bluuebunny/crossref_metadata_2025 huggingface dataset:
Silicon Nitride Films Deposited by Atmospheric Pressure Chemical Vapor Deposition
Authors: Lin Xian , Endisch Denis , Chen Xiaomeng , Kaloyeros Alain
Published: April 2011

Films of silicon nitride are widely used in semiconductor technologies for very large scale integration (VLSI), thin film transistor (TFT), and solar cell applications. Current production technologies for silicon nitride use low pressure chemical vapor deposition (LPCVD) at temperatures > 700 °C or plasma enhanced chemical vapor deposition (PECVD) at temperatures below 450 °C. In this report, successful deposition of silicon nitride films by the low temperature thermal atmospheric pressure chemical vapor deposition (APCVD) method is described. Using a novel precursor tetraiodosilane (SiI4), deposition of silicon nitride has been achieved at temperature as low as 400 °C. Data pertaining to the dependence of film properties on deposition temperature are presented, along with a evaluation of the deposition rate, composition, chemical structure, and conformality of the resulting films.
Growth of Highly Transparent Nano-Crystalline Diamond Films by Microwave CVD
Authors: Bhusari D. M. , Chen K. H. , Yang J. R. , Lin S. T. , Wang T. Y. , Chen L. C.
Published: April 2011

We report here growth of highly transparent nano-crystallinc diamond films on quartz substrates by microwave plasma enhanced CVD. Optical transmittancc of greater than 84% beyond 700 nm has been obtained for films as thick as 1 μm. Such high optical transparency of these films is primarily attributed to the high smoothness of their surface (average roughness of about 60–65 À) as well as the high content of sp3 bonded carbon therein. The effects of methane fraction in the source gas, substrate temperature and grain size of the diamond powder used for substrate pretreatment on the structural and optical properties of these films arc also studied.
Temperature-Dependent Studies of a-SiC:H Growth by Remote Plasma CVD Using Methylsilanes
Authors: Lee Moon-Sook , Lal Pratik , Bent Stacey F.
Published: April 2011

Thin hydrogenated amorphous silicon carbide (a-SiC:H) films were grown at substrate temperatures ranging from 200 K to 600 K by remote ECR plasma-enhanced CVD. Mono- and trimethylsilane were used as single source precursors. The films grown using both precursors were compared as a function of temperature by in situ multiple internal reflection Fourier transform infrared (MIR-FTIR) spectroscopy. The difference in growth temperature leads to changes in both the hydrogen content and the composition of the film. At low growth temperature, films incorporate high concentrations of intact methyl group and a mixture of SiHx (x=1–3) groups, with a polysilane-like structure. At higher temperatures, the hydrogen content decreases. This decrease is observed in two different ways: (1) a loss of highly hydrogenated SiHx groups (SiH3 or SiH2); and (2) a shift from methyl groups to CH2 and CH bonding. However, the temperature dependence of each functional group is found to be different for the two precursors.
Preparation of Ti-Based Ferroelectric Thin Films from Heterometallic Coordination Compounds
Authors: Moshnyaga V. T. , Khoroshun I. V. , Petrenko P. A. , Shaban D. G. , Kuliuk L. L.
Published: April 2011

Novel binary (Pb, Ti) coordination compound were synthesized and used as precursor for the preparation of PbTiO3 films by means of aerosol deposition and spin coating. Single-phased textured thin films of perovskite structure were fabricated on MgO(100) substrate at T=380°C.
Chemical Etching of Diamond Revisited: Past Basic Research as Guide to New Processing Technologies
Authors: Cherian K. A. , Litster J. , Rudolph V. , White E. T.
Published: April 2011

Increased rate of material removal and a high degree of surface finish during the polishing of diamond is desirable not only in the technology of gem diamond processing, but also for the tribological, optical, electronic and thermal management applications of chemical vapor deposited (CVD) diamond films. Conventional mechanical abrasion techniques, though with comparatively larger material removal rates, have limitations to the surface finish attainable due to the inherent nature of the material removal process - predominantly micro-chipping. Chemical etching of diamond, on the other hand is understood to involve atom by atom material removal preferentially from defect sites, but with lower overall material removal rates. It has been realized that a combination of these two processes, leading to chemi-mechanical polishing, may therefore provide better overall results, in terms of material removal and surface finish.

In recent work on chemi-mechanical polishing of diamond, KNO3 - an oxidizing agent shown to be a dislocation etchant for diamond by Tolansky and Patel in the 1950s - has been employed. Dislocation etchants usually lead to the formation of block patterns on diamond surfaces under the usual etching conditions because of the normal and tangential etch rates (Vn and Vt) of comparable magnitude. KNO3 therefore would impose a limitation on the degree of surface finish attainable when used for chemi-mechanical polishing. However, if a chemical etchant and conditions for which Vn ≪ Vt could be established for diamond surfaces, better chemical polishing effects may be achieved. Experimental investigations in this direction have provided encouraging results and some aspects of the new results are presented.
Composite Films of Nickel / Silicon Carbide
Authors: Hepel Maria
Published: April 2011

