JP2004177356A - Defect inspection method and apparatus thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a defect inspection method, capable of clearly distinguishing a protrusion to be a defect from a foreign matter which is not to be a defect in the case of inspecting a protrusion defect in an object work through the use of laser light. <P>SOLUTION: The surface of the work to be inspected 1 is irradiated with the laser light 19 via an S polarizing filter 18. A reflected light 23 from the work to be inspected is detected via an S polarizing filter 24. According to the level of the reflected light detected by an image processing device 30, a protrusion defect, in which the surface is protruded is distinguished from a foreign matter defect which adheres to the surface and alters the state of polarization of the incident laser light, and only the protrusion defect is detected. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a defect inspection method for detecting a defect on a target work in a manufacturing process of a semiconductor, a liquid crystal panel, a hard disk, a PDP, and the like.
[0002]
[Prior art]
As shown in FIG. 5A, the plasma display panel (PDP) is configured by bonding a front plate 1 and a back plate 7 together.
[0003]
The back plate 7 has data electrodes 10 formed at predetermined intervals on the surface of an insulating substrate 8 such as glass. After covering the data electrodes 10 with a dielectric layer 9, ribs 11 are formed on the dielectric layer 9. It is formed at a predetermined interval along the direction in which the data electrodes 10 are arranged. Between the ribs 11, any one of R, G, and B phosphor layers 12 is arranged in a predetermined order in the direction in which the ribs 11 are arranged. Is formed.
[0004]
The surface plate 1 has a structure in which a plurality of display electrodes 5 are provided on the surface of a transparent and insulating substrate 2 such as glass. The display electrode 5 is a pair of a scanning electrode 6a and a sustain electrode 6b. The display electrode 5 is formed by covering the display electrode 5 with the dielectric layer 3. The surface of the dielectric layer 3 is covered with a protective film 4.
[0005]
The front plate 1 and the back plate 7 are bonded together as shown in FIG. A voltage is applied to a rare gas such as xenon or neon sealed in a discharge space 13 between the front plate 1 and the back plate 7 to generate a plasma discharge, and the generated ultraviolet light excites the phosphor layer 12 to generate a plasma discharge. , And emits light corresponding to the color of the phosphor layer 12, and visible light 15 of each color of R, G, and B is generated through the surface glass plate 2. Specifically, the data electrode 8 and the scanning electrode 5a are separated by the partition wall 11. In addition, the discharge space 13 at the intersection with the sustain electrode 5b operates as the discharge cell 14, and a color image can be displayed.
[0006]
In the manufacturing process, defects on the surface of the front plate 1 before being bonded to the back plate 7 are inspected. This is because, if a projection defect having a height equal to or more than a predetermined height exists on the surface of the front plate 1, the rib 11 may be damaged when bonded to the back plate 7, or the bonding may not be performed normally, and the discharge cells 14 at that portion may be damaged. A serious defect of not turning on occurs.
[0007]
Therefore, it is very important to evaluate the absolute value of the height of the projection defect and determine whether the projection defect has a height equal to or higher than a predetermined height.
In the prior art, the surface of the surface plate 1 after the formation of the dielectric film 3 is irradiated with laser light, and the projection height is evaluated from the power level of the light reflected from the defective portion (Patent Document 1).
[0008]
[Patent Document 1]
JP-A-5-172547
[Problems to be solved by the invention]
However, according to the conventional inspection method using such a laser beam, it is impossible to distinguish a projection that becomes a defect and a foreign substance that is not a defect, and a foreign substance that can be removed by cleaning before forming the protective film 4 is also regarded as a defect. It will be detected.
[0010]
More specifically, when the projection height is to be evaluated from the power level of the reflected light / scattered light of the laser light applied to the surface of the surface plate 1, similar reflected light / Since the scattered light is generated, the protrusion and the foreign matter cannot be distinguished, and a foreign matter which does not become a defect is also detected.
[0011]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a defect inspection method capable of clearly discriminating between a projection serving as a defect and a foreign substance not serving as a defect when inspecting a projection defect of a target work using a laser beam.
