JP2010276463A - Method and apparatus for inspecting tft array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve positional accuracy of a pixel coordinate by compensating a position error existing inside a panel, in an inspection of a TFT array. <P>SOLUTION: Pixels of the panel are brought to be in potential states different mutually with respect to both of longitudinal and lateral directions of the panels, and an electronic line scanning is applied to the panels being in these potential states, thereby obtaining a scan image. A displacement is prevented from arising when allocating detection signal data onto the pixels, by using a checker pattern of the obtained scan image, thereby improving coordinate accuracy of pixel positions. In the step of detecting the pixel positions, a positional relation of both sides is derived from a correspondence relation between a pixel alignment and the checker pattern of the scan image obtained from a potential distribution of the checker pattern, and a scanning position of the scan image is allocated onto the pixel coordinate on the basis of the positional relation. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a TFT array inspection performed in a manufacturing process of a liquid crystal substrate or the like, and more particularly, to a TFT array inspection apparatus and a signal processing when a defect is detected from a detection signal in the TFT array inspection.

  In the manufacturing process of a semiconductor substrate on which a TFT array such as a liquid crystal substrate or an organic EL substrate is formed, a TFT array inspection process is included in the manufacturing process, and a defect inspection of the TFT array is performed in this TFT array inspection process.

  The TFT array is used as a switching element for selecting a pixel electrode of a liquid crystal display device, for example. In a substrate including a TFT array, for example, a plurality of gate lines functioning as scanning lines are arranged in parallel, and a plurality of source lines described as signal lines are arranged orthogonal to the gate lines. A TFT (Thin Film Transistor) is disposed in the vicinity of a portion where the lines intersect, and a pixel electrode is connected to the TFT.

  The liquid crystal display device is configured by sandwiching a liquid crystal layer between a substrate provided with the above TFT array and a counter substrate, and a pixel capacitor is formed between the counter electrode and the pixel electrode provided in the counter substrate. In addition to the pixel capacitor, an additional capacitor (Cs) is connected to the pixel electrode. One of the additional capacitors (Cs) is connected to the pixel electrode, and the other is connected to the common line or the gate line. A TFT array configured to be connected to the common line is referred to as a Cs on Com type TFT array, and a TFT array configured to be connected to the gate line is referred to as a Cs on Gate type TFT array.

  In this TFT array, a scanning line (gate line) or a signal line (source line) is disconnected, a scanning line (gate line) and a signal line (source line) are short-circuited, or a pixel defect due to a characteristic defect of a TFT driving a pixel. In the defect inspection, for example, the counter electrode is grounded, a DC voltage of, for example, −15 V to +15 V is applied to all or part of the gate line at a predetermined interval, and an inspection signal is applied to all or part of the source line. By doing that. (For example, the prior art of patent document 1.)

  The TFT array inspection apparatus can detect a defect by inputting the above-described inspection drive signal to the TFT array and detecting the voltage state of the array electrode at that time.

  TFT array defects that may occur during the manufacturing process include, for example, a short circuit defect (S-DSshort) between the pixel and the source line, a short circuit defect (G-DSshort) between the pixel and the gate line, and the source line. In addition to a defect in each pixel such as a short-circuit defect (S-Gshort) between the gate and the gate line and a disconnection between the pixel and the TFT (D-open), a defect between adjacent pixels in the horizontal direction (lateral PP) Adjacent defects such as defects between adjacent pixels in the vertical direction (referred to as vertical PP), short-circuits between adjacent source lines (referred to as SSshort), short-circuits between adjacent gate lines (referred to as GGshort), etc. Adjacent defects that occur between pixels that perform are known.

  In the TFT array inspection, the voltage state of the array electrode is detected by irradiating the array electrode of the pixel driven by applying the inspection signal with an electron beam and using the secondary electrons emitted from the array electrode as a detector such as a photomultiplier. Are detected and converted to analog signals, thereby detecting the voltage state of the array electrodes and detecting defects by image processing. In this defect detection, each pixel is specified by assigning detection signal data to the pixel.

  Conventionally, allocation of detection signal data to pixels is performed by associating data obtained from detection signals with pixels calculated from coordinates.

  FIG. 13 is an explanatory diagram for explaining allocation of detection signal data to pixels. In FIG. 13, a plurality of panels 101 are provided on a substrate 100. In FIG. 13A, only one panel 101 is shown. In the panel 101, a plurality of pixels 102 are arranged in a grid pattern, and each pixel includes an array electrode and a TFT element for applying a signal to the array electrode.

  When inspecting the TFT array, the substrate is positioned using the alignment mark 104 provided on the substrate 100 as an index, and then the electron beam is scanned on the substrate 100 to irradiate each pixel 102 with the electron beam. FIG. 13 shows a case in which one electron beam irradiation point is set for one pixel.

  FIG. 13B shows detection signal data obtained by scanning with an electron beam, and FIG. 13C shows a pixel arrangement. The allocation of the detection signal data to the pixels is performed by associating the detection signal data with the pixels calculated from the coordinates on the substrate 100, assuming that the detection signal data is sequentially acquired from each pixel according to the scan.

JP-A-5-307192

  Conventionally, pixel position miscalculation is known as one factor that reduces the accuracy of defect detection in array inspection. Conventionally, pixel position miscalculation has been reduced by correcting the position of the panel relative to the substrate. As correction of the position of the panel with respect to the substrate, correction relating to the electron gun and correction of the panel on the substrate are known.

  As corrections related to the electron gun, for example, a scan map is obtained by scanning an electron beam in advance, a positional deviation of irradiation of the electron beam is obtained from the scan map, correction for calibrating the obtained positional deviation, and scanning with a plurality of electron guns There are corrections of misalignment between electron guns that occur at the time, corrections of misalignment between scans that occur when the panel is scanned by a plurality of passes, and the like.

  Further, as correction of the panel on the substrate, there is a correction in units of a panel performed with reference to an alignment mark provided on the substrate and a corner of the substrate panel.

