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A Novel Structure for the Improved Switching Time of 50V Class Vertical Power MOSFET
조두형,박건식,김광수 한국전기전자학회 2015 전기전자학회논문지 Vol.19 No.1
In this paper, a novel trench power MOSFET using a Separate-W-gated technique MOSFET (SWFET) is proposed. Because the SWFET has a very low QGD compared to other forms of technology, it can be applied to high-speed power systems. The results found that the SWFET-applied QGD was decreased by 40% when compared to simply using the more conventional trench gate MOSFET. CISS (input capacitance : CGS+CGD), COSS (output capacitance : CGD+CDS) and CRSS (reverse recovery capacitance : CGD) were improved by 24%, 40%, and 50%, respectively. The switching characteristics of the inverter circuit shows a 24.9% enhancement of reverse recovery time, and the power efficiency of the DC-DC buck converter increased by 14.2%. In addition, the proposed SWFET does not require additional process steps and There was no degradation in the electrical performance of the current-voltage and on-resistance.
Gate 전하를 감소시키기 위해 Separate Gate Technique을 이용한 Trench Power MOSFET
조두형,김광수,Cho, Doohyung,Kim, Kwangsoo 한국전기전자학회 2012 전기전자학회논문지 Vol.16 No.4
이 논문에서 Trench Power MOSFET의 스위칭 성능을 향상시키기 위한 Separate Gate Technique(SGT)을 제안하였다. Trench Power MOSFET의 스위칭 성능을 개선시키기 위해서는 낮은 gate-to-drain 전하 (Miller 전하)가 요구된다. 이를 위하여 제안된 separate gate technique은 얇은(~500A)의 poly-si을 deposition하여 sidewall을 형성함으로서, 기존의 Trench MOSFET에 비해 얇은 gate를 형성하였다. 이 효과로 gate와 drain에 overlap 되는 면적을 줄일 수 있어 gate bottom에 쌓이는 Qgd를 감소시키는 효과를 얻었고, 이에 따른 전기적인 특성을 Silvaco T-CAD silmulation tool을 이용하여 일반적인 Trench MOSFET과 성능을 비교하였다. 그 결과 Ciss(input capacitance : Cgs+Cgd), Coss(output capacitance : Cgd+Cds) 및 Crss(reverse recovery capacitance : Cgd) 모두 개선되었으며, 각각 14.3%, 23%, 30%의 capacitance 감소 효과를 확인하였다. 또한 inverter circuit을 구성하여, Qgd와 capacitance 감소로 인한 24%의 reverse recovery time의 성능향상을 확인하였다. 또한 제안된 소자는 기존 소자와 비교하여 어떠한 전기적 특성저하 없이 공정이 가능하다. In this paper, We proposed Separate Gate Technique(SGT) to improve the switching characteristics of Trench power MOSFET. Low gate-to-drain 전하 (Miller 전하 : Qgd) has to be achieved to improve the switching characteristics of Trench power MOSFET. A thin poly-silicon deposition is processed to form side wall which is used as gate and thus, it has thinner gate compared to the gate of conventional Trench MOSFET. The reduction of the overlapped area between the gate and the drain decreases the overlapped charge, and the performance of the proposed device is compared to the conventional Trench MOSFET using Silvaco T-CAD. Ciss(input capacitance : Cgs+Cgd), Coss(output capacitance : Cgd+Cds) and Crss(reverse recovery capacitance : Cgd) are reduced to 14.3%, 23% and 30% respectively. To confirm the reduction effect of capacitance, the characteristics of inverter circuit is comprised. Consequently, the reverse recovery time is reduced by 28%. The proposed device can be fabricated with convetional processes without any electrical property degradation compare to conventional device.
조두형,김광수 한국전자통신연구원 2014 ETRI Journal Vol.36 No.5
In this paper, a lateral power metal–oxide–semiconductor field-effect transistor with ultra-lowspecific on-resistance is proposed to be applied to a highvoltage(up to 200 V) integrated chip. The proposedstructure has two characteristics. Firstly, a high level ofdrift doping concentration can be kept because a tiltimplantedp-drift layer assists in the full depletion of then-drift region. Secondly, charge imbalance is avoided byan extended trench gate, which suppresses the trenchcorner effect occurring in the n-drift region and helpsachieve a high breakdown voltage (BV). Compared to aconventional trench gate, the simulation result shows a37.5% decrease in Ron.sp and a 16% improvement in BV.
조두형 대한의학회 2019 Journal of Korean medical science Vol.34 No.42
Background: Apart from its blood pressure-lowering effect by blocking the renin- angiotensin-aldosterone system, telmisartan, an angiotensin II type 1 receptor blocker (ARB), exhibits various ancillary effects including cardiovascular protective effects in vitro. Nonetheless, the protective effects of telmisartan in cerebrocardiovascular diseases are somewhat variable in large-scale clinical trials. Dysregulation of endothelial nitric oxide (NO) synthase (eNOS)-derived NO contributes to the developments of various vascular diseases. Nevertheless, the direct effects of telmisartan on endothelial functions including NO production and vessel relaxation, and its action mechanism have not been fully elucidated. Here, we investigated the mechanism by which telmisartan regulates NO production and vessel relaxation in vitro and in vivo. Methods: We measured nitrite levels in culture medium and mouse serum, and performed inhibitor studies and western blot analyses using bovine aortic endothelial cells (BAECs) and a hyperglycemic mouse model. To assess vessel reactivity, we performed acetylcholine (ACh)- induced vessel relaxation assay on isolated rat aortas. Results: Telmisartan decreased NO production in normoglycemic and hyperglycemic BAECs, which was accompanied by reduced phosphorylation of eNOS at Ser1179 (p-eNOS-Ser1179 ). Telmisartan increased the expression of protein phosphatase 2A catalytic subunit (PP2Ac) and co-treatment with okadaic acid completely restored telmisartan-inhibited NO production and p-eNOS-Ser1179 levels. Of the ARBs tested (including losartan and fimasartan), only telmisartan decreased NO production and p-eNOS-Ser1179 levels, and enhanced PP2Ac expression. Co-treatment with GW9662 had no effect on telmisartan-induced changes. In line with in vitro observations, telmisartan reduced serum nitrite and p-eNOS-Ser1179 levels, and increased PP2Ac expression in high fat diet-fed mice. Furthermore, telmisartan attenuated ACh-induced rat aorta relaxation. Conclusion: We demonstrated that telmisartan inhibited NO production and vessel relaxation at least in part by PP2A-mediated eNOS-Ser1179 dephosphorylation in a peroxisome proliferator- activated receptor γ-independent manner. These results may provide a mechanism that explains the inconsistent cerebrocardiovascular protective effects of telmisartan.
조두형,박건식,유승욱,김상기,이진환,김광수 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.3
The effect of N2O direct oxidation processes with re-oxidation on SiC/SiO2 interface characteristics has been investigated. With different oxidation and post oxidation annealing (POA) processes, the flat-band voltage, effective dielectric charge density, and interface trap density are obtained from the capacitance-voltage curves. For the proposed N2O direct oxidation processes with re-oxidation, oxides were grown in N2O ambient, diluted in high-purity N2 to 10% concentration, for 5 h at 1230 C. After the growth, some samples were annealed additionally at 1200 C in O2 or H2O for 20 min. N2O direct oxidation with re-oxidation processes was confirmed that SiC/SiO2 interface properties and dielectric stability have better performance than with other conventional oxidation processes. This oxidation technique is expected to improve gate dielectric stability for application to SiC MOS devices; in particular, it can be used to obtain high-quality SiC/SiO2 interface properties.