Patent Publication Number: US-2022238396-A1

Title: Laser repair method and laser repair device

Description:
TECHNICAL FIELD 
     The present invention relates to a laser repair method and a laser repair device. 
     BACKGROUND ART 
     Laser repair is performed after an inspection process in a manufacturing process of a flat panel display (FPD) or the like to perform repair work on a multi-layer film substrate, such as a thin film transistor (TFT), as a target by irradiating a defect part identified in the inspection process with a laser beam. The laser repair is typically performed through manual operations of highly skilled operators since the shape of the defect part that is a target of work differs for each defect part and it is necessary to change working conditions and the like for each defect part. 
     Meanwhile, automation of a part of the repair process through the use of an image processing technique has been proposed. According to a technique in the related art, a defect image obtained by imaging an inspection target area is collated with a reference image with no defect to detect a defect part, and designation and the like of a work position and a work range, which are to be irradiated with the laser beam, are performed for the detected defect on the basis of content of an input command (see PTL 1 below, for example). 
     CITATION LIST 
     Patent Literature 
     [PTL 1] Japanese Patent Application Publication No. 2008-188638 
     SUMMARY OF INVENTION 
     Technical Problem 
     In a case in which laser repair is performed on a multi-layer film substrate as a target through manual operations, it is necessary to work only on a defect part without damaging a peripheral layer or an underlayer of the defect part. Operators recognize the defect part identified in the inspection process and a layer structure in the surroundings thereof, define a necessary minimum work range on the basis of their experience, and perform the operations while appropriately selecting working conditions (a laser work recipe) on the basis of information regarding the recognized layer structure. Therefore, the operations inevitably take a long time, and skills of the operators also affect repair quality. 
     Also, in a case in which a part of the repair process is automated through the use of the image processing technique as in the technique in the related art, it is not possible to obtain the information regarding the defect part and the layer structure in the surroundings thereof merely from a two-dimensional image of the surface, and a work process is thus performed under constant working conditions even when there are differences in an underlayer or variations in a layer thickness. Therefore, there may be a problem that the work is insufficiently performed, or the work is excessively performed, and this leads to a failure of the repair, or to inability of performing satisfactory repair. 
     The present invention was proposed to address such circumstances. In other words, objects of the present invention are to enable automation of laser repair to improve operation efficiency, to enable acquisition of constant repair quality independently of an operator&#39;s skill, to enable satisfactory repair even in a case in which there are differences in an underlayer or variations in a film thickness, and the like. 
     Solution to Problem 
     In order to solve such a problem, the present invention includes the following configurations. 
     There is provided a laser repair method including: a repair process of performing repair work by setting a laser radiation range for a defect part in a multi-layer film substrate and irradiating the defect part with a laser beam under set laser working conditions, in which, in the repair process, spectrum data of the defect part is acquired, and the laser working conditions of the laser beam, with which the defect part is to be irradiated, are set using a neural network after learning on the basis of the spectrum data, and the neural network has undergone machine learning using, as learning data, measurement data including multi-layer film structure data, spectrum data of each multi-layer film structure, and laser working experimental data of each multi-layer film structure. 
     There is provided a laser repair device including: a repair work part that performs repair work by setting a laser radiation range for a defect part in a multi-layer film substrate and irradiating the defect part with a laser beam under set laser working conditions, in which the repair work part is adapted to acquire spectrum data of the defect part and set the laser working conditions of the laser beam, with which the defect part is to be irradiated, using a neural network after learning on the basis of the spectrum data, and the neural network has undergone machine learning using, as learning data, measurement data including multi-layer film structure data, spectrum data of each multi-layer film structure, and laser working experimental data of each multi-layer film structure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an explanatory diagram for explaining processes in a laser repair method. 
         FIG. 2  is an explanatory diagram illustrating a configuration example of a laser repair device. 
         FIG. 3  is an explanatory diagram illustrating a configuration example and a function of a spectral camera. 
         FIG. 4  is an explanatory diagram illustrating an example of a periodic pattern in a surface of a multi-layer film substrate. 
         FIG. 5  is an explanatory diagram for explaining a defect shape identifying process. 
         FIG. 6  is an explanatory diagram for explaining a repair work process. 
         FIG. 7  is an explanatory diagram illustrating learning and operations of a neural network. 
