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Overlay (OVL) has become a critical process control and metrology challenge for current and future process nodes of logic as well as memory devices. Especially with the advent of EUV lithography and the accompanying use of two lithographical techniques (EUV and 193nm immersion) for patterning of critical layers, there is an increased need for identifying variability and its root cause in the overlay signatures. Current variability analysis uses pre-defined models mostly related to describe variability and allocating them in standard categories. These models are usually tied to the applicable exposure capabilities. As the EUV to immersion layers undergo exposure with vastly different conditions, there is a need to analyze OVL without associating to specific models. In this paper, we report on a novel model-less method for analyzing overlay data containing complex intra-field signatures. The method can identify and quantify intra-field signatures variation within a wafer as well as across wafers. These signatures enable root cause analysis of contributors to overlay variability. We applied the method on data sets of long-term overlay data of an EUV to a 193-immersion layer. While, several applications of the method with respect to identifying exposure conditions are demonstrated specific to the EUV to immersion layer, it should be noted that the method is universally applicable to any imaging wavelength for current and reference layer.

Zeolite-based catalysts are usually utilized in the form of a composite with binders, such as alumina, silica, clay, and others. However, these binders are usually known to block the accessibility of the active sites in zeolites, leading to a decreased effective surface area and agglomeration of zeolite particles. The aim of this work is to utilize carbon nanostructures (CNS) as a binding material for nano-zeolite-Y particles. The unique properties of CNS, such as its high surface area, thermal stability, and flexibility of its fibrous structure, makes it a promising material to hold and bind the nano-zeolite particles, yet with a contemporaneous accessibility of the reactants to the porous zeolite structure. In the current study, a nano-zeolite-Y/CNS composite catalyst was fabricated through a ball milling approach. The catalyst possesses a high surface area of 834 m2/g, which is significantly higher than the conventional commercial cracking catalysts. Using CNS as a binding material provided homogeneous distribution of the zeolite nanoparticles with high accessibility to the active sites and good mechanical stability. In addition, CNS was found to be an effective binding material for nano-zeolite particles, solving their major drawback of agglomeration. The nano-zeolite-Y/CNS composite showed 80% conversion for hexadecane catalytic cracking into valuable olefins and hydrogen gas, which was 14% higher compared to that of pure nano-zeolite-Y particles.

Nanosized zeolites have attracted interest for many applications including catalysis due to their higher surface area and hence more accessible active sites compared to the microsize zeolite particles. Ball milling is considered as a fast and an efficient technique to reduce the particle size down to nanometer range. However, it is usually accompanied by the formation of large undesired flakes and slabs with a loss of crystallinity and surface area. This study attempts to utilize carbon nanostructures (CNS) as a damping material to overcome the reported drawbacks. The idea of using CNS as a damping material is novel as this is the first study which reports the usage of CNS as damping material that prevents the zeolite micro particles from severe loss in crystallinity compared to the same process without CNS addition. Utilization of CNS gives two-fold advantages pertaining to its flexibility and superior mechanical properties and secondly the ease by which it can be removed off through oxidation after ball milling. Different parameters such as the ball milling solvent and post treatment conditions were varied and studied to observe the changes in final ball milled particle properties, such as morphology, crystallinity index, surface area and particle size distribution. Optimum ball milling and post treatment conditions registered a final zeolite surface area of 1522 m2/g compared to the initial 850 m2/g for micron sized particles. Moreover, x-ray diffraction and high resolution transmission electron microscopy (HR-TEM) images revealed highly crystalline zeolite nano particles with a crystallinity index of 38% which is more than 30% higher than previously reported study of ball milled zeolite particles without any damping material.

Nanosized zeolite Y is used in various applications from catalysis in petroleum refining to nanofillers in water treatment membranes. Ball milling is a potential and fast technique to decrease the particle size of zeolite Y to the nano range. However, this technique is associated with a significant loss of crystallinity. Therefore, in this study, we investigate the effect of adding biodegradable and recyclable cellulose nanofibrils (CNFs) to zeolite Y in a wet ball milling approach. CNFs are added to shield the zeolite Y particles from harsh milling conditions due to their high surface area, mechanical strength, and water gel-like format. Different zeolite Y to CNFs ratios were studied and compared to optimize the ball milling process. The results showed that the optimal zeolite Y to CNFs ratio is 1:1 to produce a median particle size diameter of 100 nm and crystallinity index of 32%. The size reduction process provided accessibility to the zeolite pores and as a result increased their adsorption capacity. The adsorption capacity of ball-milled particles for methylene blue increased to 29.26 mg/g compared to 10.66 mg/g of the pristine Zeolite. These results demonstrate the potential of using CNF in protecting zeolite Y particles and possibly other micro particles during ball milling.

