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This paper reports on design, technology and mechanical characterization in air of a piezoelectric aluminum nitride (AlN) based micromachined ultrasonic transducer (PMUT) with six radial symmetric arrays. The PMUT consists of 4018 single membranes with a resonance frequency of 3.4 MHz, a quasi-static deflection of 272 pm/V and a resonant deflection of up to 71.3 nm/V. The small standard deviation of the resonance frequency over the chip is 47 kHz.

A micromirror with piezoelectric thin film aluminum nitride (AIN) as transducer material for actuation and detection is presented. Four sensor elements are integrated for closed-loop monitoring of the resonant driven microscanner with an entire footprint of 6 mm2. The sensor and actuator elements are monolithically fabricated in 150 mm SOI technology. The micromirror is characterized in terms of its scanning and sensor characteristics. A large optical scan angle of 137.9° (34.5° mechanical tilt angle corresponding) at 3385 Hz and 20 V actuation voltage is achieved. The median resonant voltage sensitivity is 4.7 °/V. For the sensor characterization, a cross-talk compensation is introduced, which significantly improves the signal quality and thus enables an accurate charge determination. The sensor signal increases linearly to the deflection. A dynamic sensor angle sensitivity of 48.4 fC/° is reached. Possible applications of the micromirror are consumer electronics, such as LIDAR or medical applications, such as fluorescence microscopy.

In this paper micromirrors based on piezoelectric thin film aluminum nitride (AlN) are presented. The microsystems with a 6 mm² footprint are fabricated successfully in 150 mm SOI technology. A large tilt angle is achieved by FEM-based optimization of the lever arm parameters. Three micromirror types with varied spring widths are characterized, achieving tilt angles up to 51.3° at 1.9 kHz, 31.6° at 4.6 kHz, and 16.5° at 12.5 kHz for an actuation voltage of less than 5 V. For higher actuation voltages up to 20 V, a maximum scan angle of 104.9° is reached, limited by the measurement setup.

Applying quantum cascade laser absorption spectroscopy a correlation could be demonstrated between the concentration of the etching products SiF4 and CO and the etching rate of ultra-low-k SiCOH in a low-pressure rf plasma containing CF4.

The continuous scaling of transistor size towards deep submicron level demands an inevitable replacement of SiO 2 with a low-k dielectric material. Doping of methyl groups in SiO 2 network reduces the dielectric constant by replacing oxygen atoms bonded with silicon and creating a lower polarizable silicon methyl bond in the network. Further reduction in dielectric constant is possible by introducing porosity in the dense low-k network. The detailed knowledge about atomic structure of such low-k materials is a must for understanding their electronic and optical properties. In this study, electron diffraction and (density functional based tight binding) DFTB calculations are used to investigate the structure of dense and porous low-k dielectric materials. The radial distribution function (RDF) obtained from electron diffraction technique contains information about the short-range order present in the material. Bond lengths and bond angles determined from RDF indicate a significant modification occurring in the SiO 2 network after doping with methyl groups. The local density of the materials is also derived from radial distribution function. It depends on the number and distances of nearest neighbors and was found to be decreased in these low-k materials compared with amorphous SiO 2 .

Porous ultra low constant materials (ULK) for isolation within the interconnect system of integrated circuits are a promising approach to reduce crosstalk and RC-delays due to shrinking feature sizes [1]. Due to their porosity and the integration of carbon rich species like methyl groups into the Si-O-Si backbone of currently fabricated PECVD SiCOH dielectrics those materials are highly sensible towards plasma processing, e.g. dry etching or resist stripping [2]. Metal hard mask approaches, e.g. using TiN hard masks are widely used to prevent the resist stripping plasma directly attacking the low-k material [3]. To reduce further plasma damage like carbon depletion and formation of polar silanol groups the development of less aggressive etching processes is in the focus of research and development activities. Nevertheless dry etching will attack the sidewalls and cause a material degradation. That is why repair processes, mainly based on silylation, are considered to follow the patterning step to reintegrate carbon rich species and to recover the dielectric’s properties [3]. Subsequently to dry etching and repairing the dielectric the wet chemical plasma etch residue removal process is performed. Besides material compatibility and effectiveness in residue removal the wetting behavior of the applied cleaning solutions towards the surface which has to be cleaned is crucial, especially looking on wetting issues like the incomplete wetting of very small via holes or pattern collapse. In this study we investigate in which way different silylation based repair processing regimes are affecting the wettability of the dielectric by water based cleaning solutions using contact angle based surface energy calculations.

