Growth Of 3C-SiC Research Articles

TEM investigation of the interface formation during transfer of 3C-SiC(001) layer onto 6H-SiC(0001) wafer

At present, intensive research is underway in the field of vacuum-sublimation growth of 3C-SiC. Transfer of a thin (001)3C-SiC layer onto a 6H-SiC wafer is a promising way to fabricate a 3C-SiC/6H-SiC substrate for growing device-quality homoepitaxial films of low defect density. The article presents the results of the structural characterization of an interface formed during the transfer of a 3C-SiC layer onto a 6H-SiC(0001) wafer, performed with transmission electron microscopy (TEM). A 3C-SiC film with a thickness of about 10 μm, grown by chemical vapor deposition (CVD) on a Si(001) substrate, was utilized in the study. Silicon acted as a bonding material in the transfer process. The morphology and microstructure of the interface between a 6H-SiC substrate and a 3C-SiC (001)-oriented layer are under consideration. TEM investigation reveals an effect of “self”-orientation of the layer with respect to the wafer during the transfer process: an interaction between the molten silicon layer and silicon carbide throughout crystallization results in the generation of defined orientation relationships with respect to substrate axes. An analysis of selected area electron diffraction patterns taken from interfaces showed the relationships to be 3C-SiC{001}‖ 6H-SiC(0001) and 3C-SiC⟨11¯0⟩∼‖ 6H-SiC⟨112¯0⟩.

Effect of Fe-Co catalysis on the temperature field distribution during the growth of 3C-SiC fibers synthesised by microwave heating

Microwave heating produce local hot spots on materials, which result in uneven heating and other issues. Regulate the microwave temperature field using different catalyst combinations such as Fe (NO3)3·9H2O and Co (NO3)2·6H2O. The electromagnetic and temperature field distributions of 3C–SiC fibers and the molecular dynamics of the SiC interfacial growth process and interfacial oxidation reaction during microwave heating in the presence of a catalyst were simulated and calculated respectively. The results show that the combination of Fe and Co at 9 wt% catalyst concentration can effectively improve the electromagnetic loss capability of SiC fibers. The Fe and Co bimetallic catalysed synthesis of 3C–SiC fibers follows a vapor–liquid–solid growth mechanism. The Fe–Si and Fe–Co–Si alloy phases can induce 3C–SiC growth along (111) crystal faces. The simultaneous exothermic reactions provide a highly catalytically active growth environment that facilitates the enhancement of microwave temperature field uniformity. This phenomenon facilitated the synthesis of 3C–SiC fibers.

Three-Dimensional Epitaxy of Low-Defect 3C-SiC on a Geometrically Modified Silicon Substrate.

We demonstrate the growth of 3C-SiC with reduced planar defects on a micro-scale compliant substrate. Heteroepitaxial growth of 3C-SiC on trenches with a width and separation of 2 µm, etched into a Si(001) substrate, is found to suppress defect propagation through the epilayer. Stacking faults and other planar defects are channeled away from the center of the patterned structures, which are rounded through the use of H2 annealing at 1100 °C. Void formation between the columns of 3C-SiC growth acts as a termination point for defects, and coalescence of these columns into a continuous epilayer is promoted through the addition of HCl in the growth phase. The process of fabricating these compliant substrates utilizes standard processing techniques found within the semiconductor industry and is independent of the substrate orientation and offcut.

Laser-assisted formation of 3c-SiC and continuous diamond growth using Si–Q carbon on (100) silicon

Laser-assisted formation of 3c-SiC and continuous diamond growth using Si–Q carbon on (100) silicon

Templates for Homoepitaxial Growth of 3C-SiC Obtained by Direct Bonding of Silicon Carbide Wafers of Differing Polytype

Templates for Homoepitaxial Growth of 3C-SiC Obtained by Direct Bonding of Silicon Carbide Wafers of Differing Polytype

Towards vertical Schottky diodes on bulk cubic silicon carbide (3C-SiC)

In this paper, we demonstrate the feasibility of fabricating vertical Schottky diodes on bulk cubic silicon carbide (3C-SiC) material obtained by combining sublimation epitaxy and chemical vapor deposition, starting from 4°-off axis 4H-SiC. First, the good quality of the epilayers grown with this method was demonstrated by morphological and structural analyses. Then, fabricated vertical Pt/3C-SiC Schottky diodes exhibited an ideality factor of 1.21 and a barrier height of 0.6 eV, as determined by thermionic emission model. The temperature dependent forward current analysis indicated the formation of an inhomogeneous barrier, which has been related with the presence of conductive surface defects, detected by nanoscale local current measurements. On the other hand, the reverse leakage current could be described by thermionic field emission model, including image force lowering. These findings demonstrate the viability of the proposed approach for bulk 3C-SiC growth for device fabrication. The material quality and the feasibility of fabricating vertical diodes based on 3C-SiC with a low barrier pave the way for the application of this polytype for medium-voltage power devices.

