bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth and Study of Thick 3C-SiC Epitaxial Layers Produced by Epitaxy on 6H-SiC Substrates
Authors: Lebedev Alexander A. , Zelenin V.V. , Abramov Pavel L. , Bogdanova Elena V. , Lebedev Sergey P. , Nel'son D.K. , Razbirin Boris S. , Scheglov M.P. , Tregubova Alla S. , Syväjärvi Mikael , Yakimova Rositza
Published: March 2009

3C-SiC epitaxial layers with a thickness of up to 100 μm and area of ~0.3-0.5 cm2 have
been grown by sublimation epitaxy on hexagonal (6H-SiC) substrates at a maximum growth rate of
about 200 μm per hour. The epilayers obtained are of n-type (Nd-Na ~ 1017 -1018 cm-3). According
to X-ray data, the epitaxial layers are composed of the 3C-SiC polytype, without inclusions of other
polytypes. The donor-acceptor (Al-N) recombination band with hνmax ~ 2.12 eV predominates in the
photoluminescence (PL) spectrum. A detailed analysis of a PL spectrum measured at 6 K is
presented. A conclusion is made that the epitaxial layers can be used as substrates for electronic
devices based on 3C-SiC.
Absence of Dislocation Motion in 3C-SiC pn Diodes under Forward Bias
Authors: Speer Kevin M. , Spry David J. , Trunek Andrew J. , Neudeck Philip G. , Crimp M.A. , Hile J.T. , Burda C. , Pirouz P.
Published: March 2009

pn diodes have recently been fabricated from 3C-SiC material heteroepitaxially grown
atop on-axis 4H-SiC mesa substrate arrays [1,2]. Using an optical emission microscope (OEM), we
have investigated these diodes under forward bias, particularly including defective 3C-SiC films
with in-grown stacking faults (SFs) nucleated on 4H-SiC mesas with steps from screw dislocations.
Bright linear features are observed along <110> directions in electroluminescence (EL) images.
These features have been further investigated using electron channeling contrast imaging (ECCI)
[3]. The general characteristics of the ECCI images—together with the bright to dark contrast
reversal with variations of the excitation error—strongly suggest that the bright linear features are
partial dislocations bounding triangular SFs in the 3C-SiC films. However, unlike partial
dislocations in 4H-SiC diodes whose recombination-enhanced dislocation motion serves to expand
SF regions, all the partial dislocations we observed during the electrical stressing were immobile
across a wide range of current injection levels (1 to 1000 A/cm2).
An X-Ray Topographic Analysis of the Crystal Quality of Globally Available SiC Wafers
Authors: Brazil I. , McNally Patrick J. , Ren N. , O'Reilly L. , Danilewsky A. , Tuomi T.O. , Lankinen A. , Säynätjaki A. , Simon R. , Soloviev Stanislav I. , Rowland L.B. , Sandvik Peter M.
Published: March 2009

We present herein a first comparative analysis of the quality of 50 mm and 75 mm
diameter SiC wafers, purchased directly from vendors across the world, types including the most
widely available configurations. Large Area White Beam Synchrotron Back Reflection X-Ray
Topography was used to analyse selected ~1cm2 regions at various locations on up to 10 different
bulk SiC wafers. The study concentrated particularly on the density and distribution of threading
screw dislocations (TSDs). We also examined all wafers for basal plane dislocation (BPDs)
densities and distributions. Alarmingly large variation in wafer quality was observed. TSD densities
vary from a minimum of 0 cm-2 (in a-plane material) to values as large as over 2,000 cm-2 on some
n-type 4H-SiC wafers. TSD densities on individual wafers can also vary by similar magnitudes, e.g.
500cm-2 to 2,500 cm-2 on two regions only 2 cm apart on a 50 mm diameter wafer. Computer-based
image process analysis was used to present a statistical analysis of the distributions of defects. For
example algorithms created in MATLAB®, Image Processing Toolbox, isolated possible TSD
locations allowing rapid counting to be performed. These counts were confirmed by manual
counting of selected unmodified images.
A Study of the DII Defect after Electron Irradiation and Annealing of 4H SiC
Authors: Sullivan W. , Steeds John W.
Published: March 2009

The high-temperature persistent PL defect known as DII is commented on within this
study, seen for the first time in low-energy electron irradiated 4H SiC. The local vibrational modes
associated with the defect have been identified and the temperature dependence, spatial variation
and electron-energy/electron-dose variation of this defect have all been investigated.
Influence of Cooling Rate after High Temperature Annealing on Deep Levels in High-Purity Semi-Insulating 4H-SiC
Authors: Gällström Andreas , Magnusson Björn , Carlsson Patrick , Son Nguyen Tien , Henry Anne , Beyer Franziska Christine , Syväjärvi Mikael , Yakimova Rositza , Janzén Erik
Published: March 2009

The influence of different cooling rates on deep levels in 4H-SiC after high temperature
annealing has been investigated. The samples were heated from room temperature to 2300°C,
followed by a 20 minutes anneal at this temperature. Different subsequent cooling sequences down
to 1100°C were used. The samples have been investigated using photoluminescence (PL) and IV
characteristics. The PL intensities of the silicon vacancy (VSi) and UD-2, were found to increase
with a faster cooling rate.
Micro-Photoluminescence Mapping of Defect Structures in SiC Wafers
Authors: Hennessy John , Ryan Tom
Published: March 2009

Micro-photoluminescence can be used to image electrically active structural defects in
SiC. Under suitable excitation conditions it is possible to observe both band-edge PL and near bandedge
PL from recombination via a shallow boron acceptor. The intensity of the band-edge emission
is related to the carrier lifetime – and is reduced by the presence of structural or interfacial defects.
The intensity of the deep level PL is a complex function of the number of radiative centers and the
number of centers limiting carrier lifetime. Micro-PL mapping can provide information on the
spatial distribution of electrically active defects in SiC.
Micro-Raman Investigation of Defects in a 4H-SiC Homoepilayer
Authors: Liu Xing Fang , Sun Guo Sheng , Li Jin Min , Zhao Yong Mei , Li J.Y. , Wang L. , Zhao Wan Shun , Luo M.C. , Zeng Yi Ping
Published: March 2009

