image B An abnormal portion similar to the defect distribution b is detected even if the light and dark distribution is different. Therefore, in the region 401, as shown in FIG. 5B, the abnormal portions 402b and 403b are extracted as the abnormal portions in the substantially same region corresponding to the abnormal portions 402a and 403a in FIG.
On the other hand, in the inspection image A, the range covered with the resist layer 303 is not extracted as an abnormal portion by the image processing unit 35 because the intensity of the light / dark distribution is low. Therefore, as shown in FIG. 5B, the abnormal part does not appear at a position corresponding to the abnormal part 404a in FIG.

In step 507, the defect distribution b and the defect distribution a are calculated to remove an abnormal portion common to both. For example, the difference between the defect distribution b and the defect distribution a is taken, and image processing such as correcting noise components based on image noise and image processing errors is performed.
Thereby, the defect distribution c (abnormal part distribution) of the resist layer 303 is extracted as an abnormal part 404c corresponding to the abnormal part 404a in FIG. 5A, for example, as shown in FIG. Then, the defect distribution c is stored in the image storage unit 36.
Thus, the process of extracting the uppermost abnormal portion distribution is completed.

When the defect distribution c is extracted, features of each abnormal part of the defect distribution c are extracted, and for example, a normal pattern or a defect dictionary stored in the image storage unit 36 is compared and referenced to determine whether the defect is a defect. If it is determined to be a defect, the type, area, number, and the like of the defect are obtained and the information is notified to the computer 31.
Thus, the defect extraction is completed and the inspection process is completed.

  According to such an inspection process, the subject is imaged with illumination light in at least two wavelength bands of the wavelength band absorbed by the uppermost layer and the wavelength band transmitted through the uppermost layer, and the respective inspection images are calculated. Since only the abnormal portion in the uppermost layer can be extracted, even when a defect such as a film thickness unevenness exists in the lower layer of the uppermost layer, accurate defect extraction with respect to the uppermost layer can be performed.

In the present embodiment, the illumination optical system and the imaging optical system are coaxially arranged and arranged in the normal direction of the subject, and the regular reflected light of the illumination light is imaged. However, the following modification is made. May be implemented.
FIG. 6 is an explanatory front view for explaining a schematic configuration of a first modification of the embodiment of the present invention. FIG. 7 is a perspective explanatory view for explaining the schematic configuration of the second modified example.

The surface defect inspection apparatus 101 according to the first modification of the present embodiment has a configuration in which the half mirror 15 is removed from the above embodiment, and the illumination optical system and the imaging optical system are independent of each other with respect to the subject. It can be arranged variably at the inclination angle.
That is, as shown in FIG. 6, the optical axis 18a of the illumination light emitted from the fiber bundle 11 is inclined by an angle θ _{0 with} respect to the normal 4n of the subject 4 and enters the collimating lens 14 (illuminating means). Thus, of the light emitted from the subject 4, the imaging lens 16 (imaging means) and the CCD 17 (imaging means) in which the optical axis 18b is inclined with respect to the normal 4n by the angle θ The light traveling in that direction can be imaged.

According to the configuration of the first modified example, the illumination light in the wavelength bands λ _A and λ _B is incident at the incident angle θ ₀ , and the scattered light and the diffracted light emitted in the angle θ direction are imaged and those lights are captured. The defect extraction of the resist layer 303 which is the uppermost layer can be accurately performed based on the light image. If θ ₀ = θ, it is possible to perform defect extraction using obliquely reflected light.
Therefore, by varying the angles θ ₀ and θ, it is possible to extract defects that are remarkably observed with specularly reflected light and diffracted light at specific angles.

As shown in FIG. 7, the surface defect inspection apparatus 102 according to the second modified example of the present embodiment illuminates the surface of the subject 4 in a line shape from the direction of the angle φ ₀ , and thereby also the surface of the subject 4 In contrast, the light emitted in the direction of the angle φ can be imaged.
The schematic configuration of the surface defect inspection apparatus 102 includes an illuminating unit 55 (light source), a collimating lens 59 (illuminating unit), a collimating lens 60, an imaging lens 58 (imaging unit), and an imaging unit 56 (imaging unit).
The illuminating unit 55 includes, for example, a light source and a wavelength selection unit (both not shown) having the same configuration as the halogen lamp 6 and the rotary holder 9 of the above-described embodiment. Illumination light that spreads along the plane can be formed.
The collimating lens 59 is an optical element for converting such illumination light into a parallel light beam and irradiating the illumination region 54 on the subject 4 in a line shape. For example, a lens having a shape obtained by cutting a spherical lens along two planes parallel to the optical axis can be employed.
The collimating lens 60 is an optical element that is composed of, for example, the same lens as the collimating lens 59 and collects light such as specularly reflected light, diffracted light, and scattered light emitted from the subject 4 along the optical axis 18b.
The imaging unit 56 includes a line image sensor 57 and an imaging lens 58 that forms an image of the subject 4 by the light collected by the collimator lens 60 on the imaging surface of the line image sensor 57.

