Metrology system, lithographic apparatus, and calibration method
A lithographic apparatus includes an illumination system to produce a beam of radiation, a support to support a patterning device to impart a pattern on the beam, a projection system to project the patterned beam onto a substrate, and a metrology system that includes a radiation source to generate radiation, an optical element to direct the radiation toward a target, a detector to receive a first and second radiation scattered by the target and produce a first and second measurement respectively based on the received first and second radiation, and a controller. The controller determines a correction for the first measurement, an error between the correction for the first measurement and the first measurement, and a correction for the second measurement based on the correction for the first measurement, the second measurement, and the error. The lithographic apparatus uses the correction to adjust a position of a substrate.
1. A lithographic apparatus comprising:
an illumination system configured to illuminate a pattern of a patterning device;
a projection system configured to project an image of the pattern onto a substrate; and
a metrology system comprising:
a radiation source configured to generate radiation;
an optical element configured to direct the radiation toward a target;
a detector configured to receive a first radiation and a second radiation scattered by the target and to produce a corresponding first and a second measurement of the target, respectively, based on the received first and second radiation, wherein the second radiation immediately succeeds the first radiation; and
a controller configured to:
determine a first correction value associated with the first measurement,
determine an error between the first correction value and the first measurement, and
determine a second correction value associated with the second measurement based on the first correction value, the second measurement, and the error, whereby the lithographic apparatus uses the second correction value in a subsequent lithographic process to adjust a position of the substrate.
2. The lithographic apparatus of claim 1 , wherein the error is the difference between the first correction value and the first measurement.
3. The lithographic apparatus of claim 1 , wherein the second correction value is further based on the second measurement combined with the first correction value and a difference with the error.
4. The lithographic apparatus of claim 1 , wherein the second correction value is further based on a first coefficient to modify the first correction value and the second measurement, and on a second coefficient to modify the error.
5. The lithographic apparatus of claim 1 , further comprising a substrate stage, wherein the target is a fiducial of the substrate stage.
6. The lithographic apparatus of claim 1 , wherein the second correction value offsets a drift of the metrology system.
7. The lithographic apparatus of claim 1 , wherein the second correction value is applied to a subsequent measurement of a target on the substrate.
8. The lithographic apparatus of claim 4 , wherein the first coefficient is based on a delay constant.
9. A metrology system comprising:
a radiation source configured to generate radiation;
an optical element configured to direct the radiation toward a target;
a detector configured to receive a first radiation and a second radiation scattered by the target and to produce a corresponding first and a second measurement of the target, respectively, based on the received first and second radiation, wherein the second radiation immediately succeeds the first radiation; and
a controller configured to:
determine a first correction value associated with the first measurement,
determine an error between the first correction value for and the first measurement, and
determine a second correction value associated with the second measurement based on the first correction value, the second measurement, and the error, whereby the lithographic apparatus uses the second correction value in a subsequent lithographic process to adjust a position of the substrate.
10. The metrology system of claim 9 , wherein the error is the difference between the first correction value for the first measurement and the first measurement.
11. The metrology system of claim 9 , wherein the second correction value is further based on the second measurement combined with the first correction value and a difference with the error.
12. The metrology system of claim 9 , wherein the second correction value is further based on a first coefficient to modify the first correction value and the second measurement, and on a second coefficient to modify the error.
13. The metrology system of claim 9 , further comprising a substrate stage, wherein the target is a fiducial of the substrate stage.
14. The metrology system of claim 9 , wherein the second correction value offsets a drift of the metrology system.
15. The metrology system of claim 9 , wherein the second correction value for the second measurement is applied to a subsequent measurement of a target on the substrate.
16. The metrology system of claim 12 , wherein the first coefficient is based on a delay constant.