3D Memory Composite Word Lines and Multi-Strip Select Lines
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in efficiently manufacturing composite word lines and laterally divided drain-select-level electrodes, which are crucial for enhancing memory density and performance, due to complexities in layer formation and isolation techniques.
Innovation Solution
The proposed solution involves forming a three-dimensional memory device with alternating stacks of insulating and electrically conductive layers over a substrate, where drain-select-level electrically conductive layers are created in multiple levels with different vertical distances, laterally spaced apart, and connected by vertical conductive strips, incorporating a stack of first and second electrically conductive materials with air gaps at their ends, and word-line-level electrically conductive layers with specific material compositions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If composite word lines and laterally divided drain-select-level electrodes are formed in three-dimensional memory devices, then memory density and performance are enhanced, but manufacturing complexity increases due to layer formation and isolation techniques
Solution Approach 1:
The drain-select-level electrode is divided into multiple laterally spaced apart groups that are electrically isolated from one another. Each group contains drain-select-level electrically conductive layers at different vertical levels, creating segmented structures that simplify the formation process while maintaining high memory density
Solution Approach 2:
The patent utilizes vertical stacking to arrange drain-select-level electrically conductive layers at multiple vertical levels within each lateral group. This three-dimensional arrangement allows increased memory density without proportionally increasing lateral manufacturing complexity, as the vertical dimension provides additional space for electrode formation
2Reliability
If drain-select-level electrically conductive layers are laterally spaced apart and electrically isolated, then electrical isolation is improved, but manufacturing precision requirements increase
Solution Approach 1:
Insulating layers are introduced as intermediary structures between laterally spaced drain-select-level electrically conductive layers. These insulating layers provide electrical isolation and serve as structural mediators that define the lateral spacing, reducing the precision requirements for direct electrode placement while ensuring reliable electrical isolation
3Reliability
If vertical conductive strips are used to connect drain-select-level electrically conductive layers, then electrical connectivity is enhanced, but device complexity increases
Solution Approach 1:
The vertical conductive strips serve multiple functions: they provide electrical connectivity between drain-select-level electrically conductive layers at different vertical levels, act as structural support elements, and function as part of the overall electrode architecture. This multi-functionality reduces the need for additional specialized components, offsetting the increased structural complexity
Data Source
AI summary
An alternating stack of insulating layers and sacrificial material layers is formed over a substrate. Memory stack structures are formed through the alternating stack. Drain-select-level trenches through an upper subset of the sacrificial material layers, and backside trenches are formed through each layer of the alternating stack. Backside recesses are formed by removing the sacrificial material layers. A first electrically conductive material and a second electrically conductive material are sequentially deposited in the backside recesses and the drain-select-level trenches. Portions of the second electrically conductive material and the first electrically conductive material may be removed by at least one anisotropic etch process from the drain-select-level trenches to provide drain-select-level electrically conductive layers as multiple groups that are laterally spaced apart and electrically isolated from one another by cavities within the drain-select-level trenches.