Electroless cobalt alloy deposition process

Abstract

In one embodiment, a method for depositing a cobalt-containing capping layer on a metal layer is provided which includes rinsing the metal layer with a deionized water wetting step, depositing a palladium layer on the metal layer by exposing the metal layer to an electroless activation solution comprising a palladium precursor and an acid, and depositing the cobalt-containing capping layer on the palladium layer by exposing the palladium layer to an electroless cobalt-containing solution comprising a cobalt source, a tungsten source, an oxygen scavenger and a surfactant. Ascorbic acid may be used as the oxygen scavenger. In another embodiment, a composition of an electroless plating solution is provided which includes a cobalt source at a concentration in a range from about 50 mM to about 250 mM, a tungsten source at a concentration in a range from about 10 mM to about 100 mM, a complexing agent at a concentration in a range from about 10 mM to about 200 mM, at least one reductant at a concentration in a range from about 1 mM to about 100 mM, a surfactant at a concentration in a range from about 1 mg/L to about 100 mg/L, and ascorbic acid at a concentration in a range from about 30 mg/L to about 300 mg/L.

1 . A method for depositing a cobalt-containing capping layer on a metal layer, comprising: 
 rinsing the metal layer with a deionized water wetting step;    depositing a palladium layer on the metal layer by exposing the metal layer to an electroless activation solution comprising a palladium precursor and an acid; and    depositing the cobalt-containing capping layer on the palladium layer by exposing the palladium layer to an electroless cobalt-containing solution comprising a cobalt source, a tungsten source, an oxygen scavenger and a surfactant.    
     
     
         2 . The method of  claim 1 , wherein the metal layer is copper or a copper alloy.  
     
     
         3 . The method of  claim 2 , wherein the metal layer is exposed to an acidic wash solution prior to being exposed to the electroless activation solution.  
     
     
         4 . The method of  claim 3 , wherein the palladium layer is exposed to a second acidic wash solution prior to being exposed to the electroless cobalt-containing solution.  
     
     
         5 . The method of  claim 4 , wherein the palladium precursor is palladium nitrate.  
     
     
         6 . The method of  claim 5 , wherein the acid is selected from the group consisting of nitric acid, methanesulfonic acid and combinations thereof.  
     
     
         7 . The method of  claim 6 , wherein the electroless activation solution has a pH of about 4 or less.  
     
     
         8 . The method of  claim 2 , wherein the cobalt-containing capping layer comprises at least one element selected from the group consisting of tungsten, molybdenum, phosphorus, boron and combinations thereof.  
     
     
         9 . The method of  claim 8 , wherein the palladium layer is exposed to a pH basic wash solution prior to being exposed to the electroless cobalt-containing solution.  
     
     
         10 . The method of  claim 9 , wherein the electroless cobalt-containing solution comprises the surfactant at a concentration in a range from about 1 mg/L to about 100 mg/L.  
     
     
         11 . The method of  claim 10 , wherein the surfactant is a glycol ether based surfactant.  
     
     
         12 . The method of  claim 10 , wherein the electroless cobalt-containing solution has an oxygen concentration of about 4 ppm or less.  
     
     
         13 . The method of  claim 12 , wherein the deionized water wetting step comprises degassed, deionized water.  
     
     
         14 . The method of  claim 13 , wherein the palladium layer is exposed to a second wetting step prior to depositing the cobalt-containing capping layer, wherein the second wetting step comprises degassed, deionized water.  
     
     
         15 . The method of  claim 12 , wherein the oxygen scavenger is selected from the group consisting of ascorbic acid, N,N-diethylhydroxylamine, erythorbic acid, methyl ethyl ketoxime, carbohydrazide, derivatives thereof and combinations thereof.  
     
     
         16 . The method of  claim 15 , wherein the oxygen scavenger has a concentration in the electroless cobalt-containing solution in a range from about 0.01 mM to about 10 mM.  
     
     
         17 . The method of  claim 15 , wherein the oxygen scavenger is ascorbic acid at a concentration in a range from about 30 mg/L to about 300 mg/L.  
     
     
         18 . The method of  claim 16 , wherein the cobalt-containing capping layer is selected from the group consisting of CoW, CoWP, CoP, CoWBP and combinations thereof.  
     
