bluuebunny/crossref_metadata_2025 huggingface dataset:
Silicon (Oxy)Nitride Thin Films Deposited by Lpcvd From SiCl2H2-NH3-N2O Mixtures Of Variable Composition
Authors: Davazoglou D. , Iliadis A. A.
Published: April 2011

Silicon (oxy)nitride thin films were deposited on (100) 4″ silicon substrates in a conventional LPCVD reactor at 812°C and 230 mTorr, using mixtures of SiCl2H2 -NH3-N2O of variable composition in order to evaluate their optical properties for potential applications in SOI based Si technology. The depositions were carried out keeping the flow of SiCl2H2 and NH3 constant at 20 and 60 sccm respectively while that of N2O was varying between 0 and 180 sccm. Optical reflection measurements within the range 190 to 860 nm, performed on our films were analyzed within the Forouhi-Bloomer model (Phys. Rev. B34, 7018 (1986)) for amorphous semiconductors. From the analysis of the optical spectra, the constants of the model were derived. It was shown that the refractive index of the films varies between the limits set by those of silicon nitride and silicon dioxide, the increase of the N2O flow implying a decrease of the refractive index of the films. The film thicknesses were also derived from the analysis of the optical spectra. Capacitance - voltage measurements made on Metal-Insulator-Semiconductor (MIS) structures using our films as the insulator, have shown that, the electric charge density within the dielectric initially increases and then decreases with increasing the amount of oxygen into the deposition ambiance. Our films are suitable for optoelectronic applications in SOI structures compatible with C-MOS technology.
Strain Effects in InP Dots in between Barriers of GaInP
Authors: Pistol Mats-Erik , Anand Srinivasan , Carlsson Niclas , Hessman Dan , Landin Lars , Persson Christer , Samuelson Lars , Seifert Werner
Published: April 2011

We have investigated the photoluminescence emission energy of InP dots as a function of cap layer thickness. We find a strong blue-shift with increasing cap layer thickness. The strain tensor in the dot as well as in the surrounding matrix has been modelled using finite element methods and the band-gap has been calculated using deformation potential theory. We find good agreement between calculation and experiment. For uncapped dots we find that the emission energy is lower than for biaxially strained InP, and is indeed close to unstrained InP.
Molecular Beam Epitaxial Growth of ZnSe, ZnSSe and ZnMnSSe Layers on GaAs Substrates for Blue-Green Laser Structures
Authors: Chen Y. P. , Saginur M. , Kim C. C. , Sivananthan S. , Smith D. J. , Tsen S.-C.Y.
Published: April 2011

Single layers of ZnSe, ZnSxSe1−x., and Znl−y.MnySxSe1−x., were grown on the GaAs(001). Realtime reflection high energy electron diffraction was used to study the initial growth of ZnSe(001) on GaAs(001) under different conditions. Exposure of the GaAs substrate to Se flux before growth led to three-dimensional growth, whereas exposure to Zn flux led to two dimensional-growth. ZnSxSe1−x., and Znl−y.MnySxSe1−x., (energy gap less than 2.9 eV) layers with the lattice constant closely matched to that of GaAs have been grown with a good reproducibility.
Incorporation of fluorine into the n-type (AIxGayIn1−x−y)as System
Authors: Hayafuji N. , Yamamoto Y. , Fujii N. , Sonoda T. , Takamiya S.
Published: April 2011

In order to elucidate the degradation of the electrical properties of AlInAs/GaInAs high electron mobility transistors during thermal treatment due to the fluorine contamination, the material dependence of this phenomenon has been investigated in AIxGayIn1−x−y As and AlxGayIn1−x−y P systems. The thermal degradation is found to be peculiar to the material containing both of AlAs and InAs, and most serious degradation occurs when the compositional ratio of AlAs to InAs is 1:1. It is also observed that donor-fluorine bonds are formed in the thermally annealed n-type AlInAs layers. The thermal degradation is thought to be due to the fscattering effect of the donorfluorine complex.
Oxidation Resistant Dilute Copper (Boron) Alloy Films Prepared by DC-Magnetron Cosputtering
Authors: Hymes S. , Kumar K. S. , Murarka S. P. , Wang W. , Lanford W. A.
Published: April 2011

To enhance the corrosion resistance and reliability of the proposed copper interconnections in silicon integrated circuits, alloying with small amounts thermodynamically favorable elements has been pursued. In the present investigation dilute copper (boron) alloy thin films (in boron concentration range of 0-4 at % in copper) were deposited by DC magnetron co-sputtering using a high purity copper and Cu-4 at % B targets. Films were then annealed in Ar-3% H2, pure Ar, vacuum, and air ambients in the temperature range of 200–500°C. Sheet resistance, Rutherford backscattering, x-ray diffraction measurements were made to characterize the films. The residual resistivity of the as-deposited alloy films was found to be 5.3 μΩ-cm/at %. To obtain sufficiently low working resistivity, an alloy content below 0.5 at % is suggested for application as a potential “metallization material. The addition of boron, which is the common dopant in Si, to the copper films offers considerable oxidation protection. The resulting oxidation rates are considerably lower than that for pure copper films. All this will be presented and discussed.
Characteristics of Cu-Pd Films Grown by Simultaneous Chemical Vapor Deposition from Metalorganic Precursors
Authors: Bhaskaran V. , Atanasova P. , Hampden-Smith M. J. , Kodas T. T.
Published: April 2011

