bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Vacancy-Type Defects on Electrical-Activation of P+ Implanted into Silicon
Authors: Watanabe M. , Kitano T. , Asada S. , Uedono A. , Moriya T. , Kawano T. , Tanigawa S. , Suzuki R. , Ohdaira T. , Mikado T.
Published: April 2011

The effects of vacancy-type defects induced by ion implantation on the electricalactivation of implanted phosphorus by rapid thermal annealing (RTA) are investigated using the positron annihilation technique, secondary ion mass spectroscopy (SIMS) and the spreading resistance (SR) method. P÷ ions are implanted into bare Si wafers and into Si through Si02 films at 700 keV with doses of the order of l×1013 cm−2. After implantation, rapid thermal annealing (RTA) is performed at temperatures between 600 and 1100 °C for 20 sec. The result shows that vacancy-type defects compensate the electrical-activation of P implanted into Si and also recoiled- oxygen is affected on the electrical-activation of P. The species of main defects for compensating the electrical-activation is identified as a divacancy (V2) from the lifetime of positrons. Effects of recoiled oxygen on the electricalactivation are attributed to the formation of vacancy-oxygen complexes just below the SiO2/Si interface and a resultant decrease in the diffusion length of vacancy-type defects.
Surface and Interface Stress in Epitaxial Growth
Authors: Ibach H. , Grossmann. A.
Published: April 2011

Recent experimental measurements on the interface stresses in two heteroepitaxial systems have shown that the interface stresses were unexpectedly large. For thin deposited layers, the interface stress can exceed the stress caused by the lattice mismatch by far. Arguments are presented which indicate that the surface stress may be caused by the charge transfer between the deposit and the substrate. The consequences for the critical thickness of pseudomorphic films are discussed and it is shown that depending on the sign of the interface stress and the mismatch the critical thickness can be either reduced or enhanced by a large factor.
Growth of Niobium Films at High Temperatures on Sapphire
Authors: Wagner T.
Published: April 2011

The growth and microstructural evolution of Nb thin films on the basal plane of α-Al2O3were studied at different growth temperatures. The influence of island orientation, density, and misfit strain energy on the growth behavior of Nb films on (0001)α-Al2O3at high temperatures has been investigated. The films were grown by MBE at 900°C and 1100°C. At these temperatures the Nb grows in the Volmer-Weber growth mode on the basal plane.In-situreflection high energy electron diffraction (RHEED), Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) investigations revealed that in the initial growth stage, Nb nuclei with different epitaxial orientations were formed. This leads to different orientations of thicker Nb films at different growth temperatures. At a growth temperature of 900°C the Nb{111} planes are parallel to the sapphire basal plane whereas at 1100°C Nb grows with the {110) planes parallel to the basal plane of sapphire. The formation of two different epitaxial orientations of thick Nb films can only be explained by considering both the change in the total density of Nb islands with temperature and the influence of island size on their total energy.
Evolution of Surface Roughness During CVD Growth
Authors: Chason E. , Mayer T.M. , Adams D.P. , Huang H. , Diaz De La Rubia T. , Gilmer G. , Kellerman B. K.
Published: April 2011

Monte Carlo simulations of physical and chemical vapor deposition are used to study roughening kinetics of films that grow by nucleation and coalescence of clusters. The effects of interlayer transport, preferential dissociation of molecular precursors and energetic differences between the clusters and the substrate are examined.
The Effect of Stress on the Nanomechanical Properties of Au Surfaces
Authors: Houston J. E.
Published: April 2011

Stress in thin films plays a critical role in many technologically important areas. The role is a beneficial one in strained layer superlattices where semiconductor electrical and optical properties can be tailored with film stress. On the negative side, residual stress in thin-film interconnects in microelectronics can lead to cracking and delamination. In spite of their importance, however, surface and thin-film stresses are difficult to measure and control, especially on a local level. In recent studies, we used the Interfacial Force Microscope (IFM) in a nanoindenter mode to survey the nanomechanical properties of Au films grown on various substrates. Quantitative tabulations of the indentation modulus and the maximum shear stress at the plastic threshold showed consistent values over individual samples but a wide variation from substrate to substrate. These values were compared with film properties such as surface roughness, average grain size and interfacial adhesion and no correlation was found. However, in a subsequent analysis of the results, we found consistencies which support the integrity of the data and point to the fact that the results are sensitive to some property of the various film/substrate combinations. In recent measurements on two of the original substrate materials we found a direct correlation between the nanomechanical values and the residual stress in the films, as measured globally by a wafer warping technique. In the present paper, we review these earlier results and show recent measurements dealing with stresses externally applied to the films which supports our earlier conclusion concerning the role of stress on our measurements. In addition, we present very recent results concerning morphological effects on nanomechanical properties which add additional support to the suggestion that near-threshold indentation holds promise of being able to measure stress on a very local level
Low Temperature Annealing of Rh (111) Surfaces
Authors: Tsui Frank , Wellman Joanne , Xu Junhao , Uher Ctirad , Clarke Roy
Published: April 2011

