Substrate and patterning device for use in metrology, metrology method and device manufacturing method
A pattern from a patterning device is applied to a substrate by a lithographic apparatus. The applied pattern includes product features and metrology targets. The metrology targets include large targets and small targets which are for measuring overlay. Some of the smaller targets are distributed at locations between the larger targets, while other small targets are placed at the same locations as a large target. By comparing values measured using a small target and large target at the same location, parameter values measured using all the small targets can be corrected for better accuracy. The large targets can be located primarily within scribe lanes while the small targets are distributed within product areas.
1. A substrate comprising:
product areas;
product features, formed by a lithographic process, located within the product areas; and
targets, formed by the lithographic process on the substrate, configured to produce a diffraction pattern in response to being illuminated by radiation, the diffraction pattern corresponding to a parameter of performance of the lithographic process,
wherein the targets comprise:
a first set of targets located outside the product areas; and
a second set of targets comprising first and second sub-set of targets, the first and second sub-set of targets having areas equal to each other and smaller than areas of the first set of targets, the first sub-set of targets being located outside the product areas and the second sub-set of targets being located within the product areas.
2. The substrate of claim 1 , wherein:
the parameter of performance is overlay; and
the targets comprise overlay gratings formed in two patterned layers.
3. The substrate of claim 1 , wherein each of the targets comprises a composite target, the composite target comprising a plurality of overlay grating portions.
4. The substrate of claim 1 , wherein:
the parameter of performance is overlay;
the targets comprise overlay gratings formed in two patterned layers; and
the overlay gratings comprise overlay grating portions, each of the overlay grating portions having a different overlay bias than each of the other overlay grating portions.
5. The substrate of claim 1 , further comprising a scribe lane located between two of the product areas; and
wherein the first set of targets and the first sub-set of targets are located within the scribe lane.