Purely Electrical Controllable Spin–Orbit Torque‐Based Reconfigurable Physically Unclonable Functions

Abstract

physical entity; and therefore, is vulnerable to being copied. [1] Another approach is to use physical unclonable functions (PUFs), where inherent random variations introduced during sample preparation and device manufacturing process are used to generate secret keys. These uncontrollable variations in turn randomly change the characteristics of fabricated PUF device, making it impossible to create an identical physical "copy." However, most PUFs exhibit static challenge-response pairs (CRPs) behavior once prepared, [2][3][4] which cannot be refreshed and limit the application of PUF in reusable scenarios. Hence, reconfigurable PUFs (rPUFs) are proposed to introduce an update mechanism to refresh the CRPs, [5] which can be used to protect nonvolatile storage from intrusive attacks and malicious manufacturers. Accordingly, many rPUFs have been explored through various approaches, [6,7] including optical rPUFs, [8] phase change memory rPUFs, [9] resistive random access memory rPUFs, [10,11] spin-transfer torque magnetic random access memory rPUFs, [12] and spinorbit torque (SOT) based rPUFs. [13,14] Especially, SOT-based rPUFs have attracted increasing attention because SOT-induced magnetization switching has the advantages of low power consumption, fast switching speed, and high endurance. [15,16] For example, Zhang et al. [13] demonstrated two types of rPUFs in Ta/CoFeB/MgO heterojunction based on process-induced SOT switching current variations and SOT-induced nonlinear domain wall dynamics, where an in-plane assistant magnetic field was needed to achieve deterministic SOT switching. Lee et al. [14] further demonstrated highly reliable spintronic PUFs based on field-free SOT switching in IrMn/CoFeB/Ta/ CoFeB heterojunction, where randomizing the magnetization direction of the exchange-biased bottom CoFeB layer through field annealing was crucial. The presence of an external magnetic field could make the device design more complex. Hence, from the application point of view, a fully electrical controllable SOT switching based rPUF is more suitable for potential realistic applications because it has better compatibility with today's complementary metal oxide semiconductor technology. In order to achieve magnetic field-free deterministic perpendicular magnetization switching, researchers have explored various methods, including the utilization of inplane exchange bias field, [17] interlayer exchange coupling, [18][19]

Electrical Manipulation of Antiferromagnetic Random‐Access Memory Device by the Interplay of Spin‐Orbit Torque and Spin‐Transfer Torque

“…The additional write freedom introduced by the STT in threeterminal MTJs facilitates the design of new functionalities within a single MRAM device. [47][48][49][50][51] In our ARAM devices, by selecting an appropriate range for V SOT , the devices have different switching probabilities with V STT = +0.6 or −0.6 V, enabling certain logic implementations. We define STT and SOT as input A and C, respectively (Figure 5a).…”