• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.37 no.3
• /
• pp.332-336
• /
• 2024

High-energy bandgap material silicon carbide (SiC) is gaining attention as a next-generation power semiconductor material, and in particular, SiC-based MOSFETs are developed as representative power semiconductors to increase the breakdown voltage (BV) of conventional planar structures. However, as the size of SJ (Super Junction) MOSFET devices decreases and the depth of pillars increases, it becomes challenging to uniformly form the doping concentration of pillars. Therefore, a structure with different doping concentrations segmented within the pillar is being researched. Using Silvaco TCAD simulation, a SJ VVD (vertical variation doping profile) MOSFET with three different doping concentrations in the pillar was studied. Simulations were conducted for the width of the pillar and the doping concentration of N-epi, revealing that as the width of the pillar increases, the depletion region widens, leading to an increase in on-specific resistance (R_on,sp) and breakdown voltage (BV). Additionally, as the doping concentration of N-epi increases, the number of carriers increases, and the depletion region narrows, resulting in a decrease in R_on,sp and BV. The optimized SJ VVD MOSFET exhibits a very high figure of merit (BFOM) of 13,400 KW/cm², indicating excellent performance characteristics and suggesting its potential as a next-generation highperformance power device suitable for practical applications.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.7 no.3
• /
• pp.161-165
• /
• 2007

In this paper, mesoporous Pt on micro pillars Pt electrode is newly designed, fabricated, and characterized on silicon substrate for non-enzymatic electrochemical sensor micro-chip integrated with CMOS readout circuitry. The fabricated micro/nano Pt electrode has cylindrical hexangular arrayed nano Pt pores with a diameter of 3.2 nm which is formed on top of the micro pillars Pt electrode with approximately $6{\mu}m$ in diameter, $6{\mu}m$ in space, and $50{\mu}m$ in height. The measured current responses of the fabricated plane Pt, mesoporous Pt, and mesoporous Pt on the micro pillar Pt electrodes are approximately $9.9nA/mm^2,\;6.72{\mu}A/mm^2,\;and\;7.67{\mu}A/mm^2$ in 10mM glucose solution with 0.1M phosphate buffered saline (PBS) solution, respectively. In addition, the measured current responses of the fabricated plane Pt, mesoporous Pt, and mesoporous Pt on the micro pillar Pt electrodes are approximately $0.15{\mu}A/mm^2,\;0.56{\mu}A/mm^2,\;and\;0.74{\mu}A/mm^2$ in 0.1mM ascorbic acid (AA) solution with 0.1M phosphate buffered saline (PBS) solution, respectively. This experimental results show that the proposed micro/nano Pt electrode is highly sensitive and promising for CMOS integrated non-enzymatic electrochemical sensor applications. Since the micro-pillar Pt electrode can also be utilized with a micro-fluidic mixer in the sensor chip, the sensor chip can be much smaller, cheaper, and easier to be fabricated.

• Journal of Educational Research in Mathematics
• /
• v.13 no.4
• /
• pp.495-506
• /
• 2003

In this study, 1 investigated some properties on the special hyper-dimensional figures made by the principle of the performance of equivalent forms representation. I supposed 2 definitions on the making n-dimensional figure : a cone type(hypercube) and a pillar type(simplex). We can explain that there exists only 6 4-dimensional regular polytopes as there exists only 5 regular polygons. And there are many hyper-dimensional figures, they all have sufficient condition to show the general Euler' Characteristics. And especially, we could certificate that the simplest cone type and pillar types are fitted to Pascal's Triangle and Hasse's Diagram, each other.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.06a
• /
• pp.241-241
• /
• 2008

