JP3668294B2 - Surface defect inspection equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface defect inspection apparatus for inspecting a surface defect such as a wafer or a liquid crystal glass substrate.
[0002]
[Prior art]
The liquid crystal glass substrate shown in FIG. 9 is obtained by providing a resist 3 patterned through a film formation layer 2 on a substrate 1 generally made of a glass plate. However, in a photolithographic process line, if the resist applied to the substrate surface has film thickness unevenness or dust adhesion, it may cause defects such as defective line width of the pattern after etching or pinholes in the pattern. It was.
[0003]
Further, as shown in FIG. 9A, the liquid crystal panel substrate after resist development has a flat portion A on the resist residual film, a flat portion B without resist, and a side surface C of a step between them. It can be divided into three parts. However, when the side surface C is normal, for example, an inclined portion as shown in FIG. 9B is formed. On the other hand, when the side surface C is defective, for example, as shown in FIG. An inclined part was formed. For this reason, it has been usual to inspect all liquid crystal glass substrates before etching for the presence or absence of the defects.
[0004]
Japanese Patent Application Laid-Open No. 7-27709 discloses a surface defect inspection apparatus suitable for the above-described defect detection.
Below, it demonstrates using FIGS. 9-12.
The apparatus shown in FIG. 10 shows a surface defect inspection apparatus provided with a first observation method and a second observation method described later. The first observation method is to observe a light beam regularly reflected by a wafer or a liquid crystal glass substrate (hereinafter referred to as a subject) 4. An optical system capable of this observation will be described in detail below.
[0005]
The lamp house 5 is provided with a halogen lamp 6 and a condenser lens 7 via a heat ray absorption filter 8 so as to convert light from the halogen lamp 6 into a parallel light beam. The rotation holder 9 contains a plurality of interference filters and one white hole (not shown) for white light illumination, and the desired interference filter is routed to the optical path by rotating it with a motor (not shown). Can be inserted in. The light beam from the interference filter is converted into a secondary light source whose intensity distribution is averaged through the condenser lens 10, the fiber bundle 11, the diffusion plate 12, and the diaphragm 13. The diffuser plate 12 is installed at the focal position of the collimator lens 14 via the half mirror 15, and the light beam reflected by the half mirror 15 becomes a parallel light beam by the collimator lens 14, and is applied to the subject 4 placed below the collimator lens 14. Enable normal incidence. The diameter of the collimator lens 14 is such that the entire surface of the subject or one of the divided surfaces can be seen in one examination.
[0006]
Next, in order to observe the light beam reflected by the subject 4, an image of the surface of the subject 4 is formed by the imaging lens 16 and the imaging lens 16 through the half mirror 15 at the focal position of the collimator lens 14. CCD 17 is provided.
The operation of the above configuration will be described below.
The white light emitted from the lamp house 6 is converted into narrowband light by the interference filter of the rotary holder 9, and then guided to the fiber bundle 11 to irradiate the diffusion plate 12. Then, the collimator lens 14 illuminates the subject 4 with a collimated light beam. The light beam reflected by the subject 4 passes through the half mirror 15 while being converged by the collimator lens 14, and an image of the subject 4 is formed on the imaging surface of the CCD 17 by the imaging lens 16. Therefore, the film thickness unevenness of the subject 4 is observed as interference fringes.
[0007]
In the second observation method, a light beam is irradiated in parallel and close to the surface of the subject 4 to detect dust, scratches or the like on the subject 4 with scattered light.
An optical system capable of this observation will be described below.
A white light beam from a lamp house 18 provided with a halogen lamp, a heat ray absorption filter, and a condenser lens (not shown) inside is guided to the line illumination unit 20 through the fiber bundle 19. The line illumination unit 20 makes the light beam emitted from the fiber bundle 19 into a thin sheet shape so that the surface of the subject 4 can be illuminated in parallel.
[0008]
The operation of the above configuration will be described below.
The scattered light from the subject 4 illuminated by the line illumination unit 20 is converged by the collimator lens 14, passes through the half mirror 15, and is imaged on the imaging surface of the CCD 17 by the imaging lens 16. Accordingly, dust and scratches on the subject 4 are detected by the scattered light.