Three types of defects, namely defect I, defect II, defect III, in the 4H-SiC homoepilayer
were investigated by micro-raman scattering measurement. These defects all originate from a certain
core and are composed of (I) a wavy tail region, (II) two long tails, the so called comet and (III) three
plaits. It was found that there are 3C-SiC inclusions in the cores of defect II and defect III and the
shape of inclusion determines the type of defect II or defect III. If the core contains a triangle-shaped
inclusion, the defect III would be formed; otherwise, the defect II was formed. No inclusion was
observed in the core of the defect I. The mechanisms of these defects are discussed.
Growth of SiC from a Liquid Phase at Low Temperature
Authors: Ferro Gabriel , Soueidan Maher , Kim-Hak Olivier , Cauwet François , Monteil Yves
Published: March 2009

Growing good quality SiC epitaxial layers at temperature lower than 1400°C is a
challenging problem which could help reducing the costs, increasing the safety of the process or
even give new perspectives. Toward this aim, liquid based growth techniques have been used. The
Si-based melts should be carefully chosen considering several criteria. Furthermore, the
implementation of a liquid phase for growing SiC epilayer can be performed in various manners
(dipping or VLS mechanism) so that one has to choose the more appropriate technique. The
discussion is illustrated with several results showing that the growth of SiC from a liquid phase at
low temperature can address various important technological points such as experimental safety, ptype
doping, on-axis or selective epitaxy. The recent demonstration of single-domain 3C-SiC
heteroepitaxial layers on hexagonal SiC substrates confirms that liquid based growth has still
unexpected qualities.
Simultaneous Determination of the Carrier Concentration, Mobility and Thickness of SiC Homo-Epilayers Using Terahertz Reflectance Spectroscopy
Authors: Oishi Shingo , Hijikata Yasuto , Yaguchi Hiroyuki , Yoshida Sadafumi
Published: March 2009

We have simultaneously determined the carrier concentration, mobility, and thickness of
4H-SiC homo-epilayers with carrier concentration of 1016–1018 cm-3 from reflectance spectroscopy in
the wavenumber range of 20–2000 cm-1. The spectra at 20–100 cm-1 and at 80–2000 cm-1 were
measured by using the terahertz time domain spectrometer (THz-TDS) and the Fourier-transform
infrared (FTIR) spectrometer, respectively. A modified classical dielectric function (MDF) model
was employed for the curve fitting. We have compared the values of free carrier concentrations
estimated from the reflectance spectroscopy with the net doping concentrations obtained from C–V
measurements, and have discussed the validity of the electrical properties estimated from the
reflectance spectroscopy.
A Theoretical Study on Aluminium-Related Defects in SiC
Authors: Hornos T. , Gali Adam , Son Nguyen Tien , Janzén Erik
Published: March 2009

We have investigated several aluminum-related complexes in 4H-SiC by ab initio
supercell calculations. The binding energies of the defects predict high thermal stability and
complex formation between aluminum and carbon interstitials in SiC. We show that the carbon
vacancy can be attached to a shallow the aluminum acceptor and form a very stable defect.
We also found that aluminum interstitial forms stable and metastable complexes with one or
two carbon interstitials. The possible relation of these defects to the recently found aluminum-
related DLTS centers is also discussed.
Electron Paramagnetic Resonance Study of Carbon Antisite-Vacancy Pair in p-Type 4H-SiC
Authors: Umeda T. , Morishita Norio , Ohshima Takeshi , Itoh Hisayoshi , Isoya Junichi
Published: March 2009

Carbon antisite-vacancy pair (CSiVC) is a fundamental defect in SiC, and is theoretically
predicted to be very stable in p-type materials. However, this pair was found only in the form of a
negatively charged state (i.e., the SI5 center = CSiVC
−) in n-type and semi-insulating 4H-SiC, and yet,
its presence has not been shown in p-type SiC. In this report, we present the first EPR observation on
positively charged CSiVC pairs in p-type 4H-SiC. By carefully examining p-type samples after electron
irradiation, we found a pair of new defects with C3v and C1h symmetries. They correspond to “c-axial”
pairs (C3v) and “basal” pairs (C1h) of CSiVC
+, respectively. The positively charged pairs are
characterized by a strong 13C hyperfine interaction due to a dangling bond on a carbon antisite (CSi),
which is successfully resolved for the c-axial pairs.
Intrinsic Defects in Semi-Insulating SiC: Deep Levels and their Roles in Carrier Compensation
Authors: Son Nguyen Tien , Carlsson Patrick , Magnusson Björn , Janzén Erik
Published: March 2009

Vacancies, divacancies and carbon vacancy-carbon antisite pairs are found by electron
paramagnetic resonance (EPR) to be dominant defects in high-purity semi-insulating (HPSI) 4HSiC
substrates having different thermal activation energies of the resistivity ranging from ~0.8 eV to
~1.6 eV. Based on EPR results and previously reported data, the energy positions of several
acceptor states of the vacancies and vacancy-related complexes are estimated. These deep levels are
suggested to be associated to different thermal activation energies and responsible for the semiinsulating
behaviour in HPSI SiC substrates. Their role in carrier compensation is discussed.
Point Defects in 4H SiC Grown by Halide Chemical Vapor Deposition
Authors: Zvanut Mary Ellen , Chung Hun Jae , Polyakov A.Y. , Skowronski Marek
Published: March 2009

