• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.284-284
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• 2011

Ion sensitive field effect transistor (ISFET)는 용액 중의 각종 이온 농도를 측정하는 반도체 이온 센서이다. ISFET는 작은 소자 크기, 견고한 구조, 즉각적인 반응속도, 기존의 CMOS공정과 호환이 가능하다는 장점이 있다. ISFET의 기본 구조는 기존의 metal oxide semiconductor field effect transistor (MOSFET)에서 고안되었으며, ISFET는 기존의 MOSFET의 게이트 전극 부분이 기준전극과 전해질로 대체되어진 구조를 가지고 있다. ISFET소자의 pH 감지 메커니즘은 감지막의 표면에서 pH용액의 수소이온이 막의 표면에 속박되어 표면전위의 변화를 유발하는 것에 기인한다. 그 결과, 수소이온의 농도에 따라 ISFET의 문턱전압의 변화를 일으키게 되고 드레인 전류의 양 또한 달라지게 된다. 한편, ISFET의 좋은 pH감지특성과 높은 출력특성을 얻기 위하여 high-k물질들이 감지막으로써 지속적으로 연구되어져 왔다. 그 중 Al2O3와 HfO2는 높은 유전상수와 좋은 pH 감지능력으로 인하여 많은 연구가 이루어져온 물질이다. 하지만 HfO2는 높은 유전상수를 갖음에도 불구하고 화학용액에 대한 non-ideal 효과에 취약하다는 보고가 있다. 반면에 Al2O3의 유전상수는 HfO2보다 작지만 화학용액으로 인한 손상에 대하여 강한 immunity가 있는 재료이다. 본 연구에서는, 이러한 각각의 high-k 물질들의 단점을 보안하기 위하여 SiO2/HfO2/Al2O3(OHA) 적층막을 이용한 ISFET pH 센서를 제작하였으며 SOI 기판에서 구현되었다. SOI기판에서 OHA 적층막을 이용한 ISFET 제작이 이루어짐에 따라서 소자의 signal to noise 비율을 증대 시킬것으로 기대된다. 실제로 SOI-ISFET와 같이 제작된 SOI-MOSFET는 1.8${\times}$1010의 높은 on/off 전류 비율을을 보였으며 65 mV/dec의 subthreshold swing 값을 갖음으로써, 우수한 전기적 특성을 보이는 ISFET가 제작이 되었음을 확인 하였다. OHA 감지 적층막의 각 층은 양호한 계면상태, 높은 출력특성, 화학용액에 대한non-ideal 효과에 강한 immunity을 위하여 적층되었다. 결론적으로 SOI과 OHA 적층감지막을 이용하여 우수한 pH 감지 특성을 보이는 pH 센서가 제작되었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.3
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• pp.146-151
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• 2018

In this study, we compared the threshold-voltage extraction methods of accumulation-type JLDG (junctionless double-gate) MOSFETs (metal-oxide semiconductor field-effect transistors). Threshold voltage is the most basic element of transistor design; therefore, accurate threshold-voltage extraction is the most important factor in integrated-circuit design. For this purpose, analytical potential distributions were obtained and diffusion-drift current equations for these potential distributions were used. There are the ${\phi}_{min}$ method, based on the physical concept; the linear extrapolation method; and the second and third derivative method from the $I_d-V_g$ relation. We observed that the threshold-voltages extracted using the maximum value of TD (third derivatives) and the ${\phi}_{min}$ method were the most reasonable in JLDG MOSFETs. In the case of 20 nm channel length or more, similar results were obtained for other methods, except for the linear extrapolation method. However, when the channel length is below 20 nm, only the ${\phi}_{min}$ method and the TD method reflected the short-channel effect.

• Journal of Power Electronics
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• v.13 no.6
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• pp.1080-1089
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• 2013

In this paper, the superposition principle of a heat sink temperature rise is verified based on the mathematical model of a plate-fin heat sink with two mounted heat sources. According to this, the distributed coupling thermal impedance matrix for a heat sink with multiple devices is present, and the equations for calculating the device transient junction temperatures are given. Then methods to extract the heat sink thermal impedance matrix and to measure the Epoxy Molding Compound (EMC) surface temperature of the power Metal Oxide Semiconductor Field Effect Transistor (MOSFET) instead of the junction temperature or device case temperature are proposed. The new thermal impedance model for the power converters in Switched Reluctance Motor (SRM) drivers is implemented in MATLAB/Simulink. The obtained simulation results are validated with experimental results. Compared with the Finite Element Method (FEM) thermal model and the traditional thermal impedance model, the proposed thermal model can provide a high simulation speed with a high accuracy. Finally, the temperature rise distributions of a power converter with two control strategies, the maximum junction temperature rise, the transient temperature rise characteristics, and the thermal coupling effect are discussed.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.313-319
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• 2022

AlGaN/GaN based HfO₂ MOSHEMT (metal oxide semiconductor high electron transistor) with different gate recess depth was simulate to demonstrate a successful normally-off operation of the transistor. Three types of the HEMT structures including a conventional HEMT, a gate-recessed HEMT with 3 nm thick AlGaN layer, and MIS-HEMT without AlGaN layer in the gate region. The conventional HEMT showed a normally-on characteristics with a drain current of 0.35 A at V_G = 0 V and V_DS = 15 V. The recessed HEMT with 3 nm AlGaN layer exhibited a decreased drain current of 0.15 A under the same bias condition due to the decrease of electron concentration in 2DEG (2-dimensional electron gas) channel. For the last HEMT structure, distinctive normally- off behavior of the transistor was observed, and the turn-on voltage was shifted to 0 V.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.8
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• pp.593-600
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• 2010