In this study, the dielectric response of low-k dielectric materials has been characterized by electron energy loss spectroscopy. A widely accepted fast Fourier transform based Kramers–Kronig method (Johnson, 1975) [3] has been used to derive the high-frequency response of these materials. We used three different low-k dielectric materials to find out the effect of porosity and carbon content on the dielectric response of materials. Amorphous SiO 2 and SiC:H samples are used for comparison. All samples were deposited by plasma-enhanced chemical vapor deposition technique. A Lorentzian-based oscillator model has been used to determine the eigen-energy of excitations by fitting the measured loss function. The model is specially designed to let all oscillator parameters move freely and find their most probable position by using a least square fitting analysis procedure. The band gap for amorphous SiO 2 which corresponds to the first absorption peak in the imaginary part of dielectric function is found to be at around 9 eV. We observed that in the case of dense low-k material, there appears a finite density of states (DOS) inside the band gap of SiO 2 , whereas the inclusion of porosity into dense low-k network diminishes the in-gap DOS and widens the band gap to around 10 eV.

The adaptive immune system is involved in tumor establishment and aggressiveness. Tumors of the ovaries, an immune-privileged organ, spread via transceolomic routes and rarely to distant organs. This is contrary to tumors of non-immune privileged organs, which often disseminate hematogenously to distant organs. Epigenetics-based immune cell quantification allows direct comparison of the immune status in benign and malignant tissues and in blood. Here, we introduce the "cellular ratio of immune tolerance" (immunoCRIT) as defined by the ratio of regulatory T cells to total T lymphocytes. The immunoCRIT was analyzed on 273 benign tissue samples of colorectal, bronchial, renal and ovarian origin as well as in 808 samples from primary colorectal, bronchial, mammary and ovarian cancers. ImmunoCRIT is strongly increased in all cancerous tissues and gradually augmented strictly dependent on tumor aggressiveness. In peripheral blood of ovarian cancer patients, immunoCRIT incrementally increases from primary diagnosis to disease recurrence, at which distant metastases frequently occur. We postulate that non-pathological immunoCRIT values observed in peripheral blood of immune privileged ovarian tumor patients are sufficient to prevent hematogenous spread at primary diagnosis. Contrarily, non-immune privileged tumors establish high immunoCRIT in an immunological environment equivalent to the bloodstream and thus spread hematogenously to distant organs. In summary, our data suggest that the immunoCRIT is a powerful marker for tumor aggressiveness and disease dissemination.

The integration of porous ultra low dielectric constant materials (ULK) for isolation within the interconnect system of integrated circuits is a promising approach to reduce RC-delays and crosstalk due to shrinking feature sizes [1]. Actually the focus is on porous CVD-SiCOH materials, which consist of a Si-O-Si backbone and organic species (e.g. CH3) to lower polarizability and prevent moisture uptake to remarkably decrease the k-value [2]. The integration of porous low-k materials is very challenging, especially looking at patterning, resist stripping and etch residue removal, where commonly plasma processing has been applied. But plasma processing of ULK materials, especially using oxygen plasmas, is known to degrade electrical, optical and structural material properties by removing carbon from the film and densification of the surface near areas of the ULK [5]. Carbon depletion may also lead to the incorporation of-OH groups, which easily form silanols and therefore increase moisture absorption and k-values [2]. Besides the development of nondamaging plasma processes, wet cleaning is a promising alternative to avoid ULK damage while removing organic plasma etch residues. Additionally wet cleaning steps are always necessary to remove inorganic residues, which do not form volatile reaction products and can therefore not be removed by plasma processing.

