Fast timing silicon pixel detectors for new applications

Lead Research Organisation: University of Manchester
Department Name: Physics and Astronomy

Abstract

Silicon sensors are essential in a range of fields, from cutting-edge research (e.g. particle physics, chemistry, materials science) to industry (agriculture, manufacturing), and everyday devices (cameras, security). They are the eyes of our electronic world. As we develop more precise sensors, for example cameras with smaller pixels, the potential reach of these devices increases, allowing more processes to be investigated, and with more detail.
Currently the resolution of such sensors is at the micrometre level. However, the time precision is relatively much worse, due to significant technological challenges in assigning times to the signals in the silicon. The best precision for small-pixel silicon sensors is at the nanosecond (ns) level. By comparison, light travels 300,000 micrometre per ns. Our ability to observe many processes is significantly hampered by limitations in time precision.

For fast (~1ns duration) processes, adding picosecond-level (1ps = 0.001ns) timing to micrometre-level spatial measurements effectively corresponds to the difference between still images and video, and hence has the potential to open up entire new fields of research. Such processes occur, for example, in particle and nuclear physics, chemistry, and materials science. The ultimate aim of this project is to develop sensors that for the first time simultaneously reach precision at the micrometre-level in space, and picosecond-level in time: a high-speed video camera for the smallest observable scales.

We start from a new type of sensor only developed in the past decade: Low Gain Avalanche Detectors (LGAD). By adding specially-treated semiconductor layers to the silicon, the time of signal collection is significantly reduced, making it possible to reach ~30ps precision. However, the only devices so far developed have large (mm-size) pads rather than pixels. Our programme of research will focus on ways to transform these devices into pixel sensors, by considering new geometries and doping approaches, and thin sensors. The key is to maintain as uniform an electric field as possible within the pixel, to ensure fast signal development. We have started preliminary studies, including fabrication of prototype devices, and now we are ready to push forward with an aggressive research and development phase.

Researchers from the Universities of Glasgow and Manchester will work with a commercial semiconductor manufacturer (Micron) to design and fabricate a range of new LGAD sensors, and analyse their performance using several high-tech methods ('transient current technique' - TCT and 'two photon absorption' - TPA). In parallel, we will develop realistic simulations of the detectors using TCAD models, to predict the sensor characteristics under different designs. These simulations will be validated using the TCT and TPA results from our measurements. All of our results will be published in open-access journals, taking us a step closer to the dream of '4D' precision sensors.

In parallel, we will develop a network of potential beneficiaries of these new devices, in particular for the fields of materials science and proton therapy. We have already established connections with representatives within these areas, who will help us to build the network, starting with two dedicated workshops. These will be used to build a specifications document where the required technology performances are defined. They will also enable us to reach further to identify more potential users of this new technology, in the UK and beyond.

Planned Impact

The proposed 4D precision detectors will enable powerful new techniques in the fields of chemistry, medicine, and materials science for studying and visualising structures and processes. The following specific applications have been identified, which are described in more detail in the Pathways to Impact Statement (attached separately):
(1) Precise beam control for proton therapy, (2) X-ray correlation spectroscopy, (3) Cryo-Electron microscopy, (4) Time-of-Flight Mass Spectrometry.

Furthermore, expertise on the fabrication of pixelated LGAD will be developed during this project. This work will fortify the expertise of Micron in LGAD devices and strengthen the position of this UK company. This will allow Micron to bid for contracts to supply LGADs to the market. In HEP alone there are two potential large orders in the coming years for the CMS and ATLAS timing detectors. This proposal will improve the chance of Micron winning contracts for these large projects.

Publications

10 25 50
 
Description We have investigated novel types of silicon sensors that aim to provide excellent position and time resolution in combination with a fast readout rate and radiation tolerance for use primarily in future particle physics experiments. Different types of Low-Gain Avalanche Diode detectors were developed and investigated and will be further studied in experiment-specific project grants as a direct consequence of the results of this grant.
Exploitation Route The sensors will form candidate sensors for future particle physics experiments as well as other applications with similar use cases such as medical physics and material science.
Sectors Electronics,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

 
Description The industry partners linked to this award have advanced their silicon manufacturing techniques to satisfy the cutting edge requirements of silicon micro fabrication linked to this award.
First Year Of Impact 2020
Sector Manufacturing, including Industrial Biotechology
Impact Types Economic

