Person: González Díaz, Germán
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First Name
Germán
Last Name
González Díaz
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Estructura de la Materia, Física Térmica y Electrónica
Area
Electrónica
Identifiers
11 results
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Now showing 1 - 10 of 11
Item Thermal stability of a-SiNx: H films deposited by plasma electron cyclotron resonance(Journal of vacuum science & technology a: Vacuum surfaces and films, 1999) González Díaz, Germán; Martil De La Plaza, Ignacio; Prado Millán, Álvaro DelWe analyze the influence of rapid thermal annealing on Al/SiNx:H/Si structures with a nitrogen to silicon ratio of 1.55 in the insulator bulk. The SiNx:H is deposited by the electron cyclotron resonance plasma method and the films were annealed at temperatures ranging from 300 to 1050 degrees C. We have related the changes of the interface trap density with those of the insulator bulk density of dangling bonds, resistivity, and breakdown field. A sharp dip in the dangling bond density is observed at moderate annealing temperatures, from 1.8 X 10(18) cm(-3) for the as-deposited film down to 9.6 X 10(16) cm(-3) at the point of inversion of the trend between 500 and 600 degrees C. The density of interface states is also reduced in this range of temperatures from 3.6 X 10(11) to 1.2 X 10(11) eV(-1) cm(-2). Resistivity and breakdown held are maintained in the range 5 X 10(14)-5 X 10(15) Ohm cm and 6.4-6.6 MV/cm, respectively, up to a temperature of 600 degrees C. We attribute the improvement of the interface characteristics and the decrease of dangling bonds to a thermal relaxation and reconstruction of the SiNx:H lattice and its interface with the silicon substrate. For temperatures above this threshold the electrical properties suddenly deteriorate and the density of dangling bonds increase. At even higher temperatures (above 900 degrees C) a release of hydrogen from N-H bonds takes place. (C) 1999 American Vacuum Society. [S0734-2101(99)05304-X].Item Effect of substrate temperature in SiOxNy films deposited by electron cyclotron resonance(Journal of vacuum science & technology a: Vacuum surfaces and films, 1999) Martil De La Plaza, Ignacio; González Díaz, Germán; Prado Millán, Álvaro DelThe effect of deposition temperature on the physical properties of SiOxNy films has been studied. The films have ben deposited from mixtures of SiH4, O-2 and N-2, using the electron cyclotron resonance-chemical vapor deposition technique, with substrate temperature ranging from room temperature (50 degrees C) to 200 degrees C. When substrate temperature is increased, a slight decrease in both Si-H and N-H bond concentration is detected. A small shift (10-17 cm(-1)) in the dominant Fourier transform infrared (FTIR) absorption peak (Si-O/Si-N stretching band) seems to be associated with a decrease in the N-H bond concentration. This behavior is attributed to the formation of Si-N bonds at the expense of N-H bonds, with no significant change in the film composition. Full width at half maximum (FWHM) of the dominant FTIR peak decreases as temperature is increased for all the composition range, indicating an improvement in the quality of the films. Silicon oxide films (SiO2.0) deposited at 200 degrees C show improved properties with respect to those deposited at room temperature. FWHM decreases from 95 to 87 cm(-1), and the shoulder-to-peak ratio from 0.29 to 0.22. The position of the Si-O stretching band (1071 cm(-1)) is unaffected. These values are very close to those obtained for thermally grown oxides, while the thermal budget of the process is significantly reduced. (C) 1999 American Vacuum Society. [S0734-2101(99)01704-2].Item Rapid thermal annealing effects on the electrical behavior of plasma oxidized silicon/silicon nitride stacks gate insulators(Journal of Vacuum Science & Technology B, 2003) Martil De La Plaza, Ignacio; González Díaz, Germán; Prado Millán, Álvaro Del; San Andrés Serrano, EnriqueWe present a comparative study of the electrical and structural characteristics of metal-insulator-semiconductor (MIS) devices using SiN1.55:H or SiN1.55:H/SiOx stacks as gate dielectrics, with the aim of improving the thermal stability of the SiN1.55:H/Si interface. The dielectrics were grown on Si by the electron cyclotron resonance plasma method. The stacks were produced by plasma oxidation of the Si surface, resulting in a thin layer of SiOx (PO-SiOx), followed by deposition of the SiN1.55:H layer. Afterwards, the samples were rapid thermally annealed (RTA) at temperatures ranging from 300 to 1000degreesC. Some representative samples were studied by Fourier transform infrared spectroscopy to characterize the bonding structure of the SiN1.55:H/PO-SiOx stack and its evolution with the annealing temperature. The results were in good agreement with the well known model for suboxide evolution with the temperature: the formation of highly defective nanocrystalline Si clusters inside a high quality SiO2 matrix. This process