We have studied smoothing kinetics of Rh (111) surfaces during low temperature annealing using in-situ real-time reflection high energy electron diffraction and scanning tunneling microscopy. The initial surface features were produced by low temperature homoepitaxial growth of Rh (111). Two types of surfaces were studied, surfaces with two-dimensional (2D) islands at submonolayer coverages, and those with 3D multilayered features. 2D islands coarsen rapidly at the onset of the anneal. 3D features are more stable initially. Their annealing process exhibits a distinct transition from an initial slow coarsening, characterized by a nearly linear growth of lateral size, to a rapid flattening. The activation energy for the transition is ˜ 0.6 eV. The observed behavior indicates that the smoothing kinetics in the low temperature regime is limited by adatom detachment from the step-edges, and that the fast process for the 3D features is made possible by the formation of a network of “chain-like” structures which provide new pathways for diffusion thus overcoming the slow detachment kinetics. These effects determine the low temperature stability of the non-equilibrium epitaxial morphologies.
Studies of Morphological Instability and Dislocation Formation in Heteroepitaxial Si1−xGex Thin Films Via Controlled Annealing Experiments
Authors: Ozkan Cengiz S. , Nix William D. , Gao Huajian
Published: April 2011

Heteroepitaxial Si1−x Gex thin films deposited on silicon substrates exhibit surface roughening via surface diffusion under the effect of a compressive stress which is caused by a lattice mismatch. In these films, surface roughening takes place in the form of ridges aligned along either <100> or <110> directions depending on the film thickness and composition. In this paper, we compare the relaxation behaviour of capped and uncapped heteroepitaxial Si1−xGex thin films containing 22% Ge, with surface roughening being inhibited in films with a capping layer. Films with 50 nm thickness were deposited on bare silicon substrates in a LPCVD reactor. Annealing experiments were conducted in a Hydrogen atmosphere in the reactor chamber. Transmission electron microscopy and atomic force microscopy have been used to study the surface morphology and microstructure of these films. XRD measurements were conducted to determine the amount of relaxation in these films. In-situ transmission electron microscopy/annealing experiments have been performed on uncapped Si1−x Gex/Si structures to study the dynamics of surface roughening and defect formation in a vacuum ambient. Finally, we compare surface morphologies and defects in samples subjected to annealing in vacuum and H2 ambients.
Influence of Chemical Composition on the Epitaxy and Interfacial Quality of Fe/Au and Fe/Ag Multilayers
Authors: Paniago R. , Chow P. C. , Forrest R. , Moss S. C. , Parkin S. S. P. , Cookson D.
Published: April 2011

Fe/Au and Fe/Ag films grown on MgO(001) oriented substrates exhibit the same in-plane epitaxy since Au and Ag have the same fcc bulk structure and nearly equivalent lattice parameters. Using synchrotron X-ray reflectivity and high-angle Bragg scattering we show that Fe(15Å)/Au(21Å) multilayers grown by sputtering exhibit different profiles for Fe/Au and Au/Fe interfaces. We analyze this in view of the action of Au as a surfactant during the growth of Fe. Similar Fe/Ag multilayers have considerably worse interfacial quality since Fe and Ag do not interdiffuse, and this leads to the result that the interfaces cannot be described by error function profiles. Using non-specular x-ray reflectivity we show that whereas Fe/Au interfaces are self-affine, Fe/Ag interfaces exhibit two regimes of scaling behavior as a function of spatial wavelength. This suggests that two different mechanisms are important in describing the growth of Fe/Ag films.
Nucleation and Pattern Formation of Coherent Islands During Epitaxial Growth of Ge on Si(110) Surfaces
Authors: Weil J. D. , Yang Bi-Ke , Slough C. G. , Krishnamurthy M.
Published: April 2011

Molecular beam epitaxial growth of Ge on Si(110) surfaces reveals interesting aspects of the heterogeneous nucleation of coherent Ge islands. Cleaning of the Si substrate by desorption of a passivating oxide layer at high temperature creates surface pits. Two sets of experiments, including deposition of Ge on as-cleaned substrates, and surfaces with a thin Si buffer layer are compared to illustrate the nucleation behavior of Ge. Typical Ge deposition temperatures range from 600°C to 725°C.

For Ge deposition on as-cleaned surfaces, the faceted edges of pits serve as preferential sites for the heterogeneous nucleation of coherent Ge islands. Experiments were also performed on surfaces with thin (˜20nm) Si buffer layers grown on the as-cleaned surface. Though the faceted pits have not been completely covered by the Si buffer layer, they have decreased in lateral size. In addition, the Si(110) surface shows ledges that are formed along specific crystallographic directions. Ge deposited on the Si buffer nucleates first at the corners of the pits, in an interesting dipole orientation, as well as along the ledges on the surface.
Growth and Epitaxy of Au on TiO2 (110)
Authors: Cosandey F. , Persaud R. , Zhang L. , Madey T. E.
Published: April 2011

The growth of Au on TiO2 (110) has been examined by high resolution fielc emission scanning electron microscopy (HRSEM) in combination with electror backscattered diffraction (EBSD). The Au was evaporated under UHV conditions onto stoichiometric TiO2 (110) surfaces in the temperature range from 300 to 475 K. At 300 K and for low coverages (<1.5 nm), Au grows as discrete particles. For thicker coverages (>1.5 nm), the particles coalesce to form a network, but percolation is absent even aftel deposition of 5 nm Au. Upon annealing or deposition (≥ 5 nm) at 475 K, the particles, appear clearly faceted and are oriented along specific crystallographic directions. EBSE patterns taken from individual particles reveal two equivalent domain orientations rotated by 180° with epitaxial orientation relationships corresponding to (111)Au//(110)TiO and [110] // [001]TiO2 (Orientation I) and [110] // [001]TiO2.(Orientation II)
Surface Roughening During Titanium Silicide Formation: a Comparison Between Si(100) and Poly-Si Substrates
Authors: Lavoie C. , Martel R. , Cabral C. , Clevenger L. A. , Harper J. M. E.
Published: April 2011

