Pseudo-MOSFET sensors based on out-of-equilibrium potential reading

Pseudo-MOSFET sensors based on out-of-equilibrium potential reading
Deadline for application: the 1st of June 2018, beginning of contract: the 1st of Oct. 2018

Place:
IMEP – LAHC, MINATEC – INPG, 3, Parvis Louis Néel, 38016, Grenoble

Advisor:
Irina Ionica (Associate Professor Grenoble ING),  Irina.Ionica@phelma.grenoble-inp.fr  +33 (0) 4 56 52 95 23

Context and objectives:
In the context of microelectronics, the importance of semiconductor on insulator (SOI) substrates has been extensively proven, not only to produces high performance circuits, but also for embedded systems-on-chip solutions, including sensors. The classical electrical characterization method of SOI substrates uses the pseudo-MOSFET configuration, in which the current flow between two probes placed on the top silicon film is controlled by the voltage applied on the bulk substrate, which serves as a backgate.
Similar to an ISFET, the threshold voltage of the pseudo-MOSFET shifts in presence of top surface charges1. Furthermore, we recently proved that the out-of-equilibrium potential in the top silicon film is an original way to detect the presence of such surface charges2. This new reading paradigm needs to be benchmarked with respect to the classical conductance variations in ISFETs and optimized to maximize performance in terms of linearity, sensitivity, noise and consumption; this is the aim of this multidisciplinary thesis.

Research to be performed:
In order to reach a pragmatic sensor, starting from our previous proof-of-concept studies some additional steps are needed:
· replacing the probes by deposited metal or doped contacts,
· validating that the physical mechanisms responsible for the out-of-equilibrium potential with deposited contacts are similar with those measured with probes,
· finding the appropriate dynamic conditions of potential reading,
· benchmarking of potential-based vs. current-based reading in the devices,
· exploiting the sensor for realistic bio-chemical detection (liquid environment, reading electronic system …).
The PhD student will develop the complete chain, from device fabrication, electrical measurements in equilibrium and out-of-equilibrium conditions, surface functionalization for specific detection applications (collaboration with Néel Institute)… The experimental characterization part will be
completed by segments of modeling and simulation, allowing the comprehension of physical phenomena involved and the optimization for the sensor.

Knowledge and skills required:
This PhD topic belongs mainly to the field of micro-nano-electronics, and more precisely to the electrical characterization and modeling of SOI substrates. The candidate must have a solid knowledge of physics of semiconductors and devices. Electronics of the measurement systems, surface functionalization would be appreciated. The candidate is expected to enjoy experimental work and the development of adapted measurement protocols. Scientific curiosity, motivation, creativity are mandatory qualities in order to take full advantage of the scientific environment of this thesis and to gain excellent expertise for his/her future career. The topic is in the field of applied physics, but close to the fundamental physics, as well as to the industrial world.
After the PhD, the candidate will easily adapt to both academic and industrial research environments.
The candidate must have a very good academic record, with high grades.
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1 I. Ionica et.al., Proceedings of IEEE Nano(Portland, USA) 2011, pp 38-43
2 L. Benea et.al., Solid-State Electronics, vol. 143, pp. 69-76, 2018

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