Capacitance manometers and methods relating to auto-drift correction

• US 7,706,995 B2
• Filed: 04/16/2007
• Issued: 04/27/2010
• Est. Priority Date: 04/16/2007
• Status: Active Grant

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: MKS Instruments Incorporated
• Inventors: Sullivan, Philip, Alcaide, David
• Primary Examiner(s): Tsai; Carol S
• Assistant Examiner(s): Suarez; Felix E
• Application Number:
  US11/735,654
• Publication Number:
  US 20080255787A1
• Time in Patent Office: 1,107 Days
• Field of Search: 702/47, 702/50, 702/98, 702/100, 702/140, 702/183, 737/18, 737/24, 137/486, 715/749
• US Class Current: 702/85
• CPC Class Codes: G01L 19/02 Arrangements for preventing, or for compensating for, effects of inclination or acceleration of the measuring device; Zero-setting means for aneroid barometers G01L7/14
• CPC Class Codes: G01L 9/0072 using variations in capacitance
• CPC Class Codes: G01L 9/12 by making use of variations in capacitance , i.e. electric circuits therefor

Abstract

Systems, methods, and apparatus, including software implementation, are disclosed providing drift prediction of output values for manometers. A signal or other indication may be provided for or in relation to a capacitance manometer when a servicing, replacing, and/or zeroing event is predicted or determined to be required, based on a history (e.g., timestamps) associated with previous zeroing events. Previously recorded timestamps can be curve fit with suitable functions to calculate or predict future maintenance, calibration, and/or replacement events for a manometer. Such signals or indications can be generated as an on-screen indication, and could also be available upon interrogation of the manometer via a digital communications link or system.

Claims

1. A capacitance manometer comprising:

a sensor capsule with a first port and a second port;

a diaphragm disposed within the sensor capsule, wherein the diaphragm has two sides and is configured and arranged to move within the sensor capsule in response to a pressure difference between respective pressures on the two sides of the diaphragm;

an electrode structure disposed within the sensor capsule adjacent to one side of the diaphragm; and

an electronic circuit configured and arranged to (i) measure capacitance between the diaphragm and the electrode structure, (ii) produce a zero-output reading corresponding to a measured zero pressure, (iii) record two or more time stamps, each corresponding to a respective zero-output reading, and (iv) predict a future drift value of the manometer zero-output reading based on the two or more time stamps and the respective zero-output readings.

2. The manometer of claim 1, wherein the manometer is configured and arranged to produce a digital output.

3. The manometer of claim 1, wherein the manometer is configured and arranged to produce an analog output.

4. The manometer of claim 1, wherein the manometer is configured and arranged to predict a manometer zero-reading exceeding a specified drift amount based on the two or more time stamps.

5. The manometer of claim 1, wherein the first port is a measurement port for fluidic coupling to a process tool and the second port is a reference port for coupling to a vacuum or other pressure source.

6. The manometer of claim 5, wherein the vacuum source includes a getter pump connected to the sensor capsule.

7. The manometer of claim 1, wherein the first port is connected to a semiconductor process tool.

8. The manometer of claim 5, wherein the electrode structure comprises an outer ring electrode and an inner electrode disposed within the ring electrode, wherein a first electrical connection is coupled to the ring electrode and a second electrical connection is coupled to the inner electrode.

9. The manometer of claim 8, wherein the electronic circuit is connected to the first and second electrical connections.

10. The manometer of claim 9, wherein the electronic circuit includes an electrical bridge circuit connected to the first and second electrical connections and an oscillator connected to the bridge and configured and arranged to drive the bridge circuit.

11. The manometer of claim 9, wherein the electronics block further includes a stored reference value for a desired zero-reading value and a buffer configured and arranged to receive the difference signal from the bridge circuit, wherein the buffer is configured and arranged to scale and amplify the difference output signal produced by the bridge circuit.

12. The manometer of claim 9, further comprising a digital control unit configured and arranged to produce an output signal indicating that the manometer requires zeroing or replacing at a predicted time.

13. The manometer of claim 9, further comprising a digital control unit configured and arranged to correct the pressure output signal for predicted zero drifts based on two or more zero-offset values.

14. The manometer of claim 12, further comprising a computer-readable medium including computer-executable instructions for (i) recording two or more time stamps corresponding to a zero-output-reading adjustment of the manometer, and (ii) predicting a drift value of the manometer zero-output reading based on the two or more zero-offset values.

15. The manometer of claim 12, wherein the digital control unit is configured and arranged to receive computer-readable instructions from a communication link to a control system outside the manometer.

16. The manometer of claim 15, wherein the control system is a graphical user interface.

17. The manometer of claim 11, wherein the electronics block includes a span potentiometer configured and arranged to adjust a calibration curve span of the manometer.

18. The manometer of claim 9, wherein the electronics block includes a linearity potentiometer configured and arranged to adjust the linearity of a calibration curve of the manometer.

19. The manometer of claim 9, wherein the electronic blocks includes one or more zero potentiometers configured and arranged to adjust a zero-reading output value of the manometer to a desired value.

20. The manometer of claim 5, wherein the sensor capsule comprises an austenitic nickel-based super alloy.

21. The manometer of claim 9, further comprising a power supply configured and arranged to supply power to the electronics block.