Tuning 3C-SiC(100)/Si(100) Heterostructure Interface Quality

We report a systematic spectroscopic and structural investigation of 3C-silicon carbide (3C-SiC) films grown on Si(100)-(2 × 1) by codeposition of C60 molecules and Si atoms in ultrahigh-vacuum conditions. This work focuses on reducing the macroscopic defects formed at the interface in Si-SiC heterojunctions. A wide range of parameters influence the growth process, including the substrate deposition temperature, the relative effusion fluxes of C60 and Si, and the clean Si(100) surface order. By adjusting the Si and C60 deposition rates, it is possible to reduce the Si atom diffusion from the substrate and control both the surface morphology and the specific formation of the C-rich c(2 × 2) or Si-rich 3 × 2 ordered surfaces. Our results show that the growth of 3C-SiC on flat and good quality Si substrates is a crucial and necessary starting point to obtaining good quality 3C-SiC/Si interfaces with a minimum number of defects.

Controlled CVD Growth of Highly ⟨111⟩-Oriented 3C-SiC

Highly ⟨111⟩-oriented 3C-SiC coatings with a distinct surface morphology consisting of hexagonally shaped pyramidal crystals were prepared by chemical vapor deposition (CVD) using silicon tetrachloride (SiCl4) and toluene (C7H8) at T ≤ 1250 °C and ptot = 10 kPa. In contrast, similar deposition conditions, with methane (CH4) as the carbon precursor, resulted in randomly oriented 3C-SiC coatings with a cauliflower-like surface of SiC crystallites. No excess carbon was detected in the highly ⟨111⟩-oriented 3C-SiC samples despite the use of aromatic hydrocarbons. The difference in the preferred growth orientation of the 3C-SiC coatings deposited by using C7H8 and CH4 as the carbon precursors was explained via quantum chemical calculations of binding energies on various crystal planes. The adsorption energy of C6H6 on the SiC (111) plane was 6 times higher than that on the (110) plane. On the other hand, CH3 exhibited equally strong adsorption on both planes. This suggested that the highly ⟨111⟩-oriented 3C-SiC growth with C7H8 as the carbon precursor, where both C6H6 and CH3 were considered the main active carbon-containing film forming species, was due to the highly preferred adsorption on the (111) plane, while the lower surface energy of the (110) plane controlled the growth orientation in the CH4 process, in which only CH3 contributed to the film deposition.

Microscopic origins of anisotropy for the epitaxial growth of 3C-SiC (0001) vicinal surface: A kinetic Monte Carlo study

In order to investigate the microscopic evolution of the step flow growth process and reveal the microscopic origins of crystalline anisotropy during the epitaxial growth of 3C-SiC (0001) vicinal surface, a three-dimensional Kinetic Monte Carlo model is established, in which Si and C are considered individually. The helicoidal boundary condition is applied to the direction perpendicular to the step, and the periodic boundary condition is used in the direction along the step. Then, the effects of crystalline anisotropy on lateral growth rate, morphologies of step patterns, and growth mode are studied. The results show that the lateral growth rate in [1−210] is larger than that in ⟨1−100⟩, and the zigzag and meandering patterns of step are constructed in [1−210] and ⟨1−100⟩ directions, respectively, which is consistent with the experimental observations. Two possible origins of anisotropy are also revealed: one is the higher concentration of the edge sites of the step and the larger bonding energy in the [1−210] direction and another is the adatom diffusion along the edge of the step. Finally, a larger area of pure step flow growth mode is obtained in the [1−210] direction, which is good for lowering the cost for 3C-SiC epitaxial layers.

Observation of the Initial Stage of 3C-SiC Heteroepitaxial Growth on the Si Nanomembrane

One considerable concern in 3C-SiC growth is the different lattice constant between the 3C-SiC and Si substrate, which causes defects and strain at the interface. Although the heteroepitaxial growth has been achieved, there have been no experimental studies on the initial process of 3C-SiC growth. In this research, we directly observe heteroepitaxial growth of 3C-SiC on the (001) Si nanomembrane (Si NM) step by step. We used in situ heating transmission electron microscopy (TEM) to study the initial growth process of 3C-SiC growth at the nanoscale in a high-vacuum environment. We demonstrate the growth of 3C-SiC at the preferential (110) direction without defects. The heteroepitaxial grown 3C-SiC without defects is attributed to the bowing effect at the nanoscale to compensate for the lattice misfit. Based on these results, we proposed a new method to heteroepitaxially grow on the Si NM through in situ heating TEM study.

