Copper bath for electroplating fine circuitry on semiconductor chips

Abstract

Bottom-up filling of fine Damascene trenches and vias in semiconductor chips is attained using a copper pyrophosphate electroplating bath with a single accelerating additive species present at low concentration (<5 μ M ). This bath is much easier to control than the acid copper sulfate bath, which employs a complicated additive system involving a minimum of two organic additives and chloride ion (as well as significant additive breakdown products). Pyrophosphate copper deposits exhibit stable properties without annealing and are typically twice as hard as acid sulfate copper deposits, which facilitates chemical mechanical planarization. The mechanical properties and texture of the fine-grained pyrophosphate copper deposits are also much less substrate dependent, which minimizes the effects of variations and flaws in the barrier and seed layers. Attack of copper seed layers is minimized for the copper pyrophosphate bath, which operates in the pH 8 to 9 range. The resistivity of pyrophosphate and annealed acid sulfate copper deposits are substantially equivalent.

1 . A copper electroplating bath, comprising: 
 water as a solvent;    copper ions;    anions that strongly complex said copper ions so as to substantially increase the overpotential for copper electrodeposition such that the copper deposition rate at a given cathode potential is substantially suppressed; and    an organic additive compound that tends to accelerate the copper electrodeposition rate.    
     
     
         2 . The copper electroplating bath of  claim 1 , wherein said anions are of a type selected from the group consisting of pyrophosphate, cyanide, citrate, tartrate, phosphate, glycerolate, ethylenediaminetetraacetic acid, carboxylic acids, triethanolamine, amines, phosphonates, and mixtures thereof.  
     
     
         3 . The copper electroplating bath of  claim 1 , further comprising: 
 cations other than copper ions added to the electroplating bath as a salt of said anions, such that said anions are present in the electroplating bath in stoichiometric excess relative to said copper ions.    
     
     
         4 . The copper electroplating bath of  claim 3 , wherein said cations other than copper ions are not electroactive at the potential used for copper electrodeposition, such that relatively pure copper metal is deposited.  
     
     
         5 . The copper electroplating bath of  claim 4 , wherein said cations other than copper ions are selected from the group consisting of K + , Na + , and NH 4   +  ions.  
     
     
         6 . The copper electroplating bath of  claim 1 , father comprising: 
 a surfactant.    
     
     
         7 . The copper electroplating bath of  claim 1 , further comprising: 
 ions of at least one electroactive metal selected from the group consisting of silver, zinc, cadmium, iron, cobalt, nickel, tin, lead, bismuth, antimony, gallium and indium, such that a copper alloy deposit is obtained.    
     
     
         8 . The copper electroplating bath of  claim 1 , wherein said organic additive compound contains at least one chemical element selected from the group consisting of sulfur, nitrogen and phosphorous.  
     
     
         9 . The copper electroplating bath of  claim 1 , whereby copper metal is electrodeposited in Damascene trenches and vias to form circuitry on semiconductor chips.  
     
     
         10 . A copper electroplating bath, comprising: 
 water as a solvent;    copper ions;    pyrophosphate anions;    cations other than copper ions added to the electroplating bath as a salt of said anions, such that said anions are present in the electroplating bath in stoichiometric excess relative to said copper ions; and    an organic additive compound that tends to accelerate the copper electrodeposition rate.    
     
     
         11 . The copper electroplating bath of  claim 10 , wherein said cations other than copper ions are not electroactive at the potential used for copper electrodeposition, such that relatively pure copper metal is deposited.  
     
     
         12 . The copper electroplating bath of  claim 11 , wherein said cations other than copper ions are selected from the group consisting of K + , Na + , and NH 4   +  ions.  
     
     
         13 . The copper electroplating bath of  claim 10 , further comprising: 
 a surfactant.    
     
     
         14 . The copper electroplating bath of  claim 13 , wherein said surfactant is polyoxyethylene(10)isooctylphenylether.  
     
     
         15 . The copper electroplating bath of  claim 10 , further comprising: 
 ions of at least one electroactive metal selected from the group consisting of silver, zinc, cadmium, iron, cobalt, nickel, tin, lead, bismuth, antimony, gallium and indium, such that a copper alloy deposit is obtained.    
     
