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ABSTRACT: Fluorine passivation in poly-Si/TaN/HfO<sub>2</sub>/p-Si and poly-Si/TaN/HfSiON/HfO<sub>2</sub>/p-Si gate stacks with varying TaN thickness through gate ion implantation has been studied. It has been found that when TaN thickness was less than 15 nm, mobility and subthreshold swing improved significantly in HfO<sub>2</sub> nMOSFETs; while there was little performance improvement in HfSiON/HfO<sub>2</sub> nMOSFETs due to the blocking of F atoms by the HfSiON layer in gate dielectrics, as has been proved by the electron energy loss spectroscopy mapping
IEEE Electron Device Letters 04/2007; 28(3):195-197. · 2.85 Impact Factor
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M. S. Akbar,
C. H. Choi,
S. J. Rhee,
S. A. Krishnan,
C. Y. Kang, M. H. Zhang,
T. Lee,
I. J. Ok,
F. Zhu,
H.-S. Kim,
J. C. Lee
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ABSTRACT: A novel stress-anneal approach has been investigated to separate the role of electrons and hole charge trappings in Hf-based gate oxides. It is observed that heat treatment following a stress experiments on Hf-based MOSFET can effectively eliminate electron trapping in the oxide. We also report that hole accumulation in the bulk of the Hf-based dielectrics is primarily responsible for dielectric breakdown, though both holes and electrons are trapped in the dielectrics. The Si interface quality does not seem to degrade significantly
IEEE Electron Device Letters 03/2007; · 2.85 Impact Factor
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M. H. Zhang,
M. Oye,
B. Cobb,
F. Zhu,
H. S. Kim,
I. J. Ok,
J. Hurst,
S. Lewis,
A. Holmes,
J. C. Lee,
S. Koveshnikov,
W. Tsai,
M. Yakimov,
V. Torkanov,
S. Oktyabrsky
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ABSTRACT: The interfacial change of HfO2/Si/n-GaAs gate stacks after high temperature annealing has been characterized using x-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and capacitance-voltage measurement. The properties of the interface are sensitive to the amount of incorporated oxygen. XPS measurement shows the formation of gallium and arsenic oxides with increasing annealing temperature. A PL emission from the Si interfacial passivation layer was observed after 900 °C annealing. With more oxygen incorporation, this PL emission was quenched. The measurement of the interface state density proved the generation of deep traps with too much oxygen incorporation. Depletion-mode metal-oxide-semiconductor field effect transistors using postdeposition annealing at 600 °C with and without post-metal-annealing at 900 °C have also been fabricated and characterized. Too much oxygen incorporation resulted into the degradation of mobility, subthreshold swing, and transconductance. The interfacial gallium and arsenic oxides might act as deep traps.
Journal of Applied Physics 02/2007; 101(3):034103-034103-5. · 2.17 Impact Factor
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ABSTRACT: Sputtered Hf <sub>1-x</sub> Si <sub>x</sub> O <sub>2</sub>/ Si /n -type GaAs gate stacks with x=0 , 30%, and 47% have been characterized using x-ray photoelectron spectroscopy, photoluminescence, and capacitance-voltage (CV) measurements. Incorporating Si into Hf O <sub>2</sub> improves both frequency dispersion and hysteresis. Compared to Hf O <sub>2</sub> , 30% and 47% Hf <sub>1-x</sub> Si <sub>x</sub> O <sub>2</sub> have a lower interface state density and stronger photoluminescence intensity. At the same capacitance equivalent thickness, Hf O <sub>2</sub> and 30% Hf <sub>1-x</sub> Si <sub>x</sub> O <sub>2</sub> have a smaller leakage current density than 47% Hf <sub>1-x</sub> Si <sub>x</sub> O <sub>2</sub> . It is concluded that Hf <sub>1-x</sub> Si <sub>x</sub> O <sub>2</sub> with the composition near 30% is a good high- k dielectric candidate for metal-oxide-semiconductor device application.
Applied Physics Letters 08/2006; · 3.84 Impact Factor
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M. H. Zhang,
S. J. Rhee,
C. Y. Kang,
C. H. Choi,
M. S. Akbar,
S. A. Krishnan,
T. Lee,
I. J. Ok,
F. Zhu,
H. S. Kim,
Jack C. Lee
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ABSTRACT: N-type metal-oxide-semiconductor field-effect transistors (N-MOSFETs) using HfTaO with varying Ta composition (20%, 30%, 40%, and 50%) have been fabricated and characterized. Crystallization temperatures of HfTaO with varying Ta composition were also measured. It was found that HfTaO with 40% Ta exhibited the highest crystallization temperature of 900 °C, while 35% and 52% HfTaO showed crystallization temperature of 800 °C. The results demonstrate that HfTaO N-MOSFETs exhibit higher electron mobility than controlled HfO2 devices. Among them, the transistor with 40% Ta shows the highest electron mobility.
Applied Physics Letters 11/2005; 87(23):232901-232901-3. · 3.84 Impact Factor
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M.S. Akbar,
C.H. Choi,
S.J. Rhee,
S.A. Krishnan,
C.Y. Kang, M.H. Zhang,
T. Lee,
I.J. Ok,
F. Zhu,
H.-S. Kim,
J.C. Lee
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ABSTRACT: The effect of a bi-layer structure by varying the Hf composition in Hf-silicate dielectric in improving the electrical performance and reliability of high-κ gate stack n-MOSFETs has been investigated. Introducing Hf-silicate with 19.5% of Hf composition at the bottom layer and 28.5% of Hf on the top of it reduces the leakage current dramatically, while it minimally sacrifices increase in equivalent oxide thickness. Moreover, the structure reduces defect generation rate under gate injection and improves breakdown voltage in comparison to the control samples. Increase in Si-O bonds at the bottom interface, decrease in Coulomb scattering, and increase in dielectric constant in the top layer have been attributed to the overall performance increase of the gate stack.
IEEE Electron Device Letters 04/2005; · 2.85 Impact Factor
