Impact of Voltage Polarity on Time-Dependent Dielectric Breakdown of 1-nm MgO-Based STT-MRAM With Self-Heating Correction

Abstract

Time-dependent dielectric breakdown (TDDB) lifetime of ultrathin (1 nm) MgO in spin-transfer torque magnetoresistive random access memory (STT-MRAM) devices has recently been shown to be driven by factors other than voltage alone. This study focuses on the specific role of asymmetry in the current flow for different polarity pulsing modes of voltage stress on the TDDB lifetime of 1-nm MgO. Numerical analysis, based on a 3-D heat-diffusion equation and spintronic simulations, has been performed to characterize the temperature rise in the devices for precise correction of self-heating to obtain a correct interpretation of MgO TDDB. It is shown that the different lifetimes for the positive and negative modes can be attributed to different temperature increases arising from self-heating. While the positive and negative modes displayed a non-Arrhenius behavior, the bipolar mode showed an Arrhenius trend in which we observed a unique bimodal behavior of TDDB activation energy (E a ) as a function of stress voltage in the ultrathin MgO stack. We discuss the role of additional driving forces, such as current, self-heating, charge trapping, and interface strain governing the breakdown mechanism along with the voltage effect.

Demonstration of a manufacturable SOT-MRAM multiplexer array towards industrial applications

“…3(a), all WER curves show reliable switching down to 10 −4 level at a write pulse width of 100 ns. Most importantly, we do not observe ballooning effects [50] or backhopping behaviors [50,51] in the obtained WER curves for both write directions across all the measured devices. This suggests that the SOT-MTJs feature robust and reliable switching behaviors when tested under a 100 ns pulse width.…”