Sub-wavelength segmentation in measurement targets on substrates

Patent metadata

Field	Value
Publication number	US-9746785-B2
Application number	US-99552909-A
Country	US
Kind code	B2
Filing date	May 27, 2009
Priority date	Jun 2, 2008
Publication date	Aug 29, 2017
Grant date	Aug 29, 2017

Abstract

Measurement targets for use on substrates, and overlay targets are presented. The targets include an array of first regions alternating with second regions, wherein the first regions include structures oriented in a first direction and the second regions include structures oriented in a direction different from the first direction. The effective refractive index of the two sets of regions are thereby different when experienced by a polarized beam, which will act as a TM-polarized beam when reflected from the first set of regions, but as a TE-polarized beam when reflected from the second set of regions.

First claim

The invention claimed is:

1. An inspection method for inspecting an overlay error of a target on a substrate, comprising:
providing the target comprising a grating formed by an array of first regions alternating with second regions and arranged to repeat with a grating pitch of approximately 400 nm-1000 nm in a grating vector direction, the first regions comprising periodic arrays of structures oriented in a first direction and arranged to repeat with a first pitch smaller than the grating pitch and the second regions comprising periodic arrays of structures oriented in a direction different from the first direction and arranged to repeat with a second pitch smaller than the grating pitch;
illuminating the target with a polarized inspection radiation beam, the first and second pitches being less than a wavelength (λ) of the inspection radiation beam divided by a refractive index (n) of a material in which the periodic arrays are provided;
detecting the polarized inspection radiation beam reflected from the target;
determining a feature in a diffraction spectrum of the reflected polarized inspection radiation beam, wherein the determined feature is based on a misalignment of the target with a second target provided on top of or beneath the target; and
determining the overlay error based on the determined feature.

2. The method according to claim 1 , wherein the direction of the periodic arrays of structures of the second regions is substantially orthogonal to the first direction.

3. The method according to claim 2 , wherein the periodic arrays of structures of the first regions are aligned with the grating vector direction and the periodic arrays of structures of the second regions are substantially perpendicular to the grating vector direction.

4. The method according to claim 1 , wherein the first regions comprise different effective refractive indices from the second regions.

5. The method according to claim 1 , wherein the array of first and second regions is arranged such that a polarized radiation beam reflecting from a surface of the target acts as a TE-polarized beam when reflecting from the first regions and as a TM-polarized beam when reflecting from the second regions.

6. The method according to claim 1 , wherein a pattern and periodicity of the structures in the first and second regions affect real and imaginary parts of a refractive index of a material containing the structures.

7. The method according to claim 1 , wherein the array forms an anisotropic target.

8. The method according to claim 1 , wherein the array comprises a photonic crystal.

9. The method according to claim 1 , wherein the array is 2-dimensional.

10. The method according to claim 1 , wherein the target is applied to one or more resist layers on the substrate.

11. The method according to claim 1 , wherein the target is applied to a deep trench layer.

12. The method according to claim 1 , wherein the target is applied to a process layer in a lithographic apparatus.

13. The method according to claim 1 , wherein the target is used in a stacked configuration.

14. The method according to claim 1 , wherein the first pitch is different than the second pitch.

15. The method according to claim 1 , wherein the second target is on a layer of the substrate underneath the target, wherein the second target comprises a second grating formed by an array of third regions alternating with fourth regions and arranged to repeat with the grating pitch in the grating vector direction.

16. The method according to claim 1 , wherein the detecting the polarized inspection radiation beam comprises:
detecting a TE-polarized beam and a TM-polarized beam reflected from the first and second regions from the polarized inspection radiation beam;
measuring a difference between intensities of the TE-polarized beam and the TM-polarized beam; and
determining a duty cycle for the first regions to maximize the measured difference between the intensities.

17. The method according to claim 1 , wherein the target is provided in-die on the substrate.

18. An inspection method for inspecting an overlay error of a grating on a substrate, comprising:
providing an array of first regions of the grating arranged to repeat with a grating pitch of approximately 400 nm-1000 nm in a grating vector direction, the first regions containing reflective structures superimposed on the pattern on the substrate and arranged to repeat with a first pitch smaller than the grating pitch;
providing an array of second regions of the grating containing reflective structures interleaved with the first regions, the reflective structures of the second regions being arranged substantially perpendicularly to the reflective structures of the first regions and arranged to repeat with a second pitch smaller than the grating pitch;
illuminating the first and second regions with a polarized inspection radiation beam, the first and second pitches being less than a wavelength (λ) of the inspection radiation beam divided by a refractive index (n) of a material in which the periodic arrays are provided;
detecting the polarized inspection radiation beam reflected from the first and second regions;
determining a feature in a diffraction spectrum of the reflected polarized inspection radiation beam, wherein the determined feature is based on a misalignment of the target with a second target provided on top of or beneath the grating; and
determining the overlay error based on the determined feature.

19. The method according to claim 18 , wherein the first pitch is different than the second pitch.

20. The method according to claim 18 , wherein the second grating is on a layer of the substrate underneath the grating, wherein the second grating is formed by an array of third regions alternating with fourth regions and arranged to repeat with the grating pitch in the grating vector direction.

21. The method according to claim 2 , wherein the detecting the polarized inspection radiation beam comprises:
detecting a TE-polarized beam and a TM-polarized beam reflected from the first and second regions from the polarized inspection radiation beam;
measuring a difference between intensities of the TE-polarized beam and the TM-polarized beam; and
determining a duty cycle for the first regions to maximize the measured difference between the intensities.

Assignees

• Van Der Schaar Maurits
• Van De Kerkhof Marcus Adrianus
• Musa Sami
• Asml Netherlands Bv

Inventors

• Van Der Schaar Maurits
• Van De Kerkhof Marcus Adrianus
• Musa Sami

Classifications

• H10W46/301

  for alignment · CPC title

• H10W46/00

  Marks applied to devices, e.g. for alignment or identification · CPC title

• G03F7/70566 Primary

  Polarisation control · CPC title

• G03F9/7076

  Mark details, e.g. phase grating mark, temporary mark · CPC title

• G03F7/70633

  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 title