[0012]
[Means for Solving the Problems]
The defect inspection method according to the present invention includes irradiating the surface of the inspection target work with laser light through an S-polarization filter, detecting reflected light from the inspection target work through an S-polarization filter, and detecting the level of the detected reflected light. According to the method, a protrusion defect whose surface protrudes and a foreign matter defect that changes the polarization state of the incident laser light adhering to the surface and are changed are determined, and only the protrusion defect is detected.
[0013]
According to this configuration, it is not necessary to detect a foreign matter defect that can be expected to be removed by a subsequent cleaning process as a defect of the inspection target work, and it is possible to detect only the protrusion defect.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the inspection method of the present invention will be described based on specific embodiments.
A defect inspection apparatus for realizing the defect inspection method of the present invention is configured as shown in FIG. Here, in the manufacturing process of the PDP, a defect inspection of the surface of the front plate 1 before bonding to the back plate 7 will be described as an example.
[0015]
A laser beam 19 is emitted from a laser oscillator 17 via an S-polarization filter 18 to the front plate 1 set on an XY stage 16 for driving and positioning the work to be inspected.
[0016]
The laser oscillator 17 is a laser scanning illumination device using a polygon scanner, AOD, EOD, and resonance, or a laser beam illumination.
Here, the laser light 19 having the S-polarization characteristic is irradiated by the S-polarization filter 18 onto the front plate 1 at an incident angle: α.
[0017]
The occasional irradiation position of the laser beam 19 on the front plate 1 which is the work to be inspected is determined by the XY stage 16, and the occasionally reflected light 21, 23 of the irradiation position is transmitted to the position detection sensor 22 and the light receiving element 26. Is detected.
[0018]
The position detection sensor 22 is a sensor used when determining whether the shape of the defect is a convex protrusion defect 20 or a concave defect.
The light receiving element 26 is a photomultiplier and a CCD line sensor, a CCD area sensor, a TDI camera, and a cooled CCD camera.
[0019]
The reflected light 23 from the projection defect 20 at the irradiation position is detected by the light receiving element 26 via the S-polarization filter 24 and the imaging lens 25 at the light receiving angle: θ. The S-polarization filter 24 cuts off scattered light of a non-defect foreign substance on the front plate 1 as a work to be inspected, and receives the reflected light of the protrusion defect 20 by the light receiving element 26.
[0020]
Further, a half mirror 27 is incorporated in the optical path of the parallel light portion of the imaging lens 25, and the optical path is reflected by the half mirror 27 and reflected light 28A passing through the half mirror 27 and traveling toward the light receiving element 26. And is split into reflected light 28B incident on the position detection sensor 29.
[0021]
A judging process for judging, according to the level of the detected reflected light, a projection defect in which the surface protrudes and a foreign substance defect attached to the surface and changing the polarization state of the incident laser light, and detecting only the projection defect. The image processing device 30 as a means measures the inclination angle of the projection defect 20 from the output of the position detection sensor 29, and determines the irregularity of the defect from the inclination angle and the output of the light receiving element 26.
[0022]
More specifically, as shown in FIG. 2A, when the S-polarized laser light 19 is applied to the projection defect 20, the reflected light becomes a laser reflected light 23 having the same S-polarized characteristic as the incident light. Passes through the S-polarization filter 24 and forms an image on the light receiving element 26 via the imaging lens 25 at the light receiving angle: θ.
[0023]
As shown in FIG. 2B, when the S-polarized laser light 19 is irradiated on the foreign matter defect 35 that can be removed by a subsequent cleaning process, the laser reflection having the same S-polarization characteristic as the incident light is performed. Not only the light 23 but also a laser reflected light 36 having a P polarization characteristic different from that of the incident light is generated. In the case of the foreign matter defect 35 attached to the surface and changing the polarization state of the incident laser light, the reflected light is the laser reflected light 23 having the S polarization characteristic and the laser reflected light having the P polarization characteristic. 36, the level of the laser reflected light 23 having the S polarization characteristic is smaller than that in the case of FIG. Further, since the laser reflected light 36 having the P polarization characteristic is attenuated by the S polarization filter 24, the level of the laser reflected light 23 recognized by the image processing device 30 via the light receiving element 26 is significantly reduced, and The device 30 is configured not to detect the foreign matter defect 35 as a defect from the level difference.
