MEMS technologies and sensor examples for industry, mobility and smart environment

Transcription

1 MEMS technologies and sensor examples for industry, mobility and smart environment Karla Hiller, TU Chemnitz, Zentrum für Mikrotechnologien, Reichenhainer Str. 70, Chemnitz, Thomas Otto (Director of ENAS and ZfM), Martina Vogel Danny Reuter, Sven Zimmermann, Chris Stöckel, Roman Forke, Dirk Wünsch Fraunhofer ENAS und TU Chemnitz, Zentrum für Mikrotechnologien

2 Outline 1. Introduction: Sensor needs for Internet of Things 2. MEMS technologies: examples for key process steps 3. MEMS encapsulation and integration technologies 4. Examples for MEMS sensors 5. Summary

3 Internet of Things a new dimension Until now the Internet was blind the Internet only connects people at anytime and anywhere, but the environment of these people could not be connected With the Internet of Things a new dimension could be connected: ANYTHING Source: Journal Internet of Things

4 Internet of Things Definition according to Yole Développement Internet of Things devices is the aggregation of all sensing modules which are linked to the Cloud either directly or through a gateway and with which data is processed and valorized in any manner.

5 smart car The Internet of Things consists of Systems of Cyber-Physical Systems communication Virtual World E 2 MS control represent control represent Real World Electronic Engineering & Manufacturing Services

6 Smart fab industry 4.0 communication Virtual World control represent control represent Real World

7 Fields of application E 2 MS Electronic Engineering & Manufacturing Services

8 IoT Structure according to Yole Yole report lists 112 companies and research institute

9 Smart Systems Definition based on SRA 2013 of EPoSS Self-sufficient intelligent technical systems or subsystems with advanced functionality, enabled by underlying micro- nano- and biosystems and other components Able to sense, diagnose, describe, qualify and manage a given situation Bring together sensing, actuation and informatics / communications Their operation being further enhanced by their ability to mutually address, identify and work in consort with each other Highly reliable, often miniaturized, networked, predictive and energy autonomous Autonomous or collaborative systems

10 Need for diversified sensors Machine Vision Optical Ambient Light Position/Presence/Proximity Acceleration Motion/Velocity/Displacement Electric/Magnetic Temperature Leaks/Levels Humidity/Moisture Acoustic/Sound/Vibration Force/Load/Torque Strain/Pressure Flow Chemical/Gas

11 The Enabling Factors of Smart Systems 11 Silicon Technologies Moore s Law: Miniaturization More than Moore: Functionalities 3D Structure : i.e. MEMS Through-Silicon Vias Heterogeneous Integration New Materials Getters Polymers Shape Memory Alloy Piezoelectric (PZT) SiC & GaN CNT, Graphene Spintronics, nano wires C Wafer Level Packaging (Staked Multi Dice) New interconnections (Bondless. Sintering, Cu on Cu) Smart System In Package (SiP) Package Orientation & Localization Algorithms Embedded Predictive & Reactive Capabilities IPs & Software

12 Technologies established in industry for inertial sensors Example 1: Epi-Poly-Technology (Bosch) Metal pad µm Epi-poly MEMS structure Isolator Si Example 2: XMB 10 cavity-soi (X-FAB) 1st poly (inner connects) Example: Gyroscope Source: R. Neul: IEEE Sensors Journal Vol. 7. No. 2 Feb 2007 Detail: Sensing comb Source: XMB 10 X-FAB Rev. 1.0 June 2013

13 MEMS technologies in Chemnitz ZfM/ENAS MEMS processes Lithography Wet etching Dry etching Layer deposition Wafer thinning Surface treatment Waferbonding MEMS Technologie flows Bulk technologies (with membranes and optical layers/gratings) HARM technologies for capacitive MEMS Gap reduction technologies AlN technology for piezoelectric MEMS Thin film encapsulation MEMS Devices Acceleration sensors Angular rate sensors Fabry-Perot filters HF switches MEMS speaker Ultrasonic transducers Bulk HARM AIM HARM BDRIE Thin film

