Wafer Bonding Techniques for Microsystem Packaging

In this paper, the development of wafer bonding techniques of the most frequently used materials Si-to-glass, glass-to-glass and Si-to-Si is reported. To improve the bond quality of Si-to-glass and make glass-to-glass bonding viable at bonding temperatures less than 300 C, a hydrogen-free amorphous silicon layer of 20-100 nm thickness is deposited as an intermediate layer. For Si-to-glass bonding, without applying the amorphous film, both the bond efficiency and bond strength are low. With the assistance of the amorphous film, the bond quality is significantly improved and the bonding temperature is reduced. Glass-to-glass bonding has also been successfully achieved at low temperatures, the high bond quality is still maintained. For Si-to-Si bonding, a tempered sol-gel film is deposited on Si wafer surface. The results show that promising Si-to-Si can be realized at bonding temperatures less than 300 C. It is also suitable to III-V semiconductor compounds bonding. Based on the bonding techniques obtained above, any combination of Si, III-V semiconductor compounds and glass wafers can be bonded and integrated. The bonding techniques can be widely used for various microsystems packaging at low temperatures.