Double Magnetic Tunnel Junction Memory Density
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Solution Overview
Problem
Current MRAM devices face limitations in bit density due to pitch constraints, and existing double magnetic tunnel junction (DMTJ) structures are complex and prone to electrical shorts, which hinder memory scaling and write efficiency.
Innovation Solution
The method involves forming a 2-bit MRAM device with two magnetic tunnel junctions stacked vertically, sharing a reference layer and having free layers with different surface areas, eliminating the need for a non-magnetic metal spacer and reducing the number of reference layers, thereby simplifying the manufacturing process and avoiding electrical shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the pitch of devices is reduced to increase bit density, then memory density improves, but manufacturing precision deteriorates due to ion beam etching limitations at higher angles
Solution Approach 1:
The patent transitions from a planar arrangement to a three-dimensional stacked configuration by vertically stacking multiple magnetic tunnel junctions (MTJs) sharing a common reference layer. This vertical stacking enables higher bit density without further reducing the lateral pitch, thereby avoiding the ion beam etching precision limitations that arise at higher angles.
2Quantity of substance
If a conventional DMTJ structure is used to increase memory density, then bit density improves, but device complexity increases and electrical shorts become more prone
Solution Approach 1:
The patent merges multiple MTJ structures by having them share a common reference layer. Instead of using separate reference layers for each MTJ as in conventional DMTJ structures, the invention combines the reference layers into a single shared structure, thereby reducing device complexity and the risk of electrical shorts while maintaining high memory density through vertical stacking.
Solution Approach 2:
The shared reference layer serves multiple functions simultaneously: it acts as the reference layer for multiple different MTJs, provides a common magnetic reference for all stacked junctions, and reduces the overall number of layers required. This multi-functionality simplifies the device structure while enabling higher density configurations.
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 enhances memory density and write efficiency by simplifying the DMTJ structure, reducing complexity, and avoiding electrical shorts, while maintaining effective switching currents and magnetoresistance performance.
Implementation Method 1
Tunnel magnetoresistance (TMR) and write efficiency are factors that affect the performance of MRAM devices
Data Source
AI summary
A method of manufacturing a double magnetic tunnel junction device is provided. The method includes forming a first free layer, forming a first tunnel barrier layer on the free layer, forming a reference layer on the first tunnel barrier layer, forming a second tunnel barrier layer on the reference layer, and forming a second free layer on the second tunnel barrier layer. An area of the second free layer is less than an area of the first free layer. Also, the first free layer, the first tunnel barrier layer and the reference layer are a first magnetic tunnel junction, and the reference layer, the second tunnel barrier layer and the second free layer are a second magnetic tunnel junction.