THIN MEMBRANES FOR MEMS PACKAGING AT LOW T

In recent years there has been an increasing demand for low-T packaging technologies to vacuum seal MEMS devices at the wafer level. When caps are fabricated using standard surface micromachining techniques, the need for wafer bonding alignment equipment is eliminated. This book presents the different processing steps of a new surface micromachining module for MEMS packaging at temperatures ~180ºC based on electroplating and resist sacrificial layers. Sacrificial etch holes are situated above the device allowing shorter release times. Analytical and FEA methods are used to understand, to predict and to optimise the mechanical response of the membrane. The sealing material is deposited by a selective deposition technique to avoid material where this is not desired. Sealing happens by fluxless reflow, giving the freedom of choosing P and atmosphere. The sealing layer is In because it allows a low thermal budget sealing process. The conditions that govern fluxless sealing are addressed and tailored. The thermal profile is one of the key variables that significantly impacts the wetting behaviour of liquid metal. The presented work represents the first time used sealing technique.