Effect of the microstructure of Si3N4 on the adhesion strength of TiN film on Si3N4

The effect of the microstructure of silicon nitride, which was used as a substrate, on the adhesion strength of physical vapor deposited TiN film on Si₃N₄ was investigated. Silicon nitride substrates with different microstructures were synthesized by controlling the size (fine or coarse), the phase ( or β) of starting Si₃N₄ powder, and sintering temperature. The microstructure of Si₃N₄ was characterized in terms of grain size, aspect ratio of the elongated grain, and β-to- phase ratio. For a given chemical composition but different mechanical properties, such as toughness, elastic modulus, and hardness of Si₃N₄ were obtained from the diverse microstructures. Hertzian indentation was used to estimate the yield properties of Si₃N_4, such as critical loads for yield (P_y) and for ring cracking (P_c). The effect of the microstructure of Si₃N₄ on adhesion strength evaluated by scratch test is discussed. TiN films on Si₃N₄ showed high adhesion strengths in the range of 80–140 N. Hardness and the P_y of Si₃N₄ substrate were the primary parameters influencing the adhesion strength of TiN film. In TiN coating on Si₃N₄, substrates with finer grain sizes and higher phase ratios, which show high hardness and high P_y, were suitable for higher adhesion strength of TiN film.     

Coverage properties of silicon nitride film prepared by the Cat-CVD method

The coverage properties of silicon nitride (Si₃N₄) films prepared by the catalytic chemical vapor deposition (Cat-CVD) technique were systematically studied. By increasing the catalyzer–substrate distance, the coverage was improved from 46 to 67% on a 1.0-μm line and space pattern. The etching rate of Cat-CVD Si₃N₄ film measured using 16BHF solution was independent of the deposited position of the micro-patterns deposited, and was approximately 3 nm/min, one order of magnitude lower than that of plasma-enhanced CVD (PE-CVD) Si₃N₄ film. This means that Cat-CVD Si₃N₄ films are denser than PE-CVD Si₃N₄ films, and that the quality at the side wall is equivalent to that on the top surface. That is, Cat-CVD Si₃N₄ films show a passivation effect, which was excellent, even at the side wall of micro-patterns. These results suggest that Si₃N₄ films prepared by Cat-CVD are suitable for the passivation films in microelectronic devices having a step configuration, such as TFT-LCDs and ULSIs.     

Acoustic microscopy measurement of elastic constants and massdensity

A method is presented to determine the elastic constants and the mass density of isotropic and anisotropic solids and anisotropic thin films. The velocity and attenuation of leaky surface acoustic waves (SAWs) have been obtained for specified propagation directions from V(z) curves measured by line-focus acoustic microscopy (LFAM). The experimentally obtained velocities have been compared to velocities obtained from a measurement model for the V(z) curve which simulates the experiment. Since the measured and simulated V(z) curves have the same systemic errors, the material constants are free of such errors. For an isotropic solid, Young's modulus E, the shear modulus G and the mass density ρ have been determined from the leaky Rayleigh wave velocity and attenuation, measured by LFAM, and a longitudinal wave velocity measured by a pulse-echo transit-time technique. For a cubic-crystalline solid, the ratios of the elastic constants to the mass density (c₁₁ /ρ, c₁₂/ρ, c₄₄/ρ) have been determined from the directional variation of measured SAW velocities, using a preliminary estimate of ρ. The mass density ρ has subsequently been determined by additionally using the attenuation of leaky SAWs in crystal symmetry directions. For a cubic-crystalline thin film deposited on a substrate, the elastic constants and the mass density (c₁₁, c₁₂, c₄₄, ρ) of the film have been determined from the directional variation of the measured SAW velocities, and a comparison of the corresponding attenuation coefficient with the measured attenuation coefficient has been used to verify the results     

Preparation, Separation and Characterisation of Fullerene - C60 and C70

This paper reports a simple apparatus for the synthesis of fullerenes and an efficient method for the separation of C₆₀ and C₇₀ in large amounts. The positive and negative ion mass spectra of C₆₀ and C₇₀ were measured using electron ionization and in-beam methods. Vibrational Raman spectra showed that the C₆₀ molecule adsorbed on the substrate surface may be distorted and its symmetry may be reduced under the action of the substrate surface.     

