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 a 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 are easy to directly bond using the SAB method, insulator materials such as SiO2 and SiN are more difficult. In this study, we examined the bonding technique at room temperature using only Si ultrathin films for the insulator material, and investigated the relationship between the SiO2/SiO2 bonding strength and the thickness of the Si ultrathin film. We confirmed that the surface energy was about 1 J/m(2) for a Si film thickness of more than about 3 nm.