Method and apparatus for measuring asymmetry of a microstructure, position measuring method, position measuring apparatus, lithographic apparatus and device manufacturing method

Patent metadata

Field	Value
Publication number	US-9939742-B2
Application number	US-201314427942-A
Country	US
Kind code	B2
Filing date	Nov 4, 2013
Priority date	Nov 5, 2012
Publication date	Apr 10, 2018
Grant date	Apr 10, 2018

Abstract

A lithographic apparatus includes a sensor, such as an alignment sensor including a self-referencing interferometer, configured to determine the position of an alignment target including a periodic structure. An illumination optical system focuses radiation of different colors and polarizations into a spot which scans the structure. Multiple position-dependent signals are detected and processed to obtain multiple candidate position measurements. Asymmetry of the structure is calculated by comparing the multiple position-dependent signals. The asymmetry measurement is used to improve accuracy of the position read by the sensor. Additional information on asymmetry may be obtained by an asymmetry sensor receiving a share of positive and negative orders of radiation diffracted by the periodic structure to produce a measurement of asymmetry in the periodic structure.

First claim

The invention claimed is:

1. A method of measuring a geometric property, other than a position, of a structure, the method comprising:
illuminating the structure with radiation and detecting radiation diffracted by the structure using a detector;
processing signals representing the diffracted radiation to obtain a plurality of results related to the position of the structure, each result having the same form but being influenced in a different way by a variation in the property; and
calculating a measurement of the property of the structure that is at least partially based on a difference observed among the plurality of results, wherein the calculating the measurement of the property uses the difference in combination with another result obtained using radiation diffracted by the structure, the other result not related to the position of the structure.

2. The method of claim 1 , wherein the plurality of results includes results based on illumination and detection of radiation at different wavelengths.

3. The method of claim 1 , wherein the plurality of results includes results based on illumination and detection of radiation at different polarizations.

4. The method of claim 1 , wherein the plurality of results includes results based on different spatial frequencies within a position-dependent signal received by the detector.

5. The method of claim 4 , wherein the structure has a form that is substantially periodic in one or more directions, and the different spatial frequencies correspond to different orders of diffraction by the periodic structure.

6. The method of claim 1 , wherein the other result is obtained using another detector processing a different portion of the radiation diffracted by the structure at the same time as the detecting the radiation diffracted by the structure using the detector.

7. The method of claim 1 , wherein the other result includes a result obtained from the same signals as the results related to the position of the structure.

8. The method of claim 1 , wherein the property is an asymmetry related parameter of the structure.

9. A method of measuring a position of a periodic structure, the method comprising:
illuminating the structure with radiation and detecting radiation diffracted by the structure using a detector;
processing signals representing the diffracted radiation to obtain a plurality of results related to the position of the structure, each result having the same form but being influenced in a different way by a variation in a geometric property, other than the position, of the structure;
calculating a measurement of the property of the structure that is at least partially based on a difference observed among the plurality of results; and
calculating a measurement of the position of the structure using one or more of the plurality of results corrected in accordance with the measurement of the property.

10. The method of claim 9 , wherein calculating the measurement of the position comprises applying corrections to two or more of the plurality of the results using the measurement of the property, followed by calculating the position measurement using one or more of the corrected results.

11. The method of claim 9 , wherein calculating the measurement of the position comprises calculating a quality measure for each of the plurality of results and using the quality measures to determine to what degree each result contributes to the position measurement.

12. A method of manufacturing devices wherein a device pattern is applied to a substrate using a lithographic process, the method including positioning the applied pattern by reference to a measured position of a periodic structure formed on the substrate, the measured position obtained by the method of claim 9 .

13. The method of claim 9 , wherein the plurality of results includes results based on illumination and detection of radiation at different wavelengths.

14. The method of claim 9 , wherein the plurality of results includes results based on illumination and detection of radiation at different polarizations.

15. The method of claim 9 , wherein the plurality of results includes results based on different spatial frequencies within a position-dependent signal received by the detector.

16. The method of claim 15 , wherein the different spatial frequencies correspond to different orders of diffraction by the periodic structure.

17. The method of claim 9 , wherein the calculating the measurement of the property uses the difference in combination with another result obtained using radiation diffracted by the structure, but not related to the position of the structure.

18. The method of claim 17 , wherein the other result is obtained using another detector processing a different portion of the radiation diffracted by the structure at the same time as the detecting the radiation diffracted by the structure using the detector.

19. The method of claim 17 , wherein the other result includes a result obtained from the same signals as the results related to the position of the structure.

20. The method of claim 9 , wherein the property is an asymmetry related parameter of the structure.

21. A lithographic apparatus comprising:
a patterning subsystem configured to transfer a pattern to a substrate;
a measuring subsystem configured to measure a position of the substrate in relation to the patterning subsystem,
wherein the patterning subsystem is arranged to use the position measured by the measuring subsystem to apply the pattern at a desired position on the substrate, and
wherein the measuring subsystem is configured to measure the position of the substrate using a periodic structure on the substrate and measure the position of the periodic structure by:
illuminating the periodic structure with radiation and detecting radiation diffracted by the periodic structure using a detector;
processing signals representing the diffracted radiation to obtain a plurality of results related to a position of the periodic structure, each result having the same form but being influenced in a different way by a variation in a geometric property, other than the position, of the structure;
calculating a measurement of the property of the periodic structure that is at least partially based on a difference observed among the plurality of results; and
calculating a measurement of the position of the periodic structure using one or more of the plurality of results corrected in accordance with the measurement of the property.

22. The apparatus of claim 21 , wherein the property is an asymmetry related parameter of the structure.

23. An apparatus to measure a position of a structure, the apparatus comprising:
a detecting arrangement configured to detect radiation diffracted by the structure using a detector;
a processing arrangement configured to process signals representing the diffracted radiation to obtain a plurality of results related to a position of the structure, each result having the same form but being influenced in a different way by variation in a geometric property, other than the position, of the structure;
a calculating arrangement configured to calculate a position of the structure using one or more of the results obtained by the processing arrangement,
wherein the calculating arrangement is configured to include a correction in the calculated position in accordance with a measurement of the property of the structure, and wherein the calculating arrangement is configured

Assignees

• Asml Netherlands Bv

Inventors

• Tinnemans Patricius Aloysius Jacobus
• Den Boef Arie Jeffrey
• Mathijssen Simon Gijsbert Josephus

Classifications

• G03F9/7088

  Alignment mark detection, e.g. TTR, TTL, off-axis detection, array detector, video detection · CPC title

• G03F9/7069 Primary

  Alignment mark illumination, e.g. darkfield, dual focus · CPC title