• Tribology and Lubricants
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• 제33권6호
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• pp.282-287
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• 2017

SU-8 is an epoxy-type photoresist widely used for the fabrication of high-aspect-ratio (HAR) micro-structures in micro-electro-mechanical systems (MEMS). To fabricate highly integrated structures, chemical mechanical polishing (CMP) has emerged as the preferred manufacturing process for planarizing the MEMS structure. In SU-8 CMP, an oxidizer decomposes organic impurities and particles in the CMP slurry remove the chemically reacted surface of SU-8. To fabricate HAR microstructures using the CMP process, the adhesion between SU-8 and substrate material is important to avoid the delamination of the SU-8 film caused by the mechanical-dominant material removal characteristic. In this study, the friction force during the CMP process is measured with a CMP monitoring system to detect the delamination phenomenon and investigate the delamination of the SU-8 film from the silicon substrate under various pressure conditions. The increase in applied pressure causes an increase in the frictional force and wafer-edge stress concentration. The frictional force measurement shows that the friction force changes according to the delamination phenomenon of the SU-8 film, and that it is possible to monitor the delamination phenomenon during the SU-8 CMP process. The delamination at a high applied pressure is explained by the effect of stress distribution and pad deformation. Consequently, it is necessary to control the pressure of polishing, which can avoid the delamination in SU-8 CMP.

• 대한기계학회논문집A
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• 제37권4호
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• pp.467-473
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• 2013

본 연구에서는 SU-8 박막의 마이크로시스템으로의 트라이볼로지적 응용을 목적으로 하여, 원자간 힘 현미경(AFM) 과 콜로이드 프로브를 이용한 실험 및 유한요소해석 기법을 이용하여 SU-8 코팅층의 두께에 따른 트라이볼로지적 특성을 고찰하였다. SU-8 시편은 스핀 코팅기법을 이용하여 두께를 다르게하여 제작하였다. 실험결과 코팅두께가 증가함에 따라 마찰력과 점착력이 감소하여 박막두께에 따른 차이가 존재함을 알 수 있었고, SU-8 표면이 Si 표면에서보다 더 낮은 점착력과 마찰력을 보여주었다. 또한, 시뮬레이션을 통해 두께별로 박막 파손을 유발시키는 임계하중(압력)이 존재하며, 본 연구에서의 200~800 nm 두께범위에서는 1.2~1.8 GPa 로 측정되었다.

• 전자공학회논문지
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• 제52권7호
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• pp.33-39
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• 2015

본 연구에서는 SU-8을 절연층으로 사용해 솔루션 공정을 바탕으로 하여 Indium Zinc Oxide(IZO) thin film transistor(TFT)의 안정성을 향상에 대해 연구하였다. 매우 점성이 강하며 negative lithography 용으로 사용되는 SU-8은 기계적, 화학적으로 높은 안정도를 가진다. 그리고 이 SU-8을 사용해 TFT층의 위에 스핀코팅을 사용해 절연막 층을 쌓고 photo lithography를 이용해 patterning을 하였다. SU-8층에 의한 positive bias stress(PBS)에 대한 전기적 특성 향상의 이유를 연구하기 위해 TFT에 X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FTIR) 분석을 시행하였다. SU-8을 절연층으로 한 TFT는 좋은 전기적 특성을 보였으며, 전류점멸비, 전자이동도, 문턱전압, subthreshold swing이 각각 $10^6$, $6.43cm^2/V{\cdot}s$, 7.1V, 0.88V/dec로 측정되었다. 그리고 3600초 동안 PBS를 가할 시 ${\Delta}V_{th}$는 3.6V로 측정되었다. 그러나 SU-8 층이 없는 경우 ${\Delta}V_{th}$는 7.7V 였다. XPS와 FTIR을 분석한 결과, SU-8 절연층이 TFT의 산소의 흡/탈착을 차단하는 특성에 의해 PBS에 강한 특성을 나타나게 함을 확인하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.493-494
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• 2006

SU-8 can be implemented as a mask for micro Abrasive Jet Machining (micro-AJM) process [1]. In this paper, we will evaluate the quality of micro grooving result on glass substrate by micro-AJM process which using SU-8 as a mask. It was evaluated on width and edge profile of the micro grooving. The result was having distortion compare with the master film used to pattern the SU-8 mask. The value of distortion with other properties which came along with it, such as depth and surface roughness, can be optimized in order to fabricate micro-channel for micro-fluidic application.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권8호
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• pp.598-604
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• 1999

This paper describes the research to minimize the film stress and maximize the aspect ratio of photoresist structure, especially about SU-8 for electroplating mold. UV LIGA process using SU-8 allows fabricating high aspect ratio polymer structures. However, it is hard to get fine patterns in the high aspect ratio structures because of high internal stress and difficulty of removing SU-8. The purpose of this paper is to setup the process condition for the obtainment of both low film stress and high aspect ratio and to find design rules that make the pattern be less dependent on stress problem. Firstly, the process of heat treatment and exposure of SU-8 are proposed. These two conditions control the amount of cross-linkage in polymer structure, which is the most important parameter of both pattern generation and remaining stress. Heat treatment is dealed with soft bake and post-exposure-bake. Temperature and time duration of each step are varied with heat treatment condition. Some test patterns are fabricated to evaluate the proposed process. Nickel electroplating is performed with the mold fabricated through the proposed process to confirm the SU-8 as a good electroplating mold.

