• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.12-12
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• 2014

Atomic layer etching system를 이용하여 $MoS_2$를 layer by layer control를 하였다. 이 방법이 전통적인 에칭에 비해서 low damage 층간 식각이 가능하였다.

• Korean Journal of Materials Research
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• v.16 no.4
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• pp.213-217
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• 2006

In this study, atomic layer etching of Si has been carried out using $Cl_2$ adsorption followed by the irradiation Ar neutral beam of low energy. In this experiment, the etch rate of Si was dependent on the $Cl_2$ pressure(the surface coverage of chlorine) and the irradiation time of Ar neutral beam(the flux density of Ar neural beam). And the etch rate of Si(100) and Si(111) were saturated exactly at one monolayer per cycle with $1.36{\AA}/cycle\;and\;1.57{\AA}/cycle$, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.299.2-299.2
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• 2013

We investigated the potassium remaining on a crystalline silicon solar cell after potassium hydroxide (KOH) etching and its effect on the lifetime of the solar cell. KOH etching is generally used to remove the saw damage caused by cutting a Si ingot; it can also be used to etch the rear side of a textured crystalline silicon solar cell before atomic layer-deposited Al2O3 growth. However, the potassium remaining after KOH etching is known to be detrimental to the efficiency of Si solar cells. In this study, we etched a crystalline silicon solar cell in three ways in order to determine the effect of the potassium remnant on the efficiency of Si solar cells. After KOH etching, KOH and tetramethylammonium hydroxide (TMAH) were used to etch the rear side of a crystalline silicon solar cell. To passivate the rear side, an Al2O3 layer was deposited by atomic layer deposition (ALD). After ALD Al2O3 growth on the KOH-etched Si surface, we measured the lifetime of the solar cell by quasi steady-state photoconductance (QSSPC, Sinton WCT-120) to analyze how effectively the Al2O3 layer passivated the interface of the Al2O3 layer and the Si surface. Secondary ion mass spectroscopy (SIMS) was also used to measure how much potassium remained on the surface of the Si wafer and at the interface of the Al2O3 layer and the Si surface after KOH etching and wet cleaning.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2005.11a
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• pp.175-176
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• 2005

• Journal of Surface Science and Engineering
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• v.57 no.3
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• pp.125-139
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• 2024

As the limits of semiconductor integration are approached, the challenges in semiconductor processes have intensified. And, for the production of semiconductors with dimensions under a few nanometers and to resolve the issues related to nanoscale device fabrication, research on atomic layer etching (ALE) technology has been conducted. The investigation related to ALE encompasses not only silicon and dielectric materials but also metallic materials. Particularly, there is an increasing need for ALE in next-generation metal materials that could replace copper in interconnect materials. This brief review will summarize the concept and methods of ALE and describe recent studies on potential next-generation metal replacements for copper, along with their ALE processes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.259-259
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• 2008

The LTCC (Low Temperature Co-fired Ceramic) technology meets the requirements for high quality microelectronic devices and microsystems application due to a very good electrical and mechanical properties, high reliability and stability as well as possibility of making integrated three dimensional microstructures. The wet process, which has been applied to the etching of the metallic thin film on the ceramic substrate, has multi process steps such as lithography and development and uses very toxic chemicals arising the environmental problems. The other side, Plasma technology like ion beam sputtering is clean process including surface cleaning and treatment, sputtering and etching of semiconductor devices, and environmental cleanup. In this study, metallic multilayer pattern was fabricated by the ion beam etching of Ti/Pd/Cu without the lithography. In the experiment, Alumina and LTCC were used as the substrate and Ti/Pd/Cu metallic multilayer was deposited by the DC-magnetron sputtering system. After the formation of Cu/Ni/Au multilayer pattern made by the photolithography and electroplating process, the Ti/Pd/Cu multilayer was dry-etched by using the low energy-high current ion-beam etching process. Because the electroplated Au layer was the masking barrier of the etching of Ti/Pd/Cu multilayer, the additional lithography was not necessary for the etching process. Xenon ion beam which having the high sputtering yield was irradiated and was used with various ion energy and current. The metallic pattern after the etching was optically examined and analyzed. The rate and phenomenon of the etching on each metallic layer were investigated with the diverse process condition such as ion-beam acceleration energy, current density, and etching time.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.234.1-234.1
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• 2015

