Effects of temperatures on microstructures and bonding strengths of Si–Si bonding using bisbenzocyclobutene

Thermal stability and characterizations of silicon to silicon wafer bonding at low temperature using B-staged polymer, bisbenzocyclobutene (BCB), were investigated. Bare silicon to bare silicon wafer (briefly, bare to bare) and patterned silicon by chemical etching to bare silicon wafer (pattern to bare) bonding with 4in. size were achieved by heating BCB coated wafer pairs at 230°C. In case of bare to bare bonding, interfaces of bonded wafers were mechanically stable and strong enough to withstand a tensile force of at least 190kg/cm2 at room temperature. Bond strength was drastically decreased over 300°C because of decomposition of polymer. In case of pattern to bare, interfaces of bonded wafers were dense and good enough to withstand a tensile force of at least 60kg/cm2 at room temperature. Silicon to silicon wafer bonding using BCB was suitable for fabricating and packaging of microstructures for micro-electro-mechanical system (MEMS) devices at low temperatures (<300°C).