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Hollow fiber nanofiltration membranes can withstand much higher foulant concentrations than their spiral wound counterparts and can be used in water purification without pretreatment. Still, the preparation of hollow fiber nanofiltration membranes is much less established. In this work, we demonstrate the design of a hollow fiber nanofiltration membrane with excellent rejection properties by alternatively coating a porous ultrafiltration membrane with a polycation, a polyzwitterion, and a polyanion. On model surfaces, we show, for the first time, that the polyzwitterion poly N-(3-sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethylammonium betaine (PSBMA) can be incorporated into traditional polyelectrolyte multilayers based on poly(styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC). Furthermore, work on model surfaces allows a good characterization of, and insight into, the layer build-up and helps to establish the optimal membrane coating conditions. Membranes coated with these multilayers have high salt rejection of up to 42% NaCl, 72% CaCl2, and 98% Na2SO4 with permeabilities of 3.7-4.5 l·m(-2)·h(-1)·bar(-1). In addition to the salt rejections, the rejection of six distinctively different micropollutants, with molecular weights between 215 and 362 g·mol(-1), was investigated. Depending on the terminating layer, the incorporation of the polyzwitterion in the multilayer results in nanofiltration membranes that show excellent retentions for both positively and negatively charged micropollutants, a behavior that is attributed to dielectric exclusion of the solutes. Our approach of combining model surfaces with membrane performance measurements provides unique insights into the properties of polyzwitterion-containing multilayers and their applications.

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Since ethylene/ethane separation by cryogenic distillation is one of the most energy intensive processes, it can be economically interesting to combine it with energy efficient membrane technology. The effect on the viability of different process configurations in relation to the ethylene permeance (2.8 × 10–6–2.8 × 10–5 mol/(m2 s kPa)) and ethylene/ethane selectivity (3–1000) of the membrane is investigated using Honeywell’s Unisim Design Suite R390. Results are compared to conventional distillation. In addition, the membrane feed pressure, permeate pressure, and membrane surface area have been optimized to obtain the highest possible cost savings. It is concluded that the series configuration is the most beneficial with savings of 16% on the total annualized costs. Hybrid membrane–distillation technology is interesting for membranes having ethylene permeances and selectivities beyond 2.8 × 10–5 mol/(m2 s kPa) and 30, respectively. Increasing the membrane feed pressure toward its critical pressure (P c = 4850 kPa) is always beneficial, and the optimal permeate pressure increases to 2050 kPa with increasing ethylene permeance. For material scientists, it is advised to focus on increasing membrane selectivity once an ethylene permeance of 1 × 10–5 mol/(m2 s kPa) is obtained, since higher permeances beyond this point yield less additional cost savings compared to increments in selectivity.

Due to their increasingly complex 3D geometries, upcoming gate all around (GAA) devices pose new metrology challenges for which there is not yet any established HVM metrology solution, in particular for various critical timed etch steps [5]. Soft x-ray (SXR) scatterometry using 10-20 nm wavelength light is a promising next-generation metrology technique for 3D profile metrology and overlay (OVL) applications. This wavelength regime offers unique benefits over existing metrology techniques today: (1) Short wavelengths allow for higher resolution measurements than traditional visible wavelengths could offer, enabling measurement of structures at device pitches. (2) Primarily single scattering yields low correlation between parameters and aids physical interpretation of signals. This enables many parameters of interest to be extracted accurately and simultaneously. (3) SXR provides 3D capability, with stack heights up to 400 nm supported and high depth resolution due to the broadband source and sensor. These properties together make SXR suitable for measuring the 3D profiles of advanced devices such as gate all around (GAA) transistors, as well as after develop (ADI) overlay at device pitch. In this paper, we demonstrate SXR for profile metrology of GAA devices. We show sensitivity to average SiGe lateral recess etch depth as well as individual nanosheet critical dimensions, which cannot be reliably accessed by other nondestructive, inline metrology techniques available today. We furthermore demonstrate sensitivity in ADI OVL measurements directly on device-pitch structures in the presence of an underlying patterned nuisance layer.

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