• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.404-405
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• 2008

In this work, we investigated the effect of the functionalized SWNT-polymer composites for increasing sensitivity and imparting selectivity to nanotube sensors. To do this, CNT -based gas sensors were fabricated with two types of dispersed SWNT solution involving different polymer resin of TEOS (Tetraethyl orthosilicate) or MTMS (Methyl trimethoxysilane) which is blended to adhere to substrate well. As the surfaces of TEOS and MTMS surrounding SWNTs remain functionalized to -OH and $-CH_3$ groups respectively after hardening, gas adsorption will be affected differently according to the type of gases. In the experiment, we examined the response of electrical conductance for alcohol vapour gas. As the result, the conductance in the sensors using TEOS decreased considerably while that of MTMS was nearly invariable.

• Bulletin of the Korean Chemical Society
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• v.12 no.5
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• pp.537-540
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• 1991

Electrophilic methylation reactions of five-membered heteroaromatic compounds, furan, pyrrole and thiophene, with the dimethylfluoronium ion, ${CH_3}{FCH_3}(+), have been investigated theoretically by the MNDO method. The site selectivity of ${\alpha}, {\beta}$ and heteroatom (X) is related to charge density of the site, indicating that the site selectivity is dictated by electrosatic interaction between two reaction centers. The reactivity order between the three heteroaromatics can not be determined decisively since the order differs depending on which site is compared, with relatively low activation enthalpies, ${\Delta}{H^\neq}$= 20-30 kcal/mol, in all cases. These site and substrate selectivity behaviors are consistent with the gas-phase experimental results.

• Journal of the Korean institute of surface engineering
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• v.55 no.6
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• pp.328-341
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• 2022

Area selective atomic layer deposition (AS-ALD) is a bottom-up nanopattern fabrication method that can grow the ALD films only on the desired substrate areas without using photolithography and etching processes. Particularly, AS-ALD has attracted great attention in the semiconductor manufacturing process due to its advantage in reducing edge placement error by fabricating self-aligned patterns. In this paper, the basic principles and characteristics of AS-ALD are described. In addition, various approaches for achieving AS-ALD with excellent selectivity were comprehensively reviewed. Finally, the technology development to overcome the selectivity limit of AS-ALD was introduced along with future prospects.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.124-124
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• 2010

Currently, extreme ultraviolet lithography (EUVL) is being investigated for next generation lithography. EUVL is one of competitive lithographic technologies for sub-22nm fabrication of nano-scale Si devices that can possibly replace the conventional photolithography used to make today's microcircuits. Among the core EUVL technologies, mask fabrication is of considerable importance due to the use of new reflective optics having a completely different configuration compared to those of conventional photolithography. Therefore, new materials and new mask fabrication process are required for high performance EUVL mask fabrication. This study investigated the etching properties of SnO2 (Tin Oxide) as a new absorber material for EUVL binary mask. The EUVL mask structure used for etching is SnO2 (absorber layer) / Ru (capping / etch stop layer) / Mo-Si multilayer (reflective layer) / Si (substrate). Since the Ru etch stop layer should not be etched, infinitely high selectivity of SnO2 layer to Ru ESL is required. To obtain infinitely high etch selectivity and very low LER (line edge roughness) values, etch parameters of gas flow ratio, top electrode power, dc self - bias voltage (Vdc), and etch time were varied in inductively coupled Cl2/Ar plasmas. For certain process window, infinitely high etch selectivity of SnO2 to Ru ESL could be obtained by optimizing the process parameters. Etch characteristics were measured by on scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses. Detailed mechanisms for ultra-high etch selectivity will be discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.126-129
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• 2000

This paper describes on the fabrication of a SOI substrate by SDB technology and electrochemical etch-stop. The surface of the thinned SDB SOI substrate is more uniform than that of grinding or polishing by mechanical method, and this process was found to be very accurate method for SOI thickness control. During electrochemical etch-stop, leakage current versus voltage curves were measured for analysis of the open current potential (OCP) point, the passivation potential (PP) point and anodic passivation potential. The surface roughness and the controlled thickness selectivity of the fabricated a SDB SOI substrate were evaluated by using AFM and SEM, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.5
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• pp.431-436
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• 2000

This paper describes on the fabrication of a SOI substrate by SDB technology and electrochemical etch-stop. The surface of the thinned SDB SOI substrate is more uniform than that of grinding or polishing by mechanical method and this process was found to be a very accurate method for SOI thickness control. During electrochemical etch-stop leakage current versus voltage curves were measured for analysis of the open current potential(OCP) point the passivation potential(PP) point and anodic passivation potential. The surface roughness and the controlled thickness selectivity of the fabricated a SDB SOI substrate were evaluated by using AFM and SEM respectively.

