Vertical Memory Device Dummy Word Line Segmentation
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Solution Overview
Problem
Vertical memory devices face challenges in achieving improved electrical reliability due to issues with signal transfer and structural integrity in their design, particularly in the stacking and patterning of gate structures.
Innovation Solution
The proposed solution involves a vertical memory device design with specifically arranged word lines, dummy word lines, and selection lines, including openings and recesses, along with a method of manufacturing that uses alternating layers and etching processes to form a staircase shape and channel structures, enhancing electrical reliability by ensuring proper signal transfer and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If vertically stacked gate patterns are used to achieve high integration degree, then device density is improved, but electrical reliability deteriorates due to signal transfer issues
Solution Approach 1:
The gate pattern structure is segmented into multiple functional sections: control gates at different levels, dummy word lines with openings, and selection lines. This segmentation allows independent optimization of each section's electrical characteristics while maintaining overall high integration. The dummy word lines are divided into multiple segments with openings that expose underlying structures, enabling controlled signal paths.
Solution Approach 2:
Dummy word lines serve as intermediary structures between the control gates and the vertical channel structures. These dummy word lines with strategically placed openings act as mediators that facilitate proper electrical signal transfer while maintaining the vertically stacked architecture. The openings in dummy word lines expose edge portions of underlying first gate patterns, creating controlled electrical pathways.
2Reliability
If dummy word lines with openings are introduced to improve signal transfer, then electrical reliability is improved, but device complexity increases
Solution Approach 1:
The dummy word lines serve multiple functions simultaneously: they provide structural support in the vertically stacked architecture, create controlled openings for signal transfer, expose edge portions of underlying gate patterns, and maintain electrical isolation where needed. This multi-functionality reduces the need for separate dedicated structures for each function.
Solution Approach 2:
The structure employs a nested arrangement where dummy word lines are positioned between control gates and vertical channel structures, with openings that expose portions of underlying first gate patterns. This nested configuration allows multiple functional layers to be integrated vertically without requiring lateral expansion, maintaining compactness while achieving complex electrical pathways.
3Reliability
If alternating layers with openings and recesses are used to ensure proper signal transfer, then electrical reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The manufacturing process performs preliminary actions by forming the complete vertically stacked structure with all gate patterns, dummy word lines, and openings in sequence before final channel structure formation. The alternating layers with openings and recesses are prepared in advance through controlled etching processes, ensuring proper signal pathways are established before device operation.
Solution Approach 2:
The structure transitions from two-dimensional planar arrangements to three-dimensional vertically stacked configurations with alternating layers. The openings and recesses are positioned at specific vertical levels to expose edge portions of underlying structures, creating controlled electrical pathways in the vertical dimension that would be difficult to achieve in planar designs.
Data Source
AI summary
A vertical memory device may include a plurality of word lines spaced apart in a first direction, each extending in a second direction perpendicular to the first direction and having a first width in a third direction perpendicular to the first and second directions, a dummy word line over an uppermost word line, including an opening and having a portion thereof with the first width in the third direction, a first string selection line (SSL) and a second string selection line (SSL) over the dummy word line, the first and second SSLs being at substantially the same level along the first direction, each of the first and second SSLs having a second width less than the first width in the third direction, and a plurality of vertical channel structures, each through the word lines, the dummy word line, and one of the first and second SSLs.