Molybdenum disulfide (MoS2)는 van der Waals 결합을 통한 층상구조의 물질로써 뛰어난 물리화학적, 기계적 특성으로 Field Effect Transistors (FETs), Photoluminescence, Photo Detectors, Light Emitters 등의 많은 분야에서 연구가 보고 되어지고 있는 차세대 2D-materials이다. 이처럼 MoS2 가 다양한 범위에 응용될 수 있는 이유는 layer 수가 증가함에 따라 1.8 eV의 direct band gap 에서 1.2 eV 의 indirect band-gap으로 특성이 변화할 뿐만 아니라 다양한 고유의 전기적 특성을 지니고 있기 때문이다. 그러나 MoS2 는 원자층 단위의 layer control 이 어렵다는 이유로 다양한 전자소자 응용에 많은 제약이 보고 되어졌다. 본 연구에서는 MoS2 의 layer를 control 하기 위해 ICP system 에서 mesh grid 를 삽입하여 Cl2 radical을 효과적으로 adsorption 시킨 뒤, Ion beam system 에서 Ar+ Ion beam 을 통해 한 층씩 제거하는 방식의 atomic layer etching (ALE) 공정을 진행하였다. ALE 공정시 ion bombardment 에 의한 damage 를 최소화하기 위해 Quadruple Mass Spectrometer (QMS) 를 통한 에너지 분석으로 beam energy 를 20 eV에서 최적화 할 수 있었고, Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy(AFM) 분석을 통해 ALE 공정에 따른 MoS2 layer control 가능 여부를 증명할 수 있었다.

• Journal of the Semiconductor & Display Technology
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• v.18 no.4
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• pp.96-99
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• 2019

Atomic layer etching (ALE) is one of the most promising techniques in the semiconductor industry. Since ALE has to be precisely controlled on the angstrom scale to achieve ideal results, an in-situ analysis of the processes is highly required. In this regard, we found during ALE experiments with in-situ monitoring with an ellipsometer that changes in the substrate temperature affected the refractive index of a material, leading to changes in measured film thickness. In addition, more ideal ALE results could be achieved by keeping the substrate temperature constant.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.395-400
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• 2005

Nano-scale fabrication of silicon substrate based on the use of atomic force microscopy (AFM) was demonstrated. A specially designed cantilever with diamond tip, allowing the formation of damaged layer on silicon substrate by a simple scratching process, has been applied instead of conventional silicon cantilever for scanning. A thin damaged layer forms in the substrate at the diamond tip-sample junction along scanning path of the tip. The damaged layer withstands against wet chemical etching in aqueous KOH solution. Diamond tip acts as a patterning tool like mask film for lithography process. Hence these sequential processes, called tribo-nanolithography, TNL, can fabricate 2D or 3D micro structures in nanometer range. This study demonstrates the novel fabrication processes of the micro cantilever and diamond tip as a tool for TNL using micro-patterning, wet chemical etching and CVD. The developed TNL tools show outstanding machinability against single crystal silicon wafer. Hence, they are expected to have a possibility for industrial applications as a micro-to-nano machining tool.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.8 s.185
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• pp.39-46
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• 2006

Nano-scale fabrication of silicon substrate based on the use of atomic force microscopy (AFM) was demonstrated. A specially designed cantilever with diamond tip, allowing the formation of damaged layer on silicon substrate by a simple scratching process, has been applied instead of conventional silicon cantilever for scanning. A thin mask layer forms in the substrate at the diamond tip-sample junction along scanning path of the tip. The mask layer withstands against wet chemical etching in aqueous KOH solution. Diamond tip acts as a patterning tool like mask film for lithography process. Hence these sequential processes, called tribo-nanolithography, TNL, can fabricate 2D or 3D micro structures in nanometer range. This study demonstrates the novel fabrication processes of the micro cantilever and diamond tip as a tool for TNL using micro-patterning, wet chemical etching and CVD. The developed TNL tools show outstanding machinability against single crystal silicon wafer. Hence, they are expected to have a possibility for industrial applications as a micro-to-nano machining tool.