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S. Dhar,
Y. W. Song,
L. C. Feldman,
T. Isaacs-Smith, C. C. Tin,
J. R. Williams,
G. Chung,
T. Nishimura,
D. Starodub,
T. Gustafsson,
E. Garfunkel
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ABSTRACT: Nitric oxide postoxidation anneal results in a significant decrease of defect state density (D<sub>it</sub>) near the conduction bandedge of n-4 H–SiC at the oxide /(112¯0) 4H–SiC interface. Comparison with measurements on the conventional (0001) Si-terminated face shows a similar interface state density following passivation. Medium energy ion scattering provides a quantitative measure of nitrogen incorporation at the SiO <sub>2</sub>/ SiC interface. © 2004 American Institute of Physics.
Applied Physics Letters 04/2004; · 3.84 Impact Factor
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ABSTRACT: The kinetics of nitrogen incorporation in SiO <sub>2</sub>/4 H–SiC using NO are presented. Samples were annealed in NO at pressures of 100 Torr and 1 atm, at temperatures from 1050 to 1175 °C, and for times from 0.5 to 6 h. Annealing in NO incorporates ∼10<sup>14</sup> cm <sup>-2</sup> of nitrogen at the SiO <sub>2</sub>/ SiC interface. The nitrogen content initially increases with time and temperature, but nitrogen is removed at later times at temperatures above 1050 °C. This nitrogen removal, and the associated oxide growth in the SiC substrate, is caused by O <sub>2</sub> formed by the thermal decomposition of NO. Eventually, the nitridation and oxidation reactions reach equilibrium, and the nitrogen content saturates as the oxide thickness increases. © 2003 American Institute of Physics.
Journal of Applied Physics 03/2003; · 2.17 Impact Factor
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ABSTRACT: The relationship between nitrogen content and interface trap density (Dit) in SiO2/4H–SiC near the conduction band has been quantitatively determined. Nitridation using NO significantly reduces Dit near the conduction band, but the effect saturates after ≈2.5×1014 cm−2 of nitrogen. These results are consistent with a model of the interface in which defects such as carbon clusters or silicon suboxide states produce traps with energies corresponding to the sizes of the defects. Nitrogen passivation results in the dissolution of the defects, which then lowers the energies of the traps in the band gap. © 2003 American Institute of Physics.
Journal of Applied Physics 02/2003; 93(5):2719-2722. · 2.17 Impact Factor
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G.Y. Chung, C.C. Tin,
J.R. Williams,
K. McDonald,
R.K. Chanana,
R.A. Weller,
S.T. Pantelides,
L.C. Feldman,
O.W. Holland,
M.K. Das,
J.W. Palmour
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ABSTRACT: Results presented in this letter demonstrate that the effective channel mobility of lateral, inversion-mode 4H-SiC MOSFETs is increased significantly after passivation of SiC/SiO/sub 2/ interface states near the conduction band edge by high temperature anneals in nitric oxide. Hi-lo capacitance-voltage (C-V) and ac conductance measurements indicate that, at 0.1 eV below the conduction band edge, the interface trap density decreases from approximately 2/spl times/10/sup 13/ to 2/spl times/10/sup 12/ eV/sup -1/ cm/sup -2/ following anneals in nitric oxide at 1175/spl deg/C for 2 h. The effective channel mobility for MOSFETs fabricated with either wet or dry oxides increases by an order of magnitude to approximately 30-35 cm/sup 2//V-s following the passivation anneals.
IEEE Electron Device Letters 05/2001; · 2.85 Impact Factor
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ABSTRACT: Results of capacitance–voltage measurements are reported for metal–oxide–semiconductor capacitors fabricated using the 4H polytype of silicon carbide doped with either nitrogen (n) or aluminum (p). Annealing in nitric oxide after a standard oxidation/reoxidation process results in a slight increase in the defect state density in the lower portion of the band gap for p-SiC and a significant decrease in the density of states in the upper half of the gap for n-SiC. Theoretical calculations provide an explanation for these results in terms of N passivating C and C clusters at the oxide–semiconductor interface. © 2000 American Institute of Physics.
