bluuebunny/crossref_metadata_2025 huggingface dataset:
Monte Carlo Study of the early Growth Stages of 3C-SiC on Misoriented <11-20> and <1-100> 6H-SiC Substrates: Role of Step-Island Interaction
Authors: Camarda Massimo , La Magna Antonino , La Via Francesco
Published: July 2015

In this paper we use three dimensional kinetic Monte Carlo simulations on super-lattices to study the hetero-polytypical growth of cubic silicon carbide polytype (3C-SiC) on hexagonal 6H-SiC step-bunched substrates with miscuts towards the <11-20> and <1-100> directions. We find that the preferential 3C conversion observed on <1-100> misoriented substrates could be due to a different step-to-island interaction which enhances island stability and expansion in this specific direction. For this reason 3-4° degrees off step-bunched 6H substrates with miscut towards the <1-100> direction should be the best choice for the stable and reproducible hetero-polytypical growth of high quality cubic epitaxial films.
Si Surface Preparation for Heteroepitaxial Growth of SiC Using In Situ Oxidation
Authors: Wang Li , Dimitrijev Sima , Iacopi Alan , Hold Leonie , Walker Glenn , Chai Jessica , Massoubre David
Published: July 2015

To achieve high quality SiC growth on Si substrate, it is essential to get a smooth Si surface without forming SiC and graphitic islands during the surface cleaning and before the carbonisation process. In this paper, a novel in-situ surface cleaning method designed for the hetero-epitaxial growth of SiC on Si substrate is developed using a custom-made low-pressure chemical vapour deposition reactor. The results indicate that the combination of ramping in oxygen and subsequent flowing of SiH4 avoids the contamination of Si, enables the oxide layer to be removed smoothly, and subsequently creates a smooth Si surface with regular atomic steps. SiC grown on off-axis Si has better crystallinity and significantly smaller roughness than that grown on on-axis Si.
Understanding of the Growth Mechanism Leading to Twin Boundary Elimination during 3C-SiC Heteroepitaxy on α-SiC Substrate by CVD
Authors: Alassaad Kassem , Soulière Véronique , Cauwet François , Carole Davy , Doisneau Beatrice , Ferro Gabriel
Published: July 2015

Starting from the previously demonstrated twin-free 3C-SiC growth on 4H-SiC when using Ge pre-deposition treatment, this work focuses on the understanding of the growth mechanism that stands behind this result. Toward this end, short growth experiments were performed to allow the investigation of the nucleation stage. Based on the experimental observations, a mechanism is proposed which involves a Ge-induced transient homoepitaxial growth step followed by 3C nucleation when large terraces are formed by step faceting. Lateral expansion of the 3C islands leads to orientation selection and twin boundary elimination. Similar results can be obtained when applying a Si-based pre-deposition treatment so that the crucial transient homoepitaxial step is promoted in fact by the presence of a liquid phase itself, no by its chemical nature.
Temperature Dependence of 4H-SiC Ionization Rates Using Optical Beam Induced Current
Authors: Hamad Hassan , Raynaud Christophe , Bevilacqua Pascal , Scharnholz Sigo , Planson Dominique
Published: July 2015

The behavior of 4H-SiC power devices in severe environment with varying temperature is a key characteristic indicating their reliability. This paper shows the dependence of the ionization rates of 4H-SiC with respect to temperature. Optical Beam Induced Current (OBIC) measurements have been performed on PN junctions to determine the multiplication coefficient for temperature varying between 100 and 450K. That allows extracting the ionization rates by fitting the curves of multiplication coefficient.
FTIR Studies of Silicon Carbide 1D-Nanostructures
Authors: Karbovnyk Ivan , Savchyn P. , Huczko Andrzej , Cestelli Guidi Maruangela , Mirri Chiara , Popov A. I.
Published: July 2015

Stable 1D silicon carbide nanostructures (nanowires) have been obtained via combustion synthesis route. Infrared absorption and reflection spectra for as-obtained and purified SiC nanowires were compared with the spectra of commercially available SiC nanomaterials. Principal vibrational modes have been identified. Reflectivity spectrum has been reconstructed by modeling of the dielectric function
Infrared Transmission and Reflectivity Measurements of 4H- and 6H-SiC Single Crystals
Authors: Cui Ying Xin , Hu Xiao Bo , Xu Xian Gang
Published: July 2015

Room temperature infrared transmittance and reflectance spectra of 4H and 6H-SiC single crystals were measured by a NEXUS 670 Fourier Transform Infrared-Raman spectrometer. The transmittance and reflectance of non-doped, V-doped semi-insulating (SI), high purity semi-insulating, n-type and p-type SiC wafers have been compared and assessed. The effect of nitrogen and boron concentration on the transmittance is discussed. In addition, the carrier concentrations in 4H-SiC wafers were measured by Raman spectroscopy at room temperature. The influence of nitrogen concentration on the transmittance is also discussed.
The Bloch Oscillations and THz Electroluminescence in Natural Superlattices of 6H-, 8H-SiC Polytypes
Authors: Sankin Vladimir Ilich , Andrianov Alexander V. , Petrov Alexey G. , Zachar'in A.O. , Nagalyuk Sergey , Shkrebiy Pavel P. , Sablina Natalia I.
Published: July 2015

We report on the observation of the THz electroluminescence in 6H-SiC and 8H-SiC n+–n-–n+ structures of hexagonal crystals with natural superlattice, caused by applied electrical field along the lattice and natural superlattice axis. It is shown that there are the terahertz electroluminescence correspond to the narrow lines at 5.3–12.7 meV. The emission channel can be well explained by the optical intraladder transitions in the Bloch oscillations regime.
Mechanical Properties and Residual Stress of Thin 3C-SiC(100) Films Determined Using MEMS Structures
Authors: Hähnlein Bernd , Stubenrauch Mike , Pezoldt Joerg
Published: July 2015