         FIG. 8  is an explanatory diagram for explaining laser scanning in the repair work process. 
         FIG. 9  is an explanatory diagram illustrating an operation flow of a laser control part in the repair work process. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference signs in different drawings represent portions with the same functions, and overlapping explanation in each drawing will appropriately be omitted. 
     A laser repair method according to an embodiment of the present invention is for a multi-layer film substrate such as a thin film transistor (TFT) and is adapted to perform repair work on a defect part by irradiating a surface thereof with a laser beam. As illustrated in  FIG. 1 , a repair process is performed after an inspection process S 1  and includes a defect position identifying process S 2 , a defect shape identifying process S 3 , and a repair work process S 4 . 
       FIG. 2  illustrates an example of a laser repair device for executing the aforementioned repair process. A laser repair device  1  includes a repair work part  1 A that irradiates a surface of a multi-layer film substrate  100  placed on a stage S moving in a horizontal plane with a laser beam L, and the repair work part  1 A is provided with an image acquiring part  2 , a laser radiation part  3 , a spectral camera  4 , a laser control part  5 , and the like. 
     The image acquiring part  2  includes, for example, a microscope  20 , a white light source  21 , an imaging camera  26 , and the like, is adapted to acquire a surface image of the multi-layer film substrate  100  via the microscope  20 , and acquires a defect part image in a case in which there is a defect part in the multi-layer film substrate  100 . The surface of the multi-layer film substrate  100  is irradiated with white incident light from the white light source  21  via a mirror  22 , a half mirror  23 , and a lens system  24 , and light reflected by the surface of the multi-layer film substrate  100  forms an image on an image plane of the imaging camera  26  via the lens system  24 , the half mirror  23 , and a half mirror  25 . The image captured by the imaging camera  26  is subjected to appropriate image processing by an image processing part  27  and is displayed as an image enlarged at an appropriate magnification on a display device  28 . 
     The laser radiation part  3  includes, for example, a laser beam source  30 , a laser scanner  32 , and the like and is adapted to irradiate the surface of the multi-layer film substrate  100  with the laser beam L through the microscope  20 . The laser beam emitted from the laser beam source  30  is incident on the microscope  20  via the laser scanner  32  configured with a mirror  31  and galvanometer mirrors  32 A and  32 B and is used to irradiate the surface of the multi-layer film substrate  100  through an optical system in the microscope  20 . 
     The spectral camera  4  is adapted to acquire a spectral image of the surface of the multi-layer film substrate  100 . The surface of the multi-layer film substrate  100  is irradiated with white incident light that has been emitted from the white light source  21  and is coaxial with the microscope  20 , and reflected light from the surface is reflected by a mirror  29  inserted into an optical axis of the microscope  20  and is then incident on the spectral camera  4 . The spectral camera  4  separates the reflected light from the surface of the multi-layer film substrate  100  and acquires spectrum data of each pixel of the spectral image. 
     Here, an optical axis of the laser beam L in the microscope  20 , an optical axis of the image acquiring part  2  in the microscope  20 , and an optical axis of the spectral camera  4  in the microscope  20  are coaxial. In this manner, it is possible to constantly set the position of the irradiation with the laser beam L in a monitor screen of the display device  28  and to obtain a monitor image of the display device  28  and a spectral image of the spectral camera  4  as coaxial images. 
     The spectral camera  4  includes, for example, a lens  40 , a slit  41 , a spectroscope  42 , and a two-dimensional sensor  43  as illustrated in  FIG. 3 , separates reflected light corresponding to one line in an X direction in a measurement target surface M into light in a vertical direction thereof by a line spectral method, and detects space information in the X direction and spectral data thereof using the two-dimensional sensor  43 . Also, one item of spectrum data is obtained for each one pixel (Xn, Yn) of resolution of the two-dimensional sensor  43  in an X-Y direction through scanning with reflected light corresponding to one line in a Y direction as needed. 
     The laser control part  5  performs control for setting a laser radiation range on a surface of the multi-layer film substrate  100  including the defect part and irradiating the defect part with a laser beam under set laser working conditions. The laser control part  5  is controlled in accordance with setting of a neural network  50  after learning. Spectrum data of each pixel of the spectral image acquired by the spectral camera  4  is input to the neural network  50 , and the neural network  50  sets laser working conditions of the laser beam with which the defect part is to be irradiated for each pixel of the spectral image on the basis of the input spectrum data. 
