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

Abstract:

In this paper, we investigate the electrical and structural characteristics of Al₂O₃-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 Al₂O₃ 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 Al₂O₃ MOS capacitors, however, showed a clear reliability disadvantage concerning the intrinsic dielectric lifetime when comparing with the SiO₂ 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 Al₂O₃ films to transition from an amorphous state to an ordered, polycrystalline structure.

• Periodical: Materials Science Forum (Volume 1159)
• Pages: 73-79
• DOI: https://doi.org/10.4028/p-H74nVN
• Online since: September 2025
• Authors: Johannes Ziegler*, Dick Scholten, Holger Bartolf, Andrii Voznyi, Patrick Rabinzohn, Jörg Schulze
• Keywords: Atomic Layer Deposition, High-k Gate Dielectrics, MOS Capacitor, Poly-Si Gate Electrode, Time-Dependent Dielectric Breakdown, Transmission Electron Microscopy

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