bluuebunny/crossref_metadata_2025 huggingface dataset:
Interfacial Diffusion/Reaction and Electrical Properties of Pd Ultra-Thin Film on Sic at Different Annealing Temperatures
Authors: Lu W. , Shi D. T. , Collins W. E. , Chen H. , Burger A.
Published: April 2011

Pd/SiC has been used as a high temperature hydrocarbon and hydrogen gas sensor in environmental and aeronautical applications. In this work, the relationships between diffusion, reaction, and interfacial chemical composition with electrical properties for Pd ultra-thin films on 6H-SiC (∼< 30Å) are studied at different annealing temperatures.

Ultra-thin film Pd on 6H-SiC has been prepared by the RF sputtering method. The Schottky barrier heights are measured by XPS for an unannealed sample and samples annealed from 100°C to 400°C for 30 minutes, respectively. No significant change in the Schottky barrier height of the Pd/SiC contact was found in the temperature range. The morphology from UHV-STM and AFM show that the unannealed Pd thin film had good uniformity across the SiC substrate, and the Pd has dispersed, and then partially aggregated into rounded shaped precipitates with increasing annealing temperatures. At 400°C, all Pd metal has reacted and formed to silicides. From XPS, Pd2Si was found on the surface after annealing, and almost all Pd has reacted to become Pd2Si after annealing at 400°C. No other silicide was found. The intensity of Pd on XPS decreases enormously at 400°C. This is explained if Pd has diffused into SiC. The Pd diffusion and the formation of Pd silicides do not significantly affect the Schottky barrier height. The SiO2 was found at the top of surface after annealing, and increased in amount with increasing annealing temperature. The SiO2 formation was accelerated by the presence of Pd. Pd may play a role in absorbing oxygen, and activating Si from SiC to form SiO2.

Key Words: Pd thin film, SiC, X-ray photoelectron spectroscopy, scanning tunneling microscopy, and atomic force microscopy.
Growth of AlN Single Crystals
Authors: Slack Glen A.
Published: April 2011

Aluminum nitride is a wurtzite structure III–V compound, although epitaxial layers of zincblende structure AIN have been made. AlN melts congruently at 2750°C with dissociation pressure of 9 atmospheres. Boules of AIN have been successfully grown by a sublimation-recondensation technique at 2300°C employing tungsten crucibles. Growth rates of 0.3 mm per hour were attained at 1 bar pressure of N2, and crystals up to 22 mm long have been grown. An analysis of the growth process shows that the 9.75eV dissociation energy of N2is the limiting factor in the growth rate. The growth rate is predicted to depend on the N2pressure, but no experiments in this area have yet been concluded. The most satisfactory crucible material found so far for growing AIN is single crystal tungsten.
Polarity of GaN
Authors: Liliental-Weber Z. , Benamara M. , Richter O. , Swider W. , Washburn J. , Grzegory I. , Porowski S. , Yang J. W. , Nakamura S.
Published: April 2011

Convergent beam electron diffraction (CBED) was applied to study polarity of GaN heterolayers grown by MOCVD on sapphire and SiC substrates and also mechano-chemically polished bulk GaN platelet crystals grown from Ga melt under hydrostatic pressure of N. Heterolayers of GaN grown on both types of substrates showed (0001) Ga polarity, e.g. Ga to N along c-axis. Mechano-chemical etching of bulk GaN platelet crystals leaves one surface smooth and the opposite surface rough with visible damage caused by mechanical polishing. CBED studies showed that the smooth surface has (0001) N polarity, confirming our earlier studies.
Growth of Iii-Nitrides by Rf-Assisted Molecular Beam Epitaxy
Authors: Piquette E. C. , Bridger P. M. , Bandić Z. Z. , Mcgill T. C.
Published: April 2011

GaN, AlGaN, AIN were grown on (0001) A1203 substrates by MBE using a RF plasma source and employing an AIN buffer layer. The films were characterized by RHEED, AFM, and x-ray diffraction, and electrical properties were measured by Hall technique. RHEED observations indicate that the polarity of the films is likely predominantly N-face, although Ga-face inversion domains can be observed in some films by AFM. Symmetric x-ray rocking curve widths as low as 39 arcseconds are achieved for some layers, while asymmetric peaks show widths of 240–300 arcsec. Control of Si doping over a wide range is demonstrated, which is important for design of high power device structures. Gold Schottky barrier m-v-n+diodes were fabricated which achieve high reverse electric fields before edge breakdown.
Epitaxial Films of Faas and Fan on Fianit Substrates
Authors: Buzynin A. N. , Osiko V. V. , Lomonova E. E. , Buzynin Yu. N. , Usikov A. S.
Published: April 2011

Subrmicron heteroepitaxial GaAs and GaN films were grown by both conventional MOCVD and «capillary epitaxy» technique on (001) and (111) fianit (YSZ)substrates. A preliminary annealing of the substrates under vakuum was made in order to stabilize the surface by removing of some amount of oxygen. Conditions of single crystalline growth of GaAs submicron films (50–500nm) have been determined. The films had mirror-like surface morphology and high structural perfection. The distribution of Zr, O, Y across the film-substrate interface was sharp and doping impurities contents were uniform over the film. PL spectra of undoped GaN films on YSZ were studied.
Search for New Semiconductors for High Temperature Applications:The BaPb1-x BixO3 System
Authors: Ponnambalam V. , Varadaraju U. V.
Published: April 2011

