Model based measurement systems with improved electromagnetic solver performance
Methods and systems for solving measurement models of complex device structures with reduced computational effort are presented. In some embodiments, a measurement signal transformation model is employed to compute transformed measurement signals from coarse measurement signals. The transformed measurement signals more closely approximate a set of measured signals than the coarse measurement signals. However, the coarse set of measured signals are computed with less computational effort than would be required to directly compute measurement signals that closely approximate the set of measured signals. In other embodiments, a measurement signal transformation model is employed to compute transformed measurement signals from actual measured signals. The transformed measurement signals more closely approximate the coarse measurement signals than the actual measured signals. Transformed measurement signals are subsequently used for regression, library generation, or other analyses typically employed as part of an effort to characterize structural, material, and process parameters in semiconductor manufacturing.
1. A measurement system comprising:
an illumination source configured to provide an amount of illumination light to one or more metrology targets;
a detector configured to receive an amount of collected light from the one or more metrology targets in response to the amount of illumination light and generate a plurality of measured signals; and
one or more computing systems configured to:
receive the plurality of measured signals from the detector;
receive a plurality of coarse measurement signals generated by a first measurement model simulator, wherein the first measurement model simulator is configured to simulate a measurement of the one or more metrology targets by the measurement system;
transform the plurality of coarse measurement signals to a plurality of transformed measurement signals, wherein a difference between the plurality of transformed measurement signals and the plurality of measured signals is less than a difference between the plurality of coarse measurement signals and the plurality of measured signals; and
perform a regression analysis to estimate one or more parameters of interest of the one or more metrology targets based on a fitting of the transformed measurement signals to the measured signals.
2. The measurement system of claim 1 , wherein the transforming of the plurality of coarse measurement signals to the plurality of transformed measurement signals involves a measurement signal transformation model, and wherein the one or more computing systems are further configured to:
receive a plurality of measured signals associated with a plurality of Design Of Experiments (DOE) measurement samples for a particular measurement system configuration and range of parameters of interest;
receive a plurality of coarse measurement signals associated with the plurality of Design Of Experiments (DOE) measurement samples for the particular measurement system configuration and range of parameters of interest; and
train the measurement signal transformation model to transform the plurality of coarse measurement signals associated with the plurality of DOE measurement samples to the plurality of measured signals associated with the plurality of DOE measurement samples with a minimal error.
3. The measurement system of claim 1 , wherein the coarse measurement signals are associated a different measurement system configuration than the transformed measurement signals.
4. The measurement system of claim 1 , wherein the first measurement model simulator is a rigorous coupled wave analysis (RCWA) simulator.
5. The measurement system of claim 4 , wherein the plurality of coarse measurement signals are generated by the RCWA simulator with a reduced truncation order, a reduced number of slabs, a sparse numerical aperture (NA) sample set, or any combination thereof.
6. The measurement system of claim 5 , wherein a truncation order number and a truncation order sample set associated with a first portion of the plurality of coarse measurement signals is different from a truncation order number and a truncation order sample set associated with a second portion of the plurality of coarse measurement signals.
7. The measurement system of claim 6 , wherein the first portion of the plurality of coarse measurement signals is associated with a first range of wavelengths and the second portion of the plurality of coarse measurement signals is associated with a second range of wavelengths that is different from the first range of wavelengths.
8. The measurement system of claim 1 , wherein the coarse measurement signals are associated with multiple, different measurement system configurations.
9. The measurement system of claim 8 , wherein the multiple, different measurement system configurations include different measurement angles, different illumination angles, different measurement techniques, or any combination thereof.
10. The measurement system of claim 1 , wherein the transformed measurement signals include derivatives of the coarse measurement signals with respect to one or more parameters of interest, one or more measurement system parameters, or any combination thereof.
11. A measurement system comprising:
an illumination source configured to provide an amount of illumination light to one or more semiconductor structures;
a detector configured to receive an amount of collected light from the one or more semiconductor structures in response to the amount of illumination light and generate a plurality of measured signals associated with a measurement of the one or more semiconductor structures by the measurement system; and
a measurement signal transformation module comprising computer-readable instructions stored on a non-transitory, computer-readable medium, the computer-readable instructions comprising:
code for causing a computing system to receive a plurality of coarse measurement signals generated by a first measurement model simulator, wherein the first measurement model simulator is configured to simulate measurements of the one or more semiconductor structures by the measurement system;
code for causing the computing system to transform the plurality of coarse measurement signals to a plurality of transformed measurement signals, wherein a difference between the plurality of transformed measurement signals and the plurality of measured signals is less than a difference between the plurality of coarse measurement signals and the plurality of measured signals; and
code for causing the computing system to estimate one or more parameters of interest associated with the one or more semiconductor structures based on a fitting of the transformed measurement signals to the measured signals.
