Impedance Spectroscopic Quantitation of Anions and Transition Metals in IC Wafer Cleaning Water

摘要

Silicon wafers with high feature density ICs, routinely subjected to plasma etching, may display insoluble residues. Chemical remover products, such as hydroxylamine based EKC265 and semi-aqueous fluoride based EKC640 (SAC~(TM) chemistry), readily remove the post etch residues requiring only final rinsing using pure water. Incorporation of transition metals, such as copper, tungsten and titanium, into IC device physics may afford opportunities for these metals to contaminate device surfaces at trace levels so measurement methods having low detection limits are of interest. Wafer cleaning processes may be classified as optimal when metal contaminants are neither deposited from rinse solutions nor are IC surfaces corroded by ultra pure water rinse. Novel impedance spectroscopic (IS) electrochemical techniques have been developed for quantitation of transition metals, alkali anions and cations in the ppm to ppt range. A few mL of sample can be analyzed by IS at ambient temperature using bright platinum electrodes in a few minutes. Method development and preliminary measurement data will be presented and compared with ICP-MS results.