The electrodeposition of nickel/silicon carbide (Ni/SiC) composite films formed from modified Watt's bath solutions under potentiostatic conditions on steel substrates was investigated. The effects of deposition potential, pH, variable concentration of SiC in suspension, and additives, such as coumarin and EDTA, on the nickel nucleation and growth transients, as well as on the composition and morphology of Ni/SiC films are described. Improved Vickers microhardness and corrosion resistance of these composite films were found in comparison to those of particle-free deposits.
Precursors for the Chemical Vator Deposition of Titanium Nitride and Titanium Aluminum Nitride Films
Authors: Winter Charles H. , McKarns Peggy J. , Scheper Joseph T.
Published: April 2011

Titanium nitride and ternary alloys thereof are of significant interest due to their hardness, chemical resistance, and good electrical conductivity. We report the synthesis, structure, and properties of several new precursors to titanium nitride that are based upon hydrazine-derived ligands. Application of these complexes in titanium nitride film depositions is overviewed. Film properties and characterization are presented. We also describe a new process for the preparation of titanium aluminum nitride films, and focus on how the presence of small amounts of aluminum change the properties of the material.
Dispersed Complex Phosphates as Tailored Acid Catalysts: Synthesis and Properties
Authors: Sadykov Vladislav A. , Kochubei D. I. , Degtyarev S. P. , Paukshtis E. A. , Burgina E. B. , Pavlova S. N. , Maximovskaya R. I. , Litvak G. S. , Zaikovskii V. I. , Tsybulya S. V. , Tretyakov V. F. , Agrawal D. , Roy R.
Published: April 2011

The relationship between the chemical composition, bulk real structure, surface properties and catalytic activity of dispersed complex framework zirconium phosphates with a NASICON-type structure is considered. For both crystalline and amorphous samples, a model of their bulk structure is suggested. The Lewis and Bröensted acidity was shown to vary broadly and be dependent upon the composition and preparation procedure, which is important for catalysts of hydro-carbons activation. Selective catalytic reduction of NOxby methane in excess oxygen appears to be one of the application areas for these systems.
Mocvd Palladium and Platinum Supported on Alumina Catalysts: Preparation and Characterization
Authors: Lopez Z. K. , Vargas J. R. , Valenzuela M. A. , Acosta D. R.
Published: April 2011

An horizontal hot-wall MOCVD reactor was used to prepare palladium and platinum catalysts supported on alumina. A conventional impregnated Pt on alumina catalyst was prepared as comparison. The solids were characterized by XRD, Auger spectroscopy, HREM and H2-TPR. The operation conditions of the MOCVD reactor were fixed preparing several Pd catalysts until to find the appropriate deposition zone. The particle size of Pt catalysts prepared by MOCVD was at about 7 nm compared with 6 ran obtained with the Pt impregnated catalyst, measured by XRD. The HREM image of the Pt MOCVD catalyst showed a narrower particle size ranging from 1 to 4 nm. After calcination three Pt compounds were detected by TPR, which were attributed to PtO, PtO2and Pt-Al2O3interaction in MOCVD preparation. Additionally, a clear reduction of surface oxygens of alumina was also observed.
Chemical Control of Noble Metal Catalysis by Main Group Elements
Authors: Asakura K. , Okumura K. , Inoue T. , Kubota T. , Chun W-J. , Iwasawa Y.
Published: April 2011

The catalytic interaction of noble metal and main group elements in Rh/one-atomic layer GeO2/SiO2and Pt/SbOxwas investigated. The high temperature reduction produced RhGe and PtSb bimetallic particles in which Pt and Rh were electronically modified to retard catalytic activity. However, unique selective catalyses of Rh/one-atomic layer GeO2/SiO2for CO hydrogenation reaction to oxygenate compounds and for NO+CO reaction to N2were found. Under the low temperature reduction of Rh/one-atomic layer GeO2/SiO2and the high temperature calcination of Pt/SbOx, the oxide phases, GeO2and SbOx, were stable and the selective reduction of ethylacetate to ethanol and the selective oxidation of iso-C4H10to methacrolein were observed. The high selectivities were ascribed to synergistic interaction between the noble metals and the main group element oxides through the diffusion of adsorbed species and reaction intermediates. The possibility of chemical control of noble metal-catalyses by main group elements is discussed.
Tem and Eels Investigation of a-C and ta-C Coated Field Emitters
Authors: Myers A. F. , Steel E. B. , Dingt M. Q. , Camphausen S. M. , Choi W. B. , Cuomo J. J. , Hren J. J.
Published: April 2011

The microstructure of highly sp2 bonded amorphous carbon and partially tetrahedrally bonded amorphous carbon deposited on needle-shaped molybdenum field emitters by pulsed laser ablation and cathodic arc deposition techniques was studied using transmission electron microscopy and electron energy loss spectroscopy. Undoped and nitrogen-doped films were included in this study. The undoped laser ablation films were approximately 50% sp2 at the emitter tip and 65% sp2 along the shank, while the N-doped laser ablation films were highly sp2 bonded both at the tip and along the shank. These laser ablation films were continuous and relatively uniform, exhibiting an isotropie microstructure at the emitter tip and a columnar microstructure along the shank. The cathodic arc deposited films were predominantly sp2 bonded both at the tip and along the shank; these films were non-uniform, with an isotropie microstructure at the tip and regions of isotropie, columnar, and mixed microstructure appearing along the shank.
The Electronic Transport Mechanism in Amorphous Tetrahedrally-Coordinated Carbon Films
Authors: Sullivan J. P. , Friedmann T. A. , Dunn R. G. , Stechel E. B. , Schultz P. A. , Siegal M. P. , Missert N.
Published: April 2011

