Abstract:
A method for manufacturing a liquid crystal display includes the following steps. First, source/drain and a bottom electrode are formed over a color filter substrate with a color filter layer. The next step forms source/drain junction regions over the source/drain. A channel region is also formed between the source/drain in this step. A gate dielectric layer and a gate are formed over the channel region and the source/drain junction regions in this step as well. Moreover, a plurality of stack layers and an upper electrode are formed over the bottom electrode in this step, too. Then, a pixel electrode is formed to electrically connect one of the source/drain and the bottom electrode. Then, a passivation layer pattern is formed to cover the source/drain, the gate, the upper electrode and the bottom electrode by backside exposure. Finally, a plurality of steps are performed to finish the liquid crystal display.

Description:
RELATED APPLICATIONS 
       [0001]    The present application is based on, and claims priority from, Taiwan Application Serial Number 95112880, filed Apr. 11, 2006, the disclosure of which is hereby incorporated by reference herein in its entirety. 
       BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates to a liquid crystal display. More particularly, the present invention relates to a method for forming thin film transistor arrays on a color filter. 
         [0004]    2. Description of Related Art 
         [0005]    Liquid crystal displays (LCD) have been widely applied in electrical products because of their high image quality, compact size, light weight, low driving voltage and low power consumption. LCDs have been introduced into portable computers, personal digital assistants and color televisions and are becoming the mainstream display apparatus. 
         [0006]    A conventional LCD includes a transistor array substrate, a color filter substrate and liquid crystals filled between the transistor array substrate and the color filter substrate. The transistor array substrate and the color filter substrate have to be aligned properly because each of the transistors on the transistor array substrate should be aligned with one of the color filters on the color filter substrate. As the size of the LCD becomes increasingly larger, aligning the transistor array substrate with the color filter substrate is increasingly more difficult. 
         [0007]    Furthermore, the LCD manufacturer takes great effort to reduce the use of masks because masks are very expensive, and steps of exposing and developing are time consuming and have many risks about aligning error. Half tone masks are developed to reduce the use of masks. However, the manufacturing cost and risks of the half tone masks are more than the conventional masks. 
         [0008]    For the forgoing reasons, there is a need for a method for manufacturing an LCD, which can reduce the use of the masks without employing half tone masks, and reduce the difficulties in aligning the transistor array substrate and the color filter substrate. 
       SUMMARY 
       [0009]    It is therefore an objective of the present invention to provide a method for manufacturing an LCD. The method can reduce the number of steps needed for manufacturing an LCD. Therefore, the cost of manufacturing the LCD is decreased and the yield rate of the LCD production is improved, too. 
         [0010]    It is another objective of the present invention to provide a method for manufacturing an LCD. The method can form thin film transistor array on a color filter substrate to solve alignment problems, which may occur when assembling the LCD. 
         [0011]    It is still another objective of the present invention to provide a method for manufacturing an LCD. The method can reduce the use of masks without employing half tone masks. Therefore, the cost of manufacturing the LCD is decreased and the yield rate of the LCD production is improved as well. 
         [0012]    In accordance with the foregoing and other objectives of the present invention, a method for manufacturing an LCD includes the following steps. First, a color filter substrate with a color filter layer positioned thereon is provided. Then, source/drain and a bottom electrode are formed over the color filter substrate. The next step forms source/drain junction regions over the source/drain. In this step, a channel region is also formed between the source/drain. A gate dielectric layer and a gate are formed over the channel region and the source/drain junction regions in this step as well. Moreover, a capacitor junction region, a capacitor semiconductor layer, a capacitor dielectric layer and an upper electrode are formed over the bottom electrode in this step, too. Then, a pixel electrode is formed above the color filter layer of the color filter substrate to connect one of the source/drain and the bottom electrode. Then, a passivation layer pattern is formed to cover the source/drain, the gate, the upper electrode and the bottom electrode by backside exposure. Then, an upper substrate with a common electrode positioned thereon is arranged parallel to the color filter substrate. Finally, liquid crystals are filled between the color filter substrate and the upper substrate. 
         [0013]    In conclusion, the invention allows the thin film transistor array of the LCD to be formed on the color filter substrate. Thus, the pixel electrodes of the array are aligned with the color filter layers of the color filter substrate when assembling the LCD. Therefore, there would be fewer difficulties in assembling the LCD than the prior art. Moreover, the present invention reduces the use of masks without employing half tone masks because backside exposure is performed for forming the passivation layer pattern. 