Applied Physics Letters 03/2000; 76(13):1713-1715. · 3.84 Impact Factor
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ABSTRACT: We report the effect on SiO<sub>2</sub>/SiC interface state
density and effective oxide charge of different Si:C ratios (0.12 to
0.55) used during the growth of n-4H and n-6H-SiC epitaxial layers. We
also report the effects of post-growth re-oxidation anneals and post-
metalization anneals on the interface state density for both n- and
p-4H-SiC. The interface trap density near the conduction band and the
effective oxide charge increase with increasing Si:C ratio for both
polytypes; however, the n-4H polytype is found to have an order of
magnitude higher interface trap density near the conduction band
compared to n-6H-SiC. The effective oxide charge is also higher for n-4H
polytype. The distribution of interface states for 4H-SiC (measured
using n- and p-type material) is asymmetric, with a higher trap density
near the conduction band. Post-growth re-oxidation in wet O<sub>2</sub>
at 950°C increases the interface trap density near the conduction
for n-4H-SiC. Post-metalization annealing at 450°C in Ar for an Al
gate metal results in a reduction of the effective oxide charge from
9.5×10<sup>11</sup> cm<sup>-2</sup> to 3.5×10<sup>11</sup>
cm<sup>-2</sup>. The effective oxide charge for n-4H samples with Mo
gates decreases with increasing post metalization annealing temperature.
Interface state densities are not affected by the post-metalization
anneals in Ar
Aerospace Conference Proceedings, 2000 IEEE; 02/2000
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S. T. Pantelides,
R. Buczko,
M. Di Ventra,
S. Wang,
S.-G. Kim,
S. J. PennycooK,
G. Duscher,
L. C. Feldman,
K. Mcdonald,
R. K. Chanana,
R. A. Weller,
J. R. Williams,
G. Y. Chung, C. C. Tin,
T. Isaacs-Smith
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ABSTRACT: This paper presents a review of new results obtained by a combination of first-principles theory, Z-contrast imaging, and electron-energy-loss spectroscopy in the context of a broader experimental/theoretical program to understand and control the atomic-scale structure of SiCSiO2 interfaces. The ultimate purpose is to achieve low interface trap densities for device applications. Results are given for global bonding arrangements in comparison with those of the Si-SiO2 interface, the mechanism of the oxidation process, the nature of possible interface defects and their passivation by N and H, and the formation and dissolution of C clusters in SiO2 during oxidation and reoxidation.
MRS Proceedings. 12/1999; 640.
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J. R. Williams,
G. Y. Chung, C. C. Tin,
K. McDonald,
D. Farmer,
R. K. Chanana,
R. A. Weller,
S. T. Pantelides,
O. W. Holland,
M. K. Das,
L. A. Lipkin,
L. C. Feldman
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ABSTRACT: This paper describes the development of a nitrogen-based passivation technique for interface states near the conduction band edge [Dit(Ec)] in 4H-SiC/SiO2. These states have been observed and characterized in several laboratories for n- and p-SiC since their existence was first proposed by Schorner, et al. [1]. The origin of these states remains a point of discussion, but there is now general agreement that these states are largely responsible for the lower channel mobilities that are reported for n-channel, inversion mode 4H-SiC MOSFETs. Over the past year, much attention has been focused on finding methods by which these states can be passivated. The nitrogen passivation process that is described herein is based on post-oxidation, high temperature anneals in nitric oxide. An NO anneal at atmospheric pressure, 1175°C and 200–400sccm for 2hr reduces the interface state density at Ec-E ≅0.1eV in n-4H-SiC by more than one order of magnitude - from > 3×1013 to approximately 2×1012cm−2eV−1. Measurements for passivated MOSFETs yield effective channel mobilities of approximately 30–35cm2/V-s and low field mobilities of around 100cm2/V-s. These mobilities are the highest yet reported for MOSFETs fabricated with thermal oxides on standard 4H-SiC and represent a significant improvement compared to the single digit mobilities commonly reported for 4H inversion mode devices. The reduction in the interface state density is associated with the passivation of carbon cluster states that have energies near the conduction band edge. However, attempts to optimize the the passivation process for both dry and wet thermal oxides do not appear to reduce Dit(Ec) below about 2×1012cm−2eV−1 (compared to approximately 1010cm−2eV−1 for passivated Si/SiO2). This may be an indication that two types of interface states exist in the upper half of the SiC band gap – one type that is amenable to passivation by nitrogen and one that is not. Following NO passivation, the average breakdown field for dry oxides on p-4H-SiC is higher than the average field for wet oxides (7.6MV/cm compared to 7.1MV/cm at room temperature). However, both breakdown fields are lower than the average value of 8.2MV/cm measured for wet oxide layers that were not passivated. The lower breakdown fields can be attributed to donor-like states that appear near the valence band edge during passivation.
