Inspection method and apparatus

Patent metadata

Field	Value
Publication number	US-9360768-B2
Application number	US-201213482323-A
Country	US
Kind code	B2
Filing date	May 29, 2012
Priority date	Jun 21, 2011
Publication date	Jun 7, 2016
Grant date	Jun 7, 2016

Abstract

A method defines one or more monitoring target profiles, collects and stores initial calibration data of the metrology apparatus, compiling a library of spectra that would be observed from inspection of the monitoring target profiles using the metrology apparatus calibrated according to the initial calibration data. Some operations can be performed periodically, e.g., on a daily basis: obtaining current calibration data from the apparatus, modeling the effect of the current calibration data on the metrology apparatus operation, and using the result of the modeling and the contents of the library to determine any differences between one or more values of the initial calibration data and the current calibration data, and how these changes will be translated into changes in the measurement output for a given number of stacks and geometries.

First claim

What is claimed is:

1. A method of operating a metrology apparatus comprising:
defining one or more first target profiles of one or more targets;
storing initial calibration data of the metrology apparatus;
compiling a library of modeled spectra that would be observed from inspection of the one or more targets using the metrology apparatus calibrated according to the initial calibration data;
obtaining current calibration data of the metrology apparatus;
modeling one or more second target profiles of the one or more targets at least partially based on the current calibration data and the library of spectra;
determining any differences between one or more parameters of the one or more first target profiles and the one or more second target profiles; and
using any of the determined differences between the one or more parameters to determine a drift in the one or more parameters, such that subsequent measurement stability of the metrology apparatus is improved when subsequently taking measurements of a physical target with the metrology apparatus.

2. The method of claim 1 , wherein the compiling is performed using a model to determine each resultant spectra from the first target profiles.

3. The method of claim 1 , wherein:
the modeling comprises reconstructing the one or more second target profiles for one or more of the spectra compiled in the library, using the current calibration data; and
the determining comprises determining differences between each second target profile and its corresponding first target profile.

4. The method of claim 1 , wherein:
the modeling comprises using one or more of the first target profiles to determine further spectra that would be observed from inspection of the one or more target using the metrology apparatus calibrated according to the current calibration data; and
the determining comprises determining any differences between each of the further spectra determined in the modeling and its corresponding spectra in the library.

5. The method of claim 4 , wherein the determining any differences between each of the further spectra and its corresponding spectra in the library is performed by using the sensitivities of the model(s) used to obtain the spectra to translate the calculated differences into differences between the initial calibration data and the current calibration data.

6. The method of claim 1 , wherein the current calibration data is a subset of the initial calibration data.

7. The method of claim 6 , wherein the current calibration data comprises measurement data generated before each lot or wafer measurement.

8. A non-transitory computer readable medium coupled to a metrology apparatus, and having stored thereon computer-executable instructions, execution of which by a processing device causes the processing device to perform operations associated with the metrology apparatus, comprising:
defining one or more first target profiles of one or more targets;
storing initial calibration data of the metrology apparatus;
compiling a library of modeled spectra that would be observed from inspection of the one or more targets using the metrology apparatus calibrated according to the initial calibration data;
obtaining current calibration data of the metrology apparatus;
modeling one or more second target profiles of the one or more targets at least partially based on the current calibration data and the library of spectra;
determining any differences between one or more parameters of the one or more first target profiles and the one or more second target profiles; and
using any of the determined differences between the one or more parameters to determine a drift in the one or more parameters, such that subsequent measurement stability of the metrology apparatus is improved when subsequently taking measurements of a physical target with the metrology apparatus.

9. A metrology apparatus comprising:
a projection system configured to project a beam of radiation onto a target; and
a processing device configured to:
define a first target profile of the target;
store initial calibration data of the metrology apparatus;
compile a library of modeled spectra that would be observed from inspection of the target using the projection system of the metrology apparatus calibrated according to the initial calibration data;
obtain current calibration data of the metrology apparatus;
model a second target profile of the target at least partially based on the current calibration data and the library of spectra;
determine any differences between one or more parameters of the first target profile and the second target profile; and
use any of the determined differences between the one or more parameters to determine a drift in the one or more parameters, such that subsequent measurement stability of the metrology apparatus is improved when subsequently taking measurements of a physical target with the metrology apparatus.

10. The metrology apparatus of claim 9 , wherein the processing device is configured to compile a library of spectra using a model to determine each resultant spectra from the first target profile.

11. The metrology apparatus of claim 9 , wherein the processing device is configured to:
model the second target profile by reconstructing a target profile for the spectra compiled in the library, using the current calibration data; and
determine differences between each reconstructed target profile and its corresponding first target profile.

12. The metrology apparatus of claim 9 , wherein the processing device is further configured to:
use the first target profile to determine further spectra that would be observed from inspection of the target using the metrology apparatus calibrated according to the current calibration data; and
determine any differences between each of the further spectra and its corresponding spectra in the library.

13. The metrology apparatus of claim 12 , wherein the processor is configured to determine any differences between each of the further spectra and its corresponding spectra in the library by using the sensitivities of the model(s) used to obtain the spectra to translate the calculated differences into differences between the initial calibration data and the current calibration data.

14. The metrology apparatus of claim 9 , wherein the current calibration data is a subset of the initial calibration data.

15. The metrology apparatus of claim 14 , wherein the current calibration data comprises measurement data generated before each lot or wafer measurement.

16. The metrology apparatus of claim 9 , wherein the processor is configured to perform the obtaining, the modeling, and the determining every 1 to 7 days.

17. The metrology apparatus of claim 9 , wherein the processor is configured to obtain the current calibration data as a daily scheduled task.

Assignees

• Bottiglieri Gerardo
• Mc Namara Elliott Gerard
• Alvarez Sanchez Ruben
• Asml Netherlands Bv

Inventors

• Bottiglieri Gerardo
• Mc Namara Elliott Gerard
• Alvarez Sanchez Ruben

Classifications

• G03F7/70516

  Calibration of components of the microlithographic apparatus, e.g. light sources, addressable masks or detectors · CPC title

• G01N2021/95615

  with stored comparision signal · CPC title

• G03F7/705

  Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions · CPC title

• G03F7/70633

  Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching · CPC title

• G03F7/70625 Primary

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