22. The manometer of claim 1, further comprising a display configured and arranged to display information associated with the operation of the manometer.

23. The manometer of claim 1, further comprising a temperature-regulated heat source within the vicinity of the sensor capsule for maintaining temperature within the sensor capsule at a desired temperature.

24. The manometer of claim 5, wherein in the diaphragm includes a metal.

25. The manometer of claim 21, wherein the metal comprises an austenitic nickel-based super alloy.

26. A method of predicting a future drift value of a zero-output reading of a capacitance manometer, the method comprising:

zeroing a capacitance manometer two or more times;

recording a time-stamped zero-offset value for each time the manometer is zeroed, wherein two or more zero-offset values are recorded; and

predicting a future drift value of the manometer zero-output reading based on the two or more zero-offset values and the intervening time between the two or more zero-offset values.

27. The method of claim 26, wherein predicting a drift value includes determining a requirement for zeroing the manometer based on the two or more zero-offset values.

28. The method of claim 26, wherein predicting a drift value includes determining that the zero-output reading will exceed a specified threshold.

29. The method of claim 28, further comprising determining a requirement for replacing the manometer.

30. The method of claim 26 wherein predicting a requirement for a zeroing includes fitting a mathematical function to the two or more offset values.

31. The method of claim 30, wherein fitting a mathematical function includes fitting a straight line function.

32. The method of claim 31, wherein fitting a mathematical function includes fitting a polynomial function.

33. The method of claim 30, wherein fitting a mathematical function includes fitting an exponential function.

34. The method of claim 28, wherein the specified threshold is a predetermined value.

35. The method of claim 28, wherein the specified threshold is a user programmed value.

36. The method of claim 26, wherein predicting a requirement for zeroing includes determining a time to next zeroing event according to

$T=\frac{(R\times }{}$

A ×

F ) ( 100 ×

D ) ;

wherein A is an accuracy specification (% of reading);

F is a full scale pressure reading;

D is a recorded drift (pressure unit/time);

R is the ratio of the operating pressure to the manometer full scale pressure; and

T is time to next zeroing event.

37. The method of claim 26, further comprising adjusting a zero-reading output value of the manometer to a desired value in response to predicting a drift value of the manometer zero-output reading.

38. The method of claim 26, further comprising replacing the manometer to a desired value in response to in response to predicting a drift value of the manometer zero-output reading.

39. The method of claim 26, further comprising sending a drift value of the manometer zero-output reading to a control system by a communications link, wherein the control system is configured and arranged to control operation of the manometer.

40. The method of claim 26, wherein predicting a drift value of the manometer zero-output reading includes a manometer electronic controller executing computer-readable instructions.

41. The method of claim 39, further comprising using a graphical user interface to control operation of the manometer.

42. A method of predicting a future drift value of a zero-output reading of a capacitance manometer, the method comprising:

measuring a plurality of process pressures with a capacitance manometer, each process pressure being associated with one of a plurality of processes of a semiconductor device fabrication process;

determining an elapsed time for each of the plurality of processes;

calculating a plurality of drift rates for a zero-output reading of the manometer, each corresponding to one of the plurality of processes; and

predicting a future drift value of a manometer zero-output reading based on the plurality of drift rates.

43. The method of claim 42, wherein determining an elapsed time for each of the plurality of processes comprises recording a plurality of time stamps.

44. The method of claim 43, wherein recording a plurality of time stamps includes recording a pair of time stamps for each process.

45. The method of claim 44, wherein each pair of time stamps includes a process-start time stamp and a process-end time stamp.

46. The method of claim 42, wherein predicting a drift value of a manometer zero-output reading includes fitting a mathematical function to the plurality of drift rates.

47. The method of claim 42, wherein predicting a drift value of the manometer zero-output reading includes calculating a time integral of one or more of the plurality drift rates to produce one or more drift values.

48. The method of claim 42, further comprising determining a requirement for zeroing the manometer based on the plurality of drift rates.

49. The method of claim 42, wherein predicting a drift value includes determining that the zero-output reading will exceed a specified threshold at a predicted time.

50. The method of claim 42, further comprising determining a requirement for replacing the manometer.

51. The method of claim 42, wherein predicting a requirement for a zeroing includes fitting a mathematical function to the one or more drift values.

52. The method of claim 51, wherein fitting a mathematical function includes fitting a straight line function.

53. The method of claim 51, wherein fitting a mathematical function includes fitting a polynomial function.

54. The method of claim 51, wherein fitting a mathematical function includes fitting an exponential function.

55. The method of claim 49, wherein the specified threshold is a predetermined value.

56. The method of claim 49, wherein the specified threshold is a user programmed value.

57. The method of claim 42, further comprising adjusting a zero-reading output value of the manometer to a desired value in response to predicting a drift value of the manometer zero-output reading.

58. The method of claim 42, further comprising replacing the manometer to a desired value in response to predicting a drift value of the manometer zero-output reading.

59. The method of claim 42, further comprising sending a drift value of the manometer zero-output reading to a control system by a communications link, wherein the control system is configured and arranged to control operation of the manometer.

60. The method of claim 42, wherein predicting a drift value of the manometer zero-output reading includes a manometer electronic controller executing computer-readable instructions.

61. The method of claim 59, further comprising using a graphical user interface to control operation of the manometer.