Atmospheric pressure wafer processing reactor having an internal pressure control system and method

• US 20030094136A1
• Filed: 08/23/2002
• Published: 05/22/2003
• Est. Priority Date: 08/24/2001
• Status: Active Grant

• Current Assignee: Aviza Technology Inc (Sumitomo Corporation)
• Original Assignee: Aviza Technology Inc (Sumitomo Corporation)
• Inventors: Bailey, Robert J., Park, Seung G., Bartholomew, Lawrence D., Yuh, Soon K.
• Granted Patent: US 6,761,770 B2
• Time in Patent Office: Days
• US Class Current: 118/715
• CPC Class Codes: C23C 16/4412 Details relating to the exhausts, e.g. pumps, filters, scrubbers, particle traps
• CPC Class Codes: C23C 16/453 passing the reaction gases through burners or torches, e.g. atmospheric pressure CVD C23C16/513 takes precedence; for flame or plasma spraying of coating material in the molten state C23C4/00
• CPC Class Codes: C23C 16/54 Apparatus specially adapted for continuous coating
• CPC Class Codes: G05D 16/2046 the plurality of throttling means being arranged for the control of a single pressure from a plurality of converging pressures G05D16/204 takes precedence
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring

Abstract

An atmospheric pressure wafer processing system for delivering at least one gas is provided, having an exhaust control feedback system that utilizes sensors to measure the pressure within the system and adjusts control units to maintain the desired set pressures within the system. In particular the sensors measure the small differential pressures inside a muffle, and specifically the load, bypass center and unload sections of the muffle, relative to the chase ambient pressure. Controlling the muffle pressures directly within the atmospheric system yields a more stable pressure balance for processing wafers less subject to changes in the external environment and allows for compensation of varying input gas flows as occurs when the supply pressure to the system may vary. This system and method of pressure control is particularly advantageous for chemical vapor deposition application yielding improved process repeatability over an extended period of runtime.

Claims

1. A wafer processing system for delivering at least one gas to a wafer surface and removing one or more exhaust gases from said wafer surface, comprising:

an atmospheric pressure muffle;

one or more exhaust passages for exhausting gases from said muffle; and

an exhaust control feedback system coupled to said muffle and said one or more exhaust passages, said feedback system having one or more sensors to measure one or more pressure differentials between at least one selected point within said muffle or said exhaust passages and the chase ambient pressure external to said wafer processing system and to adjust one or more control units to maintain one or more desired setpoint values for said pressure differentials within said wafer processing system.

2. The wafer processing system of claim 1 wherein said muffle includes a process chamber bypass center, a load, and an unload region, and said one or more sensors are a first, a second, and a third pressure transducer that measure the differential pressures inside said bypass center, load, and unload regions, respectively, relative to the chase ambient pressure.

3. The wafer processing system of claim 2 wherein said one or more control units comprise:

a first throttle valve that meters exhaust flow from said process chamber bypass center region in response to feedback from said first pressure transducer;

a second control unit selected from the group consisting of a throttle valve that meters exhaust flow from said process chamber load region and a flowmeter that meters the flow of one or more inert gases through one or more inert gas curtains into said load region, said control unit operating in response to feedback from said second pressure transducer; and

a third control unit selected from the group consisting of a throttle valve that meters exhaust flow from said process chamber load region and a flowmeter that meters the flow of one or more inert gases through one or more inert gas curtains into said unload region, said control unit operating in response to dynamic feedback from said third pressure transducer.

4. The wafer processing system of claim 3 further comprising:

a fourth pressure transducer that measures the pressure differential between the interior of a facility exhaust line and the chase ambient pressure, said facility exhaust line carrying combined exhaust gas flows from said bypass center, load, and unload regions of said muffle; and

a fourth throttle valve that controls the rate of exhaust gas flow on said facility exhaust line in response to dynamic feedback from said fourth pressure transducer.

5. The wafer processing system of claim 3 further comprising:

a bypass exhaust manifold for venting gas from said muffle;

a fifth pressure transducer measuring the pressure drop across an inline orifice in a bypass exhaust line carrying exhaust gases from said bypass exhaust manifold; and

a fifth throttle valve that controls the rate of exhaust gas flow from said bypass exhaust manifold in response to dynamic feedback from said fifth pressure transducer.

6. The wafer processing system of anyone of claim 3 wherein said first, second, and third pressure transducers measure differential pressures to within an absolute error of approximately 0.0001 torr.

7. The wafer processing system of claim 6 wherein said first, second, and third pressure transducers have an internal signal response time in the range of approximately 0.1 to 1.0 seconds.

