• 한국전기전자재료학회논문지
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• 제23권12호
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• pp.924-928
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• 2010

In this study, $HfAlO_3$ thin films using gate insulator of MOSFET were etched in inductively coupled plasma. The etch characteristics of the $HfAlO_3$ thin films has been investigated by varying $O_2/BCl_3$/Ar gas mixing ratio, a RF power, a DC bias voltage and a process pressure. As the $O_2$ concentration increases further, $HfAlO_3$ was redeposited. As increasing RF power and DC bias voltage, etch rates of the $HfAlO_3$ thin films increased. Whereas, as decreasing of the process pressure, etch rates of the $HfAlO_3$ thin films increased. The chemical reaction on the surface of the etched the $HfAlO_3$ thin films was investigated with X-ray photoelectron spectroscopy (XPS). These peaks moved a binding energy. This chemical shift indicates that there are chemical reactions between the $HfAlO_3$ thin films and radicals and the resulting etch by-products remain on the surface.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.895-901
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• 2023

Oxide-dispersion- strengthened nickel alloys with Hf additions are expected to present high temperature mechanical properties and durable helium resistance based on first-principles density functional theory (DFT) calculations. Energetic and charge density evaluations of the helium behaviors were performed in Ni matrix, Y₂Hf₂O₇ oxide and the oxide/matrix interface. With the presence of coherent Y₂Hf₂O₇ in Ni matrix, chances of helium bubbles in Ni can be greatly diminished. The helium atoms shall occupy the interfacial site initially, then diffuse into in the octahedral sites of Y₂Hf₂O₇, and these oxide-captured He atoms prefer to separate individually. Much higher diffusion barrier of He in Y₂Hf₂O₇ than in nickel is related to the strong hybridization between interstitial He-1s and nearest-neighboring O-2p orbitals.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.359-360
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• 2013

The effect of electrode and deposition methods on non-linear interfacial resistive switching in HfO2 based $250{\times}250$ nm2 cross-point device was studied. HfO2 based device has the interfacial resistive switching properties of non-linearity and self-compliance current switching. The operating current in HfO2 based device was increased with negatively increasing the heat of formation energy in top electrode. Also, it was investigated that the operating current in HfO2 based device was changed with deposition methods of O3 reactant ALD, H2O reactant ALD and dc reactive sputtering, resulting the magnitude of the operating current and on/off ratio in order of HfO2 films deposited by dc reactive sputtering, H2O reactant ALD, and O3 reactant ALD. To investigate the effect of electrode and deposition methods on operating current of non-linear interfacial resistive switching in the cross-point device, X-ray photoelectron spectroscopy was measured. Through the analysis of O 1s spectra, non-lattice oxygen concentration, which is closely related to oxygen vacancies, was increased in order of Pt, TiN, and Ti top electrodes and in order of O3 reactant ALD, H2O reactant ALD, and O3 reactant ALD, and dc reactive sputtering deposition method. From all results, non-lattice oxygen concentration in ultra-thin HfO2 films play a crucial role in the operating current and memory states (LRS & HRS) in the non-linear interfacial resistive switching.

• 반도체디스플레이기술학회지
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• 제8권2호
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• pp.55-58
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• 2009

Density functional theory was used to investigate the adsorption and reaction of $HfCl_4$ with two hydroxyls on Si (001)-$2{\times}1$ surface in atomic layer deposition (ALD) process. We prepared a reasonable Si substrate which consisted of six inter-dimer dissociated $H_2O$ molecules and two intra-dimer dissociated $H_2O$ molecules. The $HfCl_4$must react with two hydroxyls to be a bulk-like structure. When $HfCl_4$ was adsorbed on a hydroxyl, there was energy benefit of -0.55 eV. Though there was energy loss for $HfCl_4$ to react with H of hydroxyl, thermal energy of ALD chamber would be enough to pass the energy barriers. There were five reaction pathways for $HfCl_4$ to react with two hydroxyls; inter-dimer, intra-dimer, cross-dimer, inter-row, and cross-row. Inter-row, inter-dimer and intra-dimer were relatively favorable among the five reaction pathways based on the energy difference. The electron densities between O and Hf in these three reactions were higher than the others and they had shorter Hf-O and O-O bond lengths than the other two reaction pathways.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.293-294
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• 2008