The electronic transport mechanism in tetrahedrally-coordinated amorphous carbon was investigated using measurements of stress relaxation, thermal evolution of electrical conductivity, and temperature-dependent conductivity measurements. Stress relaxation measurements were used to determine the change in 3-fold coordinated carbon concentration, and the electrical conductivity was correlated to this change. It was found that the conductivity was exponentially proportional to the change in 3-fold concentration, indicating a tunneling or hopping transport mechanism. It was also found that the activation energy for transport decreased with increasing anneal temperature. The decrease in activation energy was responsible for the observed increase in electrical conductivity. A model is described wherein the transport in this material is described by thermally activated conduction along 3-fold linkages or chains with variable range and variable orientation hopping. Thermal annealing leads to chain ripening and a reduction in the activation energy for transport.
Insulator-Metal Transition Induced by Pressure in Pb1-xGexTe Doped with Yb
Authors: Skipetrov E. P. , Chernova N. A. , Slyn'ko E. I. , Vygranenko Yu.K.
Published: April 2011

In this paper the galvanomagnetic properties (4.2≤T≤300 K) of Pb1-xGexTe(x≤0.038) doped with Yb were investigated both under atmospheric pressure and under hydrostatic compression up to 12 kbar. The variation of the energy diagram of Pb1-xGexTe under variation of Ge concentration and under pressure were proposed. It was shown that change of the energy spectrum under pressure leads to the insulator-metal transition due to redistribution of electrons between the valence band and the deep Yb level. By comparing theoretical and experimental dependences of hole concentration on pressure the parameters of the Yb-induced deep level were determined.
High Pressure Study of III-Nitrides and Related Heterostructures
Authors: Shan W. , Ager J. W. , Walukiewicz W. , Haller E. E. , Little B. D. , Song J. J. , Goldenberg B. , Feng Z. C. , Schurman M. , Stall R. A.
Published: April 2011

We present results of photoluminescence (PL) studies of GaN, InxGa1-xN and AlxGa1-xN alloys, as well as related thin film heterostructures under hydrostatic pressure using the diamond-anvil-cell technique. The GaN PL spectra are dominated by strong and sharp near-band-edge luminescence associated with annihilations of bound excitons and intrinsic free excitons in the crystals. The spectrally well-resolved emission lines allow us to accurately determine their pressure. The PL spectra of InxGa1-xN and AlxGa1-xN epitaxial films were found to exhibit strong near-band-edge luminescence emissions. By examining the pressure dependence of these spectral features, the pressure coefficients for the PL emissions associated with the direct Γ band gap of InxGa1-xN and AlxGa1-xN were determined for the first time.
Thermal Plasma Synthesis of Fe-Co Alloy Nanoparticles
Authors: Scott John Henry J. , Turgut Zafer , Chowdary Krishna , Mchenry Michael E. , Majetich Sara A.
Published: April 2011

FeCo nanoparticles are synthesized in a radio frequency (RF) plasma torch from metal powder precursors and simple gases. The first precursor consists of pre-alloyed FeCo powder; the second precursor is a mixture of elemental Fe and Co powders. A protective carbon coating on the particles is achieved by injection of acetylene gas into the plasma. X-ray diffraction reveals phase purity, low carbon concentration, and minimal oxidation. Analytical electron microscopy is used to examine the nanocomposite morphology and composition of individual nanoparticles. Both synthesis routes produce alloy product, but nanoparticles produced from pre-alloyed precursors exhibit smaller variations in Fe/Co ratio than particles produced from elemental powders.
Chemical Synthesis of Nanostructured Powders and Coatings using the Polyol method
Authors: Chow G. M. , Kurihara L. K. , Feng C. R. , Martinez-Miranda L. J. , Lawrence S. H.
Published: April 2011

An overview of our work on the synthesis of nanostructured powders and coatings using the polyol process is presented.
Assembly of polymer microspheres and the thin-film Micropatterning
Authors: Du H. , Qian X. M. , Li W. M. , Liu F. Q. , Tang J. , Tang X. Y. , Bai Y. B. , Li T. J.
Published: April 2011

Copolymer latexes of poly(styrene/acrylic acid) were closely packed into two-dimensional arrays on glass, mica and silicon substrates respectively. When the small latexes were negatively charged due to −SO4− and −COO− groups on the surface, their film formation, in some degree, was affected by the electrostatic interaction between two particles as well as capillary force. Different electrolytes were added into the colloid to adjust the particle interaction so that the attractive and the repulsive forces were properly balanced and the ordered arrays were achieved. Thin metal film was deposited on the latex monolayer through thermal evaporation in vacuum. Then, the spheres were dissolved away to leave behind a surface with features located where the interstitial spaces between the densely packed spheres had been. This process depended upon the interaction between the microspheres and the substrates, and the adhesion between the film materials and the substrates. Different patterns of honeycomb net, triangle islands and separate spots can be obtained by controlling the ultrasonic time and intensity.
Analysis of hetero-coagulation structure of colloidal mullite precursor powder - experimental approach and computer simulation -
Authors: Cho Y. I. , Kamiya H. , Takano H. , Horio M. , Suzuki H.
Published: April 2011

