JP2007280833A - Defect inspection method of pdp substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a defect inspection method capable of precisely detecting projections on a substrate when manufacturing PDP. <P>SOLUTION: A defect inspection device 21 comprises a stage 22 on which a substrate is placed, and a detecting device equipped with a laser radiation device 23 which radiates laser beam parallel to the upper surface of the stage 22, and a light receiving device 24 for receiving laser beam. In step 1, a PDP substrate 20 where a dielectric layer is formed on the substrate is placed on the stage 22. The laser beam is radiated from the laser radiation device 23, and at least the PDP substrate 20 or detecting device is moved so that the PDP substrate 20 passes between the laser radiation device 23 and the light receiving device 24, for receiving the laser beam with the light receiving device 24. The size of a projection is acquired based on the change in signal level when receiving the beam. In step 2, soundness is judged based on the size of the projection. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a defect inspection method for a PDP substrate when manufacturing a PDP (plasma display panel).

  A general PDP is a device that displays an image by arranging minute discharge cells in which a phosphor layer is formed in a vertical and horizontal matrix and controlling the discharge of each discharge cell. The PDP is configured by joining a front substrate and a rear substrate made of a glass substrate with a sealing material, and in a discharge space formed between the front substrate and the rear substrate, xenon (Xe) and neon (Ne) are formed. ), A discharge gas composed of helium (He) or the like is enclosed at a pressure lower than the normal pressure.

  A transparent electrode is formed on the front substrate, and light emission of the phosphor layer is observed through this transparent electrode. Although the transparent electrode has a high resistance, a metal wiring (bus electrode) is partially formed on the transparent electrode to allow a high discharge current to flow. A dielectric layer made of transparent low-melting glass having a thickness of several tens of μm is formed so as to cover the transparent electrode and the bus electrode. Further, on the dielectric layer, the sputtering resistance is enhanced and the discharge characteristics are improved. Further, a thin film such as magnesium oxide (MgO) having a thickness of about 1 μm is formed as a protective layer. On the rear substrate, a partition wall having a height of about 100 μm is formed to separate individual discharge cells, and phosphor layers emitting light of R (red), G (green), and B (blue) are formed in the discharge cells. It is formed by coating. A dielectric layer having a thickness of about 10 μm is formed under the phosphor layer, and an address electrode is formed in the lower layer in a direction perpendicular to the transparent electrode and the bus electrode.

  By the way, in the formation process of the dielectric layer, foreign matter adhesion, partial loss of the dielectric layer, and defects in which bubbles remain inside the dielectric layer may occur. Here, foreign matter adhesion can be corrected by cleaning, and partial loss of the dielectric layer can be corrected by repair processing. However, protrusions are formed on the surface of the dielectric layer due to bubbles present inside the dielectric layer. If it is not easy to fix it. Possible causes of bubbles present in the dielectric layer include bubbles remaining after being printed or applied, bubbles generated by firing in a dielectric glass paste in advance, degassing from electrodes or black stripes, etc. It is done.

  If protrusions larger than the specified size (height and diameter) are present on the surface of the dielectric layer formed on the front substrate, the partition walls will be damaged when bonded to the rear substrate, or normal due to the protrusions In some cases, a phenomenon such as inability to perform a proper discharge is induced, and a protrusion that induces such a phenomenon is a defect. Therefore, after forming the dielectric layer, it is very important to measure and inspect the shape (height and diameter) of the protrusion with high accuracy and determine whether or not the protrusion is a defect.

In Patent Document 1, laser light having polarization characteristics is irradiated toward a substrate to be inspected, and reflected light from the substrate is received using a light receiving element to detect the presence or absence of a protrusion defect. It is disclosed that the reflected light is separately received and image processing is performed to measure the inclination angle of the protrusion defect and then the height of the protrusion defect is measured by triangulation from the measurement result.
JP 2004-219119 A

  However, the defect inspection method disclosed in Patent Document 1 is a method in which a projection is irradiated with laser light, and scattered light detected backward is detected by a light receiving element, and adjustment of the incident angle of irradiation light determines the detection capability. Is one of the biggest factors. This indicates that it is difficult to measure with the same standard for protrusions having various elevation angles. Therefore, it is not easy to accurately measure the shape of protrusions having various elevation angles existing on the same substrate.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a defect inspection method capable of detecting protrusions on a substrate with high accuracy when manufacturing a PDP. .

