Abstract:
An array substrate for a reflective liquid crystal display device, including a gate line and a data line defining a pixel region by crossing each other; a switching element at a crossing portion of the gate line and the data line; a first passivation layer covering the switching element and the data line; and formed of an inorganic insulating material; a reflective electrode on the first passivation layer, and connected to the switching element; and a second passivation layer on the reflective electrode. The second passivation layer being formed of an organic insulating material.

Description:
This application is a Divisional of application Ser. No. 10/028,759, filed on Dec. 28, 2001, now U.S. Pat. No. 6,833,883, and for which priority is claimed under 35 U.S.C. § 120; and this application claims priority of Application No. 2001-7097 and 2001-30699 filed in Korea on Feb. 13, 2001 and Jun. 1, 2001, under 35 U.S.C. § 119; the entire contents of all are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to liquid crystal display devices, and more particularly, to an array substrate for reflective and transflective liquid crystal display devices. 
     2. Description of the Background Art 
     Generally, a reflective liquid crystal display device does not need to equip an additional light source such as a back light because it can substitute an external light source for the back light. A transflective liquid crystal display device has both properties of the reflective liquid crystal display device and a transmissive liquid crystal display device. Because the transflective liquid crystal display device utilizes both of the back light and the external light source, it can save power consumption. 
       FIG. 1  illustrates a liquid crystal panel for a conventional transflective liquid crystal display device. The conventional transflective liquid crystal display device  11  has an upper substrate  15  that includes a color filter  18  a transparent common electrode  13  and a lower substrate  21  that includes a pixel region “P”, a pixel electrode  19 , thin film transistor and an array of gate lines  25  and data lines  27 . The color filter  18  includes a black matrix  16  and sub-color filters R, G and B. The pixel electrode  19  has a transmission portion “A” and a reflection portion “PR”. Liquid crystal  23  is interposed between the upper substrate  15  and the lower substrate  21 . The lower substrate  21  is also referred to as an array substrate with thin film transistors “T”, switching elements, arranged in a matrix on the array substrate  21 . A plurality of horizontal gate lines  25  and a plurality of vertical data lines  27  cross each other defining the pixel region “P”. If the transparent pixel electrode  19  and the transmission portion “A” are omitted from the transflective liquid crystal display device, it becomes a reflective liquid crystal display device. 
       FIG. 2  is a plan view illustrating a partial array substrate for a conventional reflective liquid crystal display device. As shown in the figure, a plurality of gate lines  25  and a plurality of data lines  27  cross each other defining a pixel region “P”. A thin film transistor “T” is formed at a crossing portion of the gate line  25  and the data line  27 . The thin film transistor “T” usually includes a gate electrode  32 , a source electrode  33 , a drain electrode  35  and an active layer  34 . A pixel electrode  19  is formed in the pixel region “P” and the thin film transistor “T” connected to the drain electrode  35  drives the liquid crystal  23  of  FIG. 1 . A reflective electrode, which is formed of opaque conductive metal having a high reflexibility, is substituted for the pixel electrode  19  in the reflective liquid crystal display device. The opaque conductive metal is selected from a group consisting of aluminum (Al) and aluminum alloys (AlNd, for example), for example. 
     Because the reflective liquid crystal display device uses an external light source, incident light from the external light source passes through the upper substrate (not shown) and is then reflected at the reflective electrode  10  on the array substrate  21 . The reflected light subsequently passes through the liquid crystal and thereby polarization properties of the light are changed according to birefringence properties of the liquid crystal. Color images can be displayed when the light passing through the liquid crystal colors the color filter. 
       FIG. 3  is a cross-sectional view taken along III-III of  FIG. 2  according to the conventional art. As shown in the figure, a gate electrode  32  and a gate line  25  of  FIG. 2  are formed on a substrate  21 . A gate insulating layer  41  is formed on the substrate  21  and on the gate electrode  32 . An active layer  34  is formed on the gate insulating layer  41  and partially overlapped with a source electrode  33  and a drain electrode  35 . The source electrode  33 , the drain electrode  35  and the data line  27  are formed on the active layer  34 . A thin film transistor includes the gate electrode  32 , the source electrode  33 , the drain electrode  35  and the active layer  34 . A passivation layer  43  made of insulating material is formed on the thin film transistor. The passivation layer  43  is subsequently patterned to form a drain contact hole  45  exposing a part of the drain electrode  35 . A reflective electrode  19  contacts the drain electrode  35  through the drain contact hole  45 . The material for the reflective electrode  19  is selected from a group including aluminum (Al) and aluminum alloy (AlNd, for example), etc. 
