J. Barbolla

Universidad de Valladolid, Valladolid, Castille and León, Spain

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Publications (150)233.44 Total impact

  • MRS Online Proceeding Library 01/2011; 514.
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    ABSTRACT: As 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 Å 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.
    MRS Online Proceeding Library 01/2011; 699.
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    ABSTRACT: We present an experimental continuous-time complex delta-sigma multi-bit modulator, implemented in standard 0.25-μm CMOS technology and meeting all major requirements for application in IEEE 802.11a/b/g wireless LAN receivers. The clock frequency is 320 MHz, producing an oversampling ratio of 16 for 20 MHz channel bandwidths. The modulator supports two operation modes for zero-IF and low-IF receiver architectures respectively, requires a single 2.5-V power supply, and dissipates only 32 mW of power. The measured peak signal-to-noise ratio is 55 dB. Further experimental results using sine-wave and OFDM test signals are also presented.
    IEEE Journal of Solid-State Circuits 03/2006; · 3.11 Impact Factor
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    ABSTRACT: The energy levels and electrically active concentrations for platinum in n- and p-type Si, and for palladium in n-type silicon are measured by the dark transient capacitance technique, p+—n—p+ and n+—p—n+ structures have been platinum-diffused at low temperatures (820 to 844 °C). Two levels are found, a donor at Ev + 0.32 eV in p-type silicon and an acceptor at Ec — 0.24 eV in n-type silicon. These two levels are associated with the usual substitutional site (Pt(I)). The second usual site (Pt(II)) does not appear in samples, p+—n—p+ structures have been palladium-diffused at 898 °C. An acceptor level at Ec — 0.20 eV is found which is probably associated with the substitutional site of palladium in silicon.Nous avons déterminé, par la méthode des transitoires isothermes de capacité, les niveaux d'énergie et les densités d'atomes électriquement actifs pour le platine dans du silicium de type n et p et pour le palladium dans du silicium de type n. Des structures p+—n—p+ et n+—p—n+ ont été dopées au platine à basse température (820 à 844 °C). Nous trouvons deux niveaux, un donneur à Ev + 0.32 eV dans le type p et un accepteur à Ec — 0.24 eV dans le type n. Ces deux niveaux sont associés au site usuel substitutionnel (Pt(I)). Le second site couramment rencontré, (Pt(II)), n'est pas présent dans nos échantillons. Nous avons effectué des diffusions de palladium à 898 °C sur des structures p+—n—p+ et nous trouvons un niveau accepteur à Ec — 0,20 eV qui est probablement associé au site substitutionnel du palladium dans le silicium.
    physica status solidi (a) 02/2006; 35(2):533 - 543. · 1.21 Impact Factor
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    ABSTRACT: From capacitance measurements, the thermal capture cross-section of electrons at neutral gold centres is determined through the time dependence of the net ionized recombination centres concentration to σ = 1.24 × 10−16 (T/300)−(0.21 ± 0.03) cm2 in the temperature range 80 to 205 K.La section de capture thermique des électrons sur l'or neutre est déduite de la dépendance temporelle de la densité de centres profonds ionisés, mesurée par une technique capacitive. Pour le domaine de température 80 à 205 K le résultat est: σ = 1,24 × 10−16 (T/300)−(0,21 ± 0.03) cm2.
    physica status solidi (a) 02/2006; 36(2):495 - 498. · 1.21 Impact Factor
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    ABSTRACT: Under certain conditions, particularly for high-dose implants, {3 1 1} rod-like defects can evolve into dislocation loops (DLs). In this work, we have developed a model for the transformation of {3 1 1}-defects into DLs, with a transformation rate that is controlled by a size-dependent energy barrier. The model has been included and calibrated in an atomistic kinetic Monte Carlo simulator. This simulator includes a description of the size distribution of {3 1 1}-defects (required for a size-based model) and of the amorphization and recrystallization (needed to provide reliable information on the number of interstitials in the end-of-range region). Extended defects are implemented according to realistic geometries, giving a direct assessment of the correct capture volume for diffusing defects. The model correctly predicts the formation of DLs during the annealing that follows ion implants, both for amorphizing and non-amorphizing conditions, and provides a realistic description of damage morphology. The possible role of stress on DL formation is also discussed.
    Materials Science and Engineering B 12/2005; 124125:404-408. · 2.12 Impact Factor
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    ABSTRACT: We have analyzed the as-implanted damage produced in silicon by B, Si and Ge ions using molecular dynamics (MD) simulations. Implantations were carried out at 50K to avoid damage migration and annealing. In order to make a statistical study of the damage features, we have simulated hundreds of independent cascades for each ion for the same nuclear deposited energy. We have obtained that the average number of displaced atoms (DA) from perfect lattice positions and the size of defect clusters formed increases with ion mass. This dependence has not been obtained from equivalent binary collisions simulations. This indicates that multiple interactions play an important role in the generation of damage. Amorphous regions are directly formed during the collisional phase of the cascade of Ge and Si ions.
