Liquid crystal display

Abstract

There is provided a liquid crystal display device in which the wiring resistivity of signal lines is reduced. The liquid crystal display device includes substrates disposed in opposition to each other with a liquid crystal interposed therebetween, a thin film transistor to be driven by a scanning signal supplied from a gate signal line, and a pixel electrode to be supplied with a video signal from a drain signal line via the thin film transistor, the thin film transistor and the pixel being provided in each pixel area on a liquid-crystal-side surface of one of the substrates. The gate signal line is made of a multi-layered structure including at least an ITO film formed on the liquid-crystal-side surface and a Mo layer formed to overlie the ITO film.

1 . A liquid crystal display device comprising: 
 substrates disposed in opposition to each other with a liquid crystal interposed there between;    a thin film transistor to be driven by a scanning signal supplied from a gate signal line; and    a pixel electrode to be supplied with a video signal from a drain signal line via the thin film transistor,    the thin film transistor and the pixel being provided in each pixel area on a liquid-crystal-side surface of one of the substrates,    the gate signal line being made of a multi-layered structure including: either one of an ITO film and an IZO film which is formed on at least the liquid-crystal-side surface; and a layer formed to overlie the either one of the ITO film and the IZO film, the layer being any one of a Mo layer, a W layer, a Cr layer, a Ti layer and a Ta layer, or an alloy layer made of arbitrary ones of Mo, W, Cr, Ti and Ta.    
   
   
       2 . A liquid crystal display device comprising: 
 substrates disposed in opposition to each other with a liquid crystal interposed there between;    a thin film transistor to be driven by a scanning signal supplied from a gate signal line; and    a pixel electrode to be supplied with a video signal from a drain signal line via the thin film transistor,    the thin film transistor and the pixel being provided in each pixel area on a liquid-crystal-side surface of one of the substrates,    the gate signal line being made of a multi-layered structure including: either one of an ITO film and an IZO film which is formed on at least the liquid-crystal-side surface; and a layer formed to overlie the either one of the ITO film and the IZO film, the layer being any one of a Mo layer, a W layer, a Cr layer, a Ti layer and a Ta layer, or an alloy layer made of arbitrary ones of Mo, W, Cr, Ti and Ta,    the pixel electrode being formed on an insulating film which includes as one area a gate insulating film of the thin film transistor.    
   
   
       3 . A liquid crystal display device according to  claim 2 , wherein the thin film transistor is made of a stacked structure in which a gate electrode connected to the gate signal line, the gate insulating film, a semiconductor layer and a pair of electrodes formed on the upper surface of the semiconductor layer are stacked in that order, an extended end of the pixel electrode being formed on the upper surface of the semiconductor layer to constitute one of the pair of electrodes.  
   
   
       4 . A manufacturing method for a liquid crystal display device comprising the steps of: 
 forming, on a substrate, gate signal lines each made of a stacked structure in which a transparent conductive film and a metal layer are stacked in that order;    forming an insulating film to cover the gate signal lines;    forming, on the insulating film, a stacked structure in which a semiconductor layer, a high-concentration layer and a conductive layer are stacked in that order;    performing selective etching of the conductive layer and the high-concentration layer by using a resist reflow method, to form drain electrodes and source electrodes for thin film transistors as well as drain signal lines and to perform selective etching of the semiconductor layer;    forming pixel electrodes each of which is in part directly superposed on the source electrode of the corresponding one of the thin film transistors; and forming a protective film and opening, in the protective film, apertures for exposing the respective pixel electrodes.    
   
   
       5 . A manufacturing method for a liquid crystal display device according to  claim 4 , wherein the resist reflow method includes the steps of: 
 forming a photoresist film on an area in which to form the drain electrode and the source electrode of each of the thin film transistors as well as the corresponding one of the drain signal lines;    performing etching using the photoresist film as a mask;    sagging the photoresist film to cause the photoresist film to exist at least between the drain electrode and the source electrode; and    performing etching using the sagged photoresist film as a mask.    
   
   
       6 . A liquid crystal display device according to  claim 4 , wherein at the same time that the pixel electrodes are formed, a transparent conductive film is deposited on areas in which to form drain terminal parts of the respective drain signal lines.  
   
   
       7 . A liquid crystal display device according to  claim 4 , wherein at the same time that holes are opened in the protective film, holes at gate terminal parts and drain terminal parts are opened.  
   
