Design Of Low Noise And Anti-Blooming TDI-CMOS Image Sensor

The TDI(Time Delay Integration)image sensor based on CCD(Charge Coupled Device)can realize the observation on different objects by adjusting stage and integration time,so as to improve the observation quality and SNR(signal-to-noise ratio).In recent years,the semiconductor industry has made great progress in technology,it is possible to integrate CCD and CMOS device on the same chip.Thus,TDI CMOS image sensor was born which has CCD light sensing element and CMOS readout circuit.While this combination device keeps the excellent imaging quality of CCD,it also brings the advantages from CMOS of low power consumption,high integration density and radiation resistance,which becomes the hot spot of research recently.Therefore,it has a research significance to further restrain flicker noise and improve the anti-blooming ability of the sensor to improve the imaging quality of TDI CMOS image sensor.In order to reduce the influence of 1/f noise generated by in-pixel source follower of TDI CMOS image sensor,the author has studied a large number of references and relative designs proposed in recent years.It analyzes the production mechanism and influence factors of 1/f noise,the author proposes a pixel scheme which can effectively reduce 1/f noise.By testing the image sensor,we get the noise data of different types of transistors in the same size.Comparing low threshold voltage transistor,native transistor and other widely used transistors on flicker noise performance.In addition,we designed the same transistors in different sizes to observe size effect on 1/f noise.Finally,by comparing and analyzing the test data,we get the optimal transistor type and size to reduce 1/f noise.In order to improve the anti-blooming ability of TDI CMOS image sensor and make it obtain excellent image quality even though in strong light environment.Firstly,we analyze the principle of blooming and its impact on imaging quality.Secondly,advantages and disadvantages of two different anti-blooming structures are compared.Thirdly,we propose a lateral anti-blooming gate structure.Then we adjust the voltage of anti-blooming gate and record the anti-blooming effect and the variation of FWC(Full Well Capacity).Finally,we obtain the optimal anti-blooming gate voltage setting where the image sensor has an excellent ability of anti-blooming as well as a large FWC.Combining above two optimal schemes,this thesis designed an low noise and anti-blooming TDI CMOS image sensor,including the design of the pixel and readout circuit.In the future work,we will fabricate the optimized image sensor,and then obtain its characteristics and sample images through photoelectric test to evaluate the noise suppression ability,anti-blooming ability and dynamic range of this optimized design.