Reseach On Novel Structures And Radiation Hardening For SOI CMOS Pixel Detector

With the development of high energy particle physics,researchers have explored unceasingly the standard model of higgs boson.Then,the requirements of maximum radiation fluence and beam intensity for Large Hadron Collider(LHC)have been increased,and they speed up the development and innovation of particle detector.In recent years,Fermi national accelerator laboratory in the United States and Japanese high energy accelerator research organization,have developed a series of monolithic active pixel detectors based on SOI CMOS process for detecting the track of charged particle.Compared to the traditional CMOS pixeldetector,the SOI CMOS pixel detector can control the substrate depletion independently,improve the detection efficiency of particles,and reduce the probability of single particle effect in readout electronics.In addition,the process has been simplified,and the cost has been reduced significantly.Therefore,it has been a hot spot for the new particle detector based on SOI CMOS technology.This dissertation devotes to the electric characteristics of SOI CMOS pixel detector,such as charge collection efficiency,radiation resistance and breakdown.The main work content is summarized as follows:First of all,it is researched the plane pixel structure of SOI CMOS pixel detector,the relationship between the device structure and pixel charge collection ability and parasitic capacitance,and the impact of radiation effect on the pixel feature.Then it is analyzed the fully depleted voltage and charge collection ability of new three-dimensional(3D)pixel structure.Considering the charge crosstalk mechanism,an advanced SOI CMOS pixel detector 3D pixel structure is proposed.N+ electrodes in 3D pixel are constructed into ring fence shape trench structure and surrounding P+ electrode to limit the active region for etch pixel.The N+ and P+ electrodes are directly leads to the readout electronics from the top of the pixel to simplify the process difficulty.Compared with the general 3D pixel structure,the N+ electrode of advanced 3D pixel suppresses the charge crosstalk.The studies results show that the advanced 3D pixel structure reduces the charge collection time,increases the ability of charge collection and radiation resistance.Second,it is analyzed the recent isolation structures,Nest Well Structure(NWS)isolation Structure and Double SOI(DSOI)isolation structure of SOI CMOS pixel detector between readout electronics and pixel electrodes.It is discussed the improvement of two isolation structure on the back gate effect and crosstalk effect.Based on the DSOI isolation structure,a new isolation structure with interspace is proposed,it suppresses the total dose effect by deleting the positive charge under the readout electronics part.In addition,the conductive layer formed the trench ring structure,which surrounds the readout electronics parts,and further reduces the parasitic capacitance between the readout electronics and pixel electrode.Then,it is analyzed the guard rings termination structure of plane pixel for SOI CMOS pixel detector,the breakdown voltage and the charge collection efficiency of edge pixel are discussed.Deep trench with interspace termination structure is to improve the electric field distribution of edge pixel and isolate the termination with active region and terminal area,then the breakdown voltage and charge collection efficiency of edge pixels are increased.At the same time,a back trench termination structure is proposed for advanced 3D pixel detector to improve the process difficulty and the breakdown voltage.In addition,the studied results show that the two termination structure have the good ability to resist radiation.Finally,it is discussed the impact of conduction layer potential in DSOI on the fully depleted voltage,charge collection efficiency and the breakdown voltage,for the plane pixel detector with trench termination,and the advanced 3D pixel detector with back trench termination respectively.Due to the space charge region expands horizontally in 3D pixel,and the electric field peak exists at the buttom of P+ electrode,the breakdown voltage of 3D pixel detector increases with the conducting layer potential,but the conducting layer potential does not impact the fully depleted voltage and charge collection efficiency.Comparison results show that the conduction layer has the smaller influence on the advanced 3D pixel detector.