Ultrathin Antenna-Integrated Glass-Based Millimeter-Wave Package with Through-Glass Vias

This article presents the design and demonstration of a high-bandwidth antenna-in-package (AiP) module focusing on low-loss interconnects and Yagi-Uda antenna performance fabricated on a 100- $\mu \text{m}$ low coefficient-of-thermal-expansion (CTE) glass for the 28-GHz band. It shows the modeling, design, and characterization of key technology building blocks along with the process development of advanced 3-D glass packages. The building blocks include impedance-matched antenna-to-die signal transitions, Yagi-Uda antenna, and 3-D active-passive integration with backside die assembly on 100- $\mu \text{m}$ glass substrates. The design and stack-up optimization of antenna-integrated millimeter-wave (mm-wave) modules is discussed. Process development to achieve high-density interconnects and precise dimensional control in multilayered thin glass-based packages is also described. The characterization results of the key technology building blocks show an insertion loss of 0.021 dB per through-package via (TPV), leading to the whole-chain loss of less than 1 dB and a return loss lower than 20 dB. The fabricated Yagi-Uda antenna features high repeatability of wide bandwidth due to the process control enabled by glass substrates. The antenna measurements show a bandwidth of 28.2%, which covers the entire 28-GHz fifth-generation (5G) frequency bands (n257, n258, and n261). The flip-chip assembled low-noise amplifier with 80- $\mu \text{m}$ solder balls shows a maximum gain of 20 dB as desired. The performance of the glass-based package integrated antennas is benchmarked to other 5G substrate technologies, such as organic laminates or co-fired ceramic-based substrates.