Method and apparatus for forming metal interconnects

Abstract

The present invention provides a method and apparatus for forming reliable interconnects in which the overlap of the line over the plug or via is minimized or eliminated. In one aspect, a barrier plug comprised of a conductive material, such as tungsten, is deposited over the via to provide an etch stop during line etching and to prevent diffusion of the metal, such as copper, into the surrounding dielectric material if the line is misaligned over the via. Additionally, the barrier plug prevents an overall reduction in resistance of the interconnect and enables reactive ion etching to be employed to form the metal line. In another aspect, reactive ion etching techniques are employed to selectively etch the metal line and the barrier layer to provide a controlled etching process which exhibits selectivity for the metal line, then the barrier and then the via or plug.

1 . A method of forming a line over a via, comprising: 
 a) forming an etch barrier in an upper portion of the via;    b) depositing a metal layer over the etch barrier and via; and then    c) etching the line.    
     
     
         2 . The method of  claim 1  wherein the etch barrier is formed by depositing a metal over the via.  
     
     
         3 . The method of  claim 2  wherein the metal is tungsten.  
     
     
         4 . The method of  claim 3  wherein the tungsten is selectively deposited over the via.  
     
     
         5 . The method of  claim 1  wherein the etch barrier is formed by removing a portion of the upper surface of the via to form a recess therein, depositing a conductive material in the recess and then planarizing the upper surface of the substrate to form an barrier in the recess.  
     
     
         6 . The method of  claim 5  wherein the recess is formed using an etch process.  
     
     
         7 . The method of  claim 5  wherein the recess is formed using a chemical mechanical process.  
     
     
         8 . The method of  claim 6  wherein the upper surface of the substrate is planarized using chemical mechanical polishing.  
     
     
         9 . The method of  claim 7  wherein the upper surface of the substrate is planarized using chemical mechanical polishing.  
     
     
         10 . The method of  claim 8  wherein the via and the line are comprised of copper.  
     
     
         11 . The method of  claim 9  wherein the via and the line are comprised of copper.  
     
     
         12 . A method of forming an interconnect on a substrate, comprising: 
 a) depositing a metal over the field of a substrate and in a via formed on a substrate;    b) removing the metal from the field of the substrate;    c) depositing a conductive barrier over the via;    d) depositing a blanket metal layer over the conductive barrier and the field of the substrate; and    e) etching a line in the blanket metal layer.    
     
     
         13 . The method of  claim 12  wherein the conductive barrier is selectively deposited over the via.  
     
     
         14 . The method of  claim 12  further comprising the step of forming a recess in the top of the via prior to depositing a conductive barrier over the via.  
     
     
         15 . The method of  claim 14  further comprising the step of planarizing the surface of the substrate after the conductive barrier has been deposited in the recess.  
     
     
         16 . The method of  claim 14  wherein the recess is formed using an etch process.  
     
     
         17 . The method of  claim 15  wherein the recess is formed using a chemical mechanical process.  
     
     
         18 . The method of  claim 17  wherein the via and the line are comprised of copper.  
     
     
         19 . The method of  claim 12  wherein the line is formed using an etch process which is tuned to selectively etch two different materials.  
     
     
         20 . The method of  claim 12  wherein the conductive barrier is comprised of tantalum and the metal is comprised of copper.  
     
     
         21 . The method of claim  20  wherein the etching step comprises first etching the copper using a chlorine based chemistry and then etching the barrier comprising tantalum using a fluorine based chemistry.