3C-SiC(100) was grown on Si (100) in a thickness range between 40 and 500 nm by low pressure chemical vapor deposition. The mechanical properties and the residual stress were determined using the length dependence of the resonance frequencies of cantilevers and beams. Taking into account the influence of the cantilever bending and the stress gradients the Young’s modulus of the 3C-SiC(100) was obtained. It decreases with decreasing thickness of the epitaxial layer grown on Si (100).
Dislocation Conversion During SiC Solution Growth for High-Quality Crystals
Authors: Harada Shunta , Yamamoto Yuji , Xiao S. , Koike Daiki , Mutoh Takuya , Murayama Kenta , Aoyagi Kenta , Sakai Takenobu , Tagawa M. , Ujihara Toru
Published: July 2015

Solution growth of SiC has attracted significant attention due to its potential for the production of high-quality SiC wafers. We have recently investigated the dislocation propagation behavior during SiC solution growth with the aim of reducing the dislocation density. Threading dislocations were found to be converted to defects on the basal planes during solution growth. Utilizing this dislocation conversion phenomenon, we have proposed a dislocation reduction process during solution growth and achieved high-quality 4H-SiC crystal growth. Here we confirm the potential of SiC solution growth for the production of high-quality SiC wafers.
Identification of Stacking Faults by UV Photoluminescence Imaging Spectroscopy on Thick, Lightly-Doped n-Type 4°-off 4H-SiC Epilayers
Authors: Thierry-Jebali Nicolas , Kawahara Chihiro , Miyazawa Tetsuya , Tsuchida Hidekazu , Kimoto Tsunenobu
Published: July 2015

This work reports on description and application of a new Photoluminescence (PL) Imaging technique for in-grown stacking fault (SF) characterization and identification on 4H-SiC epilayers. The purpose of this technique is to make a spectroscopic picture from a collection of PL imaging picture taken at different output wavelengths in order to both display the shape and an approximation of the maximum PL intensity wavelength at room temperature (RT) of the characterized SF. This is why we called this technique “PL Imaging Spectroscopy”. Five types of SFs have been observed and compared to PL spectra collected at RT and 10K.
Three-Dimensional Imaging of Extended Defects in 4H-SiC by Two-Photon-Excited Band-Edge Photoluminescence
Authors: Tanuma Ryohei , Tsuchida Hidekazu
Published: July 2015

This paper demonstrates three-dimensional imaging of threading screw dislocations (TSDs) and threading edge dislocations (TEDs) in 4H-SiC using two-photon-excited photoluminescence (2PPL) band-edge emission. Three-dimensional (3D) images of TSDs and TEDs are successfully obtained as dark contrasts on a bright background of band-edge emission. The intensity inversion of a 2PPL 3D image yields a perspective to visually examine the propagation behavior of dislocations. The tilt angles of TEDs are also measured and shown to correlate with the directions of the extra half planes of TEDs.
Influences of Solution Flow and Lateral Temperature Distribution on Surface Morphology in Solution Growth of SiC
Authors: Fujii Kuniharu , Takei Koichi , Aoshima Masahiro , Senguttuvan Nachimuthu , Hiratani Masahiko , Ujihara Toru , Matsumoto Yuji , Kato Tomohisa , Kurashige Kazuhisa , Okumura Hajime
Published: July 2015

The influences of solution flow and lateral temperature distribution on the surface morphology of the 4H-SiC single crystal grown from solution was investigated. A flat surface region was enlarged by the seed-rotation rate. The solution flow simulation indicated that the higher rotation rate made the outward solution flow ordered beneath the solution surface. Such a solution flow was thought to be effective to enlarge the flat region of growth front. Furthermore, a full-flat surface was obtained with a hollow-type graphite rod at a seed-rotation rate of 60 min-1. The simulated results of temperature distribution showed the hollow-type graphite rod reduced the lateral temperature gradient at the SiC-solution interface. The ordered solution flow and the small temperature gradient at the growth front were found to be effective to make the growth front flat in the solution-growth method.
Ab Initio Calculations of Absolute Surface Energies of Clean and Hydrogen Covered 3C-SiC(001), (110) and (111) Surfaces
Authors: Filimonov Sergey N.
Published: July 2015

The absolute surface energies of three major low index surfaces of cubic silicon carbide (3C-SiC) are determined by first-principles density functional theory calculations. Calculations show that among clean 3C-SiC surfaces the Si-terminated 3C-SiC(001)-(3x2) surface has the lowest energy. The second and third lowest energy surfaces are the Si-terminated 3C-SiC(111)-(√3x√3) surface and the nonreconstructed 3C-SiC(110) surface. Hydrogen passivation greatly reduces both the absolute surface energies of the low index 3C-SiC surfaces and the surface energy anisotropy. In particular, the surface energies of fully passivated 3C-SiC(110) and (111) surfaces become indistinguishable at hydrogen-rich deposition conditions.
Starting Point of Step-Bunching Defects on 4H-SiC Si-Face Substrates
Authors: Tamura Kentaro , Sasaki Masayuki , Kudou Chiaki , Yamashita Tamotsu , Sako Hideki , Asamizu Hirokuni , Ito Sachiko , Kojima Kazutoshi , Kitabatake Makoto
Published: July 2015

On 4H-SiC Si-face substrates after H2 etching, the defect with “line” feature parallel to a step as “bunched-step line” was observed. Using X-ray topography and KOH etching, we confirmed that the bunched-step line originated from basal plane dislocation (BPD). Use of the substrate with the lowest BPD density will be effective to reduce bunched-step line that would affect oxide layer reliability on an epitaxial layer. However, more detail investigation needs to classify the BPD that would become a starting point of bunched-step line.
Estimation of Phosphorus-Implanted 4H-SiC Layer Recrystallization by Electron-Back-Scattering Diffraction Pattern Analysis
Authors: Hanafusa Hiroaki , Maruyama Keisuke , Hayashi Shohei , Higashi Seiichiro
Published: July 2015

