Bonding of Cu-based high aspect ratio microscale structures with Sn intermediate layers

Abstract

Simple and effective protocols for bonding Cubased high-aspect-ratio microscale structures (HARMSs) are essential for assembly of Cu-based microdevices. In this paper, Cu-to-Cu bonding with thin intermediate layers of elemental Sn is explored. Bonding quality is assessed through quantitative evaluation of tensile bond strength as a function of bonding parameters such as temperature and applied pressure. Structural examination of the Cu/Sn/Cu interface region is accomplished by combining focused ion beam sectioning and imaging with ion-induced secondary electrons. Successful bonding of Cu-based HARMSs to flat Cu plates with Sn intermediate layers is demonstrated, as well as assembly of all-Cu microfluidic prototypes.