PARTICLE DEPOSITION CONTROL FOR VARIOUS WAFER SURFACES IN ACIDIC SOLUTION WITH SURFACTANT

Particle deposition control for various substrate surfaces was studied using acidic solution with surfactant. It has been demonstrated that particle deposition onto the various substrate surfaces in the chemicals depends on the zeta potential of particle and of the substrate surface. An anionic surfactant addition is found to make both particles and the substrate surface negatively charged, while a cationic surfactant addition is found to make both of them positively charged. The surfactant addition, therefore, can suppress particle deposition onto the substrate surface even when some particles remain in the chemicals.

When some chemical is carried over to the subsequent ultrapure water rinsing bath, this chemical carry-over triggers particle deposition in the ultrapure water rinsing stage when a cationic surfactant is used or when a hydrophilic surface is used. However, this phenomena is not observed when an anionic surfactant is used.

These results suggest that an anionic surfactant is effective in suppressing particle deposition onto the various wafer surfaces in acidic solutions.     

A comparative study of the UV optical and structural properties of SiO2, Al2O3, and HfO2 single layers deposited by reactive evaporation, ion-assisted deposition and plasma ion-assisted deposition

Growing requirements for the optical and environmental stability, as well as the radiation resistance against high-power laser radiation, especially for optical interference coatings used in the ultraviolet spectral range, have to be met by new, optimised, thin-film deposition technologies. For applications in the UV spectral range, the number of useful oxide thin film materials is very limited due to the higher absorption at wavelengths near to the electronic bandgap of the materials. Applying ion-assisted processes offers the ability to grow dense and stable films, but in each case careful optimisation of the deposition process (evaporation rate, substrate temperature, bombarding gas, ion energy and ion current density) has to achieve a balance between densification of the layers and the absorption. High-quality coatings and multilayer interference systems with SiO₂ as the low-index material can be deposited by various physical vapour deposition technologies, including reactive e-beam evaporation, ion-assisted deposition and plasma ion-assisted deposition. In order to improve the degradation stability of dielectric mirrors for use in UV free-electron laser optical cavities, a comparative study of the properties of SiO₂, Al₂O₃ and HfO₂ single layers was performed, and was addressed to grow very dense films with minimum absorption in the spectral range from 200 to 300 nm. The films were deposited by low-loss reactive electron-beam evaporation, by ion-assisted deposition using a ‘Mark II’ ion source, and by plasma ion-assisted deposition using the advanced plasma source. Optical and structural properties of the samples were studied by spectral photometry, infrared spectroscopy, X-ray diffraction and reflectometry, as well as by investigation of the surface morphology. The interaction of UV radiation with photon energy values close to the bandgap was studied. For HfO₂ single layers, laser-induced damage thresholds at 248 nm were determined in the 1-on-1 and 1000-on-1 test modes as a function of the deposition technology and film thickness.     

用压痕试验法研究CVD金刚石膜的粘附性能

在观察与分析压入过程中CVD金刚石膜开裂方式的基础上,初步探讨了用压痕试验法评定CVD金刚石膜粘附性能的可行性．采用反映膜／基粘附性能的临界开裂或剥落载荷P_er和抗裂性参数dP／dX两指标评定了硬质合金基体表面经不同预处理方法和沉积工艺参数合成的金刚石膜的粘附性能;研究了粘附性能指标与沉积工艺参数（如甲烷浓度、沉积气压、沉积功率）之间的关系．适当的表面预处理、适中的甲烷浓度、较低的沉积气压、较高的沉积功率均有利于改善金刚石膜的粘附性能．     

Grain dependence of ferroelectric domain switching on SrBi2Ta2O9 thin films observed by Kelvin probe force microscope

We have studied grain-shape dependence of Kelvin probe force microscopy of SrBi₂Ta₂O₉ thin films on epitaxial La_0.5Sr_0.5CoO₃/LaAlO₃ substrates. By changing the growth condition in pulsed laser deposition, we have grown the SrBi₂Ta₂O₉ thin films with various grain shapes. The shape and the orientation of SrBi₂Ta₂O₉ the thin films with various growth conditions have been analyzed by X-ray diffraction and scanning electron microscope. The large number of the long rectangular grains was observed accompanied with relatively larger (220) peaks than other peaks. From the Kelvin probe force microscope study, it has been observed that the long rectangular grains showed characteristics of easy ferroelectric domain switching at a low writing bias and weaker influence of surface charges.     