Mechanical properties and adhesion strength of TiN and Al coatings on HSS, steel, aluminium and copper characterized by four testing Methods

TiN and Al coatings on substrates of high-speed steel, steel, aluminium and copper have been used to study mechanical properties of coating systems, especially the adhesion of the coating. The quantities measured are internal stress of the coating, determined by X-ray diffraction, the critical load of the scratch test, the microhardness obtained by the indenter technique, and the interface fracture energy, determined by a three-point bend test developed recently by the authors. The fracture energy, G_c, is a measure for the adhesion strength of a coating system. The effect of bias voltage, sputter cleaning and contamination of the substrates on the adhesion strength and other mechanical properties are investigated with the four methods mentioned. Each of the testing methods reveal only specific aspects of the behaviour of the coating systems. The data obtained depend on bulk properties of the film and the substrate material and on properties of the interface. Variation of the bias voltage can change them in quite different ways. In addition, the inter-relations between the adhesion strength of the coating and the failure behaviour of the three-point bend test samples are discussed.     

Perturbation method for analyzing mass sensitivity of planarmultilayer acoustic sensors

A perturbation method is developed to analyze the mass loading sensitivity of planar composite acoustic gravimetric sensors. The sensitivity formulas are obtained in explicit forms for the two lowest sagittal (D₁ and D₂) modes, the lowest shear horizontal (SH₀) mode and high-order SH_m modes in a two-layer isotropic composite plate sensor. The composite plate consists of a plate of thickness b coated by a film of thickness h on which the mass loading layer of infinitesimal thickness is deposited. This coating can be a chemically selective film which is assumed to be acoustically thin (h≪λ), where λ is the acoustic wavelength. For Love modes supported by a film coated on a semi-infinite substrate and for Rayleigh modes on a semi-infinite substrate, the sensitivity formulas are expressed in analytical form. These formulas specify the contribution of each material parameter in the substrate and film, and of the elasticity of the mass loading layer for each planar sensor, and provide a general guide for enhancing the sensor sensitivity     

Electrical properties of silicon nitride films deposited by catalytic chemical vapor deposition on catalytically nitrided Si(100)

Thin film transistor incorporating silicon nitride (SiN_x) films deposited by catalytic chemical vapor deposition (Cat-CVD) on silicon exhibit some problems such as a large-threshold voltage shift and a large hysteresis loop width of the capacitance vs. voltage (C–V) characteristics. In this work, in order to solve these problems, the surface of the silicon substrate is catalytically nitrided before SiN_x deposition. Inserting the nitridation layer, injection-type hysteresis loop of C–V curve is reduced from 1.3 to 0.05 V and large threshold voltage shift to the negative direction is reduced from 4 to 1.8 V.     

Catalytic CVD growth and properties of a-C:H and a-C:N

Hydrogenated amorphous carbon (a-C:H) and nitrided amorphous carbon (a-C:N) films have been synthesized on quartz substrates at a substrate temperature of 700 °C using a catalytic chemical vapor deposition (Cat-CVD) method. Raman spectra of a-C:H films showed two principal bands, the G-band at 1600 cm⁻¹ and the D-band at 1350 cm⁻¹. Those of a-C:N films showed similar spectra, with a G′ band at 1640 cm⁻¹, the peak energy of which is higher than that of the G-band in a-C:H. The intensity ratio /I_D, which is a measure of the degree of order in a-C:H, decreased for a-C:H with increasing CH₄/H₂ gas-flow ratio. On the contrary, the /I_D ratio increased with increasing CH₄/H₂ gas-flow ratio.     

