High Purity Gases

Abstract

Abstract High purity industrial gases are routinely delivered in large quantities having purities exceeding 99.999% (>5 nines pure). Other commodity materials, whether in liquid or solid form, much less typically have purity exceeding 99.9%. There are many applications for gases where purity even higher than 99.999% is required. To service these applications, the technology for manufacturing and delivering high purity gases has developed into a multibillion dollar business worldwide. Japan and the United States have the majority of the market. There is no universally accepted definition of what purity levels correspond to high purity. A good working definition of high purity is gases having certain individual impurities held to levels <0.1 ppm. The technology for manufacturing and delivering high purity gases has largely developed to support the manufacture of advanced semiconductor materials needed as part of the overall process of manufacturing integrated circuits. Purity requirements in some of these high performance materials have reached the point where impurity concentrations in the starting gases of 1 part in 10 12 have been related to reduced yields and poor performance in the resulting integrated circuits. Depending on a volume, high purity gases can be delivered using either bulk systems, where a plant‐wide distribution system is integrated with central gas storage facilities, or cylinders, where a short local distribution system is supplied from a single high pressure cylinder. Gases used in the manufacture of semiconductor materials fall into three principal areas: the inert gases, used to shield the manufacturing processes and prevent impurities from entering; the source gases, used to supply the molecules and atoms that stay behind and contribute to the final product, and the reactive gases, used to modify the electronic materials without actually contributing atoms or molecules.