High Performance MRAM with Spin-Transfer-Torque and Voltage-Controlled Magnetic Anisotropy Effects

Abstract

Featured Application: Non-volatile magnetic tunnel junction-based magnetoresistive random access memory as reliable, high energy efficiency Internet of Things (IoTs) node memory.Abstract: The Internet of Things (IoTs) relies on efficient node memories to process data among sensors, cloud and RF front-end. Both mainstream and emerging memories have been developed to achieve this energy efficiency target. Spin transfer torque magnetic tunnel junction (STT-MTJ)-based nonvolatile memory (NVM) has demonstrated great performance in terms of zero standby power, switching power efficiency, infinite endurance and high density. However, it still has a big performance gap; e.g., high dynamic write energy, large latency, yield and reliability. Recently, voltage-controlled magnetic anisotropy (VCMA) has been introduced to achieve improved energy-delay efficiency and robust non-volatile writing control with an electric field or a switching voltage. VCMA-MTJ-based MRAM could be a promising candidate in IoT node memory for high-performance, ultra-low power consumption targets.

Full voltage manipulation of the resistance of a magnetic tunnel junction

“…The energy consumption per unit area was therefore approximately 0.85 mJ cm −2 for a 400V operation voltage, and 0.21 mJ cm −2 for 200 V; thus, the energy dissipation for write opera tion is approximately 1.06 mJ cm −2 by applying 400 V to the AA electrodes and applying 200 V to the BB electrodes, while the energy dissipation in stateoftheart STT MTJs is about 3 to 4 mJ cm −2 (29), which is larger than the dissipation in our devices. The energy consumption per bit for a circularshaped MTJ of 100 nm in diameter is about 85 f J bit −1 for a 400V operation voltage and about 21 f J bit −1 for 200 V, which is comparable with that of STT MTJs (about 100 f J bit −1 ) (41,42). Although the present applied voltage is high for practical applications because of the thick PMNPT substrate, the voltage can be further reduced to less than several volts using PMNPT thin film (43).…”

Nonvolatile Memories Based on Graphene and Related 2D Materials

“…In that context, the development of spin transfer torque magnetic tunnel junction (STT‐MTJ)‐based nonvolatile memory has demonstrated great performance in terms of zero standby power, switching power efficiency, infinite endurance and high density, but high dynamic write energy, large latency, yield and reliability need to be improved for future market impact. The development of voltage‐controlled magnetic anisotropy has appeared as a promising solution for reaching high‐performance and ultralow power consumption targets of the IoT node memory so that any solution to improve and control the magnetic anisotropy would bring a clear competitive advantage.…”

Impact of Spin-Transfer Torque on the Write-Error Rate of a Voltage-Torque-Based Magnetoresistive Random-Access Memory

“…The field switching requires high write energy, order of 100 pJ/bit [9], because the field is generated by the current flowing through the wire separated from the MTJ. Discovery of the spin transfer torque (STT) switching method [10,11] substantially decreased the write energy to the order of 100 fJ/bit [4]. However, it is still two orders of magnitude larger than the write energy of static random-access memory, ∼ 1 fJ/bit.…”

“…Voltage-torque (VT) switching is another attractive method for low power writing, which is based on voltage control of magnetic anisotropy (VCMA) in a thin ferromagnetic film [4,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. The mechanism of the VCMA in a MgO-based MTJ is considered as the combination of the selective electron/hole doping into the d-electron orbitals and the induction of a magnetic dipole moment, which affect the electron spin through the spin-orbit interaction [35][36][37][38][39].…”