Patent Publication Number: US-6712666-B2

Title: Fabrication method of flat panel display comprising address line with mending layer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of, and claims the priority benefit of, U.S. application Ser. No. 09/767,340 filed on Jan. 23, 2001, now U.S. Pat. No. 6,515,301. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates in general to a structure and a fabrication method of a flat panel display comprising address lines. More particularly, this invention relates to a structure and a fabrication method of a flat panel display comprising address lines having mending layers. 
     2. Description of the Related Art 
     In the operation of a flat panel display, two orthogonal address lines, namely, scan lines and data lines, are used to control the pixels arranged in a matrix for image display. The scan lines and the data lines are perpendicular to each other. Each intersection of the scan lines and the data lines is located near by a pixel. During the operation of the flat panel display, each scan line is driven sequentially, and the status of each corresponding pixel, that is, the image shown on the flat panel display, is changed according to the transmission signal from each data line. 
     The scan lines and data lines have to be long enough to cross the whole display area of the flat panel display device. Due to certain amount of inevitable defects or contamination, defective scan lines or data lines are often found on the substrate. As a consequence, pixels connected to those defective lines could not receive data signal sand display properly. Accordingly, some mending methods are proposed. 
     For example, when one of the data lines is broken, a metal line deposited around the display area is welded and electrically connected with the two terminals of the broken data line. Accordingly, all pixels along the broken data line receive data signal at the same time from both terminals. However, this method might induce higer stray capacitance and resistance As a result, pixels connected with the broken data line would abnormally operat. That is, the overall image quality of the flat panel display is degraded. In addition, if a defect happens to a scan line and mended by the above-mentioned method, high stray capacitance would also cause a serious RC delay for the scan line. The RC delay would distort scan voltage waveform along the scan line result in a weak line. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method of fabricating an address line having a mending layer on a flat panel display. A substrate is provided. A first address line and a first mending layer are formed on the substrate. The first mending layer is electrically insulated from the first address line. The first mending layer is partitioned into different segments by the first address line. A first insulating layer is formed over the substrate to cover at least the first address line and the first mending layer. A second address line is formed on the first insulating layer over the first mending layer and crosses the first address line. A second insulating layer is formed over the substrate to cover at least the second address line. A second mending layer is formed on the second insulating layer over the second address line and crosses the first address line. Preferably, a coverage of the second mending layer is partly overlapped with the first mending layer at two sides of the first address line. Besides, it is preferable that the material for forming the first address line and the first mending layer is the same, and the first address line and the first mending layer are formed simultaneously. 
     In the above method, a third mending layer can further be formed over the first address line while forming the second address line. The third mending layer is electrically insulated from the second address line. 
     The present invention further provides a structure of an address line having a mending layer on a flat panel display. The structure comprises a first address line, a first mending layer, a first insulating layer, a second address line, a second insulating layer and a second mending layer. The first address line and the first mending layer are electrically insulated from each other and formed on an insulating substrate. The first mending layer is partitioned into different segments by the first address line. The first insulating layer covers at least the first address line and the first mending layer. The second address line is located on the first insulating layer over the mending layer and crosses the first address line. The second insulating layer covers at least the second address line. The second mending layer is located on the second insulating layer over the second address line and crosses the first address line. 
     The above structure further comprises a third mending layer located on the first insulating layer over the first address line and electrically insulated from the second address line. 
     In addition, in the above method and structure, the first address line includes a scan line and the second address line includes a data line. It is preferable that the second mending layer is made of a material similar to that of the pixel on the flat panel display. The second mending layer can be formed simultaneously with the pixel to simplify the fabrication process. 
     The address line having a mending layer can solve the problem of broken line on a flat panel display. As mentioned above, the first mending layer is formed under the data line in a flat panel display. When a defective point happens to the data line, the first mending layer located below the defective point is laserwelded and connected electrically with the data line. The data line is thus mended with the first mending layer. In specific case, when the defective point is located on the intersection portion of the data line over the scan line, the second mending layer is welded and electrically connected with two ends of the data line. Therefore, with the coverage of the second mending layer partly overlapping the coverage of the first mending layer on both sides of the first address line, no matter where the defective point is located on the data line, it can be easily repaired. 
