Method for forming copper interconnects

Abstract

Embodiments of the invention provide a method of plating a copper film on a substrate in an electrochemical plating apparatus. The method includes positioning a substrate in an electrolyte solution, applying a current between the substrate and an anode to generate a current density of between about 10 mA/cm2 and about 40 mA/cm2 on the substrate surface, rotating the, substrate at a rotational speed of between about 20 rpm and about 50 rpm, and plating a copper film having a sheet resistance of less than about 16.5×10 −2 Ohms/cm 2 . Embodiments of the invention further provide a copper film plated onto a semiconductor substrate, wherein the film has improved electromigration and stress characteristics

What is claimed is:  
     
         1 . A method of plating a copper film on a substrate in an electrochemical plating apparatus, comprising: 
 positioning a substrate in an electrolyte solution;    applying a current between the substrate and an anode to generate a current density of between about 10 mA/cm 2  and about 40 mA/cm 2  on the substrate surface;    rotating the substrate at a rotational speed of between about 20 rpm and about 50 rpm; and    plating a copper film having a sheet resistance of less than about 16.5×10 −2  Ohms/cm 2 .    
     
     
         2 . The method of  claim 1 , wherein the sheet resistance is between about 15.25×10 −2  Ohms/cm 2  and about 16.25×10 −2  Ohms/cm 2 .  
     
     
         3 . The method of  claim 1 , wherein the copper film has a pre-anneal stress of less than about 90 Mpa.  
     
     
         4 . The method of  claim 1 , wherein the copper film has post anneal:pre-anneal stress ratio of less than about 6.  
     
     
         5 . The method of  claim 1 , wherein the copper film has a sulfur concentration of less than about 8×10 18  atoms/cm 3 .  
     
     
         6 . The method of  claim 1 , wherein the copper film has a nitrogen concentration of less than about 25×10 18  atoms/cm 3 .  
     
     
         7 . The method of  claim 1 , wherein the copper film has an oxygen concentration of less than about 9×10 18  atoms/cm 3 .  
     
     
         8 . The method of  claim 1 , wherein the copper film has a chlorine concentration of less than about 20×10 18  atoms/cm 3 .  
     
     
         9 . The method of  claim 1 , wherein the copper film has a carbon concentration of less than about 50×10 18  atoms/cm 3 .  
     
     
         10 . The method of  claim 2 , wherein the copper film has a sulfur concentration of less than about 8×10 18  atoms/cm 3 , a nitrogen concentration of less than about 25×10 18  atoms/cm 3 , an oxygen concentration of less than about 9×10 18  atoms/cm 3 , a chlorine concentration of less than about 20×10 18  atoms/cm 3 , and a carbon concentration of less than about 50×10 18  atoms/cm 3 .  
     
     
         11 . The method of  claim 2 , wherein the current density is between about 15 mA/cm 2  and about 30 mA/cm 2 , and the rotational speed is between about 5 rpm and about 20 rpm.  
     
     
         12 . A copper film having a sheet resistance of between about 10.5×10 −2  Ohms/cm 2  and about 16.5×10 −2  Ohms/cm 2  formed onto a semiconductor substrate via an electrochemical deposition process, wherein the process includes applying a current density to the substrate surface of between about 15 mA/cm2 and about 30 mA/cm2 during the process and rotating the substrate at between about 10 rpm and about 25 rpm during the process.  
     
     
         13 . The copper film of  claim 12 , wherein the copper film comprises a sulfur concentration of less than about 8×10 18  atoms/cm 3 .  
     
     
         14 . The copper film of  claim 12 , wherein the copper film comprises a nitrogen concentration of less than about 25×10 18  atoms/cm 3 .  
     
     
         15 . The copper film of  claim 12 , wherein the copper film comprises, an oxygen concentration of less than about 9×10 18  atoms/cm 3 .  
     
     
         16 . The copper film of  claim 12 , wherein the copper film comprises a chlorine concentration of less than about 20×10 18  atoms/cm 3 .  
     
     
         17 . The copper film of  claim 12 , wherein the copper film has sheet resistance of between about 15.25×10 −2  Ohms/cm 2  and about 16.25×10 −2  Ohms/cm 2 .  
     
     
         18 . The copper film of  claim 12 , wherein the copper film has a pre-anneal stress of less than about 90 Mpa.  
     
     
         19 . The copper film of  claim 12 , wherein the copper film has post anneal: pre-anneal stress ratio of less than about 6.  
     
     
         20 . The copper film of  claim 19 , wherein the copper film has a sulfur concentration of less than about 8×10 18  atoms/cm 3 , a nitrogen concentration of less than about 25×10 18  atoms/cm 3 , an oxygen concentration of less than about 9×10 18  atoms/cm 3 , a chlorine concentration of less than about 20×10 18  atoms/cm 3 , and a carbon concentration of less than about 50×10 18  atoms/cm 3 .  
     
     
         21 . A copper layer formed on a semiconductor substrate, the copper layer comprising: 
 a sheet resistance of between about 15.5×10 −2  Ohms/cm 2  and about 16.5×10 −2  Ohms/cm 2 ;    a pre-anneal stress of less than about 90 Mpa; and    a post anneal:pre-anneal stress ratio of less than about 6.    
     
     
         22 . The copper layer of  claim 21 , wherein the copper layer has a sulfur concentration of less than about 8×10 18  atoms/cm 3 , a nitrogen concentration of less than about 25×10 18  atoms/cm 3 , an oxygen concentration of less than about 9×10 18  atoms/cm 3 , a chlorine concentration of less than about 20×10 18  atoms/cm 3 , and a carbon concentration of less than about 50×10 18  atoms/cm 3 .  
     
     
         23 . The copper layer of  claim 21 , wherein the copper layer is formed by an electrochemical deposition process using a current density of between about 10 mA/cm 2  and about 40 mA/cm 2  on the substrate surface and a substrate rotation speed of between about 20 rpm and about 50 rpm.