We demonstrate that the formation of TiSi2 for Ti films deposited on undoped Si(100) substrates leads to rougher surfaces than for Ti films deposited on undoped poly-Si substrates. The successive formations of TiSi2, C49 (high resistivity) and C54 (low resistivity) phases from titanium films deposited on either Si(100) or poly-Si substrates were monitored in situ during rapid thermal annealing using elastic light scattering, x-ray diffraction and resistance measurements. For both types of substrates, the roughening occurs only during the formation of the first TiSi2, phase (C49) by light scattered from lateral length scales of ˜0.5 μm. Atomic force microscopy (AFM) images. quantified using Fourier filtering, are consistent with the light scattering results.
Atomistic Structure of High Index Surfaces
Authors: Mutasa Batsirai , Farkas Diana
Published: April 2011

Interatomic potentials of the embedded atom (EAM) type were used to study the atomistic structure of high index surfaces in metals and ordered alloys. The results show that a structural unit model can be developed to model the structure of the high index surfaces on the basis of the structure of a few low energy surfaces. The model can predict the structural features and give an estimate of the energies of the higher index surfaces. We present examples of Fe, B2 FeAl and NiAl.
Depth Profile Of Point Defects In Ion Implanted n+p and p+n Junctions Formed By 450°C Post-Implantation Annealing And Impact Of Defects On Junction Characteristics
Authors: Oka Mauricio Massazumi , Nakada Akira , Tamai Yukio , Kanemoto Kei , Shibata Tadashi , Ohmi Tadahiro
Published: April 2011

It is shown that defects generated by ion implantation, remaining after annealing at low temperature, are deep-distributed in the bulk silicon and their amount is demonstrated to be function of the substrate type and the implanted ion species. The confirmation that defects penetrate deeply into the silicon is made by a new method that consists in damaging by ion implantation a previously formed pn junction that shows very low leakage current and has a deep junction. It is proposed that the dopants in the substrate act as nucleation centers for the formation of point defect clusters and that these clusters actually degrade the junction. It was found that point defects penetrate much more deeply in p+n junctions than in n+p junctions. It was also found that BF2+ introduces much more defects into the silicon than As+, owing to the presence of fluorine. The leakage currents at 5 V of n+p and p+n diodes made by implantation of P+ and B+, respectively, could be lowered by one to two orders of magnitude with respect to values obtained by implantation of As+ and BF2+ because the former ones produce less defects than the latter.
Effects Of Gettering On Device Characteristics
Authors: Horikawa Mitsuhiro , Yaoita Akihiko , Nagata Tsuyoshi , Kitano Tomohisa
Published: April 2011

Effective methods of gettering metallic impurities were proposed. To achieve effective gettering, an annealing process to induce gettering was modified taking fundamental gettering steps and the difference in the gettering mechanism into account. As the concentration of heavy metal is below solubility in a state-of-the-art clean room, a combination of segregation type gettering and slow cooling heat treatment is an effective technique to remove metal impurities from the device active region. Using this technique, DRAM device characteristics such as leakage current and data retention time can be improved.
Investigation On Subsurface Damage In Silicon Wafers
Authors: Zhang Xin , Zhang Tong-Yi , Zohar Yitshak , Lee Sanboh
Published: April 2011

Micro-Raman spectroscopy and chemical etching were applied to determine the depth of subsurface damage in silicon wafers undergoing different machining processes: cutting, grinding, polishing and lapping. In comparison with the Raman spectrum of perfect single crystal silicon, both the shape and intensity at the shoulder (500 cm−1) and the subpeak (300 cm−1) spectral regions were changed in all the machined wafers. The intensities at shoulder and subpeak gradually decreased and finally resumed to normal, as the depth of the investigated layer increased. According to the chemical etch rate, the depth of the subsurface damage was thus evaluated for the different wafers. TEM observations further confirmed the obtained results.
Shallow Donor Centers in Erbium-Implanted Silicon Subjected to High-Temperature Annealing
Authors: Emtsev V.V. , Poloskin D.S. , Sobolev N.A. , Shek E.I.
Published: April 2011

Consideration has been given to production processes of shallow donor centers formed in silicon after implantation of erbium ions or co-implantation of erbium and oxygen ions followed by annealing at 700° and 900°C. Analysis of the experimental data obtained in this work made it possible to put forward some suggestions concerning the nature of these defects.
Radioactive Isotopes In Photoluminescence Experiments: Identification Of Defect Levels
Authors: Magerle R.
Published: April 2011

The characteristic life-times of radioactive isotopes can be used to label and identify defect levels in semiconductors which can be detected by photoluminescence (PL). This technique is illustrated with three examples: ZnS doped with radioactive 65Zn by neutron irradiation and GaAs doped with radioactive 111In by ion implantation. Finally we report that doping GaAs with radioactive 71As which decays to stable 71Ga can be used to create GaAs antisites in GaAs in a controlled way and to identify their levels.
Low-Temperature Infrared Absorption Measurement For Oxygen Concentration and Precipitates In Heavily-Doped Silicon Wafers
Authors: Koizuka M. , Inaba M. , Yamada-Kaneta H.
Published: April 2011

