Applied Materials, Inc.
Low temperature thermal flow ratio controller

Abstract:

Methods and apparatus for a flow ratio controller are provided herein. In some embodiments, a flow ratio controller includes an inlet; a plurality of channels extending from the inlet to a corresponding plurality of outlets; a bypass pipe extending from each channel of the plurality of channels that diverts a small portion of a flow from that channel and then returns the small portion of the flow back to that channel; and a thermal mass flow meter coupled to the bypass pipe having a first temperature sensor, a second temperature sensor, and a heating element disposed therebetween. A controller is configured to determine a flow rate through each of the plurality of channels based on a measured temperature difference between the first temperature sensor and the second temperature sensor.