  In addition to the above-described position error outside the panel, there is a position error inside the panel caused by the influence of a disturbance such as a magnetic field or a substrate or a shape defect of the substrate.

  FIG. 14 shows a case where the irradiation position of the electron beam is displaced with respect to the pixel. Here, a case is shown in which there is one electron beam irradiation point for one pixel.

  FIG. 14A shows a state in which the electron beam is irradiated without positional deviation and the irradiation position 103 is irradiated into the target pixel 102. On the other hand, FIG. 14B shows a state in which the electron beam is irradiated while being shifted in position, and the irradiation position 103 is irradiated with being shifted from the target pixel 102.

  In the conventional allocation of detection signal data to pixels, when the electron beam is misaligned, this misalignment cannot be corrected. Therefore, the detection signal data is allocated to a pixel different from the pixel to be originally allocated. The detection signal data in FIG. 14C is allocated to a pixel adjacent to a pixel to be originally allocated as shown in FIG.

  There is a problem that the position error inside the panel cannot be corrected by the conventional position error correction.

  The present invention solves the above-mentioned problems, and aims to correct a positional error inside the panel in the inspection of the TFT array, and to improve the positional accuracy of pixel coordinates.

  In the present invention, the pixels of the panel are placed in different potential states alternately in both the vertical and horizontal directions of the panel, and the scanning image obtained by scanning the panel in this potential state with an electron beam is obtained. By using this checker pattern, it is possible to prevent positional deviation when the detection signal data is allocated to the pixel, and to improve the coordinate accuracy of the pixel position.

  Further, by using the checker pattern of the scanned image and performing overlapping scanning, it is possible to correct a positional deviation that occurs between passes, between electron guns, or between frames.

  It can be set as the form of a TFT array inspection method and the form of a TFT array inspection apparatus.

  The TFT array inspection method of the present invention is a TFT array in which a charged particle beam is scanned two-dimensionally on a TFT array to form a scanned image of a surface potential, and a defect inspection of the TFT array is performed from the scanned image. This is an inspection method.

  The inspection method of the TFT array of the present invention includes an inspection signal applying step of applying an inspection signal to the TFT array to form a two-dimensional potential distribution of a predetermined pattern on the TFT array, and charging the TFT array to which the inspection signal is applied. A scanning process for scanning a particle beam two-dimensionally to form a scanned image of a surface potential, a pixel position detecting process for detecting the position of each pixel from the scanned image, and a signal intensity detecting process for detecting the signal intensity of each pixel And a data processing step of extracting defective pixels by data processing of signal intensity.

  In the inspection signal applying step of the present invention, an inspection signal for alternately applying a relatively high potential and a low potential is applied between adjacent pixels among a plurality of pixels arranged in two dimensions, and applied to the TFT array. A potential distribution is formed in which a relatively high potential and a low potential are arranged in a checker pattern.

  According to the potential distribution of this checker pattern, adjacent pixels have different potentials in the scanning direction and the direction orthogonal to the scanning direction (longitudinal direction and lateral direction). Can be corrected by collating this checker pattern.

  In the pixel position detecting step of the present invention, the positional relationship between the checker pattern of the scanned image obtained by the potential distribution of the checker pattern and the pixel array is obtained, and the scanning position of the scanned image is determined based on this positional relationship. Assign to the coordinates.

  The present invention corrects the positional deviation of the pixel coordinates by utilizing the characteristics of the checker pattern, and assigns the detection signal data to the correct pixel.

  In addition, the TFT array inspection method of the present invention can apply a plurality of electron beam irradiation positions to one pixel and can be applied to scanning.

  When there are a plurality of irradiation positions for one pixel, the scanning process of the present invention irradiates a plurality of charged particle beams to one pixel. The pixel position detection step of the present invention calculates the position coordinates of the centroids of a plurality of scanning positions included in the lattice part in each lattice part of the checker pattern, and compares the calculated array of centroids with the pixel array. , Find the displacement of the center of gravity with respect to the pixel. The position coordinates of the center of gravity are corrected based on the obtained positional deviation, and the pixel position is calculated using the corrected center of gravity coordinates as the position coordinates of the pixel corresponding to the checker portion.

  Furthermore, the TFT array inspection method of the present invention can be applied not only to positional deviation correction inside the panel but also to positional deviation outside the panel. For example, when electron beam scanning is performed using a plurality of electron guns, the positional deviation between the scanning position caused by the positional deviation between the electron guns and the pixel coordinates, the inspection area is divided into a plurality of scanning areas, and scanning is performed by a plurality of passes. The misalignment between the scanning position and the pixel coordinate that occurs in some cases can be corrected by applying the misalignment between these boundaries.

  In this application, the scanning process of the present invention performs overlapping scanning at the boundary of adjacent scanning areas in a plurality of scanning areas, and the pixel position detection process of the present invention performs two scanning operations adjacent to each other across the boundary acquired by the overlapping scanning. The checker pattern of the scanning area is collated, and the pixel position of the boundary portion is detected based on the matching checker pattern. In this scanning step, when scanning with a plurality of passes, the inspection area is divided into a plurality of scanning areas and scanned, and the boundary between adjacent scanning areas is scanned repeatedly.

  The TFT array inspection apparatus according to the present invention is a TFT array in which a charged particle beam is scanned two-dimensionally on a TFT array to form a scanned image of a surface potential, and a defect inspection of the TFT array is performed from the scanned image. This is an inspection device.

  The TFT array inspection apparatus of the present invention applies an inspection signal to a TFT array to form a two-dimensional predetermined pattern of potential distribution on the TFT array, and charges the TFT array to which the inspection signal is applied. Charged particle beam source and scan controller that scans the particle beam two-dimensionally to form a scanning image of the surface potential, and detection that detects detection signals of secondary electrons emitted from the TFT substrate by scanning the charged particle beam A pixel position detector for detecting the position of each pixel from the scanning image obtained from the detection signal, a signal intensity detector for detecting the signal intensity of each pixel, and extracting defective pixels by processing the signal intensity A data processing unit.

