Method and system for identifying etch end points in semiconductor circuit fabrication

• US 6,381,008 B1
• Filed: 05/25/1999
• Issued: 04/30/2002
• Est. Priority Date: 06/20/1998
• Status: Expired due to Fees

• Current Assignee: SD Acquisition Incorporated (Teledyne Technologies Incorporated)
• Original Assignee: SD Acquisition Incorporated (Teledyne Technologies Incorporated)
• Inventors: Ivaldi, Juan C., Dyas, Michael R., Rivers, Jason A., Brown, Robert M. Jr., Branagh, Wayne A., Fry, Robert C.
• Primary Examiner(s): EVANS, FANNIE L
• Application Number:
  US09/318,402
• Time in Patent Office: 1,071 Days
• Field of Search: 356/326, 356/328, 356/334, 356/72, 700/121
• US Class Current: 356/72
• CPC Class Codes: G01J 3/0229 using masks, aperture plates, spatial light modulators or spatial filters, e.g. reflective filters
• CPC Class Codes: G01J 3/18 using diffraction elements, e.g. grating gratings per se G02B
• CPC Class Codes: G01J 3/443 Emission spectrometry

Abstract

Disclosed is a spectrometer system with unique wavelength resolution improving relative positioning of diffraction grating and detector. Also disclosed is a modified evolving windowed factor analysis based method of detecting semiconductor etch end points which is particularly well suited for use in real time monitoring and process control. Use of wavelength group selecting mask filters is also disclosed.

Claims

1. A spectrometer system comprising sequentially, as encountered by entered electromagnetic radiation:

a) at least one means for receiving electromagnetic radiation;

b) a first reflecting means with a focal length less than two-hundred-fifty (250) millimeters;

c) at least one diffracting means;

d) a second reflecting means with a focal length less than two-hundred-fifty (250) millimeters; and

e) at least one detector means consisting of centrally located active detectors and laterally disposed packaging,

said diffracting means being mounted on a stage which is positioned physically between said detector means on one side thereof, and said first and second reflecting means on a second side thereof;

such that, in use, electromagnetic radiation is caused to enter said means for receiving electromagnetic radiation and reflect from said first reflecting means, then interact with said diffracting means such that a diffracted spectrum of electromagnetic radiation is caused to reflect from said second reflecting means and enter said detector means, in which spectrometer system the first reflecting means has a focal length which is less than that of said second reflecting means and in which spectrometer system at least part of the detector means laterally disposed packaging is positioned behind said diffracting means in the sense that electromagnetic radiation reflecting from said second reflecting means is blocked direct access thereto by said diffracting means.

2. A spectrometer system as in claim 1, wherein said means for receiving electromagnetic radiation comprises a slit with dimensions of between five (5) to thirty (30) microns by one-hundred (100) to two-thousand (2000) microns, and in which further, one selection is made from the group consisting of:

the focal length of said first reflecting means is in the range of fifty (50) to seventy (70) millimeters, and the focal length of said second reflecting means is in the range of sixty (60) to ninty (90) millimeters; and

the focal length of said first reflecting means is on the order of eighty (80) millimeters to one-hundred-twenty (120) millimeters, and the focal length of said second reflecting means is on the order of one-hundred-twenty (120) to one-hundred-sixty (160) milimeters.

3. A spectrometer system as in claim 1, in which said stage is rotatable.

4. A spectrometer system as in claim 1, in which said means for receiving electromagnetic radiation is located on the same side of the diffracting means as is the detector means.

5. A spectrometer system as in claim 1, in which said means for receiving electromagnetic radiation comprises a means for accepting a fiber optic.

6. A spectrometer system as in claim 1, which further comprises a printed circuit board with plug means for effecting electrical contact to an expansion slot in a computer system, said spectrometer system being mounted to said printed circuit board via vibration absorbing and stress relieving means.

7. A spectrometer system as in claim 1, in which said detector means comprises electrical contact pins suitable for mounting to integrated circuit sockets and to printed circuit boards, wherein said detector means is, however, mounted by other than physical interconnection to said electrical contact pins, and wherein said electrical contact pins are electrically accessed via stress relieving flexible means.

8. A spectrometer system as in claim 1, which further comprises a computing means to which said detector means is electrically interconnected, such that in use signal(s) corresponding to detected electromagnetic radiation is/are input to said computing means by said detector means.