The strategy of adding alloying elements during the chemical vapor deposition (CVD) of copper to improve the reliability of copper films was investigated. Deposition of Cu-Pd alloy films was demonstrated using low-pressure CVD with (hexafluoroacetylacetonato)- copper(I)(vinyltrimethylsilane) [(hfac)Cu(I)vtms] and palladium(II)bis(hexafluoroacetyl- acetonate) [Pd(hfac)2] in the temperature range of 100-200 ° C in a cold-wall differential reactor. High growth rates of 100-500 nm/min and high-purity films as confirmed by Auger electron spectroscopy (AES) were obtained. As-deposited alloy films showed low resistivities (˜ 2.3 μΩcm) at palladium concentrations below 3 wt. %. A high degree of conformality was observed on sub-half-micron trenches with aspect ratios greater than 3.5:1. The co-deposition of copper and palladium resulted in significant inhibition of palladium growth as compared to the independent palladium deposition.
Plasma Assisted Chemical Vapor Deposition of Aluminum For Metallization In Ulsi
Authors: Kim Dong-Chan , Kim Young-Soung , Joo Seung-Ki
Published: April 2011

An aluminum thin film for ultra large scale integrated circuits(ULSI) metalization has been formed by PACVD using DMEAA(Dimethylethylamine alane) as a precursor. The selectivity was lost but the conformal step coverage was still maintained when the hydrogen plasma was added to conventional CVD process so that perfectly planarized metalization could be obtained.

Comparing to thermal CVD, the reflectivity as well as the resistivity could be much improved especially when the film was deposited on SiO2. The deposition rate and the resistivity of PACVD Al thin films deposited on various substrates such as Si, TiN and SiO2 were compared with those of thermal CVD Al thin films.
The Chemical Vapor Deposition of Al-Cu Films Utilizing Independent Aluminum and Copper Organometallic Sources in a Simultaneous Deposition
Authors: Healy Matthew D. , Norman John A. T. , Hochberg Arthur K.
Published: April 2011

The chemical vapor deposition (CVD) of aluminum is now gaining accceptance as a viable metallization technology for the fabrication of sub-0.5 micron interconnects. The incorporation of 0.5% copper into these aluminum films to enhance their electromogration resistance has been achieved by a number of different approaches. These techniques include the sequential CVD of the individual metals and the consecutive growth of CVD Al / PVD Cu followed by an interdiffusing thermal anneal. The potentially more elegant and streamlined solution explored in this paper is the simultaneous deposition of Al and Cu by CVD. A key requirement of this approach is the selection of copper precursors which are stable, volatile and free from oxygen and fluorine. The absence of the latter two elements is essential due to the high probablity of their extraction from the copper precursor by aluminum to form involatile aluminum oxyfluoride species. In our investigation of simultaneous Al/Cu we have utilized two well known aluminum hydride based precursors (DMAH and DMEAA) with two different copper precursors and we herein report the successful deposition of Al-Cu alloys using this approach. A discussion is presented of the dependence of the resulting Al-Cu film quality upon the choice of Al and Cu precursors used in addition to the CVD process parameters utilized for film growth.
Comparison of Cvd and Pvd Tungsten for Gigabit-Scale Dram Interconnections
Authors: Drynan John M. , Koyama Kuniaki
Published: April 2011

The characteristics of blanket CVD-W and PVD-W films with and without TiN/Ti underlayers have been investigated in terms of both materials properties such as resistance, stress, morphology, crystallinity, and composition, and prospective applications such as for DRAM bit line interconnections. The presence of a TiN underlayer has been found to induce preferential growth of dominant W (110) crystal orientation for both CVD-W and PVD-W whereas absence of TiN results in a W film of mixed W (110), (200), and (211) crystallites. Sheet resistance measurements of both blank films and conductor lines have shown that a 200nm-thick PVD-W film yields a lower resistance than a similar film with TiN underlayer and hence larger total thickness. This correspondence of W (110) intensity with resistance implies that reduction of the (110) oriented crystallites within a W film can yield lower resistances. Thus, by elimination of the TiN/Ti underlayer, monolayer PVD-W or CVD-W with a PVD-W underlayer can be effectively adapted to quarter-micron conductors for bit line interconnections and related structures in DRAM memory and other ULSI devices.
Encapsulation of Silver Via Nitridation of Ag/Ti Bilayer Structures
Authors: Zou Y. L. , Alford T. L. , Adams D. , Laursen T. , Tu K.-N. , Morton R. , Lau S. S.
Published: April 2011

Ag/Ti bilayer films deposited on silicon dioxide substrates were annealed in ammonia ambient in the temperature range of 400 - 600 °C. Rutherford backscattering spectrometry (RBS) and Auger electron spectroscopy (AES) have shown that Ti segregates to both the surface to form a TiN(O) layer and to the Ti/SiO2 interface to form a Ti-oxide/Ti-silicide bilayer. The annealed bilayer structure had minimal Ti accumulations in Ag. Resistivity values of ˜2 μΩ-cm were obtained in encapsulated Ag bilayer films, which are comparable to that of the as-deposited. X-ray analysis confirmed the absence of intermetallic phase transformation.
Improvement in Wet Etch of TiW Fusible links in AlCu/TiW/PtSi Metallization for 0.8μm BICMOS
Authors: Nagalingam Samuel , Parikh Suketu , Sharpe Steve , Anderson Larry , Ross Ron
Published: April 2011

