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The 3C-SiC (111) layer has been grown on Si (110) substrate by using hexachloro-disilane (HCDS) and propane. The propane flow rate was controlled in the carbonization step and the growth step for obtaining SiC layer with high crystal quality. The high quality epitaxial 3C-SiC (111) layer was successfully grown at growth temperature of 1280°C and lower propane flow rate condition. Grown 3C-SiC epitaxial layers were systematically analyzed by an optical microscope, Raman spectroscopy, FE-SEM and XRD

The chlorinated precursor is recently focused for high growth rate and high quality epitaxial layer. In the previous studies, the addition of chlorinated species from Si2Cl6 in the gas phase eliminated simultaneous Si nucleation which interferes with epitaxy. In this work, the characterization of epitaxial layers grown with chlorinated species is focused. High growth rate of 30 μm/h was achieved by using Si2(CH3)6 and Si2Cl6 as chlorinated precursors. We concluded that high growth rate was achieved by using HMDS and HCDS as the precursor of SiC at growth temperature of 1600 °C.

We adopted HMDS(Hexamethyledisilane) as a SiC(Silicon carbide) source material for epitaxial growth of 3C-SiC on Si substrate. Various growth profiles were investigated to optimize hetero-epitaxial growth of 3C-SiC layers. We also focused on the homogeneous film deposition of 3C-SiC on Si by employing two susceptor shapes, flat and tilted susceptors, to control a thickness of the boundary layer formed on the Si substrate. Fringe color patterns were observed on 3C-SiC layer on Si and hence it was easy to characterize the film uniformity by analyzing this color. 3C-SiC epitaxial layers were systematically analyzed by an optical microscope, a Raman spectroscopy, a SEM and an XRD.

The present research was focused to produce 2 inch wafers from small rectangular seeds and to investigate the quality of non-polar SiC substrates grown by a conventional PVT method. The non-polar SiC seeds were prepared by cutting along direction of 6H-SiC crystal grown on (0001) basal plane. As SiC ingot grows, many defects in connected region were gradually diminished. While the full width at half maximum (FWHM) values of m-plane SiC substrate measured along a-direction and c-direction were 60 arcsec and 70 arcsec, respectively, and the FWHM values of a-plane SiC substrate measured along m-direction and c-direction were 27 arcsec and 31 arcsec respectively. The stacking faults lying in the basal plane can be detected by molten KOH etching as linear etch pits extending along on the (11-20) surface and the carrier concentration was observed by Raman spectrum.

4H-SiC was grown on 4H-SiC (1100) substrates by sublimation boule growth, and transmission electron microscopic investigation was carried out. Two basal-plane-dislocations in the same basal plane (the BPD pair), whose dislocation line extend toward the [1100] growth direction, were observed as aligned along [0001]. The density of the BPD pairs along [0001] was in the same order with that of the stacking faults in the sample. A threading screw-dislocation was observed in between aligned BPD pairs. It is proposed that the interaction between stacking faults and threading screw-dislocations on the grown surface generates the BPD pairs. Since a high density of stacking faults is inherent to the growth on the substrates perpendicular to (0001), keeping an atomically flat grown surface is important to prevent the generation of the threading screw-dislocations, and thus to suppress the generation of the BPD pairs in case of the growth on (1100) and/or (11 2 0) substrates.

A sublimation epitaxial method, referred to as the Closed Space Technique (CST) was adopted to produce AlN epitaxial layers. In this study, we report the surface morphology of AlN epitaxial layer grown on various substrates such as 3C-SiC (100), 4H-SiC (0001) with 8o off-axis (0001) plane tilted toward the direction and on-axis 4H-SiC (0001). An average growth rate of AlN layer at 2350oC in 500 Torr of N2 was measured to be about 6μm/hr. While AlN layer grown on the 3C-SiC (100) substrate at 2350oC exhibited polycrystalline structure, AlN epitaxial layer grown on on-axis and off-axis 4H-SiC (0001) substrates had highly c-axis oriented epitaxial structure. In particular, the stacked structure of hexagonal plates was observed on off-axis substrate and the size of the hexagonal plates increased with growth time. Hexagonal plates were observed to be coalesced and the step-bunching was finally disappeared.

