Abstract:
A simplified method for forming a pad electrode without using an additional light-irradiation device is disclosed. The method includes forming a gate pad on a substrate, forming a gate insulating layer on a substrate surface, forming a data pad on the gate insulating layer, forming a passivation layer on the substrate surface, forming a first contact hole in the gate insulating layer and the passivation layer, forming a second contact hole in the passivation layer, coating a conductive photoresist on the substrate surface, and forming a gate pad electrode in the first contact hole and a data pad electrode in the second contact hole by ashing the conductive photoresist. The pad electrode is formed in a simple method of ashing the conductive photoresist, thereby decreasing costs.

Description:
[0001]    This application claims the benefit of Korean Patent Application No. 10-2005-0029937, filed on Apr. 11, 2005, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a method for forming a pad electrode of an LCD device. 
         [0004]    2. Discussion of the Related Art 
         [0005]    Ultra-thin flat type display devices include display screens having a thickness of several centimeters. Liquid crystal display (LCD) devices are ultra-thin flat type display devices that attract attention because they can be widely used for notebook computers, monitors, spacecraft, aircraft, etc. 
         [0006]    The LCD device includes a thin film transistor array substrate, a color filter array substrate, and a liquid crystal layer. The thin film transistor array substrate includes a thin film transistor and a pixel electrode. The color filter array substrate includes a color filter layer and a common electrode. The thin film transistor array substrate is provided at a predetermined interval from the color filter array substrate. The liquid crystal layer is formed between the thin film transistor array substrate and color filter array substrates. If a voltage is applied to the pixel electrode of the thin film transistor array substrate and the common electrode of the color filter array substrate, an arrangement of liquid crystal molecules of the liquid crystal layer is changed. Thus, it is possible to control the light transmittance, thereby displaying images. 
         [0007]    Hereinafter, a thin film transistor array substrate of an LCD device according to the related art will be described with reference to the accompanying drawings. 
         [0008]      FIG. 1A  is a plan view illustrating a unit pixel region of a thin film transistor array substrate in an LCD device according to the related art.  FIG. 1B  is a cross sectional view taken along line I-I′ of  FIG. 1A . 
         [0009]    As shown in  FIG. 1A , a plurality of gate lines  10  are formed in a first direction on a substrate  1 . Then, a plurality of data lines  20  are formed in a second direction substantially perpendicular to the first direction. That is, a plurality of pixel regions  32  are defined by the plurality of gate and data lines  10  and  20 . 
         [0010]    A plurality of thin film transistors T are formed at respective crossings of the gate and data lines  10  and  20 . Each of the thin film transistors T includes a gate electrode, a semiconductor layer, a source electrode, and a drain electrode. 
         [0011]    Then, a transparent pixel electrode  30  is formed in the pixel region, wherein the transparent pixel electrode  30  is electrically connected with the thin film transistor T. 
         [0012]    A gate pad  12  is formed at a terminal of the gate line  10 . Also, a gate pad electrode  40   a  is formed on the gate pad  12 , for connecting to a driving circuit. 
         [0013]    In addition, a data pad  22  is formed at a terminal of the data line  20 . Also, a data pad electrode  40   b  is formed on the data pad  22 , for connecting to the driving circuit. 
         [0014]    Referring to  FIG. 1B , a gate insulating layer  15  and a passivation layer  25  are sequentially deposited on the gate pad  12 . Thus, the gate pad  12  is connected with the gate pad electrode  40   a  by a contact hole. 
         [0015]    Also, the passivation layer  25  is formed on the data pad  22 . Thus, the data pad  22  is connected with the data pad electrode  40   b  by a contact hole. 
         [0016]    A method for connecting the gate pad electrode  40   a  with the gate pad  12  and for connecting the data pad electrode  40   b  with the data pad  22  will be described with reference to  FIGS. 2A to 2G . 
         [0017]      FIGS. 2A to 2G  are cross sectional views taken along line I-I of  FIG. 1A , and illustrate a process for respectively connecting the gate pad electrode  40   a  and the data pad electrode  40   b  with the gate pad  12  and the data pad  22 . 