Macrofore formation in silicon and other semiconductors using electrochemical etching processes has been, in the last years, a subject of great attention of both theory and practice. Its first reason of concern is new areas of macropore silicone applications arising from microelectromechanical systems processing (MEMS), membrane techniques, solar cells, sensors, photonic crystals, and new technologies like a silicon-on-nothing (SON) technology. Its formation mechanism with a rich variety of controllable microstructures and their many potential applications have been studied extensively recently. Porous silicon is formed by anodic etching of crystalline silicon in hydrofluoric acid. During the etching process holes are required to enable the dissolution of the silicon anode. For p-type silicon, holes are the majority charge carriers, therefore porous silicon can be formed under the action of a positive bias on the silicon anode. For n-type silicon, holes to dissolve silicon is supplied by illuminating n-type silicon with above-band-gap light which allows sufficient generation of holes. To make a desired three-dimensional nano- or micro-structures, pre-structuring the masked surface in KOH solution to form a periodic array of etch pits before electrochemical etching. Due to enhanced electric field, the holes are efficiently collected at the pore tips for etching. The depletion of holes in the space charge region prevents silicon dissolution at the sidewalls, enabling anisotropic etching for the trenches. This is correct theoretical explanation for n-type Si etching. However, there are a few experimental repors in p-type silicon, while a number of theoretical models have been worked out to explain experimental dependence observed. To perform ordered macrofore formaion for p-type silicon, various kinds of mask patterns to make initial KOH etch pits were used. In order to understand the roles played by the kinds of etching solution in the formation of pillar arrays, we have undertaken a systematic study of the solvent effects in mixtures of HF, N-dimethylformamide (DMF), iso-propanol, and mixtures of HF with water on the macrofore structure formation on monocrystalline p-type silicon with a resistivity varying between 10 ~ 0.01 $\Omega$ cm. The etching solution including the iso-propanol produced a best three dimensional pillar structures. The experimental results are discussed on the base of Lehmann's comprehensive model based on SCR width.

• Journal of the Korean Institute of Rural Architecture
• /
• v.15 no.4
• /
• pp.35-42
• /
• 2013

The study aims to investigate general characteristics of Jae-sil from an architectural perspective by grasping location, deployment, structure, and plan composition based on existing inhabited conditions in Jeollabukdo. Results derived from the study are as follows. First, the location of Jae-sil is classified into mountainous and village types, and the two types showed a similar distribution. The village type showed the most distribution in the foot of a mountain in the rear of village, while the mountainous type is close to graveyard. The Jae-sil were mostly exposed to south, southeast, and southeast, which was not significantly different from residence. For deployment of the Jae-sil, a "二" shaped house, where main quarter and gated building are parallel located, can be common, indicating that additional attached building is less required. Second, for the platform out of structural components, coursed masonry was conducted by using natural rocks, and placed were a prop on the platform, first line on processed foot stone, and others on natural foot stone. For pillar, front line round columns, while others square columns. The binding type of the upper part of pillar is dominated by jangyeosujang and sorosujang. For wooden frame structure, 5ryangs were the most distributed, and out of these, 1goju 5ryang was the most generally used. For a roof part, it was composed with gambrel roof with single eave, and the roof was constructed by placing traditional Korean tile roof on the top. Third, for a size of Jae-sil out of plan composition, although the facade and the side of it were presented in a diverse manner, 4 facade rooms and 1.5 side rooms were the most frequently presented, and all Jae-sil were equipped with front ceremonial space. For spatial composition of Jae-sil, main floored hall is placed at the center, and each room is placed on the left and right side to secure space for ancestral rite for participants of it, and for a house with 5 rooms or more, it shows that main floored hall and rooms are weighted from side to side.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.16 no.2
• /
• pp.82-87
• /
• 2013

Effects of material surface property, hydrophobic or hydrophilic, on the bio-fouling occurred on the bodies submerged in the sea water are investigated experimentally. 4 test models are used in the experiment, which includes aluminum foil in common use, AAO applied hydrophobic surface, HDFS coated hydrophobic surface and hydrophilic surface. Hydrophobic surfaces with numerous micro & nano-scale pillars on it seems to play very important role of preventing them from fouling in initial stage while the effects disappear in long term sense of fouling process. It is concluded that the surface hydrophobicity retards the initial fouling until the fouling thickness is smaller than the heights of the pillars on it but the effects diminish with the fouling proceeds so that the thickness grows bigger than the pillar heights.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.12 no.1
• /
• pp.106-113
• /
• 2004