  The inspection signal application unit of the present invention applies an inspection signal for alternately applying a relatively high potential and a low potential to each other between adjacent pixels among a plurality of two-dimensionally arranged pixels, and applies it to the TFT array. A potential distribution is formed in which a relatively high potential and a low potential are arranged in a checker pattern. The pixel position detection unit of the present invention obtains the positional relationship between the checker pattern of the scanned image obtained from the potential distribution of the checker pattern and the pixel arrangement, and determines the scanning position of the scanned image based on this positional relationship. Assign to the coordinates.

  The charged particle beam source and the scanning control unit of the present invention irradiate a plurality of charged particle beams to one pixel, and the pixel position detection unit of the present invention is included in the lattice unit in each lattice part of the checker pattern. The position coordinates of the center of gravity of the plurality of scanning positions are calculated, the calculated array of the center of gravity is compared with the pixel array, the position deviation of the center of gravity with respect to the pixel is obtained, and the position coordinates of the center of gravity are calculated based on the obtained position deviation. The pixel position is calculated using the corrected barycentric coordinates as the position coordinates of the pixels corresponding to the checker portion.

  Further, when the present invention is applied not only to the positional deviation correction inside the panel but also to the positional deviation outside the panel, the charged particle beam source and the scanning control unit of the present invention are arranged at the boundary between adjacent scanning areas in a plurality of scanning areas. Overlapping scanning is performed, and the pixel position detection unit of the present invention collates the checker patterns of two adjacent scanning regions across the boundary acquired by overlapping scanning, and detects the pixel position of the boundary portion based on the matching checker pattern To do.

  When scanning by a plurality of passes, the charged particle beam source and the scanning control unit of the present invention divide and scan the inspection region into a plurality of scanning regions, and perform overlapping scanning at the boundary between adjacent scanning regions.

  According to the TFT array inspection method and the TFT array inspection apparatus of the present invention, the coordinate accuracy of the pixel position can be improved in the array inspection, and scanning is separated between passes, between electron guns, or between frames. Even in this case, the coordinates of the pixel position can be calculated with high accuracy.

  In addition, when a pixel has a plurality of irradiation points, the defect detection accuracy is improved by using the center of gravity to calculate the position of the pixel and performing defect detection using detection signal data around the center of gravity. Can be improved.

  Increased pixel position accuracy improves defect detection accuracy on the production line and improves repair yield.

  Further, in the TFT array inspection of the present invention, pixel position detection can be performed in parallel with defect detection by TFT array inspection, and therefore can be performed without affecting the inspection tact.

  According to the present invention, in the inspection of the TFT array, the position error inside the panel can be corrected, and the position accuracy of the pixel coordinates can be improved.

It is a flowchart for demonstrating the process of calculating the position of a pixel in the TFT array test | inspection of this invention. It is explanatory drawing for demonstrating the process of calculating the position of a pixel in the TFT array test | inspection of this invention. It is the schematic for demonstrating an example of the TFT array test | inspection apparatus of this invention. It is a figure for demonstrating the example irradiated to several points with respect to 1 pixel in the TFT array test | inspection of this invention. It is a figure for demonstrating the example irradiated to several points with respect to 1 pixel in the TFT array test | inspection of this invention. It is a figure for demonstrating the joining of the scanning image using the overlapping image of this invention. It is a figure for demonstrating the joining of the scanning image using the overlapping image of this invention. It is a figure for demonstrating the joining of the scanning image using the overlapping image of this invention. It is a figure for demonstrating the joining of the scanning image using the overlapping image of this invention. It is a figure for demonstrating the scanning example which irradiates several irradiation points per pixel in the TFT array of this invention. It is a figure which shows the test | inspection signal for forming the potential distribution of a checker pattern. It is a figure which shows the voltage state of the pixel to which the inspection signal of the checker pattern was applied. It is explanatory drawing for demonstrating the allocation to the pixel of the conventional detection signal data. It is a figure for demonstrating the case where the irradiation position of the conventional electron beam has shifted | deviated with respect to the pixel.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 and FIG. 2 are a flowchart and an explanatory diagram for explaining a process of calculating a pixel position in the TFT array inspection of the present invention.

  First, in the inspection signal application process, an inspection signal is applied to the TFT array to form a two-dimensional predetermined pattern of potential distribution in the TFT array. In this inspection signal application process, an inspection signal for alternately applying a relatively high potential and a low potential to each other is applied between adjacent pixels among a plurality of pixels that are two-dimensionally arranged. A potential distribution in which a high potential and a low potential are arranged in a checker pattern is formed.

  This inspection signal can be applied, for example, by bringing a probe pin provided on the prober frame into contact with an electrode provided on the substrate (S1).

  In the state where the potential distribution of the checker pattern is formed in the TFT array by the inspection signal application process, the electron beam is irradiated from the electron gun and scanned on the substrate to detect secondary electrons emitted from the substrate irradiated with the electron beam. Detect with a detector and obtain the detection signal.

  FIG. 2A is a signal diagram for explaining the detection signal. Here, detection signals obtained by scanning pixels in two potential states are shown. The signal intensity of this detection signal is a value corresponding to the potential on the substrate. Since the inspection signal applied to the panel applies different voltages to adjacent pixels, a potential distribution based on a checker pattern is formed in the TFT array. As a result, the detection signal detects the signal strength at which the voltage alternately rises and falls according to the checker pattern (S2).

  A scanned image is formed based on the detection signal detected in step S2. The scanned image represents the surface potential distribution formed by the inspection signal applied to the TFT array, and becomes a checker pattern image according to the potential distribution of the checker pattern formed on the panel. In the checker pattern, different voltages are applied to adjacent pixels in units of pixels, so that an image of the checker pattern forms a checker pattern corresponding to each pixel.

  FIG. 2B shows an example of a scanned image formed from the detection signal of FIG. Here, a portion where the signal strength of the detection signal is high is shown in white, and a portion where the signal strength of the detection signal is low is shown in gray, and a checker pattern scanning image is formed (S3).

