Optical Metrology Target Evaluation With High-Resolution Deviation Feedback
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Solution Overview
Problem
Existing optical metrology techniques face challenges in ensuring measurement accuracy of device features due to deviations of optical metrology targets from reference designs, which impact the effectiveness of process control in semiconductor fabrication.
Innovation Solution
A metrology system comprising an optical metrology sub-system and a high-resolution additional metrology sub-system, where the latter measures deviations of optical metrology targets from a reference design with higher precision, allowing for accurate identification of lithography process variations and adjustments to improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If optical metrology measurements are used for process control, then measurement speed and throughput are improved, but measurement precision deteriorates due to deviations of optical metrology targets from reference designs
Solution Approach 1:
The patent introduces an additional metrology sub-system as an intermediary tool to measure the optical metrology targets with higher precision. This separate measurement system acts as a mediator to evaluate the accuracy of the primary optical metrology measurements, allowing the original optical system to maintain its high throughput while the intermediary system provides precision validation and deviation detection from reference designs
Solution Approach 2:
The patent implements a feedback mechanism where the additional metrology sub-system measures deviations of optical metrology targets from reference designs, and this deviation information is fed back to adjust and optimize the optical metrology measurements. The controller uses the deviation data to improve measurement accuracy by compensating for target variations, creating a closed-loop system that maintains both speed and precision
2Measurement precision
If additional metrology sub-system with higher resolution is introduced, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The additional metrology sub-system is designed to measure multiple parameters including deviations from reference designs, overlay accuracy, and target fabrication variations. By making this additional system multi-functional, the patent reduces the need for even more separate specialized tools, thereby limiting the increase in overall system complexity while achieving improved measurement precision across multiple dimensions
3Measurement precision
If deviations of optical metrology targets from reference design are measured, then measurement accuracy is improved, but measurement time increases
Solution Approach 1:
The patent performs preliminary measurements of the optical metrology targets using the additional metrology sub-system to establish baseline deviation data from reference designs before the main optical metrology measurement process. By pre-characterizing the targets and their deviations, the system avoids time-consuming measurements during the primary measurement process, thus improving accuracy without proportionally increasing total measurement time
Data Source
AI summary
A metrology system may include an optical metrology sub-system to generate optical metrology measurements of optical metrology based on features of the optical metrology targets associated with at least one optical pitch and an additional metrology sub-system to generate additional metrology measurements of the optical metrology targets, where the additional metrology measurements have a higher resolution than the optical metrology measurements, and where the additional metrology sub-system further measures deviations of the optical metrology targets from a reference design. The system may further include a controller to generate accuracy measurements for the optical metrology targets based on the measurements, identify variations of a lithography process based on the deviations, correlate the accuracy measurements to the variations, and adjust at least one of the optical metrology sub-system, a lithography tool, or the reference design based on the correlations.