Diagnostic Targets for Runtime EUV Mask Inspection Calibration
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Solution Overview
Problem
Existing actinic patterned mask inspection (APMI) tools face challenges in maintaining consistent image quality over time due to drifts in critical imaging metrics such as EUV illumination pupil, focus, and wavefront error, necessitating effective runtime diagnostics that are EUV-specific, minimally intrusive, and performed at appropriate frequencies.
Innovation Solution
Fabricating diagnostic samples into diagnostic targets using established fabrication processes, dicing them to meet quality standards, and integrating them proximate to the process tool for periodic EUV-specific measurements, including EUV reticle-based targets with known performance, to emulate EUV stack interactions and provide accurate system health checks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If runtime diagnostics are implemented to monitor EUV imaging metrics, then system image quality consistency is improved, but inspection overhead time increases
Solution Approach 1:
The diagnostic sample is segmented into multiple individual diagnostic targets through dicing, allowing parallel measurement of multiple EUV imaging metrics (EUV-P, EUV-F, EUV-WFE) simultaneously, thereby reducing total inspection time while maintaining comprehensive monitoring
Solution Approach 2:
Diagnostic targets are fabricated in advance using the same EUV fabrication processes as production reticles, with pre-defined patterns optimized for specific EUV imaging metric measurements, enabling ready-to-use calibration targets that minimize runtime measurement overhead
2Measurement precision
If EUV-specific diagnostic targets are fabricated using established EUV fabrication processes, then measurement accuracy for EUV metrics is improved, but manufacturing complexity increases
Solution Approach 1:
The same EUV fabrication infrastructure and processes used for production reticles are utilized to manufacture diagnostic targets, making the fabrication system multi-functional and avoiding the need for separate specialized manufacturing equipment, thereby reducing overall system complexity
Solution Approach 2:
Diagnostic targets are created as simplified copies of production reticles, using identical EUV multilayer stack structures and fabrication processes but with simpler, pre-defined diagnostic patterns, allowing accurate EUV metric measurement without full production reticle complexity
3Productivity
If diagnostic samples are diced into multiple diagnostic targets, then diagnostic coverage and measurement frequency are improved, but risk of pattern damage during dicing increases
Solution Approach 1:
Protective layers are applied to the diagnostic sample before the dicing process to shield the EUV patterns from mechanical damage, ensuring pattern integrity is maintained while still allowing the sample to be segmented into multiple usable diagnostic targets
Solution Approach 2:
The protective layering strategy is applied locally and selectively to areas containing EUV patterns during the dicing process, providing targeted protection where needed while minimizing interference with the dicing operation and maintaining pattern quality in critical regions
Data Source
AI summary
A method may comprise fabricating a diagnostic sample using a fabrication process for fabricating a runtime sample, where the runtime sample can be configured to be used in a process tool, and where the diagnostic sample may include patterns designed to provide diagnostics of the process tool. The method can further comprise dicing the diagnostic sample into a plurality of diagnostic targets. Additionally, the method may comprise generating one or more quality metrics for the plurality of diagnostic targets. The diagnostic sample may be fabricated using the same fabrication process that can be used for fabricating the runtime sample, allowing the diagnostic targets to maintain material compatibility and quality standards. The dicing process may enable the creation of multiple diagnostic targets from a single diagnostic sample, providing cost-effective manufacturing. The quality metrics may ensure that the diagnostic targets meet specified requirements for use in process tool calibration and diagnostics.