Device and method for detecting and preventing arcing in RF plasma systems

• US 6,332,961 B1
• Filed: 06/02/2000
• Issued: 12/25/2001
• Est. Priority Date: 09/17/1997
• Status: Expired due to Term

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Parsons, Richard, Johnson, Wayne L.
• Primary Examiner(s): MCDONALD, RODNEY GLENN
• Application Number:
  US09/508,102
• Time in Patent Office: 571 Days
• Field of Search: 204/192.12, 204/192.13, 204/298.03, 204/298.08, 156/345, 216/59, 216/61, 118/663, 427/8, 427/10
• US Class Current: 204/192.13
• CPC Class Codes: H01J 2237/0206 Extinguishing, preventing or controlling unwanted discharges
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32174 Circuits specially adapted for controlling the RF discharge

Abstract

A system and method for detecting and preventing arcing in plasma processing systems. Arcing is detected and characterized by measuring and analyzing electrical signals from a circuit coupled to the plasma. After characterization, the electrical signals can then be correlated with arcing events occurring during a processing run. Information can be obtained regarding location, severity, and frequency of arcing events. The system and method better diagnose the causes of arcing and provide improved protection against undesirable arcing, which can cause damage to the system and the workpiece.

Claims

1. A plasma system comprising:

(a) a chamber;

(b) a plasma generation circuit having;

(i) a power source; and

(ii) a plasma coupling element receiving power from said power source and supplying said power to a plasma region within said chamber;

(c) a convertor for obtaining a received signal from a circuit coupled to said plasma region; and

(d) a processing unit for determining whether said received signal includes a component in a predetermined frequency band, in order to detect arcing.

2. The plasma system as claimed in claim 1, wherein said processing unit comprises a neural network for detecting arcing.

3. The plasma system as claimed in claim 1, wherein said convertor includes means for determining a location of an arcing event.

4. The plasma system as claimed in claim 1, wherein said convertor includes means for determining a severity of arcing.

5. The plasma system as claimed in claim 1, wherein said convertor includes monitoring means for monitoring an amplitude of a frequency component of said received signal, and detecting arcing when the monitored amplitude exceeds a predetermined value.

6. The plasma system as claimed in claim 5, wherein said convertor includes monitoring means for monitoring an amplitude of a frequency component of said received signal at a frequency other than a fundamental frequency of said power source and other than a harmonic frequency of said fundamental frequency and detecting arcing when the monitored amplitude exceeds a predetermined value.

7. The plasma system as claimed in claim 6, wherein said convertor includes means for obtaining said received signal including means for admitting a component of said received signal in order to provide a selected sub-band signal, wherein said component is within said predetermined frequency band.

8. The plasma system as claimed in claim 7, wherein said convertor further includes means for determining that said received signal includes a component in said predetermined frequency band when an amplitude of said selected sub-band signal exceeds a predetermined value.

9. The plasma system as claimed in claim 7, wherein said means for admitting a component includes a downconverter circuit to downconvert said component to provide one of a lower frequency signal and a DC signal, thereby providing said selected sub-band signal.

10. The plasma system as claimed in claim 1, wherein said plasma system is a semiconductor processing system.

11. The plasma system as claimed in claim 1, wherein said system further comprises a signal sensing element for obtaining said received signal from said plasma region, wherein said convertor obtains said received signal from said signal sensing element.

12. The plasma system as claimed in claim 1, wherein said convertor measures a first detected amplitude of a first detected component of said received signal and a second detected amplitude of a second detected component of said received signal, and wherein said first detected component is within a first predetermined frequency sub-band and said second detected component is within a second predetermined frequency sub-band:

the system further comprising;

a memory for storing amplitude data, said amplitude data including a first stored amplitude and a second stored amplitude, wherein said first stored amplitude corresponds to said first predetermined frequency sub-band and said second stored amplitude corresponds to said second predetermined frequency sub-band; and

a central processing unit for performing a first comparison of said first detected amplitude to said first stored amplitude, and for further performing a second comparison of said second detected amplitude to said second stored amplitude.

13. The plasma system as claimed in claim 12, wherein said amplitude data further includes a third stored amplitude and a fourth stored amplitude, wherein said third stored amplitude corresponds to said first predetermined frequency sub-band and said fourth stored amplitude corresponds to said second predetermined frequency sub-bald, wherein said central processing unit performs a third comparison of said first detected amplitude to said third stored amplitude, and performs a fourth comparison of said second detected amplitude to said fourth stored amplitude.

14. The plasma system as claimed in claim 13, wherein said first and second stored amplitudes correspond to a plasma system undergoing a first stored severity of arcing and said third and fourth stored amplitudes correspond to a plasma system undergoing a second stored severity of arcing and wherein said central processing unit determines a detected severity of arcing in response to said first, second, third, and fourth comparisons.

