Abstract:
A manufacturing method of pixel structure includes forming a first conductive layer on a substrate and forming a first insulation layer thereon; forming a second conductive layer on the first insulation layer; forming a second insulation layer on the second conductive layer; forming a semiconductor layer on the second insulation layer above the gate; forming a third conductive layer on the second insulation layer, wherein the gate, the semiconductor layer, the source, and the drain together constitute a thin film transistor, and the first electrode, the second electrode, and the third electrode together constitute a capacitor; forming a third insulation layer on the third conductive layer; and forming a pixel electrode on the third insulation layer, the pixel electrode being electrically connected to the drain.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a divisional application of and claims the priority benefit of a prior application Ser. No. 13/402,883, filed on Feb. 23, 2012, now allowed, which claims the priority benefit of Taiwan application serial no. 100142006, filed on Nov. 17, 2011. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of specification. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a pixel structure and a manufacturing method thereof. 
         [0004]    2. Description of Related Art 
         [0005]    In general, a pixel structure of a liquid crystal display (LCD) includes a thin film transistor (TFT) and a pixel electrode. The TFT serves as a switching device of an LCD unit. To control each individual pixel structure, a certain pixel is usually selected according to a corresponding scan line and a corresponding data line, and display information corresponding to the certain pixel is displayed through providing an appropriate operating voltage. The pixel structure further includes a storage capacitor, such that the pixel structure can be equipped with a voltage-retaining function. Namely, the storage capacitor can store the applied operating voltage to stabilize the display image of the pixel structure. 
         [0006]    To form the storage capacitor in the pixel structure, a capacitor electrode is often required in the pixel structure. However, in order to increase the capacitance of the storage capacitor, the area occupied by the capacitor electrode need be expanded, thus reducing the aperture ratio of the pixel structure. 
         [0007]    At present, a pixel structure in which the capacitor electrode is disposed below the data line has been proposed to increase the aperture ratio of the pixel structure. However, the capacitor electrode and the data line which are overlapped increase the loading of the pixel structure. Therefore, in the pixel structure, the required power consumption for driving the display panel is increased in the pixel structure. 
       SUMMARY OF THE INVENTION 
       [0008]    The invention is directed to a pixel structure and a manufacturing method thereof, and the pixel structure can have a high aperture ratio without increasing the loading of the pixel structure. 
         [0009]    In the invention, a pixel structure that includes a first electrode, a first insulation layer, a gate, a second electrode, a second insulation layer, a semiconductor layer, a source and a drain, a third electrode, a third insulation layer, and a pixel electrode is provided. The first electrode is located on a substrate. The first insulation layer covers the first electrode. The gate is located on the first insulation layer. The second electrode is located on the first insulation layer above the first electrode. The second insulation layer covers the gate and the second electrode. The semiconductor layer is located on the second insulation layer above the gate. The source and the drain are located on the semiconductor layer. Here, the gate, the semiconductor layer, the source, and the drain together constitute a TFT. The third electrode is located on the second insulation layer above the second electrode and the third electrode is electrically connected to the first electrode. Here, the first electrode, the second electrode, and the third electrode together constitute a capacitor. The third insulation layer covers the source, the drain, and the third electrode. The pixel electrode is located on the third insulation layer and electrically connected to the drain. 
         [0010]    In the invention, a manufacturing method of a pixel structure is also provided. In the manufacturing method, a first conductive layer is formed on a substrate, and the first conductive layer includes a first electrode. A first insulation layer is formed on the first conductive layer. A second conductive layer is formed on the first insulation layer. The second conductive layer includes a gate and a second electrode, and the second electrode is located above the first electrode. A second insulation layer is formed on the second conductive layer. A semiconductor layer is formed on the second insulation layer above the gate. A third conductive layer is formed on the second insulation layer. The third conductive layer includes a source, a drain, and a third electrode. The source and the drain are located on the semiconductor layer, and the third electrode is located above the second electrode and electrically connected to the first electrode. Here, the gate, the semiconductor layer, the source, and the drain together constitute a TFT, and the first electrode, the second electrode, and the third electrode together constitute a capacitor. A third insulation layer is formed on the third conductive layer. A pixel electrode is formed on the third insulation layer, and the pixel electrode is electrically connected to the drain. 
