JPH0727709A - Inspecting apparatus surface defect - Google Patents

Abstract

PURPOSE:To obtain a surface defect inspecting apparatus which can observe a defect such as dusts, irregularity in film thickness of a to-be-inspected surface, etc., and is accordingly easy to constitute an automatic defect inspecting apparatus in combination with an image processing apparatus. CONSTITUTION:The apparatus is provided with a collimator lens 12, and light sources 2-5 of a narrow band. The collimator lens 12 arranged immediately before a to-be-inspected body 21 having a thin film on the surface thereof, is approximately the same in size as an observing visual field of the to-be-inspected body 21, makes the regularly reflect light from a light source 1 cast on the to-be-inspected body 21 as almost parallel luminous fluxes and passes the regularly reflected light from the surface of the to-be-inspected body 21. The light sources 2-5 are set in the vicinity of a focal point of the collimator lens 12, having a plurality of optionally selectable center wavelengths, to make the light incident on the collimator lens 12. Moreover, a half mirror 11 of the apparatus reflects or passes the light from the light sources 2-5 thereby to allow the light to pass through the collimator lens 12 to be cast at a right angle to the body 21. An image forming lens 13 of the apparatus passes the regularly reflected light from the surface of the body 21 through the collimator lens 12, so that the light penetrates or is reflected at the half mirror 11. The image forming lens 13 has an entrance pupil at a conjugate position to the light sources 2-5 to observe the surface of the body 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface of an object having a thin film on the surface or an object having a flat surface, such as the wafer or the liquid crystal glass substrate in the manufacturing process line of the wafer or the liquid crystal glass substrate. The present invention relates to a surface defect inspection device for inspecting defects.

[0002]

2. Description of the Related Art Photolithography for liquid crystal panels, etc.
In the process line, if the resist applied on the substrate surface has defects such as uneven film thickness or adhesion of dust,
After etching, it appears as a defective line width of the pattern or a pinhole in the pattern. Therefore, it is generally performed to inspect all the substrates before etching for the presence of the defects.

Conventionally, such a defect inspection has adopted a method of illuminating a substrate (hereinafter, referred to as an object) with a light projecting device and visually observing the defect. As an example of the inspection floodlighting device suitable for such an application, an outline of the device of the present applicant's previous application (Japanese Patent Application No. 4-31922) is described with reference to FIGS. 27 and 28. explain.

The light flux from the high-intensity light source 201 passes through the heat ray absorption filter 203, is made into uniform illumination light by the diffusion plate 204, and is then limited in spectrum width by the interference filter 205 (hereinafter referred to as narrow band light). ). Then, the object 211 is illuminated after being reflected by the plane mirror 206 and converted into convergent light beams by the large-diameter Fresnel lenses 207 and 208. Immediately after the Fresnel lens 208, the liquid crystal diffusion plate 2
09, which normally acts as a diffusing plate, so that the subject 211 is illuminated with diffused light from a large surface light source.

On the other hand, as shown in FIG. 27, when a voltage is applied to the liquid crystal diffusion plate 209 by the power supply 210, the liquid crystal becomes colorless and transparent, and at this time, the subject 211 is illuminated with convergent light. In the inspection light projecting device having such a configuration, the unevenness of the film thickness of the subject 211 is inspected under the diffused light illumination device shown in FIG. This is because when the film thickness of the resist changes, the optical path difference of the reflected light from the front surface and the back surface of the resist changes. It can recognize the unevenness.

The adhesion of dust 212 to the object 211 is inspected under convergent light illumination (FIG. 27). That is, since the light flux reflected by the plane of the subject 211 converges on the position S, if the observer's eye 213 is placed at a position avoiding it,
Only the points other than the plane, that is, the light scattered by the dust 212 are visually recognized.

The following defects are also detected by the convergent light illumination. FIG. 13 is a schematic view of a cross section of the subject after resist development, in which a film forming layer 61 is provided on a substrate 60 (glass plate or wafer), and a patterned resist 6 is formed thereon.
2 shows the state where 2 remains. FIG. 14 is an enlarged view of a part 65 of FIG. In this way, the surface of the subject can be roughly divided into three parts. That is,
A flat portion A on the residual resist film, a flat portion B without the resist, and side surfaces C and D of a step between them. Among these, defects such as uneven film thickness of the flat portion A can be detected by the above-mentioned diffused light illumination device that observes specularly reflected light.

The normal side surface is as shown in FIG. 15C, while the defective side surface is deformed as shown in FIG. 16C, for example. Since the different shapes show different scattering angle distributions of light, the defects on the side surfaces C and D are recognized as a difference in brightness from a normal portion when observed by scattered light with convergent light illumination. .

On the other hand, the unevenness of the film thickness is inspected under the diffused light illumination device shown in FIG. This is because when the film thickness of the resist changes, the optical path difference of the reflected light from the front surface and the back surface of the resist changes. It can recognize the unevenness.

This inspection light projecting device is used in combination with a swinging / rotating mechanism of a subject, which has been previously filed and published by the present applicant (Japanese Patent Laid-Open No. 5-109849). In other words, in the actual inspection, the subject 211 is illuminated by the light projecting device, and is oscillated and rotated to work on the incident / reflected angle of the light flux to the subject 211 and the direction of the diffracted light by the periodic pattern on the subject. It is possible to perform an inspection of the entire surface of the subject 211 while adjusting the adjustment by a person so that the observation of the scattered light and the reflected light that interferes is not disturbed.

[0011]

Since the work described above is an inspection by the operator's visual inspection, the degree of freedom of observation is large and it is possible to show excellent inspection ability. However, on the other hand, it is unavoidable that the detection capability varies due to individual differences among workers and differences in observation conditions, and especially when the inspection is performed frequently and over a long period of time, it causes worker fatigue.
Maintaining constant inspection capabilities becomes even more difficult. In addition, dust generation from workers has always been a problem, and automation of the inspection has been desired.

An easily conceivable automation method is to install an imaging lens and an image pickup device such as a CCD in place of the eye 213 shown in FIG. 27 or 28 to obtain an inspection screen and display it as an image. Processing to extract defects. However, this method includes the following first to fourth problems.