In our 0.8μm BICMOS process flow, TiW fusible links are defined by concentrated H2O2 wet etching. Our investigation to improve uniformity, reproducibility and reliability of TiW wet etching showed that in our etch system, the flow characteristics were the most critical. There is a tradeoff between TiW residues between metal lines and the amount of undercut of the TiW fuses: longer etch times to remove residues result in more undercut. With improved flow dynamics and optimum etch time, we achieved less residue and lower undercut. Results of the pre-etch treatment which reduces lot-to-lot induction time variation were encouraging. When the AlCu/TiW/PtSi metal stack resided on a P+/N junction, we observed an enhanced etching of the TiW due to a photovoltaic effect.
On Advanced Interconnect Using Low Dielectric Constant Materials as Inter-Level Dielectrics
Authors: Zhao Bin , Wang Shi-Qing , Anderson Steven , Lam Robbie , Fiebig Marcy , Vasudev P. K. , Seidel Thomas E.
Published: April 2011

In high performance integrated circuits, low dielectric constant (low-ε) materials are required as inter-level dielectric (ILD) for on-chip interconnect to provide advantages in high speed, low dynamic power dissipation and low cross-talk noise. A variety of low dielectric constant materials, which include fluorinated silicon-oxide, porous silica and porous organic materials, chemical vapor deposited and spin-on deposited (SOD) organic materials, have been developed or are under development to fulfill this need. In this paper, we first review the need and integration architecture of low-ε materials for on-chip interconnect. Then, we discuss the consequence of using low-ε materials as ILD in advanced interconnect with emphasis on the ILD electrical characteristics and the interconnect reliability. Although the focus is on several new promising SOD low-ε materials, the developed evaluation methodology is applicable to other type low-ε materials as well.
Thermal Stability and Interaction Between SiOF and Cu Film
Authors: Mei Yu-Jane , Chang Ting-Chang , Sheu Jeng-Dong , Yeh Wen-Kuan , Pan Fu-Ming , Chang Chun-Yen
Published: April 2011

In this work, we study the thermal stability and interaction between SiOF and Cu. Blanket SiOF films with various F concentration were deposited by PE-CVD. A dielectric constant as low as 3.2 was obtained. Copper were deposited on these SiOF and a series of post-deposition anneal were performed. Dielectric constant of SiOF was measured after deposition and again after anneal. AES and SIMS depth profile are utilized to determine the interdiffusion between Cu and SiOF under different annealing conditions. Breakdown voltage and dielectric constant were determined form C-V and I-V measurement using a MIS ( Cu/ SiOF/ p-Si) diode. This results of leakage current measurement and flat band shift measurement suggest that the fluorine in the SiOF film will retard the cu diffusion.
Do Alkali Metal Anions (M−) Exist in Zeolite A?
Authors: Barker P. D. , Anderson P. A. , Dupree R. , Kitchin S. , Edwards P. P. , Woodall L. J.
Published: April 2011

Recent NMR studies by Nakayama et al. on sodium zeolite A saturated with potassium metal have implied the presence of the anionic Na− species. This, if confirmed, would represent the first observation in a zeolite and opens up a wide range of possibilities for mixed metal zeolitic systems. We report the results of a number of metal combinations, using both sodium and potassium forms of zeolite A as hosts, studied by ESR, solid state MAS-NMR and powder neutron diffraction.
Continuum and Stochastic Modeling on the Role of Gel Microstructure in Zeolite Crystallization
Authors: Tsapatsis Michael , Vlachos Dionisios G.
Published: April 2011

Continuum and stochastic mathematical models are introduced describing zeolite nucleation and crystal growth from precursor gels. Model predictions are in agreement with existing experimental results. For example, the maximum in the nucleation rate profile under constant supersaturation is observed well before substantial crystallization occurs. Moreover, simulations indicate a strong influence of the gel microstructure on apparent crystallization kinetics, as well as particle size and morphology.
Neutron Vibrational Spectroscopy of the H5O2+ Ion and Its Deuterated Analog in Phosphotungstic Acid Hexahydrate
Authors: Maliszewskyj N. C. , Udovic T. J. , Nicol J. M.
Published: April 2011

Heteropolyacid hydrates of the general form H3PM12O40. nH2O are of interest to researchers in areas such as proton conductivity and catalysis. The water molecules in these hydrated acids reside in the interstitial volume between the large Keggin anions and can, under certain conditions, complex with the acidic protons to form stable cations such as the “dioxonium” ion (H5O2+). We have used incoherent inelastic neutron scattering (IINS) measurements of dodecatungstophosphoric acid hexahydrate (H3PW12O40 · 6H2O) to obtain the vibrational density of states spectrum of H5O2+ stabilized by the PW12O403− Keggin anions. Spectra were measure for fully hydrogenated and fully deuterated ions in order to determine the relative merit of previous assignments of the normal mode vibrations.
Special Hysteresis Effects in N2-Sorption and Mercury-Porosimetry Measurements
Authors: Giesche Herbert
Published: April 2011

Model pore structures were prepared from dispersions of submicron monodispersed silica particles by a sedimentation process. Ordered dense sphere packing structures were observedwith scanning electron microscopy. Nitrogen sorption- as well as Hg-porosimetry measurements confirmed the calculated values of the pore openings in those structures. In Hgporosimetry measurements a two step extrusion curve was observed, when the pore system was only partially filled during the intrusion process. This two step curve was not observed in case the pore system was filled with mercury to more than 95% during the intrusion run. The mercury porosimetry results can be interpreted in terms of the coexistence of octahedral and tetrahedral voids (pores) in the examined sphere packing structure and their special arrangement within the structure (connectivity). Two models will be described to explain thegeneral occurrence of hysteresis in Hg-porosimetry. The actual pore geometry is shown to have a profound influence on the hysteresis shape as well as a change in the contact angle (constant within each measurement) can result in totally different hysteresis curves. Nitrogen adsorption and desorption measurements on the same powders did not reveal any fine structure within the hysteresis range.
Synthesis, Characterization, and Reactivity of Feitknechtite
Authors: Luo J. , Segal S. R. , Wang J. Y. , Tian Z. R. , Suib S. L.
Published: April 2011

