Lithography Mark Position Evaluation via Signal Frequency Variation
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Solution Overview
Problem
In lithography apparatuses, accurately positioning substrates with high precision is challenging due to measurement errors caused by substrate manufacturing processes, such as resist thickness non-uniformity, which complicates determining a common measurement condition for multiple marks.
Innovation Solution
An evaluation method that generates multiple signals from a mark signal by altering its frequency components, estimating the mark's position from these signals, and using the variation in estimated positions as an index to evaluate the robustness of the measurement condition, allowing for the determination of a robust measurement condition applicable to multiple marks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a measurement condition is optimized for one mark, then measurement precision for that mark is improved, but the measurement condition becomes less applicable to other marks with different characteristics
Solution Approach 1:
The patent changes the parameter of measurement conditions (such as illumination wavelength, numerical aperture, or focus position) to find optimal settings that minimize measurement errors for marks with different characteristics. By systematically varying these parameters and evaluating measurement error variations, the method identifies conditions that achieve high precision across multiple mark types.
Solution Approach 2:
The patent performs preliminary evaluation of measurement conditions by calculating or measuring measurement errors for different marks under various conditions before actual measurement. This preliminary assessment allows selection of optimal measurement conditions that will work robustly for multiple marks, avoiding the need to optimize for each mark individually during actual measurement.
2Measurement precision
If measurement conditions are individually determined for each mark, then measurement precision for each mark is improved, but the process complexity increases significantly
Solution Approach 1:
The patent merges the measurement condition determination process into a unified evaluation method that simultaneously considers multiple marks. Instead of separately determining conditions for each mark, the method combines information from multiple marks to evaluate and select measurement conditions, thereby simplifying the overall process while maintaining high measurement precision.
Solution Approach 2:
The patent creates a universal measurement condition evaluation method that can be applied to multiple marks with different characteristics using the same procedure. This universal approach allows a single set of measurement conditions to be optimized for use across various mark types, reducing process complexity while maintaining adaptability.
3Adaptability or versatility
If measurement conditions are made robust for multiple marks, then adaptability is improved, but measurement precision for individual marks may be compromised
Solution Approach 1:
The patent employs feedback mechanisms where measurement errors are evaluated and used to adjust and optimize measurement conditions. By continuously monitoring measurement error variations across different marks and feeding this information back into the condition selection process, the method refines measurement conditions to achieve both robustness and high precision simultaneously.
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 method effectively reduces measurement errors and simplifies the process of determining a robust measurement condition, enhancing the accuracy and efficiency of substrate positioning in lithography processes.
Implementation Method 1
obtaining a mark signal representing an intensity distribution of reflected light by detecting the reflected light from the mark
Data Source
AI summary
The present invention provides an evaluation method of evaluating a measurement condition of a position of a mark formed on a substrate, the method comprising: obtaining a mark signal representing an intensity distribution of reflected light by detecting the reflected light from the mark under the measurement condition; generating a plurality of signals from the mark signal by changing a first signal component of a first frequency included in the mark signal obtained in the obtaining; and estimating a position of the mark from each of the plurality of signals obtained in the generating, and obtaining a variation in estimated position of the mark as an evaluation index of the measurement condition.