3D Memory Support Pillars Under Retro-Stepped Dielectric
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in efficiently manufacturing structures with support pillars underneath a retro-stepped dielectric material portion, which affects the formation of monolithic three-dimensional NAND string memory devices.
Innovation Solution
A method involving the formation of an alternating stack of insulating and sacrificial material layers over a substrate, followed by patterning to create stepped surfaces, deposition of a sacrificial retro-stepped dielectric material, and subsequent etching to form memory and support openings, allowing for the simultaneous creation of memory stack structures and support pillar structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If support pillars are formed under retro-stepped dielectric material in conventional three-dimensional memory devices, then structural support is provided, but manufacturing complexity increases and manufacturing precision deteriorates due to the difficulty of forming varying pillar heights
Solution Approach 1:
The patent applies preliminary action by forming a retro-stepped dielectric material structure before forming the support pillars. The retro-stepped structure with varying heights is created first, then support openings are formed through this pre-established structure, allowing pillars to naturally achieve different heights based on the underlying stepped geometry without requiring complex individual pillar formation processes
Solution Approach 2:
The retro-stepped dielectric material serves as an intermediary structure that mediates between the planar substrate and the memory array region. This intermediate stepped structure enables the formation of support pillars with varying heights by providing a pre-defined geometric template, thus achieving height variation without direct complex control of each pillar formation process
2Area of stationary object
If support pillars of varying heights are formed to enhance areal density, then device compactness improves, but device complexity increases due to the multi-layer alternating stack structure
Solution Approach 1:
The alternating stack of insulating and sacrificial material layers serves multiple functions simultaneously: it provides structural support during fabrication, defines the retro-stepped geometry for varying pillar heights, creates the memory array region boundaries, and enables subsequent memory structure formation. This multi-functionality reduces the need for separate dedicated structures for each function, thereby improving areal density despite the multi-layer complexity
Solution Approach 2:
The patent segments the device into distinct regions (memory array region and terrace region) with different functions. The alternating stack is patterned to create these segmented regions, allowing the support pillars to be concentrated in the terrace region with varying heights to maximize areal density, while the memory array region maintains its functional structure, thus managing complexity through spatial segmentation
3Adaptability or versatility
If retro-stepped dielectric material is deposited over stepped surfaces, then support pillar height variation is enabled, but manufacturing precision challenges arise in forming the stepped surfaces continuously
Solution Approach 1:
The stepped surfaces are formed in advance by patterning the alternating stack before depositing the retro-stepped dielectric material. This preliminary formation of continuous stepped surfaces provides a stable geometric template that ensures continuity, allowing the subsequent dielectric deposition to simply conform to the pre-established steps without requiring precise control during the deposition process itself
4Productivity
If memory openings and support openings are formed simultaneously, then productivity improves, but manufacturing precision deteriorates due to the complexity of selective etching through different material layers
Solution Approach 1:
The alternating stack is designed with local quality variations where different regions (memory array region vs. terrace region) have different layer compositions and configurations. This local differentiation allows simultaneous etching processes to selectively form memory openings and support openings based on the local material properties, enabling parallel formation while maintaining precision through spatially differentiated etch selectivity
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
This approach enables the fabrication of three-dimensional memory devices with varying support pillar heights, enhancing the structural integrity and density of the memory array while minimizing overlap and electrical shorts, thereby improving the areal density and compactness of the memory device.
Implementation Method 1
removing the sacrificial retro-stepped dielectric material portion selective to materials of the alternating stack
Implementation Method 2
forming an alternating stack of insulating layers and electrically conductive layers located over a substrate
Data Source
AI summary
A three-dimensional memory device includes an alternating stack of insulating layers and electrically conductive layers located over a substrate, the alternating stack containing a memory array region and a terrace region. Memory stack structures containing a memory film and a vertical semiconductor channel extend through the memory array region of the alternating stack. Support pillar structures extending through the terrace region of the alternating stack. The support pillar structures have different heights from each other.