Research Of Silicon Based Single Photon Detector For TOF Imaging

With the development of intelligent industrial instruments,the time of flight(TOF)based photon imaging system can be used to directly measure the depth of field /distance,which can achieve faster response speed and larger measurement range.As a photoconductive detector,single photon avalanche diode(SPAD)is integrated into standard CMOS / BCD technology,which will greatly improve the miniaturization and integration level of the device and reduce the cost.The main contents of this paper are as follows:1、This work is mainly divided into the following three parts:(1)By studying the interaction of carriers with electric field and light field in silicon-based SPAD,the internal electric field distribution is established,the structure and performance of SPAD are optimized,and the SPAD structure with high response is designed;(2)According to the theoretical research,three structures are designed: two end n well structure,two end deep N well structure and surrounding BN well structure;(3)The I-V characteristics,electric field intensity distribution,avalanche breakdown probability and spectral response of the photosensitive surface length of7μm,9μm,10μm and 11μm under three different structures were simulated and analyzed by SILVACO TCAD software.The results show that the reverse bias voltage of the two terminal n-well structure is the lowest among the three structures with 11μm photosensitive surface,and that of the surrounded BN well structure is 17.63 v,which is higher than that of the other two structures.In the electric field intensity,the electric field intensity at the corner of the surrounded BN well structure is medium and evenly distributed,avoiding edge breakdown.At the wavelength of 700 nm,the spectral response of the 11μm surrounded BN well structure is the strongest.2、The external circuit integrated by quenching circuit and delay circuit is introduced to ensure the detection efficiency and accuracy of SPAD.(1)Through the theoretical analysis of the working characteristics of the three quenching circuits,it is concluded that the active quenching circuit can avoid the device heating,reduce the post pulse rate,and achieve the purpose of rapid quenching.(2)The design is composed of an active quenching circuit and three inverters cascaded delay circuit,and the delay time is 1ns.(3)The schematic circuit and quenching reset circuit of SPAD are simulated by cadence software,and the dead time of the whole circuit of SPAD detector is 2.5 ns.