Inspection method and apparatus, lithographic apparatus, lithographic processing cell and device manufacturing method
An apparatus and method to determine a property of a substrate by measuring, in the pupil plane of a high numerical aperture lens, an angle-resolved spectrum as a result of radiation being reflected off the substrate. The property may be angle and wavelength dependent. The radiation that is reflected off the substrate is radially polarized.
1. A scatterometer, comprising:
a radiation source configured to provide a radiation beam;
a high numerical aperture lens configured to direct the radiation beam onto a substrate; and
a detector configured to detect an angle-resolved spectrum of the radiation beam reflected at a plurality of angles from a surface of the substrate,
wherein the radiation source is configured to radially polarize the radiation beam.
2. The scatterometer of claim 1 , wherein the radiation source comprises a liquid nematic cell configured to polarize the radiation beam.
3. The scatterometer of claim 1 , further comprising:
an optical system configured to focus the radially polarized radiation beam to a focal spot with a diameter of up to about 200 nm.
4. The scatterometer of claim 1 , wherein:
the detector is configured to measure an overlay of a first layer on a substrate with respect to a second layer superimposed onto the first layer; and
the detector is configured to detect at least the zeroth and first orders of the angle-resolved spectrum of the radially polarized radiation beam having been reflected from the superimposed first and second layers and to output an image of the respective intensities of the zeroth, −1 and +1 diffraction orders, a parameter of the image indicating the extent of the overlay.
5. The scatterometer of claim 4 , wherein the parameter of the image indicating the extent of the overlay comprises a value on one of a color or gray-scale pixel image.
6. The scatterometer of claim 1 , wherein the detector is configured to measure the property of the substrate by further measuring, substantially simultaneously, in the pupil plane of the high numerical aperture lens, a property of the reflected spectrum at a plurality of wavelengths.
7. The scatterometer of claim 1 , wherein the lens comprises a numerical aperture of at least about 0.9.
8. The scatterometer of claim 1 , further comprising a space between the substrate and the high numerical aperture lens containing a liquid.
9. The scatterometer of claim 1 , wherein the radiation source comprises a polarizer configured to radially polarize the radiation beam.
10. The scatterometer of claim 1 , wherein a critical dimension of a structure on the substrate is measured by measuring features in the reflected spectrum, the features being comparable to a library of predetermined features associated with known critical dimensions.
11. The scatterometer of claim 1 , wherein the features in the reflected spectrum include asymmetry.
12. A method, comprising
generating a pattern for printing onto a substrate through patterning a radially polarized radiation beam; and
measuring, in the pupil plane of a high numerical aperture lens, a reflected spectrum of the pattern.
13. The method of claim 12 , wherein the measuring the reflected spectrum comprises measuring (a) a property of the reflected spectrum at a plurality of angles, (b) a plurality of wavelengths, or both (a) and (b) simultaneously.
14. The method of claim 12 , wherein:
the pattern comprises two gratings layered in parallel and misaligned, thereby creating an overlay of one grating with respect to the other;
wherein the measuring of the reflected spectrum of the gratings is carried out using a scatterometer; and
wherein the extent of the overlay is derived from the asymmetry in the reflected spectrum.
15. A lithographic apparatus comprising:
an illumination optical system configured to illuminate a pattern;
a projection optical system configured to project an image of the pattern on to a substrate; and
an angularly resolved scatterometer configured to measure a property of the substrate, the scatterometer comprising,
a radiation source configured to provide a radiation beam,
a high numerical aperture lens configured to direct the radiation beam on the substrate, and
a detector configured to detect an angle-resolved spectrum of the radiation beam reflected at a plurality of angles from a surface of the substrate,
wherein the radiation source is configured to radially polarize the radiation beam.
16. A lithographic cell, comprising:
a coater configured to coat substrates with a radiation sensitive layer;
a lithographic apparatus configured to expose images onto the radiation sensitive layer of substrates coated by the coater;
a developer configured to develop images exposed by the lithographic apparatus; and
an angularly resolved scatterometer configured to measure a property of a substrate, the scatterometer comprising,
a radiation source configured to provide a radiation beam,
a high numerical aperture lens, and
a detector configured to detect an angle-resolved spectrum of the radiation beam reflected at a plurality of angles from a surface of the substrate,
wherein the radiation source is configured to radially polarize the radiation beam.
17. A device manufacturing method, comprising:
forming a pattern on a substrate using a lithographic apparatus; and
determining a value related to a parameter of the pattern printed by:
providing a radiation beam;
generating a pattern for printing onto the substrate; and
measuring, in the pupil plane of a high numerical aperture lens, a reflected spectrum of the pattern, the reflected spectrum being created by the reflection of a radially polarized radiation beam from the pattern on the substrate.