Abstract:
The present invention discloses a light exposure mask which comprises a substrate including: a light transmitting region for transmitting incident light perfectly; a light shielding region for shielding the incident light perfectly; and a light semi-transmitting region for transmitting part of the incident light. And the method for manufacturing the mask is also disclosed using depositing and patterning processes. The inventive mask can improve a step coverage and reduce a process time for forming a dual-layered layer.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a light exposure mask and a method of manufacturing the same, and more particularly, to a light exposure mask and a method of manufacturing the same for use in a liquid crystal display (LCD) device. 
     2. Description of Related Art 
     FIG. 1 is a plan view illustrating a typical LCD device. As shown in FIG. 1, the typical LCD device comprises gate lines  60  arranged in a transverse direction, data lines  70  arranged in a longitudinal direction perpendicular to the gate lines  60 , thin film transistors (TFTs) “S” located near cross points of the gate lines  60  and the data lines  70 , and pixel regions  40  defined by the gate lines  60  and the data lines  70 . 
     The typical LCD device is manufactured by the following processes. FIG. 2 is a cross-sectional view taken along line ∥—∥ of FIG.  1 . First, a gate electrode  60   a  is formed on a transparent substrate  10 , and then a gate insulating layer  50  made of a inorganic material such as SiNx or SiOx is formed on the whole surface of the transparent substrate  10  while covering the gate electrode  60   a.  The gate electrode  60   a  contacts the gate line  60 . Sequentially, a semiconductor layer  80  is formed over the gate electrode  60   a  in the form of an island. The semiconductor layer  80  has an amorphous silicon layer  80   a  and a doped amorphous silicon layer  80   b.  Source and drain electrodes  70   a  and  70   b  spaced apart from each other are formed overlapping a region of both ends of the doped amorphous silicon layer  80   b.  The source electrode  70   a  contacts the data line  70 , and the drain electrode  70   b  contacts a pixel electrode that is formed in a subsequent process. Then, a passivation layer  55  is formed on the whole surface of the transparent substrate  10  covering the source and drain electrodes  70   a  and  70   b,  and then a contact hole  42  is formed at a predetermined location over the drain electrode  70   b.  The pixel electrode  44  is formed on the pixel region  40  to contact the drain electrode  70   b  through the contact hole  42 . 
     Most components of the typical LCD device described above are formed using several photolithography processes. In the conventional photolithography process, as shown in FIG. 3A, a metal layer  90  is formed on the substrate  10 . Either a positive or a negative photoresist is applied on the metal layer  90 , and then a light exposure mask  88  is aligned. FIG. 3A shows the positive photoresist  100 , and the light exposure mask  88  has light transmitting regions  88   a,    88   c  and a light shielding region  88   b.  Sequentially, when UV light is irradiated toward the light exposure mask  88 , the photoresist  100  is developed, thereby forming a photoresist pattern  10   a  shown in FIG.  3 B. 
     Then, the photoresist pattern  10   a  is subjected to a predetermined temperature and atmosphere to become hardened. The metal layer  90  is etched according to the photoresist pattern  100   a  using either of a dry etching technique or a wet etching technique so that a metal pattern layer  90   a  is formed as shown in FIG.  3 C. Finally, the photoresist patter  100   a  remaining on the metal pattern layer  90   a  is removed. 
     However, when using the conventional light exposure mask  88  described above, since the light transmitting regions  88   a,    88   c  and the light shielding region  88   b  of the light exposure mask  88  transmits and shields the UV light perfectly, respectively, the metal pattern layer  90   a  formed comes to have an almost rectangular-shaped cross section. Therefore, when another metal layer (not shown) is formed on the rectangular-shaped metal pattern layer  90   a,  there arises a problem in that step coverage becomes degraded so that an open line may occur at a step portion. 
     FIGS. 4A through 4C show another photolithography process to form a dual-layered metal pattern layer. As shown in FIG. 4A, first and second metal layers  90  and  91  are sequentially formed on a transparent substrate  10 , and a positive photoresist  100  is applied on the second metal layer  91 . Then, a light exposure mask  88  having a light transmitting region  80   a  and a light shielding region  80   b  is aligned. Sequentially, when UV light is irradiated toward the light exposure mask  88 , the photoresist  100  is developed, thereby forming a photoresist pattern  100   a  as shown in FIG.  4 B. 
