The ability to precisely remove the internal structures of a semiconductor device, layer-by-layer, is a necessity for semiconductor research and failure analysis investigation. Currently, numerous techniques are used, such as mechanical polishing, chemical etching, and gas assisted plasma focused ion beam (FIB) milling. However, all of these techniques have limitations in that they are unable to: (1) delayer a millimeter-scale area with nanometer-scale uniformity, (2) rapidly remove thick (>300 nm) device layers, or (3) perform automatic and accurate end pointing, which is challenging on thin (≤300 nm) device layers.

We describe a fully integrated solution for millimeter-scale delayering of both logic and memory semiconductor devices. The flatness of the delayered device is controlled by an artificial intelligence algorithm, which uses feedback from multiple analytical detectors to control milling parameter adjustments in real time. The result is the precise removal of device layers and a highly planar surface.

Abradable seal coatings are widely employed in the gas turbine of aero-engine, which not only strength enough to resist the impact of external particles and airflow, but also excellent wear resistance. In the current study, we concentrate on APS sprayed Aluminum Bronze Polyester abradable coating that can be used in turbo engines both for seals and clearance control. A composite thermal spray powder, substantially in the form of clad particles each of which has coarse polyester powders and sub-particles of Cu-Al alloy powders, was prepared using mechanically clad process. Abradable seal coating was prepared by atmospheric plasma spraying. The microstructure, hardness, bonding strength, thermal shock resistance and corrosion resistance of coatings were researched. Properties of the coating were able to meet the application requirements. The coating microstructures and phase compositions were evaluated via SEM. The corrosion mechanisms of the coating were compared by analyzing the cross-sectional and top surface microstructures of the as-sprayed and eroded coatings.

Improvement in the performance of thermal barrier coating systems (TBCs) is one of the key objectives for further development of gas turbine applications. The material most commonly used as TBC topcoat is yttria stabilised zirconia (YSZ). However, the usage of YSZ is limited by the operating temperature range which in turn restricts the engine efficiency. Materials such as pyrochlores, perovskites, rare earth garnets, etc. are suitable candidates which could replace YSZ as they exhibit lower thermal conductivity and higher phase stability at elevated temperatures. The objective of this work was to investigate different multi-layered TBCs consisting of advanced topcoat materials fabricated by Suspension Plasma Spraying (SPS). The investigated topcoat materials were YSZ, dysprosia stabilised zirconia, gadolinium zirconiate, cerium doped YSZ and yttria fully stabilised zirconia. All topcoats were deposited with TriplexPro-210 plasma spray gun and radial injection of suspension. Lifetime of these samples was examined by thermal cyclic fatigue and thermal shock testing. Microstructure analysis of as-sprayed and failed specimens was performed with scanning electron microscope. The failure mechanisms in each case have been discussed in this article. The results show that SPS could be a promising route to produce multilayered TBCs for high temperature applications.

Yttria-Stabilized Zirconia (YSZ) suspensions are currently popular in developing strain resistant columnar structured thermal barrier coatings by Suspension Plasma Spray (SPS) as a less costly alternative to conventional EB-PVD. Coatings produced by SPS have a disadvantage of reduced usable spray distance, compared to conventional APS, due to quenching of the plasma by the suspension liquids, which are most commonly alcohol-based. The reduced spray distance can interfere with the coating process for substrates with complex geometries such as turbine blades. This paper shows how spray distance can be increased by using larger suspension particle sizes that are not normally considered for SPS. Such large particle suspensions are shown capable of producing columnar or segmented YSZ coating microstructures that are similar to those produced by submicron particle suspensions, but at longer and more practical spray distances. Another limitation to SPS process technology is the delivery system of feedstock from the point of manufacture to the SPS feed hopper. Current commercial ready-to-use suspensions have limitations involving cost, transportation and storage that effect both the producers and the end-users. An alternative suspension delivery system may be applied to SPS feedstock materials, including current sub-micron and the coarser particle size cuts described herein. Discussed is a pre-formulated dry feedstock that is constituted into fresh suspension by the end-user with locally sourced liquid media and appropriate high-speed mixing equipment. This alternative delivery system for suspensions provides lower cost materials and process flexibility that is particularly suited to commercial scale SPS coating facilities.

