bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling the Dependence of the Gate Current on Ge Content in Ultrathin Gate Dielectric Pmos Devices with Poly-Si1−Gex Gate Material
Authors: Shanware A. , Massoud H. Z. , Acker A. , Li V. Z. Q. , Mirabedini M. R. , Henson K. , Hauser J. R. , Wortman J. J. 
Published: April 2011

ABSTRACTThe performance of CMOS devices improves due to the addition of Ge in their poly-Si gate material. The presence of Ge in the gate increases the current drive due to the reduction of the flatband voltage. The change in the flatband voltage is due to a shift in the valence-band energy level in the gate. This shift results in a change in the barrier height for electrons tunneling from the gate. Thus, the presence of Ge in the gate increases the tunneling current in the gate. This increase may result in a limitation in the use of SiGe gates in future generations of MOSFETs with ultrathin gate dielectrics. The purpose of this work is to investigate the effect of Ge content on the tunneling current in CMOS devices with ultrathin gate dielectrics.
Surface Morphology of Ultrathin Oxide Formed on Si(100)
Authors: Hattori T. , Fujimura M. , Nohira H. 
Published: April 2011

ABSTRACTThe atomic-scale surface roughness of ultrathin thermal oxides formed on Si(100) were studied as a function of oxide film thickness up to the thickness of 2.0 nm. The height deviation on oxide surface is limited within single atomic-step height of 0.135 nm on Si(100) surface below the oxide film thickness of about 1 nm, but above this thickness the height deviation increases with the increase in thickness at 700°C. This increase in height deviation with thickness must be produced by the relaxation of oxidation–induced stress in bulk SiO2. Furthermore, the oscillation in surface roughness with constant amplitude and its oscillating period in oxide film thickness of 0.19 nm were found.
Electrical Characterization of a Double Barrier Direct Tunneling Diode Structure
Authors: Dons E. M. , Skowronski C. S. , Farmer K. R. 
Published: April 2011

ABSTRACTWe report the electrical characterization of a direct tunneling diode structure that incorporates a multilayer dielectric. The dielectric consists of a stack of two thermally grown, ultrathin SiO2 layers, each ∼3.5 rin thick, separated by a deposited, continuous, undoped, ultrathin nanocrystalline Si layer ∼5.0 nm thick. Electrical measurements of this structure are reported for both n-type and p-type Si substrates. We find that the room temperature transport through this structure is accounted for by describing the intermediate Si layer as a quantum well with a continuum of states, and by otherwise assuming bulk properties for the ultrathin layers, such as the existence of a bandgap in the Si well and the usual Si-SiO2 interface potential barrier height at all interfaces. This structure is expected to be useful as the active dielectric in nonvolatile memory devices.
Relationship between Interfacial Roughness and Dielectric Reliability for Silicon Oxynitride Gate Dielectrics Processed with Nitric Oxide
Authors: Sapjeta J. , Green M. L. , Chang J. P. , Silverman P. J. , Sorsch T. W. , Weir B. E. , Gladden W. , Ma Y. , Sung C. Y. , Lennard W. N. 
Published: April 2011

ABSTRACTThe greatest benefits of nitrogen incorporation into gate dielectrics may be obtained by placing nitrogen preferentially at the interfacial regions of the dielectric film. One method of distributing nitrogen in this manner is by using a three-step thermal process consisting of 1.) oxynitridation in NO, 2.) subsequent reoxidation in O2, and 3.) a final NO anneal. This study investigates the effect of NO processing on substrate/dielectric interface roughness and correlates that roughness with dielectric reliability. The initial NO-containing step can roughen the interface, as can subsequent reoxidation. Increased NO exposure yields a greater nitrogen content and a concomitant increase in interface roughness. These films show a degradation in charge to breakdown (Qbd) of at least an order of magnitude when compared with similarly prepared O2-oxide films. An O2/NO process produces films with interface roughness and Qbd comparable to that of pure SiO2, independent of nitrogen content. The oxynitride reliability depends on the exact scheme for incorporating nitrogen into SiO2.
Triggering and Suppression of Soft Breakdown During Mercury-Probe Assessment of Thin Gate Oxide Quality
Authors: Evseev S. , Cacciato A. 
Published: April 2011

