November 07, 2022
Minneapolis, United States
Automated Acquisition of Switching Dynamics in Reflexion Mode of MRAM Magnetic Tunnel Junctions
Switch timings of MRAM technologies, such as Spin Transfer Torque (STT) and Spin Orbit Torque (SOT), are critical in the context of SRAM replacement for last level
cache applications 1. The operating conditions of Magnetic tunnel junction (MTJ) result from the compromise between writing current level, retention and stability during read operation.
To optimize the operating conditions for a given application and tune the physical parameters of the MTJs, we propose a new system able to extract the incubation and switching times
under writing pulses application.
The proposed system operates by acquiring and analyzing the reflected signal of the writing pulse applied on the MTJ, which could be a 2 or 3 terminal (STT2 or SOT3) MRAM. The
test system includes a pulse generator, a set of RF circuits and a high-resolution scope. The test sequence operates in a fully automated manner, in a 2 steps process. Firstly, an average
signal in both P (red line) and AP (blue line) states are acquired as reference measurements. Secondly, single shots or averaged measurements of the switching events are acquired and the
reference data is subtracted, as shown in Fig.1 on STT-MRAM devices. The probability of switching and average switching time versus pulse amplitude and width can be extracted. The
validity of fast macrospin switching, without any domain wall formation can be verified. With single shot measurements, switching time of single events can be acquired, as well as the
incubation time before the switching occurs 2. The full test flow is executed in a few seconds, enabling the possibility to test population of devices using automated probing stations.
Using the system and our 3D magnetic generator, the test protocol can also be executed under application of an external magnetic field to study the field immunity of the device and the
corresponding influence on the switching dynamics.
1 P. Barla, V. K. Joshi, and S. Bhat, J. Comput. Electron. 20, 805–837 (2021).
2 J. Sampaio, S. Lequeux, P. Metaxas, et al., APL 103, 242415 (2013).
3 E. Grimaldi, V. Krizakova, G. Sala, et al., Nature Nanotechnology 15, pages111–117 (2020).