BaPbl-xBixO3 phases with 0.6⋚ x⋚ 1.0 were synthesized by high temperature solid state reaction. Powder X-ray diffraction measurements show that all compositions are in single phase. Linear variation of lattice parameter is observed in BaPb1-xBixO3 with change in x indicating the random distribution of Pb in Bi sites. The activation energies for conduction of phases with x=0.8−0.6 obtained from ρ −T plots are same suggesting that the band gap does not change for compositions with x-0.8−0.6. The low activation energy obtained for BaBiO3 can be attributed to the structure of the compound. S versus (1000/T) data of x=1.0−0.8 exhibit a two-slope behavior. The orthorhombic to cubic phase transition could be the possible reason for the high power factor values of BaBiO3.
Properties of GaN Homoepitaxial Layers Grown on GaN Epitaxial Wafers
Authors: Dmitriev V. , Nikolaev A. , Cherenkov A. , Tsvetkov D. , Stepanov S. , Kuznetsov N. , Nikitina I. , Kovarsky A. , Yagovkina M. , Davidov V.
Published: April 2011

The lack of GaN substrates is a limiting factor for the development of III-V nitride devices.Recently we proposed to use GaN/SiC epitaxial wafers, consisting of thin GaN layer depositedby hydride vapor phase epitaxy (HVPE) on SiC wafer, as substrates for subsequent growth of IIIVnitrides and devices development. These wafers are attractive to be used as substrates for GaNdevice fabrication because the GaN-based device structures can be grown on these wafers byhomoepitaxy without any buffer layer. Due to high SiC thermoconductivity and cleavagepossibility, these wafers are especially attractive for high-power electronic and optoelectronicapplications. In this paper, we focus on crystal structure, optical and electrical properties of GaNhomoepitaxial layers and p-n structures grown by HVPE on GaN/SiC epitaxial wafers. Newtypes of III-V nitride epitaxial wafers are described, insulating GaN/SiC epitaxial wafers andAIN/SiC epitaxial wafers.
Tem and Hrem Study Of mGH-Temperature Aluminum Ion Implantation to 6H-SiC
Authors: Suvorova A. A. , Usov I. O. , Lebedev O. I. , Tendeloo G. Van , Suvorov A. V.
Published: April 2011

6H silicon carbide wafers were implanted with 40–50 keV aluminum ions to a dose of 1.5 × 1014 – 1.5 × 1016 cm−2 at high temperatures (1100°C–1700°C). The substrate temperature and the implantation dose were varied to investigate the influence of the implantation parameters on the formation of structural defects. Conventional transmission electron microscopy (TEM) and high resolution electron microscopy (HREM) techniques were applied to study the defects. We found that for low dose implants {0001} interstitial dislocation loops are formed but for high dose implants aluminum precipitates associated with {0001} half-loops are formed.
Electrochemical Etching in the GaN-Based Technology
Authors: Sidorov V. G. , Drizhuk A. G. , Sidorov D. V. , Lundin W. V. , Pushnyi B. V. , Usikov A. S.
Published: April 2011

In this study, both single undoped GaN epilayers and GaN-based device structures was treated by electrochemical etching in the dilute water solution of KOH or NaOH. Our investigations showed that in the undoped GaN epilayers grown by MOCVD the electrical and optical properties were nonuniform in depth. In this case, high defective and high conductive sublayer adjacent to the substrate was revealed by the electrochemical etching. This high conductive region was proved to condition the results of Hall effect measurements. Electrolyte etching of i-n GaN-based device structures grown by HVPE gave rise to significant increasing of the electroluminescence intensity. Influence of electrochemical etching on luminescence properties of the device structure is discussed.
Exafs Studies of Group III-Nitrides
Authors: Jeffs N J , Blant A V , Cheng T S , Foxon C T , Bailey C , Harrison P G , Mosselmans J F W , Dent A J
Published: April 2011

The group III nitrides have important applications for blue/green LEDs, blue/UV laser diodes and for high-power high frequency FETs. In all such devices the alloys play an important role either in the active part of the structure or in the cladding regions. The properties of the group III-nitride alloys are not at present well understood and in particular there are indications that phase separation can occur. We have undertaken a comprehensive study of (InGa)N alloys using EXAFS in order to study such problems.

We have demonstrated recently that REFLEXAFS technique can be used to give interatomic distances for (InGa)N alloys using the In edge to measure the bond lengths as a function of In content over the complete range from InN to GaN. We have now extended this study by using the Total Electron Yield (TEY) EXAFS technique to study the bond lengths by using both the Ga and In edges for (InGa)N alloys. The TEY data for the (InGa)N alloy samples gives more reliable data for the In-In and In-Ga separations than the earlier REFLEXAFS studies. Data obtained for the In-Ga separation from the Ga and In edges agree well within experimental error.

