Post-CMP cleaning of semiconductor wafer surfaces using a combination of aqueous and CO2 based cryogenic cleaning techniques

Abstract

The present invention provides for a new and improved method of aqueous and cryogenic enhanced (ACE) cleaning for semiconductor surfaces as well as the surfaces of metals, dielectric films particularly hydrophobic low k dielectric films, and CMP etch stop films to remove post-CMP contaminants. It is particularly useful for removing contaminants which are 0.3 μm in size or smaller. The ACE cleaning process is applied to a surface which has undergone chemical-mechanical polishing (CMP). It includes the steps of cleaning the surface with an aqueous-based cleaning process, at least partially drying the surface, and, shortly thereafter, cleaning the surface with a CO 2 cryogenic cleaning process. This process removes such contaminants from surfaces which are hydrophobic and hence difficult to clean with aqueous-based cleaning techniques alone.

1 . A process for the removal of chemical-mechanical polishing (CMP) contaminants from the surface of a semiconductor wafer, metal, or film, comprising the steps of: 
 a) Wet cleaning the surface with deionized water and/or an aqueous or solvent-based cleaner;    b) At least partially drying the surface; and    c) Cryogenically cleaning the surface with CO 2 .    
     
     
         2 . The process of  claim 1  wherein the surface is partially dried by the removal of bulk water.  
     
     
         3 . The process of  claim 1  wherein the surface is substantially dried.  
     
     
         4 . The process of  claim 1  wherein step (a) comprises the steps of rinsing the surface with deionized water, cleaning the surface with an aqueous or solvent based cleaner, and rinsing the surface with deionized water.  
     
     
         5 . The process of  claim 4  wherein step (a) further comprises repeating the steps of cleaning the surface with one or more aqueous or solvent-based cleaners and rinsing the surface with deionized water.  
     
     
         6 . The process of  claim 1  wherein step (a) comprises the step of buffing the surface with deionized water and/or an aqueous or solvent based cleaner.  
     
     
         7 . The process of  claim 1  wherein step (c) comprises the steps of expanding liquid CO 2  through a nozzle under pressure to result in the formation of solid CO 2  entrained in a gaseous CO 2  stream; and directing the CO 2  stream at the surface to remove contaminants.  
     
     
         8 . The process of  claim 2  wherein the bulk water is removed by dipping the surface in alcohol and slowly removing the surface from the alcohol or by spinning the surface while spraying alcohol on the surface.  
     
     
         9 . The process of  claim 7  wherein step (c) is preceded by spraying the surface with a liquid having a high vapor pressure; and allowing the liquid to remain on the surface for a desired period of time.  
     
     
         10 . The process of  claim 7  wherein step (c) is preceded by the steps of covering the surface with a vapour of a liquid to reduce the force of particle-surface adhesion; and allowing the vapour to remain on the surface for a desired period of time.  
     
     
         11 . A process for the removal of contaminants having a size of 0.3 μm or smaller from a surface of a semiconductor wafer, metal, or film, produced by post-chemical mechanical polishing of said semiconductor wafer, metal, or film, comprising the steps of: 
 a) Wet cleaning the surface comprising cleaning the surface with deionized water, cleaning the surface with an aqueous-based cleaner in deionized water, or buffing the surface with deionized water and/or aqueous cleaner;  
 b) At least partially drying the surface by removing bull, water; and  
 c) Cryogenically cleaning the surface with CO 2  comprising the steps of expanding liquid CO 2  through a nozzle under pressure to result in the formation of solid CO 2  entrained in a gaseous CO 2  stream, and directing the CO 2  stream at the surface to remove contaminants.  
 
     
     
         12 . The process of  claim 11  wherein the surface is fully dried.  
     
     
         13 . The process of  claim 11  wherein step (a) comprises the steps of rinsing the surface with deionized water, cleaning the surface with an aqueous-based cleaner, and re-rinsing the surface with deionized water.  
     
     
         14 . The process of  claim 11  wherein step (c) is preceded by the steps of spraying the surface with a liquid having a high vapour pressure; and allowing the liquid to remain on the surface for a desired period of time.  
     
     
         15 . The process of  claim 11  wherein step (c) is preceded by the steps of covering the surface with a vapour of a liquid having a high vapour pressure to reduce the force of particle-surface adhesion, and allowing the vapour to remain on the surface for a desired period of time.