• Journal of Sensor Science and Technology
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• v.21 no.2
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• pp.83-89
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• 2012

A simple array of metal-insulator-metal capacitive elements was proposed for a potential application in humidity sensing platforms. We fabricated meso-scale sensors with different sizes(large-size: $2.7{\times}2.7mm^2$ ; mid-size: $1.5{\times}1.5mm^2$ ; small-size: $0.7{\times}0.7mm^2$) and characterized the performance of each design. Polyimide films were utilized as a humidity-sensitive layer. Capacitance changes of the polyimide layer were measured with respect to water absorption. The device showed sensitivity in the full range of relative humidity (RH) with excellent linearity(correlation coefficient > 0.994). This array structure exhibits unique advantages including easy fabrication process, high batch productivity, and high structural compatibility with various substrate materials. It is anticipated that this device structure will be potentially useful in unique applications including mapping spatial humidity variations over a meso-scale area and implementing flexible humidity sensing element arrays.

• Laser Solutions
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• v.8 no.2
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• pp.21-32
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• 2005

The excimer laser ablation of a polymer occurs by the excitation of chemical bonds to energy levels that are above the dissociation energy. In this process, however, fragmented debris is finally ejected explosively by the scission of bonds and accumulates on the material surface. In the present work, a process for eliminating surface debris contamination generated by the laser ablation of a polymer is developed. The proposed approach for removing surface debris utilizes an erasable ink pasted on a polymide. The ink pasted polyimide is ablated by KrF excimer laser. The surface debris ejected from the polyimide is then combined with the ink layer on the polymer. Finally, both the surface debris and the ink layer are removed using adhesive tape or alcohol solvent. The results suggest that the erasable ink method is a simple, low cost, and extremely effective debris eliminating process.

• Electronic Materials Letters
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• v.14 no.6
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• pp.749-754
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• 2018

Previous studies have reported on the mechanical robustness and chemical stability of flexible amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) on plastic substrates both in flat and curved states. In this study, we investigate how the polyimide (PI) substrate affects hydrogen concentration in the a-IGZO layer, which subsequently influences the device performance and stability under bias-temperature-stress. Hydrogen increases the carrier concentration in the active layer, but it also electrically deactivates intrinsic defects depending on its concentration. The influence of hydrogen varies between the TFTs fabricated on a glass substrate to those on a PI substrate. Hydrogen concentration is 5% lower in devices on a PI substrate after annealing, which increases the hysteresis characteristics from 0.22 to 0.55 V and also the threshold voltage shift under positive bias temperature stress by 2 ${\times}$ compared to the devices on a glass substrate. Hence, the analysis and control of hydrogen flux is crucial to maintaining good device performance and stability of a-IGZO TFTs.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.1-5
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• 2004

A multi-layer flexible substrate is composed of copper(Cu)/polyimide that are known as good electrical conductivity, and low dielectric constant, respectively. In this study. conductor line of $5{\mu}m$-pitch was successfully fabricated without non-uniform pattern shape by electroplating copper and coating polyimide on patterned stainless steel. For multi-layer flexible substrate, via holes were drilled by UV laser and filled with electroplating copper and tin. And then, the PI layer with vias and conductor lines was stripped from stainless steel substrate. The PI layers were laminated at once with careful alignment between layers. Solid state reaction between tin and copper during lamination formed the intermetallic compounds of $Cu_6Sn_5$($\eta$-phase) and $Cu_3Sn$($\epsilon$-Phase) and achieved a complete inter-connection by vertically positioning the plugged via holes on via pad. The via formation process has several advantages; such as better electrical property and lower cost than V type via and paste via.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.04b
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• pp.30-31
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• 1997

기체분리용 막에서 높은 투과성능을 얻기 위해서는 다공성 지지체 표면에 얇은 skin layer를 갖는 막을 제조하는 것이 가장 중요하다. 이 skin layer는 결함이 없고 가능한 한 얇아야 고선택도를 유지하면서 투과도를 높일 수 있다. 이러한 skin layer를 갖는 비대칭막을 wet phase inversion method를 이용하여 제조하는 연구를 하였다. 본 연구에서는 wet phase inversion method를 이용하여 표면에 skin layer를 갖는 polyimide 비대칭 평막을 제조하는데 있어서 제막조건에 따른 막 구조 조정과 투과특성을 평가하고자 하였다.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1422-1424
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• 1994

