Fraunhofer Center Nanoelectronic Technologies

Dresden, Germany

Fraunhofer Center Nanoelectronic Technologies

Dresden, Germany

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Boscke T.S.,Loberwallgraben 2 | Boscke T.S.,NaMLab gGmbH | Teichert S.,UAS Jena | Brauhaus D.,RWTH Aachen | And 5 more authors.
Applied Physics Letters | Year: 2011

We investigated phase transitions in ferroelectric silicon doped hafnium oxide (FE-Si:HfO2) by temperature dependent polarization and x-ray diffraction measurements. If heated under mechanical confinement, the orthorhombic ferroelectric phase reversibly transforms into a phase with antiferroelectric behavior. Without confinement, a transformation into a monoclinic/tetragonal phase mixture is observed during cooling. These results suggest the existence of a common higher symmetry parent phase to the orthorhombic and monoclinic phases, while transformation between these phases appears to be inhibited by an energy barrier. © 2011 American Institute of Physics.


Schunemann C.,TU Dresden | Wynands D.,Leibniz Institute of Polymer Research | Wynands D.,University of California at Santa Barbara | Wilde L.,Fraunhofer Center Nanoelectronic Technologies | And 7 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

To achieve efficient organic solar cells, donor and acceptor molecules are mixed in the photoactive layer to form a so-called bulk heterojunction. Due to molecular interactions, a certain degree of phase separation between donor and acceptor domains arises, which is necessary to achieve efficient charge extraction within the absorber layer. However, the mechanism that induces the phase separation is not fully understood and gaining detailed information about the molecular arrangement within these blend layers is quite challenging. We show that grazing incidence x-ray diffraction, combined with variable angle spectroscopic ellipsometry is a suitable way to investigate the molecular structure of blend layers in detail, consisting of a mixture of zinc-phthalocyanine (ZnPc) and C 60. The degree of phase separation within the blend layer is influenced by substrate heating during the co-evaporation of ZnPc and C 60 and by a variation of the mixing ratio. The effect of different blend layer morphologies on optical and electrical device performance is investigated by solar cell characterization and mobility measurements. We find that the molecular arrangement of C 60 provides the essential driving force for efficient phase separation. Whereas spherical C 60 molecules are able to form crystalline domains when deposited at elevated substrate temperatures, no ZnPc crystallites are observed, although the planar ZnPc molecules are not randomly oriented but standing upright within its domains. Comparing specular and grazing incidence x-ray diffraction, we find that only the latter method is able to detect nanocrystalline C 60 in thin films due to its polycrystalline nature and small sized nanocrystallites. Solar cell measurements show an increase in fill factor and external quantum efficiency signal for blends with enhanced phase separation, induced by higher substrate temperatures. However, grazing incidence x-ray diffraction measurements reveal that ZnPc and C 60 already form separate domains in unheated ZnPc:C 60 blends, which provide fill factors close to 50% in the corresponding solar cells. © 2012 American Physical Society.


Muller J.,Fraunhofer Center Nanoelectronic Technologies | Boscke T.S.,Lberwallgraben 2 | Brauhaus D.,RWTH Aachen | Schroder U.,NaMLab gGmbH | And 6 more authors.
Applied Physics Letters | Year: 2011

We report the observation of ferroelectricity in capacitors based on hafnium-zirconium-oxide. Hf0.5Zr0.5O2 thin films of 7.5 to 9.5 nm thickness were found to exhibit ferroelectric polarization-voltage hysteresis loops when integrated into TiN-based metal-insulator-metal capacitors. A remnant polarization of 16 C/cm2 and a high coercive field of 1 MV/cm were observed. Further proof for the ferroelectric nature was collected by quasi-static polarization-voltage hysteresis, small signal capacitance-voltage, and piezoelectric measurements. Data retention characteristics were evaluated by a Positive Up Negative Down pulse technique. No significant decay of the initial polarization state was observed within a measurement range of up to two days. © 2011 American Institute of Physics.


