• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 춘계학술대회
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• pp.789-790
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• 2013

기존 MOS (Metal-Oxide-Semiconductor) 소자의 게이트 산화막으로 사용된 $Er_2O_3/SiO_2$ 더블레이어 층은 낮은 누설전류와 높은 캐패시턴스를 갖는 장점을 가지고 있다. 본 논문에서는 이 더블레이어 층을 비휘발성 메모리 소자의 전하포획층으로 처음 적용하여 우수한 성능의 메모리 특성을 얻을 수 있었다. 소자를 제작하기 전에 EDISON Nanophysics 시뮬레이션을 통해 낮은 누설 전류값과 높은 캐패시턴스 값을 기준으로 하여 산화막 두께를 최적화하였다. 이 후, 최적화된 조건으로 금속실리사이드 소스/드레인, 10 um/ 10um의 채널 넓이/길이를 갖는 비휘발성 메모리 소자를 제작하였다. 그 결과, 11 V, 50 ms의 프로그램 특성, -11 V, 500 ms의 소거 특성 및 10년의 기억유지 특성, $10^4$의 내구성 특성을 얻을 수 있었다.

• 한국재료학회지
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• 제1권1호
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• pp.17-22
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• 1991

불순물이 주입된 실리콘 기판에 500 두께의 탄탈륨 박막을 증착한 후 실리사이드를 형성시키기 위해 아르곤 분위기에서 급속열처리(RTA)률 하였다. 형성된 $TaSi_2$와 불순물의 거동은 XRD, SEM, 4-point probe, HP4145와 SIMS로 조사하였다. 불순물의 종류에 관계없이 $TaSi_2$는 RTA 온도가 $800^{\circ}C$일때 형성되기 시작하였으며 $1000^{\circ}C$이상에서 증착된 Ta가 전부 $TaSi_2$로 상 전이가 일어났다. 또한 $TaSi_2/P^+$영역에 대한 접촉저항간은 contact size가 $0.9{\times}0.9({\mu}{m^2}$)일때 $22{\Omega}$ 낮은값을 가졌으며 이온 주입된 불순물은 RTA처리시 형성된 $TaSi_2$층으로 out-diffusion이 일어났다.

• 한국재료학회지
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• 제14권6호
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• pp.402-406
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• 2004

$WSi_2$, $TiSi_2$, $CoSi_2$, and $TaSi_2$ are general silicides used today in semiconductor devices. $WSi_2$ thin films have been proposed, studied and used recently in CMOS technology extensively to reduce sheet resistance of polysilicon and $n^{+}$ region. However, there are several serious problems encountered because $WSi_2$ is oxidized and forms a native oxide layer at the interface between $WSi_2$ and $Si_3$$N_4$. In this study, we have introduced 20 $slm-N_2$ gas from top to bottom of the furnace in order to control native oxide films between $WSi_2$ and $Si_3$$N_4$ film. In resulting SEM photographs, we have observed that the native oxide films at the surface of $WSi_2$ film are removed using the long injector system.

• 한국재료학회지
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• 제4권1호
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• pp.81-89
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• 1994

전자빔 증착법을 사용하여 10nm두께의 Ti과 18nm두께의 Co를 Si(100)기판에 증착한 후, $N_{2}$분위기에서 $900^{\circ}C$, 20초 급속 열처리하여, Co/Ti 이중금속박막의 역전을 유도함으로서 $CoSi_{2}$박막을 형성하였다. 4점 탐침기로 측정한 면저항은 3.9Ω/ㅁ 었으며, 열처리 시간을 증가해도 이값은 유지하여 열적 안정성을 나타내었다. XRD 결과는 형성된 실리사이드는 기판과 에피관계를 갖는 $CoSi_{2}$상 임을 보였으며, SEM 사진은 평탄한 표면을 나타내었다. 단면 TEM 사진은 기판위에 형성된 박막층은 70nm 두께의 $CoSi_{2}$ 에피박막과 그위에 두개의 C0-Ri-Si합금층등 세개의 층으로 되어 있음을 보였다. AES 분석은, 기판상의 자연산화막을 형성할 수 있었음을 보여주었다. AES분석은, 기판상의 잔연산화막이 열처리초기, Ti에 의해 제거된후 Co가 원자적으로 깨끗한 Si기판에 확산하여 $CoSi_{2}$에피박막을 형성할 수 있었음을 보여주었다. $700^{\circ}C$, 20초 + $900^{\circ}C$, 20초 이중 열처리를 한 경우, $CoSi_{2}$결정성장으로 면저항값은 약간 낮아졌으나, 박막의 표면과 계면이 거칠었다. 이 $CoSi_{2}$에피박막의 실제 소자에의 적용방안과 막의 역전을 통한 에피박막형성의 기제를 열역학 및 kinetics 관점에서 고찰하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.362-362
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• 2014

