Improved insight in charge trapping of high-k ZrO₂/SiO₂ stacks by use of tunneling atomic force microscopy

In this work, tunneling atomic force microscopy (TUNA) is used to describe the charge trapping in high-k ZrO₂ dielectric stacks at nanoscale dimensions by analyzing the alteration of the I-V curves and the I-V hysteresis phenomena with repeated measurements (up to 100 curves) at a single spot of only several nm² in area. TUNA is also suggested as a powerful technique to correlate the electrical characteristics to the physical properties of the stacks. In particular, the influence of the thin SiO₂ interfacial layer thickness and its modification with annealing conditions on the electrical properties is demonstrated. Furthermore, the appearance of an I-V hysteresis and its relation to degradation mechanisms in high-k dielectric stacks are explained. Trapping at pre-existing traps is evidenced.