bluuebunny/crossref_metadata_2025 huggingface dataset:
Low Hydrogen Content, High Quality Hydrogenated Amorphous Silicon Grown by Hot-Wire CVD
Authors: Nelson Brent P. , Crandall Richard S. , Iwaniczko Eugene , Mahan A. H. , Wang Qi , Xu Yueqin , Gao Wei
Published: April 2011

We grow hydrogenated amorphous silicon (a-Si:H) by Hot-Wire Chemical Vapor Deposition (HWCVD). Our early work with this technique has shown that we can grow a-Si:H that is different from typical a-Si:H materials. Specifically, we demonstrated the ability to grow a-Si:H of exceptional quality with very low hydrogen (H) contents (0.01 to 4 at. %). The deposition chambers in which this early work was done have two limitations: they hold only small-area substrates and they are incompatible with a load-lock. In our efforts to scale up to larger area chambers—that have load-lock compatibility—we encountered difficulty in growing high-quality films that also have a low H content. Substrate temperature has a direct effect on the H content of HWCVD grown a-Si:H. We found that making dramatic changes to the other deposition process parameters—at fixed substrate temperature and filament-to-substrate spacing—did not have much effect on the H content of the resulting films in our new chambers. However, these changes did have profound effects on film quality. We can grow high-quality a-Si:H in the new larger area chambers at 4 at. % H. For example, the lowest known stabilized defect density of a-Si:H is approximately 2 × 1016 cm-3, which we have grown in our new chamber at 18 Å/s. Making changes to our original chamber—making it more like our new reactor—did not increase the hydrogen content at a fixed substrate temperature and filament-to-substrate spacing. We continued to grow high quality films with low H content in spite of these changes. An interesting, and very useful, result of these experiments is that the orientation of the filament with respect to silane flow direction had no influence on film quality or the H content of the films. The condition of the filament is much more important to growing quality films than the geometry of the chamber due to tungsten-silicide formation on the filament.
Substrate Sensitivity of the Adhesion and Material Properties of RF-PECVD Amorphous Carbon
Authors: Paul Shashi , Clough F.J
Published: April 2011

Hydrogenated amorphous carbon (a-C:H), deposited by the if-plasma enhanced chemical vapour deposition (rf-PECVD) technique, is a promising material for large area electronic and interlayer dielectric applications. The structural and electronic properties of rf-PECVD a-C:H, deposited at room temperature from CH4/He and CH4/Ar gas mixtures, are shown to be sensitive to the substrate on which the thin film is deposited. The choice of substrate (c-Si or C7059 glass), and the existence and geometrical dimensions of any metallic pattern on the substrate surface, can result in significant spatial variations in the a-C:H adhesion and material properties. The observed effects are attributed to potential variations across the metal patterned substrates which influence the ‘local’ dc self-bias. This leads to spatial variations in the growth conditions and hence material properties. For electronic device and dielectric isolation applications this effect can result in significant variations in operating performance. The nature of the substrate and any overlying metallisation pattern are therefore important considerations.
Three and Six Channel Sensors: Realization and Colorimetric Characterization
Authors: Knippa D. , Herzog P. , Stiebig H. , Siekmann H. , König F. , Wagner H.
Published: April 2011

A novel sensor concept for detecting the fundamental components of the visible light has been developed. The multi-channel sensors based on three stacked amorphous thin film detectors are color moiré or color aliasing free due to their vertical integration. The four terminal devices enable the generation of three or six linearly independent spectral response curves at the same spatial position. The 3-channel sensor based on three stacked pin-diodes generates a red-green- blue signal with one shot, whereas the 6-channel sensor with three stacked pinip structures allows the detection of up to six linearly independent spectral response curves. The reproducibility of the complex layer sequences is enhanced by introducing a textured TCO-layer in the rear part of the device, which leads to a distinct scattering of the incoming light for longer wavelengths.

In order to gain information on how to improve the sensor performance, the sensors are characterized. The presented characterization model facilitates the quantification of color errors with regard to the human perception. Furthermore, the color errors of amorphous thin film sensors are compared with a commercial color CCD camera and a BiCMOS color-sensor.
A Study of The Viability of Poly(O-Methoxyanhine) Layer-by-Layer Films as Gas Sensors
Authors: Raposo M. , Oliveira O.N.
Published: April 2011

The electrical properties of layer-by-layer films of poly(o-methoxyaniline) (POMA) alternated with poly(vinylsulfonic acid) (PVS) have been investigated as a function of the surrounding atmosphere, in order to probe the sensitivity of POMA/PVS as a gas sensor. The POMA films have their conductivity increased with increasing humidity, near to one order of magnitude higher for 100% relative humidity when compared to nitrogen. The d.c. applied field may affect the POMA films, for these films become practically insulating if the field is applied for a prolonged time (typically 10-20 h) in humid air. In order to circumvent this problem, a.c. impedance measurements were conducted. For samples in nitrogen, oxygen and carbon dioxide, the real part of the complex impedance increases only when the frequency is lowered below 10 kHz. In a humid atmosphere, the onset for the real part occurs at higher frequencies than for dry atmospheres. Furthermore, at a fixed frequency in the range from 10 to 100 kHz this impedance component increases with the relative humidity.
Supramolecular Assembly Strategies Using Alternate Adsorption of Polyelectrolytes: Applications in Pled And Lc Display Devices
Authors: Advincula R. C. , Inaoka S. , Roitman D. , Franka C. , Knoll W. , Baba A. , Kaneko F.
Published: April 2011

