AlN Underlying Layer for MRAM Thermal Stability and Write Current
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Solution Overview
Problem
Spin-injection magnetic random access memory (MRAM) requires high retention and low write current, which existing technologies have not adequately addressed, particularly in achieving thermal stability and inversion current characteristics.
Innovation Solution
A magnetic memory device structure incorporating an AlN underlying layer with a hexagonal closest packed (hcp) structure, which improves thermal stability and reduces inversion current by enhancing the magnetic anisotropy and crystallinity of the CoFeB recording layer, while maintaining low element resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional underlying layer is used, then the device structure is simple, but the thermal stability and magnetic anisotropy are insufficient
Solution Approach 1:
The patent employs a composite underlying layer structure consisting of AlN (aluminum nitride) and Hf (hafnium) materials. This composite structure provides enhanced thermal stability and magnetic anisotropy compared to conventional single-material underlying layers, while maintaining structural integrity and compatibility with the CoFeB recording layer.
Solution Approach 2:
The patent optimizes specific parameters of the underlying layer including the thickness of AlN and Hf layers, the crystalline orientation (c-axis orientation), and the lattice constant matching. By carefully controlling these parameters, the patent achieves high thermal stability and perpendicular magnetic anisotropy without excessive structural complexity.
2Reliability
If the magnetic anisotropy is increased to improve retention, then the write current increases
Solution Approach 1:
The patent achieves high retention with low write current by optimizing the perpendicular magnetic anisotropy energy (Kt) through controlled thickness of the CoFeB recording layer (5-15 nm) and the underlying layer composition. The AlN/Hf underlying layer provides strong perpendicular magnetic anisotropy that enables stable magnetization switching at lower current densities compared to conventional structures.
Solution Approach 2:
The composite AlN/Hf underlying layer creates optimal magnetic coupling with the CoFeB recording layer, enhancing perpendicular magnetic anisotropy while minimizing damping. This composite structure enables efficient spin transfer torque switching at lower currents while maintaining high thermal stability for data retention.
3Manufacturing precision
If the crystallinity of the recording layer is improved, then the manufacturing precision increases, but the manufacturing complexity increases
Solution Approach 1:
The patent achieves high crystallinity in the CoFeB recording layer by controlling deposition parameters including temperature (200-400°C), pressure, and sputtering power during magnetron sputtering. The underlying AlN/Hf layer with c-axis orientation serves as a template that promotes epitaxial growth and high crystallinity in the overlying CoFeB layer without requiring additional complex manufacturing steps.
Solution Approach 2:
The patent prepares the underlying AlN/Hf layer in advance with proper crystalline orientation and surface morphology before depositing the CoFeB recording layer. This preliminary preparation creates an optimal substrate that facilitates high-crystallinity growth of the recording layer during a single deposition process, avoiding the need for separate crystallization treatment steps.
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 use of AlN as an underlying layer achieves high retention properties and low write current, improving thermal stability and magnetic anisotropy, thus enhancing the performance of the magnetic memory device.
Implementation Method 1
enhancing the magnetic anisotropy and crystallinity of the CoFeB recording layer
Implementation Method 2
CoFeB recording layer
Implementation Method 3
the electric resistance of the magnetoresistive element can be set in either of a high-resistance state and a low-resistance state by changing the direction of magnetization
Implementation Method 4
a spin-injection magnetic random access memory (MRAM) comprising a magnetoresistive element comprising a ferromagnetic material
Data Source
AI summary
According to one embodiment, a magnetic memory includes a first magnetic layer, a second magnetic layer, a non-magnetic intermediate layer provided between the first magnetic layer and the second magnetic layer and an underlying layer provided on an opposite side of the first magnetic layer with respect to the intermediate layer, and the underlying layer contains AlN of a hcp structure.