To control the hetero-coagulation structure of ultra-fine γ-A12O3and SiO2powders for mullite ceramics, hetero-coagulation structures in suspensions with different pH conditions were investigated by experimental approach and computer simulation. Electrophoretic mobility distribution, which was determined by a Laser Doppler method, was used for the estimation of hetero-coagulation structure. As results, a bimodal electrophoretic mobility distribution was observed when precursor powders were prepared by colloidal mixing processes at pH=9.5. Since each peak almost corresponded to the electrophoretic mobility of γ-A12O3or SiO2particles, hetero-coagulates were not formed in suspension. In the case of pH=6.0, heterocoagulates generated in suspension, however, uniform and fine hetero-coagulates could not be attained. On the other hand, narrow and single mode electrophoretic mobility distribution was observed after colloidal mixing at pH=4.4. The change of hetero-coagulation structure with different pH conditions were analyzed by using Brownian dynamic methods with considering hetero-coagulated system. The change of hetero-coagulation structure with different pH conditions were qualitatively simulated by this model.
Direct observations of the sintering of silver nanoparticles on single crystal copper by in-situ uhv tem
Authors: Yeadon M. , Yang J. C. , Averback R. S. , Bullard J. W. , Gibson J. M.
Published: April 2011

Using a novel ultrahigh vacuum (UHV) transmission electron microscope with in-situ UHV sputtering attachment we have studied the sintering of copper and silver nanoparticles with single crystal copper substrates. Copper and silver particles deposited on (001) copper initially assume random orientations. Upon annealing, however, the particles reorient and assume an epitaxial orientation with the substrate. In the case of copper on copper, homoepitaxy occurs by a process involving sintering and grain growth. In the case of silver on copper, we have observed the particles to wet the substrate surface and sinter to form a thin epitaxial film with the orientation relationship (111)Ag // (001)Cu, [110]Ag // [110]Cu.
Theoretical modeling for laser cleaning of micro-particles from solid surface
Authors: Lu Y. F. , Song W. D. , Hong M. H. , Chan D. S. H. , Low T. S.
Published: April 2011

In laser cleaning of micro-particles from solid surface, the adhesion force between the particles and the substrate surface and the thermal expansion of both particles and substrate play important roles in determining the threshold laser fluence. Taking Van der Waals force and cleaning force due to fast thermal expansion of particles and substrate surface induced by pulsed laser irradiation into account, a cleaning model was established for removal of tiny particles from substrate surfaces. The cleaning condition and cleaning threshold can be obtained from this model. This model can qualitatively and quantitatively predict how the laser cleaning process depending on laser incident direction, laser wavelength, particle size, particle material and substrate material. Theoretical predictions have been verified by the experimental results. Laser cleaning of micro-particle has wide applications in microelectronics and magnetic recording industries.
Structural Changes on SnO2 Nanoparticles for Gas Sensor Applications induced by Calcination Treatments and Grinding
Authors: Diéguez A. , Alay J. L. , Kappler J. , Romano-Rodríguez A. , Vilà A. , Bârsan N. , Weimar U. , Göpel W. , Morante J. R.
Published: April 2011

Starting with a hydrated tin dioxide powder of 3nm size obtained by the sol-gel method, the effects of thermal treatments and grinding on the final structural properties of the nanoparticles have been investigated. It is observed that two regions with different structural properties can be distinguished in the range of temperatures between 250 and 1000°C. In spite of their large grain size (>15nm), above 350–450°C, these nanocrystals can be used as precursor powders for gas sensors because of their higher stability. Grinding of the starting material before calcination will be proved as a suitable method to obtain the sarne type of stability with lower grain size.
Defect Production and Annealing in High-Tc Superconductor Euba2cu3oy Irradiated with Energetic Ions at Low Temperature
Authors: Ishikawa N. , Chimi Y. , Iwase A. , Tsuru K. , Michikami O
Published: April 2011

The in-situ measurement of fluence dependence of electrical resistivity at 100K has been performed for EuBa2Cu3Oy irradiated at 100K with various energetic ions (Cl, Ni, Br, and I) at energy of 90–200MeV. Decreasing slope of resistivity-fluence curves has been observed for irradiations with 120MeV Cl, 90MeV Ni, and 185MeV Ni, while increasing slope of the curves has been observed for irradiations with 120MeV Br, 125MeV Br, and 200MeV I. It is assumed that the damaged region has a cylindrical shape along ion path and a higher resistivity than the undamaged matrix region. The calculated resistivity-fluence curve fitted well with the experimental data when using the diameter and the resistivity of the damaged region as fitting parameters. The obtained diameter and the resistivity of the damaged region have increased with increasing the electronic stopping power, Se. Successive annealing of the specimens up to 300K after irradiation has resulted in 50–70% recovery of irradiation-induced resistivity change at 100K. The diameter of the damaged region has been larger than that of amorphous tracks observed by transmission electron microscope. This result is discussed in relation to the result of annealing experiment.
Improvement of Hydriding Property in ZrNi Alloy by Means of Implantation
Authors: Suda T. , Yonezawa T. , Arashima H. , Ohnuki S. , Kabutomori T.
Published: April 2011

Ion-implantation was applied to the surface modification of ZrNi for improving the surface activation of hydrogen absorbing alloys. At the condition of low temperature, only implanted areas showed micro-cracks and pulverization. At high temperature, the reaction was very rapid and both implanted and shielded areas showed the pulverization. The results indicate hydrogen ion-implantation can enhance the activation of this alloy, and the roles of radiation-induced implanted hydrogen and surface film are discussed.
Aluminum Acceptors in Inequivalent Sites in 4H-Sic
Authors: Smith S.R. , Evwaraye A.O. , Mitchel W.C.
Published: April 2011

P-type conductivity is normally produced in silicon carbide by doping with Al or B. The aluminum atom substitutes for silicon in the SiC lattice. Several studies have shown that nitrogen, which substitutes for carbon atoms and produces n-type conductivity in SiC, sits at the two inequivalent lattice sites in 4H-SiC, and two N activation energies of 53 meV (h) and 100 meV (k) have been reported.

