Room temperature bonding of SiO2 and SiO2 by surface activated bonding method using Si ultrathin films

Abstract The bonding of metal electrodes and insulator hybrid interfaces is one of the key techniques in three-dimensional integration technology. Metal materials such as Cu or Al are easily directly bonded by surface activated bonding at room temperature, but insulator materials such as SiO 2 or SiN are not. Using only Si ultrathin films, we propose a new bonding technique for SiO 2 /SiO 2 bonding at room temperature. Two SiO 2 surfaces, on which Si thin films were deposited, were contacted in vacuum. We confirmed that the thickness of the layer was about 7 nm by transmission electron microscopy observation and that the layer was non crystalline by electron energy loss spectroscopy analysis. No metal material was found in the bonding interface by energy-dispersive X-ray spectroscopy analysis. The surface energy was about 1 J/m 2 , and the bonding strength was more than 25 MPa. This bonding technique was successfully realized to enable SiO 2 /SiO 2 bonding without a metal adhesion layer.