3D Memory Dielectric Bridge Structures for Stable Access Trenches
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in manufacturing trench support bridge structures that provide adequate lateral support to prevent layer stack tilting and ensure reliable access trench formation.
Innovation Solution
The method involves forming alternating stacks of insulating and sacrificial material layers over a substrate, creating memory openings, filling them with memory elements, and forming dielectric bridge structures within access trenches, which are laterally supported by these bridges to maintain structural integrity during trench formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trench support bridge structures are formed to provide lateral support and prevent layer stack tilting, then structural stability and manufacturing reliability are improved, but device complexity and manufacturing process steps increase
Solution Approach 1:
Dielectric bridge structures are formed within access trenches before final trench fill structures are deposited. These preliminary bridge structures provide lateral support during subsequent processing steps, preventing layer stack tilting. The bridges are formed by depositing dielectric material conformally over sacrificial pillar structures, then performing selective etching to create the bridge geometry in advance of final trench completion.
Solution Approach 2:
Dielectric bridge structures serve as intermediary elements between the layer stacks and final access trench fill structures. These bridges act as temporary support mediators that maintain lateral spacing and prevent tilting during manufacturing, then are removed after serving their supportive function. The bridges are formed from dielectric material that can be selectively deposited and removed without affecting other device components.
2Manufacturing precision
If dielectric bridge structures with contoured sidewalls are formed, then access trench formation reliability is improved, but manufacturing precision requirements and process difficulty increase
Solution Approach 1:
Dielectric bridge structures are formed with contoured, curved sidewalls rather than straight vertical sides. The contoured geometry is achieved through conformal deposition processes that naturally create curved surfaces, followed by selective etching that preserves the contoured shape. This curvature provides better mechanical support and distributes stress more evenly, improving trench formation reliability while the conformal deposition process makes the curved shapes easier to manufacture than sharp angular features.
Solution Approach 2:
The sidewall contouring is achieved by controlling deposition parameters and etching conditions to create gradually varying thickness profiles. By adjusting deposition rate, temperature, and pressure parameters, as well as etching selectivity and duration, the bridge structures develop contoured sidewalls that are more tolerant to manufacturing variations. This parameter optimization reduces the precision requirements for subsequent trench formation steps.
3Adaptability or versatility
If multiple alternating layers of insulating and sacrificial material are deposited, then memory device functionality is improved, but manufacturing time and process duration increase
Solution Approach 1:
The memory device structure is segmented into multiple alternating layers of insulating material and sacrificial material, deposited in sequential cycles. Each cycle deposits a pair of layers that will later form distinct functional components. This segmentation enables the creation of complex three-dimensional memory architectures with vertical NAND strings and surrounding gates, but requires multiple deposition and etching cycles that extend manufacturing time. The segmented approach allows for precise control of each layer's properties while accumulating device functionality.
Data Source
AI summary
A memory device includes layer stacks, each including a respective alternating stack of respective insulating layers and respective electrically conductive layers and a respective contact-level dielectric layer, memory openings vertically extending through a respective one of the alternating stacks. memory opening fill structures located in a respective one of the memory openings and including a respective vertical stack of memory elements and a respective vertical semiconductor channel, and dielectric bridges structures located within access trenches that laterally separate the layer stacks. Each of the dielectric bridge structures includes a respective pair of contoured sidewalls. Each contoured sidewall of the dielectric bridge structures includes at least two vertically-straight and horizontally-convex surface segments that are adjoined by a vertically-extending edge. Access trench fill structures are located in the access trenches and each access trench fill structure embed a respective subset of the dielectric bridge structures.