9. A spectrometer system as in claim 1, which further comprises a filter means placed prior to said detector means.

10. A spectrometer system as in claim 9, in which said filter means placed prior to said detector means is comprised of the least one element(s) which provide utility selected from the group consisting of:

serving to separate out the wavelengths of other than a first order produced by interaction of said electromagnetic radiation with said diffraction means, from wavelengths of a first order and allow only wavelengths of said first order to enter said detector means; and

serving to selectively attenuate certain high intensity signals.

11. A spectrometer system as in claim 1, in which said diffraction means is a grating.

12. A spectrometer system as in claim 1, in which said detector means is selected from the group consisting of:

charge coupled device;

charge injection device; and

photo diode array.

13. A spectrometer system as in claim 1 wherein said diffracted spectrum of electromagnetic radiation which is caused to reflect front said second reflecting means and enter said detector means comprises wavelengths in a group selected from;

positive first order; and

negative first order.

14. A spectrometer system as in claim 2 wherein the nominal slit with dimensions are seventeen (17) by one-thousand (1000) microns;

and wherein nominal focal length of said first reflecting means is selected from the group consisting of;

sixty (60) millimeters and

one-hundred (100) milimeters;

and the nominal focal length of said second reflecting means is selected from the group consisting of;

seventy-five (75) milimeters; and

one-hundred forty (140) milimeters.

15. A semiconductor process end-point detecting system comprising a spectrometer system which sequentially comprises, as encountered by entered electromagnetic radiation:

a) at least one means for receiving electromagnetic radiation;

b) a first reflecting means with a focal length less than two-hundred-fifty (250) millimeters;

c) at least one diffracting means;

d) a second reflecting means with a focal length less than two-hundred-fifty (250) millimeters; and

e) at least one detector means consisting of centrally located active detectors and laterally disposed packaging;

said diffracting means being mounted on a stage which is positioned physically between said detector means on one side thereof, and said first and second reflecting means on a second side thereof;

such that, in use, electromagnetic radiation is caused to enter said means for receiving electromagnetic radiation and reflect from said first reflecting means, then interact with said diffracting means such that a diffracted spectrum of electromagnetic radiation is caused to reflect from said second reflecting means and enter said detector means, in which spectrometer system the first reflecting means has a focal length which is less than that of said second reflecting means and in which spectrometer system at least part of the detector means laterally disposed packaging is positioned behind said diffracting means in the sense that electromagnetic radiation reflecting from said second reflecting means is blocked direct access thereto by said diffracting means.

16. A semiconductor process end-point detecting system as in claim 15, wherein said means for receiving electromagnetic radiation comprises a slit with dimensions of between five (5) to thirty (30) microns by one-hundred (100) to two-thousand (2000) microns, and in which further, one selection is made from the group consisting of:

the focal length of said first reflecting means is in the range of fifty (50) to seventy (70) millimeters, and the focal length of said second reflecting means is in the range of sixty (60) to ninty (90) millimeters; and

the focal length of said first reflecting means is on the order of eighty (80) millimeters to one-hundred-twenty (120) millimeters, and the focal length of said second reflecting means is on the order of one-hundred-twenty (120) to one-hundred-sixty (160) milimeters.

17. A semiconductor process end-point detecting system as in claim 15, in which said stage is rotatable.

18. A semiconductor process end-point detecting system as in claim 15, in which said means for receiving electromagnetic radiation is located on the same side of the diffracting means as is the detector means.

19. A semiconductor process end-point detecting system as in claim 15, in which said means for receiving electromagnetic radiation comprises a means for accepting a fiber optic.

20. A semiconductor process end-point detecting system as in claim 15, which further comprises a printed circuit board with plug means for effecting electrical contact to an expansion slot in a computer system, said spectrometer system being mounted to said printed circuit board via vibration absorbing and stress relieving means.

21. A semiconductor process end-point detecting system as in claim 15, in which said detector means comprises electrical contact pins suitable for mounting to integrated circuit sockets and to printed circuit boards, wherein said detector means is, however, mounted by other than physical interconnection to said electrical contact pins, and wherein said electrical contact pins are electrically accessed via stress relieving flexible means.

22. A semiconductor process end-point detecting system as in claim 15, which further comprises a computing means to which said detector means is electrically interconnected, such that in use signal(s) corresponding to detected electromagnetic radiation is/are input to said computing means by said detector means.

23. A semiconductor process end-point detecting system as in claim 15, which further comprises a filter means placed prior to said detector means.