    Materials Science and Engineering B 12/2005; 124:372-375. · 2.12 Impact Factor
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    ABSTRACT: Ion beam induced amorphization in Si has attracted significant interest since the beginning of the use of ion implantation for the fabrication of Si devices. Nowadays, a renewed interest in the modeling of amorphization mechanisms at atomic level has arisen due to the use of preamorphizing implants and high dopant implantation doses for the fabrication of nanometric-scale Si devices. In this work, we briefly describe the existing phenomenological and defect-based amorphization models. We focus on the atomistic model we have developed to describe ion beam induced amorphization in Si. In our model, the building block for the amorphous phase is the bond defect or IV pair, whose stability increases with the number of surrounding IV pairs. This feature explains the regrowth behavior of different damage topologies and the kinetics of the crystalline to amorphous transition. The model provides excellent quantitative agreement with experimental results.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 12/2005; · 1.19 Impact Factor
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    ABSTRACT: Continuum downscaling of MOSFET devices requires of ultra-shallow junction formation. Performance of the source and drain from B and As low energy implant and subsequent annealing is seriously affected by the presence of the Si–SiO2 interface. Dopant loss due to segregation and dopant pileup at the interface during the transient enhanced diffusion (TED) are crucial phenomena for current and future CMOS devices. In this work we have implemented the Oh-Ward model [Y.-S. Oh, D.E. Ward, Tech. Dig. Int. Electron Devices Meet. 1998 (1998) 509] for the dopant behaviour at the interfaces integrated in an atomistic kinetic Monte Carlo simulator. Dopant traps at the interface can capture from or emit to either side of the interface. Furthermore, segregation of dopants and saturation of the interface by the presence of other species are also included. As a test of the model, low energy implants through a screen oxide have been simulated. When annealing these very shallow implants, a pileup at the interface is observed. The mechanisms involved in this process, as well as its dependence on the implant dose and energy are discussed.
    Materials Science and Engineering B 12/2005; · 2.12 Impact Factor
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    ABSTRACT: The solid phase epitaxial regrowth (SPER) technique achieves active B concentrations up to a few times 1020cm−3 after low-temperature recrystallization process, while higher B concentration regions remain immobile forming electrically inactive B clusters during SPER. Kinetic Monte Carlo simulations on B diffusion and activation in preamorphized Si during annealing after SPER are presented, providing a good insight into mechanisms that drive these phenomena. Simulations show that the presence of end of range (EOR) defects, still present beyond the amorphous/crystalline interface after recrystallization, leads to additional deactivation during subsequent anneal treatments. Moreover, B uphill diffusion towards the surface is observed in the medium concentration region, while downhill diffusion occurs in the tail region of the B profile. During prolonged anneals B activation decreases until it reaches a minimum, which becomes lower as the annealing temperature reduces. Finally, when EOR defects dissolve or reach very stable configurations such us dislocation loops, B reactivation is observed as well as B tail diffusion.
    Materials Science and Engineering B 12/2005; 124:205-209. · 2.12 Impact Factor
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    ABSTRACT: Preamorphization followed by low temperature solid phase epitaxial regrowth has been proved to provide a high activation of the dopants with minimal diffusion. However, the end of range damage present after regrowth beyond the initial amorphous/crystalline interface causes diffusion and deactivation of dopants during subsequent annealing. In this paper, we study the influence of implant conditions on the depth of the amorphous layer during Si self-implantation. We compare experimental data with our simulation results obtained using an atomistic amorphization–recrystallization model recently developed. We show that the amorphous/crystalline interface depth initially increases with dose but saturates at high doses. Beam current and wafer temperature also alter the depth of the amorphous layer and the amount of residual damage by affecting the dynamic annealing of the damage. These parameters are not always well controlled or specified in experiments and can explain differences observed in dopant profiles.
    Materials Science and Engineering B 12/2005; · 2.12 Impact Factor
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    ABSTRACT: With devices shrinking to nanometric scale, process simulation tools have to shift from continuum models to an atomistic description of the material. However, the limited sizes and time scales accessible for detailed atomistic techniques usually lead to the difficult task of relating the information obtained from simulations to experimental data. The solution consists of the use of a hierarchical simulation scheme: more fundamental techniques are employed to extract parameters and models that are then feed into less detailed simulators which allow direct comparison with experiments. This scheme will be illustrated with the modeling of the amorphization and recrystallization of Si, which has been defined as a key challenge in the last edition of the International Technology Roadmap for Semiconductors. The model is based on the bond defect or IV pair, which is used as the building block of the amorphous phase. The properties of this defect have been studied using ab initio methods and classical molecular dynamics techniques. It is shown that the recombination of this defect depends on the surrounding bond defects, which accounts for the cooperative nature of the amorphization and recrystallization processes. The implementation of this model in a kinetic Monte Carlo code allows extracting data directly comparable with experiments. This approach provides physical insight on the amorphization and recrystallization mechanisms and a tool for the optimization of solid-phase epitaxial-related processes.
