Inspection Apparatus and Methods, Substrates Having Metrology Targets, Lithographic System and Device Manufacturing Method

Patent metadata

Field	Value
Publication number	US-2016274472-A1
Application number	US-201415032507-A
Country	US
Kind code	A1
Filing date	Oct 13, 2014
Priority date	Oct 30, 2013
Publication date	Sep 22, 2016
Grant date	—

Abstract

Disclosed is an inspection apparatus for use in lithography. It comprises a support for a substrate carrying a plurality of metrology targets; an optical system for illuminating the targets under predetermined illumination conditions and for detecting predetermined portions of radiation diffracted by the targets under the illumination conditions; a processor arranged to calculate from said detected portions of diffracted radiation a measurement of asymmetry for a specific target; and a controller for causing the optical system and processor to measure asymmetry in at least two of said targets which have different known components of positional offset between structures and smaller sub-structures within a layer on the substrate and calculate from the results of said asymmetry measurements a measurement of a performance parameter of the lithographic process for structures of said smaller size. Also disclosed are substrates provided with a plurality of novel metrology targets formed by a lithographic process.

First claim

1 . An inspection apparatus for measuring a property of a lithographic process, the apparatus comprising:
a support configured to support a substrate, the substrate carrying a plurality of metrology targets comprising structures formed by the lithographic process; an optical system configured to illuminate the plurality of targets under predetermined illumination conditions and to detect predetermined portions of radiation diffracted by the targets under said illumination conditions; a processor arranged to calculate, from said detected portions of diffracted radiation, a measurement of asymmetry for a specific target; and a controller configured to cause said optical system and processor to measure asymmetry in at least two of said targets which have different known components of positional offset between structures and smaller sub-structures within a layer on the substrate and to calculate from the results of said asymmetry measurements a measurement of a performance parameter of the lithographic process for structures of said smaller size.

2 . The apparatus as claimed in claim 1 , wherein said performance parameter is an overlay parameter of the lithographic process for structures of said smaller size and is calculated by combining results of said asymmetry measurements with measurements of asymmetry in at least two overlay targets which have different known components of positional offset between first and second layers on the substrate.

3 . The apparatus as claimed in claim 2 , wherein said controller is arranged to cause said optical system and processor to measure asymmetry in at least two auxiliary targets having different known components of positional offset in each of the first and second layers.

4 . The apparatus as claimed in claim 1 , wherein said controller is arranged to cause said optical system and processor to measure asymmetry in at least two of said targets which have different known components of positional offset between interleaved populations of sub-structures within the target and to calculate from the results of said asymmetry measurements a measurement of an overlay parameter of the lithographic process used to form said sub-structures.

5 . The apparatus as claimed in claim 1 , wherein:
said optical system is arranged to form and detect images using radiation diffracted by at least two of said metrology targets simultaneously, different images using different portions of the diffracted radiation, and said processor is arranged to identify regions of interest in the detected images, each region of interest corresponding to a specific one of said targets and to process pixel values within said regions of interest to obtain said measurement of asymmetry for each target.

6 . A substrate comprising:
a plurality of metrology targets formed by a lithographic process, each target comprising structures arranged to repeat with a spatial period in at least a first direction, said metrology targets comprising:
a plurality of overlay targets, at least some of said structures in each overlay target being replicated in first and second layers on said substrate and superimposed on one another and wherein each overlay target is formed with a positional offset between the layers that is a combination of both known and unknown components, the known components being different for different targets; and
a plurality of auxiliary targets, each auxiliary target comprising sub-structures of a size several times smaller than said spatial period, wherein each auxiliary target is formed in one of said layers and is formed with a positional offset between the sub-structures and structures that is a combination of both known and unknown components, the known components being different for different targets.

7 . The substrate as claimed in claim 6 , wherein two or more overlay targets having different known offsets between layers are formed in close proximity with two or more auxiliary targets having different positional offsets between the sub-structures and structures, so as to form a composite target, while other such composite targets are distributed across the substrate.

8 . The substrate as claimed in claim 6 , wherein said auxiliary targets include at least a first pair of targets having different known positional offsets that are formed in said first layer and at least a second pair of targets having different positional offsets and that are formed in said second layer.

9 . A patterning device for use in a lithographic process, the patterning device defining a pattern which when applied to a substrate will produce a substrate comprising:
a plurality of overlay targets, at least some of said structures in each overlay target being replicated in first and second layers on said substrate and superimposed on one another and wherein each overlay target is formed with a positional offset between the layers that is a combination of both known and unknown components, the known components being different for different targets; and a plurality of auxiliary targets, each auxiliary target comprising sub-structures of a size several times smaller than said spatial period, wherein each auxiliary target is formed in one of said layers and is formed with a positional offset between the sub-structures and structures that is a combination of both known and unknown components, the known components being different for different targets.

10 . A method of measuring a performance parameter of a lithographic process, the method comprising:
(a) performing said lithographic process to produce structures forming a plurality of metrology targets on a substrate, at least two of said targets having a positional offset between structures and smaller sub-structures that is a combination of both known and unknown components, the known components of positional offset being different for different targets; (b) using the inspection apparatus to measure asymmetry in at least two of said auxiliary targets having different known components of positional offset between structures and smaller sub-structures within a layer on the substrate; and (c) calculating using the results of the asymmetry measurements made in step (b) a measurement overlay performance parameter of the lithographic process for structures of said smaller size.

11 . The method as claimed in claim 10 , wherein:
the targets formed in step (a) are auxiliary targets for at least two overlay targets, said overlay targets having different known components of positional offset between structures in first and second layers on the substrate, and results of the asymmetry measurements made in step (b) are combined with measurements of asymmetry in said at least two overlay targets to obtain a measurement of an unknown component of the positional offset in the overlay target to obtain a representation of said overlay parameter of the lithographic process for structures of said smaller size.

12 . The method as claimed in claim 11 , wherein in step (b) at least two auxiliary targets having different known components of positional offset are measured in each of the first and second layers.

13 . The method as claimed in claim 10 , wherein:
said at least two of said targets are formed in step (a) to have different known components of positional offset between interleaved populations of sub-structures within a layer on the substrate, in step (c) a measurement of an overlay parameter of the lithographic process used to form said interleaved populations of sub-structures is calculated from the results of the asymmetry measurements made in step (b).

14 . The method as claimed in claim 10 , wherein in t

Assignees

• Asml Netherlands Bv

Inventors

• Mathijssen Simon Gijsbert Josephus
• Hunsche Stefan
• Van Kraaij Markus Gerardus Martinus Maria

Classifications

• G03F7/22

  Exposing sequentially with the same light pattern different positions of the same surface {(G03F7/70 takes precedence)} · CPC title

• G03F7/213 Primary

  Exposing with the same light pattern different positions of the same surface at the same time {(G03F7/70 takes precedence)} · CPC title

• G03F7/70683 Primary

  Mark designs · CPC title

• G03F7/70633 Primary

  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

• G03F9/7076

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