<First Problem> The incident angle of the illumination light with respect to the subject 211 is largely different depending on the place.
FIG. 29 is for explaining this, and is a simplified version of FIG. 28. In the figure, 209 is a diffusion plate, 211 is a subject, 214 is an imaging lens, and 215 is an image sensor.

In such a structure, the diffusion plate 2
09 out reflected by the object 211, the incident angle theta ₀ of light reaching the image sensor 215 through the imaging lens 214 is continuously changed between a maximum value theta _0max and the minimum value theta _0min at both ends of the substrate To do.

Here, taking an example of observing the film thickness unevenness, the refractive index of the thin film (= resist) is n, the film thickness is h, the wavelength of the illumination light (monochromatic) is λ ₀ , and it is determined by the Snell's law. ) If the angle of refraction of the light beam inside the thin film is θ ′ and the phase change at the time of reflection on the lower surface of the thin film is φ (0 ≦ φ <2π), the condition that the interference fringes due to the thin film is a bright line is 2nhcos θ ′ + ( _{φ / 2π) · λ 0 =} mλ 0, m = 0, ± 1, ± 2, represented by (1) (m; order of interference). That is, in the arrangement of FIG. 29 in which the incident angle θ ₀ of the illumination light changes, even if the film thickness of the object 211 is uniform over the entire surface, a bright and dark distribution can be formed on the object according to the distribution of the incident angle θ _0. Will end up. And, the unevenness of the film thickness is observed brightly in one place and dark in another place in the light and darkness. Therefore, in the conventional inspection apparatus, it is necessary to inspect the entire surface of the subject 211 while swinging and rotating the subject 211 to change the illumination incident condition as described above.

However, when trying to extract the film thickness unevenness by using the image processing apparatus, if the same film thickness unevenness looks different depending on the place, or if it is necessary to process a plurality of images with different incident conditions. It is easily speculated that the process would be very complicated and difficult.

Similarly, regarding the defect detection on the step side surface, the scattered light to be observed is different depending on the position on the object. It should be noted that if the object 211 is about the size of a wafer, the change in the incident angle θ ₀ is small, but if an attempt is made to inspect the liquid crystal glass substrate at once or in two or four divisions,
The change in θ ₀ becomes quite large, and the above problem cannot be avoided.

<Second Problem> It is impossible to illuminate the subject 211 by vertical incidence. As can be seen from the equation (1), the detection sensitivity of the film thickness unevenness becomes the maximum at the normal incidence (θ ₀ = θ ′ = O °).

However, when the diffusion plate 209 and the image pickup device 215 are arranged as shown in FIG. 30 and the incident angle θ ₀ on the subject 211 is close to 0 °, the shadowed portion of the image pickup device 215 is illuminated. No, it cannot be observed.

If a half mirror is provided between the diffusion plate 209 and the subject 211 to bend the observation optical path, the shadow disappears. In this case, however, a half mirror larger than the subject 211 is required, and a wide field of view is obtained. It becomes difficult to deal with.

<Third Problem> It is difficult to obtain coordinates on the subject 211. Since the subject 211 is tilted with respect to the observation optical axis in the arrangement of FIG. 29, the image pickup surface of the image pickup device 215 must be tilted in order to obtain a sharp image of the entire surface (Scheinproof condition). At the same time, the closer to the imaging lens 214 of the subject 211, the larger the magnification and the distorted image. Therefore, in order to obtain the position coordinates for the cause analysis of the defect and the like, it is necessary to take measures to calibrate the coordinates.

<Fourth Problem> With the device of FIG.
When detecting the dust 212 on 11, the whole surface is illuminated by the diffracted light by the wiring pattern on the object 211, so that the contrast of the scattering points does not increase so much and it is difficult to extract it by image processing.

The present invention has been made in order to solve the above problems, and it is possible to observe defects such as dust and film thickness unevenness on the surface of a subject as a simple image, and therefore, in combination with an image processing apparatus. It is an object of the present invention to provide a surface defect inspection apparatus which makes it easy to construct an automatic defect inspection apparatus.

[0024]

In order to achieve the above-mentioned object, the invention corresponding to claim 1 is a light source, and an irradiating means for irradiating the surface of the subject with light from the light source as a substantially parallel light flux. Converging means for converging light that is specularly reflected or scattered from the surface of the subject by irradiating the surface of the subject with the light flux from the irradiation means, and the surface of the subject through the condensing means. A surface defect inspection apparatus comprising: an observation means for observing.

To achieve the above object, the invention corresponding to claim 2 is the surface defect inspection apparatus according to claim 1, wherein the light source is a narrow band light source having a center wavelength that can be arbitrarily selected.

In order to achieve the above-mentioned object, the invention corresponding to claim 3 is the surface defect inspection apparatus according to claim 1, wherein the irradiation means and the condensing means are shared by the same optical member.

To achieve the above object, in the invention according to claim 4, the observation means irradiates the light flux from the irradiation means onto the surface of the subject to be specularly reflected from the surface of the subject. The surface defect inspection apparatus according to claim 1, which is for observing the surface of the subject based on only the light that is emitted.

To achieve the above object, in the invention according to claim 5, the observation means irradiates the surface of the subject with the light flux from the irradiating means to scatter from the surface of the subject. The surface defect inspection apparatus according to claim 1, wherein the surface of the subject is observed based on only the light flux of the substantially same outgoing direction of the light.

In order to achieve the above-mentioned object, the invention according to claim 6 is that the light source has an annular light-emitting portion whose central portion is shielded, and the observation means is the irradiation means and the irradiation means. 2. The surface defect inspection apparatus according to claim 1, wherein the surface defect inspection apparatus has an entrance pupil that has a position and a shape that are substantially conjugate with the shield portion in the central portion of the light source through the subject and the light condensing unit.

In order to achieve the above-mentioned object, the invention according to claim 7 is characterized in that the observation means has a position substantially conjugate with the light emitting portion of the light source via the irradiation means, the subject and the light condensing means. It has a shield that becomes a shape,
The surface defect inspection apparatus according to claim 1.

