bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contamination Problems of Amorphous Silicon N-I-P Solar Cells on Metal Substrates
Authors: Goetz M. , Keppner H. , Pernet P. , Hotz W. , Shah A. 
Published: April 2011

AbstractCommercial aluminium and stainless steel sheets were used as substrates for thin film silicon solar cell deposition. The influence of elemental contamination and disturbed film growth on solar cell performance and yield were studied. Diffusion during film growth was found to be more pronounced than thermally activated interdiffusion of existing films. Surface irregularities of the substrate are shown to reduce the fill factor of the solar cell. Initial efficiencies of 8.5% with single-junction amorphous silicon solar cells on both types of metal sheets were reached.
Establishing a Quantitative Relationship Between Harmonic Signals and Damage in Interconnects
Authors: Wen Qingzhe , Clarke David R. 
Published: April 2011

AbstractWhen a metal conductor is driven by an AC current of frequency ω, its resistance will vary at a frequency 2ω, and a third harmonic voltage will be generated. If the conductor is also under a DC bias, a second harmonic voltage will arise as well. The magnitude of these harmonic voltages increases with damage because of nonlinear increases in the resistance caused by localized Joule heating. We use the harmonic technique to evaluate the damage in metal lines. The correlation between deliberately introduced defects of different sizes and the amplitude of the harmonic voltages has been studied experimentally. The harmonic technique shows higher damage sensitivity than the commonly used resistance method. Additionally, it has a better rejection to noise and resistance drifting.
Electromigration in Thin Metal Films in the Presence of Two Stress-Relaxation Mechanisms
Authors: Katsman A. , Levin L. 
Published: April 2011

AbstractKinetics of mass transfer in thin metal films during electromigration was analyzed as a function of the generated internal stress. Stress evolution was considered for the case when two different stress relaxation mechanisms can operate simultaneously near the anode end of the strip: thresholdless diffusional creep through a fixed aperture, and diffusional creep with a threshold stress, σt, through the same aperture. Stress distribution and electromigration rate were found as explicit functions of the film length, the aperture size, and the current density. The apparent threshold length was analyzed. It was shown that an apparent threshold product can grow with the current density, in agreement with the experimental results.
Film Crystallographic Texture and Substrate Urface Roughness in Layered Aluminum Metallization
Authors: Rodbell K. P. , Svilan V. , Gignac L. M. , Dehaven P. W. , Murphy R. J. , Licata T. J. 
Published: April 2011

AbstractMaterial anisotropy implies that many film properties are affected by crystallographic orientation in the growth direction (out-of-plane texture) and / or in the plane of growth (in-plane texture). Physical vapor deposited (PVD) Ti and Al-alloy films deposited on silicon dioxide substrates typically exhibit strong fiber textures in the growth direction with little in-plane-texture observed. The strength of these fiber textures has been found to vary substantially depending on the details of the deposition process(es) and, to a lesser degree, on any post-deposition anneals. In this paper the role of the substrate surface roughness in defining film texture is reported. It was found that the substrate surface roughness determines the overlying film crystallographic orientation for Ti and Ti/AlCu films deposited on various oxides. Furthermore, it was found that the texture of the initial metal “seed” layer defines the texture in subsequently deposited films (texture inheritance). Modifications to the oxide surface which decrease the surface roughness lead to an improved crystallographic texture in Ti, AlCu, Ti/AlCu and Ti/TiN/AlCu films. Film orientation was determined from crystallographic pole figures measured using x-ray diffraction (XRD). The oxide surface roughness was measured using atomic force microscopy (AFM), transmission electron microscopy (TEM) and glancing incidence x-ray reflectivity (GIXR).
Evaluation of Microstructure Evolution of Al-1%SI-0.5%CU Thin Film Induced By Post Deposition Processing
Authors: Zaccherini C. , Bacchetta M. , Pavia G. , Riva L. , Savoia C. 
Published: April 2011

