Method of predicting performance of a lithographic apparatus, calibration of lithographic apparatus, device manufacturing method
Measurement data is obtained for calibration fields that have been exposed by a lithographic apparatus using different field layouts and exposure sequences. The measurement data is classified in subsets by scan direction, step direction, field size and other variables. The measurement data is indexed by a time value that varies through each exposure sequence. Time values within different exposure sequences can be related using a normalized time value based on the beginning and end of each exposure sequence. An inter-field performance model is calculated for each subset. An intra-field component of a performance model is calculated with time as a third dimension. The time-indexed performance model is used to determine intra-field corrections for a variety of product exposures having product layouts and product exposure sequences different to the calibration fields, based on time and other a variables of the product layout and product exposure sequence.
1. A method comprising:
providing first measurement data for a first plurality of fields that have been exposed by a lithographic apparatus on one or more substrates using a first exposure sequence;
providing further measurement data for one or more further pluralities of fields that have been exposed by the lithographic apparatus on one or more substrates, each of the one or more further pluralities of fields having been exposed using an exposure sequence different from the first exposure sequence;
generating, by a hardware computer system, a particular performance model based on both the first measurement data and the further measurement data; and
using, by the hardware computer system, the performance model to determine a set of data for at least a first plurality of product fields having a product exposure sequence,
wherein for generating the performance model the first measurement data and further measurement data are indexed at least partly on the basis of a time value that varies over each exposure sequence, and wherein the set of data for the product fields is generated at least partly by reference to a time value that varies over the product exposure sequence.
2. The method as claimed in claim 1 , wherein the time values for different exposure sequences are related via a time scale defined by reference to a beginning and an end of each exposure sequence.
3. The method as claimed in claim 1 , wherein the first measurement data and further measurement data are further indexed on the basis of a scan direction that varies between fields within each exposure sequence, and wherein the set of data for the product fields is generated at least partly by reference to a scan direction that varies within the product exposure sequence.
4. The method as claimed in claim 3 , wherein for each scan direction the performance model includes an intra-field component and the intra-field component is indexed by the time value.
5. The method as claimed in claim 1 , wherein the further measurement data includes data relating to a second plurality of fields having the same positions as the first plurality of fields but having a second exposure sequence different from the first exposure sequence.
6. The method as claimed in claim 5 , wherein the first exposure sequence and the second exposure sequence comprise different scan directions at field positions.
7. The method as claimed in claim 1 , wherein the first measurement data and further measurement data are further indexed on the basis of a step direction that varies between fields within each exposure sequence, and wherein the set of data for the product fields is generated at least partly by reference to a stepping direction that varies within the product exposure sequence.
8. The method as claimed in claim 1 , wherein the further measurement data includes data relating to one or more further pluralities of fields having positions on the substrate different than the positions of the first plurality of fields, and/or wherein the further measurement data includes data relating to one or more further pluralities of fields having a field size different than a field size of the first plurality of fields.
9. The method as claimed in claim 1 ,
wherein generating the performance model includes:
generating, based on the first measurement data and further measurement data, an inter-field component of the performance model, and
generating, based on a residual of the first measurement data and further measurement data after applying a correction based on the inter-field performance model, an intra-field component of the performance model; and/or
wherein generating the performance model includes:
generating, based on the first measurement data and further measurement data, an inter-field component of the performance model, wherein the inter-field component includes a dynamic inter-field component that is indexed by the time value.
10. The method as claimed in claim 9 , wherein different intra-field components are generated for fields exposed with different scan directions, and/or wherein different inter-field components are generated for fields exposed with different step directions.
11. The method as claimed in claim 1 , further comprising using the performance model to determine a set of data for at least a second plurality of second product fields having a second product exposure sequence and wherein the second product exposure sequence differs from the first product exposure sequence in field size and/or exposure speed.
12. The method as claimed in claim 1 , wherein a calibration pattern has been applied repeatedly to fields on the same substrate while applying a shift between repetitions, to obtain at least some of both the first measurement data and the further measurement data from the same substrate.
13. A method of calibrating a lithographic apparatus, the method comprising:
obtaining a performance model generated by the generating step of the method as claimed in claim 1 ;
using the performance model to determine a set of data for a plurality of product fields by the using step of the method as claimed in claim 1 ; and
based on the set of data for the first plurality of product fields supplying corrections to be used by the lithographic apparatus when applying product fields on a product substrate using the product exposure sequence.
14. A method comprising:
providing first measurement data for a first plurality of fields that have been exposed by a lithographic apparatus on one or more substrates using a first exposure sequence;
providing further measurement data for one or more further pluralities of fields that have been exposed by the lithographic apparatus on one or more substrates, each of the one or more further pluralities of fields having been exposed using an exposure sequence different from the first exposure sequence; and
calibrating, by a hardware computer system, a particular performance model based on both the first measurement data and the further measurement data,
wherein the performance model is configured to generate a set of data for at least a first plurality of product fields having a product exposure sequence, and
wherein for calibrating the performance model, the first measurement data and further measurement data are indexed at least partly on the basis of a time value that varies over each exposure sequence, and wherein the set of data for the product fields is generated at least partly by reference to a time value that varies over the product exposure sequence.
15. The method as claimed in claim 14 , wherein the time values for different exposure sequences are related via a time scale defined by reference to a beginning and an end of each exposure sequence.
16. The method as claimed in claim 14 , wherein the first measurement data and further measurement data are further indexed on the basis of a scan direction that varies between fields within each exposure sequence, and wherein the set of data for the product fields is generated at least partly by reference to a scan direction that varies within the product exposure sequence.
17. A non-transitory computer program product comprising machine readable instructions which, when run on a suitable processor system, cause the processor system to at least:
obtain first measurement data for a first plurality of fields that have been exposed by a lithographic apparatus on one or more substrates using a first exposure sequence;
obtain further measurement data for one or more further pluralities of fields that have been exposed by the lithographic apparatus on one or more substrates, each of the one or more further pluralities of fields having been exposed using an exposure sequence different from the first exposure sequence;
generate a particular performance model based on both the first measurement data and the further measurement data; and
use the performance model to determine a set of data for at least a first plurality of product fields having a product exposure sequence,
wherein for generation of the performance model the first measurement data and further measurement data are indexed at least partly on the basis of a time value that varies over each exposure sequence, and wherein the set of data for the product fields is generated at least partly by reference to a time value that varies over the product exposure sequence.
18. The computer program product as claimed in claim 17 , wherein the time values for different exposure sequences are related via a time scale defined by reference to a beginning and an end of each exposure sequence.
19. The computer program product as claimed in claim 17 , wherein the first measurement data and further measurement data are further indexed on the basis of a scan direction that varies between fields within each exposure sequence, and wherein the set of data for the product fields is generated at least partly by reference to a scan direction that varies within the product exposure sequence.
20. The computer program product as claimed in claim 17 , wherein the further measurement data includes data relating to a second plurality of fields having the same positions as the first plurality of fields but having a second exposure sequence different from the first exposure sequence.