bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Ray Tracing Simulations for Direct Determination of Burgers Vectors of Threading Mixed Dislocations in 4H-SiC c-Plane Wafers Grown by PVT Method
Authors: Guo Jian Qiu , Yang Yu , Wu Fang Zhen , Sumakeris Joseph J. , Leonard R.T. , Goue Ouloide , Raghothamachar Balaji , Dudley Michael
Published: May 2016

The presence of threading mixed dislocations (TMDs) (with both edge and screw component) in 4H-SiC crystals grown by PVT method has been reported both from axial slices (wafers cut parallel to the growth axis) and commercial offcut wafers (cut almost perpendicular to the growth axis). In this paper, a systematic method is developed and demonstrated to unambiguously determine the Burgers vectors of TMDs in 4H-SiC commercial offcut wafers using both Synchrotron Monochromatic X-ray Topography (SMBXT) and Ray Tracing Simulations. The principle of this method is that the contrast of dislocations on different reflections varies with the relative orientation of Burgers vectors with respect to the diffraction vectors. Measurements confirm that in commercial offcut wafers the majority of the threading dislocations with screw component are mixed type dislocations.
4H-SiC(0001) Surface Faceting during Interaction with Liquid Si
Authors: Soulière Véronique , Carole Davy , Camarda Massimo , Woerle Judith , Grossner Ulrike , Dezellus Olivier , Ferro Gabriel
Published: May 2016

The aim of this study was to find conditions allowing the "natural" formation of a regular and controllable step bunched morphology on a 4H-SiC seed without the need of any SiC deposition. This was performed by melting a bulk piece of Si on a 4°off 4H seed in the temperature range of 1500 - 1600°C, for 15 min. After etching the remaining Si, the 4H surface was found to be successfully highly step bunched with steps very parallel and regular. A mechanism of dissolution-precipitation was proposed, which could occur both on a short (step to step) and long (centre to periphery) range. This process is kinetically limited at low temperature (1500-1550°C) and considered to be close to the equilibrium at 1600°C.
Design of Silicon Carbide Devices to Minimize the Impact of Variation of Epitaxial Parameters
Authors: Radhakrishnan Rahul , Witt Tony , Lee Seungchul , Woodin Richard
Published: May 2016

Optimized design of Silicon Carbide (SiC) power devices depends, besides power device physics, also on consideration of basic properties and technological readiness of the material. This paper presents a novel analysis of the dependence of variation of epitaxial doping and thickness on the determination of the optimum design point of SiC devices. We introduce electric field at epitaxy-substrate interface as a useful parameter in controlling the dependence of device parameters on epitaxy. Using this method as criterion for design can improve the robustness of SiC devices to epitaxial variation and hence the process yield.
Trials of Solution Growth of Dislocation-Free 4H-SiC Bulk Crystals
Authors: Danno Katsunori , Yamaguchi Satoshi , Kimoto Hiroyuki , Sato Kazuaki , Bessho Takeshi
Published: May 2016

Solution growth of high-quality 4H-SiC bulk crystals has been performed by using Si-Cr based melt at 2000°C. Through enlargement of crystal diameter which is controlled by meniscus height during growth, dislocation free area has been successfully obtained on the periphery of the crystal. However, the threading dislocations in the seed crystal have penetrated into the grown crystal and have been located around the center of the crystal. To reduce dislocation density in the grown crystals, we have used threading-dislocation-free seedcrystals prepared by solution growth on (1-100). The solution growth on the seed crystal sliced from the (1-100) crystal has resulted in very low dislocation density of grown crystals. In an area of 16 mm2 for the growth surface, no dislocation has been detected.
Hydrogen Flux Influence on Homo-Epitaxial 4H-SiC Doping Concentration Profile for High Power Application
Authors: Anzalone Ruggero , Salanitri Marco , Lorenti Simona , Campione Alberto , Piluso Nicolo , La Via Francesco , Fiorenza Patrick , Marcellino Cinzia M. , Arena Giuseppe , Coffa Salvo
Published: May 2016

Doping incorporation and good uniformity along the wafer it is a mandatory for application in high voltage electronic devices. In this work the effect of the Hydrogen (H) flux position inside the reaction chamber on homo-epitaxial 4H-SiC growth process has been studied. Capacitance-Voltage and FT-IR analyses show as the different position of the gas injector affect the doping and thickness uniformity and profile. On the other hand, By Candela and AFM analyses no morphological or surface influence by Hydrogen flux position has been observed.
Optimization of VLS Growth Process for 4H-SiC P/N Junctions
Authors: Sejil Selsabil , Lazar Mihai , Cayrel Frédéric , Carole Davy , Brylinski Christian , Planson Dominique , Ferro Gabriel , Raynaud Christophe
Published: May 2016

P/N junctions have been fabricated with N+ commercial 4H-SiC substrate on which Vapor-Liquid-Solid (VLS) selective epitaxy was used to create a localized p-type doping. The influence of the carrier gas nature (argon or hydrogen) has been investigated in terms of quality of the growth morphology, deposit thickness and electrical behavior of the P/N junction. Distinct results have been observed with a clear improvement when using VLS selective epitaxy under hydrogen.
Study of Ehrlich-Schwoebel Barrier in 4H-SiC Epitaxial Growths by Molecular Statics Method
Authors: Guo Hui Jun , Huang Wei , Peng Jun , Zhou Ren Wei , Liu Xue Chao , Zheng Yan Qing , Shi Er Wei
Published: May 2016

A molecular statics method has been used to examine the Ehrlich-Schwoebel (ES) barrier for an adatom of 4H-SiC to diffuse from the {0001} to the {11-20} facet. As the calculated results shown, for the C-terminated surface, the inverse ES barrier exist for the silicon adatom, which could cause the step bunching; for the Si-terminated surface, ES barrier exist for the carbon adatom, which could cause the step meandering and result in the transition of step-flow growth to 2D-nucleation growth. Simultaneously, the C-terminated surface is more stable than the Si-terminated surface, which may be one reason that the quality of film grown on the carbon facet substrate is better.
Study of In-Plane Orientation of Epitaxial Si Films Grown on 6H-SiC(0001)
Authors: Li Lian Bi , Chen Zhi Ming
Published: May 2016

