Investigations On Terahertz Imaging Based On CMOS Technology

THz imaging technology can be adopted for applications in medical-imaging, security, and non-destructive evaluation. Continuous improvements in CMOS technology will enable low-cost and portable THz imaging system to be realized. Currently, THz imaging based on CMOS technology has become the research focus. In this thesis, silicon CMOS based pixels and arrays for terahertz imaging applications are studied, as listed follows:1) The mechanism of terahertz detection using MOSFETs is described by hydrodynamic equations and non-quasi-static model, respectively. The relation and distinction between two methods of theoretical analysis is studied and the merits and demerits of the two methods are summarized.2) Three on-chip patch antennas are designed and simulated. The radiator is implemented with the top metal layer to improve the gain and efficiency of the antennas. Metal 1 layer forms ground plane which can eliminate the back lobe and stop substrate waves from being generated in the bulk silicon material. To improve power transfer efficiency, a matching network is inserted between the antennas and the MOSFETs.3) Three kinds of operational amplifiers are designed for different application scenarios and performance requirements. The operational amplifiers include two open-loop operational amplifiers with two stages, feedback operational amplifiers and low noise operational amplifiers. The measurement results agree well with simulation and show that the designed operational amplifiers work properly.4) The pixels and an array for terahertz imaging applications are studied. Connections between MOSFETs detectors and operational amplifiers are considered carefully. A 5kΩ load resistor is inserted between the FET detector and the operational amplifier to increase the efficiency of self-mixing. A MOS-bipolar pseudo-resistor element is used as a high-resistance element in bias network of operational amplifier. A 2×2 pixel array is implemented, in which each pixel can be separately addressed. The measurement results show that the imaging pixels and the imaging array work properly.