         [0014]    It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings, 
           [0016]      FIGS. 1A-1G  are cross sectional views showing a method for manufacturing an LCD according to one preferred embodiment of this invention; and 
           [0017]      FIGS. 2A-2G  are cross sectional views showing a method for manufacturing an LCD according to another preferred embodiment of this invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
       Embodiment I 
       [0019]    Reference is made to  FIGS. 1A-1G , which are cross sectional views showing a method for manufacturing LCD according to one preferred embodiment of this invention. 
         [0020]    In  FIG. 1A , black matrices  112 / 114 , a color filter layer  116  and a flatness layer  118  are formed over a transparent substrate  110  to provide a color filter substrate. The color of the color filter layer  116  may be red, blue or green. The flatness layer  118  may be a transparent organic material, such as a photo resistant material. 
         [0021]    Referring to  FIG. 1B , a first conductor layer  120  and a doped semiconductor layer  122  are formed over the flatness layer  118  in order. The material of the first conductor layer  120  may be molybdenum, chromium, iridium, aluminum, titanium, a combination thereof or an alloy thereof. The first conductor layer  120  may be formed by a physical vapor deposition process, such as sputtering. The material of the doped semiconductor layer  122  may be N type doped amorphous silicon. 
         [0022]    In  FIG. 1C , the doped semiconductor layer and the first conductor layer are patterned to form source/drain  132 / 134  of a thin film transistor  130 , a bottom electrode  137  of a capacitor  136  and a bottom conductive line  139  of a terminal  138  over the flatness layer  118 . As shown in  FIG. 1C , the source/drain  132 / 134  of the thin film transistor  130  are formed above the black matrix  112  of the color filter substrate. The bottom electrode  137  of the capacitor  136  is formed above the black matrix  114  of the color filter substrate. The doped semiconductor layer and the first conductor layer may be patterned by a lithography process and an etching process. 
         [0023]    In  FIG. 1D , a semiconductor layer  140 , a dielectric layer  142  and a second conductor layer  144  are formed over the source/drain  132 / 134 , the bottom electrode  137 , the bottom conductive line  139  and the flatness layer  118  in order. The material of the semiconductor layer  140  may be amorphous silicon. The material of the dielectric layer  142  may be silicon oxide, silicon nitride or a combination thereof. The dielectric layer  142  may be formed by a chemical vapor deposition process. The material of the second conductor layer  144  may be molybdenum, chromium, iridium, aluminum, titanium, a combination thereof or an alloy thereof. The second conductor layer  144  may be formed by a physical vapor deposition process, such as sputtering. 
         [0024]    In  FIG. 1E , the second conductor layer, the dielectric layer, the semiconductor layer and the doped semiconductor layer are patterned. Therefore, source/drain junction regions  150 / 151  are formed over the source/drain  132 / 134 ; a channel region  152  is formed between the source/drain  132 / 134  of the thin film transistor  130 ; a gate dielectric layer  153  and a gate  154  of the thin film transistor  130  are formed over the source/drain junction regions  150 / 151  and the channel region  152 ; a capacitor junction region  155 , a capacitor semiconductor layer  156 , a capacitor dielectric layer  157  and an upper electrode  158  of the capacitor  136  are formed over the bottom electrode  137  of the capacitor  136 ; and a terminal junction region  159 , a terminal semiconductor layer  160 , a terminal dielectric layer  161  and an upper conductive line  162  of the terminal  138  are formed over the bottom conductive line  139  of the terminal  138 . A scan line can be formed in this step to electrically connect the gate  154  of the thin film transistor  130  and the upper electrode  158  of the capacitor  136  (not shown). The second conductor layer, the dielectric layer, the semiconductor layer and the doped semiconductor layer may be patterned by a lithography process and an etching process. More specifically, the source/drain junction regions  150 / 151 , the capacitor junction region  155  and the terminal junction region  159  are ohmic contact regions to reduce the resistance of the conductors and enhance the electrical characterization of the conductors. 