Oszinda T.,Fraunhofer Center Nanoelectronic Technologies | Oszinda T.,Fraunhofer Center Nanoelektronische Techonlogien | Schaller M.,Globalfoundries | Schulz S.E.,TU Chemnitz
Journal of the Electrochemical Society | Year: 2010

A vapor phase based silylation process was used to restore plasma damaged porous ultra low- κ SiOCH dielectric films. The process was carried out with 11 different silylation agents. After the processing of blanked wafers, the restoration performance was analyzed by different analytic techniques such as Fourier infrared and Auger electron spectroscopy as well as contact angle, ellipsometric porosimetry, and mercury probe measurements. Quantum mechanic calculations and practical results suggest three repair chemicals having two reactive groups to be most promising. However, a comparable electrical improvement, i.e., κ -value improvement, was achieved with chemicals having one reactive group. The removal of water during the high temperature silylation process is suggested to be the main contributor to the κ -value improvement. The recovery of the surface free energy inhibits or retards water from returning after the silylation process. The chemicals with two reactive groups providing the highest degree of silylation are found to be most appropriate for ultra low- κ dielectric (ULK) recovery. But, depending on the requirement for ULK restoration (e.g., κ -value, surface recovery, etc.), chemicals having one reactive group can be sufficient as well. © 2010 The Electrochemical Society.


Zhou D.,Dalian University of Technology | Zhou D.,NaMLab gGmbH | Muller J.,Fraunhofer Center Nanoelectronic Technologies | Xu J.,Fraunhofer Center Nanoelectronic Technologies | And 4 more authors.
Applied Physics Letters | Year: 2012

Silicon doped hafnium oxide thin films were recently discovered to exhibit ferroelectricity. In the present study, metal-ferroelectric-metal capacitors with Si:HfO 2 thin films as ferroelectric material and TiN as electrodes have been characterized with respect to capacitance and current density as functions of temperature and applied voltage. Polarity asymmetry of the frequency dependent coercive field was explained by interfacial effects. No ferroelectric-paraelectric phase transition was observed at temperatures up to 478 K. Clear distinctions between current evolutions with or without polarization switching were correlated to the time competition between the measurement and the response of relaxation mechanisms. © 2012 American Institute of Physics.


Vasilev B.,Fraunhofer Center Nanoelectronic Technologies | Bott S.,Fraunhofer Center Nanoelectronic Technologies | Rzehak R.,Helmholtz Center Dresden | Kucher P.,Fraunhofer Center Nanoelectronic Technologies | Bartha J.W.,TU Dresden
Microelectronic Engineering | Year: 2012

Chemical mechanical planarization (CMP) models which are able to make predictions on the chip and feature scale are highly desirable in semiconductor manufacturing. Most of the models proposed in the past years have largely focused on the pattern density and neglected effects of pattern size in planarization. We here propose a new CMP feature scale model that incorporates size effects by considering the roughness of the polishing pad. It is validated by experimental data from CMP test structures containing variations of both pattern-density and -size. The results are applied to ILD- and STI-CMP as particularly important processes in industry. The derived model describes the feature step height and shape evolution with high accuracy throughout the planarization process. © 2011 Elsevier B.V. All rights reserved.


Vasilev B.,Fraunhofer Center Nanoelectronic Technologies | Bott S.,Fraunhofer Center Nanoelectronic Technologies | Rzehak R.,Helmholtz Center Dresden | Liske R.,Fraunhofer Center Nanoelectronic Technologies | Bartha J.W.,TU Dresden
Microelectronic Engineering | Year: 2013

Chemical-mechanical planarization (CMP) is one of the most demanding process steps in interconnect integration. Therefore, with respect to the pad roughness, we systematically characterize and model the planarization of special CMP test chips, which emulate integrated circuit (IC) layouts. Therefore, a novel pad roughness characterization methodology is developed and used for the extraction of important pad surface parameters like the mean asperities radius of curvature and the asperities size distribution. The obtained pad surface data is used for the derivation of a novel chip scale CMP model based on the Greenwood-Williamson theory. It is validated by experimental data from CMP test structures containing variations of both pattern-density and pattern-size and describes the wafer topology evolution with high accuracy throughout the planarization process, indicating a strong impact of the asperities size distribution on the planarization in test chip areas having trench widths smaller than the mean asperities radius of curvature. © 2012 Elsevier B.V. All rights reserved.


