• Journal of the Korean Ceramic Society
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• v.24 no.1
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• pp.33-40
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• 1987

The investigation includes phase equilibria of Al2O3-HfO2 Cr2O3-ZrO2, Cr2O3-HfO2, Al2O3-Cr2O3-ZrO2, Al2O3-Cr2O3-HfO2, Al2O3-ZrO2-HfO2, Cr2O3-ZrO2-HfO2, Al2O3-Cr2O3-ZrO2-HfO2. In the systems the solubility near the end members has been studied at 1500$^{\circ}C$ and 1600$^{\circ}C$, respectively. Selective Compositions were investigated in the area of the guarternary system where the phae relation was examined.

• Korean Journal of Materials Research
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• v.29 no.8
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• pp.463-468
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• 2019

The electrical and interfacial properties of $HfO_2/Al_2O_3$ and $Al_2O_3/HfO_2$ dielectrics on AlN/p-Ge interface prepared by thermal atomic layer deposition are investigated by capacitance-voltage(C-V) and current-voltage(I-V) measurements. In the C-V measurements, humps related to mid-gap states are observed when the ac frequency is below 100 kHz, revealing lower mid-gap states for the $HfO_2/Al_2O_3$ sample. Higher frequency dispersion in the inversion region is observed for the $Al_2O_3/HfO_2$ sample, indicating the presence of slow interface states A higher interface trap density calculated from the high-low frequency method is observed for the $Al_2O_3/HfO_2$ sample. The parallel conductance method, applied to the accumulation region, shows border traps at 0.3~0.32 eV for the $Al_2O_3/HfO_2$ sample, which are not observed for the $Al_2O_3/HfO_2$ sample. I-V measurements show a reduction of leakage current of about three orders of magnitude for the $HfO_2/Al_2O_3$ sample. Using the Fowler-Nordheim emission, the barrier height is calculated and found to be about 1.08 eV for the $HfO_2/Al_2O_3$ sample. Based on these results, it is suggested that $HfO_2/Al_2O_3$ is a better dielectric stack than $Al_2O_3/HfO_2$ on AlN/p-Ge interface.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.477-477
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• 2008

For more than three decades, the gate dielectrics in CMOS devices are $SiO_2$ because of its blocking properties of current in insulated gate FET channels. As the dimensions of feature size have been scaled down (width and the thickness is reduced down to 50 urn and 2 urn or less), gate leakage current is increased and reliability of $SiO_2$ is reduced. Many metal oxides such as $TiO_2$, $Ta_2O_4$, $SrTiO_3$, $Al_2O_3$, $HfO_2$ and $ZrO_2$ have been challenged for memory devices. These materials posses relatively high dielectric constant, but $HfO_2$ and $Al_2O_3$ did not provide sufficient advantages over $SiO_2$ or $Si_3N_4$ because of reaction with Si substrate. Recently, $HfO_2$ have been attracted attention because Hf forms the most stable oxide with the highest heat of formation. In addition, Hf can reduce the native oxide layer by creating $HfO_2$. However, new gate oxide candidates must satisfy a standard CMOS process. In order to fabricate high density memories with small feature size, the plasma etch process should be developed by well understanding and optimizing plasma behaviors. Therefore, it is necessary that the etch behavior of $HfO_2$ and plasma parameters are systematically investigated as functions of process parameters including gas mixing ratio, rf power, pressure and temperature to determine the mechanism of plasma induced damage. However, there is few studies on the the etch mechanism and the surface reactions in $BCl_3$ based plasma to etch $HfO_2$ thin films. In this work, the samples of $HfO_2$ were prepared on Si wafer with using atomic layer deposition. In our previous work, the maximum etch rate of $BCl_3$/Ar were obtained 20% $BCl_3$/ 80% Ar. Over 20% $BCl_3$ addition, the etch rate of $HfO_2$ decreased. The etching rate of $HfO_2$ and selectivity of $HfO_2$ to Si were investigated with using in inductively coupled plasma etching system (ICP) and $BCl_3/Cl_2$/Ar plasma. The change of volume densities of radical and atoms were monitored with using optical emission spectroscopy analysis (OES). The variations of components of etched surfaces for $HfO_2$ was investigated with using x-ray photo electron spectroscopy (XPS). In order to investigate the accumulation of etch by products during etch process, the exposed surface of $HfO_2$ in $BCl_3/Cl_2$/Ar plasma was compared with surface of as-doped $HfO_2$ and all the surfaces of samples were examined with field emission scanning electron microscopy and atomic force microscope (AFM).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.382-382
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• 2010

