• Transactions on Electrical and Electronic Materials
• /
• v.4 no.3
• /
• pp.34-37
• /
• 2003

[ $HfO_2$ ] and $HfO_xN_y$ films were deposited by plasma-enhanced chemical vapor deposition using $Hf[OC(CH_3)_3]_4$ as the precursor in the absence of $O_2$. The crystallization temperature of the $HfO_xN_y$ films is higher than that of the $HfO_2$ film. Nitrogen incorporation in $HfO_xN_y$ was confirmed by auger electron spectroscopy analysis. After post deposition annealing (PDA) at 800$\Box$, the EOT increased from 1.34 to 1.6 nm in the $HfO_2$ thin films, whereas the increase of EOT was suppressed to less than 0.02 nm in the $HfO_xN_y$. The leakage current density decreased from 0.18 to 0.012 $A/cm^2$ with increasing PDA temperature in the $HfO_2$ films. But the leakage current density of $HfO_xN_y$ does not vary with increasing PDA temperature because an amorphous $HfO_xN_y$ films suppresses the diffusion of oxygen through the gate dielectric.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.43 no.9 s.351
• /
• pp.64-68
• /
• 2006

Novel system-on-package (SOP) - D technology to improve the mechanical and thermal properties of a MCM-D substrate was suggested. Based on this investigation, the two types of band pass filters for the V-band application with unique structure were designed and implemented using 2-metals, 3-BCB layers. The first type using distributed resonator had the insertion loss below 2.6 dB at 55 GHz and group delay was below 0.06 ns. For the second type with edge coupled structure, the insertion loss and group delay were 3 dB and 0.1 ns, respectively. Suggested MCM-D substrate with band pass filter can be used to evaluate mm-Wave system including flip-chip bonded MMIC.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.30 no.11
• /
• pp.717-721
• /
• 2017

We studied the performance enhancement of organic light-emitting diodes (OLEDs) using 2,3,5,6-fluoro-7,7,8,8-tetracyanoquinodimethane ($F_4-TCNQ$) as the hole-transport layer. To investigate how $F_4-TCNQ$ affects the device performance, we fabricated a reference device in an ITO (170 nm)/TPD(40 nm)/$Alq_3$(60 nm)/LiF(0.5 nm)/Al(100 nm) structure. Several types of test devices were manufactured by either doping the $F_4-TCNQ$ in the TPD layer or forming a separate $F_4-TCNQ$ layer between the ITO anode and TPD layer. N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine (TPD), tri(8-hydroxyquinoline) aluminum ($Alq_3$), and $F_4-TCNQ$ layers were formed by thermal evaporation at a pressure of $10_{-6}$ torr. The deposition rate was $1.0-1.5{\AA}/s$ for TPD and $Alq_3$. The LiF was subsequently thermally evaporated at a deposition rate of $0.2{\AA}/s$. The performance of the OLEDs was considered with respect to the turn-on voltage, luminance, and current efficiency. It was found that the use of $F_4-TCNQ$ in OLEDs enhances the performance of the device. In particular, the use of a separate layer of $F_4-TCNQ$ realizes better device performance than other types of OLEDs.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.130.2-130.2
• /
• 2013

Today, chemical vapor deposition (CVD) of hydrocarbon gases has been demonstrated as an attractive method to synthesize large-area graphene layers. However, special care should be taken to precisely control the resulting graphene layers in CVD due to its sensitivity to various process parameters. Therefore, a facile synthesis to grow graphene layers with high controllability will have great advantages for scalable practical applications. In order to simplify and create efficiency in graphene synthesis, the graphene growth by thermal annealing process has been discussed by several groups. However, the study on growth mechanism and the detailed structural and optoelectronic properties in the resulting graphene films have not been reported yet, which will be of particular interest to explore for the practical application of graphene. In this study, we report the growth of few-layer, large-area graphene films using rapid thermal annealing (RTA) without the use of intentional carbon-containing precursor. The instability of nickel films in air facilitates the spontaneous formation of ultrathin (<2~3 nm) carbon- and oxygen-containing compounds on a nickel surface and high-temperature annealing of the nickel samples results in the formation of few-layer graphene films with high crystallinity. From annealing temperature and ambient studies during RTA, it was found that the evaporation of oxygen atoms from the surface is the dominant factor affecting the formation of graphene films. The thickness of the graphene layers is strongly dependent on the RTA temperature and time and the resulting films have a limited thickness less than 2 nm even for an extended RTA time. The transferred films have a low sheet resistance of ~380 ${\Omega}/sq$, with ~93% optical transparency. This simple and potentially inexpensive method of synthesizing novel 2-dimensional carbon films offers a wide choice of graphene films for various potential applications.

