Sol-gel bonding of silicon wafers

An optimum water-to-alkoxide molar ratio of 10 and hydrolysis water at pH = 2 were found. Such conditions led to relatively dense films (> 90%), resulting in bonds with a fracture energy of 3.5 J/m2, significantly higher than those obtained using classical hydrophilic bonding (typically 1.5-2.5 J/m2). Ageing of the coating solution was found to decrease the bond strength.