Embodiments of mechanisms for processing a wafer are provided. A method for processing a wafer includes creating an exhaust flow in a fluid conduit assembly that is connected to a process module used for processing the wafer. The method also includes detecting the exhaust pressure in the fluid conduit assembly. The method further includes determining whether the exhaust pressure meets a set point. In addition, the method includes regulating the exhaust flow if the exhaust pressure fails to meet the set point.