8. The wafer processing system of claim 6 wherein said first, second, and third pressure transducers have an internal signal response time of approximately 0.4 seconds.

9. The wafer processing system of claim 6 further comprising:

a signal conditioner that filters data collected by one or more of said pressure transducers before said data is provided as dynamic feedback to one or more of said control units and throttle valves.

10. The wafer processing system of claim 9 wherein said signal conditioner averages data from said one or more pressure transducers over a preset period of time to reduce the impact of measurement noise.

11. The wafer processing system of claim 10 wherein said preset period of time is in the range of approximately 1 to 10 seconds.

12. The wafer processing system of claim 10 wherein said preset period of time is approximately 3 seconds.

13. A chemical vapor deposition processing system for delivering one or more reactive gases and one or more inert gases to process a wafer or other substrate, comprising:

a muffle, said muffle being maintained at approximately atmospheric pressure and containing at least one process chamber housing at least one injector through which said one or more reactive gases are injected and at least one shield or curtain through which said one or more inert gases are injected into a deposition region and at least one exhaust vent through which reactive gases and inert gases are removed;

a load region through which wafers are inserted into said muffle;

an unload region through which wafers are removed from said muffle;

a process chamber exhaust flow path through which all of said reactive gases and at least a fraction of said one or more inert gases removed from said muffle are exhausted;

at least a first pressure transducer, said first pressure transducer measuring the pressure difference between said muffle in the process chamber region and the ambient atmospheric pressure and providing a feedback control signal in response to said pressure difference; and

a first control unit comprising a first throttle valve, said throttle valve controllable in response to said feedback control signal, said throttle valve metering the flow of gases that are exhausted from said process chamber exhaust flow path of said CVD system.

14. The wafer processing system of claim 13 further comprising:

a second pressure transducer that measures the differential pressure inside said load region relative to the ambient atmospheric pressure; and

a third pressure transducer that measures the differential pressures inside said unload region relative to the ambient atmospheric pressure.

15. The wafer processing system of claim 14 further comprising:

a second control unit selected from the group consisting of a throttle valve that meters exhaust flow from said process chamber load region and a flowmeter that meters the flow of one or more inert gases through one or more inert gas curtains into said load region, said control unit operating in response to feedback from said second pressure transducer; and

a third control unit selected from the group consisting of a throttle valve that meters exhaust flow from said process chamber load region and a flowmeter that meters the flow of one or more inert gases through one or more inert gas curtains into said unload region, said control unit operating in response to feedback from said third pressure transducer.

16. The wafer processing system of claim 15 further comprising:

a fourth pressure transducer that measures the pressure differential between the interior of a facility exhaust line and the chase ambient pressure, said facility exhaust line carrying combined exhaust gas flows from said process chamber, load, and unload regions of said muffle; and

a fourth control unit comprising a fourth throttle valve that controls the rate of exhaust gas flow on a facility exhaust line in response to dynamic feedback from said fourth pressure transducer.

17. The wafer processing system of claim 16 further comprising:

a bypass exhaust manifold for venting gas from said muffle;

a fifth pressure transducer that measures the pressure drop across an inline orifice in a bypass exhaust line carrying exhaust gases from said bypass exhaust manifold; and

a fifth control unit comprising a fifth throttle valve that controls the rate of exhaust gas flow from said bypass exhaust manifold in response to dynamic feedback received from said fifth pressure transducer.

18. The wafer processing system of any one of claim 15 wherein said first, second, and third pressure transducers measure differential pressures to within an absolute error of approximately 0.0001 torr.

19. The wafer processing system of claim 18 wherein said first, second, and third pressure transducers have an internal signal response time in the range of approximately 0.1 to 1.0 seconds.

20. The wafer processing system of claim 18 wherein said first, second, and third pressure transducers have an internal signal response time of approximately 0.4 seconds.

21. The wafer processing system of claim 18 further comprising:

a signal conditioner that filters data collected by one or more of said pressure transducers before passing said data to one or more of said respective control units.

22. The wafer processing system of claim 21 wherein said signal conditioner averages data from said one or more pressure transducers over a preset period of time to reduce the impact of measurement noise.

23. The wafer processing system of claim 21 wherein said preset period of time is in the range of approximately 1 to 10 seconds.

