# US 9,518,936 B2 · Method and apparatus for determining lithographic quality of a structure

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- Number: US 9,518,936 B2
- Document ID: US9518936B2
- Status: Granted
- Kind: B2
- Application number: 14/648,457
- Filed: 2013-10-30
- Published: 2015-10-29
- Granted: 2016-12-13
- Earliest claimed: 2012-11-30
- Assignees: ASML Netherlands B.V.
- Applicants: ASML Netherlands B.V.
- Inventors: Willem Jan Grootjans; Henricus Johannes Lambertus Megens; Jouke Krist; Miguel Garcia Granda; Lu Xu
- Web page: https://patentgrep.com/patent/US9518936B2

## CPC

- G01N 21/95607: {using a comparative method}
- G01N 21/47: Scattering, i.e. diffuse reflection (G01N21/25, G01N21/41 take precedence {G01N21/55 takes precedence})
- G03F 7/70133: {Measurement of illumination distribution, in pupil plane or field plane}
- G03F 7/70558: {Dose control, i.e. achievement of a desired dose}
- G03F 7/70625: {Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness}
- G03F 7/70641: {Focus}
- G01N 2021/4792: {Polarisation of scatter light}
- G01N 2201/06113: Coherent sources; lasers
- G01N 2201/12: Circuits of general importance; Signal processing
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)

## Abstract

Method for determining lithographic quality of a structure produced by a lithographic process using a periodic pattern, such as a grating, detects lithographic process window edges and optimum process conditions. Method steps are: 602: printing a structure using a lithographic process using a grating pattern; 604: selecting a first characteristic, such as a polarization direction, for the illumination; 606: illuminating the structure with incident radiation with first characteristic 608: detecting scattered radiation; 610: selecting a second characteristic, such as a different polarization direction, for the illumination; 612: illuminating the structure with incident radiation with the second characteristic; 614: detecting scattered radiation; 616: rotating one or more angularly resolved spectrum to line up the polarizations, thus correcting for different orientations of the polarizations; 618: determining a difference between the measured angularly resolved spectra; and 620: determining a value of lithographic quality of the structure using the determined difference.

## Claims

### Claim 1

A method comprising:
illuminating a structure with a beam;
measuring intensity of non-zeroth order radiation based on the beam being scattered by the structure;
comparing the measured intensity of non-zeroth order radiation and a value of intensity corresponding to an absence of non-zeroth order radiation; and
determining a parameter of the structure based on the comparison.

### Claim 2 (depends on 1)

The method of claim 1, wherein the beam is polarized.

### Claim 3

An apparatus comprising:
an illumination system configured to illuminate a structure with a beam;
a detection system configured to measure intensity of the non-zeroth order radiation based on the beam being scattered by the structure; and
a processor configured to:
compare the measured intensity of non-zeroth order radiation and a value of intensity corresponding to an absence of non-zeroth order radiation, and:
determine a parameter of the structure based on the comparison.

### Claim 4 (depends on 3)

The apparatus of claim 3, wherein:
the processor is further configured to perform the comparison by determining a difference between the measured intensity of non-zeroth order radiation and the value of intensity corresponding to an absence of non-zeroth order radiation.

### Claim 5 (depends on 3)

The apparatus of claim 3, wherein:
the illumination system is further configured to illuminate a plurality of structures;
the detection system is further configured to measure intensities based on the beams being scattered by the plurality of structures; and
the processor is further configured to determine a process window edge of a lithographic process used to produce the plurality of the structures based on the parameters.

### Claim 6 (depends on 3)

The apparatus of claim 3, wherein:
the illumination system is further configured to illuminate a plurality of structures;
the detection system is further configured to measure intensities based on the beams being scattered by the plurality of structures; and
the processor is further configured to determine an optimum process condition of a lithographic process used to produce the plurality of the structures based on the parameters.