Image quality (IQ) values of an electron-back-scattering diffraction (EBSD) pattern were used to investigate layer recrystallization for the phosphorus-implanted 4H SiC. We prepared a slope-structured amorphous Si on a Si substrate sample to simulate the recrystallization model of the ion-implanted layer after activation annealing. Phosphorus-implanted and recrystallize-annealed Si and SiC samples were also investigated and the Kikuchi-pattern obscuration was observed for a thicker a-Si layer on the slope-structured sample. The IQ values also decreased. Our results show that ion-implantation damage recovery can be estimated by the EBSD pattern analysis. IQ value variation is in good agreement with the sheet resistance changing with the annealing temperature. The IQ values obtained from the EBSD measurements can be used for crystalline recovery estimation on impurity-implanted SiC layer in a nanoscale resolution.
Shallow and Deep Levels in Al+-Implanted p-Type 4H-SiC Measured by Thermal Admittance Spectroscopy
Authors: Kawahara Koutarou , Watanabe Hiroshi , Miura Naruhisa , Nakata Shuhei , Yamakawa Satoshi
Published: July 2015

Shallow and deep levels in SiC significantly affect dynamic characteristics of SiC devices; larger ionization energy and/or a smaller capture cross-section of levels in the SiC bandgap lead to a larger emission time constant and slower response of carriers. Nevertheless, knowledge about those levels is very limited. In this study, we clarified the ionization energy and the capture cross section of the Al shallow acceptor in 4H-SiC in a wide range of doping concentration by preparing appropriate samples and measuring them by thermal admittance spectroscopy. Furthermore, high densities of deep levels were discovered in Al+-implanted samples, which can degrade 4H-SiC device performance without any care.
Evolution of the Electrical and Structural Properties of Ti/Al/W Contacts to p-Type Implanted 4H-SiC upon Thermal Annealing
Authors: Vivona Marilena , Greco Giuseppe , Lo Nigro Raffaella , Di Franco Salvatore , Giannazzo Filippo , Rascunà Simone , Saggio Mario , Roccaforte Fabrizio
Published: July 2015

The mechanism of Ohmic contacts formation to p-type SiC is a fundamental and technological concern continuously under debate. Typically, Ti/Al-based contacts are a good choice for Ohmic contacts to p-type SiC, even though some aspects strictly related to the specific nature of Al (susceptibility to oxidation, low melting temperature, etc.) remain to be optimized. In this work, the evolution of the electrical properties of a Ti/Al/W multiple-layer contact has been studied by TLM characterization and correlated to the changes in the morphology and microstructure upon thermal annealing. The formation of an Ohmic contact has been observed after a thermal annealing at 1100°C, discussing the possible reasons determining the transition to an Ohmic behavior.
A Study on the Chemistry of Epitaxial Ti3SiC2 Formation on 4H-SiC Using Al-Ti Annealing
Authors: Abi-Tannous Tony , Soueidan Maher , Ferro Gabriel , Lazar Mihai , Toury Berangère , Beaufort Marie France , Barbot Jean François , Penuelas J. , Planson Dominique
Published: July 2015

In order to form Ti3SiC2 on 4H-SiC(0001) 8°-off, 200 nm of Ti30Al70 was deposited onto SiC substrates by magnetron sputtering from pure Ti30Al70 targets. The samples were then annealed at 1000°C for 10 min under Ar atmosphere in a Rapid Thermal Annealing (RTA) furnace. Structural analyses reveal the formation of epitaxial hexagonal Ti3SiC2 (0001) oriented. Elemental analyses show that high amount of Al and O elements are present inside the deposit. Obviously, the formation of Ti3SiC2 is accompanied by parasitic Al oxide, probably due to some unwanted oxygen residual in the RTA chamber. By using proper backing steps before the annealing, the deposit is not anymore composed of only Ti3SiC2 but accompanied with other compounds (Al3Ti, and Al). On the oxide-free sample, the specific contact resistance ρc of the Ti3SiC2 based contact on p-type 4H-SiC (having Na= 2×1019 cm-3) was measured to be as low as 6×10-5 Ω.cm2.
Investigation of Ti/Ni Bilayer Contacts to n-Type 4H-SiC
Authors: Sundaramoorthy Vinoth Kumar , Song Yu Lun , Minamisawa Renato Amaral
Published: July 2015

The analysis of Ti/Ni metal-layer as Ohmic and Schottky contacts to 4H n-SiC (with a doping concentration of ~1E18 cm-3) is reported. Both Ti (10nm/Ni (100nm) contact and Ti (20nm)/Ni (100nm) contact were found to have Ohmic behavior with comparable specific contact resistance (~4.3 to 5.3×10-4 Ωcm2) after annealing at 1100 °C. Ti (10nm)/Ni (100nm) contact annealed at 500 °C and 600 °C was also demonstrated as Schottky contact to 4H n-SiC layers.
Extremely Enhanced Diffusion of Nitrogen in 4H-SiC Observed in Liquid-Nitrogen Immersion Irradiation of Excimer Laser
Authors: Ikeda Akihiro , Marui Daichi , Ikenoue Hiroshi , Asano Tanemasa
Published: July 2015

We report nitrogen (N) doping of 4H-SiC by KrF excimer laser irradiation in liquid N2. In comparison to phosphorus (P) doping performed using phosphoric acid solution, the liquid-N2 immersion-laser doping can introduce N atoms deeper (~ 1 μm depth) into the 4H-SiC, which results in reduction of doped layer resistance by approximately 3 orders of magnitude. Doping is shown to proceed by the thermal diffusion of species, while loss of the host material from the surface by ablation takes place at the same time. Chemical analysis shows that high density carbon (C) vacancies are generated in the N doped region, which suggests enhanced diffusion of N assisted by the presence of C vacancies. pn junction diodes are formed by using the N doping technique. Turn-on voltage is ~ -3V, which is reasonable for a pn junction diode of 4H-SiC.
Influence of Conduction-Type on Thermal Oxidation Rate in SiC(0001) with Various Doping Densities
Authors: Kobayashi Takuma , Suda Jun , Kimoto Tsunenobu
Published: July 2015

