Metrology Target Segmentation for CD Imbalance Correction
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Solution Overview
Problem
Existing metrology techniques struggle to accurately measure overlay due to CD imbalance in subsegmented targets, leading to measurement errors.
Innovation Solution
A substrate design comprising multiple sub-targets with different subsegmentation characteristics for each sub-target, allowing for the correction of CD imbalance by measuring and combining overlay values from these sub-targets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If subsegmented targets are used for overlay measurement, then measurement capability is improved, but CD imbalance causes measurement precision to deteriorate
Solution Approach 1:
The target is divided into multiple sub-targets, each with different subsegmentation characteristics (different numbers of sub-segments). This segmentation allows the system to measure overlay using multiple configurations and then combine the results to eliminate CD imbalance errors, thus resolving the contradiction between measurement capability and precision.
Solution Approach 2:
The invention changes the subsegmentation parameter (number of sub-segments) across different sub-targets. By varying this parameter, the system creates multiple measurement scenarios where CD imbalance affects each sub-target differently, enabling mathematical combination of measurements to cancel out the error and achieve high precision overlay measurement.
2Measurement precision
If multiple sub-targets with different subsegmentation characteristics are used, then overlay measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The target structure is segmented into multiple sub-targets with varying subsegmentation characteristics. While this increases structural complexity, it enables the system to obtain multiple independent measurements that can be combined mathematically to eliminate systematic errors, achieving high measurement accuracy that justifies the increased complexity.
Solution Approach 2:
The target uses a composite structure combining multiple sub-targets with different subsegmentation characteristics. This composite approach allows the system to leverage the strengths of each sub-target configuration, creating a robust measurement system that achieves high precision despite the inherent complexity of the multi-component structure.
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
Enables accurate measurement of overlay by correcting for CD imbalance, improving the precision of metrology results.
Implementation Method 1
These devices direct a beam of radiation onto a target and measure one or more properties of the scattered radiation
Data Source
AI summary
A substrate including a target. The target including a plurality of sub-targets, the plurality of sub-targets including at least a first sub-target and second sub-target, each of the plurality of sub-targets including at least one subsegmented periodic structure having repetitions of a first region and a second region, wherein at least one of the first regions or second regions comprise subsegmented regions formed of periodic sub-features. The first sub-target includes subsegmentation characteristics for its subsegmented regions and the second sub-target comprises second subsegmentation characteristics for its subsegmented regions, the first subsegmentation characteristics and second subsegmentation characteristics being different in terms of at least one subsegmentation parameter.