Process and apparatus for detecting aberrations in production process operations

• US 4,846,928 A
• Filed: 07/22/1988
• Issued: 07/11/1989
• Est. Priority Date: 08/04/1987
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Love, Robert L., Lassiter, Thomas W., Dolins, Steven B., Gunturi, Sarma S., Flinchbaugh, Bruce E., Srivastava, Aditya
• Primary Examiner(s): Powell, William A.
• Application Number:
  US07/224,205
• Time in Patent Office: 354 Days
• Field of Search: 156/626, 156/627, 156/643, 156/646, 156/653, 156/657, 156/662, 156/345, 356/316, 356/326, 356/381, 356/437, 204/192.33, 204/192.37, 204/298
• US Class Current: 438/16
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge

Abstract

An improved apparatus and process for detecting aberrations in production process operations is provided. In one embodiment, operations of a plasma etch reactor (10) are monitored to detect aberrations in etching operations. A reference end-point trace (EPT) is defined (62) for the etch process. Regions are defined in the reference end-point trace (70) and characteristics and tolerances for each region are defined (72-80). The etcher is run and an actual EPT is obtained (82) from the running of the etcher. The actual EPT is analyzed to identify proposed regions of the actual EPT (86), and then the proposed regions of the actual EPT are matched with regions of the reference EPT (96). The system employs a series of heuristic functions in matching proposed regions of the actual EPT with regions of the reference EPT. Characteristics of the matched regions of the actual end-point trace are compared (66) with characteristics of the corresponding regions of the reference end-point trace to determine whether aberrations have occurred during the etch process. The invention provides for an improved matching and improved comparison of actual end-point traces with reference end-point traces.

Claims

1. A method of monitoring end-point traces of a plasma etch reactor comprising:

establishing a reference end-point trace for a predetermined etch process;

dividing the reference end-point trace into predefined regions;

conducting the predetermined etch process on a semiconductor device;

obtaining an actual end-point trace for the etch of the semiconductor device;

dividing the actual end-point trace into candidate regions in accordance with predefined criteria based on changes in said actual trace;

matching candidate regions of the actual end-point trace with corresponding regions of the reference end-point trace by analyzing characteristics of a candidate region of the actual end-point trace over characteristics of a region of the reference end-point trace to be matched; and

comparing characteristics of regions of the actual end-point trace with corresponding characteristics of matched regions of the reference end-point trace.

2. The method of claim 1, further comprising:

generating a signal indicative of the variance of characteristics of the regions of the actual end-point trace beyond predefined limits from corresponding characteristics of matched regions of the reference end-point trace.

3. The method of claim 2, wherein said predefined criteria for dividing the actual end-point trace into candidate regions, comprise the change in slope of points along the actual end-point trace.

4. The method of claim 3, wherein said step of comparing characteristics of regions of the actual end-point trace with corresponding characteristics of matched regions of the reference end-point trace comprises:

applying a set of rules to at least one of the regions of the actual end-point trace.

5. The method of claim 4, wherein said set of rules comprises a set of process independent rules and a set of process specific rules.

6. The method of claim 5, wherein the application of the set of process independent rules comprises comparing, between a region of the actual end-point trace and a matched region of the reference end-point trace, at least one of:

the value;

the slope; and

the time

of at least one predefined point in the respective regions.

7. The method of claim 3, further comprising:

determining whether a deviation between a characteristic of the actual end-point trace and a corresponding characteristic of the reference end-point trace exceeds a predefined value;

attributing such deviation to at least one predefined cause;

generating a signal identifying said at least one predefined cause to which the deviation has een attributed.

8. The method of claim 2, wherein said step of dividing the actual end-point trace into candidate regions in accordance with predefined criteria comprises:

determining the slope of the actual end-point trace at points along the actual end-point trace;

determining critical points on the actual endpoint trace at which the slope changes beyond a first predefined value;

dividing the actual end-point trace into candidate regions between the critical points determined.

9. The method of claim 2, wherein said step of matching candidate regions of the actual end-point trace with corresponding regions of the reference end-point trace by analyzing characteristics of a candidate region of the actual end-point trace in light of characteristics of a region of the reference end-point trace to be matched comprises:

the steps of applying a set of heuristic functions to the regions of the actual end-point trace to be matched.

10. The method of claim 9, wherein said heuristic functions comprise at least one of:

identifying regions of the actual end-point trace having an average slope which varies from the average slope of the region of the reference end-point trace to be matched by less than a predefined value;

identifying regions of the actual end-point trace for which the intensity value of the last point of the region varies from the intensity value of the last point of the region of the reference end-point trace to be matched by less than a predefined intensity variation value;

identifying regions of the actual end-point trace which have a duration which varies from the duration of a region of the reference end-point trace by less than a predefined duration variation value; and

identifying regions of the actual end-point trace occurring within a predetermined time range.

