The integration of fluid control systems on a silicon wafer allows the control of a small volume of fluid by virtue of a negligible dead volume. Microvalves driven by small piezoactuators have been fabricated on a silicon wafer by micromachining. Three types, i.e. normally open, normally closed and three-way, were developed. An integrated mass flow controller consisting of a small thermal mass flow sensor and a normally closed microvalve was fabricated for precise gas control. The small thermal capacity of the flow sensor gives high sensitivity and quick response. The response time of the mass flow controller is less than 2 ms, which is faster than that of previous ones by nearly a thousand times. The integrated system gives rise to a precise flow control for advanced deposition processes, etc.
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