High Throughput Characterization Methods at the Wafer Scale for Sputtered Films Used in Micro-Supercapacitors and Li-Ion Micro-Batteries

International audience; The emergence of new miniaturized and autonomous electronic technologies leads to a request of efficient microdevices for energy storage. The development of thin film Li-ion micro-batteries or micro-supercapacitors is an interesting way to power connected sensors, as their manufacturing method is compatible with the techniques used in the microelectronics industry. These miniaturized electrochemical energy storage devices can thus be easily integrated into embedded electronics. Most of the time, for the development of such energy microsources at the laboratory scale (and more specifically at the electrode level), studies are conducted on small pieces of substrates where the area of tested electrode material is restricted. It is however important to study the homogeneity of thin film electrodes, not only on small pieces of substrates, but at the wafer scale, in the case of an industrial transfer of more fundamental researches led at the laboratory scale (i.e the upscaling of the technology, needed for the collective fabrication of hundreds/thousands of microdevices on a single wafer). We have developed a complete mapping strategy of thin film electrodes characterization at the wafer level on different techniques, such as X-ray diffraction, X-ray fluorescence, scanning electron microscopy, Raman spectroscopy, electrical conductivity and more especially for this project, an electrochemical mapping. By combining the information given by all these complimentary techniques, we can correlate the differences of properties observed for different zones of the wafer. For instance, in some vanadium nitrides for micro-supercapacitors applications, a strong variation of the preferred orientation (as measured by an XRD mapping of the full wafer) is evidenced, depending on the scanning area of the wafer, without any change of the chemical composition and of the electrochemical performance. It is not the case for some spinel-type compounds (i.e. sputtered LiNi0.5Mn1.5O4 films) used as the positive electrode for Li-ion micro-batteries, that behave differently depending on the preferred orientation (i.e compounds with privileged conduction path in the structure).