  Since there is a correspondence relationship between the scanned image and the pixel, the position of the pixel can be calculated by obtaining the coordinates of the detected point of the scanned image. The coordinates of the detection point of the scanned image can be obtained from the scanning control of the electron beam, for example, can be obtained from the coordinates of the irradiation position of the electron beam. At this time, in the case of performing multi-point hitting in which a single pixel is irradiated with a plurality of electron beams, the center of gravity of the detection point in the pixel is obtained and the center of gravity is calculated as the position coordinates of the pixel.

  In FIG. 2B, the coordinate pattern 31 is formed by connecting the detection points 30 in each lattice portion of the checker pattern 21 in the scanned image 20. When there is a position shift in the coordinates of the detection point 30, the formed coordinate pattern 31 has a shape including distortion. 2B and 2C show a case where there is a positional shift in the x direction (lateral direction, left and right direction in the figure) and y direction (vertical direction, up and down direction in the figure) (S4).

  Using the coordinates of the detection points or the coordinates of the center of gravity calculated in the step S4, the displacement of each of these coordinates is corrected. In this correction, for example, an interval between each detection point is obtained, an average of these intervals is calculated, and the position of each detection point is corrected based on the calculated average interval. FIG. 5D shows an example of a corrected coordinate pattern 32 obtained by correcting the coordinate pattern 31 (S5).

  The coordinates of the detection points or the coordinates of the center of gravity calculated in the step S4 and corrected in the step S5 are set as the positions of the corresponding pixels 40. FIG. 2E shows an example in which the lattice points of the correction coordinate pattern 32 are calculated as the position coordinates of each pixel 40 (S6).

  In the defect detection of the TFT array, for each pixel calculated in the process of S6, the signal intensity of the detection signal is detected by the signal intensity detection process, and the defect intensity is extracted by processing the signal intensity by the data processing process.

  FIG. 3 is a schematic view for explaining an example of the TFT array inspection apparatus of the present invention.

  The TFT array inspection apparatus 1 is configured to detect the potential state of the substrate 7. A charged particle beam source 2 that irradiates a charged particle beam such as an electron beam to the TFT array of the substrate 7, and the charged particle beam on the TFT array. A scanning control unit 4 for scanning and a detector 3 for detecting secondary electrons emitted from the TFT array by irradiation with a charged particle beam are provided.

  The scanning control unit 4 controls the stage 6 and the charged particle beam source 2 in order to scan the inspection position of the TFT array on the substrate 7. The stage 6 moves the substrate 7 to be placed in the XY direction, and the charged particle beam source 2 scans the irradiation position of the charged particle beam by shaking the electron beam irradiating the substrate 7 in the XY direction. The scanning position of the charged particle beam by this scanning becomes the detection position.

  The mechanism for detecting the voltage application state of the TFT substrate can have various configurations. For example, when an electron beam is used as a charged particle beam, an electron beam source that irradiates an electron beam is disposed on the substrate 7 and secondary electrons emitted from the substrate 7 are detected by the irradiated electron beam. An electronic detector is provided. Since the TFT array irradiated with the electron beam emits secondary electrons in an amount corresponding to the potential state according to the applied inspection signal, the potential state of the TFT array can be detected from the detection signal intensity of this secondary electron. it can.

  The TFT array inspection apparatus 1 generates and applies an inspection signal for array inspection as a configuration of an inspection signal application unit for applying an inspection signal to the TFT array on the substrate 7 to form a predetermined potential pattern. An inspection signal generator 10 and a prober 5 that supplies the inspection signal generated by the inspection signal generator 10 to the TFT array of the substrate 7 are provided.

  The prober 5 includes a prober frame provided with probe pins (not shown). The prober 5 brings probe pins into contact with electrodes formed on the substrate 7 by a mounting operation on the substrate 7 and supplies an inspection signal to the TFT array.

  Furthermore, the TFT array inspection apparatus 1 forms a scanned image based on the detection signal detected by the detector 3, and includes a signal intensity detection unit 11 that detects the signal intensity of each pixel from the scanned image, and a signal intensity detection unit 11. A pixel position detector 12 that detects the position of the pixel with respect to the scanned image by performing signal processing on the detected signal intensity, a pixel intensity calculator 13 that calculates the signal intensity of the pixel from the acquired data of the scanned image, and the signal intensity of the pixel And a defect extraction unit 14 for extracting defects based on the above.

  The signal intensity detection unit 11 forms a scanned image by synchronizing the detection signal detected by the detector 3 with the inspection signal of the inspection signal generation unit 10. The defect extraction unit 14 compares the signal intensity of each pixel obtained by the pixel intensity calculation unit 13 with a threshold, performs pixel defect determination based on the comparison result, and extracts defective pixels.

  A threshold value used for defect extraction may be stored in a storage unit (not shown), and the threshold value read from the storage unit may be compared by a comparison unit (not shown). In this configuration, the signal strength and comparison are performed by data comparison by software, and the comparison circuit can also be configured by hardware.

  The above-described configuration of the TFT array inspection apparatus is an example, and is not limited to this configuration.

  In the above description, an example in which there is one irradiation point (detection point) for one pixel is described. Hereinafter, an example in which there are a plurality of irradiation points (detection points) for one pixel will be described with reference to FIGS. When there are a plurality of irradiation points (detection points) for one pixel, the center of gravity of these irradiation points is calculated, and the position of the pixel is calculated using this center of gravity.

  FIG. 4A shows an example in which detection signals are acquired from four detection points by irradiating electron beams at four irradiation points per pixel.

  When an inspection signal of a checker pattern is applied to the TFT array, the potential state formed by applying the inspection signal is irradiated with four electron beams per pixel, and a scanning image is formed from the acquired detection signal. A scanned image of the checker pattern shown in FIG. In FIG. 4A, a circle indicates a detection point of a scanning image obtained from a high potential pixel, and a black circle indicates a detection point of a scanning image obtained from a low potential pixel.

