Integrated Circuit Design Of Silicon-based Microbolometer

Uncooled infrared detectors have the advantages of small size,light weight,low cost,and can work at room temperature.They are widely used in infrared detection,industrial detection,fire protection and security,and power industry.As the most commonly used structure of uncooled infrared detectors,microbolometers have developed rapidly in recent years.The microbolometer prepared by standard CMOS process can achieve a high degree of integration with the back-end circuit and other detector structures,which is the main trend in the development of uncooled detectors.In this paper,a polysilicon microbolometer is prepared based on integrated circuit technology and Post-CMOS technology.Based on the photoelectric response of the microbolometer,analog and digital readout circuits are further designed and integrated.The main research contents and results are as follows:(1)An integrating amplifier circuit is designed for the CMOS microbolometer.The circuit is designed with a capacitive feedback transimpedance(CTIA)structure with good linearity and gain controllable by integrating capacitors,which can not only amplify the weak current output by the detector but also stabilize the detector voltage.Cadence simulation results show that the output swing is 0.4-2.1V and the non-linear error is 0.2% when the integral current range is 15 n A?300n A.(2)An 8-bit counting ADC is designed to convert the analog output voltage signal of the detector into a digital voltage signal.The ADC is composed of a comparator and a counter.The simulation results show that the comparator has a transmission delay of49 ns and a resolution of 5m V;the counter simulation results show that it can work at a clock frequency of 100 MHz with a delay of 0.5ns;to save and convert digital signals Serial output,the serial output register is further designed at the back end of the ADC.(3)The integrated structure of the microbolometer array based on 40?m×40?m pixels was fabricated using SMIC 0.18?m 1P6 M process.The signal output of each row of the array takes 40 ?s.The first tape-out integration amplifier circuit was tested.The test results show that the nonlinear error of the integration amplifier circuit is 6.8%.The main source of error is the clock feedthrough effect of the MOS switch.A dummy switch is added to the MOS switch to suppress the clock feedthrough effect in this tapeout.