Film Removal Mechanism Research Articles

Research on the physical properties and film removal mechanism of silver brazing flux by micro morphology analysis and X-Ray Diffraction

The effect of KHF2 addition on silver brazing flux was studied in this paper. Results showed that the melting temperature of brazing flux would sustainably decrease with the increasing content of KHF2. KF could not be completely replaced by KHF2 in the brazing flux because it could restrain excessive spreadability, which was resulted from KHF2. F element in the flux replaced O element to form Fe2F5.

Mechanism of TCO thin film removal process using near-infrared ns pulse laser: Plasma shielding effect on irradiation direction

Substrate side irradiation is widely used for a thin film removal process because high absorption at the film/substrate or film/film interface leads to complete isolation of thin film by single shot irradiation of laser pulse with low energy. However, in the transparent thin film removal process, large thermal expansion or local phase change at the interface cannot be created by substrate side irradiation because of its large optical penetration depth compared to its small thickness. Nevertheless, substrate side irradiation works obviously for single shot film isolation process compared to film side irradiation, and the mechanism of the process was not clear in terms of difference in the irradiation direction. In order to investigate the effect of the irradiation direction, this study focused on the transient interaction between the material and nanosecond laser pulse. Experimental results showed that film was thermally ablated. Variation of temporal profile of nanosecond laser pulse during the process was experimentally investigated to detect plasma shielding. Pulse width and energy transmittance of transmitted pulse decreased by plasma shielding as pulse energy increases regardless of irradiation direction. In addition, temperature distribution in the film during the process was investigated using a 2-dimensional thermal model, which accounts for melting, vaporization, and laser induced plasma shielding. Calculated temperature distribution was used to support the scenario of the process mechanism which was investigated in the experiments. Our findings demonstrate that laser induced backward ablation is a single shot TCO film removal mechanism, and plasma shielding is dominant factor to interrupt absorption of beam thorough the film in the film side irradiation process.

Removal Mechanism and Defect Characterization for Glass-Side Laser Scribing of CdTe/CdS Multilayer in Solar Cells

Laser scribing is an important manufacturing process used to reduce photocurrent and resistance losses and increase solar cell efficiency through the formation of serial interconnections in large-area solar cells. High-quality scribing is crucial since the main impediment to large-scale adoption of solar power is its high-production cost (price-per-watt) compared to competing energy sources such as wind and fossil fuels. In recent years, the use of glass-side laser scribing processes has led to increased scribe quality and solar cell efficiencies; however, defects introduced during the process such as thermal effect, microcracks, film delamination, and removal uncleanliness keep the modules from reaching their theoretical efficiencies. Moreover, limited numerical work has been performed in predicting thin-film laser removal processes. In this study, a nanosecond (ns) laser with a wavelength at 532 nm is employed for pattern 2 (P2) scribing on CdTe (cadmium telluride) based thin-film solar cells. The film removal mechanism and defects caused by laser-induced micro-explosion process are studied. The relationship between those defects, removal geometry, laser fluences, and scribing speeds are also investigated. Thermal and mechanical numerical models are developed to analyze the laser-induced spatiotemporal temperature and pressure responsible for film removal. The simulation can well-predict the film removal geometries, transparent conducting oxide (TCO) layer thermal damage, generation of microcracks, film delamination, and residual materials. The characterization of removal qualities will enable the process optimization and design required to enhance solar module efficiency.

Oxide film on 5052 aluminium alloy: Its structure and removal mechanism by activated CsF–AlF3 flux in brazing

The oxide-film structure on the 5052 Al alloy and the film-removal mechanism by activated CsF–AlF3 flux in brazing were studied. Characterisation of the oxide film shows that thermally activated Mg, segregated from the alloy's interior, was significantly enriched and oxidised during medium-temperature brazing. Thus, the outer oxide surface consisted of the amorphous MgO-like phase, and the interior of the oxide film comprised mainly the amorphous MgO-like phase and dispersely distributed and less-ordered MgAl2O4. The MgO-like phase was the main obstacle to oxide removal in brazing. The activated ZnCl2-containing CsF–AlF3 flux effectively removed the oxide film, and the 5052 Al alloy was successfully brazed by the Zn–Al filler metal and activated flux. When Zn2+ in the molten flux permeated the oxide film through cracks, its chemical reaction with the Al substrate loosened the oxide film, which was eventually pushed out as the filler metal spread over the alloy surface.

纳秒脉冲激光熔覆温度场计算及薄膜飞溅机制分析

纳秒脉冲激光熔覆温度场计算及薄膜飞溅机制分析

纳秒脉冲激光熔覆温度场计算及薄膜飞溅机制分析

纳秒脉冲激光熔覆温度场计算及薄膜飞溅机制分析

Molecularly thick dicationic ionic liquid films for nanolubrication

Ionic liquids (ILs) are attractive as lubricants for micro- and nanoelectromechanical systems due to their superior thermal stability and electrical conductivity compared to conventional lubricants. The adhesion, friction and wear properties of two dicationic ILs based on the imidazolium cation and the triflamide anion were studied and compared to the monocationic IL 1-butyl-3-methyl-1H-imidazolium hexafluorophosphate (BMIM-PF6) using atomic force microscopy. The ionic liquid film removal mechanism was investigated by monitoring the friction force, surface potential, and contact resistance. An IL based on the triflamide anion and two imidazolium cations linked by a pentane chain exhibited the best nanolubrication properties. This is attributed to the presence of hydroxyl groups at its chain ends which can hydrogen bond with the surface, and a hydrophobic linker chain. Another dicationic liquid, with a polyether chain linking the cations, had less desirable adhesion, friction, and wear properties compared to the monocationic IL. Intermolecular hydrogen bonding in this IL reduces the chain ordering on the substrate surface, which accounts for the observed higher adhesive force and coefficient of friction relative to the other ionic liquids investigated.