  Here, four adjacent detection points of the same potential are detection points detected from the same pixel. In the present invention, the center of gravity of these four detection points is calculated, and the position of the calculated center of gravity is set as the pixel position. The hatched points G11 to G43 in FIG. 4B indicate the centers of gravity calculated from the four adjacent detection points. By connecting the centroids G11 to G43 in the x direction (horizontal direction, left and right direction in the figure) and y direction (vertical direction, vertical direction in the figure), the position arrangement of the pixels obtained from the centroid can be obtained. . The broken line in FIG. 4B shows the arrangement of the centroids. The positional deviation of the center-of-gravity array indicated by the broken line reflects the positional deviation of the position of the detection point.

  Pixels are aligned in the x and y directions within the panel. Therefore, when the calculated center of gravity array is displaced from the x direction or the y direction, it indicates that the position of the center of gravity is displaced.

  For this reason, when the pixel position is determined based on the arrangement of the center of gravity including the positional deviation, the obtained pixel position includes the positional deviation.

  In order to eliminate this pixel displacement, the present invention corrects the displacement of the center of gravity. For the correction of the displacement of the center of gravity, for example, an average of intervals between the center of gravity is calculated, and the position of the center of gravity is corrected based on the average interval so that the centers of gravity are arranged in a grid pattern in the x direction and the y direction. It can be done by calculation. The reference position can be determined, for example, as the average position of the centroids of all pixels.

  Note that the above-described correction method of the center of gravity displacement is an example, and is not limited to the above correction method.

  FIG. 5A shows the center of gravity array after correction of the center of gravity array before correction. The one-dot chain line in the figure indicates the center of gravity array before correction, and the solid line in the figure indicates the center of gravity array after correction. By determining the pixel position based on the corrected barycentric arrangement, it is possible to obtain the pixel position where the positional deviation is corrected. FIG. 5B shows a pixel arrangement determined based on the corrected centroid arrangement (indicated by a broken line).

  Next, correction of misalignment that occurs when scanning is separated between passes, between electron guns, or between frames will be described.

  When inspecting a panel having a large area in the TFT array inspection, the inspection region may be divided into a plurality of scanning regions for scanning. In the scanning of the divided scanning regions, for example, when scanning is performed by moving the scanning range using one electron gun for each scanning region, or a plurality of electron guns are used for a plurality of scanning regions. There are cases where the scanning region is scanned by each electron gun.

  As described above, when the inspection area is divided into a plurality of scanning ranges and scanned, it is necessary to connect the scanned images obtained in the respective scanning ranges to form a scanned image of the entire panel. In this combination of scanned images, it is necessary to align the scanned image at the boundary portion of the scanned image. However, if the detection signal is shifted, the image at the end of the pixel may be lost. If a defective portion of the pixel image is generated in this way, the missing pixel occurs when the scanned image of the entire panel is formed, which causes a defect detection error.

  In addition, when the inspection signal is applied to the panel using a plurality of prober frames, the same problem occurs in the joining of the scanned images obtained in each prober frame.

  In order to solve such a problem, the image defect at the end portion of the pixel is eliminated by performing overlapping scanning across the boundary portion between adjacent scanning ranges. In order to connect the scanned images obtained by this overlapping scanning, it is necessary to confirm the overlapping portion.

  However, conventionally used inspection signals form a potential pattern that places the entire panel in a high-voltage or low-voltage potential state, so it is difficult to identify the boundary portion between adjacent scanning ranges from overlapping images. Thus, it is difficult to combine adjacent scanning ranges by performing overlapping scanning.

  The present invention uses a checker pattern in which adjacent pixels have different potential states, thereby identifying the same pixel from the overlapping range acquired in the adjacent scanning range, thereby extracting the effective range from the scanning range, An all-scan image with no shortage is formed.

  Hereinafter, stitching of scanned images using overlapping images will be described with reference to FIGS. 6 and 7 show a case where a defect occurs in a part of the scanned image of the end pixel in the left scanning range in the figure, and FIGS. 8 and 9 show the right scanning range in the figure. FIG. 8 shows a case where a defect occurs in a part of the scanned image of the pixel at the end. Here, the case where the defect of the scanned image is within the range of one pixel is shown.

  First, a case where a defect occurs in a part of the scanned image of the end pixel in the left scanning range in the drawing will be described with reference to FIGS.

  FIG. 6A shows a normal scanning range A located on the left side of the drawing with the boundary C in between, and a normal scanning range B located on the right side of the drawing. When there is no positional deviation in the scanning range, a scanned image is acquired by the normal scanning range A for the left region of the boundary C, and a scanned image is acquired by the normal scanning range B for the right region of the boundary C. get.

  FIG. 6B shows a state in which the scanning range is displaced in the left direction in the figure. In this case, the boundary D between the scanning range a and the scanning range b is shifted to the left in the drawing from the normal boundary C, and a defective portion E is generated in the scanned image at the pixel at the end of the normal scanning range A. On the other hand, an excessive portion F occurs in the scanned image at the pixel at the end of the normal scanning range B. The defective portion E and the excess portion F are the same pixel portion, and if the detection signals obtained in the scanning ranges a and b are assigned to the pixels, they are shifted by one pixel, which is a factor for erroneously detecting a defect. Become.

  Therefore, overlapping scanning ranges are provided in both the scanning range a and the scanning range b, a line of matching pixels is extracted from the obtained scanning image, and the adjacent scanning ranges are combined by using the matching line as an index. A scan range that is not deficient is formed.

  FIG. 6C shows the overlapping scanning range. For the normal scanning range A, an overlapping scanning range (overlap area) OA is provided in addition to the scanning range a and overlapping on the adjacent scanning range B side. On the other hand, the normal scanning range B is provided with an overlapping scanning range (overlap area) OB that overlaps the adjacent scanning range A in addition to the scanning range b. Here, the overlapping scanning range (overlap area) OA and the overlapping scanning range (overlap area) OB have a width of 2 pixels. The width of this overlapping scanning range can be determined according to the amount of deviation assumed in the scanning range. Here, an example in which one pixel is assumed as the shift amount of the scanning range is shown.