       FIG. 5  is a cross-sectional view taken along line V-V of  FIG. 4  according to the conventional art. A thin film transistor “T” including a gate electrode  32 , a source electrode  33 , a drain electrode  35  and an active layer  34  is formed and a first passivation layer  43  is formed on the thin film transistor “T”. The first passivation layer  43  is formed by depositing a transparent organic insulating material such as benzocyclobutene (BCB) and acrylic resin. A drain contact hole  45  that exposes a part of the drain electrode  35  is formed and a etching hole  53  is formed by etching the first passivation layer  43  corresponding to the transmission hole  53  in the pixel region “P”. A reflective electrode  19   a  that contacts the drain electrode  35  through the drain contact hole  45  is formed in the pixel region “P”. The reflective electrode  19   a  is formed of aluminum (Al) and aluminum alloys (AlNd, for example), etc. A second passivation layer  47  is formed on the reflective electrode  19   a  and patterned to expose the reflective electrode  19   a  corresponding to the drain contact hole  45 . The second passivation layer  47  is formed of insulating material such as silicon oxide (SiO 2 ) or silicon nitride (SiN X ), for example. A transparent pixel electrode  19   b  that contacts the exposed reflective electrode  19   a  through the patterned second passivation layer  47  is formed on the second passivation layer  47 . 
     Several masks for patterning array elements of the array substrate are used in the manufacturing of the conventional reflective and transflective liquid crystal display device. An align key for accurate aligning of the mask and the substrate is formed on the corner of the substrate simultaneously with the gate line or the data line forming process. The shape of the align key has unevenness. Accordingly, a detector aligns the mask and the substrate by irradiating light onto the uneven surface of the align key and sensing the light reflected from the surface of the align key. 
       FIG. 6  is a plan view illustrating a partial array substrate having a coplanar type polysilicon thin film transistor for a conventional transflective liquid crystal display device. A gate line  71  and a data line  84  cross each other defining a pixel region “P” and a thin film transistor “T” is formed at a crossing portion of the gate line  71  and the data line  84 . The thin film transistor “T” is a polysilicon thin film transistor that includes a polysilicon active layer and has a coplanar structure in which a gate electrode  70  is formed under a source electrode  80  and a drain electrode  82 . A gate pad  74  and a data pad  86 , which receive an external signal, are formed respectively at one end of the gate line  71  and the data line  84 . The gate pad  74  and the data pad  86  respectively contact a gate pad terminal  94  and a data pad terminal  96  that are formed of transparent conductive material. The thin film transistor “T” includes the gate electrode  70 , the source electrode  80 , the drain electrode  82  and an active layer  66 . The active layer  66  has an active layer expanded portion  67  in the pixel region “P”. A storage line  72  is formed parallel to the gate line  71  with a same material as that of the gate line  71  and has a storage line expanded potion  73  in the pixel region “P”. The pixel electrode  63  contacts the drain electrode  82 . A storage capacitor portion “C” and a reflection portion “PR” are formed in the pixel region “P”. A reflector  102  is formed on the storage capacitor portion “C”. The rest potion of the pixel region “P” except the reflector  102  is a transmission portion “F”. 
       FIGS. 7A to 7F  are cross-sectional views taken along IV-IV, V-V, VI-VI of  FIG. 6  illustrating a fabricating sequence of an array substrate according to the related art. In  FIG. 7A , a first insulating layer  62  is formed on a substrate  60  by depositing inorganic insulating material such as silicon oxide (SiO 2 ) or silicon nitride (SiN X ) and an amorphous silicon layer  64  is formed on the first insulating layer by depositing amorphous silicon (a-Si:H). The first insulating layer  62 , referred to as a buffer layer, is for preventing an expansion of alkaline substances from the substrate  60 . The amorphous silicon layer  64  is crystallized into polysilicon by introducing a solid phase crystallization (SPC) method, a metal induced crystallization (MIC) method, a laser annealing method and a field effect metal induced crystallization (FEMIC) method. 
     In  FIG. 7B , a semi-conductor layer  66  is formed by patterning the crystallized layer and a gate insulating layer  68 , a second insulating layer, is formed on the semi-conductor layer  66 . A conductive metal layer is subsequently formed on the gate insulating layer  68 . A gate electrode  70  and a gate line  71  of  FIG. 6  are formed by patterning the deposited conductive metal layer. The semi-conductor layer  66  has a semi-conductor layer expanded portion  67  in the pixel region “P”. The gate pad  74  is formed at one end of the gate line  71 . The storage line  72  is simultaneously formed parallel to the gate line  71  and the storage line  72  has the storage line expanded portion  73  on the pixel region “P”. 