Epitaxial aluminum nitride films on sapphire formed by pulsed laser deposition

Highly oriented aluminum nitride thin films were grown on sapphire (0001)-substrate by pulsed laser deposition technique. Characterization was done by X-ray-diffraction, elastic recoil detection analysis and Rutherford backscattering/channeling measurements. The epitaxial properties were studied as function of the substrate temperature and the deposition rate. An epitaxial relation to the sapphire substrate is found to be AlN [0001] || Al₂O₃ [0001] and AlN [11 0] || Al₂O₃ [10 0]. XRD-texture-analysis on films deposited at 850°C shows a full width half maximum Δω of 0.13° (rocking curve) and Δ of 1.1° (in-plane).     

装饰薄膜ZrN的中频反应磁控溅射沉积工艺研究

利用中频反应磁控溅射技术在1Cr18Ni9Ti不锈钢基底上沉积ZrN薄膜。通过控制N/Ar、溅射功率和基体偏压等参数,得到不同实验条件的ZrN膜层。通过对膜层颜色测量和AES分析,研究N分压强对ZrN膜层质量的影响。实验结果表明：工作气压0.3Pa,溅射功率5kW,基体偏压-150V、占空比50%等工艺参数一定的前提下,N分压强在不同的范围内,可以分别制备出视觉效果类似于18K、23K和纯金的氮化锆膜层。     

Co@CNT复合电磁波吸收剂的制备及其吸波性能

以石墨相氮化碳(g-C₃N₄)和六水合硝酸钴为原料制备Co@CNT复合电磁波吸收剂,调节Co元素含量以提高其电磁波吸收性能。采用X射线衍射(XRD)、X射线光电子能谱(XPS)、拉曼光谱、扫描电镜(SEM)、能谱分析(EDS)和透射电镜(TEM)等手段表征其微结构和物相组成,使用矢量网络分析仪测量复合物电磁参数并进行Matlab模拟得到反射损耗图。结果表明,Co@CNT-1与石蜡质量比为1：3的材料,其吸波性能最优,厚度为4.1 mm时对电磁波的吸收最强,最小反射损耗(RL_min)为-45.5 dB;厚度仅为1.5 mm的材料,有效吸收带宽(RL<-10 dB)最大为4.42 GHz。     

Dielectric reference coatings for the evaluation of thin film characterization techniques

Thin film technology has an increasing demand for industrial reliable characterization techniques. A precise absolute determination of layer thickness, interface width and the quantification of depth profiles in dependence on resolution limits of the measurement are required. Certified reference materials, certified reference coatings (CRCs) and non-destructive evaluation techniques can meet these requirements. Dielectric reference coatings (SiO₂, Si₃N₄) were used for metallographic preparation (e.g. bevelled cross-sections), optical characterization techniques (e.g. spectroscopic ellipsometry (SE)), and films of SiO₂, Si₃N₄ and Al₂O₃ were applied to reference measurements in depth profiling of layer stacks (e.g. radio frequency glow discharge optical emission spectroscopy). Thickness and refractive index of these dielectric single-and multilayer coatings on different substrate materials are accurately determined in advance by means of SE. These values are subsequently used for precise angle determination of bevelled cross-sections, for reference and re-calibration purposes in thin film characterization (system reproducibility) and in surface analysis (determination of sputter and erosion rates, depth profiles). Examples are discussed for different applications and the calculated data are compared with experimental results. It is shown that reproducible commercial coatings are also of importance for use as CRCs.     

LPCVD氮化硅薄膜的化学组成

分别采用X光电子能谱(XPS)、俄歇电子能谱(AES)、傅立叶红外光谱(FTIR)以及弹性反冲探测(ERD)等方法,分析了三氯硅烷-氨气-氮气体系低压化学气相沉积(LPCVD)氮化硅(SiNx)薄膜的化学组成,并利用原子力显微镜(AFM)观察了SiNx薄膜的表面形貌.XPS分析结果表明,当原料气中氨气与三氯硅烷的流量之比小于3时获得富Si的SiNx薄膜,当流量之比大于4时获得近化学计量的SiNx薄膜(x=1.33).AES深度分析与XPS分析结果很好地吻合,在835cm-1产生的强红外吸收峰表明Si-N键的形成,ERD分析表明所制备SiNx薄膜中的氢含量很低(1.2at.%).AFM分析结果表明,所沉积的SiNx薄膜均匀、平整,薄膜的均方根粗糙度RMS仅为0.47nm.     

