Wafer Cleaning: Present and Future

Abstract

The purpose of a wafer-cleaning step is to remove surface particles as well as organic and inorganic contaminants, and to prepare a clean surface prior to specific process steps. To evaluate a wafer-cleaning technique, one must realize that a wafer-cleaning process is actually a chemical process designed to achieve a desired electrical result. The RCA cleaning process is based on oxidation and dissolution of residual organic and certain metallic impurities. In the RCA cleaning process, there is clearly a tradeoff between metallic removal rates and particle deposition rates. Recent developments have been reported on the use of dry wafer-cleaning processes as a replacement for wet chemical cleaning processes. Dry cleaning processes can be of much higher purity than wet processes, in part because of the higher degree to which a gas can be purified and filtered.