MRS Proceedings. 12/1999; 640.
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MRS Proceedings. 12/1997; 512.
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ABSTRACT: Aluminum nitride is a promising insulator for the fabrication of 6H-silicon carbide (6H-SiC) metal-insulator-semiconductor
(MIS) devices for high temperature and high power applications. Due to the fact that the electrical response of a Au/AlN/SiC
MIS structure is sensitive to the quality of the insulator-semiconductor interface as well as the insulator itself, growth
of AlN on 6H-SiC using different growth procedures will produce AlN/6H-SiC structures of different electrical characteristics.
In this study, we compared the capacitance-voltage, dc current voltage and high electric field breakdown characteristics of
various AlN/6H-SiC MIS structures grown by different low-pressure metalorganic chemical vapor deposition growth procedures.
Our results demonstrated that depending on the growth procedure, Au/AlN/SiC MIS structures with low current leakage, low interface
state density, good high temperature stability and high electric field breakdown voltage could be obtained.
Journal of Electronic Materials 02/1997; 26(3):212-216. · 1.47 Impact Factor
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ABSTRACT: Silicon carbide (SiC) is an excellent semiconductor for the
fabrication of high power and high temperature electronic devices. SiC
pn junctions are critical components of SiC high power devices and
circuits. However, the high electric field behavior of SiC p-n junction
structures is not well characterized. The study of the high field
breakdown mechanisms of SiC p-n junction plays an important role in
determining the proper design of SiC high power p-n junction-based
devices. We have determined the high field breakdown behaviors of
several types of 4H-SiC epitaxial p-n junction diodes of different
design. In our efforts to increase the breakdown voltage, we have found
that oxide passivation did not substantially affect the breakdown
voltage but edge termination using argon ion implantation is effective
in improving the breakdown voltage of SiC-p-n junction diodes
Semiconductor Electronics, 1996. ICSE '96. Proceedings., 1996 IEEE International Conference on; 12/1996
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ABSTRACT: We have characterized the high electric field breakdown process of several epitaxial 4H-SiC p-n structures with oxide passivation. The breakdown voltage was found to be dependent on the size of the diode structures as well as their proximity to any structural defects. The time dependence of the breakdown process was also measured to determine the characteristics of the breakdown mechanism. This time dependence measurement provides an indication of the quality of the diode structures. Both soft and abrupt breakdown mechanisms were observed showing the influence of defects on the high field behavior of the diode structures. Measurements done with and without the use of Fluorinert fluid did not show any difference in the breakdown voltage indicating that surface flashover breakdown mechanism did not play a major role in the avalanche breakdown process.
MRS Proceedings. 12/1995; 423.
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ABSTRACT: Capacitance‐voltage (C‐V) measurements have been made on n‐InP metal‐oxide‐semiconductor (MOS) devices damaged by 2‐MeV <sup>4</sup> He<sup>+</sup> ion bombardment. The C‐V curves for samples with thin oxide layer (∼100 Å) show the presence of a depletion layer during both forward and reverse bias. This behavior is significantly different from those of normal, undamaged MOS devices. Measurements made on n‐InP MOS samples with different oxide thicknesses show that the C‐V curves gradually approach that of a MOS device on a p‐type substrate. The anomalous behavior of the C‐V curves for the irradiated samples can be explained by the presence of an n‐p‐n structure under the oxide layer.
Journal of Applied Physics 12/1989; · 2.17 Impact Factor
