Thin-film transistor and method of making same

Abstract

A thin-film transistor includes a substrate, and a gate including a double-layered structure having first and second metal layers provided on the substrate, the first metal layer being wider than the second metal layer by 1 to 4 μm. A method of making such a thin-film transistor includes the steps of: depositing a first metal layer on a substrate, depositing a second metal layers directly on the first metal layer; forming a photoresist having a designated width on the second metal layer; patterning the second metal layer via isotropic etching using the photoresist as a mask; patterning the first metal layer by means of an anisotropic etching using the photoresist as a mask, the first metal layer being etched to have the designated width, thus forming a gate having a laminated structure of the first and second metal layers; and removing the photoresist.

What is claimed is:  
     
         1 . A method of making a thin-film transistor, comprising the step of: 
 depositing a first metal layer on a substrate;    depositing a second metal layer on the first metal layer without forming a photoresist on the first metal layer beforehand;    forming a single photoresist having a predetermined width on the second metal layer;    patterning the first and second metal layers simultaneously in a single etching step using the single photoresist as a mask; and    removing the photoresist.    
     
     
         2 . The method of making a thin film transistor as claimed in  claim 1 , wherein the second metal layer is etched to be wider than the first metal layer by about 1 μm to about 4 μm.  
     
     
         3 . The method of making a thin film transistor as claimed in  claim 1 , further comprising the steps of: 
 forming a first insulating layer on the substrate including the gate;    forming a semiconductor layer and an ohmic contact layer on a portion of the first insulating layer at a location corresponding to the gate;    forming a source electrode and a drain electrode extending onto the first insulating layer on two sides of the ohmic contact layer, and removing a portion of the ohmic contact layer exposed between the source and the drain electrodes; and    forming a second insulating layer covering the semiconductor layer, the source electrode, the drain electrode and the first insulating layer.    
     
     
         4 . The method of making a thin film transistor as claimed in  claim 1 , wherein the first and second metal layers are sequentially deposited via sputtering or a chemical vapor deposition method without breaking a vacuum state.  
     
     
         5 . The method of making a thin film transistor as claimed in  claim 1 , wherein the first metal layer includes Al, Cu, or Au.  
     
     
         6 . The method of making a thin film transistor as claimed in  claim 1 , wherein the first metal layer has a thickness of about 500 Å to about 4000 Å.  
     
     
         7 . The method of making a thin film transistor as claimed in  claim 1 , wherein the second metal layer includes Mo, Ta or Co.  
     
     
         8 . The method of making a thin film transistor as claimed in  claim 1 , wherein the first metal layer has a thickness of about 500 Å to about 2000 Å.  
     
     
         9 . The method of making a thin film transistor as claimed in  claim 1 , wherein the second metal layer is etched with an etching solution prepared with a mixture of phosphoric acid H 3 PO 4 , acetic acid CH 3 COOH and nitric acid HNO 3 .  
     
     
         10 . The method of making a thin film transistor as claimed in  claim 1 , wherein the first metal layer is removed via a dry etching process.  
     
     
         11 . The method of making a thin film transistor as claimed in  claim 1 , wherein two side portions of the first metal layer having no second metal layer deposited thereon have substantially the same width as each other.