Fabrication of GaAs/SiO2/Si and GaAs/Si heterointerfaces by surface-activated chemical bonding at room temperature*

Abstract

The room-temperature (RT) bonding mechanisms of GaAs/SiO2/Si and GaAs/Si heterointerfaces fabricated by surface-activated bonding (SAB) are investigated using a focused ion beam (FIB) system, cross-sectional scanning transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDX) and scanning acoustic microscopy (SAM). According to the element distribution detected by TEM and EDX, it is found that an intermixing process occurs among different atoms at the heterointerface during the RT bonding process following the surface-activation treatment. The diffusion of atoms at the interface is enhanced by the point defects introduced by the process of surface activation. We can confirm that through the point defects, a strong heterointerface can be created at RT. The measured bonding energies of GaAs/SiO2/Si and GaAs/Si wafers are 0.7 J/m2 and 0.6 J/m2. The surface-activation process can not only remove surface oxides and generate dangling bonds, but also enhance the atomic diffusivity at the interface.