Electronic structure and band offsets in high K oxides

The decrease of device dimensions has led to the need for alternative, high dielectric constant (K) oxides to replace silicon dioxide as the gate dielectric in CMOS devices. Silicon dioxide layers thinner than 1.6 would have unacceptably high leakage currents due to direct tunnelling. The alternative is to use thicker layers of high K dielectrics, with the same equivalent capacitance or equivalent SiO/sub 2/ thickness, which increases the tunnelling distance and greatly reduces the leakage current. The band offsets have been calculated using the theory of Schottky barriers of semiconductors, treating the oxide as a wide gap semiconductor. The offsets are found by calculating the energy of the so-called charge neutrality level (CNL) of the oxide and aligning it to the CNL of Si. The calculated conduction band offsets are compared to subsequent experimental values.