In order to achieve the above-mentioned object, the invention according to claim 8 is an illuminating means which is arranged outside the observation field of view of the subject, and which illuminates the surface of the subject obliquely to obtain scattered light. An observation device for observing scattered light from the subject, the surface defect inspection apparatus.

[0032]

According to the inventions corresponding to claims 1 to 8,
Defects such as dust and film thickness unevenness on the surface of the subject can be observed as a simple image, and thus it becomes easy to configure an automatic defect inspection apparatus in combination with an image processing apparatus.

Particularly, according to the invention corresponding to claim 1,
All fields of view can be observed under the same conditions. According to the inventions corresponding to claims 1 to 4, it is possible to detect the film thickness unevenness of the subject. According to the inventions corresponding to claims 1 to 3 and 5 to 7, it is possible to detect a defect on the step side surface of the patterned layer on the surface of the subject. Further, according to the invention corresponding to claim 8,
Detects dust or scratches on the subject.

[0034]

Embodiments of the present invention will be described below with reference to the drawings. First, an embodiment for detecting unevenness in film thickness, dust, and scratches on a subject will be described.

<First Embodiment> FIG. 1 is a side view of an optical system of a first embodiment of the surface defect inspection apparatus of the present invention. The luminous flux emitted from the halogen lamp 2 which is a light source for detecting the unevenness in film thickness passes through the heat ray absorption filter 3 and is converted into a parallel luminous flux group by the condenser lens 4. These are integrated in the lamp house 1.

A plurality of narrow band interference filters (not shown) are housed in the rotary holder 5, and a desired interference filter can be inserted into the optical path by rotating this with a motor (not shown). You can

Since the thin film to be observed has a refractive index n of 1.62 (positive resist) and a thickness h of about 1.5 μm, the optical path difference of interference is about 2 nh to 5 μm. Therefore, an interference filter of Δλ = 10 nm is used so that the coherent length λ ₀ ² / Δλ (λ _{0 to} 0.6 μm; center wavelength, Δλ; half-width of spectrum) of the illumination light is sufficiently larger than 5 μm. If the variable range of the central wavelength λ ₀ is such that the interference order of the uniform film thickness portion changes by 1, the region where the film thickness is uniform is defined as the interference fringes for the arbitrary φ in the equation (1). It can be set freely between the bright and dark lines. That is, if the variable range is λ ₀₁ to λ ₀₂ (λ ₀₁ <λ ₀₂ ), then from equation (1), 2nhcos θ ′ + (φ / 2π) · λ ₀₁ = (m + 1) λ ₀₁ 2nhcos θ ′ + (φ / 2π) · λ ₀₂ = mλ ₀₂ (2) holds, ignoring the wavelength dependence of n and φ,
If θ ′ = 0 and m is eliminated from both equations, 1 / 2nh = 1 / λ ₀₁ −1 / λ ₀₂ (3) is obtained.

That is, the smaller the optical thickness nh of the thin film to be inspected, the wider the variable range is required. Therefore, of all thin films to be inspected, the minimum optical thickness nh
If the variable range of λ ₀ is set according to the film having λ, the region of uniform film thickness can be set for any thin film regardless of the structure of the layer below the thin film (that is, even if φ changes). It is possible to select the center wavelength λ ₀ that makes the interference fringes (for example, dark lines).

In this embodiment, n = 1.62, h = 1.1 μ
The range of λ ₀ from 550 nm to 6
The wavelength is set to 50 nm, and the central wavelength can be selected at intervals of 10 nm. Therefore, the rotary holder 5 has 11 interference filters and one hole for white light illumination. The light flux narrowed by the interference filter is focused on the end surface of the fiber bundle 7 by the condenser lens 6.

The reason why the illumination light is guided by the fiber bundle 7 is that the light source section from the lamp house 1 to the condenser lens 6 is installed in the lower part of the entire apparatus to facilitate the adjustment and maintenance. The light flux emitted from the fiber bundle 7 becomes a secondary light source whose intensity distribution is averaged by the diffusion plate 9. The diaphragm 10 blocks unnecessary light beams, and these are integrated as a secondary light source unit 8. The diffusing plate 9 is installed on the focal plane of the collimator lens 12, and the light flux reflected by the half mirror 11 becomes a parallel light flux by the collimator lens 12 and is vertically incident on the subject 21.

The collimator lens 12 is a field of view for one inspection (the entire surface of the liquid crystal glass substrate or one of several divided areas).
It has a diameter that covers the surface) and is installed at a constant distance from the subject 21. Regarding the image forming performance of the observation system (described later), the smaller this interval is, the more advantageous it is. However, in order to not detect dust on the surface of the collimator lens and to pass the illumination light for scattering point detection, which will be described later, from several cm to 10 or more. Spaced in cm. The light flux reflected by the subject 21 passes through the collimator lens 12 again to become convergent light, and the component having passed through the half mirror 11 enters the imaging lens 13. The imaging lens 13 forms an image of the surface of the subject 21 on the imaging surface of the monochrome CCD 14. At this time, the image forming lens 13 is arranged such that its entrance pupil is near the focal plane of the collimator lens 12 (that is, the diffusing plate 9).
When it is installed so as to be located at a position (which is almost conjugate with), the light flux reflected by the subject 21 can be efficiently collected, and an observation visual field with uniform illuminance can be obtained.

When a CCD is used to capture an image of a periodic wiring pattern, if the pixel period of the CCD and the period of the wiring pattern image are substantially the same, moire will occur in the captured image.
It is necessary to properly select the focal length of the imaging lens 13 so that the observation magnification does not cause moire. Therefore, in the present embodiment, a zoom lens is adopted as the imaging lens 13 so that various wiring pattern periods can be dealt with. However, when zooming, the position of the entrance pupil of the imaging lens 13 changes, so that this is canceled and the entrance pupil is returned to the position described above.
A parallel movement stage (not shown) for moving the imaging lens 13 and the CCD 14 in the optical axis direction is provided. Also, CC
Since the pixel cycle of D is generally different in the horizontal direction and the vertical direction, by rotating the CCD with the optical axis as the rotation axis,
Since the moire may disappear, a rotary stage for that may be provided. The plates 15 and 16 are half mirrors 11.
This is to prevent an unnecessary object from being illuminated by the illuminating light that has passed through and to form an image superimposed on the subject image on the CCD 14 imaging surface. It is a flat plate with antireflection treatment such as black coating on the surface. is there.

