Patent Publication Number: US-7221427-B2

Title: Method of making semiconductor chips for liquid crystal display device

Description:
This application is a division of U.S. patent application Ser. No. 09/981,800, filed Oct. 19, 2001 now U.S. Pat. No. 6,680,773. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid crystal display device including two transparent substrates pasted to each other via a liquid crystal sealing space in between, with a semiconductor chip mounted directly on one of the transparent substrates. The present invention also provides a method of making semiconductor chips used in such a liquid crystal display device. 
     2. Description of Related Art 
     In some liquid crystal display devices, overall size reduction and weight reduction including miniaturization of the control and driving circuits is important. In such a liquid crystal display device, a semiconductor chip that provides the control and driving circuits is mounted directly on one of the two transparent substrates included in the liquid crystal display device. 
     As shown in  FIG. 8 , according to this kind of liquid crystal display device  10 , the two transparent substrates  11 ,  12  are pasted together, via a predetermined liquid crystal sealing space in between, to provide a display region S, and one transparent substrate  11  of the two is formed with an extension  13  extending further than an edge  12   a  of the other transparent substrate  12 . On the extension  13 , a semiconductor chip  20  is mounted directly, and further, external connection terminals  30  including a plurality of terminals are disposed. The external connection terminals  30  are connected with a cable such as a flexible flat cable  60 , thereby providing the liquid crystal display device  10  with electrical connection with e.g. an external control circuit. 
     As understood from  FIG. 8 , the liquid crystal display device  10  according to this arrangement has its extension  13  formed oblong like a belt, and the semiconductor chip  20 , which is oblong and rectangular, is disposed with its longitudinal axis laid longitudinally of the extension  13 . Further, the external connection terminals  30  are disposed more outwardly than the semiconductor chip  20  and along an outer edge  13   a  of the extension  13 . 
     In such an arrangement, each of the external connection terminals  30  must have a reliable connection with the flexible flat cable  60 , mechanically as well as electrically, using solder for example. For this reason, each terminal must be given a certain minimum dimension widthwise of the extension  13 . Thus, the extension  13  requires an extended dimension L which is at least a sum of the above-mentioned dimension of the terminal, the width of the semiconductor chip  20  and a certain margin necessary for formation of a wiring pattern. This has been a reason why the liquid crystal display device  10  cannot be further miniaturized or light-weighted. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary object of the present invention to provide a liquid crystal display device capable of facilitating further reduction in the and weight. 
     Another object of the present invention is to provide a method of making semiconductor chips suitably used in such a liquid crystal display device. 
     A liquid crystal display device provided by a first aspect of the present invention is a liquid crystal display device including a first transparent substrate and a second transparent substrate pasted to each other via a liquid crystal sealing space in between, and provided with a predetermined display region, 
     wherein the first transparent substrate is integrally formed with an extension extending further than an edge of the second transparent substrate and longitudinally of the edge of the second transparent substrate, 
     wherein the extension is provided with at least one semiconductor chip having a longitudinal axis laid longitudinally of the extension, and 
     wherein the extension is formed with an external connection terminal region including a plurality of terminals, the external connection terminal region not overlapping the semiconductor chip widthwise of the extension. 
     According to a preferred embodiment, the semiconductor chip includes a plurality of semiconductor chips. 
     Also, according to the preferred embodiment, the semiconductor chips are spaced from each other longitudinally of the extension, and the external connection terminal region is between the semiconductor chips. 
     Further, according to the preferred embodiment, the semiconductor chip includes a first semiconductor chip incorporating a driver analog circuit and a second semiconductor chip incorporating a control circuit and/or a logic circuit which includes a storage circuit and so on. 
     According to another preferred embodiment, the display region is divided into a first display portion and a second display portion. The semiconductor chip includes a first semiconductor chip serving the first display portion and a second semiconductor chip serving the second display portion. 
     According to another preferred embodiment, a circuit pattern formed in the first semiconductor chip and a circuit pattern formed in the second semiconductor chip are symmetric to each other. 
     According to any of the liquid crystal display devices having one of the arrangements described above, the semiconductor chip(s) and the external connection terminal region do not overlap each other widthwise of the extension. Therefore, it becomes possible to save the width of the extension, and as a result, further size reduction and weight reduction of the liquid crystal display device can be promoted. 