[0024]
When the light enters the position detection sensor 29 via the half mirror 27, the position information of the position detection sensor 29 and the laser reflection angle correspond one to one as shown in FIG. By linking the angle information, the laser reflection angle: β can be measured.
[0025]
As shown in FIG. 3, the detection area 31 of the projection defect 20 becomes a projection distance 32 having a distance S in the image processing device 30. Therefore, the projection height T of the projection defect 20 is expressed by the following equation by triangulation.
[0026]
T = Σti (i = 1,... N)
γi = (βi−αi) / 2
ti = sinγi · Y
Here, γi is the projection inclination angle, which is calculated from the occasional laser incident angle: αi and the laser reflection angle: βi. The protrusion height ti of the minute portion is calculated from the resolution in the scanning direction of the image processing: Y and the protrusion inclination angle: γi. The projection height: T is calculated by integrating the projection height: ti of the minute portion. Thereby, the defect height can be absolutely evaluated simultaneously with the defect detection.
[0027]
Next, a description will be given of how the image processing apparatus 30 determines the unevenness of a defect.
The output signal of the position detection sensor 22 is input to the image processing device 30 in addition to the output signal of the light receiving element 26 and the output signal of the position detection sensor 29. The irregularities of the defect are determined as follows from the order in which the outputs of the detection sensors 22 and 29 change.
[0028]
FIG. 4A shows a case where the defect is a convex defect protrusion 20. In this case, the output 34 of the position detection sensor 22 decreases after the output 33 of the position detection sensor 29 for measuring the protrusion inclination angle increases.
[0029]
On the other hand, FIG. 4B shows a case where the shape of the defect is depressed from the surface. In this case, after the output 34 of the position detection sensor 22 for unevenness determination decreases, the output 33 of the position detection sensor 29 for measuring the projection inclination angle increases.
[0030]
The image processing apparatus 30 is configured to determine the unevenness of the defect based on the difference between the timings of the outputs 33 and 34 shown in FIGS.
As described above, since the image processing apparatus 30 is configured to detect the protrusion defect 20 but not the foreign substance defect 35, it is possible to eliminate the conventional over-detection and improve the PDP productivity. Can contribute.
[0031]
In the above embodiment, the case of defect inspection of the front panel 1 of the PDP has been described as an example, but the same applies to the case of defect inspection in the manufacturing process of semiconductors, liquid crystal panels, hard disks, and the like.
[0032]
【The invention's effect】
As described above, according to the defect inspection method of the present invention, the surface of the work to be inspected is irradiated with laser light through the S-polarization filter, and the reflected light from the work to be inspected is detected through the S-polarization filter. According to the level of the reflected light, it is possible to determine only the protrusion defect by discriminating the protrusion defect from which the surface protrudes and the foreign matter defect which is attached to the surface and changes the polarization state of the incident laser light. In addition, it is possible to sort out foreign matter which is not expected to be a product defect and to detect only a defective projection defect.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an inspection apparatus that realizes a defect inspection method of the present invention. FIG. 2 is an explanatory diagram of a principle of discriminating protrusions and foreign matter. FIG. 3 is an explanatory diagram of a principle of measuring defect height. FIG. FIG. 5 is an enlarged cutaway view and a cross-sectional view showing the structure of a PDP.
1 Front panel (work to be inspected)
16 XY stage 17 Laser oscillator 18 S-polarization filter 20 Projection defect 22 Position detection sensor 24 S-polarization filter 25 Imaging lens 26 Light receiving element 27 Half mirror 30 Image processing device (determination processing means)

Claims (2)

Irradiate the surface of the work to be inspected with laser light via the S-polarization filter,
The reflected light from the inspection target work is detected through an S-polarization filter,
A defect for detecting only a protrusion defect by discriminating a protrusion defect from which the surface protrudes and a foreign matter defect that changes the polarization state of incident laser light that adheres to the surface in accordance with the level of the detected reflected light. Inspection methods. A laser oscillator that irradiates the surface of the work to be inspected with laser light via an S-polarized filter;
The reflected light from the work to be inspected is detected through the S-polarization filter, and according to the level of the detected reflected light, the polarization state of the laser light incident on the surface and the projection defect protruding from the surface and adhering to the surface. A defect inspection apparatus comprising: a determination processing unit that determines a foreign matter defect to be changed and detects only a protrusion defect.

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