Natural zeolites such as mordenite are excellent adsorbents for heavy metals. To enhance the adsorption capacity of zeolite, sodium-exchanged samples were irradiated with 13.56 MHz capacitively coupled radio frequency (RF) argon gas discharge. Hexavalent chromium [Cr(VI)] was used as the test heavy metal. Pristine and plasma-treated zeolite samples were soaked in 50 mg/L Cr solution and the amount of adsorbed Cr(VI) on the zeolites was calculated at predetermined time intervals. Compared with untreated zeolite samples, initial Cr(VI) uptake was 70% higher for plasma-treated zeolite granules (50 W 30 min) after 1 h of soaking. After 24 h, all plasma-treated zeolites showed increased Cr(VI) uptake. For a 2- to 4-month period, Cr(VI) uptake increased about 130% compared with untreated zeolite granules. X-ray diffraction analyses between untreated and treated zeolite samples revealed no major difference in terms of its crystal structure. However, for plasma-treated samples, an increase in the number of surface defects was observed from scanning electron microscopy images. This increase in the number of surface defects induced by plasma exposure played a crucial role in increasing the number of active sorption sites on the zeolite surface.

Upon contact with a polymeric material, microparticles from the polymer may adhere to a silicon (Si) substrate during device processing. The adhesion contaminates the surface and, in turn, leads to defects in the fabricated Si-based microelectronic devices. In this study, Si substrates with artificially induced high-density polyethylene (HDPE) contamination was exposed to 13.56 MHz radio frequency (RF) plasma utilizing argon and oxygen gas admixtures at a power density of 5.6 W/cm 2 and a working pressure of 110 Pa for up to 6 min of treatment. Optical microscopy studies revealed the removal of up to 74% of the polymer contamination upon plasma exposure. Surface free energy (SFE) increased owing to the removal of contaminants as well as the formation of polar groups on the Si surface after plasma treatment. Atomic force microscopy scans showed a decrease in surface roughness from 12.25 nm for contaminated samples to 0.77 nm after plasma cleaning. The smoothening effect can be attributed to the removal of HDPE particles from the surface. In addition, scanning electron microscope images showed that there was a decrease in the amount of HDPE contaminants adhering onto the surface after plasma exposure.

In 3D NAND devices, the number of stacked layers dictates the storage capacity. In the fabrication of such devices, hole channels with a high-aspect ratio (HAR) are etched through these layers. The higher the aspect ratio becomes, the more difficulties the HAR etching faces. In this study, molecular dynamics simulation was performed to examine the etching of silicon dioxide (SiO2), silicon nitride (SiN), and oxide-nitride (ON) stacked layers by energetic fluorocarbon ions. Good agreement of etching yields obtained from the simulations and ion beam experiments was observed for the etching of SiO2 and SiN by [Formula: see text] ions for the incident ion energy ranging from 200 to 2000 eV. As to the etching of the ON bilayer, the SiO2 and SiN layers were observed to be etched with their own etch rates at low ion incident energy. However, at sufficiently high incident ion energy, the oxide and nitride layers were mixed by energetic ion impact and the depth of the mixing layer exceeded the thickness of the top SiO2 layer thickness, resulting in a single etch rate limited by the etch rate of a much deeper underlying SiN material. This suggests that if the incident ion energy is high enough such that the thicknesses of the multilayers are lower than the ion penetration depth, the ON stacked layer exhibits a single etch rate determined by the mixed material of the oxide and nitride.

Molecular dynamics simulations for the scattering of neon, argon, and xenon ions on silicon and silicon dioxide surfaces were performed at grazing incidence to examine how the angular distribution of reflected ions deviates from that of the ideal specular reflection, depending on the ion mass, incident angle, and surface material and its roughness. This study is motivated to understand how energetic ions interact with the sidewalls of high-aspect-ratio (HAR) channels when reactive ion etching (RIE) is used to form such HAR channels in semiconductor manufacturing. It is found that the higher the ion mass is, the less grazing the ion incident angle is, or the rougher the surface is, the larger the angular distribution of reflected ions becomes around the corresponding specular reflection angles. Quantitative information on such reflected ions can be used to predict the profile evolution of HAR channels in RIE processes.

As the sizes of semiconductor devices continue to shrink, the fabrication of nanometer-scale device structures on material surfaces poses unprecedented challenges. In this study, molecular dynamics simulations of CF[Formula: see text] ion beam etching of SiO[Formula: see text] were performed with carbon masks to form holes with a diameter of 4 nm. It is found that, when the ion energy is sufficiently high and the etching continues, tapered holes are formed by the ion beam etching. This is because the etching under these conditions is essentially due to physical sputtering, so that tapered surfaces having high etching yields appear as the sidewalls and sputtered Si-containing species are redeposited. Furthermore, preferential removal of oxygen from SiO[Formula: see text] surfaces occurs, which leads to the formation of Si-rich sidewall surfaces. It is also found that, with simultaneous irradiation of CF[Formula: see text] radicals, the etching yield of a flat SiO[Formula: see text] surface by energetic CF[Formula: see text] ion beams can double, but too large a flux of CF[Formula: see text] radicals causes etch stop.