    Materials Science and Engineering B 12/2005; · 2.12 Impact Factor
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    ABSTRACT: Atomistic process simulation is expected to play an important role for the development of next generations of integrated circuits. This work describes an approach for modeling electric charge effects in a three-dimensional atomistic kinetic Monte Carlo process simulator. The proposed model has been applied to the diffusion of electrically active boron and arsenic atoms in silicon. Several key aspects of the underlying physical mechanisms are discussed: (i) the use of the local Debye length to smooth out the atomistic point-charge distribution, (ii) algorithms to correctly update the charge state in a physically accurate and computationally efficient way, and (iii) an efficient implementation of the drift of charged particles in an electric field. High-concentration effects such as band-gap narrowing and degenerate statistics are also taken into account. The efficiency, accuracy, and relevance of the model are discussed.
    Journal of Applied Physics 10/2005; · 2.19 Impact Factor
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    ABSTRACT: We introduce a model for damage accumulation up to amorphization, based on the ion-implant damage structures commonly known as amorphous pockets. The model is able to reproduce the silicon amorphous-crystalline transition temperature for C, Si, and Ge ion implants. Its use as an analysis tool reveals an unexpected bimodal distribution of the defect population around a characteristic size, which is larger for heavier ions. The defect population is split in both size and composition, with small, pure interstitial and vacancy clusters below the characteristic size, and amorphous pockets with a balanced mixture of interstitials and vacancies beyond that size.
    Journal of Applied Physics 09/2005; · 2.19 Impact Factor
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    ABSTRACT: In this work, an approach for the simulation of the effect of noise sources in the performance of continuous-time DeltaSigma modulators is presented. Electrical noise including thermal noise, /f noise and clock jitter are included in a simulation program and their impact on the system performance is analyzed.
    08/2005;
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    ABSTRACT: An accurate physically-based Fermi-level modeling approach, amenable to be implemented in an atomistic device-size process simulator, is reported. The atomistic kinetic Monte Carlo method is used for point and extended defects, in conjunction with a quasi-atomistic, continuum approach treatment for carrier densities. The model implements charge reactions and electric bias according to the local Fermi-level, pairing and break-up reactions between particles, clustering-related dopant deactivation and Fermi level-dependent solubility. We derive expressions that can be used as a bridge between the continuum and the atomistic frameworks. We present the implementation of two common dopants, Boron and Arsenic, using parameters that are in agreement with both ab- initio calculations and experimental results. Current microelectronic technology is facing increas- ingly complex phenomena related to very high-doping, reduced thermal budget (non-equilibrium conditions), and three dimensional efiects. Such conditions require a deep insight into the underlying physical mechanisms in order to correctly model the material properties. In particular, high-doping concentrations demand a cor- rect description of difiusion under extrinsic conditions.1,2 Other charge-related issues are Fermi-level dependent solubility,3,4 clustering-related dopant deactivation,5 and high-damage electrical compensation. Continuum modeling, based on solving partial dif- ferential equations (PDE) discretized by the flnite el- ement method, has been used since the 1980's, but this method is limited by the number of equations that can be solved without running into convergence insta- bilities. Moreover, meshing issues and dimensionality make this approach extremely complicated in 3D. The International Roadmap for Semiconductors 20036 estab- lishes the \Modeling hierarchy from atomistic to con- tinuum" among the di-cult challenges that need to be solved before 2010. The atomistic kinetic Monte Carlo (kMC) method,7 has proven to be a powerful approach that allows the inclusion of comprehensive, physically based models without signiflcantly degrading the sim- ulator's performance. Some semiconductor companies8,9 and software vendors10,11 have already started to develop simulators based on this atomistic kMC approach. Mod- elling Fermi level efiects is one of the critical steps in developing a comprehensive kMC simulator. Here we will describe a detailed Fermi-level modeling approach specially designed to be included in this methodology, which has been implemented and tested in the atomistic kMC process simulator DADOS.12 We flrst describe in detail the basic physical models and then the particular implementation of point defects and of two representative dopants (boron and arsenic), and flnally show a simulation example.
