2D Material Selector for MRAM Leakage and Density
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Solution Overview
Problem
Current Magnetic Random Access Memory (MRAM) technologies face challenges in achieving high density integration, low power consumption, and reducing leakage current, particularly in Spin-Orbit Torque MRAM (SOT-MRAM) with a three-terminal structure.
Innovation Solution
A two-dimensional material-based selector with a metal-two-dimensional semiconductor-metal structure, comprising a stack unit with Schottky diode structures connected in reverse series, is introduced. This selector is integrated with a magnetic tunnel junction to form a selection storage unit, optimizing the structure for high-speed, low-power, and high-density memory applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If SOT-MRAM with three-terminal structure is used, then data writing speed and reading/writing times are improved, but unit area increases making high density integration difficult
Solution Approach 1:
The patent merges the selector and memory functions into a single integrated structure where the two-dimensional material selector is formed directly over the magnetic tunnel junction, eliminating the need for separate three-terminal SOT-MRAM structure and reducing unit area while maintaining high-speed performance
Solution Approach 2:
The patent transitions from planar two-terminal structure to vertical stacking architecture, arranging the two-dimensional material selector, magnetic tunnel junction, and electrode structures in vertical layers to achieve high-density integration while preserving fast switching characteristics
2Reliability
If conventional transistors or diodes are used as selectors, then selection function is achieved, but device size is large and integration density is reduced
Solution Approach 1:
The patent employs an ultrathin two-dimensional semiconductor material film as the selector, which provides reliable selection functionality while occupying minimal area due to its atomic-layer thickness and compact structure
Solution Approach 2:
The patent creates a composite structure combining two-dimensional semiconductor material with magnetic tunnel junction and metal electrodes, achieving both selection function and small device footprint through the synergistic integration of different functional materials
3Reliability
If chalcogenide ovonic threshold switching selector is used, then selection function is achieved, but thickness is large and mobility is low affecting storage speed
Solution Approach 1:
The patent replaces thick chalcogenide selector with an ultrathin two-dimensional semiconductor material film that provides equivalent or superior selection functionality while reducing thickness to atomic layers, thereby improving carrier mobility and storage speed
4Reliability
If variable-resistance type selector is used, then selection function is achieved, but on-resistance is too high to match existing MTJ
Solution Approach 1:
The patent adjusts the electrical parameters of the two-dimensional material selector through material selection and structure optimization to achieve on-resistance values that are well-matched with existing magnetic tunnel junction devices, enabling effective integration
5Quantity of substance
If memory units are arranged in cross array, then storage density is increased, but leakage current in unselected units increases
Solution Approach 1:
The patent implements local quality control by designing the two-dimensional material selector to exhibit highly nonlinear current-voltage characteristics with sharp turn-on behavior, enabling effective suppression of leakage current in unselected memory units while maintaining low standby power consumption
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 two-dimensional material-based selector achieves high-speed and reliable ovonic conduction with a turn-on voltage less than 1 V, low leakage current, and a high turn-on current density, enhancing the switching speed and reducing power consumption in MRAM devices.
Implementation Method 1
each stack unit includes two Schottky diode structures connected in reverse series
Implementation Method 2
achieves high-speed and reliable ovonic conduction with a turn-on voltage less than 1 V
Implementation Method 3
an electron spin injection is performed by a polarized current, and an information writing is completed by driving the free layer to switch the magnetization direction based on spin transfer torque
Implementation Method 4
when magnetization directions between the reference layer and the free layer are anti-parallel, the MTJ exhibits a high resistance state '1'; and when the magnetization directions of the reference layer and the free layer are parallel, the MTJ exhibits a low resistance state '0'
Implementation Method 5
uses an Oersted field generated by a pulse current to realize the magnetization switching of the free layer
Implementation Method 6
a spin injection is realized by a spin-orbit coupling effect, and the material in the free layer is driven to switch the magnetization direction
Data Source
AI summary
A two-dimensional material-based selector includes: a stack unit, wherein the stack unit has a metal-two-dimensional semiconductor-metal structure comprising a two-dimensional semiconductor layer, and metal layers arranged on an upper surface and a lower surface of the two-dimensional semiconductor layer, respectively. The number of the stack units is N, where N≥1. In each stack unit, a Schottky contact is formed on two metal-two-dimensional conductor interfaces, and the stack unit includes two Schottky diode structures connected in reverse series in response to the two-dimensional material-based selector being turned on. Alternatively, the number of the stack units is M, where M≥2. In each stack unit, a Schottky contact and an Ohmic contact are formed the two metal-two-dimensional conductor interfaces, respectively. The M stack units include M Schottky diode structures connected in reverse series in response to the two-dimensional material-based selector being turned on.