Auger electron spectroscopy depth profiling studies on stationary and rotated samples of a new model metal/semiconductor multilayer structure

Multilayer structures for application in microelectronics are becoming increasingly complex. A sputter deposited multilayer structure composed of chromium, nickel and silicon layers with a total thickness of 310 nm on a smooth silicon substrate was characterized by transmission electron microscopy (TEM) and by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) depth profiling. AES depth profiles of the Ni/Cr/Si multilayers were obtained with Ar⁺ ion bombardment at various angles of incidence using stationary and rotated samples. In some cases a strong influence of semiconductor structure on the experimentally obtained metal-metal and metal-semiconductor interface widths was observed. Owing to ion beam induced Si(LVV) Auger electrons in the crater wall of the Ni/Cr/Si sample, a distortional influence on depth resolution during simultaneous AES analysis and ion sputtering was found. Silicide formation during sputtering at the silicon-metal interfaces was confirmed by XPS. The measured compositional depth profiles are explained with respect to the influence of polycrystalline metallic and amorphous semiconductor structures; the effects of ion beam induced topography, atomic mixing and silicide formation are discussed.     

Preparation and properties of TiN and AlN films from alkoxide solution by thermal plasma CVD method

Single phase TiN and AlN films were prepared on a Si wafer from titanium tetra-etoxide and aluminum tri-butoxide solutions dissolved in ethanol and toluene, respectively, using an Ar/N₂/H₂ radio-frequency (r.f.) inductive thermal plasma chemical vapor deposition (CVD) method. The films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, measurement of electrical resistivity and Vickers microhardness. Factors affecting the formation of the films (lattice parameter, chemical composition, oxygen/carbon content, and deposition rate of the films) were examined in terms of the N₂ flow rate (2.5–4.5 slm), substrate temperature (300–700°C), feed rate of the solution (0.025–0.3 ml/min), and the mole ratio of the alkoxide solution (1:1–1:3). The optimum conditions for preparation of TiN films produced a film 0.2–3 μm thick with an oxygen content of 8 at.% and a free carbon content of 4 at.%, showing an electrical resistivity of 370 μΩ cm. The optimum conditions for AlN films produced a film 0.3 μm thick containing 14 at.% oxygen and 8 wt.% carbon. The deposition rate of the TiN film was determined to be 30–35 nm/min. The Vickers microhardness of the TiN and AlN films was found to be 10±1 and 13±3 GPa, respectively.     

Thermal stability of nitride coatings formed by ion-plasma deposition

Titanium nitride and chromium nitride coatings were formed on a gray cast iron by condensation from a plasma phase in vacuum with the ion bombardment of the sample surface by titanium or chromium plasma flows in a residual nitrogen atmosphere. The element and phase composition of coatings were studied before and after annealing for 1-43 h in air at temperature 700 °C using Auger electron spectroscopy (AES) and X-ray diffraction (XRD). It is established that titanium nitride coatings are single-phase TiN system with a (1 1 1) preferred growth orientation, and chromium nitride coatings—a two-phase system: CrN and Cr₂N phases. The annealing of coatings at the atmospheric pressure and the temperature of 700 °C in the range of 1-43 h results in the deceleration of the oxidation process of the material substrate for chromium nitride with respect to titanium nitride coatings.     