         [0018]    As shown in  FIG. 2A , the gate pad  12 , the gate insulating layer  15 , the data pad  22 , and the passivation layer  25  are sequentially formed on the substrate  1 . Then, contact holes are formed on the gate pad  12  and the data pad  22 . 
         [0019]    Referring to  FIG. 2B , a material layer for a pad electrode  40  is formed on an entire surface of the substrate  1 . 
         [0020]    As shown in  FIG. 2C , a photoresist layer  50  is formed on the material layer for the pad electrode  40 . 
         [0021]    Then, as shown in  FIG. 2D , after the gate pad  12  and the data pad  22  are covered with a mask  60 , the entire surface of the substrate  1  is exposed to light. 
         [0022]    Referring to  FIG. 2E , the photoresist layer  50  is patterned by development to form photoresist pattern layers  50   a  and  50   b  on the gate pad  12  and the data pad  22 . Because the portions of the photoresist layer  50  are irradiated by light are removed, the photoresist pattern layers  50   a  and  50   b  are formed only on the gate pad  12  and the data pad  22 . 
         [0023]    Then, as shown in  FIG. 2F , the material layer for pad electrode  40  is etched using the photoresist pattern layers  50   a  and  50   b  as a mask, to form gate pad electrode  40   a  and data pad electrode  40   b.    
         [0024]    Referring to  FIG. 2G , as the photoresist pattern layers  50   a  and  50   b  are removed, the gate pad electrode  40   a  is connected with the gate pad  12 , and the data pad electrode  40   b  is connected with the data pad  22 . 
         [0025]    However, the related art method of forming the pad electrode has the following disadvantages. 
         [0026]    To form the gate pad electrode  40   a  and the data pad electrode  40   b , it is necessary to perform photolithography with exposure and development. However, the photolithography requires an additional light-irradiation device for providing light. Thus, process costs increase. In addition, the process is complicated. 
       SUMMARY OF THE INVENTION 
       [0027]    Accordingly, the present invention is directed to a method for forming a pad electrode that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
         [0028]    An advantage of the present invention is to provide a simplified method for forming a pad electrode without using an additional light-irradiation device. 
         [0029]    Another advantage of the present invention is to provide a method for manufacturing an LCD device, in which a process for forming gate and data pad electrodes is applied to another process for forming other components of the LCD device. 
         [0030]    Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure and method particularly pointed out in the written description and claims hereof as well as the appended drawings. 
         [0031]    To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, a method of forming a pad electrode of an LCD device includes: forming a gate pad on a substrate; forming a gate insulating layer on a surface of the substrate including the gate pad; forming a data pad on the gate insulating layer; forming a passivation layer on the surface of the substrate including the data pad; forming a first contact hole in the gate insulating layer and the passivation layer on the gate pad; forming a second contact hole in the passivation layer on the data pad; coating a conductive photoresist on the surface of the substrate including the first contact hole and the second contact hole; and forming a gate pad electrode in the first contact hole and a data pad electrode in the second contact hole by ashing the conductive photoresist. 
         [0032]    The pad electrode may be formed of conductive photoresist, and the pad electrode may be formed in the contact hole with a simple method of ashing the conductive photoresist. Thus, it is possible to decrease cost and realize the simplified process. Also, the ashing process may be performed with oxygen plasma. 
         [0033]    Also, the process for forming the pad electrode by ashing the conductive photoresist may be applied to another process for forming other components of the LCD device. 
         [0034]    In another aspect of the present invention, a method of manufacturing an LCD device includes: forming a metal line on a substrate; forming an insulating layer on a surface of the substrate including the metal line; forming a hole in the insulating layer on the metal line; coating a conductive photoresist on the surface of the substrate including the hole; and forming a disconnection-prevention line of conductive photoresist in the hole by ashing the conductive photoresist. 
