bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Preexisting Stress Voids on Electromigration Stress Buildup and Flux Divergence
Authors: Shen Y. -L. , Minor C. A. , Guo Y. L. 
Published: April 2011

AbstractNumerical modeling of electromigration stress buildup and flux divergence was undertaken. The objective is to provide a mechanistic understanding of the question: Do preexisting stress voids grow during later electromigration, to become potentially fatal? Conflicting experimental results have been reported. In this work the stress field in aluminum interconnects containing voids was first quantified using the finite element analysis. The averaged stress field then served as the initial condition in the one-dimensional partial differential equation of electromigration stress buildup. The finite difference method was employed to solve the evolving stress profile and the associated atomic flux and flux divergence along the conducting line. It was found that a large preexisting void suffers greater flux divergence and is therefore more prone to growth during electromigration. A single large stress void is more detrimental than populous small voids. Published experimental observations seem to support these findings.
Dimer Reconstruction at Metal-Silicide/Silicon Interfaces: A First-Principles Study
Authors: Yu B. D. , Miyamoto Y. , Sugino O. , Sakai A. , Sasaki T. , Ohno T. 
Published: April 2011

AbstractBy employing first-principles total-energy calculations we studied the atomic and chemical structure of NiSi2/Si(001) and CoSi2/Si(001) interfaces that are of great importance in understanding electronic properties, such as the Schottky-barrier height, of metal-silicide/silicon junctions. We found a new structural model that is more stable than previously proposed models of interface structures and well explains existing experimental data. The new interface model consists of sevenfold-coordinated interfacial metals and a 2×1 periodic array of interfacial Si dimers, similar to the Si(001) 2×1 surface reconstruction, reducing the number of dangling bonds.
Advanced CVD Barrier Technology for Copper Interconnect
Authors: Jain A. , Adetutu O. , Ekstrom B. , Hamilton G. , Herrick M. , Venkatraman R. , Weitzman E. 
Published: April 2011

AbstractThe adoption of copper (Cu) interconnects has imposed the challenge of developing a chemical vapor deposition (CVD) diffusion barrier technology that can be implemented for subhalf micron back-end design rules. Chemical vapor deposition (CVD) offers significantly higher film step coverage compared with sputter deposition processes. A number of materials have been proposed in literature for diffusion barriers of copper. However, the ability to suppress diffusion of Cu is only one of the barrier requirements out of a long list necessary for process integration. A number of other factors depend on the interaction of the barrier with Cu and with the underlying dielectric. We will begin with a review of some of the CVD candidate materials followed by a discussion on various interactions between barrier/Cu and barrier/dielectric that impact process reliability.In addition there are manufacturing considerations ranging from availability of high purity precursor to complex issues of process compatibility, lowering defectivity, and reducing cost-ofownership (CoO). Ultimately, the choice may not necessarily be the most robust diffusion barrier but a process which provides adequate barrier properties and can be integrated easily and cost effectively to build Cu interconnect structures. Therefore, both materials and manufacturing requirements must be considered for selecting a barrier system.A literature review is presented on some of the integration schemes and limitations they place on a barrier system. We will also share work done at Motorola on materials characterization and process development towards integration on some of the barrier processes. Finally, future trends in process development of diffusion barriers is presented.
Growth and Structure of Metallic Barrie Laye and Interconnect Films I: Exeriments
Authors: Windt D. L. , Torre J. Dalla , Gilmer G. H. , Sapjeta J. , Kalyanaraman R. , Baumann F. H. , O'Sullivan P. L. , Dunn D. , Hull R. 
Published: April 2011

AbstractWe present experimental results directed at understanding the growth and structure of metallic barrier layer and interconnect films. Numerical simulation results associated with this experimental work are presented in an accompanying paper in these proceedings. Here, thin films of Al, Ti, Cu and Ta have been grown by magnetron sputtering onto oxidized Si substrates. Using a specially-constructed substrate holder, the orientation of the substrate with respect to the growth direction was varied from horizontal to vertical. Films were grown at both low and high argon pressure; in the case of Ta, the cathode power was varied as well. The film structure and in particular the surface roughness was measured by X-ray reflectance and also by atomic force microscopy. We find that the surface roughness increases markedly with orientation angle in the case of Ta and Cu films, and in Ti films grown at high argon pressure. At low pressure, however, the Ti film surface roughness remains constant for all substrate orientations. No variation in roughness with either orientation angle or argon pressure was observed in the Al films. These results suggest that, under certain circumstances, shadowing effects and/or grain orientation (i.e., texture) competition during growth can give rise to lower density, more porous (and thus more rough) films, particularly at large orientation angles, as on sidewalls in sub-micron trenches.
Factors Affecting Passivation and Resistivity of Cu(Mg) Alloy Film
Authors: Cho Heung Lyul , Lee Jae Gab 
Published: April 2011

