Browsing by Author "Yang, Chun-Hui"

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Characteristics of atomic-layer-deposited Al(2)O(3) high-k dielectric films grown on Ge substrates
(2008)
Cheng, Chao-Ching
;
Chien, Chao-Hsin
;
Luo, Guang-Li
;
Liu, Jun-Cheng
;
Kei, Chi-Chung
This paper describes the structural and electrical properties of Al(2)O(3) thin films grown through atomic layer deposition onto Ge substrates over a wide deposition temperature range (50-300 degrees C). From grazing-incidence X-ray reflectivity and X-ray photoelectron spectroscopy, we found that increasing the deposition temperature improved the Al(2)O(3) film density and its dielectric stoichiometry; nevertheless, dielectric intermixing between main Al(2)O(3) and interfacial GeO(2) appeared at temperatures above 200 degrees C, along with degradation of the GeO(2)/Ge interface. Accordingly, a relatively large gate leakage current (J(g)) and a high density of interfacial states D(it) (> 10(13) cm(-2) eV(-1)) were observed as a result of deterioration of the entire Al(2)O(3)/Ge structure at higher deposition temperatures. In addition, although subsequent high-temperature processing at 600 degrees C in a N(2) ambient could relieve the oxygen-excessive behavior further, i.e., to provide a more stoichiometric film, the accompanying GeO(x) volatilization close to the dielectric interface caused greater damage to the electrical performance. Only forming gas annealing (H(2)/N(2), 1:10) at low temperature (300 degrees C) improved the capacitance-voltage characteristics of the Pt/Al(2)O(3)/Ge structure, in terms of providing a lower value of D(it) (ca. 6 x 10(11) cm(-2) eV(-1)), a lower value of J(g), and a reduced hysteresis width.
Effects of interfacial sulfidization and thermal annealing on the electrical properties of an atomic-layer-deposited Al(2)O(3) gate dielectric on GaAs substrate
(2008-04-01)
Cheng, Chao-Ching
;
Chien, Chao-Hsin
;
Luo, Guang-Li
;
Yang, Chun-Hui
;
Chang, Ching-Chih
In this study we investigated the interfacial chemistry occurring between an atomic-layer-deposited Al(2)O(3) high-k film and a GaAs substrate and the impact of sulfidization and thermal annealing on the properties of the resultant capacitor. We observed that sulfide passivation of the Al(2)O(3)/GaAs structure improved the effect of Fermi level pinning on the electrical characteristics, thereby providing a higher oxide capacitance, smaller frequency dispersion, and reduced surface states, as well as decreased interfacial charge trapping and gate leakage currents. Photoemission analysis indicated that the (NH(4))(2)S-treated GaAs improved the quality of the as-deposited Al(2)O(3) thin film and preserved the stoichiometry of the dielectric during subsequent high-temperature annealing. This behavior was closely correlated to the diminution of GaAs native oxides and elemental arsenic defects and their unwanted diffusion. In addition, thermal processing under an O(2) atmosphere, relative to that under N(2), decreased the thickness of the Al(2)O(3) gate dielectric and relieved the gate leakage degradation induced by metallic arsenic; as a result, superior dielectric reliability was attained. We discuss the underlying thermochemical reactions that account for these experimental observations. (C) 2008 American Institute of Physics.
Effects of oxygen addition on physical properties of ZnO thin film grown by radio frequency reactive magnetron sputtering
(2011-02-03)
Hsu, Che-Wei
;
Cheng, Tsung-Chieh
;
Yang, Chun-Hui
;
Shen, Yi-Ling
;
Wu, Jong-Shinn
We deposited a ZnO thin film on a microslide glass substrate at room temperature by employing the RF reactive magnetron sputtering process. Our results revealed that deposition rate decreases by increasing O(2)/(Ar + O(2)) ratio that was caused by two mechanisms. The first mechanism was the reduction of plasma density and, thus, argon ion density; caused by the addition of highly electronegative oxygen. While the second mechanism was target poisoning caused by the oxidation of the target. Additionally, at the O(2)/(Ar + O(2)) ratio of similar to 0.3 and the help of XPS analysis the optimum stoichiometry of ZnO thin film (the highest binding energy and content fraction of O(1) peak (O-Zn bond)) and the best polycrystallinity (the lowest FWHM with largest grain size) was found. (C) 2010 Elsevier B.V. All rights reserved.
