OFF-AXIS ILLUMINATION OVERLAY MEASUREMENT USING TWO-DIFFRACTED ORDERS IMAGING

• US 20200132446A1
• Filed: 12/14/2018
• Published: 04/30/2020
• Est. Priority Date: 08/28/2018
• Status: Active Grant

• Current Assignee: KLA-Tencor Corporation
• Original Assignee: KLA-Tencor Corporation
• Inventors: Shalibo, Yoni, Paskover, Yuri, Levinski, Vladimir, Manassen, Amnon, Eisenbach, Shlomo, Laredo, Gilad, Hildesheim, Ariel
• Granted Patent: US 11,281,111 B2
• Time in Patent Office: Days
• CPC Class Codes: G01B 11/14 for measuring distance or clearance between spaced objects or spaced apertures G01B11/26 takes precedence; rangefinders G01C3/00
• CPC Class Codes: G01B 11/272 using photoelectric detection means
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• 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: G02B 27/4233 having a diffractive element [DOE] contributing to a non-imaging application diffusers having a diffractive element G02B5/0252; filters having a diffractive element G02B5/203; systems for controlling the direction of light having diffractive elements G02B26/0808; scanning systems having diffractive elements G02B26/106; beam shaping systems using diffractive optical elements G02B27/0944; beam splitting or combining systems operating by diffraction G02B27/1086
• CPC Class Codes: G03F 7/70616 Monitoring the printed patterns
• 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

Abstract

Metrology methods and tools are provided, which enhance the accuracy of the measurements and enable simplification of the measurement process as well as improving the correspondence between the metrology targets and the semiconductor devices. Methods comprise illuminating the target in a Littrow configuration to yield a first measurement signal comprising a −1^st diffraction order and a 0^th diffraction order and a second measurement signal comprising a +1^st distraction order and a 0^th diffraction order, wherein the −1^st diffraction order of the first measurement signal and the +1^st diffraction order of the second measurement signal are diffracted at 180° to a direction of the illumination, performing a first measurement of the first measurement signal and a second measurement of the second measurement signal, and deriving metrology metric(s) therefrom. Optionally, a reflected 0^th diffraction order may be split to yield components which interact with the −1^st and +1^st diffraction orders.

Claims

1. A method of measuring a metrology target by a metrology tool having an illumination arm and a collection arm, the method comprising:

illuminating the metrology target, by the illumination arm, in a Littrow configuration to yield a first measurement signal comprising a −

1^st diffraction order and a first component of a 0^th diffraction order and a second measurement signal comprising a +1^st diffraction order and second component of the 0^th diffraction order, wherein the −

1^st diffraction order of the first measurement signal and the +1^st diffraction order of the second measurement signal are diffracted at 180°

to a direction of the illumination,

performing, by the collection arm, a first measurement of the first measurement signal and a second measurement of the second measurement signal, and

deriving at least one metrology metric from the first and second measurements.

2. The method of claim 1, wherein illuminating the metrology target is carried out by spatial light modulation and/or by digital light processing.

3. The method of claim 1, wherein illuminating the metrology target is carried out at multiple wavelengths, implementing a flexible Littrow configuration.

4. The method of claim 1, wherein performing the first measurement and the second measurement is carried out by spatial light modulation and/or by digital light processing.

5. The method of claim 1, wherein illuminating the metrology target and performing the first measurement and the second measurement are carried out simultaneously in two measurement directions.

6. The method of claim 1, wherein illuminating the metrology target is carried out using a pair of shutters applied alternately to an illumination source having four poles, corresponding to simultaneously illuminating in two measurement directions.

7. The method of claim 1, further comprising attenuating at least one of the first and second components of the 0^th diffraction orders.

8. The method of claim 1, wherein the at least one metrology metric comprises an overlay of the metrology target, calculated from an equation:

9. The method of claim 1, further comprising reducing a size of the metrology target by half, by reducing a periodic structure pitch of the metrology target by a factor of two with respect to a given metrology target design.

10. The method of claim 1, wherein the first and second measurements are carried out at 0°

and 180°

degrees of wafer orientation.

11. The method of claim 1, carried out at least partially by at least one computer processor.

12. A computer program product comprising a computer readable storage medium having a computer readable program embodied therewith and configured to carry out at least partially the method of claim 1.