Most of mechanical structures are composed of many substructures connected to one another by various types of mechanical joints. In automotive engineering, it is important to study these connected structures under various dynamic forces for the evaluations of fatigue life and stress concentration exactly. In this study, the dynamic response of vehicle structure to external forces is classified an inverse problem involving strains from the experiment and the analysis. The practical dynamic forces are determined by the combination of the analytical and experimental method with analyzed strain by quasi-static finite element analysis under unit force and with measured strain by a strain gage under driving load, respectively. In a stressed body, inter-molecular chemical bonds are failed beyond the certain magnitude. The failure of molecular structure in material is considered as a time process of which rate is determined by mechanical stress. That is, the failure of inter-molecular chemical bonds is the fatigue lift of material. This kinetic concept is expressed as lethargy coefficient. And S-N curve is obtained with the lethargy coefficient from quasi-static tensile test. Equivalent practical dynamic force is obtained from the identification of practical dynamic force for one loading point. Using the practical dynamic force and S-N curve, fatigue life of a window pillar is analyzed with FEM under the identified force by the procedure of above mentioned.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.3
• /
• pp.843-847
• /
• 2014

In Super Junction (SJ) MOSFETs, charge balance is the most important issue of the SJ fabrication process. In order to achieve the best electrical characteristics, such as breakdown voltage and on-resistance, the N-type and P-type drift regions must be fully depleted when the drain bias approaches the breakdown voltage, which is known as the charge balance condition. In conventional charge balance analysis, based on multi-epi process SJ MOSFETs, analytical model has only N, P pillar width and doping concentration parameter. But applying a conventional charge balance principle to trench filling process, easier than Multi-epi process, is impossible due to the missing of the trench angle parameter. To achieve much more superior characteristics of on-resistance in trench filling SJ MOFET, the appropriate trench angle is necessary. So in this paper, modulated charge balance analysis is proposed, in which a trench angle parameter is added. The proposed method is validated using the TCAD simulation tool.

• Journal of the Microelectronics and Packaging Society
• /
• v.21 no.3
• /
• pp.67-71
• /
• 2014

An attempt to grow high quality GaN on silicon substrate using metal organic chemical vapor deposition (MOCVD), herein GaN epitaxial layers were grown on various Si(111) substrates. Thin Platinum layer was deposited on Si(111) substrate using sputtering, followed by thermal annealing to form Pt nano-clusters which act as masking layer during dry-etched with inductively coupled plasma-reactive ion etching to generate nano-patterned Si(111) substrate. In addition, micro-patterned Si(111) substrate with circle shape was also fabricated by using conventional photo-lithography technique. GaN epitaxial layers were subsequently grown on micro-, nano-patterned and conventional Si (111) substrate under identical growth conditions for comparison. The GaN layer grown on nano-patterned Si (111) substrate shows the lowest crack density with mirror-like surface morphology. The FWHM values of XRD rocking curve measured from symmetry (002) and asymmetry (102) planes are 576 arcsec and 828 arcsec, respectively. To corroborate an enhancement of the growth quality, the FWHM value achieved from the photoluminescence spectra also shows the lowest value (46.5 meV) as compare to other grown samples.

• Journal of Electrochemical Science and Technology
• /
• v.2 no.2
• /
• pp.124-129
• /
• 2011

A simple process of fabricating micropillar structure and its influence upon enhancing electrochemical biosensor response were studied in this work. Conducting polymer PEDOT was used as a base material in formulating a composite with PVA. Micro porous PC membrane filter was used as a template for the micropillar of the composite on ITO electrode. This structure could provide plenty of encapsulating space for enzyme species. After dosing enzyme solution into this space, Nafion film tent was cast over the pillar structure to complete the micropillar cavity structure. In this way, the encapsulation of enzyme could be accomplished without any chemical modification. The amount of enzyme species was easily controllable by varying the concentration of the dosing solution. The more amount of enzyme is stored in the sensor, the higher the electrochemical response is produced. One more reason for the sensitivity improvement comes from the large surface area of the micropillar structure. Application of 0.7 V produced the best current response under the condition of pH 7.4. This biosensor showed linear response to the glucose in 0.1~1 mM range with the average sensitivity of $14.06{\mu}A/mMcm^2$. Detection limit was 0.01 mM based on S/N = 3.