AbstractWe have investigated the variables affecting passivation and resistivities of Cu alloy, which was sputter prepared from a Cu(6 at.%Mg) target. The results show that oxidation of Cu(Mg) alloy includes the surface segregation of Mg and its preferential oxidation. Sufficient surface segregation of Mg is necessary to form the high quality, protective MgO layer on the surface. The interfacial oxide layer produced from the reaction of Mg and SiO2 does not serve as a barrier against Mg diffusion, thereby the generation of free Si seems to continue until Mg is exhausted in copper. Therefore, lowering the contents of Mg in copper is required to reduce the resistivity of Cu(Mg) alloy. In-situ heating of substrate is very effective to reduce the Mg contents in copper alloy and to enhance the surface segregation of Mg, thereby facilitating the passivation of Cu(Mg) alloy with the low resistivity, especially during the low temperature oxidation.
Mechanisms for Microstructure Evolution in Electroplated Copper Thin Films
Authors: Harper J. M. E. , Cabral C. , Andricacos P. C. , Gignac L. , Noyan I. C. , Rodbell K. P. , Hu C. K. 
Published: April 2011

AbstractWe present a model which accounts for the dramatic evolution in the microstructure of electroplated copper thin films near room temperature. Microstructure evolution occurs during a transient period of hours following deposition, and includes an increase in grain size, changes in preferred crystallographic texture, and decreases in resistivity, hardness and compressive stress. As the grain size increases from the as-deposited value of 0.05–0.1 μm up to several μm, the decreasing grain boundary contribution to electron scattering lowers the resistivity by tens of percent to near-bulk values. Concurrently, as the volume of grain boundaries decreases, the stress is shown to change in the tensile direction by tens of MPa. The as-deposited grain size is also shown to be consistent with grain boundary pinning.
In-Situ Characterisation of Precipitation in Al-Cu thin films
Authors: Lokker J. P. , Bottger A. J. , Janssen G. C. A. M. , Radelaar S. 
Published: April 2011

AbstractThe precipitate formation occurring in Al-Cu thin foils with copper concentrations of either 1.15 at.% or 0.3 at.%, has been studied. In-situ X-ray diffraction analysis and differential scanning calorimetry are applied to determine the phases formed and the enthalpy changes in the same samples. Both X-ray diffraction and differential scanning calorimetry indicate that the precipitation behaviour of thin films (about 500 nm thickness) differs significantly from that of bulk material. In the films studied the precipitation of Al2Cu occurs at a much lower temperature than expected on the basis of the (bulk) phase diagram. Moreover, no intermediate phases are observed prior to Al2Cu precipitation. Also the amount of Cu in solid solution (0.20 at%Cu) observed by electron-probe micro-analysis after slowly cooling from 500°C to room temperature, exceeds the solubility of bulk Al-Cu.
Integration of Low Dielectric Constant Materials in Advanced Aluminum and Copper Interconnects
Authors: Zhao Bin , Brongo Maureen 
Published: April 2011

AbstractAdvanced on-chip interconnects using new materials and new integration architectures are necessary for current and future IC chips in order to meet the requirements in performance, reliability and manufacturing cost. Insulating materials with low dielectric constant (low-κ) and conductive materials with low-resistivity have drawn significant attention for their possible applications in IC interconnects. Dual damascene interconnect integration architectures not only offer process simplification and low cost, but also enable the use of low-resistive Cu for interconnect wiring. Use of low-κ materials in dual damascene architecture is challenging due to material and processing issues. In this paper, the evolution of advanced interconnects, materials and technology options, and some recent achievements in advanced interconnect systems of low-κ dielectric and dual damascene architectures for both Al and Cu metallization are reviewed and discussed.
The Study of Fluorinated Amorphous Carbon as Low-K Dielectric Material and its Interface with Copper Metallization
Authors: Ariel N. , Eizenberg M. , Tzou E. Y. 
Published: April 2011