     The semi-conductor layer  66  can be divided into two regions, one is a first active region “A” and the other is a second active region “B”. The first active region “A” is a pure silicon region and the second active region “B” is an impure silicon region. The second active regions “B” are positioned at both sides of the first active region “A”. The gate insulating layer  68  and the gate electrode  70  are formed on the first active region “A”. After forming of the gate electrode  70 , ion doping is performed onto the second active region “B” to form a resistant contact layer. The gate electrode  70  serves as an ion stopper that prevents dopants from penetrating into the first active region “A”. After the ion doping is finished, the semi-conductor layer  66 , the polysilicon island, implements a specific electric characteristic, which varies with types of the dopants. If the dopant is, for example, B 2 H 6  that includes a Group III element, a doped portion of the polysilicon island  66  becomes a p-type semiconductor. Whereas, if the dopant is PH 3  that includes a Group VI element, the doped portion of the polysilicon island  66  becomes an n-type semiconductor. A proper dopant should be selected to satisfy the use of a device. After the dopant is applied onto the polysilicon island  66 , the dopant is activated. 
     In  FIG. 7C , a third insulating layer  76 , i.e, an interlayer insulator, is formed over the whole area of the substrate  60  and is patterned to form a source contact hole  78   a  and a drain contact hole  78   b . A source electrode  80  and a drain electrode  82 , which contact the second active region “B” through the source contact hole  78   a  and the drain contact hole  78   b , respectively, are formed by depositing and then patterning conductive metals such as aluminum (Al), aluminum alloys, tungsten (W), copper (Cu), chromium (Cr) and molybdenum (Mo), etc. A data line  84  that contacts the source electrode  80  is simultaneously formed and a data pad  86  is formed at one end of the data line  84 . The polysilicon thin film transistor “T” is formed through the above processes. 
     In  FIG. 7D , a fourth insulating layer  88  is formed on the whole area of the substrate  60  and then the thin film transistor undergoes a hydrogenation process. The hydrogenation process is for removing defects that occurred on the surface of the active layer  66 . A fifth insulating layer  90  is formed on the fourth insulating layer  88  using transparent organic insulating material such as benzocyclobutene (BCB) or acrylic resin. A first drain contact hole  92  exposing the drain electrode  82 , a gate pad contact hole  91  exposing the gate pad  74  and a data pad contact hole  95  exposing the data pad  86  are formed by patterning simultaneously the laminated layers. 
     In  FIG. 7E , a pixel electrode  93  that contacts the exposed drain electrode  82  and is extended to the pixel region, a gate pad terminal  94  that contacts the exposed gate pad and a data pad terminal  96  that contacts the exposed data pad are formed on the fifth insulating layer  90  using transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO), for example. 
     In  FIG. 7F , a sixth insulating layer  98  is formed on the whole area of the substrate  60  using silicon oxide (SiO 2 ) or silicon nitride (SiN X ), for example. A second drain contact hole  100  that exposes the pixel electrode  93  contacting the drain electrode  82  is formed by patterning the sixth insulating layer  98 . A reflective electrode  102 , which contacts the exposed pixel electrode  93 , is formed on the sixth insulating layer  98  using conductive metal such as aluminum (Al) or aluminum alloys, for example. A first etching hole  104  that exposes the gate pad terminal  94  and a second etching hole  106  that exposes the data pad terminal  96  are formed by patterning the sixth insulating layer  98 . The reason for exposing the gate pad terminal  94  and the data pad terminal  96  in the last process is to prevent the pixel electrode  93  and the reflective electrode  102  from being etched together in etching solution during an etching process for the reflective electrode  102 . 
     Conventional reflective or transflective liquid crystal display devices have some problems described as follows. First, because a reflective electrode is formed on an organic insulating layer such as benzocyclobutene (BCB) and the contact property of the reflective electrode and the benzocyclobutene (BCB) layer is not good, the reflective electrode may not be stably deposited on the organic insulating layer. This lacks of stability lowers electric properties of a liquid crystal panel. Second, when a sputtering process is used for forming the reflective electrode on the benzocyclobutene (BCB), accelerated electrons collide into the surface of the benzocyclobutene (BCB) and separate the benzocyclobutene (BCB) particles from the surface, which produces benzocyclobutene (BCB) particles in a deposition chamber. The benzocyclobutene (BCB) particles in the deposition chamber contaminate the deposition chamber. Lastly, an align key may not be detected by a detecting apparatus if the benzocyclobutene (BCB) is deposited on the substrate and covers the align key. Accordingly, alignment error of a mask and the substrate may be occurred during a light exposing process for patterning the reflective electrode. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to an array substrate for reflective and transflective liquid crystal display devices and a manufacturing method of the array substrate for reflective and transflective liquid crystal display devices that substantially obviates one or more of problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide an array substrate for a reflective liquid crystal display device, wherein a reflective electrode is not formed on organic insulating material such as benzocyclobutene (BCB), but formed on inorganic insulating material such as silicon nitride (SiN X ) to improve contact property of the reflective electrode and to prevent a deposition chamber from being contaminated with particles of the organic insulating material. 
