Dielectrics stability for intermediate BEOL in 3D sequential integration

3D sequential integration, such as CoolCubeź, allows to stack vertically layer of devices. Levels of interconnection, also called intermediate Back-End-Of-Line, are needed between successive layers of transistors to avoid routing congestion. Thus, thermal stability of the dielectrics must be studied in order to fulfil the CoolCubeź requirement: at least to be stable up to 500°C during 2h. Consequently, the stability of several barrier layers and oxide based materials has been studied through optical characterizations (ellipsometry, Fourier Transform InfraRed spectroscopy and ellipsometric-porosimetry). SiCO (k=4.5), in replacement of standard SiCNH (k=5.6) material as barrier layer seems very promising. Regarding the inter-layer dielectric stability, the state-of-the-art porous SiOCH (k=2.5) stays suitable for a thermal budget of 500°C, 2h. Display Omitted