         [0035]    In another aspect of the present invention, a method of manufacturing an LCD device includes: forming a gate electrode and a common electrode on a substrate; forming a gate insulating layer on a surface of the substrate; forming a semiconductor layer on a predetermined portion of the gate insulating layer; forming source and drain electrodes on both sides of the semiconductor layer, forming a pixel electrode substantially in parallel with the common electrode; forming a passivation layer on the surface of the substrate; forming a contact hole in the passivation layer between the drain electrode and the pixel electrode; coating a conductive photoresist on the surface of the substrate including the contact hole; and forming a bridge electrode of conductive photoresist in the contact hole by ashing the coated conductive photoresist. 
         [0036]    The pixel electrode and the source and drain electrodes may be formed at the same time. Instead, the pixel electrode and the common electrode may be formed at the same time. 
         [0037]    In another aspect of the present invention, a method of manufacturing an LCD device includes: forming a gate electrode, a common electrode, and a pixel electrode on a substrate, wherein the common electrode is formed substantially in parallel with the pixel electrode; forming a gate insulating layer on a surface of the substrate; forming a semiconductor layer on a predetermined portion of the gate insulating layer; forming source and drain electrodes on both sides of the semiconductor layer; forming a passivation layer on the surface of the substrate; forming a contact hole in the gate insulating layer and the passivation layer between the drain electrode and the pixel electrode; coating a conductive photoresist on the surface of the substrate including the contact hole; and forming a bridge electrode of conductive photoresist in the contact hole by ashing the coated conductive photoresist. 
         [0038]    In another aspect of the present invention, an LCD device includes: a substrate; gate and data pads on the substrate; an insulating layer on a surface of the substrate, wherein the insulating layer has contact holes that correspond to the gate and data pads; and gate and data pad electrodes respectively connected with the gate and data pads through the contact holes, wherein the gate and data pad electrodes are formed of conductive photoresist. 
         [0039]    In another aspect of the present invention, an LCD device includes: a substrate; a gate line formed in a first direction on the substrate; a data line formed in a second direction substantially perpendicular to the first direction; an insulating layer on the substrate, wherein the insulating layer has a contact hole that corresponds to at least one of the gate and data lines; and a disconnection-prevention line connected with the at least one of the gate and data lines through the contact hole, wherein the disconnection-prevention line is formed of conductive photoresist. 
         [0040]    In another aspect of the present invention, an LCD device includes: a substrate; gate and data lines substantially perpendicular to each other on the substrate, so as to define a unit pixel region; common and pixel electrodes substantially parallel to each other inside the unit pixel region; a thin film transistor at a crossing of the gate and data lines, wherein the thin film transistor includes a gate electrode, a semiconductor layer, a source electrode, and a drain electrode; and a bridge electrode that connects the drain electrode and the pixel electrode, wherein the bridge electrode is formed of conductive photoresist. 
         [0041]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0042]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings: 
           [0043]      FIG. 1A  is a plan view illustrating a unit pixel region of a thin film transistor array substrate of an LCD device according to the related art; 
           [0044]      FIG. 1B  is a cross sectional view taken along line I-I of  FIG. 1A ; 
           [0045]      FIGS. 2A to 2G  are cross sectional views illustrating a process for respectively connecting gate and data pad electrodes with gate and data pads through contact holes in a thin film transistor array substrate according to the related art; 
           [0046]      FIGS. 3A to 3D  are cross sectional views illustrating a method for forming a pad electrode in an LCD device according to the present invention; 
           [0047]      FIG. 4A  is a cross sectional view illustrating a problem of the related art, for example, a disconnection of a pad electrode by photolithography; 
           [0048]      FIG. 4B  is a cross sectional view illustrating a structure for preventing a disconnection of a pad electrode in an LCD device according to the present invention; 
           [0049]      FIG. 5A  is a plan view illustrating a unit pixel region of an LCD device according to the present invention; 
           [0050]      FIG. 5B  is a cross sectional view taken along line I-I of  FIG. 5A ; 
           [0051]      FIG. 6A  is a plan view illustrating a unit pixel region of an IPS mode LCD device according to the present invention; and 
           [0052]      FIGS. 6B to 6C  are cross sectional views taken along line I-I of  FIG. 6A . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0053]    Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or similar parts. 
