Design of a CMOS On-Chip Slot Antenna With Extremely Flat Cavity at 140 GHz

A novel design for a fully on-chip antenna operating at 140 GHz that can be fabricated with standard CMOS technology is proposed. In addition to the traditional microstrip feeding, the slot antenna is backed with an extremely thin cavity formed by two CMOS inner metal layers and vias in between. The proposed cavity prevents radiation from going inside the lossy silicon substrate and enhances the radiation of the slot antenna. It is also shown that the antenna radiation is not affected significantly by other metallic parts on the chip. Good agreement is achieved between results from a frequency-domain solver, HFSS, and a time-domain solver, CST. The simulated gain is around -2 dBi, and the radiation efficiency is around 18%, despite ohmic losses enhanced by the extreme flatness. The input 10-dB bandwidth is around 5 GHz. The total area of this antenna is 1.2 × 0.6 mm² (0.56 λ₀ × 0.28 λ₀ at 140 GHz).