MTJ Stack Crystal Grain Growth Control for PMA
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fabricating stable top pinned magnetic tunnel junction (MTJ) stacks compatible with high-temperature annealing cycles required for embedded-type memory applications is challenging due to uncontrollable texturization on the tunnel barrier layer, which affects the formation of synthetic-antiferromagnetic reference layers.
Innovation Solution
Incorporating a crystal grain growth controlling layer between a first magnetic pinned layer with a body-centered cubic (BCC) texture and a second magnetic pinned layer with a face-centered cubic (FCC) or hexagonal closed packing (HCP) texture, promoting strong perpendicular magnetic anisotropy and stability even after 400°C BEOL processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a top pinned MTJ stack is fabricated to solve current asymmetry and improve power efficiency, then power efficiency is improved, but the stack becomes unstable during high-temperature annealing processes due to uncontrollable texturization
Solution Approach 1:
A crystal grain growth controlling layer is introduced as an intermediary between the tunnel barrier layer and the second magnetic pinned layer. This intermediate layer mediates the texturization process during high-temperature annealing, enabling the second magnetic pinned layer to form with the desired FCC or HCP texture while preventing uncontrollable texturization. The crystal grain growth controlling layer thus serves as a buffer that allows the top pinned MTJ stack to maintain stability during BEOL processes while retaining its power efficiency advantages.
2Adaptability or versatility
If high-temperature annealing processes (400°C BEOL) are applied to embedded-type memory applications, then device integration is improved, but texturization control is lost making it difficult to form stable reference layers
Solution Approach 1:
The crystal grain growth controlling layer acts as a mediator that enables high-temperature annealing processes to be applied without losing texturization control. During the 400°C BEOL annealing process, this intermediate layer controls the grain growth and texturization of the second magnetic pinned layer, ensuring it forms with the required FCC or HCP texture. This allows the device to achieve compatibility with embedded-type memory applications while maintaining precise manufacturing control.
Solution Approach 2:
The invention changes the crystallographic parameters of the second magnetic pinned layer by controlling its texture to be FCC or HCP rather than BCC. This parameter change in crystal structure is achieved through the crystal grain growth controlling layer during high-temperature annealing, and it results in strong perpendicular magnetic anisotropy that maintains stability during BEOL processes while enabling compatibility with embedded-type memory applications.
3Strength
If a second magnetic pinned layer with FCC or HCP texture is formed to achieve strong perpendicular magnetic anisotropy, then magnetic anisotropy is improved, but the fabrication process becomes more complex
Solution Approach 1:
The crystal grain growth controlling layer serves as an intermediary that simplifies the fabrication process of achieving strong perpendicular magnetic anisotropy. Instead of requiring complex deposition conditions or post-processing steps to obtain FCC or HCP texture in the second magnetic pinned layer, the crystal grain growth controlling layer automatically guides the formation of the desired crystal structure during standard sputtering and annealing processes. This intermediary layer thus enables strong PMA while keeping the fabrication process relatively simple.
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 solution ensures the formation of a second magnetic pinned layer with strong perpendicular magnetic anisotropy, maintaining stability and texturization control during high-temperature annealing, enhancing the power efficiency of spin-transfer torque MRAM devices.
Implementation Method 1
a second magnetic pinned layer having strong perpendicular magnetic anisotropy (PMA)... promotes strong PMA to the second magnetic pinned layer
Implementation Method 2
a magnetic free layer having a body centered cubic (BCC) texture, a tunnel barrier layer having a BCC texture
Data Source
AI summary
A top pinned magnetic tunnel junction (MTJ) stack containing a magnetic pinned layered structure including a second magnetic pinned layer having strong perpendicular magnetic anisotropy (PMA) is provided. In the present application, the magnetic pinned layered structure includes a crystal grain growth controlling layer located between a first magnetic pinned layer having a body centered cubic (BCC) texture and the second magnetic pinned layer. The presence of the crystal grain growth controlling layer facilitates formation of a second magnetic pinned layer having a face centered cubic (FCC) texture or a hexagonal closed packing (HCP) texture which, in turn, promotes strong PMA to the second magnetic pinned layer of the magnetic pinned layered structure.