Film Thicknesses Influence on the Interfacial Thermal Resistances within Ge-Rich Ge2Sb2Te5/Ge2Sb2Te5 Multilayers

Phase change memories (PCRAM) are often made of chalcogenide alloys in the form of multilayer systems (MLS). The mostly used alloys are Ge2Sb2Te5 and Ge-rich Ge2Sb2Te5. The current article reports on the thermal characterization of very thin (<5 nm) Ge-rich Ge2Sb2Te5/Ge2Sb2Te5 MLS by modulated photothermal radiometry (MPTR). The MPTR method allows for the investigation of such samples by determining, with an inverse method, the total thermal resistance of the stack deposited on the substrate. With the measurement of the total thermal resistance, it is possible to determine the thermal conductivity of the deposit and the interfacial thermal resistances between layers. The interfacial thermal resistance between Ge-rich Ge2Sb2Te5/Ge2Sb2Te5 is characterized, which is an important parameter to reduce the energy cost of the PCRAM functioning. It is also possible to highlight a decrease in interface quality inside the MLS after the beginning of the phase transition around 250 degrees C.