MEMS Sensor Elements and their Fabrication Dr.-Ing. Detlef Billep Page 1
Content 1. The Fraunhofer-Gesellschaft and / ZfM 2. MEMS Inertial Sensors 3. MEMS Design 4. Fabrication Technology 5. Characterization and Test Page 2
The Fraunhofer-Gesellschaft The Fraunhofer-Gesellschaft undertakes applied research of direct utility to private and public enterprise and of wide benefit to society. Our Customers: Industry Service sector Public administration Fraunhofer
The Fraunhofer-Gesellschaft in Germany Itzehoe Lübeck Rostock Bremerhaven Bremen 60 Institutes 17 000 employees Hannover Oberhausen Dortmund Duisburg Schmallenberg St. Augustin Aachen Euskirchen Wachtberg Braunschweig Halle Schkopau Ilmenau Potsdam Magdeburg Jena Leipzig Chemnitz Berlin Teltow Cottbus Dresden St. Ingbert Darmstadt Saarbrücken Karlsruhe Pfinztal Ettlingen Stuttgart Freiburg Kaiserslautern Würzburg Fürth Erlangen Nürnberg Freising München Holzen Efringen- Kirchen Holzkirchen Fraunhofer
Key Activity Contract Research (million euros) 919 1 068 1 032 1 164 1 291 98 million Other Revenues 61 million Revenues EU-Projects 248 million Revenues Public Projects (Federal, German Länder) 452 million Revenues Contract Financing (Industry) 432 million Institutional Funding 2004 2005 2006 2007 2008 Fraunhofer
Locations Itzehoe Lübeck Rostock Bremen Hannover Berlin Potsdam Paderborn Chemnitz Teltow Braunschweig Nuthetal Magdeburg Paderborn Oberhausen Cottbus Dortmund Halle Schmallenberg Leipzig Schkopau Duisburg Dresden Sankt Augustin Aachen Ilmenau Jena Euskirchen Chemnitz Darmstadt Würzburg Kaiserslautern Erlangen Wertheim St. Ingbert Saarbrücken Pfinztal Nürnberg Karlsruhe Stuttgart Freising Freiburg München Efringen-Kirchen Holzkirchen Page 6
Smart Systems Campus Chemnitz memsfab GmbH EDC GmbH Institute of Physics and Center for Microtechnologies Page 7
Clean room facilities Center for Micro Technologies 1000 m 2 clean rooms 300 m 2 clean room class ISO 4 (class 10) Processing of 4, 6 and 8 wafers ZfM RR1 350 m² rooms of increased cleanness ZfM RR 2 Page 8
ZfM (Center for Microtechnologies) A look behind the doors of the clean room facilities Page 9
Chemnitz University of Technology Basic Research Applied Research Industrial Projects Page 10 Commercialization
2 MEMS Inertial Sensors Acceleration Linear acceleration Tilt Vibration and shock Gyroscope Rate of rotation Page 11
Signal Processing Motion-Sensing Activity Monitoring Situational Awareness User Interface Image Stabilization Tilt Display Control Enhanced gaming experience Electronic compass compensation Keystone effect correction Vibration Condition Monitoring Rotation Directional Awareness Shock Shock detection for micro-drive protection Page 12
Inertial devices performance Main parameter is the inherent bias stability This is in-run drift or 1-y bias repeatability: The error independent of inertial rate or acceleration In µg or /hr Trend: Tactical grade IMUs integrate gyroscopes with 5 /hr to 0.1 /hr bias stability 1 Further specific requirements in term of: Dynamic range Bandwidth Run to run drift Volume Harsh environment compatibility Power consumption Certification Lifetime 1 Yole Développement SA Market Report 2009 Accelerometer long term Bias Repeatability Definition of application grades Gyroscope Bias Stability 10g 1 /s 1mg 100 /h 100mg 10 /h 10mg 1 /h 1mg 0,1 /h 100ug 0,01 /h 10µg 0,001 /h 1µg 0,0001 /h Corresponding Grade Industrial Tactical Navigation Strategic Page 13
MEMS inertial market will be a $3B market in 2013! Yole Développement SA Market Report 2009 Page 14
3 MEMS Design Page 15
MEMS design: modeling and simulation Conceptual design: F C = 2 m v Ω Operating principle (capacitive, magnetic, ) Functional elements and materials Geometrical and physical parameters Component design: Static and dynamic response Sensitivity, bandwidth, fracture strength Cross-talk, thermal drift, tolerances System design: Model order reduction and export Controller and overall system design Performance analysis and optimization Page 16
Conceptual design Coriolis force principle: Block diagram simulation methodology Architecture: Lateral bending springs Ω Detection oscillation F C = 2 m v Ω Specified performance: High quality resonators (Q up to 100,000 in vacuum) Measurement range: 100 /s Bias < 5 /h Noise < 0.2 /sqrt(h) Excitation oscillation Anchor Circuit simulation methodology Page 17
Methodology of component design for MEMS Layout: Challenges: - Interactions among physical domains - Non-linearities, tolerances, cross-talk CAD model: Coupled domain simulations: FEM model: Fluid structural interactions: Page 18 (Dr. J. Mehner, Abt. MDI)
Finite element simulations of coupled fields Warp due to packaging stress: Mechanical stress during operation: Damping in the surrounding air: Electrostatic fields needed for force balance: r F el F m M Page 19
System Design Amplitude Control Loop Phase Locked Loopx Drive Amplitude Detection MEMS Sense Amplitude Detection Quadrature Compensation Loop Rate Control Loop Simulink-model of the gyroscope according to the IEEE-Standard 1431 Page 20
4 Fabrication technology Page 21
The BDRIE technology flow for inertial sensors Cross section of the glass Si glass variant glass Active structure Si glass Contact hole with metallisation Page 22
The BDRIE technology flow for inertial sensors 1 Glass (400 µm thickness) with sandblasted holes Si 300 µm, with etched cavities on the bottom side Anodic bonding Page 23
The BDRIE technology flow for inertial sensors 2 Thinning of the Si wafer (grinding and polishing) down to 50 µm thickness of the active layer Dry etching of Si Page 24
The BDRIE technology flow for inertial sensors 3 Glass (500 µm thickness) Wet etching of a cavity Anodic bonding with active wafer Metal deposition for through contacts Page 25
5 Characterization and Test Page 26
Characterization and analysis Microscopy (SEM, EDX, AFM, SPM, ultra sonic, laser scanning, FIB) Ellipsometer, optical spectroscopy Laser and surface profilometer Nanotom computer tomography Tension/compression testing, dynamic mechanical analyser, thermo mechanical analyser, materials test Nanoindentation MicroDAC / NanoDAC / FIBDAC Page 27
MEMS Parameter Test Parameter identification of geometrical and material parameters with help of dynamic parameters Design validation Parameter: Sensitivity Surface roughness Mode shapes, eigenfrequencies Electrical parameters Optical performance RF-Properties Shock Page 28
Conclusion What is necessary to create MEMS? MEMS design, fabrication and test Reliability Integration Packaging technology Software Development ASIC Design, fabrication and test Page 29
cooperation with industry (selection) Page 30