     
         19 . A method for depositing a cobalt-containing capping layer on a metal layer, comprising: 
 exposing the metal layer to an acidic wash solution;    depositing a palladium layer on the metal layer by exposing the metal layer to an electroless activation solution comprising a palladium precursor and an acid;    exposing the palladium layer to a pH basic solution; and    exposing the palladium layer to an electroless cobalt-containing solution to deposit the cobalt-containing capping layer on the palladium layer.    
     
     
         20 . The method of  claim 19 , wherein the metal layer is copper or a copper alloy.  
     
     
         21 . The method of  claim 20 , wherein the metal layer is wetted with deionized water prior to the exposure of the acidic wash solution.  
     
     
         22 . The method of  claim 21 , wherein the metal layer is wetted with the deionized water after the exposure of the acidic wash solution and prior to depositing the palladium layer.  
     
     
         23 . The method of  claim 22 , wherein the palladium layer is exposed to the deionized water after depositing the palladium layer and prior to depositing the cobalt-containing capping layer.  
     
     
         24 . The method of  claim 23 , wherein the deionized water comprises degassed, deionized water.  
     
     
         25 . The method of  claim 21 , wherein the palladium layer is exposed to a second acidic wash solution prior to the exposure of the pH basic solution.  
     
     
         26 . The method of  claim 25 , wherein the palladium precursor is palladium nitrate.  
     
     
         27 . The method of  claim 26 , wherein the acid is selected from the group consisting of nitric acid, methanesulfonic acid and combinations thereof.  
     
     
         28 . The method of  claim 27 , wherein the electroless activation solution has a pH of about 4 or less.  
     
     
         29 . The method of  claim 20 , wherein the cobalt-containing capping layer comprises at least one element selected from the group consisting of tungsten, molybdenum, phosphorus, boron and combinations thereof.  
     
     
         30 . The method of  claim 29 , wherein the electroless cobalt-containing solution comprises a surfactant at a concentration in a range from about 1 mg/L to about 100 mg/L.  
     
     
         31 . The method of  claim 30 , wherein the surfactant is a glycol ether based surfactant.  
     
     
         32 . The method of  claim 30 , wherein the electroless cobalt-containing solution has an oxygen concentration of about 4 ppm or less.  
     
     
         33 . The method of  claim 32 , wherein the electroless cobalt-containing solution comprises an oxygen scavenger selected from the group consisting of ascorbic acid, N,N-diethylhydroxylamine, erythorbic acid, methyl ethyl ketoxime, carbohydrazide, derivatives thereof and combinations thereof.  
     
     
         34 . The method of  claim 33 , wherein the oxygen scavenger has a concentration in the electroless cobalt-containing solution at a range from about 0.01 mM to about 10 mM.  
     
     
         35 . The method of  claim 33 , wherein the oxygen scavenger is ascorbic acid at a concentration in a range from about 30 mg/L to about 300 mg/L.  
     
     
         36 . The method of  claim 34 , wherein the cobalt-containing capping layer is selected from the group consisting of CoW, CoWP, CoP, CoWBP and combinations thereof.  
     
     
         37 . A method for depositing a cobalt-containing capping layer on a metal layer, comprising: 
 cleaning the metal layer with a pre-clean solution;    rinsing the metal layer with a deionized water wetting step;    depositing a palladium layer on the metal layer by exposing the metal layer to an electroless activation solution comprising a palladium precursor and an acid; and    depositing the cobalt-containing capping layer on the palladium layer by exposing the palladium layer to an electroless cobalt-containing solution comprising a surfactant and an oxygen concentration of about 4 ppm or less.    
     
     
         38 . The method of  claim 37 , wherein the metal layer is copper or a copper alloy.  
     
     
         39 . The method of  claim 38 , wherein the metal layer is exposed to an acidic wash solution prior to being exposed to the electroless activation solution.  
     
     
         40 . The method of  claim 39 , wherein the palladium layer is exposed to a second acidic wash solution prior to being exposed to the electroless cobalt-containing solution.  
     
     
         41 . The method of  claim 40 , wherein the palladium precursor is palladium nitrate.  
     
