Gaseous Contaminant Measurement for Semiconductor Processing by Diode Laser Spectroscopy

摘要

Tunable diode laser absorption spectroscopy (TDLAS) is a novel tool for purity measurement in microelectronic process gases and environments. It is compatible with any matrix gas and extremely sensitive. This paper describes the application of a laboratory TDLAS instrument to measurement of CO, CO_2, and H_2O with sub-ppb sensitivity, including determination of a CO level of 0.35 ± 0.2 ppb in nitrogen samples from an air separation plant. Fluid dynamic simulation was used to optimize the design of the cell used for H_2O measurements. TDLAS lends itself to the study of contamination sources in situ. As examples, measurements of CO generation in sampling vessels and of CO_2 outgassing inanelectropolished stainless steel chamber are briefly discussed.