We present a new IR absorption technique of measuring the dissolved interstitial oxygen concentration [Oi] and its reduction Δ [Oi] due to oxygen precipitation of the heavily-doped silicon crystal with doping level of about 1019 atoms/cm3. The method consists of the three steps: bonding the silicon wafer to a thick FZ silicon substrate by heat-treatment, thinning the wafer, and measuring the height of the 1136-cm−1 absorption peak of Oi at a temperature below 5 K. For a heavily doped wafer and the heavily doped substrate of an epitaxial wafer, we demonstrate examples of measuring the initial [Oi] and Δ [Oi] due to heat-treatment. Using this method, we investigate oxygen precipitation characteristics of the wafer heavily doped with boron. We found that the enhanced oxygen precipitation due to heavy boron-doping is expected if we perform preanneal at temperatures below 700°C.
Dislocation-Related Photoluminescence In Strain-Relaxed Si1−xGex. Buffer Layer Structures
Authors: Shum Kai , Mooney P. M. , Chu J. O.
Published: April 2011

Low-temperature photoluminescence (PL) spectroscopy was used to study electronic states associated with threading dislocations (D lines) in strain-relaxed Si1−xGex layers. The structures investigated were grown by ultra-high vacuum chemical vapor deposition (UHV/CVD) at 550 °C and consist of an Si(001) substrate followed by a step-wise graded buffer layer followed by a thick uniform composition Si1−xGex layer. Variations in the PL intensity and peak position of the four D lines after isochronal annealing at temperatures between 600 and 800 °C have been measured. We show that the large energy shift of the D1 line is due to a change in the local band-gap energy at the dislocation core due to strain-driven diffusion of Ge away from the dislocation core with an activation energy of 2.4 eV.
Properties Of Inp Simultaneously Doped With Zinc And Sulfur Grown By Mocvd
Authors: Alavanja C. M. , Pinzone C. J. , Sputz S. K. , Geva M.
Published: April 2011

As the p-type dopant most often used in metalorganic chemical vapor deposition (MOCVD) of Group III - Group V compound semiconductors, Zn presents problems in device design and performance because of its high diffusivity in these materials. While Zn diffusion into n-type layers such as InP:S has been observed frequently, there is little known as to the electronic and optical properties of the resultant material. We have grown InP samples by MOCVD which are doped with both Zn and S to levels as high as 3×1018 cm−3. These samples were analyzed by electrochemical C-V profiling, van der Pauw-Hall analysis, secondary ion mass spectroscopy (SIMS), and low temperature (10K) photoluminescence spectroscopy (PL). We have determined that good hole mobility is maintained in InP:Zn samples that are simultaneously doped with S up to a level of 4×1017 cm−3. PL analysis of co-doped samples shows peaks between 0.91 and 0.92 μm which are indicative of donor-acceptor transitions, and broad peaks with energy levels of approximately 1.0 μm which may be indicative of ZnS complexes or precipitates. SIMS analysis of Zn diffusion into Fe doped substrates shows that Zn diffusion is reduced in the presence of S in the lattice.
Effect Of The Carbon Acceptor Concentration On The Photoquenching And Enhancement Of The Piezoelectric Photoacoustic Signals Of Semi-Insulating Gaas
Authors: Fukuyama A. , Morooka Y. , Akashi Y. , Yoshino K. , Maeda K. , Ikari T.
Published: April 2011

The spectral and the time dependent piezoelectric photoacoustic (PPA) measurements under the continuous light illumination were carried out at 85 K to investigate nonradiative recombination processes involving EL2 defect levels in carbon doped semi-insulating (SI) GaAs. The decrease of the PPA signal due to the photoquenching effect of EL2 was observed for a short period of illumination of 1.12 eV. It was found that the photoquenching becomes drastic with increasing the carbon concentration. After fully photoquenching, the PPA signal increased again through a local minimum by the continuous light illumination and finally exceeded the initial value before illumination until the saturation level was reached. The deep donor level EL6 and its metastable state are proposed. EL6 level donates electrons to compensate a part of carbon acceptors after photoquenching. The nonradiative recombination through this level generates the PPA signal. The usefulness of the PPA technique for studying the nonradiative transition through deep levels in semiconductor is suggested.
High-Temperature Reorientation Of Distortions In The Excited State Of The VGaTeAs Complexes In n-Type GaAs
Authors: Gutkin A. A. , Reshchikov M. A. , Sedov V. E.
Published: April 2011

We have investigated polarization of photoluminescence from the VGaTeAs complexes in n-GaAs induced through resonant excitation by polarized light. Experimental data in temperature range from 77 to 240 K were described by classic one-dipole approximation within the model of the VGaTeAs complex subjected to the Jahn-Teller distortion in the ground and excited states. It is shown that depolarization of photoluminescence at temperatures over ∼ 120 K may be explained by concurrent action of i) thermal emission and back capture of holes bound to the complexes in the excited state and ii) reorientation of complex distortion during a life of this state. The model parameters have been estimated.
Behavior Of Fluorine In N-AlInAs Layers Under Bias-Temperature Stresses
Authors: Yamamoto Y , Hayafuji N. , Sato K. , Otsubo M.
Published: April 2011

The electrical degradation of AlInAs /GaInAs high electron mobility transistor (HEMT) due to the fluorine contamination is quantitatively explained through the comprehensive annealing experiments and bias-temperature tests. The thermal degradation rate is found to be mainly determined by the following electrochemical reaction of fluorine with donor species after the quite fast diffusion of fluorine into the AlInAs layer. It is also confirmed that the thermal degradation is stringently affected by the electric field resulting in the one-sided degradation near the anode. These findings are important knowledges to improve the reliability of AlInAs/GaInAs HEMT under the DC accelerated life test at high temperature.
First-Principles Calculations Of Diffusion Of Chlorine Atoms In GaAs
Authors: Ohno Takahisa , Sasaki Taizo , Taguchi Akihito
Published: April 2011

