The electrical properties of n-Ge metal-oxide-semiconductor (MOS) capacitors with HfO2/LaON or HfO2/La2O3 stacked gate dielectric (LaON or La2O3 as interlayer) are investigated. It is found that better electrical performances, including lower interface-state density, smaller gate leakage current, smaller capacitance equivalent thickness, larger k value, and negligible C-V frequency dispersion, can be achieved for the MOS device with LaON interlayer. The involved mechanism lies in that the LaON interlayer can effectively block the interdiffusions of Ge, O, and Hf, thus suppressing the growth of unstable GeOx interlayer and improving the dielectric/Ge interface quality.

Improved electrical properties of Ge metal-oxide-semiconductor capacitors with high- k HfO 2 gate dielectric by using La 2 O 3 interlayer sputtered with/without N 2 ambient

Lanthanum doped zirconium oxide (Lax–Zr1−xO2−δ) films, with La contents, up to x=0.35, were studied. Films were annealed at 900 °C to crystallize them into phases with higher κ-values. Increasing the La content suppressed the monoclinic phase and stabilized the tetragonal or cubic phase. The highest dielectric constant was obtained for a lightly doped film with a La content of x=0.09, for which a κ-value of 40 was obtained. This was accompanied by a significant dielectric relaxation, following a single Curie–von Schweidler power-law dependency with frequency, changing to a mixed Curie–von Schweidler and Kohlrausch–Williams–Watts relationships after annealing. The dielectric relaxation was most severe for lightly doped films, which had the highest κ-values. The dielectric relaxation appears to be related to the size of crystal grains formed during annealing, which was dependent on the doping level.

Dielectric relaxation of lanthanum doped zirconium oxide

La-doped zirconia films, deposited by ALD at 300°C, were found to be amorphous with dielectric constants (k-values) up to 19. A tetragonal or cubic phase was induced by post-deposition annealing (PDA) at 900°C in both nitrogen and air. Higher k-values (~32) were measured following PDA in air, but not after PDA in nitrogen. However, a significant dielectric relaxation was observed in the air-annealed film, and this is attributed to the formation of nano-crystallites. The relaxation behavior was modeled using the Curie–von Schweidler (CS) and Havriliak–Negami (HN) relationships. The k-value of the as-deposited films clearly shows a mixed CS and HN dependence on frequency. The CS dependence vanished after annealing in air, while the HN dependence disappeared after annealing in nitrogen.

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Dielectric Relaxation of La-Doped Zirconia Caused by Annealing Ambient

Ge Metal–Oxide–Semiconductor (MOS) capacitors with LaON gate dielectric incorporating different Ti contents are fabricated and their electrical properties are measured and compared. It is found that Ti incorporation can increase the dielectric permittivity, and the higher the Ti content, the larger is the permittivity. However, the interfacial and gate-leakage properties become poorer as the Ti content increases. Therefore, optimization of Ti content is important in order to obtain a good trade-off among the electrical properties of the device. For the studied range of the Ti/La2O3 ratio, a suitable Ti/La2O3 ratio of 14.7% results in a high relative permittivity of 24.6, low interface-state density of 3.1×1011 eV−1 cm−2, and relatively low gate-leakage current density of 2.0×10−3 A cm−2 at a gate voltage of 1 V.

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Impacts of Ti on electrical properties of Ge metal–oxide–semiconductor capacitors with ultrathin high-k LaTiON gate dielectric

Cerium-doped hafnium oxides (CexHf1-xO2) and lanthanum-doped zirconium oxides (LaxZr1-xO2) were investigated. The highest dielectric constants, k, were obtained from lightly doped oxides with an La content of x = 0.09 and a Ce content of x = 0.1, for which k-values of 33-40 were obtained. The dielectric relaxation appears to be related to the size of crystal grains formed during annealing, which was dependent on the doping level. The physical and mathematical models were used to analyze the relationship between k-values and frequencies. The variations in the k-values up tomegahertz frequencies for both CexHf1-xO2 and LaxZr1-xO2 are simulated based on the Curie-von Schweidler (CS) or Havriliak-Negami (HN) relationships. Concerning the lightly doped CexHf1-xO2 and LaxZr1-xO2, the data extracted are best modeled by the HN law, while LaxZr1-xO2 with doping level from x = 0.22 to 0.63 are best modelled based on the CS law.

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Dielectric relaxation of lanthanide-based ternary oxides: physical and mathematical models

In this letter, the authors report on the material and electrical characterizations of high dielectric constant (k) oxide HfTiAlO for the next generation of complementary metal-oxide semiconductors. Crystallization temperature has been improved to 800–900°C versus that of HfO2. The substitution of Ti and Al in the HfO2 cubic structure results in an increased dielectric constant and an acceptable barrier height. The extracted dielectric constant is 36, and the band offset relative to the Si conduction band is 1.3eV. An equivalent oxide thickness of 11A and low leakage have been achieved with good interfacial properties.

N. Lu

Papers

HfTiAlO dielectric as an alternative high-k gate dielectric for the next generation of complementary metal-oxide-semiconductor devices