• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.3
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• pp.241-245
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• 2022

In this study, we measured and comparatively analyzed the characteristics of MPS (Merged Pin Schottky) diodes in 4H-SiC by changing the areal ratio between the Schottky and PN junction region. Increasing the temperature from 298 K to 473 K resulted in the threshold voltage shifting from 0.8 V to 0.5 V. A wider Schottky region indicates a lower on-resistance and a faster turn-on. The effective barrier height was smaller for a wider Schottky region. Additionally, the depletion layer became smaller under the influence of the reduced effective barrier height. The wider Schottky region resulted in the ideality factor being reduced from 1.37 to 1.01, which is closer to an ideal device. The leakage saturation current increased with the widening Schottky region, resulting in a 1.38 times to 2.09 times larger leakage current.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.3
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• pp.15-22
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• 2019

In these days, importance of the power electronic devices and modules keeps increasing due to electric vehicles and energy saving requirements. However, current silicon-based power devices showed several limitations. Therefore, wide band gap (WBG) semiconductors such as SiC, GaN, and $Ga_2O_3$ have been developed to replace the silicon power devices. WBG devices show superior performances in terms of device operation in harsh environments such as higher temperatures, voltages and switching speed than silicon-based technology. In power devices, the reliability of the devices and module package is the critically important to guarantee the normal operation and lifetime of the devices. In this paper, we reviewed the recent trends of the power devices based on WBG semiconductors as well as expected future technology. We also presented an overview of the recent package module and fabrication technologies such as direct bonded copper and active metal brazing technology. In addition, the recent heat management technologies of the power modules, which should be improved due to the increased power density in high temperature environments, are described.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.148-148
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• 2011

Recently, there have been many research activities to develop the large-area plasma source, which is able to generate the high-density plasma with relatively good uniformity, for the plasma processing in the thin-film solar cell and display panel industries. The large-area CCP sources have been applied to the PECVD process as well as the etching. Especially, the PECVD processes for the depositions of various films such as a-Si:H, ${\mu}c$-Si:H, Si3N4, and SiO2 take a significant portion of processes. In order to achieve higher deposition rate (DR), good uniformity in large-area reactor, and good film quality (low defect density, high film strength, etc.), the application of VHF (>40 MHz) CCP is indispensible. However, the electromagnetic wave effect in the VHF CCP becomes an issue to resolve for the achievement of good uniformity of plasma and film. Here, we propose a new electrode as part of a method to resolve the standing wave effect in the large-area VHF CCP. The electrode is split up a series of strip-type electrodes and the strip-type electrodes and the ground ones are arranged by turns. The standing wave effect in the longitudinal direction of the strip-type electrode is reduced by using the multi-feeding method of VHF power and the uniformity in the transverse direction of the electrodes is achieved by controlling the gas flow and the gap length between the powered electrodes and the substrate. Also, we provide the process results for the growths of the a-Si:H and the ${\mu}c$-Si:H films. The high DR (2.4 nm/s for a-Si:H film and 1.5 nm/s for the ${\mu}c$-Si:H film), the controllable crystallinity (~70%) for the ${\mu}c$-Si:H film, and the relatively good uniformity (1% for a-Si:H film and 7% for the ${\mu}c$-Si:H film) can be obtained at the high frequency of 40 MHz in the large-area discharge (280 mm${\times}$540 mm). Finally, we will discuss the issues in expanding the multi-electrode to the 8G class large-area plasma processing (2.2 m${\times}$2.4 m) and in improving the process efficiency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.148-148
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• 2008

Low-k dielectric materials are an alternative plan to improve the signal propagation delay, crosstalk, dynamic power consumption due to resistance and parasitic capacitance generated the decrease of device size. Now, various materials is studied for the next generation. Diethoxymethlysiliane (DEMS) precursor using this study has two ethoxy groups along with one methyl group attached to the silicon atoms. SiCOH thin films were deposited on p-type Si(100) substrate by Plasma Enhanced Chemical Vapor Deposition (PECVD) using DEMS. In this study, we studied the effect of oxygen($O_2$) flow rate for DEMS to characteristics of thin films. The characteristics of thin films deposited using DEMS and $O_2$ evaluated through refractive index, dielectric constant(k), surface roughness, I-V(MIM:Al / SiCOH / Ag), C-V(MIM), deposition rate.

• Journal of the Korean Vacuum Society
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• v.7 no.4
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• pp.368-373
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• 1998

As device dimensions approach submicrometer size in ULSI, the demand for interlayer dielectric materials with very low dielectric constant is increased to solve problems of RC delay caused by increase in parasitic resistance and capacitance in multilevel interconnectins. Fluorinated amorphous carbon in one of the promising materials in ULSI for the interlayer dielectric films with low dielectric constant. However, poor thermal stability and adhesion with Si substrates have inhibited its use. Recently, amorphous hydrogenated carbon (a-C:H) film as a buffer layer between the Si substrate and a-C:F has been introduced because it improves the adhesion with Si substrate. In this study, therfore, a-C:F/a-C:H films were deposited on p-type Si(100) by ECRCVD from $C_2F_6, CH_4$and $H_2$gas source and investigated the effect of forward power and composition on the thickness, chemical bonding state, dielectric constant, surface morphology and roughness of a-C:F films as an interlayer dielectric for ULSI. SEM, FT-IR, XPS, C-V meter and AFM were used for determination of each properties. The dielectric constant in the a-C:F/a-C:H films were found to decrease with increasing fluorine content. However, the dielectric constant increased after furnace annealing in $N_2$atomosphere at $400^{\circ}C$ for 1hour due to decreasing of flurorine content. However, the dielectric constant increased after furnace annealing in $N_2$atmosphere at $400^{\circ}C$ for 1hour due to decreasing of fluorine concentration.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.280-283
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• 2007