     Then, the photoresist pattern  100   a  is subjected to a predetermined temperature and atmosphere to become hardened. The first and second metal layers  90  and  91  are simultaneously etched according to the photoresist pattern  100   a  using either of a dry etching technique or a wet etching technique so that first and second metal pattern layers  90   a  and  91   a  are formed, as shown in FIG.  4 C. Finally, the photoresist pattern  100   a  remaining on the second metal pattern layer  91   a  is removed. 
     However, when using the conventional light exposure mask  88  described above, the metal pattern layers  90  and  91  inevitably have the same shape, thus, in order to form different shaped metal layers, an additional photolithography process should be performed again, leading to a lengthy processing time and a low yield. 
     SUMMARY OF THE INVENTION 
     To overcome the problems described above, preferred embodiments of the present invention provide a light exposure mask having a substrate defined by the following three regions: a light transmitting region, a light shielding region and a light semi-transmitting region. 
     Another embodiment of the invention provides a method for manufacturing a light exposure mask having a light transmitting region, a light shielding region, and a semi-transmitting region, comprising the steps of: preparing a transparent substrate; forming a semi-transmitting layer and a light shielding layer on the substrate in this order; patterning the light shielding layer to define the light shielding region of the substrate; and patterning the semi-transmitting layer so that the semi-transmitting region of the substrate is covered by the patterned semi-transmitting layer. 
     The light shielding layer preferably has Cr/CrOx, and the semi-transmitting layer preferably has indium tin oxide. 
     Another embodiment of the invention provides a method for manufacturing a light exposure mask having a light transmitting region, a light shielding region, and a semi-transmitting region, comprising the steps of: preparing a transparent substrate; forming a light shielding layer on the substrate; patterning the light shielding layer to define the light shielding region of the substrate; forming a semi-transmitting layer on the substrate while covering the patterned light shielding layer; and patterning the semi-transmitting layer so that the semi-transmitting region of the substrate is covered by the patterned semi-transmitting layer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which like reference numerals denote like parts, and in which: 
     FIG. 1 is a plan view illustrating a typical liquid crystal display device; 
     FIG. 2 is a cross-sectional view taken along line ∥—∥of FIG. 1; 
     FIGS. 3A to  3 C are cross-sectional views illustrating a conventional photolithography process; 
     FIGS. 4A to  4 C are cross-sectional views illustrating another conventional photolithography process; 
     FIG. 5A is a cross-sectional view illustrating a light exposure mask according to a first preferred embodiment of the present invention; 
     FIG. 5B is a similar view of FIG. 5A illustrating a light exposure mask according to a second preferred embodiment of the present invention; 
     FIG. 5C is a similar view of FIG. 5A illustrating a light exposure mask according to a third preferred embodiment of the present invention; 
     FIGS. 6A to  6 C are cross-sectional views illustrating a photolithography process using a mask of FIG. 5A; and 
     FIGS. 7A to  7 C are cross-sectional views illustrating another photolithography process using a mask of FIG.  5 A. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiment of the present invention, examples of which are illustrated in the accompanying drawings. 
     A light exposure mask according to a preferred embodiment of the present invention has a transparent substrate defined by the following three regions: a light transmitting region, a light shielding region and a light semi-transmitting region. The semi-transmitting region of the substrate can be defined by a material for transmitting a range between 60 and 80% of the incident light, for example indium tin oxide (ITO), and the light shielding region of the substrate is defined by a material for shielding the incident light perfectly, preferably Cr/CrOx. 