We have presented a combined method of microscopic measurements between Raman scattering and polarizing optical microscope to characterize inhomogeneous residual stress distributions around dislocations in 4H- and 6H-SiC wafers. First, stressed portions were found in wafers by an optical polarizing microscope under a crossed Nicole arrangement. Then, the portions were examined by Raman-imaging technique for lateral variations of phonon spectra. The residual stresses were quantified from the phonon-peak frequency shift using a known frequency-shift rate for 6H-SiC. Characterization to the depth direction was also conducted by surface etching with molten KOH. The stresses typically amounted to the order of 100 MPa. In a 4H-SiC homoepitaxial wafer sample, we observed threading dislocations transferred from the substrate to the epitaxial layer, and found that larger stress fields existed in the epitaxial layer than the substrate. We also observed stress distributions around compressively stressed sub-grain boundaries.

A sublimation epitaxial method, referred to as the Closed Space Technique (CST) was adopted to produce thick SiC epitaxial layers for power device applications. In this study, we aimed to systematically investigate surface morphologies and electrical properties of SiC epitaxial layers grown with varying a SiC/Al ratio in a SiC source powder during the sublimation growth using the CST method. The surface morphology was dramatically changed with varying the SiC/Al ratio. When the SiC/Al ratio of 90/1 was used, the step bunching was not observed in this magnification and the ratio of SiC/Al is an optimized range to grow of p-type SiC epitaxial layer. It was confirmed that the acceptor concentration of epitaxial layer was continuously decreased with increasing the SiC/Al ratio. 4H-SiC MESFETs haying a micron-gate length were fabricated using a lithography process and their current-voltage performances were characterized. It was confirmed that the increase of the negative voltage applied on the gate reduced the drain current, showing normal operation of FET device.

A sublimation epitaxial method, referred to as the Closed Space Technique (CST) was adopted to produce thick SiC epitaxial layers for power device applications. In this study, we aimed to systematically investigate surface morphologies and electrical properties of SiC epitaxial layers grown with varying a SiC/Al ratio in a SiC source powder during the sublimation growth using the CST method. It was confirmed that the acceptor concentration of epitaxial layer was continuously decreased with increasing the SiC/Al ratio. The blue light emission was successfully observed on a PN diode structure fabricated with the p-type SiC epitaxial layer. Furthermore, 4H-SiC MESFETs having a micron-gate length were fabricated using a lithography process and their current-voltage performances were characterized.

A sublimation epitaxial method, referred to as the Closed Space Technique (CST) was adopted to produce thick SiC epitaxial layers for power device applications. We aimed to systematically investigate the dependence of SiC epilayer quality and growth rate during the sublimation growth using the CST method on various process parameters such as the growth temperature and working pressure. The etched surface of a SiC epitaxial layer grown with low growth rate (30 μm/h) exhibited a low etch pit density (EPD) of ~2000 /cm2 and a low micropipe density (MPD) of 2 /cm2. The etched surface of a SiC epitaxial layer grown with a high growth rate (above 100 μm/h) contained a high EPD of ~3500 /cm2 and a high MPD of ~500 /cm2, which indicates that high growth rate aids the formation of dislocations and micropipes in the epitaxial layer.

Raman scattering studies were performed on hot-wall chemical vapor deposited (heteroepitaxial) silicon carbide (SiC) films grown on Si substrates with orientations of (1 0 0), (1 1 1), (1 1 0) and (2 1 1), respectively. Raman spectra suggested that good quality cubic SiC single crystals could be obtained on the Si substrate, independent of its crystallographic orientation. Average residual stresses in the epitaxially grown 3C-SiC films were measured with the laser waist focused on the epilayer surface. Tensile and compressive residual stresses were found to be stored within the SiC film and in the Si substrate, respectively. The residual stress exhibited a marked dependence on the orientation of the substrate. The measured stresses were comparable to the thermal stress deduced from elastic deformation theory, which demonstrates that the large lattice mismatch between cubic SiC and Si is effectively relieved by initial carbonization. The confocal configuration of the optical probe enabled a stress evaluation along the cross-section of the sample, which showed maximum tensile stress magnitude at the SiC/Si interface from the SiC side, decreasing away from the interface in varied rate for different crystallographic orientations. Defocusing experiments were used to precisely characterize the geometry of the laser probe in 3C-SiC single crystal. Based on this knowledge, a theoretical convolution of the in-depth stress distribution could be obtained, which showed a satisfactory agreement with stress values obtained by experiments performed on the 3C-SiC surface.