The etch characteristics of the $HfAlO_3$ thin films and selectivity of $HfAlO_3$ to $SiO_2$ in $Cl_2/BCl_3$/Ar plasma were investigated in this work. The maximum etch rate was 108.7 nm/min and selectivity of $HfAlO_3$ to $SiO_2$ was 1.11 at $Cl_2$(3sccm)/$BCl_3$(4sccm)/Ar(16sccm), RF power of 500 W, DC-bias voltage of - 100 V, process pressure of 1 Pa and substrate temperature of $40^{\circ}C$. As increasing RF power and DC-bias voltage, etch rates of the $HfAlO_3$ thin films increased. Whereas as decreasing of the process pressure, those of the $HfAlO_3$ thin films were increased. The chemical reaction on the surface of the etched the $HfAlO_3$ thin films was investigated with X-ray photoelectron spectroscopy (XPS).

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.5
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• pp.8-14
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• 2007

In this paper, $HfO_2$/Hf stacked film has been applied as the gate dielectric in MOS devices. The $HfO_2$ thin film was deposited on p-type (100) silicon wafers by atomic layer deposition (ALD) using TEMAHf and $O_3$ as precursors. Prior to the deposition of the $HfO_2$ film, a thin Hf metal layer was deposited as an intermediate layer. Round-type MOS capacitors have been fabricated on Si substrates with 2000${\AA}$-thick Al or Pt top electrode. The prepared film showed the stoichiometric components. At the $HfO_2$/Si interface, both Hf-Si and Hf-Si-O bonds were observed, instead of Si-O bond. The sandwiched Hf metal layer suppressed the growing of $SiO_x$ layer so that $HfSi_xO_y$ layer was achieved. It seems that the intermediate Hf metal layer has a benefit for the enhancement of electric characteristics of gate dielectric in $HfO_2$/Si structure.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.304.2-304.2
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• 2016

Hafnium oxide-aluminum oxide (HfO2-Al2O3) dielectric films have been fabricated by Pulsed Laser Deposition (PLD), and their properties are studied in comparison with HfO2 films. As a gate dielectric of the TFT, in spite of its high dielectric constant, HfO2 has a small energy band gap and microcrystalline structure with rough surface characteristics. When fabricated by the device, it has the drawback of generating a high leakage current. In this study, the HfAlO films was obtained by Pulsed Laser Deposition with HfO2-Al2O3 target(chemical composition of (HfO2)86wt%(Al2O3)14wt%). The characteristics of the thin Film have been investigated by x-ray diffraction (XRD), atomic force microscopy (AFM) and spectroscopic ellipsometer (SE) analyses. The X-ray diffraction studies confirmed that the HfAlO has amorphous structure. The RMS value can be compared to the surface roughness via AFM analysis, it showed HfAlO thin Film has more lower properties than HfO2. The energy band gap (Eg) deduced by spectroscopic ellipsometer was increased. HfAlO films was expected to improved the interface quality between channel and gate insulator. Apply to an oxide thin Film Transistors, HfAlO may help improve the properties of device.

• Journal of the Korean Magnetics Society
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• v.10 no.4
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• pp.165-170
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• 2000

The purpose of this study is to investigate the effect of annealing conditions on physical and magnetic properties of Fe-Hf-N thin films. When the thin films were annealed in $N_2$ gas, a surface oxide layer, comprised of Fe$_2$O$_3$ and Fe$_3$O$_4$, was formed at the surface of the thin films and a Fe-Hf-O-N layer was also formed under this surface oxide layer. It was found that the thicknesses of the surface oxide layer and the Fe-Hf-O-N layer increased, as the annealing temperature increased. It was also found that if the thickness of the surface oxide layer was excluded in the property calculation, the soft magnetic properties of the annealed thin films were not much different from those of the as-deposited thin films. Therefore, it was suggested that the Fe-Hf-O-N layer formed under the surface oxide layer did not lose significantly the soft magnetic properties of the Fe-Hf-N films and the Fe-Hf-N films annealed in $N_2$gas showed the soft magnetic properties of the Fe-Hf-N and Fe-Hf-O-N multi-layers.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.12a
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• pp.86-88
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• 2003

Gate 산화막을 high-k 물질인 $HfO_2$ 박막을 이용하여 N-type MOS field effect transistor를 제작하였다. 전극은 poly-Si 전극을 사용하였다. Gate 산화막은 ALD 로 $Hf(N(CH_3)_2)_4$ 원료를 이용하여 $HfO_2$ 박막을 형성하였다. 산화제는 $H_{2}O$ 와 $O_3$ 를 사용하였는데, $H_{2}O$ 가 약간 우수하였으나 그 차이는 크지 않았다. $HfO_2$ 를 증착하기 전에 in-situ 로 $O_3$ 를 흘려 줌으로써 $SiO_2$를 얇게 형성하였는데, 이 결과 threshold voltage 가 약 0.2V 높아지고 saturation current 가 커지는 것이 관찰되었다. 이러한 결과는 $HfO_2$ 박막을 직접 channel 위에 증착하는 것보다 $O_3$ 를 이용 얇은 $SiO_2$ 를 형성하고 그 위에 $HfO_2$ 박막을 증착하는 방법이 transistor의 특성을 향상시키는 데 도움이 된다.

