Investigations On Terahertz Imaging Based On Standard 0.18μm CMOS Technology

Terahertz frequencies provide an increased imaging resolution compared with millimeter wave. MOSFET has the feature of distributed resistive self-mixing when the operating frequency is much higher than cutoff frequency, which can be applied to terahertz imaging. Currently, silicon based terahertz imaging has become the research focus because of the high integration level and low cost.In this paper, terahertz imaging based on 0.18μm CMOS are studied, as listed follows:1) Based on theoretical analysis on the distributed resistive self-mixing model at frequency near or exceeding the cutoff frequency, the formula on the relationship between detection sensitivity and terahertz power are verified. By the simulation using 0.18μm CMOS process, the output characteristics of detector MOSFET are obtained. As indicated by measurement results of fabricated chips, the detector based on CMOS process is feasible for terahertz imaging.2) The antennas on chip are designed using 0.18μm CMOS process. Simulations and layouts are carried out for different antennas at 340GHz,610GHz and 700GHz.3) The operational amplifiers for terahertz imaging system are studied. Zero DC operating point are realized at the input of operational amplifier, to ensure the effective connection between detector MOSFET and the operational amplifier. In order to overcome the process tolerances, an adjustable DC point is set at the output of amplifier to ensure the proper working status under open-loop conditions.4) Based on design and analysis above, simulations and layouts for single pixel imaging unit and pixel array are finished, connection of each module are studied to ensure the maximum detection sensitivity of a single pixel unit and pixel array.