SiC/C薄膜的制备及其力学性能

以SiC 超细粉为原料、采用热等离子体物理气相沉积( TPPVD) 技术快速制备出了高质量SiC/ C 薄膜, 最大沉积速度达到225 nm/ s, 高于常规物理气相沉积( PVD) 和化学气相沉积(CVD) 法两个数量级。用扫描电子显微镜、高分辨透射电子显微镜和X 射线光电子谱对薄膜的形貌和微结构进行了观察和分析, 并用纳牛力学探针测定了薄膜的力学性能。研究结果表明, 向等离子体中导入CH₄, SiC/ C 薄膜沉积速度增大, 薄膜中C 含量增加, 薄膜断面呈现柱状结构。薄膜硬度和弹性模量随薄膜中C 含量增加而降低, 在接触深度为40 nm 时由纳牛力学探针测得沉积薄膜的最大硬度达到38 GPa。     

Pressure dependence of morphology and phase composition of SiC films deposited by microwave plasma chemical vapor deposition on cemented carbide substrates

SiC films were deposited on cemented carbide substrates by employing microwave plasma chemical vapor deposition method using tetramethylsilane (Si(CH₃)₄) diluted in H₂ as the precursor. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and scratching technique were used to characterize morphology, composition, phases present and adhesion of the films. Experimental results show that the deposition pressure has great influence on morphologies and phase composition of the films. In sequence, SiC films with a cauliflower-like microstructure, granular films with terrace-featured SiC particles coexisting with Co₂Si compound and clusters of nanometer SiC nanoplatelets appear as a function of the deposition pressure. In terms of plasma density and substrate temperature, this sequential appearance of microstructures of SiC films was explained. Adhesion tests showed that among the three types of films studied, the films with the terrace-featured SiC particles have relatively higher adhesion. Such knowledge will be of importance when the SiC films are used as interlayer between diamond films and cemented carbide substrates.     

Gas tunnel type plasma spraying deposition and microstructure characterization of silicon carbide films for thermoelectric applications

Gas tunnel type plasma spraying deposition has been applied successfully to the deposition of the SiC films on stainless-steel substrates. The microstructure and the surface morphology of the SiC films were characterized by means of X-ray diffraction (XRD) and scanning electron microscope (SEM). The control of the processing parameters such as powder feeding rate, composition of plasma working gases, spraying distance, and carrier gas flow rate allowed the deposition of dense, uniform, continuous, and high purity crystalline SiC films. The thickness of the SiC films varied from 3 to 10 μm. EDS analysis confirmed the presence of SiO₂ in the deposited SiC films.     

溅射工艺对SiCN薄膜沉积及光性能的影响

本文利用射频磁控溅射工艺制备了ＳｉＣＮ薄膜,研究了基本工艺参数如溅射功率、Ｎ分压对薄膜沉积和光学性能的影响．研究结果表明：溅射制备的薄膜中形成了复杂的网络结构,膜中三元素Ｓｉ、Ｃ和Ｎ两两之间形成了共价键．Ｎ分压的提高降低了薄膜的沉积速率．Ｎ流量的提高使光学带隙增大．溅射功率的提高使薄膜的沉积速率提高,但使得光学带隙减小．     

The effect of input gas ratio on the growth behavior of chemical vapor deposited SiC films

In an effort to protect a RBSC (reaction-bonded silicon carbide) reaction tube, SiC films were chemically vapor deposited on RBSC substrates. SiC films were prepared to investigate the effect of the input gas ratios (dilute ratio, = P _H2/P _MTS = Q _H2/Q _MTS) on the growth behavior using MTS (metyltrichlorosilane, CH₃SiCly₃) as a source in hydrogen atmosphere. The growth rate of SiC films increased and then decreased with the decrease of the input gas ratio at the deposition temperature of 1250°C. The microstructure and preferred orientation of SiC films were changed with the input gas ratio; Granular type grain structure exhibited the preferred orientation of (111) plane in the high input gas ratio region ( = 3–10). Faceted columnar grain structure showed the preferred orientation of (220) plane at the low input gas ratios ( = 1–2). The growth behavior of CVD SiC films with the input gas ratio was correlated with the change of the deposition mechanism from surface kinetics to mass transfer.     