Investigations were carried out to achieve high performance Silicon Carbide Metal-Oxide-Semiconductor device structures. 4H-SiC/SiO2 interface was prepared by growing amorphous SiO2 layers by an alternate low temperature atmospheric CVD technique using TEOS as source material and the interface properties were compared with the one prepared by conventional thermal oxidation technique. The low temperature CVD technique offered the improvement of the interface properties with reduced Dit in comparison with thermally oxidized interface. As a new attempt, an in situ post growth annealing technique in N2 atmosphere was carried out to reduce the Dit further. Both the CVD technique and the in situ annealing processes that were used in the present study have been identified to be potential approaches to improve the interface quality.

For preliminary step toward fabrication of MOSFET using 4H-SiC 8) 3 (03 prepared by sublimation method, epitaxial growth of device quality 4H-SiC on 4H-SiC (0001) 8.0° off substrate was carried out and investigated. Smooth and specular surface of 4H-SiC (0001) plane was obtained by optimum growth condition. And epitaxial growth on 4H-SiC 8) 3 (03 and ) 8 3 (03 substrates were carried out with optimum growth conditions of 4H-SiC (0001). Smooth and specular surface was obtained on 4H-SiC 8) 3 (03 and ) 8 3 (03 plane. Growth rate of epilayers of 4H-SiC (0001), 8) 3 (03 and ) 8 3 (03 face were same. Oxidation rate of 4H-SiC (0001), ) 1 (000 , 8) 3 (03 and ) 8 3 (03 face was investigated. The oxidation rate was different depending on the faces. It was observed that the difference of oxidation rate of 8) 3 (03 and ) 8 3 (03 is mainly due to the difference of polarity similar to the case of reported for (0001) and ) 1 (000 .

The selective growth of Si column was carried out by depositing Au on patterned Si (111) substrate as a solvent in chemical vapor transport method by using halides (HCl). The Si column was produced by VLS mechanism. The column was covered with SiC by conventional CVD process using HMDS ( Hexamethyldisilane ). Carbon Nano Tube ( CNT ) was deposited on Si column covered with SiC by DC assisted µ-wave plasma CVD.

The preparation of porous 4H-SiC by electrochemical etching of SiC crystals was investigated. The porous layer was created at the porous SiC (PSC)/SiC interface but not from the SiC/electrolyte interface. The nanopores at the adjacent region of PSC/SiC interface were bigger than those at the top region. In the visible light region, the optical reflectance from PSC exhibits interference fringes. In the Reststrahlen region, the fourier transform infrared (FTIR) reflectance of porous 4H-SiC shows a splitting into more bands: a broad band with high reflectivity at low frequency and several sharp peaks near the LO frequency. The width and shape of FTIR spectra depended on the anodization current density. The anodization current density is a crucial parameter which determined the porosity, porosity depth profile, and the thickness of PSC layers. A pore transformation of porous structure was observed after chemical vapor deposition process.

The pendeo epitaxial growth has been applied for the growth of 3C-SiC on (001) Si substrates. This growth was performed by VPE using hexamethyldisilane (HMDS) as a source gas. To characterize the crystallinity of the seed 3C-SiC and the pendeo epitaxial layer, the high resolution transmission electron microscopic (HRTEM) analysis was carried out. In the vertically grown layer on the seed 3C-SiC, the high-defect-density regions were observed. On the contrary, the low-defect-density regions were observed in the laterally grown layer. It was revealed from the TEM observations that lattice information can be transferred through the seed 3C-SiC while defects can be prevented from propagating into the epitaxial layer due to the presence of the air gap.

Hetero-epitaxial CVD growth of 3C-SiC on a Si(110) substrate gives a (111) crystal with low defects density. However, double positioning growth often disturbs growth of a single crystal. The growth on an off-axis Si(110) substrate suppressed propagation of the double positioning defects in the grown layer effectively. Cross-sectional transmission electron microscopy revealed the details of the suppression process on the off-axis substrate. The suppression mechanism and the origin of the defects formation at double positioning boundaries were interpreted by the growth model based on an anisotropic growth rate on (111) plane of 3C-SiC.

