Thermal Barrier Phase Change Memory

Abstract

Phase change memory is widely considered as the most promising candidate as storage class memory (SCM), bridging the performance gaps between dynamic random access memory and flash. However, high required operation current remains the major limitation for the SCM application, even after using defect engineering materials, for example, Ti-doped Sb₂Te₃. Here, we demonstrate that ∼87% current can be reduced by spatially separating Sb₂Te₃ and TiTe₂ layers, thanks to semimetallic TiTe₂ serving as a thermal barrier in the reset process. Moreover, the stable crystalline TiTe₂ layer provides an ordered interface to speed up the crystallization process of the amorphous Sb₂Te₃ layer, enabling ∼10 ns ultrafast crystallization speed. An outstanding device lifetime, up to ∼2 × 10⁷ cycles, has been obtained, which is twice as long as that of alloy-based cells. Correlative electron microscopy and atom probe tomography provide evidence that the TiTe₂/Sb₂Te₃ multilayer can keep a layer-stacked structure, avoiding phase segregation found in alloys and strong element intermixing in the GeTe/Sb₂Te₃ superlattice, which enables excellent cyclability. This study suggests that adding a semimetallic layer in the phase change layer, such as TiTe₂ and TiSe₂, can yield a phase change memory with superior properties.