Halide chemical vapor deposition (HCVD) allows for rapid growth while maintaining
the purity afforded by a CVD process. While several shallow and deep defect levels have been
identified in 6H HCVD substrates using electrical techniques, here we examine several different
point defects found in 4H n-type HCVD SiC using electron paramagnetic resonance (EPR)
spectroscopy. One spectrum, which exhibits axial symmetry and broadens upon heating, may
represent a collection of shallow defects. The other prominent defect has the g tensor of the
negatively charged carbon vacancy, but additional hyperfine lines suggest a more complex center.
The role of these defects is not yet determined, but we note that the concentrations are similar to
those found for the electrically detected defect levels, making them a reasonable source of
electrically active centers.
Electronic Properties of Thermally Oxidized Single-Domain 3C-SiC/6H-SiC Grown by Vapour-Liquid-Solid Mechanism
Authors: Lee Kin Kiong , Pensl Gerhard , Soueidan Maher , Ferro Gabriel
Published: March 2009

This paper studies the electronic properties of MOS capacitors fabricated on double
positioning boundary free 3C-SiC/6H-SiC where the 3C-SiC films were grown using the Vapour-
Liquid-Solid mechanism. The temperature- and frequency-dependent electrical properties of
SiO2/3C-SiC/6H-SiC structures have been studied. Capacitance measurements indicate that the
single-domain 3C-SiC film is doped near the surface with an average concentration of
8.3 × 1016 cm-3. The measured interface state density near the conduction band edge of 3C-SiC is
below 1011cm-2⋅eV-1 and increases towards mid-gap as obtained from conductance and capacitance
measurements. Our results are consistent with the assumption that the interfaces of SiO2/ n-type SiC
consist of two different kinds of interface traps – the carbon clusters located at the interface and the
intrinsic defects located within the oxide layer.
Etching of 4° and 8° 4H-SiC Using Various Hydrogen-Propane Mixtures in a Commercial Hot-Wall CVD Reactor
Authors: Lew Kok Keong , VanMil Brenda L. , Myers-Ward Rachael L. , Holm Ronald T. , Eddy Charles R. , Gaskill D. Kurt
Published: March 2009

Hydrogen etching of 4H-SiC has been performed in a hot-wall chemical vapor deposition
reactor to reduce surface damage and to create a bilayer-stepped surface morphology, optimal for
initiation of growth on 4H-SiC substrates offcut 4° and 8° towards the <11-20> direction. To
understand how step bunching evolves during the ramp to growth temperature, samples were etched
ending at temperatures from 1400 to 1580°C under 0, 2 or 10 sccm of propane (C3H8) addition to
hydrogen. Initial exploratory growth of 5 μm thick epilayers on the 4° etched surfaces are also
discussed. Atomic force microscopy (AFM) and Nomarski microscopy were employed to
investigate changes in the surface morphology. The 8° substrates subjected to H2-C3H8 etching up
to growth temperature routinely exhibited bilayer steps. However, when the 4° substrates were
etched with a 10 sccm C3H8 flow, considerable step bunching was observed. At 1450°C, with a
10 sccm of C3H8 flow (partial pressure is 1.25x10-5 bar), step bunching started with the formation of
ribbon-like steps. Progression to higher temperature etches have shown the coalescence of the
ribbons into larger macro-steps up to 30 nm in height. Etching 4° substrates under 2 sccm of C3H8
(partial pressure is 2.5x10-6 bar) or in pure H2 up to 1500°C results in minimal step bunching.
Generation of Amorphous SiO2/SiC Interface Structure by the First-Principles Molecular Dynamics Simulation
Authors: Miyashita Atsumi , Ohnuma Toshiharu , Iwasawa Misako , Tsuchida Hidekazu , Yoshikawa Masahito
Published: March 2009

The performance of SiC MOSFET devices to date is below theoretically expected
performance levels. This is widely considered to be attributed to defect at the SiO2/SiC interface that
degrade the electrical performance of the device. To analyze the relationship between defect
structures near the interface and electrical performances, advanced computer simulations were
performed. A slab model using 444 atoms for an amorphous oxide layer on a 4H-SiC (0001) substrate
was made by using first-principles molecular dynamic simulation code optimized for the
Earth-Simulator. Simulated heating and rapid quenching was performed for the slab model in order to
obtain a more realistic structure and electronic geometry of a-SiO2/4H-SiC interface. The heating
temperature, the heating time and the speed of rapid quenching were 4000 K, 3.0 ps and -1000 K/ps,
respectively. The interatomic distance and the bond angles of SiO2 layers after the calculation are
agree well with the most probable values of bulk a-SiO2 layers, and no coordination defects were
observed in the neighborhood of SiC substrate.
Encapsulating Annealing of N+ Implanted 4H-SiC by Diamond-Like-Carbon Film
Authors: Miyagawa Shingo , Suzuki Tomoyuki , Kudo Takahiro , Satoh Masataka
Published: March 2009

The encapsulating annealing of N+ implanted 4H-SiC(0001) is performed using diamondlike-
carbon (DLC) films for the suppression of surface roughening. 4H-SiC(0001) sample with an
off-orientation of 8o is multiply implanted by N+ with energy ranging from 15 to 120 keV at a total
dose of 2.4×1015 cm-2 at room temperature. DLC films with thickness ranging from 0.3 to 1.8 μm
are deposited on the surface of implanted sample using plasma-based ion implantation
equipment with C2H4 gas. The DLC capped sample is annealed at 1500 oC for 5 min using IR image
annealer. After annealing, DLC film is removed by the oxidization. The sample capped by DLC
film with a thickness of 0.3 μm shows the root mean square (RMS) surface roughness of 0.6 nm
while the annealed sample without DLC film shows RMS surface roughness of 5.2 nm. As the
thickness of DLC film is increased from 0.3 to 1.8 μm, the RMS surface roughness is decreased
from 0.6 to 0.2 nm.
High Temperature Implantation of Aluminum in 4H Silicon Carbide
Authors: Rambach Martin , Bauer Anton J. , Ryssel Heiner
Published: March 2009

