• Journal of Information Display
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• v.10 no.1
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• pp.33-36
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• 2009

A new hybrid silicon thin-film transistor (TFT) fabrication process using the DPSS laser crystallization technique was developed in this study to realize low-temperature poly-Si (LTPS) and a-Si:H TFTs on the same substrate as a backplane of the active-matrix liquid crystal flat-panel display (AMLCD). LTPS TFTs were integrated into the peripheral area of the activematrix LCD panel for the gate driver circuit, and a-Si:H TFTs were used as a switching device of the pixel electrode in the active area. The technology was developed based on the current a-Si:H TFT fabrication process in the bottom-gate, back-channel etch-type configuration. The ion-doping and activation processes, which are required in the conventional LTPS technology, were thus not introduced, and the field effect mobility values of $4\sim5cm^2/V{\cdot}s$ and $0.5cm^2/V{\cdot}s$ for the LTPS and a-Si:H TFTs, respectively, were obtained. The application of this technology was demonstrated on the 14.1" WXGA+(1440$\times$900) AMLCD panel, and a smaller area, lower power consumption, higher reliability, and lower photosensitivity were realized in the gate driver circuit that was fabricated in this process compared with the a-Si:H TFT gate driver integration circuit

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.8
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• pp.632-636
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• 2009

The local oxidation using an atomic force microscopy (AFM) is useful for Si-based fabrication of nanoscale structures and devices. SiC is a wide band-gap material that has advantages such as high-power, high-temperature and high-frequency in applications, and among several SiC polytypes, 4H-SiC is the most attractive polytype due to the high electron mobility. However, the AFM local oxidation of 4H-SiC for fabrication is still difficult, mainly due to the physical hardness and chemical inactivity of SiC. In this paper, we investigated the local oxidation of 4H-SiC surface using an AFM. We fabricated oxide patterns using a contact mode AFM with a Pt/Ir-coated Si tip (N-type, 0.01-0.025 ${\Omega}cm$) at room temperature, and the relative humidity ranged from 40 to 50 %. The height of the fabricated oxide pattern (1-3 nm) on SiC is similar to that of typically obtained on Si ($10^{15}^{\sim}10^{17}$ $cm^{-3}$). We perform the 2-D simulation to further analyze the electric field between the tip and the surface. We demonstrated that a specific electric field (4 ${\times}$ $10^7\;V/m$) and a doping concentration ($^{\sim}10^{17}$ $cm^{-3}$) is sufficient to switch on/off the growth of the local oxide on SiC.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.131-131
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• 2008

Silicon carbide (SiC) has attracted significant attention for high frequency, high temperature and high power devices due to its superior properties such as the large band gap, high breakdown electric field, high saturation velocity and high thermal conductivity. We performed Al ion implantation processes on n-type 4H-SiC substrate using a SILVACO ATHENA numerical simulator. The ion implantation model used a Monte-Carlo method. We studied the effect of channeling by Al implantation simulation in both 0 off-axis and 8 off-axis n-type 4H-SiC substrate. We have investigated the Al distribution in 4H-SiC through the variation of the implantation energies and the corresponding ratio of the doses. The implantation energies controlled 40, 60, 80, 100 and 120 keV and the implantation doses varied from $2\times10^{14}$ to $1\times10^{15}cm^{-2}$. In the simulation results, the Al ion distribution was deeper as increasing implantation energy and the doping level increased as increasing implantation doses. After the post-implantation annealing, the electrical properties of Al-implanted p-n junction diode were investigated by SILV ACO ATLAS numerical simulator.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.301-301
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• 2010