The synthesis of Mg2+ doped β-MnOOH which is known as feitknechtite is reported. Feitknechtite is a layered material having the Cd12 structure. The characterization of Mg2+ doped feitknechtite was done with X-ray powder diffraction, elemental analysis, energy dispersive X-ray analysis, scanning electron microscopy, alternating current (AC) impedance, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, average oxidation state titrations of manganese, and acidity measurements. The formation of feitknechtite is related to the MnO4−/Mn2+ ratio used in the synthesis. Feitknechtite can be converted to synthetic birnessite or octahedral layer birnessite (OL-1) which is a precursor to the 6.9 Å tunnel structure material todorokite.
Si3N4 Whisker Upper Layer Formation on a SiC-Al2O3 Porous Body
Authors: Toro P. , Pérez A. , Baeza G. , Piderit G. , Rojas P.
Published: April 2011

A thin upper layer on a SiC-A12O3 porous substrate was formed by spray deposition of a Si-C composite or SiC fine powder 55.0 wt% total powder suspension. The formation of a compact layer of Si3N4 whisker or a SiC smaller pore size than the porous substrate was obtained under thermal treatment up to 1400°C for 3–4 h in a nitrogen or argon gas environment, respectively. SEM microstructure observations and a qualitative (DRX-EDAX) analysis of both sintered porous bodies were performanced to confirm the nature of both layers.
Nanochannel Glass Replica Membranes for Parallel Patterning Applications
Authors: Pearson D. H. , Tonucci R. J. , Eddy C. R.
Published: April 2011

Nanochannel glass replica membranes are thin metallic films containing patterned arrays of uniform, nanometer-scale voids whose sizes, positions, geometric patterns, and packing densities may be controlled to a high degree. These membranes have been prepared from refractory and noble metals and are well suited for use as shadow masks in a variety of substrate patterning applications. Here we describe their use in the sub-micron, parallel patterning of Si and GaAs by materials deposition and reactive-ion etching respectively.
High-Pass Optical Filters Based on Gold-Coated Nanochannel Glass Materials
Authors: Rosenberg A. , Tonucci R. J.
Published: April 2011

We have fabricated high-pass optical filters from thin nanochannel glass (NCG) wafers coated with sputtered and evaporated gold films. The near-infrared (IR) transmission spectra of these filters have a sharp cutoff at a wavelength that scales linearly with the channel diameter, as expected for hollow metallic waveguides. Cutoff wavelengths approaching 1 μm have been achieved to date using NCG materials with sub-micron channel diameters. The spectra are dominated by a strongly resonant transmission peak just above the cutoff wavelength, where the peak transmission can be as much as twice that predicted based on the geometrical open area of the NCG structure. The NCG wafers were typically less than 20 μm thick, and the Au films ranged in thickness up to 600 nm.
Effect of Preparation Parameters on the Microporous Structure of Ni/SiO2 Catalysts
Authors: Castillon F. E. , Bodganchikova N. , Fuentes S. , Avalos M.
Published: April 2011

In this work we report the synthesis of Ni/SiO2 catalysts promoted by group 2 (IIA) cations (calcium and barium) which are currently used as hydrogenation catalysts. The effect of the preparation parameters aging, base agent, and type of cation, on the surface area of catalysts is evaluated. Catalysts were prepared by precipitation of the precursor silicic acid, along with nickel nitrate and calcium and barium carbonates, with NaOH, NH4OH and Na2CO3as precipitating agents. Catalysts were characterized by diffuse reflectance spectra (DRS) and by BETsurface area measurements. Results are discussed in terms of solgel chemistry (1).
Vanadium Molecular Sieve, Vapo-5: Preparation and Electrochemical Characterization
Authors: Bedioui F. , Briot E. , Devynck J. , Balkus K. J.
Published: April 2011

The vanadium containing molecular sieve VAPO-5 was characterized by using cyclic voltammetry. The as-synthesized and calcined samples contain loosely bound VO2+ species that can be removed by immersion in the aqueous electrolyte solution. The steady-state cyclic voltammograms of VAPO-5 reveal two distinct reversible V(5+)/V(4+) processes centered at Eeq(I) = 0.11 V/SCE and Eeq(II) = −0.07 V/SCE. These processes have been proposed to arise from framework vanadium located at structurally distinct sites V-O-T (T = Al or P).
Synthesis and Surface Modification of Deagglomerated Superparamagnetic Nanoparticles
Authors: Lesniak Christoph , Schiestel Thomas , Nass Riüdiger , Schmidt Helmut
Published: April 2011

