MRAM Memory Cell SAF Spacer Structure for Thermal Data Stability
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Solution Overview
Problem
The performance of magnetoresistive random access memory (MRAM) cells degrades over time, especially at high temperatures, leading to data errors due to instability in the synthetic anti-ferromagnetic (SAF) layer, which affects the reliability of non-volatile memory devices.
Innovation Solution
A method for fabricating MRAM cells involving a memory stack structure with a synthetic anti-ferromagnetic layer, where the spacer layer is made of immiscible metals like Ir or Ag, and the SAF layer is designed with Co and Pt layers, along with an oxidation process to maintain the anti-ferromagnetic state and prevent diffusion, thereby stabilizing the magnetization direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cell size is reduced to increase memory density, then the productivity and storage capacity are improved, but the performance degradation and data errors increase due to thermal instability
Solution Approach 1:
The patent changes the material parameters of the SAF layer by introducing immiscible metal elements (Ir or Ag) that phase separate from the magnetic layer materials (Co or Pt). This material parameter change creates a stable anti-ferromagnetic state that maintains data accuracy even in reduced-size cells subjected to thermal stress during operation.
Solution Approach 2:
The patent creates a composite structure within the SAF layer by combining immiscible metal elements with magnetic layer materials. The phase-separated immiscible metals form a composite material system that stabilizes the anti-ferromagnetic coupling between magnetic layers, preventing performance degradation in miniaturized memory cells.
2Ease of manufacture
If conventional SAF layer structures are used to simplify fabrication, then the ease of manufacture is improved, but the thermal stability and anti-ferromagnetic state maintenance deteriorate at high temperatures
Solution Approach 1:
The patent modifies the compositional parameters of the SAF layer by incorporating immiscible metal elements (Ir or Ag) at specific concentrations that phase separate during fabrication. This parameter change maintains the standard SAF layer fabrication process while fundamentally improving thermal stability through the formation of a stable anti-ferromagnetic state that resists high-temperature degradation.
3Adaptability or versatility
If the SAF layer is exposed to high temperatures during operation, then the operational range is extended, but the anti-ferromagnetic state degrades to a ferromagnetic state causing data errors
Solution Approach 1:
The patent changes the material composition parameters of the SAF layer by introducing immiscible metals (Ir or Ag) that phase separate to form a thermally stable structure. This parameter change enables the SAF layer to maintain its anti-ferromagnetic state at elevated temperatures, extending the operational temperature range without compromising data reliability.
Solution Approach 2:
The patent converts the potentially harmful effect of high temperatures, which normally cause anti-ferromagnetic state degradation, into a beneficial outcome by using the thermal energy to establish and maintain the phase-separated immiscible metal structure. This structure actually enhances thermal stability, turning the harmful high-temperature environment into a condition that reinforces the desired anti-ferromagnetic state.
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 effectively reduces data errors and maintains the performance of MRAM cells even at high temperatures by maintaining the anti-ferromagnetic state and preventing the SAF layer from changing to a ferromagnetic state, thus enhancing the thermal stability and reliability of the memory device.
Implementation Method 1
The first metal element is phase separated from a second metal element of the first and second magnetic layers
Implementation Method 2
the first metal element is phase separated from a second metal element of the first and second magnetic layers, and the second metal element of the first magnetic layer and the second magnetic layer interfaces with the spacer layer
Implementation Method 3
it further comprises performing an oxidation process to form an oxide side layer on a sidewall of each of the first magnetic layer and the second magnetic layer
Data Source
AI summary
A method for fabricating memory cell of magnetoresistive RAM includes forming a memory stack structure on a first electrode layer. The memory stack structure includes a SAF layer to serve as a pinned layer; a magnetic free layer and a barrier layer sandwiched between the SAF layer and the magnetic free layer. A second electrode layer is then formed on the memory stack structure. The SAF layer includes a first magnetic layer, a second magnetic layer, and a spacer layer of a first metal element sandwiched between the first magnetic layer and the second magnetic layer. The first metal element is phase separated from a second metal element of the first and second magnetic layers, and the second metal element of the first magnetic layer and the second magnetic layer interfaces with the spacer layer.