3D Memory Mesh Structure Prevents Pattern Collapse
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Solution Overview
Problem
The miniaturization of storage memory cells in planar NAND flash memory is limited by device critical dimensions, hindering the achievement of higher storage capacity and lower costs per bit, necessitating the development of three-dimensional NAND flash memory with multiple planes to meet increasing demand for storage subsystems.
Innovation Solution
A method of forming a three-dimensional memory by creating a stacked structure with alternating semiconductor and insulating layers, patterning a mesh structure, filling dielectric layers in holes, and removing extending parts to form bit line stacked structures, gate pillars, and word lines, which enhances device uniformity and reliability while preventing bending or collapsing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If planar NAND flash memory is used to increase storage capacity, then storage capacity can be increased, but device critical dimension limits further miniaturization
Solution Approach 1:
The patent transitions from planar two-dimensional memory structure to three-dimensional stacked structure with multiple planes. The bit line stacked structures extend in a first direction while word lines extend in a second direction, creating vertical stacking that increases storage capacity without being constrained by planar critical dimensions. This dimensional transition allows continued scaling as device critical dimensions reach physical limits in planar configurations.
2Quantity of substance
If high aspect ratio patterns are formed to increase storage density, then storage capacity increases, but bending or collapsing occurs
Solution Approach 1:
The mesh structure divides the continuous bit line stacked structure into discrete segments separated by spacers. This segmentation reduces the aspect ratio of individual patterned features while maintaining overall storage density through the three-dimensional array arrangement. The spacers act as support elements that prevent bending or collapsing during fabrication and operation.
Solution Approach 2:
The spacers serve as intermediary support structures between the bit line stacked structures. These spacers provide mechanical support that prevents bending or collapsing of the high aspect ratio patterns while allowing the structures to maintain their intended geometry. The spacers are formed between adjacent bit line stacked structures and extend in the third direction, providing structural reinforcement.
3Reliability
If mesh structure with spacers is formed to prevent bending, then structural stability improves, but device complexity increases
Solution Approach 1:
The spacers serve multiple functions simultaneously: they provide mechanical support to prevent bending or collapsing, define the spacing between bit line stacked structures, and serve as etch stop layers during fabrication. This multi-functionality reduces the need for additional separate support structures, thereby limiting the increase in device complexity despite the added structural stability.
Data Source
AI summary
A method of forming a three-dimensional memory is provided. A stacked structure including semiconductor layers and insulating layers arranged alternately is formed on a substrate. The stacked structure is patterned to form a mesh structure having first strips extending in a first direction and second strips extending in a second direction. The first strips and the second strips intersect with each other. The mesh structure has first holes. A dielectric layer is formed in each first hole. At least a portion of the first strips of the mesh structure is removed to form second holes and bit line stacked structures separated from each other. A charge storage layer is formed on sidewall and bottom of each second hole. A gate pillar extending in a third direction is formed on each charge storage layer in the second hole. Word lines extending in the first direction are formed on the gate pillars.