水凝胶负载的纳米银/氮化碳光催化剂的制备及性能研究

石墨相氮化碳(g-C₃N₄)具有独特的二维平面结构和半导体能带结构, 广泛应用于光催化。但其又存在光生电子空穴对复合过快、可见光利用效率低、在水中分散性差等问题, 阻碍了其实际应用。本研究以海藻酸钠制备的水凝胶为基体, 通过与负载银纳米颗粒(AgNPs)的g-C₃N₄复合, 提升光生电子-空穴的分离效率, 同时解决催化剂在水中的分散性问题, 改善其光催化性能。首先, 采用热聚合法合成g-C₃N₄, 结合超声的高能量使其剥离成纳米片; 然后采用溶液法在g-C₃N₄表面原位生成银纳米颗粒, 制备得到负载银纳米颗粒的g-C₃N₄(Ag@C₃N₄); 最后以海藻酸钠(SA)为前驱体通过钙离子交联的方法得到负载有Ag@C₃N₄的水凝胶(SA/Ag@C₃N₄)。通过不同手段表征SA/Ag@C₃N₄的形貌、微观结构和相组成; 以甲基橙为模型物, SA/Ag@C₃N₄的光催化降解速率是Ag@C₃N₄的2.5倍。通过光致发光谱、时间分辨光致发光谱、电子顺磁共振波谱等表征手段对材料的催化机理进行探究。结果显示, 体系中银纳米颗粒表面等离子体共振效应与海藻酸钠水凝胶的多孔结构及传质通道发挥协同效应, 促进了光催化性能的提升。     

Surface and electrical studies of CuO:V2O5 thin films

Results from the studies of multicomponent CuO:V₂O₅ bulk material and thermally evaporated thin films of highly conducting bulk composition prepared at different substrate temperatures are thus compared and discussed. The electronic conductivity is enhanced on increase in the substrate temperature T_s and reaches a maximum value of 12.3 × 10⁻⁶Ω⁻¹ cm⁻¹ for T_s = 423 K. X-ray photoelectron spectroscopy studies indicate an increase in the reduced states of vanadium and copper ions in going from the bulk glass to the thin film. Dynamic secondary-ion mass spectroscopy studies on thin films over a depth of 3000 Å show a strong dependence of T_s on the Cu-to-V intensity ratio. Even though stoichiometric values for thin films are achievable by varying the T_s, the oxidation states of Cu in these films are predominantly monovalent. The electrical behaviors of these materials and their thin film counterparts are finally being discussed in relation to the surface analysis data.     

Theoretical and experimental study of mass sensitivity of PSAW-APMson ZX-LiNbO3

Acoustic plate mode (APM) devices have recently been used as sensing elements, both for the physical measurement of fluid properties and in biosensor applications. One of the primary interaction mechanisms in these devices is mass loading caused by the added mass bound to the layered crystal surface. However, the material properties of these thin composite layers are not well characterized or known as is required in order to accurately predict the sensor response. In the present work, perturbation theory is used to derive expressions for the sensitivity of the APM sensors to mass loading and viscoelastic stiffening. Mass sensitivity experiment was conducted on ZX-LiNbO₃ in a liquid environment to accurately reflect the sensitivity of an actual biosensor and the results are compared to theory. The measured data show a f² dependence for the mass sensitivity for APMs on ZX-LiNbO₃ in the measured frequency range, which indicates a SAW-like behavior. This behavior is due to the fact that the acoustic plate modes on ZX-LiNBO₃ are pseudo-SAW (PSAW) derived, and the acoustic energy is confined to the sensing surface. As a result, the APMs on ZX-LiNbO₃ are referred to as PSAW-APMs. Discussions are given in terms of the added mass which occurs in typical biosensor applications     

Line-focus acoustic microscopy measurements ofNb2O5/MgO and BaTiO3/LaAlO3thin-film/substrate configurations

Line-focus acoustic microscopy has been used to measure the phase velocities of surface acoustic waves on bare MgO and bare LaAlO₃ , and on Nb₂O₅/MgO and BaTiO₃/LaAlO₃ thin-film/substrate configurations. The thin films are polycrystalline materials. The substrates are anisotropic single-crystals. The measured angular variation of the surface acoustic wave velocities has been used to determine the elastic constants of MgO substrate and Nb₂O₅ thin-film. It has been assumed that the Nb₂O₅ films may be considered as essentially isotropic. The measurements for LaAlO₃ and BaTiO₃/LaAlO₃ show anomalies which are attributed to twinning in the LaAlO₃ substrate