Gaseous Contaminant Measurement for Semiconductor Processing by Diode Laser Spectroscopy

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, CO2, and H2O 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 H20 measurements. TDLAS lends itself to the study of contamination sources in situ. As examples, measurements of CO generation in sampling vessels and of CO2 outgassing in an electropolished stainless steel chamber are briefly discussed.