Mastering the Interplay Between Active Material and Device Operation in Ge-GST ePCM

Phase Change Memory (PCM) is today one of the BEOL memories considered for embedded applications below 28nm node. Understanding the interplay between active material behavior and device operation is of critical importance to mastering the technology. In this work the effect of the electrical pulse on the material is studied along the programming curve, and the relationship between applied programming pulse, final phase and final composition is clarified. It has been shown that the states not only differ for microscopic phase distribution (crystal and amorphous) but also in chemical composition moving from a set state richer in antimony to a reset state more germanium rich. This feature of Ge-GST based ePCM has been highlighted as a key factor for cell functionality, guarantying a sufficiently low Set resistance despite the high Ge content in the as-deposited film. The compositional change in Set and Reset also can guarantee the reliability needed for the demanding mission profiles of embedded applications.