The integration of porous ultra low-k (ULK) materials within the interconnect system of integrated circuits is one of the most promising approaches to reduce RC-delay or crosstalk. The application of plasma processes for patterning, cleaning and photoresist removal is known to degrade the electrical parameters of the ULK by carbon depletion, densification and introduction of silanol species. In this study we investigate the influence of different thermally assisted immersion processes on the effectiveness of a silylation based k-restore process of plasma damaged porous low-k dielectrics. The results show that network recovery effects like methyl incorporation are different at the surface and in the depth of the damaged area addicted to precursor temperature and curing conditions. The most promising process sequence was shown to consist of an immersion at temperatures of 100-150 °C with subsequent UV anneal depending on the precursor used for recovery process.

Wet chemical plasma etch residue removal is a promising alternative to low-k dielectric degrading plasma cleaning processes. With decreasing feature dimensions the wetting behavior of the liquid on low energetic surfaces present after dielectric patterning will be an important issue in developing wet cleaning solutions. High surface energy liquids may not only be unable to wet low energetic surfaces, but can also cause nonwetting of small structures or pattern collapse. The improvement of the wetting behavior of a cleaning liquid by lowering its surface energy by the addition of surfactants is the strategy followed in this study. We show that with choosing the appropriate rinsing solution a wet chemical process using surfactant aided cleaning solutions compatible to the materials used in BEOL (porous low-k, copper, barriers) can be found. The results show a distinct improvement of the wetting behavior of the modified solutions on several low energetic solid surfaces like copper or polymers deposited during dry etching.

Reactive ion etch processes for modern interlevel dielectrics become more and more complex, especially for further scaling of interconnect dimensions. The materials will be damaged within such processes with the result of an increase in their dielectric constants. The capability of selected additives to minimize the low-k sidewall damage during reactive ion etching (RIE) of SiCOH materials in fluorocarbon plasmas was shown in different works in the past. Most of the investigated additive gases alter the fluorine to carbon ratio as well as the dissociation of the parent gas inside the etch plasma. The result is a changed etch rate, a modified polymerization behavior and other characteristics of the process induced SiCOH damage. Heavy inert ions like argon will be accelerated to the sample surface in the cathode dark space and enhance therewith the sputter yield on the SiCOH network [1]. In this paper the additives Ar, O"2, C"4F"8, H"2, N"2 and CO were added to a conventional CF"4 etch plasma. We try to provoke different changes in the plasma conditions and therewith in the process results. Contact angle measurements, spectroscopic ellipsometry, Hg-probe analysis, FTIR measurements and SEM cross-sections were used to overview the additive induced modifications. To understand the influences of the additives gases more exactly, changes in the physical and chemical plasma behavior must be analyzed. Therefore quadrupole mass spectrometry (QMS) and quantum cascade laser absorption spectroscopy (QCLAS) were used.

We apply a measurement-based closed-loop control scheme to the dissipative Lipkin–Meshkov–Glick model. Specifically, we use the Wiseman–Milburn feedback master equation to control its quantum phase transition. For the steady state properties of the Lipkin–Meshkov–Glick system under feedback we show that the considered control scheme changes the critical point of the phase transition. We show that entanglement measures such as concurrence allow one to unambiguously locate precursors of quantum-critical behaviour in the finite-size regime, unlike conventionally used operator expectation values. We find that with feedback, the position of the critical point can be shifted to smaller spin–spin interactions, which is potentially useful for setups with limited control on these.

The focus of this paper is the impact of CF"4 based plasma etch processes with the additives argon and C"4F"8 on material properties and geometrical parameters of etched trenches using dense and porous SiCOH. Argon and C"4F"8 were added to change the radical to ion composition and to shift the carbon to fluorine ratio, respectively. With several techniques, FTIR, spectral ellipsometry and contact angle measurements, modifications in the structure of the materials and their surface conditions were analyzed. To understand the influences of the additives on the plasma conditions, optical emission spectroscopy (OES) and quadrupole mass spectrometry (QMS) were used to estimate the composition of the plasma insitu. For the additive argon, a slightly enhanced etch rate and an increased refractive index due to serious plasma damage for porous SiCOH was observed. At higher Ar flow rates peaks of Si"2O"4H"x clusters in the QMS spectra and increased CO and O lines, measured with OES, indicate a higher sputter yield on the SiCOH network. SEM cross-sections show, that argon has no effect on the sidewall geometry of etched trenches. A higher CH/CN line in the OES spectra indicates an enhanced sputter effect of the SiCN films in via bottoms. For C"4F"8 addition results of spectral ellipsometry show a decreased etch rate and refractive index. Using FTIR the formation of a polymer film on the surface was observed. Higher C"2 lines in the OES spectra are indications of enhanced polymerization efficiency. Finally, the addition of C"4F"8 decreases the etch rate in the trench sidewalls and therewith assumedly the sidewall damage.