Silicon nitride films synthesized by reactive pulsed laser deposition in an electron cyclotron resonance nitrogen plasma

We report a film synthesis method called electron cyclotron resonance (ECR) plasma aided reactive pulsed laser deposition. Silicon nitride films were synthesized at low temperature by means of laser ablation of a silicon target in an ECR microwave discharge in pure nitrogen gas. It is found that silicon and nitrogen are well-distributed in the deposited films with a composition of near stoichiometric Si₃N₄. Optical emission spectroscopy indicated that nitrogen in the ECR plasma was highly activated. The presence of the ECR nitrogen plasma during the deposition is considered to lead to enhanced nitridation of the ablated silicon in the plume as well as at the substrate, and to be responsible for the effective incorporation of nitrogen in the films.     

Low-pressure synthesis and characterization of multiphase SiC by HWCVD using CH4/SiH4

Silicon carbide (SiC) thin films were deposited by low-pressure hot wire chemical vapor deposition (HWCVD) technique using SiH₄ and CH₄ gas precursors with no hydrogen dilution. Spectroscopic and structural properties of the films deposited at various methane flow rate (10-100 sccm) and low silane flow rate of 0.5 sccm were investigated. The use of low methane flow rate resulted in a sharp and intense Si-C peak in the Fourier transform infrared (FTIR) absorption spectra. The XRD spectra of the films showed the formation of SiC crystallites at low methane flow rate. The Raman spectroscopy measurements showed the coexistence of a-Si and SiC phases in the films. Increase in methane flow rate increased the carbon incorporation and deposition rate of the SiC films but also promoted the formation of amorphous Si and SiC phases in the films.     

Pressure dependent structural and optical properties of silicon carbide thin films deposited by hot wire chemical vapor deposition from pure silane and methane gases

Silicon carbide (SiC) thin films were deposited using hot wire chemical vapor deposition technique from silane (SiH₄) and methane (CH₄) gas precursors. The effect of deposition pressure on structural and optical properties of SiC films was investigated. Various spectroscopic methods including Fourier transform infrared spectroscopy, Raman scattering spectroscopy, Auger electron spectroscopy, and UV–Vis–NIR spectroscopy were used to study these properties. Films deposited at low deposition pressure were Si-rich, and were embedded with nano-crystals of silicon. These films showed strong absorption in the visible region and had low energy band gaps. Near stoichiometric SiC film, were formed at intermediate deposition pressure and these films were transparent in the visible region and exhibited a wide optical band gap. High deposition pressures caused inhomogeneity in the film as reflected by the increase in disorder parameter and low refractive index of the films. This was shown to be due to formation of sp ² carbon clusters in the film structure.     

Surface nano-structured silicon carbide thin film produced using hot filament decomposition of ethylene at low temperature on silicon wafer

The structure and spectroscopic properties of nano-structured silicon carbide (SiC) thin films were studied for films obtained through deposition of decomposed ethylene (C₂H₄) on silicon wafers via hot filament chemical vapor deposition method at low temperature followed by annealing at various temperatures in the range 300-700 °C. The prepared films were analyzed with focus on the early deposition stage and the initial growth layers. The analysis of the film's physics and structural characteristics was performed with Fourier transform infrared spectroscopy and Raman spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy, and X-ray diffraction. The conditions for forming thin layer of cubic SiC phase (3C-SiC) are found. X-ray diffraction and Raman spectroscopy confirmed the presence of 3C-SiC phase in the sample. The formation conditions and structure of intermediate SiC layer, which reduces the crystal lattice mismatch between Si and diamond, are essential for the alignment of diamond growth. This finding provides an easy way of forming SiC intermediate layer using the Si from the substrate.     

