Multi-Spot Optical Metrology for Faster Precise Inspection
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Solution Overview
Problem
Lithographic systems face a trade-off between fabrication speed and accuracy, with increased measurement speeds often leading to reduced measurement accuracy in optical inspection processes.
Innovation Solution
An inspection system utilizing a radiation source that generates non-overlapping, small-diameter radiation spots, with dedicated optical structures for projecting and collecting scattered radiation, and a detection system for generating measurement signals from each spot, enhancing measurement efficiency without sacrificing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If measurement speed is increased, then fabrication time is reduced, but measurement accuracy deteriorates
Solution Approach 1:
The inspection system divides the target area into multiple non-overlapping radiation spots, with each spot measuring a specific region. This segmentation allows parallel measurement of multiple features simultaneously, increasing throughput while maintaining the precision of individual measurements through dedicated detection channels for each spot.
Solution Approach 2:
The system transitions from single-spot sequential measurement to multi-spot parallel measurement by adding a spatial dimension. Multiple radiation spots are distributed across the target, enabling simultaneous measurement of multiple features in different spatial locations, thereby increasing productivity without sacrificing accuracy.
2Measurement precision
If radiation dose is increased, then measurement accuracy is improved, but target damage risk increases
Solution Approach 1:
The total radiation dose is segmented across multiple non-overlapping spots, each delivering a lower individual dose that is safe for the target. The cumulative measurement accuracy is achieved by combining the measurements from all spots, thus avoiding target damage while maintaining measurement precision.
Solution Approach 2:
Each radiation spot is designed with specific local characteristics (small diameter, non-overlapping arrangement) to concentrate measurement capability in specific regions without exceeding the damage threshold. The local dose distribution is optimized to ensure accurate measurement while keeping individual spot doses safe for the target material.
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
The system enables faster optical inspection processes with improved accuracy by increasing the measurement radiation dose while maintaining precise alignment and measurement of critical dimensions and overlay errors.
Implementation Method 1
a first optical structure configured to route the beams toward the target so as to project the radiation spots on the target and to generate scattered radiation from the target
Data Source
AI summary
An inspection system includes a radiation source, first and second optical structures, and a detection system. The radiation source generates beams of radiation. An image formed by the beams includes radiation spots corresponding to the beams. Diameters of the radiation spots is less than a dimension of a target and the radiation spots are non-overlapping. The first optical structure routes the beams toward the target so as to project the radiation spots on the target and generate scattered radiation from the target. The second optical structure collects the scattered radiation from the target. The detection system receives the scattered radiation collected by the second optical structure and generates measurement signals. Each of the measurement signals corresponds to each of the radiation spots.