ABSTRACTThe breakdown of ultra-thin gate oxide layers is investigated using fast-feedback Hg-probe measurements to perform Exponentially Ramped Current Stress (ERCS) tests. Several parameters have been varied in the ERCS test: oxide thickness (4nm, 5nm, 6nm and 7nm), capacitor area (0.12cm2 and 0.023cm2) and initial injected current (5×10−5 A and 5×10−4 A). Soft breakdown is detected only in case of oxides thinner than 5 nm. It is found that the fraction of points on the wafer on which soft breakdown occurs reduces by increasing the value of the injected current at the beginning of the ERCS test or completely disappears by decreasing the capacitor area. Consequences of current results for correct routine assessment of gate oxide integrity in microelectronic manufacturing are discussed.
Breakdown Characteristics of Ultra-Thin Gate Oxides Caused by Plasma Charging
Authors: Chen Chi-Chun , Lin Horng-Chih , Chang Chun-Yen , Chien Chao-Hsin , Huang Tiao-Yuan 
Published: April 2011

ABSTRACTBreakdown characteristics of ultra-thin gate oxides caused by plasma charging were studied in this work. It is observed that as oxide thickness is scaled down to 4 nm, some traditional monitor parameters may lose their sensitivity for detecting oxide degradation induced by plasma charging damage, due to insignificant trap generation. Even the gate leakage current, although sensitive for 4 nm oxide, may no longer be sensitive enough for even thinner oxide (e.g., 2.6 nm), due to the existence of large tunneling current. Moreover, several soft-breakdown events were found to occur in ultrathin oxide before the final onset of a catastrophic hard-breakdown. Finally, an equivalent local oxide thickness is calculated using local oxide thinning model to estimate the stepwise increase of gate current after soft-breakdown event.
Deposition and Treatment of TiO2 as an Alternative for Ultrathin Gate Dielectrics
Authors: Ma Yanjun , Ono Yoshi , Hsu Sheng Teng 
Published: April 2011

ABSTRACTWe investigated the use of TiO2 as an alternate gate dielectric for future CMOS applications. To reduce the leakage current, different post deposition treatments were investigated. It was found that for very thin TiO2 films, ozone plasma exposure is an effective way in lowering thermal budget of the post deposition annealing. Doping TiO2with Si and/or Al can also be effective in substantially reducing the leakage current. In addition, the doped TiO2 has the desirable property of remaining amorphous even after anneal at 850°C. We also report the fabrication of submicron MOSFETs with TiO2 gate dielectrics equivalent to 2 nm of SiO2 and TiN/Cu gate electrodes.
Atomic Layer Deposition of Ta2O5 Films Using Ta(OC2H5)5 and Nh3
Authors: Song Hyun-Jung , Koh Wonyong , Kang Sang-Won 
Published: April 2011

ABSTRACTTantalum oxide films were grown by chemical vapor deposition using an alternating supply of tantalum pentaethoxide and ammonia. The supply of one source was followed by a purge with argon gas before introducing the other source onto the substrate in order to prevent gas-phase reactions. At substrate temperature between 250-275 °C the film growth depended only on the number of source supply cycles (0.15 nm/cycle) and did not depend on the substrate temperature nor supply time of the sources. As-deposited films were amorphous, however, were crystallized after annealing at 800 °C in oxygen atmosphere by rapid thermal process. Annealed films showed increased dielectric constant and decreased leakage current density, which were 13.3 and 6.6 μA/cm2 at 1 MV/cm, respectively, for a 15-nm-thick film after annealing at 800 °C for 10 minutes.
Comparison of Valence-Band Tunneling in Pure SiO2, Composite SiO2 /Ta2O5, and Pure Ta2O5, in Mosfets with 1.0 nm-Thick SiO2-Equivalent Gate Dielectrics
Authors: Shanware A. , Massoud H. Z. , Vogel E. , Henson K. , Hauser J. R. , Wortman J. J. 
Published: April 2011

ABSTRACTThe gate tunneling current in ultrathin gate dielectric NMOSFETs with positive gate bias is due to the tunneling of electrons from the conduction and valence bands of the substrate. Valence-band electrons tunnel from the substrate of NMOS devices when the valence-band edge in the substrate rises above the conduction-band edge in the substrate. This paper reports experimental trends in the contribution of valence-band electrons tunneling to the gate current of NMOSFETs with gate oxides composed of pure SiO2. The large gate tunneling current can be reduced by replacing the conventional SiO2 gate dielectric with alternative dielectrics with larger dielectric constants. This paper reports the effect of replacing SiO2 with alternative dielectrics on the contribution of valence-band electron tunneling to the gate current. Simulations are carried out for composite SiO2/Ta2O5 gate dielectric structures.
Large-Area Pulsed Laser Deposition of Tantalum Oxide Films
Authors: Boughaba S. , Islam M. U. , Sproule G. I. , Graham M. J. 
Published: April 2011

