Methods and assemblies for gas flow ratio control
Methods and gas flow control assemblies configured to deliver gas to process chamber zones in desired flow ratios. In some embodiments, assemblies include one or more MFCs and a back pressure controller (BPC). Assemblies includes a controller, a process gas supply, a distribution manifold, a pressure sensor coupled to the distribution manifold and configured to sense back pressure of the distribution manifold, a process chamber, a one or more mass flow controllers connected between the distribution manifold and process chamber to control gas flow there between, and a back pressure controller provided in fluid parallel relationship to the one or more mass flow controllers, wherein precise flow ratio control is achieved. Alternate embodiments include an upstream pressure controller configured to control flow of carrier gas to control back pressure. Further methods and assemblies for controlling zonal gas flow ratios are described, as are other aspects.
1. A gas flow control assembly, comprising:
a first controller;
a process gas supply including a carrier gas and one or more process gases, wherein the process gas supply further includes one or more first mass flow controllers, and wherein each first mass flow controller of the one or more first mass flow controllers is coupled to the first controller;
a distribution manifold fluidly coupled to the process gas supply;
a back pressure sensor connected to the first controller and fluidly connected to the distribution manifold, and configured to sense back pressure in the distribution manifold, and further configured to provide a signal to the first controller based, at least in part, on sensed back pressure;
a process chamber including a plurality of zones;
a plurality of second mass flow controllers, each second mass flow controller of the plurality of second mass flow controllers fluidly and operatively connected between the distribution manifold and the process chamber, and configured to control gas flow into the plurality of zones of the process chamber; and
an upstream pressure controller fluidly and operatively connected to the distribution manifold and configured to control flow of the carrier gas responsive to a back pressure set point supplied by the first controller.
2. The gas flow control assembly of claim 1 , wherein the first controller is configured to set a flow set point through each of the plurality of second mass flow controllers, and wherein the first controller is a digital controller including a processor.
3. The gas flow control assembly of claim 1 , wherein each of the plurality of second mass flow controllers is configured to flow a gas from the process gas supply at a flow rate of greater than 90 slm.
4. The gas flow control assembly of claim 1 , wherein the upstream pressure controller is configured to control a flow of the carrier gas to be mixed with the one or more process gases responsive to the back pressure set point supplied by the first controller.
5. A gas flow control assembly, comprising:
a first controller;
a process gas supply including a carrier gas and one or more process gases;
a distribution manifold fluidly coupled to the process gas supply;
a back pressure sensor connected to the first controller and fluidly connected to the distribution manifold, and configured to sense back pressure in the distribution manifold, and further configured to provide a signal to the first controller based, at least in part, on sensed back pressure;
a process chamber including a plurality of zones;
a plurality of mass flow controllers, each mass flow controller of the plurality of mass flow controllers fluidly and operatively connected between the distribution manifold and the process chamber, and configured to control gas flow into the plurality of zones of the process chamber;
an upstream pressure controller fluidly and operatively connected to the distribution manifold and configured to control flow of the carrier gas responsive to a back pressure set point supplied by the first controller; and
a carrier gas mass flow controller provided in a fluid parallel relationship with the upstream pressure controller.
6. A gas flow control assembly, comprising:
a first controller;
a process gas supply including a carrier gas and one or more process gases configured to be mixed at a junction, wherein the process gas supply further includes one or more first mass flow controllers, and wherein each first mass flow controller of the one or more first mass flow controllers is coupled to the first controller;
a distribution manifold fluidly coupled to the process gas supply downstream of the junction, the distribution manifold having a plurality of outlets;
a back pressure sensor operatively connected to the first controller and configured to sense back pressure in the distribution manifold;
a process chamber including a plurality of zones;
one or more second mass flow controllers, each of the one or more second mass flow controllers fluidly and operatively connected to an outlet of the distribution manifold and to one of the plurality of zones to control a gas flow ratio into each of the plurality of zones; and
an upstream pressure controller fluidly connected to the carrier gas upstream of the junction, and operatively connected to the first controller, wherein the upstream pressure controller is configured to control the back pressure to a back pressure set point responsive to an output signal from the first controller that is responsive to an output signal from the back pressure sensor.