     FIGS. 5A to  5 C show different methods of manufacturing the inventive light exposure mask. The inventive light exposure mask is manufactured as follows. First, as shown in FIG. 5A, the ITO layer and the Cr/CrOx layer are sequentially deposited on a substrate  20  and patterned to form ITO patterns  25  and Cr/CrOx patterns  30 , respectively, thereby forming the dual-layered light exposure mask  188 . At this point, reference numerals  188   a,    188   b  and  188   c  denote the light transmitting region, the light shielding region, and the light semi-transmitting region, respectively. Further, as shown in FIG. 5B, the Cr/CrOx layer is first deposited on the transparent substrate  20  and patterned to form Cr/CrOx patterns  30 . Then, the ITO layer is deposited on the exposed surface of the substrate while covering the Cr/CrOx patterns  30  and patterned to form the ITO patterns  25 , thereby forming the light exposure mask  189 . At this point, reference numerals  189   a,    189   b  and  189   c  denote the light transmitting region, the light shielding region and the light semi-transmitting region, respectively. Furthermore, as shown in FIG. 5C, the light exposure mask  190  may have a shape that the ITO patterns  25  are located between the Cr/CrOx patterns  30  by depositing and etching processes. 
     Using the light exposure mask  188  shown in FIG. 5A, a photolithography process according to the preferred embodiment of the present invention is explained in detail hereinafter. 
     As shown in FIG. 6A, a metal layer  90  is deposited on a transparent substrate  10 , and then a photoresist of a predetermined thickness is applied on the metal layer  90 . Then, the light exposure mask  188  having the light transmitting region  188   a,  a light shielding region  188   b  and a light semi-transmitting region  188   c  is aligned. Sequentially, when UV light is irradiated toward the light exposure mask  188 , the photoresist  100  is developed, thereby forming a photoresist pattern  100   a  as shown in FIG.  6 B. The photoresist pattern  100   a  has a portion  102   a  corresponding to the light shielding region  188   b  and a portion  104   a  corresponding to the light semi-transmitting region  188   c.  The portion  104   a  is thinner in thickness than the portion  102   a  since the light semi-transmitting region transmits a range between 60 and 80% of the incident light. 
     Then, the photoresist pattern  100   a  is subjected to a predetermined temperature and atmosphere to become hardened. The metal layer  90  is etched according to the photoresist pattern  100   a  using an etching technique such as a dry etching technique so that a metal pattern layer  90   a  is formed as shown in FIG.  6 C. Finally, the photoresist pattern  100   a  remaining on the metal pattern layer  90   a  is removed. 
     Since the metal pattern layer  90   a  formed has a step shape, that is, a thickness of the metal pattern layer  90   a  can be adjusted according to a location of the light shielding region  188   c,  step coverage can be improved so that a line open of a step portion is prevented. 
     FIGS. 7A to  7 C show another photolithography process to form a dual-layered metal pattern layer. As shown in FIG. 7A, first and second metal layers  90  and  91  are sequentially formed on a transparent substrate  10 , and a positive photoresist  100  is applied on the second metal layer  91 . Then, a light exposure mask  88  having a light transmitting region  188   a,  a light shielding region  188   b  and the light semi-transmitting region  188   c  is aligned. Sequentially, when UV light is irradiated toward the light exposure mask  188 , the photoresist  100  is developed, thereby forming a photoresist pattern  100   a  as shown in FIG.  7 B. 
     Then, the photoresist pattern  100   a  is subjected to a predetermined temperature and atmosphere to become hardened. The first and second metal layers  90  and  91  are simultaneously etched according to the photoresist pattern  100   a  using an etching technique such as a dry etching so that first and second metal pattern layers  90   a  and  91   a  are formed as shown in FIG.  7 C. Finally, the photoresist pattern  100   a  remaining on the second metal pattern layer  91   a  is removed. 
     In this description, each first and second metal pattern layers  90   a  and  91   a  having a different shape from each other can be formed using only one photolithography process since the photoresist pattern  100   a  can have different thicknesses according to location. 
     As described herein before, using the light exposure mask having three regions (the light transmitting region, the light shielding region, and the light semi-transmitting region) can adjust the thickness of a formed metal pattern layer according to each location of the light transmitting region, the light shielding region and the light semi-transmitting region, so that step coverage is improved, thereby preventing a line defect. Further, since upper and lower metal pattern layers of a dual-layers of a dual-layered structure can have different shapes from each other according to each location of the light transmitting region, the light shielding region and the light semi-transmitting region using only one photolithography process, the processing time can be reduced, thereby causing high yields. 
     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.