       First Embodiment 
       [0054]      FIGS. 3A to 3D  are cross sectional views illustrating a process for forming a pad electrode of an LCD device according to the present invention, taken along line I-I of  FIG. 1A . Hereinafter, an explanation will be limited to a pad electrode. Accordingly, other components of the LCD device may be variably formed within the scope known to those skilled in the art. 
         [0055]    First, as shown in  FIG. 3A , a gate pad  120  is formed on a substrate  101 , and a gate insulating layer  150  may be formed on an entire surface of the substrate  101  including the gate pad  120 . Then, a data pad  220  is formed on the gate insulating layer  150 , and a passivation layer  250  may be formed on the entire surface of the substrate  101  including the data pad  220 . 
         [0056]    The gate insulating layer  150  and the passivation layer  250  may be formed of a same material or different materials. 
         [0057]    If the material of the gate insulating layer  150  is different than the material of the passivation layer  250 , an undercut etch may be generated when forming a contact hole. In the related art, this causes a pad electrode to possibly be disconnected by the photolithographic processing. However, in the present invention, even if the undercut etch is generated during the process of forming the contact hole, it is possible to prevent the disconnection of the pad electrode. This is explained with reference to  FIGS. 4A and 4B . 
         [0058]    Referring to  FIG. 3B , a first contact hole is formed on the gate pad  120  in the gate insulating layer  150  and the passivation layer  250 . Also, a second contact hole is formed on the data pad  220  in the passivation layer  250 . The first and second contact holes may be formed at the same time. 
         [0059]    Then, as shown in  FIG. 3C , a conductive photoresist  400  may be coated on the entire surface of the substrate  101  including the first and second contact holes. The conductive photoresist  400  is formed of conducting polymer. The conducting polymer has a conductivity based on the delocalization of a conjugated double bond material. The polymer is delocalized by removing electrons or inserting electrons, wherein the conjugated double bond material may have both single bonds and double bonds which are alternately arranged. Electrons may be removed by p-type doping. Electrons may be inserted by n-type doping. 
         [0060]    Preferably, the conducting polymer is formed of a material selected from groups of 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    However, any conducting polymer may be applied in the present invention. 
         [0061]    Referring to  FIG. 3D , a gate pad electrode  400   a  is formed in the first contact hole, and a data pad electrode  400   b  is formed in the second contact hole by ashing the conductive photoresist  400 . 
         [0062]    In the ashing process, CO and CO 2  are removed from the conductive photoresist  400  including the conducting polymer by combustion under predetermined conditions, such as, oxygen plasma. 
         [0063]    Accordingly, the gate pad electrode  400   a  and the data pad electrode  400   b  are formed in a simplified process by ashing the conductive photoresist  400 . 
         [0064]    Furthermore, the method for forming the pad electrode according to the present invention prevents the disconnection of pad electrode. 
         [0065]      FIG. 4A  is a cross sectional view illustrating a problem of the related art, for example, the disconnection of the pad electrode by photolithography.  FIG. 4B  is a cross sectional view illustrating a structure for preventing the disconnection of the pad electrode in the LCD device according to the present invention. 
         [0066]    In the related art, as shown in  FIG. 4A , if contact holes are formed by etching a gate insulating layer  15  and a passivation layer  25  on a gate pad  12  of a substrate  1 , an etching undercut is generated because an etching ratio for the gate insulating layer  15  is higher than an etching ratio for the passivation layer  25 . That is, the gate insulating layer  15  is etched inwardly more than the passivation layer  25 . The etching undercut is generated when the material of the gate insulating layer  15  is different than the material of the passivation layer  25 . 
         [0067]    If photolithography is then used in the related art as shown in  FIGS. 2A to 2G , a gate pad electrode  40   a  may be cut into three parts, as shown in  FIG. 4A . 
         [0068]    In case of the present invention, as shown in  FIG. 4B , even though the undercut etch is generated, the gate pad electrode  400   a  is not disconnected since the gate pad electrode  400   a  is formed by ashing a conductive photoresist. 
         [0069]    Accordingly, the method for forming the pad electrode according to the present invention is even more useful when the gate insulating layer  150  is made of a different material than the passivation layer  250 . 
