Design And Fabrication Of Advanced Ultra-pure High Resistivity Silicon Detector Special Chip

Semiconductor detectors,such as silicon detectors,are widely used in photons and high energy particle detection in high radiation environment with excellent performances like fast response,high sensitivity,and ease of integration.Its application fields include aerospace,scientific research,industry,environment monitoring,non-ferrous,metallurgy,food safety,archaeology,radiation monitoring,etc.One of their typical application in the radiation environment is high-energy physics experiments.For example,Silicon detectors are used in the ATLAS and CMS in the Large Hadron Collider(LHC)experiment at CERN.Based on ultra-pure high-resistivity silicon materials,this research carries out works in design,fabrication and electrical performance tests on Silicon Drift Detector(SDD),and conducts modeling and simulation on new types of 3D-trench electrode detectors and ultra-fast 3D detectors.Silicon Drift Detector(SDD)is a special member of the detector family,and its carrier collection way is entirely different from that of the traditional plane detector.The carrier drift electric field is independent of the depleted field for charge transfer/drift,which results in a small anode area and the anode area is independent of the area of detector unit cell.Even if the unit area of the detector increases to centimeters,its small anode capacitance will reduce the series noise in the preamplifier circuit and improve the system overall noise performance,thus further improving the energy resolution ofthe detector.The detector uses ultra-pure high-resistivity silicon as material.In design of the large area SDD unit cell,the calculus of variation method is used to calculate the optimal path of carrier drifting to the collection anode,and the relation between bias voltages on both sides of the SDD is calculated to obtain the minimum drift time and optimal drift path,so that the electric field intensity along the drift path is a constant.The spiral cathode ring is designed to be an automatic voltage divider.The relationship between the pitch,width,and the radius of the detector is calculated to obtain the desired detector geometry.The electric potential and electric field distribution can be obtained by calculation and simulation,from which we can clearly observe the drift path.This is the first time in the world one obtains the electric field distribution by differentiating the electric potential of the detector to display the drift path.When inappropriate bias voltages are putted on the cathode,the drift path will not point to the anode or not locate inside the detector.After simulations,a set of masks will be designed and fabricated,including those for the lithography marks,P implant and N implant etching,and metalization.A complete set of masks is used to guide the fabricating process of the detector.In spite of the fact that detailed process steps are very complex,several innovations of large area SDD process,such as gettering oxidation,marking of double-sided lithography and protective ion implantation,can be extracted.After the fabrication of large area SDD,electrical properties such as I-V,C-V,spiral ring current will be tested.The appearance of SDD chip was observed by a microscope.Large area SDD's fabricated in this work have shown good appearance without defects,as well as excellent electrical characteristics including low leakage current(?10 nA)and low anode capacitance,which all meet the design requirements.The novel 3D-Trench electrode detector is a completely different design from the planar detector and the traditional 3D column electrode detector.It has the following advantages:The detector full depletion voltage is only related to the electrode spacing,which makes it no longer being limited by the thickness of the detector,thus greatly improving the detector performance and expanding its application fields.Compared with the 3D column electrode silicon detector,the novel 3D-Trench electrode detector does not have a "saddle point" of electric potential,and there will be no too high electric field near electrodes.The electric potential and electric field distributions will be more uniform.The design of the novel 3D silicon detector with trench electrodes is optimized in this work.The shape of the trench electrode is a box shape with two complementary parts,which is also the reason for naming it as the"3D open shell electrode detector",so as to improve the sensitive area of the detector,reduce the area of low electric field and reduce the area of "dead zone".In this work,the TCAD module of Silvaco software is used for simulations of various electrical characteristics.For example,leakage current,electric potential and electric field distribution of the detector are obtained by using basic equations and basic physical models for calculation.In terms of designing the novel 3D-Trench electrode detector,the square open shell electrode detector,square compound shell electrode detector and 3D parallel plate detector are introduced.Then,the simulation and analysis of the square open shell electrode detector in the non-radiation environment are carried out,so that we can know how to obtain the optimal design.Under the strong radiation environment,the leakage current and depletion voltage of the detector have been obtained.The capacitance is only related to the detector's electrode,so it does not change with radiation and keeps its small value.From the simulation of charge collection,we have obtained the relationship between the total amount of charge collection and the electron and hole contributions.By reducing the electrode spacing of 3D electrode detector to an extreme value,the ultra-fast response 3D detector can be obtained.The ultra-fast response 3D column and trench electrode detectors have been studied through calculations and simulations.The ultra-fast response 3D detector has a collection time of tens of picoseconds(ps)with only a few volts of bias voltage.By calculation,it has been known that at an electrode spacing of 5?m,the minimum bias voltage to make the carrier reach saturation velocity is about 4 V,and the response time is about 50 ps;at an electrode spacing of 10 ?m,the minimum bias voltage for carrier saturation velocity is approximately 8 V with a response time of 100 ps.The full depletion voltage is related to the electrode spacing of the detector.When the electrode spacing is very small,the full depletion voltage is also very small,which can be applied to some portable detection devices.In the design of 3D column electrode and 3D-Trench electrode detectors,the detector's electric field is much smaller than the value of intrinsic breakdown field under the bias voltage,that makes the carrier reach the saturation drift velocity,or further increased bias voltage,so the detector can work under such bias voltages.Because of the small spacing between the electrodes,the ultra-fast response 3D detector has autonomous anti-radiation property.The ultra-fast response 3D detector can achieve position resolution by forming arrays,which can further broaden its application fields.