Structural, electrical and optical characterization of N- and P-type SiC:H films deposited using ECR-CVD

Hydrogenated silicon carbide films (SiC:H) were deposited using the electron cyclotron resonance chemical vapour deposition (ECR-CVD) method from a mixture of methane, silane and hydrogen, and using diborane and phosphine as doping gases. The effects of changes in the diborane and phosphine levels on the optical bandgap and conductivity were investigated. In the case of boron-doped films, there is evidence from Raman scattering analysis to show that films deposited at a low microwave power of 150 W were largely amorphous and the bandgap decreases as the diborane levels are highly conductive and contains the whereas films deposited at a high microwave power of 800 W at low diborane levels are highly conductive and contains the silicon microcrystalline phase. These films become amorphous as the diborane level is increased, while the optical bandgap remains relatively unaffected throughout the entire range of diborane levels investigated. In the case of phosphorus-doped films, Raman scattering analysis showed that the deposition conditions strongly influence the structural, optical and electrical properties of the SiC:H films. Unlike boron doping, doping with phosphorus can have the effect of increasing the silicon microcrystalline phase in the SiC:H films which were prepared at low (150 W) and high (600 W) microwave powers. Films prepared at high microwave power showed only small variations in the optical bandgap, suggesting that good phosphorus doping efficiency can be achieved in films which contain the silicon microcrystalline phase (mc-SiC:H).     

Growth and characterisation of SiC films deposited on a-SiO2/Si (100) substrates

Abstract

The growth of polycrystalline SiC films has been carried out by low pressure chemical vapour deposition in a horizontal quartz reaction chamber using tetramethylsilane and H2 as the precursor gas mixture. Silicon (100) wafers were used as substrates. A thin Si O₂ amorphous layer of ~6 nm was formed before SiC deposition to reduce the strain induced by the 8% difference in thermal expansion coefficients between SiC and Si. Samples were. analysed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and infrared reflectivity. The structure of films grown at temperatures between 950 and 1150°C varies from amorphous to polycrystalline SiC. Preferential [111] orientation and columnar growth of polycrystalline films develops with increasing temperature.

MST/3317     

Influence of filament-to-substrate distance on the spectroscopic,structural and optical properties of silicon carbide thin films deposited by HWCVD technique

Silicon carbide (SiC) thin films were deposited using hot wire chemical vapor deposition (HWCVD) technique from pure silane and methane gas mixture. The effect of filament distance to the substrate on the structural and optical properties of the films was investigated. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman scattering spectroscopy and UV–Vis–NIR spectroscopy were carried out to characterize SiC films. XRD patterns of the films indicated that the film deposited under highest filament-to-substrate distance were amorphous in structure, while the decrease in distance led to formation and subsequent enhancement of crystallinity. The Si–C bond density in the film structure obtained from FTIR data, showed significant increment with transition from amorphous to nano-crystalline structure. However, it remained almost unchanged with further improvement in crystalline volume fraction. From Raman data it was observed that the presence of amorphous silicon phase and sp ² bonded carbon clusters increased with the decrease in distance. This reflected in deterioration of structural order and narrowing the optical band gap of SiC films. It was found that filament-to-substrate distance is a key parameter in HWCVD system which influences on the reactions kinetics as well as structural and optical properties of the deposited films.     

化学镀Ni-P-SiC复合镀层的研究进展

综述了近年来国内外在Ni-P-SiC复合镀方面的研究进展,重点论述了SiC微粒的预处理、分散方式、SiC浓度、pH值、温度等工艺参数对镀速、复合镀层中粒子分布及含量的影响,讨论了复合镀层的硬度、耐磨性和耐蚀性能,最后指出了Ni-P-SiC复合镀应用中存在的问题和未来发展的方向.     

正交实验方法研究PECVD碳化硅薄膜的防水汽扩散性质

利用正交实验设计，研究了碳化硅薄膜的防水汽扩散性质。通过测试水汽在碳化硅薄膜中的扩散速率，初步确定了四种沉积参数影响碳化硅薄膜防水汽扩散能力的规律。实验发现，射频频率的变化对碳化硅薄膜的防水汽扩散能力的影响最大，气体流量比次之，而功率和气体压力的变化影响较小。     