The data obtained from this study suggest that the (InGa)N samples grown at low temperature do not exhibit evidence for phase separation.
Evidence for Oxygen DX Centers in AlGaN
Authors: Mccluskey M. D. , Johnson N. M. , Van De Walle C. G. , Bour D. P. , Kneissl M. , Walukiewicz W.
Published: April 2011

Experimental and theoretical evidence is presented for oxygen DX centers in AlxGa1−xN. As the aluminum content increases, Hall effect measurements reveal an increase in the electron activation energy, consistent with the emergence of a deep DX level from the conduction band. Persistent photoconductivity is observed in Al0 39Ga0. 61N:O at temperatures below 150 K after exposure to light, with an optical threshold energy of 1.3 eV, in excellent agreement with first-principles calculations. Unlike oxygen, silicon does not exhibit DX-like behavior, in agreement with previous theoretical predictions.
Flow Modulation Epitaxial Lateral Overgrowth Of Gallium Nitride On Masked 6H-Silicon Carbide And Sapphire Surfaces
Authors: Smart J. A. , Chumbes E. M. , Srivatsa L. N. , Lo Y. H. , Shealy J. R.
Published: April 2011

Selective Area Flow Modulation Epitaxial growth of GaN is carried out in a low pressure Organometallic Vapor Phase Epitaxy reactor. This process is known to enhance reactant surface migration lengths on patterned group III-arsenide and phosphide growth surfaces. With this process, high quality laterally overgrown GaN epitaxial materials result. Under the ammonia rich growth conditions used, enhanced migration (by flux modulation) across masked regions of the substrate has not been observed. The mask materials were silicon dioxide and silicon nitride, both deposited on GaN/AlGaN buffer structures on sapphire and SiC substrates. Window stripes were patterned parallel and perpendicular to the (1100) crystal directions to observe the orientation dependence of the lateral growth rate. Structures exhibited heights above the mask surface as large as 30 microns and atomically smooth surfaces. With a periodic array of stripe window openings in the mask, planarized laterally overgrown surfaces are achieved after roughly 4 microns of overgrowth. Chemical assisted ion beam etching with chlorine gas was used to delineate defects in the selectively grown layers. Additional evidence on the defect reduction is given by Atomic Force and Scanning Transmission Electron Microscopies.
Two-Step Growth of Gan Quantum Dots with Metalorganic Chemical Vapor Deposition
Authors: Chen P. , Shen B. , Zhang R. , Wang M. , Zhou Y. G. , Chen Z. Z. , Zhang L. , Zheng Y. D.
Published: April 2011

Nanometer-scale GaN dots were successfully fabricated on sapphire using metalorganic chemical vapor deposition(MOCVD) by two-step method, including depositing around 500 IC and annealing at 1050 °C. The density of GaN dots is from 5×108cm−2 to 6×109 cm−2, and the size is around 40nm in diameter. The density and size of GaN dots are determined by an atomic force microscope(AFM), and they are controllable by changing temperature and duration of the growing. GaN dots only formed after annealing at high temperature, which is explained that the initial layer deposited around 500 °C is a high energy intermediate phase in which the large strain energy can not be relaxed because of the low temperature growing.
MOCVD Growth of Gan on Silicon and Related Surfaces
Authors: Han J. , Fleming J. G. , Follstaedt D. M.
Published: April 2011

The growth of GaN on silicon (Si) substrates by MOCVD is reported in this paper. The use of a high-temperature AIN buffer layer appears to be necessary to establish an initial template morphology for the subsequent growth of GaN. Nucleation modes of GaN on SiO2, (100) Si, and (111) Si are compared; it is shown that the spatial coherency among the nuclei is most preserved when the growth occurred on the hexagonal Si (111) surface. To circumvent the problem associated with cracking due to a thermal expansion mismatch, we also investigate the possibility of using a silicon-on-insulator (SOI) scheme.
A Theoretical and Empirical Perspective of SiC Bulk Growth
Authors: Tsvetkov V. F. , Henshall D. N. , Brady M. F. , Glass R. C. , Carter C. H.
Published: April 2011

The production of large diameter, high quality boules of SiC is essential to realize the full potential of this important semiconductor material. The objective of this paper is to provide a state-of-the-art analysis of the key directions for SiC bulk growth research, as well as presenting our most recent empirical results. Based on an analytical review of current knowledge, the following topics concerning growth of large 6H and 4H-SiC bulk crystals are discussed: 1) thermodynamics of the vapor phase including the efficiency of crystal growth, 2) kinetics of growth including mass transport in the boundary layer and 3) defect formation processes including thermoelastic stress. In addition, results of growth modeling are summarized and direction for further work suggested. Results on growth of semi-insulating and 50–75 mm diameter 4H-SiC wafers are presented. A discussion on micropipes, which are currently the most harmful defect in SiC wafers is presented. Although several mechanisms, or combinations of mechanisms, cause micropipes in SiC boules grown by the seeded sublimation method, we have reduced micropipe densities by orders of magnitude over the last few years. This continual reduction and the production of wafers with micropipe densities of less than 1 cm-2 (with >1 cm2 areas void of micropipes), indicate that micropipes will be reduced to a level that makes high current devices viable and that they may soon be totally eliminated.
Quantum Diffusion of H(D) In Semiconductors and Metals, and The Role of the Interaction with Impurities
Authors: Cannelli G. , Cantelli R. , Cordero F. , Giovine E. , Trequattrini F.
Published: April 2011

The mobility of hydrogen and its isotopes in metals has been the object of investigation for several years, whereas the diffusion studies of H in doped semiconductors started more recently. Although the H diffusion coefficient in metals may be several orders of magnitudes higher than in semiconductors, the dynamics of H in metals and semiconductors presents many common features, like precipitation, trapping by heavier impurities and, as indicated by recent results, quantum tunneling at low temperature.

In boron doped silicon, the relaxation rates τ−1(T) of H around B obtained from anelastic relaxation were joined with those from infrared absorption: the remarkably wide range obtained (11 decades) clearly shows a deviation of τ−1(T) from the classical dependence at low temperature. However, the results obtained and their analysis do not allow yet to draw conclusions on the mechanism governing the H(D) dynamics.

