Lithography Target Selection Using Preliminary Optical Measurements
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Solution Overview
Problem
Existing lithography methods face challenges in maintaining high measurement accuracy due to changes in substrate characteristics, which affect the intensity and quality of measurement signals from marks on the substrate, leading to reduced alignment and overlay accuracy.
Innovation Solution
A measuring method that involves performing preliminary measurements multiple times while varying measurement parameters, analyzing the relationship between parameter values and signal information, and determining the optimal targets for main measurements based on this relationship to improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If measurement is performed on marks formed on substrates with changing characteristics, then measurement speed and productivity are maintained, but measurement accuracy deteriorates due to signal intensity and quality degradation
Solution Approach 1:
The patent performs preliminary measurements on multiple candidate marks before selecting the optimal measurement target. By acquiring relationship information between mark characteristics and measurement signals in advance, the system can quickly identify suitable marks during actual measurement without trial-and-error, thus maintaining high productivity while ensuring measurement accuracy through pre-validated mark selection criteria
Solution Approach 2:
The patent establishes a feedback mechanism where measurement results and signal quality information are continuously monitored. Based on the acquired relationship information from preliminary measurements, the system adjusts mark selection and measurement parameters in real-time, creating a closed-loop control system that maintains measurement accuracy despite substrate characteristic changes while preserving measurement speed through intelligent adaptation
2Productivity
If measurement parameters are kept fixed for efficient measurement, then productivity is maintained, but measurement accuracy deteriorates when substrate characteristics change
Solution Approach 1:
The patent implements dynamic measurement parameter selection based on acquired relationship information. Instead of using fixed parameters, the system adapts measurement parameters according to the specific mark characteristics and substrate conditions identified through preliminary measurements, enabling efficient measurements that maintain high accuracy across varying substrate characteristics
Solution Approach 2:
The patent systematically varies measurement parameters during preliminary measurements to establish relationships between parameters and measurement quality. This pre-characterization of parameter effects allows the system to quickly select optimal parameters for each measurement scenario, maintaining both efficiency and accuracy without requiring extensive trial-and-error during production measurements
3Measurement precision
If multiple measurement parameters are tested to find optimal conditions, then measurement accuracy is improved, but measurement time and complexity increase
Solution Approach 1:
The patent performs comprehensive parameter testing and relationship acquisition during a preliminary measurement phase. By investing time upfront to establish the relationships between measurement parameters and mark characteristics, the system creates a knowledge base that enables rapid, accurate measurements in subsequent operations, effectively trading initial time investment for long-term measurement efficiency and accuracy
Solution Approach 2:
The patent performs measurements on multiple candidate marks with varying parameters during the preliminary phase, which may seem excessive compared to measuring just one mark. However, this excessive action generates comprehensive relationship information that significantly reduces the time and complexity of subsequent measurements, as the optimal parameters and marks are pre-identified without requiring extensive search during production measurements
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 allows for accurate determination of measurement processing conditions, reducing measurement errors associated with substrate changes and ensuring precise alignment and overlay accuracy in lithography processes.
Implementation Method 1
signal information obtained by detecting, using measurement light, a plurality of targets formed on a substrate
Data Source
AI summary
A measuring method includes performing preliminary measurement for obtaining signal information obtained by detecting, using measurement light, a plurality of targets formed on a substrate a plurality of times while changing a parameter value of a measurement parameter, acquiring a relationship between the parameter value and the signal information based on results of the preliminary measurement performed the plurality of times, determining a target for which main measurement should be performed, in the plurality of targets, based on the acquired relationship, and performing the main measurement for the determined target.