Overlay Measuring Apparatus Using Micro-Structured Marks
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Solution Overview
Problem
Current overlay metrology solutions in semiconductor manufacturing, primarily based on optics, lack sufficient resolution to accurately measure alignment errors between layers using product features, relying instead on larger dedicated overlay targets.
Innovation Solution
An overlay measuring apparatus with a stage and imaging assembly, including optical heads and overlay marks with micro-structures, captures images of semiconductor wafers to determine relative positions of patterned layers using light reflection, allowing for precise calculation of displacement through unique intensity distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dedicated overlay targets are used for measurement, then measurement accuracy is improved, but the target size becomes much larger than product features
Solution Approach 1:
The overlay mark is segmented into multiple micro-structures (e.g., concentric rings, squares, or other geometric patterns) that can be resolved by the optical system. Each micro-structure provides measurement information, allowing accurate overlay measurement without requiring a large single target feature.
Solution Approach 2:
The patent transitions from measuring overlay using lateral dimensions of large targets to using vertical stack information through light reflection and interference patterns. The micro-structures are designed to create unique intensity distributions in the reflected light that encode overlay information, enabling measurement in a different dimensional space.
2Area of moving object
If product features are used for overlay measurement, then target size is reduced, but measurement resolution becomes insufficient
Solution Approach 1:
The overlay mark incorporates micro-structures with specific local geometric qualities (concentric rings, squares, or other patterns) that are optimized for optical measurement. These local structures create distinct light reflection and interference patterns that enhance measurement resolution while maintaining a compact overall size suitable for integration with product features.
Solution Approach 2:
The patent utilizes changes in light intensity distribution (analogous to color changes in optical measurement) as overlay marks are misaligned. The micro-structures are designed to produce unique intensity patterns in reflected light that vary systematically with overlay error, enabling high-resolution measurement through optical detection of these intensity variations.
3Measurement precision
If overlay marks with micro-structures are used, then measurement resolution is improved, but device complexity increases
Solution Approach 1:
The overlay marks with micro-structures serve multiple functions: they provide alignment references for lithography, enable overlay measurement through light reflection and interference, and can be integrated into the existing product structure. This multi-functionality reduces the need for separate dedicated measurement structures, offsetting the added complexity with operational efficiency.
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
Improves measurement accuracy by using micro-structured overlay marks that allow for higher resolution imaging, enabling better alignment precision between semiconductor layers and reducing overlay errors.
Implementation Method 1
The relative positions of the two or more successive patterned layers of the device are determined using light reflected from the device and passing through the respective overlay mark mounted on the optical head
Data Source
AI summary
The present application provides an overlay measuring apparatus, adapted to determine relative positions of two or more successive patterned layers of a device. The overlay measuring apparatus includes a stage and an imaging assembly. The device is placed on the stage. The imaging assembly includes a plurality of optical heads and a plurality of overlay marks assembled on the optical heads. The relative positions of the two or more successive patterned layers of the device are determined using light reflected from the device and passing through the overlay mark mounted on the respective optical head.