Characterization of interfacial structure for low-temperature direct bonding of Si substrates sputtered with Ag nanotwinned films

Abstract

In this study, low-temperature AgAg direct bonding was achieved at 150–250 °C in 10–60 min by using high (111)-preferred orientation films with densely-packed nanotwins fabricated by magnetron sputtering process. The focused ion beam (FIB) and transmission electron microscopy (TEM) results showed great bonding interfaces with almost no voids. The top-view electron backscattered diffraction (EBSD) results indicated that the grains on the surface before bonding were almost 100% (98.4%) (111)-preferred orientation grains, which provided a rapid path for diffusion. High thermal stability was observed, for the twin thickness remained unchanged after bonding at various temperatures. The bonding technique shows great potential for application in MEMS, optoelectronics, transducers, heat-sensitive components and 3D IC interconnections.