It was discovered that the oxidation rate for SiC depended on the conduction type. The oxidation was performed for SiC(0001) with nitrogen doping (n-type) in the range from 2×1016 cm-3 to 1×1019 cm-3, and aluminum doping (p-type) in the range from 2×1015 cm-3 to 1×1019 cm-3, exhibiting a clear dependence. For n-type SiC the oxide thickness increases for higher doping density, and for p-type the thickness decreases. Note that in the case of Si oxidation, there exists very little difference of oxidation rate between the conduction types in such low doping density, and the dependence is peculiar to SiC.
Characterization of Inhomogeneity in SiO2 Films on 4H-SiC Epitaxial Substrate by a Combination of Fourier Transform Infrared Spectroscopy and Cathodoluminescence Spectroscopy
Authors: Yoshikawa Masanobu , Seki Hirohumi , Inoue Keiko , Kobayashi Takuma , Kimoto Tsunenobu
Published: July 2015

We measured Fourier transform infrared (FT-IR) and cathodoluminescence (CL) spectra of SiO2 films with various thicknesses, grown on 4H-SiC substrates. The appearance of broad phonon modes at ~1150–1250 cm-1 in p-polarized light and their disappearance in s-polarized light confirmed that the phonon modes at ~1150–1250 cm-1originated from surface polaritons (SPPs). For the thin SiO2 film (8-nm thick), the peak frequency of the transverse optical (TO) phonon in the SiO2 film on the 4H-SiC substrate was observed at ~1080 cm-1and was higher than that in SiO2 films on the Si substrate (1074 cm-1). This suggested that the thin SiO2 film (8-nm thick) is under compressive stresses at the interface between the SiO2 film and SiC substrate. On the other hand, for the thick SiO2 films (85 and 130-nm thick), the TO phonon peak frequency tended to shift toward lower frequencies with increasing oxide layer thickness. The CL measurement indicated that the CL peak intensity at ~640 nm, attributed to non-bridging oxidation hole centers (NBOHCs), became stronger with increasing oxide layer thickness, relative to that of the CL peaks at ~460 and 490 nm due to oxygen vacancy centers (OVCs). By comparing the FT-IR and CL measurements, we concluded that the TO phonon red-shift with increasing oxide layer thickness can mainly be attributed to an increase in inhomogeneity with increasing oxide layer thickness for the thick SiO2 films.
Growth Study of p-Type 4H-SiC with Using Aluminum and Nitrogen Co-Doping by 2-Zone Heating Sublimation Method
Authors: Eto Kazuma , Kato Tomohisa , Takagi Satoru , Miura Tomonori , Urakami Yasushi , Kondo Hiroyuki , Hirose Fusao , Okumura Hajime
Published: July 2015

p-type SiC crystals doped with aluminum and nitrogen were grown by the sublimation method. We found that Al and N co-doping is effective for stabilized growth of p-type 4H-SiC polytype. We studied the relationship of polytype of grown crystals and the condition of Al and N feeding during the crystal growth. p-type 4H-SiC with p~1 x 1018 cm-3 are stably-obtained with this method.
Influence of Annealing, Oxidation and Doping on Conduction-Band near Interface Traps in 4H-SiC Characterized by Low Temperature Conductance Measurements
Authors: Noll Stefan , Rambach Martin , Grieb Michael , Scholten Dick , Bauer Anton J. , Frey Lothar
Published: July 2015

Current power MOSFET devices on Silicon Carbide show a limited inversion channel mobility, which can be a result of the expected very high density of interface states near the conduction band . In the current work, the effect of the post implantation annealing temperature, the thermal oxidation and the nitrogen doping of the n-epi layer on the density of these interface traps is investigated using capacity-conductance measurements. Instead of the usage of very high frequencies as used in , in this investigation the measurements were performed in liquid nitrogen to decrease the recharging times of the interface traps.Due to the different processing the samples showed a wide spreading of the inversion channel mobility. The conductance measurements show a characteristic peak caused by the conduction band near interface traps especially for the low temperature measurements. But these traps could not be correlated to the mobility. Instead, a correlation to the nitrogen doping of the epi layer could be observed.
High Quality 100 mm 4H-SiC Substrate
Authors: Gao Yu Qiang , Zhang Hong Yan , Song Jian , Song Sheng , Liang Qing Rui , Ning Min , Gao Chao , Wang Xi Jie , Zong Yan Min , Wang Huan Huan , Dudley M.
Published: July 2015

High-quality 100 mm 4H-SiC boules were grown using the physical vapor transport (PVT) method with optimized growth parameters. Micro-Raman spectroscopy measurement shows that the 4H-SiC polytype of the entire wafer is uniform. The micropipe density is measured to be less than 1cm-2. The 1c threading screw dislocation (TSD) density can be suppressed to the magnitude of 102 cm-2. After chemical mechanical polishing (CMP), it is found that the warp of the substrate is less than 10 μm, and the surface roughness (Ra) is as low as 0.063 nm.
An Investigation of Capacitance-Voltage Hysteresis in Al2O3/SiC MIS Capacitors
Authors: Wang Yi Yu , Wang Xiao Lei , Li Cheng Zhan , Wu Jia , Han Lin Chao , Shen Hua Jun , Wang Wen Wu , Liu Xin Yu
Published: July 2015

Charge trapping behavior in Al2O3/SiC MOS structures was investigated by C-V hysteresis measurements in combination with XPS analysis. According to the quadratic fit of C-V hysteresis vs. tox curves, the density of the injected charges in the bulk Al2O3 films are the same under different maximum electric field, while the density of sheet charges increase with the increase of maximum electric field. Thus, a simple sheet charge model has been used to evaluate the actual effect of the electron injection phenomenon. The charge trapping levels can be as high as 1013 cm-2, indicating the importance of C-V hysteresis in Al2O3/SiC structures. All the trapping charges are found to be located at a distance ranging from 3 to 4 nm from the interface. Furthermore, no detectable interface oxide between Al2O3 and SiC has been found through our XPS measurements. We conclude that the origin of charge trapping sites in Al2O3/SiC structures is the native defects in ALD Al2O3 layer and predominantly the border traps in the Al2O3 near the oxide/semiconductor interface.
Elimination of Microtrenching in Trenches in 4H-Silicon Carbide Using Shadow Masking
Authors: Mohammadi Z. , Shah Vishal Ajit , Jennings Michael R. , Fisher Craig A. , Mawby Philip  Andrew
Published: July 2015