  In order to achieve the above object, the present invention comprises a stage on which a substrate is placed, a laser irradiation device that irradiates laser light in parallel with the upper surface of the stage, and a detection device that includes a light receiving device that receives the laser light. Using the defect inspection apparatus provided, a PDP substrate having a dielectric layer formed on the substrate is placed on the stage, and the PDP substrate is irradiated with the laser beam while irradiating the laser beam from the laser irradiation device. At least the PDP substrate or the detection device is moved so as to pass between the device and the light receiving device, and the laser light is received by the light receiving device. A defect inspection of a substrate for a PDP, comprising: a step 1 for obtaining a defect; and a step 2 for performing a pass / fail determination using the size of the protrusion. It is the law.

  According to the present invention, since the shape of the protrusion on the substrate can be measured with high accuracy by the degree of shielding of the laser light, it is possible to easily determine whether or not the protrusion is a defect.

(Embodiment 1)
Hereinafter, a method for inspecting a PDP substrate according to the present invention will be described with reference to the drawings. First, the structure of the PDP will be described with reference to FIG. FIG. 1A is a cross-sectional view of a PDP, and FIG. 1B shows a cross-sectional view taken along a plane orthogonal to the cross-section.

  As shown in FIG. 1, a stripe-shaped address electrode 2 is formed on a back substrate 1 made of a glass substrate, and a dielectric layer 3 is formed so as to cover it. Striped barrier ribs 4 are formed on the dielectric layer 3 so as to be positioned between the adjacent address electrodes 2. A phosphor layer 5 that emits red, green, or blue light between the adjacent barrier ribs 4. Is formed. The partition 4 may have a lattice shape. On the front substrate 6 made of a glass substrate, a display electrode 11 made of a transparent electrode 7 and a bus electrode 8 is provided so as to be orthogonal to the address electrode 2, and a dielectric layer 9 is formed so as to cover the display electrode 11. ing. Further, a protective layer 10 made of an oxide film containing magnesium (Mg) as a main component is formed on the dielectric layer 9. In the PDP, the back substrate 1 and the front substrate 6 are disposed so as to face each other and the periphery is sealed, and a rare gas such as neon (Ne) or xenon (Xe) is sealed in a discharge space formed between the substrates. It has a structure.

  The discharge cell 12 which is the minimum unit for performing display is formed at a three-dimensional intersection of two display electrodes 11 and one address electrode 2. An AC voltage is applied between the two display electrodes 11 in the discharge cell 12, and the phosphor of the phosphor layer 5 is excited and emitted by vacuum ultraviolet rays generated by the discharge, and a color image is displayed by light transmitted through the front substrate 6. Is to do.

  Then, the manufacturing method of PDP is demonstrated. First, as a method of forming electrodes such as the display electrode 11 and the address electrode 2, a film of an electrode material is formed on a glass substrate by a vacuum deposition method, a sputtering method, a plating method, a screen printing method, a coating method, a film laminating method, or the like. There are a method of patterning by photolithography and a method of patterning by screen printing or offset printing.

  Next, as a method for forming the dielectric layers 3 and 9, a screen printing method, a roll coating method, a die coating method, a film laminating method, or the like is used. In addition, as a method of forming the partition wall 4, a partition wall material film is formed on the substrate with a material for the partition wall 4 by a coating method, a screen printing method, or the like, and the partition material film is resistant to sandblasting using a photolithography method. There is a sandblasting method in which after a certain pattern is formed with a photoresist film, unnecessary portions of the partition wall material film are scraped off using the photoresist film as a mask to leave only the partition wall 4 portion. As another method for forming the partition walls 4, a method is used in which a photosensitive paste of a material for the partition walls 4 is formed on a glass substrate by a coating method, and then the partition walls 4 are directly formed by patterning using a photolithography method. There is a screen printing method in which a partition is formed by repeating printing a plurality of times with a paste or ink of a material for the partition 4 using a screen and drying. Moreover, as a method of forming the phosphor layer 5, there are a coating method using a dispenser, a method of selectively filling each color phosphor paste between the barrier ribs 4 by a screen printing method, etc. The phosphor layer 5 is formed later through a drying process and a baking process.