         [0070]    In addition, an LCD device manufactured by the method of forming the pad electrode according to the present invention will be described as follows. 
         [0071]    Referring to  FIG. 3D , the LCD device includes the substrate  101 , the gate pad  120 , the data pad  220 , the insulating layers  150  and  250 , the gate pad electrode  400   a , and the data pad electrode  400   b . The gate pad  120  and the data pad  220  are formed over the substrate  101 . Also, the insulating layers  150  and  250  may be formed on the entire surface of the substrate  101 , wherein the insulating layers  150  and  250  have contact holes that correspond to the gate pad  120  and the data pad  220 . Then, the gate pad electrode  400   a  and the data pad electrode  400   b  are respectively connected with the gate pad  120  and the data pad  220  through the contact holes. The gate pad electrode  400   a  and the data pad electrode  400   b  are formed of the conductive photoresist including the conducting polymer. 
         [0072]    In addition, other varying components of the LCD device may be formed, and the variations may be within the scope known to those skilled in the art. 
       Second Embodiment 
       [0073]      FIGS. 5A and 5B  illustrate an example in which a conductive photoresist is applied to a disconnection-prevention line of an LCD device according to the present invention.  FIG. 5A  is a plan view illustrating a unit pixel region of an LCD device according to the present invention, and  FIG. 5B  is a cross sectional view taken along line I-I of  FIG. 5A . 
         [0074]    As shown in  FIG. 5A , a gate line  100  is formed in a first direction on a substrate  101 . Then, a data line  200  is formed in a second direction substantially perpendicular to the first direction. 
         [0075]    In addition, a disconnection-prevention line  270  is formed. As shown, the disconnection-prevention line  270  may be formed on the data line  200 . However, the disconnection-prevention line  270  may be formed on the gate line  100 . 
         [0076]    A thin film transistor (not shown) is formed at a crossing of the gate line  100  and the data line  200 . 
         [0077]    Referring to  FIG. 5B , a gate insulating layer  150  is formed under the data line  200 , thus insulating the data line  200  from the gate line  100 . Also, a passivation layer  250  is formed on the data line  200 . Then, the data line  200  is connected with the disconnection-prevention line  270  through a contact hole formed in the passivation layer  250  on the data line  200 . 
         [0078]    The disconnection-prevention line  270  is formed on the gate line  100  or the data line  200 . Accordingly, even though the gate line  100  or the data line  200  is disconnected, the disconnection-prevention line  270  prevents a malfunction of the LCD device. 
         [0079]    The disconnection-prevention line  270  may be formed of conductive photoresist. A method for forming the disconnection-prevention line  270  may be identical to a method for forming a pad electrode shown in  FIGS. 3A to 3D . 
         [0080]    That is, the gate line  100 , the gate insulating layer  150 , the data line  200 , and the passivation layer  250  may be sequentially formed on the substrate  101 . Then, the contact hole may be formed on the gate line  100  in the gate insulating layer  150  and the passivation layer  250 , or the contact hole may be formed on the data line  200  in the passivation layer  250 . Then, the conductive photoresist may be coated on an entire surface of the substrate including the contact hole. Then, the disconnection-prevention line  270  of conductive photoresist is formed in the contact hole by ashing the conductive photoresist. The material of the conductive photoresist and the ashing conditions may be identical to those of the first embodiment of the present invention. 
       Third Embodiment 
       [0081]      FIGS. 6A ,  6 B, and  6 C illustrate an example in which a conductive photoresist is applied to a bridge electrode of an IPS mode LCD device according to the present invention.  FIG. 6A  is a plan view illustrating a unit pixel region of an IPS mode LCD device according to the present invention, and  FIGS. 6B and 6C  are cross sectional views taken along line I-I of  FIG. 6A . 
         [0082]    As shown in  FIG. 6A , a gate line  100  and a data line  200  are formed substantially perpendicular to each other on a substrate  101 , whereby a unit pixel region is defined with the gate and data lines  100  and  200 . 