On the other hand, the light source unit 17 for detecting dust includes a halogen lamp (not shown), a heat ray absorbing filter, and a condenser lens therein, and makes a white light beam incident on the end face of the fiber bundle of the line illumination 18. The line illumination 18 is formed by arranging each fiber in the fiber bundle on the emitting side in a straight line in two rows with a length of 30 cm, and produces a thin sheet-like illumination light together with a semi-cylindrical condenser lens 19. A cross section of the condenser lens 19 is shown in FIG. The lens is a half cut acrylic cylinder, and aluminum is vapor-deposited on the cut surface to form an anti-slope B. The light emitted from the fiber end A of the line illuminator 18 is emitted as a nearly parallel light C. The condensing lens 19 has such a shape that the line illumination 18 and the condensing lens 19 convey the object 21 and a stage (which conveys the object 21) when the incident angle on the object 21 is close to 90 °. This is to prevent interference with (not shown).

Further, the arrangement of line illumination will be described with reference to FIGS. FIG. 2 shows the line illumination 18 and the subject 21,
The positional relationship of the collimator lens 12 is shown, and is an example of inspecting one subject 21 in four divisions. The broken line 23 is the moving range of the subject 21. The four line lights 18
While keeping the distance L from the center O of the observation visual field 22 constant,
Are placed on moving stages (not shown) that can change the incident direction φ with respect to the subject 21 in the range of Δφ with the rotation axis as the rotation axis, and the diffracted light from the wiring pattern is transmitted to the observation system for each type of the subject 21. It is set to an appropriate incident direction φ that is least incident.

The four line illuminators 18 are installed at symmetrical positions so as to have the same incident direction φ with respect to the subject 21, because they complementarily illuminate the observation visual field 22 almost uniformly. This is to supplement the detection sensitivity anisotropy of a defect having directionality such as a scratch on the surface of the specimen 21.

In FIG. 3, the line illumination 18 is used to set the incident direction φ.
This is another example in which the center O ′ of is used as the axis of rotation. The method of FIG. 3 has an advantage that the variable range Δφ can be made large, and the method of FIG. 2 is advantageous in terms of illumination efficiency because the center line of the illumination field by the line illumination 18 always passes through the center of the observation visual field 22. The line illumination 18 may be set according to FIG. 2 or FIG. 3 or a compromise between the two depending on the type and size of the subject.

Now, returning to FIG. 1 again, the description will be continued.
The subject 21 illuminated by the line illumination 18 is imaged by the imaging lens 13 and the CCD 14 which are the same as those for detecting the film thickness unevenness. At this time, in order to prevent weak attenuation of scattered light, the half mirror 11 is moved in a direction perpendicular to the paper surface by a translation stage (not shown) and is removed from the observation optical path. When the half mirror 11 is thick and the change in the optical path length cannot be ignored, a compensator having the same material and thickness and having an antireflection coating on the surface may be inserted in the optical path instead of the half mirror 11.

Further, the collimator lens 12 is the subject 21
It has a function of collecting scattered light having an equal scattering angle from the entire surface, that is, collecting scattered light in a direction perpendicular to the subject 21 and guiding it to the entrance pupil of the imaging lens 13. However, since the scattering point can be observed without the collimator lens 12, it may be removed from the optical path if necessary. The background plate 20 installed below the subject 21 substantially in parallel with the subject 21 at a constant interval,
Similar to the plates 15 and 16 described above, it is a flat plate whose surface is subjected to antireflection treatment. When inspecting a partially transparent subject 21 such as a liquid crystal glass substrate, it is inevitable that part of the illumination light will pass through the subject 21 and illuminate the background, but in such a case, defect detection is also required. The background plate 20 acts to create a simple background that does not interfere. The distance from the subject 21 is several cm so that the illumination light of the line illumination 18 that has passed through the subject does not hit the background plate 20.

Next, the configurations of the control unit and the image processing unit will be described with reference to FIG. The image processing device 35 takes in the inspection image from the CCD 14 under the control of the host computer 31,
Image processing is performed to extract defects such as uneven film thickness and dust, and data such as the type, number, position, and area are sent to the host computer 31. The monitor TV 34 displays the inspection image and the processed image. The image storage device 36 stores the inspection image and the processed image as needed. The sequencer 37 controls each control unit according to an instruction from the host computer 31. The optical system control unit 38 controls the amount of light from the optical system moving mechanism such as the rotary holder 5 of the interference filter 5 and the moving stage of the half mirror 11 and the light sources 2 and 17. The stage control unit 39 controls the suction stage that vacuum-sucks and supports the subject 21 and moves the subject 21 into the observation field of view, and the positioning mechanism thereof. The substrate transfer control unit 40 sets the subject to 1
The transport unit that takes the sheets out of the stocker one by one and places them on the suction stage and returns the inspected subject 21 to the stocker from the same stage is controlled. The stage and the transport unit are not shown. The operator operates the keyboard 32 according to the menu screen displayed on the monitor TV 30,
Give the inspection equipment the necessary instructions. The memory 33 stores inspection conditions for each type of subject (optical system setting and image processing conditions).
It also stores inspection data and the like.

Next, the operation of the inspection apparatus of this embodiment will be described mainly with reference to FIGS. 4 and 1. The operator uses the keyboard 32
When an instruction to start the examination is given together with the type of the subject 21, the host computer 31 reads the conditions corresponding to the subject 21 from the examination conditions stored in advance in the memory 33, and the optical system is executed via the sequencer 37. The control unit 38 sets the optical system.

