Top Coat Material Research Articles

Quest and Evaluation of Topcoat Materials for Environmental Barrier Coatings of SiC/SiC Composites

SiC fiber reinforced SiC matrix (SiC/SiC) composites are one of the most promising materials for high temperature structural applications such as power generation and propulsion systems. SiC/SiC composites are, however, susceptible to accelerated attacks in water vapor environments through oxidation and volatilization reaction. For protection from such attacks, Environmental Barrier Coatings (EBCs) are indispensable. We have investigated some oxides and rare-earth silicates as topcoat candidate materials for EBCs. Topcoat materials must be stable in the high-water-vapor pressurized environments at high temperatures. Also, it is important that the thermal expansion coefficient of topcoat materials is similar to that of the SiC/SiC composites. In this study, first, zirconium oxides, lutetium silicates and yttrium silicates were selected as topcoat candidate materials. They were exposed in a water-containing atmosphere at a temperature of 1673 K for 100 h under a total pressure 0.96 MPa. Mass changes, structure of crystals and microstructures were investigated after the exposure experiments in order to evaluate the thermal stability of these materials. After their estimation, lutetium silicates were considered to be promising for topcoat materials. Then, lutetium silicates were coated as the topcoat of an EBC system on SiC/SiC composites, and their fracture toughness and microstructures were investigated after exposure to an oxidizing atmosphere. The evaluation results of the topcoat materials are reported in this paper.

Advanced materials for 193 nm immersion lithography

AbstractRecently 193 nm immersion lithography is considered the most promising next generation technology which will enable a 45 nm and below node device to be manufactured. This will lead to not only depth of focus (DOF) enlargement, but immersion lithography enables the use of a hyper numerical aperture (NA) larger than 1.0 and achieve higher resolution capability. For 193 nm lithography, water is an ideal immersion fluid, providing suitable refractive index and transmission properties. Furthermore the higher refractive index fluid is expected to provide a potential extension of optical lithography to the 32 nm node. This paper describes the critical issues of the water immersion lithography process, such as photoresist component leaching into water, defectivity etc. Leaching materials were analyzed by liquid chromatography‐mass spectrometry (LC‐MS) and were found to be composed of the photoacid generator (PAG) and its decomposed chemicals. The leaching amount is in the order of 10−12 mol/cm2 with a normal 193 nm photoresist. An other issue to be studied is the water‐mark defect caused by small waters droplets left on the exposed wafer. These undesirable phenomenons could be prevented by applying a topcoat material onto the photoresist film. Material design for the topcoat material and its physical and lithographic properties are discussed in detail. Development of a high refractive index fluid is also discussed in this paper. A promising high refractive index fluid HIL‐001 was developed which has a higher refractive index (n = 1.64) than water and high transparency (98%/mm) at 193 nm wavelength. Immersion exposure experiments using high refractive index fluid with and without topcoat material was carried out and 32 nm L/S imaging capability was demonstrated by using a two‐beam interferometric exposure tool. Copyright © 2006 John Wiley & Sons, Ltd.

Novel Top-coat Materials Containing a Bulky Silicon Group for ArF Immersion Lithography

Novel alkaline developable top-coat materials containing a bulky silicon group are presented. This bulky silicon group endows transparency at 193nm wavelength and hydrophobicity to the top-coat. Good pattern profiles and negligible changes of lithographic performance are confirmed on ArF photoresists. Receding angle of this top-coat is 90o, which is the highest among alkaline developable top-coats reported to date, and only comparable by solvent soluble-typetop-coat TSP3A.

Characteristics of ArF Immersion Lithography Using Topcoat

This paper is intended as investigations of two interesting characteristics of ArF immersion lithography using topcoat (TC). On the one hand, we identified several hundreds gel-type defects over large areas of the unexposed top surface of the resist in cases where a TC was used. On the other hand, we observed that the optical proximity effect (OPE) profiles in immersion lithography varied with the type of TC materials beyond expectation. The magnitude of OPE was reduced to approximately 20 nm in the region of maximum influence. We investigated the influences on these characteristics of the TC material and the methods of application (i.e. baking conditions and exposure). The chemical interaction (e.g., mixing) between the resist and the TC was examined by employing time-of-flight mass spectrometry with gradient shaving preparation (GSP + TOF) and FT-IR measurements and by focusing on the interface of the resist and TC. We confirmed consistent correlations between lithographic properties and chemical interaction. The TC material and process which form much mixing layer due to the chemical interaction tended to cause gel-type defect and variation of OPE profile.