     A second aspect of the present invention provides a method of making a first semiconductor chip and a second semiconductor chip for a liquid crystal display device having a display region divided into a first display portion and a second display portion, the first semiconductor chip serving the first display portion, the second semiconductor chip serving the second display portion, 
     the method comprising wafer processes using a plurality of masks in making the first semiconductor chip and the second semiconductor chip, 
     a mask for use in a wafer process for the first semiconductor chip being-turned over to be a mask for use in a wafer process for the second semiconductor chip. 
     Other characteristics and advantages of the present invention will become clearer from the following description of embodiments to be presented with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overall perspective view showing an outline arrangement of a liquid crystal display device according to a first embodiment of the present invention. 
         FIG. 2  is an overall perspective view showing a detail of the liquid crystal display device in  FIG. 1 . 
         FIG. 3  is a perspective view showing pad layout in a first semiconductor chip and in a second semiconductor chip used in the liquid crystal display device presented in  FIG. 1  and  FIG. 2 . 
         FIG. 4  is a perspective view showing part of a making process of the first semiconductor chip. 
         FIG. 5  is a perspective view showing part of a making process of the second semiconductor chip. 
         FIG. 6  is an overall perspective view showing an outline arrangement of a liquid crystal display device according to a second embodiment of the present invention. 
         FIG. 7  is an overall perspective view showing an outline arrangement of a liquid crystal display device according to a third embodiment of the present invention. 
         FIG. 8  is an overall perspective view showing a convention. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereinafter, preferred embodiments of the present invention will be described specifically, with reference to  FIG. 1  to  FIG. 7 . It should be noted here that throughout these drawings, members and portions equivalent to those in the convention shown in  FIG. 8  are given the same reference codes. 
       FIG. 1  through  FIG. 3  show a first embodiment of a liquid crystal display device  10  according to the present invention. As shown in  FIG. 1  and  FIG. 2 , the liquid crystal display device  10  includes a first transparent substrate  11  and a second transparent substrate  12 . The first transparent substrate  11  and the second transparent substrate  12  are each rectangular in a plan view, and are pasted to each other, sandwiching a liquid crystal sealing space formed in between. The first transparent substrate  11  is integrally formed with an extension  13  extending outwardly by a dimension L beyond an edge  12   a  of the second transparent substrate  12 . The extension  13  is oblong rectangular along the edge  12   a  of the second transparent substrate  12 . 
     Semiconductor chips  20 A,  20 B which incorporate predetermined circuitry for controlling and driving the liquid crystal display device  10  are mounted directly on the extension  13 . The semiconductor chips have their respective main surfaces faced down, and the mounting is made directly via e.g. anisotropic electric conductor. Further, external connection terminals  30  including a plurality of terminals are disposed along an outer edge  13   a  of the extension  13 . 
     The semiconductor chips  20 A,  20 B are disposed so that their respective longitudinal axis run longitudinally of the extension  13 . Further, according to the present invention, these semiconductor chips  20 A,  20 B are disposed so as not to overlap with the external connection terminals  30  widthwise of the extension  13 . 
     According to the first embodiment, the display region S is divided into two portions, i.e. a first display portion S 1  which is the left half, and a second display portion S 2  which is the right half. With this construction, two semiconductor chips are used. Specifically, the first display portion S 1  is controlled and driven by the first semiconductor chip  20 A, and the second display portion S 2  is controlled and driven by the second semiconductor chip  20 B. The first semiconductor chip  20 A and the second semiconductor chip  20 B are spaced from each other by a predetermined distance on the extension  13 , and the external connection terminals  30  are provided between the first semiconductor chip  20 A and the second semiconductor chip  20 B. This arrangement will be described more specifically. 
     On an inner surface of the first transparent substrate  11 , a plurality of segment electrodes  41 ,  42  made of an electrically conductive transparent material such as ITO are formed to extend in a vertical direction. The segment electrodes are grouped into two, i.e. one for the first display portion and the other for the second display portion. The segment electrodes  41 , which is for the first display portion, has segment wiring patterns  41   a  gathering at a mounting position  14  of the first semiconductor chip  20 A on the extension  13 . The segment electrodes  42 , which is for the second display portion, has segment wiring patterns  42   a  gathering at a mounting position  15  of the second semiconductor chip  20 B on the extension  13 . 
