Methodology to Accurately Replicate a Non-Planar Thin-Film Microstrip BEOL in 3D EM Simulation

In this paper, we present an EM design flow that seamlessly integrates the automated creation and usage of a conformal stack to explicitly replicate the topographical relief of non-planarized backend-of-line processes using PathWave ADS. The tool is verified by the implementation of two 300 GHz quadrature couplers in the thin-film microstrip backend-of-line of a 35 nm InGaAs mHEMT technology. The on-wafer measurements show excellent agreement with the simulated characteristics, with deviations of on average less than 0.5 dB in magnitude, and 5° in phase over the frequency range of interest from 250 to 330 GHz.