15. The plasma system as claimed in claim 13 further comprising a second plasma coupling element receiving power from said at least one power source and, wherein said first and second stored amplitudes correspond to a plasma system undergoing arcing caused by said first plasma coupling element and said third and fourth stored amplitudes correspond to a plasma system undergoing arcing caused by said second plasma coupling element.

16. The plasma system as claimed in claim 13, wherein said first and second stored amplitudes correspond to a plasma system undergoing arcing in a first arcing region and said third and fourth stored amplitudes correspond to a plasma system undergoing arcing in a second arcing region.

17. The plasma system as claimed in claim 16, further comprising a second plasma coupling element receiving power from said at least one power source.

18. The plasma system as claimed in claim 12, wherein said central processing unit comprises one of a neural network and a profiler for utilizing said first and second comparisons for determining one of:

a detected severity of arcing;

a detected cause of arcing, said detected cause of arcing being one of said first plasma coupling element and a second plasma coupling element; and

a detected arcing region.

19. The plasma system as claimed in claim 18, further comprising a power controller for controlling said at least one power source, wherein said power controller reduces an amount of power provided by said at least one power source when said central processing unit determines whether said one of a detected severity of arcing, a detected cause of arcing, and a detected arcing region is potentially damaging.

20. The plasma system as claimed in claim 12, further comprising a power controller for controlling said at least one power source, wherein said amplitude data further includes a third stored amplitude and a fourth stored amplitude, wherein said third and fourth stored amplitudes correspond to said first and second predetermined frequency sub-bands, respectively, wherein said determining means measures said first and second stored amplitudes while said power controller controls said at least one power source to provide a first level of power, wherein said determining means measures said third and fourth stored amplitudes while said power controller controls said at least one power source to provide a second level of power during said second operation, and wherein said plasma system applies said first and second levels of power according to a predetermined sequence.

21. The plasma system as claimed in claim 12, wherein said central processing unit comprises a comparator for utilizing said first and second comparisons for determining one of a severity of arcing, a location of arcing and a frequency of arcing events.

22. The plasma system as claimed in claim 12, wherein said central processing unit comprises a detector for detecting a plurality of arcing events within a period of time, measuring a duration of said period of time and determining a number of said plurality of arcing events to thereby determine a detected frequency of arcing events.

23. The plasma system as claimed in claim 12, further comprising a power controller for controlling said power source to provide a first level of power to said first plasma coupling element and for controlling said power source to provide a dithered level of power to said first plasma coupling element, said dithered level of power being different from said first level of power, wherein said convertor means measures a dithered amplitude of a dithered component of a dithered response signal due to said dithered level of power, said dithered component being within said first predetermined frequency sub-band, and wherein said convertor comprises a comparator for comparing said first detected amplitude to said dithered amplitude in order to determine one of:

a detected severity of arcing;

a detected cause of arcing said detected cause of arcing being one of said first plasma coupling element and a second plasma coupling element; and

a detected arcing region.

24. A method for detecting arcing in a plasma system, the method comprising the steps of:

producing a plasma region by applying power from a first power source to a plasma generation circuit including a first plasma coupling element;

obtaining a received signal based on said power applied from said first power source;

detecting arcing by determining whether said received signal includes components in a predetermined frequency band; and

providing an indication when arcing is detected.

25. The method as claimed in claim 24, wherein said step of detecting further comprises the sub-step of detecting arcing when an amplitude of a frequency component of said received signal exceeds a predetermined value.

26. The method as claimed in claim 25, wherein said sub-step of detecting detects said frequency component at a frequency other than a fundamental frequency of said power source and other than a harmonic frequency of said fundamental frequency.

27. The method as claimed in claim 26, wherein said step of obtaining comprises the steps of:

sampling said received signal to produce a received analog signal;

converting said received analog signal into a digital received signal; and

converting said digital received signal into frequency bands using a Fast Fourier Transform.

28. The method as claimed in claim 27, wherein said step of converting comprises the sub-step of determining when an amplitude of a frequency band signal exceeds a predetermined value.

29. The method as claimed in claim 24, wherein said step of obtaining comprises the step of downconverting said received signal to provide one of a lower frequency signal and a DC signal.

30. The method as recited in claim 24, wherein said step of obtaining comprises the sub-step of obtaining said received signal from a signal sensing element coupled to said plasma region.

31. The method according to claim 24, wherein the step of detecting comprises the steps of:

(a) measuring a first detected amplitude of a first detected component of said received signal within a first predetermined frequency sub-band;

(b) measuring a second detected amplitude of a second detected component of said received signal Within a second predetermined frequency sub-band;

(c) storing amplitude data in a memory, said amplitude data including a first stored amplitude corresponding to said first predetermined frequency sub-band and a second stored amplitude corresponding to said second predetermined frequency sub-band;

(d) comparing said first detected amplitude to said first stored amplitude; and

(e) comparing said second detected amplitude to said second stored amplitude.

