Mass flow measurement and control of low vapor pressure sources

Abstract

Thermal mass flow controllers (MFC’s) have been universally accepted as the instruments of choice for the introduction and control of semiconductor process gases, and significant performance advances have been made in the technology within the past few years. However, there are many applications where standard thermal MFC’s are not the optimum choice of flow control technique. Specifically, these applications involve the accurate and repeatable delivery of low vapor pressure liquid or solid source vapors. Recent developments in pressure-based flow control have led to the successful solution of many of the liquid/solid source delivery problems, and promise to solve even more as further developments are made. A detailed discussion of these technologies will be presented.