A method for the preparation of aminosilane coated, chemically stable, agglomerate-free superparamagnetic iron oxide nanoparticles (ferrites, e.g. Fe3O4 and γ-Fe2O3) has been developed. These nanocomposite particles posess core-shell structure. The well crystallized core particles are prepared by precipitation from aqueous salt solutions (primary particle size 10 nm). The surface modification of the weakly agglomerated core particles with aminosilane (e.g. γ-aminopropyl- triethoxysilane) leads to deagglomerated particles, covered by a thin polymerized aminosilane shell. A strong dependency of the particle/agglomerate size on the silane/iron oxideratio as well as on the disintegration time was found. A ratio of aminosilane to iron oxide of 0.8 (weight ratio) and a disintegration time of 72h result in overall particle sizes in the range of 10–15 nm. After surface modification, aminogroups are present on the particle surface (IEP of 9.5). The particles show superparamagnetic behaviour (saturation magnetization 68 EMU/g) and aqueous suspensions are stable against agglomeration. A desorption of the coating in aqueous suspensions (pH 3 to 11) is not observed.
Physics and Electrochemistry of Oxide Growth
Authors: Sikora Elzbieta , Macdonald Digby D.
Published: April 2011

The growth of the passive film on tungsten in phosphate buffer solution has been described in terms of the Point Defect Model (PDM). The steady-state current and passive film thickness have been measured as a function of voltage, with the film thickness being obtained from an analysis of capacitance and reflectance data. The observed data cannot be accounted for by the High Field Model (HFM) in its classical form, but can be understood in terms of the PDM. Diagnostic criteria that have been derived from the PDM were used to identify the majority charge carriers in the passive film. The Point Defect Model was employed, together with Mott- Schottky analysis to explore the crystallographic defect structures of the passive films, whereas their electronic structures have been studied using photoelectrochemical impedance spectroscopy (PEIS). The experimental results demonstrate that these structures are strongly coupled with the vacancies acting as the dopants.
Aqueous and Surface Chemistry of Calcium - Metal Hydroxides in High pH Environments
Authors: Cocke David L. , Yousuf M. , Mollah A. , Hess Thomas R. , Lin Tien-Chih
Published: April 2011

Mixed hydroxides of calcium, zinc, cadmium and lead have been recently identified in the high pH environments of hydrating cement. FTIR, XRD, SEM, and SPM have been used to characterize these systems. A chemical equilibrium model of the early hydration of a zinc-doped cement/water system, Na-K-Ca-Zn-H-SO4-OH-Zn(OH)2-Zn(OH)3-Zn(OH)4-H2O, has been developed to better understand the mechanism of the surface formation of calcium hydroxyzincate (CHZ). The model is based on Pitzer's semi-empirical method for calculation of ion-activity coefficients at high ionic strength. The Pitzer parameters for Na+-Zn2+,Na+-Zn2+- and have been evaluated, and the results successfully predict the equilibria (solubilities) of Na2SO4-ZnSO4-H2O, NaOH-Zn(OH)2-H2O and KOH-ZnO-H2O systems. The chemical model clearly demonstrates that the formation of CHZ on the calcium-silicahydrate (C-S-H) surface is critically controlled by the Ca2+ ion concentration as well as pH of the pore water system. The results of this study suggest that the growth of CHZ is preceded by surface complex formation. Sequential charge control and sequential structure development have been used to discuss the surface selectivity of these compounds and their control of cement hydration.
Design and Properties of Multilayered Ceramic Composites
Authors: Marshall D. B.
Published: April 2011

The design of multilayered ceramic composites is reviewed, with the aim of relating the properties that can be achieved to the microstructure of the composite. Limitations on some properties, such as damage tolerance and strength, are discussed. Failure mechanism maps that define some of these limits are given.
Reactive Sputter Deposition of Superhard Polycrystalline Nanolayered Coatings
Authors: Sproul William D.
Published: April 2011

Nanometer-scale multilayer nitride coatings, also known as polycrystalline nitride superlattice coatings, such as TiN/NbN or TiN/VN with hardnesses exceeding 50 GPa, are deposited by highrate reactive sputtering. The high hardness is achieved by carefully controlling several deposition parameters in an opposed cathode, unbalanced magnetron sputtering system: the target power, the reactive gas partial pressure, the substrate bias voltage and current density, and the substrate rotation speed. Target power controls the deposition rate and the thickness for each layer in conjunction with the reactive gas partial pressure at each target, which also affects the composition of each layer, and the substrate rotation speed. Split partial pressure control is necessary when each layer requires a different partial pressure to be stoichiometric. Fully dense, well-adhered coatings with the highest hardness are deposited when the negative substrate bias exceeds -130 V and the substrate ion current density is 4–5 mA cm−2. The work on polycrystalline superlattice coatings is being extended into oxide systems. Oxide coatings can now be sputter deposited using pulsed dc power, which prevents arcing on both the target and the substrate. Pulsed dc power along with partial pressure control of the reactive gas leads to significantly higher deposition rates for the oxide films compared to sputtering with conventional rf power.
Mechanics Of Interfacial Crack Propagation In Microscratching
Authors: Boer Maarten P. de , Nelson John C. , Gerberich William W.
Published: April 2011

A new probing technique has been developed to test thin film mechanical properties. In the Microwedge Scratch Test (MWST), a wedge shaped diamond indenter tip is drawn along a fine line, while simultaneously being driven into the line. We compare microwedge scratching of Zone 1 and Zone T thin film specimens of sputtered W on SiO2. Symptomatic of its poor mechanical properties, the Zone 1 film displays three separate crack systems. Because of its superior grain boundary strength, the Zone T film displayed only one of these - an interfacial crack system. Using bimaterial linear elastic fracture mechanics, governing equations are developed for propagating interfacial cracks, including expressions for strain energy release rate, bending strain, and mode mixity. Grain boundary fracture strength information may be deduced from the Zone 1 films, while adhesion may be inferred from the Zone T films.
Time Dependent Deformation During Indentation Testing
Authors: Lucas B. N. , Oliver W. C. , Pharr G. M. , Loubet J-L.
Published: April 2011