The Si/SiC heterojunctions were prepared on 6H-SiC(0001) by low-pressure chemical vapour deposition at 900°C. X-ray diffraction was employed to investigate the in-plane orientation of Si/SiC heterojunctions. A FCC-on-HCP parallel epitaxy was achieved for the Si(111)/SiC(0001) heterostructure with a growth temperature of 900°C and the in-plane orientation relationship was [01-1]Si//[11-20]6H-SiC. Based on the in-plane orientation characterizations, the lattice-structure model of the Si/6H-SiC heterostructure was constructed. It is shown that when the in-plane orientation was (111)[01-1]Si//(0001)[11-20]6H-SiC, the Si/6H-SiC interface had a 4:5 Si-to-SiC matching mode with a residual lattice-mismatch of 0.26%, and the misfit dislocation density at the Si/SiC interface was calculated as 0.487×1014cm-2.
Study of Triangle-Shaped Defects on Nearly On-Axis 4H-SiC Substrates
Authors: Zhou Ren Wei , Liu Xue Chao , Guo Hui Jun , Kong Hai Kuan , Shi Er Wei
Published: May 2016

Triangle-shaped defects are one of the most common surface defects on epitaxial growth of 4H-SiC epilayer on nearly on-axis SiC substrate. In this paper, we investigate the feature and structure of such defects using Nomarski optical microscopy (NOM), micro-Raman spectroscopy and high resolution transmission electron microscopy (HR-TEM). It is found that triangle-shaped defects were composed of a thick 3C-SiC polytype, as well as 4H-SiC epilayer.
The Relationship between Surface Pits Density and Growth Parameters during the Epitaxial Growth of 4H-SiC
Authors: Chen Wei Yu , Ho Han Chieh , Yang Po Fei , Hsia Liang Choo
Published: May 2016

In this study, different parameters of 4H-SiC epitaxial growth were used to investigate the influence on surface pits density. It was found that the density of surface pits can be reduced significantly at lower C/Si ratio condition but doping uniformity became worse simultaneously. The background doping was higher than 2E15 cm-3 when C/Si ratio was lower than 1.0. Influences of growth temperature and growth rate are also discussed. The lower surface pits density 4H-SiC epilayer with good uniformity (s/mean below 2%) can be realized during optimal condition.
Developing Technologies of SiC Gas Source Growth Method
Authors: Kojima Jun , Tokuda Yuichiro , Makino Emi , Sugiyama Naohiro , Hoshino Norihiro , Kamata Isaho , Tsuchida Hidekazu
Published: May 2016

In order to diffuse the use of SiC, mass-production technologies of SiC wafers are needed. It is easy to be understood that high-speed and long-sized growth technologies are connected directly with mass-production technologies. The gas source growth method such as HT-CVD has the possibilities and the potential of the high-speed and long-sized growth. In this article, it was clarified that the high growth rate were achieved by the control of the source gas partial pressures and by the gas boundary layers. The average growth rate was 1mm/h on the f4 inch-diameter crystal, and the maximum growth rate reached 3.6 mm/h on the 12.5x25 mm tetragon by the above gas control. The crystal qualities of the gas source methods were also evaluated the equivalent level in comparison with the sublimation method. Concerning the 1mm/h-growth f3 inch crystal, the densities of TSDs were kept in the 102 cm-2 levels from the seed to the upper-side of the ingot. Moreover, the ingot size increased year by year and a f4 inch x 43 mm sized ingot has been developed.
Mitigation of BPD by Pre-Epigrowth High Temperature Substrate Annealing
Authors: Mahadik Nadeemullah A. , Stahlbush Robert E. , Imhoff Eugene A. , Tadjer M.J. , Ruland G.E. , Affouda C.A.
Published: May 2016

Basal Plane Dislocations (BPD) intersecting the SiC substrate surface were converted to threading edge dislocations (TED) by high temperature annealing of the substrates in the temperature range of 1750 °C – 1950 °C. Successively, epitaxial growth on annealed as well as non-annealed samples was performed, concurrently, to investigate the effect of the substrate annealing on BPD mitigation in the epilayers. For the 1950 °C/10min anneal, a 3x reduction in BPD density was observed. Additionally, surface roughness measured using atomic force microscopy revealed no degradation in surface morphology of the grown epilayers after annealing.
Determination of 4H-SiC Ionization Rates Using OBIC Based on Two-Photon Absorption
Authors: Hamad Hassan , Raynaud Christophe , Bevilacqua Pascal , Scharnholz Sigo , Vergne Bertrand , Planson Dominique
Published: May 2016

Optical Beam Induced Current (OBIC) measurements are performed on 4H-SiC avalanche diodes with a very thin and a highly doped active region. A pulsed green laser, with a wavelength of 532 nm, illuminates a reverse biased diode leading to generate electron-hole pairs in the space charge region. Comparison between the 4H-SiC bandgap and the incident photon energy shows that single photon absorption process can be neglected and two-photon absorption process dominates in this case. Ionization rates are then extracted from multiplication curve in a high electric field range (3 to 5 MV.cm–1). Results are in good agreement with previous ones obtained on the same diodes using single photon absorption process.
Electrical Transport Properties of Highly Aluminum Doped p-Type 4H-SiC
Authors: Contreras Sylvie , Konczewicz Leszek , Kwasnicki Pawel , Arvinte Roxana , Peyre Hervé , Chassagne Thierry , Zielinski Marcin , Kayambaki Maria , Juillaguet Sandrine , Zekentes Konstantinos
Published: May 2016

