Research On Infrared Readout Circuit With The Function Of Background Current Self-compensation

Uncooled infrared imaging is a prospective technology applied in various fields,which is one of the scientific frontier topics,leading the development of next generation infrared detection technology.Meanwhile,the western countries block the core technique due to its important applications in military.Read out integrated circuit(ROIC)is an integral part to infrared detection technology,and,together with sensitive material technique and bolometer micro-fabrication technique,considered as the core technology of uncooled infrared imaging.Therefore,study on ROIC is of important theoretical and practical significance.The thesis focused on the researches of ROIC applied in bolometer with novel sensitive materials.The ROIC proposed in this paper is based on the traditional structure,which addresses the problem brought by the novel sensitive materials.The thesis proposed the idea and the detail designs of background current self-compensation technology for the first time,which provides the solution to meet the requirements of the bolometer with novel sensitive materials.To start with,the thesis presents the researches about the properties of Si/SiGe multi-quantum well materials.The electrical characterizations methods were developed and the tests of Si/SiGe multi-quantum well materials were conducted with designed system.Meanwhile,the characterizations for heat conduction and heat capacity were also conducted,which provided the data and support fundamentally for the further design of ROIC.The second part focuses on the vital structures which would have impact on the ROIC performance.A novel ROIC with low noise and high bias stability was designed,which was integrated with the background current compensation interface.Furthermore,the researches about sample and hold circuit were conducted and correlated double sampling circuit with single capacitance?bias circuit?operation amplifier and integrator were designed.The simulations show that the integral linearity>99%,the injection efficiency>99%,the bias error<0.0001%,the integrator output swing>4.98 V and the RMS noise is 0.25 mV.The ROIC possess characteristics with high linearity,high injection efficiency,stable bias voltage,high swing and low noise level as the simulations.Thirdly,a new background current self-compensation circuit was proposed on the foundation of studying the traditional background current compensation method,which works as closed-loop system,can be self-adaptive with different background current and suitable to address the requirements with different sensitive materials.The background current self-compensation module design methods are introduced,and what was more,detailed analysis and design have been applied to the key components of the sub-modules.The simulations were taken and the results illustrate the background current compensation module and sub-modules meet the project requirements.The integrated circuit(IC)layout is based on AMS 0.35?m CMOS digital process standards.The digital circuit power consumption is 0.7611mW,where the consumption of core chip is 0.6544mW.The chip area is 44139?m2,in which there are 277 cells occupying 37200?m2.Fourthly,the thesis presents the current source compensation circuits,in which the influence of temperature and process errors on current source compensation circuits was studied.The current source compensation circuit with controllable output,high precision,low temperature coefficient and high process error-tolerance was designed,which meets the application requirement of micro bolometer without TEC.The simulations about the circuits was conducted and the results show that the linear area current of the source output is 416 nA?2.736 ?A and the maximum temperature coefficient within the range of 0??80? is 267 ppm/? and the current source output deviation is 0.43%.The simulation indicates that the current source compensation circuit achieves low temperature coefficient and high process error-tolerance.Finally,the performance test for chip and bolometer was taken,where the chip performance test consists of function of background current compensation,linearity and temperature coefficient of current source compensation circuit,linearity of readout circuit,function of read out,noise and dynamic range.The bolometer characterizations test consists of voltage responsivity,pixels noise,relative spectral responsivity and noise equivalent temperature difference.The results are:the linear range of background current source compensation circuit is 338 nA?2.553 ?A,output current error<2.59%,the temperature fluctuation error<3.02%,the temperature coefficient<378 ppm/?,the maximum nonuniformity noise caused by compensation current source is 0.18 V.With the 5V power supply,the output linearity of the readout circuit>99%,the output linear range is 0.503V?4.402V,the maximum output RMS noise is 0.178 mV,the dynamic range is 86.6 dB.The bolometer test results are:average voltage responsivity is 9.1×105V/W,average RMS noise is 0.189mV,average noise equivalent temperature difference is 97 mK.The experimental results show that the readout circuit not only implements the background current self-compensation capabilities,but achieves significant performance.The researches pave the way for the large-scale readout circuit and provide important basis to realize the integration of MEMS process,circuits and encapsulation.