MRAM Cell Thermally Assisted Write Reduces Field Current
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Solution Overview
Problem
Conventional MRAM cells require high field currents for writing, which is a limitation for low power applications and can lead to issues like write magnetic field asymmetry and broadening of the write magnetic field distribution.
Innovation Solution
A method for writing to an MRAM cell using a thermally assisted write operation with a heating current that acts as a spin polarized current, combined with a reduced field current, to switch the storage magnetization, where the heating current is passed to heat the magnetic tunnel junction to a high temperature threshold and then cooled to pin the magnetization in the written direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional thermally assisted write operation is used with high field current, then the storage magnetization can be switched reliably, but the power consumption is too high for low power applications
Solution Approach 1:
The patent changes the temperature parameter by heating the magnetic tunnel junction to a high temperature threshold during the write operation. This thermal assistance modifies the magnetic properties of the storage layer, enabling magnetization switching with reduced field current and thus lower power consumption while maintaining writing reliability
Solution Approach 2:
The patent applies preliminary heating to the magnetic tunnel junction before applying the field current. By pre-heating the junction to the high temperature threshold, the storage layer becomes more susceptible to magnetic field influence, allowing the subsequent field current to switch the magnetization more efficiently with reduced current magnitude
2Reliability
If high field current is used for writing, then the storage magnetization can be switched, but the field current magnitude is too high and causes write magnetic field asymmetry and broadening
Solution Approach 1:
The patent modifies the temperature parameter of the magnetic tunnel junction during the write operation by heating it to a high temperature threshold. This parameter change reduces the coercivity of the storage layer, enabling reliable magnetization switching with lower field current and minimizing write magnetic field asymmetry and broadening
Solution Approach 2:
The patent introduces thermal energy as an intermediary that facilitates the magnetization switching process. By heating the magnetic tunnel junction, the thermal energy assists the field current in switching the storage magnetization, reducing the required field current magnitude and its associated harmful effects
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 reduces the magnitude of the field current required for switching the storage magnetization, improving writing selectivity and thermal stability while minimizing power consumption.
Implementation Method 1
passing a heating current in the magnetic tunnel junction via the current line for heating the magnetic tunnel junction
Implementation Method 2
the magnitude of the heating current is such that it acts as a spin polarized current and exerts an adjusting spin transfer on the storage magnetization
Implementation Method 3
passing a field current such as to switch the storage magnetization in a written direction substantially parallel or antiparallel relative to the reference magnetization
Implementation Method 4
a storage antiferromagnetic layer exchange coupling the storage layer and pinning the storage magnetization when the magnetic tunnel junction is at the low temperature threshold
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3(a)~4
AI summary
The present disclosure concerns a method for writing to a MRAM cell (1) comprising a magnetic tunnel junction (2) formed from a storage layer (23) having a storage magnetization (230); a reference layer (21) having a reference magnetization (210); and a tunnel barrier layer (22) included between the sense and storage layers (21, 23); and a current line (3) electrically connected to said magnetic tunnel junction (2); the method comprising: passing a heating current (31) in the magnetic tunnel junction (2) for heating the magnetic tunnel junction (2); passing a field current (41) for switching the storage magnetization (230) in a written direction in accordance with the polarity of the field current (41). The magnitude of the heating current (31) is such that it acts as a spin polarized current and can adjust the storage magnetization (230); and the polarity of the heating current (31) is such as to adjust the storage magnetization (230) substantially towards said written direction.