3D Memory Support Structure With Dual-Stiffness Load Bearing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing 3D NAND memory devices face stress-induced deformation of support structures due to the weight and distribution of conductor/dielectric layer pairs, leading to alignment issues and yield loss as the number of levels increases, as conventional support structures made of low-stiffness materials like silicon oxide are unable to withstand the mechanical stress effectively.
Innovation Solution
The introduction of a support structure with a first support portion made of a high-stiffness material, such as polysilicon, and a second support portion made of a lower-stiffness material, such as silicon oxide, provides improved stress-bearing performance by distributing the stress more effectively, reducing deformation and alignment issues in the staircase region of the 3D memory device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional support structures made of low-stiffness materials like silicon oxide are used, then the device complexity is reduced and ease of manufacture is improved, but the support structures are unable to withstand mechanical stress effectively, leading to deformation and alignment issues as the number of levels increases
Solution Approach 1:
The support structure employs a composite design combining a first support portion made of high-stiffness material (polysilicon) and a second support portion made of lower-stiffness material (silicon oxide). This composite structure distributes mechanical stress effectively, with the polysilicon portion bearing the primary load while the silicon oxide portion provides structural continuity and stress distribution, thereby enhancing overall stress-bearing performance without requiring complete restructuring of the support system
Solution Approach 2:
The support structure is divided into distinct segments: a first support portion extending from the substrate surface to a first height, and a second support portion extending from the first height to a second height. This segmentation allows each portion to be optimized for its specific function - the lower polysilicon portion provides high-stiffness support where stress is greatest, while the upper silicon oxide portion provides structural continuity and stress distribution across the conductor/dielectric layer pairs
2Quantity of substance
If the number of levels in the 3D memory device is increased to improve storage capacity, then the storage density is improved, but the mechanical stress on support structures increases, leading to deformation and yield loss
Solution Approach 1:
The composite support structure with polysilicon and silicon oxide portions distributes the increasing mechanical stress from additional levels effectively. The high-stiffness polysilicon portion maintains structural integrity under increased load, while the silicon oxide portion distributes stress across the expanded structure, preventing deformation and maintaining alignment accuracy of word line contacts even as storage capacity increases
Solution Approach 2:
The support structure applies different material properties at different locations - high-stiffness polysilicon at the base where stress concentration occurs, and lower-stiffness silicon oxide at upper levels for stress distribution. This local differentiation of material quality allows the structure to handle increased mechanical loads from additional levels while maintaining overall reliability and alignment precision
Data Source
AI summary
A 3D memory device includes a memory stack and a support structure. The memory stack, on a substrate, includes a core region and a non-core region neighboring the core region. The support structure extends in the non-core region and into the substrate. The support structure includes a first support portion and a second support portion over the first support portion. The first support portion has a stiffness higher than the second support portion.