DIRECT BONDING OF THICK FILM POLYSILICON TO GLASS SUBSTRATES

摘要

In the device fabrication of microelectromechanical systems (MEMS) the encapsulation of sensors and actuators is often required. Moreover, polysilicon is proven to be indispensable material in various applications in MEMS-area. Bonding and furthermore encapsulation to polysilicon is conventionally done with the anodic bonding which has, however, drawbacks that are an initiatory force for starting an investigation of low-temperature direct bonding. In this study we have concentrated in polishing process development of polysilicon and bonding it to quartz, Pyrex and low-alkali glass. Simultaneously, basic investigation of high-temperature direct bonding of polysilicon is initiated where Si/Si- and Si/Ox-bonding is studied. The main emphasis in material selection has been in thick .atmospheric-pressure chemical-vapour-deposited polysilicon. Spontaneous bonding was achieved with all wafer combinations. Plasma-assisted polysilicon-to-glass bonding was found to yield void free interfaces whereas high-temperature bonded couples showed void formation. The low-temperature bonding for polysilicon has been enabled with an advanced polishing process.