Dependence of the Metal-Insulator-Semiconductor Schottky Barrier Height on Insulator Composition.

The effects of different high-κ tunnel oxides on the metal-insulator-semiconductor Schottky barrier height (Φ) were systematically investigated. While these high-κ interlayers have been previously observed to affect Φ, there has never been a clear consensus as to why this Φ modulation occurs. Changes in Φ were measured when adding 0.5 nm of seven different high-κ oxides to n-Si/Ni contacts with a thin native silicon oxide also present. Depending on the high-κ oxide composition and Φ measurement technique, increases in Φ up to 0.4 eV and decreases up to 0.2 eV with a high-κ introduction were measured. The results were compared to several different hypotheses regarding the effects of tunnel oxides on Φ. The experimental data correlated most closely with the model of a dipole formed at the SiO/high-κ interface due to the difference in the oxygen areal density between the two oxides. Knowledge of this relationship will aid in the design of Schottky and ohmic contacts by providing criteria to predict the effects of different oxide stacks on Φ.