Electroless deposition solutions and process control

Abstract

One embodiment of the present invention is a method of electroless deposition of cap layers for fabricating an integrated circuit. The method includes controlling the composition of an electroless deposition bath so as to substantially maintain the electroless deposition properties of the bath. Other embodiments of the present invention include electroless deposition solutions. Still another embodiment of the present invention is a composition used to recondition an electroless deposition bath.

What is claimed is: 
     
         1 . A method of electroless deposition of cap layers containing a metal on a substrate having copper and dielectric structures, the method comprising:
 (i) exposing the substrate to an electroless deposition solution to deposit the cap layers on the substrate, the electroless deposition solution having reactants for an electroless deposition reaction to deposit the cap layers and having byproducts for the electroless deposition reaction, wherein the electroless deposition solution comprises an amount of an amine identified as a byproduct of the electroless deposition reaction, wherein the amine comprises a dimethylamine at a concentration of about 0.01 gram moles per liter, and an amount of a phosphite identified as a byproduct of the electroless deposition reaction, wherein the phosphite concentration is about 0.01 gram moles per liter; and   (ii) replenishing the electroless deposition solution by adding calculated effective amounts of one or more reactants and calculated effective amounts of one or more byproducts so that cap layers can be deposited on additional substrates with the electroless deposition solution having substantially the same properties as in (i).   
     
     
         2 . The method of  claim 1 , wherein the calculated effective amounts of the one or more reactants and the calculated effective amounts of the one or more byproducts are derived from one of a mathematical model of the electroless deposition solution, or a mass balance for the electroless deposition solution. 
     
     
         3 . The method of  claim 1 , wherein the calculated effective amounts of the one or more reactants includes a concentration of a metal reactant that is from about 3 times to about 10 times higher than the concentration of the metal reactant in the electroless deposition solution; or
 is from about 5 times to about 10 times higher than the concentration of the metal reactant in the electroless deposition solution; or   is about 5.1 times higher than the concentration of the metal reactant in the electroless deposition solution.   
     
     
         4 . The method of  claim 1 , wherein the reactants are added to the deposition solution from at least two reservoirs having dissimilar compositions. 
     
     
         5 . The method of  claim 1 , wherein the electroless plating solution comprises:
 cobalt for cobalt cap layers; the replenishing the electroless plating solution comprises adding the cobalt to the solution from a first reservoir and adding other reactants and the byproducts from a second reservoir; or   cobalt, tungsten, phosphorus, and boron; the replenishing the electroless plating solution comprises adding the cobalt to the solution from a first reservoir, and adding the tungsten, the phosphorus, the boron, and the byproducts from a second reservoir.   
     
     
         6 . The method of  claim 1 , wherein (ii) includes using a replenishing composition comprising:
 (a1) a cobalt concentration about 5.1 times higher than the cobalt concentration in the electroless deposition solution for the metal,   (a2) an amount of an amine byproduct of the electroless deposition reaction, and   (a3) an amount of a phosphite byproduct of the electroless deposition reaction; or   (b1) a cobalt concentration about 5.1 times higher than the cobalt concentration in the electroless deposition solution for the metal,   (b2) an amount of dimethylamine, and   (b3) an amount of phosphate; or   (c1) a cobalt concentration about 5.1 times higher than the cobalt concentration in the electroless deposition solution for the metal,   (c2) a dimethylamine concentration of 0.038 gram moles per liter; and   (c3) a phosphite concentration of 0.037 gram moles per liter; or   (d1) a cobalt concentration about 5.1 times higher than the cobalt concentration in the electroless deposition solution for the metal,   (d2) an amount of hypophosphite,   (d3) an amount of tungstate,   (d4) an amount of citrate,   (d5) an amount of borate,   (d6) an amount of dimethylamine, and   (d7) an amount of phosphite.   
     
     
         7 . The method of  claim 1 , wherein a drag-out of the electroless deposition solution is:
 (A) 100 milliliters per substrate and (ii) includes using a replenishing composition comprising:
 (a) a cobalt concentration of about 0.0612 gram moles per liter for the metal, 
 (b) a hypophosphite concentration of about 0.325 g moles per liter, 
 (c) a tungstate concentration of about 0.09 gram moles per liter, 
 (d) a citrate concentration of about 0.481 gram moles per liter, 
 (e) a borate concentration about 0.287 gram moles per liter, 
 (f) a dimethylamine concentration about 0.038 gram moles per liter, and 
 (g) a phosphite concentration of about 0.037 gram moles per liter; or 
   (B) 60 milliliters per substrate and (ii) includes using a replenishing composition comprising:
 (a) a cobalt concentration about 5.1 times higher than the cobalt concentration in the electroless deposition solution, 
 (b) a cobalt concentration of about 0.061 gram moles per liter, 
 (c) a hypophosphite concentration of about 0.32 g moles per liter, 
 (d) a tungstate concentration of about 0.077 gram moles per liter, 
 (e) a citrate concentration of about 0.414 gram moles per liter, 
 (f) a borate concentration of about 0.240 gram moles per liter, 
 (g) a dimethylamine concentration of about 0.032 gram moles per liter, and 
 (h) a phosphite concentration of about 0.031 gram moles per liter. 
   
