Ni-Cr合金钎料激光钎焊金刚石表面金属化

为了研究激光钎焊金刚石磨粒表面金属化生成物类别与形成机制, 采用第一性原理的密度泛函理论对常见碳化物进行了计算, 并采用Ni-Cr合金钎料, 借助光纤激光热源对金刚石磨粒进行了激光钎焊试验, 获得了Cr₃C₂和Cr₇C₃两种碳化物的结构和力学性能参量以及金刚石磨粒表面微结构和碳化物种类。结果表明, Cr₃C₂和Cr₇C₃两者都具有金属性, 且后者韧性更强; 激光钎焊得到的金刚石磨粒与Ni-Cr合金钎料界面冶金反应层厚度约为4μm, 金刚石磨粒表面碳化物主要为Cr₃C₂; 超声辅助激光钎焊得到的金刚石磨粒表面碳化物为Cr₃C₂和Cr₇C₃, 超声波高频振动可以促进界面反应, 进而生成含碳量低的Cr₇C₃。此研究结果对激光钎焊金刚石技术的发展具有指导意义。     

Mechanism for the thermal dependence of the Cr to Nd energytransfer in garnets

The temperature dependence of the Cr-Nd energy transfer is found to be due to the thermal variation of the radiative decay probability of Cr. The validity of this conjecture is checked in the Gd₃Sc ₂Ga₃O₁₂ and CaMg₂Y₂ Ge₃O₁₂ crystals. It is also found that above 200 K, the nonradiative energy transfer rate from Cr to Nd is greater in Gd₃Sc₂Ga₃O₁₂ than in CaMg ₂Y₂Ge₃O₁₂     

Low Rayleigh scatteringP2O5-F-SiO2 glasses

The Rayleigh scattering and infrared absorption losses of P₂ O₅-F-doped silica glass, which is a candidate material for ultra-low-loss optical fiber, were investigated experimentally. The Rayleigh scattering loss of 8.5 wt.% P₂O₅ and 0.3 wt.% F-doped SiO₂ glass is found to be 0.8 times that of pure silica glass. It is also found that the infrared absorption property of P₂O₅-F-SiO₂ glass is almost the same as that of pure silica glass. The minimum loss for the proposed composition is estimated to be 0.11 dB/km at 1.55 μm wavelength, and 0.21 dB/km at 1.3 μm wavelength     

钡化合物辅助激光刻蚀石英玻璃的实验研究

为了提高石英玻璃对普通脉冲红外激光的吸收效率,用钡化合物粉体覆盖层辅助1064nm红外激光刻蚀石英玻璃,采用能谱仪和X射线衍射分别对BaCrO₄,BaCl₂和Ba（OH）₂粉体覆盖层辅助激光刻蚀石英玻璃得到的刻槽底面刻蚀产物进行了测试和分析,对3种刻蚀方法的刻蚀机理进行了理论分析和实验验证。结果表明,BaCrO₄和Ba（OH）₂粉体的刻蚀机理都存在化学反应去蚀石英玻璃的作用,二者去蚀率都较高;BaCl₂粉体的刻蚀过程中无化学反应起到去蚀作用,去蚀率低下。这一结果对激光加工石英玻璃的工业应用提供技术基础。     

Studies of yttrium oxide films prepared by RF magnetron sputtering

Films of yttrium oxide (Y₂O₃) were deposited on Si substrates from a Y₂O₃ target by RF magnetron sputtering. MIS capacitors in the form of Al and Y₂O₃ (400 Å)-Si were then fabricated. The leakage current density was about 10^-6 A/cm² at 1.3×10⁶ V/cm, and the breakdown field of the films was about 2.75×10⁶ V/cm. The dielectric constant of the sputtered Y₂O₃ was found to be about 12-12.7     

Preparation of SiO2-B2O3 glass forPANDA optical fibre from colloidal sol-gel process

SiO₂-B₂O₃ glass for the PANDA optical fibre is prepared from the colloidal sol-gel process. The preparation of SiO₂-B₂O₃ glass is through the gellation of fumed silica dispersed in water containing boric acid. Two processes to dry the gel are examined, and freeze-drying is selected as the better drying method. The process produces a dried gel without cracks and with a uniform distribution of boron oxide concentration. The dried gel is sintered into glass     