The first grid-connected, building-integrated transparent amorphous silicon photovoltaic installation has been operated since October 2004 in Yongin, Korea. The 2.2kWp transparent PV system was applied to the facade of entrance hall in newly constructed KOLON E&C R&D building. The PV module is a nominal 0.98m ${\times}$ 0.95m, 10% transparent, laminated, amorphous(a-Si) thin-film device rated at 44 Wp per module. To demonstrate the architectural features of thin film PV technologies for daylighting application, transparent PV modules are attached to the building envelope with the form of single glazed window and special point glazing(SPG) frames. Besides power generation, the 10% transmittance of a-Si PV module provides very smooth natural daylight to the entrance hall without any special shading devices for whole year. The installation is fully instrumented and is continuously monitored in order to allow the performance assessment of amorphous silicon PV operating at the prevailing conditions. This paper presents measured power performance data from the first 12 months of operation. For the first year, annual average system specific yield was just 486.4kWh/kWp/year which is almost half of typical amorphous silicon PV output under the best angle and orientation. It should be caused by building orientation and self-shading of adjacent mass. Besides annual power output, various statistical analysis was performed to identify the characteristics of transparent thin film PV system.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.16.2-16.2
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• 2011

Graphene has attracted significant attention due to its unique characteristics and promising nanoelectronic device applications. For practical device applications, it is essential to synthesize high-quality and large-area graphene films. Graphene has been synthesized by eloborated mechanical exfoliation of highly oriented pyrolytic graphite, chemical reduction of exfoliated grahene oxide, thermal decomposition of silicon carbide, and chemical vapor deposition (CVD) on metal substrates such as Ni, Cu, Ru etc. The CVD has advantages over some of other methods in terms of mass production on large-areas substrates and it can be easily separated from the metal substrate and transferred to other desired substrates. Especially, plasma-enhanced CVD (PECVD) can be very efficient to synthesize high-quality graphene. Little information is available on the synthesis of graphene by PECVD even though PECVD has been demonstrated to be successful in synthesizing various carbon nanostructures such as carbon nanotubes and nanosheets. In this study, we synthesized graphene on $Ni/SiO_2/Si$ and Cu plate substrates with CH4 diluted in $Ar/H_2$ (10%) by using an inductively-coupled PECVD (ICPCVD). High-quality graphene was synthesized at as low as $700^{\circ}C$ with 600 W of plasma power while graphene layer was not formed without plasma. The growth rate of graphene was so fast that graphene films fully covered on substrate surface just for few seconds $CH_4$ gas supply. The transferred graphene films on glass substrates has a transmittance at 550 nm is higher 94%, indicating 1~3 monolayers of graphene were formed. FETs based on the grapheme films transferred to $Si/SiO_2$ substrates revealed a p-type. We will further discuss the synthesis of graphene and doped graphene by ICPVCD and their characteristics.

• Journal of Sensor Science and Technology
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• v.5 no.1
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• pp.30-36
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• 1996

ZnO thin-film sensors were fabricated by RF magnetron sputtering method. The composition of the device material was 4 wt. % $Al_{2}O_{3}$, 1 wt. % $TiO_{2}$ and 0.2 wt. % $V_{2}O_{5}$ on the basis of ZnO material for developing the high sensitive TMA gas sensor which have an appropriate resistivity and the stability for practical use. They were also grown on the $SiO_{2}/Si$ substrates heated at $250^{\circ}C$ under a pure oxygen pressure of about 10 mTorr with a power of about 80 watts for 10 minutes. So as to enhance the stability of the resistivity, the thin films were annealed from $400^{\circ}C$ to $800^{\circ}C$. The sensors made with the thin film which were annealed at $700^{\circ}C$ for 60 minutes in pure oxygen gas exhibited a good sensing properties for TMA gas. The thin film grown at this condition showed the maximum sensitivity of 550 in TMA gas concentration of 160 ppm, and exhibited a good stability and excellent linearity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.241-241
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• 2009

For the Radio Frequency Integrated Passive Device (RFIPD) application, we have successfully developed and characterized high break-down voltage metal-insulator-metal (MIM) capacitors with 2,000 ${\AA}$ plasma-enhanced chemical vapor deposition (PECVD) silicon nitride which deposited with $SiH_4/NH_3$ gas mixing rate, working pressure, and RF power of PECVD at $250^{\circ}C$ chamber temperature. At the PECVD process condition of gas mixing rate (0.957), working pressure (0.9 Torr), and RF power (60 W), the AFM RMS value of about 2,000 ${\AA}$ silicon nitride on the bottom metal was the lowest of 0.862 nm and break-down electric field was the highest of about 8.0 MV/cm with the capacitance density of 326.5 $pF/mm^2$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.4
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• pp.149-153
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• 2021

ε-Ga₂O₃ thin films were grown on 4H-SiC substrates by metal organic chemical vapor deposition (MOCVD) and crystalline quality were evaluated depend on growth conditions. It was found that the best conditions of the ε-Ga₂O₃ were grown at a growth temperature of 665℃ and an oxygen flow rate of 200 sccm. Two-dimensional growth was completed after the merge of hexagonal nuclei, and the arrangement direction of hexagonal nuclei was closely related to the crystal direction of the substrate. However, it was confirmed that crystal structure of the ε-Ga₂O₃ had an orthorhombic rather than hexagonal. Crystal phase transformation was performed by thermal treatment. And a β-Ga₂O₃ thin film was grown directly on 4H-SiC for the comparison to the phase transformed β-Ga₂O₃ thin film. The phase transformed β-Ga₂O₃ film showed better crystal quality than directly grown one.