Monolithic 28.3 THz thermal image sensor incorporating 0.18-µm CMOS foundry

This paper presents a fully monolithic approach to the design and fabrication of THz CMOS image sensor operating at 28.3 THz using the mass-producible 0.18-μm 1P6M CMOS foundry. The CMOS sensor consists of antenna-coupled transducer, linearly transforming the intercepted THz (terahertz) electromagnetic energy into voltage representation in the region of interest. The THz image sensor adopts PTAT (Proportional To Absolute Temperature) sensing circuit configuration. The THz thermal sensor occupies 68 μm × 42 μm chip area. A 500 μm-thick CMOS test chip of chip size 700 μm × 700 μm was scanned by a THz laser beam of 26 μm diameter with built-in THz thermal sensors. The scanned THz thermal image of the test chip was compared with the die photo, clearly demonstrating the validity of the design concept of the proposed THz image sensor. The responsivity measured by considering the entire test chip is 6 V/W.