Recently, the investigation of the dynamics of H(D) in GaAs doped with Zn revealed a dissipation peak at 20 K in the kHz range. This relaxation has the highest rate found for H in a semiconductor: more than 15 orders of magnitude higher than in all the other semiconductors measured so far. The analysis of the dissipation curves clearly indicates that the nature of the H reorientation is quantistic.

In metals two regimes of the H mobility are observed: hopping with deviations from a classical Arrhenius motion, and a much faster tunneling within few close sites. In the latter regime the H dynamics does not consist of jumps but of transitions between the quantized energy levels of the tunnel systems. The types of interactions assisting the H transitions and the geometry of the tunnel systems are an open problem: although the two-level tunnel system (TLS) has been widely used to explain neutron diffusion, specific heat, and acoustic spectroscopy results in interstitial solutions (NbOxHy), recently this model has appeared not to be valid in substitutional solutions (NbZrxHy, NbTixHy) where the tunnel systems have a higher symmetry. The four-level systems seem to be more appropriate, although the corresponding model has not been developed as much as the TLS yet.
Diffusion Of Hydrogen In Zirconium Foil
Authors: Schur D. V. , Zaginaichenko S.Yu. , Pishuk V. K. , Adejev V. M.
Published: April 2011

The authors of present research have used in experiments the atomic hydrogen and metallic
foil 25–30 jim thick.

It have been supposed that these technical operations will permit to exclude the influence of
surface and diffusional processes on the rate of Me-H interaction.

The series of experiments have been carried out and they confirm this assumption. It have been shown that hydrogenation reaction of zirconium foil in atomic hydrogen conform to the topochemical model of volume segregation of interaction product and the rate of its flow is independent of the surface processes and hydrogen diffusion in volume.
Hydrogen Diffusion in Chalcopyrite Solar Cell Materials
Authors: Weidinger A. , Krauser J. , Riedle Th. , Klenk R. , Lux-Steiner M. Ch. , Yakushev M. V.
Published: April 2011

Hydrogen diffusion in CuInSe 2 single crystals and CuInS2 thin films was studied by measuring the spreading of implantation profiles upon annealing. Deep implantation with an ion energy of 10 keV and sub-surface implantation with 300 eV were applied. The diffusion coefficients in both materials were found to be in the order of 10-14 to 10-13 cm2/s in the temperature range between 400 and 520 K.These fairly low diffusivities are typical for a trap and release transport process rather than intrinsic diffusion of interstitial hydrogen. In the polycrystalline CuInS2 films, hydrogen leaves the sample through the grain boundaries.
The Role of Hydrogen in Semi-Insulating Inp
Authors: Han Yujie , Liu Xunlang , Jiao Jinghua , Qian Jiajun , Chen Yonghai , Wang Zhanguo , Lin Lanying
Published: April 2011

Complexes of vacancy at indium site with one to four hydrogen atoms and isolated hydrogen or hydrogen dimer and other infrared absorption lines, tentatively be assigned to hydrogen related defects were investigated by FTIR. Hydrogen can passivate imperfections, thereby eliminating detrimental electronic states from the energy bandgap.Incorporated hydrogen can introduce extended defects and generate electrically-active defects. Hydrogen also can acts as an actuator for creating of antistructure defects. Isolated hydrogen related defects(e.g. H12+) may play an important role in the conversion of the annealed wafers from semiconducting to the semi-insulating behavior. H2+ may be a deep donor, whose energy level is very near the iron deep acceptor level in the energy gap.
Hydrogen Passivation of Be-Acceptors in AiGaAs/GaAs Quantum Well Structures
Authors: Zhaoa Q. X. , Södervall U. , Willandera M. , Fimland B. O. , Crawford D. , Selvigb E. , Holtzc P. O. , Karlsteena M. , Sveinbjömssond E.
Published: April 2011

High quality Al0.3Ga0.7As/GaAs quantum wells with centrally doped Be-acceptors were grown by molecular beam epitaxy (MBE). The well width is either 10 nm or 20 nm, and the concentration of Be-acceptors is varied between 5× 1016/cm3 and 2×1018/cm3. The structures were treated systematically by dc H-plasma at different sample temperatures, gas pressures and cooling down procedures. The passivation of Be-acceptors were characterized by photoluminescence spectroscopy and secondary ion mass spectrometry (SIMS). Without causing degradation of the A1GaAs/GaAs interfaces, we have obtained, for the first time, a deactivation of above 80% of the Be-acceptors. The influence of the Be-doping on the bandgap excitons in the QW structures is also investigated in detail. A significant difference is found in comparison with the earlier reports for 150 Å wide quantum wells, in which different samples were used for different doping concentrations.
Interaction of Atomic Hydrogen with the Surface of Cu-llII-V12 Chalcopyrite Semiconductors-A Method for Controlled Stoichiometry Variation
Authors: Lippold Gerd , Otte Karsten , Schlemm Hermann , Grill Wolfgang
Published: April 2011

