Novel aqueous based metal etchant

Abstract

The present invention provides an aluminum etchant solution for etching an aluminum surface in the presence of solder bumps. The etchant solution includes about 42% to about 80% phosphoric acid; about 0.1% to about 6% nitric acid; about 5% to about 40% acetic acid; about 0.005% to about 5% of an amine oxide surfactant; about 0.1% to about 8% of a Pb solubilizing additive; and about 5 to about 25% de-ionized water; wherein the solder bumps are substantially phosphate free after the etching. Also provided is a process for etching an exposed aluminum surface in a semiconductor structure in the presence of solder bumps including the steps of: contacting the exposed aluminum surface with the etchant solution; rinsing the semiconductor structure with de-ionized water; and drying the semiconductor structure to remove residual water; wherein the solder bumps are substantially phosphate free after the etching.

1 - 6 . (canceled)  
   
   
       7 . A process for etching an exposed aluminum surface in a semiconductor structure, said process comprising step of: 
 contacting said exposed aluminum surface with an etchant solution, comprising: about 42% to about 80% phosphoric acid; about 0.1% to about 6% nitric acid; about 5% to about 40% acetic acid; about 0.005% to about 5% of an amine oxide surfactant; about 0.1% to about 8% of a Pb solubilizing additive; and about 5 to about 25% de-ionized water; wherein said contacting is carried out for a period of time sufficient to etch said aluminum surface.    
   
   
       8 . The process of  claim 7 , wherein said aluminum surface in said semiconductor structure further comprises solder bumps.  
   
   
       9 . The process of  claim 8 , wherein said solder bumps are substantially phosphate free after the etching.  
   
   
       10 . The process of  claim 7 , further comprising: 
 rinsing said semiconductor structure with de-ionized water.    
   
   
       11 . The process of  claim 10 , further comprising: 
 drying said semiconductor structure to remove residual water.    
   
   
       12 . The process of  claim 7 , wherein said contacting is carried out by a method selected from the group consisting of: multiple wafer (batch) immersion, multiple wafer spraying, single wafer immersion, single wafer spraying, and single wafer spray puddle.  
   
   
       13 . The process of  claim 7 , wherein said contacting is carried out for a period of time from about 30 seconds to about 10 minutes.  
   
   
       14 . The process of  claim 13 , wherein said contacting is carried out for a period of time from about 1 seconds to about 10 minutes.  
   
   
       15 . The process of  claim 7 , wherein said Pb solubilizing additive is selected from the group consisting of: bromic acid, perchloric acid, HCl, ammonium chloride, tetramethyl ammonium chloride, ammonium acetate, ammonium hexfluorosilicate, tetramethyl ammonium acetate, chloric acid, perchloric acid, ammonium chlorate, ammonium perchlorate, ammonium thiosulfate, ammonium citrate, citric acid and mixtures thereof.  
   
   
       16 . A process for fabricating a semiconductor structure, said process comprising the steps of: 
 providing a semiconductor structure having an exposed aluminum surface and solder bumps;    contacting said exposed aluminum surface and said solder bumps with an etchant solution for a period of time sufficient to etch said aluminum surface;    wherein said etchant solution comprises: about 42% to about 80% phosphoric acid; about 0.1% to about 6% nitric acid; about 5% to about 40% acetic acid; about 0.005% to about 5% of an amine oxide surfactant; about 0.1% to about 8% of a Pb solubilizing additive; and about 5 to about 25% de-ionized water;    rinsing said semiconductor structure with de-ionized water; and    drying said semiconductor structure to remove residual water;    wherein said solder bumps are substantially phosphate free after the etching.    
   
   
       17 . The process of  claim 16 , wherein said semiconductor structure further comprises a metal surface selected from the group consisting of: Ni, a Ni alloy and Ti.  
   
   
       18 . The process of  claim 17 , wherein said aluminum surface is selectively etched without etching said Ni, a Ni alloy and Ti metal surfaces.  
   
   
       19 . A method of selectively etching an exposed aluminum surface on a semiconductor structure having an exposed aluminum surface, an exposed metal surface selected from the group consisting of: Ni, a Ni alloy and Ti, and solder bumps; said method comprising the steps of: 
 contacting said exposed aluminum surface, said metal surface and said solder bumps with an etchant solution, wherein said etchant solution comprises: about 42% to about 80% phosphoric acid; about 0.1% to about 6% nitric acid; about 5% to about 40% acetic acid; about 0.005% to about 5% of an amine oxide surfactant; about 0.1% to about 8% of a Pb solubilizing additive; and    about 5 to about 25% de-ionized water; wherein said contacting is carried out for a period of time sufficient for selectively etching said aluminum surface without etching the Ni, a Ni alloy and Ti metal surfaces;    rinsing said semiconductor structure with de-ionized water; and    drying said semiconductor structure to remove residual water;    wherein said aluminum surface is selectively etched without etching said Ni, a Ni alloy and Ti metal surface; and    wherein said solder bumps are substantially phosphate free after the etching.    
   
   
       20 . The method of  claim 19 , wherein said contacting is carried out by a method selected from the group consisting of: multiple wafer (batch) immersion, multiple wafer spraying, single wafer immersion, single wafer spraying, and single wafer spray puddle.  
   
   
       21 . The method of  claim 19 , wherein said contacting is carried out for a period of time from about 30 seconds to about 10 minutes.  
   
   
       22 . The method of  claim 21 , wherein said contacting is carried out for a period of time from about 1 seconds to about 10 minutes.  
   
   
       23 . The method of  claim 19 , wherein said Pb solubilizing additive is selected from the group consisting of: bromic acid, perchloric acid, HCl, ammonium chloride, tetramethyl ammonium chloride, ammonium acetate, ammonium hexfluorosilicate, tetramethyl ammonium acetate, chloric acid,