Studies of the removal of hydrogenated carbon films by nitrogen glow discharges

In the present work the erosion of laboratory-produced a-C:H layers by H2/N2 plasmas is addressed. Hard hydrocarbon films were deposited using He/CH4 plasmas. These layers were exposed to H2/N2 plasmas, showing a high erosion rate, above 4 nm/min. However, thermal desorption of the films after exposure to the erosion plasmas indicates that some modifications of the binding states of H took place, leading to an increase of the temperature of desorption. The studies reported in the present work include the characterization of the plasma chemistry by differentially pumped mass spectrometry and Cryotrapping-Assisted Mass Spectrometry, erosion rates by laser interferometry and characterization of the binding states by thermal desorption spectroscopy. The detection of acetonitrile in the reaction products provides a clear indication of chemical reactions being involved in the film removal mechanism under the reported conditions.

Advanced silver-based metallization patterning for ULSI applications

Silver metallization is being investigated for potential use in future integrated circuits. Unlike the proposed copper metallization, Ag thin films can be reactive ion etched at reasonable rates using a CF 4 plasma. This etch technology is an atypical ‘dry-etch’ process since the formation of volatile products is not the main removal mechanism. The primary film removal mechanism, however, is the subsequent resist strip process. The effects of process conditions on the etch rate and post-etch surface roughness is also characterized. Our study shows that the silver etch process in the CF 4 plasma depends strongly on the reactive neutrals and the removal rate is enhanced significantly by the presence of energetic ions as well.

Novel technique to pattern silver using CF[sub 4] and CF[sub 4]/O[sub 2] glow discharges

Silver is being studied as a potential metal for future interconnects in integrated circuits. Under appropriate conditions, Ag thin films can be removed at reasonable rates using a CF4 or CF4/O2 glow discharge followed by a conventional resist strip process. This is not a typical “dry-etch” process where the formation of volatile products is the main removal mechanism. Rather, it is novel in that the glow discharge is employed to form reactive byproducts of Ag. There are simultaneous sputtering and desorption of the byproducts during the plasma exposure; but the primary film removal mechanism is in the subsequent resist strip process. Two-level-factorial design, and one-factor-at-a-time experiments are employed to study the effects of process conditions on the etch rate, and postetch surface roughness. It is found that Ag removal rate in CF4 or CF4/O2 glow discharges depends strongly on applied power. Postetch surface roughness depends on both power and pressure.

Surface cleaning by ice-particle jet(II)

A physical method of surface cleaning has been developed using the jet of micron-sized ice particles in a low pressure impactor. The substrate to be cleaned was prepared by both applying organic films and depositing polystyrene (PS) particles on substrates. The PS particles, as a source of contamination, were produced with the average sizes ranging from 0.5 to 3 micrometers and narrow size distribution under well-controlled conditions. The particles were deposited uniformly and controllably by changing the deposition time, carrier gas flow rate, and substrate temperature. Major variables for removing both the films and contaminating particles were the removal time, chamber pressure, carrier gas flow rate, nozzle-to-substrate distance and number concentration of ice particles. We proposed two models on film-removal mechanism, which could be applied, depending on the kinetic energy of the ice particles and the hardness of the film. The ice-particle jet system, as a method of cleaning, was found so effective to remove physically both films and particles adhered to a wafer.

Protection by diamond-like carbon films on fused silica slides from erosion by the impact of solid particles

Measurements were made with a new test for improved quantitative estimation of the mechanical protection of thin films on optical materials. The mechanical damage was induced by a sandblasting system using spherical glass beads. Development of the surface damage was measured by the changes in the specular transmission and reflection and by inspection using a surface profilometer (and a scanning electron microscope). The changes in the transmittance with the duration of sandblasting were measured for uncoated and coated fused silica slides. It was determined that the diamond-like carbon films double the useful optical lifetime of the fused silica. Conclusions were obtained for the fused silica surface removal mechanism and for the film removal mechanism.

Two-phase mechanism of laser-induced removal of thin absorbing films. I. Theory

A physical model of laser-induced removal of thin absorbing films is proposed. The qualitative concepts of melt surface evaporation and of melt motion under the action of the reactive vapour pressure, of surface tension forces and of adhesion, support the model. The basic equations describing the removal process are solved numerically. An analytical parameter phi , characterising the relationship between the liquid and vapour phases of the removed material, is obtained. It is shown that, depending on the direction of the inequality phi <<1 or phi >>1, evaporation or liquid phase motion respectively plays the principle role in the film removal mechanism.

Thin-film machining by laser-induced explosion

This paper describes a process for the laser machining of thin metallic films on dielectric substrates. The observation of a distinct minimum in the machining threshold and the fact that no substrate damage occurs over a wide range of incident power are explained based on an explosive film-removal mechanism. Experimental results supporting the predictions are presented.

Some physicochemical relations between thin films and solid surfaces: I. Interfacial Mechanism of Removal of Thin Films

An interface-activated mechanism of displacement of thin oily films is described which appears to be related to the Marangoni effect (spreading pressure). This mechanism is due to surface motion created by local variations in the surface tension. The use of this technique as a tool in the study of the kinetics of desorption of thin films from solid surfaces and the effects of several variables were investigated and are discussed, with derivations of the appropriate thermodynamics. The reverse step, redeposition of oil (the removed thin film) onto the stainless steel (solid surface), was shown to be negligible under the existing experimental conditions. The transport of the removed oil over the water/air interface was eliminated as a contributing factor to the observed kinetics. The thin film removal mechanism would therefore appear to be a one-step process governed by the kinetic step of the dissolution of the oil at the oil/air/water bouandry line.