Templates for homoepitaxial growth of 3C-SiC obtained by direct bonding of silicon carbide wafers of differing polytype

An approach of direct bonding of SiC wafers of differing polytypes has been implemented in order to create a template for cubic 3C-SiC homoepitaxy. Heteroepitaxial 3C-SiC layers grown by chemical vapor deposition were transferred onto a hexagonal 6H-SiC wafer. The results of structural characterization showed that the quality of 3C-SiC sublimation epitaxy on the templates is comparable to the level of epitaxy of cubic silicon carbide by chemical vapor deposition method. It was confirmed that the 3C-SiC layer transferred onto the 6H-SiC substrate plays the role of a crystalline "seed" that determines cubic polytype of the overgrown SiC layer. Keywords: Silicon carbide, polytypes, direct bonding, templates, sublimation epitaxy.

Characterization of protrusions and stacking faults in 3C-SiC grown by sublimation epitaxy using 3C-SiC-on-Si seeding layers

In this article, sublimation growth of 3C-SiC on 3C-SiC-on-Si seeding layers was evaluated by characterizing the densities of protrusions and stacking faults (SF). Both defects are among the most critical concerning the growth process and the realization of high quality material for device applications. By variation of growth parameters like temperature, growth rate and 3C-SiC-thickness we conducted a series of experiments and characterized these layers by optical microscopy and KOH etching. The protrusion density is predetermined by the seeding layers and was kept at a constant level, whereas a decrease of SF-density was observed with increasing layer thickness during subsequent sublimation growth steps. Therefore, in the case of Sublimation Epitaxy (SE) it has been found appropriate to distinguish between defects that can be reduced during SE and defects that are merely reproduced from the seeding material during sublimation growth. Furthermore, a weak trend towards a decrease of SF-density with increasing growth temperature was observed. The findings in this work demonstrates the potential of SE in growing thick and high-quality 3C-SiC layers if sufficiently good seeding layers were available. Copyright © 2017 VBRI Press.

New Approaches and Understandings in the Growth of Cubic Silicon Carbide.

In this review paper, several new approaches about the 3C-SiC growth are been presented. In fact, despite the long research activity on 3C-SiC, no devices with good electrical characteristics have been obtained due to the high defect density and high level of stress. To overcome these problems, two different approaches have been used in the last years. From one side, several compliance substrates have been used to try to reduce both the defects and stress, while from another side, the first bulk growth has been performed to try to improve the quality of this material with respect to the heteroepitaxial one. From all these studies, a new understanding of the material defects has been obtained, as well as regarding all the interactions between defects and several growth parameters. This new knowledge will be the basis to solve the main issue of the 3C-SiC growth and reach the goal to obtain a material with low defects and low stress that would allow for realizing devices with extremely interesting characteristics.

Kinetic Monte Carlo method for epitaxial 3C-SiC (0001) growth on vicinal surfaces

A kinetic Monte Carlo model has been developed to predict island nucleation and step flow growth on vicinal surface during epitaxial growth of 3C-SiC. In the model, the crystal lattice is represented by a structured mesh which retains fixed atom positions and bond partners of the 3C-SiC crystal lattice. The events considered in the model are the deposition, evaporation and diffusion of atoms, and the attachment and detachment of adsorbed atoms. Both the incorporation energy barrier and Ehrlich-Schwoebel (ES) barrier are taken into account in the model when an adatom migrates to a step or island. The growth parameters such as growth temperature, coverages and terrace width can be selected freely, and the cross process of step flow growth and island nucleation can be simulated. The simulation results show that lower growth temperatures lead to a larger number of islands forming on the vicinal surfaces. There is also an observed coupling between island nucleation and steps at higher temperature. For smaller coverages, the islands and step patterns grow independently, and the steps and islands begin eventually to coalesce over the time. Furthermore, a decrease in terrace width leads to adatoms preferentially attaching to steps and the system to go to a step flow growth system. The results are consistent with predictions for the case of the epitaxial growth on vicinal surfaces.

