• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.48-48
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• 2009

최근 빠른 동작속도와 고 집적도를 얻기 위해 metal oxide semiconductor field effect transistor (MOSFET) 의 크기는 계속 해서 줄어들고 있다. 동시에 게이트의 절연층도 얇아지게 된다. 절연층으로 사용되는 $SiO_2$ 의 두께가 2nm 이하로 얇아 지게 되면 터널링에 의해 누설 전류가 발생하게 된다. 이 문제를 해결하기 위해 $SiO_2$ 를 대체할 고유전체 물질의 연구가 활발하다. 고유전체 물질 중에는 $ZrO_2,\;Al_2O_3,\;HfO_2$ 등이 많이 연구 되어 왔다. 하지만 유전상수 이외에 band gap energy, thermodynamic stability, recrystallization temperature 등의 특성이 좋지 않아 대체 물질로 문제점이 있다. 이를 보안하기 위해 산화물을 합금과 결합시키면 서로의 장점들이 합쳐져 기준들을 만족하는 물질을 만들 수 있고 $HfAlO_3$가 그 중 하나이다. Al를 첨가하는 이유는 문턱전압을 낮추기 위해서다. $HfAlO_3$는 유전상수 18.2, band gap energy 6.5 eV, recrystallization temperature 800 $^{\circ}C$이고 열역학적 특성이 안정적이다. 게이트 절연층은 전극과 기판사이에 적층구조를 이루고 있어 이방성인 드라이 에칭이 필요하고 공정 중 마스크물질과의 선택비가 높아야한다. 본 연구는 $HfAlO_3$박막을 $BCl_3/Ar,\;N_2/BCl_3/Ar$ 유도결합 플라즈마를 이용해 식각했다. 베이스 조건은 RF Power 500 W, DC-bias -100 V, 공정압력 15 mTorr, 기판온도 40 $^{\circ}C$ 이다. 가스비율, RF Power, DC-bias, 공정 압력에 의한 마스크물질과 의 선택비를 알아보았다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.12
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• pp.939-943
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• 2011

In this paper, reliability of the two sandwiched MIM capacitors of $Al_2O_3-HfO_2-Al_2O_3$ (AHA) and $SiO_2-HfO_2-SiO_2$ (SHS) with hafnium-based dielectrics was analyzed using two kinds of voltage stress; DC and AC voltage stresses. Two MIM capacitors have high capacitance density (8.1 fF/${\mu}m^2$ and 5.2 fF/${\mu}m^2$) over the entire frequency range and low leakage current density of ~1 nA/$cm^2$ at room temperature and 1 V. The charge trapping in the dielectric shows that the relative variation of capacitance (${\Delta}C/C_0$) increases and the variation of voltage linearity (${\alpha}$/${\alpha}_0$) gradually decreases with stress-time under two types of voltage stress. It is also shown that DC voltage stress induced greater variation of capacitance density and voltage linearity than AC voltage stress.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.2
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• pp.120-126
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• 2005

We have proposed a characteristic method to estimate real composition when multi component oxide films are deposited by ALD. Final atomic concentration ratio was theoretically calculated from the film densities and growth rates for $HfO_2$ and $Al_2O_3$ using ALD processed HfxAhOz mms.W e have transformed initial source feeding ratio during deposition to fins] atomic ratio in $Hf_xAl_yO_z$ films through thickness factors ($R_{HFO_2}$ ami $R_{Al_2O_3}$) ami concentration factor(C) defined in our experiments. Initial source feeding ratio could be transformed into the thickness ratio by each thickness factor. Final atomic ratio was calculated from thickness ratio by concentration factor. It has been successfully confirmed that the predicted atomic ratio was in good agreement with the actual measured value by ICP-MS analysis.

• Journal of the Korean institute of surface engineering
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• v.29 no.1
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• pp.36-44
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• 1996

Fe-Cr-Al and Fe-Cr-Al-Hf alloys prepared either by arc melting or by single roll casting(melt spinning) were exposed to air isothermally at 900~$1100^{\circ}C$. Whisker-like alumina was observed on the surface of the specimens when oxidized at $900^{\circ}C$, but convoluted alumina above $1000^{\circ}C$. All the Hf-free specimens and Hf-added specimens produced by single roll casting formed only external scale mainly composed of $Al_2O_3$ after oxidation at 900~$1100^{\circ}C$ for 100 hours, but Hf-added specimen produced by arc melting formed Hf-rich internal oxides below the thin external $Al_2O_3$ scale except at $900^{\circ}C$. Most of the rapidly solidified Fe-Cr-Al alloys showed smaller weight gains than conventionally casted ones besides Hf-added one oxidized at $1100^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.3
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• pp.226-232
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• 2023

