Design And Process Realization Of Voltage Divider For Silicon Drift Detector (SDD)

Silicon drift detector?SDD?is a kind of lateral depletion device,which generally works under the condition of full depletion.By applying appropriate voltage on the drift rings,on the one hand,the substrate will be completely depleted,and on the other hand,a transverse drift electric field will be generated.Under the action of the drift electric field,the photocarriers will drift to the anode to form an output signal.By analyzing the size of the output signal,the energy of the incident particle can be obtained.Each drift ring is concentrically distributed around the central anode.In order to achieve higher collection efficiency and make the electrons generated by the radiation drift to the anode quickly,the appropriate voltage must be applied on all the drift rings,which requires a large number of external lines for connection.An effective method is to integrate a voltage divider between each drift ring,so that the external voltage only needs to be applied to the innermost ring adjacent to the anode and the outermost ring at the edge of the drift region,which greatly simplifies the device structure.In order to achieve a uniform voltage divide between the drift rings,the design and process realization of the voltage divider is particularly important.In this thesis,different process methods were used to prepare the voltage dividers for SDD,and the performance of the voltage dividers prepared under different process conditions was studied.The main research results are as follows:?1?The size design of the voltage divider was studied.A suitable voltage divider width of10?m was determined by a two-dimensional simulation.?2?The diffusion method was used to prepare voltage dividers.The effects of changing the diffusion time,O₂ flow during diffusion,O₂ flow during preoxidation and test temperature on the voltage divider were investigated.This method is simple and easy to implement.But it is difficult to achieve shallow doping and slight doping,and the operating temperature is high and the sheet resistance is small,so this method is not suitable for preparing voltage dividers.?3?The poly-silicon method was used to prepare voltage dividers.A poly-crystalline silicon was obtained by first depositing a layer of amorphous silicon and then annealing.The effects of changing the growth time,annealing temperature and test temperature of amorphous silicon on the voltage divider were investigated.The operating temperature of the method is relatively low,and the deposited film is relatively uniform,and the sheet resistance of the voltage divider is large,but it is difficult to achieve strict control of doping concentration.?4?Ion implantation method was used to prepare voltage dividers.The effects of ion implantation dose,energy and test temperature on the voltage divider were investigated.The process temperature is low and the depth and concentration of doping are easy to control.The sheet resistance is larger and can be precisely controlled.Finally,the ion-implanted voltage divider was integrated into the SDD and uniform voltage divide between the drift rings was achieved.