A highly thermally stable sub-20 nm magnetic random-access memory based on perpendicular shape anisotropy

Area of Science:

• Materials Science
• Electrical Engineering
• Physics

Background:

• Perpendicular spin-transfer torque magnetic random-access memory (pMTJ STT-MRAM) faces scalability challenges.
• Conventional pMTJ designs have limitations in downscaling due to demagnetizing energy opposing interfacial perpendicular magnetic anisotropy (iPMA).

Purpose of the Study:

• To present a novel approach for enhancing the downsize scalability of pMTJ STT-MRAM.
• To investigate the use of increased storage layer thickness to induce perpendicular shape anisotropy (PSA).

Main Methods:

• Depositing a thick ferromagnetic (FM) layer on an MgO/FeCoB based magnetic tunnel junction (MTJ).
• Engineering MTJ pillars where storage layer thickness is comparable to or exceeds pillar diameter.
• Utilizing magnetic characterization to assess thermal stability and performance.

Main Results:

• Achieved high and tunable thermal stability factors (>200) for MTJs as small as 8 nm in diameter.
• Demonstrated the possibility of maintaining thermal stability factors (>60) down to 4 nm diameter.
• Identified that both PSA and iPMA favor out-of-plane magnetization orientation, reducing write current requirements.

Conclusions:

• The proposed PSA-STT-MRAM architecture significantly improves downsize scalability.
• This method offers a pathway to highly stable, smaller memory cells with reduced power consumption.
• The findings pave the way for next-generation high-density MRAM technologies.