Materialien für die Nanosensorik Jörg Schuster, Department Back End of Line (BEOL) joerg.schuster@enas.fraunhofer.de Schuster Seite 1
Fraunhofer Institute for Electronic Nanosystems Systems integration by using of micro and nano technologies MEMS/NEMS design Development of MEMS/NEMS MEMS/NEMS test System packaging/waferbonding International Offices of : Since 2001/2005 Tokyo/Sendai, Japan Back-end of Line technologies for micro and nano electronics Process and equipment simulation Since 2012 Since 2002 Since 2007 Project-Center in Sendai Shanghai, China Manaus, Brazil Micro and nano reliability Printed functionalities Advanced system engineering Schuster Seite 2
Microflex Center Chemnitz 3D-Micromac AG, 3D-Micromac AG Lightweight Structures Engineering Start-up-building Institute of Physics and Center for Microtechnologies at the CUT Page 3
Smart Systems from the Device Point of View Processor Integration & Packaging & Radio Memory Power Sensor & Actuator MEMS / NEMS Electronic Components Communication Unit Prof. T. Gessner Page 4
Trends in der Nanoelektronik Seite 5
Nanosensorik? MEMS = Micro Electro Mechanical System (z. B. Inertialsensoren) NEMS = Nano Electro Mechanical System Kleiner, aber stark wachsender Markt Zukunftstechnologie Schuster Seite 6
Nanosensorik? Nanoskalig (typ. < 100 nm) Größenabhängige Eigenschaften Quanteneffekte Extrem Strukturabhängige Eigenschaften Top down - Lithografie, Si-Technologie Bottom up - Nanotechnologie, Selbstorganisation Schuster Seite 7
Nanosensorik? Chemisch - Erkennung von Molekülen - Oftmals Schlüssel Schloss-Prinzip - Selektivität! - optisches oder elektronisches Signal Viele biologische Systeme stellen funktionierende chemische Nanosensoren dar. Physikalisch - Physikalische Größen (Druck, Temperatur, Beschleunigung, Licht) Schuster Seite 8
Nanomaterialien? Nanostrukturen - Strukturierung (Si-Nanodrähte) - Synthese (Kohlenstoffnanoröhrchen, Halbleiternanokristalle) Nanokomposite - Nanoskalige Komponente in kontinuierlicher Matrix Schuster Seite 9
Silizium Nanodrähte Larysa Baraban, Cuniberti group, TU Dresden Schuster Seite 10
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Current Topics of the Group Optical and Nanocomposite-based Systems Jörg Martin Jörg Martin Page 13
Integration of Nanomaterials Humidity Sensors Schematic setup of composite sensor H 2 O Ceramic Particles Mesurement principle adsorption of water molecules on particles sensitive particles: ceramics polymer matrix: PMMA increase of dielectric constant change of capacity Jörg Martin Page 14
Integration of Nanomaterials Humidity Sensors change of sensor capacity up to nearly 130 % 10 mm response times in the range of 15 20 sec comparable with commercial sensors Change of capacity (%) Kapazitätsänderung (%) Capacity change as function of humidity 150 0 0 %% SiOCeramic 2 Particles 125 20 20 %% SiOCeramic 2 Particles 40 % SiO 40 % Ceramic 2 Particles 100 60 % SiO 60 % Ceramic 2 Particles 75 50 25 0 20 30 40 50 60 70 80 Relative Rel. Luftfeuchte humidity (%) (%) Jörg Martin Page 15
Semiconductor Nanocrystals fluorescence = recombination of electronhole-pairs (excitons) photon energy depends on size 5 P. F. Trwoga, et al., J. Appl. Phys. 83, 3789 (1998). Bandgap (ev) 4 3 2 1 2 3 4www.invitrogen.com 5 6 Particle Diameter (nm) Wavelenght (and other parameters) depend on size of the particles. Jörg Martin Page 16
Overview Semiconductor Nanocrystals Special photophysical properties Quantum Confinement Sensitivity against electrical charges Usage as light emitters LEDs, displays fluorescence markers Usage as Nanosensors Optical detection of charges and electrical fields Jörg Martin Page 17
Load Detection with Nanocrystals Nanocrystal Layer Piezoelectric Foil Lightweight Structure Force Jörg Martin Page 18
Spintronik Erzeugung und Untersuchung spintronischer Schichtsysteme Laufzeit: 3 Jahre seit 01.01.2011 Partner: TUC Professor Albrecht HSMW Prof. Exner HSMW Prof. Weißmantel ENAS Prof- Stefan Schulz Ziel: 3achsiger GMR-Sensor Ramona Ecke Page 19
Spintronik - Grundlagen Magnetwiderstand = Verhältnis des Widerstandes eines Materials ohne und mit externem Magnetfeld GMR = Riesenmagnetwiderstand in Vielfachschichtsystemen mit dünnen ferromagnetischen und nichtmagnetischen Schichten (Fe/Cr) Anlegen eines Magnetfeldes Widerstandsänderung R = ferromagnetische (parallele) Austauschkopplung R = antiferromagnetische (antiparallele) Austauschkopplung Ramona Ecke Page 20
