Tilt Calculation via Overlay Metrology Measurements
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Solution Overview
Problem
Current metrology systems are sensitive to errors from process variations, lithography processes, and metrology processes, leading to increased throughput time and potential re-work requirements for etched wafers with out-of-specification tilts.
Innovation Solution
A system and method for tilt calculation based on overlay metrology measurements, which includes a controller connected to metrology tools to receive overlay measurements, determine tilt, predict tilt using a simulator, and adjust lithography or metrology tools to correct for predicted tilt, thereby reducing tilt and overlay inaccuracies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dedicated tilt tools are used to measure tilt on a single metrology target, then tilt measurement accuracy is improved, but device complexity and measurement time increase
Solution Approach 1:
The patent makes existing overlay metrology tools perform the additional function of tilt measurement by analyzing overlay data from multiple targets across the wafer. Instead of requiring dedicated tilt measurement tools, the system utilizes the multi-functionality of overlay metrology tools to extract both overlay and tilt information from the same measurement data, thereby reducing device complexity while maintaining measurement capability.
Solution Approach 2:
The patent combines overlay measurement and tilt measurement into a single measurement process. By measuring overlay at multiple targets simultaneously and analyzing the spatial distribution of overlay errors, the system extracts tilt information as an additional parameter from the same measurement campaign, merging two measurement functions into one unified process.
2Measurement precision
If dedicated tilt tools are used to measure tilt on a single metrology target, then tilt measurement accuracy is improved, but measurement time and throughput increase
Solution Approach 1:
The patent combines overlay measurement and tilt measurement into a single measurement process. By measuring overlay at multiple targets simultaneously and analyzing the spatial distribution of overlay errors, the system extracts tilt information as an additional parameter from the same measurement campaign, merging two measurement functions into one unified process.
Solution Approach 2:
The system performs tilt measurement as a byproduct of the overlay measurement process. By collecting overlay data from multiple targets during the normal overlay measurement campaign and then analyzing this pre-collected data for tilt information, the system avoids the need for separate tilt measurement steps, thereby reducing total measurement time.
3Device complexity
If overlay metrology measurements are used to determine tilt, then device complexity is reduced, but measurement precision may be affected by error sources
Solution Approach 1:
The patent segments the wafer into multiple measurement zones and measures overlay at multiple discrete targets distributed across different regions. By analyzing the spatial distribution of overlay errors across these segmented measurement points, the system can distinguish between local overlay misalignment and global tilt effects, thereby improving measurement precision through spatial segmentation.
Solution Approach 2:
The system uses feedback from multiple overlay measurements across the wafer to distinguish between overlay errors and tilt effects. By comparing overlay measurements from multiple targets and analyzing the consistency and spatial distribution of errors, the system can identify and compensate for tilt-induced variations, thereby maintaining measurement precision while using existing overlay metrology tools.
Data Source
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AI summary
A metrology system includes a controller communicatively coupled to one or more metrology tools. In another embodiment, the controller includes one or more processors configured to execute program instructions causing the one or more processors to receive one or more overlay metrology measurements of one or more metrology targets of the metrology sample from the one or more metrology tools; determine tilt from the one or more measurement overlay measurements; and determine one or more correctables for at least one of one or more lithography tools or the one or more metrology tools to adjust for the tilt, where the one or more correctables are configured to reduce an amount of tilt in the sample or overlay inaccuracy of the one or more overlay metrology measurements. The program instructions further cause the one or more processors to predict tilt with a simulator based on at least the determined tilt.