3D Memory SSG Cut Structure for Word Line Contact Separation
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Solution Overview
Problem
Existing 3D memory devices with BSG cut structures face complexity in design and formation, leading to challenges in memory density and product yield due to complex layouts and potential short circuits.
Innovation Solution
The implementation of source-select-gate (SSG) cut structures in 3D memory devices, which include a staircase structure with a bridge and staircases, allows for a more flexible and less complex layout by separating the landing areas of word line contacts and simplifying the string control mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If BSG cut structures are used in 3D memory devices, then string control is achieved, but design complexity and formation complexity increase
Solution Approach 1:
The BSG cut structure divides the memory device into multiple independently controllable strings by introducing cut regions that separate word line contacts. This segmentation allows individual string control while maintaining a relatively simple overall design by using repetitive modular units.
Solution Approach 2:
The BSG cut structure acts as an intermediary element between the word line contacts and the memory strings, providing a controlled interface that enables precise string selection without requiring complex routing or control mechanisms.
2Reliability
If BSG cut structures are used in 3D memory devices, then string control is achieved, but formation complexity increases
Solution Approach 1:
The BSG cut structures are formed early in the fabrication process as preliminary features that define the string boundaries. This preliminary action simplifies subsequent formation steps by pre-establishing the geometric constraints and contact alignment requirements.
Solution Approach 2:
The BSG cut structures utilize the vertical dimension of the 3D memory device to achieve string control, rather than relying solely on lateral patterning. This dimensional approach reduces formation complexity by using vertical etching and deposition steps that are inherently simpler than complex lateral lithography patterns.
3Quantity of substance
If complex layouts are used in 3D memory devices, then memory density can be maintained, but short circuit risks increase
Solution Approach 1:
The layout is segmented into discrete string units separated by BSG cut structures, which physically isolate adjacent strings and prevent short circuits while maintaining high memory density through efficient packing of the segmented units.
Solution Approach 2:
The BSG cut structures introduce local variations in the layout by creating isolated regions with specific electrical properties. This local quality differentiation allows dense overall packaging while maintaining reliable electrical isolation where needed to prevent short circuits.
Data Source
AI summary
A three-dimensional (3D) memory device includes a memory stack including a memory block. The memory block includes a memory array structures and a staircase structure in a first lateral direction, and fingers in a second lateral direction perpendicular to the first lateral direction. The fingers include a first finger and a second finger. The 3D memory device also includes a source-select-gate (SSG) cut structure extending through a portion of the memory stack and between the first finger and the second finger. The staircase structure includes a first staircase connected to first memory cells in the first finger and a second staircase connected to second memory cells in the second finger.