RESET failure analysis of phase change memory based on Ge2Sb2Te5

Some nonvolatile phase change memory (PCM) cells with 80 nm heating electrodes are found early RESET failure. The causes, which result in the early failure of the PCM, have been studied. Compared the energy dispersive X-ray spectroscopy (EDS) results, it is observed some segregation has occurred in the components at the positions close to the TiN and bottom electron contact (BEC) interface for the early failed cells. The main causes are considered to be the unstable interface between the Ti-rich TiN and the Ge2Sb2Te5 (GST-225) layers and the inconsistent manufacturing process. Thanks to the segregation, the chemical components of the material close to BEC in the early failed cells are found changed. The changed material is taken as the immediate reason for the RESET failure, which has been confirmed by a two-dimensional finite analysis.