  Methods for forming the protective layer 10 on the dielectric layer 9 include screen printing, sputtering, electron beam evaporation, ion plating, and thermal CVD (chemical vapor deposition) using organometallic raw materials. and so on. At present, a deposition source composed of metal oxide pellets mainly composed of Mg is irradiated with a high-current electron beam generated using an electron gun to heat and evaporate the deposition source, so that Mg is mainly contained in an oxygen atmosphere. An electron beam evaporation method for forming an MgO thin film, which is a metal oxide as a component, is most widely used.

  Here, in particular, when there are protrusions on the surface of the dielectric layer 9 formed on the front substrate 6 and the protrusions are not less than a predetermined size (height and diameter), normal discharge cannot be performed. The display quality cannot be obtained, and the protrusion becomes a defect. For this reason, after forming the dielectric layer 9 on the front substrate 6, it is necessary to inspect whether or not there is a protrusion that may become a defect on the surface of the dielectric layer 9. A defect inspection method for a PDP substrate for performing such inspection will be described with reference to FIGS.

  As shown in FIG. 2, the defect inspection apparatus 21 for realizing the defect inspection method in the present embodiment has the following configuration. That is, a stage 22 for placing the substrate 20 to be inspected, a laser irradiation device 23 for irradiating a laser beam, a light receiving device 24 disposed opposite to the laser irradiation device 23, and a signal detected by the light receiving device 24 And an arithmetic processing unit 25 for performing arithmetic processing. The laser irradiation device 23 and the light receiving device 24 are arranged to face each other with the substrate 20 to be inspected placed on the stage 22 interposed therebetween, and are parallel to the upper surface of the stage 22 (the surface on which the substrate 20 is placed). It is installed on a driving device (not shown) that can be moved by numerical control in the direction (that is, in the horizontal direction) and in the vertical direction. The laser irradiation device 23 is configured to irradiate laser light parallel to the upper surface of the stage 22. Here, an orthogonal coordinate system is defined, an x-axis is set parallel to the laser beam, an axis in a horizontal plane perpendicular to the x-axis is a y-axis, and a vertical axis is a z-axis.

  The stage 22 includes positioning means and a vacuum suction device (not shown) for vacuum-sucking and fixing the substrate 20 to a predetermined position, and can fix the substrate 20 to a predetermined position in a horizontal state. it can. As the laser irradiation device 23, for example, a semiconductor laser that irradiates laser light having a diameter of 20 μmΦ and a wavelength of 670 nm can be used. As the light receiving device 24, for example, a photomultiplier tube having a diameter of 100 μmΦ that receives the laser light from the laser irradiation device 23 and outputs the incident light intensity as a current value by a photoelectric effect can be used. As the arithmetic processing unit 25, for example, a personal computer having a 32-bit, 3 GHz operation CPU, a 512-MB DRAM as a temporary data storage device, and an 80-GB hard disk as a storage device can be used.

  FIG. 3 is a diagram for explaining the defect inspection method in the present embodiment. FIG. 3A is a diagram showing a state in which laser light is scanned horizontally on the substrate surface, and FIG. ) Indicates a signal detected by the light receiving device 24 when the laser beam is scanned. FIG. 3A shows the axes of the aforementioned orthogonal coordinate system.

  As shown in FIG. 3A, the x-axis (FIG. 2) from the laser irradiation device 23 while maintaining a certain distance from the reference surface of the substrate 20 to be inspected (a flat portion having no protrusions on the surface of the substrate 20). The laser irradiation device 23 and the light receiving device 24 are moved in synchronization with each other in parallel with the y-axis. Thereby, a laser beam is scanned along the substrate surface.

