Simultaneous electric dipoles and flat-band voltage modulation in 4H-SiC MOS capacitors through HfO2/SiO2 interface engineering

Abstract We report an approach to simultaneously tune the electric dipoles and flat-band voltage ( V FB ) of 4H-silicon carbide (SiC) metal-oxide-semiconductor (MOS) capacitors through high- k oxide dielectric interface engineering. With an additional HfO 2 thin layer on atomic layer deposition (ALD) of SiO 2 film, a dipole layer was formed at the HfO 2 /SiO 2 interface, leading to a small positive shift of the V FB of 0.3 V in 4H-SiC MOS capacitors. The Kelvin probe method was used to examine the dipole layers induced at the direct-contact oxide/4H-SiC interfaces. It was found that a minor difference of 0.3 V in the contact potential difference ( V CPD ) is observed between the SiO 2 /4H-SiC and HfO 2 /SiO 2 /4H-SiC stacks, which signifies the presence of a weak interface dipole layer at the interface of HfO 2 and SiO 2 . Additionally, investigation of the interface state density reveals that ALD of the HfO 2 process had a negligible impact on the quality of the SiO 2 /4H-SiC interface, suggesting that the observed small positive V FB shift originated from the HfO 2 /SiO 2 interface rather than the SiO 2 /4H-SiC interface.