[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: We report recent advances in tool and process hardening of a first of its kind 300 mm wafer-to-wafer (WtW) preprocessing, aligning, and bonding integrated tool. We have demonstrated sub-500 nm post-bond alignment accuracies for 300 mm WtW face-to-face (FtF) Cu-Cu thermocompression bonds, WtW FtF Si-Si fusion bonds, and WtW FtF oxideoxide fusion bonds. All process of record (POR) recipes that were developed had undetectable voids based on scanning acoustic microscope (C-SAM) measurements on representative bonded Cu, oxide, and Si blanket wafers. Optimized bonded patterned wafer splits in the Cu-Cu WtW thermocompression bonding step have shown alignment accuracies down to ~190 nm, the highest accuracy to date. Using an infrared-enabled, high speed focused ion beam (FIB) system (with XeF2) with a CAD overlay function to assist in selective sample preparation, we have verified that the bonding interfaces at the via chain structures with 1-5 μm diameter vias show no interfacial voids. Also, there is evidence of Cu interdiffusion, as supported by transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD) data.