JP3105702B2 - Optical defect inspection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an optical defect inspection apparatus,
In particular, the present invention relates to an optical defect inspection apparatus for optically detecting a defect of a sample in which a plurality of elements are regularly arranged.

[0002]

2. Description of the Related Art In a color filter used for a color liquid crystal device, a mask pattern used for manufacturing a semiconductor device, a semiconductor memory, a CCD array, and the like, minute elements are regularly arranged. In these color filters, mask patterns, and the like, even if only one of the many constituent elements has a defect, a defect occurs in an incorporated device or the like, and the value as a product is lost.
Therefore, there is a strong demand for the development of a defect detection apparatus capable of accurately performing a defect inspection on a sample in which a large number of elements are regularly arranged.

For example, as a defect of a color filter used in a color liquid crystal element device, a projection defect due to the formation of minute projections on the surface, a white missing defect in which a part of the color element is removed, and a black missing defect due to adhesion of foreign matter. And various defects such as abnormalities in black matrix pattern. As described above, since there are a plurality of types of defects in the color filter, and the natures of the respective defects are different from each other, a defect inspection is performed by a visual inspection by an operator in the current manufacturing process.

[0004]

The defect inspection by visual inspection has an advantage that a plurality of types of defects can be detected by one inspection work, but has a disadvantage in inspection accuracy, and the defect is missed as soon as possible. There were drawbacks. If the defect is overlooked, when incorporated in a liquid crystal display device, some pixels will not be displayed,
This is unacceptable because the performance of the liquid crystal display device is significantly reduced. In addition, the visual inspection requires a skilled technique, and also has a difficulty in workability, which may cause inconvenience of giving a strong fatigue to an operator's eyes. Accordingly, an object of the present invention is to provide a defect inspection apparatus capable of simultaneously detecting a plurality of types of defects in a single inspection operation on a sample in which a plurality of elements are regularly arranged.

[0005]

SUMMARY OF THE INVENTION An optical defect inspection apparatus according to the present invention is an optical defect inspection apparatus for optically detecting a defect of a sample in which a plurality of elements are regularly arranged. An xy stage on which a sample to be mounted is placed, and x
an illumination light source that projects illumination light toward the sample on the y stage, a linear image sensor that captures a transmission image of the sample over a predetermined imaging length in the main scanning direction, and generates an output signal for each line; A first defect detection circuit for detecting a defect present in the sample based on an output signal from the linear image sensor, a light source for emitting a light beam, and a light beam emitted from the light source being parallel to the optical axis. A beam deflector that emits a light beam whose distance from the optical axis changes with time, projects the beam as a normal incidence beam toward the sample, and scans the sample surface with the normal incidence beam over a predetermined scan length, A photodetector that receives reflected light via the beam deflector; and a regular pattern formed on the sample surface, disposed in an optical path between the beam deflector and the photodetector. A light-shielding mask having a light-shielding portion substantially corresponding to the pattern of the diffracted light generated by the laser beam; and a second defect detection circuit for detecting a defect on the surface of the sample based on an output signal from the photodetector. The imaging length of the image sensor and the scanning length of the beam deflecting device are set so as to be substantially equal, so that a defect inspection using transmitted light and a defect inspection using reflected light can be simultaneously performed on a sample on the xy stage. Things.

[0006]

For example, in a color filter incorporated in a liquid crystal display device, R, G, and B color elements are regularly arranged along the x and y directions. There is a projection defect due to the formation of minute projections, a white defect due to partial peeling of the color element, a black defect due to foreign matter adhering to the surface of the color filter element, and a defect due to abnormal pattern of the black matrix. . As a result of studying these defects, the present inventor has found that a protrusion defect can be detected by a reflected scattered light pattern generated when the surface of the color filter is scanned with a vertically incident light beam. That is, when there is no protrusion defect in the color filter, a cross-shaped reflected and scattered light pattern is formed. On the other hand, when there is a protrusion defect, this pattern is broken.
Therefore, a minute projection defect can be accurately detected by detecting a pattern change due to the reflected scattered light.
In addition, the white drop defect, the black defect, and the defect due to the abnormal pattern of the black matrix can be accurately detected by the intensity change due to the transmitted light.

