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We investigate the piezoresistive effect of carbon nanotubes (CNTs) within density functional theory (DFT) aiming at application-relevant CNTs. CNTs are excellent candidates for the usage in nano-electromechanical sensors (NEMS) due to their small band gap at zero strain leading to a finite resistivity at room temperature. The application of strain induces a band gap-opening leading to a tremendous change in the resistivity. DFT with the LDA approximation yields reasonable results for pure carbon systems like CNTs and is applied to calculate the electronic structure of experimentally relevant CNTs. For the transport part, a simple ballistic transport model based on the band gap is used. We compare our DFT results for the band gaps of strained CNTs to results of tight binding (TB) models. By introducing a scaling factor of $\sqrt{2}$, an excellent agreement of the the DFT data with TB model published by Yang et al. [1] is obtained., Comment: 4 pages, 5 figures

Technologies for 3D-Wafer Level Packing (WLP) of Micro electro Mechanical Systems (MEMS) are described with respect to devices that find applications in thin packages (e.g. smart cards). An aspired final device thickness in the range of 350EL400 µm is achieved by using Cu based Through Silicon Vias (TSV's) Wafer Level Bonding (WLB) wafer thinning. In particular, two Via Last approaches using TSV's in the cap wafer and device wafer, respectively, are described. According to this, two WLB technologies are investigated: glass frit bonding as well as Silicon Direct Bonding (SDB) of Si-SiO2. The first technique has been demonstrated using a MEMS accelerometer including electrical tests and cross sectional analysis.

Ziel der elektrochemischen Abscheidung (ECD) von Aluminium (Al) und Palladium (Pd) aus ionischen Flüssigkeiten ist die Herstellung von nanoskaligen reaktiven Materialsystemen (RMS) für ein Waferbondverfahren bei Raumtemperatur. Das Schichtsystem Al/Pd ist ein hochenergetisches System, welches nach Initiierung chemisch exotherm miteinander reagiert. Durch die schnelle Reaktion erfolgt eine lokale Erhitzung, wodurch ein Fügeprozess möglich ist. Derzeit werden die RMS in einem alternierenden Sputterprozess (Kathodenzerstäubung) hergestellt, wobei die Abscheidung auf mehreren Substraten gleichzeitig große Anforderungen an die Anlagentechnik stellt.

The determination of built-in strain in semiconductor devices with nanometer spatial resolution and high sensitivity is needed for the characterization of nanoscale electronic devices. Kelvin probe force microscopy (KPFM) is an atomic force microscopy-based method that provides the spatially resolved surface potential at the sample surface, fulfilling the requirements on resolution and sensitivity. The contrast observed in KPFM imaging is often attributed to stress, but there are only a few reports on the application of KPFM for quantitative stress analysis [1]. In this contribution we focus on the application of KPFM for analysis of stress in silicon devices, such as copper through silicon vias and silicon membranes. The experimental results are compared with density functional theory calculations of strained silicon. This work provides critical insights into the quantitative determination of stress at the nanoscale that so far has gone largely unnoticed in the scanning probe microscopy community. [1] W. Li, D.Y. Li, J. Appl. Phys. 99, 073502 (2006).

Direct synthesis of poly (sodium 4-styrenesulfonate) (P(NaSS)) inside the channel of single-walled carbon nanotube (SWCNT) field-effect transistors (FETs), is shown to be highly beneficial in improving the device parameters. Starting with monomeric compounds, the FET-channel was in-situ polymerized, using the self-initiated photografting and photopolymerization process. Upon formation of the P(NaSS) polymer matrix, we report improved device-to-device consistency, lower variability in the threshold voltage, higher drain currents and higher on/off ratios. Annealing in vacuum was shown to further improve the device performance and induce an ambipolar behavior. Moreover, those FET devices showed a long-term stability even under ambient environment.

For an industrial realization of devices based on single-walled carbon nanotube (SWCNTs) such as field-effect transistors (FETs) it becomes increasingly important to consider technological aspects such as intrinsic device structure, integration process controllability as well as yield. From the perspective of a wafer-level integration technology, the influence of SWCNT length on the performance of short-channel CNT-FETs is demonstrated by means of a statistical and comparative study. Therefore, a methodological development of a length separation process based on size-exclusion chromatography was conducted in order to extract well-separated SWCNT dispersions with narrowed length distribution. It could be shown that short SWCNTs adversely affect integrability and reproducibility, underlined by a 25% decline of the integration yield with respect to long SWCNTs. Furthermore, it turns out that the significant changes in electrical performance are directly linked to a SWCNT chain formation in the transist.

