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Fabrication, Characterization and Simulation of Channel Stop for n in p-Substrate Silicon Pixel Detectors
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.ORCID iD: 0000-0002-5619-409X
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.ORCID iD: 0000-0002-8325-5177
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2014 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 9, no 7, Art. no. C07013- p.Article in journal (Refereed) Published
Abstract [en]

Silicon detectors made on p-substrates are expected to have a better radiation hardness as compared todetectors made on n-substrates. However, the fixed positive oxide charges induce an inversion layer ofelectrons in the substrate, which connects the pixels. The common means of solving this problem isby using a p-spray, individual p-stops or a combination of the two. Here, we investigate the use offield plates to suppress the fixed positive charges and to prevent the formation of an inversion layer.The fabricated detector shows a high breakdown voltage and low interpixel leakage current for astructure using biased field plates with a width of 20 μm. By using a spice model for simulation of thepreamplifier, a cross talk of about 1.6 % is achieved with this detector structure. The cross talk iscaused by capacitive and resistive coupling between the pixels

Place, publisher, year, edition, pages
2014. Vol. 9, no 7, Art. no. C07013- p.
Keyword [en]
Electronic detector readout concepts (solid-state), Radiation-hard detectors, Solid state detectors
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-22224DOI: 10.1088/1748-0221/9/07/C07013ISI: 000340050700013Scopus ID: 2-s2.0-84905165594Local ID: STCOAI: oai:DiVA.org:miun-22224DiVA: diva2:726968
Available from: 2014-06-19 Created: 2014-06-19 Last updated: 2017-03-06Bibliographically approved
In thesis
1. Characterization of interface states & radiation damage effects in duo-lateral PSDs: Using SEM microscopy and UV beam profiling techniques
Open this publication in new window or tab >>Characterization of interface states & radiation damage effects in duo-lateral PSDs: Using SEM microscopy and UV beam profiling techniques
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There has been an increase in the use of duo‐lateral position sensitive detectors inpractically every radiation and beam detection application. These devices unlike other light detection system utilize the effect of the lateral division of the generated photocurrent to measure the position of the integral focus of an incoming lightsignal. The performance of a PSD is impaired or strengthened by a number of events caused by parameters such as interface states and recombination introduced during the fabrication of the detector and/or its absorption of ionizing particles. This thesis show the results from the successful implementation of alternative characterization methods of these effects and parameters using scanning electronmicroscopy and UV beam profiling techniques on duo‐lateral position sensitive detectors (LPSDs). To help create the groundwork for the research content of this thesis, different technical reviews of previous studies on interface states, surface recombination velocity and radiation damage due to continuous absorption of ionizing irradiation on detectors are investigated. The thesis also examines published theoretical and measurement techniques used to characterize these surface/interface phenomena. The PSDs used in this research were developed using silicon technology and the various methodologies put into the fabrication of the detectors (n+p and p+n structures) were fashioned after the simulated models. The various steps associated with the clean room fabrication and the prior simulation steps are highlighted in the content of the thesis. Also discussed are the measurement techniques used incharacterizing the fixed oxide charge, surface recombination and the position deviation error of the LPSDs in a high vacuum environment of a scanning electron microscope SEM chamber. Using this method, the effects of interface states and surface recombination velocity on the responsivity of differently doped LPSDs were investigated. By lithographically patterning grid‐like structures used as scaleon n+p doped LPSD and using sweeping electrons from the SEM microscope, a very high linearity over the two‐dimensions of the LPSD total active area was observed. An improved responsivity for low energetic electrons was also achievedby the introduced n+p structure. The lithographically patterned grids helped eliminate further external measurement errors and uncertainties from the use of other typical movable measurement devices such as actuators and two dimensional adjusters which would normally be difficult to install in a remote vacuum chamber. In a similar vein, field plate and field rings were patterned around an array ofthe PSDs used as pixel detector(s). By studying the interpixel resistance and breakdown characteristics, the most effective structural arrangement of the field plate and field rings used to curb induced inversion channel between the n+ doped regions of the pixel‐detector is observed. By using UV beam profiling after the irradiation of UV (193 nm or 253 nm) beam on n+p and p+n doped PSDs, the degree of radiation damage was also investigated. The results obtained help to illustrate how prolonged UV radiation can impact on the linearity and the position deviation/error of UV detectors. The results in this thesis are most relevant in spectroscopic and microscopic applications where low energy electrons and medium UV (MUV) radiation are used.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2014. 88 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 195
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-22221 (URN)STC (Local ID)978-91-87557-71-2 (ISBN)STC (Archive number)STC (OAI)
Public defence
2014-06-17, 10:30 (English)
Supervisors
Available from: 2014-06-19 Created: 2014-06-19 Last updated: 2017-03-06Bibliographically approved
2. Monte Carlo and Charge Transport Simulation of Pixel Detector Systems
Open this publication in new window or tab >>Monte Carlo and Charge Transport Simulation of Pixel Detector Systems
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is about simulation of semiconductor X-ray and particledetectors. The simulation of a novel coating for solid state neutrondetectors is discussed as well as the implementation of a simulationframework for hybrid pixel detectors.Today’s most common thermal neutron detectors are proportionalcounters, that use 3He gas in large tubes or multi wire arrays. Globalnuclear disarmament and the increase in use for homeland securityapplications has created a shortage of the gas which poses a problemfor neutron spallation sources that require higher resolution and largersensors. In this thesis a novel material and clean room compatible pro-cess for neutron conversion are discussed. Simulations and fabricationhave been executed and analysed in measurements. It has been proventhat such a device can be fabricated and detect thermal neutrons.Spectral imaging hybrid pixel detectors like the Medipix chipare the most advanced imaging systems currently available. Thesechips are highly sophisticated with several hundreds of transistors perpixel to enable features like multiple thresholds for noise free photoncounting measurements, spectral imaging as well as time of arrivalmeasurements. To analyse and understand the behaviour of differentsensor materials bonded to the chip and to improve development offuture generations of the chip simulations are necessary. Generally, allparts of the detector system are simulated independently. However, itis favourable to have a simulation framework that is able to combineMonte Carlo particle transport, charge transport in the sensor as wellas analogue and digital response of the pixel read-out electronics. Thisthesis aims to develop such a system that has been developed withGeant4 and analytical semiconductor and electronics models. Further-more, it has been verified with data from measurements with severalMedipix and Timepix sensors as well as TCAD simulations.Results show that such a framework is feasible even for imagingsimulations. It shows great promise to be able to be extended withfuture pixel detector designs and semiconductor materials as well asneutron converters to aim for next generation imaging devices.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2015. 95 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 215
Keyword
Monte Carlo Simulation, TCAD, pixel detectors, Medipix, Timepix, Finite Element Simulation
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:miun:diva-24763 (URN)STC (Local ID)978-91-88025-06-7 (ISBN)STC (Archive number)STC (OAI)
Public defence
2015-04-08, M102, Mittuniversitetet, Holmgatan 10, Sundsvall, 10:00 (English)
Opponent
Supervisors
Available from: 2015-03-31 Created: 2015-03-31 Last updated: 2016-12-23Bibliographically approved

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