Based on the above recognition, the present invention projects illumination light having a uniform intensity distribution toward a sample to be inspected for defects, and transmits transmitted light transmitted through each element to an imaging device such as a linear image sensor. , The output signal of each light receiving element is sequentially read out and compared with a reference value to detect a white defect or a black defect.
In detecting a protrusion defect, for example, a light beam emitted from a laser light source is deflected in the main scanning direction by a beam deflector and projected as a vertically incident beam. Light reflected from the sample is made incident on a photodetector via a beam deflector. By passing the reflected light from the sample through the beam deflecting device again, the reflected beam enters the photodetector as a stationary beam. Since the reflected scattered light incident on the photodetector forms a cross-shaped scattered light pattern, the presence of protrusion defects can be accurately determined by detecting the amount of light incident on the photodetector using a light-shielding mask corresponding to that pattern. Can be detected.

An optical system for transmitted light inspection and an optical system for reflected and scattered light detection are arranged in parallel along the x direction of an xy stage,
The movement of the xy stage in the y direction is used as sub-scanning. With such a configuration, the xy stage is moved in the sub-scanning direction in the y-direction while being shifted by one pitch in the x-direction (main scanning direction), so that the movement in the y-direction of the xy stage can be shared as the sub-scanning. Through the operation, the entire surface of the sample can be scanned with the illumination light for detecting the transmitted light and the light beam for detecting the reflected and scattered light, so that the inspection time can be further shortened and the workability is further improved.

Since the pattern of the scattered light reflected from the sample greatly changes due to minute projections and recesses existing on the surface of the sample, the projection defect can be detected with higher accuracy than the visual inspection by detecting the scattering pattern. Further, if there is a minute white defect or a black defect, the intensity of the transmitted light from the sample greatly changes. Therefore, by detecting the transmitted light, it is possible to detect the white defect and the black defect with high accuracy.

[0010]

FIG. 1 is a diagram showing the configuration of an example of a defect inspection apparatus according to the present invention. In this example, an example will be described in which a defect of a color filter in which R, G, and B color elements are regularly arranged and an address of the defect are detected. The color filter 1 to be inspected for defects is placed on the xy stage 2.
The xy stage 2 freely moves in the x direction (main scanning direction) and the y direction (sub scanning direction) orthogonal thereto. Illumination light having a uniform intensity distribution emitted from a halogen lamp 3 as a first light source is projected from the opposite side of the xy stage 2 from the color filter 1 via an optical fiber. Color filter 1
The transmitted light transmitted through each of the color elements is received by the objective lens 4 and forms an image on the imaging device 5. In this example, the imaging device 5
Comprises a linear image sensor in which a plurality of light receiving elements are primarily arranged in the main scanning direction. Each light receiving element of the linear image sensor is set to correspond to each color element of the color filter 1. An output signal of each light receiving element of the imaging device 5 (linear image sensor) is sequentially read out by a synchronization signal from a video synchronization signal generation circuit 6, and a differential circuit 7 is read out.
And the variable length delay line 8. The variable length delay line 8 delays the input signal by the repetition period of the color filter element, and supplies the delayed output to the inverting input terminal of the operation circuit 7. Then, the output signal from the operation circuit 7 is supplied to the comparison circuit 9 and compared with the reference signal. The operation circuit 7, the variable length delay line 8 and the comparison circuit 9 constitute a first defect detection circuit.