We present work on the modification, processing, and analysis of ultrathin films for display devices primarily using the supramolecular assembly strategy. This involves the use of various molecular assembly techniques (organic, polymer, metal) in which layer order and functionality is achieved at defined length scales approaching that of ultrathin films (a few to several hundred nm thicknesses). The use of alternate polyelectrolyte deposition (APD) is primarily investigated in ultrathin films that have significance in the fabrication of display devices. The first application involves modifying a polymer light emitting diode (PLED) device fabricated using the ITO/MEH-PPV/Ca protocol with polyaniline derivatives. The second is the use of the “command layer” amplification concept and photo-induced alignment using polarized light with ultrathin films of azo dye/polyelectrolytes in a hybrid liquid crystal (LC) cell configuration. Both strategies rely on the use of surface sensitive spectroscopic and microscopic techniques to correlate device performance with layer ordering at the molecular level. The concept of functional ultrathin layers for device fabrication and modification is emphasized.
Doped Organic Light-Emitting Diodes Based on Random Copolymers Containing Both Hole and Electron Transport Groups
Authors: Jiang Xuezhong , Register Richard A. , Pschenitzka Florian , Sturm James C. , Killeen Kelly A. , Thompson Mark E.
Published: April 2011

Doped organic light-emitting diodes (OLEDs), such as PVK containing the electron transport molecule PBD and molecular dyes, have demonstrated three-color capabilities and efficiencies over 1%, but there are concerns about reliability due to recrystallization of the small molecule PBD. In this work we describe the incorporation of both hole and electron transport groups into a single copolymer to avoid recrystallization and phase segregation (which could occur if two separate polymers were used) as well as the application of such copolymers in dye-doped OLEDs. The polymers were synthesized through free radical copolymerization of the electron- donating monomer N-vinylcarbazole (NVK) with the electron-withdrawing monomer 2-(4-tert-butylphenyl)-5-{4-[(4'-vinyl)phenylmethoxy] phenyl}-1,3,4- oxadiazole (BVO). The radical reactivity ratios of the two monomers were estimated to be rNVK=0.052 and rBvo=12. The copolymers are transparent in the visible region, homogeneous as characterized by both GPC and DSC, and have good thermal stability. External quantum efficiencies of 0.07%, 0.3% and 0.4% were achieved in LEDs with device structures of ITO/COP:C47/Mg:Ag, ITO/COP:C6/Mg:Ag and ITO/COP:NR/Mg:Ag, respectively, where COP stands for copolymer, C47 for Coumarin 47, C6 for Coumarin 6 and NR for Nile Red. The introduction of the oxadiazole group balances the injection of holes and electrons by decreasing the hole injection and transport ability and enhancing the electron injection and transport ability of the copolymers relative to PVK.
Three-Color Doping of Polymer Oleds by Masked Dye Diffusion
Authors: Pschenitzka F. , Sturm J. C.
Published: April 2011

A method to locally pattern the distribution of dye by diffusion into the polymer film of organic light-emitting diodes is introduced. Using a large-area diffusion source, the diffusion of dye into the polymer film can be controlled with a shadow mask. The materials used are the polymer poly(9-vinylcarbazole) (PVK) combined with electron transport molecules (PBD), and the dyes bimane, coumarin 6 and Nile red. The temperature dependence of the diffusion is investigated along with the effect of annealing of the polymer film. A model of the dye distribution is introduced and estimations of the dye profile based on this model and PL measurement are discussed. A 3-color integrated device was demonstrated.
Some «Exotic» Aspects of Physics With Microtips
Authors: Baptist R.
Published: April 2011

This paper focuses on some experiments done using field emitter arrays (FEAs) produced at CEA-LETI, experiments which are outside of the display or microwave amplifier contexts. Among various studies done at CEA-LETI with FEAs we have selected:

- the search towards a spin polarized electron source,

- a study on the spatial coherence of the electron beam emitted by a single emitter,

- the incorporation of an optical command in a FEA and finally,

- the application of a FEA to electron injection into rare gas liquids.
Towards the Realization of a INP/CDS/LAS Cold Cathode
Authors: Cahay M. , Malhotra A. , Modukuru Y. , Tang H. , Bresser W. , Boolchand P. , Mumford P. , Friz W.
Published: April 2011

In the past, we have proposed a new cold cathode emitter which consists of a thin region of CdS (Cadmium Sulfide) sandwiched between a heavily doped InP (Indium Phosphide) substrate and a low work function LaS (Lanthanum Sulfide) semimetallic thin film. In this paper, we briefly review the principle of operation of the cathode and discuss the preliminary experimental steps undertaken to realize prototypes of the device. More specifically, we describe the growth of bulk samples of LaS which is used to achieve Negative Electron Affinity of the CdS/LaS surface. X-ray diffraction and micro-Raman experiments show the successful growth of the fcc cubic phase of LaS samples.
Film Preparation Conditions and Characterization of co-Deposited Tungsten Doped Zinc Oxide Phosphor
Authors: Sobti Jasleen Bombra , Bhatia V. , Babuchna P. M. , Weichold Mark H.
Published: April 2011

Need for efficient blue light emitting source for optoelectronic device applications such as flat panel displays has made the research in luminescent material ever so important. Tungsten doped zinc oxide (ZnO:W) has been identified as a blue light emitting phosphor exhibiting cathodoluminescence near 490 nm. This paper details work done on ZnO:W phosphor preparation conditions for efficient light emission from the phosphor. Material characterization to identify the possible source of blue light emission will also be discussed.
High Temperature Annealing Behaviors of Luminescent Siox:H Films
Authors: Ma Zhixun , Xiang Xianbi , Sheng Shuran , Liao Xianbo , Shao Chunlin , Umeno Masayoshi
Published: April 2011