• Journal of the Korean Magnetics Society
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• v.7 no.5
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• pp.237-242
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• 1997

The microstructure and soft magnetic properties of as-deposited Fe-Hf-O thin film alloys, which are produced at $P_{O2}=10%$ by rf magnetron sputtering method in $Ar+O_2$ mixed gas atmosphere, is investigated. Newly developed $Fe_{82}Hf_{3.4}O_{14.6}$ film exhibits good soft magnetic properties with $4{\pi}M_s=17.7$ kG, $H_c=0.7$ Oe and ${\mu}_{eff}$(0.5~100MHz)=2,500, respectively. The Fe-Hf-O films are composed of $\alpha$-Fe nanograins and amorphous phase with larger amounts of Hf and O elements which chemically combine each other. With increasing Hf area fraction, Hf and O contents increased proportionally. It was considered that O content in films was determined by Hf contents, because O was chemically combined with Hf. It results from decreasing the $\alpha$-Fe grain size by precipitates (Hf and O), high electrical resistivity. The $Fe_{82}Hf_{3.4}O_{14.6}$ film exhibits the quality factor (Q=$\mu$'/$\mu$") of 25 at 20 MHz. These good frequency characteristics are considered to be superior to other films already reported.o other films already reported.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.82.1-82.1
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• 2012

란타늄 산화물 ($La_2O_3$) 박막은 하프늄 산화물 ($HfO_2$) 박막보다 높은 유전 상수와 높은 밴드 오프셋으로 인해 dynamic random access memory(DRAM)에서 유전체 재료로써 연구되어 왔다. 그리고 Lanthanum이 도핑된 HfO2이 더 높은 유전 상수와 낮은 누설 전류 밀도를 갖는 다는 사실이 이전에 보고 된 바 있다. 본 연구에서 우리는 ALD를 이용하여, TiN 하부 전극 위에 $La_2O_3$의 위치를 달리하는 $La_2O_3/HfO_2$의 나노 층상조직 구조(두께 10 nm)를 금속 - 절연체 - 금속 (MIM) 구조로 제작 하였다. ALD는 좋은 comformality와 넓은 지역 균일성을 가지며, 원자수준의 두께를 조절할 수 있다는 장점을 갖고 있다. 또한, 다양한 화학 물질들을 이용한 복합적 계층구조를 만들 수 있는 점과 $HfO_2$ 및 $La_2O_3$ 계층의 수직 위치를 정확하게 조절할 수 있는 점으로 본 연구에 적합한 증착 방법이다. HfO2 속에 $La_2O_3$ 층을 깊이에 따라 삽입함으로써 $HfO_2$ 계층에 La 도핑의 효과와 더불어 TiN 하부 전극 위의 $La_2O_3$과 $HfO_2$의 차이점을 확인 하였다. $HfO_2$은 $250^{\circ}C$에서 TDMAH와 물을 사용하여, $La_2O_3$은 동일한 온도에서 $La(iPrCp)_3$와 물을 사용하여 제작되었다. 화학적 구성 및 binding 구조는 X선 광전자 분광법 (XPS)을 통해 분석하였다. 전기적 특성(유전 상수 및 누설 전류)은 Capacitance-Voltage (CV)와 Current-Voltage (IV) 측정으로 확인하였다. 결과적으로, $La_2O_3$ 또는 $HfO_2$을 한 종류만 사용한 절연층의 전기적 특성보다, $La_2O_3/HfO_2$의 나노 층상조직 구조가 더 나은 특성 (누설 전류 밀도 : $5.5{\times}10^{-7}\;A/cm^2$ @-1MV/cm, EOT : 14.6)을 갖는다는 것을 확인했고, 더불어 $La_2O_3$의 흡습 성질로 인한 화학 구조와 전기적 특성의 일부 차이를 확인하였다. 본 연구에서는 $HfO_2$ 속에 $La_2O_3$층이 TiN 하부 전극 바로 위에 위치할 때, 즉, 공기 중에 노출되지 않은 $La_2O_3/HfO_2$ 구조에서 가장 좋은 특성의 MIM capacitor를 얻을 수 있었다.