3D Memory SSG Cut Layout for Flexible Word Line Contacts
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Solution Overview
Problem
Planar memory cells face density limitations and complex fabrication challenges as feature sizes approach a lower limit, leading to increased costs and susceptibility to short circuits due to complex BSG cut structures in existing 3D memory devices.
Innovation Solution
Implementing SSG cut structures in 3D memory devices that separate word line contacts for memory strings and staircases, simplifying the layout and reducing the number of divisions, thereby facilitating flexible formation of landing areas and reducing the risk of short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex BSG cut structures are used in existing 3D memory devices to control memory blocks, then memory block control is achieved, but the layout complexity increases and the risk of short circuits increases
Solution Approach 1:
The source select gate (SSG) cut structure divides the memory device into separate regions, creating distinct zones for different memory strings. This segmentation simplifies the layout by providing clear spatial separation, reducing the complexity of interconnections and minimizing the risk of short circuits between adjacent structures.
Solution Approach 2:
The SSG cut structure extracts and removes the source select gate material in specific regions to create open areas or landing zones. This extraction simplifies the overall layout by eliminating unnecessary structures in certain areas, making the design less complex and reducing potential short circuit paths.
2Manufacturing precision
If more divisions are created in the memory structure to improve control of memory blocks and fingers, then control precision is improved, but the number of structures increases and fabrication becomes more complex
Solution Approach 1:
The SSG cut structure serves multiple functions simultaneously: it provides regional division for memory block control, creates landing areas for contacts, and simplifies the overall layout. This multi-functionality reduces the need for separate specialized structures, thereby maintaining control precision while reducing the total number of structures and fabrication complexity.
3Ease of manufacture
If the SSG cut structure simplifies the layout and reduces divisions, then ease of manufacture is improved, but the precision of memory block control may be reduced
Solution Approach 1:
The SSG cut structure utilizes the vertical dimension by extending cuts through multiple layers to create effective separations. This dimensional approach allows for simplified lateral layouts while maintaining precise control over memory blocks through vertical segmentation, thereby improving ease of manufacture without sacrificing control precision.
Data Source
AI summary
A method for forming a three-dimensional (3D) memory device is provided. A memory stack including a memory block is formed. The memory block includes 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. A source-select-gate (SSG) cut structure extending through a portion of the memory stack and between the first finger and the second finger is formed. 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.