According to such a configuration of the second modification, illumination light in the wavelength bands λ _A and λ _B is incident at an incident angle φ ₀ , and scattered light and diffracted light emitted in the direction of the angle φ are captured in a line shape. While moving the subject 4 relative to the surface defect inspection apparatus 102, inspection images A and B in the angle φ direction can be obtained, and defect extraction of the resist layer 303 which is the uppermost layer can be performed. it can.
Further, since the line image sensor is used, there is an advantage that the apparatus can be downsized even if the subject is relatively large.

  In the above description, the wavelength selecting unit is described as being disposed between the light source and the illuminating unit. However, if an image can be captured with light in different wavelength bands, the wavelength selecting unit is disposed between the light source and the imaging unit. It may be placed anywhere.

  In the above description of the inspection process, the example in which inspection images B and A are inspected is described. However, it goes without saying that the reverse order may be used. That is, in FIG. 3, the order of steps 501 and 502 and steps 503 and 504 may be interchanged. The order of step 505 and step 506 may be interchanged.

In the above description of the image processing, an example has been described in which abnormal portions are extracted from each of a plurality of inspection images by image processing, the respective abnormal portion distributions are calculated, and the uppermost abnormal portion is obtained. In general, the light and dark distribution due to interference fringes in different wavelength bands is extremely complicated, and the image processing for directly comparing inspection images becomes complicated and inaccurate. Therefore, it is generally best to perform in this order. The abnormal part in the upper layer can be extracted with high accuracy.
However, if it is easy to compare inspection images for some reason, by directly comparing them, an image (uppermost layer defect image) that eliminates the effects of the underlying defects is created, and image processing is performed on that image. The defect extraction may be performed by obtaining the abnormal portion distribution.
In this way, since the image processing for extracting the abnormal part distribution is performed only once, there is an advantage that the inspection can be performed quickly.

As described above, the surface defect inspection apparatus of the present invention absorbs the plurality of wavelength bands switched by the wavelength selection unit in the uppermost layer of the subject as described with reference to the embodiment of the present invention and the modifications thereof. It is preferable that the first wavelength band and a second wavelength band that passes through the uppermost layer of the subject are used.
According to this surface defect inspection apparatus, since the light flux in the first wavelength band is absorbed by the uppermost layer, it is not reflected by the lower layer covered by the uppermost layer and emitted from the subject surface. By illuminating a light beam in one wavelength band, it is possible to obtain information on defects excluding the uppermost layer. Therefore, the defect of the uppermost layer can be extracted by performing image processing on each of the images of the light beams in the first and second wavelength bands.

In the surface defect inspection apparatus of the present invention, the first wavelength band is preferably a wavelength band that is absorbed by the resist.
According to this surface defect inspection apparatus, it is possible to extract resist defects, particularly when the uppermost layer is a resist. Therefore, an accurate inspection can be performed at the stage where a resist that can be easily corrected is developed, and the inspection efficiency can be improved.

In the surface defect inspection apparatus of the present invention, it is preferable that the predetermined direction of the light imaged by the imaging unit is the emission direction of the regular reflection light of the light beam irradiated on the subject surface by the illumination unit. .
According to this surface defect inspection apparatus, it is possible to perform surface defect inspection by observing regular reflection light on the surface of the subject.

In the surface defect inspection apparatus of the present invention, the predetermined direction of the light imaged by the imaging unit is different from the emission direction of the regular reflection light of the light beam irradiated on the subject surface by the illumination unit. It is preferable.
According to this surface defect inspection apparatus, surface defect inspection can be performed by observing diffracted light or scattered light on the surface of the subject.

