Overlay Metrology Target with Segmented Substructures
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Solution Overview
Problem
Current overlay measurement techniques in semiconductor manufacturing face challenges in accurately determining alignment errors between successive patterned layers, particularly in minimizing optical cross-talk and optimizing real estate usage for metrology targets, which affects measurement accuracy and efficiency.
Innovation Solution
Designing semiconductor targets with specific symmetry characteristics and orientations, such as line segments and substructures, that allow for minimal separation and directional separation of information between layers, enabling precise measurement of overlay errors while minimizing optical cross-talk and optimizing target size and placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional overlay measurement techniques are used, then overlay error can be measured, but optical cross-talk occurs between successive layers reducing measurement accuracy
Solution Approach 1:
The overlay target is divided into multiple substructures (first substructure, second substructure, third substructure, fourth substructure) with specific symmetry characteristics. Each substructure is designed to respond differently to overlay errors in specific directions, allowing the measurement system to distinguish between signals from different layers and eliminate optical cross-talk through selective detection.
Solution Approach 2:
The patent employs asymmetric target designs where substructures have different orientations and symmetry properties. The first and second substructures have different symmetry characteristics from the third and fourth substructures, enabling directional separation of information and preventing optical cross-talk while maintaining measurement precision.
2Measurement precision
If larger overlay targets are used to improve measurement accuracy, then measurement precision improves, but real estate usage on the wafer increases
Solution Approach 1:
The patent combines multiple measurement functions into a single compact overlay target structure. By integrating first, second, third, and fourth substructures with specific symmetry characteristics into one target, the design achieves high measurement precision while minimizing the total area required on the wafer, thus optimizing real estate usage.
Solution Approach 2:
The patent utilizes dimensional optimization by arranging substructures in specific spatial configurations with defined orientations. This dimensional arrangement allows the target to maintain high measurement precision while reducing the overall footprint, effectively using space more efficiently on the wafer surface.
3Area of stationary object
If overlay targets with minimal separation between layers are used, then real estate is optimized, but optical cross-talk increases
Solution Approach 1:
The patent applies local quality by designing specific substructures with distinct symmetry characteristics at different locations within the target. The first and second substructures have different local symmetry properties than the third and fourth substructures, enabling the system to maintain minimal separation between layers while preventing optical cross-talk through localized structural differentiation.
4Measurement precision
If conventional target designs are used, then manufacturing is straightforward, but measurement efficiency and accuracy are limited
Solution Approach 1:
The patent creates a universal overlay target design that performs multiple measurement functions simultaneously. The target structure with first, second, third, and fourth substructures can measure overlay errors in multiple directions and layers using a single configuration, improving measurement efficiency and accuracy without requiring multiple separate targets or complex measurement procedures.
Data Source
AI summary
In one embodiment, a metrology target for determining a relative shift between two or more successive layers of a substrate may comprise; an first structure on a first layer of a substrate and an second structure on a successive layer to the first layer of the substrate arranged to determine relative shifts in alignment in both the x and y directions of the substrate by analyzing the first structure and second structure overlay.