   
       8 - 11 . (canceled)  
   
   
       12 . A manufacturing method for a liquid crystal display device comprising the steps of: 
 forming, on a substrate, gate signal lines each made of a stacked structure in which a transparent conductive film and a metal layer are stacked in that order;    forming an insulating film to- cover the gate signal lines;    forming, on the insulating film, a stacked structure in which a semiconductor layer, a high-concentration layer and a conductive layer are stacked in that order;    performing selective etching so that the conductive layer, the high-concentration layer and the semiconductor layer are left in each of an area in which to form drain electrodes for thin film transistors, an area in which to form source electrodes for the thin film transistors, an area between the drain electrode and the source electrode of each of the thin film transistors, and an area in which to form drain signal lines;    forming a transparent conductive film which constitutes pixel electrodes;    performing selective etching so that the transparent conductive film is left in each of the area in which to form the drain electrodes for the thin film transistors, the area in which to form the source electrodes for the thin film transistors, the area in which to form the drain signal lines, and an area in which to form the pixel electrodes;    performing selective etching of the conductive layer and the high-concentration layer between the drain electrode and the source electrode of each of the thin film transistors by using the remaining transparent film as a mask; and    forming a protective film and opening, in the protective film, apertures for exposing the respective pixel electrodes.    
   
   
       13 . A manufacturing method for a liquid crystal display device according to  claim 12 , wherein at the same time that holes are opened in the protective film, holes at gate terminal parts and drain terminal parts are opened.  
   
   
       14 . A manufacturing method for a liquid crystal display device comprising the steps of: 
 forming, on a substrate, a transparent conductive film and a conductive layer partly superposed on the transparent conductive film, and forming counter electrodes from a single layer made of the transparent conductive film, as well as gate signal lines and counter voltage signal lines from a stacked structure in which the transparent conductive film and the conductive layer are stacked;    forming an insulating film to cover the counter electrode electrodes, the counter voltage signal lines and the gate signal lines;    forming, on the insulating film, a stacked structure in which a semiconductor layer, a high-concentration layer and a conductive layer are stacked in that order;    performing selective etching of the conductive layer and the high-concentration layer by using a resist reflow method, to form drain electrodes and source electrodes for thin film transistors as well as drain signal lines and to perform selective etching of the semiconductor layer;    forming pixel electrodes each made of a transparent conductive film which is in part directly superposed on the source electrode of the corresponding one of the thin film transistors; and    forming a protective film and opening, in the protective film, apertures for exposing the respective pixel electrodes.    
   
   
       15 . A manufacturing method for a liquid crystal display device according to  claim 14 , wherein the resist reflow method includes the steps of: forming a photoresist film on an area in which to form the drain electrode and the source electrode of each of the thin film transistors as well as the corresponding one of the drain signal lines; 
 performing etching using the photoresist film as a mask;    sagging the photoresist film to cause the photoresist film to exist at least between the drain electrode and the source electrode; and    performing etching using the sagged photoresist film as a mask.    
   
   
       16 . A liquid crystal display device according to  claim 14 , wherein at the same time that the pixel electrodes are formed, a transparent conductive film is deposited on areas in which to form drain terminal parts of the respective drain signal lines.  
   
   
       17 . A liquid crystal display device according to  claim 14 , wherein at the same time that holes are opened in the protective film, holes at gate terminal parts and drain terminal parts are opened.  
   
   
       18 - 21 . (canceled)  
   
   
       22 . A manufacturing method for a liquid crystal display device comprising the steps of: 
 forming on a substrate a stacked structure in which a first material layer and a second material layer are stacked in that order;    forming a photoresist film on the upper surface of the stacked structure and forming a photoresist film of larger film thickness on a first area as well as a photoresist film of smaller film thickness on a second area by using half exposure;    etching the second material layer by using the photoresist film as a mask and vanishing the photoresist film of smaller film thickness;    etching the first material layer by using the second material layer as a mask; and    forming a stacked structure in which the first material layer and the second material layer are stacked in that order on the first area of the substrate, and forming the first material layer on the second area.    
   
   
       23 . A manufacturing method for a liquid crystal display device which includes pixel areas provided on a liquid-crystal-side surface of either one of substrates disposed in opposition to each other with a liquid crystal interposed there between, each of the pixel areas being surrounded by gate signal lines disposed to be extended in the x direction and to be juxtaposed in the y direction and drain signal lines disposed to be extended in the y direction and to be juxtaposed in the x direction; 
 each of the pixel areas including:    a switching element to be driven by a gate signal from either one of the gate signal lines;    a pixel electrode to be supplied with a video signal from a drain signal line via the switching element; and    a counter electrode for causing an electric field to be generated between the counter electrode and the pixel electrode,    the manufacturing method comprising the steps of:    forming, on either one of the substrates, a stacked structure in which a first material layer and a second material layer are stacked in that order; forming a photoresist film on the upper surface of the stacked structure and forming, by using half exposure, a photoresist film of larger film thickness on each area in which to form a gate signal line as well as a photoresist film of smaller film thickness on each area in which to form a counter electrode; etching the second material layer by using the photoresist film as a mask and vanishing the photoresist film of smaller film thickness; and    etching the first material layer by using the second material layer as a mask.    
   
   
       24 . A manufacturing method for a liquid crystal display device according to claim  21 , wherein the first material layer is made of an ITO film, and the second material layer is made of a Mo layer