APPARATUS AND METHODS FOR DETECTING OVERLAY ERRORS USING SCATTEROMETRY

• US 20080094630A1
• Filed: 12/21/2007
• Published: 04/24/2008
• Est. Priority Date: 12/05/2002
• Status: Active Grant

• Current Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Original Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Inventors: Gross, Kenneth, Dziura, Thaddeus, Fabrikant, Anatoly, Levy, Ady, Adel, Michael, Wack, Dan, Friedmann, Michael, Smith, Ian, Fielden, John, Golovanesky, Boris, Ghinovker, Mark, Bareket, Noah, Zalicki, Piotr, Dececco, Paola, Mieher, Walter, Bevis, Christopher
• Granted Patent: US 7,663,753 B2
• Time in Patent Office: Days
• US Class Current: 356/401
• CPC Class Codes: G01N 2021/213 Spectrometric ellipsometry
• CPC Class Codes: G01N 21/956 Inspecting patterns on the surface of objects contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G03F 7/70625 Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness
• CPC Class Codes: G03F 7/70633 Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching
• CPC Class Codes: G03F 7/70683 Mark designs
• CPC Class Codes: G03F 9/7049 Technique, e.g. interferometric
• CPC Class Codes: G03F 9/7084 Position of mark on substrate, i.e. position in (x, y, z) of mark, e.g. buried or resist covered mark, mark on rearside, at the substrate edge, in the circuit area, latent image mark, marks in plural levels
• CPC Class Codes: G03F 9/7088 Alignment mark detection, e.g. TTR, TTL, off-axis detection, array detector, video detection

Abstract

Disclosed are techniques, apparatus, and targets for determining overlay error between two layers of a sample. In one embodiment, a method for determining overlay between a plurality of first structures in a first layer of a sample and a plurality of second structures in a second layer of the sample is disclosed. Targets A, B, C and D that each include a portion of the first and second structures are provided. Target A is designed to have an offset Xa between its first and second structures portions; target B is designed to have an offset Xb between its first and second structures portions; target C is designed to have an offset Xc between its first and second structures portions; and target D is designed to have an offset Xd between its first and second structures portions. Each of the offsets Xa, Xb, Xc and Xd is preferably different from zero; Xa is an opposite sign and differ from Xb; and Xc is an opposite sign and differs from Xd. The targets A, B, C and D are illuminated with electromagnetic radiation to obtain spectra S_A, S_B, S_C, and S_D from targets A, B, C, and D, respectively. Any overlay error between the first structures and the second structures is then determined using a linear approximation based on the obtained spectra S_A, S_B, S_C, and S_D.

Claims

1. A method for determining overlay between a plurality of first structures in a first layer of a sample and a plurality of second structures in a second layer of the sample, the method comprising:

providing targets A, B, C and D that each include a portion of the first and second structures,

wherein the target A is designed to have an offset Xa between its first and second structures portions,

wherein the target B is designed to have an offset Xb between its first and second structures portions,

wherein the target C is designed to have an offset Xc between its first and second structures portions,

wherein the target D is designed to have an offset Xd between its first and second structures portions,

wherein each of the offsets Xa, Xb, Xc and Xd is different from zero, Xa is an opposite sign and differ from Xb, and Xc is an opposite sign and differs from Xd;

illuminating the targets A, B, C and D with electromagnetic radiation to obtain spectra S_A, S_B, S_C, and S_D from targets A, B, C, and D, respectively; and

determining any overlay error between the first structures and the second structures using a linear approximation based on the obtained spectra S_A, S_B, S_C, and S_D.

2. The method of claim 1, wherein obtaining the spectra S_A, S_B, S_C, and S_D comprises acquiring radiation from the targets A, B, C, and D using an optical apparatus.

3. The method of claim 2, wherein the optical apparatus is a system with two or more reflectometers capable of parallel data acquisition.

4. The method of claim 2, wherein the optical apparatus is a system with two or more spectroscopic reflectometers capable of parallel data acquisition.

5. The method of claim 2, wherein the optical apparatus is a system with two or more polarized spectroscopic reflectometers capable of parallel data acquisition.

6. The method of claim 2, wherein the optical apparatus is a system with two or more polarized spectroscopic reflectometers capable of serial data acquisition without moving the wafer stage or moving any optical elements or the reflectometer stage.

