Effect of biasing at elevated temperature on the electronic structure of Pt/HfO2/Si stacks
The spatial distribution of charges in a Pt/HfO2/Si stack has been manipulated by applying a cyclic bias voltage 2.5V in combination with moderate (T?630K) heating. The modifications were monitored in situ by room temperature capacitancevoltage (CV) and currentvoltage (IV) measurements and analyzed ex situ by hard X-ray photoelectron spectroscopy which additionally provides information on possible chemical changes at the interfaces. The experimental data on the charge/potential distributions resulting from the different steps of bias-temperature stress (BTS) are consistent with the model that additional oxygen vacancies, which are generated in HfO2 and positively charged by charge transfer across the interface with a high work function metal (Pt), are driven across the HfO2 layer. These vacancies ultimately control the observed growth/dissolution of SiOx at the bottom interface upon negative/positive BTS, respectively.
bts oxygen vacancies high-k dielectric band alignment haxpes