    Physical Review B 07/2005; 72. · 3.66 Impact Factor
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    ABSTRACT: A comprehensive atomistic model for arsenic in silicon which includes charge effects and is consistent with first-principles calculations for arsenic-vacancy cluster energies has been developed. Emphasis has been put in reproducing the electrical deactivation and the annealed profiles in preamorphized silicon. The simulations performed with an atomistic kinetic Monte Carlo simulator suggest a predominant role of the mobile interstitial arsenic in deactivation experiments and provide a good understanding of the arsenic behavior in preamorphized silicon during annealing.
    Applied Physics Letters 07/2005; · 3.52 Impact Factor
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    ABSTRACT: This paper presents a digital correction technique for wide-band multibit error-feedback (EF) digital-to-analog converters (DACs). The integral nonlinearity (INL) error of the multibit DAC is estimated (on line or off line) by a calibration analog-to-digital converter (CADC) and stored in a random-access memory table. The INL values are then used to compensate for the multibit DAC's distortion by a simple digital addition. The accuracy requirements for the error estimates are derived. These requirements can be significantly relaxed when the correction is combined with data-weighted averaging (DWA). Simulation and discrete-component measurement results are presented for a fourth-order 5-bit EF DAC. The results show a 14-bit DAC operating at an oversampling ratio of 8, which is suitable for digital subscriber line applications. The correction uses simple digital circuitry and a 3-bit CADC enhanced by DWA.
    Circuits and Systems I: Regular Papers, IEEE Transactions on 07/2005; · 2.30 Impact Factor
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    ABSTRACT: In this work a dual-mode complex multibit continuous-time DS modulator for a standard 0.25µm CMOS technol- ogy is presented. This modulator is intended for the analog-to-digital conversion in multi-mode wireless-LAN receivers (802.11a/b/g) which require wide bandwidth and moderate resolution. Then, a low oversampling ratio of 16 along with a clock frequency of 320 MHz provides a signal bandwidth of 20 MHz for a 9-bit resolution with a second-order modulator. The modulator can be congured for two different modes of operation depending on the type of radio receiver chosen: "zero- IF" (ZIF) and "low-IF" (LIF). The former mode is better suited for 802.11b, while LIF mode is more adequate for 802.11a/g applications. The loop lter is based on transconductors and MOS-capacitors allowing for low power consumption and small chip area. The modulator also includes two 3-bit quantizers, both with their corresponding DWA scrambler. The supply volt- age is 2.5V and the measured power consumption is 32 mW. Experimental results using both sine-wave and OFDM signals are presented. The obtained SNR and SNDR are 55dB and 53.5dB, respectively. A high image rejection of 47dB is achieved owing to proper layout techniques. When using OFDM signals, a minimum error vector magnitude of 1.3% is obtained. Finally, the active chip area is 0:44mm2.
    Proceedings of SPIE - The International Society for Optical Engineering 06/2005; · 0.20 Impact Factor
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    ABSTRACT: We use kinetic nonlattice Monte Carlo atomistic simulations to investigate the physical mechanisms for boron cluster formation and dissolution in complementary metal-oxide semiconductor (MOS) processing, and the role of Si interstitials in the different processes. For this purpose, B implants in crystalline Si as well as B implants in preamorphized Si are analyzed. For subamorphizing B implants, a high concentration of Si interstitials overlaps with the B profile and this causes a very quick B deactivation for both low- and high-dose B implants. For B implants in preamorphized silicon, B is activated during the regrowth of the amorphous layer if the B concentration is lower than 1020 cm−3 and remains active upon annealing. However, if B concentrations higher than 1020 cm−3 are present, as occurs in the formation of extensions in p-channel MOS transistors, B atoms are not completely activated during the regrowth. Moreover, the injection of Si interstitials from the end-of-range defects leads to additional B deactivation in the regrown layer during subsequent annealing. If the end-of-range defects overlap with a B profile, even of relatively low concentration, as it occurs for B pockets in n-channel MOS transistors, very quick and local B deactivation occurs in the high Si-interstitial concentration region.
    Journal of Applied Physics 05/2005; 97(10):103520-103520-7. · 2.19 Impact Factor

Publication Stats

1k Citations
233.44 Total Impact Points

Institutions

  • 1970–2006
    • Universidad de Valladolid
      • • Department of Electricity and Electronics
      • • Facultad de Ciencias
      Valladolid, Castille and León, Spain
  • 2005
    • University of Helsinki
      • Department of Chemistry
      Helsinki, Uusimaa, Finland
  • 2003
    • Universidad de Sevilla
      Hispalis, Andalusia, Spain
  • 2000
    • University of Barcelona
      • Department of Electronics
      Barcino, Catalonia, Spain
  • 1997
    • Lund University
      Lund, Skåne, Sweden
  • 1982–1983
    • University of Zaragoza
      • Faculty of Sciences (CIENCIAS)
      Zaragoza, Aragon, Spain