The effects of high temperature annealing on the microstructure and optical properties of luminescent SiOx:H films have been investigated. Micro-Raman scattering and IR absorption, in combination with atomic force microscopy (AFM), provide evidence for the existence of both a-Si clusters in the as-grown a-SiOx:H and Si nanocrystals in the 1170°C annealed films. The dependence of optical coefficients (μ) on photon energy (hv) near the absorption edge (Eg) is found to follow the square root law: (μhv)½ μ (Eg – hv), indicating that nano-Si embedded in Si02 is still an indirect material. A comparison of the deduced absorption edge with the PL spectra shows an obvious Stokes shift, suggesting that phonons should be involved in the optical transition process.
Luminescence Intermittency and Quantum Efficiency of Individual Porous Si Nanoparticles.
Authors: Mason Michael D. , Credo Grace M. , Carson Paul J. , Buratto Steven K.
Published: April 2011

We have recently observed spectrally resolved vibronic structure and luminescence intermittency from nanometer-size porous silicon nanocrystals. In this study we examine the quantum efficiency of a single nanoparticle and show that emitting nanoparticles do so with near unity quantum efficiency. This result suggests that the emission from porous Si nanoparticles, and thus bulk porous Si, results from a small number of high quantum efficiency emitters. In our previous work we have shown that our nanoparticles contain more than one coupled chromophore. In order to examine these effects more closely we employ several spectroscopy and microscopy techniques including: 1) single-particle spectroscopy, 2) shear-force microscopy, and 3) time-resolved spectroscopy, on a colloidal suspension of size-selected, surface-oxidized nanoparticles. In addition we apply statistical techniques to provide a more complete picture of the coupling between chromophores in a given nanoparticle.
Electron Paramagnetic Resonance of Cr4+ in Yx2SiO5
Authors: Rakhimov Rakhim R. , Horton Holli D. , Loutts George B.
Published: April 2011

Chromium-doped yttrium orthosilicate Cr:Y2SiO5 was studied by electron paramagnetic resonance (EPR) method at 9.5–9.7 GHz. EPR transitions were observed for Cr4+ substituting Si4+ in tetrahedral sites of Y2SiO5, and orientation dependence of the single crystal EPR spectrum was studied. The ground state of Cr4+ (electron configuration 3d2) in Y2SiO5 is a spin triplet (S = 1). Rhombic symmetry of the electron magnetic dipole-dipole interaction (zero field splitting) leads to three electron spin terms Tx, Ty and Tz in the absence of the external magnetic field. We have observed the magnetically induced anti-crossing of the terms Ty and Tz.We show that in the vicinity of energy level anti-crossing the linewidths and positions of the resonance lines depend on temperature.
Photoluminescence of Poly(P-Phenylene Vinylene) encapsulated In Mesoporous Silica
Authors: Pattantyus-Abraham Andras G. , Wolf Michael O.
Published: April 2011

The preparation of poly(ρ-phenylene vinylene) (PPV) encapsulated in a mesoporous silica, MCM-41, is reported. In situ polymerization of xylylene bis(tetrahydrothiophenium chloride) yields a highly luminescent, yellow powder with a fluorescence spectrum matching that of unencapsulated PPV. Nitrogen adsorption isotherms show that the pore size of the PPVloaded MCM-41 is significantly smaller than that of empty MCM-41 and a polymer loading of ca. 8% by weight is obtained by thermogravimetric analysis. Photoluminescence data for the encapsulated PPV are presented.
Optimization of Cerium Doped Garnets Using Combinatorial Chemistry for Application as Luminescent Conversion Phosphors in White LEDs
Authors: Wu Jennifer L. , Devenney Martin , Danielson Earl , Poojary Damadora , Weinberg Henry
Published: April 2011

An area of considerable research interest is the development of visible light, down- conversion phosphors for application in white light emitting diodes (LEDs). In such devices, a blue LED can act as the primary light source, exciting photoluminescence in a phosphor with subsequent broad band emission occurring at visible wavelengths of lower energy. A combinatorial approach to synthesize and screen potential inorganic phosphors for such an application has been developed. Using solution chemistry techniques, solid state thin film arrays of (Y1−xGdx)3-z(Al1−yGay)5O12:Ce3+Z, where x and y range from 0 to 1.0 and z is equal to 0.03 were synthesized. Subsequent characterization demonstrates that the combinatorial approach can be used to rapidly screen potential phosphors for use as luminescence down-converters in white LEDs. Emission and excitation trends match those reported in the literature for traditionally prepared powder samples. The optimal Ce3+ concentration in Y3Al5O12 (YAG) was identified as approximately 1.5 mol%, and within the YAG-substituted host specific compositions were identified as promising blue to yellow phosphor candidates.
Effect of Annealing on the Properties of thin Films of Free Base Phthalocyanine and Perylene-3,4,9,10-Tetracarboxylic Dianhydride Deposited by Organic Molecular Beam Deposition
Authors: Bayliss S.M. , Heutz S. , Rumbles G. , Jones T.S.
Published: April 2011

Organic molecular beam deposition (OMBD) has been used to deposit thin films of free base phthalocyanine (H2Pc) and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA). The structural, optical and morphological properties of the films have been measured as a function of annealing temperature using x-ray diffraction (XRD), electronic absorption spectroscopy and atomic force microscopy (AFM). A phase transition, (α-β), is observed for H2Pc films which is accompanied by changes in the bulk film properties and surface morphology. In the case of PTCDA increasing temperature does not affect the structural and optical properties of the film, but different surface morphologies are observed.
The Valence Electronic Structure of N-Doped P-Sexiphenyl
Authors: Theissl U. , List E.J.W. , Koch N. , Vollmer A. , Schrader S. , Pireaux J.-J. , Leising G.
Published: April 2011