     In addition, the third mending layer can be further formed over the scan line. Therefore, when a defective point happens to the scan line, the third mending layer can be welded and electrically connected with the broken scan line. 
     The first mending layer can be used to mend the broken data line thereon, the second mending layer is used to mend the broken part of the data line located at an intersection between the data line and the scan line, and the third mending layer is used to mend the underlying broken scan line. Therefore, without external bonding or wiring, the broken address lines (the data line and the scan line) can be mended to ensure a normal operation of every single pixel. The yield is thus greatly improved. 
     Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A,  2 A,  3 A and  4 A are top views showing a structure and fabrication process of address lines having mending layers of a thin film transistor (TFT) liquid crystal display; 
     FIGS. 1B and 2B are cross sectional views along the line I—I in FIGS. 1A and 2A, respectively; 
     FIG. 2C is a cross sectional view along the line III—III in FIG. 2A, 
     FIG. 2D is a cross sectional view of FIG. 2A along the line IV—IV; 
     FIG. 3B is a cross sectional view along the line V—V in FIG. 3A; 
     FIG. 4B is a cross sectional view along the line VI—VI in FIG. 4A; 
     FIG. 4C is a cross sectional view along the line VII—VII in FIG. 4A; 
     FIGS. 5-7 shows the mending condition when the address lines of thin-film transistor liquid crystal display are broken. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1A and 1B, a substrate  100 , for example, an insulating substrate, is provided. Using metal deposition and photolithography and etching processes, a gate  110 , a scan line  120  connected to the gate  110  and a mending layer  130  are formed on the substrate  100 . The mending layer  130  and the scan line  120  are electrically insulated from each other. The mending layer  130  is further partitioned into different sections by the scan line  120 . The material for forming the gate  110 , the scan line  120  and the mending layer  130  are similar. Furthermore, the gate  110 , the scan line  120  and the mending layer  130  can be formed simultaneously to simplify the fabrication process. 
     Referring to FIGS. 2A to  2 D, an insulating layer  135  is formed over the substrate  100  to cover at least the scan line  120  and the mending layer  130 . In this embodiment, the gate  110  is also covered with the insulating layer  135 . The portion of the insulating layer  135  covering the gate  110  is to be formed as the gate insulating layer in a thin film transistor. The material of the insulating layer  135  includes, for example, silicon nitride. 
     In FIG. 2D, a channel layer  137  is formed on the portion of the insulating layer  135  that covers the gate  110 . A heavily doped semiconductor layer  138  is further formed on the channel layer  137 . As shown in FIGS. 2A to  2 D, a data line  150  is then formed on the insulating layer  135 . A portion of the data line located on the heavily doped semiconductor layer  138 , denoted as  140 , is the source/drain conducting layer  140 . Meanwhile, a mending layer  160  is also formed on the insulating layer  135  aligned over the scan line  120 . The data line  150  is formed aligned over the mending layer  130  and crossing the scan line  120 . The mending layer  160  is electrically insulated from the data line  150 , and the mending layer  160  can be partitioned into different sections by the data line  150 , as shown in FIGS. 2A and 2C. 
     Referring to FIGS. 3A and 3B, a patterned passivation layer  170  is formed to cover the data line  170 , the mending layer  160 , the source/drain conducting layer  140  and the peripheral regions thereof. The passivation layer  170  comprises an opening  170  to expose a part of the source/drain conducting layer  140  to provide an electrical connection between the source/drain conducting layer  140  and the pixel electrodes formed subsequently. 
     As shown in FIGS. 4A and 4B, a mending layer  190  is formed on the passivation layer  170 , and a pixel electrode  180  is formed to electrically connect the source/drain conducting layer  140 . The mending layer  190  is aligned over the data line  150  and across the scan line  120 . Preferably, the mending layer  190  and the pixel electrode  180  are formed of the same material, for example, indium tin oxide (ITO) simultaneously. 
