Al-Al direct bonding with sub-μm alignment accuracy for millimeter wave SiGe BiCMOS wafer level packaging and heterogeneous integration

Official URL: https://dx.doi.org/10.1109/ECTC.2019.00147

In this work, we demonstrate an Al-Al direct bonding process for advanced wafer-level packaging and heterogeneous integration. The wafer bonding process is performed at 300°C with an alignment accuracy of <1 μm enabling fine-pitch wafer-to-wafer interconnections. The electrical performance of the Al-Al direct bonding is analyzed using different types of DC and RF test structures. Low resistance Al-Al bonding interconnections with mΩ-range contact resistance and insertion loss values <0.1 dB per interconnection are realized. An interposer based WLP process flow is developed which enables high performance mm-wave SiGe BiCMOS wafer level packaging applications.