System Design Of Sub-micron Floating-gate Image Sensor

Image sensors have become one of the most important information-inputapparatus in modern information industry, and currently the main kinds of commercialimage sensors are CCD (Charge Coupled Device) and CMOS image sensor. However,with the increase of integration degree and the decrease of the pixel size, the above twoimage sensors are facing the critical challenges such as deterioration of SNR andimage quality. This thesis designs and validates an image sensor based on floating gatedevice called floating-gate image sensor in brief.Compared with the mainstream image sensors, the significant difference of theimage sensor proposed is that each pixel unit consists of only one floating gate device,and the photoelectrons are stored in the floating gate. This brings in advantages:sub-micron pixel size and the size decreases with process node shrink. Capacity of thefloating gate increases the number of full-well electrons and SNR. The floating-gateimage sensor also has a good technology compatibility and process yield.Firstly, this article analyzes the feasibility and the possible problems of floatinggate devices used in the field of image sensors theoretically, also provides guidance forsubsequent circuit design. Secondly, the system-level design is made including theconstruction of a pixel array, the readout data path, operating timing and validationplatform. Considering that the parameter uncertainty and process characteristics offloating gate device used in the image sensor field, the thesis leaves some margin forthe convenience of testing and validation. Moreover, the key circuit modules arespecified and simulated, including CTIA,10bit cyclic ADC, readout data path, timingcircuit, high voltage circuit and decoder circuit.The image sensor is fabricated by0.13μm2P3M NOR flash memory technology.The pixel array is5120×5120, and pixel size is0.95μm×0.95μm. The testing resultsshow that the floating gate image sensor achieves the basic functions of image sensor,reset, capture, data readout. This thesis also explores its application in the field ofon-chip microscopy due to the sub-micron pixel size characteristics.