Investigation of Poly-Si Gated, Al₂O₃-Based High-k Dielectrics on 4H-SiC

In this paper, we investigate the electrical and structural characteristics of Al 2 O 3 -based high- k gate dielectrics, which were integrated into a gate-first, high-temperature manufacturing process having comparable thermal budget as needed in 4H-SiC metal-oxide-semiconductor field-effect transistor (MOSFET) production. MOS capacitors were chosen as test devices to examine the electrical performance in terms of current-voltage ( I-V ) and capacitance-voltage ( C-V ) behavior. Remarkably, even after processing temperatures of up to 1,000 °C for ohmic contact formation, the Al 2 O 3 layers revealed highly uniform breakdown characteristics, low C-V hysteresis and a flat-band voltage ( V FB ) that closely aligns with the theoretical value. Time-dependent dielectric breakdown (TDDB) measurements of the Al 2 O 3 MOS capacitors, however, showed a clear reliability disadvantage concerning the intrinsic dielectric lifetime when comparing with the SiO 2 counterpart from commercial SiC production. Finally, to better understand the electrical behavior, transmission electron microscopy (TEM) analysis was conducted, pointing out that high-temperature processing causes the Al 2 O 3 films to transition from an amorphous state to an ordered, polycrystalline structure.