Effects of ICP power and pressure on microtrenching, striation, roughness and sidewall angles in SF6 based ICP-RIE etching of SiC have been studied. The results show that ICP RIE etching parameters such as ICP power and pressure can effect both striation and microtrenches and these challenges could be eliminated by optimizing etching parameters.
Planarization of 6-Inch 4H-SiC Wafer Using Catalyst-Referred Etching
Authors: Isohashi Ai , Sano Yasuhisa , Kato Tomohisa , Yamauchi Kazuto
Published: July 2015

Catalyst-referred etching (CARE) is a planarization method based on the chemical etching reaction, which does not need abrasives. In this paper, CARE was applied to the planarization of 6-inch silicon carbide (SiC) wafers, and removal properties were investigated. The etching rate was about 20nm/h, which is almost equal to that of 2-inch SiC wafer (16 nm/h). The rms roughness was reduced along with the removal depth, and step-terrace structure was observed in whole area of the on-axis wafer surface.
Planarization of Epitaxial SiC Trench Structures by Plasma Ion Etching
Authors: Zhang A.Z. , Reshanov Sergey A. , Schöner Adolf , Kaplan Wlodek , Kwietniewski Norbert , Lim Jang Kwon , Bakowski Mietek
Published: July 2015

In this work, we present a planarization concept for epitaxial SiC trench structures involving reactive ion etching (RIE) and inductive coupled plasma (ICP) dry etching. The general idea is to transfer the flat surface from spun-on BCB/photo-resist layers to deposited silicon dioxide and finally to bulk SiC by applying process conditions with the same etch rate for the different materials. In this way several microns of unwanted material can be removed and planar SiC surfaces are obtained. With this method trench structures filled by epitaxial re-growth can be planarized with smooth surfaces and good homogeneity over the wafer. Cost-efficient device manufacturing can be achieved by using standard semiconductor process equipment. This technology makes it possible to manufacture advanced epitaxial SiC material structures for devices such as trench JBS diodes and double-gate trench JFETs.
Chlorine Trifluoride Gas Transport and Etching Rate Distribution in Silicon Carbide Dry Etcher
Authors: Yajima Dairi , Nakagomi Ken , Habuka Hitoshi , Kato Tomohisa
Published: July 2015

A SiC dry etcher using chlorine trifluoride (ClF3) gas was evaluated, particularly about the etching rate distribution. At 100%, the etching rate was high in the center region and was low in the outer region. However, that at 20% showed the opposite profile. This difference was considered to be due to the chlorine trifluoride gas distribution which was built above the gas distributor.
Low Frequency Noise in 4H-SiC Schottky Diodes Under Forward Bias
Authors: Shabunina Eugenia I. , Levinshtein Michael E. , Shmidt Natalia M. , Ivanov Pavel A. , Palmour John W. , Cheng Lin
Published: July 2015

The 1/f noise has been investigated for the first time at 300 and 77 K in high-quality 4H-SiC Schottky diodes. It is shown that, that at 77 K, the dependence of the spectral noise density on current, SI(I), differs fundamentally between the cases of the current flowing through the main part of the diode area with a comparatively high barrier and the current flowing through the nanosized patches with a comparatively low barrier.
Impact of Stacking Fault on the I-V Characteristics of 4H-SiC Schottky Barrier Diode
Authors: Jung Hyun Jin , Yun Seung Bok , Kang In Ho , Moon Jeong Hyun , Kim Won Jeong , Bahng Wook
Published: July 2015

The influence of stacking faults (SFs) and triangular defects (TDs) on the electrical properties of 4H-SiC Schottky barrier diode (SBD) were investigated. The SF types and locations were distinguished and mapped by using room-temperature photoluminescence (PL) and optical microscope. SBDs were fabricated including the location of SF’s and TD’s. The effects of the types of defects and its area portion in the fabricated SBDs were also investigated. Based on the present data, 3C-TD has more harmful effect rather than the other SFs. The fabricated SBDs including SFs showed that increase of area portion of SF’s also resulted increase of specific on resistance of SBDs.
Influence of Trench Structure on Reverse Characteristics of 4H-SiC JBS Diodes
Authors: Konishi Kumiko , Kameshiro Norifumi , Yokoyama Natsuki , Shima Akio , Shimamoto Yasuhiro
Published: July 2015

We fabricated trench Junction Barrier Schottky (JBS) diodes, and investigated the effect on the reduction of leakage current and the device yield. First, by calculating of electric field at the Schottky contact interface (Es), we found that the trench JBS structure can reduce Es one digit smaller than the planar JBS structure, setting 80o < The bevel angle θ < 90o. Then, 600 V / 50 A trench JBS diodes are developed and characterized. The leakage current of a trench JBS diode at 600V is 10-2 times smaller than that of planar JBS diode by effectively reducing Es. This enables to reduce the number of low break down samples and raise the yield compared to the planar JBS structure.
Nitrogen Incorporation during Seeded Sublimation Growth of 4H-SiC and 6H-SiC
Authors: Tsavdaris Nikolaos , Kwasnicki Pawel , Ariyawong Kanaparin , Valle Nathalie , Peyre Hervé , Sarigiannidou Eirini , Juillaguet Sandrine , Chaussende Didier
Published: July 2015