takes place for RTA temperatures higher than 700degreesC. This model also explains the results derived from C-V measurements, which show improvement of the PO-SiOx/Si interface as a result of the formation of the high quality SiO2 matrix. Additionally, the thermal stability improved with respect to the SiN1.55:H/Si interface, which suffers significant degradation when annealed above 600degreesC, while devices made with the stacks are able to hold annealing temperatures up to 900degreesC. On the other hand, the formation of nc-Si results in degradation of the reliability of the MIS devices.Item Raman scattering characterization of implanted ZnO(Zinc Oxide and Related Materials, 2007) Martil De La Plaza, Ignacio; González Díaz, GermánIn this work we investigate the lattice damage induced in ZnO implanted with potential group V acceptors by means of Raman scattering. ZnO samples were implanted with N and P to hi-h doses and Raman spectra were obtained prior and after rapid thermal annealing (RTA). Characteristic disorder-activated modes are observed in the spectra that can be used to assess the degree of lattice damage. ZnO samples were also implanted with native Zn+ and O+ ions under similar conditions to study specific effects of implantation with N+ and P+. As revealed by the intensity of disorder-activated bands, the implantation induced lattice damage is considerably higher for Zn+ than for the lighter O+ ion. In samples implanted with N+ additional Raman peaks emerge that are not observed either in the samples implanted with the native Zn+ and O+ ions or in the samples implanted with P+, thus pointing to a local vibrational mode of N or a N complex as the origin of these modes. Disorder-activated features are fully removed by RTA, indicating a high degree of lattice recovery by RTA even for the heavily damaged ZnO samples implanted with Zn+.Item Physical properties of high pressure reactively sputtered TiO2(Journal of Vaccum Scuebce & Technology A, 2005) Martil De La Plaza, Ignacio; González Díaz, Germán; Prado Millán, Álvaro Del; San Andrés Serrano, EnriqueWe present a study of the physical properties of TiO2 thin films deposited at 200 degrees C on Si by high pressure reactive sputtering, a nonconventional deposition method. Just after deposition, the TiO2 films were in situ annealed in the deposition chamber at temperatures between 600 and 900 degrees C in O-2 atmosphere. Morphological, compositional, structural and electrical characterization of the samples was performed by means of several techniques, including transmission electron microscopy, heavy-ion elastic recoil detection analysis, infrared spectroscopy, x-ray and electron diffraction and capacitance-voltage measurements. Microscopy images show that the TiO2 films are polycrystalline, and that a SiO2 film spontaneously grows at the TiO2/Si interface. The unannealed TiO2 films are oxygen rich, as shown by compositional measurements. By annealing this oxygen excess is released. For temperatures above 600 degrees C the TiO2 films are stoichiometric. Infrared spectroscopy and diffraction measurements show that as-deposited films are a mixture of anatase and rutile grains. During annealing there is a phase transformation, and at 900 degrees C the anatase phase disappears and only the rutile phase is found. The relative dielectric permittivity of the TiO2 film is calculated from capacitance-voltage measurements, and very high. values in the 88-102 range are obtained.Item Conductance-transient three-dimensional profiling of disordered induced gap states on metal-insulator-semiconductor structures(Electrically Based Microstructural Characterization, 2002) Martil De La Plaza, Ignacio; González Díaz, GermánAs it has been shown elsewhere, conductance transient measurements provide quantitative information about the disordered induced gap states (DIGS) in metal-insulator-semiconductor (MIS) structures. In this work we report for the first time the DIGS spatial and energetical distribution obtained by recording conductance transients at several temperatures (ranging from 77 to 300 K) and several frequencies (ranging from 100 Hz to 200 KHz). These measurements allow us to obtain three-dimensional defect maps of Al/SiNx:H/InP structures browsing ranges of 0.5 eV in energy and 40 Angstrom in depth. Our results show that this technique is a very useful tool for the electrical characterization of MIS structures and reveals itself as very valuable in the III-V semiconductor-field-effect transistor scenario.Item Compositional analysis of amorphous SiNx : H films by ERDA and infrared spectroscopy(Surface and interface analysis, Surface and interface analysis, 2000) Martil De La Plaza, Ignacio; González Díaz, Germán; Prado Millán, Álvaro DelThe composition of amorphous SiNx:H films grown by the electron cyclotron resonance (ECR) plasma method was studied by heavy-ion elastic recoil detection analysis (ERDA) with Xe-129 ion beams of 1.1 and 1.8 MeV amu(-1) and time-of-light (ToF) mass separation. This technique allows simultaneous determination