• Journal of the Microelectronics and Packaging Society
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• v.27 no.3
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• pp.89-93
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• 2020

Complex warpage behavior of the electronic packages causes internal stress so many kinds of mechanical failure occur such as delamination or crack. Efforts to predict the warpage behavior accurately in order to prevent the decrease in yield have been approached from various aspects. For warpage prediction, silicon is generally treated as a homogeneous material, therefore it is described as showing no warpage behavior due to thermal loading. However, it was reported that warpage is actually caused by residual stress accumulated during grinding and polishing in order to make silicon wafer thinner, which make silicon wafer inhomogeneous through thickness direction. In this paper, warpage behavior of the single-side polished wafer at solder reflow temperature, the highest temperature in packaging processes, was measured using 3D digital image correlation (DIC) method. Mechanism was verified by measuring coefficient of thermal expansion (CTE) of both mirror-polished surface and rough surface.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.1
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• pp.47-49
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• 2003

The cost of material and slicing of silicon wafer occupied more than 30% of solar cell manufacturing cost. The substitution of silicon wafer into STS 304 stainless steel could be the promising solution to decrease the material cost. Moreover the stainless steel solar cell could have the advantage of low weight and durability. However, the highly polished surface is required to meet the characteristic of solar cell. The electropolishing process in phosphoric acid based solution was used to get the surface quality. The obtained result was 28 nm obtained in current density of 2Amfi/$cm^2$ at $80^{\circ}C$. The leveller effect of glycerine, ethylene glycol and propylen glycol was studied. When the 0.4 g/l of ethylene glycol was added to the electrolyte, the surface roughness was best, 15 nm.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.5
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• pp.218-224
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• 2003

This paper describes a novel MEMS integration technique on a CMOS chip. MEMS integration on CMOS circuit has many advantages in view of manufacturing cost and reliability. The surface topography of a CMOS chip from a commercial foundry has 0.9 ${\mu}{\textrm}{m}$ bumps due to the conformal coating on aluminum interconnect patterns, which are used for addressing each MEMS element individually. Therefore, it is necessary to achieve a flat mirror-like CMOS chip fer the microelectromechanical system (MEMS) such as micro mirror array. Such CMOS chip needs an additional thickness of the dielectric passivation layer to ease the subsequent planarization process. To overcome a temperature limit from the aluminum thermal degradation, this study uses RF sputtering of silicon nitride at low temperature and then polishes the CMOS chip together with the surrounding dummy pieces to define a polishing plane. Planarization reduces 0.9 ${\mu}{\textrm}{m}$ of the bumps to less than 25 nm.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1080-1081
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• 2015

CPV system in the desert areas or areas near the equator, as is suitable for high-temperature region. As compared to silicon solar cells, CPV system have a high proportion of a BOS (balance of system). Solar cells because of its low proportion when designing a module technology is applied in a variety of ways. Applied to the CPV system is classified into two kinds of optical technology. One of those using fresnel lens uses refraction of light energy. The other is a mirror reflection of the structure using sprays. Both of these two ways to condense the sun to collect solar cell is a form of light. And goals by using a small solar cell materials is to produce more energy. This research proposes rational design approach to calculate proper system capacity in consideration of the aforementioned factors in CPV system.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.421.2-421.2
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• 2016

고효율 태양전지에서 후면 반사 방지막은 장파장대(900nm~1200nm) 빛의 내부 반사를 증가시켜 광흡수도를 개선한다. 태양전지 후면에 박형 절연층 구조를 구성함으로써 특정 파장에서 높은 반사도를 얻을 수 있는 Bragg mirror 구조를 이론적으로 계산할 수 있다. Bragg mirror 구조를 이용하여 태양전지의 후면 반사층(Rear reflector layer)을 형성함으로써 태양전지 내부의 광흡수도를 개선할 수 있다. 후면 반사 방지막(Rear anti-reflection coating)으로 사용되는 Al2O3와 SiOxNy 또는 이러한 두 가지 물질의 겹층 구조를 구성하여 장파장대 빛의 반사도 차이에 의한 광흡수도 개선 정도를 광학 시뮬레이션을 통해 계산하였다. 광학 시뮬레이션은 TCAD를 이용하였으며 두 가지 겹층 구조에서 각 반사 방지막의 두께에 따른 단락 전류(Jsc)의 개선 정도, 후면 반사층 두께의 최적화 조건을 계산하였다. 후면 반사방지막을 제외한 기본적인 태양전지 구조는 n-type PERC 구조를 사용하였으며, 후면 반사방지막만의 광학적 특성을 살펴보기 위해 전극은 광학적으로 투명하다고 가정하였다. 반사방지막 두께의 범위는 Al2O3(5-30nm), SiNx(150-300nm), SiOxNy(150-300nm)에서 수행하였으며, 각각 1nm, 2nm 간격으로 진행하였다. Al2O3/SiOxNy 구조에서는 단락 전류가 32.45-32.87mA/cm2 값을 가진다. Al2O3/SiNx 구조에서는 단락 전류가 32.59-32.87mA/cm2 값을 가진다. 결론적으로, 후면 반사방지막의 겹층 구조를 통해 광흡수도를 증가 시킬 수 있으며, TCAD 시뮬레이션을 통하여 입사되는 태양광 스펙트럼에 최적화된 구조를 설계할 수 있다.