Atomic layer deposition (ALD) can be regarded as a special variation of the chemical vapor deposition method for reducing film thickness. ALD is based on sequential self-limiting reactions from the gas phase to produce thin films and over-layers in the nanometer scale with perfect conformality and process controllability. These characteristics make ALD an important film deposition technique for nanoelectronics. Tantalum pentoxide ($Ta_2O_5$) has a number of applications in optics and electronics due to its superior properties, such as thermal and chemical stability, high refractive index (>2.0), low absorption in near-UV to IR regions, and high-k. In particular, the dielectric constant of amorphous $Ta_2O_5$ is typically close to 25. Accordingly, $Ta_2O_5$ has been extensively studied in various electronics such as metal oxide semiconductor field-effect transistors (FET), organic FET, dynamic random access memories (RAM), resistance RAM, etc. In this experiment, the variations of chemical and interfacial state during the growth of $Ta_2O_5$ films on the Si substrate by ALD was investigated using in-situ synchrotron radiation photoemission spectroscopy. A newly synthesized liquid precursor $Ta(N^tBu)(dmamp)_2$ Me was used as the metal precursor, with Ar as a purging gas and $H_2O$ as the oxidant source. The core-level spectra of Si 2p, Ta 4f, and O 1s revealed that Ta suboxide and Si dioxide were formed at the initial stages of $Ta_2O_5$ growth. However, the Ta suboxide states almost disappeared as the ALD cycles progressed. Consequently, the $Ta^{5+}$ state, which corresponds with the stoichiometric $Ta_2O_5$, only appeared after 4.0 cycles. Additionally, tantalum silicide was not detected at the interfacial states between $Ta_2O_5$ and Si. The measured valence band offset value between $Ta_2O_5$ and the Si substrate was 3.08 eV after 2.5 cycles.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.133-133
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• 2008

Recently, as the down-scailing of field-effect transistor devices continues, Schottky-barrier field-effect transistors (SB-FETs) have attracted much attention as an alternative to conventional MOSFETs. SB-FETs have advantages over conventional devices, such as low parasitic source/drain resistance due to their metallic characteristics, low temperature processing for source/drain formation and physical scalability to the sub-10nm regime. The good scalability of SB-FETs is due to their metallic characteristics of source/drain, which leads to the low resistance and the atomically abrupt junctions at metal (silicide)-silicon interface. Nevertheless, some reports show that SB-FETs suffer from short channel effect (SCE) that would cause severe problems in the sub 20nm regime.[Ouyang et al. IEEE Trans. Electron Devices 53, 8, 1732 (2007)] Because source/drain barriers induce a depletion region, it is possible that the barriers are overlapped in short channel SB-FETs. In order to analyze the SCE of SB-FETs, we carried out systematic studies on the Schottky barrier overlapping in short channel SB-FETs using a SILVACO ATLAS numerical simulator. We have investigated the variation of surface channel band profiles depending on the doping, barrier height and the effective channel length using 2D simulation. Because the source/drain depletion regions start to be overlapped each other in the condition of the $L_{ch}$~80nm with $N_D{\sim}1\times10^{18}cm^{-3}$ and $\phi_{Bn}$ $\approx$ 0.6eV, the band profile varies as the decrease of effective channel length $L_{ch}$. With the $L_{ch}$~80nm as a starting point, the built-in potential of source/drain schottky contacts gradually decreases as the decrease of $L_{ch}$, then the conduction and valence band edges are consequently flattened at $L_{ch}$~5nm. These results may allow us to understand the performance related interdependent parameters in nanoscale SB-FETs such as channel length, the barrier height and channel doping.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.302-303
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• 2010

Generally, the high energy lithium ion batteries depend intimately on the high capacity of electrode materials. For anode materials, the capacity of commercial graphite is unlike to increase much further due to its lower theoretical capacity of 372 mAhg-1. To improve upon graphite-based negative electrode materials for Li-ion rechargeable batteries, alternative anode materials with higher capacity are needed. Therefore, some metal anodes with high theoretic capacity, such as Si, Sn, Ge, Al, and Sb have been studied extensively. This work focuses on ternary Si-M1-M2 composite system, where M1 is Ge that alloys with Li, which has good cyclability and high specific capacity and M2 is Mo that does not alloy with Li. The Si shows the highest gravimetric capacity (up to 4000mAhg-1 for Li21Si5). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. Si thin film is more resistant to fracture than bulk Si because the film is firmly attached to the substrate. Thus, Si film could achieve good cycleability as well as high capacity. To improve the cycle performance of Si, Suzuki et al. prepared two components active (Si)-active(Sn, like Ge) elements film by vacuum deposition, where Sn particles dispersed homogeneously in the Si matrix. This film showed excellent rate capability than pure Si thin film. In this work, second element, Ge shows also high capacity (about 2500mAhg-1 for Li21Ge5) and has good cyclability although it undergoes a large volume change likewise Si. But only Ge does not use the anode due to its costs. Therefore, the electrode should be consisted of moderately Ge contents. Third element, Mo is an element that does not alloys with Li such as Co, Cr, Fe, Mn, Ni, V, Zr. In our previous research work, we have fabricated Si-Mo (active-inactive elements) composite negative electrodes by using RF/DC magnetron sputtering method. The electrodes showed excellent cycle characteristics. The Mo-silicide (inert matrix) dispersed homogeneously in the Si matrix and prevents the active material from aggregating. However, the thicker film than $3\;{\mu}m$ with high Mo contents showed poor cycling performance, which was attributed to the internal stress related to thickness. In order to deal with the large volume expansion of Si anode, great efforts were paid on material design. One of the effective ways is to find suitably three-elements (Si-Ge-Mo) contents. In this study, the Si based composites of 45~65 Si at.% and 23~43 Ge at.%, and 12~32 Mo at.% are evaluated the electrochemical characteristics and cycle performances as an anode. Results from six different compositions of Si-Ge-Mo are presented compared to only the Si and Ge negative electrodes.