Copper-electroplating composition and process for filling a cavity in a semiconductor substrate using this composition

Abstract

The subject-matter of the present invention is a composition especially intended for filling, by the electroplating of copper, a cavity in a semiconductor substrate such as a “through-via” structure for the production of interconnects in three-dimensional integrated circuits. According to the invention, this composition comprises in solution in a solvent: copper ions in a concentration lying between 45 and 1500 mM; a complexing agent for the copper consisting of at least one compound chosen from aliphatic polyamines having 2 to 4 amino groups, preferably ethylenediamine, in a concentration lying between 45 and 3000 mM; the molar ratio between the copper and said complexing agent lying between 0.1 and 5; thiodiglycolic acid in a concentration lying between 1 and 500 mg/l; and optionally a buffer system, in particular ammonium sulfate, in a concentration lying between 0.1 and 3M.

1 . composition especially intended for filling, by the electroplating of copper, a cavity in a semiconductor substrate such as a “through-via” structure for the production of interconnects in three-dimensional integrated circuits, characterized in that it comprises in solution in a solvent:
 copper ions in a concentration lying between 45 and 1500 mM; 
 a complexing agent for the copper consisting of at least one compound chosen from aliphatic polyamines having 2 to 4 amino groups, preferably ethylenediamine, in a concentration lying between 45 and 3000 mM; 
 the molar ratio between the copper and said complexing agent lying between 0.1 and 5; 
 thiodiglycolic acid in a concentration lying between 1 and 500 mg/l; and 
 optionally a buffer system, in particular ammonium sulfate, in a concentration lying between 0.1 and 3M. 
 
     
     
         2 . The composition as claimed in  claim 1 , wherein the copper ion concentration lies between 45 and 500 mM, preferably between 100 and 300 mM. 
     
     
         3 . The composition as claimed in  claim 1 , wherein the aforementioned copper ions are cupric ions preferably derived from copper sulfate. 
     
     
         4 . The composition as claimed in  claim 1 , wherein the complexing agent for the copper consists of at least one compound chosen from ethylenediamine, diethylenetriamine, triethylenetetramine and dipropylenetriamine. 
     
     
         5 . The composition as claimed in  claim 1 , wherein the aforementioned complexing agent is ethylenediamine. 
     
     
         6 . The composition as claimed in  claim 1 , wherein the complexing agent concentration lies between 45 and 1500 mM, preferably between 300 and 900 mM. 
     
     
         7 . The composition as claimed in  claim 4 , wherein the molar ratio between the copper and the complexing agent lies between 0.1 and 1, preferably between 0.2 and 0.4. 
     
     
         8 . A composition as claimed in  claim 7 , wherein the molar ratio between the copper and the complexing agent lies between 0.2 and 0.4 and that a part of the complexing agent in excess is in a protonated state. 
     
     
         9 . A process for filling the cavity in a semiconductor substrate, in particular a through-via for the production of interconnects in three-dimensional integrated circuits, said cavity being covered by a copper-diffusion barrier layer, in particular based on nickel, optionally itself covered with a copper seed layer, characterized in that it comprises placing said surface of the cavity in contact with an electroplating composition as claimed in  claim 1 , and a step during which said surface is biased for a long enough time to allow said cavity to be filled. 
     
     
         10 . The process as claimed in  claim 9 , wherein the aforementioned bias is produced in DC mode by applying a current per unit area lying in a range from 0.2 mA/cm 2  to 50 mA/cm 2 , preferably from 0.5 mA/cm 2  to 5 mA/cm 2 . 
     
     
         11 . The process as claimed in  claim 9 , wherein the placing of said surface in contact is carried out by cold entry. 
     
     
         12 . The process as claimed in  claim 9 , wherein the filling of the cavity is carried out at a temperature lying between 20 and 30° C. 
     
     
         13 . The process as claimed in  claim 9 , wherein during the filling of the cavity, the substrate is rotated at a speed lying between 20 and 600 revolutions per minute, preferably at a rotation speed lying between 100 and 400 revolutions per minute. 
     
     
         14 . The process as claimed in  claim 9 , wherein the surface of the cavity to be filled consists of a material forming a barrier to the diffusion of the copper comprising at least one material chosen from tantalum (Ta), titanium (Ti), tantalum nitride (TaN), titanium nitride (TiN), tungsten (W), titanium tungsten (TiW) and tungsten-carbon-nitride (WCN). 
     
     
         15 . The process as claimed in  claim 9 , wherein the surface of the cavity to be filled consists of a material forming a nickel-based barrier to the diffusion of the copper.