Composite Seed Structure Enhances PMA in pSTT-MRAM
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Solution Overview
Problem
Conventional magnetic pinning structures in perpendicular magnetic tunnel junctions face challenges in achieving stable magnetic pinning due to limitations in perpendicular magnetic anisotropy (PMA), which affects device miniaturization, current efficiency, and thermal stability.
Innovation Solution
A composite seed structure (CSS) with a face-center-cubic (FCC) crystalline structure is introduced, comprising a modulating-layer, buffer-layer, and top-seed-layer, along with an alloy anti-ferromagnetic coupling spacer, to enhance perpendicular magnetic anisotropy and stabilize the magnetic pinning layer, promoting FCC (111) growth and anti-ferromagnetic coupling for improved PMA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional magnetic pinning structures are used, then device structure is simple, but perpendicular magnetic anisotropy is insufficient leading to poor magnetic pinning stability
Solution Approach 1:
The patent applies composite materials by creating a multi-layer seed structure comprising a first seed layer (e.g., Ru), a second seed layer (e.g., Rh), and a third seed layer (e.g., Ir), where each layer contributes different properties to achieve enhanced perpendicular magnetic anisotropy and stable magnetic pinning that cannot be achieved with single-material seed layers
Solution Approach 2:
The seed structure is segmented into multiple functional layers with distinct thicknesses and materials (first seed layer 1-5 nm, second seed layer 1-3 nm, third seed layer 0.5-2 nm), where each segment performs a specific function in promoting FCC crystal structure and enhancing PMA
2Volume of moving object
If device miniaturization is pursued, then device size is reduced, but current efficiency decreases due to insufficient PMA
Solution Approach 1:
The patent changes material parameters by selecting specific materials (Ru, Rh, Ir) and optimizing their thickness parameters (1-5 nm, 1-3 nm, 0.5-2 nm respectively) to maximize perpendicular magnetic anisotropy, enabling miniaturized devices to maintain high current efficiency through enhanced magnetic pinning stability
3Temperature
If PMA is enhanced for better pinning, then thermal stability improves, but device complexity increases
Solution Approach 1:
The patent applies local quality by concentrating the complexity only in the seed layer region (first, second, and third seed layers with specific materials and thicknesses) while keeping the rest of the magnetic tunnel junction structure simple, thereby achieving enhanced thermal stability through localized structural optimization
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 CSS enhances perpendicular magnetic anisotropy, stabilizes magnetic pinning, and maintains high tunnel magneto-resistance (TMR) values, enabling device miniaturization, reduced current requirements, and improved thermal stability in magnetic memory applications.
Implementation Method 1
The CSS enhances perpendicular magnetic anisotropy, stabilizes magnetic pinning, and maintains high tunnel magneto-resistance (TMR) values, enabling device miniaturization
Implementation Method 2
A composite seed structure (CSS) with a face-center-cubic (FCC) crystalline structure is introduced, comprising a modulating-layer, buffer-layer, and top-seed-layer
Implementation Method 3
along with an alloy anti-ferromagnetic coupling spacer, to enhance perpendicular magnetic anisotropy and stabilize the magnetic pinning layer, promoting FCC (111) growth and anti-ferromagnetic coupling for improved PMA
Implementation Method 4
The magnetic state of an MRAM cell is read out by using the tunnel magneto-resistance (TMR) of the MTJ
Implementation Method 5
the magnetization direction of a free layer (FL) is reversed by applying a spin-polarized current to the magnetoresistive element
Implementation Method 6
using spin momentum transfers
Data Source
AI summary
The invention comprises a novel composite seed structure (CSS) having lattice constant matched crystalline structure with the Co layer in above perpendicular magnetic pinning layer (pMPL) so that an excellent epitaxial growth of magnetic super lattice pinning layer [Co/(Pt, Pd or Ni)]n along its FCC (111) orientation can be achieved, resulting in a significant enhancement of perpendicular magnetic anisotropy (PMA) for perpendicular spin-transfer-torque magnetic-random-access memory (pSTT-MRAM) using perpendicular magnetoresistive elements as basic memory cells which potentially replace the conventional semiconductor memory used in electronic chips, especially mobile chips for power saving and non-volatility.