Constant loading rate/load indentation tests (1/P dP/dt) and constant rate of loading followed by constant load (CRL/Hold) indentation creep tests have been conducted on high purity electropolished indium. It is shown that for a material with a constant hardness as a function of depth, a constant (1/P dP/dt) load-time history results in a constant indentation strain rate (1/h dh/dt). The results of the two types of tests are discussed and compared to data in the literature for constant stress tensile tests. The results from the constant (1/P dP/dt) experiments appear to give the best correlation to steady-state uniaxial data.
Stress Distribution in Si Under Patterned thin Film Structures
Authors: Wong S. P. , Huang L. , Guo W. S. , Cheung W. Y. , Zhao Shounan
Published: April 2011

We have employed the infrared photoelasticity (PE) method to study the stress distribution in Si substrates under patterned thin film structures such as thermal oxide layers partially covered by metal films and oxide layers with long trench openings. It is demonstrated that a lot of information on the two dimensional stress distribution in the substrate under patterned thin film structures can be obtained from PE experiments. The capability, limitation, and further development of the PE method for semiconductor applications are discussed.
Tribology Studies of Organic Thin Films by Scanning Force Microscopy
Authors: Bar G. , Rubin S. , Parikh A. N. , Swanson B. I. , Zawodzinski T. A.
Published: April 2011

Using the micro-contact printing method we prepared patterned self-assembled monolayers (SAMs) consisting of methyl-terminated alkanethiols of different chain lengths. The samples were characterized using lateral force microscopy (LFM) and the force modulation technique (FMT). In general, higher friction is observed over the short chain regions than over the long chain regions when a low or moderate load is applied to the scanning force microscopy (SFM) tip. For such cases the high friction (short chain) regions are also “softer” as measured by FMT. At high loads, a reversal of the image contrast is observed and the short chain regions show a lower friction than the long chain regions. This image contrast is reversible upon reduction of the applied load.
Near-Plastic Threshold Indentation and the Residual Stress in Thin Films
Authors: Houston J. E. , Michalske T. A.
Published: April 2011

In recent studies, we used the Interfacial Force Microscope in a nanoindenter mode to survey the nanomechanical properties of Au films grown on various substrates. Quantitative tabulations of the indentation modulus and the maximum shear stress at the plastic threshold showed consistent values over individual samples but a wide variation from substrate to substrate. These values were compared with film properties such as the surface roughness, average grain size and interfacial adhesion and no correlation was found. However, in a subsequent analysis of the the results, we found consistencies which support the integrity of the data and point to the fact that the results are sensitive to some property of the various film/substrate combinations. In the present paper, we discuss these consistencies and show recent measurements which strongly suggest that the property that is being probed is the residual stress in the films caused by their interaction with the substrate surfaces.
An Analysis of Void Nucleation In Passivated Interconnect Lines Due to Vacancy Condensation and Interface Contamination
Authors: Gleixner R. J. , Nix W. D.
Published: April 2011

Nucleation of voids due to vacancy condensation in passivated aluminum lines is analyzed within the context of classical nucleation theory. A discussion of sources of hydrostatic tensile stress in such lines provides a reasonable upper limit of 2 GPa. The void nucleation rate is then calculated at various sites within the line. Results suggest that nucleation rates are far too low to account for observed rates of voiding. Void nucleation at a flaw at the line/passivation interface is then considered as an alternative nucleation mechanism. Such flaws may be created by contaminants introduced during fabrication of the line. In this case, nucleation is feasible at greatly reduced stresses, well within the observed values. Furthermore, a simple model of void growth indicates that a fast atomic transport path, such as a grain boundary, must intersect the void for an appreciable growth rate. These results suggest that void nucleation in aluminum interconnect lines occurs at flaws at the sidewall of the line and that stress-induced and electromigration-induced voiding can be controlled by eliminating interfacial contamination.
Relationship Between The Void and Hillock Formation and The Grain Growth in Thin Aluminum Films
Authors: Kononenko O. V. , Matveev V. N.
Published: April 2011

Void and hillock formation during annealing was studied depending on the deposition conditions. Aluminum films were deposited onto oxidized silicon substrates by the self-ion assisted technique. The bias 0 or 6 kV was applied to the substrate during deposition. The films were then annealed in vacuum for 1 hour in the temperature range from 150° to 550°C. The structure of the films was investigated by transmission electron microscopy. The void and hillock formation was studied with optical and scanning electron microscopes.

It was found that recrystallization and void and hillock formation in the films depend on the bias during deposition. Normal grain growth occurred in the films deposited without bias. Abnormal grain growth was observed in the 6 kV-films. It was also found that the mechanism of stress relaxation during thermal cycling depends on the self-ion bombardment. In the films prepared without bias, stress relaxation proceeds by diffusion creep. In the films deposited at the 6 kV bias, stress relaxation proceeds by plastic deformation.
The Fluorescence X-Ray Microprobe at the Advanced Light Source
Authors: Thompson Albert C. , Chapman Karen
Published: April 2011

The fluorescence x-ray microprobe beamline at the Advanced Light Source (ALS) provides a technique to study almost any sample with excellent trace element sensitivity, high spatial resolution and minimal sample damage. During the last two years, the focused spot size has been improved from 2 μm × 4 μm to 1.6 μm × 1 μm using a pair of elliptically-bent multilayer mirrors. Two sets of mirrors have been produced for operation at 8.5 keV and 12.5 keV with a bandpass (ΔE/E) of 4 %. The intensity has also increased by a factor of 20 to over 1 × 1010 photons/sec by linearly grading the multilayer coating on the mirrors and by operation of the ALS at 1.9 GeV rather than 1.5 GeV.