14 Example: cavity-soi Principle: Wafer compound with pre-patterned cavity C-SOI-Variant: 4 Direct bonding of 2. Wafer 5 Thinning (grinding, etching, polishing), flexible thickness 1 Thermal oxidation 2 Oxide etching 3 Si etching of the cavity with flexible depth 3a optionally: new oxide

15 Example: cavity-soi 6 Sputtering Aluminium 7 Aluminium etching 8 Si etching into cavity

16 Example: Airgap Insulated Microstructure (AIM) 1. Insulating layer 2a. Conducting metal CMOS-compatible fully dry processing Patent-AIM: DE C2; U.S.No.10/296,771; PCT/DE01/02237 Increasing the sensitivity by post-process gap reduction (Aspect ratio > 75:1) Gap reduction actuation: WO 2013/ Laser welding: DE Silicon etching Silicon Isolator Metal

17 Omega DSI 75 µm STS 56 µm Key process: Deep reactive Si etching for HARM (AR ) Gyroscope 2 µm Measurement tips and actuators 50 µm height Accelerometer 2,8 µm 75 µm height

18 Advantages of AIM and BDRIE for electrostatic/capacitive MEMS AIM: Large structure height and high aspect ratio (by gap reduction): High sensitivity, low cross axis sensitivity Special stress decoupled anchors Very good stability against temperature changes BDRIE: Large structure height and high aspect ratio (by etching): High sensitivity, low cross axis sensitivity, large masses for low noise Vacuum sealing with getter: Low residual pressure, high quality factors for resonators

19 Aluminium Nitride for piezoelectric MEMS/NEMS Energy density for piezoelectric working principles is much higher compared to capacitive MEMS driving and sensing principles Allows shrinking of MEMS/NEMS Technology: Magnetron reactive sputtered AlN AlN integration into a Si technology for MEMS / NEMS processing as well as CMOS processes Piezo-MEMS compatible bonding technologies

20 Example: Thin film AlN integrated in Si-MEMS Deposition: DC sputtering full reactive mode (on surface and on sidewalls) Stable over temperature, no hysteresis, highly linear Patterning of layer stack by wet and dry etching Methods for identification of piezoelectric coefficients established

21 Example: Encapsulation of MEMS on wafer level Bonding of a cap wafer by: Silicon direct bonding Anodic bonding Glas frit bonding Metal based bonding Adhesive bonding MEMS Thin film encapsulation: Sacrifical layer: CF polymer Cap layers: SiOx, SiNx, Al 3D Integration: Integration of TSV Monolithic Integration

22 Encapsulation with glass fritt bonded cover wafer (AIM/cavity-SOI) Standard method, widely used: Cap wafer with holes Printed glass fritt paste (sealing frame width µm) Glas frit bonding (approx. 400 C) Hermetic sealing Pressure range: 10 mbar 1 bar Example: Vibration sensor Contact hole Glasfritt Contact pad Si Si SiO 2 Si

23 Example: encapsulation on wafer level using BDRIE Technology (glass-si-glass) Glass wafer with inner mettalic connections/electrodes Si wafer with etched cavities Anodic bonding Thinning of Si ( µm) DRIE of active structure in Si Glass wafer with etched cavities and getter (optionally) Anodic bonding Thinning of glass Etching of contact holes Metal deposition and patterning for outer wiring and contacts MEMS Examples (Gyroscopes)

24 Example: Encapsulation of BDRIE structures Etched holes in thinned Basic-Si-Wafer 9 Bonding of cover wafer (Si or glass) 10 Thinning of basic wafer 11 Wet etching of holes 12 Deposition of SiO2 (Isolator) 13 Opening of contact holes 14 Deposition and patterning of Metal (AL)

