Development of Scientific CMOS imagers for STFC Applications

The e2v Centre for Electronic Imaging as a collaboration between e2v and the Open University to provide training for young scientists and engineers in the field of imaging detectors for science experiments. e2v have agreed to fund up to a rolling 12 PhD CASE students as part of this collaboration, which represents one of the largest concentrations of industrially-sponsored students under the CASE scheme. At a meeting with the PPARC executive in 2004 (involving Ian Halliday and Richard Wade), the research council agreed to support this ambitious plan for PhD student training. This single application is one of 3 CASE applications proposed into the 2009 round, exploring different aspects of imaging semiconductor device R&D of relevance to STFC science. E2v is a world-leader in the design, manufacture and test of CCD detectors into the world's scientific community, and is particularly strong in the space sector. In recent years, however, new CMOS Active Pixel Sensors (APS) have been developed for scientific applications. e2v is now undertaking significant R&D at both of its design houses at Chelmsford and Grenoble, developing the technology of CMOS imagers to position themselves in the market place in a similar way to that for CCDs. In particular, the CMOS imagers have development goals of : - low noise (down to 2-3 electrons rms) -back-illumination, for enhanced detection efficiency, particularly opening up detection windows for UV and soft X-rays - Large area, with multi-Mpixels, having a variety of pixel sizes - A high degree of parallellism to achieve high frame rates - high levels of system integration, including clock generation and ADC converters on-chip. This application will be for our third PhD student to work on aspects of scientific CMOS imagers (Greig funded by EPSRC, PhD awarded 2008, and Dryer funded by STFC who will be in his 3rd year by the time the studentship starts). In addition, within the group we have a new 3-year PDRA funded jointly by e2v and the University who is working on CMOS imagers, which helps to ensure a vibrant research activity in this field, and who will help contribute to supervision of the student. The student will perform detailed evaluation of new CMOS sensors from e2v,with particular emphasis on testing low noise, and back illumination variants for space science experiments. The group has a specific interest in the use of un-coated back-thinned imagers for the readout of the grating spectrometer on the International X-ray observatory (IXO) mission concept, where the CMOS imagers may ultimately dispalce the more mature CCD technology which is currently baselined. The student will therefore perform characterisation of such sensors using in-house soft X-ray facilities, and at synchrotron beamlines. The devices will also be characterised using optical stimulation, including PSF testing in our optical beamline. In addition, space radiation damage studies will be performed. This work will be of benefit to other space missions, for example Solar Orbiter, planetary and lunar missions, plus earth observation instrumentation. During the course of the work, once the student becomes familiar with the key issues, e2v will design CMOS test sructures (which may be small imagers, e.g. 10x10 pixels), to evaluate device parameters of interest to the PhD activity, and will then get these test structures manufactured. This activity will piggy-back on other funded CMOS work from e2v. One of the key activities of the studentship will be the definition, test and evaluation of these test structures, toward providing feedback into the design process. By the end of the studentship we would anticipate that a much greater understanding is obtained into the use and limitations of CMOS technology for future space missions, and also their use in terrestrial high-performance scientific imaging applications.