The Design of Re-writeable Ultra-High Density Scanning-Probe Phase-Change Memories
Wright, C. David
Aziz, Mustafa M.
IEEE Transactions on Nanotechnology
Institute of Electrical and Electronics Engineers (IEEE)
A systematic design of practicable media suitable for rewritable, ultrahigh density (>;1Tbit/sq.in.), high data rate (>;1Mbit/s/tip) scanning-probe phase-change memories is presented. The basic design requirements were met by a Si/TiN/Ge2Sb2Te5 (GST)/diamond-like carbon structure, with properly tailored electrical and thermal conductivities. Various alternatives for providing rewritability were investigated. In the first case, amorphous marks were written into a crystalline starting phase and subsequently erased by recrystallization, as in other already established phase-change memory technologies. Results imply that this approach is also appropriate for probe-based memories. However, experimentally, the successful writing of amorphous bits using scanning electrical probes has not been widely reported. In light of this, a second approach has been studied, that of writing crystalline bits in an amorphous starting matrix, with subsequent erasure by reamorphization. With conventional phase-change materials, such as continuous films of GST, this approach invariably leads to the formation of a crystalline “halo” surrounding the erased (reamorphized) region, with severe adverse consequences on the achievable density. Suppression of the “halo” was achieved using patterned media or slow-growth phase-change media, with the latter seemingly more viable.
notes: First design of a practicable 1 Tera-bit-per-square-inch re-writable phase-change probe storage system. Co-authors from Europe's largest memory device manufacturer, Numonyx-Micron, Agrate Brianza, Italy (see www.micron.com/innovations/pcm.html). Led to invited presentation for Wright at EPCOS 2010 (European Phase Change and Ovonic Science Symposium) in Milan (www.epcos.org). Carried out under auspices of EU €9.5M Project 'ProTeM' (Probe-base Terabyte Memories) led (co-ordinated) by Wright and involving other world-leading partners such as IBM Zurich, CEA-LETI Grenoble, RWTH-Aachen, Fraunhofer Itzehoe and others. Verification contact [firstname.lastname@example.org]
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Vol. 10 (4), pp. 900 - 912