Charge trapping in high k gate dielectric stacks

Charge trapping in Al/sub 2/O/sub 3/ and HfO/sub 2/ nFETs is studied. The dependence of threshold voltage, subthreshold slope and gate leakage currents are investigated as a function of stressing time, voltage and temperature. Based on the experimental data, a model is developed for predicting threshold voltage shifts as a function stressing time. The model is compatible with both Al/sub 2/O/sub 3/ and HfO/sub 2/ data. Using the model, threshold voltage shifts after 10 years of stressing is predicted and trapping capture cross sections are estimated. A comparison between Al/sub 2/O/sub 3/ and HfO/sub 2/ is also made.