Sol-gel bonding of silicon wafers

Bonding of silicon wafers has been successfully achieved at temperatures as low as 60 °C. At 300 °C, the interfacial fracture energy was 1.55 J/m2. At 600 °C, sol-gel bonding provided superior interfacial fracture energy over classical hydrophilic bonding (3.4 J/m2 vs. 1.5 J/m2). The increase in the interfacial fracture energy is related to the increase in film density due to the sintering of the sol-gel interface with increasing temperature. The superior interfacial fracture energy obtained by sol-gel bonding at low temperature is due to the formation of an interfacial layer, which chemically bonds the two sol-gel coatings on each wafer. Application of a tensile stress on the resulting bond leads to fracture of the samples at the silicon/sol-gel interface.