Metrology apparatus, lithographic system, and method of measuring a structure

A lithographic system comprising:

• a lithographic apparatus configured to perform a lithographic process;
• and
• a metrology apparatus comprising:
• an optical system configured to illuminate a structure formed on a substrate with radiation and to detect a first scattered radiation associated with a first portion of a pupil plane distribution and a second scattered radiation associated with a second portion of the pupil plane distribution, wherein the first and second scattered radiation are scattered by the structure and the optical system comprises:
• a first dispersive element configured to spectrally disperse the first scattered radiation along a first dispersion direction;
• and
• a second dispersive element, different than the first dispersive element, configured to spectrally disperse the second scattered radiation along a second dispersion direction,
• wherein the optical system is further configured to direct the first and second scattered radiation onto respective first and second arrays of lenses, and
• wherein the lithographic apparatus is arranged to use a result of a measurement by the metrology apparatus of the structure formed by the lithographic process when performing a subsequent lithographic process.

A method of measuring a structure formed on a substrate by a lithographic process, the method comprising:

• illuminating the structure with radiation to produce first and second scattered radiation from the structure, wherein the first scattered radiation is associated with a first portion of a pupil plane distribution and the second scattered radiation is associated with a second portion of the pupil plane distribution;
• spectrally dispersing the first and second scattered radiation along respective first and second dispersion directions using respective first and second dispersive elements;
• directing the first and second scattered radiation onto respective first and second arrays of lenses;
• and
• detecting the spectrally dispersed first and second scattered radiation.