CaO stabilized cubic-$HfO_2$ is studied by using Density Functional Theory with GGA. When a Ca atom is substituted for a Hf atom, an oxygen vacancy is produced to satisfy the charge neutrality condition. When the oxygen vacancy is located at the first nearest site from the Ca atom, the total energy of $HfO_2$ is the most favorable. We calculate the energy barriers for the oxygen vacancy migration. The energy barriers between the first and the second nearest sites, the second and the third nearest sites, and the third and fourth nearest sites are 0.2, 0.5, 0.24 eV, respectively. The oxygen vacancies at the third and fourth nearest sites from the Ca atom represent the oxygen vacancies in undoped $HfO_2$. Therefore, the energy barrier for oxygen migration in $HfO_2$ gate dielectricis is 0.24eV, which can explain a leakage origin of gate dielectric.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.58-58
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• 2003

최근 전자재료분야 중 고집적 소자를 다루는 분야에서는 산화규소 유전박막의 두께가 얇아짐에 따라 상부전극과 하부기판 사이에서 발생하는 누설전류가 큰 문제가 되었다. 따라서 이를 극복하기 위해 고유전상수를 가진 두꺼운 유전박막을 사용하기 시작하였는데, 그 중 대표적 인 것이 하프늄옥사이드(HfO2)와 알루미나(A12O3)이다. HfO2의 장점은 큰 유전상수를 갖는다는 것이고, A1203의 장점은 열적 안정성 이 뛰어나며, 높은 bandgap에너지를 갖는 것인데, 이 둘의 장점을 살려서 보다 편리한 방법으로 박막을 증착한 것이 바로 HfAlO이다.

• 한국반도체및디스플레이장비학회:학술대회논문집
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• 한국반도체및디스플레이장비학회 2003년도 추계학술대회 발표 논문집
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• pp.42-44
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• 2003

최근 logic 소자의 gate oxide로 기존의 $SiO_2$, SiON보다 고유전, 작은 누설전류를 가지는 물질의 개발이 중요한 이슈가 되고 있다. 본 실험실에서는 Si 기판위에 $HfO_2$ 를 바로 증착하는 경우, 기판의 Si 이박막내로 확산하여 유전율이 저하되는 문제점을 인식하고, 기판과 $HfO_2$ 사이에 $AlO_x$를 방지막으로 사용하였다. 이 때, $AlO_x$의 Al precursor 는 TMA 로 고정하고, 산화제로는 $H_2O, O_2$-plasma, O_3$ 를 각각 사용하였다. 모든 $AlO_x/HfO_y$ 박막에서 매우 우수한 누설전류특성을 얻을 수 있었는데, 특히 $O_3$ 를 산화제로 사용한 $AlO_x$ 방지막의 경우 가장 우수한 특성을 보였다. 또한 질소 분위기에서 $800^{\circ}C$ 10 분간 열처리한 후, 방지막을 사용한 모든 경우에서 보다 향상된 열적 안정성을 관찰할 수 있었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2002년도 추계학술발표강연 및 논문개요집
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• pp.103-103
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• 2002

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 추계기술심포지움논문집
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• pp.115-121
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• 2002

In this research we have investigated the characteristics of ultra thin $HfO_2 /SiON$stack structure films using several analytical techniques. SiON layer was thermally grown on standard SCI cleaned silicon wafer at $825^{\circ}C$ for 12sec under $N_2$O ambient. $HfO_2 /SiON$$_4$/$H_2O$ as precursors and $N_2$as a carrier/purge gas. Solid HfCl$_4$was volatilized in a canister kept at $200^{\circ}C$ and carried into the reaction chamber with pure $N_2$carrier gas. $H_2O$ canister was kept at $12^{\circ}C$ and carrier gas was not used. The films were grown on 8-inch (100) p-type Silicon wafer at the $300^{\circ}C$ temperature after standard SCI cleaning, Spectroscopic ellipsometer and TEM were used to investigate the initial growth mechanism, microstructure and thickness. The electrical properties of the film were measured and compared with the physical/chemical properties. The effects of heat treatment was discussed.

• 한국전기전자재료학회논문지
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• 제36권2호
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• pp.125-128
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• 2023

Recently, as the process of the MOS device becomes more detailed, and the degree of integration thereof increases, many problems such as leakage current due to an increase in electron tunneling due to the thickness of SiO₂ used as a gate oxide have occurred. In order to overcome the limitation of SiO₂, many studies have been conducted on HfO₂ that has a thermodynamic stability with silicon during processing, has a higher dielectric constant than SiO₂, and has an appropriate band gap. In this study, HfO₂, which is attracting attention in various fields, was doped with Al and the change in properties according to its concentration was studied. Al-doped HfO₂ thin film was deposited using Plasma Enhanced Atomic Layer Deposition (PEALD), and the structural and electrical characteristics of the fabricated MIM device were evaluated. The results of this study are expected to make an essential cornerstone in the future field of next-generation semiconductor device materials.