AbstractThe evolution of grain structure of AI-1%Si-0.5%Cu film, deposited by sputtering at 150'C substrate temperature has been evaluated, comparing as deposited film microstructure and grain structure at the end of process, both on large metal areas and on narrow strips. Microstructure has been characterized by means of FIB, TEM and XRD analyses. Grain size evolution resulted to be strongly dependent from the type of substrate. In particular TiN substrate appeared to greatly inhibit AlSiCu grain growth. This behavior was attributed to the formation of Ti9AI23 intermetallic compound during the alloy thermal treatment, that pins grain boundaries thus limiting Al grain boundary mobility.
The Failure Mechanism of MOCVD TiN Diffusion Barrier at high Temperature
Authors: Lee Hoojeong , Sinclair Robert , Li Pamela , Roberts Bruce 
Published: April 2011

AbstractBy using TDEAT and ammonia gas, MOCVD TiN films were grown at 300°C and 30torr.After annealing in a vacuum furnace at 500°C, 550°C, and 600°C, the TiN films were investigated by transmission electron microscopy (TEM). After annealing at 550°C, both hexagonal and cubic AIN phase were found at the interface between Al and TiN films. A Ti rich phase such as Al3Ti was also found at Al side. The failure mechanism during high temperature annealing is discussed.
Reactive Plasma Sputter Deposition of Silicon Oxide
Authors: Vossough K. K. , Hunt C. E. 
Published: April 2011

AbstractSilicon dioxide films were reactively sputter deposited in argon/oxygen ambient using RF magnetron sputter deposition techniques. A substantial drop in the deposition rate at high enough partial pressure of the oxygen which is typical in reactive sputtering was observed. The best quality silicon dioxide films were obtained at the lower deposition rate, close to the deposition rate transition point. Higher quality films were obtained at higher RF powers with higher deposition rates. However, at 800 Watts RF, the so called negative ion effect dominates and results in higher surface roughness of the films, as seen by AFM results. Various characterization techniques including ellipsometry and wet chemical etching were used to compare stoichiometry and film density, respectively. MOS capacitor characterization along with breakdown voltages were also measured as a means of qualifying the films.
Hot Carrier Reliability in Sub-0.1 μm nMOSFET Devices
Authors: Saha Samar K. 
Published: April 2011

AbstractThis paper presents a systematic investigation of the hot-carrier effect in deep sub-micron silicon nMOSFET devices. A Hydrodynamic model for semiconductors was used to simulate the local carrier heating and the non-local transport phenomena in nMOSFETs of effective channel lengths 41, 66, 96, and 126 nrn under various biasing conditions. Test structures for device simulation were generated by using a super-steep retrograde channel profile with subsurface peak concentration of l×1018 cm−3, and a gate oxide thickness of 3 nm. Superb MOSFET device characteristics were obtained for all devices. The simulation results show a significant decrease in substrate current, electron impact ionization rate, and peak electron temperature near the drain end of the channel with the decrease in supply voltage. The distribution of electrons into the substrate due to local electron heating is shown to be responsible for hot-carrier reliability in ultra-short channel silicon nMOSFET devices.
Hot Carrier Effects in Deep Submicron Nmosfets
Authors: Phanse Abhijit , Saha Samar 
Published: April 2011

AbstractThis paper addresses hot-carrier related reliability issues in deep submicron silicon nMOSFET devices. In order to monitor the hot-carrier induced device degradation, the substrate current was measured for devices with varying channel lengths (20 um - 0.24 um) under various biasing conditions. Deep submicron devices experience velocity saturation of channel carriers due to extremely high lateral electric fields. To evaluate the effects of velocity saturation in the channel, the pinch-off length in the channel was extracted for all the devices of the target technology. It was observed that for very short channel devices, carriers in most of the channel experience velocity saturation and almost the entire channel gets pinched off. It is shown in this paper that for very short channel devices, the pinch-off length in the channel is limited by the effective channel length, and that velocity saturation effects are critical to the transport of channel carriers.
Low Temperature (850 °C) Two-Step N2O Annealed Thin Gate Oxides
Authors: Lai Chao Sung , Lee Chung Len , Lei Tan Fu , Chao Tien Sheng , Peng Chun Hung , Wang Han Ching 
Published: April 2011