Control of cleaning performance of an ammonia and hydrogen peroxidemixture (APM) on the basis of a kinetic reaction model

Ammonia and hydrogen peroxide mixtures (APM) are widely used for removing particles from substrate surfaces in semiconductor manufacturing. In the next-generation manufacturing, more precise control of the APM cleaning performance is required than what is available today. In this study, a new method for evaluating the APM cleaning performance, such as the etching rate, surface microroughness, and particle removal efficiency, was introduced based on a chemical equilibrium analysis of APM and a kinetic reaction model of a Si substrate with APM. It became clear that the etching reaction of a Si substrate proceeds along two paths (path-1, path-2) in APM. In path-1, the Si surface is oxidized by HO₂^- and then the SiO₂ layer is etched by OH^-. In path-2, the Si surface is directly etched by OH^-. Path-1 is favorable for APM cleaning because path-2 causes some problems, such as too fast etching, an increase in surface microroughness, and a decrease in particle removal efficiency. Using the contribution ratio of each path to total etching reaction, we can predict the etching rate and determine optimum APM cleaning conditions (NH₃ concentration, H₂ O₂ concentration, temperature). This method makes it possible to improve the APM cleaning performance and to decrease chemical consumption     

强脉冲激光照射TC11合金组织和抗氧化性能分析

为了改善TC11钛合金表面性能,采用强激光照射方法对其进行表面辐照处理,并研究脉冲能量密度对激光照射TC11钛合金表面形貌及性能的影响。结果表明,经过1J/cm2的强脉冲激光照射后,合金表面出现熔融,随着脉冲能量密度增大,合金表层的熔坑外径变大;激光照射后合金表层形成了约1.5μm外径的微孔,其构成元素主要为Mg,O,S,C;经脉冲照射处理后TC11合金显微硬度明显增大;当脉冲能量密度增加后,合金显微硬度也随之上升,合金试样的抗高温氧化性能得到明显的提升;合金表层形成的氧化物包含颗粒状和层状两种形貌类型,氧化物主要由Al₂O₃与Cr₂O₃构成。该研究对提高TC11钛合金表面抗氧化性能是有帮助的。     

Co3O34 mono-dispersed nanoparticle solubility in high-purity water

As more and more nanoparticles are synthesised and applied in industry and society, their safety has started to become an environmental concern. The solubility of Co₃O₃4 particles with different morphology and sizes were investigated. The solubility of the mono-dispersed Co₃O₃4 nanoparticle was discovered to be much lower than that of its micrometre counter-partners. A mechanism was proposed to interpret the inconsistency of this finding with the traditional soluble dynamic equilibrium theory. The nanometre particles exist during surface tension interaction because of their small size. The traditional Ostwald?Freundlich relationship cannot apply to nanometre sizes, as it does not include the interface dispersion force interaction.     

Demonstration of GaN MIS diodes by using AlN and Ga2O3(Gd2O3) as dielectrics

GaN MIS diodes were demonstrated utilizing AlN and Ga₂O₃(Gd₂O₃) as insulators. A 345 Å of AlN was grown on the MOCVD grown n-GaN in a MOMBE system using trimethylamine alane as Al precursor and nitrogen generated from a SVT RF N₂ plasma. For the Ga₂O₃(Gd₂O₃) growth, a multi-MBE chamber was used and a 195 Å oxide was E-beam evaporated from a single crystal source of Ga₅Gd₃O₁₂. The forward breakdown voltage of AlN and Ga₂O₃(Gd₂O₃) diodes are 5 and 6 V, respectively, which are significantly improved over 1.2 V from that of a Schottky contact. From the C–V measurements, both kinds of diodes showed good charge modulation from accumulation to depletion at different frequencies. The insulator/GaN interface roughness and the thickness of the insulator were measured with X-ray reflectivity.     

