Thin Wafer Handling for MEMS
Wafer-level packaging (WLP) is commonly used for packaging of MEMS and LED devices as it offers advantages in cost, yield, and reliability. In a WLP scheme, MEMS structures or LED die are encapsulated between bonded wafers, one of which has cavities that are fabricated most commonly by bulk micromachining.
The thinned silicon wafers are fragile and require a temporary rigid support that allows the wafer to be successfully processed for stacking. When finished, the thin processed wafer must be separated from the rigid support using a simple, cost-effective process, without resulting in damage.
The bonding materials used to attach the device wafer to the rigid support, or carrier, must meet very stringent requirements. They must survive extreme temperatures, harsh corrosive and solvent chemistries, and mechanical stresses created by thermal excursions. They must permit separation (debonding) of the very delicate wafer from the rigid carrier, and leave no residue after debonding and cleaning.