Mueller S.,NaMLab gGmbH | Mueller J.,Fraunhofer Center Nanoelectronic Technologies | Singh A.,NaMLab gGmbH | Riedel S.,Fraunhofer Center Nanoelectronic Technologies | And 3 more authors.
Advanced Functional Materials | Year: 2012

Incipient ferroelectricity is known to occur in perovskites such as SrTiO 3, KTaO 3, and CaTiO 3. For the first time it is shown that the intensively researched HfO 2 thin films (16 nm) also possess ferroelectric properties when aluminium is incorporated into the host lattice. Polarization measurements on Al:HfO 2 based metal-insulator-metal capacitors show an antiferroelectric-to-ferroelectric phase transition depending on annealing conditions and aluminium content. Structural investigation of the electrically characterized capacitors by grazing incidence X-ray diffraction is presented in order to gain further insight on the potential origin of ferroelectricity. The non-centrosymmetry of the elementary cell, which is essential for ferroelectricity, is assumed to originate from an orthorhombic phase of space group Pbc2 1 stabilized for low Al doping in HfO 2. The ferroelectric properties of the modified HfO 2 thin films yield high potential for various ferroelectric, piezoelectric, and pyroelectric applications. Furthermore, due to the extensive knowledge accumulated by various research groups regarding the HfO 2 dielectric, an immediate relevance of ferroelectric hafnium oxide thin films is anticipated by the authors. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Hermann P.,Robert Koch Institute | Hermann P.,Fraunhofer Center Nanoelectronic Technologies | Fabian H.,Robert Koch Institute | Naumann D.,Robert Koch Institute | Hermelink A.,Robert Koch Institute
Journal of Physical Chemistry C | Year: 2011

Raman spectroscopic characterization of biological nanostructures requires near-field techniques, which provide nanoscale resolution and high sensitivity simultaneously. Tip-enhanced Raman spectroscopy provides the required sensitivity to obtain chemical and structural information from such small structures. However, near-field spectra typically show significant intensity variations and band shifts when comparing the spectroscopic information acquired from sample positions even a few nm apart. In the present study, we compare far-field and near-field Raman spectra of silicon-based samples and biological nanostructures like avipox virus or amyloid fibrils. It is found that the width of the bands in tip-enhanced spectra is typically narrower than in the corresponding far-field spectra. Additionally, the observed spectral variations in near-field Raman spectra are strongly influenced by the structural and chemical heterogeneity of the sample. © 2011 American Chemical Society.


Finn A.,TU Dresden | Lu B.,TU Dresden | Kirchner R.,TU Dresden | Thrun X.,Fraunhofer Center Nanoelectronic Technologies | And 2 more authors.
Microelectronic Engineering | Year: 2013

Polymeric molds replicated from a master structure can provide intrinsic anti-sticking behavior and UVtransparency. They can be replicated from various substrates and offer cost efficient replication of multiple working stamps from only one master. They also allow the use of various imprint methods including UV- or thermal-assisted ones. Usually, the polymer material exhibits mechanical and surface-chemical properties which differ from hard mold materials like silicon, silicon dioxide or metals. Due to this, the molds might be deformed or even destroyed during imprint or cleaning. This is pronounced for high aspect ratio patterns, as they occur, if imprint is used as direct pattering method. The affinity to pattern damage of polymeric molds during cleaning is investigated in this paper. Different possible polymeric mold materials are considered. Experimental data is compared to simulation results and shows good agreement. Different exemplary patterns are investigated and a best suitable material is found. It is stable for feature aspect ratios up to 10 for half pitch gratings in the considered range of dimensions. © 2013 Elsevier B.V. All rights reserved.

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