Initial investigations into the MOS interface of freestanding 3C-SiC layers for device applications

This letter reports on initial investigation results on the material quality and device suitability of a homo-epitaxial 3C-SiC growth process. Atomic force microscopy surface investigations revealed root-mean square surface roughness levels of 163.21 nm, which was shown to be caused by pits (35 μm width and 450 nm depth) with a density of 1.09 × 105 cm−2 which had formed during material growth. On wider scan areas, the formation of these were seen to be caused by step bunching, revealing the need for further epitaxial process improvement. X-ray diffraction showed good average crystalline qualities with a full width of half-maximum of 160 arcseconds for the 3C-SiC (002) being lower than for the 3C-on-Si material (210 arcseconds). The analysis of C–V curves then revealed similar interface-trapped charge levels for freestanding 3C-SiC, 3C-SiC on Si and 4H-SiC, with forming gas post-deposition annealed freestanding 3C-SiC devices showing D IT levels of 3.3 × 1011 cm−2 eV−1 at E C−E T = 0.2 eV. The homo-epitaxially grown 3C-SiC material’s suitability for MOS applications could also be confirmed by leakage current measurements.

3C-SiC growth by sublimation in vacuum technology optimization

Results of an epitaxial growth of 3C-SiC epilayers on hexagonal 6H-SiC, 4H-SiC substrates are described. The study of the obtained epitaxial layers grown on 6H substrates was made by photoluminescence and optical microscopy. Also, an image analysis of the interface of 3C-SiC epitaxial layers with 6H, 4H, and 15R substrates obtained by Transmission Electron Microscopy (TEM) are presented. Difference between the layers on the Si and C faces are discussed.

(Invited) Stacking Faults in 3C-SiC: From the Crystal Structure, to the Electrical Behavior

Many attractive mechanical and electrical properties make silicon carbide (SiC) a material of interest in both electronic devices and sensors for nowadays technology (sustainable energies, hybrid vehicles, low power loss inverters). Silicon carbide exists in nature in several crystalline structures, called polytypes, differentiated by the stacking sequence of the tetrahedrially bonded Si-C bilayers. The only possible cubic structure, 3C-SiC, is obtained when the bilayer stacking is of the kind ABCABC..., resulting in a pure zinc-blende structure. 3C-SiC growth on Si is allowed within chemical vapour deposition (CVD) reactors, which would ensure a very high purity of the resulting product. The interface between 3C-SiC and Si is the origin of a high density of planar and volume defects, such as microtwins, anti-phase boundaries and stacking faults in the epilayer and voids in Si underneath the hetero-interface. Most of these defects, considered killers for devices, however, reduce their density, and some are totally annihilated, when very thick (several tens of microns) 3C-SiC epitaxial films are realized. The main defects that remain also after the growth of several tens of microns are the Stacking Faults (SFs). Three main SFs have been observed in 3C-SiC: the intrinsic one where only one plane is shifted with respect to the lattice position and two extrinsic SFs where two or three layers are shifted. In these last cases we observe locally the same crystallographic structure of the hexagonal polytypes: 4H-SiC and 6H-SiC. In the last period a large investigation has been done on these defects to see the crystallographic structure of these defects, the interactions between different SFs, the influence of the SFs on the internal stress of the material, the effects of several growth parameters (temperature, doping, growth rate, ...) on the density and evolution of these defects. Finally also several local electrical measurements by C-AFM has been done to understand the effect of these defects on the electrical behaviour of the devices.In Fig. 1 a three different HRTEM images of three different SFs are reported. It is possible to observe the different crystallographic structure of these defects. In Fig. 2 the interaction between these defects is reported. It is possible to observe that the SFs can annihilate or generate or close. The growth parameters have a large influence on the evolution of these defects. In Fig. 3 can be observed that, decreasing the growth rate and the growth temperature, the SFs density decreases. In Fig. 4 it is reported the effect of the doping on the SFs. Increasing the nitrogen concentration the SFs density decreases and the average length increases.At the conference more details on the SFs structure, the effect of these defects on the stress and on the electrical characteristics of the devices will be given. Figure 1

Crystal Growth of Epitaxial 3C-SiC Thin Film on Si Substrate by Chemical Vapor Deposition using Single Precursor of Vinylsilane