Growth and characterization of tin oxide films prepared by chemical vapour deposition

Undoped tin oxide films have been prepared by a chemical vapour deposition technique. The effect of different deposition parameters on the sheet resistance of the films has been studied. Films are highly transparent (about 90%) in the visible region, have a quite low sheet resistance (25 Ω/□) and have reproducible properties. X-ray diffraction shows the structure to be polycrystalline with a grain size of about 570 Å. The preferred orientation is (101) for the films deposited at substrate temperatures up to 350 °C, after which the preferred orientation changes to (200). The electrical properties of the films also exhibit a change at this deposition temperature. Direct and indirect band gaps are calculated to be 3.93 eV and 2.53 eV respectively. Degradation of the films with time has also been studied. The figure of merit = T¹⁰/R_sh (9.45 × 10^-3Ω^-1 at 0.66 μm) obtained is the highest amongst the values reported for undoped tin oxide films.     

A lapping and polishing process to achieve high quality alumina surfaces for applications in device fabrication

A lapping process for achieving high quality alumina (Al₂O₃) surfaces was investigated. Alumina films were sputter deposited on thick TiC---Al₂O₃ ceramic wafers. Polishing of these films was carried out on pitch plates (organic resin melted and set on the circular disk of a lapping machine). Abrasives with different grit sizes, 0.05–1.0 μm, were tried together with different lapping process parameters. Qualitu of the lapped surface was studied in terms of roughness and flatness. Stock removal rates were also measured. Correlation of surface quality with lapping parameters was established to achieve process optimization.

Scratch-free polished alumina surfaces were obtained by using this technique. Specific applications of the process in the fabrication of magnetic recording devices are indicated.     

Surface Modification of Iron Carbon Alloys by Plasma Detonation Treatment

Plasma detonation method (PDM) is based on the use of pulse plasma jets formed by transformation of a detonation wave into a plasma pulse. Energy density in such a jet amounts to 10⁷ W cm_-2, Consumable electrodes used here allow the vapors of various metals to be introduced into the jet. PDM is applied for heat treatment of surfaces, their alloying, as well as for coating deposition. The process of surface modification of carbon steels using various electrodes is investigated. The effect of the treatment conditions and the electrode materials on surface hardening is discussed.     

Construction of mechanically robust superamphiphobic surfaces on fiber using large particles

Superamphiphobic surfaces have attracted the attention of researchers because of their broad application prospects. Currently, superamphiphobicity is primarily achieved by minimizing the solid–liquid contact area. Over the past few decades, researchers have primarily focused on using physical deposition methods to construct superamphiphobic surfaces using fine-sized nanoparticles (< 100 nm). However, porous hollow SiO₂ particles (PH-SiO₂), which are typically large spheres, have a highly hierarchical structure and can provide lower solid–liquid contact fractions than those provided by fine-sized particles. In this study, we used PH-SiO₂ as building blocks and combined them with poly (dimethylsiloxane) to construct a mechanically robust coating on fiber by spray-coating. After chemical vapor deposition treatment, the coating exhibited excellent superamphiphobicity and could repel various liquids, covering a wide range of surface tensions (27.4–72.0 mN·m⁻¹).     

Influence of Na deposition on convoy-electron emission

The influence of surface properties on convoy-electron emission from a sputter-clean Al foil induced by H⁺ has been studied under ultrahigh-vacuum conditions. It is found that the convoy-electron yield depends strongly on the Na coverage when the downstream surface is modified by controlled Na deposition. It can be concluded that an increasing yield is observed for larger work-function values.     

Influence of Substrate Temperature and Plasma Power Density on the Properties of Plasma-Assisted Chemical Vapor Deposited Titanium Nitride

Titanium nitride films deposited onto high speed steel substrates by plasma-assisted chemical vapor deposition (PACVD) from TiCl₄, H₂, N₂, and Ar gas mixtures have been investigated. The substrate temperature was varied between 250 and 550^° C via the plasma power density or via an additional electrical heater. The influence of temperature and plasma power density on the morphology, chemical composition, hardness and adhesion of the coatings was studied. At a temperature of 500^° C different plasma power densities caused changes of the morphology of the coatings. At low plasma power densities fine grained polycrystalline layers were observed. A significant change from coarse to fine grained structures was also observed with decreasing deposition temperature. Scratch test results indicate that coatings deposited at a given substrate temperature with lower plasma power density showed increased values of the critical load.     

Investigation of process parameters influence in abrasive water jet cutting of D2 steel

In the present experimental study, abrasive water jet (AWJ) cutting tests were conducted on D2 steel by different jet impingement angles and abrasive mesh sizes. The experimental data was statistically analyzed using the simos–grey relational method and ANOVA test. In addition, the outcome of influencing cutting parameters, namely jet pressure, jet impingement angle, and abrasive mesh size on the different response parameters, namely, the jet penetration, material removal rate, taper ratio, roughness, and topography, were studied. Micro-hardness test and surface morphology analysis were employed to examine the D2 cut surfaces at different AWJ cutting conditions. The chemical element study was performed to determine the abrasive particle contamination in the AWJ kerf wall cut surfaces. The ANOVA test result indicated the jet pressure and jet impingement angle as the influencing process parameters affecting the various performance characteristics of AWJ cutting. The overall AWJ cutting performance of the D2 steel has been improved through proper identification of the optimal process parameter settings, namely jet pressure 225?MPa, abrasive mesh size #100, and jet impingement angle 70° by the simos–grey relational analysis.     

