3D NAND Memory Strings Penetrating Stacking Structure
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Solution Overview
Problem
Conventional 3D NAND memory devices face challenges with high resistance in the ground layer, leading to IR drop effects and reduced storage capacity due to the need for metal contact structures, which compress the layout space.
Innovation Solution
A memory device with a substrate, a multi-layer ground layer including a metal layer, and memory strings that penetrate through a stacking structure of insulating and conducting layers, allowing direct current transmission to the metal layer, thereby reducing the need for additional metal contacts and increasing layout space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal contact structures are disposed between memory blocks to guide current to ground, then IR drop effect is reduced, but layout space is compressed and storage capacity is reduced
Solution Approach 1:
The ground layer is merged with the substrate to form an integrated ground structure, eliminating the need for separate metal contact structures between memory blocks. This integration allows current to be guided to ground through the substrate-integrated ground layer, reducing IR drop effects while preserving layout space for memory strings.
Solution Approach 2:
The ground guidance function is transitioned from a horizontal arrangement (metal contact structures between blocks) to a vertical arrangement (memory strings penetrating through stacking structures to contact the ground layer on substrate). This dimensional change eliminates the need for intermediate metal contacts while maintaining effective current guidance to ground.
2Ease of manufacture
If poly-silicon material is used for ground layer, then manufacturing is simplified, but resistance is high and IR drop effect occurs
Solution Approach 1:
The ground layer is formed as a composite structure integrating the substrate with additional ground layer material, creating a low-resistance ground path. This composite ground structure combines the mechanical support of the substrate with the electrical conductivity of metal or doped semiconductor materials, achieving both low resistance and manufacturability.
3Reliability
If memory strings are arranged with metal contact structures, then current guidance is improved, but storage capacity is reduced due to space compression
Solution Approach 1:
The intermediate metal contact structures between memory blocks are extracted and eliminated. The ground guidance function is transferred to the substrate-integrated ground layer, allowing memory strings to be arranged more densely without the space constraints imposed by discrete metal contacts, thereby increasing storage capacity while maintaining effective current guidance.
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
The solution effectively reduces IR drop effects and increases storage capacity by allowing direct current transmission to a low-resistance metal layer, minimizing the need for metal contacts and enhancing the layout space of the memory device.
Implementation Method 1
The ground layer includes a metal layer. The memory strings penetrate through the stacking structure and electrically contact with the metal layer.
Data Source
AI summary
A memory device and a method for fabricating the same are provided. The memory device includes a substrate, a ground layer disposed on the substrate, a stacking structure having a plurality of conductive layers and a plurality of insulating layers alternatively stacked on the ground layer and a plurality of memory strings penetrating through the stacking structure. The ground layer includes a metal layer. The memory strings electrically contact with the metal layer.