Superconducting Technology Assessment - nitrd

MRAM Technology Status
FS-TMR MRAM
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Table 3.2-7. COMPARISON OF FIELD SWITCHED TUNNELING MAGNETORESISTIVE
AND SPIN MOMENTUM TRANSFER MRAM
Field Switched Tunneling Magnetoresistive MRAM
– Bit is based on tunneling through a thin insulator
encased by two ferromagnetic films
– Large current-write-pulse produces magnetic field
that flips the polarization of one ferromagnetic film
– Read by smaller current through the MTJ whose
resistance depends on the relative polarization
of the two magnetic films
– Typical resistances are 10’s of kΩ, compatible
with CMOS
– Commercial pre-production at Freescale
■ 4Mb FS-TMR MRAM chip, 1.55 µm 2 cell, 0.18 µm CMOS is in pre-production
at Freescale Semiconductor.
■ Write currents 1-10 mA, ~25 ns symmetric read-write cycle.
■ Circuit architectures can be optimized for lower power, higher speed, or higher density.
■ IBM has recently demonstrated a 128-kb, 6 ns access-time MRAM circuit.
Spin Momentum Transfer MRAM
– Bit is low resistance GMR metal
– Bit magnetoresistance is changed by spin
momentum transfer from write current
directly into the film
– Read by measuring the resistance of GMR film
– Typical GMRs are 1 – 100W, compatible
with RSFQ and favored for hard disc drives
and magnetic sensors
– Opportunity to monolithically integrate fast,
low power RSFQ circuits with high speed,
high density SMT MRAM operating at 4 K.