As a potential alternative to flash memory, HfO₂/Al₂O₃ stacks appear to be a viable option as charge capture layers in charge trapping memories. The paper undertakes a review of HfO₂/Al₂O₃ stacks as charge trapping layers, with a focus on comparing the number, thickness, and post-deposition heat treatment and γ-ray and white x-ray treatment of such stacks. Compared to a single HfO₂ layer, the memory window of the 5-layered stack increased by 152.4% after O₂ annealing at ±12 V. The memory window enlarged with the increase in number of layers in the stack and the increase in the Al/Hf content in the stack. Furthermore, our comparison of the treatment of HfO₂/Al₂O₃ stacks with varying annealing temperatures revealed that an increased annealing temperature resulted in a wider storage window. The samples treated with O₂ and subjected to various γ radiation intensities displayed superior resistance. and the memory window increased to 12.6 V at ±16 V for 100 kGy radiation intensity compared to the untreated samples. It has also been established that increasing doses of white x-rays induced a greater number of deep defects. The optimization of stacking layers along with post-deposition treatment condition can play significant role in extending the memory window.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.2
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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.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.196-197
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• 2010

NAND형 charge trap flash (CTF) non-volatile memory (NVM) 소자가 30nm node 이하로 고집적화 되면서, 기존의 SONOS형 CTF NVM의 tunnel barrier로 쓰이는 SiO2는 direct tunneling과 stress induced leakage current (SILC)등의 효과로 인해 data retention의 감소 등 물리적인 한계에 이르렀다. 이에 따라 개선된 retention과 빠른 쓰기/지우기 속도를 만족시키기 위해서 tunnel barrier engineering (TBE)가 제안되었다. TBE NVM은 tunnel layer의 전위장벽을 엔지니어드함으로써 낮은 전압에서 전계의 민감도를 향상 시켜 동일한 두께의 단일 SiO2 터널베리어 보다 빠른 쓰기/지우기 속도를 확보할 수 있다. 또한 최근에 각광받는 high-k 물질을 TBE NVM에 적용시키는 연구가 활발히 진행 중이다. 본 연구에서는 Si3N4와 HfAlO (HfO2 : Al2O3 = 1:3)을 적층시켜 staggered의 새로운 구조의 tunnel barrier Capacitor를 제작하여 전기적 특성을 후속 열처리 온도와 방법에 따라 평가하였다. 실험은 n-type Si (100) wafer를 RCA 클리닝 실시한 후 Low pressure chemical vapor deposition (LPCVD)를 이용하여 Si3N4 3 nm 증착 후, Atomic layer deposition (ALD)를 이용하여 HfAlO를 3 nm 증착하였다. 게이트 전극은 e-beam evaporation을 이용하여 Al를 150 nm 증착하였다. 후속 열처리는 수소가 2% 함유된 질소 분위기에서 $300^{\circ}C$와 $450^{\circ}C$에서 Forming gas annealing (FGA) 실시하였고 질소 분위기에서 $600^{\circ}C{\sim}1000^{\circ}C$까지 Rapid thermal annealing (RTA)을 각각 실시하였다. 전기적 특성 분석은 후속 열처리 공정의 온도와 열처리 방법에 따라 Current-voltage와 Capacitance-voltage 특성을 조사하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.319.1-319.1
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• 2016

Recently, the Al-doped ZnO (ZnO:Al) films are intensively used in thin film a-Si solar cell applications due to their high transmittance and good conductivity. The textured ZnO:Al films are used to enhance the light trapping in thin film solar cells. The wet etch process is used to texture ZnO:Al films by dipping in diluted acidic solutions like HCl or HF. During that process the glass substrate could be damaged by the acidic solution and it may be difficult to apply it for the inline mass production process since it has to be done outside the chamber. In this paper we report a new technique to control the surface morphology of RF-sputtered ZnO:Al films. The ZnO:Al films are textured with vaporized HF formed by the mixture of HF and H2SiO3 solution. Even though the surface of textured ZnO:Al films by vapor etching process showed smaller and sharper surface structures compared to that of the films textured by wet etching, the haze value was dramatically improved. We achieved the high haze value of 78% at the wavelength of 540 nm by increasing etching time and HF concentration. The haze value of about 58% was achieved at the wavelength of 800 nm when vapor texturing was used. The ZnO:Al film texture by HCl had haze ratio of about 9.5 % at 800 nm and less than 40 % at 540 nm. In addition to low haze ratio, the texturing by HCl was very difficult to control etching and to keep reproducibility due to its very fast etching speed.

• Proceedings of the Korean Vacuum Society Conference
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• 2006.02a
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• pp.91-91
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• 2006

• Proceedings of the Korean Magnestics Society Conference
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• 2002.04a
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• pp.116-117
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• 2002