Process gas distribution system and method with automatic transducer zero calibration

• US 5,508,947 A
• Filed: 05/13/1994
• Issued: 04/16/1996
• Est. Priority Date: 08/31/1990
• Status: Expired due to Fees

• Current Assignee: US Bank National Association (US Bancorp)
• Original Assignee: SCI Systems Incorporated (Sanmina-SCI Corporation)
• Inventors: Geist, Stephen G., DuRoss, Ronald R., Hayes, Gregory L., Sierk, Dennis A.
• Primary Examiner(s): Cosimano, Edward R.
• Assistant Examiner(s): PIPALA, EDWARD J
• Application Number:
  US08/242,805
• Time in Patent Office: 704 Days
• Field of Search: 364/138, 364/550, 364/551.01, 364/558, 364/567, 364/571.01, 364/571.04, 364/571.05, 364/509, 364/556, 364/510, 364/571.07, 141/65, 141/83, 73/4 R, 73/1 G, 73/1 B, 73/708
• US Class Current: 702/87
• CPC Class Codes: F17C 13/02 Special adaptations of indicating, measuring, or monitoring equipment measuring in general G01
• CPC Class Codes: F17C 13/04 Arrangement or mounting of valves valves per se F16K ; snap-coupling of nipples F16L37/00
• CPC Class Codes: F17C 2205/0111 Boxes
• CPC Class Codes: F17C 2205/0176 with ventilation
• CPC Class Codes: F17C 2205/0338 Pressure regulators
• CPC Class Codes: F17C 2205/0391 inside the pressure vessel
• CPC Class Codes: F17C 2227/044 by purging
• CPC Class Codes: F17C 2250/032 using computers
• CPC Class Codes: F17C 2250/034 using wireless transmissions
• CPC Class Codes: F17C 2250/0443 Flow or movement of content
• CPC Class Codes: F17C 2250/0636 Flow or movement of content
• CPC Class Codes: F17C 2270/0518 Semiconductors
• CPC Class Codes: H01J 37/3244 Gas supply means
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring
• CPC Class Codes: H01L 21/67276 Production flow monitoring, e.g. for increasing throughput program-control systems per se G05B19/00, e.g. total factory control G05B19/418

Abstract

A system including a plurality of gas flow control units in cabinets which are connected to distribute process gas, on demand, to a plurality of utilization locations known as "tool" locations in a semi-conductor manufacturing plant. Transducers are used in the system to measure pressures and other control parameters. Zero calibration of the transducers is provided by automatically subjecting each transducer to a reference computer routine to compute the difference between the standard value and the transducer output, and store the difference as an "offset" to correct the output of the transducer. Thus, re-calibration is performed simply and quickly, at a relatively low labor cost and with relatively little downtime for the system.

Claims

1. In or for a process gas distribution control unit handling hazardous gasses having gas conduit means for conducting said process gas from a source towards a utilization location, control means for controlling the flow of said gas through said conduit means, and at least one gas pressure measurement transducer for measuring the pressure of said gas in said conduit means, a system for calibrating said pressure transducer comprising reference means for subjecting said transducer to a known value of pressure, means for measuring an electrical output signal of said transducer, means for comparing said electrical output signal with a known standard signal and developing a difference signal corresponding to the difference between said standard signal and said output signal, memory means for storing data corresponding to said difference signal, and correction means utilizing the stored data to correct the output signal of said transducer.

2. A device as in claim 1 including a vacuum source, said reference means comprising means for selectively connecting said vacuum source to said transducer.

3. A device as in claim 2 in which said gas conduit means includes gas conduits for distributing said process gas to a plurality of utilization locations, and purge means for selectively connecting said conduits to said vacuum source for purging.

4. A device as in claim 1 which said correction means comprises digital computer means for adding or subtracting from the output of said transducer a signal corresponding to said difference signal to correct the zero reading of said transducer.

5. A device as in claim 2 in which said gas conduit means includes a plurality of process gas distribution conduits and at least one purge gas supply conduit, in which said output of said transducer represents absolute pressure, and means for selectively and alternatingly connecting first said vacuum source and then said purge gas supply conduit to at least one of said process gas distribution conduits.

6. A device as in claim 2 in which said vacuum source comprises a venturi pump with means for admitting pressurized purge gas as the driving gas for said pump, and having a vent.

7. A device as in claim 1 in which said memory means comprises non-volatile data storage means.

8. A device as in claim 7 in which said data storage means is an EEPROM.

27. A device as in claim 1 in which said reference weight is the weight bearing on said transducer when said weighing device is empty.

28. A device as in claim 27 including a controller to cause a prompt display indicating the need to empty said weighing means before calibrating said transducer, and to inhibit the calibration of said transducer when said prompt display is not responded to by an operator.