     The repair process (the defect position identifying process S 2 , the defect shape identifying process S 3 , and the repair process S 4 ) using the laser repair device  1  will be specifically described. The multi-layer film substrate  100  that is a target of repair here has a two-dimensional periodic pattern including a periodic pitch Px in the X direction and a periodic pitch Py in the Y direction that perpendicularly intersects the periodic pitch Px as illustrated in  FIG. 4 . The periodic pattern corresponds to a multi-layer film structure pattern in one display pixel in a case in which the multi-layer film substrate  100  is a TFT substrate for an FPD. 
     First, in the defect position identifying process S 2 , the position of the defect part is identified from a result of the inspection process S 1  performed prior to the repair process. At this time, an enlarged image acquired by the image acquiring part  2  is set to a low magnification, an image including a plurality of periodic patterns is acquired, and this is subjected to image processing using the image processing part  27  to thereby identify the aforementioned periodic pitches (Px, Py) and then identify the position of the periodic pattern where the defect part is present. Then, the optical axis of the microscope  20  is adjusted to the identified position, a magnification of enlargement is increased such that the shape of the defect part can be monitored, and an enlarged image centered on the defect part is thus obtained. 
     In the defect shape identifying process S 3 , the shape of the defect part is identified using the enlarged image centered on the defect part. At this time, the shape of the defect part is identified by the image processing part  27  comparing the periodic pattern image including the defect part with a periodic pattern image that does not include the defect part. 
     The neural network  50  can be used in the identification of the shape of the defect part as well. Specifically, a periodic pattern image (an enlarged image centered on the defect part) Gd including the defect part is input to a machine learning model  50 A after learning in the neural network  50 , and the image processing part  27  identifies a shape Fd of the defect part from a periodic pattern image Gs including the defect part on the basis of an output of the machine learning model  50 A, as illustrated in  FIG. 5 . 
     Not all the periodic patterns are formed to have the same shape, and the periodic patterns include errors of the pattern shapes. Therefore, it is difficult to accurately identify the shape of the defect part only from simple comparison of the images. It is possible to enhance accuracy of the identification of the shape of the defect part using the machine learning model  50 A after learning in the neural network  50 . The machine learning model  50 A uses, as learning data, multiple periodic pattern images Gs acquired using test substrates of the multi-layer film substrate  100  that is the target of the repair. 
     In the repair work process S 4 , first, the laser control part  5  sets the laser radiation range as illustrated in  FIG. 6  to include the shape of the defect part identified by the image processing part  27 . The laser radiation range is a scanning range of the laser scanner  32 , and in a case in which there are shapes Fd of defect parts at a plurality of separate locations, the scanning range is set to include all the locations. 
     Then, in the repair work process S 4 , spectrum data of each pixel of the defect part image acquired by the spectral camera  4  is input to the neural network  50  and the neural network  50  categorizes the input spectrum data, sections regions of the defect part image in accordance with the categories, and sets laser working conditions (a laser work recipe) for each of the sectioned regions. 
     In the example illustrated in  FIG. 6 , the defect part image with the shape Fd is sectioned into regions where the spectrum belongs to a category I, regions of a category II, and regions of a category III. A working condition  1  is set for the regions where the spectrum belongs to the category I, a working condition  2  is set for the regions where the spectrum belongs to the category II, and a working condition  3  is set for the regions where the spectrum belongs to the category III. 
     As illustrated in  FIG. 7 , spectrum data of each pixel at the position of the irradiation with the laser beam in the defect part image is input to the neural network  50  after learning, and laser working conditions for each pixel of the defect part image are output from the neural network  50  after learning. The neural network  50  after learning has an input layer  51 , an intermediate layer  52 , and an output layer  53 , the input spectra are categorized by the input layer  51 , and estimation of a multi-layer film structure model is performed by the output layer  53 . 
     In the multi-layer film structure model, models  1  to  8  as illustrated in  FIG. 7  are set in advance in one example. Here, the eight models (models  1  to  8 ) that are present as a multi-layer film structure are set as a combination of lamination of a substrate layer GL which is the lowermost layer, a first layer L 1 , a second layer L 2 , a third layer L 3 , and a fourth layer L 4  which are laminated at intermediate locations, and a work target layer LT which is the uppermost layer. Such a multi-layer film structure model is appropriately set in accordance with the type of the multi-layer film substrate  100  that is the target of repair. 
