Methods for detecting metal precipitates in a semiconductor wafer

Abstract

Methods are disclosed for monitoring the amount of metal contamination imparted during wafer processing operations such as polishing and cleaning. The methods include subjecting a silicon-on-insulator structure to the semiconductor process, precipitating metal contamination in the structure and delineating the metal contaminants.

1 . A method for detecting metal precipitates in a semiconductor wafer having a front surface, the method comprising:
 contacting the wafer with an aqueous HF solution to create pits, holes and/or cavities on the front surface of the wafer at or near the sites of metal precipitates at the front surface of the wafer; and   inspecting the front surface of the wafer for the presence of pits, holes and/or cavities.   
     
     
         2 . The method as set forth in  claim 1  comprising directing light to the front surface of the wafer and detecting scattered reflected light. 
     
     
         3 . The method as set forth in  claim 1  wherein the concentration of HF in the aqueous HF solution by weight is less than about 50%. 
     
     
         4 . The method as set forth in  claim 1  wherein the surface of the silicon layer is contacted with the aqueous HF solution for at least about 1 hour. 
     
     
         5 . The method as set forth in  claim 1  wherein the wafer is a silicon-on-insulator structure comprising a handle wafer, a silicon layer, and a dielectric layer between the handle wafer and the silicon layer. 
     
     
         6 . The method as set forth in  claim 5  wherein the thickness of the silicon layer is less than about 250 nm. 
     
     
         7 . The method as set forth in  claim 2  wherein the wafer is a single crystal silicon wafer. 
     
     
         8 . The method as set forth in  claim 2  wherein the wafer is an epitaxial wafer.