Eliminating the effects of gas-system pressure transients

摘要

Every time a mass flow controller in a multichamber installation shuts off or reopens, it can affect system pressure and flows. The combined effects of components reacting to pressure changes disseminates "crosstalk" through the system, disrupting low-flow MFCs in other chambers and tools. It is common to add pressure regulators immediately upstream of MFCs, which are highly sensitive to pressure transients, but this can also interfere with normal MFC flow stability. From an analysis of such problems, we developed a mass flow control concept that combines proven thermal and pressure-based techniques in a new hybrid flow controller. The controller effectively isolates itself from both upstream and downstream pressure changes, thus eliminating the need for local pressure regulators and associated hardware from the space-constrained gas box.