AbstractThe electrical characteristics of thin gate dielectrics prepared by low temperature (850 °C) two-step N20 nitridation (LTN) process are presented. The gate oxides were grown by wet oxidation at 800 °C and then annealed in N2O at 850 °C. The oxide with N2O anneal, even for low temperature (850 °C), had nitrogen incorporation at oxide/silicon interface. The charge trapping phenomena and interface-state generation (ΔDitm) induced by constant current stressing were reduced and charge-to-breakdown (Qbd) under constant current stressing was increased. This LTN oxynitride was used as gate dielectric for N-channel MOSFET, whose hot-canrier immunity was shown improved and reverse short channel effect (RSCE) was suppressed.
A New, Real-Time Method for Measuring Mobile Charge and Injected Charge in SiO2 on Si
Authors: Edelman P. , Lagowski J. , Savchouk A. , Hoff A. , Jastrzebski L. , Persson E. 
Published: April 2011

AbstractWe present a new approach to measuring mobile charge in SiO2 without MOS test structures. The measurement is done in non-contact mode and offers a whole-wafer mapping capability of the mobile charge in single minutes. Determination of the mobile charge is based on monitoring the ion drift by measuring corresponding changes in the oxide voltage. The drift is induced on the whole wafer by corona charge deposited on SiO2 followed by 200°C annealing. Surface contamination is distinguished from bulk contamination by selecting the appropriate sequence of the corona-temperature-stress, which injects ions from the surface into the SiO2.
Finite Element Modeling Of Grain Aspect Ratio And Strain Energy Density In A Textured Copper Thin Film
Authors: Vinci R. P. , Bravman J. C. 
Published: April 2011

AbstractWe have modeled the effects of grain aspect ratio on strain energy density in (100)-oriented grains in a (111 )-textured Cu film on a Si substrate. Minimization of surface energy, interface energy, and strain energy density (SED) drives preferential growth of grains of certain crystallographic orientations in thin films. Under conditions in which the SED driving force exceeds the surface- and interface-energy driving forces, Cu films develop abnormally large (100) oriented grains during annealing. In the elastic regime the SED differences between the (100) grains and the film average arise from elastic anisotropy. Previous analyses indicate that several factors (e.g. elimination of grain boundaries during grain growth) may alter the magnitude of the SED driving force. We demonstrate, using finite element modeling of a single columnar (100) grain in a (111) film, that changes in grain aspect ratio can significantly affect the SED driving force. A minimum SED driving force is found for (100) Cu grains with diameters on the order of the film thickness. In the absence of other stagnation mechanisms, such behavior could cause small grains to grow abnormally and then stagnate while large grains continue to grow. This would lead to a bimodal grain size distribution in the (100) grains preferred by the SED minimization.
Thermal- And Electromigration- Induced Stresses In Passivated Al- And Alsicu-Interconnects
Authors: Beckers D. , Schroeder H. , Eppler I. , Schilling W. 
Published: April 2011

AbstractAl and Al- alloys are commonly used as interconnect materials in integrated electronic devices. Stress induced voiding and degradation of metal lines by electromigration are closely related to the stresses in the lines.We have studied the strain and stress evolution during thermal cycling, isothermal relaxation and due to electromigration in passivated Al and AlSi(1%)Cu(0.5%) lines by Xray diffraction with variation of experimental parameters such as the aspect ratio and the electrical current density. Furthermore the extent of voiding and plastic shear deformation has been determined from the experimental metal strains with the help of finite element calculations.Main results are: 1) During thermal cycling the voiding is less than 2.10-3. The extent of plastic shear deformation increases with increasing line width and with decreasing flowstress. 2) During isothermal relaxation void growth occurs but no significant change in the plastic shear deformation. 3) An electric current in the lines causes no measurable additional change of the volume averaged stresses up to line failure.
Temperature Dependence Of Residual Stresses In Capped Blanket Cu Films Of Various Thicknesses
Authors: Langelaan G. , Saimoto S. , Moske M. 
Published: April 2011

