On the location and magnitude of trapped charge in poly- Si ALD-Al ₂O₃ capped Hf-silicate gate stacks

The magnitude and the location of trapped charge in Al2O 3 capped Hf-silicate (HfSiO) gate stacks is studied with 'stress-and-sense' type measurements using standard CV measurements to monitor the flatband voltage shifts as a function of injected charge. A simple quantitative model is used to estimate the charge location within the multilayer gate stack. To the first order, the magnitude of trapped charge is found to be on the order of 5 × 1012 cm-2, independent of the cap layer thickness, and the charge is found to be located within the Hf-silicate layer with the charge centroid situated 1 nm away from the Al 2O3/HfSiO interface.