A wide variety of samples have been studied. Some of the materials science samples that have been studied include gallium nitride samples, polycrystalline silicon solar cells, the liner material of a rocket motor and the central germanium core of an optical fiber.
An Observation of the Dimension Effect in the CKα- Spectra of the Ultra Dispersed Diamonds
Authors: Mazalov L.N. , Okotrub A.V. , Bulusheva L.G.
Published: April 2011

The fluorescent CKα - spectra of ultra dispersed diamonds (UDD), separated into fractions by size, were obtained. The distinction between the spectra are more pronounced in the short-wave region. A quantum-chemical calculation of the C136 diamond cluster was performed using the MNDO method. Hydrogen atoms were placed on the broken bonds of the edge carbon atoms. According to the results of the calculation, the theoretical CKα- spectra of the cluster's surface and volume were simulated. In the theoretical and experimental spectra the same tendencies are reflected if the surface carbon atoms are linked to oxygen groups.
Epitaxial Variants and Grain Boundary Structures in Heteroepitaxial Lithium Tantalate on Basal Sapphire
Authors: Bellman Robert A. , Raj Rishi
Published: April 2011

Single crystal heteroepitaxial ferroelectric films are desired for non-linear optical applications to maximize the electro-optic coefficient and minimize waveguide losses. In this study, lithium tantalate films were deposited on (0001) sapphire from lithium hexaethoxytantalate by chemical beam epitaxy. Characterization showed that films had nearly stoichiometric composition, epitaxial orientation, and a high degree of crystalline perfection. However, the films exhibited high optical waveguide losses. Additional characterization by TEM revealed that the films had a two dimensional grain structure with epitaxial variants related by translation and a twin orientation to the substrate. To better understand the nature of the heteroepitaxial growth of lithium tantalate on (0001) sapphire, a model was developed to explain the observed epitaxial orientations, misfit dislocation networks, and grain boundary structures of lithium tantalate on (0001) sapphire.
The Atomic Fe/Ag Exchange on Ag(100)
Authors: Langelaar M. H. , Boerma D. O.
Published: April 2011

In this paper we present a low-energy ion scattering (LEIS) study of the site exchange of Fe adatoms with Ag atoms from the Ag(100) surface. The time-of-flight (TOF) spectra obtained at low temperatures have been interpreted with a newly developed LEIS simulation program MATCH. After low temperature deposition (˜50 K) of Fe atoms oil the Ag(100) surface, the Fe atoms occupy adatom positions. These Fe adatoms exchange sites with Ag atoms from the first layer, starting at a temperature of 130(10) K.
Structural and Electrical Characterization of TiB2/TiSi2 Bilayer Barrier Structure
Authors: Sade G. , Pelleg J. , Grisaru A.
Published: April 2011

The TiB2/TiSi2 bilayer is considered as a diffusion barrier in metallization system with Cu. The TiSi2 sublayer serves as a contact and also as an additional diffusion barrier against boron, which outdiffuses from TiB2 at high temperature annealing. The attempts to form TiSi2 by vacuum annealing of TiB2/Ti film, which was obtained by co-sputtering from elemental targets are described. The composition and the structure of the films were analyzed by Auger electron spectroscopy (AES), X-ray diffraction (XRD) and high-resolution cross-sectional TEM (HRXTEM). The Cu/TiB2/(Ti-Si)/n-Si contacts were investigated using current-voltage (I–V) on Schottky diode structures, which were prepared on n-type Si (100). The thermal stability of the TiB2/(Ti-Si) barrier was studied by structural and electrical analysis.

It was observed that the lowest sheet resistance of 5.1 Ω/‪ was obtained after 850 °C annealing for 30 min, however the resulting Ti-Si layer is practically still amorphous and contains only a very small fraction of C54 TiSis in the form of microcrystallites. This layer also contained Ti5Si3 as indicated by XRD. The barrier height of Cu/TiB2/(Ti-Si)/n-Si Schottky diodes is ˜0.6 V and it does not show significant changes in the range 400–700 °C. Electrical monitoring is a very effective tool to detect deterioration of the barrier. No penetration is observed by AES at 700 °C, while the I–V curve shows changes in properties.
Initial Buffer Layers on the Growth of InGaP on Si by MBE
Authors: Kawanami H. , Ghosh S. , Sakata I. , Sekigawa T.
Published: April 2011

Single domain InxGa(1-x)P (x=0.3) films were successfully grown on Si(001) misoriented substrates by molecular beam epitaxy with a solid phosphorous source. The effects of interfacial buffer layers such as InGaP (i.e. direct growth without buffer layer), GaP, AlP, and GaAs were examined. Also a Si epitaxial buffer layer was tried to control the Si surface structure. Mirror like surfaces were obtained for all films with RHEED patterns of (2×1) single domain surface structure. PL intensities for all films indicated almost the same values except for the films with a Si epitaxial buffer layer. The films with a Si epitaxial buffer layer had almost three times larger PL intensities than the films without Si epitaxial buffer layer. The results suggest incomplete cleaning of the Si surface by the high temperature (1000 °C) treatment and possibility of surface structure control for Si substrates by a Si epitaxial buffer layer.
Microraman Spectroscopy and X-Ray Diffraction Studies of Ti-W-O Thin Films
Authors: Sangaletti Luigi , Bontempi Elza , Depero Laura E. , Galinetto P. , Groppelli Silvio , Salari Roberto , Sberveglieri Giorgio
Published: April 2011

