Capture and Analysis of Particulate Contamination in Gaseous and Liquid Processing Materials

A number of methods are available for determining the particle content in chemically reactive fluids such as liquid, gaseous or supercritical processing materials. Each method has advantages and disadvantages. This paper describes the method of particle capture on filters followed by microscopic analysis. Although this method has been widely applied to measuring particle levels in various liquids and gases, and for airborne particle sampling, it has not been extensively used for highly reactive semiconductor processing materials. A sampling system suitable for implementing this method in difficult to measure fluids, and the steps necessary to perform the capture process are described. A method for quantifying the particle concentration in the fluid based upon an analysis of the particles observed on the filter is also described. Typical results of contaminant particles detected in liquid and gaseous materials used for semiconductor wafer processing are also presented. These data provide information on the particle content of fluid source containers and transfer lines, and the efficiency of filters in removing such particles in flowing systems. Particle SEM images and compositional data obtained through energy dispersive X-ray spectroscopy (EDS) are presented. Such information aids in the tracing of particle sources, and the eventual elimination of such sources.