Junction engineering of microstrip silicon sensors to operate in controlled charge multiplication mode for enhanced radiation tolerance

Lead Research Organisation: University of Liverpool
Department Name: Physics


This project involves the high energy Physics (HEP) group of the University of Liverpool and Micron Semiconductor (UK) Ltd as the industrial partner. The Liverpool group has a world recognised track record in R&D, assembly and commissioning of silicon detectors for HEP experiments. Micron Semiconductor LTd is a leading supplier of silicon detectors to particle physics experiments, having a long track record dating from fixed target programmes, to LEP, Tevatron, PEP-II, HERA and the LHC. However, Micron have diversified into work for space (with contracts with NASA,in USA and JAXA in Japan), defence, nuclear and medical applications with particle physics representing only about 20% of current orders. However, the development of new technology and techniques for these other areas has historically always taken place in the context of meeting the challenges of particle physics and the current programme represents an excellent opportunity for both the company and the student. The over 15 years long collaboration between Micron and the University of Liverpool has lead to the production of extremely successful silicon sensors for HEP experiments like CDF at Tevatron-FNAL, DELPHI at CERN-LEP, ATLAS and LHCb at the CERN-LHC. It is worth noting that the first p-type sensors, leading to the development for the n-in-p technology now the default for sLHC, grew out of a CASE studentship between Liverpool and Micron, for which the student, Moshe Hanlon, won the Rutherglen Prize for his PhD. thesis research. The work will focus on the optimisation of the design and processing parameters of silicon detectors to operate in a controlled charge multiplication regime by mean of the shaping of the electric field at the junction side. In the first phase (a) of the project the student will perform2-d and 3-d device simulations of the, using TCAD and/or custom made charge transport models. A model of the radiation damaged silicon will be implemented by the student using the existing literature and the experimental data accumulated by the group. The performance of irradiated silicon is a subject of high interest to both industry and academy, and the ability to access a substantial amount of experimental data to compare to the simulations, with the deep understanding of the tested devices coming from the collaboration with the specialised industrial partner makes a unique working environment likely to lead to publishable results and to enhanced manufacturing methods. The student will design the photolithography mask set using a state of the art package that will be adopted by the industrial partner for processing the novel devices. Pad diodes, microstrip detectors, pixels and various test structures for process control and optimisation will be designed (phase (b)) and produced. Both task (a) and (b) will be performed at the University of Liverpool during the first semester of the thesis. The following phase (c) will start on the 2nd semester and will involve close collaboration with the company to learn the processing parameters that can be tuned for a fine shaping of the junction. The production of a first set of wafers (10-15) will be based on intuitive modifications (in the opposite directions of a steeper and smoother profile) of the current processing parameters to explore more extreme junction geometries (step or diffused junction) and their performance after irradiation. The first processed detectors can be expected within the 1st semester of the 2nd year, with measurements (performed by the student under the initial guidance of the supervisor) taking place within the end of the same year. This allows for feedback from the measurement to correct the processing parameters, verify and improve the simulation with information from measured data. The finally optimised geometries will be processed and characterised in the last year, with fine tuning of the parameters.


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Bernabeu J (2013) A portable telescope based on the ALIBAVA system for test beam studies in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

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Casse G (2013) Charge multiplication in irradiated segmented silicon detectors with special strip processing in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

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Casse G (2013) Degradation of charge sharing after neutron irradiation in strip silicon detectors with different geometries in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

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Casse G (2013) Recent developments on silicon detectors in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

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Casse, G.,Affolder, A.,Allport, P.P.,Chmill, V.,Forshaw, D.,Greenall, A.,Tsurin, I.,Huse, T. (2011) Changes of the particle detection properties of irradiated silicon microstrip sensors after room temperature annealing

Description We have demonstrated the effect of junction engineering for improving the radiation tolerance and response speed of silicon detectors deployed as tracking devices for ionizing radiation. The results we found show that the effect we wanted to create can be achieved with irradiated and non-irradiated devices. This has an impact on sensor technology because it can enable the use of segmented (tracking) devices with enhanced time resolution for application where the time domain has a role.
Exploitation Route The idea has prompted investigations for using silicon sensors where high time resolution is required (e.g. Low Gain Avalanche Detectors, LGAD devices).
Sectors Aerospace, Defence and Marine,Electronics,Other

Description The findings have prompted further research in this area, by various groups, internationally. Several are member of the CERN/RD50 collaboration, where our results have been presented several times.
First Year Of Impact 2013
Sector Electronics,Other
Impact Types Cultural

Description Improved sensor resolution in the time domain
Geographic Reach Asia 
Policy Influence Type Influenced training of practitioners or researchers
Description AIDA 
Organisation Advanced European Infrastructures for Detectors at Accelerators (AIDA)
Country Switzerland 
Sector Multiple 
PI Contribution Development of irradiation facilities.
Collaborator Contribution Advanced European Infrastructures for Detectors at Accelerators.
Impact Development of infrastructure we use for irradiating our devices. Support our research in advanced detectors. Acccess irradiation facilities across Europe.
Start Year 2012
Description CERN 
Organisation European Organization for Nuclear Research (CERN)
Department Physics Department
Country Switzerland 
Sector Academic/University 
PI Contribution Supervision of the PhD project. Scientific direction.
Collaborator Contribution Co-supervision of the PhD. Help and support for experimental work at the CERN premises.
Impact Shared scientific results, presentation to conferences and workshops, publications, impact on detector technology.
Start Year 2013
Description CERN/RD50 
Organisation European Organization for Nuclear Research (CERN)
Department CERN - Other
Country Switzerland 
Sector Academic/University 
PI Contribution Spokesperson of the collaboration. Consistent amount of research for development of advanced instrumentation for high energy physics experiments. The collaboration involves 48 institutes from Europe, US and Asia and over 250 scientists.
Collaborator Contribution R&D on extreme radiation tolerant semoconductor sensors. Contribution to common funds for research. Several papers published.
Impact Several papers and common R&D paojects, carried out partially with funding from the collaboration.
Description CNM 
Organisation Spanish National Research Council (CSIC)
Department Barcelona Institute of Microelectronics
Country Spain 
Sector Public 
PI Contribution Exchange of technical details for improvement of ionizing radiation detector. Production (CNM) and test (our project).
Collaborator Contribution CNM: silicon detector production factory. Our project: state of the art characterisation instruments and methods, Irradiation and tests.
Impact Several articles and presentations to workshop and conferences.
Start Year 2012
Title Novel connectivity in pixel detectors 
Description Novel way to route individual sensitive channels in hybrid pixel sensors to the readout electronics. Instrumentation technologies (inc. vibration, miniaturisation, ruggedness) 
Type Of Technology Systems, Materials & Instrumental Engineering 
Year Produced 2012 
Impact Decoupling of the sensor geometry from the readout ASIC geometry, adaptation of vrious geometries to the same readout chip. Cost reduction, better sensor area coverage.