METHODS FOR DETECTING METAL PRECIPITATES IN A SEMICONDUCTOR WAFER
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.