         [0025]    A transparent conductive layer is deposited above the flatness layer  118 , and the transparent conductive layer is then patterned. Therefore, a pixel electrode  170  is formed above the color filter layer  116  in  FIG. 1F , and a transparent conductive line  172  of the terminal  138  is also formed above the terminal  138  in this step. The pixel electrode  170  electrically connects the drain  134  of the thin film transistor  130  and the bottom electrode  137  of the capacitor  136 . The transparent conductive line  172  of the terminal  138  is formed to electrically connect the upper conductive line  162  and the bottom conductive line  139  of the terminal  138  to solve RC-delay problems. The material of the transparent conductive layer may be indium tin oxide. The transparent conductive layer may be patterned by a lithography process and an etching process. 
         [0026]    Referring to  FIG. 1G , a passivation layer is formed over the flatness layer  118 , and then a passivation layer pattern  180  is defined to cover the source/drain  132 / 134 , the gate  154 , the upper electrode  158 , the bottom electrode  137  and the transparent conductive line  172 . The passivation layer pattern  180  may be defined by a lithography process and an etching process. However, the passivation layer pattern  180  is formed without using any masks. More specifically, the passivation layer pattern  180  is formed by backside exposure. That is, light irradiates the passivation layer from the underside of the transparent substrate  110 . Thus, a developing process can be performed to define the passivation layer pattern in the lithography process and the etching process. The black matrices  112 / 114  of the color filter substrate and the bottom conductive line  139  of the terminal  138  can shield light while the transparent substrate  110 , the color filter layer  116  and the flatness layer  118  of the color filter substrate allows light to penetrate. Thus, the color filter substrate and structures positioned thereon may be employed as a mask to form the passivation layer pattern  180  for covering the source/drain  132 / 134 , the gate  154 , the upper electrode  158 , the bottom electrode  137  and the transparent conductive line  172 . 
         [0027]    After finishing the color filter substrate, an upper substrate with a common electrode positioned thereon is arranged parallel to the color filter substrate. Then, liquid crystals are filled between the color filter substrate and the upper substrate. The present invention may also employ one drop fill method. That is, the upper substrate and the color filter substrate are assembled after the liquid crystals have been filled. 
       Embodiment II 
       [0028]    Reference is made to  FIGS. 2A-2G , which are cross sectional views showing a method for manufacturing LCD according to another preferred embodiment of this invention. 
         [0029]    In  FIG. 2A , black matrices  212 / 214 , a color filter layer  216  and a flatness layer  218  are formed over a transparent substrate  210  to provide a color filter substrate. The color of the color filter layer  216  may be red, blue or green. The flatness layer  218  may be a transparent organic material, such as a photo resistant material. 
         [0030]    Referring to  FIG. 2B , a first conductor layer  220  and a doped semiconductor layer  222  are formed over the flatness layer  218  in order. The material of the first conductor layer  220  may be molybdenum, chromium, iridium, aluminum, titanium, a combination thereof or an alloy thereof. The first conductor layer  220  may be formed by a physical vapor deposition process, such as sputtering. The material of the doped semiconductor layer  222  may be N type doped amorphous silicon. 
         [0031]    In  FIG. 2C , the doped semiconductor layer and the first conductor layer are patterned to form source/drain  232 / 234  of a thin film transistor  230 , a bottom electrode  237  of a capacitor  236  and a bottom conductive line  239  of a terminal  238  over the flatness layer  218 . As shown in  FIG. 2C , the source/drain  232 / 234  of the thin film transistor  230  are formed above the black matrix  212  of the color filter substrate. The bottom electrode  237  of the capacitor  236  is formed above the color filter layer  216  of the color filter substrate. The doped semiconductor layer and the first conductor layer may be patterned by a lithography process and an etching process. 
         [0032]    In  FIG. 2D , a semiconductor layer  240 , a dielectric layer  242  and a second conductor layer  244  are formed over the source/drain  232 / 234 , the bottom electrode  237 , the bottom conductive line  239  and the flatness layer  218  in order. The material of the semiconductor layer  240  may be amorphous silicon. The material of the dielectric layer  242  may be silicon oxide, silicon nitride or a combination thereof. The dielectric layer  242  may be formed by a chemical vapor deposition process. The material of the second conductor layer  244  may be molybdenum, chromium, iridium, aluminum, titanium, a combination thereof or an alloy thereof. The second conductor layer  244  may be formed by a physical vapor deposition process, such as sputtering. 