Thin films of p-sexiphenyl (6P) were doped with increasing amounts of potassium in situ, and the change in the valence electronic structure of 6P upon the alkali metal deposition was followed with ultraviolet photoelectron spectroscopy. We observe the evolution of new intragap emissions, which are attributed to the formation of bipolarons, even for very low doping concentrations. The low binding energy intra-gap emission exhibits a pronounced asymmetric lineshape, in contrast to the findings when cesium is used as dopant. In order to investigate whether this lineshape is due to different emissive electronic species in the bulk and on the surface of the 6P film the take-off angle for the photoelectrons was varied. As no change in the lineshape is found when going from normal to near-grazing emission we can exclude that charged 6P molecules in the bulk and on the surface yield different valence electronic spectra. Therefore, the characteristic lineshape of the low binding energy emission is proposed to be related to the interaction of the doped organic molecule with the different counterions.
Current-Voltage Characteristics of Single Layer Polymer Light Emitting Diodes Under High Intensity Electrical Excitation
Authors: Ruhstaller B. , Scott J.C. , Brock P.J. , Carter S.A.
Published: April 2011

We study the current-voltage characteristics of both double and single carrier polymer light emitting devices in the high intensity electrical excitation regime. Single layer devices are investigated with the orange-emitting MEH-PPV as the active polymer. Performing very low duty (≈0.001 %) pulsed electroluminescence measurements with electric fields up to 1*109 V/m, we observe for the hole-dominated devices a space charge limited current with a saturating mobility and a saturating external quantum efficiency of 1%. For double carrier devices, the current starts to saturate in the high-field regime, appoaching Ohmic-like behavior. We report current densities of 100 A/cm2and brightnesses of 7*105 cd/m2. The spectral features are monitored below the onset of degradation.
Electromigration Testing of via Terminated Test Structures
Authors: Low Kia Seng , Poetzlberger Hans
Published: April 2011

In this paper we describe three phenomena that have been observed in via terminated test structures. The first is the effect of stress voiding on the electromigration current density exponent, n. We have tested stress-voided lines and the results show that the current density exponent is close to 1. This is consistent with the prediction that stress-voided lines have a lower lifetime. We propose that the current density exponent must be measured and not assumed for such lines. The second phenomenon is the reservoir effect in via-terminated lines. Void locations following electromigration stressing are shown for a via-terminated structure containing a reservoir, prepared by Focused Ion Beam (FIB), and a discussion of the reservoir effect is presented. Finally, we report on the correlation between void location and the bimodal distribution of failure mechanisms that have been observed.
Strain and Texture in Al-Interconnect Wires Weasured by X-Xay Microbeam Diffraction
Authors: Tamura Nobumichi , Chung J.-S. , Ice G. E. , Larson B. C. , Budai J. D. , Tischler J. Z. , Yoon M.
Published: April 2011

The local strain and texture in Al interconnect wires have been investigated using white and monochromatic x-ray microbeams on the MHATTCAT undulator beam line at the Advanced Photon Source. Intergrain and intragrain orientations were obtained with ∼0.01° sensitivity using white beam measurements on wide Al pads (∼100 μm) and thin (2 μm) Al wires. Orientation changes of up to 1°were found within individual grains of the (111) textured Al interconnects. Deviatoric strain measurements indicate small intragranular strain variations, but intergranular strain variations were found to be quite large.
Mechanical Stresses in Aluminum and Copper Interconnect Lines for 0.18µm Logic Technologies
Authors: Besser Paul R. , Joo Young-Chang , Winter Delrose , Ngo Minh Van , Ortega Richard
Published: April 2011

The mechanical stress state of conventional Al and damascene Cu lines of a 0.18 pm logic technology flow have been determined using a novel X-Ray diffraction method that permits measurement of stress on an array of critical-dimension lines on the product die. The effect of high density plasma oxide deposition and the influence of low-K dielectrics on the stress state of the Al lines is described. The effect of materials properties and fabrication methodology on the stress state of damascene Cu lines is shown with measurement of mechanical stress and strain in passivated lines at room temperature and during annealing. The effect of underlayer on the damascene Cu stress state is also quantified.
Diffusion Barrier Characteristics of Zirconium Diboride Films Grown by Remote Plasma CVD
Authors: Sung J. , Goedde D. M. , Girolami G. S. , Abelson J. R.
Published: April 2011

Low resistivity and fully conformal ZrB2 thin films are deposited by remote plasma chemical vapor deposition using zirconium tetrahydroborate, Zr(BH4)4. The problems with thermal CVD using this precursor – excess B incorporation, oxygen contamination, and high resistivity – are eliminated by injecting atomic hydrogen from a remote microwave plasma source onto the substrate. Using this technique, the films are stoichiometric, have ∼ 40 μΩ-cm resistivity, < 4 at.% oxygen contamination, and are fully conformal in deep trenches and vias. We show that a 50 nm thick ZrB2 film on c-Si (100) prevents Cu in-diffusion after 1 hour annealing at 650°C.
Homogeneous Ultrathin Diffusion Barriers Deposited on Low Dielectric Constant Polymers
Authors: Kiene M. , Abramowitz P. P. , Ho P. S.
Published: April 2011