Electrical and material characterization of atomic-layer-deposited Al(2)O(3) gate dielectric on ammonium sulfide treated GaAs substrates
(2008)
Cheng, Chao-Ching
;
Chien, Chao-Hsin
;
Luo, Guang-Li
;
Chang, Ching-Chih
;
Kei, Chi-Chung
This paper has studied the electrical and interfacial properties of atomic-layerdeposited Al(2)O(3) thin film on ammonium-sulfide passivated GaAs. It was found that the Al(2)O(3) deposited at 300 degrees C relative to that at 100 degrees C showed the nearly four orders of magnitude reduction in gate leakage current at the capacitance-equivalent-thickness of 40 angstrom. The capacitance-voltage (C-V) characteristics displayed the higher oxide capacitance, reduced frequency dispersion and less charge trapping when GaAs receiving (NH(4))(2)S sulfide immersion; these improvements can be reasonably explained by the suppression of both native oxides and the resultant improved interface quality. Annealing as-deposited Al(2)O(3)/GaAs structures at high temperatures further reduces the Fermi level pinning effect on accumulation capacitance, however, causes an increase in C-V frequency dispersion and gate leakage current. We suggested that these phenomena are strongly associated to the amount of As-related defects resided at the dielectric/ substrate interface during thermal desorption.
Improved electrical properties of Gd2O3/GaAs capacitor with modified wet-chemical clean and sulfidization procedures
(2008)
Cheng, Chao-Ching
;
Chien, Chao-Hsin
;
Luo, Guang-Li
;
Tseng, Chih-Kuo
;
Chiang, Hsin-Che
In this study we demonstrated improved electrical characteristics of Gd2O3 dielectric thin films on n-GaAs substrate by manipulating wet-chemical clean and (NH4)(2)S passivation. With X-ray photoelectron spectroscopy analysis, the HCl-cleaned GaAs surface was characterized to possess oxide species mainly in the form of AS(2)O(x) near the outmost surface and Ga2Ox with elemental arsenic close to the interface. These undesirable components could be suppressed through rinsing in NH4OH alkaline solution and then performing sulfidization at 80 degrees C, resulting in alleviating the Fermi level pinning effect on Gd2O3/GaAs capacitor performance. Higher oxide capacitance and alleviated frequency dispersion at the accumulation/depletion regimes were achieved, accompanied by negligible charge trapping (< 100 mV). Accordingly, gate leakage J(g) was lowered to ca. 10(-5) A/cm(2) at gate voltage V-g = (V-FB + 1) V, which was comparable to the recently reported performance of HfO2/GaAs structure with an ultrathin Si/Ge interfacial layer. We attributed the electrical improvements to the enhanced stabilization of high-k/sulfur-terminated GaAs interface due to abatement of native oxides and excess arsenic segregation. (C) 2007 The Electrochemical Society.
