Lithography Metrology Correction Model for Overlay Accuracy
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Solution Overview
Problem
Current metrology methods in lithographic processes require repeating measurements at different illumination settings, leading to a throughput penalty, as targets respond differently to various illumination settings, affecting measurement accuracy and efficiency.
Innovation Solution
A method and apparatus that measure a structure using a first illumination setting and apply a correction model to estimate measurements for a second setting, allowing for accurate measurement of asymmetry and overlay without the need for repeated measurements at each setting, using a computer program product and lithographic system to implement this method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If measurements are repeated at different illumination settings to improve measurement accuracy, then measurement precision is improved, but productivity deteriorates due to throughput penalty
Solution Approach 1:
The patent applies preliminary action by performing measurements at multiple illumination settings during a calibration phase to establish correction models beforehand. These pre-established models are then used to correct single-setting measurements during production, eliminating the need for repeated measurements at each illumination setting while maintaining measurement accuracy.
Solution Approach 2:
The patent uses copying by creating correction models that represent the relationship between different illumination settings based on calibration measurements. These models act as copies or surrogates that allow accurate measurement results to be obtained from single-setting measurements without actually performing multiple measurements, thus preserving throughput.
2Measurement precision
If multiple illumination settings are used to reduce dependency on wavelength, then measurement precision is improved, but loss of time increases due to repeated measurements
Solution Approach 1:
The calibration phase performs measurements at multiple illumination settings in advance to establish correction models. During production, these pre-established models enable accurate measurements using only a single illumination setting, dramatically reducing measurement time while maintaining accuracy by compensating for wavelength dependency through the correction models.
3Productivity
If a single illumination setting is used for measurement, then productivity is improved, but measurement precision deteriorates due to wavelength dependency
Solution Approach 1:
The patent applies parameter changes by using correction models that account for variations in illumination settings (wavelength, polarization, incident angle). These models enable accurate measurement results to be obtained from single-setting measurements by mathematically compensating for the effects of wavelength dependency and other illumination parameter variations.
Solution Approach 2:
The correction models serve as intermediaries between the single illumination setting measurement and the desired multi-setting measurement accuracy. The models mediate by translating single-setting measurements into accurate results that would otherwise require multiple illumination settings, thus preserving both throughput and precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables accurate measurement of asymmetry and overlay with reduced throughput impact by using a correction model to estimate measurements across different illumination settings, improving measurement efficiency and accuracy.
Implementation Method 1
These devices direct a beam of radiation onto a target and measure one or more properties of the scattered radiation... to obtain a diffraction 'spectrum' from which a property of interest of the target can be determined
Implementation Method 2
These devices direct a beam of radiation onto a target and measure one or more properties of the scattered radiation—e.g., intensity at a single angle of reflection as a function of wavelength; intensity at one or more wavelengths as a function of reflected angle; or polarization as a function of reflected angle
Data Source
AI summary
A method of measuring a parameter of interest relating to a structure formed by a process on a substrate, and associated apparatuses. The method includes measuring the structure with measurement radiation including a first illumination acquisition setting (determining one or more selected from: a wavelength, a polarization or an incident angle of the measurement radiation) to obtain a first measurement value for the structure. The method further includes estimating, by applying a correction model to the first measurement value, at least a second measurement value for the structure corresponding to measurement of the structure with a second illumination acquisition setting different from the first illumination acquisition setting.