vdW Multilayer Tunnel Selectors for High-Uniformity Crossbar Memory
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Solution Overview
Problem
Conventional two-terminal selectors used in crossbar arrays lack desirable characteristics such as high nonlinearity, high endurance, and uniformity, which are essential for high-density memory and computing applications.
Innovation Solution
A tunneling-based selector with a multilayer barrier structure composed of van der Waals materials is introduced, forming a staircase tunnel barrier that approximates a triangular tunnel barrier, providing high nonlinearity and endurance, and ensuring uniformity across devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional two-terminal selectors are used in crossbar arrays, then device simplicity is maintained, but high nonlinearity, high endurance, and uniformity are not achieved
Solution Approach 1:
The patent employs a composite multilayer barrier structure combining different van der Waals materials (h-BN, MoS2, WS2, WSe2, MoSe2, HfS2) with distinct electron affinities. This composite approach creates a staircase tunnel barrier that achieves superior nonlinearity (current ratio ≥10^7) and uniformity while maintaining a two-terminal simple structure suitable for crossbar arrays.
Solution Approach 2:
Each layer in the multilayer barrier structure is designed with specific local properties - different van der Waals materials are selected and positioned to create varying electron affinity profiles. The central layer has lower electron affinity than outer layers, creating a tailored energy landscape that optimizes tunneling characteristics for high nonlinearity and reliability.
2Quantity of substance
If high-density memory devices are implemented without improved selectors, then device density is limited, but manufacturing cost increases
Solution Approach 1:
The patent extracts the selector function from complex transistor-based three-terminal structures and implements it in a simplified two-terminal device. This extraction enables direct integration into crossbar arrays without additional control terminals, increasing device density while maintaining cost-effective manufacturing processes.
Solution Approach 2:
The invention changes the fundamental parameter of the barrier structure from conventional single-layer or metal-oxide configurations to a multilayer van der Waals heterostructure with staircased electron affinity profiles. This parameter change enables achieving I-V nonlinearity ratios of 10^7 or higher, which is critical for high-density crossbar operation without requiring complex selective transistor designs.
3Reliability
If conventional selector structures are used, then manufacturing process is simpler, but selector nonlinearity and selectivity are insufficient
Solution Approach 1:
The barrier structure is segmented into multiple discrete van der Waals layers (at least three layers including a central layer and outer layers) with progressively varying electron affinities. This segmentation creates a staircased tunnel barrier that provides superior nonlinearity (current ratio ≥10^7) compared to conventional single-layer barriers, while each individual layer remains manufacturable using standard van der Waals material deposition techniques.
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 selectors exhibit high nonlinearity, endurance, and uniformity, enabling efficient selection and operation in high-density memory and computing applications with a current density suitable for various memory and computing tasks.
Implementation Method 1
tunneling-based selector with a multilayer staircase tunneling barrier structure using van der Waals (vdW) materials, approximating a triangular tunnel barrier
Implementation Method 2
multilayer barrier structure includes a first layer of a first van der Waals (vdW) material; a second layer of a second vdW material; and a third layer of a third vdW material
Data Source
AI summary
In accordance with some embodiments of the present disclosure a tunneling-based selector is provided. The selector includes a multilayer barrier structure fabricated between a first electrode and a second electrode. The multilayer barrier structure includes a first layer of a first van der Waals (vdW) material; a second layer of a second vdW material; and a third layer of a third vdW material. The first layer of the first vdW material is fabricated between the second layer of the second vdW material and the third layer of the third vdW material. The electron affinity of the first layer of the first vdW material is lower than the second electron affinity of the second layer of the second vdW material and the electron affinity of the third layer of the vdW material.