A low temperature functioning CoFeB/MgO-based perpendicular magnetic tunnel junction for cryogenic nonvolatile random access memory

Abstract

We investigated the low temperature performance of CoFeB/MgO based perpendicular magnetic tunnel junctions (pMTJs) by characterizing their quasistatic switching voltage, high speed pulse write error rate and endurance down to 9 K. pMTJ devices exhibited high magnetoresistance (>120%) and reliable (error rate<10 -4 ) bi-directional switching with 2 to 200 ns voltage pulses. The endurance of the devices at 9 K surpassed that at 300 K by three orders of magnitude under the same write conditions, functioning for more than 10 12 cycles with 10 ns write pulses. The critical switching voltage at 9 K was observed to increase by 33% to 93%, depending on pulse duration, compared to that at 350 K. Ferromagnetic resonance and magnetization measurements on blanket pMTJ film stacks suggest that the increased switching voltage is associated with an increase in effective magnetic anisotropy and magnetization of free layer with decreasing temperature.

Energy-efficient and Reliable Inference in Nonvolatile Memory under Extreme Operating Conditions

“…MTJ resistance increases with decreasing temperature, to the extent that the resistance at -170 • C can be 30% higher than at room temperature [73,149]. This increases the voltage required to write MTJs, and consequently, energy consumption.…”

“…Additionally, there is a beneit of cold temperature. The ratio between the high and low resistance state increases [73,152]. This leads to more robust logic gates which are less susceptible to voltage luctuations [110,154].…”

“…Our conservative area estimates are shown in Table 4. Impact of Temperature: MTJs have been demonstrated to function over a wide range of temperatures [73,152]. However, the MTJ resistance increases at colder temperatures, which will increase energy consumption.…”

“…Fortunately, CMOS can perform well across this wide temperature range, and the performance of CMOS circuits actually tends to increase with decreasing temperature [126,149]. However, cold operation can have an adverse efect on non-volatile memory, where the energy eiciency degrades [54,73,108,148,152].…”

From MTJ Device to Hybrid CMOS/MTJ Circuits: A Review

“…MTJ with a high-performance MgO barrier can also be used for flexible wearable spintronic applications, especially for biomedical sensing in early disease diagnosis of HIV-1 antigen p24 [361], low field sensitive sensor for neuronal signal detection, and design of versatile sensors for omnidirectional detection of skin decease. Further, hybrid circuits developed using MTJ have a diversified application due to its ultra-low-power dissipation capability in circuits used in RF communication, energy harvesting, IoT, artificial intelligence-based devices, biosensor, quantum computing computers, and cryogenic nonvolatile RAM [362].…”