In this paper, High brightness LED (light-emitting diodes) driver IC (integrated circuit) using new current sensing circuit is proposed. This LED driver IC can provide a constant current with high current precision over a wide input voltage range. The proposed current-sensing circuit is composed of a cascode current sensor and a current comparator with only one reference voltage. This IC minimizes the voltage stress of the MOSFET (metal oxide semiconductor field effect transistor) from the maximum input voltage and has low power consumption and chip area by using simple-structured comparator and minimum bias current. To confirm the functioning and characteristics of our proposed LED driver IC, we designed a buck converter. The LED current ripple of the designed IC is in ${\pm}5%$ and a tolerance of the average LED current is lower than 2.43%. This shows much improved feature than the previous method. Also, protections for input voltage and operating temperature are designed to improve the reliability of the designed IC. Designed LED driver IC uses 1.0 ${\mu}m$ X-Fab. BiCMOS process parameters and electrical characteristics and functioning are verified by spectre (Cadence) simulation.

• International Journal of Contents
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• v.8 no.2
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• pp.52-59
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• 2012

This study uses digital imaging and communications in medicine (DICOM) files acquired after CT scan to obtain the absorbed dose distribution inside the body by using the patient's actual anatomical data; uses geometry and tracking (Geant)4 as a way to obtain the accurate absorbed dose distribution inside the body. This method is easier to establish the radioprotection plan through estimating the absorbed dose distribution inside the body compared to the evaluation of absorbed dose using thermo-luminescence dosimeter (TLD) with inferior reliability and accuracy because many variables act on result values with respect to the evaluation of the patient's absorbed dose distribution in diagnostic imaging and the evaluation of absorbed dose using phantom; can contribute to improving reliability accuracy and reproducibility; it makes significance in that it can implement the actual patient's absorbed dose distribution, not just mere estimation using mathematical phantom or humanoid phantom. When comparing the absorbed dose in polymethly methacrylate (PMMA) phantom measured in metal oxide semiconductor field effect transistor (MOSFET) dosimeter for verification of Geant4 and the result of Geant4 simulation, there was $0.46{\pm}4.69%$ ($15{\times}15cm^2$), and $-0.75{\pm}5.19%$ ($20{\times}20cm^2$) difference according to the depth. This study, through the simulation by means of Geant4, suggests a new way to calculate the actual dose of radiation exposure of patients through DICOM interface.

• Proceedings of the KIPE Conference
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• 2007.11a
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• pp.69-71
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• 2007

Need correct analysis of thrust for control performance improvement of HB-LPM (Hybrid type Linear Pulse Motor). It is difficult to analyze HB-LPM's thrust. In this paper, HB-LPM's thrust is expressed to mathematical expression. And it is proved validity of this numerical formula by thrust measurement system. Two phase driver is composed. It is verified validity of numerical formula that measure waveform of electric current and voltage that is supplied in each phase. In this study, composed two phase drive driver, advantage of this IGBT element 6 by accumulated IPM module 1 Driver composition possible. That is, can economize 1 moule. In other words, Driver composition is available by IGBT or metal oxide semiconductor field effect transistor element 4. This is economical big gain.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.28-30
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• 2007

Need analysis of correct thrust for control performance improvement of HB-LPM (Hybrid type Linear Pulse Motor). It is difficult to analyze HB-LPM's thrust. In this paper, HB-LPM's thrust is expressed to mathematical expression. And it is proved validity of this numerical formula by thrust measurement system. Two phase driver is composed. It is verified validity of numerical formula that measure waveform of electric current and voltage that is supplied in each Phase. In this study, composed two phase drive driver, advantage of this IGBT element 6 by accumulated IPM module 1 Driver composition possible. That is, can economize 1 module. In other words, Driver composition is available by IGBT or metal oxide semiconductor field effect transistor element 4. This is economical big gains.

• ETRI Journal
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• v.39 no.1
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• pp.62-68
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• 2017

In this paper, we present the design and characterization analysis of a cascode GaN field-effect transistor (FET) for switching power conversion systems. To enable normally-off operation, a cascode GaN FET employs a low breakdown voltage (BV) enhancement-mode Si metal-oxide-semiconductor FET and a high-BV depletion-mode (D-mode) GaN FET. This paper demonstrates a normally-on D-mode GaN FET with high power density and high switching frequency, and presents a theoretical analysis of a hybrid cascode GaN FET design. A TO-254 packaged FET provides a drain current of 6.04 A at a drain voltage of 2 V, a BV of 520 V at a drain leakage current of $250{\mu}A$, and an on-resistance of $331m{\Omega}$. Finally, a boost converter is used to evaluate the performance of the cascode GaN FET in power conversion applications.

• Journal of Sensor Science and Technology
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• v.13 no.2
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• pp.90-95
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• 2004

Protein and gene detection have been growing importance in medical diagnostics. Field effect transistor (FET) - type biosensors have many advantages such as miniaturization, standardization, and mass-production. In this work, we have fabricated metal-oxide-semiconductor (MOS) FET that operates as molecular recognitions based electronic sensor. Measurements were taken with the devices under phosphate buffered saline solution. The drain current ($I_{D}$) was decreased after forming self-assembled mono-layers (SAMs) used to capture the protein, which resulted from the negative charges of SAMs, and increased after forming protein by 11.5% at $V_{G}$ = 0 V due to the positive charges of protein.