FIG. 2 shows the defect detection operation of the first defect detection circuit.
This will be described with reference to FIG. FIG. 2 shows an output signal when there is a white defect in the color element of the color filter. FIG. 2 (a) shows a signal from the linear image sensor 5 supplied to the non-inverting input terminal of the operation circuit 7. FIG. 4B shows a signal waveform which is delayed by one line by a variable length delay line and is supplied to the inverting input terminal of the operation circuit. FIG. 4C shows a signal waveform inputted to the comparison circuit 9. Show. If the color filter has a missing white defect, strong transmitted light is generated from the element having the missing white defect, and this state is shown as a peak in FIG. Since the output signal from the delay line is delayed by one pixel, the signal is shifted by one pitch as shown in FIG. At this time, in the output signal from the differential circuit 7, as shown in FIG. 2C, a negative peak and a positive peak occur in this order in a continuous signal.
These negative and positive peaks are compared with a reference value set by the comparison circuit 9, and if the set value exceeds the set reference value, it is determined that a peak has occurred. Therefore, when negative and positive peaks occur in a continuous line signal in this order, it can be determined that a white defect is present.

Next, detection of a black defect will be described. As shown in FIG. 3, when there is a black defect in the color element, a downward peak occurs in the signal of one line of the output signal of the linear image sensor 5. Therefore, by subtracting the output signal (FIG. 3 (c)) from the variable length delay line 8 from the output signal (FIG. 3 (b)) from the linear image sensor 5 in the operation circuit 7, the positive and negative peaks are reduced. Occurs in this order. Therefore, when positive and negative peaks are continuously generated in a certain line signal and the next line signal, it is determined that a black defect is present.

The peak signal detected by the comparing circuit 9 and the synchronizing signal generated by the video synchronizing signal generating circuit 6 are supplied to a first defect address judging circuit 10 to determine the addresses of the white defect and the black defect. The operation of address determination will be described later.

Next, the operation of detecting a protrusion defect will be described. The scanning light beam is emitted from the laser light source 11. The light beam enters the rotating prism body 13 via the perforated mirror 12 having an opening at the center. The rotating prism body 13 is made of an optically transparent material, and is a prism having two pairs of optical surfaces parallel to each other. The rotating prism body has a rotation axis R existing in a direction orthogonal to the optical axis, and is rotated around the rotation axis R by a step motor (not shown).
The angle of incidence of the incident beam on the optical surface changes with time due to the rotation of the rotating prism.
The light beam emitted from 13 is emitted as a light beam that is parallel to the optical axis and changes with time from the distance from the optical axis. Therefore, the car filter 1 mounted on the xy stage 2 is one-dimensionally scanned in the x direction (main scanning direction) by the vertically incident light beam. At the same time, the xy stage 2 sequentially and intermittently moves in the y-direction (sub-scanning direction) and the x-direction in response to a drive control signal supplied from the drive control circuit 14 to the drive circuit 15. Therefore, the entire surface of the color filter 1 is two-dimensionally scanned by the vertically incident light beam.

The reflected and scattered light from the color filter 3 again enters the rotating prism 13 and is reflected by the perforated mirror 12 through the same optical path as the incident optical path.
The light enters the photodetector 18 via 17. FIG. 3 is a diagram showing an example of a diffraction image due to reflected and scattered light from a color filter. FIG. 3 (a) shows a diffraction pattern when the color filter has no defect, and FIG. 7 shows a diffraction pattern when the filter has a protrusion defect. When there is no projection defect, a cross-shaped diffraction pattern is formed, and when there is a projection defect, a diffraction pattern having a shape obtained by adding a circular pattern around the cross-shaped pattern is formed. Therefore, if the light-shielding mask 16 has a light-shielding portion having the shape shown in FIG. 4A, the amount of light incident on the photodetector 18 increases if there is a protrusion defect, and the amount of light incident on the photodetector 18 increases. Defects can be detected.

The output signal from the photodetector 18 is converted to a linear amplifier.
The output signal is supplied to a comparator 19 and an integrating amplifier 20, respectively. In the comparator 21, the linear amplifier
The output from 19 and the output from integrating amplifier 20 are compared. If there is a difference between these output signals, it is determined that there is a projection defect, and the output is output to second defect address determination circuit 22. With this configuration, even if the color filter has minute undulations or the like, it is not affected by the minute undulation, and the detection accuracy of the protrusion defect can be further improved.