     
         42 . The method of  claim 41 , wherein the acid is selected from the group consisting of nitric acid, methanesulfonic acid and combinations thereof.  
     
     
         43 . The method of  claim 42 , wherein the electroless activation solution has a pH of about 4 or less.  
     
     
         44 . The method of  claim 38 , wherein the palladium layer is exposed to a pH basic wash solution prior to being exposed to the electroless cobalt-containing solution.  
     
     
         45 . The method of  claim 37 , wherein the metal layer is wetted with deionized water prior to the exposure of the pre-clean solution.  
     
     
         46 . The method of  claim 45 , wherein the palladium layer is exposed to the deionized water after depositing the palladium layer and prior to depositing the cobalt-containing capping layer.  
     
     
         47 . The method of  claim 46 , wherein the deionized water comprises degassed, deionized water.  
     
     
         48 . The method of  claim 44 , wherein the cobalt-containing capping layer comprises at least one element selected from the group consisting of tungsten, molybdenum, phosphorus, boron and combinations thereof.  
     
     
         49 . The method of  claim 48 , wherein the electroless cobalt-containing solution comprises a surfactant at a concentration in a range from about 1 mg/L to about 100 mg/L.  
     
     
         50 . The method of  claim 49 , wherein the surfactant is a glycol ether based surfactant.  
     
     
         51 . The method of  claim 38 , wherein the electroless cobalt-containing solution comprises an oxygen scavenger selected from the group consisting of ascorbic acid, N,N-diethylhydroxylamine, erythorbic acid, methyl ethyl ketoxime, carbohydrazide, derivatives thereof and combinations thereof.  
     
     
         52 . The method of  claim 51 , wherein the oxygen scavenger has a concentration in the electroless cobalt-containing solution at a range from about 0.01 mM to about 10 mM.  
     
     
         53 . The method of  claim 51 , wherein the oxygen scavenger is ascorbic acid at a concentration in a range from about 30 mg/L to about 300 mg/L.  
     
     
         54 . The method of  claim 52 , wherein the cobalt-containing capping layer is selected from the group consisting of CoW, CoWP, CoP, CoWBP and combinations thereof.  
     
     
         55 . A method for depositing a cobalt-containing capping layer on a metal layer, comprising: 
 depositing a palladium layer on the metal layer by exposing the metal layer to an electroless activation solution comprising a palladium precursor and an acid; and    depositing the cobalt-containing capping layer on the palladium layer by exposing the palladium layer to an electroless cobalt-containing solution comprising a cobalt source, a tungsten source, ascorbic acid and an oxygen concentration of about 4 ppm or less.    
     
     
         56 . A composition of an electroless plating solution, comprising: 
 a cobalt source at a concentration in a range from about 50 mM to about 250 mM;    a tungsten source at a concentration in a range from about 10 mM to about 100 mM;    a complexing agent at a concentration in a range from about 10 mM to about 200 mM;    at least one reductant at a concentration in a range from about 1 mM to about 100 mM;    a surfactant at a concentration in a range from about 1 mg/L to about 100 mg/L; and    an oxygen scavenger at a concentration in a range from about 0.01 mM to about 10 mM.    
     
     
         57 . A composition of an electroless plating solution, comprising: 
 a cobalt source at a concentration in a range from about 50 mM to about 250 mM;    a tungsten source at a concentration in a range from about 10 mM to about 100 mM;    a complexing agent at a concentration in a range from about 10 mM to about 200 mM;    at least one reductant at a concentration in a range from about 1 mM to about 100 mM;    a surfactant at a concentration in a range from about 1 mg/L to about 100 mg/L; and    the electroless plating solution has an oxygen concentration of about 4 ppm or less.    
     
     
         58 . A composition of an electroless plating solution, comprising: 
 a cobalt source at a concentration in a range from about 50 mM to about 250 mM;    a tungsten source at a concentration in a range from about 10 mM to about 100 mM;    a complexing agent at a concentration in a range from about 10 mM to about 200 mM;    at least one reductant at a concentration in a range from about 1 mM to about 100 mM;    a surfactant at a concentration in a range from about 1 mg/L to about 100 mg/L; and    ascorbic acid at a concentration in a range from about 30 mg/L to about 300 mg/L.