  In FIG. 6C, the overlapping scanning range (overlap area) OA includes three columns of pixel lines OA1, OA2, and OA3, and includes the overlapping scanning range (overlap area) OB3 columns of pixel lines OB1, OB2, and OB3. It is out. Among these pixel lines, the pixel line OA1 and the pixel line OB1 correspond to the same pixel line G.

  Whether or not they are the same pixel line can be identified by extracting a line of pixels representing the signal intensity of the same detection signal based on the scanned image being a checker pattern. Based on the same pixel line G extracted in FIG. 6C, the effective areas of the scanning range a and the scanning range b are set, and the adjacent effective areas are combined.

  In FIG. 7A, the scanning range including the pixel line G with respect to the scanning range a is set as the effective region α, and the scanning range excluding the pixel line G with respect to the scanning range b is set as the effective region β.

  At this time, the detection data of the pixel line OA2 and the pixel line OA3 excluding the pixel line OA1 included in the pixel line G in the overlapping scanning range (overlap area) OA is discarded, and the overlapping scanning range (overlap area). The detection data of OB and pixel line G is discarded. It should be noted that it is possible to arbitrarily set which effective area the pixel line detection data extracted in the overlapping scanning range is to be incorporated.

  FIG. 7B shows a state in which the combined scanning range is acquired by combining the detection data of the effective area α and the effective area β. Since the overlapping scanning range G is set only in one effective area, it is not set twice.

  Next, a case where a defect occurs in a part of the scanned image of the end pixel in the right scanning range in the drawing will be described with reference to FIGS.

  FIG. 8A shows a normal scanning range A located on the left side of the drawing with the boundary C in between, and a normal scanning range B located on the right side of the drawing. When there is no positional deviation in the scanning range, a scanned image is acquired by the normal scanning range A for the left region of the boundary C, and a scanned image is acquired by the normal scanning range B for the right region of the boundary C. get.

  FIG. 8B shows a state where the scanning range is displaced in the right direction in the figure. In this case, the boundary D between the scanning range a and the scanning range b is shifted to the right in the drawing from the normal boundary C, and an excessive portion F is generated in the scanned image at the end pixel of the normal scanning range A. On the other hand, a defective portion E occurs in the scanned image at the pixel at the end of the normal scanning range B. The defective portion E and the excess portion F are the same pixel portion, and if the detection signals obtained in the scanning ranges a and b are assigned to the pixels, they are shifted by one pixel, which is a factor for erroneously detecting a defect. Become.

  Therefore, overlapping scanning ranges are provided in both the scanning range a and the scanning range b, a line of matching pixels is extracted from the obtained scanning image, and the adjacent scanning ranges are combined by using the matching line as an index. A scan range that is not deficient is formed.

  FIG. 8C shows the overlapping scanning range. For the normal scanning range A, an overlapping scanning range (overlap area) OA is provided in addition to the scanning range a and overlapping on the adjacent scanning range B side. On the other hand, the normal scanning range B is provided with an overlapping scanning range (overlap area) OB that overlaps the adjacent scanning range A in addition to the scanning range b. Here, the overlapping scanning range (overlap area) OA and the overlapping scanning range (overlap area) OB have a width of 2 pixels. The width of this overlapping scanning range can be determined according to the amount of deviation assumed in the scanning range. Here, an example in which one pixel is assumed as the shift amount of the scanning range is shown.

  In FIG. 8C, the overlapping scanning range (overlap area) OA includes three columns of pixel lines OA1, OA2, and OA3, and includes the overlapping scanning range (overlap area) OB3 columns of pixel lines OB1, OB2, and OB3. It is out. Among these pixel lines, the pixel line OA1 and the pixel line OB1 correspond to the same pixel line G.

  Whether or not they are the same pixel line can be identified by extracting a line of pixels representing the signal intensity of the same detection signal based on the scanned image being a checker pattern. Based on the same pixel line G extracted in FIG. 8C, the effective areas of the scanning range a and the scanning range b are set, and the adjacent effective areas are combined.

  In FIG. 9A, the scanning range including the pixel line G with respect to the scanning range a is set as the effective region α, and the scanning range excluding the pixel line G with respect to the scanning range b is set as the effective region β.

  At this time, the detection data of the pixel line OA2 and the pixel line OA3 excluding the pixel line OA1 included in the pixel line G in the overlapping scanning range (overlap area) OA is discarded, and the overlapping scanning range (overlap area). The detection data of OB and pixel line G is discarded. It should be noted that it is possible to arbitrarily set which effective area the pixel line detection data extracted in the overlapping scanning range is to be incorporated.

  FIG. 9B shows a state in which the combined scanning range is acquired by combining the detection data of the effective area α and the effective area β. Since the overlapping scanning range G is set only in one effective area, it is not set twice.

  The TFT array inspection of the present invention increases the number of electron beam irradiation points per pixel in scanning image acquisition, and determines the number of irradiation points that can irradiate the center side of the pixel without straddling the pixel boundary. By increasing, the position resolution of the scanned image can be increased.

  Hereinafter, a scanning example of irradiating a plurality of irradiation points per pixel will be described with reference to FIG. FIGS. 10A to 10D show scanning examples in which nine irradiation points per pixel are irradiated. In FIGS. 10A and 10C, Pa indicates a scanning image of a normal pixel, and Pb (Shaded pixels) shows a scanned image of defective pixels. 10B and 10D show the signal intensity of the acquired data, and the signal intensity obtained from the defective pixel is larger than the signal intensity obtained from the normal pixel.

  FIGS. 10E to 10H show scanning examples in which four irradiation points are irradiated per pixel. In FIGS. 10E and 10F, Pa denotes a scanning image of a normal pixel. , Pb (hatched pixels) indicate scanning images of defective pixels. 10B and 10D show the signal intensity of the acquired data, and the signal intensity obtained from the defective pixel is larger than the signal intensity obtained from the normal pixel.