     
         16 . The copper electroplating bath of  claim 10 , wherein said organic additive compound is 2,5-dimercapto-1,3,4-thiadiazole at a concentration in the range from 1 to 5 μ M .  
     
     
         17 . The copper electroplating bath of  claim 10 , wherein the temperature is maintained between 50° C. and 60° C.  
     
     
         18 . The copper electroplating bath of  claim 10 , wherein the pH is maintained in the 8.0 to 8.8 range.  
     
     
         19 . The copper electroplating bath of  claim 10 , further comprising; 
 ammonia or ammonium ion.    
     
     
         20 . The copper electroplating bath of  claim 10 , further comprising: 
 nitrate ion.    
     
     
         21 . The copper electroplating bath of  claim 10 , whereby copper metal is electrodeposited in Damascene trenches and vias to form circuitry on semiconductor chips.  
     
     
         22 . A copper electroplating bath, comprising: 
 water as a solvent;    copper ions;    pyrophosphate anions;    cations other than copper ions added to the electroplating bath as a salt of said anions, such that said anions are present in the electroplating bath in stoichiometric excess relative to said copper ions; and    2,5-dimercapto-1,3,4-thiadiazole at a concentration in the range from 1 to 5 μ M ,    whereby copper metal is electrodeposited in Damascene trenches and vias to form circuitry on semiconductor chips.    
     
     
         23 . A copper electroplating bath, comprising: 
 water as a solvent;    copper ions;    pyrophosphate anions;    cations other than copper ions added to the electroplating bath as a salt of said anions, such that said anions are present in the electroplating bath in stoichiometric excess relative to said copper ions;    an organic additive compound that tends to accelerate the copper electrodeposition rate; and    a surfactant.    
     
     
         24 . A copper electroplating bath, comprising: 
 water as a solvent;    copper ions;    pyrophosphate anions;    cations other than copper ions added to the electroplating bath as a salt of said anions, such that said anions are present in the electroplating bath in stoichiometric excess relative to said copper ions;    2,5-dimercapto-1,3,4-thiadiazole at a concentration in the range from 1 to 5 μ M ; and    a surfactant,    whereby copper metal is electrodeposited in Damascene trenches and vias to form circuitry on semiconductor chips.    
     
     
         25 . A copper electroplating bath, comprising: 
 water as a solvent;    copper ions;    pyrophosphate anions;    cations other than copper ions added to the electroplating bath as a salt of said anions, such that said anions are present in the electroplating bath in stoichiometric excess relative to said copper ions;    2,5-dimercapto-1,3,4-thiadiazole at a concentration in the range from 1 to 5 μ M ,    polyoxyethylene(10)isooctylphenylether as a surfactant;    ammonia or ammonium ion; and    nitrate ion,    whereby copper metal is electrodeposited in Damascene trenches and vias to form circuitry on semiconductor chips.    
     
     
         26 . A process for electrodepositing copper circuitry in trenches and vias on semiconductor chips, comprising the steps of: 
 providing a semiconductor chip with trenches and vias to be filled with copper;    placing said chip in contact with an electroplating bath, said bath comprising: 
 water as a solvent,  
 copper ions,  
 pyrophosphate anions,  
 cations other than copper ions added to the electroplating bath as a salt of said anions, such that said anions are present in the electroplating bath in stoichiometric excess relative to said copper ions, and  
 2,5-dimercapto-1,3,4-thiadiazole at a concentration in the range from 1 to 5 μ M , and  
   electrodepositing copper in said trenches and vias.    
     
     
         27 . The process of  claim 26 , wherein said cations other than copper ions are selected from the group consisting of K + , Na + , and NH 4   +  ions.  
     
     
         28 . The process of  claim 26 , wherein the electroplating bath further comprises a surfactant.  
     
     
         29 . The process of  claim 28 , wherein said surfactant is polyoxyethylene(10)isooctylphenylether.  
     
     
         30 . The process of  claim 26 , wherein the temperature of the plating bath is maintained at a temperature between 50° C. and 60° C.  
     
     
         31 . The process of  claim 26 , wherein the pH of the electroplating bath is maintained in the 8.0 to 8.8 range.  
     
     
         32 . The process of  claim 26 , wherein the electroplating bath further comprises ammonia or ammonium ion.  
     
     
         33 . The process of  claim 26 , wherein the electroplating bath further comprises nitrate ion.