SiC Interlayer Research Articles

Influence of the rapid thermal annealing on the properties of a-C:H/c-Si structures

The influence of rapid thermal annealing (RTA) on the properties of a-C: H/c-Si (p-type) structures was investigated. The carbon layers were deposited by plasma enhanced CVD at substrate temperature of 340°C from methanol (CH3OH) vapor. The C-V and I-V measurements of the a-C: H/Si structures showed that a p-n junction is formed on the silicon surface after RTA and the structures behave as a Schottky diode. The formation of a thin SiC interlayer by 1000 and 1200°C RTA was proven by the corresponding optical constants obtained from the ellipsometric measurements after RTA and subsequent carbon removal in HF acid.

Diamond nanocrystals and amorphous SiO x nanowires formed by rapid thermal annealing of carbon film

Rapid thermal annealing (RTA) has been performed on the carbon films prepared by radio frequency plasma-enhanced chemical vapor deposition on Si substrate. The RTA at 800 °C for 60 s leads to the formation of many diamond nanocrystallites agglomerating on the film surface. Higher temperature RTA at 1100 °C for 60 s induces the high-density amorphous SiO x ( x = 1.2) nanowires on the film surface without diamond nanocrystallites. At both the RTA temperatures, a well-oriented SiC interlayer is also formed simultaneously. The sp 3 sites in the carbon film and the oxygen during the RTA treatment as well as the RTA temperature are considered to play important roles in determining the final reaction products.

ＤＬＣ薄膜を成膜させた各種アルミニウム合金表面の摩擦摩耗特性に及ぼす中間層の影響

Diamond-like carbon (DLC) films have been deposited on various aluminum alloys by ion plating method. Prior to DLC deposition, various interlayers were deposited on the alloys using several deposition methods. Tribological properties of such coated materials were measured using the ball-on-disk characterization method. Aluminum alloys improved by DLC films was friction coefficient of about 0.2 to 0.3. It was also found that the nature of the interlayer has an influence on the wear properties of the DLC film. It was also found out that the best interlayer is different for each type of aluminum alloy. Between the tested combinations of interlayers/aluminum alloys, 6061 alloy with a SiC interlayer showed the most excellent wear properties.

Interfaces between 4H-SiC and SiO2: Microstructure, nanochemistry, and near-interface traps

We report on electrical and microscopic investigations aimed to clarify the origin of near-interface traps (NITs) in metal–silicon dioxide–4H-silicon carbide structures. Using capacitance–voltage and thermal dielectric relaxation current (TDRC) analysis we investigated NITs close to the 4H-SiC conduction-band edge in differently prepared thermal and deposited oxides and found that the traps give rise to two characteristic TDRC signatures belonging to two groups of trap levels. The total trapped charge exceeds 1×1013cm−2. The observed density and energy distribution of these traps are nearly identical in all thermal and deposited oxides investigated, suggesting that the NITs belong to intrinsic defects at the SiO2∕SiC interface which are readily formed during oxide deposition or thermal oxidation of 4H-SiC. Using high-resolution electron microscopy combined with nanochemical analysis (electron energy-loss near-edge spectroscopy and energy-filtered transmission electron microscopy) we investigated the SiO2∕SiC interface in samples receiving reoxidation and did not find any indication of graphitic regions at or near the SiO2∕SiC interface or in the bulk silicon dioxide within a detection limit of 0.7nm. In addition, no amorphous carbon accumulation was observed near the SiO2∕SiC interface. The overall results strongly suggest that the NITs near the 4H-SiC conduction band are not related to carbon structures in the SiO2∕SiC interlayer.

Effects of Methane Concentration in the Deposition Process on the Crystal Structure and the Adhesive Fracture Toughness of CVD Diamond

Crystal structures of CVD diamond particles were observed in detail by transmission electron microscopy. The particles were deposited on silicon substrates under various conditions and had different levels of adhesion. An interlayer of SiC was found along the interface obtained with low methane concentration in the source gas, but it disappeared when deposited with higher methane concentrations. On the other hand, the size of crystal grains became smaller with increasing methane concentrations. From the correspondence between the structures and the adhesive toughness of these particles, it was suggested that the effect of both the SiC interlayer and the variation of grain size resulted in the complicated trend of adhesion with respect to methane concentration.