The growth of ultrathin (

The synthesis of compounds [Mn(i5-C5H4SiMe3)(CO)3] (1), [Mn(i5-C5H3-1-SiMe3-3-Me)(CO)3] (2), [Mn(i5-C5H4tBu)(CO)3] (3), [Mn(i5-C5Me5)(CO)3] (4) and [Mn(i5-C5H7)(CO)3] (5) and their potential use as metal-organic chemical vapor deposition (MOCVD) precursors for the deposition of manganese-based layers is reported. The thermal behavior of 1-5 was studied by thermogravimetry showing that these compounds evaporate in the temperature range of 363-498 K depending on the cyclopentadienyl substituents and the type of pentadienyl used. Vapor pressure measurements indicate that all compounds possess vapor pressures between 60 and 630 Pa at 353 K. Compounds 1-5 could be successfully applied in manganese-based film deposition without activation steps prior to the MOCVD experiments. The as-deposited thin layers were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and X-ray powder diffraction. Under comparatively mild conditions, whereas 5 possesses the lowest deposition temperature (553 K), dense and conformal layers with growth rates up to 7.0 nm min− 1 (5) could be deposited. Metal carbonyls 1 and 2 featuring a SiMe3 group produced Si-containing manganese-based films. The as-deposited layers from 1, 2, 4 and 5 contain carbon impurities (5-8.9 mol-%), while the films from 3 are carbon-free. The layers from 1 and 2 consist of mainly manganese silicate and manganese oxide, whereas those obtained from 3 to 5 are composed of manganese oxides.

Microelectromechanical system (MEMS) actuators essentially have movable silicon structures where the mechanical motion can be activated electronically. The microscanner is one of the most successfully commercialized MEMS devices which are widely used for collecting optical information, manipulating light, and displaying images. While silicon is abundant, it is also brittle and stiff and when microprocessed, defects are not uncommon. These defects result in weakness under torsional stress and this has been the key factor limiting the scanning performance of the microscanner. Here a metallic glass (MG)-based microscanner is reported with MG as the material for the moving torsion bars. The low elastic modulus, high fracture toughness, and high strength of MG offers, for the first time, an ultralarge rotating angle of 146 degrees with power consumption lowered to the microwatt range, and a smaller driving force and better actuation performance, than conventional single crystal silicon and polycrystalline silicon. The high spatial resolution and large scanning field of the MG-based microscanner are demonstrated in the tomographic imaging of a human finger. This development of an MG-based MEMS possibly opens a new field of low-powered MEMS devices with extreme actuation and enhanced sensing.

We report about a detailed comparison of the additive manufacturing methods inkjet printing (IJP) and aerosol jet printing (AJP). Both technologies are based on the direct-writing approach enabling the non-contact deposition of various materials in flexible patterns, e.g., for printed electronic applications. The deposited pattern elements were classified as (i) drops (IJP) or splats (AJP), (ii) lines, and (iii) squares. These elements can be considered as basic elements of the deposition systems and also of printed electronics. The pattern elements were deposited with IJP and AJP using the same silver nanoparticle ink. After printing, the layers were characterized regarding their morphology by optical and topographical measurement methods as well as regarding their electrical characteristics. It turned out that drops deposited with IJP and splats deposited with AJP can have similar dimensions. However, the shapes of the deposits differ widely. In the case of lines, AJP enables narrower line widths and thinner line thicknesses in comparison to IJP. In IJP, the line morphology varies depending on the direction of the deposition. Finally, the morphology of the deposited lines determines the electrical conductivity. For printed squares, the IJP layers show much higher layer thickness and a different layer topography compared with AJP as result of a higher volume per area deposition of materials.

