A Counting Challenge
Effervescent and hot process chemicals used in the semiconductor industry pose unique challenges when trying to measure particle concentration levels. Compression liquid samplers are widely used for both mobile batch sampling and continuous on-line sampling of these chemistries because of their ability to control bubble formation and minimize the effect they have on the resulting data. Samplers also offer tighter process control capabilities by monitoring in close proximity to the product, as in the case of a production wet-bench.
Liquid samplers must be optimized for the chemical of interest based on its viscosity, density, vapor pressure and effervescence. Physical parameters such as the location of the sampler from the chemical source, length and diameter of the sample tubing, and fluid elevation changes will affect the settings of the sampler, and therefore must be considered. It is not uncommon for a single sampler to be used with five to ten different chemistries having vastly different physical properties. This broad challenge requires the operator of the equipment understand that technique is a critical determinant in success or failure of the measurement. This article offers general guidelines based on field experience for configuring and optimizing the performance of a liquid compression sampler. A detailed discussion defining a proven sequence for optimizing a compression sampler is given, as well as suggested configurations for the most common process chemistries.