The influence of the implantation temperature on the surface roughness and the resistivity
of aluminum implanted 4H-silicon carbide was determined. A dose of 1.2 ⋅1015cm-2 aluminum ions
was implanted at temperatures between room temperature and 1000°C. A decrease of the surface
roughness down to an rms-value of 12nm and a decrease in the resistivity down to 0.35Wcm were
found with increasing implantation temperature. The influence of the implantation temperature on
the resistivity was identified by modeling temperature dependent resistivity data. The results showed
an increase in mobility with temperature due to the reduction of compensation centers.
Dynamical Simulation of SiO2/4H-SiC(0001) Interface Oxidation Process: from First-Principles
Authors: Ohnuma Toshiharu , Miyashita Atsumi , Iwasawa Misako , Yoshikawa Masahito , Tsuchida Hidekazu
Published: March 2009

We performed the dynamical simulation of the SiO2/4H-SiC(0001) interface oxidation
process using first-principles molecular dynamics based on plane waves, supercells, and the projector
augmented wave method. The slab model has been used for the simulation. The heat-and-cool method
is used to prepare the initial interface structure. In this initial interface structure, there is no transition
oxide layer or dangling bond at the SiO2/SiC interface. As the trigger of the oxidation process, the
carbon vacancy is introduced in the SiC layer near the interface. The oxygen molecules are added one
by one to the empty sphere in the SiO2 layer near the interface in the simulation of the oxidation
process. The molecular dynamics simulation is carried out at 2500 K. The oxygen molecule is
dissociated and forms bonds with the Si atom in the SiO2 layer. The atoms of Si in the SiC layer at the
SiO2/4H-SiC(0001) interface are oxidized to form the SiO2 layer. Carbon clusters, which are
considered one of the candidate structures of the interface traps, are formed in the interface layer.
Oxygen molecules react with the carbon clusters and formed CO molecules.
Electrical Properties of Atomic-Layer-Deposited La2O3/Thermal-Nitrided SiO2 Stacking Dielectric on 4H-SiC(0001)
Authors: Moon Jeong Hyun , Cheong Kuan Yew , Eom Da Il , Song Ho Keun , Yim Jeong Hyuk , Lee Jong Ho , Na Hoon Joo , Bahng Wook , Kim Nam Kyun , Kim Hyeong Joon
Published: March 2009

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.
Interface Properties of SiO2/4H-SiC(0001) with Large Off-Angles Formed by N2O Oxidation
Authors: Saitoh Hiroaki , Seki Akinori , Manabe Akira , Kimoto Tsunenobu
Published: March 2009

In this study, we have investigated N2O oxidation of various off-angled 4H-SiC (0001) epilayers and
characterized the properties of MOS interfaces. The oxide thickness almost linearly increases with
increasing off-angle. Oxidation on highly off-angled (0001) 4H-SiC is faster than that on 8o off-axis
(0001). The off-angle dependence of Dit is very small for the MOS capacitors in the off-angle range
from 8o to 30o. The depth profiles of carbon and nitrogen atoms near the MOS interface on 15o
off-axis 4H-SiC(0001) are similar to those on 8o off-axis (0001).
Time-Dependent Dielectric Breakdown of Thermal Oxides on 4H-SiC
Authors: Matocha Kevin , Beaupre Richard
Published: March 2009

Thermal oxides on 4H-SiC are characterized using time-dependent dielectric breakdown
techniques at electric fields between 6 and 10 MV/cm. At 250°C, oxides thermally-grown using
N2O with NO annealing achieve a mean time to failure (MTTF) of 2300 hours at 6 MV/cm. Oxides
grown in steam with NO annealing show approximately four times longer MTTF than N2O-grown
oxides. At electric fields greater than 8 MV/cm, Fowler-Nordheim tunneling significantly reduces
the expected failure times. For this reason, extrapolation of mean-time to failure at low fields must
be performed by datapoints measured at lower electric fields.
X-Ray and AFM Analysis of Al2O3 Deposited by ALCVD on n-Type 4H-SiC
Authors: Grossner Ulrike , Servidori Marco , Avice Marc , Nilsen Ola , Fjellvåg Helmer , Nipoti Roberta , Svensson Bengt Gunnar
Published: March 2009

Al2O3 grown by Atomic Layer Chemical Vapour Deposition (ALCVD) on n-type 4H-SiC
with a nominal thickness of 100nm has been characterized by Grazing Incidence X-Ray Diffraction
(GIXD) and Specular X-Ray Reflectivity (SXR) measurements. After post-deposition, the samples
were annealed at different temperatures and durations in argon atmosphere. The GIXD results reveal
crystallization at temperatures above 900°C, most likely in the form of θ-Al2O3 or γ-Al2O3.
However, the formation of a new, non-stoichiometric Al2O3 phase cannot be excluded. The
crystalline domain size, evaluated from the peak FWHMs after subtraction of the instrumental
broadening, is found to be almost equal (18±1nm), independent of T in the range 900°C≤T≤1100°C
and time in the range 1h≤t≤3h. From SXR, mass density profiles are derived. Whereas the as grown
film exhibits the lowest mass density, at 800°C a low-density interface layer forms. At the same
time, it appears that the initial crystallization starts at the surface. At 900°C, the density increases
sharply (this process involves film crystallization) and the film thickness correspondingly reduces.
Whereas the density increase and thickness reduction still continue for T>900°C (tendency to the
density α-Al2O3), the density of the interfacial layer has a minimum at 900°C and gradually
increases for higher temperatures. From Atomic Force Microscopy (AFM) investigations it could be
revealed that the starting of the crystallization at 900°C is accompanied with a substantial surface
roughening. For annealing at higher temperatures, the surface roughness is in the range of the one of
the as-grown sample (about 6Å).
Development of Low Resistance Al/Ti Stacked Metal Contacts to p-Type 4H-SiC
Authors: Jennings Michael R. , Pérez-Tomás Amador , Walker D. , Zhu Lin , Losee Peter A. , Huang W. , Balachandran S. , Guy Owen James , Covington James A. , Chow T. Paul , Mawby Philip  Andrew
Published: March 2009