 
Description LHCb Upgrade II: Maximising HL-LHC Discovery Potential (Bridging Funding)
Amount £19,339 (GBP)
Funding ID ST/V002902/1 
Organisation Science and Technologies Facilities Council (STFC) 
Sector Public
Country United Kingdom
Start 09/2020 
End 09/2021
 
Title TCAD simulations 
Description We have developed detailed simulations (using TCAD) of both inverted-LGAD and trench-isolated LGAD devices. These are still under development, but already represent a tangible output of the grant which will further the field. 
Type Of Material Computer model/algorithm 
Year Produced 2021 
Provided To Others? No  
Impact This will allow us to compare results from device characterisation with simulation, and hence to adjust the design and processing of devices in future. 
 
Description CNM 
Organisation Institute of Microelectronics of Barcelona
Country Spain 
Sector Public 
PI Contribution We provide input from simulations and testing to support the research interests of CNM. We have also acted as a bridge between CNM and the LHCb Collaboration, culminating in them joining the collaboration as technical associate members in 2020. This was a strong motivation for their successful application to join, as mentioned in their announcement: "The team is already working with different international institutions within the LHCb community, such as the University of Santiago de Compostela, the University of Glasgow, the University of Manchester, the University of Edinburgh and the University of Science and Technology Krakow on iLGAD technology." - three out of four of these institutes work with CNM through the support of this grant. https://www.imb-cnm.csic.es/en/outreach/news/imb-cnm-joins-lhcb-collaboration-cern-technical-associate
Collaborator Contribution CNM provide expertise mainly in the person of NM (see Next Destination), who moved from Glasgow to CNM in January 2020. With the support of the organisation, NM continues to work at a level of a couple of hours a week, supporting our simulation, design, and testing efforts, as well as providing invaluable networks within CNM and other industry entities.
Impact It's currently too early to claim concrete outputs for this work.
Start Year 2020
 
Description Diamond 
Organisation Diamond Light Source
Country United Kingdom 
Sector Private 
PI Contribution We have shared information from our research with Diamond. In particular, we have propagated results based on the use of their test beam. We have also helped to create networks with industry and academic partners, including Diamond.
Collaborator Contribution Diamond provided the venue and support for one of the two community engagement workshops hosted in Nov 2019. They also provided beam time (also in Nov 2019) for testing existing devices (not funded by this grant), allowing our team to develop the techniques and procedures for subsequent testing of devices produced under this grant.
Impact Workshop (see 'Engagement Activities').
Start Year 2019
 
Description Micron 
Organisation Micron Semiconductor
Country United Kingdom 
Sector Private 
PI Contribution Micron semiconductors are a UK-based company who fabricate devices as part of this grant. We have a close relationship with them, collaborating on designs and testing. As partners in this grant, Micron benefit from our insights and data on the design and manufacturing process, allowing them to extend their product range into new emerging technology areas (e.g. inverted LGAD sensors).
Collaborator Contribution Micron provide an in-kind contribution through expertise and discounted materials (up to half the overall cost of the fabrication - £10k per submission at a conservative estimate.
Impact We have collaboratively designed new types of sensors (output: masks, processes) for both iLGAD and (in progress) trench-isolated LGAD devices.
Start Year 2019
 
Title LGAD sensors 
Description As part of the project we developed different types of Low-Gain Avalanche Diode silicon sensors. 
Type Of Technology Detection Devices 
Year Produced 2021 
Impact These sensors form the basis for further R&D work towards highly granular silicon sensors with sub-nanosecond time resolution. 
 
Description Community engagement workshop (DIAMOND) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact 20 people attended a workshop at the Diamond Light Source (RAL), to discuss potential applications of fast-timing silicon pixel sensors in the fields of chemistry, biology, and materials science (with a focus on synchrotron facilities and electron microscopy). New connections were created, new ideas developed, and the discussion was recorded in a document which was circulated to all participants.
Year(s) Of Engagement Activity 2019
URL https://indico.cern.ch/event/853712/overview
 
Description Community engagement workshop (Medical) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact 14 people attended a workshop at the University of Manchester, co-hosted by the Christie Hospital, to discuss potential applications of fast-timing silicon pixel sensors in the fields of medical science, with a focus on proton therapy and related fields. New connections were created, new ideas developed, and the discussion was recorded in a document which was circulated to all participants.
Year(s) Of Engagement Activity 2019
URL https://indico.cern.ch/event/853133/