Metrology Method and Apparatus, Lithographic Apparatus, and Device Manufacturing Method

• US 20110069292A1
• Filed: 02/23/2009
• Published: 03/24/2011
• Est. Priority Date: 02/29/2008
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Den Boef, Arie Jeffrey
• Granted Patent: US 9,110,385 B2
• Time in Patent Office: Days
• US Class Current: 355/67
• CPC Class Codes: G01J 3/18 using diffraction elements, e.g. grating gratings per se G02B
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G03F 7/70483 Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
• CPC Class Codes: G03F 7/70625 Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness
• CPC Class Codes: G03F 7/70633 Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching

Abstract

A metrology apparatus includes first (21) and second (22) radiation sources which generate first (iB1) and second (iB2) illumination beams of different spatial extent and/or angular range. One of the illumination beams is selected, e.g. according to the size of target to be measured. The beam selection can be made by a tillable mirror (254) at a back-projected substrate plane in a Kohler illumination setup.

Claims

1. A metrology apparatus configured to measure a property of a target on a substrate, the apparatus comprising:

a first source configured to emit a first illumination beam of radiation;

a second source configured to emit a second illumination beam of radiation;

a beam selection device configured to select one of the first and second illumination beams of radiation as a measurement beam of radiation;

an objective lens configured to direct the measurement beam of radiation onto the target on the substrate and to collect radiation diffracted by the target; and

a sensor configured to detect an angle resolved spectrum in a pupil plane of the objective lens.

2. The apparatus according to claim 1, wherein at least one of the first and second sources comprises:

a broadband radiation source arranged to emit a first beam of radiation having a first wavelength range; and

a wavelength selection device arranged to select from the first beam of radiation as an output beam a second beam of radiation having a second wavelength range, the second wavelength range being narrower than the first wavelength range.

3. The apparatus according to claim 2, wherein the wavelength selection device is an acousto-optical tunable filter, a dispersive element or an interference filter.

4. The apparatus according to claim 2, wherein the broadband radiation source is a supercontinuum laser.

5. The apparatus according to claim 1, wherein at least one of the first and second sources comprises a xenon lamp.

6. The apparatus according to claim 1, wherein the first source comprises a xenon lamp and the second source comprises:

a broadband radiation source arranged to emit a first beam of radiation having a first wavelength range; and

a wavelength selection device arranged to select from the first beam of radiation as an output beam a second beam of radiation having a second wavelength range, the second wavelength range being narrower than the first wavelength range.

7. The apparatus according to claim 6, wherein the wavelength selection device is an acousto-optical tunable filter, a dispersive element or an interference filter.

8. The apparatus according to claim 6, wherein the broadband radiation source is a supercontinuum laser.

9. The apparatus according to claim 1, wherein each of the first and second sources comprises a xenon lamp.

10. The apparatus according to claim 1, wherein:

the objective lens has a pupil plane;

the first and second sources are configured so that the first and second illumination beams have respective spatial extents and angular ranges at a plane conjugate with the pupil plane of the objective lens and

at least one of the spatial extent and angular range of the first illumination beam being different from the spatial extent and angular range of the second illumination beam so that a spot formed by the measurement beam of radiation on the substrate differs in size, or illumination angle, or both size and illumination angle according to whether the beam selection device selects the first or second illumination beam as the measurement beam of radiation.

11. The apparatus according to claim 1, wherein the beam selection device comprises a tiltable mirror.

12. The apparatus according to claim 11, wherein the tiltable mirror is tiltable about two axes.

13. The apparatus according to claim 11, wherein the beam selection device comprises an optical system configured to direct the first and second illumination beams onto a pivot point of the tiltable mirror.

14. The apparatus according to claim 11, wherein the tiltable mirror is configured so that changes in its orientation change the angle of incidence of the measurement beam of radiation on the substrate.

15. The apparatus according to claim 11, wherein the beam selection device further comprises a selectable aperture stop.

16. The apparatus according claim 1, further comprising:

an additional sensor;

a beam splitter configured to direct a part of the radiation collected by the objective lens to the additional sensor; and

an imaging optical system configured to form an image of the target on the additional sensor.

17. A lithographic apparatus comprising:

an illumination optical system arranged to illuminate a pattern;

a projection optical system arranged to project an image of the pattern onto a substrate; and

a metrology device configured to measure a property of a target on the substrate, the device comprising;

a first source configured to emit a first illumination beam of radiation;

a second source configured to emit a second illumination beam of radiation;

a beam selection device configured to select one of the first and second illumination beams of radiation as a measurement beam of radiation;

an objective lens configured to direct the measurement beam of radiation onto the target on the substrate and to collect radiation diffracted by the target; and

a sensor configured to detect an angle resolved spectrum in a pupil plane of the objective lens.

18. The apparatus according to claim 17, further comprising:

an exposure station; and

a measurement station,

wherein the substrate table is moveable between the exposure station and the measurement station, and

wherein the metrology device is positioned at the measurement station.

19. A method of measuring a property of a target on a substrate, the method comprising:

generating at least one of a first or a second illumination beam, the first and second illumination beams differing in at least one of spatial extent and range of angles;

selecting one of the first and second illumination beams as a measurement beam and directing the measurement beam onto the target;

collecting radiation diffracted from the target using an objective lens; and

detecting an angle-resolved spectrum in a pupil plane of the objective lens.

20. The method according to claim 19, wherein selecting one of the first or the second illumination beam is based on a size, or type, or both the size and type of the target.