Asymmetric Support Pillars for 3D Memory Structural Integrity
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Solution Overview
Problem
The mechanical robustness of three-dimensional memory devices is limited by the design constraints on support pillar structures, particularly around backside trenches, which can lead to reduced mechanical support during the replacement of sacrificial material layers with electrically conductive layers, potentially causing insulating layer buckling.
Innovation Solution
The use of asymmetric and different size support pillar structures, with first and second support pillar structures having distinct lateral dimensions, are interlaced to provide enhanced mechanical support and prevent insulating layer buckling, while maintaining a manufacturing process-friendly design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional uniform support pillar structures are used, then manufacturing simplicity is maintained, but mechanical robustness is insufficient leading to insulating layer buckling
Solution Approach 1:
The patent implements asymmetric support pillar structures where first support pillars have a first lateral dimension and second support pillars have a second lateral dimension that is smaller than the first lateral dimension. This asymmetry provides enhanced mechanical support in critical regions while maintaining manufacturing feasibility through selective placement of different sized pillars in the staircase region.
Solution Approach 2:
The patent applies different sized support pillars at different locations within the staircase region. First support pillars with larger lateral dimensions are positioned at boundary rows adjacent to backside trenches where mechanical support is most critical, while second support pillars with smaller lateral dimensions are positioned in inner rows where less support is needed. This local differentiation optimizes mechanical robustness where required while reducing overall device complexity.
2Reliability
If larger support pillars are used throughout, then mechanical support is improved, but manufacturing complexity and process difficulty increase
Solution Approach 1:
The support pillar structure is segmented into first support pillars and second support pillars with different lateral dimensions. This segmentation allows the device to achieve high structural integrity in critical areas (boundary rows near backside trenches) while using smaller pillars in less critical areas (inner rows), thereby reducing overall manufacturing complexity and process difficulty compared to using uniformly large pillars throughout.
3Strength
If asymmetric support pillar structures are implemented, then mechanical support is enhanced, but device design complexity increases
Solution Approach 1:
The patent employs asymmetric support pillar structures with first support pillars having a first lateral dimension and second support pillars having a second lateral dimension. The asymmetric configuration is strategically implemented only in the staircase region with specific patterns (boundary rows versus inner rows), which enhances mechanical support while limiting the increase in device design complexity to a manageable scope.
Data Source
AI summary
An alternating stack of insulating layers and spacer material layers is formed over a substrate. A staircase region having stepped surfaces is formed by patterning the alternating stack. Memory opening fill structures are formed in a memory array region, and support pillar structures are formed in the staircase region. Each of the memory stack structures includes a memory film and a vertical semiconductor channel. The support pillar structures include first support pillar structures and having a first maximum lateral dimension and second support pillar structures having a second maximum lateral dimension that is less than the first maximum lateral dimension and interlaced with the first support pillar structures. The sacrificial material layers are replaced with electrically conductive layers. The second support pillar structures are positioned interstitially among the first support pillar structures and contact via structures that are formed on the electrically conductive layers to provide additional structural support.