Next, the defect address determination will be described. FIG. 4 shows an example of the movement of the xy stage 2 in the x and y directions. The xy stage moves at a constant speed in the y direction (sub-scanning direction) from one end of the color filter 1 to the other end, then moves intermittently in the x direction, and again moves in the opposite direction along the y direction. The color filter 1 is moved so that the entire surface of the color filter 1 can be scanned. In this example, the imaging length (field length) of the linear image sensor 5 on the sample and the scanning length of the beam deflector 13 on the sample are set to be equal to each other. Further, the linear image sensor 5 for performing the transmission inspection and the laser light source 11 for performing the reflected scattered light inspection are arranged so as to be separated by a distance twice the scanning length or the imaging length in the x direction, and are equal to each other in the y direction. Place at the level position. Further, the amount of intermittent movement of the xy stage 2 in the x direction is set equal to the scanning length or the field length. With this setting, the reference point of the imaging position on the color filter of the linear image sensor 5 and the reference point of the scanning position of the beam deflecting device 13 are only shifted from each other by two pitches in the x direction. Both the transmitted light inspection and the reflected scattered light inspection can be performed simultaneously by one moving scan, and the inspection time can be shortened. Note that the imaging length of the linear image sensor on the sample and the scanning length of the beam deflecting device do not necessarily have to be equal, and even if the imaging length and the scanning length are different from each other, the output from the linear image sensor 5 and the photodetector 18 may be different. By temporarily storing the signal in the memory and then performing predetermined signal processing, the address of the defect can be accurately detected.

As shown in FIG. 1, a stage phase detector 23 is provided on the xy stage 2 to detect the origin position of the xy stage 2 and the address during movement, and to detect the detected x and y direction addresses in the first and second directions. Defective address determination circuit 10 and
Supply each to 22.

Next, address determination in the transmitted light inspection will be described. A synchronizing signal from a video synchronizing signal generating circuit 6 for controlling reading of the linear image sensor 5 is supplied to a first defective address judging circuit 10. In this first defect address determination circuit, the defect information supplied from the comparison circuit 9, the x and y direction addresses of the xy stage supplied from the stage position detection device 23, and the video synchronization signal generation circuit 6
The address of the detected defect is determined based on the synchronization signal supplied from. That is, the defect detected based on the address information in the x and y directions of the xy stage 2 at the time when the defect detection signal is input from the comparison circuit 9 and the address information in one imaging line supplied from the video synchronization signal generation circuit. The address is specified, and the address is output to the memory 24.

Next, address determination in the reflected scattered light inspection will be described. With the rotation of the rotating prism body 13, the scanning light beam is deflected so that the distance from the optical axis gradually changes, and the scanning spot formed on the color filter 1 is also displaced along the main scanning direction. FIG. 6 shows the displacement of the scanning spot. On the other hand, when the light beam enters an edge between the optical surfaces of the rotating prism body, the light beam reflects in a direction substantially orthogonal to the optical axis. Therefore, FIG.
As shown in (2), the photodetector 25 is arranged to receive the light beam reflected at the edge. Then, an output signal from the photodetector 25 is supplied to a beam scanning synchronizing signal generating circuit 26 to generate a horizontal synchronizing signal, and based on the generated horizontal synchronizing signal, an address of the protrusion defect in the main scanning direction is detected. The horizontal synchronization signal is supplied to the address detection circuit 27, and the address information in the main scanning direction is supplied to the second defective address determination circuit 22. still,
In the address detection circuit 27, as shown in FIG. 5, the scanning spot has a slight lack of linearity with respect to time. Therefore, for example, the linearity can be maintained by controlling the reading time from the memory. Second defective address determination circuit
At 22, a projection defect detected based on the address information in the x and y directions of the xy stage 2 at the time when the defect detection signal is input from the comparator 21 and the address information in one scan line supplied from the address detection circuit 26. And outputs it to the memory 24.

