Jeong Hyun Moon

Current conduction mechanisms in atomic-layer-deposited HfO2/nitrided SiO2 stacked gate on 4H silicon carbide

In this paper, current conduction mechanisms of an atomic-layer-deposited HfO2 gate stacked on different thicknesses of thermally nitrided SiO2 based on n-type 4H SiC have been investigated and analyzed. Current-voltage and high-frequency capacitance-voltage measurements conducted at various temperatures (25−140 °C) were performed in metal-oxide-semiconductor test structures with 13 nm thick HfO2 stacked on 0-, 2-, 4-, or 6 nm thick nitrided SiO2. Various conduction mechanisms, such as Schottky emission, Fowler-Nordheim tunneling, Poole-Frenkel emission, and space-charge-limited conduction, have been systematically evaluated. The mechanisms of the current conducted through the oxides were affected by the thickness of the nitrided oxide and the electric field applied. Finally, current conduction mechanisms that contributed to hard and soft dielectric breakdown have been proposed.

Electronic properties of atomic-layer-deposited Al2O3/thermal -nitrided SiO2 stacking dielectric on 4H SiC

We report the first electronic-property results on atomic-layer deposited Al 2 O 3 /thermal-nitrided SiO 2 stacking dielectric on n-type 4H SiC. The effects of the ultrathin thermal-nitrided SiO 2 (2, 4. and 6 nm) on the SiC-based metal oxide semiconductor (MOS) characteristics have also been investigated, compared, and explained. A significant improvement in dielectric reliability and dielectric breakdown field has been observed after an ultrathin nitrided oxide has been introduced between Al 2 O 3 and SiC. The best reported results were obtained from Al 2 O 3 stacked with the thickest nitrided oxide (6 nm).

Improved Electronic Performance of

The MOS characteristics of an atomic layer-deposited HfO2/N2O-nitrided SiO2 stacking gate dielectric on n-type 4H SiC (0001) has been investigated. Three different thicknesses of nitrided SiO2 (2, 4, and 6 nm) have been sandwiched between HfO2 and SiC. The electronic performance of the stacking dielectric depends on the thickness of the nitrided SiO2. Among the stacking dielectrics, the lowest effective oxide charge and interface-trap density as well as the most reliable dielectric has been demonstrated by a sample with the thickest nitrided . The reason for this observation is proposed.

\hbox{HfO}_{2}/ \hbox{SiO}_{2}

Current conduction mechanisms of an atomic-layer-deposited Al2O3 gate on n-type 4H SiC have been systematically investigated, analyzed, and reported in this letter. It has been revealed that space charge limited, Poole-Frenkel (PF) emission, combination of PF emission and Fowler-Nordheim tunneling are the dominate current conduction mechanisms in the dielectric. Besides, Schottky emission has also been proposed as a possible leakage path at temperature beyond the investigated range. A relationship among the conduction mechanism, temperature, and applied electric field has been presented.

Stacking Gate Dielectric on 4H SiC

The electrical properties of thermally grown and atomic-layer-deposition (ALD) oxides, followed by nitridation treatment, on 4H-SiC substrate were compared. The nitridation treatment was performed with post oxidation annealing in NO atmosphere (NO POA). The best electrical characteristics of the thermally grown and ALD oxides were observed at 120 and 180 min NO POA, respectively. The NO POA treated ALD oxide showed extremely low interface trap density (Dit), less than 1011 eV−1 cm−1. A metal-oxide-semiconductor field-effect-transistor with the ALD oxide showed high field effect mobility, especially in the high electric field region. The reasons for these superior results were also discussed.

Analysis of current conduction mechanisms in atomic-layer-deposited Al2O3 gate on 4H silicon carbide

The La2O3 and Al2O3/La2O3 layers were grown on 4H-SiC by atomic layer deposition (ALD) method. The electrical properties of La2O3 on 4H-SiC were examined using metal-insulator-semiconductor (MIS) structures of Pt/La2O3(18nm)/4H-SiC and Pt/Al2O3(10nm)/La2O3(5nm)/4H-SiC. For the Pt/La2O3(18nm)/4H-SiC structure, even though the leakage current density was slightly reduced after the rapid thermal annealing at 500 oC, accumulation capacitance was gradually increased with increasing bias voltage due to a high leakage current. On the other hand, since the leakage current in the accumulation regime was decreased for the Pt/Al2O3/La2O3/4H-SiC MIS structure owing to the capped Al2O3 layer, the capacitance was saturated. But the saturation capacitance was strongly dependent on frequency, indicating a leaky interfacial layer formed between the La2O3 and SiC during the fabrication process of Pt/Al2O3(10nm)/ La2O3(5nm)/ 4H-SiC structure.

