Stainless steel-based integrated mass-flow controller for reactive and corrosive gases

This paper describes the fabrication and characterization of an anti-corrosive integrated mass-flow controller made of stainless steel and aluminum nitride (AlN) for reactive and corrosive gases. The fabricated mass-flow controller is composed of a normally open micro valve and a thermal flow sensor. A stacked piezo valve actuator mounted on a thin diaphragm is utilized for precise and rapid control of gas flow. The flow sensor consisting of two heaters can detect a flow rate by differential resistance of the two heaters. By a feedback control from the flow sensor to the valve actuator, it is possible to keep the flow rate constant. This device shows a quick response less than 10 ins, and has a small dead volume by the miniaturization and integration. It is confirmed that this device is not attacked by chlorine gas, so the integrated mass-flow controller can be applied to advanced semiconductor processes which need fine mass-flow control of corrosive gases with quick response. (C) 2002 Elsevier Science B.V. All rights reserved.