Scientific direction Development of key enabling technologies
Transfer of knowledge to industry

PhD : selection by topics

Engineering science >> Instrumentation
3 proposition(s).

integrated electronic interface for optomecanical sensors

Département Architectures Conception et Logiciels Embarqués (LIST-LETI)



The aim of this thesis to contribute to development of a new generation of sensors by study the electronic interfaces that allow the correct use of those sensors. The work will consist to study the system architecture, its integration on silicon and its characterization after fabrication and in a first application example. Within LETI, a new generation of sensors is under study: the optomechanical sensors. Their high levels of performances in terms of sensitivity, of stimulation modes as well parallel actuations of several sensors seems very promising. These results allow a broad range of potential usages for chemical sensors, physical sensors, mass sensors, ? However, development of the use of such sensors need the realization of an electronic adapted to such sensors that outperform the setup actually used to characterize these sensors. So, it is needed to understand those sensors, to do a behavioral model for them, to develop one or more architecture that can be integrated on silicon technologies to excite and sense simultaneously several sensors in an efficient way and getting the best of their performances. The phd candidate needs to have good knowledge of electronic in analog and digital fields. A good understanding of signal processing and in technologies used for sensors will be positive points. This phd work will last 3 years and will be done in LGECA lab in CEA-LETI, which has one of its main activities in the field of integrated circuit design of sensors. The operational work will be split in 5 main parts: bibliography (10%), architecture studies and modeling (20%), electronic design (30%), measurements and validation (20%) and publications (20%).

Integrated circuit modification with focalized XRays Beam and FIB

Département Systèmes

Centre d'Evaluation de la Sécurité des Technologies de l'Information



The understanding and conception of electronic devices require tools to modify these devices after their fabrication. A device failure or a functional bug require to modify the component behavior in order to find the corresponding problem. This modification of the integrated circuit is classically done with a Focused Ion Beam (FIB). This equipment permits to etch materials and deposit conductive or insulator materials, which allows to modify the interconnections of the integrated circuit. This operation is called circuit edit because the device can be reconfigured after his conception. Previous experimentations on ESRF focalized beam line in Grenoble allowed to demonstrate that a focalized XRays perturbation changes the state of a single NMOS transistor and a single memory cell of SRAM-EEPROM and Flash memories block in a semi-permanent manner in the electronic device. This proof of concept has been realized on a new CMOS technology device (45 nm). The 50 nm focalization allows to modify one single NMOS transistor. The most aggressive technologies (<20nm) can be addressed with this technique even with a 50nm focalization diameter. Contrary to the FIB the interconnections of the device are not modified: the state of one (or several if necessary) transistor(s) is modified. This modification is semi-permanent because it is reversible with a simple heating treatment. This new circuit edit technique is very promising. The aim of this PhD is to explore and develop this new technique of integrated circuit modification by using an XRays focalized beam at ESRF. Among the different key points to study, there are: -Precise localization of the transistor to attack with the help of fluorescence scan and GDS layout of the circuit -Modification of single PMOS transistors -Adaptation of the technique to more aggressive technology -Possibility to work without preparation of the package device. The exploration of the perturbation possibilities with laboratory XRays beam (without synchrotron) will be studied with the help of lead and tungsten protection made thanks to the FIB. During the PhD the candidate will have access to beam line shift at ESRF.

Performance Improvement of silicon nano-gauges for MEMS sensors

Département Composants Silicium (LETI)

Laboratoire de Caractérisation et Fiabilité des Composants



The piezoresistivity of the silicon nano-gauges is the basis of many CEA-Léti's MEMS sensors: accelerometers, pressure sensors, gas sensors? and the performance of these sensors is directly conditioned by the performance of the nano-gauges. As part of this thesis, the student will conduct research work to optimize the performances of nano-gauges according to the main parameters related to their technological fabrication process: SOI substrates, doping level, implantation method, geometry, release step (to suspend the nano-gauges), passivation or annealing after release... In particular, the PhD student will study the low-frequency noise of nano-gauges made on SOI substrates: he will characterize various types of nano-gauges, will seek to understand the mechanisms at the origin of the low-frequency noise in nano-gauges and will make the necessary simulations to reinforce the hypotheses explaining the electrical fluctuations within the nano-gauges. The maximum mechanical stress acceptable by the nano-gauges and the linearity zone of their piezoresistivity will also be studied, and a thermal study will have to be carried out to determine the maximal current usable for the piezoresistive measurement. These studies should allow, at the end of the thesis, to propose more efficient nano-gauges, as well as their manufacturing process. The integration of this process will be studied to allow the realization of a complete sensor based on this optimized piezoresistive transduction.

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