Method for achieving copper fill of high aspect ratio interconnect features

Abstract

One aspect of the invention provides a consistent metal electroplating technique to form void-less metal interconnects in sub-micron high aspect ratio features on semiconductor substrates. One embodiment of the invention provides a method for filling sub-micron features on a substrate, comprising reactive precleaning the substrate, depositing a barrier layer on the substrate using high density plasma physical vapor deposition; depositing a seed layer over the barrier layer using high density plasma physical vapor deposition; and electro-chemically depositing a metal using a highly resistive electrolyte and applying a first current density during a first deposition period followed by a second current density during a second period.

1 . A method for filling sub-micron features on a substrate, comprising: 
 a) reactive precleaning the substrate;    b) depositing a barrier layer on the substrate using high density plasma physical vapor deposition;    c) depositing a seed layer over the barrier layer using high density plasma physical vapor deposition; and    d) electro-chemically depositing a metal using a highly resistive electrolyte and applying a first current density during a first deposition period followed by a second current density during a second period.    
     
     
         2 . The method of  claim 1  wherein the electro-chemically deposited metal is copper.  
     
     
         3 . The method of  claim 1  wherein the step of reactive precleaning the substrate comprises: 
 i) introducing a preclean gas mixture comprising 5% hydrogen and 95% helium into the chamber;  
 ii) maintaining chamber pressure at about 80 mTorr;  
 iii) providing RF power to a coil at about 450 W at 2.0 MHz; and  
 iv) biasing a substrate support at about 40 W.  
 
     
     
         4 . The method of  claim 1  wherein the step of depositing a barrier layer comprises: 
 i) providing about 1 kW DC power to a target;  
 ii) providing RF power to a coil at about 2 kW;  
 iii) maintaining chamber pressure at about 20 mTorr; and  
 iv) biasing a substrate support at about 350 W at 13.56 MHz with about a 50% duty cycle.  
 
     
     
         5 . The method of  claim 1  wherein the step of depositing a seed layer comprises: 
 i) providing about 1 kW DC power to a target;  
 ii) providing RF power to a coil at between about 2 kW and about 3 kW;  
 iii) maintaining chamber pressure at about 40 mTorr; and  
 iv) maintaining temperature at about 30° C.  
 
     
     
         6 . The method of  claim 1  wherein the metal is electro-chemically deposited using an electrolyte comprising CuSO 4  having a molar concentration between about 0.5M and about 1.1M.  
     
     
         7 . The method of claim I wherein the metal is electro-chemically deposited using an electrolyte comprising HCl at a concentration between about 50 ppm and about 100 ppm.  
     
     
         8 . The method of  claim 1  wherein the metal is electro-chemically deposited using an electrolyte comprising a carrier additive at a concentration between about 12.5 ml/l and about 20 ml/l.  
     
     
         9 . The method of  claim 1  wherein the metal is electro-chemically deposited using an electrolyte comprising H 2 SO 4  having a concentration between about 0 and 0.2 percent.  
     
     
         10 . The method of  claim 1  wherein the first power density is at about 2 mA/cm 2  and the first period is about 18 seconds.  
     
     
         11 . The method of  claim 1  wherein the second power density is at about 2 mA/cm 2  and the second period is about 90 seconds.  
     
     
         12 . The method of  claim 1  the step of electro-chemically depositing a metal further comprises applying a third power density to the substrate during a third period.  
     
     
         13 . The method of  claim 1  wherein the metal is electro-chemically deposited by flowing the electrolyte at between 2 gpm and about 4.5 gpm.  
     
     
         14 . The method of  claim 1  wherein the step of depositing the seed layer comprises: 
 i) depositing a first seed layer having thickness of about 1000 Å;  
 ii) pausing for about 60 seconds; and  
 iii) depositing a second seed layer having thickness of about 1000 Å.  
 
     
     
         15 . The method of  claim 14  wherein the first and second seed layers are deposited by: 
 i) providing about 1 kW DC power to a target;  
 ii) providing RF power to a coil at between about 2 kW and about 3 kW;  
 iii) maintaining chamber pressure at about 40 mTorr; and  
 iv) maintaining temperature at about 30° C.  
 
     
     
         16 . The method of  claim 15  wherein the chamber conditions are stabilized for about 60 seconds before the first seed layer is deposited.