Through-Stack Contact Via Structure for 3D Memory Layer Isolation
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in efficiently forming through-stack contact via structures, which are crucial for reliable electrical connections and memory performance, due to limitations in existing manufacturing methods that result in non-uniform etching and incomplete contact via formation.
Innovation Solution
The method involves forming an alternating stack of insulating and sacrificial material layers, creating stepped surfaces, and replacing sacrificial layers with conductive layers to form contact via structures that include conductive pillars and fins, with annular insulating plates surrounding the pillars to ensure reliable electrical contact and prevent short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to form through-stack contact via structures, then the manufacturing process is simple, but the etching is non-uniform and contact via formation is incomplete
Solution Approach 1:
The contact via structure is segmented into multiple functional components: a conductive pillar portion extending through the alternating stack, annular conductive fin portions laterally protruding from the pillar, and annular insulating plates surrounding the pillar. This segmentation allows each component to perform its specific function optimally, achieving uniform and complete contact via formation that conventional single-structure methods cannot accomplish
Solution Approach 2:
The annular conductive fin portions are nested around the conductive pillar portion, and the annular insulating plates are nested around the pillar to laterally surround it. This nested configuration enables the structure to achieve complete contact with conductive layers while maintaining manufacturing precision, as each nested element contributes to the overall contact effectiveness without requiring overly complex external structures
2Reliability
If contact via structures are formed to ensure reliable electrical connections, then electrical connection reliability is improved, but the risk of short circuits between adjacent conductive layers increases
Solution Approach 1:
Annular insulating plates are positioned to laterally surround the conductive pillar portion between adjacent conductive layers. These insulating plates act as intermediary barriers that prevent direct electrical contact between adjacent conductive layers, thereby eliminating the short circuit risk while allowing the conductive pillar and fin portions to maintain reliable electrical connections to the intended conductive layers
Solution Approach 2:
The contact via structure exhibits local quality differentiation: conductive regions (pillar and fins) provide electrical connection where needed, while insulating regions (annular insulating plates) provide isolation where needed. This spatial differentiation of electrical properties allows the same structure to simultaneously achieve reliable electrical connections and prevent short circuits, resolving the contradiction between connection reliability and short circuit risk
Data Source
AI summary
A memory device includes an alternating stack of insulating layers and electrically conductive layers, a memory opening vertically extending through each layer within the alternating stack, a memory opening fill structure located in the memory opening and including a vertical stack of memory elements a vertical semiconductor channel, and a contact via structure. The contact via structure includes a conductive pillar portion vertically extending at least from a first horizontal plane including a bottommost surface of the alternating stack to a second horizontal plane including a topmost surface of the alternating stack, and an annular conductive fin portion laterally protruding from the conductive pillar portion and contacting one of the electrically conductive layers. A vertical stack of annular insulating plates laterally surrounds the conductive pillar portion and underlies the conductive fin portion.