         [0011]    Based on the above, the capacitor described herein is constituted by the first electrode, the second electrode, and the third electrode, and the first electrode is located below the first insulation layer that is below the second electrode. Hence, in the invention, the storage capacitance of the capacitor can be increased without negatively affecting the aperture ratio of the pixel structure; what is more, a display with high resolution can be formed. From another aspect, since the first, second, and third electrodes of the capacitor are not configured below the data line, the capacitor described herein does not lead to an increase in the loading of the pixel structure. 
         [0012]    In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanying figures are described in detail below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The accompanying drawings are included to provide further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments and, together with the description, serve to explain the principles of the invention. 
           [0014]      FIG. 1A through 1I  are schematic cross-sectional views illustrating a process of fabricating a pixel structure according to an embodiment of the invention. 
           [0015]      FIG. 2  is a schematic top view illustrating a pixel structure according to an embodiment of the invention. Here,  FIG. 2  is taken along section lines I-I′ and II-II′ corresponding to the cross-sectional views in  FIG. 1A  to  FIG. 1I . 
           [0016]      FIG. 3  is a schematic top view illustrating a pixel structure according to an embodiment of the invention. 
           [0017]      FIG. 4  is a schematic cross-sectional view illustrating the pixel structure taken along section lines I-I′ and II-II′ depicted in  FIG. 3 . 
           [0018]      FIG. 5  is a schematic top view illustrating a pixel structure according to an embodiment of the invention. 
           [0019]      FIG. 6  is a schematic cross-sectional view illustrating the pixel structure taken along section lines I-I′ and II-II′ depicted in  FIG. 5 . 
           [0020]      FIG. 7  is a schematic cross-sectional view illustrating a pixel structure according to another embodiment of the invention. 
           [0021]      FIG. 8  is a schematic top view illustrating a pixel structure according to an embodiment of the invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0022]      FIG. 1A through 1I  are schematic cross-sectional views illustrating a process of fabricating a pixel structure according to an embodiment of the invention.  FIG. 2  is a schematic top view illustrating a pixel structure according to an embodiment of the invention. Here,  FIG. 2  is taken along section lines I-I′ and II-II′ corresponding to the cross-sectional views in  FIG. 1A  to  FIG. 1I . 
         [0023]    With reference to  FIG. 1A , in the present embodiment, a first conductive layer M 1  is formed on a substrate  100 , and the first conductive layer M 1  includes a first electrode E 1 . The substrate  100  can be made of glass, quartz, an organic polymer, an opaque/reflective material (such as a conductive material, wafer, ceramics, or any other appropriate material), or any other appropriate material. A material of the first conductive layer M 1  (the first electrode E 1 ) includes metal, an alloy, metal nitride, metal oxide, metal oxynitride, another appropriate material, or a layer in which a metal material and any other conductive material are stacked together. A method of forming the first conductive layer M 1  (the first electrode E 1 ) includes performing a deposition process to deposit a conductive material layer and performing a photolithography and etching process to pattern the conductive material layer, for instance. 
         [0024]    With reference to  FIG. 1B , a first insulation layer  102  is formed on the first conductive layer M 1  (the first electrode E 1 ). A material of the first insulation layer  102  includes an inorganic insulation material (e.g., silicon oxide, silicon nitride, silicon oxynitride, or any other appropriate dielectric material) or an organic insulation material. The first insulation layer  102  is formed by performing a chemical vapor deposition (CVD) process, a physical vapor deposition (PVD) process, or a coating process, for instance. 
         [0025]    With reference to  FIG. 1C , a second conductive layer M 2  is formed on the first insulation layer  102 , and the second conductive layer M 2  includes a gate G and a second electrode E 2  that is located above the first electrode E 1 . According to the present embodiment, the second conductive layer M 2  further includes a scan line SL and an electrode line CL (as shown in  FIG. 2 ); the scan line SL is electrically connected to the gate G, and the electrode line CL is electrically connected to the second electrode E 2 . A material of the second conductive layer M 2  includes metal, an alloy, metal nitride, metal oxide, metal oxynitride, another appropriate material, or a layer in which a metal material and any other conductive material are stacked together. A method of forming the second conductive layer M 2  includes performing a deposition process to deposit a conductive material layer and performing a photolithography and etching process to pattern the conductive material layer, for instance. 