• Journal of IKEEE
• /
• v.11 no.4
• /
• pp.272-278
• /
• 2007

In this paper, we report on the 2D (two-dimensional) simulation result of the DC (direct current) electrical and thermal characteristics of AlGaN/GaN HEMTs (high electron mobility transistors) grown on Si substrate, in comparison with those grown on sapphire and SiC (silicon carbide) substrate, respectively. In general, the electrical properties of HEMT are affected by electron mobility and thermal conductivity, which depend on substrate material. For this reason, the substrates of GaN-based HEMT have been widely studied today. The simulation results are compared and studied by applying general Drift-Diffusion and thermal model altering temperature as 300, 400 and 500 K, respectively. With setting T=300 K and $V_{GS}$=1 V, the $I_{D,max}$ (drain saturation current) were 189 mA/mm for sapphire, 293 mA/mm for SiC, and 258 mA/mm for Si, respectively. In addition, $G_{m,max}$ (maximum transfer conductance) of sapphire, SiC, Si was 38, 50, 31 mS/mm, respectively, at T=500 K.

• Journal of Sensor Science and Technology
• /
• v.9 no.3
• /
• pp.242-247
• /
• 2000

$Pb_{0.99}[(Zr_{0.6}Sn_{0.4})_{0.9}Ti_{0.1}]_{0.98}Nb_{0.02}O_3(PNZST)$ thin films were deposited by RF magnetron sputtering on $(La_{0.5}Sr_{0.5})CoO_3(LSCO)/Pt/Ti/SiO_2/Si$ substrate using a PNZST target with excess PbO of 10 mole%. The thin films deposited at substrate temperature of $500^{\circ}C$, and at RF power of 80W were crystallized to a perovskite phase after rapid thermal annealing(RTA). The thin films annealed at $650^{\circ}C$ for 10 seconds in air exhibited the good structures and electrical properties. The fabricated PNZST capacitor had a remanent polarization value of about $20\;{\mu}C/cm^2$ and coercive field of about 50 kV/cm. The reduction of the polarization after $2.2{\times}10^9$ switching cycles was less than 10%.

• Transactions on Electrical and Electronic Materials
• /
• v.11 no.6
• /
• pp.261-265
• /
• 2010

In this paper, we attempt to improve the electrical characteristics of epoxy resin at high temperature (above $80^{\circ}C$) by adding magnesium oxide (MgO), which has high thermal conductivity. Scanning electron microscopy (SEM) of the dispersion of specimens with added MgO reveals that they are evenly dispersed without concentration. The dielectric breakdown characteristics of $SiO_2$ and MgO nanocomposites are tested by measurements at different temperatures to investigate the filler's effect on the dielectric breakdown characteristics. The dielectric breakdown strength of specimens with added $SiO_2$ decreases slowly below $80^{\circ}C$ (low temperature) but decreases rapidly above $80^{\circ}C$ (high temperature). However, the gradient of the dielectric breakdown strength of specimens with added MgO is slow at both low and high temperatures. The dielectric breakdown strength of specimens with 0.4 wt% $SiO_2$ is the best among the specimens with added $SiO_2$, and that of specimens with 3.0 wt% and 5.0 wt% MgO is the best among those with added MgO. Moreover, the dielectric strength of specimens with 3.0 wt% MgO at high temperatures is approximately 53.3% higher than that of specimens with added $SiO_2$ at $100^{\circ}C$, and that of specimens with 5.0 wt% of MgO is approximately 59.34% higher under the same conditions. The dielectric strength of MgO is believed to be superior to that of $SiO_2$ owing to enhanced thermal radiation because the thermal conductivity rate of MgO (approximately 42 $W/m{\cdot}K$) is approximately 32 times higher than that of $SiO_2$ (approximately 1.3 $W/m{\cdot}K$). We also confirmed that the allowable breakdown strength of specimens with added MgO at $100^{\circ}C$ is within the error range when the breakdown probability of all specimens is 40%. A breakdown probability of up to 40% represents a stable dielectric strength in machinery and apparatus design.