ABSTRACTA large-area pulsed laser deposition (PLD) technique was used to uniformly grow tantalum pentoxide (Ta2O5) films on silicon wafers of 75 mm diameter. A KrF excimer laser beam was focused onto a 90 mm diameter Ta2O5 target to induce its ablation in oxygen gas ambient. The large-area coverage was obtained by rastering the laser beam over the radius of the rotating target, while the substrate was rotated simultaneously.The tantalum oxide films were characterized in terms of uniformity of thickness, composition, structure, and optical properties across the substrate. Average deviations typically below 1% were achieved in thickness, composition, indices of refraction and optical energy band-gap. Identical X-ray diffraction spectra were obtained at the center, middle of radius and edge of the wafers.
Sensitivity of Electrically Active Defect Spectra to Processing Conditions in Mev Heavy Ion Implanted Silicon
Authors: Mohapatra Y.N. , Giri P.K. 
Published: April 2011

ABSTRACTWe have carried out electrical characterization of defects in heavily damaged silicon, where damage is created by MeV heavy ions at doses near but below amorphization threshold and samples are subjected to different annealing conditions. Defect characterization is carried out using combination of deep level transient spectroscopy (DLTS) and isothermal time analyzed spectroscopy (TATS). The defect spectrum is observed to be sensitive to I) furnace annealing between 400–600°C, ii) low temperature oven annealing at 160°C, and iii) forward injection current. The observed changes in spectra are indicators of extreme sensitivity of dominant defects to relaxation of the disordered medium, and recombination enhanced reactions. Surprisingly the defect spectra is usually dominated by a single peak with unbroadened lineshape characteristic of discrete energy level in the bandgap, though electrical signatures keep varying for different processing conditions. In the light of these measurements, we discuss the nature of stability and metastability of the defects believed to be due to intrinsic defect clusters.
Dopant segregation to {311} defects during low temperature annealing
Authors: Taniguchi Kenji , Saito Tomoya , Xia Jianxin , Kim Ryangsu , Aoki Takenori , Kobayashi Hiroyuki , Kamakura Yoshinari 
Published: April 2011

ABSTRACTBoron segregation to {311} defects and transient enhanced diffusion (TED) of boron atoms during thermal annealing were investigated in detail using implanted superlattice and Si bulk wafers. We observed that (1)boron atoms segregate to {311} defects during low temperature annealing, (2){311} defects were formed in the area where the self-interstitial concentration exceeds 3×1017cm3, (3)free self-interstitials in the region beyond the implanted range causes initial rapid enhanced diffusion prior to the onset of normal TED.
In-Situ Photoexcitation-Induced Suppression of Point Defect Generation in Ion Implanted Silicon
Authors: Cho C. R. , Yarykin N. , Rozgonyi G. A. , Zuhr R. A. 
Published: April 2011

ABSTRACTThe formation of vacancy-related defects in n-type silicon has been studied immediately after implantation of He, Si, or Ge ions at 85 K using in-situ DLTS. A-center concentrations in He-implanted samples reach a maximum immediately after implantation, whereas, with Si or Ge ion implanted samples they continuously increase during subsequent anneals. It is proposed that defect clusters, which emit vacancies during anneals, are generated in the collision cascades of Si or Ge ions. An illumination-induced suppression of A-center formation is seen immediately after implantation of He ions at 85 K. This effect is also observed with Si or Ge ions, but only after annealing. The suppression of vacancy complex formation via photoexcitation is believed to occur due to an enhanced recombination of defects during ion implantation, and results in reduced number of vacancies remaining in the defect clusters. In p-type silicon, a reduction in K-center formation and an enhanced migration of defects are concurrently observed in the illuminated sample implanted with Si ions. These observations are consistent with a model where the injection of excess carriers modifies the defect charge state and impacts their diffusion.
Diffusion Mechanisms in Sige Alloys
Authors: Willoughby Arthur F.W. , Bonar Janet M. , Paine Andrew D.N. 
Published: April 2011