32. The method as claimed in claim 31, further comprising the steps of:

(f) storing a third stored amplitude corresponding to said first predetermined frequency sub-band and a fourth stored amplitude corresponding to said second predetermined frequency sub-band,

(g) storing that said first and second stored amplitudes correspond to a plasma system undergoing a first stored severity of arcing,

(h) storing that said third and fourth stored amplitudes correspond to a plasma system undergoing, a second stored severity of arcing,

(i) comparing said first detected amplitude to said third stored amplitude;

(j) comparing said second detected amplitude to said fourth stored amplitude; and

(k) determining a detected severity of arcing in response to said steps (d), (c), (i) and (j).

33. The method as recited in claim 31, further comprising the steps of:

(f) producing said plasma region by applying power from said first power source to said plasma generation circuit including a second plasma coupling element;

(g) storing a third stored amplitude corresponding to said first predetermined frequency sub-band and a fourth stored amplitude corresponding to said second predetermined frequency sub-band,

(h) storing that said first and second stored amplitudes further correspond to a plasma system undergoing arcing caused try said first plasma coupling element,

(i) storing that said third and fourth stored amplitudes correspond to a plasma system undergoing arcing caused by said second plasma coupling element;

(j) comparing said first detected amplitude to said third stored amplitude; and

(k) comparing said second detected amplitude to said fourth stored amplitude; and

(l) determining in response to said steps (d), (e), (j) and (k) which of said first and second plasma coupling elements caused arcing.

34. The method as recited in claim 31, further comprising the steps of:

(f) storing a third stored amplitude corresponding, to said first predetermined frequency sub-band and a fourth stored amplitude corresponding to said second predetermined frequency sub-band.

(g) storing that said first and second stored amplitudes further correspond to a plasma system undergoing arcing in a first arcing region,

(h) storing that said third and fourth stored amplitudes correspond to a plasma system undergoing arcing in a second arcing region;

(i) comparing said first detected amplitude to said third stored amplitude; and

(j) comparing said second detected amplitude to said fourth stored amplitude; and

(k) determining in response to said steps (d), (e), (i) and (j) in which of said first and second arcing regions arcing occurs.

35. The method as recited in claim 31, further comprising the steps of:

(f) producing said plasma region by applying power from a second power source to a second plasma coupling element of said plasma generation circuit; and

(g) storing a third stored amplitude corresponding to said first predetermined frequency sub-band and a fourth stored amplitude corresponding to said second predetermined frequency sub-band,

(h) storing that said first and second stored amplitudes further correspond to a plasma system undergoing arcing caused by said first plasma coupling element,

(i) storing that said third and fourth stored amplitudes correspond to a plasma system undergoing arcing caused by said second plasma coupling element;

(j) comparing said first detected amplitude to said third stored amplitude; and

(k) comparing said second detected amplitude to said fourth stored amplitude; and

(l) determining in response to said steps (d), (e), (j) and (k) which of said first and second plasma coupling elements caused arcing.

36. A method as claimed in claim 31, wherein said steps (d) and (e) comprise determining one of:

a detected severity of arcing;

a detected cause of arcing, said detected cause of arcing being one of said first plasma coupling element and a second plasma coupling element; and

a detected arcing region.

37. The method as claimed in claim 36, further comprising the step of:

reducing an amount of power provided by said first power source when said one of said detected severity of arcing, said detected cause of arcing, and said detected arcing region is potentially damaging.

38. A method as claimed in claim 31, further comprising the step of applying power from a second power source to a second plasma coupling element,

wherein said steps (d) and (e) comprise determining one of:

a detected severity of arcing;

a detected cause of arcing, said detected cause of arcing being one of said first plasma coupling element and a second plasma coupling element; and

a detected arcing region.

39. The method as claimed in claim 31, further comprising the steps of:

detecting a plurality of arcing events within a period of time;

measuring a duration of said period of time;

determining a number of said plurality of arcing events;

using said duration and said number to determine a detected frequency of arcing events; and

using said detected frequency of arcing events to predict one of a future severity of arcing and a future frequency of arcing events.

40. The method as claimed in claim 31, further comprising the steps of:

(f) controlling said first power source to provide a first level of power to said first plasma coupling element;

(g) obtaining said received signal concurrently with said step (f);

(h) controlling said first power source to provide a dithered level of power to said first plasma coupling element, said dithered level of power being different from said first level of power;

(i) obtaining a dithered response signal from said plasma generation circuit concurrently with said step (h);

(j) measuring a dithered amplitude of a dithered component of said dithered response signal, within said first predetermined frequency sub-band; and

(k) comparing said first detected amplitude to said dithered amplitude in order to determine one of;

a detected severity of arcing;

a detected cause of arcing said detected cause of arcing being one of said first plasma coupling element and a second plasma coupling element; and

a detected arcing region.