9. A method of calibrating gas pressure transducers in a process gas distribution system handling hazardous gasses having gas conduit means for conducting process gas, said method comprising the steps of:

a) subjecting each of said transducers to a reference value comprising a known gas pressure;

b) measuring the electrical output signal of said transducer;

c) utilizing a pre-programmed digital computer having a memory to compare said measured output signal with a pre-determined electrical signal corresponding to said known pressure and determining the difference between said signals;

d) storing in the memory of said computer data corresponding to said reference; and

e) utilizing said stored data to correct subsequent output signals of said transducer.

10. A method as in claim 9 in which said subjecting step comprises connecting said transducer to a vacuum source, and including the step of selectively connecting said vacuum source to process gas distribution lines to purge them.

11. A method as in claim 10 in which said transducer is adapted to produce output signals representing absolute gas pressure.

12. In or for a process gas distribution control unit handling hazardous gasses having gas conduit means for conducting process gas from a pressurized container towards a utilization location, support means for supporting at least one pressurized container of process gas and weighing means for weighing said container to determine the amount of gas in said container while said container is connected to said gas conduit means, said weighing means including at least one weight measurement transducer, a system for calibrating said weight measurement transducer comprising means for measuring and electrical output signal of said transducer, means for comparing, with a known standard signal, a reference value of said electrical output signal produced when said weighing means is subjected to a reference weight and developing a difference signal corresponding to the difference between the value of said standard signal and said reference value, memory means for storing data corresponding to said difference signal, said correction means utilizing the stored data to correct the output signal of said transducer.

13. A device as in claim 12 in which said reference weight is the weight bearing on said transducer when said weighing means is empty.

14. A device as in claim 13 including means for giving a computer prompt display indicating the need to empty said weighing means before calibrating said transducer, and for inhibiting the calibration of said transducer when said prompt display is not responded to by an operator.

15. A method of calibrating gas supply detectors in a process gas distribution system handling hazardous gasses having gas conduit means for conducting process gas from a pressurized container towards a utilization location, said detectors comprising weight transducer for weighing a pressurized container of process gas to determine the amount of gas in said container while said container is connected to said gas conduit means, said method comprising the steps of:

a) subjecting each of said transducers to a reference weight;

b) measuring the electrical output signal of each of said transducers;

c) utilizing a pre-programmed digital computer with memory to compare said measured output signal with a pre-determined electrical signal corresponding to a reference weight and determined the difference between said signals;

d) storing in said memory of said computer data corresponding to said difference; and

e) utilizing said stored data to correct subsequent output signals of said transducer.

16. A method as in claim 15 in which the step of subjecting each of said transducers to a reference weight comprises removing the weight of said container from said transducer.

17. A method as in claim 16 including the step of displaying on a computer control display a prompt to ensure that the container has been removed from said transducer before calibrating said transducer, and inhibiting the calibration routine if the operator does not respond to the prompt.

18. In or for a process gas distribution control unit handling hazardous gasses having a gas conduit to conduct said process gas from a source towards a utilization location, a control unit to control the flow of said gas through said conduit, and at least one gas pressure measurement transducer to measure the pressure of said gas in said conduit, a system for calibrating said pressure transducer comprising a reference source to subject said transducer to a known value of pressure, a measuring unit to measure an electrical output signal of said transducer, a comparator to compare said electrical output signal with a known standard signal and to develop a difference signal corresponding to the difference between said standard signal and said output signal, a memory to store data corresponding to said difference signal, and a corrector which uses the stored data to correct the output signal of said transducer.

19. A device as in claim 18 including a vacuum source, said reference source comprising a valve to selectively connect said vacuum source to said transducer.

20. A device as in claim 19 including gas conduits to distribute said process gas to a plurality of utilization locations, and a purge controller to selectively connect said conduits to said vacuum source for purging.

21. A device as in claim 18 in which said corrector comprises a digital computer for adding or subtracting from the output of said transducer a signal corresponding to said difference signal to correct the zero reading of said transducer.

22. A device as in claim 21 including a plurality of process gas distribution conduits and at least one purge gas supply conduit, in which said output of said transducer represents absolute pressure, and a controller to selectively and alternatingly connect first said vacuum source and then said purge gas supply conduit to at least one of said process gas distribution conduits.

23. A device as in claim 21 in which said vacuum source comprises a venturi pump with means for admitting pressurised purge gas as the driving gas for said pump, said pump having a vent to atmosphere.

24. A device as in claim 18 in which said memory comprises a non-volatile data storage device.

25. A device as in claim 21 in which said data storage device is an EEPROM.

26. In or for a process gas distribution control unit handling hazardous gasses having a gas conduit to conduct process gas from a pressurized container towards a utilization location, a support for supporting at least one pressurized container of process gas and a weighing device to weigh said container to determine the amount of gas in said container while said container is connected to said gas conduit, said weighing device including at least one weight measurement transducer, a system for calibrating said weight measurement transducer comprising a measuring unit to measure an electrical output signal of said transducer, a comparator to compare, with a known standard signal, a reference value of said electrical output signal produced when said weighing device is subjected to a reference weight and to develop a difference signal corresponding to the difference between the value of said standard signal and said reference value, a memory to store data corresponding to said difference signal, and a corrector utilizing the stored data to correct the output signal of said transducer.