3D Memory Through-Stack Contact Via Layout for Precise Layer Connection
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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, particularly in vertical NAND strings with one bit per cell.
Innovation Solution
The formation of a device structure involving alternating stacks of insulating and conductive layers with stepped surfaces, retro-stepped dielectric material portions, and contact via structures that include laterally bulging and vertically extending portions, along with a method that involves patterning, etching, and replacing sacrificial material layers to create conductive layers, ensuring precise lateral offsets and connectivity.
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 achieved, but manufacturing complexity and difficulty increase significantly
Solution Approach 1:
The patent applies preliminary action by forming sacrificial material layers at specific positions within the alternating stacks before forming the contact via structures. These sacrificial layers are strategically placed to define the lateral offsets and contact positions. The contact via structures are then formed using these sacrificial layers as templates, eliminating the need for complex alignment processes during subsequent manufacturing steps. This preliminary placement of sacrificial materials simplifies the overall manufacturing process while ensuring proper connectivity.
Solution Approach 2:
The patent uses sacrificial material layers as intermediary elements to facilitate the formation of contact via structures with precise lateral offsets. These sacrificial layers act as temporary mediators that define the geometric relationships between different conductive layers. After the contact via structures are formed, the sacrificial materials are removed, having served their purpose as intermediaries in the manufacturing process. This intermediary approach simplifies the direct formation of complex contact structures.
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.