3D Magnetic Tunnel Junction Array Vertical Stacking
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Solution Overview
Problem
The challenge is to increase device density in electronic devices while maintaining chip size and technology node, as shrinking line width, pitch, and film thickness approaches physical limits, necessitating a new design to enhance storage capacity and reduce costs.
Innovation Solution
The design incorporates a 3D magnetic tunnel junction array with a U-shaped free layer and tunnel layer sandwiched between electrodes, featuring through holes and trenches to create vertically stacked magnetic tunnel junctions, allowing for increased density without increasing chip size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If line width, pitch and film thickness are shrunk to increase device density, then device density is improved, but manufacturing precision and reliability deteriorate as physical limits are approached
Solution Approach 1:
The patent transitions from planar 2D magnetic tunnel junctions to vertically stacked 3D structures. Multiple MTJ cells are arranged in tiers along the vertical direction, with first electrodes extending through substrates and second electrodes positioned at different heights. This dimensional change allows significant increase in storage capacity without further shrinking lateral dimensions, thereby avoiding the manufacturing precision deterioration that occurs at physical size limits.
2Quantity of substance
If line width, pitch and film thickness are shrunk to increase device density, then device density is improved, but chip size must be reduced
Solution Approach 1:
The invention utilizes the vertical dimension to stack multiple MTJ cell tiers (e.g., four tiers with 64 cells each, totaling 256 cells) within the same chip footprint. First electrodes extend through the substrate while second electrodes are positioned at different vertical levels, enabling high-density storage without reducing the horizontal chip area. This allows increased device density while maintaining or even expanding chip size for higher total capacity.
3Quantity of substance
If technology node is reduced to increase device density, then device density is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent divides the magnetic tunnel junction structure into distinct segmented components: first electrodes extending through substrates, second electrodes at different levels, and multiple MTJ cells arranged in tiers. Each component can be independently fabricated and positioned, simplifying the manufacturing process compared to monolithic miniaturization. This segmentation approach increases device density while managing manufacturing complexity through modular assembly rather than requiring proportionally more complex processing at smaller technology nodes.
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 enables higher storage density and reduced costs by efficiently stacking magnetic tunnel junctions, maintaining chip size while enhancing storage capacity and reducing costs per chip.
Implementation Method 1
Tunnel magnetoresistance (TMR) effect was discovered in 1975. This effect was observed in a magnetic tunnel junction consisting of two ferromagnets and a tunnel barrier sandwiched between the two ferromagnets.
Data Source
AI summary
A magnetic tunnel junction cell includes a first electrode having an axis extending in a direction substantially perpendicular to an active surface of a substrate. The magnetic tunnel junction further includes a fixed layer, a U-shaped free layer, a tunnel layer sandwiched between the fixed layer and the U-shaped free layer and a second electrode embedded in the U-shaped free layer. The fixed layer, the tunnel layer and the U-shaped free layer are disposed between the first electrode and the second electrode and constitute a magnetic tunnel junction. The tunnel layer may also be U-shaped.