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1. WO2016124345 - PROCÉDÉ DE MÉTROLOGIE, APPAREIL DE MÉTROLOGIE, ET PROCÉDÉ DE FABRICATION DE DISPOSITIF

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

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CLAIMS

1. A method of measuring a property of a structure manufactured by a lithographic process, the method comprising:

(a) irradiating a periodic structure with x-radiation along an irradiation direction, the periodic structure having been formed by said lithographic process on a substrate and having a periodicity in a first direction,

(b) detecting x-radiation scattered by the periodic structure after transmission through the substrate, and

(c) processing signals representing the detected scattered radiation to determine a property of the periodic structure,

wherein the irradiation direction defines a non-zero polar angle relative to a direction normal to the substrate and defines a non-zero azimuthal angle relative to the first direction, when projected onto a plane of the substrate.

2. A method as claimed in claim 1 wherein said azimuthal angle is selected so that a diffraction efficiency of the periodic structure in one or more non-zero diffraction orders is greater than would be the case for an irradiation direction of zero azimuthal angle.

3. A method as claimed in claim 2 wherein the azimuthal angle is selected so that a diffraction efficiency of the periodic structure in a first order of diffraction is more than two times, optionally more than five times or more than ten times the diffraction efficiency for zero azimuthal angle.

4. A method as claimed in claim 2 or claim 3 wherein the azimuthal angle is selected so that a diffraction efficiency of the periodic structure in a plurality of non-zero diffraction orders is greater than would be the case for an irradiation direction of zero azimuthal angle.

5. A method as claimed in any preceding claim wherein step (c) includes detecting intensities for a plurality of diffraction orders in the scattered radiation.

6. A method as claimed in any preceding claim wherein steps (a) and (b) are repeated using different polar angles and wherein in step (c) signals representing the scattered radiation detected using a plurality of different polar angles are used to determine the property of the periodic structure.

7. A method as claimed in any preceding claim wherein the step (c) includes defining a parameterized model of the periodic structure and using the model to perform performing mathematical reconstruction of the structure based on the detected scattered radiation.

8. A method as claimed in any preceding claim wherein said property is linewidth or wherein said property is overlay and the periodic structure is an overlay grating formed in two or more patterning steps.

9. A metrology apparatus for use in measuring performance of a lithographic process, the apparatus comprising:

an irradiation system for generating a beam of x-radiation;

a substrate support operable with the irradiation system for irradiating a periodic structure formed on the substrate with x-radiation along an irradiation direction; and

a detection system for detecting x-radiation scattered by the periodic structure after transmission through the substrate, and

wherein the substrate support is adjustable in at least two angular dimensions relative to the irradiation direction, so that the irradiation direction can be selected to have a non-zero polar angle relative to a direction normal to the substrate and can simultaneously be selected to define a non-zero azimuthal angle relative to the first direction, when projected onto a plane of the substrate.

10. An apparatus as claimed in claim 9 further comprising a processing system for processing signals representing the detected scattered radiation to determine a property of the periodic structure,

11. An apparatus as claimed in claim 10 wherein the processing system is arranged to detect intensities for a plurality of diffraction orders in the scattered radiation.

12. An apparatus as claimed in claim 10 or 11 wherein the processing system is arranged to process signals representing the scattered radiation detected using a plurality of different polar angles to determine the property of the periodic structure.

13. An apparatus as claimed in any of claims 10 to 12 wherein the processing system is arranged to perform performing mathematical reconstruction of the periodic structure based on the detected scattered radiation.

14. An apparatus as claimed in any of claims 9 to 13 further comprising a controller arranged to cause operation of the irradiation system and detection system to obtain signals representing radiation scattered by the same periodic structure using different polar angles.

15. A device manufacturing method comprising:

transferring a pattern from a patterning device onto a substrate using a lithographic process, the pattern defining at least one periodic structure;

measuring one or more properties of the periodic structure to determine a value for one or more parameters of the lithographic process; and

applying a correction in subsequent operations of the lithographic process in accordance with the measured property,

wherein the step of measuring the properties of the periodic structure includes measuring a property by a method as claimed in any of claims 1 to 8.