Internal photoemission spectroscopy of [TaN∕TaSiN] and [TaN∕TaCN] metal stacks on SiO2 and [HfO2∕SiO2] dielectric stack

There is an intense search for metal gates for the next generation metal-oxide-semiconductor field-effect transistor. The barrier height (Φ0) at its interface with a gate dielectric must be known to select a suitable metal. In this letter, internal photoemission was used to determine Φ0 of two technologically important ternary metals, [TaN∕TaSiN] and [TaN∕TaCN], on a single SiO2 layer and a [HfO2∕SiO2] stack. On SiO2, Φ0 was found to be 3.36 and 3.55eV at the [TaN∕TaSiN] stack/SiO2 and [TaN∕TaCN stack]/SiO2 interfaces, respectively. However, on the [HfO2∕SiO2] stack, Φ0 was found be the same at 2.5eV for both metal stacks. These results are compared to flatband voltage measurements.