Polarization measurements of metrology targets and corresponding target designs

Patent metadata

Field	Value
Publication number	US-11060845-B2
Application number	US-201916665759-A
Country	US
Kind code	B2
Filing date	Oct 28, 2019
Priority date	Jun 27, 2013
Publication date	Jul 13, 2021
Grant date	Jul 13, 2021

Abstract

Targets, target elements and target design method are provided, which comprise designing a target structure to have a high contrast above a specific contrast threshold to its background in polarized light while having a low contrast below the specific contrast threshold to its background in non-polarized light. The targets may have details at device feature scale and be compatible with device design rules yet maintain optical contrast when measured with polarized illumination and thus be used effectively as metrology targets. Design variants and respective measurement optical systems are likewise provided.

First claim

What is claimed:

1. A system for measuring a metrology target element comprising:
a light source for generating illumination;
a set of optical elements configured to modify the illumination from the light source to form illumination of a selected polarization, wherein the set of optical elements are configured to direct the illumination of the selected polarization to a metrology target element, wherein the set of optical elements are configured to collect illumination reflected from the metrology target element,
wherein the metrology target element includes a segmented target structure and a segmented background region which provides the segmented target structure a first contrast above a specific contrast threshold to the segmented background region in polarized light and a second contrast below the specific contrast threshold to the segmented background region in non-polarized light;
a detector for measuring the illumination reflected from the metrology target element; and
at least one computer processor configured to:
acquire a first set of measurements of the target element using a first set of one or more illumination characteristics configured to produce a first contrast between the segmented target structure and the segmented background region; and
acquire a second set of measurements of the target element using a second set of one or more illumination characteristics configured to produce a second contrast between the segmented target structure and the segmented background region different from the first contrast.

2. The system of claim 1 , wherein the at least one computer processor is further configured to:
derive one or more characteristics of the target element based on the first set of measurements and the second set of measurements.

3. The system of claim 2 , wherein the one or more characteristics of the target element comprise at least one of an optical overlay measurement, a line uniformity measurement, or a line edge roughness measurement.

4. The system of claim 1 , wherein acquiring a second set of measurements of the target element using a second set of one or more illumination characteristics comprises:
selectively adjusting one or more illumination characteristics of the first set of one or more illumination characteristics in order to enhance a contrast between the segmented target structure and the segmented background region.

5. The system of claim 1 , wherein the first set of one or more illumination characteristics includes polarized light, and the second set of one or more illumination characteristics includes non-polarized light.

6. The system of claim 1 , wherein at least one of the first set of one or more illumination characteristics and the second set of one or more illumination characteristics comprise at least one of a selected polarization, a selected wavelength, or a selected focus.

7. The system of claim 1 , wherein the segmented target structure includes a first segmentation direction and a first pitch and the segmented background region includes a second segmentation direction and a second pitch.

8. The system of claim 1 , wherein one or more segmentation features of the segmented target structure and one or more segmentation features of the segmented background region provide a selected contrast level between the segmented target structure and the segmented background region when illuminated with light of a selected polarization.

9. The system of claim 1 , wherein a difference between the one or more segmentation features of the segmented target structure and the one or more segmentation features of the segmented background region provide the selected contrast level between the segmented target structure and the segmented background region when illuminated with light of a selected polarization.

10. The system of claim 8 , wherein at least one of the one or more segmentation features of the segmented target structure or the one or more segmentation features of the segmented background region comprise:
at least one of segmentation pitch, critical dimension of segments, segmentation direction or segmentation pattern.

11. The system of claim 1 , wherein the segmented background region is formed within the segmented target structure at one or more additional layers such that the segmented background region overlaps the segmented target structure.

12. The system of claim 1 , wherein the segmented background region is spaced from the segmented target structure by a selected distance.

13. The system of claim 1 , wherein the selected polarization comprises:
at least one of linear polarization, circular polarization, s-polarization, p-polarization, or modulated polarization.

14. The system of claim 1 , further comprising an interferometer configured to remove zeroth order diffraction patterns from the reflected illumination.

15. The system of claim 14 , wherein the detector is further configured to measure one or more first order diffraction patterns from the reflected illumination following the removal of the one or more zeroth order diffraction patterns from the reflected illumination.

16. A metrology target, comprising:
a first metrology target element formed in a first layer, the first metrology target element comprising:
a plurality of segmented target structures having a first segmentation direction and a first pitch, wherein the segmented target structures exhibit a first polarization activity, and
a segmented background region having a second segmentation direction different from the first segmentation direction and a second pitch different from the first pitch, wherein the segmented background region exhibits a second polarization activity different from the first polarization activity, wherein the segmented background region and the segmented target structure are formed such that at least one of the first pitch or the second pitch provides the segmented target structure a first contrast above a specific contrast threshold to the segmented background region in polarized light and a second contrast below the specific contrast threshold to the segmented background region in non-polarized light; and

a second metrology target element formed in a second layer, the second metrology target comprising:
a plurality of target structures,

wherein the first metrology target element and the second metrology target element are at least partially overlapping, wherein the plurality of segmented target structures of the first metrology target element and the plurality of target structures of the second metrology target element are not overlapping.

17. The metrology target of claim 16 , wherein the plurality of target structures of the second metrology target element formed in the second layer comprise a plurality of segmented target structures.

18. The metrology target of claim 17 , wherein the plurality of segmented target structures of the second metrology target element have a segmentation direction parallel to the first segmentation direction, and a pitch equivalent to the first pitch.

19. The metrology target of claim 17 , wherein the plurality of segmented target structures of the second metrology target element have a segmentation direction perpendicular to the first segmentation direction.

20. The metrology target of claim 16 , wherein the plurality of target structures of the second metrology target element formed in the second layer comprise a plurality of unsegmented target structures.

21. The metrology target of claim 16 , wherein the first pitch

Assignees

• Kla Tencor Corp
• Kla Corp

Inventors

• Amit Eran
• Loevsky Barry
• Hill Andrew
• Manassen Amnon
• Amir Nuriel
• Levinski Vladimir
• Volkovich Roie

Classifications

• H10P74/27

  Structural arrangements therefor · CPC title

• G01N2021/8848

  Polarisation of light · CPC title

• G01N21/956 Primary

  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 H10P74/20)} · CPC title

• G01N21/9501 Primary

  Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20) · CPC title

• G01B2290/70

  Using polarization in the interferometer · CPC title