What is set by the optical system control unit 38 is
Selection of interference filter, incident direction of line illumination 18, zooming of imaging lens 13 and accompanying movement in optical axis direction
It is positioning. Next, the first subject 21 is taken out from the stocker by the transport unit and placed on the suction stage. In the case of inspecting the subject 21 in four divisions, the suction stage fixes the subject 21 by suction and then, as shown in FIG.
Move and position so that one part is in the center of the observation field of view. In the inspection, first, the halogen lamp 2 is turned on, and the light amount thereof is adjusted according to the inspection conditions.

When the amount of light reaches a predetermined value, the inspection image is taken from the CCD 14 into the image processing device 35. At this time, the inspection image 101 includes the edge 102 of the subject 21 as shown in FIG.
In the inside of the subject, an image in which only the portion 104 with uneven film thickness becomes bright in a dark region where the film thickness is uniform. The image processing device 35 extracts only the inspection region 103 from this image by masking, extracts only the portion 104 with uneven film thickness through shade correction, binarization, etc., and outputs the data such as the position and area to the host computer 31. send. Next, the halogen lamp 2 is turned off, the light source unit 17 is turned on, and the half mirror 11 is removed from the optical path. At this time, the inspection image 105 becomes as shown in FIG. 7, and only the scattering point 108 due to dust looks bright in the dark region. From this, only the scattering points 108 are extracted by similar image processing, and data such as the positions thereof are sent to the host computer 31. The image processing process is specified by the inspection conditions.

By appropriately adjusting the light amounts of the halogen lamp 2 and the light source unit 17 and turning them on at the same time, it is possible to obtain the unevenness of the film thickness and the scattering point due to the dust on the same inspection screen. The remaining three quarters of the subject 21 are similarly examined.

When the inspection of one object 21 is completed, the host computer 31 divides the object 21 into four parts.
The defect data of 1 is combined and the type and number of defects are compared with the inspection standard included in the inspection conditions, and the object 2
The quality of 1 is judged. The inspected object 21 is sent from the suction stage to the inspected stocker that is classified as good or bad by the transport unit, and the inspection of one sheet is completed. In the above operation, the halogen lamp 2 and the light source unit 17 may be turned on and off by opening and closing a shutter provided in the optical path.

In the above embodiment, the combination of the halogen lamp 2 and the interference filter inserted into and supported by the rotary holder 5 is used in order to make the center wavelength of the quasi-monochromatic light for inspecting the film thickness unevenness variable. A monochromator or the like may be used instead of the interference filter, or a light source such as a laser which is originally quasi-monochromatic light may be used. The interference filter may be mounted on the front surface of the imaging lens 13 instead of the light source side.

<Second Embodiment> The optical system shown in FIG. 1 can be modified as follows. FIG. 8 shows a second embodiment of the present invention. The irradiation means and the condensing means consist of one collimator lens 12, are arranged immediately in front of the subject 21, and are almost in the observation field of view of the subject 21. The light from the light source, that is, the fiber bundle 7 having the same size is applied to the subject 21 as a substantially parallel luminous flux, and the subject 2 is irradiated with the light.
The reflected light from the surface of No. 1 is passed.

The fiber bundle 7 is arranged in the vicinity of the focal plane of the collimator lens 12, and the narrow band light is incident on the collimator lens 12. The observing means is composed of an imaging lens 13 and a CCD 14, has an entrance pupil at a position axially symmetrical to the fiber bundle 7 about the optical axis of the collimator lens 12, and observes the surface of the subject 21.

Also in the second embodiment constructed as described above, since the collimator lens 12 having a size substantially equal to the observation visual field is provided in the vicinity of the subject 21, the entire visual field is illuminated with the same incident angle. The uneven thickness can be observed as an equal-thickness interference fringe. Further, there is an advantage that the half mirror 11 of the embodiment of FIG. 1 is unnecessary.

<Third Embodiment> FIG. 9 shows an optical system according to a third embodiment of the present invention.
It is composed of a condensing means and an observing means. The irradiating means and the condensing means include the half mirror 11 and the first and second mirrors.
The collimator lenses 12 and 12 '.

The exit end face of the fiber bundle 7 for guiding the narrow band light beam is arranged near the focal point of the collimator lens 12.
The half mirror 11 is about 45 with respect to the surface of the subject 21.
It is arranged in an inclined state and reflects or transmits light. The collimator lens 12 includes the fiber bundle 7
The light from is made substantially parallel and is irradiated onto the subject 21 via the half mirror 11. The collimator lens 12 ′ is arranged such that the optical axis of the reflected light from the surface of the subject 21 coincides with the optical axis, and collects the reflected light from the surface of the subject 21.

The observing means comprises an image forming lens 13 and a CCD 14. The CCD 14 is arranged near the focus of the collimator lens 12 'and observes the surface of the subject 21. According to the third embodiment, the same effect as the first embodiment can be obtained.

<Fourth Embodiment> FIG. 10 shows an optical system according to a fourth embodiment of the present invention, in which the first collimator lens 12 is used.
Is arranged with its optical axis inclined with respect to the surface of the subject 21, and irradiates the subject 21 with light from the fiber bundle 7, which is a narrow band light source, as a substantially parallel light beam. The second collimator lens 12 ′ is arranged so that the optical axis of the reflected light from the surface of the subject 21 coincides with the optical axis.

An image forming lens 13 and a CCD 14 are arranged near the focal point of the collimator lens 12 'so that the surface of the subject 21 can be observed. According to the fourth embodiment, not only the same effect as in the third embodiment can be obtained, but also the half mirror 11 of the embodiment of FIG. 9 is not required.

<Fifth Embodiment> Next, an embodiment for detecting a defect on the step side surface of the patterned layer on the surface of the subject will be described.

FIG. 11 is a view showing the optical system of the fifth embodiment of the present invention. The light beam emitted from a halogen lamp, which is a light source not shown, is made into a narrow band light through an interference filter,
It is adapted to enter the fiber bundle 7.

The exit end face of the fiber bundle 7 is arranged on the rear focal plane of the collimator lens 12 at a position not on the optical axis of the collimator lens 12. This exit end surface can be moved on the same focal plane by a moving stage (not shown), and the angle θ _o of the illumination center ray with respect to the optical axis of the collimator lens 12 can be set to an arbitrary value. The collimator lens 12 is installed such that its optical axis is perpendicular to the subject and at a proper distance from the subject. The collimator lens 12 has a size that covers the inspection region of the subject 21.

