Method of applying a pattern to a substrate, device manufacturing method and lithographic apparatus for use in such methods
A substrate is loaded onto a substrate support of a lithographic apparatus, after which the apparatus measures locations of substrate alignment marks. These measurements define first correction information allowing the apparatus to apply a pattern at one or more desired locations on the substrate. Additional second correction information is used to enhance accuracy of pattern positioning, in particular to correct higher order distortions of a nominal alignment grid. The second correction information may be based on measurements of locations of alignment marks made when applying a previous pattern to the same substrate. The second correction information may alternatively or in addition be based on measurements made on similar substrates that have been patterned prior to the current substrate.
1. A lithographic apparatus configured to transfer a pattern from a patterning device onto a substrate, the lithographic apparatus comprising:
a patterning subsystem configured to apply the pattern from the patterning device to a portion of the substrate held at a patterning location;
a substrate support configured to hold the substrate while the pattern is applied;
a measurement subsystem configured to measure locations of a first set of alignment marks and a second set of alignment marks on the substrate; and
a controller configured to:
operate the lithographic apparatus to apply the pattern at a desired location on the substrate held on the substrate support;
generate a first correction information based on the locations of the first set of alignment marks measured by the measurement subsystem after loading the substrate on the substrate support;
retrieve from a data storage device a second correction information that is based on the locations of the second set of alignment marks measured by the measurement subsystem prior to loading the substrate on the substrate support; and
use the first and second correction information in combination to position the applied pattern at the desired location.
2. The lithographic apparatus of claim 1 , wherein the controller is further configured to:
process the measurements of the first set of alignment marks to generate a first alignment model; and
process the measurements of the second set of alignment marks to generate a second alignment model, the second alignment model being different from the first alignment model.
3. The lithographic apparatus of claim 1 , wherein the second correction information comprises one of a polynomial alignment model, a zone-alignment model and a radial basis function model.
4. The lithographic apparatus of claim 1 ; wherein the controller is further configured to:
generate the second correction information based at least partially on measurements of the second set of alignment marks made using the measurement subsystem while applying the pattern to the substrate during a previous lithographic step; and
store the second correction information in the data storage device.
5. The lithographic apparatus of claim 1 , wherein the controller is further configured to:
generate the second correction information based at least partially on measurements of a third set of alignment marks made using the measurement subsystem on another substrate to which the pattern has been applied during a previous lithographic step; and
store the second correction information in the data storage device.
6. The lithographic apparatus of claim 1 , wherein the controller is further configured to:
process measurements made after the substrate is loaded with measurements made in a previous lithographic step.
7. The lithographic apparatus of claim 1 , wherein:
the lithographic apparatus comprises at least two substrate supports; and
the controller is configured to:
perform patterning on another substrate using one of the at least two substrate supports; and
concurrently perform measurements of locations of alignment marks on the substrate using the other of the at least two substrate supports, respectively.
8. The lithographic apparatus of claim 1 , wherein the controller can be implemented by a data processing unit configured to execute a non-transitory computer program containing one or more sequences of machine-readable instructions.