Extending ellipsometry capabilities for ultrathin gate oxide metrology using rapid optical surface treatment technology

Abstract

Today's advanced IC manufacturers are already beginning production on 0.18 micrometer process technology. This requires gate oxidation processes that are capable of thicknesses in the 30 angstrom to 40 angstrom range. The gate oxide thickness specification will be pushed even lower as the industry moves toward sub-0.18 micrometer technology in the next few years. In order to maintain device performance and yields, it is necessary that the gate oxide thickness be very tightly controlled. Current ellipsometry techniques do not provide the precision-to-tolerance ratios required for good statistical process control of these ultra-thin gate oxides. This work demonstrates that a significant portion of the error in ellipsometry measurements is the result of organic surface contamination. Furthermore, the Rapid Optical Surface Treatment is shown as a good method for removing organic surface contaminants and extending the capabilities of ellipsometry techniques for ultra-thin gate oxides.