3D Integrated Through Fused Silica Via (TFV) Based Array Antenna for mm Wave Communications

In this paper we report the demonstration of a multilayer 4X4 array antenna using Through Fused Silica Via (TFV) glass technology targeting 28 GHz as the operational frequency for 5G applications. Due to its low loss tangent, smooth surface and excellent Coefficient of Thermal Expansion (CTE) match with silicon, glass possesses several advantages compared to other substrate materials. 4X4 antenna array patches are fabricated on the top substrate and feed lines on the bottom substrate where both the substrates are separated with a ground plane in the middle. All the metal layers are deposited using an electroplating process after the seed layer deposition by sputtering. Two resonance frequency measurements are performed. In the first method, direct Cu to Cu bonding is implemented. In the second one, fully cross linked SU-8 polymer is used as bonding material between the glass substrates. Designs are simulated using High Frequency Structural Simulator (HFSS, ANSYS Inc.) and compared with the measured ones. The total area occupied by 4X4 patches on the top substrate and feed lines on the bottom substrate is 4.29 cm
²
and 3.67 cm
²
, respectively.