Hall effect measurements and infrared absorption studies of SiC doped with Al showed only one Al activation energy, however, and the published Al activation energy in SiC (3C, 4H, and 6H) ranges from 191 meV to 280 meV. This has lead to the general conclusion that the activation energy of Al acceptors in SiC does not depend on the polytype or on the lattice site occupied.

Thermal Admittance Spectroscopy (TAS) has been used to determine the activation energy of Al in 4H-SiC specimens where NA-ND ranged from 7.2 × 1015 cm2to 5.6 × 1018 cm−2. By analogy to B in 6H-SiC, we propose two levels for Al in 4H-SiC at Ev + 0.212 eV and Ev + 0.266 eV.
Investigation of the Effect of Thermal History on Ring-OSF Formation in CZ-Silicon Crystals
Authors: Kelly G.P. , Hourai M. , Umeno S. , Sano M. , Tsuya H.
Published: April 2011

R-OSF are known to appear in CZ silicon crystals, but their nuclei are not observable in the as-grown state, and as-such have been difficult to characterize. Using a crystal grown with modifications in its pulling rate, this paper used lifetime in particular, coupled with the OPP, to investigate as-grown OSF nuclei size and density distribution and to discuss further how R-OSF are formed and how their formation interacts with that of other defects. It was found that faster cooling in the temperature range where large voids are formed (1070°C-970°C), which resulted in a larger residual vacancy concentration, caused the OSF ring to become wider, and the OSF-nuclei to become larger than normal in this area, while fast cooling in the temperature range where OSF are formed (990°C-900°C) is thought to suppress their formation, which thus resulted in smaller OSF-nuclei
Investigation of Influence of Thermal and Radiation Processing on Impurity Centers in Silicon and Silicon Based Structures
Authors: Ashurov M. , Makhkamov Sh. , Tursunov N.A. , Martynchenko S.V.
Published: April 2011

In this paper the results of studies of the influence of radiation and thermal processing on activation of impurity centers (Au, Ag, Pt, Rh) in p-n-structures based on doped silicon are presented. It is shown that the thermal processing in the temperature range of 600-700°C leads to significant increasing of the concentration of electrically active impurities in the samples irradiated by, -rays as compared to the non-irradiated samples as well as to increasing of their decay temperature. These effects depend on the type and fluence of irradiation and can be explained by formation of additional electrically active states of impurities due to decay of complexes of radiation defects and electrically non-active impurities. A possible mechanism of activation process of impurity centers in silicon under radiation and thermal processing is discussed.
The Engineering of Silicon Wafer Material Properties Through Vacancy Concentration Profile Control and the Achievement of Ideal Oxygen Precipitation Behavior
Authors: Falster R. , Gambaro D. , Olmo M. , Cornara M. , Korb H.
Published: April 2011

A new kind of silicon wafer and a new class of materials engineering techniques for silicon wafers is described. This wafer, called the “Magic Denuded Zone” or MDZ wafer, is produced through the manipulation of the vacancy concentration and, in particular, vacancy concentration depth profiles in the wafer prior to the development of oxygen precipitates in subsequent heat treatments. The result is a wafer with ideal oxygen precipitation behavior for use in all types of integrated circuit applications. The methods used to prepare such wafers combine Frenkel pair generation with injection and the use of surface sinks. Simulations of the vacancy profiles produced by these techniques are presented and discussed. It is shown that within the range of vacancy concentration accessible by these techniques (up to ca. 1013 cm−3) the rate and oxygen concentration dependence of oxygen clustering can be substantially modified. Such techniques can be used to precisely engineer unique and desirable oxygen-related defect performance in silicon wafers both in terms of distribution and rate of defect formation. One result of the application of such techniques is an ideally precipitating silicon wafer in which the resulting oxygen precipitate profile (denuded zone depth and bulk density of precipitates) is independent of the concentration of oxygen of the wafer, the details of the crystal growth process used to prepare the wafer and, to a very large extent, the details of thermal cycles used to process the wafer into an electronic device. Optimal, generic and reliable internal gettering performance is achieved in such a wafer
Systematic Analyses of Practical Problems Related to Defects and Metallic Impurities in Silicon
Authors: Kitagawara Y. , Takeno H. , Tobe S. , Hayam Izu Y. , Koide T. , Takenaka T.
Published: April 2011

Systematic approaches are introduced for (i) oxygen precipitation behavior, which is important for internal gettering, and (ii) segregation induced gettering behaviors of p/p+ epitaxial wafers and Poly-Si Back Seal (PBS) wafers. (i) Oxygen precipitation behavior during a whole sequence of a thermal process is predicted by a practical computer simulation technique involving a novel empirical function. The predicted oxygen precipitation behavior agrees with the corresponding experimental results reasonably well. (ii) For a systematic description of Fe segregation gettering, explicit expressions of the Fe segregation coefficients are obtained as functions of temperature and time. Using the determined expressions of the segregation coefficients and introducing diffusion dynamics, one can predict [Fe] behavior as a function of process time during a whole sequence of a thermal process. For both behaviors of(i) oxygen precipitation and (ii) segregation induced gettering, experimentally observed characteristics of a high-temperature process and a low-temperature process are well understood by aids of those simulations. (iii) For a high-sensitivity detection of an important heavy metal impurity Cu, we present a novel bulk impurity collection technique using a room-temperature Cu drift phenomenon accelerated by Corona charge showering on a Si wafer surface
Deep-Level Traps in CCD Image Sensors
Authors: Mccolgin William C. , Lavine James P. , Stancampiano Charles V. , Russell Jeffrey B.
Published: April 2011

