Evaluation of Wafer Bond Strength under Vacuum

Wafer bonding is a key technology for the integration, packaging, and assembly of the electronic devices. The measurement of the mechanical reliability at the bonding interface should also be reliable in order to evaluate the device reliability and robustness. Here we present a new scheme of the bond strength quantification considering the effect of the measurement atmosphere, especially ambient water. As the water attacks the Si-O-Si bonds at the crack front during the bond strength measurement, we propose the fracture test of the bonded wafers in a sealed chamber based on the double cantilever beam model under the controlled atmosphere. The bond strength is affected by the atmospherics water, indicated by the lowered bond strength in the ambient air compared to the dry N2 gas, which is also supported by the previous studies. In addition, it is also revealed that the bond strength is measured higher under high vacuum. The developed method of bond strength measurement will evaluate not only the effect of the ambient air, but also the effect of the residual water at the bonding interface.