IMEC claims two voltage-MRAM breakthroughs
The Belgian research institute is presenting several papers at the virtual 2020 Symposia on VLSI Technology and Circuits. MRAMs are a type of dense non-volatile memory that are being introduced as both discrete and embedded memories.
The first development IMEC is reporting is a deterministic write scheme for voltage-controlled magnetic anisotropy (VCMA) magnetic random access memories (MRAMs), doing away with the need for pre-reading the device before writing. This gets write speeds down to the order of nanoseconds.
As a second improvement IMEC has come up with a manufacturing scheme for VCMA switching operation that does not require an external magnetic field.
Conventional STT-MRAMs use current injection into magnetic tunnel junction to effect a write. VCMA MRAM uses voltage to create an electric field for its write operation – which consumes far less energy. This is analogous to the difference between a bipolar junction transistor (current) and a MOSFET (voltage/field).
IMEC’s scheme uses an offset energy barrier to allow distinct threshold voltages to drive parallel-to-antiparallel (P-AP) and antiparallel-to-parallel (AP-P) transitions. This is achieved by implementing a 5mT offset magnetic field in the VCMA stack design.
As a second improvement IMEC has embedded a magnetic hardmask on top of the magnetic tunnel junction which eliminates the need for an external magnetic field during VCMA switching.
Devices in CMOS compatible process and demonstrated reliable 1.1GHz switching with 20fJ switching energy. Endurance of more than 10^10 cycles has been achieved, IMEC reports.
“These characteristics bring VCMA MRAM performance beyond STT-MRAM operation, making the devices ideal candidates for high-performance, low-power and high-density memory application – serving advanced computational needs or analog compute-in-memory applications,” said Gouri Sankar Kar, program director at IMEC.
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