Manufacturing Tolerance Investigation in GaAs MMIC SIW Resonator

This work presents the evaluation of a cavity resonator based on a 70-µm GaAs substrate integrated waveguide (SIW) for E-band transceivers. The fabricated prototype demonstrated a high-quality (Q) resonance at 72.25 GHz, with a measured frequency variation of ±0.5 GHz across 20 Monolithic microwave integrated circuit (MMIC) chips. A detailed analysis of manufacturing uncertainties and process tolerances, derived from manufacturer data, identified substrate height, via pitch, and via diameter as critical factors influencing resonant frequency. Variations in doping gradient were shown to affect sheet resistance and associated substrate losses, further impacting resonator performance. The combined effects of these factors suggest a potential 1% variation in resonant frequency due to process tolerances, aligning closely with the observed measurement spread. This study provides valuable insights into the feasibility of on-chip SIW resonators in the E band and highlights necessary measures for ensuring performance consistency.