Recent advances in submicron alignment 300 mm copper-copper thermocompressive face-to-face wafer-to-wafer bonding and integrated infrared, high-speed FIB metrology

We report on recent experimental studies performed as part of a 3D integrated circuit (3DIC) production-worthy process module roadmap check for 300 mm wafer-to-wafer (WtW) copper-to-copper thermocompression bonding and face-to-face (F2F) aligning. Specifically, we demonstrate submicron alignment capabilities (3sigma alignment variability ~ 1 μm) post Cu bonding on topography M1V1-to-M2 Cu wafers with no interfacial voids observed and complete Cu interdiffusion, as supported by transmission electron microscopy (TEM) and electron back scatter diffraction (EBSD) data. Also, less than 0.1% clustered voids bonding uniformity were observed on bonded blanket Cu wafers. In addition to bonding quality characterization studies involving scanning acoustic microscopy (SAM) and confocal infra-red (IR) laser scanning microscopy, we report on the development of a prototype integrated IR, highspeed focused-ion-beam (FIB) technique with CAD overlay capabilities that enable the creation of site specific cross-sections and TEM samples to better observe bonding structures of interest.