7. The method of claim 2, wherein the optical apparatus is an imaging spectrometer.

8. The method of claim 2, wherein the optical apparatus is an imaging system with a wavelength filter.

9. The method of claim 8, wherein the optical apparatus is an imaging system with a long-pass wavelength filter.

10. The method of claim 8, wherein the optical apparatus is an imaging system with a short-pass wavelength filter.

11. The method of claim 2, wherein the optical apparatus is an interferometric imaging system.

12. The method of claim 2, wherein the optical apparatus is a system with a plurality of ellipsometers capable of parallel data acquisition.

13. The method of claim 2, wherein the optical apparatus is a system with a plurality of ellipsometers capable of serial data acquisition without moving the wafer stage or moving any optical elements or the ellipsometer stage.

14. The method of claim 2, wherein the optical apparatus is a Michelson interferometer.

15. The method of claim 2, wherein the optical apparatus is a Mach-Zehnder interferometer.

16. The method of claim 2, wherein the optical apparatus is or a Sagnac interferometer.

17. The method of claim 2, wherein the optical apparatus is a system comprising a spectroscopic normal incidence reflectometer and a spectroscopic oblique incidence polarized differential reflectometer.

18. The method of claim 2, wherein the optical apparatus is a system comprising a spectroscopic normal incidence polarized reflectometer and a spectroscopic oblique incidence polarized differential reflectometer.

19. The method of claim 2, wherein the optical apparatus is a system comprising a spectroscopic normal incidence polarized differential reflectometer and a spectroscopic oblique incidence polarized differential reflectometer.

20. The method of claim 2, wherein the optical apparatus is a system comprising a spectroscopic near-normal incidence polarized differential reflectometer and a spectroscopic oblique incidence polarized differential reflectometer.

21. The method of claim 1, wherein the illuminating the targets A, B, C and D with electromagnetic radiation takes place substantially at different times such that the corresponding spectra S_A, S_B, S_C, and S_D are obtained at substantially different times.

22. The method of claim 1, wherein the illuminating the targets A, B, C and D with electromagnetic radiation takes place substantially simultaneously such that the corresponding spectra S_A, S_B, S_C, and S_D are produced substantially simultaneously.

23. The method of claim 1, wherein the illuminating the targets A, B, C and D with electromagnetic radiation takes place substantially simultaneously for at least two of the targets A, B, C and D.

24. The method of claim 1, wherein obtaining the spectra S_A, S_B, S_C, and S_D comprises acquiring an image from the targets A, B, C, and D using an imaging apparatus having a wavelength filter, and wherein the spectra S_A, S_B, S_C, and S_D are an averaged or summed one or more intensity value(s) of one or more pixels of the corresponding target image, the method further comprising selecting a wavelength using the wavelength filter such that contrast between the S_A, S_B, S_C, and S_D is maximized.

25. The method of claim 24, further comprising analyzing the images of the targets to detect defects in the sample.

26. The method of claim 1, wherein obtaining the spectra S_A, S_B, S_C, and S_D comprises acquiring radiation from the targets A, B, C, and D using an optical apparatus, wherein the radiation is acquired at simultaneous, multiple angles of illumination.

27. The method of claim 7, further comprising focusing the optical tool only for illuminating a one of the targets A, B, C, and D and not refocusing the optical tool for illuminating the other three of the targets A, B, C, and D.

28. The method of claim 1, wherein at least one of the targets A, B, C, and D includes an imaging overlay metrology type target, and the method further comprises measuring a second overlay error on the imaging overlay metrology type target.

29. The method of claim 28, wherein the first overlay is determined simultaneously with measurement of the second overlay error.

30. A system for determining overlay between a plurality of first structures in a first layer of a sample and a plurality of second structures in a second layer of the sample, comprising:

a scatterometry module for illuminating the targets A, B, C and D with electromagnetic radiation to obtain spectra S_A, S_B, S_C, and S_D from targets A, B, C, and D, respectively; and

a processor operable for determining any overlay error between the first structures and the second structures using a linear approximation based on the obtained spectra S_A, S_B, S_C, and S_D,

wherein targets A, B, C and D each include a portion of the first and second structures,

wherein the target A is designed to have an offset Xa between its first and second structures portions,

wherein the target B is designed to have an offset Xb between its first and second structures portions,

wherein the target C is designed to have an offset Xc between its first and second structures portions,

wherein the target D is designed to have an offset Xd between its first and second structures portions, and

wherein each of the offsets Xa, Xb, Xc and Xd is different from zero, Xa is an opposite sign and differ from Xb, and Xc is an opposite sign and differs from Xd.

31. The system of claim 30, wherein the scatterometry module is an optical apparatus.

32. The method of claim 31, wherein the optical apparatus is a system with two or more reflectometers capable of parallel data acquisition.

