Lithography Metrology Target With Overlapping Pitch Regions
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Solution Overview
Problem
In lithographic processes, the size and placement of metrology targets for alignment and overlay measurements need to be carefully considered due to stringent real-estate constraints on the wafer, and variations in target position can negatively impact measured parameters.
Innovation Solution
A target arrangement comprising a first target region with multiple pitches and a second target region with overlapping pitches, allowing for both alignment and overlay metrology within a smaller footprint, thereby minimizing the aversive effects of processing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the metrology target size is reduced to fit within product features, then the real-estate constraints are satisfied, but the measurement precision deteriorates due to position variations
Solution Approach 1:
The metrology target is divided into multiple pitch regions (first pitch region and second pitch region) with different pitch values. This segmentation allows each region to contribute differently to the measurement, enabling robust overlay measurement even when the overall target size is reduced and positioned within product features.
Solution Approach 2:
Different regions of the metrology target are assigned different local properties (different pitch values). The first pitch region has a first pitch and the second pitch region has a second pitch, allowing each region to be optimized for specific measurement aspects, thereby maintaining measurement precision despite reduced target size.
2Measurement precision
If multiple separate targets are used for alignment and overlay measurements, then the measurement completeness is improved, but the device complexity increases
Solution Approach 1:
The patent combines alignment measurement functionality and overlay measurement functionality into a single integrated metrology target. The target includes both first pitch regions (for alignment) and second pitch regions (for overlay), eliminating the need for separate alignment and overlay targets, thus reducing device complexity while maintaining measurement completeness.
Solution Approach 2:
The metrology target is designed to serve multiple functions simultaneously. It can perform alignment measurements using the first pitch region and overlay measurements using the second pitch region, making it a universal target that replaces multiple specialized targets.
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 target arrangement enables efficient measurement of alignment and overlay parameters while reducing the space occupied by metrology targets, thus improving the accuracy and reliability of lithographic process control.
Implementation Method 1
These devices direct a beam of radiation onto a target and measure one or more properties of the scattered radiation
Implementation Method 2
Diffraction-based overlay using dark-field detection of the diffraction orders enables overlay measurements on smaller targets
Data Source
AI summary
Disclosed is target arrangement comprising a first target region having at least a first pitch and at least a second pitch a second target region having at least a third pitch, wherein a portion of the first target region having a second pitch overlaps with a portion of the second target region.