3D Memory Layer Stack Marks for Stress Alignment Control
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Solution Overview
Problem
In three-dimensional memory devices, the stress differences between layers of varying materials can cause displacement of structures during manufacturing, leading to defects and reduced yield due to membrane stress and misalignment of features in dicing areas.
Innovation Solution
The provision of multiple mark portions in the layer stack and separators between them helps to alleviate stress and maintain structural alignment, allowing for the separation of regions with mark portions and reducing the overall volume of the layer stack, thereby minimizing displacement and defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple mark portions are provided in the layer stack, then stress-induced displacement is reduced and manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The layer stack is divided into multiple regions with mark portions distributed throughout its volume. This segmentation allows stress to be distributed and measured at multiple points, improving alignment precision without requiring a single complex stress management system.
Solution Approach 2:
Mark portions serve as intermediary elements that indicate stress-induced displacement. By providing multiple mark portions throughout the layer stack, the system can detect and compensate for stress effects on alignment precision without directly managing the complex stress fields.
2Manufacturing precision
If separators are provided between mark portions, then stress is alleviated and manufacturing precision is improved, but device complexity increases
Solution Approach 1:
Separators divide the layer stack into distinct regions between mark portions. This segmentation isolates stress fields in different regions, preventing stress accumulation and maintaining structural alignment precision without requiring a monolithic complex structure.
Solution Approach 2:
Separators extract or remove stress concentration zones from the continuous layer stack. By placing separators between mark portions, the system eliminates potential stress pathways while maintaining the necessary structural integrity for alignment.
3Manufacturing precision
If the volume of the layer stack is reduced, then stress-induced displacement is minimized and manufacturing precision is improved, but the quantity of functional layers is reduced
Solution Approach 1:
The layer stack volume is segmented into smaller regions separated by separators. This allows the overall volume to be reduced while maintaining functional integrity through distributed mark portions that monitor and control stress-induced displacement in each segment.
Solution Approach 2:
Different regions of the layer stack are optimized with local quality variations. Mark portions and separators are strategically placed in regions where stress management is critical, allowing volume reduction in non-critical areas while maintaining precision in functional regions.
Data Source
AI summary
According to one embodiment, a memory device includes: a first layer stack provided in a first area of a substrate; second and third layer stacks provided in a second area of the substrate; a memory cell provided in the first layer stack; a first mark portion provided in the second layer stack; a second mark portion provided in the third layer stack; and a first portion provided between the second layer stack and the third layer stack.