[0009]
The apparatus shown in FIG. 11 shows a surface defect inspection apparatus provided with a third observation method for observing a difference in diffracted light.
An optical system capable of this observation will be described in detail below.
The light of a light source (not shown) incident on the fiber bundle 11 is the same as that used in the first and second observation methods described above, and the exit end face of the fiber bundle 11 is the rear side of the collimator lens 14. The collimator lens 14 is installed at a position not on the optical axis on the focal plane. This exit end face allows the angle θ ₀ of the illumination center ray with respect to the optical axis of the collimator lens 14 to be arbitrarily set. The collimator lens 14 is set so that its optical axis is perpendicular to the subject 4 and at an appropriate distance from the subject 4.
[0010]
The operation of the above configuration will be described below.
The light beam emitted from the fiber bundle 11 is converted into a parallel light beam by the collimator lens 14 and illuminates the subject 4 at an incident angle θ ₀ . The light beam specularly reflected by the subject 4 passes through the collimator lens 14 and converges to the convergence point 21 again. Scattered light indicated by a dotted line in the figure emitted from the subject 4 in the vertical direction is collected by the collimator lens 14 and imaged on the CCD 17 via the imaging lens 16 at the rear focal point. That is, the diffracted light from the subject 4 is observed by setting the exit end of the fiber bundle 11 that guides the illumination light to a position that is removed from the optical axis of the collimator lens 14 by the angle θ ₀ . Therefore, the disturbance of the resist pattern period on the object 4 or the difference in the shape of the cross section of the resist step (C in FIG. 9A) can be observed by the difference in the diffracted light.
[0011]
The apparatus shown in FIG. 12 shows a surface defect inspection apparatus provided with a fourth observation method for detection based on a difference in scattered light.
An optical system capable of this observation will be described in detail below.
Light from a light source (not shown) that is incident on the fiber bundle 11 is the same as that used in the first and second observation methods described above. A diffusing plate 22 located near the side focal point and a half mirror 15 for reflecting the light beam to the collimator lens 14 on the rear side are provided. At the center of the diffusing plate 22, a shielding plate 24 that does not transmit light having a diameter slightly larger than the entrance pupil of the imaging lens 23 at the rear focal position on the optical axis of the collimator lens 14 is provided in an annular shape. The light source unit is configured. The half mirror 15 is installed so that the light beam emitted from the light source unit is at an angle of 45 ° with respect to the optical axis of the collimator lens 14, and the light beam reflected by the half mirror 15 becomes a parallel light beam by the collimator lens 14. The subject 4 is illuminated. The specularly reflected light from the subject 4 that has passed through the collimator lens 14 and the half mirror 15 is formed as an annular image on the shielding plate 25 at a position conjugate with the diffusion plate 22. The shielding plate 25 blocks light incident on the outside of the imaging lens 23 so that only light that passes through the imaging lens 23 and reaches the imaging surface of the CCD 17 can pass therethrough.
[0012]
The operation of the above configuration will be described below.
Since the shielding plate 22 is provided at the center of the light source unit, the specularly reflected light from the subject 4 does not enter the imaging lens 23, and only the scattered light near the specularly reflected light enters the imaging lens 23 and the CCD 17 An image is formed on the imaging surface. That is, by using the diffusing plate 22 in which only the portion conjugate with the imaging lens 23 is shielded by the shielding plate 24, the scattered light near the specularly reflected light can be observed. Therefore, the difference in the shape of the cross section of the resist step on the subject 4 (C in FIG. 9A) can be detected by the difference in scattered light.
[0013]
As described above, all the captured images have almost uniform luminance, and only the defective portion becomes bright or dark in the image, so that it is extracted by image processing to obtain the type and position of the defect. It is like that. In addition, this apparatus is characterized in that a relatively large field of view can be observed under the same conditions in any of the observation methods. That is, the illumination light illuminates the entire field of view with the same incident angle, and observation is also performed on a light beam that is reflected, diffracted, or scattered at an equal angle from the entire field of view. Therefore, the image becomes simple as described above, and image processing becomes easy.
[0014]
[Problems to be solved by the invention]
However, the subject, for example, a liquid crystal glass substrate, tends to become larger as the technology improves from the conventional representative size of about 500 mm × 600 mm. When dealing with the increase in size of the subject by the conventional technique, the following problems occur.
