Crystallization Properties and their Drift Dependence in Phase-Change Memory Studied with a Micro-Thermal Stage

Ahn, C., Lee, B., Jeyasingh, R.G.D., Asheghi, M., Goodson, K.E., Wong, H.S.P., and Hurkx, G.A.M., 2011, "Crystallization Properties and their Drift Dependence in Phase-Change Memory Studied with a Micro-Thermal Stage," Journal of Applied Physics, Vol. 110, 114520.

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The crystallization properties of phase-change memory (PCM) cells are studied at microsecond
time scales using a novel micro-thermal stage. The time for recrystallization due to thermal disturbances
is measured for varying amorphous volume fractions and annealing temperatures. PCM
cells of intermediate resistances programmed with three different programming schemes are investigated
and compared. For multi-bit programming, controlling the pulse-tail duration may be preferable
as it has better retention characteristics than pulse-amplitude modulation or current-filament
control. The effect of incomplete crystalline filaments on crystallization speed is experimentally
investigated in this work, and the Arrhenius parameters are extracted from our crystallization time
measurements to support a proposed unified mechanism for crystallization and drift. We have also
found that recrystallization can be suppressed by more than 20% when there is a second of delay
time between thermal disturbances.

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