24. A semiconductor process end-point detecting system as in claim 23, in which said filter means placed prior to said detector means serves to separate out the wavelengths of other than a first order produced by interaction of said electromagnetic radiation with said diffraction means, from wavelengths of a first order and allow only wavelengths of said first order to enter said detector means.

25. A semiconductor process end-point detecting system as in claim 15, in which said diffraction means is a grating.

26. A semiconductor process end-point detecting system as in claim 15, in which said detector means is selected from the group consisting of:

Charge Coupled Device;

Charge Injection Device; and

Photo Diode Array.

27. A semiconductor process end-point detecting system as in claim 15, which further comprises a means for effecting plasma etching of semiconductor comprising:

a) at least one vacuum chamber in which a semiconductor system to be etched is present during use;

b) at least one means for entering etching gas to said vacuum chamber;

c) at least one means for applying electrical energy to said etching gas;

d) at least one means for accessing electromagnetic radiation present in said vacuum chamber during a semiconductor etching process; and

e) at least one means for guiding said accessed electromagnetic radiation into said spectrometer system means for receiving a electromagnetic radiation.

28. A spectrometer system as in claim 16 wherein the nominal slit with dimensions are seventeen (17) by one-thousand (1000) microns;

and wherein nominal focal length of said first reflecting means is selected from the group consisting of;

sixty (60) millimeters; and

one-hundred (100) milimeters;

and the nominal focal length of said second reflecting means is selected from the group consisting of;

seventy-five (75) milimeters; and

one-hundred-forty (140) milimeters.

38. A method of identifying semiconductor etch end points in real time as in claim 28 in which step b is selected and in which the critical wavelengths are identified by use of wavelength “

Mask Filter”

which passes a set of relevant wavelengths to a detector, while blocking other wavelengths.

29. A semiconductor etch end-point detecting system comprising a spectrometer system which sequentially comprises, as encountered by entered electromagnetic radiation:

a) at least one means for receiving electromagnetic radiation;

b) at least one first reflecting means with a focal length less than two-hundred-fifty (250) millimeters;

c) at least one diffracting means;

d) a second reflecting means with a focal length less than two-hundred-fifty (250) millimeters; and

e) at least one detector means consisting of centrally located active detectors and laterally disposed packaging;

said diffracting means being mounted on a stage which is positioned physically between said detector means on one side thereof, and said first and second reflecting means on a second side thereof;

such that, in use, electromagnetic radiation is caused to enter said means for receiving electromagnetic radiation and reflect from said first reflecting means, then interact with said diffracting means such that a diffracted spectrum of electromagnetic radiation is caused to reflect from said second reflecting means and enter said detector means, in which spectrometer system the first reflecting means has a focal length which is less than that of said second reflecting means and in which spectrometer system at least part of the detector means laterally disposed packaging is positioned behind said diffracting means in the sense that electromagnetic radiation reflecting from said second reflecting means is blocked direct access thereto by said diffracting means;

said semiconductor etch end-point detecting system further including, in function combination with said spectrometer system, a means for effecting plasma etching of semiconductor comprising;

a) at least one vacuum chamber in which a semiconductor system to be etched is present during use;

b) at least one means for entering etching gas to said vacuum chamber;

c) at least one means for applying electrical energy to said etching gas;

d) at least one means for accessing electromagnetic radiation present in said vacuum chamber during a semiconductor etching process; and

e) at least one means for guiding said accessed electromagnetic radiation into said spectrometer system means for receiving a electromagnetic radiation.

30. A method of identifying semiconductor etch end points comprising:

A) providing a semiconductor etch end-point detecting system comprising a spectrometer system which sequentially comprises, as encountered by entered electromagnetic radiation;

a) at least one means for receiving electromagnetic radiation;

b) a first reflecting means with a focal length less than two-hundred-fifty (250) millimeters;

c) at least one diffracting means;

d) a second reflecting means with a focal length less than two-hundred-fifty (250) millimeters; and

e) at least one detector means consisting of centrally located active detectors and laterally disposed packaging;

said diffracting means being mounted on a stage which is positioned physically between said detector means on one side thereof, and said first and second reflecting means on a second side thereof;

such that, in use, electromagnetic radiation is caused to enter said means for receiving electromagnetic radiation and reflect from said first reflecting means, then interact with said diffracting means such that a diffracted spectrum of electromagnetic radiation is caused to reflect from said second reflecting means and enter said detector means, in which spectrometer system the first reflecting means has a focal length which is less than that of said second reflecting means;

