Through-Stack Contact Via Structures in 3D Memory Devices
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in efficiently forming through-stack contact via structures that extend through an upper-tier alternating stack, which affects the performance and density of memory arrays.
Innovation Solution
The implementation of a multi-tier three-dimensional memory device structure, featuring a first-tier and second-tier alternating stack with retro-stepped dielectric material portions and laterally-isolated contact via structures that include a tubular insulating liner, allowing for vertical extension through the alternating stack and contact with electrically conductive layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If through-stack contact via structures are formed to extend through the upper-tier alternating stack, then electrical connections and vertical integration are improved, but the manufacturing complexity and difficulty of forming the structures increase
Solution Approach 1:
The contact via structure is divided into multiple segments: a first contact via structure extending through the second-tier alternating stack, and a second contact via structure extending through the first-tier retro-stepped dielectric material portion. This segmentation allows each via to be formed independently with controlled depth and positioning, reducing the overall manufacturing complexity while ensuring reliable electrical connections through the multi-tier stack.
Solution Approach 2:
The patent introduces lateral offset between the first-tier and second-tier retro-stepped dielectric material portions, creating a staggered three-dimensional arrangement. This dimensional change allows contact via structures to be formed at different lateral positions and depths, enabling vertical extension through the stack while managing manufacturing complexity through spatial distribution rather than a single complex via.
2Manufacturing precision
If laterally-isolated contact via structures with tubular insulating liner are implemented, then manufacturing precision and electrical connection reliability are improved, but the ease of manufacture decreases
Solution Approach 1:
A tubular insulating liner is formed around the first contact via structure before the second contact via structure is formed. This preliminary action establishes a precise geometric template and electrical isolation barrier that guides subsequent processing steps, ensuring manufacturing precision for the through-stack contact via structures while simplifying the overall fabrication sequence.
Solution Approach 2:
The tubular insulating liner acts as an intermediary element between the contact via structures and the surrounding dielectric materials. It provides a controlled interface that ensures precise positioning and electrical isolation, improving manufacturing precision without requiring direct complex interactions between the via structures and multiple surrounding layers.
3Productivity
If multi-tier alternating stacks with retro-stepped dielectric material portions are formed, then vertical integration and memory density are improved, but the device complexity increases
Solution Approach 1:
The first-tier and second-tier retro-stepped dielectric material portions are laterally offset from each other, creating an asymmetric staggered arrangement. This asymmetric design enables higher vertical integration and memory density by allowing contact via structures to pass through different lateral positions at different tiers, while the modular repetitive nature of the alternating stacks keeps the complexity manageable through pattern reuse.
Solution Approach 2:
The contact via structures are nested within the multi-tier alternating stack structure, with the first contact via structure positioned within the second-tier region and the second contact via structure positioned within the first-tier region. This nested arrangement achieves high vertical integration and memory density while organizing the complex structure into hierarchical levels that simplify manufacturing and design.
Data Source
AI summary
A first-tier structure includes a first vertically alternating sequence of first continuous insulating layers and first continuous sacrificial material layers and a first-tier retro-stepped dielectric material portion overlying first stepped surfaces of the first vertically alternating sequence. A second vertically alternating sequence of second continuous insulating layers and second continuous sacrificial material layers is formed over the first-tier structure. Retro-stepped dielectric material portions are formed in each of the first-tier structure and the second-tier structure. After formation of memory stack structures, electrically conductive layers replace portions of the first and second continuous sacrificial material layers. Laterally-isolated contact via structures can be formed through the second-tier structure and a first-tier retro-stepped dielectric material portion on first electrically conductive layers in the first-tier structure. Sacrificial landing pad structures can be employed to enable concurrent formation of contact via cavities through the retro-stepped dielectric material portions.