S. K. Kang

Change in the chemical state and thermal stability of HfO2 by the incorporation of Al2O3

Al2O3 incorporated HfO2 films grown by atomic layer deposition were investigated using various measurement tools. The accumulation capacitance of the Al2O3 incorporated into HfO2 film increases as the postannealing temperature increases because of changes in interfacial and upper layer thickness and in interfacial stoichiometry. The core-level energy state of a 15 A thick film shows a shift to higher binding energy, as the result of silicate formation and Al2O3 incorporation. The incorporation of Al2O3 into the HfO2 film has no effect on silicate formation at the interface between the film and Si, while the ionic bonding characteristics and hybridization effects are enhanced compared to a pure HfO2 film. Any dissociated Al2O3 on the film surface is completely removed by a vacuum annealing treatment over 850u200a°C, while HfO2 contributes to Hf silicide formation on the surface of the film.

Interfacial characteristics of HfO2 films grown on strained Si0.7Ge0.3 by atomic-layer deposition

The interfacial characteristics of gate stack structure of HfO2 dielectrics on strained Si0.7Ge0.3 deposited by atomic-layer deposition were investigated. An interfacial layer including GeOx layers was grown on a SiGe substrate, and the thickness of the GeOx layer at the interfacial layer was decreased after the annealing treatment, while SiO2 layer was increased. The ∼50-A-thick HfO2 film with an amorphous structure was converted into a polycrystalline structure after rapid annealing at temperature of over 700u200a°C for 5 min. The interfacial silicate layer was effectively suppressed by GeOx formation, while the silicate layer was formed after the annealing treatment. GeOx formation in an as-grown film resulted in a decrease in the accumulation capacitance and an increase in the oxide trap charge.

Study of ZrO2 thin films for gate oxide applications

We investigated the microstructures and electrical properties of ZrO2 films deposited by reactive dc magnetron sputtering on Si substrates for gate dielectrics applications. We observed that the refractive index value of the ZrO2 films increased with an increase in deposition powers and annealing temperatures. The ZrO2 films deposited at elevated temperatures are polycrystalline, and both the monoclinic and tetragonal phases exist in the films. Films with higher density and improved crystallinity are obtained at higher deposition temperatures. The interfacial oxide layer between ZrO2 films and Si substrates grew upon annealing in the O2 gas ambient, which is due to the oxidation of Si substrates by the diffusion of oxidizing species from O2 gas ambient. The accumulation capacitance value increased upon annealing in the N2 gas ambient due to the densification of the films, while it decreased in O2 gas ambient due to the growth of the interfacial oxide layer.

Interfacial characteristics of N-incorporated HfAlO high-k thin films

The characteristics of N-incorporated HfO2–Al2O3 alloy films (HfAlO) were investigated by high-resolution x-ray photoelectron spectroscopy (XPS), near-edge x-ray absorption fine structure (NEXAFS), medium-energy ion scattering (MEIS), and capacitance–voltage measurements. The core-level energy states, Hf4f and Al2p peaks of a 15A thick film showed a shift to lower binding energy, resulting from the incorporation of nitrogen into the films. Absorption spectra of the OK edge of HfAlO were affected mainly by the Al2O3 in the film, and not by HfO2 after nitridation by NH3 annealing. The NEXAFS of NK edge and XPS data related to the chemical state suggested that the incorporated N atom is dominantly bonded to Al2O3, and not to HfO2. Moreover, MEIS results implied that there is a significant incorporation of N at the interface between the alloy film and Si. The incorporation of N effectively suppressed the leakage current without an increase in interfacial layer thickness, while the interfacial state of the N-i...

A study on the microstructure and electrical properties of CeO2 thin films for gate dielectric applications

Abstract We investigated the evolution of microstructures and the #electrical properties of CeO 2 thin films deposited by the reactive DC magnetron sputtering method on the (100) silicon substrate upon annealing in the O 2 gas ambient. The CeO 2 thin films deposited at 300°C were polycrystalline. After annealing in ambient O 2 gas, the crystallinity of the CeO 2 film was improved and becomes more dense with annealing time and temperature. The maximum accumulation capacitance of CeO 2 thin film annealed above 700°C in the ambient O 2 gas decreased due to the growth of the interfacial SiO 2 layer between CeO 2 film and silicon substrate by the diffusion of oxidizing species through CeO 2 thin film from the ambient gas.

