3D Memory Source Layer Segmentation by Backside Isolation Trenches
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Solution Overview
Problem
Existing three-dimensional memory devices face challenges in achieving effective lateral electrical isolation of source lines, which affects the device's performance and manufacturing efficiency.
Innovation Solution
The proposed solution involves a memory device with a source layer made of doped semiconductor material, alternating stacks of insulating and conductive layers, and backside trenches that are laterally spaced apart. These trenches are filled with dielectric trench fill structures and backside contact via structures, ensuring electrical isolation and connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous source lines are used in three-dimensional memory devices, then manufacturing process is simpler, but lateral electrical isolation between source lines cannot be achieved
Solution Approach 1:
The continuous source layer is segmented into discrete source line portions by backside trenches that extend through the substrate. These trenches physically divide the source layer, creating laterally isolated source line segments that can be independently controlled, thereby achieving the required electrical isolation while maintaining a relatively simple manufacturing process.
Solution Approach 2:
Instead of attempting to isolate source lines in the horizontal plane through complex patterning, the invention introduces vertical isolation by extending trenches from the backside substrate surface through to the source layer. This dimensional approach to isolation simplifies the overall device structure while effectively achieving lateral electrical isolation between adjacent source lines.
2Reliability
If source lines are laterally isolated by complex structures, then electrical isolation is improved, but manufacturing efficiency decreases
Solution Approach 1:
The backside trenches are formed early in the manufacturing process, before the source layer is fully processed. By preparing the isolation structures in advance and extending them through to the source layer, the subsequent source line formation becomes simpler and more efficient, as the isolation boundaries are already established.
Solution Approach 2:
The invention achieves lateral electrical isolation through vertical trench structures extending from the substrate backside. This dimensional approach allows standard planar fabrication techniques to be used for the majority of the device, maintaining manufacturing efficiency while achieving the required isolation through the vertical dimension rather than complex lateral patterning.
3Reliability
If backside trenches are formed to isolate source lines, then electrical isolation is achieved, but device structure becomes more complex
Solution Approach 1:
The backside trenches serve multiple functions simultaneously: they provide lateral electrical isolation between source lines, they define the boundaries of source line portions, and they can accommodate contact structures for electrical access to the source layer. This multi-functionality reduces the need for separate isolation structures, thereby limiting the increase in device complexity.
Solution Approach 2:
The source layer is segmented into discrete portions by the backside trenches, with each segment representing an isolated source line portion. This segmentation approach achieves the required electrical isolation while maintaining a relatively simple overall structure, as the same trench structures that provide isolation also serve as the defining boundaries for each source line segment.
Data Source
AI summary
A memory device includes a horizontal source layer which is laterally separated into laterally isolated portions located in adjacent memory blocks by a dielectric backside trench fill structure or a source isolation dielectric structure.