Cubic silicon carbide (3C-SiC) has attracted much attention since it has a wide bandgap, high dielectric breakdown strength, and high thermal stability. 3C-SiC promises various electronic applications such as power devices and MEMS. Also, 3C-SiC has an advantage for a lower cost among many SiC polytypes, as it can grow epitaxially on Si substrate. Generally, two types of precursor source materials, including Si and C, are necessary to grow 3C-SiC thin films for chemical vapor deposition (CVD) method. In addition, complex processes including carbonization with a temperature as high as about 1200 °C are required for conventional epitaxial growth of 3C-SiC [1]. We focus on vinylsilane as a single precursor material for SiC growth. The Si-C bond in vinylsilane is relatively stable due to the relationship of intramolecular bond energy, that is appreciable for SiC growth. The growth of SiC crystals using vinylsilane can be achieved at a low temperature of 1000 ºC or less and the deposition process will be simplified. Recently, we have achieved the formation of polycrystalline SiC thin films on metal substrate using CVD method only with vinylsilane [2]. In this study, we examine the epitaxial growth of 3C-SiC and also report phosphorous (P) doping for SiC thin films grown on Si substrate.SiC thin films were deposited on Si(001) and Si(111) substrates using CVD method with a vinylsilane precursor (manufactured by Japan Advanced Chemicals Co., Ltd.). The substrate temperature of the growth was ranging from 900 to 1000 °C, the growth pressure was 17 kPa, and the growth time was 60 min.The surface morphology of deposited film was observed using scanning electron microscopy (SEM). We can confirm that the uniform morphology of SiC film was formed on the Si substrate for a sample prepared with Si(111) substrate at 1000 ºC and also that there are no voids or defects at the interface.We also examined X-ray diffraction measurements to characterize the crystalline structure. Out-of-plane XRD measurement (2θ/ω method) shows a sufficiently large diffraction peak related to 3C-SiC(111) for the Si(111) sample prepared at 1000 ºC, which means the growth of a well (111)-oriented 3C-SiC thin film on Si(111) substrate. On the other hand, in the case of the grazing angle XRD measurement (2θ method) for the SiC/Si(001) samples prepared at both 900 and 1000 ºC, we observed many diffraction peaks meaning the formation of polycrystalline 3C-SiC. The analysis of peak intensity and full width at half maximum value (FWHM) revealed that the crystallinity of SiC film improved with increasing the growth temperature. Raman scattering spectroscopy measurement also revealed that the dominant bonding structure in the film is Si-C and not C-Hn or C-C for samples prepared at higher than 900 ºC, that means the formation of a high crystalline quality SiC thin film.In our presentation, we will discuss pros and cons of epitaxial growth of SiC films on Si(111) substrates and also reports P-doping into the SiC films will be discussed.

Fabrication of free-standing silicon carbide on silicon microstructures via massive silicon sublimation

Heteroepitaxial thin films of cubic silicon carbide (3C-SiC) on silicon offer a promising platform for leveraging the properties of SiC, such as wide bandgap, high mechanical strength, and chemical stability on a silicon substrate. Such heteroepitaxial films also attract considerable interest as pseudosubstrates for the growth of GaN as well as graphene on silicon wafers. However, due to a substantial lattice mismatch, the growth of 3C-SiC on silicon leads to a considerable amount of stresses, defects, and diffusion phenomena at the heterointerface. We show here that the extent of such interface phenomena and stresses is so large that, after patterning of the SiC, a massive sublimation of the silicon underneath the SiC/Si interface is promoted via a high-temperature anneal, either in high or medium vacuum ambient. A micrometer-thick air gap can be formed below the SiC structures, making them suspended. Hence, the described approach can be used as a straightforward methodology to form free-standing silicon carbide structures without the need for wet or anisotropic etching and could be of great interest for devices where suspended moving parts are needed, such as micro- and nanoelectromechanical systems.

ENHANCED ELECTRICAL PROPERTIES OF NONSTRUCTURAL CUBIC SILICON CARBIDE WITH GRAPHENE CONTACT FOR PHOTOVOLTAIC APPLICATIONS

Cubic silicon carbide (3C-SiC) is successfully synthesized through a simple solid-state reaction technique at a comparatively low temperature without using any catalyst. The XRD data is also used to study other structural parameters of synthesized sample by using different method. Raman peak at 796 cm-1 supports the XRD results. Si–C vibrational mode observed at 788 cm-1 in the FTIR spectrum further confirms the growth of 3C-SiC. UV-Vis spectroscopy is used to measure optical bandgap energy (Eg = 2.36 eV). Other optical parameters such as dielectric constant and refractive index of grown sample are also studied. Electrical performance is analyzed by using graphene contact with further evaluation of dark and light IV-measurements. The use of graphene contact establishes the enhancement of electrical conductivity of as-grown samples particularly when they are exposed to light. These findings indicate that the grown sample has comparatively better transport properties than conventional metal contacts under the illuminated conditions.