Organic semiconductors have potential applications in the spintronics field due to the weak spin scattering mechanism in organic molecules, which implies that the spin polarization of the carriers can be maintained for a much longer time (in the range µs to ms) than in inorganic materials. Cost-efficient, wafer level fabrication of such devices is one of the main challenges in this field. Currently e-beam lithography is used for fabricating the required small electrode gap dimensions. Previously, we reported an alternative approach for fabricating laterally stacked organic trench devices using conventional optical lithography, where paramagnetic (CoPc, CuPc) and diamagnetic Alq3 molecules were evaporated to form the organic channels. It was observed that the molecules form a membrane between the electrodes. In this work, solution processing of organic materials was tested by drop-coating of water-soluble 3,4',4",4‴-copper(II) phthalocyanine-tetrasulfonic acid tetrasodium salt (TSCuPc). Using this approach it was possible to fill the trenches. A comparative study of a solution processed device and a device with evaporated channel material is presented.

Active Flow Control (AFC) devices in rotor blades offer a high potential to improve the efficiency of wind turbines, e.g., by increasing rotor blade lift, improving load control or reducing acoustic emission. Thus, the energy yield can be increased and/or the rotor blades be downsized - both implying positive economic consequences. However, since AFC devices also cause additional costs in different phases of their life cycle, a life cycle-related evaluation of their profitability is necessary. The paper presents a decision theory-based procedure model, which enables not only a sophisticated evaluation of AFC concepts and devices but also the identification of needs and potentials for improvement.

Atomistic mechanisms for the atomic layer deposition using the Cu(acac)(2) (acac = acetylacetonate) precursor are studied using first-principles calculations and reactive molecular dynamics simulations. The results show that Cu(acac)(2) chemisorbs on the hollow site of the Cu(110) surface and decomposes easily into a Cu atom and the acac-ligands. A sequential dissociation and reduction of the Cu precursor [Cu(acac)(2) -> Cu(acac) -> Cu] are observed. Further decomposition of the acac-ligand is unfavorable on the Cu surface. Thus additional adsorption of the precursors may be blocked by adsorbed ligands. Molecular hydrogen is found to be nonreactive towards Cu(acac)(2) on Cu(110), whereas individual H atoms easily lead to bond breaking in the Cu precursor upon impact, and thus release the surface ligands into the gas-phase. On the other hand, water reacts with Cu(acac)(2) on a Cu2O substrate through a ligand-exchange reaction, which produces gaseous H(acac) and surface OH species. Combustion reactions with the main by-products CO2 and H2O are observed during the reaction between Cu(acac)(2) and ozone on the CuO surface. The reactivity of different co-reactants toward Cu(acac)(2) follows the order H > O-3 > H2O.

Silver(I) dithiocarbamates [Ag{S2CNR(C2H4OH)}] (3a, R = Me; 3b, R = Bu) were accessible by the reaction of AgNO3 with K{S2CNR(C2H4OH)} (2a, R = Me; 2b, R = Bu). Alternatively, 3b could be prepared by the condensation of CS2 and Ag2O with NHBu(C2H4OH) (1b). The thermal behavior of 3 was studied by thermogravimetric (TG) analysis. A two-step decomposition process leads to the formation of a-Ag2S, as evidenced by X-ray powder diffraction studies. A decomposition mechanism of 3a to form Ag2S through the release of 3-methyloxazolidine-2-thione is discussed based on TG-MS, GC-MS, and NMR experiments. Because of the better solubility of 3b, this complex was tested for Ag2S spin-coating deposition studies on different substrates (SiO2/Si, TiN/SiO2/Si, glass) with subsequent annealing at 450 °C under a N2 atmosphere. Film thickness, composition, and morphology of the as-deposited films were determined by XRD, SEM, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, which showed the formation of 200 nm thick, conformal, adherent, monoclinic a-Ag2S layers.

Mask less fabricated 3D interconnects may have a big potential in future microelectronic applications by enhancing freedom of device design or power- and footprint saving capabilities along with performance improvements. Within this paper research activities are reported about evaluation of Aerosol Jet Printing (AJP) for feasibility of fabricating non-planar nano particle based electrical chip interconnects on a 3D-integrated System in a Package (SiP) including MEMS that is capable to wake up integrated electronics from power down mode using piezoelectric MEMS components. 3D-stacked multi-chip modules with a footprint of 9 mm x 10 mm are functional connected by AJP after single chips are mounted to printed circuit board (PCB) using underfiller adhesives. AJP, morphology of printed paths, and electrical resistances are investigated. Several challenging factors like printed line width, printed layer thickness, focus limiting standoff height of printhead, thermo-mechanical properties of printed interconnects along with SiP layout were identified and discussed during process development.

