• Laser Solutions
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• v.13 no.1
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• pp.11-15
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• 2010

Indium tin oxide (ITO) provides high electrical conductivity and transparency in the visible and near IR (infrared) wavelengths. Thus, it is widely used as a transparent electrode for the fabrication of liquid crystal displays (LCDs) and organic light emitting diode displays (OLRDs), photovoltaic devices, and other optical applications. Lasers have been used for removing coating on polymer substrate for flexible display and electronic industry. In selective removal of ITO layer, laser wavelength, pulse energy, scan speed, and the repetition rate of pulses determine conditions, which are efficient for removal of ITO coating without affecting properties of the polymer substrate. ITO coating removal with a laser is more environmentally friendly than other conventional etching methods. In this paper, pattering of ITO film from polymer substrates is described. The Yb:KGW femtosecond laser processing system with a pulse duration of 250fs, a wavelength of 1030nm and a repetition rate of 100kHz was used for removing ITO coating in air. We can remove the ITO coating using a scanner system with various pulse energies and scan speeds. We observed that the amount of debris is minimal through an optical and a confocal microscope, and femtosecond laser pulses with 1030nm wavelength are effective to remove ITO coating without the polymer substrate ablation.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1884-1886
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• 2005

KrF 펄스 레이저 증착법(pulsed laser deposition: PLD)으로 ZnO 박막을 증착하여 평판 디스플레이 소자 구동용 박막 트랜지스터(thin film transistor) 소자를 제작하였다. 전도성이 높은 실리콘웨이퍼(c-Si, 하부전극) 기판 위에 LPCVD 법으로 silicon nitride 박막을 절연막으로 형성하고, 다양한 공정 조건에서 펄스 레이저 증착법으로 제작한 ZnO 박막을 증착하여 채널층으로 하였으며, Al 박막을 증착하고 패터닝하여 소스 및 드레인 전극으로 하였다. ZnO 박막의 증착 시에 기판 온도를 다양하게 조절하고 산소 분압을 변화시켜 ZnO 박막의 특성을 조절하였다. 제작된 박막의 표면특성은 AFM(atomic force microscopy)로 분석하고, 결정특성은 XRD(X-ray diffraction)로 조사하였다. ZnO 박막의 전기적 특성은 Hall-van der Pauw 법으로 측정하였고, 광학 투과도(optical transparency)를 UV-visible photometer로 조사하였다. ZnO-TFT 소자는 $10^6$ 수준의 on-off ratio와 $2.4{\sim}6.1cm^2/V{\cdot}s$의 전계효과이동도(field effect mobility)를 보였다.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.2
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• pp.65-70
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• 2023

Nanoimprint lithography (NIL) has attracted much attention due to its process simplicity, excellent patternability, process scalability, high productivity, and low processing cost for pattern formation. However, the pattern size that can be implemented on metal materials through conventional NIL technologies is generally limited to the micro level. Here, we introduce a novel hard imprint lithography method, extreme-pressure imprint lithography (EPIL), for the direct nano-to-microscale pattern formation on the surfaces of metal substrates with various thicknesses. The EPIL process allows reliable nanoscopic patterning on diverse surfaces, such as polymers, metals, and ceramics, without the use of ultraviolet (UV) light, laser, imprint resist, or electrical pulse. Micro/nano molds fabricated by laser micromachining and conventional photolithography are utilized for the nanopatterning of Al substrates through precise plastic deformation by applying high load or pressure at room temperature. We demonstrate micro/nanoscale pattern formation on the Al substrates with various thicknesses from 20 ㎛ to 100 mm. Moreover, we also show how to obtain controllable pattern structures on the surface of metallic materials via the versatile EPIL technique. We expect that this imprint lithography-based new approach will be applied to other emerging nanofabrication methods for various device applications with complex geometries on the surface of metallic materials.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.51.2-51.2
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• 2009

본 실험에서는 레이저 간섭 리소그래피를 이용한 2차원 나노 패턴을 형성하였고, 수열합성법을 이용하여 90 도에서 ZnO 나노 기둥을 ZnO/Si 기판 상에 제작 하였다. ZnO 버퍼층은 스퍼터를 이용하여 200도, Ar 분위기에서 증착 하였으며, 레이저 간섭 리소그래피를 이용하여 두 번의 노광을 통해 2차원 나노 패턴을 형성하였다. 먼저, 최적화된 포토레지스트를 ZnO/Si 기판 위에 도포하고, 2500rpm에서 30초간 스핀코팅 한 후, 첫번째 노광을 실시 하였고, ZnO/Si 기판을 회전시켜 첫번째 노광과 교차 시킨 다음 두 번째 노광을 통해 교차하는 부분만 현상되도록 하였다. 기판의 회전 및 기판과 입사 레이저 사이의 각도를 조절하여 제작된 나노 패턴의 종류는 square lattice, centered rectangular lattice, oblique lattice, hexagonal lattice, rectangular lattice, 5가지로, 2차원의 모든 격자를 제작 하였다. 저온 수열합성법에서는 Na citrate를 형상제어제 (surfactant ions)로 사용하여 ZnO 나노 기둥을 형성하였다. $NH_4OH$를 이용하여 용액의 pH를 조절하였고, Zn nitrate hexahydrate를 Zn의 원료 물질로 사용하였다. 2차원 나노 패턴의 3차원 형태는 Atomic force microscopy (AFM, Veeco instruments, USA)를 이용하여 접촉 모드에서 관찰하였고, ZnO 나노 구조는 주사 전자 현미경 (FE-SEM, Model: JSM-6701F, Tokyo, Japan) 를 통하여 분석 하였다. 나노 패턴의 AFM 분석 결과 ZnO/Si 기판상에 포토레지스트가 주기적인 배열을 가지는 것을 확인하였고, ZnO/Si 기판상에 포토레지스트가 완전히 현상된 부분이 일정한 배열을 가지는 것을 확인하였다. 포토레지스트가 현상되어 기판의 표면이 드러난 부분의 크기는 약 250nm로 측정되었다. ZnO 나노 구조의 FE-SEM 분석 결과, 각각의 나노 구조가 나노패턴 중 완전히 현상된 부분만을 통하여 성장되었다는 것을 확인하였고, 형상 제어제로 사용된 Na citrate의 첨가 여부에 따라 나노 구조의 모양이 변화되었다는 것을 알 수 있었다. Na citrate 가 첨가된 나노 기둥의 경우 약 500nm의 길이를 가지는 하나의 기둥 형태로 성장하였다는 것을 확인하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.5
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• pp.377-380
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• 2012

