RandoCirc - Research project

Integrated circuits emit near-Infrared radiations and are sensitive to them. This emission, linked to the nature of semi-conductors, will vary if a transistor is turned on or off. This "photonic channel" can thus be exploited to passively observe the state of a circuit, or to modify it as a laser beam can trigger the passage of a current. Such attacks are used to access the data stored in integrated circuits or to retro-engineer their architecture. Here we propose coating the circuits' substrates with vanadium dioxide-based thin films, a thermochromic material that is transparent at low temperature and reflective at higher temperature, constantly modifying the optical properties of the chip during an attack. The transition temperature of this material, 68 °C, can be tailored by modifying its nanostructure or by doping, and will be adapted to the working temperature of the protected circuits. The doping of the material will rely on Pulsed-Laser Deposition: by alternating different targets, it is possible to precisely control the composition of the produced thin films. In particular, we will exploit GHz and MHz ultrashort pulses bursts to control the excitation of the ablation plume and optimize its contents in terms of plasma and nanoparticles. New laser systems offer numerous programmable controls over laser parameters such as power, pulse compression, etc. making it possible to precisely adapt the laser parameters to every target, which will be really relevant in the case of ultrashort ablation of metallic (vanadium, tungsten, etc.) or dielectric (MgF2, V2O5, etc.) with different absorption. To understand how the laser parameters affect the deposited material, thorough characterizations of its nano- and microstructure will be performed, such as Raman and STEM coupled with EDS and EELS. This will give us access to a wide range of thermally switching material relevant for our applications and many others such as smart windows, radiofrequency devices, thermo-optical switches etc. The requested funding will mainly allow us to buy pulverization targets, access characterization equipments (STEM, Raman, SEM, etc.) and communicate our research results through publication in Open Access peer-reviewed journals and presentations at International Conferences.