Comparison of thermal and atomic-layer-deposited oxides on 4H-SiC after post-oxidation-annealing in nitric oxide

The authors attempted to grow a semi-insulating silicon carbide (SiC) epitaxial layer by in situ iron doping. The homoepitaxial growth of the iron-doped 4H-SiC layer was performed by metal-organic chemical vapor deposition using the organo-silicon precursor bis(trimethylsilylmethane) (C7H20Si2) and the metal-organic precursor t-butylferrocene (C14H17Fe). For the measurement of the resistivity of the iron-doped 4H-SiC epilayers, the authors used the on resistance of Schottky barrier diode. Based on the measurement of the on resistance, it is shown that the free carrier concentration was decreased with increasing partial pressure of t-butylferrocene. The resistivity of the iron-doped 4H-SiC epilayer was about 108Ωcm.

Electrical Properties of the La2O3/4H-SiC Interface Prepared by Atomic Layer Deposition Using La(iPrCp)3 and H2O

We have investigated the electrical properties of metal-oxide-semiconductor (MOS) capacitors with atomic-layer-deposited La2O3, thermal-nitrided SiO2, and atomic-layer-deposited La2O3/thermal-nitrided SiO2 on n-type 4H-SiC. A significant reduction in leakage current density has been observed in La2O3 structure when a 6-nm thick thermal nitrided SiO2 has been sandwiched between the La2O3 and SiC. However, this reduction is still considered high if compared to sample having thermal-nitrided SiO2 alone. The reasons for this have been explained in this paper.

Homoepitaxial growth and electrical characterization of iron-doped semi-insulating 4H-SiC epilayer

SiO 2 was grown by dry (O 2 ) thermal oxidation (at 1175, 1300, or 1400°C) on n-type 4H-SiC substrates. The samples were prepared by subsequently exposing the grown Si0 2 film on 4H-SiC to postoxidation annealing (POA) treatment using nitric oxide (NO) gas. The SiC-Si0 2 interfaces were characterized by high frequency capacitance-voltage measurements, X-ray photoelectron spectroscopy (XPS), and ellipsometry. The interface trap density of the dry oxide grown at 1300°C was much lower than others. At a higher grown temperature (1400°C), the electrical and physical properties of the oxide were not improved compared to those oxides grown at 1175°C. The XPS measurements provided evidence for the presence of intermediate oxidation states of Si oxycarbide in all samples. The areal densities of the intermediate oxidation states affected the interface trap density. The NO POA treatment significantly improved the interface trap density, the near-interface trap density, and the effective oxide charge density of the oxides grown at 1175 and 1300°C. But, this improvement was not observed for the oxide grown at 1400°C. The electrical properties of the metal-oxide-semiconductor devices fabricated using these oxides have also been discussed in terms of the oxide chemical compositions, which were determined by XPS and an oxide etching test.

Electrical Properties of Atomic-Layer-Deposited La2O3/Thermal-Nitrided SiO2 Stacking Dielectric on 4H-SiC(0001)

The authors attempted to grow a semi-insulating 4H-SiC epitaxial layer by in situ vanadium doping. The homoepitaxial growth of the vanadium-doped 4H-SiC layer was performed by metallorganic chemical vapor deposition using the organosilicon precursor bis-trimethylsilylmethane (BTMSM, C 7 H 20 Si 2 ) and the metallorganic precursor bis-cyclopentadienylvanadium (Verrocene, C 10 H 10 V). The vanadium doping effect on the crystallinity of the epi layer was very destructive. Vanadium-doped epi layers grown under normal conditions had various crystal defects such as micropipes and polytype inclusions, but this crystallinity degradation was overcome by elevating the growth temperature. For measurement of the resistivity of the highly resistive vanadium-doped 4H-SiC epi layers, the authors used the on-resistance technique. Based on the measurements of the on-resistance of the Schottky barrier diode fabricated using the vanadium-doped epi layers, it was revealed that the residual donor concentration of the epi layers was decreased with increasing partial pressure of verrocene. The resistivity of the in situ vanadium-doped 4H-SiC epi layer was about 10 7 -10 12 Ω cm.