The objective of this work is to study the optical and electrical properties of tantalum nitride and tantalum barrier thin films used against copper diffusion in Si in integrated circuits using spectroscopic ellipsometry in the VUV and UV-visible range. Single layers of tantalum nitride and bilayer films of Ta/TaN were produced by reactive magnetron sputtering on Si(100) substrates covered with a native oxide layer. Ellip-sometric measurements were performed in the energy range from 0.73-8.7 eV and the dielectric functions were simulated using Drude-Lorentz model and effective medium mation (EMA) in order to obtain information regarding film thickness, film composition, free carrier plasma energy, mean relaxation time and electrical resistivity. The film thickness clearly affects the electrical resistivity and the electron mean free path. It was observed that for films of Ta on TaN even after maintaining the deposition condition suitable for the β-phase of Ta, it turned out to be a mixture of α- and β-phases with higher contribution of the α-phase. It is shown that even a very small intermixture of two different phases of Ta can be determined accurately using ellipsometry.

This paper describes a novel in situ restoration process to repair damaged porous low-k materials by a plasma assisted approach. The main advantage is the enhanced repair efficiency due to the formation of small plasma activated multiple repairing fragments as well as the in situ handling to avoid a further k-value increase by water uptake. A liquid repair chemistry was evaporated and inserted into downstream microwave plasma to form activated species with repair character and to prevent the contact of porous low-k materials with UV irradiation and ion bombardment. In this study Octamethylcyclotetrasiloxane (OMCTS) and Bis(dimethylamino)dimethylsilane (DMADMS) were chosen for blanket samples with a k-value of 2.4. Furthermore OMCTS was investigated on patterned ULK trench structures of 62nm width. Besides the OMCTS flow rate, the addition of oxygen, methane or nitrogen was studied with regards to the formation of repair fragments and restoration efficiency. Display Omitted

The material CoSi"2 is preferred for the fabrication of buried silicide films between silicon device layer and buried oxide of SOI substrates for BICMOS integrations. Such an application needs excellent quality of the interface between the silicide and the silicon device layer. Using the conventional cobalt salicide process the roughness and waviness of the interface is too large for a device application. In this presentation three technologies to improve the CoSi"2/Si-interface quality were characterized. Using the first technology a very thin single crystalline CoSi"2 film was fabricated on a silicon substrate. This film acts as initial layer to produce thicker single crystalline silicide films. By the second technology an interlayer between cobalt and the silicon substrate was used to mediate an epitaxial CoSi"2 growth. Different types and materials were tested. Using the third technique a sacrificial layer of polycrystalline silicon between cobalt and the silicon substrate was consumed during the silicidation reaction. This method gives the best results with interface roughness values of less than 1nm. The interface roughness was measured after CoSi"2 removal using AFM. A possible epitaxial growth of the silicide films was investigated with XRD analysis. Cross sectional SEM images were prepared to analyze the interface waviness and the CoSi"2 structure.

With the insertion of evaporated repair liquids into remote plasmas, a novel method to restore plasma damaged ultra low-k (ULK) materials will be introduced. The main advantage of this approach is the enhanced repair efficiency due to the formation of small plasma activated multiple repairing fragments. In this study Octamethylcyclotetrasiloxane (OMCTS) and Bis(dimethylamino)dimethylsilane (DMADMS) were chosen for blanket samples with a k-value of 2.4. Furthermore OMCTS with the addition of oxygen, methane or nitrogen was investigated on patterned ULK trench structures with 62 nm feature size.

