3D Memory Backside Support Pillars for Stack Stability
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Solution Overview
Problem
Existing three-dimensional memory devices face challenges in maintaining structural integrity during the replacement of sacrificial material layers with electrically conductive layers, as the stacks of insulating layers can topple or lean into backside trenches, leading to potential structural failures.
Innovation Solution
The introduction of backside support pillar structures that provide structural support to insulating layers during the replacement process, formed through a method that includes forming alternating sequences of insulating and sacrificial material layers, followed by etching and deposition of conductive layers within backside trenches, without additional photolithography or etching steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sacrificial material layers are replaced with electrically conductive layers, then the memory device achieves functional conductivity, but the insulating layers may topple or lean into backside trenches causing structural failure
Solution Approach 1:
The backside support pillar structures are formed in advance during the same etching process that creates the backside trenches, before the sacrificial material replacement occurs. These pillars are positioned to provide preliminary structural support to the insulating layers during the subsequent conductive layer deposition, preventing toppling or leaning into the trenches.
2Reliability
If additional photolithography and etching steps are added to form support structures, then structural integrity is maintained, but manufacturing complexity and process time increase
Solution Approach 1:
The formation of backside support pillar structures is merged with the existing backside trench etching process. The same etching steps that define the backside trenches also define the backside support pillar structures, eliminating the need for separate photolithography and etching steps to create support structures.
Solution Approach 2:
The backside support pillar structures serve multiple functions: they provide structural support to prevent insulating layer collapse, define the boundaries of backside trenches, and maintain spatial relationships between different layers. This multi-functionality reduces the need for additional dedicated support structures.
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 backside support pillar structures prevent the insulating layers from toppling or leaning into trenches, ensuring the structural integrity and stability of the three-dimensional memory device, facilitating the successful conversion of sacrificial material layers into conductive layers.
Implementation Method 1
providing an etchant that etches the sacrificial material layers into the backside trenches
Implementation Method 2
providing a reactant that deposits the electrically conductive layers into the backside trenches
Data Source
AI summary
A three-dimensional memory device includes alternating stacks of insulating layers and electrically conductive layers. The alternating stacks are laterally spaced apart among one another by backside isolation assemblies. At least one of the backside isolation assemblies generally extends along a first horizontal direction with lateral undulations along a second horizontal direction that is perpendicular to the first horizontal direction. At least one of the alternating stacks has a modulation in width along the second horizontal direction as a function of a position along the first horizontal direction. Memory stack structures vertically extend through a respective one of the alternating stacks. Each of the backside isolation assemblies includes a respective laterally alternating sequence of backside dielectric isolation walls and backside dielectric support pillar structures.