With the configuration shown in FIG. 11, the light beam emitted from the fiber bundle 7 becomes a parallel light beam by the collimator lens 12 and illuminates the subject 21 at the incident angle θ _o . The light beam specularly reflected by the subject 21 is again collimator lens 12
It converges on the focal point 29 through.

In the fifth embodiment, since the specular reflection light is unnecessary, the scattered light is trapped so as not to adversely affect the observation (not shown). On the other hand, scattered light emitted from the subject 21 in the vertical direction (broken line in FIG. 11) is collected by the collimator lens 12 and focused on the rear focal point. The imaging lens 13 is installed so that the entrance pupil is located in the vicinity thereof, and the CCD 14
An image of the subject 21 is formed on the imaging surface of. A zoom lens is used as the imaging lens 13 for the reason described above.

Next, the configurations of the control unit and the image processing unit in FIG. 11 will be described. Since they are almost the same as those in FIG.
Will be described with reference to. The image processing device 35 takes in an inspection image from the CCD 14 under the control of the host computer 31, performs image processing to extract defects, and sends data such as the type, number, position, and area to the host computer 31.
The monitor TV 34 displays the inspection image and the processed image.

The image storage device 36 stores the inspection image and the processed image as required. The sequencer 37 controls each control unit according to an instruction from the host computer 31. The optical system control unit 38 controls the light amount of the light source, the position of the emitting end face of the fiber bundle 7, and the like. The stage controller 39
The suction stage that holds and vacuum-supports the subject 21 and moves the subject 21 within the observation field of view, and the positioning mechanism thereof are controlled. The substrate transfer control unit 40 controls the transfer unit that takes out the test objects one by one from the stocker, places them on the suction stage, and returns the tested test objects 21 from the same stage to the stocker.

The stage and the transfer section are not shown. The operator gives a necessary instruction to the inspection apparatus by operating the keyboard 32 according to the menu screen displayed on the monitor TV 30. The memory 33 stores inspection conditions (optical system setting and image processing conditions) for each type of subject, inspection data, and the like.

Next, the operation of the inspection apparatus of the fifth embodiment will be described. When the operator gives an instruction to start the examination together with the type of the subject 21 using the keyboard 32, the conditions corresponding to the subject 21 are read into the host computer 31 from the examination conditions stored in advance in the memory 33, and the sequencer 37 The optical system control unit 38 sets the optical system via the.

What is set by the optical system control unit 38 is
These are the light amount of the light source, the position of the emitting end face of the fiber bundle 1, the zooming of the imaging lens 13, and the movement / positioning thereof in the optical axis direction. Next, the first subject 21 is taken out from the stocker by the transport unit and placed on the suction stage. The suction stage, after adsorbing and fixing the subject 21, is moved and positioned so as to come to the center of the observation visual field.

Subsequently, the inspection image is fetched from the CCD 14 into the image processing device 35. At this time, the inspection image 50 includes an edge 51 of the subject, for example, as shown in FIG. 12, and the inside of the subject 21 is an image in which only the side defect portion 53 has a different luminance in a uniform luminance region having no defect. Has become. The image processing device 35 takes out only the inspection region 52 from this image by masking, extracts only the defect portion 53 through shade correction, binarization processing, etc., and sends the data such as its position and area to the host computer 31.

When the inspection of one subject 21 is completed in this way, the host computer 31 compares the type and number of defects with the inspection criteria included in the inspection conditions, and determines whether the subject 21 is good or bad. To judge. Then, the inspected object 21 is sent from the suction stage to the inspected stocker classified as good or bad by the transport unit.

Although the halogen lamp is used as the light source in the fifth embodiment, a light source of high brightness such as a laser or a metal halide lamp may be used instead. Further, the light source may be directly installed on the back focal plane of the collimator lens 12 without guiding the illumination light by the fiber bundle 7. The interference filter may be placed on the front surface of the imaging lens 13 instead of on the light source side.

<Sixth Embodiment> The optical system shown in FIG. 11 can be modified as follows. FIG. 17 is a view showing the optical system of the sixth embodiment, in which the image forming lens 13 and the CCD 14 are installed at positions off the optical axis of the collimator lens 12,
Moreover, the observation angle θ is removed from the direction of regular reflection of the subject 21. At this time, the entrance pupil of the imaging lens 13 is located near the rear focal plane of the collimator lens 12,
This is the same as FIG. 11 of the fifth embodiment.

In this embodiment, therefore, the degree of freedom of observation can be increased as compared with the embodiment shown in FIG. <Seventh Embodiment> FIGS. 18A and 18B show the optical system of the seventh embodiment by trigonometry, in which FIG. 18A is a front view thereof, FIG. 18B is a side view thereof, and FIG. It is a figure. In this example, a plurality of (two in FIG. 18) fiber bundles 7 for guiding illumination light,
7'is provided, the incident angles θ ₁ , θ ₂ and the incident directions φ ₁ , φ ₂
Can be set freely. Since the resist pattern on the subject 21 is two-dimensionally spread, the sensitivity of defect detection can be improved by simultaneously illuminating the step side surfaces in different directions by a plurality of illuminations.

<Eighth Embodiment> FIG. 19 shows an optical system according to an eighth embodiment, which includes a collimator lens 12 and an imaging lens 1.
A half mirror 11 is provided between the two, and the illumination light from the fiber bundle 7 is reflected by the half mirror 11 to illuminate the subject 21. In this example, the imaging lens 13 is located on the optical axis of the collimator lens 12, while the exit end face of the fiber bundle 7 is off the optical axis by an angle θ _o .

In the fifth embodiment shown in FIG. 11, as the angle θ _o is made smaller, the fiber bundle 7 and the imaging lens 13 come into contact with each other. Therefore, θ _o has a lower limit. There is no limitation, and scattered light in the immediate vicinity of specularly reflected light can be observed.