In this work, we have investigated triple and innovative multiple stacked contacts onto ptype
SiC in order to evaluate whether or not there is any improvement in morphology or specific
contact resistivity. The stacked metal contacts are based on Al, Ti and Ni with the specific contact
resistivity measured at a low value of 5.02×10-6'cm2 for an Al(100 nm)/Ti(100 nm)/Al(10 nm)
(where a “/” indicates the deposition sequence) triple stacked metal contact. XRD microstructural
analysis and SEM measurements have been carried out and it has been discovered that the contacts,
which formed the compound Ti3SiC2 at the metal/SiC interface, more readily display low-resistance
ohmic characteristics after a post deposition anneal. Although the same amount of Ti (100 nm in
total) has been deposited closer to the metal/SiC interface, none of the multiple stacked structures
displayed ohmic behaviour after a post deposition anneal.
Interface Reactions and Electrical Properties of Ta/4H-SiC Contacts
Authors: Cao Yu , Pérez-García S. Alfonso , Nyborg Lars
Published: March 2009

This study deals with the interfacial reactions and electrical properties of Ta/4H-SiC
contacts. Tantalum thin films (~100 nm) were deposited onto SiC wafer at room temperature by
argon ion beam sputtering. The samples were then heated in high vacuum at 650°C, 800°C or
950°C for 30 min. X-ray photoelectron spectroscopy (XPS), glancing angle X-ray diffraction
(XRD), Auger electron spectroscopy (AES) and current-voltage (I-V) technique were used for
characterising the samples. Ohmic contact is formed in the studied samples after annealing at or
above 800°C even though considerable amount of metallic Ta still exists. The reaction zone
possesses a layered structure of Ta2C/Ta2C+Ta5Si3/SiC. High enough temperature is needed to
provide for sufficient interface change to tailor the contact properties.
Low Resistance Cathode Metallization and Die-Bonding in Silicon Carbide P-N Junction Diodes
Authors: Kim Tae Hong , Lee Seung Yong , Lee Jang Sub , Suh Duk Il , Cho Nam Kyu , Bahng Wook , Kim Nam Kyun , Choi Sung Yong , Kim Hak Jong , Lee Sang Kwon
Published: March 2009

We investigated how surface roughness, intentionally induced by chemical-mechanical
polishing, affects the formation of ohmic contacts to an n-type 4H-SiC using a common circular
transmission length method (CTLM). Nickel metal was used as the cathode ohmic contacts to n-type
SiC. The specific contact resistance (SCR) for the un-polished sample (F1) and polished samples (F2
and F3) was 5.4 × 10-3 ⋅cm2 and 4.2 × 10-3 ⋅cm2, respectively. We found out that the un-polished
sample (F1) had much higher SCR than the samples , F2 and F3. In addition, we did not see any
difference between the differently polished samples, F2 and F3, indicating that there was no
dependence on the face type of SiC (Si- or C-face) in the values of SCR. We also investigated the
die-bonding processes with the surface roughness and metallization schemes' effects.
Low Specific Contact Resistance to 3C-SiC Grown on (100) Si Substrates
Authors: Bazin Anne Elisabeth , Chassagne Thierry , Michaud Jean François , Leycuras André , Portail Marc , Zielinski Marcin , Collard Emmanuel , Alquier Daniel
Published: March 2009

In this work, ohmic contacts, formed by 100nm Ni layer RTA annealed or not, were
investigated on 3C-SiC epilayers exhibiting different nitrogen doping levels. The epilayers were
grown on (100) silicon. Doping level (N) and eventual dopant contamination (Al) were analyzed by
C-V and/or SIMS. The specific contact resistance was determined by using Transmission Line
Model (TLM) patterns for each condition (doping and annealing). Our results clearly evidence that
very low specific contact resistance (~10-51.cm²) is obtained on highly doped 3C-SiC epilayers,
enlightening the interest of both material and Ni contacts for future devices fabrication.
Plasma Etching for Backside Wafer Thinning of SiC
Authors: Robb Kenneth M.
Published: March 2009

In this initial phase of work, two methods of backside wafer thinning using ICP plasma
etching of two-inch SiC substrates have been considered. Plasma processes were optimized for nonbonded
and bonded wafers. The non-bonded process was used to etch 250μm thick substrates to a
final thickness of 100μm. The bonded process was used to etch glass bonded SiC substrates
mechanically ground to 130μm thick and plasma etched to a final thickness of 100μm. Etch rate
measurements and surface analysis were performed using a profilometer and white light
interferometry. Etch rates of 3.4μm/min were achieved for the bonded process and 2.0μm/min for
the non-bonded process. The surface morphology for the non-bonded process was three to four
times lower than the bonded process. The part mechanically ground samples showed evidence of
surface damage from the grinding process after plasma etching.
Damage-Free Planarization of 4H-SiC (0001) by Catalyst-Referred Etching
Authors: Hara Hideyuki , Sano Yasuhisa , Mimura Hidekazu , Arima Kenta , Kubota Akihisa , Yagi Keita , Murata Junji , Yamauchi Kazuto
Published: March 2009