• 한국결정성장학회지
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• 제13권2호
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• pp.68-72
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• 2003

본 논문에서는 3차원 마이크로구조물을 위한 새로운 UV-LIGA 공정을 개발하였다. 일반적으로 photoresist는 얇은 두께로 코팅이 되지만, SU-8은 수십 $\mu\textrm{m}$ 이상의 두께를 가질 수 있으며, 높은 형상비를 갖는다. SU-8과 같은 Thick photoresist는 기존의 baking 공정과 같이 급격한 cool down을 할 경우 stress에 의한 crack이 발생한다. 이와 같은 경우 도금을 위한 마이크로구조물이 구현이 되지 않는다. SU-8의 코팅, bake에서의 시간 조절, 그리고 PEB의 시간 조절 및 cool down조절을 통하여 stress에 의한 crack이 발생하지 않도록 3차원 마이크로구조물을 제작 할 수 있도록 하였다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 추계종합학술대회
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• pp.891-894
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• 2005

SU-8은 부드러운 벽면을 가지는 두꺼운 패턴을 제작하는 데 사용되는 음성 감광제(negative photoresist)이다 .이것은 처리 후에 강성이 높고 화학적으로 강인한 장점을 가지고 있으며 최근 MEMS 디바이스의 구조체로 쓰이고 있다. 그러나 SU-8은 공정 처리요소들에 대하여 매우 민감하고 사용하기 어려운 것으로 알려져 있다. 본 연구에서는 공정 처리요소로 exposure energy, post exposure bake (PEB) temperature, PEB time을 조절하여 실험을 하였다. Response Surface Methodology (RSM)를 이용해 각 인자가 delamination에 미치는 영향에 대해 분석하였고 이를 바탕으로 SU-8의 delamination을 최소화하기 위한 처리요소들의 최적화 방안을 제시하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.65-66
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• 2009

This paper describes a procedure developed to fabricate negative photo resist SUMS to a semi-insulating (SI)-GaAs-based substrate. SU-8 is attractive for micromachine multi-layer circuit fabrication, because it is photo-polymerizable resin, leading to safe, and economical processing. This work demonstrates SUMS photo resist can be used for RFIC/MMIC application.

• 반도체디스플레이기술학회지
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• 제3권2호
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• pp.23-26
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• 2004

Thin film is one of the most general structures used in micro-electro-mechanical systems (MEMS). To measure the mechanical properties of SU-8 film, tensile testing was adopted which offers not only elastic modulus but also yield strength and plastic deformation by load-displacement curve. Tensile testing system was constructed with linear guided servo motor for actuation, load cell for force measurement and dual microscope for strain measurement.

• 센서학회지
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• 제16권5호
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• pp.325-330
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• 2007

For the application to optic devices, wafer level package including spacer with particular thickness according to optical design could be required. In these cases, the uniformity of spacer thickness is important for bonding strength and optical performance. Packaging process has to be performed at low temperature in order to prevent damage to devices fabricated before packaging. And if photosensitive material is used as spacer layer, size and shape of pattern and thickness of spacer can be easily controlled. This paper presents polymer bonding using thick, uniform and patterned spacing layer of SU-8 2100 photoresist for wafer level package. SU-8, negative photoresist, can be coated uniformly by spin coater and it is cured at $95^{\circ}C$ and bonded well near the temperature. It can be bonded to silicon well, patterned with high aspect ratio and easy to form thick layer due to its high viscosity. It is also mechanically strong, chemically resistive and thermally stable. But adhesion of SU-8 to glass is poor, and in the case of forming thick layer, SU-8 layer leans from the perpendicular due to imbalance to gravity. To solve leaning problem, the wafer rotating system was introduced. Imbalance to gravity of thick layer was cancelled out through rotating wafer during curing time. And depositing additional layer of gold onto glass could improve adhesion strength of SU-8 to glass. Conclusively, we established the coating condition for forming patterned SU-8 layer with $400{\mu}m$ of thickness and 3.25 % of uniformity through single coating. Also we improved tensile strength from hundreds kPa to maximum 9.43 MPa through depositing gold layer onto glass substrate.