Commercial available Ni and Ti powder were blended together and deposited on stainless steel by atmospheric plasma spray(APS). Subsequently the as-sprayed coatings were laser remelted with a Nd -YAG pulsed laser source. Cross-sections of as-sprayed and laser-remelted coatings were characterized by scanning electron microscopy (SEM). Prior to SEM observations, the laser remelted coatings were polished and etched by Kroll etchant. Meanwhile, the energy dispersive spectrometer (EDS) was employed to analyze the chemical distribution of the coating both as-sprayed and laser remelted. The results indicated that APS sprayed NiTi coatings presented a dense microstructure with Ni splats and Ti splats distributing uniformly. Oxygen partial pressure in the argon leads to the burning of Ti splats during the laser remelting process. And Ti oxides located at the bottom of the laser molten pool because of the laser stiffness and molten flow. Moreover, the top part of the molten pool mainly involved in Ni columnar grains.

The CoCrAlSiY alloy powder with Si mass concentrations of 0, 2% and 5% was prepared in this work. The oxidation kinetics curves of all three kinds of powders after 300 h oxidation at 1000 °C were plotted. In addition, the phase constitution of alloy powder and the distribution of β phase were analyzed by SEM and EDS. Furthermore, the effect of Si-addition on the melting temperature and oxidation resistance of the alloy powder were investigated by DSC-TG from the room temperature to 1400 °C. And the element concentrations at the grain boundary of alloy powder with Si addition of 2% were also analyzed. The results show that the melting temperature of alloy powder decreases as increasing Si content, which indicates that adding Si element could influence on the selective oxidation of Al and Cr elements in the alloy system, and improve the oxidation resistance of CoCrAlY powder. In addition, the weight gain of powder with Si addition of 2% is lowest. And Si element has a enrich tendency in the grain boundary. Therefore, the higher Si content would have a negative effect on the high temperature oxidation resistance of powder.

A commercial abradable coating AlSi-hBN was fabricated by atmospheric plasma spraying and was thermal aged at 450 °C in the atmospheric environment for 1000h. Thermal aging effect on coating abradability, hardness, bond strength and microstructure were evaluated. It was found that coating abradability increased obviously after 2h thermal aging and slightly decreased for extended thermal aging time. A sharp decrease in both coating hardness and bond strength were found after 2h thermal aging and a slow increase occurred with the extended aging time. Relationships between coating properties and microstructure were studied. Decomposition of organic binder and sintering of AlSi matrix metal generated by thermal aging were found to be reasons for coating properties changes.

The Ti 2 AlNb blade is used in high pressure compressor aero-engines to provide high thrust force at relatively light weight. A series of abradability tests was carried out on CuAlNi-graphite, NiCrAl-graphite, NiCrAl-bentonite, and NiCrFeAl-hBN abradable coatings rubbed against Ti 2 AlNb dummy blades with the maximum blade-tip velocity of 300 m/s at 500 °C. In consideration of the effects of an engine’s working conditions, some tests were conducted with incursion rate as the single variable. The scratched surfaces of the samples were observed by the stereoscopic optical camera, and a ratio of the blade wear to shroud incursion depth (IDR) was evaluated to characterize the abradability of coatings. The results show that NiCrAl-graphite and NiCrFeAl-hBN abradable coatings perform very well rubbed against the Ti 2 AlNb blade, and the blade-tip wear is not obvious after abradability tests.

This study investigates the influence of particle size, nozzle diameter, gas flow rate, and stand-off distance on the microstructure and density of suspension plasma sprayed yttrium-oxide coatings and the intermediate effect of particle characteristics. Three ethanol suspensions were prepared, one with coarse Y 2 O 3 , one with fine Y 2 O 3 , and one with submicron YSZ. The suspensions were injected vertically into the plasma jet downstream of the nozzle and a thermal spray sensor was used to measure in-flight velocity and temperature. The coatings were found to have columnar and dense vertically cracked (DVC) microstructure, varying in hardness and density. Text results and examination findings are presented and correlated with spray parameters, particle properties, and possible coating formation mechanisms.

