Structural and electrical investigations of silicon wafer bonding interfaces

The structure and the electrical properties of Si/Si interfaces obtained by wafer bonding are studied by transmission electron microscopy (TEM), electron-beam-induced current (EBIC) and spreading resistance (SR). Boron-doped Czochralsky-silicon (Cz-Si) (001) wafers and float zone-silicon (FZ-Si) (001) wafers are bonded after hydrophobic cleaning of the surfaces and annealed at 1200 °C for 2 h. M experiments show that these interfaces are made of two dislocation networks: a grid of screw dislocations accommodating the misorientation between the two wafers and a set of 60 ° dislocations compensating a tilt component related to the vicinal surfaces. These dislocations are all located at the interface and no extended defects propagate in the Si wafers. IC experiments show a large electrical activity of the Cz interfaces; SR profiles show a variation of carriers concentration near the interface. Large density of oxide precipitates located at the interface are seen for Cz-Si wafers. EBIC observations performed on FZ wafer show a weak electrical activity which seems to be related to a low content of oxygen in the interface.