In the range 80 K-900 K, we have investigated the electrical properties of heavily aluminum in-situ doped, 4H-SiC samples. The temperature dependence of the hole concentration and Hall mobility was analyzed in the model taking into account heavy and light holes. The modelisation parameters were compared with experimental values of Secondary Ion Mass Spectroscopy (SIMS) and Capacitance-Voltage (CV) measurements.
Density-Functional Calculation of Carbon-Interstitial Energies in a 4H-SiC(0001)-SiO2 Interface
Authors: Lehmann Jörg
Published: May 2016

An atomistic model for an abrupt 4H-SiC(0001)-SiO2 interface is constructed. By means of density-functional calculations within the local-density approximation, the energy landscape of a carbon interstitial in this structure is investigated and estimates for the diffusion barriers within bulk SiC and the energy difference between interstitial positions in the bulk semiconductor and the amorphous oxide are extracted both for the neutral defect and two charge states. The electronic structure of the neutral defect in its energetically most favorable position is analyzed by means of a hybrid exchange-functional calculation.
Mapping the Strain State of 3C-SiC/Si (001) Suspended Structures Using μ-XRD
Authors: Colston Gerard , Rhead Stephen D. , Shah Vishal A. , Newell Oliver J. , Dolbnya Igor P. , Leadley David R. , Myronov Maksym
Published: May 2016

The residual strain has been mapped across suspended 3C-SiC membranes and wires using synchrotron based micro X-ray diffraction (μ-XRD). Residual tensile strain is observed to relax slightly upon suspension in both sets of structures. Similar maps were acquired by calculating the residual strain from the shift in 3C-SiC Raman peaks. Comparable trends in strain relaxation are observed by both methods, although the sensitivity of μ-XRD is higher using our measurement conditions. While Raman shift provides a fast and convenient method for mapping strain variations, it cannot give direct measurements of the lattice parameters that can be achieved with μ-XRD, making these techniques excellent complimentary methods of mapping residual strain in 3C-SiC.
Heteropolytypic Superlattices
Authors: Pezoldt Joerg
Published: May 2016

Based on a Kronig-Penney model the electronic properties of heteropolytypic superlattices consisting of lamellas of 3C-and 4H-SiC polytypes with thicknesses below ten nanometers are analysed. Due to the large difference in the electron negativity and the resulting high barriers between the different polytypic lamellas an increased number of minizones compared to other materials are formed. The field strength for the appearance of the negative differential resistance in the heteropolytypic superlattice is lower than the critical fields in the silicon carbide polytypes.
High Temperature Variable Range Hopping in Heavy Al Implanted 4H-SiC
Authors: Parisini Antonella , Parisini Andrea , Gorni Marco , Nipoti Roberta
Published: May 2016

In this work, we confirm and extend the results of a previous study where a variable range hopping transport through localized impurity states has been found to dominate the electrical transport properties of 3×1020 cm-3 and 5×1020 cm-3 Al+ implanted 4H-SiC layers after 1950-2000 °C post implantation annealing. In this study, samples with longer annealing times have been taken into account. The temperature dependence of these sample conductivity follows a variable range hopping law, consistent with a nearly two-dimensional hopping transport of non-interacting carriers that in the highest doped samples, persists up to around room temperature. This result indicates that the hole transport becomes strongly anisotropic on increasing the doping level. At the origin of this unusual electrical behavior, may be the presence of basal plane stacking faults, actually observed by transmission electron microscopy in one of the 5×1020 cm-3 samples
Engineering Single Defects in Silicon Carbide Bulk, Nanostructures and Devices
Authors: Lohrmann Alexander , Johnson B.C. , Almutairi A.F.M. , Lau D.W.M. , Negri Marco , Bosi Matteo , Gibson B.C. , McCallum J.C. , Gali Ádám , Ohshima Takeshi , Castelletto Stefania
Published: May 2016

We will review recent demonstrations of single photon emission in different silicon carbide (SiC) polytypes, in both bulk and nano-structured form. Due to well established doping, and micro- and nanofabrication procedures deep defects photoluminescence (PL) can be electrically excited and incorporated in SiC nanomaterials. Finally we will report on preliminary results to incorporate near infrared defects in SiC nanoparticles.
ESR Study on Hydrogen Passivation of Intrinsic Defects in p-Type and Semi-Insulating 4H-SiC
Authors: Murakami Kohki , Tanai Soki , Okuda Takafumi , Suda Jun , Kimoto Tsunenobu , Umeda Takahide
Published: May 2016

We studied the hydrogen passivation/depassivation of four types of intrinsic defects (EI5/6, HEI7/8, HEI9/10, and P6/7) in p-type and semi-insulating 4H-SiC by means of electron spin resonance (ESR) for examining the origin of career-lifetime-killing defects. We suggest that the HEI7/8 and P6/7 centers are the strongest candidate for the origin of the lifetime-killing defects.
Recombination Processes in 4H-SiC pn Structures
Authors: Strel'chuk Anatoly M. , Berenguier Baptiste , Yakimov Eugene B. , Ottaviani Laurent
Published: May 2016

Commercial 4H-SiC p+n structures with an uncompensated donor concentration (Nd-Na) of ~1.5∙1015 cm-3 in the n-type epitaxial layer are studied. The measurement of the photocurrent, electron beam induced current and transient switching characteristics (from forward to reverse voltage), altogether showed that the value of the hole diffusion length, about 2 μm at room temperature, increases to at least 7 μm at 620 K.
Surface Voltage and μPCD Mapping of Defect in Epitaxial SiC
Authors: Wilson Marshall , Savtchouk Alexandre , Findlay Andrew , Lagowski Jacek , Edelman Piotr , Marinskiy Dmitriy , D’Amico John , Korsos Ferenc , Orsos Norbert , Varga Mariann Csegazine
Published: May 2016