We report the damage-free planarization of 4H-SiC (0001) wafers using a new
planarization technique we named CAtalyst-Referred Etching (CARE). The CARE setup equipped
with a polishing pad made of a catalyst is almost the same as a lapping setup. Since the catalyst
generates reactive species that activate only when they are next to the catalyst surface, SiC can be
chemically removed in contact with the catalyst surface with a pressure noticeably lower than that in
a conventional polishing process. The processed surfaces were observed by optical interferometry
and AFM. These observations presented a marked reduction in surface roughness. A step-terrace
structure was observed with a step height of approximately 3み, corresponding to one-bilayer
thickness of Si and C, in the AFM images. To estimate the crystallographic properties of the
CARE-processed surface, the surfaces were observed by cross-sectional TEM. The TEM images
showed that a more crystallographically well-ordered surface was realized in comparison with the
conventional CMP-processed surface.
Polishing Characteristics of 4H-SiC Si-Face and C-Face by Plasma Chemical Vaporization Machining
Authors: Sano Yasuhisa , Watanabe Masayo , Yamamura Kazuya , Yamauchi Kazuto , Ishida Takeshi , Arima Kenta , Kubota Akihisa , Mori Yuzo
Published: March 2009

Silicon carbide (SiC) is a promising semiconductor material for power devices. However, it
is so hard and so chemically stable that there is no efficient method of machining it without causing
damage to the machined surface. Plasma chemical vaporization machining (PCVM) is plasma etching
in atmospheric-pressure plasma. PCVM has a high removal rate equivalent to those of conventional
machining methods such as grinding and lapping, because the radical density in atmospheric-pressure
plasma is much higher than that in normal low-pressure plasma. In this paper, the polishing
characteristics of SiC by PCVM are described. As a result of machining, the surface roughnesses of
both Si- and C-faces were improved under a relatively low-etch-rate (100-200 nm/min) condition.
The C-face was also improved under a relatively high-etch-rate (approximately 10 μm/min) condition,
and a very smooth surface (below 2 nm peak-to-valley in a 500-nm-square area) was achieved.
9 kV 4H-SiC IGBTs with 88 mΩ·cm2 of R diff, on
Authors: Zhang Qing Chun Jon , Jonas Charlotte , Heath Bradley , Das Mrinal K. , Ryu Sei Hyung , Agarwal Anant K. , Palmour John W.
Published: March 2009

SiC IGBTs are suitable for high power, high temperature applications. For the first time,
the design and fabrication of 9 kV planar p-IGBTs on 4H-SiC are reported in this paper. A
differential on-resistance of ~ 88 m(cm2
at a gate bias of –20 V is achieved at 25°C, and decreases
to ~24.8 m(cm2
at 200°C. The device exhibits a blocking voltage of 9 kV with a leakage current
density of 0.1 mA/cm2. The hole channel mobility is 6.5 cm2/V-s at room temperature with a
threshold voltage of –6.5 V resulting in enhanced conduction capability. Inductive switching tests
have shown that IGBTs feature fast switching capability at both room and elevated temperatures.
Electrical Properties of p-Channel MOSFETs Fabricated on 4H- and 6H-SiC
Authors: Okamoto Mitsuo , Tanaka Mieko , Yatsuo Tsutomu , Fukuda Kenji
Published: March 2009

It is of great importance to investigate the electrical properties of SiC p-channel MOSFETs
for development of SiC CMOS technology. In the present report, we investigated dependences of
electrical properties of the SiC p-channel MOSFETs on SiC poly-types. The on-state characteristics
(channel mobility, threshold voltage, and temperature dependences) for the 4H- and 6H-SiC
p-channel MOSFETs showed similar behavior, although those of 4H-SiC n-channel MOSFETs are
usually quite different from those of 6H-SiC. These results might be caused by the similar SiC MOS
interface state distribution around the valence band edge.
Fabrication and Characterization of 4H-SiC MOSFET with MOCVD-Grown Al2O3 Gate Insulator
Authors: Hino Shiro , Hatayama Tomohiro , Miura Naruhisa , Oomori Tatsuo , Tokumitsu Eisuke
Published: March 2009

We have fabricated and characterized MOS capacitors and lateral MOSFETs using Al2O3
as a gate insulator. Al2O3 films were deposited by metal-organic chemical vapor deposition
(MOCVD) at temperatures as low as 190 oC using tri-ethyl-aluminum and H2O as precursors. We
first demonstrate from the capacitance – voltage (C-V) measurements that the Al2O3/SiC interface has
lower interface state density than the thermally-grown SiO2/SiC interface. No significant difference
was observed between X-ray photoelectron spectroscopy (XPS) Si 2p spectrum from the Al2O3/SiC
interface and that from the SiC substrate, which means the SiC substrate was not oxidized during the
Al2O3 deposition. Next, we show that the fabricated lateral SiC-MOSFETs with Al2O3 gate insulator
have good drain current – drain voltage (ID-VD) and drain current – gate voltage (ID-VG)
characteristics with normally-off behavior. The obtained peak values of field-effect mobility (μFE) are
between 68 and 88 cm2/Vs.
SiC Field Effect Transistor Technology Demonstrating Prolonged Stable Operation at 500 °C
Authors: Neudeck Philip G. , Spry David J. , Chen Liang Yu , Okojie Robert S. , Beheim Glenn M. , Meredith Roger D. , Ferrier Terry L.
Published: March 2009

While there have been numerous reports of short-term transistor operation at 500 °C or
above, these devices have previously not demonstrated sufficient long-term operational durability at
500 °C to be considered viable for most envisioned applications. This paper reports the
development of SiC field effect transistors capable of long-term electrical operation at 500 °C. A
6H-SiC MESFET was packaged and subjected to continuous electrical operation while residing in a
500 °C oven in oxidizing air atmosphere for over 2400 hours. The transistor gain, saturation current
(IDSS), and on-resistance (RDS) changed by less than 20% from initial values throughout the duration
of the biased 500 °C test. Another high-temperature packaged 6H-SiC MESFET was employed to
form a simple one-stage high-temperature low-frequency voltage amplifier. This single-stage
common-source amplifier demonstrated stable continuous electrical operation (negligible changes to
gain and operating biases) for over 600 hours while residing in a 500 °C air ambient oven. In both
cases, increased leakage from annealing of the Schottky gate-to-channel diode was the dominant
transistor degradation mechanism that limited the duration of 500 °C electrical operation.
Temperature Stability of Heteropolytypic 6H/3C FETs
Authors: Chen Chia Ching , Horsfall Alton B. , Wright Nicolas G. , Vassilevski Konstantin
Published: March 2009

