Performance Analysis On Three-dimensional Single Photon Avalanche Diode

Single photon avalanche diodes(SPAD)are widely used in the field of single photon detection such as positron emission tomography and lidar.This article aims to study the performance of traditional SPAD used to detect 420 nm photons and proposes an innovative structure,the purpose is to improve its photon detection efficiency.First,this paper analyzes the main performance of SPAD,including photon detection efficiency and time jitter.Considering the avalanche process and the randomness of carrier motion,the analytical energy band Monte Carlo model of silicon was introduced.On this basis,the calculation method and simulation model of photon detection efficiency and avalanche establishment time suitable for the Monte Carlo model were established.The model also considered the avalanche diffusion effect.Secondly,based on the traditional SPAD,this paper proposes a new three-dimensional fin-type SPAD for detecting 420 nm wavelength photons.Three-dimensional SPAD increases the effective area of the photosensitive area by increasing the side avalanche junction.Using the Silvaco simulation software,the minimum breakdown voltage difference between the two avalanche junctions is 0.361 V when the fin height is 1?m.Input the electric field distribution into the established Monte Carlo model and calculate the photon detection efficiency and avalanche establishment time distribution under 1-3V overbias: The photon detection efficiency of 3D SPAD under 3V over-bias is about 20%,which is more traditional SPAD can be increased by 46.37%;the full width at half maximum of the avalanche establishment time is about 6ps,which is 46.55% worse than the SPAD with traditional structure and high concentration shallow junction,and about 70% better than the SPAD with traditional structure and low concentration shallow junction.Finally,this paper designs the process flow of the three-dimensional fin-type SPAD.This article uses selective epitaxy as the main process to manufacture fins.Simultaneously,the process flow was simulated using the Silvaco simulation software.The process simulation results show that the thickness of the protection ring obtained by selective epitaxy is close to the theoretical design,so the process simulation results are similar to the device simulation results.