Low copper/high halide electroplating solutions for fill and defect control

Abstract

Certain embodiments herein relate to a method of electroplating copper into damascene features using a low copper, high halide concentration electrolyte having between about 4-10 g/L copper ions, between about 150-400 ppm halide ions, and about 2-15 g/L acid. Using the low copper electrolyte produces a relatively high overpotential on the plating substrate surface, allowing for a slow plating process with few fill defects. The low copper electrolyte may have a relatively high cloud point. The use of a relatively high halide ion concentration may promote improved nucleation on a seed layer, resulting in fewer and less significant voids within the features.

What is claimed is: 
     
         1 . A method of plating copper into damascene features, comprising:
 receiving a substrate having a seed thickness of about 200 nanometers, on average, or thinner;   electrically biasing the substrate while immersing the substrate in an aqueous low copper acid-containing electrolyte comprising (i) between about 4-10 grams per liter copper cations, (ii) between about 150-400 ppm chloride ions, and (iii) at least one suppressor compound, whereby the electrolyte induces a cathodic overpotential on the seed sufficient to protect the seed from dissolution by acid in the electrolyte during immersion;   electroplating copper in a process comprising:
 (a) a first plating phase to fill the substrate features with copper via a bottom-up fill mechanism, wherein a first current density during the first plating phase is between about 0.5-10 mA/cm 2 , and 
 (b) a second plating phase to deposit an overburden layer of copper on the substrate, wherein a second current density during the second plating phase is greater than the first current density, and wherein the first and second plating phases are part of a single electroplating process; and 
   removing the substrate from the electrolyte.   
     
     
         2 . The method of  claim 1 , wherein the electrolyte further comprises about 2-15 grams per liter acid. 
     
     
         3 . The method of  claim 2 , wherein the electrolyte further comprises about 5-10 grams per liter acid. 
     
     
         4 . The method of  claim 1 , wherein the electrolyte further comprises about 10-500 ppm active organic additives. 
     
     
         5 . The method of  claim 4 , wherein the active organic additives comprise one or more accelerator compound. 
     
     
         6 . The method of  claim 4 , wherein the suppressor compound is a polymeric compound. 
     
     
         7 . The method of  claim 4 , wherein the active organic additives comprise one or more leveler compound. 
     
     
         8 . The method of  claim 4 , wherein the concentration of accelerator is less than about 100 Ppm. 
     
     
         9 . The method of  claim 1 , wherein the electrolyte comprises between about 150-300 ppm chloride ions. 
     
     
         10 . The method of  claim 1 , wherein the electrolyte comprises between about 200-300 ppm chloride ions. 
     
     
         11 . The method of  claim 1 , wherein the substrate has at least some features with openings smaller than about 20 nanometers. 
     
     
         12 . The method of  claim 1 , wherein the electrolyte has a cloud point of about 50° C. or higher, and wherein electroplating occurs at a temperature that is at least about 20° C. lower than the cloud point of the electrolyte. 
     
     
         13 . The method of  claim 1 , wherein the second current density is between about 10 and 15 mA/cm 2 . 
     
     
         14 . The method of  claim 1 , wherein the pH of the electrolyte is between about 0.2 and 2. 
     
     
         15 . The method of  claim 1 , wherein the substrate is a 450 mm semiconductor wafer. 
     
     
         16 . A method of plating copper into damascene features, comprising:
 receiving a substrate having a seed thickness of about 200 nanometers, on average, or thinner;   electrically biasing the substrate while immersing the substrate in an aqueous low copper acid-containing electrolyte comprising (i) between about 4-10 grams per liter copper ions, (ii) between about 150-400 ppm chloride ions, (iii) at least one suppressor compound, and (iv) at least one accelerator compound,   during the immersing, electroplating copper into the features by a bottom-up fill mechanism at a first current density, wherein electroplating occurs sufficiently slowly in the electrolyte at the first current density to allow the suppressor and accelerator to adsorb onto the seed and thereby enable bottom-up fill during immersion; and   removing the substrate from the electrolyte.   
     
     
         17 . The method of  claim 16 , wherein the first current density is between about 0.5-10 mA/cm 2 . 
     
     
         18 . The method of  claim 16 , wherein electroplating copper into the features is performed during a first plating phase, and further comprising a second plating phase comprising electroplating copper to deposit an overburden layer of copper on the substrate at a second current density, wherein the second current density is higher than the first current density. 
     
     
         19 . The method of  claim 16 , wherein the electrolyte further comprises about 2-15 grams per liter acid. 
     
     
         20 . The method of  claim 16 , wherein the electrolyte between about 4-6 grams per liter copper ions. 
     
     
         21 . An electrolyte comprising:
 between about 1 and 10 grams per liter copper cations;   between about 2 and 15 grams per liter acid;   between about 150-400 ppm chloride ions;   one or more suppressor compound;   one or more accelerator compound; and   the electrolyte having a cloud point above 50° C.   
     
     
         22 . The electrolyte of  claim 21 , wherein the acid is sulfuric acid. 
     
     
         23 . The electrolyte of  claim 21 , wherein the acid is methanesulfonic acid. 
     
     
         24 . The electrolyte of  claim 21 , wherein the chloride ions are provided at a concentration between about 150-300 ppm. 
     
     
         25 . The electrolyte of  claim 21 , wherein the copper cations are provided in a compound that dissociates into cations and anions, and wherein the anions associated with the copper cations are the same species as anions formed from the acid. 
     
     
         26 . The electrolyte of  claim 21 , wherein the concentration of accelerator compound in the electrolyte is less than about 100 ppm.