A piezoelectric MEMS with wake up function, Power down interrupt generator (PDIG), for inertial sensor systems is reported. The aluminum nitride based MEMS generates electric signals intrinsically in result of an inertial accelerations. The PDIG is optimized for maximum charge and voltage sensitivity. The charge sensitivity for a single electrode designed PDIG is measured with 40.1 pC/g and the maximum voltage sensitivity with 1.273 V/g. The device shows a high linearity and reproducibility. The PDIG is merged with a CMOS electronic, designed for low current consumption in sleeping mode. The minimum acceleration to wake up the system is adjustable and measured with 0.08 g.

The fabrication of a new silicon on silicide on insulator (SSOI) substrate for the integration of bipolar and CMOS devices on the same wafer is demonstrated. This structure includes a 500nm thick buried oxide (BOX) and a 90nm patterned cobalt disilicide film under a 300nm thick silicon device layer. Two different process flows were used to build the final SSOI substrate. The first process bases on the known BESOI regime and includes wafer grinding and polishing steps. The second technology is a modified variant of the SmartCut^T^M method, where the SOI substrates are formed using hydrogen implantation, wafer splitting and CMP polishing. The cobalt disilicide was produced using a conventional cobalt salicide process. This process consists of cobalt deposition, two RTA steps and a selective etch. Some modifications in the salicide regime were made to improve the interface between the CoSi"2 and the device silicon.

WD (tryptophan-aspartic acid dipeptide)-repeat proteins play a central role in signal transduction cascades by co-ordinating the interaction of key signalling molecules. We identified a novel propeller-FYVE [domain identified in Fab1p, YOTB, Vac1p and EEA1 (early endosome antigen 1)] protein, ProF, which is expressed in various cell lines and tissues and consists of seven WD-repeats and a FYVE domain. WD-repeat proteins offer a platform for protein–protein interactions by folding into a seven-bladed propeller-like structure, while the FYVE domain binds to phosphatidylinositol 3-phosphate present mainly on intracellular membranes. The ProF protein partially co-localizes with EEA1 on vesicular structures and binds to the protein kinases Akt and PKCζ/λ (protein kinase Cζ/λ) via its WD-repeat propeller. ProF interacts more strongly with the kinases after hormonal stimulation. Endogenously expressed ProF and the two kinases interact in brain and in the preadipocyte cell line 3T3-L1, suggesting a role in secretory vesicular processes. In summary, we describe a new binding partner for kinases, located on vesicular structures in specialized cells, which may play a role for the spatial organization of signalling cascades.

A silicon-on-metal-on-insulator substrate, consisting of a top Si layer, a buried CoSi2 layer and a buried SiO2 layer on a Si (1 0 0) substrate was formed using Co silicidation, wafer bonding and wafer splitting. It is shown that the buried silicide layers in this structure exhibit a much higher thermal stability than surface layers. Resistivity measurements and cross-sectional transmission electron microscopy investigations revealed that buried CoSi2 layers withstand furnace anneals at 1000 °C up to 2 h, while surface CoSi2 layers started to degrade after 10 min anneals at 1000 °C. The proposed substrate is most useful for BiCMOS applications.

The successful fabrication of a silicon on metal on insulator (SOMI) substrate with a structured buried silicide layer for BICMOS applications is shown in this paper. The cobalt silicide is used as the buried silicide layer in the SOMI substrate because of its high thermal stability, low resistivity and easier fabrication process. Conventional cobalt salicide process was used to form CoSi"2 structures. The SOMI substrate was fabricated on the wafer level using wafer bonding, CMP and back grinding technologies. A SOMI substrate, consisting of a 300nm thick top-Si, a buried thin CoSi"2 layer, a buried SiO"2 layer on a silicon substrate, was formed using an SOI substrate as the starting material. The buried silicide layer has a resistivity of 16.3@m@Wcm and shows a high thermal stability which is sufficient for device applications.

Aligned liquid crystalline nanowires within ordered porous alumina templates show a pronounced texture on a macroscopic scale. We have investigated the influence of the geometric confinement and the nature of the pore walls on the mesophase formation by means of X-ray diffraction. The apparent texture is the result of a complex interplay of the pore geometry, interfacial phenomena, and the thermal history. Pores with a diameter of a few hundred nm guide the mesophase formation more efficiently than those with a diameter below 100 nm.