To introduce atomic hydrogen into Cu-chalcopyrite samples, low energy broad beam ion implantation into heated targets was used. In addition to the expected hydrogen diffusion into the sample from the implanted thin surface layer, another hydrogen-related effect was observed. As demonstrated for single crystalline CuInSe2, at target temperatures above 150°C a surface layer becomes In-rich. Two phases, the CuInSe2 α-phase and a In-rich phase similar to the reported ordered vacancy compounds (β-phase) coexist, as detected by Raman spectroscopy. The depth profile and the thermal stability of this hydrogen-related compositional variation are investigated. Based on the results we discuss a model of this effect, involving a copper in-diffusion, caused by the hydrogenation due to filling of Cu vacancies and possible substitution of Cu by H. The observed β-phase-like compound is unstable against annealing above 180°C, but can be restored in a thermal cycling process. Annealing for 1.5 h at 400°C removes it completely and restores the asgrown CuInSe2 surface. A decrease of the hydrogen concentration in the surface layer due to redistribution and out-diffusion, followed by the recovery of the Cu content, might be responsible for this behaviour.
The Contribution of H Ion Etching Under Different Substrate Bias to the Orientation Degree of Diamond Films
Authors: Zhang W. J. , Jiang X.
Published: April 2011

An etching process of hydrogen ions was performed during the initial growth stage of diamond films. The H+ ion etching was performed by applying a negative substrate bias during a microwave plasma chemical vapor deposition process, using only hydrogen as a reactant gas. The contribution of H+ etching under different substrate bias and for different etching time to the orientation degree of diamond films was investigated by scanning electron microscopy and atomic force microscopy. It was found that an additional H+ etching process had influence on the orientation degree of deposited (001)-oriented diamond films. To achieve a significant improvement of crystal orientation, the bias voltage and etching time should be adjusted concerning to the situation of diamond films.
Thermal Desorption of Hydrogen in Si and Sic Nanoparticles Produced by Plasma-Enhanced Chemical-Vapor Deposition
Authors: Costa J. , Fort J. , Suñol J. J. , Roura P. , Viera G. , Bertran E.
Published: April 2011

Mass spectrometry and calorimetry experiments on hydrogen evolution in amorphous Si:H and SiC:H nanoparticles grown by Plasma-Enhanced Chemical-Vapor Deposition (PECVD) are reported. The evolution spectra in a-Si particles are very similar to those found in films. The dynamic constants of the low-temperature peak confirm that this process is the same as in films. It is argued that the high-temperature process may not be diffusion-controlled. Both processes are exothermic, indicating that most dangling bonds recombine after H-desorption. The Hevolution in SiC occurs at higher temperatures than in Si. The process is endothermic.
Dissociation of Deuterium-Defect Complexes in Ion-Implanted Epitaxial 4H-SiC
Authors: Janson M. , Linnarsson M. K. , Hallén A. , Svensson B. G.
Published: April 2011

Epitaxial layers of low doped 4H-SiC are implanted with 20 keV 2H+ ions to a dose of 1×1015 cm−2. The samples are subsequently annealed at temperatures ranging from 1040 to 1135 °C. Secondary ion mass spectrometry is used to obtain the concentration versus depth profiles of the atomic deuterium in the samples. It is found that the concentration of implanted deuterium decreases rapidly in the samples as a function of anneal time.

The experimental data are explained by a model where the deuterium migrates rapidly and becomes trapped and de-trapped at implantation-induced defects which exhibit a slightly shallower depth distribution than the implanted deuterium ions. Computer simulations using this model, in which the damage profile is taken from Monte Carlo simulations and the surface is treated as a perfect sink for the diffusing deuterium atoms, are performed with good results compared to the experimental data. The complexes are tentatively identified as carbon-deuterium at a Si-vacancy and a dissociation energy (ED) of approximately 4.9 eV is extracted for the deuterium-vacancy complexes.
The Effect of Hydrogen/ Deuterium Introduction on Photoluminescence of 3C-SiC Crystals
Authors: Lee B. K. , Steckl A. J. , Zavada J. M. , Wilson R. G.
Published: April 2011

The effect of the incorporation and annealing of deuterium in 3C-SiC on its photoluninescence is reported. A 3C-SiC crystal has been implanted with 100 keV deuterium and subsequently annealed at temperatures between 1015 °C and 1220 °C for 1 to 5 minutes. SIMS depth profiles indicate hydrogen is strongly trapped by defects generated through ion bombardment, but a gradual damage repairing occurs during annealing. Photoluminescence was measured with 488 nm Ar laser excitation for sample temperatures from 89 K to 400 K. The PL peak wavelength of 540 nm at room temperature has shifted to 538 nm at 89 K. The peak PL intensity decreases with measurement temperature while its full width at half maximum (FWHM) exhibits an increasing trend. PL data were taken at five annealing stages. The post-implantation peak PL intensity and its integrated area increase initially with annealing temperature and time. After the final annealing at 1218 °C for 2 minute, PL intensity and its integrated area exhibit a decrease in level.
Silicide Technology in Deep Submicron Regime
Authors: Suguro K , Iinuma T. , Ohuchi K , Miyashita K. , Akutsu H. , Yoshimura H. , Akasaka Y. , Nakajima K , Miyano K , Toyoshima Y.
Published: April 2011

Silicide technology using cobalt-titanium alloy has been developed for sub-quarter micron devices. Extremely flat and epitaxial CoSi2 films are successfully grown on a (100) Si substrate. Improved SALICIDE process is not influenced by native oxide on a Si surface. This technology will be very useful in deep sub-quarter micron devices.
Formation and Thermal Stability of Nd0.32Y0.68Si1.7 Layers Formed by Channeled Ion Beam Synthesis
Authors: Wu M. F. , Vantomne A. , Hogg S. , Pattyn H. , Langouche G. , Jin S. , Bender H.
Published: April 2011