[0015]
First, the size of the observation field is limited. The area of the observation field of view is determined by the size of the collimator lens, but since it is difficult to manufacture a collimator lens having a diameter of 400 mmφ or more, conventionally, one subject is usually observed in four parts. For this reason, the increase in the size of the subject described above has to be dealt with by increasing the number of divisions, so that the tact time of the examination becomes longer.
[0016]
Secondly, it is difficult to correct the aberration of the collimator lens. In a normal optical system, aberration correction is performed using multiple types of lenses as a combined lens. However, if a large lens is used, the glass material is limited and it is considered difficult to join. obtain. Further, when a single lens is used as the collimator lens, the image around the visual field is distorted in a pincushion shape, which makes it difficult to obtain the coordinates of the defect on the two-dimensional plane.
[0017]
Thirdly, the size of the device itself is increased. When the focal length of the collimator lens is reduced too much, the aberration increases rapidly. Therefore, a certain focal length has to be ensured as much as possible. However, widening the observation field of view with the subject placed horizontally leads to enlargement of the apparatus itself in the height direction, so that the installation location of the large apparatus may be limited. Easy to consider.
[0018]
An object of the present invention is to provide a surface defect inspection apparatus that can cope with an increase in the size of a subject without increasing the size of the apparatus itself.
[0101]
[Means for Solving the Problems]
The surface defect inspection apparatus of the present invention is a surface defect inspection apparatus for inspecting the surface of a substrate manufactured by a photolithographic process, and a stage on which the substrate is placed, and the substrate surface placed on the stage A line illumination unit for irradiating a line- shaped illumination light to the substrate , a one-dimensional imaging unit for imaging light from the line-shaped illumination light region irradiated on the substrate surface, and the line illumination unit for the substrate surface And an angle control means for changing an angle formed by the one-dimensional imaging unit to an angle observed by specularly reflected light and an angle observed by diffracted light, the line illumination unit, the one-dimensional imaging unit, and the stage are arranged in the line shape. the substrate table by capturing an image of one line and a transfer unit for relatively moving in a direction, by the one-dimensional imaging unit in synchronism with the transfer portion crossing the longitudinal direction of the illumination area The reconstructed two dimensional image, characterized in that the two-dimensional image of the substrate surface image processing equipped and image processing means for extracting a defect of the substrate surface.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment of the first invention)
The embodiment of the first invention described below with reference to FIGS. 1 to 4 uses a modification of the first observation method and the optical system described in FIG.
[0023]
The illumination unit 30 shown in FIG. 1 is connected to the illumination light source and the optical system shown in FIG. 10, and the illumination light source includes a halogen lamp, a heat ray absorption filter, and a condenser lens inside. A lamp house is used, and an interference filter, a light collecting lens, and a fiber bundle for narrowing the luminous flux from the lamp house are used for the illumination optical system.
[0024]
The illuminating unit 30 in the AA cross-sectional view of FIG. 1 shown in FIG. 2 illuminates the surface of the subject 31 at an incident angle θ ₀ with respect to the subject 31, and includes a line illumination unit 32 and a cylindrical lens 33. It is configured. Further, the line illumination unit 32 shown in FIG. 2 is configured by arranging the end faces of the above-described fiber bundle 34 in a straight line, and a cylindrical lens 33 is arranged at a position spaced in parallel to the end faces.
[0025]
An imaging unit 35 as a first imaging unit is disposed at an angle θ ₀ at a position facing the illumination unit 30 described above.
The imaging unit 35 includes a rod lens array 36 and a linear image sensor 37, and the rod lens array 36 forms an equal-magnification image of a linear region of the illuminated subject 31 on the linear image sensor 37. can do.
[0026]
FIG. 3 is a block diagram showing a configuration capable of performing control and image processing of the surface defect inspection apparatus. The linear image sensor 37 is connected to a drive circuit 39 synchronized with the stage controller 38 and an image I / F 40 for transferring an image captured by the linear image sensor 37. An image processing device 41 is connected to an image I / F 40 that reconstructs an image captured line by line. The image processing apparatus 41 is connected to the host computer 42 and, under the control of the host computer 42, processes the input image to extract defects such as film thickness unevenness and dust, and the type, number, position, and area thereof Or the like can be transferred to the host computer 42.