  At this time, as shown in FIG. 3B, the signal level of the output signal from the light receiving device 24 decreases at the portion where the protrusion is on the substrate 20 to be inspected. This is because the laser beam is irradiated in parallel with the reference surface of the substrate 20 while maintaining a certain distance from the reference surface of the substrate 20, so that there are protrusions higher than the position of the laser beam on the surface of the substrate 20. In this case, the light beam of the laser beam blocked by the protrusion does not reach the light receiving device 24, and the signal level of the output signal from the light receiving device 24 becomes small.

  On the other hand, in the portion where there is no protrusion, all the light flux of the irradiated laser light reaches the light receiving device 24, and the signal level of the output signal from the light receiving device 24 at that time is that the laser light scans the portion where the protrusion is present. In this case, a constant signal level higher than the signal level of the output signal is obtained. Further, if the diameters of the protrusions are different, the duration of the state in which the laser light does not reach the light receiving device 24 changes. That is, the state where the signal level output from the light receiving device 24 is low increases as the diameter of the protrusion increases, and conversely decreases as the diameter of the protrusion decreases.

  Further, the larger the diameter and height of the laser irradiated surface of the protrusion, the smaller the light flux reaching the light receiving device 24. The shape of the protrusion can be estimated from the time change of the signal from the light receiving device 24 detected in this way. Thus, the laser irradiation device 23 and the light receiving device 24 constitute a detection device for detecting protrusions.

  An example when a defect inspection is performed using the method described above will be described below. The inspection target is the surface of the dielectric layer 9 formed on the front substrate 6, and a predetermined material is applied and fired on the front substrate 6 so as to cover the transparent electrode 7 and the bus electrode 8. A substrate (PDP substrate) 20 to be inspected is formed. Here, the size of the front substrate 6 is 950 mm long and 480 mm short (42 inches diagonal), the thickness of the dielectric layer 9 is 50 μm, the thickness of the substrate 20, that is, the thickness of the front substrate 6 and the dielectric The total thickness of the layer 9 was 3 mm.

  In the defect inspection apparatus 21, a laser irradiation device 23 made of a semiconductor laser is installed at the end of the stage 22, and a light receiving device 24 made of a photomultiplier tube is placed at the end of the stage 22 so as to face the laser irradiation device 23. It is installed in. The laser light emitted from the laser irradiation device 23 is received by the light receiving device 24 and adjusted in advance so that the center of the light receiving surface of the light receiving device 24 and the center of the laser light coincide. Further, the position of the lower end of the laser light emitted from the laser irradiation device 23 is set to a position above the reference surface of the substrate 20 by a predetermined distance (for example, 10 μm).

  The above-described substrate 20 was placed on the stage 22 of the defect inspection apparatus 21 configured in this manner so that the dielectric layer 9 would be on top, alignment was performed, and the substrate 20 was fixed by vacuum suction. Here, the long side of the substrate 20 was arranged so as to be parallel to the y-axis.

  Next, the first laser scanning was performed. That is, in a state in which laser light is irradiated from the laser irradiation device 23, the laser irradiation device 23 and the light receiving device 24 are moved in parallel with the long side of the substrate 20 at a speed of 0.1 m / second, and the laser irradiation device in about 10 seconds. 23 and the movement of the light receiving device 24 are completed (scan 1). Here, the position of the lower end of the laser light emitted from the laser irradiation device 23 was set to a position 10 μm above the reference surface of the substrate 20.

  Next, the laser irradiation device 23 is moved so that the position of the lower end of the laser beam is 20 μm above the reference surface of the substrate 20, and the light receiving device 24 disposed opposite to the laser light device 24 is also positioned between the center of the light receiving surface and the laser. The light was moved to a position where the centers of light coincided.

