• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.4
• /
• pp.1838-1843
• /
• 2014

Nanoimprint lithography (NIL) fabrication process is regarded as the main alternative to existing expensive photo-lithography in areas such as micro- and nano-electronics including optical components and sensors, as well as the solar cell and display device industries. Functional patterns, including anti-reflective moth-eye pattern, photonic crystal pattern, fabricated by NIL can improve the overall efficiency of such devices. To successfully imprint a nano-sized pattern, the process conditions such as temperature, pressure, and time should be appropriately selected. In this paper, a cavity-filling process of the moth-eye pattern during the thermal-NIL within the temperature range, where the polymer resist shows the viscoelastic behaviors with consideration of stress relaxation effect of the polymer, were investigated with three-dimensional finite element analysis. The effects of initial thickness of polymer resist and imprinting pressure on cavity-filling process has been discussed. From the analysis results it was found that the cavity filling can be completed within 100 s, under the pressure of more than 4 MPa.

• Korean Journal of Materials Research
• /
• v.2 no.1
• /
• pp.35-42
• /
• 1992

Thermal behavior of residue and damaged layer formed by reactive ion etching (RIE) in $CHF_3/C_2F_6$ were investigated using X-ray photoelectron spectroscopy(XPS) and secondary ion mass spec-trometry(SIMS) techniques. Decomposition of polymer residue film begins at $200^{\circ}C$ and above $400^{\circ}C$ carbon compound as graphite mainly forms by in-situ resistive heating. It reveals that thermal decomposition of residue can be completed by rapid thermal anneal treatment above $800^{\circ}C$ under nitrogen atmosphere and out-diffusion of carbon and fluorine of damaged layer is observed.

• Polymer(Korea)
• /
• v.30 no.3
• /
• pp.207-209
• /
• 2006

We fabricated a capacitive-type humidity sensor using poly (p-phenylene ether sulfone: PES) as a humidity sensitive layer. The PES was dissolved in m-cresol $(CH_3C_6H_4OH)$ and spin-coated on ITO-coated glass substrate. Gold was deposited by sputtering as a water-permeable upper electrode. The capacitance of the sensor was inversely proportional to sensing film thicknesses and showed an excellent linearity of less than 1% in the humidity range of 20 to 90%. The sensor haying a $1.4{\mu}m$ sensing layer showed a hysteresis of 1.3% and a good sensitivity of 1.14 at 20 kHz.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.9
• /
• pp.669-676
• /
• 2013

In this study, we introduce a polymer(polyimide) based pressure sensor to measure real-time heart beat and blood pressure. The sensor have been designed with consideration of skin compatibility of material, cost effectiveness, manufacturability and wireless detection. The designed sensor was composed of inductor coils and an air-gap capacitor which generate self-resonant frequency when electrical source is applied on the system. The sensor was obtained with metalization, etching, photolithography, polymer adhesive bonding and laser cutting. The fabricated sensor was shaped in circular type with 10mm diameter and 0.45 mm thickness to fit radial artery. Resonant frequencies of the fabricated sensors were in the range of 91~96 MHz on 760 mmHg pressurized environment. Also the sensor has good linearity without any pressure-frequency hysteresis. Sensitivity of the sensor was 145.5 kHz/mmHg and accuracy was less than 2 mmHg. Real-time heart beat measurement was executed with a developed hand-held measurement system. Possibility of real-time blood pressure measurement was showed with simulated artery system. After installation of the sensor on skin above radial artery, simple real blood pressure measurement was performed with 64 mmHg blood pressure variation.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.37 no.4
• /
• pp.49-54
• /
• 2000

A new functional organic thin film optical waveguide ion sensor is designed, which can select a specific ion, i.e., $Ca^{2+}$ -ion. The sensing membrane was composed of PVC-PVAC-PVA copolymer matrix based on anionic cation-selective chromoionophor(ETH5294), neutral ionophore(K23El), anionic site and plasticizer and it was coated on the etched glass substrate as embeded type optical waveguide itself. The sensor sensitivity dependence on waveguide length and thickness, contence of chromoionophore, and each mode was investigated. And this sensor could detect $Ca^{2+}$ ion in concentrations ranging from 1$\times$10­6~1M(with 0.05M tris-HCI buffer solution of pH7.4) by measuring the absorbance change at 514nm of light. Utilizing thin film membrane, the fast response time and high sensitivity are obtained. Also, it is expected that this sensor can be applied to various biochemical important ions.ons.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.323-323
• /
• 2014