Organic semiconductors are considered as attractive materials for spintronic applications. One of the current challenges in this field resides in the cost-effective fabrication of devices with laterally stacked electrodes and their integration at the wafer level. In this work lateral devices with electrodes separated by sub-100 nm gaps were fabricated using conventional UV lithography combined with semiconductor processing. Following a metallization step for the preparation of Au or Co electrodes, organic films were evaporated in high vacuum. Typically an average film thickness of 350 nm was required to form a nanomembrane that closes the gap between the electrodes. These structures allow the systematic investigation of electric and magnetoresistive properties of diamagnetic and paramagnetic organic semiconductor materials (in this case Alq3 and cobalt phthalocyanine) as a function of the width of the electrode gap. These devices are intended to be used in magnetoresistive devices and molecular spintronics.

The paper shows the potential of micro machined sensors for implantation and monitoring of patients. Next to well known sensors it is focused on inertial sensors and a way for further miniaturization keeping the performance and accuracy of the sensor. Furthermore the ongoing investigation of materials used for MEMS packaging and MEMS fabrication will be described. Here, special encapsulation techniques should show a miniaturization potential realized by the substitution of thick medical packages like Titanium housings.

In this work we describe the bonding and contacting of a micro machined vertically integrated 3-D micro scanner, which is a key-component for a number of scanning imaging micro systems, such as confocal microscopes on-chip or optical coherence tomography (OCT) probes for micro endoscopy. The 3-D micro scanner is composed of two electrostatic silicon MEMS micro actuators which are vertically aligned and bonded with glass and ceramic components to create hermetically sealed cavity for scanning micro lenses. In addition, the through wafer vias (TWV) technology is employed to establish electrical connection from the top to the bottom through a stack of two SOI wafers, one glass wafer and one ceramic wafer. Presented methods are of general importance for various silicon-based vertically integrated devices.

Carbon nanotube (CNT) based interconnects with an improved bottom metallization scheme were prepared and characterized. Two procedures are introduced to enhance the CNT via performance after planarization. Both, temperature annealing of the metal-CNT contact and exposing the CNT tips to HF vapor prior to the deposition of the top metallization increased the yield and reduced the resistance of the vias. For a via of 5 µm diameter and a depth of 800 nm a resistance of 8 ohm was obtained. Further, the resistance of individual CNTs was measured by means of conductive atomic force microscopy (cAFM), giving a value of 38 kohm/CNT. We highlight the capability of cAFM to accurately predict the overall electrical performance of CNT based vias. Deviations of the measured resistance compared to the theoretical limit are either attributed to defects in the CNT's atomic structure or imperfect contacts. To separate those two aspects, different methods to investigate the microstructure of the employed materials were used.

We study quasi-ballistic electron transport in metallic $(6,0)$ carbon nanotubes (CNTs) of variable length in contact with Al, Cu, Pd, Pt, Ag, and Au electrodes by using the non-equilibrium Green's function formalism in combination with either density functional theory or self-consistent extended Hückel theory. We find good agreement between both. Visualizing the local device density of states of the systems gives a descriptive link between electronic structure and transport properties. In comparison with bare finite and infinite tubes, we show that the electronic structure of short metallic CNTs is strongly modified by the presence of the metallic electrodes, which leads to pronounced size effects in the conductance. The mean conductances and linear response currents allow a ranking of the metals regarding their ability to form low-Ohmic contacts with the nanotube: ${\rm Ag}\lesssim {\rm Au}\lt {\rm Cu}\ll {\rm Pt}\approx {\rm Pd}\ll {\rm Al}$. These findings are contrasted with similar trends in contact distance, binding energy, calculated work function of the metal surfaces, and various results from literature.

Exothermic self-propagating high-temperature synthesis of intermetallic compounds attain increasing interest in the field of wafer bonding in microelectronics and microsystems technology due to local heat generation. Numerical models of self-sustaining reactions in thin multilayer films can be used to predict velocity and shape of the reaction front. This work deals with heat losses to various substrate materials and material compounds used for wafer bonding as well as the prediction of minimal numbers of bilayers required for a self-propagating reaction front. We introduced a cylindrically symmetric finite element approach. In addition to that, the effect of temperature-dependent specific heat capacities was investigated. Numerical computations were performed for Pd/Al multilayers and are compared to experimental data. It was found that the developed formalism is suitable to determine the mutual influence of heat losses and reaction properties. Furthermore, it was demonstrated that minimal numbers of bilayers can be determined more precisely by including temperature-dependent specific heat capacities.