Kelvin-probe surface voltage mapping, SVM, on epitaxial SiC, charged with corona into deep depletion, reveals SV defects manifested as spots with decreased surface voltage. For 150μm thick epi-layer, SV defects coincide with low carrier lifetime spots revealed by microwave detected photoconductance decay, μPCD. In the photoluminescence image, these defects are seen as triangular dark spots, described in literature as stacking-fault related triangular defects. For thin epi-layers (2.2μm), defects are visible only in SVM. In this case, high resolution SVM performed with Kelvin Force Microscopy identifies a triangular defect shape. Two mechanisms are proposed, accounting for SV defects. For high intensity defects exhibiting large magnitude fast decreasing voltage, the probable mechanism is defect related leakage; causing neutralization of corona surface ions. Low intensity defects can be explained considering deep level emission. The latter mechanism has been investigated using SV transient and spectral analysis analogous to isothermal DLTS and Laplace DLTS.
Thermal Stability of Deep-Level Defects in High-Purity Semi-Insulating 4H-SiC Substrate Studied by Admittance Spectroscopy
Authors: Iwamoto Naoya , Azarov Alexander , Ohshima Takeshi , Moe Anne Marie Mardal , Svensson Bengt Gunnar
Published: May 2016

Effects of high temperature treatments on the deep-level defects in high-purity semi-insulating substrates are studied by employing electrical and chemical analyses. Thermal admittance spectroscopy reveals the presence of a deep-level defect, labeled XMID, with a state near the middle of the bandgap, playing a decisive role to realize the semi-insulating characteristics. The concentration of the XMID level decreases with increasing treatment temperature from 1400 to 1700 °C, and consequently, the substrate becomes more conductive toward p-type due to residual boron impurities. The identity of XMID is yet to be known but the carbon vacancy is briefly discussed as a possible candidate.
Three-Dimensional Imaging of Extended Defects in 4H-SiC
Authors: Tanuma Ryohei , Nagano Masahiro , Kamata Isaho , Tsuchida Hidekazu
Published: May 2016

This paper describes 3D imaging of extended defects in 4H-SiC using optical second-harmonic generation (SHG) and two-photon-exited photoluminescence (2PPL). SHG selectively yields the 3D images of 3C-inclusions in a 4H-SiC epilayer, while 2PPL provides 3D images of 3C-inclusions, 8H stacking faults and single Shockley stacking faults. 2PPL band-edge emission visualizes dislocation lines of threading screw dislocations and threading edge dislocations, the tilt angles of which are evaluated.
Effects of Basal Plane Dislocation Density in 4H-SiC Substrate on Degradation of Body-Diode Forward Voltage
Authors: Kawabata Naoyuki , Tanaka Atsushi , Tsujimura Masatoshi , Ueji Yoshinori , Omote Kazuhiko , Yamaguchi Hirotaka , Matsuhata Hirofumi , Fukuda Kenji
Published: May 2016

We investigated the effect of the basal plane dislocation (BPD) density in 4H-silicon carbide (SiC) substrates on the forward voltage (Vsd) degradation of body-diodes. Using reflection X-ray topography, the BPD density was automatically estimated from the substrates prior to fabrication of metal–oxide–semiconductor field-effect transistors (MOSFETs). A strong positive correlation was found between the Vsd shift, which was calculated from the difference before and after forward bias stress at 160 A/cm2 for ~500 hours, and the BPD density of the substrate. We show that it is possible to predict Vsd shifts from the BPD densities of SiC substrates prior to the fabrication of MOSFETs. In addition, we examined the origin of stacking faults (SFs) as a result of the application of forward bias stress. We presume that SFs are formed by BPDs converted to threading edge dislocations at the epi/sub interface, as well as by BPDs penetrating into the epitaxial layer.
Dislocation Characterization in 4H-SiC Crystals
Authors: Sumakeris Joseph J. , Leonard R.T. , Deyneka Eugene , Khlebnikov Yuri , Powell Adrian R. , Seaman Jeff , Paisley Michael J. , Tsevtkov V. , Guo Jian Qiu , Yang Yu , Dudley Michael , Balkas Elif
Published: May 2016

Definitive correlations are presented between specific types of dislocations identified via Synchrotron White Beam X-Ray Topography (SWBXRT) and identified via selective etching of 4H-SiC substrates. A variety of etch conditions and the results on different faces of SiC substrates and epiwafers are examined. Hillocks formed on the carbon face of the substrate after KOH etching correlate very well to TSDs identified via SWBXRT. Topography of substrates and of vertical crystal slices reveals a large proportion of Threading Mixed character Dislocations (TMDs) in the population of Threading Screw Dislocations.
150 mm 4H-SiC Substrate with Low Defect Density
Authors: Gao Yu Qiang , Zhang Hong Yan , Zong Yan Min , Wang Huan Huan , Guo Jian Qiu , Raghothamachar Balaji , Dudley Michael , Wang Xi Jie
Published: May 2016

150 mm diameter 4H-SiC boules were grown by the physical vapor transport (PVT) method. Synchrotron white beam X-ray topography (SWBXT) was carried out to investigate the distribution of defects in axial slices cut from the boule. It was found that an increase of dislocations and micropipes was mainly induced by inclusions. After eliminating these inclusions, which were formed in the mid to late stage of the crystal growth, both the screw dislocation density and base plane dislocation density could be decreased down to a magnitude of 102 cm-2, which is comparable to that of high quality 100 mm diameter SiC substrates.
Bipolar Degradation of 6.5 kV SiC pn-Diodes: Result Prediction by Photoluminescence
Authors: Wehrhahn-Kilian Larissa , Dohnke Karl Otto , Kaminzky Daniel , Kallinger Birgit , Oppel Steffen
Published: May 2016