TiN and TaN thin films are proposed as barrier layers between copper interconnects and low dielectric constant (low-k) polymers. As the barrier layer thickness is scaled down, the uniformity and morphology of these films will be severely affected by the nitride-polymer interface and become an important issue for the reliability of the whole interconnect structure. In order to evaluate nitride formation and the interfacial chemistry we deposited TiN and TaN on fully cured low-k polymers by two different techniques: reactive evaporation of the metal in nitrogen ambient and by ion assisted reactive deposition using a low energy (100 eV) nitrogen ion beam during evaporation. Photoelectron spectra were recorded in situ for metal coverages from 0.1 nm until bulk like metal or metal nitride spectra were obtained. Nitride concentrations, extracted from the photoelectron spectra, show that even though very similar nitride films are produced by both techniques for thicker films (>5 nm) we only find significant amounts of nitride at the interface in the ion assisted case. Thinner films formed in nitrogen ambient were very similar to those where the pure metal was deposited and were dominated by the formation of compounds with carbon and oxygen from the polymer. This shows that the composition of barrier layers can be drastically altered near the polymer interface. Low energy ions in contrast allow the growth of more homogeneous films which can significantly improve the reliability of copper based high density interconnects.
Epitaxial Growth and Thermal Stability of CoSi2 Layer on (100) Si from Co-C Films without Capping Layer
Authors: Rhee Hwa Sung , Sohn Dong Kyun , Ahn Byung Tae
Published: April 2011

A uniform epitaxial CoSi2 layer was grown on (100) Si substrate by rapid thermal annealing at 800°C in N2 ambient without capping layers from an amorphous cobalt-carbon film. The amorphous cobalt-carbon film was deposited on Si substrate by the pyrolysis of cyclopentadienyl dicarbonyl cobalt. Co(η5-C5H5)(CO)2. at 350°C. The leakage current measured on the junction, fabricated with the epitaxial CoSi2 layer and annealed at 1000°C for 30 s. was as low as that of the as-fabricated junction without silicide. indicating that epitaxial (100) CoSi2 is thermally stable at temperatures even above 1000°C and has a potential applicability to the salicide process in sub-half micron devices.
Influence of SiGe Thickness on the Co/SiGe/Si Solid State Reaction
Authors: Donaton R. A. , Jin S. , Bender H. , Maex K. , Vantomme A. , Langouche G.
Published: April 2011

The effect of the thickness of the SiGe layers in the Co-SiGe/Si reaction is investigated. Formation of the disilicide phase is retarded when compared to the reaction of Co with pure Si substrates. This delay is dependent on the thickness of the SiGe layer, which determines the effective Ge concentration at the reaction front, changing the energetics of the reaction. Besides, Ge expelled from the Co(Si1-yGey) compound blocks the Co diffusion paths, slowing down the reaction. The thermal stability of the silicide layer is also affected by the Ge segregation, with the film agglomerating at lower temperatures when formed on thicker SiGe layers. The slow supply of Co atoms to the reaction front, due to the blocking of Co diffusion paths by the segregated Ge, is believed to be the reason for the presence of the preferential (h00) orientation of the disilicide phase observed in our samples.
Formation and Characterization of Spe Grown Ultra-Thin Cobalt Disilicide Film
Authors: Qu Xin-Ping , Ru Guo-Ping , Li Bing-Zong , Detavernier C. , Meirhaeghe R L. Van , Cardon F.
Published: April 2011

Ultra-thin epitaxial CoSi2 films formed by Co(3∼5nm)/Ti(1 nm)/Si(100) and Co(3∼5nm)/Si(lnm)/Ti(Inm)/Si are studied. The multilayers are deposited by ion-beam sputtering. Rapid thermal annealing (RTA) is used for silicidation. XRD, RBS, TEM, AFM, four-point probe, I-V and C-V measurements are carried out for characterization. The XRD spectra show the CoSi2 film formed by Co/Ti/Si or Co/Si/Ti/Si solid phase epitaxy has, epitaxial characteristic. XTEM shows that the film is continuous. RBS/Channeling shows that the formed CoSi2 has sharp interface with a minimum channeling yield of Co signal of 40%. AFM shows that the surface of ultra-thin CoSi2 film is smooth with a roughness of nearly 0.7 nm. The Rs∼T relationship shows that the CoSi2 films formed by Co/Si/Ti/Si reaction have the best thermal stability (stable up to 900°C). Those formed by Co/Ti/Si reaction are stable up to 850°C, while those formed by Co/Si reaction are only stable up to 750°C. By fitting the experimental I-V and C-V curves of the epitaxial CoSi2/Si Schottky diodes, barrier heights of around 0.6 eV and close to unity ideality factors are obtained.
Formation and Stability of NI(PT) Silicide on (100)SI and (111)SI
Authors: Mangelinck D. , Dai J. Y. , Lahiri S. K. , Ho C. S. , Osipowicz T.
Published: April 2011

The effect of a small amount of Pt (5 at.%) on the thermal stability of NiSi film on (100)Si and (111 )Si has been investigated. Rutherford back scattering, Scanning Electron Microscopy, and X-ray diffraction have been used to study the formation, microstructure and orientation of the silicide. The addition of platinum results in increasing the disilicide nucleation temperature to 900°C and thus leads to a better stability of NiSi at high IC processing temperatures. The presence of Pt also induced a texture of the NiSi film both on (11 1)Si and (100)Si. The increase in thermal stability is explained in terms of nucleation controlled reaction concept and should open new possibilities for the use of NiSi in self aligned silicidation. The redistribution of Pt in the silicide is examined and explained in terms of kinetics and thermodynamics considerations. The addition of Pt also increases the temperature of agglomeration of NiSi.
New Contact Etch Process for Embedded DRAM Applications
Authors: Yang Chan-Lon , Chen Tong-Yu , Huang Keh-Ching , Jung Le-Tien , Lin Tsu-An , Lur Water
Published: April 2011