of the absolute atomic concentrations and depth profiles of all involved elements, including hydrogen, Radiation damage at extended ion beam exposure was found to decrease the N/Si ratio and the hydrogen concentration, By measuring the dose dependence, this effect was quantified in order to support correction to zero dose conditions. Monitoring the damage effects by infrared (IR) spectroscopy revealed an increase of the SI-H bond density at the expense of N-H bands. The results suggest that the damage process Is initiated by breaking of N-H bonds and that recapturing of hydrogen by Si appears as an effective competitive process to hydrogen release, Combining the ERDA and IR data, the oscillator strength ratio of the N-H and Si-H stretching bands is found to be 1.4 +/- 0.2, Copyright (C) 2000 John Wiley & Sons, Ltd.Item Compositional analysis of SiOxNy : H films by heavy-ion ERDA: the problem of radiation damage(Surface and interface analysis, 2002) Martil De La Plaza, Ignacio; González Díaz, Germán; Prado Millán, Álvaro Del; San Andrés Serrano, EnriqueFilms of SiOxNy:H were deposited at room temperature on Si substrates by the electron cyclotron resonance (ECR) plasma method. By varying the flow rates of the precursor gases SiH4, O-2. and N-2, the whole composition range between pure silicon oxide and nitride could be covered. Heavy-ion elastic recoil detection analysis (HI-ERDA) with a 150 MeV Kr-86 ion beam and time-of-flight (ToF) mass separation was applied to determine the absolute atomic concentrations of all film components, including hydrogen. Additionally, the bonding configuration of the films was studied by infrared (IR) spectroscopy. Extended ion beam exposure was found to decrease the intensity of the N-H phonon band as well as the nitrogen and hydrogen concentrations. By storing the ion scattering data event by event and by recalculating a zero-dose composition, this effect was taken into account. The corrected Hl-ERDA results revealed clear relations to the deposition parameters (e.g. the O-2/SiH4 flow ratio). The hydrogen incorporated in the films turned out to be bonded predominantly to nitrogen. The damage effects were strongest in the medium composition range. They were found to scale with the relative concentration of SiO2N2-type basic tetrahedrons, suggesting that this bonding configuration is most sensitive against irradiation during the HI-ERDA measurement. Copyright (C) 2002 John Wiley Sons, Ltd.Item Conductance transients study of slow traps in Al/SiNx : H/Si and Al/SiNx : H/InP metal-insulator-semiconductor structures(Electrically based microstructural characterization II, 1998) Martil De La Plaza, Ignacio; González Díaz, Germán; Dueñas, S.; Peláez, R.; Castán, E.; Barbolla, J.We have obtained Al/SiNx:H/Si and Al/SiNx:H/InP Metal-Insulator-Semiconductor devices by directly depositing silicon nitride thin films on silicon and indium phosphide wafers by the Electron Cyclotron Resonance Plasma method at 200 degrees C. The electrical properties of the structures were first analyzed by Capacitance-Voltage measurements and Deep-Level Transient Spectroscopy (DLTS). Some discrepancies in the absolute value of the interface trap densities were found. Later on, Admittance measurements were carried out and room and low temperature conductance transients in the silicon nitride/semiconductor interfaces were found. The shape of the conductance transients varied with the frequency and temperature at which they were obtained. This behavior, as well as the previously mentioned discrepancies, are explained in terms of a disorder-induced gap-state continuum model for the interfacial defects. A perfect agreement between experiment and theory is obtained proving the validity of the model.Item Influence of electron cyclotron resonance nitrogen plasma exposure on the electrical characteristics of SiNx : H/InP structures(Journal of Vacuum Science & Technology B, 2001) Martil De La Plaza, Ignacio; González Díaz, GermánWe have studied the influence of nitrogen plasma exposure of the InP surface on the electrical characteristics of electron cyclotron resonance deposited Al/SiNx:H/InP devices. Nitrogen plasma exposure was performed just before the SiNx:H deposition without vacuum breaking. A 30 s plasma treatment at low microwave power (60 W) sharply reduces the minimum of the interface trap density, from 4x10(12) to 1.6x10(12) eV(-1) cm(-2) (obtained by the high-low frequency capacitance method). We explain this reduction due to the formation of P-N and/or In-P-N complexes at the InP surface during the plasma-exposure step. These bonds are broken thermally after a rapid thermal annealing of the device. The minimum of the interface trap density, obtained at the optimum plasma exposure conditions, is among the lowest ones reported in the Literature and similar to those obtained with more complicated processing technologies of the SiNx:H/InP structure. This is a clear indication that plasma exposure in N-2 atmosphere seems to be a valuable and simple surface conditioning method.