Localized bonding with PSG or indium solder as intermediate layer

The feasibility of "localized bonding" with PSG (phosphosilicate glass) or indium solder as the intermediate layer have been demonstrated. Both localized PSG-to-glass and indium-to-glass bonds are accomplished on a square bonding area (/spl sim/500/spl times/500 /spl mu/m/sup 2/) encompassed by 5 /spl mu/m wide microheaters made of phosphorus doped polysilicon. Either PSG or indium solder are deposited on top of the microheater and function as the intermediate bonding material. The separation of heating and bonding materials by the intermediate layer greatly improved the controllability of the bonding process. Moreover, the whole bonding process can be achieved in less than 2 minutes at atmospheric pressure and room temperature environment. This new bonding scheme has potential application for MEMS device packaging that requires low temperature processing at the wafer-level, but high temperature at the bonding interface.