Low-temperature thin-film indium bonding for reliable wafer-level hermetic MEMS packaging

This paper reports on low-temperature and hermetic thin-film indium bonding for wafer-level encapsulation and packaging of delicate and temperature sensitive devices. This indium-bonding technology enables bonding of surface materials commonly used in MEMS technology. The temperature is kept below 140 degrees C for all process steps and no surface treatment is applied before and during bonding. This bonding technology allows hermetic sealing at 140 degrees C with a leak rate below 4 x 10(-12) mbar l s(-1) at room temperature. The tensile strength of the bonds up to 25 MPa goes along with a very high yield.