BP thinning was carried out using a monoenergetic Ar+ ion beam and the BP could be thinned without damaging the surface.

Across the most industry, the demand for nanoparticles is increasing. Therefore, many studies have been carried out to synthesize nanoparticles using various methods. The aim of this paper is to introduce an industryapplicable as well as financially and environmentally effective solution plasma process. The solution plasma process involves fewer chemicals than the traditional kit, and can be used to replace many of the chemical agents employed in previous synthesis of nanoparticles into plasma. In this study, this process is compared to the wet-reaction process that has thus far been widely used in the most industry. Furthermore, the solution plasma process has been classified into four different types (in-solution, out of solution, direct type, and remote type), according to its plasma occurrence position and plasma types. Thus, the source of radicals, nanoparticle synthesis, and modification methods are explained for each design. Lastly, unlike nanoparticles with hydrophilic functional groups that are made inside the solution, a nanoparticle synthesis and modification method to create a hydrophobic functional group is also proposed.

Atomic layer etching (ALE) has advantages such as precise thickness control, high etch selectivity, and no‐increase in surface roughness which can be applied to sub 10 nm semiconductor device fabrication. In this study, anisotropic ALE of tungsten (W), which is used as an interconnect layer and gate material of semiconductor devices, was investigated by sequentially exposing to F radicals by NF3 plasma to form a WFy layer and following exposure to an oxygen ion beam to remove the WFy layer by forming volatile WOxFy at room temperature. A wide ALE window of F radical adsorption time of ( ≥ 10 s/cycle) and Ox+ ion desorption time of (10 ≤ t ≤ 50 s/cycle at + 44–51 eV of Ox+ ion energy) could be identified, and at the ALE conditions, a precise etch rate of ~2.6 Å/cycle was obtained while increasing the W etch depth linearly with increasing the number of etch cycles. At the optimized W ALE conditions, the W surface roughness after the W ALE was similar to the as‐received W and the etch selectivity over SiO2 was close to infinite. However, after the W ALE, ~ 10% F diffused into W was observed on the etched W surface, and which could be removed by a following process.

Dry cleaning technology is an essential technique that can be applied to remove native oxide and various contaminants during the semiconductor manufacturing for nanoscale electronic devices. In this study, the in situ dry cleaning of silicon dioxide (SiO 2) with low global warming potential (GWP) gas mixtures has been investigated by sequential process steps composed of the reaction of SiO 2 surface by oxygen difluoride (OF 2) (GWP: <1)/ammonia (NH 3) remote plasma and the removal of the reacted compound layer by lamp heating. By using the optimized OF 2 /NH 3 (2:1) mixture for the surface reaction followed by the lamp heating at 200 °C to remove the reacted compound layer, a high-SiO 2 cleaning rate and etch selectivity over silicon nitride (>30:1) could be obtained due to the formation of the highest HF concentration on the SiO 2 surface at the OF 2 /NH 3 (2:1) gas ratio. The compound layer formed during the reaction was (NH 4) 2 SiF 6 observed for a previously investigated NF 3 (GWP: 17 200)/NH 3 plasma, but the dry SiO 2 cleaning rate and the etch selectivity over Si 3 N 4 obtained by the OF 2 /NH 3 plasma were higher than those by the optimized NF 3 /NH 3 plasma. The effects of OF 2 /NH 3 mixture dry cleaning on the electrical characteristics of metal-oxidesemiconductor (MOS) devices fabricated on the nano-scale trench patterned Si substrate with high aspect ratio were studied and compared with conventional wet and NF 3 /NH 3 mixture dry cleaning-based devices. Compared with other cleaning methods, OF 2 /NH 3 dry-cleaning shows the improved and reliable electrical characteristics such as sharper capacitance-voltage behavior, lower hysteresis, less interface trap charge and smaller contact resistivity. Therefore, it is believed that the in situ sequential dry SiO 2 cleaning with the OF 2 /NH 3 remote plasma can be applied as an essential cleaning method with extremely low GWP for fabricating next generation nano-scale devices.

Precise and selective removal of silicon nitride (SiNx) over silicon oxide (SiOy) in a oxide/nitride stack is crucial for a current three dimensional NOT-AND type flash memory fabrication process. In this study, fast and selective isotropic etching of SiNx over SiOy has been investigated using a ClF3/H2 remote plasma in an inductively coupled plasma system. The SiNx etch rate over 80 nm/min with the etch selectivity (SiNx over SiOy) of ~ 130 was observed under a ClF3 remote plasma at a room temperature. Furthermore, the addition of H2 to the ClF3 resulted in an increase of etching selectivity over 200 while lowering the etch rate of both oxide and nitride due to the reduction of F radicals in the plasma. The time dependent-etch characteristics of ClF3, ClF3 & H2 remote plasma showed little loading effect during the etching of silicon nitride on oxide/nitride stack wafer with similar etch rate with that of blank nitride wafer.

The ovonic threshold switch (OTS) selector device is suitable for a phase-change random access memory (PRAM) requiring instantaneous high-output power due to the high-current density and high-speed operation. An amorphous chalcogenide-based compound composed of As-Te-Ge is a candidate for OTS materials and has excellent selector performances such as low leakage current, fast switching speed, scalability, and thermal stability. However, this material is known to suffer damage due to easy halogenation when exposed to halogen gas-based plasmas. In this study, the etch damages of OTS surface during the halogen gas based-inductively coupled plasma (ICP)-reactive ion etching (RIE) using CF4 and Cl2 were investigated. The OTS etched with Cl2 showed a higher etch rate compared to that with CF4. However, the surface roughness was lower for the OST etched with Cl2 than that etched with CF4. Also, the thickness of halogenated layer during the etching was also thinner for Cl2-etched OST than CF4-etched OST. Therefore, compared to CF4-etched OST, Cl2-etched OST was less damaged by the etching. In addition, it is found that, among the OST components of As, Te, and Ge, Ge was mostly halogenated while As and Te are not significantly halogenated during the etching.

Precise and selective removal of silicon nitride in a SiNx/SiOy stack is crucial for a current 3D-NAND (not and) fabrication process. In this study, fast and ultra-high selective isotropic etching of SiNx have been studied using a ClF3/H2 remote plasma in an inductively coupled plasma system and a mechanism of SiNx etching was investigated by focusing on the role of Cl, F, and H radicals in the plasma. The SiNx etch rate over 800 Å/min with the etch selectivity of ~130 could be observed under a ClF3 remote plasma at a room temperature. Furthermore, compromising the etch rate of SiNx by adding H2 to the ClF3 plasma, the etch selectivity of SiNx over SiOy close to ~ 200 could be obtained. The etch characteristics of SiNx and SiOy with increasing the process temperature demonstrated the higher activation energy of SiOy compared to that of SiNx with ClF3 plasma.

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