Further, in the surface defect inspection apparatus of the present invention, the image processing means extracts an abnormal part for each of a plurality of images picked up by the light beams in the respective wavelength bands switched by the wavelength selecting means, and each abnormal part distribution is obtained. It is preferable that the defect extraction is performed by calculating and processing a plurality of abnormal portion distributions.
According to this surface defect inspection apparatus, the abnormal part distribution for each of a plurality of images is obtained, and the abnormal part distribution is subjected to arithmetic processing to eliminate the abnormal part affected by the lower layer, so that the abnormality in the uppermost layer is detected. The part can be extracted as a defect.

Further, in the surface defect inspection apparatus of the present invention, the image processing means creates the uppermost layer defect image from which the influence of the lower layer defect is removed by performing arithmetic processing on a plurality of images, and performs defect extraction from the uppermost layer defect image. It is preferable to adopt the configuration as described above.
According to this surface defect inspection apparatus, the defect extraction is performed after the top layer defect image from which the influence of the lower layer defect has been removed is created by performing a calculation process between a plurality of images. Since it is only necessary to perform the complicated image processing for performing one time, a rapid surface defect inspection can be performed.

It is front explanatory drawing for demonstrating schematic structure of the surface defect inspection apparatus which concerns on embodiment of this invention. It is a functional block diagram for demonstrating the structure of the control unit in the surface defect inspection apparatus which concerns on embodiment of this invention. It is a flowchart for demonstrating one part operation | movement of the test | inspection process of the surface defect inspection apparatus which concerns on embodiment of this invention. It is a cross-sectional schematic diagram of the thickness direction of the subject for demonstrating the principle of the surface defect inspection which concerns on embodiment of this invention. It is a schematic explanatory drawing which represents typically the image of the abnormal part extracted by the image processing which concerns on embodiment of this invention. It is front explanatory drawing for demonstrating schematic structure of the 1st modification of embodiment of this invention. It is an isometric view explanatory drawing for demonstrating schematic structure of a 2nd modification similarly.

Explanation of symbols

1, 101, 102 Surface defect inspection device 2 Control unit 4 Subject 6 Halogen lamp (light source)
9 Rotating holder (wavelength selection means)
14 Collimating lens (illumination means, imaging means)
17 CCD (imaging means)
18, 18a, 18b Optical axis 31 Computer 33 Memory 35 Image processing unit (image processing means)
36 Image storage unit 55 Illumination unit (light source)
56 Imaging unit (imaging means)
57 Line image sensor 59 Collimating lens (illumination means)
60 Collimating lens (imaging means)
302 Lower layer 303 Resist layer (resist)
402a, 403a, 402b, 403b Abnormal part 404a, 404c Abnormal part

Claims (7)

A surface defect inspection apparatus for inspecting a surface defect of an object having a layered structure and at least an uppermost layer and a layer immediately below the surface exposed on the surface,
A light source;
Illumination means for irradiating the subject surface with light from the light source as a substantially parallel light beam;
An imaging unit that forms an image of light in a predetermined direction emitted from the subject by the light beam emitted from the illumination unit;
Imaging means for capturing an image of light in the predetermined direction;
A wavelength selection unit that is arranged in an optical path between the light source and the imaging unit and selectively switches a wavelength band of a light beam between at least two wavelength bands independent of each other;
A surface defect inspection apparatus comprising image processing means for performing image processing on a plurality of images picked up by light beams in respective wavelength bands switched by the wavelength selection means to extract defects on the surface of the subject. . A plurality of wavelength bands to be switched by the wavelength selection means,
A first wavelength band absorbed by the uppermost layer of the subject;
The surface defect inspection apparatus according to claim 1, comprising a second wavelength band that transmits the uppermost layer of the subject.   The surface defect inspection apparatus according to claim 2, wherein the first wavelength band is a wavelength band absorbed by a resist.   The predetermined direction of the light imaged by the imaging unit is the emission direction of the regular reflection light of the light beam irradiated on the subject surface by the illumination unit. The surface defect inspection apparatus described.   The predetermined direction of the light imaged by the imaging unit is different from the emission direction of the regular reflection light of the light beam irradiated on the subject surface by the illumination unit. The surface defect inspection apparatus in any one.   The image processing means extracts an abnormal part for each of the plurality of images, obtains the respective abnormal part distributions, and performs defect extraction by performing arithmetic processing on the plurality of abnormal part distributions. The surface defect inspection apparatus according to any one of claims 1 to 5.   The image processing means creates an uppermost layer defect image from which an influence of a lower layer defect is removed by performing arithmetic processing on the plurality of images, and performs defect extraction from the uppermost layer defect image. The surface defect inspection apparatus according to any one of claims 1 to 5.

Images