Atomic structure determination of the Si-rich β-SiC(001)3×2surface by grazing-incidence x-ray diffraction: A stress-driven reconstruction

The atomic structure of the Si-rich \ensuremath{\beta}-SiC(001) $3\ifmmode\times\else\texttimes\fi{}2$ surface reconstruction is solved by grazing-incidence x-ray diffraction with surface and subsurface structure determination. The reconstruction involves three Si atomic planes $(\frac{1}{3}+\frac{2}{3}+1$ Si monolayers) in qualitative agreement with ab initio theoretical calculations. The first plane includes Si dimers that are asymmetric with a 0.1 \AA{} height difference between Si atoms while the second plane includes Si dimers having alternating long (2.41 \AA{}) and short (2.26 \AA{}) lengths resulting in long-range influence with no buckling of the top surface dimers, in strong contrast to other group-IV semiconductors. Dimerization is also shown to take place in the third Si plane with a dimer having a bond length at 2.38 \AA{}. In addition, a large Si interlayer spacing is found between the reconstructed planes at 1.56 \AA{}, significantly larger than that for bulk SiC (1.09 \AA{}) and Si (1.35 \AA{}) interlayer distances, indicating a very open surface. The results suggest that stress is at the origin of this complex surface organization.

The morphology and mechanical properties of TiN/Ni–P–SiC hybrid coatings

The current trend of coating techniques involves composite coatings, such as multilayer or multiphase, which are expected to have tailor-made properties for some specific applications. In this study, a hybrid process that combined the composite electroless plating and plasma-enhanced chemical vapor deposition (PECVD) is proposed to improve the mechanical properties of TiN coated tool steel. Experimental results show that the apparent hardness of the TiN/Ni–P–SiC hybrid coatings increases with increasing content of SiC particles in electroless Ni–P interlayer and affects the TiN hardness value. This could be due to an effect of SiC particles on the coating growth of TiN and a high load carrying capability of Ni–P–SiC interlayer. In comparison with single TiN layer and TiN/Ni–P hybrid coating, a reduction in cracking and spalling for the TiN/Ni–P–SiC layer was observed during wear tests. Wear resistance was significantly improved due to the incorporation of SiC particles into electroless Ni–P interlayer, which increased hardness and adhesion of the coated TiN layer.

Structure and mechanical properties of low stress tetrahedral amorphous carbon films prepared by pulsed laser deposition

Tetrahedral amorphous carbon films have been produced by pulsed laser deposition, at a wavelength of 248 nm, ablating highly oriented pyrolytic graphite at room temperature, in a 10-2 Pa vacuum, at fluences ranging between 0.5 and 35 Jcm-2. Both (100) Si wafers and wafers covered with a SiC polycrystalline interlayer were used as substrates. Film structure was investigated by Raman spectroscopy at different excitation wavelength from 633 nm to 229 nm and by transmission Electron Energy Loss Spectroscopy. The films, which are hydrogen-free, as shown by Fourier Transform Infrared Spectroscopy, undergo a transition from mainly disordered graphitic to up to 80% tetrahedral amorphous carbon (ta-C) above a threshold laser fluence of 5 J cm-2. By X-ray reflectivity roughness, density and cross-sectional layering of selected samples were studied. Film hardness as high as 70 GPa was obtained by nanoindentation on films deposited with the SiC interlayer. By scratch test film adhesion and friction coefficients between 0.06 and 0.11 were measured. By profilometry we obtained residual stress values not higher than 2 GPa in as-deposited 80% sp3 ta-C films.

Structural, electrical, and low-frequency-noise properties of amorphous-carbon–silicon heterojunctions

The structural, electrical, and low-frequency-noise properties of heterojunctions of amor- phous-carbon (a-C) films grown on either n- or p-type single-crystal silicon are investigated. The a-C films were deposited by rf magnetron sputtering at room temperature with varying the substrate bias Vb, from +10 to −200 V. The study includes measurements of x-ray reflectivity (XRR), low-frequency noise at room temperature, and dark current–voltage (I–V) and capacitance–voltage (C–V) characteristics over a wide temperature range. Analysis of the XRR data indicates the presence of a thin SiC layer between a-C and Si, with thickness increasing up to about 1.8 nm for Vb=−200 V. The results show that the noise properties of the devices are independent of the SiC interlayer and the a-C film deposition conditions, while the noise of the a-C/n-Si heterojunctions is about four orders of magnitude lower than that of the a-C/p-Si heterojunctions. Analysis of the I–V and C–V data shows that the rectification properties of the a-C/n-Si heterojunctions are governed by conventional heterojunction theory, while multistep tunneling is the current conduction mechanism in a-C/p-Si heterojunctions due to a high density of interface states.