ABSTRACTInterest in diffusion processes in SiGe alloys arises from their potential in HBT's, HFET's, and optoelectronics devices, where migration over distances as small as a few nanometres can be significant. Successful modelling of these processes requires a much improved understanding of the mechanisms of self- and dopant diffusion in the alloy, although recent progress has been made. It is the purpose of this review to set this in the context of diffusion processes in elemental silicon and germanium, and to identify how this can help to elucidate behaviour in the alloy. Firstly, self diffusion processes are reviewed, from general agreement that self-diffusion in germanium is dominated by neutral and acceptor vacancies, to the position in silicon which is still uncertain. Germanium diffusion in silicon, however, appears to be via both vacancy and interstitial processes, and in the bulk alloy there is evidence for a change in dominant mechanism at around 35 percent germanium. Next, a review of dopant diffusion begins with Sb, which appears to diffuse in germanium by a mechanism similar to self-diffusion, and in silicon via monovacancies also, from marker layer evidence. In SiGe, the effects of composition and strain in epitaxial layers on Si substrates are also consistent with diffusion via vacancies, but questions still remain on the role of charged defects. The use of Sb to monitor vacancy effects such as grown-in defects by low temperature MBE, are discussed. Lastly, progress in assessing the role of vacancies and interstitials in the diffusion of boron is reviewed, which is dominated by interstitials in silicon-rich alloys, but appears to change to domination by vacancies at around 40 percent germanium, although studies in pure germanium are greatly needed.
Shallow Boron Implant Activation
Authors: Fiory A. T. , Bourdelle K. K. , Agarwal A. , Gossmann H.-J. , Rafferty C. S. 
Published: April 2011

ABSTRACTBoron was implanted into n-type Si at energies from 500 eV to 1 keV and doses near 1 E14 cm-2and 1E51 cm−2. Electrical activation was achieved by rapid thermal annealing (RTA) in nominally pure N−2and 0.1% 02 with the fastest available heating rates of up to 150 °C/s, cooling rates up to 80 °C/s, and included “spike” anneals with minimum dwell time at peak temperature. Measurements of sheet resistance, Hall coefficient, and secondary ion mass spectroscopy profiling were used to determine dopant activation and diffusion. Surface oxidation was studied by film thickness ellipsometry. Analyses of electrical transport measurements are used to relate junction depths to sheet resistance and their dependence on annealing temperature and time. For spike annealing, junction leakage and adequate activation limits the minimum practical temperature while diffusion limits the maximum practical temperature for formation of shallow junctions.
Defects and Diffusion in Silicon: An Overview
Authors: Cowern N.E.B. , Mannino G. , Stolk P.A. , Theunissen M.J.J. 
Published: April 2011

ABSTRACTAt the current pace of semiconductor technology development, transistor dimensions in advanced IC products will approach the range of a few tens of nanometers within the next decade. This presents a major challenge for our understanding of defects and diffusion in these tiny devices during processing. In response, an almost explosive growth in research on process physics has taken place at universities, national institutes and industry research labs worldwide. The central issue is the phenomenon of nonequilibrium diffusion driven by processing steps such as oxide growth, high concentration gradients of impurities, and annealing of damage caused by ion implantation. Nonequilibrium diffusion arises from perturbations to the natural thermal equilibrium concentrations of point defects - interstitial atoms and vacancies - in the silicon crystal. This paper gives a snapshot of our current understanding of the atomic-scale interactions between point defects and impurity atoms, extended defects and interfaces, as revealed by recent experimental and theoretical studies. The paper emphasizes the important role played by defect cluster ripening during transient enhanced diffusion and dopant activation.
Real-Time Monitoring by Spectroscopic Ellipsometry and Desorption Mass Spectroscopy During Molecular Beam Epitaxy of AlGaAs/GaAs at High Substrate Temperatures
Authors: Taferner W. T. , Mahalingam K. , Dorsey D. L. , Eyink K. G. 
Published: April 2011

ABSTRACTA series of AlGaAs/GaAs depositions were monitored in-situ by spectroscopic ellipsometry and desorption mass spectroscopy, under various substrate temperatures (890 K - 990 K) where non-unity sticking conditions occur. An upper bound on the temperature where AlGaAs/GaAs heterostructures may be grown was determined. Ex-situ cross-sectional transmission electron microscopy verified that the AlGaAs/GaAs layer thicknesses grown by molecular beam epitaxy were accurately determined by spectroscopic ellipsometry at these elevated temperatures. The substrate temperature dependence on Ga desorption rates was consistent with Monte Carlo simulation where desorption from both physisorbed and chemisorbed states were included.
Combined Spectroscopic Ellipsometry and Ion Beam Surface Analysis for In-Situ Real-Time Characterization of Complex Oxide Film Growth
Authors: Mueller A.H. , Gao Y. , Irene E.A. , Auciello O. , Krauss A.R. , Schultz J.A. 
Published: April 2011

