Bonding of SiO2 and SiO2 at Room Temperature Using Si Ultrathin Film

The bonding of metal electrode and insulator hybrid interfaces is very important in three-dimensional integration technology. Surface activated bonding (SAB) is expected to be suitable method for three-dimensional integration technology, as the bonding method is carried out at room or low temperatures. Though metal materials such as Cu or Al is easy to directly bond by the SAB method, insulator materials such as SiO2 or SiN are difficult to directly bond. We have already reported on the bonding technique at room temperature using only Si ultrathin films for insulator materials, and we have shown that high bonding strength is achieved. In this report, we investigated the relationship between the SiO2/SiO2 bonding strength and the thickness of Si ultrathin film. We confirmed that the surface energy was about 1 J/m2 for the Si film's thickness of more than about 3nm.