Patterning Process Parameter Metrology via Wavelength Weighting
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Solution Overview
Problem
Current methods for determining patterning process parameters, such as overlay in lithographic processes, face challenges in accuracy due to feature asymmetry effects like structural asymmetry and stack differences, leading to unreliable measurements and noise in multi-wavelength techniques.
Innovation Solution
A method involving the calculation of a combined measurement for patterning process parameters using both single-wavelength and multiple-wavelength data, where the influence of structural asymmetry is accounted for by determining a measure of structural asymmetry and adjusting the weighting of single-wavelength and multiple-wavelength measurements accordingly, to improve robustness and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-wavelength measurements are used to improve robustness against feature asymmetry, then reliability of measurement is improved, but measurement precision deteriorates due to increased noise
Solution Approach 1:
The patent changes the wavelength parameter of the measurement radiation to perform multiple measurements at different wavelengths. By analyzing the variation of measurement results across different wavelengths, the system can distinguish between genuine overlay signals and noise caused by feature asymmetry, thereby improving reliability while managing precision through statistical analysis of the wavelength-dependent responses.
2Measurement precision
If single-wavelength measurements are used to maintain measurement reproducibility, then measurement precision is improved, but reliability deteriorates due to sensitivity to feature asymmetry
Solution Approach 1:
The patent introduces wavelength as a varying parameter to perform measurements at multiple wavelengths. This allows the system to maintain the reproducibility benefits of single-wavelength measurements while compensating for feature asymmetry sensitivity by comparing results across different wavelengths, where asymmetry effects manifest differently and can be identified and corrected.
3Productivity
If measurements are performed frequently for process control, then productivity is improved, but measurement precision deteriorates due to accumulation of noise
Solution Approach 1:
The patent performs preliminary measurements at multiple wavelengths before final process control decisions are made. This preliminary multi-wavelength characterization allows the system to establish baseline responses and identify asymmetry patterns, enabling faster subsequent measurements with reduced noise accumulation while maintaining high productivity through optimized measurement sequences.
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 enhances the accuracy and reproducibility of patterning process parameter measurements by balancing the benefits of single-wavelength reproducibility and multiple-wavelength robustness, specifically addressing feature asymmetry impacts and reducing measurement noise.
Implementation Method 1
A further technique is involves having the zeroth order of diffraction (corresponding to a specular reflection) blocked, and only higher orders are processed
Implementation Method 2
These devices direct a beam of radiation onto a target and measure one or more properties of the redirected (e.g., scattered) radiation
Data Source
AI summary
A method to determine a patterning process parameter, the method comprising: for a target, calculating a first value for an intermediate parameter from data obtained by illuminating the target with radiation comprising a central wavelength; for the target, calculating a second value for the intermediate parameter from data obtained by illuminating the target with radiation comprising two different central wavelengths; and calculating a combined measurement for the patterning process parameter based on the first and second values for the intermediate parameter.