Experimental investigation of transport mechanisms through HfO2 gate stacks in nMOS transistors

In order to investigate more accurately transport mechanisms through SiO₂/HfO₂ gate stacks, CV and IV measurements have been performed on several samples featuring different interfacial layer or HfO₂ thicknesses, for a large range of temperature (80 K to 400 K). Experimental gate currents have been found to have very weak temperature dependency when plotted versus total charge, except on thicker stacks, in inversion regime, at 300 and 400 K. These results have been compared with direct tunneling (DT) simulations in inversion regime. This comparison has clearly shown that interfacial layer differs from pure SiO₂, confirming previous theoretical works.