     Another object of the present invention is to provide a manufacturing method of an array substrate for a reflective liquid crystal display device. 
     Another object of the present invention is to provide an array substrate for a transflective liquid crystal display device, wherein a reflective electrode is not formed on organic insulating material such as benzocyclobutene (BCB), but formed on inorganic insulating material such as silicon nitride (SiN X ) to improve contact property of the reflective electrode and to prevent a deposition chamber from being contaminated with particles of the organic insulating material. 
     Another object of the present invention is to provide a manufacturing method of an array substrate for a transflective liquid crystal display device. 
     Another object of the present invention is to provide an array substrate for a transflective liquid crystal display device having a barrier layer between an organic insulating layer and a reflector to improve contact property of the reflective electrode and to prevent a deposition chamber from being contaminated with particles of the organic insulating material. 
     Another object of the present invention is to provide a manufacturing method of an array substrate for a transflective liquid crystal display device having a barrier layer between an organic insulating layer and a reflector. 
     To achieve these and other advantages, one embodiment of the present invention, an array substrate for a reflective liquid crystal display device includes a gate line and a data line defining a pixel region by crossing each other, a switching element at a crossing portion of the gate line and the data line, a first passivation layer covering the switching element and the data line, the first passivation layer being formed of inorganic insulating material, a reflective electrode on the first passivation layer, the reflective electrode being connected to the switching element, and a second passivation layer on the reflective electrode, the second passivation layer being formed of organic insulating material. The reflective electrode is formed of conductive metal material such as aluminum (Al) or aluminum alloys, for example. The switching element is a thin film transistor including a gate electrode, a source electrode, a drain electrode and an active layer. The first passivation layer is desirably formed of silicon nitride (SiN X ). The second passivation layer is formed of organic insulating material such as benzocyclobutene (BCB) or acrylic resin, for example. 
     In another aspect, a preferred embodiment of a manufacturing method of an array substrate for a reflective liquid crystal display device includes the steps of forming a gate line and a data line that define a pixel region by crossing each other; forming a switching element at a crossing portion of the gate line and the data line; forming a first passivation layer covering the switching element and the data line; the first passivation layer being formed of inorganic insulating material; forming a reflective electrode on the first passivation layer, the reflective electrode being connected to the switching element; and, forming a second passivation layer on the reflective electrode. The second passivation layer being formed of organic insulating material. 
     The reflective electrode may be formed of conductive metal material such as aluminum (Al) or aluminum alloys, for example. The switching element is a thin film transistor including a gate electrode, a source electrode, a drain electrode and an active layer. The first passivation layer is preferably formed of silicon nitride (SiN X ). The second passivation layer is formed of organic insulating material such as benzocyclobutene (BCB) or acrylic resin, for example. 
     In another embodiment, an array substrate for a transflective liquid crystal display device includes a gate line and a data line defining a pixel region by crossing each other; a switching element at a crossing portion of the gate line and the data line; a first passivation layer covering the switching element and the data line and being formed of inorganic insulating material; a reflective electrode on the first passivation layer, connected to the switching element and including a transmission hole; a second passivation layer on the reflective electrode, formed of organic insulating material and patterned to expose a part of the switching element; and a transparent pixel electrode on the second passivation layer, formed in the pixel region and contacting the exposed part of the switching element. 
     The reflective electrode is formed of conductive metal material such as aluminum (Al) or aluminum alloys, for example. The switching element is a thin film transistor including a gate electrode, a source electrode, a drain electrode and an active layer. The first passivation layer is desirably formed of silicon nitride (SiN X ). The second passivation layer is formed of organic insulating material such as benzocyclobutene (BCB) or acrylic resin, for example. 
     In another embodiment, a manufacturing method of an array substrate for a transflective liquid crystal display device includes the steps of forming a gate line and a data line defining a pixel region by crossing each other; forming a switching element at a crossing portion of the gate line and the data line; forming a first passivation layer covering the switching element and the data line, the first passivation layer being formed of inorganic insulating material; forming a reflective electrode on the first passivation layer, the reflective electrode being connected to the switching element and including a transmission hole; forming a second passivation layer on the reflective electrode, the second passivation layer being formed of organic insulating material and patterned to expose a part of the switching element; and forming a transparent pixel electrode on the second passivation layer. The pixel electrode being formed in the pixel region and contacting the exposed part of the switching element. The reflective electrode is formed of conductive metal material such as aluminum (Al) or aluminum alloys, for example. The switching element is a thin film transistor including a gate electrode, a source electrode, a drain electrode and an active layer. The first passivation layer is desirably formed of silicon nitride (SiN X ). The second passivation layer is formed of organic insulating material such as benzocyclobutene (BCB) or acrylic resin, for example. 
