Metrology Recipe Selection for Overlay Measurement
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Solution Overview
Problem
Existing metrology techniques in lithographic processes face inaccuracies in overlay measurement due to structural asymmetry in periodic structures, which are not distinguished from overlay errors, leading to unreliable measurements.
Innovation Solution
A method involving the evaluation and selection of substrate measurement recipes based on stack sensitivity, overlay sensitivity, and robustness indicators to optimize metrology target design and measurement parameters, ensuring accurate and robust overlay measurements by distinguishing structural asymmetry from overlay errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing metrology techniques are used to measure overlay, then measurement speed and simplicity are maintained, but measurement precision deteriorates due to inability to distinguish structural asymmetry from overlay errors
Solution Approach 1:
The measurement process is segmented into multiple evaluation steps: first evaluating measurement recipes based on stack sensitivity criteria, then evaluating based on overlay sensitivity criteria, and finally selecting recipes that meet both criteria. This segmentation allows systematic separation of structural asymmetry effects from overlay measurement, improving precision without excessive complexity
Solution Approach 2:
The patent performs preliminary evaluation of measurement recipes against stack sensitivity and overlay sensitivity criteria before actual overlay measurement. By pre-evaluating and selecting appropriate measurement recipes, the system prepares the measurement process in advance to distinguish structural asymmetry from overlay errors, improving measurement precision
2Reliability
If measurement recipes are selected without evaluating stack sensitivity, then ease of operation is maintained, but reliability deteriorates due to unreliable overlay measurements
Solution Approach 1:
The patent implements a feedback mechanism where measurement recipes are evaluated based on their stack sensitivity and overlay sensitivity characteristics. The evaluation results feed back into the recipe selection process, ensuring that only recipes meeting both criteria are selected. This feedback loop improves reliability while maintaining ease of operation through automated evaluation
Solution Approach 2:
The patent changes the selection criteria parameters from simple ease-of-use to multi-criteria evaluation including stack sensitivity and overlay sensitivity. By adjusting these evaluation parameters, the system achieves reliable measurements while maintaining operational ease through systematic recipe evaluation and selection
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 robustness of overlay measurements by isolating structural asymmetry effects, providing reliable process control and verification in lithographic processes.
Implementation Method 1
These devices direct a beam of radiation onto a target and measure one or more properties of the redirected (e.g., 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—to obtain a '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 redirected (e.g., scattered) radiation—e.g., intensity at a single angle of reflection as a function of wavelength
Data Source
AI summary
A method including evaluating a plurality of substrate measurement recipes for measurement of a metrology target processed using a patterning process, against stack sensitivity and overlay sensitivity, and selecting one or more substrate measurement recipes from the plurality of substrate measurement recipes that have a value of the stack sensitivity that meets or crosses a threshold and that have a value of the overlay sensitivity within a certain finite range from a maximum or minimum value of the overlay sensitivity.