  Subsequently, a second laser scan was performed. That is, in a state where laser light is irradiated from the laser irradiation device 23, the laser irradiation device 23 and the light receiving device 24 are moved in parallel with the long side of the front substrate 6 at a speed of 0.1 m / second, and laser irradiation is performed in about 10 seconds. The movement of the device 23 and the light receiving device 24 is completed (scan 2).

  FIG. 4A shows the time change of the output signal from the light receiving device 24 obtained by the scan 1 step. The time change of the output signal from the light receiving device 24 obtained by the scan 2 step is shown in FIG. This is shown in FIG. As shown in FIG. 4A, the signal level decreased for 1 ms in the scan 1 step. As shown in FIG. 4B, the signal level changed for 500 ns in the scan 2 step. At the place where the reduction occurred (shown as D1 in FIGS. 4A and 4B), a protrusion having a height of 20 μm or more is present, and the diameter at the lower portion of the protrusion is determined to be about 100 μm. Further, as shown in FIG. 4 (a), the height is 10 μm or more and 20 μm at the place where the signal level has decreased for 500 ns only in the scan 1 step (shown as D2 in FIG. 4 (a)). The following protrusions are present, and the diameter at the lower part of the protrusions is determined to be about 50 μm. Further, in the scan 1 step, it is determined that there is no protrusion having a height of 10 μm or more in the region where the signal level has not decreased.

  By performing the scanning 1 and scanning 2 steps described above, the presence or absence of a protrusion on the surface of the dielectric layer 9 can be confirmed, and if a protrusion exists, the size (height and diameter) of the protrusion can be detected. it can. Then, a defect on the surface of the dielectric layer 9 is performed by performing a pass / fail judgment step based on a criterion (predetermined projection size) as to whether or not the detected projection is a size that can be a defect. Inspection is performed.

  Here, in the scanning 1 and scanning 2 steps, the position of the lower end of the laser beam is set so that the distance from the reference surface of the substrate 20 is 10 μm or more, and there is a protrusion having a height of 10 μm or less. Not detected. This setting is based on the fact that when the height of the protrusion is 10 μm or less, the protrusion does not become a defect, and therefore it is not necessary to detect such a protrusion. In this way, the position of the lower end of the laser beam may be set according to the minimum value of the height of the protrusion to be detected.

  Using the result shown in FIG. 4, it is possible to know at which position in the x direction (the direction parallel to the short side of the substrate 20), the y direction (parallel to the long side of the substrate 20). I do not know the position of (direction). If all the detected protrusions are smaller than the criterion, the substrate 20 is non-defective. However, if this criterion is “the minimum size when the projection formed at the position in contact with the partition wall 4 becomes a defect”, even if the projection exceeds the criterion, the projection If this position exists at a position that does not come into contact with the barrier ribs 4 (for example, the central portion of the discharge cell), the protrusion may not be a defect. Therefore, if a protrusion that exceeds the criterion is detected in the above inspection, the position of the protrusion in the y direction is detected, the position of the protrusion on the plane is specified, and it is determined whether or not the protrusion is defective. .

  In order to detect the position of the protrusion in the y direction, the substrate 20 is fixed on the stage 22 of the defect inspection apparatus 21 so that the long side of the substrate 20 is parallel to the x axis, and laser scanning similar to the above is performed. Perform the steps. That is, a step of performing laser scanning by irradiating the substrate 20 with laser light from the laser irradiation device 23 in a state where the irradiation direction of the laser light is different from the above-described steps. Then, the position (x-direction and y-direction position) and size of the obtained protrusion are compared with a determination criterion, and a step of determining whether or not the protrusion is defective is performed.

  As described above, according to the defect inspection method according to the present embodiment, the light receiving device receives the laser beam irradiated a plurality of times while changing the distance from the reference surface of the substrate 20 in parallel with the reference surface of the substrate 20 to be inspected. By detecting at 24 and calculating the light shielding level from the detected laser light intensity, the size of the protrusion on the substrate 20 can be measured with high accuracy. Further, although it depends on the size of the substrate 20, one laser beam scan may take about 10 seconds and the number of laser beam scans may be several times, so that defect inspection can be performed at high speed.