The formation of two-dimensional electron gases (2DEG) at the polytypic 6H/3C
heterojunction is investigated. The main of study was to obtain the properties of the 3C/6H structure
using Technology Computer Aided Design (TCAD) software. The electron-density distribution and
conduction band profile in 6H/3C SiC heterojunction are calculated as a function of temperature.
Simulation of these hetero-junctions has concentrated on the I-V behaviour over a range of
temperatures between 350 and 650 K. We show that the device characteristics are substantially
degraded at high temperatures and this will limit the use of these devices to moderate temperature
applications.
Effect of Additional Silane on In Situ H2 Etching prior to 4H-SiC Homoepitaxial Growth
Authors: Kojima Kazutoshi , Kuroda Satoshi , Okumura Hajime , Arai Kazuo
Published: March 2009

We have investigated the influence of in-situ H2 etching on the surface morphology of the
4H-SiC substrate prior to homoepitaxial growth. In this study, we varied the types of gas atmosphere
during in-situ H2 etching; namely, hydrogen (H2) alone, hydrogen-propane (H2+C3H8), and
hydrogen-silane (H2+SiH4). We found that in-situ H2 etching using H2 + SiH4 significantly improved
the surface morphology of 4H-SiC substrate just after in-situ H2 etching. By adding SiH4, formation
of bunched step structure during in-situ H2 etching could be significantly suppressed. In addition, H2
etching using H2 + SiH4 was able to remove scratches by etching a thinner layer than that using H2
alone. We also discussed the in-situ H2 etching mechanism under the additional SiH4 condition.
High Voltage Silicon Carbide Schottky Diodes with Single Zone Junction Termination Extension
Authors: Vassilevski Konstantin , Nikitina Irina P. , Horsfall Alton B. , Wright Nicolas G. , O'Neill Anthony G. , Hilton Keith P. , Munday A.G. , Hydes A.J. , Uren Michael J. , Johnson C. Mark
Published: March 2009

High voltage 4H-SiC Schottky diodes with single-zone junction termination extension
(JTE) have been fabricated and characterised. Commercial 4H-SiC epitaxial wafers with 10, 20 and
45 +m thick n layers (with donor concentrations of 3×1015, 8×1014 and 8×1014 cm-3, respectively)
were used. Boron implants annealed under argon flow at 1500°C for 30 minutes, without any
additional protection of the SiC surface, were used to form JTE’s. After annealing, the total charge
in the JTE was tuned by reactive ion etching. Diodes with molybdenum Schottky contacts exhibited
maximum reverse voltages of 1.45, 3.3 and 6.7 kV, representing more than 80% of the ideal
avalanche breakdown voltages and corresponding to a maximum parallel-plane electric field of
1.8 MV/cm. Diodes with a contact size of 1×1 mm were formed on 10 +m thick layers (production
grade) using the same device processing. Characterisation of the diodes across a quarter of a 2-inch
wafer gave an average value of 1.21 eV for barrier heights and 1.18 for ideality factors. The diodes
exhibited blocking voltages (defined as the maximum voltage at which reverse current does not
exceed 0.1 mA) higher than 1 kV with a yield of 21 %.
Progress on the Development of 10 kV 4H-SiC Pin Diodes for High Current/High Voltage Power Handling Applications
Authors: Hull Brett A. , Sumakeris Joseph J. , Das Mrinal K. , Richmond Jim , Palmour John W.
Published: March 2009

The development of 4H-SiC PiN diodes capable of blocking to greater than 10 kV while
having current ratings of 20 A at 100 A/cm2 is continuing in earnest. VF instability of these diodes
continues to be a roadblock, but progress is being made, and a 20 A/10 kV 4H-SiC PiN diode wafer
with an overall device yield of 40% has been fabricated. The latest device characteristics are
discussed, along with details of approaches in improving the reverse recovery characteristics of
these diodes to satisfy the requirements needed for implementation into high voltage inverter
modules capable of switching at up to 20 kHz.
Degradation of Charge Collection Efficiency Obtained for 6H-SiC n+p Diodes Irradiated with Gold Ions
Authors: Ohshima Takeshi , Satoh Takahiro , Oikawa Masakazu , Onoda Shinobu , Hishiki Shigeomi , Hirao Toshio , Kamiya Toshio , Yokoyama T. , Sakamoto A. , Tanaka R. , Nakano I. , Wagner Günter , Itoh Hisayoshi
Published: March 2009

The charge generated in 6H-SiC n+p diodes by gold (Au) ion irradiation at an energy of 12
MeV was evaluated using the Transient Ion Beam Induced Current (TIBIC). The signal peak of the
transient current increases, and the fall-time decreases with increasing applied reverse bias. The value
of collected charge experimentally obtained is smaller than the ideal value. The Charge Collection
Efficiency (CCE) of 6H-SiC n+p diodes irradiated with Au ions is approximately 50 % in spite that the
CCE of 100 % is obtained in the case of oxygen (O) ion irradiation.
Potential Benefits of Silicon Carbide Zener Diodes Used as Components of Intrinsically Safe Barriers
Authors: Lark P. , Vassilevski Konstantin , Nikitina Irina P. , Phelps G.J. , Horsfall Alton B. , Wright Nicolas G.
Published: March 2009

