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 40 nm GaN front-end-of-line (FEOL) enables mm-wave circuit design techniques, passives and topologies traditionally limited to only silicon technologies. These “silicon-like” GaN MMIC architectures combine 1-to-3 W/cm
²
mm-wave HEMT power densities with the integration density afforded by a 7-layer silicon RF foundry BEOL. An improved GaN BEOL density enables
$\lambda/2$
aperture spacing compliance though G-band (220 GHz) 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
$\mathrm{f}_{\mathrm{M}\mathrm{A}\mathrm{X}}$
of 536 GHz.