Cross-Point Array Pillar Structure with Threshold Switching Layer
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Solution Overview
Problem
Cross-point array devices with nonvolatile memory elements face writing and reading errors due to undesired sneak currents between adjacent cells, which can be mitigated by incorporating a selection element in the pillar structure but require effective electrical connectivity and protection of the threshold switching layer.
Innovation Solution
A cross-point array device is designed with a first pillar structure having a threshold switching layer, a resistance switching layer surrounding it, and a second pillar structure with a resistance change memory layer, where conductive filaments electrically connect the first pillar structure to the second, reducing sneak currents and protecting the threshold switching layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a selection element is added to the pillar structure to prevent sneak current, then writing and reading errors are reduced, but device complexity increases
Solution Approach 1:
The threshold switching layer is nested within the pillar structure, forming a selection element that is integrated into the existing memory cell architecture. This nesting approach allows the selection element to be incorporated without significantly increasing device complexity, as it shares the same vertical pillar configuration rather than adding separate lateral structures.
Solution Approach 2:
The pillar structure is designed to serve multiple functions: it acts as both the memory element holder and the selection element container. The threshold switching layer within the pillar provides selection functionality while the same pillar structure houses the resistance switching layer for memory storage, reducing the need for additional separate structures.
2Reliability
If conductive filaments are formed to electrically connect pillar structures, then electrical connectivity is improved, but sneak current between adjacent cells increases
Solution Approach 1:
The threshold switching layer is positioned locally at specific regions within the pillar structure to control and confine current flow. This localized placement ensures that conductive filaments form only in intended paths through the threshold switching layer, preventing lateral leakage and sneak currents between adjacent memory cells while maintaining necessary electrical connectivity.
3Ease of manufacture
If the threshold switching layer is exposed during second pillar structure formation, then manufacturing precision is reduced, but ease of manufacture improves
Solution Approach 1:
The threshold switching layer is formed and positioned within the first pillar structure before the second pillar structure formation process begins. This preliminary action ensures that the threshold switching layer is already in its final protected position, eliminating the need for additional protection steps during subsequent manufacturing processes and maintaining both ease of manufacture and manufacturing precision.
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 solution effectively reduces operating current and power consumption by controlling charge conduction through conductive filaments, while enhancing the structural and electrical reliability of the threshold switching layer by protecting it from physical and chemical damage during the formation of the second pillar structure.
Implementation Method 1
The conductive filament electrically connects the first pillar structure to the second pillar structure
Implementation Method 2
a first pillar structure, including a threshold switching layer, disposed on the substrate
Data Source
AI summary
A cross-point array device according to an embodiment includes a substrate, a first pillar structure, including a threshold switching layer, disposed on the substrate, a resistance switching layer surrounding an upper surface and a sidewall surface of the first pillar structure, and a second pillar structure, including a resistance change memory layer, disposed on the resistance switching layer. The resistance switching layer has a conductive filament electrically connecting the first pillar structure to the second pillar structure.