ナノコーティング 高性能遮熱コーティングのための低弾性率トップコートの新規製造プロセス

Elastic moduli of YSZ top coats for thermal barrier coatings(TBCs) were measured, where the top coats were fabricated by the following different types of methods: a traditional atmospheric plasma spraying(APS) method; a hybrid plasma spraying(HYPS) method that has been originally developed by Yoshida group; and an electron-beam physical vapor deposition(EB-PVD) process. The top coat material was ZrO2 stabilized by 8 mass%Y2O3. Through the work special attention was paid to investigate the effects of the processing methods, the process variables in APS and the long term thermal aging at high temperature. It was found that the advanced methods; HYPS and EB-PVD methods, could provide the top coat film with lower elastic moduli, that may have a beneficial effect to prevent the failures of TBCs induced by thermal stress. Some discussions were made for their low elastic moduli, based on the analysis of the microstructure of the top coats and the Eshelby's approach.

Properties of plasma sprayed boron carbide protective coatings for the first wall in fusion experiments

In this study stainless steel substrates were coated by vacuum plasma spraying with a two-layer system consisting of a bond coat of 40 μm nickel–chromium and the top coat material B 4C of 160–200 μm thickness. The spray angle was varied from normal incidence to 60° with respect to the substrate normal. The effects of processing conditions on microstructure, mechanical properties and thermal load resistance were investigated by use of X-ray diffraction, optical microscopy, SEM, optical porosimetry, roughness- and adhesion-tests and thermal shock experiments in the electron beam test facility JUDITH. The thickness of the deposited B 4C-coatings decrease to a minimum of 40 μm with increasing spray angle. Simultaneously the average roughness increases at a constant value of porosity. It could be stated, that the coatings, deposited at a larger angle, tend to exhibit a larger erosive attack pattern at slightly lower energy.

The functional effect of top-coat system for porous asphalt

The studies made so far on the top-coat system with MMA type resin for porous asphalt have proven the effect of the system on improvement of permeability of porous asphalt and its capability for reducing deposition blocking up the voids. This effectiveness simply attributed to the difference of tackiness between asphalt binder and MMA type resin. However it was hypothesized that this effect would be developed by the difference in surface free energy (γs) between top-coat materials and asphalt binders. Therefore some porous mixes were prepared using different binders having differentγs values, then the changes in permeability were measured by repeatedly filling the voids with slurry, and the effects ofγs of the binder were examined.

Copolymerization of 4-chlorophenyl acrylate with methyl acrylate: synthesis, characterization, reactivity ratios, and their applications in the leather industry

4-Chlorophenyl acrylate (CPA) was prepared by reacting 4-chlorophenol and acryloyl chloride in the presence of triethylamine in ethyl acetate solution. Poly(4-chlorophenyl acrylate) and copoly(4-chlorophenyl acrylate–methyl acrylate) were synthesized by the free radical polymerization in ethyl acetate at 70°C. All the polymers were characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopic techniques. The composition of the copolymers was determined by the 1H-NMR spectroscopic technique, that is, by integrating the aromatic peaks corresponding to the 4-chlorophenyl acrylate unit against the carbomethoxy group in the methyl acrylate unit. The reactivity ratios were calculated by Fineman–Ross, Kelen–Tudos (K–T), and the extended Kelen–Tudos methods. The values of r1 and r2 obtained by these methods were in close agreement with each other; that is, r1(CPA) = 0.64 and r2(MA) = 0.13 by the K–T method. The number-average molecular weight (M̄n = 1.55 × 103), the weight-average molecular weight (M̄w = 8.39 × 103), and the polydispersity index (M̄w/M̄n = 5.42) of poly(CPA) were determined by gel permeation chromatography (GPC). Thermal properties of the polymers were studied in a nitrogen atmosphere using thermogravimetric analysis (TGA). As the CPA increases in the copolymer, thermal stability of the copolymer increases (e.g., 90% weight loss occurs at 480°C for 20 mol % CPA, whereas the same weight loss occurs at 571°C for 80 mol % CPA). Acrylic binders, based on the CPA–MA–BA terpolymer, of different glass transition temperatures were prepared for applications in leather industry as top coat and base coat materials. These acrylic emulsions were cast into thin films, and their characteristics were tested for physical properties. These acrylic emulsions were applied as a base coat on leather, and the compositions having Tg values of 1.08 and 9.25°C were found to have excellent properties as base coats for leather when compared with commercial samples. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1153–1160, 1999

A software tool to design thermal barrier coatings: a technical note

This paper summarizes work completed for a NASA Phase ISBIR program that demonstrated the feasi-bility of developing a software tool to aid in the design of thermal barrier coating (TBC) systems. Toward this goal, three tasks were undertaken and completed. Task 1 involved the development of a database con-taining the pertinent thermal and mechanical property data for the top coat, bond coat, and substrate materials that constitute a TBC system. Task 2 involved the development of an automated setup program for generating two-dimensional finite-element analysis (FEA) models of TBC systems. Most importantly, task 3 involved the generation of a rule base to aid in the design of a TBC system. These rules were based on a factorial design of experiments involving FEA results and were generated using a Yates analysis. A previous study had indicated the suitability and benefit of applying FEA to perform computer-based ex-periments to decrease but not eliminate physical experiments on TBCs. This program expanded on these findings by developing a larger knowledge base and a procedure to extract rules to aid in the TBC design.