Effect of Capillary Forces in Room Temperature Si-Si Direct Bonding Technique Using Velcrolike Surfaces

Abstract

Silicon surfaces were functionalized using the anodization technique to create needle-like surfaces. Such needle-like surfaces allows a Velcro-like bonding, repeated bonding and debonding of the same surfaces with an adequate bond strength at room temperature. A simple porous silicon-based technology to generate such rebondable surfaces is described. The adhesion between such needle-like surfaces is expressed by capillary forces. The proposed adhesion model is a further development of the previously presented van der Waals forces model. The model considers the existence of condensed vapor and capillary bridges resulting from humidity, which can make capillary forces dominant over van der Waals forces at any separation distance between needles above the interatomic spacing (0.3 nm) in the bonding mechanism. The capability of the technique and the validity of the model are demonstrated by comparison with experimental results and simulation results based on the van der Waals forces model. [2016-0245]