Developing advanced humidity standards to measure trace water vapor in specialty gases

摘要

Surface-adsorbed water and water vapor in gas streams can be important contaminants in the ultraclean gas-handling environments required for semiconductor manufacturing. In applications in which high-purity conditions must be maintained, water is difficult to monitor and control for two reasons: It is ubiquitous in the atmosphere and on surfaces that have been exposed to the atmosphere, and it has physical and chemical properties that make it difficult to eliminate. Small quantities of water vapor (below 1 nmol mol~(-1)) can adversely affect the perfor- mance and yield of silicon-based semiconductors and compound semiconductors used in photonic devices. Processes affected adversely by water include sample preparation, in which high-purity purge gases are used to sweep atmospheric constituents or residual compounds from prior processes, and reactive flows, in which high-purity gases are used for chemical incorporation in film growth.