Book excerpt: The proceedings of the Fourth International Symposium on Ultra Clean Processing of Silicon Surfaces (UCPSS '98) cover all aspects of ultra-clean Si-technology: cleaning, contamination control, Si-surface chemistry and topography, and its relationship to device performance and process yield. New areas of concern include: cleaning at the interconnect level, resist strip and polymer removal (dry and wet), cleaning and contamination aspects of metallization, wafer backside cleaning and cleaning after Chemical-Mechanical-Polishing (CMP).