Background :

Some failures of microelectronic components occur during thermal transients at the time of starting of the component that generates an abrupt current. The analysis means to implement to ensure the reliability of these products need to have the ability to study these transients and their impact on the functionality of the electrical circuits. The major challenge here is to map the surface temperature of components, sometimes low-emission, with nominal temporal resolution of 5μs (and optimal 0.5μs) and a spatial resolution of 15 µm, for temperatures up to the maximum of 400 °C (resolution 1 ° C).

This challenge requires exploring innovative techniques and compare their performances to select the most appropriate. Thus, to achieve such temporal resolutions, the heterodyne (or stroboscopic) method will be implemented on different experimental benches.

Planned work :

The work aims to develop two experimental benches temperature mapping to achieve the expected resolutions, with priority to the temporal resolution.

The first step is to make a study of the state of the art on the different thermal mapping techniques, applied to the field of microelectronics. The emphasis will be placed on methods using conventional infrared cameras, based on the detection of the radiation emitted by the surface, depending on the searched temperature. And will be assessed methods of thermoreflectance types where the temperature dependence lies this time in the reflexion coefficient of the surface material in the visible. The mapping of the reflected ‘probe’ light, thanks to a visible camera, gives then information on the temperature map. The state of the art will evaluate the performance of these two families of methods, including their heterodyne modes (shift of the observation frequency component relative to its excitation frequency). The state of the art will also focus on the calibration phases of each method as well as the radiative properties that are necessary to know (infrared emissivity, reflectivity in the visible) for different materials present in the field of microelectronics.

The second step is to implement the heterodyne method in emission, from an existing infrared thermography bench. This task will consist in optimizing, among others, the asynchronous control of the component excitation and of the infrared camera acquisition, knowing that the component can be weakened by a too high excitation frequency. This step will also include the measurement of the emissivity of various materials.

The third step is to implement the time resolved thermoreflectance method at  microscopic scale. This will involve building the bench by sizing the various elements and optimizing the different frequencies of component excitation, probe light and visible camera. An important phase is the calibration of the surface reflection coefficient with temperature for various visible wavelengths candidates for the illumination of the component.

At each step, modeling tools and unsteady thermal simulation of electronic components will be implemented to predict the surface temperature changes that are to be measured. Radiative calculations will also be made to predict the different radiative fluxes (emitted, reflected) that are expected in each method.

Work environment

The work will be carried out as part of a larger project called ALPES (Applications de Lasers pour Plasma fib et thErmographie pour le Semiconducteur) whose partners are the companies ST Microelectronics and Orsay Physics (Rousset, near Aix-en-Provence) and the  laboratories IUSTI and LP3 from Aix -Marseille University and aims to implement in pre-industrial mode sample preparation techniques and temperature characterization.

The candidate will work in IUSTI laboratory in collaboration with project partners. The IUSTI laboratory (University Institute of Industrial Thermal Systems, UMR CNRS 7343) from the University of Aix-Marseille is one of eight laboratories of Carnot institute STAR composing, with IRPHE, M2P2 and LMA, the pole of Mechanics and Energetics. He also belongs to the laboratory of excellence Mechanics and Complexity (LABEX MEC). In one of the four research axes of IUSTI (axis Physics of Transfers), a part of the activities concerns the temperature measurement by infrared thermography and the estimation of heat fluxes and thermophysical properties by inverse methods. These activities involve a strong coupling between metrology and modeling.

Skills :  

The candidate should have knowledge in heat transfers (radiation, conduction), optics, signal processing and interest for experimental work in a team. A first experience in the field of photothermal methods (manipulation of incident radiation emitted, reflected, in the infrared and / or visible, collection by an optical system and a sensor conversion) is an asset. It must be sufficiently mobile and autonomous to work in the IUSTI laboratory but also on CIMPACA characterization platform within the company ST Microelectronics. Finally, it should have a good practice of french and english languages for writing reports and scientific articles.

Management and earning

Fabrice Rigollet (Maitre de Conférences à Aix Marseille Université – fabrice.rigollet<στο>univ-amu.fr) and Christophe Le Niliot (Professeur à Aix Marseille Université – christophe.leniliot<στο>univ-amu.fr).

Up to 3 years of professional experience after the PhD: Monthly remuneration before taxes € 2,415 € and 1,960 monthly after taxes (medical and social insurances included)

Up to 3 years of professional experience after the PhD: Monthly remuneration before taxes € 2,833 € and 2,300 monthly after taxes (medical and social insurances included)

Work period :

the contract can start in April ou May 2015 and have a duration of one or two years.