We address the problem of nitrogen incorporation during bulk crystal growth of 4H-SiC and 6H-SiC by seeded sublimation method. The partial pressure of nitrogen and temperature dependence were considered in bulk SiC crystals. Free carrier concentration and incorporated nitrogen were determined using Raman spectroscopy and Secondary Ion Mass Spectrometry, respectively. The incorporated nitrogen at the (000-1) C-face of 4H-SiC and 6H-SiC is found to be independent of the polytype of the crystal. Higher desorption rate at Si-face compared to C-face is found, using a Langmuir equation, which is attributed to the difference in bond density between the two polar faces. The increased nitrogen desorption when growth temperature increases is believed to be the most contributing factor, based on the temperature dependent trends.
The Effect of Proton and Carbon Irradiation on 4H-SiC 1700V MPS Diode Characteristics
Authors: Hazdra Pavel , Sharma Rupendra Kumar , Popelka Stanislav
Published: July 2015

Electronic properties of radiation damage produced in 1700 V 4H-SiC MPS diodes by proton and carbon irradiation were investigated and compared. 4H-SiC epilayers, which formed the lowdoped N-base of MPS power diodes, were irradiated to identical depth with 670 keV protons and 9.6 MeV C4+ ions. Results show that irradiation with both projectiles produces strongly localized damage (deep levels) peaking at ion’s projected range. Compared to protons, heavier carbon ions introduce more defects with deeper levels in the SiC bandgap and more stable damage. Radiation damage act as electron traps and compensates donor doping of the epilayer and decreases electron mobility. Forward voltage drop of irradiated diodes then sharply increases when the peak concentration of introduced acceptor levels donor doping. The effect of both the proton and carbon irradiation can be simulated using a simple model accounting only for one dominant electron trap.
Ion Implanted Lateral p+-i-n+ Diodes on HPSI 4H-SiC
Authors: Nipoti Roberta , Moscatelli Francesco , Roncaglia Alberto , Bonafe Filippo , Mancarella Fulvio , de Nicola Pietro , Nath Anindya , Rao Mulpuri V.
Published: July 2015

Square shaped annular lateral p+–i–n+ diodes on high purity semi-insulating (HPSI) 4H-SiC are fabricated by Al+ and P+ ion implantation to obtain anode and cathode regions, respectively. All the diodes have the same size central anode surrounded by an intrinsic region, which is surrounded by an annular cathode. Anode area and annular cathode width are fixed for all diodes, only the lateral length of the intrinsic region is varied. Post implantation annealing is performed at 1950 °C for 10 min. Static forward and reverse characteristics are measured in the temperature range of 30 - 290 °C. For all diodes, the reverse current is below the instrument detection limit of 10-14 A up to 100 °C at 200 V, the maximum reverse bias employed in this study. The reverse current increased up to low 108 A for 200 V reverse bias at 290 °C. Forward currents overlap at the low voltage region once they exceed the instrument detection limit at ~1.6 V and 30 °C. The forward currents follow almost identical exponential trend at all measured temperatures while the diode series resistance increase with increasing anode-cathode distance and decreased with increasing temperature for the given intrinsic region lateral length.
Temperature Dependence of Minority Carrier Lifetime in Epitaxially Grown p+-p–-n+ 4H-SiC Drift Step Recovery Diodes
Authors: Afanasyev Alexey V. , Ivanov Boris V. , Ilyin Vladimir A. , Kardo-Sysoev Alexey F. , Luchinin Victor V. , Reshanov Sergey A. , Schöner Adolf , Smirnov A.A.
Published: July 2015

In this paper we report on the effect of temperature and injection level on the effective lifetime of non-equilibrium charge carriers in p-base of 4H-SiC PiN diodes. Studies were carried out on 1kV drift step recovery diodes (DSRDs) with p+-p--n+. The lifetime of non-equilibrium charge carriers in 4H-SiC p+-p--n+ structures increases by an average of 6 times from 250ns to 1.4μs with the increase of the samples temperature from 300K to 673K. However, increase of the injection level in the drift region from 2.3·1016cm-3 to 5.9·1016cm-3 does not affect the lifetime indicating that Shockley-Read-Hall recombination processes are dominating.
4H-Silicon Carbide p-n Diode for High Temperature (600 °C) Environment Applications
Authors: Shao Shi Qian , Lien Wei Cheng , Maralani Ayden , Cheng Jim C. , Dorsey Kristen L. , Pisano Albert P.
Published: July 2015

In this work, we demonstrate the stable operation of 4H-silicon carbide (SiC) p-n diodes at temperature up to 600 °C. In-depth study methods of simulation, fabrication and characterization of the 4H-SiC p-n diode are developed. The simulation results indicate that the turn-on voltage of the 4H-SiC p-n diode changes from 2.7 V to 1.45 V as the temperature increases from 17 °C to 600 °C. The turn-on voltages of the fabricated 4H-SiC p-n diode decreases from 2.6 V to 1.3 V when temperature changes from 17 °C to 600 °C. The experimental I-V curves of the 4H-SiC p-n diode from 17 °C to 600 °C agree with the simulation ones. The demonstration of the stable operation of the 4H-SiC p-n diodes at high temperature up to 600 °C brings great potentials for 4H-SiC devices and circuits working in harsh environment electronic and sensing applications.
Observation and Analysis of a Non-Uniform Avalanche Phenomenon in 4H-SiC 4°-Off (0001) p-n Diodes Terminated with a Floating-Field Ring
Authors: Mochizuki Kazuhiro , Okino Hiroyuki , Matsushima Hiroyuki , Toyota Yoshiaki
Published: July 2015

4H-SiC (0001) p-n diodes terminated with a floating-field ring were found to emit light at breakdown in the opposite direction to that of substrate misorientation when the diodes were fabricated by aluminum implantation and dry-oxidation passivation. Two-dimensional simulation revealed that such non-uniform breakdown was mainly attributable to the asymmetric lateral straggling of implanted aluminum acceptors, rather than the anisotropic nature of the impact ionization coefficient.
Characterization of 4H-SiC pn Structures with Unstable Excess Current
Authors: Strel'chuk Anatoly M. , Yakimov Eugene B. , Lavrent’ev Alexander A. , Kalinina Evgenia V. , Lebedev Alexander A.
Published: July 2015

