Among the emerging non-volatile binary memories, spin-torque-transfer RAM (STT-MRAM), spin-oribit-torque RRAM (SOT MRAM), and voltage controlled MRAM (VC MRAM), are particularly attractive owing to their low-voltage operation, high speed and endurance properties, and advanced CMOS technology compatibility. TSMC has developed and offers STT-MRAM solutions to overcome scaling limitations of embedded Flash technologies. TSMC is actively exploring SOT-MRAM and VC-MRAM internally and in conjunction with external research laboratories, consortia, and academic partners. TSMC SOT-MRAM exploration is driven by high-speed (<2ns) binary memory solutions that can be significantly denser than conventional 6T-SRAM solutions while also being much more energy efficient.

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  • Large and Robust Charge-to-Spin Conversion in Sputtered Weyl Semimetal WTex with Structural Disorder

    Topological insulators have recently shown great promise for ultralow-power spin-orbit torque (SOT) devices thanks to their large charge-to-spin conversion efficiency originating from the spin-momentum-locked surface states. Weyl semimetals, on the other hand, may be more desirable due to their spin-polarized surface as well as bulk states, robustness against magnetic and structural disorder, and higher electrical conductivity for integration in metallic magnetic tunnel junctions. Here, we report that sputtered WTex thin films exhibit local atomic and chemical structures of Weyl semimetal WTe2 and host massless Weyl fermions in the presence of structural disorder at low temperatures. Remarkably, we find superior spin Hall conductivity and charge-to-spin conversion efficiency in these sputtered WTex films compared with crystalline WTe2 flakes. Besides, the strength of unidirectional spin Hall magnetoresistance in annealed WTex/Mo/CoFeB heterostructure is up to 20 times larger than typical SOT/ferromagnet bilayers reported at room temperature. We further demonstrate room temperature field-free magnetization switching at a current density as low as 0.97 MA/cm2. These large charge-to-spin conversion properties that are robust in the presence of structural disorder and thermal annealing pave the way for industrial production of Weyl semimetals. Our results open up a new class of sputtered Weyl semimetals for memory and computing based on magnetic tunnel junctions as well as broader planar heterostructures containing SOT/ferromagnet interfaces.
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