For embedded DRAM (E-DRAM) devices with feature sizes of 0.25 µm and beyond, contact processes with low contact resistance and low junction leakage current are required. The contact etch process needs to etch through multi-layer structures with SiO2, SiON/SiN layers and stop on Ti-polycide gate and Ti-salicide active regions at the same time. The key issues include high selectivity to TiSix, vertical profile, complete removal of SiON/SiN cap layer and no polymer residues. In this paper, multi-layer contact etching without attacking TiSix is reported. Using new process chemistry, the new contact etch process has been demonstrated for the manufacturing of 0.25 µm E-DRAM and beyond.
Chemical Vapor Deposition of Ti-Si-N Films with Alternating Source Supply
Authors: Min Jae-Sik , Park Hyung-Sang , Koh Wonyong , Kang Sang-Won
Published: April 2011

Titanium-silicon-nitride films were grown by atomic layer deposition using an alternating supply of tetrakis(dimethylamido)titanium (TDMAT), silane. and ammonia, at substrate temperature of 180°C. The supply of a reactant was followed by a purge with inert gas before introducing another reactant onto the substrate in order to prevent gas-phase reactions. In one set of experiments the reactants were supplied separately in the sequence of TDMAT. silane. and ammonia. The Si content of the films remained constant at 18 at.%. and the film growth rate varied little from 0.24 nm per reactant-supply-cycle, even though silane partial pressure varied from 0.002 to 0.1 torr. In the other set of experiments silane and ammonia were simultaneously supplied in the sequence of TDMAT and silane/ammonia. The Si content varied from 3 to 23 at.% as the silane-to-ammonia ratio varied from 0.01 to 10. Atomic layer deposition of Ti-Si-N films allows the precise control of Si content as well as film thickness.
Integration of PECVD Tungsten Nitride as a Barrier Layer for Copper Metallization
Authors: Ivanova A. R. , Galewski C. J. , Sans C. A. , Seidel T. E. , Grunow S. , Kumar K. , Kaloyeros A. E.
Published: April 2011

Amorphous tungsten nitride (WNx) is a promising diffusion barrier for extending Cu metallization beyond 0.18 μm. This study evaluates the barrier performance, adhesion, and step coverage of PECVD WN 0.5 integrated with a CVD Cu seed layer. The WN0.5 films exhibit amorphous structure with 33% bottom and side-wall step coverage in 0.14 μm wide structures with 9:1 aspect ratio. The potential of 50 Å WN0.5 as an effective Cu barrier is shown by the absence of Secco etch-pits in the Si substrate after a 30 min anneal at 500°C. When deposited on PECVD WN0.5 the CVD Cu films exhibit uniform nucleation, and as deposited resistivity of 2.5 μΩ-cm. Step coverage of the CVD Cu is better than 95% in 0.14 μm structures. Adhesion exceeding epoxy strength of the CVD Cu seed layer even to air-exposed WN0.5 is demonstrated using stud-pull adhesion tests.
Highly Conformal Diffusion Barriers of Amorphous Niobium Nitride
Authors: Gordon R. G. , Liu X. , Broomhall-Dillard R. N. R. , Shi Y.
Published: April 2011

Electrically conductive films of niobium nitride were formed by chemical vapor deposition from tetrakis(diethylamido)niobium and ammonia. The films were found to be highly conformal, with step coverage nearly 100% for substrate temperatures near 350°C. The structure of the films was amorphous by diffraction of X-rays and electrons. The reliability of the films as barriers to diffusion of copper was also tested.
Characterization of Plated Cu Thin Film Microstructures
Authors: Gignac L. M. , Rodbel K. P. , Cabral C. , Andricacos P. C. , Rice P. M. , Beyers R. B. , Locke P. S. , Klepeis S. J.
Published: April 2011

Electroplated Cu was found to have a fine as-plated microstructure, 0.05 ± 0.03 μm, with multiple grains through the film thickness and evidence of twins and dislocations within grains. Over time at room temperature, the grains grew to greater than 1 μm in size. Studied as a function of annealing temperature, the recrystallized grains were shown to be 1.6 ± 1.0 μm in size, columnar and highly twinned. The grain growth was directly related to the time dependent decrease in sheet resistance. The initial grain structure was characterized using scanning transmission electron microscopy (STEM) from a cross-section sample prepared by a novel focused ion beam (FIB) and lift-out technique. The recrystallized grain structures were imaged using FIB secondary electron imaging. From these micrographs, the grain boundary structures were traced, and an image analysis program was used to measure the grain areas. A Gaussian fit of the log-normal distribution of grain areas was used to calculate the mean area and standard deviation. These values were converted to grain size diameters by assuming a circular grain geometry.
Electroplated Damascene Copper: Process Influences on Recrystallization and Texture
Authors: Gross M. E. , Drese R. , Lingk C. , Brown W. L. , Evans-Lutterodt K. , Barr D. , Golovin D. , Ritzdorf T. , Turner J. , Graham L.
Published: April 2011

Electroplated Cu films undergo a remarkable recrystallization at room temperature that has been associated with dislocations and defects arising from the influence of surface-active additives during plating. In the process of plating, the composition of the bath changes as the organic additives are depleted by incorporation into the Cu films or electrolytic decomposition and replenished by fresh additions. Given the sensitivity of the plating process to low concentrations of additives, the properties of the plated Cu might be expected to differ between a freshly prepared bath and an older bath that has processed thousands of wafers and achieved a steady state composition of additives and by-products.

