3D Memory Support Pillars With Fins for Lower Word Line Resistance
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Solution Overview
Problem
Existing three-dimensional memory devices face challenges in reducing word line resistance and minimizing deformation of insulating layers due to compressive stress, while also requiring precise control over the depth of support openings during etching.
Innovation Solution
The implementation of finned support pillar structures, which comprise a central columnar structure and a set of fins laterally protruding from the central columnar structure at levels of a subset of the electrically conductive layers, allows for increased spacing between support pillar structures, reduced word line resistance, and decreased deformation of insulating layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If support pillar structures are placed closer together to reduce word line resistance, then word line resistance decreases, but deformation of insulating layers increases due to compressive stress
Solution Approach 1:
The support pillar is segmented into a central columnar structure and multiple fin structures that laterally protrude from the central structure. This segmentation allows the support function to be distributed across multiple elements, providing adequate support while maintaining spacing between pillars to reduce word line resistance.
Solution Approach 2:
The support pillar structure transitions from a simple vertical column to a three-dimensional structure with lateral fin protrusions. This adds horizontal dimensionality to the support function, allowing the pillar to provide structural support in multiple directions while maintaining vertical spacing between pillars.
2Manufacturing precision
If support openings are etched deeper to reach underlying layers, then etching precision is improved, but control over etching depth becomes more difficult
Solution Approach 1:
The fin structures act as intermediary elements that extend laterally from the central support structure. These fins provide intermediate support points that help define the etching depth indirectly, making it easier to control the overall etching process without requiring precise direct depth measurement.
Solution Approach 2:
The alternating stack of insulating and sacrificial material layers is formed beforehand with predetermined thicknesses. This preliminary structuring provides built-in depth references that guide the etching process, allowing support openings to be etched to the correct depth without requiring complex real-time depth control.
3Stability of the object's composition
If support pillar structures are spaced farther apart to reduce compressive stress on insulating layers, then deformation of insulating layers decreases, but word line resistance increases
Solution Approach 1:
The support function is segmented into a central columnar structure and multiple lateral fin structures. This segmentation allows the support pillar to provide adequate structural support with a smaller footprint, enabling closer spacing between pillars without increasing compressive stress on insulating layers beyond acceptable levels.
Solution Approach 2:
The support pillar structure combines a central columnar structure with lateral fin structures to create a composite support element. This composite structure provides enhanced mechanical support efficiency, allowing closer pillar spacing while maintaining insulating layer stability through the distributed support provided by the fin 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 use of finned support pillar structures effectively reduces word line resistance, minimizes deformation of insulating layers, and allows for better control over the depth of support openings, thereby enhancing the performance and manufacturing efficiency of three-dimensional memory devices.
Implementation Method 1
laterally recessing the sacrificial material layers selective to the insulating layers around the support openings by introducing into the support openings an isotropic etchant that etches the sacrificial material layers selective to the insulating layers
Implementation Method 2
forming support pillar structure in volumes of the support openings and the fin cavities by depositing at least one fill material in the support openings and the fin cavities
Data Source
AI summary
A three-dimensional memory device includes an alternating stack of insulating layers and electrically conductive layers located over a substrate, memory openings vertically extending through a first region of the alternating stack, memory opening fill structures located in the memory openings, and support pillar structures vertically extending through a second region of the alternating stack. Each of the support pillar structures includes a central columnar structure and a set of fins laterally protruding from the central columnar structure at levels of a subset of the electrically conductive layers.