The properties of chlorine atoms in crystalline GaAs, such as stable configurations, migration paths, charge-state effects, and interaction with dopant atoms are theoretically investigated. The calculations are based on the local density functional theory using first-principles pseudopotentials in a supercell geometry. We determine the stable charge state of an isolated Cl atom as a function of the Fermi energy. When the Fermi level is situated at the top of the valence band of GaAs, the Cl atom occupies preferentially the bond-center site of a Ga-As bond in the positive charge state. The Cl atom diffuses through the GaAs crystal via a path in the region of high electron density, with a fairly large energy barrier. When the Fermi level is at the bottom of the conduction band, the lowest-energy configuration of the Cl atom is the tetrahedral interstitial site in the negative charge state and the bond center site is very slightly higher in energy. In Si-doped GaAs, the C1 atom occupies the tetrahedral interstitial site with the substitutional Si donor atom as a nearest neighbor, forming a neutral Cl-Si complex. The Cl-Si complex is weak and easily dissociates into the isolated C1 and Si atoms in GaAs. A comparison will be made between the behavior of Cl and F atoms in GaAs.
The Differences between the InyGa1−yAs/GaAs Interface and GaAs/InyGa1−yAs Interface in Superlattice over a InxGa1−xAs (x<y) Buffer Layer
Authors: Wang X.J , Zheng L.X , Xiao Z.B , Zhang Z.P , Hu X.W , Wang Q.M
Published: April 2011

The InyGa1−yAs/GaAs superlattice on InxGa1−x.As (x<y) buffer layer was grown by MOCVD. The well layer is under compressive strain and the barrier layer is under tensile strain. However, both layers do not exceed the calculated critical value based on the M−yAs interface was smoother than the InyGa1−yAs/GaAs interface; the Indium composition gradual region at the GaAs/InyGal1−yAs interface was narrower than that at the InyGa 1−yAs/GaAs interface; in InyGa1−yAs alloy layer, the Indium composition near the GaAs/InyGa1-yAs interface was higher than that near another interface. For the first time, we explained the composition profile in this kind of superlattice based on the indium segregation theory. A new strain relaxation model, in which the 30-degree and 90-degree shockley partial dislocations were taken into account under both tensile and compressive strains, was presented to explain the difference of the smoothness between the GaAs/InyGa1−yAs interface and the InyGa 1−yAs/GaAs interface.
The Effects Of Substitutional Alkaline Metals In Zinc Vacancy Of Zincselenide Single Crystals Grown By The Sublimation Method
Authors: Yoshino Kenji , Maeda Kouji , Fukuyama Atsuhiko , Akashi Yoshito , Imada Kiyohisa , Ikari Tetsuo
Published: April 2011

The photoluminescence measurements of alkaline metal doped zincselenide (ZnSe) single crystals were carried out to investigate how the impurity atoms substitute the intrinsic vacancy. Sample are grown by the sublimation method and the Li and Na with the concentrations of 0.1, 0.25 and 0.5 mol% were incorporated simultaneously. In the PL spectra with lower impurity concentrations, bound exciton lines of deep acceptor and donor-acceptor pair (DAP) bands were clearly observed accompanied by a weak free exciton line. Although the bound exciton lines becomes smaller with increasing the impurity concentration, the DAP band remains strong and its peak energy shift to lower energy side with the concentration. The decrease of the bound exciton lines is drastic for Li-doped sample than Na-doped sample. This indicates that Li atoms more easily occupy the Zn vacancies than Na.
Investigation Of Deep Energy Levels In II-VI Compounds
Authors: Castaldini A. , Cavallini A. , Fernandez P. , Fraboni B. , Piqueras J.
Published: April 2011

Deep levels in II-VI compounds have been investigated to understand their role in the compensation mechanism and their influence on the material electrical and optical properties. The electrical properties have been studied by current and capacitance transient spectroscopy, while the optical properties have been studied by cathodoluminescence. We have focused our attention on the traps involved in the compensation process, such as centre A and the deep levels located near midgap.
Nondestructive Characterization Of The Surface Aging Of HgI2 Crystal
Authors: Yao H. , Erickson J. C. , James R. B. , Natarajan M.
Published: April 2011

Variable angle spectroscopic ellipsometry (VASE) and atomic force microscopy (AFM) measurements have been employed to characterize the surface aging of HgI2 crystals. A surface model including top surface roughness and subsurface defects was established and studied by VASE analysis, as a function of real time, after the 10% KI chemical etching. In this model, the surface defects associated with the surface aging were modeled by the Bruggeman effective-medium approximation (EMA) as a HgI2/voids mixed layer. The relative 2-dimensional (2D) surface-defectdensities were monitored as the surface aging proceeds. The VASE measurements indicated that high surface aging rates were related to high initial effective 2D surface-defect densities. The AFM profile revealed increasing physical surface roughness as surface aging took place. The cleaved HgI2 crystal surface presented a smooth surface and the lowest surface aging rate, while the as-grown HgI2 surface also presented a very low surface aging. The HgI2 surfaces baked at elevated temperatures presented accelerated surface aging phenomena after a 30 min. baking.
Vacancies In Electron Irradiated 6H-SiC
Authors: Friessnegg T. , Dannefaer S.
Published: April 2011

