Polarization stabilizer additive for electroplating

Abstract

Provided herein are methods and apparatus for electroplating metal into recessed features. The techniques described herein utilize a polarization stabilizer compound to increase the stability of polarization at the substrate-electrolyte interface over time. Polarization stabilizers minimize changes in polarization to achieve improved plating results for a single substrate, and more uniform plating results over the course of several substrates. Furthermore, the polarization stabilizers discussed herein may be used to extend the lifetime of a particular electrolyte, thereby reducing manufacturing costs.

What is claimed is: 
     
         1 . A method of electroplating copper on a workpiece, the method comprising:
 (a) contacting a surface of the workpiece with an electroplating solution comprising copper ions, a suppressor, an accelerator, and a polarization stabilizer compound comprising a phenol group; and   (b) applying a negative potential to the workpiece to thereby electroplate copper onto the surface of the workpiece, wherein electroplating occurs over a duration of at least about 10 minutes.   
     
     
         2 . The method of  claim 1 , wherein the polarization stabilizer compound comprises two phenol groups. 
     
     
         3 . The method of  claim 2 , wherein the polarization stabilizer compound is a bisphenol compound. 
     
     
         4 . The method of  claim 3 , wherein the bisphenol compound is bisphenol A. 
     
     
         5 . The method of  claim 3 , wherein the bisphenol compound is bisphenol S. 
     
     
         6 . The method of  claim 1 , wherein the polarization stabilizer compound is an antioxidant. 
     
     
         7 . The method of  claim 1 , wherein the polarization stabilizer compound contains no nitrogen atoms. 
     
     
         8 . The method of  claim 1 , wherein applying the negative potential to the workpiece produces a current density on the surface of the workpiece of about 5 mA/cm 2  or less, on average, over the course of the electroplating. 
     
     
         9 . The method of  claim 8 , wherein the electroplating is conducted for a duration of at least about 20 minutes. 
     
     
         10 . The method of  claim 8 , wherein the electroplating is conducted for a duration of at least about 60 minutes. 
     
     
         11 . The method of  claim 1 , wherein the surface of the workpiece comprises recessed features. 
     
     
         12 . The method of  claim 11 , wherein the recessed features are through silicon vias. 
     
     
         13 . The method of  claim 1 , wherein during the electroplating, the polarization of the workpiece-electroplating solution interface does not vary by more than about 0.02 V for at least about 20 minutes. 
     
     
         14 . The method of  claim 1 , wherein the polarization stabilizer compound provides leveling characteristics to the electroplating solution. 
     
     
         15 . The method of  claim 1 , wherein the copper ions are present in the electroplating solution at a concentration of between about 40-70 g/L. 
     
     
         16 . The method of  claim 1 , wherein the electroplating solution further comprises an acid, and wherein the electroplating solution has a pH of at most about 2. 
     
     
         17 . The method of  claim 1 , wherein the accelerator comprises at least one material selected from the group consisting of: dimercaptopropane sulfonic acid, dimercaptoethane sulfonic acid, mercaptopropane sulfonic acid, mercaptoethane sulfonic acid, bis-(3-sulfopropyl) disulfide (SPS), and derivatives thereof. 
     
     
         18 . The method of  claim 1 , wherein the suppressor comprises at least one material selected from the group consisting of: polyethylene oxide, polypropylene oxide, polyethylene glycol, and polypropylene glycol, any of which may optionally include S- and/or N-containing functional groups. 
     
     
         19 . The method of  claim 1 , wherein the electroplating solution does not contain a leveler. 
     
     
         20 . The method of  claim 1 , wherein the polarization stabilizer compound is provided at a concentration of about 10 ppm or less.