         [0083]    Then, a thin film transistor is formed at a crossing of the gate and data lines  100  and  200 . The thin film transistor includes a gate electrode  100   a , a semiconductor layer  160 , a source electrode  200   a , and a drain electrode  200   b . The gate electrode  100   a  protrudes from the gate line  100 , the source electrode  200   a  protrudes from the data line  200 , and the drain electrode  200   b  is opposite to the source electrode  200   a . A structure of the thin film transistor may be varied within the scope known to those in the related art. 
         [0084]    In the unit pixel region, a common electrode  140  and a pixel electrode  300  are formed substantially in parallel. Then, a bridge electrode  500  electrically connects the drain electrode  200   b  with the pixel electrode  300 . 
         [0085]    Referring to  FIG. 6B , the pixel electrode  300  may be formed at the same layer as the drain electrode  200   b . In this case, the bridge electrode  500  electrically connects the drain electrode  200   b  with the pixel electrode  300  through a contact hole formed in the passivation layer  250 . 
         [0086]    As shown in  FIG. 6C , the pixel electrode  300  may be formed on the same layer as the common electrode  140 . In this case, the bridge electrode  500  electrically connects the drain electrode  200   b  with the pixel electrode  300  through a contact hole formed in the gate insulating layer  150  and the passivation layer  250 . 
         [0087]    The bridge electrode  500  may be formed of conductive photoresist. A method for forming the bridge electrode may be identical to a method for forming a pad electrode shown in  FIGS. 3A to 3D . 
         [0088]    As shown in  FIG. 6B , if the pixel electrode  300  is formed at the same layer as the drain electrode  200   b , the gate electrode  100   a  and the common electrode  140  are formed on the substrate  101 . Then, the gate insulating layer  150  may be formed on the entire surface of the substrate  101 . Then, the semiconductor layer  160  may be formed on a predetermined portion of the gate insulating layer  150 . Also, the source and drain electrodes  200   a  and  200   b  may be positioned on both sides of the semiconductor layer  160 , and the pixel electrode  300  may be formed substantially in parallel with the common electrode  140 . Thereafter, the passivation layer  250  may be formed on the entire surface of the substrate  101 . Also, the contact hole may be formed in the passivation layer  250  between the drain electrode  200   b  and the pixel electrode  300 . Then, the conductive photoresist may be coated on the entire surface of the substrate  101  including the contact hole, and the bridge electrode  500  of conductive photoresist is formed in the contact hole by ashing the conductive photoresist. 
         [0089]    Referring to  FIG. 6C , if the pixel electrode  300  is formed in the same layer as the common electrode  140 , the gate electrode  100   a , the common electrode  140  and the pixel electrode  300  are formed on the substrate  101 , wherein the pixel electrode  300  is formed substantially in parallel with the common electrode  140 . Then, the gate insulating layer  150  may be formed on the entire surface of the substrate  101 . Also, the semiconductor layer  160  may be formed on a predetermined portion of the gate insulating layer  150 , and the source and drain electrodes  200   a  and  200   b  may be formed on both sides of the semiconductor layer  160 . Thereafter, the passivation layer  250  may be formed on the entire surface of the substrate  101 . Then, the contact hole may be formed in the gate insulating layer  150  and the passivation layer  250  between the drain electrode  200   b  and the pixel electrode  300 . Then, the conductive photoresist may be coated on the entire surface of the substrate including the contact hole, and the bridge electrode  500  of conductive photoresist is formed in the contact hole by ashing the conductive photoresist. 
         [0090]    The material of conductive photoresist and the ashing conditions may be identical to those of the first embodiment of the present invention. 
         [0091]    In addition, other varying components of the IPS mode LCD device may be formed, and the variations may be within the scope known to those skilled in the art. 
         [0092]    As mentioned above, the method for forming the pad electrode and the LCD device manufactured by the method according to the present invention have the following advantages. 
         [0093]    In the present invention, it is possible to form the pad electrode, the disconnection-prevention line, and the bridge electrode of the IPS mode LCD device in a simple method by ashing the conductive photoresist. Thus, costs are decreased and a simplified process is obtained. 
         [0094]    It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.