<Ninth Embodiment> FIG. 20 is a view showing the optical system of the ninth embodiment, in which an independent collimator lens 12 'is provided for illumination light, and the exit end face of the fiber bundle 7 is focused on the front side thereof. It is installed. The collimator lens 12 'is rotationally symmetrical with respect to its optical axis, and thereby illuminates the subject 21 with a parallel light beam having an incident angle θ _o . This example is advantageous for observing scattered light at a large angle with respect to specular reflection.

<Tenth Embodiment> FIG. 21 shows a tenth embodiment of the present invention.
It is a side view which shows the optical system of an Example. A light beam emitted from a halogen lamp, which is a light source (not shown), is incident on the fiber bundle 7. The light flux emitted from the emission end surface of the fiber bundle 7 is incident on the diffusion plate 42 located near the rear focal point of the collimator lens 12 via the half mirror 11.

As shown in FIG. 22, the central portion of the diffuser plate 42 is shielded by a shield plate 43 having a diameter slightly larger than the entrance pupil of the imaging lens 45, which will be described later. Make up part.

The light flux emitted from the light source unit is collimator lens 12
It is reflected by the half mirror 11 installed at an angle of 45 ° with respect to the optical axis of, and is collimated by the collimator lens 12 to illuminate the subject 21 as a parallel light flux group. The collimator lens 12 has a size that covers the inspection region of the subject 21, and is installed such that its optical axis is perpendicular to the subject 21 and at a proper distance from the subject 21. . The light specularly reflected by the subject 21 passes through the collimator lens 12 again to become convergent light.

Of these, the light flux transmitted through the half mirror 11 forms a circular image of the light source on the shield plate 44 shown in FIG. 23, which is at a position conjugate with the diffusion plate 42. The shielding plate 44 is provided around the imaging lens 7 and serves to block the light reaching the image pickup surface of the CCD 14 without passing through the imaging lens 45. Therefore, if the image forming lens 45 is of a type screwed into the CCD 14 like a normal TV photographing lens, this shielding plate is unnecessary. Now, in the central part of the light source part, the shielding plate 4
3, the specularly reflected light from the subject 21 does not enter the imaging lens 45, only the scattered light in the vicinity of the specularly reflected light enters the imaging lens 45, and the image of the subject 21 is displayed on the CCD 14 imaging surface. To make.

As described above, in the tenth embodiment, it is possible to illuminate the subject 21 with one illuminating means by forming a parallel luminous flux group rotationally symmetric with respect to the optical axis of the observing means. Therefore, the subject 21 can be simultaneously observed by scattered light in all directions in the vicinity of regular reflection.

Note that this embodiment is advantageous in terms of the brightness of the inspection image, because the entrance pupil of the imaging lens can be used more widely than in the configuration described later in which the central portion of the imaging lens is shielded.
When the light source is changed from a halogen lamp to a high-intensity light source such as a metal halide lamp in the tenth embodiment described above, higher detection capability can be obtained. Further, the light source unit may be a ring-shaped light source directly placed instead of the diffusion plate 42. Furthermore, if there is a margin in the amount of light, inserting an interference filter into the light source
Even when the collimator lens 12 has chromatic aberration, the shielding plate 4
The shielding by 3 can be performed well.

<Eleventh Embodiment> FIG. 24 shows an optical system of the eleventh embodiment, which has substantially the same structure as that of FIG. 21 and which constitutes a light source section, including a fiber bundle 7, a diffusing plate 42, and a shielding plate 43.
The image forming lens 45 and the CCD 14 are installed at positions off the optical axis of the collimator lens 12. here,
Similar to the tenth embodiment, the diffusion plate 42 and the shielding plate 43, the imaging lens 45 and the shielding plate 44 are in the vicinity of the rear focal plane of the collimator lens 12, and have a conjugate positional relationship with each other. This embodiment is advantageous in terms of light quantity because it does not require a half mirror, and also gives some degree of freedom in illumination and viewing angle.

<Twelfth Embodiment> FIG. 25 shows the optical system of the twelfth embodiment, in which an independent collimator lens 12 'is provided for the illumination light, and the diffuser plate 42 and the shield plate 43 are provided near the front focus thereof. It is installed in. The imaging lens 45 and the shielding plate 44 are located near the rear focal point of the second collimator lens 12, and the first and second collimator lenses 12 ′, 1
2 and the diffusion plate 42 and the shielding plate 43 through the subject 21 are in a mutually conjugate positional relationship.

In this embodiment, scattered light near the regular reflection from the subject 21 can be observed under illumination light having an incident angle larger than that of the eleventh embodiment. Since the optimum value of the incident angle of the illumination light varies depending on the type of the subject 21 to be inspected (for example, the inclination angle of the pattern step side surface), it is necessary to select an optical system suitable for it.

<Thirteenth Embodiment> FIG. 26 shows a thirteenth embodiment of the present invention.
It is a side view which shows the optical system of an Example. This embodiment is shown in FIG.
The difference from the first optical system is that the emission end face of the fiber bundle 7 as a light source unit is near the rear focal point of the collimator lens 12, and the shield plate 43 is installed at a position conjugate with that immediately before the imaging lens 45. It is a point. The shield plate 43 has a diameter slightly larger than the emission end face of the fiber bundle 7. Therefore, the specularly reflected light from the subject 21 is blocked by this shielding plate 43, and only the scattered light in the vicinity of the specularly reflected light enters the imaging lens 45, and C
An image of the subject 21 is formed on the image pickup surface of the CD 14. Subject 2
21 is the same as that of FIG. 21 in that it can be simultaneously observed by scattered light in all directions in the vicinity of regular reflection, and thus the obtained image and effect are also the same. The same applies to the points that can be modified as shown in FIGS.

The optical systems of the fifth to thirteenth embodiments described above can be combined with the optical systems of the first to fourth embodiments by sharing the collimator lens, the imaging lens and the CCD. There are cases. In that case, by switching the illumination with one defect inspection apparatus, it becomes possible to detect all of the film thickness unevenness, dust, scratches, and defects on the side surface of the step of the pattern of the subject.

