3D Memory Through-Stack Contact Via Layout for Vertical NAND
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Solution Overview
Problem
Existing three-dimensional memory devices face challenges in efficiently forming through-stack contact via structures, which are crucial for enhancing connectivity and performance in vertical NAND strings.
Innovation Solution
The formation of a device structure with alternating stacks of insulating and conductive layers, including retro-stepped dielectric material portions and contact via structures with laterally bulging and offset portions, along with a method involving sacrificial material replacement and isotropic etching to create efficient contact via structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional through-stack contact via structures are formed in three-dimensional memory devices, then connectivity is provided, but manufacturing complexity and difficulty increase
Solution Approach 1:
The patent applies preliminary action by forming sacrificial material layers and structures before the final contact via formation. The sacrificial material layers are deposited and patterned in advance to define the contact via locations and shapes, enabling subsequent etching processes to create precise through-stack contact vias without requiring complex direct patterning
Solution Approach 2:
The patent uses sacrificial material layers as intermediary structures that facilitate contact via formation. These sacrificial materials serve as temporary placeholders and etch stop layers that guide the formation of contact vias through the alternating stack, and are removed after serving their purpose, simplifying the overall manufacturing process
2Reliability
If through-stack contact via structures are formed to enhance connectivity, then device performance improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements self-service through self-aligned contact via formation where the sacrificial material layers automatically define the contact via positions and dimensions. The etching process uses these sacrificial structures as self-aligned guides, eliminating the need for separate alignment steps and reducing manufacturing precision requirements
Solution Approach 2:
The patent replaces mechanical alignment systems with chemical etching processes that use the sacrificial material layers as etch stop layers. This substitution allows precise contact via formation through selective chemical etching rather than mechanical positioning, improving precision while reducing manufacturing complexity
3Productivity
If alternating stacks with stepped surfaces are formed, then three-dimensional memory structure is created, but contact via formation becomes more difficult
Solution Approach 1:
The patent applies local quality by forming sacrificial material layers with specific local properties at different positions in the alternating stack. The sacrificial materials are selectively deposited and patterned to create local etch stop layers that facilitate contact via formation through the stepped surfaces, making the manufacturing process easier despite the complex three-dimensional structure
Data Source
AI summary
A device structure includes at least one alternating stack of respective insulating layers and respective electrically conductive layers; at least one retro-stepped dielectric material portion; a memory opening vertically extending through each layer within the at least one alternating stack; a memory opening fill structure located in the memory opening and including a vertical stack of memory elements; and a contact via structure including a laterally bulging portion in contact with a first electrically conductive layer, an upper portion, and a lower portion. In one embodiment, each insulating layer may comprise a respective carbon-doped silicate glass layer. In one embodiment, second electrically conductive layers that underlie the first electrically conductive layer may be laterally offset from the lower portion by a greater lateral offset distance than an outermost surface of the laterally bulging portion.