The Nd-disilicide, which exists only in a tetragonal or an orthorhombic structure, cannot be grown epitaxially on a Si(111) substrate. However, by adding Y and using channeled ion beam synthesis, hexagonal Nd0.32Y0.68Si1.7 epilayers with lattice constant of aepi = 0.3915 nm and cepi = 0.4152 nm and with good crystalline quality (χmin of Nd and Y is 3.5% and 4.3 % respectively) are formed in a Si(111) substrate. This shows that the addition of Y to the Nd-Si system forces the latter into a hexagonal structure. The epilayer is stable up to 950 °C; annealing at 1000 °C results in partial transformation into other phases. The formation, the structure and the thermal stability of this ternary silicide have been studied using Rutherford backscattering/channeling, x-ray diffraction and transmission electron microscopy.
C49-TiSi2 Epitaxial Orientation Dependence of the C49-to-C54 Phase Transformation Rate
Authors: Nakamura T. , Ikeda K. , Tomita H. , Komiya S. , Nakajima K.
Published: April 2011

Effects of the C49-TiSi2 epitaxial orientation on the C49-to-C54 phase transformation rate have been studied for samples with different pre-amorphization implantation (PAI) conditions. The C49 epitaxial orientation to the Si(001) substrate is characterized by use of grazing-incidence X-ray diffraction (GIXD) measurements. We found that the PAl treatment suppresses the epitaxial growth of C49-TiSi2 on Si(001) substrates and the poorer orientational alignment of C49-TiSi2 causes a more rapid transformation to C54-TiSi2. We believe this suppression of epitaxial alignment is a possible mechanism to understand the effect of the PAl treatment on the C49-C54 transformation.
Selective Rapid Thermal Chemical Vapor Deposition of Titanium Silicide on Arsenic Implanted Silicon
Authors: Fang Hua , Özttirk Mehmet C. , Seebauer Edmund G.
Published: April 2011

This work explores the effects of arsenic on rapid thermal chemical vapor deposition (RTCVD) of TiSi2. The films were deposited using TiCI4 and SiH4 on 100 mm oxide patterned silicon wafers selectively at temperatures ranging from 750°C to 850°C. Arsenic dose levels ranging from 3×1014 cm−2 to 5*times;1015 cm−2 at 50 keV were considered. Experimental results reveal that arsenic results in a resistance to TiSi2 nucleation and enhanced silicon substrate consumption. These effects are enhanced at higher arsenic dose levels and reduced at higher deposition temperatures. We propose an arsenic-surfacepassivation model to explain the effects.
Process Design & Integration of Salicide and Source/Drain process Modules for Improved Device Performance
Authors: Apte Pushkar P. , Saxena Shared , Rao Suraj , Vasanth Karthik , Prinslow Douglas A. , Kittl Jorge A. , Breedijk Terence , Pollack Gordon
Published: April 2011

To enable swift integration of process modules into manufacturable process flows; three components – individual process modules, their interactions and their variability-must be understood well. At dimensions ≤ 0.25 μm, this understanding is especially critical, and also quite challenging. We present here an approach to address this challenge by joint process design, using two key modules-salicide and source/drain-as an example. Together, these modules impact the silicide-to-diffusion contact resistance, (Rc), and the gate sheet resistance (Rs); which, in turn, significantly affect transistor series resistance and circuit delays respectively. We have built a model to help provide insight into the underlying physical mechanisms, and to help provide a quantitative framework for optimizing performance and variability. Rc, depends critically on the doping concentration immediately adjacent to the silicide, and this concentration is determined by the combined effect of silicide processing and the two-dimensional source/drain dopant profile. Rs depends on the thickness and phase of the silicide film formed, which, in turn, depend on the salicide process variables as well as the source/drain doping concentration, because both affect the silicide growth kinetics. Process conditions favoring Rs. and Rc are opposite to each other: thicker silicide films and higher thermal budgets help in the phase-transformation to the low-resistivity C54 phase and improve Rs but they increase dopant redistribution and worsen Rc. Optimal process design can improve the transistor drive current (Id) by ≈5%, and circuit performance, as measured by the figure-of-merit (FOM) by ≈ 4%. This improvement is significant, and an added benefit of this approach is that other transistor characteristics such as effective channel length, off-current, substrate current, etc. remain unchanged. In summary, we have demonstrated that by joint process design and integration of the salicide and source/drain modules, insight can be gained into the underlying physical mechanisms, and device and circuit performance can be improved significantly.
A Study of Transistor Optimization in A 0.25 Micron CMOS Flow Using S/D and Silicide Process Modules and Their Interactions
Authors: Vasanth K. , Apte P. , Davis J. , Saxena S. , Burch R. , Rao S. , Mozumder P. K.
Published: April 2011

