Memory Selector Using 2D Material Schottky Barriers
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Solution Overview
Problem
Existing back-to-back Schottky diodes in memory selectors face issues with metal diffusion, thickness variation, and thermal crosstalk, which affect the performance and scalability of memory devices in crossbar architectures.
Innovation Solution
Incorporating a metal-semiconductor-metal (MSM) back-to-back Schottky diode with an intermediate layer stack comprising one or more atomic layers of two-dimensional (2D) materials at the interfaces between the metal electrodes, which modulates the Schottky barrier heights to reduce metal diffusion and thermal crosstalk, and is compatible with the back-end-of-line (BEOL) process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional back-to-back Schottky diodes are used in memory selectors, then the basic memory function is achieved, but metal diffusion occurs at the electrode interfaces
Solution Approach 1:
A two-dimensional material layer (such as graphene, h-BN, or TMDs) is introduced as an intermediary between the metal electrode and the semiconductor layer. This intermediate layer acts as a diffusion barrier that prevents metal atoms from migrating into the semiconductor, thereby eliminating metal diffusion while maintaining the Schottky barrier functionality.
Solution Approach 2:
The electrode structure is transformed from a simple metal-semiconductor interface to a composite structure consisting of metal electrode + 2D material layer + semiconductor layer. This composite structure combines the electrical conductivity of metal, the barrier properties of 2D materials, and the semiconductor functionality, resolving the metal diffusion issue.
2Reliability
If conventional Schottky diodes are used, then the memory selector function is provided, but thickness variation in the intermediate layer causes performance variation
Solution Approach 1:
The patent utilizes two-dimensional material layers (atomically thin films) as the intermediate layer. These 2D material films provide uniform thickness at the atomic level and can be deposited over large areas with consistent properties, eliminating thickness variation issues that plague conventional thick intermediate layers.
Solution Approach 2:
The intermediate layer thickness is changed from conventional nanometer-scale thickness to atomically thin layers (single or few layers of 2D materials). This parameter change fundamentally improves thickness uniformity while maintaining the desired electrical barrier properties through controlled Schottky barrier height.
3Reliability
If conventional Schottky diodes are used, then the basic rectification function is achieved, but thermal crosstalk occurs between adjacent memory cells
Solution Approach 1:
The two-dimensional material layer serves as a thermal isolation intermediary between adjacent memory cell structures. This ultrathin barrier layer has low thermal conductivity, which suppresses thermal crosstalk between neighboring cells while maintaining electrical functionality, thereby eliminating the harmful thermal effects.
4Ease of manufacture
If conventional fabrication processes are used, then manufacturing is simplified, but high-temperature processing is required
Solution Approach 1:
The fabrication temperature parameter is dramatically reduced by changing from conventional high-temperature metal-semiconductor interface formation to low-temperature deposition of two-dimensional materials. 2D materials can be deposited at temperatures compatible with back-end-of-line (BEOL) processes, enabling integration without high-temperature steps.
Solution Approach 2:
The conventional thermal annealing process used to form Schottky barriers is replaced by direct deposition of 2D material layers that inherently provide the desired barrier properties. This substitution eliminates the need for high-temperature processing while achieving the same functional outcome.
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 use of 2D materials at the interfaces in the MSM back-to-back Schottky diode effectively reduces metal diffusion, thickness-induced variations, and thermal crosstalk, enhancing the performance and scalability of memory devices while reducing fabrication costs and eliminating the need for high-temperature processing.
Implementation Method 1
A bottom Schottky barrier having a bottom Schottky barrier height (ΦB) may be formed at the interface between the metal bottom electrode and an intermediate layer stack. A top Schottky barrier having a top Schottky barrier height (ΦT) may be formed at the interface between the metal top electrode and the intermediate layer stack.
Implementation Method 2
Each atomic layer forms or modulates the respective Schottky barrier height... effectively reduces metal diffusion
Implementation Method 3
The use of 2D materials at the interfaces in the MSM back-to-back Schottky diode effectively reduces metal diffusion, thickness-induced variations, and thermal crosstalk
Data Source
AI summary
The disclosed technology generally relates to a memory selector and to a memory device including the memory selector, and more particularly to the memory selector and the memory device implemented in a crossbar memory architecture. In one aspect, a memory selector for a crossbar memory architecture comprises a metal bottom electrode, a metal top electrode and an intermediate layer stack between and in contact with the metal top and bottom electrodes. A bottom Schottky barrier having a bottom Schottky barrier height (ΦB) is formed at the interface between the metal bottom electrode and the intermediate layer stack. A top Schottky barrier having a top Schottky barrier height (ΦT) is formed at the interface between the metal top electrode and the intermediate layer stack. The disclosed technology further relates to a random access memory (RAM) and a memory cell including the memory selector.