         [0026]    With reference to  FIG. 1D , a second insulation layer  104  is formed on the second conductive layer M 2  (the gate G and the second electrode E 2 ). A material of the second insulation layer  104  includes an inorganic insulation material (e.g., silicon oxide, silicon nitride, silicon oxynitride, or any other appropriate dielectric material) or an organic insulation material. The second insulation layer  104  is formed by performing a CVD process, a PVD process, or a coating process, for instance. 
         [0027]    With reference to  FIG. 1E , a semiconductor layer SE is formed on the second insulation layer  104  above the gate G. According to the present embodiment, the semiconductor layer SE includes a channel layer CH and an ohmic contact layer OH. A method of forming the semiconductor layer SE includes performing a deposition process to sequentially deposit a channel material layer and an ohmic contact material layer and performing a photolithography and etching process to pattern the two material layers, for instance. However, the semiconductor layer SE is not required to include both the channel layer CH and the ohmic contact layer OH in the invention; namely, according to another embodiment, the semiconductor layer SE may merely contain the channel layer CH. 
         [0028]    With reference to  FIG. 1F , the second insulation layer  104  is patterned to faun a contact opening C 1  that exposes the first electrode E 1 . 
         [0029]    With reference to  FIG. 1G , a third conductive layer M 3  is formed on the second insulation layer  104 , and the third conductive layer M 3  includes a source S, a drain D, and a third electrode E 3 . Here, the third conductive layer M 3  may further include a data line DL. The source S and the drain D are located on the semiconductor layer SE, the third electrode E 3  is located above the second electrode E 2 , and the data line DL is electrically connected to the source S. According to the present embodiment, the drain D is connected to the third electrode E 3 ; thus, the drain D is electrically connected to the third electrode E 3 . Here, the gate G, the semiconductor layer SE, the source S, and the drain D together constitute a TFT T, and the first, second, and third electrodes E 1 , E 2 , and E 3  together constitute a capacitor CS. Besides, the third electrode E 3  is electrically connected to the first electrode E 1  through the contact opening C 1  formed in the second insulation layer  104 . 
         [0030]    It should be mentioned that the contact opening C 1  for electrically connecting the first and third electrodes E 1  and E 3  is disposed at a region away from the TFT T according to the present embodiment. This is mainly to prevent the contact opening C 1  from causing short circuit between the electrode (the gate G) of the TFT T and the electrode (the second electrode E 2 ) of the capacitor CS. However, the location of the contact opening C 1  is not limited in the invention; as a matter of fact, the contact opening C 1  can be located at any region where the first and third electrodes E 1  and E 3  are overlapped without causing short circuit between the TFT T and the capacitor CS. 
         [0031]    With reference to  FIG. 1H , a third insulation layer ( 106 ,  110 ) is formed on the third conductive layer M 3  (the source S, the drain D, and the third electrode E 3 ). In the present embodiment, the third insulation layer includes a passivation layer  106  and a planarization layer  110 , which should not be construed as a limitation to the invention. In another embodiment, the third insulation layer may also contain one of the passivation layer  106  and the planarization layer  110 . The third insulation layer  110 ,  106  is patterned to form a contact opening C 2 , and the contact opening C 2  exposes the third electrode E 3 . 
