Metrology Target Segmentation for Feature Size Control
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Solution Overview
Problem
Current metrology targets face challenges in maintaining feature size transitions below certain thresholds, leading to inaccuracies in measurements due to processing effects like etch bias, dishing, and parasitic capacitance, which are not compatible with semiconductor manufacturing design rules.
Innovation Solution
The design involves segmenting the background and optionally the target elements to maintain feature size transitions below specific thresholds, optimizing feature widths, pitches, and segment heights to enhance optical differentiation and process compatibility, thereby reducing biases and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional solid bar or segmented bar target elements are used, then the target structure is simple and easy to manufacture, but the feature size transitions exceed certain thresholds leading to measurement inaccuracies due to processing effects
Solution Approach 1:
The patent applies segmentation by dividing both the target elements and the background into multiple segments with controlled feature sizes. This creates a segmented target structure where all transitions maintain feature sizes below specific thresholds (e.g., below 300 nm or below 100 nm), thereby reducing processing effects like etch bias and dishing while improving measurement accuracy.
2Measurement precision
If feature sizes are reduced below certain thresholds to reduce processing effects, then measurement accuracy improves, but manufacturing complexity increases due to stricter design rules
Solution Approach 1:
The patent applies local quality by implementing different feature size thresholds at different locations within the target structure. Specifically, transitions between target elements and background are designed to maintain feature sizes below certain thresholds (e.g., below 300 nm) in critical measurement regions, while other regions may have different specifications. This localized approach optimizes measurement accuracy where needed while managing manufacturing complexity overall.
3Reliability
If target elements are segmented to maintain feature size transitions below thresholds, then optical differentiation between target and background is enhanced, but the design and fabrication complexity increases
Solution Approach 1:
The patent applies segmentation by dividing both the target elements and the background into multiple segments with controlled feature sizes. This creates a segmented target structure where all transitions maintain feature sizes below specific thresholds (e.g., below 300 nm or below 100 nm), thereby reducing processing effects like etch bias and dishing while improving measurement accuracy.
Solution Approach 2:
The patent applies parameter changes by systematically varying feature size parameters (width, height, pitch) across different segments of the target structure. By controlling these geometric parameters to maintain transitions below specific thresholds, the patent enhances optical differentiation between target elements and background, improving measurement reliability while managing design complexity through parameter optimization.
Data Source
AI summary
Methods of designing metrology targets are provided, which comprise distinguishing target elements from their background area by segmenting the background area and optionally segmenting the target elements. The provided metrology targets may maintain a required feature size when measured yet be finely segmented to achieve process and design rules compatibility which results in higher accuracy of the metrology measurements. Particularly, all transitions between target features and adjacent background features may be designed to maintain a feature size of the features below a certain threshold.