A multi-scale approach to wafer to wafer metallic bonding in MEMS

Abstract

A three-scale approach to thermo-compression, metallic wafer bonding is here presented. The approach focuses on the purely mechanical side of the process, identifying three different length-scales: the macro-scale, at which the whole wafer is considered, to define the average contact pressure within each single die; the mesoscale, at which the aforementioned average pressure at the die level is applied to the MEMS bonding ring, to study stress diffusion in it; and the micro-scale, at which a micro-mechanically informed morphology of a representative volume of the two metallic rings in contact is considered along with their surface roughness, to get insights into local features of the sealing. The proposed approach can describe local effects due to a space-varying pressure, and can help to enhance and speedup the design phase of the bonding rings.