Zur Wandlung einer mechanischen Spannung in ein elektrisches Signal finden häufig Piezowiderstände Anwendung. Um den Flächenbedarf zu reduzieren und die Kompatibilität zu CMOS-Prozessen zu erhöhen, ist es möglich, MOS-Transistoren als Wandlerelement einzusetzen. Die Wandlung einer mechanischen Spannung in ein elektrisches Signal erfolgt unter Ausnutzung des piezoresistiven Effekts. Im Fokus dieser Arbeit stehen die Simulation und Charakterisierung von MOS-Transistoren als Wandlerelement für mechanische Spannungen. Zur Erzeugung der mechanischen Spannung fanden dünne Siliziummembranen Anwendung. Um die Transistoren in den Gebieten der maximalen mechanischen Spannung zu platzieren, wurden die Membranen mit einer FEM-Software simuliert. Der Stresseinfluss auf das elektrische Verhalten der Transistoren ist mit einem angepassten BSIM3v3-Modell simuliert worden. Die Skalierbarkeit wurde durch Simulationen von Halbleitertechnologien unterschiedlicher minimaler Strukturweiten nachgewiesen. Mit Hilfe der Messungen wurde der Stresseinfluss auf die Transistorkennlinien und Transistorparameter untersucht.

A polymer-based uniaxial accelerometer with piezoelectric polyvinylidene fluoride copolymer (P(VDF-TrFE)) transducers and micro injection molded polypropylene (PP) structures has been designed, manufactured and characterized. The mass-loaded cantilever structure shows a quasi-static charge sensitivity of 0.69 pC/g and a resonance frequency of 735 Hz. Because of its efficient processing and its small dimensions the polymer-based sensor (polySENS) can be integrated into polymer-based compound structures in order to measure low-frequency vibrations. The focus of this contribution is on the design, processing as well as on the characterization of the polySENS accelerometer to determine the sensor properties of the accelerometer due to manufacturing particularities. Additionally, investigations regarding the applied materials and the manufacturing, in particular the mold filling have been done to qualify the novel technological approach.

In this paper, we present our results of experimental and numerical pull-out tests on carbon nanotubes (CNTs) embedded in palladium. We prepared simple specimens by employing standard silicon wafers, physical vapor deposition of palladium and deposition of CNTs with a simple drop coating technique. An AFM cantilever with known stiffness connected to a nanomanipulation system was utilized inside a scanning electron microscope (SEM) as a force sensor to determine forces acting on a CNT during the pull-out process. SEM-images of the cantilever attached to a CNT have been evaluated for subsequent displacement steps with greyscale correlation to determine the cantilever deflection. We compare the experimentally obtained pull-out forces with values of numerical investigations by means of molecular dynamics and give interpretations for deviations according to material impurities or defects and their influence on the pull-out data. We find a very good agreement of force data from simulation and experiment, which is 17 nN and in the range of 10-61 nN, respectively. Our findings contribute to the ongoing research of the mechanical characterization of CNT-metal interfaces. This is of significant interest for the design of future mechanical sensors utilizing the intrinsic piezoresistive effect of CNTs or other future devices incorporating CNT-metal interfaces.

Extended Hückel theory (EHT) is a well established method for the description of the electronic structure of molecules and solids. In this article, we present a set of extended Hückel parameters for carbon nanotubes (CNTs), obtained by fitting the ab initio band structure of the (6,0) CNT. The new parameters are highly transferable to different types of CNTs. To demonstrate the versatility of the approach, we perform self-consistent EHT-based electron transport calculations for finite length CNTs with metal electrodes.

On-chip nanoporous gold (NPG) fabrication has been successfully developed by Au-Sn alloys electrodeposition and dealloying process, to use its compressible body and nanostructured surface for micro electro mechanical systems (MEMS) applications. Anodically-bondable low temperature cofired ceramic (LTCC) substrates are proposed to provide electrical connective packaging by using novel nano-structured gold. The porous structure offers sponge-like functions which forms electrical contacts as well during anodic bonding. Nanoporous gold with porosity in nanoscale indicates a highly reactive surface which makes it possible to be a promising candidate for bonding process to reduce the bonding temperature. Low temperature bonding has been achieved by using nanoporous gold. These encouraging results imply good possibilities of nanoporous gold for MEMS packaging applications.