The stability of 6.5 kV pn-diodes is dependent on the absence of critical crystal defects, such as basal plane dislocations. In this paper, we present a method to detect these defects on wafer level by utilizing photoluminescence (PL). The PL scan is performed immediately after epitaxy and also after the implantation process steps with subsequent high temperature annealing. The analysis of both scans enables the prediction of devices that will drift due to bipolar degradation, and devices that will exhibit non-drifting behaviour. To validate this PL scanning technique, forward bias electrical stress tests have been performed on the fabricated 6.5 kV pn-diodes.
4H-SiC Surface Structures and Oxidation Mechanism Revealed by Using First-Principles and Classical Molecular Dynamics Simulations
Authors: Yamasaki Takahiro , Tajima Nobuo , Kaneko Tomoaki , Nishikawa Nobutaka , Nara Jun , Schimizu Tatsuo , Kato Koichi , Ohno Takahisa
Published: May 2016

The 4H-SiC(000-1)C and (0001)Si surface reconstructed structures and the oxidation processes of these surfaces are investigated using a first-principles calculation method. The most stable reconstructed 4H-SiC(000-1)C and (0001)Si surfaces have p-bonded chains. In the topmost SiC bilayer, half of Si and C atoms exchange their positions and C-C or Si-Si bonds formed densely below the surfaces. When we place a SiO2 layer on the p-bonded chain (000-1)C surface, C-C bonds are formed more densely below the interface. We simulate a sequence of O2 molecules arrivals at an interface of tridymite-phase-SiO2 and 4H-SiC(000-1)C. Dissociated O atoms at the interface tended to make bonds with Si atoms. The C-C bonds in the SiC substrate break easily and a local C surface occasionally appears. We have examined how the surface structure changes through an O2 molecule exposure by using a classical molecular dynamics simulation program and confirmed the formation of C-C bonds below the surface and the interface.
A Novel Approach to Analysis of F-N Tunneling Characteristics in MOS Capacitor Having Oxide Thickness Fluctuation
Authors: Yamada Keiichi , Senzaki Junji , Kojima Kazutoshi , Okumura Hajime
Published: May 2016

The new indicators, effective gate oxide thickness tc and effective gate electrode area D, and their combination are applied for a new analysis method of Fowler-Nordheim (F-N) tunneling characteristics in MOS capacitor having oxide thickness fluctuation. This method considering the conduction properties of F-N tunneling characteristics correlates its characteristics to the oxide reliability. These indicators quantified with the influence of the oxide thickness fluctuation can provide the net values of the electric field and the current density on the gate oxide. This new analysis method will lead to reducing the evaluation time for the reliability assessment.
Analysis of Gate Oxide Nitridation Effect on SiC MOSFETs by Using Hall Measurement and Split C–V Measurement
Authors: Tsujimura Masatoshi , Kitai Hidenori , Shiomi Hiromu , Kojima Kazutoshi , Fukuda Kenji , Sakamoto Kunihiro , Yamasaki Kimiyoshi , Takagi Shin-Ichi , Okumura Hajime
Published: May 2016

In this study, 4H–SiC inversion layers were experimentally evaluated by Hall and split C–V measurements, and scattering mechanisms related to gate oxide nitridation were analyzed. Three typical samples with different crystal plane directions and gate oxidation conditions were prepared, and their total trap density and Hall mobility were compared. Based on the temperature dependence of the Hall mobility, we found that scattering mechanisms differed for each sample. The sample C-face oxynitride which had a high nitrogen density at the metal–oxide–semiconductor (MOS) interface, showed a similar temperature dependency to that of ionized impurity scattering. This result suggests that high-density nitrogen acts as donors that supply free carriers and cause ionized impurity scattering, just like in a bulk crystal. In addition, the sample C-face wet has lowest influence of the Coulomb scattering because of the lowest temperature dependence of Hall mobility and the lowest total trap density.
A Competitive Lattice Model Monte Carlo Method for Simulation of Competitive Growth of Different Polytypes in SiC Single Crystal
Authors: Huang Wei , Guo Hui Jun , Liu Xi , Liu Xue Chao , Zheng Yan Qing , Yang Jian Hua , Shi Er Wei
Published: May 2016

A competitive lattice model was developed for the Kinetic Monte Carlo (KMC) simulation of the competition of 4H and 6H polytypes in SiC crystal growth based on the on-lattice model. In the competitive lattice model, site positions are fixed at the perfect crystal lattice positions without any adjustment of the site positions. The effect of surface steps was investigated, and behavior similar to step-controlled homoepitaxy was observed in KMC simulation of PVT grown SiC. Maintaining the step growth mode is an important factor to maintain a stable single polytype during SiC growth.
Pragmatic Approach to the Characterization of SiC/SiO2 Interface Traps near the Conduction Band with Split C-V and Hall Measurements
Authors: Hatakeyama Tetsuo , Takao Kazuto , Yonezawa Yoshiyuki , Yano Hiroshi
Published: May 2016

A simple and practical method of characterizing traps at SiC/SiO2 interfaces close to the bottom of the conduction band by using the split C−V and Hall measurements is proposed. This technique was applied to the characterization of traps at a wet-oxidized SiC/SiO2 interface on C-face and those at an oxynitrided SiC/SiO2 interface on Si-face. It was shown that the density of traps near the conduction band of the oxynitrided SiC/SiO2 interface was more than 10 times larger than that of the wet-oxidized SiC/SiO2 interface.
Failure Analysis of a SiC MOS Capacitor with a Poly-Si Gate Electrode
Authors: Sato Soshi , Yamabe Kikuo , Endoh Tetsuo , Niwa Masaaki
Published: May 2016

The failure mechanism of a SiC metal-oxide-semiconductor capacitor with a poly-Si gate electrode was investigated by time-dependent dielectric breakdown testing under a 200-nA constant current stress. The capacitor exhibited both hard and soft breakdowns. After dielectric breakdown in both cases, adjacent concaves were observed on the capacitor with a field-emission scanning electron microscope. Additional optical beam-induced resistance changes and photo-emission analysis of a capacitor after hard-breakdown located a failure point on the periphery of a group of adjacent concaves. Cross-sectional scanning transmission electron microscope observation revealed that a narrow, vertical defect had formed at this point on the SiC substrate.
Ultra-Fast SiC Wafer Surface Roughness Mapping
Authors: Nakano Yoshihiro , Asakawa Yuji , Seki Hirokazu , Seaman Jeff , Burk Albert A.
Published: May 2016