We have extended by five the number of deep-level traps known to create dark current in charge-coupled device (CCD) image sensors. These include Mn, Pt, and three much weaker traps that are as yet unidentified. Using dark current spectroscopy (DCS) we show that the generation rates at 55°C range from 6400 electrons/s for Mn to only 2 electrons/s for the weakest trap, which lies 0.27 eV off mid-gap. These weak traps determine the bandwidths and resolution of the trap peaks seen in the dark current spectra.
Influence of Defect Clusters on the Performance of Silicon Solar Cells
Authors: Sopori Bhushan , Chen Wei , Nemire Karen
Published: April 2011

Improvements in the techniques for the growth of Si substrates, used for commercial solar cells, have yielded wafers that exhibit low average defect density × typically less than 105 cm−2. We have observed that low defect density leads to the formation of defect clusters. This defect configuration influences the device performance in a unique way × by primarily degrading the voltage-related parameters. We discuss the nature of the defect clusters and show that they constitute regions of high carrier recombination. Network modeling is used to show that, in a device, these regions act as shunts that dissipate power generated within the cell.
Evaluating the Denuded Zone Depth by Measurements of the Recombination Activity of Bulk Defects
Authors: Polignano M. L. , Brambilla M. , Cazzaniga F. , Pavia G. , Zanderigo F. , Spiga S. , Moro L. , Castaldini A. , Cavallini A.
Published: April 2011

A method for measuring denuded zone depth from lifetime measurements is proposed and compared to observations by microscopy techniques and to Electron Beam Induced Current (EBIC) analyses. The surface photovoltage (SPV) method is chosen for measuring lifetime, as it is found to be extremely sensitive to oxygen precipitation. Samples prepared according to three typical thermal hystories are used as test vehicles.

Correlating the results given by the different techniques, this study points out a few relevant features from the point of view of wafer processing. For instance, processes starting with a low temperature treatment are poorly reproducible for what concerns oxygen precipitation and denuding, as shown by SPV data, and do not guarantee a defect-free denuded zone, as seen in EBIC images. Additional high temperature treatments during the process increase the denuded zone depth and improve uniformity.

Techniques which rely on a selective etching for defect detection, such as the Secondary Electron method of Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), are limited by etching sensitivy. On the other hand, the Transmission Electron Microscopy (TEM) statistics is too poor for this sort of observations. Instead, as a technique based on the recombination activity of defects, EBIC has roughly the same sensitivity as SPV. Both these techniques detect the formation of a denuded zone even when other methods fail, and can be considered as complementary tools.
Measurement of the Temperature Dependence of Silicon Recombination Lifetimes
Authors: Johnston S. , Ahrenkiel R. K.
Published: April 2011

Lifetime spectroscopy is a valuable tool in a number of silicon-based technologies. Currently, lifetime measurement is the most sensitive diagnostic for identification of lowlevel metal impurities in silicon by using the ratio of high-injection to low-injection lifetime. When a single impurity dominates recombination, the lifetime as a function of injection level provides a measure of the defect concentration. Another measurement parameter, that has not been commonly used, is the lifetime as a function of temperature. Temperaturedependent lifetime analysis leads to a better understanding of trapping-delayed recombination rates, trapping and recombination center energy levels and activation energies, temperaturedependent capture cross sections, and surface or grain boundary recombination or trapping effects. A contactless measurement technique has been developed that provides the sample's recombination lifetime over a temperature range from 80 K to 300 K. A sample is coupled to the measurement circuitry that is placed into a Dewar where it is cooled by liquid nitrogen. Lifetimes are then measured as the sample is allowed to warm to room temperature. Data will be shown on these variable-temperature lifetime measurements, which have been made on silicon wafer material ranging from high-quality float-zone-grown wafers to low-cost polycrystalline materials used in photovoltaics.
Point Defects in Relaxed Si1-xGex Alloy Layers
Authors: Mesli A. , Nylandsted Larsen A.
Published: April 2011

The use of compositionally graded buffer layers in the growth of fully relaxed epitaxial Si1−xGex alloy layers has led to a major improvement in crystalline quality. A considerable reduction in the density of the threading dislocations has become possible, facilitating point defect studies in these materials. The issues addressed in this review are inherent to the coupling between band gap engineering and defect-related levels. Among them, the pinning behaviour, charge state effects and their consequence upon the thermal stability of point defects are discussed together with the impact of the fluctuation in Ge distribution
High-Density, High-Thermal Dissipation Substrates Fabricated Using a Conductive Composite Material
Authors: Brandt Lutz , Matijasevic Goran , Gandhi Pradeep , Gallagher Catherine
Published: April 2011

Thermal performance of conventional printed circuit materials can be increased with the use of heat sinks. Even better thermal dissipation can be achieved with the use of insulated metal boards as substrates. However, this technology is limited in the number of circuit layers and the circuit density. A novel material based on transient liquid phase sintering (TLPS) was developed and used to make additive multilayer circuits on metal substrates. The partial sintering operation of the polymer-based conductive composite is akin to that of Cermet materials, but processing is at temperatures of < 250° C. A metallurgically alloyed web is formed by TLPS, providing good conductivity and stability with respect to humidity and heat exposure. An interpenetrating polymer network provides adhesion to a variety of substrates.