Low-pressure rf plasmas have been applied for etching of ultra-low-k SiCOH wafers using an Oxford Plasmalab System 100. In pure CF4 plasmas, SiCOH layers have been etched for different power values. Using quantum cascade laser absorption spectroscopy in the mid-infrared spectral range, the correlation of online and in situ measured concentrations of two etching products, CO and SiF4, with the ex situ determined etching rates has been studied. The concentration of SiF4 was found to range between 0.6 and 1.4 × 1013 molecules cm−3. In contrast the concentrations of CO were measured to be only about 50 % of the SiF4 density with 7 × 1012 molecules cm−3 in maximum. The production rate of SiF4, determined from the time behavior of its concentration after plasma ignition, was found to be between 1 and 5 × 1012 cm−3 s−1. The etching rates varied between 2 and 7 nm s−1. Both parameters increase nearly linearly with the applied rf power. It was found that for power values of up to 1.1 kW, the etching rate depends nearly linearly on the in situ monitored concentrations of both etching products. Therefore, the concentration of the etching products can be directly used as a measure of the etching rate.

The availability of efficient low-cost ultraviolet (UV) film polarizers is of vital importance to a number of applications, which rely on the use of polarized light in the near-UV regime. We describe here the preparation of such elements based on stretch-oriented films comprising poly(vinyl alcohol) and a combination of two commercially available azo dyes, Congo Red and Chrysophenine. Films of various dye contents were prepared and oriented by uniaxial tensile deformation. Moderately stretched films (draw ratio l/l0 = 4–8) exhibit a pronounced optical dichroism, characterized by a polarizing efficiency up to 0.98 at a wavelength of 365 nm. Initial experiments suggest that, even under rather harsh irradiation conditions and without any packaging, these azo-dye-based polarizers are surprisingly inert under simulated operating conditions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1235–1239, 2002

The present paper explores the possibility of orienting columnar discotic liquid-crystalline (LC) materials and causing a uniaxial “in-plane” orientation of the columns along the orientation direction. The discotic LCs employed were based on 2-hydroxy-3,6,7,10,11-penta(1-butoxy)triphenylene, which was derivatized with 1-adamantenecarboxylic acid (Ada-PBT) and 10-undecenoic acid (ω-undecenoyl-PBT), respectively. As unequivocally shown by optical microscopy, uniaxial alignment of columnar Ada-PBT structures was readily achieved by spin-coating this material onto a poly(tetrafluoroethylene) orientation layer. Annealing of the films at temperatures at which the Ada-PBT was in its hexagonal plastic or hexagonal ordered mesophase slightly increased the degree of orientation. The optical absorption and photoluminescence spectra of oriented Ada-PBT films were significantly polarized, with absorption and emission dichroic ratios of 6.5 and 3, respectively. The optical anisotropy is unambiguously related to the uni...

Dielectric lens antennas are proposed for wireless broadband communication systems in the mm-wave range. Two lens antenna configurations for base station applications are presented and evaluated in terms of radiation characteristics, feeding system, input reflection loss, bandwidth and fabrication tolerances. The system requirements to provide optimum power distribution over the cell and good control of the cell boundaries are achieved. These lens antennas are designed for circular symmetric cell coverage and use a circular waveguide as the feed targeting typical applications at 60 GHz and 40 GHz range. The same concept is applicable for non- symmetrical cells with other feeds. Simulations are performed using Geometrical and Physical Optics codes as well as Finite Elements codes. Theoretical results are verified by measurements, showing good agreement.

Process of plasma etching of CVD low-k dielectric was studied. We used CF3Br low pressure ICP plasma for etching at cryo temperatures (-20°C — -100°C), pressures (5-20 mTorr) and RF bias with effective DC voltage 80-140 V. Refractive index of film and its thickness were measured by spectral ellipsometry. Ellipsometric porosimetry was employed to compare pore size distribution before and after etching of films. Measurements show increasing of etch rate increase with decreasing sample temperature.