In this work, the thermoelectric (TE) properties of poly(3,4- ethylenedioxylthiophene):poly(styrene sulfonate) (PEDOT:PSS) thin films at room temperature are studied. Different methods have been applied for tuning the TE properties: 1st addition of polar solvent, dimethyl sulfoxide (DMSO), into the PEDOT:PSS solution; 2nd post-treatment of thin films with a mixture of DMSO and ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4). It is verified that DMSO post-treatment is more efficient than DMSO addition in improving the electrical conductivity with a trivial change in the Seebeck coefficient. The power factor is increased up to 30.1 W mK-2 for the film with DMSO post-treatment, while the optimized power factor by DMSO addition is 18.2 W mK-2. It is shown that both DMSO addition and post-treatment induce morphological changes: an interconnected network of elongated PEDOT grains is generated, leading to higher electrical conductivity. In contrast, for t hose films post-treated in the presence of EMIMBF4, an interconnected network of short and circular PEDOT grains with increased polaron density is created, resulting in the improvement in the Seebeck coefficient and a concomitant compromise in the electrical conductivity. An optimized power factor of 38.46 W mK -2 is achieved at 50 vol% of EMIMBF4, which is the highest reported so far for PEDOT:PSS thin films to our knowledge. Assuming a thermal conductivity of 0.17 W mK-1, the corresponding ZT is 0.068 at 300 K. These results demonstrate that post-treatment is a promising approach to enhance the TE properties of PEDOT:PSS thin films. Furthermore, ionic liquid, EMIMBF4, shows the potential for tuning the TE properties of PEDOT:PSS thin films via a more environmentally benign process.

Carbon nanotubes (CNTs) are a promising material for novel sensor and interconnect applications. In both cases, the device performance depends strongly on the electronic properties of the tubes. Methods for tuning the electronic structure and especially the band gap are highly desirable. A computational study of cobalt decorated CNTs, by means of density functional theory, reveals that very few cobalt atoms can have a significant impact on the electronic structure, turning semiconducting CNTs into the metallic state. This is further verified by quantum transport simulations. The influence of different amounts of cobalt is also investigated.

Non-covalent functionalization based on surfactants has become one of the most common methods for dispersing of single-walled carbon nanotubes (SWCNTs). Previously, efforts have mainly been focused on experimenting with different surfactant systems, varying their concentrations and solvents. However sonication plays a very important role during the surfactant-based dispersion process for SWCNTs. The sonication treatment enables the surfactant molecules to adsorb onto the surface of SWCNTs by overcoming the interactions induced by the hydrophobic, electrostatic and van der Waals forces. This work describes a systematic study of the influence of the sonication power and time on the dispersion of SWCNTs. UV-vis-NIR absorption spectra is used to analyze and to evaluate the dispersion of SWCNTs in an aqueous solution of 1 w/v% sodium deoxycholate (DOC) showing that the resonant and nonresonant background absorption strongly depends on the sonication conditions. Furthermore, the diameter and length of SWCNTs under different sonication parameters are investigated using atomic force microscopy (AFM).

This paper presents a novel post-process gap reduction technique for high aspect ratio microstructures. The gap reduction procedure is based on electrostatic deflection of a movable microstructure and micro welding for permanently locking the final position. The gap reduction technique is demonstrated for MEMS devices fabricated by the air gap insulated microstructures technology. The functional principle of the gap reduction mechanism, the fabrication technology and the experimental set-up is presented. As a result, the initial gap width between vertical comb electrodes was decreased from 4500 nm to 385 nm, leading to a final aspect ratio of 150.

To realize fast and efficient integrated circuits the interconnect system gains an increasing importance. In particular, this is the case for logic and processor circuits with up to 12 metallization layers. In order to optimize this technology and the according processes it is desirable to generate flexible test structures in small lot production. In opposition to standard optical lithography using masks, Electron Beam Direct Write (EBDW) lithography can rapidly deliver special test structures at low cost. Furthermore, critical dimensions of future technology nodes which are not yet manufacturable by standard optical lithography tools can be produced. In this paper we demonstrate the potential of the 50 kV variable shaped EBDW cluster for patterning of future back-end-of-line (BEOL) structures on full 200 mm wafers. The patterned wafers have been used to develop next generation copper damascene interconnect processes for critical dimensions down to 50 nm.

