CHARACTERISTICS OF SILICON WAFER-BOND STRENGTHENING BY ANNEALING

The role of bond strengthening by annealing after wafer bonding was studied. The bonded interfaces of various wafer bonding systems were microscopically examined using a scanning tunneling microscope and by making cross-sectional transmission electron microscopic analyses. These observations provided the basis for an understanding of a wafer-bond strengthening model using a sintering mechanism analogously applied, in metal-surface physics. The model is a mass-transfer model at the interface. In the Si/SiO2 wafer bonded system, both Si and SiO2 atoms could easily be transferred geometrically so as to smooth micro-corrugations at the bonded interface during high temperature annealing after bonding. This smoothening condition corresponds well with the measured excellent bond-strength characteristics.