This paper describes a three-step process regime for the integration of porous SiCOH based ultra low-k materials in existing copper damascene technologies. During the work with these complex and sensitive materials, it became more and more clear, that a successful patterning depends not only on the etch step but also on the adjustment between the etch and the following cleaning and k-restore processes. The presented process regime starts with a reactive ion etch process for trench patterning followed by a post etch clean to remove etch residues. Finally a k-restore process was performed to repair the damaged regions in the trench sidewalls. In this work it became clear, that the etch chemistry influences not only the results of the etch process ostensibly sidewall damage but also kind and effect of the post etch clean. Each plasma composition results in the necessity of a customized post etch cleaning solution. Finally a k-restore process using Hexamethyldisilazane (HMDS) as restore chemical was demonstrated successfully. Enhanced temperatures and an additional UV-treatment are possibilities to promote the restore effect.

Spectroscopic ellipsometry is emerging as a routine tool for in-situ and ex-situ thin-film characterization in semiconductor manufacturing. For interconnects in ULSI circuits, diffusion barriers of below 10nm thickness are required and precise thickness control of the deposited layers is indispensable. In this work, we studied single films of tantalum and two stoichiometries of tantalum nitride as well as TaN/Ta film stacks both on bare and oxidized silicon. Spectroscopic ellipsometry from the UV to the NIR was applied to determine the optical properties of the films for subsequent modeling by a Lorentz-Drude approach. These models were successfully applied to TaN/Ta thin-film stacks where the values of the film thickness could be determined exactly. Moreover, it is shown that considerable differences in the optical properties arise from both film thickness and substrate. ©2006 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

Dielectric etching plasma processes for modern interlevel dielectrics become more and more complex by the introduction of new ultra low-k dielectrics. One challenge is the minimization of sidewall damage, while etching ultra low-k porous SiCOH by fluorocarbon plasmas. The optimization of this process requires a deeper understanding of the concentration of the CF2 radical, which acts as precursor in the polymerization of the etch sample surfaces. In an industrial dielectric etching plasma reactor, the CF2 radical was measured in situ using a continuous wave quantum cascade laser (cw-QCL) around 1106.2 cm−1. We measured Doppler-resolved ro-vibrational absorption lines and determined absolute densities using transitions in the ν3 fundamental band of CF2 with the aid of an improved simulation of the line strengths. We found that the CF2 radical concentration during the etching plasma process directly correlates to the layer structure of the etched wafer. Hence, this correlation can serve as a diagnostic tool ...

We have recently shown that the Ras-Raf-MEK-ERK and phosphatidylinositol 3-kinase (PI3K)-Akt signaling pathways can cross-talk in the human breast cancer cell line MCF-7. High Raf activity induces growth arrest and differentiation in these cells, whereas high PI3K/Akt activity correlates with cell survival and proliferation. Here we show that the Raf-Akt cross-talk is regulated in a concentration- and ligand-dependent manner. High doses of insulin-like growth factor I (IGF-I) activate Akt quickly and strongly enough to suppress Raf kinase activity via phosphorylation of Ser-259, whereas low doses of IGF-I do not trigger this cross-talk but are still mitogenic. Phorbol 12-myristate 13-acetate, a differentiation-inducing stimulus, potently activates the Ras-Raf-MEK-ERK pathway but only weakly activates PI3K/Akt and does not trigger the cross-talk. Thus, the herein analyzed parameters such as ligand type, concentration, and time course may contribute to the cellular response of either proliferation or differentiation. This is highly relevant to understanding cellular transformation and may be of use in areas like tissue engineering.

