Low temperature wafer anodic bonding

In this paper, anodic bonding between silicon wafer and glass wafer (Pyrex 7740) has been achieved at low temperature. The bond strength is measured using a tensile testing machine. The interfaces are examined and analyzed by scanning acoustic microscopy (SAM), scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS). The effects of the bonding parameters on bond quality are investigated using the Taguchi method. The bonding temperature used ranges from 200 °C to 300 °C. Almost bubble-free interfaces have been obtained. The bonded area increases with increasing bonding temperature. The unbonded area is less than 1.5% within the whole wafer for bonding temperature between 200 °C and 300 °C. The bond strength is higher than 10 MPa and increases with the bonding temperature. Fracture mainly occurs inside the glass wafer other than in the interface when the bonding temperature is higher than 225 °C. Higher bonding temperature results in more oxygen migration to the interface and more Si-O bonds. The bonding mechanisms consist of hydrogen bonding and Si-O chemical reaction.