     
     
         8 . The method of  claim 1 , wherein the electroless deposition solution further includes:
 an amount of borane at a concentration of about 0.015 gram moles per liter; and   an amount of hypophosphite at a concentration of about 0.083 gram moles per liter.   
     
     
         9 . The method of  claim 1 , wherein the cap layer comprises cobalt, tungsten, phosphorous, and boron; the electroless deposition solution further including:
 an amount of cobalt at a concentration of about 0.012 gram moles per liter;   an amount of tungstate at a concentration of about 0.023 gram moles per liter;   an amount of borate at a concentration of about 0.077 gram moles per liter.   
     
     
         10 . The method of  claim 1 , wherein the method is utilized to make at least one part of an integrated circuit. 
     
     
         11 . A method of electroless deposition of cap layers containing a metal on a substrate having copper and dielectric structures, the method comprising:
 (i) exposing the substrate to an electroless deposition solution to deposit the cap layers on the substrate, the electroless deposition solution having reactants for an electroless deposition reaction to deposit the cap layers and having byproducts for the electroless deposition reaction;   (ii) replenishing the electroless deposition solution by adding a replenishing composition, the replenishing composition including a concentration of the metal derived from a mathematical model of the electroless deposition solution, an amount of dimethylamine at a concentration of about 0.038 gram moles per liter and an amount of phosphite at a concentration of about 0.037 gram moles per liter.   
     
     
         12 . The method of  claim 11 , wherein the concentration of the metal is derived from a mass balance for the electroless deposition solution. 
     
     
         13 . The method of  claim 11 , wherein the concentration of the metal is:
 (A) from about 3 times to about 10 times higher than the concentration of the metal reactant in the electroless deposition solution, or   (B) from about 5 times to about 10 times higher than the concentration of the metal reactant in the electroless deposition solution.   
     
     
         14 . The method of  claim 11 , wherein the concentration of the metal is about 5.1 times higher than the concentration of the metal reactant in the electroless deposition solution. 
     
     
         15 . The method of  claim 11 , wherein the metal comprises cobalt. 
     
     
         16 . The method of  claim 11 , wherein the concentration of the metal comprises a cobalt concentration of about 0.0612 gram moles per liter, or the metal comprises nickel. 
     
     
         17 . The method of  claim 11 , wherein the amount of dimethylamine is identified as a by-product of the electroless deposition reaction; and wherein the amount of phosphite is identified as a by-product of the electroless deposition reaction. 
     
     
         18 . The method of  claim 11 , further comprising:
 an amount of cobalt for the metal;   an amount of hypophosphite;   an amount of tungstate;   an amount of citrate; and   an amount of borate   
     
     
         19 . The method of  claim 11  for a cobalt tungsten phosphorous boron cap layer deposition with a drag-out of 100 milliliters per substrate, the composition comprising:
 a cobalt concentration of about 0.0612 gram moles per liter for the metal; 
 a hypophosphite concentration of about 0.325 gram moles per liter; 
 a tungstate concentration of about 0.09 gram moles per liter; 
 a citrate concentration of about 0.481 gram moles per liter; and 
 a borate concentration of about 0.287 gram moles per liter. 
 
     
     
         20 . The method of  claim 11 , wherein the method is utilized to make at least one part of an integrated circuit. 
     
     
         21 . A method for replenishing an electroless deposition solution for deposition of a cap layer that includes a metal, the method comprising:
 adding a replenishing composition to the electroless deposition solution, the replenishing composition comprising a concentration of the metal derived from a mathematical model of the electroless deposition solution, the replenishing composition for a cobalt tungsten phosphorous boron cap layer deposition with a drag-out of 60 milliliters per substrate;   wherein the replenishing composition further includes,
 a cobalt concentration of about 0.061 gram moles per liter for the metal, 
 a hypophosphite concentration of about 0.32 gram moles per liter, 
 a tungstate concentration of about 0.077 gram moles per liter, 
 a citrate concentration of about 0.414 gram moles per liter, 
 a borate concentration of about 0.240 gram moles per liter, 
 a dimethylamine concentration of about 0.032 gram moles per liter, and 
 a phosphite concentration of about 0.031 gram moles per liter. 
   
     
     
         22 . The method of  claim 21 , wherein the electroless deposition solution further includes an amount of citrate at a concentration of about 0.123 gram moles per liter. 
     
     
         23 . The method of  claim 21 , wherein the method is utilized to make at least one part of an integrated circuit.