AbstractResidual strains in thin films of 1.0 μm, 0.5 μm and 0.25 μm Cu capped with 24 nm Ta and a 62 nm Ta diffusion barrier were measured using x-rays during continuous temperature ramping. Cycles up to 300°C and 400°C were performed. At ambient temperature, the flow stresses after heating to 400°C were found to increase wth decreasing film thickness. The stresses were sufficiently high below 100°C to cause plastic yielding. The diffracted intensities from the in-plane and out-of-plane (111) planes were recorded with temperature and the intensity changes were attributed to the necessary dislocation density and distribution variation to accomodate the mismatch strain due to thermal expansion differences.
Activation Energy of Electromigration in Copper Thin Film Conductor Lines
Authors: Gladkikh A. , Lereah Y. , Karpovski M. , Palevski A. , Kaganovskii Yu. S. 
Published: April 2011

AbstractActivation energy of electromigration damage was determined as 1.2 eV for Cu
lines, indicating grain boundary paths for electromigrationo The surface diffusion was found to play a role during electromigration in Cu and impeded the failure process.
Residual Stress And Lattice Distortion Mapping Of Patterned Devices Which Failed Electromigration Testing Using The Microbeam X-Ray Diffraction (MXRD) Technique
Authors: York B. R. , Pfizenmayer H. L. , Lee C. H. , Carnes R. O. 
Published: April 2011

AbstractSpatially resolved residual stress and lattice distortion measurements have been made or experimental RF NPN devices which failed electromigration testing. The experimental devices underwent a steady state long term life test for 38272 hours at a die temperature of 100 degrees Celsius and device emitter currents of 100 mA. Residual stress contour maps of the Au interconnect metallurgy of these patterned devices were constructed with spatial resolution approaching 13 microns. The stress contour maps clearly show areas of the Au interconnect emitter lines, approximately 17 microns wide, which buckled when the local stresses exceeded the adhesion limits of these films. A stress gradient was observed going along the Au line from the emitter to the wire bonded pad which went from slightly compressive near the emitter to tensile approaching the wire bonded lead, and consistent with electromigration failures. In addition, lattice distortions as determined by integral line breadths, which were least square fitted by a gaussian*orentzian convolution of the instrument function, show a large continuous increase along the Au interconnect line in going from the emitter to the wire bond pad. The data was acquired using a 4-circle x-ray diffractometer which was specifically constructed to study electromigration issues in-situ. The diffractometer has a very low sphere of confusion (< 5 microns) and is equipped with tapered glass capillary optics, a mechanical, electrical, and thermal stressing stage and various energy dispersive (EDX) or position sensitive (PSD) detectors.
Electromigration In Submicron Wide Copper Lines
Authors: Kononenko O. V. , Matveev V. N. , Koval Yu. I. , Dubonos S. V. , Volkov V. T. 
Published: April 2011

AbstractCopper films were deposited onto oxidized silicon wafers by the self-ion assisted technique. A 0 and 6 kV bias was applied to the substrate during the deposition. The films were patterned into parallel line arrays of 20 lines 0.5 mm long, using electron lithography and dry etching. After patterning, the lines were covered by silicon oxide and annealed in vacuum for 1 hour at the temperature 450° C. Electromigration testing was performed in air in the temperature range from 280° to 350° C and at a current density 3.106 A/cm2.It was found that the resistivities of the films deposited at 6 kV and without bias were 1.7 and 2.0 μΩ-cm, respectively. The median times to failure are 398.6 and 240 h and the deviations in the time to failure are 0.8 and 0.54 for 6 kV lines and 0 kV lines, respectively. An electromigration activation energy of 0.89 eV was found for 0 kV films.
Characterization of Electromigration Failures Using a Novel Test Structure
Authors: Gall Martin , Jawarani Dharmesh , Kawasaki Hisao 
Published: April 2011