Thin films of the Ti-W-O system grown by r.f. reactive sputtering from a Ti-W (10%–90% weight) target have been studied by Raman and microraman spectroscopy, X-ray diffraction and scanning electron microscopy with the aim to investigate their microstructural and morphological properties. To this purpose, the kinetics of structural transformations at different temperatures (600 °C, and 800 °C) have been studied, and the effect of Ti on the WO3 lattice has been singled out. The results show that annealing at different temperatures induces a microstructural evolution from the amorphous phase of the as-deposited thin film to WO3 crystalline phases via an intermediate cubic disordered phase of WO3. The effect of Ti on this cubic phase and on the thin film morphology is also investigated with the aid of microraman and scanning electron microscopy analysis. The results show that two distinct phases arise upon long annealing treatments; namely, small crystallites belonging to the WO3 monoclinic phase are dispersed on a layer composed of a disordered cubic WO3 phase with a high Ti content.
Stress and Temperature Dependence of Misfit Dislocation Nucleation Rate in SiGe Alloys: Evidence of Homogeneous Nucleation
Authors: Labovitz S. M. , Xie Y. H. , Pope D. P.
Published: April 2011

A recent theory on the brittle-to-ductile transition (BDT) sheds new light on the issue of the generation of misfit dislocations- in strained epitaxial layers. The Khantha-Pope-Vitek model of the BDT states that thermal fluctuations in the lattice, assisted by an applied stress, can result in the spontaneous generation of dislocations. Application of the KPV model to the problem of epitaxial layers predicts that at a critical temperature and stress, a sudden onset of homogeneous islocation generation will occur.

In this paper the dislocation nucleation rate in SiGe strained layers of varying isfit stress is investigated as a function of temperature. Using the wafer curvature echnique, real-time strain relaxation curves are generated. These measurements how a sudden onset of relaxation of up to 22% of the epitaxial strain upon reaching emperatures in the range of 500 to 550C. The strong temperature dependence of his initial relaxation event is indicative of a BDT as predicted by the KPV model.
Plasma Etching and Patterning of CVD Diamond at <100° for Microelectronics Application
Authors: Ramesham R. , Welch W. , Neely W. C. , Rose M. F. , Askew R. F.
Published: April 2011

Oxidation resistance of diamond is an important characteristic to be considered in many high temperature microelectronics and other applications. We have tested the stability of CVD diamong by exposing to Ground State Atomic Oxygen (GSAO) at a temperature of 70°C. Polycrystalline diamond is quite stable at this temperature using GSAO. We have tested the stability of diamond using Excited State Atomic Oxygen (ESAO). Initially, CVD diamond was exposed to ESAO for 15 mind at 63°C and noted that the diamond was etched. We have also carried out the experiments at different time intervals such as 30 and mine. Etching rate of the diamond using ESAO is ≈ 0.2 – 0.25 μm/min at 63°C. We have successfully patterned the diamond using a Ni mask by exposing the sample to ESAO for longer time. ESAO has etched the diamond uniformly in all the directions of the diamond crystal as opposed to the molecular oxygen. Stability of the single crystal diamond has been tested using ESAO by using Ni mask material. We were able to etch the single crystal diamond (type Iia, 100 orientation) quite uniformly. An etching rate of single crystal diamond using ESAO was observed to be 0.3 μm/min.
A Study on the Residual Stress of Diamond-Like Carbon Films Deposited by Magnetically Enhanced RF PECVD
Authors: Choi Woon , Shin Dong-Hoon , Nam Seoung-Eui , Kim Hyoung-June
Published: April 2011

Hydrogenated DLC films were synthesized by RF plasma deposition with and without magnetic enhancement, and their film stresses were investigated as a function of process parameters. Under investigated process conditions, Vb/P1/2 (where Vb is the self-bias voltage and P is the working pressure) is the appropriate scaling factor representing impinging ion energy. Film stress is influenced by not only ion impinging energy but also by ion to adspecies flux ratios. As ion energy increases, film stresses increase to a maximum value corresponding to the highest number of sp3 carbon bonds. As ion/adspecies flux ratio increases, the maximum stress value decreases and the corresponding ion energy increases. Induction of a magnetic field promotes film stresses as high as 15.2 GPa, which is one of the highest value reported in hydrogenated DLC films. The magnetic-induced increase of stress can be explained by increased ion/adspecies flux ratio, thus, enhanced sp3 formation. Rapid reduction of stresses observed at high ion energies may stem from the formation of graphite (sp2 bond) phases. Inclusion of hydrogen in the films is not directly responsible for the stress generation.
Observation of Film Growth Phenomena Using Micromachined Structures
Authors: DiMeo F. , Cavicchi R. E. , Sernancik S. , Suchle J. S. , Tea N. H. , Kelliher J. T.
Published: April 2011

A method of studying thin film growth and materials processing using micromachined Si-based structures is presented. The microsubstrate platforms (called “microhotplates”) allow temperature control during deposition, andin situmonitoring of the electrical properties of connected coatings. The efficiency of the approach is amplified when multiple. Independentlyoperated elements are used in array configurations. Illustrations here involve chemical vapor deposition of semiconducting oxides, but the methodology can be employed to investigate the growth of other classes of materials as well.