Method and apparatus for low temperature copper to copper bonding

Abstract

A method comprising: coating a conductive bump on a first substrate with a conductive material to form a coated conductive bump; coating a conductive bump on a second substrate with a conductive material to form a coated conductive bump; and bonding the coated conductive bump on the first substrate to the coated conductive bump on the second substrate to electrically connect the first substrate to the second substrate.

1 . A method comprising: 
 coating a conductive bump on a first substrate with a conductive material to form a coated conductive bump;    coating a conductive bump on a second substrate with a conductive material to form a coated conductive bump; and    bonding the coated conductive bump on the first substrate to the coated conductive bump on the second substrate to electrically connect the first substrate to the second substrate.    
   
   
       2 . The method of  claim 1 , wherein the conductive bumps are comprised of copper.  
   
   
       3 . The method of  claim 1 , wherein the conductive material comprises a noble metal.  
   
   
       4 . The method of  claim 3 , wherein the noble metal comprises silver.  
   
   
       5 . The method of  claim 3 , wherein bonding occurs at a temperature lower than 300° C.  
   
   
       6 . The method of  claim 5 , wherein the first substrate is a semiconductor die substrate and the second substrate is a package substrate.  
   
   
       7 . The method of  claim 5 , wherein the first substrate and the second substrate are semiconductor substrates.  
   
   
       8 . A method comprising: 
 forming a layer of a conductive material on a first set of copper bumps provided on a first substrate to form a first set of coated copper bumps;    forming a layer of a conductive material on a second set of copper bumps provided on a second substrate to form a second set of coated copper bumps; and    bonding the first set of coated copper bumps to the second set of coated copper bumps.    
   
   
       9 . The method of  claim 8 , wherein the first substrate is a semiconductor die substrate and the second substrate is a package substrate.  
   
   
       10 . The method of  claim 8 , wherein the first and second substrates are semiconductor substrates.  
   
   
       11 . The method of  claim 8 , wherein the conductive material comprises a noble metal.  
   
   
       12 . The method of  claim 8 , wherein the noble metal comprises silver.  
   
   
       13 . The method of  claim 12 , wherein the layer of silver is formed by displacement deposition.  
   
   
       14 . The method of  claim 12 , wherein the layer of silver is formed by one of: sputtering, electro-beam evaporation from a silver target, chemical vapor deposition, atomic layer deposition followed by an etch-back.  
   
   
       15 . The method of  claim 8 , wherein bonding occurs at a temperature lower than 300° C.  
   
   
       16 . The method of  claim 8 , further comprising cleaning the surface of the copper bumps before forming a layer of a noble metal on the copper bumps.  
   
   
       17 . The method of  claim 16 , further comprising aligning the first set of copper bumps on the first substrate with the second set of copper bumps on the second substrate before bonding.  
   
   
       18 . The method of  claim 16 , wherein the surface of the copper bumps is cleaned using one of an acid etch, exposure to methanol vapor, or a gas anneal to remove any native oxide.  
   
   
       19 . A method comprising: 
 cleaning a first set of copper bumps provided on a first substrate;    cleaning a second set of copper bumps provided on a second substrate;    forming a layer of silver on a first set of copper bumps provided on a first substrate to form a first set of coated copper bumps;    forming a layer of silver on a second set of copper bumps provided on a second substrate to form a second set of coated copper bumps;    aligning the first set of coated copper bumps on the first substrate with the second set of coated copper bumps on the second substrate; and    bonding the first set of coated copper bumps to the second set of coated copper bumps at a temperature of less than 300° C.    
   
   
       20 . The method of  claim 19 , wherein the surface of the copper bumps is cleaned using one of an acid etch, exposure to methanol vapor, or a gas anneal to remove any native oxide.  
   
   
       21 . The method of  claim 19 , wherein the layer of silver is formed by displacement deposition.  
   
   
       22 . The method of  claim 19 , wherein the layer of silver is formed by one of: sputtering, electro-beam evaporation from a silver target, chemical vapor deposition, atomic layer deposition followed by an etch-back.  
   
   
       23 . The method of  claim 19 , wherein the first substrate is a semiconductor die substrate and the second substrate is a package substrate.  
   
   
       24 . The method of  claim 19 , wherein the first and second substrates are semiconductor substrates.  
   
   
       25 . A device comprising: 
 two stacked substrates; and    a plurality of conductive bumps provided on each substrate, wherein each of the plurality of conductive bumps is coated with a conductive material and opposing coated conductive bumps are bonded to one another to electrically connect the two stacked substrates.    
   
   
       26 . The device of  claim 25 , wherein each of the plurality of conductive bumps is comprised of copper.  
   
   
       27 . The device of  claim 25 , wherein the conductive material comprises a noble metal.  
   
   
       28 . The device of  claim 27 , wherein the noble metal comprises silver.  
   
   
       29 . The device of  claim 28 , wherein the two stacked substrates comprise a semiconductor die substrate and a package substrate.  
   
   
       30 . The device of  claim 28 , wherein the two stacked substrates comprise semiconductor substrates.