4H-SiC p+nn+ structures fabricated by implantation of Al into a commercial n-type 4H-SiC epitaxial layer doped to (3-5)1015cm-3 have been studied. Structures with unstable excess forward current were characterized by electron beam induced current (EBIC) and secondary electron (SE) methods and by Auger-electron spectroscopy (AES). Numerous defects were found with a depth which exceed the thickness of the p+-layer. Also, it was demonstrated that the concentration of carbon on the SiC surface always exceeds that of silicon, which may be the reason for the initially unstable conductivity via the defects.
Proton and Electron Irradiation in Oxynitrided Gate 4H-SiC MOSFET: A Recent Open Issue
Authors: Florentin Matthieu , Alexandru Mihaela , Constant Aurore , Michel Philippe , Montserrat Josep , Millan José , Godignon Philippe
Published: July 2015

Long-term degradation of MOS devices has to be avoided in different harsh irradiated environments, especially for aerospace or military applications. In this paper, an overview of the irradiation experiments recently performed on 4H-SiC MOSFETs having an oxynitrided gate oxide is given, with a special focus on the threshold voltage and the effective channel mobility drifts. The general mechanisms taking place during irradiation and post-annealing treatments are described. Finally, new open issues recently observed by performing the temperature measurement on irradiated MOSFETs will be introduced and discussed.
Bias-Temperature-Stress Response of Commercially-Available SiC Power MOSFETs
Authors: Green Ronald , Lelis Aivars J. , El Mooro , Habersat Daniel B.
Published: July 2015

The stability of the threshold voltage of commercial SiC MOSFETs from two device manufactures has been evaluated and compared when subject to positive and negative bias-temperature-stress conditions. For both device groupings, the worse-case stress occurred under negative bias temperature conditions with VGS = –15 V and a stress temperature of 200 °C. Devices in the Vendor A grouping exhibited acceleration in their bias-temperature-stress response that occurred earlier in time as a strong function of stress-temperature and to a lesser degree on gate-bias magnitude. Devices in the Vendor B grouping showed some evidence of acceleration, but only for the worse-case stress condition. Threshold voltage shifts for this device group were very low and extremely stable, with recorded values below 0.4 V for most conditions.
Degradation and Reliability of Bare Dies Operated up to 300°C
Authors: Hamilton Dean , Jennings M. , York Stephen , Hindmarsh Steven A. , Sharma Y. , Fisher C. , Mawby P.
Published: July 2015

In this paper, we demonstrate the degradation of commercially available 1.2kV SiC MOSFET bare dies subjected to long periods of isothermal heating at 300°C in air. Periodic electrical measurements indicated an increase in on-state resistance to different extents for three different vendor designs, and the discovery of a progressive rectifying type forward characteristic at low drain-source voltages. Subsequent investigations to determine the cause of the degraded electrical characteristics including sectioning and SEM/TEM analysis revealed some mechanical degradation within the device gate-source cross-sections and backside drain contact metal layers. While one vendor device was severely degraded after approximately 24 hours of heating, another vendor device was only just beginning to degrade after 100 hours, indicating that these devices may be used successfully in real applications at 300°C junction temperatures for relatively long periods.
Channel Mobility Improvement in 4H-SiC MOSFETs Using a Combination of Surface Counter-Doping and NO Annealing
Authors: Ahyi Ayayi Claude , Modic Aaron , Jiao C. , Zheng Y. , Liu Gang , Feldman L.C. , Dhar Sarit
Published: July 2015

Lateral MOSFET devices with a thin surface counter-doped layer using Sb and As with and without NO passivation have been fabricated and characterized. The results demonstrate that Sb and As counter-dope the interface without significant trap passivation while in combination with NO there is a superposition of both trap passivation and counter-doping related performance enhancement. In addition, by varying the counter doping level, a universal mobility characteristics of NO passivated devices has been identified.
Simulating the Influence of Mobile Ionic Oxide Charge on SiC MOS Bias-Temperature Instability Measurements
Authors: Habersat Daniel B. , Goldsman Neil , Lelis Aivars J.
Published: July 2015

We report here on results obtained using a time-dependent drift-diffusion model to simulate ion transport in the gate oxide of a SiC MOS device during bias-temperature instability measurements to assess the impact on threshold voltage under typical testing conditions. Measured threshold voltage is found to depend strongly on the temperature and mobile ion species, which in combination with the measurement parameters determine how the ions react to the stress and measurement sequence. Simulations show that, based on their mobilities, both potassium-like and copper-like ions may be responsible for experimental observations of a negative trend in threshold instability above 100 °C for SiC MOS devices.
Recovery of the Electrical Characteristics of SiC MOSFETs Irradiated with Gamma-Rays by Thermal Treatments
Authors: Yokoseki Takashi , Abe Hiroshi , Makino Takahiro , Onoda Shinobu , Tanaka Yuki , Kandori Mikio , Yoshie Toru , Hijikata Yasuto , Ohshima Takeshi
Published: July 2015

Effects of gamma-ray irradiation and subsequent thermal annealing on the characteristics of vertical structure power Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) fabricated on 4H-SiC were studied. After irradiation at 1.2 MGy, the drain current – gate voltage curves of the MOSFETs shifted to the negative voltage side and the leakage drain current at inverse voltage increased. No significant change in the degraded electrical characteristics of SiC MOSFETs was observed by room temperature annealing. The degraded characteristics of SiC MOSFETs began to recover by annealing above 120 °C, and their characteristics reached almost the initial ones by annealing at 360 °C.
Study of Mobility Limiting Mechanisms in (11-20) 4H-SiC NO Annealed MOSFETs
Authors: Yamamoto Kensaku , Chowdhury Sauvik , Chow T. Paul
Published: July 2015