Inorganic membranes hold great potential for various mainstream applications such as in wastewater treatment, drug manufacturing, food and beverage production, and dairy purification. There are numerous commercially available ceramic membranes which possess high corrosion resistance, high strength, and good heat resistance. However, these membranes are still prone to fouling causing a considerable decline in membrane performance and hence shorter life-times. Conventional methods for flux recovery include rigorous chemical backwashing, producing large amounts of sludge leading to disposal problems. In this work, commercial α-Alumina (Al2O3) ultrafiltration (UF) membranes were coated with titanium through an e-beam deposition process. The titanium coating rendered the membrane conductive, without changing the superhydrophilicity and average pore size of the membrane. Thermal degradation profiles suggested good thermal characteristics of the membrane. Good electrocatalytic activity for hydrogen evolution reaction was observed for the membrane, with an over-potential of 450 mV and 400 mV vs. Reference Hydrogen Electrode in acid and base solutions. The conductive membrane allowed for periodic electrolysis which is a fast and simple technique for fouling control and prevention. The membrane was used as a cathode during a cross-flow filtration setup, where 2.0 V was applied for 5 min during intervals. Without electrolysis, a considerable decline in flux was observed reaching almost 10% and 40% of its original value during yeast and sodium alginate (SA) filtration respectively. However, substantial flux recovery to 87% and 97.5 % was achieved after the first cleaning cycle during yeast and sodium alginate (SA) filtration respectively. Thereafter, considerable flux recovery was achieved during each subsequent electrolysis cycle. Membrane’s good electrocatalytic properties led to the generation of hydrogen bubbles which helped in sweeping away the foulants from the membrane’s surface.

Zeolite nanoparticles have attracted much interest in various catalytic applications due to their reportedly superior performance when compared with the microparticle counterpart. In this study, we report hydrocracking catalysts made from nano zeolite Y- NiO-WO3. The nano hydrocracking particles were compared for their performance with the micro hydrocracking particles. Both were prepared through the impregnation of nickel and tungsten salts, and tested under similar catalytic conditions at 350 °C and 400 °C, using n-heptane as the feed molecule. The nanoparticles registered superior total conversions of 98.3 wt. % and 95.7 wt. % at 350 °C and 400 °C respectively while the micro counterpart gave overall conversions of 78.3 wt. % and 34.6 wt. % at 350 °C and 400 °C respectively at the end of total time on stream of 180 min. The higher conversions for the nano zeolite Y hydrocracking particles suggest more accessibility of the active sites for the reaction to occur. This work may provide a further insight on utilizing zeolite nanoparticles for different catalytic applications, especially in conjunction with metallic elements.

Ultrafiltration (UF) and nanofiltration (NF) membranes have attracted great research interest to treat dye wastewaters. However, UF membranes suffer from low dye rejection and NF membranes have low salt recovery. There is a tradeoff between the dye rejection and salt recovery in the UF and NF membranes. A novel membrane is required for dye rejection with high salt recovery. Herein, we report a novel UF conductive ceramic membrane made from nano-zeolite and carbon nanostructures (CNS) combined with an external electric potential to treat crystal violet (CV) dye/NaCl-Na2SO4 salt solution. The membrane showed trimodal hierarchical porosity, a water contact angle of ≈40°, good flexibility and high electrical conductivity. Voltages from 2 to 15 V were applied to the membrane acting as a cathode in a cross-flow filtration setup. High dye rejections ≈100% with a flux of 210 LMH at a voltage as low as 3 V were achieved. Contemporaneous dye degradation was observed with several intermediate compounds, identified through mass spectroscopy. It was observed that higher potentials produced nitrates/nitrites from organic intermediates as deduced from ion chromatography results. Donnan steric repulsion increased with higher potentials, leading to increased ion transfer resistance for anions and improved permeation for cations. Various permeate properties such as pH and conductivity were monitored, along with high salt recoveries, hence providing a huge advantage of using such a membrane for treating dye wastewaters with selective dye/salt rejection. The versatile properties, together with its facile fabrication process indicates tremendous prospect of zeolite/CNS membranes for multipurpose applications treating wastewaters containing charged molecules and ions.