ABSTRACTIn-situ real time characterization of chemically and structurally complex thin films is becoming important as complex materials are finding more applications in electronic devices. To this end, a unique thin film growth and deposition system was constructed combining a multi-target sputter deposition system with spectroscopic ellipsometry and time-of-flight ion scattering and recoil spectroscopy. This system is demonstrated with studies on YBa2Cu3O7−δand BaSrTiO3 films.
In Situ Growth Studies of Artificial Layered (BA,SR,CA)CUO2 on Quasi-Ideal SrTiO3 Substrates by High Pressure Rheed
Authors: Koster Gertjan , Rijnders Guus J.H.M. , Blank Dave H.A. , Rogalla Horst 
Published: April 2011

ABSTRACTThe layered structure of oxides, like the high-T, cuprates, has been topic of research for some years now. The possibility to control thin film deposition on an atomic level has made fabrication of artificial structures and junctions accessible by depositing atomic layers or molecular blocks sequentially. Perfectly smooth substrate surfaces are hereby a prerequisite.Using Pulsed Laser Deposition (PLD), different perovskite oxide materials have been deposited on SrTiO3 substrates. With in situ high pressure Reflection High Energy Electron Diffraction we studied growth at different temperatures and oxygen pressures. Ex situ XRD and AFM have been used to study the morphology after deposition.Here we applied a new approach in obtaining layer-by-layer growth implied by the way of depositing the material, almost regardless of the deposition conditions. By alternating intervals of high supersaturation depositing one unit cell layer with intervals of lower supersaturation, one is able to force a layer-by-layer growth mode, which is in principle only feasible with PLD. We applied this technique to fabricate the layered infinite structure (Ba,Sr,Ca)CuO2 with artificial layered modulation, which have been characterized by XRD and AFM.
Role of Microscopic Stress Fluctuations in Glass Transition and Glass Formation
Authors: Egami T. , Vitek V. 
Published: April 2011

AbstractAlthough the structure of liquids and glasses may appear highly disordered, the atomic motions in these phases are rather strongly correlated. Such a correlation, however, cannot be readily described by a pair density function, and higher order correlation functions are necessary. We suggest that the microscopic stresses defined at each atom are quite useful in describing such high order correlations. We discuss how the concept of the microscopic stress fluctuation helps to describe and understand the glass transition and glass formation phenomena. In a molecular dynamics study the local shear stresses were found to become orientationally correlated below a transition temperature, Ts, which is close to the melting temperature. Below Ts the viscosity shows a rapid increase and transverse phonons become more stable. Thus Ts could be viewed as a dynamical glass transition temperature. The conventional glass transition can be described in terms of the elastic percolation of the orientationally correlated regions. On the other hand, the microscopic stresses in the crystalline solid solutions define the topological stability limit of the crystalline phase, and predict the minimum solute concentration to form stable amorphous alloys.
Velocity and Orientation Dependence of Solute Trapping
Authors: Aziz M. J. , Tsao J. Y. , Thompson M. O. , Peercy P. S. , White C. W. 
Published: April 2011

AbstractThe fraction of impurity atoms in the liquid at the solid-liquid interface that join the crystal, known as the segregation coefficient k, during rapid crystal growth is known to deviate away from the equilibrium value towards unity as the interface speed v increases. Several plausible models have been proposed that account qualitatively for this behavior with different functional forms of k(v). We report measurements of the segregation behavior during rapid solidification following pulsed laser melting of Bi-implanted Si. The velocity dependence and the orientation dependence of the segregation coefficient of Bi in Si has been determined to sufficient accuracy to allow us to distinguish between models. Implications for the mechanism of solute trapping are discussed.
Inter-Sub-Level Spectroscopy of P-Type Modulation-Doped Ge Quantum Dots
Authors: Liu J. L. , Wu W. G. , Jin G. , Luo Y. H. , Thomas S. G. , Lu Y. , Wang K. L. 
Published: April 2011

ABSTRACTInter-sub-level transitions in p-type modulation-doped Ge quantum dots are observed. The structure is grown by molecular beam epitaxy and consists of 30 periods of Ge quantum dots separated by 6 nm boron-doped Si layers. An absorption peak in the mid-infrared range is observed at room temperature by Fourier transform infrared spectroscopy, and is attributed to the transition between the first two heavy hole states of the Ge quantum dots. This study suggests the possible use of modulation-doped Ge quantum dots for improved infrared detector application.