• The Korean Journal of Ceramics
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• v.1 no.1
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• pp.7-12
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• 1995

When a $Ta_O_5$ dielectric film is deposited on a bare silicon, the growth of $SiO_2$ at the $Ta_O_5$/Si interface cannot be avoided. Even though the $SiO_2$ layer is ultrathin (a few nm), it has great effects on the electrical properties of the capacitor. The concentration depth profiles of the ultrathin interfacial $SiO_2$ and $SiO_2/Si_3N_4$ layers were obtained using an Auger electron spectroscopy (AES) equipped with a cylindrical mirror analyzer (CMA). These AES depth profiles were quantitatively analyzed by comparing with the theoretical depth profiles which were obtained by considering the inelastic mean free path of Auger electrons and the angular acceptance function of CMA. The direct measurement of the interfacial layer thicknesses by using a high resolution cross-sectional TEM confirmed the accuracy of the AES depth analysis. The $SiO_2/Si_3N_4$ double layers, which were not distinguishable from each other under the TEM observation, could be effectively analyzed by the AES depth profiling technique.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.348-351
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• 1995

A modified silicon direct bonding method has been developed alloying an intimate contact between grooved and smooth mirror-polished oxide-free silicon wafers. A regular set of grooves was formed during preparation of heavily doped $p^+$-type grid network by oxide-masking und boron diffusion. Void-free bonded interfaces with filing of the grooves were observed by x-ray diffraction topography, infrared, optical. and scanning electron microscope techniques. The presence of regularly formed grooves in bending plane results in the substantial decrease of dislocation over large areas near the interface. Moreover two strongly misoriented waters could be successfully bonded by new technique. Diodes with bonded a pn-junction yielded a value of the ideality factor n about 1.5 and the uniform distribution of series resistance over the whole area of horded pn-structure. The suitability of the modified technique was confirmed by I - V characteristics of power diodes and reversly switched-on dynistor(RSD) with a working area about $12cm^2$. Both devices demonstrated breakdown voltages close to the calculation values.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.195-201
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• 2005

A laterally driven electromagnetic microactuator (LaDEM) is presented, and a micro-optical switch is designed and fabricated as a possible application. LaDEM provides parallel actuation of the microactuator to the silicon substrate surface (in-plane mode) by the Lorentz force. Poly-silicon-on-insulator (Poly-SOI) wafers and a reactive ion etching (RIE) process were used to fabricate high-aspect-ratio vertical microstructures, which allowed the equipment of a vertical micro mirror. A fabricated arch-shaped leaf spring has a thickness of $1.8{\mu}m$, width of $16{\mu}m$, and length of $800{\mu}m$. The resistance of the fabricated structure fer the optical switch was approximately 5$\Omega$. The deflection of the leaf springs increases linearly up to about 400 mA and then it demonstrates a buckling behavior around the current value. Owing to this nonlinear phenomenon, a large displacement of $60{\mu}m$ could be measured at 566 mA. The displacement-load relation and some dynamic characteristics are analyzed using the finite element simulations.

• Bulletin of the Korean Chemical Society
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• v.28 no.4
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• pp.533-537
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• 2007

This paper describes the heteroepitaxial growth of single-crystalline 3C-SiC (cubic silicon carbide) thin films on Si (100) wafers by atmospheric pressure chemical vapor deposition (APCVD) at 1350 oC for micro/nanoelectromechanical system (M/NEMS) applications, in which hexamethyldisilane (HMDS, Si2(CH3)6) was used as a safe organosilane single-source precursor. The HMDS flow rate was 0.5 sccm and the H2 carrier gas flow rate was 2.5 slm. The HMDS flow rate was important in obtaing a mirror-like crystalline surface. The growth rate of the 3C-SiC film in this work was 4.3 μm/h. A 3C-SiC epitaxial film grown on the Si (100) substrate was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Raman scattering, respectively. These results show that the main chemical components of the grown film were single-crystalline 3C-SiC layers. The 3C-SiC film had a very good crystal quality without twins, defects or dislocations, and a very low residual stress.

• Bulletin of the Korean Chemical Society
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• v.28 no.11
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• pp.2079-2082
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• 2007

Photonic crystals containing rugate structure result in a mirror with high reflectivity in a specific narrow spectral region and are prepared by applying a computer-generated pseudo-sinusoidal current waveform. Well defined 1-dimentional photonic polymer replicas showing a reflectivity at 534 nm have been successfully obtained by the removal of rugate porous silicon (PSi) template from the polystyrene composite film. XRD measurement indicates that the oxidized rugate PSi has been completely removed from the composite films. Polymer replicas exhibit a sharp resonance in the reflectivity spectrum. Optical characteristics of photonic polymer replicas indicate that the surface of polymer film has a negative structure of rugate PSi. These replicas are stable in aqueous solutions for several days without any degradation. The methods have been provided for the construction of photonic structures with polymers.