said semiconductor etch endpoint detecting system further including, in function combination with said spectrometer system, a means for effecting plasma etching of semiconductor comprising;

a) at least one vacuum chamber in which a semiconductor system to be etched is present during use;

b) at least one means for entering etching gas to said vacuum chamber;

c) at least one means for applying electrical energy to said etching gas;

d) at least one means for accessing electromagnetic radiation present in said vacuum chamber during a semiconductor etching process; and

e) at least one means for guiding said accessed electromagnetic radiation into said spectrometer system means for receiving a electromagnetic radiation;

said method of identifying semiconductor etch end points further comprising chronologically repeatedly performing steps B through F in an evolving windowed factor analysis sequence until detecting semiconductor etch end point;

said steps B through F being;

B) during a semiconductor etch procedure in said vacuum chamber, obtaining a chronological sequence of electromagnetic radiation intensity vs. wavelength spectra from said spectrometer system detector means, said spectrometer system detector means being caused to access electromagnetic radiation present in said vacuum chamber during a semiconductor etching process;

C) selecting some number of electromagnetic radiation intensity vs. wavelength spectra from said chronological sequence of electromagnetic radiation intensity vs. wavelength spectra and forming them into a data matrix;

D) optionally selecting and deleting some set-off number of rows and/or columns in said data matrix;

E) by applying mathematical matrix decomposition techniques to said data matrix determining value(s) of at least one representative parameter(s), each said representative parameter(s) being selected from the group consisting of;

members of a diagonal matrix; and

eigenvalues;

F) detecting semiconductor etch end point based upon change in said repeatedly calculated at least one representative parameter value(s) resulting from said chronologically repeated performance of steps B through F.

31. A method of identifying semiconductor etch end points as in claim 30, which further comprises at least one step selected from the group consisting of:

a) in conjunction with said step B obtaining of a chronological sequence of electromagnetic radiation intensity vs. wavelength spectra from said detector means, the performing of signal to noise ratio enhancing techniques such that said each of said electromagnetic radiation intensity vs. wavelength spectra in said chronological sequence thereof utilized to form said data matrix in step C are composite electromagnetic radiation intensity vs. wavelength spectra with improved signal to noise ratios; and

b) in conjunction with said step C the step of identifying critical wavelengths and deleting intensity values at other wavelengths in said spectra.

32. A method of identifying semiconductor etch end points in real time comprising chronologically repeatedly performing steps a through f in an evolving windowed factor analysis sequence until detecting semiconductor etch end point, said steps a through f being;

a) while performing a semiconductor etch procedure in a vacuum chamber, obtaining a chronological sequence of electromagnetic radiation intensity vs. wavelength spectra from a detector means, said detector means being positioned so as to receive electromagnetic radiation eminating from said vacuum chamber during said semiconductor etch procedure;

b) selecting a period of time and for each of a sequence of said selected time periods performing signal to noise ratio enhancing technique(s) to two or more electromagnetic radiation intensity vs. wavelength spectra obtained thereduring, with the result being a chronological sequence of composite spectra with improved signal to noise ratios;

c) selecting some number of composite spectra in said chronological sequence of composite spectra, and forming them into a data matrix consisting of a definite number of rows and columns;

d) optionally selecting and deleting some set-off number of rows and/or columns in said data matrix;

e) by mathematical matrix decomposition techniques determining values for at least one representative parameter(s) selected from the group consisting of;

members of a diagonal matrix; and

eigenvalues;

which representative parameter(s) monitor changes in said chronological sequence of composite spectra;

f) detecting semiconductor etch end point based upon change in said repeatedly calculated at least one representative parameter value(s) resulting from said chronologically repeated performance of steps a through f.

33. A method of identifying semiconductor etch end points in real time as in claim 32 which further comprises the step of identifying critical wavelengths and deleting intensity values at other wavelengths in said composite spectra.