Photoimageable dielectrics have been used to image circuit traces (as fine as 50 μm) and vias (down to 75 μm). The conductive composite is filled into the grooves and cured to form circuits. Sequential building of circuit and via layers yields the desired planarized circuit with blind and buried solid vias throughout the multilayer structure. Metal substrates have been chosen to achieve high thermal dissipation. The thermal conductivity of the polymer-based conductive composite itself was measured to be 25 W/mK, comparable to that of solder materials. Thermally resistive adhesive interfaces have been minimized in the fabricating the structure, resulting in a high thermal dissipation, as well as high density substrate.
On The Influence Of Titanium Alloy Composition And Layer Thickness On The Mechanical Properties Of A Polyimide Substrate
Authors: Muralidharan G. , Narayanan B. , Wong C. C. , Manoharan M.
Published: April 2011

Metal-polymer bilayers and multilayers are being increasingly used in the microelectronics industry. In many cases, the reliability of the device or the package is determined by the mechanical behavior of these composite layers. Finite element analyses are being widely used to model these systems. An accurate experimental understanding of the mechanical behavior of these systems would further enhance the usefulness of such analyses. The present study focuses on the mechanical behavior of composite bilayers consisting of polyimide and sputtered Ti and Ti alloy thin films. Tensile tests and stretch-deformation tests have been performed on bilayers consisting of a polyimide substrate sputter-coated individually with a 50 nm and a 500 nm Ti layer, a 500 nm Ti-Cu layer, and a 500 nm Ti-Ni layer. Tensile moduli, stresses for 0.2%, 2% and 15% offset strains, and strains to failure have been obtained and compared. These values are discussed with reference to the known mechanical properties of the individual layers in the composite material.
Alloy Joints for High Temperature Electronic Packaging
Authors: So William W. , Lee Chin C.
Published: April 2011

High temperature joints are required for packaging and assembling the emerging high temperature semiconductor devices. A technique of producing high temperature joints at relatively low process temperature is presented. The technique uses liquid-solid interdiffusion to formulate the joint and subsequent solid-state diffusion and interaction to convert the joint material into high temperature alloy. Processes have been developed using the indium-silver binary material system. Joint melting temperature higher than 700°C has been achieved while the process temperature stays below 210°C. In this development effort, the constituent element materials are deposited in multilayer structure in high vacuum to prevent oxidation. As a result, no flux is used and no scrubbing action is applied. The joints produced are examined with a scanning acoustic microscope (SAM) to evaluate the bonding quality. The joint cross-sections are studied using SEM and EDX to find the microstructure and composition. In conventional processes, the process temperature needs to exceed the alloy melting temperature in order to produce a joint. High stresses can develop due to thermal expansion mismatch among materials involved. In the present technique, the relatively low process temperature can significantly reduce the stresses. The multilayer bonding method also facilitates control of the alloy composition and the joint thickness.
In-Plane Anisotropy In CoCr(Ta,Pt)/Cr Films Deposited onto Substrates with Controlled Topography
Authors: Twisselmann D.J. , Adekor B.T. , Farhoud M. , Smith Henry I. , Dorsey P.C. , Ross C.A.
Published: April 2011

In-plane magnetic anisotropy can be induced in Cr-underlayer/Co-alloy thin films by grooves or scratches in the substrate. To quantify this effect, silica substrates have been prepared with large areas of submicron grooves using interferometric lithography. The growth of Cr films and Cr/Co-alloy bilayer films on these substrates has been investigated, and in-plane magnetic anisotropy has been observed.
Compositional Microstructure and Micromagnetics of Co-Based Thin Film Media
Authors: Futamoto M. , Inaba N. , Hirayama Y. , Ito K. , Honda Y.
Published: April 2011

Elemental segregation of CoCrTa and CoCrPt thin films for longitudinal and perpendicular media is investigated using high spacial resolution transmission electron microscopes equipped with compositional analysis facilities. Strong Cr segregation exceeding 20 at% within 1.5-2 nm width is observed along the grain boundaries for both types of CoCrTa films prepared at elevated substrate temperatures. Weaker Cr segregation is observed along the grain boundaries of the longitudinal and the perpendicular CoCrPt films. The strong Cr segregation at grain boundaries is related with the small magnetic cluster size and the low media noise characteristics of CoCrTa thin film media. The Cr content inside the grain is several % lower than the average composition of the CoCrTa films. The magnetocrystalline anisotropy constants(Ku) for different Cr compositions are determined using single crystalline thin film technology to discuss the thermal stability of recorded information.
Effects of DC Bias on the Thermal Stability of DC In-Line Sputtered CoCrTa/Cr Thin Film Media
Authors: Wang J. P. , Tan L. P. , Liew T. Y. F. , Low T. S. , Wong H. L. , Lee Y. K.
Published: April 2011

