A new bonding technique for microwave devices

Over the past five years, a great deal of work has been done to perform semiconductor die attach with AuSn alloys. Successful die attach has recently been achieved using Au and Sn multilayers evaporated onto the die or the host substrate. However, bonding techniques with thin (below 5 μm) AuSn layers for very thin semiconductor devices have not yet been reported. The increasing demand for more advanced optoelectronic integrated circuits has created the need to bond materials having different lattice constants (e.g., GaAs on Si). In this paper we report a new way for the bonding of epitaxial liftoff (ELO) devices onto host substrates. Three of the multilayer structures investigated in this work produce a AuSn alloy bond with approximately 84 wt.% gold, but can be bonded with a peak temperature below 280°C. The bonded samples were investigated with several standard surface analysis techniques: Optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). We conclude that much thinner bonding layers can be attained than thus far reported. The results of our research allow us to optimize the layer structure and bonding parameters