AbstractIn order to achieve better performance of devices, the interconnects RC delay time, the limiting factor of the device speed today, must be reduced. This calls for a new interconnect stack: lower resistivity Copper and low k materials (k<3) as dielectrics.Fluorinated amorphous carbon (a-F:C) prepared by HDP- CVD is an attractive candidate as a low-k material. In this work we have studied the film, its stability and its interface with Copper metallization. The high density plasma CVD process resulted in a film which contains C and F at a ratio of 1:0.6 as determined by Nuclear Reactions Analysis. XPS analysis of the C Is transition indicated four types of bonds: C-C, C-CF, CF, and CF2. X-ray diffraction as well as high resolution TEM analyses proved that the film was amorphous at least up to 500°C anneal. For various applications, the advantage of adding a thin bi-layer of a-SiC/SiOx for adhesion promotion purposes was demonstrated. In addition, the interface of a-F:C and the adhesion promoter layer with Ta, TaN and Cu was studied. No interdiffusion was observed by SIMS after 400°C annealing. 500°C annealing caused F outdiffusion from the film and Cu diffusion into the adhesion promoter layer.
A New Low Dielectric Constant Polymer Material (k < 2): Microstructure, Electrical Properties, and Mechanical Properties
Authors: Tsai Yi-Pin , Liao C. N. , Xu Yuhuan , Tu K. N. , Zhao Bin , Liu Q.-Z. , Brongo Maureen 
Published: April 2011

AbstractA porous polymer material, which is made of a two-phase composite and contains 35% porosity with a pore size less than 50Å, is found to have a dielectric constant of 1.8. It absorbs almost no water. The electrical properties, such as capacitance and leakage current, do not change with time and temperature.
Preparation and Properties of Polysilsesquioxanes - Polysilsesquioxanes as a Candidate to a Low Dielectrics for Electronic Devices -
Authors: Abe Yoshimoto , Kagayama Keiko , Takamura Norihiro , Gunji Takahiro 
Published: April 2011

AbstractPolysilsesquioxanes PSSQ as a candidate of coatings for interlayer low dielectric films were synthesized by acid and base catalyzed hydrolytic polycondensation of RSi(OMe)3 (R=methyl, vinyl, 3-methacryloxypropyl). Dip and spin coating of PSSQ on organic and inorganic substrates followed by curing at 100 °C, 400 °C, and 450 °C provided transparent and tough coating films of thickness 2000–9000 A. Polysilsesquioxanes adhered strongly to the substrates to form coating films of which the adhesion strength and hardness were 10 and 9H based on JIS K5400 comparable to ISO standard, as heating time and molecular weight increase. On curing at the elevated temperatures, they provided the films with a very smooth surface and the dielectric constants of 3.2∼3.6 (R=3-methacryloxypropyl), 3.8∼4.0 (R=vinyl), and 2.5∼2.7 (R=methyl) depending on film thickness and molecular weight of PSSQ. The films from PSSQ (R=methyl) were found to be porous compared with those from PSSQ (R=vinyl).
In-Situ Studies of the Formation of GA and AL Wires on SI(112) Facet Surfaces
Authors: Prokes S.M. , Glembocki O.J. 
Published: April 2011

ABSTRACTReflectance difference anisotropy (RDA) and low energy electron diffraction (LEED)have been used to study the formation of Ga or Al chains and nanowires on the Si(112) surface. At T > 350°C, the Ga or Al chains form at the step edges by a self-limiting process, while at lower temperatures, Ga or Al nanowires form on the terraces in addition to the chains on the ledges. The process has been tracked in real time from the rapid change of the (2×1) Si(112) reconstruction under subcritical coverage to chain formation leading to a 5×1 reconstruction followed by a 6×1 reconstruction’. During sequential deposition of Ga and Al, we observe (in RDA and AES) that Ga atoms forming the chains can be replaced by Al, indicating a stronger Al-Si bond strength and confirming the chemical sensitivity of the light scattering in RDA. Low temperature depositions (in the 300’C range) are shown to lead to the formation of Al (or Ga) metallic wires on the Si(111) terraces. Continued deposition of less than 10 monolayers at T below 250°C leads to a very anisotropic but patterned Al or Ga structure in registry with the substrate which retains an unexpectedly large polarizability for coverages as thick as 40 ml.
Multifunctional Optical In Situ Monitoring of Semiconductor Film Growth
Authors: Bertness K. A. , Hays S. P. , Hickernell R. K. 
Published: April 2011