SiC wafer surface roughness is known to affect the electrical properties of certain power devices. As a result, inspection of the surface roughness can be a very important step for SiC device manufacturing processes. In this paper, we propose a newly fast surface roughness measurement method using Differential Interference Contrast (DIC) microscopy image. Results from this method were compared against white-light interference measurement system and a good correlation was confirmed. The comparison result confirmed that this method was a valid method to measure the surface roughness. This method enables users to inspect the surface roughness in 5 minutes (100mm wafer) and 10 minutes (150mm wafers), respectively.
Application of In Situ 3D Computed Tomography during PVT Growth of 4H-SiC for the Study of Source Material Consumption under Varying Growth Conditions
Authors: Wellmann Peter J. , Fahlbusch Lars , Salamon Michael , Uhlmann Norman
Published: May 2016

2D and 3D in-situ X-ray visualization was applied to study the behavior of the SiC source material during PVT growth under various growth conditions. Experiments were carried out in two growth chambers for the growth of 3 inch and 4 inch crystals. Growth parameters were varied in the gas room in terms of axial temperature and inert gas pressure. The study addresses the stability of the SiC source material surface. It is shown that a higher inert gas pressure (e.g. 25 mbar) inhibits an unintentional upward evolution of the SiC feedstock that interferes with the crystal growth interface. The latter is related to a suppression of a pronounced recrystallization inside the SiC source. For a low inert gas pressure (e.g. 10 mbar) it is concluded that the axial temperature gradient inside the source material needs to be decreased to less than ca. 10 K/cm.
Photoluminescence Enhancement in Nanotextured Fluorescent SiC Passivated by Atomic Layer Deposited Al2O3 Films
Authors: Lu Wei Fang , Ou Yi Yu , Jokubavicius Valdas , Fadil Ahmed , Syväjärvi Mikael , Buschmann Volker , Rüttinger Steffen , Petersen Paul Michael , Ou Hai Yan
Published: May 2016

The influence of thickness of atomic layer deposited Al2O3 films on nanotextured fluorescent 6H-SiC passivation is investigated. The passivation effect on the light emission has been characterized by photoluminescence and time-resolved photoluminescence at room temperature. The results show that 20nm thickness of Al2O3 layer is favorable to observe a large photoluminescence enhancement (25.9%) and long carrier lifetime (0.86ms). This is a strong indication for an interface hydrogenation that takes place during post-thermal annealing. These result show that an Al2O3 layer could serve as passivation in fluorescent SiC based white LEDs applications.
Concentration Profile Simulation of SiC/Si Heterostructures
Authors: Pezoldt Joerg , Kharlamov V.S. , Kulikov Dmitri V. , Lubov Maxim N. , Trushin Yuri V.
Published: May 2016

Computer simulation of the concentration profiles evolution in SiC/Si heterostructures during growth and subsequent ion sputtering is presented. Simulation is based on a complex self-consistent approach combining kinetic and ballistic methods. Within the framework of the proposed method concentration depth profiles in SiC/Si heterostructure with pre-deposited Ge impurity are calculated and compared with experimental sputtering profiles obtained by secondary ion mass spectrometry.
Development of the Compact Furnace for the In Situ Observation under Ultra-High Temperature by Synchrotron x-Ray Surface Diffraction
Authors: Yoshida Masahiro , Kutsuma Yasunori , Dohjima Daichi , Ohwada Kenji , Inami Toshiya , Ohtani Noboru , Kaneko Tadaaki , Mizuki Jun'ichiro
Published: May 2016

We have established the grazing-incidence x-ray diffraction (GIXD) method under ultra- high temperature for in-situ crystal growth observation. For this purpose, we have developed the compact furnace which can be mounted on a goniometer used for the GIXD experiment. Using the custom-designed furnace, we have succeeded in controlling very high temperature around 1800°C. Subsequently, we have proved the performance of the furnace through the measurement of the tem- perature dependence of a-lattice constant of 4H-SiC in the range from room temperature to 1500 °C.
Characterization of Lattice Plane Bending and Stress Distribution in Physical Vapor Transport-Grown 4H-SiC Crystals
Authors: Teramoto Yoshihito , Tabuchi Yuki , Fukunaga Daisuke , Ohtomo Kohei , Ohtani Noboru , Katsuno Masakazu , Fujimoto Tatsuo , Sato Shinya , Tsuge Hiroshi , Yano Takayuki
Published: May 2016

Basal plane bending and stress distribution in physical vapor transport-grown n-type 4H-SiC crystals were investigated. High resolution X-ray diffraction measurements were performed on commercially available 3-inch-diameter 4H-SiC substrates and along the growth front surface of as-grown 1-inch-diameter 4H-SiC boules. The measurements revealed that structural parameters such as the c-lattice constant, basal plane tilting, and FWHM showed characteristic variations across the substrates and as-gown boules, indicating that the crystals had a non-uniform distribution of dislocations comprising domain structures. Residual stress measured by micro Raman spectroscopy showed a similar behavior, which was an oscillatory spatial variation. On the basis of these results, defect structures in the crystals are elucidated.
Alternative Highly Homogenous Drift Layer Doping for 650 V SiC Devices
Authors: Rupp Roland , Schustereder Werner , Höchbauer Tobias , Kern Ronny , Rüb Michael , Csato Constantin , Krippendorf Florian , Akhmadaliev Shavkat , von Borany Johannes
Published: May 2016

