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Commercial prospect of phase-change random access memory (PCRAM), considered as an encouraging option for future “universal” memory, is however challenged by its large programming current that severely impairs device scalability. The recent advent of the blade-type PCRAM configuration can effectively address this issue by shrinking the heated region. However, the thermoelectric (TE) effects that play a key role in write performances of conventional Lance-type PCRAM have not been systematically studied for this blade-type case to date. The influence of TE effects on the amorphization process of the blade-type PCRAM cell is therefore investigated here through the establishment of a comprehensive 3-D electrothermal and phase-transformation model. Two main typical TE effects, i.e., Thomson heat inside the Ge2Sb2Te5(GST) bulk region and Peltier heat at the GST-TiN heater interface, have been mimicked and discussed in detail. Simulation results show that both TE effects depend on the polarities of the programming currents, and the calculated Thomson heat is more than 20 times as much as Peltier heat. Accordingly, a novel skutterudite-based heater that exhibits more pronounced TE effects than TiN heater has been proposed. The practicality of reducing programming current by 13.8% and peak power by 17.9% is demonstrated using the improved version of the PCRAM cell. [ABSTRACT FROM AUTHOR]

Joule heating in phase change memory (PCM) controls programming characteristics, read disturb, and programming disturb. To optimize the energy consumption and reliability of PCM, a thorough understanding of Joule heating as a function of the electrical operation of the device is thus strongly required. This paper presents a comprehensive characterization of thermoelectric (TE) effects in PCM operated at positive and negative voltage polarity. The impact of polarity was studied for all major temperature-dependent properties of the PCM device, namely, melting, crystallization, ion migration, threshold switching, and holding. It was demonstrated that heating is less efficient under negative voltage, compared with positive voltage. It was also shown that the positive and negative voltages needed to induce all above phenomena display a universal correlation. We propose a unified finite-element model for the PCM, which correctly accounts for the observed polarity-dependent heating and the universal voltage characteristics. The impact of isotropic scaling on TE is finally addressed. [ABSTRACT FROM PUBLISHER]

Abstract: In this work thermoelectromagnetic convection (TEMC) is evaluated at different scales and the result shows that the effect of TEMC is different for different scales. To validate this analysis, Al–Cu hypoeutectic alloys were solidified directionally under a magnetic field, and both the interface shape and cellular morphology in the mushy zone investigated. The experimental results show that a weak magnetic field (B ⩽0.5T) has a significant affect on the cellular liquid–solid interface and the cellular morphology. This is attributed to the TEMC caused by the interaction between the field and the thermoelectric (TE) current, which is consistent with the analysis. Under a higher magnetic field, the field causes the cells to break and makes the liquid–solid interface uneven; these effects are attributed to the magnetic force and the TE torque. [Copyright &y& Elsevier]