27. The method of claim 8, wherein the duration of said candidate regions is modified to improve the match of candidate regions of the actual end-point trace to regions of the reference end-point trace.

11. A method of monitoring operations in process equipment which carries out a predetermined process, which process is first monitored by a detector which provides a continuously variable signal curve corresponding to the progress of the process, and wherein a reference continuously variable signal curve can be defined which corresponds to a predefined acceptable operation of the predetermined process, the method comprising:

defining a reference continuously variable signal curve for the predetermined process;

defining characteristics for at least one region of said reference continuously variable signal curve;

conducting said predetermined process;

acquiring from the detector an actual continuously variable signal curve corresponding to the progress of the process conducted;

dividing the actual continuously variable signal curve acquired into candidate regions on the basis of changes in characteristics of the actual continuously variable signal curve;

matching candidate regions of the actual continuously variable signal curve with regions of reference continuously variable signal curve by analyzing characteristics of the candidate region of the actual continuously variable signal curve over characteristics of a region of the reference continuously variable signal curve to be matched;

comparing characteristics of at least one of the regions of the actual continuously variable signal curve with the characteristics of a matched region in the reference continuously variable signal curve; and

generating a signal indicative of the variance of a characteristic of one of the regions of the actual continuously variable signal curve beyond predefined limits from a corresponding characteristic of a matched region of the reference continuously variable signal curve.

13. The method of claim 11, wherein said actual continuously variable signal curve is divided into candidate reagions by identifying critical points in the actual continuously variable signal curve, said candidate regions lying between said critical points.

14. The method of claim 13, wherein said critical points are identified on the basis of changes in slope of the actual coninuously variable signal curve.

15. The method of claim 11, wherein said step of matching candidate regions of the actual continuously variable signal with regions of the reference continuously variable signal curve comprises applying a heuristic set of functions to the candidate regions.

16. The method of claim 15, wherein said heuristic functions comprise at least one of:

identifying regions of the actual continuously variable signal curve having an average slope which varies from the average slope of the region of the reference continuously variable signal curve to be matched by less than a predefined average slope value;

identifying regions of the actual continuously variable signal curve for which the intensity value of the last point of the region varies from the intensity value of the last point of the region of the reference continuously variable signal curve to be matched by less than a predefined intensity variation value;

identifying regions of the actual continuously variable signal curve which have a duration which varies from the duration of a region of the reference continuously variable signal curve by less than a predefined duration variation value; and

identifying regions of the actual continuously variable signal curve occurring within a predetermined time range.

17. The method of claim 13, wherein said step of matching candidate regions of the actual continuously variable signal with regions of the reference continuously variable signal curve comprises applying a heuristic set of functions to the candidate regions.

18. The method of claim 17, wherein said heuristic functions comprise at least one of:

identifying regions of the actual continuously variable signal curve having an average slope which varies from the average slope of the region of the reference continuously variable signal curve to be matched by less than a predefined average slope value;

identifying regions of the actual continuously variable signal curve for which the intensity value of the last point of the region varies from the intensity value of the last point of the region of the reference continuously variable signal curve to be matched by less than a predefined intensity variation value;

identifying regions of the actual continuously variable signal curve which have a duration which varies from the duration of a region of the reference continuously variable signal curve by less than a predefined duration variation value; and

identifying regions of the actual continuously variable signal curve occurring within a predetermined time range.

19. The method of claim 11, wherein said steps of comparing characteristic regions of the actual continuously variable signal curve with corresponding characteristics of matched regions of the reference continuously variable signal curve comprises:

applying a set of rules to at least one of the regions of the actual continuously variable signal curve.

20. The method of claim 19, wherein said set of rules comprises a set of process independent rules and a set of process specific rules

21. The method of claim 20, wherein the application of set of process independent rules comprises comparing, between a region of the actual continuously variable signal curve and a matched region of the reference continuously variable signal curve, at least one of:

the value;

the slope; and

the time

of at least one predefined point in the respective regions.

22. The method of claim 11, further comprising:

determining whether a deviation between a characteristic of the actual continuously variable signal curve and a corresponding characteristic of the reference continuously variable signal curve exceeds a predefined value;

attributing such deviation to at least one predefined cause; and

generating a signal identifying said at least one predefined cause to which the deviation has been attributed.

23. The method of claim 11, wherein said step of dividing the actual continuously variable signal curve into candidate regions comprises:

determining the slope of the actual continuously valuable signal curve at points along the actual continuously variable signal curve;

determining critical points on the actual continuously variable signal curve at which the slope changes beyond a first predefined value; and

dividing the actual continuously variable signal curve into candidate regions between the critical points determined.

