1 research outputs found
Impact of Magnetic Coupling and Density on STT-MRAM Performance
As a unique mechanism for MRAMs, magnetic coupling needs to be accounted for
when designing memory arrays. This paper models both intra- and inter-cell
magnetic coupling analytically for STT-MRAMs and investigates their impact on
the write performance and retention of MTJ devices, which are the data-storing
elements of STT-MRAMs. We present magnetic measurement data of MTJ devices with
diameters ranging from 35nm to 175nm, which we use to calibrate our intra-cell
magnetic coupling model. Subsequently, we extrapolate this model to study
inter-cell magnetic coupling in memory arrays. We propose the inter-cell
magnetic coupling factor Psi to indicate coupling strength. Our simulation
results show that Psi=2% maximizes the array density under the constraint that
the magnetic coupling has negligible impact on the device's performance. Higher
array densities show significant variations in average switching time,
especially at low switching voltages, caused by inter-cell magnetic coupling,
and dependent on the data pattern in the cell's neighborhood. We also observe a
marginal degradation of the data retention time under the influence of
inter-cell magnetic coupling