A method and electrical model for the anodic bonding of SOI and glass wafers

This paper provides a method for the anodic bonding of SOI and glass wafers, and it explains the bonding mechanism with an electrical model, for the first time in the literature. SOI-glass anodic bonding can be achieved at voltages as low as 250 V similar to Si-glass anodic bonding, and the underlying principles can be understood by modeling the overall system with a series-connected capacitor-resistor network. The SOI-oxide layer can be added as a capacitor to the classical anodic bonding model, and the behavior of the bonding can be estimated with the basic circuit theory. The oxide capacitance in the model acts as a short circuit at the time instant when the bonding potential is applied, and then it gradually becomes an open circuit. The model is also successfully adapted to triple stack glass-Si-glass anodic bonding, which enables wafer level packaging and offers many opportunities to MEMS designers.