         [0032]    With reference to  FIG. 1I , a pixel electrode PE is formed on the third insulation layer  106 ,  110 , and the pixel electrode PE is electrically connected to the drain D. According to the present embodiment, the contact opening C 2  is located on and exposes the third electrode E 3 , and thus the pixel electrode PE can be electrically connected to the third electrode E 3  through the contact opening C 2 . Since the drain D is directly connected to the third electrode E 3 , the pixel electrode PE can be electrically connected to the drain D through the contact opening C 2  and the third electrode E 3 . The pixel electrode PE may be a transparent pixel electrode, a reflective pixel electrode, or a combination of the transparent pixel electrode and the reflective pixel electrode. A material of the transparent pixel electrode may include metal oxide, such as indium tin oxide (ITO), indium zinc oxide (IZO), aluminum tin oxide (ATO), aluminum zinc oxide (AZO), indium germanium zinc oxide, other suitable oxide, or a stacked layer having at least two of the above materials. The reflective pixel electrode is made of a metal material that is characterized by high reflectivity, for instance. 
         [0033]    The pixel structure formed by conducting the aforesaid method is shown in  FIG. 1I  and  FIG. 2 , and the pixel structure includes the first electrode E 1 , the first insulation layer  102 , the gate G, the second electrode E 2 , the second insulation layer  104 , the semiconductor layer SE, the source S and the drain D, the third electrode E 3 , the third insulation layer  106 ,  110 , and the pixel electrode PE. The first electrode E 1  is located on the substrate  100 . The first insulation layer  102  covers the first electrode E 1 . The gate G is located on the first insulation layer  102 . The second electrode E 2  is located on the first insulation layer  102  above the first electrode E 1 . The second insulation layer  104  covers the gate G and the second electrode E 2 . The semiconductor layer SE is located on the second insulation layer  104  above the gate G. The source S and the drain D are located on the semiconductor layer SE. The gate G, the semiconductor layer SE, the source S, and the drain D together constitute a TFT T. The third electrode E 3  is located on the second insulation layer  104  above the second electrode E 2 . Here, the third electrode E 3  is electrically connected to the first electrode E 1 , and the first electrode E 1 , the second electrode E 2 , and the third electrode E 3  together constitute the capacitor CS. The third insulation layer  106 ,  110  covers the source S, the drain D, and the third electrode E 3 . The pixel electrode PE is located on the third insulation layer  110  and electrically connected to the drain D. 
         [0034]    It should be mentioned that the TFT T and the capacitor CS in the pixel structure shown in  FIG. 2  are located at the edge portion of the pixel structure (the pixel electrode PE). However, the invention is not limited thereto, and the TFT T and the capacitor CS in another embodiment may be located at the central portion of the pixel structure (the pixel electrode PE). 
         [0035]    In view of the previous embodiments, the capacitor CS is constituted by the first electrode E 1 , the second electrode E 2 , and the third electrode E 3 , and the first electrode E 1  is located below the first insulation layer  102  that is below the second electrode E 2 . Hence, in the invention, the storage capacitance of the capacitor CS can be increased without negatively affecting the aperture ratio of the pixel structure. From another perspective, since the first, second, and third electrodes E 1 , E 2 , and E 3  of the capacitor CS are not overlapped with the data line DL, the capacitance of the capacitor CS does not interfere with the data line DL and thus does not increase the loading of the pixel structure. 
         [0036]      FIG. 3  is a schematic top view illustrating a pixel structure according to an embodiment of the invention.  FIG. 4  is a schematic cross-sectional view illustrating the pixel structure taken along section lines I-I′ and II-II′ depicted in  FIG. 3 . With reference to  FIG. 3  and  FIG. 4 , the embodiment shown herein is similar to the embodiment shown in  FIG. 2 , so that identical components in these figures will be denoted by the same numerals and will not be reiterated herein. In the present embodiment, the first conductive layer M 1  not only includes the first electrode E 1  but also includes a light shielding portion SH 1 . The light shielding portion SH 1  is correspondingly disposed below and at one side of the gate G but does not extend to an underside of the data line DL. Here, the light shielding portion SH 1  may be connected to the first electrode E 1 , and thus the light shielding portion SH 1  and the first electrode E 1  of the first conductive layer M 1  constitute a lump or block pattern. That is to say, the light shielding portion SH 1  extends from the first electrode E 1  to an underside of the gate G. 
