Circuit board, display device, and process for production of circuit board

Abstract

The present invention provides a circuit board having excellent productivity, particularly a circuit board having excellent productivity with respect to a semiconductor layer and source layer forming step, a display device, and a process for producing a circuit board. The circuit board of the present invention is a circuit board including an oxide semiconductor layer and an electrode connected to the oxide semiconductor layer, wherein the electrode is formed by essentially laminating a layer made of a metal other than copper and a layer containing copper.

1 . A circuit board comprising:
 an oxide semiconductor layer; and   an electrode which is connected to the oxide semiconductor layer,   wherein the electrode is formed by essentially laminating a layer made of a metal other than copper and a layer containing copper.   
     
     
         2 . The circuit board according to  claim 1 , wherein the layer made of a metal other than copper contains at least one selected from a group consisting of titanium and molybdenum. 
     
     
         3 . The circuit board according to  claim 1 , wherein the oxide semiconductor layer is formed of indium gallium zinc composite oxide. 
     
     
         4 . The circuit board according to  claim 1 , wherein the electrode includes a source electrode and a drain electrode, and
 the source electrode and the drain electrode include portions connected to the oxide semiconductor layer, respectively, and the portion of the source electrode which is connected to the semiconductor layer and the portion of the drain electrode which is connected to the semiconductor layer face each other with a gap interposed therebetween.   
     
     
         5 . The circuit board according to  claim 4 , wherein the portion of the source electrode which is connected to the semiconductor layer and the portion of the drain electrode connected to the semiconductor layer are located further inside than the semiconductor layer when a main surface of the board is seen in plan view. 
     
     
         6 . A display device comprising the circuit board according to  claim 1 . 
     
     
         7 . A process for producing a circuit board including an oxide semiconductor layer and an electrode connected to the oxide semiconductor layer, the process comprising:
 a semiconductor layer forming step of forming an oxide semiconductor layer;   an electric conductor layer forming step of forming an electric conductor layer by essentially laminating a layer made of a metal other than copper and a layer containing copper; and   a processing step of processing the electric conductor layer by using wet etching,   wherein the processing step includes forming the electrode.   
     
     
         8 . The process for producing a circuit board according to  claim 7 , wherein the processing step includes a first etching step of etching the electric conductor layer and the oxide semiconductor layer and a second etching step of etching the electric conductor layer by using wet etching, and
 the second etching step separates the electric conductor layer into a source electrode and a drain electrode, and causes a portion of the source electrode which is connected to the semiconductor layer and a portion of the drain electrode which is connected to the semiconductor layer to face each other with a gap interposed therebetween.   
     
     
         9 . The process for producing a circuit board according to  claim 8 , wherein in the first etching step and/or the second etching step, the layer containing copper is etched by using an etchant containing hydrogen peroxide and an acid. 
     
     
         10 . The process for producing a circuit board according to  claim 8 , wherein the layer made of a metal other than copper is a layer made of a metal containing molybdenum, and in the first etching step and/or the second etching step, the layer made of a metal containing molybdenum is etched by using an etchant containing hydrogen peroxide and an acid. 
     
     
         11 . The process for producing a circuit board according to  claim 8 , wherein in the first etching step and/or the second etching step, the layer containing copper is etched by using an alkaline etchant. 
     
     
         12 . The process for producing a circuit board according to  claim 8 , wherein the layer made of a metal other than copper is a layer made of a metal containing titanium, and in the first etching step and/or the second etching step, the layer made of a metal containing titanium is etched by using an alkaline etchant. 
     
     
         13 - 14 . (canceled) 
     
     
         15 . The process for producing a circuit board according to  claim 8 , wherein in the first etching step, the oxide semiconductor layer is etched by using an etchant containing oxalic acid. 
     
     
         16 . The process for producing a circuit board according to  claim 7 , wherein the processing step includes a gap portion etching step of etching the electric conductor layer by using wet etching, and
 the gap portion etching step separates the electric conductor layer into a source electrode and a drain electrode, and causes a portion of the source electrode which is connected to the semiconductor layer and a portion of the drain electrode which is connected to the semiconductor layer to face each other with a gap interposed therebetween.   
     
     
         17 . The process for producing a circuit board according to  claim 16 , wherein in the gap portion etching step, the layer containing copper is etched by using an etchant containing hydrogen peroxide and an acid. 
     
     
         18 . The process for producing a circuit board according to  claim 16 , wherein the layer made of a metal other than copper is a layer made of a molybdenum-based metal, and in the gap portion etching step, the layer made of a molybdenum-based metal is etched by using an etchant containing hydrogen peroxide and an acid. 
     
     
         19 . The process for producing a circuit board according to  claim 16 , wherein in the gap portion etching step, the layer containing copper is etched by using an alkaline etchant. 
     
     
         20 . The process for producing a circuit board according to  claim 16 , wherein the layer made of a metal other than copper is a layer made of a titanium-based metal, and in the gap portion etching step, the layer made of a titanium-based metal is etched by using an alkaline etchant. 
     
     
         21 - 22 . (canceled) 
     
     
         23 . The process for producing a circuit board according to  claim 16 , wherein in the semiconductor layer forming step, the oxide semiconductor layer is etched by using an etchant containing oxalic acid. 
     
     
         24 . The process for producing a circuit board according to  claim 7 , wherein the oxide semiconductor layer is formed of indium gallium zinc composite oxide.