     In another embodiment, an array substrate for a transflective liquid crystal display device includes a thin film transistor including an active layer a gate electrode and source and drain electrodes, being formed on a substrate in sequence; a gate line including a gate pad at one end of it, the gate line being connected to the gate electrode; a storage line being formed parallel to the gate line and being spaced apart from the gate line; a data line defining a pixel region by crossing the gate line, including a data pad at one end of it and being connected to the source electrode; an organic insulating layer over the thin film transistor and the data line; a barrier layer on the organic insulating layer and formed of inorganic insulating material; a reflector on the barrier layer, and a transparent pixel electrode on an inorganic insulating layer. The pixel electrode contacting the drain electrode, and the inorganic insulating layer being formed between the reflector and the pixel electrode. The array substrate for a transflective liquid crystal display device may further include a buffer layer beneath the active layer using inorganic insulating material such as silicon oxide (SiO 2 ) or silicon nitride (SiN X ), for example. The active layer is formed of polysilicon. The storage line is desirably formed with a same material as that of the gate line on a same layer as that of the gate line. The reflector is formed of conductive metal material such as aluminum (Al) or aluminum alloys, for example. The pixel electrode is formed of transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO), for example. The reflector may desirably be extended to the data line and simultaneously cover the thin film transistor. The reflector may be partially overlapped with the gate line and the gate line. The barrier layer is formed using inorganic insulating material such as silicon oxide (SiO 2 ) or silicon nitride (SiN X ), for example. The array substrate further may include an insulating layer beneath the organic insulating layer to perform a hydrogenation process of the thin film transistor. The barrier layer is desirably formed of silicon nitride (SiN X ). 
     In another embodiment, a manufacturing method of an array substrate for a transflective liquid crystal display device includes the steps of forming a thin film transistor including an active layer, a first insulating layer, a gate electrode, a second insulating layer being formed on a substrate in sequence; forming a gate line and a storage line such that, the gate line includes a gate pad at one end of it and being connected to the gate electrode; and the storage line is formed parallel to the gate line and spaced apart from the gate line; forming a data line defining a pixel region by crossing the gate line including a data pad at one end of it and being connected to the source electrode, forming a third insulating layer over the thin film transistor and the data line, the third insulating layer being formed of transparent organic insulating material; forming a fourth insulating layer on the third insulating layer, the third insulating layer being a barrier layer and being formed of inorganic insulating material; forming a reflector on the barrier layer; forming a drain contact hole over the drain electrode by depositing and patterning a fifth insulating layer on the reflector; and forming a transparent pixel electrode on an inorganic insulating layer, the pixel electrode contacting the drain electrode. The inorganic insulating layer being formed between the reflector and the pixel electrode. The array substrate for a transflective liquid crystal display device may further include a buffer layer beneath the active layer using inorganic insulating material such as silicon oxide (SiO 2 ) or silicon nitride (SiN X ), for example. The active layer is formed of polysilicon. The storage line is desirably formed with a same material as that of the gate line on a same layer as that of the gate line. The reflector is formed of conductive metal material such as aluminum (Al) or aluminum alloys, for example. The pixel electrode is formed of transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The reflector may desirably be extended to the data line and cover the thin film transistor. The reflector may be partially overlapped with the gate line and the gate line. The barrier layer is formed using inorganic insulating material such as silicon oxide (SiO 2 ) or silicon nitride (SiN X ), for example. The manufacturing method of the array substrate according to the present invention further includes forming an insulating layer beneath the organic insulating layer to perform a hydrogenation process of the thin film transistor. The barrier layer is desirably formed of silicon nitride (SiN X ). 