(Embodiment 2)
Next, the defect inspection method in Embodiment 2 of this invention is demonstrated, referring FIGS. FIG. 5 shows a defect inspection apparatus 26 for realizing the defect inspection method according to the second embodiment, and the same constituent elements as those shown in FIG.

  As shown in FIG. 5, the defect inspection apparatus 26 includes a stage 22 on which a substrate 20 to be inspected is placed, a laser irradiation apparatus 27 that irradiates laser light, and a light receiving apparatus that is disposed to face the laser irradiation apparatus 27. 28 and an arithmetic processing unit 25 that performs arithmetic processing on signals detected by the light receiving device 28. The laser irradiation device 27 and the light receiving device 28 are arranged to face each other with the substrate 20 to be inspected placed on the stage 22 interposed therebetween, and are parallel to the upper surface of the stage 22 (that is, in the horizontal direction) and in the vertical direction. It is installed on a drive device (not shown) that can be moved by numerical control. The laser irradiation device 27 is configured to irradiate laser light parallel to the upper surface of the stage 22. Here, an orthogonal coordinate system is defined, an x-axis is set parallel to the laser beam, an axis in a horizontal plane perpendicular to the x-axis is a y-axis, and a vertical axis is a z-axis.

  As the laser irradiation device 27, for example, a device in which three semiconductor lasers 29a, 29b, and 29c that irradiate laser light having a diameter of 20 μmΦ and a wavelength of 670 nm are arranged side by side can be used. As the light receiving device 28, for example, three photomultiplier tubes 30a, 30b, and 30c having a diameter of 30 μm that detect laser light from the laser irradiation device 27 and output the incident light intensity as a current value by a photoelectric effect are arranged side by side. Things can be used. The photomultiplier tube 30a detects the laser beam of the semiconductor laser 29a, the photomultiplier tube 30b detects the laser beam of the semiconductor laser 29b, and the photomultiplier tube 30c detects the laser beam of the semiconductor laser 29c. The number of semiconductor lasers used as the laser irradiation device 27 is not limited to three, and an appropriate number may be selected according to the resolution required for detection.

  FIG. 6 shows a cross-sectional view of an example of the laser light emitted from the laser irradiation device 27. The laser lights emitted from the three semiconductor lasers 29a, 29b, and 29c are denoted by reference numerals 31a, 31b, and 31c, respectively. Yes. The semiconductor lasers 29a, 29b, and 29c are arranged so that the distances between the lower ends of the laser beams 31a, 31b, and 31c and the reference surface of the substrate 20 are 10 μm, 20 μm, and 30 μm, respectively. Further, the horizontal distance between the center of the laser beam 31a and the center of the laser beam 31b is set to 50 μm so that the laser beams 31a, 31b, and 31c do not interfere with each other, and the center of the laser beam 31b and the center of the laser beam 31c are The horizontal distance is 50 μm. Here, the position of the lower end of the laser beam 31a which is the laser beam closest to the reference surface of the substrate 20 may be set according to the minimum height of the protrusion to be detected.

  An example when the defect inspection is performed using the defect inspection apparatus 26 described above will be described below. The inspection target is the surface of the dielectric layer 9 formed on the front substrate 6, and a predetermined material is applied and fired on the front substrate 6 so as to cover the transparent electrode 7 and the bus electrode 8. A substrate 20 to be inspected is formed. Here, the size of the front substrate 6 is 950 mm long and 480 mm short (42 inches diagonal), the thickness of the dielectric layer 9 is 50 μm, the thickness of the substrate 20, that is, the thickness of the front substrate 6 and the dielectric The total thickness of the layer 9 was 3 mm.

  In the defect inspection device 26, a laser irradiation device 27 including three semiconductor lasers 29a, 29b, and 29c is installed at the end of the stage 22, and a light receiving device 28 including three photomultiplier tubes 30a, 30b, and 30c. Is installed at the end of the stage 22 so as to face the laser irradiation device 27. The laser irradiation device 27 was configured such that the positions of the three laser beams were the distance described with reference to FIG. 6 and the distance from the reference surface of the substrate 20. The three laser beams 31a, 31b, and 31c irradiated from the laser irradiation device 27 are received by the photomultiplier tubes 30a, 30b, and 30c arranged in correspondence with each other, and the photomultiplier tube 30a is received. , 30b, 30c are arranged so that the centers of the light receiving surfaces coincide with the centers of the laser beams 31a, 31b, 31c.

