3D Memory Device U-Shaped String Architecture
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Solution Overview
Problem
Existing 3D semiconductor memory architectures face limitations in compactness, which restrict further increases in data storage capacity per unit area.
Innovation Solution
A 3D memory device architecture featuring multiple groups of 'U'-shaped strings of memory cells with varying depths and lengths, interconnected by buried string portions, and controlled by source and bit line selectors, allowing for efficient data storage with reduced area requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional 2D memory structure is used, then manufacturing process is simple, but data storage capacity per unit area is limited
Solution Approach 1:
The patent transitions from traditional 2D memory cell arrangement to a 3D architecture by introducing U-shaped strings that extend vertically through multiple substrate layers. Memory cells are stacked along the vertical dimension, with buried string portions connecting source and bit line selectors at different depths, thereby increasing storage capacity per unit area through spatial dimensionality expansion
Solution Approach 2:
The U-shaped memory string structure nests multiple functional components within a compact geometry: the buried string portion is embedded in the substrate, while the source line selector side string portion and bit line selector side string portion rise vertically and are interconnected through shared control gates, creating a nested configuration that maximizes space utilization
2Area of stationary object
If memory blocks are compacted to increase storage density, then area is reduced, but electrical connectivity and control become more difficult
Solution Approach 1:
The memory block is segmented into multiple U-shaped strings, each independently connected to source and bit line selectors through buried string portions. This segmentation allows parallel electrical pathways, where each string can be selectively activated, maintaining reliable connectivity while accommodating high density through modular organization of memory cells
Solution Approach 2:
The buried string portion acts as an intermediary element that establishes electrical connection between the source line selector and bit line selector through the substrate. This intermediate structure enables reliable signal transmission across compacted memory blocks by providing dedicated conduction paths that traverse the vertical depth of the device
Data Source
AI summary
A 3D memory device comprising: a substrate; at least one first group of at least three first U-shaped memory cells strings each including a first buried string portion, a first source line selector side string portion and a first bit line selector side string portion, wherein the first buried string portion is formed in the substrate and connects the first source line selector side string portion and the first bit line selector side string portion, each of the first U-shaped memory cells strings including memory cells stacks along the first source line selector side string portion and along the first bit line selector side string portion; and at least one second group of at least three second U-shaped memory cells strings each including a second buried string portion, a second source line selector side string portion and a second bit line selector side string portion. The second buried string portion is formed in the substrate and connects the second source line selector side string portion and the second bit line selector side string portion, each of the second U-shaped memory cells strings including memory cells stacks along the second source line selector side string portion and along the second bit line selector side string portion. The first and second source line selector side string portions are between the first and second bit line selector side string portions. The at least three first U-shaped memory cells strings are mutually co-planar and one surrounded by the other, and the at least three second U-shaped memory cells strings are mutually co-planar and one surrounded by the other.