Interfaces between a Si(110) substrate and 3C-SiC crystals grown hetero-epitaxially by CVD were investigated by cross-sectional transmission electron microscopy. Gas flow condition during the carbonization process affects the roughness of the substrate surface and there is an optimum condition to preserve the flat surface. High quality 3C-SiC crystals grew only on the flat substrate, with crystallographic relationship of Si[1-10]//SiC[1-10] and Si[001]//SiC[1-1 - 2], because the well-lattice-match relationship was limited in a two-dimensional region at the SiC(111)/Si(110) interface. Using the optimum condition, some kinds of roughness at an atomic scale remained on the surface of the substrate. Nanoscopic observation of the crystals grown on an off-axis substrate revealed the influence of the roughness on the epitaxial growth and the defects generation at the interface.

Most of the ion implanter is large scale, high acceleration voltage and expensive. For research and development, such a huge implanter is not required. Our motivation is to make desktop type ion implanter for SiC device. We report the fabrication of a compact 100 kV ion implanter. In order to miniaturize the equipment, an ion source, an accelerator tube and a main chamber were vertically arranged. We implanted Argon (Ar) and Nitrogen (N) ions to 6H-SiC substrate and the implanted 6H-SiC substrates were characterized by Fourier Transform Infrared Spectrometer (FTIR), Rutherford Backscattering Spectrometry (RBS) and Secondary Ion Mass Spectrometry (SIMS). In this report, concept of desktop ion implanter, evaluation of implanted substrate and its device application are presented. In order to characterize capability, with using the newly made compact ion implanter, it was possible to make implantation on SiC to get amorphous layer suitable for deices.

Lateral epitaxial overgrowth (LEO) is known as method of defects reduction for GaN. LEO is expected to reduce crystal defects on hetero-epitaxial growth of 3C-SiC. (100) Si substrate patterned with SiO2 mask was used as the substrate. Before CVD process, V shape crater was made on Si surface by HCl etching. And growth condition of CVD was optimized. Single crystal of 3C-SiC was grown laterally on SiO2 layer. Cross-sectional transmission electron microscopic observation indicated that crystal quality of LEO region was single and no defect crystal.

Chemical vapor deposition of (111) 3C-SiC on (110) Si substrate was carried out, and the effect of the substrate off-axis introduced on (110) Si substrate for suppressing the twin formation in 3C-SiC hetero-epitaxial layers was investigated. From the growth on hemispherically polished (110) Si substrate, it was found that the off-axis toward the [001] Si axis had a noble effect for suppressing the twin formation, while the off-axis toward the [110] Si axis was ineffective. The growth of single 3C-SiC crystal containing few double positioning boundaries, which are related with the twin formation, was demonstrated on the (110) Si substrate 3° off-axis toward the [001] Si axis. Transmission electron microscopic observation revealed that double positioning boundaries on the (110) Si substrate off-axis toward the [001] Si axis were nearly eliminated within the initial a few hundreds nano meter in thickness.

Selective growth and reduction of defects of cubic silicon carbide (3C-SiC) crystals grown within windows and laterally over SiO2 masks patterned on Si substrates are presented. The growth has been performed via chemical vapor deposition using hexachlorodisilane and propane, as well as hexamethyldisilane. Lateral epitaxial overgrowth (LEO) was achieved at selected areas where windows are square or array of stripes. The LEO process was characterized mainly by atomic force microscopy. 3C-SiC grew epitaxially on Si inside the window of SiO2 mask, and after filling up the window area, SiC grew laterally onto the SiO2 mask. The LEO begins with appearance and growth of (1 1 2) facets of 3C-SiC, and finally, the fronts of laterally overgrown SiC from the opposite sides of windows coalesce with each other. If the mask is an array of rectangular stripes, the coalescence point becomes a seam. Cathodoluminescence micrographs showed the absence of dislocations in the LEO region and the presence at the seam lines. Although many rectangular-shaped pits are observed in the area of epitaxially grown 3C-SiC, they disappeared in the LEO regions. This suggests the pits being originated upon epitaxy of 3C-SiC on Si and expanded to form rectangular shape on the final surface.