AbstractElectromigration failures occur at locations where Al mass transport flux divergences exhibit a maximum. In VLSI circuits, these locations correspond to tungsten plug contact / via areas. Characterizing and understanding electromigration failures at tungsten plug contact / via areas are essential in assuring the reliability of 0.5 μm and smaller devices. In this study, a novel test structure with four vias connecting metal 1 and metal 2 levels was used to separate two stages in the Al-Cu interconnect electromigration process. These stages are the incubation time during which Cu in the Al-Cu alloy is swept away from the via area and an Al drift time which leads to interconnect failure. By the use of this structure, a non-destructive method has been established to measure incubation times and Al drift times separately, monitoring discrete increases in line resistance corresponding to a sequential depletion of all four vias. Activation energies for both processes have been determined. The temperature dependence of the incubation time is characterized by a thermal activation energy of Q=1.08 ± 0.15 eV, indicative of Cu grain boundary diffusion through Al grains. Al depletion was found to occur with an activation energy of Q=0.72 ± 0.12 eV. We therefore conclude that Al self-grain boundary diffusion constitutes the Al depletion mechanism. The application of this novel test structure enables distinct determination of dominating failure mechanisms under operating conditions and therefore provides a realistic reliability assessment of actual on-chip interconnect structures.
The Effects of Accelerated Stress Conditions on Electromigration Failure Kinetics and Void Morphology
Authors: Bauguess S. , Liu L. H. , Dreyer M. L. , Griswold M. , Hurley E. 
Published: April 2011

AbstractAccelerated life testing has long been used to measure the electromigration reliability of integrated circuit (IC) metallization systems. In order to establish or verify electromigration design rules for IC products the measured data is extrapolated over a wide range of operating conditions using phenomenological models. These models assume that the components of the diffusional flux, thermal stress and resulting void morphology are independent of test/operating condition. In this paper, electromigration void morphology and failure criteria are studied over a range of stress conditions and microstructures for non-layered AlCu and AlCuSi metallurgies. The failure criteria, defined as the average change in conductor resistance prior to an open circuit condition, was strongly dependent on test current density. Moreover, the nature of the relationship between failure criteria and current density was governed by the linewidth (W) relative to the median grain size (D50). This dependence can be explained qualitatively in terms of the Blech Effect.
Study of Cobalt Salicide Fabrication on Sub-Quarter Micron Polysilicon Lines
Authors: Chen Wei-Ming , Pozder Scott , Limb Young , Sitaram A R , Fiordalice Bob 
Published: April 2011

AbstractComparison of anneal temperatures, sheet resistance, gate to source/drain leakage current, and implant pre-amorphization are studied for a conventional 2-step cobalt salicide process and a TiN capped cobalt salicide. The TiN capped cobalt silicide process is found to be superior to the conventional cobalt salicide process in producing lower sheet resistance and tighter sheet resistance distribution. The use of a TiN cap also suppresses Si out diffusion, which can prevent shorting between the gate and source/drain areas when pre-amorphization of Si substrate is used to enhance silicidation. The metal residue on oxide and nitride substrates after metal anneal and metal etch are compared using total reflection x-ray fluorescence. It is found that both Ti and Co residue on silicon nitride is higher than on silicon oxide after metal anneal and metal strip.
Influence of HCL on Rapid Thermal Oxides
Authors: Hames G. A. , Beck S. E. , Gilicinski A. G. , Henson W. K. , Wortman J. J. 
Published: April 2011

AbstractThe influence of HCl on the quality of gate oxides grown by rapid thermal oxidation has been investigated. HCl was added to oxidation ambient for some rapid thermal oxides while for others the silicon surface was annealed in a partial HCl ambient prior to rapid thermal oxidation. Improvements in gate oxide integrity were monitored on MOS capacitors and MOSFET devices by I-V and C-V testing. The levels of chlorine incorporated in the oxide from the addition of HCl to the process was measured by secondary ion mass spectroscopy. Atomic force microscopy was performed to measure surface roughening during HCl pre-oxidation treatments.