• Journal of the Microelectronics and Packaging Society
• /
• v.21 no.4
• /
• pp.1-13
• /
• 2014

The paper gives an overview of the concepts, basic requirements, and trends regarding packaging technologies of power modules in hybrid (HEV) and electric vehicles (EV). Power electronics is gaining more and more importance in the automotive sector due to the slow but steady progress of introducing partially or even fully electric powered vehicles. The demands for power electronic devices and systems are manifold, and concerns besides aspects such as energy efficiency, cooling and costs especially robustness and lifetime issues. Higher operation temperatures and the current density increase of new IGBT (Insulated Gate Bipolar Transistor) generations make it more and more complicated to meet the quality requirements for power electronic modules. Especially the increasing heat dissipation inside the silicon (Si) leads to maximum operation temperatures of nearly $200^{\circ}C$. As a result new packaging technologies are needed to face the demands of power modules in the future. Wide-band gap (WBG) semiconductors such as silicon carbide (SiC) or gallium nitride (GaN) have the potential to considerably enhance the energy efficiency and to reduce the weight of power electronic systems in EVs due to their improved electrical and thermal properties in comparison to Si based solutions. In this paper, we will introduce various package materials, advanced packaging technologies, heat dissipation and thermal management of advanced power modules with extended reliability for EV applications. In addition, SiC and GaN based WBG power modules will be introduced.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.12 no.4
• /
• pp.449-455
• /
• 2019

This paper proposes a flyback diode of bridgeless PFC converter as SiC SBD (Schottky Barrier Diode) to achieve high efficiency. In addition, through the explanation of the operation principle of the bridgeless PFC converter, the conduction section of the freewheel diode is shown in the bridgeless PFC converter to verify the contribution of system loss due to the loss of the freewheel diode. The advantages of the SiC SBD device's physical properties and the reverse recovery characteristics are explained, and the efficiency is measured by measuring the turn-on and turn-off losses. The loss was calculated. The simulation results were calculated in consideration of device characteristics and verified through the waveform analysis and comparison of the actual system. In order to consider the device characteristics, the simulation was conducted using the thermal module of PSIM. As a result of the prototype test, the turn-on loss was 0.608W and the turn-off loss was 21.62W, resulting in the total switching loss of 22.228W. The comparison of the two results proved the validity of the experimental method. In addition, a high efficiency of 94.58% is achieved.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.397-397
• /
• 2013

The electrical, electronic, optical properties and the local structure of Nickel Oxide (NiO) thin film have been investigated by X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), UV-spectrometer,Hall Effect measurement and X-ray absorption spectroscopy (XAS). The XPS results show that the Ni 2p spectra for all films consist of $Ni2p_{3/2}$ at around 854.5 eV which indicate the presence of Ni-O bond from NiO phase and for the annealed film at temperature above $200^{\circ}C$ shows the coexist Ni oxide and Ni metal phase. The REELS spectra showed that the band gaps of the NiO thin films were abruptly decreased with increasing temperature. The values of the band gaps are consistent with the optical band gaps estimated by UV-Spectrometer. The optical transmittance spectra shows that the transparency of NiO thin films in the visible light region was deteriorated with higher temperature due to existence of $Ni^0$. Hall Effect measurement suggest that the NiO thin films prepared at relatively low temperatures (RT and $100^{\circ}C$) are suitable for fabricating p-type semiconductor which showed that the best properties was achieved at $100^{\circ}C$, such as a low resistivity of $7.49{\Omega}.cm$. It can be concluded that the annealing process plays a crucial role in converting from p type to n type semiconductor which leads to reducing electrical resistivity of NiO thin films. Furthermore, the extended X-ray absorption fine structure (EXAFS) spectrum at the Ni K-edge was used to address the local structure of NiO thin films. It was found that the thermal treatments increase the order in the vicinity of Ni atom and lead the NiO thin films to bunsenite crystal structure. Moreover, EXAFS spectra show in increasing of coordination number for the first Ni-O shell and the bond distance of Ni-O with the increase of substrate temperature.