MRAM Cell Oxidized Side Surfaces Reduce Write Current
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Solution Overview
Problem
Magnetoresistive random access memories (MRAM) using the tunneling magnetoresistive (TMR) effect face challenges in increasing integration density due to the need for high current densities for writing, which complicates the reduction of select transistor size and magnetic body volume, leading to degradation in retention and signal strength.
Innovation Solution
The design incorporates a magnetoresistive random access memory with a vertical MTJ element structure where the side surfaces of the metal magnetic layers are oxidized, reducing the effective area and write current, while maintaining current density, and using a multilayer configuration with specific film thicknesses and materials to enhance integration and reduce leak currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the film thickness of the magnetic body is decreased to reduce write current, then the write current can be reduced, but the magnetic anisotropy energy decreases causing degradation in retention or signal amount
Solution Approach 1:
The patent applies local quality by oxidizing only the side surfaces of the magnetic body while maintaining the central region intact. This creates a localized modification where the oxidized side surfaces provide magnetic anisotropy and retention without requiring increased volume, thus enabling thin film thickness while maintaining reliability.
Solution Approach 2:
The patent uses composite materials by combining the magnetic body material (e.g., CoFeB) with an oxide layer on its side surfaces. This composite structure provides both the desired magnetic properties for low write current and the magnetic anisotropy for reliable retention, resolving the contradiction between reducing write current and maintaining retention.
2Use of energy by moving object
If the film thickness of the magnetic body is decreased to reduce write current, then the write current can be reduced, but the signal amount decreases
Solution Approach 1:
The localized oxidation of side surfaces enhances the magnetic anisotropy field, which improves the magnetization switching efficiency and signal detection capability. This allows thin magnetic bodies to maintain strong signal amounts despite reduced thickness.
Solution Approach 2:
The patent changes the physical and chemical parameters of the magnetic body by introducing oxide layers on side surfaces. This modification alters the magnetic anisotropy energy density, enabling thin films to achieve sufficient signal strength without increasing volume or requiring high write currents.
3Productivity
If the area of the MTJ element is reduced to increase integration density, then integration density increases, but the write current density requirement increases the transistor size
Solution Approach 1:
The side surface oxidation creates a localized magnetic anisotropy that enhances the TMR effect efficiency. This allows smaller MTJ elements to achieve sufficient signal strength and switching capability, enabling reduced transistor size while maintaining integration density improvements.
Solution Approach 2:
By modifying the magnetic anisotropy through side surface oxidation, the patent enables smaller MTJ elements to operate effectively at lower current densities. This parameter change allows integration density to increase without proportionally increasing transistor size, as the oxidized structure improves switching efficiency.
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
This approach allows for a higher integration density of MRAM while reducing the write current and transistor size, improving retention and signal strength by optimizing the current flow and suppressing leak currents through the use of oxidized side surfaces and specific material compositions.
Implementation Method 1
the side surfaces of the metal magnetic layers are oxidized, reducing the effective area and write current
Implementation Method 2
magnetoresistive random access memories using a tunneling magnetoresistive effect have been proposed
Data Source
AI summary
According to one embodiment, a magnetoresistive random access memory includes a magnetoresistive element in a memory cell, the magnetoresistive element including a first metal magnetic layer, a second metal magnetic layer, and an insulation layer interposed between the first and second metal magnetic layers. An area of each of the first and second metal magnetic layers is smaller than an area of the insulation layer.