  The above-described substrate 20 was placed on the stage 22 of the defect inspection apparatus 26 configured as described above, alignment was performed, and the substrate 20 was fixed by vacuum suction. Here, the long side of the substrate 20 was arranged so as to be parallel to the y-axis.

  Next, laser scanning was performed. That is, in a state where the three laser beams 31a, 31b, and 31c are irradiated from the laser irradiation device 27, the laser irradiation device 27 and the light receiving device 28 are moved parallel to the long side of the substrate 20 at a speed of 0.1 m / second. The movement of the laser irradiation device 27 and the light receiving device 28 was completed in about 10 seconds.

  FIG. 7 shows the time change of the output signal from the light receiving device 28 obtained by the above laser scanning step. FIG. 7A shows an output signal from the photomultiplier tube 30a that receives the laser light 31a, and FIG. 7B shows an output signal from the photomultiplier tube 30b that receives the laser light 31b. ) Is an output signal from the photomultiplier tube 30c that receives the laser beam 31c. As shown in FIGS. 7 (a) to (c), the signal output from the photomultiplier tubes 30a, 30b, and 30c has a decrease in signal level for 1 ms, 750 ns, and 500 ns, respectively (FIG. 7). In (a) to (c), indicated as D1), it is determined that there is a protrusion having a height of 30 μm or more and the diameter of the lower portion of the protrusion is 100 μm. At the point where the signal output from only the photomultiplier tubes 30a and 30b has a decrease in signal level for 500 ns and 300 ns (shown as D2 in FIGS. 7A and 7B), the height is high. There are protrusions of 20 μm or more and 30 μm or less, and the diameter at the lower part of the protrusion is determined to be 50 μm. At a point where the signal level of the signal output only from the photomultiplier tube 30a has decreased for 2 ms (shown as D3 in FIG. 7A), there is a protrusion having a height of 10 μm or more and 20 μm or less. The diameter at the lower part of the protrusion is determined to be 200 μm. Further, in FIG. 7A, it is determined that there is no protrusion having a height of 10 μm or more in a region where the signal level does not decrease.

  By performing the laser scanning step described above, the presence or absence of a protrusion on the surface of the dielectric layer 9 can be confirmed, and if a protrusion exists, the size (height and diameter) of the protrusion can be detected. Then, whether or not the detected protrusion is a size that can be a defect is determined based on a determination criterion (a predetermined protrusion size), thereby performing a defect inspection on the surface of the dielectric layer 9. Is called.

  Here, if a projection exceeding the determination criterion is detected in the above inspection in the second embodiment, the position of the projection in the y direction is detected and the position on the plane of the projection is detected as in the first embodiment. And determine whether or not the protrusion is defective. In order to detect the position of the protrusion in the y direction, the substrate 20 is fixed on the stage 22 of the defect inspection apparatus 26 so that the long side of the substrate 20 is parallel to the x axis, and laser scanning similar to the above is performed. Perform the steps. Then, a step of comparing whether or not the protrusion becomes a defect is performed by comparing the position (the position in the x direction and the y direction) and the size of the obtained protrusion with a criterion.

  As described above, according to the defect inspection method according to the second embodiment of the present invention, a plurality of laser beams having different distances from the reference surface of the substrate 20 are irradiated in parallel with the reference surface of the substrate 20 to be inspected. Then, the size of the protrusion on the substrate 20 can be measured with high accuracy by detecting the light receiving device 28 and calculating the light shielding level from the detected laser light intensity. Further, although it depends on the size of the substrate 20, it takes about 10 seconds for one scan of the laser beam, so that defect inspection can be performed at high speed.