Particle deposition and removal in wet cleaning processes for ULSImanufacturing

Particle deposition on wafer surfaces in solutions can be described by the well-documented principles of colloid science. Particle concentration, solution pH, and ionic strength in solutions are all important factors which determine the number of particles which deposit on wafer surfaces immersed in liquids. maximum particle deposition is observed in high ionic strength acidic solutions and is reduced as solution pH increase. Particle removal efficiencies in various solutions were also investigated; NH₄OH-H₂O₂-H ₂O solutions were optimized in NH₄OH content around the ratio of 0.05:1.15 (0.05 part NH₄OH, 1 part H₂O₂, 5 parts H₂O). Wafer damage as measured by surface micro-roughness was not increased during NH₄ OH-H₂O₂-H₂O treatment using this ratio     

Template patterning of YBa2Cu3O7

We demonstrate the use of thin chromium layers to define structures in YBa₂Cu₃O₇ deposited by laser ablation. The chromium reacts with copper to form an insulating crystalline compound containing copper and chromium in equal amounts. Although the reaction will proceed up to approximately 1 μm into the defined pattern, the formation of a crystalline compound means that the extent of the reaction is limited by the availability of chromium. We have defined large-area, regular grids of tiny chromium pads, yielding a grid of insulating islands of approximately 600 nm in size after YBa₂Cu₃O₇ deposition. Electrical measurements show the influence of such a pattern on the R-T characteristics of the YBa₂Cu₃O₇.     

Transmission loss of a 125-μm diameter PANDA fiber with circularstress-applying parts

The transmission loss of a 125-μm diameter polarization-maintaining and absorption-reducing optical fiber (the PANDA fiber) with circular stress-applying parts (SAPs) has been investigated. The loss is calculated at a 1.55- μm wavelength for SAPs consisting of B₂O₃ doped silica glasses. The experimental measurements show the validity of the analysis. It is shown that, when the half distance between SAPs is more than 2.2 times the core radius, the additional transmission loss due to B₂O₃ absorption is less than 0.05 dB/km with normalized frequency of 2.2 to 2.4 and a B₂O₃ dopant concentration of 20 mol.%. As a result, it has been confirmed that transmission losses of 125-μm diameter PANDA fibers can be comparable to those of commercially available single-mode optical fibers     

Particle removal from silicon wafer surface in wet cleaning process

Particle removal from silicon wafer surfaces was studied using acid and alkaline solutions employed in wet cleaning processes found in semiconductor manufacturing. It was demonstrated that alkaline solutions are superior to acid solutions in terms of particle removal efficiency. The following particle removal mechanism in the alkaline solutions was confirmed: the solutions etch the wafer surfaces to lift off particles, and the particles are then electrically repelled by the wafer surfaces. It was determined experimentally that an etch rate of 0.25 nm/min or more is required to lift off the particles adsorbed on the wafer surfaces. It was also confirmed that when the pH value of NH₄OH-H₂O₂-H₂O solution becomes higher, polystyrene latex spheres and natural organic particles are oxidized, with their surface turning into a gel and their shape changing. The particle removal efficiency was demonstrated to be degraded by the oxidation of organic particles. The results suggest that the mixing ratio of the NH₄OH-H₂O₂-H ₂O solution should be set at 0.05:1:5     

Infrared extinction of the powder of brass 70Cu/30Zn calculated bythe FDTD and turning bands methods [military smoke screeningapplications]

The finite-difference time-domain (FDTD) method is used to calculate the specific extinction cross section of the powder of brass 70Cu/30Zn with 10³ to 2.16-10⁵ cubical particles for cell sizes in the range of 0.025 to 0.5 μm at infrared frequency. The digitized models with a random process using the turning bands method are simulated for the powder of brass 70Cu/30Zn. From theoretical calculations, the value of the specific extinction cross section of the powder of brass 70Cu/30Zn is between 0.1 to 4.6 m²/g. While from the experimental measurement, the value of the specific extinction cross section is between 0.58 to 3.78 m²/g. Most of the theoretical results make a good agreement with those obtained from the experimental measurements for the cell sizes of particles in the range of 0.925 to 0.5 μm. From the numerical calculations, it is also found that there is a resonant extinction value occuring at the resonant particle size d₀ which is approximately 2.54-n_p ^-0.293 μm determined by a least square curve fitting method, where n_p is the number of particles. The resonant value calculated by the numerical solution is larger than the maximum value obtained from the experimental measurement. The work has applications to military smoke screening     

Preparation of Fine Copper Powder With Chemical Reduction Method and Its Application in MLCC

