May 19, 2016

Electrical properties of reactive-ion-sputtered Al2O3 on 4H-SiC


O2 annealed RIS-Al2O3 on 4H-SiC showed better performance than other reported result.
FN, FN + PF tunneling was found in O2 annealed RIS-Al2O3 for different temp. ranges.
Al2O3/SiC barrier height increased from 1.7 eV to 2.53 eV after O2 annealing.
Increase in barrier height is attributed to interfacial SiO2, confirmed by XPS study.
Forming gas annealing further improved the C-V hysteresis of these devices.


Al2O3 was deposited on n-type 4H-SiC by reactive-ion-sputtering (RIS) at room temperature using aluminum target and oxygen as a reactant gas. Post deposition oxygen annealing was carried out at a temperature of 1100 °C. Metal-oxide-semiconductor (MOS) test structures were fabricated on 4H-SiC using RIS-Al2O3 as gate dielectric. The C-V characteristics reveal a significant reduction in flat band voltage for oxygen annealed RIS-Al2O3 samples (Vfb = 1.95 V) compared to as-deposited Al2O3 samples (Vfb > 10 V), suggesting a reduction in negative oxide charge after oxygen annealing. Oxygen annealed RIS-Al2O3 samples also showed significant improvement in I-V characteristics compared to as-deposited RIS-Al2O3 samples. A systematic analysis was carried out to investigate the leakage current mechanisms present in oxygen annealed RIS-Al2O3 on 4H-SiC at higher gate electric field and at different operating temperature. For measurement temperature (T) < 303 K, Fowler–Nordheim (FN) tunneling was found to be the dominant leakage mechanism and for higher temperature (T ≥ 303 K), a combination of FN tunneling and Poole-Frenkel (PF) emission was confirmed. The improvement in I-V characteristics of oxygen annealed RIS-Al2O3/4H-SiC MOS devices is attributed to large effective barrier height (ΦB = 2.53 eV) at Al2O3/SiC interface, due to the formation of an interfacial SiO2 layer during oxygen annealing, as confirmed from X-ray Photoelectron Spectroscopy results. Further improvement in C-V characteristics for oxygen annealed RIS-Al2O3/4H-SiC MOS devices was observed after forming gas annealing at 400 °C.


  • Aluminum oxide
  • 4H-SiC
  • Reactive-ion sputtering
  • Fowler–Nordheim tunneling
  • Poole-Frenkel tunneling
  • Oxygen annealing
  • Forming gas annealing
  • Metal-oxide-semiconductor capacitor
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