     Referring to FIGS. 4A to  4 C, after the above processes, in the thin film transistor liquid crystal display, the address lines include the data line  150  and the scan line  120  and the mending layers  130 ,  160  and  190 . In addition, the thin film transistor liquid display further includes the substrate  100 , the gate  110 , the insulating layers  135 , the channel layer  137 , the heavily doped semiconductor layer  138 , the source/drain conducting layer  140 , the passivation layer  170  and the pixel electrode  180 . 
     The above scan line  120 , gate  110  and mending layer  130  are formed on the substrate  100 . The mending layer  130  and the scan line  120  are electrically insulated from each other. The mending layer  130  is further partitioned into different sections by the scan line  120 . The insulating layer  130  is located on the scan line  120 , the mending layer  130  and the gate  110 . The channel layer  137  is located on the insulating layer  135  aligned over the gate  110 . The heavily doped semiconductor layer  138  is located on the channel layer  137 . The data line  150  is located on the insulating layer  130  aligned over the mending layer  130  crossing the scan line  120 . The source/drain conducting layer  140  is formed on the heavily doped semiconductor layer  138 . The mending layer  160  is located on the insulating layer  135  aligned over the scan line  120  and is electrically insulated from the data line  150 . The passivation layer  170  is located on the source/drain conducting layer  140 , the data line  150  and the mending layer  160 . The pixel electrode  180  penetrates through the passivation layer  170  to electrically connect the source/drain conducting layer  140 . The mending layer  190  is located on the passivation layer  170  aligned over the data line  150  crossing the scan line  120 . 
     In the above structure, the mending layer  160  can be made of a material for forming the data line  150  and the source/drain conducting layer  140 . The material for forming the mending layer  130  is the same as those for forming the scan line and the gate  110 . The materials for forming the mending layer  190  and the pixel electrodes are, for example, indium tin oxide. In addition, preferably, the coverage of the mending layer  130  and the coverage of the mending layer  130  partly overlap with each other to ensure every portion of the data line  150  can be mended as required. 
     In FIG. 5, as a mending layer  130  is formed under the data line  150 , when the data line  150  is broken, the broken part  190  of the data line  150  can be mended by laser welding and electrically connecting the data line  150  on both sides of the broken part  190  with the mending layer  130 . In other words, by melting portions of the data line  150 , the insulating layer  135  and the mending layer  130 , two conductive material  202  are formed between the mending layer  130  and the data line  150 . Therefore, two broken parts of data line  150  are electrically connected with each other. 
     In FIG. 6, as the mending layer  190  is formed across the scan line  120 , when the data line  150  across the scan line  120  is broken, the data line  150  can be electrically connected again by laser welding the mending layer  190  and the data line  150 . That is, portions of the mending layer  190 , the passivation layer  170  and the data line  150  are melted to electrically connect the broken parts of the data lines  150  via two conducting blocks  204  between the mending layer  190  and the data line  150  in the passivation layer  170 . Therefore, as the coverage of the mending layer  190  and the coverage of the scan line  120  partly overlap with each other, it is ensured that no matter where the broken part occurs, the data line  150  can be mended. 
     In FIG. 7, the mending layer  160  is formed over the scan line  120 . When the scan line  120  is broken, the scan line  120  at the two sides of the broken part  196  can be electrically connected again by laser welding the scan line  120 , the insulating layer  135  and the mending layer  160  into two conductive blocks  206 . Each side of the scan line  120  is thus connected with the mending layer  160  via each of the conductive blocks  206 . 
     As mentioned above, the mending layer  130  under the data line  150  can be used to mend the broken data line  150 . The mending layer  190  over the data line  150  can be used to mend the data line  150  over the scan line  120 , and the mending layer  160  can be used to mend the broken scan line  120 . Therefore, instead of using the conventional bonding or wiring via external metal line, the broken data line and scan line can be mended to maintain a normal operation of the pixels. The display quality of the display can be improved, and the products that comprise such defects can be mended easily. 
     Other embodiments of the invention will appear to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples to be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.