Methods and assemblies for gas flow ratio control

1. A method comprising:

controlling, by a master controller operatively connected to a mass flow controller, gas flow through the mass flow controller to a dynamically-controllable flow set point, wherein the mass flow controller is fluidly coupled between a process chamber and a distribution manifold, wherein the distribution manifold is fluidly coupled to the process chamber and to a process gas supply providing a process gas, and wherein the process gas has a process gas flow controlled by a supply mass flow controller that is operatively connected to the master controller;

receiving, by the master controller, an indication of a back pressure of the distribution manifold from a back pressure sensor operatively connected to the master controller; and

controlling, by the master controller, the back pressure of the distribution manifold to a back pressure set point by controlling carrier gas flow of a carrier gas with a pressure controller in view of the indication received from the back pressure sensor, wherein the pressure controller is fluidly coupled to a carrier gas supply providing the carrier gas and operatively connected to the master controller.

2. The method of claim 1 , further comprising:

flowing the gas flow through the mass flow controller and into a zone of the process chamber.

3. The method of claim 1 , wherein the pressure controller controls the carrier gas flow to a junction where the carrier gas flow and the process gas flow are mixed.

4. A method comprising:

providing a carrier gas via a carrier gas supply and one or more process gases via a process gas supply to a distribution manifold;

sensing, by a back pressure sensor fluidly coupled to the distribution manifold and operatively coupled to a first controller, back pressure in the distribution manifold;

transmitting, by the back pressure sensor, a signal to the first controller based at least in part on the back pressure;

determining, by the first controller, a back pressure set point based at least in part on the signal transmitted by the back pressure sensor to the first controller;

controlling, by one or more mass flow controllers, a flow of a gas mixture comprising the carrier gas and the one or more process gases into one or more zones of a process chamber, wherein the one or more mass flow controllers are fluidly coupled between the distribution manifold and the process chamber and operatively coupled to the first controller; and

controlling, by a pressure controller fluidly coupled to the distribution manifold and the carrier gas supply and operatively connected to the first controller, a carrier gas flow of the carrier gas based on the back pressure set pointy.

5. The method of claim 4 , further comprising:

setting, by the first controller, a flow set point through each of the one or more mass flow controllers, wherein the first controller is a digital controller including a processor.

6. The method of claim 4 , further comprising:

flowing, by the one or more mass flow controllers, the gas mixture at a flow rate of greater than 90 slm.

7. The method of claim 4 , further comprising:

controlling, by the pressure controller, the carrier gas flow to be mixed with the one or more process gases responsive to the back pressure set point.

8. The method of claim 4 , wherein the process chamber comprises a plurality of zones, wherein the one or more mass flow controllers comprise a plurality of mass flow controllers, and wherein each mass flow controller of the plurality of mass flow controllers is configured to control flow of the gas mixture into a respective zone of the plurality of zones.

9. The method of claim 4 , further comprising:

controlling, by an additional mass flow controller provided in a fluid parallel relationship with the pressure controller, a flow rate of the carrier gas.

10. The method of claim 4 , wherein the one or more process gases are controlled by one or more supply mass flow controllers, respectively, the method further comprising:

controlling, by the first controller, set points for each of the one or more supply mass flow controllers to control a ratio of the one or more process gases in the gas mixture.

11. The method of claim 4 , further comprising:

flowing the gas mixture into the one or more zones of the process chamber.

12. The method of claim 4 , further comprising:

controlling, by the pressure controller, flow of the carrier gas to a junction where the carrier gas and the one or more process gases are mixed.

13. The method of claim 4 , wherein the pressure controller is fluidly coupled upstream of the distribution manifold.

14. The method of claim 4 , wherein the pressure controller controls flow of the carrier gas in parallel with an additional mass flow controller for the carrier gas.

15. The method of claim 4 , wherein 100% of the carrier gas and 100% of the one or more process gases are delivered to the process chamber.

16. The method of claim 4 , wherein only a portion of the carrier gas flows through the pressure controller.

17. The method of claim 4 , further comprising:

setting an additional mass flow controller for the carrier gas to a carrier gas flow set point; and

modulating the pressure controller to control the back pressure.

18. A method comprising:

providing, by a master controller, a carrier gas via a carrier gas supply and a process gas via a process gas supply to a distribution manifold operationally coupled to a process chamber, wherein the carrier gas supply is fluidly coupled to a pressure controller, and wherein the process gas has a process gas flow that is controlled by a first mass flow controller, the pressure controller and the first mass flow controller operatively connected to the master controller;

controlling, by the master controller, flow of a gas mixture comprising the carrier gas and the process gas through a second mass flow controller to a dynamically-controllable flow set point, wherein the second mass flow controller is fluidly coupled between the process chamber and the distribution manifold and operatively connected to the master controller;

receiving, by the master controller, an indication of a back pressure of the distribution manifold from a back pressure sensor operatively connected to the master controller; and

controlling back pressure of the distribution manifold to a back pressure set point by controlling carrier gas flow with the pressure controller in view of the indication received from the back pressure sensor.

19. The method of claim 18 , further comprising:

flowing the gas mixture through the second mass flow controller and into a zone of the process chamber.

20. The method of claim 18 , further comprising:

controlling, by the pressure controller, the carrier gas flow to a junction where the carrier gas and the process gas are mixed to form the gas mixture.