Patent ID: 7610117

Claim:
A flow control device adapted for use in semiconductor manufacturing comprising: an inlet to receive a semiconductor manufacturing process fluid; an outlet in fluid communication with the inlet; a pressure loss element between the inlet and the outlet, wherein the inner diameter of the pressure loss element has a predetermined cross-sectional area; a pressure sensor to measure the pressure of the process fluid flowing through the flow control device, wherein the pressure sensor is positioned downstream or upstream of the pressure loss element; a valve responsive to a valve control signal for regulating the fluid flow; a controller coupled to the pressure sensor and the valve, wherein the controller is configured to generate valve control signals for opening and closing the valve to regulate the fluid flow at predefined low flow rates and wherein the controller is further configured to: at the predefined low flow rates, compare a current pressure reading of the semiconductor manufacturing process fluid received from the pressure sensor coupled to the controller to one or more previous pressure readings of the semiconductor manufacturing process fluid obtained from the same pressure sensor coupled to the controller, wherein the current pressure reading of the semiconductor manufacturing process fluid received from the pressure sensor coupled to the controller and the one or more previous pressure readings of the semiconductor manufacturing process fluid obtained from the same pressure sensor coupled to the controller had been read by the same pressure sensor at different times; determine a fluctuation between the current pressure reading of the semiconductor manufacturing process fluid received from the pressure sensor coupled to the controller and the one or more previous pressure readings of the semiconductor manufacturing process fluid obtained from the same pressure sensor coupled to the controller; and if the fluctuation between the current pressure reading of the semiconductor manufacturing process fluid received from the pressure sensor coupled to the controller and the one or more previous pressure readings of the semiconductor manufacturing process fluid obtained from the same pressure sensor coupled to the controller is outside of a predefined range, generate an alarm.