         [0033]    In  FIG. 2E , the second conductor layer, the dielectric layer, the semiconductor layer and the doped semiconductor layer are patterned. Therefore, source/drain junction regions  251 / 252  are formed over the source/drain  232 / 234 ; a channel region  253  is formed between the source/drain  232 / 234  of the thin film transistor  230 ; a gate dielectric layer  254  and a gate  255  of the thin film transistor  230  are formed over the source/drain junction regions  251 / 252  and the channel region  253 ; a capacitor junction region  256 , a capacitor semiconductor layer  257 , a capacitor dielectric layer  258  and an upper electrode  259  of the capacitor  236  are formed over the bottom electrode  237  of the capacitor  236 ; and a terminal junction region  260 , a terminal semiconductor layer  261 , a terminal dielectric layer  262  and an upper conductive line  263  of the terminal  238  are formed over the bottom conductive line  239  of the terminal  238 . A scan line semiconductor layer  265 , a scan line dielectric layer  266  and a conductive line  267  of a scan line  264  can be formed above the black matrix  214  in this step. The second conductor layer, the dielectric layer, the semiconductor layer and the doped semiconductor layer may be patterned by a lithography process and an etching process. More specifically, the source/drain junction regions  251 / 252 , the capacitor junction region  256  and the terminal junction region  260  are ohmic contact regions to reduce the resistance of the conductors and enhance the electrical characterization of the conductors. 
         [0034]    A transparent conductive layer is deposited above the flatness layer  218 , and the transparent conductive layer is then patterned. Therefore, a pixel electrode  270  is formed above the color filter layer  216  in  FIG. 2F , and a transparent conductive line  272  of the terminal  238  is also formed over the terminal  238  in this step. The pixel electrode  270  electrically connects the drain  234  of the thin film transistor  230  and the bottom electrode  237  of the capacitor  236 . The transparent conductive line  272  of the terminal  238  is formed to electrically connect the upper conductive line  263  and the bottom conductive line  239  of the terminal  238  to solve RC-delay problems. The material of the transparent conductive layer may be indium tin oxide. The transparent conductive layer may be patterned by a lithography process and an etching process. 
         [0035]    Referring to  FIG. 2G , a passivation layer is formed over the flatness layer  218 , and then a passivation layer pattern  280  is defined to cover the source/drain  232 / 234 , the gate  255 , the upper electrode  259 , the bottom electrode  237  and the transparent conductive line  272 . The passivation layer pattern  280  may be defined by the lithography process and an etching process. However, the passivation layer pattern  280  is formed without using any masks. More specifically, the passivation layer pattern  280  is formed by backside exposure. That is, light irradiates the passivation layer from the underside of the transparent substrate  210 . Thus, a developing process can be performed to define the passivation layer pattern in the lithography process and etching process. The black matrices  212 / 214  of the color filter substrate, the bottom electrode  237  of the capacitor  236  and the bottom conductive line  239  of the terminal  238  can shield light while the transparent substrate  210 , the color filter layer  216  and the flatness layer  218  of the color filter substrate allows light to penetrate. Thus, the color filter substrate and structures positioned thereon may be employed as a mask to form the passivation layer pattern  280  to cover the source/drain  232 / 234 , the gate  255 , the upper electrode  259 , the bottom electrode  237  and the transparent conductive line  272 . 
         [0036]    After finishing the color filter substrate, an upper substrate with a common electrode positioned thereon is arranged parallel to the color filter substrate. Then, liquid crystals are filled between the color filter substrate and the upper substrate. The present invention may also employ one drop fill method. That is, the upper substrate and the color filter substrate are assembled after the liquid crystals have been filled. 
         [0037]    As embodied and broadly described herein, the method for manufacturing an LCD according to the preferred embodiment of the invention has the following advantages. 
         [0038]    (1) The present invention allows the thin film transistor array of the LCD to be formed on the color filter substrate. Thus, the pixel electrodes of the array have been aligned with the color filter layers of the color filter substrate when assembling the LCD. Thus, the problem of bad alignment is eliminated. 
         [0039]    (2) The present invention employs backside exposure to form the passivation layer pattern. Therefore, in comparison with prior transistor array substrate manufacturing process, at least one mask is saved. 
         [0040]    (3) The present invention reduces the use of masks without employing any half tone masks. Therefore, the cost and risks of manufacturing the LCD are decreased. 
         [0041]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.