[0027]
The image processing device 41 is connected to a monitor TV 43 for displaying inspection images and processed images, and an image storage device 44 for storing inspection images and processed images as necessary. The sequencer 45 connected to the host computer 42 is connected to a stage controller 38, an optical system controller 46, and a substrate transport controller 47.
[0028]
The stage control unit 38 is for controlling a moving stage (not shown) that adsorbs and supports the subject 31 shown in FIG. 1 and its positioning mechanism, and the optical system control unit 46 is an interference shown in FIG. This is for controlling the light quantity of the rotary holder 9 of the filter and the halogen lamp 6.
Further, the substrate transport control unit 47 controls a transport unit (not shown) that takes out the specimens 31 one by one from the stocker, places them on the moving stage, and returns the specimens 31 after examination from the stage to the stocker. Is to do. Further, the host computer 42 has a monitor TV 48 on which a menu screen is displayed, a keyboard 49 for instructing a menu necessary for the inspection apparatus, and inspection conditions for each type of subject (optical system setting, inspection area, image processing). And a memory 50 that can store inspection data and the like.
[0029]
Next, the operation of the surface defect inspection apparatus having the above-described configuration will be described below.
When the operator instructs the start of the examination together with the type of the subject 31 from the keyboard 49, the condition of the subject 31 is read into the host computer 42 from the examination conditions stored in the memory 50 in advance. The optical system control unit 46 sets the interference filter and the light amount via the sequencer 45.
[0030]
Next, the first subject 31 is taken out from a stocker (not shown), transported, and placed on the moving stage. The moving stage moves the subject 31 in a direction orthogonal to the imaging unit 35 at a constant speed, and the linear image sensor 37 captures an image line by line by the imaging unit 35 synchronized therewith. Transfer to the image I / F 40. When the entire scanning of the subject 31 is completed, the examination image 51 of the subject 31 transferred from the image I / F 40 to the image processing apparatus 41 includes the edge 52 of the subject as shown in FIG. An image is formed in which only the uneven thickness portion 53 becomes bright in the dark portion having a uniform thickness. The image processing apparatus 41 extracts only the inspection area 54 from this image by masking, extracts only the uneven film thickness portion 53 through shade correction, binarization processing, and the like, and stores data such as the position and area thereof on the host computer 42. Forward to. The host computer 42 compares the film thickness unevenness and the number thereof with the acceptance criteria included in the inspection conditions to determine pass / fail of the subject 31.
[0031]
The subject 31 that has been inspected is classified as good or bad from the moving stage by the transport unit and transferred to the inspected stocker, and the inspection of one subject is completed.
In the above operation, instead of moving the subject 31, the illumination unit 30 and the imaging unit 35 can be moved to scan the entire surface of the subject 31, and the same processing can be performed.
Further, when the width of the subject 31 is larger than the lengths of the illumination unit 30 and the imaging unit 35, the entire surface of the subject is covered by a plurality of scans. A plurality of sets of illumination units and imaging units are arranged to cover the width of the subject 31.
(Embodiment of the second invention)
FIG. 5 is a side sectional view of a detection unit of the surface defect inspection apparatus according to the second embodiment of the invention, and includes optical systems corresponding to the first, third, and fourth observation methods. In addition, the illumination unit 30 arranged at one place illuminates the subject 31 at the incident angle θ ₀ , and the second imaging unit 35a, the first imaging unit 35b, the reflected light from the subject 31 arranged at different angles, The third imaging unit 35c is configured to be able to capture images simultaneously. The second, first, and third imaging units 35a, 35b, and 35c have rod lens arrays 36a, 36b, and 36c, linear image sensors 37a, and the like, as in the configuration described in the embodiment of the first invention. 37b and 37c, the same members are denoted by the same reference numerals and the description thereof is omitted.
