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RADSIMOS Résumé de rapport

Project ID: 513476
Financé au titre de: FP6-MOBILITY
Pays: Spain

Final Activity Report Summary - RADSIMOS (Radiation Effects Study for Development of Radiation-Hard Silicon Detectors and CMOS Devices)

This Marie Curie (MC) European Re-integration Grant has facilitated the re-incorporation of the fellow and the implementation of the proposed research activities in the host institute of his country of origin. At the same time, it has allowed to keep some scientific collaboration activities with the host group of the previous MC Individual Fellowship (MCIF), as well as with other scientific contacts established during the initial MCIF period, thus establishing international collaboration with the current host institute in his country of origin.

The research activities involved three different but connected branches or objectives. A first objective has been devoted to the study and evaluation of silicon materials candidates to be used in future high-energy physics experiments. The studies have focused on both, the radiation effects, as well as on some critical issues for detectors processing using these materials. The main results of this objective have been related to characterization of a first batch of p-on-n pad diodes using the new High resistivity (HR) Magnetic Czochralski (MCZ) material, as well as the results from heavy irradiation with 24 GeV protons at CERN (up to a fluence of 10^16 protons/cm2) and subsequent thermal annealing studies compared to previous results of the Group in standard and oxygenated Float zone (FZ) material. Apart from the detectors technology and radiation-hardness activities, some first evaluation of the properties of these HR Si materials with high oxygen contents when subjected to different critical treatments that can be found during the silicon detectors fabrication process has been carried out. In this way, some samples of the new HR MCZ material were subjected to hydrogenation and thermal treatments at critical conditions for Thermal donors (TDs) formation. The results have shown the formation of hydrogen-related shallow donors (STDH) and Oxygen thermal donors (OTD).

A second branch has been mainly devoted to keep some collaboration activities on the study of radiation effects in new advanced deep-submicron CMOS technologies and devices. As for current scaled down CMOS nodes the interest in SOI technologies is strongly increasing, our objective has been to evaluate the degradation experienced by basic devices of both, Partially and Fully depleted (PD and FD) SOI when subjected to irradiation. Regarding to the FD SOI devices, under the different experimental conditions studied, the main radiation-induced effect has been found to be originated by positive charge trapping in the Buried oxide (BOX), leading to front channel characteristics degradation via gate coupling effects. On the other hand, only a subthreshold leakage current increase has been observed for the PD-SOI NMOSFETS case. The impact of the radiation-induced hole trapping in the Floating body effects (FBEs) has been particularly assessed.

Finally, a third branch of the research activities, but not less important, has been devoted to special characterisation studies which have been found necessary to understand some new phenomena appearing in the advanced deep-submicron CMOS devices studied. These device physics studies have also allowed an improved understanding of device physics for a better assessment of the radiation effects. Particularly, it has been shown that the HCD leads to a similar degradation but of opposite sign (negative charge trapping in the buried oxide), which results in a partial compensation or neutralisation of the previous irradiation damage by means of the HCD. Some first results about the temperature annealing of the HCD have been also carried out. An important effort has been devoted to the study of the Floating body effects (FBEs) in the presence of a new physical phenomenon (Linear kink effect (LKE)) which was observed during the initial MCIF. This appears in advanced SOI and bulk devices with ultra-thin gate dielectrics, which enable electron valence band tunnelling. Due to the history and memory effects induced, this phenomenon could be a limitation for PD SOI CMOS circuits operation.


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