Pre-metal dielectric PE TEOS oxide pitting in 3D NAND: Mechanism and solutions

In 3D NAND, as the stack number increases, the process cost becomes higher and higher, and the stress problem becomes more and more serious. Therefore, the low cost and low stress plasma enhanced Tetraethyl orthosilicate (PE TEOS), compared to high density plasma (HDP) oxide, shows its superiority as pre-metal dielectric (PMD) oxide layer in 3D NAND. This paper explores the challenges in the application of PE TEOS in 3D NAND PMD oxide layer.In our experiments, both PE TEOS and HDP are employed as the PMD oxide for 3D NAND staircase protection. There is not any void found in the two oxide structures. However, oxide pitting is spotted in the subsequent diluted hydrofluoric acid wet etching in the PE TEOS split. Moreover, we observe that the top silicon nitride corrodes in hot phosphoric acid. We investigate the mechanism of PE TEOS oxide pitting and silicon nitride corroding, and propose two solutions: 1) HDP oxide + PE TEOS, and 2) PE TEOS + dry etching.Experimental results demonstrate that our solutions can well address the issue of PE TEOS oxide pitting and effectively protect the staircase structure. This work extends the application of PE TEOS oxide of which the cost and the stress are both low in 3D NAND.

Simulating fusion alpha heating in a stellarator reactor

Gyrocenter following simulations of fusion born alpha particles in a stellarator reactor are preformed using the BEAMS3D code. The Wendelstein 7-X high mirror configuration is scaled in geometry and magnetic field to reactor relevant parameters. A 2×1020 m−3 density plasma with 20 keV core temperatures is assumed and fusion birth rates calculated for various fusion products assuming a 50/50 deuterium-tritium mixture. It is found that energetic He4 ions comprise the vast majority of the energetic particle inventory. Slowing down simulations of the He4 population suggest plasma heating consistent with scaled energy confinement times for a stellarator reactor. Losses for this configuration appear large suggesting optimization beyond the scope of the W7-X device is key to a future fusion reactor. These first simulations are designed to demonstrate the capability of the BEAMS3D code to provide fusion alpha birth and heating profiles for stellarator reactor designs.

Phytosterol Profiling of Apiaceae Family Seeds Spices Using GC-MS

Phytosterols are nutritionally vital phytoconstituent owing to their cholesterol (low-density plasma lipoprotein-cholesterol, LDL-C)-lowering, anti-inflammatory, and antioxidant properties. Among the widely used spices and herbs, the seeds spices of the Apiaceae family represented the healthiest fatty acid profile. Thus, to explore the other health-beneficial lipids, the present study was aimed to analyze the phytosterol profile of eight seed spices of the Apiaceae family, utilizing gas chromatography (GC)-mass spectrometry (MS). The sterols contents calculated on an oil (mg/100 g of oil) and spice weight (mg/100 g spices; dry weight) basis varied significantly among the seed spices (p < 0.05; Turkey HSD). The β-sitosterol and stigmasterol were the most dominating sterols among the studied spices, together accounted for 40.3 (Ajwain) to 69.8% (celery) of total sterols in the seed oil. Among the studied spices, the oil extracted from caraway seeds showed the highest total sterols (602.2 mg/100 g of oil). Interestingly, based on spice weight, fennel seeds also showed the similar highest number of total sterols (134.2 mg/100 g in fennel and 133.3 mg/100 g in caraway), owing to the high contents of oil (25.9%) in fennel seeds. Overall, celery, caraway, fennel, and anise seeds oil are rich sources of health-beneficial phytosterols.

AZIMUTHAL SURFACE WAVES IN LOW-DENSITY PLASMA LOADED, COAXIAL HELIX TRAVELING-WAVE-TUBE-LIKE WAVEGUIDES

The dispersion properties of flute electromagnetic waves propagating across an external axial static magnetic field in traveling-wave-tube-like waveguides with low-density plasma filling are investigated. The cylindrical structure consists of a central dielectric rod, placed inside a plasma coaxial layer with a metallic helix sheath on its outer interface, and a metal screen separated from the helix by another dielectric layer.