System and Method for Focus Determination Using Focus-Sensitive Overlay Targets

Patent metadata

Field	Value
Publication number	US-2016334716-A1
Application number	US-201615154051-A
Country	US
Kind code	A1
Filing date	May 13, 2016
Priority date	May 15, 2015
Publication date	Nov 17, 2016
Grant date	—

Abstract

A lithography mask is disclosed. The lithography mask includes at least one asymmetric segmented pattern element. A particular asymmetric segmented pattern element includes at least two segments with a separation distance between consecutive segments smaller than a resolution of a set of projection optics for generating an image of the particular asymmetric segmented pattern element on a sample such that the image of the particular asymmetric segmented pattern element is an unsegmented pattern image. A position of the unsegmented pattern image on the sample is indicative of a location of the sample along an optical axis of the set of projection optics.

First claim

What is claimed:

1 . A lithography mask, comprising:
at least one asymmetric segmented pattern element, wherein a particular asymmetric segmented pattern element includes at least two segments, wherein a separation distance between consecutive segments of the particular asymmetric segmented pattern element is configurable to be smaller than a resolution of a set of projection optics for generating an image of the particular asymmetric segmented pattern element on a sample such that the image of the particular asymmetric segmented pattern element is an unsegmented pattern image, wherein a position of the unsegmented pattern image on the sample is indicative of a location of the sample along an optical axis of the set of projection optics.

2 . The lithography mask of claim 1 , further comprising:
at least one additional pattern element different than the asymmetric segmented pattern element.

3 . The lithography mask of claim 2 , wherein a position of an image of the at least one additional pattern element on the sample generated by the set of projection optics is constant with respect to the location of the sample along the optical axis of the set of projection optics

4 . The lithography mask of claim 3 , wherein the at least one additional pattern element comprises:
at least one of an unsegmented pattern element or a symmetric segmented pattern element.

5 . The lithography mask of claim 2 , wherein the at least one additional pattern element is an additional asymmetric segmented pattern element, wherein a separation distance between consecutive segments of a particular additional pattern element is configurable to be smaller than the resolution of the set of projection optics such that an image of the particular additional pattern element on the sample generated by the set of projection optics is an additional unsegmented pattern image, wherein a position of the additional unsegmented pattern image on the sample is indicative of the location of the sample along an optical axis of the set of projection optics, wherein a deviation of sample along the optical axis of the set of projection optics generates a deviation of the position of the unsegmented pattern image along a first direction and a deviation of the additional unsegmented pattern image along a second direction opposite the first direction.

6 . The lithography mask of claim 2 , wherein the at least one asymmetric segmented pattern element includes two or more segmented pattern elements distributed across a plurality of cell structures, wherein the at least one additional pattern element includes two or more additional pattern elements distributed across a plurality of cell structures.

7 . The lithography mask of claim 1 , wherein the at least one asymmetric segmented pattern element comprises a substantially opaque material.

8 . The lithography mask of claim 7 , wherein the substantially opaque material includes a metal.

9 . The lithography mask of claim 1 , wherein the at least one asymmetric segmented pattern element comprises a binary pattern element.

10 . A lithography system, comprising:
a mask support device configured to secure a lithography mask, wherein the lithography mask includes at least one asymmetric segmented pattern element, wherein a particular asymmetric segmented pattern element includes at least two segments; an illumination source configured to direct illumination to the lithography mask; and a set of projection optics configured to generate an image of the particular asymmetric segmented pattern element on a sample, wherein a separation distance between consecutive segments of the particular asymmetric segmented pattern element is configurable to be smaller than a resolution of the set of projection optics such that the image of the particular asymmetric segmented pattern element is an unsegmented pattern image, wherein a position of the unsegmented pattern image on the sample is indicative of a location of the sample along an optical axis of the set of projection optics.

11 . The lithography system of claim 10 , wherein the lithography mask further comprises:
at least one additional pattern element different than the asymmetric segmented pattern element.

12 . The lithography system of claim 11 , wherein a position of an image of the at least one additional pattern element on the sample generated by the set of projection optics is constant with respect to the location of the sample along the optical axis of the set of projection optics.

13 . The lithography system of claim 12 , wherein the at least one additional pattern element comprises:
at least one of an unsegmented pattern element or a symmetric segmented pattern element.

14 . The lithography system of claim 11 , wherein the at least one additional pattern element is an additional asymmetric segmented pattern element, wherein a separation distance between consecutive segments of a particular additional pattern element is configurable to be smaller than the resolution of the set of projection optics such that an image of the particular additional pattern element on the sample generated by the set of projection optics is an additional unsegmented pattern image, wherein a position of the additional unsegmented pattern image on the sample is indicative of the location of the sample along an optical axis of the set of projection optics, wherein a deviation of sample along the optical axis of the set of projection optics generates a deviation of the position of the unsegmented pattern image along a first direction and a deviation of the additional unsegmented pattern image along a second direction opposite the first direction.

15 . The lithography system of claim 11 , wherein the at least one asymmetric segmented pattern element includes two or more segmented pattern elements distributed across a plurality of cell structures, wherein the at least one additional pattern element includes two or more additional pattern elements distributed across a plurality of cell structures.

16 . The lithography system of claim 10 , wherein the at least one asymmetric segmented pattern element comprises a substantially opaque material.

17 . The lithography system of claim 16 , wherein the substantially opaque material includes a metal.

18 . The lithography system of claim 10 , wherein the at least one asymmetric segmented pattern element comprises a binary pattern element.

19 . A metrology system, comprising:
a sample stage configured to support a substrate with a metrology target disposed upon the substrate, wherein the metrology target is associated with an image of a lithography mask, wherein the lithography mask includes at least one asymmetric segmented pattern element, wherein a particular asymmetric segmented pattern element includes at least two segments, wherein a separation distance between consecutive segments of the particular asymmetric segmented pattern element is configurable to be smaller than a resolution of a set of projection optics for generating an image of the particular asymmetric segmented pattern element on a sample such that the image of the particular asymmetric segmented pattern element is an unsegmented pattern image, wherein a position of the unsegmented pattern image on the sample is indicative of a location of the sample along an optical axis of the set of projection optics; at least one illumination source configured to illuminate the metrology target; at least one detector configured to receive illumination from the metrology target; and at least one cont

Assignees

• Kla Tencor Corp

Inventors

• Mieher Walter Dean

Classifications

• G03F7/70683

  Mark designs · CPC title

• G03F7/70641 Primary

  Focus · CPC title

• G03F1/44 Primary

  Testing or measuring features, e.g. grid patterns, focus monitors, sawtooth scales or notched scales · CPC title

• G03F1/50

  Mask blanks not covered by G03F1/20 - G03F1/34; Preparation thereof · CPC title

• H04N5/2256

  Electricity · mapped topic