  In each of the above-described embodiments, the description has been made assuming that the aperture of the laser beam is 20 μmΦ and the wavelength of 670 nm. However, the present invention is not particularly limited to this value, and a laser beam having an appropriate performance may be selected according to the detection target. . In addition, although a photomultiplier tube has been exemplified as a laser beam receiving device, a device such as a CCD may be used.

  Further, in each of the above-described embodiments, the entire surface of the substrate 20 is scanned by moving the detection device including the laser irradiation device 23 (27) and the light receiving device 24 (28) horizontally. The entire surface of the substrate 20 may be scanned with laser light by fixing the irradiation device 23 (27) and the light receiving device 24 (28) and moving the substrate 20 horizontally. That is, at least the substrate 20 or the detection device is placed so that the substrate 20 passes between the laser irradiation device 23 (27) and the light receiving device 24 (28) while irradiating the laser beam from the laser irradiation device 23 (27). The surface state of the substrate 20 can be grasped by moving and detecting the laser beam with the light receiving device 24 (28). That is, the substrate 20 is placed on the stage 22 and the substrate 20 passes between the laser irradiation device 23 (27) and the light receiving device 24 (28) while irradiating the laser beam from the laser irradiation device 23 (27). As described above, at least the substrate 20 or the detection device is moved, the laser beam is received by the light receiving device 24 (28), and the size of the protrusion can be obtained from the change in the signal level due to the light reception.

  As can be seen from the above description, according to the defect inspection method according to the present invention, since the protrusions on the substrate can be detected accurately and at high speed, the yield of the PDP can be increased, and is particularly useful as a defect inspection method during mass production of PDPs. It is.

(A), (b) is sectional drawing which shows an example of PDP The figure which shows the defect inspection apparatus in Embodiment 1 of this invention (A), (b) is a figure for demonstrating the defect inspection method using the same defect inspection apparatus. (A), (b) is a figure which shows the test result using the same defect inspection apparatus The figure which shows the defect inspection apparatus in Embodiment 2 of this invention. The figure which shows the arrangement of the laser beam in the same defect inspection equipment (A)-(c) is a figure which shows the test result using the same defect inspection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Back substrate 2 Address electrode 3, 9 Dielectric layer 4 Partition 6 Front substrate 7 Transparent electrode 8 Bus electrode 11 Display electrode 20 Substrate (PDP substrate)
21, 26 Defect inspection device 22 Stage 23, 27 Laser irradiation device 24, 28 Light receiving device 25 Arithmetic processing device

Claims (4)

A defect inspection apparatus comprising a stage for placing a substrate, a laser irradiation device for irradiating a laser beam in parallel with the upper surface of the stage, and a detection device having a light-receiving device for receiving the laser light is used. A PDP substrate on which a body layer is formed is placed on the stage so that the PDP substrate passes between the laser irradiation device and the light receiving device while irradiating laser light from the laser irradiation device. Next, at least the PDP substrate or the detection device is moved, the laser beam is received by the light receiving device, and the size of the projection is obtained by determining the size of the projection from the change in the signal level due to the received light. A defect inspection method for a substrate for a PDP, comprising: step 2 for performing pass / fail judgment using the PDP substrate. While the direction of the laser beam is different from that in step 1 with respect to the PDP substrate, the PDP substrate is disposed between the laser irradiation device and the light receiving device while irradiating the laser beam from the laser irradiation device. Moving at least the PDP substrate or the detection device so as to pass, and receiving the laser light by the light receiving device, and determining a projection size from a change in signal level due to the light reception, The step 2 obtains the position of the protrusion from the data obtained in the step 1 and the step 3, and performs pass / fail determination using the position and the size of the protrusion. Defect inspection method for PDP substrate. 3. The defect inspection method for a PDP substrate according to claim 1, wherein the laser beam is irradiated a plurality of times while changing a position in a vertical direction of the laser beam. 4. 3. The defect inspection method for a PDP substrate according to claim 1, wherein a laser irradiation apparatus that irradiates a plurality of laser beams having different vertical positions is used.

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