Ring Overlay Targets for Precise Center Detection in Semiconductor Layers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing overlay measurement targets in semiconductor fabrication are large, which limits their size reduction due to accuracy concerns, and reducing their size further decreases measurement accuracy, necessitating a solution for precise and accurate center location detection in small targets.
Innovation Solution
The use of ring targets with detectable features arranged in a circular manner, allowing for accurate center location detection through mathematically constructed circles and signal overlap analysis, enabling reduced target size while maintaining measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If overlay measurement targets are reduced in size, then space utilization improves, but measurement accuracy deteriorates
Solution Approach 1:
The patent employs circular ring targets with features arranged in a circular pattern. The curved geometry of the ring targets provides stronger signal definition for center location detection compared to linear arrangements, enabling accurate measurement even when the overall target size is reduced to below 11 or 5 micrometers.
Solution Approach 2:
The patent transitions from traditional linear or grid-based target patterns to circular ring patterns, utilizing the radial dimension and rotational symmetry. This dimensional change allows the center location to be determined through circular averaging of feature positions, which provides more robust and accurate center detection in small targets.
2Productivity
If overlay measurement targets are reduced in size, then fabrication process efficiency improves, but positioning accuracy deteriorates
Solution Approach 1:
The circular arrangement of detectable features in ring targets provides enhanced symmetry and signal definition, allowing for accurate center location detection even in miniaturized targets. This curvature-based design maintains positioning accuracy while enabling smaller target dimensions that improve fabrication efficiency.
Solution Approach 2:
The patent changes the geometric parameters of the target from traditional large-scale patterns to compact circular rings with specific radius and feature spacing. This parameter optimization allows the target to maintain sufficient signal strength for accurate measurement while occupying minimal space on the wafer, thereby improving overall fabrication efficiency.
Data Source
AI summary
An overlay target for a semiconductor device is disclosed. The overlay measurement target includes a first ring target located on a first measured layer of the semiconductor device. The first ring target includes a plurality of detectable features arranged in a circular manner having a first circumference. The overlay measurement target also includes a second ring target located on a second measured layer of the semiconductor device. The second ring target includes a plurality of detectable features arranged in a circular manner having a second circumference different from the first circumference. The displacement between a detected center of the first ring target and a detected center of the second ring target indicates an overlay error between the first measured layer and the second measured layer.