First Demonstration of Highly Scaled RF GaN-on-Si Dielets Embedded in Glass Interposer

This paper presents the first demonstration of a Gallium Nitride (GaN)-on-Si high-electron mobility transistor (HEMT) fully embedded in a glass package. AlGaN/GaN-on-Si HEMTs featuring n++ regrown contacts and a scaled Lg = 90 nm copper t-gate are fabricated and thinned to 300 µm. The fabricated HEMTs are singulated to a size of 350 µm × 540 µm via femtosecond laser dicing. Using a 300 µm AGC Inc. glass panel, the dielet is embedded and encapsulated with Ajinomoto Build-Up Film (ABF) GL102. For final back-end-of-line (BEOL) fabrication, two metal and two dielectric redistribution layers (RDL) are fabricated above the dielet. The effects of the RDL are analyzed and quantified through small-signal RF measurements of the integrated dielet. This integration scheme shows co-optimization from transistor to package-level design. This work lays the ground work for the future advanced packaging of such highly scaled GaN-on-Si dielets in a novel device-in-package platform for RF front ends.