Dresden 2009 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 48: Poster 2

HL 48.30: Poster

Donnerstag, 26. März 2009, 15:00–17:30, P2

Electrical Properties of Phase Change Memory Cells — •Daniel Krebs^1,2, Martin Salinga^1,2, Stephan Kremers¹, Hanno Volker¹, Matthias Wuttig^1,2, Simone Raoux², Charles T. Rettner², Robert M. Shelby², and Geoffrey W. Burr² — ¹I. Physikalisches Institut IA, RWTH Aachen University, 52056 Aachen, Germany — ²IBM/Macronix PCRAM Joint Project: IBM Almaden Research Center, 650 Harry Road, San Jose, California 95120

Phase change random access memory has become one of the most promising candidates for future non-volatile memory applications, prompting an intensive search for suitable phase change materials with optimized properties. Attaining both rapid cyclability and long-term retention requires the proper combination of fast crystallization speed yet high crystallization temperature. In addition, it has been observed that the resistance of the amorphous phase tends to increase slowly yet significantly after device programming, which complicates multilevel storage. In this work, the phase change memory candidates Ge₁₅Sb₈₅, Ag and In doped Sb₂Te, Ge₂Sb₂Te₅, GeTe and thin Sb are systematically analyzed by electrical and optical testing of bridge cell devices and thin films. We show that the as-deposited and melt-quenched amorphous phases exhibit pronounced differences in crystallization speed and temperature. Our experimental evidence shows clearly that the critical parameter for threshold switching is a critical electrical field rather than a threshold voltage. The post-programming resistance dynamics of bridge cells are also analyzed, and linked to electrical and structural relaxation in the phase change material.