Fouling is major concern in several industries involving separation of heavy oil components such as crude and motor oils. In this work, a novel free-standing, conductive ceramic membrane, made from nanozeolite and carbon nanostructures (CNS) was fabricated. Various nano-zeolite: CNS ratios were studied. The membranes were tested for oil/water separation with oil concentration of 600 ppm using a dead-end filtration setup under an applied vacuum of 70 kPa on the permeate side. The zeolite nanoparticles provide excellent underwater oleophobicity and a hydrophilic interface, resulting in efficient oil/water separation with a high rejection of 98% for crude oil. The role of CNS in the composite membrane is three-fold; acting as a binder for zeolite nanoparticles, to provide flexibility and to make the membrane conductive. The hierarchical membrane structure formed from hydrophilic zeolite nanoparticles embedded with the CNS greatly facilitates the rapid permeation of water with a high flux of ˃400 L/m2 h for oil/water separation. With increasing zeolite composition relative to CNS, membrane separation performance was observed to increase till 60 wt. % zeolite content. However, higher percentage decreased the flux considerably while keeping the oil rejection constant. Membrane repeatability was studied by performing 10 filtration cycles, where a decrease in flux to about 50% was observed by the end of the 5th cycle. The conductive nature of the membrane (electrical conductivity = 4.9 × 103 S/m) allowed periodic electrolysis of the membrane, hence recovering the flux considerably after each cycle, and reaching about 80% by the end of the 10th cycle. This work provides a new way to develop ceramic based self-cleaning membranes which are applicable in various industries where fouling in ceramic membranes is a major drawback.

Hydrocracking of Athabasca vacuum residue (AVR) was carried out in an autoclave using particle and fiber forms of NiO-WO3 zeolite-supported catalyst. AVR hydrocracking was performed at 400 °C at low and high H2 pressure of 70 and 365 psi, together with the corresponding control thermal cracking runs. The yield of the different products and the quality of the upgraded liquid was used to assess the catalyst performance. Similarity among energy consumption for the different samples suggested major thermal cracking endothermic reactions. In general, the catalytic runs provided better quality maltene product, whereas better quality product oil was only attained at high pressure. The catalytic runs at low H2 pressure gave the highest yield of combined asphaltenes and toluene insolubles. This yield, on the other hand, was the lowest for the fiber form at high H2 pressure. Simulated distillation results captured the superior performance of the fiber catalyst at high H2 pressure and showed ∼50% conversion of the r...

Electrospun tungsten oxide/nickel tungstate (WO3/NiWO4) composite nanofibers were tested for photoelectrochemical (PEC) performance under visible light irradiation under three voltages, 1.6, 1.8 and 2.0 V with reference to Ag/AgCl electrode in 0.5 M H2SO4. It was found that the photocurrent density of this novel nanostructure fiber is about 70% higher than the pristine electrospun WO3 fibers under similar conditions. WO3/NiWO4 heterojunction was identified within the fiber through high-resolution transmission electron microscopy imaging. The fibrous form is expected to provide greater exposure to the WO3/NiWO4 heterojunctions for the photocatalytic reaction. This heterojunction within the fibrous form is expected to provide a higher photoanode performance due to a lower charge-transfer resistance than the pristine WO3 fibers as also confirmed through the electrochemical impedance spectra. Interestingly, calcination of these composite fibers at 800 °C instead at 550 °C increased the percentage of NiWO4 phase, yet with a contemporaneous increase in larger crystallites of metal tungstate. The latter was responsible for giving lower photocurrents which helped in understanding the PEC performance with respect to material structure for the composite fiber under the current study.

