Design of the AiP feeding lines for 6G applications in a high definition fan-out technology

Abstract

Since 2018, a race on 6G technology between many countries and institutions has started.
As 6G mobile communication utilizes sub-THz frequency band, the antenna packaging requires higher level integration. Antenna in Package (AiP) is seen as a promising solution when it comes to the integration problem. At 100GHz operation frequency band, AiP is not only feasible but also mandatory for a high-density interconnect and efficient IC-antenna integration. Current packaging technologies such as LTCC, HDI, and E-WLB, and their feeding concepts limit the possibilities to achieve an optimum
for the given silicon and antenna configuration, such as the complexity of the feeding network, the realizable thickness of metal or substrate material, and so on. To overcome these limitations, a novel high definition fan-out technology is investigated. This high
definition fan-out technology enables complex-shaped vertical interconnects. Yet there is a lack of research focused on the performance of such interconnects as well as the impact of its manufacturing process on the RF performance.

This thesis work is aimed to provide a scope of how the high definition fan-out technology benefits the performance of an AiP by applying coaxial structure as an antenna
feeding path in such a package. This new feeding concept is aimed to optimize the interface structure between the RF front end in silicon and the antenna array in the same
package, to reduce the routing size, reduce the insertion loss between the antenna array
and the silicon interface, and increase the isolation between the two adjacent feeds. An
initial model is fully parameterized for performance improvements via tuning. A benchmark model built up by the traditional laminate technology with vias is compared with
the performance of the proposed feeding structure regarding matching, insertion loss,
and port isolation. The presented model achieves 0.25dB insertion loss, 25dB return loss
and 80dB isolation. Compare to the benchmark model, on average, the model from the
high definition fan-out technology has significantly decreased the insertion loss, and
increased the channel isolation, while maintaining a similar return loss.

The impact of this high definition fan-out technology’s manufacturing process on the
model performance is discussed through parameters’ sensitivity analysis and system
robustness. The robustness analysis shows this feeding system has acceptable reliability
if the manufacturing error can be restricted within 10%, and it has good reliability if the
manufacturing error can be restricted within 5%.