Zener diodes are widely used in electrical barriers to protect equipment operating in a
potentially explosive atmosphere. Although normally not conducting, the zeners must have a high
power rating so that their junction temperature meets safety factors when shunting the maximum
fuse current. This often requires two or three lower voltage commercial zeners connected in series.
Silicon carbide diodes have much higher thermal conductivity and maximum allowed junction
temperature, so it should be possible to use one SiC zener in the place of two or three commercial
diodes and/or allow use of higher fuse ratings. Low voltage SiC Zener diodes were fabricated and
tested to evaluate potential benefits of their application as a component of intrinsically safe barriers.
The diodes demonstrated mixed avalanche-tunnel breakdown at reverse bias voltages of 23 V with
positive temperature coefficients of breakdown voltages of about 0.4 mV/°C. The diodes with mesa
area of 4×10-4cm2 had maximum DC Zener current of 1.2 A and were capable of operating at
ambient temperatures up to 500°C.
4H-SiC High Temperature Spectrometers
Authors: Kalinina Evgenia V. , Strokan Nikita B. , Ivanov Alexander M. , Sadohin A. , Azarov A. , Kossov V. , Yafaev R. , Lashaev S.
Published: March 2009

The detector structures based on Al ion-implanted p+-n junctions in 4H-SiC have been
manufactured and tested at temperatures up to 170oC by α-particles with energies of 3.9 and 5.5
MeV. Structural peculiarities of thin Al high dose ion implanted layers before and after short high
temperature activation annealing were studied by combination of Rutherford back
scattering/channeling spectrometry and cross-sectional transmission electron microscopy. The
detector structures fabricated on this thin ion implanted p+-n junctions operated in the temperature
range of 16-170 oC with reproducible stable spectrometric characteristics. The charge collection
efficiency and the energy resolution of detectors improved with rising temperature up to 170 oC,
that was obtained in SiC detectors for the first time.
Improved Efficiency in Power Factor Correction Circuits with a pn-Gated SiC FET
Authors: Kelley Robin L. , Mazzola Michael S. , Draper William L.
Published: March 2009

The purpose of this paper is to present an all-SiC switched AC-DC converter using active
power factor correction. The typical boost-converter approach is employed using continuous
conduction mode. A SiC Schottky barrier diode performs the free-wheeling diode function, and a
600 V, 0.12 % SiC vertical junction field effect transistor performs the switching function under the
control of a Fairchild ML4821 integrated circuit. The converter is operable off-line over the full
universal voltage range (85-260 VAC), but it was optimized for a 400-600 W application operating
at 208 VAC. Results are presented that demonstrate extremely high efficiency at a switching
frequency of 500 kHz, the highest operating frequency of the ML4821.
Microstructure Refinement of a Low Interstitial Ferritic Stainless Steel by Cold Rolling and Annealing of Martensite
Authors: Azizi-Alizamini H. , Sinclair Chad W. , Militzer Matthias , Mithieux J.D.
Published: March 2009

Several studies have shown that recrystallization of cold rolled martensite results in low
carbon steels with very fine microstructures. Correspondingly, these materials exhibit promising
combinations of strength and elongation. Most of the work on this processing route has focused on
low carbon steels (0.1-0.2wt% carbon) where the interstitial content may play an important role in
the microstructure refinement. In this note we describe experiments performed on a low interstitial
stainless steel containing 0.02wt%C. It has been possible to achieve materials with high strengths
(UTS > 1 GPa) and significant uniform elongation (> 8%), however, the microstructures associated
with these properties are very different from those previously reported for low carbon steels.
Phase-Field Modeling of Recrystallization - Effects of Second-Phase Particles on the Recrystallization Kinetics
Authors: Suwa Yoshihiro , Saito Yoshiyuki , Onodera Hidehiro
Published: March 2009

The effects of second-phase particles on the recrystallization kinetics in two-dimensional polycrystalline structures were investigated. Numerical simulations of recrystallization were performed by coupling the unified subgrain growth theory with a phase-field methodology. Simple assumptions based on experimental observations were utilized for preparing initial microstructures. The following results were obtained: (1) The presence of second-phase particles retarded recrystallization speeds. (2) If the mean subgrain size was small enough recrystallized region covered whole system for various values of the particle fraction, f. (3) On the other hand, if the mean subgrain size was not small enough the progress of recrystallization was frozen at some point.
Effect of Annealing on the Microstructure Change and Strength of Irradiated Quasi-Nano-Filamentary Copper-Silver Composites
Authors: Choi K.S. , Choi Y. , Inoue Hirofumi
Published: March 2009

Copper-silver quasi-nano filamentary composites prepared by hot isostatic pressing followed by heavy
drawing were irradiated in CT hole of a domestic experimental nuclear reactor, HANARO to study the
morphological change of the poly-crystalline nano-filaments with irradiation and annealing conditions.
The irradiation was carried out for 36 days at 320
o
C with the maximum neutron flux of 4.8x10
20
n/cm
2
(E>1.0 MeV). The gamma heating rate was in the range of 2.0-6.45 W/gm. Polycrystalline silver
nano-filaments of the composites were equilibrium shape like the faceted sphere shape. Annealing
results in the increase of the faceting rate of the irradiated specimen. Nano-indentation results supported
that the morphology change of nano-filaments by annealing in this study is more effective on strength
change of the irradiated nano-filamentary composites than irradiated hardening.
High Temperature Deformation of a Structural Steel
Authors: Gonzalez B.M. , Santos O.J. , Castro C.S.B. , Santos Dagoberto Brandão , Barbosa Ronaldo
Published: March 2009

The mechanical behavior of a fire resistant steel was studied by means of tensile tests
performed in the temperature interval from 25 to 600oC, at strain rates from 10-4 to 10-2 s-1, aiming
at analyzing the role of alloying elements in the dynamic strain aging (DSA) phenomena occurring
in this steel. Typical features of DSA were observed: serrated flow (the Portevin-LeChatelier – PLC
effect), the presence of a maximum and a minimum in ultimate tensile strength and elongation
versus temperature curves, respectively and a plateau in yield strength versus temperature curves.
Apparent activation energies were calculated based on the onset of PLC effect and the maximum in
ultimate tensile strength. Results suggest that changes in mechanical properties associated with
DSA in the fire resistant steel are related to the dynamic interaction of C-substitutional dipoles and
dislocations.