     On an inner surface of the second transparent substrate  12 , a plurality of common electrodes  51 ,  52  made of an electrically conductive transparent material are formed to extend in a lateral direction, perpendicularly to the segment electrodes  41 ,  42 . The common electrodes are grouped into two, i.e. a first group  51  for an upper portion of the display region S, and a second group  52  for a lower portion thereof. The first group  51  has common wiring patterns  51   a  which run through the left portion of the display region S, go on to the first transparent substrate  11 , and then gather at the mounting position  14  of the first semiconductor chip  20 A on the extension  13 . The second group  52  has common wiring patterns  52   a  which run through the right portion of the display region S, go on to the first transparent substrate  11 , and then gather at the mounting position  15  of the second semiconductor chip  20 B on the extension  13 . 
     Each of the first semiconductor chip  20 A and the second semiconductor chip  20 B has, as shown in  FIG. 3 , a main surface formed with a predetermined circuit pattern (not illustrated) and electrode pads  21 ,  22 ,  23  along circumferential edges. The layout of these electrode pads  21 ,  22 ,  23  facilitates appropriate connection with each of the segment wiring patterns  41   a ,  42   a , and common wiring patterns  51   a ,  52   a . Specifically, in  FIG. 3 , the electrode pads  21  are those for the segments, and the electrode pads  22  are those for the commons. The layout pattern of these electrode pads  21 ,  22  in the first semiconductor chip  20 A and that in the second semiconductor chip  20 B are symmetrical to each other. The electrode pads  23  in  FIG. 3  are for supply of power as well as controlling and signaling inputs. These input pads are connected to the external connection terminals  30  formed between the two semiconductor chips  20 A,  20 B on the extension  13 , via unillustrated wiring patterns formed on the extension  13 . The external connection terminals  30  are soldered to a flexible flat cable  60  for example, where by the liquid crystal display device  10  is connected to an external controlling circuit. 
     The wiring patterns  41   a ,  42   a ,  51   a ,  52   a , the external connection terminals  30 , and the wiring patterns for connecting the external connection terminals  30  with the semiconductor chips  20 A,  20 B can be formed simultaneously on the extension  13 , when the segment electrodes  41 ,  42  are formed on the inner surface of the first transparent substrate  11  by means of a photo-litho process. 
     With the above-described arrangement, on the extension  13 , the semiconductor chips  20 A,  20 B are disposed so as not to overlap with the external connection terminals  30  widthwise of the extension  13 . Thus, as clearly shown in  FIG. 2 , it becomes possible to dispose the semiconductor chips  20 A,  20 B and the external connection terminals  30  in a row, longitudinally of the extension  13 . This enables to save the extended dimension L of the extension  13 , and as a result, size reduction and weight reduction of the liquid crystal display device  10  can be further promoted. 
     Also, according to the first embodiment, two semiconductor chips are used, i.e. the first semiconductor chip  20 A serves the left half of the display region, and the second semiconductor chip  20 B serves the right half. This enables to reduce the width of the semiconductors themselves, contributing further to the reduction of the extended dimension L of the extension  13 . In addition, density in the segment wiring patterns  41   a ,  42   a  for connection to the semiconductor chips  20 A,  20 B respectively can now be decreased, which means that a dimension D, i.e. a distance from the semiconductor chips  20 A,  20 B to the display region S, can be reduced. This also enables to save the extended dimension L of the extension  13 , making possible to further promote the size reduction and weight reduction of the liquid crystal display device  10 . 
     Now that it has become possible to reduce the size of the liquid crystal display device  10 , particularly of the extension  13  on which the semiconductor chips  20 A,  20 B are mounted, this offers an advantage in the following case for example. Specifically, in a portable telephone in which a microphone and various button switches are disposed to sandwich the liquid crystal display, the microphone or the button switches can be disposed more closely to the liquid crystal display. This contributes greatly to further size reduction of the portable phone. 
     As described earlier, the circuit pattern formed on the main surface of the first semiconductor chip  20 A and that of the second semiconductor chip  20 B according to the first embodiment are mirror symmetric to each other. Such semiconductor chips  20 A,  20 B can be made efficiently through a method to be described here below. 