A new method for homogenous drift layer doping is introduced. Instead of in-situ doping during epitaxial growth a subsequent high energy ion implant step is used to dope the drift layer of 650V MPS (Merged-PN-Schottky) diodes. In order to avoid multiple implant steps with various energies for emulating a box-like doping profile, a novel “energy filter” membrane is used to transform the monochromatic ion beam to a beam with a continuous energy spectrum suited for box-like doping. The electrical characteristics of the diodes manufactured by this means show a very homogenous blocking behavior on wafer level, however the expected improved homogeneity in differential resistance of the wafers could not be confirmed by wafer level measurements. More work is needed to understand this discrepancy between experiment and theory.
High Efficiency Activation of Phosphorus Atoms in 4H-SiC by Atmospheric Pressure Thermal Plasma Jet Annealing
Authors: Hanafusa Hiroaki , Maruyama Keisuke , Ishimaru Ryosuke , Higashi Seiichiro
Published: May 2016

In this study, the application of atmospheric pressure thermal plasma jet (TPJ) annealing for impurity activation in 4H–SiC is reported. The activation of phosphorus atoms implanted at 300°C in 4H–SiC by TPJ irradiation and analysis of its crystallinity are investigated. At the maximum annealing temperature of 1630°C, the minimum resistivity value is 3.1 mΩ·cm and the maximum carrier concentration value is 2.0 × 1020 cm−3. Orientation analysis suggests that the sample implanted at 300°C was recrystallized to a 4H–SiC(0001) structure after 1630°C annealing. Furthermore, a significant increase in the carrier concentration was observed with the increasing cooling rate during the activation annealing process. Rapid cooling may suppress the impurity deactivation. These results suggest that short-time high-temperature TPJ irradiation annealing is effective for P dopant activation in 4H–SiC.
Warpage Structure of 4H-SiC after Implantation and Annealing Processes
Authors: Ishiji Kotaro , Kawado Seiji , Hirai Yasuharu , Nagamachi Shinji
Published: May 2016

The warpage structure of 4°-off-axis (0001) 4H-SiC samples after implantation and annealing processes was investigated using white light interferometry (WLI) and X-ray rocking curve (XRC) measurements. The WLI images showed that the surface warpage of the 300 °C-implanted/annealed SiC sample was small and almost the same as that of the un-implanted SiC sample, but the 30 and 150 °C-implanted/annealed SiC samples had a typically saddle-like warpage. The XRCs of the 0008-reflection were measured using monochromatic X-rays with different energies to change the X-ray penetration depth. The subtracted XRCs were reconstructed, and then the depth-dependence of the curvature radius of the 0008-reflection was evaluated. The results indicated that the saddle-like warpage of the 30 and 150 °C-implanted/annealed samples relaxed with increasing depth.
Low Resistance Ohmic Contact Formation on 4H-SiC C-Face with NbNi Silicidation Using Nanosecond Laser Annealing
Authors: De Silva Wijemuni , Ishikawa Seiji , Kikkawa Takamaro , Kuroki Shin Ichiro
Published: May 2016

Non-equilibrium laser silicidations for low-resistance ohmic contact to 4H-SiC C-face with carbon-interstitial type metal, Nb was demonstrated. In a conventional nickel silicide (NiSi) electrode on SiC, a carbon agglomeration at the silicide/SiC interface occurs, and constant resistance between NiSi and SiC substrate becomes larger. For suppressing the carbon agglomeration, in this research, nanoseconds non-equilibrium laser annealing was introduced, and also carbon-interstitial type metal Nb to form metal carbides was introduced. Ni/Nb/SiC multilayer contact and NbNi mixed contact were formed on C-face side of 4H-SiC wafers. Electrical contact properties were investigated after 45 nanoseconds pulse laser annealing in N2 ambient. As the result, at the NbNi mixed contact, specific contact resistance of 2.4×10-4 Ωcm2 was realized.
Thermally Stable Ohmic Contact to p-Type 4H-SiC Based on Ti3SiC2 Phase
Authors: Abi-Tannous Tony , Soueidan Maher , Ferro Gabriel , Lazar Mihai , Raynaud Christophe , Gardiola Bruno , Planson Dominique
Published: May 2016

In this study, the electrical properties of Ti3SiC2 based ohmic contacts formed on p-type 4H-SiC(0001) 4°-off substrates were studied. The Ti3SiC2 thin films were grown by thermal annealing (from 900°C to 1200°C) of Ti50Al50 layer deposited by magnetron sputtering. XRD analyzes were performed on the samples to further investigate the compounds formed after annealing. Using TLM structures, the Specific Contact Resistance (SCR) at room temperature of all contacts was measured. The temperature dependence (up to 600°C) of the SCR was studied to understand the current mechanisms at the interface and to determine the barrier height value by fitting the experimental results using the thermionic field emission theory. Aging tests showed that Ti3SiC2 based contacts were stable up to 200h at 600°C under Ar.
Ohmic Contact Reliability of Commercially Available SiC MOSFETs Isothermally Aged for Long Periods at 300°C in Air
Authors: Hamilton Dean , Hindmarsh Steven A. , York Stephen , Walker David , Russell Stephen , Jennings Michael R. , Fisher Craig A. , Mawby Philip  Andrew
Published: May 2016

In this paper, the source contacts of three different SiC MOSFET power device dies have been investigated using TEM and EDX analysis before and after long-term isothermal heating at 300°C in air. The device type with Al-Ni based ohmic source contacts showed degradation of its contacts after only 24 hours, as indicated by the EDX analysis. The other two device types with Ti-based source contacts and Al-Ni-based with a carbon layer were found to be thermo-mechanically stable. An XRD analysis was also carried out on the backside drain contact of the first device type in order to try to identify a new layer within the associated metal stack that had appeared during aging.
Low Thermal Budget Ohmic Contact Formation by Laser Anneal
Authors: Mazzamuto Fulvio , Halty Sebastien , Tanimura Hideaki , Mori Yoshihiro
Published: May 2016

