Surface-active conditional inhibitors for the electroplating of copper on a surface

Abstract

Electrolytes for the electroplating of copper comprising, as inhibitor, a poly(alkylene-biguanide) salt. The inhibition developed by poly(alkylene-biguanide) salts is conditioned by the concentration of an accelerator on the surface of the copper. The surfactancy of poly(alkylene-biguanide) salts enables them to be instantly transferred from the electrolyte/air interface to the electrolyte/copper interface during contact between the cathode and the electrolyte. The electrolytes according to the invention are suitable for obtaining smooth and bright electroplated coatings and for depositing copper on surfaces having submicron-scale concavities useful in microelectronics.

1 . An electrolyte for the electroplating of copper on a cathode, characterized in that it contains an effective amount of a poly (alkylene-biguanide) salt having the general formula (B)
   R—NH—C(:NH)—NH—[—(CH 2 ) p —NH—C(:NH)—NH—C(:NH)—NH—] n —(CH 2 ) p —NH 2   , x AH   
       wherein:
 p is an integer comprised between 2 and 12 
 n is an integer comprised between 2 and 100 
 R— represents NC— or H 2 N—C(:O)— 
 AH represents an acid 
 x is comprised between (n+1) and 2(n+1) if AH is a monoacid, and between (n+1)/2 and (n+1) if AH is a diacid. 
 
     
     
         2 . The electrolyte for the electroplating of copper on a cathode according to  claim 1 , characterized in that in formula (B) of the poly (alkylene-biguanide) salt,
 p is equal to 6   n is comprised between 6 and 20   R— represents NC—.   
     
     
         3 . The electrolyte for the electroplating of copper on a cathode according to one of  claim 1  or  2 , characterized in that in formula (B) AH represents sulfuric acid. 
     
     
         4 . The electrolyte for the electroplating of copper on a cathode according to any of  claims 1  to  3 , characterized in that the poly (alkylene-biguanide) salt concentration is comprised between 5 10 −7  mole per liter and 10 −5  mole per liter. 
     
     
         5 . The electrolyte for the electroplating of copper on a cathode according to any of  claims 1  to  4 , characterized in that it includes an accelerator of the electrolytic deposition of copper taken among mercapto-alkyl sulfonic acids and dialkyl disulfide disulfonic acids, or among their salts. 
     
     
         6 . A process for the electroplating of copper on a cathode, characterized in that the deposit is obtained starting from an electrolyte according to any of  claims 1  to  5 . 
     
     
         7 . The process for the electroplating of copper on a cathode according to  claim 6 , characterized in that the cathode comprises submicronic concavities. 
     
     
         8 . The process for the electroplating of copper on a cathode according to one of  claim 6  or  7 , characterized in that a voltage is applied between the anode and the cathode before said cathode is contacted with the electrolyte. 
     
     
         9 . A copper electrodeposit on a cathode, characterized in that it has been obtained from an electrolyte according to any of  claims 1  to  5 . 
     
     
         10 . A copper electrodeposit on a cathode, characterized in that it has been obtained by a process according to any of  claims 6  to  8 .