A modular approach to CMOS process development requires an understanding of individual process modules (channel, gate, etc.) and their interactions. The reverse short channel effect, (RSCE) in NMOS devices is one such interaction between the channel and source/drain (S/D) modules. Similarly the interaction between the S/D and silicide modules affects the contact and gate sheet resistance. This paper presents (a) an investigation of the effects of S/D processing (As and P implant conditions) on the RSCE, (b) effects of S/D and silicide processing on the contact and gate sheet resistance, (c) the use of an integrated system to optimize process modules and their interactions and (d) the validity of the modules and system in process development by obtaining a 4% improvement in drive current of a 0.25 micron NMOS device. The outputs of the S/D module include the doping profiles as a function of implant and anneal conditions. The interaction between the channel and S/D is caused by the damage created during the S/D implants, leading to channel dopant redistribution during subsequent thermal anneals. This interaction causes the RSCE in NMOS devices and has to be taken into account before the modules can be used for process optimization. The interaction is studied by varying the dose and energy of the As and P S/D implants and observing their effect of the RSCE. Further, to model this interaction, parameters of a 2D dopant profile model are extracted from device data and form a part of the S/D module in addition to the doping profile information. The system integrates the outputs from the process modules and their interactions and allows for a rapid search of the process space. The search criteria can be varied to include performance (e.g. drive and off current) and manufacturability criteria.
Properties of Cu3Ge Films for Contacts to Si and SiGe and Cu Metallization
Authors: Borek Mark A. , Oktyabrsky S. , Aboelfotoh M. O. , Narayan J.
Published: April 2011

We have formed thin films of Cu3Ge on (100) Si and (100) Si50Ge50 for low resistivity ohmic contacts and interconnects by the sequential room temperature e-beam deposition of a layer of amorphous Ge, followed by a polycrystalline layer of Cu. We have also deposited thin films of Cu on the Si50Ge50 to compare the behavior of films of Cu3Ge relative to that of pure Cu. We have determined by transmission electron microscopy (TEM) that films of Cu3Ge form an abrupt interface with Si and Si50Ge50, with no indication of interaction between the film and substrate. We have also shown by secondary ion mass spectrometry (SIMS) that Cu diffusion into the underlying substrate is not observed for films of Cu3Ge as compared to that of pure Cu. We have shown that Cu reacts with Si50Ge50 when annealed or 30 min. at 400°C to form a layer of Cu3Si1−xGe.. We have also observed that room temperature oxidation of the underlying Si50Ge50 does not occur as compared to the room temperature formation of SiO2 that is observed in Cu3Si/Si structures.
Multilevel Interconnection Technologies and Future Requirements for Logic Applications
Authors: Brillouët M.
Published: April 2011

The performance and cost of the logic ICs is more and more dominated by the interconnections. Reducing the capacitances in the advanced processes, especially with low k dielectrics, is a priority, while a differentiated approach can be applied for lowering the connection resistances, e.g. in adapting the interconnect material to specific levels. Integrating new materials leads to difficult trade-offs in order to achieve a good electrical performance of the circuit. Finally the increased number of levels of interconnection addresses other fields like integration density, defectivity reduction or cost.
Interconnection Limits on XXI Century Gigascale Integration (GSI)
Authors: Meindl James D.
Published: April 2011

Throughout the past four decades, both the productivity and performance of microelectronics technology have advanced at exponential rates. In reality, exponential advances do not continue endlessly. Consequently, the purpose of this discussion is a systematic assessment of early XXI century opportunities for multi-billion transistor chips or gigascale integration (GSI).
The Effect of Impurities in Tin Film When Used As Mos Gate Electrodes
Authors: Yag H. , Hu J. C. , Lu J. P. , Brown G. A. , Rotondara A. L. P. , Luttmer J. D. , Magel L. K. , Liu H.-Y. , Chen P. J.
Published: April 2011

Refractory metal gates have been studied for CMOS gate electrodes on ultra thin gate oxide due to its midgap work function, low resistivity and no gate depletion, etc. In particular, titanium nitride received most attention because of its process maturity and its good diffusion barrier properties for backend applications. Different TiN film properties are important when TiN is used as a gate material than when it is used for backend applications. One issue is the effect of TiN film impurities on the gate oxides and their high temperature stability since some high temperature processes are usually needed after gate formation. This paper reports the study of different TiN films used as MOS gate electrodes on ultra thin gate oxide and the effects of their impurities on gate oxide electrical performance. PVD TiN films deposited with different process conditions show different oxygen content, and different gate oxide properties were observed when these PVD TiN films were used as gate electrodes. On the other hand CVD TiN films deposited using different precursors also showed different impurities, including carbon, oxygen or silicon, which largely affect CVD TiN performance when used as gate material. The different TiN films were characterized by X-ray glancing angle reflection, XPS, SIMS and TEM, and the electrical properties were studied by I-V, C-V, charge to breakdown (Qbd) and ramp voltage breakdown tests on MOS capacitors. The results showed that the high purity TiN films provide stable gate material with small damage to the gate oxide, but impurities, especially oxygen, affect the gate oxide properties after high temperature anneal. However, due to the different TiN process capabilities, TiN films with impurities may still have advantages over pure TiN film in some cases of different MOS gate applications.
A Main Factor Determining the Uniform Step Coverage in Chemical Vapor Deposition
Authors: Shin Chee Burm , Hwang Gyeong Soon
Published: April 2011

Profile evolution simulations during chemical vapor deposition based on a 2-D continuum model reveal that the type of surface kinetics plays an important role as a measure of determining step coverage of films deposited in a high aspect ratio trench or via. The linear surface kinetics, resulting from adsorption rate limitation, is found to be difficult to bring about conformal step coverage in a deep narrow trench without reducing the growth rate considerably; that is, under such a condition void free filling can not be achievable with holding an appropriate growth rate. High tendency of the precursor for chemical equilibrium on a surface, tending to cause the non-linear surface kinetics by surface reaction limitation, is mainly responsible for the significant improvement of step coverage in TEOS-based depositions.
Characterization of Thin Titanium and Titanium Nitride Layers Using Sims
Authors: Li-Fatou Andrei V. , Sardela Mauro R. , Tian Chunsheng
Published: April 2011

Titanium (Ti) and titanium nitride (TiN) films are widely used as barrier stack to prevent junction spiking. It is also an important material for an anti-reflection coating (ARC) on aluminum (Al) films to facilitate lithography processes during multilevel metallization for the manufacture of integrated circuits on silicon-based (Si) semiconductor devices. Secondary Ion Mass Spectrometry (SIMS) is proven to be very powerful analytical technique for the semiconductor materials. However, quantitative analysis of very thin structures using SIMS constitutes an ultimate challenge since a large fraction of the profile is located in the transient region where a stable concentration of primary beam species has not been established.