Growth kinetics of sputtered amorphous carbon thin films: composition studies and phenomenological model

The kinetics of carbon sputter deposition on Si(100) substrates were studied by spectroscopic ellipsometry (SE) and X-ray reflectivity (XRR). The energy of ions bombarding the growing film varied by applying a bias voltage on the substrate inducing considerable changes of film density and composition. Both SE and XRR detected an initial nucleation stage during which a SiC interlayer was formed. A phenomenological model based on the rate equations for the carbon deposition on Si is proposed to describe the experimental results. The model includes the processes of carbon adsorption, formation of SiC and transition from sp 2 to sp 3 sites induced by low-energy ion bombardment. The calibration of the model was performed with the experimental results regarding the variation of deposition rates. It is shown that the non-monotonous kinetics of film growth is determined by the variations of surface composition at different stages of growth. The variation of model parameters, such as reaction constants and sticking coefficients, during fitting the experimental results for various ion energies extracted information regarding the prevailing processes taking place at each stage of the deposition process.

Epitaxial thin films of MgO on Si using metalorganic molecular beam epitaxy

Epitaxial cubic MgO thin films have been deposited on single crystal Si(001) substrates by metalorganic molecular beam epitaxy. The Mg source was the solid precursor magnesium acetylacetonate and a rf excited oxygen plasma was the oxidant. The growth process involved initial formation of an epitaxial β-SiC interlayer followed by direct deposition of a MgO overlayer. The films were characterized by in situ reflection high energy electron diffraction, x-ray diffraction, conventional and high resolution transmission electron microscopy, atomic force microscopy, Auger electron spectroscopy, and Fourier transform infrared spectroscopy. The β-SiC interlayer had an epitaxial relationship such that SiC(001)∥Si(001) and SiC [110]∥Si [110]. The SiC interlayer showed a columnar grain structure with planar defects including twin bands and stacking faults. The MgO overlayer showed an epitaxial relationship given by MgO(001)∥Si(001) and MgO[110]∥Si[110]. No evidence of twins in the MgO layers was observed.

Structural and Mechanical Properties of Diamond-Like Carbon Films Prepared by Pulsed Laser Deposition With Varying Laser Intensity

ABSTRACTDiamond-like carbon (DLC) films have been prepared by pulsed laser deposition (PLD) (wavelength 248 nm), ablating highly oriented pyrolytic graphite (HOPG) at room temperature in a vacuum of 10−2Pa, at fluences between 0.5 and 35 Jcm−2. Films have been deposited on Si(100) with and without a SiC interlayer. Structural analysis, such as visible and UV Raman, Infrared and Electron Energy Loss (EEL) spectroscopies show that the films are hydrogen-free and undergo a transition, from mainly disordered graphitic to up to 80% tetrahedral amorphous carbon (ta-C), above a laser threshold fluence of 5 J cm−2. The measured residual stresses of as deposited ta-C films do not exceed 2 GPa. Scratch tests show excellent adhesion properties. Low friction coefficients (0.05-0.1) have been measured in ambient humidity. Nanoindentation indicates that film hardness is as high as 70 GPa

Limiting processes for diamond epitaxial alignment on silicon

For the heteroepitaxial deposition of diamond on silicon using the bias-enhanced nucleation procedure, several different processes contributing to the final misalignment of the layers can be identified: (i) The interface of Si/diamond or Si/SiC and SiC/diamond, respectively. (ii) The growth of individual grains during the biasing process. (iii) The growth competition between differently oriented grains and their coalescence during the growth of thick films. X-ray-diffraction texture studies revealed that the azimuthal alignment is essentially determined by the nucleation step. Oriented nucleation is only possible within a defined time window. Within this time window the azimuthal misalignment shows a characteristic variation depending on the absolute value of the bias voltage. The alignment of the SiC interlayer as measured by synchrotron radiation cannot explain the observed variation. In contrast, texture measurements of thick oriented films after exposure to the bias conditions suggest that the limitation of the process time window for oriented nucleation as well as the variation of misorientation with biasing time can be traced back to the detrimental effect of bias-assisted growth. Based on this mechanism, a model is proposed which allows one (a) to describe the temporal development of the azimuthal misorientation within the process time window, and (b) to estimate the contribution of bias-assisted growth on the misorientation. Finally, some epitaxial diamond films have been deposited on high-quality \ensuremath{\beta}-SiC layers. A minimum value of 2.9\ifmmode^\circ\else\textdegree\fi{} for the width of the azimuthal distribution has been found.

