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_B) were systematically investigated. While these high-κ interlayers have been previously observed to affect Φ_B, there has never been a clear consensus as to why this Φ_B modulation occurs. Changes in Φ_B 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_B measurement technique, increases in Φ_B 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_B. The experimental data correlated most closely with the model of a dipole formed at the SiO_x/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_B.