This paper reports a SIMS technique for advanced characterization of very thin titanium and titanium nitride layers. Improvements in depth resolution were achieved by reducing the angle of incidence and the impact energy maintaining enhanced ionization yield associated with oxygen bombardment. Significant improvements in characterization of the film surface were developed by using oxygen flooding technique. Optimized oxygen pressure was used to achieve a stable ion yield due to the complete surface oxidation of titanium and titanium nitride layers during the analysis. The method was employed in the SIMS characterization of multiple Ti/TiN films deposited on silicon substrate. The example presents dramatic enhancement in depth resolution due to minimized matrix related ion yield variations at the interfaces.
Growth and Characterization of Rare-Earth Phosphide/Arsenide Schottky Contacts to GaAs
Authors: Lee P. P. , Chem J. H. , Sadwick L. P. , Hwu R. J. , Balasubramaniam H. , Kumar B. R. , Alvis R. , Lareau R. L. , Streit D. C.
Published: April 2011

The lack of high-temperature thermodynamically stable contacts has been a limiting factor for III-V compound semiconductor metallization. The instability of metal/semiconductor contacts at higher temperatures arises due to factors such as thermodynamic instability at the interface, lack of chemical inertness especially to oxygen containing ambients and a large lattice mismatch to the substrate. Our studies of two rare-earth compounds, dysprosium phosphide (DyP) and dysprosium arsenide (DyAs), demonstrate their potential to address the above problems. The growth and characterization of these two materials and their heterostructures will be presented.

Both the DyP and DyAs epilayers were grown using MBD. DyP has an excellent room temperature lattice match to GaAs with a mismatch of about 0.01%, whereas DyAs has a lattice mismatch to GaAs on the order of about 2.4%. Consistent high quality DyP and good quality DyAs epilayers, as characterized by TEM, XRD, AES and AFM were obtained for growth temperatures between 500°C and 600°C. The growth rate was about 0.5 μm/hr and and the RMS roughness of the epilayer surface was typically about 0.5 nm and 1.3 nm for Dyp and DyAs, respectively.

Electrical characterization of DyP and DyAs include variable temperature Hall measurements, four point probe, TLM, I-V and C-V measurements. Results show that both DyP and DyAs epilayers are n-type with electron concentration between 3–4 × 1020cm−3 and 2–3×1021cm−3, respectively. The room temperature mobility and resistivity of DyP are 300 cm2/Vsec and 60 μ Ω cm, respectively. The room temperature mobility of DyAs is about 50 cm2/Vsec. DyP forms a Schottky barrier to GaAs with a barrier height of 0.81eV and DyAs forms a weak Schottkyt barrier to GaAs. All relevant data will be presented along with schemes for using DyP and DyAs as potential interconnects to III-V compound semiconductors.
Organically Deposited Metallic Films for Device Fabrication
Authors: O'Keefe T. , Stroder M. , O'Keefe M.
Published: April 2011

Advances in integrated circuit density, speed and complexity are dependent on lower resistance, finer line width on-chip interconnections. Methods for incorporating copper interconnects into IC fabrication processes have been developed which accomplish this objective but most of these methods use some form of blanket metal deposition that requires mechanical and/or chemical removal of excess material. To date, investigations into the selective deposition of conductor materials for device fabrication have met with limited success. A new process for selectively depositing metallic conductors using inexpensive, organic-based chemical solutions could potentially force a paradigm shift in the deposition of metals for microelectronic applications. Reversing the process currently used for selectively removing impurities from metal bearing waste streams, electrochemically controlled deposition of metals from electrically non-conducting organic solutions on submicron feature sizes is possible. A description of the fundamental electrochemical processes involved and parameter space available to engineer the solution chemistry will be presented along with experimental results from model systems. A discussion of the technology in light of ULSI issues and applications will be included.
Conducting Thin Films of Ruthenium Oxide Prepared by Mocvd
Authors: Hones P. , Kohli C.-H. , Sanjinés R. , Lévy F. , Gerfin T. , Grätzel M.
Published: April 2011

Conducting thin films of RuO2 were grown at temperatures down to 623K on glass by metalorganic chemical vapor deposition (MOCVD). Tris-trifluoroacetylacetonate-ruthenium(III) (Ru(tfa)3) served as precursor. Smooth, specular and well adherent films were deposited, if the reaction gas contained water. The films were investigated by X-ray diffraction, SEM, and fourprobe resistivity measurement. Growth kinetics were also studied by in situ ellipsometry. The results are compared with films prepared by d.c. reactive sputtering before and after annealing. The properties of the MOCVD films, in particular the resistivity (ρ down to 72 μΩcm), are comparable to CVD films deposited at much higher temperatures and sputtered films after high temperature annealing.