In this work, we demonstrate the possibility to achieve an ohmic contact using a low thermal budget applicable to backside processing after wafer thinning. The process window for laser annealing as a function of the thinning process is investigated. By laser melt annealing, we demonstrate the possibility for different silicide phases from pure nickel deposition on thinned 4H-SiC, formation of uniform carbon nanoclusters at the metal/SiC interface and recovery of thinning-induced defects. This has been demonstrated as a function of different thinning process and surface conditions.
Impact of Contact Material Deposition Technique on the Properties of Ti/4H-SiC Schottky Structures
Authors: Stöber Laura , Schneider Michael , Schmid Ulrich
Published: May 2016

In this paper, we report on the performance of Ti/4H-SiC Schottky junctions, whereas the contact material is either e-beam evaporated or magnetron sputter deposited. When applying the first technique, the Schottky barrier height is lowered at room temperature by about 80 meV or by about 160 meV extracted from current/voltage and capacitance/voltage measurements, respectively. Furthermore, e-beam evaporation of the Ti contact results in an ideality factor closer to 1 when comparing structures of the same design.
4H-SiC nMOSFETs with As-Doped S/D and NbNi Silicide Ohmic Contacts
Authors: Nagatsuma Hirofumi , Kuroki Shin Ichiro , De Silva Wijemuni , Ishikawa Seiji , Maeda Tomonori , Sezaki Hiroshi , Kikkawa Takamaro , Östling Mikael , Zetterling Carl Mikael
Published: May 2016

4H-SiC nMOSFETs with As-doped S/D and NbNi silicide ohmic contacts were demonstrated for radiation-hard CMOS electronics. The threshold voltage Vth was designed to be 3.0 V by TCAD simulation, and was 3.6 – 3.8 V at the fabricated devices. On / off ratio was approximately 105.
Threshold-Voltage Instability in SiC MOSFETs Due to Near-Interfacial Oxide Traps
Authors: Lelis Aivars J. , Green Ronald , Habersat Daniel B.
Published: May 2016

There are two basic mechanisms that affect the threshold-voltage (VT) stability: oxide-trap activation and oxide-trap charging. Once additional oxide traps are activated, then they are free to participate in the charge-trapping processes that can, especially for older vintage devices, result in large VT shifts and potential device failure. More recent commercially-available devices show much smaller effects, and minimal trap activation. Given the dramatic improvements, it is now imperative that improved test methods be employed to properly separate out bad devices from good devices.
Quantified Density of Active near Interface Oxide Traps in 4H-SiC MOS Capacitors
Authors: Moghadam Hamid Amini , Dimitrijev Sima , Han Ji Sheng , Aminbeidokhti Amirhossein , Haasmann Daniel
Published: May 2016

This paper presents a new method to quantify near interface oxide traps (NIOTs) that are responsible for threshold voltage instability of 4H-SiC MOSFETs. The method utilizes the shift observed in capacitance–voltage (C–V) curves of an N-type MOS capacitor. The results show that both shallow NIOTs with energy levels below the bottom of conduction band and NIOTs with energy levels above the bottom of the conduction band of SiC are responsible for the C–V shifts, and consequently, for the threshold voltage instabilities in MOSFETs. A higher density of NIOTs is measured at higher temperatures.
Time Dependent Dielectric Breakdown in High Quality SiC MOS Capacitors
Authors: Chbili Zakariae , Cheung Kin P. , Campbell Jason P. , Chbili Jaafar , Lahbabi Mhamed , Ioannou Dimitris E. , Matocha Kevin
Published: May 2016

In this paper we report TDDB results on SiO2/SiC MOS capacitors fabricated in a matured production environment. A key feature is the absence of early failure out of over 600 capacitors tested. The observed field accelerations and activation energies are higher than what is reported on SiO2/Si of similar oxide thickness. The great improvement in oxide reliability and the deviation from typical SiO2/SiC observations are explained by the quality of the oxide in this study.
Microscopic Difference between Dry and Wet Oxidations of C-Face 4H-SiC MOSFFETs Studied by Electrically Detected Magnetic Resonance
Authors: Kagoyama Yohei , Okamoto Mitsuo , Harada Shinsuke , Arai Ryo , Umeda Takahide
Published: May 2016

We studied interface defects of C-face 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) by means of electrically-detected-magnetic-resonance (EDMR) spectroscopy. EDMR measurements were carried out on opposite types of C-face MOSFETs, which were prepared by dry oxidation and wet oxidation, and we found EDMR signals of interface defects from both the MOSFETs. Judging from their spectroscopic features, the interface signals of the two MOSFETs are assigned to be the same type, and we call them “C-face defects.” The density of C-face defects was found to be larger in the dry-oxide MOSFETs than in the wet-oxide MOSFETs. It is also revealed that part of C-face defects in wet-oxide MOSFETs are coupled with hydrogen atoms.
High Temperature Nitridation of 4H-SiC MOSFETs
Authors: Rong Hua , Sharma Yogesh K. , Dai Tian Xiang , Li Fan , Jennings Michael R. , Russell Stephen , Martin David M. , Mawby Philip  Andrew
Published: May 2016

This paper presents and analyse the experimental results of 4H-SiC(0001) lateral MOSFETs and MOS capacitors with gate oxides grown directly in N2O environment or in O2 ambient followed by a N2O post oxidation annealing process. Different nitridation temperatures of 1200°C, 1300°C, 1400°C and 1500°C have been investigated. Results have demonstrated that at high temperature (>1200°C) there is a significant improvement in the interface trap density (~1.5×1011 cm-2eV-1 at 0.2 eV) and field effect channel mobility (19 cm2/V.s) of 4H-SiC MOSFET compare with those at lower temperature (1×1012 cm-2eV-1 at 0.2 eV and 4 cm2/V.s). Among those nitridation temperatures, 1300°C has found to be the most effective in increasing the field effect channel mobility and reducing threshold voltage.