12. The measurement system of claim 11 , the measurement signal transformation module further comprising computer-readable instructions stored on the non-transitory, computer-readable medium, the computer-readable instructions further comprising:
code for causing the computing system to receive the plurality of measured signals associated with the measurements of the one or more semiconductor structures by the one or more measurement systems; and
code for causing the computing system to perform a regression analysis to estimate the one or more parameters of interest of the one or more semiconductor structures.
13. The measurement system of claim 11 , wherein the plurality of measured signals are associated with spectroscopic measurements of the one or more semiconductor structures by the measurement system.
14. The measurement system of claim 11 , wherein the plurality of measured signals are generated by a second measurement model simulator that is different from the first measurement model simulator.
15. The measurement system of claim 11 , wherein the coarse measurement signals are associated a different measurement system configuration than the transformed measurement signals.
16. The measurement system of claim 11 , wherein the transforming of the plurality of coarse measurement signals to the plurality of transformed measurement signals involves a measurement signal transformation model, the measurement signal transformation module further comprising computer-readable instructions stored on the non-transitory, computer-readable medium, the computer-readable instructions comprising:
code for causing the computing system to receive a plurality of measured signals associated with a plurality of Design Of Experiments (DOE) measurement samples for a particular measurement system configuration and range of parameters of interest;
code for causing the computing system to receive a plurality of coarse measurement signals associated with the plurality of Design Of Experiments (DOE) measurement samples for the particular measurement system configuration and range of parameters of interest; and
code for causing the computing system to train the measurement signal transformation model to transform the plurality of coarse measurement signals associated with the plurality of DOE measurement samples to the plurality of measured signals associated with the plurality of DOE measurement samples with a minimal error.
17. A measurement system comprising:
an illumination source configured to provide an amount of illumination light to one or more semiconductor structures;
a detector configured to receive an amount of collected light from the one or more semiconductor structures in response to the amount of illumination light and generate a plurality of measured signals associated with a measurement of the one or more semiconductor structures by the measurement system; and
a measurement signal transformation module comprising computer-readable instructions stored on a non-transitory, computer-readable medium, the computer-readable instructions comprising:
code for causing a computing system to receive the plurality of measured signals;
code for causing the computing system to transform the plurality of measured signals to a plurality of transformed measurement signals, wherein a difference between the plurality of transformed measurement signals and the plurality of measured signals is less than a difference between a plurality of coarse measurement signals and the plurality of measured signals, wherein the plurality of coarse measurement signals are generated by a measurement model simulator; and
code for causing the computing system to estimate one or more parameters of interest of the one or more semiconductor structures based on a fitting of the transformed measurement signals to the coarse measurement signals.
18. The measurement system of claim 17 , the measurement signal transformation module further comprising computer-readable instructions stored on the non-transitory, computer-readable medium, the computer-readable instructions further comprising:
code for causing the computing system to receive the plurality of coarse measurement signals generated by the measurement model simulator, wherein the measurement model simulator is configured to simulate the measurements of the one or more semiconductor structures by the measurement system, wherein the estimating of the one or more parameters of interest involves a regression analysis.
19. The measurement system of claim 17 , wherein the measured signals are associated a different measurement system configuration than the transformed measurement signals.
20. The measurement system of claim 17 , wherein the transforming of the plurality of coarse measurement signals to the plurality of transformed measurement signals involves a measurement signal transformation model, the measurement signal transformation module further comprising computer-readable instructions stored on the non-transitory, computer-readable medium, the computer-readable instructions comprising:
code for causing the computing system to receive a plurality of measured signals associated with a plurality of Design Of Experiments (DOE) measurement samples for a particular measurement system configuration and range of parameters of interest;
code for causing the computing system to receive a plurality of coarse measurement signals associated with the plurality of Design Of Experiments (DOE) measurement samples for the particular measurement system configuration and range of parameters of interest; and
code for causing the computing system to train the measurement signal transformation model to transform the plurality of measured signals associated with the plurality of DOE measurement samples to the plurality of coarse measurement signals associated with the plurality of DOE measurement samples with a minimal error.