Nickel oxide-tungsten oxide/zeolite hydrocracking fibers were prepared by the electrospinning method and compared with the hydrocracking particles prepared by wet impregnation method. Scanning electron microscope, BET and XRD were used to characterize the two catalysts. The two catalysts were tested in a continuous flow fixed-bed reactor under 5 bars hydrogen pressure at 400 °C for n-heptane hydrocracking and hydroisomerization. The fibers registered a higher BET surface area compared to the particles as well as promising catalytic activity with C3 and iC4 formed as major cracking products; a higher conversion by 17 wt. % and 6 wt. % during the first 60 and 120 min on stream respectively compared to the hydrocracking particles. Apart from providing the hydrogenation function, the addition of the metallic component provided superior mechanical strength to the fibers when compared with the pure zeolite fibers. In addition, less coke was formed with the fibers. These novel composite fibers showed a uniform elemental distribution which is beneficial for a hydrocracking catalyst, providing close proximity of the acidic and hydrogenation sites. The latter which was reflected in less olefin formation and superior n-heptane isomerization. This study paves the way for promising research on utilizing zeolites in the form of fibers for various catalytic applications.

Novel crystalline nickel–tungsten oxide composite fibers were synthesized for the first time, to the best of our knowledge, through the electrospinning method using nickel acetate and ammonium metatungstate as precursor solutions. Fibers with five different Ni:W molar ratios, 2:1, 1:1, 1:2, 3:1 and 1:3, were prepared. After calcination, the produced fibers were composed of tungsten oxide (WO3), nickel oxide (NiO) and nickel tungstate (NiWO4). Fiber morphology and structure were studied using scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Selected fibers were investigated for electrocatalytic hydrogen evolution reaction (HER) in 0.5 M H2SO4 and 0.1 M KOH electrolytes. The electrospun composite fibers showed good electrocatalytic activity compared to pure NiO and WO3 fibers with an overpotential of 80 mV and 60 mV in acidic and basic media, respectively. Low Tafel slopes were also registered as 50.27 mV/dec and 41.29 mV/dec in H2SO4 and KOH, respectively. The presence of NiWO4 compound, formed during the composite fabrication, was responsible for improving the electrocatalytic performance of the fibrous catalyst.

The utilization of seawater for drinking purposes is limited by the high specific energy consumption (SEC) (kW-h/m3) of present desalination technologies; both thermal and membrane-based. This is in turn exasperated by high water production costs, adding up to the water scarcity around the globe. Most technologies are already working near their thermodynamic limit, while posing challenges in further SEC reductions. Understanding the current energy status and energy breakdowns of leading desalination technologies will further help in realizing limitations and boundaries imposed while working for improved system performances. This paper comprehensively reviews the energy requirements and potential research areas for reduced SEC of various thermal, membrane-based and emerging desalination technologies. For thermal desalination processes, which consume a large chunk of energy for heating, renewable energy sources can be a viable option for bringing down the energy requirements. Hence, this review also focuses on the potential of desalination-renewable energy integrations. The review extends beyond conventional energy reduction possibilities to utilizing novel, advanced membranes and innovative techniques for energy offsets. The future of desalination for optimized energy requirements is projected to include ultra-high permeability membranes, fouling resistant membranes, hybrid systems, and renewable-energy driven desalination.

Membrane fouling is a major drawback in membrane-based separation processes. In this work, periodic electrolytic membrane cleaning was used for the first time on ceramic-based electrically conductive membranes made from nano-zeolite and carbon nanostructures (CNS). Highly conductive nano zeolite/CNS, hydrophilic microfiltration membranes were fabricated through vacuum filtration, with PVDF as a binder for improved mechanical strength. Membrane cross-section revealed a uniform nano-zeolite distribution within the CNS. The membrane was subjected to periodic electrolysis during the filtration of yeast and sodium alginate (SA) as model foulants. High flux recoveries were obtained, with flux increasing to 95% and 90% for yeast and SA after the first cycle compared to without electrolysis. Subsequent increase in flux was observed thereafter each cleaning cycle reducing the concentration boundary layer. The composite membrane possessed high electrical conductivity and good electrocatalytic behavior for hydrogen evolution, which enabled membrane surface cleaning through the generation of hydrogen bubbles which led to the sweeping away of the foulant layer during the electrocatalytic cleaning between each filtration cycle. The membrane also showed good anti-microbial properties with low bacterial proliferation for both gram-positive and gram-negative bacteria. These electro-ceramic self-cleaning membranes hold immense potential in several types of separation processes where ceramic membranes are a choice of material, and where bio-fouling is a predominant factor for flux decline.