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

The effects of different high-kappa tunnel oxides on the metal-insulator-semiconductor Schottky barrier height (Phi(B)) were systematically investigated. While these high-kappa interlayers have been previously observed to affect Phi(B), there has never been a clear consensus as to why this Phi(B) modulation occurs. Changes in Phi(B) were measured when adding 0.5 nm of seven different high-kappa oxides to n-Si/Ni contacts with a thin native silicon oxide also present. Depending on the high-kappa oxide composition and Phi(B) measurement technique, increases in Phi(B) up to 0.4 eV and decreases up to 0.2 eV with a high-kappa introduction were measured. The results were compared to several different hypotheses regarding the effects of tunnel oxides on Phi(B). The experimental data correlated most closely with the model of a dipole formed at the SiOx/high-kappa 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 Phi(B).