Since the type and address of the detected defect are stored in the memory 24, the operation of repairing the defect and the precise photographing of the defect can be performed based on the stored defect information and address information. In this case, an address read circuit 28 is connected to the memory 24, and the defect position can be reproduced by moving the xy stage via the drive circuit 15 based on the read address information.

The present invention is not limited to the above-described embodiment, and various modifications and changes are possible. For example, in the above-described embodiment, an output signal from the photodetector is supplied to the linear amplifier and the integration amplifier in the defect inspection using the backscattered light,
Defect detection was performed by comparing these output signals. However, the output signal from the photodetector was amplified and directly compared with a reference voltage, and when the output signal exceeded the reference voltage, it was determined that a defect was present. You can also.

[0023]

As described above, according to the present invention, since a transmission image of a sample to be inspected is taken and a scattering pattern originating from the sample surface is detected, physical properties of the sample differ. Even if a defect exists, each defect can be detected with high accuracy. As a result, the defect inspection accuracy can be further improved as compared with the visual inspection.
Further, the transmission image imaging optical system and the scattering pattern detection optical system
By disposing the y stage in the x direction, the movement of the xy stage in the y direction can be shared for both optical systems as sub-scanning. As a result, a plurality of types of defects can be simultaneously formed by one scanning operation. Detection can be performed, and the work time required for the inspection can be further reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an example of a defect inspection apparatus according to the present invention.

FIG. 2 is a signal waveform diagram showing a detection signal of a white spot defect.

FIG. 3 is a signal waveform diagram showing a detection signal of a black drop defect.

FIG. 4 is a diagram showing an example of a reflection scattering pattern by a sample.

FIG. 5 is a diagram showing the movement of the xy stage in the x and y directions.

FIG. 6 is a graph showing displacement of a beam spot on a sample.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 sample 2 xy stage 3 illumination light source 4 objective lens 5 imaging device 6 video synchronization signal generation circuit 7 differential circuit 8 variable length delay line 9 comparison circuit 10 first defect address determination circuit 11 light source 12 perforated mirror 13 beam deflection device 16 Shading mask 18 Photodetector 19 Linear amplifier 20 Integrating amplifier 21 Comparator 22 Second defect address determination circuit 23 Stage position detector 24 Memory

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01N 21/956 G01N 21/892-21/894 G01B 11/30 G06T 7/00

Claims (3)

(57) [Claims] An optical defect inspection apparatus for optically detecting a defect of a sample in which a plurality of elements are regularly arranged, comprising: an xy stage on which a sample to be inspected is placed; An illumination light source that projects illumination light toward the sample, a linear image sensor that captures a transmission image of the sample over a predetermined imaging length in the main scanning direction, and generates an output signal for each line, and the linear image A first defect detection circuit for detecting a defect present in the sample based on an output signal from the sensor, a light source for emitting a light beam, and a light beam emitted from the light source, which is parallel to the optical axis from the optical axis. A beam deflecting device that emits a light beam whose distance varies with time, projects the beam as a normal incidence beam toward the sample, and scans the sample surface with the normal incidence beam over a predetermined scanning length. A light detector for receiving the reflected light from the beam deflecting device through the beam deflecting device; and a light detector arranged in an optical path between the beam deflecting device and the light detector, generated by a regular pattern formed on the sample surface. A light-shielding mask having a light-shielding portion substantially corresponding to a pattern of diffracted light to be detected, and a second defect detection circuit for detecting a defect on a sample surface based on an output signal from the photodetector; The scanning length of the beam deflecting device is set to be substantially equal to the imaging length of the XY stage, and the defect inspection using the transmitted light and the defect inspection using the reflected light can be simultaneously performed on the sample on the xy stage. Defect inspection equipment. 2. The optical defect inspection apparatus according to claim 1, wherein the sample to be inspected is a color filter. 3. The first defect detection circuit includes a delay line for delaying an output signal for each line from the linear image sensor by one line, and a comparator.
3. The optical defect detection device according to claim 2, wherein the presence of the defect is detected by comparing the signal delayed with the line and the signal not delayed.