[0093]

According to the present invention, the entire field of view can be observed under the same condition, that is, the subject can be illuminated with the same incident angle, and the subject can be observed by the light reflected or scattered from the subject in the same direction. Further, according to the present invention, by selecting the center wavelength of the narrow band light source of the illumination, regardless of the type of the subject, a portion having a uniform film thickness and a portion having a film thickness unevenness are made to have arbitrary luminance differences. be able to. This narrow band light source also has the effect of improving the image by removing the wavelength dependence of the reflected or scattered light from the subject and the chromatic aberration of the optical system.

According to the present invention, uneven film thickness, dust,
Optimal observation conditions can be set for defects such as scratches and side surfaces of pattern steps. As described above, it is possible to provide a surface defect inspection apparatus in which an image of a defect inspection is simple and has high sensitivity, and therefore it is easy to configure an automatic defect inspection apparatus in combination with an image processing apparatus.

[Brief description of drawings]

FIG. 1 is a side view showing an optical system of a first embodiment of a surface defect inspection apparatus of the present invention.

FIG. 2 is a plan view for explaining the arrangement of line illumination according to the embodiment shown in FIG.

FIG. 3 is a plan view for explaining the arrangement of line illumination according to the embodiment of FIG.

FIG. 4 is a block diagram illustrating a configuration of a control unit and an image processing unit in FIG.

5 is an explanatory view of the line-illumination condenser lens of FIG. 1. FIG.

FIG. 6 is a view for explaining the inspection image of FIG.

FIG. 7 is an explanatory diagram of the inspection image of FIG.

FIG. 8 is a side view showing an optical system of a second embodiment of the surface defect inspection apparatus of the present invention.

FIG. 9 is a side view showing an optical system of a third embodiment of the surface defect inspection apparatus of the present invention.

FIG. 10 is a side view showing an optical system of a fourth embodiment of the surface defect inspection apparatus of the present invention.

FIG. 11 is a side view showing an optical system of a fifth embodiment of the surface defect inspection apparatus of the present invention.

FIG. 12 is a diagram for explaining the operation of FIG. 11.

FIG. 13 is a diagram for explaining a subject of the present invention.

FIG. 14 is a diagram for explaining a subject of the present invention.

FIG. 15 is a diagram for explaining a subject of the present invention.

FIG. 16 is a diagram for explaining a subject of the present invention.

FIG. 17 is a side view showing the optical system of the sixth embodiment of the surface defect inspection apparatus of the present invention.

FIG. 18 is a side view showing an optical system of a seventh embodiment of the surface defect inspection apparatus of the present invention.

FIG. 19 is a side view showing an optical system of an eighth embodiment of the surface defect inspection apparatus of the present invention.

FIG. 20 is a side view showing an optical system of a ninth embodiment of the surface defect inspection apparatus of the present invention.

FIG. 21 is a side view showing an optical system of a tenth embodiment of the surface defect inspection apparatus of the present invention.

FIG. 22 is a diagram for explaining the effect of FIG. 21.

FIG. 23 is a diagram for explaining the effect of FIG. 21.

FIG. 24 is a side view showing an optical system of an eleventh embodiment of the surface defect inspection apparatus of the present invention.

FIG. 25 is a side view showing the optical system of the twelfth embodiment of the surface defect inspection apparatus of the present invention.

FIG. 26 is a side view showing an optical system of a thirteenth embodiment of the surface defect inspection apparatus of the present invention.

FIG. 27 is a diagram for explaining a conventional technique.

FIG. 28 is a diagram for explaining a conventional technique.

FIG. 29 is a diagram for explaining a conventional technique.

FIG. 30 is a diagram for explaining a conventional technique.

[Explanation of symbols]

1 ... Lamp house, 2 ... Halogen lamp, 3 ... Heat absorption filter, 4 ... Condenser lens, 5 ... Rotation holder, 6
... Condensing lens, 7 ... Fiber bundle, 8 ... Secondary light source section, 9 ...
Diffuser, 10 ... Aperture, 11 ... Half mirror, 12, 1
2 '... collimator lens, 13 ... imaging lens, 14 ... C
CD, 15, 16 ... Plate, 17 ... Light source part, 18 ... Line illumination, 19 ... Condensing lens, 20 ... Background plate, 21 ... Subject.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoji Kozu 2-43-2, Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd.

Claims (8)

[Claims] 1. A light source, irradiation means for irradiating the surface of the subject with light from the light source as a substantially parallel light flux, and irradiating the surface of the subject with the light flux from the irradiation means. A surface defect inspection apparatus comprising: a condensing unit that condenses light that is specularly reflected or scattered from the surface; and an observing unit that observes the surface of the subject through the condensing unit. 2. The surface defect inspection apparatus according to claim 1, wherein the light source is a narrow band light source having a freely selectable center wavelength. 3. The surface defect inspection apparatus according to claim 1, wherein the irradiation unit and the light converging unit are shared by the same optical member. 4. The observation means observes the surface of the subject based on only the light specularly reflected from the surface of the subject by irradiating the surface of the subject with the light flux from the irradiation means. The surface defect inspection apparatus according to claim 1. 5. The observing means irradiates the surface of the subject with the light flux from the irradiating means, and based on only the light flux in substantially the same emission direction among the light scattered from the surface of the subject. The surface defect inspection apparatus according to claim 1, which is for observing the surface of a subject. 6. The light source has an annular light-emitting portion whose central portion is shielded, and the observation means has a center of the light source through the irradiation means, the subject and the light condensing means. The surface defect inspection apparatus according to claim 1, wherein the surface defect inspection apparatus has an entrance pupil having a position and a shape that are substantially conjugate with the shielding portion of the portion. 7. The observation means includes a shield having a position and a shape which are substantially conjugate with the light emitting portion of the light source through the irradiation means, the subject and the light condensing means. The surface defect inspection device described. 8. A plurality of devices are arranged outside the observation field of view of the subject,
A surface defect inspection apparatus comprising: an illuminating unit that illuminates the surface of the subject obliquely to obtain scattered light; and an observing unit that observes the scattered light from the subject.