Investigation of Characteristics of Multi-Function ZnO Thin Film Deposited With Various Argon and Oxygen Ratios
(2009)
Hsu, Che-Wei
;
Cheng, Tsung-Chieh
;
Yang, Chun-Hui
;
Shen, Yi-Ling
;
Wu, Jong-Shin
The ZnO thin film was deposited on a glass substrate at RT by the RF reactive magnetron sputtering method. Structural, chemical, optical, and hydrophilic/hydrophobic properties are measured by using a surface profilometer, an x-ray diffractometry (XRD), an x-ray photoelectron spectroscopy (XPS), a UV-VIS spectrophotometer, and a contact angle system, respectively. Results show that the deposition rate decreases with increasing O(2)/(Ar+O(2)) ratio. In additiion, the best stoichiometric and quality of ZnO thin film was observed at 0.30 Of O(2)/(Ar+O(2)) ratio, which shows the smallest FWHM and the strongest O-Zn strength. Regardless Of O(2)/(Ar+O(2)) ratio effect or thickness effect, high transmittance (> 86%) in the visible region is observed, while the UV-shielding characteristics depend upon both the magnitude of film thickness. The film thickness plays a more prominent role in controlling optical properties, especially in the UV-shielding characteristics, than the O(2)/(Ar+O(2)) ratio. However, the hydrophobic characteristics can be obtained when the glass coating with ZnO thin films. In general, with properly coated ZnO thin film, we can obtain a glass substrate which is highly transparent in the visible region, has good UV-shielding characteristics, and possesses highly hydrophobic characteristics (self-clean capability), which is highly suitable for applications in the glass industries.
Study of thermal stability of HfOxNy/Ge capacitors using postdeposition annealing and NH3 plasma pretreatment
(2007)
Cheng, Chao-Ching
;
Chien, Chao-Hsin
;
Luo, Guang-Li
;
Yang, Chun-Hui
;
Kuo, Mei-Ling
We studied the thermal stability of the as-deposited HfOxNy thin films on the Ge substrate by employing rapid thermal annealing. After undergoing high-temperature processing, we observed several interesting physical and electrical features presented in the HfOxNy/Ge system, including a large Ge out-diffusion (>15 atom %) into high-k films, positive shift of the flatband voltage, severe charge trapping, and increased leakage current. These phenomena are closely related to the existence of GeOx defective layer and the degree of resultant GeO volatilization. We abated these undesirable effects, especially for reducing the amount of Ge incorporation (< 5 atom %) and the substoichiometric oxide at dielectric-substrate interface, through performing NH3 plasma pretreatment on the Ge surface. These improvements can be interpreted in terms of a surface nitridation process that enhanced the thermal stability of the high-k/Ge interface. In addition, we measured that the conductance loss in inversion was still high and it revealed independence with respect to gate bias, reflecting the fact that the minority carriers in Ge can rapidly respond either through a diffusion mechanism or through midgap trap states residing in Ge bulk substrates. (C) 2007 The Electrochemical Society.
Thermochemical reaction of ZrOx(N-y) interfaces on Ge and Si substrates
(2006-07-03)
Cheng, Chao-Ching
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Chien, Chao-Hsin
;
Lin, Je-Hung
;
Chang, Chun-Yen
;
Luo, Guang-Li
We have studied the thermochemical characteristics of ZrOx(N-y)/Ge and Si interfaces by employing postdeposition annealing. We found that Ge oxide species severely desorbed from the inherent interfacial layer, which was speculated to retard the formation of Zr germanate during high-temperature processing. These unique features enable ZrOx(N-y)/Ge gate stack to show a better equivalent-oxide-thickness scalability as compared to ZrOx(N-y)/Si gate stack. However, the volatilization of GeOx-contained interfacial layer also caused the formation of small pits and/or holes in the overlying ZrOx(N-y) gate dielectrics, which was expected to cause deterioration in the electrical properties of fabricated high-k/Ge devices. (c) 2006 American Institute of Physics.
Ultrathin Si capping layer suppresses charge trapping in HfOxNy/Ge metal-insulator-semiconductor capacitors
(2007-01-01)
Cheng, Chao-Ching
;
Chien, Chao-Hsin
;
Luo, Guang-Li
;
Yang, Chun-Hui
;
Kuo, Mei-Ling
In this study the authors investigated the Ge outdiffusion characteristics of HfOxNy/Ge metal-insulator-semiconductor capacitors to determine their charge trapping behavior. Capping the Ge substrate with an ultrathin Si layer inhibits the incorporation of Ge into the high-k bulk dielectric in the form of GeOx, thereby diminishing the resultant oxide charge trapping. The thermal stability of the entire capacitor structure was also improved after performing an additional Si passivation process. (c) 2007 American Institute of Physics.