34. A method of identifying semiconductor etch end points in real time comprising chronologically repeatedly performing steps a through e in an evolving windowed factor analysis sequence until detecting semiconductor etch end point, said steps a through e being:

a) while performing a semiconductor etch procedure in a vacuum chamber, obtaining a chronological sequence of electromagnetic radiation intensity vs. wavelength spectra from a detector means, said detector means being positioned so as to receive electromagnetic radiation emanating from said vacuum chamber during said semiconductor etch procedure;

b) selecting some number of electromagnetic radiation intensity vs. wavelengths spectra in said chronological sequence of electromagnetic radiation intensity vs. wavelengths spectra, and forming them into a data matrix consisting of a definite number of rows and columns;

c) selecting and deleting some set-off number of rows and/or columns in said data matrix;

d) by mathematical matrix decomposition techniques determining values for at least one representative parameter(s) selected from the group consisting of;

members of a diagonal matrix; and

eigenvalues;

which representative parameter(s) monitor changes in said chronological sequence of electromagnetic radiation intensity vs. wavelength spectra;

e) detecting semiconductor etch end point based upon change in said repeatedly calculated at least one representative parameter value(s) resulting from said chronologically repeated performance of steps a through e.

35. A method of identifying semiconductor etch end points in real time as in claim 34 which further comprises at least one step selected from the group consisting of:

a) in conjunction with said step b obtaining of a chronological sequence of electromagnetic radiation intensity vs. wavelength spectra from said detector means, the performing signal to noise ratio enhancing technique(s), such that said each of said electromagnetic radiation intensity vs. wavelength spectra in said chronological sequence thereof utilized to form said data matrix are composite electromagnetic radiation intensity vs. wavelength spectra with improved signal to noise ratios; and

b) identifying critical wavelengths and deleting intensity values at other wavelengths in said obtained electromagnetic radiation intensity vs. wavelength spectra.

39. A method of identifying semiconductor etch end points in real time as in claim 35 in which step b is selected and in which the critical wavelengths are identified by use of wavelength “

Mask Filter”

which passes a set of relevant wavelengths to a detector, while blocking other wavelengths.

36. A method of identifying semiconductor etch end points in real time comprising chronologically repeatedly performing steps a through g in an evolving windowed factor analysis sequence until detecting semiconductor etch end point, said steps a through g being:

a) by performing test semiconductor etch procedures in a vacuum chamber, determining, on a pixel by pixel basis, mean and standard deviations for a normal chronological sequence of electromagnetic radiation intensity vs. wavelength spectra from data obtained from a detector means, said detector means being positioned so as to receive electromagnetic radiation eminating from said vacuum chamber during said semiconductor etch procedure;

b) while performing an actual real time semiconductor etch procedure in a vacuum chamber, obtaining, on a pixel by pixel basis, a chronological sequence of electromagnetic radiation intensity vs. wavelength spectra from a detector means, said detector means being positioned so as to receive electromagnetic radiation eminating from said vacuum chamber during said semiconductor etch procedure;

c) on a pixel by pixel basis, for a normal chronological sequence of electromagnetic radiation intensity vs. wavelength spectra from data obtained from a detector means, subtracting said normal mean from corresponding obtained real time semiconductor etch procedure values, and dividing the result by the corresponding normal data standard deviation, and forming a reduced electromagnetic radiation intensity vs. wavelengths spectra;

d) selecting some number of reduced electromagnetic radiation intensity vs. wavelengths spectra in said chronological sequence of electromagnetic radiation intensity vs. wavelengths spectra, and forming them into a data matrix consisting of a definite number of rows and columns;

e) optionally selecting and deleting some set-off number of rows and/or columns in said data matrix;

f) by mathematical matrix decomposition techniques determining values for at least one representative parameter(s) selected from the group consisting of;

members of a diagonal matrix and

eigenvalues;

which representative parameter(s) monitor changes in said chronological sequence of new electromagnetic radiation intensity vs. wavelength spectra;

g) detecting semiconductor etch end point based upon change in said repeatedly calculated at least one representative parameter value(s) resulting from said chronologically repeated performance of steps a through g.

37. A method of identifying semiconductor etch end points in real time as in claim 36 which further comprises at least one step selected from the group consisting of:

a) in conjunction with said step b obtaining of a chronological sequence of electromagnetic radiation intensity vs. wavelength spectra from said detector means, the performing signal to noise ratio enhancing technique(s), such that said each of said electromagnetic radiation intensity vs. wavelength spectra in said chronological sequence thereof utilized to form said data matrix are composite electromagnetic radiation intensity vs. wavelength spectra with improved signal to noise ratios; and

b) identifying critical wavelengths and deleting intensity values at other wavelengths in said obtained electromagnetic radiation intensity vs. wavelength spectra.

40. A method of identifying semiconductor etch end points in real time as in claim 37 in which step b is selected and in which the critical wavelengths are identified by use of wavelength “

Mask Filter”

which passes a set of relevant wavelengths to a detector, while blocking other wavelengths.