     These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein: 
         FIG. 1  is an exploded perspective view illustrating a liquid crystal panel for a conventional transflective liquid crystal display device; 
         FIG. 2  is a plan view illustrating a partial array substrate for a conventional reflective liquid crystal display device; 
         FIG. 3  is a cross-sectional view taken along line III-III of  FIG. 2  according to the conventional art; 
         FIG. 4  is a plan view illustrating a partial array substrate having an inverted stagger type thin film transistor for a conventional transflective liquid crystal display device; 
         FIG. 5  is a cross-sectional view taken along line V-V of  FIG. 4  according to the conventional art; 
         FIG. 6  is a plan view illustrating a partial array substrate having a coplanar type polysilicon thin film transistor for a conventional transflective liquid crystal display device; 
         FIGS. 7A to 7F  are cross-sectional views taken along lines IV-IV, V-V, VI-VI of  FIG. 6  illustrating a fabricating sequence of an array substrate according to the conventional art; 
         FIG. 8  is a plan view illustrating a partial array substrate for a reflective liquid crystal display device according to a first embodiment of the present invention; 
         FIGS. 9A to 9C  are cross-sectional views taken along III-III of  FIG. 8  illustrating a method of manufacturing an array substrate according to the first embodiment of the present invention; 
         FIG. 10  is a plan view illustrating a partial array substrate having an inverted stagger type thin film transistor for a transflective liquid crystal display device according to a second embodiment of the present invention; 
         FIGS. 11A to 11E  are cross-sectional views taken along line V-V of  FIG. 10  illustrating a fabricating sequence of an array substrate according to the second embodiment of the present invention; 
         FIG. 12  is a plan view illustrating a partial array substrate having a coplanar type polysilicon thin film transistor for a transflective liquid crystal display device according to a third embodiment of the present invention; and 
         FIGS. 13A to 13F  are cross-sectional views taken along lines IV-IV, V-V, VI-VI of  FIG. 12  illustrating a fabricating sequence of an array substrate according to the third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiment of the present invention, which is illustrated in the accompanying drawings. 
     A first embodiment of the present invention will be described hereinafter with reference to  FIG. 8  and  FIGS. 9A to 9C .  FIG. 8  is a plan view illustrating a partial array substrate for a reflective liquid crystal display device according to the first embodiment of the present invention.  FIGS. 9A to 9C  are cross-sectional views taken along III-III of  FIG. 8  illustrating a fabricating sequence of an array substrate according to the first embodiment of the present invention. In  FIG. 9A , a gate line  125  and a gate electrode  132  are formed on the substrate  111  by depositing conductive metal such as aluminum (Al), aluminum alloys, molybdenum (Mo), copper (Cu), tungsten (W) and chromium (Cr), for example, and patterning it. If the gate electrode  132  and the gate line  125  are formed of aluminum (Al), an additional conductive metal layer for protecting the gate electrode  132  and the gate line  125  may be formed. A gate insulating layer  141  is formed on the substrate  111  and on the gate electrode  132  by depositing or coating organic insulating material or inorganic insulating material. The organic insulating material for the gate insulating layer  141  is selected from a group including benzocyclobutene (BCB) and acrylic resin. The inorganic insulating material for the gate insulating layer  141  is selected from a group including silicon oxide (SiO 2 ) and silicon nitride (SiN X ). A semi-conductor layer  134  is formed on the gate insulating layer  141  by depositing an amorphous silicon layer and impure amorphous silicon layer on the gate insulating layer  141  and patterning it. A data line  127  crossing the gate line  125 , a source electrode  133  connected to the data line  127  and a drain electrode  135  being spaced apart from the source electrode  133  are formed by depositing conductive metal material on the whole area of the substrate  111  and patterning it. Though it is not shown in the figure, an align key is formed on the corner of the substrate  111  during the gate line  125  of  FIG. 8  forming process or the data line  127  forming process. 
     In  FIG. 9B , a first passivation layer  143  is formed on the substrate by depositing an inorganic insulating material such as silicon oxide (SiO 2 ) or silicon nitride (SiN X ) and then patterning it to form a drain contact hole  145  exposing a part of the drain electrode  135 . The first passivation layer  143  is formed thin. As a result, it can be formed thin on the align key allowing an uneven shape of the align key be remained. 
     In  FIG. 9C , a reflective electrode  147  that contacts the drain electrode  135  through the drain contact hole  145  is formed on the first passivation layer  143  by depositing and patterning a conductive metal material such as aluminum (Al) or aluminum alloys that has a low electric resistance and high reflexibility. At this time, a detection of the align key can be performed well during the depositing and etching process for the reflective electrode  147 . Accordingly, a process error caused by an alignment error of the mask and the substrate does not occur during the reflective electrode forming process. A second passivation layer  149  is formed on the substrate  111  by depositing organic insulating material. 
     If silicon nitride (SiN X ) is formed beneath the reflective electrode  147 , the electrical conduction property of the liquid crystal panel can be improved and contact property between the reflective electrode  147  and the first passivation layer  143  can be improved, which results in an improvement of electric properties of a liquid crystal panel. 
     A second embodiment of the present invention will be described hereinafter with reference to  FIG. 10  and  FIGS. 11A to 11E .  FIG. 10  is a plan view illustrating a partial array substrate having an inverted stagger type thin film transistor for a transflective liquid crystal display device according to the second embodiment of the present invention.  FIGS. 11A to 11E  are cross-sectional views taken along line V-V of  FIG. 10  illustrating a fabricating sequence of an array substrate according to the second embodiment of the present invention. In  FIG. 11A , because a thin film transistor forming process is the same as that of the first embodiment, i.e., a reflective liquid crystal display device, it will not be described in detail herein. 
