Development of a High Accuracy, Fast Response Mass Flow Module Utilizing Pressure Measurement with a Laminar Flow Element (Resistive Element) — Criterion D200 Series —

By: Tadahiro Yasuda

31 August 2011

As semiconductor processes are being scaled to ever smaller sizes, there is a demand for greater accuracy. Wide rangeability is also required for the sake of lower prices. To meet such needs, we have developed a pressure-based mass flow control module utilizing a new technique.

A laminar flow element (resistive element) has a property in which more pressure is lost at a lower pressure and lower flow rate. The Criterion D200 Series utilizes this property to change the error in the flow rate when converting the pressure into the mass flow rate. By doing so, higher pressure sensor output can be maintained when measuring a low flow rate, thereby increasing the flow rate accuracy in the low flow rate region and providing better rangeability. By collecting the data of complex properties of the element and performing numerical calculations, the flow rate can be controlled to a minimum controlled level of 0.3%, achieving six times greater range than with the minimum rate of 2% in the previous MFCs. The new mass flow module is more resistant to variations in supply pressure, because the pressure sensor provides fast response. It meets all the required performance demanded by the next generation processes. The Criterion D200 Series is also equipped with a diagnostic mechanism that utilizes the relationship between pressure and flow rate based on the internal volume of the MFC.

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