Selective isotropic etching of SiO over SiN using NF/H remote plasma and methanol vapor.

In this study, an isotropic etching process of SiO selective to SiN using NF/H/methanol chemistry was investigated. HF was formed using a NF/H remote plasma, and in order to remove the F radicals, which induces spontaneous etching of Si-base material, methanol was injected outside the plasma discharge region. Through this process, etch products were formed on the surface of SiO, and then the (NH)SiF was removed by following heating process.

Atomic layer etching of Sn by surface modification with H and Cl radicals.

Sn is the one of the materials that can be used for next generation extreme ultraviolet (EUV) mask material having a high absorption coefficient and, for the fabrication of the next generation EUV mask, a precise etching of Sn is required. In this study, the atomic layer etching (ALE) process was performed for the precise etch thickness control and low damage etching of Sn by the formation SnHClcompounds on the Sn surface using with H and Cl radicals during the adsorption step and by the removal of the compound using Arions with a controlled energy during the desorption step. Through this process, optimized ALE conditions with different H/Cl radical combinations that can etch Sn at ∼2.

Selective etching of silicon nitride over silicon oxide using ClF/H remote plasma.

Precise and selective removal of silicon nitride (SiN) over silicon oxide (SiO) 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 SiN over SiO has been investigated using a ClF/H remote plasma in an inductively coupled plasma system. The SiN etch rate over 80 nm/min with the etch selectivity (SiN over SiO) of ~ 130 was observed under a ClF remote plasma at a room temperature.

Determination of Motivating Factors of Urban Forest Visitors through Latent Dirichlet Allocation Topic Modeling.

Despite the unique characteristics of urban forests, the motivating factors of urban forest visitors have not been clearly differentiated from other types of the forest resource. This study aims to identify the motivating factors of urban forest visitors, using latent Dirichlet allocation (LDA) topic modeling based on social big data. A total of 57,449 cases of social text data from social blogs containing the keyword "urban forest" were collected from Naver and Daum, the major search engines in South Korea.

Etch characteristics of magnetic tunnel junction materials using H/NH reactive ion beam.

Magnetic tunneling junction (MTJ) materials such as CoFeB, Co, Pt, MgO, and the hard mask material such as W and TiN were etched with a reactive ion beam etching (RIBE) system using H/NH. By using gas mixtures of H and NH, especially with the H/NH( 2:1) ratio, higher etch rates of MTJ related materials and higher etch selectivities over mask materials (>30) could be observed compared to those etching using pure H( no etching) and NH. In addition, no significant chemical and physical damages were observed on etched magnetic materials surfaces and, for CoPt and MTJ nanoscale patterns etched by the H/NH( 2:1) ion beam, highly anisotropic etch profiles >83° with no sidewall redeposition could be observed.

Reactive ion etching of an ovonic threshold switch (OTS) material using hydrogen-based plasmas for non-volatile phase change memories.

Etch characteristics of ovonic threshold switch (OTS) materials composed of Ge-As-Te for a phase-change random access memory (PCRAM) has been investigated using reactive ion etching hydrogen-based gases such as H, CH, NH, CH + H, and CH + NH. Among the investigated hydrogen-based gases, NH showed the highest etching rate of about 0.52 nm s, but the formation of nitride compounds and the increased roughness were observed on the OTS surface by nitrogen.

Atomic layer etching of chrome using ion beams.

In this study, two Cr atomic layer etching (ALE) methods have been applied for the precise control of Cr etching. The first one involves O radical adsorption followed by Cl ion desorption (ALE with chemical ion desorption; chemical anisotropic ALE), and the second one involves Cl/O radical adsorption followed by Ar ion desorption (ALE with physical ion desorption; physical anisotropic ALE). Their effects on Cr etch characteristics were also investigated.