Getting a grip on in situ biasing – A clean method for sample preparation for in situ biasing TEM experiments

For state-of-the-art in situ TEM characterization of electrical material properties thin sample lamellas are cut from the bulk material and transferred to Micro Electro Mechanical Systems (MEMS) devices, employing a Ga-FIB instrument [1]. However, FIB based preparation procedures currently used for in situ biasing lamella preparation often lead to poor sample quality.
Here we present an optimized dual beam SEM/FIB based preparation method for high quality in situ biasing TEM lamellas. The process starts with the FEBID/FIBID deposition of a thick Pt protective layer and the milling of three stepped trenches followed by the pre-thinning of the lamella in the trenches. The lamella is
then extracted using a special microgripper by Kleindiek (Figure 1a,b) and directly thinned and polished to electron transparency. Backside milling can be applied if necessary. Finally, the lamella is transferred to the biasing chip and fixed by FEBID. In order to minimize Pt contamination while maximizing the conductivity, a custom FEBID procedure was developed in collaboration with the research group for functional nanofabrication at FELMI.
First TEM results show that a high sample quality and little to no Pt contamination can be achieved (Figure 1c). The present work has established a framework for artefact free sample preparation for future research in the field of biasing TEM material characterization.