  10 (a) to 10 (d), when nine irradiation points are irradiated to the irradiation area inside one pixel, if the positional deviation occurs in the irradiation position, nine irradiation points irradiated to the irradiation area. Among these, the irradiation points arranged on the edge side straddle adjacent pixels, which causes an error factor of signal intensity. On the other hand, the irradiation points arranged on the center side do not straddle adjacent pixels even when the irradiation position is displaced, and do not cause an error factor of signal intensity. Here, it is assumed that the displacement at the irradiation position is one beam pitch or less.

  The present invention calculates the signal intensity of a pixel using a detection signal obtained from an irradiation position around the calculated center of gravity, so that irradiation that does not straddle adjacent pixels even when a positional shift occurs. By ensuring the number of points, the S / N ratio can be improved. For example, when irradiating nine irradiation points per pixel, four irradiation points can be secured in the pixel even when the positional deviation is the largest. Even if a displacement occurs in the irradiation position by obtaining a pixel detection signal using acquired data obtained at a plurality of irradiation points (here, four irradiation points) arranged on the center side, Avoid error factors due to straddling adjacent pixels.

  FIG. 10A shows an example of a scanned image and an example of acquired data when the irradiation position is not displaced from the pixel. In this case, nine irradiation points are irradiated in one pixel.

  When there is no positional shift in the irradiation position, the irradiation points around the center of gravity of the pixel are nine irradiation points in the pixel, and the S / N is improved by using the signal intensity of these detection signals. be able to. This is because most of the noise components are generated in units of irradiation points, and noise hardly occurs at the same time for all irradiation points irradiated in the pixel, and most of them are noise of one irradiation point. It is possible to improve the S / N ratio by reducing the ratio of the noise component by averaging using the signal intensity of the detected signal.

  FIG. 10C shows an example of a scanned image and an example of acquired data when the irradiation position is displaced from the pixel. When the irradiation position is displaced, the irradiation point on the edge side among the nine irradiation points irradiated per pixel straddles adjacent pixels, which causes an error factor of signal intensity. On the other hand, the four irradiation points on the center side do not straddle with adjacent pixels even when the irradiation position is displaced, and do not cause a signal intensity error. Here, it is assumed that the displacement at the irradiation position is one beam pitch or less.

  Therefore, by increasing the number of irradiation points irradiated per pixel in the scanned image and using the acquired data obtained from the irradiation points around the calculated center of gravity, regardless of whether or not the irradiation position is misaligned, Acquired data that does not cause an error can be acquired.

  In the example of the signal intensity when the irradiation position is not displaced as shown in FIG. 10B, the signal intensity of the acquired data detected by the defective pixel Pb is generated due to noise because the level indicating the defect appears continuously. Can be distinguished from the peak value.

  Further, in the signal intensity example in the case where there is a positional deviation in the irradiation position shown in FIG. 10D, the signal intensity of the acquired data detected by the defective pixel Pb continuously appears at the level indicating the defect. Similar to the case of FIG. 10B, it can be distinguished from a peak value generated by noise.

  On the other hand, FIG.10 (e)-FIG.10 (h) have shown the example of 4 irradiation points per pixel. FIG. 10E shows a case where four irradiation points are irradiated within one pixel, and FIG. 10F shows one irradiation point representing the signal intensity of the pixel with the irradiation position shifted relative to the pixel. Only the case is shown.

  As shown in FIG. 10 (g), when four irradiation points are irradiated in one pixel, a signal intensity of a predetermined level or higher appears continuously in the defective pixel, so that the noise generated at the peak is easy. Can be identified. On the other hand, as shown in FIG. 10 (h), when only one irradiation point is irradiated within one pixel, the signal intensity of a predetermined level or higher does not appear continuously at the defective pixel, and thus occurs at a peak. It is difficult to distinguish it from noise.

  By reducing the beam pitch, the position resolution of the scanned image can be increased. However, if the beam pitch is reduced, the number of irradiation points per pixel increases and the overall inspection time becomes longer. Can not do it. As described above, in the method of integrating scanning images of a plurality of frames, since it is necessary to perform beam irradiation for each pixel by the number of frames multiplied by the irradiation point per pixel, the inspection time becomes longer. . For example, in order to irradiate 4 points per pixel and obtain a scanned image for 20 frames, it is necessary to irradiate 80 irradiation points per pixel (= 4 irradiation points × 20 frames) with an electron beam.

  As shown in FIGS. 10A to 10D, by increasing the number of irradiation points in one pixel and using the signal intensity of the detection signal of the irradiation points around the center of gravity, FIGS. In addition to the effect of improving the S / N, the scanning time can be shortened and the inspection time can be shortened as compared with the case where the number of irradiation points in one pixel is small as shown in FIG. The effect that it is possible can be produced.

  FIG. 11 shows inspection signals for forming the potential distribution of the checker pattern. FIGS. 12A and 12B show the pixel (ITO) generated when the pixels are driven by applying the inspection signals shown in FIG. The voltage state is shown.

  11A and 11B show gate signals, and FIGS. 11C and 11D show source signals. A combination of the gate signals of FIGS. 11A and 11B and the source signals of FIGS. 11C and 11D applies a positive voltage (here 10V) and a negative voltage (here −10V) to the pixel of the TFT array. ) Are alternately applied in a checkered pattern, and as shown in FIGS. 12 (a) and 12 (b), different voltages (in this case, 10v and −10V) are alternately driven to drive adjacent pixels to each other. Different potential states.

  According to the aspect of the present invention, since the defect detection can be performed based on the scan image acquired by one scan without adding the scan images of a plurality of frames acquired by the plurality of scans, the inspection time Can be shortened. For example, when the number of irradiation points per pixel is four and a scanned image for a total of 20 frames is acquired, it is necessary to irradiate 80 points per pixel. By obtaining a scanning image for 2 frames with 9 irradiation points, the number of irradiation points per pixel can be reduced to 18 points, and the time required for scanning can be reduced to about 18/80. .

  Further, according to the embodiment of the present invention, it is possible to detect a defect smaller than the pixel size by increasing the number of irradiation points per pixel, and it is also possible to detect the shape of the defective portion.

  Further, according to the embodiment of the present invention, by detecting the coordinate error of the pixel position and improving the position accuracy of the defect position, the size of the defective part is detected to be larger than the actual size, or conversely reduced. Thus, it is possible to suppress a decrease in detection accuracy of defects such as detection.

