Electroplated interconnection structures on integrated circuit chips

Abstract

A process is described for the fabrication of submicton interconnect structures for integrated circuit chips. Void-free and seamless conductors are obtained by electroplating Cu from baths that contain additives and are conventionally used to deposit level, bright, ductile, and low-stress Cu metal. The capability of this method to superfill features without leaving voids or seams is unique and superior to that of other deposition approaches. The electromigration resistance of structures making use of CU electroplated in this manner is superior to the electromigration resistance of AlCu structures or structures fabricated using Cu deposited by methods other than electroplating.

1 . A structure for use in interconnections on an electronic device comprising: 
 a dielectric layer having a substantially planar upper surface and having a pattern of recesses therein,    the recesses having a width at the upper surface less than one micrometer,    the recesses being filled with a conductor material that is seamless and/or void-free; and    wherein the conductor material comprises substantially copper.    
   
   
       2 . The structure of  claim 1  wherein the recesses have a depth to width ratio equal to or greater than 1.  
   
   
       3 . The structure of  claim 1  further including a metal liner between the conductive layer and the dielectric layer in the recesses.  
   
   
       4 . The structure of  claim 1  wherein the copper includes small amounts of a material in said copper selected from the group consisting of C (less than 2 weight percent), O (less than 1 weight percent), N (less than 1 weight percent), S (less than 1 weight percent), and Cl (less than 1 weight percent).  
   
   
       5 . The structure of  claim 1  wherein the copper includes specific film microstructures including large grain size relative to film thickness and/or randomly oriented grains.  
   
   
       6 . The structure of  claim 5  wherein the small amounts of material include atoms and/or molecular fragments.  
   
   
       7 . The structure of  claim 1  wherein the conductor has an activation energy for electromigration equal to or greater than 1.0 eV and further includes specific film microstructures including large grain size relative to film thickness and/or randomly oriented grains.  
   
   
       8 . The structure of  claim 1  wherein the conductor material further includes positive amounts of atoms and/or molecular fragments containing atoms selected from the group consisting of C, O, N, S, and Cl.  
   
   
       9 . The structure of  claim 8  wherein the electromigration resistance of the copper is enhanced over pure copper.  
   
   
       10 . The structure of  claim 1  which comprises a double damascene structure.  
   
   
       11 . The structure of  claim 1  wherein each of the recesses has a bottom surface and side surfaces intersecting the bottom surface, and wherein the conductor material is deposited on the bottom surface and side surfaces.  
   
   
       12 . The structure of  claim 11  wherein the bottom surface of each recess is substantially horizontal with respect to a major plane of the substrate.  
   
   
       13 . A process for fabricating an interconnect structure on an electronic device with void-free seamless submicron conductors comprising the steps of: 
 forming an insulating material on a substrate,    lithographically defining and forming recesses for submicron lines and/or submicron vias in said insulating material in which interconnection conductor material will be deposited,    forming a conductive layer in said recesses serving as a plating base,    forming a through-mask,    depositing by a through-mask plating process said conductor material in a seamless and void-free manner by electroplating from a bath containing additives, said bath additives causing the plating rate to increase with depth along the sidewall of a recess, thereby preventing the formation of a seam or void in a conductor in said recesses, and wherein said conductor material comprising copper.    
   
   
       14 . The process of  claim 13  wherein said step of depositing includes depositing Cu as said conductor material.  
   
   
       15 . The process of  claim 13  further including the step of adding additives to said bath for incorporating in said conductor material positive amounts of atoms and/or molecular fragments containing atoms selected from the group consisting of C, O, N, S, and Cl.  
   
   
       16 . The process of  claim 13  further including the step of adding additives to said bath for inducing in said conductor specific film microstructures including large grain size relative to film thickness and/or randomly oriented grains.  
   
   
       17 . The process of  claim 13  further including the step of adding additives to said bath for incorporating in said conductor material molecular fragments containing atoms selected from the group consisting of C, O, N, S and Cl whereby the electromigration resistance is enhanced over pure Cu.  
   
   
       18 . The process of  claim 13  further including the step of adding additives to said bath for inducing in said conductor specific film microstructures including large grain size relative to film thickness and/or randomly oriented grains whereby the electromigration behavior is enhanced over non-electroplated Cu.  
   
   
       19 . The process of  claim 13  wherein the depth to width ratio of a conductor is equal to or greater than 1.  
   
   
       20 . The process of  claim 13  wherein the depth to width ratio of a via exceeds 1.  
   
   
       21 . The process of  claim 20  wherein the depth to width ratio of a conductor is equal to or greater than 1.  
   
   
       22 . The process of  claim 13  wherein said step of depositing further includes the step of placing the upper surface of said substrate in contact with the surface of said bath.  
   
   
       23 . The process of  claim 22  wherein said step of depositing further includes flowing said bath at said surface of said bath.  
   
   
       24 . The process of  claim 13  wherein said step of depositing further includes the step of electroplating using a cup plater.  
   
   
       25 . The process of  claim 13  further including the step of electroplating from a plating solution comprising a copper salt, a mineral acid, and one or more additives selected from the group consisting of an organic sulfur compound with water solubilizing groups, a bath-soluble oxygen-containing compound, a bath-soluble polyether compound, or a bath-soluble organic nitrogen compound that may also contain at least one sulfur atom.  
   
   
       26 . The process of  claim 25  wherein said plating solution contains small amounts of a chloride ion in the range from 10 to 300 parts per million.  
   
   
       27 . The process of  claim 25  wherein said Cu salt is cupric sulfate.  
   
   
       28 . The process of  claim 25  wherein said mineral acid is sulfuric acid.  
   
   
       29 . The process of  claim 30  wherein said organic sulfur compound carries at least one sulfonic group.  
   
   
       30 . The process of  claim 25  wherein said organic sulfur compound has at least two sulfur atoms that are vicinal.  
   
   
       31 . The process of  claim 31  wherein said organic sulfur compound has at least two sulfur atoms that are vicinal and carries at least one terminal sulfonic group.  
   
   
       32 . The process of  claim 25  wherein said organic sulfur compound is selected from the group consisting of mercaptopropane sulfonic acid, thioglycolic acid, mercaptobenzthiozol-S-propansulfonic acid and ethylenedithiodipropyl sulfonic acid, dithiocarbamic acid, alkali metal salts of said compounds, and amine salts of said compounds.  
   
   
       33 . The process of  claim 25  wherein said organic sulfur compound has the formula X—R 1 —(Sn)—R 2 —SO 3 H where the R groups are the same or different and contain at least one carbon atom, X is selected from the group consisting of a hydrogen and a sulfonic group, and n is 2-5 inclusive.  
   
   
       34 . The process of  claim 25  wherein said oxygen-containing compound is selected from the group consisting of polyethylene glycol, and carboxymethylcellulose.  
   
   
       35 . The process of  claim 26  wherein said organic nitrogen compound is selected from the group containing pyridines and substituted pyridines, amides, quaternary ammonium salts, imines, phthalocyanines and substituted phthalocyanines, phenazines, and lactams.  
   
   
       36 . The process of  claim 13  wherein said process preferentially deposits said conductor material in corners at a bottom of said recesses defined in said insulating material.  
   
   
       37 . The process of  claim 13  wherein the additives are polarizing.  
   
   
       38 . The process of  claim 37  wherein the bottom surface of each recess intersects the side surfaces at a 90° angle.  
   
   
       39 . The process of  claim 38  wherein the bottom surface of each recess is substantially horizontal with respect to a major plane of the substrate.