24. The wafer processing system of claim 21 wherein said preset period of time is approximately 3 seconds.

25. A method of delivering and exhausting one or more gases in an atmospheric pressure wafer processing system that comprises a muffle with at least one process chamber for chemical vapor deposition while maintaining an approximately constant pressure that is close to atmospheric throughout said system comprising the steps of:

temporarily fixing the positions of each of two throttle valves controlling exhaust gas flow from a load and unload region of said system;

measuring the pressure in a chamber exhaust plenum of said system and adjusting a first pressure differential setpoint, δ

P₁, between said process chamber region and an ambient chase room pressure to establish a desired pressure in said chamber exhaust plenum for sufficient exhaust of process chemicals;

regulating gas flow through a main process exhaust line to maintain δ

P₁ at a constant preset value by controlling a first throttle valve on said main exhaust line;

determining the position of said first throttle valve and controlling the flow through a fourth throttle valve controlling a total system exhaust rate to permit operation of said first throttle valve within an optimum range of positions and to isolate said system from potential perturbations in downstream vacuum;

measuring the differential pressures, δ

P₂ and δ

P₃, respectively, between said load and said unload regions and said ambient chase room pressure;

obtaining a pressure difference between δ

P₂ and δ

P₃ in the range of approximately less than 0.002 torr by adjusting one or more gas flows in said load and unload regions;

entering δ

P₂ and δ

P₃ as setpoints for one or more valve controllers controlling said load and unload region throttle valves and returning said load and unload valves to automatic operation; and

allowing said system to stabilize before beginning process operation.

26. A chemical vapor deposition processing system for delivering one or more reactive gases and one or more inert gases to process a wafer or other substrate, comprising:

a muffle, said muffle being maintained at approximately atmospheric pressure and containing at least one process chamber housing at least one injector through which said one or more reactive gases are injected and at least one shield or curtain through which said one or more inert gases are injected into a deposition region and at least one exhaust vent through which reactive gases and inert gases are removed;

a load region through which wafers are inserted into said muffle;

an unload region through which wafers are removed from said muffle;

a process chamber exhaust flow path through which all of said reactive gases and at least a fraction of said one or more inert gases removed from said muffle are exhausted;

a bypass exhaust manifold for venting gas from said muffle;

a first pressure transducer, said first pressure transducer measuring the pressure difference between said muffle in the process chamber region and the ambient atmospheric pressure and providing a feedback control signal in response to said pressure difference;

a second pressure transducer that measures the differential pressure inside said load region relative to the ambient atmospheric pressure;

a third pressure transducer that measures the differential pressures inside said unload region relative to the ambient atmospheric pressure;

a fourth pressure transducer that measures the pressure differential between the interior of a facility exhaust line and the chase ambient pressure, said facility exhaust line carrying combined exhaust gas flows from said process chamber, load, and unload regions of said muffle;

a fifth pressure transducer that measures the pressure drop across an inline orifice in a bypass exhaust line carrying exhaust gases from said bypass exhaust manifold;

a first control unit comprising a first throttle valve, said throttle valve controllable in response to said feedback control signal, said throttle valve metering the flow of gases that are exhausted from said process chamber exhaust flow path of said CVD system;

a second control unit selected from the group consisting of a throttle valve that meters exhaust flow from said process chamber load region and a flowmeter that meters the flow of one or more inert gases through one or more inert gas curtains into said load region, said control unit operating in response to feedback from said second pressure transducer; and

a third control unit selected from the group consisting of a throttle valve that meters exhaust flow from said process chamber load region and a flowmeter that meters the flow of one or more inert gases through one or more inert gas curtains into said unload region, said control unit operating in response to feedback from said third pressure transducer.

a fourth control unit comprising a fourth throttle valve that controls the rate of exhaust gas flow on a facility exhaust line in response to dynamic feedback from said fourth pressure transducer.

a fifth control unit comprising a fifth throttle valve that controls the rate of exhaust gas flow from said bypass exhaust manifold in response to dynamic feedback received from said fifth pressure transducer.

27. The wafer processing system of claim 26 wherein said first, second, and third pressure transducers measure differential pressures to within an absolute error of approximately 0.0001 torr.

28. The wafer processing system of claim 26 wherein said first, second, and third pressure transducers have an internal signal response time in the range of approximately 0.1 to 1.0 seconds.

29. The wafer processing system of claim 26 wherein said first, second, and third pressure transducers have an internal signal response time of approximately 0.4 seconds.

30. The wafer processing system of claim 26 further comprising:

a signal conditioner that filters data collected by one or more of said pressure transducers before passing said data to one or more of said respective control units by averaging data from said one or more pressure transducers over a preset period of time to reduce the impact of measurement noise.

31. The wafer processing system of claim 30 wherein said preset period of time is in the range of approximately 1 to 10 seconds.

32. The wafer processing system of claim 30 wherein said preset period of time is approximately 3 seconds.