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 degrees C. Tetraethyl orthosilicate source PECVD oxide is found to exhibit suitable bonding properties and can be used in applications such as silicon layer transfer. (C) 2004 The Electrochemical Society.