     Learning data for causing the neural network  50  to perform learning is measurement data obtained using test substrates with the same multi-layer film structure as that of the multi-layer film substrate  100  that is the target of repair as illustrated in  FIG. 7 . The measurement data is multi-layer film structure data (such as a film thickness of each layer pattern of the multi-layer film), spectrum data of each multi-layer film structure (spectrum data of each pixel in the defect part image with the periodic pattern), laser working experimental data of each multi-layer film structure (a laser work recipe for when the work target layer is removed through irradiation with a laser), and the like, and these are measured in advance for each of periodic patterns of the multiple test substrates. 
     As illustrated in  FIG. 8 , in regard to execution of the repair in the repair work process S 4 , raster scanning within the laser radiation range (scanning range) is performed by the laser scanner  32 , and only in a case in which the scanning position of lateral scanning is located in the shape Fd of the defect part, an output of the laser beam is turned on as illustrated by the thick line, and the work is then performed there under the working conditions set in advance for each pixel of the defect part image. In a case in which the scanning position is located out of the defect part, the output of the laser beam is turned off (or reduced) as illustrated by the dashed line. 
     Operations of the laser control part  5  in the repair work process S 4  will be described with reference to  FIG. 9 . Once the operations are started (S 40 ), the laser radiation range is set for the defect part (S 41 ), and further, laser working conditions are set for each pixel of the defect part image (S 42 ) as illustrated in  FIG. 6 . In the setting, the inside of the shape Fd of the defect part is sectioned for each laser working condition in advance as illustrated in  FIG. 6 . 
     Thereafter, once laser scanning is started (S 43 ), whether or not the scanning position (the position of the irradiation with the laser beam) is in the defect part is determined (S 44 ), and the laser beam is turned off (S 45 ) in a case in which the scanning position is out of the defect part (S 44 : NO), or the laser beam is turned on (S 46 ) if the scanning position is in the defect part (S 44 : YES). At this time, the irradiation with the laser beam is performed under the laser working conditions set in advance. Such laser scanning (S 43 ) is continued until an end point is detected (S 47 : NO). Then, in a case in which the repair work for the defect part has ended, and the end point has been detected (S 47 : YES), the operations of the laser control part  5  are ended (S 48 ). 
     According to the laser repair method using such a laser repair device  1 , it is possible to recognize the multi-layer film structure of the multi-layer film substrate  100  that is a target of repair, then to extract a defect part, and to irradiate only the defect part with a laser beam under appropriate working conditions. Also, such repair work can be automatically performed. In this manner, it is possible to improve operation efficiency as compared with operator&#39;s manual operations and to obtain constant repair quality independently of an operator&#39;s skill. Also, even in a case in which there are differences in an underlayer of the work target layer or variations in a film thickness of the multi-layer film structure, it is possible to appropriately perform repair work only on the defect part without damaging the peripheral layer or the underlayer of the defect part in the automation of the laser repair. 
     Although embodiments of the present invention have been described in detail with reference to the drawings, specific configurations are not limited to the embodiments, and modifications and the like in design without departing from the gist of the present invention are also included in the present invention. Also, the aforementioned embodiments can be combined by applying the techniques to one another as long as there are no particular conflicts or problems in purposes, configurations, and the like. 
     REFERENCE SIGNS LIST 
     
         
           1  Laser repair device 
           1 A Repair work part 
           2  Image acquiring part 
           20  Microscope 
           21  White light source 
           22 ,  29 ,  31  Mirror 
           23 ,  25  Half mirror 
           24  Lens system 
           26  Imaging camera 
           27  Image processing part 
           28  Display device 
           3  Laser radiation part 
           30  Laser beam source 
           32  Laser scanner 
           32 A,  32 B Galvanometer mirror 
           4  Spectral camera 
           40  Lens 
           41  Slit 
           42  Spectroscope 
           43  Two-dimensional sensor 
           5  Laser control part 
           50  Neural network 
           50 A Machine learning model 
           51  Input layer 
           52  Intermediate layer 
           53  Output layer 
           100  Multi-layer film substrate 
         S Stage 
         L Laser beam