Most semiconductor electronic components are susceptible to radiation damage. Energetic particles such as alpha particles and heavy ions result in ionized radiation of the semiconductor material and potentially cause a non-destructive change in the state of CMOS devices. Naturally occurring alpha particles, impinging on the transistors in a circuit, generate electron-hole pairs during several nanoseconds.
When a memory point is involved, the transient current generated in the system can induce Single Event Upsets (SEU). The sensitivity of the memory device may increase together with increasing level of integration and decreasing size of individual cells. Thus, the charge necessary to induce a bit flip has decreased considerably.
The mainstream market for space applications is currently dominated by the Floating Gate (FG) technology such as Flash technology. FG technology is based on charge storage mechanism which is sensitive to radiation, for the obvious reason that the main effect of ionizing radiation is to generate electron-hole pairs, which can get trapped in dielectric layers and generate interface states (TID)  or give rise to transient currents (SEE) .
To overcome these limitations, rad-hard FG memories have been in production for many years. However, the rad-hard market is characterized by small-capacity devices and a high cost.
In this context, an alternative to flash memories is highly desirable. Among possible candidates, RRAM has attracted a lot of attention as this technology is believed to be hard and totally immune to radiation effects, because storage mechanism is not based on charge. Resistive RAM (RRAM) generally denotes all memory technologies relying on resistance change to store information. In RRAM, the data is stored as two or multiple resistance states of the resistive switching device. Thanks to their scalability  and performances such as fast switching speed , high retention , good endurance [6-7], and great compatibility with CMOS technology , RRAM are believed to become a good choice for embedded space applications.
However, RRAM reliability needs to be demonstrated to be considered for space application.
The PhD proposal targets Hafnium oxide-based RRAM evaluation for space applications. Hafnium oxide-based RRAM has been shown to have some degree of resistance to radiation damage. Nevertheless, further investigations with hafnium oxide need be performed.
The thesis is divided in two parts: it will first study the different oxide-based resistive memory cells and determine the most suited to space applications. The second part is dedicated to the development and implementation of the memory array circuitry built from the elementary cells. Two level of innovation are proposed: firstly, the innovation is related to the type of memory cell studied and secondly to the evaluation of the memory circuit under radiation.
1] J. Schwank, M. Shaneyfelt, D. Fleetwood, J. Felix, P. Dodd, P. Paillet, and V. Ferlet-Cavrois, “Radiation effects in MOS oxides,” IEEE Trans. Nucl. Sci., vol. 55, pp. 1833–1853, (2008).
 P. Dodd and L. Massengill, “Basic mechanisms and modeling of single-event upset in digital microelectronics,” IEEE Trans. Nucl. Sci., vol. 50, pp. 583–602 (2003).
 Yang Lu et al., “Scalability of voltage-controlled filamentary and nanometallic resistance memory devices,” Nanoscale, 9, pp.12690-12697 (2017).
 A. C. Torrezan, “Sub-nanosecond switching of a tantalum oxide memristor,” Nanotechnology 22, 485203 (2011).
 H. S. P. Wong et al., "Metal–Oxide RRAM," in Proceedings of the IEEE, 100(6), pp. 1951-1970 (2012).
 M-J lee et al. “A fast, high-endurance and scalable non-volatile memory device made from asymmetric Ta2O5−x/TaO2−x bilayer structures,” Nature Materials 10, pp.625–630 (2011).
 C. Nail et al., “Understanding RRAM endurance, retention and window margin trade-off using experimental results and simulations”, IEDM 2016 Tech. Dig., pp.95-98 (2016).
 S. Yu et al. “HfOx-Based Vertical Resistive Switching Random Access Memory Suitable for Bit-Cost-Effective Three-Dimensional Cross-Point Architecture,” ACS Nano 7(3), 2320-2325 (2013).
The PhD candidate will come from the American University of Beirut (https://www.aub.edu.lb).
IM2NP laboratory (UMR 7334) has already developed strong collaborations with AUB (mainly through Joint supervision thesis).
Financial support from AUB: 1000 euros/month.
Master in Electrical and Computer Engineering.
To apply, we invite you to contact the PhD/research supervisor and fill, with him/her, the co-financing part of the online application form (Reply to the offer) by April 1st, 2019.