Method of determining critical-dimension-related properties, inspection apparatus and device manufacturing method

Patent metadata

Field	Value
Publication number	US-10180628-B2
Application number	US-201414892176-A
Country	US
Kind code	B2
Filing date	May 23, 2014
Priority date	Jun 12, 2013
Publication date	Jan 15, 2019
Grant date	Jan 15, 2019

Abstract

A method of determining a critical-dimension-related property, such as critical dimension (CD) or exposure dose, includes illuminating each of a plurality of periodic targets having different respective critical dimension biases, measuring intensity of radiation scattered by the targets, recognizing and extracting each grating from the image, determining a differential signal, and determining the CD-related property based on the differential signal, the CD biases and knowledge that the differential signal approximates to zero at a 1:1 line-to-space ratio of such periodic targets. Use of the determined CD-related property to control a lithography apparatus in lithographic processing of subsequent substrates. In order to use just two CD biases, a calibration may use measurements on a “golden wafer” (i.e. a reference substrate) to determine the intensity gradient for each of the CD pairs, with known CDs. Alternatively, the calibration can be based upon simulation of the sensitivity of intensity gradient to CD.

First claim

The invention claimed is:

1. A method of determining a critical-dimension-related property of a structure produced by a lithographic process, the method comprising:
illuminating with radiation each of at least two periodic targets with different respective critical dimension biases;
measuring respective intensities of radiation scattered by the at least two targets;
determining a differential signal from the measured intensities; and
determining the critical-dimension-related property based on calculations using a value of the differential signal and using values of the at least two critical dimension biases, wherein the differential signal approximates to zero at a 1:1 line-to-space ratio of such periodic targets.

2. The method of claim 1 , wherein the measuring intensity of radiation comprises measuring intensity of at least one non-zero order of scattered radiation.

3. The method of claim 1 , wherein the illuminating comprises using at least two different polarization directions of illumination radiation with respect to a direction of periodicity of the periodic targets, the measuring intensity of radiation comprises measuring intensity of zeroth order scattered radiation for each of the polarization directions and the determining a differential signal from the measured intensities is based on a difference between measured intensity for the different polarization directions.

4. The method of claim 1 , wherein the illuminating comprises illuminating at least three targets with different respective critical dimension biases, the measuring intensity of radiation comprises measuring at least three respective intensities and the determining the critical-dimension-related property is based on calculations using values of the at least three critical dimension biases.

5. The method of claim 1 , further comprising a calibration to determine a response of the differential signal to the critical-dimension-related property by determining a differential signal from measured respective intensities of radiation scattered by at least two targets with known critical dimensions.

6. The method of claim 1 , further comprising a calibration to determine a response of the differential signal to the critical-dimension-related property by simulation of sensitivity of the differential signal to critical dimension.

7. A method of manufacturing devices wherein a device pattern is applied to a series of substrates using a lithographic process, the method including determining a critical-dimension-related property of a structure produced by the lithographic process using at least one of the substrates and using a method as claimed in claim 1 , and controlling the lithographic process for later substrates in accordance with the result of the method of determining the critical-dimension-related property.

8. An inspection apparatus to determine a critical-dimension-related property of a structure produced by a lithographic process, the inspection apparatus comprising:
an illumination system configured to illuminate with radiation each of at least two periodic targets with different respective critical dimension biases;
a detection system configured to measure respective intensities of radiation scattered by the at least two targets; and
a processor configured to determine a differential signal from the measured intensities and to determine the critical-dimension-related property based on calculations using a value of the differential signal and using values of the at least two critical dimension biases, wherein the differential signal approximates to zero at a 1:1line-to-space ratio of such periodic targets.

9. The inspection apparatus of claim 8 , wherein the detection system is configured to measure intensity of radiation by measuring intensity of at least one non-zero order of scattered radiation.

10. The inspection apparatus of claim 8 , wherein the illumination system is configured to use at least two different polarization directions of illumination radiation with respect to a direction of periodicity of the periodic targets, the detection system is configured to measure intensity of radiation by measuring intensity of zeroth order scattered radiation for each of the polarization directions and the processor is configured to determine a differential signal from the measured intensities based on a difference between measured intensity for the different polarization directions.

11. The inspection apparatus of claim 8 , wherein the illumination system is configured to illuminate at least three targets with different respective critical dimension biases, the detection system is configured to measure at least three respective intensities and the processor is configured to determine the critical-dimension-related property based on calculations using values of the at least three critical dimension biases.

12. The inspection apparatus of claim 8 , wherein the processor is configured to determine the critical-dimension-related property using a calibrated response of the differential signal to the critical-dimension-related property.

13. The inspection apparatus of claim 8 , wherein the processor is configured to determine the critical-dimension-related property using a simulated response of the differential signal to the critical-dimension-related property.

14. A non-transitory computer-readable medium comprising instructions configured to cause a processor to at least:
obtain a differential signal from measured respective intensities of radiation scattered by each of at least two targets having different respective critical dimension biases; and
determine a critical-dimension-related property of a structure produced by a lithographic process based on calculations using a value of the differential signal and using values of the at least two critical dimension biases, wherein the differential signal approximates to zero at a 1:1 line-to-space ratio of such periodic targets.

15. The non-transitory computer-readable medium of claim 14 , wherein the measured intensity of radiation is of at least one non-zero order of scattered radiation.

16. The non-transitory computer-readable medium of claim 14 , wherein the measured intensities are of zeroth order scattered radiation for each of at least two polarization directions of illumination radiation with respect to a direction of periodicity of the periodic targets and the differential signal is based on a difference between measured intensity for the different polarization directions.

17. The non-transitory computer-readable medium of claim 14 , wherein the measured intensities are of at least three targets with different respective critical dimension biases and the determination of the critical-dimension-related property is based on calculations using values of the at least three critical dimension biases.

18. The non-transitory computer-readable medium of claim 14 , wherein the instructions are further configured to determine the critical-dimension-related property using a calibration determined from a differential signal obtained from measured respective intensities of radiation scattered by at least two targets with known critical dimensions.

19. The non-transitory computer-readable medium of claim 14 , wherein the instructions are further configured to determine the critical-dimension-related property using a calibration determined by simulation of sensitivity of the differential signal to critical dimension.

20. The non-transitory computer-readable medium of claim 14 , wherein the instructions are further con

Assignees

• Asml Netherlands Bv

Inventors

• Cramer Hugo Augustinus Joseph
• Den Boef Arie Jeffrey
• Megens Henricus Johannes Lambertus
• Van Der Schaar Maurits
• Huang Te-Chih

Classifications

• G03F7/70625 Primary

  Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness · CPC title

• G03F7/70133 Primary

  Measurement of illumination distribution, in pupil plane or field plane · CPC title

• G03F7/70683

  Mark designs · CPC title