In this paper we compare the recrystallization rates of Cu films deposited from two such baths on wafers with damascene trenches of widths from 0.3 to 5 μm. Films deposited from the older bath consistently recrystallize at a faster rate for all trench widths and both barrier materials (Ta, TaN) studied. The concentration of impurities is comparable in the two films. Therefore, the difference in rates is likely due to a difference in defect densities in the film due to different adsorbate/surface interactions during plating. Although the recrystallization rates vary, X-ray diffraction pole figure analysis of films plated from the two baths show no differences in texture. Sidewall growth components are visible in both sets of samples. Data on the influence of the barrier material and trench width on recrystallization rates are also presented.
Influence of Cu Seed Deposition Temperature on Electroplated Cu Texture Formation in Damascene Structures
Authors: Jiang Qing-Tang , Mikkola Robert , Ortega Richard , Blaschke Volker
Published: April 2011

The deposition temperature of the PVD Cu seed layer has a critical impact on the subsequent electroplated Cu film. Sheet resistance transformation of electroplated Cu on 50°C seeded Cu was more than twice faster than on 150°C seeded Cu. X-ray pole figure analysis on a 3 mm × 3 mm dense array of 0.35 μm Cu damascene lines at spacing of 0.4 μm revealed significant grain orientation differences between directions parallel and perpendicular to the Cu lines. It was observed that for both seed process temperatures, the (II I) pole figures showed a sharper texture parallel to the trench direction than to the perpendicular direction. After annealing at 450°C for 30 minutes, a (511) secondary orientation emerged and the (111) texture along the trench direction became even sharper. Perpendicular to the trench, the (111) texture split into two peaks after anneal, exhibiting near fiber texture. The deviation of the two splits from normal was 2.40 tilt towards the trench wall indicating strong interaction between trench sidewall and electrodeposited Cu inside the trench. The (111) pole figure analysis also revealed a 20% contribution of Cu growth directly from the side walls. Although the pole figure pattern of 150°C seeded sample resembles that of the 50°C seeded sample, the (111) fiber texture of a 50°C seeded sample was always stronger and sharper.
Cu concentration dependence of the mechanical behaviour of Al-Cu alloys
Authors: Lokker J. P. , van Winden R. S. A. , Janssen A. M. , Radelaar S.
Published: April 2011

This paper reports on the influence of the copper concentration on the mechanical behaviour during thermal cycling and during isothermal holds of Al-Cu thin films on Si substrates. The Cu concentration has been varied in the range between 0 to 1 at.%

Upon heating, the films with the larger amount of Cu showed a clear maximum in compressive stress. Moreover, during cooling these samples show a tensile stress increase at the onset precipitation temperature. Further cooling below 200 °C leads to the characteristic tensile stress increase often observed for Al-Cu thin films. An isothermal hold during cooling at 250 °C leads to temporary strengthening of all Al-Cu. The extent of the strengthening is dependent on the Cu concentration and is clearly dependent on the duration of the isothermal hold. Upon further cooling the strengthening disappears and the stress develops according to the original stress temperature dependence. The observations are discussed in terms of solid solution hardening and precipitation hardening.
Integration Issues for Low Dielectric Constant Materials in each Generation of ULSI's
Authors: Gomi Hideki , Kishimoto Koji , Usami Tatsuya , Koyanagi Ken-ichi , Yokoyama Takashi , Oda Noriaki , Matsubara Yoshihisa
Published: April 2011

The technologies utilizing Fluorinated Silicon Oxide (FSG, k=3.6) and Hydrogen Silsesquioxane (HSQ, k=3.0) have been established for 0.25-µm and 0.1 8-µm generation ULSIs. However, low-k materials for the next generation ULSIs, which have a dielectric constant of less than 3.0, have not become mature yet. In this paper, we review process integration issues in applying FSG and HSQ, and describe integration results and device performance using Fluorinated Amorphous Carbon (a-C:F, k=2.5) as one of the promising low-k materials for the next generation ULSIs.
Low Resistance Copper Via Technology
Authors: Ueno K. , Donnelly V. M. , Tsuchiya Y. , Aoki H.
Published: April 2011

In order to reduce specific contact resistance at via/interconnect interface and to avoid device degradation with Cu diffusion into dielectrics, via cleaning technology is a critical issue for a scaled down Cu multilevel metallization. Effects of cleaning processes are investigated for CHF3 plasma-etched SiO2/SiN/Cu via-structures. Effects of dilute HF (DHF) cleaning, hydrogen plasma cleaning, oxygen plasma cleaning, hexafluoroacetylacetone (H(hfac)) vapor cleaning, and vacuum anneal cleaning are investigated using an angle-resolved x-ray photoelectron spectroscopy (XPS). Cu contamination removal using dilute oxalic acid (DOA) is investigated using total reflection xray fluorescence analysis (TRXRF). Based on the results, we developed an optimized cleaning sequence which consists of a brief oxygen plasma exposure, DHF dipping, followed by exposure to H(hfac) vapors. The cleaning sequence is effective in obtaining a clean dielectric surface and an oxide-free Cu surface at via bottom. Direct-contacted via structures were fabricated by a dualdamascene process using the cleaning sequence. The specific contact resistance reduces to 20% of the reported values. We expect that the via resistance is low enough to be used in 0.13 µm generation and beyond.
Evaluation of Copper Penetration in Low-κ Polymer Dielectrics by Bias-Temperature Stress
Authors: Loke Alvin L. S. , Wong S. Simon , Talwalkar Niranjan A. , Wetzel Jeffrey T. , Townsend Paul H. , Tanabe Tsuneaki , Vrtis Raymond N. , Zussman Melvin P. , Kumar Devendra
Published: April 2011

The industry is strongly interested in integrating low–κ dielectrics with Damascene copper. Otherwise, with conventional materials, interconnects cannot continue to scale without limiting circuit performance. Integration of copper wiring with silicon dioxide (oxide) requires barrier encapsulation since copper drifts readily in oxide. An important aspect of integrating copper wiring with low-K dielectrics is the drift behavior of copper ions in these dielectrics, which will directly impact the barrier requirements and hence integration complexity.

