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 ±2.5 V in combination with moderate (T ∼ 630 K) heating. The modifications were monitored in situ by room temperature capacitance–voltage (C–V) and current–voltage (I–V) 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.

Graphical abstractThe spatial distribution of charges in a Pt/HfO2/Si stack manipulated by a bias-temperature stress was monitored by C-V, I-V in combination with hard X-ray photoelectron spectroscopy revealing that oxygen vacancies generated in HfO2 are driven across the dielectric layer and control the growth/dissolution of SiOx at the bottom interface.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Charge distribution in Pt/HfO2/Si probed by hard X-ray photoelectron spectroscopy. ► O vacancies generation and drift in HfO2 during bias-temperature stress (BTS). ► Growth/dissolution of SiOx at the bottom interface upon negative/positive BTS.