24. The method of claim 11, wherein said predetermined process comprises a plasma etch.

26. The method of claim 21, wherein said predetermined process comprises a plasma etch.

12. A method of monitoring end-point traces of a plasma etch reactor comprising:

establishing a reference end-point trace for a predetermined etch process;

dividing the reference end-point trace into predefined regions;

conducting the predetermined etch process on a semiconductor device;

obtaining an actual end-point trace for the etch of the semiconductor device;

dividing the actual end-point trace into candidate regions in accordance with predefined criteria based on changes in said actual trace; and

matching candidate regions of the actual end-point trace with corresponding regions of the reference end-point trace by analyzing characteristics of a candidate region of the actual end-point trace over characteristics of a region of the reference end-point trace to be matched.

25. The method of cliam 18, wherein said predetermined process comprises a plasma etch.

28. A method of monitoring end-point traces of a plasma etch reactor comprising:

establishing a reference end-point trace for predetermined etch process;

identifying critical points in the reference end-point trace;

identifying regions of said reference end-point trace between said critical points;

conducting the predetermined etch process on a semiconductor device;

obtaining an actual end-point trace for the etch of the semiconductor device;

identifying candidate critical points in the actual end-point trace on the basis of changes in slope of the actual end-point trace;

dividing the actual end-point trace into candidate regions between said candidate critical points;

matching candidate regions of the actual end-point trace with regions of the reference end-point trace;

comparing at least one characteristic of at least one region of the actual end-point trace with a corresponding characteristic of a corresponding region of the reference end-point trace; and

generating an indication if said at least one characteristic of the said at least one region of the actual end-point trace varies beyond a predefined limit from the corresponding characteristic of the corresponding region of the reference end-point trace.

29. The method of claim 28 wherein said step of matching candidate regions of the actual end-point trace with regions of the reference end-point trace comprises comparing characteristics of a candidate region of the actual end-point trace with characteristics of a region of the reference end-point trace.

30. The method of claim 29 wherein said step of matching candidate regions of the actual end-point trace with corresponding regions of the reference end-point trace further comprises:

applying a heuristic set of functions which compare characteristics of a candidate regions with characteristics of a region of the reference end-point trace.

31. The method of claim 30 wherein said set of heuristic functions compares at least one of the following characteristics:

the slope at the end of the candidate region;

the average slope of the region;

the intensity of the final point of the region;

the average intensity of the region;

the duration of the region; and

the time of the region from the beginning of the end-point trace.

32. The method of claim 31 wherein said step of matching a candidate region of the actual end-point trace with a region of the reference end-point trace further comprises:

comparing the characteristics of at least one region neighboring the candidate region of the actual end-point trace with characteristics of a corresponding region neighboring the region of the reference end-point trace to be matched.

33. The method of claim 32, wherein the limits of said candidate region being matched are adjusted beyond the candidate critical points identified on the basis of changes in slope, said adjustment being made to more accurately match candidate regions of the actual end-point trace with regions of the reference end-point trace.

34. A process monitoring apparatus comprising:

a data storer for receiving reference data representing a reference continuously variable signal curve corresponding to a predefined process;

an acquirer for acquiring actual data representing an actual continuously variable signal curve corresponding to an actual operation of said predefined process;

a processor which divides the actual data into candidate regions based on changes in characteristics of the actual data;

a matcher which matches at least one candidate region of the actual data with a region of the reference data by analyzing characteristics of the candidate region over characteristics of at least one region of the reference data;

a comparer for comparing characteristics of at least one region of the actual data with characteristics of a region of the reference data with which the region of the actual data has been matched; and

a generator which generates a signal indicative of the variance of a characteristic of a region of the actual data beyond a predefined limit from a corresponding characteristic of a region of the reference data which has been matched with the region of the actual data.

35. The apparatus of claim 34, wherein said processor serves to divide the actual data into candidate regions on the basis of changes in slope of the actual data.

36. The apparatus of claim 35, wherein said matcher applies a heuristic set of functions to the candidate region to match it with a region of the reference data.

37. The apparatus of claim 36 wherein said predefined process comprises a plasma etch operation.

38. The apparatus of claim 37, wherein said actual continuously variable signal curve comprises an end-point trace signal from a plasma etcher.

39. A process monitoring apparatus comprising:

a data storer for receiving reference data representing a reference continuously variable signal curve corresponding to a plasma etch process;

an acquirer for acquiring actual data representing an actual continuously variable signal curve corresponding to an actual operation of said plasma etch process;

a processor which divides the actual data into candidate regions based on changes in characteristics of the actual data; and

a matcher which matches at least one candidate region of the actual data with a region of the reference data by analyzing characteristics of the candidate region over characteristics of at least one region of the reference data.