Design and fabrication of a terahertz imaging array in 180-nm CMOS process technology

Using terahertz waves for imaging is gaining increased interest. A CMOS cascode amplifier biased near the threshold voltage of a MOSFET for terahertz direct detection is proposed. A test chip composed of 4×4 pixel CMOS terahertz imaging array is designed and fabricated on the basis of a low-cost 180-nm CMOS process technology. Each pixel consists of a microstrip patch antenna, an impedance-matching circuit, and the direct detector. The imaging pixels achieve a responsivity of 51.9 kV/W at 0.915 THz and noise equivalent power (NEP) of 358 pW/Hz1/2 at modulation frequency of 31 Hz. NEP is estimated to be reduced to 33.5 pW/Hz1/2 at 10 kHz. The imaging pixel occupies 250×180 µm. These results suggest that cost-efficient terahertz imaging is possible in the near future.