This work evaluates and compares the copper drift properties in six low-κ organic polymer dielectrics: parylene-F; benzocyclobutene; fluorinated polyimide; an aromatic hydrocarbon; and two varieties of poly(arylene ether). Copper/oxide/polymer/oxide/silicon capacitors are subjected to bias-temperature stress to accelerate penetration of copper from the gate electrode into the polymer. The oxide-sandwiched dielectric stack is used to overcome interface instabilities occurring when a low-κ dielectric is in direct contact with either the gate metal or silicon substrate. The copper drift rates in the various polymers are estimated by electrical techniques, including capacitance- voltage, current-voltage, and current-time measurements. Results correlate well with timeto- breakdown obtained by stressing the capacitor dielectrics. Our study shows that copper ions drift readily into fluorinated polyimide and poly(arylene ether), more slowly into parylene-F, and even more slowly into benzocyclobutene. A qualitative comparison of the chemical structures of the polymers suggests that copper drift in these polymers may possibly be retarded by increased crosslinking and enhanced by polarity in the polymer.
Reduction of The Phase Transition Temperature of TiSi2 on Si(111) Using a Ta Interlayer
Authors: Jung Bokhee , Kim Young Do , Yang Woochul , Nemanich R. J. , Jeon Hyeongtag
Published: April 2011

The effect of a thin Ta interlayer on the C49 to C54 phase transition of TiSi2 on Si(111) was examined. The Ta interlayered samples were prepared by depositing Ta and Ti films sequentially on Si(111) substrates in a UHV system. As control samples, 100Å Ti films were deposited directly on clean Si(111) substrates. The deposited substrates were annealed for 10 min, in-situ, at temperatures between 500°C and 750°C using 50°C increments. The TiSi2, which formed in this UHV process, was analyzed with XRD, AES, SEM, TEM, and four-point probe measurements. The control samples exhibited the C49 to C54 transition at a temperature of 750°C. However, the TiSi2 samples with 5Å and 10Å Ta interlayers displayed a significant reduction of the phase transition temperature. The XRD analysis indicated that the C49 to C54 transition temperature of TiSi2 was lowered by ∼200°C. The sheet resistance measurement showed a low resistivity characteristic of C54. The SEM and TEM micrographs showed that the Ta interlayer also suppressed the surface agglomeration of the C54 TiSi2 film. The AES analysis data indicated that the composition of the titanium silicide showed the expected Ti:Si stoichiometry of 1:2.
Comparative Study on Lateral Silicide Growth in Self-Aligned Ti and Co Silicidation: Interaction and Reactivity with SiO2 and Si3N4
Authors: Park Ji-Soo , Sohn Dong Kyun , Bae Jong-Uk , Huh Yun-Jun , Park Jin Won
Published: April 2011

The interaction and reactivity of Ti and Co with SiO2 and Si3N4 have been investigated. In the case of Ti salicide, SiO2 sidewall spacer showed no lateral silicide overgrowth and low leakage current between gate and source/drain up to silicidation temperature of 750 1C. However, Si3N4 sidewall spacer showed dopant dependence of the lateral silicide growth and leakage current. This discrepancy between SiO2 and Si3N4 and dopant dependence is closely related to the reactivity. For Co, lateral silicide overgrowth is greatly reduced. Instead, Co films on SiO2 and Si3N4 layer were agglomerated by annealing. An annealing at 1050°C caused not only agglomeration of Co film but penetration of Co agglomerates through the layers. Interestingly, the CoSi2 spike of B type epitaxial and twinned orientation was formed in the Si substrate by the penetrated Co source.
Characterization of Thin Dielectric Films as Copper Diffusion Barriers Using Triangular Voltage Sweep
Authors: Cohen S. A. , Liu J. , Gignac L. , Ivers T. , Armbrust D. , Rodbell K. P. , Gates S. M.
Published: April 2011

As technology progresses, the need for thinner Cu diffusion barrier caps is becoming more important, and it is advantageous if these barriers have low dielectric constants (κ). Towards this end, we characterized Cu penetration in several thin (35 nm to 70 nm) dielectrics, including silicon nitrides, silicon oxynitrides, an amorphous hydrogenated carbon film, and a methyl silsesquioxane layer. Metal Insulator Silicon (MIS) structures were used as the test vehicle. The barrier dielectrics were deposited on 100 nm thermal oxide which was grown on 2 Ω-cm, n-type Si wafers. After the deposition of 50 nm TEOS capping layers, both Al and Cu dots were evaporated on each wafer through a mask. Both Al and Cu dot samples were stressed at +2.7 MV/cm at 300°C for 10 minutes. For Cu dots, the applied stress pushed Cu ions into the dielectric stack. Stressing Al dots characterized the effects of the stress on the dielectric stacks and the quantity of Na ions in the films. Since C-V shifts are subject to stress-related instabilities in the interfaces as well as within the dielectrics themselves, triangular voltage sweep (TVS) was used after the applied stress to measure the concentration of Cu which reached the underlying thermal oxide film. The sensitivity of the TVS test with the structures used is about 5×109/cm2. Secondary ion mass spectroscopy (SIMS) analyses were performed on some of these samples to verify the electrical results.