Optimization and evaluation of black zinc selective solar absorber surfaces

Black zinc oxide surfaces produced by anodix oxidation in an alkaline electrolyte have been studied for potential application as solar-selective absorber surfaces for low temperature photothermal solar energy conversion. Multiple linear regression analysis has been used to estimate the functional dependence of the surface optical properties and thermal stability on the anodizing parameters. Anodizing parameters studied, at various stages of the investigation, include NaOH, NaNO₂, NaNO₃ and zinc concentrations, bath temperature, current density, anodizing time (as charge transfer) and substrate form. Reproducibility of the coating surfaces was demonstrated and the models obtained were used to specify optimized ranges of values for the parameters in terms of the production of surfaces exhibiting high solar absorptance and good thermal stability. The effects of aging on optical properties as a function of temperature (up to 350 °C) and time (up to 320 h) were evaluated. Structural features of the coatings were evaluated utilizing the techniques of scanning electron microscopy, transmission electron microscopy, Auger electron spectroscopy and reflection high energy electron diffraction. Possible mechanisms for solar absorptance and thermal degradation are suggested on the basis of the structural observations.     

Application of design of experiment on electrophoretic deposition of glass-ceramic coating materials from an aqueous bath

A process for application of abrasion- or corrosion-resistant glass-ceramic coating materials on metal substrate by electrophoretic deposition technique in an aqueous medium has been described. The effects of various process parameters, e.g. coating material concentration, time of deposition, applied current, pH of the suspension and concentration of the polymeric dispersant on the deposition efficiency have been studied. The process has been studied using a 2³-factorial design technique of three independent variables; i.e. coating material concentration, applied current, and the time taken to achieve the best combination. The regression equation obtained explains the experimental results satisfactorily.     

The effect of thermal annealing on aerosol-gel deposited SiO2 films: a FTIR deconvolution study

Aerosol-gel process has been used for the deposition of SiO₂ thin films. Layers were deposited from a solution with pH = 3.5 and water to TEOS molar ratio (rw) 2.2 and then treated at various temperatures ranging from room temperature to 700°C. As-prepared thin films have been characterized by FTIR spectroscopy. Spectra were acquired in transmission at 65° angle of incidence or at perpendicular incidence. Characteristic absorption bands of the SiO₂ sol-gel system have been studied with respect to the posttreatment temperature. Bands located at 1250–1000 cm⁻¹ and around 960 cm⁻¹ have been deconvoluted in several peaks. The origin and temperature dependence of these peaks are discussed.     

The Deposition of Cubic Boron Nitride Fillms by Ion Beam Assisted Sputter Deposition

The relationship between film properties and assisting ion beam parameters such as the ion-to-atom arrival ratio, the mean energy transfer or the mean momentum transfer to a depositing atom has been established with a new method. We have made use of a focused assisting ion beam which generates zones of locally varying current densities on the film surface. By mapping these and the deposition rate, and measuring film properties as function of surface coordinates, we can determine their relationship from few samples. The: advantage is that the number of deposition runs can considerably be reduced, and errors can be avoided which may originate from slightly different deposition conditions (pressure, temperature, gas flow etc.) in different deposition runs.

This method has been applied to establish the relationship between the cubic phase formation of a boron nitride film and various assisting beam parameters. The BN films were characterized by transmission FTIR spectroscopy. The spectra were evaluated by fitting the absorption lines to Gaussian functions. The experiments show that the momentum transferred to a depositing atom is the relevant control parameter for the formation of the cubic phase and that a threshold exists at 250 (eV.amu)^1/2 above which the cubic phase is synthesized in accordance with results obtained by Kester and Messier. Below this threshold a small fraction of c-BN was also observed.     