     Specifically, when making this kind of semiconductor chips, a wafer is divided into a matrix of plural regions. These regions are then simultaneously formed with respective circuit patterns, electrodes and so on, and then, a dicing process cuts the wafer into each individual unit semiconductor chip. In such a wafer process, the circuit pattern formation for each region is achieved by means of so called mask work, i.e. a photosensitive process that uses a mask. 
     As has been described earlier, the circuit pattern formed on the main surface of the first semiconductor chip  20 A and that of the second semiconductor chip  20 B according to the first embodiment are symmetric to each other. Therefore, even if the circuit patterns are different from each other, these two patterns can be made with a same mask M, and through the following method. Specifically, as shown in  FIG. 4 , the mask M is first used with its top surface facing upward, to be placed on a wafer W 1  to perform a mask work for the first semiconductor chip. Then, as shown in  FIG. 5 , the mask M is turned over to make its top surface facing downward, to be placed on a wafer W 2  to perform a mask work for the second semiconductor chip. Thus, necessary mask works can be performed for the formation of circuit patterns and electrodes on each of the regions in the wafers W 1 , W 2 . Then, by cutting the wafers into each individual region through the dicing process, the first semiconductor chip  20 A and the second semiconductor chip  20 B can be made efficiently. 
     It should be appreciated that turning the mask M includes, in its scope of meaning, making of a new mask by reversing mask data. 
       FIG. 6  shows a second embodiment of the liquid crystal display device according to the present invention. This embodiment is the same as the first embodiment in that a liquid crystal display device  10  includes a first transparent substrate  11  and a second transparent substrate  12  each rectangular in a plan view, that these substrates are pasted to each other via a liquid crystal sealing space, and that the first transparent substrate  11  is formed with an extension  13  extending outwardly beyond an edge  12   a  of the second transparent substrate  12 . 
     According to the second embodiment, there is only one semiconductor chip  20  to be mounted on the extension  13 . Therefore, in this case, the semiconductor  20  controls and drives the entire display region S. With this arrangement, the external connection terminals  30 , which are disposed along the circumferential edges of the extension  13  and are to be connected to the flexible flat cable  60  and so on, are disposed in the same way as in the first embodiment, i.e. so as not to overlap the semiconductor chip  20  widthwise of the extension  13 . With this arrangement again, it becomes possible to dispose the semiconductor chip  20  and the external connection terminals  30  in a row, longitudinally of the extension  13 , enabling to save the extended dimension L of the extension  13 , and thereby enabling to promote size reduction and weight reduction of the liquid crystal display device  10 . 
       FIG. 7  shows a third embodiment of the liquid crystal display device according to the present invention. 
     This embodiment differs from the second embodiment in that the semiconductor chip  20  is divided into a first semiconductor chip  20   a  which is formed only with a driver analog circuit, and a second semiconductor chip  20   b  which is formed only with a logic circuit that controls the first semiconductor chip  20   a . Otherwise, all the other aspects are the same as the second embodiment. In this arrangement again, the external connection terminals  30  to be connected to the flexible flat cable  60  and so on are disposed so as not to overlap the semiconductor chips  20   a ,  20   b , in the widthwise direction of the extension  13 . Thus, it becomes possible to dispose the semiconductor chips  20   a ,  20   b  and the external connection terminals  30  in a row, longitudinally of the extension  13 , enabling to save the extended dimension L of the extension  13 , and thereby enabling to promote size reduction and weight reduction of the liquid crystal display device  10 . 
     According to the third embodiment, there is an advantage that the first semiconductor chip  20   a , which should have the output pads for the segments and/or the commons formed at a required pitch, can be made at a low circuit fineness. Another advantage is that the second semiconductor chip  20   b , which may not be formed with the output pads for the segments and/or the commons, can be made at a high circuit fineness. Further, the first semiconductor chip  20   a  can be small, to the extent that it does not include the logic circuit, and likewise the second semiconductor chip  20   b  can be small, to the extent that it is not formed with the output pads for the segments and/or the commons. These allow efficient making of the semiconductor chips  20   a ,  20   b  from wafers. In addition, because of the small size, the semiconductor chips  20   a ,  20   b  do not occupy a large area on the extension  13 , and in particular the size of the width can be reduced, which leads to further reduction of the extended dimension L of the extension  13 . 
     Obviously, the present invention is not limited to the embodiments thus far described above, and any variation within the scope of each claim is included in the scope of the present invention.