Bonding of epitaxial lift off (ELO) devices with AuSn

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 which were pre-evaporated on the die or on the 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 for combining materials with different lattice constants (e.g. GaAs on Si). In this paper we report a new way for the bonding of Epitaxial Lift Off (ELO) devices onto Substrates. Two of the investigated multilayer structures produce a resulting AuSn alloy 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. The results show that much thinner bonding layers than already published can be reached. The results of our research allow us to optimize the layer structure, the bonding parameters and diffusion barriers