         [0037]    The light shielding portion SH 1  disposed below the gate G may shield the light from the backside of the substrate  100 , so as to prevent the TFT T from generating photo-leakage current. In general, the liquid crystal is a non-self-illuminating display medium, and thus a backlight module is required to be additionally configured at the back side of the display panel for supplying the planar light source needed by the display panel. With the development of the display panel with high resolution, the light intensity of the backlight module need be improved to comply with the brightness standard required by the display panel with high resolution. Nonetheless, when the light intensity of the backlight module increases, the light is much more likely to cause photo-leakage current in the TFT in the display panel. Accordingly, the light shielding portion SH 1  is configured in the first conductive layer in the present embodiment, so as to prevent the light coming from the backside of the substrate  100  (i.e., the light of the backlight module) from generating photo-leakage current in the TFT T. In other words, the light coming from the backside of the substrate  100  (the light of the backlight module), after being blocked by the light shielding portion SH 1  and the gate G, can be precluded from entering the semiconductor layer SE, and thereby the issue of photo-leakage current does not arise in the TFT T. 
         [0038]      FIG. 5  is a schematic top view illustrating a pixel structure according to an embodiment of the invention.  FIG. 6  is a schematic cross-sectional view illustrating the pixel structure taken along section lines I-I′ and II-II′ depicted in  FIG. 5 . With reference to  FIG. 5  and  FIG. 6 , the embodiment shown herein is similar to the embodiment shown in  FIG. 2 , so that identical components in these figures will be denoted by the same numerals and will not be reiterated herein. In the present embodiment, the first conductive layer M 1  not only includes the first electrode E 1  but also includes a light shielding portion SH 1  and a light shielding portion SH 2 . The light shielding portions SH 1  and SH 2  are correspondingly disposed below and respectively at two sides of the gate G and extend to an underside of the data line DL. Here, the light shielding portions SH 1  and SH 2  may be connected to the first electrode E 1 , and thus the light shielding portions SH 1  and SH 2  and the first electrode E 1  of the first conductive layer M 1  constitute a lump or block pattern. 
         [0039]    Similarly, the light shielding portions SH 1  and SH 2  configured below the gate G may shield the light from the underside of the substrate  100 , so as to prevent the TFT T from generating photo-leakage current. In other words, the light coming from the underside of the substrate  100  (the light of the backlight module), after being blocked by the light shielding portions SH 1  and SH 2  and the gate G, can be precluded from entering the semiconductor layer SE, and thereby the issue of photo-leakage current does not arise in the TFT T. 
         [0040]      FIG. 7  is a schematic cross-sectional view illustrating a pixel structure according to another embodiment of the invention.  FIG. 8  is a schematic top view illustrating a pixel structure according to an embodiment of the invention. Specifically, the cross-sectional view taken along the sectional lines I-I′ and II-II′ of  FIG. 8  is shown in  FIG. 7 . With reference to  FIG. 7  and  FIG. 8 , the embodiment shown herein is similar to the embodiment shown in  FIG. 6 , so that identical components in these figures will be denoted by the same numerals and will not be reiterated herein. In this embodiment, the contact opening C 1  is located between the gate G and the second electrode E 2 . The gate G and the second electrode E 2  both belong to the second conductive layer M 2 ; therefore, when the contact opening C 1  is defined, the contact opening C 1  need be located at a region where the gate G and the second electrode E 2  are not located, so as to prevent the subsequent short circuit between the gate G and the second electrode E 2 . Besides, in the present embodiment, the contact opening C 2  is located above the contact opening C 1 . However, the contact opening C 2  is not necessarily located right above the contact opening C 1  in the invention. 
         [0041]    In light of the foregoing, the capacitor described herein is constituted by the first electrode, the second electrode, and the third electrode, and the first electrode is located below the first insulation layer that is below the second electrode. Hence, in the invention, the storage capacitance of the capacitor can be increased without negatively affecting the aperture ratio of the pixel structure. From another aspect, since none of the first, second, and third electrodes of the capacitor are configured below the data line, the capacitor described herein does not lead to an increase in the loading of the pixel structure. Moreover, the light shielding portion disposed below the gate may shield the light from the underside of the substrate, so as to prevent the TFT from generating photo-leakage current. 
         [0042]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.