Polarization measurements of metrology targets and corresponding target designs

• US 10,458,777 B2
• Filed: 11/23/2015
• Issued: 10/29/2019
• Est. Priority Date: 06/27/2013
• Status: Active Grant

• Current Assignee: KLA-Tencor Corporation (KLA Corporation)
• Original Assignee: KLA-Tencor Corporation (KLA Corporation)
• Inventors: Amit, Eran, Loevsky, Barry, Hill, Andrew, Manassen, Amnon, Amir, Nuriel, Levinski, Vladimir, Volkovich, Roie
• Primary Examiner(s): Akanbi, Isiaki O
• Application Number:
  US14/949,444
• Publication Number:
  US 20160178351A1
• Time in Patent Office: 1,436 Days
• Field of Search: 356399-401, 3562372-2376, 3562434, 356601-614
• CPC Class Codes: G01B 11/06 for measuring thickness ; e.g. of sheet material thickness measurement by thermal means G01B21/085
• CPC Class Codes: G01B 11/272 using photoelectric detection means
• CPC Class Codes: G01B 2210/56 Measuring geometric parameters of semiconductor structures, e.g. profile, critical dimensions or trench depth
• CPC Class Codes: G01B 2290/70 Using polarization in the interferometer
• CPC Class Codes: G01N 2021/8848 Polarisation of light
• 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: G06F 30/392 Floor-planning or layout, e.g. partitioning or placement
• CPC Class Codes: G06F 30/398 Design verification or optimisation, e.g. using design rule check [DRC], layout versus schematics [LVS] or finite element methods [FEM] optical proximity correction [OPC] design processes G03F1/36
• CPC Class Codes: H01L 22/30 Structural arrangements specially adapted for testing or measuring during manufacture or treatment, or specially adapted for reliability measurements

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.

Claims

1. A method of measuring a metrology target element comprising:

illuminating, with illumination of a selected polarization, the metrology target element including a segmented target structure having a first segmentation direction, a segmented background region having a second segmentation direction perpendicular to the first segmentation direction, wherein the segmented target structure and the segmented background region are formed in a single layer, wherein an area of the segmented target structure and an area of the segmented background region combine to substantially fill an area of the metrology target element, wherein at least one of a segmentation pitch of the segmented background region or a segmentation pitch of the segmented target structure provide a first contrast above a specified contrast threshold under polarized light and a second contrast below the specific contrast threshold to the segmented background region in non-polarized light,

measuring illumination reflected from the metrology target element, wherein the illumination measured is at least one of polarized light above the specific contrast threshold to the segmented background region or non-polarized light below the specific contrast threshold to the segmented background region;

measuring one or more side wall angles of the segmented target structure; and

determining one or more distances between the segmented target structure and the segmented background region along a boundary between the segmented target structure and the segmented background region based on the measured one or more side wall angles of the segmented target structure.

2. The method 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.

3. The method of claim 2, 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.

4. The method of claim 3, 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.

5. The method of claim 2, 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.

6. The method of claim 2, wherein the segmented background region is spaced from the segmented target structure by a selected distance.

7. The method of claim 2, wherein the illuminating the metrology target element with illumination of a selected polarization comprises:

illuminating the metrology target element with illumination of at least one of linear polarization, circular polarization, s-polarization or p-polarization.

8. The method of claim 2, wherein the illuminating the metrology target element with illumination of a selected polarization comprises:

illuminating the metrology target element with illumination having modulated polarization.

9. The method of claim 2, the measuring illumination reflected from the metrology target element comprises:

measuring one or more first order diffraction patterns from the reflected illumination following removing of one or more zeroth order diffraction patterns from the reflected illumination.

10. The method of claim 1, further comprising:

identifying a difference between a first measured side wall angle and a second measured side wall angle; and

determining at least one of a pattern placement error or edge quality metric based on the identified difference between the first measured side wall angle and the second measured side wall angle.

11. An apparatus 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 having a first segmentation direction and a first pitch and a segmented background region having a second segmentation direction and a second pitch perpendicular to the first segmentation direction, wherein the segmented target structure and the segmented background region are formed in a single layer, wherein an area of the segmented target structure and an area of the segmented background region combine to substantially fill an area of the metrology target element, 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;

a detector for measuring the illumination reflected from the metrology target element; and

at least one computer processor configured to;

measure one or more side wall angles of the segmented target structure; and

determine one or more distances between the segmented target structure and the segmented background region along a boundary between the segmented target structure and the segmented background region based on the measured one or more side wall angles of the segmented target structure.

12. The apparatus of claim 11, 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.

13. The apparatus of claim 12, 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.

14. The apparatus of claim 13, 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.

15. The apparatus of claim 11, 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.

16. The apparatus of claim 11, wherein the segmented background region is spaced from the segmented target structure by a selected distance.

17. The apparatus of claim 11, wherein the selected polarization comprises:

at least one of linear polarization, circular polarization, s-polarization or p-polarization.

18. The apparatus of claim 11, wherein the selected polarization comprises:

modulated polarization.

19. The apparatus of claim 11, wherein the detector is further configured to measure one or more first order diffraction patterns from the reflected illumination following removing of one or more zeroth order diffraction patterns from the reflected illumination.

20. The apparatus of claim 11, wherein the at least one computer processor is further configured to:

identify a difference between a first measured side wall angle and a second measured side wall angle; and

determine at least one of a pattern placement error or edge quality metric based on the identified difference between the first measured side wall angle and the second measured side wall angle.