Towards improved atom probe tomography analysis of semiconductors : unraveling the dynamic evolution of the semiconductor emitter
To improve performance, the building blocks of electronics are continuously downsizing requiring control of their material properties and chemical composition at the nanoscale. This can be achieved using high resolution microscopes, such as the atom probe. Here, atoms are successively (ionized and) removed from the surface of the sample (shaped as a nanoscale needle) via a very high electric field and a laser pulse. Subsequently, the ionized atoms are accelerated onto a detector, in which the ions flight time (chemical nature) and its impact position can be retrieved. During data analysis, the ions are projected back to their original position in the sample, enabling to reconstruct a 3D atomic map and revealing near atomic scale information such as the distribution small concentrations of atoms, called dopants, which alter device performance strongly. This project will investigate the physical mechanisms underpinning atom probe analysis such as the atom “removal” process, which depends on the chemical nature of the atom itself leading to the preferential removal of one atomic species over another, the way the laser is absorbed in the sample or the way ions are projected onto the detector, as the ions flight path towards the detector is a complex interplay between the sample properties and the electric field close to and far away from the sample. It is this knowledge that allows us to understand where the ions originated from and hence to correctly build the 3D atomic map.