Vacuum processing equipment designed for high-end commercial silicon production does not operate in the ultrahigh vacuum region (10(-9)-10(-12) Torr). However, for reasons of reducing process and gas impurities to the sub-part per billion level and increasing product throughput, UHV technology is required and is being incorporated into production equipment. This article reviews progress in the field of extremely clean device processing systems. It highlights progress in pump design, chamber design, operational procedures, and materials developments that have made today’s clean processes possible and suggests directions for improvements.