Methods of and apparatus for controlling pressure in multiple zones of a process tool
A method of and a multiple zone pressure controller system for controlling the pressure of a gas or vapor flowing to at least two zones of a process tool such as a vacuum deposition chamber. The system comprises: at least two channels configured and arranged so as to provide the flow of the gas or vapor to corresponding zones of the process tool, each channel including a pressure controller configured and arranged to control the pressure of gas or vapor in each channel, a leakby orifice or nozzle configured to provide a leak rate of gas or vapor from the channel; and a controller configured and arrange to determine the true flow information to each zone of the process tool so that the true leak rate in the chamber can be determined.
1. A multiple zone pressure controller system for controlling the pressure of a gas or vapor flowing to at least two zones of a process tool, the system comprising:
at least two channels configured and arranged to provide the flow of the gas or vapor to corresponding zones of the process tool, each channel including:
a flow sensor configured and arranged to sense the flow of gas or vapor in the channel; and
a leak-by orifice or nozzle configured to provide a leak rate of gas or vapor from the channel;
a pressure transducer configured and arranged to measure the pressure of gas or vapor in the channel;
a valve configured and arranged to control the pressure of gas or vapor in the channel;
a controller configured and arranged to determine a true flow information to each zone of the process tool and a true leak rate away from a chamber of the process tool; and
a pressure transducer for measuring an upstream pressure of an inlet line so as to provide an upstream pressure signal to the controller, wherein the upstream pressure signal is used by the controller to provide a regulated constant downstream pressure that includes proactive control of downstream pressure for each channel to reduce disturbance in the downstream pressure otherwise cause by changes in upstream pressure.
2. The multiple zone pressure controller system according to claim 1 wherein each valve controls the pressure in its channel as a function of a set point and the sensed pressure in its channel.
3. The multiple zone pressure controller system according to claim 1 , wherein the flow sensor in each channel is configured and arranged so as to provide a mass flow signal as a function of the flow through the associated channel, wherein the true flow information to each zone is a function of the corresponding mass flow signal.
4. The multiple zone pressure controller system according to claim 3 , wherein the true flow information is a function of the flow through the corresponding leak-by orifice nozzle.
5. The multiple zone pressure controller according to claim 4 , wherein the leak-by orifice nozzle is configured to operate under choke flow conditions.
6. The multiple zone pressure controller system according to claim 4 , wherein the leak-by orifice or nozzle is configured to operate under choke flow and non-choke flow conditions.
7. The multiple zone pressure controller system according to claim 3 , wherein the controller includes a calibration table of flow rate vs. pressure for each leak-by orifice or nozzle.
8. The multiple zone pressure controller system according to claim 3 , wherein the controller calculates true flow information based upon the following relationship:
Q
chamber
,
i
=
Q
mpc
,
i
-
Q
leakby
,
i
-
V
d
,
i
·
T
stp
T
·
P
stp
·
ⅆ
P
d
,
i
ⅆ
t
wherein Q chamber,i is the flow rate into the process tool for channel i,
Q mpc,i is the flow rate measured by the flow sensor in channel i;
Q, leakby,i is calculated based on the properties of the orifice or nozzle in channel i. and
V
d
,
i
·
T
stp
T
·
P
stp
·
ⅆ
P
d
,
i
ⅆ
t
is a function of the rate of change in downstream pressure,
P d,i , measured by the pressure transducer of the channel i, the downstream volume, V d,i , between the control valve and the process tool for channel i, the measured gas/vapor temperature, T; T stp is the standard temperature which is 273.15K, and P stp is the standard pressure which is 1.01325e5 Pa.
9. The multiple zone pressure controller system according to claim 1 , wherein the upstream pressure signal is used by the controller for compensating pressure disturbance on a raw flow sensor signal such that the flow sensor signal is pressure insensitive.