25 300 µm 100 µm Encapsuletion of BDRIE structures: comparison of hole size Variant 1: Pre-etched holes in cover, glass fritt bonding Variant 2: Pre-etched holes in basic, direct bonded 600 µm 500 µm 400 µm Variant 3: Holes in basic etched after thinning, direct bonded 200 µm

26 System integration 3D Integration: Integration of TSV 2,5D integration by interposer Direct stacking of MEMS and ASIC Monolithic Integration Hybrid Integration by Aerosol Jet Printing AccS WUG Aerosoljet Printed line

27 Internet of Things industrial monitoring Environment: Control the emission, waste water, wastes, radioactivity Information about environmental processing for public Security: Control of components of machines and equipment Monitoring of lifetime, damages, maintenance Process controlling: Monitoring of process flow Monitoring of employee s security Stock-keeping: Check in and out of materials Monitoring of dangerous materials Locating materials in the warehouse Order automatically

28 Examples: Wideband vibration sensors for condition monitoring Prototypes for low g Acceleration, vibration and inclination sensors Patented, series fabrication technology for high precision at low costs Low noise, outstanding temperature stability co-operation with GEMAC, ELMOS, Wyler AG, Sensorsysteme SRL, memsfab, First sensors Application: tilt measurement, shock measurement, vibration monitoring high aspect ratio overdamped system Detail of vibration sensor Data Sheet (brief version) GC-AS1500 No. of Axis 1 Range Corner Frequency Operating Voltage Range Supply Current Bias Voltage Sensitivity AIM7E sensor, M ASIC (ELMOS) ±50 g 1500 Hz +5.0V ±100 mv 10 ma typ. 2,50 V typ. 50m V/g

29 High precision wide-band vibration sensors General: Range 2,5 KHz 15 KHz Benefits: Patented AIM technology High aspect ratio Excellent thermal stability Large signal to noise ratio Integration of TSVs Cooperation: AMAC (ASIC), Gemac, Lenord & Bauer Applications: Vibration measurement Condition monitoring MEMS Structure Vibration sensor in AIM technology (Gemac mbh)

30 Application of AlN Sensor application: AlN is arranged between two electrodes and mechanically coupled with a movable Si structure External mechanical energy deforms movable silicon element and so the coupled AlN structure electric charges emerge Based on this working principle a Power- Down-Interrupt Generator (MEMS with spring-mass-system and mechanically coupled AlN) was developed charge is used to wake up sensor device Integrated Low Power Force and Shock Sensors earthquake detection

31 Accelerometer for power-down interrupt generater General: Range 1 g demonstrated Motion detection for wake-up functionality Wake-up MEMS on wafer and chip level Benefits: Based on piezoelectric detection: no external power supply necessary Applications: W1 Acceleration measurement Vibration measurement W2 W3 Packaged chips Schematic cross section

32 High performance Gyroscope FG4/FG5 General: Tuning fork principle, two coupled Coriolis masses Open-loop system, quadrature compensation loop Range: 499 /s (sensitive to z-axis rotation) Resolution 5 /hr Bias instability < 5 /hr ARW < 0.2 /hr Bandwidth 120 Hz Output rate of 2000 Hz possible Benefits: High stability and bandwidth Availability QIV/2016 Transfer of BDRIE technology possible (ZfM) Cooperation: EDC Chemnitz (ASICs) Applications: Platform stabilization Motion detection (IMU) Gyro compass (north finding capability proven) SEM of comb drive MEMS chip Gyro system on rate table Allan Variance BI 2.23 /h ARW 0.16 / h ASIC on MEMS Allan Variance plot Metal package

33 Summary IoT provides big opportunities for technologies Device business will reach $45B in 2024 contributing to total IoT market of $400B (Yole) Currently many smart devices are under development, which will be the basis of IoT IoT needs lots of sensors for a wide range of applications Sensor technologies, encapsulation and 3D integration technologies play a mayor role Three examples of sensors demonstrated Beside sensing modules a lot of regulations need to be established Moreover data handling and processing, software protocols and standards are essential for IoT

34 Thank you for your attention >>