     As shown in  FIG. 11A , a gate electrode  132 , a source electrode  133 , a drain electrode  135 , an active layer  134  and a data line  127  are formed on a substrate  111  in sequence. Though it is not shown in the Figures, an align key for accurate aligning of the mask and the substrate is formed on the corner of the substrate simultaneously with the gate line or the data line forming process. The shape of the align key is uneven. Accordingly, a detector aligns the mask and the substrate by irradiating light onto the uneven surface of the align key and sensing the light reflected from the surface of the align key. 
     In  FIG. 11B , a first passivation layer  149  is formed on the substrate  111  and on the thin film transistor “T” by depositing inorganic insulating material such as silicon nitride (SiN X ), for example, on the substrate  111 . Because the first passivation layer  149  is formed thin on the substrate  111  compared with organic insulating material such as benzocyclobutene (BCB), for example, the uneven shape of the align key may remain. A first drain contact hole  150   a  for exposing a part of the drain electrode  135  is formed by patterning the first passivation layer  149 . 
     In  FIG. 11C , a reflector  153  that includes a transmission hole  151  in the pixel region is formed by depositing and patterning a metal such as aluminum (Al) and aluminum alloys, for example, on the first passivation layer  149 . At this time, a detection of the align key can be achieved well during the depositing and etching process for the reflector  153 . Accordingly, a process error caused by an alignment error of the mask and the substrate is not occurred during the reflective electrode forming process. 
     In  FIG. 11D , a second passivation layer  154  is formed on the substrate  111  by depositing transparent organic insulating material such as benzocyclobutene (BCB) and acrylic resin. A second drain contact hole  150   b  that exposes a part of the drain electrode  135  is formed by etching the second passivation layer  154  corresponding to the first drain contact hole  150   a  of  FIG. 11C  and an etching hole  155  is formed by etching the second passivation layer  154  corresponding to the transmission hole  151 . At this time, the first passivation layer  149  may be etched simultaneously with the second passivation layer  154 . 
     In  FIG. 11E , a transparent pixel electrode  157  that contacts the drain electrode  135  through the drain contact hole is formed by depositing and patterning transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO), for example, on the second passivation layer  154 . 
     Whereas the drain electrode is exposed by etching the first passivation layer  149  and the second passivation layer  154  respectively in a different process as in  FIG. 11B  and  FIG. 11D , the drain contact hole can be formed by etching the first passivation layer  149  and the second passivation layer  154 , simultaneously in a single process. 
     A third embodiment of the present invention will be described hereinafter with reference to  FIG. 12  and  FIGS. 13A to 13F .  FIG. 12  is a plan view illustrating a partial array substrate having a coplanar type polysilicon thin film transistor for a transflective liquid crystal display device according to the third embodiment of the present invention.  FIGS. 13A to 13F  are cross-sectional views taken along lines IV-IV, V-V and VI-VI of  FIG. 12  illustrating a fabricating sequence of an array substrate according to the third embodiment of the present invention. 
     In  FIG. 13A , a first insulating layer  162 , i.e., a buffer layer, is formed on the transparent insulating substrate  160  by depositing inorganic insulating material such as silicon oxide (SiO 2 ) or silicon nitride (SiN X ). The buffer layer  162  is optional. A polysilicon layer  164  is formed by depositing amorphous silicon (a-Si: H) on the buffer layer  162  and crystallizing the amorphous silicon. 
     In  FIG. 13B , a semi-conductor layer  166  is formed by patterning the polysilicon layer  164 . The semi-conductor layer  166  has a semi-conductor layer expanded portion  167  corresponding to a pixel region “P” of  FIG. 12 . The semi-conductor layer  166  can be divided into a first active region “A” that serves as an active channel and a second active region “B” that is ion doped. A second insulating layer  168 , i.e., a gate insulating layer, is formed on the substrate  160  and on the semi-conductor layer  166  by depositing inorganic insulating material such as silicon oxide (SiO 2 ) or silicon nitride (SiN X ), for example, on the substrate  160 . A gate electrode  170  over the first active region “A”, a gate line  171  connected to the gate electrode  170  and a gate pad  174  connected to one end of the gate line  171  are formed by depositing and patterning conductive metal material on the second insulating layer  168 . A storage line  172  is simultaneously formed parallel to the gate line  171  and the storage line  171  has a storage line expanded portion  173 . 