Single-walled carbon nanotubes (SWNTs) have been successfully synthesized in the gas phase by hot filament chemical vapor deposition (HF CVD) and plasma-assisted-hot filament chemical vapor deposition (PHF CVD) in hydrogen-diluted ethylene and vaporized ferrocene. It was shown that a large amount of SWNTs can be synthesized by HF CVD. Moreover, it was demonstrated that PHF CVD enables the synthesis of a larger amount of SWNTs by the electrostatic confinement of fine particles for a long time in a plasma generated by dc (direct current) voltage application between a hot filament and a collecting plate.

Raman piezo-spectroscopy characterizations of a silicon carbide (SiC) semiconductor device, epitaxially grown on a Si(1 1 1) substrate, are described. The device was grown by a selective epitaxial growth approach, based on a chemical vapor deposition (CVD) method, which enabled us to reduce to a significant extent the high density of interfacial defects in the deposited 3C-SiC phase. Upon preliminary piezo-spectroscopic calibrations, made in bending geometry on a bulk SiC sample with the same phase composition of the device, mapping of microscopic residual stress fields both on surface and side of the semiconductor device was attempted. It is shown that the present Raman microprobe assessments allowed: (i) to quantitatively evaluate the impact of the manufacturing process on the final device microstructure; and, (ii) to visualize a model for residual stress intensification during the CVD growth process.

Single crystal growth of 3C–SiC on (100), (110), (111), and (211) Si substrates was carried out by CVD with the source gases of Si2Cl6 and C3H8, for its applications as substrates for nitride semiconductors. Depending on the substrate orientations, the flow rate of C3H8 during the growth of carbonized buffer layer and the C/Si ratio in the supplied source gases during the CVD growth were varied and optimized. The crystal orientation of 3C–SiC epitaxial layers was identical with that of Si substrates on (100), (111), (211) substrates, although that on (110) Si substrates was twined (111) 3C–SiC. It revealed from the growth on hemispherically polished (111) substrates that off-axis toward 〈2–1–1〉 is effective to achieve smooth surface on (111) Si substrates. The surface morphology of as-grown (211) 3C–SiC was superior to that of other substrate orientations. The present research enabled various orientations of single crystal 3C–SiC/Si structures being available for substrates of nitride semiconductors. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

An optical-capacitance-transient spectroscopy (O-CTS) method was used to characterize defects in epitaxial 6H-SiC. The O-CTS measurements enable us to estimate the optical ionization energy and the optical cross section of these defects. By the deep level transient spectroscopy (DLTS), three peaks were observed, and two of them were identified as E2 and R centers which have been previously reported. We measured the optical cross section for both the centers. By fitting the experimental data with theoretical curves for the optical cross section, we obtained optical ionization energy of 1.58 eV for the R center and 1.0 eV for the E2 center. From the DLTS measurements, the thermal activation energy of the R center is 1.30 eV and that of the E2 center is 0.43 eV. From these results and the previously reported capture energy barrier, the Franck–Condon shift, dFC is estimated to be 0.28 eV for the R center and 0.62 eV for the E2 center.

Thermal etching was investigated as one of the methods of obtaining atomically flat surfaces of SiC substrates. The formation of a graphite layer on substrate surface was suppressed by reducing the C/Si ratio in the vapor phase. Although (1120) substrates etched in argon atmosphere had round pits on their surface, such pits were not observed and an atomically flat surface with an RMS roughness of approximately 0.3 nm was obtained in nitrogen atmosphere even at the high etching rate of 250 µm/h. The substrates with higher nitrogen concentrations had both higher surface flatness and higher etching rate. The thermal etching method was found to be an effective technique for obtaining the flat surface of SiC substrates that is suitable for crystal growth and/or device fabrication. The etching mechanisms of (0001) and (1120) surfaces were compared, and the result was discussed by taking into consideration the bond configuration on the surface.

Cubic silicon carbide has a potential for high power, high frequency and high temperature devices. Sublimation growth is an established technique to prepare silicon carbide wafers, due to the possibility to obtain high quality crystals with high growth rates. However, the sublimation growth of cubic silicon carbide has not been very successful owing to the poor temperature stability of the polytype. In this study, bulk crystal growth of cubic silicon carbide on hexagonal silicon carbide substrates was tried by sublimation epitaxy. In previous work, the (0 0 0 1) basal plane of hexagonal silicon carbide have been used as substrate for cubic silicon carbide growth by the sublimation method. In this study, crystal growth was carried out not on the (0 0 0 1) basal plane but on the off-axis (0 0 0 1) plane tilted towards 11 2 0 . This tilted plane was used in order to form step-free (0 0 0 1) basal plane and to grow cubic silicon carbide on this step-free plane. A step-free surface was formed on the off-axis oriented seed crystal by limiting the growth area and single crystal cubic silicon carbide could be successfully grown. Cubic silicon carbide with a size of 4.0 mm×4.0 mm and 2.0 mm thick was obtained.

