3D Memory Word Line Contact Through Drain-Select Isolation
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Solution Overview
Problem
Existing three-dimensional memory devices face challenges in efficiently integrating word line contacts through drain-select-level isolation structures, which affect the performance and reliability of the memory devices.
Innovation Solution
The integration of word line contacts through drain-select-level isolation structures is achieved by forming an alternating stack of insulating and sacrificial material layers, replacing sacrificial material layers with conductive layers, and creating a laterally-insulated contact via assembly that contacts both the word line and isolation structure, using a first layer contact via structure and tubular insulating spacer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If word line contacts are integrated through drain-select-level isolation structures, then electrical connectivity is improved, but structural complexity increases
Solution Approach 1:
The contact via structure is nested within the drain-select-level isolation structure, with the tubular insulating spacer positioned inside the isolation structure and the conductive material filling the interior of the spacer. This nesting approach allows the contact via to be formed through the isolation structure without requiring separate processing steps, thereby improving electrical connectivity while managing structural complexity.
Solution Approach 2:
The contact via structure is segmented into distinct functional components: a tubular insulating spacer and conductive material. This segmentation allows each component to perform its specific function (isolation and conduction) independently, ensuring proper electrical connectivity while maintaining a manageable structural complexity through modular design.
2Strength
If laterally-insulated contact via assembly is formed, then structural integrity is improved, but manufacturing complexity increases
Solution Approach 1:
The tubular insulating spacer is formed preliminarily before the conductive material is deposited. This preliminary action establishes the structural framework and isolation boundaries in advance, ensuring structural integrity is built into the device architecture from the ground up, while the subsequent filling step completes the contact via formation in a straightforward manner.
Solution Approach 2:
The tubular insulating spacer acts as an intermediary structure between the isolation structure and the conductive material. It provides a pre-formed template that guides the deposition of conductive material and ensures proper positioning, thereby maintaining structural integrity while simplifying the manufacturing process by eliminating the need for complex alignment procedures.
3Reliability
If drain-select-level electrically conductive strips are divided, then electrical isolation is improved, but device complexity increases
Solution Approach 1:
The drain-select-level electrically conductive strips are segmented into separate regions by the contact via assembly. The tubular insulating spacer and conductive material create distinct electrical zones, improving electrical isolation between adjacent conductive strips while maintaining a relatively simple overall device structure through this natural segmentation.
Solution Approach 2:
The contact via assembly extracts a portion of the drain-select-level isolation structure to create a pathway for electrical contact. By selectively removing or modifying the isolation structure in specific regions, proper electrical isolation is achieved between conductive strips while avoiding the need for complex additional isolation layers or structures throughout the entire device.
Data Source
AI summary
A three-dimensional memory device includes an alternating stack of insulating layers and electrically conductive layers, where the electrically conductive layers include word lines and drain select gate electrodes that contain plurality of drain-select-level electrically conductive strips which are located above the word lines, memory stack structures vertically extending through the alternating stack, drain-select-level isolation structures located between a respective neighboring pair of drain-select-level electrically conductive strips, and a first laterally-insulated contact via assembly including a first layer contact via structure and a first tubular insulating spacer. The first laterally-insulated contact via assembly contacts a top surface of a first word line of the word lines, and the first laterally-insulated contact via assembly laterally contacts a first drain-select-level isolation structure of the drain-select-level isolation structures.