Annealing of electron irradiated bulk n-type 6H-SiC has shown that neutral carbon vacancies and neutral silicon vacancies undergo a major reduction in concentration in the 20–200 °C temperature interval after which only slight changes occur up to 1200 °C. The experiments suggest that the positively charged carbon vacancy, detected by electron paramagnetic resonance, constitutes only a small fraction of all carbon vacancies.
Imaging Of Micropipes In Silicon Carbide Under High Field Stress
Authors: Gradinaru G. , Helmi M. , Khlebnikov Y. , Korony G. , Mitchel W. C. , Sudarshan T. S.
Published: April 2011

A new technique for investigation of the electrical effects of micropipes in single-crystal 6H-SiC is presented. The setup allows the application of a parallel or normal electric field to MSM (metal-semiconductor-metal) test structures and the visualization of light emission sites in the test gap, including light activity underneath the metal contact. A special transparent metal [indium-tin-oxide(ITO)] was chosen for the metallic contacts. A map of micropipe locations was initially obtained at zero applied field using a laser scattering method. The initial map is compared with that of light emissions at different applied fields.

Several tests on undoped and vanadium-doped (compensated) SiC, using NiCr/Au or ITO contacts, indicated the rapid activation of micropipes at relatively low fields in vertical MSM devices. A good match between the laser imaging map of micropipes at zero field and the map of field-induced light emission sites indicates that micropipes are the main current paths in vertical devices, carrying a large current density, and leading to light emissions and partial or total bulk breakdown of the test device.
X-Ray Topography Of A Single Superscrew Dislocation In 6H-SiC Through All {100} Faces
Authors: Vetter W. M. , Dudley M.
Published: April 2011

Micropipes, the hollow cores of superscrew dislocations that lie along the c-direction in SiC single crystals, are quite deleterious to the performance of semiconductor devices. In the x-ray topography of longitudinal-cut samples of these crystals, topographs in the reflection (006) show dislocation image contrast associated with the superscrew dislocations lying along the c-axis of the crystal, which is also the direction of the dislocations' Burgers vectors. In the (110) reflection, whose g-vector is perpendicular to the c-axis and the dislocations' Burgers vector, there is also an image of the superscrew dislocation formed, albeit weaker than the corresponding image in the (006) reflection. This dislocation image is thought to represent stress components of the superscrew dislocation in directions perpendicular to the c-axis.

In order to investigate the origin of these stress components, steps have been carried out to determine whether the dislocation image is anisotropic in all possible reflections where g={110}. To achieve this we have excised a hexagonal prism-shaped sample from a 6H-SiC wafer, 100μm wide, polished along the six {100} crystallographic faces, such that a single micropipe ran along the axis of the sample. This enabled x-ray topographs to be taken through each of these {100} faces
The Influence Of The Incorporation And Desorption Of Chn, Groups On The Defect Structure Of a-SiC:H Films
Authors: Friessnegg T. , Boudreau M. , Mascher P. , Simpson P.J. , Puff W.
Published: April 2011

Changes in the defect structure in carbon rich a-SiC:H films deposited on various substrates using ditertiary butyl silane were investigated as a function of thermal treatment. Films grown at high deposition rates exhibit hydrogen trapped in voids. The incorporation of CHn, groups is thought to be the origin for these microvoids. With increasing annealing temperature the effusion of CHn, groups as determined by thermal desorption experiments promotes void growth which was studied using a variable energy positron beam. At annealing temperatures above 600 °C the films densify due to the breaking of C-H bonds and the formation of additional C-C bonds when the voids anneal out.
Correlation Between Defects and Electrical Conduction in Surface Conductive Layer of CVD-diamond Films
Authors: Show Y. , Matsuoka F. , Ri S. , Akiba Y. , Kurosu T. , Iida M. , Izumi T.
Published: April 2011

Correlation between defects and electrical conduction in surface conductive layers of CVD diamond films has been studied using electron spin resonance ( ESR ) and two points probe technique methods. The ESR analysis revealed the presence of Pac-center with spin density of 1020 spins/cm3. The Pac-center is composed from two ESR signals: ESR signal from carbon dangling bond with carbon atom neighbors and ESR signal from carbon dangling bond associated with nearest neighbor hole ( hole associated Pac-center ). The hole associated Pac-center is an electrically active defect.
Coexistence Of Two Carbon Phases At Grain Boundaries In Polycrystalline Diamond
Authors: Shenderova O. , Brenner D. W.
Published: April 2011

Energies and structures for two models of <001> tilt grain boundaries in diamond have been calculated using a many-body empirical bond-order potential. The first model contains all four-fold coordinate atoms. The second model is a two-phase system in which a graphitic region connects the diamond grains. At selected misorientation angles we predict that the two-phase structures are energetically competitive with the sp 3 bonded structures when the width of the graphitic regions exceed 10–15Å.
Hydrogen-Induced Luminescent States In The Subsurface Region Of Homoepitaxial Diamond Films
Authors: Hayashi Kazushi , Watanabe Hideyuki , Yamanaka Sadanori , Sekiguchi Takashi , Okushi Hideyo , Kajimura Koji
Published: April 2011

