Computationally efficient x-ray based overlay measurement

Patent metadata

Field	Value
Publication number	US-11428650-B2
Application number	US-201916717475-A
Country	US
Kind code	B2
Filing date	Dec 17, 2019
Priority date	Apr 28, 2015
Publication date	Aug 30, 2022
Grant date	Aug 30, 2022

Abstract

Methods and systems for performing overlay and edge placement errors of device structures based on x-ray diffraction measurement data are presented. Overlay error between different layers of a metrology target is estimated based on the intensity variation within each x-ray diffraction order measured at multiple, different angles of incidence and azimuth angles. The estimation of overlay involves a parameterization of the intensity modulations of common orders such that a low frequency shape modulation is described by a set of basis functions and a high frequency overlay modulation is described by an affine-circular function including a parameter indicative of overlay. In addition to overlay, a shape parameter of the metrology target is estimated based on a fitting analysis of a measurement model to the intensities of the measured diffraction orders. In some examples, the estimation of overlay and the estimation of one or more shape parameter values are performed simultaneously.

First claim

What is claimed is:

1. An overlay metrology target comprising:
a first structure disposed in a first layer fabricated at a first height above a surface of a planar substrate; and
a second structure disposed in a second layer fabricated at a second height above the surface of the planar substrate such that the second structure is offset from the first structure in a first direction parallel to the surface of the planar substrate by a first overlay parameter value, wherein the first structure is periodic with a first periodicity, and wherein the second structure is periodic with a second periodicity, wherein the first periodicity and the second periodicity are selected such that a first diffraction order number associated with the first structure constructively interferes with a second diffraction order number associated with the second structure, and wherein the overlay metrology target diffracts incident x-ray radiation from multiple, different angles of incidence and multiple, different azimuth angles such that a measured intensity associated with each x-ray diffraction order of a plurality of diffraction orders is modulated.

2. The overlay metrology target of claim 1 , further comprising:
a third structure disposed in a third layer fabricated at a third height above the surface of the planar substrate such that the third structure is offset from the first structure and the second structure in the first direction parallel to the surface of the planar substrate by a second overlay parameter value and a third overlay parameter value, respectively, wherein a first separation distance between the first and second heights, a second separation distance between the first and third heights, and a third separation distance between the second and third heights are each different, independent distances.

3. The overlay metrology target of claim 1 , wherein a direction of the periodicity of the first structure is aligned with a direction of periodicity of the second structure.

4. The overlay metrology target of claim 1 , wherein the first structure is periodic with a first periodicity, and wherein the second structure is periodic with a second periodicity, wherein the first periodicity is a first integer multiple of a constant value and the second periodicity is a second integer multiple of the constant value.

5. The overlay metrology target of claim 1 , wherein the first structure, the second structure, or both, is not periodic.

6. The overlay metrology target of claim 1 , wherein the overlay metrology target is a design rule target.

7. The overlay metrology target of claim 1 , wherein the overlay metrology target is disposed in-die.

8. The overlay metrology target of claim 1 , wherein the first structure is spatially periodic in at least one direction parallel to a planar surface of the planar substrate.

9. The overlay metrology target of claim 1 , wherein the first structure, the second structure, or both, is spatially periodic in two directions.

10. The overlay metrology target of claim 9 , wherein the two directions are orthogonal.

11. An overlay metrology target comprising:
a first structure disposed in a first layer fabricated at a first height above a surface of a planar substrate; and
a second structure disposed in a second layer fabricated at a second height above the surface of the planar substrate such that the second structure is offset from the first structure in a first direction parallel to the surface of the planar substrate by a first overlay parameter value, wherein the first structure is spatially periodic in a first direction, wherein the second structure is spatially periodic in a second direction different from the first direction, and wherein the overlay metrology target diffracts incident x-ray radiation from multiple, different angles of incidence and multiple, different azimuth angles such that a measured intensity associated with each x-ray diffraction order of a plurality of diffraction orders is modulated; and
a third structure disposed in a third layer fabricated at a third height above the surface of the planar substrate such that the third structure is offset from the first structure and the second structure in the first direction parallel to the surface of the planar substrate by a second overlay parameter value and a third overlay parameter value, respectively, wherein a first separation distance between the first and second heights, a second separation distance between the first and third heights, and a third separation distance between the second and third heights are each different, independent distances.

12. The overlay metrology target of claim 11 , wherein the first structure is periodic with a first periodicity, and wherein the second structure is periodic with a second periodicity, wherein the first periodicity is a first integer multiple of a constant value and the second periodicity is a second integer multiple of the constant value.

13. The overlay metrology target of claim 11 , wherein the overlay metrology target is a design rule target.

14. The overlay metrology target of claim 11 , wherein the overlay metrology target is disposed in-die.

15. The overlay metrology target of claim 11 , wherein the first structure, the second structure, or both, is spatially periodic in two directions.

16. The overlay metrology target of claim 15 , wherein the two directions are orthogonal.

17. An overlay metrology target comprising:
a first structure disposed in a first layer fabricated at a first height above a surface of a planar substrate; and
a second structure disposed in a second layer fabricated at a second height above the surface of the planar substrate such that the second structure is offset from the first structure in a first direction parallel to the surface of the planar substrate by a first overlay parameter value, wherein the first structure is spatially periodic with a first periodicity that is a first integer multiple of a constant value, wherein the second structure is spatially periodic with a second periodicity that is a second integer multiple of the constant value, and wherein the overlay metrology target diffracts incident x-ray radiation from multiple, different angles of incidence and multiple, different azimuth angles such that a measured intensity associated with each x-ray diffraction order of a plurality of diffraction orders is modulated.

18. The overlay metrology target of claim 17 , further comprising:
a third structure disposed in a third layer fabricated at a third height above the surface of the planar substrate such that the third structure is offset from the first structure and the second structure in the first direction parallel to the surface of the planar substrate by a second overlay parameter value and a third overlay parameter value, respectively, wherein a first separation distance between the first and second heights, a second separation distance between the first and third heights, and a third separation distance between the second and third heights are each different, independent distances.

Assignees

• Kla Corp

Inventors

• Hench John
• Shchegrov Andrei V
• Bakeman Michael S

Classifications

• G01N2223/611

  patterned objects; electronic devices · 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

• G03F7/0035

  Multiple processes, e.g. applying a further resist layer on an already in a previously step, processed pattern or textured surface · CPC title

• G21K1/062

  Devices having a multilayer structure · CPC title

• G01N23/201

  by measuring small-angle scattering · CPC title