2D Charge Density Probing at Aluminum / SiNx Interface: a Sub-micrometric Investigation by Kelvin Probe Force Microscopy

Charge injection and transport mechanisms occurring at metal/dielectric interface may strongly impact devices performance and reliability. However, these phenomena remain partially understood, mainly due to the lack of adapted characterization tools. In this paper, we propose an investigation of the charging behavior at the Al/SiNx interface using Kelvin Probe Force Microscopy (KPFM). Indeed, KPFM measurements permit to probe space charge density with a sub micrometric resolution. Results presented here emphasize that electrons and holes are injected and trapped close to cathode and anode, respectively. The charge clouds remain stacked to the interface $(2-3 \mu \mathrm{m})$. Moreover, the amount of injected charges increases with the applied bias. The injected electrons and holes follow the same dissipation mechanism in time after bias removal.