We found the existence of hydrogen-induced luminescent states in the subsurface region of chemical-vapor-deposited homoepitaxial diamond films by means of cathodoluminescence (CL). A specific broad peak at around 540 nm is observed in both as-deposited diamond films and those treated by hydrogen plasma at 800 °C, but not in conventional oxidized films. The accelerating voltage dependence of the CL spectra indicates that the luminescent states related to the 540 nm peak exist in the surface region and decrease abruptly with increasing the depth from the surface, showing that the depth distribution of the states slightly depends on the hydrogenation duration. Although the 540 nm peak is not observed in the films hydrogenated at 500 °C, it appears once the films are irradiated by an incident electron beam. It indicates the existence of a metastable configuration of hydrogen or its complex forms in the diamond films hydrogenated at low temperatures and a relaxation occurs into a stable one which produces luminescent states by the electron-beam irradiation.
Low K Mesoporous Silica Films Through Template-Based Processing
Authors: Bruinsma P.J. , Hess N.J. , Bontha J.R. , Liu J. , Baskaran S.
Published: April 2011

Low dielectric-constant mesoporous silica films were prepared by condensation of a silicate network around surfactant micellar structures. Adherent, porous films 0.5–1.0 μm in thickness, and containing an ordered assemblage of ≈2 nm diameter pores were synthesized by spin-coating water/ethanol-based solutions containing a silica precursor and surfactant template. In this paper, film deposition conditions are described, and film thickness, porosity, refractive index and dielectric constant measured by ellipsometry are presented. Using a coating solution containing tetraethyl orthosilicate (TEOS) and a cationic cetyltrimethylammonium chloride (CTAC) surfactant template, the film porosity and dielectric properties were controlled over a wide range by adjusting the CTAC/TEOS molar ratio. With the CTAC/TEOS ratio between 0.1 and 0.15, the pores were highly ordered in hexagonal arrays after heat treatment at 550 °C. With a CTAC/TEOS ratio of 0.21, films with a pore volume of ≈64% (≈36 vol% silica) could be synthesized. The measured index of refraction for these highly porous films at 500 nm wavelength was 1.16, indicating that these films are potentially useful as low K interlayer dielectrics.
PE-CVD of F-Doped SiO2 Thin Films Using Tetraisocyanatesilane and Tetrafluorosilane
Authors: Shirafuji T. , Sawada M. , Nakagami Y. , Hayashi Y. , Nishino S.
Published: April 2011

SiO2 films have been prepared from tetraisocyanatesilane (TICS, Si(NCO)4) by using a conventional capacitively coupled RF(13.56MHz) plasma-enhanced CVD method. The films show poor water resistivity, which originates in inclusion of NCO in the films. This has been improved by mixing O2 to the source gas. SiO:F films have been prepared by mixing SiF4. The film with F concentration of 6at.% has shown dielectric constant of 3.3, resistivity of 3.6×1015Ωcm at 1MV/cm and break-down electric field of 7.7MV/cm. Infrared spectrum of the film have contained no noticeable OH peak even after exposing to the air for 2 weeks.
A Study Of Anisotropy Of Spin Cast And Vapor Deposited Polyimide Films Using Internal Reflection Techniques
Authors: Liberman Vladimir , Malba Vincent , Bernhardt Anthony F.
Published: April 2011

We have compared anisotropy of spin cast and vapor deposited polyimide (VDP) films, using internal reflection infrared spectroscopy. The films were deposited directly on the internal reflection element. We find that spin cast films are more anisotropic than their VDP counterparts, with the polyimide chains tending to align parallel to the substrate. Both films are found to contain more and less ordered regions. Within the ordered regions, the plane of the phenyl ring tends to align parallel to the substrate.
Fluorocarbon Films from Plasma Polymerization of Hexafluoropropylene and Hydrogen
Authors: Mountsier T. W. , Kumar D.
Published: April 2011

Fluorocarbon polymers exhibit excellent dielectric properties; however, their limited thermal and mechanical stability render them unsuitable for most interlevel dielectric applications. In this work we explore the plasma assisted deposition of fluorocarbon films from hexafluoropropylene (C3F6) and hydrogen in order to understand how the mechanical and thermal properties might be improved. Plasma activation and ion bombardment promote the formation of a crosslinked, amorphous film structure. Several process parameters were examined including temperature and rf driving frequency. The results demonstrate that crosslinked fluorocarbon polymers with enhanced mechanical strength can be produced from C3F6 in a plasma environment. Most of the films studied here had dielectric constants in the range of 2 to 2.5. Thermal stability (to 400 °C), however, was not achieved.
Nanoporous Silica for Low k Dielectrics
Authors: Ramos Teresa , Roderick Kevin , Maskara Alok , Smith Douglas M.
Published: April 2011

Considerable progress has been made in development of thin films of nanoporous silica (also known as aerogels or low density xerogels) for ILD and IMD applications. Advantages of these materials include high thermal stability, small pore size, and similarity to conventional deposition processes, precursors and final material (silica). We have previously reported success in synthesizing low density, low dielectric constant (K<2) thin films using ambient pressure processing. However, processing of those films was complicated due to large number of process steps and difficulties in independently controlling both film thickness and film porosity.

