DEPOSITION CHARACTERISTICS OF METAL CONTAMINANTS FROM HF-BASED PROCESS SOLUTIONS ONTO SILICON-WAFER SURFACES

Metal contamination levels are a growing concern in integrated circuit manufacturing because they degrade electrical performance. This work uses statistical design of experiments to determine deposition characteristics of metal contaminants onto silicon surfaces from process chemicals that are used in wafer cleaning. Copper, gold, molybdenum, silver, lead, chromium, tin, titanium, manganese, and tungsten were added to buffered oxide etchant and HF solutions. Wafers were immersed in these solutions and evaluated by total reflectance x-ray fluorescence spectroscopy surface analysis. Most contaminant deposition characteristics are simple, dependent on bath type and contamination level alone. Some contaminant deposition characteristics are complex, dependent on multifactors including bath type, contaminant level, and the presence of other contaminants as well.