13. A metrology module comprising the computer program product of claim 12.

14. (canceled)

15. A metrology tool comprising:

an illumination arm configured to illuminate a metrology target in a Littrow configuration to yield a first measurement signal comprising a −

1^st diffraction order and a first component of a 0^th diffraction order and a second measurement signal comprising a +1^st diffraction order and a second component of the 0^th diffraction order, wherein the −

1^st diffraction order of the first measurement signal and the +1^st diffraction order of the second measurement signal are diffracted at 180°

to a direction of the illumination,

a collection arm configured to perform a first measurement of the first measurement signal and a second measurement of the second measurement signal, and

a processing unit configured to derive at least one metrology metric from the first and second measurements.

16. The metrology tool of claim 15, wherein at least one of the illumination arms and the collection arm comprises a spatial light modulator and/or a digital light processor configured to implement a flexible Littrow configuration corresponding to illumination by multiple wavelengths.

17. The metrology tool of claim 15, wherein the illumination arm and the collection arm are configured to illuminate the metrology target and perform the first and second measurements simultaneously in two measurement directions.

18. The metrology tool of claim 15, wherein the illumination arm comprises a pair of shutters applied alternately to an illumination source having four poles, corresponding to simultaneous illumination in two measurement directions.

19. The metrology tool of claim 15, wherein the collection arm comprises at least one 0^th diffraction order attenuator.

20. The metrology tool of claim 15, wherein a size of the metrology target is reduced by half and has a periodic structure pitch of the metrology target reduced by a factor of two with respect to a given metrology target design.

21. The metrology tool of claim 15, wherein the first and second measurements are carried out at 0°

and 180°

degrees of wafer orientation.

22. A method of measuring a metrology target by a metrology tool having an illumination arm and a collection arm, the method comprising:

illuminating the metrology target, by the illumination arm, to yield a reflected 0^th diffraction order and −

1^st and +1^st diffraction orders,

splitting, in the collection arm, the reflected 0^th diffraction order into a first component which is captured with the −

1^st diffraction order to yield a first measurement and a second component which is captured with the +1^st diffraction order to yield a second measurement, and

deriving at least one metrology metric from the first and second measurements.

23. The method of claim 22, wherein illuminating the metrology target and the splitting the reflected 0^th diffraction order are carried out simultaneously in two measurement directions for each of the first and second measurements.

24. The method of claim 22, further comprising attenuating at least one of first and second components of the 0^th diffraction order.

25. The method of claim 22, wherein the at least one metrology metric comprises an overlay of the metrology target, calculated from an equation:

26. The method of claim 22, further comprising calibrating the first and second measurements for layer-dependent telecentricity.

27. The method of claim 22, further comprising deriving focus information from telecentricity parameters of the first and second measurements.

28. The method of claim 22, further comprising obtaining focus sensitivity data using a non-Littrow, off-axis illumination and measuring the focus from a position shift in the metrology target.

29. The method of claim 22, carried out at least partially by at least one computer processor.

30. A computer program product comprising a computer readable storage medium having a computer readable program embodied therewith and configured to carry out at least partially the method of claim 22.

31. A metrology module comprising the computer program product of claim 30.

32. (canceled)

33. A metrology tool comprising:

an illumination arm configured to illuminating a metrology target to yield a reflected 0^th diffraction order and −

1^st and +1^st diffraction orders,

a collection arm comprising an image splitter configured to split the reflected 0^th diffraction order into a first component which is captured with the −

1^st diffraction order to yield a first measurement and a second component which is captured with the +1^st diffraction order to yield a second measurement, and

a processing unit configured to derive at least one metrology metric from the first and second measurements.

34. The metrology tool of claim 33, wherein the illumination arm and the collection arm are configured to illuminate the metrology target and perform the first and second measurements simultaneously in two measurement directions.

35. The metrology tool of claim 33, wherein the collection arm comprises at least one 0^th diffraction order attenuator configured to attenuate at least one of first and second components of the 0^th diffraction order.

36. The metrology tool of claim 33, wherein the processing unit is further configured to carry out at least one of:

calibrating the first and second measurements for layer-dependent telecentricity, deriving focus information from telecentricity parameters of the first and second measurements and/or obtaining focus sensitivity data using a non-Littrow, off-axis illumination and measuring the focus from a position shift in the metrology target.