In this paper, the preparation of fine copper powder with chemical reduction method was investigated. Polyhedron nonagglomerated monodispersed copper powders by the reaction of CuSO₄ldr5H₂O and ascorbic acid were synthesized at pH 6~7 and reaction temperature of 60degC~70degC. It was also found by X-ray diffraction (XRD) analysis that a mixture of copper and cuprous oxide could be obtained when [Cu(NH₃)₄]²⁺ was reduced by ascorbic acid. Reaction temperature and pH have great effects on efficiency and particle size of copper powders. Copper powders were applied as terminal electrode materials of base metal electrode-multilayer ceramic capacitor (BME-MLCC), and the microstructures, including cross section and interface, of copper thick film were discussed with scanning electron microscopy. The results indicated that copper thick film has a loose, porous cross section and a rough interface. The adhesion strength of copper electrode is high due to rough microstructure caused by interfacial reaction.     

Influence of slurry components on uniformity in copper chemical mechanical planarization

Many researchers studying copper chemical mechanical planarization (CMP) have been focused on mechanisms of copper removal using various chemicals. On the basis of these previous works, we studied the effect of slurry components on uniformity. Chemical mechanical planarization of copper was performed using citric acid (C₆H₈O₇), hydrogen peroxide (H₂O₂), colloidal silica, and benzotriazole (BTA, C₆H₄N₃H) as a complexing agent, an oxidizer, an abrasive, and a corrosion inhibitor, respectively. As citric acid was added to copper CMP slurry (pH 4) containing 3 vol% hydrogen peroxide and 3 wt% colloidal silica, the material removal (MRR) at the wafer center was higher than its edge. Hydrogen peroxide could not induce a remarkable change in the profile of MRR. Colloidal silica, used as an abrasive in copper CMP slurry containing 0.01 M of citric acid and 3 vol% of hydrogen peroxide, controlled the profile of MRR by abrading the wafer edge. BTA as a corrosion inhibitor decreased the MRR and seems to control the material removal around the wafer center. All the results of in this study showed that the MRR profile of copper CMP could be controlled by the contents of slurry components.     

Ga2O3(Gd2O3)/InGaAsenhancement-mode n-channel MOSFETs

We have demonstrated the first Ga₂O₃(Gd₂O₃) insulated gate n-channel enhancement-mode In_0.53Ga_0.47As MOSFET's on InP semi-insulating substrate. Ga₂O₃(Gd₂ O₃) was electron beam deposited from a high purity single crystal Ga₅Gd₃O₁₂ source. The source and drain regions of the device were selectively implanted with Si to produce low resistance ohmic contacts. A 0.75-μm gate length device exhibits an extrinsic transconductance of 190 mS/mm, which is an order of magnitude improvement over previously reported enhancement-mode InGaAs MISFETs. The current gain cutoff frequency, f_t, and the maximum frequency of oscillation, f_max, of 7 and 10 GHz were obtained, respectively, for a 0.75×100 μm² gate dimension device at a gate voltage of 3 V and drain voltage of 2 V     

Electrical characterization of Al2O3n-channel MOSFETs with aluminum gates

High-effective mobilities are demonstrated in Al₂O₃ based n-channel MOSFETs with Al gates. The Al₂O₃ was grown in ultra-high vacuum using a reactive atomic beam deposition system. The mobility with maximum values at approximately 270 cm²/Vs, is found to approach that of SiO ₂ based MOSFETs at higher fields     

High-performance polycrystalline SiGe thin-film transistors usingAl2O3 gate insulators

The use of aluminum oxide as the gate insulator for low temperature (600°C) polycrystalline SiGe thin-film transistors (TFTs) has been studied. The aluminum oxide was sputtered from a pure aluminum target using a reactive N₂O plasma. The composition of the deposited aluminum oxide was found to be almost stoichiometric (i.e., Al₂O₃), with a very small fraction of nitrogen incorporation. Even without any hydrogen passivation, good TFT performance was measured an devices with 50-nm-thick Al₂O₃ gate dielectric layers. Typically, a field effect mobility of 47 cm²/Vs, a threshold voltage of 3 V, a subthreshold slope of 0.44 V/decade, and an on/off ratio above 3×10⁵ at a drain voltage of 0.1 V can be obtained. These results indicate that the direct interface between the Al₂ O₃ and the SiGe channel layer is sufficiently passivated to make Al₂O₃ a better alternative to grown or deposited SiO₂ for SiGe field effect devices