Spintronik Grundlagen der Schichtsysteme Klassisch Spin-Valve Spin Valve mit AAF 2 magnetische (M) Schichten durch eine durch eine nichtmagnetische (NM) getrennt Dicke der NM so, dass sich ohne Magnetfeld eine antiferromagnetische Kopplung einstellt äußeres Magnetfeld erzwingt parallele Ausrichtung der Magnetisierung R NM so dick, dass keine magn. Kopplung Untere M stark an antiferromagn. Schicht gekoppelt Hard Layer obere M weichmagnetisch Ummagnetisierung durch äußere Magnetfelder R-Änderung vergleichbar mit Variante 2, aber untere M ist ein künstlicher Antiferromagnet höhere Temperaturstabilität Reduzierung von Hysterese-Effekten Ramona Ecke Page 21
Displacement detection with CNTs integrated in NEMS Sascha Hermann, Sergei Loschek, Stefan E. Schulz, Contact Dr. Sascha Hermann Group leader CNT Integration and Application Fraunhofer Institute for Electronic Nano Systems (ENAS) Sascha.hermann@enas.fraunhofer.de Tel.: +49 371 531 35675
Motivation Capacitive silicon based MEMS for displacement detection 30 µm 30 µm MEMS acceleration sensor MEMS gyroscope Dienel, Dissertation, TU Chemnitz, 2009 Page 23 Sascha Hermann
Introduction: CNT-Structure Visualization of a CNT: roll-up of graphene sheet a 1 a 2 Θ C = na 1 + ma 2 Single-Walled Carbon Nanotube (SWCNT) - Graphene sheet: sp 2 hybridized C atoms - Definition of CNT by (n, m) Multi-Walled Carbon Nanotube (MWCNT) Page 24 Sascha Hermann
Introduction: CNT-Structure zigzag e.g. (9,0) armchair e.g. (5,5) chiral e.g. (7,3) Possible SWCNT types: semiconducting semimetallic metallic MWCNTs are metallic (n,m) Page 25 Sascha Hermann
Transducer principles Piezoresistive transducer principle Field emitting transducer principle Strain of a semiconducting SWCNT changes the band gap. A displacement changes electrical field strength on the CNT tip. Page 26 Sascha Hermann
Preparation of CNT dispersion CNT dispersion for the piezoresistive transducer Dry CNT dispersion for the Field emitting transducer Dispersion Semiconducting SWCNTs Metallic SWCNTs MWCNTs Dispersions with defined properties: Non-covalent functionalization Preparation procedures for mild separation but high separation grade Use of preselected SWCNTs (type/chirality) Use of length restricted CNTs Yu, H.; Hermann, S.; Schulz, S.E.; Geßner, T.; Dong, Z.; Li, W.J.: Optimizing Sonication Parameters for Dispersion of Single-walled Carbon Nanotubes Chem. Phys. (in press) Page 27 Sascha Hermann
Integration method for displacement sensors: Examples 15 µm 15 µm CNT deposition and alignment on 6 wafers demonstrated Integration of Pd electrodes CNT density can be controlled Coupling DEP for large CNT arrays Assembly of metallic, semiconducting SWCNTs and MWCNTs 2 µm 2 µm Page 28 Sascha Hermann
MEMS tool for test and characterization of CNT transducer Piezoresistive transducer principle Field emitting transducer principle CNT strain Contact reliability CNT to electrode displacement Field emission properties Page 29 Sascha Hermann
Piezoresistive Effect of CNTs Chirality dependent piezoresistive effect (6,2) CNT semiconducting (7,4) CNT semimetallic (6,6) CNT metallic Low diameter, High curvature Band gap [ev] Overlap of π-orbitals Analytical model DFT required! (Tight binding) Improved analytical model for high diameter CNTs Strain [%] Piezoresistive effect for (nearly) all CNTs available by DFT or AM Florian Fuchs, Bachelor thesis, ENAS/TUC 2012 C. Wagner, JS et al., phys. stat. sol. B, in press Schuster Seite 30
Nanomodels for Sensor System Simulation Piezoresistive effect Band gap by DFT or AM Simple resistivity model sensor window C. Wagner, JS et al., phys. stat. sol. B, in press Schuster Seite 31
DFG Research unit 1713: Sensoric Micro- and Nanosystems (SMINT) FEM-Model Design of components and systems based on new technologies Simulation of CNTs for sensor application Nanocharacterization Development of new materials and technologies Integration of Components and systems Opto-fluidic sensor element Array of rolled-uptubes Array of magnetic multilayer nano caps Functionalization of CNTs for sensors and interconnects 1,5 µm MOS-Detection
ENAS, TUC, HSMW, Nanosystemintegration, u.v.m. Zentrum für Materialien, Architekturen und Integration von Nanomembranen (MAIN) TUC, ENAS, IFW DD ENAS, TUC Nanosensoren in Leichtbaumaterialien, u.v.m. ENAS, TUC, TU DD CNT-Nanoelektronik, u.v.m. ENAS, FhG, Sensorik, Aktorik, u.v.m. Schuster Seite 33