NO annealed Lateral (11-20) MOSFETs were fabricated and mobility limiting mechanisms were investigated by MOS-gated Hall measurements, impedance analysis of MOS capacitor and so on. We have clarified that about 1×1012 cm-2 of inversion electrons are trapped at the interface and mobility is largely limited by Coulombic scattering. We attribute that the Coulombic scattering is caused by electrons trapped at interface states and positive fixed charges, which might be due to donor-like states.
Study of Geometrical Effects in Charge Pumping Current for Lateral SiC nMOSFETs Electrical Characterization
Authors: Florentin Matthieu , Rafi Joan Marc , Chevalier Florian , Soler Victor , Konczewicz Leszek , Contreras Sylvie , Juillaguet Sandrine , Montserrat Josep , Godignon Philippe
Published: July 2015

In this work, a charge pumping characterization has been carried out on 4H-SiC nMOSFETs built with different SiC doping processes. Because charge pumping (CP) measurements on SiC are complex to implement, three different CP methods have been used for Dit characterization. The impact of geometrical and electrical parameters on each method is studied. Finally, it is detailed the full measurement flow chosen for a deeper and more accurate understanding of Dit electrical characterization.
Polarity Inversion of SiC(0001) during the Al Doped PVT Growth
Authors: Eto Kazuma , Miura Tomonori , Kato Tomohisa , Okumura Hajime
Published: July 2015

We found that the polarity of the 4H-SiC is reversed from Si-face to C-face by high Al doping during the physical vapor transport (PVT) growth. KOH etching and deep ultraviolet (DUV) Raman spectroscopy were used to confirm the polarity of the grown crystals. The results show the polarity inversion is occurred in the samples grown on Si-face SiC with using Al doped SiC source material.
Characterization of Interface State Density from Subthreshold Slope of MOSFETs at Low Temperatures (≥ 10 K)
Authors: Yoshioka Hironori , Senzaki Junji , Shimozato Atsushi , Tanaka Yasunori , Okumura Hajime
Published: July 2015

We have evaluated interface state density (DIT) for EC−ET > 0.00 eV from the subthreshold slope deterioration of MOSFETs at low temperatures. We have compared two n-channel MOSFETs on the C- and a-faces with the gate oxide formed by pyrogenic oxidation followed by annealing in H2. The peak field-effect mobility (µFE,peak) for the C-face MOSFET was 57 cm2V-1s-1 at 300 K, which is lower than the half of 135 cm2V-1s-1 for the a-face MOSFET. We have shown that DIT very close to EC can well explain why µFE for C-face MOSFETs is lower than that for a-face MOSFETs. The value of DIT at 0.00 eV corresponding to the subthreshold slope at 11 K was 1.6×1014 cm-2eV-1 for the C-face MOSFET, which is more than the double of 6.4×1013 cm-2eV-1 for the a-face MOSFET.
High-Mobility SiC MOSFETs with Chemically Modified Interfaces
Authors: Lichtenwalner Daniel J. , Cheng Lin , Dhar Sarit , Agarwal Anant K. , Allen Scott , Palmour John W.
Published: July 2015

Alkali (Rb, Cs) and alkaline earth elements (Sr, Ba) provide SiO2/SiC interface conditions suitable for obtaining high metal-oxide-semiconductor field-effect-transistor (MOSFET) channel mobility on the 4H-SiC Si-face (0001), without the standard nitric oxide (NO) anneal. The alkali elements Rb and Cs result in field-effect mobility (μFE) values >25 cm2/V.s, and the alkaline earth elements Sr and Ba resulted in higher μFE values of 40 and 85 cm2/V.s, respectively. The Ba-modified MOSFETs show a slight decrease in mobility with heating to 150 °C, as expected when mobility is not interface-trap-limited, but phonon-scattering-limited. The interface state density is lower than that obtained with nitric oxide (NO) passivation. Devices with a Ba interface layer maintain stable mobility and threshold voltage under ±2 MV/cm gate bias stress at 175 °C, indicating no mobile ions.
CIMOSFET: A New MOSFET on SiC with a Superior Ron·Qgd Figure of Merit
Authors: Zhang Qing Chun Jon , Duc Jennifer , Hull Brett , Young Jonathan , Ryu Sei Hyung , Allen Scott , Palmour John W.
Published: July 2015

A new MOSFET structure named the CIMOSFET (Central Implant MOSFET) has been presented and experimentally confirmed on SiC. The novelty of the CIMOSFET lies in a p-type implant introduced in the middle of the JFET area to shield the oxide interface field from the drain bias. Compared to the commercially available 1200 V SiC DMOSFET, this new concept has significantly reduced the on-resistance (Ron) and gate-drain capacitance (Cgd) simultaneously, produced a record low Ron·Qgd Figure of Merit of 455 mΩ·nC at 25°C, and 700 mΩ·nC at 150°C (~30% of the best data found). Only a 55% increase in Ron from 25°C to 150°C has been achieved due to the highly doped drift layer used on the CIMOSFET. Inductive load switching measurements have shown the CIMOSFET exhibits a fast switching performance. The CIMOSFET blocks 1600 V even though its drift doping is higher than that of the conventional DMOSFETs.
Cryogenic Characterization of Commercial SiC Power MOSFETs
Authors: Chen Han , Gammon Peter Michael , Shah Vishal A. , Fisher C.A. , Chan Chun W. , Jahdi Saeed , Hamilton D.P. , Jennings Michael R. , Myronov Maksym , Leadley David R. , Mawby Philip  Andrew
Published: July 2015

The cryogenic performance of two commercially available SiC power MOSFETs are presented in this work. The devices are characterised in static and dynamic tests at 10 K intervals from 20-320 K. Static current-voltage characterisation indicates that at low temperatures threshold voltage, turn-on voltage, on-state resistance, transconductance, and the body diode turn-on voltage all increase while saturation current decreases. Dynamic, 60 V, 3A switching tests within the cryogenic chamber are also reported and the trends of switching speed, losses, and total power losses, which rise at low temperature, are presented. Overall, both MOSFETs are fully operable down to 30 K with both positive and negative changes in behaviour.