Very thin poly-SiC films for micro/nano devices

We report characterization of nitrogen-doped, very thin, low-stress polycrystalline silicon carbide (poly-SiC) films suitable for fabricating micro/nano devices. The poly-SiC films are deposited on 100 mm-diameter (100) silicon wafers in a large-scale, hot-wall, horizontal LPCVD furnace using SiH2Cl2 and C2H2 as precursors and NH, as doping gas. The deposition temperature and pressure are fixed at 900 degrees C and 4 Torr, respectively. The deposition rate increases substantially in the first 50 minutes, transitioning to a limiting value thereafter. The deposited films exhibit (111)-orientated polycrystalline 3C-SiC texture. HR-TEM indicates a 1 nm to 4 nm amorphous SiC layer at the SiC/silicon interface. The residual stress and the resistivity of the films are found to be thickness dependent in the range of 100 nm to 1 microm. Films with thickness less than 100 nm suffer from voids or pinholes. Films thicker than 100 nm are shown to be suitable for fabricating micro/nano devices.     

铁诱导低温SiC薄膜的合成

采用热丝化学气相沉积法，以铁作为催化剂，在较低的衬底温度合成纳米SiC薄膜，铁粒子是在400Pa氢气的气氛中，通过用脉冲激光烧蚀铁靶5min引入的。用扫描电镜和拉曼谱对样品进行了分析。扫描电镜观察到了直径为10-30nm，长度短于1μm的无序SiC棒，拉曼谱中的横向生子模式的红移表明生长方向的限制效应，所有这些说明Fe粒子的大小将影响到SiC棒的生长。     

High-rate deposition of nanostructured SiC films by thermal plasma PVD

With ultrafine SiC powder as starting material, thermal plasma physical vapor deposition has been applied successfully to the deposition of SiC films on Si substrates. The control of processing parameters such as substrate temperature, powder feeding rate and composition of plasma gases, permits the deposition of SiC films on a wide area of around 400 cm² with a variety of microstructures from amorphous to nanostructured and with various morphologies from dense to columnar. For the nanostructured case, the crystallite size was between 3 and 15 nm and the maximum deposition rate calculated based on the actual deposition duty time reached 200 nm/s. The deposition mechanism is discussed briefly.     

Thermal Conductivity of AlN and SiC Thin Films

The thermal conductivity of AlN and SiC thin films sputtered on silicon substrates is measured employing the 3ω method. The thickness of the AlN sample is varied in the range from 200 to 2000 nm to analyze the size effect. The SiC thin films are prepared at two different temperatures, 20 and 500°C, and the effect of deposition temperature on thermal conductivity is examined. The results reveal that the thermal conductivity of the thin films is significantly smaller than that of the same material in bulk form. The thermal conductivity of the AlN thin film is strongly dependent on the film thickness. For the case of SiC thin films, however, increased deposition temperature results in negligible change in the thermal conductivity as the temperature is below the critical temperature for crystallization. To explain the thermal conduction in the thin films, the thermal conductivity and microstructure are compared using x-ray diffraction patterns.     

SiC在异质衬底生长金刚石膜的作用分析

利用扫描电子显微镜 (SEM)、Raman光谱分析了Si衬底上金刚石膜核化和生长的过程 ,并着重分析了核化过程产生的SiC的性能。利用划痕法测量了在WC衬底上沉积SiC和未沉积SiC时生长金刚石膜的粘附力 ,同时还分析了WC衬底上有和没有SiC沉积层时表面附近金刚石膜的内应力。结果表明 ,SiC层大大地增强了含碳粒子的聚集和金刚石膜与衬底之间的粘附性 ,降低了金刚石膜与衬底之间的内应力     

Heteroepitaxial Growth and Characterization of 3C-SiC Films on Si Substrates Using LPVCVD

3C-SiC films have been deposited on Si (111) substrates by the low-pressure vertical chemical vapor deposition (LPVCVD) with gas mixtures of SiH4, C3Hg and H2- The growth mechanism of SiC films can be obtained through the observations using field emission scanning electron microscope (FESEM). It is found that the growth process varies from surface control to diffusion control when the deposition temperature increases from 1270 to 1350℃. The X-ray diffraction (XRD) patterns show that the SiC films have good crystallinity and strong preferred orientation. The results of the high resolution transmission electron microscopy (HRTEM) image and the transmission electron diffraction (TED) pattern indicate a peculiar superlattice structure of the film. The values of the binding energy in the high resolution X-ray photoelectron spectra (XPS) further confirm the formation of SiC.