Novel SiO2 and Al2O3 High-K Gate Dielectrics on 4H-SiC MOS Capacitors
Date Issued
2009
Date
2009
Author(s)
Hsu, Chia-Ming
Abstract
This thesis contains three novel dielectric processes about gate dielectric on 4H-SiC substrate. SiO2 was prepared by anodization in DI water followed by rapid thermal nnealing. The oxide breakdown strengths are greater than 6.3 MV/cm and the capacitance–voltage hysteresis is negligible. The interface state density was extracted using the conductance method and the value is of 3×1011cm-2eV-1. The first demonstration of anodized aluminum oxide (Al2O3) was grown in aqueous Ammonium Adipate solution as dielectric on 4H-SiC MOS capacitors. Ultrathin Al2O3 film (1.9nm) was prepared by anodic oxidation of ultrathin Al film followed by furnace annealing. The capacitance-voltage hysteresis is negligible and the interface trap density is low to ~8×1011 cm-2eV-1. The much higher breakdown field of 14.5 MV/cm and lower gate leakage current of 6×10-3 A/cm2 at 2 V are obtained.urthermore, we present the SiC MOS capacitor with Al2O3 film fabricated by plasma sputtering oxidation. The leakage current was one order This thesis contains three novel dielectric processes about gate dielectric on 4H-SiC substrate. SiO2 was prepared by anodization in DI water followed by rapid thermal annealing. The oxide breakdown strengths are greater than 6.3 MV/cm and the capacitance–voltage hysteresis is negligible. The interface state density was extracted using the conductance method and the value is of 3×1011cm-2eV-1. The first demonstration of anodized aluminum oxide (Al2O3) was grown in aqueousmmonium Adipate solution as dielectric on 4H-SiC MOS capacitors. Ultrathin Al2O3 film (1.9nm) was prepared by anodic oxidation of ultrathin Al film followed by furnace annealing. The capacitance-voltage hysteresis is negligible and the interface trap density is low to ~8×1011 cm-2eV-1. The much higher breakdown field of 14.5 MV/cm and lower gate leakage current of 6×10-3 A/cm2 at 2 V are obtained.Furthermore, we present the SiC MOS capacitor with Al2O3 film fabricated by plasma sputtering oxidation. The leakage current was one order smaller than the typical thermal SiO2 and with good stress reliability. The low-frequency C-V curves are close near to ideal condition than high frequency and exhibit linear dependency on frequency from 1k to 500 kHz. We proposed a two-element equivalent circuit model including inductance to explain this phenomenon. It’s suggested that under the sputtering oxidation process, not all of the metal was oxidized completed and nanocrystal could be left inside the dielectric. Based on the reported results, the three processes could be useful to SiC MOS high-power devices.
Subjects
MOS
capacitor
SiO2
Al2O3
high-k
dielectric
Ammonium Adipate
anodization
sputter
Type
thesis
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