Direct bonding of titanium layers on silicon

Direct metal bonding is a key technology for 3D integration that will allow semiconductor industry to go beyond predicted problems of future ICs. In this paper, for the first time, we show room temperature direct bonding of titanium layers on silicon wafers at atmospheric pressure and ambient air. Transmission electron microscopy and spreading scanning resistance microscopy are used to investigate bonding interface. Several physical mechanisms of titanium–titanium interface sealing during subsequent thermal annealing are observed and compared to copper and tungsten in terms of bonding mechanism and temperature dependence.