     In  FIG. 13C , a third insulating layer  176 , i.e., interlayer insulating layer, is formed by depositing insulating material on the whole area of the substrate  160 . A first contact hole  178   a  and a second contact hole  178   b , which expose the second active region “B” of the semi-conductor layer  167  are formed. A source electrode  180  and a drain electrode  182 , which contact the exposed second active region “B” are formed by depositing and patterning conductive metal such as aluminum (Al), aluminum alloys, chromium (Cr), tungsten (W), molybdenum (Mo) and niobium (Nb), for example, on the third insulating layer  176 . A data line  184 , which is connected to the source electrode  180  and vertically extended form the source electrode  180  is formed on the third insulating layer  176 . A data pad is formed at one end of the data line  184 . The data line  184  defines a pixel region “P” by crossing the gate line  171 . A polysilicon thin film transistor is formed through the above processes. 
     In  FIG. 13D , a fourth insulating layer  188  is formed by depositing inorganic insulating material such as silicon oxide (SiO 2 ) or silicon nitride (SiN X ), for example, on the substrate  160 . The thin film transistor then undergoes a hydrogenation process. The hydrogenation process is for removing defects occurred on the surface of the active layer  166  and the fourth insulating layer  188  may be formed of silicon nitride (SiN X ) that includes hydrogen. A fifth insulating layer  190  is formed by depositing transparent organic insulating material such as benzocyclobutene (BCB) or acrylic resin, for example, on the fourth insulating layer  188 . A sixth insulating layer  200 , i.e., a barrier layer, is formed by depositing inorganic insulating material such as silicon oxide (SiO 2 ) or silicon nitride (SiN X ), for example, on the fifth insulating layer  190 . 
     In  FIG. 13E , a reflector  202  is formed in the pixel region “P” by depositing and patterning conductive metal material such as aluminum (Al) or aluminum alloys, for example, on the barrier layer  200 . As shown in the figure, the reflector  202  is formed over the storage line expanded portion  173 . However, the reflector  202  may be formed over the thin film transistor and extended to cover the gate line  171  and the data line  184 . The reflector and the storage line expansion portion  173  constitute a reflection portion “E” of  FIG. 12  in the pixel region “P” of  FIG. 12  and the remaining portion of the pixel region “P” of  FIG. 12  is a transmission portion “F” of  FIG. 12 . Accordingly, an area ratio between the reflection portion and the transmission portion can be controlled by varying the reflector  202  and the storage line expansion portion  173 . A seventh insulating layer  205  is formed by depositing inorganic insulating material such as silicon oxide (SiO 2 ) or silicon nitride (SiN X ), for example, on the substrate  130  and on the reflector  202 . A drain contact hole  192  that exposes a part of the drain electrode  182  is formed by etching the fourth insulating layer  188 , the fifth insulating layer  190 , the sixth insulating layer  200 , i.e., the barrier layer and the seventh insulating layer  205  over the drain electrode  182 . A gate pad contact hole  194  that exposes the gate pad  174  is formed by etching laminated insulating layers from the third insulating layer  176  to the seventh insulating layer  205  over the gate pad  174 . A data pad contact hole  196  that exposes the data pad is formed by etching laminated layers from the fourth insulating layer  188  to the seventh insulating layer  205  over the data pad  186 . 
     An under-cut and an inversed taper, which occurs in the wall of the plurality of the contact holes can be prevented by equalizing an etching speed of the transparent organic insulating layers with the etching speed of the plurality of inorganic insulating layers. The equalizing of the etching speeds of the laminated layers is performed by adding about 65˜80% of oxygen gas to etching gas (SF 6 , CF 4 ). 
     In  FIG. 13F , a pixel electrode  198  contacts the exposed drain electrode  182  through the drain contact hole  192 . A gate pad terminal  201  contacts the gate pad  174  through the gate pad contact hole  194 . A data pad terminal  204  contacts the data pad  186  through the data pad contact hole  196 . The pixel electrode  198 , gate pad terminal  201  and data pad terminal  204  are formed by depositing and patterning transparent conductive metal material such as indium tin oxide (ITO) or indium zinc oxide (IZO), for example, on the seventh insulating layer  205  and in the respective contact holes  192 ,  194  and  196 . 
     The transflective liquid crystal display device of the present invention having a high aperture ratio can be manufactured through the manufacturing process described above. 
     As described above, an array substrate for reflective and transflective liquid crystal display devices includes a reflective electrode that avoids being formed directly on an organic insulating layer such as benzocyclobutene (BCB) by exchanging a forming order of the organic insulating layer and an inorganic insulating layer such as silicon nitride (SiN X ) or by introducing a barrier layer between the organic insulating layer and the reflective electrode. Accordingly, the array substrate with reflective electrode formed in this matter avoids the problems of the conventional art discussed above. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.