Low-Temperature Direct CVD Oxides to Thermal Oxide Wafer Bonding in Silicon Layer Transfer

The bonding strength of low-pressure chemical vapor deposition and plasma-enhanced chemical vapor deposition (PECVD) oxides to thermal oxide is studied. Prior to bonding, all CVD oxide wafers are subjected to careful surface preparation including densification, chemical-mechanical polishing, activation, and post-bond annealing to ensure high-quality bonding. All wafers show surface roughness and wafer bow suitable for bonding after the surface preparations. It is found that bonding strength increases upon annealing and saturates beyond 2 h of annealing for the temperature range of 200-300°C. Tetraethyl orthosilicate source PECVD oxide is found to exhibit suitable bonding properties and can be used in applications such as silicon layer transfer.