Laser direct patterning of indium tin oxide(ITO) is one of new methods of direct etching process to replace the conventional photolithography. A diode pumped Q-switched Nd:$YVO_4$ (${\lambda}$= 1,064 nm) laser was used to produce ITO electrode on various transparent oxide semiconductor films such as zinc oxide(ZnO). The laser direct etched ITO patterns on ZnO were compared with those on glass substrate and were considered in terms of the overlapping rate of laser beam. In case of the laser etching on double-layer, it was possible to obtain the higher overlapping rate of laser beam.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.11
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• pp.969-975
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• 2000

Laser direct writing of micro-patterned copper lines has been achieved by pyrolytic decomposition of copper formate films (Cu(HCOO)$_2$.4$H_2O$), as a metallo-organic precursor, using a focused CW Ar$^{+}$ laser beam (λ=514nm) on PCB boards and glass substrates. The linewidth and thickness of the lines wee investigated as a functin of laser power and scan speed. The profiles of the lines were measured by scanning electron microscope (SEM), surface profiler ($\alpha$-step) and atomic force measured by scanning electron microscope (SEM), surface profiler ($\alpha$-step) and atomic force microscopy (AFM). The electrical resistivities of the patterned lines were also investigated as a function of laser parameters using probe station and semiconductor analyzer. We compared resistivities of the patterned copper lines with these of the Cu bulk. Resistivities decreased due to changes in morphology and porosity of the deposit, which were about 3.8 $\mu$$\Omega$cm and 12$\mu$$\Omega$cm on PCB and glass substrates after annealing at 30$0^{\circ}C$ for 5 minutes.s.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1539-1542
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• 2005

Self-assembled monolayers (SAMs) formed by the adsorption of alkanethiols, $HS(CH_2)_nX$, where X is an organic functional group, onto gold surfaces have attracted widespread interest as templates for the fabrication of molecular and biomolecular microstructures. Previously photopatterning has been thought of as being restricted to the micron scale, because of the wellknown diffraction limit. So, we have explored a novel approach to nanofabrication by utilizing a femtosecond laser coupled to a near-field scanning optical microscope (NSOM).

• Journal of Institute of Convergence Technology
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• v.5 no.2
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• pp.21-25
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• 2015

This paper proposes a fabrication process of deposited layer with micro patterns that uses a combination of a pulsed laser beam machining and an electrodeposition. This process consists of the electrodeposition and the laser beam machining. The deposited layer on metal can be selectively eliminated by laser ablation. As a result, the deposited layer with micro patterns can be fabricated without a mask. The characteristics of the deposited layer on stainless steel were investigated according to the average power and marking speed in the pulsed laser beam machining. The optimal laser beam conditions for precise micro patterning of the deposited layer were determined. Finally, the deposited copper layer with micro text was successfully fabricated by the pulsed laser beam machining.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.889-891
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• 1998

Copper films have been deposited on glass substrate via a thermal decomposition of copper(II) formate using a focused $Ar^+$ laser emitting at 514 nm. The growth kinetics of these Cu films was investigated as a function of laser power and scan speed which varied in the range of 70-150 mW and 0.1-20 mm/s, respectively. The resistivity of the copper films was a factor of about 20 higher than· that of bulk value, but the resistivity decreased due to changes in morphology and porosity of the deposit after annealing at $300^{\circ}C$, 5 min. and was about $10{\mu}{\Omega}cm$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.612-615
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• 2003

Maskless laser patterning process is developed using 3rd harmonic Diode Pumped Solid State Laser with near visible wavelength of 355 nm. Photo-sensitive curable polymer is irradiated by UV laser and developed using polymer solvent to obtain quasi-3D patterns. We performed basic experiments for the various process conditions such as laser power, writing speed, laser focus, and polymer optical property to gain the optimal conditions. Experimentally, the patterns of trapezoidal shape were manufactured into dimension of 8${\mu}{\textrm}{m}$ width and 5.4${\mu}{\textrm}{m}$ height. This process could be applied to fabricate a single mode waveguide without expensive mask projection method.