• Journal of Microbiology and Biotechnology
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• v.30 no.1
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• pp.146-154
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• 2020

With the advantages of biocatalytic method, enzymes have been excavated for the synthesis of chiral amino acids by the reductive amination of ketones, offering a promising way of producing pharmaceutical intermediates. In this work, a robust phenylalanine dehydrogenase (PheDH) with wide substrate spectrum and high catalytic efficiency was constructed through rational design and active-site-targeted, site-specific mutagenesis by using the parent enzyme from Bacillus halodurans. Active sites with bonding substrate and amino acid residues surrounding the substrate binding pocket, 49L-50G-51G, 74M,77K, 122G-123T-124D-125M, 275N, 305L and 308V of the PheDH, were identified. Noticeably, the new mutant PheDH (E113D-N276L) showed approximately 6.06-fold increment of k_cat/Km in the oxidative deamination and more than 1.58-fold in the reductive amination compared to that of the wide type. Meanwhile, the PheDHs exhibit high capacity of accepting benzylic and aliphatic ketone substrates. The broad specificity, high catalytic efficiency and selectivity, along with excellent thermal stability, render these broad-spectrum enzymes ideal targets for further development with potential diagnostic reagent and pharmaceutical compounds applications.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.376-377
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• 2013

반도체산업이 발전함에 따라 패턴이 점점 더 복잡해 지고 있다. 이에 따라 웨이퍼 위에 올려지는 layer도 개수도 많아지고 점점 더 두꺼워진다. 예전에는 수백 nm였지만 최근에는 um단위까지 두꺼워지고 있다. 하지만 mask 역할을 하는 ACL과 substrate (SiO2)의 selectivity는 일정하기 때문에 mask 역할을 하는ACL layer 역시 두꺼워지는 것이 불가피하다. 이로인해 예전에는 없었던 문제들이 발생하기 시작한다. Mask 역할을 하는 ACL layer가 얇고 패턴 크기가 클 때에는 아무런 문제도 없었지만 ACL layer도 두꺼워 지고 패턴 크기도 수십 nm로 작아졌기 때문에 ACL 역시 식각 공정을 할 때 어려움이 생기기 시작한다. 이를 해결하기 위한 하나의 방법으로 자화된 ICP 챔버 substrate에 Dual bias frequency 인가하여 식각해 보고 이와같이 하였을 때 식각특성을 분석해 보았다. 자화된 ICP 챔버에서 substrate에 dual bias frequency를 인가함으로써 ion energy와 ion flux에 변화가 생기게 되고 이로 인해 다른 식각 특성이 나타나게 되었다. Dual bias frequency의 비율을 변화시켜 보고 변화에 따른 식각 특성을 분석해 보았다. 이와 같은 과정을 통하여 높은 주파수와 낮은 주파수의 각각의 변화에 따른 식각특성의 변화에 대한 이해를 할 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.301-306
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• 2000

This paper describes on the fabrication of a SOI substrate by SDB technology and electrochemical etch-stop. The surface of the thinned SDB SOI substrate is more uniform than that of grinding or polishing by mechanical method, and this process was found to be a very accurate method for SOI thickness control. During electrochemical etch-stop, leakage current versus voltage curves were measured for analysis of the open current potential(OCP) point, the passivation potential(PP) point and anodic passivation potential. The surface roughness and the controlled thickness selectivity of the fabricated a SDB SOI substrate were evaluated by using AFM and SEM, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.285-285
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• 2011

EUVL (Extreme Ultra Violet Lithography) is one of competitive lithographic technologies for sub-30nm fabrication of nano-scale Si devices that can possibly replace the conventional photolithography used to make today's microcircuits. Among the core EUVL technologies, mask fabrication is of considerable importance since the use of new reflective optics having a completely different configuration compared to those of conventional photolithography. Therefore new materials and new mask fabrication process are required for high performance EUVL mask fabrication. This study investigated the etching properties of SnO2 (Tin Oxide) as a new absorber material for EUVL binary mask. The EUVL mask structure used for etching is SnO2 (absorber layer) / Ru (capping / etch stop layer) / Mo-Si multilayer (reflective layer) / Si (substrate). Since the Ru etch stop layer should not be etched, infinitely high selectivity of SnO2 layer to Ru ESL is required. To obtain infinitely high etch selectivity and very low LER (line edge roughness) values, etch parameters of gas flow ratio, top electrode power, dc self - bias voltage (Vdc), and etch time were varied in inductively coupled Cl2/Ar plasmas. For certain process window, infinitely high etch selectivity of SnO2 to Ru ESL could be obtained by optimizing the process parameters. Etch characteristics were measured by on scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses. Detailed mechanisms for ultra-high etch selectivity will be discussed.