Method and apparatus for pulse gas delivery with isolation valves
A fluid control system for pulse delivery of a fluid include a flow channel, an isolation valve to initiate and terminate a pulse of fluid from the flow channel, and a pulse mass flow controller (MFC). The MFC includes a control valve to control flow of fluid in the flow channel, a flow sensor to measure flow rate in the flow channel, and a controller to control flow of fluid through the control valve and switching of the isolation valve, to control a mass of fluid delivered during the pulse of fluid. Controlling the flow of fluid through the control valve can be based on feedback from the flow sensor during the pulse initiated and terminated by the isolation valve.
1. A fluid control system for pulse delivery of a fluid, the system comprising:
a flow channel;
an isolation valve to initiate and terminate a pulse of fluid from the flow channel; and
a mass flow controller (MFC), including a control valve to control flow of fluid in the flow channel, a flow sensor to measure flow rate in the flow channel, and a dedicated controller to control flow of fluid through the control valve based on feedback from the flow sensor, the dedicated controller connected to the isolation valve to control switching of the isolation valve to initiate and terminate the pulse, to control a mass of fluid delivered during the pulse of fluid, wherein the dedicated controller is configured to determine an estimated number of moles of fluid delivered as a function of i) the measured flow rate, ii) a start time of the pulse of fluid, and iii) a stop time of the pulse of fluid, and wherein the dedicated controller is configured to control the flow through the control valve and the switching of the isolation valve based on the estimated number of moles of fluid delivered.
2. The system of claim 1 , wherein the controller controls the flow of fluid through the control valve during the pulse initiated and terminated by the isolation valve.
3. The system of claim 1 , wherein the flow sensor comprises:
a flow restrictor within the flow channel and positioned between the control valve and the isolation valve;
an upstream pressure sensor configured to detect an upstream pressure in the flow channel at an upstream position between the control valve and the flow restrictor; and
a downstream pressure sensor configured to detect a downstream pressure in the flow channel at a downstream position between the flow restrictor and the isolation valve, the flow sensor measuring flow rate based on the upstream pressure and the downstream pressure.
4. The system of claim 3 , wherein the dedicated controller is configured to close the isolation valve based on a computation of the mass of fluid delivered during the pulse of fluid.
5. The system of claim 3 , wherein the dedicated controller is configured to determine the estimated number of moles of fluid delivered based on a determination of a residual flow rate and the measured flow rate.
6. The system of claim 5 , wherein the dedicated controller is configured to receive an upstream pressure signal corresponding to the upstream pressure and a downstream pressure signal corresponding to the downstream pressure, and to determine the residual flow rate as a function of i) the downstream pressure and ii) a dead volume between the flow restrictor and the isolation valve as
(
V
d
2
·
d
P
d
d
t
)
,
where V d2 is the dead volume between the flow restrictor and the isolation valve and P d is the downstream pressure.
7. The system of claim 5 , wherein the dedicated controller is configured to determine the estimated number of moles of fluid delivered according to the following equation:
Δ
n
=
∫
t
1
t
2
(
Q
m
-
V
d
2
·
d
P
d
d
t
)
·
d
t
where Δ n is the estimated number of moles, Q m is the measured flow rate by the flow sensor, V d2 is the dead volume between the flow restrictor and the isolation valve, P d is the downstream pressure, t 1 is the start time of the pulse, and t 2 is the stop time of the pulse.
8. The system of claim 3 , wherein the flow rate is measured as a function of the upstream pressure, the downstream pressure, and one or more properties of the fluid.
9. The system of claim 8 , wherein the one or more properties of the fluid include molecular weight MW and specific heat ratio γ.
10. The system of claim 8 , further comprising a temperature sensor configured to measure temperature of the fluid in the flow channel, and wherein the flow rate is further measured as a function of the temperature of the fluid.
11. The system of claim 1 , wherein the dedicated controller is configured to receive a control signal from a host controller, the control signal including an identification of the fluid, a desired number of moles of the pulse of fluid, and a duration of the pulse of fluid.
12. The system of claim 1 , wherein the isolation valve is integrated into the MFC.
13. The system of claim 1 , wherein the isolation valve is external to the MFC.
14. The system of claim 13 , wherein the isolation valve is a 3-way valve coupled to a process chamber and a dump line.
15. The system of claim 13 , wherein the system includes plural isolation valves, and wherein one of the isolation valves is coupled to a process chamber and another of the isolation valves is coupled to a dump line.
16. The method of claim 1 , wherein the dedicated controller is configured to determine the estimated number of moles of fluid delivered based on a determination of a residual flow rate and the measured flow rate.
17. A method of delivering a pulse of fluid, the method comprising:
controlling flow of fluid into a flow channel with a control valve of a mass flow controller (MFC);
measuring flow rate in the flow channel with a flow sensor of the MFC;
controlling switching of an isolation valve to initiate and terminate a pulse of fluid from the flow channel; and
with a dedicated controller in the MFC, determining an estimated number of moles of fluid delivered, controlling flow of fluid through the control valve based on feedback from the flow sensor, and switching of the isolation valve to control a mass of fluid delivered during the pulse of fluid, wherein the estimated number of moles of fluid delivered is determined as a function of i) the measured flow rate, ii) a start time of the pulse of fluid, and iii) a stop time of the pulse of fluid, and wherein the flow of fluid through the control valve and the switching of the isolation valve are controlled based on the estimated number of moles of fluid delivered.
18. The method of claim 17 , wherein controlling the flow of fluid through the control valve is based on feedback from the flow sensor during the pulse initiated and terminated by the isolation valve.
19. The method of claim 17 , further comprising:
detecting an upstream pressure in the flow channel at an upstream position between the control valve and a flow restrictor positioned between the control valve and the isolation valve; and
detecting a downstream pressure in the flow channel at a downstream position between the flow restrictor and the isolation valve;
and wherein measuring flow rate in the flow channel is based on the upstream pressure and the downstream pressure.
20. The method of claim 19 , further comprising determining a residual flow rate as a function of i) the downstream pressure and ii) the dead volume between the flow restrictor and the isolation valve, and wherein the estimated number of moles of fluid delivered is determined based on the residual flow rate and the measured flow rate.
21. The method of claim 17 , wherein the estimated number of moles of fluid delivered is determined based on a determination of a residual flow rate and the measured flow rate.
22. A fluid control system for pulse delivery of a fluid, the system comprising:
a flow channel;
plural isolation valves to initiate and terminate a pulse of fluid from the flow channel, one of the isolation valves being coupled to a process chamber and another of the isolation valves being coupled to a dump line; and
a mass flow controller (MFC), including a control valve to control flow of fluid in the flow channel, a flow sensor to measure flow rate in the flow channel, and a controller to control flow of fluid through the control valve and switching of the isolation valves, to control a mass of fluid delivered during the pulse of fluid.