[0032]
The optical system corresponding to the first observation method is composed of the illumination unit 30 and the first imaging unit 35b arranged with an angle θ ₀ so that the specularly reflected light from the subject 31 can be observed. . The optical system corresponding to the third observation method is configured such that the subject 31 can be observed with diffracted light by the illumination unit 30 and the second imaging unit 35a arranged perpendicular to the subject 31. The optical system corresponding to the fourth observation method has an angle θ ₁ (θ ₀ <θ ₁ ) slightly different from the angle θ ₀ so that the illumination unit 30 and the subject 31 can be observed with scattered light in the vicinity of the regular reflection light. And the third imaging unit 35c set to
[0033]
The operation according to the above configuration is performed based on the block diagram shown in FIG. 3 as in the first embodiment.
According to the embodiment of the second invention, three types of observation methods are performed to detect the uneven thickness of the specimen, the disturbance of the resist pattern period, and the difference in the shape of the side surface of the resist step. A screen can be obtained simultaneously.
[0034]
As a modification, a configuration in which a plurality of illumination units are installed and one image pickup unit is provided is possible, and the illumination unit is fixed and the angle of one image pickup unit is appropriately controlled and changed. It is also possible to implement the first to fourth observation methods using the illumination unit and the imaging unit.
(Embodiment of the third invention)
FIG. 6 is a side sectional view of the detection unit of the surface defect inspection apparatus according to the third embodiment of the present invention, and includes optical systems corresponding to the first, third, and fourth observation methods. The second illumination unit 30a, the first illumination unit 30b, the third illumination unit 30c, and the second imaging unit 35a, the first 35b, and the third 35c are installed separately in three locations, respectively. In addition, the second, first, and third imaging units 35a, 35b, and 35c arranged in the respective units can be simultaneously imaged. In addition, the same code | symbol is attached | subjected to the member similar to embodiment of 1st and 2nd invention, and description is abbreviate | omitted.
[0035]
The optical system corresponding to the first observation method includes a second illumination unit 30a and a second imaging unit 35a arranged with an angle θ ₀ so that the light regularly reflected by the subject 31 can be observed. Constitute. The optical system corresponding to the third observation method can observe the subject 31 with diffracted light by the first illumination unit 30b and the first imaging unit 35b arranged perpendicular to the subject 31. Constitute. The optical system corresponding to the fourth observation method has an angle θ ₁ (θ ₀ <θ slightly different from the angle θ ₀ so that the third illumination unit 30c and the subject 31 can be observed with scattered light in the vicinity of the regular reflection light. ₁ ) and the third imaging unit 35c set in ₁ ).
[0036]
The operation of the above configuration is the same as that of the second embodiment.
According to the embodiment of the third aspect of the invention, it is possible to set the optimal illumination light amount, angle, wavelength band, and the like for each illumination unit, and it is also possible to easily arrange each imaging unit. Further, there is an advantage that each observation method can be performed in parallel. If the incident angle of the illumination unit is set to be close to 90 ° and the imaging unit is installed in a direction perpendicular to the subject, observation with scattered light corresponding to the second observation method is also possible.
(Embodiment of 4th invention)
This will be described in detail below with reference to an external perspective view of the detecting portion of the surface defect inspection apparatus according to the fourth embodiment of the present invention shown in FIG. 7 and an AA sectional view of FIG. 7 shown in FIG. Note that members similar to those in the first to third embodiments are denoted by the same reference numerals, and description thereof is omitted.
[0037]
The embodiment of the fourth invention includes an optical system corresponding to the first observation method, and an illumination unit 55 having a light source is disposed at an incident angle θ ₀ with respect to the subject, and the subject An imaging unit 56 for observing the light regularly reflected by 31 is arranged at an angle θ ₀ at a position facing the illumination unit 55. The imaging unit 56 includes a reduction type line image sensor 57 and an imaging lens 58 disposed in front of the line image sensor 57. Each of the collimator lenses 59 and 60 has a shape cut out by two planes parallel to the optical axis of a spherical lens whose one surface is a plane, and is arranged in the illumination unit 55 and the imaging unit 56, respectively.
[0038]
The operation of the above configuration will be described below.
The diffused light beam emitted from the light source is converted into a parallel light beam by the collimator lens 59 to illuminate the subject 31 with a line. The light beam reflected by the subject 31 is incident on the imaging lens 58 by the collimator lens 60, and an image of the subject 31 is formed on the imaging surface of the line image sensor 57 by the imaging lens 58. Therefore, in the embodiment of the present invention, there is an advantage that the imaging magnification can be selected by changing the focal length of the imaging lens.