ABSTRACTWe have modified a normal-incidence optical reflectance spectroscopy system to allow rapid switching between the measurement of sample reflectance and sample emission. The resulting optical system is capable of “smart” pyrometry, in which sample emissivity is measured rather than assumed. The emissivity measurement makes use of the principle of detailed balance, which states that for specular, opaque samples, the sum of the emissivity and reflectance at each wavelength is equal to 1. We present data based on multilayer III-V semiconductor structures grown by molecular beam epitaxy, but the optical system would function equally well in any growth or deposition system with optical access to the substrate. The “smart” pyrometry temperatures we measure typically differs from conventional pyrometry by 5 to 10°C, and occasionally as much as 20°C, for multilayer structures of AIGaAs and GaAs. We present details of the optical components and arrangement that minimize the effect of sample wobble and allow the system operator regular visual access to the sample. Calibration techniques for the combined system are also discussed.
Dislocation-Induced Surface Strain on (001) Silicon-On-Insulator
Authors: Sutter P. , Lagally M.G. 
Published: April 2011

ABSTRACTWe demonstrate a novel technique, based on low-energy electron microscopy, by which inhomogeneous uniaxial strain at the (001) surface of Si can be mapped quantitatively. Using this technique on silicon-on-insulator wafers, we determine the surface strain field induced by a single 60° dislocation and show that such extended defects can be used as monitors of heteroepitaxy-induced changes in the surface strain.
Nucleation and Growth of Supported Metal Clusters at Defect Sites on Mgo and NaCl (001) Surfaces: The Cases of Pd and Ag
Authors: Venables J. A. , Haas G. , Brune H. , Harding J.H. 
Published: April 2011

ABSTRACTNucleation and growth of metal clusters at defect sites is discussed in terms of rate equation models, which are applied to the cases of Pd and Ag on MgO(001) and NaCl(001) surfaces. Pd/MgO has been studied experimentally by variable temperature atomic force microscopy (AFM). The island density of Pd on Ar-cleaved surfaces was determined in-situ by AFM for a wide range of deposition temperature and flux, and stays constant over a remarkably wide range of parameters; for a particular flux, this plateau extends from 200 K ≤ T ≤ 600 K, but at higher temperatures the density decreases. The range of energies for defect trapping, adsorption, surface diffusion and pair binding are deduced, and compared with earlier data for Ag on NaCl, and with recent calculations for these metals on both NaCl and MgO
UHV-Investigation on MOCVD-grown InP(100) Surfaces
Authors: Visbeck S. , Hannappel T. , Vogt P. , Mahrt J. , Zorn M. , Knorr K. , Neges M. , Esser N. , Richter W. , Willig F. 
Published: April 2011

ABSTRACTEpitaxial InP(100)-films were prepared with TBP (tertiarybutylphosphine) and TMIn (trimethylindium) as precursors in a commercial MOCVD reactor. During growth, the V-III-ratio and TBP partial pressure were varied between 50 and 1 and possible changes of the surface structure monitored with the corresponding RAS (reflectance anisotropy spectroscopy) signal based on a correlation established with corresponding LEED measurements. Bulk properties of these films were investigated ex-situ with photoluminescence at 2 K, showing no noticeable difference between the samples. The MOCVD apparatus was modified to facilitate transfer of the sample from the MOCVD environment to UIHV in less than 20 seconds (to the 10−9 mbar range). After transfer, the same RA spectrum was recovered also in the critical case of the P-rich, as-grown surface. A corresponding Auger electron spectrum (AES) did not show any trace of contamination. Furthermore, the surface structure was investigated with LEED and STM. The LEED picture shows a clear (2×l)-pattern with a weak twofold symmetry along the [011] direction, STM pictures revealed a disordered surface terminated by P-dimers
Structural and Electrical Properties of Beryllium Implanted Silicon Carbide
Authors: Henkel T. , Tanaka Y. , Kobayashi N. , Tanoue H. , Gong M. , Chen X. D. , Fung S. , Beling C. D. 
Published: April 2011

ABSTRACTStructural and electrical properties of beryllium implanted silicon carbide have been investigated by secondary ion mass spectrometry, Rutherford backscattering as well as deep level transient spectroscopy, resistivity and Hall measurements. Strong redistributions of the beryllium profiles have been found after a short post-implantation anneal cycle at temperatures between 1500 °C and 1700 °C. In particular, diffusion towards the surface has been observed which caused severe depletion of beryllium in the surface region. The crystalline state of the implanted material is well recovered already after annealing at 1450 °C. However, four deep levels induced by the implantation process have been detected by deep level transient spectroscopy.
The Effect of Annealing on Argon Implanted Edge Terminations for 4H-SiC Schottky Diodes
Authors: Knights A P , Morrison D J , Wright N G , Johnson C M , O'Neill A G , Ortolland S , Homewood K P , Lourenço M A , Gwilliam R M , Coleman P G 
Published: April 2011

