Detection and suppression of electrical arcing

• US 20060049831A1
• Filed: 06/10/2005
• Published: 03/09/2006
• Est. Priority Date: 09/04/2004
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Anwar, Suhail, Choi, Soo Young, Yim, Dong-Kil, Park, Chung-Hee, Manacio, Remegio
• Granted Patent: US 7,292,045 B2
• Time in Patent Office: Days
• US Class Current: 324/536
• CPC Class Codes: G01R 31/1254 of gas-insulated power appliances or vacuum gaps testing switches G01R31/327; detecting electrical or mechanical defects in encased switchgear H02B13/065

Abstract

Method and apparatus for detecting or suppressing electrical arcing or other abnormal change in the electrical impedance of a load connected to a power source. Preferably the load is a plasma chamber used for manufacturing electronic components such as semiconductors and flat panel displays. Arcing is detected by monitoring one or more sensors. Each sensor either responds to a characteristic of the electrical power being supplied by an electrical power source to the plasma or is coupled to the plasma chamber so as to respond to an electromagnetic condition within the chamber. Arcing is suppressed by reducing the power output for a brief period. Then the power source increases its power output, preferably to its original value. If the arcing resumes, the power source repeats the steps of reducing and then restoring the power output.

Claims

1. A method of detecting an abnormal change in an electrical load to which a power source supplies electrical power, comprising the steps of:

supplying electrical power from a power source;

coupling said electrical power to an electrical load;

producing one or more sensor signals, wherein each sensor signal is responsive to said electrical power or to an electromagnetic condition of the load;

establishing one or more sensor-derived values, wherein each sensor-derived value is a function of one or more of the sensor signals;

establishing one or more thresholds so that each threshold is associated with one of said sensor-derived values;

comparing each sensor-derived value to its associated threshold; and

signaling an alert if at least one of the sensor-derived values crosses its associated threshold.

2. The method of claim 1, wherein:

the step of establishing one or more thresholds further comprises establishing the thresholds so that each sensor-derived value normally does not cross its associated threshold in the absence of electrical arcing in the load.

3. The method of claim 2, wherein:

the step of establishing one or more thresholds further comprises establishing the thresholds so that each sensor-derived value is likely to cross its associated threshold if electrical arcing occurs in the load.

4. The method of claim 1, wherein one of the sensor-derived values is one of the sensor signals.

5. The method of claim 1, wherein one of the sensor-derived values is the rate of change of one of the sensor signals.

6. The method of claim 1, wherein:

the electrical load is a plasma chamber; and

one of the sensor signals is responsive to radiation from the plasma chamber.

7. The method of claim 1, wherein:

the electrical load is a plasma chamber; and

one of the sensor signals is responsive to an electromagnetic field within the plasma chamber.

8. The method of claim 1, wherein:

the power source supplies RF power to the load;

one of the sensor signals is responsive to reflected RF power between the power source and the load; and

the signaling step comprises signaling an alert if said reflected RF power exceeds its associated threshold.

9. The method of claim 1, wherein:

the power source supplies RF power to the load;

one of the sensor signals is responsive to reflected RF power between the power source and the load; and

the signaling step comprises signaling an alert if the rate of change of said reflected RF power exceeds its associated threshold.

10. The method of claim 1, further comprising the steps of:

producing a power set point signal; and

controlling the power source so that the electrical power supplied by the power source has a level responsive to the power set point signal;

wherein, concurrently with the step of supplying electrical power, the step of establishing one or more thresholds comprises the steps of;

monitoring the power set point signal; and

adjusting at least one of the thresholds in response to the power set point signal.

11. The method of claim 10, wherein the step of establishing one or more thresholds comprises adjusting at least one of the thresholds to be proportional to the power set point signal.

12. The method of claim 10, further comprising the step of:

storing in a memory a table that defines a plurality of ranges of power set point values, and that associates with each range respective values for one or more of said thresholds;

wherein the step of establishing one or more thresholds further comprises the steps of;

determining the current value of the power set point signal; and

setting the respective values of one or more of the thresholds to the values stored in the table that are associated with a range of power set point values that includes the current value of the power set point signal.

13. The method of claim 1, wherein:

each of said sensor-derived values is characterized by a normal range of values in the absence of an abnormal change in the load; and

the step of signaling an alert further comprises the step of changing at least one of the thresholds to a value closer to the normal range of values of the sensor-derived value associated with that threshold.

14. The method of claim 13, further comprising the steps of, subsequent to the step of changing at least one of the thresholds to a value closer to said normal range:

performing the comparing step until every sensor that previously crossed its associated threshold crosses back to the original side of its associated threshold; and

then

restoring to their original values every threshold that was changed in the step of changing at least one of the thresholds to a value closer to said normal range.

15. A method of suppressing electrical arcing in an electrical load to which a power source supplies power, comprising the sequential steps of:

reducing the power supplied by the power source to the load for a predetermined period of time;

restoring said power to its value prior to the reducing step;

detecting whether electrical arcing is occurring in the electrical load; and

if the detecting step detects that said arcing is occurring, repeating the reducing and restoring steps.

16. The method of claim 15, further comprising repeating the reducing, restoring and detecting steps until the detecting step does not detect that said arcing is occurring.

17. The method of claim 15, further comprising the steps of:

before the step of reducing the power, resetting to zero a count stored in a memory;

between the detecting step and the repeating step, performing the steps of;

incrementing the count;

comparing the count to a predetermined maximum value; and

if the count is greater than or equal to the maximum value, halting the performing of the method before performing the repeating step.

18. The method of claim 17, wherein the comparing step is performed before the incrementing step.

19. The method of claim 15, wherein the electrical load is a plasma chamber.

20. An electrical circuit for detecting an abnormal change in an electrical load to which a power source supplies power, comprising:

one or more sensors, wherein each sensor produces a sensor signal responsive to said electrical power or to an electromagnetic condition of the load;

a sensor signal receiving circuit for receiving each sensor signal and for producing one or more sensor-derived signals so that the value of each sensor-derived signals is a function of one or more of the sensor signals; and

a comparator circuit for receiving the sensor-derived signals and producing for each sensor-derived signal a corresponding comparison result, wherein each comparison result has a value that can be either true or false, and wherein the comparator determines the value of each comparison result according to whether the corresponding sensor-derived signal is greater than or less than a threshold value associated with that sensor-derived signal; and

an alert circuit for signaling an alert signifying an abnormal change in the electrical load if any of the comparison results is positive.

21. The electrical circuit of claim 20, wherein:

the comparator circuit and the alert circuit are a programmable computer; and

the sensor-derived signals are values stored in a memory of the computer.

22. An electrical circuit for suppressing electrical arcing in an electrical load to which a power source supplies power, comprising:

a power source adapted to supply electrical power to an electrical load, wherein the power source has a control input for controlling the power supplied by the power source;

an arc detection circuit having an output responsive to whether electrical arcing is occurring in the electrical load; and

a control circuit connected to receive the output of the arc detection circuit and to send a control signal to the control input of the power source;

wherein, after the arc detection circuit detects that electrical arcing is occurring in the electrical load, the control circuit sets the control signal to a value that commands the power source to reduce the level of said power for a period of time, and then after said period of time sets the control signal to a value that commands the power source to return said power to its level prior to said period of time.

23. The electrical circuit of claim 22, wherein:

at least one of the arc detection circuit and the control circuit are a programmable computer.