The stimulation of platelet-derived growth factor (PDGF) receptors shifts vascular smooth muscle (VSM) cells toward a more proliferative phenotype. Thrombin activates the same signaling cascades in VSM cells, namely the Ras/Raf/MEK/ERK and the phosphatidylinositol 3-kinase (PI 3-kinase)/Akt pathways. Nonetheless, thrombin was not mitogenic, but rather increased the expression of the smooth muscle-specific myosin heavy chain (SM-MHC) indicative of an in vitro re-differentiation of VSM cells. A more detailed analysis of the temporal pattern and relative signal intensities revealed marked differences. The strong and biphasic phosphorylation of ERK1/2 in response to thrombin correlated with its ability to increase the activity of the SM-MHC promoter whereas Akt was only partially and transiently phosphorylated. By contrast, PDGF, a potent mitogen in VSM cells, induced a short-lived ERK1/2 phosphorylation but a complete and sustained phosphorylation of Akt. The phosphorylated form of Akt physically interacted with Raf. Moreover, Akt phosphorylated Raf at Ser(259), resulting in a reduced Raf kinase activity and a termination of MEK and ERK1/2 phosphorylation. Disruption of the PI 3-kinase signaling prevented the PDGF-induced Akt and Raf-Ser(259) phosphorylation. Under these conditions, PDGF elicited a more sustained MEK and ERK phosphorylation and increased SM-MHC promoter activity. Consistently, in cells that express dominant negative Akt, PDGF increased SM-MHC promoter activity. Furthermore, expression of constitutively active Akt blocked the thrombin-stimulated SM-MHC promoter activity. Thus, we present evidence that the balance and cross-regulation between the PI 3-kinase/Akt and Ras/Raf/MEK signaling cascades determine the temporal pattern of ERK1/2 phosphorylation and may thereby guide the phenotypic modulation of vascular smooth muscle cells.

Extracellular signals often result in simultaneous activation of both the Raf-MEK-ERK and PI3K-Akt pathways (where ERK is extracellular-regulated kinase, MEK is mitogen-activated protein kinase or ERK kinase, and PI3K is phosphatidylinositol 3-kinase). However, these two signaling pathways were shown to exert opposing effects on muscle cell hypertrophy. Furthermore, the PI3K-Akt pathway was shown to inhibit the Raf-MEK-ERK pathway; this cross-regulation depended on the differentiation state of the cell: Akt activation inhibited the Raf-MEK-ERK pathway in differentiated myotubes, but not in their myoblast precursors. The stage-specific inhibitory action of Akt correlated with its stage-specific ability to form a complex with Raf, suggesting the existence of differentially expressed mediators of an inhibitory Akt-Raf complex.

Activation of the protein kinase Raf can lead to opposing cellular responses such as proliferation, growth arrest, apoptosis, or differentiation. Akt (protein kinase B), a member of a different signaling pathway that also regulates these responses, interacted with Raf and phosphorylated this protein at a highly conserved serine residue in its regulatory domain in vivo. This phosphorylation of Raf by Akt inhibited activation of the Raf-MEK-ERK signaling pathway and shifted the cellular response in a human breast cancer cell line from cell cycle arrest to proliferation. These observations provide a molecular basis for cross talk between two signaling pathways at the level of Raf and Akt.

Fur den Workshop „Gesellschafts- und steuerrechtliche Strategien ftir Familienunternehmen“ thematisierte Herr Hemmelrath die Strategien zur Gestaltung von Untemeh- mensstrukturen, Strategien bei Familienuntemehmen mit Kapitalbedarf und Strategien zur Nachfolgeregelung im Familienuntemehmen.1

Growth factor stimulated receptor tyrosine kinases activate a protein kinase cascade via the serine/threonine protein kinase Raf-1. Direct upstream activators of Raf-1 are Ras and Src. This study shows that MEK1, the direct downstream effector of Raf-1, can also stimulate Raf-1 kinase activity by a positive feedback loop. Activated MEK1 mediates hyperphosphorylation of the amino terminal regulatory as well as of the carboxy terminal catalytic domain of Raf-1. The hyperphosphorylation of Raf-1 correlates with a change in the tryptic phosphopeptide pattern only at the carboxy terminus of Raf-1 and an increase in Raf-1 kinase activity. MEK1-mediated Raf-1 activation is inhibited by co-expression of the MAPK specific phosphatase MKP-1 indicating that the MEK1 effect is exerted through a MAPK dependent pathway. Stimulation of Raf-1 activity by MEK1 is independent of Ras, Src and tyrosine phosphorylation of Raf-1. MEK1 can however synergize with Ras and leads to further increase of the Raf-1 kinase activity. Thus, MEK1 can mediate activation of Raf-1 by a novel positive feedback mechanism which allows fast signal amplification and could prolong activation of Raf-1.

not Available.