Nanoglass has now developed a new process which considerably reduces the number of process steps and allows independent control of both film thickness and porosity. The dielectric constant of the films can be tailored between 1.3 and 2.5. These films have improved mechanical properties due to controlled pore size and narrow pore size distribution and also because of higher density. The trade-offs between density, mechanical strength and dielectric constant for these types of porous solids will be elucidated. The known properties of the film and the process flow for deposition and post-deposition curing and the role of the relative rates of reaction, gelation, aging, and drying will be presented.
Controlled Incorporation of Nitrogen at The Top Surface of Silicon Oxide Gate Dielectrics
Authors: Niimi H. , Koh K. , Lucovsky G.
Published: April 2011

During a high RF power (60–100 W) N20/He remote plasma oxidation of Si(100) at 300 °C, nitrogen atoms have been incorporated at the top surface of an ultra-thin (1.0–2.5 nm) oxide. Online Auger electron spectroscopy (AES) has been used to estimate the dielectric film thickness and track the evolution of the film growth. A chemically shifted Si-LW feature from the high RF power oxidation sample indicates that the nitrogen is bonded to the silicon at the top surface of the oxide film. The stability of the bonded nitrogen is also evident in the persistence of the N-KLL Auger peak following (i) a 30 s rapid thermal anneal (RTA) in Ar at 900 °C and (ii) a remotely excited He plasma treatment at 300 °C for 15 s.
Electronic Structure of Si-Si Bond in Si3n4 and Sio2: Experiment and Simulation by Mindo/3
Authors: Gritsenko V.A. , Milov A.D. , Morokov Yu.N. , Novikov Yu.N. , Wong H. , Cheng Y.C.
Published: April 2011

The trapping properties of the Si-Si bond in Si3N4 and SiO2 were investigated. The MINDO/3 calculations show that the spin polarization of the Si-Si bond with a captured hole takes place in both SiO2 and Si3N4. The ESR (Electron Spin Resonance) measurements were made in Si3N4 with captured electrons and holes. The number of localized carriers was of two orders of magnitude larger than that used by others. The ESR signal of localized electrons and holes was not observed. A new mechanism of the antiferromagnetic ordering of localized electrons and holes in an insulator with a large concentration of traps is proposed. According to this mechanism, the antiferromagnetic ordering in Si3N4 may be caused by the resonance tunneling of localized spins through nonoccupied traps. We believe that the deep traps responsible for the electron and hole capturing in Si3N4 are the Si-Si bonds.
Effect of Post-Oxidation on the Oxygen Deficiency of Buried Oxides
Authors: Soo Seol Kwang , Karasawa Toshifumi , Koike Hidemi , Ohki Yoshimichi , Tachimori Masaharu
Published: April 2011

The effect of post-oxidation of the silicon-on-insulator structure produced by implantation of oxygen (SIMOX) upon neutral oxygen vacancies (O3=Si-Si=O3, “=” denotes bonds with three separate oxygens) in the buried oxide has been investigated. It is observed that the photoluminescence intensity from the vacancies and the thickness of buried oxide increase after the post-oxidation. An Ar plasma was used to expose the buried oxide in order to convert the vacancies to E'r (O3=Si, “” denotes an unpaired electron) centers which are detectable by electron-spin-resonance. The total number of E’ r centers was found to increase, which should suggest a similar increase in the number of the vacancies in the buried oxide. Similar measurements repeatedly done on the buried oxide by changing its thickness by etching revealed that the increased part of oxide by the post-oxidation contains the vacancies with a similar density to the original part of oxide, and that the post-oxidation scarcely affects the oxygen deficiency of the original part.
Observation of the Full Interface of Multi-level Interconnects for Sub-Half-Micron Devices
Authors: Hirose Y. , Katayama T. , Fujiki N. , Ohno T. , Sekine M. , Koyama H.
Published: April 2011

1. Abstract

In recent years, the problem of electrical resistance of vias and contact holes has become greater because a thin insulated layer formed at the interface of the hole has become a serious difficulty in the manufacture of ULSIs. In using conventional techniques of cross sectional analysis to examine the cause, only one cross section of the hole can be analyzed, therefore there is the problem that the two-dimensional interface layer formed cannot be analyzed exactly.

In this paper, we have developed a new observation method to inspect two dimensions of the layer formed locally at the interface of the holes. This new observation method gives the configuration, coverage, and element map of the interface layer because the full interface of holes can be inspected; therefore, the process margin can be discussed. The present technique is demonstrated in failure analysis of sub-half-micron vias filled with tungsten.
A Quantum Mechanical Investigation of Positively Charged Defects In SiO2 Thin Film Devices
Authors: Ferreira Antonio M. , Kama Shashi P. , Brothers Charles P. , Pugh Robert D. , Singaraju Babu B. K. , Vanheusden Karel , Warren William L. , Devine Roderick A. B.
Published: April 2011

Ab initio Hartree-Fock and second-order Möller-Plesset theory calculations have been performed to investigate the stability of triply-coordinated 0+ centers in the Si-O-Si network of amorphous SiO2. The calculations reveal that the H+ ion binds with a bridging O center to form a very stable (De > 6 eV) trivalent O complex. Capture of an electron by the positively charged protonated complex, however, is predicted to immediately lead to the dissociation of the O-H bond. A relatively weaker, but stable bond is also formed between the bridging O atom and a +SiH3 ion.
Reaction Pathways for Nitrogen Incorporation at Si-SiO2 Interfaces
Authors: Koh K. , Niimi H. , Lucovsky G.
Published: April 2011

This paper presents experimental studies in which N-atoms have been incorporated at Si-SiO2 interfaces by forming the interface and oxide film by a 300°C remote plasma assisted nitridation/oxidation process using N2O. Process dynamics have been studied by on-line Auger electron spectroscopy (AES) by interrupted plasma processing. Plasma-activated species have been identified by in-situ mass spectrometry (MS) and optical emission spectroscopy (OES). Based on AES studies using N2O, O2 and sequenced N2O and O2 source gases, reaction pathways for N-atom incorporation i) at and/or ii) removal from buried Si-SiO2 interfaces have been identified, and contrasted with reaction pathways for nitridation using conventional furnace processing. The active species for N-atom incorporation is NO+, and for oxide growth, O2.