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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$n++$</tex> regrown contacts and a scaled <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$L_{g}=90$</tex> nm copper t -gate are fabricated and thinned to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$300 \mu \mathrm{m}$</tex>. The fabricated HEMTs are singulated to a size of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$350 \mu \mathrm{m} \times 540 \mu \mathrm{m}$</tex> via femtosecond laser dicing. Using a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$300 \mu \mathrm{m}$</tex> 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.