Low Angle Annular Dark Field Scanning Transmission Electron Microscopy Analysis of Phase Change Material

In this work, we investigate mushroom type phase-change material (PCM) memory cells based on Ge₂Sb₂Te₅. We use low-angle annular dark field (LAADF) STEM imaging and energy dispersive X-ray spectroscopy (EDX) to study changes in microstructure and elemental distributions in the PCM cells before and after SET and RESET conditions. We describe the microscope settings required to reveal the amorphous dome in the RESET state and present an application example involving the failure analysis of a PCM test array made with devices fabricated at IBM’s Albany AI Hardware Research Center.