In Situ Thermocouples in Macro-Components Fabricated Using SALD and SALDVI Techniques. II. Evaluation of Processing Parameters

In order to fabricate well-control led in situ SiC/C thermocouples embedded within macro-structural SiC components using an integrated selective area laser deposition (SALD) and the selective area laser deposition and vapor Infiltration (SALDVI) technique, the major processing parameters affecting the crystal structure, the deposition rate, surface morphology of deposits, and shapes and sizes of the cross section of deposited lines are evaluated. It is found that the growth rate of SiC deposits increases with temperature and tetramethy Isilane (TMS) gas pressure over the temperature and pressure range studied. The apparent activation energy for depositing SiC from TMS is 61 kJ/mole in the temperature range from 700 to 1200°C and independent of the TMS gas pressure ranging from 20 to 60 torr. The shape and size of the cross section of SiC lines depend strongly on the deposition temperature. XRD examination indicates that the deposition product using a C₂H₂ precursor at 900°C is crystalline graphite. The crytallinity of Si₃N₄ deposits is affected by the substrate material even though the deposition temperature and other process parameters are the same. These phenomena have been explained in terms of the growth controlling mechanisms of deposits, the temperature distribution induced by an incident laser beam, and the thermal conductivity of the substrate.     

Microstructural evolution of titanium nitride (TiN) coatings produced by reactive ion beam-assisted, electron beam physical vapor deposition (RIBA, EB-PVD)

Titanium nitride (TiN) coatings have been successfully deposited on 304 stainless steel substrates by reactive ion beam-assisted, electron beam-physical vapor deposition (RIBA, EB-PVD). The hardness values of the TiN coatings varied from 800 to 2500 VHN depending on the processing condition. The lattice parameter and hardness variation were correlated with processing parameters such as: deposition rate, bias, ion source energies, process gas, substrate temperature, and coating composition. The hardness of the TiN coatings increased with increasing ion energy. The ion energies combined with the deposition rate were the limiting factors controlling the degree of surface texturing. Surface texturing was only observed for those coatings deposited >8 Å/s.     

Molecular beam epitaxial growth of SmBa2Cu3O7−δ thin films and effect of substrate temperature on the surface roughness

Stoichiometrically optimized, epitaxial SmBa₂Cu₃O_7-δ thin films with high T_{c, R = 0} and high critical current densities j_c have been prepared for the first time in a tightly controlled molecular beam epitaxy process in non-reactive molecular oxygen, followed by an in situ loading process with molecular oxygen. The surface roughness (on a submicrometre scale) of single-crystal films with their c axes perpendicular to the surface depends markedly on the surface temperature of the substrate during the deposition of the epitaxial films, within a range of only a few degrees centigrade. The calibrated optimal temperature for the preparation of epitaxial films 200 nm thick of this single orientation is found to be 680 ± 5 °C. In scanning tunnelling microscopy investigations, they show a surface roughness of less than 6 nm (five SmBa₂Cu₃O_7−δ unit cells) on a 2 μm × 2 μm scale. At deposition temperatures below this optimal deposition temperature, the well-known a-axis growth increases rapidly, whereas higher temperatures give a significantly higher surface roughness, which can be observed by scanning electron microscopy.     

Pulsed Laser Deposition of Superhard Nitride Coatings

Nitrides coatings have a large number of applications in high-technology industries due to many unique physical, chemical, and mechanical properties. Thin films of aluminum nitride (AIN), silicon nitride (Si₃N₄), and carbon nitride (CN_x) were deposited on Si (100) substrates using the pulsed laser deposition (PLD) method. The seeding of titanium nitride (TiN) before the CN_x deposition has promoted the growth of the predominantly crystalline CN_x films. The laser deposition parameters and substrate temperature play an important role in fabricating high quality films. The structural and microstructural properties of these films have been characterized using x-ray diffraction, and scanning electron microscope techniques. The Fourier Transform Infrared (FTIR) and x-ray photoelectron spectroscopy (XPS) have been used to investigate the bonding properties in CN_x films. The mechanical properties of the films were evaluated to correlate with the processing parameters of the deposited films. It has been shown that the films with crystalline quality structure have higher hardness and modulus values.     

Effective mechanical properties of layered rough surfaces

In contact mechanics of layered rough surfaces, found in various systems such as magnetic storage devices and micro/nanoelectromechanical systems, it is of interest to calculate effective elastic modulus and hardness so as to obtain contact parameters using simple analyses for homogeneous surfaces. In this study, effective elastic modulus and hardness of layered rough surfaces are defined on the basis of real area of contact. A numerical model developed by the first author to simulate the contact of layered rough surfaces is used to derive these equations. Completely nondimensionalized empirical equations for these effective mechanical properties are presented. Separate equations are developed for the contact of a single conical asperity on a flat surface, a single spherical asperity on a flat surface, and for multiple asperity contact between two rough surfaces. These equations establish the dependence of effective mechanical properties on indentation depth, layer thickness, hardness and elastic modulus ratios of layer and substrate and surface roughness/asperity geometry. Comparisons of values predicted by the equations with experimentally obtained results are presented. Contact stress contours obtained from this model are analyzed to get a better understanding of the mechanics of contact.