Evolution of tungsten-oxide whiskers synthesized by a rapid thermal-annealing treatment

Tungsten oxide whiskers were prepared on a tungsten thin film by oxidation with H2O and a subsequent annealing treatment at a temperature of over 900u200a°C in a vacuum. The tungsten oxide formed by oxidation was transformed into smooth, straight whiskers with a monoclinic-crystalline structure after the vacuum annealing treatment. The whiskers showed an oxygen-deficient stoichiometry and a crystalline structure consistent with W18O49, which was dependent on the annealing temperature and vacuum used. The competition between the whisker growth and the dissociation of W oxide has a significant effect on the crystal shape, as well as the size of the whiskers. A change in the binding state during whisker formation indicates that some of the dissociated W oxide contributes to whisker formation and that crystalline whiskers are grown at nucleation sites through this process.

Properties of Polycrystalline Si1 − x Ge x Films Grown by Ultrahigh Vacuum CVD Using Si2 H 6 and GeH4

Polycrystalline Si 1-x Ge x films have been suggested as a promising alternative to the currently employed polycrystalline silicon (poly-Si) gate electrode for complementary metal oxide semiconductor field effect transistor technology due to lower resistivity, less boron penetration, and less gate depletion effect than that of poly-Si gates. We investigated the formation of poly-Si 1-x Ge x films by using ultrahigh vacuum chemical vapor deposition CVD with Si 2 H 6 and GeH 4 gases, and studied their physical properties as well as electrical characteristics. The deposition rate and Ge content of poly-Si 1-x Ge x films increased linearly with the flux of GeH 4 up to a critical GeH 4 flux, while, above this critical flux, it is slightly changed. The resistivity of poly-Si 1-x Ge x films decreased as the Ge content increased, and was about one-half of that of poly-Si films at a Ge content of 45%. The capacitance-voltage measurements of metal oxide semiconductor capacitor structures with WSi x /poly-Si 1-x Ge x gates demonstrated that the flatband voltage of the poly-Si 0.55 Ge 0.45 films was lower than that of poly Si films by 0.2 V. In addition, the changes of flatband voltage with the dosage of boron and the sudden decrease of accumulation capacitance in the WSi x /poly Si 0.55 Ge 0.45 gate structure were investigated. Leakage current levels increased slightly due to the difference in V FB with the increase of Ge content in poly Si 1-x Ge x films.

Wet oxidation behaviors of polycrystalline Si1−xGex films

We investigated the oxidation behaviors of poly Si1−xGex films with a 15% and 42% Ge content. The films were deposited using ultrahigh vacuum chemical vapor deposition on a 1000 A thick thermal SiO2 layer, and were oxidized using a conventional furnace in wet oxygen ambient at 700 and 800u200a°C. The physical and chemical properties of the oxide were analyzed by using Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy before and after the oxidation. We observed that the Ge content in the oxide layer and oxidation rate increased with the increase of Ge content in poly Si1−xGex films. We also observed that Ge content in the oxide layer decreased with the increase of oxidation temperature.

N-Type Dopant Activation Behaviors in Poly Si1 − x Ge x Films with Ge Contents and Activation Temperatures

We investigated the electrical properties and microstructures of n-type doped poly Si 1-x Ge x films with Ge contents using hall measurement, four-point probe, transmission electron microscopy, and energy dispersive X-ray spectrometry to apply to gate electrode of complementary metal oxide semiconductor field effect transistor. The sheet resistance of poly Si 1-x Ge x films implanted with arsenic decreased with the decrease of Ge content and the increase of activation temperature due to the increase of carrier mobility and activated carrier concentration. In addition, we found that the segregation of dopant increased at the grain edge and the activated carrier concentration decreased with the increase of Ge content due to higher diffusivity and lower solid solubility limit of As in poly Si 1-x Ge x films.

Interfacial Reaction in Poly Si1 − x Ge x / ZrO2 with Ge Content in Poly Si1 − x Ge x Films

The interfacial reaction between poly Si 1 - x Ge x (x = 0, 0.2, 0.4) and ZrO 2 films after annealing was investigated to use ZrO 2 films as an alternative gate dielectric. In the poly Si/ZrO 2 structure, silicidation was the dominant reaction due to continuous formation of Zr-silicide and SiO during annealing. However, in poly Si 1 - x Ge x (x = 0.2. 0.4)/ZrO 2 , silicate formation was the main reaction after annealing at 900°C for 30 min. In addition, after annealing at 800°C, the silicate layer was observed only in the poly Si 0 . 6 Ge 0 . 4 /ZrO 2 system.