Metrology Mark Aberration Sensitivity Matching
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Solution Overview
Problem
In lithographic processes, metrology targets and device patterns often have mismatched aberration sensitivities, leading to irregularities in printed patterns due to different responses to optical parameter adjustments, which complicates the reproduction of intended designs on substrates.
Innovation Solution
A method is introduced to optimize metrology targets by matching their aberration sensitivity with that of device patterns, involving the computation of aberration sensitivity differences and the use of cost functions to iteratively adjust the metrology targets, such as modifying dimensions or adding assist features, to minimize sensitivity differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metrology targets and device patterns are designed with different aberration sensitivities to serve their respective functions, then each can be optimized for its specific purpose, but the mismatched sensitivities cause irregularities in printed patterns and complicate design reproduction
Solution Approach 1:
The patent applies parameter changes by adjusting the geometric parameters of the metrology target (such as ring radius, line width, spacing) to modify its aberration sensitivity characteristics. This allows the metrology target's sensitivity to be tuned to match that of the device pattern, thereby resolving the contradiction between functional optimization and pattern reproduction fidelity
Solution Approach 2:
The patent introduces a dynamic optimization process where the metrology target design is iteratively adjusted based on calculated aberration sensitivity differences. The design parameters are dynamically modified to achieve matching sensitivity, enabling the system to adapt to specific optical conditions while maintaining consistent performance across both metrology and device patterns
2Manufacturing precision
If the aberration sensitivity of metrology targets is adjusted to match device patterns, then pattern reproduction fidelity improves, but additional design and optimization steps are required
Solution Approach 1:
The patent applies preliminary action by calculating the aberration sensitivity of the device pattern in advance and using this information to guide the design of the metrology target. The sensitivity matching is performed during the design phase before manufacturing, which simplifies the overall process despite the additional optimization step
Solution Approach 2:
The patent implements a feedback mechanism where the aberration sensitivity difference between the metrology target and device pattern is calculated and used to iteratively refine the metrology target design. This closed-loop optimization process systematically reduces the sensitivity mismatch while providing clear guidance for design adjustments
Data Source
AI summary
Generating a design (e.g., a metrology mark or a device pattern to be printed on a substrate) that is optimized for aberration sensitivity related to an optical system of a lithography system. A metrology mark (e.g., a transmission image sensor (TIS) mark) is optimized for a given device pattern by matching the aberration sensitivity of the metrology mark with the aberration sensitivity of the device pattern. A cost function that includes the aberration sensitivity difference between the metrology mark and the device pattern is evaluated based on an imaging characteristic response (e.g., a critical dimension (CD) response to focus) obtained from a simulation model that simulates lithography. The cost function is evaluated by modifying the metrology mark until the cost function is minimized and an optimized metrology mark is output when the cost function is minimized.