기존의 태양전지 기술은 기술 장벽이 매우 낮고 대량 생산을 통한 단가 절감하는 구조를 가지고 있어 대규모 자본을 가진 후발 기업에게 잠식되기 쉽다. 그러나, III-V족 화합물 반도체를 이용한 집광형 고효율 태양전지는 기술 장벽이 매우 높은 기술 집약 산업이므로 독자적인 기술을 확보하게 되면 독점적인 시장을 확보 할 수 있어 미래 고부가 가치 산업으로 적합하다. 특히 III-V족 화합물 반도체 태양전지는 III족 원소(In, Ga, Al)와 V족 원소(As, P)의 조합으로 0.3 eV~2.5 eV까지 밴드갭을 가지는 다양한 박막 제조가 가능하여 다양한 흡수 대역을 가지는 태양전지 제조가 가능하기 때문에 다중 접합 태양전지 제작이 가능하다. 또한 III-V 화합물 반도체는 고온 특성이 우수하여 온도 안정성 및 신뢰성이 우수하고, 또한 집광 시 효율이 상승하는 특성이 있어 고배율 집광형 태양광 발전 시스템에 가장 적합하다. Si 태양전지의 경우 100배 이하의 집광에서 사용하나, III-V 화합물 반도체 태양전지의 경우 500~1000배 정도의 고집광이 가능하다. 이러한 특성으로 III-V 화합물 반도체 태양전지 모듈 가격을 낮출 수 있고, 따라서 Si 태양전지 시스템과 비교하여 발전 단가 면에서 경쟁력을 확보할 수 있다. III-V 화합물 반도체는 다양한 밴드갭 에너지를 가지는 박막 제조가 용이하고, 직접천이(direct bandgap) 구조를 가지고 있어 실리콘에 비해 광 흡수율이 높다. 또한 터널정션(tunnel junction)을 이용하면 광학적 손실과 전기적 소실을 최소화 하면서 다양한 밴드갭을 가지는 태양전지를 직렬 연결이 가능하여 한 번의 박막 증착 공정으로 넓은 흡수대역을 가지며 효율이 높은 다중접합 태양전지 제작이 가능하다. 이에 걸맞게 본연구에서는 화학기상증착장치(MOCVD)를 이용하여 InAsP 나노선을 코어 쉘 구조로 성장하여 태양전지를 제작하였다. P-type Dopant로는 Disilane (Si2H6)을 전구체로 사용하였다. 또한 Benzocyclobutene (BCB) 폴리머를 이용하여 Dielectric을 형성하였고 Sputtering 방법으로 증착한 ZnO을 투명 전극으로 사용하여 나노선 끝부분과 실리콘 기판에 메탈 전극을 형성하였다. 이를 통해 제작한 태양전지는 솔라시뮬레이터로 측정했을때 최고 7%에 달하는 변환효율을 나타내었다.

• Korean Journal of Materials Research
• /
• v.9 no.5
• /
• pp.509-514
• /
• 1999

Interest in the integrated capacitors, which make it possible to reduce the size of and to obtain improved electrical performance of an electronic system, is expanding. In this study, $Ta_2$O\ulcorner thin film capacitors for MCM integrated capacitors were fabricated on a Upilex-S polymer film by DC magnetron reactive sputtering and the effects of low temperature annealing at various atmospheres and substrate surface morphology on the capacitor characteristics were discussed. The low temperature($150^{\circ}C$) annealing produced improved capacitor yield irrespective of the annealing at mosphere. But the leakage current of the $O_2$-annealed film was larger than that of any other films. This is presumably mosphere. But the leakage current of the $O_2$-annealed film was larger than that of any other films. This is presumably due to the change of the $Ta_2$O\ulcorner film surface by oxygen, which was explained by conduction mechanism study. Leakage current and breakdown field strength of the capacitors fabricated on the Upilex-S film were 7.27$\times$10\ulcornerA/$\textrm{cm}^2$ and 1.0 MV/cm respectively. These capacitor characteristics were inferior to those of the capacitors fabricated on the Si substrate but enough to be used for decoupling capacitors in multilayer package. Roughness Analysis of each layer by AFM demonstrated that the properties of the capacitors fabricated on the polymer film were affected by the surface morphology of the substrate. This substrate effect could be classified into two factors. One is the surface morphology of the polymer film and the other is the surface morphology of the metal bottom electrode determined by the deposition process. Therefore, the control of the two factors is important to obtain improved electrical of capacitors deposited on a polymer film.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.153-153
• /
• 2011