33. The system of claim 31, wherein the optical apparatus is a system with two or more spectroscopic reflectometers capable of parallel data acquisition.

34. The system of claim 31, wherein the optical apparatus is a system with two or more polarized spectroscopic reflectometers capable of parallel data acquisition.

35. The system of claim 31, wherein the optical apparatus is a system with two or more polarized spectroscopic reflectometers capable of serial data acquisition without moving the wafer stage or moving any optical elements or the reflectometer stage.

36. The system of claim 31, wherein the optical apparatus is an imaging spectrometer.

37. The system of claim 31, wherein the optical apparatus is an imaging system with a wavelength filter.

38. The system of claim 31, wherein the optical apparatus is an imaging system with a long-pass wavelength filter.

39. The system of claim 31, wherein the optical apparatus is an imaging system with a short-pass wavelength filter.

40. The system of claim 31, wherein the optical apparatus is an interferometric imaging system.

41. The system of claim 31, wherein the optical apparatus is a system with a plurality of ellipsometers capable of parallel data acquisition.

42. The system of claim 31, wherein the optical apparatus is a system with a plurality of ellipsometers capable of serial data acquisition without moving the wafer stage or moving any optical elements or the ellipsometer stage.

43. The system of claim 31, wherein the optical apparatus is a Michelson interferometer.

44. The system of claim 31, wherein the optical apparatus is a Mach-Zehnder interferometer.

45. The system of claim 31, wherein the optical apparatus is or a Sagnac interferometer.

46. The system of claim 31, wherein the optical apparatus is a system comprising a spectroscopic normal incidence reflectometer and a spectroscopic oblique incidence polarized differential reflectometer.

47. The system of claim 31, wherein the optical apparatus is a system comprising a spectroscopic normal incidence polarized reflectometer and a spectroscopic oblique incidence polarized differential reflectometer.

48. The system of claim 31, wherein the optical apparatus is a system comprising a spectroscopic normal incidence polarized differential reflectometer and a spectroscopic oblique incidence polarized differential reflectometer.

49. The system of claim 31, wherein the optical apparatus is a system comprising a spectroscopic near-normal incidence polarized differential reflectometer and a spectroscopic oblique incidence polarized differential reflectometer.

50. The system of claim 30, wherein the illuminating the targets A, B, C and D with electromagnetic radiation takes place substantially at different times such that the corresponding spectra S_A, S_B, S_C, and S_D are obtained at substantially different times.

51. The system of claim 30, wherein the illuminating the targets A, B, C and D with electromagnetic radiation takes place substantially simultaneously such that the corresponding spectra S_A, S_B, S_C, and S_D are produced substantially simultaneously.

52. The system of claim 30, wherein the illuminating the targets A, B, C and D with electromagnetic radiation takes place substantially simultaneously for at least two of the targets A, B, C and D.

53. The system of claim 36, wherein an illumination and imaging NA'"'"'s of the spectroscopic imaging system are chosen to optimize the performance of the instrument on scattering structures by ensuring that only the zero'"'"'th diffraction order is collected.

54. The system of claim 53, wherein the spectroscopic imaging system is an imaging spectroscopic ellipsometer.

55. The system of claim 30, wherein obtaining the spectra S_A, S_B, S_C, and S_D comprises acquiring an image from the targets A, B, C, and D using an imaging apparatus having a wavelength filter, and wherein the spectra S_A, S_B, S_C, and S_D are an averaged or summed one or more intensity value(s) of one or more pixels of the corresponding target image, the method further comprising selecting a wavelength using the wavelength filter such that contrast between the S_A, S_B, S_C, and S_D is maximized.

56. The system of claim 55, wherein the processor is further operable for analyzing the images of the targets to detect defects in the sample.

57. The system of claim 30, wherein the scatterometry module is an optical apparatus, wherein the radiation is acquired at simultaneous, multiple angles of illumination.

58. The system of claim 36, wherein the processor is further operable for focusing the optical tool only for illuminating a one of the targets A, B, C, and D and not refocusing the optical tool for illuminating the other three of the targets A, B, C, and D.

59. The system of claim 30, wherein at least one of the targets A, B, C, and D includes an imaging overlay metrology type target, and the method further comprises measuring a second overlay error on the imaging overlay metrology type target.

60. The system of claim 59, wherein the obtained spectra S_A, S_B, S_C, and S_D are images and are also used to perform the overlay error measurement of the imaging overlay metrology type target.

61. The system of claim 59, wherein the first overlay is determined simultaneously with measurement of the second overlay error.