  Moreover, according to the form of this invention, by increasing the number of irradiation points per pixel, the data number of acquisition data can be increased and noise resistance can be improved.

  The present invention can be applied not only to a TFT array inspection process in a liquid crystal manufacturing apparatus but also to a defect inspection of a TFT array provided in an organic EL or various semiconductor substrates.

  DESCRIPTION OF SYMBOLS 1 ... Array inspection apparatus, 2 ... Charged particle beam source, 3 ... Detector, 4 ... Scan control part, 5 ... Prober, 6 ... Stage, 7 ... Substrate, 10 ... Inspection signal generation part, 11 ... Signal intensity detection part, DESCRIPTION OF SYMBOLS 12 ... Pixel position detection part, 13 ... Pixel intensity calculation part, 14 ... Defect extraction part, 20 ... Scanned image, 21 ... Checker pattern, 30 ... Detection point, 31 ... Coordinate pattern, 32 ... Correction coordinate pattern, 40 ... Pixel, DESCRIPTION OF SYMBOLS 100 ... Board | substrate, 101 ... Panel, 102 ... Pixel, 103 ... Irradiation position, 104 ... Alignment mark.

Claims (8)

A TFT array inspection method in which a charged particle beam is scanned two-dimensionally on a TFT array to form a scanning image of a surface potential, and a defect inspection of the TFT array is performed from the scanned image,
An inspection signal application step of applying an inspection signal to the TFT array to form a two-dimensional predetermined pattern of potential distribution in the TFT array;
A scanning step of two-dimensionally scanning a charged particle beam on the TFT array to which the inspection signal is applied to form a scanning image of a surface potential;
A pixel position detecting step of detecting the position of each pixel from the scanned image;
A signal strength detection step of detecting the signal strength of each pixel;
A data processing step of extracting defective pixels by data processing the signal intensity,
In the inspection signal applying step, an inspection signal for alternately applying a relatively high potential and a low potential to each other is applied between adjacent pixels among a plurality of pixels arranged in a two-dimensional array, and relative to the TFT array. A potential distribution in which a high potential and a low potential are arranged in a checker pattern,
The pixel position detecting step obtains the positional relationship between the checker pattern of the scanned image obtained from the potential distribution of the checker pattern and the pixel arrangement, and determines the scanning position of the scanned image based on the positional relationship. A method for inspecting a TFT array, wherein the method is assigned to coordinates. The scanning step irradiates a pixel with a plurality of charged particle beams,
The pixel position detection step calculates the position coordinates of the center of gravity of a plurality of scanning positions included in the lattice portion in each lattice portion of the checker pattern,
Comparing the calculated array of centroids with the pixel array to determine the displacement of the centroid relative to the pixel, correcting the position coordinates of the centroid based on the determined displacement,
2. The TFT array inspection method according to claim 1, wherein the pixel position is calculated using the corrected barycentric coordinates as the position coordinates of the pixel corresponding to the checker portion. In the scanning step, multiple scanning areas are overlapped at the boundary of adjacent scanning areas,
In the pixel position detecting step, checker patterns of two scanning regions adjacent to each other with the boundary acquired by the overlap scanning are compared, and a pixel position of the boundary portion is detected based on the matching checker pattern. The method for inspecting a TFT array according to claim 1 or 2.   4. The TFT array inspection method according to claim 3, wherein in the scanning step, the inspection area is divided into a plurality of scanning areas and scanned, and a boundary between adjacent scanning areas is overlapped. A TFT array inspection apparatus that scans a charged particle beam two-dimensionally on a TFT array, forms a scanning image of a surface potential, and performs defect inspection of the TFT array from the scanned image,
An inspection signal applying unit that applies an inspection signal to the TFT array to form a two-dimensional predetermined pattern of potential distribution in the TFT array;
A charged particle beam source and a scanning control unit that form a scanning image of a surface potential by two-dimensionally scanning a charged particle beam on the TFT array to which the inspection signal is applied;
A detector for detecting a detection signal of secondary electrons emitted from the TFT substrate by scanning the charged particle beam;
A pixel position detector for detecting the position of each pixel from the scanned image obtained by the detection signal;
A signal intensity detector for detecting the signal intensity of each pixel;
A data processing unit for extracting defective pixels by data processing the signal intensity,
The inspection signal applying unit applies an inspection signal for alternately applying a relatively high potential and a low potential to each other between adjacent pixels among a plurality of pixels arranged in a two-dimensional array. A potential distribution in which a high potential and a low potential are arranged in a checker pattern,
The pixel position detection unit obtains a positional relationship between the checker pattern of the scanned image obtained from the potential distribution of the checker pattern and the pixel arrangement, and determines the scanning position of the scanned image based on the positional relationship. A TFT array inspection apparatus, characterized by being assigned to coordinates. The charged particle beam source and the scanning control unit irradiate a plurality of charged particle beams to one pixel,
The pixel position detection unit calculates a position coordinate of the center of gravity of a plurality of scanning positions included in the grid part in each grid part of the checker pattern;
Comparing the calculated array of centroids with the pixel array to determine the displacement of the centroid relative to the pixel, correcting the position coordinates of the centroid based on the determined displacement,
6. The TFT array inspection apparatus according to claim 5, wherein the pixel position is calculated using the corrected barycentric coordinates as the pixel position coordinates corresponding to the checker portion. The charged particle beam source and the scanning control unit perform overlapping scanning at a boundary between adjacent scanning regions in a plurality of scanning regions,
The pixel position detection unit collates checker patterns of two adjacent scanning regions across the boundary acquired by the overlap scanning, and detects the pixel position of the boundary part based on the matching checker pattern. The TFT array inspection device according to claim 5 or 6.   8. The TFT according to claim 7, wherein the charged particle beam source and the scanning control unit divide and scan the inspection region into a plurality of scanning regions and perform overlapping scanning at a boundary between adjacent scanning regions. 9. Array inspection equipment.