The inhibition of Cu oxidation by alloying C into the Ru/TaN barrier stack is investigated. By using in-situ XRD measurement, severe copper oxide formation was observed for the Cu/Ru/barrier system during annealing process in He atmosphere. This phenomenon is explained using thermodynamics from the viewpoint of Gibbs free energy of oxide formation. The Cu oxidation can be inhibited by alloying C into the Ru layer, and the more C content in the RuC layer, the more evident the inhibition effect. The RuC/TaN stack also shows better diffusion barrier properties than the Ru/TaN bi-layer. Atomic layer deposition of Cu(2)O on the RuC substrate was carried out and reduction of the Cu(2)O to Cu was observed. The mechanism of inhibition of Cu oxidation on C alloyed Ru was investigated by a first principles calculation based on the density functional theory.

The subject of this paper is the extension of the simulation tool T2 for the application to Reactive Physical Vapor Deposition. The implemented models are briefly described and applied to the deposition of TaNx barriers. The influence of the nitrogen flow and the substrate bias on the deposition rate, the thickness uniformity, and the film composition is discussed.

The thermal atomic layer deposition (ALD) of copper oxide films from the non-fluorinated yet liquid precursor bis(tri-n-butylphosphane)copper(I)acetylacetonate, [(nBu3P)2Cu(acac)], and wet O2 on Ta, TaN, Ru and SiO2 substrates at temperatures of < 160°C is reported. Typical temperature-independent growth was observed at least up to 125°C with a growth-per-cycle of ~ 0.1 Å for the metallic substrates and an ALD window extending down to 100°C for Ru. On SiO2 and TaN the ALD window was observed between 110 and 125°C, with saturated growth shown on TaN still at 135°C. Precursor self-decomposition in a chemical vapor deposition mode led to bi-modal growth on Ta, resulting in the parallel formation of continuous films and isolated clusters. This effect was not observed on TaN up to about 130°C and neither on Ru or SiO2 for any processing temperature. The degree of nitridation of the tantalum nitride underlayers considerably influenced the film growth. With excellent adhesion of the ALD films on all substrates studied, the results are a promising basis for Cu seed layer ALD applicable to electrochemical Cu metallization in interconnects of ultralarge-scale integrated circuits. © 2009 The Electrochemical Society. All rights reserved. Es wird die thermische Atomlagenabscheidung (ALD) von Kupferoxidschichten, ausgehend von der unfluorierten, flüssigen Vorstufenverbindung Bis(tri-n-butylphosphan)kupfer(I)acetylacetonat, [(nBu3P)2Cu(acac)], sowie feuchtem Sauerstoff, auf Ta-, TaN-, Ru- und SiO2-Substraten bei Temperaturen < 160°C berichtet. Typisches temperaturunabhängiges Wachstum wurde zumindest bis 125°C beobachtet. Damit verbunden wurde für die metallischen Substrate ein Zyklenwachstum von ca. 0.1 Å erzielt sowie ein ALD-Fenster, das für Ru bis zu einer Temperatur von 100°C reicht. Auf SiO2 und TaN wurde das ALD-Fenster zwischen 110 und 125°C beobachtet, wobei auch bei 135°C noch gesättigtes Wachstum auf TaN gezeigt werden konnte. Die selbständige Zersetzung des Precursors ähnlich der chemischen Gasphasenabscheidung führte zu einem bimodalen Schichtwachstum auf Ta, wodurch gleichzeitig geschlossene Schichten und voneinander isolierte Cluster gebildet wurden. Dieser Effekt wurde auf TaN bis zu einer Temperatur von 130°C nicht beobachtet. Ebensowenig trat er im untersuchten Temperaturbereich auf Ru oder SiO2 auf. Der Nitrierungsgrad der TaN-Schichten beeinflusste hierbei das Schichtwachstum stark. Mit einer sehr guten Haftung der ALD-Schichten auf allen untersuchten Substratmaterialien erscheinen die Ergebnisse vielversprechend für die ALD von Kupferstartschichten, die für die elektrochemische Kupfermetallisierung in Leitbahnsystemen ultrahochintegrierter Schaltkreise anwendbar sind.