Core-Shell Chalcogenide Switching Layer for Low-Leakage 3D Memory
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Solution Overview
Problem
In three-dimensional cross point array memory devices like PRAM, the generation of sneak currents and leakage currents due to the integration of ovonic threshold switching devices with chalcogenide-based materials leads to performance issues, such as increased off-currents and cross-talk between memory cells, making low-power operation difficult.
Innovation Solution
Implementing a core-shell structured switching material layer in the memory cells, where the shell portion has a higher electrical resistance than the core portion, composed of chalcogenide materials with specific dopants, to reduce leakage currents by directing most current flow through the core portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ovonic threshold switching devices with chalcogenide-based materials are integrated into memory cells, then high integration and simplified wiring are achieved, but sneak currents and leakage currents are generated leading to increased off-currents and cross-talk
Solution Approach 1:
The switching material layer is segmented into a core portion and a shell portion with different material compositions and electrical resistances. The core portion contains chalcogenide material for switching functionality, while the shell portion contains material with higher electrical resistance to block leakage currents. This segmentation allows the device to maintain high integration density while reducing sneak currents and off-currents by directing current flow primarily through the core portion.
Solution Approach 2:
Different regions of the switching material layer are assigned different local qualities: the core portion has lower electrical resistance to enable current flow during switching operations, while the shell portion has higher electrical resistance to suppress leakage currents. This local differentiation of material properties allows the device to achieve both high integration and low leakage current simultaneously.
2Reliability
If chalcogenide-based switching material is used, then switching functionality is achieved, but cross-talk between memory cells increases
Solution Approach 1:
The switching material layer is divided into a core portion containing chalcogenide material for switching functionality and a shell portion with higher resistance material. This segmentation confines current flow primarily to the core portion during switching operations, preventing current from spreading to adjacent memory cells and thereby reducing cross-talk while maintaining reliable switching functionality.
Solution Approach 2:
The shell portion acts as an intermediary barrier between the active chalcogenide core and the surrounding environment/adjacent cells. By providing a high-resistance interface layer, it mediates the current flow to prevent unwanted electrical interaction between neighboring memory cells, thus reducing cross-talk while preserving the switching function of the core.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The core-shell structure effectively reduces leakage currents, ensuring low off-currents and enabling low-power operation of the memory device by minimizing cross-talk and sneak currents.
Implementation Method 1
the shell portion covering a side surface of the core portion and including a material having an electrical resistance greater than an electrical resistance of the core portion
Data Source
AI summary
Provided are a switching device and a memory device including the switching device. The switching device includes first and second electrodes, and a switching material layer provided between the first and second electrodes and including a chalcogenide. The switching material layer includes a core portion and a shell portion covering a side surface of the core portion. The switching layer includes a material having an electrical resistance greater than an electrical resistance of the core portion, for example in at least one of the core portion or the shell portion.