유리나 폴리머를 기판으로 하는 TFT(Thin film transistor), solar cell에서는 낮은 공정 온도에서($200{\sim}500^{\circ}C$) amorphous semiconductor thin film을 poly-crystal semiconductor thin film으로 결정화 시키는 기술이 매우 중요하게 대두 되고 있다. Ge은 Si에 비해 높은 carrier mobility와 낮은 녹는점을 가지므로, 비 저항이 낮을 뿐만 아니라 더 낮은 온도에서 결정화 할 수 있다. 하지만 일반적으로 쓰이는 Ge의 결정화 방법은 비교적 높은 열처리 온도를 필요로 하거나, 결정화된 원소에 남아있는 metal이 불순물 역할을 한다는 문제점, 그리고 불균일한 결정크기를 만든다는 단점이 있었다. 그 중에서도 현재 가장 많이 쓰이고 있는 MIC, MILC는 metal과 a-Ge이 접촉되는 interface나, grain boundary diffusion에 의해 핵 생성이 일어나고, 결정이 성장하는 메커니즘을 가지고 있으므로 단순 증착과 열처리 만으로는 앞서 말한 단점을 극복하는데 한계를 가지고 있다. 이에 PIII&D 장비를 이용하면, 이온 주입된 원소들이 모재와 반응 할 수 있는 표면적이 커짐으로 핵 생성을 조절 할 수 있을 뿐만 아니라, 이온 주입 시 발생하는 self annealing effect로 결정 크기까지도 조절할 수 있다. 또한 이러한 모든 process가 한 진공 장비 내에서 이루어지므로 장비의 단순화와, 공정간 단계별로 발생하는 불순물과 표면산화를 막을 수 있으므로 절연체 위에 저항이 낮고, hall mobility가 높은 poly-crystalline Ge thin film을 만들 수 있다. 본 연구에서는, 주로 핵 생성과정에서 seed를 만드는 이온주입 조건과, 결정 성장이 일어나는 증착 조건에 따라서 Ge의 결정방향과 크기가 많은 차이를 보이는데, 이는 HR-XRD(High resolution X-ray Diffractometer)와 Raman spectroscopy를 이용하여 측정 하였으며, SEM과 AFM으로 결정의 크기와 표면 거칠기를 측정하였다. 또한 Hall effect measurement를 통해 poly-crystalline thin film 의 저항과 hall mobility를 측정하였다.

• Korean Journal of Materials Research
• /
• v.10 no.6
• /
• pp.450-455
• /
• 2000

For further scaling down of the silicon devices, the application of low dielectric constant materials instead of silicon oxide has been considered to reduce power consumption, crosstalk, and interconnection delay. In this paper, the effect of $O_2/SF_6$ plasma chemistry on the etching characteristics of polyimide-one of the promising low-k interlayer dielectrics-has been studied. The etch rate of polyimide decreases with the addition of $SF_6$ gas due to formation of nonvolatile fluorine compounds inhibiting reaction between oxygen and hydrocarbon polymer, while applying substrate bias enhances etching process through physical attack. However, addition of small amount of $SF_6$ is desirable for etching topography. $SiO_2$ hard mask for polyimide etching is effective under $O_2$plasma etching(selectivity~30), while $O_2/SF_6$ chemistry degrades etching selectivity down to 4. Based on the above results, $1-2\mu\textrm{m}$ L&S PI2610 patterns were successfully etched.

• Journal of the Microelectronics and Packaging Society
• /
• v.13 no.4
• /
• pp.1-7
• /
• 2006

A major failure mode for wafer level chip size package (WLCSP) is thermo-mechanical fatigue of solder joints. The mechanical strains and stresses generated by the coefficient of thermal expansion (CTE) mismatch between the die and printed circuit board (PCB) are usually the driving force for fatigue crack initiation and propagation to failure. In a WLCSP process peripheral or central bond pads from the die are redistributed into an area away using an insulating polymer layer and a redistribution metal layer, and the insulating polymer layer affects solder joints reliability by absorption of stresses generated by CTE mismatch. In this study, several insulating polymer materials were applied to WLCSP to investigate the effect of insulating material. It was found that the effect of property of insulating material on WLCSP reliability was altered with a solder ball layout of package.