Wafer bonding strength increased by mobile ions

Paper in proceeding, 2009

Mechanical bonding energies of oxygen plasma treated and room temperature wafer bonded silicon surfaces have been measured as a function of storage time in parallel with measurements of electrical interface properties. We find that the surface energy increases with a time dependence similar to that of decreasing interface state concentration. The current versus voltage behaviour reveals the existence of mobile ions. We conclude that these mobile charges after reaction with the interface states give rise to the increased surface energy responsible for the bonding.