This study investigates the influence of particle size and solid concentration in suspension on the microstructure of suspension plasma sprayed YSZ coatings. It also assesses the influence of plasma gases, plasma power, injector size, spray distance, and suspension feed rate. It is shown that suitable spray distance is necessary to achieve dense coatings with relatively coarse (0.6 μm) particles and that a columnar-like structure tends to be produced when fine (0.2 μm) particles are sprayed. The results also show that using Ar-He plasma and increasing total gas flow is an effective way to create dense vertically cracked (DVC) microstructure.

A series of abradability tests were conducted on AlSi-hBN coatings, which are commonly used in the compressor section of aeroengines for clearance control. The coatings were sprayed on test plates to a thickness of 1.9-2.0 mm and ground to a finish of 10 μm with 400 grit paper. The tests were carried out in an automated test rig with adjustable temperature, blade tip velocity, and incursion rate. The rig is configured such that the coatings are exposed to rotating blades, making contact with the tips as they pass. In this study, investigators monitored the number of contacts, removing and examining abraded coating samples at a given count total ranging from 200 to 4000. It was found that wear characteristics change with each contact between the coating and blade tip, indicating that pass number is a factor that must be considered when testing abradable coatings.

In this work, numerical modeling is used to simulate the effects of laser remelting as a post treatment and as an in-situ component of a hybrid plasma spraying process. Initially, a single-pass 2D model is used to simulate the laser post-treatment process in order to obtain relationships between melting pool depth, relative scanning velocity, and laser power. A 3D finite-element model is then used to study temperature variations during multi-layer deposition of a NiCr alloy by plasma spraying with in-situ laser melting. The effects of phase change are taken into account by defining the enthalpy of the material as a function of temperature. Predicted melting pool depth corresponded well with experimental values.

Heavy polymer residue has been observed on the sidewall of thick metal during the process release. The thickness of metal line is more than 3 micron. This thick polymer residue on the aluminum metal sidewall is seen from tilt Scanning Electron Microscope (SEM) profile analysis. This polymer residue on the metal sidewall with chlorine ( Cl 2) trapped will result in metal corrosion. The focus on this paper is on the removal of this polymer residue on the thick metal sidewall. The experiments were run with splits of varying the chemical dispensing time and the rinsing time in the process. The success criteria are determined by passing the Defect Source Analysis (DSA) and tilt SEM profile analysis. These wafers are sent for electrical test, wet box test (corrosion test) and electrical sort test to ensure the reliability of the post metal cleaning condition.

Nickel clad hexagonal boron nitride (h-BN) powders were prepared by reducing nickel ions from a solution under hydrogen pressure in the presence of ammonia as a complexing agent, and plasma spraying was carried out to deposit the corresponding coating. The microstructure, morphology and phase composition of the powders and the coating were characterized by optical microscope (OM), Scanning Electronic Microscope (SEM) and X-ray Diffraction (XRD), respectively. The results show that alkali solution pretreatment and activation procession are necessary for acquiring a dense and uniform nickel coating on the surface of the h-BN particles, and the h-BN particles are distributed well throughout the coating with the porosity of about 26%, which indicate that the coating was potential for abradable sealing application.

The control of microstructure of TiO 2 coating through preparation methods influences significantly the performance of the coating. In this study, vacuum cold spray process as a new coating technology is employed to deposit nanocrystalline TiO 2 coatings on glass and stainless steel substrates. TiO 2 deposits were formed using two types of nanocrystalline TiO 2 powders having mean particle diameters of 200 nm and 25 nm. The microstructure of the coating was characterized by scanning electron microscopy, x-ray diffraction analysis. The results demonstrate that a thick nanocrystalline TiO 2 coating can be deposited by vacuum cold spray process. The coating was stacked of particles in agglomerate of several hundred nanometers. The coating presents a mesoporous microstructure which would be effective for applications in photocatalytic degradation, dye-sensitized solar cell and so on.