ABSTRACTThe edge termination of SiC by the implantation of an inert ion species is used widely to increase the breakdown voltage of high power devices. We report results of the edge termination of Schottky barrier diodes using 30keV Ar+ ions with particular emphasis on the role of postimplant, relatively low temperature, annealing. The device leakage current measured at 100V is increased from 2.5nA to 7μA by the implantation of 30keV Ar+ ions at a dose of 1×1015 cm−2. This is reduced by two orders of magnitude following annealing at 600°C for 60 seconds, while a breakdown voltage in excess of 750V is maintained. The thermal evolution of the defects introduced by the implantation was monitored using positron annihilation spectroscopy (PAS) and deep-level-transient spectroscopy (DLTS). While a concentration of open-volume defects in excess of 1×1019cm−3 is measured using PAS in all samples, electrically active trapping sites are observed at concentrations ∼1×1015cm−3 using DLTS. The trap level is well-defined at Ec−Et = 0.9eV.
Characterization of P-Type Buffer Layers for SiC Microwave Device Applications
Authors: Konstantinov A. O. , Karlsson S. , Nilsson P.-Å , Saroukhan A.-M. , Svedberg J.-O. , Nordell N. , Harris C. I. , Eriksson J. , Rorsman N. 
Published: April 2011

ABSTRACTLow-loped p-type silicon carbide buffer layers are grown by chemical vapor deposition on conducting and semi-insulating substrates. Capacitance-voltage and electrical admittance techniques are developed for accurate non-destructive characterization. The electrical admittance techniques suggested are capable of measuring the resistivity in a very wide range, up to 7 orders of magnitude. MESFET devices using thick buffer layers on conducting substrates are reported with Ft=8.4 GHz and Fmax=32 GHz.
Growth of SiC Thin Films on (100) and (111) Silicon by Pulsed Laser Deposition Combined with a Vacuum Annealing Process
Authors: Huang Jipo , Wang Lianwei , Wen Jun , Wang Yuxia , Lin Chenglu , Zetterling Carl-Mikael , Ostling Mikael 
Published: April 2011

ABSTRACTCrystalline 3C-SiC thin films were successfully grown on (100) and (111) Si substrates by using ArF pulsed laser ablation from a SiC ceramic target combined with a vacuum annealing process. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were employed to study the effect of annealing on the structure of thin films deposited at 800°C. It was demonstrated that vacuum annealing could transform the amorphous SiC films into crystalline phase and that the crystallinity was strongly dependent on the annealing temperature. For the samples deposited on (100) and (111) Si, the optimum annealing temperatures were 980 and 920°C, respectively. Scanning electron microscope (SEM) micrographs exhibited different characteristic microstructure for the (100) and (111) Si cases, similar to that observed for the carbonization layer initially formed in chemical vapor deposition of SiC films on Si. This also showed the presence of the epitaxial relationship of 3C-SiC[100]//Si[100] and 3C-SiC[111]//Si[111] in the direction of growth.
On the Role of Foreign Atoms in the Optimization of 3C-SiC/Si Heterointerfaces
Authors: Masri P. , Moreaud N. , Averous M. , Stauden Th. , Wohner T. , Pezoldt J. 
Published: April 2011

ABSTRACT3C-SiC/Si structures with Ge incorporation are elaborated by solid source molecular beam epitaxy (SSMBE). A comparison of the flatness of the SiC-surface and the interface between SiC and Si by comparing the deposition with and without Ge is made. The results are analyzed within the framework of a theoretical approach based on the theory of elasticity.
Current Status of SiC Power Switching Devices: Diodes & GTOs
Authors: Seshadri S. , Agarwall A. K. , Hall W. B. , Mani S. S. , MacMillan M. F. , Rodrigues R. , Hanson T. , Khatri S. , Sanger P. A. 
Published: April 2011

ABSTRACTThe progress that has been made in SiC diodes and GTOs is reviewed. A 100 A/1000 V SiC pi- n diode package, the highest current rating reported for any SiC device, a 69 A conduction/ 11 A turn-off of a SiC GTO and MTOTM, as well as the first all-SiC, 3 phase Pulse Width Modulated (PWM) inverter are reported, herein, for the first time. The inverter achieves voltage controlled turn off with a high temperature capable, hybrid SiC JFET. Material and process technology issues that will need to be addressed before device commercialization can be realized are discussed.