Post rinse to improve selective deposition of electroless cobalt on copper for ULSI application

Abstract

A method for depositing a passivation layer on a substrate surface using one or more electroplating techniques is provided. Embodiments of the method include selectively depositing an initiation layer on a conductive material by exposing the substrate surface to a first electroless solution, depositing a passivating material on the initiation layer by exposing the initiation layer to a second electroless solution, and cleaning the substrate surface with an acidic solution. In another aspect, the method includes applying ultrasonic or megasonic energy to the substrate surface during the application of the acidic solution. In still another aspect, the method includes using the acidic solution to remove between about 100 Å and about 200 Å of the passivating material. In yet another aspect, the method includes cleaning the substrate surface with a first acidic solution prior to the deposition of the initiation layer.

1 . A method of processing a substrate, comprising: 
 polishing a substrate surface to expose a conductive material disposed in a dielectric material;    cleaning the substrate surface with a first acidic solution;    selectively depositing an initiation layer on the conductive material by exposing the substrate surface to an initiation solution;    depositing a passivating material comprising cobalt or a cobalt alloy on the initiation layer by exposing the substrate surface to an electroless solution; and    cleaning the substrate surface with a cleaning process.    
     
     
         2 . The method of  claim 1 , wherein the first acidic solution comprises a mixture selected from a group consisting of nitric acid and deionized water at a ratio of about 1:2 to about 3:1, nitric acid and hydrogen peroxide at a ratio of about 1:2 to about 3:1, sulfuric acid and hydrogen peroxide at a ratio of about 2:1 to about 4:1, or hydrochloric acid and hydrogen peroxide at a ratio of about 2:1 to about 4:1.  
     
     
         3 . The method of  claim 2 , wherein the initiation solution comprises a noble metal source selected from the group consisting of palladium, platinum or ruthenium.  
     
     
         4 . The method of  claim 2 , wherein the initiation solution comprises a borane reductant.  
     
     
         5 . The method of  claim 2 , wherein the first acidic solution comprises between about 0.2 wt % and about 5 wt % of hydrofluoric acid and is applied to the substrate surface for about  300  seconds or less at a temperature in a range from about 15° C. to about 60° C.  
     
     
         6 . The method of  claim 5 , wherein the electroless solution comprises a cobalt source, a tungsten source, a hypophosphite source, a borane reductant, a citrate source and a surfactant.  
     
     
         7 . A method of processing a substrate, comprising: 
 cleaning a substrate surface with a first acidic solution;    selectively depositing a noble metal on the substrate surface by exposing the substrate surface to an acidic electroless solution containing a noble metal salt and an inorganic acid;    electrolessly depositing cobalt or a cobalt alloy on the noble metal;    cleaning the substrate surface with a second acidic solution selected from the group consisting of nitric acid and deionized water at a ratio of about 1:2 to about 3:1, nitric acid and hydrogen peroxide at a ratio of about 1:2 to about 3:1, sulfuric acid and hydrogen peroxide at a ratio of about 2:1 to about 4:1, or hydrochloric acid and hydrogen peroxide at a ratio of about 2:1 to about 4:1; and    applying ultrasonic or megasonic energy to the substrate surface while cleaning the substrate surface with the second acidic solution.    
     
     
         8 . The method of  claim 7 , wherein the first acidic solution comprises between about 0.2 wt % and about 5 wt % of hydrofluoric acid and is applied to the substrate surface for about 300 seconds or less at a temperature in a range from about 15° C. to about 60° C.  
     
     
         9 . The method of  claim 8 , wherein the second acidic solution is applied to the substrate surface at a flow rate between about 700 mL/min and about 900 mL/min for about 300 seconds or less at a temperature in a range from about 15° C. to about 35° C.  
     
     
         10 . The method of  claim 9 , wherein the second acidic solution removes between about 100 Å and about 200 Å of the cobalt or cobalt alloy disposed on the substrate surface.  
     
     
         11 . The method of  claim 10 , wherein the cobalt alloy comprises cobalt and at least a second element selected from the group consisting of tungsten, molybdenum, tin, phosphorous, boron and combinations thereof.  
     
     
         12 . The method of  claim 11 , wherein depositing the cobalt alloy includes exposing the substrate surface to a cobalt electroless solution comprising a cobalt source, a tungsten source, a hypophosphite source, a borane reductant, a citrate source and a surfactant.  
     
     
         13 . A method of depositing a cobalt-containing layer on a conductive material, comprising: 
 exposing a substrate surface to a first acidic solution to clean the conductive layer;    exposing the substrate surface to a water rinse process;    exposing the substrate surface to an initiation solution to form an initiation layer on the conductive layer;    exposing the substrate surface to the water rinse process; and    exposing the substrate surface to an electroless solution to form the cobalt-containing layer on the initiation layer, wherein the electroless solution comprises a cobalt source, a tungsten source, a hypophosphite source, a borane reductant, a citrate source, a surfactant and a pH adjusting agent in a concentration such that the electroless solution has a pH at a value in a range from about 9 to about 11.    
     
     
         14 . The method of  claim 13 , wherein the conductive layer comprises copper.  
     
     
         15 . The method of  claim 14 , wherein the cobalt-containing layer comprises cobalt and at least a second element selected from the group consisting of tungsten, molybdenum, tin, phosphorous, boron and combinations thereof.  
     
     
         16 . The method of  claim 15 , wherein the first acidic solution comprises nitric acid.  
     
     
         17 . The method of  claim 16 , further comprises exposing the substrate surface containing the cobalt-containing layer to a second acidic solution.  
     
     
         18 . The method of  claim 17 , wherein the second acidic solution comprises nitric acid.  
     
     
         19 . The method of  claim 16 , wherein the initiation solution comprises a noble metal source selected from the group consisting of palladium, platinum or ruthenium.  
     
     
         20 . The method of  claim 16 , wherein the initiation solution comprises a borane reductant.