Enabling Monolithic Integration of an Advanced 7-Layer Silicon Back-End-Of-Line (BEOL) on 40nm GaN for Next Generation MMICs

Monolithically integrating a state-of-the-art commercial silicon back-end-of-line (BEOL) with a 40nm GaN front-end-of-line (FEOL) enables mm-wave circuit design techniques and topologies traditionally limited to only silicon technologies. These “silicon-like” GaN MMIC architectures combine 1-to-3 W/cm2 mm-wave HEMT power densities with the integration density afforded by a 7-layer silicon RF foundry BEOL. An improved GaN BEOL density enables λ/2 aperture spacing compliance though G-band (220GHz) for phase array applications. A compatible HEMT airbox process was developed to minimize frequency degradation due to the additional BEOL layers and demonstrates a 40nm HEMT fMAX of 536 GHz.