Department of Mechanical Engineering
Stanford University
Principal Investigator
Kenneth E. Goodson
Phase Change Memory
Sponsors:
NSF, Intel, NXP, Ovonyx, SRC
Collaborators:
H.S.P. Wong group, Stanford EE Phase change memory (PCM or PCRAM) is based on rapid, thermally-induced phase transitions in Ge2Sb2Te5 (GST) and related compounds. Because the phase change is induced by temperature changes, thermal conduction and thermally-induced phase transitions govern the critical device figures of merit including the time and energy required for switching. PCRAM is now available commercially in memory products, and is arguably the most promising technology for ultra-high-density nonvolatile storage in the coming decades.
Stanford has built the world leading team for PCM investigations with a focus on the fundamental physics governing electrical, thermal and electrothermal transport phenomena. Progress includes detailed characterization of the thermal and electrical conductivities of GST as a function of material stoichiometry and grain orientation and size (crystalline phase), as well as the first studies revealing the interface resistance magnitudes and their impact in devices. Ongoing and future work is focused on the multibit storage challenge with associated fundamental activities on temperature-induced drift in reset resistance and threshold voltage enabled by our novel micro thermal stage (MTS). We are also characterizing the thermoelectric properties of GST layers as well as the thermal and thermoelectric properties of GST nanowires.
This material is based upon work supported by the National Science Foundation under Grant No. CBET-0853350. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
PROJECT PUBLICATIONS
Lee, J., Bozorg-Grayeli, E., Kim, S., Asheghi, M., Wong, H.-S., and Goodson, K.E., 2013, "Phonon and Electron Transport through Ge2Sb2Te5 Films and Interfaces Bounded by Metals," Applied Physics Letters, Vol. 102, 191911.
Li, Z., Jeyasingh, R.G.D., Lee, J., Asheghi, M., Wong, H.S.P., and Goodson, K.E., 2012, "Electrothermal Modeling and Design Strategies for Multibit Phase Change Memory," IEEE Transactions on Electron Devices, Vol. 59, pp. 3561-3567.
Won, Y., Lee, J., Asheghi, M., Kenny, T.W., and Goodson, K.E., 2012, "Phase and Thickness Dependent Modulus of Ge2Sb2Te5 Films down to 25 nm Thickness," Applied Physics Letters, Vol. 100, 161905.
Lee, J., Kim, S., Marconnet, A., in t' Zandt, M.A.A., Asheghi, M., Wong, H.S.P., and Goodson, K.E., 2012, "Thermoelectric Characterization and Power Generation using a Silicon-on-Insulator Substrate," Journal of MicroElectroMechanical Systems, Vol. 21, pp. 4-6.
Bozorg-Grayeli, E., Reifenberg, J.P., Asheghi, M., Wong, H.-S. P., and Goodson, K.E., 2013, "Thermal Transport in Phase Change Memory Materials," Annual Review of Heat Transfer, Vol. 16, pp. 397-428.
Bozorg-Grayeli, E.; Reifenberg, J.P.; Chang, K.W.; Panzer, M.; Goodson, K.E.; , "Thermal conductivity and boundary resistance measurements of GeSbTe and electrode materials using nanosecond thermoreflectance," Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm), 2010 12th IEEE Intersociety Conference on , vol., no., pp.1-7, 2-5 June 2010 doi: 10.1109/ITHERM.2010.5501263
Lee, J., Kodama, T., Won, Y., Asheghi, M., and Goodson, K.E., 2012, "Phase and Temperature Dependent Thermoelectric Properties of Ge2Sb2Te5 Films down to 25 nm Thickness," Journal of Applied Physics, Vol. 112, 014902.
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Ahn, C., Lee, B., Jeyasingh, R.G.D., Asheghi, M., Hurkx, F., and Goodson, K.E., Wong, H.-S.P., 2012, "Effect of Resistance Drift on the Activation Energy for Crystallization in Phase Change Memory," Japanese Journal of Applied Physics, Vol. 51, 02BD06.
Lee, J., Asheghi, M., Goodson, K.E., 2012, "Impact of thermoelectric phenomena on phase-change memory performance metrics and scaling," Nanotechnology, Vol. 23, 205201.
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.
Lee, J., Kim, S., Jeyasingh, R., Asheghi, M., Wong, H.S.P., and Goodson, K.E., 2011, "Micro Thermal Stage for Electrothermal Characterization of Phase Change Memory," IEEE Electron Device Letters, Vol. 32, pp. 952-954.
Li, Z., Lee, J., Reifenberg, J.P., Asheghi, M., Jeyasingh, R.G.D., Wong, H.S.P., and Goodson, K.E., 2011, "Grain Boundaries, Phase Impurities, and Anisotropic Thermal Conduction in Phase Change Memory," IEEE Electron Device Letters, Vol. 32, pp. 961-963.
Lee, J., Li, Z., Reifenberg, J.P., Lee, S., Sinclair, R., Asheghi, M., and Goodson, K.E., 2011, "Thermal Conductivity Anisotropy and Grain Structure in Ge2Sb2Te5 Films," Journal of Applied Physics, Vol. 109, 084902.
Kim, S., Lee, B., Asheghi, M., Hurkx, F., Reifenberg, J.P., Goodson K.E., and Wong H.S.P., 2011, "Resistance and Threshold Switching Voltage Drift Behavior in Phase-Change Memory and Their Temperature Dependence at Microsecond Time Scales Studied Using a Micro-Thermal Stage," Transactions on Electron Devices, Vol. 58, pp. 584-592.
Wong, H.S.P., Raoux, S., Kim, S., Liang, J., Reifenberg, J.P., Rajendran, B., Asheghi, M., and Goodson, K.E., 2010, "Phase Change Memory," Proceedings of the IEEE, Vol. 98, pp. 2201-2227.
Reifenberg, J.P., Chang, K.W., Panzer, M.A., Kim, S., Rowlette, J.A., Asheghi, M., Wong, H.S.P., and Goodson, K.E., 2010, "Thermal Boundary Resistance Measurements for Phase-Change Memory Devices," IEEE Electron Device Letters, Vol. 31, pp. 56-58.
Reifenberg, J.P., Kencke, D.L., and Goodson, K.E., 2008, "The Impact of Thermal Boundary Resistance in Phase-Change Memory Devices," IEEE Electron Device Letters, Vol. 29, pp. 1112-1114.
Goodson, K.E., 2007, "Ordering up the Minimum Thermal Conductivity of Solids," Science Vol. 315, 342-343.
Reifenberg, J.P., Panzer, M.A., Kim, S., Gibby, A.M., Zhang, Y., Wong, S., Wong, H.S., and Goodson, K.E., 2007, "Thickness and Stoichiometry Dependence of the Thermal Conductivity of GeSbTe Films," Applied Physics Letters, Vol. 91, pp. 111904-111906.
Bozorg-Grayeli, E., Reifenberg, J.P., Panzer, M.A., Rowlette, J.A., and Goodson, K.E., 2011, "Temperature-Dependent Thermal Properties of Phase-Change Memory Electrode Materials," IEEE Electron Device Letters, Vol. 32, pp.1281-1283.