Large-area synthesis of well-aligned carbon nanotubes (CNTs) by surface-wave-excited microwave-plasma chemical vapor deposition (CVD) using slot antennas has been developed. By a one-slot antenna system, aligned CNTs were successfully synthesized on a 3 × 3 cm2 substrate. In order to synthesize on a larger-area substrate, we generated large-area surface-wave-plasma by a two-slot antenna system and synthesized CNTs on substrates set at the center and around the edge of a 7.5 × 7.5 cm2 substrate holder. Grown CNTs were aligned and uniform in diameter and density. Surface-wave excited microwave-plasma CVD has a potential for large-area synthesis of well-aligned carbon nanotubes.

Carbon nanotubes were synthesized by hot filament assisted direct current plasma enhanced chemical vapor deposition (HF/DC-P CVD) in CH4/H2 plasmas. Well-aligned and high density carbon nanotubes were grown. By I-V characteristics and SEM images, it was found that there is a close relation between well-aligned carbon nanotubes and field emission properties. It was also found by the F-N plot of I-V characteristics that the current is due to the tunnelling effect and there are no relations between the feld enhancement factor and the diameter of carbon nanotubes for the grown carbon nanotubes.

A new synthesis method of aligned carbon nanotubes on large substrates by surface-wave-excited microwave-plasma chemical vapor deposition (CVD) using slot antennas has been developed. Under the optimized conditions, well-aligned, high-density, uniform carbon nanotubes were successfully synthesized on the entire surface of a 3×3 cm2 substrate by a one-slot antenna system. The practical value of an electron field emission density of more than 1 mA/cm2 was obtained at -650 V. For large-scale synthesis of carbon nanotubes, we generated uniform surface-wave-excited microwave plasma of 12 cm diameter by a two-slot antenna system and confirmed the growth of carbon nanotubes in a preliminary experiment.

Single crystal 3C-SiC (cubic silicon carbide) thin-films were deposited on Si(100) wafer up to the thickness of 4.3 by APCVD (atmospheric pressure chemical vapor deposition) method using HMDS (hexamethyildisilane; ｛CH｝ Si) at 135. The HMDS flow rate was 0.5 sccm and the carrier gas flow rate was 2.5 slm. The HMDS flow rate was important to get a mirror-like crystal surface. The growth rate of the 3C-SiC film was 4.3 /hr. The 3C-SiC epitaxial film grown on Si(100) wafer was characterized by XRD (X-ray diffraction), AFM (atomic force microscopy), RHEED (reflection high energy electron diffraction), XPS (X-ray photoelecron spectroscopy), and Raman scattering, respectively. Two distinct phonon modes of TO (transverse optical) near 796 / and LO (longitudinal optical) near 9741 / of 3C-SiC were observed by Raman scattering measurement. The heteroepitaxially grown film was identified as the single crystal 3C-SiC phase by XRD spectra (2

SiC direct bonding technology is very attractive for both SiCOI(SiC-on-insulator) electric devices and SiC-MEMS(micro electro mechanical system) fields because of its application possibility in harsh environments. This paper presents pre-bonding techniques with variation of HF pre-treatment conditions for SiC wafer direct bonding using PECVD(plasma enhanced chemical vapor deposition) oxide. The PECYD oxide was characterized by XPS(X-ray photoelectron spectrometer) and AFM(atomic force microscopy). The characteristics of the bonded sample were measured under different bonding conditions of HF concentration and an applied pressure. The bonding strength was evaluated by the tensile strength method. The bonded interface was analyzed by using SEM(scanning electron microscope). Components existed in the interlayer were analyzed by using FT-IR(fourier transform infrared spectroscopy). The bonding strength was varied with HF pre-treatment conditions before the pre-bonding in the range of 5.3 kgf/cmto 15.5 kgf/cm