The effects of DC bias on the thermal stability and magnetic anisotropy of CoCrTa/Cr thin film media fabricated by using a DC in-line sputtering machine is presented in this paper. In sputtering, a negative DC bias voltage, varying from 0 to 400 V, was applied for the CoCrTa layer. The coercivity was observed to increase almost linearly from 1800 to 2300 Oe for negative bias voltage from 0 to 400V. The thermal stability of these media was studied by measuring the time decay of remanent magnetization under various reverse magnetic fields. The maximum value of the magnetic viscosity coefficient, which happens around remanent coercivity of each samples, decreases with increasing substrate bias voltage. This implies an improvement in the thermal stability of the CoCrTa/Cr thin film media. The magnetic anisotropy constants were measured using both a torque magnetometer and a vibrating sample magnetometer. The magnetic anisotropy measured using torque magnetometer decreases, while that measured using the method of the law of approach to saturation was found to be almost constant, with increasing bias voltage. The activation volumes decreased with increasing bias voltage. The magnetic hardness coefficient determined using the law of approach to saturation, indicating the number of in-depth defects in the CoCrTa layer, increased with increasing bias voltage. The internal stress in these films measured using X-ray diffractometer also supported the existence of in-depth defects. The pinning of the rotation of magnetization by these defects in the magnetic grains maybe responsible for the improvement of thermal stability.
A Simulation of Rotational Hysteresis Energy Loss in Longitudinal Thin-Film Media
Authors: Yang Wei , Lambeth David N.
Published: April 2011

The field dependence of the rotational hysteresis energy loss was simulated for longitudinal thin-film media with the purpose of examining the validity of this method for measuring the anisotropy field. The field at which the rotational hysteresis vanishes, which is usually taken as the experimentally measured anisotropy field, was found to be smaller than the real anisotropy field when intergranular magnetostatic and exchange interactions are included in the simulations. Hence the rotational hysteresis method may result in an underestimation of the anisotropy field for the films with non-negligible grain interactions. To confirm this experimentally, two CoCrTa films, one with strong in-plane easy axis texture and the other with uniaxially aligned grain easy axes, were prepared under the same conditions. The anisotropy field determined by the rotational hysteresis of the first sample was found to be smaller than the more accurate value obtained from the hard axis hysteresis loop of the second sample.
Structural and Magnetic Properties of Co50 ± x Pt50 ± x Thin Films Prepared by Mbe Co-Evaporation on (001) MgO Substrate at Various Temperatures
Authors: Parasote V. , Cadevwlle M.-C. , Pierron-Bohnes V. , Grange W.
Published: April 2011

Structural and magnetic properties of Co50 ± x Pt50± x films 25-50 nm thick, prepared by molecular beam epitaxy onto a Pt buffer grown on MgO (001) substrate have been investigated. A series of 3 samples with different compositions (x = 6, 0, -6) was grown at 800 K on a 10 nm thick Pt buffer and another series of 5 samples of equiatomic composition was prepared at various growth temperatures (390 K≤ TG≤ 780 K) on a Pt buffer 4 nm thick. X-ray diffraction and TEM studies show the presence of grains with [111] and [002] orientations, the [002] grains being a mixture of the tetragonal L10 ordered phase and of the fcc disordered one. Both the thickness of the buffer layer and the deposition temperature are determinant parameters of the structural quality of the films and of the degree of long range order (LRO). An apparent LRO parameter (ηapp) is deduced from the superstructure and main peak intensity ratio. Its increase with the growth temperature is described through a thermally activated model that yields a small activation energy of 0.28 eV, illustrating the role played by both surface diffusion and surface interactions in building the L10 compound in agreement with theoretical predictions. An average uniaxial magnetocrystalline anisotropy energy (Kuav) is deduced from the magnetization curves measured by a SQUID. The anisotropy energy of the [002] grains (Ku002) is deduced, assuming a linear relationship between the anisotropies and the phase percentages. One observes a continuous but not linear increase of Ku002 with ηapp.
Characterization of Thin DLC Films Using Film Stress and Raman Techniques
Authors: Turlo J. E. , Gan Danny , Gopinathan Niranjan
Published: April 2011

Diamond like carbon (DLC) films are deposited on thin film heads in the magnetic recording industry to reduce friction and “stiction” and to provide a durable, abrasion resistant coating. The films are a mixture of graphitic phases with sp2 bonding and diamond phases with sp3 bonding. The present work provides the results of thin film stress measurements and Raman tests performed on 10 rim DLC films deposited on 75 mm silicon test wafers using standard optical lever techniques. Stress is measured after deposition and in-situ during thermal cycling. Isothermal relaxation data is also obtained. Raman is performed before and after annealing.

The deposited stress of 10 nrm films was over 2000 MPa. The stress relaxed entirely to zero during thermal cycling to 500°C. Isothermal relaxation at 300°C also resulted in complete relaxation of an initial 1500 MPa stress to zero in less than 24 hours. The Raman data is consistent with prior results in the literature. The position of the G band shifts from 1513 to 1581 cm-1 during annealing, and the intensity ratio of the D band to the G band rises from 0.201 to 0.814 during annealing.

The decrease of the film stress to zero during thermal processing implies that the entire thickness of the film is undergoing a structural change while the stress relaxation data implies that the stress is relaxing by a fast diffusive process. The Raman data implies that the film is becoming more graphitic and the crystallites are growing in number and size during thermal processing. We suggest that the structure of the extremely thin carbon film is modified by a surface diffusion mechanism.