Structural studies of diamond thin films grown from dc arc plasma

Diamond thin films grown from a dc-arc discharge in CH4/H2mixtures on Si wafers were examined by transmission electron microscopy and Raman spectroscopy. This deposition method provides good diamond crystallinity at high CH4concentrations (3%–9%). Seeding the substrate with 5 nm diamond particles at a density of 2 × 1012cm−1followed by argon laser irradiation to reduce their agglomeration gives, just after starting deposition, a density of growth centers of 1010cm−2. At 3% CH4concentration the film grows with almost perfect crystallites. Richer CH4mixtures (5% and 9%) produce crystallites with twins and stacking faults. An amorphous 20–70 nm SiC interlayer is present at these CH4concentrations, which was not observed at 3% CH4. Amorphoussp3- andsp2-bonded carbon was detected by Raman spectroscopy at all CH4concentrations and correlated with TEM data.

HRTEM and energy filtering TEM study of interfacial reaction between diamond film and silicon

Diamond was deposited on Si(100) substrates by microwave plasma assisted chemical vapor deposition in three steps: carburization, biasing and growth. High-resolution transmission electron microscopy (TEM) in cross-sectional view has been used to observe the evolution of microstructures around the interfacial region between diamond and Si in each processing step. The chemistry near the interface was characterized with elemental mapping using an energy-filtered TEM imaging technique. In the carburization stage, an amorphous SiC interlayer 1.5 nm thick was formed between an amorphous carbon layer and Si. In the following biasing stage, β-SiC can form in epitaxial orientation with Si. In the growth stage, diamond grains aligned in a strongly textured condition developed, while the initially grown diamond had polycrystalline characteristics. Processing conditions for epitaxial diamond deposition on Si substrates are briefly discussed.

The effect of substrate position on the orientation and interfacial reaction of epitaxial diamond on silicon

Diamond was grown on silicon substrates by microwave plasma-enhanced chemical vapour deposition with pretreatment consisting of carburization and biasing. Cross-sectional transmission electron microscopy shows that epitaxial diamond can be directly grown on Si(110). The orientation of epitaxial diamond varies with the substrate position under the plasma ball. At the central part of the substrate, diamond is mainly in a cube-on-cube orientation relationship with silicon which is <110>dia//<110>Si and {111}dia//{111}Si. Away from the centre, five different orientation relationships are observed. The defect density of the diamond film is also dependent on the substrate position. For Si(100) substrates, the interfacial structure between diamond and Si also varies as a function of the substrate position. An SiC interlayer is formed after the bias and growth stages of deposition. The amorphous carbon, deposited in the carburization step, may react with Si to form SiC. Plasma inhomogeneity plays an important role in the variation of the diamond orientation. In addition, the composition and structure of the interlayer formed between diamond and silicon depend on the position under the plasma.

Growth and Characterization of Si-GaP and Si-GaP-Si Heterostructures

AbstractThe low temperature epitaxial growth of Si / GaP / Si heterostructures is investigated with the aim using GaP as a dielectric isolation layer for Si circuits. GaP layers have been deposited on Si(100) surfaces by chemical beam epitaxy (CBE) using tertiarybutyl phosphine (TBP) and triethylgallium (TEG) as source materials. The influence of the cleaning and passivation of the GaP surface has been studied in-situ by AES and LEED, with high quality epitaxial growth proceeding on vicinal GaP(100) substrates. Si / GaP / Si heterostructures have been investigated by cross sectional high resolution transmission electron microscope (HRTEM) and secondary ion mass spectroscope (SIMS). These methods reveal the formation of an amorphous SiC interlayer between the Si substrate and GaP film due to diffusion of carbon generated in the decomposition of the metalorganic precursors at the surface to the GaP/Si interface upon prolonged growth (layer thickness &gt; 300Å). The formation of twins parallel to {111} variants in the GaP epilayer are extended into the subsequently grown Si film with minor generation of new twins.

Heterojunction silicon-carbon films with SiC interlayer

Electrical and optical properties and surface energy of heterojunction silicon-carbon films were analysed. The carbon films were obtained by the RF CVD method. A diode reactor, in which RF electrical energy was supplied to one electrode, was used. The density of surface states and the effective charge were measured. It was shown that during the etching of a silicon substrate, a SiC interlayer was produced at the interface between the silicon substrate and carbon film. Without etching, SiO 2 was detected at the silicon surface. Analysis of the phenomena occurring in the SiC interface region shows the problems involved in the application of the electronic structures, including the SiC heterojunction in microelectronics. On the basis on our own investigations and results presented in the literature, an energetic band gap model of the examined AlC SiCSi and AlCSiO 2Si structures is introduced.