2010년경 2.5G APD 시장은 3, 000억원 규모로 증가하는데 이는 FTTH 망의 확산에 힘입은 바 크다. 이와 같이 중요한 APD 소자는 현재 광통신 부품시장을 석권해 가고 있는 대만, 중국 업체들은 제조기술을 갖고 있지 않고 주로 미국-일본 기술에 의존하고 있기 때문에 Niche market으로 중요한 부품이라 할 수 있다. APD의 증폭은 높은 전기장에 의해 얻어지는데, 이 때문에 메사형 구조로는 신뢰성을 확보하기 어렵게 되고 따라서 평면형(Planar) 구조로 설계-제작하게 된다. APD 소자는 증폭층의 너비에 의해 APD의 이득-대역폭이 정해지므로 증폭층 폭을 정확하게 조절하는 것은 매우 중요하다. 증폭층의 폭은 에피 성장과 같은 높은 정밀성을 갖는 장비에 의해 조절하는 것이 아니라, Planar 구조의 특성상 Zn-확산에 의해 조절하게 된다. 대부분의 경우 Zn-확산은 Zn 또는 $Zn_3P_2$를 증착하여 drive-in 시키는 방법을 사용하는데, 이 경우 Zn가 interstitial site를 치고 들어감으로 인해 캐리어 농도가 $2{\times}10^{17}\;cm^{-3}$ 정도로 낮게 형성된다. 따라서 높은 인가 바이어스에서 p-side로 공핍층이 전개되기 때문에 증폭층의 폭을 조절하기가 매우 어렵다. 이 현상은 APD 제작에 있어서 수율과 관련이 깊다. 따라서 APD의 증폭층 폭을 tight하게 조절하기 위해서는 p-type 캐리어 농도를 높일 수 있는 gas-phase 확산 방식의 개발이 필요하다. 이 방식에는 Ampoule과 같은 closed tube 방식과 확산로와 같이 Gas를 지속적으로 흘려주면서 확산시키는 open-tube 방식이 있다. Ampoule 방식은 캐리어 농도 측면에서는 가장 좋은 방식이나, Ampoule의 size 및 온도 균일성 등으로 인해 생산성에 문제가 있다. 따라서 open-tube 방식의 확산기술개발은 매우 중요하다 할 수 있다. 본 연구에는 rapid thermal annealing (RTA) 방법에 의한 $Zn_3P_2$ 고체의 확산 방식과 DEZn MO source에 의한 Gas 확산 방식을 바탕으로 InP로의 확산된 Zn원자와 doping의 분포를 비교하였다. 실험결과, Gas 확산방식의 경우 Zn원자가 더욱 더 깊게 확산이 되었으며, 확산된 원자의 대부분이 도펀트로 작용함을 확인할 수 있었다.

• Journal of IKEEE
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• v.26 no.4
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• pp.728-735
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• 2022

In this work, we investigated a high-voltage (~4.5 kV) 4H-SiC power DMOSFET with modifications of current spreading layer (CSL), which was introduced below the p-well region for low on-resistance. These include the following: 1) a thickness of CSL (T_CSL) from 0 um to 0.9 um; 2) a doping concentration of CSL (N_CSL) from 1×10¹⁶ cm^-3 to 5×10¹⁶ cm^-3. The design is optimized using TCAD 2D-simulation, and we found that CSL helps to reduce specific on-resistance but also breakdown voltage. The resulting structures exhibit a specific on-resistance (R_on,sp) of 59.61 mΩ·cm², a breakdown voltage (V_B) of 5 kV, and a Baliga's Figure of Merit (BFOM) of 0.43 GW/cm².

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.1
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• pp.10-15
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• 2023

The carbonaceous materials have attracted much attention for utilization of anode materials for lithium-ion batteries. Among them, hollow carbon spheres have great advantages (high specific capacity and good rate capability) to replace currently used graphite anode materials, due to their unique features such as high surface areas, high electrical conductivities, and outstanding chemical and thermal stability. Herein, we have synthesized various sizes of hollow carbon spheres by a facile hardtemplate method and investigated the anode properties for lithium-ion batteries. The obtained hollow carbon spheres have uniform diameters of 350 ~ 600 nm by varying the template condition, and they do not have any cracks after the optimization of the process. Increasing the diameter of hollow carbon spheres decreases their specific capacities, since the larger hollow carbon spheres have more useless spaces inside that could have a disadvantage for lithium storage. The hollow carbon spheres have outstanding rate and cyclic performance, which is originated from the high surface area and high electrical properties of the hollow carbon spheres. Therefore, hollow carbon spheres with smaller diameters are expected to have higher specific capacities, and the noble channel structures through various doping approaches can give the great possibility of high lithium storage properties.