[0039]
Further, unlike the conventional technique, since the distortion caused by the collimator lens is one-dimensional, it is easy to correct the coordinates.
As another modification, it is also possible to execute the second to fourth observation methods other than the first observation method by appropriately changing the angle between the illumination unit and the imaging unit.
Further, the collimator lenses 59 and 60 can be improved in image formation characteristics (distortion and the like) as aspherical plastic lenses instead of spherical surfaces. In all the embodiments, further miniaturization can be achieved by using an LED array as the line illumination.
[0040]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a surface defect inspection apparatus that can cope with an increase in size of a subject.
[Brief description of the drawings]
FIG. 1 is an external perspective view of a surface defect inspection apparatus.
FIG. 2 is a cross-sectional view taken along the line AA in FIG.
FIG. 3 is a block diagram illustrating a configuration of control and image processing of the surface defect inspection apparatus.
4 is a diagram for explaining the inspection image of FIG. 1; FIG.
FIG. 5 is a cross-sectional view of a surface defect inspection apparatus.
FIG. 6 is a cross-sectional view of a surface defect inspection apparatus.
FIG. 7 is an external perspective view of a surface defect inspection apparatus.
FIG. 8 is a cross-sectional view taken along the line AA in FIG.
FIG. 9A is a cross-sectional view for explaining a configuration of a liquid crystal panel substrate.
FIG. 9B is a partially enlarged view when the side surface C of FIG. 9A is normal.
FIG. 9C is a partially enlarged view when a defect is generated on the side surface C of FIG.
FIG. 10 is an external view of a conventional surface defect inspection apparatus.
FIG. 11 is an external view of a conventional surface defect inspection apparatus.
FIG. 12 is an external view of a conventional surface defect inspection apparatus.
[Explanation of symbols]
30, 55 Illumination unit 30a Second illumination unit 30b First illumination unit 30c Third illumination unit 31 Subject 32 Line illumination unit 33 Cylindrical lens 34 Fiber bundle 35, 56 Imaging unit 35a Second imaging unit 35b First Imaging unit 35c third imaging unit 36 rod lens array 37 linear image sensor 38 stage control unit 39 drive circuit 40 image I / F
41 Image processing device 42 Host computer 43, 48 Monitor TV
44 Image storage device 45 Sequencer 46 Optical system control unit 47 Substrate transport control unit 49 Keyboard 50 Memory 57 Line image sensor 58 Imaging lens 59, 60 Collimator lens

Claims (3)

In a surface defect inspection apparatus for inspecting the surface of a substrate manufactured by a photolithographic process,
A stage on which the substrate is placed;
A line illumination unit that irradiates a line- shaped illumination light to the substrate surface placed on the stage;
A one-dimensional imaging unit that images light from the linear illumination light region irradiated on the substrate surface ;
An angle control means for changing an angle formed between the line illumination unit and the one-dimensional imaging unit with respect to the substrate surface to an angle observed with specularly reflected light and an angle observed with diffracted light;
A transfer unit that relatively moves the line illumination unit and the one-dimensional imaging unit and the stage in a direction intersecting a longitudinal direction of the line-shaped illumination region;
The synchronization with the transfer unit and an image of the one line by the one-dimensional imaging unit reconstructs the two-dimensional image of the substrate surface, the substrate surface a two-dimensional image of the substrate surface image processing Image processing means for extracting defects;
A surface defect inspection apparatus comprising: The image processing unit binarizes the two-dimensional image captured by the observation method different by the one-dimensional imaging according to the angle changed by the angle control unit , extracts the defect, and position information of each defect 2. The defect data of the area information is transferred to a computer, and the computer compares the defect data sent from the image processing unit with an acceptance criterion to determine whether the substrate is good or bad. Surface defect inspection equipment. One line illumination unit and one one-dimensional imaging unit are arranged, and one of the line illumination unit or the one-dimensional imaging unit observes the angle reflected by the regular reflection light and the diffracted light by the angle changing unit. The surface defect detection device according to claim 1, wherein the surface defect detection device is changed to an angle .

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