This paper deals with piezoresistive humidity sensor using polycrystalline silicon (Poly-Si ) with membrane in sensors of semiconductor. Poly-Si piezoresistors which have no temperature dependancy are deposited on silicon wafer, membrane is formed with micromachining technology, then polyimide is formed as a hygroscopic layer. Whereas the principle of conventional humidify sensors are based on the change in electrical properties of the material, the humidity induced volume change of a polyimide layer leads to a deformation of a silicon membrane in this case. This deformation is transformed into an output voltage by Poly-Si piezoresistive. Wheatstone bridge. Fabricated piezoresistive humidity sensors showed good linearity, response time, and long term stability.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1754-1756
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• 2000

Organic semiconductors based on fused-ring polycyclic aromatic hydrocarbon have great potential to be utilized as an active layer for electronic and optoelectronic devices. In this study, pentacene thin films and electrode materials were deposited by Organic Molecular Beam Deposition(OMBD) and vacuum evaporation respectively. For the gate dielectric, polyamic acid was spin-coated and cured into polyimide at 350$^{\circ}C$. Electrical characteristics of the devices were investigated, where the channel length and width was 50${\mu}m$ and 5mm. It was found that field effect mobility was 0.012$cm^{2}/Vs$, and on/off current ratio was $10^5$.

• Journal of the Korean Applied Science and Technology
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• v.15 no.4
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• pp.21-25
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• 1998

Organic-based electroluminescent devices have attracted lots of interests because of their possible application as a large-area flat panel display. Polyimides have been used for photo-alignment in LCD(Liquid Crystal Display). However, the devices used in this study were fabricated with polyimide doped with N,N'-Diphenyl-N,N'-di(m-tolyl)-benzidine(TPD) (3, 10, 30wt%) for electroluminescent hole tranforting layer(EHTL). The photochemical and physical properties of EHTL was studied. The film thicknesses were reduced under illumination with UV light. Polyimide films doped with TPD(3wt%) was irradiated and the electrical properties of the films were studied.

• Laser Solutions
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• v.12 no.4
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• pp.1-5
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• 2009

Conventional patterning based on wet-process for multi-layered film is a relatively complex and costly process though it is a necessary step for fabrication of TFT-LCD module. Recently, a direct pattering by laser has been studied because it is low cost and simple process compared to the wet process. In this work, the selective removal process of multi-layered film (polyimide/indium tin oxide/glass) is studied by modeling the thermal and mechanical behavior for multi-layered structure. Especially, the effects of thickness of polyimide layer are examined.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.11a
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• pp.67-67
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• 2002

패키지 기술의 개발은 저비용, 고성능, 높은 패키징 효율의 추세로 가고 있다. 이러한 추세에 따라 기판재료의 개발 및 구조의 변형이 요구된다. 패키지의 한 형태인 MCM(Multi-Chip Module)에 연성기판을 사용할 경우 fine pattern이 가능하고 부피가 작기 때문에 패키지의 효율이 좋고 또한 reel to reel process에 적용이 가능하기 때문에 대량생산의 이점을 가지고 있다. 연성기판은 좋은 전기적 특성을 가진 polyimide와 구리 층으로 구성된다. 그러나 polyimide와 구리 계층 사이에 약한 접착력과 구리로의 polyamic acid의 diffusion, 다층 기판의 제조의 어려움 등의 문제점을 남겨두고 있다. 본 연구는 일반적인 polyimide/copper가 구조가 가지고 있는 문제점을 해결하고 구리 패턴을 제작하기 위해 에칭을 쓰는 것을 배제함으로 fine pattern을 이루어 내었으며 전기도금으로 완전하게 채워진 pluged via을 사용함으로 각층간의 연결에 신뢰성을 부여하였다. 또한, 연성기판의 구조적인 문제점인 해결하여 다층 연성기판을 제조하려고 한다.