A nested electrostatically-actuated microvalve for an integrated microflow controller

Many semiconductor processes such as molecular beam epitaxy, low-pressure chemical vapor deposition, and reactive ion etching require precise control of ultraclean gas flows at very low flow rates. These applications are well suited to small electrostatically-actuated microvalves that can be merged with micromachined flow channels to form an integrated microflow controller (μFC). This paper presents such a microvalve structure and its integration into a simple prototype μFC. Produced using a nested bulk dissolved-wafer process, the microvalves utilize a three-electrode configuration which allows them to be actively pulled into both the on- and off-states. The valves actuate at 45-60 V, depending on dimensions. The μFC reported here was designed for a maximum flow rate of ISCCM and a leak rate of less then O.1 SCCM at a differential pressure of 100 Torr and outlet pressures from vacuum to atmospheric. The paper illustrates the design process used to optimize the structure to prevent stiction and ensure operation with the desired performance