Perpendicular spin transfer torque magnetic random access memories with high spin torque efficiency and thermal stability for embedded applications (invited)

TLDR

STT‑MRAMs are a leading candidate for next‑generation memory due to their high speed, endurance, read margin, low power, scalability, and non‑volatility. This work presents perpendicular STT‑MRAM stack designs achieving STT efficiency >5 kBT/µA, energy barriers >100 kBT at room temperature for sub‑40 nm devices, and tunnel magnetoresistance >150 %. The authors assess single‑device and 8‑Mb array data to demonstrate retention sufficient for automotive applications. They also show thermal stability up to 400 °C, exceeding Si CMOS back‑end requirements and opening STT‑MRAM for embedded memory.

Abstract

Magnetic random access memories based on the spin transfer torque phenomenon (STT-MRAMs) have become one of the leading candidates for next generation memory applications. Among the many attractive features of this technology are its potential for high speed and endurance, read signal margin, low power consumption, scalability, and non-volatility. In this paper, we discuss our recent results on perpendicular STT-MRAM stack designs that show STT efficiency higher than 5 kBT/μA, energy barriers higher than 100 kBT at room temperature for sub-40 nm diameter devices, and tunnel magnetoresistance higher than 150%. We use both single device data and results from 8 Mb array to demonstrate data retention sufficient for automotive applications. Moreover, we also demonstrate for the first time thermal stability up to 400 °C exceeding the requirement of Si CMOS back-end processing, thus opening the realm of non-volatile embedded memory to STT-MRAM technology.