Room Temperature Wafer Bonding Using Oxygen Plasma Treatment in Reactive Ion Etchers With and Without Inductively Coupled Plasma

The effects of oxygen plasma treatment on silicon surface topography and the properties of bonded interfaces formed using the oxygen plasma pretreatment were investigated. Bonded samples of silicon or oxidized silicon wafers using oxygen plasma pretreatment in reactive ion etchers with and without inductively coupled plasma were characterized in terms of surface energies obtained at room temperature. Annealing experiments at 1000°C were made to study the origin of thermally generated voids. Atomic force microscopy was used to study how the surface roughness of plasma-treated silicon wafers evolved over time. Furthermore, the influence of water dipping on the roughness of plasma-treated silicon surfaces was investigated. The results showed that plasma treatment of one wafer results in a surface energy of approximately I J m 2 at room temperature. The role of water in the increase of surface energy was found to be crucial. From annealing experiments it is concluded that water present at the wafer surfaces before bonding has a pronounced influence on void generation upon annealing. A dramatic change in the topography of silicon surfaces treated in oxygen plasma was observed during storage at room temperature, while water dipping the wafers after plasma treatment appeared to stabilize the surface topography.